Biomedical subjects

R Wang

Publications and source records attributed to R Wang.

At least 415 records · Page 23Linked to original sources

PubMed1997

Malaria DNA vaccines in Aotus monkeys.

In preparation for the development of DNA vaccines designed to produce protective antibodies against Plasmodium falciparum antigens (Ag), we conducted studies to optimize antibody responses in Aotus monkeys after immunization with the P. yoelli circumsporozoite (CSP) DNA vaccine. We demonstrate in Aotus monkeys that an intradermal route of immunization with a PyCSP plasmid DNA vaccine generates antibody responses equivalent to a multiple antigen peptide/adjuvant based vaccine, and that these data support the use of the intradermal route for initial studies of the efficacy of DNA vaccines in inducing protective antibodies against P. falciparum antigens in Aotus monkeys.

Animals↗

PubMed1997

Strategy for development of a pre-erythrocytic Plasmodium falciparum DNA vaccine for human use.

Data generated in the Plasmodium yoelii rodent model indicated that plasmid DNA vaccines encoding the P.yoelii circumsporozoite protein (PyCSP) or 17 kDa hepatocyte erythrocyte protein (PyHEP17) were potent inducers of protective CD8+ T cell responses directed against infected hepatocytes. Immunization with a mixture of these plasmids circumvented the genetic restriction of protective immunity and induced additive protection. A third DNA vaccine encoding the P. yoelii sporozoite surface protein 2 (PySSP2) also induced protection. The P. falciparum genes encoding the homologues of these three protective P. yoelii antigens as well as another P. falciparum gene encoding a protein that is expressed in infected hepatocytes have been chosen for the development of a human vaccine. The optimal plasmid constructs for human use will be selected on the basis of immunogenicity data generated in mice and nonhuman primates. We anticipate that optimization of multi-gene P. falciparum DNA vaccines designed to protect against malaria by inducing CD8+ T cells that target infected hepatocytes will require extensive clinical trials during the coming years.

Animals↗

PubMed1997

Fluoxetine-induced cardiotoxicity with response to bicarbonate therapy.

This report describes a patient with an acute intentional fluoxetine exposure who developed unique cardiovascular and neurovascular toxicity. The patient presented with lethargy and cardiac conduction delays (QRS 110 msec, QTc 458 msec) and developed a delayed seizure. On admission, therapy with intravenous sodium bicarbonate promptly narrowed the QRS to 90 msec. A comprehensive toxicology screen demonstrated only a serum fluoxetine concentration of 901 ng/mL (therapeutic range, 37-301), a serum norfluoxetine concentration of 451 ng/mL (29-329) and a serum acetaminophen concentration of 174 mg/L. Tricyclic antidepresants were specifically noted to be absent. A self-limiting generalized seizure was witnessed 16 hours after ingestion. At this time the bicarbonate infusion had been ceased and the QRS interval was not prolonged. The patient improved over time and no other apparent causes for the observed clinical effects could be discovered. Emergency physicians need to be aware of the uncommon occurrence of fluoxetine-induced cardiotoxicity and the potential benefit of sodium bicarbonate therapy.

Adult↗

PubMed1997

A chemoenzymatic synthesis of UDP-(2-deoxy-2-fluoro)-galactose and evaluation of its interaction with galactosyltransferase.

Uridine 5'-diphospho-(2-deoxy-2-fluoro)galactose (UDP-2FGal), prepared and characterized for the first time by a chemoenzymatic method, was found to be a competitive inhibitor of beta-1,4-galactosyltransferase with a Ki value of 149 microM. This study supports that the glycosyltransferase reaction mechanism proceeds through a glycosidic cleavage transition state with sp2 character developed at the anomeric center.

Enzyme Inhibitors↗

PubMed1997

A search for pyrophosphate mimics for the development of substrates and inhibitors of glycosyltransferases.

The design and synthesis of several beta-1,4-galactosyltransferase inhibitors are reported. Mimics of the pyrophosphate-Mn2+ complex were the focus of the design. Malonic, tartaric, and monosaccharide moieties were used as replacements of the pyrophosphate moiety, and galactose or azasugars with potent galactosidase inhibitory activity were used as the 'donor' component. Compound 6, in which glucose was used as the pyrophosphate-Mn2+ complex mimic and galactose as the 'donor' component, showed the best inhibitory activity towards the transferase with a Ki of 119.6 microM.

Aminoglycosides↗

PubMed1997

A network model of motion processing in area MT of primates.

A simple and biologically plausible model is proposed to simulate the visual motion processing taking place in the middle temporal (MT) area of the visual cortex in the primate brain. The model is a hierarchical neural network composed of multiple competitive learning layers. The input layer of the network simulates the neurons in the primary visual cortex (V1), which are sensitive to the orientation and motion velocity of the visual stimuli, and the middle and output layers of the network simulate the component MT and pattern MT neurons, which are selectively responsive to local and global motions, respectively. The network model was tested with various simulated motion patterns (random dots of different direction correlations, transparent motion, grating and plaid patterns, and so on). The response properties of the model closely resemble many of the known features of the MT neurons found neurophysiologically. These results show that the sophisticated response behaviors of the MT neurons can emerge naturally from some very simple models, such as a competitive learning network.

Animals↗

PubMed1997

Toward clinical trials of DNA vaccines against malaria.

In mid 1997 the first malaria DNA vaccine will enter clinical trials. This single gene DNA vaccine encoding the Plasmodium falciparum circumsporozoite protein (PfCSP) will be studied for safety and immunogenicity. If these criteria are met, a multi-gene DNA vaccine designed to induce protective CD8+ T cell responses against P. falciparum infected hepatocytes will be subsequently assessed for safety, immunogenicity and capacity to protect immunized volunteers against experimental challenge with P. falciparum sporozoites. Our perspectives on malaria vaccine development in general, and on a multi-gene DNA vaccine in particular, have been recently reviewed. Herein, we review the rationale and experimental foundation for the anticipated P. falciparum DNA vaccine trials.

Animals↗

PubMed1997

Carbon monoxide-induced vasorelaxation and the underlying mechanisms.

1. Carbon monoxide (CO) induced a concentration-dependent relaxation of isolated rat tail artery tissues which were precontracted with phenylephrine or U-46619. This vasorelaxing effect of CO was independent of the presence of the intact endothelium. 2. The CO-induced vasorelaxation was partially inhibited by the blockade of either the cyclicGMP pathway or big-conductance calcium-activated K (KCa) channels. When both the cyclicGMP pathway and KCa channels were blocked, the CO-induced vasorelaxation was completely abolished. 3. Incubation of vascular tissues with hemin, in order to enhance the endogenous production of CO, suppressed the phenylephrine-induced vasocontraction in a time- and concentration-dependent manner. The hemin-induced suppression of the vascular contractile response to phenylephrine was abolished after the vascular tissues were co-incubated with either oxyhaemoglobin or zinc protoporphyrin-IX, suggesting an induced endogenous generation of CO from vascular tissues. 4. The effect of hemin incubation on vascular contractility did not involve the endogenous generation of nitric oxide. 5. Our results suggest that CO may activate both a cyclicGMP signalling pathway and KCa channels in the same vascular tissues, and that the endogenously generated CO may significantly affect the vascular contractile responses.

Animals↗

PubMed1997

Association analysis of the dopamine D4 gene exon III VNTR and heroin abuse in Chinese subjects.

Although social and cultural influences are clearly important, family, twin and adoption studies indicate that genes contribute significantly to substance abuse. Substance abuse is associated with novelty seeking, a heritable human personality trait which may be influenced by alleles of the dopamine D4 (DRD4) gene exon III VNTR. Consequently Kotler et al analysed the DRD4 VNTR in opiate-dependent subjects from Israel, and found a significant excess of the 7-repeat allele. We have attempted to replicate this finding using a Han Chinese case-control sample of 121 heroin-dependent subjects and 154 normal controls. We found two 7-repeat alleles which occurred exclusively in the patient group, and overall there was an excess of longer alleles, which did not reach significance (chi 2 = 7.04; P = 0.07). When the D4 VNTR was divided into 'long' (5-7 repeats) and 'short' (2-4 repeats), a significant excess of long alleles was observed in the patient group (P = 0.023, one-tailed), with an odds ratio of 2.30 (95% CI 1.07-4.93). We conclude that our findings support the hypothesis that alleles of the DRD4 exon III VNTR are susceptibility factors for heroin abuse.

Adolescent↗

PubMed1997

Effect of tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) on human sperm motility, viability and motion parameters.

Male genital tract infections and non-specific inflammatory conditions may be associated with unexplained infertility. Previous studies have shown the presence of cytokines such as tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) in the semen of infertile men. However, the mechanism of effect of these cytokines on human sperm function is still controversial. The present study was undertaken to investigate the in-vitro effects of TNF-alpha and IFN-gamma on human sperm motion, viability and the hypoosmotic swelling test (HOST). Washed spermatozoa from normal volunteers (n = 9) were incubated in the presence/absence of TNF-alpha (1 microgram/mL) plus IFN-gamma (0.1 microgram/mL). Sperm motility, viability, HOST, and video sequences were recorded at different time intervals (0, 30, 60 and 180 min). Sperm motion parameters were analysed using computer-assisted semen analysis. There was a time-dependent negative effect of TNF-alpha plus IFN-gamma on sperm motility, viability, HOST, and lateral-head displacement (ALH). The maximum decrease was observed between 60 and 180 min for sperm motility (50.8 +/- 5.6%), viability (52.8 +/- 4.0%), HOST (38 +/- 2%) and ALH (4.7 +/- 0.1 microns) compared to control samples (62.2 +/- 2.8, 62.4 +/- 2.9, 58 +/- 4, and 5.3 +/- 0.4, respectively; All p < 0.05). There was no significant effect on sperm straight-line velocity and mean linearity when compared to control. These data suggest that the common inflammatory cytokines TNF-alpha plus IFN-gamma have only partial detrimental effects on sperm motility, viability, membrane integrity and lateral head displacement, which may contribute to the poor fertilizing potential of human spermatozoa during inflammatory conditions.

Cell Membrane↗

PubMed1997

Regulation of the human TRH (hTRH) gene by human thyroid hormone receptor beta 1 (hTR beta 1) mutants.

TRH is negatively regulated by T3 both in the hypothalamic paraventricular nucleus and transient transfection models. Mutations in hTR beta 1 genes are associated with the syndrome of generalized resistance to thyroid hormone. To investigate potential effects of mutant TRs on T3 regulation of the hTRH gene, transient gene expression assays were performed in human neuroblastoma (HTB-11) cells with an hTRH promoter-luciferase construct, wild type (WT) hTR beta 1, and three qualitatively distinct hTR beta 1 mutant forms (ED, OK and PV). In the presence of T3 (10(-9) M), liganded WT-hTR beta 1 inhibited hTRH promoter activity significantly (40%). Cotransfection of each of the two mutants (ED and OK) achieved similar levels of inhibition only at 10 to 100 fold increased T3 concentrations. Of interest, a 10x excess of mutant ED or OK could also exert dominant negative effects upon WT hTR beta 1-T3 mediated inhibitory actions on the hTRH promoter. In contrast, mutant TR-PV exerted neither inhibitory nor dominant negative effects at even higher concentrations of T3. Moreover, all three unliganded mutant forms stimulated TRH promoter activity significantly in the absence of T3, despite their different mutations in the ligand-binding domain (LBD). These data demonstrate that thyroid hormone resistance at the level of TRH gene regulation, due to reduced inhibitory actions of mutant TR-T3 complexes, as well as dominant negative effects upon WT hTR beta 1 mediated inhibition, likely contribute to elevated TSH values observed in the syndrome of thyroid hormone resistance.

Dose-Response Relationship, Drug↗

PubMed1997

A novel a-factor-related peptide of Saccharomyces cerevisiae that exits the cell by a Ste6p-independent mechanism.

Many secreted signaling molecules are synthesized as precursors that undergo multiple maturation steps to generate their mature forms. The Saccharomyces cerevisiae mating pheromone a-factor is a C-terminally isoprenylated and carboxylmethylated dodecapeptide that is initially synthesized as a larger precursor containing 36 or 38 amino acids. We have previously shown that the maturation of a-factor occurs by an ordered biogenesis pathway involving 1) three C-terminal modification steps, 2) two N-terminal proteolytic processing events, and 3) a nonclassical export mechanism mediated by the ATP-binding-cassette (ABC) transporter Ste6p. In the present study, we demonstrate that an unexpected and abundant a-factor-related peptide (AFRP) exists in the culture fluid of MATa cells and that its biogenesis is integrally related to that of mature a-factor itself. We show by purification followed by mass spectrometry that AFRP corresponds to the C-terminal 7 amino acids (VFWDPAC) of mature a-factor (YIIKGVFWDPAC), including both the farnesyl- and carboxylmethylcysteine modifications. The formation and export of AFRP displays three striking features. First, we show that AFRP is produced intracellularly and that mutants (ste24 and axl1) that cannot produce mature a-factor due to an N-terminal processing defect are nevertheless normal for AFRP production. Thus, AFRP is not derived from mature a-factor but, instead, from the P1 form of the a-factor precursor. Second, fusion constructs with foreign amino acids substituted for authentic a-factor residues still yield AFRP-sized molecules; however, the composition of these corresponds to the altered residues instead of to AFRP residues. Thus, AFRP may be generated by a sequence-dependent but length-specific proteolytic activity. Third, a-factor and AFRP use distinct cellular machinery for their secretion. Whereas a-factor export is Ste6p-dependent, AFRP is secreted normally even in a ste6 deletion mutant. Thus, AFRP may exit the cell by another ATP-binding-cassette transporter, a different type of transporter altogether, or possibly by diffusion. Taken together, these studies indicate that the biogenesis of AFRP involves novel mechanisms and machinery, distinct from those used to generate mature a-factor. Because AFRP neither stimulates nor inhibits mating or a-factor halo activity, its function remains an intriguing question.

ATP-Binding Cassette Transporters↗

PubMed1997

Blockade of cerebral blood flow response to insulin-induced hypoglycemia by caffeine and glibenclamide in conscious rats.

The possibility that adenosine and ATP-sensitive potassium channels (KATP) might be involved in the mechanisms of the increases in cerebral blood flow (CBF) that occur in insulin-induced hypoglycemia was examined. Cerebral blood flow was measured by the [14C]iodoantipyrine method in conscious rats during insulin-induced, moderate hypoglycemia (2 to 3 mmol/L glucose in arterial plasma) after intravenous injections of 10 to 20 mg/kg of caffeine, an adenosine receptor antagonist, or intracisternal infusion of 1 to 2 mumol/L glibenclamide, a KATP channel inhibitor. Cerebral blood flow was also measured in corresponding normoglycemic and drug-free control groups. Cerebral blood flow was 51% higher in untreated hypoglycemic than in untreated normoglycemic rats (P < 0.01). Caffeine had a small, statistically insignificant effect on CBF in normoglycemic rats, but reduced the CBF response to hypoglycemia in a dose-dependent manner, i.e., 27% increase with 10 mg/kg and complete elimination with 20 mg/kg. Chemical determinations by HPLC in extracts of freeze-blown brains showed significant increases in the levels of adenosine and its degradation products, inosine and hypoxanthine, during hypoglycemia (P < 0.05). Intracisternal glibenclamide had little effect on CBF in normoglycemia, but, like caffeine, produced dose-dependent reductions in the magnitude of the increases in CBF during hypoglycemia, i.e., +66% with glibenclamide-free artificial CSF administration, +25% with 1 mumol/L glibenclamide, and almost complete blockade (+5%) with 2 mumol/L glibenclamide. These results suggest that adenosine and KATP channels may play a role in the increases in CBF during hypoglycemia.

Animals↗

PubMed1997

Liposome-associated interferon-alpha-2b functions as an anti-fibrogenic factor for human dermal fibroblasts.

This study was conducted to determine whether interferon-alpha-2b (IFN-alpha-2b) can be encapsulated in liposomes without compromising its anti-fibrogenic effects on human dermal fibroblasts. The rationale for this approach is that systemic administration of IFN-alpha-2b by injection for treatment of dermal fibrosis is uncomfortable, requires a large quantity of the cytokine, and cannot be easily used in children. Liposomes are potentially useful as vehicles for the topical delivery of drugs if they can be encapsulated without loss of biologic activity. Empty sonicated vesicles composed of dioleoyl-phosphatidylcholine:dioleoyl-phosphatidylglycerol at a molar ratio of 7:3 were mixed with various concentrations of IFN-alpha-2b and then dried and rehydrated. An enzyme-linked immunosorbent assay (ELISA) was used to determine the efficiency of encapsulation and the stability of the preparation under experimental conditions. Greater than 80% of added IFN-alpha-2b became associated with the liposomes and remained encapsulated for up to 5 d at 4 degrees C. The rate of release increased markedly at 37 degrees C. Liposome-encapsulated IFN-alpha-2b (2000 units per ml) significantly reduced the proliferation of dermal fibroblasts (60 +/- 8.8 vs. 100 +/- 8, mean +/- SEM, p < 0.05, n = 8) and the levels of mRNA for type I (41.5 +/- 8.7% vs 100 +/- 18, p < 0.05, n = 4) and type III (68 +/- 8.4% vs 100 +/- 4.9%, p < 0.05, n = 3) procollagen, as analyzed on northern blots. This was consistent with the reduction found in collagen in conditioned medium from treated fibroblasts. In contrast, treatment increased levels of mRNA for collagenase (241 +/- 42% vs 100 +/- 3.4, p < 0.05, n = 3) and collagenase activity (289 +/- 5.8% vs 100 +/- 10.9%, p < 0.05, n = 9) in conditioned medium. This last effect was probably not due to a reduction in TIMP-1 (tissue inhibitor of metalloproteinase-1) because levels of mRNA for this inhibitor were not lower in treated cells. The efficacy of liposome-associated IFN-alpha-2b in vitro supports the concept of the topical use of this anti-fibrogenic agent for treatment of fibroproliferative disorders.

Cell Division↗

PubMed1997

Nitric oxide synthase expression and nitric oxide production are reduced in hypertrophic scar tissue and fibroblasts.

We have recently demonstrated that human dermal fibroblasts express both constitutive and inducible nitric oxide synthases (NOS) and produce nitric oxide (NO). In this study, NOS expression and NO production were compared in human fibroblasts derived from hypertrophic scar (HSc) and site-matched normal dermis. NOS expression and NO production in HSc fibroblasts are significantly reduced when compared with normal fibroblasts. Without stimulation, the HSc fibroblasts produced 7.37 +/- 1.17 nmol and the normal fibroblasts produced 11.15 +/- 0.79 nmol/10(6) cells/96 h (paired t test, p < 0.01, n = 6) NO as determined by the Griess reaction. After stimulation with 200 units interferon-gamma per ml and 40 microg lipopolysaccharide per ml, both HSc and normal fibroblasts produced significantly higher NO, indicating that the HSc fibroblasts retain the capacity to express inducible NOS (iNOS). The Ca2+-dependent NOS (cNOS) activity in the cytosol of HSc fibroblasts (1.43 pmol/min/g of protein) was significantly lower than that in normal fibroblasts (2.60 pmol/min/g of protein), as determined by citrulline assay (p < 0.01, n = 4). The mRNAs for endothelial cNOS and iNOS in both HSc and normal fibroblasts were detectable by RT-PCR. Flow cytometry confirmed that the untreated HSc fibroblasts expressed less endothelial cNOS protein than untreated normal fibroblasts. Because NO markedly inhibits cell proliferation, our results suggest that after thermal injury, fibroblasts in the scar tissue may undergo phenotypic alteration leading to reduced endothelial cNOS expression. The low levels of endogenous NO in HSc fibroblasts might be responsible for the cellularity of post-burn HSc, a characteristic feature of this fibrotic condition.

Adolescent↗

PubMed1997

Interactions between heterologous FtsA and FtsZ proteins at the FtsZ ring.

FtsZ and FtsA are essential for cell division in Escherichia coli and colocalize to the septal ring. One approach to determine what regions of FtsA and FtsZ are important for their interaction is to identify in vivo interactions between FtsA and FtsZ from different species. As a first step, the ftsA genes of Rhizobium meliloti and Agrobacterium tumefaciens were isolated and characterized. In addition, an FtsZ homolog that shared the unusual C-terminal extension of R. meliloti FtsZ1 was found in A. tumefaciens. In order to visualize their localization in cells, we tagged these proteins with green fluorescent protein (GFP). When R. meliloti FtsZ1-GFP or A. tumefaciens FtsZ-GFP was expressed at low levels in E. coli, they specifically localized only to the E. coli FtsZ ring, possibly by coassembly. When A. tumefaciens FtsA-GFP or R. meliloti FtsA-GFP was expressed in E. coli, they failed to localize detectably to the E. coli FtsZ ring. However, when R. meliloti FtsZ1 was coexpressed with them, fluorescence localized to a band at the midcell division site, strongly suggesting that FtsA from either A. tumefaciens or R. meliloti can bind directly to its cognate FtsZ. As expected, GFP-tagged FtsZ1 and FtsA from either R. meliloti or A. tumefaciens localized to the division site in A. tumefaciens cells. Therefore, the 61 amino acid changes between A. tumefaciens FtsA and R. meliloti FtsA do not prevent their direct interaction with FtsZ1 from either species, suggesting that those residues are not essential for protein-protein contacts. Moreover, the failure of the two non-E. coli FtsA derivatives to interact strongly with E. coli FtsZ in this in vivo system unless their cognate FtsZ was also present suggests that FtsA-FtsZ interactions have coevolved and that the residues which differ between the E. coli proteins and those of the two other species may be important for specific interactions.

Agrobacterium tumefaciens↗

PubMed1997

Identification of a protein that binds to the Ho endonuclease recognition sequence at the yeast mating type locus.

Mating type switching in Saccharomyces cerevisiae initiates when Ho endonuclease makes a site-specific double-stranded break at MAT, the yeast mating type locus. To identify other proteins involved in this process, we examined whether extracts prepared from ho- mutants contain additional factors that bind near the recognition sequence for Ho. Using an electrophoretic mobility shift assay, we isolated a chromatographic fraction that contains an activity, named YZbp, which binds to two sequences flanking the recognition sequence at MATalpha and to one sequence overlapping it at MATa. MAT plasmids carrying mutations in the YZbp recognition sequence are cleaved by purified Ho at wild-type efficiencies in an in vitro assay. These same plasmids, however, are not cleaved by Ho inside cells, demonstrating that YZbp acts as a positive activator of in vivo cleavage. YZbp is present in all cell types, even those not undergoing mating type switching, suggesting that it has additional cellular functions.

Binding Sites↗

PubMed1997

Nociceptin, a novel endogenous ligand for the ORL1 receptor, has potent erectile activity in the cat.

The heptadecapeptide nociceptin, also known as orphanin FQ, is a newly discovered endogenous ligand for the opioid-like G protein-coupled receptor ORL1. The present study was undertaken to investigate the effects of intracavernosal injections of nociceptin on penile erection in anesthetized cats. Responses to nociception were compared with erectile responses elicited by intracavernosal injection of vasoactive intestinal polypeptide (VIP), adrenomedullin (ADM), the novel nitric oxide donor diethylaminenitric oxide complex sodium (DEA/NO), and the control triple-drug combination (papaverine, phentolamine, and prostaglandin E1). The order of potency was VIP > ADM > nociceptin > DEA/NO. Intracavernosal injections of nociceptin in doses of 0.3-30 nmol elicited dose-related increases in cavernosal pressure and penile length that were comparable to those induced by the triple-drug combination, which is used in the treatment of erectile dysfunction. The response to nociceptin was rapid in onset, and the duration of the peak pressure increase and total response was significantly shorter than the response to the control triple-drug combination but longer in duration than responses to VIP and ADM. Intracavernosal injection of the triple-drug combination resulted in a greater decrease in mean systemic arterial blood pressure than did nociceptin. These data demonstrate that intracavernosal injection of this novel endogenous ligand for the ORL1 receptor induces a potent and relatively long-lasting erectile response in the cat.

Animals↗