Substrate-dependent degradation patterns in the decay of wheat straw and beech wood by ligninolytic fungi

Summary The ability of 45 fungal strains to degrade wheat straw and beech wood was studied. Degradation patterns were defined in terms of chemical evolution of substrates and changes in lignin and polysaccharides. Trametes versicolor produced an important degradation of lignin and increased substrate digestibility, but it caused high weight losses and gave rise to similar decay patterns on both substrates. A preferential degradation of lignin was produced during straw transformation by Pleurotus eryngii. The increase of soluble lignin and decreases of lignin content and H/C ratio defined the degradation tendency after principal component analysis. The cation exchange capacity and water and alkali solubility presented the highest loading factors for the characterization of fungal transformation of beech wood. Offprint requests to: A. T. Martínez     

Degree of correspondence between contractile and oxidative capacities in horse muscle fibres: a histochemical study

Samples taken from the middle gluteal muscle of 95 untrained adult horses of different ages and sex were subjected to histochemical analysis using the myosin adenosine triphosphatase (m-ATPase) and nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR) staining techniques. Fibres were classified into types I, IIA and IIB according to m-ATPase activity after preincubation at pH 4.4. The percentage of FT (Fast-Twitch Glycolytic) fibres and the proportion of IIB fibres with "high" and "low" oxidative capacity were determined in serial sections stained for NADH-TR. Statistical analysis revealed a significantly higher proportion of IIB fibres than FT fibres (P less than 0.001), though both percentages were correlated. Thus, 72.2 +/- 17.6% of type IIB fibres showed low oxidative capacity, but the remaining 27.8 +/- 17.6% showed high aerobic potential, and thus did not correspond to FT fibres. These results confirm that the contractile capacity of a muscle fibre does not determine its oxidative profile. The different types of muscle fibre should thus be classified solely according to m-ATPase activity, since this characteristic is related to the molecular structure of contractile proteins. Oxidative capacity should be assessed separately, and not be used as a criterion for fibre classification in horses.     

A Go-like protein in Drosophila melanogaster and its expression in memory mutants.

G proteins couple receptors for extracellular signals to several intracellular effector systems and play a key role in signalling transduction mechanisms. In particulate preparations of Drosophila melanogaster heads, only one substrate for pertussis toxin at 39-40 kd was detected. This substrate, which showed only one isoform when analysed by isoelectric focusing, was recognized by immunoblotting and immunoprecipitation techniques using a polyclonal antibody against the alpha subunit of the Go protein purified from bovine brain and can be thus considered as a Go-like protein. Antibodies obtained against a carboxy-terminal sequence of the alpha subunit of Go (but not of Gi1 or Gi2) and against an internal sequence shared by all the alpha subunits, were also able to cross-react with the alpha subunit of this protein in insects. We have also studied the Go-like protein in several D.melanogaster mutants, primarily in memory and learning mutants. In these mutants there was a sex-dependent enhancement in pertussis toxin-catalysed ADP-ribosylation with respect to the wild-type. This increase could be attributed in part to an increase in the alpha subunit of the Go-like protein, as revealed by immunoblotting with anti-Go alpha polyclonal antibody. This report constitutes the first evidence for the participation of a Go protein in learning and memory.     

Chemical mechanism of lysophosphatidylcholine: lysophosphatidylcholine acyltransferase from rabbit lung. pH-dependence of kinetic parameters.

Lysophosphatidylcholine: lysophosphatidylcholine acyltransferase is an enzyme that catalyses two reactions: hydrolysis of lysophosphatidylcholine and transacylation between two molecules of lysophosphatidylcholine to give disaturated phosphatidylcholine. Following the kinetic model previously proposed for this enzyme [Martín, Pérez-Gil, Acebal & Arche (1990) Biochem. J. 266, 47-53], the values of essential pK values in free enzyme and substrate-enzyme complexes have now been determined. The chemical mechanism of catalysis was dependent on the deprotonation of a histidine residue with pK about 5.7. This result was supported by the perturbation of pK values by addition of organic solvent. Very high and exothermic enthalpy of ionization was measured, indicating that a conformational re-arrangement in the enzyme accompanies the ionization of the essential histidine residue. These results, as well as the results from previous studies, enabled the proposal of a chemical mechanism for the enzymic reactions catalysed by lysophosphatidylcholine: lysophosphatidylcholine acyltransferase from rabbit lung.     

Penetration of intact bovine ova with ram sperm in vitro

In culture, mature bovine ovarian oocytes were fertilized in vitro with freshly ejaculated ram spermatozoa treated with heparin. The zona pellucida does not prevent penetration of ram spermatozoa. The penetration rate varied between 10 and 84%, and in most instances, after 24 hr of culture, two normal-looking pronuclei and sperm tail were present in the cytoplasm. These results suggest that the zona pellucida of bovine oocytes does not represent a barrier for the penetration of ram spermatozoa.     

Ultrastructural localization of silver-staining nuclear proteins at the onset of transcription in early bovine embryos.

Argyrophilic nuclear proteins, known to be functionally associated with ribosomal genes, were localized, in four-, eight-, and 16-cell bovine embryo blastomere nuclei using two different silver-staining procedures. Within the eight-cell cleavage stage by the process of embryonal nucleologenesis in the cow embryo the full-capacity ribosome-producing machinery is established. In the four-cell embryo, many patches and islands of argyrophilic (Ag+) material were detected in the nucleoplasm. The nucleolus-precursor bodies (NPBs), composed uniformly of a homogeneous compact mass, were completely devoid of any silver staining. On the other hand, clear-cut localization of argyrophilic proteins was detected during the eight-cell stage either inside the transforming NPBs or in the close vicinity, or in the already differentiated nucleolus. In compact, nonvacuolated NPB, an intensive Ag+ area was detected, in the form of a lenticle, at the periphery of the NPB. During and following vacuolation of the NPB, no Ag+ was detected inside these vacuoles. It was seen, however, in the dense fibrillar nucleolar component surrounding the smaller vacuoles formed at the time of the establishment of nucleolar structure. Ag+ areas were seen repeatedly in the vicinity of NPBs, probably a part of the nucleolus-associated chromatin or, alternatively, representing the extranucleolar bodies. In blastomere nuclei of 16-cell embryos, already possessing reticulated nucleoli known from intensively synthesizing somatic cells, the silver-staining pattern corresponded to the usual situation in differentiated cells: slight staining of fibrillar centers, heavy labelling in the dense fibrillar component, and absence of silver deposits in the granular component.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rapid colorimetric detection of in vitro amplified DNA sequences

A colorimetric assay to detect immobilized amplified nucleic acids has been designed. This approach provides a rapid assay, suitable for clinical diagnosis, to analyze DNA sequences amplified by the polymerase chain reaction. The specific DNA sequences are captured on a solid support by the use of a recombinant fusion protein consisting of the Escherichia coli lac repressor and staphylococcal protein A. The biotin streptavidin system is used to detect the immobilized material. Positive samples can be analyzed by direct solid-phase sequencing. Here, we show that this nonradioactive concept can be used for analysis of Staphylococci and Streptococci and for specific detection of the protozoa Plasmodium falciparum in clinical samples.