NADPH-diaphorase activity in the nodose ganglion of normal and vagotomized guinea-pigs

The activity and distribution of reduced nico-tinamide adenine dinucleotide phosphate diaphorase (NADPH-diaphorase) in the nodose ganglion of normal and vagotomized guinea-pigs were examined by light and electron microscopy. Light microscopy confirmed a remarkable increase in the number of NADPH-diaphorase-reactive neurons in the nodose ganglion following unilateral cervical vagotomy. The increase was present at 5 days but became more prominent at 10 days and was sustained until at least 30 days after vagotomy when compared with the non-lesioned side. The NADPH-diaphorase reaction product was associated with the membrane of the rough endoplasmic reticulum, Golgi apparatus, mitochondria and nucleus of the nodose neurons. In animals killed 5 days post-operation, there was no noticeable degeneration in the nodose neurons. However, at 10 days, the mitochondria in some neurons appeared swollen and vacuolated with disrupted cristae. These changes were accentuated in some nodose neurons 20 and 30 days after vagotomy but there was no evidence of cell death. All the degenerating neurons exhibited NADPH-diaphorase activity. The increase in NADPH-diaphorase activity in the neuronal somata after vagotomy suggests that the enzyme is involved in either the retrograde degeneration or the recovery of the lesioned neurons. Received: 15 June 1995 / Accepted: 15 February 1996     

Altered cardiovascular reflex responses during positive pressure breathing

Cardiovascular responses during hyperinflation produced by positive end-expiratory pressure (PEEP) are considered to be reflexly influenced by pulmonary mechanoreceptors. Numerous studies have indicated heart and vascular effects attributed to mechanical events and cardiopulmonary mechanoreflexes. Yet interactions of these modalities with the systemic baroreflexes are not clear. We examined aspects of these modulatory interactions by distinguishing changes in pulmonary, heart, and vascular responses during PEEP-hyperinflation before and after progressive elimination of chemo-, mechano-, and baroreflex influences in the closed-chest anesthetized rabbit. During respiratory alkalosis PEEP was imposed in increments of 2.5 cm H2O (range 0.0 to 7.5 cm H2O) before and during control of carotid intrasinus pressure and following aortic denervation and vagotomy. Heart rate responses during PEEP increased prior to aortic denervation, decreased following elimination of baroreflexes, and were abolished after vagotomy. The fall in mean arterial pressure (MAP) during PEEP was accentuated during elimination of the baroreflexes and ameliorated following vagotomy. Mean right atrial (MRAP), intrapleural (MIP), and right atrial transmural pressure increased during PEEP prior to vagotomy. Regression analyses of MAP versus MRAP and MAP versus MIP suggest that vagally receptors reflexly influence venous as well as systemic arterial vascular pressure. Conclusion indicate that when superimposed on mechanical events, cardiopulmonary mechanoreceptors and arterial baroreceptors effect conflicting facilitory reflex influences on heart and vascular responses during PEEP-hyperinflation.     

Innervation of the canine pancreas after vagotomy

This contribution deals with the ultrastructure of the pancreatic nervous system of the dog 14 days and 5 months after bilateral truncal vagotomy. No major ultramorphological changes in the axons or their organelles (vesicles, mitochondria, microtubuli) were observed, and there appeared to be no reduction in the numbers of sympathic and cholinergic axis cylinders (material fixed in glutaraldehyde and potassium permanganate) or neurocellular contacts.     

Gastrin release after truncal vagotomy in fistula dogs: Hypersensitivity to bombesin but not bethanechol

Integrated gastrin response was measured by the serial changes in serum immunoreactive gastrin after various stimuli in three dogs with gastric fistula and highly selective fundic vagotomy, who were then subjected to truncal vagotomy. Truncal vagotomy eliminated the gastrin as well as the gastric acid response to vagal excitation by 2-deoxy-glucose, but did not significantly change the responses to bethanechol (20 or 120 μg/kg/hr by IV infusion). Acid output was the same with bombesin or its nonapeptide in the dogs with fundic vagotomy as it was after subsequent truncal vagotomy, but gastrin release was very much increased by truncal vagotomy. For a 3-hour infusion of bombesin integrated gastrin release was 65 and 143 ng/ml/min and for its nonapeptide 43 and 109 ng/ml/min in the dogs with fundic and truncal vagotomy respectively. The marked hypersensitivity of the gastrin response after truncal vagotomy to bombesin but not to a cholinergic agonist suggests that the antral denervation led to a post-denervation hyper-response to the putative transmitter, bombesin, and that the vagal release of antral gastrin may thus represent a peptidergic neurohormonal mechanism. Also, a long half-life of effect suggests that bombesin binds avidly to its receptors.     

Evidence for intrinsic regulation of met-enkephalin-immunoreactivity in gastroenteropancreatic tissues of the rat

In a study whether gastrointestinal endogenous opioids can be modified by vagal denervation or by pharmacological application of an opiate, we examined met-enkephalin-immunoreactivity in gastrointestinal tissue in rats with and without truncal vagotomy and with and without subcutaneously implanted morphine pellets. The immunoreactivity of the tissue extracts gave dose-response lines in the radioimmunoassay for met-enkephalin which were near parallel to that for the standard. On Sephadex chromatography the met-enkephalin immunoreactivity eluted at a position similar to synthetic met-enkephalin. Tissue concentration of met-enkephalin immunoreactivity was not significantly different from the respective control after vagotomy and after morphine treatment. Total gastric met-enkephalin immunoreactive content increased significantly after vagotomy in line with gastric hypertrophy occurring after vagotomy without a drainage procedure. From these results it is concluded that met-enkephalin immunoreactivity in the rat gastrointestinal tract is regulated intrinsically, it is neither altered by vagal denervation nor by exogenous opiate administration.     

Vagotomy without Diarrhoea

The incidence of diarrhoea after three types of vagotomy was assessed “blind” at a gastric follow-up clinic one year after operation. Diarrhoea was recorded in 24% of patients after truncal vagotomy and pyloroplasty, in 18% after selective vagotomy and pyloroplasty, but in only 2% of patients after highly selective vagotomy without a drainage procedure. The incidence of diarrhoea was significantly less (P < 0·01) after highly selective vagotomy than after either of the other procedures.Hypertonic glucose solution given by mouth to 15 representative patients from each group and to 15 patients before operation provoked the onset of diarrhoea in 67% of the patients who had undergone truncal vagotomy and pyloroplasty, in 60% of those who had undergone selective vagotomy and pyloroplasty, in 13% of those who had undergone highly selective vagotomy without a drainage procedure, and in none of the preoperative patients. Again the difference between the “highly selective” group and the other two groups of vagotomized patients was statistically significant.It is suggested that postvagotomy diarrhoea is attributable both to unregulated gastric emptying after truncal or selective vagotomy with a drainage procedure and to the extragastric denervation produced by truncal vagotomy. “Postvagotomy” diarrhoea can be virtually eliminated by using highly selective vagotomy without a drainage procedure.     

Use of dibunol in pharmacological correction of post-vagotomy hypoxia of digestive organs in rats

1, 7, 14, 30 and 60 days after bilateral sub-diaphragmatic truncal vagotomy tension of oxygen (pO2) in liver, stomach and small intestine (jejunum) was determined. It was demonstrated that vagotomy leads to a decrease of pO2 in all investigated organs 1 day after the operation (such changes were observed in sham-operated rats) and 30 days, in jejunum--after 7 days, in liver--after 14 days, in stomach--after 60 days. Dibunol introduction in vagotomized rats during 29 days (starting from the second day after operation) results in pO2 normalization in all investigated organs.     

Compensatory recovery of vagal control of hemodynamics after unilateral vagotomy

This study investigated whether each part of the heart is evenly innervated by the left or right vagus and observed the mechanism of compensatory recovery after unilateral cervical vagotomy. HR, BP, LVSP and +/-dp/dt max all decreased one week after left vagotomy, whereas only BP and -dp/dt max decreased one week after right vagotomy. Western blot analyses revealed that the expression of M(2) receptors in the left atrium and left ventricle was upregulated after subacute (1 week) left/right vagotomy. However, significantly more cholinesterase-positive nerves in LV and RV were seen one week after unilateral vagotomy compared to the sham-operated group. In addition, baroreflex sensitivity was increased after subacute right vagotomy. The decreasing effects of ACh (0.5 microg/kg) on LVSP and +/-dp/dt max (but not on HR and BP) were facilitated by subacute unilateral vagotomy. Our present experiments indicate that 1) the working myocardium is innervated bilaterally by the vagus, 2) ventricular contractility is influenced more by denervation of the left than the right vagus and 3) up-regulation of M(2) muscarinic receptors in the left heart, increase of cholinergic nerves, and high baroreflex sensitivity could be involved in the mechanism of compensatory hemodynamic recovery via contralateral vagus overactivity, thereby amplifying contralateral vagal activity and decreasing cardiac contractility.     

Effect of prior chronic contractile activity on mitochondrial function and apoptotic protein expression in denervated muscle.

Skeletal muscle is highly adaptable in response to increases and decreases in contractile activity. The purpose of this study was to determine whether the preconditioning of skeletal muscle has a protective effect against subsequent denervation-induced apoptotic protein expression. To investigate this, we chronically stimulated the tibialis anterior and extensor digitorum longus muscles for 7 days (10 Hz, 3 h/day) before 7 days of denervation. Denervation reduced total cytochrome-c oxidase activity by 39%, which was likely a consequence of a decrease in subsarcolemmal (SS) mitochondria. This decrease in the SS subfraction was prevented by prior chronic stimulation and, as a result, maintained total mitochondrial content at control levels. The expression of Bax was elevated 2.2-fold by denervation, and prior chronic stimulation did not attenuate this increase. This produced a increase in the Bax-to-Bcl-2 ratio, indicating greater muscle apoptotic susceptibility. Denervation also decreased state 3 respiration in SS and intermyofibrillar mitochondria and elevated state 4 reactive oxygen species production within both mitochondrial subfractions. These changes were not prevented by prior chronic stimulation. Furthermore, the antioxidant protein MnSOD was also reduced by denervation, whereas Beclin-1 was markedly elevated. This suggests that autophagic cell death could also play a significant part in denervation-induced muscle atrophy. Thus, despite prior chronic stimulation, denervation increases the apoptotic susceptibility of skeletal muscle by altering the Bax-to-Bcl-2 ratio, by increasing reactive oxygen species production, and by reducing the expression of MnSOD. Whether a more extensive stimulation paradigm would be more effective in attenuating apoptosis before muscle disuse remains to be determined.     

Neural control of airway pressures in rabbits

In twenty anaesthetized and spontaneously breathing rabbits airway pressures were measured above and below the larynx during tidal respiration through the larynx. Peak inspiratory and expiratory pressures at both sites were recorded in control conditions and then compared to values obtained in the course of progressive denervation of the airways. The two methods of denervation consisted of (1) bilateral section of superior and recurrent laryngeal nerves and of the midcervical vagotomy (horizontal method); (2) right-sided sections of the three nerves followed by left-sided sections (vertical method). Motor denervation of the larynx due to RLNs neurotomy (horizontal method) produced significant increases in intratracheal pressures in both phases of the respiratory cycle. Less prominent increments in pressures were achieved on RLNs neurotomy in the vertical method. SLNs section and vagotomy had little additional effect on airway pressures. Our results indicate that unilateral laryngeal palsy poses far smaller obstruction to breathing than simultaneous bilateral denervation, and that afferent denervation of the larynx has no effect on airway pressures.     

Activity of some enzymes of energy metabolism during denervation and reflex atrophy in rat slow and fast muscles

The loss of muscle weight in the soleus (SOL) and extensor digitorum longus (EDL) muscles was compared after denervation and in the course of reflex muscle atrophy induced by unilateral fracture of metatarsal bones of the paw and local injection of 0.02 ml turpentine oil subcutaneously. This so-called reflex atrophy is significantly greater after 3 days than that after denervation. Seven days after the nociceptive stimulus, reflex and denervation atrophy are grossly similar in both muscles. This also applies in case that the nociceptive stimulus had been repeated on the third day. The EDL:SOL enzyme activities of energy supply metabolism reflect the differences between a glycolytic-aerobic (EDL) and predominantly aerobic type (SOL) of muscle. No consistent changes were found in either type of atrophy after 3 days. In 7 days' denervation, the activity of hydroxyacetyl-CoA-dehydrogenase (HOADH) and citrate synthase (CS) was decreased in the SOL, while glycerolphosphate:NAD dehydrogenase (GPDH) was enhanced. In the EDL, the activity of triosephosphate dehydrogenase (TPDH), GPDH, malate dehydrogenase (MDH), CS and HOADH was decreased. Acid phosphatase (AcP) was greatly increased in both muscles. Seven days after application of the nociceptive stimulus, all enzyme activities were altered in a grossly analogous manner as after denervation.     

ON THE DIFFERENTIAL RESPONSE OF SARCOPLASM AND MYOPLASM TO DENERVATION IN FROG MUSCLE

Electron microscopic evidence is presented that the early response to denervation ("simple atrophy") of the semitendinosus m. of the frog is characterized by a greater prominence of the sarcoplasmic reticulum and by the presence, in the interfibrillar spaces, of mitochondria which are more numerous and smaller than in normal muscle. In contrast with the dynamic changes of the sarcoplasmic structural components, the myofibrils showed a progressive decrease in diameter after denervation and throughout the period studied. By carrying out tissue fractionation experiments, the yield of microsome-protein was found significantly greater in the denervated muscles, as compared with the contralateral controls, in this initial stage. Under the conditions attending the overdevelopment of the sarcoplasmic reticulum (SR), denervated semitendinosus m. incorporated valine-C¹⁴ into proteins more actively than the control pairs. The denervated muscles also showed an increase in the number of freely scattered and membrane-bound ribosomes and of polyribosomes, suggesting a more active synthesis of the SR membranes. Pronounced atrophy of the myofibrils, disorganization of the SR, and an increased number of ribonucleoprotein particles lying in the enlarged interfibrillar spaces were the main ultrastructural features of "degenerative atrophy" in frog muscle in the late periods after denervation. The probably adaptive character of the early changes occurring on denervation of frog muscle is discussed.     

Effects of truncal,selective, and highly selective vagotomy on glucose tolerance and insulin secretion in patients with duodenal ulcer. Part I-Effect of vagotomy on response to oral glucose.

An oral glucose tolerance test was performed in patients who had undergone truncal vagotomy and pyloroplasty, bilateral selective vagotomy and pyloroplasty, or highly selective vagotomy without a drainage procedure at least six months earlier. The results were compared with those from patients with chronic duodenal ulcer before operation. In all three groups of patients after vagotomy more rapid rates of rise of blood glucose and higher peak concentrations were observed than in patients who were tested before operation. These differences were statistically significant only in patients who had undergone truncal or selective vagotomy with pyloroplasty and were probably due to more rapid rates of gastric emptying after these operations. Plasma insulin concentrations were lower after truncal vagotomy than after selective or highly selective vagotomy, the difference between truncal vagotomy and highly selective vagotomy being statistically significant. Truncal vagotomy resulted in a diminished insulin response to oral glucose, which could have been due to vagal denervation of the pancreas or, more probably, impaired release of small-bowel hormones which normally augment the pancreatic insulin response.     

Electrophysiological characteristics of muscle fibers during denervation

Experimental material obtained on mouse extensor digitorum longus was presented concerning the dynamics of changes in the membrane potential (MP) of muscle fibres after chronic denervation (1-12 days), the effect of ouabain and increase of extracellular potassium on MP of normal and denervated muscles, changes of input resistance and volumes of muscle fibres after denervation.     

Effect of acute and chronic renal denervation on renal function after release of unilateral ureteral obstruction in the rat.

The role of the renal nerves in determining renal function after relief of 24-h unilateral ureteral obstruction (UUO) was studied using clearance techniques in anaesthetized rats. Acute renal denervation during the first 1--2 h after relief of UUO resulted in a significant increase in glomerular filtration rate (GFR), renal plasma flow (RPF), urine flow, and sodium and potassium excretion, changes which were not seen in the sham-denervated postobstructive kidney. Acute denervation of sham-operated normal kidneys caused a similar natriuresis and diuresis but with no change in GFR or RPF. Chronic renal denervation 4--5 days before UUO denervated postobstructive controls, while chronic denervation alone was associated with a significantly higher urine flow and sodium excretion rate from the denervated kidney. The effectiveness of renal denervation was confirmed by demonstrating marked depletion of tissue catecholamines in the denervated kidney. It was concluded that renal nerve activity plays a significant but not a major role in the functional changes present after relief of UUO. Chronic renal denervation did not protect against the functional effects of unilateral ureteral obstruction.     

Importance of neural input and thyroid hormones in the control of brown fat atrophy in mice

In euthyroid mice, a 48-h fast caused brown fat (BAT) atrophy characterized by loss of tissue proteins, succinate dehydrogenase (SDH), and a significant reduction in mitochondrial uncoupling protein (UCP) content. Chemical sympathectomy and surgical denervation failed to mimic the changes in BAT protein and SDH contents observed after food deprivation. However, suppression of sympathetic activity could account for the loss of UCP from the mitochondria. In mice made hyperthyroid by repeated triiodothyronine injections, losses of tissue SDH and proteins caused by food deprivation or surgical denervation were markedly suppressed, while the loss of UCP from the mitochondria remained unchanged. These results suggest that reduced sympathetic activity to BAT in fasted mice is not the exclusive cause of the tissue atrophy and that thyroid hormones may play a role in the control of brown fat atrophy in mice.     

Effects of nerve stimulation and denervation on secretory material in submandibular striated duct cells of cats,and the possible role of these cells in the secretion of salivary kallikrein

Striated ducts in cats after 24 hours starvation normally contained glycogen, especially in the basal regions. They also contained neutral mucin and tryptophan in apical parts of "light" cells and small irregular "secretory" granules were found in a similar distribution by electron microscopy.--Parasympathetic nerve stimulation caused a loss of glycogen but no apparent change in the apical secretory material, despite a copious secretion.--Sympathetic stimulation caused a loss of glycogen and an extensive depletion of apical secretory material, although the salivary flow was small.--Parasympathetic denervation caused progressive atrophy of striated ducts and oedematous degeneration of some cells occurred. Persisting "light" cells tended to contain few basal infoldings, few mitochondria and little apical secretory material.--Sympathetic denervation caused a loss of apical secretory material between 2-4 days, which may have been due to "degeneration activation". Thereafter little change was evident but some ductal atrophy had occurred by 32 days.--These changes in ductal secretory material correspond more closely than acinar changes to the alterations in glandular and salivary kallikrein resulting from similar experiments by other workers. It therefore seems likely that submandibular salivary kallikrein in the cat is present in the secretory material of striated ducts.     

Mechanism of cardioventilatory coupling: insights from cardiac pacing, vagotomy, and sinoaortic denervation in the anesthetized rat

Cardioventilatory coupling (CVC), a temporal alignment between the heartbeat and inspiratory activity, is a major determinant of breath-to-breath variation in observed respiratory rate (f(o)). The cardiac-trigger hypothesis attributes this to adjustments of respiratory timing by baroreceptor afferent impulses to the central respiratory pattern generator. A mathematical model of this hypothesis indicates that apparent CVC in graphical plots of ECG R wave vs. inspiratory time is dependent on the heart rate (HR), the rate of the intrinsic respiratory oscillator (f(i)), and the strength of the hypothetical cardiovascular afferent impulse. Failure to account for HR and f(i) may explain the inconsistent results from previous attempts to identify the neural pathways involved in CVC. Cognizant of these interactions, we factored in the HR-to-f(i) ratio in our examination of the role of the vagus nerve and arterial baroreceptors in CVC by cardiac pacing 29 anesthetized Sprague-Dawley rats and incrementally changing the HR. With the assumption of a relatively constant f(i), CVC could be examined across a range of HR-to-f(o) ratios before and after vagotomy, sinoaortic denervation, and vagotomy + sinoaortic denervation. We confirmed the relation between CVC, HR-to-f(o) ratio, and breath-to-breath respiratory period variability and demonstrated the loss of these relations after baroreceptor elimination. Sham experiments (n = 8) showed that these changes were not due to surgical stress. Our data support the notion that inspiratory timing can be influenced by cardiac afferent activity. We conclude that the putative cardiovascular input arises from the arterial baroreceptors and that the vagus nerve is not critical for CVC.