Epithelial sodium channel regulated by aldosterone-induced protein sgk

Sodium homeostasis in terrestrial and freshwater vertebrates is controlled by the corticosteroid hormones, principally aldosterone, which stimulate electrogenic Na+ absorption in tight epithelia. Although aldosterone is known to increase apical membrane Na+ permeability in target cells through changes in gene transcription, the mechanistic basis of this effect remains poorly understood. The predominant early effect of aldosterone is to increase the activity of the epithelial sodium channel (ENaC), although ENaC mRNA and protein levels do not change initially. Rather, the open probability and/or number of channels in the apical membrane are greatly increased by unknown modulators. To identify hormone-stimulated gene products that modulate ENaC activity, a subtracted cDNA library was generated from A6 cells, a stable cell line of renal distal nephron origin, and the effect of candidates on ENaC activity was tested in a coexpression assay. We report here the identification of sgk (serum and glucocorticoid-regulated kinase), a member of the serine-threonine kinase family, as an aldosterone-induced regulator of ENaC activity. sgk mRNA and protein were strongly and rapidly hormone stimulated both in A6 cells and in rat kidney. Furthermore, sgk stimulated ENaC activity approximately 7-fold when they were coexpressed in Xenopus laevis oocytes. These data suggest that sgk plays a central role in aldosterone regulation of Na+ absorption and thus in the control of extracellular fluid volume, blood pressure, and sodium homeostasis.

Environmental risk factors and Parkinson's disease: a case-control study in Taiwan

To explore environmental risk factors for Parkinson's disease (PD) in Taiwan, we investigated 120 patients with PD and 240 hospital control subjects matched with patients on age (+/-2 years) and sex. Based on a structured open-ended questionnaire, we carried out standardized interviews to obtain history of exposure to environmental factors, including place of residence, source of drinking water, and environmental and occupational exposures to various agricultural chemicals. In the univariate analysis, the history of living in a rural environment, farming, use of herbicides/pesticides, and use of paraquat were associated with an increased PD risk in a dose-response relationship. After adjustment for multiple risk factors through conditional logistic regression, the biological gradient between PD and previous uses of herbicides/pesticides and paraquat remained significant. The PD risk was greater among subjects who had used paraquat and other herbicides/pesticides than those who had used herbicides/pesticides other than paraquat. There were no significant differences in occupational exposures to chemicals, heavy metals, and minerals between PD patients and matched control subjects. The duration of drinking well water and alcohol consumption was not significantly associated with PD. There was an inverse relationship between cigarette smoking and PD. Environmental factors, especially exposures to paraquat and herbicides/pesticides, may play important roles in the development of PD in Taiwan.

Suppression of hepatitis B virus expression and replication by hepatitis C virus core protein in HuH-7 cells

Hepatitis B and C viruses (HBV and HCV, respectively) are associated with acute and chronic liver diseases and hepatocellular carcinoma. To elucidate the molecular status of superinfection with these two hepatitis viruses, we cotransfected the full-length or truncated version of HCV structural genes (core and envelope 1) together with the cloned HBV DNA into a human hepatoma cell line (HuH-7). Expression of HBV-specific major transcripts (3.5 and 2.1 kb), as well as HBV antigens (hepatitis B surface antigen and hepatitis B e and core antigens), was reduced about two- to fourfold by the presence of the HCV structural genes. In addition, the secretion of HBV viral particles, including the viral nucleocapsid and mature virion, was drastically suppressed about 20-fold. Analysis of the intracellular HBV core protein-associated nucleic acid indicated that the encapsidated HBV pregenomic RNA was similarly reduced about 14-fold. Deletion analysis of the HCV structural genes demonstrated that the core gene alone or the fragment containing the core protein's N-terminal 122 amino acid residues conferred the same level of suppressive activity as the full-length structural genes. By indirect immunofluorescence, we found that the core protein of HCV was located in the cytoplasm of transfected HuH-7 cells at day 3 posttransfection and was targeted to the nucleus at day 6. Thus, the kinetics of the suppressive effect exerted by HCV constructs matched the timing of core protein entrance into the nucleus. Our results substantiate the clinical finding that HBV markers are suppressed by superinfection with HCV and further imply that this inhibitory effect may occur in the processes of transcription and encapsidation of HBV pregenomic RNA and may be mediated by the core protein of HCV. The deduced amino acid sequence of the HCV core protein has revealed that it is a basic protein which contains a putative DNA-binding motif (SPRG), as well as triplicate nuclear localization signals and several putative protein kinase A and C recognition sites. These characteristics imply that the HCV core protein can also function as a gene-regulatory protein.

Design, intracellular expression, and activity of a human anti-human immunodeficiency virus type 1 gp120 single-chain antibody

A single-chain antibody, derived from a human monoclonal antibody that recognizes the CD4 binding region of the human immunodeficiency virus type 1 (HIV-1) envelope protein, has been designed for intracellular expression in eukaryotic cells. The single-chain antibody is composed of an immunoglobulin heavy-chain leader sequence and heavy- and light-chain variable regions that are joined by an interchain linker. The antibody is stably expressed and retained in the endoplasmic reticulum and is not toxic to the cells. The antibody binds to the envelope protein within the cell and inhibits processing of the envelope precursor and syncytia formation. The infectivity of the HIV-1 particles produced by cells that express the single-chain antibody is substantially reduced. These studies illustrate the feasibility of designing antibodies that bind and inactivate molecules intracellularly. Antibodies that act on target molecules within cells should provide a useful tool for research as well as for control of infectious and other diseases.

Ingested inorganic arsenic and prevalence of diabetes mellitus

To examine the association between ingested inorganic arsenic and prevalence of diabetes mellitus, in 1988, the authors studied 891 adults residing in villages in southern Taiwan where arseniasis is hyperendemic. The status of diabetes mellitus was determined by an oral glucose tolerance test and a history of diabetes regularly treated with sulfonylurea or insulin. The cumulative arsenic exposure in parts per million-years was calculated from the detailed history of residential addresses and duration of drinking artesian well water obtained through standardized interviews based on a structured questionnaire and the arsenic concentration in well water. The body mass index was derived from body height and weight measured according to a standard protocol, while the physical activity at work was also obtained by questionnaire interviews. Residents in villages where the chronic arseniasis was hyperendemic had a twofold increase in age- and sex-adjusted prevalence of diabetes mellitus compared with residents in Taipei City and the Taiwan area. There was a dose-response relation between cumulative arsenic exposure and prevalence of diabetes mellitus. The relation remained significant after adjustment for age, sex, body mass index, and activity level at work by a multiple logistic regression analysis giving a multivariate-adjusted odds ratio of 6.61 and 10.05, respectively, for those who had a cumulative arsenic exposure of 0.1-15.0 and greater than 15.0 ppm-year compared with those who were unexposed. These results suggest the chronic arsenic exposure may induce diabetes mellitus in humans.

12-month Tai Chi training in the elderly: its effect on health fitness

PURPOSE

The objective of this study was to evaluate the effect of Tai Chi Chuan (TCC) on health fitness in older individuals.

METHODS

Thirty-eight community-dwelling persons aged 58 to 70 yr completed this study. The TCC group included 9 men and 11 women; the control group included 9 men and 9 women. The TCC group practiced TCC for 11.2+/-1.4 months, with the attendance of 4.6+/-1.3 times x wk(-1). Each session included 20 min of warm-up, 24 min of TCC practice, and 10 min of cooldown. The exercise intensity was 52-63% of the heart rate range. Cardiorespiratory function, strength, flexibility, and percent of body fat were evaluated before and at the end of this study.

RESULTS

The male TCC group showed 16.1% increase in VO2max (P < 0.01), 11 degrees increase in thoracic/lumbar flexibility (P < 0.05), 18.1% increase in muscle strength of knee extensor (P < 0.01), and 15.4% increase of knee flexor (P < 0.05). The female TCC group showed 21.3% increase in VO2max (P < 0.01), 8.8 degrees increase in flexibility (P < 0.05), 20.3% increase in muscle strength of knee extensor (P < 0.05), and 15.9% increase of knee flexor (P < 0.05). The control group showed no significant change in these variables.

CONCLUSIONS

The results indicate that a 12-month Tai Chi Chuan program is effective for improving health fitness of the elderly.

Ethanol-induced teratogenesis: free radical damage as a possible mechanism

To investigate the possibility of a free radical mechanism for ethanol-induced teratogenesis, gestational day 8 mouse embryos were exposed for 6 hr in whole embryo culture to a teratogenic dosage of ethanol alone (500 mg%) or in conjunction with an antioxidant, superoxide dismutase (SOD; 300 U/ml). For subsequent analysis, some embryos were examined at the end of this 6-hr period, while others were removed to control medium and cultured for an additional time period. Ethanol exposure resulted in increased superoxide anion generation and increased lipid peroxidation (as noted 6 hr after initial ethanol exposure) and in excessive cell death (as noted 12 hr after initial exposure) in the embryos. Following a total of 36 hr in culture, a high incidence of malformation, including failure of the anterior neural tube to close in 63% of the ethanol-exposed embryos, was noted. The ethanol-induced superoxide anion generation, lipid peroxidation, excessive cell death, and dysmorphogenesis were diminished in embryos co-treated with SOD, suggesting that the teratogenicity of ethanol is mediated, at least in part, by free radical damage.

Inhibition of HIV-1 Tat-mediated LTR transactivation and HIV-1 infection by anti-Tat single chain intrabodies

Genes encoding the rearranged immunoglobulin heavy and light chain variable regions of anti-HIV-1 Tat, exon 1 or exon 2 specific monoclonal antibodies have been used to construct single chain intracellular antibodies 'intrabodies' for expression in the cytoplasm of mammalian cells. These anti-Tat single chain intrabodies (anti-Tat sFvs) are additionally modified with a C-terminal human C kappa domain to increase cytoplasmic stability and/or the C-terminal SV40 nuclear localization signal to direct the nascent intrabody to the nuclear compartment, respectively. The anti-Tat sFvs with specific binding activity against the N-terminal activation domain of Tat, block Tat-mediated transactivation of HIV-1 LTR as well as intracellular trafficking of Tat in mammalian cells. As a result, the transformed lymphocytes expressing anti-Tat sFvs are resistant to HIV-1 infection. Thus, these studies demonstrate that stably expressed single chain intrabodies and their modified forms can effectively target molecules in the cytoplasm and nuclear compartments of eukaryotic cells. Furthermore, these studies suggest that anti-Tat sFvs used either alone or in combination with other genetically based strategies may be useful for the gene therapy of HIV-1 infection and AIDS.

RAM2, an essential gene of yeast, and RAM1 encode the two polypeptide components of the farnesyltransferase that prenylates a-factor and Ras proteins

In the yeast Saccharomyces cerevisiae, mutations in either of two unlinked genes, RAM1 or RAM2, abolish the farnesyltransferase activity responsible for prenylation of Ras proteins and the a-factor mating pheromone. Here we report that the function of RAM1 and RAM2 genes is required for the membrane localization of Ras proteins and a-factor. The RAM2 gene was sequenced and can encode a 38-kDa protein. We examined the functional interaction of RAM2 and RAM1 by expressing the genes in Escherichia coli. Extracts derived from an E. coli strain that coexpressed RAM1 and RAM2 efficiently farnesylated a-factor peptide and Ras protein substrates. In contrast, extracts derived from E. coli strains that expressed either RAM gene alone were devoid of activity; however, when the latter extracts were mixed, protein farnesyltransferase activity was reconstituted. These results indicate that the yeast farnesyl-protein transferase is comprised of Ram1 and Ram2 polypeptides. Although Ram1 is a component of the enzyme, disruption of the RAM1 gene in yeast was not lethal, indicating that the Ram1-Ram2 farnesyltransferase is not essential for viability. In contrast, disruption of RAM2 was lethal, suggesting that Ram2 has an essential function in addition to its role with Ram1 in protein farnesylation.

Modulation of the trans-suppression activity of hepatitis C virus core protein by phosphorylation

We previously demonstrated that the core protein of hepatitis C virus (HCV) can suppress gene expression and replication of hepatitis B virus (HBV) in a human hepatoma cell line (HuH-7). In this study, we have characterized the phosphorylation property of HCV core protein and examined the effect of phosphorylation on its suppressive activity of HBV. Our results indicated that both the full-length HCV core protein (22 kDa) and its processed or degraded forms (14 to 18 kDa) were phosphorylated in insect cells. As demonstrated by using the glutathione S-transferase fusion protein expression system and in vitro transcription and translation system, the phosphorylation of HCV core protein was carried out by protein kinase A (PKA) and protein kinase C (PKC) in vitro. In both kinase reactions, it was determined that the phosphorylated amino acid was a serine residue. The potential phosphorylated sites in core protein were identified as residues Ser-53 and Ser-116 for PKA and Ser-53 and Ser-99 for PKC. Comparison of the phosphorylation intensities of the wild type and Ser mutants suggested that Ser-99 and Ser-116 were the major phosphorylation sites for PKC and PKA, respectively. The phosphorylation of Ser-99 and Ser-116, but not Ser-53, in HCV core protein was essential for the suppressive activity of HCV core protein on HBV gene expression and replication in HuH-7 cells. Mutation of the former two serine residues to alanine or aspartate residues led to a drastic loss of the inhibitory effects of HCV core protein on HBV gene expression (both transcription and antigen production) and pregenomic RNA encapsidation, as well as the release of HBV virus particles. In contrast, the Ser-53 mutant conferred the same level of suppressive activity as the wild type did. This property is in accordance with the observation that Ser-99 and Ser-116 are the predominant phosphorylation sites in the HCV core construct. All serine mutants (including those with mutations in PKA, PKC, and both kinase recognition sites) of HCV core protein retained the ability to translocate into the nucleus. Furthermore, wild-type HCV core protein diminished its suppressive activity when cells were treated with PKA or PKC inhibitor. In conclusion, HCV core protein is a phospho-protein and in HuH-7 cells, its trans suppression of HBV gene expression and replication is positively regulated by PKA and PKC. The role of phosphorylation in the control of trans-suppressive activity cannot be reproduced by introducing an acidic residue.(ABSTRACT TRUNCATED AT 250 WORDS)

Tai Chi Chuan to improve muscular strength and endurance in elderly individuals: a pilot study

OBJECTIVE

To evaluate the training effect of a Tai Chi Chuan (TCC) program on knee extensor muscular strength and endurance in elderly individuals.

DESIGN

Before-after trial.

SETTING

Community setting.

PARTICIPANTS

Forty-one community dwelling subjects aged 61.1 +/- 9.8 years undertook a TCC program. Nine dropped out during the study. Pretraining and posttraining measurements were obtained from 15 men and 17 women.

INTERVENTION

Subjects participated in a 6-month TCC program. Each session consisted of 20 minutes of warm-up, 24 minutes of structured TCC training, and 10 minutes of cool-down exercises.

MAIN OUTCOME MEASURES

Peak torque of dominant and nondominant knee extensors was tested at speeds of 60 degrees , 180 degrees , and 240 degrees/sec concentrically and eccentrically. Muscular endurance of the knee extensor was tested at the speed of 180 degrees /sec.

RESULTS

In the group of men, concentric knee extensor peak torque increased by 15.1% to 20.0% and eccentric peak torque increased by 15.1% to 23.7%. The group of women also showed increases, ranging from 13.5% to 21.8% in concentric peak torque, and 18.3% to 23.8% in eccentric peak torque. In addition, the knee extensor endurance ratio increased by 9.6% to 18.8% in the men and 10.1% to 14.6% in the women.

CONCLUSION

TCC training may enhance muscular strength and endurance of knee extensors in elderly individuals.

Free radicals and ethanol-induced cytotoxicity in neural crest cells

Associations between ethanol-induced cranial neural crest cell (NCC) damage in mammalian embryos and subsequent malformations as observed in human fetal alcohol syndrome have previously been illustrated. The vulnerability of NCCs to this teratogen may result, at least in part, from their sensitivity to free radical damage. To examine relationships between free radical generation and NCC cytotoxicity, primary culture of mouse NCCs was used. NCC viability was determined in both dose- and time-response studies involving ethanol exposure. After 48 hr of culture, cell viability was significantly diminished at all doses tested (i.e., 50, 100, 150, and 200 mM ethanol). At 100 mM ethanol (a dosage that is teratogenic in vivo and in whole embryo culture), cell viability decreased to approximately 50% of control values over the first 12 hr of culture, and decreased further, to approximately 20% by 48 hr. Using nitroblue tetrazolium as a probe, it was observed that exposure of NCCs to ethanol stimulated the production of superoxide anion radicals. Co-treatment of the ethanol-exposed NCCs with free radical scavengers including 300 units/ml of superoxide dismutase, catalase (500 units/ml), or alpha-tocopherol (300 microM) significantly improved NCC viability. These results suggest that the ethanol-induced NCC injury is mediated, at least in part, through the generation of free radicals. To test this hypothesis further, NCCs were exposed in culture to xanthine/xanthine oxidase. Exogenous free radicals generated by the xanthine/xanthine oxidase system resulted in reduced NCC viability, the severity of which increased in a time and enzyme concentration-related manner. Superoxide dismutase (300 units/ml) and catalase (500 units/ml) significantly reduced the effects of the xanthine/xanthine oxidase-generated free radicals on NCC viability. The similarity between the susceptibility of NCCs to ethanol and their susceptibility to exogenous free radicals in concert with the free radical scavenger-mediated amelioration of ethanol and exogenous free radical-induced NCC death strongly suggest that free radicals play a significant role in ethanol-induced NCC death.

Transduction of human PBMC-derived dendritic cells and macrophages by an HIV-1-based lentiviral vector system

Professional antigen-presenting cells, such as dendritic cells (DCs) and macrophages, are target cells for gene therapy of infectious disease and cancer. However, transduction of DCs and macrophages has proved difficult by most currently available gene transfer methods. Several recent studies have shown that lentiviral vector systems can efficiently transduce many nondividing and differentiated cell types. In this study, we examined the gene transfer to DCs and macrophages using a lentiviral vector system. Human DCs were propagated from the adherent fraction of peripheral blood mononuclear cells (PBMCs) by culture in medium containing GM-CSF, IL-4, and TNF-alpha. Human macrophages were propagated from adherent PBMCs in medium containing GM-CSF. High titers of a replication-defective vesicular stomatitis virus glycoprotein G pseudotyped HIV-1-based vector encoding the enhanced yellow fluorescent protein were produced. In immature DCs (culture days 3 and 5), transduction efficiencies of 25 to 35% were achieved at a multiplicity of infection of 100. However, the transduction efficiency was decreased in more mature DCs (culture day 8 or later). Furthermore, monocyte-derived macrophages were also transduced by the lentiviral vector system. In addition, Alu-LTR PCR demonstrated the integration of the HIV-1 provirus into the cellular genome of the transduced DCs and macrophages. Allogeneic mixed lymphocyte reactions revealed similar antigen-presenting functions of untransduced and lentivirally transduced DCs. Thus, the results of this study demonstrate that both PBMC-derived DCs and macrophages can be transduced by lentiviral vectors.

The effect of Tai Chi on cardiorespiratory function in patients with coronary artery bypass surgery

PURPOSE

This study prospectively evaluated the training effect of a 1-yr Tai Chi Chuan (TCC) program for low-risk patients with coronary artery bypass surgery (CABS) after a postoperative outpatient (phase II) cardiac rehabilitation program.

METHODS

Twenty patients with mean age of 56.5+/-7.4 yr completed this study. The TCC group included nine men who practiced classical Yang TCC with an exercise intensity of 48-57% heart rate range (HRR). The control group included 11 men whom were recommended to do a home-based self-adjusted exercise program with similar intensity of phase II cardiac rehabilitation. Graded exercise tests were performed before and after 1 yr of training for all subjects.

RESULTS

Mean attendance of the TCC group was 3.8+/-1.5 times weekly in contrast to 1.7+/-1.1 times for the control group. During the follow-up examination, the TCC group increased 10.3% in VO2peak (from 26.2+/-4.4 to 28.9+/-5.0 mL x kg(-1) min(-1), P<0.01) and increased 11.9% in peak work rate (from 135+/-26 W to 151+/-28 W, P<0.01). However, the control group showed slight decrease in VO2peak from 26.0+/-3.9 to 25.6+/-4.6 mL x kg(-1) x min(-1) and in peak work rate from 131+/-23 W to 128+/-32 W. At the ventilatory threshold, the TCC group also showed significant increase in VO2 and work rate (P<0.05). The control group did not significantly change in these variables.

CONCLUSIONS

The study demonstrated that a 1-yr TCC program for low-risk patients with CABS could favorably enhance cardiorespiratory function.

Effect of granulocyte-macrophage colony-stimulating factor on oral mucositis in head and neck cancer patients after cisplatin, fluorouracil, and leucovorin chemotherapy

PURPOSE

To evaluate prospectively the efficacy of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the reduction of chemotherapy-induced oral mucositis.

PATIENTS AND METHODS

Twenty patients with stage IV squamous cell carcinoma of head and neck were studied. Two-cycles (periods) of identical doses of cisplatin, fluorouracil (5-FU), and leucovorin (PFL) chemotherapy with cisplatin 20 mg/m2/d, 5-FU 800 mg/m2/d, leucovorin 90 mg/m2/d by 96-hour continuous intravenous infusion every 3 weeks were given to each patient. After PFL chemotherapy, GM-CSF 4 micrograms/kg subcutaneously from days 5 to 14 or no therapy was given by a randomized self-controlled crossover study design. Oral mucositis was graded with modified Radiation Therapy Oncology Group criteria.

RESULTS

In the first cycle of PFL chemotherapy, GM-CSF significantly reduced the incidence, mean duration, and mean area under the curve (AUC) of severe oral gross mucositis (grade > or = 3) compared with no therapy. These beneficial effects continued into the second cycle of PFL chemotherapy after crossover to no GM-CSF. The incidence of severe mucositis was reduced when GM-CSF was given in the second cycle of PFL. Analysis of variance indicated significant direct GM-CSF treatment effects on the mean AUC of gross/functional scores and duration of moderate gross mucositis (grade > or = 2) over both periods. There was a significant period effect in favor of giving GM-CSF in the first cycle of chemotherapy.

CONCLUSION

GM-CSF can significantly reduce the severity and duration of chemotherapy-induced oral mucositis after PFL chemotherapy.

Studies of inhibition of rat spermidine synthase and spermine synthase

1. S-Adenosyl-l-methionine, S-adenosyl-l-homocysteine, 5'-methylthioadenosine and a number of analogues having changes in the base, sugar or amino acid portions of the molecule were tested as potential inhibitors of spermidine synthase and spermine synthase from rat ventral prostate. 2. S-Adenosyl-l-methionine was inhibitory to these reactions, as were other nucleosides containing a sulphonium centre. The most active of these were S-adenosyl-l-ethionine, S-adenosyl-4-methylthiobutyric acid, S-adenosyl-d-methionine and S-tubercidinylmethionine, which were all comparable in activity with S-adenosylmethionine itself, producing 70-98% inhibition at 1mm concentrations. Spermine synthase was somewhat more sensitive than spermidine synthase. 3. 5'-Methylthioadenosine, 5'-ethylthioadenosine and 5'-methylthiotubercidin were all powerful inhibitors of both enzymes, giving 50% inhibition of spermine synthase at 10-15mum and 50% inhibition of spermidine synthase at 30-45mum. 4. S-Adenosyl-l-homocysteine was a weak inhibitor of spermine synthase and practically inactive against spermidine synthase. Analogues of S-adenosylhomocysteine lacking either the carboxy or the amino group of the amino acid portion were somewhat more active, as were derivatives in which the ribose ring had been opened by oxidation. The sulphoxide and sulphone derivatives of decarboxylated S-adenosyl-l-homocysteine and the sulphone of S-adenosyl-l-homocysteine were quite potent inhibitors and were particularly active against spermidine synthase (giving 50% inhibition at 380, 50 and 20mum respectively). 5. These results are discussed in terms of the possible regulation of polyamine synthesis by endogenous nucleosides and the possible value of some of the inhibitory substances in experimental manipulations of polyamine concentrations. It is suggested that 5'-methylthiotubercidin and the sulphone of S-adenosylhomocysteine or of S-adenosyl-3-thiopropylamine may be particularly valuable in this respect.

Reactive oxygen species mediate cyclic strain-induced endothelin-1 gene expression via Ras/Raf/extracellular signal-regulated kinase pathway in endothelial cells

Endothelin-1 (Et-1) is a peptide synthesized by endothelial cells (ECs) both in culture and in vivo. Cyclic strain induces gene expression of Et-1, however, the molecular mechanisms remain unclear. Since cyclic strain induces a sustained increase in intracellular reactive oxygen species (ROS), we hypothesized that the ROS could be a modulator in strain-induced Et-1 gene expression. Human umbilical vein ECs (HUVECs) subjected to cyclic strain had increased Et-1 secretion. Pretreatment of HUVECs with antioxidants, catalase (300 U/ml) or 1,3-dimethyl-2-thiourea (DMTU, 0.1 mm), abolished the strain-induced Et-1 release. ECs strained for 6 h had elevated Et-1 mRNA levels. In contrast, ECs treated with catalase or DMTU did not have increase Et-1 mRNA levels stimulated by cyclic strain. Bovine aortic ECs (BAECs) transfected with fusion plasmid containing Et-1 5'-flanking sequence (4.4 kb) and chloramphenicol acetyltransferase reporter gene produced a maximal Et-1 promoter activity after undergoing strain for 6 h, whereas pretreatment with catalase decreased this activity. BAECs cotransfected with a dominant negative mutant of Ras (RasN17), Raf-1 (Raf301), or catalytically inactive mutant of extracellular signal-regulated kinase (mERK2) had inhibited strain-induced Et-1 promoter activity, indicating the Ras/Raf/ERK pathway was involved; moreover, ERK phosphorylation was induced in ECs which were strained. This strain-activated ERK phosphorylation was attenuated in the presence of catalase. Functional analysis of the Et-1 promoter with site-directed mutagenesis indicates that the activator protein-1 (AP-1) binding site had to be within 143 base-pairs upstream of transcription initiation site for strain-induced promoter activity. Pretreatment of ECs with catalase also decreased the strain-induced promoter activity in the minimal construct (-143 bp). Our data demonstrate that strain-induced Et-1 gene expression is modulated by ROS via Ras/Raf/ERK signaling pathway, and indicate the responsiveness of the AP-1 binding site for strain-induced Et-1 expression.

Vision Sensor Planning for 3–D Model Acquisition

A novel method is proposed in this paper for automatic acquisition of three-dimensional (3-D) models of unknown objects by an active vision system, in which the vision sensor is to be moved from one viewpoint to the next around the target to obtain its complete model. In each step, sensing parameters are determined automatically for incrementally building the 3-D target models. The method is developed by analyzing the target's trend surface, which is the regional feature of a surface for describing the global tendency of change. While previous approaches to trend analysis are usually focused on generating polynomial equations for interpreting regression surfaces in three dimensions, this paper proposes a new mathematical model for predicting the unknown area of the object surface. A uniform surface model is established by analyzing the surface curvatures. Furthermore, a criterion is defined to determine the exploration direction, and an algorithm is developed for determining the parameters of the next view. Implementation of the method is carried out to validate the proposed method.

Manganese in infant formulas and learning disability

The concentration of manganese in the hair of normal newborn infants was found to increase significantly from 0.19 micrograms/g at birth to 0.965 micrograms/g at 6 weeks of age and 0.685 micrograms/g at 4 months when they were fed infant formula. There was an insignificant increase to 0.330 micrograms/g at age 4 months in breast-fed infants. After this age there was a slow decline in hair manganese to 0.268 micrograms/g in normal children at age 8 years and 0.434 in learning disabled (hyperactive) children. This is the third study reporting elevated hair manganese in learning disabled children.

Aldosterone responsiveness of A6 cells is restored by cloned rat mineralocorticoid receptor

A6 cells, derived from Xenopus laevis renal tubule, form a high-resistance ion-transporting monolayer when grown on permeable supports and can generate a short-circuit current (SCC) that is stimulated by high levels of the mineralocorticoid aldosterone. Surprisingly, A6 SCC is more responsive to glucocorticoids than to mineralocorticoids, suggesting the possibility that these cells do not contain transcriptionally active mineralocorticoid receptor (MR) and that glucocorticoid receptor (GR) mediates MR-like responses in these collecting duct-like cells. We have examined the response of both SCC and a transfected reporter gene to mineralocorticoids and glucocorticoids in the presence and absence of transfected rat MR (rMR). We found that, in the absence of transfected MR, a reporter gene that can be activated by MR or GR was more responsive to glucocorticoids such as dexamethasone and RU-28362 than to mineralocorticoids such as aldosterone. Transfected rMR underwent mineralocorticoid-dependent nuclear localization and restored both transcriptional sensitivity of a reporter gene and SCC response to mineralocorticoids. These data demonstrate that A6 cells contain transcriptionally active GR but not MR and thus suggest a molecular basis for the defect in A6 cell SCC response to aldosterone. Our results also demonstrate that GR is capable of mediating hormone stimulation of SCC, a classic mineralocorticoid response. Finally, the observation that heterologous expression of rMR can localize normally to the A6 nucleus in a hormone-dependent fashion and restore both the transcriptional and SCC response to mineralocorticoids suggests that MR function is conserved in species as distantly related as toads and mammals.

Inactivation of HIV-1 chemokine co-receptor CXCR-4 by a novel intrakine strategy

CXC-chemokine receptor (CXCR)-4/fusin, a newly discovered co-receptor for T-cell line (T)-tropic HIV-1 virus, plays a critical role in T-tropic virus fusion and entry into permissive cells. The occurrence of T-tropic HIV viruses is associated with CD4-positive cell decline and progression to AIDS, suggesting that the T-tropic HIV-1 contributes to AIDS pathogenesis. In this study, we used a novel strategy to inactivate CXCR-4 by targeting a modified CXC-chemokine to the endoplasmic reticulum (ER) to block the surface expression of newly synthesized CXCR-4. The genetically modified lymphocytes expressing this intracellular chemokine, termed "intrakine", are immune to T-tropic virus infection and appear to retain normal biological features. Thus, this genetic intrakine strategy is uniquely targeted at the conserved cellular receptor for the prevention of HIV-1 entry and may be developed into an effective treatment for HIV-1 infection and AIDS.

p53 represses androgen-induced transactivation of prostate-specific antigen by disrupting hAR amino- to carboxyl-terminal interaction

Prostate-specific antigen (PSA) is highly overexpressed in prostate cancer. One important regulator of PSA expression is the androgen receptor (AR), the nuclear receptor that mediates the biological actions of androgens. AR is able to up-regulate PSA expression by directly binding and activating the promoter of this gene. We provide evidence here that that this AR activity is repressed by the tumor suppressor protein p53. p53 appears to exert its inhibition of human AR (hAR) by disrupting its amino- to carboxyl-terminal (N-to-C) interaction, which is thought to be responsible for the homodimerization of this receptor. Consistent with this, p53 is also able to block hAR DNA binding in vitro. Our previous data have shown that c-Jun can mediate hAR transactivation, and this appears to result from a positive effect on hAR N-to-C interaction and DNA binding. Interestingly, c-Jun is able to relieve the negative effects of p53 on hAR transactivation, N-to-C interaction, and DNA binding, demonstrating antagonistic activities of these two proteins. Importantly, a p53 mutation found in metastatic prostate cancer severely disrupts the p53 negative activity on hAR, suggesting that the inability of p53 mutants to down-regulate hAR is, in part, responsible for the metastatic phenotype.

Reactive oxygen species modulate endothelin-I-induced c-fos gene expression in cardiomyocytes

OBJECTIVES

Recent evidence indicates that reactive oxygen species (ROS) may act as second messengers in receptor-mediated signaling pathways. The possible role of ROS during Et-1 stimulation in cardiomyocytes was therefore investigated.

METHODS

Intracellular ROS levels were measured with fluorescence probe 2',7'-dichlorofluorescin diacetate by confocal microscopy in cultured neonatal rat cardiomyocytes. The ROS-inducible c-fos expression was analyzed by Northern blotting and promoter activity.

RESULTS

Et-1 applied to cardiomyocytes dose-dependently increased intracellular ROS levels. The increase of ROS levels was attenuated by pretreating cardiomyocytes with Et-A receptor antagonist-BQ485, but not with Et-B receptor antagonist. Cardiomyocytes pretreated with catalase or an antioxidant N-acetylcysteine (NAC) reduced Et-1-induced ROS levels. Et-1 or H2O2 treatment of cardiomyocytes rapidly induced the expression of an immediate early gene c-fos. Et-1-treated cardiomyocytes enhanced the c-fos gene expression as revealed by functional analysis using a reporter gene construct containing c-fos promoter region (-2.25 kb) and reporter gene chloramphenicol acetyltransferase. The induction of mRNA levels and the promoter activities of c-fos gene by Et-1 or H2O2 were abolished by pretreating cardiomyocytes with catalase or NAC. Cells transiently transfected with the dominant positive mutant of p21ras (RasL61) led to a significant increase in intracellular ROS. Concomitantly, the mRNA levels and the promoter activities of c-fos were also induced. In contrast, cells transfected with the dominant negative mutant of Ras (RasN17) inhibited Et-1-induced ROS. Consistently, the increase of c-fos mRNA levels and promoter activities by Et-1 were also inhibited.

CONCLUSIONS

These findings clearly indicate that Et-1 treatment to cardiomyocytes can induce ROS via Ras pathway and the increased ROS are involved in the increase of c-fos expression. Our studies thus emphasize the importance of ROS as second messengers in Et-1-induced responses on cardiomyocytes.

Intracellular antibodies as a new class of therapeutic molecules for gene therapy

Intracellularly expressed antibodies, referred to as "intrabodies" can be designed to bind and inactivate target molecules inside cells. In our previous study, mammalian cells were transduced to produce an anti-gp120 single-chain intrabody sFv105 to inactivate human immunodeficiency virus type-1 (HIV-1) infection. Here, an inducible expression vector was constructed in which the sFv105 intrabody, which reacts with the CD4-binding site of HIV-1 gp120, is under the control of the HIV-1 long terminal repeat (LTR)/promoter. The sFv105 intrabody is inducibly expressed after HIV-1 infection or in the presence of Tat protein and is retained intracellularly. A human CD4+ lymphocyte line transformed with the expression vector exhibits resistance to the virus-mediated syncytium formation and a decreased ability to support HIV-1 production. Surface gp120 expression is markedly reduced and surface CD4 is restored to normal following HIV-1 infection in the transformed lymphocytes. Cell-surface phenotype, replication rate, morphology, and response to mitogenic stimulation of the transformed cells are also normal. Thus, intrabodies are a new class of active molecules that may be useful for the gene therapy of acquired immunodeficiency virus (AIDS) and other diseases.