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Biomedical subjects

S Hu

Publications and source records attributed to S Hu.

At least 325 records · Page 18Linked to original sources
PubMed1995

Change of water-soluble-protein, urea-soluble-protein and membrane intrinsic protein in human senile cataract.

PURPOSE: To analyze the change of water-soluble-protein (WSP), urea-soluble-protein (USP) and membrane intrinsic protein (MIP) in human senile cataract. METHODS: The water-soluble-fractions (WSF) were prepared basically according to the method of Kibbelear, et al. But in this study, 5 mmol/L B-mercaptoethanol was added to the buffer solution. The urea-soluble-fractions (USF) were prepared basically according to the method of Kibbelear, et al. Lens fiber cell membranes were purified basically according to the method of Russell, et al. SDS-PAGE were performed according to the procedure of Laemmili, et al. using resolving gel 13% and 3% stacking gel. RESULTS: The WSP was fractionated into HM+ alpha-, beta(1-3)- and gamma-crystallin components. In nuclear cataractous lenses HM+ alpha- and B-crystallin increase, while r-crystallin decrease. The USP from clear lenses contains mainly alpha beta chains of 22KD, whereas in cataractous lenses, especially in nuclear cataractous lenses, the relative amount of the 28- and 23KD polypeptide (the components of beta-crystallin) increased markedly. Lens fiber cell MIP, clear lens and cataract lens contained the main polypeptide of 27KD (MIP) and 23KD (MP23). CONCLUSION: The water-insoluble protein, whether in quantity or in quality, plays an important role in cataract formation.

Aged↗
PubMed1994

Role of interleukin-6 and transforming growth factor-beta in anorexia nervosa.

Anorexia nervosa is a serious eating disorder characterized by extreme weight loss and abnormalities of the neuroendocrine and immune systems. To determine the potential role of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and transforming growth factor-beta (TGF-beta) in anorexia nervosa, serum concentrations of these cytokines were measured in patients with anorexia nervosa during starvation and after weight gain. Serum IL-6 and TGF-beta concentrations were both significantly elevated during starvation and returned to levels comparable to those of normal-weight controls by the end of therapy. In contrast, serum TNF-alpha levels were undetectable in all patients and controls. Cytokines may play previously unsuspected roles in anorexia nervosa and its complications.

Adolescent↗
PubMed1994

Vascular actions of C-type natriuretic peptide in isolated porcine coronary arteries and coronary vascular smooth muscle cells.

C-type natriuretic (CNP) caused concentration-dependent relaxations in porcine coronary arteries with a maximal relaxation (10(-6)M) of 46%. Relaxations to CNP in isolated coronary arteries were significantly attenuated with potassium channel antagonists charybdotoxin (10(-7)M) and glibenclamide (10(-7)M). Membrane potential and K+ currents were measured in enzymatically dissociated smooth muscle cells from porcine coronary arteries with patch-clamp techniques in a whole-cell mode (n = 5). CNP caused K+ channel activation and membrane hyperpolarization in a dose-dependent manner. This hyperpolarization was markedly suppressed by the potassium channel inhibitor tetraethylammonium (TEA, 5 mM). These results demonstrate that CNP relaxes porcine coronary arterial smooth muscle by hyperpolarization of vascular smooth muscle through potassium channel stimulation.

Animals↗
PubMed1994

Thrombin-bound structure of an EGF subdomain from human thrombomodulin determined by transferred nuclear Overhauser effects.

The EGF-like domains in human thrombomodulin interact with and change the specificity of thrombin from a procoagulant enzyme to an anticoagulant enzyme. Recent experiments identified the minimal thrombin-binding region of thrombomodulin as the most acidic loop of the fifth EGF-like domain with a sequence of E408CPEGYILDDGFI420CTDIDE. High-resolution NMR spectroscopy was employed to characterize the interaction of a des-Ile420 thrombomodulin peptide, Cys1(409)Pro2Glu3Gly4Tyr5Ile6- Leu7Asp8Asp9Gly10Phe11Cys12Thr13Asp14Ile15Asp16Glu17(426), with its target coagulation protein, thrombin. The disulfide-bonded peptide was found to be structured only upon binding, while neither the linear nor the cyclized peptide exhibited any structural preference free in solution. The thrombin-bound structure of the cyclic thrombomodulin peptide was determined by transferred nuclear Overhauser effects (transferred NOEs) and by distance geometry and Monte Carlo calculations. The thrombin-bound cyclic peptide assumes an overall conformation similar to those observed in the free but intact EGF molecules. There is a type II beta-turn involving residues Pro2-Tyr5, followed by an optimized antiparallel beta-sheet involving residues Gly4-Asp8 and residues Phe11-Ile15. The thrombomodulin peptide provides a potential thrombin-binding surface between residues Tyr5 and Phe11, which are brought close by a chain reversal within the central beta-sheet. Comparison of the thrombin-bound structure of the EGF-like subdomain with other thrombin-peptide complexes revealed that a common thrombin-binding surface can be organized by different secondary structure elements with entirely different peptide sequences. The thrombin-bound structure of the thrombomodulin peptide may serve as a basis to understand the regulatory functions of thrombomodulin and as a guide for the design of specific inhibitors for thrombin.

Amino Acid Sequence↗
PubMed1994

NDF/heregulin stimulates the phosphorylation of Her3/erbB3.

Her3/erbB3 has been identified as a third member of the epidermal growth factor receptor (EGFR) family [(1989) Proc. Natl. Acad. Sci. USA 86, 9193-9197; (1990) Proc. Natl. Acad. Sci. USA 87, 4905-4909]. The natural ligand for Her3 has not been identified. Although recently NDF has been proposed as a specific ligand for Her4 [(1993) Nature 366, 473-475; (1993) J. Biol. Chem. 268, 18407-18410], we report here that Her3 was phosphorylated on tyrosine not only in three breast carcinoma cell lines, MDAMB453, MDAMB468 and SKBR3, but also in Her3-transfected CHO cells in response to NDF stimulation. In further studies, cells were reacted with 125I-labeled NDF and then chemically crosslinked. Immunoprecipitation with anti-Her3 revealed a dense high Mw band, greater than 400 kDa. The results suggest that NDF may be a ligand of Her3 and induces receptor hetero-oligomerization.

Animals↗
PubMed1994

Human microglial cell defense against Toxoplasma gondii. The role of cytokines.

Microglia may play an important role in host defense of the central nervous system against Toxoplasma gondii, and cytokines produced by these glial cells may participate in their antitoxoplasma activity. In our study, the antitoxoplasma activity of human fetal microglia was investigated. The RH strain of T. gondii multiplied readily in these glial cells. IFN-gamma/LPS-treated microglia limited (p < 0.01) T. gondii growth by reducing entry of this parasite rather than intracellular multiplication. More than 90% of the antitoxoplasma activity of activated microglia was blocked (p < 0.01) by neutralizing antibodies to TNF-alpha or IL-6 (but not to IL-1 or TGF-beta), suggesting that these proinflammatory cytokines play a role in the inhibitory process. Consistent with this hypothesis, treatment of microglia with TNF-alpha or IL-6 (in the presence or absence of IFN-gamma) inhibited (p < 0.01), in a dose-dependent manner, T. gondii growth. Inasmuch as NGMA did not affect cytokine-mediated antitoxoplasma activity of microglia, nitric oxide appears not to be involved in this host defense function of human fetal microglia. Results of our study suggest that the host defense activity of human microglia against T. gondii is dependent primarily on the activating properties of IFN-gamma, TNF-alpha, and IL-6.

Animals↗
PubMed1994

Unbleachable rhodopsin with an 11-cis-locked eight-membered ring retinal: the visual transduction process.

Visual transduction occurs through photorhodopsin, the primary photoproduct of rhodopsin, which relaxes to bathorhodopsin and a series of other intermediates until it reaches the metarhodopsin II stage, upon which the enzymatic cascade leading to vision is activated. Despite advances in areas related to visual transduction, the triggering process itself, a key problem in the chemistry of rhodopsin, has remained unsolved. In order to clarify the extent of involvement of the chromophoric excited state versus the 11-cis to trans isomerization, and as an extension of past studies with 11-cis-locked seven-membered ring rhodopsin (Rh7), 11-cis eight- and nine-membered ring retinal analogs, ret8 and ret9, respectively, have been synthesized. The bulkiness of the tetramethylene bridge in ret8 led to numerous unexpected obstacles in attempts to reconstitute a ret8-containing rhodopsin (Rh8) embedded in lipid bilayer membranes. These obstacles were solved by using methylated rhodopsin which gave MeRh8 containing 11-cis-ret8 as its chromophore. MeRh8 exhibited UV-vis and CD spectra very similar to those of native rhodopsin (Rh); furthermore, the quantum efficiency of photorhodopsin formation was comparable to that of Rh.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Role of cytokines in lipopolysaccharide-induced functional and structural abnormalities of astrocytes.

The mechanism underlying meningitis-associated brain injury is unclear. This study investigated the hypothesis that lipopolysaccharide (LPS) alters astrocyte function and structure via the release of proinflammatory cytokines. In enriched murine astrocyte cultures, LPS inhibited (P < 0.05) glutamine synthetase activity, 3H-gamma aminobutyric acid uptake, and DNA synthesis; LPS also induced ultrastructural changes. Antibodies to tumor necrosis factor-alpha, interleukin-1, and interleukin-6 blocked (P < 0.05) in part the LPS-induced inhibition of astrocyte function. Also, treatment of astrocyte cultures with cytokines significantly altered these astrocyte functions and ultrastructure. Taken together, the present findings support the hypothesis that LPS affects astrocyte function and structure via the release of proinflammatory cytokines, especially tumor necrosis factor-alpha.

Animals↗
PubMed1994

Morphine amplifies HIV-1 expression in chronically infected promonocytes cocultured with human brain cells.

Previous studies have shown that morphine promotes the replication of human immunodeficiency virus (HIV)-1 in peripheral blood mononuclear cell cocultures. In the present study, we tested the hypothesis that morphine would amplify HIV-1 expression in the chronically infected promonocytic clone U1 when cocultured with lipopolysaccharide-stimulated human fetal brain cells. Marked upregulation of HIV-1 expression was observed in these cocultures (quantified by measurement of HIV-1 p24 antigen levels in supernatants), and treatment of brain cells with morphine resulted in a bell-shaped dose-dependent enhancement of viral expression. The mechanism of morphine's amplifying effect appears to be opioid receptor-mediated and to involve enhanced production of tumor necrosis factor-alpha by microglial cells.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Substrate and pseudosubstrate interactions with protein kinases: determinants of specificity.

Protein crystallography has revealed that protein kinases have extended protein-substrate-binding grooves associated with their active sites. Some protein kinases are autoinhibited by a mechanism in which part of their structure, termed a pseudosubstrate, occupies the active site. Substrates and pseudosubstrates occupy overlapping regions within the extended substrate-binding groove, making multiple specific electrostatic and non-polar contacts. With masterly economy, Nature has exploited the active site in many protein kinases to both recognize substrates with great specificity and autoregulate by remaining inactive until the appropriate activation signal is received.

Amino Acid Sequence↗
PubMed1994

Recombinant and cellular expression of the murine chemotactic protein, CP-10.

The S100 protein CP-10 (chemotactic protein, 10 kD), a potent chemotactic factor for murine and human polymorphonuclear cells (PMN) and murine monocytes, has been purified in small amounts from supernatants of activated murine spleen cells (Lackmann et al., 1992). To obtain a more abundant source of the protein, CP-10 was expressed in Escherichia coli as a fusion protein with glutathione S-transferase (GST). The property of S100 proteins to undergo calcium-dependent conformational changes was used in a novel approach to optimize the release of recombinant (r) CP-10 by thrombin cleavage. Purified rCP-10 was characterized by amino-terminal sequence analysis and bioassays. Optimal chemotactic activity of rCP-10 for murine PMN and WEHI-265 monocytoid cells was 10(-11) M (native protein has optimal chemotactic activity between 10(-11) and 10(-13) M). Immunization of rabbits with the GST/CP-10 fusion protein bound to glutathione-agarose beads resulted in high titer, specific antibodies that neutralized CP-10-initiated chemotaxis and were suitable for immunoblotting. A combination of Western and Northern analyses identified CP-10 in murine peritoneal exudate PMN and macrophages, splenocytes, bone marrow cells, and WEHI-265 cells (all of myeloid origin), but not in thymus, liver, lung, 3T3 fibroblasts, EL4 lymphoma cells, or bEND 3 brain endothelial cells, indicating cell-specific regulation of CP-10 expression.

Animals↗
PubMed1994

Cytomegalovirus replication in murine microglial cell cultures: suppression of permissive infection by interferon-gamma.

The pathogenesis of encephalitis due to cytomegalovirus (CMV), particularly the role of microglial cells in the spread or control of infection, remains incompletely defined. In this study, microglial cells were isolated from the brains of newborn mice and infected in vitro with murine CMV (MCMV). Microglial cells supported productive MCMV replication, and the MCMV-infected microglia manifested a cytopathic effect (CPE) characteristic of CMV infection. Exposure of microglia to interferon-gamma (IFN-gamma) 24 h before infection markedly suppressed virus production and resultant CPE in a dose-dependent fashion. Furthermore, the addition of IFN-gamma 2 h after infection demonstrated an antiviral effect equivalent to that achieved when IFN-gamma was administered 2 h before infection. These results demonstrate that murine microglial cells are fully permissive to MCMV replication and that IFN-gamma markedly suppresses virus expression in these cells.

Animals↗
PubMed1994

Nitric oxide production and neurotoxicity mediated by activated microglia from human versus mouse brain.

Recent studies indicate that human macrophages lack a high-output inducible nitric oxide synthase (NOS) antimicrobial system. In the present study, microglial cells derived from fetal human versus neonatal mouse brain were compared in a coculture assay of human and murine neuronal cell injury. Neurotoxicity (reflected by lactate dehydrogenase release and impaired neuronal uptake of [3H] gamma-amino butyric acid) and nitric oxide (NO) production (assessed by measurement of nitrite) were observed only in cocultures containing interferon (IFN)-gamma-lipopolysaccharide (LPS)-stimulated murine microglia. Cultures of purified human fetal microglia, however, did produce low levels of NO upon stimulation with IFN-gamma-LPS. These findings support the proposal that human macrophages have an inefficient IFN-gamma-inducible NOS and suggest that in tissues, such as brain, this deficiency could be advantageous for neighboring cells.

Aged↗
PubMed1994

Anti-human immunodeficiency virus type 1 activities of U-90152 and U-75875 in human brain cell cultures.

Antiviral activities of the reverse transcriptase inhibitors U-90152 and 3'-azido-2',3'-dideoxythymidine and the protease inhibitor U-75875 were compared in two culture models of human immunodeficiency virus type 1 brain infection. In a model involving acutely infected microglial cells, U-90152 was the most active, whereas in a model using chronically infected promonocytes, U-75875 was the most active.

Antiviral Agents↗
PubMed1994

Transforming growth factor beta in Alzheimer's disease.

Alzheimer's disease (AD) has been hypothesized to be an inflammatory condition. We hypothesized that anti-inflammatory cytokines, such as transforming growth factor beta (TGF-beta), counteract the inflammatory process. In the present study, we found that TGF-beta levels were elevated in both cerebrospinal fluid and serum samples obtained from AD patients < 6 h after death. Serum TGF-beta levels were also markedly elevated before death. These results suggest that elevated TGF-beta levels in AD may represent a protective host response to immunologically mediated neuronal injury.

Aged↗
PubMed1994

Effects of mild exercise on cytokines and cerebral blood flow in chronic fatigue syndrome patients.

Chronic fatigue syndrome (CFS) is an idiopathic disorder characterized by fatigue that is markedly exacerbated by physical exertion. In the present study, we tested the hypothesis that mild exercise (walking 1 mph [1 mile = 1.609 km] for 30 min) would provoke serum cytokine and cerebral blood flow abnormalities of potential pathogenic importance in CFS. Interleukin-1 beta, interleukin-6, and tumor necrosis factor alpha were nondetectable in sera of CFS patients (n = 10) and healthy control subjects (n = 10) pre- and postexercise. At rest, serum transforming growth factor beta (TGF-beta) levels were elevated in the CFS group compared with the control group (287 +/- 18 versus 115 +/- 5 pg/ml, respectively; P < 0.01). Serum TGF-beta and cerebral blood flow abnormalities, detected by single-photon emission-computed tomographic scanning, were accentuated postexercise in the CFS group. Although these findings were not significantly different from those in the control group, the effect of exercise on serum TGF-beta and cerebral blood flow appeared magnified in the CFS patients. Results of this study encourage future research on the interaction of physical exertion, serum cytokines, and cerebral blood flow in CFS that will adopt a more rigorous exercise program than the one used in this study.

Adult↗
PubMed1994

Serum cytokine levels in patients with Alzheimer's disease.

Alzheimer's disease (AD) has been proposed to be an inflammatory disorder. In a recent study, markedly elevated levels of the anti-inflammatory cytokine transforming growth factor beta (TGF-beta) in the serum and cerebrospinal fluid of patients with advanced AD suggested a potential predictive value of this cytokine in patients with AD. In the present prospective study, we tested the hypothesis that the levels of TGF-beta in serum would be increased in patients with AD and could thereby serve as a diagnostic marker. We found that serum TGF-beta levels but not proinflammatory cytokine levels were significantly (P < 0.05) elevated in patients with AD (n = 22) in comparison with the levels in their healthy spousal controls. Also, serum TGF-beta levels were positively correlated (r = 0.45; P < 0.05) with disease severity. Nevertheless, the elevation in serum TGF-beta levels in patients with Ad was modest, and considerable overlap with the control values suggests that the diagnostic usefulness of this cytokine for AD is limited.

Aged↗