Biomedical subjects
D L Allen
Publications and source records attributed to D L Allen.
A perspective of dental education in the twenty-first century.
With the beginning of the twenty-first century only twelve years away, it is clearly not too early for dental educators to be planning for it. If one compares the practice of dentistry and the nature of dental education in 1888 with that of 1988, and then tries to project what they will be like in the year 2088, we have a difficult task indeed. As Alvin Toffler has pointed out in his book Future Shock, we are in an ever escalating period of change. Dentistry and dental education will change much more in the next one hundred years than they have in the last one hundred years.
The involvement of United States dental schools in international dental education.
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[Philosophy and justification for reform in dental education].
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Philosophy and rationale of curriculum change.
There are several factors in curriculum design of universal importance. Faculty members at all levels must be free to contribute but it must be recognized that decisions have to be made at department, school and university levels. Programme goals must be defined so that there is adequate education of dental practitioners and not just training for dental students. Preclinical teaching should not be an end in itself but should be closely relevant to clinical practice. Basic concepts must be taught; factual overload should be avoided and outdated material eliminated. The curriculum should meet local needs and not be based on one developed for another part of the world. In re-designing a curriculum, attention should be paid to new content, new teaching methods, the introduction of early clinical experience, evaluation methods and the effects of specialization in practice. Above all, curriculum revision must be an ongoing process.
Temporal effects of intrahypothalamic 5,7-dihydroxytryptamine: relationship between serotonin levels and [3H]serotonin binding.
The relationship between serotonin (5-HT) levels and [3H]5-HT binding in discrete hypothalamic areas was examined in separate groups of animals at various times, following unilateral intrahypothalamic injection of 5,7-dihydroxytryptamine (5,7-DHT). Seven days post-5,7-DHT lesion, 5-HT levels were significantly decreased in both the ipsilateral and contralateral ventromedial and dorsomedial hypothalamic nuclei (VMN, DMN). In the lateral hypothalamic area (LHA), 5-HT levels were significantly decreased only ipsilaterally. Fifty days postlesion, 5-HT levels in the ipsilateral VMN remained significantly below sham, while the DMN and LHA returned to sham values. Seven days after 5,7-DHT there was a significant increase in [3H]5-HT labeling densities in the ipsilateral and contralateral ventromedial hypothalamic area as well as in the ipsilateral LHA. In contrast, in the dorsomedial hypothalamic area there was no increase in [3H]5-HT binding. Fifty days postlesion, no significant differences in [3H]5-HT binding between 5,7-DHT and sham were observed in any areas examined. This data provides further evidence for the regeneration of 5-HT fibers in the hypothalamus and demonstrates that the relationship between [3H]5-HT binding and 5-HT levels varies from one hypothalamic area to another.
Monoamine levels and turnover in brain: relationship to priming actions of estrogen.
Norepinephrine (NE), dopamine (DA) and serotonin (5HT) levels and turnover rates were studied in 8 discrete brain nuclei of ovariectomized rats 24 hours after the administration of 5 microgram of estradiol benzoate (EB) or sesame oil vehicle. This estrogen paradigm, by itself, did not induce sexual behavior or alter LH levels at the time these parameters were evaluated. However, combined with progesterone, the estrogen treatment was sufficient to generate an LH surge and induce sexual receptivity. Steady state concentrations of NE were significantly higher in the diagonal band of Broca (NDB) and the periventricular nucleus (PVE2; anterior hypothalamic level) following EB treatment. In addition, 5-hydroxyindole acetic acid (5HIAA) concentrations were elevated in the dorsal raphe of EB treated animals. Estrogen did not affect steady state concentrations of DA or 5HT in any of the brain nuclei studied. Turnover rates (K, pg/microgram protein/hr) and rate constants (k, hr-1) for NE were increased in the lateral septum (K, 140%; k, 120%), NDB (K, 160%; k, 130%) and the PVE2 (K, 140%; k, 70%) in EB treated animals. Estrogen decreased the rate constant for NE by 30% in the medial preoptic area. In contrast, DA and 5HT turnover rates were not significantly affected by estrogen. These results localize sites where estrogen induces changes in noradrenergic activity and suggest that these changes may be involved in the priming action of the steroid in inducing sexual behavior and/or gonadotropin secretion.
Blood group antibody screening tests during pregnancy.
In a 2-year period 667 sera from approximately 70,000 (0.95%) antenatal patients were found to contain 726 atypical red blood cell antibodies. Overall, 66% of the immunized mothers were rhesus (D) positive. Apart from four antibody specificities to rhesus system antigens, knowledge of the rhesus (D) group gave no guide to the ability of the patients to form any of the remaining 21 specificities encountered. Of the 726 antibodies 221 (30%) were not detected in the initial sample tested and 50 of the 92 patients who produced antibodies during pregnancy had not developed detectable antibody when they were sampled at 28 weeks. The significance of these late onset antibodies is discussed both in relation to the risk of haemolytic disease in the newborn and transfusion reactions in the mother. An optimum protocol for testing is defined which takes account of antibody production during the pregnancy and use of this protocol constitutes an attempt to combine maximum clinical safety with minimal consumption of resources.
Adapting to the hearing impaired dental student.
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Naltrexone facilitation of sexual receptivity in the rat.
Naltrexone hydrochloride (3mg/kg) facilitated sexual receptivity in ovariectomized female rats given estradiol benzoate 44 hr previously. The latency of naltrexone facilitation is 3 hr, which is similar to that by progesterone. Other doses of naltrexone (1 and 5 mg/kg) were ineffective. Unlike the effect of progesterone, the facilitation of behavior by naltrexone is not blocked by the protein synthesis inhibitor anisomycin. Naltrexone facilitation was blocked by pargyline, a monoamine oxidase inhibitor.
Reliability of a survey of residency graduates in evaluating a behavioral science curriculum.
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A protocol for sensitive large-scale screening of blood donors for IgA deficiency.
A protocol for large-scale screening of blood donors for IgA deficiency using a tanned cell passive haemagglutination-inhibition (PHI) technique and enzyme-linked immunosorbent assay (ELISA) is described. Evidence presented suggests that native serum from a case of IgA paraproteinaemia, suitably diluted and heated to 56 degrees C for 60 min, can act as a satisfactory and simple alternative to purified IgA preparations in the PHI test. When PHI and ELISA techniques were used in combination to screen 41,851 random donors, 58 were found to contain less than 200 ng/ml of IgA and were classified as totally IgA-deficient (1:721). This is in close agreement with the data from other workers.
The implications of changing patterns in oral health for dental education.
Reports from many countries indicate that there has recently been a significant reduction in the prevalence of dental caries. Survey questionnaires were sent to 131 dental schools in 58 countries to determine the perceptions of dental educators to changing oral disease patterns. The educators were asked to indicate changes which had occurred in their respective curricula relative to the disease trends. They were asked to speculate on future curricular changes. Thirty-six schools in 21 countries replied. Most respondents indicated a decrease in the prevalence of dental caries, but little perception of changes in other oral diseases. Whereas, many adjustments have been made in dental curricula, there is little to indicate that the changes are related to variations in oral disease patterns. A new dilemma faces dental education for there is a need to broaden the scope of skills to be attained by the dental student to support a wide range of dental practice, while maintaining skills in restorative dentistry. More intensive continuous epidemiological studies of oral diseases need to be conducted. Dental school administrators need to be informed about oral disease trends and should adjust their curricula accordingly.
Genetic effects on various measures of ethanol dependence in mice: a diallel analysis.
A complete 5 X 5 diallel cross was performed using mice from 5 highly inbred strains. Five hundred and fifty-five offspring were fed ethanol in a liquid diet for 9 days, then tested during a withdrawal period using a battery of tests designed to measure physical dependence on ethanol ( McClearn et al., Sub. Alcohol Use/Abuse, 3 (1982) 135; Allen et al., Alcohol Clin. Exp. Res., 7 (1983) 443). The analyses were done separately for each sex. The results show significant, but low genetic effects for most of the measures and no maternal effects for any measure. There was also evidence for a sex-by-genotype interaction that was not due to sex-linkage, i.e., the same autosomal genes are acting differently in the two sexes during withdrawal from ethanol. Males tended to exhibit more genetic influence than females for most of the traits measured. The results are discussed in terms of the use of these measures for creating genetically defined models of physical dependence on ethanol.
Similarities and differences between high-affinity binding sites for cocaine and imipramine in mouse cerebral cortex.
Previously we found close similarities between high-affinity binding sites for [3H]cocaine and those for [3H]imipramine in the mouse cerebral cortex in regard to their association with neuronal uptake of serotonin. In the present study we investigated whether the two ligands bind to the same site. The two ligands had the following high-affinity binding properties in common: localization in both synaptosomal and microsomal fractions; vulnerability to treatment with N-ethylmaleimide, trypsin, and phospholipase A2; and resistance to exposure to dithiothreitol. In contrast, cocaine binding in the cerebral cortex was more sensitive to heat inactivation than imipramine binding. In addition, the mechanism by which cocaine inhibited [3H]imipramine binding differed from that by which imipramine inhibited [3H]cocaine binding. These data suggest that the high-affinity binding sites for [3H]cocaine and [3H]imipramine in the cerebral cortex are distinct entities.
Comparative trial of six methods for the detection of CMV antibody in blood donors.
Six techniques were compared to find the most suitable method for determining the cytomegalovirus (CMV) antibody status of blood donors. Five hundred and ninety-six random sera were tested by immunofluorescence (IF), complement fixation (CFT), two enzyme linked immunosorbent assays (ELISA), a commercial indirect haemagglutination test (IHA)--used as supplied, and a locally devised micromodification of the same IHA test. Five hundred and thirty-five sera shared total agreement of results by all tests. The ELISA tests were the most discordant with other methods (10.5% discordancies both positive and negative). IF and CFT correlated well with other tests (0.8% discordances each) but for different reasons are unsatisfactory for donor screening. The IHA test used as supplied and its micromodification gave the most consistent results (0.8% and 0.5% discordancies respectively). The micromodification is easy to perform and read; it compares very favourably with CFT and IF for material costs and expertise required, and readily lends itself to the testing of large numbers of sera in a reasonable time. Within certain provisos the micro-IHA technique described is recommended as the most suitable test for blood donor screening.
Imipramine does not act as a false transmitter in the rat hypothalamus.
[3H]Imipramine was accumulated by rat hypothalamic slices mostly by a passive low-affinity process. Accumulated [3H]imipramine was released by 60 mM potassium, but the release was small and was not Ca2+-dependent. Imipramine induced some release of [3H]norepinephrine. None of these events were abolished by pretreatment of the rats with reserpine. These results do not favor the view that imipramine acts as a false transmitter in the rat hypothalamus. Rather, imipramine appears to be accumulated in an extragranular pool from which it releases extragranular norepinephrine.
Selective breeding for a multivariate index of ethanol dependence in mice: results from the first five generations.
Starting with a population of genetically heterogeneous mice (HS/lbg), selection for a multivariate index of the ethanol withdrawal syndrome has been initiated. The study uses within-litter selection to minimize inbreeding and includes replicate high, low, and control lines. After five generations, results indicate that selection is proceeding successfully. There is evidence of asymmetry in the selection, i.e., selection is proceeding more rapidly for signs of severe withdrawal than for mild withdrawal signs. The realized heritability after five generations of within-family selection is approximately 0.15. These selected lines should eventually prove useful in determining some of the underlying genetic, physiological, and biochemical mechanisms involved in ethanol dependence.