Patterns of proliferation and cell differentiation during hepatic ontogeny in the alpaca.

The liver has multiple functions that change throughout ontogeny. South American camelids (SAC) have unique characteristics related to adaptation to extreme environments and metabolism. However, the process of hepatic cell differentiation has not been studied in any SAC. We study the patterns of cell differentiation and proliferation in the liver of the alpaca at different times of the ontogeny, excluding the hematopoietic components. Immunohistochemical techniques were performed in 66 specimens, including embryos, fetuses, neonates and adults. Supplementary analyses were performed by lectinhistochemistry. The hepatocytic differentiation was performed by the identification of Hepatocyte (Clone: ​​OCH1ES Dako®). It began in the specimens of 1.8-2.5 cm of crown to rump length (CRL), from Days 25-29 (ovulation = Day 0), continued during gestation and intensified towards its end. The cholangiocytic differentiation was performed by the identification of cytokeratin 7 (CK7, Dako®). It was manifested at the final of gestation (specimens of 28.4 cm CRL, from Day 223 onwards). Parenchymal cells underwent a process of gradual differentiation (differentiation of hepatocytes preceded that of cholangiocytes). Cell proliferation was observed along gestation using the nuclear proliferation antigen (PCNA) and Ki-67. Hepatic organogenesis in the alpacas shares similar differentiation and proliferation mechanisms with other altricial, but phylogenetically distant, species.

Development of the Liver in Alpaca (Vicugna pacos): A Microscopic and Macroscopic Description.

South American camelids have several biological, morphological and behavioural adaptations that allow them to live in geographical areas dominated by high altitudes. The liver has hematopoietic functions during the prenatal life, which could be modified in response to the unfavorable habitat. However, there are no previous data on the prenatal development of the liver in these species. In the present work, a study on the macroscopic and microscopic morphology of the liver of the alpaca during ontogeny was performed. Forty-one animals ranging in age from 20 days of embryonic development to adults were studied. Macroscopic and microscopic observations were performed on samples subjected to different techniques. Less than 7-g specimens were studied with stereoscopic magnifying glass. The general characteristics of the prenatal liver are similar to those of other mammals, and the structures related to hematopoietic function follow an ontogenic pattern similar to that of previously studied precocial species. However, there are differences in morphology when compared to descriptions for the Old World camelids, including the absence of relation between the caudate lobe and the right kidney and the lack of interlobular connective tissue.

Conformation and anatomical relations of the liver of llama (Lama glama).

Morphological studies of the liver of the llama are structural supportive to the clinical practice, surgery and specific diagnostic techniques. The aims of this study were first to determine the location of the organ and the direction of its major axis to project it to the abdominal wall, identifying visible and palpable bony references. Secondly, to characterize and determine anatomical relations of the surfaces, borders and angles of the llama liver, as well as, of its lobulation. Twenty adult llamas of both sexes and two foetuses of 6.5- and 7-month-old were used. Llama liver is a post-diaphragmatic organ located in the cranial abdominal region, in the right hypochondrium, in relationship with the last six ribs. Dorsally, it can exceeds the last (twelfth) rib. Its major axis presents a cranio-ventral bent. Its shape is irregularly triangular. It presents two surfaces (parietal and visceral), three borders (cranial, caudal and ventral) and three angles (dorsal, cranial and caudal).

Desarrollo morfológico del estómago en terneros alimentados con dos sustitutos lácteos / Morphologic development of the stomach of calves feed with milk substitute

Los terneros comienzan a rumiar a las 2 ó 3 semanas de edad, pasando de lactante a rumiante de acuerdo a la influencia de estímulos que recibe de la dieta. (Brody, 1945; Swanson, 1960 y National Research Council, 1989). El objetivo del presente trabajo fue evaluar los cambios en el desarrollo morfohistológico del estómago de terneros lactantes, alimentados con dos sustitutos (tratamientos) que difieren en su composición. Tratamiento A consistió en: derivados de la leche (dl) 65 por ciento, fibra detergente neutro (FDN) 1,75 por ciento y almidón (al) 24,6 por ciento. Tratamiento B: dl 50 por ciento, FDN 6,5 por ciento y al 19,2 por ciento. Se trabajó con un total de 18 terneros machos (9 en cada tratamiento), de raza Holando Argentino a los que se les suministró una dieta consistente en 240 g de sustituto en cada una de las 2 tomas diarias durante 45 días, concentrado ad libitum, disponibilidad de forraje fresco y agua, durante 50 días. Para la evaluación anatómica, se muestrearon 6 terneros, seleccionados para cada fecha y tratamiento, a los días 18-41 y 50, tomando en cada una de ellas un ternero de cada tratamiento. La evaluación consistió en efectuar mediciones de capacidad, longitud, peso vacío, peso relativo de la digesta de los distintos compartimentos del estómago. Utilizando el test de análisis de varianza (ANDEVA), no se observaron diferencias (P > igual 0,05) en peso vivo (PV) entre dietas para las tres fechas, observándose una tendencia de mayor PV en la dieta A. En cambio, en la capacidad del contenido del retículo, como en el espesor del epitelio del mismo, se evidenciaron diferencias significativas (P < 0,05) con R²0,75 y 0,8 respectivamente. Debido a la falta de repeticiones del ensayo y al efecto tiempo, los resultados sólo tienen valor descriptivo. Si bien a temprana edad (18 días) se evaluó mayor capacidad del rumen en terneros alimentados con el sustituto de menor calidad B, a los 50 días, se observa un incremento en el desarrollo del estómago en los alimentados con sustituto de mayor calidad A. Al incorporar al sustituto lácteo mayor por ciento de derivados de la leche, se favorece la capacidad anatómica del estómago, lo cual permitía a los terneros convertirse en rumiantes más tempranamente. Para la evaluación histológica se muestrearon seis terneros seleccionados para cada fecha y tratamiento a los días 18, 41 y 50 días. Las muestras fueron fijadas en formol bufferado al 10 por ciento, luego procesadas por técnicas histológicas