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1.
To investigate dietary protein level effects on digestive mechanisms, weaned piglets were fed for 45 d with diets containing 20%, 17%, or 14% crude protein (CP) supplemented to meet requirements for essential amino acids. This article describes the influence of dietary protein on gastrointestinal hormones and expression of an array of digestive enzymes in the gastrointestinal tract and pancreas. Results indicated that there were no significant differences in expression of enzymes involved in carbohydrate digestion, except for maltase in the duodenum. In the jejunum, amylase expression in pigs fed 20% CP was much higher than that in pigs fed other diets (P<0.05) and maltase expression in those fed 17% CP was higher than that in other treatments (P<0.05). Although there were no remarkable differences in expression of aminopeptidase in the small intestine or carboxypeptidase in the pancreas (P>0.05), there was a trend towards higher expression of various proteases in pigs fed 17% CP. The duodenal expression of enteropeptidase in diets with 14% and 17% CP was significantly higher than that with 20% CP (P<0.05), but treatment differences did not existed in jejunum (P>0.05). The expression of GPR93 as a nutrient-responsive G protein-coupled receptor in 14% and 17% CP diets was significantly higher than that in 20% CP diet in the small intestine (P<0.05). The expressions of genes for pancreatic enzymes, lipase and elastase, were significantly higher in pigs fed diets with low CP, while similar trends occurred for carboxypeptidase, chymotrypsin and amylase. Conversely, the gastric expressions of pepsinogen A and progastricsin were lower with the 17% CP diet. Differences between treatments were found in the gastric antral contents of cholecystokinin and somatostatin: both increased in pigs fed 17% CP, accompanied by decreased content of motilin, which was also seen in plasma concentrations. These patterns were not reflected in duodenal contents. In general, 17% dietary CP was beneficial to the digestion of nutrient substance in the gastrointestinal tract.  相似文献   

2.
A total of 64 patients with β-lactam allergy and 30 control subjects were enrolled in a case-control study. This study is aimed to analyze the relationship between β-lactam allergy and 10 single nucleotide polymorphisms (SNPs) in interleukin-10 (IL-10), IL-13, IL-4Rα, high-affinity immunoglobulin E-receptor β chain (FcεRIβ), interferon γ receptor 2 (IFNGR2), and CYP3A4, and within the Han Chinese population of Northwest China. Genotyping for the SNPs was conducted using the Sequenom MassARRAY®platform. SPSS 17.0 was employed to analyze the statistical data and SHEsis was used to perform the haplotype reconstruction and analyze linkage disequilibrium of SNPs of IL-10 and IL-13. The results showed that the genotype distribution of CYP3A4 rs2242480/CT differed significantly between case and control groups of males (P=0.022; odds ratio (OR)=0.167, 95% confidence interval (CI): 0.032–0.867). Further analysis showed that CCA, CCG, and TAA haplotypes of IL-10 had no significant correlation in patients with β-lactam allergy. The correlation between CCT and CAC haplotypes of IL-13 and β-lactam allergy needs to be further studied. The analysis did not reveal any differences in the distribution of others gene polymorphisms between cases and controls.  相似文献   

3.
A standard genetic/bioinformatic activity in the genomics era is the identification within DNA sequences of an "open reading frame" (ORF) that encodes a polypeptide sequence. As an educational introduction to such a search, we provide a webapp that composes, displays for solution, and then solves short DNA exemplars with a single ORFTo the Editor: We wish to bring a new Web resource to the attention of CBE—Life Sciences Education readers.When being introduced to the central dogma of nucleic acid transactions, students are often required to identify the 5′→3′ DNA template strand in a double-stranded DNA (dsDNA) molecule; transcribe an antiparallel, complementary 5′→3′ mRNA; and then translate the mRNA codons 5′→3′ into an amino acid polypeptide by means of the genetic code table. Although this algorithm replicates the molecular genetic process of protein synthesis, experience shows that the series of left/right, antiparallel, and/or 5′→3′ reversals is confusing to many students when worked by hand. Students may also obtain the “right” answer for the “wrong” reasons, as when the “wrong” DNA strand is transcribed in the “wrong” 3′→5′ direction, so as to produce a string of letters that “translates correctly.”In genetics and bioinformatics education, we have found it more intuitively appealing to demonstrate and emphasize the equivalence of the mRNA to the DNA sense strand complement of the template strand. The sense strand is oriented in the same 5′→3′ direction and has a sequence identical to the mRNA, except for substitution of thymidine in the DNA for uracil in the mRNA. It is thus more computationally efficient to “read” the polypeptide sequence directly from this strand, with mental substitution of thymidine in the triplets of the genetic code table. (By definition, “codons” occur only in mRNA: the equivalent three-letter words in the DNA sense strand may be designated “triplets.”) This is the same logic used in DNA “translation” software programs.A further constraint often imposed on dsDNA teaching exemplars is that five of the six possible reading frames are “closed” by the occurrence of one or more “stop” triplets, and only one is an open reading frame (ORF) that encodes an uninterrupted polypeptide. We designate this the “5&1” condition. The task for the student is to identify the ORF and “translate” it correctly. Other considerations include correct labeling of the sense and template DNA strands, their 5′ and 3′ ends (and of the mRNA as required), and the amino (N) and carboxyl (C) termini of the polypeptide.Thus, instructors face the logistical challenge of creating dsDNA sequences that satisfy the “5&1” condition for homework and exam questions. Instructors must compose sequences with one or more “stops” in the three overlapping read frames of one strand, while simultaneously creating two “stopped” frames and one ORF in the other. We have explored these constraints as an algorithmic and computational challenge (Carr et al., 2014 ). There are no “5&1” exemplars of length L ≤ 10, and the proportion of exemplars of length L ≥ 11 is very small relative to the 4L possible sequences (e.g., 0.0023% for L = 11, 0.048% for L = 15, 0.89% for L = 25). This makes random exploration for such exemplars inefficient.We therefore developed a two-stage recursive search algorithm that samples 4L space randomly to generate “5&1” exemplars of any specified length L from 11 ≤ L ≤ 100. The algorithm has been implemented as a Web application (“RandomORF,” available at www.ucs.mun.ca/~donald/orf/randomorf). Figure 1 shows a screen capture of the successive stages of the presentation. The application requires JavaScript on the computer used to run the Web browser.Open in a separate windowFigure 1.Successive screen captures of the webapp RandomORF. First panel: the Length parameter is the desired number of base pairs. Second panel: Clicking the “Generate dsDNA” button shows the dsDNA sequence to be solved, with labeled 5′ and 3′ ends. The button changes to “Show ORF.” Third panel: A second click shows the six reading frames, with the ORF highlighted. Here, the ORF is in the sixth reading frame on the bottom (sense) strand. The polypeptide sequence, read right to left, is N–EITHLRL–C, where N and C are the amino and carboxyl termini, respectively. The conventional IUPAC single-letter abbreviations for amino acids are centered over the middle base of the triplet; stop triplets are indicated by asterisks (*).The webapp provides a means for students to practice identifying ORFs by efficiently generating many examples with unique solutions (Supplemental Material); this can take the place of the more standard offering of a small number of set examples with an answer key. The two-stage display makes it possible for problems to be worked “cold,” with the correct ORF identified only afterward. For examinations, any exemplar may be presented in any of four ways, by transposing the top and bottom strands and/or reversing the direction of the strands left to right. Presentation of the 5′ end of the sense strand at the lower left or upper or lower right tests student recognition that sense strands are always read in the 5′→3′ direction, irrespective of the “natural” left-to-right and/or top-then-bottom order. We intend to modify the webapp to include other features of pedagogical value, including constraints on [G+C] composition and the type, number, and distribution of stop triplets. We welcome suggestions from readers.  相似文献   

4.
A response to Maskiewicz and Lineback''s essay in the September 2013 issue of CBE-Life Sciences Education.Dear Editor:Maskiewicz and Lineback (2013) have written a provocative essay about how the term misconceptions is used in biology education and the learning sciences in general. Their historical perspective highlights the logic and utility of the constructivist theory of learning. They emphasize that students’ preliminary ideas are resources to be built upon, not errors to be eradicated. Furthermore, Maskiewicz and Lineback argue that the term misconception has been largely abandoned by educational researchers, because it is not consistent with constructivist theory. Instead, they conclude, members of the biology education community should speak of preconceptions, naïve conceptions, commonsense conceptions, or alternative conceptions.We respectfully disagree. Our objections encompass both the semantics of the term misconception and the more general issue of constructivist theory and practice. We now address each of these in turn. (For additional discussion, please see Leonard, Andrews, and Kalinowski , “Misconceptions Yesterday, Today, and Tomorrow,” CBE—Life Sciences Education [LSE], in press, 2014.)Is misconception suitable for use in scholarly discussions? The answer depends partly on the intended audience. We avoid using the term misconception with students, because it could be perceived as pejorative. However, connotations of disapproval are less of a concern for the primary audience of LSE and similar journals, that is, learning scientists, discipline-based education researchers, and classroom teachers.An additional consideration is whether misconception is still used in learning sciences outside biology education. Maskiewicz and Lineback claim that misconception is rarely used in journals such as Cognition and Instruction, Journal of the Learning Sciences, Journal of Research in Science Teaching, and Science Education, yet the term appears in about a quarter of the articles published by these journals in 2013 (National Research Council, 2012 ).

Table 1.

Use of the term misconception in selected education research journals in 2013
Journal (total articles published in 2013a)Articles using misconception (“nondisapproving” articles/total articles)Articles using other terms
LSE (59)23/24Alternative conception (4)
Commonsense conception (2)
Naïve conception (1)
Preconception (4)
Cognition and Instruction (16)3/3None
Journal of the Learning Sciences (17)4/4Commonsense science knowledge (1)
Naïve conception (1)
Prior conception (1)
Journal of Research in Science Teaching (49)11/13Commonsense idea (1)
Naïve conception (1)
Preconception (5)
Science Education (36)10/11Naïve conception (1)
Open in a separate windowaAs of November 25, 2013. Does not include very short editorials, commentaries, corrections, or prepublication online versions.A final consideration is whether any of the possible alternatives to misconception are preferable. We feel that the alternatives suggested by Maskiewicz and Lineback are problematic in their own ways. For example, naïve conception sounds more strongly pejorative to us than misconception. Naïve conception and preconception also imply that conceptual challenges occur only at the very beginning stages of learning, even though multiple rounds of conceptual revisions are sometimes necessary (e.g., see figure 1 of Andrews et al., 2012 ) as students move through learning progressions. Moreover, the terms preferred by Maskiewicz and Lineback are used infrequently (Smith et al. (1993) that they object to statements that misconceptions should be actively confronted, challenged, overcome, corrected, and/or replaced (Smith et al. (1993) argue on theoretical grounds that confrontation does not allow refinement of students’ pre-existing, imperfect ideas; instead, the students must simply choose among discrete prepackaged ideas. From Maskiewicz and Lineback''s perspective, the papers listed in Maskiewicz and Lineback (2013) as using outdated views of misconceptionsa
ArticleExample of constructivist languageExample of language suggesting confrontation
Andrews et al., 2011 “Constructivist theory argues that individuals construct new understanding based on what they already know and believe.… We can expect students to retain serious misconceptions if instruction is not specifically designed to elicit and address the prior knowledge students bring to class” (p. 400).Instructors were scored for “explaining to students why misconceptions were incorrect” and “making a substantial effort toward correcting misconceptions” (p. 399). “Misconceptions must be confronted before students can learn natural selection” (p. 399). “Instructors need to elicit misconceptions, create situations that challenge misconceptions.” (p. 403).
Baumler et al., 2012 “The last pair [of students]''s response invoked introns, an informative answer, in that it revealed a misconception grounded in a basic understanding of the Central Dogma” (p. 89; acknowledges students’ useful prior knowledge).No relevant text found
Cox-Paulson et al., 2012 No relevant text foundThis paper barely mentions misconceptions, but cites sources (Phillips et al., 2008 ; Robertson and Phillips, 2008 ) that refer to “exposing,” “uncovering,” and “correcting” misconceptions.
Crowther, 2012 “Prewritten songs may explain concepts in new ways that clash with students’ mental models and force revision of those models” (p. 28; emphasis added).“Songs can be particularly useful for countering … conceptual misunderstandings.… Prewritten songs may explain concepts in new ways that clash with students’ mental models and force revision of those models” (p. 28).
Kalinowski et al., 2010 “Several different instructional approaches for helping students to change misconceptions … agree that instructors must take students’ prior knowledge into account and help students integrate new knowledge with their existing knowledge” (p. 88).“One strategy for correcting misconceptions is to challenge them directly by ‘creating cognitive conflict,’ presenting students with new ideas that conflict with their pre-existing ideas about a phenomenon… In addition, study of multiple examples increases the chance of students identifying and overcoming persistent misconceptions” (p. 89).
Open in a separate windowaWhile these papers do not adhere to Smith et al.''s (1993) version of constructivism, they do adhere to the constructivist approach that advocates cognitive dissonance.Our own stance differs from that of Maskiewicz and Lineback, reflecting a lack of consensus within constructivist theory. We agree with those who argue that, not only are confrontations compatible with constructivist learning, they are a central part of it (e.g., Gilbert and Watts, 1983 ; Hammer, 1996 ). We note that Baviskar et al. (2009) list “creating cognitive dissonance” as one of the four main tenets of constructivist teaching. Their work is consistent with research showing that focusing students on conflicting ideas improves understanding more than approaches that do not highlight conflicts (e.g., Kowalski and Taylor, 2009 ; Gadgil et al., 2012 ). Similarly, the Discipline-Based Education Research report (National Research Council, 2012 , p. 70) advocates “bridging analogies,” a form of confrontation, to guide students toward more accurate ways of thinking. Therefore, we do not share Maskiewicz and Lineback''s concerns about the papers listed in Price, 2012 ). We embrace collegial disagreement.Maskiewicz and Lineback imply that labeling students’ ideas as misconceptions essentially classifies these ideas as either right or wrong, with no intermediate stages for constructivist refinement. In fact, a primary goal of creating concept inventories, which use the term misconception profusely (e.g., Morris et al., 2012 ; Prince et al., 2012 ), is to demonstrate that learning is a complex composite of scientifically valid and invalid ideas (e.g., Andrews et al., 2012 ). A researcher or instructor who uses the word misconceptions can agree wholeheartedly with Maskiewicz and Lineback''s point that misconceptions can be a good starting point from which to develop expertise.As we have seen, misconception is itself fraught with misconceptions. The term now embodies the evolution of our understanding of how people learn. We support the continued use of the term, agreeing with Maskiewicz and Lineback that authors should define it carefully. For example, in our own work, we define misconceptions as inaccurate ideas that can predate or emerge from instruction (e.g., Andrews et al., 2012 ). We encourage instructors to view misconceptions as opportunities for cognitive dissonance that students encounter as they progress in their learning.  相似文献   

5.
Despite the impact of genetics on daily life, biology undergraduates understand some key genetics concepts poorly. One concept requiring attention is dominance, which many students understand as a fixed property of an allele or trait and regularly conflate with frequency in a population or selective advantage. We present the Dominance Concept Inventory (DCI), an instrument to gather data on selected alternative conceptions about dominance. During development of the 16-item test, we used expert surveys (n = 12), student interviews (n = 42), and field tests (n = 1763) from introductory and advanced biology undergraduates at public and private, majority- and minority-serving, 2- and 4-yr institutions in the United States. In the final field test across all subject populations (n = 709), item difficulty ranged from 0.08 to 0.84 (0.51 ± 0.049 SEM), while item discrimination ranged from 0.11 to 0.82 (0.50 ± 0.048 SEM). Internal reliability (Cronbach''s alpha) was 0.77, while test–retest reliability values were 0.74 (product moment correlation) and 0.77 (intraclass correlation). The prevalence of alternative conceptions in the field tests shows that introductory and advanced students retain confusion about dominance after instruction. All measures support the DCI as a useful instrument for measuring undergraduate biology student understanding and alternative conceptions about dominance.  相似文献   

6.
Although we agree with Theobold and Freeman (2014) that linear models are the most appropriate way in which to analyze assessment data, we show the importance of testing for interactions between covariates and factors.To the Editor:Recently, Theobald and Freeman (2014) reviewed approaches for measuring student learning gains in science, technology, engineering, and mathematics (STEM) education research. In their article, they highlighted the shortcomings of approaches such as raw change scores, normalized gain scores, normalized change scores, and effect sizes when students are not randomly assigned to classes based on the different pedagogies that are being compared. As an alternative, they propose using linear regression models in which characteristics of students, such as pretest scores, are included as independent variables in addition to treatments. Linear models that include both continuous and categorical independent variables are often termed analysis of covariance (ANCOVA) models. The approach of using ANCOVA to control for differences in students among treatments groups has been suggested previously by Weber (2009) . We largely agree with Theobald and Freeman (2014) and Weber (2009) that ANCOVA models are an appropriate method for situations in which students cannot be randomly assigned to treatments and controls. However, in describing how to implement linear regression models to examine student learning gains, Theobald and Freeman (2014) ignore a fundamental assumption of ANCOVA.ANCOVA assumes homogeneity of slopes (McDonald, 2009 ; Sokal and Rohlf, 2011 ). In other words, the slope of the relationship between the covariate (e.g., pretest score) and the dependent variable (e.g., posttest score) is the same for the treatment group and the control. This assumption is a strict assumption of ANCOVA in that violations of this assumption can result in incorrect conclusions (Engqvist, 2005 ). For example, in Figure 1, both pretest score and treatment have statistically significant main effects in a linear model with only pretest score (F(1, 97) = 25.6, p < 0.001) and treatment (F(1, 97) = 42.6, p < 0.01) as independent variables. Therefore, we would conclude that all students in the class with pedagogical innovation had significantly greater posttest scores than those students in the control class for a given pretest score. Furthermore, we would conclude that the pedagogical innovation led to the same increase in score for all students in the treatment class, independent of their pretest scores. Clearly, neither of these conclusions would be justified.Researchers must first test the assumption of the homogeneity of slopes by including an interaction term (covariate × treatment) in their linear model (McDonald, 2009 ; Weber 2009 ; Sokal and Rohlf, 2011 ). For example, if we measured student achievement in two courses with different instructional approaches in a typical pretest/posttest design, then the interaction between students’ pretest scores and the type of instruction must be considered, because the instruction may have a different effect for high- versus low-achieving students. If multiple covariates are included in the linear model (see Equation 1 in Theobald and Freeman, 2014 ), then interaction terms need to be included for each of the covariates in the model. If the interaction term is statistically significant, this suggests that the relationship between the covariate and the dependent variable is different for each treatment group (F(1, 96) = 25.1, p < 0.001; Figure 1). As a result, the effect of the treatment will depend on the value of the covariate, and universal statements about the effect of the treatment are not appropriate (Engqvist, 2005 ). If the interaction term is not statistically significant, it should be removed from the model and the analysis rerun without the interaction term. Failure to remove an interaction term that was not statistically significant also can lead to an incorrect conclusion (Engqvist, 2005 ). Whether there are statistically significant interactions between the “treatment” and the covariates in the data set used by Theobald and Freeman (2014) is unclear.Open in a separate windowFigure 1.Simulated data to demonstrate heterogeneity of slopes. Pretest values were generated from random normal distributions with mean = 59.8 (SD = 18.1) for the treatment course and mean = 59.3 (SD = 17.0) for the control course, based on values given in Theobald and Freeman (2014) . For the treatment course, posttest values were calculated using the formula posttesti = 80 + 0.1 × pre-testi + Ɛi, where Ɛi was selected from a random normal distribution with mean = 0 (SD = 10). For the control course, posttest values were calculated using the formula posttesti = 42 + 0.5 × pre-testi + Ɛi, where Ɛi was selected from a random normal distribution with mean = 0 (SD = 10). n = 50 for both courses.In addition to being a strict assumption of ANCOVA, testing for homogeneity of slopes in a linear model is important in STEM education research, as slopes are likely heterogeneous for several reasons. First, for many instruments used in STEM education research, high-achieving students score high on the pretest. As a result, their ability to improve is limited due to the ceiling effect, and differences between treatment and control groups in posttest scores are likely to be minimal (Figure 1). In contrast, low-achieving students have a greater opportunity to change their scores between their pretest and posttest. Second, pedagogical innovations are more likely to have a greater impact on the learning of lower-performing students than higher-performing students. For example, Beck and Blumer (2012) found statistically greater gains in student confidence and scientific reasoning skills for students in the lowest quartile as compared with students in the highest quartile on pretest assessments in inquiry-based laboratory courses.Theobald and Freeman (2014, p. 47) note that “regression models can also include interaction terms that test whether the intervention has a differential impact on different types of students.” Yet, we argue that these terms must be included and only should be excluded if they are not statistically significant.  相似文献   

7.
Objective: To compare the peri-operative outcomes for laparoscopic distal pancreatectomy (LDP) and open distal pancreatectomy (ODP) for benign or premalignant pancreatic neoplasms in two institutions. Methods: This prospective comparative study included 91 consecutive patients who underwent LDP (n=45) or ODP (n=46) from Jan. 2010 to Dec. 2012. Demographics, intra-operative characteristics, and post-operative outcomes were compared. Results: The median operating time in the LDP group was (158.7±38.3) min compared with (92.2±24.1) min in the ODP group (P<0.001). Patients had lower blood loss in LDP than in the ODP (122.6±61.1) ml vs. (203.1±84.8) ml, P<0.001). The rates of splenic conservation between the LDP and ODP groups were similar (53.3% vs. 47.8%, P=0.35). All spleen-preserving distal pancreatectomies were conducted with vessel preservation. LDP also demonstrated better post-operative outcomes. The time to oral intake and normal daily activities was faster in the LDP group than in the ODP group (1.6±0.5) d vs. (3.2±0.7) d, P<0.01; (1.8±0.4) d vs. (2.1±0.6) d, P=0.02, respectively), and the postoperative length of hospital stay in LDP was shorter than that in ODP (7.9±3.8) d vs. (11.9±5.8) d, P=0.006). No difference in tumor size (4.7±3.2) cm vs. (4.5±1.8) cm, P=0.77) or overall pancreatic fistula rate (15.6% vs. 19.6%, P=0.62) was found between the groups, while the overall post-operative complication rate was lower in the LDP group (26.7% vs. 47.8%, P=0.04). Conclusions: LDP is safe and effective for benign or premalignant pancreatic neoplasms, featuring lower blood loss and substantially faster recovery.  相似文献   

8.

Objective

Helicobacter pylori maintains long-term persistence in the host and combats oxidative stress via many antioxidant proteins, which are expected to be relevant to bacterial-associated gastric diseases. We aimed to investigate the expression of three essential antioxidants in H. pylori strains isolated from patients with different clinical outcomes. Methods: Forty H. pylori strains were isolated from endoscopic biopsy specimens of gastric mucosa from 13 patients with gastric cancer, 13 with peptic ulcer, and 14 with gastritis. The expression of thioredoxin 1 (Trx1), arginase (RocF), and alkyl hydroperoxide reductase (AhpC) in H. pylori was measured by real-time PCR. Comparisons among multiple sample sets were analyzed using a one-way ANOVA test. Pearson’s correlation test was used to assess relationships among multiple continuous variables.

Results

Trx1 expression of H. pylori in gastric cancer and peptic ulcer tissues was higher than that in tissues with gastritis. RocF expression of H. pylori in gastric cancer tissues was higher than that in tissues exhibiting peptic ulcer and gastritis. However, we did not find any differences in AhpC expression in samples from patients with different clinical outcomes. The expression of Trx1 and RocF had a positive, linear correlation. The expression of Trx1 and AhpC had a positive correlation without a linear trend. We found no correlation between the expression of RocF and AhpC.

Conclusions

Our observations indicate that the expression of Trx1 and RocF in H. pylori might be related to gastric carcinogenesis. In H. pylori, the expression of members of the antioxidant system may be correlated and relevant to gastric cancer.  相似文献   

9.
The presence of yeast cells could stimulate hydrogen utilization of acetogens and enhance acetogenesis. To understand the roles of acetogens in rumen fermentation, an in vitro rumen fermentation experiment was conducted with addition of acetogen strain (TWA4) and/or Saccharomyces cerevisiae fermentation product (XP). A 2×2 factorial design with two levels of TWA4 (0 or 2×107 cells/ml) and XP (0 or 2 g/L) was performed. Volatile fatty acids (VFAs) were increased (P<0.05) in XP and TWA4XP, while methane was increased only in TWA4XP (P<0.05). The increase rate of microorganisms with formyltetrahydrofolate synthetase, especially acetogens, was higher than that of methanogens under all treatments. Lachnospiraceae was predominant in all acetogen communities, but without close acetyl-CoA synthase (ACS) amino acid sequences from cultured isolates. Low-Acetitomaculum ruminis-like ACS was predominant in all acetogen communities, while four unique phylotypes in XP treatment were all amino acid identified low-Eubacterium limosum-like acetogens. It differs to XP treatment that more low-A. ruminis-like and less low-E. limosum-like sequences were identified in TWA4 and TWA4XP treatments. Enhancing acetogenesis by supplementation with an acetogen strain and/or yeast cells may be an approach to mitigate methane, by targeting proper acetogens such as uncultured low-E. limosum-like acetogens.  相似文献   

10.
Objective: The intoxications caused by 2,4-dinitrophenol (2,4-DNP), even death, have been frequently reported in recent years. This study aims to investigate the dynamic changes of plasma toxin concentration and explore the clinical value of resin hemoperfusion (HP) in the treatment of patients with acute 2,4-DNP poisoning. Methods: We reported 16 cases of acute 2,4-DNP poisoning through occupational exposure due to ignoring the risk of poisoning. The blood samples were collected from the 14 survivors. According to the different treatments of resin HP, the survivors were divided into routine HP (n=5) and intensive HP (n=9) groups. Ultra high performance liquid chromatography/tandem mass spectroscopy (UPLC-MS/MS) was used to detect the 2,4-DNP concentration in plasma in this study. Results: The 14 survivors recovered very well after treatment. The initial plasma 2,4-DNP concentrations (C 1) of survivors ranged from 0.25 to 41.88 µg/ml (mean (12.56±13.93) µg/ml). A positive correlation existed between initial plasma 2,4-DNP concentration (C 1) and temperature. The elimination of 2,4-DNP was slow and persistent, and the total clearance rates of plasma toxin from the 1st to 3rd day (R 3), the 3rd to 7th day (R 3–7), and the 1st to 7th day (R 7), were only (53.03±14.04)%, (55.25±10.50)%, and (78.29±10.22)%, respectively. The plasma toxin was cleared up to 25 d after poisoning in most of the patients. The R 3, R 3–7, and R 7 in the intensive HP group were all apparently higher than those in the routine HP group, with statistical significance (P<0.05). Simultaneously, the elimination half-life (t 1/2) of 2,4-DNP in the intensive HP group was apparently shorter than that in the routine HP group, with statistical significance (P<0.05). Conclusions: The clinicians should be aware of this slow and persistent process in the elimination of plasma 2,4-DNP. Higher initial plasma toxin concentration resulted in a more severe fever for the patient. According to the limited data, longer and more frequent resin HP may accelerate to eliminate the poison.  相似文献   

11.
目的:研究离体热处理和顺铂联合热处理对术中回收血红细胞功能的影响及其中混杂的肝肿瘤细胞株(HepG2)的杀灭作用。创新点:(1)采用多种评价指标研究了不同时间离体热处理对术中回收血中混杂的HepG2的杀灭作用及对红细胞的影响,并确定了对红细胞安全且能有效杀灭HepG2的离体热处理时间。(2)从多个角度评价了离体顺铂联合热处理对术中回收血红细胞的影响及对其中混杂的HepG2的杀灭作用,确定了该方案中对红细胞安全且能有效去除HepG2的顺铂浓度。方法:采用3-(4,5-二甲基噻唑-2)-2,5-二苯基四氮唑溴盐(MTT)、5-乙炔基-2’脱氧尿嘧啶核苷(EdU)和平板克隆形成评估HepG2的细胞存活率、DNA复制率和克隆形成能力(图1和3);从红细胞渗透脆性、携氧能力(2,3-二磷酸甘油酸(2,3-DPG)、半饱和氧分压(P50))、能量代谢(Na+-K+-ATPase、pH)、膜完整性(游离血红蛋白(Hb)、血清K+和Na+浓度、细胞膜磷脂酰丝氨酸外翻比例)等角度评估红细胞功能(图2和4;表3)。结论:肝肿瘤术中回收血经离体顺铂联合热处理(42°C,50μg/ml)60min后,能有效清除其中混杂的HepG2,但对红细胞无显著影响,值得体内进一步研究顺铂热处理有效应用于肿瘤手术自体血液回输的安全方案。  相似文献   

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14.
In this study, we isolated an environmental clone of Ochrobactrum intermedium, strain 2745-2, from the formation water of Changqing oilfield in Shanxi, China, which can degrade crude oil. Strain 2745-2 is aerobic and rod-shaped with optimum growth at 42 °C and pH 5.5. We sequenced the genome and found a single chromosome of 4 800 175 bp, with a G+C content of 57.63%. Sixty RNAs and 4737 protein-coding genes were identified: many of the genes are responsible for the degradation, emulsification, and metabolizing of crude oil. A comparative genomic analysis with related clinical strains (M86, 229E, and LMG3301T) showed that genes involved in virulence, disease, defense, phages, prophages, transposable elements, plasmids, and antibiotic resistance are also present in strain 2745-2.  相似文献   

15.
Objective: To investigate the distribution ofH. pylori antigens in the gastric mucosa in patients withH. pylori infection, and the relationship between the distribution and gastric cancer. Methods: Of 112 patients confirmed by pathological study to have chronic superficial gastritis, precancerous changes (chronic atrophic gastritis, intestinal metaplasia or atypical hyperplasia) and gastric cancer, 28 wereH. pylori negative and 84 wereH. pylori positive.H. pylori antigens in the gastric mucosa were detected by immunohistochemistry. Results: TheH. pylori positive group, comprised 12 of 22 (50.0%) in the chronic superficial gastritis group, 22 of 25 (88.0%) in the precancerous changes group and 13 of 35 (37.1%) in the gastric cancer group. The positive rates ofH. pylori antigens in the cytoplasm progressively increased, respectively at 0.0% (0/12), 63.6% (14/22) and 84.6% (11/13) for the same groups (χ 2=19.76,P=0.000);H. pylori antigens were located in the mucus layer and above the neck of the mucosal gland in 9 of 12 (75.0%) cases with chronic superficial gastritis, at the neck of the mucosal gland and the isthmus in 12 of 22 (54.5%) cases with precancerous changes, below the isthmus in 9 of 13 (69.2%) cases with gastric cancer (χ 2=25.30,P=0.000). In theH. pylori negative group, noH. pylori antigen was observed. Conclusion: With the progression of chronic superficial gastritis→precancerous changes→gastric cancer,H. pylori antigens progressively migrated from the outer part to the inner part of the cell, and from the superficial to the deep gastric mucosa.  相似文献   

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17.
Graduate teaching assistants (GTAs) in science, technology, engineering, and mathematics (STEM) have a large impact on undergraduate instruction but are often poorly prepared to teach. Teaching self-efficacy, an instructor’s belief in his or her ability to teach specific student populations a specific subject, is an important predictor of teaching skill and student achievement. A model of sources of teaching self-efficacy is developed from the GTA literature. This model indicates that teaching experience, departmental teaching climate (including peer and supervisor relationships), and GTA professional development (PD) can act as sources of teaching self-efficacy. The model is pilot tested with 128 GTAs from nine different STEM departments at a midsized research university. Structural equation modeling reveals that K–12 teaching experience, hours and perceived quality of GTA PD, and perception of the departmental facilitating environment are significant factors that explain 32% of the variance in the teaching self-efficacy of STEM GTAs. This model highlights the important contributions of the departmental environment and GTA PD in the development of teaching self-efficacy for STEM GTAs.Science, technology, engineering, and mathematics (STEM) graduate teaching assistants (GTAs) play a significant role in the learning environment of undergraduate students. They are heavily involved in the instruction of undergraduate students at master’s- and doctoral-granting universities (Nyquist et al., 1991 ; Johnson and McCarthy, 2000 ; Sundberg et al., 2005 ; Gardner and Jones, 2011 ). GTAs are commonly in charge of laboratory or recitation sections, in which they often have more contact and interaction with the students than the professor who is teaching the course (Abraham et al., 1997 ; Sundberg et al., 2005 ; Prieto and Scheel, 2008 ; Gardner and Jones, 2011 ).Despite the heavy reliance on GTAs for instruction and the large potential for them to influence student learning, there is evidence that many GTAs are completely unprepared or at best poorly prepared for their role as instructors (Abraham et al., 1997 ; Rushin et al., 1997 ; Shannon et al., 1998 ; Golde and Dore, 2001 ; Fagen and Wells, 2004 ; Luft et al., 2004 ; Sundberg et al., 2005 ; Prieto and Scheel, 2008 ). For example, in molecular biology, 71% of doctoral students are GTAs, but only 30% have had an opportunity to take a GTA professional development (PD) course that lasted at least one semester (Golde and Dore, 2001 ). GTAs often teach in a primarily directive manner and have intuitive notions about student learning, motivation, and abilities (Luft et al., 2004 ). For those who experience PD, university-wide PD is often too general (e.g., covering university policies and procedures, resources for students), and departmental PD does not address GTAs’ specific teaching needs; instead departmental PD repeats the university PD (Jones, 1993 ; Golde and Dore, 2001 ; Luft et al., 2004 ). Nor do graduate experiences prepare GTAs to become faculty and teach lecture courses (Golde and Dore, 2001 ).While there is ample evidence that many GTAs are poorly prepared, as well as studies of effective GTA PD programs (biology examples include Schussler et al., 2008 ; Miller et al., 2014 ; Wyse et al., 2014 ), the preparation of a graduate student as an instructor does not occur in a vacuum. GTAs are also integral members of their departments and are interacting with faculty and other GTAs in many different ways, including around teaching (Bomotti, 1994 ; Notarianni-Girard, 1999 ; Belnap, 2005 ; Calkins and Kelly, 2005 ). It is important to build good working relationships among the GTAs and between the GTAs and their supervisors (Gardner and Jones, 2011 ). However, there are few studies that examine the development of GTAs as integral members of their departments and determine how departmental teaching climate, GTA PD, and prior teaching experiences can impact GTAs.To guide our understanding of the development of GTAs as instructors, a theoretical framework is important. Social cognitive theory is a well-developed theoretical framework for describing behavior and can be applied specifically to teaching (Bandura, 1977 , 1986 , 1997 , 2001 ). A key concept in social cognitive theory is self-efficacy, which is a person’s belief in his or her ability to perform a specific task in a specific context (Bandura, 1997 ). High self-efficacy correlates with strong performance in a task such teaching (Bandura, 1997 ; Tschannen-Moran and Hoy, 2007 ). Teaching self-efficacy focuses on teachers’ perceptions of their ability to “organize and execute courses of action required to successfully accomplish a specific teaching task in a particular context” (Tschannen-Moran et al., 1998 , p. 233). High teaching self-efficacy has been shown to predict a variety of types of student achievement among K–12 teachers (Ashton and Webb, 1986 ; Anderson et al., 1988 ; Ross, 1992 ; Dellinger et al., 2008 ; Klassen et al., 2011 ). In GTAs, teaching self-efficacy has been shown to be related to persistence in academia (Elkins, 2005 ) and student achievement in mathematics (Johnson, 1998 ). High teaching self-efficacy is evidenced by classroom behaviors such as efficient classroom management, organization and planning, and enthusiasm (Guskey, 1984 ; Allinder, 1994 ; Dellinger et al., 2008 ). Instructors with high teaching self-efficacy work continually with students to help them in learning the material (Gibson and Dembo, 1984 ). These instructors are also willing to try a variety of teaching methods to improve their teaching (Stein and Wang, 1988 ; Allinder, 1994 ). Instructors with high teaching self-efficacy perform better as teachers, are persistent in difficult teaching tasks, and can positively affect their student’s achievement.These behaviors of successful instructors, which can contribute to student success, are important to foster in STEM GTAs. Understanding of what influences the development of teaching self-efficacy in STEM GTAs can be used to improve their teaching self-efficacy and ultimately their teaching. Therefore, it is important to understand what impacts teaching self-efficacy in STEM GTAs. Current research into factors that influence GTA teaching self-efficacy are generally limited to one or two factors in a study (Heppner, 1994 ; Prieto and Altmaier, 1994 ; Prieto and Meyers, 1999 ; Prieto et al., 2007 ; Liaw, 2004 ; Meyers et al., 2007 ). Studying these factors in isolation does not allow us to understand how they work together to influence GTA teaching self-efficacy. Additionally, most studies of GTA teaching self-efficacy are not conducted with STEM GTAs. STEM instructors teach in a different environment and with different responsibilities than instructors in the social sciences and liberal arts (Lindbloom-Ylanne et al., 2006 ). These differences could impact the development of teaching self-efficacy of STEM GTAs compared with social science and liberal arts GTAs. To further our understanding of the development of STEM GTA teaching self-efficacy, this paper aims to 1) describe a model of factors that could influence GTA teaching self-efficacy, and 2) pilot test the model using structural equation modeling (SEM) on data gathered from STEM GTAs. The model is developed from social cognitive theory and GTA teaching literature, with support from the K–12 teaching self-efficacy literature. This study is an essential first step in improving our understanding of the important factors impacting STEM GTA teaching self-efficacy, which can then be used to inform and support the preparation of effective STEM GTAs.  相似文献   

18.
BackgroundThe Child Sexual Behavior Inventory (CSBI) is one of the few instruments available to assess sexual behavior in children. Because of cross-cultural differences in the definition of normal and atypical sexual behaviors, the CSBI is not generalizable to other countries.ObjectiveThe current study examined psychometric properties of the Dutch version of the CSBI.Participants and settingThe study represents 3206 children from a normative sample, and 932 children from clinical samples.MethodsParents ratings on the CSBI, and questionnaires for psychosocial problems were obtained to assess psychometric properties.ResultsResults showed that Dutch parents interpret more CSBI items as developmentally appropriate than USA parents. Reliability coefficients indicated internal consistency (α = .39–.82), test-retest (r = .86, p < .000) and interrater reliability (Cohen's d =0.47, p >.05). Positive correlations between the CSBI total scale and the subscales demonstrated content validity (r = .32–.96, p < .01). Differences between normative and clinical samples on the CSBI total (ηp2 = .01–.65, p < .000), DRSB (ηp2 = .00–.03, p = .00–.38) and SASI scales (ηp2 =.00–.18, p < .01) indicated construct validity. Within the clinical samples, highest associations were found between the CSBI score and convergent measures (r = .64, p < .000). Lowest associations were found between the CSBI scores and divergent measures r = .14–.54, p = n.s.−<.000.ConclusionsCross-cultural differences in the perception of developmental appropriate sexual behavior underscore the importance of country-specific normative data. Good psychometric properties of the Dutch version of the CSBI were supported by this study.  相似文献   

19.
Course-based undergraduate research experiences (CUREs) may be a more inclusive entry point to scientific research than independent research experiences, and the implementation of CUREs at the introductory level may therefore be a way to improve the diversity of the scientific community.The U.S. scientific research community does not reflect America''s diversity. Hispanics, African Americans, and Native Americans made up 31% of the general population in 2010, but they represented only 18 and 7% of science, technology, engineering, and mathematics (STEM) bachelor''s and doctoral degrees, respectively, and 6% of STEM faculty members (National Science Foundation [NSF], 2013 ). Equity in the scientific research community is important for a variety of reasons; a diverse community of researchers can minimize the negative influence of bias in scientific reasoning, because people from different backgrounds approach a problem from different perspectives and can raise awareness regarding biases (Intemann, 2009 ). Additionally, by failing to be attentive to equity, we may exclude some of the best and brightest scientific minds and limit the pool of possible scientists (Intemann, 2009 ). Given this need for equity, how can our scientific research community become more inclusive?Current approaches to improving diversity in scientific research focus on graduating more STEM majors, but graduation with a STEM undergraduate degree alone is not ­sufficient for entry into graduate school. Undergraduate independent research experiences are becoming more or less a prerequisite for admission into graduate school and eventually a career in academia; a quick look at the recommendations for any of the top graduate programs in biology or science career–related websites state an expectation for ­undergraduate research and a perceived handicap if recommendation letters for graduate school do not include a ­discussion of the applicant''s research experience (Webb, 2007 ; Harvard ­University, 2013 ).Independent undergraduate research experiences have been shown to improve the retention of students in scientific research (National Research Council, 2003 ; Laursen et al., 2010 ; American Association for the Advancement of Science, 2011 ; Eagan et al., 2013 ). Participation in independent research experiences has been shown to increase interest in pursuing a PhD (Seymour et al., 2004 ; Russell et al., 2007 ) and seems to be particularly beneficial for students from historically underrepresented backgrounds (Villarejo et al., 2008 ; Jones et al., 2010 ; Espinosa, 2011 ; Hernandez et al., 2013 ). However, the limited number of undergraduate research opportunities available and the structure of how students are selected for these independent research lab positions exclude many students and can perpetuate inequities in the research community. In this essay, we highlight barriers faced by students interested in pursuing an undergraduate independent research experience and factors that impact how faculty members select students for these limited positions. We examine how bringing research experiences into the required course work for students could mitigate these issues and ultimately make research more inclusive.  相似文献   

20.
Docetaxel (DTX), as a member of taxoid family, has been widely used in the treatment of cancers. The present study prepared pH-sensitive DTX-loaded liposomes (DTX-Lips) by thin-film dispersion method and various physico-chemical and morphological properties were examined. The pH sensitivity of in vitro DTX release and the in vivo pharmacokinetics and tissue distribution using Kunming mice were also investigated. The mean particle size and zeta potential of DTX liposomes were (277±2) nm and (−32.60±0.26) mV, respectively. Additionally, in vitro drug release study showed that the cumulative release rate was 1.3 times more at pH 5.0 than at pH 7.4, suggesting a pH-dependent release ability of DTX-Lips. Pharmacokinetic and pharmaceutical studies in comparison with Duopafei® showed that the half-time period (t 1/2) and area under the curve (AUC) of DTX-Lips in mouse plasma were 1.8 times longer and 2.6 times higher, respectively, and that DTX-Lips selectively accumulated in macrophage-rich organs such as liver and spleen. These results together suggest that the DTX-Lips could be a promising formulation for the clinical administration of DTX.  相似文献   

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