Goshawk predation during winter, spring and summer in a boreal forest area of central Sweden

Predation by goshawks was studied in a central Swedish boreal forest area. Data were collected in winter (January–February) 1977-81 by tracking radio-tagged goshawks, and in the breeding season (April–July) by collecting prey remains at the nest. In the breeding season birds dominated the prey, amounting to 86% of prey number and 91% of prey biomass. Wood pigeon Columba palumbus , black grouse Tetrao tetrix , hooded crow Corvus corone cornix and jay Garrulus glandarius accounted for more than 50% of the prey animals, whereas capercaillie Tetrao urogallus and black grouse accounted for more than 50% of prey biomass. There was no functional response to black grouse density fluctuations. Every year goshawks killed significantly more females than males of both capercaillie and black grouse, due to high vulnerability of the grouse hens while laying and incubating. It was estimated that during spring and early summer goshawk predation removed 25% of the female, and 14% of the male black grouse population. In winter squirrel was the dominating prey, both in terms of number (79%) and weight (56%). The proportion of squirrel in the diet was equally high both in winters of low and high squirrel density. The high proportion of squirrel in the winterdiet, as compared to the breeding season, is believed to be due to squirrels having to accept an increased predation risk in winter, in order to feed efficiently enough.     

Genetic polymorphism of GPT and GLO-I in Galicia (northwest Spain): a comparative study

GPT and GLO-I phenotypes were determined by means of isoelectric focusing and starch gel electrophoresis, respectively, in a sample of the Galician population (Northwest Spain); GPT: n = 302, GLO-I: n = 500. The gene frequencies come to: GPT1 = 0.5099, GPT2 = 0.4901; GLO1 = 0.4930, GLO2 = 0.5070. No rare variants were found. The Galician gene frequencies are compared with those obtained on other populations from different parts of the world.     

Evaluation of the effectiveness factor along immobilized enzyme fixed-bed reactors: Design of a reactor with naringinase covalently immobilized into glycophase-coated porous glass

A design equation is presented for packed-bed reactors containing immobilized enzymes in spherical porous particles with internal diffusion effects and obeying reversible one-intermediate Michaelis-Menten kinetics. The equation is also able to explain irreversible and competitive product inhibition kinetics. It allows the axial substrate profiles to be calculated and the dependence of the effectiveness factor along the reactor length to be continuously evaluated. The design equation was applied to explain the behavior of naringinase immobilized in Glycophase-coated porous glass operating in a packed-bed reactor and hydrolyzing both p-nitrophenyl-alpha-L-rhamnoside and naringin. The theoretically predicted results were found to fit well with experimentally measured values.     

In vitro and in vivo synthesis of dolichol and other main mevalonate products in various organs of the rat

The relative rate of biosynthesis of dolichol from [3H]mevalonate in nine rat organs was studied in slices and in the whole animal. This biosynthesis was also compared to that of cholesterol and ubiquinone. All tissues examined are able to synthesize dolichol, as well as ubiquinone and cholesterol. Comparison of the data from slices in vitro with the in vivo studies demonstrated relatively good agreement for dolichol and ubiquinone synthesis. Although dolichol of high specific radioactivity was recovered in the blood, redistribution between organs, such as occurs with cholesterol, appears to be insignificant. The highest rates of dolichol biosynthesis were found in kidney, spleen and liver. On the other hand, muscle makes the largest contribution to total body dolichol synthesis. Newly synthesized dolichol also appears in the bile, but excretion by this route is far from sufficient to account for dolichol turnover. Incorporation of mevalonate into the final products is mainly dependent on biosynthetic activity. For comparison of the biosynthetic rates in different organs, possible sources of errors (such as variations in the size of the precursor pool, limitation by the rate of precursor uptake or non-linear incorporation) were investigated the size of the mevalonate pool in various organs. Equilibration of this pool with exogenous mevalonate is a rapid and passive process. The size of the mevalonate pool does not determine the rates of cholesterol and dolichol biosynthesis, indicating the presence of regulatory steps in the terminal portion of these biosynthetic pathways.     

Is the binding of magnesium (II) to calmodulin significant? An investigation by magnesium-25 nuclear magnetic resonance

Previous reports on the interaction between calmodulin (CaM) and Mg2+ range from no binding to a binding constant of 10(4) M-1 [for a summary, see Cox, J. A., Comte, M., Malnoe, A., Berger, D., & Stein, E. A. (1984) Met. Ions Biol. Syst. 17, 215-273]. In order to resolve the controversy, we used 25Mg NMR to study the binding of Mg2+ to apo-CaM, CaM.Ca2(2)+ (in which sites III and IV are occupied by Ca2+), CaM.La2(3)+ (in which sites I and II are occupied by La3+), and the two tryptic fragments of calmodulin, TR1C (containing sites I and II of CaM) and TR2C (containing sites III and IV of CaM). In each system, a "titration set" and a "temperature set" were obtained, and the spectral data were analyzed by total band-shape analysis to calculate the association constant (Ka) and off-rate (koff). As in the case of Ca2+ binding, sites I and II and sites III and IV were treated as two sets of equivalent sites, and a Ca2+/Mg2+ competition experiment suggested that Mg2+ competes with Ca2+ for the same sites. For both CaM.Ca2(2)+ and TR1C, moderately large Ka (2000 and 3500 M-1, respectively) and moderate off-rates (koff = 2300 and 3000 s-1, respectively, at 25 degrees C) were observed. For both CaM.La2(3)+ and TR2C, binding of Mg2+ was weaker by a factor of ca. 10 (Ka = 300 and 200 M-1, respectively) while the off-rates were also moderate (koff = 3500 and 2200 s-1, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation and characterization of an induced chondroitinase ABC from Flavobacterium heparinum

During the investigation of alternative methods for the large scale preparation of chondroitinases AC, B and C from Flavobacterium heparinum, a new chondroitinase activity was observed. This new enzyme, like the other chondroitinases, acts as an eliminase, forming unsaturated sulfated disaccharides from dermatan and chondroitin sulfates. In contrast to the chondroitinases previously described, which are endoglycosidases, this chondroitinase ABC cleaves the glycosidic linkages in an exolytic fashion, beginning at the reducing end of the substrate molecules. The oligosaccharides formed as transient products by the action of either chondroitinases or testicular hyaluronidase upon dermatan and chondroitin sulfates are also rapidly degraded by the chondroitinase ABC, regardless of their size or the presence of delta-4,5 unsaturation in the terminal uronic acid residue. The maximum activity of the chondroitinase ABC occurs at 30 degrees C and at pH 6.0-7.5. Only 15% of the activity was observed at 37 degrees C, indicating that the enzyme is very sensitive to thermal denaturation. It is strongly inhibited by phosphate ions and is also inhibited by the unsaturated disaccharides formed.     

Cell wall mannoproteins during the population growth phases in Saccharomyces cerevisiae

Mannoproteins from cell walls of Saccharomyces cerevisiae synthesized at successive stages of the population growth cycle have been solubilized with Zymolyase and subsequently analyzed. The major change along the population cycle concerned a large size mannoprotein material; the size of the newly-synthesized molecules varied from 120,000–500,000 (mean of about 200,000) at early exponential phase to 250,000–350,000 (mean of about 300,000) at late exponential phase. These differences are due to modifications in the amount of N-glycosidically linked mannose residues, since the size of the peptide moiety was 90,000–100,000 at all growth stages and the level of O-glycosylation changed only slightly. After, incubation of the purified walls with concanavalin A-ferritin and subsequent analysis by electron microscopy, labelling was localized at the external and internal faces of the walls. The middle space of these was labelled after digestion of the glucan network with Zymolyase, which demonstrate the presence of mannoproteins in close contact with the structural glucan molecules throughout the wall.Abbreviations BSA bovine serum albumin - Con A concanavalin A - SDS sodium dodecyl sulphate