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PubMed1985

Renal excretory function after renal denervation and administration of diuretics to unanaesthetized dogs evaluated by a mathematical model for describing the dynamics of the excretory process.

A mathematical model has been employed for describing the cumulative curve of excretion after diuretic administration. The program, developed in accordance with the model and the criteria of evaluation, allows an easy and rapid comparison of the effects of different kinds of diuretics in different doses. The experiments were carried out prior to and after left kidney denervation in unanaesthetized dogs with exteriorized ureters. Acetazolamide 3.0 mg/kg b.w., Furosemide 0.2 mg/kg b.w. or Amiloride 1.0 mg/kg b.w. were injected intravenously. The amount of excreted urine as well as of sodium, chloride and potassium was studied. No statistically significant differences in the dynamics of renal excretory function between the denervated and innervated kidneys were observed after the administration of Acetazolamide and Amichloride. After Furosemide, the flow-rate during maximum diuresis and the maximum chloride excretion rate were greater in the denervated kidney. No statistically significant differences were noted in sodium excretion. It appears that the greater part of compensatory reabsorption in the distal tubules of the denervated kidney takes place in the zone up to macula densa.

Acetazolamide↗
PubMed1987

[Influence of upper abdominal autonomic denervation on pancreatic and gut hormone secretion].

The influence of the upper abdominal autonomic denervation on the secretions of insulin (IRI), vasoactive intestinal polypeptide (VIP), secretin, pancreatic glucagon (IRG) and gut glucagon-like immunoreactivity (Gut GLI) was studied. Adult mongrel dogs, which were divided into control, truncal vagotomy and upper abdominal autonomic denervation groups, were investigated by intraduodenal glucose infusion test under general anesthesia. The glucose level and the response of insulin, VIP, secretin, IRG and Gut GLI secretions in the truncal vagotomy group showed no significant difference compared with those in the control group. These findings suggested that the vagus nerve is not concerned largely in the glucose level and in response of insulin VIP, secretin, IRG, and Gut GLI induced by intraduodenal glucose loading. In the upper abdominal denervation group, severe diarrhea was manifested within 60 minutes after the intraduodenal glucose infusion test, and significantly increased responses were shown in secretions of insulin, VIP, secretin, IRG, and Gut GLI. These findings suggested that upper abdominal autonomic denervation acted acceleratory on the secretions of insulin, VIP, secretin, IRG and Gut GLI by intraduodenal glucose infusion test. In addition, it was suggested that dissection of upper abdominal autonomic plexus caused diarrhea after the intraduodenal glucose infusion test.

Abdomen↗
PubMed1987

The effect of caffeine on normal and denervated gastrocnemius muscles of Uromastix hardwickii.

The effect of time and 5 mM caffeine was studied on the maximum twitch tension of the normal and 11-13 days denervated gastrocnemius muscles of Uromastix hardwickii. The maximum twitch tension was found to decrease with time and it remained about 68% of initial after 60 minutes at 20 degrees C. Five mM caffeine only produced potentiation in normal and denervated muscles while there was no contracture in either muscle. Although caffeine increased the overall contraction and relaxation times in control muscles, it was more effective on the contraction time of the denervated muscles in which the contraction time increased with time. Denervated muscles were seen to be less sensitive to caffeine as the contraction times increased with time (at about 30-40 minutes) in these muscles while in normal control muscles the contraction time increased immediately. The action of caffeine in relation to these effects is discussed.

Animals↗
PubMedDate not supplied

[Intrathyroid deiodination of thyroxine: the effect of thyrotropic hormone and denervation of the thyroid].

Intrathyroid transformation of thyroxin (T4) into triiodothyronine (T3) and the role of thyrotropic hormone and denervation in this process were studied with in vivo blood perfusion of dog thyroid gland in situ and at 37 degrees C. Both labelled 125I-T4 (200,000 imp/min) and nonlabeled T4 (1000 ng) were administrated in the arteries of thyroid lobules in situ and in a constant-temperature cabinet. Enhanced excretion of triiodothyronine (both labeled and nonlabeled) observed two hours after the injection in the thyroid blood output was suggested as an evidence of denervation-independent deiodination occurring in the thyroid tissue. Without T4 load the proportion of T3 in the thyroid venous blood was significantly increasing under the thyroid denervation thus attesting inhibitory effect of nervous impulse on T4 deiodination in the thyroid gland. TTH being administrated into thyroid arteries in a dose of 20 I.U. produced a pronounced elevation of T4 thyroid conversion in T3 which was less manifest in the process of denervation thus evidencing the high sensitivity of the process to TTH.

Animals↗
PubMed1985

Insulin action in denervated skeletal muscle. Evidence that the reduced stimulation of glycogen synthesis does not involve decreased insulin binding.

The motor nerves to rat soleus and epitrochlearis muscles were sectioned 1-3 days before the muscles were incubated in vitro to assess insulin action and binding. The hormonal stimulation of [U-14C]glucose into glycogen in both muscles was decreased by over 80% after 3 days of denervation. Associated with the reductions in glycogen synthesis were losses in the ability of insulin to activate glycogen synthase. Even so, denervated and control muscles bound the same amounts of 125I-labeled insulin over a wide range of insulin concentrations. Scatchard analysis indicates that denervation changed neither receptor numbers nor affinities. The results presented strongly suggest that the loss of the ability of insulin to stimulate glycogen synthesis following denervation is the result of a postreceptor defect.

Animals↗
PubMed1985

Comparison of in vivo and in vitro cholinergic responses of normal and denervated canine hearts.

Ten dogs were subjected to total extrinsic cardiac denervation. The negative inotropic responses of their hearts were compared with those of nine normal controls with respect to acetylcholine (ACh; 0.1-1.0 micrograms) and nicotine (0.5-100 micrograms) administered intra-coronary. The dogs were on cardiopulmonary bypass and atrial and ventricular contractility were measured by means of a four-chamber isovolumic technique. At the end of this phase of the experiment, atrial strips were removed for in vitro evaluation of negative inotropic responses to Ach (1 X 10(-8) to 1 X 10(-6) M) and nicotine (1 X 10(-6) to 1 X 10(-4) M). Both in vivo and in vitro methods demonstrated a leftward shift of the dose-response curve for nicotine in denervated hearts, indicative of denervation hypersensitivity. Hypersensitivity to ACh was seen in atria in vitro but not in vivo. An additional 13 dogs were used only for in vitro studies. There was no difference in response between these dogs and those which had been used for both in vivo and in vitro studies. The results support the in vivo observation that the intrinsic cardiac neurons become supersensitive to nicotinic activation after extrinsic denervation. In addition, in vitro testing revealed atrial hypersensitivity to ACh which was not detected by in vivo methods. Inasmuch as the in vivo and the in vitro testing were done on the same animals, a method for determining equivalence for in vivo doses and in vitro concentrations is presented.

Acetylcholine↗
PubMed1985

Effect of denervation and/or reserpine-induced changes on adrenomedullary catecholamines in pigeon: a fluorescence histochemical study.

Splanchnic denervation of the left adrenal gland was made in adult pigeons of both sexes. Denervation of the adrenal medulla alone did not produce any appreciable change in adrenomedullary catecholamine fluorescence in pigeon. Reserpine, at the doses of 0.05 mg, 0.2 mg and 0.8 mg/100 gm body weight was injected in both innervated and denervated pigeons. Reserpine, at all doses, induced catecholamine fluorescence depletion from the innervated pigeon adrenal medulla. Denervation failed to affect reserpine-induced epinephrine depletion while it prevented reserpine-induced norepinephrine depletion only at a low dose of reserpine.

Adrenal Medulla↗
PubMed1984

Neonatal denervation inhibits the normal postnatal decrease in endplate channel open time.

The apparent mean channel open time (tau) of acetylcholine receptors (AChR) at skeletal muscle endplates decreases greater than 3-fold during development. In rat soleus muscles, the change occurs between postnatal days 8 and 18 as channels with long apparent open times (tau = 4.5 msec) disappear while channels with short apparent open times (tau = 1.5 msec) increase in number. We studied the role of innervation in this process by denervating neonatal soleus muscles prior to channel conversion. Tau at the denervated endplates was assayed at various times between days 8 and 18 by using fluctuation analysis. We found that early denervation blocked, or at least delayed, channel conversion. Unexpectedly, there was enhanced extrajunctional ACh sensitivity in the innervated muscles contralateral to the denervated ones. This observation allowed us to compare the apparent open times of junctional AChRs with those of extrajunctional AChRs 200 micron distant in the same innervated fibers. In developing muscles, tau at the extrajunctional sites decreased in parallel with tau at the endplates. Thus, neural regulation of AChR channel gating extends well beyond the endplate boundaries.

Acetylcholinesterase↗
PubMedDate not supplied

[Metabolic influences on the onset of fibrillation and on membrane potentials of denervated muscles].

Fibrillation activity and membrane depolarization which follow denervation, were studied in skeletal muscles of control and pretreated adult rats. The investigation was carried out on both fast (Tibialis Anterior) and slow (Soleus) muscles. The pretreatment consisted in prolonged (4 days) starvation, or Streptozotocin-induced diabetes, preceding denervation. Denervation was performed by cutting the sciatic nerve. In fast as well as in slow muscle, both pretreatment significantly delayed the onset of fibrillation. Starvation enhanced depolarization only in fast muscle, while diabetes was effective also in slow muscle. The results support the view that membrane depolarization (but not fibrillation activity) in denervated muscle is related to an altered carbohydrate metabolism.

Animals↗
PubMedDate not supplied

Effect of denervation on cyclic amp regulating enzymes in the rat gastrocnemius muscle.

The activities of cyclic AMP regulatory enzymes (adenylate cyclase and phosphodiesterase) were studied in rat gastrocnemius muscle after denervation. Basal adenylate cyclase activity in whole homogenate increased progressively from the 3rd day reaching values more than 7-fold those of the controls 30 days after denervation. No significant differences between the contralateral and denervated muscle were detected as regards adenylate cyclase activation by catecholamines or NaF. Carbamylcholine was with effect. Cyclic AMP phosphodiesterase activity increased significantly at 3 days after denervation as was still significantly elevated at 60 days.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1984

Effect of venous drainage to the vena cava and denervation on endocrine function of pancreatic segments in dogs.

IVGTTs and OGTTs (0.5 g/kg glucose) were performed in 36 normal dogs (group N) and one to two weeks postoperatively in 22 dogs after partial pancreatectomy [( ppx ] group I); nine dogs after ppx and pancreatic venous drainage to the inferior vena cava (group II); nine dogs after ppx and pancreatic denervation (group III); and in seven dogs after ppx , venous drainage to the vena cava, and denervation (group IV). Fasting glucose and insulin were in the same range in all dogs. In IVGTT peak insulin levels were diminished by ppx , but total insulin secretion was similar in all dogs. Systemic venous drainage and denervation had no effect on glucose tolerance, peak insulin, and total amount of insulin appearing in the peripheral circulation. In groups II and IV, there was a linear correlation between individual K values and the area under the insulin curve, whereas there was no such correlation in groups I and III. In OGTTs , glucose tolerance and the total amount of insulin were equal in groups I through IV but diminished compared to group N. Venous transposition resulted in an early increase of insulin secretion and a late insulin peak. Thus, glucose load and islet cell mass are the determinants of glucose tolerance and insulin secretion in this model. Neither drainage of the pancreatic blood to the vena cava nor denervation have measurable influence on magnitude and effectivity of fasting and stimulated insulin secretion.

Animals↗
PubMed1984

The response of denervated axolotl arms to delayed amputation.

Forearms of juvenile axolotls can be kept denervated for up to 4 weeks by deflecting brachial nerves to the flank. A more orthodox second denervation prolongs this state up to a total of six weeks. The denervated arms are unable to regenerate for the whole period, but eventually become reinnervated and then regenerate normally. These results and analogous experiments on adult newts prompt a partial retraction and reinterpretation of my previous report on regeneration after prolonged denervation.

Ambystoma mexicanum↗
PubMedDate not supplied

Effect of in vivo electrical stimulation on the carbohydrate metabolism of control and denervation atrophied muscle of dog, Canis domesticus.

The standardized programme of electrical stimulation was applied to the control and denervation atrophied muscle of dog, Canis domesticus and the pattern of changes in the carbohydrate metabolism was analysed in the control (C), denervated control (DC), control stimulated (CS) and denervated stimulated (DS) gastrocnemius muscles. The programme of electrical stimulation of the control muscle has elevated glycogenolysis, glycolysis and increased the level of operation of TCA cycle with decreased mobilization of carbohydrates into hexose monophosphate pathway, indicating the setting in of trained condition. Sciatectomy, on the other hand, lowered the level of operation of glycogenolysis and decreased the utilization of carbohydrates through hexose-mono and di-phosphate pathways and TCA cycle. The programme of electrical stimulation applied to the denervated muscle has restored the utilization of carbohydrates through hexose mono and diphosphate pathways and oxidative metabolism indicating the applicability of this programme of electrical stimulation in the treatment of muscular atrophy.

Animals↗
PubMed1982

Feedback regulation of glomerular filtration rate in the denervated rat kidney.

Micropuncture studies were done in anesthetized rats to determine whether the sensitivity of tubuloglomerular feedback might be modified by acute renal denervation. The proximal single nephron glomerular filtration rate (SNGFR) was significantly greater than the distal SNGFR was, when measured in a paired manner from the same nephron. Early proximal flow rate (EPFR) was measured during orthograde perfusion of the loop of Henle with Ringer's solution. A change of loop perfusion rate from 0 to 40 nl/min decreased EPFR in normal, sham-denervated, and denervated kidneys. The differences between proximal and distal SNGFR and the percent reduction of EPFR were not different among the three groups. These results indicate that the sensitivity of the tubuloglomerular feedback may not be affected by acute denervation.

Animals↗
PubMedDate not supplied

[Change in concentration of microelements in denervated muscles].

Concentration of Zn, Br, and Rb in intact and denervated rat muscles was estimated by X-ray fluorescent analysis. Differences in the content of these elements at different times after denervation were found. Concentration of microelements (microgram/g dry weight) in denervated muscles was shown to increase by the end of the third week, while that in the intact muscle decreased. The analysis of microelement content in the intact muscle revealed two steps of postdenervational changes: hypertrophic and atrophic ones. Differences between the above changes in microelement concentrations and their content in the intact muscle suggest a hypothesis that protein dissociation and utilization of microelements in muscle cells after denervation proceeds with different rates.

Animals↗
PubMed1978

Electrical and mechanical activities in the denervated semitendinosus muscle of the frog.

Denervated frog's semitendinosus muscles were studied. No differences in resting potential were found between denervated and control fibres. Spontaneous discharges of fibrillation potentials were recorded from random points along the length of denervated fibres. The frequency of the potentials varied between 2 and 30/sec; the duration of the discharges varied between 5 and 120 sec. Each potential originated from a prepotential, reversed the sign of the membrane potential between 10--20 mV, and was followed by a transient hyperpolarization. The time course of the spontaneous potential produced by a fibre was slower than that of a spike elicited by an electrical pulse applied to the same fibre. After the cessation of a train the fibrillation potentials were replaced by small rhythmic potentials 10--15 mV in amplitude; this activity lasted for periods as long as 7 min. Some reduction of the resting potential was usually observed during the discharge of a train of fibrillation potentials, however, repolarization occurred after the end of electrical activity and a second discharge of full size fibrillation potentials could be observed in most of the fibres. Mechanical activity was not always present. When observed, it was reduced to light movements unable to eject the microelectrode. In general, no one-to-one correlation could be observed between fibrillation potentials and mechanical activity. In those fibres in which the correlation was present, the tension developed by a single fibrillation was less than 0.2/kg/cm2. Some denervated fibres developed tetanus-like contractions, the maximal tension developed by these fibres was less than 1.0 kg/cm2. The data are discussed according to the current ideas on generation of fibrillation potentials.

Action Potentials↗
PubMed1981

Effects of motor denervation of the external ear muscles on the audio-visual targeting reflex in cats.

The effect of uni- and bilateral denervation of muscles of the pinna on the audio-visual targeting reflex reinforced by food was studied. In comparison with the normal group the unilaterally denervated animals showed a decreased capacity to localize sound sources placed behind the animal ipsi- and contralaterally to the operated side. The denervation of the second ear in these animals induced a further decrease of the localization scores, especially of the sources placed behind them. The localization behavior strategies were different depending on the integrity of the innervation of muscles of the pinna. The stimulation of the operated side with tones of a 30 dB higher intensity than in the normal side did not improve the animals’performance in localizing the sound sources. The shortening of duration from 500 to 50 ms reduced, the capacity to localize the loudspeakers placed ipsilaterally to the denervated side, especially those behind the animal. The role for the targeting reflex of the feedback information from the muscles controlling the pinna movements, and the significance of the postural changes induced by the tone are discussed.

Animals↗
PubMed1981

A correlation of the alpha-bungarotoxin binding sites (acetylcholine receptors) and intramembranous particles in denervated skeletal muscle of rat.

A quantitative distribution of alpha-bungarotoxin (alpha-BGT) binding sites i.e. acetylcholine receptors (AchR) has been investigated and correlated with the distribution of intramembranous particles (approximately 15 nm in diameter) observed on the freeze-fractured face (P-face) of the non-synaptic sarcolemma of denervated muscle. By both light and electron microscopy autoradiography, randomly distributed clusters of alpha-BGT sites are visualized on the plasma membrane of the denervated muscle. Such distributions of the toxin binding sites correspond with that of the 15 nm particles on the P-face of the denervated muscle. Quantitative studies suggest that upon denervation the toxin binding sites increase approximately 60-fold in the non-synaptic sarcolemma. However, the density of these alpha-BGT sites is 4--5 times more than the density of the 15 nm particles. On the basis that there are two alpha-BGT binding sites per AchR molecule, these results suggest that each 15 nm particle is composed of more than one AchR receptor. In addition to the increase in toxin binding sites on the non-synaptic sarcolemma, a notable increase in the number of silver grains is observed in the peripheral sarcoplasm and is speculated to be part of the intracellular pool of receptors.

Animals↗