Induction of apoptosis in host cells: a survival mechanism for Leishmania parasites?

Leishmania parasites invade host macrophages, causing infections that are either limited to skin or spread to internal organs. In this study, 3 species causing cutaneous leishmaniasis, L. major, L. aethiopica and L. tropica, were tested for their ability to interfere with apoptosis in host macrophages in 2 different lines of human monocyte-derived macrophages (cell lines THP-1 and U937) and the results confirmed in peripheral blood mononuclear cells (PBMC). All 3 species induced early apoptosis 48 h after infection (expression of phosphatidyl serine on the outer membrane). There were significant increases in the percentage of apoptotic cells both for U937 and PBMC following infection with each of the 3 species. Early apoptotic events were confirmed by mitochondrial membrane permeabilization detection and caspase activation 48 and 72 h after infection. Moreover, the percentage of infected THP-1 and U937 macrophages increased significantly (up to 100%) following treatment with an apoptosis inducer. Since phosphatidyl serine externalization on apoptosing cells acts as a signal for engulfment by macrophages, induction of apoptosis in the parasitized cells could actively participate in spreading the infection. In summary, parasite-containing apoptotic bodies with intact membranes could be released and phagocytosed by uninfected macrophages.     

Life history of a malaria parasite (Plasmodium mexicanum) in its host, the western fence lizard (Sceloporus occidentalis): host testosterone as a source of seasonal and among-host variation?

The course of infection of a malaria parasite (Plasmodium mexicanum) is highly variable in its host, the fence lizard (Sceloporus occidentalis). However, a seasonal trend is superimposed on this variation such that gametocyte production is intensified during mid- to late summer. Host testosterone levels follow a similar seasonal fluctuation and are variable among individual lizards. We sought to determine if testosterone levels affect seasonal and among-host variation in 11 P. mexicanum life history traits: rate of increase in level of infection (3 measures), peak parasitemia (3 measures), duration of increase (3 measures), time to detectable infection, and timing of production of gametocytes. We followed the course of infection in 125 male S. occidentalis, each randomly assigned to 1 of 4 treatment groups: castrated, castrated and implanted with exogenous testosterone, sham implanted, and unmanipulated controls. Median values for the 11 life history traits did not differ among treatment groups, and variances were homogeneous among the treatment groups for 10/11 traits. However, elevated testosterone significantly reduced the variation in timing of the onset of gametocyte production. Therefore, testosterone does not appear to be a primary regulator of P. mexicanum life history, yet testosterone may have some effect on when gametocytes first become detectable.     

New data on aphid fauna (Hemiptera,Aphididae) in?Algeria

A survey of aphids was carried out during the period 2008-2011 in different regions of Algeria by collecting and identifying aphids and their host plants. Aphids were collected from 46 host plants. Forty-six species were reported including thirty-six species which were recorded for the first time in this country and thirty species which were recorded for the first time in the Maghreb (North Africa). This study extends the number of known Algerian aphid to 156 species.     

Extracellular matrix metalloproteinase inducer (EMMPRIN) and matrix metalloproteinases (MMPs) as regulators of tumor–host interaction in a spontaneous metastasis model in rats

EMMPRIN has a role in invasion and metastasis through the induction of MMPs and the consequent modulation of cell-substrate and cell–cell adhesion processes. The present study evaluates the expression of EMMPRIN protein and MMP-2/9 activity in tumor and parenchymal cells in a spontaneous metastasis model in rats. Moreover, we explore the regulation of EMMPRIN and MMP-9 by tumor-epithelial cell interactions in vitro. By zymography, we observed an increased proMMP-9 expression in both metastasized liver and spleen samples from tumor bearing rats. Immunohistochemical studies showed EMMPRIN-positive tumor cells in tumor biopsies as well as in spleen and liver samples from tumor bearing rats. Interestingly, a significant increase in EMMPRIN expression in hepatic cells was also detected. The regulation of EMMPRIN expression in tumor and liver cells in response to tumor–host interaction was investigated in vitro through a tumor cell line culture on extracellular matrix (ECM) molecules or in co-culture with normal rat liver cells (BRL3A cells). No significant changes in EMMPRIN expression were detected in tumor cells cultured on ECM molecules. On the other hand, EMMPRIN protein and MMP-9 mRNA expression were induced in BRL3A cells. The increase in EMMPRIN expression in BRL3A cells was inhibited by an anti-EMMPRIN antibody. These results reinforce the main role of EMMPRIN mediating tumor–host interactions that may evolve new opportunities for therapeutic interventions.     

Effects of anthropogenic factors on spider communities (Arthropoda: Araneae) in Chréa National park (Blida,Algeria)

Chréa National Park, one of the 11 national parks in Algeria, is natural and diverse but under different pressures: urbanisation, fires caused by the high flux of visitors. Several ecological and systematic studies have been conducted on the Araneae, the most important epigeal fauna, but no attention was given to the anthropogenic parcels of the Park. To assess the effects of urbanisation and fires on the ecology of this fauna, spiders were collected monthly for 2 years, using ‘Pitfall’ traps in three disturbed stations: burned, urbanised and reforested and three natural sites as control. In total, 1,476 specimens were sampled (19 families, 42 genera and 68 species). Zodarion algericum was the dominant species (13.25%), particularly in the burned station. Mann–Whitney U test showed a significant difference between urbanised and nonurbanised sites in contrast to other ones and no significant differences with the control. Our results show that fires transform the forest into a mosaic of habitats, with open gaps of different stages of succession. In addition, the reforestation of cedars without any agricultural practices has no negative effects on the Park. No loss of biodiversity was observed; this would encourage the restoration of the forest to protect its fauna and flora.     

Patterns in the Distribution of Cladocerans (Crustacea: Branchiopoda) in Lakes Across a North–south Transect in Alaska, USA

The remains of cladocerans were examined from the surface sediments of 51 freshwater sites along a north–south transect spanning Alaska. We identified 27 cladoceran taxa from the sediments, consisting primarily of littoral chydorid species. Variations in cladoceran assemblages were related to measured physical and chemical variables using multivariate techniques. Redundancy analysis (RDA) indicated that lake depth, total phosphorus (TP), and altitude all had a significant influence in determining the composition of cladoceran assemblages. Cladoceran communities in tundra and forest-tundra lakes, which were relatively shallow and nutrient-poor, had relatively low abundances of pelagic Cladocera, and were primarily composed of several littoral chydorid species. Among pelagic cladoceran species, there was a distinct shift in dominance from the Bosminidae in lakes in the southern boreal forest region to Daphniidae in lakes in the northern boreal forest. Daphnia dominated lakes had significantly higher total phosphorus, specific conductivity, and calcium concentrations than lakes dominated by Eubosmina. Overall, the relative importance of physical and chemical factors in structuring cladocerans is similar to other previously studied regions, and suggests the Cladocera may be useful as ecological and paleoenvironmental indicators in this region.     

Gap-phase regeneration in a semideciduous mesophytic forest, south–eastern Brazil

The study was carried out in ten natural canopy gaps in the SantaGenebra County Reserve (22°4945S, 47°0633W)in the county of Campinas, São Paulo State, Brazil. The size and canopyopenness of the gaps were studied using hemispherical photographs. Thevegetation survey included all shrubs and trees with height 0.50m in the gaps interiors and all the individuals with PBH(perimeterat breast height) 15 cm in a 3 m surroundingborder of the gaps. The similarity among the gaps and among their surroundingareas was assessed by the Jaccard similarity index and by cluster analyzes. Thegap size varied from 20.09 to 468 m², with apredominance of small gaps. The families with the greatest species richness inthe gaps were Rutaceae, Rubiaceae and Euphorbiaceae. The species with thegreatest number of individuals in the gaps were Coffeaarabica L., Hybanthus atropurpureus (St. Hil.)Taub. and Actinostemon klotschii (Muell. Arg.) Pax, allwidely distributed in the understorey. Shade-tolerant species (late secondaryspecies) predominated in function of the predominance of small gaps. The highnumber of species found in the gaps reflects the importance of thesedisturbances in the maintenance of species diversity in the studied forest.     

Leishmania infection in humans, dogs and sandflies in a visceral leishmaniasis endemic area in Maranhão, Brazil

Leishmania infection in humans, dogs and sandflies was examined in the endemic visceral leishmaniasis (VL) municipality of Raposa, state of Maranh?o, Brazil. In this study, we examined Leishmania chagasi infection in the blood serum of both humans and Canis familiaris and the natural Leishmania sp. infection rate in the sandfly vector, Lutzomyia longipalpis. Enzyme-linked immunosorbent assay, indirect immunofluorescence reaction and polymerase chain reaction were performed to detect Leishmania infections in humans, dogs and sandflies, respectively. Overall, 186 out of 986 studied human beings were infected with L. chagasi parasites, representing an infection prevalence of 18.9%. An even higher infection rate was detected in dogs, where 66 (47.8%) out of 138 were infected. Among all Lu. longipalpis captured (n = 1,881), only 26.7% were females. The Leishmania infection frequency for the vector Lu. longipalpis was 1.56%. Remarkably, all infected sandflies were found in the peridomiciliary area. Furthermore, a high incidence of asymptomatic forms of VL in the human and canine populations was observed. The results of this study suggest autochthonous transmission of L. chagasi in this endemic area for visceral leishmaniasis because infection by Leishmania sp. was identified in all important elements of the transmission chain.     

Cluster analysis as a method for evaluation of genetic similarity in specific host — parasite interaction (Lactuca sativa — Bremia lactucae)

Summary In gene-for-gene systems, specificity of hostparasite interactions is most often estimated qualitatively using the symbols +, –, (i.e. susceptibility and/or resistance). In large sets (interaction patterns) it becomes impossible to analyze numerous data by mere comparison. This is overcome by application of cluster analysis. In our experiments the methods in question were used to estimate the data obtained in a study on interactions between more than 220 Lactuca sativa cultivars and 12 Bremia lactucae physiological races (isolates) of Czechoslovak origin. The matrix of similarity coefficients was analyzed by hierarchical clustering. Similarity and/or dissimilarity of host R-genotypes was graphically expressed using the method of two principal components. The results obtained are related to genetic constitution of race specific resistance of the host and the possibility of predicting effective resistance sources.     

Tree population changes in a tropical dry evergreen forest of south India over a decade (1992–2002)

Changes in species composition and density of trees >10 cm gbh in a tropical dry evergreen forest in Puthupet, south India are interpreted for the period between 1992 and 2002. A 1-ha plot was inventoried in 1992 and was recensused in 2002. During the 10-year interval tree taxa diversity as well as stand density increased, but the basal area value decreased. Tree species richness increased by 21% (from 24 to 29 species) by an addition of eight species and local extinction of three species. The tree density increased just by eight individuals (from 1330 stems ha⁻¹ in 1992 to 1338 ha⁻¹ in 2002), but the basal area decreased by 8% (from 37.5 to 34.5 m² ha⁻¹). Many species (11 numbers) have increased in abundance rather than decreased. Many surviving species seem to have considerable stability in abundance at the local scale. The density of smaller stems (10 29 cm gbh) increased by 15.3%, while that of the larger trees decreased drastically (81.6%). Ninety percent of the missing stems were from the middlestorey of the forest. Tree density changes among the three ecological guilds revealed a decrease in stem density and an increase in basal area in the lowerstorey; while the middlestorey exhibited a reverse trend. Family-wise, tree density changes revealed that the majority of families (67%) showed an increase in stem density. Long-term studies on tree population changes are essential to estimate tree mortality and recruitment rates, which will provide a greater insight in tropical forest dynamics.     

Phytoplankton seasonal variation in a shallow stratified eutrophic reservoir (Garças Pond, Brazil)

This study aimed at describing the phytoplankton dynamics and structure in a shallow eutrophic reservoir, the Garças Pond, located in the Parque Estadual das Fontes do Ipiranga (23°38′40.6′′ S, 46°37′28.0′′ W), in the Municipality of São Paulo, southeast Brazil. Samples were collected monthly from January to December 1997 in five depths (subsurface, 1 m, 2 m, 3 m, and 20 cm above the bottom) in the pelagic zone (Z _max = 4.7 m). Abiotic variables studied were: water temperature, turbidity, transparency, conductivity, pH, dissolved oxygen, alkalinity, inorganic carbon, and N and P dissolved and total forms. Altogether 236 phytoplankton taxa distributed among 10 classes were identified. Phytoplankton seasonal and vertical variation was related to shifts in the water chemical features as a consequence of a warm-wet season with stratified water column (phase 1, January–March and September–December) alternating with a cool-dry season with mixed water column (phase 2, April–August). There were shifts in cyanobacterial dominance over the entire year. During phase 1, Raphidiopsis/Cylindrospermopsis was one of the most important taxon. During phase 2, Raphidiopsis/Cylindrospermopsis biomass decreased, whereas richness and diversity increased and diatoms were relatively abundant. In September, when the water column was markedly stratified, a cyanobacterial bloom (Sphaerocavum brasiliense) occurred. Changes in water chemical variables caused by the bloom allowed recognition of a phase 3, in which pH and chlorophyll a, TP and CO₃ ^2? concentration reached their highest values. According to Reynolds and collaborators’ functional groups approach, phase 1 was marked by groups S/W1/W2/H1/Y, phase 2 by groups K/L _M /L _O /D/P/X1/F, and phase 3 by group M. This sequence was corroborated by canonical correspondence analysis (CCA) results.     

Exploitation or cooperation? Evolution of a host (ciliate)-benefiting alga in a long-term experimental microcosm culture

Controversy persists as to whether the acquisition of beneficial metabolic functions via endosymbiosis can occur suddenly on an evolutionary time scale. In this study, an early stage of endosymbiotic associations, which evolved from previously unassociated auto (photo)- and heterotrophic unicellular organisms was analyzed using an experimental ecosystem model, called CET microcosm. This ecosystem model was composed of a green alga (Micractinium sp.; formerly described as Chlorella vulgaris), a bacterium (Escherichia coli), and a ciliate (Tetrahymena thermophila). Our previous study using a CET microcosm that was cultured 3–5 years revealed that fitness of the ciliate increased by harboring algal cells within its own cells. This fact suggested three possibilities: (i) the ciliate evolved the ability to exploit intracellular algal cells (“exploiter ciliate hypothesis”), (ii) the alga evolved the ability to benefit the host ciliate by providing photosynthates (“cooperator alga hypothesis”), and (iii) a combination of (i) and (ii). To test these hypotheses, two-by-two co-cultures were conducted between the ancestral or derived ciliate and the ancestral or derived alga. The experimental results demonstrated that a cooperative alga evolved in the microcosm, although the possibility remains that an exploitative genotype of the ciliate might also exist in the population as a polymorphism. Remarkably, an algal isolate prolonged the longevity of not only the isolated ciliate, but also the ancestral ciliate. This result suggests that once a cooperative algal genotype evolves in a local population, it can then be transmitted to other individuals of the prospective host species and spread rapidly beyond the local range due to its positive effect on the host fitness. Such transmission suggests the possibility of a sudden acquisition of beneficial autotrophic function by the pre-associated host.     

Twisted hyperboloid (strophoid) as a model of β-barrels in proteins

Using a least-squares fitting procedure, polypeptide backbones of one parallel and seven antiparallel β-barrels were approximated with various curved surfaces. Although the hyperboloid gave better approximations to all the β-barrel backbones than the ellipsoid, elliptical cylinder or catenoid, the best approximations were obtained with a novel surface, a twisted hyperboloid (strophoid). The root-mean-square errors between individual β-barrels and the fitted strophoid surfaces ranged from 0.75 Å to 1.64 Å. The parameters which determine the strophoid surface allow groups of β-barrel shapes to be defined according to their barrel twists (i.e. angles subtended by directions of the long axis of cross-section at the top and the bottom of the barrel), course of elliptical cross-sections (either monotonically increasing along the barrel axis, as in cones, or having a middle “waist”, as in hyperboloids), and types of backbone curvatures (either convex or concave). The curvatures at individual points of strophoid surface are local, variable quantities related to the local helicity (coil) of the polypeptide backbone, in contrast to values of β-sheet twist (i.e. dihedral angles subtended by adjacent β-strands) known to be virtually identical in all the β-sheets. The variability found in parameters such as barrel shapes and curvatures suggests that simple models (isotropically stressed surfaces, principle of minimal surface tension) proposed in the past to account for β-barrel shapes are not sufficient. Rather, the complex nature of best-fit theoretical surfaces points to an important role played by a local variability of the forces involved.     

在中国西北地区发现的两种副蛉亚属白蛉——亚历山大白蛉(Phlebotomus alexandri Sinton,1928)及高加索白蛉(P.caucasicus Marzinovsky,1917)

根据国外文献记载,白蛉属(Genus Phlebotomus)副蛉亚属(Subgenus Paranhlebotomus)的蛉种已有6种和两个变种。过去在我国仅发现蒙古白蛉(P.mongolensis Sinton,1928)一种。1958年至1961年间,我们在新疆维吾尔自治区的阿图什及甘肃省的酒泉与玉门等地的荒漠地区中发现了属于副蛉亚属的亚历山大白蛉(P.alexandri Sinton,1928),同时     

Phytoplankton as a monitoring tool in a tropical urban shallow reservoir (Garças Pond): the assemblage index application

This study aimed at evaluating phytoplankton as a monitoring tool for water quality assessment in an urban shallow eutrophic reservoir considering temporal and vertical scales. Garças Reservoir is located in the Parque Estadual das Fontes do Ipiranga Biological Reserve (23°38′08″S and 23°40′18″S; 46°36′48″W and 46°38′00″W) that lies in the southeastern part of the Municipality of São Paulo, southeast Brazil. Samplings were carried out monthly during 8 consecutive years (1997–2004) following the water column vertical profile (5 depths: subsurface, 1, 2, 3 m and ~20 cm from the bottom). Abiotic variables analyzed were: water temperature, electric conductivity, DO, pH, total alkalinity, free CO₂, dissolved inorganic carbon, N series, P series and SiO₄H₄. Biological variables studied were: total density, total biomass and chlorophyll a, which were integrated arithmetically. At the beginning of the 8 year series, Garças Reservoir was an eutrophic ecosystem with 20% of its surface covered by Eichhornia crassipes (phase I: January 1997–March 1998). Water hyacinth reached 70% of pond surface coverage (phase II: April 1998–August 1999), and then it was mechanically removed (phase III: September 1999–December 2004). After this intervention, drastic alteration in the limnological features was detected, leading to the conclusion that removal of the aquatic macrophyte modified nutrient dynamics drastically reduced water transparency and led to photosynthetic productivity and phytoplankton biomass increase, the latter becoming a physical barrier to light penetration. Twenty one functional groups ‘sensu’ Reynolds were identified. Cyanobacteria contribution played the main role during the drastic alterations that occurred after water hyacinth removal. Results of ecological status of reservoir using Q index showed statistical difference among the 3 limnological phases (one way ANOVA; F = 119.4; P = 0.000). Regarding Q index classification, Garças Reservoir limnological phases were characterized as follows: (1) phase I: 0 ≥ Q ≤ 2.9, medium to bad; (2) phase II: 1.4 ≥ Q ≤ 3, tolerable to medium; and (3) phase III: 0 ≥ Q ≤ 1.5, bad to tolerable ecological states.     

Phlebotomus from Madagascar (Diptera: Psychodidae). II--Description of the female Phlebotomus (Anaphlebotomus) fertei Depaquit, Léger & Robert, 2002; description of the male and new data for the female Phlebotomus (Anaphlebotomus) berentiensis (Léger & Rodhain, 1978) comb. nov

The female of Phlebotomus (Anaphlebotomus) fertei Depaquit, Léger & Robert, 2002 is described from Madagascar. The spermathecae have separated ducts, a body with an enlarged-sclerified dilatation and a deriviated large bladder with thin walls and long head. P. fertei female has the following characters: long antennal segments, pharyngeal armature with small teeth and cibarium with 15 to 30 denticles, and very long legs. Its remarkable spermatheca is closely related to that of P. berentiensis. The status of P. (Anaphlebotomus) berentiensis (Léger & Rodhain, 1978) is revised into this paper. The female is redescribed and the male is described for the first time. The latter has an unusual antennal formula (2/III-XII), a cibarium with four teeth and about 30 denticles, no tuft of setae on the coxite, four spines on the style, including a very long proximal one. Males and females were linked to each other based on morphological and molecular characteristics (second internal transcribed spacer of the ribosomal DNA and ND4 gene of the mitochondrial DNA). The inclusion of these taxa into the subgenus Anaphlebotomus Theodor, 1948 is exclusively based on male characters as listed by Theodor (style with four spines, no basal lobe on the coxite, paramere with two or three branches). The very heterogeneous characters of the females do not allow their use for the definition of this subgenus, which is probably not homogeneous.