Mikrostrukturelle Veränderungen von Magnesium‐Druckgusslegierungen nach langzeitiger thermischer Beanspruchung

Microstructural Changes of Pressure Die Cast Magnesium Alloys after Long‐Term Thermic Loading The expansion of the application of pressure die cast magnesium alloys for automobiles requires the development of new alloys and the comprehensive assessment of available alloys on aggravated conditions, too. Such conditions are also given at higher temperatures, which can cause the creep of the material and lead to the component failure. Because the microstructural stability decisively depends on the thermic loading, this paper deals with the change of the microstructure and the hardness of the alloys AZ91, AM50 and AE42 after a long‐term annealing at 150 °C and 200 °C in comparison to the pressure die as‐cast condition. The results reveal clear differences of the microstructural stability of the alloys AZ91 and AM50 on the one hand and the alloy AE42 on the other hand. Due to the long‐term annealing at 150 °C the alloys AZ91 and AM50 show chiefly an intense precipitation of Mg₁₇Al₁₂ from the Al‐rich eutectic α‐phase. Furthermore at 200 °C, it is observed the coagulation and coarsening of these precipitates, too. The last appearances are connected with a weakening of the material. Regarding the alloy AE42, the changes of the precipitation state are not so intensely and do yet not lead to a microstructural weakening.     

Endonasal frontal sinus surgery with permanent implantation of a place holder

BACKGROUND: Endonasal frontal sinus surgery is well established. It is not yet clear what degree of enlargement of the frontal sinus neoostium is required to achieve permanent drainage or whether stenting improves the results. PATIENTS AND METHODS: Prospective survey with two groups: Group 1. included 10 patients (15 operations) who underwent endonasal sinus surgery because of chronic polypoid sinusitis with stenting of the frontal sinus neoostium for 6 months. Group 2. included 11 patients (21 operations) without stenting. INTERVENTION: Endonasal frontal sinus surgery with extended drainage Draf Type II (NFA II according to May) with (group 1) and without (group 2) long-term stenting of the neoostium for 5 months using a silicone stent. MAIN OUTCOME MEASURE: 12-16 months postoperatively: flexible endoscopy of nose and frontal sinus; computed tomography; magnetic resonance tomography; Wilcoxon-Mann Withney-Test. RESULTS: With stenting: neoostium endoscopically patent in 80% (including 20% with edematous swelling only at the opening to the frontal sinus), occluded by scar tissue in 6.7%, occluded by polyps in 13.3%. Endoscopy and CT/MRT together: normal mucosa and aeration in 93.3%, complete opacification in 6.7%. Without stenting: neoostium endoscopically patent in 33%, occluded by scar tissue in 48%, occluded by polyps in 19%. Endoscopy and CT together: normal mucosa and aeration in 71.4%, aeration and mucosal swelling in 14.3%, complete opacification in 14.3%. With stenting of the frontal sinus neoostium for six months endoscopic evaluation of the frontal sinus was possible in a significantly higher proportion of cases (p = 0.0416). CONCLUSION: Long-term stenting of the frontal sinus significantly reduces the rate of recurrent stenosis of the frontal neoostium and is recommended in all cases where an extended frontal sinus drainage is necessary. The optimal design for such a stent has not yet been clearly defined.     

alpha-Conotoxin ImI exhibits subtype-specific nicotinic acetylcholine receptor blockade: preferential inhibition of homomeric alpha 7 and alpha 9 receptors

Through a study of cloned nicotinic receptors expressed in Xenopus oocytes, we provide evidence that alpha-conotoxin ImI, a peptide marine snail toxin that induces seizures in rodents, selectively blocks subtypes of nicotinic acetylcholine receptors. alpha-Conotoxin ImI blocks homomeric alpha 7 nicotinic receptors with the highest apparent affinity and homomeric alpha 9 receptors with 8-fold lower affinity. This toxin has no effect on receptors composed of alpha 2 beta 2, alpha 3 beta 2, alpha 4 beta 2, alpha 2 beta 4, alpha 3 beta 4, or alpha 4 beta 4 subunit combinations. In contrast to alpha-bungarotoxin, which has high affinity for alpha 7, alpha 9, and alpha 1 beta 1 gamma delta receptors, alpha-conotoxin ImI has low affinity for the muscle nAChR. Related Conus peptides, alpha-conotoxins MI and GI, exhibit a distinct specificity, strictly targeting the muscle subtype receptor but not alpha 7 or alpha 9 receptors. alpha-Conotoxins thus represent selective tools for the study of neuronal nicotinic acetylcholine receptors.     

Interaction of rabbit C-reactive protein with phospholipid monolayers studied by microfluorescence film balance with an externally applied electric field

C-reactive protein (CRP) is one of the most characteristic acute-phase proteins in humans and many other animals. It binds to phosphorylcholine in a calcium-dependent manner. In addition, CRP activates the complement systems via the classical pathway. The interaction between rabbit CRP (rCRP) and model biological membrane is studied using dimyristoylphosphatidylethanolamine and dipalmitoylphosphatidylcholine monolayers. Observations with fluorescence microscopy indicate that rCRP is more likely to be incorporated in the liquid phase of monolayers. Such incorporation does not depend on the presence of calcium and is not inhibited by phosphocholine. The area occupied by the protein when incorporated into the monolayer was estimated. The dipole moment density of the protein crossing the air/water interface was measured by applying an external electric field. Our results indicate that calcium binding leads to a conformational change in CPR, which might modify the orientation of CRP in the monolayer. In addition, a negative charge or negative difference in dipole moment density facilitates the incorporation of CPR into the monolayer.     

Pharmacologic atrial natriuretic peptide reduces human leg capillary filtration

Atrial natriuretic peptide (ANP) is produced and secreted by atrial cells. We measured calf capillary filtration rate with prolonged venous-occlusion plethysmography of supine healthy male subjects during pharmacologic infusion of ANP (48 pmol/kg/min for 15 min; n = 6) and during placebo infusion (n = 7). Results during infusions were compared to prior control measurements. ANP infusion increased plasma [ANP] from 30 +/- 4 to 2,568 +/- 595 pmol/l. Systemic hemoconcentration occurred during ANP infusion: mean hematocrit and plasma colloid osmotic pressure increased 4.6 and 11.3%, respectively, relative to preinfusion baseline values (p < 0.05). Mean calf filtration, however, was significantly reduced from 0.15 to 0.08 ml/100 ml/min with ANP. Heart rate increased 20% with ANP infusion, whereas blood pressure was unchanged. Calf conductance (blood flow/arterial pressure) and venous compliance were unaffected by ANP infusion. Placebo infusion had no effect relative to prior baseline control measurements. Although ANP induced systemic capillary filtration, in the calf, filtration was reduced with ANP. Therefore, pharmacologic ANP infusion enhances capillary filtration from the systemic circulation, perhaps at upper body or splanchnic sites or both, while having the opposite effect in the leg.     

Bleomycin-induced DNA damage and repair in wild-type and thymidine kinase-deficient Friend mouse erythroleukaemia cells

In this paper the DNA damage and repair induced by the radiomimetic agent bleomycin are compared in murine Friend erythroleukaemia wild-type 707 cells and a thymidine kinase-deficient sub-clone BUF. Comparisons are made using results obtained from the alkaline comet assay and unscheduled DNA synthesis experiments. Further analysis to determine the fidelity of bleomycin-induced repair as indicated by mutagenesis to hypoxanthine-phosphoribosyltransferase deficiency was also conducted. Similar sensitivities to bleomycin treatments were observed in the two cell types with the comet assay, while similar levels of dose-dependent excision repair following bleomycin treatments were also detected in unscheduled DNA synthesis experiments. Comet assay and unscheduled DNA synthesis experimental results are in agreement. Survival and induced hypoxanthine-phosphoribosyltransferase mutant frequencies were observed to be unaffected by a thymidine kinase-deficiency in Friend erythroleukaemia cells. The results of this investigation suggest no overall difference in the repair capacities or the repair fidelity of Friend 707 relative to BUF cells following bleomycin treatments.     

Cladribine (2-CDA) given as subcutaneous bolus injections is active in pretreated Waldenstr?m's macroglobulinaemia. Swiss Group for Clinical Cancer Research (SAKK)

Clinical trials with intravenous cladribine infusions in pretreated patients with Waldenstr?m's macroglobulinaemia have shown a response rate of 40%. Our pharmacokinetic studies revealed that the bioavailability of subcutaneous cladribine is complete but that the concentration-time profile is very different from intravenous administration. We designed this phase II multi-institutional trial to study the activity and toxicity of cladribine given as s.c. bolus injections in patients with symptomatic Waldenstr?m's macroglobulinaemia. Between May 1993 and October 1995, 25 patients were accrued: male/female 18/7, median age 65 years (range 44-85). All except one patient had been pretreated with more than one regimen (median 2, range 0-10). 18 patients had progressed under previous therapy and six were in relapse. All patients received cladribine for a total dose of 0.5 mg/kg per cycle as s.c. bolus injections divided over 5 d at > or = 4 week intervals, for a maximum of six cycles. All 25 patients were evaluable for toxicity and response. A total of 67 cycles were administered (median 3 cycles, range 1-6). Overall response rate including disease stabilization which had been progressive under previous therapy was 68%. 10 patients (40%, 95% CI 21-61%) achieved a partial remission. Seven responders had been progressive under previous therapy. Maximum responses were reached no later than the third cycle. Median time to treatment failure and remission duration were 4.4 (range 0.5-33) and 8 months (5-29), respectively. Four patients (16%) suffered from infections W.H.O. grade > or = 2 (pneumonia grade 2, Staphylococcus septicaemia grade 3, viral encephalitis and pneumonia, both grade 4 with complete resolution). No other severe adverse events were observed. Cladribine given as s.c. 5 d bolus injections was found to be active in pretreated Waldenstr?m's macroglobulinaemia and resulted in durable remissions.     

When people with pre-existing disabilities age in place: implications for social work practice

Dental implants are subject to large and highly complex loads of varying magnitude, duration and vector. Bridge performance is closely related to load transmission both at the bone to implant interface and between components within the implant-abutment-bridge cylinder complex. The design of the interface between components within this complex may have a profound influence on the long term function of the implant supported prosthesis. An in vitro evaluation of implants 3.5 mm in diameter, utilizing an internal conical interface has demonstrated increased resistance to bending moments at the fixture-abutment interface (P = 0.00010) and at the abutment-bridge cylinder interface (P < 0.01), when compared to a standard 3.75 mm implant with a hex mediated, butt joint interface. The relatively small values for coefficient of variance measured in both systems would confirm that whilst the size of data is small, it is nonetheless a reliable indication of the relative strength of these implant designs.