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Biomedical subjects

J Bonner

Publications and source records attributed to J Bonner.

At least 19 recordsLinked to original sources
PubMed1995

Activated T cells of nonneural specificity open the blood-nerve barrier to circulating antibody.

Recent studies from our laboratory and by other investigators have shown that autoreactive CD4+ cells specific for peripheral nerve P2 protein have a powerful effect on blood-nerve barrier permeability. In this study we injected CD4+ T cells reactive to a nonneural antigen (ovalbumin) systemically and achieved their accumulation in the tibial nerve of Lewis rats by previous intraneural injection of ovalbumin. Selected rats were given systemic demyelinating antibody (antigalactocerebroside) to provide an indicator of changes in the permeability of the blood-nerve barrier, and the animals were monitored by sequential neurophysiological studies and histology. Circulating ovalbumin-specific T cells accumulated at sites of intraneural ovalbumin injection without inducing demyelination in control animals. In rats with circulating galactocerebroside antibodies, local conduction block and demyelination were seen in the region of T-cell accumulation. Electron microscopy demonstrated dissolution of some tight junctions between endothelial cells in areas of T-cell accumulation, and T cells traversing the endothelium between endothelial cells and through their cytoplasm. Endothelial cell damage was evident in these areas. This study demonstrates breakdown of the blood-nerve barrier by activated T cells, even of nonneural specificity, allowing the development of focal conduction block and demyelination in the presence of circulating antimyelin antibodies.

Action Potentials↗
PubMed1992

Characterization of platelet-derived growth factor and platelet-derived growth factor receptor expression in asbestos-induced rat mesothelioma.

Although altered expression of platelet-derived growth factor (PDGF) is a hallmark of human mesothelioma, expression of PDGF receptors has not been characterized in this cell type. In addition, the expression of this growth factor and its cognate receptor in rodent mesothelioma has not been investigated. In this study, examination of transformed mesothelial cells derived from asbestos-induced rat mesotheliomas revealed that these cells expressed high affinity PDGF receptors (Kd = 0.5 nM) and receptor number was 1.6 x 10(5)/cell. Western analysis using antibodies specific for either the alpha-type or beta-type PDGF receptor and Northern analysis using probes specific for alpha- and beta-type receptor RNA transcripts indicated that these cells expressed beta-type PDGF receptors but that alpha-type receptors could not be detected. However, when the mesothelioma-derived cells were examined for the expression of PDGF, no expression of this growth factor could be detected. The transformed cells expressed no detectable A- or B-chain PDGF RNA transcripts; and using a competitive enzyme immunoassay specific for isoforms containing the B chain of PDGF and a sandwich enzyme-linked immunosorbent assay specific for A-chain-containing isoforms, neither AA, nor AB, nor BB isoforms of this growth factor could be detected in medium conditioned by these cells. The absence of alterations in PDGF expression in rat mesothelioma, in contrast to the data for the human disease, suggests that the production of this growth factor by transformed mesothelial cells may be species specific.

Animals↗
PubMed1992

Interactions between CD4+ T-cells and rat Schwann cells in vitro. 1. Antigen presentation by Lewis rat Schwann cells to P2-specific CD4+ T-cell lines.

Interactions between CD4+ P2-specific T-cell lines and Schwann cells were examined in vitro by scanning electron microscopy (SEM) and T-cell proliferation studies. CD4+ T-cell lines clustered around and attached to Schwann cells which expressed Major histocompatibility complex (MHC) class II molecules. Only those P2-specific T-cell lines capable of inducing experimental allergic neuritis (EAN) when injected into adult Lewis rats clustered around the Schwann cells. T-cell lines responsive to P2 but not able to induce EAN did not cluster around Schwann cells. The addition of exogenous P2 protein inhibited in a dose-dependent way clustering and proliferation of the P2-specific T-cell lines. Cytoplasmic P2 was detected in Schwann cells by immunofluorescent labelling and the results of proliferation assays in this study suggest that endogenous P2 protein was processed by the Schwann cells and presented to T-cell lines in association with MHC class II molecules. The clustering and proliferation of class II-restricted CD4+ P2-specific T-cell lines in the presence of Schwann cells provides evidence for a role for Schwann cells as facultative antigen presenting cells, processing and presenting 'self' endogenous antigen to CD4+ T-cell lines capable of inducing EAN.

Animals↗
PubMed1992

Interactions between CD4+ T-cells and rat Schwann cells in vitro. 2. Cytotoxic effects of P2-specific CD4+ T-cell lines on Lewis rat Schwann cells.

The cytotoxic effects of CD4+ P2-specific T-cell lines on Schwann cells were examined in vitro with 51Cr-release cytotoxicity assays. Only those P2-specific T-cell lines capable of inducing EAN when injected back into adult Lewis rats were cytotoxic to the Schwann cells. The addition of exogenous P2 protein was not necessary for the cytotoxic effect. The monoclonal antibody (mAb) OX6 directed against Major histocompatibility complex (MHC) class II molecules blocked cytotoxicity, indicating an essential role for MHC class II molecules in this interaction between CD4+ T-cell lines and Schwann cells.

Animals↗
PubMed1991

Self-reported eating disorders of black, low-income adolescents: behavior, body weight perceptions, and methods of dieting.

This study identified black, low-income adolescents who thought they had anorexia nervosa or bulimia nervosa, identified behaviors common to those who thought they had the disorders, and compared their actual and perceived body weight as well as methods of dieting. Of the 1,930 students in grades 7-12 who participated, about 12% thought they might have an eating disorder. These students also reported having food-related behaviors similar to individuals with eating disorders and which differed significantly from those reported by their peers. Gender was more likely to affect food behavior than age. Though most students were within their expected weight range, those with self-reported eating disorders perceived themselves to be heavier more often than their peers and when their actual weights were compared, they were more likely to weigh more. Of those who had dieted to lose weight, fasting was the most frequently reported restrictive method used.

Adolescent↗
PubMed1991

Transcriptional activation in an improved whole-cell extract from Saccharomyces cerevisiae.

We report an improved in vitro transcription system for Saccharomyces cerevisiae. Small changes in assay and whole-cell extraction procedures increase selective initiation by RNA polymerase II up to 60-fold over previous conditions (M. Woontner and J. A. Jaehning, J. Biol. Chem. 265:8979-8982, 1990), to levels comparable to those obtained with nuclear extracts. We have found that the simultaneous use of distinguishable templates with and without an upstream activation sequence is critical to the measurement of apparent activation. Transcription from any template was very sensitive to the concentrations of template and nontemplate DNA, extract, and activator (GAL4/VP16). Alterations in reaction conditions led to proportionately greater changes from a template lacking an upstream activation sequence; thus, the apparent ratio of activation is largely dependent on the level of basal transcription. Using optimal conditions for activation, we have also demonstrated activation by a bona fide yeast activator, heat shock transcription factor.

Base Sequence↗
PubMed1991

Microwave assisted staining of nerve and muscle biopsy tissue.

This paper reports a technique using microwaves to assist penetration of stains into biopsy sections of muscle and peripheral nerve. The technique results in more consistent and reliable staining of tissue sections for examination by light microscopy.

Biopsy↗
PubMed1986

Involvement of the 5'-leader sequence in coupling the stability of a human H3 histone mRNA with DNA replication.

Two lines of evidence derived from fusion gene constructs indicate that sequences residing in the 5'-nontranslated region of a cell cycle-dependent human H3 histone mRNA are involved in the selective destabilization that occurs when DNA synthesis is terminated. The experimental approach was to construct chimeric genes in which fragments of the mRNA coding regions of the H3 histone gene were fused with fragments of genes not expressed in a cell cycle-dependent manner. After transfection in HeLa S3 cells with the recombinant plasmids, levels of fusion mRNAs were determined by S1 nuclease analysis prior to and following DNA synthesis inhibition. When the first 20 nucleotides of an H3 histone mRNA leader were replaced with 89 nucleotides of the leader from a Drosophila heat-shock (hsp70) mRNA, the fusion transcript remained stable during inhibition of DNA synthesis, in contrast to the rapid destabilization of the endogenous histone mRNA in these cells. In a reciprocal experiment, a histone-globin fusion gene was constructed that produced a transcript with the initial 20 nucleotides of the H3 histone mRNA substituted for the human beta-globin mRNA leader. In HeLa cells treated with inhibitors of DNA synthesis and/or protein synthesis, cellular levels of this histone-globin fusion mRNA appeared to be regulated in a manner similar to endogenous histone mRNA levels. These results suggest that the first 20 nucleotides of the leader are sufficient to couple histone mRNA stability with DNA replication.

Animals↗
PubMed1985

Weight reduction methods of college women.

Weight reduction attitudes and practices were obtained from a sample of 400 female students. Forty-eight percent reported using a weight loss program since admission to college. The programs most often selected included hypocaloric diets and exercise. Although the majority of subjects rated hypocaloric diets and exercise as good methods for weight reduction and indicated that they would recommend them to others, these methods supported the slowest rate of weight loss. Evidently, the side effects and costs of the other programs offset the rapid weight loss. Other methods, in descending order of use, included the Cambridge diet, drugs, weight loss clinics, and low-carbohydrate diets. Improved appearance was most often given as the reason for losing weight.

Adolescent↗
PubMed1983

Turtle headaches.

Explore the source record for details and available documents.

Headache↗
PubMed1982

Studies on histone acetyltransferase. Partial purification and basic properties.

A rapid and reproducible method for the purification of rat liver histone acetyltransferase is presented. Extraction of nuclei in low salt, followed by phenyl-Sepharose hydrophobic affinity chromatography, G-200 gel filtration in the presence of 1 M urea, CM-cellulose ion exchange and acetyllysine affinity chromatography minimize exposure of the enzyme to high salt. Evidence is provided which indicates that the instability of the enzyme activity is due in part to hydrophobic interactions. The molecular weight of the enzyme is 96,000 as judged by gel filtration. In agreement with others, the enzyme is unstable in the presence of divalent cations, although a requirement for low concentration of Mg2+ or Ca2+ was observed. The enzyme is also sensitive to sulfhydryl blocking agents and is susceptible to rapid thermal denaturation at 37 and 45 degrees C (t1/2 = 22.2 and 9.54 min, respectively). The optimum pH and the energy of activation for the reaction were pH 7.5 and 5230 +/- 378 cal/mol, respectively. In the presence of all five histones, the enzyme catalyzes the acetylation in the order of H3 greater than H4 greater than H2b greater than H2a greater than H1 and appears to operate in a nonprocessive manner. While no other isozymic forms of nuclear acetyltransferase were detected, the enzyme exhibits the properties of both nuclear isozymic forms which have been reported, histone acetyltransferase A and DB, observed in calf thymus and bovine lymphocytes, respectively.

Acetyltransferases↗
PubMed1981

Purification and some properties of a deoxyribonucleic acid endonuclease endogenous to rat liver chromatin.

A deoxyribonucleic acid (DNA) endonucleolytic activity has been purified from a 0.3 M KCl extract of rat liver chromatin by a combination of selective precipitation and ion-exchange and gel filtration chromatography. The purified protein has a molecular weight of 35 000 as determined by Sephadex G-200 gel filtration and sodium dodecyl sulfate-acrylamide gel electrophoresis. The nuclease activity is stimulated by the addition of Mg2+ and thus may represent the Mg2+-activated DNase endogenous to chromatin. The purified enzyme has the ability to make both single-strand nicks and double-strand cuts in DNA.

Animals↗