Capacity for plasticity in the adult owl auditory system expanded by juvenile experience

In the process of creating a multimodal map of space, auditory-visual neurons in the optic tectum establish associations between particular values of auditory spatial cues and locations in the visual field. In the barn owl, tectal neurons reveal these associations in the match between their tuning for interaural time differences (ITDs) and the locations of their visual receptive fields (VRFs). In young owls ITD-VRF associations can be adjusted by experience over a wide range, but the range of adjustment normally becomes quite restricted in adults. This normal range of adjustment in adults was greatly expanded in owls that had previously learned abnormal ITD-VRF associations as juveniles. Thus, the act of learning abnormal associations early in life leaves an enduring trace in this pathway that enables unusual functional connections to be reestablished, as needed, in adulthood, even when the associations represented by these connections have not been used for an extended period of time.     

Dynamics of clot growth induced by thrombin diffusing into nonstirred citrate human plasma

We have tested whether action potential-evoked Ca2+ influx is required to initiate clathrin-mediated synaptic vesicle endocytosis in the lamprey reticulospinal synapse. Exo- and endocytosis were temporally separated by a procedure involving tonic action potential stimulation and subsequent removal of extracellular Ca2+ (Ca2+e). A low concentration of Ca2+ ([Ca2+]e of 11 microM) was found to be required for the induction of early stages of endocytosis. However, the entire endocytic process, from the formation of clathrin-coated membrane invaginations to the generation of synaptic vesicles, proceeded in the absence of action potential-mediated Ca2+ entry. Our results indicate that the membrane of synaptic vesicles newly incorporated in the plasma membrane is a sufficient trigger of clathrin-mediated synaptic vesicle endocytosis.     

Pneumococcal trafficking across the blood-brain barrier. Molecular analysis of a novel bidirectional pathway

Although Streptococcus pneumoniae is a major cause of meningitis in humans, the mechanisms underlying its traversal from the circulation across the blood-brain barrier (BBB) into the subarachnoid space are poorly understood. One mechanism might involve transcytosis through microvascular endothelial cells. In this study we investigated the ability of pneumococci to invade and transmigrate through monolayers of rat and human brain microvascular endothelial cells (BMEC). Significant variability was found in the invasive capacity of clinical isolates. Phase variation to the transparent phenotype increased invasion as much as 6-fold and loss of capsule approximately 200-fold. Invasion of transparent pneumococci required choline in the pneumococcal cell wall, and invasion was partially inhibited by antagonists of the platelet-activating factor (PAF) receptor on the BMEC. Pneumococci that gained access to an intracellular vesicle from the apical side of the monolayer subsequently were subject to three fates. Most opaque variants were killed. In contrast, the transparent phase variants were able to transcytose to the basal surface of rat and human BMEC in a manner dependent on the PAF receptor and the presence of pneumococcal choline-binding protein A. The remaining transparent bacteria entering the cell underwent a previously unrecognized recycling to the apical surface. Transcytosis eventually becomes a dominating process accounting for up to 80% of intracellular bacteria. Our data suggest that interaction of pneumococci with the PAF receptor results in sorting so as to transcytose bacteria across the cell while non-PAF receptor entry shunts bacteria for exit and reentry on the apical surface in a novel recycling pathway.     

Detection of an Actinobacillus pleuropneumoniae serotype 2 lipopolysaccharide (LPS) variant

Until now 12 serotypes of Actinobacillus pleuropneumoniae have been recognized. The specificity of the serotypes reside in the carbohydrate composition of the capsular polysaccharides and lipopolysaccharides (LPS). The LPS of A. pleuropneumoniae serotype 2 is a smooth type LPS with O-chains of linear repeating pentasaccharide units with an O-acetyl group linked to a glucose unit. A monoclonal antibody (MAb 102-G02) directed against A. pleuropneumoniae serotype 2 was characterized in enzyme linked immunosorbent assay (ELISA) and in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The MAb 102-G02 was directed against an epitope on the O-chain of the LPS and was used to define a new. LPS variant of A. pleuropneumoniae serotype 2 (referred to as A. pleuropneumoniae serotype 2X). Investigation of the reactivity of the MAb 102-G02 against an A. pleuropneumoniae serotype 2X, field isolate (9008) and the Danish App-2 strain 4226 in electron microscopy, confirmed the different binding patterns.     

Correction of alimentary methemoglobinemia in children of preschool age by inclusion in the diet of products rich in antioxidants, vitamins and dietary fiber]

Supplementation of children diet with food enriched by vitamins, antioxidants and dietary fiber food (beverage 'Zolotoy shar', bread with addition of bran, 'doctorskije' rolls inhibited or normalized the lipid peroxidation of cell membranes, methemoglobin production and increased some indices of humoral immunity. The results allow to recommend the studied special food for prophylactic use for children dietary intake in regions of ecological pollution.     

Gcn5p, a transcription-related histone acetyltransferase, acetylates nucleosomes and folded nucleosomal arrays in the absence of other protein subunits

Gcn5p is the catalytic subunit of several type A histone acetyltransferases (HATs). Previous studies performed under a limited range of solution conditions have found that nucleosome core particles and nucleosomal arrays can be acetylated by Gcn5p only when it is complexed with other proteins, e.g. Gcn5-Ada, HAT-A2, and SAGA. Here we demonstrate that when assayed in buffer containing optimum concentrations of either NaCl or MgCl2, purified yeast recombinant Gcn5p (rGcn5p) efficiently acetylates both nucleosome core particles and nucleosomal arrays. Furthermore, under conditions where nucleosomal arrays are extensively folded, rGcn5p acetylates folded arrays approximately 40% faster than nucleosome core particles. Finally, rGcn5p polyacetylates the N termini of free histone H3 but only monoacetylates H3 in nucleosomes and nucleosomal arrays. These results demonstrate both that rGcn5p in and of itself is catalytically active when assayed under optimal solution conditions and that this enzyme prefers folded nucleosomal arrays as a substrate. They further suggest that the structure of the histone H3 N terminus, and concomitantly the accessibility of the H3 acetylation sites, changes upon assembly into nucleosomes and nucleosomal arrays.     

Time-dependent changes in heart rate and pupil size during desflurane or sevoflurane anesthesia

To better characterize alterations in autonomic function associated with prolonged anesthesia, we tested the hypothesis that the time-dependent effects of sevoflurane and desflurane differ. We studied seven male volunteers, each anesthetized for 8 h with 1.25 minimum alveolar anesthetic concentration desflurane on one study day and with 8 h sevoflurane on another. These volunteers did not undergo surgery and were minimally stimulated during the study. Measurements included blood pressure, heart rate, pupillary size and light reactivity, concentrations of serum catecholamines, and carbon dioxide production. Over time, heart rate and pupil size increased significantly. During 6 of the 14 anesthetics (45%), heart rate at some point exceeded 95 bpm; similarly, pupil size at some time exceeded 5 mm during 8 anesthetics (57%). In contrast, plasma catecholamine concentrations and carbon dioxide production remained unchanged, and blood pressure remained nearly constant. There are thus substantial time-dependent changes in autonomic functions during prolonged anesthesia, even in unstimulated, nonsurgical volunteers, but we could not detect a difference in these changes during desflurane compared with sevoflurane anesthesia. Implications: Pupil size and heart rate changes are used to guide the delivery of anesthesia. In volunteers, pupil size and heart rate increased with increasing duration of constant desflurane or sevoflurane anesthesia. Thus, anesthetic duration alters heart rate and pupil size independent of surgery and changes in anesthetic delivery.