Two types of portasystemic shunts were investigated in the rat; low pressure shunts (portacaval shunt, PCS, and portacaval transposition, PCT) and a high pressure shunts (Portasystemic shunt by ligation of the portal vein after splenic transposition, PSSL). liver atrophy was seen in all groups but PCT. Simplification of intestinal villi was observed in all groups and related to the degree of portal pressure alteration. Liver function and clinical status improved if some blood, either systemic or splanchnic, perfused the liver through surgical deviation (PCT) or accidental collateral formation (PSSL + C). In the prevention of the PCS syndromes selective portacaval shunting is advocated, leaving some blood to flow to the liver. A high as possible splanchnic pressure prevents intestinal villi simplification and loss of resorptional surface.

Animals↗

PubMedDate not supplied

Development and long-term fate of a cellular lining in fibrous polyurethane vascular prostheses implanted in the dog carotid and femoral artery. A scanning and light microscopical study up to 53 months after implantation.

The development and long-term fate of the inner cellular lining in 72 small caliber (3 mm inner diameter) fibrous polyurethane vascular prostheses explanted from dog carotid and/or femoral arteries at times ranging from 1.5 weeks up to 53 months after implantation were studied by scanning electron and light microscopy. A continuous cellular ingrowth from the vascular stumps into the 3 cm long prostheses was observed, which eventually resulted in a complete cellular lining 6 months after implantation. No other ways of endothelialization were noted. In fully endothelialized prostheses, the cellular ingrowth extended approximately 8 mm into the prostheses and consisted of several layers of fibroblasts and smooth muscle cells, covered by a very thin endothelioid cell layer. The newly developed lining was firmly anchored onto the inner prosthetic surface by means of cellular protrusions extended into the fibrous texture of the prosthetic wall. It was concluded that under experimental conditions in the dog complete endothelialization can be obtained in fibrous polyurethane vascular prostheses and that the lining remained thin and stable throughout the observation period of 53 months after implantation.

Anastomosis, Surgical↗

PubMedDate not supplied

Endothelialization of polyurethane vascular prostheses implanted in the dog carotid and femoral artery.

A new type of vascular prosthesis made of polyurethane with a fibrous structure of the wall was implanted in the carotid and/or femoral artery of dogs. The healing process and neo-intima formation after implantation of this type of prosthesis was followed with light- and scanning electron microscopy. A total of 18 prostheses, which had been implanted for 1, 3, 6, 9 or 20 weeks were studied. Endothelial like cells invaded the prosthesis over the anastomoses, starting the first week after implantation. The growth zones advanced steadily, and prostheses measuring 3 cm in length were completely endothelialized by 20 weeks after implantation, a mean growth rate of the endothelial like cells of 0.09 mm/day. Subsequently, fibroblasts and smooth muscle cells grew between the neoendothelial layer and the prosthetic inner surface, forming a new multi-layered neo-intima. Cellular elements of the neo-intima were firmly anchored onto the inner wall of the prosthesis by cells with extending cytoplasmic protrusions between the fibers of the prosthetic wall. Since in this type of fibrous polyurethane prosthesis, endothelial like cells continually grew until a new lining was formed, apparently facilitated by the fibrous structure of the wall, further investigations are indicated for progression toward clinical implantation of this type of prosthesis.

Animals↗

PubMedDate not supplied

Validation of liquid chromatographic method for assay of chlorthalidone in tablet formulations.

A stability-indicating, reverse phase liquid chromatographic (LC) method was developed for assay of chlorthalidone in tablet formulations. The chromatographic system separates the parent compound from its potential hydrolysis product (4'-chloro-3'-sulfamoyl-2-benzophenone carboxylic acid), which can be quantitated at low levels, and another degradation product (2-chloro-5-(1-methoxy-3-oxo-1-isoindolinyl)benzenesulfonamide), which was found during the experimental work. The procedure can also be used for content uniformity determinations. The general utility of the method was demonstrated by the assay of several product brands. The validated procedure was shown to be accurate, precise, reproducible, and specific.

Chlorthalidone↗

PubMedDate not supplied

A fibrous polyurethane microvascular prosthesis. Morphological evaluation of the neo-intima.

A fibrous polyurethane microvascular prosthesis with an inner diameter of 1.5 mm was implanted to replace the rat aorta between the left renal artery and the bifurcation of the aorta. Twenty-four implantations, using three different lengths (0.5; 1; 1.5 cm), were carried out. Rats were sacrificed 3, 6, 9 and 12 weeks after implantation. Only 1 prosthesis was occluded (probably due to a technical error). Grafts were already lined with a neo-intima by the third week, irrespective of their length. Different shapes of endothelial cells were recognized. It appeared that cells arise and migrate from the aortic stumps into the prosthesis, since the neo-intima is thicker in the anastomotic area than in the middle of the graft. The well-defined neo-intima consisted of several layers of smooth muscle cells embedded in a glycoprotein matrix and covered by a very flat continuous endothelium. The structure of the prosthesis allowed anchoring of the lining cells. Migration of cells through the wall of the prosthesis was not observed. At those places in the prosthesis where fibres had fused together to form flat areas the neo-intima became torn by the contraction of the myofibroblasts. This was because the cells had evidently failed to become anchored to the prosthetic wall. The neo-intima retained the ability of immediate repair of small defects which develop occasionally on the non-fibrous areas of the luminal surface of the prosthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

The endothelialization process of a fibrous polyurethane microvascular prosthesis after implantation in the abdominal aorta of the rat. A scanning electron microscopic study.

The endothelialization process of a fibrous microvascular polyurethane prosthesis (inner diameter 1.6 mm) was studied by scanning electron microscopy. Forty-seven prostheses (1 cm) were implanted into the abdominal aorta of rats between the left renal artery and the bifurcation. Specimens were taken on day 1, 3, 5, 7, 10, 14, 18, 21 and 25, as well as 6 and 9 months after implantation, to evaluate immediate and delayed response and complications. The patency rate of the implants was 91.2%. After an initial recovery period of five days, endothelial cells started to migrate onto the inner surface of the prosthesis with a velocity of approximately 0.3 mm per day, resulting in a completely endothelialized prosthesis at day 21. A smooth continuous inner lining was achieved. A difference in growth pattern between the proximal and distal growth zone was observed, and may be attributed to the direction of the blood flow through the prosthesis. The endothelial cells advanced in a close arrangement. No cells were seen to settle and grow in between the two growth zones on the fibrin layer. If no immediate complications occur, the endothelialization process (21 days) proceeds uneventfully and no late complications are observed. Though it may be argued that the new cells lack some authentic endothelial features, this study indicates that they are at least of endothelial orgin, and behave morphologically like endothelial cells. It can be concluded that the adequate texture of the prosthesis and the cell anchoring, in combination with both an optimal surgical performance and blood flow, ensure that the microvascular prostheses are rapidly endothelialized and retain high patency rates over long periods of time.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗