Synthesis, binding affinity, and cross-linking of monodentate photoactive phenothiazines to calmodulin

Various photoactive phenothiazines were synthesized that possessed a 2-azido, 3-azido, 2-benzoyl, or 1,3,4-trifluoro-2-azido functionality in combination with various modifications of the N-alkyl side chain. These phenothiazines were evaluated for their ability to inhibit the calmodulin-mediated activation of phosphodiesterase (PDE). All were active in inhibiting the action of calmodulin (CaM), but those possessing either a 3-azido and a 4-(4-methyl-1-piperazinyl)butyl side chain or a 2-benzoyl group and 3-(dimethylamino)propyl side chain proved to be most active (I50 = 14 +/- 3 microM and 7 +/- 1 microM, respectively) when compared to the known inhibitor, chlorpromazine (CPZ, I50 = 30 microM). Calmodulin was photolabeled with ca. 35% efficiency in a light- and calcium-dependent fashion using a radiolabeled analog, 3-azido-10-(4-(4-[14C]methyl-1-piperazinyl)butyl)phenothiazine, of one of these compounds. Competition studies using this radiolabeled analog and CPZ were consistent with binding to one or both of the hydrophobic binding pockets of CaM.     

Differential effects of X-irradiation and cyclosporin-A administration on the thymus with respect to the generation of cyclosporin-A-induced autoimmunity

A new insertion sequence in Streptococcus pneumoniae was identified as a 1435-bp segment of the genome containing 24-bp terminal inverted repeats and flanked by 8-bp direct repeats. A copy of the element, named IS1167, adjacent to the comAB genes was sequenced; seven additional copies were found in the genome of strain CP1200 and relatives descended from strain R36A. Among 22 independent pneumococcal isolates, 11 contained copies of elements hybridizing to IS1167 in nine distinct restriction fragment patterns, with 3-12 copies each. The bulk of the element was occupied by two overlapping open reading frames, encoding basic proteins which together exhibited strong similarity to the full length of the putative transposase of the staphylococcal transposable element, IS1181, as well as significant similarity to those of seven additional known or putative insertion sequences related to the mycobacterial element, IS1096.     

Effect of a nitric oxide synthase inhibitor and a glucocorticosteroid on exhaled nitric oxide

Nitric oxide (NO) is produced by a variety of cells within the respiratory tract, including inflammatory epithelial cells. NO has been detected in the exhaled air of normal human subjects, and its concentration is raised in asthmatic patients. To study whether exhaled NO arises from the respiratory tract, we administered a NO synthase (NOS) inhibitor, NG-monomethyl-L-arginine (L-NMMA), by inhalation (490 mg) in a double-blind randomized manner in nine normal and six asthmatic subjects. Because exhaled NO may arise from an inducible isoform of NO synthase that may be inhibited by glucocorticosteroids, we also studied the effects of oral prednisolone (30 mg orally for 3 d) in seven normal and six asthmatic subjects in a separate double-blind crossover study with matched placebo. After nebulized L-NMMA, there was a significant fall in peak exhaled NO compared with saline control values, with a mean fall of 43.6 +/- 5.6% in normal subjects (p < 0.01) and of 39.7 +/- 6.5% (p < 0.01) in asthmatic subjects, which persisted for 4 h. There were no effects of L-NMMA inhalation on heart rate, blood pressure, or FEV1 in either normal or asthmatic patients. Administration of oral prednisolone (30 mg) resulted in a fall in exhaled NO concentrations in asthmatic subjects by 21.6 +/- 5.0% at 48 h (p < 0.01) but no significant change in normal subjects. These data suggest that NOS inhibitors may be safely given in normal and asthmatic patients and that the increased exhaled NO seen in asthmatic patients is likely to be caused by induction of inducible NOS.     

Hepatoprotection in ethinylestradiol-treated rats is provided by tauroursodeoxycholic acid, but not by ursodeoxycholic acid

Ursodeoxycholic acid (UDCA) and tauroursodeoxycholic acid (TUDCA) have been suggested as potential treatments for drug-induced cholestasis. It was therefore decided to study the effects of administration of UDCA or TUDCA on individual serum bile acid concentration, conventional liver tests and associated hepatic ultrastructural changes in ethinylestradiol-treated (EE) rats mg/kg per day). Control rats were treated s.c. with propylene glycol. EE-treated rats were randomly assigned to receive daily i.p. injections of placebo, TUDCA or UDCA. Four rats in each group were treated for 4 consecutive days, and a second four for 14 days. After 4 days of treatment, the serum levels of cholic acid and taurocholic acid were significantly increased in EE-treated rats. None of the conventional liver tests were significantly different among the four groups. After 14 days of treatment the serum levels of cholic acid, chenodeoxycholic acid, glycocholic acid, glycochenodeoxycholic acid, taurocholic acid, taurochenodeoxycholic acid, bilirubin, alkaline phosphatase and gamma glutamyltransferase were significantly raised in EE and EE plus UDCA treated rats. EE plus TUDCA treated rats, however, had no significant changes in these individual serum bile acids or conventional liver tests. The ultrastructure of livers from EE plus TUDCA treated rats was similar to those of controls. On the other hand, EE and EE plus UDCA rats both showed a significant reduction in sinusoidal microvilli. These results show that treatment of rats for 4 days with EE induces significant rises in the serum concentrations of two individual bile acids and that TUDCA protects against this.(ABSTRACT TRUNCATED AT 250 WORDS)     

Toxicology of chemical mixtures: challenges for today and the future

A major challenge for the toxicologist involved in safety evaluation of chemical mixtures is to test the hypothesis that as a rule exposure to mixtures of chemicals at (low) non-toxic doses of the individual chemicals is of no health concern. A series of repeated dose studies in rats with defined mixtures of chemicals with the same or different target organs revealed that exposure to a combination of chemicals compared with exposure to the individual compounds did not constitute an evidently increased hazard, provided each chemical was administered at a level similar to, or slightly lower than, its own 'No-Observed-Adverse-Effect-Level'. The results of subacute oral toxicity studies in rats with defined mixtures of nephrotoxicants with similar mode of action underlined the applicability of the additivity assumption for a mixture of chemicals with simple similar action. Safety evaluation of complex chemical mixtures is a challenge that can be tackled as follows: first, identify the (e.g. ten) most risky chemicals in the mixture, and, second, assess the hazard and the potential health risk of the mixture of the most risky chemicals, using procedures developed for defined mixtures. To identify interactions between individual compounds, a most promising testing strategy appeared to be a statistical approach using a fractional two-level factorial design. A challenge for today and the future is to gradually substitute mixture-oriented (real life-oriented) standard setting for (unrealistic) single chemical-oriented standard setting.     

Effects of response and trial repetition on sight-word training for students with learning disabilities

Alternating treatments designs were used to compare the effects of trial repetition (one response within five trials per word) versus response repetition (five response repetitions within one trial per word) on sight-word acquisition for 3 elementary students diagnosed with specific learning disabilities in reading. Although both interventions occasioned the same number of accurate responses per word during training, the trial-repetition condition, which involved complete antecedent-response-feedback sequences, resulted in more words mastered for all 3 students.     

Pain associated with spinal cord injury

Management of pain after spinal cord injury remains a difficult clinical problem. In particular, neuropathic spinal cord injury pain, like other forms of deafferentation pain in which there is loss or modification of normal afferent sensory inputs, is notoriously resistant to currently available modes of treatment. Although there have been some advances in our understanding of spinal cord injury pain, the mechanisms of neuropathic spinal cord injury pain remain largely unknown and treatment is often ineffective. This review presents findings from recent publications that deal with the mechanisms and management of spinal cord injury pain.     

Some aspects of activation and inhibition of rat brain lipoxygenase

1. Regulatory properties of lipoxygenase activity in rat brain cytosol were studied using linoleic acid (LA) as a substrate. 2. A change in the absorbance at 234 nm was biphasic when a mixture of LA and pre-formed hydroperoxide (LA-OOH) was incubated with freshly isolated native brain cytosol. Initially, a rapid depletion of LA-OOH was observed with a concomitant formation of LA-oxo compounds. This phase was followed by LA dioxygenation. 3. Both hydroperoxidase and dioxygenase activities of lipoxygenase were inhibited by micromolar concentrations of classic lipoxygenase inhibitors (phenidone, 5,8,11-eicosatriynoic acid and nordihydroguaiaretic acid). 4. The dioxygenase activity in dialysed cytsool was stimulated by nanomolar concentrations of H2O2 and micromolar concentrations of LA-OOH and it was inhibited by serotonin, dopamine and norepinephrine (IC50 25-43 microM).