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Biomedical subjects

J Christensen

Publications and source records attributed to J Christensen.

At least 253 records · Page 14Linked to original sources
PubMed1978

Regional differences in potassium content of smooth muscle from opossum esophagus.

Strips from the proximal part of the smooth muscle segment of opossum esophagus have a significantly higher potassium content (50 +/- 3 meq/kg) than those from the distal part (38 +/- 3 meq/kg). There are no significant differences between the two regions in content of sodium (65 +/- 4 meq/kg in proximal, 71 +/- 3 meq/kg in distal) or chloride (48 +/- 10 meq/kg in proximal, 42 +/- 5 meq/ kg in distal). The mean [14C]inulin uptake is 240 +/- 10 ml/kg in both proximal and distal strips. [14C]polyethylene glycol uptake is smaller and [14C]sucrose and [14C]mannitol uptake in both areas are larger than that of inulin. Intracellular potassium concentration (based on the inulin uptake as an estimate of the extracellular space volume) is significantly higher proximally (71 +/- 3 mM) than distally (52 +/- mM). Ouabain, 10(-4) M, increases the intracellular concentration of sodium and decreases the intracellular concentration of potassium in both the proximal and distal segment. The efflux of 86Rb, measured by a washout technique, is higher in the distal than in the proximal smooth muscle segment. A difference in membrane permeability to rubidium and hence, potassium between proximal and distal smooth muscle segments may account in part for the different intracellular potassium concentrations.

Animals↗
PubMed1978

A familial visceral myopathy.

A kindred contained at least 18 members with visceral myopathy. Sixteen had symptoms of chronic obstruction of the gastrointestinal or urinary tracts. Of six patients with megaduodenum on contrast roentgenograms, two were asymptomatic. Four patients had redundant colon on barium enema, and four had megacystis. Specimens from duodenum, jejunum, ileum, colon, or urinary bladder from five patients showed thinning and extensive collagen replacement of the longitudinal muscle layer; ganglion cells were normal by light and electron microscopy. Esophageal manometry in three patients showed decreased gastroesophageal sphincter pressures and no contractions in the smooth muscle segment of the esophagus; duodenal manometry showed a low frequency and amplitude of contractions. Three patients developed fever and signs of peritonitis after operations to bypass dilated segments. This seems to be a generalized smooth muscle disease with variable clinical manifestations and with an autosomal dominant or sex-linked dominant mode of inheritance.

Adolescent↗
PubMed1977

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.

Adult↗
PubMed1977

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.

Animals↗
PubMed1977

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.

Animals↗
PubMed1977

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.

Animals↗
PubMed1977

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.

Acetylcholine↗
PubMed1977

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.

Animals↗
PubMed1977

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.

Animals↗
PubMed1977

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.

Aged↗
PubMed1977

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.

Acetylcholine↗
PubMed1976

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.

Adult↗