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H Wang

Publications and source records attributed to H Wang.

At least 1,099 records · Page 61Linked to original sources
PubMed1999

Visualizing ion relaxation in the transport of short DNA fragments.

Ion relaxation plays an important role in a wide range of phenomena involving the transport of charged biomolecules. Ion relaxation is responsible for reducing sedimentation and diffusion constants, reducing electrophoretic mobilities, increasing intrinsic viscosities, and, for biomolecules that lack a permanent electric dipole moment, provides a mechanism for orienting them in an external electric field. Recently, a numerical boundary element method was developed to solve the coupled Navier-Stokes, Poisson, and ion transport equations for a polyion modeled as a rigid body of arbitrary size, shape, and charge distribution. This method has subsequently been used to compute the electrophoretic mobilities and intrinsic viscosities of a number of model proteins and DNA fragments. The primary purpose of the present work is to examine the effect of ion relaxation on the ion density and fluid velocity fields around short DNA fragments (20 and 40 bp). Contour density as well as vector field diagrams of the various scalar and vector fields are presented and discussed at monovalent salt concentrations of 0.03 and 0.11 M. In addition, the net charge current fluxes in the vicinity of the DNA fragments at low and high salt concentrations are briefly examined and discussed.

Biophysical Phenomena↗
PubMed1999

Pharmacological activities of fusaric acid (5-butylpicolinic acid).

This review article aims at summarizing research findings on the various pharmacological activities of fusaric acid (5-butylpicolinic acid), a mycotoxin produced by several Fusarium species which commonly infect cereal grains and other agricultural commodities. The actions of the toxin on mammals, birds, arthropods, crustaceans and plants are covered. The effects on mammals are diverse and are apparent in the nervous, cardiovascular and immune systems. Fusaric acid is toxic to some mammalian tumor cell lines.

Animals↗
PubMed1999

M3 muscarinic receptor activation of a delayed rectifier potassium current in canine atrial myocytes.

Growing body of evidence indicates that the functional responses of cells to muscarinic acetylcholine receptors (mAChRs) are mediated by multiple receptor subtypes. It is commonly thought that the M2 receptor is the only functional mAChR subtype in the heart and little data regarding the potential roles of other subtypes in cardiac tissues has been reported. In the present study, we provide functional evidence for the presence and physiological function of an M3 receptor in canine atrial myocytes. Using whole-cell patch-clamp techniques, we consistently found that pilocarpine, an mAChR agonist, induced a K+ current similar to but distinct from the classical delayed rectifier K+ current. Same observations were obtained when choline or tetramethylammonium (TMA) was applied to the bath. The currents were abolished by 1 microM atropine. Antagonists selective to M1 (pirenzepine, 100 nM), M2 (methoctramine 100 nM), or M4 (tropicamide 200 nM) receptors failed to alter the currents. Conversely, three different M3-selective inhibitors, p-F-HHSiD (20-200 nM), 4-DAMP methiodide (2-10 nM) and 4-DAMP mustard (4-20 nM), all produced concentration-dependent suppression of the currents. A cDNA fragment representing the M3 receptor was isolated from dog atrial RNA and the mRNA level of this construct was 0.7 +/- 0.1 pg/microg total RNA, as quantified by the competitive RT-PCR methods. Our data strongly suggested that an M3 receptor exists and is coupled to a K+ channel in the heart.

Animals↗
PubMed1999

Nicotine depresses the functions of multiple cardiac potassium channels.

Nicotine is the main constituent of tobacco smoke responsible for the elevated risk of the cardiovascular disease and sudden coronary death associated with smoking, presumably by provoking cardiac arrhythmias. The cellular mechanisms may be related to the ability of nicotine to prolong action potentials and to depolarize membrane potential. However, the underlying ionic mechanisms remained unknown. We showed here that nicotine blocked multiple types of K+ currents, including the native currents in canine ventricular myocytes and the cloned channels expressed in Xenopus oocytes: A-type K+ currents (I(to)/Kv4.3), delayed rectifier K+ currents (I(Kr)/HERG) and inward rectifier K+ currents (I(K1)/Kir2.1). Most noticeably, nicotine at a concentration as low as of 10 nM significantly suppressed I(to) and Kv4.3 by approximately 20%. The effects of nicotine were independent of nicotinic receptor simulation or catecholamine release. Our results indicate that nicotine is a non-specific blocker of K+ channels and the inhibitory effects are the consequence of direct interactions between nicotine molecules and the channel proteins. Our study provided for the first time the evidence for the direct inhibition of cardiac K+ channels by nicotine and established a novel aspect of nicotine pharmacology.

Action Potentials↗
PubMed1999

Proliferative characteristics of intestinalized mucosa in the distal esophagus and gastroesophageal junction (short-segment Barrett's esophagus): a case control study.

Intestinalized epithelium in traditional long-segment Barrett's esophagus (BE) shows increased proliferative activity, which is postulated to be an early step in the metaplasia-dysplasia-carcinoma sequence. The aim of this study was to evaluate the proliferative activity of intestinalized epithelium of the distal esophagus and gastroesophageal junction (IMEGEJ). Tissue sections from 78 consecutive patients (20 with IMEGEJ, 58 without IMEGEJ) who had elective upper gastrointestinal endoscopy over a 6-month period were immunohistochemically stained with MIB-1, the Ki-67 proliferation-antigen-associated marker, for evaluation of the crypt MIB-1 proliferation index (PI), size of the proliferative zone (PZ), and the presence of surface epithelial staining. Data from the IMEGEJ and non-IMEGEJ groups, and from 15 age-matched patients with traditional long-segment BE (>3.0 cm), were compared statistically. IMEGEJ patients showed a statistically significant increase in the mean crypt PI compared with non-IMEGEJ controls (21.9+/-19.5 v 14.3+/-9.3; P=.01). In addition, IMEGEJ cases showed an increase in the mean crypt PZ (52.3+/-16.4 v 45.2+/-17.2; P=.05), and a trend toward an increase in the percentage of cases with MIB-1-positive surface epithelial cells (50% v 33%, P=.18). Patients with IMEGEJ did not differ from patients without IMEGEJ with respect to any other clinical or histological feature, including signs or symptoms of gastroesophageal reflux disease and presence or absence of esophagitis or carditis. The MIB-1 results of the patients with long-segment BE (MIB-1 PI = 22.6+/-20.5, MIB-1 PZ = 51.8+/-19.6, proportion of cases with MIB-1-positive surface cells = 66%) were similar to those with IMEGEJ. Intestinalized epithelium in the distal esophagus or gastroesophageal junction shows increased proliferative activity in comparison with patients without intestinalized epithelium. This finding supports an increased risk of carcinogenesis in patients with IMEGEJ.

Adult↗
PubMed1999

Prognostic significance and effect of chemoradiotherapy on microvessel density (angiogenesis) in esophageal Barrett's esophagus-associated adenocarcinoma and squamous cell carcinoma.

Previous studies have shown that intratumoral microvessel density (IMD) correlates with clinical outcome in a variety of human neoplasms, such as those that arise in the breast, colon, and stomach, suggesting that angiogenesis is important in cancer progression. The aims of this study were to evaluate the prognostic utility of IMD in esophageal Barrett's-associated adenocarcinoma (AdCa) and squamous cell carcinoma (SCC), and to determine the effect of preoperative chemoradiotherapy (chemrad) on this process. Tissue sections of tumor from 67 patients with esophageal carcinoma (45 with Barrett's-associated AdCa, 22 with SCC) were stained with the vascular marker CD31. The IMD was calculated by evaluating at least 5 different 200 x fields of tumor hot spot areas to obtain the mean microvessel count (MVC). The data then were correlated with the clinical and pathological features, chemrad status, and patient survival. The MVC was significantly higher in AdCa (143 +/- 63.2) compared with SCC (77.2 +/- 38.6, P = 0.0001). In AdCa, no correlation was noted between the MVC and any of the clinical or pathological features, including chemrad status. In contrast, in SCC, a statistically significant higher MVC was detected in patients who did not receive chemrad (97.2 +/- 37.3) compared with those who did (48.3 +/- 15.9, P = .002) and in tumors that were larger in size (P = .02). However, the MVC did not correlate with survival in either AdCa or SCC (P > .05). The degree of angiogenesis is not a significant prognostic indicator in either esophageal AdCa or SCC. Preoperative chemrad has a positive effect on reducing the degree of angiogenesis in esophageal carcinoma, particularly SCC.

Adenocarcinoma↗
PubMed1999

Cavernous hemangiomas in the cavernous sinus. Case reports.

BACKGROUND: Extra-axial cavernous hemangiomas are rare and have a propensity to develop within the cavernous sinus. Total removal of these vascular tumors is difficult due to the risk of severe intraoperative bleeding and the complicated neurovascular structures of the cavernous sinus. Only a small number of cases have been reported to be successfully totally removed. METHODS: Retrospective studies were done in three cases of extraaxial cavernous hemangiomas located in the cavernous sinus. All three patients presented with clinical symptoms common to other tumors located in the region, such as headache and impairment of cranial nerve function. Their preoperative MRI results showed significant hyperintensity on T2-weighted images and marked enhancement with gadolinium-DTPA that delineated a sharp tumor margin. RESULTS: All three patients underwent total tumor removal, with an uneventful postoperative course. There was no postoperative neurological deficit in one patient, and a complete ophthalmoplegia and diminished sensation in the V1 distribution in two patients. Three months after operation, follow-up MRI or CT scan showed no residual tumor. CONCLUSION: Surgical resection of these lesions was possible but difficult because of severe bleeding. Avoiding piecemeal removal before the main feeding arteries are interrupted can minimize intraoperative bleeding.

Adult↗
PubMed1999

Novel non-apoptotic morphological changes in neurons of the mouse hippocampus following transient hypoxic-ischemia.

Apoptosis has been recently implicated in the dying process of neurons under several pathological conditions including ischemia. However, although apoptosis was originally defined on the basis of its unique ultrastructural features (Kerr et al., 1972. Br. J. Cancer 26, 239-257; Wyllie et al., 1980. Int. Rev. Cytol. 68, 251-306), unambiguous ultrastructural evidence of apoptosis has been rarely demonstrated in the adult brain. In this study, we examined ultrastructural changes in mouse hippocampal neurons after transient hypoxic-ischemia. A small population of dentate granule cells showed typical apoptotic ultrastructures that could be used as internal morphological standards of apoptosis, whereas most other hippocampal neurons consistently showed a distinct form of cellular disintegration. Nuclei of the latter cells shrank and became TUNEL-positive but were distinguishable from apoptotic nuclei by both the presence of characteristic reticular-formed chromatin condensation and the absence of nuclear fragmentation. Perikarya of degenerating neurons also shrank as in apoptosis, but apoptotic bodies were not observed. Although organelles other than mitochondria disappeared almost completely from the perikarya, neither plasma nor mitochondrial membranes were disrupted, indicating that these changes were also different from typical necrosis. The presence of a novel form of cell death suggests the necessity of morphological re-examination of neuronal death, particularly in mature neurons in vivo.

Animals↗
PubMed1999

Results of tympanoplasty with titanium prostheses.

To improve the hearing results associated with tympanoplasty, we performed the operation in 113 cases (124 ears) using ossicular replacement prostheses made of titanium. The results demonstrated that among all the operated ears, 115 of 124 (92.7%) had a hearing gain of more than 10 dB. The average improvement of pure-tone hearing was 24.6 dB, and the average reduction of the air-bone gap was 23.2 dB. No rejection reaction or recurrent cholesteatoma was found. This operative technique, based on animal experiments and applied anatomic study of the suprastapedial structure in human beings, has had a good rate of success and has resulted in remarkable hearing improvement of a relatively large magnitude. The application of a new material-titanium-which has high biocompatibility with human body tissues, is in large measure the reason for this success. The ossicular replacement prosthesis was appropriately designed and manufactured. It fit well, could be tightly joined to the suprastapedial structure, and was difficult to displace. We also adopted the method of enlarging the tympanic isthmus, which led to good aeration of the mastoid and attic, resulting in the best state of mobility of the tympanic membrane. All these factors contributed to the effective hearing gain.

Adolescent↗
PubMed1999

A cardioactive peptide from the southern armyworm, Spodoptera eridania.

A cardioactive peptide was isolated from extracts of whole heads of the southern armyworm, Spodoptera eridania. This peptide has the sequence ENFAVGCTPGYQRTADGRCKPTF (Mr = 2516.8), determined from both Edman sequencing and tandem mass spectrometry in combination with off-line micropreparative capillary liquid chromatography. This peptide, termed Spoer-CAP23, has excitatory effects on a semi-isolated heart from larval Manduca sexta, causing an inotropic effect at low concentrations of peptide and chronotropic and inotropic effects at high doses. The threshold concentration for stimulatory effects of the synthetic peptide on the semi-isolated heart was about 1 nM, suggesting a physiological role as a neuropeptide.

Amino Acid Sequence↗
PubMed1999

In vitro human Th-cell responses to a recombinant hepatitis C virus antigen: failure in IL-2 production despite proliferation.

Hepatitis C Virus (HCV) causes chronic infection in 80-90% of those exposed and persists despite evidence of immune recognition. To understand the immunological basis of this phenomenon, we have synthesized a non structural (NS) protein that is critical to HCV infection and replication, NS3, and used it to study in vitro helper T-cell responses from infected individuals. Strong proliferative responses were generated by peripheral T-cells isolated from a subset of chronically infected patients, but not by normal, non-infected controls. Interestingly, though gamma-interferon (gammaIfn) and IL-10 were both secreted in response to stimulation by NS3 antigen, IL-2 was not. In contrast, IL-2 was secreted in response to influenza virus vaccine antigen. Lack of IL-2 induction was confirmed by a failure to amplify IL-2 mRNA upon NS3 antigen stimulation, whereas IL-4, IL-15, and gammaIfn mRNA were seen as early as 24 h. The predominance of IL-4 and IL-10 and the lack of IL-2 suggests that in vitro responses to at least some HCV antigens are biased towards a Th2 phenotype, which may be conducive to viral persistence.

Hepatitis C↗
PubMed1999

Effects of oestrogen upon nitric oxide synthase NADPH-diaphorase activity in the hypothalamo-neurohypophysial system of the rat.

An understanding of the interaction between oestrogen and the nitric oxide synthase/nitric oxide system is important for determining the roles of nitric oxide in central nervous control of osmotic homeostasis and certain aspects of reproduction. The effects of oestrogen on nitric oxide synthase and nitric oxide synthase activity were investigated in the magnocellular neurosecretory system. Ovariectomized female rats were injected subcutaneously with 17beta-estradiol benzoate either 10 microg daily for four days (short-term low-dose) or 200 microg daily for 21 days (long-term high-dose). In the neurohypophysis the density of NADPH-diaphorase staining--a marker for nitric oxide synthase activity--was increased after both short-term low-dose and long-term high-dose estradiol treatment, but no difference in nitric oxide synthase immunoreactivity was observed after either treatment. In the magnocellular supraoptic and paraventricular nuclei, short-term low-dose oestrogen treatment did not induce any detectable changes in nitric oxide synthase gene expression, the proportion of nitric oxide synthase-immunoreactive neurons, or the proportion of NADPH-diaphorase-positive neurons. Long-term high-dose oestrogen treatment also had no effect on nitric oxide synthase gene expression or immunoreactivity, but caused a reduction of the proportion of NADPH-diaphorase-positive neurons in the supraoptic nucleus and a reduction in the intensity of this histochemical staining. Qualitatively similar changes were observed in the magnocellular part of the paraventricular nucleus. The results provide, for the first time, evidence of a complex interaction between oestrogen and nitric oxide synthase in the neuroendocrine system in which nitric oxide synthase activity is regulated differently in the magnocellular cell bodies and axonal terminals and in which the activity of the enzyme rather than its expression is controlled.

Animals↗
PubMed1999

Inflammation-induced up-regulation of protein kinase Cgamma immunoreactivity in rat spinal cord correlates with enhanced nociceptive processing.

Activation of various second messengers contributes to long-term changes in the excitability of dorsal horn neurons and to persistent pain conditions produced by injury. Here, we compared the time-course of decreased mechanical nociceptive thresholds and the density of protein kinase Cgamma immunoreactivity in the dorsal horn after injections of complete Freund's adjuvant in the plantar surface of the rat hindpaw. Complete Freund's adjuvant significantly increased paw diameter and mechanical sensitivity ipsilateral to the inflammation. The changes peaked one day post-injury, but endured for at least two weeks. In these rats, we recorded a 75-100% increase in protein kinase Cgamma immunoreactivity in the ipsilateral superficial dorsal horn of the L4 and L5 segments at all time-points. Electron microscopy revealed that the up-regulation was associated with a significant translocation of protein kinase Cgamma immunoreactivity to the plasma membrane. In double-label cytochemical studies, we found that about 20% of the protein kinase Cgamma-immunoreactive neurons, which are concentrated in inner lamina II, contain glutamate decarboxylase-67 messenger RNA, but none stain for parvalbumin or nitric oxide synthase. These results indicate that persistent changes in protein kinase Cgamma immunoreactivity parallel the time-course of mechanical allodynia and suggest that protein kinase Cgamma contributes to the maintenance of the allodynia produced by peripheral inflammation. The minimal expression of protein kinase Cgamma in presumed inhibitory neurons suggests that protein kinase Cgamma-mediated regulation of excitatory interneurons underlies the changes in spinal cord activity during persistent nociception.

Animals↗
PubMed1999

Mapping of estrogen receptors alpha and beta in the inner ear of mouse and rat.

The sex hormone estrogen is classically known to influence growth, differentiation and function of peripheral tissues of both the female and male reproductive tract, mediated through the estrogen receptors alpha and beta. The influence of estrogens on the ear and hearing is yet not fully investigated, though some studies have suggested that estrogens may influence hearing functions. The aim of this study was to map eventual estrogen receptors in the inner ear in mouse and rat. Paraffin embedded sections of mouse and rat inner ear were immunostained with antibodies against estrogen receptors alpha and beta. Estrogen receptors alpha and beta containing cells were found in the inner ear, showing a unique distribution pattern, both in the auditory pathways and in the water/ion regulating areas. The presence of estrogen receptors indicates that estrogens may have an effect on the inner ear and hearing functions.

Animals↗
PubMed1999

Quantifying cellular oxidative stress by dichlorofluorescein assay using microplate reader.

Oxidative stress (OS) has been implicated in various degenerative diseases in aging. In an attempt to quantify OS in a cell model, we examined OS induced by incubating for 30 min with various free radical generators in PC12 cells by using the dichlorofluorescein (DCF) assay, modified for use by a fluorescent microplate reader. The nonfluorescent fluorescin derivatives (dichlorofluorescin, DCFH), after being oxidized by various oxidants, will become DCF and emit fluorescence. By quantifying the fluorescence, we were able to quantify the OS. Our results indicated that the fluorescence varied linearly with increasing concentrations (between 0.1 and 1 mM) of H2O2 and 2,2'-azobios(2-amidinopropane) dihydrochloride (AAPH; a peroxyl radical generator). By contrast, the fluorescence varied as a nonlinear response to increasing concentrations of 3-morpholinosydnonimine hydrochloride (SIN-1; a peroxynitrite generator), sodium nitroprusside (SNP; a nitric oxide generator), and dopamine. Dopamine had a biphasic effect; it decreased the DCF fluorescence, thus acting as an antioxidant, at concentrations <500 microM in cells, but acted as a pro-oxidant by increasing the fluorescence at 1 mM. While SNP was not a strong pro-oxidant, SIN-1 was the most potent pro-oxidant among those tested, inducing a 70 times increase of fluorescence at a concentration of 100 microM compared with control. Collectively, due to its indiscriminate nature to various free radicals, DCF can be very useful in quantifying overall OS in cells, especially when used in conjunction with a fluorescent microplate reader. This method is reliable and efficient for evaluating the potency of pro-oxidants and can be used to evaluate the efficacy of antioxidants against OS in cells.

Amidines↗
PubMed1999

Structure-activity relationships of quercetin in antagonizing hydrogen peroxide-induced calcium dysregulation in PC12 cells.

Oxidative stress can induce neurotoxic insults by increasing intracellular calcium (Ca2+), which has been implicated in various neurodegenerative diseases in aging. Previously, we showed that hydrogen peroxide induced calcium dysregulation in PC12 cells, as evidenced by (i) an increase in calcium baselines, (ii) a decrease in depolarization-induced calcium influx, and (iii) a failure to recover the Ca2+ levels. In the present experiments, we investigated whether a dietary flavonoid, quercetin, can antagonize the effects of hydrogen peroxide in the same cell model. We also investigated the possible structure-activity relationships of quercetin by comparing the results with four other flavonoids, each having a slightly different structure from quercetin. Our results indicated that two structural components, including (i) 3', 4'-hydroxyl (OH) groups in the B ring and (ii) a 2,3-double bond in conjugation with a 4-oxo group in the C ring, along with the polyphenolic structures were crucial for the protection. These structural components are found in quercetin, and this compound was also the most efficacious in reducing both the H2O2-induced Ca2+ dysregulation in cells and oxidative stress assessed via the dichlorofluorescein assay. Collectively, these data indicated that the particular polyphenolic structural components of quercetin provided its strong antioxidant property of protecting cells against H2O2-induced oxidative stress and calcium dysregulation.

Animals↗
PubMed1999

Stable markers of oxidant damage to proteins and their application in the study of human disease.

The mechanisms of formation and the nature of the altered amino acid side chains formed on proteins subjected to oxidant attack are reviewed. The use of stable products of protein side chain oxidation as potential markers for assessing oxidative damage in vivo in humans is discussed. The methods developed in the authors laboratories are outlined, and the advantages and disadvantages of these techniques compared with other methodologies for assessing oxidative damage to proteins and other macromolecules. Evidence is presented to show that protein oxidation products are sensitive markers of oxidative damage, that the pattern of products detected may yield information as to the nature of the original oxidative insult, and that the levels of oxidized side-chains can, in certain circumstances, be much higher than those of other markers of oxidation such as lipid hydroperoxides.

Amino Acids↗