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Biomedical subjects

S Luo

Publications and source records attributed to S Luo.

194 records · Page 11Linked to original sources
PubMed1989

Hepatitis B virus, aflatoxins, and hepatocellular carcinoma in southern Guangxi, China.

We examined the roles of the hepatitis B virus and aflatoxin B1 in the development of primary hepatocellular carcinoma (PHC) in a cohort of 7917 men aged 25 to 64 yr old in southern Guangxi, China, where the incidence of PHC is among the highest in the world. After accumulating 30,188 man-yr of observation, 149 deaths were observed, 76 (51%) of which were due to PHC. Ninety-one% (69 of 76) of PHC deaths were hepatitis B surface antigen (HBsAg) positive at enrollment into the study in contrast to 23% of all members of the cohort (RR = 38.6). Three of the four patients who died of liver cirrhosis also were HBsAg positive at enrollment. There was no association between HBsAg positivity state and other causes of death. Within the cohort, there was a 3.5-fold difference in PHC mortality by place of residence. When estimated aflatoxin B1 levels in the subpopulations were plotted against the corresponding mortality rates of PHC, a positive and almost perfectly linear relationship was observed. On the other hand, no significant association was observed when the prevalence of HBsAg positivity in the subpopulations was compared with their corresponding rates of PHC mortality.

Adolescent↗
PubMed1989

Spontaneously ruptured pineal epidermoid cyst associated with a thalamic germinoma.

We describe a rare case of a patient who had a spontaneously ruptured pineal epidermoid cyst concurrent with a thalamic germinoma. Computed tomographic scans led to the detection of both tumors. A definite diagnosis of the free fat in the ventricle was made by its movable feature and characteristic absorption value on computed tomographic scan. Surgical treatment produced a good result.

Adolescent↗
PubMed1985

A serological case-control study of primary hepatocellular carcinoma in Guangxi, China.

Guangxi is a very high-risk area for primary hepatocellular carcinoma (PHC); the age-standardized (world population) rates for males and females in that Chinese Autonomous Region were 32.5 and 8.5, respectively. Blood specimens from 50 PHC patients and 50 age- and sex-matched controls in Guangxi were analyzed for hepatitis B surface antigen, antibody to hepatitis B surface antigen, and antibody to hepatitis B core antigen. Eighty-six % of cases were hepatitis B surface antigen positive, compared to 22% of controls (relative risk, 17.0). We estimate from the data that persistent hepatitis B virus infection can account for at least 80% of all PHC cases occurring in Guangxi. The consistency of our findings with those from Hong Kong and Taiwan strongly suggests that hepatitis B virus infection is also an important risk factor for PHC in other parts of southern China.

Adolescent↗
PubMed1982

Complete amino acid sequence of mung bean trypsin inhibitor.

The mung bean trypsin inhibitor has been found to be microheterogeneous at N-terminal region due to the presence of several isomers. After treatment with aminopeptidase M it becomes homogeneous and is suitable for sequence determination. Based on the determination of the structures of two active fragments the complete amino acid sequence of mung bean trypsin inhibitor has been elucidated. It consists of 72 amino acid residues with 7 pairs of disulfide bonds. The results show that this inhibitor belongs to the Bowman-Birk inhibitor family.

Amino Acid Sequence↗
PubMedDate not supplied

EM-652 (SCH 57068), a third generation SERM acting as pure antiestrogen in the mammary gland and endometrium.

Breast cancer is the most frequent cancer in women while it is the second cause of cancer death. Estrogens are well recognized to play the predominant role in breast cancer development and growth and much efforts have been devoted to the blockade of estrogen formation and action. The most widely used therapy of breast cancer which has shown benefits at all stages of the disease is the use of the antiestrogen Tamoxifen. This compound, however, possesses mixed agonist and antagonist activity and major efforts have been devoted to the development of compounds having pure antiestrogenic activity in the mammary gland and endometrium. Such a compound would avoid the problem of stimulation of the endometrium and the risk of endometrial carcinoma. We have thus synthesized an orally active non-steroidal antiestrogen, EM-652 (SCH 57068) and the prodrug EM-800 (SCH57050) which are the most potent of the known antiestrogens. EM-652 is the compound having the highest affinity for the estrogen receptor, including estradiol. It has higher affinity for the ER than ICI 182780, hydroxytamoxifen, raloxifene, droloxifene and hydroxytoremifene. EM-652 has the most potent inhibitory activity on both ER alpha and ER beta compared to any of the other antiestrogens tested. An important aspect of EM-652 is that it inhibits both the AF1 and AF2 functions of both ER alpha and ER beta while the inhibitory action of hydroxytamoxifen is limited to AF2, the ligand-dependent function of the estrogen receptors. AF1 activity is constitutive, ligand-independent and is responsible for mediation of the activity of growth factors and of the ras oncogene and MAP-kinase pathway. EM-652 inhibits Ras-induced transcriptional activity of ER alpha and ER beta and blocks SRC-1-stimulated activity of the two receptors. EM-652 was also found to block the recruitment of SRC-1 at AF1 of ER beta, this ligand-independent activation of AF1 being closely related to phosphorylation of the steroid receptors by protein kinase. Most importantly, the antiestrogen hydroxytamoxifen has no inhibitory effect on the SRC-1-induced ER beta activity while the pure antiestrogen EM-652 completely abolishes this effect, thus strengthening the need to use pure antiestrogens in breast cancer therapy in order to control all known aspects of ER-regulated gene expression. In fact, the absence of blockade of AF2 by hydroxytamoxifen could explain why the benefits of tamoxifen observed up to 5 years become negative at longer time intervals and why resistance develops to tamoxifen. EM-800, the prodrug of EM-652, has been shown to prevent the development of dimethylbenz(a)anthracene (DMBA)-induced mammary carcinoma in the rat, a well-recognized model of human breast cancer. It is of interest that the addition of dehydroepiandrosterone, a precursor of androgens, to EM-800, led to complete inhibition of tumor development in this model. Not only the development, but also the growth of established DMBA-induced mammary carcinoma was inhibited by treatment with EM-800. An inhibitory effect was also observed when medroxyprogesterone was added to treatment with EM-800. Uterine size was reduced to castration levels in the groups of animals treated with EM-800. An almost complete disappearance of estrogen receptors was observed in the uterus, vaginum and tumors in nude mice treated with EM-800. EM-652 was the most potent antiestrogen to inhibit the growth of human breast cancer ZR-75-1, MCF-7 and T-47D cells in vitro when compared with ICI 182780, ICI 164384, hydroxytamoxifen, and droloxifene. Moreover, EM-652 and EM-800 have no stimulatory effect on the basal levels of cell proliferation in the absence of E2 while hydroxytamoxifen and droloxifene had a stimulatory effect on the basal growth of T-47D and ZR-75-1 cells. EM-652 was also the most potent inhibitor of the percentage of cycling cancer cells. (ABSTRACT TRUNCATED)

Animals↗
PubMedDate not supplied

[The effect of specific deimination of glycogen phosphorylase b by peptidylarginine deiminase on the allosteric properties of the enzyme and dimer-tetramer transition].

The kinetics of the native glycogen phosphorylase b from rabbit skeletal muscle and of the enzyme specifically deiminated by peptidylarginine deiminase have been studied. According to the data on amino acid composition one arginine residue per phosphorylase b monomer is transformed into citrulline after 3 hours of incubation with peptidylarginine deiminase. The kinetics of the phosphorylase reaction were studied in the direction of glycogen synthesis. The native and the deiminated forms of phosphorylase b showed similar affinity to glucose 1-phosphate. The maximal velocity of the enzymatic reaction for the modified phosphorylase b is 8-20% higher than that for the native enzyme. Deiminated phosphorylase b like the native enzyme shows a positive kinetic cooperatively with respect to glucose 1-phosphate in the presence of the allosteric inhibitors (FMN, glucose), S-shaped dependences of the velocity of the enzymatic reaction on glucose 1-phosphate concentration (in the presence of FMN) pronouncing more distinctly for deiminated phosphorylase b than for the native enzyme (Hill coefficient is equal to 1.7 +/- 0.2 and 1.3 +/- 0.1, respectively). The affinity of the modified phosphorylase b to the allosteric activator AMP is one order of magnitude higher than that to the native enzyme. The cooperativity of AMP binding doesn't change significantly after deimination. The kinetics of inhibition of the native and modified phosphorylase b by FMN, glucose and glucose 6-phosphate are cooperative (the value of Hill coefficient is higher than unity). The more pronounced distinctions between two forms of the enzyme concern with the value of the "semisaturation" concentration [I]0.5. The deimination causes a pronounced reduction of the values of [I]0.5 for FMN and glucose, but the sensitivity of the deiminated enzyme to glucose 6-phosphate is much lower than that of the native phosphorylase b. Deiminated phosphorylase b unlike the native enzyme shows the positive cooperativity of the FMN binding (the value of the Hill coefficient is equal to 1.37 +/- 0.05). Deiminated phosphorylase b shows less capability to form tetramer in the presence of AMP as compared to the native enzyme.

Allosteric Regulation↗