Variação temporal do zooplâncton da Praia de Tramandaí, Rio Grande do Sul, com ênfase em Copepoda

Com o objetivo de conhecer a variação temporal da composição, abundância, diversidade e biomassa do zooplâncton da zona de arrebentação da Praia de Tramandaí, Rio Grande do Sul, amostragens quinzenais foram realizadas entre agosto de 2005 e agosto de 2006. Os arrastos foram efetuados com rede cilindro-cônica com 150 cm de comprimento, 50 cm de diâmetro de boca e malha de 300 µm. Dados de clorofila-a, direção do vento, corrente de deriva litorânea, salinidade, temperatura do ar e da água também foram obtidos. O grupo dos Copepoda foi responsável pela maior diversidade de espécies, sendo que Temora turbinata (Dana, 1849) apresentou maior abundância relativa e freqüência de ocorrência. Outras espécies de Copepoda também foram importantes numericamente como Acartia tonsa (Dana, 1849), Subeucalanus pileatus (Glesbrecht, 1888) e Ctenocalanus vanus (Glesbrecht, 1888). O Mysidacea Metamysidopsis elongata atlantica (Bascescu, 1968) apresentou freqüência de 58,33% e abundância relativa de 44%, sendo o pico de biomassa de mesozooplâncton (96 mg.m-3) registrado em setembro de 2005 correspondente ao máximo valor de densidade apresentado pela espécie (3.535 org.m-3). Informações sobre o zooplâncton desta região são muito escassos e os dados levantados servirão de base para o conhecimento dos processos biológicos que ocorrem na coluna d'água da Praia de Tramandaí.

Diversity and structure of microcrustacean assemblages (Cladocera and Copepoda) and limnological variability in perennial and intermittent pools in a semi-arid region, Bahia, Brazil

Temporary wetlands undergo recurrent drought due to the scarcity of water, which disrupts the hydrological connectivity with adjacent aquatic systems. However, some environments retain water for longer periods, allowing greater persistence of the community. The current study evaluated differences in the microcrustacean assemblages and limnological variability between perennial and intermittent pools in a semi-arid region of Brazil. The abiotic features (water temperature, pH, total alkalinity, electrical conductivity and depth) of intermittent pools were affected more than perennial pools due to loss of water volume. This may have contributed to a higher average richness and diversity index in some intermittent pools and differences in the structure of the assemblages. The lowest species richness and diversity were recorded where physical factors, such as a large quantity of suspended solids and variability in the electrical conductivity of the water and pH, make the environment unsuitable for these organisms. These results suggest that community development in intermittent pools is interrupted by the dry season; when the water returns, due to rainfall or rising groundwater, each pond undergoes a different process of colonization. In these circumstances, the biological importance of temporary aquatic environments is clear, since such pools provide shelters and have an important role in the maintenance of the regional diversity of aquatic environments.

Establishment of a new genus for Parastenocaris itica (Copepoda, Harpacticoida) from El Salvador, Central America, with discussion of the Parastenocaris fontinalis and P. proserpina groups

A new genus of Parastenocarididae is described from the Neotropical region. Iticocaris gen. nov. is established to include Parastenocaris itica Noodt, 1962. Iticocaris gen. nov. is defined by the following characters: 1) male leg 3 with 2-segmented exopod; 2) first exopodal segment short and rectangular; 3) thumb hypertrophic, longer than the second exopodal segment and inserted on the distal edge of exopod segment 1, occupying the whole distal margin; 4) exopod 2 or apophysis strongly sclerotized, articulated with the exopod segment 1 on its inner margin and curved against the thumb, forming a strong forceps; 5) leg 4 endopod without dimorphism in shape and size vs. minor dimorphism in ornamentation; 6) leg 5 with three setae and 7) lack of the anterolateral furcal seta II. The new genus is monotypic, represented by Iticocaris itica (Noodt, 1962) comb. nov., from El Salvador, Central America. A close relationship is hypothesized between I. itica and the genus Brasilibathynellocaris Jakobi, 1972, the males of which both share the forceps-like elongated apophysis.

Morphometric differences in two calanoid sibling species, Boeckella gracilipes and B. titicacae (Crustacea, Copepoda)

Calanoid copepods are abundant in South American inland waters and include widespread species, such as Boeckella gracilipes (Daday, 1902), which occurs from the Ecuador to Tierra del Fuego Island. This species occurs under various environmental conditions, and is found in oligotrophic lakes in Patagonia (39-54°S) and in shallow mountain lakes north of 39°S. The aim of the present study is to conduct a morphometric comparison of male specimens of B. titicacae collected in Titicaca and B. gracilipes collected in Riñihue lakes, with a third population of B. gracilipes collected in shallow ponds in Salar de Surire. Titicaca and Riñihue lakes are stable environments, whereas Salar de Surire is an extreme environment. These ponds present an extreme environment due to high exposure to solar radiation and high salinity levels. The results of the study revealed differences among the three populations. These results agree well with systematic descriptions in the literature on differences between the populations of Titicaca and Riñihue lakes, and population of Salar de Surire differs slightly from the other two populations. It is probable that the differences between the population of Salar de Surire and the other two populations result from the extreme environment in Salar de Surire. High exposure to solar radiation, high salinity and extreme variations in temperature enhance genetic variations that are consequently expressed in morphology.

Inhibitory effect of cyclophosphamide on the biosynthesis of a perchloro-soluble protein fraction of ehrlich ascites carcinoma cells

The perchloro-soluble mucroptotein fraction was determined in the cells of Ehrlich ascites carcinoma on the 10th and 12th days post-inoculation of the tumor. After 3 days of a single subcutaneous dose of cyclophosphamide (200 mg/kg) the mucoprotein levels were found considerable lower. This difference was highly significant statistically.

Cellular immune response of humans to the circumsporozoite protein of Plasmodium vivax

The cellular immune response to the circumsporozoite (CS) protein of plasmodium vivax of individuals from malaria-endemic areas of Brazil was studied. We examined the in vitro proliferative response of the peripheral blood mononuclear cells (PBMC) of 22 individuals when stimulated with a CS recombinant protein (rPvCS-2) and two other synthetic peptides based on the sequenceof the P. vivax CS protein. Seven of the individuals from malaria-endemic area displayed an antigen specific in vitro proliferative responseto the recombinant protein PvCS-2 and one out of 6, proliferative response to the peptide 308-320. In contrast, none of the individuals displayed a proliferative reponse when stimulated with the D/A peptide which represent some of the repeated units present in this CS protein. Our study, therefore, provides evidence for the presence, withinthe major surface antigen of P. vivax sporozoites, of epitopes capble to induce proliferation of human PBMC.

A malaria merozoite surface protein (MSP1)-structure, processing and function

Merozoite surface protein-1 (MSP-1, also referred to as P195, PMMSA or MSA 1) is one of the most studied of all malaria proteins. The proteins. The protein is found in all malaria species investigated and structural studies on the gene indicate that parts of the molecule are well-conserved. Studies on Plasmodium falciparum have shown that the protein is in a processed form on the merozoite surface, a result of proteolytic cleavage of the large percursor molecule. Recent studies have identified some of these cleavage sites. During invasion of the new red cell most of the MSP1 molecule is shed from the parasite surface except for a small C-terminal fragment which can be detected in ring stages. Analysis of the structure of this fragment suggests that it contains two growth factor-like domains that may have a functional role.

Human IgG responses against the N-terminal region of Merozoite Surface Protein 1 of Plasmodium vivax

The complete primary structure of the gene encoding the Merozoite Surface Protein 1 of Plasmodium vivax (PvMSP-1) revealed the existence of interspecies conserved regions among the analogous proteins of other Plasmodia species. Here, three DNA recombinant clones expressing 50, 200 and 500 amino acids from the N-terminal region of the PvMSP-1 protein were used on ELISA and protein immunoblotting assays to look at the IgG antibody responses of malaria patients from the Brasilian amazon region of Rondônia. The results showed the existance of P. vivax and P. falciparum IgG antibodies directed against PvMSP-1 antigenic determinants expressed in the clones containing the first 200 and the following 500 amino acids of the molecule, but not within the one expressing the most N-terminal 50 amino acids. Interestingly, there was no correlation between the levels of these IgG antibodies and the previous number of malaria infections.

The Pf332 gene codes for a megadalton protein of Plasmodium falciparum asexual blood stages

We characterized the Plasmodium falciparum antigen 332 (Ag332) which is specifically expressed during the asexual intraerythrocytic cycle of the parasite. The corresponding Pf332 gene has been located in the subtelomeric region of chromosome 11. Furthermore, it is present in all strais so far analyzed and shows marked restriction length fragment polymorphism. Partial sequence and restriction endonuclease digestion of cloned fragments revealed that the Pf332 gene is composed of highly degenerated repeats rich is glutamic acid. Mung been nuclease digestion and Northern blot analysis suggested that Pf332 gene codes for a protein of about 700 kDa. These data were further confirmed by Western blot and immunoprecipitation of parasites extracts with an antiserum raised against a recombinant clone expressing part of the Ag332. Confocal immunofluorescence showed that Ag332 is translocated from the parasite to the surface of infected red blood cells within vesicle-like structures. In addition, Ag332 was detected on the surface of monkey erythrocytes infected with Plasmodium falciparum.

A recombinant hybrid protein as antigen for an anti-blood stage malaria vaccine: a study on the conservation of a protective component

Recently we have shown that two hybrid proteins expressed in Escherichia coli confer protective immunity to Aotus monkeys against an experimental Plasmodium falciparum infection (Knapp et al., 1992). Both hybrid proteins carry a sequence containing amino acids 631 to 764 of the serine stretch protein SERP (Knapp et al., 1989b). We have studied the diversity of this SERP region in field isolates of P. falciparum. Genomic DNA was extracted from the blood of six donors from different endemic areas of Brazil and West Africa. The SERP region encoding amino acids 630 to 781 was amplified by polymerase chain reaction (PCR) and sequenced. Only conserved amino acid substitutions in maximally two positions of the analyzed SERP fragment could be detected which supports the suitability of this SERP region as a component of anti-blood stage malaria vaccine.

Development of an immunoenzymatic assay using a monoclonal antibody against a 50-kDa catabolite from the P126 Plasmodium falciparum protein to the diagnosis of malaria infection

The WHO criterion of defering any donation of blood by a confirmed case of malaria for three years after cessation of therapy can not be applied in areas where malaria in endemic. For this reason we developed an immunoenzymatic assay for the detection of plasmodial antigens for blood screening in malararial endemic areas. So, we tested sera from 191 individuals. Among patients with active disease 100% of the cases of Plasmodium falciparum or mixed infections and 91.7% of those with P. vivax were positive for the presence of plasmodial antigens. The lower parasitaemia detected was 0.0003% for P. vivax malária. When the frequency of positive circulating malarial antigens was evaluated among asymptomatic and symptomatic individuals with negative TBS, positive results were found in respectively 38.7% and 17.7% of the individuals studied in the 30 days after confirmed malaria attack. Data provide by these assays have shown that ELISA seemed to be more sensitive than parasitological examination for malaria diagnosis. This test by virtue of its high sensivity and the facilities in processing a large number of specimens, can prove to be useful in endemic areas for the recognition of asymptomatic malaria and screening of blood donors.

T cell responses to repeat and non-repeat regions of the circumsporozoite protein detected in volunteers immunized with Plasmodium falciparum sporozoites

The design of malarial vaccine based on the circumsporozoite (CS) protein, a majuor surface antigen of the sporozoite stage of the malaria parasite, requires the identification of T and B cell epitopes for inclusion in recombinant or synthetic vaccine candidates. We have investigated the specificity and function of a series of T cell clones, derived from volunteers immunized with Plasmodium falciparum sporozoites in an effort to identify relevant epitopes in the immune response to the pre-erythrocytic stages of the parasite. CD4+ T cell clones were obtained wich specifically recognized a repetitive epitope located in the 5'repeat region of the CS protein. This epitope, when conjugated to the 3'repeat region in a synthetic MAPs construct, induced high titers of antisporozoite antibodies in C57B1 mice. A second T cell epitope, which mapped to aa 326-345 of the carboxy terminal, was recognized by lytic, as well as non-lytic, CD4+ T cells derived from the sporozoite-immunized volunteers. The demonstration of CD4+ CTL in the volunteers, and the recent studies inthe rodent model (Renia et al., 1991; Tsuji et al., 1990), suggested that CS-specific CD4+ T cells, in addition to their indirect role as helper cells in the induction of antibody and CD8 + effector cells, may also play a direct role in protection against sporozoite challenge by targeting EEF within the liver.

Plasmodium falciparum CS protein - prime malaria vaccine candidate: definition of the human CTL domain and analysis of its variation

Studies in mice have shown that immunity to malaria sporozoites is mediated primarily by citotoxic T lymphocytes (CTL) specific for epitopes within the circumsporozoite (CS) protein. Humans, had never been shown to generate CTL against any malaria or other parasite protein. The design of a sub-unit vaccine for humans ralies on the epitopes recognized by CTL being identified and polymorphisms therein being defined. We have developed a novel technique using an entire series of overlapping synthetic peptides to define the epitopes of the Plasmodium falciparum CS protein recognized by human CTL and have analyzed the sequence variation of the protein with respect to the identified CTL epitopic domain. We have demonstrated that some humans can indeed generate CTL. against the P. falciparum CS protein. Furthermore, the extent of variation observed for the CTL recognition domain is finite and the combination of peptides necessary for inclusion in a polyvalent vaccine may be small. If ways can be found to increase immune responsiveness, then a vaccine designed to stimulate CS protein-specific CTL activity may prevent malaria.