Biomedical subjects

K B Thor

Publications and source records attributed to K B Thor.

41 records · Page 3Linked to original sources

PubMed1987

Reappraisal of the flap valve mechanism in the gastroesophageal junction. A study of a new valvuloplasty procedure in cadavers.

This study in cadavers was carried out to resolve whether a functional flap valve exists at the gastroesophageal (GE) junction and whether an accentuation of this valve (valvuloplasty) could increase the GE pressure gradient. Cadavers were investigated with open manometry catheters in the esophagus and stomach. Stepwise (50 ml) filling of the stomach demonstrated a GE pressure gradient of 4.6 +/- 1.6 cmH2O. This gradient could be significantly increased to 12.5 +/- 3.1 cmH2O (p less than 0.05) by performing a valvuloplasty procedure through a gastrostomy. By depressing the fundus of the stomach, the angle of His was made more obtuse and the flap valve component eliminated. This maneuver resulted in reflux in all cadavers before as well as after valvuloplasty. These experiments and observations taken together with our valvuloplasty procedure, confirm that a flap valve mechanism exists at the GE junction.

Adult↗

PubMed1983

Parasympathetic ganglia: naloxone antagonizes inhibition by leucine-enkephalin and GABA.

Synaptic transmission in parasympathetic ganglia of the cat urinary bladder was depressed by low doses (0.1-10 micrograms i.a.) of Leu- or Met-enkephalin but only by larger doses (10 micrograms-1 mg i.a.) of morphine. Naloxone blocked the depressant effects of the opiates as well as the depression produced by GABA, but did not block the depressant effects of norepinephrine. Intracellular recording revealed that Leu-enkephalin reduced EPSP-amplitude and lowered the probability of synaptically evoked firing without altering postsynaptic membrane potential or resistance. These findings suggest that enkephalinergic inhibition in bladder ganglia is mediated at least in part by a presynaptic site of action on delta opiate receptors.

Animals↗

PubMed1983

Naloxone induced micturition in unanesthetized paraplegic cats.

In chronic spinal cats 2 to 10 weeks after transection of the spinal cord at the lower thoracic level (T12-T13), the administration of naloxone, an opiate antagonist, (32-500 micrograms./kg. i.p.), stimulated micturition. The total quantity of urine released after administration of naloxone ranged from 10 to 70 per cent, (mean 39 per cent) of the initial bladder volume. The response to the drug occurred 5 to 10 minutes after injection and was characterized by repeated periodic expulsion of small quantities of urine (5 to 10 ml.) which coincided with a pattern of hind-limb movement which resembled walking behavior. The effects of naloxone persisted for about 1 hour. The motor activity following administration of naloxone was dependent upon activation of bladder afferents since it did not occur when the bladder was empty. Naloxone also facilitated the release of urine induced by stimulation of somatic afferents. With repeated administration of naloxone, tolerance developed which was evident for several days. These observations suggest that an endogenous opiate may have a tonic inhibitory role in regulation of micturition. Pharmacologic manipulation of this putative inhibitory mechanism may facilitate management of neurogenic bladder dysfunction.

Animals↗

PubMed1979

Effects of clonidine on the lumbar sympathetic pathways to the large intestine and urinary bladder of the cat.

The effects of clonidine on lumbar sympathetic outflow to the colon and urinary bladder were examined by recording drug-induced changes in spontaneous postganglionic firing and spinal viscero-sympathetic reflexes in the lumbar colonic and hypogastric nerves of the cat. Clonidine in doses between 2--40 micrograms/kg produced a dose dependent depression of spontaneous and evoked discharges in efferents of the hypogastric nerve but did not alter activity in the lumbar colonic nerves. Clonidine also reduced arterial blood pressure and spontaneous firing in the renal nerves. These data coupled with previous observations in this laboratory indicate that spinal sympathetic pathways can exhibit a considerable variation in the sensitivity to the depressant actions of clonidine. This variation in sensitivity may reflect the relative importance of noradrenergic inhibitory mechanisms in the respective pathways.

Animals↗

PubMedDate not supplied

Serotonin and substance P colocalization in medullary projections to the nucleus tractus solitarius: dual-colour immunohistochemistry combined with retrograde tracing.

Serotonin (5HT) and substance P (SP) are colocalized in terminals within the nucleus tractus solitarius (NTS). The purpose of the present study was to determine the origin of these terminals. 5HT- and SP-immunoreactivities (IR) were visualized using dual-colour immunofluorescence histochemistry with amino-4-methylcoumarin-3-acetic acid- and fluorescein isothiocyanate-conjugated secondary antisera, while NTS-afferent neurons were visualized by retrograde labelling with rhodamine beads. Extensive colocalization of 5HT- and SP-IR was seen in NTS-afferent neurons located in the nucleus raphe pallidus, nucleus raphe obscurus, nucleus raphe magnus, and in the parapyramidal region. Over 80 per cent of the SP-IR NTS-afferent neurons contained 5HT-IR, while 68 per cent of the 5HT-IR neurons contained SP-IR. Thus, 5HT- and SP-IR are extensively colocalized in NTS-afferent neurons in the medullary raphe nuclei and associated areas of the ventral medulla.

Animals↗