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Biomedical subjects

Z Shi

Publications and source records attributed to Z Shi.

144 records · Page 8Linked to original sources
PubMed1994

Nickel carbonyl: toxicity and human health.

Because of its volatility and other unique properties, nickel tetracarbonyl has specialized industrial uses. It is an extremely toxic substance and induces systemic poisoning, with the lungs and brain being especially susceptible targets. The clinical symptoms and management of patients accidentally exposed are reviewed in considerable detail. Although there is some suggestion that nickel tetracarbonyl is a carcinogen in animals, the available epidemiologic data do not support such a link in humans. Continual monitoring and long-term follow-up of exposed workers is recommended.

Animals↗
PubMed1994

Studies on the extracellular polysaccharide from Agrobacterium radiobacter biovar I S-1231.

A strain S-1231 isolated from specimen of soil around Beijing area is gram-negative, non-sporing, motile by peritrichous flagella. It produces exopolysaccharide succinoglycan from carbohydrates as its carbon source but not starch and cellulose. Acid is produced during fermentation of glucose. Growing for 12-24 hr, the cells are rods 0.7-0.8 x 1.3-1.5 microns, round ended, single or in pairs. Colonies on nutrient agar plate are unpigmented, circular, raised, smooth and moist-glistening, edge entire. The organism produces 3-ketolactose and is unable to invade sunflower tissue. The G+C content of DNA is 62.8-63.4 mol%. The organism is referred to as Agrobacterium radiobacter. Moreover, the strain is oxidase-positive, catalase-positive, H2S-produce and can grow at 35 degrees C and 2% NaCl also. Litmus milk is alkalified. Thus, the organism was renamed Agrobacterium radiobacter biovar I. Component analyses showed that the exopolysaccharide (Agran-S) from A. radiobacter biovar I S-1231 consisted of D-glucose (69.1%), D-galactose (8.6%), pyruvic acid (9.5%) and succinic acid (10.5%). Methylation analyses revealed that the polysaccharide Agran-S contained following main structural units: (1-->3)-linked D-glucose (21.2%), (1-->3)-linked D-galactose (11.4%), (1-->6)-linked D-glucose (10.5%), (1-->4)-linked D-glucose (30.4%), (1-->4, 1-->6)-linked D-glucose (22.2%) and terminal D-glucose (4.3%). The -1H-NMR spectrum of the polysaccharide indicated that the linkages in the polymer are all beta-glycosidic. The IR spectra of the polysaccharide revealed the presence of ester linkage in polysaccharide Agran-S.

Bacterial Typing Techniques↗
PubMed1994

[Comparative study on three serologic tests for detecting antibodies in cases with bancroftian microfilaremia].

A comparative study was conducted for detecting antibody levels of bancroftian microfilaremia cases by using three serologic tests, IFAT, ELISA and dot-ELISA. A total of 102 serum specimens were collected from bancroftian microfilaremia cases. The positive rate was 89.2% (91/102) with IFAT (serum dilution > or = 1:20), 84.3% (86/102) with ELISA (OD value > or = 0.440) and 89.2% (91/102) with dot-ELISA (serum dilution > or = 1:80), respectively (P > 0.05); while in healthy individuals from non-endemic areas the false positive rate was 0(0/30), 1.8(1/55) and 0(0/54), respectively. The results indicated that there were no statistically significant differences among the three serologic tests. There was no correlation found in this study between microfilaria density and the antibody level. It was also proved that the detection rate of the combined use of either 2 or 3 tests was higher than each of the three tests; the positive rates being 94.1%-98.0%.

Animals↗
PubMed1993

Mechanism of adenylate kinase. What can be learned from a mutant enzyme with minor perturbation in kinetic parameters?

The structural and functional roles of threonine-23 in the chicken muscle adenylate kinase (AK) were investigated by site-directed mutagenesis coupled with proton nuclear magnetic resonance (NMR) and phosphorus stereochemistry. The residue is potentially important because it is conserved among all types of AK and is part of the consensus P-loop sequence, 15GXPGXGKGT23. A mutant enzyme T23A (replacing threonine-23 with alanine) was constructed. Analyses of conformational stability and proton NMR indicate that the side chain of this residue contributes little to the structure of AK, which suggests that the side chain of Thr-23 does not play a structural role. The steady-state kinetic data of the mutant enzyme T23A showed no change in kcat and only 5-7-fold increases in Km and dissociation constants. Such minor changes in kinetic data are insufficient to suggest a functional role of Thr-23. However, two-dimensional NMR analyses of WT.MgAP5A and T23A.MgAP5A complexes indicated that the side chain of Thr-23 is in proximity to the adenine ring of the ATP moiety in the WT.MgAP5A complex in solution. In addition, T23A showed a significant perturbation in the stereospecificity toward the diastereomers of (Rp)- and (Sp)-adenosine 5'-(1-thiotriphosphate) (ATP alpha S), with the Rp/Sp ratio increased from < 0.02 in wild-type to 0.37 in T23A. Detailed 31P NMR analysis indicated that the stereospecificity at the AMP site was not perturbed. These results suggest that the side chain of Thr-23 is involved in catalysis, most likely via a hydrogen bonding interaction Thr-OH...O-P alpha(ATP).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗
PubMed1993

Diagnosis of active Paragonimus westermani infections with a monoclonal antibody-based antigen detection assay.

We evaluated the performance of Dot-enzyme-linked immunosorbent assays designed to detect species- and stage-specific antigens of Paragonimus westermani in sera with monoclonal antibodies as serodiagnostic tests for active paragonimiasis. Sera from all donors with parasitologically confirmed infections with P. westermani contained adult worm antigens, as did a high proportion of sera from persons suspected to be infected with this parasite. A smaller proportion of these sera also contained metacercarial stage-specific antigens. Sera from donors with other helminth infections, with confirmed pulmonary tuberculosis, or from healthy Chinese donors were nonreactive in the assay. Treatment of experimentally infected animals with praziquantel triggered a marked but transient increase in serum levels of adult P. westermani antigens, which then gradually disappeared within the next two months. The results of our studies indicate that the antigen-detection assay we have developed is a highly specific and sensitive diagnostic test for active infections with P. westermani.

Acute Disease↗
PubMed1992

Mechanism of adenylate kinase. Structural and functional roles of the conserved arginine-97 and arginine-132.

The structural and functional roles of two conserved active site residues, Arg-97 and Arg-132, in chicken muscle adenylate kinase (AK) were evaluated by site-directed mutagenesis in conjunction with one- and two-dimensional proton nuclear magnetic resonance (NMR), kinetics, and guanidine hydrochloride-induced denaturation. In addition, 31P NMR analysis was used to evaluate the contribution of Arg-97 to the phosphorus stereospecificity of AK. The results and conclusions are summarized as follows: (i) Kinetic analysis of R97M reveals 6- and 28-fold increases in the dissociation constant Ki and Michaelis constant K of AMP, respectively, and a moderate 30-fold decrease in kcat. The Ki and K values of MgATP are relatively unperturbed. The localized effect of AMP stabilization was independently confirmed by proton NMR titration, which showed a ca. 20-fold increase in the dissociation constant of AMP but not of MgATP. (ii) R132M affords a dramatic decrease in kcat by a factor of 8.0 x 10(3), with unchanged dissociation and Michaelis constants for either substrate. The lack of perturbation in the affinities toward substrates was confirmed by proton NMR titration. (iii) Although small chemical shift changes were observed for the free mutants and their complexes with substrates, further analyses by nuclear Overhauser enhanced spectroscopy with the bisubstrate analogue inhibitor, P1,P5-bis(5'-adenosyl)pentaphosphate (AP5A), indicated little perturbation in the global conformation. (iv) Contributions to conformational stability by Arg-97 and Arg-132 are negligible on the basis of the free energy of unfolding, delta GdH2O. (v) R97M was predicted and demonstrated to exhibit enhanced stereospecificity at the AMP site by at least 10-fold relative to WT in the conversion of adenosine 5'-monothiophosphate to adenosine 5'-(1-thiodiphosphate). This result for R97M was predicted on the basis of the orientation of Arg-97 relative to Arg-44 and AMP in the active site as observed in available crystal structures and the stereospecificity results of R44M [Jiang, R.-T., Dahnke, T., & Tsai, M.-D. (1991) J. Am. Chem. Soc. 113, 5485-5486]. (vi) The above structural and functional analyses led us to conclude that Arg-97 interacts with the phosphoryl group of AMP, beginning at the binary complex (1-2 kcal/mol), continuing through the transition state (3.5 kcal/mol), and that Arg-132 stabilizes the transition state by greater than 5 kcal/mol. (vii) The functional importance of Arg-97 appears to be similar to that of Arg-44 [Yan, H., Dahnke, T., Zhou, B., Nakazawa, A., & Tsai, M.-D. (1990) Biochemistry 29, 10956-10964].(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Diphosphate↗
PubMed1992

The role of endotoxin in the pathogenesis of experimental multiple system organ failure: a preliminary report.

In this study, an animal model of multiple system organ failure (MSOF) in rabbits, engendered by feeding E. coli prior to severe hemorrhagic shock, was used for the purpose of investigating 1) the relationship between lipopolysaccharide (LPS) and MSOF, and 2) the effectiveness of Re-LPS antiserum in preventing MSOF. The results showed that endotoxemia occurred very early, and its degree correlated well with that of organ dysfunction. Re-LPS antiserum administration abated the toxic effects and lowered the incidence of MSOF. These results suggest that sequential analysis of circulating LPS levels may be useful for the early diagnosis of MSOF, and that gut-derived endotoxin might play an important role in the pathogenesis of experimental MSOF.

Animals↗
PubMed1991

Effect of stress on glucoregulation in physiology and diabetes.

To examine the glucoregulatory responses to stress and their impact on diabetes, we used the following models of stress: A) Hypoglycemia; B) Epinephrine infusion; C) intracerebroventricular (ICV) injection of carbachol, an analog of acetylcholine. A) Hypoglycemia induces release of all counterregulatory hormones. During acute hypoglycemia, glucose production increases initially mainly due to glucagon release but eventually also due to a very large increment in catecholamines. In newborn dogs, neither epinephrine nor glucagon respond to a decrease in plasma glucose. This lack of a safeguard against hypoglycemia may indicate that the brain in pups is less dependent on a normal supply of glucose as a fuel, than in adult dogs. Counterregulation is enhanced when the effects of endogenous opiates are blocked by naloxone, indicating that endogenous opiates play a regulatory role during hypoglycemia. However, beta-endorphins which can be released with epinephrine during various stress situations, potentiate the peripheral effect of epinephrine. Glucoregulatory responses, even to slight changes in plasma glucose, are greatly enhanced during glucocorticoid treatment. This apparently reflects the greater sensitivity of the liver to glucagon. In diabetic dogs, similar to human diabetics, the glucagon response is abolished and the response of the catecholamines is partially decreased. On the basis of histological studies, we proposed that the deficient glucagon response in diabetes could be related to an increase in the somatostatin-glucagon ratio in the diabetic pancreas. This ratio is further augmented when normoglycemia is maintained with insulin. In response to a decrease in plasma glucose, there is a biphasic increment in glucose production in normal dogs, which is missing in diabetes. When normoglycemia is restored in diabetic dogs with phlorizin treatment, the second but not the first increment in glucose production is restored. We postulated, therefore, that the toxic effect of hyperglycemia, in addition to the lack of glucagon response, is the main reason why in diabetes, glucose production cannot respond promptly to a decrease in plasma glucose. The low rate of metabolic clearance of glucose seen in diabetes in the post-absorptive state, also reflects, at least in part, the toxic effect of glucose, because with acute normalization of glucose with phlorizin, metabolic glucose clearance substantially improves. Hyperglycemia is the main reason for the decreased number of glucose transporters in diabetic muscle. B) Epinephrine infusion in normal dogs mimics some effects of stress, in that it increases glucose production, inhibits metabolic glucose clearance and increases lipolysis. These metabolic effects of epinephrine are independent of glucagon release.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

The embryonal development of the human eye photoreceptors.

The development of the photoreceptors of human embryos and fetuses dating from 7 weeks to term were studied. The outer segments of rods and cones began to form at the seventh month. The arrangement of the newly formed discs were not regular, but at term they were arranged parallel to each other and perpendicular to the long axes of the outer segments. At the 9th month, no phagosome containing discs was seen in the pigment epithelial cells, but they were discerned in those of the term fetuses.

Cilia↗
PubMed1990

[Effect of a mixture of Acanthopanax senticosus and Elsholtzia splendens on serum-lipids in patients with hyperlipemia].

The serum-lipids were determined in 31 hyperlipemia patients before and after treated with the mixture of Acanthopanax senticosus and Elscholtzia splendens. While the mean value of serum beta-lipoprotein decreased from 902 +/- 228 mg/dl to 608 +/- 189 mg/dl (P less than 0.001), the mean value of HDL-C increased from 52.6 +/- 12.5 mg/dl to 61.2 +/- 15.4 mg/dl (P less than 0.001). Thus the ratios of HDL-C to total cholesterol (HDL-C/TC) and to LDL-C (HDL-C/LDL-C) increased significantly, the arteriosclerosis index (AI) decreased significantly. The results indicate that the mixture of Acanthopanax senticosus and Elsholtzia splendens could improve the lipid-metabolism in hyperlipemia patients so that it might play a good role in preventing or alleviating arteriosclerosis.

Cholesterol↗
PubMed1987

Microencapsulated hepatocytes: an in vitro and in vivo study.

Using a modified alginate-polylysine membrane, we have successfully encapsulated rat hepatocytes with little loss of viability. Urea and albumin release from encapsulated liver cells was comparable to that from non-encapsulated cells during the first 4 days in culture. Histological studies also showed that more than 50% of the encapsulated hepatocytes remained viable 35 days after implantation in the peritoneal cavity of both normal rats and rats with galactosamine induced fulminant hepatic failure. Transplantation of microencapsulated hepatocytes provides a potential clinical treatment for liver failure.

Albumins↗
PubMed1986

Preparation and evaluation of inorganic anion-exchange sorbents not based on silica.

The use of alternate macroporous (greater than 200 A) inorganic support materials in the preparation of pellicular anion-exchange packings was explored. Alumina, magnesia, titania, and a zirconia-coated silica were chosen for comparison with silica. The stationary phase attached to the support surfaces was an adsorbed polyethyleneimine, crosslinked with 1,4-butanediol diglycidyl ether. Packing materials were characterized by static elemental analyses, chromatographic retention, static loading capacity and pH stability. Titania, alumina, and zirconyl-clad silica packings were found to be substantially more stable under alkaline conditions than silica-based materials. The data show that the stationary phase was successfully bonded in all cases and functioned in anion-exchange chromatography. When the surface area and pore diameter of these alternate materials is equivalent to silica, there is little difference in chromatographic properties.

Animals↗
PubMedDate not supplied

Inheritance of resistance to zucchini yellow mosaic virus and watermelon mosaic virus in watermelon.

High resistance to zucchini yellow mosaic virus-China strain (ZYMV-CH) and moderate resistance to watermelon mosaic virus (WMV) were found in a selection of PI 595203 (Citrullus lanatus var. lanatus), an Egusi type originally collected in Nigeria. Mixed inoculations showed primarily that these two viruses have no cross-protection. This fact may explain the high frequency of mixed infection often observed in commercial fields. When plants were inoculated with a mixture of the two viruses, the frequency of plants resistant to ZYMV was lower than expected, indicating that WMV infection may reduce the ability of a plant to resist ZYMV. We studied inheritance of resistance to ZYMV-CH and WMV, using crosses between a single-plant selection of PI 595203 and the ZYMV-susceptible watermelon inbreds 9811 and 98R. According to virus ratings of the susceptible parents, the resistant parent, and the F1, F2, and BC1 generations, resistance to ZYMV-CH was conferred by a single recessive gene, for which the symbol zym-CH is suggested. The high tolerance to WMV was controlled by at least two recessive genes.

Citrullus↗
PubMedDate not supplied

Plethysmographic findings in normal subjects using a capacitance mode.

A new strain-gauge plethysmographic system, Phlebotest, was evaluated in 19 normal subjects, yielding 38 lower limbs for study. A capacitance mode was used which allowed both the left and right calves to reach their maximal volume expansion before releasing the cuff pressure (60 mmHg in this study). Parameters such as the maximum volume change (V sec), the outflow rate during the first second after deflation (F 1.0), the expelled volume in four seconds (EV 4.0) and the surface area over the curve during the first four seconds after deflation (IND) were automatically calculated and their side differences between the left and right legs were determined respectively. There was a good linear correlation between EV 4.0 and V sec (r = 0.9274, p less than 0.0005) and the EV 4.0/V sec ratio was calculated. In contrast to the previous reports, between three consecutive determinations there were no significant differences in the measurements of these parameters, and V sec consistently kept an identical mean value. These results suggest that using this new system only one determination of calf expansion is required. The reason might be that, in addition to some technical improvements, the computer-controlled capacitance function can secure the optimal venous filling in every determination.

Adult↗
PubMedDate not supplied

Detection of deep vein thrombosis with a computerized strain gauge plethysmograph.

Forty patients suspected clinically the first episode of deep vein thrombosis (DVT) were studied using a new computerized strain gauge plethysmographic (SGP) system, the Phlebotest. A capacitance mode was used to secure the obtaining of maximum venous filling before deflation in every determination. Following parameters were calculated automatically and instantly: the maximum volume change (V sec), the outflow rate during the first second after deflation (F 1.0), the expelled volume in four seconds (EV 4.0) and the surface area over the curve during the first four seconds after deflation (IND). The eighty lower limbs of the patients were divided into three groups according to the Duplex scanning results: proximal (n = 19), distal (n = 13) and no DVT (n = 48) groups. The diagnostic accuracy of the Phlebotest parameters was determined and compared with that of another widely used SGP system, the Perivein. In this case the maximum volume change and the maximum venous outflow (MVO) were calculated manually. The results of the two systems were compatible. For the detection of proximal DVT, the parameters of venous outflow were better than maximum volume change and the best single parameter was maximum venous outflow: F 1.0 for Phlebotest and MVO for Perivein. The two parameters had a similar sensitivity of 79% when 50 and 27 ml/100 ml/min were used as the lower limits of normal respectively. The best criterion for the diagnosis of proximal DVT was F 1.0 < 50 ml/100 ml/min plus the EV 4.0/V sec ratio < 60%, which had a sensitivity of 90%, specificity of 96% and overall accuracy of 94%.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗