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Biomedical subjects

H Xue

Publications and source records attributed to H Xue.

At least 127 records · Page 7Linked to original sources
PubMed1992

Mutational identification of an essential tryptophan in tryptophanyl-tRNA synthetase of Bacillus subtilis.

The strongly conserved single tryptophan residue, Trp92, in Bacillus subtilis tryptophanyl-tRNA synthetase has been mutagenized via site direction singly into Gln, Ala, and Phe. All three mutant enzymes were inactive toward the catalysis of tRNA tryptophanylation. The Trp92----Phe mutant has been subcloned into the high expression plasmid pKK223-3 to yield the recombinant plasmid pKSW-F92. Growth of bacteria carrying the latter plasmid made possible the purification of the mutant TrpRS-F92 enzyme to homogeneity. This mutant enzyme was deficient in ultraviolet absorbance and fluorescence relative to the wild type enzyme and inactive in the partial reaction of Trp-activation as well as the overall reaction of tRNA tryptophanylation. Furthermore, unlike the wild type B. subtilis trpS gene, the mutant trpS-F92 gene upon transformation into Escherichia coli trpS 10343 failed to complement the temperature sensitive trpS mutation of the host cells. Trp92 therefore represents an essential residue both in vitro and in vivo for the function of the tryptophanyl-tRNA synthetase.

Amino Acid Sequence↗
PubMed1992

Pulmonary fat embolism in rabbits induced by forced immobilization.

In the study reported here, rabbits were used to develop an experimental model for inducing pulmonary fat embolism by forced immobilization. The emboli were quantitated by a computerized system. The activity of lipoprotein lipase in post-heparin plasma (PHP-LPL) and concentrations of free fatty acids (FFA) were measured. Also, blood gases were analyzed and pulmonary morphology and ultrastructure were observed. Forced immobilization for 5 hours was found to induce pulmonary embolism. This was accompanied by elevation of PHP-LPL and FFA levels in the blood, hypocapnia, and a tendency for insufficiency of pulmonary surfactant. The results suggest that the disorder of homeostasis caused by immobilization is strong enough to bring about pulmonary embolism without bone fracture.

Animals↗
PubMed1992

Properties of hemoglobin and dextran-hemoglobin rightshifted by oxidized inositol tetrakisphosphate.

Phytate was digested by wheat bran phytase to yield inositol tetrakisphosphate. Periodate-oxidized inositol tetrakisphosphate (oxyIP4) was coupled by means of reductive alkylation to hemoglobin and the covalent dextran-hemoglobin conjugate to yield the rightshifted (rs) compounds rsHb and rsDxHb, respectively. The variations of the oxygen dissociation curves of these molecules with pH and temperature were compared to those of hemoglobin. The variations with pH were found to be less pronounced for these rightshifted forms. An extensive decrease in the half-saturation oxygen tension was observed, however, with both rsHb and rsDxHb, as in the case of unmodified Hb. Modification of hemoglobin by oxyIP4 at the polyphosphate site was suggested by the lack of a further rightshifting effect of phytate on rsHb, and by the similarity between the difference spectrum of rs-methemoglobin and the difference spectrum induced by the addition of phytate.

Dextrans↗
PubMed1991

Rate of deoxygenation and rheologic behavior of blood in sickle cell anemia.

To understand the relationship between deoxygenation rate, rheologic behavior, and red blood cell (RBC) morphologic characteristics of blood in sickle (SS) cell anemia, washed oxy SS RBC suspensions (hematocrit, 40%) were subjected to relatively fast and gradual deoxygenation procedures. Relatively fast deoxygenation resulted in 50% decline in percent hemoglobin oxygen saturation (%HbO2) within 1 minute. The SS suspensions following relatively fast deoxygenation showed two distinct phases in viscosity profiles. First, there was a sharp increase in individual viscosities to a peak value at 7 minutes of deoxygenation. Second, prolonged deoxygenation resulted in a 27% to 37% decrease in individual viscosities at 30 minutes as compared with the respective peak values at 7 minutes. Most of the viscosity increase (ie, about fourfold) occurred within the first 3 minutes of relatively fast deoxygenation. Scanning electron microscopy and differential morphologic analysis of deoxy cells showed that at 7 minutes a majority of cells had a granular appearance that was characterized by a bumpy irregular surface and the presence of small spicule-like projections. Prolonged deoxygenation resulted in the appearance of a large percentage of elongated cells that were unlike typical sickle cells. Transmission electron microscopy showed that the elongated shape resulted from the alignment of HbS polymers into long projections. In contrast, gradual deoxygenation over a period of 30 minutes resulted in a progressive increase in viscosity and in the formation of typical sickle shapes and holly leaf cells. The results show that at matching %HbO2, the SS suspensions containing mainly granular shaped cells after 7 minutes of relatively fast deoxygenation are as viscous as the gradually deoxygenated suspensions that contain classic sickle shapes and holly leaf forms, while the suspensions having a large percentage of elongated cells (30 minutes after relatively fast deoxygenation) are the least viscous. The two distinct time-dependent viscosity phases observed after relatively fast deoxygenation probably result from differences in the RBC shape characteristics reflecting physical attributes of the polymer, which could affect cell orientation in the viscometric flow.

Anemia, Sickle Cell↗
PubMed1991

1,25 (OH)2 vitamin D3 attenuates the loss of resistance artery contractile function associated with incubation in culture media.

Contractile properties of rat mesenteric resistance arteries were studied immediately after isolation or after 48-hr incubation in culture medium [Dulbecco's modified Eagle's/Ham's F-12 (1:1) with insulin, transferrin and antibiotics]. Incubation in culture medium depressed active stress generating capacity, increased sensitivity to norepinephrine and ablated endothelium-dependent relaxation. The decrease in stress generation results from the loss of a releasable pool of intracellular Ca2+; the enhanced sensitivity is associated with decreased neuronal amine pump function. Addition of 300 pg/ml 1,25 (OH)2 vitamin D3 to the culture medium afforded nearly complete protection against the loss of stress generating capacity and partially preserved endothelial function. It is concluded that 1,25 (OH)2 vitamin D3 partially prevents phenotypic modulation of the vascular myocyte induced by culture conditions.

Acetylcholine↗
PubMed1991

1,25 (OH)2 vitamin D3-induced 45CA uptake in vascular myocytes cultured from spontaneously hypertensive and normotensive rats.

The effect of 1,25 (OH)2 vitamin D3 on basal 45Ca uptake was examined in vascular smooth muscle cells cultured from mesenteric arteries of spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) normotensive rats. Basal uptake of 45Ca was significantly greater in myocytes of WKY than SHR at 5, 10, 30 and 60 min incubation with the isotope. Incubation with 1 ng/ml 1,25 (OH)2 vitamin D3 for 48 hr increased basal 45Ca uptake between 1-10 min in SHR and between 5-10 min in WKY. The dose-response relationship indicated that cells from both strains are equally sensitive to the calciotropic effects of 1,25 (OH)2 vitamin D3 with half-maximal stimulation occurring at approximately 0.3-0.4 ng/ml. In cells of both strains maximal stimulation of 45Ca uptake was achieved only after a 12-24 hr period of incubation with hormone and pretreatment with cycloheximide inhibited 1,25 (OH)2 vitamin D3-enhanced 45Ca uptake. Although 45Ca binding by extracellular matrix material was significantly greater in WKY than SHR, 1,25 (OH)2 vitamin D3 had no effect on the amount of matrix 45Ca binding in either strain. These results suggest that 1,25 (OH)2 vitamin D3 induces an increase in intracellular protein synthesis that results in enhanced 45Ca uptake. The similar responses of the two strains indicate that hypertensive smooth muscle is not more sensitive to 1,25 (OH)2 vitamin D3 and the Ca2+ response is a general property of vascular muscle.

Animals↗
PubMed1991

Three New Dibenzocyclooctadiene Lignans from Kadsura longipedunculata.

Five dibenzocyclooctadiene lignans were isolated from the stems of KADSURA LONGIPEDUNCULATA collected in Guangxi province. Three of them are new compounds, named benzoyl-, isovaleroyl-, and isobutyroylbinankadsurin A. Binankadsurin A was isolated from nature for the first time. The absolute configuration of isovaleroyloxokadsurane, a spirobenzofuranoid lignan from K. COCCINEA, was confirmed by chemical correlation with isovaleroylbinankadsurin A.

Journal Article↗
PubMed1991

[Screening studies on anti-inflammatory function of traditional Chinese herb Gardenia jasminoides Ellis and its possibility in treating soft tissue injuries in animals].

This paper reports the study of six fractions and one chemical constituent isolated from the traditional Chinese herb Gardenia jasminoides. The results showed that two fractions (G5.G6,), alcohol extract (G1) and genipoiside(A) had obvious anti-inflammatory effects and were comparatively effective in treating soft tissue injuries in animals.

Animals↗
PubMed1990

The role of substance P of the central nervous system in the pathogenesis of spontaneously hypertensive rats.

In comparing the involvement of substance P (SP) in the central regulation of vasomotor tone in Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR), we found that: the degree of SP-like immunoreactivity (SPLI) in the hypothalamus, rostral ventral surface of the medulla oblongata (RVM) and intermediolateral cell column (IML) of the thoracic spinal cord of SHR rats was significantly higher than in WKY rats; intrathecal injection (ith) of SP receptor antagonist D-Pro2, D-Phe7, D-Trp9-SP (D-SP) caused a decrease of mean blood pressure (MBP) in both SHR and WKY rats. These results indicate that SP might participate in the pathogenesis of hypertension and the regulation of normal blood pressure.

Animals↗
PubMed1989

Mesenteric artery contractile properties during dietary calcium manipulation in spontaneously hypertensive and Wistar Kyoto normotensive rats.

The hypothesis that elevated Ca2+ intake lowers blood pressure in the spontaneously hypertensive rat (SHR) by altering intrinsic contractile properties of vascular smooth muscle was tested. The effect of 0.5, 1, and 2% Ca2+ in the diet on systolic blood pressure, serum-ionized Ca2+, and contractile properties of mesenteric arteries isolated from SHR and normotensive Wistar-Kyoto (WKY) rats maintained on diets for 6 and 12 weeks was examined. Blood pressure was significantly elevated in SHR on 0.5% Ca2+ diets after both 6 and 12 weeks, as well as in WKY receiving 1% Ca2+. After six weeks on the diets for the SHR and 6 and 12 weeks for the WKY, serum-ionized Ca2+ was a function of the amount of Ca2+ in the diet. When contractile force generation in response tp KCl or norepinephrine was examined, small diet-related differences were detected, but no consistent linear effect associated with the level of Ca2+ in the diet was observed in either strain. When the sensitivity of the vessels to KCl and norepinephrine was examined, no effects of oral Ca2+ intake were detected. The results indicate that oral Ca2+ loading has modest effects on blood pressure at both 12 and 18 weeks of age in the SHR and WKY and in the younger rat, where Ca2+ intake modulates serum ionized Ca2+ levels. At no age does modification of Ca2+ intake have a consistent effect on mesenteric artery sensitivity or force-generating ability in response to KCl or norepinephrine. These findings do not support the hypothesis that oral Ca2+ loading lowers blood pressure in the rat by altering intrinsic contractile properties of vascular smooth muscle.

Animals↗
PubMed1989

Persistence of asymmetry in nonaxisymmetric entry flow in a circular cylindrical tube and its relevance to arterial pulse wave diagnosis.

In an experiment motivated by the study of arterial blood flow along the lines suggested by the traditional Chinese medicine, the flow in a pipe whose lumen was blocked by a semi-circular plug two tube-diameters long was visualized by suspended particles, recorded by cinematography, and analyzed digitally. The Reynolds number was in the range of 100 to 450 based on the pipe diameter, similar to that of blood flow in the radial artery in the arms of man. The blockage was found to have a profound effect on the velocity profile of the flow in the wake, but it had little influence on the symmetry of the velocity profile upstream of the block, except in its immediate neighborhood. When the end conditions far away from the block were steady, the flow in the wake was steady. The asymmetry of the flow in the wake can be judged by the deviation of the location of the maximum axial velocity from the center line of the pipe as seen in the plane of symmetry of the blockage. Our results show that the deviation can be described as the sum of two components. The first is a strong one which decays exponentially in an entry length which is about twice as long as the classical Boussinesq entry length of axisymmetric flow. The second is a weaker component which is wavy spatially and persists far downstream (many times the entry length). The separated flow and vortex system behind the blockage are sensitive to the flow rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1989

[Observation on propagating experiments with Polygala tenuifolia Willd seed].

This paper reports the harvesting and storing of Polygala tenuifolia seed, the operating process and method of seed propagation both in the laboratory and in the field, the relationship between Palygala tenuifolia seed germination, seed treatment and temperature and humidity, and the importance of suitable conditions and climatic factors in the sexual propagation of the seed.

Climate↗
PubMed1989

Vascular actions of cicletanine.

Vascular wall hypertrophy and enhanced vascular reactivity are characteristic of the hypertensive state. Pharmacologic reversal or prevention of these changes might be of therapeutic benefit. We examined the mechanism by which cicletanine, an antihypertensive vasodilator, induces relaxation of isolated mesenteric resistance arteries and assessed its effects on growth of cultured mesenteric artery myocytes. Initial experiments determined the effect of cicletanine on aortic rings and superior mesenteric arteries isolated from spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats. Cicletanine induced dose-dependent relaxation of pre-contracted segments of both artery types. Aortas of SHR were more sensitive to cicletanine than those of the WKY, while no difference in sensitivity of mesenteric arteries was observed between the two strains. Within-strain comparisons showed that aortas of SHR were more sensitive to cicletanine than mesenteric arteries while no differences were detected in vessels of the WKY. To assess the mechanism of action, the effect of cicletanine on intracellular Ca2+ was determined in mesenteric resistance arteries loaded with fura-2. In 4 of 4 preparations tested, 100 microM cicletanine induced a rapid fall in the level of free ionized Ca2+. When the endothelial lining of superior mesenteric arteries was removed or vessels were pre-treated with either 1 microM propranolol, 0.1 mM ouabain or 5 microM indomethacin, no effect on cicletanine-induced relaxation (10-300 microM) was detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Effect of 1,25(OH)2 vitamin D3 and ionized Ca2+ on 45Ca uptake by primary cultures of aortic myocytes of spontaneously hypertensive and Wistar Kyoto normotensive rats.

The effect of several regulators of whole animal Ca2+ homeostasis on 45Ca uptake by primary cultures of aortic myocytes isolated from spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats was examined. Exposure of confluent cells to 1.0, 1.25 or 1.50 mM ionized Ca2+ in serum-free medium for seven days resulted in increased 45Ca uptake at the higher concentrations of Ca2+ in cells of the SHR but not the WKY. 1,25 (OH)2 vitamin D3 (1 ng/ml) for 7 days caused enhanced influx in cells from both the SHR and WKY while parathyroid hormone (1-34) (1 ng/ml) was without effect. The data indicate that humoral factors that serve to regulate whole animal Ca2+ homeostasis may also play a role in the regulation of Ca2+ metabolism of the vascular smooth muscle cell.

Animals↗