Inhibition of adenylate cyclase of rat hepatic membranes by glycosaminoglycans

Glycosaminoglycans are long non-branched polysaccharides composed of repeating disaccharide units. In a previous in vitro study we have shown that such molecules are able to modulate substrate phosphorylation catalyzed by cAMP-dependent protein kinase. Here, we investigate the impact of glycosaminoglycans, such as heparan sulfate, dermatan sulfate, chondroitin 4- and 6-sulfate, keratan sulfate and hyaluronic acid upon adenylate cyclase, which directly regulates cAMP-dependent protein kinase activity via cAMP synthesis. In rat liver plasma membrane preparation we have determined forskolin- and guanosine-5'-beta, gamma-imidotriphosphate-induced cAMP formation catalyzed by adenylate cyclase in the presence of increasing concentrations of glycosaminoglycans. The results indicate that glycosaminoglycans strongly influence enzymic conversion of ATP into cAMP. The highest reduction of adenylate cyclase activity is observed in the presence of dermatan sulfate and heparan sulfate. Moreover, the inhibitory effect of these two glycosaminoglycans is higher when guanosine-5'-beta, gamma-imidotriphosphate, instead of forskolin, is used as stimulator of adenylate cyclase. Further characterization of enzyme inhibition mediated by dermatan sulfate shows that this molecule exerts an inhibitory effect of mixed type.     

Induction of circulating IL-1 receptor antagonist by IFN treatment

This study was undertaken to determine whether IFN induce IL-1 receptor antagonist (IL-1Ra), a specific inhibitor of IL-1. Plasma samples were obtained from healthy volunteers (n = 5) and patients with chronic hepatitis C (n = 5) treated with IFN-alpha, and from patients with renal cell carcinoma (n = 6) treated with IFN-gamma and assayed for IL-1Ra by a specific radioimmunoassay. Both types of IFN were administered subcutaneously. In vitro studies were carried out with PBMC from healthy volunteers. A single, low and nontoxic dose (1 x 10(6) U) of IFN-alpha induced circulating IL-1Ra, which reached peak levels within 12 h. This effect was dose-dependent and more pronounced with a higher dose (5 x 10(6) U). Peak IL-1Ra levels 12 h after 5 x 10(6) U IFN-alpha were 4.16 +/- 0.35 ng/ml in healthy volunteers and 5.7 +/- 0.73 ng/ml in patients with chronic hepatitis C (difference not significant). Thereafter levels declined but remained elevated for 24 h. IFN-gamma treatment led only to a modest increase of circulating IL-1Ra even at a dose of 400 micrograms; this dose, however, was associated with side effects similar to those seen after injection of 5 x 10(6) U IFN-alpha. PBMC stimulated with IFN-alpha or IFN-gamma produced IL-1Ra in vitro. The induction of IL-1Ra may contribute to the antiviral, anti-inflammatory, and antiproliferative effects of IFN.     

Abciximab-induced thrombopenia during treatment of acute coronary syndromes by angioplasty

ReoPro (abciximab) is the Fab fragment of a chimeric monoclonal antibody directed against platelet glycoprotein IIb-IIIa. Its efficacy to prevent ischaemic complications after PTCA has been demonstrated in 3 studies: EPIC, EPILOG, UPTAKE. One hundred and sixty five cases of thrombocytopenia (< 100,000/microliter) were reported in a series of 5461 patients randomized in these 3 studies (i.e. 3.0%), including 46 (2.03%) with placebo and 119 (3.73% with abciximab. Among the 2270 patients randomized to receive placebo, 11 (0.48%) cases of severe thrombocytopenia (< 50,000/microliter) were observed versus 34 (1.07%) with abciximab. Major acute thrombocytopenia (< 20,000/microliter and < 24 hours) occurred in 0.60% (20 patients) of cases with abciximab. Their mechanism remains unknown. A therapeutic challenge did not modify either their incidence, or their severity. The development of thrombocytopenia did not worsen the patient's prognosis and course was always favourable. Twenty five cases of thrombocytopenia (0.60%), including 3 cases of acute major thrombocytopenia (0.08%) were spontaneously reported in France among the first 4000 patients treated with abciximab post-marketing. All patients treated with abciximab must be monitored by platelet count, 2 to 4 hours after the bolus administration, then 12 and 24 hours later. These platelet counts should be performed on 3 tubes (EDTA, citrate, heparin) in order to eliminate pseudothrombocytopenia and a differential diagnosis. In the case of true thrombocytopenia (< 10,000/l), treatment should be suspended and the platelet count should be repeated daily until return to normal. In the case of thrombocytopenia less than 60,000/microliter, heparin and aspirin should also be systematically discontinued and, below 50,000/microliter, platelet transfusion is justified.     

Evaluation in dogs of cross-circulation in the treatment of acute hepatic necrosis induced by yellow phosphorus

The efficacy of cross-circulation in the treatment of acute liver failure has been evaluated in dogs. Four of 5 dogs administered a dose of yellow phosphorus that is lethal 90% of the time survived after treatment by cross-circulation of whole blood for between 1 and 8 hr with a normal dog. In 2 normal unmatched dogs plasma cross-circulations were performed over a period of 31 days without any clinical or laboratory manifestation of hypersensitivity except for lymphocytotoxic antibody titer rise. The results suggest that whole blood cross-circulation is effective and imply that a single donor could be utilized for prolonged periods of plasma cross-circulation with avoidance of immunological consequences of whole blood exchange.     

Acute modulation of rat hepatic lipid metabolism by sulphur-substituted fatty acid analogues

A single oral dose of two 3-thia (3-thiadicarboxylic and tetradecylthioacetic acids) and of 4-thia (tetradecylthiopropionic acid) fatty acids were administered to normolipidemic rats and their effects on lipid metabolism over a 24 hr period were studied. All three thia fatty acids could be detected in plasma 2 hr after treatment. Tetradecylthioacetic and tetradecylthiopropionic acids were detected in different hepatic lipid fractions but were incorporated mainly into hepatic phospholipids. Two hours after administration hepatic mitochondrial beta-oxidation and the total liver level of long-chain fatty acyl-CoA increased with a concomitant decrease in saturated fatty acids, total hepatic malonyl-CoA and plasma triacylglycerol levels in the 3-thia fatty acid groups. Tetradecylthiopropionic acid administration caused a decrease in mitochondrial beta-oxidation and an increase in plasma triacylglycerol at 24 hr. The activities of key lipogenic enzymes were unaffected in all treatment groups. Plasma cholesterol level was reduced only at 8 hr in 3-thiadicarboxylic acid treated rats although 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase was suppressed already at 2, 4, 8 and 12 hr. The results show that thia fatty acids are rapidly absorbed and are systemically available after oral administration but the 3-thia fatty acids reached systemic circulation more slowly and less completely than the 4-thia fatty acid. Very low levels of the thia fatty acids are detected in plasma 24 hr after a single administration. They are incorporated into all hepatic lipid classes, especially phospholipids. Rapid incorporation of a non beta-oxidizable thia fatty acid into hepatic lipids may cause a diversion of other fatty acids from glycerolipid biosynthesis to mitochondrial beta-oxidation. Stimulation of mitochondrial beta-oxidation and suppression of HMG-CoA reductase are primary events, occurring within hours, after 3-thia fatty acid administration. The hypotriglyceridemic effect of the 3-thia fatty acids observed at 2-4 hr is independent of the activities of key lipogenic and triacylglycerol synthesising enzymes.     

Liver granulomas in schistosomiasis: mast cell-dependent induction of SCF expression in hepatic stellate cells is mediated by TNF-alpha

Abnormalities of vasomotor tone are characteristic of heart failure. This study was designed to assess the effects of chronic heart failure on endothelium-dependent relaxation in both large conduit arteries and small resistance vessels and to determine whether or not impaired nitric oxide (NO) production is involved. Segments of pulmonary artery (PA), abdominal aorta (AA), and small mesenteric artery (MA) were harvested from rats with heart failure resulting from coronary artery ligation and from sham-operated controls. Organ-bath experiments done in the presence of indomethacin to avoid the influence of vasodilatory prostanoids demonstrated that relaxation to acetylcholine (ACh) was impaired in the PA but not the AA or MA of the group with heart failure. Endothelium-independent relaxation to nitroglycerin was not significantly affected by the development of heart failure. Constriction to prostaglandin (PG) F(2alpha) was enhanced in PA but not in AA or MA segments. Preincubation with N(omega)-nitro-L-arginine (NNA) to inhibit the production of NO increased baseline force in vessels from all three beds, but the effect was greatest in the PA. Although relaxation to ACh was significantly diminished by NNA in the PA, it was not completely abolished. Furthermore, ACh-mediated relaxation in the presence of NAA was still impaired in the group with heart failure compared with the sham-operated control group. NNA had only mild effects on ACh-mediated relaxation in MA. These results demonstrate that (a) the mediators of endothelium-dependent relaxation may vary throughout the arterial circulation, (b) the contribution of NO to endothelium-dependent relaxation is substantial in PA and minimal in mesenteric resistance vessels, (c) endothelium-dependent relaxation is not uniformly impaired throughout the arterial bed by the development of heart failure, and (d) although a defect in NO production may account for enchanced vasoconstriction seen in response to PGF(2alpha), it does not account for the diminished vasodilatory response to ACh in this experimental model of heart failure.     

Phase transformation behavior of gamma titanium aluminide alloys during supertransus heat treatment

Microstructure evolution in a wrought near-gamma titanium alloy, Ti-45Al-2Cr-2Nb, was investigated by a series of heat treatments comprised of initial heating high in the alpha-plus-gamma phase field followed by short-time heating in the single-phase alpha field. The initial heating step led to a dispersion of gamma particles which pinned the alpha grain boundaries. The kinetics of the gamma grain dissolution during subsequent heating in the single-phase field were interpreted in terms of models for both interface reaction-controlled and diffusion-controlled processes. The model for diffusion-controlled dissolution yielded predictions comparable to the observed times, whereas the model for interface reaction-controlled behavior predicted dissolution kinetics over an order of magnitude slower than observed. The growth of the alpha grains, both before and after the dissolution of the gamma phase, was also modeled. Section size limitations to the ability to use supertransus heating to obtain uniform and moderately fine alpha grain sizes were examined using the transformation models and a simple heat transfer analysis approach. The results were validated through the heat treatment of subscale and full-scale forgings. This article is based on a presentation made in the symposium “Fundamentals of Gamma Titanium Aluminides,” presented at the TMS Annual Meeting, February 10–12, 1997, Orlando, Florida, under the auspices of the ASM/MSD Flow & Fracture and Phase Transformations Committees.     

Review: molecular pathogenesis of hepatic acute porphyrias

The molecular cloning of cDNA and genes encoding enzymes of the haem biosynthetic pathway have permitted the genetic defects underlying acute intermittent porphyria (AIP) and hereditary coproporphyria to be unravelled. In AIP, many different gene abnormalities have been documented since 1989. The prevalence of specific defective alleles among AIP families depends on which human population is studied. Founder effects are likely to account for a high frequency of a single mutation in Finland and, to a lesser extent, in Holland, while many other mutations have only been found once, each of them in a single family. In hereditary coproporphyria several different mutations have already been identified since 1994, suggesting that a large allelic heterogeneity also exists. The search for mutations in variegate porphyria has just started since the recent publication of the human cDNA sequence. Direct detection of the mutations using DNA analysis brings a growing contribution to the detection of asymptomatic carriers among relatives of porphyric patients and will, therefore, improve the prevention of acute attacks.     

Changes of ultrasonography and two serum biochemical indices for hepatic fibrosis in schistosomiasis japonica patients one year after praziquantel treatment

OBJECTIVE: To observe the changes of abdominal sonography and 2 biochemical indicators for hepatic fibrosis before and after treatment with praziquantel in schistosomiasis japonica patients. METHODS: Fifty-five persons infected with Schistosoma japonicum and treated with praziquantel were examined with ultrasonography and serum hyaluronic acid (HA) and type III procollagen (PC III) before and 1 year after treatment, and their data were compared with those in 55 normal controls. RESULTS: With comparison of the data before praziquantel treatment, the length of the left liver lobe and the spleen in 55 patients all decreased (P < 0.01) 1 year after treatment. No significant change was seen in interior diameter (d) of the portal vein, while a decrease in the ratio of the exterior diameter (D) and interior diameter of the second branch of the portal vein was very significant (P < 0.01). Compared with the data in normal control, significantly higher levels in the thickness of the left lobe, the maximum oblique diameter of the right lobe, the length of the spleen, spleen index, the interior diameter of the portal vein and D/d ratio were seen in the patients both before and after treatment. The abnormal rate of the 2 serum parameters for hepatic fibrosis decreased significantly after treatment. CONCLUSIONS: Parameters of hepatic fibrosis either by ultrasonography or by the 2 biochemical tests showed a significant improvement in 55 patients 1 year after treatment, although some of the indices did not yet return to normal levels.     

Distribution of metal droplets in top slags during ladle treatment

Abstract

The investigation focused on the mixing of the metal and slag phases during ladle refining from the point of tapping the EAF to casting. Steel droplet distributions were determined for slag samples taken at different stages in the ladle refining process at two different steel plants in Sweden. The droplet distributions were determined using light optical microscopy and classification according to the standard SS111116. Sample analysis results showed the slag samples taken before vacuum degassing to contain the greatest concentration of steel droplets. The total interfacial area between the steel droplets and slag was determined to be 3–14 times larger than the projected flat interfacial area between the steel and slag. The effects of slag viscosity and reactions between steel and slag on metal droplet formation in slag were also considered.     

Methods for measuring the modulation transfer function of gamma camera systems

The MTFs of three different gamma camera systems have been measured using two methods. In one method a step function was used as the object and the calculations were made by means of a pocket calculator. This method has been compared with a conventional line source method, where a computer is needed in performing the calculations. The methods give the same results with a fairly good accuracy. Both of the methods are well suited to a regular control of the condition and functioning of a gamma camera, provided that the camera is connected to a data-processing system so that the profile curves measured can be converted into the digital form.     

Tumour cell vaccines that secrete interleukin-2 (IL-2) and interferon gamma (IFN gamma) are recognised by T cells while resisting destruction by natural killer (NK) cells

The inoculation into mice of genetically engineered tumour cells that secrete IL-2 or IFN gamma results in rejection, while unmodified parental tumour cells grow progressively. In vivo studies demonstrated synergy between IL-2 and IFN gamma leading to the rejection of the transduced tumour cells. IL-2 is required for T cell proliferation and differentiation. IFN gamma induced the upregulation of MHC class I molecules that present peptides to CD8+ T cells. Furthermore, IFN gamma can correct defects in antigen processing. Thus, for T cells, IL-2/IFN gamma-secreting double cytokine tumour cell vaccines might serve as class I+ peptide/antigen presenting depots for developing effector cells. In contrast to T cells, NK cells exert spontaneous killing and kill class I+ targets less well than those that are class I-. For this reason, they may actually have a detrimental effect by destroying a class I+ tumour cell vaccine before adequate T cell stimulation occurs. Based upon this rationale, we tested the hypothesis that an unrecognised benefit of increased class I expression by tumour cells in response to IFN gamma secretion would be to enable cytokine-secreting vaccine cells to resist destruction by NK cells. Our results demonstrated that T cells recognised tumour cells secreting IFN gamma better than those secreting IL-2. NK cells, in contrast, were inhibited by tumour cells that secreted IFN gamma, but not by those that secreted IL-2. The findings suggest that, in addition to upregulating adhesion molecules, MHC molecules, and correcting defects in antigen presentation pathways, IFN gamma secretion may protect tumour cell vaccines from early NK-mediated destruction, keeping them available for T cell priming.     

Down modulation of MHC surface molecules on B cells by suppressive immune complexes obtained from chronic intestinal schistosomiasis patients

The effect of repeated maximal isometric knee extensions on electromechanical delay (EMD) and associated muscle temperature changes were investigated on seven college aged subjects. The exercise produced a significant reduction in muscle contraction force, rate of force development and muscle conduction velocity, whilst the muscle temperature increased by 2.1 degrees C. The EMD increased from a pre-exercise value of 38.4 (SEM 3.4) ms to 55.7 (SEM 3.4) ms post-exercise. In an attempt to evaluate the effect of muscle temperature on EMD, hot and ice-water bags were placed on the quadriceps muscle to alter muscle temperature. The EMD in isometric maximal knee extension was measured at 38, 36, 34, 32 and 30 degrees C. The results showed that the EMD elongated at muscle temperatures either lower or higher than 36 degrees C. It was speculated that the increased muscle temperature might contribute to 20-25% of the EMD elongation found during the fatiguing intermittent exercise. The information of the effects of muscle temperature on EMD could be useful when evaluating the effects of strenuous exercise, in which a substantial muscle temperature change might occur, on the time delay between myoelectrical activity and force generation.     

Defensive behavior and hippocampal cell proliferation: Differential modulation by naltrexone during stress.

The present study investigated the role of endogenous opioids in the expression of defensive behaviors (DBs) and the suppression of cell proliferation (CP) in the dentate gyrus (DG) induced by exposure to predator odor, trimethyl thiazoline (TMT). Adult male rats were injected with either naltrexone (an opioid antagonist, 5 mg/kg) or saline 30 min before exposure to either TMT or a control odor. Behavior was scored for the first 15 min of odor exposure. Bromodeoxyuridine (BrdU, 200 mg/kg) was then injected, and the rats were perfused 1 hr later. Exposure to TMT increased the expression of DBs and suppressed the number of proliferating cells in the DG. Pretreatment with naltrexone attenuated the effects of TMT on DB expression but did not attenuate the effects of TMT on CP. In addition, naltrexone administration suppressed CP in the absence of TMT. These results demonstrate a dissociation between DBs and regulation of CP in the DG. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The biosynthesis of glycosaminoglycans in normal rat liver and in response to experimental hepatic injury

The synthesis of glycosaminoglycans in slices from normal and acutely injured rat liver was studied. The rates of incorporation of [14C]-glucosamine into specific types of glycosaminoglycans varied markedly; nearly 90% was incorporated into a fraction containing predominantly heparan sulfate and far less if any heparin; about 9.5% was incorporated into chondroitin 4-and 6-sulfate, and only 0.2% of the radioactivity was found in hyaluronic acid. The rate of synthesis of a fraction having several of the characteristics of keratan sulfate comprised only 0.3% of the synthesis of total glycosaminoglycans. No [14C]hexosamine was incorporated into dermatan sulfate. Following acute hepatic injury, the synthesis of glycosaminoglycans was stimulated by 80 to 100%, and the proportions of various types changed. If calculated on the basis of the specific activity of the precursors of glycosaminoglycans, which was found to be strongly reduced in injured liver, the maximum enhancement of total glycosaminoglycan synthesis was 6.6-fold 5 days after onset of liver injury.