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Biomedical subjects

M Tang

Publications and source records attributed to M Tang.

At least 109 records · Page 6Linked to original sources
PubMed1996

Pigment epithelial and retinal phenotypes in the vitiligo mivit, mutant mouse.

PURPOSE: To describe the abnormal phenotype in retinal pigment epithelium (RPE) and neural retina of vitiligo mutant mice from embryonic stages to old age. METHODS: Eyes of wild-type controls and congenic vitiligo mutants were examined by light and electron microscopy from embryonic day (E) 12 to 2 years of age. The amount and distribution of pigment in the RPE was studied in wholemounts. RESULTS: Earliest phenotypic expression of mivit is seen in the RPE, which is abnormally multilayered dorsally at E12 to E13, and contains both hyperpigmented and hypopigmented patches. Postnatally, most RPE cells have abnormally short, compact, apical microvilli not containing melanosomes and not interdigitating with rod outer segments (ROS). Rod outer segments begin to degenerate relatively late, at approximately postnatal day (P) 30, and fragments accumulate in the subretinal space; photoreceptor nuclei decrease in number progressively from approximately P60 to P500. Retinal detachment, more prominent than in most other retinal degenerations, begins as ROS break up. Additional unusual events are the appearance of macrophage-like cells in the subretinal space by P21 to P60 and extensive shedding of photoreceptor nuclei across the external limiting membrane and into the subretinal space from approximately P180 to P500. Photoreceptor cell degeneration follows a radial gradient, more severe centrally, and is more advanced superiorly than inferiorly. By 2 years, almost all rod and cone cells are gone, and the residual neural retina is invaded by heavily pigmented cells. CONCLUSIONS: The initial ocular target of the mivit gene is the RPE, which is abnormal for many weeks before photoreceptor cells differentiate and become demonstrably affected. The authors hypothesize that the slowly progressive photoreceptor cell degeneration is secondary to abnormal function of the RPE. This mutation serves to refocus attention on critical influences of the RPE on function and maintenance of photoreceptor cells.

Animals↗
PubMed1996

Increased cell genesis in retinal pigment epithelium of perinatal vitiligo mutant mice.

PURPOSE: To compare cell proliferation in vitiligo and control mouse retinal pigment epithelium (RPE) perinatally. METHODS: C57BL/6J-mivit/mivit mice and congenic +/+ controls were injected once with bromodeoxyuridine 1 hour before they were killed between embryonic day 18 and postnatal day 8. Wholemounts of Carnoy-fixed posterior eyecups, minus lens and neural retina, were stained immunohistochemically to detect DNA synthesis (bromodeoxyuridine incorporation) and mitotic cells (R3 antibody binding). Cells were counted in carefully controlled sampling sites, and total RPE area and face-view cell areas were calculated. Retinal pigment epithelial cell heights were measured on light and electron micrographs. RESULTS: Total surface areas of the mutant and control RPE monolayer were similar (I.E., RPE wholemount area was normal), but cell number was approximately doubled in the mutant RPE. By postnatal day 6, mutant cells had approximately 70% the face-view area as controls, but their heights were increased approximately 80%, so that cell volumes were near normal despite the higher packing density. Regional differences in cell size in the control RPE were absent in the mutant specimens. The mutant RPE showed an increased bromodeoxyuridine labeling index, as well as an absolute increase in the number of cells engaged in DNA synthesis and in mitosis. CONCLUSIONS: Cell genesis in the vitiligo RPE is quantitatively abnormal perinatally, well before the neural retina has been recognized to display functional or morphologic defects. Cells are being generated at an abnormally high rate, so that twice the normal number of cells are packed into a RPE of normal total area.

Animals↗
PubMed1996

[Comprehensive cost-benefit evaluation for the improvement of rural water supply in Hunan province].

Comprehensive cost-benefit evaluation for the improvement of rural water supply was conducted according to the national standard methods for analysis of water quality. Results showed total bacteria count and coliform group count in the water declined by 51% after the improvement, and synthetic index of water quality declined to 19% of that before the Improvement. Environmental epidemiological studies showed yearly incidence of hepatitis A, typhoid fever, diarrhea and enteritis decreased by 2.20/1,000, 0.39/1,000, 2.70/1,000 and 14.30/1,000, respectively, as compared with those before the improvement, and with the manpower capital method, economic loss caused by the above-mentioned diseases lowered by 37,238 yuan, economic benefit gained by saving labor-time for water-taking reached 198,644 yuan, and family income increased 164,188 yuan per year. It suggests the above indicators all can be used in comprehensive cost-benefit evaluation of the improvement of rural water supply.

China↗
PubMed1996

[A clinical study on the incidence of retroperitoneal lymph node metastasis and its risk factors in ovarian cancer].

OBJECTIVE: To investigate the incidence and the significant risk factors of retroperitoneal lymph node metastasis (LNM) in primary ovarian cancer for considering the necessity of systematic lymphadenectomy. METHODS: 117 cases of retroperitoneal lymphadenectomy performed on primary ovarian cancers in our hospital from November, 1987 to January, 1994 were studied. The relationship between clinicopathologic characters and the incidence of LNM were determined by univariate and multivariate analysis. RESULTS: In 44 (37.6%) of the 117 patients studied, LNM was confirmed pathologically. The chances of pelvic LNM (29.9%) were smilar to that of para-aortic LNM (20.9%) (P > 0.05). Univariate analysis showed that significantly increased incidence of LNM was clinically associated with bilateral involvement of the ovaries, presence of ascites, advanced stages, poor tumor differentiation, rather large residual tumors and some histopathological subtypes such as undifferentiated and serous adenocarcinoma. The size of the residual tumor, clinical stage and grade of differentiation were the most important risk factors for LNM (P < 0.05) by multivariate analysis. The indication, optimum time, the scope and model of systematic lymphadenectomy were evaluated and discussed. CONCLUSION: systematic lymphadenectomy was suggested only for early cases with high risk factors. For late cases with residual tumor the operation may be done at a chosen time, for instance, at second cytoreductive or second-look surgery.

Adenocarcinoma↗
PubMed1995

The LAR/PTP delta/PTP sigma subfamily of transmembrane protein-tyrosine-phosphatases: multiple human LAR, PTP delta, and PTP sigma isoforms are expressed in a tissue-specific manner and associate with the LAR-interacting protein LIP.1.

The transmembrane protein-tyrosine-phosphatases (PTPases) LAR, PTP delta, and PTP sigma each contain two intracellular PTPase domains and an extracellular region consisting of Ig-like and fibronectin type III-like domains. We describe the cloning and characterization of human PTP sigma (HPTP sigma) and compare the structure, alternative splicing, tissue distribution, and PTPase activity of LAR, HPTP delta, and HPTP sigma, as well their ability to associate with the intracellular coiled-coil LAR-interacting protein LIP.1. Overall, these three PTPases are structurally very similar, sharing 64% amino acid identity. Multiple isoforms of LAR, HPTP delta, and HPTP sigma appear to be generated by tissue-specific alternative splicing of up to four mini-exon segments that encode peptides of 4-16 aa located in both the extracellular and intracellular regions. Alternative usage of these peptides varies depending on the tissue mRNA analyzed. Short isoforms of both HPTP sigma and HPTP delta were also detected that contain only four of the eight fibronectin type III-like domains. Northern blot analysis indicates that LAR and HPTP sigma are broadly distributed whereas HPTP delta expression is largely restricted to brain, as is the short HPTP sigma isoform containing only four fibronectin type III-like domains. LAR, HPTP delta, and HPTP sigma exhibit similar in vitro PTPase activities and all three interact with LIP.1, which has been postulated to recruit LAR to focal adhesions. Thus, these closely related PTPases may perform similar functions in various tissues.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Yeast two-hybrid system demonstrates that estrogen receptor dimerization is ligand-dependent in vivo.

Previous studies using in vitro procedures have not clearly established whether the estrogen receptor (ER) acts as a monomer or dimer in the cell. We have used the yeast two-hybrid system as an in vivo approach to investigate the dimerization of the estrogen receptor in the absence and presence of estrogen and anti-estrogens. This system is independent of ER binding to the estrogen response element. Two vectors, expressing GAL4 DNA binding domain-human ER and GAL4 transactivation domain-human ER, were constructed. Control experiments showed that each fusion protein had a high affinity binding site for estradiol-17 beta and could transactivate an ERE-LacZ reporter gene in yeast similar to the wild type ER. The two fusion proteins, GAL4 DB-hER and GAL 4 TA-hER, were expressed in the yeast strain, PCY2, which carries a GAL1 promoter-lacZ reporter. ER dimerization was measured via reconstitution of GAL4 through interaction of the fusion proteins, which transactivates LacZ through the GAL1 promoter. When both ER fusion proteins were expressed, beta-galactosidase activity was estradiol-17 beta-inducible. Furthermore, we showed that both tamoxifen and ICI 182,780 also induced beta-galactosidase activity, albeit lower than that induced by estradiol-17 beta. These results strongly argue that ER dimerization is ligand-dependent and the dimer can be induced by estradiol-17 beta, tamoxifen, or ICI 182,780. We also treated the yeast containing the two fusion proteins with estradiol-17 beta and tamoxifen or ICI 182,780 simultaneously to determine the effects on ER dimerization. beta-Galactosidase activity was lower when the yeast was treated with a higher ratio of tamoxifen or ICI 182,780 to estrogen than estradiol-17 beta alone. Taken together, we conclude that ER dimerization is ligand (estradiol-17 beta, tamoxifen, or ICI 182, 780)-dependent, and we suggest that estradiol-17 beta-induced dimers are destabilized when estradiol-17 beta is used with tamoxifen or ICI 182,780 simultaneously.

Base Sequence↗
PubMed1995

Cholest-3,5-dien-7-one formation in peroxidized human plasma as an indicator of lipoprotein cholesterol peroxidation potential.

Lipoprotein peroxidation susceptibility is routinely evaluated using products of unsaturated fatty acids as markers (e.g., malonaldehyde). The significance and factors influencing peroxidation of cholesterol moiety of lipoproteins are relatively unknown due to lack of a reliable marker product which can be measured easily. Under the influence of Cu2+ ions, the major product of lipoprotein cholesterol peroxidation (isolated after saponification) was cholest-3-5-dien-7-one (CSD). Apart from gas-liquid chromatography, this compound lends itself for measurement by alternative methods. Due to lack of the 3 beta-hydroxyl group, CSD was separated from the rest of the oxysterols and cholesterol by passing through digitonin-coated silica-gel G and its concentration was determined by absorption at 283 nm. The recovery of CSD by this method exceeded by 87%. The formation of CSD was also sensitive to vitamin E and therefore could be used as an index of lipoprotein cholesterol susceptibility to peroxidation.

Cholestenones↗
PubMed1995

Effect of radiofrequency catheter ablation on calcium channel of ventricular myocytes.

Using whole-cell patch-clamp technique, the effect of radiofrequency catheter ablation (RFCA) on calcium current (Ica) of guinea pig ventricular myocytes was examined. The radiofrequency energy delivered was 20 W x 10 s. RF-CA decreased Ica apparently with the affected area reaching up to 1.2 cm from the ablation focus. In the meanwhile, the pathological lesion size resulted from RFCA was merely 0.41 +/- 0.11 cm. These findings indicate that RFCA, apart from causing tissue necrosis by heat, can affect myocyte membrane currents in a large area. This may explain why RFCA has a very high success rate with a small pathological lesion.

Animals↗
PubMed1995

Qualitative analysis of Kolmogorov-type models of predator-prey systems.

The qualitative behaviors of Kolmogorov-type models are investigated under assumptions that are consistent with models of predator-prey systems and biologically realistic. The main purpose of this paper is to prove the boundedness of solutions and to give criteria for the existence of limit cycles for the system. In the case that the positive equilibrium is locally asymptotically stable, an example shows that there could be more limit cycles. This example serves as a counterexample to the global stability criterion of Huang.

Animals↗
PubMed1995

Consistency of clinical diagnosis in a community-based longitudinal study of dementia and Alzheimer's disease.

We evaluated the consistency of the diagnosis of dementia in a multicultural, longitudinal community-based study of cognitive impairment and dementia. We diagnosed dementia using a fixed neuropsychological paradigm; the diagnosis also required historical evidence of functional impairment. In a sample of 656 subjects with at least one annual follow-up examination, dementia was confirmed at 1 year in 89% of the 304 subjects initially demented, and in 90% of the 136 subjects with the initial diagnosis of probable Alzheimer's disease (AD). The 34 initially demented subjects who failed to meet criteria for dementia at follow-up included 13 with an initial diagnosis of probable AD. All 34 still had evidence of cognitive impairment; this group was more likely to have a history of pulmonary disease, multiple medication use, or chronic alcohol use than other demented patients. Consistency of dementia diagnosis did not vary according to educational attainment or ethnic background. The use of a neuropsychological paradigm such as ours in large longitudinal studies of dementia may minimize interobserver diagnostic variability or diagnostic drift over time while contributing the benefits of a comprehensive cognitive evaluation to the diagnostic process.

Aged↗
PubMed1995

[Some biochemical indexes in white rabbit's blood affected by acute high intensity microwave].

Irradiation of white rabbits by 10, 50, 100 and 200 mW/cm2 microwave respectively can cause the disorder of protein metabolism, the abnormality of blood sugar, and the change of the activity of serum alpha-hydroxybutyrate dehydrogenase, lactate dehydrogenase, glutamic oxalacetic transaminase, glutamic pyruvic transaminase, acid phosphatase ect. These changes can be used as indexes in the evaluation of the effect of acute high intensity microwave exposure. The effect on the organism mainly depends on the intensity of exposure provided the dose of microwave remains the same.

Acid Phosphatase↗
PubMed1995

[Flow cytometry used to distinguish between complete and partial hydatidiform moles].

The nuclear ploidy of 14 placentas was determined by flow cytometry. All histologically classified complete moles (4 cases), hydropic villi (4 cases) and control placentas (3 cases) were diploid; whereas two of three histologically classified partial moles were triploid. The remaining case classified as partial mole was diploid, most likely a complete mole. It was concluded that DNA flow cytometric analysis offers an informative supplement to the histological interpretation of hydropic placentas.

DNA, Neoplasm↗