Nephelometric and turbidometric assays of cellulase activity

Extensively ball-milled cellulose fibers were used as natural substrate for the determination of cellulase activity. This physical treatment breaks the large cellulose fibers to small but insoluble particles yielding a substrate accessible for complete enzymatic breakdown. The parameters studied to estimate the activity of cellulases were (a) the decrease in optical density of ball-milled suspension of fibers and (b) simultaneous measurement of liberated sugars during hydrolysis. A good correlation was found between the initial rate of reaction and the amount of sugar released at given times.     

A new appraisal of the endoglucanases of the fungus Trichoderma reesei.

The properties and enzymic activity of endoglucanases (EC 3.2.1.4) of the fungus Trichoderma reesei were studied by means of immunological methods and by using polyglycosidic substrates. Endoglucanases exist in the culture liquid as a series of immunologically related components. The most active endoglucanase component has an Mr of 43 000 and pI value of 4.0. The most abundant components have a value of pI about 5.0, an Mr of 56 000-67 000 and specific activity only one-fifth of that of the pI-4.0 component. During purification and storage the endoglucanases are spontaneously modified; the relative proportion of components having greater Mr values, more alkaline pI values and lower specific activities is increased. The hexose content of the endoglucanase components is 2-7%. Endoglucanases hydrolyse soluble beta-1,4 glycans. The enzymes described here differ from endoglucanase preparations described previously in not showing activity towards insoluble substrates. The role of endoglucanases in wood hydrolysis is consequently limited to the stage where wood constituents are already in soluble form.     

Sequential Expression of Nucleoproteins during Rat Spermiogenesis

Transition proteins and protamines are highly basic sperm-specific nuclear proteins that serve to compact the DNA during late spermiogenesis. To understand their sequential role in this function, transition protein 1 (TP1), transition protein 2 (TP2), and protamine 1 (P1) were assayed by polyacrylamide gel electrophoresis in pools of microdissected, staged seminiferous tubule segments in the rat. The results were compared with immunocytochemical analyses of squash preparations from accurately identified stages of the epithelial cycle. TP2 was the first to appear as a faint band at stages IX–XI, followed by high levels at stages XII–XIV of the cycle. TP1 showed a low expression at stage XII of the cycle and peaked at stages XIII–I, whereas protamine 1 first appeared at stage I of the cycle and remained high throughout the rest of spermiogenesis. Immunocytochemical analyses and Western blots largely confirmed these results: TP2 in steps 9–14, TP1 in steps 12–15, and P1 from late step 11 to step 19 of spermiogenesis. We propose that TP2 is the first nucleoprotein that replaces histones from the spermatid nucleus, and its appearance is associated with the onset of nuclear elongation. TP1 shows up along with the compaction of the chromatin. The two transition proteins seem to have distinct roles during transformation of the nuclei and compaction of spermatid DNA.     

Species composition of dabbling duck assemblages: ecomorphological patterns compared with null models

Ecomorphological patterns of breeding dabbling duck (Anas spp.) assemblages were studied in six regions in northern Europe. Observed spacings among species in terms of bill lamellar density and body length were compared with expected spacings based on null models incorporating different levels of constraints (regional species pools, species relative abundances, lake size and habitat requirements of species). Deviations of observed spacings from expected ones were compared with prey abundance and prey size diversity in the lakes. Observed spacings in terms of body length, but not in terms of bill lamellar density, were greater than expected on the basis of null models. The most abundant species were generally relatively more different than less abundant species in terms of body length but not in terms of bill lamellar density. Deviations between observed and expected spacings in terms of body length were more like those predicted by the competition hypothesis in lakes with low food abundance than in lakes with high food abundance. Patterns in bill lamellar spacings were not related to food abundance nor to food size diversity. In general, patterns in body length spacings were consistent with the competition hypothesis whether the null model used in comparisons was constrained or not.     

Factors affecting species number and density of dabbling duck guilds in North Europe

We addressed how species number and pair density in guilds of co-existing species is related to habitat structure, and to the abundance and diversity of food resources using the assemblage of seven species of dabbling ducks (genus Anas ) breeding in 60 lakes distributed over six regions in temperate north Europe
Partial correlation and multiple regression revealed that species richness was best predicted by habitat structural diversity as indexed by a principal component analysis based on 18 vegetation and lake characteristics, and by the abundance of aquatic and emergent prey We found no effect of lake size or prey size diversity on species richness Pair density was correlated with the percentage of shoreline with horsetails ( Equisetum ), by habitat structural diversity and by the abundance of emergent invertebrate prey Neither prey size diversity nor abundance of aquatic prey correlated with pair density Species richness and pair density in North European duck guilds vary both with habitat structure and prey availability     

Density-dependent decline of breeding success in an introduced, increasing mute swan Cygus olor population

An increasing population of the mute swan Cygnus olor , was studied from its very establishment in 1976 until 1998. As the number of pairs increased, there was a decline in all production parameters, including the average number of clutches per pair, the average number of broods per clutch, and the average number of fledged young per brood. In a multiple regression analysis covering the whole breeding season, the number of pairs and the average number of clutches per pair explained 71% of the variation in the average number of fledglings per pair. During the brood season, the average number of fledglings per brood was an additionally important parameter in explaining fledgling production. Habitat quality seemed to affect breeding: in places occupied earlier more cygnets fledged from a clutch than in habitats inhabited later. The decreased production of young very likely reflects density-dependent effects on reproduction. This density dependence seems to operate on the breeding grounds, since winter harshness did not affect breeding success. Density-dependent processes started acting already when pairs were beginning to nest, and continued during the brood period. Density dependence has apparently not been detected at the pair stage in earlier studies of bird populations.     

Biological activities of lipopolysaccharides from Pectinatus cerevisiophilus

Abstract A procedure is described in which the protein crystals produced by Bacillus thuringiensis var. israelensis were solubilized in 50 mM NaOH with 10 mM EDTA at pH 11.7. This solubilization procedure gave protein gel profiles identical with those for intact crystals while maintaining full biological activity in the form of erythrocyte lysis capability. Crystals with and without protease activity were equally toxic to Aedes aegypti larvae.     

Formation of Fusarium metabolites in barley grain

Summary The influence of moisture content and temperature during storage of grain on the formation of Fusarium metabolites was studied. Naturally and artificially contaminated barley grain samples were stored at 15%, 25%, and 30% moisture contents, and at temperatures of + 5°C + 25°C, and + 30°C. Time of storage varied between one week and six months and the occurrence of Fusarium species and metabolites was analysed. The only Fusarium metabolite detected was zearalenone. The extent of Fusarium contamination decreased during storage whilst the concentration of zearalenone increased. To avoid the danger of mycotoxicoses, grains must be dryed immediately after harvest and then stored at a low temperature.     

Transport of material between the nucleus,the chromatoid body and the golgi complex in the early spermatids of the rat

Summary The movement and transport of material between intranuclear dense particles, the chromatoid body and the Golgi complex have been studied in early spermatids of the rat. The analyses involved observation of living accurately identified cells, time-lapse cinemicrography and electron microscopy.The chromatoid body establishes transient contacts with intranuclear material during early spermiogenesis. The chromatoid body also makes contacts with the Golgi complex. It is suggested that the chromatoid body receives material from the nucleus during the postmeiotic period and participates in the early formation of the acrosomic system.This work was supported by the Finnish National Research Council for Medical Sciences. The authors are grateful to Mrs. Marita Aaltonen and Mrs. Raija Andersen for their skilful technical assistance