Predicted distribution and movement of Glossina palpalis palpalis (Diptera: Glossinidae) in the wet and dry seasons in the Kogo trypanosomiasis focus (Equatorial Guinea).

The aim of this study was to predict the distribution and movement of populations of the tsetse fly, Glossina palpalis palpalis (Diptera: Glossinidae), in the wet and dry seasons and to analyze the impact of the use of mono-pyramidal traps on fly populations in the Kogo focus in 2004 and 2005. Three Glossina species are present in Kogo: Glossina palpalis palpalis, major HAT vector in West-Central Africa, Glossina caliginea, and Glossina tabaniformis. The apparent density (AD) of G. p. palpalis clearly fell from 1.23 tsetse/trap/day in July 2004 to 0.27 in December 2005. A significant reduction in the mean AD for this species was noted between seasons and years. The diversity of Glossina species was relatively low at all the sampling points; G. p. palpalis clearly predominated over the other species and significantly dropped as a consequence of control activities. The predictive models generated for the seasonal AD showed notable differences not only in the density but in the distribution of the G. p. palpalis population between the rainy and dry season. The mono-pyramidal traps have proven to be an effective instrument for reducing the density of the tsetse fly populations, although given that the Kogo trypanosomiasis focus extends from the southern Equatorial Guinea to northern Gabon, interventions need to be planned on a larger scale, involving both countries, to guarantee the long-term success of control.     

Activation of p38MAPK by TGF-beta in fetal rat hepatocytes requires radical oxygen production, but is dispensable for cell death.

We have previously found that transforming growth factor-beta (TGF-beta) induces an increase in radical oxygen species (ROS) production that mediates its apoptotic effects in fetal hepatocytes. In this paper we show that TGF-beta activates p38 mitogen-activated protein kinase (p38MAPK) and ROS may be responsible for this activation. Activation of p38MAPK occurs late, coincident with the maximal production of ROS, it is inhibited by radical scavengers and it is accentuated by the presence of glutathione synthesis inhibitors. However, p38MAPK does not appear to be involved in any of the apoptotic events: loss of Bcl-x(L) levels, cytochrome c release, cleavage of caspase substrates and loss of cell viability.     

Phosphoenolpyruvate carboxykinase and glucose-6-phosphate dehydrogenase expression in fetal hepatocyte primary cultures under proliferative conditions

Fetal hepatocytes cultured for 64 h in the presence of glucagon and dexamethasone maintain a quiescent state, showing a low expression of glucose-6-phosphate dehydrogenase (G6PD) and a high induction of phosphoenolpyruvate carboxykinase (PEPCK). Under these culture conditions, the presence of EGF produced hepatocyte proliferation, with a concomitant increase of DNA synthesis, DNA content, and G6PD expression, meanwhile the expression of PEPCK was drastically reduced. The presence of forskolin plus IBMX nearly suppressed the increase in DNA synthesis and G6PD expression induced by EGF, showing a very high expression of PEPCK. Accordingly, it is possible to establish an inverse relation between G6PD, highly expressed in proliferating fetal hepatocytes, and PEPCK expression, highly expressed in quiescent fetal hepatocytes under specific hormonal stimulation.     

Methylated cycloamyloses (cyclodextrins) and their inclusion properties

2,3,6-Tri-O-methyl and 2,6-di-O-methyl derivatives of cyclohexa- and cyclo-hepta-amylose (2,3,6-tri-O-methyl- and 2,6-di-O-methyl-α- and -β-cyclodextrin) have been prepared and shown to be versatile complexing agents. Their complexes in aqueous solution are usually more stable than the corresponding complexes of un-substituted cycloamyloses. The methylated cycloamyloses also form crystalline complexes, the stability of which depends on the size and shape of the guest molecule. The decomposition temperature of the crystalline complexes with homologous n-alkanes, which is relatively high increases with increasing chain-length of the hydro-carbon. The shift of the i.r. carbonyl band of oleic acid in its solid complex with methylated α-cyclodextrin probably reflects inclusion of the fatty acid in the mono-meric form. The methylated cycloamyloses, when used as the stationary phases for g.l.c. or dissolved in a conventional stationary phase, affect the retention times of organic compounds in a manner which suggests that inclusion phenomena are operative.     

Solar Radiation Induces Non-Nuclear Perturbations and a False Start to Regulated Exocytosis in Cryptosporidium parvum

Stratospheric ozone depletion, climate warming and acidification of aquatic ecosystems have resulted in elevated levels of solar radiation reaching many aquatic environments with an increased deleterious impact on a wide range of living organisms. While detrimental effects on living organisms are thought to occur primarily through DNA damage, solar UV can also damage cellular proteins, lipids and signalling pathways. Cryptosporidium, a member of the eukaryotic phylum Apicomplexa, contain numerous vesicular secretory organelles and their discharge via regulated exocytosis is essential for the successful establishment of infection. Using flow cytometric techniques we demonstrate that solar UV rapidly induces sporozoite exocytosis resulting in a significant reduction in the ability of sporozoites to attach and invade host cells. We found that solar UV induced sporozoite membrane depolarization, resulting in reduced cellular ATP and increased cytosolic calcium. These changes were accompanied by a reduction in the internal granularity of sporozoites, indicative of apical organelle discharge, which was confirmed by analysis of sporozoites with an exocytosis-sensitive dye. The precise timing of apical organelle discharge in the presence of a compatible host cell is critical for sporozoite attachment and invasion. Our results demonstrate for the first time how solar UV radiation can interfere with exocytosis, a fundamental cellular process in all eukaryotic cells. We contend that not only may the forecast increases in solar radiation in both aquatic and terrestrial environments significantly affect members of the Apicomplexa, solar UV-induced membrane depolarizations resulting in cytosolic calcium perturbation may affect a wider range of eukaryotic organisms through antagonistic effects on a myriad of calcium dependant cellular functions.     

Regulation of glycogenolysis in the liver of the newborn rat in vivo inhibitory effect of glucose

Newborn rats were injected immediately after delivery with glucose or glucose plus mannoheptulose, and the time-courses of liver glycogen, plasma glucose, insulin and glucagon concentration were studied. The administration of glucose prevented both liver glycogenolysis and the increase in plasma glucagon concentration which normally occurs immediately after delivery. In addition, the administration of glucose prevented the decrease of plasma glucose and insulin concentration which normally occurs during the first hour of extrauterine life. Supplementation of glucose with mannoheptulose prevented the increase of plasma insulin concentrations caused by the administration of glucose; liver glycogenolysis, however, was not stimulated in these circumstances. The increase in the rate of glycogenolysis caused by the administration of glucagon was prevented in newborn rats previously treated with glucose. These results suggest that glucose exerts an inhibitory effect on the stimulation of neonatal liver glycogenolysis by glucagon.     

Adenine nucleotide compartmentation in foetal rat hepatocytes. Effects of atractyloside, oligomycin, calcium ionophore and adrenergic agonists

In the presence of lactate plus pyruvate, or glucose or alanine as substrates, ATP/ADP ratios in the cytosol were higher than in mitochondria in isolated rat foetal hepatocytes. The cytosolic ATP/ADP ratios were dependent on substrate (lactate + pyruvate greater than glucose greater than alanine). Oleate increased the cytosolic ATP/ADP ratios in the presence of the other substrates studied. Atractyloside decreased the cytosolic ATP/ADP ratios, oligomycin decreasing these values in both compartments. Isoproterenol, phenylephrine and Ca2+ ionophore decreased the cytosolic ATP/ADP ratio, without altering this value in mitochondria.     

Plasmodium falciparum-infected mice: more than a tour de force

Up until recently, the relevance of Plasmodium falciparum-infected humanized mice for malaria studies has been questioned because of the low percentage of mice in which the parasite develops. Advances in the generation of new immunodeficient mouse strains combined with the use of protocols that modulate the innate immune defenses of mice have facilitated the harvesting of exoerythrocytic and intraerythrocytic stages of the parasite. These results renew the hope of working with P. falciparum in a laboratory animal and indicate that the next challenge (i.e. a complete parasite cycle in the same mouse, including transmission to mosquito) could be reached in the future.