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Biomedical subjects

Y Zou

Publications and source records attributed to Y Zou.

At least 163 records · Page 9Linked to original sources
PubMed1997

Formation of DNA repair intermediates and incision by the ATP-dependent UvrB-UvrC endonuclease.

The Escherichia coli UvrB and UvrC proteins play key roles in DNA damage processing and incisions during nucleotide excision repair. To study the DNA structural requirements and protein-DNA intermediates formed during these processes, benzo[a]pyrene diol epoxide-damaged and structure-specific 50-base pair substrates were constructed. DNA fragments containing a preexisting 3' incision were rapidly and efficiently incised 5' to the adduct. Gel mobility shift assays indicated that this substrate supported UvrA dissociation from the UvrB-DNA complex, which led to efficient incision. Experiments with a DNA fragment containing an internal noncomplementary 11-base region surrounding the benzo[a]pyrene diol epoxide adduct indicated that UvrABC nuclease does not require fully duplexed DNA for binding and incision. In the absence of UvrA, UvrB (UvrC) bound to an 11-base noncomplementary region containing a 3' nick (Y substrate), forming a stable protein-DNA complex (Kd approximately 5-10 nM). Formation of this complex was absolutely dependent upon UvrC. Addition to this complex of ATP, but not adenosine 5'-(beta,gamma-iminotriphosphate) or adenosine 5'-(beta, gamma-methylene)triphosphate, caused incision three or four nucleotides 5' to the double strand-single strand junction. The ATPase activity of native UvrB is activated upon interaction with UvrC and enhanced further by the addition of Y substrate. Incision of this Y structure occurs even without DNA damage. Thus the UvrBC complex is a structure-specific, ATP-dependent endonuclease.

Bacterial Proteins↗
PubMed1997

Protein kinase A and protein kinase C synergistically activate the Raf-1 kinase/mitogen-activated protein kinase cascade in neonatal rat cardiomyocytes.

Adrenoceptor agonists play an important role in cardiac hypertrophy. In cardiomyocytes, activation of alpha- and beta-adrenoceptors induces a variety of hypertrophic responses via activation of protein kinase C (PKC) and protein kinase A (PKA), respectively. Although PKC evokes activation of the Raf-1 kinase (Raf-1)/mitogen-activated protein (MAP) kinase cascade, PKA has been shown to inhibit the activation of Raf-1 and MAP kinases induced by growth factors in various cell types. The present study was performed to elucidate the role of PKA and PKC in cardiomyocyte hypertrophy. PKA activators such as forskolin (FSK), isobutylmethylxanthine, dibutyryl cAMP and isoproterenol, significantly activated Raf-1 and MAP kinases with a peak at 2 and 8 min, respectively, followed by an increase in protein synthesis in cardiac myocytes. Similar responses were observed when cardiomyocytes were stimulated with PKC activators such as 12-O-tetradecanoylphorbol-13-acetate (TPA), angiotensin II, phenylephrine and mechanical stretch. After depleting extracellular Ca2+ with EGTA, FSK did not activate MAP kinases, while down-regulation of PKC by long exposure with TPA did not influence FSK-induced MAP kinase activation. Furthermore, FSK and TPA synergistically activated Raf-1. Similar synergistic activation of MAP kinases was observed when other PKC activators were added to cardiac myocytes with FSK at the same time. In conclusion, unlike other cell types, PKA activates Raf-1 and MAP kinases followed by an increase in protein synthesis in cardiac myocytes.

1-Methyl-3-isobutylxanthine↗
PubMed1997

Risk factors for bladder cancer: a case-control study in northeast China.

A case-control study of risk factors for bladder cancer was carried out in Heilongjing Province, China. Between May 1989 and May 1990, 217 histologically confirmed cases of bladder cancer and 254 controls with non-neoplastic and non-urine system disease were recruited. Individuals were interviewed in the wards of six major hospitals. Controls were matched by sex, age and area of residence. Information was collected concerning economic status, occupation, histories of smoking and consumption of alcohol, use of tea, the taking of analgesics, dietary histories and previous diseases. Odds ratios (ORs) were calculated from stratified analysis and conditional logistic regression models. Increased risk was observed with increasing times per year and number of years of saccharine use. Compared with non-users, the use of saccharine for more than 19 times per year, and for more than 15 years, the adjusted ORs were 3.9 (95% CI = 1.8-8.67) and 5.1 (95% CI = 2.3-11.6), respectively. Statistically significant associations were also found for diseases related to the urinary system (OR = 2.8; 95% CI = 1.1-7.6). Increased consumption of fruit and vegetable may reduce the risk of bladder cancer. Cigarette smoking had no effect on the risk of bladder cancer in both genders. There was no association between the consumption of alcohol or tea, or types of water supply, with bladder cancer risk.

Adult↗
PubMed1997

Angiotensin II stimulates c-Jun NH2-terminal kinase in cultured cardiac myocytes of neonatal rats.

Many lines of evidence have suggested that angiotensin II (Ang II)plays an important role in cardiac hypertrophy. Ang II not only increases protein synthesis but also induces the reprogramming of gene expression in cultured cardiac myocytes. In the present study, to elucidate the mechanism by which Ang II regulates gene expression in cardiac myocytes, we examined whether Ang II activates c-Jun NH2-terminal kinase (JNK), which is a member of the mitogen-activated protein kinase family and activates the transcription factor, activator protein-1 (AP-1). The activity of JNK increased 5 minutes after the addition of Ang II, peaked at 20 minutes, and gradually decreased thereafter. Examination of the Ang II dose-response relation revealed detectable JNK activation at 10(-9) mol/L and maximal activation at 10(-6) mol/L. Ang II activated JNK through the AT1 receptor, and the activation was attenuated by the downregulation of protein kinase C or the chelation of intracellular Ca2+. Although the addition of either Ca2+ ionophore or phorbol ester resulted in little or no activation of JNK, simultaneous addition of both Ca2+ ionophore and phorbol ester markedly activated JNK. Slight expressions of the c-jun gene were observed in unstimulated cardiac myocytes, and Ang II increased expressions of the c-jun gene as well as the c-fos gene. Ang II increased transcription of the endothelin-1 gene through the AP-1 binding site. In conclusion, Ang II may activate JNK in cultured cardiac myocytes through an increase in intracellular Ca2+ and activation of protein kinase C, and the activated JNK may regulate gene expression by activating AP-1 during Ang II-induced cardiac hypertrophy.

Angiotensin II↗
PubMed1997

CARP, a cardiac ankyrin repeat protein, is downstream in the Nkx2-5 homeobox gene pathway.

To identify the molecular pathways that guide cardiac ventricular chamber specification, maturation and morphogenesis, we have sought to characterize factors that regulate the expression of the ventricular myosin light chain-2 gene, one of the earliest markers of ventricular regionalization during mammalian cardiogenesis. Previously, our laboratory identified a 28 bp HF-la/MEF-2 element in the MLC-2v promoter region, which confers cardiac ventricular chamber-specific gene expression during murine cardiogenesis, and showed that the ubiquitous transcription factor YB-1 binds to the HF-la site in conjunction with a co-factor. In a search for interacting co-factors, a nuclear ankyrin-like repeat protein CARP (cardiac ankyrin repeat protein) was isolated from a rat neonatal heart cDNA library by yeast two-hybrid screening, using YB-1 as the bait. Co-immunoprecipitation and GST-CARP pulldown studies reveal that CARP forms a physical complex with YB-1 in cardiac myocytes and immunostaining shows that endogenous CARP is localized in the cardiac myocyte nucleus. Co-transfection assays indicate that CARP can negatively regulate an HF-1-TK minimal promoter in an HF-1 sequence-dependent manner in cardiac myocytes, and CARP displays a transcriptional inhibitory activity when fused to a GAL4 DNA-binding domain in both cardiac and noncardiac cell context. Northern analysis revealed that carp mRNA is highly enriched in the adult heart, with only trace levels in skeletal muscle. During murine embryogenesis, endogenous carp expression was first clearly detected as early as E8.5 specifically in heart and is regulated temporally and spatially in the myocardium. Nkx2-5, the murine homologue of Drosophila gene tinman was previously shown to be required for heart tube looping morphogenesis and ventricular chamber-specific myosin light chain-2 expression during mammalian heart development. In Nkx2-5(-/-)embryos, carp expression was found to be significantly and selectively reduced as assessed by both whole-mount in situ hybridizations and RNase protection assays, suggesting that carp is downstream of the homeobox gene Nkx2-5 in the cardiac regulatory network. Co-transfection assays using a dominant negative mutant Nkx2-5 construct with CARP promoter-luciferase reporter constructs in cardiac myocytes confirms that Nkx2-5 either directly or indirectly regulates carp at the transcriptional level. Finally, a carp promoter-lacZ transgene, which displays cardiac-specific expression in wild-type and Nkx2-5(+/-) background, was also significantly reduced in Nkx2-5(-/-) embryos, indicating that Nkx2-5 either directly or indirectly regulates carp promoter activity during in vivo cardiogenesis as well as in cultured cardiac myocytes. Thus, CARP is a YB-1 associated factor and represents the first identified cardiac-restricted downstream regulatory gene in the homeobox gene Nkx2-5 pathway and may serve as a negative regulator of HF-1-dependent pathways for ventricular muscle gene expression.

Amino Acid Sequence↗
PubMed1997

[Protection of hepatocyte growth factor against carbon tetrachloride injury in primary rat hepatocyte culture].

The protective effect of recombinant human hepatocyte growth factor (r-hHGF) against carbon tetrachloride (CCl4) injury in cultured rat hepatocytes was investigated. It was found that r-hHGF had cytoprotective effect on hepatocytes anainst CCl4 poisoning. Pretreatment with r-hHGF significantly increased the viability of cultured hepatocytes, reduced the leakage of intracellular alanine transaminase and potassium into the culture medium, as compared with the CCl4 group. The results suggest that r-hHGF may protect hepatocytes against CCl4 injury through lessening the severity of membrane lesion, preventing intracellular alanine transaminase and potassium leakage and sustaining the integrity of hepatocyte membrane.

Animals↗
PubMed1997

[Effects of hepatocyte growth factor on dose- and time-response of DNA synthesis in rat hepatocytes in vitro].

Effects of recombinant human hepatocyte growth factor (r-hHGF) on dose- and time-response of DNA synthesis were observed by using the method of 3H-TdR incorporation into DNA in rat hepatocytes in vitro. The results showed that r-hHGF was the most potent mitogen for initiating DNA synthesis of hepatocytes, and there were dose-dependent increase in the range of 1 ng/ml (10 pmol/L)-10 ng/ml (100 pmol/L). The significant effect of r-hHGF was observed even at 1 ng/ml, and the maximal stimulatory effect was found at 10 ng/ml, which was 7-fold rise than the control. Beyond 10 ng/ml, r-hHGF inhibited hepatocyte DNA synthesis. In addition, time-response of r-hHGF on DNA synthesis was observed at 24 h, 48 h, 72 h and 96 h respectively, 3H-thymidine incorporation was higher than control group after 24 hours of incubation with r-hHGF, and reached top at 48 hours. DNA synthesis decreased after 72 and 96 hours of incubation with r-hHGF.

Animals↗
PubMed1997

[Study on substance P immunoreactivity after acute crush injury to facial nerve].

This paper presents the change in substance P immunoreactivity (SP-IR) after acute crush injury to the vertical part of facial nerve of normal cats by using immunohistochemical and immunocytochemical techniques combined with immunoelectronic microscopy. The electroneuromyogram (ENOG) shows that the cats have suffered from fully peripheral facial paralysis. It is found that the SP-IR positive products and fibers increase in the other part of facial nerve (including the non-injured part of vertical segment and level segment) after injury, especially six days later. As a result, it is suggested that the regeneration and repair of facial nerve might be in close relationship with substance P after acute crush injury to it.

Animals↗
PubMed1997

Non-trans-scleral suture fixation of posterior chamber intraocular lenses in the absence of posterior capsular support.

PURPOSE: To develop a new technique for fixation of posterior chamber intraocular lens (IOL) in the absence of posterior capsule support. MATERIALS AND METHODS: We performed non-trans-scleral fixation of intraocular lenses on 24 cases (24 eyes) without posterior capsule support. Two scleral flaps with limbal incisions and two peripheral iridectomies were made at 1 o'clock and 7 o'clock positions respectively. A suture-leading needle was used to lead the prolene suture from the limbal incision and iridectomy on one side through the iridectomy and limbal incision on the other side. Intraocular lens (IOL) was then fixed in the ciliary sulcus. RESULTS: After a mean follow-up of 6.6 months (range from 3 to 14 months), corrected visual acuity of 16 cases (16 eyes, 66.7%) got 0.5 or better. Postoperative complications included discoria (4 eyes), surface membrane formation (1 eye), choroidal detachment (1 eye) and tilt of IOL (1 eyes), but all were not severe. CONCLUSION: In some situations such as low intraocular pressure, non-penetration scleral fixation may be a good way to implant IOL in the absence of posterior capsule support.

Adolescent↗
PubMed1996

Protein kinase C, but not tyrosine kinases or Ras, plays a critical role in angiotensin II-induced activation of Raf-1 kinase and extracellular signal-regulated protein kinases in cardiac myocytes.

Angiotensin II (AngII) induces cardiac hypertrophy through activating a variety of protein kinases. In this study, to understand how cardiac hypertrophy develops, we examined AngII-evoked signal transduction pathways leading to the activation of extracellular signal-regulated protein kinases (ERKs), which are reportedly critical for the development of cardiac hypertrophy, in cultured cardiac myocytes isolated from neonatal rats. Inhibition of protein kinase C (PKC) with calphostin C or down-regulation of PKC by pretreatment with a phorbol ester for 24 h abolished AngII-induced activation of Raf-1 and ERKs, and addition of a phorbol ester conversely induced a marked increase in the activities of Raf-1 and ERKs. Pretreatment with two chemically and mechanistically dissimilar tyrosine kinase inhibitors, genistein and tyrphostin, did not attenuate AngII-induced activation of ERKs. In contrast, genistein strongly blocked insulin-induced ERK activation in cardiac myocytes. Although pretreatment with manumycin, a Ras farnesyltransferase inhibitor, or overexpression of a dominant-negative mutant of Ras inhibited insulin-induced ERK activation, neither affected AngII-induced activation of ERKs. Overexpression of a dominant-negative mutant of Raf-1 completely suppressed ERK2 activation by AngII, endothelin-1, and insulin. These results suggest that PKC and Raf-1, but not tyrosine kinases or Ras, are critical for AngII-induced activation of ERKs in cardiac myocytes.

Angiotensin II↗
PubMed1996

Endothelin-1 is involved in mechanical stress-induced cardiomyocyte hypertrophy.

We have recently shown that mechanical stress induces cardiomyocyte hypertrophy partly through the enhanced secretion of angiotensin II (ATII). Endothelin-1 (ET-1) has been reported to be a potent growth factor for a variety of cells, including cardiomyocytes. In this study, we examined the role of ET-1 in mechanical stress-induced cardiac hypertrophy by using cultured cardiomyocytes of neonatal rats. ET-1 (10(-8) approximately 10(-7) M) maximally induced the activation of both Raf-1 kinase and mitogen-activated protein (MAP) kinases at 4 and 8 min, respectively, followed by an increase in protein synthesis at 24 h. All of these hypertrophic responses were completely blocked by pretreatment with BQ123, an antagonist selective for the ET-1 type A receptor subtype, but not by BQ788, an ET-1 type B receptor-specific antagonist. BQ123 also suppressed stretch-induced activation of MAP kinases and an increase in phenylalanine uptake by approximately 60 and 50%, respectively, but BQ788 did not. ET-1 was constitutively secreted from cultured cardiomyocytes, and a significant increase in ET-1 concentration was observed in the culture medium of cardiomyocytes after stretching for 10 min. After 24 h, an approximately 3-fold increase in ET-1 concentration was observed in the conditioned medium of stretched cardiomyocytes compared with that of unstretched cardiomyocytes. ET-1 mRNA levels were also increased at 30 min after stretching. Moreover, ET-1 and ATII synergistically activated Raf-1 kinase and MAP kinases in cultured cardiomyocytes. In conclusion, mechanical stretching stimulates secretion and production of ET-1 in cultured cardiomyocytes, and vasoconstrictive peptides such as ATII and ET-1 may play an important role in mechanical stress-induced cardiac hypertrophy.

Animals↗
PubMed1996

Activation of p70 S6 protein kinase is necessary for angiotensin II-induced hypertrophy in neonatal rat cardiac myocytes.

Although many lines of evidence have suggested that angiotensin II (Ang II) plays an important role in development of cardiac hypertrophy, the mechanism by which Ang II increases protein synthesis in cardiac myocytes remains unclear. It has been reported that the phosphorylation of S6 protein in 40 S ribosome is correlated to the efficiency of protein synthesis. In the present study, we have examined whether Ang II activates p70 S6 kinase (p70S6K), which has been reported to phosphorylate S6 protein. Ang II activated p70S6K through AT1 receptor. An immunosuppressant agent, rapamycin, inhibited Ang II-induced p70S6K activation but not the activation of MAP kinases or the induction of c-fos gene expression. Rapamycin also abolished Ang II-induced increase in protein synthesis. These results suggest that Ang II induces cardiac hypertrophy by activating p70S6K.

Angiotensin I↗
PubMed1996

Lipid-complexed camptothecin: formulation and initial biodistribution and antitumor activity studies.

Water-soluble derivatives of camptothecin, and active topoisomerase I inhibitor, have shown a broad spectrum of activity against human tumors. Early clinical trials with the water-soluble sodium salt of camptothecin were hindered by significant cystitis, gastroenteritis, and leukopenia. Furthermore, the sodium salt of camptothecin has been shown to have significantly less activity than the water-insoluble lactone form of the compound. We describe a formulation of lipid-complexed CPT (LC-CPT; particle size range 20.8-208.1 nm) that is very easy to prepare and allows for intravenous administration in vivo in clinically relevant lipid-drug ratios (12.5:1 w/w). The lipid formulation had in vitro antitumor activity similar to that of CPT formulated without lipids and displayed similar cytotoxicity against MDR-1-negative and -positive tumor cells. The biodistribution of CPT was profoundly affected by lipid complexation; free CPT achieved the greatest concentration in the pulmonary parenchyma while LC-CPT achieved the highest concentration in the gastrointestinal tract. LC-CPT had significant antitumor activity in vivo against intraperitoneal L1210 and P338 leukemia and appeared to be more potent then free CPT.

Animals↗
PubMed1996

Lyophilized preliposomal formulation of the non-cross-resistant anthracycline annamycin: effect of surfactant on liposome formation, stability and size.

We report a method of preparing a submicron and stable liposome formulation of the non-cross-resistant anthracycline annamycin. The lipids were dimyristoylphosphatidyl choline (DMPC) and dimyristoylphosphatidyl glycerol (DMPG) at a 7:3 molar ratio and the optimal lipid:drug ratio was 50:1 (w/w). The selected formulation was a preliposome lyophilized powder that contained the phospholipids, annamycin, and Tween 20. The liposome suspension was obtained on the day of use by adding normal saline at 37 degrees C (1 ml/mg annamycin) and hand shaking for 1 min. The presence of Tween 20 was essential in shortening the reconstitution step (from > 2 h to 1 min), avoiding the early formation of free drug crystals, and reducing the median particle size by tenfold (from 1.5 microm to 0.15 microm) without destroying the liposome vesicles. At room temperature, the preliposome powder was chemically stable for > 3 months, and the liposome suspension was chemically and physically stable for > 24 h. The in vitro cytotoxicity of the formulation was equivalent to that of the same lipid composition prepared by the standard evaporation method. The results of the study indicate that small amounts of surfactant may be used to enhance the reconstitution step and reduce the size of liposome suspensions obtained from lyophilized preliposome powders. The formulation described is being used for ongoing clinical trials with liposomal annamycin.

Antibiotics, Antineoplastic↗
PubMed1996

Mechanical stretch activates the stress-activated protein kinases in cardiac myocytes.

We have recently shown that mechanical stress activates a phosphorylation cascade of protein kinases including Raf-1 and the extracellular signal-regulated kinases (ERKs) in cultured cardiac myocytes partially through the enhanced secretion of angiotensin II. Osmotic stress in budding yeast has been shown to activate similar signaling molecules including Hog-1, a distant relative of the ERK family. In the present study, we examined whether mechanical stretch of cardiac myocytes activates the stress-activated protein kinases (SAPKs)/c-Jun NH2-terminal kinase, the mammalian homologs of yeast Hog-1 that regulate gene expression through activation of the transcription factor, AP-1. When cardiac myocytes of neonatal rats cultured on a deformable silicone dish were stretched, activity of SAPKs was increased from 10 min, peaked at 30 min, and gradually decreased thereafter. The increase in activity of SAPKs was proportional to the stretch. Unlike ERKs, the activation of SAPKs by stretching cardiac myocytes was not dependent on the secreted angiotensin II. The chelation of extracellular Ca2+ or down-regulation of protein kinase C did not attenuate activation of SAPKs by stretch. Transfection experiments using an AP-1 binding site-containing reporter gene revealed that stretch increases AP-1 activity in cardiac myocytes. In conclusion, like osmotic stress in yeast, mechanical stretch activates SAPKs in cardiac myocytes without the participation of angiotensin II. These results suggest that the activation of SAPKs may regulate gene expression during mechanical stress-induced cardiac hypertrophy.

Angiotensin II↗
PubMed1996

Artificial neural network to assist psychiatric diagnosis.

BACKGROUND: Artificial Neural Network (ANN), as a potential powerful classifier, was explored to assist psychiatric diagnosis of the Composite International Diagnostic Interview (CIDI). METHOD: Both Back-Propagation (BP) and Kohonen networks were developed to fit psychiatric diagnosis and programmed (using 60 cases) to classify neurosis, schizophrenia and normal people. The programmed networks were cross-tested using another 222 cases. All subjects were randomly selected from two mental hospitals in Beijing. RESULTS: Compared to ICD-10 diagnosis by psychiatrists, the overall kappa of BP network was 0.94 and that of Kohonen was 0.88 (both P < 0.01). In classifying patients who were difficult to diagnose, the kappa of BP was 0.69 (P < 0.01). ANN-assisted CIDI was compared with expert system assisted CIDI (kappa = 0.72-0.76); ANN was more powerful than a traditional expert system. CONCLUSION: ANN might be used to improve psychiatric diagnosis.

Adult↗
PubMed1996

[Control of growth and expression of protooncogenes in regenerating liver].

There are many humoral factors involved in the control of growth in regenerating liver. The complete hepatocyte mitogens such as hepatocyte growth factor (HGF), hepatic stimulator substance (HSS) can strongly stimulate hepatocyte DNA synthesis and mitosis. The hepatocyte growth inhibitors such as transforming growth factor beta 1 (TGF beta 1), however, do not stimulate DNA synthesis, but inhibit EGF mitogenesis. In addition, the comitogens such as norepinephrine and insulin are necessary to regulate the growth of regenerating liver. It has become clear that the hepatocyte proliferation and protooncogenes are linked closely. Some protooncogenes can express specifically as markers in the different phases of the cell cycle and in hepatocytes that enter the cell cycle (G0 to G1 transit) and continue to progress.

Animals↗