Melanin in <Emphasis Type="Italic">Fonsecaea pedrosoi</Emphasis>: a trap for oxidative radicals

Background  

The pathogenic fungus Fonsecaea pedrosoi constitutively produces the pigment melanin, an important virulence factor in fungi. Melanin is incorporated in the cell wall structure and provides chemical and physical protection for the fungus.     

Patch-clamp recording of charge movement, Ca(2+) current, and Ca(2+) transients in adult skeletal muscle fibers

Intramembrane charge movement (Q), Ca(2+) conductance (G(m)) through the dihydropyridine-sensitive L-type Ca(2+) channel (DHPR) and intracellular Ca(2+) fluorescence (F) have been recorded simultaneously in flexor digitorum brevis muscle fibers of adult mice, using the whole-cell configuration of the patch-clamp technique. The voltage distribution of Q was fitted to a Boltzmann equation; the Q(max), V(1/2Q), and effective valence (z(Q)) values were 41 +/- 3.1 nC/&mgr;F, -17.6 +/- 0.7 mV, and 2.0 +/- 0.12, respectively. V(1/2G) and z(G) values were -0.3 +/- 0.06 mV and 5.6 +/- 0.34, respectively. Peak Ca(2+) transients did not change significantly after 30 min of recording. F was fit to a Boltzmann equation, and the values for V(F1/2) and z(F) were 6.2 +/- 0.04 mV and 2.4, respectively. F was adequately fit to the fourth power of Q. These results demonstrate that the patch-clamp technique is appropriate for recording Q, G(m), and intracellular [Ca(2+)] simultaneously in mature skeletal muscle fibers and that the voltage distribution of the changes in intracellular Ca(2+) can be predicted by a Hodgkin-Huxley model.     

Correlation between thyroid hormone status and hepatic hyperplasia and hypertrophy caused by the peroxisome proliferator-activated receptor alpha agonist Wy-14,643

BACKGROUND: The metabolic inhibitor rotenone inhibits hepatocellular proliferation and the incidence of liver cancer resulting from exposure to the PPARalpha agonist Wy-14,643, via unknown mechanisms. Since the absence of thyroid hormones diminishes hepatomegaly, an early biomarker for the hepatocarcinogenicity induced by PPARalpha agonists, this study was undertaken to investigate whether rotenone might interference with the ability of Wy-14,643 to alter the animal thyroid status. METHODS: Male B6C3F1 mice were given Wy-14,643 (100 ppm), rotenone (600 ppm) or a mixture of both, in the feed for 7 days. Bromodeoxyuridine (BrDU), marker of cell replication, was delivered through subcutaneously implanted osmotic mini-pumps. At the end of the experiment, sera were collected and corticosterone and thyroid hormone levels were measured by solid-phase radioimmunoassay kits. In addition, liver tissue samples were stained immunohistochemically for BrDU to determine percentages of labeled cells. Further, cell surface area was determined from images generated by a Zeiss Axioplan microscope equipped with a plan Neofluar x40 0.75 na objective. Tracings of individual hepatocyte perimeters were then analyzed and cell-surface areas were calculated using MicroMeasure FL-4000. RESULTS: Wy-14,643 caused a significant increase in liver weights, hepatocyte BrDU labeling index (LI), and hepatocyte surface area. In animals which received both Wy-14,643 and rotenone simultaneously, all of these effects were significantly less pronounced compared with mice that received Wy-14,643 alone. Rotenone alone decreased liver weights, LI and surface area. The Free Thyroid Index (FTI), which provides an accurate reflection of the animal's thyroid status, was 5.0 +/- 0.3 in control mice. In animals exposed to rotenone, these values decreased to 2.0 +/- 0.9, but in animals which received Wy-14,643, levels increased significantly to 7.7 +/- 0.9. FTI values decreased to 3.4 +/- 0.8 in mice receiving both rotenone and Wy-14,643. CONCLUSION: A strong correlation was observed between the animal thyroid status and both, hepatocyte proliferation (r2 = 0.62), and hepatocyte surface area (r2 = 0.83). These results support the hypothesis that the thyroid status of the animal plays a role in PPARalpha-induced hepatocellular proliferation and liver cell enlargement. Both these events are known to contribute to the expression of liver cancer in response to the activation of PPARalpha.     

Fishers' knowledge and seahorse conservation in Brazil

From a conservationist perspective, seahorses are threatened fishes. Concomitantly, from a socioeconomic perspective, they represent a source of income to many fishing communities in developing countries. An integration between these two views requires, among other things, the recognition that seahorse fishers have knowledge and abilities that can assist the implementation of conservation strategies and of management plans for seahorses and their habitats. This paper documents the knowledge held by Brazilian fishers on the biology and ecology of the longsnout seahorse Hippocampus reidi. Its aims were to explore collaborative approaches to seahorse conservation and management in Brazil; to assess fishers' perception of seahorse biology and ecology, in the context evaluating potential management options; to increase fishers' involvement with seahorse conservation in Brazil. Data were obtained through questionnaires and interviews made during field surveys conducted in fishing villages located in the States of Piauí, Ceará, Paraíba, Maranhão, Pernambuco and Pará. We consider the following aspects as positive for the conservation of seahorses and their habitats in Brazil: fishers were willing to dialogue with researchers; although captures and/or trade of brooding seahorses occurred, most interviewees recognized the importance of reproduction to the maintenance of seahorses in the wild (and therefore of their source of income), and expressed concern over population declines; fishers associated the presence of a ventral pouch with reproduction in seahorses (regardless of them knowing which sex bears the pouch), and this may facilitate the construction of collaborative management options designed to eliminate captures of brooding specimens; fishers recognized microhabitats of importance to the maintenance of seahorse wild populations; fishers who kept seahorses in captivity tended to recognize the condtions as poor, and as being a cause of seahorse mortality.     

Science – A life fully lived: Joe Sodroski wins the 2006 Retrovirology Prize

The 2006 M Jeang Retrovirology Prize for HIV research has been awarded to Dr Joe Sodroski