Effect of baroreceptor activity on ventilatory response to chemoreceptor stimulation.

This study tested the hypothesis that ventilatory responses to chemoreceptor stimulation are affected by the level of arterial pressure and degree of baroreceptor activation. Carotid chemoreceptors were stimulated by injection of nicotine into the common carotid artery of anesthetized dogs. Arterial pressure was reduced by bleeding the animals and raised by transient occlusion of the abdominal aorta. The results indicate that ventilatory responses to chemoreceptor stimulation were augmented by hypotension and depressed by hypertension. In additional studies we excluded the possibility that the findings were produced by a direct effect of changes in arterial pressure on chemoreceptors. Both carotid bifurcations were perfused at constant flow. In one carotid bifurcation, perfusion pressure was raised to stimulate carotid sinus baroreceptors. In the other carotid bifurcation, pressure was constant and nicotine was injected to stimulate carotid chemoreceptors. Stimulation of baroreceptors on one side attenuated the ventilatory response to stimulation of contralateral chemoreceptors. This inhibition was observed before and after bilateral cervical vagotomy. We conclude that there is a major central interaction between baroreceptor and chemoreceptor reflexes so that changes in baroreceptor activity modulate ventilatory responses to chemoreceptor stimulation.     

Effects of hypoxic blood on baroreceptor activity in the dog

The effects of perfusing arterial baroreceptors with venous blood have been tested on eleven single fibres in nine dogs using a discrete pouch preparation. The frequency of discharge on the afferent baroreceptor fibres was not altered by the composition of blood perfusing them. It is concluded that the reduction in impulse discharge from these baroreceptors during sympathetic nerve stimulation is probably not due to anoxia (or reduced blood flow) at the nerve terminals.     

Changes in tissue monoamine oxidase activity and resistance to acute hypoxia in rats during stress

Male Wistar rats exposed to different stresses developed shifts in the brain and liver monoaminoxidase activity. In the so called "cognitive" stimulation, the activity was enhanced in the brain and reduced in liver. Mild stresses also enhanced the activity in the brain. Extreme stimulation (starch peritonitis) caused a significant diminishing of the activity in the brain. All the stress schedules accompanied by enhancement of the brain monoaminoxidase activity increased the rats' tolerance of acute hypoxic hypoxia. Negative correlations between the blood lactic acid contents and the brain monoaminoxidase activity were revealed in rats of both the control and the "cognitive" groups. The findings suggest a direct interrelationship between post-stress shifts of the brain monoaminoxidase activity and the hypoxia tolerance.     

Aspects of cardiovascular reflexes in pathologic states

Cardiovascular reflexes that are mediated by receptors in the heart and blood vessels control a variety of important hemodynamic and humoral functions. The action of these receptors can be shown to be abnormal in several pathologic states. Left atrial receptors exhibit a depressed discharge sensitivity in dogs with chronic congestive heart failure caused by an aortocaval fistula. The reflex effects of atrial receptor stimulation are also depressed in heart failure. Left ventricular receptor stimulation has been implicated in the abnormal vascular responses to exercise in patients with aortic stenosis. The arterial baroreflex control of heart rate is abnormal in animals and humans with various forms of hypertension. Arterial baroreceptors from hypertensive animals show a resetting of their pressure-discharge curve to higher pressures. The arterial baroreflex is also depressed in chronic heart failure. This effect may result from an abnormality of the efferent limb of the reflex arc or from changes in the interaction between baroreceptors and cardiac receptors centrally. A final possibility may be abnormal arterial baroreceptor discharge characteristics in heart failure.     

Observations on the fine structure of the baroreceptors and adrenergic innervation of the guinea-pig carotid sinus

We examined the fine structure of the baroreceptors and the adrenergic innervation of the guinea-pig carotid sinus. The tunica adventitia contained many nerve bundles whose perineuria enclosed unmyelinated nerve fibers, alone or together with myelinated nerve fibers. Baroreceptors, which lay close to elastic and collagen fibers in the adventitia and media, were surrounded by “terminal” cells with ultrastructural features characteristic of Schwann cells and contained inclusions of various types. Morphologic features of the baroreceptors included densely packed mitochondria, osmiophilic lamellated and homogeneous bodies, clear and granular vesicles, lamellar systems, glycogen granules, neurofilaments, neurotubuli, and vacuolated mitochondria. In animals that had been treated with 6-hydroxydopamine, occasional electrondense endings (or fibers) were observed in the adventitial layer. The baroreceptors in the guinea-pig carotid sinus appear to have most of the morphologic features reported for other species.     

Activation of factor XIII by beta-thrombin]

It was found that similar to alpha-thrombin, beta-thrombin (possessing a high esterase and only a trace coagulating activities) converts plasmic transglutaminase (factor XIII) into its active form, thus promoting stabilization of fibrin. Activation of pure and plasmic preparations of factor XIII after incubation with beta-thrombin was observed in vitro. alpha-Thrombin at concentration corresponding to the trace coagulating activity of beta-thrombin had no activating effects. An intravenous injection of beta-thrombin to animals with aminazine-inhibited anticoagulating system reflectory arc resulted in an increase of factor XIII activity in the same way as was observed in vitro. On the other hand, an intravenous injection of beta-thrombin to intact animals did not increase factor XIII activity, which may be accounted for by a decrease in the level of factor XIII due to activation of the anticoagulating system.     

Cholin- and adrenergic components of the vegetative innervation of the dura mater]

Cholin- and adrenergic nerves in the fornix and base of the dura mater of rats, cats and dogs have been studied by methods of Kelle, Falck and Glenner. It has been established that the dura mater has a developed cholin- and adrenergic nervous apparatus innervating arteries, veins and the connective tissue of the mater. The concentration of nerve fibres is always greater on a meningea media and its daughter branches. The statistical processing of the data obtained has shown that the maximum quantity of nerve fibres is in cats, less in dogs and still less in rats. It has been established that in the dura fornix of cats and dogs there are more cholinergic nerve fibres than in the base. In rats there is no such difference. The amount of fibres with monoaminoxidase approximately corresponds to the amount of conductors with noradrenaline.     

Monoamine oxidase activity in gastrointestinal tract tissues of animals after irradiation and administration of pyridoxal phosphate

The X-ray irradiation in a dose of 450 R is shown to decrease the monoaminoxidase activity in the cell fractions of the mucous membrane of small intestine as against the fractions of the stomach mucosa. The administration of pyridoxalphosphate to the irradiated rabbits increases the monoaminoxidase activity in the fraction and subfractions of small intestine mucosa mitochondria, but the enzyme activity being compared with the control group has a tendency to decrease.     

Histochemical profiles of rat soleus intrafusal fibres after chronic exercise.

Intrafusal fibres from the rat soleus were investigated for representative histochemical profiles in sedentary animals and animals chronically exercised for 17 weeks on a treadmill. The pattern of myosin adenosine triphosphatase (ATPase) activity in the polar region revealed three intrafusal fibre types: (1) myosin ATPase-dark (MD) fibres, alkali- and acid-stabile; (2) myosin ATPase-light (ML) fibres, alkali- and acid-labile; and (3) myosin ATPase-reversible (MR) fibres, alkali-stabile and acid-labile. The three fibre types were correlated with the level of reduced NADH diaphorase activity, with MR, ML and MD fibres staining dark, moderate and light, respectively. In the equatorial region the morphological features of representative ML and MD fibres revealed that they were nuclear bag fibres, while representative MR fibres were identified as nuclear chain fibres. The MR fibres in the exercised animals had higher levels of myosin ATPase alkaline stability and acid lability than MR fibres in the sedentary animals, suggesting the MR fibre profiles are selectively influenced by chronic exercise. The mean cross-sectional area of MR fibres from the exercised animals was significantly less than the MR fibres from the sedentary animals. In contrast to the effect of endurance training on NADH diaphorase activity in extrafusal muscle fibres, there was evidence of less activity in the MD fibres of the exercised animals.     

The increase in activity of acid hydrolases in muscles of rats after subcutaneous administration of dimethyl-para-phenylene diamine. A combined histochemical and biochemical investigation. I. The histochemical investigation.

The activity of acid hydrolases in skeletal muscles of normal rats and of rats after subcutaneous administration of dimethyl-para-phenylene diamine (DPPD) was studied with a combined histochemical and biochemical investigation. In this communication the histochemical findings are presented. After 4 days of DPPD treatment, coagulation necrosis, fragmentation and disintegration of fibres were seen in the muscles. An inflammatory infiltrate was seen between the muscle fibres. These pathological changes reached maximum intensity after 7 to 9 days. After 11 days the changes became less, despite continued treatment with DPPD. From the histochemical findings it appeared that the activity of acid phosphatase, beta-glucuronidase and E600 resistant non-specific esterase was increased in both a granular and a diffuse pattern in the skeletal muscles of the DPPD rats. The increase in activity of leucine aminopeptidase was much less pronounced and was mainly granular. The increase in the activity of acid hydrolases ran parallel to the severity of the pathological changes and reached a maximum after 7 to 9 days of DPPD treatment. The statistical calculations of the histochemical findings revealed that the increased activity of one acid hydrolase was significantly paralleled by an increased activity of a second hydrolase. There was a moderate probability that the activity of all other histochemically studied acid hydrolases, with the exception of leucine aminopeptidase, was increased. There was no difference in activity and localization of the acid hydrolases studied in aerobic type I and anaerobic type II fibres. The localization of acid phosphatase and beta-glucuronidase activity in muscle fibres and in inflammatory infiltrate mostly coincided. In cases where these enzymes were localized both centrally and in the subsarcolemnal areas of the muscle fibres, the activity of E600 resistant non-specific esterase was usually, and the activity of leucine aminopeptidase was exclusively located in the subsarcolemnal areas. All of the acid hydrolases examined were found to be present in the inflammatory exudate and in the connective tissue.     

Stimulating effect of cocaine in rats with different levels of blood esterase activity

It was shown in experiments on male random-bred rats that motor stimulating effect of cocaine (10 mg/kg, intraperitoneally) was dependent on the spectrum of blood serum esterase activity. The determination of esterase spectrum was performed by disc-electrophoresis in 7.5% PAAG (50-75 gamma of protein per gel), with enzyme activity estimated using alpha-naphthylacetate. Proserine (10(-5) M) and butyrylthiocholine controls were used. Motor stimulating effect of cocaine in animals with 3 esterase fractions was 3 times higher than in animals with 4 enzyme fractions.     

Regulation of juvenile hormone esterase activity in the European corn borer, Ostrinia nubilalis

The regulation of juvenile hormone esterase in last-instar diapause and nondiapause larvae of Ostrinia nubilalis was investigated using topically applied juvenile hormone I and a juvenile hormone mimic, methoprene. The influence of the head on juvenile hormone esterase was also investigated. Both juvenile hormone and methoprene caused increases in esterase levels when applied to feeding animals. Neither the hormone nor methoprene was capable of elevating nondiapause esterase activity to levels comparable to those found in untreated prediapause larvae. The esterase levels could be elevated in the larval body, without the head, during prepupal development of nondiapause larvae and in post-feeding diapause larvae. In both cases, juvenile hormone or methoprene induced juvenile hormone esterase activity in head-ligated animals. Topically applied methoprene prolonged feeding and delayed the onset of diapause. When methoprene was applied to larvae that had entered diapause, it disrupted diapause by inducing a moult.     

Reformation of the severed septohippocampal cholinergic pathway in the adult rat by transplanted septal neurons

Summary Transplants containing developing cholinergic neurons were obtained from the septum-diagonal band area of rat fetuses and were implanted into a lesion of the septohippocampal cholinergic pathway or into a cavity of the occipital cortex in adult recipient rats. The growth of new cholinergic fibres from the implant into the hippocampal formation was followed with choline acetyltransferase (ChAT) determinations and acetylcholine esterase (AChE) histochemistry. A fimbrial lesion alone, transecting the septohippocampal pathway, caused an almost complete cholinergic denervation of the hippocampal formation that persisted throughout the five month experimental period. A septal transplant implanted into the cavity of the fimbrial lesion restored a new AChE-positive innervation pattern in the hippocampus and the dentate gyrus that closely mimicked the original innervation removed by the lesion. In parallel, there was a progressive recovery in the ChAT levels, starting in the septal end, and progressing in a temporal direction. A new cholinergic fibre supply could be established in the hippocampal formation also along an abnormal route, i.e. from the transplants implanted into a cavity in the occipital cortex (involving also the dorsal part of the entorhinal cortex). Provided the hippocampus previously had been denervated of its normal cholinergic innervation, a partly normal AChE-positive terminal pattern was thus re-established also from this abnormal position. If, on the other hand, the cholinergic afferents were left intact, the ingrowing fibres were restricted mainly to the outer portion of the dentate molecular layer, i.e. the terminal zone of the lesioned entorhinal perforant path fibres. This suggests that the growth of the sprouting AChE-positive fibres into the normal cholinergic terminal fields was blocked by the presence of an intact cholinergic innervation. It is concluded that regrowing cholinergic axons can be guided over large distances within the hippocampal formation, and that their patterning within the terminal fields is very precisely regulated by mechanisms released by deafferentation.     

Enzymatic activity of some tissues and blood serum from animals and humans exposed to microwaves and hypothesis on the possible role of free radical processes in the nonlinear effects and modification of emotional behavior of animals

The dependence of activities of actomyosin ATPase, alkaline phosphatase, aspartataminotranspherase, monoaminoxidase and that of affective rat behavior on frequency of modulation of microwaves (0.8-10 microW/cm2) was explored at short-time actions. Series of nonlinear phenomenons, inexplicable from positions of the energy approaches are revealed, The working hypothesis explaining opportunity of high performance of weak and super-weak microwaves and other revealed phenomena by resonance interaction of such electromagnetic radiofrequency radiation with paramagnetic molecules of biological tissues was proposed. This resonance interaction activate free radicals and initiate auto-supporting and auto-intensifying of chain chemical reactions. The spontaneous autocatalytic oxidation of catecholamines enlarges a common pool of free radicals, capable to participate in such enhanced generating. The protective role of monoaminoxidase is postulated. Monoaminoxidase is basically located on an outer surface of mitochondrias and it is deaminating monoamines. The deaminating prevents penetration of catecholamines inside of mitochondrias and their quinoid oxidation there with formation of free-radical semi-quinons, capable to destroy system of ATP synthesis. These inferences are obliquely confirmed by the experimentally revealed correlation between activity of monoaminoxidase and integrative activity of the rat brain.     

A comparative study on the distribution of non-specific esterase amongst the various constituents of retinas of some vertebrates

A wide coverage of the retinae of a large number of animals (Calotes, Varanus, Naja, Athene, Passer, Streptopelia, Psittacula and Funambulus) from the point of view of the histoenzymological distribution of non-specific esterase amongst the various constituents reveals mostly identical patterns. They are as follows: 1. Outer segments - positive in all cases. 2. Outer plexiform layer - equipped with enzymatic activity in all the instances. 3. Inner nuclear layer - thin cytoplasmic rim of the neurons characterized by positive activity; the nuclei of the neurons are completely negative. 4. Inner plexiform layer - this layer is endowed with the enzymatic activity. 5. Ganglion cells - negative in all cases. 6. Nerve fibres of the layer of nerve fibres, situated adjasent to ganglion cells are positive in all the animals; in case of squirrel oligodandroglial cells present in the region have demonstrated activity of a high order. On of the high-lights of the present contribution is demarcation of the inner plexiform layer into three stratified zones, equipped with enzymatic activity in Calotes, Streptopelia, Naja and Funambulus. Such stratifications are not seen in Varanus, Passer and Psittacula. The significance of the various patterns and the equipment of the enzyme in various constituents at various locals have been discussed in relation to the metabolic functions, zone-wise and interzone-wise in visual processes of various animals.     

Optokinetic horizontal head nystagmus in the frog after regeneration of transected retinal fibres

The recovery of optokinetic responses during regeneration of transected retinal fibres was studied. Regenerated optic fibres were demonstrated by the cobaltfilling technique. After transection of the chiasma in the midline in most of the cases regenerating retinal fibres did not cross, but terminated in ipsilateral visual centres. Aberrant fibres were found in the telencephalon, the periventricular region of the diencephalon, anterior-, posterior- and ventral tegmental commissures and in the isthmic nucleus. In one group of animals optokinetic responses did not return after regeneration of retinal fibres. Re-innervation was either symmetrical on both sides from one eye, or terminal fibres were disorganized. In the second group of animals normal optokinetic nystagmus (OKN) returned. In these cases the fibres were symmetrically distributed on both sides or, alternatively, the crossed fibres outnumbered the ipsilateral ones. The third group of animals showed reversed OKN, spontaneous turning of the head, circling or head nystagmus. Here the majority of regenerated fibres termined ipsilaterally. When the OKN returned, the retinal projection was always restored in the pretectal region. Contrary to our earlier work, we concluded that the basal optic nucleus is not essential for horizontal optokinetic head nystagmus because in a few animals, retinal fibres did not invated this nucleus, and in spite of this the OKN could be evoked. We think now that the most important structure (as an input channel) for horizontal OKN of frogs is the pretectal region.     

Immunological comparison of cholesterol esterases.

Rat pancreas cholesterol esterase has been immunologically compared with rat intestinal cholesterol esterase. Monospecific precipitating antisera against purified rat pancreas cholesterol esterase were produced in rabbits. Immune IgG, isolated from the antisera, crossreacted with the cholesterol esterase of intestine in the immunodiffusion assay with a pattern of complete identity. Titration of the pancreatic and intestinal enzyme with immune IgG revealed a maximum precipitation (99 and 98%) and maximum inhibition of enzyme activity (66 and 65%) when the ratio of enzyme activity (units) to immune IgG (mg) was 4.1 and 4.0, respectively. The immunological identity demonstrated in these studies lend support to the concept that intestinal cholesterol esterase is derived from the pancreatic enzyme. In additional studies, the immune IgG was employed in the immunodiffusion assay to test for cross-reaction with cholesterol esterases prepared from rat aorta, adrenal, and liver and with cholesterol esterases prepared from the pancreas of rabbit, dog, cow, and guinea pig. There was no evidence of cross-reaction in any case. Further, cholesterol esterase prepared from the pancreas of rabbit, dog, and cow retained full enzymatic activity when titrated with immune IgG.     

Electron microscopic observations of elastic fibres in the lung and aorta of tight-skin and beta-aminopropionitrile-fed mice.

The lung of the tight-skin (TSK) mouse was characterized by enlargement of the air spaces. Elastin in the alveolar walls of the TSK mouse exhibited fragmentation. The aorta of the TSK mouse was characterized by marked hyperplasia of loose connective tissue in the adventitia. Collagen fibres and ruthenium red-positive materials were markedly increased. Microfibrils surrounding elastin in the adventitia of the aorta were not clear in the TSK mouse. In the lung of the beta-aminopropionitrile (BAPN)-fed mouse, enlargement of the alveolar air spaces was not prominent compared with the TSK mouse. Elastic fibres in the alveolar walls did not show the fragmentation observed in the TSK mouse, and microfibrils surrounding elastin were clearly observed. However, elastic laminae in the media of the BAPN-fed mouse aorta were swollen and fragmented. Elastic fibres in the adventitia exhibited a normal appearance and microfibrils surrounding elastin in the adventitia were clearly observed. The results suggest that the mechanism of the connective tissue abnormality in the TSK mouse is different from that of BAPN, which inhibits the activity of lysyl oxidase. The abnormality of elastin and microfibrils surrounding elastin in the TSK mouse probably plays a role in the deformity or degradation of elastic fibres and the structural changes of the lung.     

Adrenergic pattern of aorta and superior mesenteric arteries in young and senescent rats

The noradrenergic innervation of two portions of the aorta (thoracic and abdominal) was studied by the fluorescence method in rats belonging to two different age groups (3 and 28 months). Adrenergic fibres were clearly visible only in the abdominal tract of the aorta, and appeared to be more distinct and more numerous in young rats compared with the older ones. By contrast, the superior mesenteric artery was regularly found to possess a rich adrenergic plexus, even if catecholamines were more densely present in younger animals.     

Unloading arterial baroreceptors causes neurogenic hypertension

We developed a new model to examine the role of arterial baroreceptors in the long-term control of mean arterial pressure (MAP) in dogs. Baroreceptors in the aortic arch and one carotid sinus were denervated, and catheters were implanted in the descending aorta and common carotid arteries. MAP and carotid sinus pressure (CSP) averaged 104 +/- 2 and 102 +/- 2 mmHg (means +/- 1 SE), respectively, during a 5-day control period. Baroreceptor unloading was induced by ligation of the common carotid artery proximal to the innervated sinus (n = 6 dogs). MAP and CSP averaged 127 +/- 7 and 100 +/- 3 mmHg, respectively, during the 7-day period of baroreceptor unloading. MAP was significantly elevated (P < 0.01) compared to control, but CSP was unchanged. Heart rate and plasma renin activity increased significantly in response to baroreceptor unloading. Removal of the ligature to restore normal flow through the carotid resulted in normalization of all variables. Ligation of the carotid below a denervated sinus (n = 4) caused a significant decrease in CSP but no systemic hypertension. These results indicate that chronic unloading of carotid baroreceptors can produce neurogenic hypertension and provide strong evidence that arterial baroreceptors are involved in the long-term control of blood pressure.