Long-acting dihydropyridine calcium antagonists. 1. 2-Alkoxymethyl derivatives incorporating basic substituents

A series of dihydropyridines substituted at the 2-position by basic side chains are described and their potencies as calcium antagonists listed. One compound, 2-[(2-aminoethoxy)methyl]-4-(2-chlorophenyl)-3-ethoxycarbonyl-5- methoxycarbonyl-6-methyl-1,4-dihydropyridine (17, amlodipine) was found to be comparable in potency to nifedipine and to have an elimination half-life of 30 h in dogs. Oral bioavailability approached 100%, and hemodynamic responses were gradual in onset and long-lasting in effect. The two enantiomers have been prepared, and the bulk of the activity was found to reside with the (-) isomer, 18. X-ray crystallographic studies, carried out on a close analogue of 17, suggest the existence of a weak hydrogen bond between the side-chain oxygen and the proton on the ring nitrogen.     

The role of Na+/K+ ATPase activity during low flow ischemia in preventing myocardial injury: A 31P, 23Na and 87Rb NMR spectroscopic study

An increase in intracellular Na⁺ during ischaemia has been associated with myocardial injury. In this study, we determined whether inhibition of Na⁺/K⁺ ATPase activity contributes to this increase and whether Na⁺/K⁺ ATPase activity can be maintained by provision of glucose to perfused rat hearts during low flow, 0.5 ml/min, ischemia. We used ³¹P NMR spectroscopy to determine changes in myocardial energetics and intracellular and extracellular volumes. ²³Na NMR spectroscopy, with DyTTHA^3- present as a shift reagent, was used to measure changes in intracellular Na⁺ and ⁸⁷Rb NMR spectroscopy was used to estimate Na⁺/K⁺ ATPase activity from Rb⁺ influx rates, Rb⁺ being an NMR-sensitive congener of K⁺. In hearts provided with 11 mM glucose throughout ischemia, glycolysis continued and ATP was twofold higher than in hearts without glucose. In the glucose-hearts, Rb⁺ influx rate was threefold higher, intracellular Na⁺ was fivefold lower at the end of ischemia and functional recovery during reperfusion was twofold higher. We propose that continuation of glycolysis throughout low flow ischemia allowed maintenance of sufficient Na⁺/K⁺ ATPase activity to prevent the increase in intracellular Na⁺ that would otherwise have led to myocardial injury.     

The immediate consequences of middle cerebral artery occlusion on GABA synthesis in mouse cortex and cerebellum.

The effect on gamma-aminobutyric acid (GABA) synthesis of focal ischaemia in the right cortex of the mouse was investigated by performing a right middle cerebral artery (MCA) occlusion. Synthesis of GABA was determined by measurement of the rate of GABA accumulation in tissue following injection of amino oxyacetic acid (AOAA; 30 mg/kg, i.p.). Five min following the MCA occlusion, the rate of GABA synthesis in the right (ischaemic) cortex was decreased by approximately 70% compared to either the left cortex or the right cortex of untreated controls. The basal GABA concentration was however unaffected. Four hours after the occlusion the rate of GABA synthesis was similar in the right and left cortex. The rate of GABA accumulation in the cerebellum was unchanged at both times after the right MCA occlusion compared with untreated control mice. The data suggest that there is a rapid but short lasting decrease in GABA synthesis following an ischaemic insult and it is suggested that this might be associated with the EEG spiking activity that occurs at this time.     

The effect of carbon dioxide in the airways and alveoli on ventilation; a vagal reflex studied in the dog

1. The inhalation of CO(2) produces a tachypnoea only in the presence of intact vagus nerves; the present study was designed to examine the mechanism of this phenomenon in the dog.2. Closed-chest cardiopulmonary bypass was established in dogs weighing 16-24 kg, anaesthetized with chloralose. When the ;bypass' was established pulmonary blood flow ceased, P(A, CO2) was reduced and the respiratory rate slowed. 3-10% CO(2) in O(2) could then be inhaled without change in the level of P(a, CO2) set at the oxygenator.3. The addition of CO(2) in these concentrations to the inspired oxygen resulted in an increase in respiratory frequency, maximal at the first breath and sustained for the 1 min period of exposure. The increase in respiratory frequency was due to a shortening of expiratory duration. Inspiratory duration did not change. The response was absent after vagotomy.4. Inert gases in O(2), given as a control, had no effect on breathing.5. The effect of raising P(a, CO2) (by increasing the concentration of CO(2) in the gas equilibrating the blood in the oxygenator), was primarily to increase tidal volume.6. The ventilatory effect of inspiring CO(2)/O(2) mixtures was shown to be additive to the effect of raising P(a, CO2).7. These experiments show that an afferent vagal reflex originating from the lungs causes tachypnoea, when a dog, on ;bypass', inhales low concentrations of CO(2) in O(2).     

Value systems and delinquency: parental and generational discrepancies in value systems for delinquent and non-delinquent boys.

A sample of 82 delinquent boys in two institutions and a matched sample of 82 nondelinquent boys from three secondary schools ranked values from the Rokeach Value Survey in their order of importance for self, mother and father. Order of rankings was counter-balanced. Results indicated that the sets of rankings (value systems) were more discrepant between boys and their parents and between the parents themselves in the delinquent sample than in the non-delinquent sample, but only in regard to the set of terminal values. Marked differences in the relative importance of particular values occurred between the two groups both in relation to rankings for self and for parents, and (for both groups) between the boys and their parents (generational) and between mother and father (parental). Favourability towards father correlated positively with degree of value similarity between sons and fathers but only for the terminal values.     

Rapid identification of Candida dubliniensis using a species-specific molecular beacon

Candida dubliniensis is an opportunistic fungal pathogen that has been linked to oral candidiasis in AIDS patients, although it has recently been isolated from other body sites. DNA sequence analysis of the internal transcribed spacer 2 (ITS2) region of rRNA genes from reference Candida strains was used to develop molecular beacon probes for rapid, high-fidelity identification of C. dubliniensis as well as C. albicans. Molecular beacons are small nucleic acid hairpin probes that brightly fluoresce when they are bound to their targets and have a significant advantage over conventional nucleic acid probes because they exhibit a higher degree of specificity with better signal-to-noise ratios. When applied to an unknown collection of 23 strains that largely contained C. albicans and a smaller amount of C. dubliniensis, the species-specific probes were 100% accurate in identifying both species following PCR amplification of the ITS2 region. The results obtained with the molecular beacons were independently verified by random amplified polymorphic DNA analysis-based genotyping and by restriction enzyme analysis with enzymes BsmAI and NspBII, which cleave recognition sequences within the ITS2 regions of C. dubliniensis and C. albicans, respectively. Molecular beacons are promising new probes for the rapid detection of Candida species.     

The architecture of variant surface glycoprotein gene expression sites in Trypanosoma brucei

Trypanosoma brucei evades the immune system by switching between Variant Surface Glycoprotein (VSG) genes. The active VSG gene is transcribed in one of approximately 20 telomeric expression sites (ESs). It has been postulated that ES polymorphism plays a role in host adaptation. To gain more insight into ES architecture, we have determined the complete sequence of Bacterial Artificial Chromosomes (BACs) containing DNA from three ESs and their flanking regions. There was variation in the order and number of ES-associated genes (ESAGs). ESAGs 6 and 7, encoding transferrin receptor subunits, are the only ESAGs with functional copies in every ES that has been sequenced until now. A BAC clone containing the VO2 ES sequences comprised approximately half of a 330 kb 'intermediate' chromosome. The extensive similarity between this intermediate chromosome and the left telomere of T. brucei 927 chromosome I, suggests that this previously uncharacterised intermediate size class of chromosomes could have arisen from breakage of megabase chromosomes. Unexpected conservation of sequences, including pseudogenes, indicates that the multiple ESs could have arisen through a relatively recent amplification of a single ES.