Cytology of β-cells in rabbit pancreas pieces incubatedin vitro; Effects of glucose and tolbutamide

Summary The electron microscopic appearances of rabbit pancreas -cells takenin vivo and afterin vitro incubation have been compared and the effects of high glucose and tolbutamide stimulation of insulin releasein vitro on -cell cytomorphology investigated. Normal structure was maintained onin vitro incubation in a proportion of -cells; this varied in different samples from 35–100 per cent. The cause of this variation was not apparent but it was not influenced by the time of incubation, medium glucose concentration or tolbutamide. Quantitative measurements have been made of the proportion of -cell profiles showing marginal distribution of granules, of the number of contacts between granule sac membranes and the plasma membrane, of the number of granule sacs showing perforations, of the population density of specific secretion granules, lysosomes and autophagic bodies, and estimates have been made of the extent of the Golgi apparatus in cross section. No consistent change in these parameters was observed following stimulation of insulin release with glucose or tolbutamide. There was no evidence in any of the specimens examined of continuity between the interior of a granule sac and the outside of a -cell. Calculations based on the rate of release of insulin and the insulin content of the pancreas indicate that the chance of visualising granule extrusion by electron microscopy is small. The significance of these results in relation to the emiocytosis theory of insulin release (Lacy andHartroft) is discussed.Supported by grants from the Wellcome Trust (to J.D.L.) and the Medical Research Council and British Diabetic Association (to P.J.R.).     

Positive chronotropic effect,of ouabain in the excised and blood-perfused canine SA node preparation of the dog

Summary The effect of ouabain on the sinus rate was investigated in excised and blood-perfused canine SA node preparations which had 101±3 regular beats/min (mean±S.E., N=46) and 3.2±0.3 ml/min of blood flow through the sinus node artery. When ouabain was rapidly injected in a wide range of doses from 0.3 to 30 g into the sinus node artery, it caused a dose-dependent acceleration of the regular sinus rate without any latency. The positive chronotropic response to ouabain was not blocked by tetrodotoxin, -adrenoceptor blocking agents such as propranolol and alprenolol, or pretreatment with reserpine. These observations suggest that the ouabain-induced acceleration is not mediated through adrenergic mechanism. Although a decrease of sinus rate by 7.3±2.3% (mean±S.E., N=6) of the control level was induced by MnCl₂ infusion at a rate of 30 or 60 g/min, the acceleration response to ouabain was selectively blocked by MnCl₂ while that to noradrenaline was not modified. These results suggest that ouabain causes an increase of influx of Ca ions across the membrane of the SA nodal pacemaker cell, resulting in the acceleration response, and that this increase of Ca ion influx is probably linked with potassium and/or sodium permeability in the slow diastolic depolarization.     

Effects of compound 48/80 on mast cells,histamine and cyclic AMP in isolated superior cervical ganglia

Summary Superior cervical ganglia of the rat contain mast cells which are sensitive to degranulation by compound 48/80. The granulation process is shown to the independent of the ATP content of the ganglion. Compound 48/80 released histamine into the incubation medium, thereby decreasing the histamine content of the ganglia. Moreover, the release of ³H-noradrenaline was accelerated by the compound. Histamine and adrenaline induced a rapid accumulation of cyclic AMP in the ganglia. This effect of the amines was specifically blocked by diphenhydramine or propranolol with an ID₅₀ of 1.5×10^–9 M and 2.2×10^–7 M, respectively.In contrast to other findings with isolated mast cell preparations, compound 48/80 induced a rapid and marked accumulation of cyclic AMP in intact ganglia and an enhanced release of cyclic AMP into the incubation fluid. Diphenhydramine prevented the accumulation in the tissue but only partly inhibited the enhanced appearance of cyclic AMP in the medium. The accumulation of the cyclic nucleotide in the tissue was partly blocked by propranolol, suggesting an additional action of compound 48/80 on cyclic AMP through catecholamines.The cyclic nucleotide phosphodiesterase activity in homogenates of superior cervical ganglia was completely inhibited by compound 48/80 at 7 g/ml when low cyclic AMP concentrations were used.In addition to cyclic AMP release, rapid and marked efflux of ATP into the medium was observed during incubations with compound 48/80. The lactate dehydrogenase activity in the incubation medium was significantly enhanced with incubation periods of 40 to 60 min indicating rather slowly occurring toxic damage to cell membranes by compound 48/80.This work was supported by the Deutsche Forschungsgemeinschaft (SFB 70).     

A study of the capacity of myelinated and unmyelinated nerves to induce experimental allergic neuritis

Summary The capacity of myelin-free Schwann cells to induce EAN was investigated. Human foetal peripheral nerve and human adult abdominal vagus nerve, both containing little or no myelin, failed to induce EAN when injected intradermally (together with Freund's adjuvant) into rabbits. In contrast, human adult sciatic nerve, which is heavily myelinated, induced characteristic signs and histopathology of EAN. Thus in the myelin-free antigens Schwann cell plasma membrane, from which myelin is apparently derived, failed to induce EAN. Reasons for this paradox are discussed.     

Behavioral effects in rhesus monkeys of repeated intravenous doses of δ-9-tetrahydrocannabinol

In two separate experiments effects were evaluated of chronic administration of -9-THC (i.v.) on the behavior of rhesus monkeys trained on a multiple schedule of food reinforcement and a shock avoidance schedule. Rapid tolerance to drug effect was observed on avoidance responding; but only partial tolerance on food reinforced responding. Only a minor degree of tolerance was noted on gross behavior. In both experiments, tolerance to the drug carried over a 30-day drugfree period.Research supported by NIMH grant MH 19651.     

Potassium tolerance and bronchial reactivity in asthmatic and nonasthmatic atopic subjects

Abnormal autonomic nervous system responsiveness may contribute to the pathogenesis of allergic diseases. Therefore, we measured the -adrenergic systemic (metabolic) responsiveness by means of acute potassium load in 10 normal healthy subjects and in 19 patients with allergic asthma and/or rhinitis. Ten allergic patients showed a greater potassium increment, as in normal subjects, when potassium was infused in the presence of propranolol. There was no difference between asthmatic and rhinitic patients. We then examined the relation between the response to potassium tolerance and the nonspecific, nonpharmacological bronchial reactivity in response to inhalation of ultrasonically nebulized distilled water. Some allergic patients showed bronchial hyper-reactivity, while others did not show a difference compared with the controls; there was no significant difference between asthmatics and rhinitics, and there was no relation between nonspecific bronchial reactivity and potassium load tolerance. These findings suggest that systemic -adrenergic hyporesponsiveness may be present only in some allergic patients. There is no demonstrable relation among atopic state, nonspecific, nonpharmacological bronchial reactivity, and systemic -adrenergic hyporesponsiveness.     

Effect of sympathomimetic drugs and corresponding receptor antagonists on the rate of cerebrospinal fluid production.

The bulk production of cerebrospinal fluid (CSF) was measured in rabbits on the basis of ventriculocisternal perfusion and dilution of [¹⁴C]inulin. Intraventricular or intravenous (i.v.) infusion of norepinephrine produced a dose-related decrease in the production by as much as 50%, the effect being counteracted by both α- and β-antagonists (except when the latter was given i.v., which potentiated the i.v. norepinephrine response). Also intraventricular (but not i.v.) administration of the β₁-receptor agonist, $\text{H80}\text{62}$, reduced CSF formation (effect blocked by practolol), in contrast to the β₂ agonist, terbutaline, which had little or no effect. It is suggested that the sympathomimetic reduction in the rate of CSF formation is the result of a combined β₁-receptor-mediated inhibition of the secretion from the plexus epithelium and a reduced blood flow in the tissue resulting from stimulation of the vascular α-receptors.     

Acanthocytosis associated with tics and involuntary movements

Summary A resume of the clinical features presented in the 3 families previously reported with acanthocytosis and normolipoproteinaemia is presented and particular attention paid to the nature of the oro-facial dyskinetic movements seen.No defects were detected in the red cell membranes but a plasma abnormality, possibly related to the increased fibrinogen levels, was examined by study of the electrokinetic properties of the pathological platelet-plasma system. These results were compared with those of the pathological platelet-plasma system of a patient with abetalipoproteinaemia but no correlation was found.The link between the haematological and neurological abnormalities in the acanthocytotic syndromes has yet to be discovered.     

Hallervorden-spatz disease—Late infantile and adult types,report of two cases

Summary Two cases of Hallervorden-Spatz disease are reported, one of whom was a late infantile variety and the other an adult variety who died at the end of the fourth decade of life. The clinical and neuropathological aspects were similar to previously reported cases. Both cases were characterized by a slowly progressive illness featured by dementia, seizures, dysarthria, rigidity, spasticity and athetoid and myoclonic movements. Neuropathological examination disclosed excessive pigmentation of the globus pallidus and red zone of substantia nigra associated with neuroaxonal dystrophy. The latter was more generalized in the first case and was confined to the pallidonigral area, cerebellum and lower medulla in the adult case.In spite of a striking increase in the iron content of the pallidonigral system, as demonstrable by histological techniques, the chemical analysis disclosed only slight rise of iron in this area. There was a generalized reduction of cerebral lipids compatible with a diffuse degenerative process associated with demyelination.Our sincere thanks are due to Dr.G. A. Ives, the Director of the Yorkton Psychiatric Centre, and to Dr.N. L. Hoffmann, the Pathologist of Regina General Hospital, for the brain specimens, general pathological report and the clinical notes of the two cases. Dr.J. Horbaczewski of the Saskatchewan Hospital, Weyburn, made available for us the files of the patient W.D. The technical assistance of Mrs.N. Nebeluk, R.T., and that of Mr.H. Goodwin and Mr.R. C. Shortman is gratefully acknowledged.