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Biomedical subjects

G R Smith

Publications and source records attributed to G R Smith.

At least 217 records · Page 12Linked to original sources
PubMed1988

In vitro metabolism of formononetin and biochanin A in bovine rumen fluid.

The phyto-estrogens formononetin (7-hydroxy-4'methoxyisoflavone) and biochanin A (5-7-dihydroxy-4'-methoxyisoflavone) were independently incubated in vitro at 39 degrees C in bovine rumen fluid from a fistulated steer receiving an alfalfa hay diet. Formononetin was incubated in studies 1 and 2, whereas biochanin A was incubated in study 3. The isoflavones were separated and quantified by high performance liquid chromatography. In study 1, formononetin concentration, 14.80 micrograms/ml at time 0, declined to 1.16 micrograms/ml by 12 h and to .76 micrograms/ml by 24 h. Daidzein (7,4-dihydroxyisoflavone), .18 micrograms/ml at time 0, peaked at 12.92 micrograms/ml at 6 h and decreased to 1.30 micrograms/ml by 24 h. Equol (7,4'-dihydroxyisoflavan), detected at 6 h, peaked at 16.94 micrograms/ml at 18 h and dropped to 12.64 micrograms/ml at 24 h. In incubation study 2, formononetin declined from 17.57 micrograms/ml at time 0 to 7.08 micrograms/ml by 6 h. Daidzein concentration was 1.75 micrograms/ml at time 0 and increased to 12.03 micrograms/ml by 6 h. Equol was detected at 3 h and increased to 2.32 micrograms/ml at 6 h. The half-lives were 4.3 for formononetin and 9.8 h for daidzein in this in vitro system. In study 3, biochanin A, 8.54 micrograms/ml at time 0, decreased to 0 micrograms/ml by 12 h in incubation 3, whereas genistein (5,7,4'-trihydroxyisoflavone), 3.17 micrograms/ml at 1 h, peaked at 7.35 micrograms/ml at 4 h and decreased to .32 micrograms/ml at 24 h. Equol was not detected in incubation study 3. The half-lives of biochanin A and genistein were 3.9 and 5.5 h, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Haemolytic effect of Pasteurella haemolytica on blood from young mammals.

On agar plates containing young lamb blood, Pasteurella haemolytica produces a wide outer zone of partial haemolysis in addition to the narrow zone of complete clearing seen on adult sheep blood agar. To determine whether this phenomenon was limited to lamb blood, samples from young animals of 20 mammalian species were examined. Two species--the barbary sheep (Ammotragus lervia) and scimitar horned oryx (Oryx tao)--possessed blood that gave this effect provided that the samples were taken from young animals. The 18 species that gave negative results included an ovine species, the bighorn sheep (Ovis canadensis).

Animals↗
PubMed1987

Cutting of chi-like sequences by the RecBCD enzyme of Escherichia coli.

Chi, 5' G-C-T-G-G-T-G-G 3', stimulates coliphage lambda recombination mediated by the major recombination pathway of Escherichia coli, the RecBC pathway. Purified RecBCD enzyme makes a single strand endonuclease cleavage four to six nucleotides to the 3' side of the chi sequence. Three sequences similar to chi, 5' A-C-T-G-G-T-G-G 3', 5' G-T-T-G-G-T-G-G 3' and 5' G-C-T-A-G-T-G-G 3', have partial recombinational hotspot activity in genetic crosses. We report here that purified RecBCD enzyme preferentially cuts four nucleotides to the right of the two most active chi-like octamers. The degree of cutting correlated with the genetic activities of these sequences; this result indicates that these cleavages are essential to the genetic activity of chi and chi-like sequences.

Bacteriophage lambda↗
PubMed1987

Factors affecting the toxicity of rotting carcasses containing Clostridium botulinum type C.

Mice killed shortly after receiving 1300-3000 spores of Clostridium botulinum type C per os were incubated at one of four chosen temperatures together with bottles of cooked meat medium seeded with a similar inoculum. After incubation the rotting carcasses were homogenized. Sterile membrane filtrates of the homogenates (10-20.8%, w/v) and pure cultures were then titrated for toxicity. A temperature of 37 degrees C produced less toxicity in most carcasses than in cultures. At 30 degrees C, however, toxicity (often 2 X 10(5) to 2 X 10(6) mouse intraperitoneal LD/g or ml) was roughly similar in both systems, and some carcasses and cultures were still toxic (2 X 10(4) to 2 X 10(5) LD/g or ml) after 349 days. Surprisingly, at 23 degrees C, through greatly reduced in the cultures, toxicity was high in many carcasses for at least 28 days. Little or no toxin was produced in either system at 16 degrees C. Unfiltered homogenates (17.8-22.5%, w/v; dose 0.25 ml per os) of toxic carcasses incubated at 30 degrees C for 7 days invariably produced death from botulism, often within as little as 4 h, but a 1 in 10 dilution produced less than 100% mortality.

Animals↗
PubMed1987

Genetic functions promoting homologous recombination in Escherichia coli: a study of inversions in phage lambda.

We have studied homologous recombination in a derivative of phage lambda containing two 1.4-kb repeats in inverted orientation. Inversion of the intervening 2.5-kb segment occurred efficiently by the Escherichia coli RecBC pathway but markedly less efficiently by the lambda Red pathway or the E. coli RecE or RecF pathways. Inversion by the RecBCD pathway was stimulated by Chi sites located to the right of the invertible segment; this stimulation decreased exponentially by a factor of about 2 for each 2.2 kb between the invertible segment and the Chi site. In addition to RecA protein and RecBCD enzyme, inversion by the RecBC pathway required single-stranded DNA binding protein, DNA gyrase, DNA polymerase I and DNA ligase. Inversion appeared to occur either intra- or intermolecularly. These results are discussed in the framework of a current molecular model for the RecBC pathway of homologous recombination.

Bacteriophage lambda↗
PubMed1987

Taxonomy of the Mycoplasma mycoides cluster.

Some of the mycoplasmas found in diseases of ruminants, Mycoplasma capricolum, M. mycoides subsp. capri (PG3), bovine group 7 (PG50), strain F38 and strain Y goat show various degrees of relationship to M. mycoides subsp. mycoides (PG1) and to one another, such that they are referred to as the M. mycoides cluster. Studies using serology, DNA homology, isoenzyme analysis and two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) of proteins have been carried out on the type and reference strains of these organisms and some representative strains in an effort to resolve this cluster into well-defined taxa. An ad hoc committee set up by the Subcommittee on the Taxonomy of the Mollicutes examined the known data, but found that it led to conflicting opinions on the classification of the unspeciated strains, partly because of the lack of guidelines on the relative weight to be given to each criterion, and partly because insufficient strains of each member of the cluster had been examined. Although classifications were proposed, total agreement was not achieved on any one proposal, and the committee believes that decisions on the taxonomy would have to await the results of repeat tests, in which several representative strains of each of the six groups would be included with the type strain.

Animals↗
PubMed1986

Susceptibility of wallabies to Fusobacterium necrophorum.

Wallabies (Macropus rufogriseus) were not appreciably more susceptible than rabbits or mice to Fusobacterium necrophorum, a fact established by the subcutaneous injection of a series of graded doses into animals of each species. The strikingly frequent occurrence of necrobacillosis in captive macropods is therefore not due to a uniquely high susceptibility. A vaccine containing inactivated F necrophorum culture emulsified with Freund's complete adjuvant failed to increase the resistance of wallabies to subcutaneous challenge with a moderate dose of the homologous strain. The control of necrobacillosis in captive wallabies must therefore depend on managemental measures aimed at minimising faecal contamination of the environment and damage to the buccal mucous membrane and skin.

Animals↗
PubMed1986

Conservation of Chi cutting activity in terrestrial and marine enteric bacteria.

Homologous recombination in Escherichia coli occurs at increased frequency near Chi sites, 5'G-C-T-G-G-T-G-G3'. Cutting of DNA close to the Chi sequence by the E. coli RecBC enzyme is essential to Chi's stimulation of recombination. We have detected Chi-dependent cutting activity in extracts of several genera of terrestrial enteric bacteria (family Enterobacteriaceae) and of two genera of marine enteric bacteria (family Vibrionaceae). More distantly related bacteria had no detectable Chi-dependent cutting activity. These results support the view that recognition of this specific nucleotide sequence as a signal activating recombination has been maintained during the evolution of certain groups of bacteria. We discuss the possibility that other sequences play a similar role in other groups of bacteria.

Autoradiography↗
PubMed1986

Psychiatric consultation in somatization disorder. A randomized controlled study.

The per capita expenditure for health care of patients with multiple physical symptoms but no apparent physical disease (somatization disorder) is up to nine times the average per capita amount. We conducted a randomized controlled trial to determine whether psychiatric consultation would reduce the medical costs of these patients, without effecting a substantial change in patient outcome. Thirty-eight patients were randomly assigned to treatment or control groups and studied prospectively for 18 months. Treatment consisted of a psychiatric consultation and suggestions on management given to primary physicians. After nine months, the control group was crossed over to receive treatment with the same intervention. After the psychiatric consultation, the quarterly health care charges in the treatment group declined by 53 percent (P less than 0.05). In contrast, the charges in the control group showed wide variations but no overall change. The quarterly charges in the control group were significantly higher than those in the treatment group (P less than 0.05). After the control group was crossed over to receive treatment, their quarterly charges declined by 49 percent (P less than 0.05). The reductions in expenditures in both groups were due largely to decreases in hospitalization. We conclude that psychiatric consultation in the care of patients with somatization disorder reduced subsequent health care expenditures without inducing changes in health status or patients' satisfaction with their health care.

Adult↗
PubMed1986

Immunologic responses following serial skin testing.

Twenty volunteers underwent intradermal skin testing with tetanus toxoid (TT) and varicella-zoster (VZ) antigens weekly for 7 weeks. In addition to measurements of delayed hypersensitivity skin test responses, in vitro antigen specific lymphocyte stimulation and antibody levels were monitored. Data for TT exhibited more variability than VZ, demonstrating a marked boost in antibody titers after the first skin test and a shift in the kinetics of the skin test reaction to later maximum responses after the first 3 weeks. In contrast, serial skin testing with VZ was not associated with changes in cellular immune assays. Following the initial VZ skin test there was a slight rise in antibody levels for one-third of studied individuals. These observations suggest that VZ skin test antigen is ideal for monitoring immune function and that repeated testing should not significantly influence in vitro assays.

Adolescent↗
PubMed1986

Observations on experimental inactivated vaccines for contagious bovine pleuropneumonia.

In two trials the efficacy of inactivated vaccines against contagious bovine pleuropneumonia was tested by exposing vaccinated cattle to droplet infection provided by close contact with experimentally infected 'donors'. Complete protection was given by an extreme form of vaccination in which a heavy suspension of killed Mycoplasma mycoides subsp. mycoides emulsified with Freund's complete adjuvant was given in two large doses. 'Mouse-protective antibody' (MPA) was also produced, i.e. serum transferred to mice 2-4 h before intraperitoneal challenge prevented the development of mycoplasmaemia. However, the study did not answer the question 'Is MPA protective for cattle?'. No protection was given by a milder form of vaccination in which a lighter suspension of killed mycoplasmas emulsified with Freund's incomplete adjuvant was given in a comparatively small dose on a single occasion.

Animals↗