cAMP-dependent protein phosphorylation in mitochondria of bovine heart

A study is presented of the cAMP-dependent phosphorylation in bovine heart mitochondria of three proteins of 42, 16 and 6.5 kDa associated to the inner membrane. These proteins are also phosphorylated by the cytosolic cAMP-dependent protein kinase and by the purified catalytic subunit of this enzyme. In the cytosol, proteins of 16 and 6.5 kDa are phosphorylated by the cAMP-dependent kinase. It is possible that cytosolic and mitochondrial cAMP-dependent kinases phosphorylate the same proteins in the two compartments.     

Characterization of a wilty sunflower (Helianthus annuus L.) mutant II. Water relations, stomatal conductance, abscisic acid content in leaves and xylem sap of plants subjected to water deficiency

The response of w-1, a wilty sunflower (Helianthus annuus L.)mutant, to water stress is described in comparison with thecontrol line (W-1). Detached leaves of w-1 strongly dehydratedduring the first 30 min without significant changes in leafconductance, whereas W-1 responded rapidly to water loss byreducing stomatal aperture. After 2 h stress ABA increased slightlyin w-1, while W-1 leaves showed a 20-fold increase. When waterstress was imposed to potted plants by water withholding, w-1quickly dehydrated, and lost turgor, while W-1 maintained positiveturgor values for a longer period. Wild-type plants respondedto small changes in leaf water potential by accumulating ABAand by closing stomata, whereas in the mutant significant changesin ABA content and in stomatal conductance were found only atvery low water potentials. In another experiment in which waterwas withheld under high relative humidity, when soil water contentstarted to decrease W-1 rapidly closed stomata in the absenceof any change in leaf water status and the reduction in conductancewas paralleled by a rise in xylem sap ABA concentration. Bycontrast the mutant started to accumulate ABA in the xylem sapand to close stomata when soil water content and leaf waterpotential were dramatically reduced. The low endogenous ABAlevels and the inability to synthesize the hormone rapidly eitherin the leaves or in the roots seem to be responsible for thehigh sensitivity of w-1 to water stress. Key words: ABA, Helianthus annuus L, water relations, stomatal conductance, drought, wilty mutant     

Lipoprotein-associated paf (LA-paf) was found in washed human platelets and monocyte/macrophage-like U937 cells

Beyond cholesterol, inflammatory ether phospholipids such as platelet-activating factor (paf) may play a role in atherogenesis. (1) We detected a paf-like compound (‘LA-paf’) associated with human serum lipoproteins, mainly in LDL but not with the lipoprotein-poor fraction. (2) LA-paf was also found in washed human platelets, from where it was partially released during platelet aggregation in response to paf (50 nM) or thrombin (1 U). In addition, resident monocyte/macrophage-like U937 cells carried huge amounts of LA-paf (41 ng per 10⁷ cells) and metabolized added [³H]paf to a labelled compound co-eluting with the retention time of LA-paf in standard HPLC. (3) Functionally, LA-paf had a comparable potency to synthetic paf, because LA-paf aggregated washed aspirin-treated platelets in a concentration-dependent manner. The specific paf receptor antagonist WEB2086 inhibited the platelet aggregation induced by three distinct LA-paf preparations as compared with synthetic paf with similar inhibitory concentrations (IC₅₀: 35.6 ± 12.8, 24.0 ± 4.0, 38.0 ± 15.8 nM for LA-paf, and 43.6 ± 6.5 nM for synthetic paf), indicating that LA-paf interacted with paf receptors. (4) However, LA-paf had a distinct retention time using high-pressure liquid chromatography (HPLC) as compared with synthetic paf. LA-paf eluted at 9–15 min and synthetic paf at 21–24 min. In addition, total and non-specific [³H]paf binding to intact washed human platelets was affected differently by the two unlabelled agonists: while LA-paf increased total and non-specific (but not specific) binding in a significant manner (P < 0.002 and P < 0.007) as LDL did (P < 0.006 and P < 0.03), synthetic paf decreased total binding (P < 0.03). Similarly, low-density lipoproteins (LDL) increased significantly the total [³H]paf binding. In contrast, paf did not affect specific [¹²⁵I]LDL binding to human fibroblasts. Our results show the presence of LA-paf in lipoproteins,     

Changes in drinking water selenium and mortality for coronary disease in a residential cohort

In a part of the municipal territory of Reggio Emilia, northern Italy, selenium in drinking water decreased from 7 μg/L to less than 1 μg/L. In a cohort of 4419 individuals, previously exposed for at least 5 yr to the drinking water with higher selenium content, the 7-yr temporal distribution of deaths for coronary disease and for stroke was analyzed to examine a possible relationship with changes in drinking water selenium. From January 1986 until August 1988, when tap water selenium was 7 μg/L, deaths for coronary disease were one in males and two in females. After the decrease in drinking water selenium, 21 and 10 coronary deaths were observed, respectively, in males and in females from September 1988 to December 1992. No significant difference in the temporal distribution of stroke deaths was observed both in males and in females. Even if an effect of chance and aging in the temporal distribution of coronary deaths may not be excluded, findings of the study seem to be consistent with the hypothesis of a beneficial effect of selenium on coronary disease mortality.     

Complex duplications in maize lines

Rp1 is a disease resistance complex and is the terminal morphological marker on the short arm of maize chromosome 10. Several restriction fragment length polymorphisms (RFLPs), which map within 5 map units of Rp1, were examined to determine if they are also complex in structure. Two RFLP loci, which mapped distally to Rp1, BNL3.04 and PIO200075, existed in a single copy in all maize lines examined. These two loci cosegregated perfectly in 130 test cross progeny. Two RFLP loci that map proximally to Rp1 had unusual structures, which have not yet been reported for maize RFLPs; the loci were complex, with variable numbers of copies in different maize lines. One of the loci, NPI285, occasionally recombined in meiosis to yield changes in the number of copies of sequences homologous to the probe. The other proximal locus, detected by the probes NPI422, KSU3, and KSU4, was relatively stable in meiosis and no changes in the number of restriction fragments were observed. The similarity in map position between Rp1 and the complex RFLP loci indicate there may be genomic areas where variable numbers of repeated sequences are common. The structure of these complex loci may provide insight into the structure and evolution of Rp1.     

Effects of osmotic preconditioning on nuclear replication activity in seeds of pepper (Capsicum annuum)

Routing of cytosolically synthesized precursor proteins into chloroplasts is a specific process which involves a multitude of soluble and membrane components. In this review we wil1 focus on early events of the translocation pathway of nuclear coded plastidic precursor proteins and compare import routes for polypeptide of the outer chloroplast envelope to that of internal chloroplast compartments. A number of proteins housed in the chloroplast envelopes have been implied to be involved in the translocation process, but so far a certain function has not been assigned to any of these proteins. The only exception could be an envelope localized hsc 70 homologue which could retain the import competence of a precursor protein in transit into the organelle.     

Multiple attractors,catastrophes and chaos in seasonally perturbed predator-prey communities

A classical predator-prey model is considered in this paper with reference to the case of periodically varying parameters. Six elementary seasonality mechanisms are identified and analysed in detail by means of a continuation technique producing complete bifurcation diagrams. The results show that each elementary mechanism can give rise to multiple attractors and that catastrophic transitions can occur when suitable parameters are slightly changed. Moreover, the two classical routes to chaos, namely, torus destruction and cascade of period doublings, are numerically detected. Since in the case of constant parameters the model cannot have multiple attractors, catastrophes and chaos, the results support the conjecture that seasons can very easily give rise to complex populations dynamics.     

Cloning and characterization of the gene encoding an esterase from Spirulina platensis

The gene encoding a 23 kDA serine esterase from the cyanobacterium Spirulina platensis has been identified, cloned, characterized and expressed in Escherichia coli. The primary structure of the esterase deduced from the DNA sequence displayed 32% sequence identity with the carboxylesterase (esterase II) encoded by estB of Pseudomonas fluorescens; the highest degree of homology is found in a stretch of 11 identical or highly conserved amino acid residues corresponding to the GXSXG consensus motif found in the catalytic site of many serine proteases, lipases and esterases.     

Monoclonal antibodies and idiotypic network activation for ovarian carcinoma

Antibodies can be processed by the B- and T-cell systems and may lead to a selective activation of the immune system. The network structure of the immune system implicates the possibility of a selective immunization by the activation of idiotypic cascades. In a retrospective analysis, patients with advanced ovarian carcinoma, who had received MAb, against the cancer-associated antigen CA125 for diagnostic purposes, were analyzed for the production of anti-idiotypic antibodies, survival rate, and immunological effects. Furthermore, we started a prospective and randomized study for ovarian cancer patients, using a different antigen, TAG72, for the induction of idiotypic cascades. Our first results on 58 patients with advanced ovarian carcinomas showed that the induction of anti-idiotypic-antibodies against OC125 mimicking the TAA Class III CA125 leads to a prolongation of the survival rate, and, in extended stages, to an induction of antitumoral immunity, and that the induction of idiotypic cascades is also possible for different antigens like TAG72. Summarizing the activation of idio-typic network cascades seems to be a very effective way of intervention in the immune system of patients with advanced stages of ovarian carcinoma. A prospective study of the adjuvant approach seems to be necessary.