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The atheroprotective effects of estrogen are well established and the presence of an estrogen receptor in vascular tissues has recently been reported. Therefore, we investigated the localization of the estrogen-producing enzyme aromatase in vascular tissues to assess the possible contribution of endocrine, paracrine, and autocrine modes of action. Aromatase was found in human vascular smooth muscle cells (SMCs) but not in endothelial cells on in situ hybridization. These observations were further supported by quantitative analysis of aromatase mRNA and the activity in 15 human vascular specimens. Only trace levels of expression were detected in the 3 infants examined, whereas 0.0088 to 0.0806 amol/ microg RNA of aromatase mRNA and 12.9 to 122.3 fmol. h-1. mg-1 protein of the activity were detected in 12 of the adult individuals. The switching of tissue-specific exon 1 of the human aromatase gene was also observed in some cases. Aromatase was found to be expressed only in cultured SMCs and not in cultured endothelial cells of human aorta and pulmonary artery and to be regulated through dexamethasone and the signaling pathways of protein kinase A and C. Study results revealed the localized expression of aromatase in vascular SMCs, which indicated a possible direct action of locally produced estrogen in an autocrine or paracrine manner, with possible cross talk between smooth muscle and endothelial cells.

Recent data suggest that nitric oxide (NO) plays a role in the modulation of sympathetic nerve activity and baroreflex sensitivity. Most of these studies have been carried out in anesthetized preparations, and little if any comparison has been made on the relative role of NO on the baroreflex control of heart rate and sympathetic nerve activity. In the present studies, the effect of the NO synthase inhibitor NG-nitro-L-arginine (L-NNA) on the baroreflex control of heart rate (HR) and renal sympathetic nerve activity (RSNA) were investigated in conscious, instrumented rabbits. Intravenous bolus injections of 13 mg/kg of L-NNA decreased baseline HR (from 205.0 +/- 6.0 to 145.5 +/- 8.2 beats/min; P < 0.05) without significant changes in mean arterial pressure (MAP) and RSNA. L-NNA significantly reduced the lower plateau of the HR-MAP curves and increased the sensitivities of baroreflex control of HR and RSNA. L-Arginine (600 mg/kg i.v.) but not D-arginine reversed the above effects. The effects of L-NNA on baseline HR were not completely blocked by metoprolol (2 mg/kg) or by atropine (0.2 mg/kg). After pretreatment with metoprolol, baroreflex sensitivity was reduced and L-NNA increased baroreflex sensitivity back to the control level. After pretreatment with atropine, L-NNA still reduced the lower plateau but did not significantly affect baroreflex sensitivity. L-NNA increased the HR responses but not the RSNA response to electrical stimulation of the aortic nerve in chloralose-anesthetized, sinoaortic-denervated (SAD) rabbits. L-NNA had no effect on the HR response to right vagal stimulation. In both conscious intact and SAD rabbits, L-NNA did not increase baseline RSNA. These results suggest that endogenous NO decreases baroreflex control of HR and RSNA. Both sympathetic and parasympathetic components play a role in the effects of NO on the baroreflex control of HR. The effects of NO in the central nervous system play a more important role in the baroreflex control of HR than of RSNA.

The biological role of phosphatidylinositol (PI)-3 kinase was examined in osteoclast-like multinucleated cells (OCLs) formed in co-cultures of mouse osteoblastic ceils and bone marrow cells. The expression of PI-3 kinase in OCLs was confirmed by Western blot analysis. Wortmannin (WT), a specific inhibitor of PI-3 kinase, inhibited PI-3 kinase activity in OCLs both in vitro and in vivo. WT also inhibited pit-forming activity on dentine slices and disrupted a ringed structure of F-actin-containing dots (an actin ring) in OCLs in a dose-dependent manner. The inhibitory profiles of WT for pit and actin ring formation were similar to that for PI-3 kinase activity in OCLs. Electron microscopic analysis revealed that OCLs treated with WT did not form ruffled borders. Instead, numerous electron lucent vacuoles of differing sizes were found throughout the cytoplasm. These results suggest that PI-3 kinase is important in osteoclastic bone resorption.

Increasing evidence suggests that endogenous NO inhibits sympathetic outflow in anesthetized animals. However, in a recent study from this laboratory, we were unable to find any evidence of increased renal sympathetic nerve activity (RSNA) in response to blockade of NO synthesis in conscious rabbits. Because angiotensin II (Ang II) increases sympathetic outflow, one factor for this discrepancy may be the difference in the resting level of Ang II, which may be lower in well-trained conscious animals. In the present study, the effects of blockade of NO synthesis with Nomega-nitro-L-arginine methyl ester (L-NAME, 30 mg/kg IV) on resting RSNA with and without a background intravenous infusion of Ang II (10 ng.kg(-1).min(-1)) was investigated in conscious rabbits. Intravenous administration of L-NAME (30 mg/kg) caused an increase in mean arterial blood pressure (MAP, from 80.4+/-2.9 to 92.8+/-2.5; P=.0001) and a decrease in RSNA (from 100+/-0% to 53.4+/-8.6%, P=.0016). When the elevated blood pressure was returned to control by infusion of hydralazine (0.01 to 0.06 mg.kg(-1).min(-1)), RSNA returned to the level before L-NAME administration. During a sustained infusion of Ang II (10 ng.kg(-1).min(-1)), L-NAME increased MAP from 89.2+/-2.9 to 109.0+/-4.3 mm Hg (P=.0101) and decreased RSNA from 100.0+/-0% to 53.7+/-7.5% (P=.0013). Under this circumstance, however, when the MAP was returned to the level that existed before the administration of L-NAME, RSNA increased significantly above the level that existed before the administration of L-NAME (164.5+/-17.7% versus 100+/-0%, P=.0151). The enhancement of the sympathetic response by Ang II was completely blocked by the AT1 receptor antagonist, losartan. In contrast, during a background infusion of phenylephrine, which increased MAP to the same level as produced by Ang II, L-NAME had no effect on RSNA when MAP was returned to the control level. Nomega-Nitro-D-arginine methyl ester had no effect on MAP and RSNA. Intravenous infusion of Ang II alone for 75 minutes had no effect on RSNA when MAP was returned to control levels. These data suggest that an elevated level of Ang II is critical for the inhibitory effect of NO on sympathetic outflow in conscious rabbits and imply that these two substances have a major impact on the regulation of sympathetic outflow.

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Recent studies have identified a family of proteins referred to as cyclins, which control the cell cycle. Cyclin B1 activates cdc2, which regulates cell progression through the G2 and M phases. The main aim of this study was to examine the relationships between the cyclin B1 expression in human esophageal squamous cell carcinoma (SCC) and clinicopathological factors and prognosis of the patients. Eighty-seven cases of primary human SCC consecutively obtained at esophagectomy were immunohistochemically studied using an anti-human cyclin B1 protein antibody (2H1-H6). The relationship between cyclin B1 expression and clinicopathological factors, including prognosis, were also statistically assessed. Positive immunostaining of cancer cells, mainly in the cytoplasm, was detected in 72.4% (63/87): heterogeneous pattern in 37.9% (33/87) and homogeneous pattern in 34.5% (30/87). The prevalence of cyclin B1 expression was significantly higher in cases with invasion deeper than the muscularis propria (P<0.005) and with venous invasion (P<0.01) than in other cases. Patients whose SCCs expressed high levels of cyclin B1 protein had a significantly poorer prognosis than did the other patients (P<0.05). Multivariate analysis demonstrated that cyclin B1 status was an important factor affecting survival (P<0.05). These findings demonstrated that overexpression of cyclin B1 protein is associated with tumor behavior and prognosis for patients with human esophageal SCC.