Endothelin-1 secretion from cultured vascular endothelial cells of DOCA-salt hypertensive rats

The profile of endothelin-1 (ET-1) release from cultured vascular endothelial cells (ECs) obtained from deoxycorticosterone acetate (DOCA)-salt hypertensive rats, was examined and compared with that from normotensive sham rats. ET-1 release from ECs was increased in a time-dependent manner, and the level of DOCA-salt hypertensive rats was higher than that of sham rats. Incubation of ECs with transforming growth factor (TGF)-beta 1 or thrombin resulted in a significant increase in the ET-1 release, while FK409, a novel nitric oxide donor, produced a dose-dependent decrease in the release. In the case of ECs from DOCA-salt hypertensive rats, the potencies of TGF-beta 1- or thrombin-induced action was much less than that seen with sham rats, while the difference of reactivity to FK409 was not observed between ECs of DOCA-salt rats and sham rats. Thus, ET-1 production in ECs appears to be up-regulated in DOCA-salt hypertensive rats. In addition, there seems to be an abnormalities in the signaling pathway via TGF-beta 1- or thrombin-induced enhancement of ET-1 production in ECs of DOCA-salt hypertensive rats.     

Production of hydrogen peroxide by alveolar macrophages from rats exposed to subacute and chronic hypoxia

The optimum age for surgical closure of cleft palate remains an unresolved question, despite the fact that many clinicians have studied the issue since the 1930s. This article reviews the debate as it has taken shape over the last several decades, with a prospective view toward how standards of practice may evolve in the foreseeable future.     

Transformation of tracheal epithelium exposed in vitro to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)

Using an organ culture/cell culture system, we transformed rat tracheal epithelial cells in vitro by exposure to MNNG. Ten tracheal organ cultures per group were exposed twice (at days 3 and 6) to 0,0.001, 1.0 or 10.0 microgram MNNG/ml of medium. Following this exposure, the explants were placed on the bottom of culture dishes to initiate epithelial cell outgrowths and establish primary cultures. Each explant was replanted 8-10 times to produce multiple outgrowths. The number of primary cultures and the number of subsequently established cell lines obtained was carcinogen-dose-dependent. The average number of primary epithelial cell cultures per explant after exposure to 0, 0.001 1.0 and 10.0 microgram MNNG/ml was 1.3, 1.5, 3.3, and 4.6, respectively. The average yield of cell lines per explant in these groups was 0, 0.8, 1.3, and 2.0, respectively. It is apparent that cell lines could only be established from carcinogen-exposed epithelium. These cell lines are currently being tested for tumorigenicity in vivo. To date, of 35 cell lines tested between the 5th and 15th passages, 5 cell lines from the 10 microgram MNNG/ml group and 2 from the 1.0 microgram MNNG/ml group have produced palpable tumors upon injection into immunosuppressed recipients.     

Na(+)-H+ exchanger in isolated epithelial tracheal cells from sheep. Involvement in tracheal proton secretion

Heavy metals have been shown to exert immunotoxic effects on humoral immunity. To ascertain the mechanisms by which these immunotoxic effects are exerted, the effects of CdCl2 and HgCl2 on the biology of murine B-lymphocytes were studied. It was shown that CdCl2 and HgCl2 inhibited B-cell RNA and DNA synthesis. The IC50 (the concentration required to inhibit a specific B-cell function by 50%) for CdCl2 was 30 microM for RNA synthesis and DNA synthesis. The IC50 for HgCl2 was 50 and 120 nM for RNA and DNA synthesis, respectively. Cell cycle analysis revealed that B-cells were arrested throughout the cell cycle with CdCl2 and HgCl2. The inhibitory effects exerted by CdCl2 and HgCl2 were rapid, inhibiting RNA synthesis within 2 h of activation. Differentiation to Ig secretion was inhibited by CdCl2 and HgCl2 in culture and there appeared to be selective effects on specific Ig isotypes. IgG3 production was most sensitive to inhibition by CdCl2 and HgCl2 followed by IgG1 and IgG2b and then IgM and IgG2a. Changes in the expression of B-cell surface antigens induced by LPS were also influenced by CdCl2. LPS-induced increases in class II MHC expression was inhibited by CdCl2, as was the constitutive expression of class I MHC antigen. A summary of the IC50 for CdCl2 and HgCl2 are presented. In summary, both CdCl2 and HgCl2 exert early, inhibitory effects on B-cell activation. This is manifested by the inhibition of RNA, DNA and antibody synthesis. However, selective effects on the production of specific Ig isotypes by these metals may influence the ability of B-cells to mount effective immune responses to pathogens.     

Antioxidant supplementation and respiratory functions among workers exposed to high levels of ozone

Ozone exposure has been related to adverse respiratory effects, in particular to lung function decrements. Antioxidant vitamins are free-radical scavengers and could have a protective effect against photo-oxidant exposure. To evaluate whether acute effects of ozone on lung functions could be attenuated by antioxidant vitamin supplementation, we conducted a randomized trial using a double-blind crossover design. Street workers (n = 47) of Mexico City were randomly assigned to take daily a supplement (75 mg vitamin E, 650 mg vitamin C, 15 mg beta carotene) or a placebo and were followed from March to August 1996. Pulmonary function tests were done twice a week at the end of the workday. During the follow-up, the mean 1-h maximum ozone level was 123 ppb (SD = 40). During the first phase, ozone levels were inversely associated with FVC (beta = -1.60 ml/ppb), FEV1 (beta = -2.11 ml/ppb), and FEF25-75 (beta = -4.92 ml/ppb) (p < 0.05) in the placebo group but not in the supplement group. The difference between the two groups was significant for FVC, FEV1, and FEF25-75 (p < 0.01). During the second phase, similar results were observed, but the lung function decrements in the placebo group were smaller, suggesting that the supplementation may have had a residual protective effect on the lung. These results need to be confirmed in larger supplementation studies.     

Lysosomal alterations in cultured macrophages exposed to anorexigenic and psychotropic drugs

Intravenous urography was performed in fourteen children with Ullrich-Turners syndrome. Renal abnormalities have been noted in twelve cases (85,7%). The most frequent kidney anomalies were malrotations (28,5%), horseshoe kidneys (21,4%) and double kidneys (21,4%). Malformations of kidney are thus a very frequent feature in Ullrich-Turners syndrome. It is therefore recommendable to perform in any case of Ullrich-Turners syndrome an intravenous urography, since these abnormalities are clinically latent.     

Calcium dynamics in cultured heart cells exposed to defibrillator-type electric shocks

Spatial and temporal changes in intracellular calcium ion concentration and transmembrane voltage were recorded optically from single-isolated cultured chick-embryo heart cells exposed to high-voltage, defibrillator-type shocks. Fluorescence changes were measured during 5 msec electric shocks of field strengths up to 56 volts/cm in single myocytes stained with a Ca(++)-sensitive or voltage-sensitive dye. Shocks caused a reversible period of depolarization, elevated cytosolic Ca++, and refractoriness. Intracellular Ca++ elevation had two temporal phases: first, a Ca++ spike with morphology independent of shock intensity; and second, a prolonged Ca++ elevation with a shock-intensity-dependent magnitude and duration, and with greatest Ca++ elevation at the poles of the cell adjacent to the electrodes. The prolonged elevation (second phase) was initiated earlier at the anode-facing pole of the cell than at the cathode-facing pole. These results suggest that postshock Ca++ entry consists of two parts: early normal entry through excitation channels plus a prolonged elevation which may be related to cellular damage.     

Evidence that glucose metabolism regulates leptin secretion from cultured rat adipocytes

Circulating leptin secreted from adipocytes is correlated with fat mass and plasma insulin concentrations in humans and rodents. Plasma leptin, insulin, and glucose decrease during fasting and increase after refeeding; however, the underlying mechanisms regulating the changes of leptin secretion are not known. To investigate the role of insulin-stimulated glucose metabolism in the regulation of leptin secretion, we examined the effects of insulin and inhibitors of glucose transport and metabolism on leptin secretion from rat adipocytes in primary culture. Insulin (0.16-16 nM) increased leptin secretion over 96 h; however, the increase in leptin was more closely related to the amount of glucose taken up by the adipocytes (r = 0.64; P < 0.0001) than to the insulin concentration per se (r = 0.20; P < 0.28), suggesting a role for glucose transport and/or metabolism in regulating leptin secretion. 2-Deoxy-D-glucose (2-DG), a competitive inhibitor of glucose transport and phosphorylation, caused a concentration-dependent (2-50 mg/dl) inhibition of leptin release in the presence of 1.6 nM insulin. The inhibitory effect of 2-DG was reversed by high concentrations of glucose. Two other inhibitors of glucose transport, phloretin (0.05-0.25 mM) and cytochalasin-B (0.5-50 microM), also inhibited leptin secretion. Inhibition of leptin secretion by these agents was proportional to the inhibition of glucose uptake (r = 0.60 to 0.86; all P < 0.01). Two inhibitors of glycolysis, iodoacetate (0.005-1.0 mM) and sodium fluoride (0.1-5 mM), produced concentration-dependent inhibition of leptin secretion in the presence of 1.6 nM insulin. In addition, both 2-DG and sodium fluoride markedly decreased the leptin (ob) messenger RNA content of cultured adipocytes, but did not affect 18S ribosomal RNA content. We conclude that glucose transport and metabolism are important factors in the regulation of leptin expression and secretion and that the effect of insulin to increase adipocyte glucose utilization is likely to contribute to insulin-stimulated leptin secretion. Thus, in vivo, decreased adipose glucose metabolism may be one mechanism by which fasting decreases circulating leptin, whereas increased adipose glucose metabolism would increase leptin after refeeding.     

Factors that influence the suppression of pulmonary antibacterial defenses in mice exposed to ozone

Exposure to ozone (O3) has been shown to increase susceptibility of mice to bacterial infection; however, the underlying mechanism has not been well elucidated. This study investigated the effect of O3 exposure on the ability of mice to combat an infectious challenge of Streptococcus zooepidemicus. Following a 3-h exposure to either air, 0.4 ppm O3, or 0.8 ppm O3, 5- and 9-week-old mice received an aerosol infection of bacteria. Intrapulmonary killing of the bacteria was impaired in the O3-exposed mice. The effect was most severe at the higher dose of O3 in the younger mice, and showed good correlation to subsequent mortality assessed over a 20-day period. Alveolar macrophages (AM) from O3-exposed mice had an impaired ability to phagocytose the bacteria. Additionally, prostaglandin E2 (PGE2) levels, which are known to depress AM function, were increased in the bronchoalveolar lavage fluid of the younger mice following exposure to O3, while pretreatment with indomethacin in the drinking water blunted the increased of PGE2 and reduced O3 enhanced mortality from 53 to 33%. The data show that O3 inhalation can reduce the defensive capability of the murine lung and that this is associated with a reduction in AM phagocytosis. The defect is more marked in young mice, suggesting that they may be more susceptible to oxidant exposure. Further studies are required to distinguish between direct toxicity of O3 on the AM and indirect suppression due to modulation of pharmacologic or inflammatory mediators.     

Increased oxidant resistance of alveolar macrophages isolated from rats repeatedly exposed to cadmium aerosols

This study investigated potential mechanisms of oxidant resistance in alveolar macrophages (AM) isolated from Lewis rats exposed repeatedly to cadmium aerosols. Macrophages from Cd-adapted animals significantly greater resistance to oxidant-induced cytotoxicity than control cells when challenged with hydrogen peroxide in vitro. Elevations in glutathione peroxidase and glutathione reductase activities were associated with increased oxidant tolerance but catalase activity was unchanged. Metallothionein (MT) expression (protein and mRNA) was dramatically up-regulated in response to in vivo Cd exposure. A study using immunocytochemistry and in situ hybridization techniques revealed significantly heterogeneity in the expression of metallothionein by AMs. The percentage of AMs positive for MT (protein and mRNA) and the degree of MT expression within individual cells increased in response to additional Cd exposures. A putative state of activation was suggested by differences in size and number of inclusion bodies in macrophages from Cd-adapted animals and by secretion of a cytokine with interleukin-1-like characteristics. In summary, AMs from Cd-adapted animals are distinguished from control cells with respect to: (1) increased oxidant resistance, (2) secretion of cytokines, (3) elevations in enzymes associated with glutathione metabolism, and (4) up-regulation in metallothionein expression.     

Failure to learn to escape by rats previously exposed to inescapable shock is partly produced by associative interference.

2 experiments demonstrated that the effects of prior exposure to inescapable shock on the subsequent acquisition of an escape response in rats is determined by the nature of the contingency that exists between responding and shock termination during the escape learning task, and not by the amount of effort required to make the response or the amount of shock that the S is forced to receive during each trial. Exp I, using 48 male Simonsen rats, showed that inescapably shocked Ss did not learn to escape shock in a shuttle box if 2 crossings of the shuttle box were required (fixed ratio, FR, -2) to terminate shock, but did learn this FR-2 response if a brief interruption of shock occurs after the 1st crossing of the FR-2. Exp II with 72 Ss showed that inescapably shocked Ss learned a single-crossing escape response as rapidly as did controls, but were severely retarded if a brief delay in shock termination was arranged to follow the response. Results are discussed in terms of the learned helplessness hypothesis, which assumes that prior exposure to inescapable shock results in associative interference. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contractile responses and structure of small bronchi isolated from rats after 20 months' exposure to ozone

Short-term exposure to high concentrations of ozone has been shown to increase airway responsiveness in normal humans and in all laboratory animal species studied to date. While our knowledge concerning the pulmonary effects of single exposures to ozone has increased rapidly over recent years, the effects of repeated exposures are less understood. The goal of the present study was to determine whether airway responsiveness is increased after near-lifetime exposure to ozone. Airway segments representing approximately eighth generation airways were isolated from Fischer 344 rats of both genders that had been exposed for 6 hr per day, 5 days per week for 20 months to 0, 0.12, 0.5, or 1.0 parts per million (ppm) ozone. Circumferential tension development was measured in isolated airways in response to bethanechol, acetylcholine, and electrical field stimulation. Responsiveness of the airways to the contractile stimuli was described by the effective dose or frequency that elicited half-maximum contraction (ED50) and the maximum response. Since ozone exposure is associated with remodeling of peripheral airways, smooth muscle area was determined and tension responses were normalized to the area measurements. Before normalization of tension data to smooth muscle area, neither the ED50 nor maximum response of small bronchi to the contractile stimuli was altered after chronic ozone exposure. Smooth muscle area was greater in airways isolated from animals that had been exposed to 0.5 ppm ozone. After accounting for smooth muscle area, maximum responses of the small bronchi isolated from male rats were significantly reduced after 0.12 and 0.5 ppm ozone. Although not significant statistically, a similar trend was observed in airways isolated from female rats. These results suggest that the increase in airway responsiveness associated with acute ozone exposure does not persist during near-lifetime exposure. Although the mechanism responsible for the adaptation to the effects of O3 on airway responsiveness is unknown, the results indicate that smooth muscle cell function was compromised by the chronic exposure. The mechanism(s) responsible for mediating this effect and the relevance of these results to humans remains to be determined.     

Uremic medium increases cytokine-induced PAI-1 secretion by cultured endothelial cells

The overall fibrinolytic activity is depressed in patients with chronic renal failure where a prothrombotic state is described, thereby enhancing the risk of vascular occlusive events. The mechanism responsible for fibrinolysis derangement has not yet been elucidated. To evaluate the effect of the uremic environment on the fibrinolytic activity of endothelial cells, we studied plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAI-1) production by human umbilical vein endothelial cells (HUVEC) in culture, exposed either to uremic or normal sera, before and after cytokine stimulation. Twenty uremics were studied: 11 were on conservative dietary treatment and nine were on maintenance hemodialysis. Eight healthy subjects served as controls. Before cytokine stimulation, no difference in the HUVEC supernatant concentration of t-PA and PAI-1 was found among the groups studied. After stimulation with interleukin (IL)-1 and tumor necrosis factor (TNF)-alpha, the HUVEC supernatant levels of PAI-1 in the uremics were higher than in the controls, whereas the supernatant levels of t-PA did not differ. Our data provide evidence that uremic serum, in concert with IL-1 or TNF-alpha, can enhance PAI-1 secretion by endothelial cells, thereby depressing the fibrinolytic system. This impaired endothelial fibrinolytic response to hypercoagulation could favor vascular events, which are the major cause of morbidity and mortality in patients with chronic uremia.     

PMA inhibits both spontaneous and glucocorticoid-mediated leptin secretion by human omental adipose tissue explants in vitro

The activation of PKC by the acute administration of the phorbol ester PMA (1 microM, 2h) to omental adipose tissue explants in vitro resulted in a marked (about 75%) and persistent (up to at least 96 h) inhibition of leptin secretion. This PKC-mediated inhibition was not observed after the administration of an inactive phorbol ester (phorbol 12,13-dicecanoate). The inhibition by PMA of leptin secretion was not restricted to the spontaneous secretion, but blocked also effectively the leptin response to a powerful stimulus, such as the glucocorticoid dexamethasone. As the PKC activity has been shown to be elevated during fasting, the negative relation here described between PKC activity and leptin secretion could be of physiological relevance.     

Glycoprotein secretion in the mouse submandibular gland as revealed by radioautography after L-3H-fucose injection

Glycoprotein secretion in the mouse submandibular gland was investigated by light microscope radioautography of semi-thin sections after the administration of L-3H-fucose. The incorporation of the precursor in the acini was negligible. 3H-fucose was taken up in the paranuclear region of the cells lining the intercalated, secretory, striated and excretory ducts. This labeling pattern was interpredted as addition of the precursor to glycoproteins within the Golgi apparatus. Incoropration in the intercalated duct was restricted to the cells with fine cytoplasmic granules. The glycoproteins synthesized by the intercalated and secretory ducts were transported to the saliva by the secretion granules. It is assumed that the glycoproteins synthesized in the striated and excretory ducts are plasma membrane glycoproteins which seem to renew continuously. Quantitation of the radioautographs supplied data concerning the incorporation of 3H-fucose into newly synthesized glycoproteins as well as the renewal of the labeled macromolecules in each duct.     

Hematological changes in rats exposed to weak electromagnetic fields

A number of experimental studies report that biological systems can be affected by in vivo exposure to low frequency and extremely low frequency electromagnetic fields. However, attempts to independently replicate some of these studies have shown the reported effects to be elusive. The difficulty in replicating results could be due to unidentified physical and/or biological parameters which may affect the response of a sample to electromagnetic fields. The present paper reports a failure to independently replicate a study showing that in vivo exposure to a pulsed magnetic field of 1.5 mT caused significant changes on plasma proteins in rats. Although the possibility has to be considered that the results from the seminal work were artifactual, substantial differences in levels of plasma proteins were observed between the control groups of the two studies indicating that the animals in the first study had an infectious illness. This observation supports the hypothesis that the state of physiological equilibrium of a biological system is crucial to its response to a potentially effective electromagnetic field.     

Insulin secretion in pancreatic islets from rats with cirrhosis

Cirrhosis was induced in rats by subcutaneous injections of CCl4 for 13 or 17 weeks. The morphology of the pancreatic islets from the CCl4-treated rats was found to be normal. The CCl4-treated rats had lower fasting serum glucose levels and higher serum insulin levels than the controls. After an oral glucose load (3 g/kg body weight), glucose levels in CCl4-treated rats stayed within the normal range, whereas the serum insulin levels remained higher with a delayed decline of insulin with time. In vitro perifusion of islets from the CCl4-treated rats showed that the response to 16.7 mmol/l glucose was reduced with both lower total insulin output and stimulated insulin output, whereas the patterns of first and second phase of insulin release did not differ. The insulin content of the perifused islets was not affected by 13 weeks of CCl4 treatment. Islets from rats treated with CCl4 for 17 weeks showed normal secretory response to 20 mmol/l L-arginine. Taken together, the results, showing normal or reduced capacity for insulin secretion, suggest that the hyperinsulinemia accompanying CCl4-induced cirrhosis is not due to increased secretion of the pancreatic islets. It may rather be associated with decreased insulin degradation by the liver with cirrhosis.     

脂多糖预刺激对大脑皮质星形胶质细胞和小胶质细胞NO分泌水平的影响

目的:探讨脂多糖(lipopolysaccharide,LPS)预刺激对大脑皮质星形胶质细胞和小胶质细胞NO分泌水平的影响.方法:体外分离、纯化、培养星形胶质细胞和小胶质细胞.培养细胞分设LPS预刺激组(先用10 ng/ml LPS预刺激18 h后,改用1μg/ml的LPS再刺激),LPS 10 ng/ml单次刺激组,LPS 1μg/ml单刺激组与对照组(不用LPS刺激).分别于LPS刺激后6、24、48 h收集细胞培养上清,用硝酸还原酶法检测NO水平.结果:星形胶质细胞和小胶质细胞,LPS预刺激组在24 h后,NO水平增加,明显高于相应时间点LPS 1 μg/ml单次刺激组(P均<0.05);其中,星形胶质细胞分泌NO的时间较长,可持续到48 h,与相应单次刺激组比较差异具有统计学意义(P<0.05).结论:LPS体外预刺激神经胶质细胞,可促使细胞分泌NO的水平升高.     

Hypoxia stimulates cytokine production by villous explants from the human placenta

It has been hypothesized that inadequate placentation in the hypertensive disorder of pregnancy known as preeclampsia creates foci of placental ischemia/hypoxia leading to the elaboration of factors that compromise systemic endothelial function to produce disease sequelae. As tumor necrosis factor-alpha (TNF alpha) and interleukin-1 (IL-1) are inflammatory cytokines capable of eliciting endothelial cell dysfunction, we investigated whether the production of these inflammatory cytokines by cultured villous explants from the human placenta was affected by incubation in reduced oxygen (2% O2). The term placenta produced TNF alpha, IL-6, and low levels of IL-1alpha and IL-1beta under standard tissue culture conditions. Hypoxia significantly increased TNF alpha, IL-1alpha, and IL-1beta production by 2-, 6-, and 23-fold, respectively, but did not affect IL-6 production. Further, cytokines were immunolocalized to the syncytiotrophoblast layer as well as to some villous core cells. Hypoxic regulation of placental TNF alpha and IL-1beta production also appeared to differ based on gestational age. Finally, treatment with either cobalt chloride or an iron chelator mimicked the hypoxic response, suggesting that stimulation of placental cytokine production may involve a heme-containing, O2-sensing protein. These results suggest that placental hypoxia can lead to the elaboration of inflammatory cytokines, which may contribute to the pathophysiology of preeclampsia.     

Modifications of thalamo-cortical circuitry in rats prenatally exposed to ethanol

The present study aimed to investigate the organization of thalamo-cortical connections in adult rats exposed to ethanol during the last week of foetal life. Animals underwent thalamic injections of lectin-conjugated HRP. Results demonstrate that the thalamic-recipient zone of sensorimotor cortex is significantly thinner in ethanol-exposed than in control cases. Animals exposed to ethanol also display aberrant thalamo-cortical terminations in layer 5a. Neurones of origin of cortico-thalamic projections are normally located in layers 5 and 6; they appear quantitatively comparable in control and ethanol-exposed cases. Developmental alterations underlying the establishment of anomalous thalamo-cortical relationships are discussed.