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Biomedical subjects

M Singer

Publications and source records attributed to M Singer.

At least 91 records · Page 5Linked to original sources
PubMed1986

Unemployment and its impact on adolescent work values.

This study examines the impact of unemployment on the work values orientation of adolescents. Using Super's (1970) Work Values Inventory, data were collected from 187 youths residing in a large midwestern city in the United States. Youths from families where the head of household had been unemployed for more than one year prior to the time of the study were compared to youths from a working-family environment. The findings of this study show little difference between work values orientation of youths from unemployed and employed families. The only variable which did prove to be significantly different settings appear to is "esthetics" (p less than .05), i.e., youths from unemployed settings appear to value new experiences and outlets for their abilities more than do youths of the comparison group.

Achievement↗
PubMed1985

Necessity of an adequate nerve supply for regeneration of the amputated pectoral fin in the teleost Fundulus.

The present work deals with determination of the threshold of nerve fibers per unit of amputation surface necessary for regeneration of the pectoral fins of a teleost, Fundulus. Partial denervation of the amputated pectoral fins, i.e., resection of one or two of the three nerves of the brachial (=pectoral) plexus revealed that the presence of a single one allows the amputated fin to regenerate. From these data and others obtained previously, it is concluded that the nervous requirements for a teleost fin to regenerate are similar or slightly lower than those for tetrapods, for example in the newt, which are capable of appendage regeneration.

Animals↗
PubMed1985

Human bites of the hand: a study of one hundred six patients.

One hundred six patients with human bites of the hand (HBH) were studied in detail. This study was characterized by a higher than expected incidence among women, by a large number of patients who presented for treatment more than 1 week after injury, and by a high complication rate and a low incidence of hospitalization. The overall morbidity rate of these patients was considerable. Early and delayed cases of HBH were typified by an absence of complications. Except for partial or complete traumatic amputations, their recovery time was short, and the final functional result was usually favorable. Late cases were characterized by a high rate of infection-related complications, a prolonged morbidity period, and a less favorable final functional result. One hundred of our patients were successfully treated as outpatients. This led us to believe that most HBH can be treated on an outpatient basis. Hospitalization should be mainly reserved for patients with infection-related complications and for extremely unreliable patients. The time interval between injury and the commencement of treatment appears to be the single most important factor governing the final result in HBH.

Adult↗
PubMed1984

Gangliosides stimulate protein synthesis, growth, and axon number of regenerating limb buds.

When a newt limb is amputated and begins to regrow, regenerating axons exert a neurotrophic influence on the limb regeneration process. Previous studies have shown that direct manipulation of limb nerves, by electrical stimulation or a conditioning lesion, elevates protein synthesis, increases neurotization and accelerates growth of the limb bud. Since exogenously supplied gangliosides accelerate axonal sprouting in regenerating nerves, we wanted to know whether gangliosides would similarly affect limb regeneration. To test this, regrowing limb buds were either infused with or immersed into gangliosides, or animals were injected intraperitoneally with gangliosides. Infused gangliosides elevated protein synthesis in limb buds 15% and increased the number of axons in limb buds 45% by 6 hours after infusion. Regenerating limb bud morphogenesis was initiated 3-4 days earlier in animals receiving i.p. injections of gangliosides every 12 hours. Similarly, limbs immersed daily in gangliosides began regrowth sooner than contralateral controls and this advantage was maintained throughout the period of observation. These findings indicate that treatment with gangliosides has a salutary effect on limb regeneration.

Animals↗
PubMed1984

Neurotrophic and neuronotrophic effects in the regenerating newt limb bud after electrical stimulation of brachiospinal nerves.

An earlier work demonstrated that electrical stimulation of newt brachiospinal nerves produces a 20% increase in protein synthesis in the regenerating limb bud at 6 h post-stimulation. The present study shows that if stimulation of nerve cell bodies is prevented by placing procaine between the cell bodies and the stimulating electrode, there is no increase in limb bud protein synthesis compared to the non-stimulated, contralateral control limb bud. Similarly, if colchicine is applied to the brachiospinal nerves at the site of and prior to stimulation, there is no increase in limb bud protein synthesis after stimulation. Colchicine applied to brachiospinal nerves in the absence of stimulation results in a reduction of limb bud protein synthesis that is of the same magnitude as the increase seen with stimulation. The results suggest that the neurotrophic increase in limb bud protein synthesis after stimulation is under the control of the cell body and that this control is mediated by changes in fast axonal transport. A neuronotrophic increase in axonal density in the stimulated side limb bud is seen at the same time as the increase in protein synthesis after stimulation.

Animals↗
PubMed1984

A nerve-conditioning lesion accelerates limb regeneration in the newt.

A nerve-conditioning lesion induced sustained acceleration of limb regeneration. Newt limb nerves were subjected to a conditioning lesion by unilateral axotomy at the elbow 2 weeks prior to amputating both limbs above the elbows. Limbs on the side that had received a conditioning lesion began the regeneration process 3-4 days earlier than contralateral controls and this difference was observed up to recognizable digit formation. Limb buds on the conditioned sides had a twofold greater axonal density than contralateral counterparts at 2 weeks after amputation. Since limb bud formation is dependent on a sufficient quantity of axonal regrowth, accelerated limb regeneration is apparently due to accelerated reinnervation.

Amputation, Surgical↗
PubMed1984

Parent and daughter axon density in the limb stump and regenerating limb bud of the newt.

Axonal density in the amputated limb stump and regenerating limb bud of the newt was determined by axon counts and planimetry of silver-stained sections at various distances from the amputation level. Traumatic degeneration occurred for at least 250 micron proximal to the amputation level. Axonal density at 250 micron distal to the amputation was less than half that at 100 micron. Attempts to increase in situ axonal density in limbs of animals naturally incapable of limb regeneration can be based on specific knowledge of natural traumatic degeneration and sprouting prior to axonal manipulation.

Amputation, Surgical↗
PubMed1984

Permeability of bilayers composed of mixtures of saturated phospholipids: evidence for compositional segregation of lipids at phase boundaries.

Lipid bilayers composed of a binary mixture of saturated phospholipids display broad permeability maxima in the temperature region of phase separation. We have proposed that this enhanced diffusion occurs through defects which develop at boundaries between liquid crystal and gel state domains and that one of the lipid components of the mixture might specifically congregate at these defects. To explore this postulate we have performed the following type of experiment. Liposomes were formed from different mole ratios of the lipid pairs 1,2-dimyristoyl-sn-glycero-3-phosphocholine (dimyristoyl GPC)--1,2-distearoyl-sn-glycero-3-phosphocholine (distearoyl GPC) and dimyristoyl GPC--1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (dimyristoyl GPE) and 22Na effluxes measured over an extensive temperature span (15 to 60 degrees C). For a given mixture we plotted 22Na movement through the boundary regions which develop during phase separation against the fraction of dimyristoyl GPC in the coexisting solid and liquid phases at that temperature. As dimyristoyl GPC is added to either distearoyl GPC or dimyristoyl GPE, boundary efflux remains low until the mole fraction of dimyristoyl GPC in the coexisting solid and liquid phases reaches 0.1 and 0.4 (for dimyristoyl GPC--distearoyl GPC) and 0.3 and 0.7 (for dimyristoyl GPC--dimyristoyl GPE), respectively. As the fraction of dimyristoyl GPC in the coexisting phases exceeds these values, boundary permeability rises and with further increments in this phospholipid, the mixtures begin to assume permeability characteristics similar to that of dimyristoyl GPC alone. These observations suggest that at low mole fractions of dimyristoyl GPC, the boundary regions are populated by the distearoyl GPC or dimyristoyl GPE molecules and hence efflux rates are small.(ABSTRACT TRUNCATED AT 250 WORDS)

Dimyristoylphosphatidylcholine↗
PubMed1983

Effect of Tween 80 on lipid vesicle permeability.

As part of an examination of procedures for protein/lipid reconstitution we incubated solubilized cytochrome oxidase at different temperatures with preformed vesicles composed of saturated lipids. We observed that the 22Na permeability of these vesicles was increased following such an incubation step, with the maximal effect occurring following incubations at temperatures in the vicinity of the lipid gel to liquid-crystal phase change. However, these permeability changes could be completely duplicated by incubating similar vesicles with concentrations of Tween 80 used to solubilize the extracted oxidase. Thus detergent molecules used to solubilize extracted membrane proteins can induce significant changes in the reconstituting lipid environment and the possibility of such changes must be taken into account when interpreting the properties of the reconstituted lipid/protein system under study.

Animals↗
PubMed1983

In vitro measurement of cytosol and cell nuclear androgen receptors in male rat brain and pituitary.

An in vitro assay procedure is described for measuring androgen receptor binding in cytosol and cell nuclei of brain and pituitary tissue using [3H]R1881 as ligand. The cell nuclear assay uses the exchange method, which permits assessment of endogenous occupancy of androgen receptors in brain and pituitary. Competition and saturation analysis indicated that [3H]R1881 binding has the specificity and nanomolar affinity expected of an androgen receptor. Moreover, we demonstrated that androgen receptor binding predominated in cytosol from castrated rats and in cell nuclei of male rats treated in vivo with testosterone. Furthermore, as expected, testicular feminized male rats showed low levels of putative androgen receptors in both cytosol and cell nuclei.

Animals↗
PubMed1983

In vivo metabolic intermediates of phospholipid biosynthesis in Rhodopseudomonas sphaeroides.

The in vivo metabolic pathways of phospholipid biosynthesis in Rhodopseudomonas sphaeroides have been investigated. Rapid pulse-chase-labeling studies indicated that phosphatidylethanolamine and phosphatidylglycerol were synthesized as in other eubacteria. The labeling pattern observed for N-acylphosphatidylserine (NAPS) was inconsistent with the synthesis of this phospholipid occurring by direct acylation of phosphatidylserine (PS). Rather, NAPS appeared to be kinetically derived from an earlier intermediate such as phosphatidic acid or more likely CDP-diglyceride. Tris-induced NAPS accumulation specifically reduced the synthesis of PS. Treatment of cells with a bacteriostatic concentration of hydroxylamine (10 mM) greatly reduced total cellular phospholipid synthesis, resulted in accumulation of PS, and stimulated the phosphatidylglycerol branch of phospholipid metabolism relative to the PS branch of the pathway. When the cells were treated with a lower hydroxylamine dosage (50 microM), total phospholipid synthesis lagged as PS accumulated, however, phospholipid synthesis resumed coincident with a reversal of PS accumulation. Hydroxylamine alone was not sufficient to promote NAPS accumulation but this compound allowed continued NAPS accumulation when cells were grown in medium containing Tris. The significance of these observations is discussed in terms of NAPS biosynthesis being representative of a previously undescribed branch of the phospholipid biosynthetic sequence.

Hydroxylamine↗
PubMed1983

Evaluating alcoholism treatment programs: considerations and caveats.

There are many pitfalls in the design and implementation of treatment evaluations which can be avoided by careful scrutiny of previous efforts. To this end, the author reviews several key methodological and conceptual issues which affect evaluations of treatment outcome. The issue of sampling is discussed with primary attention given to biases resulting from common sampling errors. The measurement of treatment outcome is explored, underscoring the limitations and benefits of employing drinking behavior indices. Suggestions are made to improve follow-up response rates, and a strategy for analyzing follow-up losses is outlined. Finally, a number of frequently overlooked variables which may relate to treatment outcome are reviewed.

Alcohol Drinking↗
PubMed1982

The effect of limiting light to the pineal on the rate of forelimb regeneration in the newt.

Newts with bilaterally amputated forelimbs were exposed to either continuous light (LL), total darkness (DD), or continuous light with the dorsal head epithelium painted with an India ink and Nile blue sulfate mixture (LL-II-NBS) that limited light penetration through the skull to the pineal. The LL-II-NBS animals regenerated their forelimbs more slowly then their counterparts in LL.

Animals↗