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Biomedical subjects

E Barnes

Publications and source records attributed to E Barnes.

16 recordsLinked to original sources
PubMed1991

L-lyxose metabolism employs the L-rhamnose pathway in mutant cells of Escherichia coli adapted to grow on L-lyxose.

Escherichia coli cannot grow on L-lyxose, a pentose analog of the 6-deoxyhexose L-rhamnose, which supports the growth of this and other enteric bacteria. L-Rhamnose is metabolized in E. coli by a system that consists of a rhamnose permease, rhamnose isomerase, rhamnulose kinase, and rhamnulose-1-phosphate aldolase, which yields the degradation products dihydroxyacetone phosphate and L-lactaldehyde. This aldehyde is oxidized to L-lactate by lactaldehyde dehydrogenase. All enzymes of the rhamnose system were found to be inducible not only by L-rhamnose but also by L-lyxose. L-Lyxose competed with L-rhamnose for the rhamnose transport system, and purified rhamnose isomerase catalyzed the conversion of L-lyxose into L-xylulose. However, rhamnulose kinase did not phosphorylate L-xylulose sufficiently to support the growth of wild-type E. coli on L-lyxose. Mutants able to grow on L-lyxose were analyzed and found to have a mutated rhamnulose kinase which phosphorylated L-xylulose as efficiently as the wild-type enzyme phosphorylated L-rhamnulose. Thus, the mutated kinase, mapped in the rha locus, enabled the growth of the mutant cells on L-lyxose. The glycolaldehyde generated in the cleavage of L-xylulose 1-phosphate by the rhamnulose-1-phosphate aldolase was oxidized by lactaldehyde dehydrogenase to glycolate, a compound normally utilized by E. coli.

Acetaldehyde↗
PubMed1988

Recycling of surfactant in black and beige mice: pool sizes and kinetics.

Lung disaturated phosphatidylcholine (DSPC) turnover was investigated in normal C57 black and mutant beige mice; the latter have been postulated to have microtubular defects. Turnover experiments were performed on 117 black and 74 beige mice that were assayed for lamellar body-rich fraction (LB) and alveolar lavage fluid (AF) DSPC from 0.5 to 100 h after injection of [3H]glycerol. The data were analyzed by a program that derived the best-fit rate constants for an operator-chosen compartmental model. For black mice, a simple model with bidirectional exchange of DSPC between LB and AF compartments fitted the data almost as well as more complex models. This model yielded a turnover time of 5.9 h, a biological half-life of 16 h, and recycling of AF DSPC into LB of 47%. There was some evidence to suggest that DSPC might be degraded rather than recycled as a unit. For beige mice, the DSPC turnover time was 4.8 h, and its biological half-life was 40 h. The AF DSPC pool was smaller than in black mice, but the LB pool was larger. The bidirectional flux of DSPC between AF and LB was much greater than in black mice, the percent of recycling being 85. These data do not support a microtubular defect in beige mice, but the calculations for beige mice are based on a model of questionable validity.

Animals↗
PubMed1987

A clinical study of Sudocrem in the management of dermatitis due to the physical stress of incontinence in a geriatric population.

A double blind controlled trial was carried out to measure the efficacy of Sudocrem, compared with zinc cream BP, in the treatment and prevention of incontinence-associated dermatitis in an elderly inpatient population. Three objective measures of skin condition were used to assess efficacy. Sudocrem was shown to be superior to zinc cream BP in the treatment of dermatitis, with no significant difference shown in terms of prophylaxis. The objective measures of skin health seemed to be a promising advance on earlier, subjective methods, and their further development is recommended. There was some indication that the normal skin of an incontinent patient does not deteriorate when managed with Sudocrem or zinc cream.

Aged↗
PubMed1986

The role of personality in the management of partial dentures.

A sample of fifty-three partially dentate subjects who had had partial dentures provided in the last 3 years completed a personality questionnaire (Cattell's 16 PFQ). At the same time they completed a clinical questionnaire and were examined by two of the authors. The purpose of this was to assess the patients' satisfaction with their partial dentures. The results of the personality questionnaire showed that this group of partial denture wearers differed from the general population on only two factors. They were less intelligent and more self-sufficient. Interestingly they differed from a similar group of complete denture wearers on a further three factors. The partial denture group were more self-assured, self-sufficient and more relaxed. On the basis of the clinical questionnaire and examination, five partially dentate patients were found to be dissatisfied. Their personality scores were significantly more unstable than the satisfied group of partial denture wearers. Although based on a relatively small group, the results do suggest that personality may have a marked effect on the patients' adaption to partial dentures. When compared to a similar group of edentulous patients, marked differences were found, suggesting that the loss of the natural teeth in some individuals affects behaviour.

Adolescent↗
PubMed1985

Cholinergic modulation of memory in rats.

Central cholinergic systems have long been implicated in the modulation of learning and memory processes in animals and man. Drugs that affect the central cholinergic system have been found either to enhance or to hinder performance in tests of learning and memory. Few studies have evaluated the effects of different cholinergic drugs within a single experimental paradigm and with a relatively wide dose range. The studies reported here investigated the effects of cholinergic drugs with diverse modes of action on the retention of a passive avoidance response. Physostigmine, arecoline, oxotremorine, nicotine, and 4-aminopyridine were administered IP immediately following the acquisition of a one-trial passive avoidance task. All of the drugs were found to enhance 72-h retention of passive avoidance; however, the effective doses were different for each of the drugs studied.

4-Aminopyridine↗
PubMed1975

Release of norepinephrine and dopamine-beta-hydroxylase by nerve stimulation. IV. An evaluation of a role for cyclic adenosine monophosphate.

The effects of several cyclic nucleotide analogs and of phosphodiesterase inhibitors on the release of norepinephrine (NE) and dopamine-beta-hydroxylase activity (DBH) by electrical stimulation were studied in the isolated, perfused cat spleen. N-6-butyryl-3',5'-adenosine monophosphate (mbcAMP), 8-methylthio-3',5'-adenosine monophosphate, 8-bromo-3',5'-guanosine monophosphate (8-Br-cGMP) and two potent phosphodiesterase inhibitors: 1-methyl-3-isobutylxanthine and 4-(3-butoxy-4-methoxy-benzyl)-2-imidazolidinone (Ro 20-1724) enhanced the overflow of NE and total H and reduced pressure responses elicited by nerve stimulation. A concomitant outflow of DBH activity was observed in the presence of mbcAMP, 8-Br-cGMP or Ro 20-1724. Synergistic effects on the nerve stimulation-mediated overflow of NE and DBH were obtained with low concentratons of Ro 20-1724 and mbcAMP (5 muM). Adenosine 5'-monophosphate produced a very slight increase in nerve stimulated release of NE and DBH activity in concentrations which inhibited pressor responses considerably. cAMP produced slight inhibition of pressure responses but failed to influence the release of either NE or DBH activity during nerve stimulation. In contrast to the enhanced overflow of NE and DBH activity induced by nerve stimulation, with the exception of Ro 20-1724, the spontaneous release of these substances was not modified by any of the cyclic nucleotide analogs or phosphodiesterase inhibitors examined. This effect of Ro 20-1724 can probably be explained by the ability of this compound to inhibit the activity of monoamine oxidase and therefore reduce the formation of deaminated metabolites. The present results suggest that cyclic nucleotides are not directly responsible for the release of the adrenergic neurotransmitter, but may facilitate the normal process of release by nerve stimulation. Phentolamine, a blocker of the alpha adrenergic receptors, produced a marked increase in the nerve stimulation-mediated overflow of NE, total H and DBH activity and inhibited pressure responses. This effect was several times greater than that produced by either cyclic nucleotide analogs or phosphodiesterase inhibitors. In addition, the effect of phentolamine was not modified by prior treatment with 1-methyl-3-isobutylxanthine or Ro 20-1724, suggesting that the effect of phentolamine is not related to its ability to inhibit phosphodiesterase and is probably not mediated via an increase in cAMP.

4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone↗