Use of electrochemical sensors for on-line monitoring of ionized calcium, potassium, and glucose in whole blood of living dogs

We report the development and evaluation of electrochemical sensors for continuous on-line measurement of whole-blood ionized calcium, potassium, and glucose in living animals. Ionized calcium and potassium are measured with ion-selective electrodes, by using a unique differential approach. A polarographic sensor coupled with a membrane with bound glucose oxidase is used in the glucose analyzer. The modular concept of instrument design permits one mainframe, computer, and pump system to house any analyzer module or a combination of modules. A small volume of venous blood (about 2 mL/h) is continuously withdrawn from the subject through a double-lumen catheter and pumped through the analyzer(s). Results of in vitro correlation studies and studies in normal dogs (including responses of ionized calcium, potassium, and glucose to various stresses) support the validity of the measurements.

Effect of low calcium and low phosphorus diets on the intestinal absorption of water in intact and parathyroidectomized pigs

Young pigs, each surgically prepared beforehand with a Thiry-Vella loop of jejunum, were used to study the effect of feeding low calcium and low phosphorus diets on the intestinal absorption of water. Feeding a low phosphorus diet caused a highly significant stimulation in the absorption of water in parathyroid gland-intact and parathyroidectomized pigs; low calcium diets were without effect.

Human relevance: epidemiology and occupational exposure

This paper reviews briefly some industrial applications which may result in occupational exposure of the workforce to preformed N-nitroso compounds. It considers exposure to nitrate in more detail, discussing epidemiological evidence which lends support to the hypothesis that high nitrate ingestion is related to high mortality from gastric cancer, through the formation in vivo of carcinogenic N-nitroso compounds. It presents the preliminary findings in a census-based mortality study of industrial workers exposed to nitrate-containing dust in the manufacture of fertilizers.

Effects of hydroxylated derivatives of vitamin D3 and of aqueous extracts of Solanum malacoxylon on the absorption of calcium, phosphate, sodium, potassium and water from the jejunum of pigs

The effects of hydroxylated derivatives of vitamin D3 and aqueous extracts of Solanum malacoxylon on the intestinal absorption of calcium, phosphate, sodium, potassium and water have been studied in unstressed vitamin D-replete pigs each of which was surgically prepared beforehand with a Thirty–Vella loop of jejunum. The addition, for six 1 h periods of perfusion, of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) or 1α-hydroxycholecalciferol at similar concentrations (3·6–3·75 pmol/ml) to the solution used to perfuse the intestinal loop caused a rapid increase in the absorption of calcium but increased the absorption of phosphate only after a delay of at least 12 h. The absorption of both calcium and phosphate reached a maximum on the day following the addition of the vitamin D derivative to the perfusate. The addition of 25-hydroxycholecalciferol (25-(OH)D3) at a concentration of 3·75 pmol/ml was without effect on absorption except for a small increase in the absorption of phosphate on the following day. However, at higher concentrations (> 250 pmol 25-(OH)D3/ml) the absorptions of calcium and phosphate were both increased rapidly. 24,25-Dihydroxycholecalciferol was without effect on absorption at the concentration tested (3·6 pmol/ml).

Aqueous extracts (1%) of the leaf of S. malacoxylon showed similar effects on absorption to those of 1,25-(OH)2D3. However, there was one point of difference; the absorption of phosphate was stimulated with a similar time course to that of calcium in contrast to its delayed response to 1,25-(OH)2D3.

The absorption rates of water, sodium and potassium were not consistently affected by 1,25-(OH)2D3 or S. malacoxylon. However, the major effects of these derivatives were usually seen on the day following the day of addition to the perfusate. In contrast, 25-(OH)D3 at high concentrations had a marked effect on the absorption of water, sodium and potassium on the day of addition.

Differential effects of age and cerebral atrophy upon span of immediate recall and paired-associate learning in older patients suspected of dementia

Seventy-eight patients suspected of dementia, 50 years of age or older and without evidence of focal cerebral lesion or systemic illness, were administered the Digit-Span Forward and Paired-Associate Learning subtests of the Wechsler Memory Scale. Computerized axial tomography, allowing a visualization and measurement of the lateral ventricles and cortical sulci, was employed to measure cerebral atrophy. Four groups were defined as follows: (1) age 50-69, without atrophy (N = 27), (2) age 50-69, with atrophy (N = 17), (3) age 70-89, without atrophy (N = 18), (4) age 70-89, with atrophy (N = 16). Results of analyses of variance indicate that Digit-Span is affected by cerebral atrophy but not by age, while Paired-Associate Learning is affected by both age and cerebral atrophy. No interaction effect between age and cerebral atrophy was found for either task. These results are discussed within the context of previous research, and implications for both models of memory and theories of the effects of cerebral atrophy in different ag groups are suggested.

Effects of on-line symptom-processing on history-taking and diagnosis--a simulation study

Techniques for computer-assisted diagnosis have been largely confined to off-line use, and there has been little examination of their potential role directly in the clinical setting. It is argued that the potential benefits of on-line diagnostic aids are considerable. A major barrier to such developments is uncertainty that the practical use of an on-line system would lead to the improvements in diagnostic effectiveness that more conventional off-line systems have already demonstrated. A series of studies in which clinicians took the histories of computer-simulated 'patients' presenting with dyspepsia, and formed diagnoses on the basis of these histories with and without computer assistance, suggested that diagnostic effectiveness may be greatly improved with on-line computer assistance. Some reasons for this improvement are discussed and it is concluded that the clinician and the on-line computer bring different but complementary types of knowledge to the diagnostic task. Though many practical questions remain to be answered the findings establish the principle of on-line symptom processing.

Texture discrimination and the analysis of proximity

A major theory of early visual processing has recently been proposed by Marr, which considers a number of aspects of visual perception in great detail, including grouping and texture discrimination. New phenomena associated with texture discrimination are described and experiments reported which allow a preliminary comparison of Marr's theory, as it applies to texture discrimination, with more established theories such as that due to Julesz. One experiment produced results which are clearly consistent with Marr's account, but the ability of his theory to deal with additional data on region suppression is not established. The theory of the analysis of proximity relations proposed by Fox offers a broadly satisfactory account of many texture perception results, while relying on the more fundamental parts of Marr's theory of primitive visual processes to deal with the remainder. A further attraction of proximity analysis is that it may shed new light on the classical paradox of symmetry perception. Some ways in which the preliminary proximity analysis model is incomplete are discussed, and it is concluded that development of the model may be profitable for theories of early visual processing.

Stimulation of duodenal and ileal absorption of phosphate in the chick by low-calcium and low-phosphorus diets

The intestinal absorption of phosphate has been studied in vivo in the chick using ligated segments of duodenum and ileum. Feeding diets low in calcium (0.1%) and/or low in phosphorus (0.25%) caused an increase in the absorption of phosphate from both the duodenum and ileum. These changes are consistent with a putative increase in the renal production and mucosal uptake of 1,25-dihydroxycholecalciferol.

Effect of low phosphorus diets on intestinal calcium absorption and the concentration of calcium-binding protein in intact and parathyroidectomized pigs

The effect of changing the dietary concentration of phosphorus on the intestinal absorption of calcium has been studied in conscious pigs each prepared with a Thiry--Vella loop of jejunum. A reduction in the percentage of phosphorus in the diet from 0.7 to 0.3% caused an increase in the efficiency of absorption of calcium from the fluid used to perfuse the jejunal loop in both intact and parathyroidectomized animals. There was a marked increase in the amount of calcium-binding protein (CaBP) in the small intestine of pigs fed the low phosphrous diet. Parathyroidectomy did not affect the amount of CaBP in the small intestine when either the normal or the low phosphorus diets were fed.

Effects of low calcium and low phosphorus diets on the duodenal absorption of calcium in betamethasone-treated chicks

The effect of oral administration of betamethasone (25 microgram kg-1 day-1) on the duodenal absorption of calcium has been studied in chicks using the ligated loop technique in vivo. The chicks were fed normal calcium, normal phosphorus (NCaNP), low calcium, normal phosphorus (LCaNP) or normal calcium, low phosphorus (NCaLP) diets. Daily oral administration of betamethasone for 2-3 weeks markedly reduced the absorption of calcium in chicks fed the NCaNP diet, but did not significantly affect the adaptation in absorption when the NCaLP or LCaNP diets were fed for the same period of time. In one group of chicks, betamethasone was administered daily for 10 days before the birds were transferred to the NCaLP or LCaNP diets. Adaptation was again unaffected by betamethasone treatment. Administration of betamethasone caused a marked retardation in growth-rate, hypercalcaemia and an increased percentage of ash in the tibiae.

Reversal of betamethasone-induced inhibition of intestinal calcium absorption by 1alpha-hydroxycholecalciferol

The intestinal absorption of calcium has been studied in conscious, unstressed pigs, using a modification of the double isotope technique. The oral administration of betamethasone (1 mg/day) to four pigs (25--33 kg) for 4 weeks reduced the calcium absorption coefficient, calculated after the intravenous and oral administration of 47Ca2+, by a mean value of 66%. The oral administration of 1alpha-hydroxycholecalciferol (2 microgram/day) in combination with beta-methasone (1 mg/day) for a further 4 weeks returned the absorption coefficient to the control value.

The in vitro metabolism of 25-hydroxycholecalciferol by pig kidney: effect of low dietary levels of calcium and phosphorus

1. Homogenates of pig kidney incubated in vitro convert 25-hydroxycholecalciferol to the dihydroxymetabolites almost as efficiently as homogenates of chick kidney under similar conditions. 2. The cortex of the kidney carries out this conversion more efficiently than does the medulla. 3. Kidneys from pigs given low calcium or low phosphorus diets produce about 40% more 1,25-dihydroxycholecalciferol than those from pigs given diets containing normal levels of Ca and P.

Coupling of Escherichia coli lipopolysaccharide to epoxy-activated Sepharose 6B

Escherichia coli O111:B4 lipopolysaccharide was coupled to epoxy-activated Sepharose 6B. The bound lipopolysaccharide was immunogenic and immunoadsorptive although at less efficiency than free lipopolysaccharide.

The use of a Thiry-Vella loop of jejunum to study the intestinal absorption of calcium and inorganic phosphate in the conscious pig

1. Pigs, each surgically prepared with a Thiry-Vella jejunal loop were used to study the absorption of calcium and inorganic phosphate from the intestine.

2. The loops were perfused daily for 6–8 h with a nutrient solution and absorption from the perfusate was measured.

3. The technique employed minimized atrophy of the jejunal mucosa and enabled the measurement of hourly or daily changes in absorption rate of components of the luminal fluid.

4. No differences were observed when polyethylene glycol (PEG; molecular weight 4000), [14C]PEG or 51Cr-EDTA were used as markers of net water movement.

5. Increasing the concentration of Ca in the perfusate resulted in the demonstration of a two-component relationship between net absorption rate of Ca and intraluminal Ca concentration. An initial rapid absorption rate from 0 to 4 mm was found, then a slower rate from approximately 5 mm upwards which did not saturate at the highest concentration tested (25 mm).

6. Increasing the concentration of phosphate in the perfusion solution increased the net absorption of phosphate from that solution. Although a two-component system, similar to that for Ca, was not evident, net absorption of phosphate was not saturated at the highest concentration tested (50 mm).

7. The absorption of Ca was unaffected by the presence of phosphate in the solution but Ca (2.5 mm) enhanced the absorption of phosphate.

Effect of low calcium and low phosphorus diets on the intestinal absorption of phosphate in intact and parathyroidectomized pigs

The intestinal absorption of phosphate has been studied in conscious pigs, each prepared with a Thiry-Vella loop of jejunum. The feeding of diets low in either calcium or phosphorus caused a significant increase in the efficiency of absorption of phosphate from the solution used to perfuse the jejunal loop in both intact and parathyroidectomized (PTX) pigs. An intravenous infusion of parathyroid hormone (0.22 u. kg-1 h-1) into a PTX pig also enhanced the absorption of phosphate. The increase in the absorption of phosphate when the low phosphorus diet was fed was not caused by an increase in the concentration gradient of phosphate ions between the jejunal lumen and blood. It is concluded that the intestinal absorption of phosphate shows similar changes to those of calcium when diets low in calcium or phosphorus are fed and that parathyroid hormone, although capable of stimulating the absorption of phosphate, is not essential for this adaptation. These effects are probably brought about by changes in the renal production and mucosal uptake of 1,25-dihydroxycholecalciferol, the active metabolite of vitamin D3.