Effects of K+ channel agonists cromakalim and pinacidil on rat basilar artery smooth muscle cells are mediated by Ca(++)-activated K+ channels

Whole-cell and cell-free inside-out patch-clamp recording techniques were used to examine the actions of potassium channel openers pinacidil and cromakalim in enzymatically isolated smooth muscle cells of rat basilar artery. Delayed rectifier and calcium-dependent potassium currents were identified from the whole-cell recordings. Only the calcium-dependent potassium current was increased by cromakalim and pinacidil. Recordings from inside-out membrane patches revealed a large conductance voltage- and calcium-dependent potassium channel, which was blocked by charybdotoxin but unaffected by ATP less than 10 mM. Cromakalim and pinacidil increased the open probability of this channel. On the basis of these results, we suggest that such drugs, acting on cerebral arterial smooth muscle cell potassium channels, may be of some benefit in the treatment of cerebral vasospasm following subarachnoid hemorrhage.     

Expression of an autoprocessing CAT-HIV-1 proteinase fusion protein: purification to homogeneity of the release 99 residue proteinase

The 99 residue human immunodeficiency virus type 1 proteinase has been expressed in Escherichia coli as part of an autocleaving fusion protein. Expression of the fusion protein is toxic to the host cells, however yields of the released proteinase have been improved by optimising induction nad harvest times to increase culture biomass, and decrease degradation of the proteinase. Soluble proteinase was extracted from these cells by a simple and highly efficient three step process. N-terminal sequence analysis confirms that the enzyme preparation is highly pure and correctly autoprocessed. The proteinase cleaves peptide substrate IGCTLNFPISPIETV between F and P at pH 6.0 with a Km of 310 microM and a Kcat of 14s-1. The enzyme is sensitive to its ionic environment, showing stimulation of activity at high salt concentrations, and shows a pH optimising 5.5.     

Attachment of Pneumocystis carinii to Primary Cultures of Rat Alveolar Epithelial Cells

Pneumocystis carinii (PC) is an exclusively extracellular pathogen which causes pneumonia in immunocompromised individuals. Histologic studies have demonstrated that PC organisms attach preferentially to type I alveolar epithelial cells and rarely bind to type II cells. Previous reports have demonstrated that cultured type II cells develop a type I cell-like phenotype and express type I cell surface antigens. The current study examines the attachment of PC organisms to isolated rat type H alveolar epithelial cells as a function of time in culture. PC attachment to isolated type II cells increased as the type II cells differentiated in culture from 2.3 ± 1.2% on Day 2 to 18.4 ± 2.7% by Day 8. Previous studies have indicated a role for fibronectin (Fn) and Fn receptors as mediators of PC attachment. Addition of anti-Fn antibodies decreased attachment of PC to Day 8 type II cells from 19.4 ± 2.5% to 9.4 ± 1.9% (P < 0.01). Addition of antibodies to the α_v and α₅ integrin subunits resulted in significant decreases in PC attachment to Day 8 type II cells. Examination of expression of α_v and α₅ integrins on Day 2 and Day 8 type II cells demonstrated increased expression of both α_v and α₅ integrin subunits on Day 8 type II cells. Overall these data indicate that attachment of PC to isolated rat type II cells increases as the cells differentiate into a type I cell-like phenotype in vitro and correlates with increased expression of Fn-binding integrins on the cell surface of the cultured type II cells.     

Effects of unilateral isometric strength training on joint angle specificity and cross-training

The purpose of this study was to examine the effects of unilateral isometric leg extension strength training on the strength and integrated electromyogram (IEMG) of both the trained and untrained limbs at multiple joint angles. A training (TRN) group [nine women; mean (SD) age, 20(1) years] exercised for 6 weeks with isometric leg extensions at 80% of maximal isometric torque. A control (CTL) group [eight women; 21(1) years] did not exercise. The training was performed three times per week on a Cybex II isokinetic dynamometer at a joint angle where the lever arm was 0.79 rad below the horizontal plane. The subjects were tested pre- and posttraining for maximal unilateral isometric torque in both limbs at joint angles of zero, 0.26, 0.79,1.31, and 1.57 rad below the horizontal plane. Bipolar surface electrodes were used to record the IEMG of the vastus lateralis (VL) and vastus medialis (VM) during the isometric tests. Three univariate (torque, IEMG-VL, and IEMG-VM) four-way (group x time x limb x angle) mixed factorial ANOVAs were used to analyze the data. The results indicated joint angle specificity for isometric torque in the TRN group only, with significant increases in torque at 0.79 (P = 0.0004) and 1.31 (P = 0.0039) rad. No significant increases in torque were found in the untrained limb of the TRN group or in either limb of the CTL group. Similarly, there were no significant changes in IEMG as a result of the training for the VL or VM. The joint-angle-specific strength increases without concomitant increases in IEMG were hypothesized to result from joint-angle-specific decreases in antagonistic co-contraction and/or preferential hypertropy of the quadriceps femoris at specific levels of the muscle group.     

The antigen-binding capacity of the peptide chains of horse antibodies

The antigen-binding capacity of the peptide chains of horse anti-(diphtheria toxin) has been studied by using (125)I-labelled toxoid and electrophoresis of antibody-antigen mixtures on cellulose acetate. The heavy chains retained about 20% of the activity of the whole antibody and the light chains less than 5%. Recombination of specific heavy and light chains gave about 60% recovery of activity and recombination of specific heavy chains and non-specific light chains about 40% recovery. It is suggested that these results favour the heavy chain as the major site of the antigen-binding activity.     

Analysis of complex allozyme polymorphisms in a barley population

Genotypes of 68,230 individuals taken from 10 generations (F₄–F₆, F₁₄–F₁₇, F₂₄–F₂₆) of an experimental population of barley were determined for four esterase loci. The results show that frequencies of gametic ditypes changed significantly over generations and that striking gametic phase disequilibrium developed within a few generations for each of the six pairwise combinations of loci which were monitored. The complex behavior of these four enzyme loci in the population is attributed to interactions between selection and restriction of recombination resulting from the effects of linkage and/or inbreeding.