Antagonism by theophylline of respiratory inhibition induced by adenosine

The effects on respiration of an analogue of adenosine, L-2-N6-(phenylisopropyl)adenosine (PIA), and of the methylxanthine, theophylline, were determined in 19 vagotomized glomectomized cats whose end-tidal PCO2 was kept constant by means of a servo-controlled ventilator. Integrated phrenic nerve activity was used to represent respiratory output. Our results show that PIA, whether given systemically or into the third cerebral ventricle, depressed respiration. Systemically administered theophylline stimulated respiration. Theophylline given intravenously, or into the third ventricle not only reversed the depressive effects of previously administered PIA but caused further increases of respiration above the control level. Prior systemic administration of theophylline blocked both respiratory and hypotensive effects of subsequently administered PIA. Effects of either agent on medullary extracellular fluid pH did not explain the results. We conclude that the adenosine analogue PIA, acts to inhibit neurons in the brain that are involved in the control of respiration and that its effects are blocked by theophylline. We suggest that adenosine acts as a tonic modulator of respiration and that theophylline stimulates breathing by competitive antagonism of adenosine at neuronal receptor sites.     

Beta 2-receptors in the rat anterior pituitary mediate adrenergic stimulation of prolactin release

As previously shown, the beta-adrenergic agonists isoproterenol, epinephrine and norepinephrine stimulate prolactin (PRL) release from superfused rat anterior pituitary cell aggregates. In order to further characterize the beta-adrenergic response in this tissue preparation, the effects of various beta-adrenergic agents were investigated. The beta 2-agonist, zinterol, stimulated PRL release at concentrations more than 4 orders of magnitude lower than prenalterol, a beta 1-agonist with high potency in rat heart. The order of potency of the antagonists IPS 339 (beta 2), ICI 118.551 (beta 2), propranolol, sotalol, practolol (beta 1), metoprolol (beta 1) and H 35/25 for inhibition of beta-agonist-stimulated PRL release provided additional support for a beta 2-stimulatory effect. beta-Agonists were also capable of stimulating PRL release from superfused intact pituitaries. The beta-adrenergic response desensitized rapidly during prolonged exposure of the aggregates to beta-agonists.     

Spatially resolved cytosolic calcium response to angiotensin II and potassium in rat glomerulosa cells measured by digital imaging techniques

The response of cytosolic calcium [Ca2+]i to angiotensin II (AII) and potassium (K+) in individual rat glomerulosa cells was determined using the calcium-sensitive fluorescent dye, fura-2 and digital imaging. Control (4 mM K+) cytosolic calcium levels were generally in the 80-120 nM range and increased monotonically as [K+] was increased from 4 to 12 mM. There was no delay in the onset of the response. In most cells the [Ca2+]i decreased from its peak after 3-4 min, even in the presence of superfusate containing elevated K+. The time course of the change in [Ca2+]i in response to AII stimulation, on the other hand, was more variable. It was most often characterized by an early decrease followed by a large delayed increase. The response also was observed to decline during sustained AII stimulation. The majority of the cells showed some response to one or the other secretagogue with a sizeable minority (25%) having an increase in [Ca2+]i in excess of 200%. While the majority showed a response, the cell to cell variation was substantial. Finally, the pattern of cytosolic calcium increase sometimes showed a marked dependence on the secretagogue used, with different regions of the same cell being more strongly affected by one agent or the other. A few cells (10%) responded to AII only at one pole, establishing a large concentration gradient of calcium across the cell. Because of differences in time course, pattern, and degree of responsiveness, it is likely that the mechanisms underlying the Ca2+ elevation with K+ and AII are different.     

PATTERNS OF REPRODUCTION IN THREE SANDY BEACH WHELKS OF THE GENUS BULLIA GRIFFITH

The breeding cycles of two species of sandy beach whelk (Bulliadigitalis and B. pura) are presented and compared with a thirdspecies (B. rhodostoma). In all three species, egg maturationand copulation occur in spring while summer marks the depositionand spawning of egg capsules. B. digitalis and B. pura migrateoffshore to lay their eggs, the juveniles of both species restrictingthemselves to beyond the breaker zone. Newly hatched snailsof B. rhodostoma appear in the intertidal towards late summer.The discovery of a penis-like structure on females of B. rhodostomais investigated. The pseudopenis was also found on B. pura butnever on B. digitalis. The possibility of a sex-change was eliminatedon the histological investigation of the gonads of a range ofsnails and the examination of sex-ratios over a period of fivemonths. General trends in reproductive behaviour are also discussed. (Received 18 March 1984;     

Controlled trial of methylprednisolone pulses and low dose oral prednisone for the minimal change nephrotic syndrome.

In a multicentre, randomised, prospective trial 89 patients (67 children and 22 adults) with the minimal change nephrotic syndrome were treated with three intravenous pulses of methylprednisolone followed by low dose oral prednisone for six months (group given methylprednisolone) or with high dose oral prednisone for four weeks followed by low dose oral prednisone for five months (control group). Five patients in the group given methylprednisolone and one in the control group did not respond initially. The time to response was shorter in children treated with methylprednisolone. No significant differences between the two groups were observed in the number of patients who relapsed or number of relapses per patient per year. Patients given methylprednisolone tended to relapse earlier than patients in the control group. Side effects related to treatment were significantly fewer in the group given methylprednisolone than in the control group. These data suggest that a short course of methylprednisolone pulses followed by low dose oral prednisone is only marginally less effective than a regimen of high dose oral steroids but can improve the ratio of risk to benefit associated with treatment of the minimal change nephrotic syndrome.     

Nucleic acid relationships among Acholeplasma species.

3H-labeled Acholeplasma DNA probes were generated in vitro by the nick-translation method and used to determine the nucleotide sequence homology among the type strains of the eight currently recognized species of Acholeplasma. Very little nucleotide sequence homology (less than or equal to 18%) was found among the eight species, with heteroduplexes showing at least 12% or more mismatching as determined by thermal elution midpoints. The small amount of nucleotide sequence homology among the eight species indicates that these species are quite distinct and are not closely related to each other genomically.     

Monosomy 21: a new case confirmed by in situ hybridization

Summary A new case of total monosomy 21 in a newborn is described. The diagnosis was first made using the cytogenetic data; it was then confirmed by the dosage of copper-superoxide dismutase (SOD-1) which showed a 50% decrease. In situ hybridization with a probe previously assigned to chromosome 21 was used to rule out the possibility of a partial monosomy with an unbalanced reciprocal translocation.     

Influence of arm position on measurement of blood pressure.

A series of measurements of blood pressure in normotensive and hypertensive subjects showed that measurements made with a sphygmomanometer with the arm dependent by the side were consistently higher than those made with the arm horizontal at heart level. The mean difference in a group of 90 hypertensive outpatients was 11/12 mm Hg. Failure to appreciate the importance of arm position may lead to erroneous measurements of blood pressure. This has important implications for clinical practice and research.