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Biomedical subjects

M B Brown

Publications and source records attributed to M B Brown.

At least 145 records · Page 8Linked to original sources
PubMed1987

Reproductive refractoriness of the ewe to inductive photoperiod is not caused by inappropriate secretion of melatonin.

The 24-h pattern of melatonin secretion was evaluated in Suffolk ewes during prolonged exposure to an inductive photoperiod to assess whether altered secretion of melatonin could account for the eventual loss of response to stimulatory photoperiod (photorefractoriness). Secretory patterns of melatonin were determined approximately every two weeks in samples obtained hourly for 24-48 h. Sampling was begun one week before the switch from inhibitory (long) to inductive (short) photoperiod and continued for 150 days, by which time all but one of the ewes were unresponsive to that stimulatory day length. Melatonin was measured in two different radioimmunoassay systems. Reproductive state was monitored by luteinizing hormone secretion in ovariectomized ewes bearing constant-release estradiol implants. No evidence for disruption of the melatonin pattern was observed on any occasion. The duration and the phase of the melatonin elevation relative to the light/dark cycle did not vary with time of exposure to short days. These findings indicate that refractoriness of the Suffolk ewe to an inductive photoperiod is not caused by an inappropriate secretory pattern of melatonin.

Animals↗
PubMed1986

Prevalence of urinary incontinence and other urological symptoms in the noninstitutionalized elderly.

The prevalences of urinary incontinence, difficulty in bladder emptying and irritative bladder symptoms are not known in the noninstitutionalized elderly in this country. A survey, consisting of a multi-stage probability sample of 13,912 households, was done in Washtenaw County, Michigan to estimate these prevalences. A total of 1,955 senior citizens 60 or more years old was interviewed. The prevalences of urinary incontinence, difficult bladder emptying and irritative bladder symptoms were 18.9, 22.1 and 11.8 per cent, respectively, in men, and 37.7, 10.8 and 17.4 per cent, respectively, in women. Urinary incontinence was significantly more prevalent among all respondents with bladder emptying and irritative symptoms than those without such symptoms (p less than 0.001). The frequency of voiding was significantly increased among respondents with incontinence, or emptying or irritative symptoms compared to asymptomatic respondents (p less than 0.001). These survey data are of importance to senior citizens, care providers and governmental agencies.

Aged↗
PubMed1984

Effect of four primary prostaglandins and relaxin on blood flow in the ovine endometrium and myometrium.

The effect of the prostaglandins (PG) D2, E2, F2 alpha and I2 (infusions of 250 ng/min for 10 min into the uterine artery) and relaxin (1 microgram/min) on uterine contractions and on the myometrial and endometrial blood flow to the uterus of ovariectomized, estrogen-primed ewes was investigated. The 85Kr clearance method was used to measure blood flow. PGD2 and PGI2 increased both myometrial and endometrial capillary blood flow, whereas PGE2 and relaxin did not. PGF2 alpha reduced the myometrial blood flow only at a significance level of P less than 0.1 but induced no significant changes in the endometrial flow. PGE2, PGF2 alpha and, notably, PGD2 caused a uterine hypertonus. PGI2 and relaxin did not affect the uterine motility. There is a parallel effect of the investigated substances on the blood flow of myometrium and endometrium but PGD2 induces contractions of the smooth muscle cells in the myometrium while relaxing comparative cells in blood vessels.

Animals↗
PubMed1984

Immunoglobulin A1 protease activity in strains of Ureaplasma urealyticum.

Thirteen serovars of Ureaplasma urealyticum were analyzed for the ability to cleave human IgA. Strains of all of the serovars tested cleaved IgA 1 in the hinge region of the alpha-chain, resulting in intact Fc and monomeric Fab fragments. IgA 1 protease activity was also observed in concentrated cell-free extracts of spent cultivation medium, indicating that the IgA 1 protease was excreted into the medium during growth of the micro-organisms. Five clinical isolates of U. urealyticum obtained from urine, cervix, vagina, amniotic fluid, and synovial fluid were positive for IgA 1 protease activity. No proteolytic activity was observed against human IgA 2, IgG, or IgM. Strains of Mycoplasma fermentans, M. salivarium and seven serovars of M. hominis were negative for IgA 1 protease activity.

Immunoglobulin A↗
PubMed1984

Identification of cross-reactive antigens between Mycoplasma pulmonis and Mycoplasma arthritidis.

Serological cross-reactivity between Mycoplasma pulmonis and Mycoplasma arthritidis was investigated by enzyme-linked immunosorbent assay, immunoanalysis of electrophoretic blots, and protein A immunoprecipitation reactions. The results demonstrate that one-way cross-reactivity was present in both hyperimmunized and naturally infected rats and that the predominant cross-reactive antigens were M. pulmonis surface proteins. Distinct immunoblot patterns were demonstrated for M. pulmonis and M. arthritidis, allowing differentiation of the two species. The response to M. arthritidis antigens during natural infections differed greatly from that during hyperimmunization. Evidence suggested that nonprotein antigens were major determinants eliciting the antibody response to this mycoplasma.

Antigens, Bacterial↗
PubMed1984

A prospective study of mycoplasma infection in the preterm infant.

The nasopharyngeal aspirates of 235 infants admitted to the neonatal intensive care unit over a 14-month period were tested for the presence of Ureaplasma urealyticum and Mycoplasma hominis. Serological studies were carried out on 41 infants. U. urealyticum was isolated from 53 (22%) babies and was not associated with illness. There was a significant association between U. urealyticum colonization and preterm birth, low birth weight and prolonged rupture of membranes (PROM). M. hominis was isolated in six babies (2.6%). Three of these developed an immune response; in two of these pneumonia was seen. M. hominis may be a cause of pneumonia in the preterm infant.

Antibodies, Bacterial↗
PubMed1983

Measurement of antibody to Ureaplasma urealyticum by an enzyme-linked immunosorbent assay and detection of antibody responses in patients with nongonococcal urethritis.

The optimum conditions for the detection of human immunoglobulin G (IgG), IgM, and IgA antibodies to Ureaplasma urealyticum by an enzyme-linked immunosorbent assay (ELISA) were established by using a cell lysate antigen and commercially available alkaline phosphatase conjugates. No significant cross-reactions were observed among rabbit antisera to a variety of mycoplasmas of human origin and ureaplasma antigen, thus demonstrating the specificity of the ELISA. All human sera were assayed at a 1:200 dilution. Antigen was used at 20 mug of protein/ml and conjugates were diluted 1:500. Presence of IgG antibody to U. urealyticum was significantly associated with isolation of U. urealyticum (P < 0.001) in 110 women. Seventeen acute-phase and 19 convalescent-phase sera from male nongonococcal urethritis (NGU) patients were tested for the presence of antibody by both the metabolism inhibition assay and by ELISA, with overall agreements of 82 and 95% for acute- and convalescent-phase sera, respectively. Serum antibody responses were demonstrated to selected serotypes in the metabolism inhibition test, but the response as measured by the ELISA was independent of the serotype of the antigen used. Serum antibody levels in NGU patients were significantly higher (P < 0.002) than the normal serum standard in the IgG, IgM, and IgA classes. Additionally, the magnitude of change between acute- and convalescent-phase sera was greater for NGU patients than for normal asymptomatic ureaplasma-positive male controls. A significant change in antibody levels of one or more antibody classes was detected for 12 of 18 (67%) NGU patients by ELISA. Ten of the 12 (83%) individuals had a change in the IgM class, which is suggestive of an active infectious process. The ELISA is advantageous in that it requires only a single serotype antigen, uses one serum dilution, is class specific, and allows quantitative detection of differences between acute- and convalescent-phase sera.

Antibodies, Bacterial↗
PubMed1983

Feature-positive effect in adults and attention to portion of stimulus array.

In three experiments, adult humans were tested in a feature-positive or feature-negative simultaneous symbol task. In Experiment 1, some persons focused on the correct side of the stimulus cards, whereas other persons focused on the not-correct side of the stimulus cards. The feature-positive group learned faster than the feature-negative group did in the correct side condition; the feature-negative group learned faster than the feature-positive group did in the not-correct side condition. In Experiments 2 and 3, all persons focused on both the correct and not-correct sides of the stimulus cards. Under these circumstances, feature-positive and feature-negative performances were comparable. These results indicated that the usual superiority of feature-positive over feature-negative learning results from a tendency to attend to only a portion of the stimulus array.

Attention↗
PubMed1983

Association of genital mycoplasmas with exudative vaginitis in a 10 year old: a case of misdiagnosis.

A 10-year-old girl with a 1-year history of lower genitourinary tract symptoms suggestive of bacterial infection but with numerous negative urine cultures was referred to the University of Alabama urology clinic after empirical treatment with multiple antibiotics failed to resolve her symptoms. An extensive urologic evaluation revealed no structural or physiologic abnormalities, but an exudative vaginitis was noted and large numbers of Ureaplasma urealyticum and Mycoplasma hominis were isolated from the lower genital tract. Cultures for Chlamydia, viruses, and routine bacterial pathogens were negative. After initiation of tetracycline therapy, symptoms resolved and subsequent cultures for mycoplasmas were negative. In addition, a seroconversion was noted for M hominis but not for U urealyticum. Chlamydia serology was negative. It was later learned that the patient had been sexually molested just prior to the onset of symptoms. This case illustrates the necessity of early consideration of a mycoplasmal etiology in the patient with persistent genitourinary symptoms and no obvious bacterial pathogen, or in the patient whose condition is refractory to routine antibiotic therapy.

Child↗
PubMed1983

Discussion of statistical methods for determining purity of citrus juice.

It is difficult to develop statistical methods to determine the purity of fruit juice because of country-to-country and environmental differences among fruit. A test of an unknown sample of citrus juice can err in 2 ways: Pure juice can mistakenly be rejected as adulterated, or adulterated juice can be accepted as pure. Many of the statistical procedures proposed may misclassify a high proportion of samples of pure juice as adulterated. It is necessary to develop a statistical test that will only rarely reject samples of pure juice, and will have a good chance of rejecting adulterated juice.

Beverages↗
PubMed1982

Murine respiratory mycoplasmosis in F344 and LEW rats: evolution of lesions and lung lymphoid cell populations.

By comparison of two strains, LEW and F344, which are known to differ in susceptibility to Mycoplasma pulmonis respiratory disease, it was shown that differences in lesion severity and progression were associated with changes in lung lymphocyte populations. Lung lesions in LEW rats developed earlier after infection, became more severe, and were characterized by continued proliferation of all classes of lymphoid cells, T lymphocytes, B lymphocytes, and plasma cells, throughout the 120-day observation period. In contrast, lymphoid proliferation in F344 rats reached a plateau at 28 days and was restricted to an increase in T lymphocytes, immunoglobulin A (IgA)-bearing B lymphocytes, and IgA and IgG plasma cells. Although approximately 10 times as many IgG B cells and 4 times as many IgG plasma cells were found in infected LEW rats as compared with F344 rats, the specific anti-M. pulmonis IgG response in the two strains was roughly parallel. The same relationships held true, although to a lesser extent, for specific IgA antibody responses and cellular responses. Whereas lung lesions showed a tendency to resolve in F344 rats by 120 days, severe lesions persisted in LEW rats. The disparity between the cellular response and specific antibody response, the seemingly uncontrolled lymphocyte proliferation in LEW rats, and the mitogenic potential of M. pulmonis suggest that differences between LEW and F344 rats in lung lesion severity and progression are related to differences in the degree of nonspecific lymphocyte activation in the two strains, an imbalance in regulation of lymphocyte proliferation in LEW rats, or both.

Animals↗
PubMed1981

Comparison of methods for detection of Mycoplasma pulmonis in experimentally and naturally infected rats.

Isolation, indirect immunofluorescence, an enzyme-linked immunosorbent assay (ELISA), and histopathological examination of tissues for characteristic lesions were evaluated for their efficiency in detecting Mycoplasma pulmonis infection in rats. Whereas all of the methods were efficient in naturally infected Sprague-Dawley rats, none of the methods consistently detected infection in F344 rats experimentally infected with low doses of the organism. In the experimental infections, however, the success rate of any method was directly related (P less than 0.05) to increasing inoculum dose and time postinoculation. Collectively, the data indicated that isolation of M. pulmonis was the most efficient single detection method and the nasopharyngeal duct was the best single site to culture, although sampling of multiple sites within the respiratory tract increased the rate of isolating the organism. The ELISA was understandably the least sensitive method in the low-dose, experimentally infected rats because of the time required for development of a detectable serum antibody response. Although each of the four methods identified a high percentage of naturally infected rats, the ELISA was the most efficient method in these animals as it was uniformly positive. The use of combinations of methods was found to increase the rate of detection of M. pulmonis infection in both experimentally and naturally infected rats.

Animals↗
PubMed1981

Infant pneumonitis associated with cytomegalovirus, Chlamydia, Pneumocystis, and Ureaplasma: a prospective study.

In a prospective study of 104 infants between 1 and 3 months of age hospitalized with pneumonitis, 65 (63%) had evidence of infection with one or more potential respiratory pathogens. Single infections were noted in 48 (74%) whereas mixed infections occurred in 17 (26%) of 65 infected infants. The four most common infections were Chlamydia trachomatis (15/59, 25%), Ureaplasma urealyticum (8/38, 21%), cytomegalovirus (21/104, 20%), and Pneumocystis carinii (19/104, 18%). In sharp contrast, the incidence of these infections in control infants was 0% (0/25), 4% (2/49), 3% (3/97), and 0% (0/64), respectively. The clinical, radiologic, and laboratory characteristics of the pneumonitis syndrome associated with Chlamydia, cytomegalovirus, and Pneumocystis were indistinguishable from each other. Patients with mixed infections had a more severe pneumonitis as measured by the occurrence of apnea and the need of oxygen therapy an mechanical ventilation. The patients enrolled in this study are being followed-up to determine the longitudinal course of these infections.

Chlamydia Infections↗
PubMed1981

Detection of natural Mycoplasma pulmonis infection in rats and mice by an enzyme linked immunosorbent assay (ELISA).

A total of 2,194 rats and mice representing 10 rat and nine mouse strains from eight commercial breeding facilities and 19 research institutions were tested for Mycoplasma pulmonis antibodies of the IgG and IgM classes by an enzyme-linked immunosorbent assay (ELISA). Cultural data also were obtained from 1,139 of these animals and histopathological data from 410. Reliability of the IgG ELISA for detection of infection in rats and mice was found to be excellent. Virtually no rat or mouse colony was culturally negative and IgG ELISA positive, or vice versa. However, discrepancies between ELISA and cultural results were observed in individual animals. Discrepancies occurred significantly more often with the IgM than IgG ELISA and more so in mice than in rats, particularly in barrier-maintained animals. Agreement of the IgG and IgM ELISA with culture in barrier-maintained rats was 100% and 94%, respectively and in barrier-maintained mice 87% and 69%, respectively. Available evidence suggested that some of the discrepancies in mice could be due to either active or previous low level infection or failure to culture multiple sites. However, the greatly reduce correlation of the IgM ELISA and culture in mice was incompletely understood, and in the absence of other evidence of infection must be interpreted with caution. Even though the present study was not designed to determine comprehensive incidence figures, the results indicated widespread Mycoplasma pulmonis infection both in conventional and "barrier-maintained" colonies as demonstrated by ELISA a well as cultural isolation.

Animals↗