The role of an alpha subtype M2-M3 His in regulating inhibition of GABAA receptor current by zinc and other divalent cations

Sensitivity of GABAA receptors (GABARs) to inhibition by zinc and other divalent cations is influenced by the alpha subunit subtype composition of the receptor. For example, alpha6beta3gamma2L receptors are more sensitive to inhibition by zinc than alpha1beta3gamma2L receptors. We examined the role of a His residue located in the M2-M3 extracellular domain (rat alpha6 H273) in the enhanced zinc sensitivity conferred by the alpha6 subtype. The alpha1 subtype contains an Asn (N274) residue in the equivalent location. GABA-activated whole-cell currents were obtained from L929 fibroblasts after transient transfection with expression vectors containing GABAA receptor cDNAs. Mutation of alpha1 (alpha1(N274H)) or alpha6 (alpha6(H273N)) subtypes did not alter the GABA EC50 of alphabeta3gamma2L receptors. alpha1(N274H)beta3gamma2L receptor currents were as sensitive to zinc as alpha6beta3gamma2L receptor currents, although alpha6(H273N)beta3gamma2L receptor currents had the reduced zinc sensitivity of alpha1beta3gamma2L receptor currents. We also examined the activity of other inhibitory divalent cations with varying alpha subtype dependence: nickel, cadmium, and copper. alpha6beta3gamma2L receptor currents were more sensitive to nickel, equally sensitive to cadmium, and less sensitive to copper than alpha1beta3gamma2L receptor currents. Studies with alpha1 and alpha6 chimeric subunits indicated that the structural dependencies of the activity of some of these cations were different from zinc. Compared with alpha6beta3gamma2L receptor currents, alpha6(H273N)beta3gamma2L receptor currents had reduced sensitivity to cadmium and nickel, but the sensitivity to copper was unchanged. Compared with alpha1beta3gamma2L receptor currents, alpha1(N274H)beta3gamma2L receptor currents had increased sensitivity to nickel, but the sensitivity to cadmium and copper was unchanged. These findings indicate that H273 of the alpha6 subtype plays an important role in determining the sensitivity of recombinant GABARs to the divalent cations zinc, cadmium, and nickel, but not to copper. Our results also suggest that the extracellular N-terminal domain of the alpha1 subunit contributes to a regulatory site(s) for divalent cations, conferring high sensitivity to inhibition by copper and cadmium.     

Risk stratification using the Society of Thoracic Surgeons Program

In an era of progressive cost containment and public scrutiny, the wisdom of aggressive surgical therapy for high-risk candidates has been questioned. At our center in the previous 24 months, 728 patients with coronary artery disease were entered into The Society of Thoracic Surgeons national database, and the hospital outcomes plus length of stay were analyzed. Patients were separated according to the predicted mortality based on the groupings in The Society of Thoracic Surgeons database: 0 to 5% (453 patients); 5% to 10% (126 patients); 10% to 20% (96 patients); 20% to 30% (17 patients); and 30% and greater (36 patients). There was a close correlation with the predicted rates of mortality. Importantly, the preoperative risk stratification demonstrated a strong correlation with the significant morbidity and excessive length of stay in the highest-risk groups (predicted risk of 20% to > or = 30%). The incidences of the most common complications in the group with the highest predicted risk (> or = 30%) were 28%, renal failure; 33%, ventilator dependence; and 17%, cardiac arrest. In addition, at short-term follow-up (6 to 8 months), a 24.3% mortality was identified in patients with a predicted mortality that exceeded 20%. These data quantify the risks and morbidities associated with the care of seriously ill patients with coronary artery disease and demonstrate the need for professional and public discussions focusing on the association of a high preoperative risk status and the consumption of resources.     

Herniography in the investigation of groin pain in adults

Herniography is a useful investigation in adults with unexplained groin pain in whom there is no clinical evidence of a hernia, thus ensuring appropriate surgery. The technique is described, normal anatomy and different types of hernias illustrated.     

Chinese and American college students'' body-image: perceived body shape and body affect

We established an in vitro model of the phagocytosis of Mycobacterium tuberculosis by human peripheral blood monocytes to evaluate the subsequent inhibition of intracellular replication of the organism. Highly purified T cells (94% CD3(+)/CD16(-)) or natural killer (NK) cells (96% CD16(+)/CD3(-)) isolated by Percoll discontinuous density gradient of peripheral blood mononuclear cells were incubated with M. tuberculosis-infected monocyte monolayers. Monocytes were lysed immediately and at 4, 7, and 10 d after infection for quantification of intracellular replication, which was assessed by quantitative plating techniques as colony-forming units (CFU). Whereas control monocytes permitted intracellular replication, T cells activated monocytes to kill 77% (p < 0.01) of intracellular M. tuberculosis compared with control monocytes by 10 d after infection. NK cells activated monocytes to kill 84% (p < 0.01) of M. tuberculosis in comparison with control monocytes. Lymphokine (IL-2)-activated-killer (LAK) cells were capable of activating monocytes to kill 97% (p < 0.01) of the intracellular organisms compared with control monocytes. In purified protein derivative (PPD)-positive donors, PPD-specific-CD4(+) lymphocytes stimulated monocytes to kill intracellular M. tuberculosis in a Class II major histocompatibility complex-restricted manner. In contrast, in PPD-negative donors, CD4(-) lymphocytes activated monocytes in a genetically unrestricted manner. Both T cell supernatant and NK cell supernatant generated from cocultivation with M. tuberculosis-infected monocytes also activated monocytes to augment mycobactericidal function. In conclusion, T cells, NK cells, LAK cells, and their supernatants activated mycobactericidal function of monocytes, although these pathways of activation differed in terms of antigenic specificity and genetic restriction.     

Ergonomics in rehabilitation: a comparison of two methods of moving an empty manual wheelchair short distances

Phthalimidomethyl derivatives 1, encompassing a wide range of leaving group abilities, are rapidly hydrolysed to the corresponding phthalamic acid via rate-determining attack at the phthalimide carbonyl group.     

Peptide growth factors in the prostate as mediators of stromal epithelial interaction

Peptide growth factors play a role in the maintenance of normal prostatic growth and differentiation (Fig. 2). It seems likely that the androgen sensitivity of human prostate is mediated by the production of peptide growth factors from stromal cells which act as the direct intermediate of androgen action on epithelial cells. TGF-beta 1 inhibition of epithelial cells is opposed by the stimulatory action of EGF, IGF and FGFs to maintain an equilibrium of epithelial cell numbers. The indirect mitogenic action of androgens appear to act by down-regulation of TGF-beta 1 and possibly EGF receptors. There is also interaction with the effects of IGF-II, produced by prostatic stromal cells and acting on epithelial cells to increase proliferation. The growth of normal prostatic fibroblasts is under the control of bFGF and TGF-beta 1. However, although our understanding of the actions of these growth factors in the normal prostate has improved over the last decade, their role in the development and maintenance of prostate cancer is less clearly defined. TGF-beta 1, classically considered to be inhibitory for epithelial cells, may be up-regulated in prostatic tumours, stimulating growth. Alternatively, autocrine production of such growth factors by tumour cells may lead to loss of inhibitory effects from exogenous TGF-beta 1, a mechanism also witnessed with TGF-alpha and bFGF. The role of EGF in the development of prostate cancer is confusing because results from the use of different cell types and experimental conditions is contradictory. It may be that a switch in the production of the predominant EGFr ligand from EGF to TGF-alpha is an important feature in the development and maintenance of the malignant phenotype. The presence of TGF-alpha autocrine loops has been shown clearly in some tumour cell lines. This switch in the production of a particular ligand may also be a feature of IGFs in prostate cancer. IGF-II may be replaced by IGF-I during malignant progression, both of which are able to act via the type 1 receptor. This change in IGF expression appears to be accompanied by altered expression of the IGF-BP2, with less detectable within prostatic tissues but elevated serum levels [58]. Basic FGF is normally produced by prostatic fibroblasts but is also produced by some prostatic cancer cell lines [64]. However, as with all growth factors, the expression of the bFGF protein and its receptor is dependent on the cell line examined. The autocrine and paracrine control of normal and abnormal prostatic growth by growth factors is important in determining their role in the development and maintenance of prostate cancer. Better understanding of such mechanisms is essential for the development of novel therapeutic strategies in the control and treatment of prostate cancer.