A Symmetric Two-Locus Fertility Model

A model in which selection is mediated by differential fertilities among the genotypes at two diallelic loci is proposed. Fertility depends only on the number of heterozygous loci participating in the mating. Classes analogous to symmetric equilibria in symmetric viability models are determined explicitly and shown to exhibit stability behavior very different from the viability results. Linkage equilibrium is shown to occur in a relatively asymmetric fashion and to overlap in stability with linkage disequilibrium. In many cases single-locus or two-locus polymorphism is shown to be stable simultaneously with chromosome fixation even under very tight linkage. It is suggested that historical effects may be of great significance in the evolution of systems in which fertility is the primary agent of natural selection.     

Yield, transpiration and growth of tomatoes under combined excess boron and salinity stress

Boron is essential to growth at low concentrations and limits growth and yield when in excess. Little is known regarding plant response to excess boron (B) and salinity occurring simultaneously. The influences of B and salinity on tomatoes (Lycopersicon esculentum Mill. Cv `5656') were investigated in lysimeters. Salinity levels were 1, 3, 6 and 9 dSm^–1 and B levels were 0.028, 0.185, 0.37, 0.74, 1.11, 1.48 mol m^–3. Excess boron was found to decrease yield and transpiration of tomatoes. This effect was inhibited when plants were exposed to simultaneous B and salinity stresses. Both irrigation water salinity and boron concentration influenced water use of the plants in the same manner as they influenced yield. While yield was found to decrease with increased boron concentration in leaf tissue, increased salinity led to decreased boron accumulation. Yield response was found to correlate better to B concentration in irrigation water and soil solution than to plant tissue B content. A dominant-stress-factor model was assumed and validated. The model applies the principle that when a plant is submitted to conditions of stress caused by B in conjunction with salinity, the more severe stress determines yield. The results of this study have significance in modeling and management of high salinity high boron conditions. Under saline conditions, differences in crop yield and in water use may not be experienced over a significant range of boron concentrations.     

Ethnic groups and high sensitivity C-reactive protein in Israel

High-sensitivity C-reactive protein (hs-CRP) is a biomarker that correlates with atherothrombotic risk and outcome. hs-CRP is influenced by various modifiable and non-modifiable factors. We studied the relationship between ethnic background and hs-CRP level, among the Jewish population in Israel. A total of 3659 men and 2180 women were divided into two ethnic groups (Ashkenazi and Sephardic Jews), based on the knowledge of Jewish immigration patterns throughout the centuries. Mean hs-CRP levels were calculated for each group and were adjusted for various factors known to influence hs-CRP. Sephardic Jews were found to have higher adjusted mean hs-CRP levels (2.0 mg l^-1 for men and 3.9 mg l^-1 for women) compared with Ashkenazi Jews (1.5 mg l^-1 for men and 2.9 mg l^-1 for women). Ethnic background emerged as an independent significant predictor of hs-CRP levels. We demonstrated that ethnicity is an important factor when considering hs-CRP as a marker of atherothrombotic risk.     

Complex histories of genes encoding 3-hydroxy-3-methylglutaryl-CoenzymeA reductase

The mevalonate pathway for the synthesis of isoprenoids can be found in organisms from all domains of life. It has been previously demonstrated that the first gene specific to that pathway, which encodes the enzyme 3-hydroxy-3-methylglutaryl-CoenzymeA reductase (HMGR), has been transferred between domains by lateral gene transfer on several occasions. Here we look within the domain Bacteria at lateral acquisition of HMGR, whether as a single gene or as part of a mevalonate pathway cluster. We observe a complex history of multiple transfer events probably reflecting the fact that HMGR could be beneficial in a variety of physiological and genetic contexts. We demonstrate that even in Vibrio species, where HMGR is not clustered with other genes to form an operon or a metabolic cluster, it is under strong purifying selection.     

Quantitative trait locus mapping in dairy cattle by means of selective milk DNA pooling using dinucleotide microsatellite markers: analysis of milk protein percentage.

"Selective DNA pooling" accomplishes quantitative trait locus (QTL) mapping through densitometric estimates of marker allele frequencies in pooled DNA samples of phenotypically extreme individuals. With poly(TG) microsatellites, such estimates are confounded by "shadow" ("stutter") bands. A correction procedure was developed on the basis of an observed linear regression between shadow band intensity and allele TG repeat number. Using this procedure, a selective DNA pooling study with respect to milk protein percentage was implemented in Israel-Holstein dairy cattle. Pools were prepared from milk samples of high and low daughters of each of seven sires and genotyped with respect to 11 markers. Highly significant associations with milk protein percentage were found for 5 of the markers; 4 of these markers confirmed previous reports. Selective DNA pooling accessed 80.6 and 48.3%, respectively, of the information that would have been available through individual selective genotyping or total population genotyping. In effect, the statistical power of 45,600 individual genotypings was obtained from 328 pool genotypings. This methodology can make genome-wide mapping of QTL accessible to moderately sized breeding organizations.     

Kinetic analysis of inhibition of cAMP-dependent protein kinase catalytic subunit by the peptide-nucleoside conjugate AdcAhxArg6

Kinetic analysis of the inhibition of the phosphorylation of Kemptide, (LRRASLG), catalyzed by the catalytic subunit of cAMP-dependent protein kinase, by a peptide-nucleoside conjugate inhibitor AdcAhxArg6 was carried out over a wide range of ATP and peptide concentrations. A simple procedure was proposed for characterization of the interaction of this inhibitor with the free enzyme, and with the enzyme-ATP and enzyme-peptide complexes. The second-order rate constants, calculated from the steady-state reaction kinetics, were used for this analysis to avoid the complications related to the complex catalytic mechanism of the protein kinase catalyzed reaction.     

The comparative biologies of two hymenopterous parasites of the chaff scale,Parlatoria pergandii

Résumé La biologie des aphelinidesAphytis hispanicus (Mercet) etProspaltella inquirenda Silvestri, respectivement ecto et endoparasite deParlatoria pergandii Comstock, a été étudiée comparativement en laboratoire.A. hispanicus accomplit son cycle en 34 jours environ à 20 °C et en 16 jours à 28 °C; il produit en moyenne 23,8 descendants, tandis que pourP. inquirenda ces durées sont de 62 et 26 jours et le nombre moyen de descendants 20,6. Le comportement pendant l'oviposition et les interactions diverses entre l'h?te et le parasite ont été notés. Le nectar d'agrumes a prolongé la vie des deux parasites autant que le miel.A. hispanicus a généralement une vie plus prolongée queP. inquirenda. Le premier parasite a mieux survécu dans des conditions de forte humidité relative (61%, 80%), maisP. inquirenda s'est trouvé favorisé dans des conditions de faible humidité relative, ainsi qu'après une exposition à des températures extrêmes. En conclusion,A. hispanicus a un taux plus rapide de croissance, tandis queP. inquirenda est mieux adapté aux conditions naturelles.

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This research has been finaneed in part by Grant No. FG-Is-227 made by the United States Department of Agriculture under P.L. 480.     

Relationship between suicide and myocardial infarction with regard to changing physical environmental conditions

In recent years, the possible association of changes in mortality from cardiovascular disease and myocardial infarction (MI) and deaths related to violence and the suicide rate has been repeatedly discussed. This study examined the relationship between cosmic physical changes (solar, geomagnetic and other space activity parameters) and changes in the total number of in-hospital and MI-related deaths and deaths from suicide to determine if a relationship exists between the distribution of total and MI-related deaths with suicide over time; some differences in the serotonergic mechanisms involved in the pathogenesis of MI and suicide were also taken into account. All suicides (n=2359) registered in the State of Israel from 1981 to 1989 (108 months) were analysed and compared with the total number of deaths (n=15601) and deaths from MI (n=1573) in a large university hospital over 180 months (1974–1989). The following were the main features of the Results. (1) Monthly suicide rate was correlated with space proton flux (r=0.42,P=0.0001) and with geomagnetic activity (r=–0.22,P=0.03). (2) Total hospital and MI-related deaths were correlated with solar activity parameters (r=0.35,P<0.001) and radiowave propagation (r=0.52-0.44,P<0.001), an with proton flux (r=–0.3 to –0.26,P<0.01). (3) Monthly suicide distribution over 108 months was correlated with MI (r=–0.33,P=0.0005) and total hospital mortality (r=–0.22,P=0.024). (4) Gender differences were prominent. We conclude that the monthly distributions of suicides and deaths from MI are adversely related to many environmental physical parameters and negatively correlated with each other.     

The arboreal vegetation of the Central Negev Highlands, Israel, at the end of the Pleistocene: Evidence from archaeological charred wood remains

Charcoal assemblages from five Terminal Pleistocene sites in the Central Negev Highlands, Israel, have been analyzed. Eleven taxa have been identified, two of which, juniper andPaliurus, no longer grow in this district, and one,Pinus (of which only a single occurrence was encountered), is considered intrusive, and the rest are taxa which still characterize the region today. Among these latter,Pistacia atlantica (which is the dominant tree in this area today) was the most common. Association of juniper andPaliurus is found today only in the northern Near East. It can not be ascertained that such an association characterized the Central Negev Highlands throughout the entire period spanned by the charcoal assemblages, since it is possible thatPistacia atlantica may have become temporarily extinct. In any case the former occurrence of juniper and particularlyPaliurus in the Central Negev Highlands clearly point to higher humidity in this region during the final stages of the Pleistocene. This conclusion is corroborated by a variety of proxy climatic indicators throughout the southern Levant.     

1,25-Dihydroxyvitamin D3 and agents that increase intracellular adenosine 3′, 5′-monophosphate synergistically inhibit fibroblast proliferation

Summary Agents that increase intracellular cAMP (cAMP elevating agents) and 1,25(OH)₂D₃ inhibit the proliferation of many cell types. We investigated the combined effect of 1,25(OH)₂D₃ and cAMP elevating agents on exponentially growing mouse 3T3 fibroblasts. The following cAMP elevating agents were used: theophylline and pentoxyfilline, which inhibit cAMP-dependent phosphodiesterase; prostaglandin E₂ which activates adenylate cyclase by a receptor-mediated mechanism; forskolin, which directly stimulates adenylate cyclase; and the cell permeable cAMP analogs 8-bromo cAMP and N⁶ benzoyl cAMP. 1,25(OH)₂D₃ and cAMP elevating agents were added to exponentially growing fibroblasts cultured in 96-well microtiter plates and cell number was monitored 3–7 d later. 1,25(OH)₂D₃ and the cAMP elevating agents as single agents inhibited the growth of the 3T3 cells. The combined treatment of the fibroblasts with 1,25(OH)₂D₃ and the cAMP elevating agents resulted in an antiproliferative effect that was more than additive. The synergistic interaction depended on the dose of 1,25(OH)₂D₃ and was apparent already at 10⁻⁸ M of the hormone. The specificity of the effect of 1,25(OH)₂D₃ was demonstrated by the finding that 24,25-dihydroxyvitamin D₃, a vitamin D metabolite with low affinity for the vitamin D receptor, did not affect the antiproliferative effect of cAMP elevating agents. From the synergistic interaction between 1,25(OH)₂D₃ and the cell permeable cAMP analogs, we infer that the site of interaction between the two signaling pathways is distal to the cAMP generating and degrading machinery.