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Biomedical subjects

G Yang

Publications and source records attributed to G Yang.

At least 433 records · Page 24Linked to original sources
PubMed1993

Interaction of myeloperoxidase with peroxynitrite. A comparison with lactoperoxidase, horseradish peroxidase and catalase.

Polymorphonuclear neutrophils generate both nitric oxide and superoxide and these molecules can combine to form peroxynitrite. Neutrophils also contain myeloperoxidase which reacts with peroxynitrous acid (HOONO). On mixing myeloperoxidase with HOONO compound II was formed. Compound I could not be detected as an intermediate. The apparent second-order rate constant of formation of compound II was strongly pH-dependent (2.5 x 10(5) M-1 x s-1 at pH 8.9 and 6.2 x 10(6) M-1 x s-1 at pH 7.2). The pKa of this effect is 6.9 and it was concluded that the enzyme reacts with the protonated form of the peroxide, that is peroxynitrous acid, with a pH-independent second-order rate constant of 2.0 x 10(7) M-1 x s-1 at 12 degrees C. The interaction of HOONO with lactoperoxidase was studied for comparison. As was observed for myeloperoxidase, compound I could not be detected as an intermediate. The apparent second-order rate constant of compound II formation is pH-dependent and is 3.3 x 10(5) M-1 x s-1 at pH 7.4 and 8.4 x 10(4) M-1 x s-1 at pH 9.0. In contrast, horseradish peroxidase reacts with HOONO to form compound I, which is subsequently followed by the formation of compound II. The second-order rate constant for the formation of compound I is 3.2 x 10(6) M-1 x s-1 and is pH-dependent, the pKa for this effect is 6.8. Catalase (up to 3 microM) does not affect the rate of decomposition of peroxynitrite and no compound I formation is observed. Since nitrite may be present in the peroxynitrite preparation and to discriminate between the reaction of the enzyme with nitrite or peroxynitrite, the effect of nitrite on myeloperoxidase was studied. The dissociation constant for the myeloperoxidase-nitrite complex is pH-dependent and has values of 580 microM at pH 6.0 and 55 mM at pH 8.5.

Catalase↗
PubMed1993

Expression of terminin in the rat brain during neuronal differentiation.

Terminin is a cytoplasmic protein originally found in senescent cultured human fibroblasts. In the present study, we investigated terminin expression during development in three brain regions: the cerebral cortex, the neural retina and the cerebellum of the rat brain. By immunocytochemistry we found that terminin immunoreactivity in the brain is mainly localized in neurons. Immunoreactivity to terminin antibody was first noticed in the brain as early as embryonic day 15, and the staining intensity in the cerebral cortex reached maximum level at the first postnatal week, when the cerebral neurons become postmitotic and their synaptic connections with target cells are established. A similar pattern of terminin development was seen in the neural retinas of the same animals as well. Biochemical characterization shows that the anti-terminin antibody recognizes a 90 kDa (Tp90) and a 60 kDa (Tp60) polypeptide in immunoblots of the detergent insoluble fraction of rat brains, while Tp90 was found in the detergent-soluble fraction. Both the Tp90 and Tp60 polypeptides appeared at embryonic day 15 and reached highest levels at postnatal day 1. With the advance of further neural differentiation, however, Tp90 in the detergent-insoluble fraction diminished, and remained only in the detergent-soluble fraction. In the detergent insoluble fraction Tp60 became the predominant species during the first postnatal week. In the cerebellum, where neuronal differentiation is known to be relatively late, quantitative densitometric measurement of terminin abundance on the immunoblots showed that Tp60 in the detergent-insoluble fraction was the predominant form in the second week. Thus, the appearance of a predominant Tp60 coincided with terminal neuronal differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Evidence of DNA bending in transcription complexes imaged by scanning force microscopy.

Complexes of Escherichia coli RNA polymerase with DNA containing the lambda PL promoter have been deposited on mica and imaged in air with a scanning force microscope. The topographic images reveal the gross spatial relations of the polymerase relative to the DNA template. The DNA appears bent in open promoter complexes containing RNA polymerase bound to the promoter and appears more severely bent in elongation complexes in which RNA polymerase has synthesized a 15-nucleotide transcript. This difference could be related to the conformational changes that accompany the maturation of open promoter complexes into elongation complexes and suggests that formation of the elongation complex involves a considerable modification of the spatial relations between the polymerase and the DNA template.

DNA↗
PubMed1993

Detection of hepatitis B virus in plasma using flow cytometric analyses of polymerase chain reaction-amplified DNA incorporating digoxigenin-11-dUTP.

Blood donations are routinely screened by multiple serologic assays for antigens/antibodies associated with infection by blood-borne viruses, including hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency viruses (HIV-1 and HIV-2), and human T-cell lymphotropic virus (HTLV-I and HTLV-II). A direct detection of these viruses would be more effective for the prevention of transfusion-transmitted infections than the indirect measurement of the variable host immune response to these agents. Because the polymerase chain reaction (PCR) for viral gene amplification offers the most sensitive and direct means of detecting viruses in blood, we have developed a nonisotopic PCR procedure for the detection of HBV, chosen as a prototype. The problems, common to previously described PCR methods, of nucleic acid extraction and inhibition of the PCR by plasma proteins were overcome by isolation of HBV from plasma by means of 450-microns polystyrene beads covalently coated with monoclonal antibody to the Pre-S1 region of the viral envelope protein. Detergent lysis and proteinase K digestion of the immunocaptured virions isolated from plasma released the HBV DNA. A modified PCR-amplification protocol, incorporating digoxigenin-labeled dUTP in the amplified gene products followed by hybridization with a specific biotinylated oligonucleotide probe bound to streptavidin-coated 2.8-microns magnetic beads, allowed flow cytometric analyses of HBV-specific PCR products by means of antibodies to digoxigenin labeled with fluorescein isothiocyanate. The endpoint serial dilutions of pedigreed human plasma samples containing chimpanzee infectious dose (CID50) of 10(7) for adw and CID50 of 10(7.5) for the ayw subtypes were compared in repeated testing of PCR products by our immunoreactive bead (PCR-IRB) assay. HBV DNA was consistently detected in a 5 x 10(-10) dilution of each sample. In testing 20 coded specimens of blood donors, with or without serologic markers of HBV infection, the PCR-IRB was specific and more sensitive than the PCR analyses by slot blot hybridization with radioactive probe. The PCR-IRB assay can be adapted for simultaneous detection of multiple blood-borne viruses by an automated flow cytometric analysis system.

Bacterial Proteins↗
PubMed1993

Malignant epithelioid hemangioendothelioma arising in an intramuscular lipoma.

BACKGROUND: A malignant epithelioid hemangioendothelioma (EH) developed within a peripheral intramuscular lipoma. It was seen as a painful calf mass. At the time of biopsy and en bloc resection, lung metastases were observed. METHODS: Radiologic, histologic, immunohistochemical, and ultrastructural features of the neoplasm are described, and the literature pertaining to EH is reviewed. RESULTS: The features of this tumor permitted its classification as a malignant EH. CONCLUSIONS: This case illustrates the potential for aggressive behavior in an EH, often considered to be a low-grade malignant neoplasm. Because such tumors can metastasize, they should be removed with wide margins whenever possible. This malignant neoplasm was located within a benign intramuscular lipoma, demonstrating the diagnostic problem that may exist in such a complex lesion.

Epithelium↗
PubMed1993

Cloning and analysis of the mating type genes from Cochliobolus heterostrophus.

Cochliobolus heterostrophus, a heterothallic Ascomycete, has a single mating type locus with two alternate forms called MAT-1 and MAT-2. MAT-1 was cloned by complementing a MAT-2 strain using a cosmid library from a MAT-1 strain and screening for a homothallic transformant. The cosmid recovered from this transformant was able to re-transform a MAT-2 strain to homothallism and MAT identity was proven by restriction fragment length polymorphism and conventional genetic mapping. All homothallic transformants could mate with either MAT-1 or MAT-2 strains, although the number of ascospores produced by self matings or crosses to MAT-2 strains was low. Progeny of selfed homothallic transformants were themselves homothallic. MAT-2 was cloned by probing a cosmid library from a MAT-2 strain with a fragment of insert DNA from a MAT-1 cosmid. A 1.5 kb subclone of either MAT-containing cosmid was sufficient to confer mating function in transformants. Examination of the DNA sequence of these subclones revealed that MAT-1 and MAT-2 contain 1297 bp and 1171 bp, respectively, of completely dissimilar DNA flanked by DNA common to both mating types. Putative introns were found (one in each MAT gene) which, when spliced out, would yield open reading frames (ORFs) that occupied approximately 90% of the dissimilar DNA sequences. Translation of the MAT-1 ORF revealed similarity to the Neurospora crassa MATA, Podospora anserina mat-, and Saccharomyces cerevisiae MAT alpha 1 proteins; translation of the MAT-2 ORF revealed similarity to the N. crassa MATa, P. anserina mat+, and Schizosaccharomyces pombe mat-Mc proteins. These gene products are all proven or proposed DNA binding proteins. Those with similarity to MAT-2 are members of the high mobility group.

Amino Acid Sequence↗
PubMed1993

Factors contributing to reinfection with schistosomiasis japonica after treatment in the lake region of China.

The prevalence of schistosomiasis due to S. japonicum is focally high in the lake regions of China, and reinfection after treatment with praziquantel is frequent. In this study, the total reinfection rate among 740 treated persons was 12.9%. Factors associated with reinfection were age and sex, water contact and the distance from homes to snail habitats. The reinfection rate was higher among men (15.0%) than among women (8.3%). The frequency of water contact is the main factor in reinfection. Among persons with more than 120 and 10-120 water-contact days, the reinfection rates were 24.0% and 16.4%, respectively. The reinfection rates among people living 0 m, 500 m and 1000 m from snail-ridden areas were 14.1%, 8.3% and 4.3%, respectively. Fishing was the most frequent reason for water-contact, followed by herding animals and playing in water; reinfection rates among those engaging in these activities were 36.4%, 16.3% and 22.9%, respectively. Reinfection is clearly a problem, and since much of it is connected with essential economic activities, the cycle of infection and reinfection is not likely to be broken until effective methods for eliminating reservoirs of infection are developed.

Adolescent↗
PubMed1993

The epidemiology of selenium deficiency in the etiological study of endemic diseases in China.

The distribution of chemical elements in rocks and soils varies widely. Selenium is one of the elements that has remarkable regional variations in distribution and bioavailability. This paper reviews the epidemiology of selenium deficiency in China in connection with the etiology of human selenium-responsive diseases, the well-defined Keshan disease (KD) and the less-well-defined Kashin-Beck disease (KBD).

Bone Diseases↗
PubMed1993

Gastric intramural PCO2 during peritonitis and shock.

OBJECTIVE: To define whether increases in gastric intramural tissue CO2 and H+ increase during experimentally induced peritonitis with circulatory shock as they do under conditions of hemorrhagic shock and cardiac arrest. DESIGN AND SETTING: Peritonitis was induced in Sprague-Dawley rats by cecal ligation and fecal spillage. MEASUREMENTS AND RESULTS: Over an interval of 260 +/- 20 min in 5 animals, there was a progressive reduction in mean aortic pressure from 153 +/- 12 to 40 +/- 20 mm Hg and a decline in cardiac index from 429 +/- 135 to 178 +/- 7 ml/min. This was associated with increases in gastric intramural [H+] from 34 +/- 5 to 217 +/- 93 mmol/L (p = 0.001). Arterial blood lactate content concurrently increased from 0.9 +/- 0.1 to 4.6 +/- 0.7 mmol/L (p = 0.001). Only a late increase in gastric intramural PCO2 from 45 +/- 5 to 128 +/- 38 mm Hg (p = 0.01) was observed. CONCLUSION: In contrast to the gastric acid base changes that accompany hemorrhagic shock, in which there is an early and prominent increase in both PCO2 and [H+] in close relationship to decreases in cardiac output and arterial pressure, there was a prominent increase in gastric [H+] but only a delayed rise in gastric intramural PCO2. Arterial blood lactate and central venous oxygen saturation were earlier indicators of perfusion failure. Since the bicarbonate concentration in the stomach wall was substantially greater than that of simultaneously measured arterial blood, this has bearing on the current clinical method of gastric tonometry which assumes that arterial blood bicarbonate is equivalent to gastric wall bicarbonate.

Animals↗
PubMed1993

[Study on monoclonal antibodies against porcine serum E receptor].

Three hybridoma cell lines producing monoclonal antibodies (McAbs) against porcine serum E receptor (PSER) were established by fusing mouse myeloma SP2/o cells with spleen cells of BALB/c mouse immunized with PSER. The ascites McAbs were purified by ammonium sulfate precipitation and DEAE-cellulose chromatography. The McAbs were found to belong to the IgG1 and IgG2b subclasses, respectively. These McAbs inhibited reverse E-rosette formation and enhanced or depressed lymphocyte proliferation induced by PHA or ConA. The specificity of these McAbs was proved by immuno-dot blot and Western blot assay. The potential application of these McAbs in the study of structure and biological function of the E-receptor is discussed.

Animals↗
PubMed1993

[Relationship between colorectal cancer and ten inorganic elements].

A population-based case-control study including 726 patients with colon cancer, 575 with rectum cancer, and 1400 population controls matched on age (+/- 5 yrs.) and sex was carried out to evaluate the association of ten inorganic elements, including potassium, sodium, calcium, magnesium, iron, manganese, zinc, copper, phosphorus and selenium, and other dietary factors with colorectal cancer. Single variable analysis adjusted for age and sex showed most of the ten elements, except sodium and selenium, may reduce the risk of the development of colorectal cancer. Correlation analysis indicated these eight elements correlated closely to the "vegetable factors", e.g., dietary fibre, and so on, since the major sources (about 80%) of these elements were from vegetables. Multi-variable logistic regression analysis showed nine elements (except sodium) may confound the effects of some dietary factors (such as dietary fibre and vitamin C) on the occurrence of colorectal cancer and only contribute to it. The results showed a close association between saturated fatty acid, mono-unsaturated fatty acid, dietary fibre, vitamins C and E, and colorectal cancer.

Adult↗
PubMed1993

Growth factor gene expression in bronchoalveolar lavage cells from patients with lung fibrosis.

We have studied the gene expression of ten growth factors in bronchoalveolar lavage (BAL) cells from patients with lung fibrosis by using a reverse-transcription-DNA polymerase chain reaction (RT-PCR) technique. IL-1 beta mRNA was detected in almost all of the samples, and TGF beta and IGF-I mRNA were detected in some. The BAL supernatant from the patients was found to have mitogenic activity for lung fibroblasts. Moreover, human recombinant IL-1 beta, TGF beta and IGF-I were found to promote the proliferation of lung fibroblasts. These data suggest that IL-1 beta, TGF beta and IGF-I gene expression in BAL cells might be involved in the development of lung fibrosis.

Adult↗
PubMed1993

Humidity effects on atomic force microscopy of gold-labeled DNA on mica.

Recent work in atomic force microscopy (AFM) of deoxyribonucleic acid (DNA) has relied on immobilizing DNA molecules by drying a small volume of buffered DNA solution onto cleaved mica. When imaging in air, relative humidity has been known to affect both the resolution and measured height of the DNA strands. We present data of measured height versus humidity for DNA and attached gold labels, and we propose a model for this data based on swelling of coadsorbed buffer salts upon exposure to moisture. In this model, small particles (e.g., DNA) stay near the top of the swelling salt layer, whereas larger particles (e.g., gold spheres) tend to be anchored down to the substrate until a moderate humidity is reached. At high humidity (around 65%), the salt layer becomes fluid-like and susceptible to tip-induced motion; the salts are either removed from the scan area or aggregate into island structures, depending on initial salt concentration on the surface.

Aluminum Silicates↗
PubMed1993

[Changes of angiotensin II contents in rat plasma, brain, cardiovascular system and adrenal during stress].

The changes of content of angiotensin II (A II) in plasma, anterior hypothalamus, medulla oblongata, myocardium, vasculature and adrenals during acute and chronic stress were studied in rats. Compulsive cold-water swimming and trauma by limb-breaking were used to set acute stress models while cold environment of 4-8 degrees C was used to set chronic stress model. The results showed that: (1) The A II levels in plasma were significantly increased in all three stress- model groups, reaching to 900%, 390% and 134% of the control in the swimming group, the limb-broken group and the cold environment group, respectively. It's clear that the level of angiotension II in the acute stress groups were much higher than those in the chronic stress group. (2) The A II levels of the rat brain, myocardium and blood vessel were also increased in the stress animals except the limb-broken group. Furthermore, the contents of angiotensin II of the chronic stress animals were significantly higher than those of the acute stress animals in the brain, myocardium and blood vessels, but not in the adrenals. (3) The adrenal A II content was significantly higher than that of the control in all stressed animals. (4) The plasma corticosterone was also significantly increased over the control level in both the acute and chronic stress groups. These results suggest that circulating angiotensin II and tissue angiotensin II may play a role during the development of acute and chronic stress, respectively.

Adrenal Glands↗
PubMed1993

[Comparison between large bowel cancer in young people and that in middle-aged and old-aged people].

In order to understand the difference in risk factors of large bowel cancer in different age groups, a population-based case-control study including two age groups, one group with the age of < or = 40 (180 cases and 184 controls). And the other group with the age of > 40 (1148 cases and 1161 controls), was conducted in Shanghai. The study indicated that: 1. The patients of age > 40 with large bowel cancer had closer relationship with the environmental factors (esp. dietary and nutritional factors) than the patients of age < or = 40. 2. The familial genetic risk factor which affected development of the cancer in younger group was two-fold higher than that in elder group. The results suggested that both genetic and environmental factors influenced the occurrence of the cancer, and the role of the genetic factor in < or = 40-yr group and that of the environmental factors in > 40-yr group appeared to be important.

Adult↗
PubMed1992

Direct visualization of the dendritic and receptive fields of directionally selective retinal ganglion cells.

Optical methods were used to locate the cell bodies of directionally selective ganglion cells in isolated rabbit retinas. These neurons detect the direction in which images move across the retinal surface and transmit that information to the brain. The receptive field of each identified cell was determined, after which the cell was injected with Lucifer yellow. An image of the receptive field border was then projected onto the fluorescent image of the dendrites, allowing precise comparison between them. The size of the receptive field matched closely the size of the dendritic arbor of that cell. This result restricts the types of convergence that can be postulated in modeling the mechanism of retinal directional selectivity.

Amidines↗