Topographical Studies of the Nicotinic Acetylcholine Receptor

All four subunits of the nicotinic acetylcholine receptor in membrane vesicles isolated from Torpedo californica have been labeled with the photoactivated hydrophobic probe, [3H]adamantanediazirine, which selectively labels regions of integral membrane proteins in contact with the hydrocarbon core of the lipid bilayer. As all of the homologous subunits are exposed to the lipid bilayer, it is probable that they each interact with the surrounding membrane in a similar fashion. All four subunits of the acetylcholine receptor in membrane vesicles isolated from Torpedo californica have been labeled with [3H]cholesteryl diazoacetate. As this probe incorporates into lipid bilayers analogously to cholesterol, this result indicates that acetylcholine receptor interacts with cholesterol. This investigation also demonstrates that this probe is a useful reagent for studying the interaction of cholesterol with membrane proteins. Since the photogenerated carbene is situated near the lipid-water interface, this probe has potential as a topographic tool for mapping membrane protein structure. The labeling studies with both [3H]adamantanediazirine and [3H]cholesteryl diazoacetate support the concept that the acetylcholine receptor is a pseudosymmetric complex of homologous subunits, all of which interact with and span the membrane. The syntheses of the fluorine-containing agonists for the Torpedo californica nicotinic acetylcholine receptor, fluoroacetylcholine bromide and p-fluorophenyltrimethylammonium iodide, are described. It is demonstrated that both are agonists using a cation flux assay with acetylcholine receptor enriched membrane vesicles. The potential for their use in ligand binding studies using 19F NMR spectroscopy is discussed. The affinity cleavage reagent, p-thiocyanophenyltrimethylammonium iodide, specifically cleaves a peptide bond of the nicotinic acetylcholine receptor in membrane vesicles isolated from Torpedo californica. It is demonstrated that this reagent is an agonist using a cation flux assay. The cleavage is blocked by stoichiometric quantities of α-bungarotoxin. The yield of the cleavage reaction is reduced with addition of the agonist, phenyltrimethylammonium iodide. This affinity cleavage reaction provides evidence for a low-affinity binding site for agonists on the 60K subunit.</p

Intracerebroventricular Ghrelin Administration Increases Depressive-Like Behavior in Male Juvenile Rats

Major depressive disorder (MDD) is arguably the largest contributor to the global disease and disability burden, but very few treatment options exist for juvenile MDD patients. Ghrelin is the principal hunger-stimulating peptide, and it has also been shown to reduce depressive-like symptoms in adult rodents. We examined the effects of intracerebroventricular (icv) injection of ghrelin on depressive-like behavior. Moreover, we determined whether ghrelin increased neurogenesis in the hippocampus. Ghrelin (0.2-nM, 0.5-nM, and 1.0-nM) was administered acutely by icv injection to juvenile rats to determine the most effective dose (0.5-nM) by a validated feeding behavior test and using the forced swim test (FST) as an indicator of depressive-like behavior. 0.5-nM ghrelin was then administered icv against an artificial cerebrospinal fluid (aCSF) vehicle control to determine behavioral changes in the tail suspension test (TST) as an indicator of depressive-like behavior. Neurogenesis was investigated using a mitogenic paradigm, as well as a neurogenic paradigm to assess whether ghrelin altered neurogenesis. Newborn hippocampal cells were marked using 5′-bromo-2′-deoxyuridine (BrdU) administered intraperitoneally (ip) at either the end or the beginning of the experiment for the mitogenic and neurogenic paradigms, respectively. We found that ghrelin administration increased immobility time in the TST. Treatment with ghrelin did not change mitogenesis or neurogenesis. These results suggest that ghrelin administration does not have an antidepressant effect in juvenile rats. In contrast to adult rodents, ghrelin increases depressive-like behavior in male juvenile rats. These results highlight the need to better delineate differences in the neuropharmacology of depressive-like behavior between juvenile and adult rodents

Precision and accuracy of Dahl-Lea back-calculated smolt lengths from adult scales of Atlantic salmon (Salmo salar L.)

Using tagged and recaptured Atlantic salmon Salmo salar (n = 106) the present analysis shows that the most commonly applied linear back-calculation method for estimating past length, the Dahl-Lea method, resulted in overestimation of the length of large smolts and underestimation of small smolts.  A correction equation (y = 0.53x + 6.23) for estimating true smolt length (y) from lengths back-calculated from adult scale measures (x) to account for these systematic discrepancies is proposed.PostprintPeer reviewe

Chronic SSRI Treatment, but Not Norepinephrine Reuptake Inhibitor Treatment, Increases Neurogenesis in Juvenile Rats

There has been growing recognition that major depressive disorder is a serious medical disorder that also affects children. This has been accompanied by an increased use of antidepressant drugs in adolescents; however, not all classes of antidepressants are effective in children and adolescents. There is an increasing need to understand the differences in antidepressant action in different developmental stages. There are some data indicating that the behavioral effect of chronic antidepressant treatment in adult rodents is dependent on hippocampal neurogenesis; however, it is not known which classes of antidepressant drugs induce hippocampal neurogenesis in adolescent rodents. Three classes of antidepressant drugs were tested in two age groups of Sprague Dawley rats, pre-adolescent (postnatal days 11&ndash;24) and adolescent (postnatal days 21&ndash;34): monoamine oxidase inhibitors (MAOIs); selective serotonin reuptake inhibitors (SSRIs); serotonin norepinephrine reuptake inhibitors (SNRIs); and tricyclic antidepressants (TCAs). To address which classes of antidepressant drugs might alter the rate of mitogenesis in neural progenitor cells in an adolescent rodent model, adolescent Sprague Dawley rats were treated with the thymidine analog 5-bromo-deoxy-2&prime;-uridine (BrdU) on postnatal days 21 and 22 and antidepressant drugs or vehicle for 14 days (postnatal days 21&ndash;34). To address which classes of antidepressant drugs might alter the rate of neurogenesis, postnatal day-21 Sprague Dawley rats were treated with antidepressant drugs or vehicle for 14 days (postnatal days 21&ndash;34) and BrdU on postnatal days 33 and 34. In both experimental paradigms, BrdU-positive cells in the subgranular zone and the granule cell layer were counted. Newborn neurons were identified in the neurogenic paradigm by identifying cells expressing both the neuronal specific marker NeuN and BrdU using confocal microscopy. Only the SSRI fluoxetine significantly altered the basal mitogenic and neurogenic rates in adolescent rats. Treatment with the monoamine oxidase inhibitor (MAOI) tranylcypromine (TCP) and the TCA desipramine did not alter the rate of hippocampal neurogenesis in the adolescent rats. This is consistent with human clinical observations, where only SSRIs have efficacy for treatment of depression in patients under the age of 18. In pre-adolescent rats, postnatal days 11&ndash;24, none of the drugs tested significantly altered the basal mitogenic or neurogenic rates. All of the classes of antidepressant drugs are known to induce hippocampal neurogenesis in adult rats. The mechanisms of action underlying this developmental difference in antidepressant drug action between juveniles and adults are not known

What should I eat? Experimental evidence for prey selection in grey seals

Understanding the responses of predators, such as seals, to variations in prey availability is key to understanding their role in marine ecosystems. Individual variation in prey preference is likely to be important but we have little information on this aspect of predator behaviour. Operant conditioning techniques and an underwater feeding apparatus were used to test the prey species and size preferences of five captive grey seals, Halichoerus grypus, in a series of paired choice trials. The experimental procedure was designed to present simple foraging choices to remove as many potentially confounding variables as possible. Results suggest that individual grey seals exhibit prey preferences. When presented with different numbers of items of the same species, seals generally selected the larger number of prey items. When presented with choices between two species, seals apparently showed consistent preferences for particular species. However, the apparent species preferences may be simply explained in terms of size selection

Predicting Performance on the National Athletic Trainers' Association Board of Certification Examination From Grade Point Average and Number of Clinical Hours

OBJECTIVE: To determine whether grade point average, hours of clinical education, or both are significant predictors of performance on the National Athletic Trainers' Association Board of Certification examination and whether curriculum and internship candidates' scores on the certification examination can be differentially predicted. DESIGN AND SETTING: Data collection forms and consent forms were mailed to the subjects to collect data for predictor variables. Subject scores on the certification examination were obtained from Columbia Assessment Services. SUBJECTS: A total of 270 first-time candidates for the April and June 1998 certification examinations. MEASUREMENTS: Grade point average, number of clinical hours completed, sex, route to certification eligibility (curriculum or internship), scores on each section of the certification examination, and pass/fail criteria for each section. RESULTS: We found no significant difference between the scores of men and women on any section of the examination. Scores for curriculum and internship candidates differed significantly on the written and practical sections of the examination but not on the simulation section. Grade point average was a significant predictor of scores on each section of the examination and the examination as a whole. Clinical hours completed did not add a significant increment for any section but did add a significant increment for the examination overall. Although no significant difference was noted between curriculum and internship candidates in predicting scores on sections of the examination, a significant difference by route was found in predicting whether candidates would pass the examination as a whole (P = .047). Proportion of variance accounted for was less than R(2) = 0.0723 for any section of the examination and R(2) = 0.057 for the examination as a whole. CONCLUSIONS: Potential predictors of performance on the certification examination can be useful to athletic training educators in assisting students. These findings must be used cautiously because of the low proportion of explained variance. Low R (2) values suggest that the largest contributors to performance on the examination were not identified in this study. Although the results of this study support the decision to discontinue the internship route to certification, continued research focusing on identification and investigation of the constructs that contribute to examination success is needed