Absorption of calcium measured by intubation and perfusion of the intact hyman small intestine

Absorption of calcium was measured by direct intubation and perfusion of the small intestine in 10 volunteer normal adult subjects, two adults with celiac-sprue, and one with a parathyroid adenoma. A total of 60 studies were completed using one of two different levels, duodenojejunum or ileum. Solutions containing stable calcium, radiocalcium(47), and a nonabsorbable dilution-concentration marker, polyethylene glycol, were infused at a uniform rate via the proximal lumen of a triple-lumen polyvinyl tube. The mixed intraluminal contents were continuously sampled by siphonage from two distal sites, 10 and 60 cm below the point of infusion. Unidirectional flux rates, lumen to blood and blood to lumen, and net absorption of calcium for the 50 cm segment of small intestine between the two collection sites were calculated from the measured changes in concentration of stable calcium, calcium-47, and polyethylene glycol.Flux of calcium from lumen to blood in the duodenojejunum of normal subjects was appreciable even when the concentration of calcium in the perfusate was below that of extracellular fluid and, as the intraluminal concentration of calcium was increased through a range of 0.5-3.5 mumoles/ml, was positively correlated, ranging from 1.9 to 7.0 mumoles/min per 50 cm. Repeated studies of individual subjects demonstrated a consistent pattern of absorptive efficiency in each, but significant variability from person to person. Flux from lumen to blood in the ileal segment occurred at a much lower rate than that found in the proximal intestine, and there was not a significant dependence upon intraluminal calcium concentration. The opposite flux, from blood to lumen, was low both in the duodenojejunum and ileum (average 0.76 mumoles/min per 50 cm) and was independent of the intraluminal calcium concentration. Unidirectional flux, lumen to blood, from the duodenojejunum was not altered by parathyroid extract administered at the time of the infusion, but was accelerated in the subject with a parathyroid adenoma and markedly reduced in the two subjects with celiac-sprue.

Psychiatric practice in Great Britain and America: a comparative study

The methods of treatment employed for most forms of psychiatric disorder are still largely empirical. Furthermore, they are subject to powerful socio-cultural influences. Hence, it is not surprising that examination of medical practice in different countries reveals wider variation in the treatment of psychiatric disorder than in that of most other forms of morbidity (Shepherd, 1962). To establish the patterns of variation, and to assess their importance, it is necessary to develop techniques which permit direct comparison between the therapeutic practices of representative national groups of psychiatrists. This cannot be an easy matter, since in addition to difficulties of language and protocol there are problems specific to the subject of enquiry. There is as yet no internationally accepted nomenclature for psychiatric disorders, and perusal of the available prevalence statistics suggests that there must be considerable variation in the diagnostic criteria recognized by clinical psychiatrists of different nationalities (Lin and Standley, 1962). Moreover, clinicians whose chief concern is with the treatment and management of individual patients, in part through the manipulation of inter-personal relations, may be reluctant to accept any simple, mutually exclusive classification of their therapeutic techniques.

The AC impedance of frog skin and its relation to active transport

The AC electrical impedance of frog skin was measured in the range 1 cycle/second to 50 kc/second by injecting current sinusoidally at low current density. The behavior of the skin was found to be linear so the usual concepts of impedance could be validly employed. In the range 1 cycle/second to 5 kc/second, the impedance traces out a circular arc locus with its center off the real axis; thus the skin could be represented by a series resistance and a parallel combination of a conductance and a phase shift element. The phase shift element has an impedance angle of about 80 degrees , current leading voltage, with an equivalent capacitance of about 2 muf/cm(2). The phase shift and the equivalent capacitance were independent of the experimental conditions. The parallel conductance, which was responsible for most of the low frequency impedance, could be subdivided into two approximately equal conductances, one associated with sodium ion current and the other associated with chloride ion current. Both currents were determined mainly by the concentrations of the respective ions bathing the outside of the skin. The response to changes in concentration and the response to CO(2) indicated that the chloride current was passive, but the sodium current appeared to be associated with the active transport mechanism; little sodium could pass through the skin unless associated with active transport.