Lower sphincter of the opossum esophagus in pseudopregnancy

To seek a possible role of estrogen and progesterone in the development of changes in esophageal function during pregnancy, we produced a state of pseudopregnancy by administration of hormones to a suitable animal model. Twenty-two female opossums weighing an average of 2.5 kg, were divided into two groups. The treated group received intramuscular injections of 100 microgram of estradiol valerate daily from day 1 to day 12 and 15 mg of medroxyprogesterone acetate from day 7 to day 12. The control group received no injections. Both groups underwent manometry on days 1, 7, and 12. Lower esophageal sphincter pressure decreased (P less than 0.05) in treated animals from 58 +/- 13 mm Hg and 57 +/- 11 on days 1 and 7, respectively, to 44 +/- 10 mm Hg on day 12. The lower esophageal sphincter pressure remained unchanged in control animals. In both groups, there was no change in peristaltic wave pressure, duration, or velocity in the distal 6 cm of the esophagus. No abnormal peristaltic phenomena were observed. Esophageal muscle strips prepared from treated animals showed responses to electrical field stimulation of intrinsic nerves that were like those from control animals. The same was true for responses to acetylcholine and pentagastrin. Total tissue water and total tissue potassium content did not differ in treatment and control animals.

Oral health status of 65- to 74-year-old Danes: a preliminary report of the replication of W.H.O.'s international collaborative study in Denmark

The survey has demonstrated that oral health is poor in the present old-age generation in Denmark. A striking relationship between social class and tooth mortality has been demonstrated. In the present dental care system in Denmark, treatment rather than prevention has had priority. A change is however necessary. Greater emphasis on preventive measures and a change in the attitude of the public to dental health is needed, if the dental health of the population is to be improved. However, the majority of the present old population cannot benefit from new, improved programs to preserve the teeth. We are therefore still left with the obligation not to neglect the need and demand for dental treatment--of whatever nature it may be--in the old generation. The survey has clearly demonstrated that, so far, these demands have not been met.

Esophageal manometry in the opossum

The opossum esophagus is commonly used as an animal model of the human esophagus. We used esophageal manometry in normal animals to provide basal data about normal esophageal motor functions in vivo in this species. At rest, separate and distinct high pressure zones can be recorded at the level of the lower esophageal sphincter, diaphragmatic hiatus, aortic arch, and upper esophageal sphincter. Each zone demonstrates a characteristic pattern of pressures in the radii of the coronal section and a characteristic response to swallowing. The hiatal and aortic zones can be mistaken for the esophageal sphincters. Pressures in the sphincters fall with swallowing. Peristalsis is not bolus-dependent and occurs with 98% of swallows. Pressures generated by peristalsis are greater in the middle of the esophagus than at the ends. Values for resting lower esophageal sphincter pressure and the characteristics of peristalsis were reproducible between different studies in the same animals.

Effect of capsaicin on electrical slow waves in the isolated cat colon

Because of the laxative effect of capsaicin, we examined the effect of that agent on the electromyogram of the isolated cat colon. At a concentration of 10(-4)M, it caused a significant reduction in the frequency of the electrical slow waves in the proximal half of the colon. Frequency fell to its lowest value, 45% of control (P less than 0-001), in the most proximal 10% of the organ below the ileocecal junction, and the effect progressively diminished along the colon. In the distal half of the colon, the change in frequency was not significant. Sectioning of the colon into segments reduced the frequency of the slow waves in the proximal half of the colon, and capsaicin, in a concentration of 10(-4)M, further reduced the frequency in the segments representing the proximal 30% of the colon. This effect of capsaicin is like that reported previously with other laxative agents.

A comparison of intrinsic nerve supplies of two muscular layers of duodenum

The duodenums of opossums and cats were cut into strips 2 mm wide and 2-2.5 cm long. Strips cut in the direction of the oral-caudal axis were called longitudinal strips, and those cut at 90 degrees to that axis were called circular strips. Each muscle strip was stimulated with trains of electrical rectangular pulses (10 Hz, 50-70 V, 0.5 ms). In the longitudinal strips, electrical field stimulation caused contraction, and this contraction was abolished by atropine, 10(-7) M. In the circular strips, electrical field stimulation caused relaxation. This relaxation was abolished by tetrodotoxin, 10(-7) M, but it was not affected by antagonists to adrenergic and cholinergic transmission, nor by some gastrointestinal hormones. Reserpinization of the opossums or alteration of the frequencies of electrical field stimulation from 0.1-50 Hz did not affect or alter the relaxation of the circular strips or the contraction of the longitudinal strips. These findings suggest that the longitudinal muscle is dominated by an excitatory cholinergic innervation, and the circular muscle is dominated by a nonadrenergic, noncholinergic inhibitory innervation.

Calcium dependence of neuromuscular events in esophageal smooth muscle of the opossum

Intramural nerves in smooth muscle strips from opossum esophagus were stimulated electrically to cause contractions of longitudinal body muscle, off responses of transverse body muscle and relaxations of sphincter muscle. Krebs solution was modified by calcium removal by strontium substitution for calcium, by adding magnesium, and by adding nitroprusside. Longitudinal muscle contractions were abolished by calcium removal and by excess magnesium; they were unaffected by nitroprusside; strontium could not replace calcium. Off responses were abolished by calcium removal and by excess magnesium; they were depressed by nitroprusside; strontium effectively replaced calcium. Resting active tension in sphincter strips was partly reduced by calcium removal and by excess magnesium; it was abolished by nitroprusside; strontium could not replace calcium. Relaxations in sphincter strips were unaffected by all experimental conditions. Longitudinal contractions, off responses, and resting active tension of the sphincter represent different kinds of calcium activation of muscle. The excitatory nerves (which are cholinergic) in longitudinal muscle are calcium dependent, the nerves that produce off responses may not be, and the nerves that relax the sphincter are not.

Temperature dependence of responses of esophageal smooth muscle to electrical field stimulation

Strips of smooth muscle, cut transversely from the smooth-muscle segment of opossum esophagus, were superfused with oxygenated Krebs-Ringer solution at 37 degrees C in a system that allowed electrical field stimulation of the intrinsic nerves. Three-to-five-second trains of rectangular pulses (0.5 ms long at 10 Hz) were delivered at 30-s intervals at supramaximal maximal current strength. In strips from the esophageal body, each train resulted in a twitch which followed after the end of train with a particular latency, the off-response. Strips from the esophagogastric sphincter relaxed during the train. Temperature was varied above and below 37 degrees C to observe the temperature dependence of the responses. Latency of the off-response varied exponentially with temperature. Amplitude of the off-response showed a linear decline with changes in temperature, both above and below 35 degrees C, the zero-intercepts being 19.6 and 42.3 degrees C, respectively. Amplitude of relaxation of strips from the junction varied little between 20 and 37 degree C but declined sharply beyond those limits, the zero-intercepts being 14.2 and 42 degrees C, respectively.

Dimension discrimination at two different degrees of mouth opening and the effect of anaesthesia applied to the periodontal ligaments

The dimension discrimination ability of twenty-five young persons was tested at two different degrees of mouth opening. One reference stick of 10-0 mm and another of 45-0 mm was placed between the teeth, alternating with test sticks of different heights. The subjects were asked to assess whether a test stick felt higher or lower than the reference stick. The experiment was performed with and without anaesthesia applied to the periodontal ligaments. Anaesthesia did not impair the discrimination ability. At dimensions in the region of the 10-0 mm stick the incorrect assessments occurred predominantly among sticks higher than the reference stick. Around the 45-0 mm stick incorrect assessments were distributed evenly between dimensions higher or lower than the reference stick.

A potassium gradient in smooth muscle segment of the opossum esophagus

Sodium and potassium content were determined in the smooth muscle segment of the opossum esophagus. Extracellular space measurements were also made using inulin and mannitol as markers. The muscle also made using inulin and mannitol as markers. The muscle was sampled at five sites spaced equally along the esophageal segment. On site in the stomach was also examined. The mean tissue sodium content was 36.6 +/- 10.7 meg/kg, and the mean tissue sodium content was 83.5 +/- 2.9 meg/kg wet wt. The mean inulin space was 184 +/- 34 ml/kg, and the mean mannitol space was 249 +/- 20 ml wet wt. The tissue potassium content was found to decline from 48.4 /- 10.1 meg/kg at the proximal site to 23.6 +/- 8.0 meg k/g at the distal site. The slope of electrolyte values from sites 1 through 5 was significant for both potassium and sodium. Extracellular space volume did not differ significantly from one end of the smooth muscle segment to the other.

The fallacy of facial measurements of occlusal height in edentulous subjects

A controlled trial was made using fifteen subjects and making 120 measurements with a caliper gauge between marks disposed on the upper lip and the point of the chin when maxillo-mandibular relationships were altered vertically by known amounts within a range of 6 mm. It was found that mean facial measurements could account for only half of the skeletal movement involved. The variability of soft tissue translation in relation to skeletal movement led to the conclusion that such facial measurements are inappropriate to clinical practice.

Histamine receptors in esophageal smooth muscle of the opossum

Esophageal smooth muscle was examined for histamine receptors. The effects of histamine, the histamine analogs 4-methylhistamine (4-MH) and 2-(2-pyridyl) ethylamine (PEA), the histamine receptor antagonists mepyramine and metiamide, and the histamine-releasing substance compound 48/80, on lower esophageal sphincter (LES) and esophageal body (EB) smooth muscle of the opossum were studied in a superfused tissue bath. Histamine, PEA, an H1 receptor agonist, and compound 48/80 caused a dose-related increase in LES basal tension and in EB off response amplitude, the threshold for histamine being 6.7 X 10(-8) M and that for PEA being 6.7 X 10(-7) M. In the presence of mepyramine, and H1 receptor antagonist, the effects of histamine and compound 48/80 were reversed to inhibition of both LES basal tension and EB off response amplitude, while the effect of PEA was abolished. Metiamide, an H2 receptor antagonist, did not alter responses to histamine, PEA, or compound 48/80. The H2 receptor agonist 4-methylhistamine caused a reduction of LES tension and EB off response amplitude, but caused an increase in those parameters in the presence of metiamide. A combination of mepyramine and metiamide abolished responses to all agonist drugs. The results indicate that LES and EB smooth muscle contain both excitatory H1 and inhibitory H2 receptors for histamine. Endogenous histamine released from storage sites in LES and EB and exogenous histamine both preferentially activate H1 receptors.

Intestinal propulsion in the dog. Its relation to food intake and the migratory myoelectric complex

We studied electrical events and flow in the canine small intestine in vivo. The transit of a small radioactive bolus injected into the jejunum was monitored by counting from a Biebl loop. After feeding, the rate of propulsion of the bolus varied within a narrow range. When food and water were withheld for more than 12 hr, transit of the bolus hecame highly variable. The variability increased at about the same time as the onset of the migratory myoelectric complex associated with fasting. Electrical recordings from the intestinal muscle demonstrated that the bolus was propelled into the loop in advance of the band of intense spike potentials which travels along the small intestine in the fasted state. The bolus was cleared from the loop when the spike potentials reached this segment. Variability of transit after prolonged fasting can be explained by (1) variability in the rate of migration of the phase of intense spike potentials, and (2) the timing of the injection of the bolus in relation to the component phases of the electrical complex. Flow is highly dependent upon the electrical activity and the resulting contraction patterns of the small intestine, which are themselves dependent upon feeding.

A dopamine receptor in esophageal smooth muscle of the opossum

We examined the possibility that dopamine may play a role in nerve-mediated "off" responses of esophageal body (EB) and relaxations of lower esophageal spincter (LES) smooth muscle. The effects of dopamine, epinine, and dopamine antagonists on EB and LES smooth muscle were studied on these responses. Dopamine and epinine caused a dose-related fall in basal LES muscle tension and in amplitude of EB muscle "off" responses. Threshold dose for both was about 10(-7) M, and maximal dose was about 10(-4) M. At high concentrations, they also caused repetitive transient contractions of both LES and EB muscle after the period of inhibition. These effects were antagonized by haloperidol, 10(-5) M, and bulbocapnine, 10(-5) M, but were not influenced by propranolol, 10(-5) M, nor by phenoxybenzamine, 10(-5) M. Neither haloperidol nor bulbocapnine influenced responses to electrical field stimulation. Tetrodotoxin 10(-7) M abolished the responses to electrical field stimulation but did not antagonize the effects of dopamine and epinine. EB and LES smooth muscle contain a dopamine receptor. It is unlikely that dopamine is involved in responses to electrical field stimulation.

An uncontrolled comparison of treatments for achalasia

A series of 78 patients with achalasia, seen during a 10-year period, was like those reported by others with regard to age at onset, nature of symptoms, and duration of symptoms. Analysis of the results of 5 different treatment modalities administered allows an uncontrolled comparison heretofore not available from an institution at which no one treatment was favored over all others. Those who were not treated or who received only anticholinergic medication did not become asymptomatic. Those treated by single or repeated bougienage were not improved for more than a few weeks and suffered a 6% incidence of esophageal perforation. Forty-six per cent of those treated by a single pneumatic dilatation were asymptomatic for 1 year or more. Although esophagocardiomyotomy provided symptomatic relief for 1 year or more in 85%, there was a 25% incidence of gastroesophageal reflux.

Distributions of spike bursts in cat duodenum

The histograms of spike bursts over short distances were examined in the isolated cat duodenum with multiple electrodes arranged circumferentially and longitudinally. At a single cross section of the duodenum, spike bursts occurred simultaneously in any single slow-wave cycle, but all eight monitored sites in the circumference participated simulatenously only in a bout 25% of the spike-burst cycles. There also were wide variations in the incidence of spike bursts at different locations in a planar cross section. In a longitudinal section, net level of activity over short distances varied widely. Also, spike bursts were out of phase in the longitudinal axis, appearing to spread caudad; 80% of spike burst groups involved less than an average of 5.5 consecutive electrode sites (spaced at 5-mm intervals). Since spike bursts seem to be correlated with ring contractions of the circular muscle, the fact that they appear sequentially in time along the duodenum indicates that such contractions must always be peristaltic. An estimated 80% of such contractions sweep less than about 3 cm. Records of spike bursts from a single electrode do not accurately reflect activity beyond that one point site.

Three layers of the opossum stomach: responses to nerve stimulation

The three muscle layers of the opossum stomach were compared in their responses to electrical field stimulation. Strips were cut from the muscular wall of the stomach with their longer axes in the direction of the longitudinal, circular, and oblique muscle layers and stimulated at 1-min intervals with 20-sec trains of 1-msec pulses at 10 Hz and supramaximal strength at 500 ma. Strips either contracted, relaxed, or did not respond during the stimulus trains. Responses were abolished by tetrodotoxin, 10(-6) M. Contractions, but not relaxations, were abolished by atropine, 10(-6) M. Relaxations were not antagonized by propranolol, tolazoline, or phenoxybenzamine. Thus, the responses represent excitation of both cholinergic excitatory and nonadrenergic inhibitory nerves. In strips cut longitudinally, cholinergic contractions occurred more frequently than in the other two kinds of strips. After atropine treatment, the incidence of relaxation was greater in strips cut in the direction of the oblique layer than in the other two groups. The results suggest that, of the two kinds of nerves, the cholinergic excitatory innervation is usually dominant in the longitudinal muscle layer, and that the nonadrenergic inhibitory innervation is more complete in the oblique muscle layer.

Phase lock of electrical slow waves and spike bursts in cat duodenum

The phase relationship between slow waves and spike bursts was studied in vitro in the cat duodenum. Electrodes were arranged radially about the duodenum. Records were read for T1, the time between the slow-wave "valley" and the first spike, and T2, the time between successive valleys. The distributions of the ratio T1/T2 showed very small differences, not uniquely attributable to radial electrode position. The distribution of T1/T2 indicated that spike bursts began 58.8% of the way through a slow-wave cycle, measured from the valley. Also, electrodes were arranged longitudinally and records were read to determine deltaSW, the slow-wave delay time between adjacent electrode positions, and deltaS, the spike burst delay time between adjacent electrode positions. The correlation of deltaS and deltaSW suggested a linear relation, and a regression resulted in a good linear description. These results are consistent with an assumed phase lock of spike bursts to slow waves.

Stochastic model of contractions at a point in the duodenum

Contractions at one point in the human duodenum were studied as a time series. Manometric records were made over long time periods from the duodenum in fed human subjects. A 5-s grid was superimposed on the time axis of the records. Each 5-s interval was treated as a slow-wave cycle within which either a contraction or a no-contraction could occur. The resulting series of alternating runs of contractions and no-contractions was tested for the existence of trends. Trends were found indicating possible temporal dependence. A Markov-type model was used to try to generate data similar to the real data. Success was achieved by a model that assumed a probability of contraction dependent on the three previous slow-wave cycles. The frequency distributions obtained from the real and generated data were compared using Chi-square goodness-of-fit tests and found to be statistically similar. The correlations in time found for the contractions might be due to a time dependency in the controls for contraction over four successive slow-wave periods, 20 s in humans.

[Parathion poisoning in cattle (author's transl)]

In a herd of dairy cattle half of the cows showed symptoms of acute poisoning. Blood- and hair samples were taken from seven of the cows, of which two did not show any clinical symptoms. The cholinesterase activities were in all the blood samples decreased to about 10 per cent of normal and parathion was found in all hair samples. The cholinesterase activities rose gradually during a 31/2 month period to the lower part of the normal range. Parathion was found in samples from the inner walls of the cowstable, and it was concluded that the poisoning was probably due to parathion spraying in the stable, while a suspicion of winddrift as a source of poisoning was rejected as less probable.

Longitudinal contractions in the duodenum: their fluid-mechanical function

The hypothesis examined was that contractions of the longitudinal muscle layer occurin the duodenum which are independent of those of the circular muscle layer and that they induce flow of duodenal contents. A segment of opossum duodenum isolated in vitro was marked and photographed during periods of longitudinal muscle contraction, when the circular muscle layer appeared inactive. The prequency of longitudinal oscillation of the marked points was 20.5 cycles/min. The longitudinal displacement wave spread caudad with an average velocity of 3.27 cm/s. Frequency and velocity of electrical slow waves were determined in similiar duodenal segments. Slow-wave frquencywas 18.9 cycles/min. In a two-dimensional mechanical model, flow induced by simulatedlongitudinal muscle layer appear to be driven by the electrical slow waves of the duodenum. They are capable of inducing a pattern of flow in which ocntents flow betweenthe core and the periphery of the intestinal conduit.

Pharmacology of the esophageal motor funciton

In the striated muscle of the upper esophageal sphincter, tonic maintenance of closure is probably mediated via tonic central excitation of the extrinsic motor innervation; relaxation represents central inhibition of this mechanism. The motor nerves are probably cholinergic and act through nicotinic receptors like those of somatic striated muscle. In the striated muscle of the esophageal body, swallowing-induced contraction is also probably a cholinergic and nicotinic response. In the smooth muscle of the esophageal body, the control of contractions is cholinergic and muscarinic in part, but there is evidence for a nonadrenergic and noncholinergic component as well. The muscarinic component may arise from the cholinergic innervation of the longitudinal muscle layer. The other component may lie in the cryptic innervation of the circular muscular layer. In the smooth-muscled lower esophageal sphincter, resting closure tension appears to reflect a variety of possible control mechanisms. No single control system predominates. The evidence for muscarinic excitation is equivocal. An excitatory adrenergic alpha mechanism and inhibitory adrenergic beta receptors may contribute. A role for the polypeptide hormones from the gastrointestinal tract seems unlikely. Relaxation of the lower sphincter with swallowing seems not to involve any of these mechanisms, but is apparently accomplished by nonadrenergic noncholinergic inhibitory nerves like those present elsewhere in the gut (87). The possibility that the transmitter of these nerves is an adenine nucleotide has been raised from studies of other parts of the gut, but that hypothesis has not yet been examined critically in the lower esophageal sphincter.

Local specialization at ileocecal junction of the cat and opossum

In 10 cats and 10 opossums, serial transverse strips of muscularis propria 2 mm wide, from about 1.5 cm above to about 1.5 cm below the ileocecal mucosal junction, were separately stretched to discover the relationship between length and tension and were separately subjected to electrical field stimulation. In both species, ileal strips showed stimulus relaxations, sometimes accompanied by contractions after the stimulus trains (off responses), whereas colonic strips generally did not. These responses were abolished by tetrodotoxin, 3 times 10-7 M in the opossum, 3 times 10-6 M in the cat. Length-tension slopes were greatest just above the ileocecal junction where stimulus relaxation occurred. Tetrodotoxin at 3 times 10-7 M raised basal tension in ileal strips in both species and in colonic strips only in the cat. Muscle of the ileocecal junction resembles that of the esophagogastric and gastroduodenal junctions in showing a relatively high degree of resistance to stretch and prominent neurogenic stimulus relaxation. However, the ileocecal junction, in contrast, also possesses a tonic inhibitory innervation.

An inhibitory innervation at the gastroduodenal junction

Transverse muscle strips, 2-mm wide, were cut serially from the gastroduodenal junction in opossums, cats, dogs, and man. Electrical field stimulation with trains of rectangular current pulses of 0.5 ms in all opossums, all cats, some dogs, and the one human specimen induced relaxation in strips from the thickened circular muscle proximal to the mucosal junction. In some opossums weak relaxations also occurred in the first few strips below the mucosal junction. All other strips contracted or showed no response. This relaxation in opossums was abolished by tetrodotoxin but was not affected by antagonists to adrenergic and cholinergic transmission, nor by tripelennamine, methysergide, pentagastrin, secretin, cerulein, or cholecystokinin. Optimal frequency for stimulus-relaxation was 12 Hz. Chronaxie was 0.85 ms. The junctional strips also showed greater resistances to stretch than those remote from the junction. With apparent species variations, the junctional muscle possesses a nonadrenergic inhibitory innervation which is either absent or unexpressed in adjacent muscle of stomach and duodenum. This suggests the existence of a distinctive inhibitory neural control mechanism for pyloric muscle.