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Y H Chu

Publications and source records attributed to Y H Chu.

At least 37 records · Page 2Linked to original sources
PubMed1993

A convenient procedure for transfer blotting of coomassie blue stained proteins from PAGE gels to transparencies.

Proteins stained with Coomassie Brilliant Blue I were transferred effectively by blotting from polyacrylamide gel electrophoresis (PAGE) gels to transparencies of the type used in plain-paper copiers. The details of the original electropherogram were retained on transfer and did not fade over a period of three years. Both the protein and the associated dye transfer; however, protein does not transfer in the absence of dye. Protein patterns present in several types of gels--sodium dodecyl sulfate (SDS)-PAGE, non-denaturing PAGE, isoelectric focusing PAGE and SDS-agarose--all transferred successfully after staining with dye 1. Proteins visualized with other organic dyes such as Fast Green FCF 2, Uniblue A 3 and Procion Blue MX-R 4 also transferred, but proteins stained with Stains-all 5 or silver did not. This transfer provides a simple, economical way to preserve data from slab gel electrophoresis and a convenient method to display data using an overhead projector. The blotted transparencies are also excellent substrates for use with gel scanning densitometers.

Coloring Agents↗
PubMed1992

[The blood schizontocidal effects of pyronaridine, amodiaquine, mefloquine and qinghaosu on mice infected with Plasmodium berghei].

The asexual stages of P. berghei ANKA were completely eliminated as revealed in a "4-day suppressive test" with the daily dose of pyronaridine 12.5 mg base/kg or amodiaquine 25 mg base/kg. Mefloquine 25 mg base/kg and qinghaosu 100 mg/kg though exerted obvious suppressive effect, the cure rates were only 50% and 0%, respectively. In treating chloroquine-sensitive P. berghei ANKA strain pyronaridine exhibited the best therapeutic activity, which was followed by amodiaquine, mefloquine and quinghaosu. In treating moderately chloroquine-resistant P. berghei NS line the cure rate of pyronaridine 12.5 mg/kg.d x 4 was 70%, but none of the 10 infected mice from any group was cured by amodiaquine 100 mg/kg.d, mefloquine 100 mg/kg.d or qinghaosu 200 mg/kg.d. Though the latter 3 drugs showed prominent suppressive effects, parasitemia remained positive or recrudesced after dosing. We demonstrate that parasites resistant to chloroquine had cross resistance to amodiaquine, mefloquine and inghaosu at various degrees. Amodiaquine 100 mg/kg.d, mefloquine 100 mg/kg.d and qinghaosu 200 mg/kg.d exhibited no obvious suppressive activity on highly pyronaridine-resistant line of P. berghei, indicating the existence of cross resistance to pyronaridine.

Amodiaquine↗
PubMed1992

Comparison of effects of pyronaridine, amodiaquine, mefloquine and qinghaosu on rodent malaria.

Blood schizontocidal effect of antimalarials were compared by 4-day suppressive test with an extended observation period of 31 days. On a drug-sensitive Plasmodium berghei ANKA strain, pyronaridine (PND) exhibited the best effect, followed by amodiaquine (ADQ), mefloquine (MFQ), and qinghaosu (QHS). On a moderately chloroquine-resistant P. berghei NS line, the order of effects was the same, PND greater than ADQ greater than MFQ greater than QHS. On a highly pyronaridine-resistant P. berghei RP line, ADQ, MFQ and QHS showed cross resistance with PND.

Amodiaquine↗
PubMed1991

[Rediffusion system and cuff pressure of Brandt's endotracheal tube].

During anesthesia increase of the endotracheal cuff pressure might be caused by anesthetic gases used, especially nitrous oxide (N2O), which easily diffuses into the cuff. In 1983, Brandt developed a blocking system which is called Rediffusion System. The principle of Rediffusion System is to make use of an enlarged pilot balloon to facilitate the removal of nitrous oxide which has diffused into the cuff during anesthesia. This study was designed to test and verify the function of Brandt tube's Rediffusion System during anesthesia using nitrous oxide as an anesthetic. Twenty four patients (age 19-82 yr; ASA physical status I-III) who underwent surgery under general anesthesia were allocated into three groups. For endotracheal intubation, in group I (n = 11) and group II (n = 5), Mallinckrodt Brandt tubes respective of internal diameter (ID) = 7 mm and ID = 8 mm were used, and in group III (n = 8) Portex Blue-line tubes with ID = 7 mm was used. Anesthesia was maintained with N2O, isoflurane, and oxygen and the FiN2O was kept around 50%. The cuff pressure was measured at the intervals of 30 min for 3 h. There were no significant differences of initial cuff volumes between group I and group II, but the initial cuff volumes of Portex blue-line tube were significantly larger than Brandt tubes at desired pressure level. Cuff pressures increased as the duration of anesthesia lengthened in all types of endotracheal tubes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Effects of antiestrogenic drug tamoxifen on human placental secretion of progesterone and human chorionic gonadotropin during early gestation].

Placental villus tissue obtained from pregnant women of 6 to 7 weeks was cultured in vitro for four days, with or without addition of tamoxifen (Tam), an antiestrogenic drug. The levels of both progesterone (P) and human chorionic gonadotropin (hCG) in culture medium collected every day were measured by using radio-immuno assay, so as to observe the effects of Tam on the secretion of P and hCG by villus tissue as well as the time course of these effects. The experimental results showed that the levels of both P and hCG in the culture medium collected on the 3rd and 4th days in the Tam-treated group were significantly lower than those in the control group, indicating that Tam could have a direct inhibitory effect on the secretory function of the placental villus tissue during early pregnancy. The slow onset of the inhibitory effect was in correspondence with the clinical observation that the early pregnancy terminating effect of PGS would be potentiated after 4-5 days of Tam medication. In addition, this inhibitory effect of tamoxifen on the placental secretory function was suggested to be associated with a decrease in the responsiveness of placental tissue to GnRH.

Chorionic Gonadotropin↗
PubMed1990

[The inhibitory effect of disodium cromoglycate on substance P sensory nerve fibres].

Electrical field stimulation of sensitized guinea pig hilus bronchi induced a long lasting contractile response which was insensitive to atropine, but could be antagonized by a substance P (SP) antagonist. Antigen challenge of sensitized guinea pig main and hilus bronchi evoked a double-phase contractile response which consisted of a rapid contraction and a slow contraction. Both of them were sensitive to SP-antagonist, especially its slow contraction. Disodium cromoglycate (DSCG) inhibited the contractile responses induced by electrical field stimulation and antigen challenge. significantly. These results suggest that DSCG has inhibitory effect on the release of SP sensory nerve fibre endings induced by some stimulators, which might be related to the effect of DSCG against asthma.

Animals↗
PubMed1990

Drug responses in antigen-induced contractions of tracheal strips of ovalbumin-sensitized guinea pigs.

Guinea pig trachea strips were isolated after 21 d of ovalbumin-sensitization. Challenging the preparations with antigen induced a double-phase contractile response (DPCR) which consisted of a rapid contraction (RC) and a tonic contraction (TC). The effects of tetrodotoxin (TTX), atropine, hexamethonium, diphenhydramine and a substance P (SP) antagonist on the DPCR were observed. DPCR was insensitive to atropine or hexamethonium at 1 mumol/L. Diphenhydramine 2 mumol/L abolished RC, and inhibited TC by 48.0 +/- 5.6%. TTX 1 mumol/L and lidocaine 2 mumol/L almost completely abolished TC and reduced RC by 49.6 +/- 6.7% and 44.6 +/- 8.4%, respectively. The substance P antagonist, (D-Arg1, D-2,4-diCl2-Phe5, Asp6, D-Trp7,9, Nle11)-SP 10 mumol/L, inhibited RC by 49.9 +/- 6.1% and TC by 90.7 +/- 9.3%. The results suggest that SP sensory nerve fibers in respiratory tract play an important role in the pathogenesis of DPCR, especially in that of TC.

Animals↗
PubMed1990

[Studies on the antipregnancy effect of LHRH-A in mid gestational rats].

In the present study, the antipregnancy effect of (D-Ala6, Pro9-Ethylamide10) LHRH (LHRH-A) on midgestation rats was observed. The results indicate that LHRH-A could terminate pregnancy of all experimented rats by abortion after subcutaneous administration of 200 micrograms LHRH-A (dissolved in vegetable oil) once a day at days 9 to 11 of their pregnancy. It was also found that the serum progesterone level was significantly lowered after the administration of LHRH-A (P less than 0.05); the concomitant administration of megestrol acetate with LHRH-A could almost completely block the antipregnancy effect of LHRH-A on the midgestation rats; LHRH-A showed a strong direct inhibitory effect on luteal cell progesterone secretion in pseudopregnant and midgestation rats. Hence, it is considered that the probable mechanisms for the antipregnancy effect of LHRH-A may be mainly due to the decrease of serum progesterone level caused by the direct inhibitory effect of LHRH-A on midgestation corpus luteum progesterone production.

Abortion, Induced↗
PubMed1990

[The effects of HCG and LHRH-A on progesterone secretion by human placenta villi cells of early and term gestation in vitro].

In the present study, the method of collagenase-pepsin prepared cell suspension of human placental villi from early (10-12 weeks) and term (38-40 weeks) gestation cultured in vitro combined with progesterone radioimmunoassay was employed. The results indicated that: 1. In the placenta villi cells from early and term gestation in vitro, both exogenous and endogenous hCG showed a stimulatory effect on progesterone secretion, and the effect was approximately proportional to the concentration of the exogenous hCG added. 2. In the placenta villi cells from term gestation in vitro, after addition of sufficient rabbit antihCG IgG to the culture medium, LHRH-A exhibited no obvious influence on this hCG-independent progesterone secretion. However, in the absence of rabbit anti-hCG IgG in the culture medium, LHRH-A showed a stimulatory action on progesterone secretion probably via its stimulatory effect on hCG secretion which could subsequently increase the progesterone secretion. 3. In the placenta villi cells from early gestation, LHRH-A exhibited an inhibitory effect on both hCG-independent and hCG-dependent progesterone secretion.

Chorionic Gonadotropin↗
PubMed1989

[Design and synthesis of LHRH analogs].

In the hope to find new superagonists of LHRH, here we report the synthesis of six analogs by changing residue 5 of [D-Trp6 (or D-Arg6), des-Gly10]-LHRH-EA. For the convenience of comparison, the known compound [D-Trp6, desGly10]-LHRH-EA was also synthesized.

Animals↗
PubMed1987

Rapid hydrolysis of proteins and peptides by means of microwave technology and its application to amino acid analysis.

A rapid heating method of hydrolysis by the use of microwave oven has been applied to amino acid analysis of proteins and peptides. This convenient method has been compared with the conventional 6 N HCl hydrolysis at 110 degrees for 24 h. The advantages of this new method are its expedition and the accurate and comparable results as compared to the tedious conventional technique. The method provides a rapid processing of multiple samples within minutes instead of days and inexpensive access to the important data of amino acid compositions of proteins by the commonly used microwave oven. The necessary change in the design of hydrolysis vials and the safety precautions accompanying this novel use of microwave acid-digestion method are also described.

Amino Acids↗
PubMed1985

Methylated purines formed in DNA by dimethylnitrosamine in rats previously exposed to hepatotoxic and hepatocarcinogenic regimes: effects on the repair of O6-methylguanine.

Studies of mammalian systems for the repair of O6-methylguanine in DNA have revealed large differences in the capacities of tissues and cells to perform this function and in the case of rat liver it has been shown that the O6-methylguanine repair system can be stimulated by exposure to hepatotoxic and hepatocarcinogenic regimes. In this report an assessment is made of possible relationships between toxic liver injury, DNA synthesis, cell proliferation and DNA repair by treating Wistar rats with agents selected to provide differing degrees of liver involvement. The effects of long-term (20 week) treatments with acetylaminofluorene (15 mg/kg/day), quinoxaline 1,4-dioxide (10 mg/kg/day), 4-aminobiphenyl-HCl (15 mg/kg/day) and pronethalol (20 mg/kg/day) were assessed, using the same strain of animals in which the original toxicity and carcinogenicity data were obtained. Repair of O6-methylguanine produced in liver DNA by a low, non-toxic dose (2 mg/kg) of [14C]dimethylnitrosamine was increased 3-4-fold throughout the period of treatment with acetylaminofluorene, to a lesser extent by quinoxaline 1,4-dioxide and 4-aminophenyl-HCl and not at all in the case of pronethalol. No evidence was obtained to indicate a direct relationship between O6-methylguanine repair and either the induced hepatotoxicity or the ensuing increased rates of DNA synthesis which occur following exposure to these agents.

2-Acetylaminofluorene↗