Possible roles of insulin,glucagon, growth hormone and free fatty acids in the pathogenesis of insulin resistance of subjects with chronic liver diseases

Summary In the present investigation, insulin sensitivity and fasting levels of insulin, C-peptide, glucagon, growth hormone and free fatty acids were estimated and correlated in a population of individuals suffering from liver cirrhosis or chronic hepatitis. Insulin sensitivity, assessed by glucose disappearance rate after intravenous bolus injection of insulin, was reduced but not significantly different from controls in subjects with chronic persistent hepatitis, while it was significantly reduced in individuals suffering from chronic active hepatitis or liver cirrhosis. Insulin, glucagon, growth hormone, and free fatty acid fasting levels were higher than in healthy subjects in individuals with liver cirrhosis or chronic active hepatitis but not in subjects with chronic persistent hepatitis. C-peptide concentrations did not differ from controls in subjects with liver disease. Significant negative correlations occurred between coefficients of insulin sensitivity and fasting concentrations of insulin, glucagon, growth hormone and free fatty acids, but not with fasting levels of C-peptide. Positive relationships were present between fasting levels of free fatty acids and both glucagon and growth hormone concentrations. These results show that, unlike subjects with liver cirrhosis and chronic active hepatitis, individuals suffering from chronic persistent hepatitis do not differ from healthy subjects in insulin sensitivity and fasting levels of insulin, glucagon, growth hormone, and free fatty acids. Moreover, they suggest that both hyperinsulinemia and high concentrations of counterregulatory substances might play a role in the pathogenesis of insulin resistance in subjects suffering from chronic liver disease. Supported by grants from the Ministry of Public Education and grant No. 83/02132.04 from the National Research Council (C.N.R.), Rome.     

The JAK2 617V>F mutation triggers erythropoietin hypersensitivity and terminal erythroid amplification in primary cells from patients with polycythemia vera

The JAK2 617V>F mutation is frequent in polycythemia vera (PV) and essential thrombocythemia (ET). Using quantitative polymerase chain reaction (PCR), we found that high levels of JAK2 617V>F in PV correlate with increased granulocytes and high levels of hemoglobin and endogenous erythroid colony formation. We detected normal progenitors and those that were heterozygous or homozygous for the mutation by genotyping ET and PV clonal immature and committed progenitors. In PV patients, we distinguished homozygous profiles with normal, heterozygous, and homozygous progenitors from heterozygous profiles with only heterozygous and normal progenitors. PV patients with a heterozygous profile had more mutated, committed progenitors than did other PV and ET patients, suggesting a selective amplification of mutated cells in the early phases of hematopoiesis. We demonstrated that mutated erythroid progenitors were more sensitive to erythropoietin than normal progenitors, and that most homozygous erythroid progenitors were erythropoietin independent. Moreover, we observed a greater in vitro erythroid amplification and a selective advantage in vivo for mutated cells in late stages of hematopoiesis. These results suggest that, for PV, erythrocytosis can occur through two mechanisms: terminal erythroid amplification triggered by JAK2 617V>F homozygosity, and a 2-step process including the upstream amplification of heterozygous cells that may involve additional molecular events.      

Monoclonal antibodies against idiotypic determinant(s) of the T cell receptor from HPB-ALL cells induce IL2 production in Jurkat cells without apparent evidence of binding

Two monoclonal antibodies (mAb) directed against idiotypic determinants of the T cell receptor (anti-Ti) from HPB-ALL cells induce interleukin 2 (IL2) production in Jurkat T cells without evidence of binding to these cells as judged by fluorescence-activated cell sorter (FACS) analysis, indirect antibody-binding radioimmunoassay and direct binding studies with 125I-labeled mAb. The IL2 response induced by these mAb observed both in the presence and absence of phorbol myristate acetate was in the range of that obtained when Jurkat cells were stimulated with phytohemagglutinin or anti-T3 mAb (Leu 4). The idiotypic specificity of the two anti-HPB-ALL Ti mAb was demonstrated by several criteria. Both mAb bound specifically to HPB-ALL cells as determined by radioimmunoassay or FACS analysis but not with 8 other T cell lines. The anti-HPB-ALL Ti mAb precipitated a disulfide-linked heterodimer of 85 kDa only from 125I-labeled HPB-ALL cells and not from other cell lines tested. Incubation of HPB-ALL cells with anti-T3 abrogated the expression of T3 and induced co-modulation of the idiotypic structures detected by the two anti-HPB-ALL Ti mAb. Conversely, incubation of HPB-ALL cells with either one of the anti-Ti mAb abrogated the expression of T3 and of the idiotypic structures. Our results suggest that mAb with an apparent unique specificity for the receptor of the immunizing T cell line HPB-ALL can activate Jurkat cells by a very weak cross-reaction with these cells, which is not detectable by conventional binding tests.     

A longitudinal study for investigating the exposure level of anesthetics that impairs neurobehavioral performance

There is conflicting evidence on the level of anesthetics that impairs neurobehavioral performance, leading to differences in exposure standards (25 or 50 ppm for N(2)O). Thirty-eight operating room nurses and 23 unexposed nurses were asked to provide information on confounding variables: age, gender, years of schooling, alcohol and coffee consumption, smoking, length of work, symptoms (Euroquest) and results of Block Design test. Afterward, all workers were repeatedly examined (on Monday and Friday of a working week, before and after workshift) for stress and arousal (Mood Scale) and complex reaction times (Color Word Vigilance, CWV), the latter being the outcome. Individual exposure was assessed through urinary end-shift concentrations of nitrous oxide (N(2)O) and isoflurane. According to the highest value of urinary excretion of N(2)O in the week, exposed workers were subdivided in three groups (<13; > or =13 and <27; and > or = 27 microg/l). The values of 13 and 27 microg/l correspond to environmental concentrations of 25 and 50 ppm, respectively. In order to take into account the pre-existing abilities of exposed and reference workers, and investigate the neurobehavioral changes over time, longitudinal data were analyzed by a two-stage regression model and analysis of variance for repeated measures (MANOVA). The former method, controlling for confounding factors and Monday morning CWV (which conveyed the pre-existing ability of the subjects), showed that, with respect to unexposed nurses, reaction times were significantly (p<0.020) higher only in workers with urinary N(2)O> or = 27 microg/l. Therefore, at MANOVA, all subjects were categorized in two classes (N(2)O urinary concentrations or = 27 microg/l), and CWV results were adjusted for the confounding variables and effects of stress and arousal, taken concurrently with CWV. CWV significantly (p<0.039) decreased over a working week (indicating a learning effect) in workers with urinary N(2)O<27 microg/l, while remained steady (indicating impairment of neurobehavioral performance) in those with urinary N(2)O> 27 microg/l.     

Serological Markers of Hepatitis B Virus Infection in Healthy Volunteer Blood Donors in Campania (Southern Italy)

The prevalence of hepatitis B virus (HBV) serological markers was determined in a prospective fashion by radioimmunoassay in 2,084 healthy volunteer blood donors. The results showed that 51.2% of the donors were positive for at least one marker, and the percentage of occurrence of each marker was: HBsAg 5.3, anti-HBs alone 1.7, anti-HBc alone 10.8, anti-HBs and anti-HBc 33.3. Because of the size of the problem this investigation strongly demands further studies on the potential role of blood positive for anti-HBc in transmitting HBV infection in our geographical area.     

The primary reflex effects of distension of the stomach on heart rate,arterial pressure and left ventricular contractility in the anaesthetized pig

The present study was planned to investigate whether distension of the stomach primarily affects the heart rate, arterial blood pressure and left ventricular inotropic state and to explore the reflex mechanisms involved. In 16 anaesthetized pigs, distension of gastric balloons with 0.8 1 of Ringer solution (gastric transmural pressure of about 13 mmHg) without controlling any haemodynamic variable caused an increase in arterial blood pressure. When this response was prevented, an increase in heart rate was obtained in each animal. In five pigs, the increase in heart rate was graded by step increments of distension. No significant changes in maximum rate of change of left ventricular pressure were observed in the sixteen pigs during gastric distensions performed whilst preventing changes in heart rate and arterial blood pressure. The responses of arterial blood pressure and heart rate were not influenced by the administration of atropine (four and six pigs respectively), while they were abolished by the administration of bretylium tosylate (ten pigs) and by bilateral vagotomy (six pigs; three cervical, three subdiaphragmatic). The present study showed that gastric distension which was likely to be innocuous in the anaesthetized pig reflexly increased arterial blood pressure and heart rate. The afferent limb of the reflex was in the vagal nerves and the efferent limb involved sympathetic pathways.     

Peripheral blood flows during colorectal distension in anaesthetised dogs

Distension of the descending colon elicits reflex cardiovascular responses, including increases in heart rate and arterial blood pressure. To study the relative contribution of vasoconstriction in individual vascular beds to this reflex response, experiments were performed on seven dogs anaesthetised with chloralose and instrumented with electromagnetic flowmeters around the superior mesenteric, the left renal and the left external iliac arteries. The colorectal portion of the intestine was distended at constant pressure (36.6 mm Hg, 4.9 kPa mean; range 25–50 mm Hg, 3.3–6.7 kPa) with warm Ringer solution for periods of 2 min. After a set of control distensions, the experiments were performed whilst the reflex rise in arterial pressure was prevented by removal of blood from the arterial tree. In control distensions arterial pressure increased by 11.3±1.5 mm Hg, 1.51±0.12 kPa (mean±SEM). In distensions at constant arterial pressure, peripheral blood flows were altered to different extents in the three territories studied: vascular resistance increased by 30.8±5.6% (P<0.01) in the mesenteric, by 4.1±1.5% (P<0.03) in the renal, and by 15.2±6.8% (NS) in the external iliac bed. We conclude that colorectal distension may reflect activation of a function-specific pathway of the sympathetic nervous system, which leads to much greater vasoconstriction in the splanchnic circulation than in renal or musculocutaneous circulations.