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Biomedical subjects

H He

Publications and source records attributed to H He.

At least 235 records · Page 13Linked to original sources
PubMed1994

Growth stimulation followed by growth inhibition in livers of female rats treated with ethinyl estradiol.

Ethinyl estradiol (EE) is a strong promoter of hepatocarcinogenesis in female rats. A common effect shared by many non-genotoxic hepatic promoters is the stimulation of hyperplastic growth. However, studies by others with several hepatic promoters have shown that following an initial, transient increase in liver growth, continued exposure causes an inhibition in basal and/or induced growth. We have shown that EE also causes an initial, transient increase in hepatocyte proliferation (Carcinogenesis, 7, 2007-20014, 1986). The objective of the investigation reported here was to determine whether chronic EE treatment also becomes inhibitory to basal and/or induced liver growth. Female Lewis rats were treated with EE at 2.5 and 5.0 micrograms/rat/day using time-release tablets. Seven days prior to sacrifice, the rats were implanted with osmotic minipumps containing bromodeoxyuridine (BrdU) to allow the cumulative labeling of replicating hepatocytes. At sacrifice, liver tissue was fixed, sectioned and the percent labeled hepatocyte nuclei determined by immunohistochemistry. The results of these experiments revealed that, as expected, during the first 7 days of treatment, EE increased hepatocyte proliferation. However, after 28 and 42 days of EE treatment, the basal level of liver growth was dramatically inhibited. Thus, hepatocyte nuclear labeling indices, compared to controls, were reduced by 72 and 88% after 28 and 42 days of treatment respectively. An analysis of 125I-labeled EGF binding to isolated liver membranes revealed that EGF receptor levels decreased during the initial period of growth, but had returned to control levels by day 21 when replication had ceased. In another experiment, rats were treated with EE at 5.0 micrograms/rat/day for 21 days; control rats received placebo time-release tablets. At the end of that time, the rats were surgically partially hepatectomized and the level of subsequent regenerative DNA synthesis was determined using [3H]thymidine administered 2 h prior to sacrifice 24, 48, 72 and 96 h later. The results showed that EE caused an inhibition of regenerative growth. While at each time point the level of DNA synthesis in EE-treated rats was not significantly less than in corresponding controls, statistical analysis indicated that overall, EE caused a significant reduction in liver growth. The results of these studies demonstrate that chronic EE treatment leads to the appearance of a mitosuppressed state in the liver which is characterized by reduced cell turnover and decreased growth responsiveness.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Biological activities of two fungistatic antibiotics produced by Bacillus cereus UW85.

Cultures and culture filtrates of Bacillus cereus UW85 suppress damping-off of alfalfa caused by Phytophthora medicaginis. We studied the role in disease suppression of two antibiotics from culture filtrates of UW85 that reversibly inhibited growth of P. medicaginis. We purified the two antibiotics by cation-exchange chromatography and high-voltage paper electrophoresis and showed that one of them, designated zwittermicin A, was an aminopolyol of 396 Da that was cationic at pH 7.0; the second, designated antibiotic B, appeared to be an aminoglycoside containing a disaccharide. Both antibiotics prevented disease of alfalfa seedlings caused by P. medicaginis. Purified zwittermicin A reversibly reduced elongation of germ tubes derived from cysts of P. medicaginis, and antibiotic B caused swelling of the germ tubes. Mutants generated with Tn917 or mitomycin C treatment were screened either for antibiotic accumulation in an agar plate diffusion assay or for the ability to suppress damping-off disease of alfalfa. Of 2,682 mutants screened for antibiotic accumulation, 5 mutants were substantially reduced in antibiotic accumulation and disease-suppressive activity. Of the 1,700 mutants screened for disease-suppressive activity, 3 mutants had reduced activity and they accumulated less of both antibiotics than did the parent strain. The amount of antibiotic accumulated by the mutants was significantly correlated with the level of disease suppression. Addition of either zwittermicin A or antibiotic B to alfalfa plants inoculated with a culture of a nonsuppressive mutant resulted in disease suppression. These results demonstrate that B. cereus UW85 produces two fungistatic antibiotics that contribute to suppression of damping-off disease of alfalfa.

Anti-Bacterial Agents↗
PubMed1994

Nitric oxide may participate in V2 vasopressin-receptor-mediated renal vasodilation.

Using pentobarbital-anesthetized euvolemic dogs, we investigated whether vasopressin V2-receptor stimulation induced renal vasodilation and whether nitric oxide (NO) had a role in the process. Intrarenal infusion of arginine-vasopressin (AVP) resulted in renal vasoconstriction with pressor response. After preadministration of a V1-receptor antagonist, however, intrarenal infusion of AVP caused an increase in renal blood flow (RBF) without pressor action, indicating renal vasodilation. This renal vasodilation was not observed when we infused AVP after-simultaneous pretreatment with V1- and V2-receptor antagonists. Even in the absence of the V2-receptor antagonist, this renal vasodilation was attenuated by intrarenal infusion of L-NG-nitroarginine (L-NNA). Concomitant infusion of L-arginine prevented the inhibitory effect of L-NNA on renal vasodilation induced by intrarenal infusion of AVP in the presence of the V1-antagonist. These data indicate that the renal vasodilation caused by intrarenal infusion of AVP in the presence of a V1-antagonist was mediated by V2-receptor stimulation, and the inhibitory effect of L-NNA on V2-receptor-mediated renal vasodilation was attributed to its inhibitory effect on NO synthesis, suggesting that NO may participate in V2-receptor-mediated renal vasodilation.

Animals↗
PubMed1994

Effects of Panax notoginseng saponins on receptor-operated Ca2+ channels in vascular smooth muscle.

The effects of saponins of Panax notoginseng (PNGS) on the alpha-adrenoceptor agonists-induced contractile responses and Ca2+ movement were studied in dog mesenteric artery (MA) and saphenous vein (SV). PNGS reduced the contractions and the 45Ca influx (from 0.36 +/- 0.03 to 0.14 +/- 0.05 mumol.g-1 wet strip) induced by phenylephrine (Phe) without effect on KCl-induced contraction and 45Ca influx which were nearly completely inhibited by nifedipine 0.1 mumol.L-1. PNGS did not change the 45Ca efflux induced by Phe and the Kd value (from 0.76 +/- 0.04 to 0.72 +/- 0.15 nmol.L-1) for [3H]prazosin binding on the microsomal membrane isolated from MA. Our results indicate that PNGS selectively inhibits Ca2+ entry through receptor-operated Ca2+ channel.

Adrenergic alpha-Agonists↗
PubMed1994

Thyroid hormone regulation of Na,K-ATPase alpha 2 gene expression in cardiac myocytes.

Thyroid hormone (T3) stimulates Na,K-ATPase activity and alpha and beta subunit mRNA abundances in myocardial cells in vivo and in vitro. In this study, we used transient transfection and nuclear run-on assays to determine whether T3 regulates the transcription rate of the Na,K-ATPase alpha 2 subunit gene. Primary cultures of neonatal rat cardiac myocytes were incubated with 100 nM T3 for 1, 3, and 6 d, and alpha 2 mRNA levels were measured by Northern blot hybridization analysis. There was no change in the abundance of alpha 2 mRNA by 1 d of T3 treatment, whereas a two- and threefold increase in alpha 2 mRNA was evident when cells were exposed to T3 for 3 and 6 d, respectively. A portion of the rat alpha 2 gene containing 1700 base pairs (bp) of 5'-flanking DNA sequence was isolated and fused to the firefly luciferase gene. Transient transfection experiments utilizing this chimeric gene showed no T3 trans-activation of reporter gene activity either in the absence or presence of cotransfected beta 1 or alpha 1 isoforms of rat T3 receptor (T3R). In contrast, cotransfection of T3R facilitated a strong stimulation of luciferase activity driven by a construct containing a single copy of a palindromic T3 response element (TRE). Nuclear run-on analysis indicated that the rate of transcription of the endogenous alpha 2 gene was enhanced 1.2-fold at 3 d of T3 treatment, and was not regulated at either 1 or 6 d. These results indicate that the T3-dependent increase in alpha 2 mRNA content at 6 d is mediated at a post-transcriptional level. Unexpectedly, we observed a T3-dependent three-to sixfold repression of alpha 2/luciferase expression in cardiac myocytes cotransfected with T3R. Deletion analysis of the 5' end of the alpha 2 gene revealed a negative TRE between nucleotides -354 and -100.

Animals↗
PubMed1994

A north-south comparison of blood pressure and factors related to blood pressure in the People's Republic of China: a report from the PRC-USA Collaborative Study of Cardiovascular Epidemiology.

OBJECTIVES: To compare blood pressures in northern (Beijing) and southern (Guangzhou) Chinese population samples aged 35-54 years, males and females, urban and rural, and to assess the role of blood pressure-related traits in explaining north-south differences. DESIGN: Cross-sectional surveys were conducted in 1983-1984 of northern and southern populations employed in industry (urban) or farming (rural). METHODS: In the north samples were selected from the Capital Iron and Steel Complex (urban) and Shijingshan district (rural); in the south samples from the Guangzhou Shipyard (urban) and Panyu County (rural) were used. RESULTS: The number of subjects surveyed in north and south were 4706 and 4179, respectively: 1500 and 1052 urban males, and 717 and 914 rural males; and 1300 and 1061 urban females, and 1189 and 1152 rural females, respectively. Average systolic (SBP) and diastolic (DBP) blood pressures, were consistently higher in the north than in the south. SBP and DBP were significantly and independently related to age, body mass index, heart rate, use of antihypertensive drugs, serum triglycerides level, alcohol use (males only) and inversely to cigarette smoking. Northerners were older, taller, heavier and had higher body mass index and triglycerides level than southerners. With adjustment of SBP and DBP for blood pressure-related traits, north-south blood pressure differences decreased, but remained significant for urban males, rural males and rural females, with sizeable differences for rural samples in particular. CONCLUSIONS: North-south differences in blood pressure in these samples are accounted for only partly by north-south differences in the cited blood pressure-related traits. The role of other traits requires assessment.

Adult↗
PubMed1994

Effects of CV-11974 on renal haemodynamics and renal function in dogs.

The effects of CV-11974, a nonpeptide angiotensin II (Ang II) receptor antagonist, on renal haemodynamics and function were examined in pentobarbital-anaesthetised dogs to evaluate the physiological role of endogenous Ang II in regulating renal haemodynamics and urine formation. Intrarenal infusion of CV-11974 (1 microgram/kg/min) increased renal blood flow (RBF), glomerular filtration rate (GFR), urine flow, and urinary electrolyte excretion (Na and K), with no change in mean arterial pressure (MAP). In another group of dogs, intrarenal infusion of CV-11974 (1 microgram/kg/min) increased the fractional excretion of sodium, the fractional proximal excretion of sodium, and the fractional distal excretion of sodium. CV-11974 did not affect the linear relationship between the free water reabsorption rate (TCH2O) and osmolar clearance (Cosm). These results suggest that endogenous Ang II may play an important role in regulating renal haemodynamics and stimulating sodium reabsorption. Our data indicates that endogenous Ang II may stimulate sodium reabsorption at the proximal and the distal portions of the tubule, with the exception of the medullary portion of the ascending limb of Henle.

Anesthesia↗
PubMed1994

[Chemical components of Trachelospelmun jasminoides (Lindl.) Lem. var. heterophyllum Tsiang].

Five kind of crystal products were isolated from the methyl alcohol extract of Trachelospelmum jasminoides var. heterophyllum. By using chemical analysis and spectrogrophical identification, four of these five products were proved to be arctigenin-4'-beta-gentiobiosid,tracheloside and two kinds of optical isomer of beta-tracheloside. The last two were found in this genus for the first time.

4-Butyrolactone↗
PubMed1994

[Longitudinal surveillance of chloroquine resistance of Plasmodium falciparum after cessation of medication in south Yunnan].

The resistance of P. falciparum to chloroquine was assayed by in vitro microtest in 1981 and after cessation of medication in 1984, 1988-1990 and 1992 in south Yunnan Province of China. The resistance rates were 97.4% (38/39), 100% (25/25), 96.1% (73/76) and 93.7% (59/63), respectively; ID50 were 170, 132, 125 and 110 nmol/L; ID95 were 1,000, 740, 707 and 576 nmol/L; mean dosages for complete inhibition of schizont formation were 55.4, 46.7, 45.8 and 35.4 (pmol/well). A comparison of the results in 1981, 1984, 1988-1990 and 1992, the resistance rate showed no marked change, ID50 dropped 22.3% (P < 0.05), 26.4% (P < 0.05) and 35.3% (P < 0.01); ID95 declined 26.0% (P < 0.05), 29.3% (P < 0.05) and 42.2% (P < 0.01); mean dosage of inhibition dropped 15.7% (P > 0.05), 17.3% (P < 0.05) and 36.1% (P < 0.01). The results show that the extent of resistance in chloroquine-resistant P. falciparum to chloroquine in south Yunnan has been declined markedly, indicating that coresistance was variable and dropped along with the declining of drug pressure.

Animals↗
PubMed1994

Involvement of G proteins in the effect of insulin-like growth factor I on gonadotropin-induced rat granulosa cell differentiation.

Insulin-like growth factor I (IGF-I) promotes gonadotropin-induced granulosa cell differentiation and proliferation. In order to investigate whether guanine nucleotide binding proteins (G proteins) may be linked, directly or indirectly, to some of the actions of IGF, the effects of cholera toxin (CT) and pertussis toxin (PT) on the enhancement by IGF-I of PMSG (pregnant mare serum gonadotropin)-induced rat granulosa cell differentiation have been studied. This was done by the determination of progesterone production, aromatase activity and cAMP accumulation after a 48 h incubation with PMSG, IGF-I and PMSG plus IGF-I in cells treated with either CT or PT. Both CT and PT treatment stimulated PMSG-induced progesterone production in granulosa cells after 48 h of culture with PMSG. CT treatment also stimulated aromatase activity in cells treated with PMSG and increased cAMP secretion under basal conditions (untreated cells) and in PMSG treated cells. Both CT and PT increased the stimulation by IGF-I of PMSG-induced progesterone production after 48 h of culture with PMSG plus IGF-I. Furthermore, CT augmented the enhancement by IGF-I of PMSG-induced aromatase activity and cAMP accumulation. In the absence of PMSG, CT did not increase steroidogenesis either alone or in the presence of IGF-I within the time frame studied even though CT was able to stimulate cAMP accumulation in untreated and IGF-I treated cells. These results suggest that G proteins have a role in the signalling cascade involved in gonadotropin-induced granulosa cell differentiation measured as PMSG-mediated steroidogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effects of EXP3174, a non-peptide angiotensin II receptor antagonist, on renal hemodynamics and renal function in dogs.

We examined the effects of intrarenal infusion of EXP3174, a non-peptide angiotensin II receptor antagonist, in order to evaluate the physiological role of endogenous angiotensin II in regulating renal hemodynamics and urine formation and to assess the possibility of a tubular site(s) of action of endogenous angiotensin II in anesthetized dogs. Intrarenal infusion of EXP3174 at 15 micrograms/kg per min caused increases in renal blood flow (RBF), glomerular filtration rate (GFR), urine, flow and urinary electrolyte excretion. The lower dose of EXP3174 (0.5 micrograms/kg per min) did not change mean arterial pressure, RBF and GFR, but did increase urine flow. The fractional excretion of sodium, the fractional proximal excretion of sodium and the fractional distal excretion of sodium increased with lower doses of EXP3174 infusion. EXP3174 did not affect the linear relationship between the free water reabsorption rate and osmolar clearance. These data suggest that endogenous angiotensin II plays a significant role in regulating renal hemodynamics and urine formation and endogenous angiotensin II stimulates sodium reabsorption in the proximal and the distal portions of the tubules, with the exception of the medullary portion of the ascending limb of Henle.

Angiotensin II↗
PubMed1993

Beta-adrenergic receptor-mediated release of norepinephrine in the human forearm.

Because of difficulties in separating the systemic from local effect, the role of presynaptic beta 2-adrenergic receptors in facilitating the neural release of norepinephrine has not been defined previously in humans in vivo. To determine whether stimulation of presynaptic beta-receptors alters local release of norepinephrine, we examined the effects on norepinephrine kinetics of 60 and 400 ng/min intra-arterial isoproterenol in seven healthy male volunteers. Isoproterenol, 60 ng/min, increased forearm norepinephrine spill-over sixfold from a baseline spillover of 0.45 +/- 0.08 to 2.89 +/- 0.69 ng/min (p < 0.01), whereas 400 ng/min isoproterenol increased forearm norepinephrine spillover to 13.25 +/- 2.49 ng/min (p < 0.005), a 29-fold increase above baseline. Coinfusion of 20 to 40 micrograms/min propranolol with 400 ng/min isoproterenol in four subjects significantly attenuated the isoproterenol-induced increase in local norepinephrine spillover to 2.09 +/- 0.92 ng/min (p < 0.05 versus 400 ng/min isoproterenol). This study shows that presynaptic beta-adrenergic receptors facilitate local release of norepinephrine in vivo in humans.

Adult↗
PubMed1993

Clinical evaluation of rapid serodiagnosis of pulmonary tuberculosis by ELISA with cord factor (trehalose-6,6'-dimycolate) as antigen purified from Mycobacterium tuberculosis.

Immunoglobulin G (IgG) antibodies against purified cord factor (trehalose-6,6'-dimycolate) prepared from Mycobacterium tuberculosis H37Rv were determined by enzyme-linked immunosorbent assay (ELISA), and its diagnostic usefulness was evaluated. Serum specimens from 65 patients with active pulmonary tuberculosis, 58 patients with inactive pulmonary tuberculosis, 36 patients with diseases other than tuberculosis, and 66 healthy adults were examined. Patients with active pulmonary tuberculosis showed significantly higher titers of IgG antibodies against cord factor than did other groups (p < 0.001). The antibody titer greater than 0.29 in absorption difference (492 to 630 nm) of 160-times diluted serum was set as positive in ELISA. For patients with active and untreated pulmonary tuberculosis, the ELISA had a sensitivity of 81% and a specificity of 96%. From these results, it was concluded that the detection of IgG antibodies against cord factor is useful for serodiagnosis of active pulmonary tuberculosis. It was also indicated that the anticord factor antibody titers decline to the normal level as a result of antituberculosis chemotherapy.

Adult↗
PubMed1993

[A study on risk factors and control of neonatal tetanus during 1975-1990 in Yichang City].

Retrospective survey on the mortality of 21 cases of neonatal tetanus during 1975-1990 and their case-control study on death risk factors were reported in Yichang City. Surveillance and control of neonatal tetanus were emphasized on suburbs. Serological survey of tetanus antibody in women aged 15 to 40 and mothers and their newborn babies were carried out. The protective rate was 3.75% (GMT = 0.0014 IU/ml). The result showed that tetanus antibody in the women of childbearing age was at the lowest level. There was a significant positive correlation through vertical transmission between mothers and their newborn babies (r = 0.7096, P < 0.0005). And the successful immunization in 65 pairs of children was 100%. It was suggested that we should consolidate EPI and promote maternal and child health plan and a primary-health-care program in Yichang City.

Adolescent↗
PubMed1993

Development of a sensitive and specific radioimmunoassay for benztropine.

A benztropine RIA based on polyclonal antisera raised in New Zealand white rabbits has been developed. The drug-protein conjugates employed had a variety of moles of benztropine hemisuccinate coupled per mole of protein (bovine serum albumin or bovine thyroglobulin). Six antisera were developed and the one with the highest titer was further evaluated for its cross reactivity to N-desmethylbenztropine (4%) and the antipsychotic agents fluphenazine, flupenthixol, chlorpromazine, and haloperidol (all < 1%). The selected antiserum demonstrated sufficient sensitivity to measure benztropine from 0.156 to 100 ng/mL plasma in a 200-microL plasma sample, with a mean CV of < 6%. The RIA was applied to the analysis of steady-state plasma samples obtained from patients undergoing treatment with benztropine and plasma samples obtained from human volunteers and dogs orally dosed with the drug. Both the human and dog plasma samples, when analyzed after hydrolysis with beta-glucuronidase/sulfatase, demonstrated increments in benztropine concentrations, suggesting the drug may be undergoing biotransformation to phase II metabolite(s). In addition, when benztropine was selectively extracted from the unhydrolyzed plasma samples, there was a significant decrease in drug level, which further suggested that the antiserum cross reacted with phase II metabolite(s). The shape of the plasma concentration versus time profile obtained from the dog studies suggested that the drug might also undergo enterohepatic recycling.

Animals↗
PubMed1993

[Mapping of the transforming gene by fluorescence in situ hybridization].

A transforming gene of human nasopharyngeal carcinoma was cloned from Chinese nasopharyngeal carcinoma cell line CNE2. This gene was different from a number of known oncogenes as was reported previously. The NPC transforming gene was 16kb in size, and the Alu negative 2.8kb fragment was cloned into pSP70 plasmid. Linearized Tx pSP70 recombinant plasmid was nick translated in the presence of biotin-11-dUTP, incubated with an excess of sonicated human DNA, and used as a probe for fluorescence in situ hybridization. Signals of hybridization were detected by successive treatments with FITC-labeled avidin. 57% of grains were located on chromosome 8; 51.8% of them were mapped to the 8q23-->8q24.1 region of chromosome 8's. The Tx gene, therefore, could be assigned to the band 8q23-->8q24.1.

Chromosome Mapping↗
PubMed1993

[New method for selectivity optimization in thin layer chromatography and its application in pharmaceutical analysis].

A new experimental design method named the step climbing method (SCM), as well as a new global criterion (NRC), are proposed for the selectivity optimization of thin layer chromatography. The method offers chromatographers a convenient means to decide the optimum developer composition for thin layer chromatography. The principle of the method is described, and examples of applications in pharmaceutical analysis are given to certify the feasibility of the method. Clearly, it may also be used for the selectivity optimization in high performance liquid chromatography.

Cephalothin↗