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Biomedical subjects

H M Huang

Publications and source records attributed to H M Huang.

At least 91 records · Page 5Linked to original sources
PubMed1991

Cross-resistance to UV radiation of a cisplatin-resistant human cell line: overexpression of cellular factors that recognize UV-modified DNA.

A human cell line selected for cisplatin resistance (CPR) was irradiated with UV light and showed cross-resistance to UV light. Applying a modified chloramphenicol acetyltransferase assay, we observed that CPR cells acquired enhanced host cell reactivation of a transfected plasmid carrying UV damage. Gel mobility shift analysis indicated that two nuclear factors that recognize UV-modified DNA were overexpressed in CPR cells. In addition, factors that bind UV-modified DNA were independent from the factors that bind cisplatin-modified DNA. The significance of the identified binding factors, possibly DNA repair enzymes, is discussed.

Binding, Competitive↗
PubMed1989

Effects of in vitro hypoxia on depolarization-stimulated accumulation of inositol phosphates in synaptosomes.

The effects of potassium and in vitro histotoxic hypoxia (i.e. KCN) on phosphatidylinositol turnover in rat cortical synaptosomes were determined. [2-3H] Inositol prelabelled rat synaptosomes were prepared from cerebral cortex slices that had been incubated with [2-3H] inositol. Depolarization with 60 mM KCl increased [2-3H] inositol phosphates in a time dependent manner. Depolarization with 60 mM KCl increased [2-3H] inositol trisphosphate transiently at 5 s. K+ induced rapid formation of [2-3H]-inositol bisphosphate and maintained an elevated level for at least 5 min. K+ stimulated gradual formation of [2-3H] inositol monophosphate with time. One minute of hypoxia enhanced potassium-stimulated [2-3H] inositol bisphosphate formation. However, 30 min of hypoxia impaired potassium-stimulated accumulation of [2-3H] inositol phosphates. The effects of histotoxic hypoxia were all dependent upon calcium in the medium and on K+-depolarization. Thus, hypoxia altered the K+-induced accumulation of inositol phosphates in prelabelled synaptosomes in a time dependent, biphasic manner that was calcium dependent.

Analysis of Variance↗
PubMed1989

The effect of vitamin B2 and its derivatives on a dry-reagent strip theophylline assay.

This report describes the effect of flavin adenine dinucleotide (FAD) and its precursor vitamin B2 on an apoenzyme reactivation immunoassay system (ARIS) both in vitro and in vivo. It was observed that 10 nM/L FAD in the buffer causes a false-positive result in ARIS for theophylline by the value of 94 microM/L, whereas vitamin B2, flavin mononucleotide, adenosine, adenosine monophosphate, and adenosine diphosphate (ADP) at the same concentration caused no such effect. Nevertheless, ADP at 2 microM/L can cause a drop in theophylline reading of 55 microM/L. However, the sera from four volunteers with normal liver functions who had taken 30 mg of vitamin B2 daily for a week showed no effect on theophylline reading.

False Positive Reactions↗
PubMed1989

Phosphatidylinositol metabolism during in vitro hypoxia.

The effects of in vitro histotoxic hypoxia (0.5 mM KCN) on potassium-stimulated phosphatidylinositol turnover were determined. In rat cortical slices that were prelabeled with [2-3H]inositol, depolarization with 60 mM KCl increased [2-3H]inositol monophosphate and [2-3H]inositol bisphosphate accumulation in a Ca2+-dependent manner. At early times (10 s and 1 min), histotoxic hypoxia enhanced potassium-stimulated [2-3H]inositol monophosphate and inositol bisphosphate accumulation. Under basal conditions, hypoxia did not alter the accumulation of [2-3H]inositol phosphates. These results are consistent with the following hypothesis. The hypoxic-induced increase in cytosolic free calcium that we reported previously may lead to the early stimulation of inositol phosphates formation during hypoxia through activation of phospholipase C. The impairment of inositol phosphates formation during more prolonged hypoxia may be due to negative feedback regulation of the phosphatidylinositol cascade by protein kinase C or to a reduction in ATP levels.

Animals↗
PubMed1989

Simple enzymatic determination of total cholesterol in gallstones.

In this simple method for rapid enzymatic determination of total cholesterol in human gallstones, gallstone powder is dissolved in an 80/20 by vol mixture of N,N-dimethylformamide and dimethyl sulfoxide and reacted directly with the aqueous enzymatic reagent, without further treatment. The organic solvents do not interfere with enzymatic activities of cholesterol oxidase, esterase, and peroxidase in the assay mixture. The method is reproducible (CVs 3.7% to 6.6%), analytical recoveries ranged from 98.6% to 102%, and linearity is good. Furthermore, results correlated well with those obtained by infrared spectroscopic measurements.

Cholelithiasis↗
PubMed1988

Oxidative damage in DNA. Lack of mutagenicity by thymine glycol lesions.

Thymine glycol (5,6-dihydroxy-5,6-dihydrothymine) is a base damage common to oxidative mutagens and the major stable radiolysis product of thymine in DNA. We assessed the mutagenic potential of thymine glycols in single-stranded bacteriophage DNA during transfection of Escherichia coli wild-type and umuC strains. cis-Thymine glycols were induced in DNA by reaction with the chemical oxidant, osmium tetroxide (OsO4); modification of thymines was quantitated by using anti-thymine glycol antibody. Inactivation of transfecting molecules showed that one lethal hit corresponded to 1.5 to 2.1 thymine glycols per phage DNA in normal cells, whereas conditions of W-reactivation (SOS induction) reversed 60 to 80% of inactivating events. Forward mutations in the lacI and lacZ' (alpha) genes of f1 and M13 hybrid phage DNAs were induced in OsO4-treated DNA in a dose-dependent manner, in both wild-type and umuC cells. Sequence analysis of hybrid phage mutants revealed that mutations occurred preferentially at cytosine sites rather than thymine sites, indicating that thymine glycols were not the principal pre-mutagenic lesions in the single-stranded DNA. A mutagenic specificity for C----T transitions was confirmed by OsO4-induced reversion of mutant lac phage. Pathways for mutagenesis at derivatives of oxidized cytosine are discussed.

Base Sequence↗
PubMed1988

Effects of ATP on phosphatidylinositol-phospholipase C and inositol 1-phosphate accumulation in rat brain synaptosomes.

Incubation of rat brain synaptosomes prelabeled with [2-3H]inositol resulted in a time-dependent release of labeled inositol 1-phosphate. This process was Ca2+ dependent, and ATP (1 mM) enhanced the inositol 1-phosphate formation three- to fivefold. Using [1-14C]arachidonoyl-phosphatidylinositol which was introduced into saponin-permeabilized synaptosomes, ATP (1 mM) and free Ca2+ (approximately 20 microM) enhanced the phospholipase C hydrolysis of this substrate to form labeled diacylglycerol. When the same permeabilized synaptosomal preparation was incubated with [2-3H]inositol-phosphatidylinositol, ATP not only enhanced the formation of labeled inositol 1-phosphate, but also inhibited the conversion of inositol 1-phosphate to inositol. Furthermore, ATP appeared to reduce the Ca2+ requirement of the phosphatidylinositol-phospholipase C. Inhibition of the conversion of inositol 1-phosphate to inositol could not be overcome by increasing the Mg2+ concentration in the incubation medium. Although the ATP effect is not viewed as a receptor-mediated event, it is possible that such an event may occur in synaptosomes under conditions in which intrasynaptic Ca2+ concentration becomes elevated.

Adenosine Triphosphate↗
PubMed1988

Alterations in rat brain polyphosphoinositide metabolism due to acute ethanol administration.

The effects of acute ethanol administration on the polyphosphoinositide metabolism of rat brain cerebral cortex were examined. Intracerebral injections of [gamma-32P]ATP proved to be an effective in vivo method to prelabel brain phospholipids, especially the polyphosphoinositides. High acute doses of ethanol (8 or 6 g/kg b.wt.) administered by gavage significantly inhibited the breakdown of polyphosphoinositides as judged by an elevation in the concentration as well as the labeling of these compounds. Concomitantly, there was a significant reduction in the level of diacylglycerols. Low acute doses of ethanol (2 g/kg b.wt.) did not seem to have any effects on the basal levels or labeling of these compounds. The changes in polyphosphoinositide labeling due to ethanol intoxication were reverted to near control values when animals regained their righting reflex (approximately 4 hr). These studies demonstrate that, under normal conditions, polyphosphoinositides and diacylglycerols are maintained in a dynamic equilibrium and that acute doses of ethanol can suppress the signal transduction process and disturb this equilibrium.

Adenosine Triphosphate↗
PubMed1987

Acute tachycardia and pressor effects following injections of kainic acid into the antero-dorsal medial hypothalamus.

The responses of systemic arterial blood pressure and heart rate to intra-cerebral injections of the excitatory neurotoxin, kainic acid, were examined in urethane-anesthetized rats. Injections of kainic acid into the antero-dorsal medial hypothalamus produced dose-related increases in both blood pressure and heart rate over a range of 30-1000 ng. Exophthalmos, mydriasis, increased respiratory rate and movements of the vibrissae were also noted. Injections of 1000 ng of kainic acid into the antero-dorsal medial hypothalamus produced significantly greater increases in blood pressure and heart rate than comparable injections of equimolar doses of the excitatory neurotoxins, quisqualic acid, N-methyl-D-aspartic acid or quinolinic acid. No differences in the magnitude of the cardiovascular responses to 1000 ng of kainic acid were detected between injections directed towards the paraventricular nucleus of the hypothalamus (PVN), lateral hypothalamus or lateral cerebral ventricle. In contrast, at doses of 30 ng, injections directed towards the paraventricular nucleus produced significantly greater responses than comparable injections into the lateral hypothalamus, medial thalamus or lateral cerebral ventricle. The distribution of radiolabelled kainic acid at this dose was found to extend ipsilaterally in the medial hypothalamus as far as 1 mm rostral and caudal to the injection site. The results suggest that excitation of neuronal cell bodies within the medial hypothalamus by excitatory neurotoxins produces acute increases in blood pressure and heart rate. However, widespread diffusion of kainic acid, in particular, was documented and caution in interpretation of the results produced by local intra-cerebral injections of this agent is recommended.

Animals↗
PubMed1987

Effects of chronic ethanol administration on rat brain phospholipid metabolism.

Alterations in brain phospholipid metabolism were observed after chronic ethanol administration for 16 days to developing rats. Animals were injected intraperitoneally with 32Pi 16 h prior to killing. Overall uptake of 32Pi by brain did not differ between the control and ethanol-treated groups, which were killed 2 h and 24 h after the last ethanol feeding. Except for an increase in the labeling of myelin after ethanol treatment, the amount of radioactivity recovered in the synaptosomal-mitochondrial and plasma membrane fractions of control and ethanol-treated groups was not different. Relative to the radioactivity of phosphatidylcholines, which indicated no change, there were increases (20-44%) in labeling of ethanolamine plasmalogens, phosphatidic acids, and phosphatidylinositols in cortical synaptosomes from the 2-h ethanol-treated group. In the plasma membrane fractions, however, increases (9-14%) in labeling of phosphatidylserines and phosphatidylinositols were observed in both 2- and 24-h ethanol-treated groups. In both membrane fractions, there was an obvious increase (44-86%) in labeling of polyphosphoinositides at 24 h after withdrawal from ethanol. Results thus indicate an adaptive increase in the biosynthesis of ethanolamine plasmalogen and brain acidic phospholipids due to chronic ethanol administration. Furthermore, the increase in labeling of polyphosphoinositides in the 24-h withdrawal group may reflect the hypoactivity associated with ethanol withdrawal.

Animals↗
PubMed1987

Chronic ethanol effect on the acidic phospholipids of synaptosomes isolated from cerebral cortex of C57BL/6NNIA mice--a comparison with age.

A total of six groups of C57BL/6NNIA male mice at 6, 18 and 28 months of age were administered a liquid diet containing either ethanol (8 g/kg body wt/day) or an isocaloric amount of glucose for three weeks. Sixteen hours after the last ethanol feeding, homogenates of cerebral cortices were prepared for isolation of the synaptosome-mitochondrial fraction. Phospholipids were separated by two-dimensional tlc and the level of individual phospholipids was determined by assaying the lipid phosphorus content. Based on protein content, there was a decrease (18%) in the level of phosphatidylserines between samples from 6 and 28 month-old mice; no age difference was observed in other phospholipids. Ethanol consumption resulted in a three-fold increase in poly-phosphoinositide level in the 6 month-old group, but the difference diminished considerably with age. The increase in poly-phosphoinositide level suggests a link between chronic ethanol administration and the receptor-mediated signal transduction mechanism involving phosphoinositide turnover. Results further indicate that animals in the younger age group are more readily influenced by the chronic effect of ethanol than those in the older age group.

Aging↗
PubMed1984

Increased acidic phospholipids in rat brain membranes after chronic ethanol administration.

Two types of plasma membranes isolated from rat brain cortex were used to study the membrane-perturbing properties of ethanol. Rats administered ethanol in the form of a liquid diet showed an increase in levels of phosphatidylserines, phosphatidylinositols and phosphatidic acids as compared to controls. The results present evidence that chronic ethanol treatment results in an increase in the acidic phospholipids in brain membranes. This type of membrane modification may have important implications for the function of membrane transport enzymes such as (Na+, K+)-ATPase, which also increases in activity upon chronic ethanol administration.

Alcoholism↗
PubMed1983

Different RNA patterns of globin and non-globin 40S heterogeneous nuclear RNA-protein complexes in chicken reticulocyte nuclei.

40s heterogeneous nuclear RNA-protein complex (HnRNP) was isolated from chicken reticulocyte nuclei after digestion of RNA by the endogenous nuclease. The size of the total RNA and beta globin RNA was compared by agarose and high resolution acrylamide gel electrophoresis. The results show that size of the total RNA ranges between 20 to 650 bases and the most prominent sizes are between 20 and 70-80 bases. The size of the RNA increases at roughly 10 base intervals between 40 and 70 bases on an acrylamide gel. The size of the beta globin RNA is smaller (25-50 bases) than the total RNA and also the RNA pattern is considerably different from that of total RNA. This suggests that, although the overall structure of 40s HnRNP might be the same, there is significant differences in the interaction of globin RNA with HnRNP protein and that of non-globin RNA with HnRNP protein in chicken reticulocyte nuclei.

Animals↗
PubMedDate not supplied

Inositol phosphates and intracellular calcium after bradykinin stimulation in fibroblasts from young, normal aged and Alzheimer donors.

Several studies suggest that alterations in the receptor-mediated phosphoinositide cascade and cytosolic free calcium concentration ([Ca2+]i) are involved in the pathophysiology of aging and Alzheimer's disease. Therefore, the phosphoinositide cascade and [Ca2+]i were determined under resting conditions and after stimulation with bradykinin (100 nM) in cultured human skin fibroblasts from young (21 +/- 3 years), normal aged (59 +/- 6 years) and Alzheimer subjects (58 +/- 6 years). The inositol polyphosphates (IP3, IP2 and IP) were monitored after prelabeling the cells with [3H]inositol in serum free medium. [Ca2+]i was determined with the fluorescent probe, fura-2AM, under exactly analogous conditions. The bradykinin-induced formation of IP3 and IP2 increased significantly in fibroblasts from normal aged and Alzheimer donors compared to young subjects, but did not differ from each other. Bradykinin-induced IP3 formation was 63-117% above the young group at time points between 10-60 s in normal aged or Alzheimer donors. Bradykinin-induced IP2 formation was 49-59% above the young group at time points between 10-60 s in normal aged or Alzheimer subjects. Neither the basal [Ca2+]i, nor the bradykinin-stimulated [Ca2+]i, differed among fibroblasts from young, normal aged and Alzheimer donors. The precise molecular basis and pathophysiological significance of the enhanced bradykinin-induced phosphoinositide cascade in fibroblasts from aged donors remains to be determined.

Adult↗
PubMedDate not supplied

Synthesis of biotinylated glyfoline for immunoelectron microscopic localization.

Antineoplastic glyfoline (1) has potent antitumor efficacy against various murine and human solid tumors. To elucidate the actual mechanism of action, we synthesized biotinylated glyfoline (B-Gly) and used it for the visualization of glyfoline-binding sites in nasopharyngeal carcinoma (NPC) cells. Under the electron microscope (EM), after cells were incubated for 6-36 h, the reaction products of anti-B-Gly were seen on some areas of the external cell surface and on the outer and inner membranes of the mitochondria. Pure EM morphology of NPC cells after glyfoline treatment revealed the similar morphological change of mitochondria. These findings indicate that the binding site of glyfoline in NPC is the inner membrane of the mitochondria, suggesting that B-Gly can be used as a marker for glyfoline localization.

Acridines↗