Biomedical subjects

H Zhao

Publications and source records attributed to H Zhao.

At least 343 records · Page 19Linked to original sources

PubMed1998

Maternal physical activity in pregnancy and infant size for gestational age.

PURPOSE: To estimate the effect of several types of maternal physical activity in pregnancy on size for gestational age and length of gestation. METHODS: Telephone interviews, birth certificates, and medical records provided data on physical activity and other factors for a random sample of 291 Colorado residents. Backward polychotomous logistic regression modeling yielded estimates of the odds ratios for size for gestational age (appropriate versus small or large) and length of gestation (term versus pre-term or post-term) in relation to second and third trimester maternal physical activity. RESULTS: Performance of any moderate or vigorous physical activity for two hours per week or more in any month was associated with a decreased risk of large infant size for gestational age (LGA; odds ratio = 0.3, 95% confidence interval = 0.2, 0.7), but had no significant effect on risk of small infant size for gestational age (SGA; odds ratio (OR) = 0.8, 95% confidence interval (CI) = 0.3, 2.3). Length of gestation was not affected by prenatal physical activity. CONCLUSIONS: These results suggest that prenatal physical activity may decrease risk of LGA, as might be expected given its salutary effects on glucose tolerance.

Birth Weight↗

PubMed1998

A new model for phenotypic suppression of frameshift mutations by mutant tRNAs.

According to the prevailing model, frameshift-suppressing tRNAs with an extra nucleotide in the anticodon loop suppress +1 frameshift mutations by recognizing a four-base codon and promoting quadruplet translocation. We present three sets of experiments that suggest a general alternative to this model. First, base modification should actually block such a four-base interaction by two classical frameshift suppressors. Second, for one Salmonella suppressor tRNA, it is not mutant tRNA but a structurally normal near cognate that causes the +1 shift in-frame. Finally, frameshifting occurs in competition with normal decoding of the next in-frame codon, consistent with an event that occurs in the ribosomal P site after the translocation step. These results suggest an alternative model involving peptidyl-tRNA slippage at the classical CCC-N and GGG-N frameshift suppression sites.

Anticodon↗

PubMed1998

The bladder as a bioreactor: urothelium production and secretion of growth hormone into urine.

Uroplakin genes are expressed in a bladder-specific and differentiation-dependent fashion. Using a 3.6-kb promoter of mouse uroplakin II gene, we have generated transgenic mice that express human growth hormone (hGH) in their bladder epithelium, resulting in its secretion into the urine at 100-500 ng/ml. The levels of urine hGH concentration remain constant for longer than 8 months. hGH is present as aggregates mostly in the uroplakin-delivering cytoplasmic vesicles that are targeted to fuse with the apical surface. Using the bladder as a bioreactor offers unique advantages, including the utility of all animals throughout their lives. Using urine, which contains little protein and lipid, as a starting material facilitates recombinant protein purification.

Animals↗

PubMed1998

Molecular evolution by staggered extension process (StEP) in vitro recombination.

We have developed a simple and efficient method for in vitro mutagenesis and recombination of polynucleotide sequences. The staggered extension process (StEP) consists of priming the template sequence(s) followed by repeated cycles of denaturation and extremely abbreviated annealing/polymerase-catalyzed extension. In each cycle the growing fragments anneal to different templates based on sequence complementarity and extend further. This is repeated until full-length sequences form. Due to template switching, most of the polynucleotides contain sequence information from different parental sequences. The method is demonstrated by the recombination of two genes encoding thermostable subtilisins carrying two phenotypic markers separated by 113 base pairs and eight other point mutation markers. To demonstrate its utility for directed evolution, we have used StEP to recombine a set of five thermostabilized subtilisin E variants identified during a single round of error-prone PCR mutagenesis and screening. Screening the StEP-recombined library yielded an enzyme whose half-life at 65 degrees C is 50 times that of wild-type subtilisin E.

Bacillus subtilis↗

PubMed1998

Statistical analysis of ordered tetrads.

Ordered tetrad data yield information on chromatid interference, chiasma interference, and centromere locations. In this article, we show that the assumption of no chromatid interference imposes certain constraints on multilocus ordered tetrad probabilities. Assuming no chromatid interference, these constraints can be used to order markers under general chiasma processes. We also derive multilocus tetrad probabilities under a class of chiasma interference models, the chi-square models. Finally, we compare centromere map functions under the chi-square models with map functions proposed in the literature. Results in this article can be applied to order genetic markers and map centromeres using multilocus ordered tetrad data.

Centromere↗

PubMed1998

Statistical analysis of half-tetrads.

Half-tetrads, where two meiotic products from a single meiosis are recovered together, arise in different forms in a variety of organisms. Closely related to ordered tetrads, half-tetrads yield information on chromatid interference, chiasma interference, and centromere positions. In this article, for different half-tetrad types and different marker configurations, we derive the relations between multilocus half-tetrad probabilities and multilocus ordered tetrad probabilities. These relations are used to obtain equality and inequality constraints among multilocus half-tetrad probabilities that are imposed by the assumption of no chromatid interference. We illustrate how to apply these results to study chiasma interference and to map centromeres using multilocus half-tetrad data.

Animals↗

PubMed1998

Synergistic cytotoxicity of topoisomerase I inhibitors with alkylating agents and etoposide in human brain tumor cell lines.

To evaluate potential synergistic interactions between topoisomerase I (Topo I) inhibitors, i.e. camptothecin (CPT) and topotecan (TPT), and chemotherapeutic agents known to be active in treatment of brain tumors, in vitro studies were conducted with human glioma and medulloblastoma cell lines. Tumor cells were exposed to CPT or TPT alone or in combination with cisplatin, 4-hydroperoxycyclophosphamide (4-HC), BCNU or etoposide (VP-16). Cytotoxicity was assessed by colony formation assays. Drug interactions were evaluated by means of a novel analytical model which permits statistical evaluation over a range of dose combination. Experimental results were corroborated by published models of drug interaction. Our findings indicate that in vitro cytotoxic interactions in brain tumor cells between Topo I inhibitors and alkylating agents or etoposide depend on drug dose, dose schedule and tumor cell line. Treatment of DAOY medulloblastoma cells with CPT and either cisplatin, 4-HC or VP-16 produced significant synergistic cytotoxicity over a wide range of dose combinations. When VP-16 was administered after CPT, synergy was reduced to a narrow range of dose combinations. For U251 glioma cells, incubation with CPT and cisplatin or 4HC also produced synergistic cytotoxicity over a broad range of dose combinations. By contrast, antagonistic interactions were observed after administration of CPT with BCNU or VP-16. Treatment of U251 cells with CPT and cisplatin produced synergistic or antagonistic cytotoxicity depending on the dose combination used. These findings support a role for pharmacokinetic analysis in multiagent phase 11 trials involving Topo I inhibitors and have important implications for clinical trial design strategies.

Antineoplastic Agents↗

PubMed1998

Release of endogenous nitric oxide mediates arteriolar dilation to endothelin in rat striated muscle.

Previous studies demonstrated that endothelin-1 is a potent vasoconstrictor in the microcirculation. In this study, we assessed the ability of endothelin-1 to induced dilation of small arterioles in the rat cremaster muscle. Responses to topical application of endothelin-1 were assessed by using intravital microscopy. Exposure to increasing concentrations of endothelin-1 (10[-13]-10[-8] M) produced a dose-dependent constriction of third-order arterioles (20 +/- 1.4 microm). Pretreatment with hydroquinone (HQ) or N omega-nitro-L-arginine methyl ester (L-NAME), antagonists of nitric oxide production, caused a significant potentiation in the reactivity of third-order arterioles to endothelin-1. In addition, we observed a significant vasodilation to low levels of endothelin-1 (10[-14]-10[-12] M) in the presence of the endothelin type-A receptor (ET-A) antagonist, BQ123. This dilation was abolished in the presence of a 10(-4) M bath concentration of L-NAME. These results indicated that endothelin-1 caused arteriolar dilation by stimulating endogenous production of nitric oxide. This effect appeared to attenuate the constrictor effects of endothelin-1 on small resistance vessels in striated muscle.

Animals↗

PubMed1998

The M1 and NP proteins of influenza A virus form homo- but not heterooligomeric complexes when coexpressed in BHK-21 cells.

The nucleoprotein (NP) and matrix protein (M1) are the most abundant structural proteins of influenza A virus. M1 forms a protein layer beneath the viral envelope and NP constitutes the protein backbone of the ribonucleoproteins (RNPs). In order to elucidate the functions of these proteins in virus assembly we have expressed NP and M1 in BHK-21 cells using Semliki Forest virus replicons and analysed their molecular interactions. We found that both M1 and NP engaged in extensive homooligomerization reactions soon after synthesis. However, there was no detectable heterooligomerization taking place between the two viral proteins, nor between these and host proteins. One interpretation of these results is that homooligomers, and not monomers, of NP and M1 are used as building blocks during RNP assembly and formation of the submembranous M1 layer, respectively. The complete absence of M1-NP heterooligomers suggests, on the other hand, that these two major viral proteins do not interact directly with each other during virus assembly. We also found that a fraction of M1 associated with cellular membranes. This did not, however, result in membrane budding or vesicularization as was the case with the matrix protein of vesicular stomatitis virus when expressed separately (P. A. Justice and others, Journal of Virology 69, 3156-3160, 1995).

Animals↗

PubMed1998

Human tyrosinase related protein-1 (TRP-1) does not function as a DHICA oxidase activity in contrast to murine TRP-1.

Tyrosinase related protein-1 is a melanocyte specific protein and a member of the tyrosinase gene family which also includes tyrosinase and TRP 2 (DOPAchrome tautomerase). In murine melanocytes, TRP-1 functions as a 5,6-dihydroxyindole-2-carboxylic acid [DHICA] oxidase during the biosynthetic conversion of tyrosine to eumelanin and mutations affecting TRP-1 result in the synthesis of brown rather than black pelage coloration. In this study, we examined the putative DHICA oxidase activity of TRP-1 in human melanocytes using several approaches. We first utilized a line of cultured melanocytes established from a patient with a form of oculocutaneous albinism completely lacking expression of TRP-1 (OCA3). This line of melanocytes endogenously exhibited the same amount of DHICA oxidase activity as control melanocytes expressing TRP-1. In other experiments, cultured human fibroblasts were transfected with a cDNA for TRP-1, in either the sense or antisense direction, or with the retroviral vector alone. TRP-1 expression was induced in fibroblasts transfected with the TRP-1 cDNA in the sense direction only. Although TRP-1 was expressed by sense-transfected cells, there was no significant DHICA oxidase activity above controls. These results demonstrate that human TRP-1 does not use DHICA as a substrate for oxidation.

Animals↗

PubMed1998

Use of green fluorescent protein to assess urease gene expression by uropathogenic Proteus mirabilis during experimental ascending urinary tract infection.

Proteus mirabilis, a cause of complicated urinary tract infection, expresses urease when exposed to urea. While it is recognized that the positive transcriptional activator UreR induces gene expression, the levels of expression of the enzyme during experimental infection are not known. To investigate in vivo expression of P. mirabilis urease, the gene encoding green fluorescent protein (GFP) was used to construct reporter fusions. Translational fusions of urease accessory gene ureD, which is preceded by a urea-inducible promoter, were made with gfp (modified to express S65T/V68L/S72A [B. P. Cormack et al. Gene 173:33-38, 1996]). Constructs were confirmed by sequencing of the fusion junctions. UreD-GFP fusion protein was induced by urea in both Escherichia coli DH5alpha and P. mirabilis HI4320. By using Western blotting with antiserum raised against GFP, expression level was shown to correlate with urea concentration (tested from 0 to 500 mM), with highest induction at 200 to 500 mM urea. Fluorescent E. coli and P. mirabilis bacteria were observed by fluorescence microscopy following urea induction, and the fluorescence intensity of GFP in cell lysates was measured by spectrophotofluorimetry. P. mirabilis HI4320 carrying the UreD-GFP fusion plasmid was transurethrally inoculated into the bladders of CBA mice. One week postchallenge, fluorescent bacteria were detected in thin sections of both bladder and kidney samples; the fluorescence intensity of bacteria in bladder tissue was higher than that in the kidney. Kidneys were primarily infected with single-cell-form fluorescent bacteria, while aggregated bacterial clusters were observed in the bladder. Elongated swarmer cells were only rarely observed. These observations demonstrate that urease is expressed in vivo and that using GFP as a reporter protein is a viable approach to investigate in vivo expression of P. mirabilis virulence genes in experimental urinary tract infection.

Animals↗

PubMed1998

In vivo phase variation of Escherichia coli type 1 fimbrial genes in women with urinary tract infection.

Type 1 fimbriae, expressed by most Escherichia coli strains, are thought to attach to human uroepithelium as an initial step in the pathogenesis of urinary tract infections (UTI). Numerous reports using both in vitro and murine models support this role for type 1 fimbriae in colonization. Unfortunately, only a limited number of studies have directly examined the expression of fimbriae in vivo. To determine whether type 1 fimbrial genes are transcribed during an acute UTI, we employed a modification of an established method. The orientation (ON or OFF) of the invertible promoter element, which drives transcription of type 1 fimbrial genes, was determined by PCR amplification using primers that flank the invertible element, followed by SnaBI digestion. The orientation of the type 1 fimbrial switch was determined under three experimental conditions. First, E. coli strains from different clinical sources (acute pyelonephritis patients, cystitis patients, and fecal controls) were tested under different in vitro culture conditions (agar versus broth; aerated versus static). The genes in the more-virulent strains (those causing acute pyelonephritis) demonstrated a resistance, in aerated broth, to switching from OFF to ON, while those in fecal strains readily switched from OFF to ON. Second, bladder and kidney tissue from CBA mice transurethrally inoculated with E. coli CFT073 (an established murine model of ascending UTI) was assayed. The switches directly amplified from infected bladder and kidney tissues were estimated to be 33 and 39% ON, respectively, by using a standard curve. Finally, bacteria present in urine samples collected from women with cystitis were tested for type 1 fimbria switch orientation. For all 11 cases, an average of only 4% of the switches in the bacteria in the urine were ON. In 7 of the 11 cases, we found that all of the visible type 1 fimbrial switches were in the OFF position (upper limit of detection of assay, 98% OFF). Strains recovered from these urine samples, however, were shown after culture in vitro to be capable of switching the fimbrial gene to the ON position and expressing mannose-sensitive hemagglutinin. The results from experimental infections and cases of cystitis in women suggest that type 1 fimbrial genes are transcribed both in the bladder and in the kidney. However, those bacteria found in the urine and not attached to the uroepithelium are not transcriptionally active for type 1 fimbrial genes.

Adolescent↗

PubMed1998

Morphometric and histologic assessment of remodeling associated with restenosis after percutaneous transluminal coronary angioplasty.

The role of remodeling in restenosis of coronary arteries on which percutaneous transluminal coronary angioplasty (PTCA) had been performed was investigated. At autopsy, presence (n = 6) or absence of restenosis (n = 5) based on the cross-sectional area of stenosis was determined in 11 coronary lesions. Remodeling was defined as a ratio of the artery area at the PTCA site to that at the reference site of <1.0. According to this definition, remodeling had occurred in all of the lesions in the restenosis group, and in only 1 lesion in the group with no restenosis which had the least residual plaque (p < 0.05). Dense caps of collagen fibers in the adventitia in the vicinity of the disrupted internal elastic laminae were present in all of the remodeling lesions. We suggest that remodeling, which results in adventitial scarring, is one of the major causative factors of restenosis.

Aged↗

PubMed1998

Calcitonin gene-related peptide is a depressor in subtotal nephrectomy hypertension.

We previously demonstrated that the neuronal expression of calcitonin gene-related peptide (CGRP), a potent vasodilator, is increased in deoxycorticosterone-salt-induced hypertension where it acts as a compensatory vasodilator to attenuate the elevated blood pressure. To determine whether CGRP is playing a similar role in subtotal nephrectomy-salt-induced hypertension, hypertension was induced in Sprague-Dawley rats (n=6) by subtotal nephrectomy and 1.0% saline drinking water. Control rats (n=6) were sham operated and given tap water to drink. CGRP(8-37), a CGRP receptor antagonist, was used to assess the hemodynamic role of CGRP in this setting. CGRP mRNA and peptide levels in dorsal root ganglia were also determined. Three weeks after either protocol, all rats had intravenous (for drug administration) and arterial (for continuous mean arterial pressure monitoring) catheters surgically placed and were studied in the conscious, unrestrained state. CGRP(8-37) (3.2 or 6.4 x 10(4) pmol/L in 0.1 mL saline) and vehicle were administered intravenously to all rats. Baseline mean arterial pressure was higher in the subtotal nephrectomized rats compared with the controls (173+/-5 versus 113+/-5 mm Hg, P<.001). Vehicle administration did not change mean arterial pressure in either group, and CGRP(8-37) administration did not alter mean arterial pressure in the normotensive group. In contrast, CGRP(8-37) administration to the subtotal nephrectomized rats rapidly increased the already elevated mean arterial pressure at both the 3.2 x 10(4) pmol/L dose (7.8+/-1.1 mm Hg, P<.05) and the 6.4 x 10(4) pmol/L dose (9.6+/-0.8 mm Hg, P<.01). CGRP mRNA and peptide levels in the dorsal root ganglia were not significantly different between the two groups. These data suggest that in subtotal nephrectomy-salt-induced hypertension, CGRP may play a compensatory depressor role in an attempt to lower the elevated blood pressure.

Animals↗

PubMed1998

Altered lung mechanics after double-lung transplantation.

We studied lung mechanics and small airways function in 15 patients after double-lung (DL) transplantation. Patients were classified as stable (DL-S, n = 11), or having obliterative bronchiolitis syndrome (DL-OBS, n = 4). We performed pulmonary function tests (PFT), measured slope of phase 3 of the single-breath nitrogen test (N2SP3), and obtained pressure-volume curves and values: chord compliance (Cst,L), specific chord compliance (SCst,L), and elastic recoil pressure at 90% TLC. PFT showed mild restrictive pattern in DL-S and severe obstructive lung disease in DL-OBS. The N2SP3 measurement indicated small airways dysfunction in 82% of DL-S and in all DL-OBS patients. The Cst,L was 0.24 +/- 0.08 L/cm H2O in DL-S and 0.16 +/- 0.05 L/cm H2O in DL-OBS, both lower than control subjects 0.34 +/- 0. 09 L/cm H2O (p < 0.01; p < 0.001). Moreover, SCst,L was 0.09 +/- 0. 03 cm H2O-1 in DL-S, and 0.05 +/- 0.02 cm H2O-1 in DL-OBS, significantly lower than control subjects 0.12 +/- 0.02 cm H2O-1 (p < 0.05; p < 0.001). Elastic recoil at 90% TLC was normal in 14 of 15 patients. We found a linear correlation between N2SP3 and FEV1, and between FEV1 and Cst,L and SCst,L for combined DL-S and DL-OBS. Reduced compliance near FRC with normal elastic recoil at high lung volumes does not suggest changes in lung parenchyma. We speculate that structural or functional alterations in small airways may have contributed to low compliance measurements. Of special concern are our findings that DL-S had significant small airways dysfunction and reduced compliance in a pattern similar to the DL-OBS, only smaller in magnitude.

Adult↗

PubMed1998

Idoxifene: a novel selective estrogen receptor modulator prevents bone loss and lowers cholesterol levels in ovariectomized rats and decreases uterine weight in intact rats.

Idoxifene, a novel selective estrogen receptor modulator, was tested for its effects on bone loss, serum cholesterol, and uterine wet weight and histology in the ovariectomized (Ovx) rat. Idoxifene (0.5 mg/kg x day) completely prevented loss of both lumbar and proximal tibial bone mineral density (BMD). In an intervention study, idoxifene (0.5 and 2.5 mg/kg x day) completely prevented further loss of both lumbar and proximal tibial BMD during a 2-month treatment period commencing 1 month after surgery, when significant loss of BMD had occurred in the Ovx control group. Idoxifene reduced total serum cholesterol, which was maximal at 0.5 mg/kg x day. Idoxifene alone displayed minimal uterotrophic activity in Ovx rats and inhibited the agonist activity of estrogen in intact rats. Histologically, myometrial and endometrial atrophy were observed in both idoxifene and vehicle-treated Ovx rats. In this report, we also provide molecular-based evidence to support the observations in vivo of a novel selective estrogen receptor modulator (SERM) mechanism of action in bone and endometrial cells. Idoxifene is an agonist through the estrogen response element (ERE) and exhibits similar postreceptor effects to estrogen in bone-forming osteoblasts. Idoxifene also stimulates osteoclast apoptosis, and these pleiotropic effects ultimately could contribute to the maintenance of bone homeostasis. However, idoxifene differs from estrogen in a tissue-specific manner. In human endometrial cells, where estrogen is a potent agonist through the ERE, idoxifene has negligible agonist activity. Moreover, idoxifene was able to block estrogen induced gene expression in endometrial cells, which is in agreement with the observation in the intact rat study. In the uterus, idoxifene has a pharmacologically favorable profile, lacking agonist and therefore growth-promoting activity. Together with its cholesterol lowering effect and lack of uterotrophic activity, these data suggest that idoxifene may be effective in the prevention of osteoporosis and other postmenopausal diseases without producing unwanted estrogenic effects on the endometrium.

Animals↗

PubMed1998

[An epidemiologic analysis of brucellosis in Liaoning province].

In order to understand the increasing incidence rate of Brucellosis, the relationship between the epidemic trend and physical conditions of humans, data regarding Brucellosis in Liaoning province, in 1990-1996 was analysed. Results showed that the major cause which led to the Brucellosis recurrence was the importation of sheep named short-tail cold-resistant. The distribution of disease was widely spread. However, most endemic foci were being expanded. The spots in Tieling and Fushun area were merged and became one endemic area. Brucellosis maily involved in the farmer's family that raise sheep while pregnancy make women at reprodactive age susceptible to the disease. The incidence rate in city and rural areas were significantly different despite that they had the same environment that bacteria-carrier sheep were raised.

Animals↗

PubMed1998

[Studies on hepatitis B virus infection in blood donors with positive anti-HBc and negative HBsAg].

OBJECTIVE: To study if it is necessary to screen for core antibody against hepatitis B (anti-HBc) to prevent post-transfusion hepatitis B and what is its criteria for screening. METHODS: Relationship between the titer of anti-HBc and HBV DNA in blood from qualified donors by routine testing was conducted. HBV DNA was detected in 297 units of blood with anti-HBc at various titers by immuno-nested polymerase chain reaction (RT-PCR). RESULTS: HBV DNA was detected in one of four units of blood with positive anti-HBc at a dilution of equal to or greater than 1:128, and no HBV DNA was detected in other 75 units of blood with a dilution of anti-HBc less than 1:128. There was significant relationship between HBV DNA and the titer of anti-HBc. No HBV DNA was detected in 218 units of blood with both positive anti-HBc and anti-HBs and in 50 units with negative anti-HBc. Detection rate of HBV DNA in blood with positive anti-HBc was only 0.34% (1/297). CONCLUSION: Blood containing higher titer of single anti-HBc may be infectious. It is suggested that sensitivity of the reagents for detecting HBsAg currently used (1 ng/ml) be improved with the limited budget.

Adult↗