Insulin inhibition of 5' adenosine monophosphate-activated protein kinase in the heart results in activation of acetyl coenzyme A carboxylase and inhibition of fatty acid oxidation

Acetyl coenzyme A (CoA) carboxylase (ACC) is an important regulator of fatty acid oxidation in the heart, since it produces malonyl CoA, a potent inhibitor of mitochondrial fatty acid uptake. Under conditions of metabolic stress, 5'adenosine monophosphate-activated protein kinase (AMPK), which is highly expressed in cardiac muscle, can phosphorylate and decrease ACC activity. In this study, we determined if fatty acid oxidation in the heart could be regulated by insulin, due to alterations in AMPK regulation of ACC activity. Isolated working rat hearts were perfused with Krebs-Henseleit solution containing 11 mmol/L glucose, 0.4 mmol/L [9,10(-3)H]palmitate, and either 100 microU/mL insulin or 1,000 microU/mL insulin. Increasing insulin concentration resulted in a decrease in fatty acid oxidation rates (P < .05), a decrease in AMPK activity (P < .05), and an increase in ACC activity (P < .05) compared with the low-insulin group. A negative correlation was observed between AMPK and ACC activity (r = -.76). We conclude that insulin, acting through inhibition of AMPK and stimulation of ACC, is capable of inhibiting myocardial fatty acid oxidation.     

The effect of magnesium sulphate on hemodynamics and its efficacy in attenuating the response to endotracheal intubation in patients with coronary artery disease

Laryngoscopy and endotracheal intubation may produce adverse hemodynamic effects. Magnesium has direct vasodilating properties on coronary arteries and inhibits catecholamine release, thus attenuating the hemodynamic effects during endotracheal intubation. We studied 36 patients with coronary artery disease (CAD) scheduled for elective coronary artery bypass grafting to evaluate the hemodynamic effects of magnesium and its efficacy in attenuating the response to endotracheal intubation. Patients received either 0.1 mL/kg (50%) magnesium sulfate (50 mg/kg) (Group A, n = 19) or isotonic sodium chloride solution (Group B, n = 17) before the induction of anesthesia and 0.05 mL/kg of isotonic sodium chloride solution (Group A) or lidocaine 2% (1 mg/kg) (Group B) before intubation. The hemodynamic variables were recorded before induction, after the trial drug, after induction, and after endotracheal intubation. Automatic ST segment analysis was performed throughout the study period. Magnesium sulfate administration was associated with increased cardiac index (P < 0.01), a minimal increase in heart rate, and a significant decrease in mean arterial pressure (MAP) and systemic vascular resistance (SVR) (P < 0.001). None of the patients in the magnesium group had significant ST depression compared with three patients in the control group. The magnesium group patients had a significantly lesser increase in MAP (P < 0.05) and SVR (P < 0.01) compared with the control group patients who received lidocaine before endotracheal intubation. Thus, magnesium is an useful adjuvant to attenuate endotracheal intubation response in patients with CAD. IMPLICATIONS: Endotracheal intubation produces adverse hemodynamic effects, which may be more detrimental in patients with coronary artery disease than in healthy patients. The present study shows that magnesium administered before endotracheal intubation can attenuate this response better than lidocaine.     

Modeling the carbohydrate-binding specificity of pig edema toxin

The wild-type binding pentamer of Shiga-like toxin IIe (SLT-IIe) binds both the globotriaosylceramide (Gb3) and globotetraosylceramide (Gb4) cell surface glycolipids, whereas the double mutant GT3 (Q65E/K67Q) exhibits a marked preference for Gb3 [Tyrrell, G. J., et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 524-528]. We modeled three unique sites (sites 1-3) for binding of the carbohydrate moiety of Gb3 to GT3 and SLT-IIe, on the basis of the three sites observed for the SLT-I pentamer [Ling, H., et al. (1998) Biochemistry 37, 1777-1788]. Examination of the three sites in light of various mutation and binding data strongly suggested that one of the binding sites plays a role in the change of specificity observed for the GT3 mutant. We applied several modeling techniques, and developed a model for binding of the carbohydrate moiety of Gb4 to this site of the SLT-IIe binding pentamer. This model is consistent with a wide variety of mutation and binding data and clearly shows the importance of the terminal GalNAc residue of Gb4, as well as that of the two mutated residues of GT3, to the intermolecular interaction.     

Impact of smoking cessation on salivary function in healthy volunteers

BACKGROUND: Salivary bicarbonate and epidermal growth factor (EGF) have an important protective role in the oesophagus. The effect of smoking cessation on these aspects of salivary function is unknown. METHODS: Salivary bicarbonate secretion and EGF output were measured before and after attempted smoking cessation in 28 healthy volunteers. Urinary cotinine excretion was used to assess compliance. RESULTS: Negative correlations were found between salivary flow rate and age (rho = -0.34) and between cigarette consumption and salivary flow (rho = -0.27) and salivary bicarbonate concentrations (rho = -0.32). Smoking cessation was associated with a significant increase in salivary bicarbonate secretion (day 0, 1.7 (0.14-6.2); day 7, 3.6 (0.52-6.4); day 21, 3.3 (0.44-6.6) micromol min(-1); P < 0.01) but left salivary EGF output unchanged. CONCLUSION: Smoking cessation is associated with significant improvements in salivary bicarbonate secretion. This would benefit patients with reflux disease who stop smoking.     

Onychomycosis: diagnosis and systemic treatment

Onychomycosis, a persistent fungal infection affecting the toenails and fingernails, can interfere with standing, walking, and exercising. Associated physical impairments can result in paresthesia, pain, discomfort, and loss of manual dexterity. Patients may also suffer from loss of self-esteem and social interaction. A definitive diagnosis is crucial for effective treatment, because many other skin and nail disorders mimic onychomycosis. Diagnosis involves microscopic potassium hydroxide preparation, cultures, nail biopsy, and histologic analysis. Treatment can include topical and systemic antifungal therapies as well as nonpharmaceutical methods. This paper discusses pathophysiology, diagnosis, and treatment options for this common nail dystrophy, including the newer antifungal medications now available.     

Extracellular nucleotide signaling in the inner ear

Extracellular nucleotides, particularly adenosine 5'-triphosphate (ATP), act as signaling molecules in the inner ear. Roles as neurotransmitters, neuromodulators, and as autocrine or paracrine humoral factors are evident. The diversity of the signaling pathways for nucleotides, which include a variety of ATP-gated ion channels (assembled from different subtypes of P2X-receptor subunit) and also different subtypes of G protein-coupled nucleotide receptors (P2Y receptors) supports a major physiological role for ATP in the regulation of hearing and balance. Almost invariably both P2X and P2Y receptor expression is apparent in the complex tissue structures associated with the inner-ear labyrinth. However P2X-receptor expression, commonly associated with fast neurotransmission, is apparent not only with the cochlear and vestibular primary afferent neurons, but also appears to mediate humoral signaling via ATP-gated ion channel localization to the endolymphatic surface of the cochlear sensory epithelium (organ of Corti). This is the site of the sound-transduction process and recent data, including both electrophysiological, imaging, and immunocytochemistry, has shown that the ATP-gated ion channels are colocalized here with the mechano-electrical transduction channels of the cochlear hair cells. In contrast to this direct action of extracellular ATP on the sound-transduction process, an indirect effect is apparent via P2Y-receptor expression, prevalent on the marginal cells of the stria vascularis, a tissue that generates the standing ionic and electrical gradients across the cochlear partition. The site of generation of these gradients, including the dark-cell epithelium of the vestibular labyrinth, may be under autocrine or paracrine regulation mediated by P2Y receptors sensitive to both purines (ATP) and pyrimidines such as UTP. There is also emerging evidence that the nucleoside adenosine, formed as a breakdown product of ATP by the action of ectonucleotidases and acting via P1 receptors, is also physiologically significant in the inner ear. P1-receptor expression (including A1, A2, and A3 subtypes) appear to have roles associated with stress, acting alongside P2Y receptors to enhance cochlear blood flow and to protect against the action of free radicals and to modulate the activity of membrane conductances. Given the positioning of a diverse range of purinergic-signaling pathways within the inner ear, elevations of nucleotides and nucleosides are clearly positioned to affect hearing and balance. Recent data clearly supports endogenous ATP- and adenosine-mediated changes in sensory transduction via a regulation of the electrochemical gradients in the cochlea, alterations in the active and passive mechanical properties of the cells of the sensory epithelium, effects on primary afferent neurons, and control of the blood supply. The field now awaits conclusive evidence linking a physiologically-induced modulation of extracellular nucleotide and nucleoside levels to altered inner ear function.     

Repair processes in human cultured cells upon exposure to nickel salts and their modification

PURPOSE: To describe four cases of delusions of parasitosis in which self-inflicted ocular trauma occurred. Delusions of parasitosis is a somatic delusional disorder in which patients have the irrational belief that their bodies are infested by parasites or other infectious organisms. Self-inflicted trauma can result from attempts to eliminate the supposed infestation. METHODS: We reviewed the case histories of four patients (one male, three females, 35 to 45 years of age) who presented with complaints of ocular infestation but had no evidence of infectious ocular disease. The characteristics of these cases were compared with the features of delusions of parasitosis. RESULTS: All patients maintained their beliefs regarding infestation, despite extensive clinical and laboratory investigations that found no evidence of infectious diseases. Self-inflicted eye injury, associated with attempts to eliminate the infestation, occurred in each case. CONCLUSIONS: The cases presented in this report are consistent with a diagnosis of delusions of parasitosis. The eye can be a principal focus of attention in this disorder, which may lead to vision loss caused by self-inflicted injury.     

Two high-resolution crystal structures of the recombinant N-lobe of human transferrin reveal a structural change implicated in iron release

The N-lobe of human serum transferrin (hTF/2N) has been expressed in baby hamster kidney cells and crystallized in both orthorhombic (P212121) and tetragonal (P41212) space groups. Both crystal forms diffract to high resolution (1.6 and 1.8 A, respectively) and have been solved by molecular replacement. Subsequent refinement resulted in final models for the structure of hTF/2N that had crystallographic R-factors of 18.1 and 19.7% for the two crystal forms, respectively; these models represent the highest-resolution transferrin structures determined to date. The hTF/2N polypeptide has a folding pattern similar to those of other transferrins, including the presence of a deep cleft that contains the metal-binding site. In contrast to other transferrins, both crystal forms of hTF/2N display disorder at the iron-binding site; model building suggests that this disorder consists of alternative conformations of the synergistically bound carbonate anion, the side chain for Arg-124, and several solvent molecules. Subsequent refinement revealed that conformation A has an occupancy of 0.63-0. 65 and corresponds to the structure of the iron-binding site found in other transferrins. The alternative conformation B has an occupancy of 0.35-0.37; in this structure, the carbonate has rotated 30 degrees relative to the iron and the side chain for Arg-124 has moved to accommodate the new carbonate position. Several water molecules appear to stabilize the carbonate anion in the two conformations. These structures are consistent with the protonation of the carbonate and resulting partial removal of the anion from the metal; these events would occur prior to cleft opening and metal release.     

Abiotic nitrogen reduction on the early Earth

The production of organic precursors to life depends critically on the form of the reactants. In particular, an environment dominated by N2 is far less efficient in synthesizing nitrogen-bearing organics than a reducing environment rich in ammonia. Relatively reducing lithospheric conditions on the early Earth have been presumed to favour the generation of an ammonia-rich atmosphere, but this hypothesis has not been studied experimentally. Here we demonstrate mineral-catalysed reduction of N2, NO2- and NO3- to ammonia at temperatures between 300 and 800 degrees C and pressures of 0.1-0.4 GPa-conditions typical of crustal and oceanic hydrothermal systems. We also show that only N2 is stable above 800 degrees C, thus precluding significant atmospheric ammonia formation during hot accretion. We conclude that mineral-catalysed N2 reduction might have provided a significant source of ammonia to the Hadean ocean. These results also suggest that, whereas nitrogen in the Earth's early atmosphere was present predominantly as N2, exchange with oceanic, hydrothermally derived ammonia could have provided a significant amount of the atmospheric ammonia necessary to resolve the early-faint-Sun paradox.     

Pharmaceutical development and specification of stereoisomers

The pharmaceutical development of chiral drugs requires the activities of many different research and development groups. Guidelines which help to coordinate the activities of these groups and assist in the successful development of compounds with either single or multiple chiral centers are outlined and discussed.