Absence of endothelin receptors and receptor mRNA in mammalian fibroblasts transformed with SV40 or ras oncogene

Endothelin-1 (ET-1), a peptide isolated from the culture medium of endothelial cells, mediates a variety of physiological and pathological responses including mitogenesis. We have compared the expression of ET receptors in untransformed versus ras-transformed NIH-3T3 murine fibroblasts and in untransformed versus SV40-transformed W138 (VA13) human fibroblasts by ligand binding and Northern analysis. NIH-3T3 and W138 cells displayed high affinity (200 and 220 pM) and high density (23,000 sites/cell and 14,000 sites/cell for NIH-3T3 and W138 cells, respectively) ET receptors. Competition binding experiments using subtype-selective ligands identified these receptors as the ETA subtype. Addition of ET-1 to the cells produced a concentration-dependent increase in intracellular calcium release. Both ras-transformed NIH-3T3 cells and SV40-transformed W138 cells (VA13) completely lacked [125I]ET-1 binding and failed to release calcium when exposed to ET-1. Northern analysis of the polyadenylated RNA (polyA RNA) isolated from untransformed and transformed cells revealed that the steady-state level of ETA receptor RNA was 90-95% less in transformed cells compared to untransformed cells. Thus, the loss of ET receptors as well as the receptor-mediated responses in transformed cells can be explained by down-regulation of ET receptor mRNA.

Assembly of hepatitis delta virus-like empty particles in yeast

Large delta antigen (L-HDAg) of hepatitis delta virus (HDV) and small-form hepatitis B surface antigen (HBsAg) of helper hepatitis B virus have previously been shown to be the minimum components for the assembly of HDV-like particles in mammalian cells. Extending from this finding, we coexpressed L-HDAg and small HBsAg in Saccharomyces cerevisiae to study their assembly in yeast cells. The assembly of virus particles from L-HDAg and HBsAg in yeast was demonstrated by their coexistence in the same isopycnic fractions and by the coimmunoprecipitation of L-HDAg with HBsAg using an antibody against HBsAg (anti-HBs). Furthermore, after purification by affinity chromatography with anti-HBs, HDV-like particles with size and morphology similar to those derived from mammalian cells could be visualized by electron microscopy. Mice immunized with yeast-derived HDV-like particles simultaneously acquired antibodies against HBsAg and HDAg, indicating that both viral proteins are antigenic. The results indicated that S. cerevisiae could serve as a host for the assembly of HDV-like empty particles. This system may be useful in investigating cellular processes involved in HDV assembly and in producing ample amount of HDV-like particles for structural and immunological studies.

Susceptibility of endothelial cells to bovine herpesvirus type 4 (BHV-4)

The sensitivity of two different types of cells to bovine herpesvirus type 4 (BHV-4) was compared by median tissue culture infectious dose (TCID50) assays. The bovine arterial endothelial (BAE) cell culture derived from bovine carotid arteries was 100-1000 times more sensitive to two strains of BHV-4, Movar 33/63 and DN 599, than Madin Darby bovine kidney (MDBK) cell line commonly used for the propagation of these viruses. BAE cell cultures infected with BHV-4 displayed cytopathic effects (CPE) earlier and more prominently than the MDBK cells infected with the same viruses. BAE cells were also more sensitive than MDBK cells in conventional plaque assays in that the former developed well characterized and easily recognized plaques after infection with the viruses. BAE cells, which are proved to be exceptionally susceptible to BHV-4, can be used in the detection and quantitation of BHV-4.

Molecular characterization of a novel human endothelin receptor splice variant

Endothelin receptors are widely distributed throughout a number of tissues. A novel ETB receptor splice variant (ETB-SVR) was identified from a human placental cDNA library. Sequence analysis indicated that the ETB-SVR is 436 amino acids long and shares 91% identity to the human ETB-R. Northern blot analysis indicated an mRNA species of 2.7 kilobases, which is expressed in the lung, placenta, kidney, and skeletal muscle. Ligand binding studies of the cloned ETB-SVR and ETB-R receptors expressed in COS cells showed that ET peptides exhibited similar potency in displacing 125I-ET-1 binding. Functional studies showed that ET-1, ET-3, and sarafotoxin 6c displayed similar potencies for inositol phosphates accumulation in ETB-R-transfected COS cells, whereas no increase in inositol phosphate accumulation was observed in ETB-SVR-transfected cells. In addition, exposure of ETB-R-transfected cells to ET-1 caused an increase in the intracellular acidification rate whereas ETB-SVR-transfected cells did not respond to ET-1. These data suggest that the ETB-SVR and ETB-R are functionally distinct and the difference in the amino acid sequences between the two receptors may determine functional coupling. Availability of cDNA clones for endothelin receptors can facilitate our understanding of the role of ET in the pathophysiology of various diseases.

Incidence of post-transfusion hepatitis in Taiwan before and after introduction of anti-HCV testing

The effectiveness of second-generation anti-hepatitis C virus antibody (anti-HCV) screening of blood donations for the prevention of non-A, non-B post-transfusion hepatitis (NANB PTH) was assessed. A prospective study of 192 transfusion recipients was performed to compare the incidence of NANB PTH after the introduction of the second-generation anti-HCV test with the incidence before its introduction. We used a polymerase chain reaction to detect HCV-RNA and HBV-DNA in the sera of patients with NANB PTH. The incidence of acute post-transfusion hepatitis C was 11% (8 of 71) before the screening for anti-HCV as compared with 2.5% (3 of 121) after the screening (p < 0.05). Viremia was detected within the first five weeks of infection in 10 patients with acute post-transfusion hepatitis C. However, there was no significant difference in the incidence of non-A, non-B, non-C (NANBNC) PTH before screening (3 of 71, 4.2%) compared with after screening (3 of 121, 2.5%). Usually, NANBNC PTH was not clinically important. Anti-HCV screening of blood donors significantly reduces the incidence of post-transfusion hepatitis C, but not the incidence of NANBNC PTH.

Nonpeptide endothelin receptor antagonists. VII: Binding characteristics of [3H]SB 209670, a novel nonpeptide antagonist of endothelin receptors

The data presented in this manuscript describes the binding characteristics of [3H]SB 209670, a potent nonpeptide tritium-labeled endothelin (ET) receptor antagonist. The binding of this antagonist to cloned human ETA and ETB receptors was specific, saturable and of high affinity. The apparent dissociation constants were 0.20 and 1.0 nM for ETA and ETB receptors, respectively. The maximum binding was 4.7 and 22.5 pmol/mg protein for ETA and ETB receptors, respectively. Unlike [125]ET-1, the binding of [3H]SB 209670 was reversible. The half-times (T1/2) for dissociation of this ligand from ETA and ETB receptors were approximately 60 and 10 min, respectively. Competition binding studies using [3H]SB 209670 and unlabeled agonists ET-1, ET-3 and S6c indicated that these agonists displayed similar affinities for human ETB receptors, whereas with ETA receptors, ET-1 was approximately 50-fold and 1500-fold more potent than ET-3 and S6c, respectively. Of the peptide antagonists tested, BQ123 (ETA-selective peptide antagonist), displayed Ki values of 40 and > 2300 nM for ETA and ETB, whereas RES701 (ETB-selective antagonist) displayed Ki values of > 1600 and 81 nM for ETA and ETB receptors, respectively. The nonselective peptide antagonist, PD 142893, was approximately 2-fold more potent for ETA compared with ETB receptors. Similar observations were made with nonselective nonpeptide antagonists, Bosentan, (+/-) SB 209670, SB 209670, and (-) SB 209670. All these compounds were 2 to 10 times more potent for ETA than ETB receptors.

Hepatitis C virus RNA in peripheral blood mononuclear cells: comparing acute and chronic hepatitis C virus infection

Hepatitis C virus (HCV) can infect peripheral blood mononuclear cells (PBMC) of patients with chronic HCV infection. No data are available on PBMC testing for HCV RNA in acute hepatitis C. This study investigated the presence of HCV RNA in PBMC of patients with acute posttransfusion hepatitis C, compared with those with chronic HCV infection. Nested polymerase chain reaction (PCR) was applied to detect HCV RNA in 111 and 48 paired samples of serum and PBMC of 11 patients with acute posttransfusion hepatitis C and 48 patients with chronic HCV infection, respectively. In patients with acute posttransfusion hepatitis C, HCV RNA was detected in 17 of 29 (59%) and 67 of 82 (82%) serum samples collected during the incubation period and acute phase, respectively. Meanwhile, of the 48 patients with chronic HCV infection, 41 had serum HCV RNA (85%). HCV RNA was not detected in PBMC samples from incubation period or from acute-phase hepatitis, although it was detected in 12 of the 48 PBMC samples of chronically infected patients (25%) P < .005). Of the 12 PBMC specimens positive for positive-stranded HCV RNA, 6 were also positive for negative-stranded HCV RNA. Among patients with chronic HCV infection, HCV infection of PBMC was not related to age, sex, blood transfusion, serum alanine transaminase (ALT) levels, or serum virus titers. In conclusion, HCV infection of PBMC rarely exists in patients with acute hepatitis C. As HCV infection persists, the incidence of HCV infection of PBMC becomes higher.

Determination of thiocyanate anion by high-performance liquid chromatography with fluorimetric detection

A simple and sensitive high-performance liquid chromatographic (HPLC) method was established for the trace determination of thiocyanate anion as a fluorogenic derivative. The method is based on the chemical derivatization of thiocyanate anion with 3-bromomethyl-7-methoxy-1,4-benzoxazin-2-one. The resulting derivative was separated by a Nova-Pak C18 reversed-phase column. Optimization conditions for the derivatization of thiocyanate anion were investigated by HPLC with fluorimetric detection. The linear range for the quantitation of thiocyanate anion was 1-0.05 nmol in 0.1 mL of sample; the detection limit (with a signal-to-noise ratio of 5) of a 20-microL injected aliquot was approximately 3.3 +/- 1.2 fmol. Application of the method to the analysis of thiocyanate anion in saliva and plasma proved to be feasible.

Regulation of plasminogen activator inhibitor activity by plasmin in endothelial cells

The fibrinolytic activity in endothelial cells was regulated by balance of plasminogen activators and plasminogen activator inhibitors. Plasmin can specifically inhibit the biosynthesis of tissue-type plasminogen activator (t-PA), but not plasminogen activator inhibitor, type 1 (PAI-1) in endothelial cells. The PAI activity in the conditioned medium of endothelial cells was low and remained constant in 24 hours. However, the PAI activity in the conditioned medium of the plasmin-pretreated cells increased linearly in 24 hours. Pretreatment with protein kinase C inhibitors, H-7 or staurosporine, partially suppressed the PAI activity induced by plasmin. Pretreatment of endothelial cells with a G-protein inhibitor pertussis toxin resulted in an inhibition of the plasmin-induced PAI activity. The phospholipase A2 inhibitor mepacrine specifically eliminated the effect of plasmin stimulation on PAI activity. Cyclooxygenase and lipoxygenase inhibitors also partially inhibited the plasmin-stimulated PAI activity in endothelial cells. All these inhibitors did not affect the biosynthesis of the PAI-1 antigen in the presence or absence of plasmin. The results indicate that plasmin increased the PAI activity of endothelial cells via pathways in which protein kinase C, G protein, and phospholipase A2 may be involved.

Interaction of streptokinase and plasminogen. Studied with truncated streptokinase peptides

The interaction of streptokinase (SK) with human plasminogen (HPlg) was investigated using truncated SK peptides prepared by gene cloning techniques. SK(16-414) and SK(16-378) could activate HPlg as efficiently as the authentic SK. SK(60-414), which had been preincubated with SK(1-59), could also activate HPlg. SK(91-414), SK(127-414), and SK(158-414), at a concentration of one-tenth of HPlg, all failed to activate HPlg. However, the truncated SK peptides in complexes with equimolar HPlg could form amidolytically active virgin enzymes that slowly converted to human plasmin (HPlm) after a lag period of 15 min. SK(16-316) could not activate HPlg. No virgin enzyme was detected when SK(16-316) was incubated with equimolar HPlg, but the HPlg in the complex was modified to HPlm after reaction for 20 min. SK(220-414) and SK(16-251) had no ability to transform HPlg to virgin enzyme or to HPlm in equimolar complex with HPlg, although they could bind to HPlg. The functions of five regions in the SK molecule (a, Ile1-Lys59; b, Ser60-Asn90; c, Val158-Arg219; d, Tyr252-Ala316; e, Ser317-Ala378) in interaction with HPlg are deduced. Region a is important in stabilizing the conformation of the SK molecule, and region b is essential for HPlg activation. Region c is required for induction of the conformational changes of HPlg to virgin enzyme. Regions c and d are required for the conversion of HPlg to HPlm in the HPlg.SK equimolar complex. Coordination of regions c, d, and e of SK is essential for a virgin enzyme formation, and coordination of regions b, c, d and e is required for an effective SK-type HPlg activator.

Thrombin-mediated down-regulation of endothelin receptors in mesangial cells coincides with the down-regulation of neutral endopeptidase activity

Thrombin-mediated down-regulation of endothelin (ET) receptors was studied in rat glomerular mesangial cells. Overnight incubation of mesangial cells with thrombin (10 nM) resulted in a significant decrease (67%) in the number of ET receptors, with no change in affinity. Northern analysis of the mRNA from these cells showed a corresponding decrease in the ETA receptor message. Such a decrease in ET receptors could result from an increase in ET levels caused by an increase in synthesis and/or a decrease in degradation. It has been previously reported that thrombin stimulates ET production in endothelial and mesangial cells. Because ET is known to be degraded by neutral endopeptidase (NEP), which is present at high levels in the kidney, the potential effects of thrombin on NEP activity were evaluated. There was a decrease of NEP activity in mesangial cells at 16 and 24 hr after treatment with 10 nM thrombin. This effect was specific for thrombin, because NEP activity was not altered after treatment with thrombin in the presence of hirudin, an inhibitor of thrombin activity. The thrombin-mediated decrease in NEP activity correlated with a decrease in NEP protein and mRNA levels, as determined by Western and Northern analyses, respectively. To determine whether the thrombin-mediated decrease in ET receptors had a functional corollary, ET-1-stimulated intracellular calcium mobilization was measured. Overnight incubation with 10 nM thrombin resulted in a significant inhibition of ET-stimulated intracellular calcium mobilization. This effect was specific for ET, because thrombin pretreatment did not affect vasopressin-stimulated intracellular calcium mobilization in mesangial cells. These results indicate that the thrombin-mediated down-regulation of ET receptors is due, in part, to a thrombin-stimulated increase in ET resulting from the down-regulation of NEP and the reported increase in ET synthesis. In addition, pretreatment of mesangial cells with ET-1 caused a significant decrease (85%) in ET receptor number and ET-1-mediated intracellular calcium release (84%), without affecting vasopressin- or thrombin-mediated responses.

Identification and characterization of endothelin receptors on rat osteoblastic osteosarcoma cells: down-regulation by 1,25-dihydroxy-vitamin D3

Endothelins (ETs) (ET-1, ET-2, and ET-3), a family of 21-amino acid peptides, mediate a host of biological responses by binding to specific cell surface receptors termed ETA and ETB. Because a role for ET in bone remodeling has been suggested, the present study was undertaken (a) to characterize ET receptors and their responses in the rat osteosarcoma cell line ROS 17/2.8 and (b) to study their regulation by 1,25-dihydroxy-vitamin D3. Binding studies using 125I-ET-1 (a nonselective agonist) and 125I-IRL-1620 (an ETB receptor-selective agonist) indicated that these cells display high affinity ETA and ETB receptors in the ratio of 3:1. Addition of ET-1 or sarafotoxin 6c to myo-[3H]inositol-labeled cells resulted in an increase in inositol phosphate accumulation as well as in intracellular Ca2+ release, suggesting that these receptors are coupled to phospholipase C. In addition, ET-1 but not sarafotoxin 6c induced a modest increase in the expression of osteocalcin protein that was completely blocked by BQ123 (an ETA receptor-selective antagonist), indicating that activation of ETA receptors plays a role in the induction of osteocalcin. Treatment of ROS osteoblasts with 10 nM 1,25-dihydroxy-vitamin D3 for 14 hr resulted in a significant (> 50%) decrease in 125I-ET-1 and 125I-IRL-1620 binding. This decrease in binding was shown to be due to a decrease in the number of ET receptors, with no change in affinity. Although both ETA and ETB receptors were down-regulated in response to 1,25-dihydroxy-vitamin D3, only ETA receptor mRNA levels were significantly decreased, with very little change in ETB mRNA levels. These data indicate that ROS osteoblasts display both ETA and ETB receptors that are functional. Induction of osteocalcin was primarily mediated by ETA receptors, and these receptors were also down-regulated at the mRNA level by 1,25-dihydroxy-vitamin D3.

Interstitial myofibroblasts in experimental renal infection and scarring

We have examined the temporal and spatial distribution of myofibroblast-like cells, a phenotype with fibroblast and smooth muscle features, in an experimental model of renal infection. Escherichia coli organisms (10(5)) were inoculated directly into the renal cortex of Sprague-Dawley rats weighing 270 g. Saline was substituted in a control group. The animals were sacrificed at five time points up to day 24 (E. coli n = 8, controls n = 3 each interval). Myofibroblasts were identified by morphology and immunohistochemistry for alpha smooth muscle actin (alpha-SMA) and compared with staining for monocytes (ED-1), collagen III, and bromodeoxyuridine incorporation. Histological changes included a focal lesion in E. coli infected animals. Interstitial alpha-SMA staining was confined to spindle-shaped cells resembling myofibroblasts. The percent fractional area of alpha-SMA staining in the lesion increased from 0.12 +/- 0.09 at day 1 to 20.0 +/- 7.1 at day 3 (p < 0.005), decreasing progressively to 2.0 +/- 2.6 by day 24. This paralleled bromodeoxyuridine incorporation in myofibroblasts: 0.4 +/- 0.5 cells/0.25 mm2 at day 1, 105.0 +/- 36.3 at day 3, and 2.6 +/- 2.2 cells/0.25 mm2 at day 24. ED-1-positive cells increased from 374 +/- 200/0.25 mm2 at day 1 to 894 +/- 88 at day 3 (p < 0.01), declining to 230 +/- 108/0.25 mm2 by day 24. Intracellular collagen III and alpha-SMA stainings were colocalized at day 3. The fractional area of collagen III increased by day 24 (p < 0.05). In conclusion, myofibroblasts accumulate transiently during renal interstitial fibrosis and are derived at least in part from local proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)

Function of streptokinase fragments in plasminogen activation

Several peptide fragments of streptokinase (SK) were prepared by incubating SK with immobilized human plasmin (hPlm) and purified by h.p.l.c. with a reverse-phase phenyl column. The N-terminal sequences, amino acid compositions and molecular masses of these peptide fragments were determined. The SK peptide fragment of 36 kDa consisting of Ser60-Lys387 (SK-p), was the only peptide fragment that could be tightly bound to immobilized hPlm. Another three large SK peptide fragments, SK-m, SK-n and SK-o, with molecular masses of 7 kDa, 18 kDa and 30 kDa, and consisting of Ile1-Lys59, Glu148-Lys333, Ser60-Lys333 respectively, were also obtained from the supernatant of the reaction mixture. The purified SK-p had high affinity with hPlm and could activate human plasminogen (hPlg) with a kPlg one-sixth that of the native SK. SK-o had low affinity with hPlm and could also activate hPlg, although the catalytic constant was less than 1% of the native SK. SK-n, as well as SK-m, which is the N-terminal 59 amino acid peptide of the native SK, had no activator activity. However, SK-m could enhance the activator activity of both SK-o and SK-p and increase their second-order rate constants by two- and six-fold respectively. It was concluded from these studies that (1) SK-o, the Ser60-Lys333 peptide of SK, was essential for minimal SK activator activity, (2) the C-terminal peptide of SK-p, Ala334-Lys387, was essential for high affinity with hPlm, and (3) the N-terminal 59-amino-acid peptide was important in maintaining the proper conformation of SK to have its full activator activity.

Nonpeptide endothelin receptor antagonists. I. Effects on binding and signal transduction on human endothelinA and endothelinB receptors

The effect of a series of endothelin (ET) receptor antagonists, including the novel nonpeptide receptor antagonist, SB 209670, on [125I]ET-1 binding to human ET receptors (ETA and ETB) cloned and stably expressed in Chinese hamster ovary cells was studied. SB 209670 was found to compete for [125I]ET-1 binding with apparent Ki values of 0.43 +/- 0.09 and 14.7 +/- 3.0 nM for ETA and ETB receptors, respectively. This inhibition was competitive because addition of SB 209670 in saturation binding experiments resulted in decreased affinity, with no change in maximum binding. In addition, SB 209670 inhibited ET-1-mediated accumulation of inositol phosphates and intracellular calcium release in a concentration-dependent manner. The racemic mixtures, (+/-)-SB 209670 and (-)-SB 209670, were approximately 1.5 and at least 200-fold less potent than SB 209670. The binding affinity of (+/-)-SB 209670 therefore resides in (+)-antipode. The peptide antagonists, BQ123 (ETA-selective) and RES 701 (ETB-selective), were 40- and 6-fold less potent than SB 209670 in inhibition of [125I] ET-1 binding to ETA and ETB receptors, respectively. The nonselective peptide antagonist, PD 142893, was 75- and 10-fold less potent than SB 209670, whereas the nonpeptide antagonist, bosentan, was approximately 80- and approximately 30-fold less potent than SB 209670 in inhibition of [125I]ET-1 binding to ETA and ETB receptors, respectively. Thus, the present studies indicate clearly that SB 209670 is the most potent nonpeptide ET receptor antagonist yet described.

Packaging of hepatitis delta virus RNA via the RNA-binding domain of hepatitis delta antigens: different roles for the small and large delta antigens

Hepatitis delta virus (HDV) is composed of four specific components. The first component is envelope protein which contains hepatitis B surface antigens. The second and third components are nucleocapsid proteins, referred to as small and large hepatitis delta antigens (HDAgs). The final component is a single-stranded circular RNA molecule known as the viral genome. In order to study the mechanism of HDV RNA packaging, a four-plasmid cotransfection system in which each viral component was provided by a separate plasmid was employed. Virus-like particles released from Huh-7 cells receiving such a cotransfection were found to contain HDV RNA along with three proteins. Therefore, the four-plasmid cotransfection system could lead to successful HDV RNA packaging in vitro. The system was then used to show that the large HDAg alone was able to achieve a low level of HDV RNA packaging. Analysis of a variety of large HDAg mutants revealed that the RNA-binding domain was essential for viral RNA packaging. By increasing the incorporation of small HDAg into virus-like particles, we found a three- to fourfold enhancement of HDV RNA packaging. This effect was probably through a direct binding of HDV RNA, independent from that of large HDAg, with the small HDAg. The subsequent RNA-protein complex was packaged into particles. The results provided insight into the roles and functional domains of small and large HDAgs in HDV RNA packaging.

Diacylglycerol formation induced by human plasmin in cultured endothelial cells

Treatment of cultured bovine carotid artery endothelial cells with 10(-7) M plasmin increased the cellular diacylglycerol which was determined by the formation of [3H]palmitate-labeled diacylglycerol and diacylglycerol mass. Upon the stimulation with plasmin, a gradual increase in diacylglycerol formation was observed within 20 min then slightly declined. The maximal effect during the 1-h time course study was 45 and 55% increases in [3H]palmitate-labeled diacylglycerol and diacylglycerol mass, respectively, at 20 min after plasmin treatment. Formation of phosphatidylethanol was also studied in [3H]palmitate-prelabeled cells in the presence of ethanol. Treatment with plasmin for 20 min induced a significant 45% increase in phosphatidylethanol formation. The present results indicate that the plasmin-induced diacylglycerol formation in endothelial cells was at least in part mediated through the phospholipase D activation.

Carrier screening and prenatal diagnosis for alpha-thalassemia with biphasic polymerase chain reaction

Alpha-thalassemia is the most common single gene disorder in Taiwan and Southeast China. The majority of alpha-thalassemic mutations in this area are alpha-thalassemia 1. Homozygous alpha-thalassemia 1 has been recognized as the most important cause of hydrops fetalis. To investigate the incidence of alpha-thalassemia 1 mutations and to characterize its molecular defects, cord blood electrophoresis was performed on 2,000 newborns, of which 99 (5%) cases were found to have hemoglobin (Hb) Bart's levels > 3.0%. A methodology using biphasic polymerase chain reaction (PCR) with nesting primers was developed to characterize the alpha-thalassemia 1 Southeast Asia type (SEA) deletion in the cases with detectable Hb Bart's levels. The SEA deletion was found in 92 (93%) of 99 cases. Prenatal screening was performed on couples with abnormal hematologic indices, and PCR was used to detect couples heterozygous for SEA deletion. Prenatal diagnosis was performed in 21 cases, and four cases were found to have a homozygous SEA deletion. This strategy can be applied to couples who need prenatal genetic counseling for alpha-thalassemia major in this area.

Trace analysis of acetaldehyde as fluorogenic derivative by high performance liquid chromatography

A sensitive method is described for the determination of acetaldehyde as a fluorogenic derivative of decahydroacridin-1,8-dione by high performance liquid chromatography. The analytical derivatization is based on the reaction of acetaldehyde in an acidic aqueous system with 1,3-cyclohexanedione and ammonium acetate. The resulting derivative was separated by a reversed-phase C-18 column and monitored with a fluorescent detector (lambda ex, 375nm; lambda em, 512nm). Several parameters affecting the derivatization of acetaldehyde were studied. The linear range of the method for the quantitation of acetaldehyde was between 20 and 800 pmol in aqueous sample (0.5 mL). Application of the method to the analysis of acetaldehyde in plasma was performed.

Cloning and characterization of a novel endothelin receptor from Xenopus heart

Endothelin (ET) receptors display subtype heterogeneity and so far three subtypes of ET receptors, namely ETA, ETB, and ETC, have been identified, cloned, sequenced, and characterized. Based on the binding profile of ET and related peptides, a novel ET receptor (ETAX) was identified in the follicular membranes of Xenopus laevis oocytes (Kumar, C. S., Nuthulaganti, P., Pullen, M., and Nambi, P. (1993). Mol. Pharmacol. 44, 153-157). Here we report the cloning and characterization of this ETAX subtype from X. laevis heart. A cDNA was isolated that encodes a protein of 415 amino acids that shares 74, 60, and 51% identities with human ETA, human ETB, and Xenopus ETC receptors, respectively. Competition binding studies of the cloned receptor expressed in COS cells using ET-related peptides suggested that this receptor is pharmacologically identical to that expressed in Xenopus oocyte follicular, heart, and lung membranes. Phosphoinositide turnover and oocyte electrophysiological studies indicated that the cloned receptor is functionally coupled to a second messenger system.

Effect of monounsaturated fatty acids under fixed P/S and n-6/n-3 ratios on lipid metabolism in rats

The purpose of the present study was to investigate the effect of monounsaturated fatty acid (MUFA), in particular oleic acid, under fixed P/S and n-6/n-3 ratios on serum and liver lipid metabolism in rats. The male Sprague-Dawley rats aged 28 days were fed diets low in MUFA (LM) or high in MUFA (HM) with or without 1% cholesterol for 4 weeks. The experimental diets contained 10% (w/w) fat. The body weight gain, food efficiency, and liver weight were comparable among the groups except for an increase in liver weight by dietary cholesterol. When cholesterol-added diets were fed, the concentration of serum cholesterol in the HM group was higher than that of the corresponding LM group at second week and at the end of experiment. The concentration of serum triacylglycerol in rats fed a cholesterol-enriched HM diet was markedly lower than that of cholesterol-free counterpart. Both MUFA and cholesterol tended to increase serum low density lipoprotein-cholesterol concentration, but they had no interaction. Serum high density lipoprotein-cholesterol in cholesterol-enriched groups was lower than that in the cholesterol-free counterparts, but it was independent of the MUFA content. Dietary cholesterol markedly increased the concentration of liver cholesterol and triacylglycerol and the increase in liver cholesterol was more marked in the HM group than in the LM group, while the level of liver triacylglycerol was comparable. The fecal excretion of neutral and acidic steroids increased when 1% cholesterol was added to the diets, irrespective of the MUFA content in the diets. Thus, the results indicate that the proposed beneficial effect of MUFA on cholesterol can be modified when diet contains cholesterol.

Electron-capture gas chromatographic determination of cyanide, iodide, nitrite, sulfide, and thiocyanate anions by phase-transfer-catalyzed derivatization with pentafluorobenzyl bromide

A sensitive gas chromatographic method has been established for the simultaneous determination of biologically active inorganic anions, including cyanide, iodide, nitrite, sulfide, and thiocyanate anions as their volatile organic derivatives. The method is based on the formation of ion pairs from the anions and a complex cryptand and on the resulting neutral ion-pair partition to an organic phase for derivatization with pentafluorobenzyl bromide. Several parameters affecting the partition and derivatization of the anions were investigated. Individual and simultaneous determination of the anions can be achieved at sub-nmol levels with an electron-capture detector. Partial application of the method for the analysis of cyanide, nitrite, and thiocyanate in real samples proved satisfactory.

Human AT1 receptor is a single copy gene: characterization in a stable cell line

To address conflicting reports concerning the number of angiotensin II (AII) receptor type 1 (AT1) coding loci in vertebrates, Southern blot analysis was used to determine the genomic representation of AT1 receptor genes in animals comprising a divergent evolutionary spectrum. The data demonstrate that the AT1 receptor gene is present as a single genomic copy in a broad spectrum of animals including human, monkey, dog, cow, rabbit, and chicken. In contrast, members of the rodent taxonomic order contain two genes in their genomes. These two genes may have arisen in rodents as a consequence of a gene duplication event that occurred during evolution following the branching of rodents from the mammalian phylogenetic tree. In order to investigate the properties of the human AT1 receptor in a pure cell system, the recombinant human AT1 receptor was stably expressed in mouse L cells. An isolated cell line, designated LhAT1-D6, was found to express abundant levels of recombinant receptor [430 +/- 15 fmol/mg] exhibiting high affinity [KD = 0.15 +/- 0.02 nM] for [125I][SAR1, Ile8] angiotensin II (SIA). The pharmacological profile of ligands competing for [125I] SIA binding to the expressed receptor was in accordance with that of the natural receptor. Radioligand binding of the expressed receptor was decreased in the presence of the non-hydrolyzable analog of GTP, guanosine 5'-(gamma-thio) triphosphate [GTP gamma S]. Angiotensin II evoked a rapid efflux of 45Ca2+ from LhAT1-D6 cells that was blocked by AT1 receptor specific antagonists. In addition, AII inhibited forskolin-stimulated cAMP accumulation in these cells which was blocked by the AT-1 antagonist. Thus, the LhAT1-D6 cell line provides a powerful tool to explore the human AT1 receptor regulation.

Regional differences in prostaglandin production rates among porcine intrathoracic vessels

To investigate the regional variability in intrathoracic vascular prostaglandin (PG) synthesis, we obtained vessel segments from porcine coronary artery (COA), thoracic aorta (AT), common carotid artery (CRA), pulmonary artery (PA), pulmonary vein (PV), and inferior vena cava (IVC). Vascular production rates of 6-keto-PGF1 alpha (an indicator for PGI2), PGF2 alpha, and PGE2 were measured both in unstimulated state and in arachidonic acid-stimulated state using immunosorbent assays. Our results indicated that PGI2 production rate in all vessel segments decayed with time after vessel dissection. In all vessel segments tested under unstimulated conditions, PGI2 production rates were about one order of magnitude higher than PGF2 alpha and PGE2 production rates of the same specimens. Results from unstimulated, 1.5 hr pre-incubated specimens indicated that i) PGI2 production rates in COA, AT, and PV were greater than those in CRA, PA, and IVC; ii) PGF2 alpha production rates from the same specimens were higher in PV than in AT, CRA, and IVC, while these in PA were higher than in IVC; and iii) PGE2 production rates from the same specimens were not significantly different from one another. Arachidonic acid added at about 1.5 hr after vessel harvest stimulated the PGI2 and PGF2 alpha synthesis rates by 3 to 15 folds. However, this arachidonic acid treatment caused 70 to 300-fold increases in PGE2 production rates, reaching levels comparable to PGI2. All three prostanoid production rates under stimulated conditions were also variable among different intrathoracic vessels. Although either physiological gas concentrations or local hemodynamic conditions alone can partially explain our results, which physiological parameter(s) actually causes these regional differences remains to be verified.

Intrafamilial transmission of hepatitis C virus: the important role of inapparent transmission

To evaluate the intrafamilial transmission of hepatitis C virus (HCV) 104 index patients with type C chronic liver disease and their 307 family contacts were interviewed. After a questionnaire on the risk factors of parenteral exposure, blood samples were obtained and tested for liver biochemistry and anti-HCV antibody by enzyme-linked immunosorbent assay (Abbott II). Overall, 52 family contacts (17%) were positive for anti-HCV, indicating a higher anti-HCV prevalence among family contacts than among the general population in Taiwan. The anti-HCV prevalences in parents, spouses, children, and other contacts of the patients were 54% (14/26), 28% (25/91), 6.9% (10/143), and 6.4% (3/47), respectively. The contacts of index patients had increasingly greater risk of HCV infection when they became older and had lived longer with index patients. All family contacts were divided into two groups categorized by whether the index patients had or did not have a history of parenteral exposure. Among 126 family contacts of the 42 patients without parenteral exposure, blood transfusion and surgery were the factors significantly associated with HCV infection in these family contacts (odds ratio = 7.26, 95% confidence interval = 2.32-32.67; odds ratio = 3.95, 95% CI = 1.29-12.11, respectively). Risk factors were not significantly associated with HCV infection among 181 family contacts of the 62 index patients with parenteral exposure. It is concluded that the index patients without parenteral exposure appeared to have acquired the disease from HCV-infected family members with risk factors. Most of the index patients had a history of parenteral exposure and in turn served as the source of the disease for family members.