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Biomedical subjects

W Wu

Publications and source records attributed to W Wu.

At least 451 records · Page 25Linked to original sources
PubMed1993

[Restriction endonuclease analysis of leptospiral DNA from different serogroup and serovar].

The DNAs of different serogroups and serovars of leptospires were analyzed with seven kinds of restriction endonuclease (Bam HI, Bgl II, Cfo I, Eco RI, Hind III, Kpn I and Pst I). The results showed that there are significant differences among the leptospiral DNAs of different serovars, especially in the high molecular-weight region, but the patterns of different strains belonging to the same serovar are similar. In addition, Cfo I and Eco RI are more effective for differentiating leptospires.

DNA Restriction Enzymes↗
PubMed1993

Magnesium, potassium flux and photosynthesis.

Photosynthetic capacity of chloroplasts is regulated by stromal pH. The pH of the stroma must be maintained higher than external pH during illumination in order to optimize photosynthetic carbon reduction cycle activity. Stromal pH is affected by K+/H+ counterexchange across the chloroplast envelope. Magnesium ion external to the chloroplast affects K+/H+ counterfluxes and hence stromal pH and photosynthesis. K+/H+ counterfluxes across the envelope are facilitated by K+ and H+ conducting ion channels, and an H+ pumping envelope ATPase. External magnesium affects K+/H+ exchange by binding to negative surface charges on the envelope membrane. Magnesium binding restricts currents through K+ channels. Magnesium block of K+ uptake through this channel impairs H+ efflux, inhibiting photosynthesis. Under conditions which lead to net K+ efflux through the channel, envelope-bound magnesium restricts K+ efflux, reducing the driving force for electroneutral H+ uptake. External magnesium has a profound effect on chloroplast photosynthetic capacity by an indirect control of H+ movement across the envelope and hence of stromal pH.

Chloroplasts↗
PubMed1992

Identification of neurons expressing thyrotropin releasing-hormone receptor mRNA in spinal cord and lower brainstem of rat.

The distribution of mRNA coding for a pituitary thyrotropin releasing-hormone (TRH) receptor was examined on sections of spinal cord and lower brainstem of rat using in situ hybridization. Hybridization signals were observed over large neurons in the ventral horn in cervical, thoracic, and lumbar segments of spinal cord, and over neurons in the motor nuclei of the lower brainstem. Although significant thyrotropin-releasing hormone binding has been reported in the superficial dorsal horn, only background levels of hybridization were observed over neurons in this region. These findings suggest that mRNA coding for thyrotropin-releasing hormone receptor is expressed in some spinal and brainstem motor neurons. Since many of these neurons are innervated by TRH-containing afferents, TRH may exert a direct effect upon at least some of these cells.

Animals↗
PubMed1992

Human cerebrospinal fluid protein database: edition 1992.

Two-dimensional electrophoresis maps of human cerebrospinal fluid proteins are presented in the form of labeled images. 931 protein spots are identified in spinal fluid from a normal volunteer. Distinct spots that represent variants of the same protein, especially posttranslational modifications, are estimated to reduce the 931 different spots to < 200 different proteins. 248 spots of 29 protein groups have been identified and are indicated on enlargements of specific gel regions. The distribution of protein abundance, mass, charge and shape characteristics of these normal 931 spinal fluid spots are graphically profiled. Analysis of the shape parameter "vertical height: width ratio" reveals that a ratio > 3.5 correlates with glycoproteins, enabling their identification simply by image analysis. Proteins that are not present on the normal map, but appear in spinal fluid in patients with schizophrenia and Creutzfeldt-Jakob disease are illustrated on additional maps.

Cerebrospinal Fluid Proteins↗
PubMed1992

Organization of the serotonergic innervation of spinal neurons in rats--I. Neuropeptide coexistence in varicosities innervating some spinothalamic tract neurons but not in those innervating postsynaptic dorsal column neurons.

Previous studies have suggested that peptides such as substance P and thyrotropin-releasing hormone coexist with serotonin in the same varicosities in the ventral horn and intermediate gray of the spinal cord in rat. However, coexistence of these peptides with serotonin is rare in fibers in the superficial dorsal horn. Since it has been proposed that serotonergic fibers in the superficial dorsal horn act to modulate nociception, it was hypothesized that the serotonergic neurons that contain neither substance P nor thyrotropin-releasing hormone might constitute a specifically antinociceptive subset of serotonergic neurons. This being the case, it would be expected that different types of serotonergic neurons innervate nociceptive and non-nociceptive spinal neurons. In order to test this hypothesis, a group of cells that include nociceptive neurons (spinothalamic tract neurons) and a group of predominantly non-nociceptive neurons (postsynaptic dorsal column neurons) in the spinal cord of rat were retrogradely labeled. Sections of the spinal cord containing retrogradely labeled spinothalamic tract or postsynaptic dorsal column neurons were stained for serotonin and either substance P or thyrotropin-releasing hormone using two-color immunohistochemistry. A retrogradely labeled cell was classified as "apposed" if there was no discernible distance between an immunohistochemically labeled varicosity and the cell. Eighty per cent of spinothalamic tract and 83% of postsynaptic dorsal column profiles were apposed by serotonin-immunoreactive varicosities in the spinal cord. Thirty-one per cent of the spinothalamic tract profiles that were apposed by serotonergic varicosities were apposed by serotonergic varicosities that were also stained for thyrotropin-releasing hormone. The distribution of the latter spinothalamic neurons was similar to that reported for spinothalamic tract neurons responsive to joint movement. In addition, at least 63% of the spinothalamic tract profiles which were apposed by serotonergic varicosities were apposed by "serotonin-only" varicosities, including most spinothalamic tract neurons in the marginal zone, suggesting that at least some "serotonin-only" neurons are antinociceptive. However, contrary to the hypothesis, at least 94% of the postsynaptic dorsal column profiles apposed by serotonergic varicosities were apposed by "serotonin-only" varicosities. These findings suggest that there may be a relationship between the sensory modality to which a spinal neuron responds and the type of serotonergic innervation it receives. However, it appears that "serotonin-only" neurons may not constitute a specifically antinociceptive category of serotonergic neurons.

Animals↗
PubMed1992

Differential effects of cyclo-oxygenase and thromboxane synthetase inhibition on ventilation-perfusion relationships in acid aspiration-induced acute lung injury.

Cyclo-oxygenase metabolites are important regulators of pulmonary vascular and airway tone and may act to regulate ventilation-perfusion (VA/Q) relationships. Hypoxemia that follows aspiration of gastric acid is associated with increased venous admixture, and plasma levels of thromboxane (TX) B2 and 6-keto-PGF2 alpha are increased after experimental acid-induced acute lung injury. The present study was designed to determine the effects of cyclo-oxygenase metabolites on VA/Q relationships in canine acid aspiration. Eighteen anesthetized dogs received 0.2 mL/kg 0.1 N HCl intratracheally; six were pretreated with ibuprofen (IBU), a cyclo-oxygenase inhibitor, 12.5 mg/kg IV, and six other dogs received OKY-046 (OKY), a TX synthetase inhibitor, 0.5 mg/kg IV. The remaining six animals (ACID) served as controls. Continuous distributions of ventilation and perfusion were evaluated with the multiple inert gas elimination technique. Within 30 minutes, acid injury resulted in significant (p < 0.05) decreases in PaO2 from baseline values by 44.7 +/- 5.4 and 47.6 +/- 4.8 mm Hg in the ACID and OKY groups, respectively. Although decreased, the change in PaO2 of 21.0 +/- 4.8 mm Hg in IBU animals was significantly (p < 0.05) attenuated in comparison with the other groups. Ibuprofen increased pulmonary vascular resistance, attenuated perfusion to shunt and low VA/Q areas, and reduced ventilation to unperfused areas for the first 2 hours after acid injury (all p < 0.05), whereas OKY exacerbated hypoxemia and VA/Q inequality.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Stromal pH and Photosynthesis Are Affected by Electroneutral K and H Exchange through Chloroplast Envelope Ion Channels.

Potassium movement across the limiting membrane of the chloroplast inner envelope is known to be linked to counterex-change of protons. For this reason, K(+) efflux is known to facilitate stromal acidification and the resultant photosynthetic inhibition. However, the specific nature of the chloroplast envelope proteins that facilitate K(+) fluxes, and the biophysical mechanism which links these cation currents to H(+) counterflux, is not characterized. It was the objective of this work to elucidate the nature of the system regulating K(+) flux linked to H(+) counterflux across the chloroplast envelope. In the absence of external K(+), exposure of spinach (Spinacia oleracea) chloroplasts to the K(+) ionophore valinomycin was found to increase the rate of K(+) efflux and H(+) influx. These data were interpreted as suggesting that H(+) counterexchange must be indirectly linked to movement of K(+) across the envelope. Studies using the K(+) channel blocker tetraethylammonium indicated that K(+) likely moves, in a uniport fashion, into or out of the stroma through a monovalent cation channel in the envelope. Blockage of K(+) efflux from the stroma by exposure to tetraethylammonium was found to restrict H(+) influx, further substantiating an indirect linkage of these cation currents. Further studies comparing the effect of exogenous H(+) ionophores and K(+)/H(+) exchangers suggested that K(+) uniport through this ion channel likely is the main endogenous pathway for K(+) currents across the envelope. These experiments were also consistent with the presence of a proton channel in the envelope. Movement of H(+) through this channel was speculated to be regulated and rate limited by an electroneutral requirement for K(+) countercurrents through the separate K(+) uniport pathway. K(+) and H(+) fluxes across the chloroplast envelope were envisioned to be interrelated via this mechanism. The significant effect of cation currents across the envelope, as mediated by these channels, on photosynthetic capacity of the isolated chloroplast was also demonstrated.

Journal Article↗
PubMed1992

K stimulation of ATPase activity associated with the chloroplast inner envelope.

Studies were conducted to characterize ATPase activity associated with purified chloroplast inner envelope preparations from spinach (Spinacea oleracea L.) plants. Comparison of free Mg(2+) and Mg.ATP complex effects on ATPase activity revealed that any Mg(2+) stimulation of activity was likely a function of the use of the Mg.ATP complex as a substrate by the enzyme; free Mg(2+) may be inhibitory. In contrast, a marked (one- to twofold) stimulation of ATPase activity was noted in the presence of K(+). This stimulation had a pH optimum of approximately pH 8.0, the same pH optimum found for enzyme activity in the absence of K(+). K(+) stimulation of enzyme activity did not follow simple Michaelis-Menton kinetics. Rather, K(+) effects were consistent with a negative cooperativity-type binding of the cation to the enzyme, with the K(m) increasing at increasing substrate. Of the total ATPase activity associated with the chloroplast inner envelope, the K(+)-stimulated component was most sensitive to the inhibitors oligomycin and vanadate. It was concluded that K(+) effects on this chloroplast envelope ATPase were similar to this cation's effects on other transport ATPases (such as the plasmalemma H(+)-ATPase). Such ATPases are thought to be indirectly involved in active K(+) uptake, which can be facilitated by ATPase-dependent generation of an electrical driving force. Thus, K(+) effects on the chloroplast enzyme in vitro were found to be consistent with the hypothesized role of this envelope ATPase in facilitating active cation transport in vivo.

Journal Article↗
PubMed1992

Normal mode solution for low-frequency sound propagation in a downward refracting atmosphere above a complex impedance plane.

The development of the fast field and parabolic equation solutions to the wave equation has made it possible to solve for the combined effects of refraction in a layered atmosphere and the interaction of sound with a complex impedance ground surface. In many respects the numerical methods have advanced beyond our understanding of the basic phenomena. In an earlier study [J. Acoust. Soc. Am. 89, 107-114 (1991)], the residue series solution for upward refraction was investigated and provided insight into the nature of the interaction of refraction and ground reflection. In this paper results are presented of a similar normal mode solution for downward refraction above a complex impedance ground surface. This model is used to investigate when the surface wave is excited for downward refraction conditions and to develop criteria for the maximum range of cylindrical decay as a function of phase and magnitude of the ground impedance and the magnitude of the sound velocity gradient.

Acoustics↗
PubMed1992

Decreased immunological responses by wortmannin-containing rice culture of Fusarium oxysporum and by purified wortmannin in avian species.

Immunological assays were performed in young chicken and duck after they had been fed wortmannin-containing culture of Fusarium oxysporum or purified wortmannin for 2 weeks. The culture significantly decreased humoral response to sheep red blood cell, cell-mediated cutaneous hypersensitivity to phytohemagglutinin and phagocytic activity in isolated peritoneal exudate adherent cells, but only when the concentration was high enough to cause concurrent reduction in body weight gain and hematocrit. Increased dietary metabolizable energy and protein did not affect the toxicity of the culture. On the other hand, purified wortmannin (1 mg/kg diet) significantly inhibited the aforementioned immunological responses prior to the adverse effects on body growth and hematocrit. The data strongly indicate that wortmannin is an immunotoxic substance. The possibility that macrophage is the primary target cell type is discussed.

Androstadienes↗
PubMed1992

The effect of radix Salviae miltiorrhizae on the changes of ultrastructure in rat brain after cerebral ischemia.

The effect of RSM on ultrastructural alterations of the cortical, hippocampal and caudate neucleus areas brought about by forebrain ischemia in rats were studied. In both RSM-treated and saline-treated groups the ischemic damage was detected in nearly all animals three hours after bilateral common carotid artery ligation, while it was much more mild in RSM-treated animals. The ultrastructural changes consisted of swollen mitochondria, partial loss of cristae, dilatation of rough endoplasmic reticulum and Golgi's complex. In addition, some dark neurons were present, capillary endothelial cells and processes of astrocytes were swollen and active pinocytosis appeared in the endothelial cells. Their presence was most severe in the hippocampus region and the least in the caudate nuclear area. No ultrastructural changes exhibited in the sham-operated animals. The findings of the present experiment demonstrate that RSM can reduce ultrastructural abnormalities of cerebral ischemia and are also direct evidence of the protective effect of RSM on cerebral ischemia.

Animals↗
PubMed1991

Surface Charge-Mediated Effects of Mg on K Flux across the Chloroplast Envelope Are Associated with Regulation of Stromal pH and Photosynthesis.

Studies of Spinacia oleracea L. were undertaken to characterize further how Mg(2+) external to the isolated intact chloroplast interacts with stromal K(+), pH, and photosynthetic capacity. Data presented in this report were consistent with the previously developed hypothesis that millimolar levels of external, unchelated Mg(2+) result in lower stromal K(+), which somehow is linked to stromal acidification. Stromal acidification directly results in photosynthetic inhibition. These effects were attributed to Mg(2+) interaction (binding) to negative surface charges on the chloroplast envelope. Chloroplast envelope-bound Mg(2+) was found to decrease the envelope membrane potential (inside negative) of the illuminated chloroplast by 10 millivolts. It was concluded that Mg(2+) effects on photosynthesis were likely not mediated by this effect on membrane potential. Further experiments indicated that envelope-bound Mg(2+) caused lower stromal K(+) by restricting the rate of K(+) influx; Mg(2+) did not affect K(+) efflux from the stroma. Mg(2+) restriction of K(+) influx appeared consistent with the typical effects imposed on monovalent cation channels by polyvalent cations that bind to negatively charged sites on a membrane surface near the outer pore of the channel. It was hypothesized that this interaction of Mg(2+) with the chloroplast envelope likely mediated external Mg(2+) effects on chloroplast metabolism.

Journal Article↗
PubMed1991

Lidocaine and ATPase inhibitor interaction with the chloroplast envelope.

Photosynthetic capacity of isolated intact chloroplasts is known to be sensitive to K(+) fluxes across the chloroplast envelope. However, little is known about the system of chloroplast envelope proteins that regulate this K(+) movement. The research described in this report focused on characterizing some of the components of this transport system by examining inhibitor effects on chloroplast metabolism. Digitoxin, an inhibitor of membrane-bound Na(+)/K(+) ATPases, was found to reduce stromal K(+) at a range of external K(+) and inhibit photosynthesis. Scatchard plot analysis revealed a specific protein receptor site with a K(m) for digitoxin binding of 13 nanomolar. Studies suggested that the receptor site was on the interior of the envelope. The effect of a class of amine anesthetics that are known to be K(+) channel blockers on chloroplast metabolism was also studied. Under conditions that facilitate low stromal pH and concomitant photosynthetic inhibition, the anesthetic, lidocaine, was found to stimulate photosynthesis. This stimulation was associated with the maintenance of higher stromal K(+). Comparison of the effects on photosynthesis of lidocaine analogs which varied in lipophilicity suggested a lipophilic pathway for anesthetic action. The results of experiments with lidocaine and digitoxin were consistent with the hypothesis that a K(+) channel and a K(+)-pumping envelope ATPase contribute to overall K(+) flux across the chloroplast envelope. Under appropriate assay conditions, photosynthetic capacity of isolated chloroplasts was shown to be much affected by the activity of these putative envelope proteins.

Journal Article↗
PubMed1991

No difference in day-night serum melatonin concentration after pineal grafting into the third cerebral ventricle of pinealectomized rats.

Serum melatonin concentration and its day-night difference in pinealectomized, stereotaxically grafted rats with pineal transplants was examined. The nighttime serum melatonin concentration increased significantly only in pinealectomized rats that received two pineal transplants. In neither pinealectomized rats receiving two pineal glands and one cotransplant of superior cervical sympathetic ganglion nor pinealectomized-ganglionectomized rats receiving two pineal transplants was there a demonstrable increased in serum melatonin concentration. Although some pineal transplanted hosts demonstrated increases in serum melatonin concentration, there was no day-night variation in serum melatonin concentration. This may be due to a number of mitigating factors. Pineal grafts may not receive the appropriate functional reinnervation from the host brain due to the location of the transplantation in the cerebral ventricle or due to lack of sufficient time for the growth of invading host neurites.

Analysis of Variance↗
PubMed1991

Short acting soft mydriatics.

Three soft drug analogs of atropine have been tested for mydriatic activity in rabbits' eyes and their in vitro metabolic pathway has been investigated in rat, rabbit and human blood. The three soft drugs were found to produce an equieffective mydriatic activity to atropine and tropicamide. At equieffective concentrations, their durations were shorter with AUC's 12-21% that of 0.25% atropine and 44-80% that of 0.2% tropicamide. The untreated control eyes were observed to dilate after unilateral ocular administration of atropine, but not with unilateral soft drug treatment. In vitro stability studies showed that the soft ethyl analog was less stable in rat blood and rat liver homogenate than in rabbit or human blood. The metabolic product of the soft ethyl derivative in biological media was proven to be the corresponding inactive acidic metabolite predicted by the soft drug design. The ultrashort durations and the potentially nontoxic systemic properties of the soft mydriatics offer promise for use in ophthalmoscopy and in other ocular procedures where a short acting anticholinergic type of mydriatic would be indicated.

Animals↗