Effect of alkylresorcin on biological membranes during activation of lipid peroxidation

The effect of alkyl resorcin isolated from the cells of Azotobacter chroococcum and of its structural analog devoid of the alkyl chain (resorcin) on liver microsomes and brain synaptosomes of the rat as well as on rabbit skeletal muscle sarcoplasmic reticulum fragments during activation of lipid peroxidation was studied. Alkyl resorcin was shown to produce a much more potent antioxidant effect as compared with resorcin, since it inhibited lipid peroxidation in all the three types of membranes under study at much lower concentrations. Both alkyl resorcin and resorcin which inhibit lipid peroxidation prevented lipid peroxidation-induced structural-functional damages of synaptosomal and sarcoplasmic reticulum fragment membranes. Unlike resorcin, alkyl resorcin exerted an additional effect on brain synaptosomal membranes which consisted in the stabilization of barrier functions of membranes during incomplete inhibition of lipid peroxidation. The cumulative data suggest that stabilization necessitates the presence of both resorcin radical and alkyl chain in the alkyl resorcin molecule.     

Block by phencyclidine of acetylcholine and barium induced adrenal catecholamine secretion

Activation of the sympathetic system by phencyclidine (PCP) should result in catecholamine release from the adrenals. However, adrenalectomy does not reduce PCP-induced hypertension. In an attempt to rectify this inconsistency, the direct effects of PCP on the bovine adrenal medulla were examined. At (3×10^?6M), PCP reduced the acetylcholine-(ACh)-induced catecholamine release by 50%. Surprisingly, barium-induced secretion of catecholamines was also reduced by PCP. ACh-induced catecholamine release was not altered by 10^?3M 4-aminopyridine (4 AP), the potassium channel blocker. Thus, calcium antagonist actions of PCP and consequent block of catecholamine secretion from adrenal medulla may explain the lack of effect of adrenalectomy on PCP-induced hypertension. Possible contributions of calcium and/or potassium channel blockade to other manifestations of PCP overdosage are discussed.     

Developmental regulation of myelin basic protein expression in mouse brain

Developmental regulation of myelin basic protein expression in mouse brain has been examined by comparing the myelin basic protein coding potential of mRNA in vitro with the accumulation of myelin basic protein-related polypeptides in vivo. In vitro translation of mRNA isolated from mouse brain generated eight myelin basic protein-related polypeptides with apparent molecular weights of 34K, 30K, 29K, 26K, 21.5K, 18.5K, 17K, and 14K. A similar set of eight myelin basic protein-related polypeptides with corresponding molecular weights was identified in vivo when total brain proteins were analyzed by immunoblotting. Each of the myelin basic protein-related polypeptides shows a characteristic developmental profile in terms of mRNA level and rate of accumulation implying a complex developmental program of myelin basic protein gene expression with regulation and modulation at several different biosynthetic levels.     

Mercuric chloride-induced nephrotoxicity in the rat following unilateral nephrectomy and compensatory renal growth

The nephropathy induced by mercuric chloride was assessed in unilaterally nephrectomized (NPX) and sham-operated (SO) rats using histological and urinalysis techniques. This assessment was carried out in order to test whether or not rats are more susceptible to the nephrotoxic effects of mercuric chloride after unilateral nephrectomy and a period allowing for compensatory renal growth. Twelve days after surgery both NPX and SO rats were given a single 1.5, 2.0 or 2.5 mumol/kg dose of mercuric chloride (i.v.). Twenty-four hours after the 1.5 or 2.0 mumol/kg dose of mercuric chloride was administered, cellular and tubular necrosis in the pars recta segments of proximal tubules in the outer medulla was more severe in NPX rats than in SO rats. Moreover, the urinary excretion of a number of cellular enzymes (e.g. lactate dehydrogenase) and plasma solutes (e.g. albumin) was greater in NPX rats than in SO rats. At the 2.5 mumol/kg dose of mercuric chloride, renal tubular damage was quite extensive in both groups of rats; to such an extent that possible differences in renal tubular damage between the NPX and SO rats could not be determined histologically. However, the urinary excretion of alanine aminopeptidase was greater in the NPX rats than in the SO rats. Therefore, based on the aforementioned findings, rats that have undergone and adapted to a reduction in renal mass (i.e. unilateral nephrectomy) appear to be more vulnerable to the nephrotoxic effects of mercuric chloride than rats with two normal kidneys.     

Dehalogenation of 4-chlorobenzoate by 4-chlorobenzoate dehalogenase from pseudomonas sp. CBS3: an ATP/coenzyme A dependent reaction

Pseudomonas sp. CBS3 was grown with 4-chlorobenzoate as sole source of carbon and energy. Freshly prepared cell-free extracts converted 4-chlorobenzoate to 4-hydroxybenzoate. After storage for 16 hours at 25 degrees C only about 50% of the initial activity was left. Treatment at 55 degrees C for 10 minutes, dialysis or desalting of the extracts by gel filtration caused a total loss of the activity of the 4-chlorobenzoate dehalogenase. The activity could be restored by the addition of ATP, coenzyme A and Mg2+. If one of these cofactors was missing, no dehalogenating activity was detectable. The amount of 4-hydroxybenzoate formed was proportional to the amount of ATP available in the test system whereas CoA served as a real coenzyme. A novel ATP/coenzyme A dependent reaction mechanism for the dehalogenation of 4-chlorobenzoate by 4-chlorobenzoate dehalogenase from Pseudomonas sp. CBS3 is proposed.     

Effects of detergent on substrate binding and spin state of purified liver microsomal cytochrome P-450LM2 from phenobarbital-treated rabbits

Spectral changes accompanying the binding of the nonionic detergent n-octyl beta-D-glucopyranoside (n-octyl glucoside) to cytochrome P-450LM2 purified from liver microsomes of phenobarbital-treated rabbits have been compared to changes in catalytic activity obtained in a reconstituted system consisting of various levels of detergent, P-450LM2, and NADPH-cytochrome P-450 reductase. In the absence of substrate and reductase, addition of n-octyl glucoside to 2-3 mM resulted in a difference spectrum (detergent-bound minus detergent-free cytochrome) characterized by a small maximum at 390 nm and a minimum at 410 nm, suggestive of a slight stabilization of the high-spin (S = 5/2) state of the cytochrome. As the detergent concentration was increased to 4-8 mM (corresponding to maximal activity and pentameric or hexameric P-450), a new peak appeared at 427 nm while the minimum remained at 410 nm. Between 10 and 30 mM n-octyl glucoside (conditions which produced catalytically inactive and monomeric P-450) the minimum in the difference spectrum shifted to 390 nm and the maximum to 425 nm, characteristic of a shift in spin equilibrium toward low-spin (S = 1/2) cytochrome. At low and high detergent concentrations, substrate [d-benzphetamine with n-octyl glucoside or cyclohexane with the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS)] was bound to P-450LM2 with formation of high-spin P-450, although the increase in high-spin cytochrome was less at high detergent levels than at low. The affinity of P-450 for substrate decreased by 2-3-fold at high detergent.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relative performance of monohaploid potato clones and their diploid parents at plant level and after protoplast isolation and subsequent fusion

Summary Plant growth performance was studied in 118 potato monohaploids and in their diploid parents. Of these monohaploids 76 were also investigated at the protoplast level and eight of these were used in protoplast fusion experiments as well. No correlation was found between relative performance of greenhouse grown and in vitro grown plants. No or only weak correlations were found between different in vitro characteristics such as plant growth, protoplast yield per gram plant material, plating efficiency and callus growth. This indicates the unpredictability of these characters.The protoplast fusion experiments indicated that only in some genotype combinations increased callus growth rates may be found. However, it is not clear whether such calli were hybrids or not. In protoplast monocultures only diploid and tetraploid regenerants were obtained. After fusion, tetraploids but also some triploids could be regenerated. The finding of triploids indicates that monoploid protoplasts were involved in fusion. Isozyme analysis and morphological assessment of the plants pointed out that the majority of the fusion regenerants were hybrids. The implications of these results are discussed.