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Biomedical subjects

R C Johnson

Publications and source records attributed to R C Johnson.

At least 361 records · Page 20Linked to original sources
PubMed1981

Evidence for two cholesterol ester hydrolases in human cerebrospinal fluid.

In the present study, the properties, such as pH optima, detergent requirement, and effects of various lipids, of cholesterol ester hydrolase in human cerebrospinal fluid (CSF) were examined, and the activity levels of the enzyme in CSF from multiple sclerosis (MS) patients and non-MS individuals were compared. Our data indicate that the enzyme in CSF exhibits two pH optima: pH 6.0 in the presence of Triton X-100 and pH 7.0 in the presence of sodium taurocholate. Both phosphatidylethanolamine (PE) and phosphatidylserine (PS) enhanced the hydrolase activity at pH 6.0. The activity at pH 7.0, on the other hand, was enhanced slightly in the presence of PE but was inhibited in the presence of PS. These data suggest the presence of two cholesterol ester hydrolases in CSF and also indicate that the activity at pH 6.0 may be due to microsomal enzyme in brain and that at pH 7.0 may be due to myelin enzyme. The hydrolase activity at pH 7.0 was significantly lower in CSF from MS patients. The activity at pH 6.0 in CSF from MS and non-MS patients, however, did not differ significantly. This indicates that the reduction in pH 7.0 hydrolase activity in CSF may be related to demyelination.

Carboxylic Ester Hydrolases↗
PubMed1981

In vivo evidence that an intact lytic complement pathway is not essential for successful removal of circulating Borrelia turicatae from mouse blood.

Complement component C5-deficient mice were found to be able to eliminate blood-borne Borrelia turicatae as effectively as normocomplementemic control animals. The absence of C5 and the resultant loss of hemolytic complement activity were confirmed for the deficient mouse strains used. Immunofluorescent staining of complement component C3 on blood-derived borreliae could be readily accomplished as early as 2 days before spirochetal elimination from all mice tested. These observations would suggest that C3 deposition was occurring, even though the terminal lytic steps were blocked in the complement-deficient mice. We propose that spirochetolysis is not requisite for successful removal of borreliae from the circulation of mice.

Animals↗
PubMed1981

Surface colonies of Leptospira interrogans.

Observations of colonial growth of Leptospira interrogans serovar pomona, BJ, on soft-agar (1% agar) plates revealed the presence of both surface and subsurface colonies. The organisms from both types of colonies appeared to be similar in motility, morphology, antigenic composition, and pathogenicity. Passage in vivo tended to produce a higher incidence of surface colonies, whereas passage in vitro tended to produce a higher incidence of subsurface colonies, suggesting the importance of environmental factors in determining the type of colony produced.

Antigens, Bacterial↗
PubMed1981

Intranasal vaccination of dogs with liver avirulent Bordetella bronchiseptica: correlation of serum agglutination titer and the formation of secretory IgA with protection against experimentally induced infectious tracheobronchitis.

Dogs inoculated intranasally with a live avirulent Bordetella bronchiseptica vaccine were monitored for the development of resistance to experimentally induced infectious tracheobronchitis (canine cough). Dogs were challenge exposed with a virulent strains of B bronchiseptica at various times after they were vaccinated. Clinical protection was detectable as early as 48 hours. At postvaccination days 4, 5, and 14, 56%, 83%, and 95% protection was observed. Humoral immunoglobulin (Ig) titers ranged from 1:8.6 on day 0 to 1:147 on postvaccination day 21. In the monitoring of B bronchiseptica-specific secretory IgA by indirect immunofluorescence, titers appeared as early as day 4 after vaccination. The IgA titers ranged from 1:16 on day 4 to 1: 1,024 on day 21. The appearance of IgA titers correlated with the development of resistance to clinical infection.

Administration, Intranasal↗
PubMed1980

Effects of alpha-methylphenylalanine plus phenylalanine treatment during development on myelin in rat brain.

The effects of hyperphenylalaninemia induced by treatment with alpha-methylphenylalanine (MPA) plus phenylalanine (PHE) on body and brain weight, on myelin and synaptosome formation, and on the lipids and fatty acids of myelin were studied in rats. The administraton of MPA (2.4 mumol/g body wt) plus PHE (2.6 mumol/g body wt) for 25 and 35 days beginning on the fifth postnatal day did not affect brain development. On doubling the dosage of PHE, body and brain weights and myelin yields were significantly lowered. The lipid composition of myelin from the brains of treated animals was largely unaffected; however, the concentration of sulfatides ws significantly reduced. Unsaturated fatty acid levels in myelin from hyperphenylalaninemic rat brains were reduced while long-chain fatty acids were unaffected. We conclude that as in hyperphenylalaninemia induced by other methods, MPA + PHE treatment impairs body and brain growth, reduces myelin formation, and causes inhibition of fatty acid desaturation in the brain.

Age Factors↗
PubMed1980

Reported lactose tolerance of members of various racial/ethnic groups in Hawaii and Asia.

Subjects from various racial/ethnic groups in Hawaii and homeland Chinese, Japanese, and Koreans reported on their milk drinking in childhood and adulthood, as well as on whether or not milk drinking produced symptoms of intolerance. Intolerance was comparatively infrequent in all groups, although significant differences existed between groups in the frequency with which they manifested symptoms and in discomfort scores. Differences between Hawaiian subjects of Asian ancestry and homeland Asians in the frequency of reported symptoms, in mean discomfort scores, and in amount of milk needed to produce symptoms, as well as the high proportion of symptomatology among Hapa-Haoles (persons of Caucasian and Oriental ancestry) and other data reported herein, are not supportive of the usual genetic explanation of lactose tolerance and are supportive of the belief that dietary practice influences tolerance.

Adult↗
PubMed1980

Family resemblances in serum uric acid level.

There is substantial relation between individuals serum uric acid level and their heights and weights. Even when the association of uric acid level with height/weight is partialed out, significant resemblances in uric acid level are found between biologically related persons (parents and offspring; siblings) but not between spouses. When the association of height/weight is partialed out, uric acid level does not have a significant association with measures of cognitive ability or with educational or occupational attainment.

Body Height↗
PubMed1980

Influence of testicular fluid infected with Treponema pallidum on intradermal lesions.

A viscous mucoid fluid occasionally accumulates after intratesticular inoculation of rabbits with Treponema pallidum. Experiments were performed to assess the effects of this testicular fluid on the development of syphilitic lesions. Intramuscular injections of this fluid altered host defences as indicated by shorter incubation periods, by reactivation of healing lesions, and by the presence of lesions at a time when solid immunity should have developed.

Animals↗
PubMed1980

Sulfhydryl oxidation using procedures and experimental conditions commonly used for Treponema pallidum.

Certain reducing agents containing sulfhydryl groups are important to the in-vitro survival of Treponema pallidum. Discrepancies occur, however, concerning the agents and the concentrations that are optimal. To clarify some of this confusion, sulfhydryl oxidation was determined using procedures and experimental conditions commonly used for T pallidum. Sulfhydryl oxidation varied according to the type of culture medium, the size of the culture vessels, the volume of the culture medium, and the gaseous environment within the culture vessels, as well as the method of extracting treponmes from infected testicular tissue. Dithiothreotol maintained highly reduced conditions by reducing disulfide groups to sulfhydryl groups. Lastly, the organisms influenced the sulfhydryl concentration by either direct oxidation or specific uptake. The sulfhydryl content was sharply decreased in the presence of viable preparations of T pallidum compared with heated preparations or membrane filtrates of viable preparations.

Animals↗
PubMed1980

Morphologic study of cultured pancreatic fetal islets during maturation of the insulin stimulus-secretion mechanism.

We recently described a tissue culture system in which 21.5-day-old fetal rat islets underwent an in vitro maturation of insulin stimulus-secretion coupling over a period of 7 days. During the same period, the acinar part of the explanted fragments degenerated and the islets became isolated, seeming to increase in mass. In the present study, we have utilized these characteristic morphologic changes in an attempt to evaluate the extent that apparent islet growth reflects multiplication of preformed beta cells or the neogenesis of these cells from ductular or acinar cells. In the first days of culture, continuity between islets and ducts could be demonstrated, and the islets appeared to "bud" from the ducts. During this time, only insulin- and glucagon-positive cells could be demonstrated immunocytochemically, and the 3H-thymidine incorporation index of the beta cells (expressed as the percentage of beta cells labeled during 24 h or exposure to 3H-thymidine and 3 h of "chase") in the "budding" islets was 28.7 +/- 2.6. After 7 days in culture, i.e., after maturation of the insulin stimulus-secretion mechanism, the islets were no longer associated with ductular epithelium. At this stage, insulin-, glucagon-, and occasional somatostatin-positive islet cells could be demonstrated, and the 3H-thymidine incorporation index of the beta cells was significantly decreased to 16.7 +/- 2.8. These observations are taken to support previous suggestions of a possible neogenesis of beta cells from duct epithelium in the rat. This tissue culture technique appears well suited for further detailed studies of this neogenesis.

Animals↗