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Biomedical subjects

Z Hu

Publications and source records attributed to Z Hu.

At least 253 records · Page 14Linked to original sources
PubMed1997

Compressibility, Phase Transitions, and Oxygen Migration in Zirconium Tungstate, ZrW2O8

In situ neutron diffraction experiments show that at pressures above 2 kilobars, cubic zirconium tungstate (ZrW2O8) undergoes a quenchable phase transition to an orthorhombic phase, the structure of which has been solved from powder diffraction data. This phase transition can be reversed by heating at 393 kelvin and 1 atmosphere and involves the migration of oxygen atoms in the lattice. The high-pressure phase shows negative thermal expansion from 20 to 300 kelvin. The relative thermal expansion and compressibilities of the cubic and orthorhombic forms can be explained in terms of the "cross-bracing" between polyhedra that occurs as a result of the phase transition.

Journal Article↗
PubMed1997

Expression of alpha-fetoprotein and stem cell factor/c-kit system in bile duct ligated young rats.

The existence of a facultative hepatic stem cell compartment in bile ductules that participates in the renewal process of epithelial cell populations in the liver is well documented. The present study was undertaken to determine whether the immature bile epithelium responds differently to growth stimulus induced by bile stasis to that seen in the adult animal. In addition, the possible involvement of the growth factor/receptor systems associated with early activation of hepatic stem cells in bile duct proliferation was also examined. Bile duct ligation was used to induce the proliferation of bile epithelial cells. The expression of full-length alpha-fetoprotein (AFP) was used as an indicator for activation of the stem cell compartment. AFP was highly and selectively expressed in small bile ducts 7 days after bile duct ligation in immature rats up to 5 weeks of age. Although no significant increase in the expression of stem cell factor (SCF) c-kit, hepatocyte growth factor (HGF), and transforming growth factor-alpha (TGF-alpha) was observed 7 days after bile duct ligation in adult rats, the expression of all these growth factors was increased in bile duct ligated rats up to 5 weeks of age. These results suggest that the bile ductular epithelium in the young rats responds to bile stasis in a fashion that is phenotypically similar to that seen during early activation of hepatic stem cells in adult liver.

Age Factors↗
PubMed1997

Genomic mapping of chemokine and transforming growth factor genes in swine.

Five chemokine genes, transforming growth factors alpha, beta 2 and 3 (TGFBA, TGFB-2, and TGFB-3), interleukin 8 (IL-8), and monocyte chemoattractant protein 2 (MCP-2), were mapped to porcine linkage groups on Chromosomes 3q, 10p, 7q, 8, and 12q, respectively. Restriction fragment length polymorphisms (RFLPs) for these genes were developed by Southern blot hybridization after digestion of porcine genomic DNA with BamHI and MspI (TGFBA), BamHI and PvuII (TGFB-2), HindIII (TGFB-3), BglII (IL-8), and PstI (MCP-2) and used to genotype the USDA-MARC Swine Reference Population pigs. Sufficient informative meioses, 61 (TGFBA), 58 (TGFB-2), 28 (TGFB-3), 38 (IL-8), and 156 (MCP-2), were available to pursue two-point pairwise linkage analysis with over 1,000 existing loci in the USDA-MARC genome database to establish initial linkage (LOD > 3). Multi-point analysis with CRIMAP determined the most likely order for each new marker. The assignment of the five chemokine genes in swine concurs with previous porcine/human chromosomal homologies based on results from ZOO-FISH and chromosomal painting experiments. These findings add five new informative Type I markers within a single gene family to the swine genome and may help us understand the genetic basis for disease resistance in livestock.

Animals↗
PubMed1997

Linkage assignment of eleven genes to the porcine genome.

We report comparative linkage mapping of eleven genes in the swine genome by RFLP analysis. These genes include: Acid phosphatase type 5 (ACP5), Cholecystokinin Type B Receptor (CCKBR), Antibiotic Peptide (FALL39), Insulin-like Growth Factor 1 Receptor (IGF1R), Integrin Alpha M (ITGAM), Integrin Beta 2 (ITGbeta2), Opioid Receptor Mu-1 (OPRM1), Pro-hormone Converter (PC1/3), Retinol Binding Protein 3 (RBP3), Ribosomal DNA (RNR1), and Zona Pellucida Glycoprotein 1 (ZP1). The CCKBR and ITGbeta2 loci define the ends of the linkage groups on Chromosomes (Chro) (SSC) 9p and 13qter, respectively.

Animals↗
PubMed1997

Analysis of the ecdysteroid UDP-glucosyltransferase gene of Heliothis armigera single-nucleocapsid baculovirus.

An ecdysteroid UDP-glucosyltransferase (egt) gene was identified from the single (S) nucleocapsid nucleopolyhedrovirus of Heliothis armigera (HearNPV). In baculovirus-infected insects the viral enzyme (EGT) plays a pivotal role in abrogating the insect molting process. The open reading frame of the egt gene is 1545 nucleotides long, encoding a putative protein of 515 amino acids with a Mr of 59.1. The 5'-noncoding region contains a putative early (CAGT) and late (TAAG) motif for transcription initiation, a transcription enhancer sequence (CGTCGC) and two TATA boxes. A putative polyA signal, AATAAA, was found downstream of the translation stop codon. A putative signal peptide of 21 residues was present at the N-terminus of the EGT. The HearNPV egt gene has a high degree of nucleotide and amino acid sequence homology to the egt genes of Buzura suppressaria SNPV and Spodoptera exigua MNPV. The HearNPV EGT shares ten conserved motifs with other EGTs. A phylogenetic tree of twelve baculovirus EGTs was constructed by using maximum parsimony analysis, suggesting that SNPVs do not form a separate clade within the baculovirus family.

Amino Acid Sequence↗
PubMed1997

Constitutive mutations of the Saccharomyces cerevisiae MAL-activator genes MAL23, MAL43, MAL63, and mal64.

We report the sequence of several MAL-activator genes, including inducible, constitutive, and noninducible alleles of MAL23, MAL43, MAL63, and mal64. Constitutive alleles of MAL23 and MAL43 vary considerably from inducible alleles in their C-terminal domain, with many of the alterations clustered and common to both alleles. The 27 alterations from residues 238-461 of Mal43-C protein are sufficient for constitutivity, but the minimal number of alterations needed for the constitutive phenotype could not be determined. The sequence of mal64, a nonfunctional homologue of MAL63, revealed that Mal64p is 85% identical to Mal63p. Two mutations that activate mal64 and cause constitutivity are nonsense mutations resulting in truncated proteins of 306 and 282 residues. We conclude that the C-terminal region of the MAL-activator, from residues 283-470, contains a maltose-responsive negative regulatory domain, and that extensive mutation or deletion of the entire region causes loss of the negative regulatory function. Additionally, certain sequence elements in the region appear to be necessary for efficient induction of the full-length Mal63 activator protein. These studies highlight the role of ectopic recombination as an important mechanism of mutagenesis of the telomere-associated family of MAL loci.

Alleles↗
PubMed1997

Sequencing, genomic organization, and preliminary promoter analysis of a black cherry (R)-(+)-mandelonitrile lyase gene.

The flavoprotein (R)-(+)-mandelonitrile lyase (MDL; EC 4.1.2.10) plays a key role in cyanogenesis in rosaceous stone fruits. An MDL gene (mdl3) and its corresponding cDNA (MDL3) were isolated from black cherry (Prunus serotina) and characterized. The mdl3 gene contains 2292 bp of the 5' flanking region, the entire coding region, and 300 bp of the 3' flanking region. The coding region is interrupted by three short introns, of which one possesses the usual GC-AG splice junction dinucleotides. This gene encodes a polypeptide of 573 amino acids that includes a putative signal sequence, 13 potential N-glycosylation sites, and a presumptive flavin adenine dinucleotide-binding site. To determine whether the 5' flanking region of the mdl3 gene is capable of driving MDL expression, it was fused to the beta-glucuronidase reporter gene for Agrobacterium-mediated transformation into tobacco. Matching endogenous MDL expression patterns, beta-glucuronidase staining was observed in maturing embryos and seeds; it also occurred in postembryonic tissues, especially in association with vascular tissues. After developing a homologous transient transformation system to facilitate identification of putative regulatory sequences, we demonstrated that 125 bp (-107 to +18) of the 5' flanking sequence of the mdl3 gene is sufficient for MDL expression in protoplasts derived from immature black cherry embryos.

Aldehyde-Lyases↗
PubMed1997

Chronic loss of glucocorticoids following adrenalectomy down-regulates the expression of glucocorticoid receptor mRNA in the rat forebrain.

In the negative feedback model, loss of endogenous glucocorticoids up-regulates the expression of glucocorticoid receptor mRNA. To elucidate further the effect of chronic lack of glucocorticoids on the expression of glucocorticoid receptor mRNA and protein, in situ hybridization and immunohistochemical methods were used to examine the long-term alteration of glucocorticoid receptor mRNA and its immunoreactivity in the forebrain of adrenalectomized rats. Constant lack of glucocorticoids resulted in marked decrease in the expression of glucocorticoid receptor mRNA and disappearance of glucocorticoid receptor immunoreactivity in many forebrain structures. In particular, in the suprapyramidal blade of the hippocampal granule cell layer and cerebral cortex, many cells showed almost no glucocorticoid receptor mRNA signals. These results suggest that long-term loss of endogenous glucocorticoids down-regulates the levels of glucocorticoid receptor mRNA, leading to reduction in the synthesis of glucocorticoid receptors in the rat forebrain. Therefore, the presence of endogenous glucocorticoids is vital to the continued expression of glucocorticoid receptor mRNA.

Adrenal Glands↗
PubMed1997

Effect of oxidant challenge on contractile function of the aging rat diaphragm.

Although controversial, growing evidence indicates that reactive oxygen species (ROS) alter contractions of skeletal muscle, including the diaphragm. However, the impact of ROS on contractility of the aging diaphragm is unknown. The xanthine oxidase (0.01 U/ml) system was used as an ROS generator, imposing an oxidant challenge. Contractile function [twitch tension; twitch time to peak tension; twitch one-half relaxation time; tension at 10 and 20 Hz; maximal tetanic tension (Po) at 100 Hz] of costal diaphragm fiber bundles from young (4 mo) and old (25 mo) Fischer 344 rats was examined in vitro before and after treatment with control Krebs solution [young control (YC) and old control (OC)], or with xanthine oxidase (XO; 0.01 U/ml) plus hypoxanthine (0.29 mg/ml) substrate [young XO treated (YXO) and old XO treated (OXO)]. Contractile function of fiber bundles was reassessed after oxidant challenge in an unfatigued state (Post-u) or 10 min after a fatiguing stimulation protocol (Post-f). Oxidant challenge in the unfatigued fiber bundles increased twitch tension and tension at 10 and 20 Hz in YXO, but not OXO, without increasing Po. Conversely, XO significantly depressed fatigued diaphragm twitch and low-frequency tension in both OXO and YXO, compared with controls. Po was depressed Post-f in OXO but not YXO. Oxidant challenge also increased twitch one-half relaxation time of the fatigued diaphragm in both age groups. Furthermore, fiber bundles from old rats suffered greater fatigue during the stimulation protocol. We conclude that the response to oxidant challenge and increased contractile demand is impaired in the aging diaphragm.

Aging↗
PubMed1997

Effect of oxidative stress and acidosis on diaphragm contractile function.

Acidosis during exercise has long been associated with skeletal muscle fatigue. Recent evidence also has linked reactive oxygen species (ROS) with fatigue in skeletal muscle, including the diaphragm. We hypothesized that acidosis (designed to mimic blood pH during maximal exercise) would worsen ROS-induced depression of diaphragm contractility. The xanthine oxidase (XO) reaction in solution (0.01 U/ml) allows direct assessment of the effects of oxidant stress by ROS. Costal diaphragm fiber bundles from 24 Sprague-Dawley rats (200-250 g) were divided into four treatment groups: 1) pH 7.4, no XO (H); 2) pH 7.4 + XO (HXO); 3) pH 7.0, no XO (L); and 4) pH 7.0 + XO (LXO). Baseline twitch mechanics and force-frequency relationships (Pre) were determined in control Krebs solution (pH 7.4, no XO) before treatment. Treatment solutions were introduced, and the diaphragm underwent 2 min of contractions at 25 Hz (250 ms) at a rate of 1/s. After 10 min of recovery, the control solution was reintroduced into the bath and postcontractile function (Post) was measured. Significant reductions in twitch tension and low-frequency tetanic tension were greater in HXO and LXO compared with H, without an effect on maximal tetanic tension. One-half relaxation time was prolonged only by the combination of acidosis and oxidative stress. Addition of superoxide dismutase (50 U/ml) worsened and catalase (1,800 U/ml) attenuated XO-induced depression of diaphragm contractility. We concluded that XO induced a reduction of low-frequency tension in the fatigued diaphragm, which was mediated directly or indirectly through hydrogen peroxide and was exacerbated to a modest extent with acidosis.

Acidosis↗
PubMed1997

Regulation of type 1 angiotensin II receptor in adrenal gland: role of alpha1-adrenoreceptor.

We have previously shown that sodium restriction upregulates the genes encoding angiotensin II receptor (AT1) subtypes, AT1A and AT1B, in the adrenal gland and that this upregulation is mediated by activation of the AT1 receptor. There are multiple interactions between the renin-angiotensin and the adrenergic nervous systems; thus, we conducted the present experiment to investigate whether low sodium-induced upregulation of adrenal AT1A and AT1B is modulated by the alpha1-adrenoreceptor. Seven-week-old male Wistar rats were divided into four groups and given normal sodium diet (0.5%, NS), NS+prazosin (3.5 microg x kg(-1) x min(-1) by osmotic pump), low sodium diet (0.07%, LS), or LS+prazosin. Body weight and mean arterial pressure were not modified over the 2 weeks of treatment (P>.05). Pressor responses to bolus injection of the alpha1-agonist phenylephrine were inhibited in both prazosin groups, compared with NS and LS rats (P<.05). Adrenal AT1A mRNA, determined by Northern blot analysis, was increased in LS (P<.05) but not in NS+prazosin (P>.05), compared with NS. Prazosin enhanced the LS-induced increase of AT1A mRNA (P<.05). Adrenal AT1B mRNA was increased in both LS and NS+prasozin rats, compared with NS rats (P<.05). Prazosin also enhanced the LS-induced increase in AT1B mRNA (P<.05). Therefore, blockade of alpha1-adrenoreceptor results in an enhancement of LS-induced upregulation of adrenal mRNA for AT1A and AT1B. These data suggest that the sympathetic nervous system exerts an inhibitory action, via activation of the alpha1-adrenoreceptor, on AT1A and AT1B gene expression in the adrenal gland during sodium depletion.

Adrenal Glands↗
PubMed1997

[Efficacy of prostaglandin E1 in treatment of cor pulmonale patients with heart failure].

OBJECTIVE: To investigate the effects of prostaglandin E1 (PGE1) by intravenous drip in cor pulmonale patients with heart failure. METHODS: Thirty caseas of cor pulmonale with heart failure were treated with PGE1 at a dose of 200 micrograms.d-1 for 5 days and in 30 patients with cor pulmonale heart failure (no PGE1) and in 20 healthy subjects as controls. The level of serum endogenous digoxin-like factor (EDF), serum lipoid superoxide (LPO), serum superoxide dismutase (SOD) and blood PaO2, PaCO2 were determined. Their symptoms and signs were observed before and after treatment. RESULTS: The level of serum EDF, LPO were significantly increased (P < 0.001) and serum SOD was significantly decreased (P < 0.001) in PGE1 group and controls group (no PGE1) as compared with healthy subjects. In PGE1 group the level of serum EDF, LPO were markedly decreased (P < 0.001), and serum SOD was markedly elevated (P < 0.001), and their symptoms, signs and blood gas parameters had noteworthyly improved (P < 0.01-0.001). But in the control group (no PGE1) the level of serum EDF, LPO, SOD, blood gas parameters and their symptoms and signs, showed no significant difference (P > 0.05). CONCLUSIONS: PGE1 is effective in therapy of cor pulmonale with heart failure. Treatment with PGE1 shows more significant benefits in cor pulmonale patients with heart failure.

Aged↗
PubMed1997

[Spectrophotometric method for determination of protein in food with Hantzsch reaction].

A new spectrophotometric method for the determination of protein in food was developed. The method is based on the reaction of ammonia in Kjeldahl digest with acetylacetone for maldehyde reagent in pH4.8 acetate medium to yield a yellow compound 3,5-diacetyl-2,6-dimethyl-1,4-dihydropyridine. Beer's law is obeyed in the concentration range of 0-10.0 mg/L at 400 nm. The molar absorptivity in terms of nitrogen was 1.7 x 10(-3). The recoverites of the added standard samples were 99.6%-101.2%, and relative standard deviation was below 3.7%.

Dietary Proteins↗
PubMed1997

[Relationship between insulin resistance and coronary heart disease in non-insulin-dependent diabetes mellitus patients].

Recent clinical studies showed that an independent association between hyper-insulinaemia and coronary heart disease (CHD) in men with normal glucose tolerance. In non-insulin-dependent diabetes mellitus (NIDDM) it is less clear. Therefore, we evaluated insulin-sensitivity index, plasma glucose, insulin, lipoproteins and apolipoproteins in 40 male NIDDM patients with CHD, and compared them with 36 male NIDDM patients without CHD. The insulin-sensitivity index determined by the reverse of fasting plasma glucose and insulin product. The results showed that the subjects with CHD had significantly lower insulin-sensitivity index (P < 0.01) compared to those without CHD. Using step-wise logistic regression analgsis, we found insulin-sensitivity indexes (OR 0.237, 95%CI 0.0909-0.6167, P = 0.0032) were negatively associated with CHD, and were independent from other cardiovascular risk factors such as age, body mass index, hypertension, and hyperlipemia. We conclude that in NIDDM patients with CHD are more insulin resistant compared to those without CHD. Insulin resistance is associated with CHD, and independent from other cardiovascular risk factors.

Coronary Disease↗
PubMed1997

[Forty six cases of application of free femoris forelateralis flap in trauma].

In serious scar or chronic ulcer caused by burn or trauma, skin graft can not be survival and the local flap can not be found in these cases. Also skin grafts can not improve function of these places. Free flap transplantation should be used in these cases. Femoris forelateralis flap has some advantages. It is hidden from view and there is no effect after it is taken. It has constant blood vessels which are easy anastomosed. So the flap is more widely used. Forty-six cases were given femoris forelateralis flaps (hand burn scar deformity 15 cases, foot scar 10, forearm or leg scar or tissue defect 8, leg or foot chronic ulcer 8, face or neck tissue defect or serious scar 8). Forty-five cases (97.8%), were survival. Only one case had necrosis. The key of survival is choice of the operative indication, excellent anastomosis technique, good fixation postoperatively, care observation, and timely handling. In vasculitis or phlebitis ulcer, the vessel condition is bad. In old people, especial with heart or vessel diseases, condition is also bad. We shoule be careful in these situations.

Adolescent↗
PubMed1997

[Development of an expert system for assessment of criminal responsibility capacity of mentally ill offenders].

The objective of this study was to develop an expert system for the assessment of legal capacity (ESALC). Visual Basic for Windows 3.0 was employed in establishing ESALC, and 281 cases were assessed by the system. The results were in substantial agreement with those of expert assessment. Kappa = 0.68 (P < 0.01); accuracy 90.04%, sensitivity, 85.63% and specificity 96.49%. ESALC can be used as a supplementary instrument in forensic psychiatric assessment.

Adolescent↗