Experimental activation of ascidian eggs.

The effects of the ionophore A23187 on the activation of the eggs of Ascidia malaca have been studied. No common external ion in the sea water is found to be essential for the activation but lanthanum and manganese inhibit the response. These observations support the interpretation that activation of these eggs results from changes in free intracellular calcium levels. This has led to the prediction of two other activating treatments, namely high external calcium and addition of theophylline.     

Experimental hydroxyapatite cement cranioplasty.

Hydroxyapatite cement is a calcium phosphate-based material that when mixed with water forms a dense paste that sets within 15 minutes and isothermically converts in vivo to a microporous hydroxyapatite implant. This cement was used to reconstruct bilateral 2.5-cm-diameter full-thickness critical-sized parietal skull defects in six cats. One side was reconstructed with 100 percent hydroxyapatite cement, and the other with a mixture of 50 percent hydroxyapatite cement and 50 percent ground autogenous bone by weight. These animals were sacrificed at 6 and 12 months after implantation. Positive and negative controls also were prepared. The anatomic contour of the soft tissue overlying all hydroxyapatite cement implants was well maintained, there were no wound infections or structural failures, and the implants were well tolerated histologically. None of the negative (unreconstructed) control defects was completely filled with repair bone, and all positive (methyl methacrylate) controls demonstrated foreign-body giant-cell formation and fibrous encapsulation of the implants. Examination of decalcified and undecalcified sections revealed progressive but variable replacement of the cement by new bone and soft tissue without a change in the shape or volume of the hydroxyapatite cement-reconstructed areas. New bone comprised 77.3 and 64.7 percent of the tissue replacing the hydroxyapatite cement and hydroxyapatite cement-bone implants, respectively. Replacement of the hydroxyapatite cement implants by new bone is postulated to occur by a combination of osteoconduction and implant resorption. These results indicate that further experimental research leading to the possible application of hydroxyapatite cement for full-thickness calvarial defect reconstruction in humans is warranted.     

Experimental hypersplenism in mice.

The authors induced experimental hypersplenism in mice with repeated intraperitoneal injections of methylcellulose ("Tylosa", Messrs. Kabl). Detailed haematological tests of the peripheral blood, a cytomorphological examination of bone marrow and spleen from puncture material and histological tests of the bone marrow, spleen, lymph nodes, thymus, liver, kidneys and lung tissue of hypersplenic mice were carried out. Among the haematological results, apart from findings of marked erythrocyto-, leucocyto- and thrombocytopenia, attention is drawn to the finding, not previously described in the literature, of lowered osmotic resistance and elevated phagocytic activity of the leucocytes of hypersplenic mice.     

Experimental thioacetamide-induced cirrhosis of the liver.

Hepatic cirrhosis is a complex disease in which several biological, biochemical and chemical alterations are combined, none of these alone being sufficient for diagnosis. The morphological characteristics of the final stages of cirrhosis are well known, but the initial lesions and intermediate stages still have not been fully clarified. An experimental model of hepatic cirrhosis by chronic administration over 30 weeks of thioacetamide (50 mg/kg twice weekly) to female Wistar rats has been produced. In a macroscopic, microscopic and ultrastructural study. The different lesions that appeared were evaluated according to the dose of the toxic agent administered up, until hepatic cirrhosis was finally installed; this was after 60 doses of the toxic agent (30 weeks). Discussion is made of the different types of administration and the doses employed to obtain a suitable survival rate for these cases; in our experiments this was 95%. It has been demonstrated in both human and experimental pathology that once the disease itself has been installed, currently there is no rational or useful treatment for it. A beneficial effect has been demonstrated for certain substances, improving the initial and intermediate lesions, so we conclude by stating that it is necessary to further study the hepatic lesions preceeding cirrhosis. Knowledge of these lesions could form the basis for establishing a useful and rational therapy for such cases.