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Biomedical subjects

J H Brown

Publications and source records attributed to J H Brown.

At least 19 recordsLinked to original sources
PubMed1992

Binding of influenza virus hemagglutinin to analogs of its cell-surface receptor, sialic acid: analysis by proton nuclear magnetic resonance spectroscopy and X-ray crystallography.

The interaction between influenza virus hemagglutinin and its cell-surface receptor, 5-N-acetylneuraminic acid (sialic acid), was probed by the synthesis of 12 sialic acid analogs, including derivatives at the 2-carboxylate, 5-acetamido, 4-, 7-, and 9-hydroxyl, and glycosidic positions. The equilibrium dissociation constants of these analogs were determined by nuclear magnetic resonance spectroscopy. Ligand modifications that reduced or abolished binding included the replacement of the 2-carboxylate with a carboxamide, the substitution of azido or N-benzyloxycarbonyl groups for the 5-acetamido group, and the replacement of the 9-hydroxyl with amino or O-acetyl moieties. Modifications having little effect on binding included the introduction of longer chains at the 4-hydroxyl position, the replacement of the acetamido methyl group with an ethyl group, and the removal of the 7-hydroxyl group. X-ray diffraction studies yielded 3 A resolution crystal structures of hemagglutinin in complex with four of the synthetic analogs [alpha-2-O-methyl-, 4-O-acetyl-alpha-2-O-methyl-, 9-amino-9-deoxy-alpha-2-O-methyl-, and alpha-2-O-(4'-benzylamidocarboxybutyl)-N-acetylneuraminic acid] and with the naturally occurring cell-surface saccharide (alpha 2-3)sialyllactose. The X-ray studies unambiguously establish the position and orientation of bound sialic acid, indicate the position of the lactose group of (alpha 2-3)sialyllactose, and suggest the location of an alpha-glycosidic chain (4'-benzylamidocarboxybutyl) that increases the binding affinity of sialic acid by a factor of about 3. Although the protein complexed with alpha-2-O-methylsialic acid contains the mutation Gly-135-->Arg near the ligand binding site, the mutation apparently does not affect the ligand's position. The X-ray studies allow us to interpret the binding affinities in terms of the crystallographic structure. The results suggest further experiments which could lead to the design of tight binding inhibitors of possible therapeutic value.

Amino Acid Sequence↗
PubMed1992

Transcriptional activation of the cardiac myosin light chain 2 and atrial natriuretic factor genes by protein kinase C in neonatal rat ventricular myocytes.

A cultured myocardial cell model was used to examine the role of protein kinase C-dependent pathways in the transcriptional activation of two cardiac muscle genes [myosin light chain 2 (MLC-2) and atrial natriuretic factor (ANF)] during alpha-adrenergic receptor-mediated hypertrophy. Phorbol ester (phorbol 12-myristate 13-acetate) and the alpha-adrenergic agonist phenylephrine both activate protein kinase C (PKC) and induce 4- to 5-fold increases in the expression of MLC-2 and ANF promoter/luciferase reporter genes with little effect on Rous sarcoma virus/luciferase or minimal prolactin promoter/luciferase genes. To further assess the role of PKC in cardiac gene regulation, PKC expression vectors encoding constitutively activated PKC-alpha or PKC-beta, or a catalytically inactive PKC, were transiently cotransfected with the cardiac promoter/luciferase constructs. Cotransfection of either activated PKC-alpha or PKC-beta cDNA induces the expression of MLC-2 and ANF promoter/luciferase genes and of a reporter gene responsive to the transcription factor AP-1. The Rous sarcoma virus/luciferase and minimal prolactin promoter/luciferase genes are not concomitantly induced by cotransfectin with the PKC genes, indicating specificity of the transcriptional effect. The finding that activated PKC increases cardiac gene transcription suggests that activation of this enzyme may be a proximal signal for coregulation of two cardiac genes, MLC-2 and ANF, during the course of myocardial cell hypertrophy.

Amino Acid Sequence↗
PubMed1992

Family functions and children's postdivorce adjustment.

Data on school-age children of divorced parents were examined to determine which dimensions of family dynamics were most associated with the children's socioemotional adjustment. Those factors found to be most significant were family roles, behavior control, and affective involvement, as well as children's reaction to and insight into the divorce, and conflict in the home after the divorce. Implications for parent education and early intervention are discussed.

Adaptation, Psychological↗
PubMed1992

Biphasic increase in c-jun mRNA is required for induction of AP-1-mediated gene transcription: differential effects of muscarinic and thrombin receptor activation.

Activation of either muscarinic cholinergic or thrombin receptors increases phosphoinositide turnover, Ca2+ mobilization, and redistribution of protein kinase C and induces rapid transient increases in c-fos mRNA and c-jun mRNA in 1321N1 cells. To determine whether the increases in c-fos and c-jun mRNA induced by carbachol and thrombin are sufficient to stimulate AP-1-mediated transactivation, 1321N1 cells were transfected with a reporter carrying two copies of the tetradecanoyl phorbol acetate response element and the firefly luciferase gene. Thrombin was significantly more effective than carbachol at stimulating AP-1-mediated transactivation. To identify the factors underlying the difference in AP-1 activity induced by carbachol and thrombin, members of the fos and jun families which encode components of AP-1 were examined. Carbachol and thrombin have similar effects on expression of c-fos, fosB, fra-2, junB, and junD, both acutely and over a 24-h time course. However, whereas carbachol leads only to transient induction of c-jun (maximal at 0.5 h), thrombin induces a biphasic increase in c-jun mRNA--an initial peak at 0.5 h and a second, more-prolonged increase at 12 h. Thrombin but not carbachol also induces a late increase in fra-1 mRNA, which peaks at 12 h. The secondary increase in c-jun mRNA is associated with marked increases in c-Jun protein levels and AP-1 DNA-binding activity. The late induction of c-jun and fra-1 mRNA can be prevented by adding the antagonist hirudin 30 min after thrombin, which results in loss of thrombin-stimulated increases in c-Jun protein, AP-1 DNA-binding activity, and AP-1-mediated transactivation. These findings suggest that rapid and transient conduction of c-fos and c-jun mRNA is insufficient to induce prominent changes in gene transcription, while the sustained increase in c-jun mRNA and perhaps the late induction of fra-1 mRNA are required for generation of AP-1 DNA-binding activity and transactivation through AP-1.

Blotting, Northern↗
PubMed1992

White sponge nevus presenting in the esophagus--case report and literature review.

White sponge nevus (WSN) is a rare inherited disorder which usually presents as non-painful white plaques primarily involving the buccal mucosa, gingiva and palate. Extra-oral lesions most often occur in the esophagus or anogenital area but almost invariably follow the development of typical buccal lesions. We present a non-familial case in which the first manifestation of the disease was in the esophagus in the absence of oral lesions. This sequence of events has not previously been reported in the literature. The cytohistological and electron microscopical appearances which allow the recognition and differentiation of WSN from other conditions presenting as esophageal white lesions are discussed.

Biopsy↗
PubMed1992

Growth plate injuries: Salter-Harris classification.

Fracture of the growth plate is an injury unique to childhood. Most such fractures heal without permanent deformity. A small percentage, however, are complicated by growth arrest and subsequent deformity. The Salter-Harris classification of growth plate injuries aids in estimating both the prognosis and the potential for growth disturbance. The Salter-Harris system classifies growth plate fractures into five groups: type I, fracture through the growth plate; type II, fracture through the growth plate and metaphysis; type III, fracture through the growth plate and epiphysis; type IV, fracture through the growth plate, epiphysis and metaphysis, and type V, crush or compression injury of the growth plate.

Biomechanical Phenomena↗
PubMed1992

Imaging of sinonasal tumors.

Imaging of the paranasal sinuses and the nasal cavity provides important anatomic information in the evaluation of suspected neoplasia. The primary modalities employed are conventional films, computed tomography (CT) and magnetic resonance imaging (MRI). Although plain sinus films remain the screening procedure of choice, CT is the preferred modality for more detailed assessment of the paranasal sinuses and the nasal cavity. When soft tissue discrimination is required, MRI is indicated. Imaging studies are used to define the limits of disease, not to diagnose malignancy.

Humans↗
PubMed1991

The alpha-adrenergic stimulation of atrial natriuretic factor expression in cardiac myocytes requires calcium influx, protein kinase C, and calmodulin-regulated pathways.

It has been shown recently that alpha-adrenergic agonists can stimulate atrial natriuretic factor (ANF) expression in ventricular cardiac myocytes; however, little is known about the intracellular signals mediating this activation. The present study focused on the potential roles of calcium-regulated kinases and calcium influx in the alpha-adrenergic stimulation of ANF gene expression in ventricular myocardial cell cultures. Myocardial cells maintained for 48 h in serum-free medium supplemented with phenylephrine (PE) possessed up to 15-fold higher levels of ANF peptide and ANF mRNA than control cells. The removal of PE, or the addition of nifedipine, resulted in a rapid decline in ANF expression, suggesting that the sustained elevation of some intracellular messenger (e.g. calcium and/or phospholipid hydrolysis products) was required for the adrenergic response. The calcium channel agonist BAY K 8644 was capable of increasing ANF expression in a nifedipine-sensitive manner; however, unlike PE, it did not stimulate phosphoinositide hydrolysis. The protein kinase C inhibitor, H7, caused an approximate 75% reduction in PE-stimulated ANF expression, but had no effect on BAY K-stimulated expression. W7, a calcium/calmodulin inhibitor, completely blocked the effects of both PE and BAY K 8644. The addition of either H7 or W7 24 h after the PE addition resulted in a decline of ANF expression. These results indicate that alpha-adrenergic agonists augment ANF gene expression through at least two pathways, one that is H7-sensitive, perhaps involving the sustained activation of protein kinase C, and the other that is W7-sensitive, perhaps involving the sustained activation of calmodulin-regulated kinases. Further, it appears that BAY K 8644-mediated increases in ANF expression are independent of protein kinase C activation and dependent on calmodulin-regulated events.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Regulation of c-fos and c-jun protooncogene expression by the Ca(2+)-ATPase inhibitor thapsigargin.

Thapsigargin, a non-phorbol-ester-type tumor promoter, discharges intracellular Ca2+ stores by specific inhibition of the endoplasmic reticulum Ca(2+)-ATPase. We used this drug to analyze the involvement of Ca2+ and Ca(2+)-ATPases in the control of growth- and transformation-related genes. Here we show that treatment of mouse NIH 3T3 fibroblasts with thapsigargin induced rapid expression of the c-fos and c-jun protooncogenes. Inhibition or depletion of protein kinase C partially diminished the c-fos but not the c-jun response. Furthermore, thapsigargin could synergize with the tumor promoter phorbol 12-myristate 13-acetate to induce c-fos but not c-jun. However, thapsigargin had no effect on basal or phorbol ester-induced protein kinase C activity. Our results indicate that Ca2+ is a potent second messenger that controls expression of growth- and transformation-related genes. Since inhibition of the endoplasmic reticulum Ca(2+)-ATPase results in a strong induction of these genes, our data suggest that this Ca2+ pump may act as a negative regulator of cell growth.

Animals↗
PubMed1991

Dissociation of protein kinase C redistribution from the phosphorylation of its substrates.

Increases in cytoplasmic [Ca2+] caused by receptor activation are thought to stimulate the redistribution of loosely associated protein kinase C (PKC) to a tightly membrane-bound form that is activated by diacylglycerol. The precise role of Ca2(+)-dependent redistribution of PKC in the activation of this enzyme has not been critically assessed. We examined the relationship between PKC redistribution and substrate phosphorylation by comparing the kinetics and the Ca2+ dependence of the two events. Using immunoblotting with specific PKC antibodies, we find that 1321N1 cells express the alpha form of PKC, approximately 10-20% of which is membrane-associated in unstimulated cells. This fraction is increased to 60% in response to muscarinic receptor stimulation. Agonist-induced redistribution of PKC is rapid and transient, peaking at 30 s and returning to control levels by 2-5 min. Stimulation of muscarinic receptors also rapidly increases phosphorylation of both an endogenous 80-kDa protein and the peptide substrate, VRKRTLRRL. However, unlike the time course of PKC redistribution, PKC-mediated phosphorylation of these substrates is sustained for up to 30 min. To compare the Ca2+ dependence of PKC redistribution and substrate phosphorylation, we buffered muscarinic receptor-induced increases in cytoplasmic [Ca2+] with the divalent cation chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. Under these conditions, redistribution of PKC and phosphorylation of the exogenous peptide substrate are inhibited by about 80%. In contrast, muscarinic receptor-stimulated phosphorylation of the 80-kDa protein occurs even when increases in cytoplasmic [Ca2+] are prevented. Taken together, these data demonstrate that the redistribution of PKC does not correlate in extent or duration with phosphorylation of PKC substrates.

Amino Acid Sequence↗
PubMed1991

c-fos and c-jun are induced by muscarinic receptor activation of protein kinase C but are differentially regulated by intracellular calcium.

It has become increasingly clear that agents classically thought to act as neurotransmitters can also alter gene expression. To understand the early events by which neurotransmitters could effect genetic responses, we have studied the induction of two immediate early genes, c-fos and c-jun. These genes encode proteins that form a dimeric complex (AP-1) active as a transcriptional factor. Using the stable acetylcholine analog carbachol to activate muscarinic receptors (mAChR) in a glial cell line (1321N1), we show that c-fos and c-jun mRNA levels are transiently increased, reaching a maximum at 30 min after agonist addition. Experiments in which the actions of carbachol are blocked by adding atropine at various times demonstrate that only 1.5 min of agonist stimulation is needed to give maximal increases in c-fos or c-jun mRNA at 30 min. These results suggest that events previously shown to occur in the first minute of mAChR occupation (the mobilization of intracellular Ca2+, activation of protein kinase C) are sufficient for induction of these immediate early genes. In cells in which protein kinase C has been down-regulated, carbachol no longer stimulates c-fos or c-jun expression, indicating a critical role for protein kinase C in these responses. In cells loaded with bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) to buffer increases in cytosolic [Ca2+], mAChR-mediated induction of c-fos is markedly reduced; in contrast there is enhanced c-jun expression. The strong enhancement of c-jun induction by carbachol in BAPTA-treated cells is due at least in part to mRNA stabilization. Experiments using phorbol ester (phorbol 12-myristate 13-acetate) in combination with the Ca2+ ionophore ionomycin confirm that activation of protein kinase C induces c-fos and c-jun expression and that a concomitant increase in cytosolic [Ca2+] potentiates the induction of c-fos while repressing that of c-jun. The data suggest that the ability of neurotransmitters or growth factors to mobilize Ca2+ would modulate the effect of concomitant protein kinase C activation on AP-1 generation and consequent target gene expression.

Blotting, Northern↗
PubMed1991

Outcome of pregnancy following renal transplantation.

Successful renal transplantation improves fertility with 1 in 50 women of childbearing age becoming pregnant. Pregnancy following renal transplantation is associated with increased maternal and fetal complications. In Belfast 118 women of childbearing age (15-45 yrs) have received a renal allograft and of these 14 (12%) have become pregnant. Twenty-seven pregnancies have resulted in 23 live births (including one set of identical twins), 1 still birth and 4 first trimester abortions. The most frequent complications were hypertension and prematurity. In this group of patients, whose sole immunosuppressive therapy was azathioprine and prednisolone, pregnancy post transplantation was associated with frequent successful outcome and a low incidence of maternal and fetal complications.

Adolescent↗
PubMed1991

Solvent abuse, toluene acidosis and diabetic ketoacidosis.

Solvent abuse in adolescents and young adults has been reported to cause a metabolic acidosis with a normal or increased anion gap (Streicher et al., 1981; Voights & Kaufman, 1983, Anonymous, 1988). We report a particularly severe clinical problem produced by the combination of toluene intoxication and diabetic ketoacidosis.

Acetone↗