Biomedical subjects
Publications and source records attributed to J Christensen.
Three mice chose between concurrent variable-ratio variable-interval schedules to produce a warm air stream while they were housed in a cold chamber. Across conditions, the duration of the warm air stream was varied between 10 and 80 s and was equal for both schedules. Preference for the VI schedule covaried with reinforcer duration as predicted by maximizing accounts of choice.
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The impact on public health of head injury as a major source of death and disability, especially among adolescents and young adults, is well recognized. In Maryland the primary annual incidence of head injury severe enough to result in death or hospitalization has been estimated to be 149 per 100,000 population. These figures are comparable to national and other regional estimates reported in the literature. Improvements in the acute care management of head injury have generally led to improved survival.
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It has been suggested that dilatation of the ureter seen in pregnancy is caused by progesterone. Twenty-four patients with ureteral calculi, therefore, were given an intramuscular injection of 250 mg hydroxyprogesterone in order to facilitate the discharge of the stones. Irrespective of the duration of symptoms there was a potential effect of treatment in up to 66% of the patients. In patients with symptoms of less than three weeks duration the stones were discharged within three weeks after the first symptom in 75% of the cases, which is a much higher incidence rate than that stated in the literature for spontaneous stone discharge (18-30%). In patients with longstanding symptoms 50% of the stones had passed, as compared to 39% reported in the literature. Especially concrements with a diameter larger than 4 mm had a better discharge rate. As the treatment is simple, cheap and without side effects, it seems worthwhile trying it in order to avoid surgery.
In the small intestine, the myenteric plexus contains several different forms of ganglion cells. We examined the whole gut of the American opossum to see if these forms exist in other organs. Sections were stained by silver-impregnation. About half the ganglion cells were argyrophilic in all regions. Argyrophilic cells were described as to dendrite shape (filiform or lamellar), number, and grouping on the nerve cell body (radiating or focal), and in respect to nuclear position (central or peripheral). Cells with lamellar dendrites were sparse in esophagus (less than 5%), in gastric fundus (17.2%) and in antrum (8.2%), increased from duodenum (18.5%) to ileum (64.3%) and increased along the colon from the cecum (62.3%) to the rectum (94.9%). The proportion of cells with filiform dendrites diminished correspondingly along the gut. The number of dendrites per cell increased caudad along the gut. Cells with focally distributed dendrites were rare in all regions. More cells had central nuclei than peripheral nuclei in all regions, and nuclear position did not correlate with dendrite morphology. Thus, the forms of myenteric plexus ganglion cells differ systematically in the gut. The results do not support the idea that a specific function can be assigned to a ganglion cell of a specific form.
Out of 15 consecutive deep graft-infections during a 5-year-period, 12 cases were treated by local debridement, disinfectants, graft replacement and sartorius muscle transposition. The treatment was successful in 10 cases, which have shown no sign of re-infection. Three grafts occluded during the observation period (2 weeks, 2 months and 15 months), resulting in amputation in one patient. The method is recommended as the treatment of choice in Szilagyi type III infections limited to the groin.
Humans chose 10 times between two roulette wheels projected on a monitor. During the first trial, the left wheel provided a hypothetical $100 with p = .94, and the right wheel provided $250 with p = .39. A titration procedure adjusted the probability of a $250 win across trials to permit estimation of an indifference point between alternatives. In Experiment 1, intertrial-interval duration (25 vs. 90 s) and whether sessions began with an intertrial interval or a trial were varied in a 2 x 2 design in this risky-choice procedure. Risk aversion (preference for the $100 wheel) increased with intertrial interval but was unaffected by whether sessions began with a trial or an intertrial interval. In Experiment 2, all sessions began with a trial, and subjects were informed that the experiment ended after 10 trials. Intertrial-interval duration had no effect on choice. In Experiment 3, intertrial-interval duration and whether subjects were given $10 or $10,000 before beginning were varied among four groups in a 2 x 2 design. In all other ways, the procedure was unchanged from Experiment 2. Intertrial interval had no effect on choice, but the $10,000 groups showed less risk aversion than the $10 groups. These results can be explained more readily in terms of Kahneman and Tversky's (1984) notion of "framing of the prospect" than in terms of Rachlin, Logue, Gibbon, and Frankel's (1986) behavioral account of risky choice.
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Explore the source record for details and available documents.
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The parts of the colon differ in motor function and in responses to extrinsic and intrinsic nerve stimulation. The distribution of myelinated nerve fibers in the colonic myenteric plexus is not known. Because these fibers might be largely extrinsic in origin, their distribution might indicate the domain of influence of extrinsic nerves and help to explain the different behaviors of the different parts of the colon. Myelinated fibers were examined by electron microscopy in cross sections of the ascending nerves and in myelin-stained whole-mount preparations in the colon. The ascending nerves are much like one another. They have the structure of peripheral nerves, not that of myenteric plexus. The proportion of myelinated fibers in the ascending nerves declines rostrad with no uniform change in total nerve fiber number. Cross-sectional areas of ascending nerves, 3,304 to 7,448 microns 2; total number of nerve fibers per profile, 703-2,651; and mean myelin coat thickness, 0.45 +/- 0.01 micron, do not change uniformly along the ascending nerves. Myelinated fibers are about 2% of total fibers in the extramural colonic nerves, 7-9% in the ascending nerves in the sigmoid colon, and 2-3% at the rostrad ends of the ascending nerves in the transverse colon. Blood vessels lie at the core of each ascending nerve and on the nerve sheath. Myelinated fibers in the ascending nerves degenerate after section of colonic branches of the pelvic plexus and after section of the pudendal nerves, indicating that myelinated nerves reach the colon through both pathways.(ABSTRACT TRUNCATED AT 250 WORDS)
Physiologic evidence that vasoactive intestinal polypeptide (VIP) regulates esophageal smooth muscle in the opossum has been gathered without knowledge of the distribution of VIP in that organ. We examined planar sections stained for VIP by the avidin-biotin complex method, measured VIP content in mucosa and muscularis propria by radioimmunoassay, and compared neural structures reactive to VIP antiserum with those revealed by osmication in the presence of zinc iodide. Immunoreactive terminal nerves interlaced smooth muscle bundles in all layers in all smooth muscle regions, formed loose tangled knots about widely dispersed muscle cells in striated muscle, and supplied vessels and submucosal glands. Bipolar interstitial cells in the circular muscle layer stained by osmication were not VIP-immunoreactive. Perikarya in both submucous and myenteric plexuses were VIP-immunoreactive. Vasoactive intestinal polypeptide-immunoreactive oval cells with round unstained nuclei and a faintly granular cytoplasm were scattered in the muscle in all regions and were concentrated in the planes of the plexuses. Vasoactive intestinal polypeptide content of muscularis propria in the smooth muscle esophageal body exceeded (p less than or equal to 0.05) that in the striated muscle esophageal body and the sphincter region, but contents in the latter two regions did not differ (p greater than or equal to 0.05). Mucosal content exceeded that of muscularis propria. The broad distribution and diversity of immunoreactive structures suggest that VIP may have functions in this organ besides the regulation of smooth muscle.
Pulmonary lymphatics are believed to play a major role in preventing the formation of pulmonary edema, but their role in clearance of established edema has not been defined. To measure the lymphatic contribution to the clearance of acute hydrostatic pulmonary edema, a lung lymph fistula was established in 16 anesthetized sheep. Pulmonary edema was induced by a rapid volume infusion of Ringer's lactate (six animals) or homologous plasma (six animals). Four control animals received no fluid. Simultaneous measurements of lymph flow and extravascular lung water (EVLW) were made. Data were analyzed for the resolution phase of pulmonary edema. The contribution of the pulmonary lymphatics to resolution was expressed as a percentage of total lung water resolved. Resolution rates for crystalloid and plasma infusion groups were 3.8 +/- 2.4 cc/kg/hr and 2.7 +/- 1.0 cc/kg/hr, respectively. There was no statistically significant difference between the groups in terms of EVLW increases or resolution rates. Net measured pulmonary lymph flow during the resolution phase of pulmonary edema was 0.33 +/- 0.18 cc/kg/hr and 0.39 +/- 0.20 and accounted for only 8.8 and 14.6% of resolved pulmonary edema in these respective groups. These data suggest the pulmonary lymphatic drainage plays a very minor role in the clearance of acute hydrostatic edema. The lungs appear to be capable of resolving as much as 40% per hour of increased extravascular lung water produced under these circumstances.
The 3 layers of smooth muscle of the opossum esophagus exhibit distinctly different and characteristic functions in response to nerve stimulation. These behaviors might be related to differences in patterns of innervation. Serial sections, stained with osmic acid and zinc iodide, were examined from all parts of the esophagus to describe in full the innervation of opossum esophageal smooth muscle. Linear beaded structures identified as terminal nerves were abundant in all 3 layers of smooth muscle. They were aligned with muscle bundles in bundles of 1-5 in mucosal muscle and up to about 10 in the longitudinal layer of muscularis propria. In the circular layer of muscularis propria they were less dense and more arborized and they crossed the muscle obliquely to also innervate bipolar interstitial cells; these cells resembled type III interstitial cells of Cajal, were specific for the circular muscle layer and were uniformly distributed throughout the thickness of that layer. Their distribution density in the circular muscle was slightly greater, 8777/cm2 in the most caudad 1.5 cm of the esophagus (which encompasses the sphincter) than in the 6 cm above that level. Terminal nerves also innervated submucosal glands, vessels and the epithelium. Ganglion cells and nerve bundles in the submucous and myenteric plexuses were variably stained. Ganglia of the latter plexus contained intraganglionic laminar endings as described previously in other species. In the striated muscle there were nerves terminating in motor end-plates. Other leafy stellate cells resembling interstitial cells of Cajal of other types were stained, as were oval interstitial cells.
Slow waves in the small intestine seem to arise in plexuses of neurites with interstitial cells of Cajal. In the colon, slow waves appear to arise at the circular muscle - submucosal interface. We therefore sought a plexus at this surface in the colon in the cat, dog, ferret, opossum, rabbit, rat, guinea-pig and man. Segments from all levels of the colon were stained by the Champy-Maillet osmic acid-zinc iodide method and cut into serial 25 micron sections in the plane of the muscle layers. A dense network of neurites with abundant interstitial cells of Cajal was found at the circular muscle - submucosal interface in all species except rabbit. Neurites in this plexus appeared to arise from the deep plexus of the submucosa (Schabadasch's or Henle's plexus). It was not found in the small intestine and stomach. A similar plexus was found in the interstices of the myenteric plexus in the colon. Interstitial cells of Cajal in both plexuses were positive for the NADH-diaphorase stain, but not for silver impregnation. The possible roles of the plexuses of neurites and interstitial cells of Cajal at the circular muscle - submucosal interface and at the plane of the myenteric plexus in the generation of rhythmic activity in the colon are discussed.
Using a transurethral approach intravesical pressure and blood pressure were recorded in 10 males with acute urinary retention during either continuous or fractionated drainage. Upon evacuation of the initial 100 cm3 urine the intravesical pressure declined to approximately 50% of the initial value in both groups relieving pain in all patients. Blood pressure was significantly lowered following the procedure, but clinical manifestations were absent. One patient demonstrated hematuria, but treatment was not necessary. The study renders no support for previous recommendations of fractionated outlet of urine in this condition.