Search PubMed⌕ Search

Biomedical subjects

W Huang

Publications and source records attributed to W Huang.

At least 289 records · Page 16Linked to original sources
PubMed1999

Noxious thermal stimulation of c-fos activity induced in rat lumbar spinal cord is reduced by AP-5 but not by glycine.

The effects of intrathecal administration of NMDA (N-methyl-D-aspartic acid) receptor antagonist AP-5 (2-Amino-5-phosphonopentanoic acid), a competitive and specific NMDA antagonist, and glycine on the neuronal expression of c-fos protein (Fos) in the dorsal neurons lumbar segments four and five were studied after noxious heat stimulation. Heat (52 degrees C, 3 s per application, repeated 10 times) was applied to the hindpaws of rats. NMDA receptor antagonist AP-5 (0.1 mmol/10 ml, i.t.) suppressed the noxious heat-induced Fos immunoreactivity by 65% as compared to animals pre-treated with saline. In contrast, glycine (0.1 micromol/10 microl, it.) did not influence Fos expression induced by the noxious heat stimulation. This study suggests that excitatory amino acids, e.g. glutamate but not the inhibitory aminos acid, glycine, plays a role in thermal nociception which in turn is mediated, in part, by c-fos activity.

2-Amino-5-phosphonovalerate↗
PubMed1999

The Genome Sequence DataBase: towards an integrated functional genomics resource.

During 1998 the primary focus of the Genome Sequence DataBase (GSDB; http://www.ncgr.org/gsdb ) located at the National Center for Genome Resources (NCGR) has been to improve data quality, improve data collections, and provide new methods and tools to access and analyze data. Data quality has been improved by extensive curation of certain data fields necessary for maintaining data collections and for using certain tools. Data quality has also been increased by improvements to the suite of programs that import data from the International Nucleotide Sequence Database Collaboration (IC). The Sequence Tag Alignment and Consensus Knowledgebase (STACK), a database of human expressed gene sequences developed by the South African National Bioinformatics Institute (SANBI), became available within the last year, allowing public access to this valuable resource of expressed sequences. Data access was improved by the addition of the Sequence Viewer, a platform-independent graphical viewer for GSDB sequence data. This tool has also been integrated with other searching and data retrieval tools. A BLAST homology search service was also made available, allowing researchers to search all of the data, including the unique data, that are available from GSDB. These improvements are designed to make GSDB more accessible to users, extend the rich searching capability already present in GSDB, and to facilitate the transition to an integrated system containing many different types of biological data.

Animals↗
PubMed1999

Purification and crystallization of a novel membrane-anchored protein: the Schistosoma haematobium serpin.

A unique serine-protease inhibitor (serpin) of the blood fluke S. haematobium has been crystallized. It is an antitrypsin with an unusual residue (phenylalanine) at its reactive center. Unlike any known member of this gene family, it is a membrane-anchored protein on the surface of the parasite. The location of this serpin and immunological response to the protein indicate that it may play a important role in host-parasite interaction. The crystals belong to the trigonal space group P3221 or P3121 with unit-cell parameters a = b = 64.7, c = 186.7 A, alpha = 90.0, beta = 90.0, gamma = 120.0 degrees. There is one molecule per asymmetric unit and the crystals diffracted to 2.2 A.

Animals↗
PubMed1999

Parent-youth concordance regarding violence exposure: relationship to youth psychosocial functioning.

PURPOSE: To examine the relationship between parent-youth concordance with regard to youth exposures to violence and youth psychosocial functioning, including perpetration of violence, distress symptomatology, and social skillfulness. METHODS: A battery of self-report questionnaires were completed by 333 parent-youth dyads residing in urban public housing developments. Concordance status (<50%, 50-80%, and >80%) was based on dyad agreement regarding youth's violence exposures. The relationship between concordance and psychosocial factors was assessed by a series of analyses of covariance tests. RESULTS: Parents underestimated the extent to which their children were victims of or witnesses to violence and suffered from distress symptoms. Low concordance status was associated with youth perpetration of violence and distress symptomatology, as well as lower self-esteem and problem-solving skillfulness. Youth in the low concordance group characterized their families as exhibiting less involvement, open communication, and parental monitoring. CONCLUSIONS: Concordance between parents and youth is associated with youth psychosocial competence and strong family functioning. Findings underscore the need to incorporate a parent component in primary and secondary violence-prevention programs. Further examination of the processes which contribute to concordance may enhance our ability to prevent youth engagement in violence and its untoward psychosocial sequelae.

Adolescent↗
PubMed1999

The 19S regulatory complex of the proteasome functions independently of proteolysis in nucleotide excision repair.

The 26S proteasome degrades proteins targeted by the ubiquitin pathway, a function thought to explain its role in cellular processes. The proteasome interacts with the ubiquitin-like N terminus of Rad23, a nucleotide excision repair (NER) protein, in Saccharomyces cerevisiae. Deletion of the ubiquitin-like domain causes UV radiation sensitivity. Here, we show that the ubiquitin-like domain of Rad23 is required for optimal activity of an in vitro NER system. Inhibition of proteasomal ATPases diminishes NER activity in vitro and increases UV sensitivity in vivo. Surprisingly, blockage of protein degradation by the proteasome has no effect on the efficiency of NER. This establishes that the regulatory complex of the proteasome has a function independent of protein degradation.

Acetylcysteine↗
PubMed1999

Femoral vein ligation increases bone mass in the hindlimb suspended rat.

Bone remodeling in response to changing mechanical demands is well recognized. It has been hypothesized that alterations in interstitial fluid flow (IFF), due to intraosseous pressure changes, influence bone remodeling. The goal of this study was to investigate the role of IFF in bone in the absence of mechanical strain using an in vivo model, the hindlimb suspended rat. Bone remodeling was assessed by direct measurements of weight, dimensions, bone mineral content (BMC) and bone mineral density (BMD) by dual-energy X-ray absorptiometry (DEXA), and trabecular density using peripheral computed tomography (pQCT). Ligation of one femoral vein was performed as a means to alter the IFF within the ipsilateral femur; the contralateral limb was sham-operated as control. Animals were suspended for a period of 19 days. Intramedullary pressure in the venous-ligated femurs increased relative to the sham-operated control femurs (27.8 mmHg vs. 16.4 mmHg, p < 0.05), suggesting venous ligation increased IFF proportional to the pressure drop across the bone. Bone mineral content (BMC), when normalized to body weight, increased significantly in the venous-ligated femurs relative to control limbs (115.9 +/- 15.6% vs. 103.8 +/- 13.2%, p < 0.001); similarly, gains in length (106.2 +/- 2.4% vs. 104.5 +/- 2.1%, p < 0.05) and distal width (110.8 +/- 10.3% vs. 106.2 +/- 8.2%, p < 0.05) for the femurs with venous ligation were significantly greater relative to sham control. Furthermore, trabecular density was significantly higher in the femurs with venous ligation (351 +/- 12 g/cm3 vs. 329 +/- 11 g/cm3, p < 0.05). Daily administration of the cyclooxygenase inhibitor, indomethacin, via drinking water, suppressed the length increases observed for the venous ligated femur, suggesting a role for prostaglandins in IFF-mediated remodeling. These results suggest that IFF can directly influence bone adaptation independent of mechanical loading, and supports the hypothesis that fluid flow modulates bone remodeling.

Animals↗
PubMed1999

Platelet-activating factor receptor mRNA is localized in eosinophils and epithelial cells in rat small intestine: regulation by dexamethasone and gut flora.

Platelet-activating factor (PAF) is a potent mediator involved in bowel injury. We investigated PAF receptor transcription and its mRNA localization in the small intestine of normal (conventionally fed) and germ-free rats, by competitive polymerase chain reaction (PCR) and in situ hybridization. A dose of PAF (1.5 microg/kg, i.v.) insufficient to cause gross bowel injury was injected into rats. Some rats were pretreated with dexamethasone (1 mg/kg). We found: (1) PAF receptor (PAF-R) mRNA localized predominantly in lamina propria eosinophils and in epithelial cells; (2) PAF increased PAF-receptor signals in the epithelial cells; (3) Dexamethasone depleted eosinophils in the intestine and markedly decreased PAF-receptor transcripts; the response to PAF was also weaker than control rats; (4) Germ-free rats had less PAF-R mRNA than normal rats, and showed a weaker response to PAF than conventionally fed rats. Thus, we conclude: (1) PAF receptor mRNA is constitutively expressed in the epithelium and in lamina propria eosinophils in the intestine. (2) PAF-R transcription is up-regulated by PAF and gut flora, mostly in the epithelium. (3) PAF-R transcription is down-regulated by glucocorticoids, mainly as a result of eosinophil depletion. These results suggest a functional role for PAF receptors both in host defence and the inflammatory response in the small intestine.

Animals↗
PubMed1999

Effects of hypotonic swelling on the cellular distribution and expression of pI(Cln) in human nonpigmented ciliary epithelial cells.

PURPOSE: It has been proposed that pI(Cln), a highly acidic protein, is a candidate gene product related to the swelling-activated chloride (Cl-) channel Icl.swell in mammalian cells. However, no consensus has been reached as to whether this relationship is direct or indirect. Recently the cDNA for pI(Cln) was isolated from human ciliary epithelial cells. To learn more about the structure-function of pI(Cln) we attempted to: i) overexpress pI(Cln) as a fusion protein in bacteria; ii) carry out its purification; iii) generate polyclonal antibodies to study its expression and cellular localization in the ciliary epithelial cells; and iv) determine whether cell-swelling affects pI(Cln) expression in ciliary epithelial cells. METHODS: The open reading frame (ORF) of human pI(Cln) was subcloned in the pET-20b(+) plasmid and established as a recombinant vector in E. coli BL21(DE3)pLysS cells. Upon induction with iso-propyl-beta-thio-galactopyranoside (IPTG), pI(Cln) was isolated as a His-Tag fusion protein and purified to homogeneity. Polyclonal antibodies were raised in rabbits after immunization with pI(Cln) purified protein, and its expression and cellular distribution in ciliary epithelial cells determined by Western blot, immunoprecipitation and indirect immunofluorescence respectively. Cell-swelling effect on ciliary epithelial cells was carried out upon treatment of cultured cells with hypotonic solution up to 60 min and pI(Cln) expression measured by Northern and Western blot analysis. RESULTS: By Western blot analysis or immunoprecipitation, pI(Cln) antisera recognized a main band of 37-kDa in total cell extracts from ciliary body or metabolically labeled ciliary epithelial cells. By indirect immunofluorescence, pI(Cln) antibodies stained the cytoplasm of NPE in the intact tissue, and the perinuclear region of cultured ciliary epithelial cells. When subjected to hypotonic treatment, NPE cells did not induce translocation of pI(Cln) protein from the cytoplasm into the plasma membrane, nor changes in pI(Cln) expression at the protein level, but did down regulate up to 30% the level of pI(Cln) mRNA in continued hypotonic treatment. CONCLUSIONS: These observations indicate that, contrary to previous suggestions, the pI(Cln) protein is not likely to be in contact with the plasma membrane of ciliary epithelial cells, and its influence on Cl- -channel activity is more likely to be expressed indirectly, (i.e. through cytoskeletal restructuring).

Amino Acid Sequence↗
PubMed1999

Intrathecal treatment with MK-801 suppresses thermal nociceptive responses and prevents c-fos immunoreactivity induced in rat lumbar spinal cord neurons.

Sensitization of the second order neurons in the spinal dorsal horn after somatic noxious stimuli is partly mediated by the N-methyl-D-aspartate (NMDA) subtype of the glutamate receptor. These neurons also express c-Fos immunoreactivity in response to the somatic noxious stimuli. The present study assessed the influence of intrathecal pre-treatment with MK-801, a non-competitive antagonist of NMDA receptor, on thermal sensitization following peripheral noxious heat stimulation. In addition, the influence of MK-801 on c-Fos immunoreactivity in the rat lumbar spinal cord neurons after the peripheral noxious heat was examined. Sprague-Dawley rats were subject to intrathecal catheterization and administration of MK-801 or saline before and after noxious heat (52 degrees C) stimulation of rat hindpaws. Thermal sensitization was tested after MK-801 (0.1 mumol 10 microliters-1). Fos-like immunoreactivity was evaluated 2 h after noxious stimulation in a separate group of animals. MK-801 significantly increased the thermal withdrawal threshold by 60% following noxious heat stimulation and reduced c-Fos immunoreactivity in the second order neurons by 70% in the dorsal horn. The study suggests that glutamate plays a pivotal role in the thermal nociceptive pathway and indicates that the NMDA receptor is necessary to maintain normal thermal sensitization, possibly by regulating c-fos gene expression in second order neurons.

Animals↗
PubMed1999

Y-Chromosome evidence for a northward migration of modern humans into Eastern Asia during the last Ice Age.

The timing and nature of the arrival and the subsequent expansion of modern humans into eastern Asia remains controversial. Using Y-chromosome biallelic markers, we investigated the ancient human-migration patterns in eastern Asia. Our data indicate that southern populations in eastern Asia are much more polymorphic than northern populations, which have only a subset of the southern haplotypes. This pattern indicates that the first settlement of modern humans in eastern Asia occurred in mainland Southeast Asia during the last Ice Age, coinciding with the absence of human fossils in eastern Asia, 50,000-100,000 years ago. After the initial peopling, a great northward migration extended into northern China and Siberia.

Africa↗
PubMed1999

stumps, a Drosophila gene required for fibroblast growth factor (FGF)-directed migrations of tracheal and mesodermal cells.

Fibroblast growth factors (FGFs) bind to FGF receptors, transmembrane tyrosine kinases that activate mitogenic, motogenic, and differentiative responses in different tissues. While there has been substantial progress in elucidating the Ras-MAP kinase pathway that mediates the differentiative responses, the signal transduction pathways that lead to directed cell migrations are not well defined. Here we describe a Drosophila gene called stumps that is required for FGF-dependent migrations of tracheal and mesodermal cells. These migrations are controlled by different FGF ligands and receptors, and they occur by different cellular mechanisms: the tracheal migrations occur as part of an epithelium whereas the mesodermal migrations are fibroblast-like. In the stumps mutant, tracheal cells fail to move out from the epithelial sacs, and only rudimentary tracheal branches form. Mesodermal cells fail in their dorsal migrations after gastrulation. The stumps mutation does not block all FGF signaling effects in these tissues: both random cell migrations and Ras-MAP kinase-mediated induction of FGF-specific effector genes occurred upon ectopic expression of the ligand or upon expression of a constitutively activated Ras protein in the migrating cells. The results suggest that stumps function promotes FGF-directed cell migrations, either by potentiating the FGF signaling process or by coupling the signal to the cellular machinery required for directed cell movement.

Animals↗
PubMed1999

Roles of nitric oxide synthases in platelet-activating factor-induced intestinal necrosis in rats.

OBJECTIVE: To examine the role of constitutive and inducible nitric oxide synthases (cNOS and iNOS) in platelet-activating factor (PAF)-induced shock and intestinal injury. DESIGN: Prospective, randomized, controlled experimental study. SETTING: Hospital research laboratory. SUBJECTS: Young adult male Sprague-Dawley rats were anesthetized and studied. INTERVENTIONS: Rats were injected with PAF, either alone or after the following pretreatments: a) selective iNOS inhibitors aminoguanidine or S-methylisothiourea; b) 3-morpholinosydnonimine, a NO donor; c) S-methylisothiourea + 3-morpholinosydnonimine; and d) antineutrophil antibody (to deplete neutrophils). MEASUREMENTS AND MAIN RESULTS: Blood pressure, hematocrit, white blood cell counts, intestinal injury, and intestinal cNOS and iNOS activities were assessed. We found that: a) cNOS is the predominant NOS in the intestine and its activity is inversely correlated to the level of tissue injury; b) there is a time-dependent increase in cNOS activity in sham-operated animals, which was abolished by PAF; c) Western blotting and immunohistochemistry showed iNOS present in the normal intestine, localizing mainly in crypt cells; d) iNOS inhibitors attenuated PAF-induced injury in animals with high cNOS activity, but had no protective effect in animals with low cNOS activity; e) 3-morpholinosydnonimine, alone or together with S-methylisothiourea, alleviated PAF-induced injury; and f) neutrophil depletion blocked the suppressive effect of PAF on cNOS and prevented injury. CONCLUSIONS: We conclude that cNOS and iNOS play different roles in PAF-induced intestinal injury. Caution should be exerted concerning potential therapeutic uses of iNOS inhibitors.

Animals↗
PubMed1999

Transdermal photopolymerized adhesive for seroma prevention.

The purpose of this study was to determine whether or not a synthetic photopolymerized tissue adhesive (polyethylene oxide hydrogel) is useful in seroma prevention using a well established rat mastectomy seroma model. Twenty-three Sprague-Dawley rats received mastectomies. The rats were randomly assigned to either the control group (n = 13) or the experimental group (n = 10). The control animals received 0.2 cc of saline into the wound before closure. The experimental group received either 0.2 cc (n = 5) or 0.4 cc (n = 5) of the polyethylene oxide polymer into their wounds before closure. The experimental animals were placed under an ultraviolet A lamp for 3 minutes to polymerize the adhesive. On postoperative day seven, the resultant seromas were quantified, and wound tissues were harvested for histologic evaluation. The rats in the control group had a mean seroma volume of 3.25 cc (SD = 2.41), whereas the rats treated with polymer had a mean seroma volume of 0.37 cc (SD = 0.51). A Student's t test was performed showing a statistically significant difference between the control and experimental groups (p < 0.005). The volume of polymer used (0.2 cc versus 0.4 cc) did not significantly impact the volume of the resultant seromas. This study demonstrates that photopolymerizable polyethylene oxide hydrogels can be used as a tissue adhesive and that such an adhesive significantly reduces seroma formation in the rat mastectomy model.

Animals↗
PubMed1999

The septal chondromucosal island pedicle flap: anatomic study and clinical application.

A study was made of the facial regions of 10 fresh cadavers. The vascular anatomy of the perinasal region and the septum consistently confirmed the existence of a nasal alar basal artery and a nasal alar basal nerve to the septum. A new septal chondromucosal flap, supplied by the nasal alar basal artery and nerve, is proposed in this article. The composite flap can be used safely to restore partial or entire tarsoconjunctival defects of the upper or lower eyelid or combined defects of the upper and lower eyelid.

Adult↗
PubMed1999

Injectable tissue-engineered cartilage using a fibrin glue polymer.

The purpose of this study was to demonstrate the feasibility of using a fibrin glue polymer to produce injectable tissue-engineered cartilage and to determine the optimal fibrinogen and chondrocyte concentrations required to produce solid, homogeneous cartilage. The most favorable fibrinogen concentration was determined by measuring the rate of degradation of fibrin glue using varying concentrations of purified porcine fibrinogen. The fibrinogen was mixed with thrombin (50 U/cc in 40 mM calcium chloride) to produce fibrin glue. Swine chondrocytes were then suspended in the fibrinogen before the addition of thrombin. The chondrocyte/polymer constructs were injected into the subcutaneous tissue of nude mice using chondrocyte concentrations of 10, 25, and 40 million chondrocytes/cc of polymer (0.4-cc injections). At 6 and 12 weeks, the neocartilage was harvested and analyzed by histology, mass, glycosaminoglycan content, DNA content, and collagen type II content. Control groups consisted of nude mice injected with fibrin glue alone (without chondrocytes) and a separate group injected with chondrocytes suspended in saline only (40 million cells/cc in saline; 0.4-cc injections). The fibrinogen concentration with the most favorable rate of degradation was 80 mg/cc. Histologic analysis of the neocartilage showed solid, homogeneous cartilage when using 40 million chondrocytes/cc, both at 6 and 12 weeks. The 10 and 25 million chondrocytes/cc samples showed areas of cartilage separated by areas of remnant fibrin glue. The mass of the samples ranged from 0.07 to 0.12 g at 6 weeks and decreased only slightly by week 12. The glycosaminoglycan content ranged from 2.3 to 9.4 percent for all samples; normal cartilage controls had a content of 7.0 percent. DNA content ranged from 0.63 to 1.4 percent for all samples, with normal pig cartilage having a mean DNA content of 0.285 percent. The samples of fibrin glue alone produced no cartilage, and the chondrocytes alone produced neocartilage samples with a significantly smaller mass (0.47 g at 6 weeks and 0.46 g at 12 weeks) when compared with all samples produced from chondrocytes suspended in fibrin glue (p < 0.03). Gel electrophoreses demonstrated the presence of type II collagen in all sample groups. This study demonstrates that fibrin glue is a suitable polymer for the formation of injectable tissue-engineered cartilage in the nude mouse model. Forty million chondrocytes per cc yielded the best quality cartilage at 6 and 12 weeks when analyzed by histology and content of DNA, glycosaminoglycan, and type II collagen.

Animals↗
PubMed1999

Multiple layers of cooperativity regulate enhanceosome-responsive RNA polymerase II transcription complex assembly.

Two coordinate forms of transcriptional synergy mediate eukaryotic gene regulation: the greater-than-additive transcriptional response to multiple promoter-bound activators, and the sigmoidal response to increasing activator concentration. The mechanism underlying the sigmoidal response has not been elucidated but is almost certainly founded on the cooperative binding of activators and the general machinery to DNA. Here we explore that mechanism by using highly purified transcription factor preparations and a strong Epstein-Barr virus promoter, BHLF-1, regulated by the virally encoded activator ZEBRA. We demonstrate that two layers of cooperative binding govern transcription complex assembly. First, the architectural proteins HMG-1 and -2 mediate cooperative formation of an enhanceosome containing ZEBRA and cellular Sp1. This enhanceosome then recruits transcription factor IIA (TFIIA) and TFIID to the promoter to form the DA complex. The DA complex, however, stimulates assembly of the enhanceosome itself such that the entire reaction can occur in a highly concerted manner. The data reveal the importance of reciprocal cooperative interactions among activators and the general machinery in eukaryotic gene regulation.

Allosteric Regulation↗
PubMed1999

The role of xanthine oxidase in platelet activating factor induced intestinal injury in the rat.

BACKGROUND: Xanthine oxidase (XO) is an important source of reactive oxygen species in the small intestine. AIMS: To examine the interaction of platelet activating factor (PAF), XO, and neutrophils in mediating intestinal injury in rats. METHODS: Two doses of PAF were used to induce either reversible hypotension, or irreversible shock with intestinal necrosis. The activities of XO, and its precursor xanthine dehydrogenase (XD), in both the whole intestinal tissue and epithelial cells, were measured. XO was localised by histochemical staining. RESULTS: PAF dose dependently induced an increase in XO activity, predominantly in the ileal epithelium, without altering the total activity of XD+XO. Most of the XD to XO conversion was via proteolysis. PAF induced XO activation and intestinal injury were prevented by prior neutrophil depletion. PAF induced XO activation is probably not due to reperfusion, as XO activation preceded the recovery of mesenteric flow. Allopurinol pretreatment substantially inhibited intestinal neutrophil sequestration induced by high dose (but not low dose) PAF. CONCLUSIONS: PAF rapidly activates intestinal XO through proteolytic XD-XO conversion, predominantly in the ileal epithelium. This effect is mediated by neutrophils. XO activation promotes PAF induced polymorphonuclear leucocyte sequestration in the intestine.

Allopurinol↗