Are there differences in the growth adaptation processes of growing and mature organism models of short bowel syndrome?

OBJECTIVES: The purpose of this study was to present an experimental model of short bowel syndrome (SBS) in weaning rats and to compare the adaptative mechanisms of the remaining bowel in weaning rats and adult animals by means of morphometric, histologic and molecular methods. METHODS: Twenty-four weaning rats were divided into 3 groups of 8 animals, one control group and two short bowel groups (euthanasia after 4 and 21 days), and were compared with similar adult groups. Morphometric evaluations of the animals and histopathological and molecular studies of the remaining bowel were performed. RESULTS: The weight of young rats increased after enterectomy, whereas that of adult rats decreased after enterectomy (p<0.0001). The ratio of intestinal length/body weight was significantly higher in weaning rats than in adults (p<0.002), showing that intestinal growth was more intense in weaning rats. Intestinal resection promoted increased thickness of the small bowel lamina propria (p=0.001) and reduced thickness of the colon lamina propria (p=0.04) in weaning rats relative to those in adults. In addition, intestinal resection promoted increased expression of the Bcl-xl gene (antiapoptotic) in adult animals compared with that in weaning rats (p=0.001). CONCLUSION: Morphometric, histological and molecular differences were shown in the adaptation processes of growing and mature organisms.

Immediate expression of c-fos and c-jun mRNA in a model of intestinal autotransplantation and ischemia-reperfusion in situ

OBJECTIVE: Intestinal ischemia-reperfusion injury occurs in several clinical conditions and after intestinal transplantation. The aim of the present study was to investigate the phenomena of apoptosis and cell proliferation in a previously described intestinal ischemia-reperfusion injury autograft model using immunohistochemical markers. The molecular mechanisms involved in ischemia-reperfusion injury repair were also investigated by measuring the expression of the early activation genes c-fos and c-jun, which induce apoptosis and cell proliferation. MATERIALS AND METHODS: Thirty adult male Wistar rats were subjected to surgery for a previously described ischemia-reperfusion model that preserved the small intestine, the cecum and the ascending colon. Following reperfusion, the cecum was harvested at different time points as a representative segment of the intestine. The rats were allocated to the following four subgroups according to the reperfusion time: subgroup 1: 5 min; subgroup 2: 15 min; subgroup 3: 30 min; and subgroup 4: 60 min. A control group of cecum samples was also collected. The expression of c-fos, c-jun and immunohistochemical markers of cell proliferation and apoptosis (Ki67 and TUNEL, respectively) was studied. RESULTS: The expression of both c-fos and c-jun in the cecum was increased beginning at 5 min after ischemia-reperfusion compared with the control. The expression of c-fos began to increase at 5 min, peaked at 30 min, and exhibited a declining tendency at 60 min after reperfusion. A progressive increase in c-jun expression was observed. Immunohistochemical analyses confirmed these observations. CONCLUSION: The early activation of the c-fos and c-jun genes occurred after intestinal ischemia-reperfusion injury, and these genes can act together to trigger cell proliferation and apoptosis. .

Effects of ischemic preconditioning in a pig model of large-for-size liver transplantation

OBJECTIVE: In most cases of pediatric liver transplantation, the clinical scenario of large-for-size transplants can lead to hepatic dysfunction and a decreased blood supply to the liver graft. The objective of the present experimental investigation was to evaluate the effects of ischemic preconditioning on this clinical entity. METHODS: Eighteen pigs were divided into three groups and underwent liver transplantation: a control group, in which the weights of the donors were similar to those of the recipients, a large-for-size group, and a large-for-size + ischemic preconditioning group. Blood samples were collected from the recipients to evaluate the pH and the sodium, potassium, aspartate aminotransferase and alanine aminotransferase levels. In addition, hepatic tissue was sampled from the recipients for histological evaluation, immunohistochemical analyses to detect hepatocyte apoptosis and proliferation and molecular analyses to evaluate the gene expression of Bax (pro-apoptotic), Bcl-XL (anti-apoptotic), c-Fos and c-Jun (immediate-early genes), ischemia-reperfusion-related inflammatory cytokines (IL-1, TNF-alpha and IL-6, which is also a stimulator of hepatocyte regeneration), intracellular adhesion molecule, endothelial nitric oxide synthase (a mediator of the protective effect of ischemic preconditioning) and TGF-beta (a pro-fibrogenic cytokine). RESULTS: All animals developed acidosis. At 1 hour and 3 hours after reperfusion, the animals in the large-for-size and large-for-size + ischemic preconditioning groups had decreased serum levels of Na and increased serum levels of K and aspartate aminotransferase compared with the control group. The molecular analysis revealed higher expression of the Bax, TNF-alpha, I-CAM and TGF-beta genes in the large-for-size group compared with the control and large-for-size + ischemic preconditioning groups. Ischemic preconditioning was responsible for an increase in c-Fos, IL-1, IL-6 and e-NOS ...

A simplified experimental model of large-for-size liver transplantation in pigs

OBJECTIVE: The ideal ratio between liver graft mass and recipient body weight for liver transplantation in small infants is unknown; however, if this ratio is over 4%, a condition called large-for-size may occur. Experimental models of large-for-size liver transplants have not been described in the literature. In addition, orthotopic liver transplantation is marked by high morbidity and mortality rates in animals due to the clamping of the venous splanchnic system. Therefore, the objective of this study was to create a porcine model of large-for-size liver transplantation with clamping of the supraceliac aorta during the anhepatic phase as an alternative to venovenous bypass. METHOD: Fourteen pigs underwent liver transplantation with whole-liver grafts without venovenous bypass and were divided into two experimental groups: the control group, in which the weights of the donors were similar to the weights of the recipients; and the large-for-size group, in which the weights of the donors were nearly 2 times the weights of the recipients. Hemodynamic data, the results of serum biochemical analyses and histological examination of the transplanted livers were collected. RESULTS: The mortality rate in both groups was 16.5% (1/7). The animals in the large-for-size group had increased serum levels of potassium, sodium, aspartate aminotransferase and alanine aminotransferase after graft reperfusion. The histological analyses revealed that there were no significant differences between the groups. CONCLUSION: This transplant method is a feasible experimental model of large-for-size liver transplantation. .

Estabilidade da mistura de uma nova emulsäo lipídica com soluçoës de nutriçäo parenteral / Stability of the mixture of a new fat emulsion with solutions of parenteral feeding

Foi estudada a estabilidade da mistura de soluçöes de nutriçäo parenteral (NP) com uma nova emulsäo lipídica, contendo óleo de soja e triglicérides de cadeia média (em partes iguais) (Lipofundin MCT 10%). Foram realizados cinco preparados, analisados 24 horas após, em microscopia eletrônica de transmissäo: 1) emulsäo lipídica pura a 10% (EL); 2) El + soluçäo de NP contendo glicose a 5% (NP5); 3) EL + soluçäo de NP contendo glicose a 12,5% (NP 12,5); 4) El + soluçäo de NP contendo glicose a 25% (NP 25); 5) EL + glicose a 50%. Adicionalmente, foi medido o pH de cada soluçäo nutriente, da emulsäo lipídica e das misturas finais, com o objetivo de verificar a influência do pH na estabilidade das misturas. Verificou-se que a mistura da emulsäo lipídica com soluçöes de nutriçä parenteral näo acarretou qualquer coalescência das partículas lipídicas, alteraçäo nas membranas ou no tamanho dos liposomas. No entanto, a adiçäo de glicose hipertônica (pH = 3,5) à emulsäo lipídica acarretou agregaçäo e aumento do diâmetro das partículas lipídicas, provavelmente em decorrência da queda do pH da mistura final. Conclui-se que as misturas da emulsäo lipídica com soluçöes de nutriçäo parenteral com concentraçäo de glicose até 25% säo estáveis por períodos de até 24 horas e podem ser utilizadas rotineiramente em nutriçäo parenteral