Search PubMed⌕ Search

Biomedical subjects

Y Cai

Publications and source records attributed to Y Cai.

At least 271 records · Page 15Linked to original sources
PubMed1994

Effects of acetylsalicylic acid on parameters related to peroxisome proliferation in mouse liver.

Male C57 BL/6 mice were exposed to 1.0% (w/w) acetylsalicylic acid (ASA) in their diet for 10 days and effects related to peroxisome proliferation were subsequently examined. A 2.2-fold increase in mitochondrial protein content was obtained. The activities of the peroxisomal enzymes, lauroyl-CoA oxidase, palmitoyl-CoA oxidation and catalase, were enhanced 4.5-, 4.0- and 2.1-fold, respectively. There was a dramatic increase (9.1-fold) in microsomal cytochrome P450 IVA-catalysed activity, a 1.6-fold induction of total microsomal P450 content and a 2-fold induction of microsomal cytochrome P450 reductase activity (measured as NADPH-cytochrome c reductase). Catalase activity in the cytosol was induced 5.2-fold and DT-diaphorase activity was increased 3.5- and 3.2-fold in the cytosol and mitochondria, respectively. There was a significant increase in the susceptibility of microsomes to lipid peroxidation. Smaller increases in superoxide dismutase, glutathione transferase and glutathione peroxidase activities were also observed. The possible relevance of these effects to the pharmacology of ASA is discussed.

Animals↗
PubMed1994

Stimulation of area postrema by vasopressin and angiotensin II modulates neuronal activity in the nucleus tractus solitarius.

There is an abundance of evidence suggesting that the area postrema (AP) is involved in the central actions of arginine-vasopressin (AVP) and angiotensin II (Ang II) on cardiovascular regulation. Furthermore, recent studies have shown that activation of the AP facilitates the response of nucleus tractus solitarius (NTS) neurons to tractus stimulation. In the present study, using the perfused rabbit brain slice preparation, we examined the response of NTS neurons when AVP and Ang II were microinjected onto the AP. Spontaneous or solitary tract stimulation-induced neuronal activity was recorded extracellularly from the medial NTS before, during and after AVP or Ang II application. An increase or decrease in activity by more than 30% of the baseline value was considered excitatory or inhibitory. The effects of AVP were studied in 57 NTS cells, 14 of which were spontaneously active and 43 were driven by tract stimulation. Of the cells with evoked activity, 49% were excited, 19% were inhibited, and 32% did not respond. The percentage of cells responding to AVP was similar in spontaneously active cells. The effects of Ang II were tested in 85 cells including 54 with evoked activity and 31 with spontaneous activity. In NTS cells with evoked activity, AP application of Ang II caused inhibition in 37%, excitation in 7%, while 56% did not respond. The proportion of cells responding to Ang II was similar in spontaneously active cells. These results suggest that AVP may act on the AP to increase the excitatory response of NTS neurons while the actions of Ang II result in an inhibitory influence.

Angiotensin II↗
PubMed1994

Dithiothreitol reversal of allyl alcohol cytotoxicity in isolated rat hepatocytes.

Reversal by dithiothreitol (DTT) of allyl alcohol cytotoxicity was investigated in isolated rat hepatocytes. Allyl alcohol-induced protein sulfhydryl loss, bleb formation, and cell death were prevented by DTT, when it was added to hepatocytes 30 min after the toxicant. The protective effect of DTT also was demonstrated in cells that were washed after 30 min of exposure to allyl alcohol, indicating that protection was not related to inhibition of allyl alcohol metabolism or inactivation of acrolein. DTT reversed the cell surface protrusions that formed during exposure to allyl alcohol, but reversal of blebbing did not insure that the cells would remain viable. Glutathione disulfide was not formed in allyl alcohol-treated cells, and DTT reversal of cytotoxicity occurred without restoring glutathione levels. Moreover, protection against allyl alcohol toxicity required the continuous presence of DTT. The results suggest that initial events in the toxic process are reversible, and that DTT can prevent cytotoxicity if added to hepatocytes before irreversible damage occurs; however, the mechanism by which DTT exerts its protection is not clear.

1-Propanol↗
PubMed1994

Allyl alcohol cytotoxicity in isolated rat hepatocytes: mechanism of cell death does not involve an early rise in cytosolic free calcium.

We examined the effect of a toxic concentration of allyl alcohol (0.5 mM) on intracellular calcium concentrations in isolated rat hepatocytes. An increase in phosphorylase a activity was evident in the hepatocytes after 30 min of incubation with allyl alcohol, suggesting that the toxicant may produce an early rise in cytosolic free calcium. The increase in phosphorylase a activity was not reversed by the addition of dithiothreitol (DTT), a sulfhydryl compound that reverses the events that initiate cell killing by allyl alcohol. When intracellular calcium concentrations were measured directly, using fura-2 as the calcium indicator, there was no effect of allyl alcohol on cytosolic free calcium during the first 60 min of exposure, a critical period for development of irreversible damage. Incubation with allyl alcohol did not interfere with the measurement of intracellular calcium. The increases in cytosolic free calcium produced by phenylephrine or ATP were similar to those reported by others and not affected by the presence of allyl alcohol. The results from this study demonstrate that increased cytosolic free calcium is not essential for allyl alcohol-induced cytotoxicity to isolated rat hepatocytes.

1-Propanol↗
PubMed1994

Studies on the anti-tumour, anti-bacterial, and wound-healing properties of dragon's blood.

Three in-vitro assays have been adopted to examine the cytotoxicity and anti-bacterial activity of the blood-red sap of Croton lechleri from Ecuador, and to examine its effect upon the proliferation of endothelial cells. The sap was found not to be cytotoxic. Several simple phenolic compounds and diterpenes showed a potent anti-bacterial activity. The sap has little effect upon the proliferation of endothelial cells, and no single active ingredient was identified. A mechanism for the wound-healing property of the sap has been proposed.

Animals↗
PubMed1994

Diurnal variation in concentrations of plasma urea nitrogen and amino acids in pigs given free access to feed or fed twice daily.

A repeated-measures experiment was conducted to test the effect of sampling times after feeding on concentrations of plasma urea nitrogen (PUN) and plasma free amino acids (PFAA) in pigs fed by two feeding methods. Seven castrated male pigs (mean weight of 65 kg) were randomly assigned to switchback treatments that were 3-d periods of either free access to feed or twice daily feeding. Blood was sampled at 2-h intervals (sampling points) during the day (0800 to 1800 h) and again during the night (2000 to 0600 h) on the last day of each of three 3-d feeding treatment periods. Concentrations of PUN and most PFAA were not affected by the feeding method and time of day (day and night), but they were affected by sampling points. The pigs fed twice daily had postprandial peak PUN at 4 h (32% increase over prepandial) and peak PFAA at 2 h after feeding during 12-h day and night periods. However, the pigs with free access to feed exhibited only a slight fluctuation of PUN during the day and night and almost constant concentrations of most PFAA during a 24-h period. The PFAA results suggest that concentrations of most plasma essential and nonessential amino acids varied relatively more than those of other amino acids in response to sampling times.

Amino Acids↗
PubMed1994

Conduction of pEC22, a plasmid coding for MR.EcoT22I, mediated by a resident Tn3-like transposon, Tn5396.

pEC22 is a small plasmid that encodes the restriction-modification system MR.EcoT22I. Restriction and functional analysis of the plasmid identified the positions of genes encoding that system. The plasmid is able to be conducted by conjugal plasmids, a process mediated by a transposon contained within pEC22. This cryptic transposon, called Tn5396, was isolated from pEC22 and partially sequenced. The sequence of Tn5396 is for the most part typical of transposons of the Tn3 family and is most similar to that of Tn1000. The transposon differs from closely related transposons in that it lacks well-conserved sequences in the inverted-repeat region and has an unusually long terminal inverted repeat. Consideration of regions of internal sequence similarity in this and other transposons in the Tn3 family supports a theory of the mechanism by which the ends of Tn3-like transposons may maintain substantial identity between their inverted repeats over the course of evolutionary time.

Base Sequence↗
PubMed1994

Morphological changes in rat aortic endothelial cell line stimulated by endothelin.

We have reported that endothelin (ET)-1 activates interleukin (IL)-6 production in rat aortic endothelial cell line (WAE-1 cell). In this experiment, we investigated the morphological changes induced by ET-1 in cultured WAE-1 cells. The cells were treated with ET-1 for 8 h or 24 h, and then compared with untreated cells by light and electron microscopies. The WAE-1 cells treated with ET-1 for 8 h showed remarkable alterations as following: by light microscopic observation, the cells were enlarged and filled with many vesicles in the cytoplasm, and by electron microscopic observation, the cells showed the increases of nuclear membrane infoldings, increased density of chromatin granules just inside the nuclear membrane, and multivesicular bodies in the cytoplasm. These morphological changes were hardly observed in WAE-1 cells-treated with ET-1 for 24 h. It was suggested that ET-1 stimulated DNA synthesis and secretion of cytoplasmic products in WAE-1 cells.

Animals↗
PubMed1994

Enhanced expression of catalytic subunits of protein phosphatase type 1 and high S-phase fraction in liposarcoma.

The expression of the three catalytic subunits of protein phosphatase (PP) type 1 and 2A, PP1 alpha, PP1 gamma 1, and PP2AC, was examined in 8 cases of lipoma as a benign tumor and 4 cases of liposarcoma as a malignant tumor using immunohistochemical analysis. Both types of of tumor cells stained positively with antisera against PP1 catalytic subunit isoforms PP1 alpha and PP1 gamma 1 were significantly higher in liposarcoma than in lipoma. Furthermore, liposarcoma showed a markedly high S-phase fraction in the cell cycle of tumor cells, as compared with lipoma. These results suggest that PP1 is involved in the accelerated growth of malignant cells in liposarcoma.

Adult↗
PubMed1994

[The phenotypic change of smooth muscle cells in the media of pulmonary intra-acinar arteries during hypoxia].

The phenotypic change of smooth muscle cells (SMCs) in the media of pulmonary intraacinar arteries (IAA) was observed in rats during hypoxia. From 3 to 40 exposure days, pulmonary arterial pressure (PAP) and right ventricular hypertrophy increased parallely. From 1 to 5 exposure days, SMCs still displayed the "contractile" phenotype, but the amount of intercellular collagen slightly increased. After 7 exposure days, some medial SMCs changed into the "fully" or "partially" "synthetic" phenotype with an excess of intercellular collagen. From 14 to 40 exposure days, other than some SMCs of partially "synthetic" phenotype, a great number of SMCs acquired the "contractile" phenotype characteristics, but the synthetic and secretive organelles and intercellular collagen were still more than those in the groups from 1 to 5 exposure days. Our results suggested that along with the prolongation of hypoxic exposure, the kinetic changes of SMC phenotype might not parallel with PAP change.

Animals↗
PubMed1994

Endogenous growth factor patterns modulate hemopoietic lineage development.

Hemopoietic growth factors play an important role during stem cell differentiation, and multipotent hemopoietic cells expressing abl oncogenes can cause stem cell diseases in mice. To further elucidate the mechanism of disease development, we examined the initial changes of normal and abl-transduced progenitor cells early in culture, including the endogenous production of growth factors. From 2-3 days methylcellulose cultures, we isolated colonies of early cells and subjected them to RT-PCR analysis. They were found to produce endogenous IL-1 alpha and IL-4. Treatment of these early cells with the antisense oligonucleotides directed against the mRNA of the growth factors did not prevent colony formation. However, the percentage of pure macrophage colonies in cultures containing the antisense IL-1 alpha was increased from 26-60%. This effect was not observed when the antisense oligomers were added 2 days after initiation of culture. We also transduced the progenitor cells with retrovirus vectors carrying either a neor gene (N2) or a v-abl oncogene (A-MuLV or NSabl). After their culture in methylcellulose, we examined the types of colonies developed, growth factor expression by the early cells and their proliferation rate. While the ratio of erythroid to non-erythroid hemopoietic colonies in uninfected culture and N2-infected culture was 0.8, the ratio in A-MuLV-infected culture was 6.0, and in NSabl-infected culture, 3.1. RT-PCR analysis on colonies of abl-transduced cells from 2-3 day cultures indicated a reduction of IL-4 and IL-1 alpha in these cells, and they entered cell division sooner. Our data suggest that hematopoietic lineage development may be a function of the pattern of endogenous as well as exogenous growth factors, and alteration of this pattern either through antisense treatment or v-abl transduction affects the hemopoietic differentiation program.

Animals↗
PubMed1994

[The expression of HLA, Epstein-Barr virus nuclear antigen and the infiltration of T lymphocyte subsets in nasopharyngeal biopsy tissues].

The HLA typing, EBV-EBNA expression and the infiltration of T cell subsets in nasopharyngeal biopsies were investigated using APAAP (Alkaline phosphatase and anti-alkaline phosphatase) and anti-complement immunofluorescence method with a panel of monoclonal antibodies which are W6/32 (anti-HLA-A,B,C), CR3/43 (anti-HLA-DR, DP, DQ), serum from nasopharyngeal carcinoma (NPC, anti-EBNA) and T4, T8, T11(anti-Th, Tc, T3, respectively). There were 25 cases of NPC, 10 of chronic nasopharyngitis (CNP), CNE-2Z cell line and transplants of CNE-2Z, NCN-Z-1 and fetal nasopharynx mucosa under detection. The results showed that the tumor cells of NPC expressed not only HLA-I but also HLA-II. The expression of HLA-II was stronger than that of HLA-I in NPC. The expression of HLA-I and II in epithelial cells of CNP was weak. There was a significant distinction between those groups (P < 0.05). The expression of HLA-I, II was the strongest in CNE-2Z smears and transplants in under mice of CNE-2Z, NCN-Z-1, both negative in fetal nasopharyngeal epithelial transplants. It suggested that HLA express abnormally during carcinogenesis, the cancer cells with HLA-II be not recognized by EBV specific T cells, hence escape from the immune surveillance. Also it demonstrated that the EBNA expression in the cancer cells of NPC was strongly positive, the cells of T3, Th, and Tc in NPC were decreased. It needs further study whether or not the EB virus infection can induce HLA phenotype changes in tumor cells and what the biological functions of HLA-II expression in tumor cells are.

Antigens, Viral↗
PubMed1993

Diquat-induced oxidative damage in BCNU-pretreated hepatocytes of mature and old rats.

The effects of postmaturational aging on the toxicity of diquat, a redox cycling compound, were investigated in hepatocytes that were isolated from mature (6 months) and old (27 months) male Fischer 344 rats and pretreated with 1,3-bis(2-chloroethyl)-1- nitrosourea (BCNU), an inhibitor of glutathione reductase. The hepatocytes were incubated for 2 hr with 0, 0.5, or 2.0 mM diquat dibromide, and samples were taken at various time points for measurements of glutathione, glutathione disulfide, thiobarbituric acid reactive substances, lactate dehydrogenase leakage, protein sulfhydryl groups, and protein carbonyl groups. Diquat cytotoxicity was intensified in hepatocytes of old rats compared with those of mature rats, and the enhanced toxicity was associated with increased lipid peroxidation and protein carbonyl formation. However, the enhanced toxicity in old rat hepatocytes was also accompanied by a decrease in diquat-induced GSH oxidation and there was no difference in protein sulfhydryl loss. Concentrations of total nonheme iron and low-molecular-weight chelatable Fe2+, measured with ferene as the chromogen, were several times higher in freshly isolated hepatocytes of old rats than in those of mature rats. We hypothesize that the age-associated enhancement of diquat toxicity could be due to an increased availability of iron for reaction with diquat-generated hydrogen peroxide and for stimulation of lipid and protein oxidation.

Aging↗