Interaction between fatty-acid and starch synthesis in isolated amyloplasts from cauliflower floral buds

The interaction of fatty-acid synthesis with starch synthesis has been studied in intact amyloplasts isolated from floral buds of cauliflower (Brassica oleracea L.). These amyloplasts perform acetate-dependent fatty acid synthesis at maximum rates only at high external ATP concentrations. Neither pyruvate nor malate inhibit acetate-dependent fatty-acid synthesis. In contrast, acetate is inhibitory to the low pyruvate-dependent fatty acid synthesis. These observations indicate that neither pyruvate nor malate are used as natural precursors of fatty-acid synthesis. In contrast to fatty-acid synthesis, the rate of glucose-6-phosphate-dependent starch synthesis is already saturated in the presence of much lower ATP concentrations. Rising rates of starch synthesis influence negatively the process of acetate-dependent fatty acid synthesis. This inhibition appears to occur under both limiting and saturating concentrations of external ATP, indicating that the rate of ATP uptake is limiting when both biochemical pathways are active. The rate of starch synthesis is modulated specifically by the concentration of 3-phosphoglycerate in the incubation medium. This observation leads to the conclusion that the activity of ADP-glucose pyrophosphorylase is of primary importance for the control of both, starch and fatty-acid synthesis. Using the modified approach of Kacser and Burns (1973; Symp. Soc. Exp. Biol.27, 65–104) we have quantified the contribution of the rate of starch synthesis to the control of the metabolic flux through fatty-acid synthesis.Abbreviations ADPGlc-PPase ADPglucose pyrophosphorylase - Glc6P glucose-6-phosphate - PGA 3-phosphoglyceric acid     

Interactions of native and modified cytochrome C with a negatively charged reverse micellar liquid interface

Native and chemically modified cytochrome C were dissolved in sodium bis(2-ethylhexyl) sulphosuccinate (AOT)-oil-buffer microemulsions. The native cytochrome C contains 19 lysine residues, these groups were modified by 1) acetic anhydride or 2) succinic anhydride. At pH 8.4 the native, acetylated and succinylated proteins carry +8, –3 and –12 elementary charges, respectively. The phase behaviour of the microemulsion systems was found to be highly dependent on the charge of the proteins. Compared to a protein free system the native protein induces a L-2 phase separation at lower temperatures. The acetylated protein has a small effect on the temperature for the phase transition, whereas in the case of succinylated cytochrome C the phase transition takes place at higher temperatures. When dissolved in AOT microemulsions, the native cytochrome C has a perturbed tertiary structure, as indicated by loss of the 695 nm absorption band, while both the modified proteins retain the same optical properties when dissolved in an AOT microemulsion as in a pure buffer solution. The pertubed structure of the native cytochrome C was further investigated by testing the stability of the reduced form of the protein dissolved in the microemulsion media. The native cytochrome is unstable at W > 10, whereas the two modified proteins were found to be stable at all W-values investigated. The average location of the three proteins was determined by pulse radiolysis. The quenching rate constant of the hydrated electron depends upon the location of the probe in the reverse micelle; the succinylated protein is localised in the aqueous core of the reverse micelles, but both the native and the acetylated forms were found to be localised close to or at the AOT interface.     

Homozygotes for the autosomal dominant neoplasia syndrome (MEN1).

Families in which both parents are heterozygotes for the same autosomal dominant neoplasia syndrome are extremely unusual. Recently, we had the unique opportunity to evaluate three symptomatic siblings from the union between two unrelated individuals affected by multiple endocrine neoplasia type 1 (MEN1). When the three siblings and their parents and relatives were genotyped for 12 markers tightly linked to the MEN1 locus, at 11q13, two of the siblings were found to be homozygotes, and one a heterozygote, for MEN1. With regard to the MEN1 syndrome, no phenotypic differences were observed between the two homozygotes and the heterozygotes. However, the two homozygotes showed unexplained infertility, which was not the case for any of the heterozygotes. Thus, MEN1 appears to be a disease with complete dominance, and the presence of two MEN1 alleles with mutations of the type that occur constitutionally may be insufficient for tumor development.     

A scale-down two-compartment reactor with controlled substrate oscillations: Metabolic response of Saccharomyces cerevisiae

Substrate concentration gradients are likely to appear during large scale fermentations. To study effects of such gradients on microorganisms, an aerated scale-down reactor system was constructed. It consists of a plug flow reactor (PFR) and a stirred tank reactor (STR), between which the medium is circulated. The PFR, which is an aerated static mixer reactor, was characterized with respect to plug flow behaviour and oxygen transfer. A Bodenstein number of 15–220, depending on residence time and aeration rate, and a k_La of 500–1130 h^–1, depending mainly on aeration rate, were obtained. The biological test system used, was aerobic ethanol production by Saccharomyces cerevisiae, due to sugar excess. The ethanol concentration profile and the yield of biomass were compared in two fed-batch fermentations. In the first case, the feeding point of molasses was located at the inlet of the PFR. This simulates location of the feeding point in the segregated part of a heterogeneous reactor, with local high sugar concentrations. In the second mode of operation, as a control with good mixing conditions, the PFR was disconnected from the STR, into which the substrate was fed. Differences were found: Up to 6% less biomass was produced and a larger amount of ethanol was formed in the two-compartment reactor system, due to the uneven sugar concentration distribution. This emphasizes the importance of the location of, and the mixing conditions at, the feeding point in a bioreactor.     

High prevalence of asthma in cross country skiers.

OBJECTIVES--To study the prevalence of asthma (asthma symptoms and bronchial hyperresponsiveness) in Swedish cross country skiers compared with non-skiers and monitor changes in symptoms and bronchial hyperresponsiveness during the year. DESIGN--Cross sectional study during the winter ski season and in the summer. SETTING--Six ski clubs for élite skiers (total 47) in two different areas of Sweden. SUBJECTS--42 élite cross country skiers and 29 non-skiing referents. MAIN OUTCOME MEASURES--Bronchial responsiveness, asthma symptoms, and lung function. RESULTS--Bronchial responsiveness was significantly greater and asthma symptoms more prevalent in the skiers than in the referents. There was no difference in bronchial responsiveness within either group between winter and summer. 15 of the 42 skiers used antiasthmatic drugs regularly and 23 had a combination of asthma symptoms and hyperresponsive airways or physician diagnosed asthma, or both. Altogether 33 skiers had symptoms of asthma or bronchial hyperresponsiveness. One of the referents had symptoms of asthma and bronchial hyperresponsiveness, and none used antiasthmatic drugs regularly. CONCLUSIONS--Asthma, asthma-like symptoms, and bronchial hyperresponsiveness are much more common in cross country skiers than in the general population and non-skiers. Strenuous exercise at low temperatures entailing breathing large volumes of cold air is the most probable explanation of persistent asthma in skiers.     

Reversal of sexual impotence in male patients with chronic obstructive pulmonary disease and hypoxemia with long term oxygen therapy

Erectile impotence is commonly encountered in male patients with respiratory failure and hypoxia. In this study, 42% of the patients experienced reversal of sexual impotence during long term oxygen therapy (LTOT). We examine the association between sexual impotence, gonadal axis hormones, hypoxia, and oxygen therapy. Nineteen sexually impotent male patients eligible for LTOT (pO₂ < 7.3 kPa during stable disease) and with sexual impotence received oxygen therapy for 1 month (n = 12) or 24 h (n = 7). pO₂, LH, FSH, testosterone, and SHBG (sex hormone binding globulin) were monitored. Five of 12 patients receiving oxygen for 1 month regained sexual potency. The responders showed a significant increase in arterial pO₂ and serum testosterone, and a decline in SHBG compared to non-responders. None of the patients receiving oxygen for 24 h experienced reversal of sexual impotence, despite a significant increase in pO₂. In these patients, serum testosterone did not increase significantly. Reversal of sexual impotence may be achieved in some patients with respiratory failure. The oxygen therapy must, however be administered for an adequate length of time.     

The synthesis and biochemical evaluation of new A1 selective adenosine receptor agonists containing 6-hydrazinopurine moieties

The synthesis and SAR of a series of novel derivatives of N-aminoadenosine is described, along with their in vitro effects in biochemical assays. The rat brain A₁ adenosine receptor binding of these compounds is very dependent upon the purine 2-substituent. The novel agonist, 2-chloro-N-[4-(phenylthio)-1-piperidinyl]adenosine, exhibits a L_i value for A₁ receptor binding of <1 nM.     

GENETIC AND SOCIAL INHERITANCE OF BODY AND EGG SIZE IN THE BARNACLE GOOSE (BRANTA LEUCOPSIS)

We present heritability estimates for final size of body traits and egg size as well as phenotypic and genetic correlations between body and egg traits in a recently established population of the barnacle goose (Branta leucopsis) in the Baltic area. Body traits as well as egg size were heritable and, hence, could respond evolutionarily to phenotypic selection. Genetic correlations between body size traits were significantly positive and of similar magnitude or higher than the corresponding phenotypic correlations. Heritability estimates for tarsus length obtained from full-sib analyses were higher than those obtained from midoffspring-midparent regressions, and this indicates common environment effects on siblings. Heritabilities for tarsus length obtained from midoffspring-mother regressions were significantly higher than estimates from midoffspring-father regressions. The results suggest that this discrepancy is not caused by maternal effects through egg size, nor by extra-pair fertilizations, but by a socially inherited foraging site fidelity in females.