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Biomedical subjects

M C Cheng

Publications and source records attributed to M C Cheng.

At least 55 records · Page 3Linked to original sources
PubMed1986

Beta-endorphin and its congeners in rat pituitary and thyroid: effects of propylthiouracil and thyroid hormone administration.

Immunoreactive beta-endorphin (ir-beta EP) and immunoreactive N-acetyl-endorphin (ir-NacEP) have been demonstrated in the rat thyroid by specific RIA and characterized by reverse phase HPLC. In addition, pituitary and thyroid ir-beta EP and ir-NacEP levels have been determined after manipulation of the pituitary-thyroid axis by chronic (21 days) treatment with 1) propylthiouracil (PTU), 2) L-T4, 3) L-T3, or 4) T3 plus PTU. No difference in anterior pituitary or neurointermediate lobe ir-beta EP was seen between controls and treated groups (n = 8/group). In contrast, levels of ir-NacEP were markedly lower (P less than 0.01) in both hypo- and hyperthyroid groups than in controls, in both anterior pituitary and neurointermediate lobe. In the thyroid, levels of both ir-beta EP and ir-NacEP were profoundly depressed (P less than 0.01) in all treated groups, with no change in calcitonin levels, suggesting that the thyroid effect of PTU and T3/T4 may be specific for the synthesis, processing, and/or release of pro-opiomelanocortin derived peptides. The findings in this study suggest 1) that acetylation of pituitary and thyroid beta EP is similarly sensitive to PTU and thyroid hormone administration and 2) that in the thyroid, but not in the pituitary, both PTU and thyroid hormones markedly lower levels of pro-opiomelanocortin-derived peptides.

Acetylation↗
PubMed1985

The identification and characterization of alpha-N-acetylated beta-endorphin in the human pituitary gland.

By using a radioimmunoassay specific for alpha-N-acetyl beta-endorphin and its C-terminally shortened forms, we have established the presence of immunoreactive alpha-N-acetyl endorphin (irNacEP) in extracts of five postmortem human pituitary glands (2.27 +/- 0.64 ng/gland). This immunoreactivity has been further characterized by subjecting these extracts to reverse-phase high-performance liquid chromatography (RP-HPLC). In all cases the major peaks of irNacEP co-migrated with synthetic human standard alpha-N-acetyl alpha-endorphin (Nac alpha EP), alpha-N-acetyl gamma-endorphin (Nac gamma EP) and Nac beta EP. These studies thus represent the initial demonstration that alpha-N-acetylation of beta-endorphin and its shorter molecular forms occurs in the human pituitary gland.

Acetylation↗
PubMed1985

N-acetyl endorphin in rat spermatogonia and primary spermatocytes.

In previous reports modest levels of beta-endorphin have been found by radioimmunoassay in rat testis, and localized by immunofluorescence to the interstitial cells. We have confirmed these previous reports and extended them by showing that the majority of testicular endorphins are acetylated forms, N-acetyl gamma-endorphin, N-acetyl alpha-endorphin, and N-acetyl beta-endorphin1-27. In addition, N-acetylated endorphins are not found in interstitial cells, but are confined to spermatogonia and primary spermatocytes.

Aging↗
PubMed1979

Safety of postabortion sterilisation compared with interval sterilisation. A controlled study.

406 women--about one-fifth of those requesting an induced abortion and sterilisation over a thirty-three-month period--volunteered to be allocated randomly to either a concurrent induced-abortion/sterilisation group or a group which was sterilised six weeks after abortion. The abortion-attributable and sterilisation-attributable complication rates of 3.8% and 5.2%, respectively, for the concurrent group did not differ significantly from the 6.7% and 6.9% rates for the interval group. The estimated 2%-10% of women who would have changed their minds must be set against the 4% of women who became pregnant again before being sterilised. Efforts should be made to identify women likely to regret sterilisation.

Abortion, Induced↗
PubMed1977

The safety of combined abortion-sterilization procedure.

To determine the safety of tubal sterilization performed at the time of induced abortion, we compared data on 616 women who underwent induced abortion and concurrent tubal ligation (Group 1) with 1,805 women who had induced abortion only (Group 2). These two groups of women were healthy, seven to 12 weeks pregnant, and between the ages of 16 and 44 years. The partly-standardized morbidity rates for Group 1 and Group 2 were 5.4 and 3.6%, respectively. Thus, the sterilization procedure added 1.8% to the complication rate of induced abortion only. The complication rate for women who had interval culdoscopic ligation under the same conditions in the same department was 2.4%. This is not significantly different from the complication rate of 1.8% attributable to sterilization procedures in women who had abortion and concurrent ligation. We conclude that these data support our present practice of performing tubal ligation at the time of induced abortion, rather than changing to the practice of abortion followed by interval sterilization six weeks later, with its many disadvantages to the patient as well as to those providing family-planning services.

Abortion, Induced↗
PubMed1977

Psychological sequelae of sterilization in women in Singapore.

The Chinese in Singapore erroneously believe that there is an association between sterilization and castration. This belief has led to deep-seated fears that sterilization may result in obesity, physical weakness, and impairment of sexual function. Beginning in 1969, Singapore authorities introduced increasingly stronger social policies to help reduce family size. Subsequently, there was a large increase in the number of tubal ligations. It was initially thought that this might result in a high incidence of psychological sequelae. A study of 150 women who had had culdoscopic ligations showed that 6.3 percent were dissatisfied at the end of 2 years. Women with fewer than 4 children and those with fewer than 2 sons tended to be more dissatisfied with sterilization.

Adult↗
PubMed1977

Sterilization failures in Singapore: an examination of ligation techniques and failure rates.

The University Department of Obstetrics and Gynecology, Kandang Kerbau Hospital in Singapore, initiated a study in early 1974 of failure rates for various methods of sterilization and the factors responsible for the failures. During the period January 1974 to March 1976, 51 cases of first pregnancy following ligation were discovered. Cumulative failure rates at 24 months were 0.34 per 100 women for abdominal sterilization, 1.67 for culdoscopic, 3.12 for vaginal, and 4.49 for laparoscopic procedures. Findings for 35 patients who underwent religation showed that recanalization and the establishment of a fistulous opening caused the majority of failures. Clearly, more effective methods of tubal occlusion in sterilization are needed.

Abdomen↗
PubMed1977

A component analysis of recent fertility decline in singapore.

To aid in achieving demographic goals, since 1968 the government of Singapore has passed a series of laws designed to limit family size. Policies were instituted in 1968 to discourage couples from having more than three children; policies introduced in 1973 discouraged having more than two. Trends in fertility rates and in the numbers of abortions and sterilizations in recent years are consistent with the intent of these social policies. Decline in third and subsequent births was the most important factor in fertility decline after 1972, and the numbers of abortions and sterilizations undergone by higher parity women have increased substantially sin"e 1970. Although other factors have affected fertility in Singapore, the data suggest that the disincentives have played a role in continued fertility decline in recent years.

Abortion, Legal↗
PubMed1976

Novel bis(benzamidino) compounds with an aromatic central link. Inhibitors of thrombin, pancreatic kallikrein, trypsin, and complement.

A series of novel aromatic diamidines was synthesized and evaluated for antiproteolytic activity. The compounds were distignuished by inclusion of an aromatic ring structure--either benzene or bisbenzene or naphthalene--in the link between two amidinobenzene moieties. A highly potent inhibitor of bovine thrombin was discovered in alph, alph'-bis(4-amidino-2-iodophenoxy)-p-xylene with a Ki value of 1.1 X 10(-7) M (pH 8.1, 37 degrees), while alpha, alpha'-bis(4-amidino-2-iodophenoxy)-m-xylene was found to be an outstanding inhibitor of porcine pancreatic kallikrein (Ki = 3.1 X 10(-8) M). Several of the compounds investigated also demonstrated a considerable blocking effect on typsin and on the complement-dependent immune lysis of red cells.

Amidines↗
PubMed1975

Culdoscopic ligation as an outpatient procedure.

The increasing demand for abortion and sexual sterilization has caused the need to perform such operations on an outpatient basis. The University Department of Obstetrics and Gynaecology, Singapore, started a prospective study of culdoscopic ligation as an outpatient procedure in November, 1972. To date, over 600 operations have been performed. Analysis of the first 405 cases showed a low complication rate of 2.4 per cent. This study showed that culdoscopic ligation performed in the hospital outpatient is safe and feasible.

Adult↗
PubMed1975

The inhibition of urokinase by aromatic diamidines.

1. Structure-activity relationships have been established for the inhibition of urokinase by aromatic diamidines. In an assay system employing purified urokinase and human plasminogen the most potent inhibitor was found in 4',4''-diamidino-2-hydroxy-1,4-diphenoxybutane which proved 5600 times more active on a molar bases than epsilon-aminocaproic acid (E-ACA). 2. 4',4''-diamidino-2-hydroxy-1,4-diphenoxybutane behaved as a competitive inhibitor of the urokinase catalyzed hydrolysis of N-alpha-acetyl-L-lysine methyl ester. At pH 7.85 and 37 degrees C the K-1 value was determined as 3.18 times 10-6 M which compares with a value of 6.79 times 10-5 M for p-aminobenzamidine and 3.57 times 10-2 M for E-ACA. 3. In two fibrinolytic tests including urokinase as activator the superiority of diamidines over E-ACA was less marked than in the pure plasminogen activation system. This was due to the presence of certain plasma proteins in the fibrinolysis assays which augmented the inhibitory strength of E-ACA. The order of effectiveness of diamidines in the lysis tests was also different from the one in the activation test. In a human fibrin clot lysis test the most active inhibitor was 3',3''-diamidino-2-hydroxy-1,4-diphenoxybutane which was 1700 times more effective on a molar basis than E-ACA. In a human plasma clot lysis test the strongest inhibitor, 2-hydroxy-stilbamidine, was 70 times more powerful than E-ACA.

Amidines↗