Sedative but not anxiolytic properties of benzodiazepines are mediated by the GABA(A) receptor alpha1 subtype

Inhibitory neurotransmission in the brain is largely mediated by GABA(A) receptors. Potentiation of GABA receptor activation through an allosteric benzodiazepine (BZ) site produces the sedative, anxiolytic, muscle relaxant, anticonvulsant and cognition-impairing effects of clinically used BZs such as diazepam. We created genetically modified mice (alpha1 H101R) with a diazepam-insensitive alpha1 subtype and a selective BZ site ligand, L-838,417, to explore GABA(A) receptor subtypes mediating specific physiological effects. These two complimentary approaches revealed that the alpha1 subtype mediated the sedative, but not the anxiolytic effects of benzodiazepines. This finding suggests ways to improve anxiolytics and to develop drugs for other neurological disorders based on their specificity for GABA(A) receptor subtypes in distinct neuronal circuits.     

Vibriophage VcA-3 as an epidemic strain marker for the U.S. Gulf Coast Vibrio cholerae O1 clone.

Toxigenic and nontoxigenic Vibrio cholerae O1, El Tor biotype strains, which are endemic to the U.S. Gulf Coast, can be lysogenic for bacteriophage VcA-3. To evaluate the presence of VcA-3 as an indicator of toxigenicity and as an epidemic strain marker, phage production and the presence of phage and cholera toxin genes were assayed in 98 strains of V. cholerae O1 (35 U.S. and 63 foreign strains). By using a HindIII chromosomal digest for Southern blot analysis, 39 of the study strains hybridized with the VcA-3 probe in 10 banding patterns. The 15 toxigenic and 6 of the 20 nontoxigenic U.S. isolates gave four VcA-3-related patterns. Among the foreign isolates, 12 of 12 toxigenic classical biotype strains, 1 of 43 toxigenic El Tor biotype strains, and 3 of 8 nontoxigenic atypical strains gave six patterns that were clearly distinct from that of VcA-3. Compared with Southern blot analysis, the phage production assay had a sensitivity of 1.0 and a specificity of 0.48, while the colony hybridization assay had a sensitivity of 1.0 and a specificity of 0.77 for identification of VcA-3. Neither assay reliably identified the toxigenic Gulf Coast clone. The presence of VcA-3, as defined by Southern blot analysis, always separated toxigenic U.S. from foreign isolates and often from nontoxigenic U.S. isolates of V. cholerae O1.     

Sequences of two kinetoplast minicircle DNAs of Trypanosoma (Nannomonas) congolense

Random minicircle DNA molecules were released from isolated kinetoplast network DNA of Trypanosoma congolense by BamHI digestion and cloned into plasmid pUC19. The sequences of two cloned minicircles (958 bp and 964 bp) were determined. Both minicircles contain the 13 bp sequence, 5'-GGGGTTGGTGTAA-3', thought to be the replication origin of minicircles in other trypanosomatids. The two minicircles have extensive homology in the 120 bp preceeding, and the 20 bp following, this 13-mer but only scattered homology elsewhere. Both possess tandem repeats downstream of the 13-mer. Comparison of these minicircles with minicircle sequences from other trypanosomatids reveals that they have the same general sequence organization as the others although only the 13-mer and its flanking regions are homologous.     

Curing efficiency and ocular hazards of dental photopolymerization sources

The spectral distributions of a range of dental photocuring sources were measured at the exit window and at a distance of 10 cm. The former enabled the evaluation of a newly proposed photocuring efficiency index which correlates well with the depth of cure of the photopolymerized resins, thus providing a basis for the comparison of different photocuring sources. The spectral irradiante of the sources obeyed the inversesquare law, allowing a comparison with the ACGIH threshold limit values. According to these criteria, no ocular hazard is posed to the patient or clinician by u.v.-A or u.v.-B radiation nor to the patient by the visible light when momentarily exposed to the sources. Similarly the ACGIH criterion indicates that the clinician does not risk chorioretinal injury provided the exposure is restricted to less than 140 s in a 3 h period.     

Mouse monoclonal antibodies to the human C3b receptor

Mouse monoclonal antibodies were raised against the human C3b receptor (CR1) molecule that had been purified from solubilized erythrocytes membranes. Four hybridomas were selected, cloned and expanded because their supernatants reacted strongly with insolubilized CR1 by ELISA and intensely stained B-dependent areas of the spleen and glomerular podocytes by indirect immunofluorescence. The four monoclonal antibodies, named J3D3, J8B10, J3B11 and J7C2, were IgG1 immunoglobulins. J3D3 immunoprecipitated two protein bands of apparent mol. wts 200,000 and 220,000 from 125I-surface-labeled human erythrocytes, which correspond to the two major allotypic forms of CR1. By indirect immunofluorescence, monoclonal antibodies stained polymorphonuclear leucocytes (PMN), most peripheral blood B-cells and a small subset of peripheral blood T-cells. J3D3 bound to CR1 on erythrocytes, PMN and lymphocytes with an affinity of 1-3 X 10(9) M-1 and recognized 170-1330 antigenic CR1 sites with an average of 740 sites/erythrocyte in 100 healthy individuals, approx. 50,000 sites/PMN and 15,000 sites/lymphocyte. There was a bimodal distribution of CR1 numbers on erythrocyte in the normal population. The four monoclonal antibodies similarly inhibited CR1-mediated decay of preformed cell-bound alternative- and classical-pathway C3 convertase sites. Two antibodies, J3D3 and J3B11, inhibited C3b-dependent rosette formation with lymphocytes, although much less efficiently than F(ab')2 polyclonal anti-CR1 antibody. Differences that were observed in the relative capacity of the antibodies to inhibit some of the functions of CR1 and in their ability to compete for binding of 125I-J3D3 to CR1 on erythrocytes, suggested that they are directed against different epitopes on CR1. Monoclonal antibodies provide useful means to assess and analyze the biological and immunoregulatory functions of the C3b receptor.     

Structure and properties of methacrylate based dental restorative materials

The chemistry and structure of the dimethacrylate resins and the nature of the filler systems in dental composite resins are reviewed in relation to their influence on the setting behaviour, dimensional stability, aesthetics, fracture behaviour and adhesive potential. It is clear that a deeper understanding of the structure of the polymeric matrix and the mechanism of clinical wear is required. As a result of ongoing research in this area and with the development of dentine adhesives, the future prospects of composite resins are encouraging.     

Effect of articular disease and total knee arthroplasty on knee joint-position sense

Joint proprioception in the human knee has been studied using two previously described tests. Threshold of detection of slow, constant, passive motion and ability to reproduce angles to which the knee was passively placed were accurately measured. A group of postoperative total knee arthroplasty (TKA) patients were examined. All patients also had documented articular disease in the unoperated knee. Results were compared to age-matched controls. In addition, a young control group was studied for comparison to both groups. A significant difference was seen between the young control group and the older control group in both tests performed. Age-matched controls and the postoperative patients demonstrated an even greater difference. There was, however, no difference between the operated and unoperated knee among the TKA patients. It is concluded that joint proprioception declines to some degree with normal aging. A more marked decline is associated with degenerative joint disease. Total joint replacement, however, did not lead to a further decrease in sensation.     

Development of Na+-dependent hexose transport in a cultured line of porcine kidney cells

LLC-PK1 cells in culture do not concentrate alpha-methylglucoside (alpha-meG) during their early growth phase but develop the capacity to concentrate this hexose as the growth rate decreases in confluent cultures. The concentrating ability is dependent on the Na+ electrochemical gradient and is inhibited by phlorizin with KI,0.5 approximately 0.2 microM. The development of the concentrative capacity can be accelerated by the Friend cell inducer hexamethylene bisacetamide (HMBA) and by the phosphodiesterase inhibitors dibutyryl cAMP, theophylline, and 1-methyl-3-isobutylxanthine (MIX). In cultures treated with any of these differentiation-accelerating chemicals, the development of alpha-meG concentrating capacity is severely inhibited by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) but not by inactive (in tumor promotion) analogs of TPA. In all cases, an early event in the development of alpha-meG accumulating capacity is an elevated intracellular cAMP concentration; however the results suggest that this increase in cAMP may be necessary but not sufficient to induce the differentiated hexose-accumulating capacity.     

Longitudinal studies on the egg drop syndrome 1976 (eds-76) in the fowl following experimental infection at 1-day-old

Following oral infection of 1-day-old chicks with egg drop syndrome - 1976 (EDS-76) virus (strain D61) lateral transmission of the virus was demonstrated throughout the rearing period. At point of lay, pullets previously infected at 1-day-old responded to EDS-76 inactivated vaccine given intramuscularly with a pronounced rise in haemagglutination inhibition antibody titre, but failed to respond to oral challenge with live virus. Egg production and shell quality were not affected following EDS-76 infection at 1-day-old, but egg weight was reduced and internal egg quality adversely affected.     

Marek's disease as a model for the Landry--Guillain--Barré syndrome: latent viral infection in nonneuronal cells accompanied by specific immune responses to peripheral nerve and myelin.

In the chicken, Marek's disease virus (MDV) induces a demyelinating peripheral neuropathy that, early in the course of the disease, is histopathologically indistinguishable from that seen in the Landry--Guillain--Barré syndrome in man. A continuing role for a productive infection in the pathogenesis of this disease is unlikely, since neither MDV nor MDV antigens can be characteristically detected in nerves or spinal ganglia examined at necropsy. The authors investigated the possible role of a latent viral infection by explanting and maintaining in vitro the sciatic nerves and spinal ganglia from diseased birds. In these tissues, viral specific products were induced and detected by immunofluorescence and ultrastructural methods early after explanation in well-isolated Schwann cells, satellite cells, and lymphocytes. Later, virus was detected in fibroblasts, macrophages, and neoplastic lymphoblastoid cells. Neurons and myelinating Schwann cells, in contrast, did not replicate the agent. Specific cell-mediated and humoral immune responses to chicken peripheral nerve and peripheral nerve myelin were demonstrated early in the course of the disease. When considered relative to potential pathogenetic mechanisms, these results suggest that Marek's disease neuropathy is initiated by the establishment of a latent viral infection in neuronal supporting cells. A specific immune response to viral-induced antigens on these cells could, in turn, result in subsequent demyelination.