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Biomedical subjects

H He

Publications and source records attributed to H He.

At least 19 recordsLinked to original sources
PubMed1997

Synergistic induction of CTLA-4 expression by costimulation with TCR plus CD28 signals mediated by increased transcription and messenger ribonucleic acid stability.

T cell activation requires at least two signals transduced by the Ag-specific TCR plus a costimulatory receptor. The CD28 costimulatory molecule has been shown to promote T cell proliferation and cytokine production. CTLA-4, a cell surface molecule homologous to CD28, can function as a repressor of T cell activation. Thus, CTLA-4 and CD28 may have opposing functions during T cell activation. CTLA-4 is expressed at low levels on resting T cells and up-regulated after T cell activation. Regulation of CTLA-4 expression is critical to the normal regulation of immunity. For example, CTLA-4-deficient mice develop early onset lethal autoimmunity. We previously showed that CTLA-4 transcription is increased after T cell activation and that induction was controlled by 335 bp of CTLA-4 upstream sequence. In this work, we show that cell surface CTLA-4 expression is increased synergistically by TCR plus CD28 signals. Synergistic induction is mediated by two mechanisms: an enhanced rate of transcription and increased mRNA stability. In contrast to the regulation of IL-2 and IL-2R expression, which is inhibited by cyclosporin A-, but not rapamycin-dependent signal transduction pathways, CTLA-4 expression is inhibited by either cyclosporin A or rapamycin. Thus, synergistic induction of CTLA-4 expression requires both cyclosporin A- and rapamycin-dependent signals.

Abatacept↗
PubMed1997

The small subunit is required for functional interaction of DNA polymerase delta with the proliferating cell nuclear antigen.

DNA polymerase delta is usually isolated as a heterodimer composed of a 125 kDa catalytic subunit and a 50 kDa small subunit of unknown function. The enzyme is distributive by itself and requires an accessory protein, the proliferating cell nuclear antigen (PCNA), for highly processive DNA synthesis. We have recently demonstrated that the catalytic subunit of human DNA polymerase delta (p125) expressed in baculovirus-infected insect cells, in contrast to the native heterodimeric calf thymus DNA polymerase delta, is not responsive to stimulation by PCNA. To determine whether the lack of response to PCNA of the recombinant catalytic subunit is due to the absence of the small subunit or to differences in post-translational modification in insect cells versus mammalian cells, we have co-expressed the two subunits of human DNA polymerase delta in insect cells. We have demonstrated that co-expression of the catalytic and small subunits of human DNA polymerase delta results in formation of a stable, fully functional heterodimer, that the recombinant heterodimer, similar to native heterodimer, is markedly stimulated (40- to 50-fold) by PCNA and that the increase in activity seen in the presence of PCNA is the result of an increase in processivity. These data establish that the 50 kDa subunit is essential for functional interaction of DNA polymerase delta with PCNA and for highly processive DNA synthesis.

Animals↗
PubMed1997

Myocardial alpha1-adrenoceptor: inotropic effect and physiologic and pathologic implications.

Alpha1-adrenergic receptors have been found in myocardium of all mammalian species. Although the exact underlying mechanisms have not been conclusively determined, it would appear that the myocardial effects of alpha1-adrenoceptors may vary in importance according to the pathophysiologic process involved. In physiological conditions, this receptor system plays a role in cardiac growth, cardiac contraction, and has both an antiarrhythmic function as well as a role in cardiac adaptation to various situations. This system is also involved in some pathological processes such as ischemia/reperfusion, ischemic preconditioning, and cardiac hypertrophy. The role of alpha1-adrenoceptors in heart failure is somewhat controversial. Experimental evidence suggests that myocardial alpha1-adrenoceptors can have either beneficial or deleterious effects on the heart. It thus seems possible that the development of agents specific to certain subtypes of alpha1-adrenoceptor and a better understanding of their role in pathophysiologic states could be clinically relevant.

Animals↗
PubMed1997

Alpha 1-adrenergic stimulation inhibits 3,5,3'-triiodothyronine-induced expression of the rat heart sarcoplasmic reticulum Ca2+ adenosine triphosphatase gene.

The interactions between the beta-adrenergic system and thyroid hormone (T3) on cardiac function have been investigated in detail. In addition to beta-adrenoceptors, alpha 1-adrenergic receptors are present in the mammalian heart. The interactions between T3 and the alpha 1-adrenergic system remain, however, poorly understood. T3 stimulates the expression and transcription of the sarcoplasmic reticulum Ca2+ adenosine triphosphatase (SERCA2) gene, a protein vital in the control of cardiac calcium transients and contractility. We show that in rat cardiac myocytes, the stimulatory effect of T3 on SERCA2 messenger RNA expression and gene transcription is inhibited by an alpha 1-adrenergic agonist. We demonstrate that direct activation of the alpha 1-adrenergic signaling pathway, using a mutant constitutively active G protein (Gq) similarly down-regulated the T3 effect on SERCA2 transcription. The combined effect of thyroid hormone receptor and retinoid X receptors on T3-stimulated SERCA2 gene transcription was also markedly attenuated by alpha 1-adrenergic stimulation. These results suggested that activation of the alpha 1-adrenergic signaling pathway has an inhibitor effect on T3-dependent SERCA2 gene transcription. As this inhibitory effect of alpha 1-adrenergic stimulation occurs when only one thyroid hormone response element (TRE) drives reporter expression, it is most likely mediated by an alteration of the nuclear factors binding to the TRE or by influencing the interaction of the TRE complex with the basal transcriptional machinery.

Animals↗
PubMed1996

Transcription, translation, and cellular localization of three Autographa californica nuclear polyhedrosis virus structural proteins: ODV-E18, ODV-E35, and ODV-EC27.

This paper identifies two structural proteins of the occluded derived viral envelope of Autographa californica nuclear polyhedrosis virus (AcMNPV): ODV-E18 and ODV-E35. In addition, we identify a protein, ODV-EC27, that is incorporated into the capsid of occluded virus, which is not detected in budded virus. The genes for these proteins reside within the IE0 intron. The intron was sequenced, and five open reading frames (ORF) were identified. ORF 3 (genomic ORF 143) codes for the ODV envelope protein, ODV-E18. ORF 4 (genomic ORF 144) codes for ODV-EC27, and Western blot analyses locate this protein to both the ODV capsid and envelope. Transcripts for both ODV-E18 and ODV-EC27 initiate from conserved TAAG motifs, and transcripts are detected from 16 through 72 hr p.i. Antiserum to ODV-E18 recognizes a band of 18 kDa on Western blots of extracts from infected cells and bands of 18 and 35 kDa on Western blots of proteins from purified ODV envelope. N-terminal amino acid sequencing reveals that both ODV-E18 and ODV-E35 contain the same N-terminus. Antiserum to ODV-EC27 recognizes a protein of 27 kDa on Western blots of extracts from infected cells and bands of 27 and 35 kDa on Western blots of proteins from purified ODV. Using immunogold labeling techniques, ODV-E18 and/or ODV-E35 are detected in viral induced intranuclear microvesicles and are not detected in the plasma membrane, cytoplasmic membranes, or the nuclear envelope. Immunogold labeling using antisera to ODV-EC27 detects this protein on both the ODV envelope and capsid.

Amino Acid Sequence↗
PubMed1996

Regulation of CTLA-4 expression during T cell activation.

T cell activation requires at least two distinct signals, including signaling via the Ag-specific TCR and a costimulatory pathway. The best characterized costimulatory pathway involves the CD28 molecule, which is expressed constitutively on T cells and binds the family of B7 counter-receptors on APCs. Inhibition of this costimulatory pathway prevents T cell activation and can lead to long-term T cell unresponsiveness or anergy. In contrast, CTLA4, which is homologous to CD28, has been shown to be a negative regulator of T cell activation. The CTLA4 molecule is not expressed on resting T cells, but is induced after the initial steps of T cell activation. To address the regulation of CTLA4 expression, we have analyzed CTLA4 at the level of cell surface expression, mRNA, rate of transcription, and rate of decay of message. Nuclear runoff results show an increase in the rate of transcription following T cell activation. Our analyses of non-T cells, including B cells, mastocytoma, and fibroblasts, by Northern blot analysis detect only T cell expression of CTLA4. Reporter gene analysis indicates that 335 bp of upstream CTLA4 sequence are sufficient to control inducibility. We have identified important regulatory regions that control inducible and cell-specific CTLA4 expression. These results also suggest that both positive and negative response elements modulate the transcriptional regulation of CTLA4 gene expression. Understanding the regulation of CTLA4 should provide insight into the regulation of T cell activation at the molecular level.

Abatacept↗
PubMed1996

Lack of vasodilatory response in skeletal muscle blood vessels of aged spontaneously hypertensive rats.

Regional hemodynamic responses to the vasodilators, hydralazine (1 mg/kg, i.v.) and verapamil (0.1 mg/kg/min, i.v.), were examined in conscious Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR), 15 and 50 weeks of age, using the radioactive microsphere method. The flow rates of heart and skeletal muscle in SHR were higher than those in WKY, and the flow rates of liver, kidney, intestines, and skin in SHR were lower than those in WKY. These differences between the regional blood flow in WKY and SHR were observed in both aged and young rats. The changes in organ blood flow induced by hydralazine and verapamil were similar for WKY and SHR in most organs. Both drugs increased the skeletal muscle blood flow in WKY and young SHR, but not in aged SHR, that is, the skeletal muscle blood vessels in aged SHR lost their vasodilatory response. These results suggest that, although a lack of vasodilatory responses in the skeletal muscle vasculature of aged SHR may be triggered by persistent hypertension, the vital organ vasculature maintains its normal vasodilating capacity.

Age Factors↗
PubMed1996

Vasodilation induced by vasopressin V2 receptor stimulation in afferent arterioles.

We have previously reported that vasopressin (AVP) V2 receptor stimulation increased renal blood flow in dogs anesthetized with pentobarbital. In this study, we examined the direct effects of AVP on afferent arterioles to clarify the role played by V2 receptors in regulating afferent arteriolar tone. We microdissected a superficial afferent arteriole with glomerulus from the kidney of a New Zealand White rabbit. Each afferent arteriole was cannulated with a pipette system and microperfused in vitro at 60 mm Hg. The effects of vasoactive substances were evaluated by changes in the lumen diameter of afferent arterioles. We found that AVP decreased the lumen diameter of microperfused afferent arterioles dose-dependently and that a V1 antagonist, OPC21268, inhibited the vasoconstrictor action of AVP. However, AVP 10(-8) M increased the lumen diameter of norepinephrine (NE)-constricted afferent arterioles pretreated with OPC21268 (OPC + NE, 8.2 +/- 0.7 microns; OPC + NE + AVP, 9.9 +/- 0.9 microns*; *P < 0.05, N = 13). This vasodilatory effect of AVP was abolished by pretreatment with a V2 antagonist, OPC31260. Desmopressin (dDAVP), a V2 agonist, increased the lumen diameter of the NE-constricted afferent arterioles (NE, 7.4 +/- 0.9 microns; NE + dDAVP, 10.1 +/- 0.7 microns*; *P < 0.05, N = 9). These results suggest that AVP V2 receptors are present in rabbit afferent arterioles and that V2 receptor stimulation induces vasodilation in rabbit afferent arterioles.

Animals↗
PubMed1996

Production of kanosamine by Bacillus cereus UW85.

Bacillus cereus UW85 produces two antibiotics that contribute to its ability to suppress certain plant diseases (L. Silo-Suh, B. Lethbridge, S. J. Raffel, H. He, J. Clardy, and J. Handelsman, Appl. Environ. Microbiol. 60:2023-2030, 1994). To enhance the understanding of disease suppression by UW85, we determined the chemical structure, regulation, and the target range of one of the antibiotics. The antibiotic was identified as 3-amino-3-deoxy-D-glucose, also known as kanosamine. Kanosamine was highly inhibitory to growth of plant-pathogenic oomycetes and moderately inhibitory to certain fungi and inhibited few bacterial species tested. Maximum accumulation of kanosamine in B. cereus UW85 culture supernatants coincided with sporulation. Kanosamine accumulation was enhanced by the addition of ferric iron and suppressed by addition of phosphate to rich medium. Kanosamine accumulation was also enhanced more than 300% by the addition of alfalfa seedling exudate to minimal medium.

Anti-Bacterial Agents↗
PubMed1996

Negative regulation of the rat Na-K-ATPase alpha 3-subunit gene promoter by thyroid hormone.

Na-K-ATPase alpha 3-subunit mRNA levels are both positively and negatively controlled by thyroid hormone [3,5,3'triiodothyronine (T3)] in primary cultures of neonatal rat cardiac myocytes. In this study, transient transfection analysis indicated that two regions of the rat alpha 3 gene between nucleotides -116 and -6 and -6 and +80 conferred T3-mediated inhibition of reporter gene expression. Electrophoretic mobility shift assays showed specific binding of T3 receptor monomers and T3 receptor-retinoid X receptor heterodimers at each alpha 3 gene negative T3-response region. The alpha 3 gene region from -116 to -6 base pairs also mediates repression in response to retinoic acid (RA) and binds RA receptor. In the absence of ligand, reporter gene expression driven by the -116 to -6-base pair region is repressed with cotransfection of T3 receptor, whereas it is unaffected by overexpression of RA receptor. These data demonstrate that the proximal promoter of the rat Na-K-ATPase alpha 3 gene contains sequence motifs that mediate repression of alpha 3 gene transcription in response to either T3 or RA in neonatal rat cardiac myocytes.

Animals↗
PubMed1995

Effects of a synthetic rat adrenomedullin on regional hemodynamics in rats.

The effects of rat adrenomedullin, a novel vasorelaxant peptide, on systemic and regional hemodynamics were examined in conscious Sprague Dawley (SD) rats and spontaneously hypertensive rats (SHR). The intravenous infusion of adrenomedullin at rates of 1.67 and 5 micrograms/kg per min decreased the mean arterial pressure in a dose-dependent fashion in both types of rats. Adrenomedullin at a rate of 5 micrograms/kg per min increased the heart rate and cardiac output. As a result, the total peripheral resistance significantly decreased. With regards to the regional hemodynamics, adrenomedullin significantly increased the flow rates in the lungs, heart, spleen, kidneys, adrenal glands and small intestine of SHR. The flow rates in the brain and skin did not change and the flow rates in the skeletal muscle and testis were decreased. These regional hemodynamic changes were also observed in SD rats and there was no qualitative difference in the regional responses to adrenomedullin between SHR and SD rats. Thus, adrenomedullin predominantly increased the flow rates in organs in which adrenomedullin gene was highly expressed. It therefore seems that adrenomedullin may act as a local vasodilatory hormone rather than as a circulatory hormone.

Adrenomedullin↗
PubMed1995

Polymorphic SINEs in chironomids with DNA derived from the R2 insertion site.

A short interspersed repeat (SINE) in the two sibling species Chironomus pallidivittatus and Chironomus tentans is described. It is present at many sites in the genome and is surrounded by 10 to 14 bp target site duplications. It consists of two sequence modules in different numbers and variable order relative to each other and often has large inversions of different sizes at one end. One of the modules contains pol III promoter consensus sequences. This SINE, nevertheless, is likely to have been dependent on an outside promoter for its formation. It is therefore interesting that both modules start with a 22 bp region with striking similarity to the R2 insertion site in the preribosomal gene of insects. We suggest that this type of SINE, termed Cp1, was formed after a series of events among which the first step was the retroposition of a tRNA gene into the R2 site in the preribosomal gene by the R2 coded protein. The final step is likely to have been due to retroposition from this site.

Animals↗
PubMed1995

Development and application of a specific and sensitive radioimmunoassay for trihexyphenidyl to a pharmacokinetic study in humans.

A radioimmunoassay (RIA) for trihexyphenidyl was developed through the use of a bovine thyroglobulin conjugate of trihexyphenidyl hemisuccinate. Immunization of New Zealand white rabbits with this drug-protein conjugate yielded antisera, for which the antibody titer and specificity were evaluated. An antiserum that had the highest titer and minimal cross-reactivities to major metabolites of trihexyphenidyl, such as trihexyphenidyl N-oxide (2%), hydroxytrihexyphenidyl (1%), and the antipsychotic drugs fluphenazine (< 1%), flupenthixol (< 1%), chlorpromazine (< 1%), and haloperidol (< 1%), was selected for development of a RIA. The described RIA enables the quantitation of 7.8 pg of trihexyphenidyl in 200 microL of human plasma with a mean coefficient of variation of < 6% across the range of the standard curve. Assay specificity was further demonstrated by comparison of results obtained directly and after selective extraction of trihexyphenidyl from replicate samples. This RIA procedure was applied to the analysis of steady state plasma samples obtained from patients undergoing treatment with trihexyphenidyl (2-8 mg) and plasma samples obtained from eight healthy male volunteers after administration of a single 4 mg oral dose of the drug. The results of the latter single dose studies demonstrated that the mean +/- SD for the peak concentration (Cmax), the time to Cmax (Tmax), the rate of absorption (Ka), and the area under the curve from 0 to 72 h (AUC0-72) were found to be 7.15 +/- 2.58 ng/mL, 1.32 +/- 0.58 h, 2.07 +/- 0.93 1/h, and 201 +/- 71 ng h/mL, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Dietary sodium intake modulates systemic but not forearm norepinephrine release.

INTRODUCTION: Sodium intake has profound effects on systemic and renal sympathetic activity, but its effects on sympathetic activity in skeletal muscle vascular beds, a site at which local regulatory mechanisms could alter vascular tone directly, are unclear. METHODS: To determine the effect of dietary sodium intake on basal and isoproterenol-stimulated systemic and forearm norepinephrine kinetics, we studied seven healthy male volunteers twice, 4 weeks apart, while they were receiving a low-sodium (10 mmol sodium/24 hours) diet and a high-sodium diet (250 mmol sodium/24 hours). Forearm blood flow, measured by plethysmography, and systemic and forearm norepinephrine spillover, measured by radioisotope dilution, were determined before and after intra-arterial infusion of 60 and 400 ng/min isoproterenol. RESULTS: Baseline (before isoproterenol) systemic norepinephrine spillover was higher when subjects received the low-sodium diet (448.1 +/- 55.7 ng/min) compared with the high-sodium diet (269.7 +/- 42.7 ng/min; p < 0.05). In contrast, sodium intake did not affect local forearm norepinephrine spillover, either at baseline (low-sodium diet, 2.05 +/- 0.48 ng/min versus high-sodium diet, 2.63 +/- 0.79 ng/min; p = 0.50) or after stimulation with isoproterenol in doses of 60 ng/min (low-sodium diet, 8.84 +/- 2.2 ng/min versus high-sodium diet, 6.1 +/- 1.9 ng/min; p = 0.38) or 400 ng/min (low-sodium diet, 16.4 +/- 4.5 ng/min versus high-sodium diet, 16.7 +/- 2.5 ng/min; p = 0.93). CONCLUSIONS: Under conditions of low sodium intake, systemic norepinephrine spillover was increased but forearm norepinephrine spillover was not, suggesting that alteration in sodium intake may produce a differential effect on norepinephrine spillover in different tissues but that decreased local sympathetic activity in skeletal muscle is not the likely mechanism by which a low-sodium diet may lower blood pressure or attenuate stress-induced pressor responses.

Adrenergic beta-Agonists↗
PubMed1995

Effect of protein kinase C modulation on gonadotrophin-induced granulosa cell steroidogenesis.

The effect of protein kinase C (PKC) modulation on gonadotrophin-induced ovarian granulosa cell differentiation was investigated by using an activator of PKC, phorbol 12-myristate 13-acetate (PMA) and inhibitors of PKC, sphingosine (SPH) and staurosporine (ST). The effects of PMA (at doses which activate PKC (10 ng mL-1), and down-regulate PKC (1000 ng mL-1)), sphingosine (25 microM) and staurosporine (10(-10)-10(-7) M) on gonadotrophin-induced granulosa cell differentiation were studied by the determination of steroidogenesis and cAMP accumulation in immature rat ovarian granulosa cells treated with or without pregnant mare serum gonadotrophin (100 mU mL-1). PMA (10 ng mL-1) inhibited gonadotrophin-induced granulosa cell steroidogenesis and cAMP accumulation. PMA (1000 ng mL-1)-induced down-regulation of PKC did not affect gonadotrophin-induced steroidogenesis. The inhibitory effect of PMA (10 ng mL-1) on gonadotrophin-induced granulosa cell steroidogenesis was not present in PKC-down-regulated cells. These data indicate that PKC activation by PMA inhibits gonadotrophin-induced steroidogenesis. SPH also inhibited gonadotrophin-induced steroidogenesis and cAMP accumulation. This effect of SPH was not affected by PMA-induced PKC down-regulation, indicating that this action of SPH does not require PKC or is mediated via a phorbol ester-insensitive PKC isoform. ST induced steroidogenesis in the absence of gonadotrophin, but was not synergistic with gonadotrophin. PMA-induced down-regulation of PKC abolished the effect of ST, suggesting that the action of ST requires PKC. The data suggest that ST and PMA, which antagonize each other in gonadotrophin-induced steroidogenesis, act via a PKC-mediated mechanism whereas the cAMP-associated actions of gonadotrophins and SPH are not dependent on PKC.

Alkaloids↗
PubMed1995

A pharmacological, pharmacokinetic and clinical overview of risperidone, a new antipsychotic that blocks serotonin 5-HT2 and dopamine D2 receptors.

Risperidone is a benzisoxazole derivative with antipsychotic activity that is chemically unrelated to other currently available antipsychotic agents. Its neuropharmacological properties, characterized by potent central antagonism of both serotonin 5-HT2 and dopamine D2 receptors, also differ from those of most other antipsychotic drugs. The pharmacokinetics of risperidone are well understood, having been studied in healthy subjects as well as in psychotic patients. The absolute oral bioavailability of risperidone is nearly 70%, and after oral administration, it is rapidly absorbed with the plasma level reaching a peak at about 1 h. 9-Hydroxyrisperidone, one of the metabolites of risperidone, is equally active with the parent compound and so the clinical activity of a dose of risperidone is due to the combined actions of both moieties. The plasma concentrations of risperidone and its active metabolite remain dose proportional even at doses exceeding the therapeutic range. In clinical trials with chronic schizophrenia patients, risperidone has an overall therapeutic activity comparable with that of haloperidol, but at doses that produce similar improvements in the positive symptoms of schizophrenia, risperidone has a greater effect on the negative symptoms and produces less extrapyramidal side effects than does haloperidol. However, additional controlled clinical studies are needed before the claims that risperidone is therapeutically superior to haloperidol can be considered to be established firmly. Although risperidone is effective in acute schizophrenia and in non-treatment-resistant schizophrenics, studies adequately comparing risperidone with clozapine in treatment-resistant schizophrenic patients remain to be published. In addition, risperidone has been reported to be of value in patients with schizodepressive disorders. The clinical success of risperidone suggests that the development of compounds with selective affinity for 5-HT2 or other serotonin receptors may result in even further improvements in the pharmacotherapy of psychiatric disorders.

Animals↗
PubMed1995

T cell proliferative responses to five human cytomegalovirus proteins in healthy seropositive individuals: implications for vaccine development.

Cell-mediated immunity plays an important role in the host response against human cytomegalovirus (HCMV) infection. For the development of HCMV subunit vaccines it is essential to identify which HCMV proteins can induce protective immune responses in humans. We have studied the T cell proliferative responses to five HCMV proteins (IE1, IE2, pp71, gpUL18 and gB). These five proteins were produced using the maltose-binding protein (MBP) fusion protein system. T cell proliferative responses in 23 seropositive and six seronegative individuals were evaluated. None of the six seronegative individuals showed significant responses to any of the proteins. Of the 23 seropositive individuals, five responded to all five proteins, 14 responded to between one and four proteins and four responded to none of the proteins. The most commonly recognized proteins were gB (17/23, 74%) and IE2 (16/23, 70%). pp71 and IE1 were recognized by 10 of 23 (43%) individuals. Nine of 22 (41%) individuals tested responded to gpUL18, providing evidence that this protein is produced during infection. Our data indicate that a subunit vaccine composed of gB alone may not be sufficient to induce protective immunity in all individuals. The combination of two or three proteins may be more efficient as a potential vaccine.

Capsid↗