Seasonal incidence and ecology of the tick Ixodes ricinus (Acari: Ixodidae) on grazing pastures in Western France

A longitudinal survey was carried out during a 2 year period in Western France to assess the infestation level of grazing pastures byIxodes ricinus ticks. Four farms were visited once a month and each of the grazing pastures was sampled in the centre and at the border using the blanket dragging method. A total of 3562I. ricinus (34 adults, 900 nymphs and 2628 larvae) were collected and the infestation was significantly higher during the first year (p<0.0001). The infestation level byI. ricinus varied between grazing pastures and farms. Grazing pastures in the vicinity of forest were more infested than the others, all through the study. The seasonal distribution of ticks showed peaks, with low fluctuations between farms, years and stages. Tick abundance could not be related to vegetation, but only to the vicinity of woods.     

Molecular cloning and complete nucleotide sequence of the repeated unit and flanking gene of the scallop Pecten maximus mitochondrial DNA: Putative replication origin features

In the bivalve mollusc Pecten maximus, the size of the mitochondrial DNA molecules ranges from 20 to 25.8 kbp. This variability is mainly correlated with the occurrence of a variable domain composed with two to five 1.6-kbp repeated units tandemly arrayed in the genome. DNA fragments spanning the 1,586-base-pair-long repeated element and the nearest flanking gene have been cloned and sequenced. This sequence was analyzed regarding its base composition and potential secondary structures. The repeated unit domain was positioned and oriented with regard to the known flanking gene. It ends 2 base pairs upstream relative to the beginning of the tRNA^gly gene. The peculiar properties of the repeated unit were compared with those of the 1,442-bp repeated element found in the mitochondrial genome of the deep sea scallop Placopecten magellanicus. This comparison provided evidence for the absence of nucleotide conservation, except for a small sequence engaged in a secondary structure, but argued for a strong pressure maintaining domains with specific nucleotide content. A possible role for the conserved sequence is discussed.Correspondence to: A. Rigaa     

Identification of members of gene families in Arabidopsis thaliana by contig construction from partial cDNA sequences: 106 genes encoding 50 cytoplasmic ribosomal proteins

Partial cDNA sequencing to obtain expressed sequence tags (ESTs) has led to the identification of tags to about 8000 of the estimated 20 000 genes in Arabidopsis thaliana . This figure represents four to five times the number of complete coding sequences from this organism available in international databases. In contrast to mammals, many proteins are encoded by multigene families in A. thaliana . Using ribosomal protein gene families as an example, it is possible to construct relatively long sequences from overlapping ESTs which are of sufficiently high quality to be able to unambiguously identify tags to individual members of multigene families, even when the sequences are highly conserved. A total of 106 genes encoding 50 different cytoplasmic ribosomal protein types have been identified, most proteins being encoded by at least two and up to four genes. Coding sequences of members of individual gene families are almost always very highly conserved and derived amino acid sequences are almost, if not completely, identical in the vast majority of cases. Sequence divergence is observed in untranslated regions which allows the definition of gene-specific probes. The method can be used to construct high-quality tags to any protein.     

Hypoxia Dramatically Increases the Nonspecific Transport of Blood-Borne Proteins to the Brain

Abstract: Increased cerebrovascular permeability is an important factor for the development of cerebral edema. To investigate the effect of hypoxia on the transport of blood-borne proteins to the brain, we used a cell culture model of the blood-brain barrier (BBB) consisting of a coculture of brain capillary endothelial cells and astrocytes that closely mimics the in vivo situation. The permeability of albumin, a marker of the nonspecific transcellular route, is extremely low in this in vitro model of the BBB. After hypoxia, a huge increase in the permeability of albumin is detected. Despite the opening of the tight junctions already demonstrated after hypoxia, the increase in the permeability of albumin is mainly attributed to an increase of the nonspecific vesicular transport in the cell, attested by the temperature dependence of the phenomenon and the visualization of labeled apotransferrin in the cytoplasm. The increase of this pathway could participate in the development of brain edema during hypoxia.     

Investigation of the dynamics of the spread of human immunodeficiency virus to brain and other tissues by evolutionary analysis of sequences from the p17gag and env genes.

The time of spread of human immunodeficiency virus type 1 (HIV-1) from lymphoid to nonlymphoid tissues in the course of infection was investigated by sequence comparisons of variants infecting a range of lymphoid and nonlymphoid tissues from three individuals with AIDS in the pl7gag gene and regions flanking the V1/V2 hypervariable regions. Phylogenetic analysis in both regions revealed several lineages in each individual that contained sequences from both lymphoid and nonlymphoid tissues such as the brain. This observation contrasts strongly with the previously described organ-specific sequences in the V3 region in this study population and other investigations. Although individual pairwise comparisons of relatively short sequences such as p17gag are subject to considerable stochastic error, we found that the diversity of gag sequences in variants from lymphoid tissue was consistently lower than that found among variants amplified from the brain. By estimating mean synonymous pairwise distances in the p17gag region, we were able to make an approximate calculation of the ages of populations in different tissues. Those from lymphoid tissue ranged from 2.65 to 5.6 years in the three study subjects, compared with 4.1 to 6.2 years for variants in the brain. Indeed, variants infecting the brain were no more closely related to each other than they were to variants infecting other tissues in the body. In two of the three individuals, these times of divergence indicate that infection of the brain may have occurred as an early event in the progression to disease, preceding the onset of AIDS by several years. This study is the first in which it was possible to estimate times of diversification in different tissues in vivo and is of importance in understanding the dynamics of the spread of HIV-1 into nonlymphoid tissues and its possible adaptation for replication in different cell types.     

Glutamine synthetase (GS) expression is reduced in senile dementia of the Alzheimer type

Glutamine synthetase (GS), a metabolic marker of the mature astrocyte, was investigated in the temporal neocortex of postmortem brain samples of 8 cases, either not demented or affected by senile dementia of the Alzheimer type. A negative correlation between the GS protein level and the density of both classical A4 deposits and senile plaques was evidenced. Such a correlation for GS underlies a dysfunction of the astroglial metabolism and particularly of the glutamate and ammonia neutralization. Since GS is sensitive to oxidative lesioning, the changes in GS level that were observed, occurring at the posttranslational stage, might reflect oxidative damage and have severe consequences on the pathological cascade of events.     

Some significant differences in wall chemistry among four commercial Agaricus bisporus strains

Significant differences in gross wall chemical composition were detected in four commercial Agaricus bisporus strains. All were grown under the same conditions and their walls prepared by a mild method of breakage. A more detailed analysis of the wall fractions, isolated by means of their distinct solubilities, also showed striking structural differences among the four strains studied. The detected differences, not only in the overall composition of the wall but also in the polysaccharide structure, could assist in the characterization of strains and/or varieties of the commercial basidiomycete A. bisporus.     

The heterogeneity of bovine growth hormone. Extraction from the pituitary of components with different biological and immunological properties.

Evidence is available to suggest that Ca2+-calmodulin and cyclic nucleotides are involved in the regulation of ion transport in rabbit ileum. Since both Ca2+-calmodulin and cyclic nucleotides exert many of their effects by phosphorylation, the effects of Ca2+-calmodulin and cyclic nucleotides on phosphorylation of purified microvillus membrane from rabbit ileal mucosa were evaluated. Ca2+-calmodulin increased phosphorylation of five microvillus-membrane peptides, with Mr values of 137000, 77000, 58000, 53000 and 50000. The increases in phosphorylation caused by Ca2+-calmodulin were: Mr-137000 peptide, 111 +/- 26%; Mr-77000 peptide, 71 +/- 17%; Mr-58000 peptide, 51 +/- 8%; Mr-53000 peptide, 113 +/- 20%. These increases were maximal at 1 microM-calmodulin and 0.3-0.9 microM free Ca2+; concentrations of Ca2+ causing half-maximal effects on phosphorylation for the different peptides were 0.06-0.12 microM. Cyclic AMP and cyclic GMP increased phosphorylation of two peptides, of Mr 137000 and 85000. The concentrations of cyclic nucleotides giving half-maximal phosphorylation of the Mr-137000 peptide were 0.3 microM-cyclic AMP and 4.6 microM-cyclic GMP, and for the Mr-85000 peptide, 3.9 microM-cyclic AMP and 0.05 microM-cyclic GMP. The maximal increase in phosphorylation of the Mr-137000 peptide was 200% for cyclic AMP and 95% for cyclic GMP, and that of the Mr-85000 peptide was 220% for cyclic AMP and 120% for cyclic GMP. These studies demonstrate the existence of Ca2+-calmodulin-, cyclic AMP- and cyclic GMP-dependent protein kinases and substrate proteins in purified rabbit ileal microvillus membranes and that Ca2+ can regulate phosphorylation of these proteins over the presumed physiological concentration range of cytosol free Ca2+.     

In vitro autoradiographic localization of vasoactive intestinal peptide (VIP) binding sites in the rat central nervous system

This paper describes the autoradiographic distribution of VIP binding sites in the rat central nervous system using monoiodinated ¹²³I-labeled VIP. High densities of VIP binding sites are observed in the granular layer of the dorsal dentate gyrus of the hippocampus, the basolateral amygdaloid nucleus, the dorsolateral and median geniculate nuclei of the thalamus as well as in the ventral part of the hypothalamic dorsomedial nucleus.