Causes and effects of individual quality in bark beetles

A summary of the present knowledge of variation in individual quality within a bark beetle population is given, with emphasis on the spruce bark beetle Ips typogrophus , A major causal factor is density, mediated by competition during larval development. Density negatively influences individual quality measured as weight, fat content and pheromone production. Together with decreasing mean values at higher densities, the skewness of the frequency distributions goes from negative to positive, while variance changes little. High densities, which often occur in the field, thus result in a large fraction of "low quality beetles". They have lower reproductive capacity and presumably lesser dispersal ability, lower survival, and earlier response to pheromone. This might concentrate the population in the next generation with increased competition as a result. It is suggested that a decrease in beetle "quality" due to increasingly intense intraspecific competition can contribute to the decline of an epidemic population.     

Regulation of the 2',5'-oligoadenylate level in mouse L cells

A study of pH dependence for ppp5'A2'p5'A2'p5'A hydrolysis in interferon treated and untreated mouse L-cells extracts led to the detection of two types of the 2'-phosphodiesterase activities: interferon dependent and interferon resistant. Several pH-optima were observed for hydrolysis of ppp5'A2'p5'A2'p5'A in cell extracts after their treatment with non-ionic detergent NP-40 or their differential centrifugation. The 2'-phosphodiesterase activity was found in the membrane fraction as well as in the cytoplasmic one. The presence of several pH-optima for 2'-phosphodiesterase activity in L-cells and changes of the level of this activity depending on the growth stage of cells and time of their interferon treatment indicate the complicated character of the regulation of 2'-5'-oligoadenylate's concentration and localization. The results obtained suggest that in mouse L-cells several 2'-phosphodiesterases or one enzyme in different forms may be present.     

Maternal Height and Preterm Birth: A Study on 192,432 Swedish Women

BackgroundThere is increasing evidence that lower maternal stature is associated with shorter gestational length in the offspring. We examined the association between maternal height and the likelihood of delivering preterm babies in a large and homogeneous cohort of Swedish women.MethodsThis study covers antenatal data from the Swedish Medical Birth Register on 192,432 women (aged 26.0 years on average) born at term, from singleton pregnancies, and of Nordic ethnicity. Continuous associations between women''s heights and the likelihood of preterm birth in the offspring were evaluated. Stratified analyses were also carried out, separating women into different height categories.ResultsEvery cm decrease in maternal stature was associated with 0.2 days shortening of gestational age in the offspring (p<0.0001) and increasing odds of having a child born preterm (OR 1.03), very preterm (OR 1.03), or extremely preterm (OR 1.04). Besides, odds of all categories of preterm birth were highest among the shortest women but lowest among the tallest mothers. Specifically, women of short stature (≤155 cm or ≤-2.0 SDS below the population mean) had greater odds of having preterm (OR 1.65) or very preterm (OR 1.47) infants than women of average stature (-0.5 to 0.5 SDS). When compared to women of tall stature (≥179 cm), mothers of short stature had even greater odds of giving birth to preterm (OR 2.07) or very preterm (OR 2.16) infants.ConclusionsAmong Swedish women, decreasing height was associated with a progressive increase in the odds of having an infant born preterm. Maternal short stature is a likely contributing factor to idiopathic preterm births worldwide, possibly due to maternal anatomical constraints.     

The Relationship between the Growth Rate of Young Plants and their Total-N Concentration is Unique and Simple: a Comment

A series of experiments with cabbage and lettuce, where nitrogensupply is interrupted at a given and the future developmentof plants mass and of nitrogen concentration are observed, isre-analysed. Using the nitrogen productivity theory, it is shownthat plant properties determined from growth under unlimitednitrogen supply also explain the behaviour under interruptednitrogen supply. This is in contrast to the suggestion of theoriginal author Burns 1994, Annals of Botany 74: 143-157, whoquestions the existence of a unique relationship between plantrelative growth rate (RGR) and nitrogen concentration. Someserious problems in the models suggested by the author are alsoindicated.Copyright 1995, 1999 Academic Press Cabbage, lettuce, model, nitrogen limitation, nitrogen productivity, relative growth rate     

Immunological characterization of hydrogenases in the nitrogen-fixing cyanobacterium Nostoc sp. strain PCC 73102

N₂-fixing Nostoc sp. strain PCC 73102 was examined for the presence of hydrogenases. Native-PAGE/immunoblots demonstrated that two proteins with molecular masses of approximately 200 kDa and 215 kDa are immunologically related to hydrogenases purified from Bradyrhizobium japonicum, Azotobacter vinelandii, Methanosarcina barkeri, and Thiocapsa roseopersicina. SDS-PAGE/immunoblots showed that one polypeptide, with a molecular mass of about 58 kDa, is immunologically related to the hydrogenases purified from all the microorganisms mentioned above. In addition, two polypeptides, with molecular masses of approximately 34 and 70 kDa, are immunologically related to the hydrogenases purified from T. roseopersicina and M. barkeri respectively. Immunogold/transmission electron microscopy showed that the hydrogenase proteins are present in both the heterocysts and the vegetative cells.     

Specificity of Candida antarctica lipase B (SP 435) in the presence of lipase A in a double enantioselective transesterification

Summary In the lipase-catalyzed double enantioselective transesterification between the meso-diol 1 and the racemic 2,2,2-trifluoroethyl 2-chloropropanoate (rac-2) by the immobilized lipase preparation SP 382 from Candida antarctica, consisting of the components A and B, component B only is responsible for the enantioselectivity.     

Hypothermia Prevents the Ischemia-Induced Translocation and Inhibition of Protein Kinase C in the Rat Striatum

The effect of hypothermia on the ischemia-induced changes in the subcellular distribution of protein kinase C (PKC) (gamma), -(beta II), and -(alpha) and the activity of PKC was studied in striatal homogenates of rats subjected to 20 min of cerebral ischemia. The effect of postischemic cooling was also studied. During normothermic ischemia, PKC(gamma) and -(beta II) increased 3.9- and 2.9-fold, respectively, in the particulate fraction, signifying a translocation of PKC to cell membranes. The levels of PKC(alpha) did not change significantly. PKC activity decreased during ischemia by 52% and 47% (p less than 0.05) in the particulate and cytosolic fractions, respectively, and remained inhibited for the 1 h recovery period. In hypothermic animals, there was no evidence of translocation, and the inhibition of PKC activity was completely abolished. Hypothermia induced in the recovery phase, however, did not affect PKC distribution or activity. The protective effect of intraischemic hypothermia may in part be due to the prevention of the ischemia-induced translocation and subsequent downregulation of PKC, possibly through a temperature-dependent modification of the cell membranes.     

On the meaning of enzymatic superactivity in reverse micelles

Summary Two types of superactivity can be defined. One, is with respect to the activity for a fixed average substrate concentration in the water pool; the pushing of the charged substrate by the likewise charged micellar surface is responsible for the superactivity and its bell-shaped dependence on the hydration ratio. The other, is with respect to the activity in a bulk aqueous solution having a substrate concentration equal to a fixed overall concentration [S^–]_ov in the entire reverse micellar solution. In this case, the pushing effect, the constraint of a fixed [S^–]_ov and the partitioning of the substrate in the surfactant layer are responsible for the bell-shaped dependence. Superactivity exists for low substrate partitioning in the surfactant layer, subactivity for high partitioning.     

Photosystem II characteristics of a constructedSynechocystis 6803 mutant lacking synthesis of the D1 polypeptide

Photosystem II (PSII) composition was studied in a mutant of the cyanobacteriumSynechosystis 6803 in which synthesis of the reaction center polypeptide D1 has been inactivated. The mutant thylakoids had lost also the other reaction center polypeptide D2 and the chlorophylla-binding protein CP47. Cytochromeb559 and the chlorophylla-binding protein CP43 accumulated to almost wild-type amounts in mutant thylakoids. Also the 33 kDa polypeptide involved in water oxidation was present and membrane-bound in mutant thylakoids. The intrinsic 22 kDa polypeptide, so far known only from plants, was detected both in wild-type and mutant thylakoids.