Spleen Fragments Research Articles

Toxoplasma gondii diagnosis in ovine aborted fetuses and stillborns in the State of Pernambuco, Brazil

The aim of this research was to study the contribution of Toxoplasma gondii to reproductive failure using nested PCR and histopathological examination of fetuses, stillborns and placentas. We examined 245 organs of fetuses and 28 placentas from 35 abortions and stillborns from naturally occurring miscarriages in sheep in the State of Pernambuco, Brazil. At necropsy, fragments of brain, cerebellum, medulla, lung, heart, spleen, liver and placenta were taken for nested PCR and histopathological tests. Pathological examination revealed macroscopic lesions, suggesting T. gondii infection in 5/35 (14.3%) of the placentas. The histopathological examination revealed no lesions characteristic of toxoplasmosis in the organs investigated. In the five placentas, lesions consistent with toxoplasmosis were observed as an inflammatory non-suppurative infiltrate, along with multiple necrosis and mineralization. Nested PCR showed three aborted fetuses and two stillborns (14.3%) to test positive for T. gondii, with DNA amplification in all organs and the placenta, especially the heart and the placenta, which are the tissues of choice. This study substantiates the theory that T. gondii is involved in miscarriages and stillbirths and in the placentas of naturally infected sheep in Brazil. Such findings have not previously been described in the national literature.

Splenic autotransplantation reverses interferon-gamma and nitric oxide production and resistance to Listeria monocytogenes in splenectomized mice

Splenectomized mice control Listeria monocytogenes infection better than non-splenectomized mice. Here, BALB/c mice subjected to splenectomy and autogenous grafting of spleen were evaluated after 3 and 7 days of intravenous L. monocytogenes infection. The group of splenectomized animals (SP) presented a lower number of bacteria in the liver in comparison with both the sham-operated control group (CT) and the group that received splenic autotransplantation (AT) in the retroperitoneal site. The AT group presented bacterial counts in the liver similar to the CT group. SP animals showed larger production of interferon-gamma (IFN-γ) and nitric oxide (NO) in the liver in comparison with CT and AT, this being associated with greater accumulation of mononuclear cells. IFN-γ production by spleen cells after stimulation with heat-killed Listeria was similar between the AT and CT groups, suggesting that the implanted fragments behaved like the original organ. The autogenous grafting of spleen fragments reverses the resistance to L. monocytogenes infection found in splenectomized mice, associated with a reduced IFN-γ and NO production in the liver. The present study shows that splenic autotransplantation restores the function of the spleen in splenectomized mice, even though in this case it does favor the susceptibility to L. monocytogenes infection.

Effects of the povidone-iodine (PVPI) in treatment of bacterial peritonitis induced in rats

To evaluate the effectiveness of the use of the povidone-iodine (PVI) added to the liquid of wash of the peritoneal cavity in the reduction of bacterial absorption and in the remainder non-phagocyted bacteria in the circulating blood of rat. Thirty four Wistar females rats were used, distributed in the following groups: A (n=10), non-treated; B (n=9), wash of the peritoneal cavity with solution of PVI to 1% in saline solution; C (n=15), wash of the cavity with saline solution. After anesthesia, it was made intraperitoneal infusion of solution of Escherichia coli labeled with 99mTc containing 10(8) CFU/ml. After 40 minutes, it was made the treatment, in the group A, manipulation of the viscera; in the group B, irrigation of the peritoneal cavity with warm solution of 1% PVPI to 37,5 degrees C, and in the group C irrigation with warm saline (37,5 degrees C). After 15 minutes of the treatment, blood samples and fragments of liver, spleen and lung was obtained for count of the radioactivity, and animals killed by abdominal aorta section. There were determined the bacterial absorption index and the remainder index in the bloodstream. Of the total of bacteria infused in the peritoneum, there was absorption of 0,92% (0,14% to 2,13%) in the animals of the group A (controls), 0,49% (0,18% to 0,71%) after use of topical PVPI (group B) and 0,80% (0,04% to 3,8%) after wash with saline solution (group C). There was significant reduction of the absorption when compared the treated animals with PVPI and the controls (p=0,003). Of the total of bacteria absorbed for the circulatory current, the percentile amount of bacteria non-phagocyted in the outlying blood was of 2,9% (1,1% to 17,7%) in the control group, 15,2% (8,3% to 21,4%) in those treated with PVPI (group B) and 6,9% (0,8% to 29,7%) after wash with saline solution (group C), with difference among controls and treated with PVPI (p=0,01). The wash of the cavity peritoneal of mice with solution containing PVPI showed to be capable to reduce the absorption of bacteria by peritoneum of rat; however it seems to interfere with the function of the phagocytic cells for the observation of the increase of viable bacteria in the outlying blood of those animals.

ASPECTOS MACROSCÓPICOS, MORFOLÓGICOS E MORFOMÉTRICOS DO BAÇO DE RATOS APÓS O CLAMPEAMENTO TOTAL DO PEDÍCULO HEPÁTICO

One of the complications of hepatic pedicle total clamping is the splanchnic congestion and consequently a splenic congestion. The aim of this study was to observe the macro and microscopic alterations that occurred in the spleen during an ischemia produced by the hepatic pedicle clamping. Fourth male rats were divided in four groups of ten animals each. The control group (C) was not submitted to ischemia and the experimental groups (E1, E2 and E3) were submitted to the total clamping during 10, 20 and 30 minutes, respectively. After these periods, spleen fragments were collected and histological analyzed by the eosin-hematoxilin and ferric ferrocyanide staining technique. The results showed microscopic alterations at the E1, E2 and E3 groups that permitted to conclude that the total clamping of the hepatic pedicle promote intense vascular congestion, increase of the hemosiderin granules, decrease of the white pulp and increase of the red pulp, being these alterations more pronounced at the 30 minutes. KEY WORDS: Congestion, hemossiderina, spleen, rats.

Aspectos morfológicos, morfométricos e ultraestruturais do baço de ratos após o clampeamento total do pedículo hepático

Avaliaram-se as alterações morfológicas, morfométricas e ultraestruturais que ocorreram no baço devido à isquemia produzida pelo clampeamento total do pedículo hepático. Para tanto, foram utilizados 40 ratos machos, distribuídos em quatro grupos de 10 animais. O grupo-controle (C) não foi submetido à isquemia, e os grupos tratados (E1, E2e E3) foram submetidos ao clampeamento por 10, 20 e 30 minutos, respectivamente. Fragmentos do baço foram retirados e analisados histologicamente pela microscopia de luz (hematoxilina-eosina, ferrocianeto-férrico) e pela microscopia eletrônica de transmissão. Os resultados demonstraram que 10 minutos de clampeamento do pedículo hepático são suficientes para apresentar sinais de congestão esplênica e 20 e 30 minutos promovem intensa digestão de hemácias pelos macrófagos, com presença de grânulos de ferro (hemossiderina) no parênquima esplênico.

Toxoplasma gondii in experimentally infected Bos taurus and Bos indicus semen and tissues

Eighteen young steers were inoculated with Toxoplasma gondii and randomly distributed into three groups of six animals each: GI, 2.5x10(5) "P" strain oocysts, GII, 5.0x10(6) "RH" strain tachyzoites, and GIII (Control). Clinical, serological and parasitemia exams were realized. Parasite investigation by bioassay and PCR was realized on semen and fragments of skeletal musculature, lymph nodes, brain, retina, spleen, liver, lung, testicle, epididymis and seminal vesicle. Blood and semen samples were collected on days -2, -1, 1, 3, 5, 7, 14 and weekly thereafter, up to postinfection day (PID) 84. The inoculated steers (GI and GII) presented hyperthermia from PID 3 to 16. Antibodies against T. gondii were detected through the indirect fluorescence antibody test (IFAT) on PID 5 (1:16) in both inoculated groups (oocysts and tachyzoites), reaching peaks of 1:4096 on PID 7. Parasitemia outbursts occurred in all infected bovines, principally from PID 7 to 28, independent of the strain and inoculate used. Bioassays revealed the presence of parasites in semen samples of animals infected with oocysts (GI) and tachyzoites (GII) on several experimental days between PID 7 and 84. Tissue parasitism by T. gondii was diagnosed by bioassay and the PCR technique in several organ and tissue fragments. These findings suggest the possibility of sexual transmission of T. gondii in the bovine species.

Effects of tissue handling and processing steps on PCR for detection of Mycobacterium tuberculosis in formalin-fixed paraffin-embedded samples

Development and standardization of reliable methods for detection of Mycobacterium tuberculosis in clinical samples is an important goal in laboratories throughout the world. In this work, lung and spleen fragments from a patient who died with the diagnosis of miliary tuberculosis were used to evaluate the influence of the type of fixative as well as the fixation and paraffin inclusion protocols on PCR performance in paraffin embedded specimens. Tissue fragments were fixed for four h to 48 h, using either 10% non-buffered or 10% buffered formalin, and embedded in pure paraffin or paraffin mixed with bee wax. Specimens were submitted to PCR for amplification of the human beta-actin gene and separately for amplification of the insertion sequence IS6110, specific from the M. tuberculosis complex. Amplification of the beta-actin gene was positive in all samples. No amplicons were generated by PCR-IS6110 when lung tissue fragments were fixed using 10% non-buffered formalin and were embedded in paraffin containing bee wax. In conclusion, combined inhibitory factors interfere in the detection of M. tuberculosis in stored material. It is important to control these inhibitory factors in order to implement molecular diagnosis in pathology laboratories.

Trypanosoma cruzi: Serum levels of nitric oxide and expression of inducible nitric oxide synthase in myocardium and spleen of dogs in the acute stage of infection with metacyclic or blood trypomastigotes

The participation of nitric oxide (NO) in the control of blood parasitemia and parasitism during the acute phase of infection in dogs inoculated with blood trypomastigotes (BT) or metacyclic trypomastigotes (MT group) of Berenice-78 Trypanosoma cruzi strain has been evaluated. Animals of the MT group ( n = 4) presented increased levels of serum NO throughout the infection when compared with the BT ( n = 4) or control ( n = 4) groups, and a delay in parasitemia peak compared with the BT group. In spleen fragments, tissue parasitism was not observed but the MT group presented larger areas associated with inducible NO synthase (iNOS) in relation to BT and control groups. Heart fragments of MT-infected animals exhibited comparatively low tissue parasitism and high iNOS expression, while animals of the BT group presented high inflammatory infiltrate, high tissue parasitism and low iNOS expression. These results indicate that the source of inoculum can interfere with the development of the acute phase of Chagas disease, and may also trigger a distinct parasite–host interaction during this phase.

Canine visceral leishmaniasis in urban and rural areas of Northeast Brazil

The purpose of this study was to determine the clinical and laboratory profiles of canine leishmaniasis in two distinct areas. Dogs from urban and rural areas were examined. The population studied in the metropolitan area included 54 dogs. Of these, 20 (37%) animals did not present with any signs suggestive of visceral leishmaniasis (VL). Among these, only eight were confirmed negative by ELISA (rK39 and CE) and 12 dogs, clinically negative for leishmaniasis, were seropositive by ELISA (rK39 and CE). Thinness, conjunctivitis and onychogryphosis were the most frequent clinical signs in the urban areas, followed by crusty lesions, alopecia, ulcerated lesions, hyperkeratosis and exfoliation. In the metropolitan area human VL cases occurred mainly in 1991, 1992, 1999 and 2000. In the rural areas the ELISA rK39 test detected a seroprevalence of 11.3% and ELISA CE ( Leishmania crude extract) of 20.6%. Thirty-nine dogs were examined 6 months after the first visit. Serological exams using rK39 antigen showed seroconversion of only one dog, whereas Leishmania CE showed seroconversion of 13 (33.4%) dogs. In this rural environment 83.3% of the positive dogs were asymptomatic. Lutzomyia intermedia and Lu. longipalpis were the most predominant sandfly vector species. Amastigotes were identified in spleen and liver fragments of symptomatic necropsied animals. PCR amplification of DNA isolated from promastigote culture indicated that the species was Leishmania chagasi. This finding suggests that delayed diagnosis and euthanasia of potentially infectious animals may occur with an increased transmission risk to sandflies and subsequently to humans.

Late histological aspects of spleen autologous transplantation in rats

To evaluate macro and microscopically the late evolution of autotransplants of fragments of spleen in the greater omentum, mesenterium and peritoneal cavity, after 24 weeks of observation. Fifty two Wistar rats were used, males and adults, submitted to total splenectomy and divided in four groups. The group I--seventeen animals with implant of spleen fragment in the peritoneal cavity; group II--eighteen animals with implant in the omentum and group III--seventeen animals with implant fixed in mesenterium root. The group control (group IV) was formed by eight animals chosen aleatorily among the three groups. It was analyzed macro and microscopically the evolution of the implant, and in the histological study qualitative and quantitative criteria were adopted, with the counting of no cellular e cellular elements. It was observed adherences to the adjacent tissues and vascularization in all of the fragments transplanted. The group I presented white pulp and preserved vascularization. In the group II were observed white pulp with follicular formations and lymphoid tissue preserved, and the red pulp in cordon aspect and hemorrhagic. In the group III were observed with depletion of white and red pulp, while others evidenced better preservation of the pulps. The counting of lymphocytes revealed significant difference between the groups I and IV and the group III and IV (p < 0.05). The counting of active macrophages revealed significant difference between the groups II and III (p < 0.05) and similarity between II and IV (p > 0.05). The other elements: active macrophages phagocyting hemosiderine, plasmocytes, fibroblasts, fibrocytes, giant cells, monocytes, interstitial spaces and fibers of collagen, did not show significant difference among the groups. The splenic autotransplantation is feasible, being the better place the greater omentum. This research demonstrated through qualitative and quantitative histological analysis that the splenic tissue autotransplanted in the omentum of Wistar rats preserves its function of defense of the organisms.

Selective 5-Lipoxygenase Expression in Langerhans Cells and Impaired Dendritic Cell Migration in 5-LO-Deficient Mice Reveal Leukotriene Action in Skin

5-Lipoxygenase (5-LO) catalyzes the initial steps in the formation of leukotrienes (LTs), which are implicated in immune reactions. Recently, it was shown that FITC-triggered epidermal Langerhans cell (LC) emigration to draining lymph nodes (LNs) is impaired in LTC4 export pump (multidrug resistance-associated protein 1)-deficient mice. Here, we sought genetic evidence for a role of endogenous LTs in dendritic cell function through the study of 5-LO-deficient mice. Though DC numbers in skin, spleen, and peripheral LNs were similar in both 5-LO-deficient and wild-type (WT) mice, DC homing from skin to draining LNs induced by FITC was reduced by 75% in 5-LO-deficient mice. Moreover, in WT mice, all epidermal LCs, dermal langerin+ LCs, and subsets of dermal macrophages and langerin+ LCs in T-cell areas of skin-draining LNs markedly expressed 5-LO. However, the enzyme was noticeably absent in all DC subsets of the dermis, thymus, spleen, Peyer's patches, mesenteric LNs, and mucosal surfaces of lung and intestine. As all epidermal cells other than LCs lacked 5-LO and because differentiation and activation of DCs generated from 5-LO-deficient mice in vitro were normal, these data support a selective role of endogenous LTs in DC homing following skin sensitization.

Can fleas from dogs infected with canine visceral leishmaniasis transfer the infection to other mammals?

In order to investigate the possible role of dog fleas in the transmission of trypanosomatids, ectoparasites were removed from 59 dogs testing positive for canine zoonotic visceral leishmaniasis according to the indirect fluorescent antibody test (IFAT). Of the fleas collected, 4/207 (1.9%) showed the presence of promastigotes in smears stained by Giemsa, whilst 43/144 (29.9%) exhibited positive polymerase chain reaction (PCR) amplification assays for Leishmania DNA. Fleas (409) from 9 Leishmania chagasi-infected dogs, each hosting more than 20 fleas per animal, were macerated and administered by peritoneal injection or orally to 36 hamsters. After 6 months, the 30 surviving hamsters were sacrificed and liver and spleen fragments were removed for PCA assay and to produce imprint smears, whilst blood samples were subjected to IFAT assay. Sixteen hamsters tested positive for Leishmania infection, 14 on the basis of PCR amplification and four by IFAT assay (two animals testing positive in both assays). Of the infected hamsters, 11/16 (68.7%) had been infected peritoneally and 5/16 (31.2%) orally. The imprint smears for all animals were, however, negative. Since both PCR and IFAT could present cross-reactivity for Leishmania and Leptomonas, the possibility of oral transmission of L. chagasi by fleas cannot be proven unambiguously even though the hamsters developed infection.

Comparison of parasitological, immunological and molecular methods for the diagnosis of leishmaniasis in dogs with different clinical signs

Aiming to improve the diagnosis of canine leishmaniasis (CanL) in an endemic area of the Northwest region of São Paulo State, Brazil, the efficacy of parasitological, immunological and molecular diagnostic methods were studied. Dogs with and without clinical signs of the disease and positive for Leishmania, by direct parasite identification on lymph node smears and/or specific antibody detection by ELISA, were selected for the study. According to the clinical signs, 89 dogs attending the Veterinary Hospital of UNESP in Araçatuba (SP, Brazil) were divided into three groups: symptomatic (36%), oligosymptomatic (22%) and asymptomatic (22%). Twenty-six dogs from an area non-endemic for CanL were used as negative controls (20%). Fine-needle aspiration biopsies (FNA) of popliteal lymph nodes were collected and Diff-Quick ®-stained for optical microscopy. Direct immunofluorescence, immunocytochemistry and parasite DNA amplification by PCR were also performed. After euthanasia, fragments of popliteal lymph nodes, spleen, bone marrow and liver were collected and processed for HE and immunohistochemistry. Parasite detection by both HE and immunohistochemistry was specifically more effective in lymph nodes, when compared with the other organs. Immunolabeling provided higher sensitivity for parasite detection in the tissues. In the symptomatic group, assay sensitivity was 75.61% for direct parasite search on Diff-Quick ®-stained FNAs, 92.68% for direct immunofluorescence, 92.68% for immunocytochemistry and 100% for PCR; the corresponding values in the other clinical groups were: 32, 60, 76 and 96% (oligosymptomatic), and 39.13, 73.91, 100 and 95.65% (asymptomatic). Results of the control animals from the CanL non-endemic area were all negative, indicating that the methods used were 100% specific.

Evaluation of transformation growth factor β 1, interleukin-10, and interferon-γ in male symptomatic and asymptomatic dogs naturally infected by Leishmania ( Leishmania) chagasi

The aims of this study were to evaluate the immunomodulatory role of TGF-β 1, IL-10, and INF-γ in spleen and liver extracts and supernatant cultures of white spleen cells from male symptomatic and asymptomatic dogs, naturally infected by Leishmania ( Leishmania) chagasi. Thirty dogs from Araçatuba, São Paulo, Brazil, an endemic leishmaniosis area, were selected by positive ELISA serological reaction for Leishmania sp. and divided into two groups: asymptomatic ( n = 15) and symptomatic ( n = 15) consisting of animals with at least three characteristic signs (fever, dermatitis, lymphoadenopathy, onychogryphosis, weight loss, cachexia, locomotion problems, conjunctivitis, epistaxis, hepatosplenomegaly, edema, and apathy). After euthanasia, spleen and liver fragments were collected for ex vivo quantification of TGF-β 1, IL-10, and INF-γ. Naturally active in vitro produced TGF-β 1 was also evaluated in spleen cell culture supernatant. Spleen and liver extract of asymptomatic dogs had higher mean TGF-β 1 levels than symptomatic dogs. High concentrations of IL-10 were found in spleen, and mainly in liver extract of both groups. Higher INF-γ concentrations were found in spleen extracts of symptomatic dogs, and in liver extracts of asymptomatic dogs. Extract of this cytokine was lower in spleen extract. Although INF-γ is being produced in canine infection, mean levels of TGF-β 1 and IL-10 from spleen and liver extracts were quantitatively much higher; suggesting that immune response in both asymptomatic and symptomatic dogs was predominantly type Th2.

Mixed infection with Leishmania ( Viannia) braziliensis and Leishmania ( Leishmania) chagasi in a naturally infected dog from Rio de Janeiro, Brazil

We report here the first case of co-infection with Leishmania (Viannia) braziliensis and Leishmania (Leishmania) chagasi in a naturally infected dog from Rio de Janeiro, Brazil. Isoenzyme characterisation identified the parasites isolated in culture from the cutaneous lesion as L. (V.) braziliensis and the isolates from blood and lymph node as L. (L.) chagasi. PCR analysis using specific primers followed by molecular hybridisation for direct Leishmania species identification in tissue fragments confirmed the presence of L. (V.) braziliensis DNA in the cutaneous lesion and of L. (L.) chagasi DNA in spleen and popliteal lymph node fragments. This report emphasises the importance of identification of Leishmania species infecting seropositive dogs in endemic areas, and the consequent re-assessment of control and epidemiological surveillance measures for the control of leishmaniasis, as is the case in Brazil.

Estudo da regeneração esplênica autóloga e heterotópica em ratos

verify the cytological and histological aspects of the regeneration of fragments of autologous and heterotopic spleen implanted in peritoneal cavity and subcutaneous screen in Wistar albino rats. forty four Wistar rats were assigned to one of two groups A (n=22) and B (n=22), which received their implants in subcutaneous screen and peritoneal cavity, respectively, under anesthesia. Those groups were redistributed in two other subgroups A1 (n=11) and B1 (n=11), which received one and four splenic fragments in the areas of study. The remaining spleen was guided for cytological and histological processing, and was used as a control group. After five weeks, they were submitted to euthanasia, and peritoneal cavity opening took place as well as subcutaneous screen was taken off in order to search for regenerated splenic tissue. Cytological and histological assessment in the regenerated splenic tissue was performed, and the results were compared to the control group. Statistical analysis no parametric tests (p => 0.05) were used for. there were no statistically significant differences in relation to regenerated splenic tissue in subcutaneous screen (n=22) and the peritoneal cavity (n=22). In relation between presence and absence of regeneration, they're no statistically significant differences (p = 0.182). Cytological and histological assessment did not show any statistically significant difference in relation to the control group. regeneration of autologous and heterotopic splenic tissue in mice is viable, and occurs frequently. Cytological and histological aspects are similar to normal spleen.

Dengue Virus Type 3, Cuba, 2000–2002

Dengue Virus Type 3, Cuba, 2000–2002

Participation of Rhipicephalus sanguineus (Acari: Ixodidae) in the epidemiology of canine visceral leishmaniasis

The vectorial competence of the tick Rhipicephalus sanguineus is discussed in relation to the epidemiology of canine visceral leishmaniasis, taking into account its strict association with dogs and the low indices of natural infection presented by its known vector, the phlebotomine sand fly Lutzomyia longipalpis. In order to evaluate natural infection by Leishmania chagasi and the infectivity of these parasites in the tick, 39 specimens (6 females, 11 males and 22 nymphs) of R. sanguineus were removed from 21 dogs showing diverse symptoms of zoonotic visceral leishmaniasis (ZVL). Six ticks (15.4%) gave positive results for the genus Leishmania using the PCR technique. To determine the infectivity of the parasites, 36 hamsters were inoculated orally and peritoneally with macerates of ticks removed from nine dogs symptomatic for visceral leishmaniasis. After 6 months the hamsters were sacrificed and necropsied. Serum was removed for IFAT, as well as spleen and liver fragments to make imprint smears and for PCR. Eight (88.9%) of these dogs presented ticks that were infective for 14 hamsters (41.2%), 12 (85.7%) of them infected peritoneally and two (14.3%) orally. PCR revealed 27 smears (40.9%) to be positive, 20 (62.5%) of them infected peritoneally and seven (20.6%) orally. IFAT showed 14 positive animals (41.2%). Based on these findings, we suggest that the vectorial capacity of R. sanguineus for L. chagasi should be evaluated further, opening new perspectives in the epidemiology of ZVL.

Intra-thymic/splenic engraftment of human T cells in HLA-DR1 transgenic NOD/scid mice

A HLA-DR1 transgenic mouse (NOD/scid-DR1) was derived by breeding the existing B10.M/J-[Tg]DR1 mouse with the NOD/scid mouse. The intention was to enhance engraftment of human T cells by providing human class II elements in the tissues. Thymus and spleen fragments from adult NOD/scid-DR1 mice were transplanted under the syngeneic kidney capsules, followed by injection of human cord blood mononuclear cells (CBMNC) into transplanted tissues. FACS analyses showed that human T and B cells were consistently detected in the peripheral blood and spleen, of the chimeric mice. An average of 20% of human cells was found in the spleen and the engrafted thymus/spleen tissues. Furthermore, human cells from these tissues could proliferate with anti-human CD3 antibody and these mice could generate humoral and cellular responses to allogeneic human cells. Cytokines, such as IL-10, GMCSF, IFN-γ, and TNF-α were also detected in the supernatants of the cultured human cells from the chimeric mice, when they were stimulated with allogeneic cells. Therefore, a novel mouse model with functional circulating human T and B cells was established that would facilitate the exploration of vaccine, the disease processes of autoimmunity, HIV infection, and human cancer.

Tissue stages of Hepatozoon canis in naturally infected dogs from Sao Paulo State, Brazil.

A total of 222 dogs were examined by blood smear examination and Hepatozoon canis infection was detected in 13 dogs (5.9%). Five H. canis-infected dogs were necropsied to observe tissue stages in the organs. Fragments of spleen, liver, lungs, heart, kidneys, lymph nodes, bone marrow and skeletal muscles were used to made touch-impression smears. No macroscopic lesions were found in the organs. Two dogs had gamonts within polymorphonuclear cells and schizonts in various stages of development within the spleen and the bone marrow. Nevertheless, no mature meronts were found.