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Biomedical subjects

G R Smith

Publications and source records attributed to G R Smith.

At least 271 records · Page 15Linked to original sources
PubMed1983

Immunogenic variation among the so-called LC strains of Mycoplasma mycoides subspecies mycoides.

Much evidence of immunogenic heterogeneity among the LC strains of Mycoplasma mycoides ssp. mycoides emerged from cross-immunization and -hyper-immunization experiments in mice in which three LC strains (Vom/Plum Island, 74/2488, and Mankefår 2833) were used for challenge purposes. All heterologous LC-strain vaccines cross-immunized against the three challenge strains, but protection was usually only 'partial', i.e. significantly less than that given by homologous vaccine. Cross-hyperimmunization with all heterologous LC but not SC strains produced protection against challenge with Vom/Plum Island that was virtually 'complete', i.e. similar to that produced by homologous vaccine. Challenge with 74/2488 gave generally similar results; but against Mankefår 2833 six heterologous LC vaccines gave complete protection and six did not. Vaccines prepared from the Smith (1423) strain of M. mycoides ssp. capri gave some protection against Vom/Plum Island but none against 74/2488 or Mankefår 2833. The cross-immunizing ability of three further M. mycoides ssp. capri strains appeared to resemble that of Smith (1423). In a cross-hyperimmunization experiment, vaccines prepared from SC strains of M. mycoides ssp. mycoides varied greatly in their ability to protect against challenge with strains 74/2488 and Mankefår 2833.

Animals↗
PubMed1983

Psychologically mediated effect on the delayed hypersensitivity reaction to tuberculin in humans.

Recent research with animals has indicated a central nervous system effect on the immune system. This report describes findings of a possible psychologically mediated effect on the delayed hypersensitivity reaction to tuberculin in humans. Seven tuberculin positive subjects evidenced a decreased response to tuberculin (as measured by erythema and induration) when a paradigm similar to behavioral conditioning was followed where the subjects expected their reactions to be negative.

Conditioning, Psychological↗
PubMed1983

Escherichia coli RecBC pseudorevertants lacking chi recombinational hotspot activity.

Pseudorevertants of an Escherichia coli exonuclease V (RecBC enzyme)-negative mutant have been isolated after ethyl methane sulfonate mutagenesis of a recC73 (presumed missense) mutant. The remedial mutations in each of the four pseudorevertants studied in detail map and complement as recC mutations. By several criteria, such as recombination proficiency, support of phage growth, RecBC nuclease activity, and cell viability, the pseudorevertants appear to have regained partially or completely various aspects of RecBC activity. However, chi recombinational hotspots, which stimulate exclusively the RecBC pathway of recombination, have no detectable activity in lambda vegetative crosses in the pseudorevertants. The properties of these mutants, in which the RecBC pathway of recombination is active yet in which chi is not active, are consistent with the hypothesis that wild-type RecBC enzyme directly interacts with chi sites; alternatively, the mutants may block or bypass the productive interaction of another recombinational enzyme with chi.

Coliphages↗
PubMed1983

Alexithymia in medical patients referred to a consultation/liaison service.

Seventy-three medically ill patients referred to a consultation/liaison service over a 4-month period were evaluated for alexithymia. Twenty-two (30%) of these patients had alexithymia. Age, race, and marital status were not associated with alexithymia scores. Patients in lower socioeconomic groups and men had significantly higher scores than their counterparts. The idea that alexithymia is prevalent in individuals with a diagnosis of a "psychosomatic disease" was not supported.

Affective Symptoms↗
PubMed1982

Clostridium botulinum type C in the Mersey estuary.

Nineteen of 98 samples of mud or sand taken from the Mersey estuary in 1981 contained Clostridium botulinum type C, the organism almost always responsible for botulism in water birds. In the Dungeon and Score Bank areas, where many dead and dying birds were found during the period September-December 1979, almost half the samples contained type C. Most of the positive samples were essentially muddy rather than sandy. The findings do not prove that botulism contributed to the 1979 mortality but are nonetheless thought-provoking, particularly because type C--unlike type B--is by no means ubiquitous in Britain. Type B was present in 12.2% of samples from the Mersey estuary.

Animals↗
PubMed1982

Some in-vitro characters of the subspecies of Mycoplasma mycoides.

So-called LC strains of Mycoplasma mycoides subsp. mycoides and, where appropriate, SC strains, were examined, together with M. mycoides subsp. capri strains, by growth, fermentation, and antibiotic-sensitivity tests. Growth curves in BVF-OS medium showed that, from the 6th until at least the 19th day of incubation, strain Mankefår 2833 had a viable count strikingly higher than that of any other LC strain. Its robust growth properties may explain its ability--unusual among LC strains--to produce mycoplasmaemia readily in mice. Strain 143-A66 Conn, also shown by earlier experiments in mice to possess unusual properties, lost viability more rapidly than any other LC strain between the 13th and 19th days of incubation. The viable count of a subsp. capri strain was considerably lower than that of any LC strain for much of the period between days 6 and 19. In fermentation tests with 27 substrates and sensitivity tests with 11 antibiotics the strains gave results that, in all but the following respects, were uniform. Sorbitol was fermented to varying degrees by all the LC and subsp. capri strains tested but was unaffected by the SC strains. The LC and subsp. capri strains were in general more resistant than the SC strains to streptomycin. The growth of the LC strains, much more than that of the other strains, was greatly stimulated by the presence of fermentable substrate.

Fermentation↗
PubMed1981

Structure of chi hotspots of generalized recombination.

Chi recombinational hotspots are sites around which the rate of Rec-promoted recombination in bacteriophage lambda is elevated. Examination of a derivative of lambda into which the plasmid pBR322 was inserted reveals that pBR322 lacks Chi sites. Using this lambda-pBR322 hybrid, we obtained mutations creating Chi sites at three widely separated loci within pBR322. Nucleotide sequence analysis reveals that the mutations are single base-pair changes creating the octamer 5' GCTGGTGG 3'. This sequence is present at three previously analyzed Chi sites in lambda, and all analyzed mutations creating or inactivating these Chi sites occur within this octamer. We conclude that Chi is 5' GCTGGTGG 3', or its complement, or both.

Bacteriophage lambda↗
PubMed1981

The ability of Mycoplasma mycoides subspecies mycoides and closely related strains from goats and sheep to immunize mice against subspecies capri.

Small colony (SC) strains of Mycoplasma mycoides subsp. mycoides from contagious bovine pleuropneumonia (CBPP) and from goats were compared with large colony (LC) strains of so-called M. mycoides subsp. mycoides from goats and sheep by means of a cross-protection test in which mice were challenged with M. mycoides subsp. capri. Of 13 LC strains, all gave partial cross-protection, and 11 were shown to be more closely related than four SC strains to subspecies capri. In a further experiment, six SC strains--three from CBPP and three from goats--all gave weak partial cross-protection against subspecies capri.

Animals↗
PubMed1981

Observations on the antigenic differences between the so-called SC and LC strains of Mycoplasma mycoides subsp. mycoides.

The so-called SC (small colony) and LC (large colony) strains of Mycoplasma mycoides subsp. mycoides are said to be indistinguishable by the in vitro serological tests of generally used in mycoplasmology. In mice the immunity given by a single dose of killed LC-strain vaccine against challenge with SC strains is - unlike that given by SC-strain vaccine - only partial. When multiple doses of killed or living vaccines were given, the majority of 13 LC strains still failed to immunize completely against a SC strain. This suggests that, although some protective antigens are shared between both types of strain, at least one of importance is present in the SC strains but absent from the majority of LC strains. The difference between the protective-antigen content of SC and most LC strains is thus qualitative, and not merely quantitative.

Animals↗
PubMed1981

Nucleotide sequence of the chi recombinational hot spot chi +D in bacteriophage lambda.

Chi sites in bacteriophage lambda stimulate recombination promoted by the RecBC pathway of Escherichia coli. Mutations which create these sites occur at four widely separated loci in lambda. We report here the nucleotide sequence surrounding the site of one of these loci, chi D, located near the S gene. The mutations creating the active Chi site, designated chi +D, are transversions from CG to AT. This mutation, like the chi +B and chi +C mutations previously analyzed, leads to a nucleotide sequence common to all three active chi sites.

Bacteriophage lambda↗