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Biomedical subjects

W L Paraense

Publications and source records attributed to W L Paraense.

At least 19 recordsLinked to original sources
PubMed1978

Differential susceptibility of Biomphalaria tenagophila populations to infection with a strain of Schistosoma mansoni.

Experiments to determine the susceptibility of Biomphalaria tenagophila from 20 localities over the species range exposed to a strain of Schistosoma mansoni showed widely varying infection rates, from 0% to 91.5%, this latter having been observed in a sample from an area where the natural infection rate of B. tenagophila has been the highest in the country. Comparison with similar studies involving B. glabrata seems to indicate that a process of adaptation between S. mansoni and B. tenagophila is evolving, the 2 organisms having reached a high degree of compatibility in a few areas. The present results point to the possibility of expansion of schistosomiasis to a wide South American area where B. tenagophila occurs.

Adaptation, Biological↗
PubMed1976

The fine structure of Schistosoma mansoni sperm (Trematoda: Digenea).

The sperm of the blood fluke Schistosoma mansoni consist of a bulbous head 8 by 2 mum, with a rounded anterior tip and tapering posterior region, followed by a relatively short flagellum ca. 20 mum long. Electron microscopic observations revealed that these sperm are devoid of an acrosome, while a few undifferentiated mitochondria accumulate at the anterior part of the head. The nucleus appears dense, except for some electron-lucent patches. The flagellum starts at the basal body, posterior and slightly lateral to the nucleus, and the axial complex is of the 9 + 0 type. A layer of microtubules runs longitudinally, just beneath the plasmalemma, from the anterior part of the head to the initial part of the flagellum, where they overlap with the axial complex. It is suggested that this relatively rudimentary type of the S. mansoni sperm is probably related to the low activity required for fertilization.

Animals↗
PubMed1976

A natural population of Helisoma duryi in Brazil.

A well established natural population of Helisoma duryi (Wetherby) was recently found in central Brazil, where it was introduced probably with aquatic plants conveyed by aquarists. A morphological description based on the observation of 10 specimens is presented, involving the shell, cephalopodal mass, mantle organs, reproductive system and buccal apparatus.

Animals↗
PubMedDate not supplied

[Biomphalaria glabrata in the state of Piaui].

The occurrence of Biomphalaria glabrata is recorded for the first time in the state of Piaui, where it was collected from several breeding places in the city of Parnaíba. Examination of 694 specimens showed that a part of them were infected with trematodes other than Schistosomatidae. So far no autochthonous cases of schistosomiasis have been identified in the city. The presence of B. glabrata in Parnaíba extends by 20 km eastward its range on the Northern Coastal Region of the Great Northeastern Region of Brazil, where it had been found as far as Araioses, on the eastern extreme of the state of Maranhão.

Animals↗
PubMedDate not supplied

[New foci of transmission of Schistosoma mansoni in the state of Pará].

Two new foci of transmission of Schistosoma mansoni in the state of Pará are recorded, with the finding of naturally infected Biomphalaria glabrata in the municipalities of Viseu and Belém. Uninfected specimens of Biomphalaria straminea, as well as the planorbid species Biomphalaria schrammi, Drepanotrema lucidum and D. anatinum, were found in the same area.

Animals↗
PubMedDate not supplied

Further experiments on susceptibility of Biomphalaria amazonica to Schistosoma mansoni.

A sample of Biomphalaria amazonica from Porto Velho, Rondônia state, was exposed to miracidia of Schistosoma mansoni (SJ2 strain) from São José dos Campos, São Paulo state (five miracidia per snail). Water freshly taken from the snails' breeding place was used to make sure that its quality was compatible with hatching of miracidia and their penetration into the snails. The resulting infection rate was 3.5%, as against 45% in B. tenagophila controls. In comparison with the controls, B. amazonica, besides a lower infection rate, showed a longer prepatent period and a lower cercarial production. These characteristics seem to indicate that it is a poor host of S. mansoni, like B. straminea, but it should be considered that, this notwithstanding, the latter is admittedly a good vector of the parasite in hyperendemic areas of northeastern Brazil. These results point to the possibility of introduction of schistosomiasis mansoni into the western Amazonian region, where B. amazonica is widespread.

Animals↗
PubMedDate not supplied

Differentiation of the sibling species Biomphalaria occidentalis and Biomphalaria tenagophila by the electrophoretic patterns of their hemoglobin.

A simple and rapid method for differentiating the sibling species Biomphalaria tenagophila and Biomphalaria occidentalis by agarose gel electrophoresis (AGE) is described. Snail hemolymph is used as the test sample and the red coloration of the hemoglobin fraction permits visualization of the migration patterns without resorting to specific stains. Moreover, hemolymph samples may be obtained without killing the snail, thus permitting its use for other studies or for breeding.

Animals↗
PubMedDate not supplied

Self-fertilization in the freshwater snails Helisoma duryi and Helisoma trivolvis.

Fifty specimens of five strains (10 per strain) of Helisoma duryi from Lima (Peru), St. Croix (Virgin Islands), Formosa (Brazil), Cartago (Costa Rica) and St. Vincent (Lesser Antilles), reared in isolation for about 150 days, laid 103 eggs. The numbers of eggs laid by the 10 specimens of each strain were respectively (viable eggs in parenthesis): 44 (26), 1 (1), 5 (0), 15 (7) and 38 (0). Egg production widely varied between the individuals of each strain, there being in all strains, except St. Vincent, a number of specimens (3 to 9) which did not lay any eggs. After the observation period the isolated specimens, including those that laid no eggs, readily engaged in cross-breeding when mated and brought forth large numbers of eggs. Self-fertilized F1S are fully interfertile, producing normal cross-fertilized offspring. Ten specimens of Helisoma trivolvis (strain from Zempoala, Mexico), also reared in isolation for about 120 days, laid 646 eggs, of which 74 were inviable. Our data, added to those from a few previous studies cited in the text, show that self-fertilization is not so efficient an alternative mode of reproduction in H. duryi as in many other planorbids (it is a little more efficient in H. trivolvis than in H. duryi). Thus, H. duryi benefits much less from functional hermaphroditism which, besides other advantages, enables a single virgin individual to found a new population.

Animals↗