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The adjustment of Calomys callosus (Rodentia, Cricetidae) to food deprivation
Ades, César;Kolde, Renate Edla;
Revista Brasileira de Zoologia , 1989, DOI: 10.1590/S0101-81751989000200005
Abstract: the adjustment of calomys callosus (rodentia, cricetidae) to intermittent food deprivation was investigated. animals subjected either to 24-hr or to 48-hr repeated periods of deprivation successfully compensated, showing (1) increases in post-fast intake relatively to the intake by control animals; (2) rapid recovery of the baseline levels of body wieght. the regulatory ability of c. callosus is comparable, in such respects, to the ability of the common rat and some other rodents but it is remarkably different from the hamster's.
Acquired and Congenital Ocular Toxoplasmosis Experimentally Induced in Calomys callosus (Rodentia, Cricetidae)
Pereira, Maria de Fátima;Silva, Deise Aparecida Oliveira;Ferro, Eloisa Amália Vieira;Mineo, José Roberto;
Memórias do Instituto Oswaldo Cruz , 1999, DOI: 10.1590/S0074-02761999000100021
Abstract: an experimental model for acquired and congenital ocular toxoplasmosis as well as a model to induce experimental autoimmune uveitis (eau) was investigated in calomys callosus. toxoplasma gondii, me-49 strain, was used to infect males and pregnant- and not pregnant-females while s-antigen, a major glycoprotein of the retinal photoreceptor cell, was used to induce eau. the ocular lesions elicited by t. gondii were characterized by the presence of cysts, free tachyzoites and inflammatory cells in the retina or related tissues. in the congenital form, 40% of the fetus presented ocular lesions, i.e., presence of cysts in the retina, vitreous, and extra-retinal tissues. in the acquired form, 75% of the females and 50% of the males presented unilateral ocular cysts both at 21 and 47 days post-infection. it was also demonstrated that s-antigen was not uveitogenic in the c. callosus model. no lesion was observed in the animals exclusively immunized with this retinal component, even when jacalin was used as additional adjuvant for polyclonal response to the retinal antigen. it can be concluded that c. callosus may constitute in a promising model for study both acquired and congenital ocular toxoplasmosis, particularly when it is important to make sure that a non autoimmune process is involved in the genesis of the ocular infection.
Acquired and Congenital Ocular Toxoplasmosis Experimentally Induced in Calomys callosus (Rodentia, Cricetidae)  [cached]
Pereira Maria de Fátima,Silva Deise Aparecida Oliveira,Ferro Eloisa Amália Vieira,Mineo José Roberto
Memórias do Instituto Oswaldo Cruz , 1999,
Abstract: An experimental model for acquired and congenital ocular toxoplasmosis as well as a model to induce experimental autoimmune uveitis (EAU) was investigated in Calomys callosus. Toxoplasma gondii, ME-49 strain, was used to infect males and pregnant- and not pregnant-females while S-antigen, a major glycoprotein of the retinal photoreceptor cell, was used to induce EAU. The ocular lesions elicited by T. gondii were characterized by the presence of cysts, free tachyzoites and inflammatory cells in the retina or related tissues. In the congenital form, 40% of the fetus presented ocular lesions, i.e., presence of cysts in the retina, vitreous, and extra-retinal tissues. In the acquired form, 75% of the females and 50% of the males presented unilateral ocular cysts both at 21 and 47 days post-infection. It was also demonstrated that S-antigen was not uveitogenic in the C. callosus model. No lesion was observed in the animals exclusively immunized with this retinal component, even when jacalin was used as additional adjuvant for polyclonal response to the retinal antigen. It can be concluded that C. callosus may constitute in a promising model for study both acquired and congenital ocular toxoplasmosis, particularly when it is important to make sure that a non autoimmune process is involved in the genesis of the ocular infection.
Study of the social hierarchy and territoriality of Calomys callosus Rengger, 1830 (Rodentia: Cricetidae)
Póvoa, CP.;Brandeburgo, MAM.;
Brazilian Journal of Biology , 2007, DOI: 10.1590/S1519-69842007000300007
Abstract: the genus calomys comprises a lot of species distributed throughout south america. the species c. callosus rengger, 1830 occur in brazil, been often used in laboratory experiments. this work involved a study of aggressive behavior and dominance, which are aspects related to hierarchy and territoriality, among c. callosus males kept in a laboratory. the establishment of a hierarchy was observed, with the dominant animals controlling the space, food and water, while the remaining animals were confined to a restricted space. the intensity of aggression and variations in the number of attacks declined over time as a result of the formation of the hierarchy. no wounds were observed, probably due to the ritualistic nature of the attacks.
Infection of Calomys callosus (Rodentia Cricetidae) with strains of different Trypanosoma cruzi biodemes: pathogenicity, histotropism, and fibrosis induction
Magalh?es-Santos, Isis Fernandes;Souza, Márcia Maria;Lima, Carolina Silva Costa;Andrade, Sonia G;
Memórias do Instituto Oswaldo Cruz , 2004, DOI: 10.1590/S0074-02762004000400011
Abstract: the influence of different trypanosoma cruzi biodemes on the evolution of the infection and on the histopathological lesions of the heart and skeletal muscles, during the experimental infection of calomys callosus, was investigated. three groups of c. callosus were infected, respectively, with parasite strains representative of three different biodemes: type i (y strain), type ii (21 sf strain), and type iii (colombian strain). for each group, normal c. callosus were also used as controls. marked differences have been detected in the responses of c. callosus to the infection with the three strains in this model. the strains types i and ii (y and 21 sf) determined moderate lesions, mostly in the myocardium, with low parasitism, a rapid course, and total regression of the lesions by the 60th day of infection. differently, type iii strain (colombian), was more pathogenic for c. callosus and induced necrotic-inflammatory lesions in skeletal muscles and myocardium, in correspondence to intracellular parasitism. proliferation of fibroblasts and amorphous matrix deposits, followed by interstitial fibrosis were present. progressive regression of the inflammatory changes and collagen deposits occurred spontaneously. the progression and regression of both inflammation and fibrosis induced by the colombian strain were further submitted to quantitative evaluation by morphometry. results of the morphometric studies presented good correlation with the histopathological findings. the results confirm the importance of the different biodemes in the determination of tissue lesions and the peculiarities of response of c. callosus to infection with t. cruzi.
Modulation of parasitemia and antibody responce to Trypanosoma cruzy by cyclophosphamide in Calomys callosus (Rodentia, Cricetidae)
Borges, Monamaris Marques;Curi, Paulo Roberto;Kloetzel, Judith Kardos;
Revista do Instituto de Medicina Tropical de S?o Paulo , 1992, DOI: 10.1590/S0036-46651992000100001
Abstract: calomys callosus a wild rodent, previously described as harboring trypanosoma cruzi, has a low susceptibility to infection by this protozoan. experiments were designed to evaluate the contribution of the immune response to the resistance to t. cruzi infection exhibited by c. calossus. animals were submitted to injections of high (200 mg/kg body weight) and low (20 mg/kg body weight) doses of cyclophosphamide on days -1 or -1 and +5, and inoculated with 4 x 103 t. cruzi on day o. parasitemia, mortality and antibody response as measured by direct agglutination of trypomastigotes were observed. two hundred mg doses of cyclophosphamide resulted in higher parasitemia and mortality as well as in suppression of the antibody response. a single dose of 20 mg enhanced antibody levels on the 20th day after infection, while an additional dose did not further increase antibody production. parasitemia levels were not depressed, but rather increased in both these groups as compared to untreated controls. passive transfer of hyperimmune c. callosus anti-t. cruzi serum to cyclophosphamide immunosuppressed animals resulted in lower parasitemia and mortality rates. these results indicate that the immune response plays an important role in the resistance of c. callossus to t. cruzi.
Morphological changes in the vaginal epithelium during the oestrous cycle of Calomys callosus (Rodentia, Cricetidae)
RODRIGUES, JEAN FáBIO TORRES;FERRO, ELOISA AMáLIA VIEIRA;
Revista Brasileira de Biologia , 1998, DOI: 10.1590/S0034-71081998000300018
Abstract: this study describes changes in the pattern of microridges, keratinization, desquamation, secretion, leukocyte infiltration as well as the increasing number of mitotic cells in the vaginal epithelium of calomys callosus during the oestrous cycle. in proestrus, the epithelium is squamous and stratified with a fine layer of keratin and it is overlain by secretory prismatic cells. in oestrous, the epithelium is squamous, stratified and keratinized. in metoestrus, the epithelium is squamous and stratified with loss of the keratin layer. a leukocyte infiltration, extending from the base to the surface of the epithelial layer is also present. at the end of this phase, the surface cells start to become pas-positive. in dioestrus, the epithelium is stratified. the superficial cells are prismatic, exhibiting the structural and ultrastructural characteristics of glycoprotein secreting cells supported by a layer of squamous cells. at the end of this phase, kerato-hyaline granules appear in the granular layer of the epithelium, indicating the beginning of the keratinization process, present in the next proestrus.
Morphological changes in the vaginal epithelium during the oestrous cycle of Calomys callosus (Rodentia, Cricetidae)
RODRIGUES JEAN FáBIO TORRES,FERRO ELOISA AMáLIA VIEIRA
Revista Brasileira de Biologia , 1998,
Abstract: This study describes changes in the pattern of microridges, keratinization, desquamation, secretion, leukocyte infiltration as well as the increasing number of mitotic cells in the vaginal epithelium of Calomys callosus during the oestrous cycle. In proestrus, the epithelium is squamous and stratified with a fine layer of keratin and it is overlain by secretory prismatic cells. In oestrous, the epithelium is squamous, stratified and keratinized. In metoestrus, the epithelium is squamous and stratified with loss of the keratin layer. A leukocyte infiltration, extending from the base to the surface of the epithelial layer is also present. At the end of this phase, the surface cells start to become PAS-positive. In dioestrus, the epithelium is stratified. The superficial cells are prismatic, exhibiting the structural and ultrastructural characteristics of glycoprotein secreting cells supported by a layer of squamous cells. At the end of this phase, kerato-hyaline granules appear in the granular layer of the epithelium, indicating the beginning of the keratinization process, present in the next proestrus.
Infec??o experimental de Calomys callosus (Rodentia-Cricetidae) com Leishmania donovani chagasi (Laison, 1982)
Mello,Dalva A.; Teixeira,Maria Lucia;
Revista de Saúde Pública , 1984, DOI: 10.1590/S0034-89101984000400009
Abstract: in the current paper experimental infection of calomys callosus with leishmania donovani is reported for the first time. a group of 22 c. callosus aged 20 months and weighing 25 g were inoculated with 0.1 of a homogeneous saline preparation of infected spleens of homologous animals. the l. donovani strain used in the experiments was isolated from a case of human visceral leishmaniasis from the state of maranh?o, brazil. the animals infected were weighed and killed 3 months after the experimental infection. spleens and livers were also weighed and pieces from them were fixed in 10% formaline and stained with hematoxilin-eosin for histological studies. impression smears stained with giemsa were made and cultivation "in vitro" (nnn and lit) was done, with material from blood, spleen, liver and bone marrow. at the end of the experiments the animals showed low of body weight. splenomegaly was observed in all the inoculated animals. the "in vitro" cultures were positive from liver and spleen in 67% of the animals. many extracellular and intracellular amastigote forms were seen in the smears of spleen, liver and bone marrow. blood showed negative results. histological studies of the liver showed proliferation of kupffer cells and granulomatous reaction in the portal areas with multinucleated cells and amastigote forms of the parasites. loss of folicular pattern with parasitism in great numbers of cells around which there were granulomatous reactions were observed in the spleen.
Infec??o experimental de Calomys callosus (Rodentia Cricetidae) com Trypanosoma cruzi
Borges,Monamaris M.; Mello,Dalva A.; Teixeira,Maria Lucia;
Revista de Saúde Pública , 1982, DOI: 10.1590/S0034-89101982000400004
Abstract: an albino "swiss" strain of mus musculus was used for comparison purposes with regard to the following parameters: parasitemia, prepatent period, patency of the infection and lethality. histopathological studies were carried out with the aim of observing the tissue tropism and aggressiveness of t. cruzi against c. callosus. the experiments showed that the evolution of the infection in c. callosus was different according to the two t. cruzi strains utilized. they strain produced higher parasitemia than the berenice strain. the prepatent period varied as a result of the inocula being shorter in the animals inoculated with the strain y (2, 2-3, 2 days) than in those infected with the berenice strain (3, 2-7, 0 days). although both strains were shown to be myotropic, the tissue alterations were more pronounced in the animals inoculated with the y strain. results indicated the possibility that c. callosus may be used as experimental animals for t. cruzi infection.
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