The functional anatomy of the lower limb of the howler monkey (Alouatta caraya)

The howler monkey possesses unique anatomical adaptations associated with its arboreal habit. The behavioral elements are described by locomotor pattern, substrate, timing and rhythm of movement. The most significant motor adaptations are correlated clearly and directly with musculoskeletal features of the lower limb. The orientation of the joints within the limb, the shape of the joint surfaces, their bony environments, and the important planes of muscular control are the foundations for the observable locomotor behaviors.     

Kinetics and mechanism of acetohydroxy acid synthase isozyme III from Escherichia coli

Acetohydroxy acid synthase (AHAS, EC 4.1.3.18) isozyme III from Escherichia coli has been studied in steady-state kinetic experiments in which the rates of formation of acetolactate (AL) and acetohydroxybutyrate (AHB) have been determined simultaneously. The ratio between the rates of production of the two alternative products and the concentrations of the substrates pyruvate and 2-ketobutyrate (2KB) leading to them, R, VAHB/VAL = R[( 2KB]/[pyruvate]), was found to be 40 +/- 3 under a wide variety of conditions. Because pyruvate is a common substrate in the reactions leading to both products and competes with 2-ketobutyrate to determine whether AL or AHB is formed, steady-state kinetic studies are unusually informative for this enzyme. At a given pyruvate concentration, the sum of the rates of formation of AL and AHB was nearly independent of the 2-ketobutyrate concentration. On the basis of these results, a mechanism is proposed for the enzyme that involves irreversible and rate-determining reaction of pyruvate, at a site which accepts 2-ketobutyrate poorly, if at all, to form an intermediate common to all the reactions. In the second phase of the reaction, various 2-keto acids can compete for this intermediate to form the respective acetohydroxy acids. 2-Keto acids other than the natural substrates pyruvate and 2-ketobutyrate may also compete, to a greater or lesser extent, in the second phase of the reaction to yield alternative products, e.g., 2-ketovalerate is preferred by about 2.5-fold over pyruvate. However, the presence of an additional keto acid does not affect the relative specificity of the enzyme for pyruvate and 2-ketobutyrate; this further supports the proposed mechanism. The substrate specificity in the second phase is an intrinsic property of the enzyme, unaffected by pH or feedback inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Altered patterns of protein phosphorylation in articular chondrocytes treated with interleukin-1 or synovial cytokines

Cultures of lapine articular chondrocytes were exposed to purified, human, recombinant interleukin-1 alpha or partially purified preparations of lapine, synovial, cytokines in the presence of [32P]orthophosphate. After 30 min incubation, phosphoproteins were extracted from the cells, separated by two-dimensional gel electrophoresis and visualized autoradiographically. Analysis of the autoradiograms revealed that interleukin-1 and the synovial factors produced marked changes in the pattern of protein phosphorylation. The synovial cytokines induced many of the same changes as interleukin-1, as well as a number of unique changes. This finding is consistent with the notion that, in addition to interleukin-1, synoviocytes secrete other cytokines which modulate the metabolism of chondrocytes. These data support the idea that signal transduction in chondrocytes responding to interleukin-1 involves the activation of one or more protein kinases.     

Relations between anxiolytic effects of diazepam and changes in the EEG spectral power

The influence of diazepam (1; 5; 10 mg/kg, i. p.), chlorpromazine (1 mg/kg) and amphetamine (1; 5 mg/kg) on the Fourier's spectral EEG power of sensomotor cortex and dorsal hippocampus and conflict behavior freely moving albino and cotton (Sigmondon hispidus) rats was studied. Effects of diazepam (5 mg/kg) in cotton rats were similar, but influence on the theta-activity was more expressed. Correlation between slowing of theta-activity and extent of anxiolytic effect in conflict situation was showed. On the basis of the results obtained the authors discuss possible mutual relations between the influence of diazepam on EEG and anxiolytic effect of benzodiazepines.     

Penetration and proliferation of BHK and HeLa cells into a three-dimensional collagen matrix of bone stroma type. Preliminary results

Some preliminary data regarding the test of penetration and proliferation of BHK and HeLa cells biocompatibility to a three dimensional stroma saturated with phosphorous and calcium salts (a biomaterial replacing bone) are presented. These data suggest that the analysed biomaterial might be used in surgical practices of prosthesis appliance on interfaces of fractured bone.