Primary fibrinolysis during supraceliac aortic clamping

PURPOSE: An increased incidence of bleeding complications has been observed after supraceliac aortic clamping (SCC). This study was performed to identify possible hemostatic abnormalities that contribute to this problem. METHODS: A prospective cohort study over a 3-month period was performed by comparing hemostatic parameters in 10 consecutive patients who required elective SCC with those of eight concurrent randomly selected control subjects who required infrarenal clamping (IRC) for abdominal aortic reconstruction. Measures of coagulation, fibrinolysis, platelet function, temperature, hemodilution, and hepatic function were performed at selected times before, during, and after operation. RESULTS: Aneurysm size, fibrinogen, D-dimers, prothrombin, partial thromboplastin time, platelet counts, bleeding times, hemodilution, and temperature were comparable in both groups. Patients in the SCC group, however, consistently developed a primary fibrinolytic state within 20 minutes after supraceliac clamping, reflected by significantly decreased euglobulin clot lysis times (ECLT; p < 0.0001), elevated tissue plasminogen activator (t-PA) levels (p < 0.0006), elevated t-PA-to-plasminogen activator inhibitor-1 ratios (p < 0.0001), and reduced alpha 2-antiplasmin levels (p < 0.002). SCC produced hepatocellular injury documented by elevations in both aspartate transaminase (p < 0.0001) and lactate dehydrogenase (p < 0.009). CONCLUSIONS: SCC rapidly induces a primary fibrinolytic state manifested by increased circulating t-PA, reduced alpha 2-antiplasmin, and increased fibrinolytic activator-to-inhibitor ratios. These effects may be a result of hepatic hypoperfusion caused by SCC leading to insufficient clearance of t-PA. Antifibrinolytic agents may be of benefit if bleeding develops after aortic procedures that require supraceliac clamping.     

Variability of hydroxyapatite-coated dental implants

Uniformity, surface roughness, and chemical phase structure are all important features of implant coatings. While the first two variables are important for implant placement, the phase structure affects implant fixation. This study examined the coating morphology and the amount, size, and distribution of crystalline regions of press-fit and screw-type dental implants. Implants obtained from five commercial vendors were sectioned sagittally, mounted, and polished to reveal the coating microstructure. The crystalline phase content varied depending on the implant supplier; however, general trends were observed. Amorphous regions were predominantly found at the metal interface and decreased toward the outside of the coating, producing a crystallinity graded coating. The distal end of the implant, where heat build-up was more likely during the coating procedure, displayed a higher crystalline content and larger crystalline regions. Similarly, the thread apex consisted of more of a crystalline phase. The results of this study of coating microstructure may be used to improve the quality and performance of implants and may help to explain different in vivo responses to the many available varieties of hydroxyapatite-coated dental implants.     

Overexpression and characterization of a prolyl endopeptidase from the hyperthermophilic archaeon Pyrococcus furiosus

The maltose-regulated mlr-2 gene from the hyperthermophilic archaeon Pyrococcus furiosus having homology to bacterial and eukaryal prolyl endopeptidase (PEPase) was cloned and overexpressed in Escherichia coli. Extracts from recombinant cells were capable of hydrolyzing the PEPase substrate benzyloxycarbonyl-Gly-Pro-p-nitroanilide (ZGPpNA) with a temperature optimum between 85 and 90 degrees C. Denaturing gel electrophoresis of purified PEPase showed that enzyme activity was associated with a 70-kDa protein, which is consistent with that predicted from the mlr-2 sequence. However, an apparent molecular mass of 59 kDa was obtained from gel permeation studies. In addition to ZGPpNA (K(Mapp) of 53 microM), PEPase was capable of hydrolyzing azocasein, although at a low rate. No activity was detected when ZGPpNA was replaced by substrates for carboxypeptidase A and B, chymotrypsin, subtilisin, and neutral endopeptidase. N-[N-(L-3-trans-Carboxirane-2-carbonyl)-L-Leu]-agmatine (E-64) and tosyl-L-Lys chloromethyl ketone did not inhibit PEPase activity. Both phenylmethylsulfonyl fluoride and diprotin A inhibited ZGPpNA cleavage, the latter doing so competitively (K(lapp) of 343 microM). At 100 degrees C, the enzyme displayed some tolerance to sodium dodecyl sulfate treatment. Stability of PEPase over time was dependent on protein concentration; at temperatures above 65 degrees C, dilute samples retained most of their activity after 24 h while the activity of concentrated preparations diminished significantly. This decrease was found to be due, in part, to autoproteolysis. Partially purified PEPase from P. furiosus exhibited the same temperature optimum, molecular weight, and kinetic characteristics as the enzyme overexpressed in E. coli. Extracts from P. furiosus cultures grown in the presence of maltose were approximately sevenfold greater in PEPase activity than those grown without maltose. Activity could not be detected in clarified medium obtained from maltose-grown cultures. We conclude that mlr-2, now called prpA, encodes PEPase; the physiological role of this protease is presently unknown.     

Effect of erythromycin and itraconazole on the pharmacokinetics of intravenous lignocaine

The effect of mechanical toothbrush stimulation on gingival microcirculatory functions was examined with and without removal of supragingival plaque in inflamed gingiva of 6 dogs. After removal of the ligatures, 4 treatment modalities: mechanical stimulation by vibration (MS), removal of supragingival plaque (PR), combination (MS+PR) and no treatment (NT), were administered to each quadrant for 2 weeks. Both quadrants with plaque removal showed a marked decrease in the gingival index score, while slight and moderate decreases were observed in NT and MS quadrants, respectively. Changes in gingival crevicular fluid flow, pocket oxygen tension and hemoglobin oxygen saturation in the gingiva were significant in the MS, PR and MS+PR quadrants. Significant treatment-by-time effects were found for all of the parameters of microcirculatory function between NT and MS quadrants, and gingival crevicular fluid flow between PR and MS+PR quadrants, respectively. These findings suggest that mechanical stimulation with a toothbrush may offer an additional benefit to gingival microcirculatory functions in inflamed gingiva.     

Structural motif and characteristics of the extracellular domain of P2X receptors

OBJECTIVES: We attempted to evaluate nonsurgical methods of treating postcatheterization pseudoaneurysm. BACKGROUND: The value of reapplication of a compression bandage, ultrasound-guided compression repair (UGCR) and awaiting spontaneous thrombosis in the treatment of postcatheterization pseudoaneurysms is unsettled. METHODS: We followed a stepwise treatment strategy of primarily conservative management using 1) reapplication of a compression bandage, followed by 2) UGCR, if needed, and 3) observation of the natural course. Surgical repair was reserved for patients with a rapidly expanding or complicated lesion. RESULTS: Reapplication of a compression bandage was performed in 128 patients and was successful in 32%. The success rate correlated inversely with anticoagulant therapy and the size of the aneurysm. In case of failure this pretreatment with a compression bandage significantly enhanced the success rate of subsequent UGCR (p = 0.04). UGCR was performed in 124 cases with a success rate of 84%. In 54 patients with a stable lesion, refraining from any (further) active measures resulted in spontaneous thrombosis of the aneurysm in 50 patients (93%) after 1 to 180 days (median 40 days). The course of the remaining four femoral artery aneurysms was uneventful. Definitive repair by operation or collagen plug implantation was required in only 20 patients (9%). CONCLUSIONS: The first measure performed in the treatment of pseudoaneurysms should be reapplication of a compression bandage, followed, if necessary, by UGCR. After failure of UGCR, spontaneous healing occurs in the majority of patients. Operation can be reserved for progressive and complicated lesions.     

1/f voltage noise in silicon planar bipolar transistors

Measurements on silicon planar transistors in the frequency range 1 Hz?1 kHz have shown conclusively that 1/f noise is present on the equivalent input noise-voltage generator. In some samples of transistors, correlation between the 1/f components of voltage and current noise was detected. In one sample, an estimate of the correlation coefficient was made, the result being a coefficient of approximately ?0.1.     

Performance degradation of Jaumann absorbers due to curvature

The normal-incidence flat-plate performance of radar absorbers can seldom be realized when the absorbers are used on cylindrical structures. This is also true of Jaumann absorbers, which consist of alternating layers of resistive sheets and light-weight spacers. A method based on Richmond's stepping theory [4] is used to predict the performance more accurately for cylindrical structures.