Biomedical subjects

T C Ng

Publications and source records attributed to T C Ng.

58 records · Page 4Linked to original sources

PubMed1974

Inactivation of pea leaf chloroplastic and cytoplasmic glucose 6-phosphate dehydrogenases by light and dithiothreitol.

Chloroplastic and cytoplasmic forms of pea (Pisum sativum L.) leaf glucose-6-P dehydrogenase can be separated by gel electrophoresis. Both forms are found in etiolated seedlings. When light-grown plants are illuminated or when crude extracts are treated with dithiothreitol, the chloroplastic and cytoplasmic forms of this enzyme are inactivated. Michaelis-Menten kinetics are obtained for inactivation of the chloroplastic and cytoplasmic glucose-6-P dehydrogenases and for activation of two dehydrogenases involved in photosynthetic carbon metabolism with dithiothreitol. The mechanism for the activation of the two light-activated enzymes appears to be similar to the mechanism for the inactivation of the chloroplastic and cytoplasmic forms of the light-inactivated oxidative pentose phosphate enzyme glucose-6-P dehydrogenase.

Journal Article↗

PubMedDate not supplied

Growth and magnetic resonance characteristics of human squamous cell carcinoma xenografts implanted with cells suspended in Matrigel.

Growth and magnetic resonance characteristics of a human squamous cell carcinoma SQ20B were studied in vivo as xenografts in nu/nu nude mice. Tumor cells injected subcutaneously in the flank using either Matrigel (MTG, an extract of basement membrane proteins) or growth medium (GM) as a vehicle were compared. Much higher tumor growth rates and cell density were observed with Matrigel than with GM implantation. Histology also showed that MTG implanted cells grew as vascularized solid tumors compared to GM tumors which formed cysts. As a result of increased cell density with the improved method, tumors as small as 0.3 cm3 provide high S/N magnetic resonance spectra which yield smaller standard deviations with fewer experiments.

Animals↗

PubMedDate not supplied

Effect of adenosine deaminase inhibitors on the heart's functional and biochemical recovery from ischemia: a study utilizing the isolated rat heart adapted to 31P nuclear magnetic resonance.

The concept of limiting irreversible damage due to ischemic arrest by inhibiting nucleoside breakdown was tested in the isolated perfused rat heart. Functional recovery measurements were combined with continuous high-energy phosphate measurements by means of 31P nuclear magnetic resonance (NMR) and with nucleoside release measurements in the reperfusion period. The adenosine deaminase inhibitors erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) and 2'-deoxycoformycin (DCF) were given 5 min before ischemia and for the first 5 min of reperfusion. These treated groups were compared with a control, untreated group. These were further compared with a group of hearts arrested with potassium and to a group combining potassium arrest and EHNA. It was found that all treated groups recovered mechanical function significantly better than the untreated group. DCF, K+, and K+ + EHNA slowed ATP decline and resulted in better ATP recovery than untreated or EHNA-treated, and all treatments decreased nucleoside base release. Intracellular pH fell equally in all groups and recovered to preischemic values. Thus, these adenosine deaminase inhibitors improve functional recovery following ischemia, although this improvement was not well correlated with purine losses observed during reperfusion.

Adenine↗

PubMedDate not supplied

Gd-DISIDA--a potential contrast agent for magnetic resonance imaging of the hepatobiliary system.

Gadolinium (Gd) labeled diisopropyliminodiacetic acid (DISIDA) was prepared by mixing a Gd solution and a DISIDA solution in appropriate proportions and at controlled pH. Optimal complexation was obtained at a Gd:DISIDA molar ratio of 1:2.5 and the pH of the final solution was 7.3 to 7.5. The complex was found to be stable both in vitro and in vivo. Gd-DISIDA (12.5 mumol/kg) was injected into mice, and T1 and T2 relaxation times of various tissues were measured and compared with those of normal tissues. Only the T1 values of the blood and the liver markedly decreased after Gd-DISIDA administration and also the reduction in T1 values depended on the dose of Gd-DISIDA. Magnetic resonance imaging of the rabbit liver showed considerable contrast enhancement at 30 minutes after administration of 12.5 mumol/kg of Gd-DISIDA.

Animals↗