Angiotensin-converting enzyme gene I/D polymorphism and carotid plaques in Japanese

To clarify the role of genetic factors in atherosclerotic plaque formation in the carotid artery and magnetic resonance imaging abnormalities in the brain, we investigated the association of these abnormalities with the angiotensin-converting enzyme (ACE) genotype. One hundred sixty-nine subjects (age, 59.2+/-0.8 years, mean+/-SE) admitted to our hospital for health checkups underwent brain magnetic resonance imaging to evaluate lacunar infarction. B-mode ultrasound examinations of the carotid arteries were performed to detect atherosclerotic plaque. The I/D polymorphism of the ACE gene was determined by the polymerase chain reaction method. Multivariate regression analysis was performed to assess the effects of the following variables on the presence of plaque, mean plaque thickness, and number of plaques: fibrinogen, sex, age, body mass index, mean blood pressure, glycosylated hemoglobin, LDL cholesterol, HDL cholesterol, hematocrit, and the D allele of the ACE gene. The frequency of carotid atherosclerotic plaque was significantly (P=.034) higher in subjects with the D allele than in those without this allele. However, the frequency of lacunar stroke was similar in these groups. A multivariate regression analysis showed that the presence of plaque was independently associated with the D allele (odds ratio=3.27, P=.016). However, mean plaque thickness and the number of plaques were not associated with the D allele. The D allele of the ACE gene may be involved in the presence of carotid plaque but not in the extent of this plaque or asymptomatic lacunar stroke in Japanese subjects.

Doxazosin suppresses the morning increase in blood pressure and sympathetic nervous activity in patients with essential hypertension

To investigate the effects of doxazosin on blood pressure and sympathetic nervous activity, we analyzed the circadian variation of blood pressure and the power spectrum of R-R intervals using an ambulatory multibiomedical monitoring system (TM2425) in 10 untreated outpatients with essential hypertension. After a 2-wk placebo period (P-period), we administered 1 to 4 mg of doxazosin mesilate to the patients for 2 to 6 wk (T-period). We measured systolic and diastolic blood pressure (SBP, DBP), heart rate, R-R intervals, posture, and activity with the use of TM2425. Power spectral analysis of R-R intervals was used to calculate the ratio of low to high frequency components (LF/HF). The values were compared between the P-period and T-period. Although daytime blood pressure significantly decreased during the T-period (SBP, 148.1 +/- 5.9 vs. 130.3 +/- 4.4 mmHg; DBP, 92.3 +/- 3.2 vs. 83.6 +/- 2.6 mmHg, p < 0.01), nighttime DBP did not. The LF/HF of R-R intervals in the daytime (5.8 +/- 2.0 vs. 4.9 +/- 1.2, p < 0.01) and the morning rise in blood pressure also decreased significantly (SBP, 17.5 +/- 9.4 vs. 12.1 +/- 6.5 mmHg; DBP, 12.5 +/- 6.5 vs. 8.3 +/- 5.3 mmHg, p < 0.05). We conclude that doxazosin may suppress the morning rise in blood pressure in association with a decrease in sympathetic nervous activity.

Changes in nitric oxide synthase activity during exposure to hydrogen peroxide in cultured endothelial cells

This study clarified the changes in maximum nitric oxide synthase (NOS) activity in cultured bovine aortic endothelial cells during exposure to hydrogen peroxide (H2O2). NOS activity was determined by measuring the conversion of [3H]arginine to [3H]citrulline. Ionomycin, a Ca2+ ionophore, was used to stimulate NOS activity. Addition of ionomycin (10(-5) M) increased the level of L-citrulline formation, and the ionomycin-induced increase in L-citrulline formation was stimulated by H2O2 pretreatment (15-90 min). Longer exposure to H2O2 (> or = 180 min) markedly inhibited the ionomycin-induced L-citrulline formation. The stimulation of ionomycin-induced L-citrulline formation by H2O2 was completely inhibited by N(G)-nitro-L-arginine (L-NNA) or N(G)-methyl-L-arginine (L-NMA), both blockers of NOS. Cell death which was determined by lactate dehydrogenase (LDH) release was induced from 120 min after the addition of H2O2. These findings suggest that the maximum L-citrulline formation from L-arginine, coupled with NOS activity, was increased by H2O2 treatment before cell death. The stimulation of NOS activity may be implicated in H2O2-induced endothelial cell death.

[Hemodynamic effects of right ventricular outflow pacing]

The effects of right ventricular outflow pacing were studied in 13 patients (mean [+/-SD] 69.8 +/- 8.2 years old). All patients received DDD pacemakers except two patients with implanted VVI pacemakers who had chronic atrial fibrillation. Cardiac output and pulmonary capillary wedge pressure were measured by Swan-Ganz catheter. Pacing rate was fixed at 70-80/min and atrioventricular delay was fixed at 165 msec. When the pacing site was changed from the right ventricular apex to the right ventricular outflow during right ventricular pacing in 11 patients, cardiac output increased from 3.3 +/- 0.6 to 3.4 +/- 0.5 l/min (p < 0.001), and wedge pressure decreased from 9.3 +/- 1.9 to 8.8 +/- 2.0 mmHg (p < 0.05). When the pacing site was changed from the right ventricular apex to the right ventricular outflow during atrioventricular pacing in eight patients, cardiac output increased from 3.9 +/- 0.4 to 4.0 +/- 0.4 l/min (p < 0.05), and wedge pressure decreased from 7.1 +/- 2.3 to 6.6 +/- 2.1 mmHg (p < 0.05). When the pacing site was changed from the right ventricular apex to the right ventricular outflow in seven patients with ejection fraction (EF) greater than 55%, cardiac output increased from 3.6 +/- 0.5 to 3.7 +/- 0.4 l/min (p < 0.05), and in four patients with EF less than 55%, it increased from 2.9 +/- 0.4 to 3.0 +/- 0.4 l/min (p < 0.01). Cardiac function was improved by right ventricular outflow pacing compared to right ventricular apex pacing regardless of the pacing mode or cardiac function.

Glutathione metabolism in mice is enhanced more with hapten-induced allergic contact dermatitis than with irritant contact dermatitis

Cutaneous inflammation induced by electrophilic compounds involves irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD). Reduced glutathione (GSH) and related thiols have been postulated to play important roles in detoxification of electrophilic xenobiotics, protection of tissues against reactive oxygen species, and modulation of immunologic functions in normal and diseased subjects. The dynamic aspects of GSH metabolism, however, and its significance in patients with ICD and ACD remain to be clarified. The current study was carried out to elucidate the pathogenesis and possible involvement of GSH in both types of inflammation. Normal mice and mice sensitized with dinitrochlorobenzene (DNCB) were challenged by cutaneous administration of DNCB, and changes in GSH metabolism in skin and liver were determined. Kinetic analysis revealed that 24 h after challenge with DNCB, levels of hepatic glutathione and its secretion increased more markedly in the sensitized mice than in the unsensitized animals. Administration of buthionine-L-sulfoximine (BSO), a specific inhibitor of GSH synthesis, inhibited the increase in glutathione levels in the liver and the skin of both groups. Histologic examination revealed that cutaneous inflammation was enhanced by BSO more significantly in mice with ACD than with ICD. These results suggest that GSH might play an important role in the suppression of the immune reaction in mice with ACD.

Angiotensin-converting enzyme gene polymorphism adds risk for the severity of coronary atherosclerosis in smokers

To investigate the relation between the angiotensin-converting enzyme (ACE) gene polymorphism and acute coronary syndromes with respect to environmental factors, we analyzed the association of genotype with the coronary angiographic findings of patients with acute myocardial infarction or unstable angina pectoris, and we examined the linkage of each genotype with established risk factors for coronary artery disease. We determined the ACE genotype in 152 Japanese patients with acute coronary syndromes and 399 healthy individuals. The genotype distributions were not different between the two groups (P=.74, chi2 test). In the former group, coronary angiograms were evaluated by criteria based on the number of diseased vessels, the number of stenotic lesions (> or = 50%), and the relative abnormal arterial portion (extent index). Although the number of stenotic lesions was higher in patients with the DD genotype than in those with the ID or II genotype (P=.006), there were no differences in the number of diseased vessels or the extent index. When only smokers were analyzed, the number of diseased vessels (P=.032), number of stenotic lesions (P=.003), and extent index (P=.019) were all higher in patients with the DD genotype than in those with the ID or II genotype. In contrast, these differences in the respective parameters did not exist in nonsmokers. The results indicate smoking-associated effects of the ACE genotype on the severity of coronary atherosclerosis.

Coil occlusion of patent ductus arteriosus with detachable coils

Twenty-five patients (mean age 7.0 +/- 4.8 years) underwent transcatheter coil occlusion of patent ductus arteriosus with detachable coils. The minimum diameter of the ductus arteriosus ranged from 1.0 to 4.2 mm (mean 2.6 +/- 0.9 mm). A single-coil technique was used in 17 patients, double- (six patients) or triple-coil (two patients) techniques were used in eight patients. The coil was not detached until sufficient shape and position of implanted coils were confirmed. All patients had successful implantation of coils regardless of the morphologic characteristics of the ductus. Immediately after the occlusion, heart murmurs were abolished in all patients. Color-flow mapping showed complete closure in 16 (64%) patients immediately after and 20 (80%) patients 1 month after the procedure. No significant complications occurred. The advantages of this detachable coil system may reduce coil migration and allow safer and more reliable execution of this procedure.

DX-8951f, a water-soluble camptothecin analog, exhibits potent antitumor activity against a human lung cancer cell line and its SN-38-resistant variant

We previously reported that DX-8951f, a novel water-soluble camptothecin analog, significantly inhibits the growth of various human and murine tumors in vitro and in vivo. The antitumor effects and topoisomerase I inhibitory activity of DX-8951f are stronger than those of other current camptothecin analogs. In this study, we established an SN-38-resistant cell line, PC-6/SN2-5, from the human oat cell carcinoma PC-6 cell line by a stepwise selection system, investigated the mechanism of resistance of this cell line and then compared the antitumor activity of camptothecin analogs against the cell line. PC-6/SN2-5 cells were resistant to SN-38 (32-fold) and SK&F 104864 (topotecan; 14-fold), but barely resistant to CPT-11 (3-fold) and DX-8951f (2-fold). Topoisomerase I protein levels and topoisomerase I activities of parental cells were similar to those of resistant cells. Determination of the cellular drug concentration by either flow cytometric analysis or the high-performance liquid chromatography method confirmed that the cellular accumulation of SN-38 and topotecan was significantly reduced in PC-6/SN2-5 cells, whereas that of DX-8951f was only slightly reduced. Furthermore, DX-8951f stabilized the cleavable complex formations in intact PC-6/SN2-5 cells as well as in parental cells, but SN-38 and topotecan did not in the resistant cells. Our data suggest that PC-6/SN2-5 cells may have acquired resistance to camptothecin analogs by a decrease in intracellular drug accumulation and that DX-8951f may have the potency to overcome such a type of resistance mechanism induced by camptothecin compounds.

Characterization of bunazosin-sensitive alpha1-adrenoceptors in human renal medulla

We studied the characteristics of bunazosin-sensitive alpha1-adrenoceptors in human renal medullae by using renal-clearance studies and radioligand-binding assay. In 12 patients with hypertension, renal-clearance studies demonstrated that bunazosin significantly increased renal blood flow from 683 +/- 82 (SD) to 829 +/- 103 ml/min (p < 0.05) and decreased renal vascular resistance from 0.18 +/- 0.02 to 0.14 +/- 0.02 mm Hg/(ml/min) (p < 0.05), but that prazosin had little effect on renal function. In a radioligand-binding assay, specific, saturable, and stereoselective [3H]bunazosin binding, with a single class of binding sites (Kd = 2.7 +/- 1.4 nM; Bmax = 44 +/- 16 fmol/mg protein; n = 11) was detected in membrane preparations of human renal medullae. The rank order of potency of antagonists that inhibited [3H]bunazosin-binding was bunazosin (Ki in nM = 49) > prazosin (57) > yohimbine (3,900) > propranolol (29,000), and that of agonists, l-norepinephrine (7,400) > l-epinephrine (19,000) > d-norepinephrine (71,000). The competition curves fit a one-site model. These findings suggest that bunazosin-sensitive alpha1-adrenoceptors exist in human renal medullae and participate in the regulation of renal hemodynamics.

A novel proximal element mediates the regulation of mouse Ren-1C promoter by retinoblastoma protein in cultured cells

The protein product of the retinoblastoma susceptibility gene, RB, is a nuclear phosphoprotein that modulates transcription of genes involved in growth control via interactions with transcription factors. Renin is a rate-limiting enzyme of the renin-angiotensin system that regulates blood pressure and water-electrolyte balance. Renin gene expression is regulated in a tissue-specific and developmentally linked manner. Similarly, the expression of RB is controlled in a differentiation-linked manner. Thus, to investigate whether RB is involved in the regulation of renin gene expression, we examined the effects of RB on transcriptional activity of the mouse renin (Ren-1C) promoter. The Ren-1C promoter contains two transcriptionally important elements; the RU-1 (-224 to -138) and RP-2 (-75 to -47) elements. RB activated the Ren-1C promoter in human embryonic kidney cells. The promoter element responsible for RB-mediated transcriptional regulation was the RP-2 element. The results of DNA-protein binding experiments showed that RB increased nuclear binding activity to the RP-2 element, and site-directed mutation which disrupted binding of nuclear factors to the RP-2 element markedly reduced RB-mediated activation of Ren-1C promoter in human embryonic kidney cells. These results indicate that the RP-2 element plays an important role in RB-mediated transcriptional regulation of Ren-1C promoter activity in human embryonic kidney cells, thereby suggesting an interesting mechanism by which RB may modulate the renin-angiotensin system.

Carotid artery approach to balloon aortic valvuloplasty in infants with critical aortic valve stenosis

We compare the clinical efficacy of two approaches for balloon aortic valvuloplasty (BAV) in infants with critical aortic valve stenosis. The approaches were through the carotid artery and the femoral artery. Eight catheterizations for BAV were performed in seven consecutive patients with critical aortic stenosis: four BAVs were approached through the femoral artery and four through the right common carotid artery. We inserted a 5F sheath into the right common carotid artery by a cutdown procedure; after BAV the sheath was removed and the carotid arteriotomy sutured with 7-0 monofilament. Two cases in which the femoral artery approach was used resulted in failure to perform BAV; two cases had complications. All four cases with the carotid artery approach were successful, with no complications; aortography performed 3 months after one balloon valvuloplasty revealed a smooth, unobstructed right carotid artery. Use of the carotid artery approach may reduce serious complications with BAV and offers quicker, easier maneuvering in infants and neonates with critical aortic valve stenosis.

Erythromycin derivative improves gastric emptying and insulin requirement in diabetic patients with gastroparesis

OBJECTIVE

To evaluate the effect of the erythromycin derivative EM523L on gastric emptying and postprandial insulin requirement in insulin-dependent diabetic patients with severe gastroparesis.

RESEARCH DESIGN AND METHODS

In six IDDM patients with severe gastroparesis (two men and four women, mean age 44.5 years [range 36-53]), the insulin infusion pattern during feedback control with an artificial endocrine pancreas device (Biostator) after intake of a test meal, the retention rate of residual isotope ([99m]Tc-labelled Sn-colloid) in the stomach, and the time-concentration curve of plasma acetaminophen as the marker for liquid emptying were studied with EM523L or a control placebo

RESULTS

Time courses of insulin infusion rates peaked within 120 min after intake of the test meal in the EM523L phase, whereas no apparent peak rates were observed in the control phase. The total amount of insulin required in the first 90 min postprandial was significantly greater in the EM523L phase than in the control phase. EM523L significantly decreased the residual isotope ratio in the stomach at > or =50 min postprandial and increased the plasma acetaminophen concentrations at 30-120 min postprandial, compared with respective values in the control phase.

CONCLUSIONS

Preliminary results obtained from a small number of patients suggest that EM523L or erythromycin analogs, which have agonistic activity to motilin receptors as well as no antibacterial effect, may be useful to accelerate gastric emptying and improve insulin requirement patterns, thereby establishing more stable glycemic control.

Intravascular ultrasound assessment of regional aortic wall stiffness, distensibility, and compliance in patients with coarctation of the aorta

BACKGROUND

Impaired aortic pulsatility has been demonstrated by angiography in children and in studies of experimental animals with coarctation of the aorta.

OBJECTIVES

The purpose of this study was to assess regional aortic stiffness, distensibility, and compliance before and after balloon dilation in patients with coarctation of the aorta.

METHODS AND RESULTS

Intravascular ultrasound examination was performed in 13 pediatric patients with the diagnosis of coarctation of the aorta to yield aortic diameter. Area transverse sections at both systolic and diastolic period were measured at three aortic levels: the proximal, distal, and coarctation segments. Balloon dilation was also performed in eight of 13 patients. By using pressures measured in the same areas, an aortic stiffness index (beta) was calculated as In(Ps/Pd)/(Ds-Dd), where In is natural logarithm, Ps is systolic pressure, Pd is diastolic pressure, Ds is systolic diameter, and Dd is diastolic diameter. Aortic distensibility and an estimation of aortic compliance were also calculated. The beta stiffness index of the coarctation and the proximal segments of the aorta were significantly greater than that of the distal segment of the aorta (p < 0.01). The aortic wall stiffness beta index did not acutely change after successful balloon dilation, but the distensibility and compliance of distal aorta were nonetheless significantly decreased after balloon dilation (p < 0.01, p < 0.05) as a function of changes of pulsatility of flow.

CONCLUSIONS

Abnormal proximal aortic stiffness may be a strong contributing factor that promotes the genesis of hypertension in patients with coarctation even after successful repair or balloon angioplasty.

Simple technique for pancreatogastrostomy and the histological findings of pancreatogastric anastomosis

The leakage of pancreatic juice is the most serious complication after pancreatoduodenectomy. In an attempt to lessen the incidence of this complication, we have developed a simple technique for the anastomosis of pancreatogastrostomy. Since March 14, 1995, we have already performed surgical procedures on 8 cases of pancreatogastrostomy using this technique and as yet have never experienced fatal complications. We report the autopsy findings of pancreatogastric anastomosis histologically. The specimen taken from the anastomosis reveals good mucosal continuity. This result suggests the importance of reliable sutures between the pancreatic parenchyma and the full thickness of the gastric wall for the anastomosis of pancreatogastrostomy.

Longitudinal MR imaging and proton MR spectroscopy in herpes simplex encephalitis

Longitudinal MR imaging and proton MR spectroscopy were performed in an 11 year-old female case of herpes simplex encephalitis with a complete recovery. On MR imaging, the white matter lesions, which could be seen in the subacute stage, but not in the acute or chronic stage, might represent edema due to postinfectious neuroallergic phenomena. Proton MR spectroscopy revealed marked reduction of the NAA/Cr ratio in the chronic stage, which increased gradually to within normal range in a year.

Stretch-induced MAP kinase activation in cardiomyocytes of angiotensinogen-deficient mice

The renin-angiotensin system plays an important role in the hypertrophic responses in cardiac myocytes through the activation of signal transduction pathways and expression of oncogenes. In the present study, we examined mechanical stretch-induced activation of mitogen-activated protein kinases (MAP kinases) using cultured cardiac myocytes derived from neonatal angiotensinogen gene deficient mice (Agt-/-) and neonatal wild type mice (Agt+/+). Within 2 minutes of being added to cardiac myocytes, angiotensin II activated MAP kinases and the response was completely blocked by pretreatment of the cardiac myocytes with CV-11974, a selective antagonist of angiotensin II type 1 receptors. Interestingly, mechanical stretch resulted in significantly greater activation of MAP kinases in Agt-/- cardiac myocytes than in Agt+/+ cardiac myocytes. CV-11974 failed to suppress the stretch-induced activation of MAP kinases in Agt-/- cardiac myocytes while it inhibited the activation in Agt+/+ cardiac myocytes. BQ123, an endothelin type A receptor antagonist, had no effect on stretch-induced activation of MAP kinases in cardiac myocytes from either mouse strain. These results suggest that cardiac RAS is important for stretch-induced MAP kinase activation in Agt+/+ cardiac myocytes; however, angiotensin II is not indispensable for mechanical stretch-induced activation of MAP kinases in Agt-/- cardiac myocytes.

[Assessment of auscultatory blood pressure measurements versus intra-arterial pressure in patients with atrial fibrillation]

The accuracy of auscultatory blood pressure (BP) determination was assessed in patients with chronic atrial fibrillation by performing simultaneous auscultatory BP determination on the upper arm and a direct BP determination on the contralateral arm. The subjects were three hospitalized patients, aged from 52 to 75 years. A Teflon catheter was introduced into the radial artery which was connected to a pressure transducer, and a cuff was twisted around the contralateral upper arm in the supine position. Simultaneous recording of directly determined BP and cuff pressure enabled the comparison of direct BP with auscultatory BP. The appearance of the Korotkoff I sound (systolic BP) and V sound (diastolic BP) was marked on the cuff pressure curve. This maneuver was repeated five times in each patient. The method of Bland and Altman was employed to assess the agreement between auscultatory and direct determinations. The auscultatory method estimated BP with differences of -14.3 to +27.3 mmHg in systolic BP and -12.1 to +11.9 mmHg (+/-2SD) in diastolic BP compared with the direct method. The difference in systolic BP between the auscultatory and the direct methods was greater than that in diastolic BP. Thus, there are unacceptable differences in systolic BP between auscultatory and direct methods that can be attributed to BP fluctuations. The auscultatory method in diastolic BP is more accurate than that in systolic BP and may be more useful in the clinical setting.

Modulation of tissue angiotensinogen gene expression in genetically obese hypertensive rats

Wistar fatty rats (WFR) show obesity and obesity-related features, including hypertension. In this study, we examined the expression of angiotensinogen mRNA in a variety of tissues at different times in WFR and control Wistar lean rats (WLR). WFR were obese and hypertensive at 16 and 24 wk. Plasma renin activity and plasma angiotensinogen concentration showed age-dependent increases in WFR but decreases in WLR. Northern blot analysis showed no significant differences in the levels of hepatic and renal angiotensinogen mRNA between WFR and WLR, and the levels of fat and adrenal angiotensinogen mRNA were lower in WFR than in WLR. On the other hand, the levels of cardiac angiotensinogen mRNA at 16 and 24 wk and those of aortic angiotensinogen mRNA at 16 wk were significantly higher in WFR than in WLR. These results show that the expression of tissue angiotensinogen mRNA is regulated differently in WFR and WLR and indicate that the development of hypertension in WFR is accompanied at least temporally with increases in plasma angiotensinogen concentration as well as in cardiac and aortic angiotensinogen mRNA. Moreover, these results suggest the existence of obesity hypertension-linked and tissue-specific regulation of angiotensinogen gene expression.

Changes in liver function parameters after occlusion of gastrorenal shunts with balloon-occluded retrograde transvenous obliteration

OBJECTIVE AND METHODS

To evaluate the effects of portal blood flow on liver function, this pilot study investigated the correlation between changes in portal blood flow as measured by image-directed Doppler ultrasonography and liver function tests in nine patients with cirrhosis who were treated with balloon-occluded retrograde transvenous obliteration. All patients had large gastric varices and prominent gastrorenal shunts.

RESULTS

Treatment caused a significant increase (p < 0.01) in portal blood flow; we documented reversion from hepatofugal to hepatopetal portal flow in one patient and increases in hepatopetal flow from 5.4 +/- 1.1 to 7.85 +/- 1.4 cm/s (mean +/- SD) in eight patients. All patients showed decreases in gastric variceal size. However, portal pressure rose significantly in all patients after treatment from 25.4 +/- 7.6 to 30.7 +/- 5.8 mmH2O (n = 7, mean +/- SD), and two of nine patients had worsening of esophageal varices. All nine patients showed improvement in the 15-min retention rate of indocyanine green from 31.8 +/- 16.1 to 21.8 +/- 12.4% (mean +/- SD, p < 0.01), whereas seven patients showed increased serum albumin levels after treatment.

CONCLUSIONS

These results suggest balloon-occluded retrograde transvenous obliteration increases hepatic portal blood flow, which may be accompanied by improvements in liver function.

Plasma angiotensinogen concentrations in obese patients

A close relationship between obesity and hypertension has been recognized, and plasma angiotensinogen concentrations (p-AGT) have been reported to correlate with blood pressure (BP). However, little is known about AGT in obese patients with hypertension. To define the role of AGT in obese hypertension, we measured p-AGT in obese patients. The subjects were 42 obese patients diagnosed on the basis of a body mass index (BMI) of more than 25 kg/m2, and 21 sex- and age-matched nonobese patients, whose BMI was less than 25 kg/m2. The hypertensive patients had not previously received antihypertensive drugs. P-AGT (P < .05) and mean BP (P < .0001) was increased in the obese patients as compared with the nonobese patients. Positive correlations were observed between BMI and p-AGT, mean BP and p-AGT, and BMI and mean BP (all P < .05). However, after adjustment for blood pressure, p-AGT was not different between groups, and after adjustment a positive correlation remained only between BMI and mean BP. These results suggested the possible involvement of increased p-AGT in hypertension in obese patients, although this may be a secondary change to hypertension or obesity.

Clustering and enhanced activity of an inwardly rectifying potassium channel, Kir4.1, by an anchoring protein, PSD-95/SAP90

An inwardly rectifying potassium channel predominantly expressed in glial cells, Kir4.1/KAB-2, has a sequence of Ser-Asn-Val in its carboxyl-terminal end, suggesting a possible interaction with an anchoring protein of the PSD-95 family. We examined the effects of PSD-95 on the distribution and function of Kir4.1 in a mammalian cell line. When Kir4.1 was expressed alone, the channel immunoreactivity was distributed homogeneously. In contrast, when co-expressed with PSD-95, prominent clustering of Kir4.1 in the cell membrane occurred. Kir4.1 was co-immunoprecipitated with PSD-95 in the co-expressed cells. Glutathione S-transferase-fusion protein of COOH terminus of Kir4.1 bound to PSD-95. These interactions disappeared when the Ser-Asn-Val motif was deleted. The magnitude of whole-cell Kir4.1 current was increased by 2-fold in cells co-expressing Kir4.1 and PSD-95 compared with cells expressing Kir4. 1 alone. SAP97, another member of the PSD-95 family, showed similar effects on Kir4.1. Furthermore, we found that Kir4.1 as well as SAP97 distributed not diffusely but clustered in retinal glial cells. Therefore, PSD-95 family proteins may be a physiological regulator of the distribution and function of Kir4.1 in glial cells.

Analysis of molecular heterogeneity of Dahl/Iwai salt-sensitive rats and salt-resistant rats

Molecular evidence, using DNA fingerprint analyses, of extensive genetic heterogeneity between spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) and even within some of the WKY colonies has been reported. Thus we investigated the genetic relations between Dahl S and R rats newly inbred by Dr. Iwai. Genomic DNA was isolated from the liver of four Dahl S and four Dahl R rats, digested with the restriction enzyme HinfI or AluI, and separated in 1.2% agarose gel by electrophoresis. Then, DNA fingerprinting was performed by Southern blot analysis using the human myoglobin 33.6 minisatellite probe. Bands were detected in an alkaline phosphatase reaction system. Within the same strains, there was no heterogeneity of these fingerprinting patterns. The S and R rats shared 82% of the bands in the HinfI-digested DNA and 93% of those in the AluI-digested DNA. These shared values were much greater than the reported value (54%) between SHR and WKY from Charles River Laboratories. These newly inbred Dahl S and R rats may be appropriate, although still limited, experimental animals for investigating the pathophysiology of salt-sensitive hypertension.

Purification and characterization of pyruvate:ferredoxin oxidoreductase from Hydrogenobacter thermophilus TK-6

Pyruvate:ferredoxin oxidoreductase was purified to electrophoretic homogeneity from an aerobic, thermophilic, obligately chemolithoautotrophic, hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6, by precipitation with ammonium sulfate and fractionation by DEAE-Sepharose CL-6B, polyacrylate-quaternary amine, hydroxyapatite, and Superdex-200 chromatography. The native enzyme had a molecular mass of 135 kDa and was composed of four different subunits with apparent molecular masses of 46, 31.5, 29, and 24.5 kDa, respectively, indicating that the enzyme has an alphabetagammadelta-structure. The activity was detected with pyruvate, coenzyme A, and one of the following electron acceptors in substrate amounts: ferredoxin isolated from H. thermophilus, FAD, FMN, triphenyltetrazolium chloride, or methyl viologen. NAD, NADP, and ferredoxins from Chlorella spp. and Clostridium pasteurianum were ineffective as the electron acceptor. The temperature optimum for pyruvate oxidation was approximately 80 degrees C. The pH optimum was 7.6-7.8. The apparent Km values for pyruvate and coenzyme A at 70 degrees C were 3.45 mM and 54 microM, respectively. The enzyme was extremely thermostable under anoxic conditions; the time for a 50% loss of activity (t50%) at 70 degrees C was approximately 8 h.

Distribution of alpha 1B-adrenergic receptor mRNA expression along rat nephron segments

Although several alpha-adrenergic receptor genes are expressed in the rat kidney, little information is available on their expression in the renal nephron segments. We investigated the distribution of alpha 1B-adrenergic receptor mRNA in rat nephron segments using reverse transcription and polymerase chain reaction (RT-PCR). The nephron segments of six- to eight-week-old male Sprague-Dawley rats were microdissected. Total RNA was prepared by the acid-guanidinium-phenol-chloroform method and used in the following RT-PCR assay. The PCR products were size-fractionated with electrophoresis, visualized with ethidium bromide staining and confirmed by Southern blot analysis. Because the PCR primers spanned an intron, the amplification product of the predicted size was considered to be from alpha 1B-adrenergic receptor cDNA and not from genomic DNA. The PCR products were detected in glomerulus (Glm), proximal convoluted and straight tubules (PCT, PST) and cortical and medullary thick ascending limbs of Henle (CTAL, MTAL). No signals were detected in cortical or medullary collecting ducts (CCD, MCD). Large signals were detected in the PCT, and PST, while small signals were found in the Glm, CTAL and MTAL. The alpha 1B-adrenergic receptor mRNA was detected for the first time in rat Glm, PCT, PST and TAL using RT-PCR. alpha 1BAR mRNA seems to be expressed in the specific sites along the nephron and may play significant roles in renal functions, although the specific physiological effects of the renal alpha 1B-adrenergic receptor are unknown.