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PubMedDate not supplied

[Biological characteristics and ecological factors determining mammalian radioresistance in the Rodentia order].

Both the results of our investigations and published data on mammalian radioresistance, biological characteristics and ecological factors which modify it are generalized in this paper. The described diversity among large taxa in radioresistance is based on the data obtained on the rodents from the Old and the New Worlds (totally 51 samples from 22 genera of four families--Sciurudae, Muridae, Cricetidae, Heteromyidae). It was found that radioresistance substantially depended on which family the species belonged. The main biological characteristics and ecological factors (body size, nutrition type, biotopical restriction) were revealed; in sum they determined 40% of radioresistance of small mammals.

Animals↗
PubMed2004

C-banding karyotype and relationship of the dipodids Allactaga and Jaculus (Mammalia: Rodentia) in Egypt.

The C-banding karyotype of the jerboas Allactaga tetradactyla, Jaculus jaculus jaculus, and Jaculus orientalis was described and interspecific relationships were discussed. Despite the conservation of a relatively small amount of C-heterochromatin located at the centromeric region of some chromosomes in all karyotypes, a striking loss of C-heterochromatin was clearly observed in J. orientalis. C-bands were totally absent in 33 of the 48 chromosomes of J. orientalis, compared to only 7 for J.j.jaculus and 11 for A. tetradactyla. The differences in C-banding amongst karyotypes of the three species were attributed either to transformation of heterochromatin into euchromatin or vice versa, deletion of heterochromatic segments resulting from pericentric inversions, or to variation of euchromatin content and its correlation with the chromosome size and arrangement of heterochromatin. The present findings are consistent with the main hypotheses derived from morphological, chromosomal, and biochemical data that the genera Allactaga and Jaculus have independently developed from a common ancestral form and that J. jaculus and J. orientalis are both distinct congeneric species, but revealed that the C-banding karyotypes of both J.j.jaculus and J. orientalis are distantly related to each other. Therefore, it is concluded that the karyotype of J.j.jaculus may be ancestral and that of J. orientalis may have derived from it.

Animals↗
PubMedDate not supplied

[Morphology and biometry of eggs and larvae of Strongyloides sp. Grassi, 1879 (Rhabditoidea: Strongyloididae), a gastrointestinal parasite of Hydrochaeris hydrochaeris (Linnaeus, 1766) (Rodentia: Hydrochaeridae), in the municipality of Juiz de Fora, Minas Gerais, Brazil].

An important method to diagnose and study the helminthofauna of wild animals is to examine the host's feces to find eggs and larvae, seeking to identify the parasites and study their morphobiology. The objective of the present work is to provide morphological and biometric data on the eggs and larvae of Strongyloides sp., a capybara gastrointestinal parasite. Using the technique of Gordon and Whitlock, simple flotation and the modified Baermann examination, capybara fecal samples were selected based on a criterion of the highest proportion of eggs and larvae in the initial development stages, for morphometric description of eggs, L1, L2 and L3 of Strongyloides sp. From past reports of parasitism in Hydrochaeris hydrochaeris, we suspect that the eggs and larvae in this study are of Strongyloides chapini Sandground, 1925, which constitutes the first description of these stages for this species of nematode. Nevertheless, the morphology and biometry data of these stages demonstrate that they are similar to those of other species of the Strongyloides genus.

Animals↗
PubMed1991

[Chromosome differentiation of spiny rats of the genus Proechimys (Rodentia, Echimyidae)].

Karyological analysis of spiny rats of the genus Proechimys revealed four chromosome forms: 2n = 30; 2n = 29; 2n = 28; 2n = 24. 30-chromosome spiny rats are characterized by unique karyotype constitution. 27-chromosome spiny rats from the territory near Iquitos differ from the same of Pucalpa (Ucayali Department) by Y-chromosome structure and banding of long arms with two pairs of autosomes. 24-chromosome rats from the regions mentioned above do not differ in G-banded chromosomes. Diploid chromosome set equal to 29, has a family originated from the parents which had 2n = 30 and 2n = 28 under the laboratory conditions. The absence of clear morphological differentiation, similarity of constituent parts of the karyotype and hybridization possibility point to relatively recent origination of the chromosome forms under study.

Animals↗
PubMed1990

[Cytogenetic differentiation of Apodemus peninsulae populations (Rodentia, Muridae) in eastern Siberia].

Population and cytogenetics studies of geographical karyotype changes in East Asiatic mice in East Siberia showed that each population has unique cytogenetic structure, owing to different variants of B-chromosomes system, including 1 to 18 B-chromosomes differing in morphology and size. For each population, we observed the prevalence of mice with a definite number and morphology of B-chromosomes, which is probably the result of homeostatic processes in the population. Local changes were revealed, due to increase in the number of dot-like B-chromosomes in the direction from the West to the East.

Animals↗
PubMed1989

Anti-leishmanial antibodies during natural infection of Psammomys obesus and Meriones shawi (Rodentia, Gerbillinae) by Leishmania major.

Sera from 77 rodents (Psammomys obesus: 64; Meriones (M.) shawi: 10; M. libycus: 3) trapped in a focus of zoonotic cutaneous leishmaniasis (ZCL) (Leishmania (L.) major) were examined for the presence of anti-leishmanial antibodies by the indirect fluorscence antibody technique (IFAT) (L. major antigens) using homologous antiglobulins and/or anti-Rattus conjugates. Sera from 21 animals were positive with titres that ranged from 1: 20 up to 1: 640. The investigation revealed that a good correlation existed between the occurrence of antileishmanial antibodies in the sera and amastigotes in the rodents' ears. The data also suggest the suitability of the IFAT as an epidemiological tool to estimate rates of infection by L. major in Psammomys obesus and Meriones Spp. in foci of ZCL.

Animals↗
PubMed1986

[An enigmatic gestation in Ctenodactylus vali (Rodentia)].

A parturition occurred in a female isolated since a duration longer than a gestation period. The most consistent hypothesis was the existence of sperm stocked inside the female and used for fertilization without the need of subsequent mating.

Animals↗
PubMed1987

Modulation of antibody response to sheep red blood cells by cyclophosphamide in Calomys callosus (Rodentia).

1. Calomys callosus, a wild rodent reservoir of Trypanosoma cruzi, notably resistant to laboratory infection with this parasite, is currently under study as a new experimental model for Chagas' disease. 2. To investigate the humoral immune response of C. callosus, rodents were injected with sheep red blood cells (SRBC) and the resulting antibody titers measured 0, 5, 9, 14, 20, 27 and 37 days later by the direct agglutination test. 3. Modulation of the antibody response by cyclophosphamide (Cy) was also studied, showing that the administration of 400 or 200 mg Cy/kg body weight one day prior to SRBC inoculation had an immunosuppressive effect. When the 200 mg/kg dose was given on day 0, antibody levels were significantly lower than those of controls on the 5th day after SRBC inoculation; subsequent differences were not statistically significant. 4. When SRBC were injected 5 or 10 days after Cy administration, the same effect was observed, indicating that the time of antigen inoculation is important in antibody modulation. A second dose of 200 mg Cy/kg on day 5 resulted in significant antibody suppression up to the 37th day. The administration of 20 mg Cy/kg resulted in a slight antibody enhancement seen on the 5th day after SRBC inoculation given on day 0. 5. These data demonstrate that cyclophosphamide modulates the T-dependent antibody response in C. callosus in a manner similar to the mouse model.

Agglutination Tests↗
PubMed1988

Echinococcus vogeli Rausch and Bernstein, 1972, from the paca, Cuniculus paca L. (Rodentia: Dasyproctidae), in the Departamento de Santa Cruz, Bolivia.

Among approximately 2,000 mammals examined for helminths in various regions of Bolivia during 1983-1987, cysts of Echinococcus vogeli Rausch and Bernstein, 1972, were found in a single paca, Cuniculus paca L., collected at La Laguna, Departamento de Santa Cruz (lat. 16 degrees 36'W; long. 62 degrees 42'S). This record, the first from Bolivia, represents a considerable extension of the known geographic range of this species in South America. Upon analysis of the morphologic characteristics of the protoscoleces derived from the cysts, the sizes of rostellar hooks from the material from the paca were found to be well within the ranges reported in previous studies. Statistical analysis of frequency distributions of hook characteristics revealed some deviations from normality. These results indicate that parametric statistics should be applied with caution in analyses of inter-and intraspecific variation of morphologic characteristics of hooks of metacestodes of the genus Echinococcus.

Animals↗
PubMedDate not supplied

[Natural infection of Calomys musculinus (Rodentia, Cricetidae) by Trypanosoma cruzi].

In the rural area of Las Higueras, Río Cuarto, Córdoba, Argentina, a trypanosoma was isolated from a wild rodent (C. musculinus). The trypanosome was classified as Trypanosoma cruzi because of the following characteristics: morphology as described by Hoare for the Schizotrypanum sub-genus: thin shaped, pointed back end, nucleus placed approximately in the middle of the body, prominent and subterminal kinetoplast and short free flagellum. The size measurements were as follows: total lengh 22.02 +/- 0.40 micron, flagellum lengh 5.93 +/- 0.29 mu, Nuclear mean index (NP/NA) 1,21 +/- 0.07 (Table 1). For some authors, this last value is very important for diagnosis of the parasite. BALB/c albino mice were infected with blood of the captured animal; those mice showed a mild parasitemia and amastigotes nests in cardiac fiber (Fig 2 a y b). The xenodiagnosis performed with nimphs of Triatoma infestans on the laboratory mice was positive. The trypanosome grew very well in blood-agar medium. According with these findings along with the wide geographic distribution and density of C. musculinus in Argentina, one should wonder whether or not this rodent is infested withT. cruzi on its whole distribution range. Passages through T. infestans and laboratory mice produced a virulence enhancement of this strain. With these findings, the question is if this situation should take place in nature, affecting domestic animals in any way. The stated questions and findings should estimulate further research on the role of the wild fauna in the epidemiclogy of Chagas' disease in Argintina.

Animals↗