Biomedical subjects
Publications and source records attributed to L Margolin.
Plasma waveguides generated by focusing a moderate intensity laser into neutral gas with an axicon lens can be unstable to the generation of axial modulations in the channel parameters. A model is proposed in which the modulations are due to the nonlinear coupling between the axicon field and a scattered mode in the evolving channel. Good agreement is found with experimental measurements of these modulations.
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We report a 30-year-old European (Ashkenazi Jewish) male with Laurence-Moon-Biedl syndrome (Bardet-Biedl type) who was hospitalized because of severe recalcitrant plaque-type psoriasis. Laurence-Moon-Biedl syndrome has been shown to be linked to the chromosome 11q region in the majority of the patients of European descent. The same 11q region had increased frequency of aberrations in the study that included cytogenetic analysis of 477 psoriatic patients. The animal model of the syndrome (mice) showed abnormalities in hair growth and epidermal differentiation. This genetic association between Laurence-Moon-Biedl syndrome and psoriasis can contribute to the understanding of the factors involved in the initiation of psoriasis and factors that modulate its severity and resistance to therapy.
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Using a sample of 982 mothers who reported on child care and living arrangements involving uncles, and case records documenting the sexual abuse of 171 children by 148 uncles, this study examined the ways uncles ordinarily become involved with children, the conditions under which that involvement becomes associated with sexual abuse, and the role gender plays in this dysfunction. Among the findings, it was noted that although aunts were responsible for 28 times more child care than uncles, uncles were responsible for 48 times more child sexual abuse. Although female children do not have more exposure to uncles than do males, they appeared four times more likely to be victimized. About 19% of the abusive uncles lived with the children they abused, and most of the remainder came into contact with them as child care providers or during overnight visits. Implications for practice are discussed.
Ischemic insults to the brain in stroke or traumatic brain injury produce excessive release of glutamate from depolarized nerve terminals. This excessive glutamate release in turn stimulates massive calcium entry into nerve cells, activating a biochemical cascade that results in cell death. A major pathway of calcium entry into depolarized nerve cells is through voltage-sensitive, high threshold calcium channels. A large fraction of this calcium entry is mediated through "R-type" calcium channels, channels resistant to blockage by dihydropyridine calcium antagonists such as nimodipine. A newly discovered compound derived from spider venom, CNS 2103, antagonizes both R-type channels and dihydropyridine-sensitive ("L-type") calcium channels. This broad spectrum of action, coupled with selectivity for calcium channels over other classes of voltage-sensitive and ligand-gated ion channels, makes CNS 2103 an interesting lead for development of drugs to treat ischemic brain injury. Activation of presynaptic ("N-type") calcium channels in nerve terminals is a primary cause of excessive neurotransmitter release in brain ischemia. Prevention of glutamate release by blockade of N-type channels in glutamatergic nerve terminals may, at an early stage in the pathophysiological cascade, abort the process leading to nerve cell death. Cambridge NeuroScience has developed a novel rapid kinetic approach for monitoring glutamate release from brain nerve terminals in vitro, and this has led to CNS 1145, a substituted guanidine that selectively blocks a kinetic component of calcium-dependent glutamate release mediated by persistent depolarization. Additional evidence suggests that CNS 1145 antagonizes presynaptic N-type calcium channels, and this may account at least in part for its ability to block glutamate release.
Methods have been developed that permit repetitive radiographic measurement of the lumbar intervertebral disc space in a rostral-caudal direction (width) in the anesthetized laboratory rabbit. Using isolated control discs and injured discs in which narrowing has been induced for chronic and acute periods, the widths of the lumbar intervertebral disc spaces determined ratio-graphically correlate with widths determined histologically (p less than 0.000, r = 0.75). Both an increase (widening) and a decrease (narrowing) in disc width were observed using radiography after different experimental treatments. Anesthesia and lower-body paralysis (an experimentally induced inability to bear weight on and to perceive a pinch stimulus in hind limbs) caused widening of the discs: anesthesia causing a general widening throughout the lumbar spine and lower-body paralysis causing a specific widening low in the lumbar spine. Both disc injection and piercing the disc with needles to recover nucleus pulposus material caused narrowing of the discs. Acridine-orange injection induced a narrowing accompanied by osteophytosis. Experimentally induced narrowing at L4-5 (the result of injury to the disc) resulted in narrowing also at L2-3. These findings are consistent with the hypothesis that in vivo disc-width size in the young rabbit depends on both the quantity of nucleus pulposus material and the force-generating activities of the adjacent spinal muscles, and that disc injury at one level stimulates narrowing at other levels.
This study examined the social contexts in which sexually abusive child care providers came into contact with children and parents. Content analysis of 325 case records resulted in the identification of seven main child care arrangements in which sexual abuse occurred. These arrangements varied by the routinization and formality of the caregiving relationship, as well as the methods of caregiver selection and reimbursement. The main finding was that the vast majority of female perpetrators were adolescents whose abusive behavior took place in the caregiving arrangement in which she is selected by parents, engaged on a routine basis, and paid a sum of money for her child care. In contrast, sexually abusive male caregivers represented a wide range of ages and committed sexual abuse over a significantly broader range of situations than female caregivers.
Although the literature on gender and status consistently asserts that men receive greater support for sexual self-determination than women do, this study found the contrary to be true in the case of noncoercive kissing. College students assessed a vignette in which one dating partner says he/she does not want to be kissed, but the other partner does not listen, and kisses him/her anyway. There was significantly more support for the female to violate the male's consent in this situation than vice versa, and there was significantly less support for the male to withhold sexual consent. The paper concluded by suggesting that men received less support to violate a partner's sexual consent than women did because men are seen as more threatening than women. Correspondingly, men received less support to withhold sexual consent because the appearance of diffidence conflicts with the cultural norm of male aggressiveness.
The purpose of this analysis was to estimate the frequency and severity of child abuse committed by adolescents who were in nonparental caregiving roles. The sample was composed of cases in which either physical or sexual abuse was substantiated through child welfare investigation. The main comparisons were between adolescent and adult caregivers. While caregiver age did not appear to have a consistent effect on the occurrence of physical abuse, notable differences between adolescents and adults were found in the area of sexual abuse. Not only were adolescents observed to commit substantially more sexual abuse than older caregiver cohorts, but the sexual abuse they committed was more likely to involve intercourse and physical assault. These findings have implications for future research and practice.
This study compares approval for minor violations of sexual consent in three contexts: marriage, long-term dating, and a first date. Quantitative and qualitative data from a vignette experiment show that as couples progress from a first date to marriage, men gain support to violate their partner's consent, and, to a lesser degree, women lose support to assert their rights. Evidence is presented that men are more approving of male dominance and female passivity in dating and marriage than are women.
Methods have been developed that permit repetitive radiographic measurement of the lumbar L4-5 intervertebral disc space area in the laboratory rat. In using this approach, the coefficient of variation in repetitive determinations was 7.6 +/- 0.7%. Normal rats have been shown to manifest statistically significant increase in disc space area size between 2.5 and 5 months of age.
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Rats, with their fur clipped, pressed a lever to turn on an infrared lamp while in a cold chamber. When they were exposed to continuous-wave microwaves at 2450 megahertz for 15-minute periods, the rate at which they turned on the infrared lamp decreased as a function of the microwave power density, which ranged between 5 and 20 milliwatts per square centimeter. This result indicates that behaviorally significant levels of heating may occur at an exposure duration and intensities that do not produce measurable changes in many other behavioral measures or in colonic temperature. Further study of how microwaves affect thermoregulatory behavior may help us understand such phenomena as the reported "nonthermal" behavioral effects of microwaves.
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Ten children were tested repeatedly for five motor tasks commonly labeled "soft signs." Finger approximation, walking hell to toe, and the equivocal Babinski improved significantly with practice. These results are interpreted as eliminating these tasks from evidence of "minimal brain damage" and questioning the validity of their inclusion in developmental tests.