Relationship between melanin content and superoxide dismutase (SOD) activity in the liver of various species of animals

The scavenger effect of melanin and of superoxide dismutase (SOD) activity on superoxide anion has been shown. In this work we show the relationship between melanin content and SOD activity in livers containing different quantities of melanin which were taken from various species of animals. The mitochondrial SOD activity disappears when the melanin content in the liver is very high; moreover it increases, in the liver of various species of animals examined, proportionally to the decrease of melanin content. No significant variation of the SOD activity localized in the soluble fraction has been detected when related to the melanin content. We think that in the pigmented liver the antioxidant activity of the melanin could mimic part of the function of SOD. The loss of Mn SOD activity could be mediated by a low intracellular level of superoxide anion due to the scavenger effect of melanin on superoxide anion; in fact, it is well known that the biosynthesis of Mn SOD is induced by intracellular levels of superoxide anion.     

Melanosomes from liver and skin of Rana esculenta L. A comparative chemical study

1. Melanosomes from skin and liver of Rana esculenta L. have been isolated and some chemical properties of the relevant melanin and protein components were compared. 2. In both cases the pigments show spectroscopic (ESR) and chemical characteristics similar to those of eumelanins. The melanin content in skin melanosomes is higher than in the liver counterparts. 3. Amino acid patterns of the two protein components are different in their quantitative composition and both are characterized by high levels of glycine and proline. 4. The results as a whole indicate that skin and liver melanosomes from the same animal markedly differ in their chemical composition.     

Inhibition of serine proteinases by tetra-p-amidinophenoxy-neo-pentane: thermodynamic and molecular modeling study

The inhibitory effect of the aromatic tetra-benzamidine derivative tetra-p-amidinophenoxy-neo-pentane (TAPP) on the catalytic properties of beta-trypsin (EC 3.4.21.4), alpha-thrombin (EC 3.4.21.5), factor Xa (EC 3.4.21.6), Lys77-plasmin (EC 3.4.21.7) and beta-kallikrein-B (EC 3.4.21.35) was investigated (between pH 2 and 8, I = 0.1 M; T = 37 +/- 0.5 degrees C), and analyzed in parallel with that of benzamidine, commonly taken as a molecular inhibitor model of serine proteinases. Over the whole pH range explored, TAPP and benzamidine show the same values of the dissociation inhibition constant (Ki) for beta-trypsin; at variance with the affinity of TAPP for alpha-thrombin, factor Xa, Lys77-plasmin and beta-kallikrein-B which is higher than that found for benzamidine association around neutrality, but tends to converge in the acidic pH limb. On lowering the pH from 5.5 to 3.0, values of Ki for TAPP binding to beta-trypsin as well as for benzamidine association to all the enzymes investigated decreased thus reflecting the pK-shift, upon inhibitor binding, of a single ionizing group. Over the same pH range, values of Ki for TAPP binding to alpha-thrombin, factor Xa, Lys77-plasmin and beta-kallikrein-B may be described as depending on the pK-shift, upon inhibitor association, of two equivalent proton-binding amino acid residues. Considering the X-ray three-dimensional structures and the computer-generated molecular models of serine proteinases: TAPP and :benzamidine adducts, the observed binding behaviour of TAPP and benzamidine to the enzymes considered has been related to the inferred stereochemistry of proteinase: inhibitor contact region(s).     

Analysis of conjugated bile acids by packed-column supercritical fluid chromatography

A rapid method has been developed for the simultaneous separation of the polar glycine- and taurine-conjugated bile acids by packed-column supercritical fluid chromatography. Samples were analysed on a cyanopropyl-bonded silica column with ultraviolet detection at 210 nm and carbon dioxide modified with methanol as the mobile phase. The influence of the stationary phase, modifier concentration, temperature, column pressure and modifier identity on retention was also studied. This new chromatographic method is applicable to the assay of conjugated bile acids in duodenal bile samples from patients with hepatobiliary diseases.     

A benign approach to the preparation of freshwater bryozoan statoblasts for scanning electron microscopy (SEM) imaging

Abstract

Several different species of freshwater Bryozoa, belonging to the genera Plumatella, Rumarcanella and Fredericella, were detected within the Northern Mallee Pipeline (NMP) system in Victoria, Australia, that required definitive identification. These organisms produce asexual buds called statoblasts, with valves composed of sclerotised chitin that bear minute micro-ornamentations of considerable taxonomical significance. Imaging and analysis of these distinctive micro-ornamentations using scanning electron microscopy (SEM) is often employed for species identification. Meticulous preparation of statoblast samples is therefore required that necessitates the removal of adhering debris, dehydration and drying—whilst mitigating specimen damage and distortion. This technical note describes an approach whereby each of these three steps have been individually designed to be as benign as possible, using mild detergent/sonication to remove debris, a gradual and gentle dehydration procedure using ethanol, and critical point drying. For the overall process, these methods are chosen to optimise control and to minimise the use of harsh and hazardous chemicals.     

The use of adjunctive GPIIb/IIIa inhibitors in patients with unstable angina/non-Q-wave MI undergoing percutaneous coronary intervention

Glycoprotein IIb/IIIa receptor inhibitors represent a relatively new therapeutic approach in the field of antiplatelet therapy. Following the development of abciximab a number of small molecule GPIIb/IIIa inhibitors have been introduced such as tirofiban and eptifibatide. In this fast-moving field the interventional cardiologist needs a framework to guide decision-making for the individual patient. This review covers the efficacy and safety data from the clinical trials of GPIIb/IIIa inhibitors in the context of patients undergoing percutaneous coronary intervention for unstable angina/non-Q-wave myocardial infarction. There is an increasing body of evidence to support the efficacy of GPIIb/IIIa inhibitors in reducing the risk of adverse ischemic events in high and low risk patients undergoing percutaneous coronary intervention. A number of unresolved efficacy and safety issues remain, including the duration of treatment before and after intervention; whether a reduction in the heparin dose would further decrease the risk of hemorrhage without affecting the periprocedural thrombotic rate in patients undergoing PTCA with adjunctive GPIIb/IIIa inhibitors; and the cost-effectiveness of this therapy. When a thorough analysis of cost-effectiveness has been made, it will be easier to advocate the widespread use of these agents in all patients undergoing coronary intervention.     

Phosphorylation-dependent regulation of skeletogenesis in sea urchin micromere-derived cells and embryos

Sea urchin embryo micromeres when isolated and cultured in vitro differentiate to produce spicules. Although several authors have used this model, almost nothing is known about the signaling pathways responsible for initiating skeletogenesis. In order to investigate the potential involvement of phosphorylation events in spiculogenesis, the effect of inhibitors of protein kinases and phosphatases on skeleton formation was studied. Results obtained using both cultured micromeres and embryos revealed that protein tyrosine kinase and phosphatase inhibitors blocked skeleton formation, but not serine/threonine phosphatase inhibitors. The inhibitors showed a dose-dependent effect and when removed from micromere or embryo culture, spicule formation resumed. Inhibition of tyrosine phosphatases resulted in an increase in the tyrosine phosphorylation level of two major proteins and a modest decrease in the expression of the mRNA coding for type I fibrillar collagen. These findings strongly suggest that tyrosine phosphorylation and dephosphorylation is required for micromere differentiation and for normal skeletogenesis during sea urchin embryo development.     

Insulin receptor isoform A, a newly recognized, high-affinity insulin-like growth factor II receptor in fetal and cancer cells

Insulin-like growth factor II (IGF-II) is a peptide growth factor that is homologous to both insulin-like growth factor I (IGF-I) and insulin and plays an important role in embryonic development and carcinogenesis. IGF-II is believed to mediate its cellular signaling via the transmembrane tyrosine kinase type 1 insulin-like growth factor receptor (IGF-I-R), which is also the receptor for IGF-I. Earlier studies with both cultured cells and transgenic mice, however, have suggested that in the embryo the insulin receptor (IR) may also be a receptor for IGF-II. In most cells and tissues, IR binds IGF-II with relatively low affinity. The IR is expressed in two isoforms (IR-A and IR-B) differing by 12 amino acids due to the alternative splicing of exon 11. In the present study we found that IR-A but not IR-B bound IGF-II with an affinity close to that of insulin. Moreover, IGF-II bound to IR-A with an affinity equal to that of IGF-II binding to the IGF-I-R. Activation of IR-A by insulin led primarily to metabolic effects, whereas activation of IR-A by IGF-II led primarily to mitogenic effects. These differences in the biological effects of IR-A when activated by either IGF-II or insulin were associated with differential recruitment and activation of intracellular substrates. IR-A was preferentially expressed in fetal cells such as fetal fibroblasts, muscle, liver and kidney and had a relatively increased proportion of isoform A. IR-A expression was also increased in several tumors including those of the breast and colon. These data indicate, therefore, that there are two receptors for IGF-II, both IGF-I-R and IR-A. Further, they suggest that interaction of IGF-II with IR-A may play a role both in fetal growth and cancer biology.     

PR-39, a potent neutrophil inhibitor, attenuates myocardial ischemia-reperfusion injury in mice

We investigated the effects of PR-39, a recently discovered neutrophil inhibitor, in a murine model of myocardial ischemia-reperfusion injury. Mice were given an intravenous injection of vehicle (n = 12) or PR-39 (n = 9) and subjected to 30 min of coronary artery occlusion followed by 24 h of reperfusion. In addition, the effects of PR-39 on leukocyte rolling and adhesion were studied utilizing intravital microscopy of the rat mesentery. The area-at-risk per left ventricle was similar in vehicle- and PR-39-treated mice. However, myocardial infarct per risk area was significantly (P < 0.01) reduced in PR-39 treated hearts (21.0 +/- 3.8%) compared with vehicle (47.1 +/- 4.8%). Histological analysis of ischemic reperfused myocardium demonstrated a significant (P < 0.01) reduction in polymorphonuclear neutrophil (PMN) accumulation in PR-39-treated hearts (n = 6, 34.3 +/- 1.7 PMN/mm(2)) compared with vehicle-treated myocardium (n = 6, 59.7 +/- 3.1 PMN/mm(2)). In addition, PR-39 significantly (P < 0.05) attenuated leukocyte rolling and adherence in rat inflamed mesentery. These results indicate that PR-39 inhibits leukocyte recruitment into inflamed tissue and attenuated myocardial reperfusion injury in a murine model of myocardial ischemia-reperfusion.