Biomedical subjects

H Zhu

Publications and source records attributed to H Zhu.

At least 199 records · Page 11Linked to original sources

PubMed2000

Naltrexone-precipitated morphine withdrawal in infant rat is attenuated by acute administration of NOS inhibitors but not NMDA receptor antagonists.

RATIONALE: There is increasing evidence that the N-methyl-D-aspartate (NMDA) receptor and the nitric oxide system are involved in opiate dependence in the adult rat, but whether these results in the adult apply to the infant rat is unknown. OBJECTIVES: Here we examined the effects of NMDA receptor antagonists and nitric oxide synthase (NOS) inhibitors, which reduce the opiate abstinence syndrome in adult animals, on morphine withdrawal in the infant rat. METHODS: Neonatal rats were injected with morphine sulfate (10.0 mg/kg) twice daily for 6.5 days. On the 7th day, pups were injected with NOS inhibitors (L-NAME or 7-NI), NMDA receptor antagonists (MK-801 or AP-5), or vehicle. After 15 min, the pups were injected with naltrexone (1 mg/kg) to precipitate withdrawal. Behavior for each pup was identified and recorded every 15 s for 10 min before naltrexone injection and 15 min after naltrexone injection. RESULTS: Both L-NAME and 7-NI significantly reduced most withdrawal behaviors in the infant rat, a result in line with previous studies in the adult rat. In contrast, AP-5 reduced some withdrawal behaviors but also increased others (e.g., moving paws). MK-801 was likewise ineffective in reducing most withdrawal behaviors and increased certain withdrawal behaviors (walking and wall climbing). CONCLUSIONS: In the infant rat, the production of nitric oxide is involved in opiate withdrawal whereas the NMDA receptor may not yet be functionally active or may play only a minor role.

2-Amino-5-phosphonovalerate↗

PubMed2000

Sonographic guidance of air enema for intussusception reduction in children.

BACKGROUND: Fluoroscopically guided air reduction of intussusception is a well-accepted technique. There are only two previous reports in which US has been used to monitor pneumatic reduction. OBJECTIVE: To assess the ability of US to monitor the success of air reduction of intussusception. MATERIALS AND METHODS: Sonographically guided air-enema reduction of intussusception in 199 children. In phase I (11 children), the success or failure of reduction was confirmed by fluoroscopy. In phase II (188 children), complete reduction was confirmed by clinical improvement of the child and repeat sonography 1 h later showing no persistent intussusception. RESULTS: In phase I, fluoroscopy confirmed the accuracy of US in all 11 children. In phase II, the success rate of initial reduction was 95%. Following successful reduction, US repeated 1 h later showed no recurrence of intussusception in 92%. In ten (5%) of 188, initial reduction was unsuccessful; fluoroscopically guided air reduction successfully reduced only three of these ten failures. CONCLUSIONS: Air enema guided by US is a practical and reliable technique for the reduction of intussusception.

Air↗

PubMed2000

Autoradiographic comparison of [3H]-clonidine binding to non-adrenergic sites and alpha(2)-adrenergic receptors in human brain.

UNLABELLED: Clonidine is a partial agonist at brain alpha(2)-adrenoceptors (alpha(2)AR), but also has high affinity (K(D) = 51 nM) in homogenate binding assays for non-adrenergic imidazoline-binding sites (I-sites; imidazoline receptors). Herein, an autoradiographic comparison of [3H]-clonidine binding to I-sites and alpha(2)AR in sections of human brain is reported. For I-sites, the adrenergic component of 50 nM [3H]-clonidine binding was masked with either 60 microM norepinephrine (NE; alpha(2)AR agonist) or 12.5 microM methoxy-idazoxan (MIDX; selective alpha(2)AR antagonist), whereas the remaining non-adrenergic sites were studied by displacement with 20 microM cirazoline. Levels of [3H]-clonidine binding to alpha(2)AR and I-sites, determined in adjacent tissue sections, were positively correlated across 27 brain regions (p = 0.0003; r(2) = 0.385). The principal olivary nucleus and the rostral portion of the ventrolateral medulla had highest ratios of I-sites: alpha(2)AR (>4:1). Quantitative transepts drawn across hippocampal images revealed alpha(2)AR enrichments in the CA-1 and inner molecular layers of the dentate gyrus-areas not enriched in I-sites. Competition curves were generated for I-sites in caudate sections using 10 ligands known to distinguish between I(1) and I(2) subtypes. The rank-order of affinities were cirazoline > harmane > BDF6143 > idazoxan = tizanidine (affinities of agmatine, efaroxan, moxonidine, NE, and oxymetazoline were too low to be reliable). Only the endogenous I-site ligand, harmane, had a monophasic displacement curve at the non-adrenergic sites (Ki = 521 +/- 12 nM). IN CONCLUSION: 1) the distribution of non-adrenergic [3H]-clonidine binding sites in human brain sections was correlated with, but distinct from alpha(2)AR; and 2) the affinities of these sites was distinct from alpha(1)AR, alpha(2)AR, I(1) or I(2) sites as previously defined in membrane binding assays. The properties of this non-adrenergic [3H]-clonidine binding site are consistent with I-sites previously labeled by [3H]-cirazoline in rat brain.

Adult↗

PubMed2000

Smad7 binds to Smurf2 to form an E3 ubiquitin ligase that targets the TGF beta receptor for degradation.

Ubiquitin-mediated proteolysis regulates the activity of diverse receptor systems. Here, we identify Smurf2, a C2-WW-HECT domain ubiquitin ligase and show that Smurf2 associates constitutively with Smad7. Smurf2 is nuclear, but binding to Smad7 induces export and recruitment to the activated TGF beta receptor, where it causes degradation of receptors and Smad7 via proteasomal and lysosomal pathways. IFN gamma, which stimulates expression of Smad7, induces Smad7-Smurf2 complex formation and increases TGF beta receptor turnover, which is stabilized by blocking Smad7 or Smurf2 expression. Furthermore, Smad7 mutants that interfere with recruitment of Smurf2 to the receptors are compromised in their inhibitory activity. These studies thus define Smad7 as an adaptor in an E3 ubiquitin-ligase complex that targets the TGF beta receptor for degradation.

Animals↗

PubMed2000

Binding properties of an orally active platinum anti-tumor drug JM216 with metallothionein in vivo.

The abilities of the orally active platinum anti-tumor drug JM216 [trans-bis-acetato-cis-dichloroammine (cyclohexylamine) platinum (IV)] to induce the biosynthesis of metallothionein (MT) were investigated in rabbits given oral administrations or injections s.c. It is revealed that oral administration of JM216 can induce the MT synthesis in the liver but not in the kidney. The hepatic MT contained 7.11 +/- 0.11 Zn and only little Pt or Cu. Injections of JM216 to rabbits can greatly elevate the MT levels in the liver, but increase the renal MT levels only slightly. The MT content as well as Pt concentration in the liver was much higher than that in the kidney. The metal stoichiometry in the purified renal MT was determined to be 4.41 +/- 0.04 Zn, 0.36 +/- 0.11 Pt and 2.50 +/- 0.18 Cu per mole protein. The hepatic MT was still characterized as Zn7MT. Both the treatment with oral administration and injections s.c. cannot lead to the increase of Pt content in the kidney. The oxidation state of platinum in the MT from the kidney was determined to be +2 by X-ray photoelectron spectroscopy. As compared with zinc compounds, JM216 was a very poor stimulator for MT biosynthesis in vivo. Pre-injections with Zn(NO3)2 significantly enhanced the MT levels as well as the Pt concentration compared with that resulting from injections with JM216 alone. Based on the experimental data, the role of MT in relation to its involvement in the metabolism and the mechanism of detoxification of Pt(IV) complexes are discussed.

Animals↗

PubMed2000

Development of early melanocytic lesions in transgenic mice predisposed to melanoma.

We have previously described a line of transgenic mice (TG3) that spontaneously develops heritable malignant melanoma. Histological analysis of these animals during the first postnatal month is described here. In the TG3 line, the number of melanocytes is increased at all anatomical sites to which neural-crest-derived melanocytes normally migrate. Clonal expansion and morphological changes of these melanocytes can be detected as early as postnatal day (PND) 15. By PND 30, cells morphologically indistinguishable from the tumor cells of adult transgenic mice were detected in the ear, eye lid and perianal region. These cells are believed to be the precursors of the primary tumors in adult mice. The stepwise development of melanoma in the TG3 line is similar to the stepwise development of melanoma in humans.

Animals↗

PubMed2000

Receptor-dependent cell stress and amyloid accumulation in systemic amyloidosis.

Accumulation of fibrils composed of amyloid A in tissues resulting in displacement of normal structures and cellular dysfunction is the characteristic feature of systemic amyloidoses. Here we show that RAGE, a multiligand immunoglobulin superfamily cell surface molecule, is a receptor for the amyloidogenic form of serum amyloid A. Interactions between RAGE and amyloid A induced cellular perturbation. In a mouse model, amyloid A accumulation, evidence of cell stress and expression of RAGE were closely linked. Antagonizing RAGE suppressed cell stress and amyloid deposition in mouse spleens. These data indicate that RAGE is a potential target for inhibiting accumulation of amyloid A and for limiting cellular dysfunction induced by amyloid A.

Amyloid↗

PubMed2000

Analysis of yeast protein kinases using protein chips.

We have developed a novel protein chip technology that allows the high-throughput analysis of biochemical activities, and used this approach to analyse nearly all of the protein kinases from Saccharomyces cerevisiae. Protein chips are disposable arrays of microwells in silicone elastomer sheets placed on top of microscope slides. The high density and small size of the wells allows for high-throughput batch processing and simultaneous analysis of many individual samples. Only small amounts of protein are required. Of 122 known and predicted yeast protein kinases, 119 were overexpressed and analysed using 17 different substrates and protein chips. We found many novel activities and that a large number of protein kinases are capable of phosphorylating tyrosine. The tyrosine phosphorylating enzymes often share common amino acid residues that lie near the catalytic region. Thus, our study identified a number of novel features of protein kinases and demonstrates that protein chip technology is useful for high-throughput screening of protein biochemical activity.

Adenosine Triphosphate↗

PubMed2000

Expression of mouse apolipoprotein SAA1.1 in CE/J mice: isoform-specific effects on amyloidogenesis.

Amyloid A (AA) amyloid deposition in mice is dependent upon isoform-specific effects of the serum amyloid A (SAA) protein. In type A mice, SAA1.1 and SAA2.1 are the major apolipoprotein-SAA isoforms found on high-density lipoproteins. During inflammation, both isoforms are increased 1000-fold, but only SAA1.1 is selectively deposited into amyloid fibrils. Previous studies showed that the CE/J mouse strain is resistant to amyloid induction. This resistance is not due to a deficiency in SAA synthesis, but is probably related to the unusual SAA isoform present. The CE/J mouse has a single acute-phase SAA protein (SAA2.2), which is a composite of the SAA1.1 and SAA2.1, with an amino terminus similar to the nonamyloidogenic SAA2.1. Recently, genetic experiments suggested that the SAA2.2 isoform might provide protection from amyloid deposition. To determine the amyloidogenic potential of the CE/J mouse, we generated SAA adenoviral vectors to express the various isoforms in vitro and in vivo. Purified recombinant SAA proteins demonstrated that SAA1.1 was fibrillogenic in vitro, whereas SAA2.2 was unable to form fibrils. Incubation of increasing concentrations of the nonamyloidogenic SAA2.2 protein with the amyloidogenic SAA1.1 did not inhibit the fibrillogenic nature of SAA1.1, or alter its ability to form extensive fibrils. Injection of the mouse SAA1.1 or SAA2.2 adenoviral vectors into mice resulted in isoform-specific expression of the SAA proteins. Amyloid induction after viral expression of the SAA1.1 protein resulted in the deposition of amyloid fibrils in the CE/J mouse, whereas SAA2.2 expression had no effect. Similar expression of the SAA2.2 protein in C57BL/6 mice did not alter amyloid deposition. These data demonstrate that the failure of the CE/J mouse to deposit amyloid is due to the structural inability of the SAA2.2 to form amyloid fibrils. This mouse provides a unique system to test the amyloidogenic potential of altered SAA proteins and to determine the important structural features of the protein.

Adenoviridae↗

PubMed2000

Phenylephrine protects neonatal rat cardiomyocytes from hypoxia and serum deprivation-induced apoptosis.

Previous studies have shown that alpha-adrenergic activation reduces myocardial damages caused by ischemia/reperfusion. However, the molecular mechanisms of how alpha-adrenergic activation protects the myocardium are not completely understood. The objective of this study was to test the hypothesis that alpha-adrenergic activation protects the myocardium by, at least in part, inhibiting apoptosis in cardiomyocytes. The current data has shown that apoptosis in neonatal rat cardiomyocytes, induced by 24 h treatment with hypoxia (95% N2 and 5% CO2) and serum deprivation, was inhibited by co-treatment with phenylephrine. Pre-treatment with phenylephrine for 24 h also protected cardiomyocytes against subsequent 24 h treatment with hypoxia and serum deprivation. Exposure of cardiomyocytes to phenylephrine for up to 9 days under normoxic conditions did not cause apoptosis. The phenylephrine-mediated cytoprotection was blocked by an alpha-adrenergic antagonist, phentolamine. beta-adrenergic activation with isoproterenol did not protect cardiomyocytes against hypoxia and serum deprivation-induced apoptosis. Under hypoxic conditions, phenylephrine prevented the down-regulation of Bcl-2 and Bcl-X mRNA/protein and induced hypertrophic growth. Phenylephrine-mediated protection was abrogated by the phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor wortmannin and was mimicked by the caspase-9 peptidic inhibitor LEHD-fmk. These results suggest that alpha-adrenergic activation protects cardiomyocytes against hypoxia and serum deprivation-induced apoptosis through regulating the expression of mitochondrion-associated apoptosis regulatory genes, preventing activation of mitochondrial damage-induced apoptosis pathway (cytochrome C-caspase-9), and activating hypertrophic growth.

Actinin↗

PubMed2000

Invasive strains of Pseudomonas aeruginosa are able to cause epithelial cell cytotoxicity that is dependent on bacterial cell density.

The purpose of this study was to investigate the hypothesis that quorum-sensing systems are involved in the ability of invasive Pseudomonas aeruginosa strains to cause corneal epithelial cell death. Two invasive strains, 6294 and PAOI, were co-cultured with human corneal epithelial cells at different bacterial concentrations (10(5), 10(7) and 10(9) CFU/mL). Cytotoxicity was measured using a cytotoxicity assay kit. The levels of autoinducer in the supernatant were examined using a reporter strain of Agrobacterium tumefaciens (A136). Protease production was also monitored. Cytotoxicity of both strains was dependent on bacterial density; a moderate to high concentration of bacterial cells (10(7) and 10(9) CFU/mL) caused 70% to 94% loss of cell variability. Cytotoxicity was significantly correlated with enhanced autoinducer and protease production (r>0.95, P<0.05). These results indicate that the invasive strains regulate the production of virulence factors and, in turn, induce chronic dose-related cytotoxicity.

Agrobacterium tumefaciens↗

PubMed2000

The catalytic subunit of telomerase protects neurons against amyloid beta-peptide-induced apoptosis.

The catalytic subunit of telomerase (TERT) is a specialized reverse transcriptase that has been associated with cell immortalization and cancer. It was reported recently that TERT is expressed in neurons throughout the brain in embryonic and early postnatal development, but is absent from neurons in the adult brain. We now report that suppression of TERT levels and function in embryonic mouse hippocampal neurons in culture using antisense technology and the telomerase inhibitor 3' -azido-2' 3' -dideoxythymidine significantly increases their vulnerability to cell death induced by amyloid beta-peptide, a neurotoxic protein believed to promote neuronal degeneration in Alzheimer's disease. Neurons in which TERT levels were reduced exhibited increased levels of oxidative stress and mitochondrial dysfunction following exposure to amyloid beta-peptide. Overexpression of TERT in pheochromocytoma cells resulted in decreased vulnerability to amyloid beta-peptide-induced apoptosis. Our findings demonstrate a neuroprotective function of TERT in an experimental model relevant to Alzheimer's disease, and suggest the possibility that restoration of TERT expression in neurons in the adult brain may protect against age-related neurodegeneration.

Alzheimer Disease↗

PubMed2000

Somatic mutations of the multiple endocrine neoplasia type 1 (MEN1) gene in patients with sporadic, nonfamilial primary hyperparathyroidism.

BACKGROUND: Multiple endocrine neoplasia type 1 (MEN 1) is a syndrome with tumors of many endocrine tissues. Germline MEN1 gene mutations were found in most patients with familial or sporadic MEN 1. Recently, somatic MEN1 gene mutations were also detected in sporadic non-MEN 1 endocrine tumors. METHODS: We used direct sequence analysis to investigate MEN1 gene mutations in 30 parathyroid tumors obtained from 30 patients with sporadic, nonfamilial primary hyperparathyroidism. RESULTS: Four patients had somatic mutations of the MEN1 gene, comprising 1 small insertion (1091insAGC), one missense mutation (G42S), and 2 non-sense mutations (E388X, R460X). Identical missense and non-sense mutations were found in patients with familial and non-familial MEN 1. There were no differences between clinical features of patients with and without MEN1 gene mutations. CONCLUSIONS: The incidence of somatic MEN1 gene mutations (13.3%) in Japanese patients with sporadic, nonfamilial primary hyperparathyroidism is almost equal to those of such patients in the United States and Sweden. Occasionally, the MEN1 gene mutation sites in sporadic parathyroid tumors are identical to those reported in tumors from patients with familial or sporadic MEN 1.

DNA↗

PubMed2000

Imidazoline receptor antisera-selected (IRAS) cDNA: cloning and characterization.

The imidazoline-1 receptor (IR1) is considered a novel target for drug discovery. Toward cloning an IR1, a truncated cDNA clone was isolated from a human hippocampal lambda gt11 cDNA expression library by relying on the selectivity of two antisera directed against candidate IR proteins. Amplification reactions were performed to extend the 5' and 3' ends of this cDNA, followed by end-to-end PCR and conventional cloning. The resultant 5131-basepair molecule, designated imidazoline receptor-antisera-selected (IRAS) cDNA, was shown to encode a 1504-amino acid protein (IRAS-1). No relation exists between the amino acid sequence of IRAS-1 and proteins known to bind imidazolines (e.g., it is not an alpha2-adrenoceptor or monoamine oxidase subtype). However, certain sequences within IRAS-1 are consistent with signaling motifs found in cytokine receptors, as previously suggested for an IR1. An acidic region in IRAS-1 having an amino acid sequence nearly identical to that of ryanodine receptors led to the demonstration that ruthenium red, a dye that binds the acidic region in ryanodine receptors, also stained IRAS-1 as a 167-kD band on SDS gels and inhibited radioligand binding of native I1 sites in untransfected PC-12 cells (a source of authentic I1 binding sites). Two epitope-selective antisera were also generated against IRAS-1, and both reacted with the same 167-kD band on Western blots. In a host-cell-specific manner, transfection of IRAS cDNA into Chinese hamster ovary cells led to high-affinity I1 binding sites by criteria of nanomolar affinity for moxonidine and rilmenidine. Thus, IRAS-1 is the first protein discovered with characteristics of an IR1.

Amino Acid Motifs↗

PubMed2000

MASIA: recognition of common patterns and properties in multiple aligned protein sequences.

SUMMARY: MASIA is a software tool for pattern recognition in multiple aligned protein sequences. MASIA converts a sequence to a properties matrix that can be scanned in both vertical and horizontal steps. Consistent patterns are recognized based on the statistical significance of their occurrence. Preset macros can be altered on-line to seek any combination of amino acid properties or sequence characteristics. MASIA output can be used directly by our programs to predict the 3D structure of proteins. AVAILABILITY: Access MASIA at http://www.scsb.utmb.edu/masia/ma sia.html.

Sequence Alignment↗

PubMed2000

Once a month administration of mifepristone improves bleeding patterns in women using subdermal contraceptive implants releasing levonorgestrel.

It has been suggested that the administration of an anti-progesterone might improve bleeding patterns in women with irregular bleeding while using low-dose progestin-only contraception. We report the findings of a double-blind, randomized, placebo-controlled trial of mifepristone 50 mg taken once every 4 weeks in 100 Chinese women (50 subjects and 50 controls) complaining of frequent and irregular bleeding while using a levonorgestrel-releasing subdermal contraceptive implant. In all women, regardless of treatment, the frequency of bleeding decreased significantly over 360 days of observation. Women recorded significantly shorter episodes of bleeding (P: < 0.0002) during mifepristone treatment than during the 90 days before treatment started. In contrast, the duration of bleeding episodes fell more gradually in placebo-treated controls. Women using mifepristone were more likely to find treatment acceptable than women receiving a placebo tablet (P: < 0.01). Despite concern that anti-progestogenic effects may jeopardize contraception, there were no pregnancies. This approach may offer a useful strategy to improve continuation rates by alleviating unwanted side-effects until bleeding patterns improve spontaneously with time.

Adolescent↗

PubMed2000

Functional characterization of mammalian mitochondrial carnitine palmitoyltransferases I and II expressed in the yeast Pichia pastoris.

Mitochondrial carnitine palmitoyltransferases I and II (CPTI and CPTII), together with the carnitine carrier, transport long-chain fatty acyl-CoA from the cytosol to the mitochondrial matrix for beta-oxidation. Recent progress in the expression of CPTI and CPTII cDNA clones in Pichia pastoris, a yeast with no endogenous CPT activity, has greatly facilitated the characterization of these important enzymes in fatty acid oxidation. It is now well established that yeast-expressed CPTI is a catalytically active, malonyl CoA-sensitive, distinct enzyme that is reversibly inactivated by detergents. CPTII is a catalytically active, malonyl CoA-insensitive, distinct enzyme that is detergent stable. Reconstitution studies with yeast-expressed CPTI have established for the first time that detergent inactivation of CPTI is reversible, suggesting that CPTI is active only in a membrane environment. By constructing a series of deletion mutants of the N-terminus of liver CPTI, we have mapped the residues essential for malonyl CoA inhibition and binding to the conserved first six N-terminal amino acid residues. Mutation of glutamic acid 3 to alanine abolished malonyl CoA inhibition and high affinity malonyl CoA binding, but not catalytic activity, whereas mutation of histidine 5 to alanine caused partial loss in malonyl CoA inhibition. Our mutagenesis studies demonstrate that glutamic acid 3 and histidine 5 are necessary for malonyl CoA inhibition and binding to liver CPTI, but not catalytic activity.

Amino Acid Sequence↗

PubMed2000

Left ventricular myocardial adenosine triphosphate changes during reperfusion of ventricular fibrillation: the influence of flow and epinephrine.

OBJECTIVE: To determine whether epinephrine in combination with high flow worsens left ventricular (LV) myocardial high-energy phosphate stores during reperfusion of ischemic ventricular fibrillation (VF). DESIGN: Blinded, prospective block randomized, placebo controlled study. SETTING: University medical center research laboratory. SUBJECTS: A total of 22 mixed breed swine weighing 22.0+/-3.3 kg (SD). INTERVENTIONS: Open-chest swine, anesthetized with alpha-chloralose, underwent 10 mins of nonperfused VF followed by reperfusion with cardiopulmonary bypass for 90 mins and then defibrillation. Animals were block randomized to four groups for reperfusion: Group 1 (n = 5), high flow (100 mL/kg/min) and epinephrine (2.5 microg/kg/min); Group 2 (n = 5), high flow and placebo; Group 3 (n = 6), low flow (30 mL/kg/min) and epinephrine; and Group 4 (n = 6), low flow and placebo. MEASUREMENTS AND MAIN RESULTS: In vivo LV creatine phosphate (CP) and adenosine triphosphate (ATP) were determined using whole wall and spatially localized 31P NMR spectroscopy at 4.7 Tesla. During perfusion of the fibrillating myocardium, epinephrine significantly increased aortic pressure (p < .05) and improved defibrillation rates (p < .01). ATP levels during reperfusion were significantly decreased within all groups compared with baseline. There were no differences in ATP levels between groups. High flow, independent of epinephrine, was associated with increased preservation of ATP (p < .05), increased CP/ATP ratios (p < .02) in all layers of the LV wall, and decreased aortic and cardiac vein lactates (p < .001). CONCLUSIONS: Epinephrine, in combination with flow higher than standard cardiopulmonary resuscitation flows, increased perfusion pressure and defibrillation rates, but did not significantly alter myocardial ATP during VF reperfusion in the in vivo heart Reperfusion flow, independent of epinephrine, is a critical determinant of myocardial ATP preservation.

Adenosine Triphosphate↗