No abstract is provided for this article.
An isocratic high pressure liquid Chromatographic system was developed for the estimation of purine nucleosides and oxypurines in blood. Use was made of a reversed-phase column. Nucleotides derived from erythrocytes affected the separation; these compounds were removed with Al2O3. The recovery of the whole clean-up procedure exceeded 75%, and the lower detection limit of the assay for blood metabolites was 0.1 μmol/l. In 6 healthy volunteers, non-resting, the following blood concentrations (mean values ± S.D. in μmol/l) were observed: adenosine (< 0.1), inosine (0.2 ± 0.1), hypoxanthine (2.2 ± 1.3) and xanthine (0.2 ±0.1). In plasma and serum the total amount of these compounds was 1.9 and 5.4 times higher, respectively, presumably due to nucleotide breakdown during blood processing. The myocardial arterial-venous differences of blood purine nucleosides, oxypurines and lactate were subsequently measured in blood samples from 13 patients with angiographically documented ischemic heart disease, undergoing an atrial pacing stress test. No significant release of adenosine, inosine and xanthine by the heart was detectable in this study. The myocardial arterial-venous difference of lactate changed from 0.01 ± 0.03 mmol/1 (mean ± SEM) at rest, to −0.10 ± 0.04 mmol/1 during pacing (p < 0.002). Relatively larger changes were observed for hypoxanthine: pacing increased the arterial-venous difference from −0.01 ± 0.05 to −0.51 ± 0.17 μmol/1 (p <0.02). We conclude that the high pressure liquid chromatographic assay of blood hypoxanthine is a useful tool in the diagnosis of ischemic heart disease.
Abstract The sections in this article are: Sympathetic Nervous System Sympathetic Innervation Circulating Catecholamines β‐Receptors α‐Receptors Nonadrenergic Inhibitory Nervous System Parasympathetic Nervous System General Considerations Altered Parasympathetic Activity Studies of Asthmatic Patients Conclusion
We have investigated the effects of chlorpheniramine, atropine and capsaicin pretreatment on inhaled sodium metabisulphite (MBS)‐induced airway microvascular leakage and bronchoconstriction in anaesthetized guinea‐pigs in order to clarify the mechanisms involved in these responses. The effects of frusemide and nedocromil sodium were also examined. Lung resistance (R L ) was measured for 6 min after inhalation of MBS (20, 40, 80 and 200 m m ; 30 breaths), followed by measurement of extravasation of Evans blue dye into airway tissues, used as an index of airway microvascular leakage. MBS caused an increase in R L and leakage of dye at all airway levels in a dose‐dependent manner. Chlorpheniramine (10 mg kg −1 , i.v.), atropine (1 mg kg −1 , i.v.), their combination or inhaled nedocromil sodium (10 mg ml −1 , 7 min) had no effect against the airway microvascular leakage induced by 80 m m MBS (30 breaths). Capsaicin pretreatment (50 mg kg −1 , s.c.) caused a significant decrease in the leakage of dye in the main bronchi and inhaled frusemide (10 mg ml −1 , 7 min) also in the main bronchi and proximal intrapulmonary airway. Chlorpheniramine, atropine, their combination, capsaicin pretreatment and frusemide, but not nedocromil sodium, inhibited significantly the peak R L induced by 80 m m MBS (30 breaths) by approximately 50%. We conclude that a cholinergic reflex and neuropeptides released from sensory nerve endings may participate in the mechanisms of MBS‐induced airway responses. Frusemide but not nedocromil sodium may have an inhibitory effect on these neural mechanisms. The inhibitory effect of nedocromil sodium against lower doses of MBS is not excluded.
An analytical pilot model for interactive buckling in sandwich struts with cores made from a functionally graded material based on total potential energy principles is presented. Using a Timoshenko beam approach, a system of nonlinear differential and integral equations is derived that predicts critical and secondary instabilities. These are validated against numerical simulations performed within the commercial finite-element package Abaqus. Good agreement is found, and this offers encouragement for more elaborate models to be devised that can account for face-core delamination—a feature where functionally graded materials are known to offer distinct advantages.
