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Biomedical subjects

M P Li

Publications and source records attributed to M P Li.

12 recordsLinked to original sources
PubMed2004

Smoking and depressive symptoms in Chinese elderly in Hong Kong.

OBJECTIVE: To examine the association between smoking and depressive symptoms among Chinese elderly in Hong Kong. METHOD: Cross-sectional data on smoking and depressive symptoms from 56,167 Chinese elderly aged 65 or over in Hong Kong were analysed using logistic regression. RESULTS: Current smokers and former smokers were more likely to have depressive symptoms than never smokers. The adjusted odds ratios (OR) and 95% confidence interval (CI) in males and females respectively were 1.62 (1.34-1.96) and 1.43 (1.20-1.70) for current smokers, and were 1.18 (0.99-1.40) and 1.29 (1.12-1.47) for former smokers. Former smokers were less likely to have depressive symptoms than current smokers (OR = 0.80, 95% CI: 0.70-0.92). CONCLUSION: Smoking is positively associated with depressive symptoms in Chinese elderly. Health care workers should be vigilant about the detection of depressive symptoms in elderly smokers.

Aged↗
PubMed1985

Modification of vesicle surfaces with amphiphilic sterols. Effect on permeability and in vivo tissue distribution.

In this paper, we describe the permeability of vesicles prepared with various synthetic cholesterol derivatives. Cholesterol derivatives with side-chains ending in hydroxyl groups reduced the permeability of unilamellar vesicles. However, addition of cholesterol derivatives with terminal amino groups makes the vesicles more permeable. Vesicles prepared with a short-chain amino-cholesterol derivative were found to be less permeable in phosphate-buffered saline, but not in bovine serum, while long-chain amino-cholesterol-containing vesicles were very permeable in both media. Studies in vivo indicate a rapid clearance rate for intravenously administered amino-cholesterol-containing vesicles with a concomitant increase in liver uptake. However, no difference was found in either the clearance or tissue distribution of control vesicles and the less permeable hydroxyl-cholesterol-containing vesicles.

Animals↗
PubMed1984

The pharmacological efficacy of a rigid non-phospholipid liposome drug delivery system.

Hydration of an ethoxylate derivative of cholesterol, triethoxycholesterol, results in the formation of stable, rigid, bilayer-like structures capable of encapsulating polar compounds. Studies on the stability and tissue distribution of these liposomes in mice indicate that they are suitable as a drug delivery system. Intraperitoneal injection of triethoxycholesterol encapsulated methotrexate into mice bearing hepatoma ascites tumor results in a doubling of the survival time, relative to untreated mice and those receiving unencaptulated drug. These studies show that fluid, acyl chains are not required for the formation of pharmacologically useful vesicles and that such formulations need not be limited to phospholipid-containing systems.

Animals↗
PubMed1983

Steroid derivatives for electrophilic affinity labelling of glucocorticoid binding sites: interaction with the glucocorticoid receptor and biological activity.

To investigate the possible use of electrophilic affinity labelling for the characterization of glucocorticoid receptors, different chemically reactive derivatives of deoxycorticosterone (deoxycorticosterone 21-mesylate and deoxycorticosterone 21-(1-imidazole) carboxylate), dexamethasone (dexamethasone 21-mesylate, dexamethasone 21-iodoacetate and dexamethasone 21-bromoacetate) and progesterone (21-chloro progesterone) were tested for their ability to bind irreversibly to the glucocorticoid receptor from goat lactating mammary gland. Using partially purified receptor, only one of the steroids tested, dexamethasone 21-mesylate (DXM-M) was found more effective than dexamethasone (DXM) in preventing exchange of radioactive dexamethasone in the receptor binding site. The affinity of DXM-M for the glucocorticoid receptor, measured by competitive binding assay, was 1/15 that of DXM. Polyacrylamide gel electrophoresis in sodium dodecyl sulphate of the [3H]-DXM-M labeled glucocorticoid receptor revealed a specific covalently radiolabeled fraction corresponding to an apparent molecular weight of 75,000 to 80,000. The biological activity of DXM-M was studied in RPMI 3460-clone 6 Syrian hamster melanoma cells, a cell line which is sensitive to growth inhibition by glucocorticoids. Like DXM, DXM-M inhibits the growth of RPMI 3460-clone 6 cells and it acts as a slowly reversible glucocorticoid agonist at concentrations which correlate with the affinity of DXM-M for the glucocorticoid receptor in vitro.

Affinity Labels↗
PubMed1983

Suppression of liver uptake of liposomes by dextran sulfate 500.

The effect of dextran sulfate (DS, 500,000 Mr) and multilamellar vesicles (MLV) as liver blockade agents has been investigated in mice. Intravenous injection of unlabeled MLV prior to radioactive MLV caused moderate reduction in the liver uptake and increased tibia, lung, and spleen uptake. More drastic differences were observed with intraperitoneal injection of DS. When tested in the range of 0-50 mg of DS per kg of body weight, maximal liver blockade occurred at a dose of 50 mg. By using 50 mg of DS per kg, maximal liver blockade occurred at 12 hr after DS injection. The liver blockade was temporary, ending within 48 hr. The intraperitoneal route of injection for DS was more effective for liver blockade than the intravenous route.

Animals↗
PubMed1982

Oxidative peptide (and amide) formation from Schiff base complexes.

One hypothesis of the origin of pre-modern forms of life is that the original replicating molecules were specific polypeptides which acted as templates for the assembly of poly-Schiff bases complementary to the template, and that these polymers were then oxidized to peptide linkages, probably by photo-produced oxidants. A double cycle of such anti-parallel complementary replication would yield the original peptide polymer. If this model were valid, the Schiff base between an N-acyl alpha amino aldehyde and an amino acid should yield a dipeptide in aqueous solution in the presence of an appropriate oxidant. In the present study it is shown that the substituted dipeptide, N-acetyl-tyrosyl-tyrosine, is produced in high yield in aqueous solution at pH 9 through the action of H2O2 on the Schiff-base complex between N-acetyl-tyrosinal and tyrosine and that a great variety of N-acyl amino acids are formed from amino acids and aliphatic aldehydes under similar conditions.

Amides↗
PubMed1973

Hypertensive action of 18-hydroxydeoxycorticosterone.

18-Hydroxydeoxycorticosterone is an adrenal steroid hormone causing salt and water retention and is secreted in greatly increased amounts in response to the pituitary hormone adrenocorticotropic hormone. Its production is abnormally high in some forms of hypertension in man and rat. Direct proof that 18-hydroxydeoxycorticosterone is capable of causing hypertension is present. Daily subcutaneous injections of 200 micrograms, a low physiological dose, significantly increase the blood pressure of unilaterally nephrectomized saline-treated rats after 2 weeks. This strengthens the hypothesis that 18-hydroxydeoxycorticosterone contributes to the etiology of hypertension, possibly by a mechanism involving stressinduced release of adrenocorticotropic hormone.

Adrenocorticotropic Hormone↗