Role for interleukin-1 (IL-1) in benzene-induced hematotoxicity: inhibition of conversion of pre-IL-1 alpha to mature cytokine in murine macrophages by hydroquinone and prevention of benzene-induced hematotoxicity in mice by IL-1 alpha

Chronic exposure of humans to benzene (BZ), a myelotoxin, causes aplastic anemia and acute leukemia. The stromal macrophage that produces interleukin-1 (IL-1), a cytokine essential for hematopoiesis, is a target of BZ's toxicity. Monocyte dysfunction and decreased IL-1 production have been shown to be involved in aplastic anemia in humans. Hydroquinone (HQ), a toxic bone marrow (BM) metabolite of BZ, causes time- and concentration-dependent inhibition of processing of the 34-Kd pre-interleukin-1 alpha (IL-1 alpha) to the 17-Kd mature cytokine in murine P388D1 macrophages and BM stromal macrophages, as measured by Western immunoblots of cell lysate proteins using a polyclonal rabbit antimurine IL-1 alpha antibody. HQ over a 10-fold concentration range had no effect on the lipopolysaccharide (LPS)-induced production of pre- IL-1 alpha precursor or on cell viability or DNA and protein synthesis. Stromal macrophages obtained from the femoral BM of C57Bl/6 mice exposed to BZ (600 or 800 mg/kg body weight) for 2 days were incapable of processing the 34-Kd pre-IL-1 alpha to the mature 17-Kd cytokine when stimulated in culture with LPS. Stromal macrophages from mice coadministered BZ and indomethacin, a prostaglandin H synthase (PHS) inhibitor that has been shown to prevent BZ-induced myelotoxic and genotoxic effects in mice when coadministered with benzene were able to convert the pre-IL-1 alpha to mature cytokine. Administration of recombinant murine IL-1 alpha (rMuIL-1 alpha) to mice before a dose of BZ that causes severe depression of BM cellularity completely prevents BM depression, most probably by bypassing the inability of the stromal macrophage in BZ-treated animals to process pre-IL-1 alpha to the mature cytokine.     

Connective tissue metabolism in children with chronic renal failure

To assess the characteristics of connective tissue metabolism in chronic renal failure (CRF), urinary excretion of glycosaminoglycan (GAG) fractions and hydroxyproline (HYP) was determined in ten patients with CRF and in ten age-matched healthy children. CRF was found to be associated with elevated free HYP (19.9±6.1 vs 9.8±3.6 mol/day,P<0.05) and depressed peptide HYP excretion (33.1±13.5 vs 225.2±17.7 mol/day,P<0.01), a low rate of total GAG excretion (7.0±2.4 vs 16.1±1.9 mol uronic acid/day,P<0.05) with low chondroitin 4 — sulphate + chondroitin 6 — sulphate (Ch-Ss) (14.0±9.9 vs 65.0±22.1%) and a high proportion of non-sulphated or under-sulphated fractions, i.e. hyaluronic acid + chondroitin + heparan sulphate (HA+Ch+HS) (75.3±11.4 vs 31.5±5.7%). Urinary 3-methyl-histidine (3-met-HIS) excretion and plasma essential free amino acids did not differ in the two groups. In response to haemodialysis no consistent change occurred in urinary excretion of 3-met-HIS, peptide-bound HYP, total GAG or percentage distribution of individual GAG fractions. After haemodialysis all plasma amino acids decreased significantly, and there was a significant increase in urinary excretion of free HYP (P<0.05). We conclude that the alterations in urinary excretion of total and individual GAGs observed in CRF may reflect disturbed connective tissue metabolism which does not appear to be accounted for by protein malnutrition or enhanced protein breakdown and remains uninfluenced by haemodialysis therapy.     

<Emphasis Type="Italic">TCF7L2</Emphasis>variant genotypes and type 2 diabetes risk in Brazil: significant association,but not a significant tool for risk stratification in the general population

Background  

Genetic polymorphisms of the TCF7L2 gene are strongly associated with large increments in type 2 diabetes risk in different populations worldwide. In this study, we aimed to confirm the effect of the TCF7L2 polymorphism rs7903146 on diabetes risk in a Brazilian population and to assess the use of this genetic marker in improving diabetes risk prediction in the general population.     

Direct evidence for the involvement of carbohydrate sequences in human sperm-zona pellucida binding

Several lines of evidence indicate that mammalian fertilization is initiated via a binding process that is dependent upon the recognition of oligosaccharide sequences associated with zona pellucida (ZP) glycoproteins. Here, specific chemical and enzymatic methods were employed to modify human ZP and to test their effects on sperm binding in the hemizona assay system (HZA). Periodate oxidation of human ZP under very mild conditions (10 min, 0 degrees C, 1 mM sodium m- periodate) that attacks only terminal sialic acid resulted in a 30% loss of human sperm binding in the HZA [hemizona index (HZI) = 70.2 +/- 10.9, n = 22; P < 0.05]. Periodate oxidation under mild conditions (1 h, 23 degrees C, 10 mM sodium m-periodate) caused a 40% decrease in binding (HZI = 60.8 +/- 10.3; n = 24; P< 0.01). Treatment of human ZP with neuraminidase caused a substantial increase in sperm binding to human ZP (HZI = 297 +/- 45, n = 22; P < 0.01). These findings indicate that there are sialic acid dependent binding sites coexisting with binding sites that are obscured by sialic acid. To determine the periodate sensitivity of these obscured sites, hemizona were first digested with neuraminidase and subsequently subjected to mild periodate oxidation. The combined enzymatic and chemical treatments caused a 79% decrease in sperm binding compared to control hemizona (HZI = 20.7 +/- 4.4, n = 16; P < 0.001). Human sperm-ZP interaction was also increased by digestion of human ZP with endo-beta-galactosidase (HZI = 710 +/- 232, n = 14; P < 0.01), indicating that potential binding sites for spermatozoa are also obscured by lactosaminoglycan sequences. These studies support a definitive role for the involvement of ZP-associated glycans in the binding of human spermatozoa to oocytes.      

Sensitivity of three activated partial thromboplastin time reagents to coagulation factor deficiencies

Three activated partial thromboplastin time (APTT) reagent test systems, General Diagnostics Automated APTT, American Dade Actin FS, and Pacific Hemostasis (Thromboscreen KAPTT) reagent, containing different activators for the APTT assay, were evaluated for their precision and sensitivity to factor deficiencies in the intrinsic coagulation system. The data suggest that micronized silica and ellagic acid reagent systems were similar in sensitivity to Factor VIII, X, and XII deficiencies, whereas, the micronized kaolin reagent was significantly less sensitive to these deficiencies. Factor XI deficiency was detected equally well with the use of all three reagent systems. The ellagic acid reagent was somewhat more sensitive to Factor IX deficiency than the micronized silica reagent, and the micronized kaolin reagent was again least sensitive. Both the micronized silica and ellagic acid based reagents were insensitive to all but severe deficiencies in prekallikrein, whereas the micronized kaolin reagent was unable to detect this deficiency. All three reagents were insensitive to all but severe deficiencies in high-molecular-weight kininogen. The authors conclude that the reagent systems tested, containing micronized silica or ellagic acid as activators, are similar in sensitivity when used in a routine activated partial thromboplastin time to screen for factor deficiencies, whereas the reagent system containing micronized kaolin as an activator is less sensitive.     

Current guidelines for the treatment of patients with rheumatic fever

Rheumatic fever is a multisystem inflammatory disease that occurs as a delayed sequelae to group A streptococcal pharyngitis. The important clinical manifestations are migratory polyarthritis, carditis, chorea, subcutaneous nodules and erythema marginatum occurring in varying combinations. The pathogenesis of this disorder remains elusive: an antigenic mimicry hypothesis best explains the affliction of various organ systems after a lag period following pharyngeal infection. In its classic milder form, the disorder is largely self-limited and resolves without sequelae, but carditis may be fatal in severe forms of the disease. Chronic and progressive damage to the heart valves leads to the most important public health manifestations of the disease. Anti-inflammatory agents provide dramatic clinical improvement, but do not prevent the subsequent development of rheumatic heart disease. The role of corticosteroids in treatment of carditis is uncertain and controlled studies have failed to demonstrate improved long term prognosis. Chorea, once considered a benign self-limited disease, is now felt to require more aggressive treatment, in particular with sedatives. Prevention of first and subsequent attacks of rheumatic fever is the mainstay in the limited arsenal available to alter the natural history of this disease.     

Nitric oxide-independent inhibitory effects of L-arginine analog NG-monomethy-L-arginine on the generation of interleukin-2 activated cytotoxic activity in humans

Nitric oxide (NO) derived intracellularly from L-arginine (Arg) is indispensable for optimalgeneration of lymphokine-activated killer (LAK) cell activity in rodents. Still unclear, however, is its role in humans. To address this question human peripheral blood mononuclear cells (PBMC) from healthy donors were cultured in L-arginine free medium supplemented with recombinant interleukin-2 (rIL-2) and in the presence of exogenous L-arginine analog NG-monomethyl-L-arginine (NMMA), a specific inhibitor of the NO synthetic pathway. Cultured PBMC were tested for cytotoxic activity, proliferative capacity, and expression of phenotypic and activation markers (CD3, CD4, CD8, CD16, CD56 and CD25). Culture supernatants were assayed for nitrite (NO2-) and tumor necrosis factor-alpha (TNF-alpha) production. We found that NMMA inhibits the generation of optimal LAK cell activity when no exogenous Arg is supplied. Similar effects were also observed on proliferation, expression of IL-2 receptor induced upon rIL-2 stimulation and on TNF-alpha production. Sodium nitroprusside (SNP), used as a source of exogenous NO could not overcome this effect of NMMA on LAK cell activity. NO2- production was virtually undetectable in culture supernatants. Thus, NMMA affects in an NO-independent manner rlL-2 induced LAK activity in human PBMC.     

The use of beta-blockers after myocardial infarction

Several beta-blockers have now been shown to be effective in reducing total mortality during the extended recovery period after myocardial infarction. The rate of occurrence of reinfarction and sudden death is also reduced. While the exact mechanisms of this beneficial effect are unknown, it appears to result from a "class" effect, ie, secondary to beta-blockade, since neither cardioselectivity, intrinsic sympathomimetic activity, nor membrane-stabilizing activity appears to be requisite. The reduction in mortality is seen in all age groups, for all types of infarction, and in all risk groups. On the basis of presently available evidence, in patients without contraindication to beta-blockade, prophylactic treatment with beta-blockers should be initiated between one and four weeks after myocardial infarction. The dosage should be sufficient to blunt the heart rate response to exercise, and therapy should be continued for at least two years. The positive results of several well-designed and conducted studies have proved that the concept of secondary prevention is a valid one and should help to save thousands of lives in the coming decade. It is expected that ongoing investigations will determine the efficacy and safety of earlier institution of beta-blockade, including IV administration in the peri-infarction period. The effectiveness of secondary prevention with other agents, including calcium channel blockers, antiplatelet agents, anticoagulants, lipid-lowering drugs, antiarrhythmics, prostacyclin analogues, and thromboxane synthetase inhibitors, should be investigated further. Additional information is needed on the mechanisms by which beta-blockers reduce mortality, sudden death, and reinfarction, on whether specific beta-blockers and/or specific types of beta-blockers have the greatest benefit, and, as a result of further analysis from some of the studies already published, the effect of beta-blockade after myocardial infarction on angina, rhythm disturbances, lipid profile abnormalities, and the quality of life.