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Biomedical subjects

J M Scott

Publications and source records attributed to J M Scott.

At least 127 records · Page 7Linked to original sources
PubMed1990

In vitro responses to Leishmania antigens by lymphocytes from patients with leishmaniasis or Chagas' disease.

T cell responses are correlated with recovery from and resistance to leishmaniasis. Antigens of Leishmania chagasi were evaluated by determining their ability to elicit in vitro proliferation and cytokine production in peripheral blood lymphocytes and in T cell lines and clones from patients with histories of leishmaniasis or Chagas' disease. Antigens tested were selected by their reactivity with patient antibodies. Several of the antigens induced proliferative responses in peripheral blood lymphocytes from patients recovered from visceral or cutaneous leishmaniasis or with chronic Chagas' disease. Two purified glycoproteins, 30 and 42 kD, were consistently among the most effective in eliciting high proliferative responses and IL-2 production. Lymphocytes from a recovered visceral leishmaniasis patient were used to produce T cell lines against either the 30- or 42-kD antigen. Each of the lines responded to both of these antigens as well as to crude leishmania lysate. CD4+ T cell clones specific for either or both of these antigens were also isolated from a visceral leishmaniasis patient. In contrast, rabbit antisera produced against these two antigens were not crossreactive. Both antigens were effective in inducing the production of IFN-gamma from T cell lines from both leishmaniasis and Chagas' disease patients. These studies demonstrate the potential for defining parasite antigens with broad immunostimulatory capabilities.

Animals↗
PubMed1990

An improved serodiagnostic procedure for visceral leishmaniasis.

The enzyme-linked immunosorbent assay (ELISA) is a sensitive and specific serodiagnostic method for leishmaniasis. In this report, we describe how this versatile assay can be improved by the use of protein A or protein G conjugates for the specific detection of Leishmania antibody in the sera of patients with visceral leishmaniasis. In direct comparisons with anti-immunoglobulin conjugate, enzyme-linked protein A gave significantly higher absorbance values for positive sera without a corresponding increase in absorbance values for sera from normal individuals or from patients with other diseases known to cross-react with leishmaniasis. The effect was to increase the distance between positive and negative values, which aided in the interpretation of the results. This also permitted visual distinction between positive sera and negative or weakly reactive sera. The assay was effective using either blood or serum as the source of primary antibody. A further advantage of protein A over anti-Ig conjugate was its ability to detect specific antibody in dog as well as human sera. Finally, we demonstrated the usefulness of the protein A ELISA with a recombinant leishmania antigen, gp63.

Animals↗
PubMed1990

Cryo-preservation of Lactobacillus leichmannii for vitamin B12 microbiological assay.

An optimised method for preparing cryo-preserved cultures of Lactobacillus leichmannii for vitamin B12 microbiological assay is described. Cultures are mixed with an equal volume of 800 ml/l sterile glycerol before freezing. The percentage recovery of viable cells after thawing is highest when cultures are enclosed in polystyrene insulation and cooled to -70 degrees C. Cells cryo-preserved in the stationary phase of growth have a higher percentage recovery after thawing, but the same numbers of log phase cells give a larger growth response to cyanocobalamin under assay conditions. Cryo-preserved cultures are stable for many months, giving consistency of standard curve shape. Results obtained for control sera are also more consistent over time, with a range of CV values from 2.58% to 4.82%, as compared to a range of 4.63% to 6.11% for control sera in assays using conventionally prepared fresh cultures. The use of large inocula also allows for assay completion after overnight incubation.

Biological Assay↗
PubMed1988

Methylation deficiency causes vitamin B12-associated neuropathy in the pig.

Pigs were treated with N2O which is known to impair vitamin B12 function in vivo. Such pigs demonstrated an inability to gain weight, progressive ataxia, and spinal neuropathy. The ataxia was totally and the neuropathy partially preventable by dietary methionine supplementation. Methionine synthase activity was inhibited in both the liver and brain. There was a marked elevation of S-adenosylhomocysteine in the neural tissues and a concomitant failure of S-adenosylmethionine to rise and thus maintain the methylation ratio, except when supplementary dietary methionine was added. In contrast, the methylation ratio in the rat was affected to a lesser extent. The neuropathy, it is suggested, is caused by raised S-adenosylhomocysteine levels in neural tissue; as a result, the methylation ratio is inverted and S-adenosylmethionine-dependent methylation reactions are inhibited.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1987

Microbiological assay for vitamin B12 with use of a colistin-sulfate-resistant organism.

In this simplified microbiological assay for serum vitamin B12, Lactobacillus leichmanii (NCIB 8117) adapted to tolerate high concentrations (500 mg/L) of the polymyxin antibiotic colistin sulfate is used. Results were similar in parallel experiments in which we used both the parent strain of L. leichmanii (NCIB 8117), and the new adapted strain. Evaluation of assay performance showed excellent analytical recovery of added cyanocobalamin (97%, SD 3%) and good interassay and intra-assay precision (CV less than 5%). This modified assay system obviates the need to sterilize culture medium and glassware. Consequently, assay manipulations may be carried out openly, without aseptic precautions. Moreover, this adapted organism would be suitable for use in an automated microbiological assay system.

Bacteriological Techniques↗
PubMed1987

Folate catabolism in normal subjects.

All official recommendations for folate tend to be far in excess of current estimated intakes. Several recent studies have highlighted this, showing satisfactory folate status in healthy populations consuming considerably less than official RDAs. This study takes a critical look at current RDAs for folate. We have recently developed an assay to quantify the end product of folate catabolism in human urine, thus affording the possibility of a more rational and scientific approach to setting the RDA for folate. Results of this study (now confirmed by further work) suggest that, under normal dietary conditions, the body appears to catabolize only about 100 micrograms total folate per day. Furthermore, this rate of catabolism remained relatively unchanged in response to saturating doses of a 5 mg folic acid supplement over several days. It is therefore most unlikely that our diet is as seriously deficient in folate as current official RDAs seem to imply.

Adult↗
PubMed1986

A long-term study following Bennett's fracture.

Twenty-five patients with documented Bennett's Fractures were reviewed five to sixteen years following injury (Mean 9.6 years). The majority of fractures affected the dominant hand and occurred in males. Twenty-two patients were managed conservatively by plaster immobilisation. At review ten patients were asymptomatic and only two had significant symptoms. Examination revealed loss of movement in the trapeziometacarpal joint of the thumb in twenty-one cases. Five of these exhibited malrotation of the thumb. Review of the post reduction radiographs revealed separation of the fragments by 1 mm or more in sixteen patients, but symptoms at follow-up could not be correlated with accuracy of reduction. Twenty-three patients had a varus angulation of the first metacarpal base which could be correlated to the initial post-reduction displacement. There was no correlation with the restriction of movement. Although metacarpal length will only be maintained by reduction of the fracture, there was little evidence that imperfect reduction leads to significant symptomatic arthritis in the long term.

Adolescent↗
PubMed1985

The effect of ethanol consumption on folate polyglutamate biosynthesis in the rat.

Contrary to previous studies, the folate polyglutamate chain length in the rat liver appears to be unaffected by ethanol ingestion for periods of 2-13 weeks. The appearance of short chain length folates after 13 weeks has been shown to arise as a result of increased in vitro folate polyglutamate breakdown during extraction due to a greater release of lysosomal conjugase in these animals.

Animals↗
PubMed1985

Demonstration of methionine synthetase in intestinal mucosal cells of the rat.

Methionine synthetase was measured in the mucosal cells of the rat duodenum, jejunum and ileum by a previously employed method for mucosal cell isolation. No activity was found in these cells. When a dual buffer system for the isolation of villous and crypt cell population was substituted, however, methionine synthetase was found to be active in the duodenum, jejunum and ileum, both in the villous and crypt cell populations. The activity was significantly higher in the crypt cells than in the villous cells throughout the intestine, and higher levels were found in the ileum than in the duodenum or jejunum. As had been previously reported for the rat liver, nitrous oxide in vivo reduced the enzyme activity in both the villous and crypt cell populations, suggesting a role in vivo for the enzyme. We conclude that methionine synthetase is both present and active in the small intestinal mucosal cells of the rat.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1985

Maternal serum folate and vitamin B12 concentrations in pregnancies associated with neural tube defects.

Serum folate and vitamin B12 concentrations in early pregnancy were compared for 32 mothers with pregnancies affected by neural tube defects and 395 randomly selected pregnant control women from the same maternity hospitals. No significant differences were found between the affected mothers and the controls in the median values and frequency distributions of either vitamin. Sixteen of the samples from mothers whose infants had neural tube defects were taken between 9 and 13 weeks' gestation and 11 of these had both serum folate and vitamin B12 concentrations within the normal ranges for our laboratory. These findings are discussed in relation to the concept of folate deficiency as a major factor in the aetiology of neural tube defects.

Female↗
PubMed1985

Antioxidant modulation of phacoanaphylactic endophthalmitis.

Catalase treatment reduces the expected inflammation in experimental phacoanaphylactic endophthalmitis. Catalase is a scavenger of hydrogen peroxide and presumably protects against the cytolytic effects of reactive oxygen metabolites. Recent work indicates that oxygen-derived free radicals may play a critical role in the early tissue damage in immune complex disease.

Animals↗
PubMed1984

Acute Trypanosoma vivax infection of Ethiopian cattle in the apparent absence of tsetse.

Investigations of acute trypanosomiasis in a group of 1,200 cattle provided strong evidence for mechanical transmission by haematophagous flies other than tsetse. Although recently introduced cattle may have had previous contact with tsetse flies the incident occurred in an area remote from their known range. Mortality exceeded 6% before the outbreak was controlled by chemotherapy. Mechanically transmitted Trypanosoma vivax infection may be of widespread occurrence in eastern Ethiopia.

Acute Disease↗