PubMed Health⌕ Search

Biomedical subjects

P C Huang

Publications and source records attributed to P C Huang.

At least 19 recordsLinked to original sources
PubMed1997

Effects of n-3 and n-6 fatty acids on plasma eicosanoids and liver antioxidant enzymes in rats receiving total parenteral nutrition.

The effect of total parenteral nutrition (TPN) enriched with n-3 or n-6 fatty acids on the concentration of plasma eicosanoids was evaluated in rats. Rats were divided into three groups: the control group (n = 6) was fed a chow diet and infused with saline only. Two experimental groups (n = 11, 13) received TPN solutions at an energy level of 30 kcal/100g body weight with 40% energy provided as fat. The experimental groups were maintained on TPN for a period of 7 d. The basal TPN solutions were isonitrogenous and identical in nutrient composition except for differences in lipid source. One experimental group received a safflower oil emulsion, whereas the other group received a fish oil emulsion. At the end of the experimental period, plasma 6-keto prostaglandin F1 alpha, thromboxane B2, bleeding time, lipid peroxidation products, and antioxidant enzymes of liver were analyzed. The results demonstrated that the fish oil group had lower 6-keto prostaglandin F1 alpha concentration than the safflower oil group. Also, plasma thromboxane B2 was the lowest in the fish oil group among the three groups. There was no difference in bleeding time among the groups. With regard to liver lipid peroxidation products, malondialdehyde concentration was not higher in the fish oil group, whereas superoxide dismutase and glutathione peroxidase activities were lower in the fish oil group compared with the control and safflower oil groups. The results suggest that TPN prepared with fish oil fat emulsion causes less accumulation of lipid peroxidation products in the liver of rats, and may be beneficial in preventing platelet aggregation.

6-Ketoprostaglandin F1 alpha↗
PubMed1996

RNA expression patterns of a type 2 metallothionein-like gene from rice.

A type 2 metallothionein-like gene from rice, OsMT-2 (Oryza sativa metallothionein-like gene-2), was isolated in its cDNA form and sequenced. By northern analyses OsMT-2 expression was shown to be induced under stress by sucrose starvation, heat shock and, to a lesser extent, abscisic acid, but not excess metals, including copper. Its response to sucrose starvation was transient and different from OsMT-1, a type 1 metallothionein-like gene of rice inducible by copper. These results suggest that while OsMT-2 is also involved in cellular response to stress, its function may be complementary to that of OsMT-1.

Abscisic Acid↗
PubMed1996

A high cholesterol, (n-3) polyunsaturated fatty acid diet induces hypercholesterolemia more than a high cholesterol (n-6) polyunsaturated fatty acid diet in hamsters.

This study was designed to study the effects of (n-3) polyunsaturated fatty acids (PUFA) on plasma and liver lipids, particularly lipoprotein cholesterol concentrations, in hamsters. Diets rich in (n-3) PUFA (21 g/100 g fatty acid) or (n-6) PUFA (37.4 g/ 100 g fatty acid) with or without 5 g/kg cholesterol (C) supplements were given for 4 wk to male hamsters weighing 70-90 g. The VLDL- and (IDL + LDL)-cholesterol concentrations were 114 and 128% higher in hamsters fed the (n-3) PUFA + C diet than in those fed the (n-6) PUFA + C diet. However, these differences were not observed when cholesterol was not supplemented. Hamsters fed the (n-3) PUFA diet had significantly lower plasma and hepatic triglyceride concentrations than those fed the (n-6) PUFA diet. Concentrations were comparable in hamsters fed (n-6) PUFA + C and (n-3) PUFA + C. Hepatic cholesteryl esters were significantly lower, while hepatic microsomal acyl-CoA:cholesterol acyltransferase activity and VLDL cholesteryl esters were significantly higher in hamsters fed the (n-3) PUFA + C diet than in those fed the (n-6) PUFA + C diet. Our results demonstrate that elevation of VLDL- and (IDL + LDL)-cholesterol in hamsters by (n-3) PUFA, compared with (n-6) PUFA, is dependent on dietary cholesterol supplementation and may be due to decreased catabolism of these lipoproteins.

Acetyl-CoA C-Acyltransferase↗
PubMed1996

Semi-empirical simulation of Zn/Cd binding site preference in the metal binding domains of mammalian metallothionein.

Metallothionein, a two-domain protein, naturally binds seven gram atoms of divalent ions such as Zn and Cd. Four of the metals (M1, M5, M6 and M7) are found in the alpha-domain and three (M2, M3 and M4) in the beta-domain. Previous studies have shown that metals in the beta-domain are more readily exchangeable, and the level of avidity is site specific. By semi-empirical MNDO modified neglect of diatomic overlap calculations, we found the tendency of binding energy for Cd to be M4 > M2 > M3 [corrected] in the beta-cluster and M5 > M7 > M1, M6 in the alpha-cluster. Thus, the replacement of Zn by Cd can be expected to follow the order M4-->M2-->M3 in the beta-domain and M5-->M7-->M1 or M6 in the alpha-domain. This is reflected by energy differences computed with a series of simulated structures derived from either X-ray crystallography or NMR coordinates.

Animals↗
PubMed1995

The effects of apolipoprotein E polymorphism on the distribution of lipids and lipoproteins in the Chinese population.

The effects of apolipoprotein E (apo E) polymorphism on the distribution of serum levels of total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C) and low density lipoprotein cholesterol (LDL-C) were studied in 546 unrelated Chinese in Taiwan. By isoelectric focusing and immunoblotting, three common alleles were demonstrated. The frequencies of the epsilon 2, epsilon 3 and epsilon 4 alleles were 0.076, 0.875 and 0.049, respectively. The relative frequency of the epsilon 3 allele was higher than that in Caucasians, whereas the frequency of epsilon 4 was lower in the Chinese population. Individuals with apo E4/4 phenotype had the highest serum TC and LDL-C concentrations, while the lowest levels were associated with apo E2/2 phenotype. There was a trend for individuals carrying the epsilon 2 allele to have a higher HDL-C level. No relationship between apo E phenotype and TG level was observed in this study. These data indicated that a given apo E allele acted in a relatively similar way in determining individual differences between Chinese and Caucasian populations in serum lipid and lipoprotein.

Adolescent↗
PubMed1995

A novel stress-inducible metallothionein-like gene from rice.

A novel rice genomic sequence encoding coding segments homologous to other metallothionein-like genes was isolated from Oryza sativa genomic library. This sequence, hereby designated as rgMT (rice genomic metallothionein-like gene), consists of two exons and one intron. From the coding sequence, it is predicted that rgMT encodes one protein of 74 amino acids. Differential expression of rgMT in rice plants was observed as mature transcripts were more abundant in roots than in leaves and sheaths. Under different stress conditions, such as excess heavy metals and heat shock, expression of rgMT was significantly elevated. This was especially noticeable with 250 microM CuCl2 for 16 h, 40 degrees C heat for 2 h and 0.06% DMSO for 1 h. Under sucrose starvation, rgMT transcripts also increased with time up to 72 h. During recovery from sucrose starvation, the transcripts declined slightly within 12 h of recovery. rgMT transcripts were also seen to have increased expression in senescent leaves. These results support the notion that rgMT is a stress-inducible gene in rice heretofore unreported.

Abscisic Acid↗
PubMed1995

Sources of triacylglycerol accumulation in livers of rats fed a cholesterol-supplemented diet.

The source of free fatty acids (FFA) and the pathways contributing to the accumulation of neutral fats in livers of rats fed a cholesterol-enriched diet were investigated in this report. Supplementation with 1% cholesterol in the diet for four weeks resulted in hepatomegaly in the rats. The contents of cholesterol and triacylglycerols (TG) per gram liver measured in rats fasted overnight increased by 48 mg (approximately tenfold) and 66 mg (approximately fourfold), respectively. The activities of glycerophosphate acyltransferase and diacylglycerol acyltransferase, the two key enzymes for TG synthesis in liver microsomes, were found to increase by 23 and 19%, respectively, in the cholesterol-fed rats. The secretion of plasma TG present predominantly in very low density lipoprotein was found to decrease by approximately 30%. The incorporation of tritium from tritiated water in liver FFA increased by twofold in rats fed the cholesterol-supplemented diet, whereas the activity of CPT I in liver mitochondria decreased by 23%. The uptake of plasma FFA in vivo in livers of fasted rats maintained on the cholesterol-supplemented diet decreased by 60%. Our data thus indicate that the excess TG accumulated in livers of rats fed the cholesterol-enriched diet resulted from increased synthesis and decreased secretion of TG. To meet the demand of fatty acids for this purpose, de novo lipogenesis increased, whereas beta-oxidation decreased. Although difference in the uptake of extrahepatic FFA may be discounted, a difference in the uptake of chylomicron remnants between the control and cholesterol-fed rats may not be ruled out.

Acyltransferases↗
PubMed1995

Transcripts of metallothionein genes in Arabidopsis thaliana.

Using oligonucleotides with highly conserved cysteine-rich codons as probes, we isolated from a lambda YES Arabidopsis thaliana cDNA library two different sequences, each encodes an unique protein. These proteins, hereby designated as AtMT-q (AtMT-2) and AtMT-k (AtMT-1), are characteristic of metallothionein, carrying 13 and 14 cysteines in a total of 45 and 81 amino acids, respectively.

Amino Acid Sequence↗
PubMed1995

Effects of L-glutamine on induced hepatosteatosis in rats receiving total parenteral nutrition.

Glutamine (Gln) supplementation in total parenteral nutrition (TPN) has been shown to have a preventive effect on high glucose induced hepatic steatosis. This animal study was undertaken to evaluate whether Gln could prevent hepatic steatosis induced by high fat or high glucose infusion. After placement of internal jugular catheters, rats were divided into three groups: control (n = 8), high fat (n = 13) and high glucose (n = 14) groups. The control group was fed with a chow diet and infused with saline alone. The experimental groups were infused with either a high fat (65% of nonprotein calories) or high glucose (83% of total kilocalories) solution. Energy intake was 35 kcal/100 g body weight per day. TPN solutions were isocaloric, isonitrogenous and isovolemic. Each experimental group was divided into two subgroups, with one receiving a Gln supplement to replace 40% of total amino acid nitrogen. The results demonstrated obvious fatty infiltration in the experimental groups, mainly from triglyceride (TG) accumulation. Plasma very low density lipoprotein-triglyceride (VLDL-TG) was significantly lower in the experimental groups than in the control group, suggesting that liver secretion of TG may have been inhibited in the experimental groups. Liver fatty acid synthetase (FAS) activity and plasma free fatty acid were lower in the high fat group than in the control and high glucose groups. There was no difference in hepatic lipids content, FAS activity, VLDL-TG, hepatic uptake of fatty acids and liver histologic change in the subgroups with and without Gln supplementation. Thus, Gln supplementation in a TPN solution has no effect in preventing hepatic steatosis induced by either high glucose or high fat infusion in rats under these experimental conditions.

Analysis of Variance↗
PubMed1995

Lipoprotein responses to fish, coconut and soybean oil diets with and without cholesterol in the Syrian hamster.

Thirty-six young male Syrian hamsters were fed with test diets containing coconut oil, soybean oil or fish oil with and without 0.5% cholesterol for 6 weeks. Without dietary cholesterol supplementation, animals on the fish oil diet had significantly lower plasma total triglyceride (TG) and total cholesterol than those on the coconut oil or soybean oil diet. The decrease of TG was seen mainly in the very low density lipoprotein (VLDL) fraction. The degree of decrease in cholesterol was similar in all of the lipoprotein fractions. With 0.5% dietary cholesterol supplementation, there was no significant difference in plasma TG level among the three dietary groups. However, the fish oil group had significantly higher plasma cholesterol than the coconut oil and soybean oil groups. The increase of cholesterol was mainly in the VLDL and low density lipoprotein (LDL) fractions. In contrast to the plasma cholesterol level, the hepatic cholesteryl ester content was significantly lower in the cholesterol-supplemented fish oil group than in the coconut oil and soybean oil counterparts. The cholesterol-supplemented fish oil group showed higher liver microsomal acyl-coenzyme A:cholesterol acyltransferase activity than the other two groups, while there was no significant difference in the excretion of fecal neutral and acidic sterols among the three dietary groups.

Animals↗
PubMed1994

Replacement of all alpha-domain lysines with glutamates reduces metallothionein detoxification function.

Mammalian metallothioneins (MTs) possess eight highly conserved lysine residues, including three in each of two metal binding domains. We used site-directed mutagenesis to replace these intradomain lysines in Chinese hamster ovary MT2 with glutamic acid and/or glutamine. These mutant MTs were expressed in a metal sensitive yeast host. One mutant which had all three lysines in the alpha-domain replaced by glutamates (K43,51,56E) exhibited a reduced ability, relative to native MT, to protect yeast transformants against otherwise toxic levels of cadmium. This triply substituted mutant also exhibited anomalous migration on a non-denaturing gel relative to wild type MT and other MT lysine mutants, suggesting that the intradomain lysines are important in maintaining the conformational integrity of MT.

Binding Sites↗
PubMed1994

Substitution of glutamic acids for the conserved lysines in the alpha domain affects metal binding in both the alpha and beta domains of mammalian metallothionein.

Lysine residues are highly conserved in mammalian metallothioneins (MTs). Recombinant mutant Chinese hamster MT2 in which all of the lysines (K) in the alpha-domain were substituted by glutamic acids (E) was assayed with, expressed in and purified from a cadmium sensitive strain of yeast Saccharomyces cerevisiae. Circular dichroism analyses of the mutated protein, mutein K43,51,56E, revealed that the overall structure remained unchanged. However, a 1-D 113Cd NMR study detected significant differences in the chemical shifts of the corresponding resonances between wild type protein and the recombinant mutein. Reduction of integrated intensity in the NMR spectra was also observed for resonances from the four-metal cluster (I and V-VII) in the alpha-domain of the mutein. At various temperatures, facile intermolecular exchange of metals in the beta-domain of the mutein was also observed, which was unexpected and was different from wild type. Our results thus demonstrate that replacing all three lysines by glutamic acids in the alpha-domain changed metal-thiolate interactions in both domains of the recombinant mutein. This may explain the reduced ability of the mutein to convey cadmium resistance. We propose that while the lysine residues in the alpha-domain of wild type MT are not critical for maintaining protein structure, they play a role in regulating the microenvironment and stability of both metal-binding clusters, a feature critical to metal detoxification.

Amino Acid Sequence↗
PubMed1993

Cellular interactions implicated in the mechanism of photoreceptor degeneration in transgenic mice expressing a mutant rhodopsin gene.

Photoreceptors of transgenic mice expressing a mutant rhodopsin gene (Pro347-->Ser) slowly degenerate. The mechanism of degeneration was studied by aggregation of embryos of normal and transgenic mice to form chimeras. In these chimeras, mosaicism was observed in the coat color, retinal pigment epithelium, and retina. In the retina, the genotype of adjacent patches of normal and transgenic photoreceptors was determined by in situ hybridization with a transgene-specific RNA probe. Photoreceptors in the chimeric retina degenerated uniformly, independent of the genotype and similar to the photoreceptors in transgenic mice. However, the chimeric retinas showed varying proportions of normal and transgenic cells. The chimeric retina with a nearly even proportion of normal and transgenic photoreceptors displayed uniform but slower degeneration than that observed in a transgenic mouse of the same age. Our results demonstrate non-autonomy of gene action for the mutated rhodopsin gene and imply that cellular interactions between photoreceptors in the retina probably play a role in degeneration.

Amino Acid Sequence↗
PubMed1993

Metallothionein detoxification function is impaired by replacement of both conserved lysines with glutamines in the hinge between the two domains.

Mammalian metallothioneins (MTs) possess eight highly conserved lysine residues, two of which constitute the hinge between two metal binding domains. By site-directed mutagenesis and recombinant DNA techniques, we replaced the interdomain lysines in Chinese hamster ovary MT2 with all possible combinations of glutamic acid and/or glutamine. The resultant MTs were expressed and assayed for detoxification function in a transformed yeast system. Results showed that these mutant MTs, like the native protein, bound seven atoms of divalent metal per molecule and conferred cadmium resistance to a metal-sensitive yeast host. Replacement of one or both of the lysines in the interdomain region was inconsequential to the structure and function of MT, unless both substituted residues were uncharged. When both lysines were replaced by glutamine (K30,31Q), a reduction in the ability of MT to protect yeast transformants against otherwise toxic levels of cadmium was observed. This diminished metal detoxification capacity was due to a decrease in the steady-state level of MT. These results suggest that at least one charged amino acid must be present in the hinge for the proper expression of MT.

Animals↗
PubMed1993

[Change and effect of Epstein Barr virus (EBV) antigen induced T8 cells in nasopharyngeal carcinoma patients and EBV seropositive individuals].

T8 cells from peripheral blood mononuclear cells (PBMC) of nasopharyngeal carcinoma (N PC) patients, IgA/VCA positive and negative normal individuals were induced by Epstein Barr virus (EBV) antigen, and their effects on the EBV infected auto-PBMC were observed. The data showed: after PBMC were induced by EBV antigen for 5 days, the T8 cells increased in the all three groups, but less remarkably in NPC group than in the other two groups. The T8 cells induced by EBV antigen could inhibit the activation, proliferation and differentiation of EBV infected auto-B cells in IgA/VCA positive and negative groups. But they had an enhancing effect in NPC group. The results suggest that the production of these cells was reduced and their function altered in NPC patients. Therefore it may be related to the enhancement of EBV activated B cells.

Adult↗
PubMed1992

The complete nucleotide sequence of the Crossostoma lacustre mitochondrial genome: conservation and variations among vertebrates.

The complete mitochondrial (mt) genome of Crossostoma lacustre, a freshwater loach from mountain stream of Taiwan, has been cloned and sequenced. This fish mt genome, consisting of 16558 base-pairs, encodes genes for 13 proteins, two rRNAs, and 22 tRNAs, in addition to a regulatory sequence for replication and transcription (D-loop), is similar to those of the other vertebrates in both the order and orientation of these genes. The protein-coding and ribosomal RNA genes are highly homologous both in size and composition, to their counterparts in mammals, birds, amphibians, and invertebrates, and using essentially the same set of codons, including both the initiation and termination signals, and the tRNAs. Differences do exist, however, in the lengths and sequences of the D-loop regions, and in space between genes, which account for the variations in total lengths of the genomes. Our observations provide evidence for the first time for the conservation of genetic information in the fish mitochondrial genome, especially among the vertebrates.

Animals↗
PubMed1992

Effects of dietary supplementation with fish oil on atherosclerosis and myocardial injury during acute coronary occlusion-reperfusion in diet-induced hypercholesterolemic rabbits.

We studied myocardial injury during acute coronary occlusion-reperfusion and atherosclerosis in rabbits fed a high cholesterol diet with or without fish oil supplementation. New Zealand white male rabbits were divided into 3 groups. Eight control rabbits fed with laboratory standard rabbit chow were group I. In addition to the standard chow, 15 rabbits fed with a 1% cholesterol-enriched diet for 6 weeks were group II, and 10 rabbits fed with a 1% cholesterol-enriched and 10% fish oil supplemented diet for 6 weeks were group III. Acute coronary occlusion was induced by ligating the marginal branch of the left circumflex coronary artery for 1 h, followed by reperfusion for 4 h. Myocardial injury was assessed by tissue creatine kinase activities and amino-nitrogen concentrations from the ischemic (infarct) and nonischemic (normal) myocardium, and the infarct area/risk area ratios of the left ventricle. The surface area of the atherosclerotic lesions of the aorta and pulmonary artery was measured by planimeter. There was significantly more myocardial loss of creatine kinase and amino-nitrogen in the cholesterol-fed rabbits than the controls (p less than 0.01 and 0.02, respectively). The cholesterol and fish oil-treated rabbits had a nonsignificant reduction in myocardial loss of both agents as compared to their corresponding cholesterol-fed ones. The same trend was also found in the infarct area/risk area ratio. Fish oil treated rabbits had a good effect on the reduction of atherosclerotic lesions and tissue cholesterol levels in the aorta and pulmonary artery, but not in the left ventricle.(ABSTRACT TRUNCATED AT 250 WORDS)

Amines↗