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Biomedical subjects

P Tong

Publications and source records attributed to P Tong.

At least 55 records · Page 3Linked to original sources
PubMed1995

Cell membrane dynamics and insulin resistance in non-insulin-dependent diabetes mellitus.

Insulin resistance in non-insulin-dependent diabetes mellitus (NIDDM) could be related to changes in cell membrane properties. We measured insulin sensitivity and mononuclear leucocyte membrane fluidity by fluorescence polarisation in fifteen NIDDM patients and twenty-one normal subjects. Core-region anisotropy was significantly lower in leucocytes from diabetic subjects (mean 0.164 vs 0.174, p < 0.001). Insulin sensitivity was positively correlated with such anisotropy before and after acute in-vitro insulin treatment. There was no difference in superficial membrane anisotropy. This study suggests that altered membrane dynamics in NIDDM may contribute to insulin resistance.

Cell Membrane↗
PubMed1994

Membrane fluidity is different in intact erythrocytes and ghost membranes.

The fluorescence anisotropy of 1,6-diphenylhexatriene (DPH) and trimethylammonium-DPH in the membranes of intact human erythrocytes and ghost membranes was compared. The anisotropy of fluorophores is significantly higher in intact erythrocytes compared to that in ghost membranes. Perturbation of membranes by heating at 47 degrees C and use of a rotating stirrer affected the anisotropy of fluorophores in intact erythrocytes only. These results suggest that: (a) spectrin has a significant modulating effect on membrane fluidity, and (b) the physical properties of the cell membrane are different between intact erythrocytes and erythrocyte ghost membranes.

Erythrocyte Membrane↗
PubMed1994

[Changes of plasma motilin concentration in pregnancy and early postpartum period].

Plasma motilin concentration were determined by radioimmunoaction from 180 women during pregnancy and early postpartum period as compared with 20 healthy non-pregnant women. The results showed that mean plasma motilin concentration (384.40 +/- 110.30 ng/L) was higher in the first trimester of pregnancy than that of healthy non-pregnant women (366.12 +/- 96.23 ng/L), however, this difference did not reach statistical significance (P > 0.05). The mean plasma motilin concentration (323.90 +/- 125.10 ng/L) was lower in the second trimester of pregnancy than in the first trimester of pregnancy (P < 0.05), while the mean plasma motilin concentration in the third trimester of pregnancy (121.04 +/- 27.00 ng/L) was significantly lower than in second (P < 0.01) and the mean plasma motilin concentration in 3-5 d after delivery (443.05 +/- 140.79 ng/L) reached an even higher value (P < 0.01). Our results suggests that pregnancy appears to have a profound inhibitory effect on plasma motilin and this may in part be responsible for the gastrointestinal hypomotility during pregnancy.

Adult↗
PubMed1992

Preparation and in vitro antiviral activity of liposomes of lipophilic esters of acyclovir.

The long chain acyclovir such as the acyclovir laurate and acyclovir palmitate were prepared directly from acyclovir by application of the usual esterification methods with appropriate acyl chlorides. The lipophilic prodrugs were found to be retained easier by liposomes whereas acyclovir escaped readily from liposomes. When assayed in African green monkey cell cultures against herpes simplex virus type I strain, the acyclovir palmitate liposomes proved to be more active compared with the parent drug and its liposome, suggesting an enhanced compatibility between the ester and liposomal lipids and an increased uptake of encapsulated prodrug by infected cells.

Acyclovir↗
PubMed1990

UM4D4+ (CDw60) T cells are compartmentalized into psoriatic skin and release lymphokines that induce a keratinocyte phenotype expressed in psoriatic lesions.

UM4D4 (CDw60), the surface molecule of a novel antigen-independent T-cell activation pathway, was found to be highly expressed on lesional psoriatic T cells. To examine whether UM4D4 represents a T-cell activation pathway for psoriatic T cells, a T-cell line was initiated from an acute skin lesion and cloned by limiting dilution. Clonality was verified by analysis of T-cell receptor gene rearrangement. All T-cell clones tested, whether CD4+2H4+CD8-, CD4+2H4-CD8-, or CD4-CD8+CD11b-, expressed UM4D4 and were activated by the monoclonal antibody anti-UM4D4. Lesional psoriatic T-cell clones were heterogeneous in the degree of anti-UM4D4-induced proliferation and in their production of IL-2 and gamma-interferon. Lymphokines released by anti-UM4D4 activation were capable of inducing ICAM-1 and HLA-DR expression on cultured normal keratinocytes. Thus, the high expression of UM4D4 on T-cells in psoriatic skin provides an alternative mechanism for T-cell activation that may be operative in the psoriatic lesional milieu. Indeed, activation of lesional T-cells through the UM4D4 molecule resulted in release of lymphokines that directly induced keratinocytes to express a phenotype displayed in psoriatic skin lesions.

Antigens, CD↗
PubMed1986

Extracellular calcium alters the effects of retinoic acid on DNA synthesis in cultured murine keratinocytes.

The rate of proliferation of epidermal keratinocytes was manipulated by growing the cells in medium containing high or low concentrations of calcium. Keratinocytes cultured in high extracellular Ca++ (1.4 mM and 2.8 mM) proliferated twice as fast as those grown in low Ca++ medium (0.09 mM) as measured by incorporation of [3H]thymidine into DNA. Exposure of high calcium keratinocytes to all-trans retinoic acid for 4 days caused a dose-related inhibition of DNA synthesis with an IC50 of about 10 microM. In contrast, incubating low calcium keratinocytes with all-trans retinoic acid caused a dose-related stimulation of DNA synthesis with maximum increase of 278% over control at 10 microM. This increase was accompanied by increases in culture confluency with maximum increase of 109% in cell number over control at 10 microM. These results are of importance since they suggest Ca++ may influence the effect of retinoids on keratinocytes.

Animals↗