Delayed cardiac protection against harmful consequences of stress can be induced in experimental atherosclerosis in rabbits.

Multiple brief periods of rapid ventricular pacing confer both short- and long-term protection on the ischaemic heart. The duration of the short-term protection does not exceed 2 h, whereas the long-term protective effect appears several hours after the inducing insults, with maximal protection 24-48 h later. Up to now, delayed cardiac protection by preceding ischaemic insults against harmful consequences of stress has been produced in the normal, healthy animal only. The purpose of this study was, therefore, to test whether delayed cardiac protection can be induced in experimental atherosclerosis in rabbits produced by feeding cholesterol-rich diet over 2 months. Repeated brief periods of rapid ventricular pacing were used to induce delayed protection of the heart. Moderation of post-pacing right intracavitary ST segment elevation and that of the left ventricular end-diastolic pressure (both produced by ventricular overpacing: 500 beats/min for 15 min) were found in normal animals as well as in those fed cholesterol-enriched diet. The short-lived protection induced by a single 'preconditioning' pacing was reproducible only in normal animals. As measured by means of radioimmunoassay, the protective effect of either short- or long-term protection appeared in parallel with an attenuation of ischaemia-induced increase in cardiac cyclic AMP content, in both normal and atherosclerotic rabbits. An increase in cardiac cyclic GMP content was characteristic of the short- but not long-term protection. These results suggest that the delayed cardiac protection by preceding multiple brief rapid pacings operates even in experimental atherosclerosis, but the short-term protection induced by a single preconditioning stimulus is lost.

Cholinoceptive neurons without acetylcholinesterase activity and enzyme-positive neurons without cholinergic synaptic innervation are present in the main olfactory bulb of adult rat.

Light and electron microscopic histochemistry revealed acetylcholinesterase-positive and acetylcholinesterase-negative neurons in the main olfactory bulb of adult rat. Their distribution patterns on various neuron types have been analysed in detail. (1) No acetylcholinesterase staining could be demonstrated in the granule cells which receive a large number of the cholinergic synapses. (2) In contrast, enzyme activity was present in the soma and dendrites in most of the non-cholinergic and non-cholinoceptive relay cells (mitral cells and tufted cells) and in a subset of short-axon interneurons, where cholinergic synapses could not be detected. (3) Within the neuropil of glomeruli, two compartments were present, one of which was free of acetylcholinesterase-positive structures, while many enzyme-positive neuronal elements were seen in the other. (4) Characteristically, cholinergic and non-cholinergic neuronal structures showed triadic arrangements. (5) The axonal release of acetylcholinesterase from cholinergic axons is probable. It is suggested that, in the olfactory bulb, acetylcholinesterase is release by cholinergic afferent axons, and it is the cholinergic synapses that determine which postsynaptic neurons are cholinoceptive rather than the intraneuronal presence of acetylcholinesterase. In the main olfactory bulb, the acetylcholinesterase present in the relay cells therefore appears to have functions other than the hydrolysis of acetylcholine.

The loss of pacing-induced preconditioning in atherosclerotic rabbits: role of hypercholesterolaemia.

A brief rapid pacing has been shown to protect rabbit heart against global myocardial ischaemia induced by subsequent longer pacing. We studied whether pacing-induced preconditioning was reproducible in experimental hypercholesterolaemia. In conscious rabbits with an implanted right ventricular electrode and left ventricular polyethylene catheters, pacing of 500 bpm over 20 min induced an intracavitary ST-segment elevation of 3.2 +/- 0.41 mV, shortened ventricular effective refractory period and increased left ventricular end-diastolic pressure from prepacing 105 +/- 3.9 ms and 4.0 +/- 0.93 mmHg to post-pacing 62 +/- 6.4 ms and 27.9 +/- 7.2 mmHg, respectively. A 10-min preconditioning pacing followed by a 5-min interval markedly attenuated these test pacing-induced ischaemic changes. Rabbits were fed a cholesterol-enriched diet over 4, 8 and 12 weeks, responded to a 5- or 10-min pacing with ischaemic changes of the same degree as did controls to a 10- or 20-min pacing, respectively. A 4-week diet elevated total serum cholesterol from 1.7 +/- 0.4 to 24.1 +/- 2.9 mmol/l without apparent atherosclerotic lesions in the thoracic aorta assessed by Oil-Red O staining and planimetry, but it abolished protection induced by a 5-min preconditioning pacing. A 12-week diet increased serum cholesterol and lesion surface area to 26.9 +/- 3.2 mmol/l and 89.6 +/- 6.4%, respectively, and continued to block preconditioning. When these animals were refed normal chow over additional 6 weeks, serum cholesterol level dropped to 2.6 +/- 0.80 mmol/l with no change in atherosclerotic lesions, the preconditioning effect, however, recovered. We conclude that hypercholesterolaemia blocks preconditioning irrespective of the development of atherosclerosis.

Adenomatous leydig cell hyperplasia of the testicle remnant after subtotal orchidectomy in the rat.

Subtotal orchidectomy is a suitable method to induce adenomatous Leydig cell hyperplasia in the testicular remnant without irradiation or toxic chemicals. Very expressed hyperplasia of the smooth endoplasmic reticulum was detectable electronmicroscopically in the newly formed Leydig cells. The activity of Δ5-3ß-hydroxysteroid dehydrogenase in the homogenate of the testicular remnant was found considerably elevated. These observations suggest a steroidogenetic activity of the proliferating Leydig cells.

7-oxo PGI2 dramatically increases the safety margin of digitalis.

In our earlier experiments pretreatment with 7-oxo PGI2 was found to be effective against ouabain induced rhythm disturbances in guinea pigs. Maximal protection appeared 48 hours after a single dose of 50 micrograms/kg administered i.m. In the present study we wanted to clarify how cardiac glycoside induced positive inotropic responses as well as appearance of rhythm disturbances in higher doses were influenced by 7-oxo PGI2 pretreatment in dogs. The experiments were performed on anesthetized, artificially ventilated mongrel dogs weighing 9-11 kg. The ECG, left ventricular pressure, as well as +dP/dtmax and -dP/dtmax were continuously recorded. Ouabain was applied by intermittent infusion, i.e. an initial i.v. dose of 30 micrograms/kg was infused during 5 min followed by a 25 min interval, then 15 micrograms/kg was infused every 10 min for 2.5 min until cardiac arrest. Ouabain induced increasingly severe patterns of rhythm disturbances, ventricular extrasystoles (ES), ventricular tachycardia (VT), ventricular fibrillation (VF) and cardiac arrest (CA). In the case of 7-oxo PGI2 (50 micrograms/kg) pretreatment the dose of ouabain necessary to provoke ES was 62 +/- 5.0 micrograms/kg versus (v.s.) 53.3 +/- 3.4 micrograms/kg in the control group, VT: 97 +/- 5.0 micrograms/kg v.s. 80 +/- 6.2 micrograms/kg and CA: 100 +/- 4.2 micrograms/kg v.s. 87 +/- 7.7 micrograms/kg. In the pretreated group 25% of the maximal positive inotropic effect was produced by 14.2 +/- 3.6 micrograms/kg ouabain v.s. 31.7 +/- 3.6 micrograms/kg. According to the above results 7-oxo PGI2 increases the safety margin of ouabain.

Delayed protection by 7-oxo-PGI2 against cardiac transmembrane ion shifts and early morphological changes due to ischemia and reperfusion.

In previous experiments on dogs subjected to local myocardial ischemia, we have shown a late and prolonged anti-ischemic and anti-arrhythmic effect of a single injection of the stable prostacyclin analogue, 7-oxo-PgI2. The protection was dependent on dose and time. Maximal effects were observed 48 hours after an optimal intramuscular dose of 50/micrograms/kg. To study the mechanism of this protective effect we have followed the time-dependent changes in transmembrane cation homeostasis induced by ischemia and reperfusion by measuring the intracellular potassium, sodium and calcium ion concentrations in Langendorff guinea pig heart preparations isolated from untreated control animals and from animals receiving a single intramuscular injection of 50/micrograms/kg 7-oxo-PgI2 48 hours before preparation. Global ischemia was produced by stopping perfusion for 25 minutes and was followed by reperfusion. In a second series, similarly treated and untreated hearts were fixed for electron microscopy after 25 minutes' global ischemia as well as after 15 minutes' reperfusion. Ischemia and reperfusion evoked a rapid loss of intracellular potassium and gain of sodium as well as an accumulation of calcium in the reperfusion phase. Pretreatment with 7-oxo-PgI2 prevented all these changes. It also prevented the shortening of the sarcomers and swelling of mitochondria induced by ischemia and the deposition of calcium-dense granules in mitochondria appearing after reperfusion. The findings support the hypothesis that 7-oxo-PgI2 has a delayed cytoprotective action which preserves normal transmembrane ion transport and normal structure of myocardial cells under conditions of ischemic and reperfusion injury.

[Experiences with the use of ioxithalamate (Telebrix)]. / Erfahrungen mit der Anwendung des Ioxitalamat (Telebrix).

The effects of Ioxitalamate/Telebrix-BYK GULDEN were tested for excretion urography and various angiographic applications and in animal experiments (selective renal angiography in 36 dogs). The contrast medium was well tolerated and the radiographs were of good quality. Significant effects were not detected, neither in blood pressure, heart rate and ECG, nor in Se-creatinine, nor in UN-, SGOT and Se-bilirubin values. In 4 cases transient proteinuria was observed. In the kidneys of the dogs no mentionable effects, histological or ultrastructural, were found. The use of Ioxitalamate seems advisable for investigations that require contrast media with low osmotic pressure.

[Significance of low osmolarity contrast media in state of the art roentgen diagnosis]. / Alacsony ozmotikus nyomású kontrasztanyagok jelentösége a korszerü röntgendiagnosztikában.

The authors used low-osmolality contrast material intravascularly in 546 patients, in 371 cases ioxaglate, in 80 patients iopamidol and in 95 iohexol. On each occasion good detail-rich pictures were obtained. Sensation of heat was indicated only by 1 patient (iopamidol), pain by 7 patients (ioxaglate 4, iohexol 2, iopamidol 1). The blood pressure, pulse rate and the UN, SGOT and SeBiru values showed no significant changes. The experiments were carried out on 101 dog kidneys. Selective renal angiography was done with the aforementioned materials and compared with the conventional, high-osmolality materials (iodamide, metrizoate). The histological changes were only slight, of small extent, and reversible when the new materials were used. Use of the new, low-osmolality contrast materials is justified whenever they must be given intravascularly, but it is imperative in the examination of children, patients of high risk groups and sensitive organs (nervous system, kidney, coronary vessels).

On the 7-oxo-PGI2 induced late appearing long-lasting cytoprotective effect.

Our results indicate that 7-oxo-PgI2 pretreatment may induce a long lasting cytoprotective effect by preventing ischemia induced intracellular potassium loss and sodium accumulation in myocardial cells of guinea pigs furthermore by protecting from ischemic ultrastructural changes as sarcomere shortening, mitochondrial swelling and irregularity of I, A and Z bands in the rabbit myocardium.

Effect of the anti-oestrogen tamoxifen on the development of renal cortical necrosis induced by oestrone + vasopressin administration in rats.

Bilateral renal cortical necrosis was observed after vasopressin administration in rats pretreated with oestrone acetate. Histochemical (succinic dehydrogenase, trichrome, periodic acid Schiff) and electronmicroscopic methods were used to examine how the anti-oestrogen, Tamoxifen, influences the development of this renal cortical necrosis. The experiments revealed that in most rats vasopressin did not induce renal tubular necrosis if the anti-oestrogen was administered simultaneously, even during oestrogen pretreatment. The results suggest that oestrogen receptors in the kidney are involved in the induction of renal cortical necrosis by vasopressin.

Histochemical and ultrastructural study of renal cortical necrosis in rats treated with oestrone + vasopressin, and its prevention with a vasopressin antagonist.

Renal cortical necrosis was induced by the administration of vasopressin to oestrogen-pretreated rats. Histochemical (succinic dehydrogenase, trichrome, perjod acid Schiff) and electronmicroscopic methods were applied to examine how the vasopressin antagonist d(CH2)5Tyr(Met)AVP influences the development of this renal cortical necrosis. The experiments revealed that vasopressin did not induce hypoxia or necrosis in the renal tubules if the antagonist was administered simultaneously, even after oestrogen pretreatment. The conclusion is drawn that this pressor antagonist may be of value for the prevention of renal cortical necrosis in rats or in human beings.

Ultrastructural study of peripheral lymphocytes and polymorphonuclear leukocytes in children with lysosomal enzymopathies and hyperlipoproteinemia.

On the basis of electronmicroscopic examinations of the peripheral lymphocytes and polymorphonuclear leukocytes (PMNL) in mucopolysaccharidosis of types I and II in Gaucher and Nieman-Pick diseases, in metachromatic leukodystrophy and in hyperlipoproteinemia, the ultrastructural characteristics are described. Pathological findings with vacuoles formations were observed in Gaucher disease and in metachromatic leukodystrophy against the preliminary literature. The ultrastructural pathological changes are reported from the first ultrastructural PMNL examinations in hyperlipoproteinemias. Electronmicroscopic analysis of the leukocytes is considered to give information equivalent in value to that from liver biopsy studies, but is advantageous in view of its non-invasive nature.

Neurotoxicity of monosodium-L-glutamate in pregnant and fetal rats.

Monosodium-L-glutamate given subcutaneously to pregnant rats caused acute necrosis of the acetylcholinesterase-positive neurons in the area postrema. The same effect has been observed in the area postrema of fetal rats. The process of neuronal cell death and the elimination of debris by microglia cells proved to be similar in pregnant animals and in their fetuses. However, embryonal neurons were more sensitive to glutamate as judged by the rapidity of the process and the dose-response relationship. These observations raise the possibility of transplacental poisoning in human fetuses after the consumption of glutamate-rich food by the mother.

A glutamate-sensitive neuronal system originating from the area postrema terminates in and transports acetylcholinesterase to the nucleus of the solitary tract.

The possible cellular mechanism of action of systemically administered monosodium-L-glutamate and the projections of glutamate-sensitive area postrema neurons have been studied in rats. Parenteral administration of monosodium-L-glutamate induced a selective degeneration of a particular population of AChE-containing area postrema neurons. Electron microscopic cytochemistry and X-ray microanalysis revealed the presence of calcium-containing electron-dense deposits in the mitochondria of degenerating area postrema neurons indicating the possible pathogenetic role of an enhanced intracellular calcium level in the mechanism of monosodium-L-glutamate-induced nerve cell degeneration. Degeneration of area postrema neurons was followed by the appearance of degenerating axon terminals in a well-defined region of the nucleus of the solitary tract, the area subpostrema. Degenerating area postrema neurons and axon terminals were rapidly engulfed by phagocytes predominantly of microglial character. AChE activity, localized to the basal lamina of the capillaries of the area subpostrema under normal conditions, could no longer be detected in rats treated with monosodium-L-glutamate 3-4 weeks previously. These findings provide evidence for the existence of a particular population of glutamate-sensitive, AChE-containing area postrema neurons which project and transport AChE to the nucleus of the solitary tract. This specific neuronal pathway connecting the area postrema with the nucleus of the solitary tract may play an important role in some of the functions attributed to the area postrema. The results also strengthen the hypothesis that brain capillary AChE activity may be of neuronal origin.

[Ultrastructural changes in the supraoptica-neurohypophyseal system after induction of lesions in the pituitary stalk in rats]. / Ultrastrukturelle Veränderungen des supraoptico-neurohypophysären Systems nach Läsion des Hypophysenstiels bei der Ratte.

Fine structural changes occurring in the supraoptic nucleus and the neural lobe have been studied in rats following the electrolytic lesion of the hypophysial stalk. Supraoptic neurosecretory neurones undergo a typical chromatolytic reaction. In addition, proliferating microglial cells disconnect axosomatic synapses and phagocytose degenerating neurones. Surviving neurones show signs of structural restitution 3 to 4 weeks after surgery. In the neurohypophysis degeneration of secretory nerve endings started with the disintegration of secretory vesicles 3 to 4 d postoperatively. Degenerated axon terminals were engulfed by pituicytes. Signs indicative of axonal regeneration were not observed in the neural lobe up to the end of the 4th postoperative week.

Neurotoxin induced nerve cell degeneration: possible involvement of calcium.

Neurotoxin induced nerve cell degeneration has been studied in sensory ganglia of newborn and in the area postrema of adult rats following the administration of the selective sensory neurotoxin, capsaicin and the amino acid excitotoxin, glutamic acid, respectively. Light microscopic histochemical, autoradiographic, electroncytochemical and X-ray microanalytical studies revealed that degeneration of certain small-sized, type B primary sensory neurons, induced by capsaicin, was associated with a marked accumulation of calcium predominantly in mitochondria of the damaged ganglion cells. Similarly, monosodium glutamate treatment resulted in the appearance of calcium-containing electron-dense granules in mitochondria of degenerating area postrema neurons. In addition, after a combined administration of 45Ca2+ and capsaicin or monosodium glutamate, significantly higher levels of radioactivity have been detected by liquid scintillation spectroscopy in the Gasserian ganglia and the area postrema, respectively. It is concluded that an enhancement in intracellular calcium level may be intimately involved in the process of neuronal cell death and may represent a common basic mechanism responsible for the development of cellular events leading ultimately to the degeneration of nerve cells.

Calcium-containing mitochondrial granules in neurohypophysial axon terminals disappear following vasopressin treatment of Brattleboro rats.

The presence of intramitochondrial calcium-containing electron-dense granules was demonstrated in axon terminals of chronically hyperactive neurosecretory neurons of untreated homozygous Brattleboro rats. Following vasopressin treatment for 30 days, which has been shown to attenuate this neuronal hyperactivity, calcium-containing deposits could not be detected in mitochondria. It is concluded that the presence of intramitochondrial calcium-containing dense deposits is connected with the functional state of neurosecretory neurons.