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Biomedical subjects

Y Sun

Publications and source records attributed to Y Sun.

At least 919 records · Page 51Linked to original sources
PubMed1993

Leukemia inhibitory factor mediates an injury response but not a target-directed developmental transmitter switch in sympathetic neurons.

Leukemia inhibitory factor (LIF; also known as cholinergic differentiation factor) is a multifunctional cytokine that affects neurons, as well as many other cell types. To examine its neuronal functions in vivo, we have used LIF-deficient mice. In culture, LIF alters the transmitter phenotype of sympathetic neurons, inducing cholinergic function, reducing noradrenergic function, and altering neuropeptide expression. In vivo, a noradrenergic to cholinergic switch occurs in the developing sweat gland innervation, and changes in neuropeptide phenotype occur in axotomized adult ganglia. We find that the gland innervation of LIF-deficient mice is indistinguishable from normal. In contrast, neuropeptide induction in ganglia cultured as explants or axotomized in situ is significantly suppressed in LIF-deficient mice. Thus, LIF plays a role in transmitter changes induced by axotomy but not by developmental interactions with sweat glands.

Animals↗
PubMed1993

Effects of axotomy on protein synthesis in the rat hypoglossal nucleus: examination of the influence of local recycling of leucine derived from protein degradation into the precursor pool.

The quantitative autoradiographic L-[1-14C] leucine method for the determination of regional rates of cerebral protein synthesis (lCPSleu) requires knowledge of the degree of recycling of leucine derived from protein degradation into the precursor pool for protein synthesis, which can be evaluated by measuring lambda i, the steady-state ratio of the leucine-specific activity in the precursor amino acid pool (tRNA-bound leucine) to that of the arterial plasma. To define the changes in lCPSleu during regeneration of the hypoglossal nerve, we examined the effects of axotomy on the value of lambda i. Because the concentration of tRNA-bound leucine in the hypoglossal nucleus is too low to measure, we measured the equivalent ratio for the total acid-soluble pool (psi i) and applied the linear relationship between lambda and psi found in the whole brain to calculate a value of lambda i in the ipsilateral and contralateral hypoglossal nuclei of 22 adult female rats 2, 18, 35, and 60 days after unilateral hypoglossal axotomy. Statistically significant but quantitatively inconsequential effects of axotomy on values of psi i and lambda i were found. Therefore, the mean value for lambda i (0.64) of the left and right hypoglossal nuclei in all 22 axotomized rats was used to calculate lCPSleu. In a separate group of 15 unilaterally axotomized rats, lCPSleu was determined by the autoradiographic technique; lCPSleu was increased on the axotomized side by 23% on day 2, 30% on day 18, and 13% on day 35. By postaxotomy day 60, lCPSleu had returned to normal.

Animals↗
PubMed1993

Lowered antioxidant enzymes in spontaneously transformed embryonic mouse liver cells in culture.

Normal embryonal mouse liver cells in culture were shown to undergo spontaneous transformation during prolonged subculture. The spontaneously transformed cells lost their anchorage dependence, as measured by a soft agar assay, and gave rise to tumors in nude mice. Accompanying this transformation, the antioxidant enzymes, copper- and zinc-containing superoxide dismutase (CuZnSOD), manganese superoxide dismutase (MnSOD), catalase (CAT) and glutathione reductase, decreased significantly in activity; the decline in enzymatic activity of CuZnSOD, MnSOD and CAT was due to a decline in the levels of immunoreactive protein. These spontaneously transformed high passage in vitro liver cells appeared similar in morphology, antioxidant enzyme activity and tumorigenicity to their counterparts transformed by N-methyl-N-nitro-N-nitrosoguanidine and Simian virus 40. These data provide experimental evidence that changes in antioxidant enzymes are associated with spontaneous in vitro cellular transformation of mouse embryonal liver cells.

Animals↗
PubMed1993

Depression of catalase gene expression after immortalization and transformation of mouse liver cells.

To understand the molecular basis of the remarkable decrease of catalase activity after immortalization and malignant transformation of mouse liver cells, expression of the catalase gene was studied in in vivo mouse liver cells and nontransformed normal mouse liver cell line as well as liver cell lines transformed by N-methyl-N-nitro-N-nitrosoguanidine, SV40 virus or by conventional subcultivation. In vivo liver cells had much greater levels of catalase mRNA and immunoreactive protein than in vitro cell lines, which correlates with elevated enzyme activity. Among the cell lines, normal cells had in general higher mRNA levels and more catalase protein than that of the transformed cell lines, also correlating with enzyme activity. The down regulation of catalase gene expression seen in transformed lines may occur transcriptionally rather than posttranscriptionally as demonstrated by cycloheximide and/or actinomycin D treatment. The striking difference in catalase gene expression seen between liver tissue and liver cell lines was unlikely due to gross structural alterations in the catalase gene, but might be explained by a remarkable difference in methylation status of the catalase gene, as demonstrated by Southern blot analysis following HpaII digestion. Our results suggested that during cellular immortalization and malignant transformation, a change in the oxidant stress ultimately led to a cellular response that, in turn, led to down regulation of the catalase gene.

Animals↗
PubMed1993

Dosage-dependent dominance over wild-type p53 of a mutant p53 isolated from nasopharyngeal carcinoma.

Mutational inactivation of p53, a tumor suppressor gene, is the most common genetic alteration found in human cancer. Most mutated p53s either lose tumor suppressor function or gain oncogenic activity. We recently reported the detection of a heterozygous point mutation of p53 at codon 280 in nasopharyngeal carcinoma (NPC) (1), a high-incidence malignancy in southern China and southeast Asia. Given its heterozygous state, in which both wild-type and mutated p53 gene were expressed, p53-thr280 should function dominantly in the presence of the wild-type form if it is to play a role in nasopharynx carcinogenesis. We tested this dominance hypothesis in the cells of two model systems: 1) human Saos-2 cells lacking endogenous p53, and 2) mouse JB6 tumor promotion-resistant cells (P-) expressing endogenous wild-type p53. The results showed dosage-dependent dominance of p53-thr280 in controlling WT p53-driven transcriptional activity; in governing cell growth; and in progressing P- phenotype to tumor promotion-sensitive (P+) phenotype. This dominant negative effect was seen at a 1:1 (WT:MU) ratio and was more striking at a ratio of 1:3. A model is proposed to explain the dominant negative effect of mutant p53. We conclude from this study that p53-thr280 is likely to be dominant in the heterozygous state found in NPC and that this dominant-negative mutated p53 may contribute to the genesis of NPC or of other carcinomas in which both mutant and wild-type p53 are expressed.

Animals↗
PubMed1993

Relationship between the characteristics of immunopathological expression of hepatitis C virus antigen and hepatocytic injury.

Biopsied liver tissues from 352 cases were tested for hepatitis C virus (HCVAg) with improved PAP immunohistologic chemical method. Furthermore, corresponding seroantibody to hepatitis C virus was also tested. The total HCVAg positive rate was 9.1%. The HCVAg positive rate in chronic persistent hepatitis (CPH) was 5%. The HCVAg positive rate in chronic active hepatitis (CAH) was 11.2%. The HCVAg positive rate raised gradually along with the severity of hepatocytic injury. HCVAg may be seen in necrotic liver cells exfoliating into the liver sinus, indicating a close relationship between HCVAg and hepatocytic injury. Expression of HCVAg was mostly of the nucleus type in CPH cases and was mostly of the plasma type in CAH cases. The periphery of nucleus type-expressed positive cells generally had no marked inflammatory cell infiltration. The periphery of plasma type-expressed positive cells had a certain amount of inflammatory cell infiltration. Along with the severity of hepatocytic injury, HCVAg expressed itself in a positive correlation according to the nucleus and plasma types. The HCVAg positive cells were located mostly in the lobular peripheral band and rarely located in the venoperipheral band. It was possible that this had some relation with the lobular microcirculation of blood and blood supply. In this study, there was no obvious correlation between the HCVAg positive rate in hepatic tissues and the anti-HCV positive rate in sera. Neither the patients with HCVAg positive liver tissues nor the patients with seropositive anti-HCV had any history of blood transfusion and the use of blood products.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Hemodynamic and nonhemodynamic mechanisms of experimental pulmonary edema in rats and the effects of anisodamine and tetramethylpyrazine--estimation of blood gas analysis, RBC superoxide dismutase and prostaglandin E2 in plasma and bronchoalveolar lavage (Part 3).

Anisodamine (ADM, 654-2, 30 mg/kg) and tetramethylpyrazine (TMP, 120 mg/kg) have shown an apparent preventive effect on pulmonary edema (PE). In this study, the nonhemodynamic mechanism was studied: The dynamic changes of PaO2, O2Sat, PaCO2, and blood pH were measured, and RBC superoxide dismutase (SOD) and plasma and bronchoalveolar lavage (BAL) PGE2 levels were estimated. It was concluded that ADM and TMP exerted inhibitory effects on the hypoxic state. The ability of ADM and TMP to adjust RBC SOD and PGE2 levels may be one of the preventive mechanisms of the drugs.

Animals↗
PubMed1993

[Relaxation of coronary arterial smooth muscle and depolarization of cell membrane potential by selenium].

Selenium (Se) is an important trace element to the human being. The effects of selenium on contraction and cell membrane potential of coronary arterial smooth muscle were studied in guinea pig by isometric force development of strips and intracellular recording method. It was showed that Se caused vascular smooth muscle relaxation and depolarization of the cells in a dose dependent manner. Inhibitory effect of Se on KCl- or ACh-induced contraction could be quantitatively assessed by a rightward shift of the concentration-response curve. Furthermore, Se increased KCl-induced depolarization and decreased ACh-induced hyperpolarization.

Animals↗
PubMed1993

[The relation between the volume of gastric mucosal blood flow and acid secretion in patients with gastric and duodenal ulcer].

The relationship between gastric mucosal blood flow and acid secretion was studied in 39 patients. In the active stage of gastric ulcer, the volume of gastric mucosal blood flow (GMBF) was decreased, and that of GMBF at the ulcer margin was decreased significantly and increased markedly at the healing stage. The volume of gastric acid output showed no significant difference between the patients with gastric ulcer and controls. The volume of GMBF was slightly increased at all stages of duodenal ulcer. The volume of gastric acid output was increased in the patients with duodenal ulcer. A positive relationship was noted between the volume of maximal acid output and GMBF in the patients with duodenal ulcer. The results indicated that there is a great difference between gastric ulcer and duodenal ulcer in the functions of mucosal microcirculation and acid secretion cells. The reduction of mucosal protective function may be attributable to the pathogenesis of gastric ulcer. The strengthening of the injury factors plays an important role in causing duodenal ulcer. Increased mucosal blood supply may promote the healing of the ulcer.

Adult↗
PubMed1993

Angiotensin-converting enzyme and myocardial fibrosis in the rat receiving angiotensin II or aldosterone.

Angiotensin-converting enzyme (ACE) is present in tissues composed largely of fibrillar collagen such as heart valves, the adventitia of great vessels and intramyocardial coronary arteries, and the scar that follows myocardial infarction. We tested the hypothesis that such tissue ACE is related to fibrous tissue formation and that its appearance is independent of circulating renin and angiotensin peptides. For this purpose we selected experimental models that simulate primary and secondary hyperaldosteronism, each of which are associated with the appearance of myocardial fibrosis. ACE in the excised heart and aorta was localized by in vitro autoradiography with [125I]351A, while fibrosis was identified by light microscopy in sections stained with collagen specific picrosirius red. Tissue was obtained at 2, 4, and 6 weeks from various experimental groups: unoperated, untreated, age- and sex-matched controls; age- and sex-matched uninephrectomized control rats on a high sodium diet; and rats that had received either aldosterone (ALDO) or angiotensin II (AII). Compared with controls, we found ACE binding (1) unchanged after 2 weeks of ALDO, but increased in the adventitia of intramural coronary arteries after 4 weeks, in keeping with the perivascular fibrosis that appeared in each ventricle; (2) markedly increased after 6 weeks of ALDO, where it not only involved coronary vessels but also microscopic scars that appeared in atria and ventricles; (3) increased in the coronary adventitia and sites of scarring, each of which were present 2 weeks after AII; and (4) markedly increased after 4 and 6 weeks of AII as fibrosis became more extensive.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗
PubMed1993

Angiotensin II and aldosterone receptor binding in rat heart and kidney: response to chronic angiotensin II or aldosterone administration.

Angiotensin II (AII) and mineralocorticoid receptors (MRs) have been identified in the mammalian heart and kidney. Their response to chronic elevations in circulating AII or aldosterone (ALDO) (or both) is unknown in either primary or secondary hyperaldosteronism. Nonendothelial angiotensin-converting enzyme (ACE) activity has been found in the fibrous tissue response that involves intramyocardial coronary arteries and microscopic scarring. Whether this tissue ACE could affect AII receptors and MRs in the area of myocardial fibrosis is likewise unknown. To address these questions, we monitored AII and MR binding in the rat heart and kidney after chronic AII or ALDO infusion. All receptor and MR binding were localized by in vitro autoradiography with 125I-[Sar1, Ile8]-labeled AII and [1,2,6,7 3H]-labeled ALDO, respectively. To characterize AII receptor subtypes, a type I antagonist (DuP753) or type II antagonist (PD 123177) was used. Four experimental groups were examined: unoperated, untreated, age- and sex-matched controls; age- and sex-matched uninephrectomized control rats receiving a high sodium diet; animals that received AII (9 micrograms/hr sc) for 2, 4, 6, or 8 weeks; and uninephrectomized rats on a high sodium diet that received ALDO (0.75 microgram/hr sc) for similar periods of time.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗
PubMed1993

[Study on the degradation kinetics of vitamin K3 powder].

The effect of temperature and humidity on the rate of discoloration and degradation of vitamin K3 powder was studied via accelerated test under isothermal, constant humidity and dark conditions. The photodegradation of vitamin K3 powder was studied under room temperature and constant humidity. The changes of color and concentration of vitamin K3 were monitored by diffuse reflectance spectroscopy and high performance liquid chromatography, respectively. At temperatures 50-90 degrees C and relative humidities 50-93%, the rate equation of discoloration is -dR/dt = KRR, that of degradation is d(c(o)-c)/dt = kc (c(o)-c)1/2, and that of photodegradation is -dR/dt = kp (Ro-R)-1, where Ro and R are initial relative reflectance and relative reflectance at time t, respectively, c(o) and c are initial concentration and concentration at time t, respectively, kR, kc and kP are apparent rate constants of discoloration, degradation and photodegradation, respectively. The general equation of the relationship between the apparent rate constant k, absolute temperature T and relative humidity RH is k = k' exp (-Ea/RT) exp (m' RH), where Ea is apparent activation energy, k' and m' are constants. Within the ranges of experimental temperatures and humidities, the average apparent activation energies of discoloration and degradation are 105.51 and 130.72 kJ/mol, respectively.

Color↗
PubMed1993

Decreased expression of manganese superoxide dismutase mRNA and protein after immortalization and transformation of mouse liver cells.

Altered levels of superoxide dismutase (SOD), the enzyme that scavenges toxic superoxide anion produced during normal metabolism or after oxidative insult, have been implicated in multistage carcinogenesis of both rodents and humans. Using a mouse liver cell model, we report here that after cellular immortalization, both copper- and zinc-containing superoxide dismutase (Cu,ZnSOD) and manganese superoxide dismutase (MnSOD) activities decreased dramatically and that cellular transformation further decreased MnSOD but not Cu,ZnSOD activity. Decreased enzyme activities seen in transformed cells (Tx) were due to decreased amounts of immunoreactive enzyme protein that results from decreased superoxide dismutase mRNA expression. This downregulation of gene expression may occur at the transcriptional level, as suggested by results with cycloheximide (Chx) and actinomycin D (AcD) treatments.

Animals↗
PubMed1993

[Comparative study on the anti-free-radical damage by vital energy-reinforcing method and blood-tonifying method].

A comparative study has been conducted on the anti-free-radical damage by the vital energy-reinforcing and blood-tonifying methods. The results shows that Sijunzi decoction and Siwu decoction can increase the vitality of SOD, accelerate the elimination of free-radical and inhibit the growth of LPO and MAO-B. This means that both these two methods help to delay senility and the vital energy-reinforcing one is more effective.

Aging↗