Phosphorylation of factor Va and factor VIIIa by activated platelets

Platelet activation leads to the incorporation of 32[PO4(2-)] into bovine coagulation factor Va and recombinant human factor VIII. In the presence of the soluble fraction from thrombin-activated platelets and (gamma-32P) adenosine triphosphate, radioactivity is incorporated exclusively into the M(r) = 94,000 heavy chain (H94) of factor Va and into the M(r) = 210,000 to 90,000 heavy chains as well into the M(r) = 80,000 light chain of factor VIII. Proteolysis of the purified phosphorylated M(r) = 94,000 factor Va heavy chain by activated protein C (APC) gave products of M(r) = 70,000, 24,000, and 20,000. Only the intermediate M(r) = 24,000 fragment contained radioactivity. Because the difference between the M(r) = 24,000 and M(r) = 20,000 fragments is located on the COOH-terminal end of the bovine heavy chain, phosphorylation of H94 must occur within the M(r) = 4,000 peptide derived from the carboxyl-terminal end of H94 (residues 663 through 713). Exposure of the radioactive factor VIII molecule to thrombin ultimately resulted in a nonradioactive light chain and an M(r) = 24,000 radioactive fragment that corresponds to the carboxyl-terminal segment of the A1 domain of factor VIII. Based on the known sequence of human factor VIII, phosphorylation of factor VIII by the platelet kinase probably occurs within the acidic regions 337 through 372 and 1649 through 1689 of the procofactor. These acidic regions are highly homologous to sequences known to be phosphorylated by casein kinase II. Results obtained using purified casein kinase II gave a maximum observed stoichiometry of 0.6 mol of 32[PO4(2-)]/mol of factor Va heavy chain and 0.35 mol of 32[PO4(2-)]/mol of factor VIII. Phosphoamino acid analysis of phosphorylated factor Va by casein kinase II or by the platelet kinase showed only the presence of phosphoserine while phosphoamino acid analysis of phosphorylated factor VIII by casein kinase II showed the presence of phosphothreonine as well as small amounts of phosphoserine. The platelet kinase responsible for the phosphorylation of the two cofactors was found to be inhibited by several synthetic protein kinase inhibitors. Finally, partially phosphorylated factor Va was found to be more sensitive to APC inactivation than its native counterpart. Our findings suggest that phosphorylation of factors Va and VIIIa by a platelet casein kinase II- like kinase may downregulate the activity of the two cofactors.     

Engraftment of dogs with Ia-positive marrow cells isolated by avidin- biotin immunoadsorption

Previous work has shown failure of engraftment in lethally irradiated dogs when autologous marrow was depleted of Ia-positive cells with an anti-Ia antibody and complement before infusion. In the current study, we have utilized an avidin-biotin immunoadsorption procedure to obtain a population of highly enriched Ia-positive cells for autologous bone marrow transplantation in dogs given lethal irradiation. Dog marrow cells (2.4 to 7.0 X 10(9) cells) that contained 8.6% to 19.9% Ia- positive cells were treated successively with monoclonal antibody 7.2, which reacts with a framework determinant of Ia-antigen, and biotin- conjugated goat antimouse immunoglobulin. These treated cells were passed over a column of avidin-Biogel (polyacrylamide) and the adherent cells removed by mechanical agitation. Seven lethally irradiated dogs were transplanted with 5.9 to 33.4 X 10(6) recovered adherent cells per kilogram of which 69.0% to 88.0% were Ia-positive. All dogs had hematologic recovery; six are alive and well with durable engraftment and one died on day 15 posttransplant. They are immunologically normal as determined by lymph node and bone marrow biopsies, lymphocyte function, and immunophenotyping of peripheral blood and bone marrow cells. These data provide further evidence that canine hematopoietic stem cells express Ia-like antigens and that these cells are capable of complete hematopoietic and immunologic reconstitution in an autologous model.     

Age and bioavailability of alcohol

It has been shown that advanced age results in a decreased first pass metabolism (FPM) of ethanol with elevated serum ethanol concentrations (SECs). It is still unknown if this is due to age by itself or to other factors like for example atrophic gastritis with decreased activity of alcohol dehydrogenase (ADH). To study the effect of age on SECs and on bioavailability of ethanol, 15 volunteers with a mean age of 71 +/- 1 year (8males and 7 females) and 16 volunteers with a mean age of 37 +/- 2 years (8males and 8 females) showing normal gastric histology received ethanol (0.225 g/kg b. w.) intravenously (iv.) and orally.RESULTS: The difference between the SEC time curves after iv. and oral ethanol administration (so called FPM of ethanol) was significantly increased in elderly subjects (54 +/- 6 vs. 12 +/- 9 %, p < 0.001). The SEC time curves after iv. ethanol application were significantly increased in the elderly (p < 0.001), whereas SECs following oral alcohol administration were significantly lower in elderly as compared to younger individuals (p < 0.02). Peak SECs following iv. application was also significantly elevated with age (52 +/- 4 vs. 31 +/- 1 mg/100 ml, p < 0.001) and occurrence of peak SECs following oral ethanol intake was significantly delayed (47 +/- 4 vs. 28 +/- 4 min, p < 0.001). No gender effect at all was observed.CONCLUSION: FPM of ethanol is inexpectedly increased in elderly with normal gastric morphology compared to young people. The elevation of SECs after iv. ethanol administration in the elderly could be explained by the reduction of the water distribution space with age, whereas the increased FPM of ethanol in elderly subjects with normal gastric morphology is probably due to a deceleration of the speed of gastric emptying leading to an increased contact time of alcohol with gastric alcohol dehydrogenase (ADH). Our data do not confirm results from other research groups showing increased SECs in the elderly after alcohol consumption. Increased SECs are therefore not due to age by itself, but are probably caused by other factors as for example atrophic gastritis which is frequently found in the elderly people and which decreases FPM of ethanol.     

Endoscopic sealing of pancreatic fistula by using N-butyl-2-cyanoacrylate

BACKGROUND: The treatment of pancreatic fistula can be difficult. A novel endoscopic approach to sealing pancreatic fistulas by using N-butyl-2-cyanoacrylate is described. METHODS: Twelve patients with pancreatic fistulas underwent endoscopic injection of N-butyl-2-cyanoacrylate into the fistulous tract, in addition to endoscopic drainage. RESULTS: Fistulas were closed successfully in 8 of 12 patients. A single treatment session was successful in 7 patients; a second session was required in one patient. In two patients, closure was temporary, and, in one patient, the treatment failed. One patient died 24 hours after treatment. He developed a pulmonary thromboembolism from a left popliteal vein thrombosis and died from complications of surgical thromboembolectomy. At autopsy, a pulmonary embolus was found, but there was no evidence of N-butyl-2-cyanoacrylate in the lungs. No procedure-related complication occurred over a median follow-up of 20.7 months (range 9-51 months). CONCLUSIONS: In this preliminary study, occlusion of pancreatic fistulas by using N-butyl-2-cyanoacrylate glue was safe and effective, and obviated the need for surgery in a substantial proportion of patients. Further studies of the use of N-butyl-2-cyanoacrylate for closure of pancreatic fistula are warranted.     

Liver toxicity of drugs of plant origin

Herbal drugs are widely used and often contain highly active pharmacological compounds. Recently, reports have mounted about hepatotoxicity of herbal remedies which ranges from mild liver enzyme alterations to chronic liver disease and liver failure. Hepatotoxicity of Chinese herbs has been recognized, e.g. during treatment of patients with atopic eczema. However, the toxic compounds remain to be determined. Hepatic veno-occlusive disease may result from pyrrolizidine alkaloids which are contained in numerous plants worldwide. Teucrium chamaedrys, commonly referred to as germander, may cause hepatitis and even liver cirrhosis. Significant hepatotoxicity has also been observed after the ingestion of chaparral. Recently, greater celandine, which is widely used for biliary disorders and dyspepsia, was identified as a cause of cholestatic hepatitis. Hepatotoxic reactions have also been observed after the ingestion of Atractylis gummifera, Callilepsis laureola, Senna, Kavapyrone and Pulegium. The aim of this review is to summarize potentially hepatotoxic herbal remedies, to further elucidate their mechanisms of toxicity and thereby underline the likelihood of plants to be the cause of liver damage.