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Biomedical subjects

Y Zhou

Publications and source records attributed to Y Zhou.

At least 757 records · Page 42Linked to original sources
PubMed1995

Development of a titanium alloy suitable for an optimized coating with hydroxyapatite.

By means of the metallurgical method of alloying, the thermal expansion coefficient of commercially pure titanium was adapted to that of hydroxyapatite (HA) in order to produce a tailored composite material with a maximum adhesion strength of HA to the metallic material. The alloying element chosen was manganese, which is an important trace element in the human organism. With the alloy TiMn6 a good compromise concerning the expansion coefficient, the mechanical properties and the biocompatible behaviour was found. With this alloy coatings with an extremely high adhesion strength could be produced, especially when the sol-gel process was used for HA precipitation. In addition, these layers fulfil the requirements of favourable thin coatings according to theoretical considerations.

Alloys↗
PubMed1995

Platinum binding to metallothionein. Analysis of circular dichroism spectra of complexes formed between metallothionein and platinum from cis- and trans-diamminedichloroplatinum.

The first observation of the circular dichroism (CD) spectral features of platinum-saturated metallothionein, Pt7MT, is presented. It is characterized by two intensive bands with maxima at 235 nm (-) and 255 nm (+). Properties of the reactions of cis- and trans-diamminedichloroplatinum (DDP) with rabbit liver MT have been studied by monitoring the CD spectral changes. The overall rate of the reaction between trans-DDP and MT is determined to be significantly faster than that for cis-DDP and MT. The stepwise incorporation of Pt into Zn7MT resulted in a nonsystemic changes in the CD spectral envelope. These data argue that Pt(II) replaces Zn(II) in ZnMT in a nonspecific, "distributed" manner across both domains, because the onset of clustering was observed after 5 mol equiv of Pt was bound. A dynamic mechanism has been proposed in which the reaction proceeds via the formation of an intermediate, RS-Pt (NH3)2-SR. As it is converted to the product, the ammine ligands are lost very slowly, especially in the case of cis-DDP, because of the strong requirement of Pt for square planar coordination, which comprises the rate-limiting step.

Animals↗
PubMed1995

Long-term habituation of brain evoked potential responses and pituitary-adrenal secretion with repeated (placebo) testing.

To study whether changes in late auditory evoked potentials (AEPs) and/or in stress-sensitive hormones of the hypothalamic-pituitary-adrenal (HPA) system take place between a first and a second placebo experiment and if so, whether these changes are possibly related to each other, we conducted two identical placebo sessions (2 ml 0.9% saline) and one cortisol session (50 mg) with 10 subjects on three different days. Plasma cortisol concentrations were significantly higher at the beginning of the first placebo experiment than the second, with a concordant decrease of plasma adrenocorticotropin hormone (ACTH) concentrations. In the AEP domain, a consistently lower P2 amplitude was observed in the first session. Since the change in late auditory processing could not be demonstrated after exogenous administration of cortisol, a direct mediation through an elevation of plasma cortisol concentrations or indirect mediation through a decrease of plasma ACTH concentrations seems unlikely. We rather propose that other stress-sensitive mechanisms, such as CCK, might account for the novelty-induced P2 amplitude lowering.

Acoustic Stimulation↗
PubMed1995

Effect of dietary restriction on glutathione S-transferase activity specific toward aflatoxin B1-8,9-epoxide.

Dietary restriction (DR) reduced the metabolic activation of aflatoxin B1 (AFB1) in rats. This reduction may be attributed to the decrease of cytochrome P-450-mediated AFB1 epoxidation and/or increase in the detoxification of AFB1 catalyzed by hepatic glutathione S-transferase (GST) and other phase II detoxification enzymes. In this study the effect of DR on male rat liver cytosolic GST activity toward AFB1-8,9-epoxide was studied. The chemically-synthesized AFB1-8,9-epoxide was used as the substrate in this assay, and the formation of AFB1-GSH conjugate was analyzed by HPLC. Male Fischer 344 rats fed DR diets (60% of the food consumption of ad libitum (AL)-fed rats) showed a 2.4-fold increase in GST activity when AFB1-epoxide was used as the substrate. The results from the enzyme kinetic study showed that DR increased Vmax of the liver cytosolic GST but not the Km. Acute DR has little or no impact on GST activity when 1-chloro-2,4-dinitrobenzene and 2,4-dichloronitrobenzene were used as substrates. The mouse liver GST activity toward AFB1-epoxide was 3-fold greater than that of phenobarbital-induced rats, 4.5-fold greater than DR rats, and 14.7-fold greater than the GST activity of AL rats. This direct assay of liver GST activity using AFB1-epoxide as the substrate is useful for studying AFB1-induced biomarkers, such as AFB1-GSH conjugation and AFB1-DNA adducts.

Aflatoxin B1↗
PubMed1995

Dexamethasone stimulation of rat insulin-like growth factor binding protein-1 (IGFBP-1) promoter activity involves the interaction of multiple transcription factors.

Using an improved procedure for transient transfection of H4-II-E rat hepatoma cells, we characterized the cis elements in the proximal promoter of the rat insulin-like growth factor binding protein-1 (rat IGFBP-1) gene that are required for basal (unstimulated) and dexamethasone-stimulated promoter activity. Three sites are required for optimal basal promoter activity: an AP-2 site (nt -286 to -293), the M4 region of the insulin response element (nt -108 to -99), and a hepatocyte nuclear factor-1 (HNF-1) site (nt -62 to -50). In addition to the glucocorticoid response element (nt -91 to -77), participation of two of three accessory sites is required for optimal stimulation by dexamethasone: the M4 and HNF-1 sites, and a third site located between nt -252 and -236. Further study will focus on how the interactions of tissue-specific and hormonally-responsive transcription factors are integrated.

Animals↗
PubMed1995

Expression of G protein alpha subunits in the aging cardiovascular system.

Alterations in responsiveness to stimulation of G protein-coupled receptors in the cardiovascular system have been noted during aging and may be due to changes in the G proteins. The levels of G protein alpha subunits and their mRNAs were examined in the aorta and heart of adult (6-month-old) and senescent (24-month-old) Fischer 344 rats. Western blot analysis using anti-Gs alpha antiserum revealed 4 bands in the aorta (38, 42, 45, and 52 kD). The 42 kD band decreased significantly in 24-month-old rats, whereas the other bands did not change. Western blots using anti-Go alpha and anti-Gi alpha revealed single bands of 39 kD and 41 kD respectively, which decreased significantly in the aortas from 24-month-old rats. There were no significant changes in the levels of G alpha mRNAs in the aorta during aging. In the heart, anti-Gs alpha antiserum detected 3 bands (42, 45, and 52 kD) which did not change with age. Levels of Gi alpha (41 kD) and Go alpha (39 kD) also did not change with age in the heart. The mRNAs for Gi2 alpha and Gi3 alpha were significantly increased in the heart, but there was no change in Go alpha or Gs alpha mRNAs. Reduced expression of Gi alpha may provide the molecular basis for alterations in receptor responsiveness in the aging vasculature. Altered expression of G protein alpha subunits does not appear to account for age-related alterations in cardiac function.

Aging↗
PubMed1995

Human immunodeficiency virus type 1 infection: relationship of risk group and age to rate of progression to AIDS. Transfusion Safety Study Group.

Age differences among risk groups may account for rate differences in progression of human immunodeficiency virus type 1 (HIV-1) infection to AIDS. Institutions in 6 US cities used a common protocol to study infected homosexual blood donors, recipients of blood components, and factor VIII-treated hemophiliacs. Follow-up was every 6 months. Actuarial risk for AIDS 8 years after infection was 51% among blood recipients, 36% among homosexual donors, and 24% among hemophiliacs. Significant risk group differences were explained by age differences among cohorts (medians of 61, 29, and 22 years, respectively). When age was adjusted for and both CD4 cell value and zidovudine treatment were used as time-dependent covariates, homosexual donors had more rapid progression than the other groups. Omitting Kaposi's sarcoma as an AIDS-defining condition removed any significant differences among risk groups except CD4 cell count and age. Thus, major factors in AIDS progression are age-related.

Acquired Immunodeficiency Syndrome↗
PubMed1995

The genes for the Clostridium botulinum type G toxin complex are on a plasmid.

Clostridium botulinum type G produces a toxin complex that is composed of neurotoxin, hemagglutinin, and nontoxic nonhemagglutinin. The three genes encoding these proteins were closely linked on a plasmid of about 114 kb (76 MDa) but not on chromosomal DNA. In contrast to the genes of other C. botulinum serotypes, the genes encoding type G toxin are on a plasmid.

Base Sequence↗
PubMed1995

Direction biases of X and Y type retinal ganglion cells in the cat.

1. It has been reported that in the cat only a specialized group of retinal ganglion cells constituting approximately 1% of the overall population are direction sensitive. Two major groups of retinal ganglion cells, the X and Y cells, have been reported not to be sensitive to the direction of stimulus motion. 2. We recorded action potentials of retinal ganglion cells intraocularly. We studied quantitatively the visual responses elicited by drifting sinusoidal gratings of various spatial frequencies, bars, and spots. 3. The results confirm previous reports that most cat retinal ganglion cells exhibit orientation biases when tested with gratings of relatively high spatial frequency. 4. Additionally, we find that 22% of X and 34% of Y type retinal ganglion cells exhibit direction biases. Overall, Y cells displayed significantly stronger direction biases than did X cells. 5. In general, direction biases are clearest when the test gratings are of relatively low spatial frequency. 6. The direction biases of X and Y cells subserving the central 15 degrees of retina were weaker than those of cells subserving more peripheral regions. 7. The direction-biased responses of cat ganglion cells were similar to those of X and Y type relay cells in the cat dorsal lateral geniculate nucleus (LGNd). Thus we suggest that the direction biases of LGNd cells are a reflection of their retinal inputs.

Animals↗
PubMed1995

Estrogen receptor protein is differentially regulated in the preoptic area of the brain and in the uterus during the rat estrous cycle.

A previous in situ hybridization study in our laboratory has shown that the level of estrogen receptor mRNA in the preoptic area of the brain varied during the rat estrous cycle and differed between the sexes. While these observations suggest that the receptor protein levels may also change, a direct measurement of receptor protein is required to substantiate this regulation. The present study utilized a quantitative Western blot method to evaluate changes in the total content of estrogen receptor protein in the cycling female and intact male preoptic area and to compare changes in the brain with those which occur in the uterus. Tissue samples from brain and uterus were homogenized, separated by electrophoresis, and transferred to membranes. Estrogen receptor was then detected with two different antibodies, ER-715 and H-222, using a chemiluminescent Western blot assay to generate film autoradiographic images. A 66-kD band in tissue samples from brain and uterus was evaluated. Densitometric analysis of autoradiograms detected significant alterations in estrogen receptor content over the estrous cycle, with brain levels being highest during metestrus, attenuated on diestrus, and lowest during proestrus and estrus. A comparison of the male and female preoptic area revealed that the level of estrogen receptor in the cycling female was significantly higher than in the male. In contrast, the uterine estrogen receptor content was low during metestrus, diestrus, and estrus and elevated on proestrus. These results suggest that expression of the estrogen receptor in the preoptic area changes during the estrous cycle and is greater in the female than the male brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Molecular analysis of isophthalate and terephthalate degradation by Comamonas testosteroni YZW-D.

Comamonas testosteroni YZW-D was isolated from Passaic River sediment for its ability to degrade isophthalate and terephthalate. Degradation of the two isomeric compounds proceeds via separately inducible catabolic pathways that converge at protocatechuate. Analysis of the catabolic pathways by which these two isomers are degraded demonstrated that a cis-dihydrodiol intermediate is involved in both pathways. The genes for the conversion of isophthalate and terephthalate to protocatechuate were cloned on a single fragment of genomic DNA from C. testosteroni YZW-D. The two operons were located by subcloning and mutant complementation experiments. The regions coding for the two degradative pathways were sequenced. Analysis of the nucleotide sequence for the isophthalate degradation operon located genes for a dioxygenase, a transport protein, a cis-dihydrodiol dehydrogenase, and a reductase. Analysis of the nucleotide sequence for the terephthalate degradation operon located genes for a regulatory protein, a transport protein, a dioxygenase large subunit, a dioxygenase small subunit, a cis-dihydrodiol dehydrogenase, and a reductase.

Base Sequence↗
PubMed1995

An experimental study of spinal cord evoked potential.

The characteristics of spinal cord-evoked potentials were investigated by using an in vitro spinal cord preparation. The spinal cord isolated from adult rats was immersed in a bathing chamber filled with oxygenated artificial cerebrospinal fluid (aCSF). The spinal cord-evoked potentials elicited by the stimulation of the spinal cord were recorded by using bipolar platinum electrodes. The potentials recorded consisted of early and late negative components (N1, N2). The inhibitory effect of lowered temperature on the N1 potential was clearly demonstrated. The oxygen deprivation of aCSF showed the higher sensitivity of N2 potential to hypoxia than that of N1. It was also possible to analyze the effects of potassium and magnesium ion concentration and pH on the evoked potentials. These results showed that the pure effects of various physiological and chemical factors on the spinal cord-evoked potentials can be analyzed by this experimental model.

Animals↗
PubMed1995

[Epidemiological study on risk factors of pelvic endometriosis].

In order to study the risk factors associated with pelvic endometriosis, a case-control study was carried out from Mar. 1991 to Feb. 1993 in our gynecological ward. A total of 190 cases with endometriosis and 192 patients with non-endometriosis diseases (control group) were interviewed. Single factor analysis indicated that risk factors related to endometriosis were menorrhagia (OR = 3.09), short menstrual cycle (< 27 days) (OR = 1.89), complicated with uterine leiomyoma and (or) adenomyosis (OR = 1.84), occupation as cader (OR = 1.71), all with statistical significance (P < 0.05). The artificial abortion rate of married patients was similar between the two groups, but the abortion frequency was fewer in endometriosis patients (P < 0.05). Multifactor analysis confirmed that the risk factors associated with endometriosis were menorrhagia and occupation as cadre only.

Adult↗
PubMed1995

[Clinical study on effect of bushen jiangu capsule on postmenopausal osteoporosis].

The therapeutic effect of Kidney Tonifying principle and Bushen Jiangu (BSJG) capsule on postmenopausal osteoporosis (17 cases) was observed and compared with calcium treatment group (17 cases) in double-blind method. The result showed that 3 months after treatment with BSJG capsule, the symptoms of 92.85% patients were improved, and 6 months after treatment, the bone density (BD) of lumbar vertebra of 68.8% patients was significantly higher than that of before treatment, but the BD of control group was lower (P < 0.05). This suggested that BSJG capsule could prevent and improve postmenopausal osteoporosis. The therapeutic mechanisms probably is improving the bone formation and declining the bone absorption.

Bone Density↗