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Biomedical subjects

J Y Pan

Publications and source records attributed to J Y Pan.

At least 19 recordsLinked to original sources

Which depressed patients respond to nefazodone and when?

BACKGROUND: Retrospective data analyses were conducted of a single-blind trial of 993 outpatients with nonpsychotic major depression (DSM-III-R) treated for 12 weeks with nefazodone to provide a more specific picture of the nature and timing of response or remission to acute-phase treatment. METHOD: All patients participated in a single-blind, 16-week lead-in to obtain responders eligible for a subsequent double-blind, randomized continuation phase trial. Outcomes were defined by the 17-item Hamilton Rating Scale for Depression (HAM-D). A > or = 50% reduction from baseline defined response, and a total HAM-D exit score of < or =8 defined remission. RESULTS: Of all patients who entered the trial, 41.8% (last observation carried forward) responded at or before week 4 (early responders), and an additional 25.2% responded thereafter; 18.3% achieved remission at or before week 4; 33.6% achieved remission after week 4. Thus, 77.3% of those responding ultimately remitted. On average, remission followed response by 2 weeks. The average end-of-treatment dose was 376 mg/day at exit (last observation carried forward). Responders or remitters (as opposed to nonresponders or nonremitters) had lower baseline depressive symptomatology and were more likely to be married or cohabiting. CONCLUSION: The full symptomatic benefit of antidepressant medication may not be apparent until completion of an 8- to 10-week trial. A high number of responders ultimately attained remission. Baseline demographic and clinical features were not highly predictive of who would or would not benefit from nefazodone. For routine care, a minimal acute-phase trial, using a 50% reduction in baseline symptom severity to define response, should be 8 weeks. Whether ultimate nonresponders can be identified earlier than 8 weeks deserves further study.

Adult↗

[Role of conditioned growth medium for ventricular fibroblasts in promoting fibroblast collagen synthesis and proliferation].

Ventricular fibroblasts were cultured using conditioned growth medium for ventricular fibroblasts (FCGM). The rate of the total collagen synthesis of ventricular fibroblasts was measured by assaying the incorporation rate of [3H]-proline, whereas the proliferation of ventricular fibroblasts was assessed by determining the incorporation rate of [3H]-TdR and the expression of c-fos genes. FCGM significantly increased the [3H]-proline incorporation rate and [3H]-TdR incorporation rate of fibroblasts in a dose-dependent manner. Furthermore, FCGM promoted the c-fos gene expression of fibroblasts, which attained its maximum in 1 h. BQ123, an ETA receptor antagonist, partially blocked the above effects of FCGM, but AT1 receptor antagonist CV11974 and alpha-adrenergic receptor antagonist regitin did not. It is suggested that the ventricular fibroblast has an autorine function in promotion of collagen synthesis and proliferation of fibroblasts by secreting endothelin and other bioactive substances.

Animals↗

[Effect of aldosterone on the secretion of endothelin by ventricular fibroblasts].

Using cell culture, radioimmunoassay for endothelin and RT-PCR, the effect of aldosterone on the endothelin secretion of ventricular fibroblasts was studied. The results showed that aldosterone (1 x 10(-7) mol/L) promoted the expression of ppET-1 mRNA, which began to increase in 2 hours and attained the highest level in 4 hours, thereafter decreased; aldosterone increased the endothelin level in ventricular fibroblasts and fibroblast conditioned growth medium (FCGM) as well, which was blocked by spironolactone (1 x 10(-6) mol/L), an aldosterone receptor antagonist. The results suggest that aldosterone can increase endothelin secretion by ventricular fibroblasts, which can be inhibited by its receptor antagonist spironolactone.

Aldosterone↗

[Role of mitogen-activated protein kinase in the inhibition of myocardial hypertrophy by nitric oxide in renovascular hypertensive rats].

The aim of this study was to examine the effects of L-arginine, a nitric oxide (NO) precursor, on protein expression of endothelial nitric oxide (eNOS), nitrite/nitrate content, protein expression of mitogen-activated protein kinase phosphatase-1 (MKP-1) and the activity of mitogen-activated protein kinase (MAPK) in cardiac tissues in renovascular hypertensive rats (RHR). The Goldblatt renovascular hypertensive model was established by two-kidney one clip method. The rats were divided into four groups, respectively treated with 50, 150 and 450 mg/kg L-arginine and 150 mg/kg L-arginine plus 10 mg/kg L-NAME (an eNOS inhibitor) (i.p.). Another group did not receive specific treatment from the 5th week after renal artery constriction. Control group was sham-operated. Mean arterial blood pressure (MABP) and the ratio of left ventricular weight to body weight (LVW/BW) were measured 8 weeks after treatment. eNOS protein expression, nitrite/nitrate content, MKP-1 protein expression and MAPK activity in cardiac tissues were detected using Western blot analysis, enzyme-reduction method and substrate in-gel kinase assay, respectively. It was found that L-arginine significantly inhibited the increase of MABP and LVW/BW, attenuated the activity of MAPK, increased protein expression of eNOS and MKP-1 and potentiated production of NO in cardiac tissue with the most effective dosage of 150 mg/kg, and these effects of L-arginine could be inhibited by L-NAME. These results suggest that MKP-1 may play an important role in the NO-induced inhibition of myocardial hypertrophy. The anti-hypertrophic effects of L-arginine may involve increase of eNOS protein expression and NO production, potentiation of MKP-1 protein expression, and inhibition of MAPK activity in the cardiac tissue of RHR.

Animals↗

[Down-regulation of ETA receptor of vascular smooth muscle cells by 17 beta-estradiol].

In the present study, the effects of 17 beta-estradiol on vascular reactivity of ovariectomized rats and proliferation of cultured rat aortic smooth muscle cells were studied. The vascular reactivity was significantly increased in ovariectomized rats compared with the sham-operated animals. The selective ETA receptor antagonist BQ123 inhibited the increase in [3H]-TdR incorporation in response to ET-1 on vascular smooth muscle cells (VSMCs). 17 beta-estradiol also attenuated the ET-1 effects in a dose-dependent manner. The results of RT-PCR and Western blot show that expression of ETA receptor was decreased after treatment with 17 beta-estradiol. The effect of 17 beta-estradiol was partially inhibited by estrogen receptor antagonist tamoxifen. The above results demonstrate that proliferation of VSMCs stimulated by ET-1 was mainly mediated through ETA receptor. Due to the down-regulation of ETA receptor and mediation of estrogen receptor, 17 beta-estradiol inhibits the ET-1-induced proliferation of VSMCs and decreases the vascular reactivity of ovariectomized rats.

Animals↗

Ges, A human GTPase of the Rad/Gem/Kir family, promotes endothelial cell sprouting and cytoskeleton reorganization.

Rad, Gem/Kir, and mRem (RGK) represent a unique GTPase family with largely unknown functions (Reynet, C., and C.R. Kahn. 1993. Science. 262:1441-1444; Cohen, L., R. Mohr, Y. Chen, M. Huang, R. Kato, D. Dorin, F. Tamanoi, A. Goga, D. Afar, N. Rosenberg, and O. Witte. Proc. Natl. Acad. Sci. USA. 1994. 91:12448-12452; Maguire, J., T. Santoro, P. Jensen, U. Siebenlist, J. Yewdell, and K. Kelly. 1994. Science. 265:241-244; Finlin, B.S., and D.A. Andres. 1997. J. Biol. Chem. 272:21982-21988). We report that Ges (GTPase regulating endothelial cell sprouting), a human RGK protein expressed in the endothelium, functions as a potent morphogenic switch in endothelial cells (ECs). Ges function is sufficient to substitute for angiogenic growth factor/extracellular matrix (ECM) signals in promoting EC sprouting, since overexpression of Ges in ECs cultured on glass leads to the development of long cytoplasmic extensions and reorganization of the actin cytoskeleton. Ges function is also necessary for Matrigel-induced EC sprouting, since this event is blocked by its dominant negative mutant, Ges(T94N), predicted to prevent the activation of endogenous Ges through sequestration of its guanine nucleotide exchange factor. Thus, Ges appears to be a key transducer linking extracellular signals to cytoskeleton/morphology changes in ECs.

Actins↗

[MKP-1 regulates the cardiomyocyte hypertrophic responses induced by angiotensin II].

The aim of this study was to determine the regulation by MKP-1 of MAPK activity and protein expression in cardiomyocyte hypertrophic response induced by Ang II. Neonatal rat cardiomyocyte hypertrophic response was assayed by cell surface area, protein synthesis rate and protein content. MAPK activity was determined by an in-gel kinase assay. Protein expression of MAPK and MKP-1 were detected by Western blotting. The results are as follows. (1) Ang II induced promotion of (3)H-leucine incorporation and increase in cell protein content and cell surface area in a dose-dependent manner. Pretreatment with a selective AT(1) receptor antagonist CV11974 or a specific MEK inhibitor PD098059, cardiomyocyte hypertrophic response induced by Ang II was inhibited by 85% and 32.5%, respectively. (2) After pretreatment with PD098059 or CV11974, AngII-induced increases in p44MAPK and p42MAPK protein expression and enzyme activity (expressed by gamma-(32)P-ATP incorporation) were all inhibited obviously. (3) With treatment of myocytes by Ang II for 5 min, MAPK activity determined by p44MAPK and p42MAPK protein expression began to increase, while MKP-1 protein expression was detected within 30 min and lasted more than 2 h following treatment with Ang II. (4) Pretreatment of cardiomyocytes with actinomycin D (3 microgram/ml) for 30 min inhibited MKP-1 protein expression, while p44MAPK and p42MAPK protein expression was still detected 120 min after Ang II treatment. The above results demonstrate that activation of MAPK plays an important role in Ang II-induced cardiomyocyte hypertrophic response in neonatal rat cardiomyocytes through MKP-1 mediated inactivation of p44MAPK and p42MAPK.cardiomyocyte hypertrophic response in neonatal rat cardiomyocytes through MKP-1 mediated inactivation of p44MAPK and p42MAPK.

Angiotensin II↗

Nitric oxide inhibits the expression of proto-oncogene c-fos induced by angiotensin II and endothelin-1 in cardiomyocytes.

The effect of nitric oxide (NO) on the hypertrophic response and the proto-oncogene c-fos expression induced by angiotensin II (AII) or endothelin-1 (ET-1) was investigated in the primary culture of neonatal rat cardiomyocytes. Total protein content of cardiomyocytes (used as the index of cardiac myocyte hypertrophy) was determined by the Bradford method. The proto-oncogene c-fos expression was assessed using reverse transcription-polymerase chain reaction (RT-PCR) standardized with glyceraldehyde-3-phosphate dehydrogenase (GAPDH). RT-PCR was performed in a single tube using gene-specific primers and the SuperScript One-Step RT-PCR System. Total protein content of cardiomyocytes increased significantly on day 5 after A II treatment or on day 3 after ET-1 treatment and the increased protein content was inhibited by SNP (NO donor). A II, ET-1 and PMA (protein kinase C activator) induced the c-fos gene expression of cardiomyocytes, while L-arginine inhibited it. The L-arginine effect was blocked by L-NAME (NOS inhibitor). SNP inhibited the c-fos gene expression of cardiomyocytes induced by A II,ET-1 or PMA as well. These results suggest that NO can inhibit the hypertrophic response and the proto-oncogene c-fos expression of cardiomyocytes induced by A II or ET-1 and the cross-link may be located at the site of protein kinase C.

Angiotensin II↗

[17beta -estradiol induced nitric oxide release in vascular endothelial cells].

Bovine aortic endothelial cells (BAECs) were used to study the effect of 17beta -estradiol (E(2)) on nitric oxide (NO) release, nitric oxide synthase (eNOS) mRNA expression and intracellular free calcium con~cen~tration ([Ca(2+)](I)) and modulation of the effect of E(2) by estrogen receptor (ER) antagonist tamoxifen and NOS inhibitor L-NAME. E(2) (10(-12) 10(-8) mol/L) induced NO release of BAECs in a concentration-dependent manner and the abundant expression of eNOS mRNA in BAECs increased obviously after treatment with E(2) (10(-8)mol/L) for 48 h. These effects were evidently inhibited by tamoxifen (10(-7)mol/L) and L-NAME (10(-6) mol/L). Furthermore treatment with E(2) (10(-8) mol/L) for 48 h significantly increased the resting [Ca(2+)](I) and the rise of [Ca(2+)](I) induced by ATP in BAECs. These results suggest that E(2)-induced NO release and eNOS mRNA expression in BAECs may be mediated by ER and related to calcium mobilization.

Animals↗

[Effect of protein kinase C on inhibition of nitric oxide synthesis in cultured neonatal rat cardiomyocytes by angiotensin II].

The purpose of the present study was to investigate the effect of angiotensin II (Ang II) on nitric oxide (NO) concentration and its signal transduction pathway in cultured neonatal rat cardioymocytes. NO content was measured in cultured neonatal rat cardiomyoctes using a nitrite/nitrate colormetric method kit. NO content was represented by measured nitrite (NO(2)) and nitrate (NO(3)) level (NO(2)/NO(3)). The results are as follows. NO production was decreased by Ang II in a dose dependent manner but increased by L Arg. The Saralasin, an antagonist of Ang II receptor, inhibited the effect of Ang II on NO production. The effect of Ang II on NO production was inhibited by NOS blocker N(G)-nitro-L-arginine methyl ester L-NAME but not by L-Arg. Pretreatment of Phorbol 12-myristate 13-acetate PMA , a PKC activator, decreased NO concentration significantly. This effect was strengthened by L-NAME. Staurosporine, a PKC inhibitor, abolished the inhibiting effect of Ang II on production of NO. The above results suggest that Ang II could decrease NO content in cultured neonatal rat cardiomyocytes significantly. Activity of NOS may be inhibited by Ang II. Ang II receptor was involved in the inhibitory effect of Ang II on NO production. Activation of protein kinase C (PKC) decreased significantly NO production in cultured neonatal rat cardiomyoctes, which appears to be associated with PKC in the signal transduction pathway.

Angiotensin II↗

[Nitric oxide changes aortic function in rats with renal hypertension].

This work was undertaken to investigate the effect of nitric oxide (NO) on aortic function of two-kidney and one-clip (2K1C) rats with renal hypertension. Animals were divided into 5 groups: the sham operation, 2K1C, captopril, L-arginine and L-NAME groups. The results are as follows. At the 4th week after constriction of the left renal artery, the mean arterial pressure was significantly elevated. In isolated aortic rings, acetylcholine-induced dilation was attenuated, and phenylephrine induced contractile response was markedly enhanced. The level of aorta cGMP content was significantly lowered. These changes were abolished in 2K1C rats treated with captopril. L-arginine partially reversed the aortic vascular reactivity of 2K1C rats, and elevated aortic cGMP content. In 2K1C rats treated with nitric oxide synthase inhibitor, L-NAME, blood pressure was increased further, acetylcholine-induced aorta diastolic response was attenuated further and cGMP content reduced, while phenylephrine-induced contractile response was unaffected. These results suggest that deficiency of nitric oxide production and increase in renin-angiotensin system activity may contribute to vascular endothelial dysfunction of 2K1C rats, and these factors may be involved in development and maintenance of 2K1C renal hypertension.

Animals↗

[Cardiocyte hypertrophy induced by cultured neonatal rat ventricular fibroblast conditioned growth medium].

The present work demonstrated that cultured neonatal rat ventricular fibroblast conditioned growth medium (FCGM) could significantly increase cell surface area and protein content and promote (3)H -Leucine incorporation on neonatal rat cardiomyocyte. The above effect was strongest on the third day, and was dose-dependent. BQ(123), an ET-A receptor antagonist, significantly blocked the effect, while CV11974, an Ang II I-type receptor antagonist, and regitin, an alpha-adrenergic receptor antagonist, did not. These results suggest that there are some substances promoting hypertrophy of cardiomyocytes in FCGM, which may be ET-1. The FCGM-induced increases in cardiomyocyte protein synthesis and cell surface area were inhibited partially by pertusis toxin (PTX) and PKC inhibitor staurosporine (ST), suggesting that the hypertrophic effect is related with PTX sensitive G protein and PKC.

Animals↗

[The role of nitric oxide in the angiotensin II-induced hypertrophy of cardiac myocytes].

The purpose of this study was to determine the role of nitric oxide (NO) in the angiotensin II-induced hypertrophic response in cultured neonatal rat cardiac myocytes. Angiotensin II induced significant increase of protein content, decrease of NOS activity in cultured neonatal rat cardiomyocytes and decrease of NO concentration in the culture medium. Angiotensin II decreased significantly the eNOS mRNA level of cardiomyocytes. Saralasin and PTX inhibited significantly the increased protein content, the decreased NOS activity and the decreaseed NO production of cardiomyocytes induced by angiotensin II. Sodium nitroprusside increased significantly NO concentration in the culture medium and inhibited significantly the increased protein content of cardiomyocytes induced by angiotensin II. The results suggest that angiotensin II may induce hypertrophy of cultured neonatal rat cardiomyocytes. The effect of angiotensin II is mediated by receptors which are coupled with PTX-sensitive G protein and may be related to the decreased eNOS gene expression, NOS activity and NO production. Exogenous NO can prevent the hypertrophy of cardiomyocytes induced by angiotensin II.

Angiotensin II↗

[Effect of angiotensin II on c-fos expression and protein synthesis in cultured rat myocardial cells].

The present study was to investigate the effects of angiotensin II on c-fos mRNA expression and protein synthesis in cultured neonatal rat myocardial cells. The results showed that angiotensin II induced c-fos mRNA expression, increased protein content in a dose-dependent manner and stimulated 3H-leucine incorporation rate. All these effects were blocked by angiotensin II receptor antagonist saralasin. The angiotensin II-induced expression of c-fos gene was also blocked by Ca2+ channel antagonist nicardipine.

Angiotensin II↗

[Effect of ET-1 on intracellular free calcium in cultured neonatal myocardial cells].

In this present study, the effects of ET-1 on intracellular free calcium concentration ([Ca2+]i) and the underlying mechanisms were investigated in cultured neonatal rat myocardial cells loaded with fura-2/AM. The results are as follows. ET-1 induced an increase of [Ca2+]i in a dose-dependent manner, which consisted of a transient and sustained phase. BQ123, a selective ETA receptor antagonist, blocked the ET-1 induced [Ca2+]i responses, suggesting that these responses were mediated by ETA receptors. After removal of extracellular Ca2+, ET-1 induced the transient increase of [Ca2+]i without the sustained change. Protein kinase C (PKC) agonist PMA attenuated the ET-1 induced transient [Ca2+]i increase. Amiloride and nifedipine did not block the [Ca2+]i change induced by ET-1. After pretreatment of myocardial cells with pertussis toxin, ET-1 also induced the transient increase of [Ca2+]i but did not affect the sustained increase. These results suggest that the transient [Ca2+]i increase may involve pertussis toxin-insensitive G protein and the sustained one may be caused by extracellular calcium influx, in which pertussis toxin sensitive G protein is involved. Furthermore, PKC, but not Na+/H+ exchange, plays an important role in these effects.

Animals↗

[ET-1 induces the expression of prooncogene c-fos in cultured neonatal rat myocardial cells].

In the present study, the effect of endothelin-1 (ET-1) on the expression of proto-oncogene c-fos in cultured neonatal rat myocardial cells was investigated. The results are as follows: ET-1 induced c-fos expression in a dose-dependent manner. Selective ET(A) receptor antagonist blocked ET-1-induced responses. Protein kinase C(PKC) agonist PMA induced c-fos expression.PKC inhibitor staurosporine blocked ET-1 induced c-fos expression. Calcium channel blocker, nifedipine did not significantly affect the expression of c-fos induced by ET-1. These results suggest that in cultured neonatal cardiomyocytes, ET-1 induced c-fos gene expression is mediated by ET(A) receptor with the participation of protein kinase C, while the voltage-dependent L-type Ca(2+) channel is not involved.

Animals↗

GEF-mediated GDP/GTP exchange by monomeric GTPases: a regulatory role for Mg2+?

GTPases share highly conserved guanine nucleotide-binding domains and fulfill diverse functions through a common molecular switch. An inactive GDP-bound protein is turned on by a guanine nucleotide exchange factor (GEF) that catalyzes exchange of GTP for GDP, but unfortunately little is known about the mechanism of GEF action. A common mechanism for GDP/GTP exchange can be envisioned wherein GEFs activate monomeric GTPases through transient disruption of Mg2+ coordination in the nucleotide-binding pocket while stabilizing a nucleotide-free (and cation-free) conformation. After guanine nucleotide exchange, Mg2+ coordination is restored to complete the conformational switch to the active GTP-bound state. Evidence in the literature highlighting an important regulatory role for Mg2+ in the mechanism of GEF-mediated GDP/GTP exchange by monomeric GTPases is summarized.

Animals↗

[The role of G protein, protein kinase C and Na(+)-H+ exchanger in endothelin-1-induced cardiomyocyte hypertrophic responses].

Endothelin-1 (ET-1) has been shown to be a potent growth factor and to induce cardiac hypertrophy. In the present study, we examined the role of G protein, protein kinase C (PKC) and Na(+)-H+ exchanger in ET-1-induced cardiac hypertrophy in cultured neonatal rat cardiac myocytes. ET-1 (10(-10)-10(-7) mol/L) induced promotion of 3H-leucine incorporation, increase in cell protein content and cell surface area in a dose-dependent manner with EC50 value of 5.2 x 10(-10), 5.2 x 10(-10) and 7.3 x 10(-10) mol/L respectively. All of these ET-1-induced cardiomyocyte hypertrophic responses were completely blocked by pretreatment with staurosporine (2 nmol/L), a protein kinase C inhibitor, and stimulated by 4-phorbol, 12-myristate, 13-acetate (PMA) (10(-8)-10(-6) mol/L), a protein kinase C activator, in a dose-dependent manner. Pretreatment of amiloride (10(-4) mol/L), a Na(+)-H+ exchange inhibitor completely inhibited the ET-1-induced, but not PMA-induced cardiomyocyte hypertrophic responses. The ET-1-induced increase in cardiomyocyte protein synthesis and cell surface area was significantly inhibited by pretreatment with pertussis toxin (150 ng/ml). These results suggest that ET-1-induced cardiomyocyte hypertrophy was linked with pertussis toxin sensitive G protein, and PKC and Na(+)-H+ exchange may be an important intracellular signaling transduction pathway during ET-1-induced cardiac hypertrophy in cultured neonatal rat cardiac myocytes.

Animals↗