Self-efficacy is defined as a person's beliefs in his or her own abilities to successfully complete a task and has been shown to influence student motivation and academic behaviors. More specifically, anatomical self-efficacy is defined as an individual's judgment of his or her ability to successfully complete tasks related to the anatomy curriculum; these include dissecting, learning anatomical concepts, and applying anatomical knowledge to clinical situations. The purpose of this study was to investigate the influence of anatomical self-efficacy on the academic performance of students enrolled in a medical gross anatomy course. To obtain students' anatomical self-efficacy ratings, surveys containing the same anatomical self-efficacy instrument were completed by first-year medical students at a southeastern United States allopathic medical school after each of four gross anatomy assessments. Additional data collected included student demographic information, Medical College Admission Test(®) (MCAT(®)) scores, and anatomy assessment scores, both written examination and laboratory practical. To investigate the potential predictive nature of self-efficacy for academic performance on both the written examination and the laboratory practical components of medical anatomy assessments, hierarchical linear regression analyses were conducted. For these analyses, academic ability (defined as the sum of the physical sciences and biological sciences MCAT scores) was controlled. The results of the hierarchical linear regressions indicated that all four laboratory practical scores were predicted by the corresponding self-efficacy ratings, while two (i.e., thorax/abdomen and pelvis/lower limb) of the four written examination scores were predicted by the corresponding self-efficacy ratings (P ≤ 0.05).
Juvenile hormones play a crucial role in development, metamorphosis, and reproduction of insects. This mini‐review discusses the nature of the juvenile hormones identified in insects and their changes in concentration in the hemolymph during development and reproduction. The hemolymph titer is largely determined by the rate at which juvenile hormones are synthesized and released by the corpora allata, but other factors are also involved in titer regulation, such as the affinity and concentration of juvenile hormone binding proteins in the hemolymph and the rate of juvenile hormone degradation in hemolymph and tissues. Juvenile hormone specific esterases occur in hemolymph and tissues, whereas epoxide hydrolases, which may degrade the hormone, are exclusively tissue bound. The activities of these degradative enzymes and the concentration of binding proteins change during the insect life cycle and these changes are related to fluctuations in hormone titer. However, we are still a long way from understanding the subtle interactions between these components in regulation of juvenile hormone titers. In particular, our knowledge is hampered by lack of information about the types, concentrations, and affinities of intracellular juvenile hormone receptors. © 1996 Wiley‐Liss, Inc.
The way in which anatomy is taught to first year medical students at the University of North Carolina at Chapel Hill was recently changed, so that first year students are now divided into two groups that dissect alternately. The effect of this change on both written and practical test performance was analyzed by comparing grades from 2004 with those from the previous year (2003), when students performed all the dissections. A statistically significant decrease (P < or = 0.05) from 2003 was noted on three of the four written test scores in 2004, while practical examination scores in 2004 fluctuated from lower to higher than those in 2003, depending on the unit of material being covered. However, the number of students failing each of the examinations (written and practical combined) was statistically greater on only one of the four examinations in 2004. Scores of the two groups dissecting alternately in 2004 were essentially the same on the practical examinations. There was no difference in the number of questions answered incorrectly between these two groups in the two practical examinations where comparisons were made. Furthermore, students who dissected a particular structure did not score significantly better on practical questions concerning that structure than students who had not dissected it. The effect of the availability of step-by-step dissection videos on student practical examination scores is also discussed. We conclude that the change in the curriculum had a significant impact on the students' written examination performance, given the same material in the course. The reasons for this include student course load, increased need for self-study, and a loss of a learning opportunity in the dissection laboratory, all of which affect student comprehension and retention of the material and their ability to use it in problem solving.
The distribution of prothoracicotropic hormone in the pupal brain of Manduca sexta has been determined by an in vitro assay for prothoracic gland activation. Prothoracicotropic activity was observed in both the brain and retrocerebral complex, but predominantly in the dorsolateral regions of the protocerebrum. Of the two groups of neurosecretory cells present in this area of the brain, only the two lateral type III neurosecretory cells exhibited significant prothoracicotopic hormone activity. Further analysis revealed that the neurohormone was localized in only one of the two type III cells, suggesting that a single neurosecretory cell in each hemisphere is the source of the hormone at the stage examined (day 0). Prothoracicotropic hormone activity was detected in both the corpora allata and the corpora cardiaca, but the corpora allata contained 2 to 9 times the activity of the corpora cardiaca, depending on developmental stage. The significantly higher level of activity in the corpora allata suggests that they may be the neurohemal organs through which the prothoracicotropic hormone of Manduca is released.The role of the brain in the neuroendocrine control of insect molting was demonstated about 4 decades ago in a series of classical experiments utilizing ligation, decapitation, and implantation techniques (1). Since that time, various other approaches, both indirect (2-5) and direct (6), have confirmed the tenet that the brain produces a neurohormone that stimulates the prothoracic glands to synthesize the prohormone ecdysone (7), whose hydroxylation product ecdysterone then elicits the molt. Although the prothoracicotropic hormone (PTTH) is the primary effector of insect postembryonic development (8), neither the source of PTTH within the brain nor the site of its release into the hemolymph has been directly demonstrated.It is presumed that PTTH is the product of specific cerebral neurosecretory cells (NSC) (9). Studies attempting to localize PTTH by the implantation of different groups of NSC or injection of homogenates of portions of the brain have yielded various results among the several insect species investigated. For example, in the reduviid bug Rhodnius prolixus, and the aphid Megoura viciae, PTTH activity appears to be located in the medial neurosecretory cells (M-NSC) of the protocerebrum (10, 11), whereas in the sphingid Manduca sexta the lateral neurosecretory cells (L-NSC) of the pupal brain may be the source of the neurohormone (5). By contrast, in the saturniid Hyalophora cecropia, both M-NSC and L-NSC are thought to produce PTTH (12).Definitive identification of the NSC that produce PTTH has not been made, in part due to the nature of the bioassays used to assess hormone activity (6, 9). However, with the recent development of a specific and sensitive in vitro assay for PTTH (6), the localization of this neurohormone in specific cerebralThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in ac...
An in vitro assay for the prothoracicotropic hormone has been developed that utilizes an ecdysone radioimmunoassay to quantify the increase in the rate of ecdysone synthesis elicited by the neurohormonal activation of the prothoracic glands. The rapidity, reproducibility, and accuracy of the assay were maximized by using one member of a gland pair as the control and the other as the test gland. This was possible because the basal rates of ecdysone synthesis by the members of a gland pair were equivalent. Activation was demonstrated to be dose dependent'and specific, with prothoracicotropic hormone activity present only in homogenates of brain. The in vitro activation of the prothoracic glands was verified with the Manduca bioassay for the prothoracicotropic hormone in which the morphological responses to the hormone were correlated with increased in vivo ecdysone titers. These results provide unequivocal evidence that the activation of the prothoracic glands by the prothoracicotropic hormone is direct and suggest that activation represents an increase in a basal rate of ecdysone synthesis. The endocrine function of the insect brain in the process of metamorphosis was first demonstrated in 1922 (1), but nearly 2 decades passed before it was demonstrated that this function involved the control of molting (2, 3). The initial observations on the role of a cerebral neurohormone in the molting process have since been confirmed by various implantation, extirpation, and ligation experiments (4-6). On the basis of these in vvo studies, it has been assumed that this brain hormone, now termed prothoracicotropic hormone (PTTH), acts directly on the prothoracic glands (PGs) to stimulate the synthesis of the steroid prohormone ecdysone (7). Hydroxylation of ecdysone at C-20 to form ecdysterone (20-hydroxyecdysone) then occurs in tissues peripheral to the PGs, and it is ecdysterone that initiates the molting process (7).Although PTTH was the first hormone to be discovered in insects, of the three major hormones involved in metamorphosis it alone remains to be chemically characterized. A necessary prerequisite to the chemical characterization of this putative peptide hormone is the unequivocal demonstration that PTTH directly activates the PGs. Recent attempts have not been successful due in part to the assay methods used to measure PTTH activity (8-10). Current PTTH assays are biological in nature and indirect by definition, in that they measure secondary morphological responses presumably elicited by a PTTH-stimulated increase in ecdysterone titer (10-12). However, with the. availability of a radioimmunoassay for ecdysteroids (13) and culture techniques for maintaining prothoracic glands in vitro (14), it is now possible to demonstrate the direct activation of the PGs by PTTH.This study details the development of an assay for PTTH that utilizes these two methods and proves that PTTH acts directly on the PGs to stimulate ecdysone synthesis.MATERIALS AND METHODS Animals. The tobacco hornworm (Manduca sexta) was used for...
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