Biomedical subjects

H Chen

Publications and source records attributed to H Chen.

At least 613 records · Page 34Linked to original sources

PubMed1999

Synergistic effect of rapamycin and cyclosporine in prevention of acute kidney allograft rejection in the mouse.

The effect of rapamycin (RAPA) and cyclosporine A (CsA) monotherapy and combination therapy was examined in prevention of kidney allograft rejection in the mouse. Both drugs were administered orally for up to 14 days in BALB/c (H-2(d)) to C57BL/6 (H-2(b)) mice strong combination. Six groups were treated with RAPA and/or CsA. This study shows that concomitant therapy of RAPA and CsA produces strong synergistic interaction in prolonging renal allograft survival in mice when compared with monotherapy of RAPA or CsA.

Animals↗

PubMed1999

Rotational Pattern Difference in Resolved Fluorescence Spectra with Different Detection Schemes.

The relative intensities of rotational lines in resolved fluorescence spectra are dependent on the detection direction and the choice of the detection scheme when a grating monochromator is used. These differences arise from the spatially anisotropic distribution of the fluorescence, the rotational branch dependence of the fluorescence polarization, and the polarization dependence of the monochromator grating efficiency. Both the anisotropy of the emission and the rotational branch dependence of the fluorescence polarization are enhanced in double-resonance excitation schemes. In the present work, we analyze the relative intensities in the (7)Li(2) 1(3)Sigma(-)(g) --> 1(b)(3)Pi(u) and 1(3)Delta(g) --> 1(b)(3)Pi(u) resolved fluorescence spectra, observed following double-resonance excitation, for three different detection schemes. Copyright 1999 Academic Press.

Journal Article↗

PubMed1999

The 6svarsigma, 6dvarsigma, and 7dvarsigma Rydberg (1)Sigma(+)(g) States and Two Doubly Excited (1)Sigma(+)(g) States of Na(2).

Five highly excited (1)Sigma(+)(g) states of Na(2) were observed for the first time by pulsed optical-optical double resonance (OODR) fluorescence excitation spectroscopy. Three of the five states are assigned to the 6svarsigma (1)Sigma(+)(g), 6dvarsigma (1)Sigma(+)(g), and 7dvarsigma (1)Sigma(+)(g) Rydberg states. The other two states are assigned to doubly excited (1)Sigma(+)(g) states. Copyright 1999 Academic Press.

Journal Article↗

PubMed1999

Acute exercise enhances receptor-mediated endothelium-dependent vasodilation by receptor upregulation.

The effects of acute exercise on receptor-mediated endothelium-dependent vasodilation and its possible mechanisms were investigated in the presence of indomethacin. Male Wistar rats (16-20 weeks old) were divided into control and exercise groups. The exercise group ran on a drum exerciser until exhaustion, followed by immediate decapitation. Acetylcholine (ACh)- or clonidine (CLO)-induced vasodilating responses in thoracic aortae of the control and exercise groups were compared. Receptor-binding assays were performed to determine whether there were any upregulations of endothelial receptors after acute exercise. Our results indicated that acute exercise induced the following effects: (1) the dose-response curves of ACh and CLO shifted to the left; (2) the high-affinity M3 binding sites increased in number but not in affinity; (3) the alpha2 binding sites decreased in number but increased in affinity. We conclude that acute exercise enhances receptor-mediated vasodilation responses, at least in part, by regulating either endothelial receptor number or receptor affinity.

Acetylcholine↗

PubMed1999

Clinically significant, isolated metastatic disease to the thyroid gland.

Despite being second only to the adrenal glands in terms of relative vascular perfusion, the thyroid gland is a rare site of metastatic disease; but when thyroid metastases occur, long-term survival has been reported to be dismal. To determine the incidence and management of isolated, metastatic disease to the thyroid, we reviewed our clinical experience. Between June 1986 and August 1994 ten patients underwent thyroidectomy for isolated, metastatic disease of nonthyroidal origin (mean +/- SD age 58 +/- 6 years, 30% female). The primary tumors were renal cell carcinomas (RCCs) (n = 5), esophageal adenocarcinoma (n = 1), pulmonary squamous cell carcinoma (n = 1), gastric leiomyosarcoma (n = 1), lingual squamous cell carcinoma (n = 1), and parotid gland carcinoma (n = 1). Three patients underwent preoperative fine-needle aspiration (FNA), all of which were suggestive of metastatic disease. The mean time from resection of the primary tumor to thyroid metastases was 3.5 +/- 6.0 years (range 0-19.5 years). Total thyroidectomy (n = 5) or lobectomy (n = 5) was performed without morbidity or mortality. After a median follow-up of 5.2 years six patients are alive and two are free of disease. Moreover, no patients have had recurrent disease in the neck. Thus carcinomas metastatic to the thyroid represent a rare cause of clinically significant thyroid disease, with RCCs comprising 50%. Most thyroid metastases (80%) present within 3 years of primary tumor resection, but with RCC they can occur as late as 19 years. The diagnosis of metastatic disease should be suspected in patients with even a remote history of cancer, especially RCC, and an FNA revealing clear cell or spindle cell carcinoma. Contrary to previous reports, long-term survival can be achieved after resection of the metastatic tumor. Furthermore, thyroidectomy may also palliate/prevent the potential morbidity of tumor recurrence in the neck.

Adenocarcinoma↗

PubMed1999

Identification of a bovine beta-mannosidosis mutation and detection of two beta-mannosidase pseudogenes.

Beta-mannosidase deficiency results in beta-mannosidosis, a severe neurodegenerative lysosomal storage disease identified in cattle, goats, and humans. To more fully understand the molecular pathology of this disease, the mutation associated with bovine beta-mannosidosis was identified by sequence analysis of cDNA from an affected calf. A transition mutation of G to A at position 2574 of the cDNA coding sequence creates a premature stop codon near the 3' end of the protein coding region. To aid commercial breeders of Salers cattle, a PCR-based test was developed to detect the mutation for beta-mannosidosis carrier screening. Application of this test also revealed the presence of two beta-mannosidase pseudogenes. Portions of the pseudogenes were amplified with allele-specific primers and then sequenced. One pseudogene was highly homologous (>99% sequence identity) to the expressed cDNA sequence over the 1292 bp that were sequenced, while the other showed more divergence (83% sequence identity) in the 477 bp that were sequenced. Both are processed pseudogenes that are not expressed. The severity of the bovine beta-mannosidosis phenotype suggests that the 22 C-terminal amino acids of beta-mannosidase play an important role in the function of this enzyme.

Animals↗

PubMed1999

A testis-specific gene, TPTE, encodes a putative transmembrane tyrosine phosphatase and maps to the pericentromeric region of human chromosomes 21 and 13, and to chromosomes 15, 22, and Y.

To contribute to the creation of a transcription map of human chromosome 21 (HC21) and to the identification of genes that may be involved in the pathogenesis of Down syndrome, exon trapping was performed from HC21-specific cosmids covering the entire chromosome. More than 700 exons have been identified to date. One such exon, hmc01a06, maps to YAC 831B6 which contains marker D21Z1 (alphoid repeats) and had previously been localized to the pericentromeric region of HC21. Northern-blot analysis revealed a 2.5-kb mRNA species strongly and exclusively expressed in the testis. We cloned the corresponding full-length cDNA, which encodes a predicted polypeptide of 551 amino acids with at least two potential transmembrane domains and a tyrosine phosphatase motif. The cDNA has sequence homology to chicken tensin, bovine auxilin and rat cyclin-G associated kinase (GAK). The entire polypeptide sequence also has significant homology to tumor suppressor PTEN/MMAC1 protein. We termed this novel gene/protein TPTE (transmembrane phosphatase with tensin homology). Polymerase chain reaction amplification, fluorescent in situ hybridization, Southern-blot and sequence analysis using monochromosomal somatic cell hybrids showed that this gene has highly homologous copies on HC13, 15, 22, and Y, in addition to its HC21 copy or copies. The estimated minimum number of copies of the TPTE gene in the haploid human genome is 7 in male and 6 in female. Zoo-blot analysis showed that TPTE is conserved between humans and other species. The biological function of the TPTE gene is presently unknown; however, its expression pattern, sequence homologies, and the presence of a potential tyrosine phosphatase domain suggest that it may be involved in signal transduction pathways of the endocrine or spermatogenetic function of the testis. It is also unknown whether all copies of TPTE are functional or whether some are pseudogenes. TPTE is, to our knowledge, the gene located closest to the human centromeric sequences.

Amino Acid Sequence↗

PubMed1999

Dorsoventral patterning of the vertebrate limb: a process governed by multiple events.

In this review, we detail recent studies which have led to the first molecular insights into dorsoventral vertebrate limb patterning. In keeping with classical experiments which defined ectodermal-mesodermal signaling as an important component of limb bud dorsoventral axis specification, the genes identified to date to be critically important for proper dorsoventral limb patterning include both ectodermally and mesodermally expressed cell:cell signaling molecules and transcription factors. A surprising complexity to dorsoventral vertebrate limb patterning has been revealed by gene targeting in the mouse and lineage tracing in the chick, with current models suggesting that the dorsoventral limb axis is specified by distinct mechanisms in the proximal versus distal limb.

Animals↗

PubMed1999

Introduction of the human PLTP transgene suppresses the atherogenic diet-induced increase in plasma phospholipid transfer activity in C57BL/6 mice.

The human plasma phospholipid transfer protein (PLTP) has been shown to facilitate the transfer of phospholipids between lipoproteins and convert high-density lipoproteins into larger and smaller particles in vitro. To explore the lipid transport function in vivo, transgenic C57BL/6 mice that express the human PLTP gene, driven by its natural promoter, were generated. Little difference in PLTP activity and lipoprotein lipids was observed between transgenic mice and non-transgenic control mice fed the chow diet. In response to an atherogenic high-fat, high-cholesterol, cholic acid containing diet, the PLTP activity increased significantly with time in control mice (62% in males and 34% in females after the high-fat diet for 18 weeks). In contrast, the PLTP activity did not change appreciably in the transgenic mice fed the atherogenic diet. Thus, the introduction of the human transgene suppressed the diet-induced increase in plasma PLTP activity, as evidenced by a decrease in PLTP mRNA in a variety of tissues. High-density lipoprotein levels decreased in mice fed the atherogenic diet, but there was a proportionally greater decrease in transgenic animals than in controls. After 18 weeks on the atherogenic diet, the transgenic animals had high-density lipoprotein-cholesterol and PLTP activity approximately one-half of that of control animals. Non-denaturing gradient gel electrophoresis of plasma indicated that the atherogenic diet decreased the high-density lipoprotein size distribution in control mice. However, high-density lipoprotein particle size distribution of the transgenic mice was shifted to smaller particles compared with control animals (P < 0.001). These findings suggest that PLTP activity can modulate the effects of an atherogenic diet on high-density lipoproteins.

Animals↗

PubMed1999

Structural organization and mutational analysis of the human uncoupling protein-2 (hUCP2) gene.

Uncoupling proteins (UCPs) are mitochondrial membrane transporters which are involved in dissipating the proton electrochemical gradient thereby releasing stored energy as heat. This implies a major role of UCPs in energy metabolism and thermogenesis which when deregulated are key risk factors for the development of obesity and other eating disorders. From the three different human UCPs identified so far by gene cloning both UCP2 and UCP3 were mapped in close proximity (75-150 kb) to regions of human chromosome 11 (11q13) that have been linked to obesity and hyperinsulinaemia. At the amino acid level hUCP2 has about 55% identity to hUCP1 while hUCP3 is 71% identical to hUCP2. In this study we have deduced the genomic structure of the human UCP2 gene by PCR and direct sequence analysis. The hUCP2 gene spans over 8.7 kb distributed on 8 exons. The localization of the exon/intron boundaries within the coding region matches precisely that of the hUCP1 gene and is almost conserved in the recently discovered hUCP3 gene as well. The high degree of homology at the nucleotide level and the conservation of the exon /intron boundaries among the three UCP genes suggests that they may have evolved from a common ancestor or are the result from gene duplication events. Mutational analysis of the hUCP2 gene in a cohort of 172 children (aged 7 - 13) of Caucasian origin revealed a polymorphism in exon 4 (C to T transition at position 164 of the cDNA resulting in the substitution of an alanine by a valine at codon 55) and an insertion polymorphism in exon 8. The insertion polymorphism consists of a 45 bp repeat located 150 bp downstream of the stop codon in the 3'-UTR. The allele frequencies were 0.63 and 0.37 for the alanine and valine encoded alleles, respectively, and 0.71 versus 0.29 for the insertion polymorphism. The allele frequencies of both polymorphisms were not significantly elevated in a subgroup of 25 children characterized by low Resting Metabolic Rates (RMR). So far a direct correlation of the observed genotype with (RMR) and Body Mass Index (BMI) was not evident. Expression studies of the wild type and mutant forms of UCP2 should clarify the functional consequences these polymorphisms may have on energy metabolism and body weight regulation.

3' Untranslated Regions↗

PubMed1999

HPV in situ hybridization with catalyzed signal amplification and polymerase chain reaction in establishing cerebellar metastasis of a cervical carcinoma.

We report an unusual case of cerebellar metastasis from a cervical adenosquamous carcinoma in which molecular techniques assisted in establishing the correct diagnosis. The patient was a 43-year-old woman with surgically unresectable cervical carcinoma diagnosed 2 years before presenting with neurological symptoms. A magnetic resonance imaging scan showed a large, enhancing cerebellar lesion with significant brain stem compression. The excised cerebellar tumor resembled a small cell carcinoma and was initially not thought to be a metastasis from the cervical adenosquamous carcinoma. In situ hybridization with catalyzed signal amplification and polymerase chain reactions with primers specific for human papilloma virus (HPV) types 16 and 18 were used to determine the relationship between the cervical and the cerebellar neoplasms. A positive signal was present in the nuclei of both neoplasms by in situ hybridization using HPV16/18 DNA probes. Polymerase chain reaction revealed the presence of HPV-18 DNA sequences in the cervical and cerebellar neoplasms confirming that the cerebellar neoplasm was a metastasis from the cervical primary.

Adult↗

PubMed1999

Enhanced Fas/CD95-mediated apoptosis by epidermal growth factor in human endometrial epithelial cells.

Epidermal growth factor (EGF) has been reported to regulate apoptosis in various cell lineages. Throughout the menstrual cycle overexpression of the EGF receptor in the secretory epithelium and constitutive expression of EGF in all types of endometrial cells were identified by immunohistochemical study of normal human endometrial tissues. However, it is not known whether EGF also regulates endometrial apoptosis. This study examined the regulatory functions of EGF in endometrial apoptosis by using a human endometrial epithelial cell line HHUA which is susceptible to Fas-mediated apoptosis. Although EGF alone did not affect the cell growth of HHUA, EGF pretreatment of HHUA enhanced Fas-mediated growth suppression and Fas-mediated DNA fragmentation in the cells. Flowcytometric analyses demonstrated that EGF did not induce Fas expression on the cell surface while expressions of the EGF receptor were down-regulated. These results suggest that EGF may enhance apoptotic susceptibility of the endometrial epithelium, especially in the secretory epithelium.

Apoptosis↗

PubMed1999

Primary hyperalgesia to mechanical and heat stimuli following subcutaneous bee venom injection into the plantar surface of hindpaw in the conscious rat: a comparative study with the formalin test.

To elucidate the underlying mechanisms of pathological pain, it is important and necessary to develop an animal model characterized by both spontaneous tonic pain and hyperalgesia with a prolonged duration post-tissue injury. In this report, we investigated whether the two animal models of spontaneous tonic pain (the formalin test and the bee venom test) could develop a hyperalgesia to mechanical and thermal stimuli in the injured area following subcutaneous (s.c. ) administration of the two chemical agents into the plantar surface of one hindpaw in the conscious rats. It was found that the persistent nociceptive response (flinching and lifting/licking the injected hindpaw) was monophasic and lasted for 1-2 h followed by a 72-96 h period of reduction in mechanical threshold and heat latency of withdrawal reflex in the bee venom injection area; however, in contrast, the spontaneous pain-related response was biphasic followed by a permanent hypoalgesia or analgesia in the formalin injection area although the duration and response intensity of spontaneous pain was comparable with those following bee venom treatment. Subcutaneous. bee venom injection also produced a distinct reduction of heat latency on the contralateral hindpaw, while s.c. formalin did not. On the other hand, s.c. bee venom injection produced a striking edema and redness of the plantar surface for nearly the same period as the development of hyperalgesia, while the edema and redness could not be obviously observed after the formalin treatment. In the control study, repetitive suprathreshold mechanical or heat stimuli applied to the plantar surface with or without saline treatment did not significantly influence the mechanical threshold or heat latency, suggesting that the phenomena of mechanical and heat hyperalgesia were not the effects of vehicle treatment or those of the stimulus modalities themselves. Taken together, our present results showed that in contrast to s.c. formalin injection, subcutaneous. bee venom injection produced little tissue damage but a striking inflammation accompanied by a prolonged spontaneous pain and a pronounced primary hyperalgesia to mechanical and heat stimuli in the treated hindpaw and a heat, but not mechanical, hyperalgesia in the contralateral hindpaw, implicating that bee venom model may have more advantages over the formalin test and probably other chemoirritants to study the neural mechanisms underlying pathological pain and, especially, the relationship between spontaneous pain and development of hyperalgesia.

Animals↗

PubMed1999

5-Hydroxytryptamine2A receptor stimulation induces activator protein-1 and cyclic AMP-responsive element binding with cyclic AMP-responsive element-binding protein and Jun D as common components in cerebellar neurons.

Previous studies from our laboratory have demonstrated that stimulation of 5-hydroxytryptamine2A receptors in rat cerebellar granule cells produces an increase in the levels of 5-hydroxytryptamine2A receptor messenger RNA and binding sites, and that this up-regulation requires de novo RNA and protein synthesis. Here we showed that up-regulation of 5-hydroxytryptamine2A receptor binding sites induced by stimulation with the 5-hydroxytryptamine2A/2C receptor agonist, (+/-)-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), is associated with an increase in the 5-hydroxytryptamine2A receptor transcription rate. To examine the possible role of transcriptional activation in DOI-induced 5-hydroxytryptamine2A receptor up-regulation, we studied the effects of DOI on transcription factor binding to activator protein-1 and cyclic AMP-responsive element (CRE) DNA consensus sequences. We found that DOI induces a time-dependent increase in activator protein-1 and CRE transcription factor binding activity, which is blocked by 5-hydroxytryptamine2A receptor antagonists. Similar to 5-hydroxytryptamine2A receptor up-regulation, DOI-induced activator protein-1 binding is suppressed by inhibitors of calmodulin and Ca2+/calmodulin-dependent kinases. The increased activator protein-1 binding is effectively competed by excessive activator protein-1 and CRE sequences as well as endogenous activator protein-1-like sequences present in the rat 5-hydroxytryptamine2A receptor gene. Supershift assays revealed that cAMP-responsive element-binding protein (CREB) and Jun D are common components of both activator protein-1 and CRE binding complexes. DOI also increased the level of phospho-CREB in a time-dependent manner. The binding of phospho-CREB transcription factor to the activator protein-1 site suggests that CREB may modulate the transcription of genes that contain activator protein-1 but lack CRE site in their promoters, through interaction with the activator protein-1 site. The rat 5-hydroxytryptamine2A receptor up-regulation may involve such a mechanism.

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

PubMed1999

Capability of serum to convert streptomycin to cytotoxin in patients with aminoglycoside-induced hearing loss.

Individual variations in sensitivity to the ototoxic effects of aminoglycoside antibiotics are well documented. Our research demonstrates that there is an apparent difference in serum from patients who are resistant or susceptible to aminoglycoside ototoxicity. In the first study, the cytotoxicity of sera from patients with and without hearing loss after various time periods following the discontinuation of aminoglycoside treatment was assayed using the isolated outer hair cell toxicity assay. The results indicate that sera from patients with hearing loss were significantly more toxic than sera from patients with normal hearing or minimal hearing loss. This toxicity may persist for up to 1 year after discontinuation of aminoglycoside therapy. In a second study, sera were obtained from patients who had received aminoglycoside therapy several years previously. None of these sera was toxic to isolated outer hair cells in vitro. Streptomycin was then incubated with the sera or a protein fraction isolated from sera, and the incubation mixtures were tested for toxicity. The percentage of damaged outer hair cells was significantly higher when streptomycin had been treated with sera or a serum protein fraction from patients with hearing loss (58+/-10% and 68+/-9%, respectively) than with sera or a serum protein fraction from a control group (10+/-5% and 17+/-4%, respectively). In addition, several incubation mixtures were analyzed using high performance liquid chromatography. A new chromatographic peak was only found in the incubations of streptomycin with serum protein from patients with hearing loss. The results suggest that sera from individuals sensitive to aminoglycoside antibiotics may metabolize these drugs to cytotoxins.

Adolescent↗

PubMed1999

Bicuculline sensitive depressor response to ethanol infusion into the lateral hypothalamus.

Decreased GABA function in the hypothalamus increases mean arterial pressure (MAP) and heart rate (HR). Since ethanol acts on GABA-A receptors, blocking GABA-A receptors can prevent a decrease of MAP and HR by ethanol in the lateral hypothalamus (LH). Ethanol at 5-30 mM, with or without 25 ng/microl bicuculline, was infused into the LH, and the activity of the site was validated with 100 nmoles of serotonin. Male rats were anesthetized with pentobarbital, and the femoral artery was catheterized to measure MAP and HR. Microinfusion was performed with a 28-gauge cannula placed into the LH. Serotonin increased MAP and HR within 15 sec. Ethanol decreased the MAP by -21.15 +/- 3.92 mmHg and HR by -53.61 +/- 14.95 BPM, at 15 min, which recovered by 15 min after the infusion was terminated. These maximum decreases were produced by 20 mM ethanol giving a U-shaped dose response. The aCSF vehicle had no effect. Bicuculline prevented ethanol-induced changes and had no effect when administered alone. Both serotonin and ethanol have direct effects on LH neurons with cardiovascular function. Ethanol produces this effect through GABA-A receptors.

Animals↗

PubMed1999

SEM study on the dorsal lingual surface of the flying squirrel, Petaurista leucogenys.

The dorsal lingual surface of the flying squirrel was examined by scanning electron microscopy (SEM). Filiform (FI), fungiform (FU), foliate (FO) and vallate papillae (VA) were observed. The FI were distributed over the entire dorsal surface of the tongue. In the region of the VA, the FI appeared as giant cones. The FU were present as rounded bodies scattered over the dorsal surface of the tongue. They were relatively scarce and appear to be concentrated around the edges of the tongue. The FO were observed on the posterolateral regions of the tongue. The flying squirrel showed the triangular arrangement of the three VA, with the apex of the triangle directed posteriorly.

Animals↗

PubMed1999

Mediation of sperm-egg fusion: evidence that mouse egg alpha6beta1 integrin is the receptor for sperm fertilinbeta.

BACKGROUND INTRODUCTION: A key step leading to fertilization is the binding of sperm to the egg plasma membrane. When a mammalian sperm reaches the egg plasma membrane, fertilinbeta, an extracellular sperm membrane protein, is believed to bind to an egg plasma membrane receptor triggering fusion. We set out to identify the fertilinbeta binding partner on the egg plasma membrane. RESULTS: We synthesized an 125-labeled peptide with the consensus Asp-Glu-Cys-Asp (DECD) sequence of fertilinbeta's disintegrin domain. This peptide contains a benzophenone photoaffinity probe and inhibits sperm-egg fusion. Upon photoactivation in the presence of whole mouse eggs, a single polypeptide was covalently labeled. This polypeptide has been identified by immunoprecipitation as an alpha6 integrin complexed with beta1 integrin. CONCLUSIONS: Our experiments establish that small peptides containing the consensus DECD sequence of sperm fertilinbeta bind specifically to an alpha6beta1 integrin receptor on the egg membrane. We conclude that fertilinbeta binds directly to the alpha6beta1 integrin on the egg surface and this partnership mediates sperm-egg fusion.

ADAM Proteins↗