Risk factors related to the appearance of umbilical disorders in dairy calves / [Fatores de risco relacionados ao surgimento de afecções umbilicais em bezerros leiteiros]

The objective of this study was to determine the types of calve housing used in dairy farms, the prevalence of umbilical disorders and related risk factors. The 16 farms studied were visited to characterize the types of installation and possible risk factors, as well as information obtained from a questionnaire applied to the farmers. 806 Holstein calves were physically examined, in addition to collecting blood samples for the evaluation of Failures in Passive Immunity Transfer (FPIT), in animals that manifested inflammatory omphalopathies, and were also submitted to ultrasound examination. The prevalence of omphalopathies was assessed by Fisher's test, and multivariate logistic regression to assess risk factors. Eight types of installation were found: tropical house, suspended cage, collective stall, collective picket, Argentinean type, single-story cage, individual stall, and collective picket with chain. Omphalopathies accounted for 6.45% of the calves. Small size farms (up to 99 lactation cows) had high risk for umbilical disorders, ground floor collective calves, without side protection, with sand floor, in closed sheds and without heatstroke were considered risk factors for omphalopathies. Adequate colostrum and umbilical antisepsis are not associated with disease, its appearance being related to the housing conditions of the animals.(AU)

O objetivo deste estudo foi determinar os tipos de alojamento para bezerros leiteiros, a prevalência de onfalopatias e os fatores de risco relacionados. As 16 fazendas estudadas foram visitadas buscando-se caracterizar os tipos de instalação e os possíveis fatores de risco, além de informações obtidas de um questionário aplicado aos fazendeiros. Foram examinados fisicamente 806 bezerros da raça Holandesa, além da coleta de amostras de sangue, para avaliação da falha de transferência de imunidade passiva (FTIP), nos animais que manifestaram onfalopatias inflamatórias, sendo submetidos também ao exame ultrassonográfico. A prevalência das onfalopatias foi avaliada por teste de Fisher, e foi feita regressão logística multivariada a fim de se avaliarem os fatores de risco. Verificou-se oito tipos de instalação: casinha tropical, gaiola suspensa, baia coletiva, piquete coletivo, bezerreiro tipo argentino, gaiola térrea, baia individual e piquete coletivo com corrente. As onfalopatias corresponderam a 6,45% dos bezerros. Os bezerreiros coletivos térreos, sem proteções laterais, com piso de areia, borracha, concreto ou madeira, em galpões fechados, sem insolação, com alta densidade animal, antissepsia umbilical realizada por três dias e FTIP acima de 50% foram considerados fatores de risco para onfalopatias e possuem relação com o bezerreiro, sendo decisivas para evitar essas condições a colostragem e a antissepsia umbilical adequadas.(AU)

Aspectos ultrassonográficos dos componentes umbilicais de bezerros da raça Holandesa durante o processo de involução fisiológica / Ultrasonographic aspects of umbilical components of Holstein calves during the physiological involution process

Afecções umbilicais são comumente encontradas nos bezerros durante o período neonatal, podendo ocasionar graves complicações. Seu diagnóstico muitas vezes não é preciso pela palpação abdominal, sendo a ultrassonografia um valioso exame complementar, pois permite precisão na localização e na extensão das onfalopatias intra-abdominais. Diante disso e da raridade de pesquisas com estabelecimento de padrões ultrassonográficos do umbigo, o presente estudo propôs padronizar os aspectos das imagens ultrassonográficas dos componentes umbilicais em decorrência de sua involução. Foram avaliados 23 bezerros Holandeses, do nascimento até os 30 dias de vida, em cuja região umbilical se usou como antisséptico tintura de iodo em diferentes concentrações. Os resultados evidenciaram que veia e artérias umbilicais perdem suas características de vasos, assumindo aspecto de ligamento por proliferação de tecido fibroso. Nesse processo, o tecido fibroso, inicialmente presente na região interna da parede do vaso, segue, com a involução, em direção à luz, sendo observado mais precocemente em porções dos vasos mais distantes do umbigo externo, não havendo distinção de comportamento determinada pela antissepsia. Para aproveitamento do exame ultrassonográfico, é importante o conhecimento dos aspectos das imagens durante o processo de involução dos componentes umbilicais, de acordo com cada fase, sendo assim possível o diagnóstico das diferentes alterações nessas estruturas.(AU)

Umbilical diseases of calves happen during neonatal period and may lead to severe complications. The diagnosis is usually through abdominal palpation although it is not very accurate, thus ultrasound provides a valuable complementary exam to establish a precise diagnosis of location and extent of intra-abdominal umbilical diseases. Given those facts and the lack of established standards for umbilical ultrasound imaging the present study proposal was to standardize the physiological aspects of umbilical components during involution. Ultrasound images were obtained for 23 Holstein calves, from birth until 30 days of life. Iodine tincture of different concentrations was used for umbilical region antisepsis. Results show that umbilical vein and arteries lose their vessel characteristics, becoming similar to ligament, due to the proliferation of fibrous tissue. The growth pattern of the fibrous tissue was from the vessel walls growing toward vascular lumen. The involution process begins at the most distant part and did not vary with antiseptic concentrations. To obtain a reliable ultrasound exam it's important to know the aspects of imaging patterns according to each phase of umbilical involution, thus leading to an accurate diagnosis of structural variations and umbilical diseases.(AU)

Avaliação da zinco protoporfirina (ZPP) em ruminantes domésticos / Zinc protoporphyrin (ZPP) evaluation in domestic ruminants

Nos sistemas de criação de ruminantes, a anemia crônica pode levar a grandes prejuízos econômicos, sendo decorrente da deficiência de ferro no organismo. Quando este se torna indisponível para ser incorporado à hemoglobina, forma-se um composto denominado zinco protoporfirina (ZPP), que pode ser um marcador precoce para a anemia, útil, portanto, para seu diagnóstico. Porém, para a utilidade dessa mensuração, é necessário que se conheçam os valores normais de ZPP para cada espécie. Assim, foram utilizados 30 bezerros, 30 caprinos e 30 ovinos, todos saudáveis, nos quais foram mensurados esses valores. Essa mensuração foi determinada em amostras de sangue refrigeradas, coletadas com EDTA, obtendo-se valores em hemácias não lavadas e lavadas. A lavagem visou à eliminação de substâncias interferentes nessas medidas. A média da ZPP nas amostras não lavadas foi de 80,9µmol ZPP/mol de heme nos bezerros; 55,09µmol ZPP/mol de heme nos caprinos e 73,76µmol ZPP/mol de heme nos ovinos. Após a lavagem, os valores foram 61,4µmol ZPP/mol de heme; 43,92µmol ZPP/mol de heme e 59,36µmol ZPP/mol de heme, nos bezerros, caprinos e ovinos, respectivamente. Devido à praticidade da técnica, essa pode ser empregada para a detecção precoce da anemia ferropriva, sendo recomendada a prévia lavagem das hemácias.(AU)

In ruminant breeding systems, chronic anemia can lead to economic losses, resulting from iron deficiency in the organismo. When iron is unavailable for incorporation into hemoglobin, a compound called zinc protoporphyrin (ZPP) is formed, may be an early marker for anemia and is useful for its diagnosis. However, for this measurement to be useful, it is necessary to know the normal values for the species. Therefore, 30 calves, 30 goats and 30 sheep, all of them healthy, to standardize the values were used. This measurement was determined on refrigerated blood samples collected with EDTA, obtaining values in red blood cells not washed and washed. The washing aimed at the elimination of interfering substances in these measures. The mean of the ZPP in the unwashed samples was 80,9µmol ZPP/mol of heme in calves; 55,09µmol ZPP/mol of heme in goats and 73,76µmol ZPP/mol of heme in sheep. After washing, the values were 61,4µmol ZPP/mol of heme; 43,92µmol ZPP/mol of heme e 59,36µmol ZPP/mol of heme, in calves, goats and sheep, respectively. Due to its practicality, the techniquecan be used for the early detection of iron deficiency anemia, recommending the previous lavage of the red blood cells.(AU)

Apoptosis in parasites and parasite-induced apoptosis in the host immune system: a new approach to parasitic diseases

Apoptosis, a form of programmed cell death (PCD), has been described as essential for normal organogenesis and tissue development, as well as for the proper function of cell-renewal systems in adult organisms. Apoptosis is also pivotal in the pathogenesis of several different diseases. In this paper we discuss, from two different points of view, the role of apoptosis in parasitic diseases. The description of apoptotic death in three different species of heteroxenic trypanosomatids is reviewed, and considerations on the phylogenesis of apoptosis and on the eventual role of PCD on their mechanism of pathogenesis are made. From a different perspective, an increasing body of evidence is making clear that regulation of host cell apoptosis is an important factor on the definition of a host-pathogen interaction. As an example, the molecular mechanisms by which Trypanosoma cruzi is able to induce apoptosis in immunocompetent cells, in a murine model of Chagas' disease, and the consequences of this phenomenon on the outcome of the experimental disease are discussed.

Murine polyclonal T-lymphocyte activation induced by phytohemmagglutinin; differential lymphokine requirements of two unusual activation pathways defined by resistance to blockade by barium and by cyclosporin A.

We have recently demonstrated that polyclonal T-cell activation induced by PHA defines an activation pathway which is resistant to blockade by barium (Ba2+) ions. Other modes of T-cell activation, including ConA-induced responses, are completely blocked by Ba2+, which seems to affect an early Ca2+-dependent step of T-cell activation, as determined by kinetic and competition experiments. In the present study, we have analysed the lymphokine requirements of Ba2+-resistant pathway of PHA-induced T-cell activation by means of functional blocking experiments with monoclonal antibodies (mAbs) directed against mouse IL-2 (mAb S4B6) and against mouse IL-4 (mAb 11B11). We found that Ba2+-resistant T-cell activation can be blocked by either S4B6 or 11B11. Thus, both IL-2 and IL-4 participate in Ba2+-resistant T-cell growth induced by PHA. In addition, we found that cyclosporin A (CsA) completely blocks T-cell activation induced by either ConA or by PHA plus Ba2+, but not T-cell activation induced by PHA in the absence of Ba2+, which is reduced by less than 50% in most experiments. This CsA-resistant proliferative component of the PHA response is, thus, distinct from the Ba2+-resistant response, and is carried out by proliferating T-cells. Although mAbs S4B6 and 11B11 are potent blockers of ConA-induced responses, they failed to block CsA-resistant T-cell growth induced by PHA. At the doses of CsA employed, no IL-2 and/or IL-4 activity could be detected in the supernatants of CsA-treated, PHA-stimulated T-cell cultures. The data indicate that this CsA-resistant pathway is both IL-2 and IL-4-independent. The lymphokine involved in this T-cell activation pathway remains to be identified.

Antigen-presenting cells from nonresponder strain 2 guinea pigs are fully competent to present bovine insulin B chain to responder strain 13 T cells. Evidence against a determinant selection model and in favor of a clonal deletion model of immune response gene function.

To test directly the determinant selection hypothesis of immune response gene function, we primed strain 13 T lymphocytes in vitro with allogeneic bovine insulin pulsed strain 2 macrophages. Strain 2 macrophages were found to be fully competent to present bovine insulin B chain to strain 13 T cells despite the fact that strain 2 guinea pigs are normally totally unresponsive to this antigen. These results are incompatible with a strict interpretation of the determinant selection hypothesis, which would have predicted that strain 2 macrophages would have been restricted to the presentation of A chain loop determinants. In addition, a comparison of the reactivity profiles of self-Ia- and allo-Ia-restricted strain 13 T cells to a series of synthetic B chain peptide fragments revealed that the allo-Ia-restricted populations could be activated by autologous guinea pig insulin. Taken together, these observations strongly suggest that the clonal deletion of self-reactive cells is likely to be I region restricted and that nonresponsiveness to any protein antigen may result from a restriction in the T cell repertoire that is generated during ontogeny by a clonal deletion mechanism of tolerance to self.

Effect of cyclosporin A on T cell function in vitro: the mechanism of suppression of T cell proliferation depends on the nature of the T cell stimulus as well as the differentiation state of the responding T cell.

We have studied the effects of the immunosuppressive agent cyclosporin A (CY A) on T cell activation in the guinea pig both in the presence and in the absence of exogenous interleukin 2 (IL 2). CY A suppressed T cell activation by the mitogen, concanavalin A, by blocking IL 2 production and not by blocking the induction of IL 2 receptors. In contrast, the primary T cell proliferative responses to self-Ia antigens in the syngeneic mixed leukocyte reaction (SMLR) and to trinitrophenyl-modified syngeneic macrophages were blocked by CY A and this suppressive effect could not be corrected by addition of exogenous IL 2. T cells primed to syngeneic stimulator cells in the presence of CY A failed to develop IL 2 responsiveness even in the presence of exogenous IL 2, suggesting that CY A directly blocked induction of IL 2 receptors on the responding T cell population. In contrast, the secondary SMLR was suppressed by CY A in the absence of IL 2, but was normal when IL 2 was added to the cultures. CY A completely blocked the primary allogeneic MLR but this inhibitory effect could be reversed when exogenous IL 2 was added to the cultures. Moreover, in the presence of exogenous IL 2, CY A had no effect on the development of IL 2 responsiveness by alloreactive T cells. In addition, CY A induced a population of radiosensitive cells with suppressor activity for the primary MLR. Thus, in the guinea pig, CY A inhibits Ti cell activation both by blocking IL 2 production as well as by inhibiting the induction of IL 2 responsiveness. These two effects occur in the same range of CY A concentrations and are differentially dominant depending on the nature of the stimulating signal and the differentiation state of the responding T cell.

Immune recognition in the streptococcal carditis of mice: the role of macrophages in the generation of heart-reactive lymphocytes.

The role of immune T cells and of streptococcus-pulsed M phi in the production of cardiac lesions, as well as the ability of M phi to present streptococcal antigens to mouse lymphocytes, was investigated. Cells of mice infected with extracts of group A streptococcus were able to induce the appearance of heart lesions when transferred to syngeneic receptors as well as to transfer DTH reactions to syngeneic heart extracts. Streptococcus-pulsed M phi were also able to induce heart lesions and an increase in the serum CPK activity when injected into syngeneic receptors. This last phenomenon was only observed in mice aged 5 mo or more. Furthermore, it was shown in an in vitro model of T cell proliferation that peritoneal M phi pulsed with group A streptococci are able to induce a specific response to syngeneic cardiac extracts. M phi pulsed with group G streptococcus failed to induce such a response. Those findings are discussed as part of a model for the induction of rheumatic cardiac lesions in which M phi display a central role by selecting antigenic determinants from the pathogenic organism for presentation to immunocompetent cells.

Electrophysiology of phagocytic membranes. III. Evidence for a calcium-dependent potassium permeability change during slow hyperpolarizations of activated macrophages.

The roles of potassium and calcium in the slow hyperpolarizations of membranes of activated macrophages are investigated using standard intracellular electrical recording techniques. The amplitude of spontaneous slow hyperpolarizations decreases as a logarithmic function of the external potassium concentration in the culture medium. Similar dependence on the potassium gradient is observed when different levels of membrane potentials are imposed by constant current injection. The reversal potential for electrically evoked slow hyperpolarizations is -90 mV. A 10-fold increase in external potassium concentration causes a 60 mV shift of the reversal potential towards zero. Divalent cation ionophores (A23187 and X537A) can induce slow hyperpolarization responses in quiescent cells or permanent hyperpolarization in spontaneously active cells. The amplitude of the ionophore-induced hyperpolarizations is reduced by an increase in external potassium concentration in a manner consistent with data on slow hyperpolarization responses in the absence of ionophore. The calcium antagonist, verapamil, depresses the slow hyperpolarization responses at the concentration of 10(-5) M. It is suggested that the development of the hyperpolarizing response is due to a calcium-dependent potassium channel. The data support the assumption that spontaneous and artificially elicited slow hyperpolarization responses share a common calcium-dependent mechanism.

Role of macrophage-dependent determinant selection in induction phase of streptococcal carditis.

A genetically controlled antigen-presentation function in macrophages is proposed to explain the induction phase of streptococcal carditis. Antigenic determinants in strains of beta-haemolytic streptococci causing rheumatic fever are selected by macrophages, through the operation of immune response (Ir) genes, to be presented to T lymphocytes. Cross-reactivity between the selected determinants and heart tissue components generates clones of autoreactive T cells. Autoimmunity will develop if, coincidental with the presentation of the relevant antigenic determinant, regulation of T-cell production is disturbed. This hypothesis explains the capacity of different strains of streptococcus to produce rheumatic fever and also the variability in host susceptibility to the disease.

Frequency distribution of Trypanosoma cruzi in macrophages from resistant and susceptible strains of mice.

The frequency distribution of Trypanosoma cruzi inside macrophages from normal or chronically infected resistant and susceptible mice obeys a negative binomial type of distribution. This implies that an "aggregating mechanism" operates in T. cruzi: macrophage interaction.

Electrophysiology of phagocytic membranes. II. Membrane potential and induction of slow hyperpolarizations in activated macrophages.

The potential differences measured on the cell surface and after penetration into the cytoplasm of activated macrophages are described. Linear regressions are made of the measured potential differences as functions of the tip potential of each microelectrode. The surface potential of the macrophage is not significantly different from zero. Mouse macrophages have a transmembrane potential of--26 mV, whereas in guinea-pig cells this value is--18 mV. The input resistances of guinea-pig cells are higher than those of mouse macrophages. The cytoplasmic location of the electrode was characterized both by fluorescent dye injection and by electric criteria. Slow membrane hyperpolarizations are directly elicited by mechanical stimulation. Electric responses evoked by current pulses were further characterized. Our results lead to the extablishment of objective criteria to validate intracellular recordings from macrophage.

Electrophysiology of phagocytic membranes. I. Potassium-dependent slow membrane hyperpolarizations in mice macrophages.

Electrophysiological properties of activated mouse macrophages cultured in vitro were studied using microelectrode techniques. In a high percentage of the individual cells analysed a slow hyperpolarization (SH) was observed with a concomitant decrease (2--4 times) of the input resistance. Increasing doses of tetraethyl ammonium progressively reduce the amplitude of the SH and at a concentration of 15 mM complete blockade of the phenomena is observed. Valinomycin, at a concentration of 10(-7) M produces rapid and permanent hyperpolarization, with a shift in the membrane potential to about --50 mV. These data strongly support the previously proposed hypothesis that the development of SH is due to an increase in the membrane permeability to potassium ions.