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Biomedical subjects

G A Jones

Publications and source records attributed to G A Jones.

At least 55 records · Page 3Linked to original sources
PubMed1987

The antibacterial activity of alamethicins and zervamicins.

Consistent results were obtained in biological assays of alamethicins on agar gels only when the antibiotics were allowed to diffuse under strictly defined conditions of temperature and time before inoculation. In liquid culture obligatory anaerobic rumen bacteria were sensitive to these antibiotics and in certain cases their ability to produce volatile fatty acids was reduced. Among the bacteria examined there was a 1000-fold difference in their sensitivity. Modifications of the structure of the peptaibol, e.g. substitution of an alanine residue for a 2-methylalanine residue resulted in ca two-fold changes in activity.

Alamethicin↗
PubMed1986

Effect of nickelous and other metal ions on the inhibition of rumen bacterial metabolism by 3-(3'-isocyanocyclopent-2-enylidene)propionic Acid and related isocyanides.

3-(3'-Isocyanocyclopent-2-enylidene)propionic acid at a concentration of 2 to 5 mug ml inhibited cellulose digestion by a mixed culture of rumen microorganisms and in other experiments inhibited the degradation of timothy hay (Phleum pratense) in a digestibility test. At isocyanide concentrations of 12 mug ml the fermentation activity of rumen fluid, measured by its dehydrogenase activity, was inhibited but not abolished. All of these isocyanide effects were reversed by the incorporation of nickelous ion into the solutions of the systems under study. The activity of 1 mol of isocyanide is reversed by about 1 mol of Ni and, in the case of the cellulose digestion test, by about 1 mol of Co. Of some 15 other ions tested only Pd and possibly chromium reversed the effect of the isocyanide.

Journal Article↗
PubMed1986

Dental X rays found to have no effect on hearing aids.

Each of the two manufacturers supplied one pair of behind-the-ear hearing devices for testing. The control group had the volume turned off and the test group had the volume turned on fully. All units were subjected to a series of 21 exposures of 90kV(p) and 15 mA, resulting in cumulative doses of 5.465 to 5.516 R. All devices were analyzed for any changes that resulted from radiation exposure. Both vendors reported that no changes had occurred. For legal reasons, however, one vendor suggested that it would be best to remove the hearing device before exposure to radiation. Such prudent action might prevent the occurrence of a very unusual accident. A third company that conducted a similar experiment on its own units indicated that no changes had occurred. The company's testing facility also suggested that a vendor should not give any warranty and recommended the hearing aid device be removed before radiographic examination.

Hearing Aids↗
PubMed1985

Demonstration of a reduction in postoperative body protein breakdown using the Clinitron fluidized bed with an ambient temperature of 32 degrees C.

Patients managed at an elevated ambient temperature after major surgery have a less pronounced rise in postoperative urinary nitrogen excretion. To investigate the mechanism involved, body protein breakdown was assessed, using a tracer dose of labelled amino acid, in patients following aorto-bifemoral bypass surgery nursed on either a Clinitron fluidized bed at 32 degrees C or a hospital bed at 22 degrees C and correlated with urinary total nitrogen excretion. Results showed a small reduction in measured body protein breakdown on the second postoperative day in patients managed on the Clinitron fluidized bed at 32 degrees C (2.92 +/- 0.91 versus 3.23 +/- 0.84 g protein kg-1 day-1; mean +/- s.d.), which was equivalent to the mean protein sparing (0.29g protein kg-1 day-1) demonstrated by the significant improvement in urinary total nitrogen excretion (9.20 +/- 2.0 versus 12.48 +/- 3.9 g N day-1; mean +/- s.d.: P less than 0.05). Urinary total nitrogen excretion (N) and body protein breakdown (B) showed a weak though significant positive correlation (B = 1.25 + 13.13N; r = +0.55: P = 0.05), whereas no correlation existed between urinary total nitrogen excretion and the derived rate of body protein synthesis. There was also a significant decrease in postoperative stress, measured during the isotope infusion, in patients managed on the Clinitron fluidized bed at 32 degrees C (12.3 +/- 2.2 versus 16.1 +/- 3.2 per cent activity incorporated into plasma proteins; mean +/- s.d.: P less than 0.05). These results show the beneficial effect of managing postoperative patients on a Clinitron fluidized bed at 32 degrees C in conserving body nitrogen through a reduction in body protein breakdown, probably as a consequence of decreased postoperative stress.

Aged↗
PubMed1985

The incidence and type of reactions to plain and adsorbed DTP vaccines.

The incidence and type of reactions after administration of plain and adsorbed diphtheria-tetanus-pertussis vaccine were recorded in a blind controlled prospective study of 2041 vaccinations in 1075 infants receiving routine childhood immunization. There was no significant difference in the total incidence or type of general reactions after plain and adsorbed vaccine, but local reactions were significantly less frequent after plain vaccine. General reactions were recorded after 41.5% of vaccinations with plain vaccine and after 40.8% of vaccinations with adsorbed vaccine. Local reactions were reported in 66.7% and 76.5% of recipients respectively. The most commonly reported systemic reactions were irritability and fever. Three recipients of plain vaccine and one of adsorbed vaccine suffered hyporesponsiveness or collapse. One recipient of each vaccine suffered a convulsion. No persisting sequelae were recorded.

Adsorption↗
PubMed1985

Antibiotic activity of an isocyanide metabolite of Trichoderma hamatum against rumen bacteria.

A metabolite of Trichoderma hamatum, 3-(3-isocyanocyclopent-2-enylidene)propionic acid, was tested for its effects on growth of and carbohydrate metabolism in 11 strains of functionally important rumen bacteria. To standardize the biological activity of this unstable metabolite, a rapid, aerobic disc diffusion assay was developed using Escherichia coli ATCC 11775. In an anaerobic broth dilution assay using a medium lacking rumen fluid and containing a soluble carbohydrate, the minimum inhibitory concentration of the metabolite which completely inhibited growth of the rumen bacteria for 18 h at 39 degrees C was generally less than 10 micrograms X mL-1; however, the minimum inhibitory concentrations for Megasphaera elsdenii B159 and Streptococcus bovis Pe(1)8 were 10-25 and 25-64 micrograms X mL-1, respectively. In general, the Gram-negative strains were more sensitive than the Gram positive. The minimum inhibitory concentration for Bacteroides ruminicola 23 grown with glucose was 1 micrograms X mL-1; for B. ruminicola GA33 (glucose), B. succinogenes S85 (cellobiose), and Succinivibrio dextrinosolvens 24 (maltose), it was 2 microgram X mL-1. When added to a cellulose-containing rumen fluid medium, 1-4 micrograms X mL-1 of the metabolite delayed cellulose hydrolysis by B. succinogenes S85, Ruminococcus albus 7, and R. flavefaciens FD1 for up to 4 days, and 6-7 micrograms X mL-1 prevented hydrolysis for at least 1 month. In the presence of the metabolite, the proportion of acetate produced from soluble carbohydrate by the majority of strains increased, but with some strains net production of acetate decreased relative to production of other acidic fermentation products.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

The antibacterial activity of some naturally occurring 2,5-dihydroxy-1,4-benzoquinones.

Polyporic acid, atromentin, bovinone, and oosporein are common metabolic products of a number of species of fungi. The related compound cochliodinol and its congeners are produced by several Chaetomium spp. These quinonoid metabolites have been shown to inhibit the growth and metabolism of a range of bacterial genera. The antibiotic activity of the quinones depends on the substituents at the 3 and 6 positions of the 2,5-dihydroxy-1,4-benzoquinone ring; in aerobic systems the activity appears to be inversely proportional to the polarity of the metabolite. It has been shown that reduction of the quinone to the hydroquinone changes the antibiotic activity of these metabolites but does not abolish it. Contrary to previous reports, the activity of these hydroquinones is not reversed by cysteine.

Animals↗
PubMed1983

Musculoskeletal problems at an accident and emergency department, and in general practice.

A retrospective study of the numbers and range of musculoskeletal conditions presenting to the accident and emergency (A and E) department of a general hospital over two one-week periods, in February and May 1980 is described. Over a third of the patients had musculoskeletal disorders most commonly affecting the hand (19%), ankle (13%), foot (9%) and spine (8%). One in three cases involved fracture. As judged by a physiotherapist, only 20% of cases which should have been referred for physiotherapy were actually referred. The frequency and range of musculoskeletal conditions encountered in general practice, and the undergraduate curriculum for the musculoskeletal system at the Auckland Medical School is reviewed. Postgraduate education in the musculoskeletal system is essential where emphasis should be given to conditions of the hand and the spine.

Bone Diseases↗
PubMed1983

Effects of chetomin on growth and acidic fermentation products of rumen bacteria.

Chetomin, an antibiotic metabolite of Chaetomium spp., was tested in the form of its tetrathiol derivative for its effects on growth and carbohydrate metabolism by five strains of functionally important rumen bacteria. The compound was bacteriostatic for the strains tested and Gram-positive bacteria were more sensitive to inhibition than Gram-negative bacteria. In an anaerobic broth dilution assay using a medium lacking rumen fluid, the minimum inhibitory concentration (MIC) of chetomin which completely inhibited growth of Butyrivibrio fibrisolvens D1 for 18 h at 39 degrees C was 40 micrograms X mL-1. The MICs determined under the same conditions for Megasphaera elsdenii B159, Selenomonas ruminantium GA192, and Succinivibrio dextrinosolvens 24 were 160, 600, and 60 micrograms X mL-1, respectively. The MIC for cellulose hydrolysis by Ruminococcus albus 7 was 20 micrograms X mL-1. Chetomin at concentrations below the MIC appeared to inhibit the separation and division of cells in cultures of B. fibrisolvens D1. Chetomin consistently stimulated acetate production from glucose by B. fibrisolvens D1, M. elsdenii B159, and S. ruminantium GA192 at the expense of compounds which comprised major soluble end products of fermentation in cultures lacking chetomin.

Animals↗
PubMed1981

Hydrolysis of leaf Fraction 1 protein by the proteolytic rumen bacterium Bacteroides ruminicola R8/4.

Proteolytic activity in a batch culture of Bacteroides ruminicola R8/4 was maximal and largely (greater than 90%) cell-associated during the mid-exponential phase of growth. The cell-bound protease was not inactivated during storage at --70% C, was not significantly affected by pH over the range 5.9 to 8.2, but was subject to substrate inhibition by Fraction 1 protein (ribulose-1,5-bisphosphate carboxylase; EC 4.1.1.39) and was most active in the presence of thiol reagents. Radioactive Fraction 1 protein was hydrolysed by non-growing and growing cells of B. ruminicola R8/4 with the production of peptides and free amino acids. Deaminase activity was absent. Radioactive amino acids were incorporated into bacterial proteins from [14C]Fraction 1 protein without substantial change in specific radioactivity.

Amino Acids↗
PubMed1981

Isolation and presumptive identification of adherent epithelial bacteria ("epimural" bacteria) from the ovine rumen wall.

One hundred sixty-one strains of adherent bacteria were isolated under anaerobic conditions from four sites on the rumen epithelial surface of sheep fed hay or a hay-grain ration. Before isolation of bacteria, rumen tissue was washed six times in an anaerobic dilution solution, and viable bacteria suspended in the washings were counted. Calculation indicated that unattached bacteria would have been removed from the tissue by this procedure, but a slow and progressive release of attached bacteria also occurred. Nevertheless, a wide range of characteristic morphological types remained associated with the epithelium as demonstrated by scanning electron microscopy. Most of these types were represented among the isolates. Characterization and presumptive identification of the isolates showed that 95.0% belonged to previously described genera of functionally significant rumen bacteria, including Butyrivibrio sp. (31.1%), Bacteroides sp. (22.4%), Selenomonas ruminantium (9.9%), Succinivibrio dextrinosolvens (8.7%), Streptococcus bovis (8.1%), Propionibacterium sp. (4.3%), Treponema sp. (3.1%), and Eubacterium sp., Lachnospira multiparus, and Ruminococcus flavefaciens (2.5% each). Eight isolates (5.0%) were not identified. L. multiparus was recovered only from hay-fed animals; all other genera were obtained from animals fed either ration. All S. bovis strains and two strains each of Bacteroides sp. and Butyrivibrio sp. were aerotolerant; all other strains were strictly anaerobic. Bacteria representing the gram-positive, facultatively anaerobic flora associated with rumen wall tissue (R. J. Wallace, K.-J. Cheng, D. Dinsdale, and E. R. Ørskov, Nature (London) 279:424-426, 1979) were therefore not recovered by the techniques used; instead a different fraction of the adherent population was isolated. The term "epimural" is proposed to describe the flora associated with the rumen epithelium.

Anaerobiosis↗
PubMed1981

Catabolism of phloroglucinol by the rumen anaerobe coprococcus.

A rumen isolate, Coprococcus, sp. Pe(1)5, was found to carry phloroglucinol reductase, which catalyzed the initial step in the breakdown of phloroglucinol. The organism uses phloroglucinol as the sole source of carbon and energy when grown in the absence of oxygen. Induced levels of enzyme were detected in cells grown either on phloroglucinol or on other carbon sources in the presence of limiting quantities of phloroglucinol. Although the organism is a strict anaerobe, the enzyme from anaerobically grown cells was insensitive to air. The partially purified enzyme required reduced nicotinamide adenine dinucleotide phosphate as an electron donor and was specific for phloroglucinol. However, partial enzyme activity (14 to 17%) was also detected in the presence of 2-methyl-1,4-naphthoquinone but not in the presence of several other phenolic compounds. The enzyme exhibited a higher affinity for phloroglucinol than for reduced nicotinamide adenine dinucleotide phosphate, with K(m) values of 3.0 x 10 M and 29.0 x 10 M, respectively. The optimum pH for maximal enzyme activity was 7.4, and the molecular weight of the native protein was about 130,000, as determined by the Sephadex gel filtration technique.

Journal Article↗
PubMed1980

Effect of titanium (III) citrate as reducing agent on growth of rumen bacteria.

We compared the growth of 10 strains of rumen bacteria in an anaerobic medium reduced with cysteine hydrochloride, dithiothreitol, or titanium (III) citrate. The redox potential of medium reduced with cysteine hydrochloride was -167.8 mV; with dithiothreitol it was -175.8 mV; and with titanium(III) citrate it was -302.4 mV at a concentration of 5 X 10(-4) M titanium and -403.9 mV at 2 X 10(-3) M titanium. Maximum growth of the strains was generally lower with dithiothreitol or titanium(III) citrate than with cysteine hydrochloride, although growth was greater than in medium lacking an added reducing agent. Strains for which cysteine was required or markedly stimulatory grew only poorly with titanium(III) citrate. No strain grew in medium with sodium citrate as the energy source. Titanium(III) citrate could be used to reduce anaerobic media for some rumen bacteria if the exclusion of a sulfur-containing reducing agent is required.

Anaerobiosis↗
PubMed1976

Use of the Hungate anaerobic technique in the isolation of phloroglucinol-negative mutants of Coprococcus species.

The Hungate anaerobic technique was used with a standard procedure for bacterial mutagenesis employing N-methyl-N-nitro-N'-nitrosoguanidine to obtain mutants of an obligate anaerobe. Three mutant strains were derived from a Coprococcus sp., strain Pe15, a rumen anaerobe capable of growing on phloroglucinol. The mutants did not grow on phloroglucinol but did degrade the compound in anaerobic washed-cell suspensions, producing the same end products in approximately the same proportions as the wild type. It was concluded that the mutants were blocked in a unique step or steps necessary for carbon skeleton or energy synthesis from phloroglucinol and not in formation of an enzyme involved in the pathway of phloroglucinol degradation.

Anaerobiosis↗