Biomedical subjects
R J Nelson
Publications and source records attributed to R J Nelson.
Discount chores.
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2D NMR studies of aminoglycoside antibiotics. Use of relayed coherence transfer for 1H resonance assignment and in situ structure elucidation of amikacin derivatives in reaction mixtures.
Phase-sensitive 2D 1H/1H COSY spectra can be used to identify the structures of individual pure specimens of the aminoglycoside antibiotic amikacin and its N-hemisuccinyl derivatives. However, even at 500 MHz the 2D chemical shift dispersion does not allow for unambiguous assignment of all cross-peaks. By use of 2D relayed coherence transfer experiments (RELAY) optimized to detect two-step 1H/1H scalar interactions in which one of the J-values is small, sufficient additional correlations can be obtained from the frequency-isolated resonances to allow facile tracing of all scalar connectivities. Complete assignments of the 1H NMR spectra of amikacin, its 6'-N-hemisuccinamide, and a novel bis(acylate) [gamma-N-(p-vinylbenzoyl)amikacin 6'-N-hemisuccinamide] were obtained for aqueous media. The NMR spectrum of amikacin free base was also assigned in dimethyl sulfoxide solution. The RELAY experiment can be extended to the analysis of reaction mixtures, which allows for the identification and resonance assignment of regioisomeric amikacin haptens in the mixture state. All of the N-monohemisuccinyl isomers of amikacin have been identified in reaction mixtures through the RELAY experiment. The relative reactivities of the amino functions of amikacin toward acylating agents were found to be 6'-N greater than 3-N equal to or greater than 3"-N equal to or greater than gamma-N. However, this reactivity order is altered after the initial acylation event.
Cytochrome oxidase activity in brown fat varies with reproductive response and use of torpor in deer mice.
Reproductive responses and thermogenic properties of brown adipose tissue (BAT) were evaluated in individuals from an outbred population of deer mice (Peromyscus maniculatus nebrascensis) after 10 weeks exposure to short photoperiod (8:16 light:dark) and cold ambient temperature (2 degrees C). Deer mice populations are composed of phenotypes that differ in their reproductive response to environmental cues. These phenotypes also differ in body temperature regulation as indicated by their use of daily torpor. By comparing BAT responses among individuals of different phenotypes, we were able to assess the association between environmentally induced changes in reproduction and metabolism. Short/cold days caused increased proliferation of BAT and higher cytochrome oxidase activity. However, the magnitude of these changes varied with reproductive phenotype and use of daily torpor. BAT weight in short/cold day exposed males with normal sized testes more than doubled while total cytochrome oxidase activity increased by 30% as compared to controls. In contrast, short/cold day exposed deer mice with atrophic testes that employed daily torpor exhibited a 64% increase in BAT weight and 100% increase in total cytochrome oxidase activity, compared to control mice. Cytochrome oxidase activity in nontorpid deer mice with atrophic testes was intermediate to these two groups. Our results demonstrate a response of BAT to short/cold days that varies with individual reproductive response. This finding suggests that there exists a common integrative mechanism for temperature and photoperiod to regulate both seasonal reproductive and metabolic adjustments.
Restricted water intake influences male reproduction in two strains of house mice (Mus musculus).
Males from two strains of house mice (Mus musculus) were subjected to ten weeks of simulated drought in the laboratory. Water availability was reduced to 50% of ad lib intake for 5 weeks, then further restricted to 25% of ad lib consumption for an additional 5 weeks. Individuals of the highly inbred (CF1) strain were generally unaffected by water restriction. Testicular and epididymal mass of restricted CF1 animals did not change relative to control mice with ad lib access to water. Seminal vesicle mass decrease in water restricted CF1 males, but spermatogenesis was not significantly influenced. Body mass was reduced 25.4% after water restriction. In contrast, male F4 progeny of wild-caught Mus substantially reduced reproductive organ mass after limited water intake. Spermatogenesis was significantly diminished, but no animals became completely aspermatic. Body mass declined 12.6% in water restricted wild-strain Mus as compared to animals with ad lib water availability. These results are discussed in terms of their possible ecological significance.
Pineal melatonin content in photoperiodically responsive and non-responsive phenotypes of deer mice.
1. The pineal melatonin content of photoperiod responsive and photoperiod non-responsive male deer mice was assessed. 2. Pineal melatonin content did not differ between short-day mice with regressed testes or those that maintained their reproductive systems. 3. These data suggest that differential phasing of melatonin release or post-pineal mechanisms are responsible for the differential responsiveness to day length among deer mice.
Set related and premovement related activity of primate primary somatosensory cortical neurons depends upon stimulus modality and subsequent movement.
The activity of primate primary somatosensory (SI) cortical neurons was examined in monkeys trained to perform wrist movements in response to visual or vibratory cues using single-unit, extracellular recording techniques. Neuronal discharge rates associated with peripheral stimulus onset often differed depending upon the modality of the stimulus and whether the animals were instructed to make wrist movements or withhold them. Premovement activity changes that led muscle activation commonly were of different magnitude depending on the modality of the triggering stimulus. This was true both for neurons that responded to vibratory stimuli and those that exhibited no vibratory response. These observations suggest that the activity of SI neurons may be influenced by central modulatory as well as peripheral inputs during task behavior.
Self-inflicted shotgun wounds of the face: surgical and psychiatric considerations.
This study reviews the evaluation and treatment of patients with extensive self-inflicted shotgun wounds to the face. Five cases are presented and assessed with regard to reason for suicide, psychological reaction to facial reconstruction, and the potential for social rehabilitation. Mechanisms of injury, acute management, and definitive surgical and psychiatric treatment programs are discussed. Survival is expected for most patients, and carefully planned surgical reconstruction must be coordinated with skilled psychiatric intervention.
Daylength influences pelage and plasma prolactin concentrations but not reproduction in the prairie vole, Microtus ochrogaster.
Short daylengths did not affect testes weight or spermatogenic index in male voles or uterine weight in female voles. Short daylengths did stimulate the growth of a winter pelage in both sexes; short-day voles had longer underhairs and guard hairs and a thicker, more dense pelage than did long-day voles. Plasma prolactin concentrations were five times higher in long-day than in short-day females and 25% higher in long-day males than in short-day males. The effect of short daylength on pelage was prevented by pinealectomy. We suggest that the growth of a winter coat is an obligate adaptation for winter survival, stimulated by exposure to short daylengths, but that changes in breeding activity are facultative and dependent to a greater extent on other cues for seasonal synchronization.
Transcranial Doppler sonography.
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Variability in hand surface representations in areas 3b and 1 in adult owl and squirrel monkeys.
Detailed microelectrode maps of the hand representation were derived in cortical areas 3b and 1 from a series of normal adult owl and squirrel monkeys. While overlap relationships were maintained, and all maps were internally topographic, many map features varied significantly when examined in detail. Variable features of the hand representations among different monkeys included a) the overall shapes and sizes of hand surface representations; b) the actual and proportional areas of representations of different skin surfaces and the cortical magnifications of representations of specific skin surfaces, which commonly varied severalfold in area 3b and manyfold in area 1; c) the topographic relationships among skin surface representations, with skin surfaces that were represented adjacently in some monkeys represented in locations many hundreds of microns apart in others; d) the internal orderliness of representations; e) the completeness of representations of the dorsal hand surfaces; and f) the skin surfaces represented along the borders of the hand representation. Owl monkey maps were, in general, internally more strictly topographic than squirrel monkey maps. In both species, area 3b was more strictly topographic and less variable than was area 1. The degree of individual variability revealed in these experiments is difficult to reconcile with the hypothesis that details of cortical maps are ontogenetically specified during a period in early life. Instead, we propose that differences in the details of cortical map structure are the consequence of individual differences in lifelong use of the hands. This conclusion is consistent with earlier studies of the consequences of peripheral nerve transection and digital amputation, which revealed that cortical maps are dynamically maintained and are alterable as a function of use or nerve injury in these monkeys (Merzenich et al., '83a,b, '84a; Merzenich, '86; Jenkins et al., '84; Jenkins and Merzenich, '87).
Activity of monkey primary somatosensory cortical neurons changes prior to active movement.
Changes in the discharge rates of monkey primary somatosensory cortical neurons were recorded during the performance of wrist flexion and extension. Neurons with activity changes that occurred early before movement onset were often found in areas 3a, 1 and 2, but rarely in area 3b. Based on timing considerations, these observations suggest that somatosensory cortical neurons receive central as well as peripheral inputs that modulate their activity and that may be related to changes in tactile threshold before movement.
Pinealectomy blocks vernal courtship behavior in red-sided garter snakes.
Male red-sided garter snakes (Thamnophis sirtalis parietalis) court only on emergence from winter dormancy. The salient proximate factor responsible for the initiation of courtship behavior appears to be warm ambient temperatures subsequent to sustained exposure to cold temperatures. In the present study, autumn-captured garter snakes were pinealectomized or sham-pinealectomized 1-2 weeks prior to hibernation. After 17 weeks of maintenance in several ambient lighting and temperature conditions, all males were tested for the presence of courtship behavior. No pinealectomized animals exhibited any indications of reproductive behavior, whereas 53% of sham-pinealectomized males actively courted females. Photoperiod did not influence the prevalence of mating behavior. These results suggest that the pineal gland mediates non-photoperiodic seasonal information in the garter snake. This is the first demonstration, in any vertebrate species, that the pineal gland can directly influence reproductive behavior.
Spontaneous testicular recrudescence of Syrian hamsters: role of stimulatory photoperiods.
The gonads of hamsters maintained in short photoperiods first undergo regression and then spontaneous recrudescence. The latter is indicative of refractoriness of the neuroendocrine axis to short day lengths. We tested the hypothesis that the absence of long-day stimulation contributes to the development of refractoriness to short photoperiods. Male Syrian hamsters were maintained for 26 weeks in a short-day photoperiod (8 hr light/day). Testicular regression was confirmed in all animals at week 10; thereafter different groups of hamsters were stimulated with one long day (16 hr light) every 10, 15, 20 or 30 days until week 26. Control groups were maintained continuously in long or short photoperiods, respectively. The rate of gonadal recrudescence of short-day hamsters was not affected by intermittent stimulation with long photoperiods. After 26 weeks, testes in all short-day groups had undergone recrudescence. Refractoriness to short day lengths is not counteracted by long photoperiods. The role of the pineal gland in the development of refractoriness is considered.
Treatment of intraoperative acute right heart failure by a right ventricular assist device.
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Water availability affects reproduction in deer mice.
Water restriction impaired sperm production in deer mice, a seasonally breeding mammal that encounters aperiodic droughts in its natural habitat throughout North America. Water-induced spermatogenic responses were sorted into three categories based upon epididymal sperm numbers: aspermic, oligospermic, and euspermic. Average gonadal mass was reduced after 10 wk of limited water consumption. Inter-individual variation in gonadal response to a simulated drought was similar to phenotypic differences in reproductive function in response to other environmental cues that direct annual reproductive cycles. Our findings suggest that water availability may act as a cue to suppress gametogenesis in deer mice independently from food, temperature, and day length.
Gonadal regression induced by caloric restriction is not mediated by the pineal gland in deer mice (Peromyscus maniculatus).
The role of the pineal gland in mediating reproductive regression in response to nonphotoperiodic cues was assessed. A proportion of deer mice (Peromyscus maniculatus) undergo gonadal regression subsequent to moderate food restriction. The reproductive regression after inanition qualitatively and quantitatively resembles short-day-induced regression. The physiological mechanisms responsible for gonadal regression after food restriction are unknown. The hypothesis that the mechanisms underlying photoperiodic responsiveness also mediate testicular regression caused by reduced food consumption was tested. Males were pinealectomized or received sham operations. Upon recovery, food availability was restricted to 70% of ad libitum intake. After 8 weeks, the reproductive condition was examined. Pinealectomy did not prevent gonadal regression, suggesting that the pineal gland does not mediate caloric information in this species.
Changes in cerebral blood flow during anaesthesia and surgery in the sitting position.
Serial measurements of global cerebral blood flow (CBF) were made in 15 patients undergoing elective neurosurgical procedures in the sitting position, using a modified intravenous 133Xenon technique. The mean supine CBF rose from 43 (+/-3) ml/100g/min to 62 (+/-6) ml/100g/min in the sitting position and remained elevated at the end of surgery at 62 (+/-5) ml/100g/min. Both increases in CBF were statistically significant with respect to baseline supine values.