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Biomedical subjects

A B Brown

Publications and source records attributed to A B Brown.

16 recordsLinked to original sources
PubMed1997

Inverted conversions: reading the Bible and writing the lesbian subject in Oranges are not the only fruit.

The prominence of the Bible as intertext in Oranges Are Not the Only Fruit, both a coming-of-age and a coming-out story, has puzzled readers. This paper argues that Winterson's articulation of a lesbian subject is actually inseparable from her revisionary engagement of the Bible. By repeatedly turning and re-turning several types of narrative about the origins of identity and story-making. Winterson reconstructs both some biblical texts and a hallmark of the gay and lesbian literary tradition as precursors for the prophetic voice of the main character.

Bible↗
PubMed1994

Thyroid hormone receptor messenger ribonucleic acid in human granulosa and ovarian stromal cells.

OBJECTIVE: To examine whether mRNA for thyroid hormone receptors alpha and beta is present in human granulosa cells in nonstimulated ovaries. DESIGN: Paraffin-embedded sections of ovaries from normally cycling women were analyzed by in situ hybridization with oligonucleotide probes for thyroid hormone receptors alpha and beta. The sense strand oligonucleotide was used as a control for each of the probes. RESULTS: Granulosa cells from the preovulatory antral follicles examined showed positive staining for both the thyroid hormone receptor alpha and beta probes. Positive staining of ovarian stromal cells also was observed for both probes. CONCLUSION: Thyroid hormone receptor mRNAs are expressed in both granulosa cells and ovarian stromal cells found in nonstimulated ovaries. It is, therefore, conceivable that thyroid hormone may play a direct role in human ovarian physiology.

Adult↗
PubMed1993

A novel, tissue-restricted zinc finger protein (HF-1b) binds to the cardiac regulatory element (HF-1b/MEF-2) in the rat myosin light-chain 2 gene.

The AT-rich element MEF-2 plays an important role in the maintenance of the muscle-specific expression of a number of cardiac and skeletal muscle genes. In the MLC-2 gene, an AT-rich element (HF-1b) which contains a consensus MEF-2 site is required for cardiac tissue-specific expression. The present study reports the isolation and characterization of a cDNA which encodes a novel C2H2 zinc finger (HF-1b) that binds in a sequence-specific manner to the HF-1b/MEF-2 site in the MLC-2 promoter. A number of independent criteria suggest that this HF-1b zinc finger protein is a component of the endogenous HF-1b/MEF-2 binding activity in cardiac muscle cells and that it can serve as a transcriptional activator of the MLC-2 promoter in transient assays. These studies suggest that, in addition to the previously reported RSRF proteins, structurally divergent transcriptional factors can bind to MEF-2-like sites in muscle promoters. These results underscore the complexity of the regulation of the muscle gene program via these AT-rich elements in cardiac and skeletal muscle.

Amino Acid Sequence↗
PubMed1991

Acute regulation of the epidermal growth factor receptor in response to nerve growth factor.

PC12 cells possess specific receptors for both nerve growth factor and epidermal growth factor, and by an unknown mechanism, nerve growth factor is able to attenuate the propagation of a mitogenic response to epidermal growth factor. The differentiation response of PC12 cells to nerve growth factor, therefore, predominates over the proliferative response to epidermal growth factor. We have observed that the addition of nerve growth factor to PC12 cells rapidly produces a decrease in surface 125I-epidermal growth factor binding capacity. Unlike previously described nerve growth factor effects on 125I-epidermal growth factor binding capacity, which required several days of nerve growth factor exposure, the decreases we report occur within minutes of nerve growth factor addition: A 50% decrease in 125I-epidermal growth factor binding capacity is evident at 10 min. This rapid nerve growth factor response is concentration dependent; inhibition of 125I-epidermal growth factor binding is detectable at nerve growth factor levels as low as 0.2 ng/ml and is maximal at approximately 50 ng/ml, consistent with known ranges of biological activity. No demonstrable differences in the rate of epidermal growth factor receptor synthesis or degradation were observed in cells acutely exposed to nerve growth factor. Scatchard analysis revealed that acute nerve growth factor treatment decreased the number of both high- and low-affinity 125I-epidermal growth factor binding sites, while the receptor affinity remained unchanged. We have also investigated the involvement of various potential intracellular mediators of nerve growth factor action and of known intracellular modulatory systems of the epidermal growth factor receptor for their capacity to participate in this nerve growth factor activity.

Animals↗
PubMed1990

Activation of a membrane-associated phosphatidylinositol kinase through tyrosine-protein phosphorylation by naphthoquinones and orthovanadate.

We have previously reported that several naphthoquinones stimulated tyrosine-specific protein phosphorylation in isolated rat liver membranes. Our more recent study demonstrated a similar effect by orthovanadate, which concomitantly stimulated phosphorylation of protein-tyrosine and phosphatidylinositol (Ptd-Ins). Results presented here show a simultaneous increase in PtdIns phosphorylation along with stimulation of tyrosine-protein phosphorylation by naphthoquinones. This PtdIns kinase resembles the type I PtdIns kinase in that it was insensitive to adenosine inhibition. The product, nevertheless, comigrated with a PtdIns-4-phosphate standard in TLC using three different solvent systems. Stimulation of PtdIns phosphorylation by vanadate or naphthoquinones could be achieved in the following preparations: intact rat liver membranes, Triton X-100-solubilized membranes, solubilized membranes partially purified by Sephacryl chromatography, solubilized membranes purified by wheat germ agglutinin chromatography. The naphthoquinone or vanadate-activated PtdIns kinase activity could be isolated by antiphosphotyrosine antibody-agarose affinity chromatography. The relative potencies of a series of ring-substituted naphthoquinones in the stimulation of tyrosine-protein phosphorylation, PtdIns kinase activity, dithiothreitol-dependent oxygen consumption, and cytochrome c reduction were highly correlated. We conclude that oxidant(s) produced by redox cycling of naphthoquinones stimulated an adenosine-insensitive PtdIns kinase through tyrosine phosphorylation of the enzyme.

1-Phosphatidylinositol 4-Kinase↗
PubMed1990

Feedback regulation of phospholipase C-beta by protein kinase C.

Treatment of a variety of cells and tissues with 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C (PKC) results in the inhibition of receptor-coupled inositol phospholipid-specific phospholipase C (PLC) activity. To determine whether or not the targets of TPA-activated PKC include one or more isozymes of PLC, studies were carried out with PC12, C6Bu1, and NIH 3T3 cells, which contain at least three PLC isozymes, PLC-beta, PLC-gamma, and PLC-delta. Treatment of the cells with TPA stimulated the phosphorylation of serine residues in PLC-beta, but the phosphorylation state of PLC-gamma and PLC-delta was not changed significantly. Phosphorylation of bovine brain PLC-beta by PKC in vitro resulted in a stoichiometric incorporation of phosphate at serine 887, without any concomitant effect on PLC-beta activity. We propose, therefore, that rather than having a direct effect on enzyme activity, the phosphorylation of PLC-beta by PKC may alter its interaction with a putative guanine nucleotide-binding regulatory protein and thereby prevent its activation.

Amino Acid Sequence↗
PubMed1990

Positive adaptations to weight-lifting training in the elderly.

Maximal weight-lifting performance, isometric strength, isokinetic torque, whole muscle and individual fiber cross-sectional areas, and muscle evoked contractile properties were assessed in 14 elderly males before and after 12 wk of weight-lifting training. Dynamic elbow flexion training of one arm resulted in a significant 48% mean increase in the maximal load that could be lifted once (1 RM) and a smaller improvement in isokinetic torque (8.8%) but no change in isometric strength. In the contralateral control arm, 1 RM and isokinetic torque increased by 12.7 and 6.5%, respectively, but isometric strength did not change. The interpolated twitch technique confirmed complete motor unit activation during a maximal isometric contraction of the elbow flexors before and after the training. Bilateral leg press training effected mean increases of 17 and 23% in isokinetic torque and dynamic lifting capacity, respectively. The mean maximal cross-sectional area of the elbow flexors (biceps brachii and brachialis) increased by 17.4% in the trained arm but did not change the control arm. The increase in the mean area of type II fibers in the biceps brachii muscle in the trained arm (30.2%) was greater than the corresponding change in the control arm (10.7%, P less than 0.05). The most significant change in the evoked contractile properties of the trained elbow flexors was the increase in twitch half-relaxation time. It is concluded that older individuals retain the potential for significant increases in strength performance and upper limb muscle hypertrophy in response to overload training.

Adaptation, Physiological↗
PubMed1989

Stimulation of tyrosine-specific protein phosphorylation and phosphatidylinositol phosphorylation by orthovanadate in rat liver plasma membrane.

Orthovanadate stimulated the incorporation of 32P from [gamma-32P]ATP by Triton X-100-solubilized rat liver plasma membrane into endogenous, trichloroacetic acid-precipitable materials as well as added (Glu4:Tyr1) copolymers. Extraction of incubation mixture with chloroform-methanol-HCl revealed that the increase in 32P incorporation by vanadate was predominantly into endogenous phospholipids. [32P]Phosphatidylinositol 4-phosphate (PtdIns-4-P) was identified by thin-layer chromatography as the major phosphorylated product of vanadate stimulation, which also resulted in elevated 32P, predominantly in P-Tyr in endogenous membrane proteins. Vanadate effects on protein tyrosine and phosphatidylinositol phosphorylation were concomitant and exhibited similar sensitivity. These effects of vanadate were enhanced by the presence of either dithiothreitol or NAD(P)H. Phosphatidylinositol phosphorylation could also be stimulated by a substrate of and inhibited by a synthetic inhibitory copolymer of tyrosine kinase. These results suggest that vanadate, an oxygen radical producer, stimulates a tyrosine kinase-PtdIns kinase coupled system much like those described for a number of growth factors and oncogene encoded products.

Animals↗
PubMed1985

Atrial natriuretic factor inhibits vasopressin secretion from rat posterior pituitary.

The effects of synthetic atrial natriuretic factor (ANF) were studied in superfused rat posterior pituitary gland. ANF (10(-6)M, 10(-10)M) significantly inhibited basal as well as KC1 (50 mM) or angiotensin II-stimulated immunoreactive arginine vasopressin secretion. The magnitude of inhibition was greater at 10(-6)M than at 10(-10)M. ANF also decreased cAMP secretion and increased cGMP secretion from the posterior pituitary. These results suggest that ANF directly acts on the posterior pituitary to inhibit arginine vasopressin secretion and that this effect is, at least, partly mediated by the changes in cyclic nucleotide production.

Angiotensin II↗
PubMedDate not supplied

The Bridge Program evaluation process.

The Bridge Program was designed to enrich the undergraduate nursing experience of students from underrepresented groups at three schools of nursing in the Baltimore area. An evaluation of the Program was conducted in the Spring of 1996 using data from a variety of sources. Data were collected using student, faculty and mentor surveys, and student interviews. The evaluation demonstrated that students were enthusiastic about the Bridge Program despite the heavy work load. Students identified the connection with the faculty mentor as the Program's greatest benefit. Faculty and mentors generally viewed the Program as satisfactory. The strengths of the Program as seen by faculty and mentors were in the areas of students' personal and professional growth, faculty-student relationships, learning resources, and preparation for graduate study.

Education, Nursing, Baccalaureate↗