Search PubMed⌕ Search

Biomedical subjects

I M Robinson

Publications and source records attributed to I M Robinson.

At least 37 records · Page 2Linked to original sources
PubMed1985

Construction of the mycoplasma evolutionary tree from 5S rRNA sequence data.

The 5S rRNA sequences of eubacteria and mycoplasmas have been analyzed and a phylogenetic tree constructed. We determined the sequences of 5S rRNA from Clostridium innocuum, Acholeplasma laidlawii, Acholeplasma modicum, Anaeroplasma bactoclasticum, Anaeroplasma abactoclasticum, Ureaplasma urealyticum, Mycoplasma mycoides mycoides, Mycoplasma pneumoniae, and Mycoplasma gallisepticum. Analysis of these and published sequences shows that mycoplasmas form a coherent phylogenetic group that, with C. innocuum, arose as a branch of the low G+C Gram-positive tree, near the lactobacilli and streptococci. The initial event in mycoplasma phylogeny was formation of the Acholeplasma branch; hence, loss of cell wall probably occurred at the time of genome reduction to approximately to 1000 MDa. A subsequent branch produced the Spiroplasma. This branch appears to have been the origin of sterol-requiring mycoplasmas. During development of the Spiroplasma branch there were several independent genome reductions, each to approximately 500 MDa, resulting in Mycoplasma and Ureaplasma species. Mycoplasmas, particularly species with the smallest genomes, have high mutation rates, suggesting that they are in a state of rapid evolution.

Base Sequence↗
PubMed1985

Nucleic acid relationships among the anaerobic mycoplasmas.

The genetic relatedness between twelve selected strains among four distinct serovars of anaerobic mycoplasmas was studied using [3H]DNA-DNA hybridization, and the results were compared with data obtained from biochemical and serological tests. Radiolabelled DNA probes were prepared from five strains representing four serovars. Based on the homology results, the anaerobic mycoplasmas can be divided into five distinct groups representing five distinct species and two distinct genera. There are two species in the Anaeroplasma bactoclasticum serovar 1 group represented by strains JR and A-2, one species in serovar 2, one species in A. abactoclasticum serovar 3 and one among the unclassified serovar 4 anaerobic mycoplasmas. The probe to nonsterol-requiring strain 161 of serovar 4 showed no homology with any of the established nonsterol-requiring Acholeplasma species DNAs, or with Mycoplasma hominis DNA, or with avian DNA which served as a negative control. There was good correlation between the phenotypic and genotypic properties of the five distinct anaerobic mycoplasma species but the results indicate that phenotypic properties are not always adequate for speciation of the anaerobic mycoplasmas.

Base Composition↗
PubMed1984

Cellulolytic bacteria from pig large intestine.

An anaerobic, cellulose-degrading, gram-negative rod and a gram-positive coccus, identified as Bacteroides succinogenes and Ruminococcus flavefaciens, respectively, were isolated from pig fecal samples. These organisms were isolated from cellulolytic most-probable-number dilutions which represented 4 or 6% of the viable bacterial count when pigs were fed a low- or high-fiber diet, respectively.

Animals↗
PubMed1984

Characterization of predominant bacteria from the colons of normal and dysenteric pigs.

Bacterial populations adherent to the mucosa of the proximal colons of weaned, healthy pigs were compared with populations from pigs with dysentery induced by inoculation with a culture of Treponema hyodysenteriae. Isolates (136) representative of the predominant flora adherent to colonic epithelia of normal pigs and isolates (162) from pigs with dysentery were cultured anaerobically on a rumen fluid-based medium and characterized. Most (71%) of the isolates from colonic epithelia of normal pigs were gram positive, whereas 88% of the epithelia-associated isolates from pigs with dysentery were gram negative. The geometric mean of colony counts was 5.7 X 10(7)/cm2 of colonic tissue from three normal pigs and 7.7 X 10(8)/cm2 from four pigs with dysentery. A number of isolates obtained from contents of the lumens of normal pigs with dysentery were also characterized. Comparison of isolates from epithelial tissue and from contents of the lumens of the same pig indicated that these populations were different. Our results indicate that physiological changes that occur in the colons of pigs with dysentery are accompanied by marked changes in the microbial populations in the colons. The factors which regulate the population changes are not yet understood.

Animals↗
PubMed1984

DNA characterization of the spirochete that causes Lyme disease.

Lyme disease, a tick-borne disease long recognized in Europe but only recently recognized in the United States, was shown in 1982-1983 to be caused by a spirochete, the Lyme disease spirochete. Whether one or more species of the spirochete exists is unknown, as is its taxonomic status. To answer these questions, we determined (i) the DNA base (guanidine-plus-cytosine) content for five strains; (ii) the DNA relatedness of 10 strains from Europe or the United States (isolated from ticks, humans, and a mouse) by DNA hybridization (hydroxyapatite assay at 50 and 65 degrees C); and (iii) the DNA relatedness to other pathogenic spirochetes. The guanine-plus-cytosine content of the Lyme disease spirochete strains was 27.5 to 29.0 mol%, most similar to those of Borrelia hermsii (30.6 mol%) and Treponema hyodysenteriae (25.6 mol%) among the other spirochetes tested. DNA hybridization studies with 32P-labeled DNA from Lyme disease spirochete strain TLO-005, a human blood isolate, revealed divergence (unpaired bases) within related nucleotide sequences of only 0.0 to 1.0% for all nine Lyme disease spirochete strains tested for relatedness to TLO-005. Relatedness values of seven strains to TLO-005 were 58 to 98% (mean, 71%) in 50 degrees C reactions and 50 to 93% (mean, 69%) in 65 degrees C reactions. Two other strains, from which very low yields of DNA were obtained, showed less relatedness (36 to 50 degrees C, 38 to 47% at 65 degrees C). These were nonetheless considered to belong to the same species because of the low amount of divergence in the sequences related to TLO-005 and the absence of decreased relatedness in reactions done at 65 degrees Celsius compared with those done at 50 degrees Celsius. DNA from strain TLO-005 showed relatedness of 1% to DNAs of two leptospires and 16% relatedness to DNA from T. hyodysenteriae. B. hermsii DNA was 30 to 40% related to three Lyme disease spirochete strains in 50 degrees Celsius reactions. Divergence in these reactions was 16.5 to 18.5%, and relatedness in 65 degree Celsius reactions was 8 to 10%. On the bases of phenotypic similarity, guanine-plus-cytosine content, and DNA relatedness to B. hermsii, we conclude the Lyme disease spirochete is single previously undescribed species which belongs in the genus Borrelia.

Animals↗
PubMed1983

Pathology of liver granulomas in turkeys.

Liver granulomas from five- and seven-week-old turkeys were studied by light and electron microscopy and by bacterial culture. Granulomas of five-week-old poults were composed of a caseous, necrotic center surrounded by consecutive zones of heterophils, giant cells, macrophages, and finally by lymphocytes. Tissue Gram and modified Dieterle stains demonstrated numerous gram-positive, filamentous bacteria in necrotic centers with radial extension of the bacteria to the zone of giant cells. Electron microscopic examination revealed septate, filamentous bacteria within an electron-dense milieu between heterophils, macrophages, and giant cells. An anaerobic, gram-positive bacillus and a staphylococcus were isolated from most granulomas examined. In broth, the bacillus formed long filaments or chains morphologically similar to those in tissue sections. The bacillus was identified tentatively as Eubacterium tortuosum. The staphylococcus had cultural reactions typical for Staphylococcus epidermidis. Intravenous inoculation of three-week-old poults with a mixture of E. tortuosum and S. epidermidis produced granulomas in liver and spleen and multiple mucosal ulcers in the duodenum and colon.

Animals↗
PubMed1981

Characterization of the cecal bacteria of normal pigs.

One hundred ninety-two isolates from cecal contents of three normal weaned pigs were obtained by means of anaerobic roll tube methods and were characterized. Seventy-eight percent of the isolates were gram-negative. The most numerous species isolated from each of the pigs was Bacteroides ruminicola. This species accounted for 35% of the isolates that were characterized, and Selenomonas ruminantium accounted for 21% of the isolates. Other gram-negative bacteria isolated from all three pigs were Butyrivibrio fibrisolvens (6.0%) and Bacteroides uniformis (3.0%); predominant gram-positive isolates were Lactobacillus acidophilus (7.6%), Peptostreptococcus productus (3.0%), and Eubacterium aerofaciens (2.5%). The other 42 isolates were placed in 14 other species, and 5 additional isolates that did not fit well into existing species were not placed taxonomically. Fifteen of the isolates (representing nine species) produced urease.

Animals↗
PubMed1981

Production of lesions in gnotobiotic mice by inoculation with Treponema hyodysenteriae.

Treponema hyodysenteriae was established in the ceca of gnotobiotic mice in the absence of other organisms. Superficial mucosal lesions characteristic of swine dysentery were present in the ceca of mice inoculated with T. hyodysenteriae in combination with viable Bacteroides vulgatus. Deep crypt necrosis was detected in the ceca of mice inoculated with T. hyodysenteriae alone.

Animals↗
PubMed1981

Acetate kinase activity in mycoplasmas.

Acetate kinase activity was assayed in 13 mycoplasmas. Nine species exhibited the enzymic activity in the direction of either synthesis of acetylphosphate or adenosine triphosphate. On the other hand Mycoplasma orale, Mycoplasma arthritidis, Ureaplasma urealyticum (10 serotypes), and two strains of Anaeroplasma species exhibited only minimal levels of the enzymic activity. In these four species, the enzyme does not seem to play a key role in adenosine triphosphate formation.

Acetate Kinase↗
PubMed1981

Muriel Driver Memorial Lecture 1981: the mists of time.

In honour of the fiftieth anniversary of the first "Convention" held by the Canadian Association of Occupational Therapists (CAOT) in 1931, a brief history of the founding of the CAOT and the early development of the profession in Canada is presented. The early beginnings and activities of the CAOT are traced from its conception during World War 1, through its formation in 1926 to its "coming of age" in 1966. Significant events in the growth of the Association and the practice of occupational therapy in Canada, and the Canadian influence on occupational therapy in Great Britain are outlined. Some issues relevant to yesterday and today are suggested.

Canada↗
PubMed1979

Comparison of bacterial populations of the pig cecum and colon based upon enumeration with specific energy sources.

Concentrations of bacteria in the ceca and colons of pigs were measured by determinations of colony counts on rumen fluid-based media in anaerobic roll tubes. With our most complete medium (medium CCA), the mean colony count of cecal samples from 20 pigs was 2.37 X 10(10) +/- 1.0 X 10(10) (+/- standard deviation)/g (wet weight). The mean number of bacteria attached to or associated with cecal epithelial tissues from three pigs on medium CCA was 2.67 X 10(7) +/- 0.81 X 10(7)/cm2 of tissue. The proportions of gut bacterial populations able to use various energy substrates were estimated on the basis of relative colony counts. The following substrates are listed in descending order of their capacity to support growth of cecal bacteria: glucose, starch, cellobiose, xylose, Trypticase, gastric mucin from swine, mannitol, glycerol, and lactate. The effect of diet upon this distribution was not examined. The relative proportions of bacteria from a given population that were able to grow on various selective media were used as population profiles. Comparisons of populations in this way indicated that differences could be detected between (i) populations from the cecum of littermate pigs, (ii) populations from the cecum and colon of the same pig, and (iii) populations in the lumen of the cecum as compared with populations associated with cecal mucosa.

Animals↗
PubMed1979

Pathogenic synergism between Treponema hyodysenteriae and other selected anaerobes in gnotobiotic pigs.

Gnotobiotic pigs were orally exposed to various anaerobes at 6 to 9 days of age and similarly inoculated with Treponema hyodysenteriae B204 3 to 6 days later. Watery diarrhea and fecal excretion of large quantities of mucus and some fibrin clots were observed 4 to 20 days after inoculation with B204 if other anaerobes were present. Colonic lesions characteristic of swine dysentery were observed when B204 was present with Fusobacterium necrophorum, three strains of Bacteroides vulgatus, a Clostridium species, and Listeria denitrificans individually and when some of these microbes were present in various combinations, but not when B204 was present alone. These results are consistent with the conclusion that T. hyodysenteriae is the primary pathogen in the etiology of swine dysentery and that the presence of one or more other anaerobes is a prerequisite for expression of pathogenicity of T. hyodysenteriae. This prerequisite can be met by a variety of anaerobes.

Anaerobiosis↗
PubMed1979

Synthesis of alpha-ketoglutarate by reductive carboxylation of succinate in Veillonella, Selenomonas, and Bacteriodes species.

Evidence for reductive carboxylation of succinate to synthesize alpha-ketoglutarate was sought in anaerobic heterotrophs from the rumen and from other anaerobic habitats. Cultures were grown in media containing unlabeled energy substrates plus [14C]succinate, and synthesis of cellular glutamate with a much higher specific activity than that of cellular asparate was taken as evidence for alpha-ketoglutarate synthase activity. Our results indicate alpha-ketoglutarate synthase functions in Selenomonas ruminantium, Veillonella alcalescens, Bacteroides fragilis, Bacteroides vulgatus, Bacteroides uniformis, Bacteroides distasonis, and Bacteroides multiacidus. Evidence for this carboxylation was not found in strains representative of 10 other species.

Amino Acids↗
PubMed1978

Swine dysentery: studies of gnotobiotic pigs inoculated with Treponema hyodysenteriae, Bacteroides vulgatus, and Fusobacterium necrophorum.

Transmission experiments were carried out in gnotobiotic pigs to determine whether lesions typical of swine dysentery could be produced by oral inoculation of Treponema hyodysenteriae in combination with Bacteroides vulgatus or Fusobacterium necrophorum, or both. Each of the organisms had been isolated from swine with early lesions of the disease. Lesions were not found in 6 pigs inoculated with T hyodysenteriae alone, in 4 pigs given F necrophorum and T hyodysenteriae, or in 4 pigs given B vulgatus and F necrophorum. Lesions typical of swine dysentery developed in 8 pigs given B vulgatus, F necrophorum, and T hyodysenteriae as well as in 3 of 4 pigs given B vulgatus and T hyodysenteriae. In both of these groups, the inoculated bacteria were recovered from the colon, and T hyodysenteriae was demonstrated in the colonic crypts, epithelium, and lamina propria. The pathogenicity of the T hyodysenteriae was shown by the development of characteristic signs and lesions of swine dysentery in 12 of 14 naturally farrowed pigs inoculated with T hyodysenteriae alone.

Animals↗
PubMed1975

Plasmalogen composition of Anaeroplasma.

The polar lipids of Anaeroplasma contained 33.1 percent alk-1'-enyl glyceryl ether (plasmalogen) form. Phosphatidylglycerol was the major polar lipid (55.2 percent) and contained nearly all of the plasmalogen. The alk-1'-enyl glyceryl ether form accounted for 58.3 percent of the phosphatidylglycerol.

Aldehydes↗
PubMed1975

Grain overload in cattle and sheep: changes in microbial populations in the cecum and rumen.

Samples from the rumen and cecum of cattle and sheep were cultured to determine changes in microbial populations resulting from overfeeding with grain. Before the animals were overfed, the predominant organisms from both sides were those that grew anaerobically on a relatively nonselective ruminal fluid medium and would not grow on selective mediums designed to culture lactobacilli, streptococci, coliforms, or Clostridium perfringens. By 24 hours after overfeeding, lactic acid bacteria had increased in numbers so that they were the most numerous organisms in both the rumen and the cecum. The concentrations of coliforms and C perfringens also increased after overfeeding and were generally higher in the cecum than in the rumen.

Animal Feed↗