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Biomedical subjects

H Huang

Publications and source records attributed to H Huang.

At least 379 records · Page 21Linked to original sources
PubMed1997

Effect of limited proteolysis on the stability and enzymatic activity of human placental S-adenosylhomocysteine hydrolase.

Human placental S-adenosylhomocysteine (AdoHcy) hydrolase was subjected to limited papain digestion. The multiple cleavage sites in the enzyme were identified to be Lys94-Ala95, Tyr100-Ala101, Glu243-Ile244, Met367-Ala368, Gln369-Ile370, and Gly382-Val383. Despite multiple cleavage sites in the backbone of the protein, the digested enzyme was able to maintain its quaternary structure and retain its full catalytic activity. The enzyme activity of the partially digested AdoHcy hydrolase was essentially identical to that of the native enzyme at several pH values. The thermal stabilities of the native and partially digested enzymes were only slightly different at all temperatures tested. The stability of both native and partially digested enzymes were examined in guanidine hydrochloride and equilibrium unfolding transitions were monitored by CD spectroscopy and tryptophan fluorescence spectroscopy. The results of these experiments can be summarized as follows: (1) CD spectroscopic analysis showed that the overall secondary and tertiary structures of the partially digested enzyme are essentially identical with those of the native enzyme; and (2) tryptophan fluorescence spectroscopic analysis indicated that there are small differences in the environments of surface-exposed tryptophan residues between the partially digested enzyme and the native enzyme under unfolding conditions. The differences in the free energy of unfolding, delta(delta Gu) [delta Gu(native)-delta Gu(digested)], is approximately 1.3 kcal/mol. When NAD+ was removed from the partially digested enzyme, the secondary and tertiary structures of the apo form of the digested AdoHcy hydrolase were completely lost and the enzymatic activity could not be recovered by incubation with excess NAD+. These results suggest that AdoHcy hydrolase exists as a very compact enzyme with extensive intramolecular bonding, which contributes significantly to the overall global protein stabilization. Identification of the surface-exposed peptide bonds, which are susceptible to papain digestion, has provided some constraints on the spatial orientations of subunits of the enzyme. This information, in turn, has provided supplemental data for X-ray crystallographic studies currently ongoing in our laboratories.

Adenosylhomocysteinase↗
PubMed1997

Measurement and clinical significance of endothelin in neonatal urine.

The present study was undertaken to figure out the source of urinary endothelin (ET) and the clinical significance of its possible variations. Urinary ET levels were measured by radioimmunoassay (RIA) in 17 healthy newborns and 20 asphyxiated neonates on days 1, 3, 7 after birth. Plasma ET concentrations of healthy premature infants on day 7 and urinary ET levels in 10 healthy children were also observed at the same time. Results showed that: (1) Urinary ET levels and ET excretion rates were higher than plasma ET in preterm infants on days 7 after birth; (2) Both in preterm and full term infants, urinary ET concentrations fell from the 1st day to the 7th day after birth, ET excretion rates elevated markedly at the end of the 1st week, and they were significantly higher than that of children; (3) Urinary ET levels of asphyxiated group on days 1 and 3 were much higher than those of healthy neonates, and positively correlated with the severity of the illness and urinary NAG. We conclude that: (1) urinary ET mainly comes from the production in renal cells; (2) ET levels in healthy neonatal urine reflect the maturity of kidney; (3) measurement of urinary ET levels in asphyxiated neonates is helpful to judge the degree and to evaluate the prognosis of renal injury.

Acute Kidney Injury↗
PubMed1997

Molecular recognition of diketide substrates by a beta-ketoacyl-acyl carrier protein synthase domain within a bimodular polyketide synthase.

BACKGROUND: Modular polyketide synthases (PKSs) are large multifunctional proteins that catalyze the biosynthesis of structurally complex bioactive products. The modular organization of PKSs has allowed the application of a combinatorial approach to the synthesis of novel polyketides via the manipulation of these biocatalysts at the genetic level. The inherent specificity of PKSs for their natural substrates, however, may place limits on the spectrum of molecular diversity that can be achieved in polyketide products. With the aim of further understanding PKS specificity, as a route to exploiting PKSs in combinatorial synthesis, we chose to examine the substrate specificity of a single intact domain within a bimodular PKS to investigate its capacity to utilize unnatural substrates. RESULTS: We used a blocked mutant of a bimodular PKS in which formation of the triketide product could occur only via uptake and processing of a synthetic diketide intermediate. By introducing systematic changes in the native diketide structure, by means of the synthesis of unnatural diketide analogs, we have shown that the ketosynthase domain of module 2 (KS2 domain) in 6-deoxyerythronolide B synthase (DEBS) tolerates a broad range of variations in substrate structure, but it strongly discriminates against some others. CONCLUSIONS: Defining the boundaries of substrate recognition within PKS domains is crucial to the rationally engineered biosynthesis of novel polyketide products, many of which could be prepared only with great difficulty, if at all, by direct chemical synthesis or semi-synthesis. Our results suggest that the KS2 domain of DEBS1 has a relatively relaxed specificity that can be exploited for the design and synthesis of medicinally important polyketide products.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗
PubMed1997

Epstein-Barr virus BHRF1 prohibits the cells of nasopharyngeal carcinoma from apoptosis.

Epstein-Barr virus (EBV) is associated with nasopharyngeal carcinoma (NPC). The BHRF1 EBV protein is expressed at high levels in productively infected cells and certain latently infected cells. In order to investigate the effect of expression of BHRF1 on the biological behaviour of NPC cells, we constructed the BHRF1 high expression vector and transfected it into the NPC cell line, CNE2. Then, the alteration of proliferation and apoptotic rates in the cells were tested before and after camptothecin treatment. After treatment by camptothecin, BHRF1-CNE2 cells could constantly and slowly proliferate and its apoptotic rate was less than in control groups, and the number of cells in the G phase decreased and in the S phase increased. So, it suggests that BHRF1 expression can enhance the resistibility of CNE2 cells to DNA-damaging agents that cause apoptosis.

Antineoplastic Agents, Phytogenic↗
PubMed1997

Reduced fecundity in insulin-like growth factor-binding protein-1 transgenic mice.

Transgenic mice that overexpress insulin-like growth factor-binding protein-1 (IGFBP-1) demonstrate a reduced litter size compared to nontransgenic, wild-type mice derived from the same genetic background. To determine the mechanism underlying this phenomenon, we examined the number of ovulatory follicles per cycle in naturally mated transgenic and wild-type mice by counting the corpora lutea and the blastocysts harvested by uterine flushing. In addition, we investigated the effects of insulin-like growth factor-I (IGF-I) on blastocyst DNA synthesis and examined the effects of a transgenic maternal environment on fetal outcome by cross transfer of blastocysts. Significantly fewer corpora lutea were observed in ovaries from transgenic vs. wild-type mice (7.6 +/- 1.8 vs. 11.8 +/- 1.5), and fewer blastocysts were harvested from transgenic mice compared to wild-type mice (7.6 +/- 2.3 vs. 10.1 +/- 2.0). DNA content and basal DNA synthesis were similar in blastocysts from nontransgenic and transgenic mice. However, unlike wild-type blastocysts, transgenic blastocysts did not respond to IGF-I with an increase in DNA synthesis. To determine the effects of maternal environment on fetal outcome, a mixture of equal numbers of transgenic and nontransgenic blastocysts was transferred into foster mothers. The ratio of transgenic to nontransgenic pups was not significantly different from the theoretically predicted value of 1. However, the litter size was significantly reduced in wild-type compared to transgenic foster mothers. These data suggest that the reduced fecundity is due to reduced ovulation and blastocyst number. Furthermore, expression of the transgene in neither the blastocyst nor the maternal tissues had any significant negative effect on implantation or fetal wastage.

Animals↗
PubMed1997

FON1, an Arabidopsis gene that terminates floral meristem activity and controls flower organ number.

A novel gene that regulates floral meristem activity and controls floral organ number was identified in Arabidopsis and is designated FON1 (for FLORAL ORGAN NUMBER1). The fon1 mutants exhibit normal vegetative development and produce normal inflorescence meristems and immature flowers before stage 6. fon1 flowers become visibly different from wild-type flowers at stage 6, when the third-whorl stamen primordia have formed. The fon1 floral meristem functions longer than does that of the wild type: after the outer three-whorl organ primordia have initiated, the remaining central floral meristem continues to produce additional stamen primordia interior to the third whorl. Prolonged fon1 floral meristem activity also results in an increased number of carpels. The clavata (clv) mutations are known to affect floral meristem activity. We have analyzed the clv1 fon1, clv2 fon1, and clv3 fon1 double mutants. These double mutants all have similar phenotypes, with more stamens and carpels than either fon1 or clv single mutants. This indicates that FON1 and CLV genes function in different pathways to control the number of third- and fourth-whorl floral organs. In addition, to test for possible interactions between FON1 and other floral regulatory genes, we have constructed and analyzed the relevant double mutants. Our results suggest that FON1 does not interact with TERMINAL FLOWER1, APETALA1, APETALA2, or UNUSUAL FLORAL ORGAN. In contrast, normal LEAFY function is required for the expression of fon1 phenotypes. In addition, FON1 and AGAMOUS both seem to affect the domain of APETALA3 function, which also affects the formation of stamen-carpel chimera due to fon1 mutations. Finally, genetic analysis suggests that FON1 interacts with SUPERMAN, which also regulates floral meristem activity.

Arabidopsis↗
PubMed1997

Unusual fatty acid compositions of the hyperthermophilic archaeon Pyrococcus furiosus and the bacterium Thermotoga maritima.

The fatty acid compositions of the hyperthermophilic microorganisms Thermotoga maritima and Pyrococcus furiosus were studied and compared. A total of 37 different fatty acids were identified in T. maritima, including the novel 13,14-dimethyloctacosanedioic acid. In contrast, a total of 18 different fatty acids were characterized, as minor components, in P. furiosus, and these included saturated, monounsaturated, and dicarboxylic acids. This is the first report of fatty acids from an archaeon.

Archaea↗
PubMed1997

The ubiquitin-conjugating enzyme Rad6 (Ubc2) is required for silencing in Saccharomyces cerevisiae.

It has been previously shown that genes transcribed by RNA polymerase II (RNAP II) are subject to position effect variegation when located near yeast telomeres. This telomere position effect requires a number of gene products that are also required for silencing at the HML and HMR loci. Here, we show that a null mutation of the DNA repair gene RAD6 reduces silencing of the HM loci and lowers the mating efficiency of MATa strains. Likewise, rad6-delta reduces silencing of the telomere-located RNAP II-transcribed genes URA3 and ADE2. We also show that the RNAP III-transcribed tyrosyl tRNA gene, SUP4-o, is subject to position effect variegation when located near a telomere and that this silencing requires the RAD6 and SIR genes. Neither of the two known Rad6 binding factors, Rad18 and Ubr1, is required for telomeric silencing. Since Ubrl is the recognition component of the N-end rule-dependent protein degradation pathway, this suggests that N-end rule-dependent protein degradation is not involved in telomeric silencing. Telomeric silencing requires the amino terminus of Rad6. Two rad6 point mutations, rad6(C88A) and rad6(C88S), which are defective in ubiquitin-conjugating activity fail to complement the silencing defect, indicating that the ubiquitin-conjugating activity of RAD6 is essential for full telomeric silencing.

DNA-Binding Proteins↗
PubMed1997

Estradiol induces C-type natriuretic peptide gene expression in mouse uterus.

Previous experiments have demonstrated that C-type natriuretic peptide (CNP) expression in the uterus varies during the estrous cycle with maximal expression at proestrus. The present study was designed to determine whether exogenous steroid hormones regulate uterine CNP expression in ovariectomized mice. Estradiol increased significantly (3-fold) uterine immunoreactive CNP (irCNP) rapidly and dose dependently in ovariectomized mice as measured by radioimmunoassay. Other steroids produced either no significant change (testosterone, 1 mg; 2-methoxyestradiol, 1 microgram) or weak induction (estriol, 1 microgram) from vehicle controls. Progesterone (1 mg) significantly attenuated the estrogen-stimulated irCNP response by 50% when injected 30 min before estrogen (1 microgram) in estrogen-primed ovariectomized mice. Estrogen-stimulated increases in uterine CNP transcripts detected by ribonuclease protection analyses were blocked by actinomycin D (160 micrograms) or ICI-164,384 (20 micrograms), a specific nuclear estrogen receptor antagonist. These results indicate that a nuclear estrogen receptor is required for estrogen to stimulate uterine CNP transcription and that progesterone negatively regulates estrogen-stimulated CNP expression.

Animals↗
PubMed1997

Expression of insulin-like growth factor binding proteins (IGFBPs) in IGFBP-1 transgenic mice.

The hepatic and renal expressions of the insulin-like growth factor binding proteins (IGFBPs) were examined in transgenic (Tg) mice which overexpress a rat IGFBP-1 transgene driven by the phosphoglycerate kinase-1 promoter. There were no significant difference in the abundance of serum IGFBPs in Tg and wild-type (Wt) mice. Although total hepatic IGFBP-1 mRNA mouse and transgene-derived) levels were similar in Tg mice to the levels of mouse IGFBP-1 mRNA in Wt mice on day 1 of life, in Tg mice only approximately 30% of the IGFBP-1 mRNA was derived from transcription of the mouse gene. An age-related decline in hepatic IGFBP-1 mRNA levels was apparent in both Tg and Wt mice. Food deprivation resulted in increased levels of mouse IGFBP-1 mRNA but the total IGFBP-1 mRNA levels were not significantly different in Tg and Wt mice. In the kidney, unlike the liver, IGFBP-1 mRNA levels in Tg mice were markedly elevated compared with Wt mice and no significant decline was seen with age. Northern blots of hepatic and renal RNA demonstrated similar levels of IGFBP-3, -4, -5 and -6 mRNAs in Tg and Wt mice. From these data we can conclude that in the liver expression of the transgene leads to a coordinated reduction in mouse IGFBP-1 mRNA levels.

Aging↗
PubMed1997

[Monocyte tumor necrosis factor and tumor necrosis factor receptor expression in patients with alcoholic liver cirrhosis].

We evaluated the spontaneous production of tumor necrosis factor alpha(TNF alpha) and soluble tumor necrosis factor receptor (sTNFR) and determined whether TNF alpha and sTNFR expression on mononuclear cells in vitro in patients with alcoholic liver cirrhosis (AC) was induced by lipopolysaccharide (LPS) or ethanol stimulation. Their levels were examined by an enzyme-linked immunosorbent assay (ELISA). Patients with alcoholic cirrhosis showed higher spontaneous expression in TNF alpha and sTNFRp55, p75 on monocyte than controls. The concentration of TNF alpha and both sTNFR from LPS-stimulated peripheral blood monocyte either in patients or in healthy controls was markedly increased as compared with spontaneous production. The patients showed significantly higher level of TNF alpha and both sTNFRp55, p75 than controls (P < 0.05, P < 0.01, P < 0.005 respectively). Increased TNF alpha and both sTNFR expressions following ethanol stimulation were not found neither in patients nor in controls. These data suggest that elevated TNF alpha and sTNFR levels in serum are correlated with activation of mononuclear cells in vivo, which is closely correlated with endotoxin, but no direct correlation with ethanol is found.

Adult↗
PubMed1997

[Significance of glycosaminoglycans content in developing mechanism of cleft palate].

To explore significance of Glycosaminoglycans content in the development of embryo and forming mechanism of cleft palate, Dexamethason acetate was injected into the abdomen of NIH mouse on the 12th day of gestation to induce cleft palate mouse embryo model. Then by taking cranio-maxillary coronary sections, stained with Alcian blue/PAS and quantitatively analysing the area of the palatal process covered by glycosaminoglycans using a TDS-90 photodigital system with computer. Results indicate that on 13(12) day(hour) of gestation the colour of Alcian blue starts to show in the palatal process. By then, the area covered by glycosaminoglycans in the normal group is 4.69 mm whereas for the experimental group is 2.40 mm, showing a significant statistical difference (P < 0.05). The area of the palatal process covered by glycosaminoglycans gradually increases as the embryo developes, but is distinctly smaller in experimental than in the normal group (P > 0.05). This proves that there's a relationship between the level of glycosaminoglycans in the palatal process and development of cleft palates.

Animals↗
PubMed1997

[High-methylprednisolone treatment in acute cervical spinal cord injury without fracture and dislocation].

We compared methylprednisolone (MP), surgical decompression and both in acute cervical spinal cord injury without fracture and dislocation. The study involved 32 acute cervical spinal cord injury without fracture and dislocation. MP was given to 8 cases (high-MP group) within 8 hours after injury. 12 cases (surgical group) underwent surgical decompression (anterior or posterior approach) within 48 hours after injury. 12 cases (combined group) were treated with MP within 8 hour of their injury and surgical decompression within 48 hours after injury. Neurological function was assessed using scores according to international standards for neurological and functional classification of spinal cord injury. The results showed that combined group were more effective than high-MP or surgical group, in the complete or incomplete spinal cord injury, and in motor and sensory. The risk of such complication as gastrointestinal bleeding or delayed wound healing is not significant with using high-MP.

Aged↗
PubMed1997

[The study of chronobiology of CT features of liver cancer].

OBJECTIVE: To explore the biological cycle of malignant biological behavior of liver cancer, and to provide a research basis for the excepically specific phase of drugs for clinical treatment of liver cancer. METHODS: 24 kinds of CT features reflected varying degree of malignant biological behavior. There were 360 cases altogether from randam sampling 30 cases each month. The analytic method is each CT feature fitting a group data of yearly cycle using cosine curve made the analysis of the cyclic sequence character of each CT feature (cosinor). RESULTS: With 95% confidence, there were 10 CT features which showed biologic rhythm (P < 0.05). The acrophase of CT features for invasive growth concentrated between -60 degrees and -120 degrees (March and April). But for non-invasive growth, the CT features were relatively low and concentrated between -180 degrees and -270 degrees (July and September). No acrophase was shown in between -120 degrees and -180 degrees (May and June) and between -270 degrees and -330 degrees (October and November). CONCLUSION: Between CT features of the invasive and non-invasive growths of liver cancer, a sequential difference in biologic cycles can be observed.

Chronobiology Phenomena↗
PubMed1997

[The effect of the expression of BHRF1 gene of EB virus on the proliferation of the cells of nasopharyngeal carcinoma].

In order to learn the effect of the expression of BHRF1 of Epstein-Barr virus on the growth of the cell of nasopharyngeal carcinoma, high BHRF1 expressive vector was set up and transfected in low grade cell line of nasopharyngeal carcinoma, CNE2. Then the cells were cultivated under the condition of insufficient nutrition. The results show that the BHRF1 expression can prohibit the expression of PCNA, and enhance the survival of tumor cells under conditions of nutrition deprivation. So, it suggests that BHRF1 of EB virus could be involved in the development of nasopharyngeal carcinoma.

Cell Division↗
PubMed1997

Radioimmunoimaging of human breast cancer xenografts in nude mice by using human anti-human breast cancer monoclonal antibodies.

In this study, the human breast cancer-bearing nude mice model has been established and the radioimmunoimaging was carried out by using human anti-human monoclonal antibodies. The results showed that the breast tumor-bearing nude mice received 131I-McAb-CM-1 had a clear image of the xenograft during 4 to 6 days after injection and at the same time T/NT all over 1.0. The highest T/NT reached 7.1. It demonstrates that McAb-CM-1 can specially combine with breast cancer tissues and hopefully it could be used clinically to improve accurate rate of the early breast cancer diagnosis.

Animals↗
PubMed1997

[Detection of point mutation of p53 gene in head and neck squamous cell carcinoma by non-isotopic PCR-SSCP].

Non-isotopic PCR-SSCP technique was used to detect point mutation of p53 gene in fresh tissue taken from head and neck squamous cell carcinoma. The abnormal band of the single-stranded DNA (ssDNA) was identified in 7 of 13 cases. The results showed that point mutation occurred in the related DNA fragments. The point mutation of exon 5 was found in one case and that of exon 6, 7, 8 in two respectively. These results indicated that the p53 gene mutation was closely correlated with the development of head and neck squamous cell carcinoma. Compared with the traditional isotopic PCR-SSCP technique, the non-isotopic PCR-SSCP one is a kind of simpler, safer, quicker and more effective way to detect the mutation of p53 tumor suppressor gene. It is especially useful in the screening of point mutation when handling a large number of samples.

Adult↗