Electron inelastic mean free path formula and CSDA-range calculation in biological compounds for low and intermediate energies.

In this study, for low atomic number targets and biological compounds, an inelastic mean free path (IMFP) formula and energy straggling parameter formula are presented, being valid for low and high electron energies. In addition, calculation of the continuous slowing down approximation-range (CSDA-range) from the stopping power is also made. The IMFP and the energy straggling parameter formulae are evaluated using the generalized oscillator strength (GOS) model and the exchange correction to the inelastic differential cross section (IDCS) given by Inokuti, M., [1978. Inelastic collisions of fast charged particles with atoms and molecules--the Bethe theory revisited. Rev. Mod. Phys. 50, 23-35]. The IMFP and CSDA-range for the biological compounds C5H5N5 (adenine), C5H5N5O (guanine), C4H5N3O (cytosine), C5H6N2O2 (thymine), C20H27N7O13P2 (cytosine-guanine) and C19H26N8O13P2 (thymine-adenine) have been introduced for incident electrons in the energy range 20 eV-1 MeV. The calculated results are compared with semi-empirical results and other theoretical results, good agreement being found with experimental data and Monte Carlo (PENELOPE code) predictions. All the IMFP versus energy curves exhibit minima around 80 eV.     

Long-term results of above knee femoro-popliteal bypass depend on indication for surgery and graft-material.

OBJECTIVE To determine the long-term results of above-knee femoro-popliteal bypass with autologous saphenous vein (SV) or expanded polytetrafluoroethylene (ePTFE) in routine surgical practice. METHODS: Data from the Swedish vascular registry, Swedvasc, was reviewed retrospectively. Patients with bypass surgery in 1996 and 1997 were assessed 5-7 years later. Data were gathered from the case-records and from clinical follow-up. The composite endpoint of graft failure included death within 30 days, occlusion, major amputation, extension of the graft to below-knee position and removal of an infected graft. Kaplan-Meier curves and Cox' proportional hazard ratios were calculated. RESULTS: Four hundred and ninety-nine patients undergoing bypass for critical limb ischemia (CLI) (56%) or claudication (44%), SV (28%) or ePTFE (72%), were included. There were no significant differences in patient characteristics between patients with SV or ePTFE. CLI and ePTFE were risk factors for graft failure. For patients with both claudication and CLI SV grafts yielded better long-term results than ePTFE grafts ( p <0.03) and ( p <0.003), respectively. Symptom aggravation after graft occlusion was almost exclusively restricted to ePTFE grafts. CONCLUSIONS: Femoro-popliteal bypass above-knee with SV gives good long-term results, especially for claudication. ePTFE grafts cannot be recommended in claudicants, since occlusion occurs often and frequently leads to CLI.     

Coulter Counter measurements of solubility and dissolution rate of sparingly soluble compounds using micellar solutions

A Coulter Counter, Model TAII, was used to determine both solubility and surface specific dissolution rate of two sparingly soluble materials suspended in micellar solutions. The equilibrium solubility increased linearly with surfactant concentration, thereby making it possible by extrapolation to characterize materials with an aqueous solubility down to 1 ppm or less. At high concentrations (greater than 0.1% w/v) the effect of surfactant concentration on the surface specific dissolution rate was less than that predicted from the increased bulk solubility.     

Long-term effects of physical exercise on working capacity and pulmonary function in cystic fibrosis

Seven patients with cystic fibrosis aged 6 to 20 were enrolled for 30 months in a daily exercise program. After 12 months conventional chest physiotherapy was withdrawn. Patients with low initial Shwachman scores improved as regards maximal working capacity. Spirometric data and volume of trapped gas indicated opening of closed airways. We suggest that physical exercise in general should be the basis of pulmonary therapy in cystic fibrosis. Other forms of physiotherapy are advisable when hard physical exercise is not feasible.     

Fracture repair during external fixation: Torsion tests of rabbit osteotomies

Bone repair was studied in the rabbit tibiofibular bone after a midshaft transverse osteotomy stabilized by external fixation and heavy compression. Both subendosteal and subperiosteal callus formation with concomitant contact healing were observed within 3 weeks, and were further succeeded by subendosteal resorption and increased porosis resulting in atrophy of the cortical bone. Subjected to the torsion test, the bones exhibited restoration of strength within 3 weeks, with maximal energy absorption and elasticity at 6 weeks. The failure of the osteotomy in the torsion test, with radiographic visibility of the osteotomy, characterized the soft-tissue type of behavior of the bones. Hard-tissue like behaviour of the bones with resistance to torsion at the osteotomy site and radiographic obliteration of the osteotomy line occurred by 12 weeks, indicating complete union of the osteotomy. Our experiments demonstrate that elastic external fixation is preferable to the rigid compression plate.     

Studies of the human oropharyngeal airspaces using magnetic resonance imaging IV--the oropharyngeal retention effect for four inhalation delivery systems.

Magnetic resonance imaging (MRI) of the oropharyngeal region from 20 adult volunteers using four model inhalation devices (varying mouthpiece diameters, airflow resistances) and tidal breathing was carried out. Statistical analysis (convex hull method) selected 12 scans from 80 data sets representing the extremes of all dimensions in the population. Twelve physical mouth-throat models were made by stereolithography using the exact scan data. The aim was to produce models with varying dimensions to span the adult population, and to investigate if oropharyngeal dimensions affected throat retention for different delivery systems. In an in vitro analysis, the models were used to determine the retention effect of the oropharyngeal airspaces when drug aerosols were administered from four inhalation delivery systems: a pressurised metered dose inhaler (pMDI), two different dry powder inhalers (DPIs A and B), and a nebulizer. The aims of this work were to determine the key parameters governing mouth-throat retention and whether retention was dependent on the delivery system used. Characterizing the throat models by measuring 51 different dimensional variables enabled determination of the most influential variables for dose retention for each inhalation delivery system. Throat model retention was found to be dependent on the delivery system (pMDI approximately DPI(A) > DPI(B) > Neb.). The most influential variable was the total throat model volume. Throat models representing high, median, and low oropharyngeal filtration in healthy adults have been identified.     

Prenatal diagnosis by isoenzymic differentiation of Treacher Collins' syndrome induced by retinoids in rats

A series of branchial arch malformations was induced in 618 embryos from 72 pregnant rats by a single intraperitoneal injection of 10 mg/kg etretinate at 8.5 days of gestation. The litters developed several malformations, including microtia, low set and dorsally placed outer ears, defective middle ear ossicles, short cochleas, defectively differentiated Meckel's cartilages, micrognathia, rudimentary malar bones, lateral facial clefts, fistulas and skin tags, all of which were similar to Treacher Collins' syndrome in man. The defects were accompanied by a pathological differentiation pattern of various isoenzymes in maxillary and mandibular processes. These isoenzymes could be detected in amniotic fluid from the 9th to the 20th days of pregnancy and showed a pathological differentiation pattern here as well. We conclude that a teratogenically induced syndrome affecting the first and second branchial arches is accompanied by a pathological differentiation pattern that can be traced by determinations of isoenzymes in the branchial arches as well as in amniotic fluid.     

Blood cell trauma and postoperative bleeding: comparison of bubble and membrane oxygenators and observations on coronary suction

Blood cell trauma and postoperative bleeding were studied in 96 patients following coronary artery bypass grafting, with bubble oxygenator used in 47 cases and membrane oxygenator in 49. The haemocompatibility of membrane oxygenators was superior to that of the bubble type, as reflected by less haemolysis, better preservation of platelet function, less release of betathromboglobulin and less degranulation of neutrophil granulocytes. Coronary suction contributed to haemolysis, but did not affect platelet or granulocyte function. Fibrinolysis, postoperative blood loss and need for blood transfusion did not differ between the bubble and membrane oxygenator groups.