Physical properties of methylcelluloses in relation with the conditions for cellulose modification

A high molecular weight glycoprotein antigen was isolated by size exclusion chromatography on Sepharose 4B from an extract of the yeast Saccharomyces cerevisiae. The glycoprotein antigen Sc 500 was shown to be identical to the antigen termed gp200 previously isolated (Heelan et al., 1991). The MW of Se 500 was determined to be about 500 kDa by size exclusion chromatography on Superose 6 and 460 kDa ± 20k Da by size-exclusion chromatography/multi-angle laser light scattering (SEC/MALLS). Sc 500 contained 90% mannose and traces of N-acetylglucosamine. The amino acid composition revealed that serine and threonine were the most abundant amino acids of the protein part. By alkaline borohydride treatment some, but not all bonds between protein and carbohydrate were broken. This indicates that the main type of linkage between protein and carbohydrate is O-glycosidic and that a minor type is of N-glycosidic nature. Methylation analysis revealed that the mannose residues were connected by 1 → 2 and 1 → 3 linkages with 1 → 2, 1→ 6 linked branch points.

Purified Sc 500 was subjected to a series of chemical and enzymatic modifications followed by studies of antibody binding activity. Treatments with both periodate and alkaline sodium borohydride reduced the human serum IgA, IgG and monoclonal IgM antibody binding activity of Sc 500 whereas trypsin and pronase did not affect its ability to bind these antibodies. The mannosidase Man1 → 2,3,6Man reduced the IgM binding to Sc 500 while the other enzymes included in this experiment (Man1→2 Man, Manβ1 →4GlcNAc and PNGase F) had no effect on the antibody binding.     

Tahiti's native flora endangered by the invasion of Miconia calvescens DC. (Melastomataceae)

Abstract. The native flora of tropical oceanic islands is known to be particularly susceptible both to displacement and extinction, following the invasion of alien organisms. Miconia calvescens DC. (Melastomataceae), first introduced to Tahiti (French Polynesia, South Pacific Ocean) in 1937 as an ornamental plant, now covers over two-thirds of the Island. As it forms dense monotypic stands which have progressively overwhelmed the native forests, this plant pest is a direct threat to the rich Tahitian indigenous flora. Between 40 and 50 species of the 107 species endemic to Tahiti are thought to be on the verge of extinction. M. calvescens was finally declared a'noxious species in French Polynesia'in 1990. Without efficient control efforts and effective endangered plant conservation and protection legislation, M. calvescens could cause Tahiti and all the high islands of French Polynesia to become ecological deserts.     

Some prerequisites for a study of the evolution of cognition in the animal kingdom

A distinction is made between two definitions of animal cognition: the one most frequently employed in cognitive sciences considers cognition as extracting and processing information; a more phenomenologically inspired model considers it as attributing to a form of the outside world a significance, linked to the state of the animal. The respective fields of validity of these two models are discussed along with the limitations they entail, and the questions they pose to evolutionary biologists are emphasized. This is followed by a presentation of a general overview of what might be the study of the evolution of knowledge in animals.     

Genomic Analysis of a New Mammalian Distal-less Gene: Dlx7

We have cloned a new Dlx gene (Dlx7) from human and mouse that may represent the mammalian orthologue of the newt geneNvHBox-5.The homeodomains of these genes are highly similar to all other vertebrate Dlx genes, and regions of similarity also exist between mammalian Dlx7 and a subset of vertebrate Dlx genes downstream of the homeodomain. The sequence divergence between human and mouse Dlx7 in these regions is greater than that predicted from comparisons of other vertebrate Dlx genes, however, and there is little sequence similarity upstream of the homeodomain both between these two genes and with other Dlx genes. We present evidence for alternative splicing of mouseDlx7upstream of the homeodomain that may account for some of this divergence. We have mapped humanDLX7distal to the 5′ end of the HOXB cluster at an estimated distance of between 1 and 2 Mb by FISH. Both the human and the mouse Dlx7 are shown to be closely linked to Dlx3 in a convergently transcribed orientation. These mapping results support the possibility that vertebrate distal-less genes have been duplicated in concert with the Hox clusters.     

Inheritance and genetic mapping of resistance to Alternaria alternata f. sp. lycopersici in Lycopersicon pennellii

The fungal pathogen Alternaria alternata f. sp. lycopersici produces AAL-toxins that function as chemical determinants of the Alternaria stem canker disease in the tomato (Lycopersicon esculentum). In resistant cultivars, the disease is controlled by the Asc locus on chromosome 3. Our aim was to characterize novel sources of resistance to the fungus and of insensitivity to the host-selective AAL-toxins. To that end, the degree of sensitivity of wild tomato species to AAL-toxins was analyzed. Of all members of the genus Lycopersicon, only L. cheesmanii was revealed to be sensitive to AAL-toxins and susceptible to fungal infection. Besides moderately insensitive responses from some species, L. pennellii and L. peruvianum were shown to be highly insensitive to AAL-toxins as well as resistant to the pathogen. Genetic analyses showed that high insensitivity to AAL-toxins from L. pennellii is inherited in tomato as a single complete dominant locus. This is in contrast to the incomplete dominance of insensitivity to AAL-toxins of L. esculentum. Subsequent classical genetics, RFLP mapping and allelic testing indicated that high insensitivity to AAL-toxins from L. pennellii is conferred by a new allele of the Asc locus.     

Kurloff cell lysosomal arylsulphatases: Presence of both cationic and highly anionic isoforms of the sole B class

Following the previous ultrastructural demonstration of the presence of arylsulphatase (Asase) activities in Kurloff cells (KC) and of their quasi-exclusive localization in the Kurloff body (KB), this work investigates their biochemical and zymographic properties after extraction from purified KC suspensions. Using the discriminative inhibitory conditions of both the Baum or LeeVaupel and Conzelmann methods, nitrocatechol sulphate hydrolyzing enzymes of the KC were assumed to belong to the B class of the type II Asase alone. After electrophoretic separation under non-denaturing conditions in a 4–23% polyacrylamide gel, they were characterized by 55 kDa and 62 kDa zymographic bands. After isoelectric focusing, ‘classical’ cationic isoforms (pI 8.5) and two anionic isoforms (pI 4.4 and 4.6) were observed on zymograms. As expected for class B Asase, the different zymographic forms of KC Asase were only recovered in the unadsorbed fraction after anion-exchange chromatography on DEAE-cellulose column equilibrated with high ionic strength buffer. Their K_m (2.1 mM), their optimum pH (5.8) and their inhibitions by sulfite, phosphate, sulphate and ascorbic acid as well as their slight stimulation by AgNO₃ were also characteristic of this class of Asase. Finally, chondroitin4-sulphate was shown to potentially be a physiological substrate for these lysosomal enzymes.     

Dynamics of colony development in the paper waspPolistes dominulus Christ (Hymenoptera,Vespidae): The influence of prey availability

This study focused on how a decrease in prey availability affected the development of aP. dominulus Christ colony. Nutritional oophagy and larval development were parameters found to be most directly affected. The more indirect effects on the growth of the nest and on offspring production were also analyzed.     

Times to exhaustion at 100% of velocity at [(V)\dot]\textO\text2 \dot V{\text{O}}_{\text{2}} max and modelling of the time-limit / velocity relationship in elite long-distance runners

The aim of this study was to measure running times to exhaustion (Tlim) on a treadmill at 100% of the minimum velocity which elicits _{max max} in 38 elite male long - distance runners _max = 71.4 ± 5.5 ml.kg^–1.min^–1 and _max = 21.8 ± 1.2 km.h^–1). The lactate threshold (LT) was defined as a starting point of accelerated lactate accumulation around 4 mM and was expressed in _max. Tlim value was negatively correlated with _max (r = -0.362, p< 0.05) and _max (r = –0.347, p< 0.05) but positively with LT (%v _max) (r = 0.378, p < 0.05). These data demonstrate that running time to exhaustion at _max in a homogeneous group of elite male long-distance runners was inversely related to _max and experimentally illustrates the model of Monod and Scherrer regarding the time limit-velocity relationship adapted from local exercise for running by Hughson et al. (1984) .     

CHROMOSOMAL VERSUS MITOCHONDRIAL DNA EVOLUTION: TRACKING THE EVOLUTIONARY HISTORY OF THE SOUTHWESTERN EUROPEAN POPULATIONS OF THE SOREX ARANEUS GROUP (MAMMALIA,INSECTIVORA)

The shrews of the Sorex araneus group have undergone a spectacular chromosome evolution. The karyotype of Sorex granarius is generally considered ancestral to those of Sorex coronatus and S. araneus. However, a sequence of 777 base pairs of the cytochrome b gene of the mitochondrial DNA (mtDNA) produces a quite different picture: S. granarius is closely related to the populations of S. araneus from the Pyrenees and from the northwestern Alps, whereas S. coronatus and S. araneus from Italy and the southern Alps represent two well-separated lineages. It is suggested that mtDNA and chromosomal evolution are in this case largely independant processes. Whereas mtDNA haplotypes are closely linked to the geographical history of the populations, chromosomal mutations were probably transmitted from one population to another. Available data suggest that the impressive chromosome polymorphism of this group is quite a recent phenomenon.     

Conformational studies of an undecapeptide reproducing the consensus sequence around the cleavage site of the RXVRG endoprotease from Xenopus laevis skin

Two synthetic fragments, corresponding to the 4–9 and 4–14 sequences of a tetradecapeptide used as a model to test the RXVRG-endoprotease activity from Xenopus laevis skin, have been studied by two-dimensional nmr spectroscopies, correlated spectroscopy, and nuclear Overhauser effect (NOE) spectroscopy. Both peptides wore the 5–9 consensus sequence found in several hormonal precursors. The nmr data for the 4–9 hexapeptide did not indicate any particular organization, either in water or in dimethylsulfoxide (DMSO), whereas, the 4–14 undecapeptide, a substrate for the RXVRG endoprotease, showed, in DMSO solution, significant trends of structural organization involving the amino acids pertaining to the consensus domain. From variations of integrated NOE peaks with temperature, the appearent interproton correlation times τ_c were estimated and the maxima observed with Va17, the central residue in the consensus sequence. A defined tertiary structure in that domain was also supported by medium-and long-range NOEs between As6 and Arg8, Glu4 and Gly9, and by the likely involvement of Arg8 and Gly9 NHs in intramolecular hydrogen bonds. Most of these observations could be rationalized by an equilibrium between a 5–3 β-turn and a 9 → 4 H-bonded loop. The predominance of one rotamer for the Cα-Cβ bond was established in four residues. Finally, the average ? and ψ angles were derived from two models taking, or not, into account variations in the correlation times along the sequence. This allowed us to discuss the artifacts generated by using an average correlation time through the whole molecule. © 1994 John Wiley & Sons, Inc.