In vivo metabolism of a mutant apolipoprotein, apoA-IIowa, associated with hypoalphalipoproteinemia and hereditary systemic amyloidosis.

Apolipoprotein (apo) A-I is the major protein constituent of plasma high density lipoproteins (HDL). A kindred has been identified in which a glycine to arginine mutation at residue 26 in apoA-I is associated with hypoalphalipoproteinemia and hereditary systemic amyloidosis. We isolated the mutant protein, termed apoA-IIowa, from the plasma of an affected subject and studied its in vivo metabolism compared to that of normal apoA-I in two heterozygous apoA-IIowa subjects and two normal controls. Normal and mutant apoA-I were radioiodinated with 131I and 125I, respectively, reassociated with autologous plasma lipoproteins, and simultaneously injected into all subjects. Kinetic analysis of the plasma radioactivity curves demonstrated that the mutant apoA-IIowa was rapidly cleared from plasma (mean fractional catabolic rate [FCR] 0.559 day-1) compared with normal apoA-I (mean FCR 0.244 day-1) in all four subjects. The FCR of normal apoA-I was also substantially faster in the heterozygous apoA-IIowa subjects (mean FCR 0.281 days-1) than in the normal controls (mean FCR 0.203 days-1). Despite the rapid removal from plasma of apoA-IIowa, the cumulative urinary excretion of its associated radioactivity after 2 weeks (44%) of the injected dose) was substantially less than that associated with normal apoA-I (78% of injected dose), indicating extravascular sequestration of radiolabeled apoA-IIowa.(ABSTRACT TRUNCATED AT 250 WORDS)     

Molecular characterisation of inter and intra-specific somatic hybrids of potato using randomly amplified polymorphic DNA (RAPD) markers

Summary Protoplast fusion allows the transfer of both mono- and polygenic traits between species that are sexually incompatible. This approach has particular relevance for potato, and somatic hybridisation has been used to introduce a range of disease resistance genes from sexually incompatible wild species into the cultivated potato gene pool. In addition, protoplast fusion allows the resynthesis of tetraploid genotypes from pre-selected diploid or dihaploid donor parents. A limiting factor for the efficient exploitation of this technology in potato breeding is the difficulty of unequivocally identifying nuclear hybrids (heterokaryons). In order to facilitate the identification of hybrids at an early stage following fusion, Randomly Amplified Polymorphic DNA markers (RAPDs) have been used to characterise molecularly both inter- and intra-specific somatic hybrids of potato. RAPD markers detect naturally occurring polymorphism in the donor genotypes and utilise short oligonucleotide primers of arbitrary nucleotide sequence in combination with the polymerase chain reaction (PCR). The exploitation of RAPDs in the characterisation of both somatic and sexual hybrids is discussed.     

Tolerance to imidazolinone herbicides in wheat

An imidazolinone-tolerant wheat (Triticum aestivum L. em Thell) mutant in the winter wheat cultivar Fidel has been identified and characterized. The mutant was isolated from a population derived through seed mutagenesis of the variety with an aqueous solution containing sodium azide. Imidazolinone-tolerant wheat seedlings were selected from the M₂ generation of the population in the presence of imazethapyr herbicide and identified as herbicide-insensitive individuals. The trait is inherited as a single semidominant gene and confers high levels of tolerance to imazethapyr. Acetohydroxyacid synthase activity in extracts from imidazolinonetolerant plants was less inhibited by imazethapyr than the enzyme from the wild type. The herbicide-tolerant plants have a completely normal phenotype and display no negative effects on growth and yield in either the absence or presence of imazethapyr.     

Assessment of inter- and intra-population variation in quinoline alkaloid profile of juvenile shoot cultures of Cinchona ledgeriana: effect of method of nutrient delivery on alkaloid profile

Intra-population quinoline alkaloid profiles surveying quinine, quinidine, cinchonine and cinchonidine were determined for each of five populations of Cinchona ledgeriana grown as shoot-culture for 125 days. No significant difference in respect of mean alkaloid content between populations was detected. In contrast, there was considerable between-seedling variation in alkaloid content within each population. When nutrients were delivered to shoot-cultures in droplet form by means of an aerosol spray (as compared to the supply of nutrients direct from agar-or liquid-based reservoirs) alkaloid profile was greatly perturbed; most notable in this respect was a four-fold increase in the production of cinchonidine concomitant with a four-fold decrease in the production of cinchonine. These data are discussed with reference to the optimisation of quinoline alkaloid production by juvenile shoot-cultures of Cinchona ledgeriana.     

An investigation of dye reduction by food-borne bacteria

S.A. LEAROYD, R.G. KROLL AND C.F. THURSTON. 1992. The rates of reduction of seven redox dyes by 13 bacterial strains were measured and found to vary greatly between different bacterium/dye combinations. Phenazine ethosulphate and toluidine blue were the most rapidly reduced dyes by the majority of bacteria and resorufin and 2-hydroxy-1,4-naphthoquinone were reduced slowly, if at all. There was also considerable variation in the rates of reduction with any single dye/organism combination. Glucose stimulated the rates of endogenous dye reduction in about half of the organisms. For Bacillus cereus, Pseudomonas fluorescens and Escherichia coli , dye reduction was stimulated by a range of exogenous substrates but lactose, the primary available carbon and energy source in milk, had little effect. In Lactococcus lactis , dye reduction was stimulated by sugars but not by organic acids. Oxygen successfully competed with dye reduction in organisms containing respiratory chains, but with membrane fractions, dye reduction was more rapid than oxygen consumption. All the organisms showed little cytosolic dye reduction, except L. lactis which showed substantial rates of reduction of some dyes by this fraction. With the membrane fraction of E. coli and Ps. fluorescens , cyanide inhibited NADH and succinate-dependent dye reduction, Antimycin A inhibited lactate and succinate and rotenone had no significant effect, but inhibition was not always observed with membrane from both organisms.     

Effect of exercise training on intracellular free Ca2+ transients in ventricular myocytes of rats.

The purpose of this study was to test the hypothesis that exercise training induces enhanced intracellular free Ca2+ (Cai) availability to the contractile elements of cardiac cells. Cai transients were directly measured in single isolated contracting ventricular myocytes from exercise-trained (EX) and sedentary control (SED) rats. Male Sprague-Dawley rats underwent 16 wk of progressive treadmill exercise (32 m/min, 8% grade, 1.5 h/day) (EX) or were cage confined (SED). EX rats had lower resting heart rate and elevated skeletal muscle oxidative capacity. Cai was measured with the fluorescent Cai indicator fura-2. Simultaneous video monitoring indicated that myocytes suspended in physiological salt solution were quiescent until stimulated electrically at a frequency of 0.2 Hz (12-36 V, 2-ms duration). Stimulated Cai transients, measured from changes in fura-2 fluorescence, were similar in cells from EX and SED groups. Peak shortening, time to peak shortening, velocity of shortening, contraction duration, and time to half-relaxation were also similar in cells from EX and SED rats. Ryanodine (10 microM) was applied to eliminate the contribution of Ca2+ release from sarcoplasmic reticulum to the Cai transient. Verapamil was applied to eliminate the contribution of voltage-gated Ca2+ channels to Cai transients. Cai transients were also similar in cells from EX and SED groups after these pharmacological interventions. These results suggest that treadmill training of rats does not alter Cai availability to the contractile elements in isolated ventricular myocytes.     

The Crustacea of some chalk streams in southern England

Records of Crustacea from chalk streams in southern England are described. Classification of sites suggested that flow regime was an important influence on the fauna and the distribution of individual species are discussed in this respect.