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Biomedical subjects

Y Peng

Publications and source records attributed to Y Peng.

At least 181 records · Page 10Linked to original sources
PubMed1995

Comparison of systemic and direct intrarenal angiotensin II blockade on sodium excretion in rats.

To dissociate the renal effects from the systemic effects of angiotensin II blockade, the present study was designed to determine the effects of systemic and renal interstitial infusion of the specific angiotensin II (ANG II) receptor antagonist, losartan, on blood pressure and sodium excretion in rats fed a low-, normal, or high-sodium diet. Fractional sodium excretion (FENa) and mean arterial pressure (MAP) were measured in rats before and during systemic infusion of losartan (10 mg/kg) or renal interstitial infusion of losartan (3 mg/kg) by means of a chronically implanted matrix. In rats fed a low- or normal sodium diet, systemic infusion of losartan markedly decreased MAP (delta -21 +/- 2, delta -10 +/- 2 mmHg, respectively; P < 0.05) with an accompanying fall in FENa (delta -0.10 +/- 0.05, delta -0.91 +/- 0.40%, respectively; P < 0.05). In contrast, preferential blockade of renal ANG II with renal interstitial losartan infusion resulted in an increase in FENa (delta 0.13 +/- 0.04, delta 0.95 +/- 0.45%, respectively; P < 0.05) and no significant change in MAP. In rats fed a high-sodium diet, both systemic and renal interstitial infusion of losartan increased FENa (delta 1.90 +/- 0.26, delta 1.40 +/- 0.56%, respectively; P < 0.05). Although systemic infusion of losartan decreased MAP (delta -4.4 +/- 0.6 mmHg, P < 0.05) in rats fed a high-sodium diet, the reduction in MAP was much less than that in rats fed a low- and normal sodium diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1995

Changes of cellular morphology and nuclear DNA content in different nasopharyngeal epithelium from different patients.

Cellular morphology and nuclear DNA content were measured with point-counting technique and flow cytometry (FCM) respectively in normal nasopharyngeal epithelium (NE), tissue adjacent to carcinoma (ATC) and nasopharyngeal carcinoma (NPC). The results showed that all 20 patients with NE showed diploid, whereas 38 (38%) of 101 patients with NPC, 7 (58%) of 12 patients with recurrent NPC, 6 (30%) of 20 patients with ATC and 2 (33%) of 6 patients with NE positive to EBVCA-IgA test showed nondiploid. A total of 19 morphometric parameters of the cell were measured and calculated. The results showed that with malignant transformation of NE, most of the cellular morphometric parameters gradually increased in numerical values while no marked difference was shown between normal NE and simple hyperplasia or metaplasia in terms of cytomorphometric characteristics. Most of the parameters in dysplasia changed significantly as compared with those normal NE, simple hyperplasia or metaplasia and NPC groups. Cytomorphometric analysis seems to give strong support to the concept that dysplasia is among the transitional stages of disease process between normal NE and NPC. Our results show that morphometric analysis and FCM may offer valuable and objective criteria in the early diagnosis of NPC and premalignant disease.

Aneuploidy↗
PubMed1995

Development of a polymer-enzyme immunoassay method and its application.

Both poly(N-isopropylacrylamide) and poly(N-isopropylacrylamide)-antibody (PINP-Ab)-labelled enzyme adhered quickly and tightly to cellulose acetate/nitrate membrane either below (less efficiently) or above (more efficiently) the lower critical solution temperature, and the retention of PINP-Ab on the membrane increased over 30-fold when compared with the unconjugated Ab. These characteristics were used to develop a novel polymer-enzyme-linked immunoassay method: homogeneous antigen-antibody immune-complexation reaction and a heterogeneous separation process. By using a simple horseradish-peroxidase-labelled antibody as a probe, we applied this method to the detection of human serum hepatitis B surface antigen (HBsAg). This immunoassay system can detect as little as 1 ng/ml of HBsAg. The advantages of this method are: (a) fast homogeneous immune complexation; (b) a rapid heterogeneous separation process; (c) high sensitivity; and (d) low non-specific background.

Acrylic Resins↗
PubMed1995

[The effect of intra-aortic balloon pumping in case of left main coronary artery stenosis].

In order to improve perfusion of coronary artery in case of coronary artery stenosis, effect of intra-aortic balloon pumping (IABP) on coronary blood flow (CBF) was investigated. To this end hemodynamic parameters of heart functions with and without stenosis were analysed under IABP. Hemodynamic effect of IABP was obviously influenced by the coronary artery stenosis.

Animals↗
PubMed1994

Glycine and GABAA antagonists reduce the inhibition of primate spinothalamic tract neurons produced by stimulation in periaqueductal gray.

Amino acids are demonstrated to be important neurotransmitters mediating the inhibitory transmission from nucleus raphe magnus to spinal nociceptive dorsal horn neurons. In this study, the role of glycine and GABA in the inhibitory processes evoked by stimulation in periaqueductal gray (PAG) of responses of primate spinothalamic tract (STT) neurons to cutaneous mechanical and thermal stimuli was investigated by examining the effects of strychnine and bicuculline, antagonists of glycine and GABAA receptors, respectively, introduced into the dorsal horn through a microdialysis fiber. The inhibitory effects of iontophoretic application of glycine and GABAA agonists on STT cell activity evoked by noxious mechanical stimulation of the skin were selectively blocked by their specific antagonist, strychnine or bicuculline, infused into the dorsal horn. Similarly, intra-spinal application of strychnine or bicuculline resulted in a significant reduction in the PAG stimulation-induced inhibition of responses of STT cells to cutaneous stimuli. This reduction was mainly on the PAG-induced inhibition of the responses to noxious mechanical stimuli. Our results suggest that glycinergic and GABAergic inhibitory interneurons in the spinal cord dorsal horn synapsing on STT cells are activated during stimulation in PAG and contribute to descending antinociceptive actions.

Animals↗
PubMed1994

Hyperglycemia delays rostral initiation sites during neural tube closure.

Neural tube defects contribute greatly to perinatal loss, physical handicap, mental retardation and other developmental defects, yet the mechanisms through which they occur are poorly understood. One hindrance to the study of these defects at the cellular and molecular levels is the low frequency with which they arise in susceptible animals. The present study utilizes a culture system for the study of rodent exencephaly, an animal model of human anencephaly, in which a high frequency of affected animals are obtained by culture in hyperglycemic rat serum. Rat embryos were dissected at day 9.5 from timed-pregnant Sprague-Dawley dams and cultured under standard conditions developed by New [Biol. Rev. (1978) 53,81-122]. Embryos cultured under elevated glucose conditions are able to close the caudal neural tube with the failure of neural tube closure limited to the rostral neuralepithelium. In this report we present the novel finding that, although at the end of culture frequently only the hindbrain region remains open, the normal sequence of events expected during rostral closure anterior to the hindbrain is markedly delayed. In embryos cultured in hyperglycemic serum, both rostral initiation sites II and III are significantly delayed. The degree of delay increases with increasing glucose concentration in the culture medium. These studies support the use of this defined in vitro model of anencephaly for studies of the molecular and cellular bases underlying the failure of hindbrain closure and demonstrate that sufficient numbers of affected animals can be produced to obtain significant results.(ABSTRACT TRUNCATED AT 250 WORDS)

Anencephaly↗
PubMed1994

High-specificity neurological localization using a connectionist model.

Most previous connectionist models for diagnosis have been developed using error backpropagation. While these systems function reasonably well, they have been limited by their need for a large database of test cases, to situations where a single disorder is present, and by the large number of connections required between fully-connected sets of processing units. Here we describe a recently developed connectionist model that overcomes these limitations. This approach can reuse existing causal knowledge bases, works well in situations where multiple disorders can occur simultaneously, and does not require fully-connected sets of processing units. We demonstrate that the accuracy of this model is comparable to that of more conventional AI programs using the same knowledge base in determining precisely the site of brain damage in a group of 50 stroke patients. These results support the conclusion that connectionist models can effectively use pre-existing causal knowledge bases from AI systems, and that they can function accurately when handling actual clinical problems.

Artificial Intelligence↗
PubMed1994

[Studies on Clonorchiasis sinensis control in Sanshui City, Guangdong province].

During 1986 to 1988 and 1990 to 1992, Dongyong Township and Guanyuan Township in Sanshui City, Guangdong Province were selected as demonstration areas for clonorchiasis sinensis control by using measures of repeated examination and treatment respectively. After two years' examination and treatment, the population infection rates were from 43.6% to 13.2% in Dongyong Township and from 78.5% to 36.3% in Guanyuan Township. The first intermediate host was Alocimma longicornis, and the second intermediate hosts were Parabramis bransula and Ctenopharyngodon idellus. The adult worms of Clonorchis sinensis were found in the bile ducts of cats, dogs and pigs which may be the reservoir hosts.

China↗
PubMed1994

[Hypertension inducing cerebrovascular damage and effecting on cerebral infarction].

Cerebrovascular damage of renovascular hypertensive rats (RHR) was observed under light microscope and electron microscope, and the cerebral collateral vessels of RHR were observed with vascular casts. In focal cerebral ischemia of RHR, the infarct volume was measured by TTC staining in combination with computer image processing and analysis. When hypertension persisting longer, there were hyalinosis in small arterial walls, luminal narrowing and basement membrane thickening in capillaries, decreased collateral vessels, and occluded microvessels. In cerebral ischemia, the infarct volume was large and could not be improved. The results demonstrated that the key to prevent stroke is to prevent and treat hypertension as early as possible.

Animals↗
PubMed1993

Minimizing complexity in cellular automata models of self-replication.

Understanding self-replication from an information processing perspective is important because, among other things, it can shed light on molecular mechanisms of biological reproduction and on prebiotic chemical evolution. Intuition, biological knowledge, and early computational models of self-replication all suggested that self-replication is an inherently complex process. In this paper we describe recent computational studies that challenge this viewpoint. We summarize our recent work with cellular automata models of simple yet non-trivial self-replicating structures called unsheathed loops. For example, one unsheathed loop consists of only six components and requires only 20 rules to specify the local intercomponent interactions needed to bring about replication. The implication of this work is that, when viewed as an emergent property of numerous local, concurrent interactions between components, self-replicating systems can be substantially simpler than is generally recognized.

Computer Simulation↗
PubMed1993

[Preliminary mechanism studies of siwenmycin on the inhibition of nucleic acid syntheses].

Siwenmycin, isolated from a streptomyces culture, is a new member of aclacinomycin analogues. It exhibited a remarkable inhibitory effect on the biosynthesis of DNA and RNA in vivo. In order to recognize the mechanism of the inhibitions, the reactions of siwenmycin to DNA template, DNA polymerase I and RNA polymerase were studied. Experimental results showed that siwenmycin could intercalate DNA, but it did not inhibit DNA polymerase I-mediated DNA repair replication and T7RNA polymerase-mediated DNA transcription. This indicates that siwenmycin is not a damage to the DNA template function, nor will it inhibit DNA polymerase I and T7RNA polymerase, though it can intercalate DNA.

Aclarubicin↗
PubMed1993

[Study on endocytosis and nuclear accumulation of epidermal growth factor (EGF) in normal C3H mouse fibroblast cells C3H10 T1/2C18 and 3H-TdR transformed counterpart cells].

In this study, we investigated endocytosis and nuclear accumulation of epidermal growth factor (EGF) in normal C3H mouse embryo fibroblast cells C3H10 T1/2 C18 (designated NC3H10) and 3H-TdR transformed counterpart cells (designated TC3H10). The results revealed that 125I-labelled EGF bound to the receptor on the cell surface of the two cell lines was subsequently endocytosed and translocated from the cell membrane to the nucleus, where it progressively accumulated. NC3H10 showed more EGF accumulation in nucleus than TC3H10 (p < 0.05). SDS-polyacrylamide gel electrophoresis revealed that the endocytosed 125I-EGF associated with the nucleus was intact, with negligible breakdown products present. The nuclear accumulation of intact EGF in the mentioned cell lines exposed to ammonium chloride (a lysosomal inhibitor) was higher than the control (p < 0.05). These results suggested that receptor-mediated endocytosis and nuclear accumulation of EGF may play an important role in mediation some of the action of EGF.

Animals↗
PubMed1993

[Electrophoretic analysis of isoenzyme and protein patterns of Romanomermis yunanensis and R. culicivorax (Nematoda:Mermithidae)].

Isoenzyme electrophoretic patterns of lactate dehydrogenase (LDH), malate dehydrogenase (MDH), esterase (EST) and peroxidase (PO) of post-parasitic juveniles and adults of Romanomermis yunanensis and R. culicivorax were analysed by disc electrophoresis, respectively. The protein patterns of the two species of Romanomermis were compared by vertical slab SDS polyacrylamide gel electrophoresis. The results showed marked differences in isoenzyme patterns (number of bands and/or Rf) of LDH and MDH between the two species of Romanomermis, but the similar positions of isoenzyme bands denoted a certain genetic relationship between them. No band was found in the isoenzyme patterns of PO and EST. Distinct differences in protein pattern were observed between the two species of Romanomermis, but some common bands in pattern reflected the phylogenetic relationships of these species. The differences of isoenzyme and protein patterns observed in this study have provided the reason for identifying and differentiating the two species of Romanomermis at the molecular level.

Animals↗
PubMed1992

Synergistic and antagonistic effects on genotoxicity of chemicals commonly found in hazardous waste sites.

Synergistic and antagonistic effects on genotoxicity of mixtures of four chemicals; i.e., lead tetraacetate (LTA), arsenic trioxide (ATO), dieldrin (DED), and tetrachloroethylene (TCE), were evaluated by the Tradescantia-micronucleus (Trad-MCN) assay. The chemicals were mixed in ratios of 1:1, 1:2 and 2:1 for mixtures of two chemicals and 1:1:1 each for three chemicals. The concentration of stock solution of these chemicals was around the minimum effective dose (MED) or below the MED for these chemicals as reported by Sandhu et al. (1989). Treatments were applied to plant cuttings by hydroponic uptake of the mixed solutions through the stems of the plant for 30 h followed by fixation of the flower buds in aceto-alcohol (1:3 ratio) without a recovery period. Microslides were prepared for scoring MCN frequencies. Results of two series of repeated experiments indicated that all mixtures of LTA/ATO exhibited antagonistic effects. On the other hand, all mixtures of TCE and DED exhibited synergistic effect. These data indicate that for evaluating biological hazards at chemical waste sites, it is prudent to evaluate the genotoxicity of complex chemical mixtures as these exist in nature because the biological effects based on evaluating individual chemicals may not be true predictors of the interactive effects of the pollutants.

Arsenic↗
PubMed1992

[Susceptibility of thirty-one species of mosquitoes to Romanomermis yunanensis].

A new species of Mermithidae was found parasitizing the larvae of Culex tritaeniorhynchus and Culex fatigans in Henan, China and then named Romanomermis yunanensis. Thirty-one species of Mosquitoes involving six genera have been tested for susceptibility to R. yunanensis and Culicinae mosquito have consistently been highly susceptible. At a 1:5 ratio of mosquito larvae to nematode juveniles, the parasitisms of Aedes aegypti, Ae. albopictus, Culex fatigans, Culex tritaeniorhynchus, Anopheles sinensts, Psorophora columbiae and Culesta inornata were 98.2%, 98.5%, 98.6%, 97.1%, 0%, 98.8%, and 99.0% respectively. R. yunanensis presented a phenomenon of retarted development in Anopheles maculatus, which remained at the parasitic stage both in the larvae and pupa of An. maculatus. The parasitism of An. dirus was 89.7%, but most (88.8%) parasitizing mermithids underwent melanization and died. The comparative susceptibility of some North American mosquitoes to R. yunanesis and R. culicivorax at a 1:5 infective ratio showed that both percentage infection and intensity of infection statistically supported the generalization that, under laboratory conditions, R. yunanesis is a more vigorous and aggressive parasite of Culicinae.

Aedes↗
PubMed1992

Differential effects of transition metal ions on in vitro lipid peroxidation of human serum and protein precipitated from serum.

Elevated concentrations of lipid peroxidation products in serum have been documented in some common human diseases. In addition, several reports indicate that peroxidative damage of tissues in laboratory animals are enhanced in acute toxicity from transition metal ions. We studied the effects of four commonly encountered transition metal ions in human acute toxicity: copper, iron, mercury and lead on in vitro lipid peroxidation of human sera. Cupric and ferric ions caused a significant increase in lipid peroxidation products while mercuric and lead ions had no effects. Lipid peroxidation products in sera incubated with 1 mM cupric ion were increased by 210-248% following 24 h of incubation and 340-480% after 48 h of incubation, while the increases were significantly lower in the aliquots of same serum pools supplemented with same molar concentration of ferric ions (110-115% after 24 h and 137-141% following 48 h). On the other hand the effects were reversed when lipoproteins coprecipitated with other serum proteins were incubated with cupric and ferric ions. Under such conditions increases of lipid peroxidation products were significantly higher with ferric ions (240% after 24 h and 600% after 48 h) compared to cupric ions (20% following 24 h and 25% following 48 h). Such differential behavior of cupric and ferric ions in promoting lipid peroxidation can be explained with a different degree of binding of such ions with serum proteins.

Blood Proteins↗