Olfactory memory in rats, cholinergic agents and benzodiazepine receptor ligands.

Drugs and their effects on olfactory learning processes in rats were tested using a modified version of the runway apparatus developed by Ades. Rats were first exposed to a conspecific urine sample and 24 h later were exposed to the same stimulus in the runway. Observations recorded the time spent investigating the urine and the number of sniffs at the site, these being considered to be indices of memory. Diazepam-treated rats (4 or 6 mg/kg) and scopolamine-treated rats (0.5 or 1 mg/kg) showed increases for both parameters. When both drugs were administered simultaneously, the impairing effect was potentiated. However, no changes in learning responses were observed in rats treated with physostigmine (0.125, 0.25, 0.5 mg/kg) or methyl beta-carboline-3-carboxylate (0.3, 0.5, 1 mg/kg), although the administration of physostigmine or methyl beta-carboline-3-carboxylate was shown to antagonize the impairing effect of diazepam or scopolamine respectively. These observations support the hypothesis of interactions existing between cholinergic agents and benzodiazepine receptor ligands and of such interactions affecting olfactory acquisition processes. The runway apparatus appears to be a valid candidate model to be used for the assessment of pharmacological influences on olfactory learning in rats.     

Nuclear progesterone receptors are up-regulated by estrogens in neurons and radial glial progenitors in the brain of zebrafish

In rodents, there is increasing evidence that nuclear progesterone receptors are transiently expressed in many regions of the developing brain, notably outside the hypothalamus. This suggests that progesterone and/or its metabolites could be involved in functions not related to reproduction, particularly in neurodevelopment. In this context, the adult fish brain is of particular interest, as it exhibits constant growth and high neurogenic activity that is supported by radial glia progenitors. However, although synthesis of neuroprogestagens has been documented recently in the brain of zebrafish, information on the presence of progesterone receptors is very limited. In zebrafish, a single nuclear progesterone receptor (pgr) has been cloned and characterized. Here, we demonstrate that this pgr is widely distributed in all regions of the zebrafish brain. Interestingly, we show that Pgr is strongly expressed in radial glial cells and more weakly in neurons. Finally, we present evidence, based on quantitative PCR and immunohistochemistry, that nuclear progesterone receptor mRNA and proteins are upregulated by estrogens in the brain of adult zebrafish. These data document for the first time the finding that radial glial cells are preferential targets for peripheral progestagens and/or neuroprogestagens. Given the crucial roles of radial glial cells in adult neurogenesis, the potential effects of progestagens on their activity and the fate of daughter cells require thorough investigation.     

Blood flow vs. venous pressure effects on filtration coefficient in oleic acid-injured lung

On the basis ofchanges in capillary filtration coefficient(K_fc) in 24 rabbit lungs, we determined whether elevations in pulmonary venouspressure (Ppv) or blood flow (BF) produced differences infiltration surface area in oleic acid-injured (OA) or control (Con)lungs. Lungs were cyclically ventilated and perfused under zone 3 conditions by using blood and 5% albumin with no pharmacological modulation of vascular tone. Pulmonary arterial, venous, and capillary pressures were measured by using arterial, venous, and double occlusion. Before and during eachK_fc-measurementmaneuver, microvascular/total vascular compliance was measured by usingvenous occlusion.K_fc was measuredbefore and 30 min after injury, by using a Ppv elevation of 7 cmH₂O or a BF elevation from 1 to2 l · min¹ · 100 g¹ to obtain a similardouble occlusion pressure. Pulmonary arterial pressure increased morewith BF than with Ppv in both Con and OA lungs [29 ± 2 vs. 19 ± 0.7 (means ± SE) cmH₂O;P < 0.001]. In OA lungscompared with Con lungs, values ofK_fc (200 ± 40 vs. 83 ± 14%, respectively; P < 0.01) and microvascular/total vascular compliance ratio (86 ± 4 vs. 68 ± 5%, respectively; P < 0.01) increased more with BF than with Ppv. In conclusion, for a given OA-induced increase in hydraulic conductivity, BF elevation increased filtration surface area more than did Ppv elevation. The steep pulmonary pressure profile induced by increased BF could result in therecruitment of injured capillaries and could also shift downstream thecompression point of blind (zone 1) and open injured vessels (zone 2).

     

Ruminococcin A, a new lantibiotic produced by a Ruminococcus gnavus strain isolated from human feces

When cultivated in the presence of trypsin, the Ruminococcus gnavus E1 strain, isolated from a human fecal sample, was able to produce an antibacterial substance that accumulated in the supernatant. This substance, called ruminococcin A, was purified to homogeneity by reverse-phase chromatography. It was shown to be a 2,675-Da bacteriocin harboring a lanthionine structure. The utilization of Edman degradation and tandem mass spectrometry techniques, followed by DNA sequencing of part of the structural gene, allowed the identification of 21 amino acid residues. Similarity to other bacteriocins present in sequence libraries strongly suggested that ruminococcin A belonged to class IIA of the lantibiotics. The purified ruminococcin A was active against various pathogenic clostridia and bacteria phylogenetically related to R. gnavus. This is the first report on the characterization of a bacteriocin produced by a strictly anaerobic bacterium from human fecal microbiota.     

Post-glacial colonization of Western Europe brown bears from a cryptic Atlantic refugium out of the Iberian Peninsula

The European brown bear (Ursus arctos) shows a particular phylogeography that has been used to illustrate the model for contraction-expansion dynamics related to glacial refugia in Southern European peninsulas. Recent studies, however, have nuanced the once generally accepted paradigm, indicating the existence of cryptic refugia for some species further north. In this paper we collected available data on chronology and mitochondrial haplotypes from Western European brown bears, adding new sequences from present day individuals from the Cantabrian (North Iberia) area, in order to reconstruct the dynamics of the species in the region. Both genetics and chronology show that the Iberian Pleistocene lineages were not the direct ancestors of the Holocene ones, the latter entering the Peninsula belatedly (around 10,000 years BP) with respect to other areas such as the British Isles. We therefore propose the existence of a cryptic refugium in continental Atlantic Europe, from where the bears would expand as the ice receded. The delay in the recolonization of the Iberian Peninsula could be due to the orographic characteristics of the Pyrenean-Cantabrian region and to the abundant presence of humans in the natural entrance to the Peninsula.     

Binding of benzyl penicilloyl to human serum albumin. Evidence for a highly reactive region at the junction of domains 1 and 2 of the albumin molecule

Tryptic digests of fragment C124-298 of penicilloylated serum albumin, obtained from a penicillin-treated patient or prepared by in vitro conjugation, were analyzed by HPLC. Determinations of benzyl penicilloyl groups (BPO) were performed on the different fractions. Three BPO-containing peptides were identified by their amino acid sequence and the bound BPO was located on lysines 190, 195 and 199 and serine 193. These four main BPO-binding sites are all located on a very short region (10 amino acid residues) of the albumin molecule at the junction of domains 1 and 2.