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Biomedical subjects

J McLaughlin

Publications and source records attributed to J McLaughlin.

At least 145 records · Page 8Linked to original sources
PubMed1985

Activation of a heat-stable cytolytic protein associated with the surface membrane of Naegleria fowleri.

Surface membrane-enriched fractions of Naegleria fowleri obtained after isopycnic centrifugation experiments contain a potent cytolytic activity as determined by hemolysis and 51Cr release assays. This surface membrane cytolysin was unaffected by a treatment at 75 degrees C for 30 min and accounted for 70 to 90% of cytolysis by whole-cell lysates of amoebae. This heat resistance as well as intimate membrane association distinguished the surface membrane cytolytic activity from a second heat-labile cytolytic activity which appears to be latent within lysosomes. The surface membrane cytolysin was found to be specifically activated by diluted samples of lysosomal fractions. The possible role of this surface membrane cytotoxin in the pathogenicity of N. fowleri is discussed.

Amoeba↗
PubMed1985

Subcellular distribution of hydrolases in Naegleria fowleri.

The presence and particle association of various hydrolytic enzymes in Naegleria fowleri has been studied in whole cell extracts of trophozoites in an effort to establish authentic markers for surface membrane and lysosomal components. Evidence from the experiments reported here indicates that in N. fowleri a) acid proteinase, N-acetylglucosaminidase, and acid phosphatase are associated with cytoplasmic granules closely resembling lysosomes; b) 5'-nucleotidase is associated with the surface membrane, probably on the external surface; c) aspartate aminotransferase is associated with mitochondria; d) alpha-D-glucosidase and an aminopeptidase have bimodal distributions, activity being associated with both the surface membrane and lysosomal particles.

5'-Nucleotidase↗
PubMed1984

Evidence for lipid-protein interactions in the attachment of antigens to a low-density membrane fraction isolated from Trypanosoma rhodesiense.

A putative Trypanosoma rhodesiense flagella pocket membrane fraction (FPM) was previously found to possess a range of antigenic components that were released after exposure to a detergent mixture containing 0.1% Zwittergent 3-12 and 0.4% Triton X-100. In the present investigation, and effort was made to determine the role of membrane lipid in binding FPM antigens, using phospholipases A2 and C as membrane probes. Exposure to the former was notable for the release of one antigen in particular that was only poorly extracted with the above detergents. Evidence was obtained suggesting that this release was not due to the detergent action of degradation products formed by the action of phospholipase A2 on membrane phospholipids. This phospholipase-released antigen, as were most other FPM antigens, was a glycoprotein, although the carbohydrate sequences do not appear to influence antigenicity. It was also possible to demonstrate the presence of a group of three cross-reacting FPM antigens that partitioned as hydrophobic membrane proteins by using Triton X-114 extraction. This was in contrast to the predominantly hydrophilic nature of most other FPM antigens.

Animals↗
PubMed1984

A multicomponent hemolytic system in the pathogenic amoeba Naegleria fowleri.

A hemolytic activity associated with postnuclear supernatant fractions of Naegleria fowleri has been partially characterized in an attempt to isolate cytolytic molecules that may participate in naeglerial cytopathogenicity. Hemolysis by naeglerial postnuclear supernatant fractions was sensitive to heat and trypsin hydrolysis, and was inhibited by divalent cations. The majority of the hemolytic activity was nonlatent and associated with a particle fraction sedimenting at 48,000 X g (maximum) for 1 h. This particle-associated hemolytic activity appears to be membrane associated, as high salt concentration, chelating agents, and pH extremes were ineffective in solubilizing the hemolytic activity, whereas treatment with 0.15% Zwittergent 3-12, a dipolar ionic detergent, results in 98% release of the sedimentable hemolysin. The sigmoidal nature of the progress curve of postnuclear supernatant hemolysis, as well as synergistic interactions between fractions of amoebal whole cell extracts, suggests that the hemolytic activity has a multicomponent nature, with at least two and possibly three components participating in the hemolytic event. The significance of these findings in the context of naeglerial cytopathogenicity is discussed.

Amebiasis↗
PubMed1984

Midazolam for upper gastrointestinal endoscopy.

A water-soluble benzodiazepine, midazolam, was used in 400 patients undergoing upper gastrointestinal endoscopy, alone or in combination with pentazocine and compared with 68 patients given diazepam (Valium). In the last 200 patients the endoscopist used midazolam without the presence of an anaesthetist. The absence of injection pain was the most notable feature of midazolam. The degree of co-operation was similar in all groups but the operating conditions were significantly better when midazolam was combined with pentazocine. There was no significant difference in recovery times between the groups as assessed by the pegboard test. Midazolam is an acceptable alternative to diazepam for upper gastrointestinal endoscopy.

Adult↗
PubMed1983

Importance and accuracy of bone age ratings in a computerized growth evaluation system.

Bone age ratings according to Greulich and Pyle and to Tanner and co-workers (RUS) of 88 children from two pediatric endocrine centers were compared with ratings from 2 trained technicians and independent ratings from a consulting pediatric endocrinologist. Considering the mean of all ratings as 'true bone age', the mean errors of the individual estimations were small (0.15-0.38 years for the Greulich and Pyle method, 0.12-0.27 years for the method according to Tanner and co-workers). Only in 2 of 338 ratings were differences larger than 1 year observed. In these 2 cases, there was marked dissociation between the maturation of carpal and phalangeal bones. It is concluded that estimations of bone maturation can be carried out reliably by properly trained technicians.

Age Determination by Skeleton↗
PubMed1982

Subcellular distribution of particle-associated antigens in Trypanosoma rhodesiense.

Bloodstream forms of the African trypanosome Trypanosoma rhodesiense were subjected to analytic cell fractionation procedures using isopycnic sucrose gradient centrifugation. The fractions obtained were analyzed using fused rocket immunoelectrophoresis, which revealed the most antigenic components to be associated with particles sedimenting between density increments of 1.10 to 1.15 and 1.20 and 1.22. From the distribution of various marker enzymes and the fluorogenic label fluorescamine, these particle populations were identified as derived from flagella pocket and surface membrane, respectively. Crossed immunoelectrophoresis of postulated flagella pocket and surface membrane fractions demonstrated at least seven and 10 distinct antigens, respectively, with only limited cross-reactivity. On the basis of crossed affini-immunoelectrophoresis four to five of each of these membrane antigens were glycoproteins, being precipitated in a concanavalin A-containing gel. Of the various detergent treatments used, it was found that optimum extraction of these glycoprotein antigens was achieved using the zwitterionic detergent Zwittergent 3-12 (0.1%) in the presence of 0.4% Triton X-100. Fused rocket immunoelectrophoresis also revealed a single prominent antigen associated with a particle population having an equilibrium density of approximately 1.180, which was identified as lysosomal from the distribution of marker enzymes. Other intracellular sites were not significantly antigenic.

Acid Phosphatase↗
PubMed1981

A calcium regulated adenosine triphosphatase in Entamoeba histolytica.

Axenically grown trophozoites of Entamoeba histolytica (NIH-200 strain) contain an active ATPase (170 nmol PO4/min per mg protein) with maximal activity at pH 8.8, a high affinity for ATP (Km approximately 40 micro M) and an absolute and specific requirement for Ca2+. The activation by Ca2+ shows positive cooperativity (nH = 2.48) at calcium concentrations below 8 micro M and no cooperativity between 8 and 25 micro M. The latter concentration fully saturates the enzyme. The observed activity is insensitive to oligomycin, ouabain and ruthenium red and is unaffected by a range of inhibitors of electron transport and uncouplers of oxidative phosphorylation. The enzyme exhibits structure bound latency and is tightly bound to cellular membranes. It is sedimentable ( greater than 80%) by high speed centrifugation of cell homogenates which are either protected osmotically or in which subcellular structures are damaged by sonication or treatment with Triton X-100. Arrhenius plots of V in the temperature range of 0-38 degrees C are linear without breaks, similar to other pyrophosphatases of E. histolytica. The calculated activation energy is 14.8 kcal/mol. This finding as well as the failure of phospholipase treatment to affect activity indicate that interactions with membrane lipids play no role in the catalytic function of this tightly membrane-bound ATPase.

Animals↗
PubMed1981

Cancer induction following single and multiple exposures to a constant amount of vinyl chloride monomer.

Vinyl chloride monomer (VCM), already identified as a human animal carcinogen, was selected as a model agent to explore an area of concern for single and intermittent low level exposure. In traditional cancer bioassay, animals are repeatedly exposed over their lifespan to a dose of suspected chemical. In the current studies rats and mice were exposed in an inhalation chamber to single one-hour doses of VCM ranging from 50 to 50,000 ppm. A second group was given 10 one-hour exposures to 500 ppm or 100 one-hour exposures to 50 ppm of the same chemical. All animals were then observed for the remainder of their lives, generally 18-24 months. Moribund animals were euthanized, and survivors were sacrificed on schedule and their tissues examined for pathological changes. Specifically, the oncogenic study demonstrated dose related effects for single one-hour exposure of VCM at high levels, i.e., 5,000 and 50,000 ppm. These concentrations increased the incidence of pulmonary adenomas and carcinomas in mice. Repeated exposure of A/J mice to the same chemical at 500 ppm X 10 one-hour exposures also increased the incidence of pulmonary adenomas and carcinomas which are considered highly one-hour exposure, no significant increase in tumors was observed. Rats exposed to identical concentrations of VCM failed to elicit a tumorigenic response.

Adenoma↗
PubMed1980

Immuno-histological diagnosis of lymphoproliferative diseases by selected combinations of antisera and monoclonal antibodies.

Tissue sections of frozen biopsy specimens obtained from normal and hyperplastic human lymphoid tissues, 33 cases of non-Hodgkin lymphomas as well as various forms of immunoregulatory disorders (angioimmunoblastic and dermatopathic lymphadenopathy) were analysed in immunofluorescence tests (using red TRITC and green FITC double-labelling). A panel of antisera including well-characterized conventional reagents to immunoglobulin classes, T lymphoid and Ia-like antigens, and monoclonal antibodies was used. In selected cases the results were compared with the observations of membrane-marker staining on viable cells in suspension. the findings show that the immunological methods can give a very accurate analysis of the normal and malignant lymphoid cells, and can provide complementary information to conventional histology. The investigator can choose the reagent combinations which give answers to various specific questions: e.g. antisera to light chains establish the monoclonality of lymphomas, whilst staining combinations for human T and Ia-like antigens are particularly useful in various immunoregulatory disorders. Monoclonal antibodies will be particularly useful in various immunoregulatory disorders. Monoclonal antibodies will be particularly useful reagents for analysing the tissue distribution of lymphoid subpopulations and ancillary cells in tissue biopsy specimens.

B-Lymphocytes↗
PubMed1980

Randomized trial of high- and low-dose ampicillin therapy for treatment of severe dysentery due to Shigella dysenteriae type 1.

To establish optimal therapy for severe dysentery due to Shigella dysenteriae type 1 and Shigella flexneri, we compared in a prospective randomized trial two oral ampicillin doses (50 and 150 mg/kg per day) in 57 children and 39 adults in Dacca, Bangladesh. Clinical failure did not occur in either group, indicating that conventional doses need not be increased even in severe disease. Among children 3 years of age or under, bacteriological relapses tended to be more frequent in the low-dose group and were not related to serum levels of ampicillin, nutritional status, or the severity of colitis on admission. Therefore, we recommend that younger children be treated with 100 mg/kg per day of oral ampicillin.

Administration, Oral↗