Prolongation in expiration evoked from ventrolateral pons of adult rats

Jodkowski, Józef S., Sharon K. Coles, and Thomas E. Dick. Prolongation in expiration evoked from ventrolateral pons ofadult rats. J. Appl. Physiol. 82(2):377-381, 1997.Activation of neurons in the ventrolateral (vl)pons was hypothesized to alter the breathing pattern becauseprevious studies demonstrated apneusis after inhibitingneuronal activity with bilateral muscimol (10 mM) microinjectionsinto the vl pons (17). The excitatory amino acid L-glutamate (10 mM) was microinjected(10-100 nl) into the vl pons in anesthetized, vagotomized,paralyzed, and ventilated adult rats(n = 8). In four of these animals, thetarget site was approached from the ventral surface of the pons toavoid penetrating the dorsolateral (dl) pons. The expiratory phase wasprolonged transiently and concurrently with the microinjection. Thelocation of the injection sites included the A5 area, was independentof the approach, and was distinct from the dl pons. These results complement our previous data and indicate that neurons located in thevl pons influence respiration specifically by prolonging expirationwhen activated and by delaying the inspiratory-to-expiratory phasetransition when inhibited.

     

Mechanism of the gas-phase decomposition of trifluoro-, trichloro-, and tribromomethanols in the presence of hydrogen halides

Ab initio calculations at the G2 level were used in a theoretical analysis of the kinetics of the decomposition of trifluoro-, trichloro-, and tribromomethanols. The high-pressure limiting rate coefficients k_diss,∞ for the thermal dissociation of CF₃OH, CCl₃OH, and CBr₃OH were calculated using the conventional transition state theory. The results of potential surface calculations show that in the presence of the hydrogen halides HX (X = F, Cl, and Br), considerably lower energy pathways are accessible for the decomposition of CF₃OH, CCl₃OH, and CBr₃OH. The mechanism of the reactions appears to be complex and consists of three consecutive elementary processes with the formation of pre- and post-reaction adducts. The presence of hydrogen halides considerably decreases the energy barrier for the bimolecular decomposition of the alcohols CF₃OH, CCl₃OH, and CBr₃OH. Results of this study indicate that hydrogen halides can considerably accelerate the homogeneous decomposition of perhalogenated methanols when they are present in the reaction area at sufficiently high concentrations. However, the atmospheric concentrations of hydrogen halides are too small for efficient removal of atmospheric CF₃OH, CCl₃OH, and CBr₃OH.     

Influences from laryngeal afferents on expiratory bulbospinal neurons and motoneurons

The purpose of this study is to analyze the reflex effects of laryngeal afferent activation on respiratory patterns in anesthetized, vagotomized, paralyzed, ventilated cats. We recorded simultaneously from the phrenic nerve, T10 internal intercostal nerve, and single bulbospinal expiratory neurons of the caudal ventral respiratory group (VRG). Laryngeal afferents were activated by electrical stimulation of the superior laryngeal nerve (SLN) or by cold-water infusion into the larynx. Both types of stimuli caused inhibition of phrenic activity and facilitation of internal intercostal nerve activity, indicating expiratory effort. The activity of 46 bulbospinal expiratory cells was depressed during SLN electrical stimulation, and 13 of them were completely inhibited. In 44 of 56 neurons tested, mean firing frequency (FFmean) was decreased in response to cold-water infusion and 8 others responded with increased FFmean; in the remaining 4 neurons, FFmean was unchanged. Possible reasons for different neuronal responses to SLN electrical stimulation and water infusion are discussed. We conclude that bulbospinal expiratory neurons of VRG were not the source of the reflex motoneuronal expiratory-like activity produced by SLN stimulation. Other, not yet identified inputs to spinal expiratory motoneurons are activated during this experimental condition.     

Theoretical study of the kinetics and mechanism of the decomposition of trifluoromethanol, trichloromethanol, and tribromomethanol in the gas phase

Ab initio calculations at the G2 level were used in a theoretical analysis of the kinetics of unimolecular and water-accelerated decomposition of the halogenated alcohols CX₃OH (X = F, Cl, and Br) into CX₂O and HX. The calculations show that reactions of the unimolecular decomposition of CX₃OH are of no importance under atmospheric conditions. A considerably lower energy pathway for the decomposition of CX₃OH is accessible by homogenous reactions between CX₃OH and water. It is shown that CX₃OH + H₂O reactions proceed via the formation of intermediate complexes. The mechanism of the reactions appears to be complex and consists of three consecutive elementary processes. The calculated values of the second-order rate constants are of 2.5 × 10⁻²¹, 2.1 × 10⁻¹⁹, and 1.2 × 10⁻¹⁷ cm³molecule⁻¹s⁻¹ at 300 K for CF₃OH + H₂O, CCl₃OH + H₂O, and CBr₃OH + H₂O, respectively. The theoretically derived atmospheric lifetimes of the CX₃OH molecules indicate that the water-mediated decomposition reactions CX₃OH + H₂O may be the most efficient process of CF₃OH, CCl₃OH, and CBr₃OH loss in the atmosphere.     

Conformational analysis of flephedrone using quantum mechanical models

Flephedrone is an analogue of cathinone - chemically similar to ephedrine, cathine and other amphetamines. Conformations of all isomers of flephedrone have been studied at the quantum-chemical level. Calculations have been performed using DFT and MP2 methods with two basis sets - 6-31G and 6-31G(d,p). Results show that there are low energy conformers for the ortho, meta, and para isomers that are connected by way of low-barrier transition states. Boltzmann distribution of population predicts the highest population for the 1-meta conformer with a 10 % increase in solution. The molecular electrostatic potential surface data for each molecule has been calculated revealing likely reaction sites.