Sodium salicylate centrally augments ventilation through cholinergic mechanisms.

Several different stimuli, including hydrogen ions, may exert their effect on central ventilatory control through cholinergic mechanisms. Salicylates are known to be central respiratory stimulants. Therefore this study explored whether the ventilatory effect of sodium salicylate (SAL) is through cholinergic mechanisms. Ventriculocisternal perfusion was used in spontaneously breathing anesthetized (pentobarbital sodium, 30 mg/kg) mongrel dogs to study the effects of SAL (50 mM), atropine (ATR, 4.8 mM), and SAL-ATR on ventilation. After 15 min of perfusion with mock cerebrospinal fluid, each test agent was perfused for 15 min at a rate of 1 ml/min. Cardiovascular and ventilatory parameters were monitored. Values at 15 min of test agent perfusion were compared with values at 15 min of mock cerebrospinal fluid perfusion, with each animal used as its own control. Body temperature was kept between 37.5 and 39.0 degrees C. Perfusion with SAL increased minute ventilation (VE) by 54% (P less than 0.005) and respiratory frequency by 50% (P less than 0.005). Tidal volume was not changed, but mean inspiratory flow rate increased (P less than 0.05). Perfusion with ATR decreased VE by 22% (P less than 0.1), and perfusion with SAL-ATR decreased VE by 20% (P = 0.01). No significant cardiovascular changes were noted in any group. We conclude that SAL increases VE centrally, primarily by increasing respiratory frequency. Because ATR blocked this effect, cholinergic mechanisms are probably involved in the salicylates' central stimulation of ventilation.     

Glutamic acid and gamma-aminobutyric acid neurotransmitters in central control of breathing.

We review recent cross-disciplinary experimental and theoretical investigations on metabolism of the amino acid neurotransmitters glutamic acid and gamma-aminobutyric acid (GABA) in the brain during hypoxia and hypercapnia and their possible role in central control of breathing. The roles of classical modifiers of central chemical drive to breathing (H+ and cholinergic mechanisms) are summarized. A brief perspective on the current widespread interest in GABA and glutamate in central control is given. The basic biochemistry of these amino acids and their roles in ammonia and bicarbonate metabolism are discussed. This review further addresses recent work on central respiratory effects of inhibitory GABA and excitatory glutamate. Current understanding of the sites and mechanisms of action of these amino acids on or near the ventral surface of the medulla is reviewed. We focus particularly on tracer kinetic investigations of glutamatergic and GABAergic mechanisms in hypoxia and hypercapnia and their possible role in the ventilatory response to hypoxia. We conclude with some speculative remarks on the critical importance of these investigations and suggest specific directions of research in central mechanisms of respiratory control.     

Clinical spectrum and carrier state of nontyphoidal salmonella infections in infants and children

A study was done of 117 children with nontyphoidal salmonellosis from the clinic and inpatient populations of The Montreal Children''s Hospital. Uncomplicated gastroenteritis was the most common clinical presentation and the mean duration of illness was 8.7 days. Eleven (24%) of 45 patients tested had bacteremia; retrospective analysis of these patients did not reveal major differences in clinical presentation, laboratory findings, underlying disease or complications when compared with the patients from whom blood cultures were not taken. There were no complications in any of the patients and no deaths. Prolonged stool carriage beyond eight weeks was not a problem except in infants under the age of 3 months, of whom 27% were carriers eight weeks after the onset of illness. Antibiotic therapy was not effective in treating the acute illness and seemed to prolong carriage in young infants.     

Mechanism of activation of bovine kidney pyruvate dehydrogenase a kinase by malonyl-CoA and enzyme-catalyzed decarboxylation of malonyl-CoA

The activity of the pyruvate dehydrogenase kinase, which phosphorylates and thereby inactivates the pyruvate dehydrogenase complex, was stimulated by malonyl-CoA. Treatment with [2-14C]malonyl-CoA resulted in acylation of sites in the complex. Both acylation and activation of kinase activity increased in a time-dependent manner with a parallel increase in those activities when the malonyl-CoA:CoA ratio was varied. Protein-bound acyl groups were labilized by performic acid treatment indicating their attachment to protein at thiol residues; however, the product released was volatile, which is not characteristic of malonic acid. While malonyl-CoA was initially free of acetyl-CoA, stimulation of kinase activity and acylation of sites in the complex by malonyl-CoA were shown to be contingent upon enzyme-catalyzed decarboxylation. Decarboxylation appeared to be catalyzed by a trace contaminant present in highly purified preparations of both the pyruvate and 2-oxoglutarate dehydrogenase complexes. Under conditions in which both free CoA was removed (by conversion to succinyl-CoA) and then, after various periods, free acetyl-CoA was removed (by enzymic conversion to acetyl phosphate), both acetylation of sites in the complex and activation of kinase activity increased in a time-dependent manner. Concomitantly there was a decrease in the concentration dependence for activation of the kinase by malonyl-CoA. Our results strongly support the conclusion that activation of kinase activity is associated with acylation of sites in the complex, and that, in the case of malonyl-CoA, those processes depend on enzyme-catalyzed decarboxylation.