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Biomedical subjects

G Yang

Publications and source records attributed to G Yang.

At least 415 records · Page 23Linked to original sources
PubMed1994

Black-ear gene and blood polymorphism in four southern Chinese cattle groups.

The gene for black-ear coat colour pattern, commonly found among cattle of tropical origin, was observed in 809 animals of four breeds of local cattle in southern China. Gene frequencies for Tf, Hb and Alb demonstrated that these groups of cattle were quite divergent from Bos taurus. These breeds of cattle are thought to be descended from ancient Chinese cattle. At the same time certain influences observed in coat colour may be derived from Bali cattle.

Animals↗
PubMed1994

Flow cytometric immunodetection of human immunodeficiency virus type 1 proviral DNA by heminested PCR and digoxigenin-labeled probes.

PCR is the most sensitive and direct method for detecting blood-borne viruses, as well as an efficient means for producing vector-free probes. However, the application of PCR, especially in the laboratory diagnosis of human immunodeficiency virus (HIV) infection, is impeded by the current use of radiolabeled oligonucleotide probes. Therefore, we have developed a nonisotopic PCR immunoreactive bead (PCR-IRB) assay to detect HIV type 1 proviral DNA from peripheral blood mononuclear cells (PBMC). We used a biotinylated primer in a set of three oligonucleotides selected from the HIV long terminal repeat region for heminested PCR amplification. An internal probe was synthesized by PCR with incorporation of digoxigenin-labeled dUTP. After solution hybridization of the probe with PCR-amplified products (amplicons), the hybridized DNA was captured with streptavidin-coated magnetic beads. For the detection of hybrids, flow cytometric analyses were carried out by two procedures: (i) direct detection with fluorescein isothiocyanate (FITC)-labeled antidigoxigenin immunoglobulin G (IgG) antibody and (ii) indirect detection with antidigoxigenin sheep IgG antibody followed by FITC-labeled anti-sheep IgG antibody. Both procedures in the PCR-IRB assay detected two to three copies of HIV proviral DNA sequences, a sensitivity that is comparable with that of the conventional radioactive detection of amplicons following probe hybridization and electrophoresis. To compare the PCR-IRB assay with the conventional method, we tested 53 pedigreed PBMC specimens from blood donors and newborns; the results obtained were identical. This nonisotopic PCR-IRB assay can also be automated for potential application in laboratory diagnosis of HIV infection, blood bank screening, and therapeutic monitoring of viremia and perinatal transmission.

Base Sequence↗
PubMed1994

Human copper-zinc superoxide dismutase transgenic mice are highly resistant to reperfusion injury after focal cerebral ischemia.

BACKGROUND AND PURPOSE: We have demonstrated in a previous study that superoxide radicals play a role in the pathogenesis of cerebral infarction, using a transgenic mouse model of distal middle cerebral artery occlusion, permanent ipsilateral cerebral carotid artery occlusion, and 1-hour contralateral cerebral carotid artery occlusion that produced infarction only in the cortex. However, the role of superoxide radicals in reperfusion injury in transgenic mice overexpressing superoxide dismutase (SOD) is unknown. Using a mouse model of intraluminal blockade of middle cerebral artery that produced both cortical and striatal infarction, we now further examined the role of superoxide radicals in ischemic cerebral infarction after reperfusion in transgenic mice overexpressing human CuZn-SOD activity. METHODS: Transgenic mice of strain Tg HS/SF-218, carrying human SOD-1 genes, and nontransgenic littermates were anesthetized with chloral hydrate (350 mg/kg IP) and xylazine (4 mg/kg IP). Physiological parameters were maintained at a normal range using a 30% O2/70% N2O gas mixture inserted via an inhalation mask. Body temperature was maintained at 37 +/- 0.5 degrees C by using a heating pad throughout the studies. The middle cerebral artery occlusion was achieved with a 5-0 rounded nylon suture placed within the internal cerebral artery for 3 hours followed by the removal of the suture to allow reperfusion for another 3 hours. Cerebral infarct size in brain slices and infarct volume, neurological deficit, cortical blood flow, and glutathione levels were measured in both transgenic and nontransgenic mice. RESULTS: Compared with the nontransgenic mice, the infarcted areas were significantly decreased in coronal slices from transgenic mice. The infarct volume (in cubic millimeters) was reduced by 26% in transgenic mice after ischemia and reperfusion. This decrease in the infarct volume in transgenic mice closely paralleled the reduced neurological deficits. Introduction of the suture to block blood supply to the middle cerebral artery territory produced a rapid decrease in the relative surface blood flow in the ipsilateral core and the peri-ischemic (penumbra) areas. There were no significant differences in the local cerebral blood flow in the ischemic core or the penumbra areas between the transgenic and nontransgenic groups. However, the level of reduced glutathione in the penumbra area was significantly higher in transgenic mice than in nontransgenic mice, whereas there was no difference in the reduced glutathione levels in the ischemic core between these two groups. CONCLUSIONS: Our study demonstrated that superoxide radicals play a major role in the pathogenesis of cerebral infarction in reperfusion injury after a focal stroke. The reduction in infarct volume and neurological deficits is not dependent on the changes in cerebral blood flow but rather correlate with reduced oxidative stress in the ischemic brain tissue, which was indicated by the relatively high levels of endogenous reduced glutathione in transgenic mice.

Animals↗
PubMed1994

Reduction of vasogenic edema and infarction by MK-801 in rats after temporary focal cerebral ischemia.

Blood-brain barrier permeability alteration, vasogenic brain edema, and infarction, which are more extensive after 3 hours of temporary middle cerebral artery occlusion (MCAO) and 3 hours of reperfusion than after 6 hours of permanent MCAO, develop in rats after prolonged focal cerebral ischemia. Protective effects of excitatory amino acid receptor antagonists have been previously demonstrated after temporary global ischemia and permanent focal ischemia in rats. The purpose of this study was to evaluate the effectiveness of MK-801, a noncompetitive N-methyl-D-aspartate receptor antagonist, in temporary middle cerebral artery occlusion in rats maintained at physiological levels of brain temperature. Rats were anesthetized with chloral hydrate (350 mg/kg, intraperitoneally). The MCAO of rats was occluded by cannulation with a nylon suture for 3 hours, followed by 3 hours of reperfusion accomplished by withdrawing the suture. MK-801 (1 mg/kg, intravenously) or saline (S) was injected immediately before the onset of MCAO. Water content (MK-801, n = 6; S, n = 6), Evans blue dye extravasation (MK-801, n = 6; S, n = 6), infarct volume (MK-801, n = 10; S, n = 10), histology (MK-801, n = 6; S, n = 6), and neurological deficit (MK-801, n = 15; S, n = 18) were measured at the end of 3 hours of reperfusion. Brain temperature was monitored during the experiment. The infarction area (measured by 2, 3, 5-triphenyltetrazolium chloride staining) was reduced (P < 0.001) in the MK-801-treated rats, as was the infarct volume and the severity of neuronal damage (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Further observations on the human maximum safe dietary selenium intake in a seleniferous area of China.

This report is a summarization of preliminary results from a study of dietary Se intake in a seleniferous area in order to determine safe levels. All patients have symptoms of toxicity: broken hair strands or various levels of nail damage. Finger-nail signs were the first symptoms used for diagnosis of selenosis in this work. Based upon the lowest blood-Se level of five subjects with persistent overt finger-nail signs of selenosis, it was found in 1986 that the individual marginal toxic blood Se level (LOAEL) and the corresponding Se intake were 1054 micrograms/L and 910 micrograms/d, respectively. To re-examine the clinical signs and blood Se levels of the five individuals and to see how the two are correlated, a study was conducted in July 1992 at the same location in the seleniferous area. The results showed that along with the absence of clinical signs, the average blood Se level had decreased from 1346 to 968 micrograms/L. The corresponding safe Se intake per day would be 819 +/- 126 micrograms (15 micrograms/kg B.W. or approximately 800 micrograms per day, which is suggested as the mean No Adverse Effect Level (NOAEL), and the lower limit of the 95% confidence interval, 600 micrograms per day would approximately the maximum individual safe Se intake. For safety, 400 micrograms is again proposed as the Maximum Safe Daily Dietary Se Intake. Problems inherent in this estimation have been discussed.

China↗
PubMed1994

[Detection of B-cell clonality in paraffin-embedded bone marrow biopsy specimens by polymerase chain reaction].

In order to estimate the clonality of B-cell lymphoproliferative disorders, polymerase chain reaction (PCR) was used to detect the Ig heavy chain gene rearrangement in DNA extracted from formalin-fixed and paraffin-embedded bone marrow biopsies. 16 out of 19 cases (84%) of B-CLL (n = 9), multiple myeloma (n = 7) and B-non-Hodgkin's lymphoma (n = 3) showed sharp monoclonal bands, while polyclonal smears or no PCR-products were observed in non-neoplastic bone marrow or AML specimens. The results showed that the DNA from paraffin-embedded bone marrow biopsies could be used to detect monoclonal IgH rearrangement by PCR method. This forms the basis for the studies of minimal residual disease or B-ML bone marrow infiltrated diseases.

Biopsy↗
PubMed1994

[The value of nuclear morphometry in analysing heterogeneity of grade-II colorectal adenocarcinomas].

A nuclear morphometric analysis was performed on the histologic sections of 39 grade-II, 17 grade-I and 8 grade-II colorectal adenocarcinomas. The parameters selected were nuclear area, nuclear perimeter, nuclear volume and standard deviation of nuclear area. The results showed that grade-II colorectal adenocarcinomas were a group of heterogeneous tumours and they could be divided into various subgroups by nuclear morphometry so that their biological behaviour could be better reflected.

Adenocarcinoma↗
PubMed1994

[A case-control study on colorectal cancer and dietary fiber and calcium of various sources].

A population-based case-control study was conducted in 726 incident cases with colorectal cancer and 1400 controls matched on age and sex in Shanghai, to explore the possible difference in associations between colorectal cancer and dietary fiber and calcium of various sources. The results showed reverse correlation between intake of vegetable fiber and ascending and descending colon cancer and rectal cancer, and between intake of fruit fiber and ascending colon cancer only. Dietary intake of calcium from animal sources could reduce the relative risk of ascending and descending colon cancer. These associations still existed after adjustment of the effects of the factors such as age, sex, intakes of total calorie, vitamin C, saturated fatty acid, etc. with logistic regression model, which indicated all of those variables were independent of other ones. Intake of dietary fiber from grains and calcium from plant sources had no significant protection from colorectal cancer. This study also showed the protective effects of dietary fiber and calcium on colorectal cancer not only correlated to their intake, but also closely to their sorts and sources.

Adult↗
PubMed1994

[The case-control study of hepatitis risk factors in Shashi City].

Hepatitis was regarded as a main health problem in Shashi city, Hubei province, according to DSP data at present. The case-control study of hepatitis risk factors were carried out among 115 hepatitis cases and 60 controls that all were negative serologically in Shashi city. The result indicates that economic status, way of having breakfast outside, habits of washing hands before meals and after feces, levels of knowing about route of infection of hepatitis are independently associated with morbidity probability of hepatitis A, the comprehensive preventive measures are presented in the light of these conclusions.

Case-Control Studies↗
PubMed1994

[Dietary factors and cancer of the colon and rectum in a population based case-control study in Shanghai].

The study was a population-based case control one, to compare possible difference in the risk factors between colonic and rectal cancer. This study showed that: (1) High intake of pork and saturated fat was an important risk factor for colon cancer, and only slightly related to rectal cancer. (2) Low consumption of vegetables especially cruciferous vegetables, rhizome vegetables, sea weeds, legume vegetables, dietary fiber and some vitamins mainly derived from vegetables, e.g. vitamin c and carotene, was associated with an increased risk for both colonic and rectal cancer, and these factors were closer relationship with rectal cancer than colon cancer. (3) High intake of the fried and pickled foods significantly increase the risk of occurrence of these cancers. (4) The ratio of bowel cancer in first degree relatives of colon cancer cases was 2.9 times of control group (P < 0.01), but the ratio for rectal cancer was only 1.6 times (P > 0.05) compared with control group.

Adult↗
PubMed1994

[Studies on the ecological distribution of Bacillus thuringiensis in forest soils of China].

A total of 384 forest soils samples at 0-5cm depth collected from 8 forest site zones (13 Natural Reserves) in China were examined for the distribution of Bacillus and Bacillus thuringiensis. The 79 cultures (4.21%) in 1873 isolates of Bacillus collected referable to the Bacillus thuringiensis. Soil pH, moisture content and soil nutrient were determined. Rules of the ecological distribution of Bacillus thuringiensis of 8 forest site zones in China were analysed. Toxicities against 6 species of insect were tested. Strain some efficient serains were obtained. It was shown that resource of Bacillus thuringiensis is much fruitful in forest soils of China.

Bacillus thuringiensis↗
PubMed1994

[Comparison of risk factors between left and right-sided colon cancer].

To compare differences of risk factors between left-sided and right-sided colon cancer, a population-based comparative case-control study involving 267 patients with left colon cancer, 247 with right colon cancer and 1451 population controls matched by age (+/- 5 yrs) and sex was carried out in Shanghai. The major causes in the two cancer groups were dietary and nutritional factors. Vegetables, ascorbic acid, riboflavin, tocopherol and carotenes played a protective role in the two groups, but various other foods and some vitamins displayed different relations with the two types of cancer. A negative association was observed between dietary fiber and right colon cancer. Animal fat and some fatty acids (e.g. saturated fatty acids, mono-unsaturated fatty acids and oleic acid) significantly elevated the risk for left colon cancer, but only slightly for right colon cancer. Physical activity and familial history of colorectal cancer in first degree relatives showed a more remarkable relationship with left- than right-sided colon cancers.

Adult↗
PubMed1994

Receptive fields and dendritic structure of directionally selective retinal ganglion cells.

We studied the relationship between the receptive fields of directionally selective retinal ganglion cells and the dendritic arbors of the same cells. The cells were recorded from extracellularly under visual control and then injected with Lucifer yellow. The arbor of Lucifer-filled dendrites could then be directly compared with the properties of the receptive field. A large population of on-off directionally selective cells was injected and drawn. The directionally selective ganglion cells had bistratified receptive fields similar to those previously described by others in the central retina. In the periphery, the dendritic fields became larger, rounder, and sparser than centrally. The diameters of the dendrites were measured in living or lightly fixed retinas; they were found to be somewhat larger than previously estimated by electron microscopy. The local structure of the dendritic arbor bore no obvious relation to the directional properties of the cell. The receptive fields of most cells were centered symmetrically around their dendritic fields. For about 10% of the cells, however, the receptive field was displaced. The displacement was always toward the preferred direction, relative to the dendritic field. The meaning of these shifts is not clear. In both cases, the diameter of the receptive field exceeded the diameter of the dendritic field only slightly; in our sample, the diameters of the receptive fields averaged 6% larger than the dendritic fields. This means that the neurons afferent to the directionally selective ganglion cells must either have narrow dendritic fields or, if they are wide spreading, have dendrites that do not conduct effectively along their length. It also means that the observed spread of neurobiotin between DS ganglion cells (Vaney, 1991) must be due to a very few gap junctions, or to some mechanism other than a gap junction.

Animals↗
PubMed1993

Brain infarction is not reduced in SOD-1 transgenic mice after a permanent focal cerebral ischemia.

Using a mouse model with intraluminal blockade of the middle cerebral artery (MCA) which produced both cortical and striatal infarction, the effect that superoxide radicals have on cerebral infarction, local cerebral blood flow, and neurological deficits after 24 h of permanent focal cerebral ischemia in transgenic mice (Tg) overexpressing human CuZn-superoxide dismutase (SOD-1) was examined. There were no difference between SOD-1 Tg mice and non-Tg littermates observed in the infarct areas of brain slices, the infarct volume, the local cerebral blood flow, or the neurological deficits. These data suggest that pre-existing high levels of antioxidant enzyme failed to provide neuronal protection against permanent focal cerebral ischemia.

Animals↗
PubMed1993

Specificity of 4-chlorobenzoyl coenzyme A dehalogenase catalyzed dehalogenation of halogenated aromatics.

Steady-state and transient kinetic techniques were used to evaluate the efficiency of 4-chlorobenzoyl coenzyme A (4-CBA-CoA) turnover catalyzed by 4-CBA-CoA dehalogenase from Pseudomonas sp. CBS-3. The kcat for a single turnover on the enzyme was found to be 2 s-1, while that for multiple turnovers was found to be 0.6 s-1. Catalysis rather than product release was judged to be rate limiting. Comparison of the rates of turnover of 4-bromobenzoyl-CoA (1.4 s-1), 4-iodobenzoyl-CoA (1.1 s-1), and 4-fluorobenzoyl-CoA (8 x 10(-6) s-1) indicated that cleavage of the carbon-halogen bond occurs in the rate-limiting transition state of the reaction. Structure-activity measurements made with 4-CBA-CoA analogs bearing electron-donating or -withdrawing substituents at C(2) or C(3) suggested the importance of steric/solvation effects on the enzymatic reaction and failed to provide insight into the nature of the reaction intermediate. The inhibition constants measured for benzoyl-CoA (72 microM), CoA (140 microM), and 4-chlorobenzoate (21 mM) compared to the Km measured for 4-CBA-CoA (4 microM) suggest the dominant role played by the CoA moiety in substrate anchoring.

Acyl Coenzyme A↗