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Y P Sun

Publications and source records attributed to Y P Sun.

At least 37 records · Page 2Linked to original sources

Effects of L-arginine on atherogenesis and endothelial dysfunction due to secondhand smoke.

Secondhand smoke (SHS) and hypercholesterolemia increase cardiovascular risk. We hypothesized that L-arginine, the precursor of nitric oxide (NO), might protect against atherogenesis and endothelial dysfunction caused by SHS. The effects of L-arginine supplementation (2.25% solution ad libitum) and SHS (smoking chambers for 10 weeks) were examined in 32 hypercholesterolemic rabbits. Eight normal rabbits served as controls. Acetylcholine- and nitroglycerin-induced vasorelaxation was assessed in aortic rings precontracted with norepinephrine. Hypercholesterolemia increased intimal lesion area (P=0.012), reduced endothelium-dependent relaxation (P=0.009), and reduced basal (P=0.005) and stimulated (P<0.0005) production of NOs. SHS increased intimal lesion area (P=0. 01) norepinephrine-induced contraction (P=0.001) and reduced endothelium-dependent relaxation (P=0.02). SHS-induced increase in norepinephrine contraction was abolished by the inhibition of NO synthase and removal of endothelium. L-Arginine improved endothelium-dependent relaxation (P=0.001) and attenuated SHS-induced endothelial dysfunction (P=0.007) and atherogenesis (P=0. 001). Basal production of nitrogen oxides correlated inversely with intimal lesion area (r=-0.66; P<0.0005) and stimulated production of NOs correlated with endothelium-dependent relaxation (r=-0.66; P<0. 001). SHS causes endothelial dysfunction and increased adrenergic responsiveness and atherogenesis in hypercholesterolemic rabbits. Chronic dietary supplementation with the NO precursor L-arginine mitigates these effects. The adverse vascular consequences of SHS appear to be mediated via deleterious effects on endothelial function.

Animals↗

Calcitonin inhibits anterior pituitary cell proliferation in the adult female rats.

Previous studies have shown that CT-like immunoreactive peptide(s) (pit-CT) is synthesized by the anterior pituitary (AP) gland, and exogenously added salmon(s) CT inhibits PRL release and PRL gene transcription in cultured AP cells. Anti-sCT serum, which immunoreacts with pit-CT, stimulates PRL secretion, suggesting pit-CT is a physiologically relevant PRL-inhibiting hormone. Using proliferating cell nuclear antigen (PCNA) staining and 5-bromo-2'deoxyuridine (BrdU) incorporation into newly replicated DNA, the effect of calcitonin (CT) on cellular proliferation in the rat anterior pituitary gland (AP) was examined. CT significantly attenuated PCNA-immunopositive as well as BrdU-positive AP cell populations in dispersed rat AP cells. A second series of experiments tested the effects of CT on AP cell proliferation in vivo. OVX + E2 rats were injected with 200 microg CT (iv), the rats killed at various time points, and the APs were processed for BrdU staining. CT inhibited BrdU incorporation at all time points up to 15 h after the injection, and this inhibitory effect was reversed at later time points. The effect of CT was concentration dependent, and a maximal inhibition was observed 10 h after the CT injection. Subsequent experiments identified CT-responsive AP cell populations using double immunofluorescence for BrdU and either PRL or FSH. The number of BrdU-labeled lactotropes in the AP gland declined by 74% in the CT-treated rats. Neutralization of endogenous pit-CT by passive immunization with anti-sCT serum caused a 2-fold increase in AP cell proliferation. These results suggest an important role for the endogenous pit-CT in regulation of lactotrope population of the AP gland.

Animals↗

Expression of sperm Ca2+-activated K+ channels in Xenopus oocytes and their modulation by extracellular ATP.

Ionic fluxes across the sperm membrane have been shown to be important in the initiating process of sperm activation and gamete interaction; however, electrophysiological investigation of the ion channels involved has been precluded by the small size of the sperm, especially in mammalian species. In the present study sperm ion channels were expressed in Xenopus oocytes by injection of RNAs of spermatogenic cells isolated from the rat testes. The RNA-injected oocytes responded to ATP, a factor known to regulate sperm activation, with the activation of an outwardly rectifying whole-cell current which was dependent on K+ concentrations and inhibitable by K+ channel blockers, charybdotoxin (CTX) and tetraethylammonium (TEA). The ATP-induced current could be mimicked by a Ca2+ ionophore but suppressed by a Ca2+ chelator applied intracellularly, indicating a Ca2+ dependence of the current. Single-channel measurements on RNA-injected oocytes revealed channels of large conductance which could be blocked by CTX and TEA. Co-injection of germ cell RNAs with the antisense RNA for a mouse gene encoding slowpoke 'Maxi' Ca2+-activated K+ channels resulted in significant reduction of the ATP- and ionomycin-induced current. The expression of the 'Maxi' Ca2+-activated K+ channels in sperm collected from the rat epididymis was also confirmed by Western blot analysis. These results suggest that sperm possess Ca2+-activated K+ channels which may be involved in the process of sperm activation.

Amino Acid Sequence↗

Functional expression of a Ca2+-activated K+ channel in Xenopus oocytes injected with RNAs from the rat testis.

The present study investigated the feasibility of using Xenopus oocytes to express sperm ion channel by injection of RNAs extracted from the rat testis. The RNA-injected oocytes expressed an outwardly rectifying current which was dependent on K+ concentration and inhibitable by K+ channel blockers, charybdotoxin (CTX) and tetraethylammonium (TEA). The Ca2+ ionophore, ionomycin, could also stimulate current activation with similar current characteristics in the RNA-injected oocytes, suggesting the expression of a Ca2+-activated K+ channel. Immunolocalization indicated predominant Ca2+-activated K+ channel immunoreactivity associated with spermatogenic cells. Reverse transcriptase-polymerase chain reaction studies confirmed the expression of the Ca2+-activated K+ channel mRNA in isolated spermatogenic cells. Our results suggest that ion channels and/or receptors of spermatogenic cells could be investigated using the Xenopus oocyte as an expression system. The present study also suggests that sperm may possess a Ca2+-activated K+ channel which has been implicated in the process of sperm activation and gamete interaction.

Animals↗

Functional expression of P2U receptors in rat spermatogenic cells: dual modulation of a Ca(2+)-activated K+ channel.

Previous study has demonstrated functional expression of a sperm Ca(2+)-activated K+ channel in Xenopus oocytes injected with RNAs from the rat testes. Using the same expression system, the present study investigated the specific purinoceptor subtype involved in mediating the effect of extracellular ATP. The effect of ATP on an outwardly rectifying current, previously demonstrated to be mediated by a "Maxi" Ca(2+)-activated K+ channel, was compared to the current responses to different nucleotides using the two-electrode voltage-clamp technique. An order of relative effectiveness appeared to be UTP > ATP > ADP > adenosine, consistent with the pharmacological classification of P2U receptors. ATP was also found to exert an inhibitory effect on the Ca(2+)-activated K+ current, elicited by the Ca2+ ionophore ionomycin. A similar inhibitory effect was observed with UTP, again suggesting the involvement of P2U receptor. RT-PCR study also confirmed the expression of P2U receptor mRNA in isolated spermatogenic cells. The present results demonstrate the expression of P2U receptor and its dual role, both stimulatory and inhibitory, in the modulation of the Ca(2+)-activated K+ channel in spermatogenic cells. The present finding lends support to an important role of extracellular ATP in sperm functions.

Adenosine↗

In-utero and neonatal exposure to secondhand smoke causes vascular dysfunction in newborn rats.

OBJECTIVES: We sought to determine the effects of secondhand smoke (SHS) exposure on vascular reactivity in newborn and infant rats. BACKGROUND: Secondhand smoke exposure increases cardiovascular risk. Secondhand smoke-induced endothelial dysfunction has been demonstrated in older teenagers and young adults. We have previously shown in adult rabbits that SHS induces atherogenesis and endothelial dysfunction. The effects of SHS on vascular function in the offspring of SHS-exposed mothers and in infants are unknown. METHODS: In this study the effects of in-utero (21 days) and neonatal (28 days) exposure to SHS were examined in 80 rats, 4 weeks of age, in a 2-by-2 design study. Rats were exposed to sidestream smoke in smoking chambers. Aortic rings were excised and isometric force responses to phenylephrine, acetylcholine, A23187 and nitroglycerin were studied in organ baths. RESULTS: Neonatal SHS exposure reduced animal weight (p=0.009). In-utero exposure increased the sensitivity (decreased the EC50) of aortic rings to phenylephrine (p < 0.0005), as did neonatal exposure (p=0.01). Maximal contraction to phenylephrine was reduced by in-utero exposure (p=0.04). In-utero SHS exposure reduced maximal endothelium-dependent relaxation to acetylcholine (p=0.04) and increased the EC50 (p=0.05), suggesting impaired sensitivity to acetylcholine. In-utero exposure decreased the sensitivity (increased the EC50) to the endothelium-independent vasodilator nitroglycerin (p=0.003). CONCLUSIONS: Secondhand smoke has detrimental effects on vascular smooth muscle function in the newborn.

Acetylcholine↗

Antioxidant diet preserves endothelium-dependent vasodilatation in resistance arteries of hypercholesterolemic rabbits exposed to environmental tobacco smoke.

Environmental tobacco smoke (ETS) has been shown to impair endothelium-dependent vasodilation in vitro. This study was performed to investigate the effect of ETS on acetylcholine (ACh)-mediated blood pressure changes in vivo. Seventeen New Zealand White rabbits were fed a cholesterol diet (0.3%) for 13 weeks. Ten animals were exposed to ETS for 6 h/day, and seven animals were not exposed to ETS (non-ETS). Four of the ETS and three of the non-ETS-exposed rabbits received an antioxidant vitamin diet before and during their cholesterol diet for 21 weeks. Six rabbits served as healthy controls. To determine endothelium-dependent and independent blood pressure (BP) responses, BP was measured through a Tygon catheter, inserted into the right carotid artery at baseline and after each of three incremental intravenous doses of norepinephrine (NE; 1, 4, and 20 microg/kg), ACh (3.3, 10, and 30 microg/kg), and nitroglycerin (NTG; 1, 10, and 40 microg/kg). After NE, BP increases were significantly attenuated in the ETS group (p = 0.001) but not in animals receiving the antioxidant supplement. At both the middle and high ACh concentrations, ETS (p = 0.03 and p = 0.01, respectively) and hypercholesterolemia (p = 0.03 and p = 0.06, respectively) attenuated ACh-induced reductions in BP. At the highest ACh concentration, vitamins enhanced the reduction in BP (p = 0.002) and blocked the effect of ETS (p = 0.04). Neither ETS nor vitamins influenced NTG-induced decreases in BP. A combined antioxidant-vitamin diet can preserve endothelium-dependent vasodilatation in the hypercholesterolemic rabbit exposed to ETS.

Acetylcholine↗

Effects of antioxidant vitamins C and E on atherosclerosis in lipid-fed rabbits.

BACKGROUND: Antioxidant vitamins are hypothesized to help prevent atherosclerosis by blocking lipoprotein oxidation. We investigated the effects of dietary vitamins C and E on atherosclerosis in rabbits. METHODS AND RESULTS: Forty New Zealand male rabbits were divided into 4 groups: 0.3% cholesterol diet with (LV) and without vitamin (LC), and 0.5% cholesterol diet with (HV) and without vitamins (HC). The treated groups consumed 137 +/- 8 mg/day vitamin C and 80 +/- 4 mg/day vitamin E for 10 weeks. Vitamin treatment did not significantly affect serum lipids. Alpha-tocopherol values were significantly higher in both serum (mg/dl) and omental fat (microg/g) among the treated rabbits (3.9 +/- 0.5 and 31.6 +/- 2.1 for LV, 1.7 +/- 0.2 and 12.1 +/- 1.9 for LC, 5.6 +/- 0.8 and 51.3 +/- 9.3 for HV and 1.9 +/- 0.3 and 8.2 +/- 0.4 for HC; p < 0.001). Vitamin treatment did not affect the percent of surface lesions in the aorta and pulmonary artery (23.8 +/- 5.2 and 20.1 +/- 3.3% for LV, 19.8 +/- 5.6 and 23.2 +/- 3.5% for LC, 28.1 +/- 6.5 and 51.1 +/- 4.2% for HV and 32.4 +/- 5.5 and 43.7 +/- 3.9% for HC, respectively; p = 0.981 and p = 0.562. CONCLUSIONS: Although significantly higher values of alpha-tocopherol were found in both serum and omental fat, antioxidant vitamins C and E did not demonstrate a significant protective effect on atherosclerosis in lipid-fed rabbits during the 10-week study period.

Animals↗

Testosterone worsens endothelial dysfunction associated with hypercholesterolemia and environmental tobacco smoke exposure in male rabbit aorta.

OBJECTIVES: To assess the effects of interaction of sex hormones, hypercholesterolemia (HC) and environmental tobacco smoke (ETS) exposure on endothelium-dependent relaxation, we examined vascular reactivity in vitro in an animal model of atherogenesis. BACKGROUND: Animal and human studies indicate the presence of interactions between classic coronary artery disease risk factors and endothelium-dependent relaxation. Sex hormones have also been shown to influence release of endothelium-derived relaxing factor. METHODS: New Zealand White rabbits were randomized to receive either an HC diet (n = 8) or ETS exposure plus HC diet (n = 8). Eight rabbits receiving a normal diet, without exposure to ETS, served as the control group. The HC diet consisted of 3% soybean oil and 0.3% cholesterol by weight over 13 weeks. The source of ETS was sidestream smoke of 4 cigarettes/15 min, 6 h/day, 5 days/week over 10 weeks in a smoking chamber. Rabbits were killed, and fresh aortic rings were harvested and maintained in oxygenated Krebs solution in an organ bath at 37 degrees C. Rings were precontracted with norepinephrine and exposed to acetylcholine in increasing doses, and isometric tension was recorded. Rings were also exposed to physiologic concentrations (1 nmol/liter) of either 17-beta-estradiol, testosterone or progesterone before pre-contraction with norepinephrine and relaxation with acetylcholine. Endothelium-independent relaxation was studied using nitroglycerin. The surface area of the ring covered by lipids was measured by Sudan IV staining. RESULTS: HC and ETS significantly reduced endothelium-dependent relaxation (p = 0.01 and p < 0.0005, respectively) and caused atherogenesis (p < 0.0005 and p = 0.047, respectively) but did not affect endothelium-independent relaxation. Incubation with estradiol and estradiol plus progesterone did not influence endothelium-dependent relaxation. Testosterone reduced endothelium-dependent relaxation (p = 0.049) and augmented the endothelial dysfunction associated with ETS exposure and HC (p = 0.03). CONCLUSIONS: Both HC and ETS are atherogenic and impair endothelial function but do not affect endothelium-independent relaxation. Physiologic levels of estradiol and estradiol plus progesterone do not affect endothelium-dependent relaxation. Physiologic levels of testosterone impair relaxation and augment the endothelial dysfunction associated with ETS exposure and HC.

Animals↗

Effects of second-hand smoke and gender on infarct size of young rats exposed in utero and in the neonatal to adolescent period.

OBJECTIVES: We sought to assess the effects of second-hand smoke (SHS) and gender on infarct size in young rats exposed in utero or in the neonatal to adolescent period, or both. BACKGROUND: We previously demonstrated that exposure to SHS increases infarct size in a rat model of ischemia and reperfusion, with a dose-response relation. These results are consistent with epidemiologic studies demonstrating that SHS increases risk of death from heart disease. METHODS: Thirty-one pregnant female rats were randomly divided into two groups: those exposed to SHS and a control group (non-SHS). After 3 weeks, each rat had given birth to 10 to 12 rats. One hundred one neonatal rats were divided into four groups according to exposure to SHS in utero (SHSu) and randomized to SHS exposure in the neonatal to adolescent period (SHSna). After 12 weeks, all rats were subjected to 17 min of left coronary artery occlusion and 2 h of reperfusion. RESULTS: Birth mortality was higher in the SHSu group than in the non-SHSu group (11.9% vs. 2.8%, p < 0.001). Body weight of neonatal rats at 3 and 4 weeks in the two SHSu groups was lower than that of rats in the two non-SHSu groups (p < 0.001). Exposure to SHSna increased endothelin-1 levels in plasma (p = 0.001). In all 70 young rats who survived the neonatal period, infarct size (Infarct mass/Risk area x 100%) was greater in the SHSna groups than in the non-SHSna groups (p = 0.005) and in the male groups than in the female groups (p < 0.001). CONCLUSIONS: Exposure to SHS in the neonatal to adolescent period and male gender increased myocardial infarct size in a young rat model of ischemia and reperfusion. These results are consistent with epidemiologic studies demonstrating that SHS increases the health risk to neonates and adolescents.

Angiotensin II↗

Identification and expression of epidermal growth factor gene in mouse testis.

Epidermal growth factor (EGF) is produced primarily by Leydig cells of human testis. Expression of the EGF gene was assessed in mouse testis during the course of sexual maturation by the application of the RT-PCR method and the use of specific oligonucleotide primers. Testis EGF mRNA content increased with the developmental age of the mice, i.e., day 15 < day 30 < day 45 postnatal. The expression of the EGF gene appears to correlate with maturation of the testis and proliferation of Leydig-cells.

Animals↗

Development of the undulation pump total artificial heart.

The undulation pump is a small size continuous flow displacement type blood pump that has been developed for an artificial heart. Using undulation pumps, 2 types of implantable total artificial hearts (TAHs), the undulation pump TAH (UPTAH) type 1 (UPTAH 1) and UPTAH type 2 (UPTAH 2) were developed. Both UPTAHs were designed to be small enough to implant into the chest of a goat, the experimental animal. UPTAH 1 could be reduced in size to 75 mm in diameter and 78 mm in length. The weight was 520 g. UPTAH 2 could be reduced in size to 75 mm in diameter and 80 mm in length. The weight was 650 g. UPTAH 2 could be tested in an animal experiment using an adult female goat weighing 52.3 kg. The UPTAH 2 could be implanted successfully into the goat's chest with a good fit. The goat stood after the surgery and extubation and survived for 3 h and 40 min; thus, the potential of the UPTAH for a practical implantable TAH was demonstrated.

Animals↗

Chronic dietary L-arginine prevents endothelial dysfunction secondary to environmental tobacco smoke in normocholesterolemic rabbits.

Our goal was to determine whether environmental tobacco smoke causes endothelial dysfunction in the absence of hypercholesterolemia and whether such an effect can be prevented by supplementation with L-arginine. Environmental tobacco smoke exposure is associated with an increase in coronary artery disease events and mortality. We have previously demonstrated that environmental tobacco smoke causes endothelial dysfunction and atherosclerosis in rabbits with diet-induced hypercholesterolemia and atherosclerosis and that chronic dietary L-arginine supplementation prevents this. The effects of L-arginine supplementation (2.25% solution ad libitum) and environmental tobacco smoke (smoking chambers for 10 weeks) were examined with a 2 x 2 design in 32 rabbits fed a normal diet. Acetylcholine, calcium ionophore A23187, and nitroglycerin-induced vasorelaxation were assessed in aortic rings precontracted with phenylephrine. Endothelial L-arginine levels were measured by chromatography. Chronic L-arginine supplementation increased serum (P < .001) and endothelial (P = .003) L-arginine levels. Environmental tobacco smoke reduced endothelium-dependent acetylcholine-induced relaxation, and L-arginine blocked this adverse effect (P = .04). Environmental tobacco smoke tended to increase phenylephrine-induced contraction (P = .06). Neither environmental tobacco smoke nor L-arginine influenced A23187-induced relaxation nor endothelium-independent nitroglycerin-induced relaxation. Endothelial dysfunction secondary to environmental tobacco smoke may occur in the absence of diet-induced hypercholesterolemia and atherosclerosis. Chronic dietary supplementation with a nitric oxide donor such as L-arginine offsets the endothelial dysfunction associated with environmental tobacco smoke in normocholesterolemic rabbits, possibly through substrate loading of the nitric oxide pathway.

Animals↗

[Effect of jiangtangkang on blood glucose, sensitivity of insulin and blood viscosity in non-insulin dependent diabetes mellitus].

OBJECTIVE: To study the hypoglycemic effect of Jiangtangkang (JTK), a Chrysanthemum product and its influence on sensitivity of insulin in non-insulin dependant diabetes mellitus (NIDDM). METHODS: Newly discovered (71 cases) and poorly controlled (117 cases) NIDDM were divided to JTK, 8 g each time, 3 times per day, and the control (Glibenclazide in newly discovered, no treatment in poorly controlled) group respectively. RESULTS: After 2 months of treatment, the fasting blood glucose (FBG), postprandial blood glucose (PBG), glucosylated hemoglobin (GHb) improved remarkably and insulin of plasma remained unchanged in JTK group, their blood viscosity and triglyceride decreased after 6-month reatment, the FBG, PBG lowered in the control group while their viscosity and lipids were unaffected. Insulin tolerance test on newly discovered NIDDMs showed an increased sensitivity to insulin, their serum chromium elevated, and the urinary albumin in poorly controlled persons lowered significantly. CONCLUSIONS: JTK might improve the sensitivity to insulin and decrease the blood viscosity in NIDDM.

Adult↗

The utero-placental circulation, eugenics and the prevention and treatment of high risk pregnancies.

Through systematic experimental and clinical studies, the physiological regulation of utero-placental circulation and the relation of the disturbance in this acirculation to pathogenic mechanisms of high risk pregnancies-Intrauterine Growth Retardation (IUGR) and Pregnancy-induced hypertension (PIH) were explored. The pharmacological effects and mechanism of a Chinese herbal medicine-Qingxintong in improving, the utero-placental circulation and the therapeutic efficacy in treatment of IUGR and PIH, both accompanied by disturbance of utero-placental circulation, were investigated as well.

Acetophenones↗

Is the reduction of myocardial infarct size by dietary fish oil the result of altered platelet function?

Sprague-Dawley rats fed a diet containing 12% fish oil (18% eicosapentaenoic acid [EPA] and 12% docosahexaenoic acid [DHA]), for 1 week (group I, n = 9) or 8 weeks (group III, n = 42) and controls (group II, n = 8; group IV, n = 36, respectively) were subjected to 35 minutes of left coronary artery occlusion followed by 120 minutes of reperfusion. Compared to the controls, infarct size was significantly reduced in group III (15% +/- 2%, n = 42 vs 34% +/- 4%, n = 36; p < 0.001; infarct mass/risk area x 100%), but no change in group I (39% +/- 5%, n = 9 vs 35% +/- 5%, n = 8; p = not significant). Bleeding time was prolonged in group III (290 +/- 73 sec) compared to group IV (99 +/- 10 sec, p = 0.015). Omega-3 fatty acid (EPA and DHA) levels in platelets were significantly higher in the rats fed 8 weeks of fish oil (group III) compared to the controls (group IV) and the rats fed 8 weeks of fish oil and then a regular diet until bleeding time normalized (group V) (7.2% +/- 0.6% vs 1.2% +/- 0.2% and 4.9% +/- 0.5%; 3.8% +/- 0.7% vs 1.8% +/- 0.3% and 2.8% +/- 0.6%, p < 0.001 and 0.05, respectively). These data indicate that long-term (8 weeks) dietary fish oil supplementation significantly reduces infarct size; short-term (1 week) does not. This reduction of infarct size appears to correlate with altered platelet function and EPA and DHA levels in platelets.

Animals↗

Effects of etidronate and lovastatin on the regression of atherosclerosis in cholesterol-fed rabbits.

Eighty New Zealand rabbits in eight groups (10 each) were fed a 0.5% cholesterol diet for 12 weeks. One group served as a control and was sacrificed at the end of 12 weeks. Seven other groups were shifted to a normal diet and received a drug(s) or placebo for the second 12 weeks. The high dose of etidronate (3 mg/kg/day) with lovastatin (6 mg/kg/day) significantly reduced the percent of aortic atherosclerotic lesions [56 +/- 21 vs. 77 +/- 17% (mean +/- SD), p < 0.05] in the regression study. Compared to the control groups for etidronate and lovastatin, the high or low dose (0.15 mg/kg/day) of etidronate significantly reduced aortic standardized plaque volume per unit (18.7 +/- 7.9 or 18.8 +/- 9.1 vs. 28.4 +/- 11.8 mm.%, p < 0.05). Lovastatin reduced pulmonary artery maximum plaque thickness (0.13 +/- 0.10 vs. 0.23 +/- 0.11 mm, p < 0.05). There were no differences in serum lipid and calcium levels in the control and treated groups. The high dose of etidronate inhibited bone mineralization as expected, whereas the low dose of etidronate did not. These data suggest that etidronate with lovastatin can regress aortic atherosclerosis in the cholesterol-fed rabbit placed on a normal diet.

Animals↗