Dominant effects of the bcr-abl oncogene on Drosophila morphogenesis

The Ras protein and its homolog, Rap1A, have an identical "effector region" (residues 32-40) preceded by Asp30-Glu31 and Glu30-Lys31, respectively. In the complex of the "Ras-like" E30D/K31E mutant Rap1A with the Ras-binding domain (RBD), residues 51-131 of Raf-1, Glu31 in Rap1A forms a tight salt bridge with Lys84 in Raf-1. However, we have recently found that Raf-1 RBD binding of Ras is indeed reduced by the E31K mutation, but is not affected by the E31A mutation. Here, the "Rap1A-like" D30E/E31K mutant of Ras was prepared and shown to bind the Raf-1 RBD less strongly than wild-type Ras, but slightly more tightly than the E31K mutant. The backbone 1H, 13C, and 15N magnetic resonances of the Raf-1 RBD were assigned in complexes with the wild-type and D30E/E31K mutant Ras proteins in the guanosine 5'-O-(beta,gamma-imidotriphosphate)-bound form. The Lys84 residue in the Raf-1 RBD exhibited a large change in chemical shift upon binding wild-type Ras, suggesting that Lys84 interacts with wild-type Ras. The D30E/E31K mutant of Ras caused nearly the same perturbations in Raf-1 chemical shifts, including that of Lys84. We hypothesized that Glu31 in Ras may not be the major salt bridge partner of Lys84 in Raf-1. A molecular dynamics simulation of a model structure of the Raf-1 RBD.Ras.GTP complex suggested that Lys84 in Raf-1 might instead form a tight salt bridge with Asp33 in Ras. Consistent with this, the D33A mutation in Ras greatly reduced its Raf-I RBD binding activity. We conclude that the major salt bridge partner of Lys84 in Raf-1 may be Asp33 in Ras.     

Direct sequencing of neuropeptides in biological tissue by MALDI-PSD mass spectrometry

Dissected tissue pieces of the pituitary pars intermedia from the amphibian Xenopus laevis was directly subjected to matrix-assisted laser desorption/ionization (MALDI) mass analysis. The obtained MALDI peptide profile revealed both previously known and unexpected processing products of the proopiomelanocortin gene. Mass spectrometric peptide sequencing of a few of these neuropeptides was performed by employing MALDI combined with postsource decay (PSD) fragment ion mass analysis. The potential of MALDI-PSD for sequence analysis of peptides directly from unfractionated tissue samples was examined for the first time for the known desacetyl-alpha-MSH-NH2 and the presumed vasotocin neuropeptide. In addition, the sequence of an unknown peptide which was present in the pars intermedia tissue sample at mass 1392.7 u was determined. The MALDI-PSD mass spectrum of precursor ion 1392.7 u contained sufficient structural information to uniquely identify the sequence by searching protein sequence databases. The determined amino acid sequence corresponds to the vasotocin peptide with a C-terminal extension of Gly-Lys-Arg ("vasotocinyl-GKR"), indicating incomplete processing of the vasotocin precursor protein in the pituitary pars intermediate of X. laevis. Both vasotocin and vasotocinyl-GKR are nonlinear peptides containing a disulfide (S-S) bridge between two cysteine residues. Interpretation of the spectra of these two peptides reveals three different forms of characteristic fragment ions of the cysteine side chain: peptide-CH2-SH (regular mass of Cys-containing fragment ions), peptide-CH2-S-SH (regular mass + 32 u) and peptide = CH2 (regular mass -34 u) due to cleavage on either side of the sulfur atoms.     

Optimal selection and preparation of fresh frozen corticocancellous allografts for cervical interbody spinal fusion

STUDY DESIGN: Iliac crest corticocancellous allografts for anterior interbody fusion were harvested from six cadavers. The grafts were cut sequentially from left and right crests and randomly assigned to tricortical or bicortical preparations. Their compression strengths then were determined and compared by matched pair analysis. OBJECTIVES: To quantify the failure strength of the grafts from different iliac locations and determine the optimal type of preparation of the grafts for anterior interbody fusion. SUMMARY OF BACKGROUND DATA: Iliac crest corticocancellous autografts and allografts commonly are used for interbody cervical fusions. However, graft strengths for specific sites have not been determined fully. METHODS: Six paired, fresh frozen, iliac crests were sectioned using a customized miter box into multiple 1-cm-thick grafts 1.5 cm in depth to simulate cervical interbody grafts. The left and right sides of each pair were randomly assigned to tricortical and bicortical preparations. The samples were tested by applying a compressive load to failure using a specialized fixture to simulate vertebral body loading. RESULTS: The grafts closer to the anterosuperior iliac spine had significantly higher failure loads and failure strengths than those closer to the posterosuperior iliac spine. The strengths of the bicortical grafts were 72 +/- 14% of the strengths of the tricortical grafts (P < 0.001). CONCLUSIONS: Anterior iliac crest grafts were stronger in compression, even after removal of one cortical surface, than posterior iliac crest grafts.     

Primary leiomyosarcoma. A rare tumor of the adrenal gland

OBJECTIVE: To report on a rare case of primary leiomyosarcoma of the adrenal. To our knowledge, this is the fourth case reported in the literature. METHODS: A patient with primary leiomyosarcoma of the adrenal gland is presented. The clinical features are described, and the diagnostic and therapeutic aspects of this rare primary mesenchymal tumor are discussed. RESULTS/CONCLUSIONS: The aggressive nature and the poor prognosis of this rare tumor type are emphasized.     

The relation between arterial oxygen tension and cerebral blood flow during cardiopulmonary bypass

BACKGROUND: The precise mechanisms involved in islet xenograft rejection remain unknown. The purpose of the present study was to determine cellular mechanisms responsible for islet xenograft rejection in the liver to facilitate finding a procedure for prevention of immune rejection. METHODS: Hepatic mononuclear cells (MNC) as well as splenocytes, peripheral blood MNC, and thymocytes from streptozotocin-induced diabetic mice (BALB/c) rejecting the intrahepatic rat (Lewis) islet xenografts were isolated and examined by two-color FACS analysis. RESULTS: The characteristic finding of the hepatic MNC from the mice rejecting islet xenografts compared with mice receiving isografts was a significant increase in the yield as well as in the percentage of the cells expressing CD3+ interleukin-2 receptor (IL-2R) alpha- beta+, CD3+ CD8alpha+ beta+, and T cell receptor (TCR) alphabeta+ lymphocyte function-associated antigen-1+. The expression of CD3 and TCR alphabeta of these T cells was found to be of intermediate intensity (TCR(int) cells). The expansion of these TCR(int) cells occurred predominantly in the liver. There was no significant difference in the cells expressing CD3+ IL-2R alpha+, CD3+ CD4+, CD3+ TCRgammadelta+, CD3- IL-2Rbeta+ (natural killer cells), and B220+ (B cells). In vivo administration of anti-IL-2Rbeta monoclonal antibody directed to the expanded cells produced a prevention of rejection. CONCLUSIONS: These findings suggest that islet xenograft rejection in the liver from rat to mouse is an event for which the TCR(int) cells are responsible.     

Renal changes induced by nitric oxide and prostaglandin synthesis reduction: effects of trandolapril and verapamil

The benefits of the simultaneous administration of low doses of a calcium antagonist and a converting enzyme inhibitor in the treatment of hypertension and renal vasoconstriction are well established. The objective of this study was to evaluate whether the administration of low doses of a calcium antagonist and a converting-enzyme inhibitor have beneficial effects in treating the renal alterations induced by the acute administration of a cyclooxygenase inhibitor when nitric oxide synthesis is reduced. These effects were examined in anesthetized dogs before and during an acute sodium load. It was found that the intrarenal infusion of meclofenamate (5 microg x kg[-1] x min[-1]), simultaneously with a low dose of NG-nitro-L-arginine methyl ester (1 microg x kg[-1] x min[-1]), produced a 40% decrease of renal blood flow and glomerular filtration rate and a reduction in the renal excretory response to the sodium load. In a second group of dogs, intrarenal verapamil (0.5 microg x kg[-1] x min[-1]) was effective in blocking the effects of nitric oxide and prostaglandin synthesis inhibition on sodium excretion and glomerular filtration rate but did not modify the effects on renal blood flow. An intrarenal infusion of trandolapril (0.3 microg x kg[-1] x min[-1]) was effective in a third group of dogs in reducing the renal hemodynamic effects but not in preventing the antinatriuretic effect observed in the first group. Finally, in a fourth group, the simultaneous administration of verapamil and trandolapril was effective in treating all the renal changes induced by the cyclooxygenase inhibitor when nitric oxide synthesis was reduced. These results suggest that the combination of low doses of trandolapril and verapamil has additive effects in treating the renal vasoconstriction and antinatriuresis induced by the acute administration of a cyclooxygenase inhibitor, when nitric oxide synthesis is reduced.     

Anatomy of the cranial nerves

The anatomy of cranial nerves I and III through XII are presented. Each nerve is diagrammatically illustrated from its nuclear or its sensory origin and correlated with magnetic resonance and computed tomography images. The important identifying anatomical landmarks are demonstrated along the course of each nerve. Peripheral motor and sensory components are also discussed.     

The use of irreversible ligands to inactivate receptor subtypes: 4-DAMP mustard and muscarinic receptors in smooth muscle

Irreversible ligands are useful tools for investigating the function of receptor subtypes in various physiological processes. The mechanism for alkylation involves the formation of a reversible receptor complex followed by a covalent reaction. The extent of receptor alkylation is determined by the dissociation constant of the reversible complex and the rate constant for conversion to the covalent complex. Selectivity can be achieved if the irreversible ligand exhibits a difference in its dissociation constants for receptor subtypes. Selective alkylation can also be achieved using a selective competitive inhibitor to protect the desired receptor subtype. By using the non-M2-selective irreversible antagonist, 4-DAMP mustard, in combination with the competitive M2-selective antagonist, AF-DX 116, it has been possible to achieve a highly selective inactivation of all non-M2 subtypes of the muscarinic receptors in smooth muscle and has enabled the discovery of the functional role of M2 receptors in smooth muscle.     

Evaluation of atypical cytochrome P450 kinetics with two-substrate models: evidence that multiple substrates can simultaneously bind to cytochrome P450 active sites

Some cytochrome P450 catalyzed reactions show atypical kinetics, and these kinetic processes can be grouped into five categories: activation, autoactivation, partial inhibition, substrate inhibition, and biphasic saturation curves. A two-site model in which the enzyme can bind two substrate molecules simultaneously is presented which can be used to describe all of these observed kinetic properties. Sigmoidal kinetic characteristics were observed for carbamazepine metabolism by CYP3A4 and naphthalene metabolism by CYPs 2B6, 2C8, 2C9, and 3A5 as well as dapsone metabolism by CYP2C9. Naphthalene metabolism by CYP3A4 and naproxen metabolism by CYP2C9 demonstrated nonhyperbolic enzyme kinetics suggestive of a low Km, low Vmax component for the first substrate molecule and a high Km, high Vmax component for the second substrate molecule. 7, 8-Benzoflavone activation of phenanthrene metabolism by CYP3A4 and dapsone activation of flurbiprofen and naproxen metabolism by CYP2C9 were also observed. Furthermore, partial inhibition of 7, 8-benzoflavone metabolism by phenanthrene was observed. These results demonstrate that various P450 isoforms may exhibit atypical enzyme kinetics depending on the substrate(s) employed and that these results may be explained by a model which includes simultaneous binding of two substrate molecules in the active site.