Biomedical subjects

R Wang

Publications and source records attributed to R Wang.

At least 55 records · Page 3Linked to original sources

PubMed2003

Patterning hydroxyapatite biocoating by electrophoretic deposition.

Patterned bioceramic coatings may find potential applications in orthopedic implants and biosensors. In this study, various hydroxyapatite (HA) patterns were created on silicon and titanium substrates. Electrophoretic deposition technique was used together with surface patterning of the cathode specimen. When gold/palladium patterns (hexagons, spherical dots, etc.) were created on the cathode surface, HA colloidal particles in ethanol would preferentially deposit on the gold-coated area and form patterns. When silicon, instead of gold, was evaporated onto a conducting cathode surface, HA mainly deposited on the exposed area of the substrate. Detailed mechanisms for forming HA patterns may involve local concentration of the electric field when a second metal is patterned on the cathode. The difference in electric field across the two metals on the cathode also enhances HA patterning through an electrohydrodynamic process. This study demonstrated the possibility and flexibility of electrophoretic deposition in patterning charged particles onto a substrate.

Chemistry, Physical↗

PubMed2003

Enhanced evoked excitatory transmitter release in experimental neuropathy requires descending facilitation.

Nerve injury-induced afferent discharge is thought to elicit spinal sensitization and consequent abnormal pain. Experimental neuropathic pain, however, also depends on central changes, including descending facilitation arising from the rostral ventromedial medulla (RVM) and upregulation of spinal dynorphin. A possible intersection of these influences at the spinal level was explored by measuring evoked, excitatory transmitter release in tissues taken from nerve-injured animals with or without previous manipulation of descending modulatory systems. Spinal nerve ligation (SNL) produced expected tactile and thermal hyperesthesias. Capsaicin-evoked calcitonin gene-related peptide (CGRP) release was markedly enhanced in lumbar spinal tissue from SNL rats when compared with sham-operated controls. Enhanced, evoked CGRP release from SNL rats was blocked by anti-dynorphin A(1-13) antiserum; this treatment did not alter evoked release in tissues from sham-operated rats. Dorsolateral funiculus lesion (DLF) or destruction of RVM neurons expressing mu-opioid receptors with dermorphin-saporin, blocked tactile and thermal hypersensitivity, as well as SNL-induced upregulation of spinal dynorphin. Spinal tissues from these DLF-lesioned or dermorphin-saporin-treated SNL rats did not exhibit enhanced capsaicin-evoked CGRP-IR release. These data demonstrate exaggerated release of excitatory transmitter from primary afferents after injury to peripheral nerves, supporting the likely importance of increased afferent input as a driving force of neuropathic pain. The data also show that modulatory influences of descending facilitation are required for enhanced evoked transmitter release after nerve injury. Thus, convergence of descending modulation, spinal plasticity, and afferent drive in the nerve-injured state reveals a mechanism by which some aspects of nerve injury-induced hyperesthesias may occur.

Afferent Pathways↗

PubMed2003

Optical detection of hot-electron spin injection into GaAs from a magnetic tunnel transistor source.

Injection of spin-polarized hot-electron current from a magnetic tunnel transistor into GaAs is demonstrated by the observation of polarized light emission from a GaAs/In(0.2)Ga(0.8)As multiple quantum well light-emitting diode. Electroluminescence from the quantum wells shows a polarization of approximately 10% after subtraction of a linear background polarization. The polarization shows a strong dependence on the bias voltage across the diode, which may originate from changes in the electron spin relaxation rate in the quantum wells under varying bias conditions.

Journal Article↗

PubMed2003

A threonine residue (Thr71) at the intracellular end of the M1 helix plays a critical role in the gating of Kir6.2 channels by intracellular ATP and protons.

ATP-sensitive K+ (K(ATP)) channels are known to be gated by several intracellular molecules, but the gating mechanisms remain unclear. To understand the relationship of channel gating to ligand binding, we studied Kir6.2 channel gating by ATP and protons, which inhibit and activate the channel, respectively. We have previously shown that a threonine residue (Thr71) is critical for the pH sensitivity of Kir6.2 channel. If this site is involved in channel gating rather than ligand binding, it should affect channel gating by both ATP and proton. To test this hypothesis we performed a mutation analysis. Site-specific mutations of Thr71 to a bulky residue reduced the ATP sensitivity by >100-fold and eliminated the pH sensitivity. Single-channel activity of these mutants was stabilized at the open state with no detectable rundown. Mutations to a small amino acid had little effect on the ATP and pH sensitivities. Mutations to intermediate amino acids reduced but did not abolish the ATP and pH sensitivities. Hydrophobicity is not critical, as both polar and nonpolar amino acids are found in each group. Mutation to a positively charged lysine markedly exacerbated the pH- but not ATP-sensitivity, whereas mutation to glutamate moderately reduced ATP and pH sensitivities. These results indicate that the residue mass is critical for Kir6.2 channel gating, a mass that should be below 120 daltons with no charge. The existence of such a site as Thr71 involved in channel gating by both ATP and proton suggests that channel gating in the K(ATP) channel likely is separate from ligand binding.

Adenosine Triphosphate↗

PubMed2003

The blue copper ceruloplasmin induces aggregation of newly differentiated neurons: a potential modulator of nervous system organization.

Ceruloplasmin (CP) is a copper-dependent ferroxidase. It regulates iron metabolism and is involved in inflammation, angiogenesis, and protection against oxidative stress. CP also modulates K(+) channel activity in neuroblastoma cells and affects cardiodynamics of isolated hearts. Considering the presence of CP in the nervous system and the importance of iron ions and K(+) channels in neuronal activity, we postulated a role of CP in neuronal development. This hypothesis was tested using the P19 mouse embryonal carcinoma cell line, a model of neuronal differentiation. Addition of CP to the culture medium of newly differentiated P19 neurons induced cell aggregation within 24 h. This effect was concentration-dependent half-maximal at 50 nM, and not associated with necrosis, apoptosis or changes in secretory function. Deglycosylated CP was aggregative but not denatured CP, copper salts, His(2)Cu complex, or other copper enzymes or serum proteins. CP-induced aggregation was less pronounced with aging neurons and seemed not to involve K(+) channels. Immunocytofluorescence analysis demonstrated that digoxigenin-labeled CP bound to P19 neurons and the proportion of responding neurons decreased with aging. The interaction of digoxigenin-labeled CP with neurons was half-maximal at 120 nM by enzyme-linked immunosorbent assay and displaced by unlabeled CP. Our data indicate a specific aggregative action of CP on young neurons in vitro, possibly involving CP receptors. A potential developmental role of CP in nervous system organization is thus demonstrated.

Animals↗

PubMed2003

Glial cell line-derived neurotrophic factor normalizes neurochemical changes in injured dorsal root ganglion neurons and prevents the expression of experimental neuropathic pain.

Glial cell line-derived neurotrophic factor (GDNF) is necessary for the development of sensory neurons, and appears to be critical for the survival of dorsal root ganglion (DRG) cells that bind the lectin IB4. Intrathecal infusion of GDNF has been shown to prevent and reverse the behavioral expression of experimental neuropathic pain arising from injury to spinal nerves. This effect of GDNF has been attributed to a blockade of the expression of the voltage gated, tetrodotoxin-sensitive sodium channel subtype, Na(V)1.3, in the injured DRG. Here we report that GDNF given intrathecally via osmotic-pump to nerve-injured rats (L5/L6 spinal nerve ligation) prevented the changes in a variety of neurochemical markers in the DRG upon injury. They include a loss of binding of IB4, downregulation of the purinergic receptor P2X(3), upregulation of galanin and neuropeptide Y immunoreactivity in large diameter DRG cells, and expression of the transcription factor ATF3. GDNF infusion concomitantly prevented the development of spinal nerve ligation-induced tactile hypersensitivity and thermal hyperalgesia. These observations suggest that high dose, exogenous GDNF has a broad neuroprotective role in injured primary afferent. The receptor(s) that mediates these effects of GDNF is not known. GDNF's ability to block neuropathic pain states is not likely to be specific to Na(V)1.3 expression.

Activating Transcription Factors↗

PubMed2003

Contact damage in model dental multilayers: an investigation of the influence of indenter size.

This paper presents a combined experimental and computational study of the influence of indenter ball size on contact damage in model multilayered structures with equivalent elastic properties to bonded dentin/crown structures. Following a brief description of restored tooth structures, prior work on the development of model dental multilayered structures is reviewed. The effects of indentation ball size are investigated within a combined experimental and computational/analytical framework. The observed cracking patterns at the onset of crack nucleation are shown to be associated with principal stress contours computed using finite element analysis. The implications of the results are discussed for the design of dental multilayers that are more resistant to crack nucleation and propagation.

Journal Article↗

PubMed2003

Joint effects of social class and community occupational structure on coronary mortality among black men and white men, upstate New York, 1988-92.

STUDY OBJECTIVE: Occupational structure represents the unequal geographical distribution of more desirable jobs among communities (for example, white collar jobs). This study examines joint effects of social class, race, and county occupational structure on coronary mortality rates for men, ages 35-64 years, 1988-92, in upstate New York. DESIGN: Upstate New York's 57 counties were classified into three occupational structure categories; counties with the lowest percentages of the labour force in managerial, professional, and technical occupations were classified in category I, counties with the highest percentages were in category III. Age adjusted coronary heart disease (CHD) mortality rates, 35-64 years, (from vital statistics and census data) were calculated for each occupational structure category. MAIN RESULTS: An inverse association between CHD mortality and occupational structure was observed among blue collar and white collar workers, among black men and white men, with the lowest CHD mortality observed among white collar, white men in category III (135/100,00). About two times higher mortality was observed among blue collar than white collar workers. Among blue collar workers, mortality was 1.3-1.8 times higher among black compared with white workers, and the highest rates were observed among black, blue collar workers (689/100,00). Also, high residential race segregation was shown in all areas. CONCLUSIONS: Results suggest the importance of community conditions in coronary health of local populations; however, differential impact on subpopulations was shown. Blue collar and black workers may especially lack economic and other resources to use available community services and/or may experience worse working and living conditions compared with white collar and white workers in the same communities.

Adult↗

PubMed2003

Concentric sclerosis: imaging diagnosis and clinical analysis of 3 cases.

Baló's Concentric sclerosis (BCS) is a rare demyelinating disease considered to be a variant of multiple sclerosis (MS). The typical magnetic resonance imaging (MRI) changes associated with BCS consist of concentric rings or onions' cross-section on T1-weighted (T1W) images. Because MRI reveals pathological changes consistent with autopsy in the focus of BCS, it plays an important role in the before-death diagnosis of BCS. We report three cases of BCS diagnosed antemortem on the basis of the typical concentric rings pattern on MRI and on the basis of clinical findings and cerebrospinal fluid (CSF) examination. BCS often occurs in the prime of life, acutely or subacutely. Then come cerebral multifocal symptoms and signs. We find that BCS is not always an acute and irreversible pathological process as described in the past.

Adult↗

PubMed2002

Application of cereals and cereal components in functional foods: a review.

The food industry is directing new product development towards the area of functional foods and functional food ingredients due to consumers' demand for healthier foods. In this respect, probiotic dairy foods containing human-derived Lactobacillus and Bifidobacterium species and prebiotic food formulations containing ingredients that cannot be digested by the human host in the upper gastrointestinal tract and can selectively stimulate the growth of one or a limited number of colonic bacteria have been recently introduced into the market. The aim of these products is to affect beneficially the gut microbial composition and activities. Cereals offer another alternative for the production of functional foods. The multiple beneficial effects of cereals can be exploited in different ways leading to the design of novel cereal foods or cereal ingredients that can target specific populations. Cereals can be used as fermentable substrates for the growth of probiotic microorganisms. The main parameters that have to be considered are the composition and processing of the cereal grains, the substrate formulation, the growth capability and productivity of the starter culture, the stability of the probiotic strain during storage, the organoleptic properties and the nutritional value of the final product. Additionally, cereals can be used as sources of nondigestible carbohydrates that besides promoting several beneficial physiological effects can also selectively stimulate the growth of lactobacilli and bifidobacteria present in the colon and act as prebiotics. Cereals contain water-soluble fibre, such as beta-glucan and arabinoxylan, oilgosaccharides, such as galacto- and fructo-oligosaccharides and resistant starch, which have been suggested to fulfil the prebiotic concept. Separation of specific fractions of fibre from different cereal varieties or cereal by-products, according to the knowledge of fibre distribution in cereal grains, could be achieved through processing technologies, such as milling, sieving, and debranning or pearling. Finally, cereal constituents, such as starch, can be used as encapsulation materials for probiotics in order to improve their stability during storage and enhance their viability during their passage through the adverse conditions of the gastrointestinal tract. It could be concluded that functional foods based on cereals is a challenging perspective, however, the development of new technologies of cereal processing that enhance their health potential and the acceptability of the food product are of primary importance.

Bacteria↗

PubMed2002

Low frequency of somatic mutations in the FH/multiple cutaneous leiomyomatosis gene in sporadic leiomyosarcomas and uterine leiomyomas.

Germline mutations in the fumarate hydratase gene at 1q43 predispose to dominantly inherited skin and uterine leiomyomata and leiomyosarcomas. The enzyme, which is a component of the tricarboxylic acid cycle, acts as a tumour suppressor. To evaluate fumarate hydratase in respective sporadic tumours, we analysed a series of 26 leiomyosarcomas and 129 uterine leiomyomas (from 21 patients) for somatic mutations in fumarate hydratase and allelic imbalance around 1q43. None of the 26 leiomyosarcomas harboured somatic mutations in fumarate hydratase. Fifty per cent of leiomysarcomas tested showed evidence of allelic imbalance at 1q, but this was not confined to the vicinity of fumarate hydratase. Only 5% (seven out of 129) of the leiomyomas showed allele imbalance at 1q42-q43 and no somatic mutations in fumarate hydratase were observed. Our findings indicate that mutations in fumarate hydratase do not play a major role in the development of sporadic leiomyosarcomas or uterine leiomyomas

Adult↗

PubMed2002

Apposition of enkephalinergic axons with cGnRH I-containing perikarya in turkey hen brain.

Several lines of evidence support a role of endogenous opioids in the brain's regulation of gonadotropin secretion in birds and mammals, although the neuroanatomic basis of such regulation is not clear. We used double-label fluorescence immunohistochemistry employing polyclonal antisera raised in sheep against chicken gonadotropin-release hormone I (cGnRH I) and in rabbits against met-enkephalin to determine whether the potential exists for synaptic contact between neurons containing these neuropeptides in the preoptic/septal region of domestic turkey breeder hens. The cGnRH I antiserum was highly specific for cGnRH I, while the met-enkephalin antiserum showed some cross-reactivity with leu-enkephalin. We found numerous instances in which enkephalinergic neuronal elements appeared to contact cGnRH I perikarya and axons in and around the diagonal band of Broca, the bed nucleus of the pallial commissure and in the lateral septal nucleus. These appositions, confirmed by confocal scanning microscopy, appear to provide a neuroanatomic basis for how enkephalinergic innervation might influence gonadotropin secretion in turkey hens by directly regulating activity of cGnRH I neurons.

Animals↗

PubMed2002

Diffusion NMR methods applied to xenon gas for materials study.

We report initial NMR studies of (i) xenon gas diffusion in model heterogeneous porous media and (ii) continuous flow laser-polarized xenon gas. Both areas utilize the pulsed gradient spin-echo (PGSE) techniques in the gas phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients--a brief overview of this area is provided in the Introduction. The heterogeneous or multiple-length scale model porous media consisted of random packs of mixed glass beads of two different sizes. We focus on observing the approach of the time-dependent gas diffusion coefficient, D(t) (an indicator of mean squared displacement), to the long-time asymptote, with the aim of understanding the long-length scale structural information that may be derived from a heterogeneous porous system. We find that D(t) of imbibed xenon gas at short diffusion times is similar for the mixed bead pack and a pack of the smaller sized beads alone, hence reflecting the pore surface area to volume ratio of the smaller bead sample. The approach of D(t) to the long-time limit follows that of a pack of the larger sized beads alone, although the limiting D(t) for the mixed bead pack is lower, reflecting the lower porosity of the sample compared to that of a pack of mono-sized glass beads. The Pade approximation is used to interpolate D(t) data between the short- and long-time limits. Initial studies of continuous flow laser-polarized xenon gas demonstrate velocity-sensitive imaging of much higher flows than can generally be obtained with liquids (20-200 mm s-1). Gas velocity imaging is, however, found to be limited to a resolution of about 1 mm s-1 owing to the high diffusivity of gases compared with liquids. We also present the first gas-phase NMR scattering, or diffusive-diffraction, data, namely flow-enhanced structural features in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack.

Diffusion↗

PubMed2002

Modulation of A(beta) peptides by estrogen in mouse models.

Clinical studies have shown that estrogen deprivation through menopause is a risk factor in both the initiation and progression of Alzheimer's disease (AD) and that estrogen replacement therapy may be protective. One of the major pathological features in the human AD brain is the senile plaque, a proteinaceous structure composed mainly of heterogeneous peptides collectively known as A-beta (A(beta)). In vitro studies have linked estrogen with A(beta) modulation, suggesting that one-way that estrogen depletion at menopause may exacerbate the features of AD is through A(beta) accumulation. To test this, two studies were performed on transgenic models of amyloidosis. Firstly, transgenic mice without detectable amyloid aggregates were subjected to ovariectomy and estradiol supplementation, and A(beta) levels were assessed. Secondly, the effects of estrogen modulation were assessed in mice at an age when plaques would be forming initially. Overall, A(beta) levels were higher in estrogen-deprived mice than intact mice, and this effect could be reversed through the administration of estradiol. These data suggest that, in vivo, estrogen depletion leads to the accumulation of A(beta) in the CNS, which can be reversed through replacement of estradiol. These results provide evidence that post-menopausal estrogen depletion may be linked to an increased risk of AD through A(beta) modulation.

Amyloid beta-Peptides↗

PubMed2002

Analysis of intra-operative bleeding and recurrence of juvenile nasopharyngeal angiofibromas.

The purpose of this study is to present our experience with 34 patients diagnosed with juvenile nasopharyngeal angiofibromas and treated in the Chinese PLA General Hospital between 1986 and 1999, and to examine the factors influencing intra-operative bleeding and tumour recurrence. The age of the patient, the duration of symptoms and tumour stage were related to the amount of intra-operative bleeding. The tumours were totally resected in 30 patients and recurred in five patients (16.7%), with a mean follow-up time of 77 months. The mean time to tumour recurrence after operation was 3.2 months (1-6 months). The incidence of recurrence had no correlation with the age of the patient, duration of symptoms, peri-operative treatment or surgical approaches (P > 0.05); but strongly correlated with tumour stage (P < 0.05).

Adolescent↗

PubMed2002

Production of an exopolysaccharide bioflocculant by Sorangium cellulosum.

AIMS: To isolate a new exopolysaccharide bioflocculant produced by the myxobacterium Sorangium cellulosum NUST06, and to characterize its chemical composition and expolysaccharide production relative to carbon source. METHODS AND RESULTS: Exopolysaccharide levels and biomass production by S. cellulosum NUST06 were analysed relative to carbon source. Glucose in the medium at a level of 3 g l(-1) completely inhibited cell growth and exopolysaccharide production, but low concentrations of glucose (1-2 g l(-1)) could stimulate cell utilization of starch. The chemical composition and flocculating activity of the NUST06 exopolysaccharide was investigated. The flocculant comprised 38.3% proteins and 58.5% carbohydrates, of which glucose, mannose and glucuronic acid were present at 51.3%, 39.2% and 10.5%, respectively. The flocculating activity of the NUST06 flocculant depended strongly on cations. CONCLUSIONS: It is feasible to produce an exopolysaccharide bioflocculant by the strain NUST06 in a mineral salts medium using starch as a carbon source. SIGNIFICANCE AND IMPACT OF THE STUDY: This strain may be advantageous for commercial bioflocculant production and may enrich existing knowledge of myxobacteria.

Carbon↗

PubMed2002

Trends in coronary mortality and community services, associated with occupational structure in New York State, 1980-96.

STUDY OBJECTIVE: Examine the association between county occupational structure, services availability, prevalence of risk factors, and coronary mortality rates by sex, for 1980-96, in New York state. DESIGN: New York's 62 counties were classified into three occupational structure categories; counties with the lowest percentages of the labour force in managerial, professional, and technical occupations were classified in category I, counties with the highest percentages were in category III. Directly age adjusted coronary heart disease (CHD) mortality rates, aged 35-64 years, (from vital statistics and census data), per capita services (Census County Business Patterns), and the prevalence of CHD risk factors (BRFSS data) were calculated for each occupational structure category. RESULTS: CHD mortality rates and the prevalence of risk factors were inversely associated with occupational structure for men and women. Income from manufacturing jobs declined most in category I and per capita numbers of producer services for banking, business credit, overall business services, and personnel/employment services were 9-15 times greater in category III compared with I counties. Consumer services such as grocery stores, fitness facilities, doctors offices, and social services were 1.5-4 times greater in category III compared with I counties. CONCLUSIONS: An ecological model for conceptualizing communities and health and for intervention design is discussed; key community characteristics are occupational and industrial structure, availability and diversity of consumer services, prevalence of health practices, and level of premature CHD.

Adult↗

PubMed2002

[Nphe1]nociceptin(1-13)-NH2 antagonizes nociceptin-induced hypotension, bradycardia, and hindquarters vasodilation in the anesthetized rat.

The purpose of this study was to investigate the effects of [Nphe1]nociceptin(1-13)-NH2 on nociceptin-induced decreases in mean arterial pressure (MAP), heart rate (HR), and hindquarters vascular bed resistance (HVBR) of the anesthetized rat. The results showed that i.c.v. or i.v. [Nphe1]nociceptin(1-13)-NH2 (1.5-12 nmol/kg and 5-120 nmol/kg, respectively) could antagonize the depressor effects of i.c.v. or i.v. nociceptin (3 and 30 nmol/kg, respectively) on MAP and HR. Furthermore, [Nphe1]nociceptin(1-13)-NH2 (5-120 nmol/kg) could reverse nociceptin (30 nmol/kg)-induced decrease of HVBR. However, [Nphe1]nociceptin(1-13)-NH2 had no significant effects on similar effects induced by morphine. Our results suggest that [Nphe1]nociceptin(1-13)-NH2 acts as a selective antagonist of the nociceptin receptor in the cardiovascular system of the rat.

Anesthesia↗