Heterologous expression of a mammalian protein tyrosine phosphatase gene in Leishmania: effect on differentiation

Leishmania is a protozoan pathogen which is transmitted to humans through the bite of an infected sandfly. This infection results in a spectrum of diseases throughout the developing world, collectively known as leishmaniasis. During its life cycle, Leishmania differentiates from the promastigote stage in the sandfly vector into the amastigote stage in the mammalian host where it multiplies exclusively in macrophage phagolysosomes. Although differentiation of Leishmania is essential for its survival and pathogenesis in the mammalian host, this process is poorly understood. In higher eukaryotic cells, protein tyrosine phosphorylation plays a central role in cell proliferation, differentiation and overall function. We have therefore investigated the role of protein tyrosine phosphorylation in Leishmania differentiation by undertaking complementary approaches to mediate protein tyrosine dephosphorylation in vivo. In the present study, L. donovani were engineered to express a mammalian protein tyrosine phosphatase, or were treated with inhibitors of protein tyrosine kinases, and the resulting phenotype was examined. Both approaches resulted in a partial differentiation from promastigotes to amastigotes including the expression of the amastigote specific A2 protein, morphological change and increased virulence. These data provide support for the involvement of tyrosine phosphorylation in the differentiation of Leishmania.     

Composition of volatiles of banana cultivars from Madeira Island

The composition of the volatiles of banana fruit from various cultivars grown on Madeira Island has been determined. Using GC-MS, the volatiles were shown to be complex mixtures of several classes of components, mainly esters, alcohols, aldehydes, ketones and acids. The average contents of the total volatiles from cultivars "Dwarf Cavendish", "Giant Cavendish", "Robusta" and "Williams" were 93.0, 116.5, 157.3 and 157.0 mg/kg, respectively. The ester and alcoholic fractions appear to play a decisive role in the organoleptic characteristics of banana fruit, presenting a substantial content ranging from 57.2 to 89.8 mg/ kg and 19.0 to 47.7 mg/kg, respectively, in all cultivars from Madeira Island studied. 3-Methyl butyl butanoate ester was the major constituent.     

Conformationally-restricted analogues and partition coefficients of the 5-HT3 serotonin receptor ligands meta-chlorophenylbiguanide (mCPBG) and meta-chlorophenylguanidine (mCPG)

The present investigation examined two features of arylbiguanide and arylguanidine 5-HT(3) ligands: conformation and partition coefficients. Several conformationally-constrained analogues of mCPBG (2) and mCPG (11; K(i)=32 nM) were prepared and of these only 2-amino-5-chloro-3,4-dihydroquinazoline (14; K(i)=34 nM) retained high affinity. The partition coefficient of compound 11 (LogP(app)=-0.64) was less than that of its corresponding arylbiguanide 2 (LogP(app)=-0.38). The quinazoline structure may represent a pharmacologically-active conformation of these agents, and the arylbiguanides were found more lipid soluble than their arylguanidine counterparts at physiological pH.     

Platelet-Activating Factor (PAF) Modulates Peritoneal Mouse Macrophage Infection by Leishmania amazonensis

The effects of platelet-activating factor (PAF) on the infection of peritoneal mouse macrophages by Leishmania amazonensis were investigated. Prior to the infection, the parasites and/or the macrophages were treated with PAF and/or one of the following modulators: WEB 2086 (PAF antagonist), and the modulators of protein kinase C, phorbol-12-myristate-13-acetate (PMA), and sphingosine. The infection was inhibited when the macrophages or both the parasites and the macrophages were treated with PAF, but stimulated by PAF-treated parasites. WEB 2086 abrogated PAF effects in both systems. The infection was stimulated when the macrophages were treated with sphingosine plus PAF, but inhibited when the macrophages were treated with sphingosine and the parasites with sphingosine plus PAF. The infection was inhibited by sphingosine-treated parasites, either in the presence or in the absence of PAF. Leishmania amazonensis–macrophage infection was inhibited by PMA in all systems tested. Received: 27 September 2000 / Accepted: 15 December 2000     

Orbit, a novel microtubule-associated protein essential for mitosis in Drosophila melanogaster

We describe a Drosophila gene, orbit, that encodes a conserved 165-kD microtubule-associated protein (MAP) with GTP binding motifs. Hypomorphic mutations in orbit lead to a maternal effect resulting in branched and bent mitotic spindles in the syncytial embryo. In the larval central nervous system, such mutants have an elevated mitotic index with some mitotic cells showing an increase in ploidy. Amorphic alleles show late lethality and greater frequencies of hyperploid mitotic cells. The presence of cells in the hypomorphic mutant in which the chromosomes can be arranged, either in a circular metaphase or an anaphase-like configuration on monopolar spindles, suggests that polyploidy arises through spindle and chromosome segregation defects rather than defects in cytokinesis. A role for the Orbit protein in regulating microtubule behavior in mitosis is suggested by its association with microtubules throughout the spindle at all mitotic stages, by its copurification with microtubules from embryonic extracts, and by the finding that the Orbit protein directly binds to MAP-free microtubules in a GTP-dependent manner.     

Educational differences in smoking: international comparison

ObjectiveTo investigate international variations in smoking associated with educational level.DesignInternational comparison of national health, or similar, surveys.SubjectsMen and women aged 20 to 44 years and 45 to 74 years.Setting12 European countries, around 1990.ResultsIn the 45 to 74 year age group, higher rates of current and ever smoking among lower educated subjects were found in some countries only. Among women this was found in Great Britain, Norway, and Sweden, whereas an opposite pattern, with higher educated women smoking more, was found in southern Europe. Among men a similar north-south pattern was found but it was less noticeable than among women. In the 20 to 44 year age group, educational differences in smoking were generally greater than in the older age group, and smoking rates were higher among lower educated people in most countries. Among younger women, a similar north-south pattern was found as among older women. Among younger men, large educational differences in smoking were found for northern European as well as for southern European countries, except for Portugal.ConclusionsThese international variations in social gradients in smoking, which are likely to be related to differences between countries in their stage of the smoking epidemic, may have contributed to the socioeconomic differences in mortality from ischaemic heart disease being greater in northern European countries. The observed age patterns suggest that socioeconomic differences in diseases related to smoking will increase in the coming decades in many European countries.     

Human milk fractions inhibit the adherence of diffusely adherent Escherichia coli (DAEC) and enteroaggregative E. coli (EAEC) to HeLa cells

Binding to a specific receptor is an essential step for most enteropathogens to initiate an intestinal infection. We analyzed the inhibitory effect of human milk and its protein components on adhesion of two diarrheagenic Escherichia coli strains, diffusely adherent E. coli (DAEC) and enteroaggregative E. coli (EAEC), to HeLa cells. Defatted milk, whey proteins, immunoglobulin and non-immunoglobulin fractions, in concentrations lower than usually found in whole milk, inhibited both DAEC and EAEC adhesion, indicating that human milk components may contribute to the defense of the infants against enteropathogens.     

Participation of the rat caudate nucleus in the immunostimulating effect of DAGO

The data obtained suggest that administration of the DAGO increased the number of plaque- and rosette-forming cells after immunisation with the sheep red blood cells in the sham-operated Wistar rats. Following destruction of the caudate nucleus, the DAGO administration prevented the immune activation. Bilateral destruction of the caudate nucleus resulted in a considerable inhibition of the immune response as compared with the control rats. Thereupon the caudate nucleus seems to be involved in realisation of the DAGO-induced immune activation.