A photometric assay for blood coagulation factor XIII

An assay for a direct photometric determination of F XIII in untreated and undiluted plasma was developed. In a one-step procedure F XIII is activated by thrombin and Ca2+ and cross-links glycine-ethylester to a specific glutamine containing peptide substrate. The released ammonia is incorporated into alpha-ketoglutarate by glutamate dehydrogenase, and the NADH consumption of this reaction is measured photometrically at 340 nm. NADH-consumption is directly proportional to the F XIII activity. Fibrin polymerization and the corresponding turbidity is avoided by the use of a fibrin aggregation inhibitor. The procedure is rapid and simple and enables to measure within the range of 0 to 150% F XIII. It can be performed with automated analyzers as well as with common photometric equipment. The normal range of F XIII activity in 167 healthy donors was determined to be 70 to 140%.     

Regular low-intensity aquatic exercise improves cardio-respiratory functional capacity and reduces proteinuria in chronic renal failure patients.

Sir, Results from several studies indicate that patients with chronicrenal failure (CRF) can benefit from regular exercise trainingby improving their cardio-respiratory capacity and quality oflife [1,2]. However, there have been no studies examining theeffect of exercise on renal function in patients with moderaterenal failure. Although experiments have shown that swimmingsignificantly lowers proteinuria and reduces glomerulosclerosisin rats [3–5], human non-swimming exercise studies werenot able to confirm these findings [6].     

Oxidative inactivation of purified human alpha-2-antiplasmin, antithrombin III, and C1-inhibitor

Oxidative inactivation of alpha-1-proteinase inhibitor (A1-PI) and plasminogen activator inhibitor-1 (PAI-1), both members of the serine protease inhibitor (serpin) superfamily, using mild oxidation conditions has been already demonstrated. The oxidation mechanism has been shown to involve conversion of methionine to methionine sulfoxide in the reactive center of the inhibitors.In this study evidence is presented that alpha-2-antiplasmin (A2-PI) and antithrombin III (AT III) can also be inactivated by means of oxidation. For total inactivation of 50 pM Al-PI about 10 nM chloramine T (CT) and for the same molar concentration of A2-PI and AT III about 250 nM CT were found necessary. C1-inhibitor (C1-INH) showed some resistance to oxidation that could be overcome only by increasing CT to an amount (> 2000 nM) already beginning to inactivate the corresponding C1-esterase. As target enzymes for A2-PI, AT III, and A1-PI plasmin, thrombin and elastase, respectively, were used. Their activity was not impaired by the oxidation conditions applied.As there is no methionine in the reactive center of AT III an additional mechanism for oxidative inactivation of serpins has to be taken into consideration. Oxidation seems to be a general mechanism for altering the balances between serine proteases and their inhibitors in favour of the protease.     

Rate of tension development in isometric contractions of a human hand muscle

The amplitude and rate of tension development during both electrical stimulation and voluntary activation of a human hand muscle were compared. The contractile responses from the first dorsal interosseous muscle of 14 normal human subjects were studied to provide the experimental data. At different forces less than 400g, under conditions of both electrical stimulation and voluntary contraction, force was directly proportional to speed of contraction. This linear relationship between the speed and force of contraction, as the proportion of active motor units varied, implies that these two parameters are similarly related in motor units of various sizes. In fast voluntary contractions, the rate of rise of tension at any given force level was greater than that observed in response to repetitive stimuli delivered to the motor nerve. Even at 200 and 500 impulses per second at maximal intensity, the speed of tension development was less than that found in fast voluntary contractions. The importance of asynchronous impulses and optimum discharge sequencing in generating a faster speed of tension development in fast voluntary contractions is underscored by these findings.     

Components of postural dyscontrol in the elderly: A review

The concept of a generalized aging effect on a generalized balance mechanism is discussed, and an alternative, multicomponent approach to understanding the heterogeneity of postural dyscontrol in the elderly is presented. Neural sensorimotor components of normal postural control mechanisms are identified and discussed. The effects of Parkinson's disease, hemiplegia, cerebellar degeneration, peripheral vestibular loss, and other disorders on the components of postural control are summarized. Quantitative posturography is advocated to detect preclinical manifestation of multiple musculoskeletal and neuromuscular pathologies and reduced compensatory abilities in posturally unstable elderly adults.     

Microtensile bond strength of a resin cement to feldpathic ceramic after different etching and silanization regimens in dry and aged conditions.

OBJECTIVES: This study evaluated the durability of bond strength between resin cement and a feldspathic ceramic submitted to different etching regimens with and without silane coupling agent application. METHODS: Thirty-two blocks (6.4 mm x 6.4 mm x 4.8 mm) were fabricated using a microparticulate feldspathic ceramic (Vita VM7), ultrasonically cleaned with water for 5 min and randomly divided into four groups, according to the type of etching agent and silanization method: method 1, etching with 10% hydrofluoric (HF) acid gel for 1 min + silanization; method 2, HF only; method 3, etching with 1.23% acidulated phosphate fluoride (APF) for 5 min + silanization; method 4, APF only. Conditioned blocks were positioned in their individual silicone molds and resin cement (Panavia F) was applied on the treated surfaces. Specimens were stored in distilled water (37 degrees C) for 24h prior to sectioning. After sectioning the ceramic-cement blocks in x- and y-axis with a bonded area of approximately 0.6mm(2), the microsticks of each block were randomly divided into two storage conditions: Dry, immediate testing; TC, thermal cycling (12,000 times)+water storage for 150 d, yielding to eight experimental groups. Microtensile bond strength tests were performed in universal testing machine (cross-head speed: 1mm/min) and failure types were noted. Data obtained (MPa) were analyzed with three-way ANOVA and Tukey's test (alpha=0.05). RESULTS: Significant influence of the use of silane (p<0.0001), storage conditions (p=0.0013) and surface treatment were observed (p=0.0014). The highest bond strengths were achieved in both dry and thermocycled conditions when the ceramics were etched with HF acid gel and silanized (17.4 +/- 5.8 and 17.4 +/- 4.8 MPa, respectively). Silanization after HF acid gel and APF treatment increased the results dramatically (14.5+/-4.2-17.4+/-4.8 MPa) compared to non-silanized groups (2.6 +/- 0.8-8.9 +/- 3.1 MPa) where the failure type was exclusively (100%) adhesive between the cement and the ceramic. SIGNIFICANCE: Silanization of the feldspathic ceramic surface after APF or HF acid etching increased the microtensile bond strength results significantly, with the latter providing higher results. Long-term thermocycling and water storage did not decrease the results in silanized groups.