Hydroxyapatite ceramics with selected sintering additives.

Several sintering additives for hydroxyapatite (HA) have been tested in order to enhance its sinterability without decomposing the HA and/or decreasing bioactivity and biocompatibility, additionally providing a weak interface for HA ceramics. The ion species of sintering additives were selected from those in the mineral constituents of hard tissues and bioactive glasses. After investigation of phase diagrams in the CaO-P2O5-additive systems, and analysis of physiochemical properties of the additives, several sintering aids for HA have been chosen. Subsequently, densification, phase composition, grain growth and fracture behaviour of HA containing 5 wt% of each additive, sintered at 1000-1100 degrees C, have been studied. H3BO3, CaCl2, KCl, KH2PO4, (KPO3)n and Na2Si2O5 did not enhance densification of HA. K2CO2, Na2CO3, KF and sodium phosphates improved the densification significantly. Expect for KCl and some sodium phosphates, all the additives caused formation of large quantities of undesired beta-tricalcium phosphate or CaO; therefore, they are not appropriate for HA. In the case of sodium phosphate additives, it was possible to avoid formation of CaO or beta-tricalcium phosphate by control of the additive quantity and chemical composition. beta-NaCaPO4 has been found to be an effective sintering agent which causes neither decomposition of HA nor formation of other undesired phases.

Processing and mechanical properties of hydroxyapatite reinforced with hydroxyapatite whiskers.

Hydrothermally synthesized HAp fine crystals/HAp whiskers mixtures have been used for the preparation of HAp/0-30% (whiskers) composites. The composites have been fabricated by pressureless sintering and hot-pressing. The best mechanical properties and the highest densities have been achieved for composites hot pressed at 1000 degrees C (2 h, 30 MPa in flowing Ar). Their density was in the range of 90-97% of the theoretical density. Fracture toughness (Klc) of the composites reflected their microstructure and had the value of 1.4 MPa m1/2 (as compared with Klc = 1.0 MPa m1/2 for the non-reinforced HAp matrix). Compressive prestressing of the HAp matrix and crack deflection (both derived from the residual stress field) contributed to the increase of fracture toughness. Other toughening mechanisms have not been observed. HAp/HAp (whiskers) composites exhibited improved toughness without degradation of biocompatibility, because the HAp whiskers acted both as a reinforcement and as a biocompatible phase. Problems related to biocompatibility and mechanical properties of available HAp-based composites were also discussed.

[Pancreatic ascites]. / Wodobrzusze trzustkowe.

Two cases of pancreatic ascites have been presented. 1. A 29 year old man, heavy alcoholic, with fast growing ascites presented since long biochemic features of pancreatitis. The diagnosis of the pancreatic origin of ascites was made on the ground of the high level of amylase in the ascitic fluid. Conservative treatment was effectless. The patients refused surgical therapy. Then he died in septic shock. Autopsy confirmed the pancreatic origin of ascites. 2. A 43 year old man heavy alcoholic as well admitted because of fast growing ascites. As in the first case examination of the fluid confirmed the diagnosis of pancreatic origin of ascites. Again a high level of amylase and protein was found. After clinical treatment and parenteral nutrition the condition of the patient improved and he was dismissed 4 weeks later.

Siderophore activity in Rhizobium species isolated from different legumes.

Rhizobium strains isolated from nodules of the different legumes including wild-growing plants were examined for their siderophore activity. Fifteen of the 84 screened rhizobial strains were able to grow under conditions of limited iron supply. Nine of them gave orange halos in the assay with Chrom azurol S. Among these strains were Rhizobium sp. (Ononis) and Rhizobium (Genista), producing hydroxamates and phenolates. These compounds could promote the growth of siderophore-negative bacteria on iron-deficient media. The results imply that the hydroxamates from G1 and O1 strains may belong to the monohydroxamate class of siderophores.

[Attempt at evaluation of certain parameters of gastric secretion in patients with duodenogastric reflux]. / Próba oceny niektórych parametrów wydzielania zoladkowego u chorych z zarzucaniem dwunastniczo-zoladkowym.

There were four groups of patients: duodenal ulcer patients (32), duodeno-gastric reflux patients (31), patients with duodenal ulcer and reflux (33) and 12 healthy men. All of them aged 20-40. In all patients we performed gastroscopy, cholecystography, Kay's test for secretion and isotope proteolytic secretion test. High activity of proteolytic secretion in both groups of reflux patients was found. There were also the high percentage of false positive scores in endoscopy estimation of reflux, in comparison to the non-invasive isotope method. We suggest: reflux may be the important factor in duodenal ulcer pathogenesis; endoscopy cannot be used in duodeno-gastric reflux estimation.

Disturbances of the pulmonary perfusion after endoscopic sclerotherapy of oesophageal varices.

Haemorrhage from oesophageal varices is one of the most common reason of death of patients with liver cirrhosis. The possibility of treatment and prevention of the haemorrhage by endoscopic sclerotherapy (ES) has become one of the achievements of contemporary medicine. Nevertheless there are some complications described after this procedure, the most severe being the pulmonary embolia. In our study we analyzed the pulmonary circulation by perfusion scintigraphy after ES. Among twelve patients treated by ES we found two cases of disturbed pulmonary perfusion. We did not find clinical or gasometric changes in these patients. We suggest there should be done pulmonary perfusion monitoring after ES.