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Biomedical subjects

J Montgomery

Publications and source records attributed to J Montgomery.

At least 55 records · Page 3Linked to original sources
PubMed1996

Reduced conception rates in dairy cattle associated with serological evidence of Leptospira interrogans serovar hardjo infection.

Fertility data from 673 cows in five dairy herds with a moderate to high seroprevalence of microscopic agglutination titres (MAT) of > or = 1:10 against Leptospira interrogans serovar hardjo were collated to assess the relationship between pregnancy rates and antibody titres to serovar hardjo. A significant proportion of failures of conception (10 to 13 per cent, P < 0.001) were associated with MATs of 1:10 to 1:100; the overall pregnancy rate of the seronegative cows was 28.5 per cent higher (P < 0.001) than that of the cows with MATs of > or = 1:100. First service pregnancy rates showed a similar trend but the differences were significant (P < 0.05) only in cows with antibody titres > or = 1:30. An assessment of other possible risk factors for reduced pregnancy rates, such as lactation number and calving to first service interval, had no effect on the statistical results of the study or its conclusions.

Animals↗
PubMed1996

Immunization with granulocyte-macrophage colony-stimulating factor-transduced, but not B7-1-transduced, lymphoma cells primes idiotype-specific T cells and generates potent systemic antitumor immunity.

Recently, genetically modified tumor cell vaccines have been described for nonhematopoietic cancers in which the relevant Ags are unknown. Several of these cell-based vaccine strategies have been shown to induce T cell-mediated systemic antitumor immunity, either by enhancing the processing and presentation of tumor Ags by host APCs or by facilitating effective Ag presentation by the tumor vaccine itself. These strategies were compared in a model B cell lymphoma, a tumor derived from APCs, which have the inherent capacity to activate Ag-specific T cells. Eradication of pre-established systemic lymphoma was achieved following immunization with lymphoma cells engineered to produce granulocyte-macrophage (GM)-CSF, and to a lesser extent cells producing IL-4, whereas vaccination with lymphoma cells transfected with the genes encoding IL-2 or B7-1 had no effect. The systemic immunity generated by GM-CSF- or IL-4-transfected lymphoma required both CD4+ and CD8+ T cells. Previous immunotherapeutic strategies for the treatment of lymphoma have focused on the generation of Ab responses targeted to the unique Ig Id as a tumor-specific Ag. Anti-idiotypic Abs were undetectable in animals vaccinated with GM-CSF-transduced lymphoma cells. In contrast, such immunization did result in the induction of Id-specific T cell responses. This is the first demonstration that T cell responses specific for a native tumor Ag are generated by GM-CSF-transduced tumor cell-based vaccination, suggesting that B cell lymphoma may be a suitable disease for genetically modified tumor vaccine strategies.

Animals↗
PubMed1996

In vivo hydroxylation of the neurotoxin, 1-methyl-4-phenylpyridinium, and the effect of monoamine oxidase inhibitors: electrospray-MS analysis of intra-striatal microdialysates.

The neurotoxin 1-methyl-4-phenylpyridinium (MPP+) has been shown to increase hydroxyl radical formation in the striatum. The production of hydroxyl radicals correlates with the MPP(+)-driven dopamine release which presumably leads to increased metabolism via monoamine oxidase or increased dopamine autoxidation. Both processes result in enhanced production of hydrogen peroxide, which in the presence of iron(II) ions decomposes to the hydroxyl radical. Monoamine oxidase inhibitors decrease the production of hydroxyl radicals as measured by salicylate and 4-hydroxybenzoate trapping. As both MPP+ and monoamine oxidase inhibitors, such as deprenyl and MDL-72,974A, possess aromatic rings, hydroxyl radical adduct formation was investigated in vitro in defined Fenton systems and also in vivo using intra-striatal microdialysis to infuse MPP+ to rats pretreated systemically with either deprenyl or MDL-72,974A. Electrospray mass spectrometric analysis, using full-scan, fragment ion and constant neutral loss spectra, demonstrated ring hydroxylation of all three compounds in the Fenton systems. Spectral comparison of microdialysis samples with spectra from the Fenton reactions indicated the in vivo hydroxyl radical adduct attachment to MPP+, deprenyl and possibly MDL-72,974A.

1-Methyl-4-phenylpyridinium↗
PubMed1996

Presence of antigen and antibodies in serum and genital discharges of heifers after experimental intrauterine inoculation with Leptospira interrogans serovar hardjo.

The excretion of Leptospira interrogans serovar hardjo in cervico-vaginal mucus (CVM) or urine and the local and systemic immune responses to the organism were monitored in eight susceptible heifers after intrauterine inoculation while six similar heifers served as controls. All the heifers were inseminated at the subsequent oestrous periods. The overall percentage pregnancy rate (the number of pregnancies divided by the total number of inseminations) was lower in the infected heifers than in the controls though not significantly (33.3 v 50.0 per cent). Leptospires were detected, in either the urine or the CVM of six of the eight infected heifers during the study period of 15 weeks, either by direct immunofluorescence or dark ground microscopy; the bacteria did not grow in culture from any of the CVM samples. The control heifers remained free from evidence of infection. In the infected heifers, mean titres of at least 1:100 in a microscopic agglutination test were maintained for one to two weeks before declining to 1:10 to 1:30, whereas in serum IgG-ELISA tests (developed by using either protein or carbohydrate antigens), antibody titres of at least 1:100 were maintained throughout the study. During oestrous periods, IgA antibodies were detected more frequently in CVM with titres which were usually higher than the titres of IgG.

Agglutination Tests↗
PubMed1996

Presence of antigen and antibodies in serum and genital discharges of cows from dairy herds naturally infected with Leptospira interrogans serovar hardjo.

Samples of cervico-vaginal mucus from 163 bulling cows (group 1) and post calving discharges from 59 newly calved cows (group 2) in five dairy herds naturally infected with Leptospira interrogans serovar hardjo were examined for the presence of antigen and IgG and IgA antibodies by using two ELISA systems which were protein or carbohydrate based. Corresponding serum samples were examined for systemic immune responses by using a microscopic agglutination test (MAT) and IgG-ELISA tests. Antigen was detected by direct immunofluorescence in six of the 163 samples of cervico-vaginal mucus. Both IgG and IgA antibodies were detected by ELISA in the genital discharges with a prevalence much higher than that obtained by the MAT but lower than that observed with the serum IgG-ELISA. Combining both groups, none of the MAT-positive cattle was negative by serum-ELISA. By using the protein or carbohydrate fraction serum IgG-ELISA assays, respectively, 29 or 41 per cent of the MAT-negative cows were positive at a titre of at least 1:40. Similarly, eight or 23 samples (10 or 27 per cent) had titres of at least 1:20 in the genital discharge ELISA for IgG and IgA antibodies, respectively. The serum IgG-ELISA was the most efficient in detecting hardjo antibodies, but in group 2 the IgG- and IgA-ELISA of the post calving discharge proved to be equally effective.

Animals↗
PubMed1996

Hindbrain signal processing in the lateral line system of the dwarf scorpionfish Scopeana papillosus

Recordings were made from primary afferent fibres and secondary projection neurones (crest cells) in the mechanosensory lateral line system of the dwarf scorpionfish. Crest cells were identified by antidromic stimulation from the contralateral midbrain. Differences between primary afferent fibre and crest cell response characteristics are indicative of signal processing by the neuronal circuitry of the medial octavolateralis nucleus. There are a number of differences between primary afferent fibres and crest cells. Primary afferents have relatively high levels of spontaneous activity (mean close to 40 impulses s-1) and many of them are strongly modulated by ventilation. By contrast, crest cells have a much lower rate of spontaneous activity that is not obviously modulated by ventilation. Primary afferents show a simple tonic response to a maintained stimulus, whereas crest cells show a variety of temporal response properties, but in general show a phasic/tonic response to the same prolonged stimulus. Afferents are most sensitive to frequencies of stimulation around 100 Hz; in contrast, crest cells show a strong suppression of activity at this frequency. Crest cells are most responsive around 50 Hz. These afferent/secondary comparisons show similarities with those reported for allied electrosensory and auditory pathways.

Journal Article↗
PubMed1996

A case-control study of diet in newly diagnosed NIDDM in the Wanigela people of Papua New Guinea.

OBJECTIVE--To study the association between diet and newly diagnosed NIDDM in the Wanigela people of Papua New Guinea, a population with an extraordinary susceptibility for NIDDM. RESEARCH DESIGN AND METHODS--We performed a case-control study of Wanigela people from an urban settlement (Koki). Case patients (n = 145) were asymptomatic subjects in whom NIDDM was newly diagnosed using a 2-h 75-g oral glucose tolerance test. Control subjects with glucose tolerance (n = 140) were group-matched on the basis of age and sex. A detailed food frequency questionnaire was used to determine energy and nutrient intakes. Nutrient intakes were compared directly and after calculation of residuals to correct for energy intake. Odds ratios for NIDDM were computed in relation to total energy and specific nutrient intakes, adjusting for age, sex, BMI, waist-to-hip ratio, and physical activity. RESULTS--There were no differences between case patients and control subjects in mean values of total energy-adjusted nutrient intakes. In logistic regression models, neither total energy nor any specific nutrients were associated with increased risk of NIDDM. When models were repeated with nutrients categorized by textiles, there were marginally significant associations with intakes of fiber (positive) and cholesterol, protein, and sugar (negative). CONCLUSIONS--This study does not support the hypothesis that saturated fat is an independent risk factor for NIDDM. The weak associations of intakes of fiber and cholesterol with newly diagnosed NIDDM were in the opposite directions to those expected and are probably due to chance. Relative homogeneity of diet within a community, such as that found in Koki, makes it difficult to demonstrate risk factor-disease associations. However, changes in diet and reduced levels of physical activity accompanying urbanization undoubtedly contribute to the high prevalence of obesity observed in this community, and hence diet is likely to contribute to NIDDM risk at least by indirect means.

Adult↗
PubMed1995

Hydroxylation of aromatic compounds as indices of hydroxyl radical production: a cautionary note revisited.

While setting up an intracerebral microdialysis system to estimate the extent of oxidative stress induced by the neurotoxin, N-methylphenylpyridinium ion (MPP+), we encountered a problem in the use of hydroxybenzoic acids as traps of hydroxyl radicals. Using either 2-hydroxybenzoate (salicylate) or 4-hydroxybenzoate as trapping agents, we observed a nonspecific, that is, nontissue derived, production of hydroxyl radicals as measured by the hydroxylation products, 2,3- and 2,5-dihydroxybenzoate from 2-hydroxybenzoate and 3,4-dihydroxybenzoate from 4-hydroxybenzoate. This production of dihydroxybenzoates was 10 times that expected due to the administration of MPP+, thus making it impossible to interpret our results. Careful investigation of the various components of the microdialysis system indicated that contact of the microdialysate with metal surfaces resulted in dihydroxybenzoic acid formation. These results should serve as a reminder to perform stringent tests of the experimental system prior to experiments with biological tissues to evaluate the contribution of hydroxyl radical production from nonbiological sources. Therefore, along with the possibility of enzymatic production of dihydroxybenzoates, artefactual production by components of the experimental apparatus must be considered before assuming that one is measuring hydroxyl radical production by a biological system.

1-Methyl-4-phenylpyridinium↗
PubMed1995

Environmental design, work, and well being: managing occupational stress through changes in the workplace environment.

The physical environment can be an important contributor to occupational stress. Factors that contribute to stress and other negative outcomes include: lack of control over the environment, distractions from coworkers, lack of privacy, noise, crowding, and environmental deprivations (such as lack of windows and aesthetic impoverishment). The design of "salutogenic" environments requires not only the elimination of negative stress inducing features, but also the addition of environmental enhancements, including such factors as increased personal control, contact with nature and daylight, aesthetically pleasing spaces, and spaces for relaxation alone or with others. Salutogenic environments also take into consideration positive psychosocial "fit," as well as functional fit between people and environments. At the heart of the current interest in the work environment are two major concerns: organizational productivity and employee well being.

Burnout, Professional↗
PubMed1995

A method for isolation and partial purification of Trichinella spiralis nurse cells.

Invasion of vertebrate muscle cells by larvae of Trichinella spiralis is accompanied by redifferentiation of the host myofiber into a novel structure called the nurse cell. The nurse cell protects and nurtures the enclosed parasite during its long stay in host muscle. It is anatomically independent of the surrounding uninfected muscle cells and can be isolated from host tissue by mechanical or enzymatic means. Current methods employed for this purpose have yielded only small numbers of nurse cells. An apparatus designed to isolate large numbers of nurse cells and a method for removal of all free larvae and most host muscle debris is described. Homogenization and trypsin digestion of muscle tissue was followed by passage of muscle/parasite suspensions maintained at 37 C through a jacketed glass column fitted with a 40-mesh stainless steel screen at the top and a Nitex screen with 150-microns-diameter pores at the bottom. Nurse cells were retained by the Nitex screen. Density gradient centrifugation using Percoll removed all free larvae and most contaminating muscle debris from nurse cell suspensions. The large quantities of nurse cells made available by this method will allow evaluation of the molecular biology, nutrition, biochemistry, and metabolism of the enclosed parasite and of the Trichinella-modified host muscle cell.

Animals↗