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S C Lu

Publications and source records attributed to S C Lu.

84 records · Page 5Linked to original sources
PubMed1990

Hormonal regulation of glutathione efflux.

The efflux of GSH has been shown previously to be a saturable process in both isolated rat hepatocytes and perfused liver, suggesting a carrier-mediated transport mechanism. The possibility in hormonal regulation of this process has been raised by recent reports. Our present work examined the role of hormones known to affect intracellular signal transduction mechanisms on GSH efflux in cultured rat hepatocytes and perfused rat livers. We found that cAMP-dependent factors, such as cholera toxin (CT), dibutyryl cAMP, forskolin, and glucagon all stimulated GSH efflux in cultured rat hepatocytes. The efflux kinetics were compared in cultured cells incubated with or without CT; the stimulation of GSH efflux was related to a near doubling of the Vmax while exhibiting no significant alteration of the Km. The increase in intracellular cAMP level associated with the threshold for this stimulatory effect was 25% above control. The stimulatory effect of CT could not be blocked by cyclohexamide pretreatment or reversed by colchicine treatment. The stimulatory effect of glucagon was abolished in the presence of ouabain but not in the presence of barium. On the other hand, hormones which act through Ca2+ and protein kinase C, such as phenylephrine and vasopressin, had no effect on GSH efflux in the cultured cells. In the perfused liver model, glucagon (10 nM) and dibutyryl cAMP (8 microM) stimulated sinusoidal GSH efflux to 130 and 144% of control values, respectively, and increased bile flow while not affecting biliary GSH efflux. Finally, the physiological significance of glucagon-mediated stimulation of sinusoidal GSH efflux was assessed by both plasma GSH and glucose levels in response to in vivo glucagon infusion. The threshold dose of glucagon for significant increase in plasma GSH (5.21 pmol/min) was lower than for glucose (15.61 pmol/min). At the highest glucagon infusion rate (261 pmol/min), plasma GSH level doubled while glucose level increased 80%. In conclusion, increased cAMP stimulates GSH efflux in cultured rat hepatocytes and perfused livers. The stimulatory effect of cAMP is exerted at the sinusoidal pole and appears to be mediated by hyperpolarization of hepatocytes by stimulation of Na(+)-K(+)-ATPase. In vivo studies confirmed the importance of cAMP-mediated stimulation of sinusoidal GSH efflux as it resulted in significant elevation of the plasma GSH level.

Animals↗
PubMed1989

Frontiers of gallstone therapy. How far have we come with nonsurgical methods?

In the next few years, much will be learned about nonsurgical treatment of gallstones, and the role of each method will be more clearly defined. At present, each used alone has limitations (table 1). Oral chemolysis can be used for any number of gallstones, but only about 20% of patients are candidates for this method. Complete dissolution of stones can take months to years. Direct-contact dissolution therapy is rapidly effective, is inexpensive, and can be used for any size and number of gallstones. However, it is invasive, and only about 20% of patients are suitable candidates. Extracorporeal shock wave lithotripsy is noninvasive and avoids the complications and long recovery period of surgery. Up to three stones can be treated, but patients with certain medical conditions are excluded. About 20% to 30% of patients can undergo this treatment. None of these nonsurgical treatments prevents recurrence. Shock wave lithotripsy and dissolution with methyl tert-butyl ether are still in the experimental stage, so results of further study--particularly of combinations of the methods--are eagerly awaited by persons who have had symptomatic gallstones.

Cholelithiasis↗
PubMed1989

Role of glutathione status in protection against ethanol-induced gastric lesions.

The role of glutathione status in gastric mucosal cytoprotection has been a subject of controversy. Cysteamine, an exogenous sulfhydryl agent and diethyl maleate (DEM), an endogenous glutathione (GSH) depletor both appear to protect rats from ethanol-induced gastric lesions. In this study, we used various agents to alter gastric mucosal GSH levels and assessed the effects on susceptibility to ethanol injury. We found that DEM and buthionine sulfoximine both depleted gastric GSH but only DEM protected against ethanol-induced gastric lesions. L-Oxothiazolidine-4-carboxylate (OXT) and N-acetyl-L-cysteine (NAC) both potentiated ethanol-induced gastric lesions even though only NAC significantly raised the GSH level. The depletion of GSH by DEM was reversed by supplying cysteine in the form of OXT or NAC so that the net result was a GSH level close to normal control. The potentiation of ethanol injury by NAC and OXT was still apparent. These experiments show no relation between gastric GSH levels and susceptibility to ethanol injury.

Acetylcysteine↗
PubMed1989

[A study on the histologic basis of human bile duct peristalsis].

In 62 human cadavers, full length specimen of bile duct including right hepatic intersegmental duct (from fetus, infants, children and adult up to 74 yrs of age) was examined with light and electron microscopy. 1 for longitudinal maximum section, 61 for cross serial section of each of 6 selected tissue blocks stained with HE for general survey, Mallory, Van-Gieson stain and PAP anti-desmin for smooth muscle, Weigert stain for elastic fiber. No muscle bundles were found in the bile-duct. Some cases have scattered smooth muscle cells in the fibrous duct wall, with the frequency in pancreatic portion as 54/62, supraduodenal portion 33/62, common hepatic 15/62, right hepatic 2/61, and intrahepatic o/62, but never in full layers, circular or longitudinal, nor right joint of cell membrane existed. Total area of muscle cells measured in slide is less than 8% that of the fibrous wall. No myofibroblast was found. It is concluded that, there is no characteristic histologic structure of contractile potential and wave transmission. There is no other contractile element in intrahepatic duct capable of initiating propulsive movement. The so-called bile duct movement is most likely passive and should not be interpreted as peristalsis.

Adult↗
PubMed1975

Parasitological studies at a new breeding area of Oncomelania hupensis chiui in Taipei county, Taiwan.

Oncomelania hupensis chiui was found at the Jui-Ping area, Linkow District, Taipei County, Taiwan, which is located on the north coast of the island approximately 10 km of the mouth of the Tamasui River. The habitat of the snails at this area is similar to the type locality at Alilao, on the slope of the hills along of coast. The snails from this new breeding area, are similar to the Alilao snails, and are highly susceptible to the infection with geographic strains of Schistosoma japonicum including the Changhua, Ilan, Japanese, Philippine and Chinese strains. Examinations of 7,758 snails and intradermal tests on 736 inhabitants along with stool examinations of 622 people indicated that there was no evidence of the presence of Schistosoma japonicum at this area. Results obtained from stool examination demonstrated high prevalence of hookworm infection (53.4%) and relatively low infection rates of Asearis lumbricoides (37.0%) and Trichuris trichiura (14.1%). The protozoan infections were low in general. A single Scotch-tape technique for Enterobius vermicularis among 499 school children yielded a 55.7% infection rate.

Adolescent↗
PubMed1975

Culture and morphological observations on Trypanosoma melphagium.

The cultural characteristics of Trypanosoma melophagium of sheep were studied. Aspects investigated were size of the inoculum and population growth in Modified Monophasic Medium for Trypanosomes (MMMT), population growth in Medium 199 with 10% inactivated calf serum containing 5, 10, and 15% hemolyzed defibrinated rabbit blood (199-CS-5, 199--CS-10, 199-CS-15) at 27 degrees C, effects on population growth of temperature and hydrogen ion concentration in MMMT, and morphology and morphometrics of the developmental stages found under different experimental conditions. The best growth occurred in medium MMMT at 30 degrees, C, pH 7.25. Temperature seemed to be a critical factor for differentiation of epimastigotes to trypomastigotes. Statistically significant differences were found between the trypomastigotes in MMMT and 199--cs-5 at 37 degrees C on day 4 of incubation for the following measurements: PK (distance from posterior end to kinetoplast), KN (from kinetoplast to middle of nucleus), PN (from posterior end to middle of nucleus), and nuclear and kinetoplastic indices. The trypomastigotes formed in both media were much smaller in size than the blood forms reported by Hoare (1972).

Animals↗