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Biomedical subjects

R A Edwards

Publications and source records attributed to R A Edwards.

At least 55 records · Page 3Linked to original sources
PubMed1989

Metabolic effects of adding sucrose and aspartame to the diet of subjects with noninsulin-dependent diabetes mellitus.

This study compared the effects of adding sucrose and aspartame to the usual diet of individuals with well-controlled noninsulin-dependent diabetes mellitus (NIDDM). A double-blind, cross-over design was used with each 6-wk study period. During the sucrose period, 45 g sucrose (9% of total daily energy) was added, 10 g with each main meal and 5 g with each between-meal beverage. An equivalent sweetening quantity of aspartame (162 mg) was ingested during the aspartame period. The addition of sucrose did not have a deleterious effect on glycemic control, lipids, glucose tolerance, or insulin action. No differences were observed between sucrose and aspartame. Sucrose added as an integral part of the diabetic diet does not adversely affect metabolic control in well-controlled NIDDM subjects. Aspartame is an acceptable sugar substitute for diabetic individuals but no specific advantage over sucrose was demonstrated.

Aged↗
PubMed1989

Volatile compounds associated with microbial growth on normal and high pH beef stored at chill temperatures.

Volatile compounds produced by Pseudomonas fragi and mixed, natural floras on beef of normal pH (5.5-5.8; glucose greater than 1500 micrograms/g) and high pH (6.3-6.8; glucose less than 10 micrograms/g) included a range of alkyl esters and a number of sulphur-containing compounds including dimethylsulphide but not hydrogen sulphide. Production of the last was a property common to the other Gram-negative organisms tested viz. Hafnia alvei, Enterobacter agglomerans, Serratia liquefaciens, Alteromonas putrefaciens and Aeromonas hydrophila, all of which produced similar off-odours and, with the exception of E. agglomerans, 'greening' on high pH meat. Serratia liquefaciens also produced greening of normal pH meat. Acetoin and diacetyl were major end products of Brochothrix thermosphacta but the related 2,3-butanediol was formed only on normal pH meat. The Enterobacteriaceae produced the same compounds but only on normal pH meat and together with Br. thermosphacta were probable sources of these compounds and of the free and esterified branched-chain alcohols detected in the naturally contaminated samples.

Animals↗
PubMed1989

Relationship between energy expenditure and ion channel density in the turtle and rat brain.

Synaptosomes were isolated from turtle and rat brains to determine whether differences in brain ion channel densities accounted for the turtle's ability to survive anoxia compared with the mammal. The Na(+)-channel binding neurotoxin brevetoxin showed high-affinity specific binding in both turtle and rat synaptosomes, suggesting specific ligand-receptor interaction. The maximum binding capacity (Bmax) value for the turtle was only about one-third of that found for the rat synaptosomes, suggesting that the turtle synaptosome has a correspondingly lower Na+ channel density than the rat. This apparent difference in Na+ channel density is not reflected in metabolic rates, since at the same temperature (31 degrees C) the O2 consumption of both the rat and turtle synaptosome was almost identical. The large reductions in energy expenditure seen in synaptosomes incubated in Na(+)-free media and in media containing ouabain (approximately 50% turtle, 80% rat) are probably related to the halting of transmembrane Na(+)-K+ exchange. The greater reduction in the rat may be related to the apparent greater density of Na+ channels in the rat brain. However, compared with the 90% reduction in brain metabolism that occurs when the turtle brain becomes anoxic, the differences in ion channel density and in the costs of ion pumping between the rat and turtle brain are trivial. Closing Na+ channels with tetrodotoxin and increasing Na+ channel activation with veratridine caused substantial decreases and increases in synaptosome energy consumption, respectively. This suggests that the modulation of ion channel conductance has a significant effect on metabolic cost and may be an important mechanism to reduce energy consumption and electrical activity in the anoxic turtle brain, while still maintaining ionic gradients.

Animals↗
PubMed1988

Brevetoxin binding: molecular pharmacology versus immunoassay.

Brevetoxin PbTx-3 isolated from Florida's red tide dinoflagellate Ptychodiscus brevis has been produced recently in tritiated form by reductive tritiation of brevetoxin PbTx-2. Tritiated PbTx-3 has been used as a specific probe in competitive radioimmunoassays developed to detect brevetoxins in food sources, and this probe has also been utilized to characterize the brevetoxin binding component in rat brain synaptosomes. Brevetoxins PbTx-2 and PbTx-3, possessing the same structural backbone (type-1) as the tritiated probe, and PbTx-1 and PbTx-7, possessing a second structural backbone (type-2), have been compared quantitatively in their individual abilities to competitively displace tritiated PbTx-3 from its specific binding site in each assay. Type-1 toxins displaced labeled probe with ED50 values of 20-22 nM and 12-17 nM in radioimmunoassay and synaptosomes, respectively. Type-2 toxins displaced labeled probe with ED50 values of 92-93 nM and 3.5-4.1 nM in RIA and synaptosomes, respectively. Synaptosome assays reflect potency of each toxin examined, while radioimmunoassay reflects structural similarities to the immunizing toxin PbTx-3.

Animals↗
PubMed1987

Volatile compounds produced by meat pseudomonads and relate reference strains during growth on beef stored in air at chill temperatures.

Volatile compounds produced by 31 strains of pseudomonads and by reference strains of Pseudomonas fragi and Ps. fluorescens biotype 1 during growth on beef stored at 6 degrees C in air were analysed by gas chromatography-mass spectrometry of headspace gases. Compounds of major sensory significance were ethyl and methyl esters of C2-C8 fatty acids and sulphur-containing compounds which included methane- and isopropanethiols and their related sulphides and thioesters but not hydrogen sulphide. Ester production was mainly associated with growth of some, but not all, Ps. fragi and related meat strains but sulphur-containing compounds were produced by all but a single meat strain. A minority of other meat strains produced greater amounts of methyl ketones, secondary alcohols and unsaturated hydrocarbons believed to be of lipid origin.

Alcohols↗
PubMed1987

Amines in fresh beef of normal pH and the role of bacteria in changes in concentration observed during storage in vacuum packs at chill temperatures.

The amine content of fresh and vacuum-packaged beef of normal pH stored at 1 degree C was evaluated by high performance liquid chromatography of dansyl derivatives. Fresh samples contained five amines, viz. putrescine, cadaverine, histamine, spermine and spermidine. Development of a natural spoilage flora during storage led to increases in concentration of putrescine and cadaverine and the production of a sixth amine, tyramine. Pure culture meat inoculation experiments showed tyramine formation to be restricted to lactobacilli and to strains of Lactobacillus divergens and Lact. carnis in particular; strains of leuconostocs, Enterobacteriaceae, Pseudomonas spp. and Brochothrix thermosphacta were negative. Production of tyramine at cell densities less than log10 6/cm2 indicated its potential as an objective measure of acceptability/spoilage.

Amines↗
PubMed1986

Bacterial sources of putrescine and cadaverine in chill stored vacuum-packaged beef.

Of the meat strains of streptobacteria, leuconostocs, Enterobacteriaceae and Brochothrix thermosphacta tested, only Hafnia alvei and Serratia liquefaciens showed diamine-producing potential during growth in pure culture on beef stored in vacuum packs at 1 degree C. Both organisms produced cadaverine at concentrations similar to those reported previously in naturally contaminated beef stored under the same conditions. Putrescine concentrations produced by the two organisms, however, were an order of magnitude lower. During the growth on beef of either H. alvei or S. liquefaciens in mixed culture with arginine-utilizing strains of streptobacteria, putrescine as well as cadaverine concentrations were similar to those detected in naturally contaminated samples.

Animals↗
PubMed1985

Putrescine and cadaverine formation in vacuum packed beef.

Bacterial numbers, putrescine and cadaverine concentrations and pH were measured at regular intervals during the chill storage of vacuum packed beef. Odours on opening the packs were also assessed. Cadaverine concentration increased more rapidly than that of putrescine and measurable increases were evident before maximum bacterial numbers were attained and before any permanent off-odours were detected. Diamine concentrations correlated better with total viable count (TVC) than with counts of Gram negative organisms.

Animals↗
PubMed1985

Time course of volatile compound formation during refrigerated storage of naturally contaminated beef in air.

The microbial flora of naturally contaminated beef stored in air was similar to that frequently recorded for meat stored under gas permeable films. Compounds produced as a result of microbial growth were acetoin, diacetyl, 3-methyl-1-butanol, 2-methyl-1-propanol, ethyl esters of acetic, propionic, butyric, isovaleric and hexanoic acids, methane thiol, dimethylsulphide, dimethyl disulphide, 1-undecene and 1,4-undecadiene. The first four compounds, which are known end-products of Brochothrix thermosphacta metabolism, were consistently detected at earlier stages of storage than the others, all of which have been shown to be produced by Pseudomonas spp. A pattern of odour development consistent with the chemical changes was also observed.

Air↗
PubMed1984

Volatile compounds associated with the aerobic growth of some Pseudomonas species on beef.

Five strains representing four clusters of meat spoilage pseudomonads were grown on sterile beef at 5 degrees C. After 7 days incubation sensory assessments were made and the chemical composition of the headspace gases determined by gas chromatography-mass spectrometry. There was good correlation between odour descriptions and chemical data for three of the strains. The most numerous types of product were esters and sulphur-containing compounds. Of 45 compounds identified only 1-undecene was common to all the tested strains.

Animals↗
PubMed1980

Advantages and disadvantages of benzodiazepine prescription.

There is little evidence to warrant the long term prescribing of benzodiazepine as anxiolytics and there is an urgent need for research into the long term effects of these drugs. Benzodiazepine abuse with dependence and serious withdrawal symptoms is increasingly recognised as a major problem. Various studies show that the benzodiazepines can release aggressive impulses and that serious disinhibition can result from their use. Their suicidogenic potential in depressed patients is part of this disinhibiting effect. There is strong evidence that the benzodiazepines especially in combination with alcohol render individuals accident prone. Cognitive defects are being increasingly recognised in benzodiazepine users. While these are reversible in short term users the question as to whether long term users suffer an increasing dementia urgently requires further research.

Accidents↗
PubMed1979

Tetanus and psychiatry: unexpected bedfellows.

Six patients who were admitted with the initial diagnosis of tetanus to a general hospital serving 130 000 people over a 10-year period are reviewed. In three of these patients psychogenic factors played a major part in the presenting pictures. These cases followed a markedly different course from the others. Guidelines to the early differentiation of such atypical cases, and to the way psychogenic factors can be identified and their importance evaluated, are discussed.

Adult↗
PubMed1977

A trial of lactose hydrolysed milk in Australian Aboriginal children.

Weight gains in 50 young Australian Aboriginal children were studied in a blind controlled hospital trial of reconstituted, lactose hydrolysed milk powder (test) and full-cream milk powder (control). The mean weight gains (+/- SEM) were 4.80 +/- 0.80 g kg-1 day-1 for children receiving the lactose hydrolysed milk, and 2.20 +/- 0.75 g kg-1 day-1 for those receiving the normal milk P less than 0.0125). Weight gain of infants (that is, those under one year of age) in the control group was less than 10% of that in the test group (P less than 0.0025). Weight gain was higher in children fed hydrolysed milk irrespective of percentage of Standard Weight for Age or the presence or absence of recognizable symptoms of lactose intolerance. Lactose malabsorption appears to be a major factor in the growth retardation of Aboriginal children. It is recommended that lactose hydrolysed milk replace normal milk in the supplementary feeding of Aboriginal infants and children.

Animals↗