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D Bieger

Publications and source records attributed to D Bieger.

At least 55 records · Page 3Linked to original sources
PubMed1988

Similarity of relaxations evoked by BRL 34915, pinacidil and field-stimulation in rat oesophageal tunica muscularis mucosae.

1. In the rat oesophageal tunica muscularis mucosae (TMM) the potassium channel openers, BRL 34915 and pinacidil, raised the threshold for concentration-dependent K+ contractions, suppressed contractions evoked by field stimulation of the TMM in the presence of tetrodotoxin (TTX) and tetraethylammonium (TEA), and relaxed tonic contractions resulting from muscarinic cholinoceptor stimulation. 2. BRL 34915 and both (+)- and (--)-pinacidil increased 86Rb efflux from tracer-loaded tissues; nifedipine abolished this effect. 3. Relaxations produced by potassium channel openers were inhibited by a temperature drop from 37 degrees C to 26.5 degrees C, an increase in extracellular K+ concentration to 64 mM, and treatment with the calcium channel antagonist, nifedipine. The same treatments also blocked field stimulation-evoked TTX-insensitive relaxations. 4. It is concluded that field stimulation of rat oesophageal smooth muscle in the presence of cholinoceptor-induced tone results in an increase in K+ permeability that is directly or indirectly coupled to Ca2+ influx through potential-operated channels.

Animals↗
PubMed1988

Activity of in vivo canine cardiac plexus neurons.

The activity of 394 spontaneously active neurons located in the ganglionated plexus of the ventral epicardial fat pad overlying the right atrium and pulmonary veins was recorded. Ganglia that contained various numbers of neurons, many with two or more nucleoli, were identified adjacent to the recording sites. Spontaneous activity was correlated with the cardiac cycle in 39% and with the respiratory cycle in 8% of the identified neurons. Neuronal activity occurred in specific phases of the cardiac cycle when arterial pressure was between approximately 70 and 175 mmHg. During increases in systolic pressure induced by positive inotropic agents or aortic occlusion, responses of neurons that displayed cardiovascular-related activity were enhanced. These responses persisted after acute decentralization. The activity of 14% of all identified neurons was altered when discrete regions of the heart, great thoracic vessels, or lungs were mechanically distorted by gentle touch. Trains of stimuli, but not single stimuli, delivered to the vagosympathetic complexes, stellate ganglia, or cardiopulmonary nerves activated ganglionic neurons in intact or acutely decentralized preparations. It is concluded that the activity of some cardiac ganglion neurons is related to cardiovascular or respiratory dynamics and that some of these neurons receive inputs from sympathetic and parasympathetic efferent axons as well as from cardiac mechanoreceptors.

Adipose Tissue↗
PubMed1987

Viscerotopic representation of the upper alimentary tract in the medulla oblongata in the rat: the nucleus ambiguus.

The nucleus ambiguus has been reported to innervate various thoracic and abdominal viscera in addition to the musculature of the upper alimentary tract. However, the literature is contradictory as to how different regions of the nucleus ambiguus innervate specific organs. Therefore, a systematic investigation of the viscerotopic organization of the nucleus ambiguus was undertaken. In 102 rats, 0.5-10.0 microliter of HRP, WGA-HRP, cholera toxin-HRP or fluorescent tracers were injected into the IXth, Xth, and XIth cranial nerves and the major branches of the Xth as well as organs supplied by them. The results demonstrate that the nucleus ambiguus in the rat is made up of two major longitudinal divisions: a dorsal division comprised of three rostrocaudally aligned subdivisions representing the special visceral efferent component, and a ventral division comprised of at least two subdivisions representing the general visceral efferent component. The dorsal division corresponds to the nucleus ambiguus in the narrow sense and comprises a rostral esophagomotor compact formation, an intermediate pharyngolaryngomotor semicompact formation, and a caudal laryngomotor loose formation. Each of these formations displays a characteristic dendroarchitecture. The stylopharyngeal and cricothyroid motoneurons are displaced rostrad from the main pharyngeal and laryngeal motoneuronal pools. Thyropharyngeal (lower constrictor) motoneurons occupy the rostral half of the semi-compact formation and hyopharyngeal (middle constrictor) motoneurons its entire length. The ventral division of the nucleus ambiguus corresponds to the external formation, extends along the entire length of the medulla oblongata, and contains preganglionic neurons innervating the heart and supradiaphragmatic structures innervated by the glossopharyngeal and the superior laryngeal nerves.

Animals↗
PubMed1987

Cholinoceptor-mediated mechanical and electrical responses of rat oesophageal striated musculature. A comparison of two in vitro methods.

1. Both muscarinic and nicotinic cholinoceptor agonists produce a contractile response of the rat oesophageal tunica muscularis externa (TME) in vitro. 2. The muscarinic receptor-mediated responses were confined to the distal 0.5 cm of the TME, which contains an admixture of smooth muscle. 3. Nicotinic receptor-mediated responses were obtained throughout the length of the TME striated musculature and consisted of a fast and slow component, representing TTX-sensitive contractions, associated with muscle action potentials, and electrically silent contractures, respectively. 4. Contractions were observed only in superfused preparations. 5. Contractures were resistant to changes in extracellular cation concentrations designed to eliminate generation of nerve and muscle action potentials or release of neurotransmitters.

Animals↗
PubMed1987

Excitatory action of 5-HT on deglutitive substrates in the rat solitary complex.

The excitatory effect of serotonin (5-HT) on the pharyngeal stage of swallowing was investigated in urethane anaesthetised rats with respect to the involvement of neural substrates located in the central and intermediolateral regions of the nucleus tractus solitarii (NTS). Micropneumophoretic ejection of 5-HT 5-50 pmol either produced deglutitory responses or selectively facilitated the S-glutamate-evoked pharyngeal responses when applied in 1-10 pmol prepulses. The excitatory/facilitatory effect of 5-HT was enhanced by intravenous threshold doses of the 5-HT-mimetic, quipazine (0.3-1 mumol/kg) and reversibly blocked by the 5-HT2-receptor antagonists, methysergide, metergoline and ketanserin. 5-HT doses exceeding 10-60 pmol gave rise to a non-selective reversible inhibition of glutamate- and acetylcholine (ACh)-evoked pharyngeal or oesophageal responses which was not prevented or reversed by 5-HT2-receptor antagonists, but was readily overcome by increasing the amount of glutamate or ACh ejected. Non-selective deglutitive inhibition after high doses of 5-HT could, therefore, result from neuronal desensitization secondary to excessive stimulation or activation of a different type of 5-HT receptor. These results corroborate an excitatory role of 5-HT in both reflex and automatic swallowing and demonstrate that the NTS is a major site of serotoninergic facilitation of swallowing.

Acetylcholine↗
PubMed1987

Re-investigation of the innervation of the thymus gland in mice and rats.

Central to the postulated relationship between the brain and the immune system has been evidence for the direct neural innervation of primary organs of the immune system. It has been reported previously that the thymus gland in rats and mice receives a substantial innervation from the "retrofacial" nucleus of the brain stem and ventral horn cells of the upper cervical spinal cord. Based on the proximity of the thymus to thoracic viscera and neck musculature known to receive motor fibers from these same areas of the brain stem and spinal cord, we examined the possibility that retrogradely labeled cells in the brain stem and spinal cord following injections of tracers into the thymus are due to spread of tracer into the esophagus and neck musculature. Small injections (0.5-2.0 microliter) of wheatgerm agglutinin-horseradish peroxidase (WGA-HRP) were made into the thymus, the esophagus, and the longus colli muscle of rats or mice. Also, the effects of a unilateral cervical vagotomy on cholinesterase activity in the thymus were examined. Finally, the source of the sympathetic supply to the thymus and the presence of catecholamine and cholinesterasic fibers in the thymus was reassessed. Injections of WGA-HRP into the thymus produced little or no labeling in the brain stem and spinal cord. In contrast, control injections into the esophageal wall resulted in numerous intensely labeled cells in the compact formation of the nucleus ambiguus, irrespective of the rostral-caudal level of the esophageal injection. Similarly, tracer injections into the longus colli muscle resulted in numerous intensely labeled cells in the ventral horn of the upper cervical spinal cord. Unilateral vagotomy did not alter cholinesterase activity in the thymus even though it was largely depleted in the ipsilateral nucleus ambiguus. The histochemical studies verified a major sympathetic innervation of the thymus gland. In keeping with this result, in animals in which no labeled cells were observed in the brain stem or spinal cord following thymus injection, labeled cells were, however, observed in the sympathetic chains from the superior cervical ganglia caudal to the T3 ganglia. In summary, all labeled cells in the brain stem and cervical spinal cord observed following tracer injections into the thymus can be accounted for by spread of the tracer into surrounding structures, leading to spurious labeling.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Effects of cold storage on relaxation responses in the rat oesophageal tunica muscularis mucosae.

Tetrodotoxin-resistant relaxations produced by electrical field stimulation, 5-hydroxytryptamine (5-HT), and A23187 (calimycin) were investigated in the rat isolated oesophageal tunica muscularis mucosae subjected to cold storage of varied duration. Cold storage for 2 days abolished cholinergic nerve mediated contractions to field stimulation; however, field stimulation evoked relaxations and muscarinic agonist evoked contractions persisted undiminished. After 5 days of cold storage, field-stimulated relaxations, as well as tension generating capacity of the tissue, were significantly reduced. Proximodistal differences were observed in tunica muscularis mucosae sensitivity to the relaxant effects of serotonin and A23187 and these were exaggerated after cold storage. In the distal segment, cold storage for 2 days unmasked ketanserin-sensitive 5-HT receptors mediating contractions. Similarly, A23187 induced contractions rather than relaxation in cold-stored distal tunica muscularis mucosae; however, this effect was resistant to ketanserin. Immunohistochemical staining by means of the peroxidase-antiperoxidase technique revealed 5-HT-like immunoreactive "mast cells" within the tunica muscularis mucosae. These cells appeared to be associated with the smooth muscle rather than the vasculature. It is concluded that field-stimulated relaxation is not dependent on intramural nerves, and it is unlikely that the release of 5-HT from mast cells or other cells mediates field-stimulated relaxation. However, confirmation awaits the provision of an antagonist against the novel 5-HT receptor that mediates 5-HT-induced relaxations.

Animals↗
PubMed1986

Tetrodotoxin-sensitive and -insensitive relaxations in the rat oesophageal tunica muscularis mucosae.

1. Relaxation responses were produced by vagal and field stimulation, respectively, of the whole oesophagus preparation from the rat and of the isolated tunica muscularis mucosae (t.m.m.) preparation from the rat. These relaxation responses persisted in the presence of antagonists of histamine, serotonin, noradrenaline and acetylcholine. 2. Unlike vagally evoked relaxation, that evoked by low-frequency field stimulation, i.e. field-stimulated relaxation (f.s.r.) was generally resistant to tetrodotoxin (TTX). 3. Both types of relaxations exhibited remarkable temperature sensitivity and were abolished by lowering the bath temperature from 37 to 28 degrees C. 4. TTX-resistant relaxations were also produced by scorpion (Leiurus quinquestriatus) venom, the calcium ionophore, A23187 (calimycin) and by increasing the extracellular potassium by 2 mM. The failure of these agents to inhibit f.s.r. is inconsistent with a releasing and/or depleting action on any endogenous mediator. 5. Relaxations produced by vasoactive intestinal peptide (VIP) could be blocked by alpha-chymotrypsin which, however, failed to abolish f.s.r., suggesting that VIP is not the mediator of f.s.r. 6. F.s.r. was completely blocked by the calcium channel antagonists, verapamil (10(-6) M), nifedipine (10(-7) M), and by magnesium (20 mM). 7. Our results indicate that TTX-insensitive relaxations in the isolated t.m.m. are dependent upon extracellular calcium, are due to activation of potential-operated calcium channels and are not mediated by VIP.

Animals↗
PubMed1985

Serotonin immunoreactivity in spinal cord axons and terminals of rodents with experimental allergic encephalomyelitis.

Spinal cord axons and terminals stained for serotonin-like immunoreactivity were examined in rats and guinea-pigs with experimental allergic encephalomyelitis, an animal disease model for multiple sclerosis. During the paraplegic stage of experimental allergic encephalomyelitis, many serotonin-positive axons in the ventral and lateral funiculi of both rats and guinea-pigs were found to be grossly distorted, often appearing to end in bulbous enlargements. Serotonin-immunoreactive terminal varicosities in the gray matter were swollen and diminished in number in paraplegic rats with experimental allergic encephalomyelitis. In addition, the intervaricose segments which were observed in control rats appeared to be missing in rats with experimental allergic encephalomyelitis. Depletion of serotonin-positive terminals was much more pronounced in paraplegic guinea-pigs with experimental allergic encephalomyelitis than in rats with experimental allergic encephalomyelitis, but those terminals which remained in the guinea-pigs were morphologically similar to those of control guinea-pigs. The greater depletion of serotonin-positive terminals in guinea-pigs may reflect a more severe disease state in this species, as none of the guinea-pigs survived the acute stage of paralysis. As the time period between recovery from paralysis and sacrifice increased in rats with experimental allergic encephalomyelitis, serotonin-positive terminals in the gray matter became increasingly more normal in appearance. Even by the first day of recovery, some intervaricose segments could again be observed, and after two weeks of recovery, the terminals were much more numerous and less swollen than during the paraplegic stage of disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Atypical indolamine-immunoreactive cell groups in the dorsal myelencephalon of the rat.

The presence of atypical indolamine-immunoreactive (IAI) neurones in the dorsal myelencephalon of the rat was demonstrated by means of peroxidase-antiperoxidase (PAP) immunocytochemistry. Besides the area postrema, two other regions, viz. the solitary complex and the superficial rostral cuneate fascicle, were found to contain neuronal perikarya displaying a normally weak staining which was markedly enhanced after monoaminoxidase (MAO) inhibition. In contrast to immunoreactive cells of the periaqueductal central gray, the dorsal myelencephalic IAI neurons were undetectable after serotonin synthesis inhibition with p-chlorophenylalanine (PCPA), as were immunoreactive terminal neuropils in most brainstem areas. However, sequential treatment with the MAO inhibitor, iproniazid, completely reversed the PCPA-induced suppression of perikaryal immunoreactivity and partially restored axonal staining. None of the atypical cell groups displayed a detectable formaldehyde-induced specific histofluorescence. Since brain levels of tryptamine are likely to increase significantly after MAO inhibitor/PCPA treatment, and furthermore tryptamine can be assumed to cross-react with serotonin, it is suggested that the observed atypical IAI neurons may represent either a subpopulation of serotoninergic neurons; previously postulated true tryptamine neurons; or non-indolaminergic neurons endowed with a selective uptake mechanism for serotonin or tryptamine. These results corroborate the view that different types of indolamine neurons exist in the rat brainstem. Moreover, they underscore the need for cautious interpretation of serotonin neuron mapping studies involving the use of MAO inhibitors.

Animals↗
PubMed1985

Pharmacological properties of mechanical responses of the rat oesophageal muscularis mucosae to vagal and field stimulation.

Electrical stimulation applied to vagal oesophageal branches of the isolated curarized oesophagus, or via field electrodes to the isolated tunica muscularis mucosae (TMM), increased longitudinal tension and intraluminal pressure in a frequency-dependent manner. Differences between cervical and distal TMM segments were noted in frequency-response relationships, as well as in the pulse-width dependence of contractions to field stimulation. Vagally- and field-stimulated contractions were eliminated by tetrodotoxin or hyoscine, indicating their mediation by cholinergic neurones. The field-stimulated postganglionic responses were resistant to hexamethonium or (+)-tubocurarine and weakly inhibited by morphine. Vagally- and field-stimulated TMM contractions were mimicked by muscarinic agonists, augmented by acetylcholinesterase inhibitors, and inhibited more effectively by beta-than by alpha 1-or alpha 2-adrenoceptor agonists. 5-Hydroxytryptamine (5-HT) exerted excitatory and/or inhibitory effects: TMM in situ responded with a hexamethonium-resistant, ketanserin-sensitive transient increase in tension comparable to that produced by field stimulation. In the isolated TMM, moderate excitatory responses were limited to the distal portion with inhibition predominating in the remaining proximal portion. 5-HT-induced inhibitory effects on field-stimulated tension responses were paralleled by relaxant effects on muscarinic agonist-induced tonic contractile responses, both of which were resistant to 5-HT-receptor antagonists including ketanserin, lysergic acid diethylamide (LSD), methysergide or methergoline. Field stimulation at a low frequency and pulse durations greater than 1.0 ms produced a relaxation response in preparations exposed to tetrodotoxin or hyoscine, provided that active muscle tonus was present. The relaxation in response to field stimulation was insensitive to antagonists of 5-HT, catecholamines, histamine, or indomethacin, suggesting a non-neurogenic origin. Histochemical examination of the isolated TMM preparation for cholinesterases revealed the presence of an extensive submucosal ganglionic plexus. It is concluded that: (i) intrinsic cholinergic neurones of the submucosal plexus form the final common pathway for extrinsic vagal and local (myenteric) projections to the TMM; (ii) the neural basis, if any, of non-cholinergic non-adrenergic inhibitory mechanisms remains to be established; (iii) the TMM may assist in generating propulsive oesophageal motility.

Animals↗
PubMed1984

Muscarinic activation of rhombencephalic neurones controlling oesophageal peristalsis in the rat.

The role of muscarinic cholinergic mechanisms in the brainstem in the control of oesophageal peristalsis was investigated in rats anaesthetized with urethane. Primary deglutitive peristalsis, evoked by electrical stimulation of the brainstem or intravenous administration of the serotonin agonist quipazine, was abolished for periods of 1.5 to 2 h by scopolamine and atropine (0.1-0.2 microM/kg) as well as by methscopolamine (1.25-5 microM/kg). In contrast, the buccopharyngeal stage of evoked swallowing was facilitated. A deglutitive effector area was mapped in the intermediolateral portion of the solitary complex by the use of micropneumophoretic application of S-glutamate (35-350 pM) and the cholinoceptor agonists D,L-muscarine and acetylcholine (50-100 pM). Scopolamine partially antagonized single propulsive contractions of the oesophagus evoked by S-glutamate, but completely inhibited rhythmic propulsive or synchronous oesophageal contractions evoked by muscarinic agonists or acetylcholine. Injection of S-glutamate or acetylcholine into the ambiguus complex produced propulsive or non-propulsive oesophageal responses depending on location. Responses evoked by acetylcholine were potentiated by systemic administration of physostigmine, but were resistant to scopolamine; propulsive responses evoked by S-glutamate were partially inhibited by scopolamine. Injection of the retrogradely-transported fluorescent tracer bisbenzimide into the rostral ambiguus complex resulted in labelling of a discrete cell group located within the deglutitive region of the solitary complex. It is concluded that this region contains premotor elements forming part of the internuncial network organizing oesophageal peristalsis. The source of postulated cholinergic afferents to these neurones remains to be identified.

Acetylcholine↗
PubMed1984

Selective accumulation of hydroxytryptamines by frog tectal neurones.

By means of histofluorescence microscopy, 5,7-dihydroxytryptamine was shown to be taken up by selective populations of brain neurones of the frog, Rana pipiens, following both intracranial administration and in vitro incubation with isolated brain preparations. Presumptive non-aminergic cell bodies of the superficial aspect of tectal lamina 6 exhibited more avid uptake than did putative serotonin perikarya of the raphe complex. Within the tectum, 5,7-dihydroxytryptamine uptake appeared to be restricted to large piriform neurons; in the torus semicircularis, it occurred in a morphologically dissimilar group of scattered cells. The same tectal cell system accumulated 5-hydroxytryptamine and 6-hydroxytryptamine, but not N-acetylserotonin, melatonin, or noradrenaline. 5,7-Dihydroxytryptamine uptake was insensitive to cold or imipramine; however, it was blocked by ouabain at high but not low temperature. At concentrations greater than or equal to 100 microM, 5,7-dihydroxytryptamine-induced fluorescence was sufficiently intense to permit tracing of intratectal dendrites and tectofugal axonal processes projecting to a lateral diencephalic neuropil and an ipsilateral isthmic neuropil. While previous monoamine histofluorescence and immunohistologic studies have not revealed serotonin-containing perikarya in the ranid tectum, our findings demonstrate that lamina 6 piriform projection neurones, presumably lacking indolamine-synthesizing enzymes, possess a striking capability for accumulating hydroxylated tryptamines.

5,7-Dihydroxytryptamine↗
PubMed1983

Mineral metabolism and vitamin D status before and up to five years following highly selective vagotomy in duodenal ulcer patients.

The influence of highly selective vagotomy (HSV) upon mineral metabolism was investigated in patients with duodenal ulcer (DU). Data obtained before HSV were compared with those from healthy control subjects and, additionally, with data from pre- and post-HSV observations. In DU the function of the parathyroid glands is unsettled because of decreased renal phosphate threshold, normal serum parathyroid hormone and decreased nephrogenous urinary cAMP. HSV decreases the phosphate threshold further, but does not change parathyroid hormone, calcitonin, or nephrogenous cAMP. Conversely, besides hypergastrinemia, HSV accounts for a decrease in total calcium in serum in the presence of an increase of the intestinal calcium absorption, while the bone mineral content is stable up to 5 years following HSV. Moreover, HSV normalizes the decreased serum concentration of 25-hydroxyvitamin D found pre-operatively in DU, while that of 24,25-dihydroxyvitamin D, known to be effective upon bone and gut, remains unaltered. A classification according to pre-operative gastric acid secretion (normo- and hypersecretors) does not provide further insights into variables of mineral metabolism encountered in DU pre- and post-HSV.

Adult↗
PubMed1982

Acetylcholinesterase in pontomedullary catecholamine neurons of the adult albino rat.

This study investigated the cholinesterasic reactivity of catecholamine neurons in the rat hindbrain with the aid of a two-step histochemical procedure. First, catecholamine cells were visualized by their formaldehyde/glutaraldehyde induced specific histofluorescence and then poststained in the same tissue with a thiocholine technique for acetylcholinesterase (AChE). Processing the vibratome-sectioned tissue in phosphate buffer subsequent to initial aldehyde fixation permitted satisfactory preservation of both amine fluorophores and esterasic reactivity. Our results, in both randomly sampled and serially sectioned material, unequivocally establish the presence of AChE in all pontomedullary cell groups emitting catecholamine fluorescence, the majority of which are known to consist of noradrenaline perikarya. Hence in contrast to previous reports the occurrence of AChE in central noradrenaline neurons appears to be generalized. The intensity of histofluorescence and esterasic staining were uncorrelated in most regions. It remains for future study to determine whether AChE in brain catecholamine neurons indicates their cholinoceptivity or subserves the catabolism of other neuromediators such as substance P.

Acetylcholinesterase↗
PubMed1980

Interaction between primary afferent nerves in the elicitation of reflex swallowing.

In adult cats anesthetized with urethan, a number of observations were made that support the concept that some control over the rate of reflexly induced swallowing occurs in the intermediate network at the level of the nucleus of the solitary tract. It was shown that different nerves, e.g., the two superior laryngeal and glossopharyngeal nerves, when activated in sequence interact in such a manner as to facilitate reflex swallowing. It was also shown that the decrement in the reflex response observed to continuous stimulation of a primary afferent nerve, e.g., one superior laryngeal, can be reversed by switching the stimulation to another nerve either on the same or contralateral side. And finally, following discrete medullary lesions, it was observed that that portion of the nucleus of the solitary tract located 2 mm or more rostral to the rostralmost point of the dorsal medial sulcus appears to contain an integral component of the intermediate network that governs reflexly induced swallowing, whereas lesions restricted to the ventrolateral portion of the nucleus of the solitary tract have no effect on the reflex response.

Action Potentials↗