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Biomedical subjects

F L Coe

Publications and source records attributed to F L Coe.

At least 127 records · Page 7Linked to original sources
PubMed1981

Kinetic characteristics of calcium absorption and secretion by rat colon.

The kinetic characteristics of calcium active transport in rat descending colon were determined by measuring unidirectional transmural calcium fluxes in vitro. The absorptive flux from mucosa to serosa (Jm leads to s) was saturable, with a calculated affinity (Kt) of calcium for the transport system of 1.6 mM and a maximal transport capacity (Vmax) of 133 nmol.cm-2.h-1. The administration of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] increased Jm leads to s by increasing Vmax to 236 nmol.cm-2.h-1 without changing Kt (1.8 mM). The secretory flux from serosa to mucosa (Js leads to m) was not saturable and was not increased by 1,25(OH)2D3. Mannitol, a marker of transepithelial extracellular flux, underwent net absorption in the absence of electrochemical gradients, and its Jm leads to s and Js leads to m were not altered by 1,25(OH)2D3 administration. Addition of 11 mM D-glucose to the bathing medium consistently increased calcium Js leads to m and mannitol Jm leads to s and Js leads to m. Glucose reduced net calcium absorption except when sodium was removed from the medium. Calcium Js leads to m varied linearly with mannitol Js leads to m over the range of medium calcium from 0.125 to 5.0 mM. The behavior of calcium absorption by descending colon is compatible with a carrier-mediated, active-transport mechanism, whereas calcium secretion occurs by a nonsaturable process via a predominately paracellular pathway.

Animals↗
PubMed1981

Effects of somatostatin on intestinal calcium transport in the rat.

The addition of somatostatin (SRIF) to rat descending colon in vitro increased the calcium secretory flux from serosa to mucosa (Js leads to m) and reduced tissue short-circuit current (Isc) but did not alter the absorptive flux from mucosa to serosa (Js leads to m). Js leads to m increased by 37% at 10(-9) M SRIF and by 48% at 10(-6) M. The response to SRIF was not altered by 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], and SRIF did not interfere with stimulation of calcium Jm leads to s by 1,25(OH)2D3. Removal of sodium from the buffer abolished the stimulation of Js leads to m by SRIF without reducing basal Js leads to m. Secretory fluxes of mannitol and calcium were strongly correlated in the presence and absence of SRIF, suggesting that SRIF stimulates a paracellular transepithelial pathway for calcium. In the duodenum, SRIF altered neither calcium Js leads to m nor Isc. In the ileum, calcium Js leads to m increased and Isc decreased, as in the colon, but only by 28 and 12%, respectively. The maximal change in calcium Js leads to m caused by SRIF in these three intestinal segments was negatively correlated with the tissue concentration of immunoreactive SRIF. These results suggest that intestinal calcium secretion could, in part, be regulated by intestinal SRIF.

Animals↗
PubMed1980

Uric acid saturation in calcium nephrolithiasis.

Hyperuricosuria appears to cause calcium oxalate nephrolithiasis by promoting the formation of monosodium urate or uric acid crystals, which either act as seed crystals for calcium oxalate or adsorb normally occurring macromolecular inhibitors of calcium oxalate crystallization. Both mechanisms require that hyperuricosuria cause excessive supersaturation of the urine, but this has not yet been studied under conditions of normal lifestyle. We have measured the saturation with respect to sodium hydrogen urate and the concentration of undissociated uric acid in the urine samples of 67 patients with calcium nephrolithiasis, who had idiopathic hypercalciuria, hyperuricosuria, both, or neither disorder. Patients with hyperuricosuria excreted urine that was supersaturated with respect to monosodium urate or undissociated uric acid more frequently than did other stone formers or normal subjects, and are therefore at a greater risk of forming a solid phase of monosodium urate or uric acid. Treatment measures that lowered uric acid excretion also lowered urine saturation, and this may be the reason that such treatment tends to prevent calcium stone recurrence.

Adolescent↗
PubMed1980

Effects of diet calcium and 1,25-dihydroxyvitamin D3 on colon calcium active transport.

Unidirectional fluxes of calcium were studied in the absence of electrochemical gradients across rat descending colon segments in vitro. Dietary calcium restriction and 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]enhanced absorption by increasing the mucosal-to-serosal fluxes, whereas secretory (serosal-to-mucosal) fluxes were unchanged. Low-calcium diet also stimulated calcium uptake by everted gut sac segments of ascending as well as descending colon, whereas transverse colon was unresponsive. These results show that the colon is a target organ for 1,25-(OH)2D3 and demonstrate the participation of colon in the intestinal adaptation to calcium deprivation.

Animals↗
PubMed1980

Viomycin-induced electrolyte abnormalities.

Severe hypokalemia (2.6 mEq/l), hypomagnesemia (0.6 mg/dl), mild hypercalcemia (10.9 mg/dl), and secondary hyperaldosteronism developed in a patient receiving viomycin for pulmonary tuberculosis. Reversible renal wasting of both potassium (K+) and magnesium (Mg++) was documented. Viomycin administered to 40 rats resulted in severe damage to the proximal tubule and mild damage to the distal tubule. THe case report and experimental data suggest viomycin induces proximal tubule dysfunction that results in renal wasting of sodium, K+ and Mg++ and secondary hyperaldosteronism. Hypercalcemia, not previously associated with viomycin therapy, may be secondary to hypomagnesemia-induced hyperparathyroidism.

Adult↗
PubMed1980

Clinical characteristics and pathogenetic mechanisms in hyperuricosuric calcium oxalate renal stone disease.

Studies of patients with hyperuricosuria have provided four kinds of evidence linking their hyperuricosuria to calcium stone formation and identifying them as a distinct entity apart from other calcium stone formers. The evidence includes a more virulent natural history of stone disease, in vitro evidence for heterogeneous nucleation of calcium oxalate crystallization by seed crystals for uric acid or sodium hydrogen urate, and a reduction by uric acid or urate of the inhibitory activity which urine normally has upon calcium oxalate crystal growth. The fourth bit of evidence, the dramatic reduction in stone formation rates with allopurinol treatment, will be discussed in detail in a following paper.

Adolescent↗
PubMed1980

The effects of allopurinol treatment on stone formation on hyperuricosuric calcium oxalate stone-formers.

The syndrome of hyperuricosuric calcium oxalate nephrolithiasis, consisting of calcium oxalate stones, hyperuricosuria and the absence of known causes of calcium stones, follows a course of particularly severe stone disease. This course can be dramatically altered by the reduction in new stone formation by the chronic administration of allopurinol. The mechanisms proposed in linking hyperuricosuria to calcium oxalate stones are both dependent upon the presence of oversaturation of the urine with one or both species of uric acid. Allopurinol reduces the saturation of the urine with respect to sodium hydrogen urate and reduces urine concentration of undissociated uric acid, thus directly altering the pathogenetic mechanisms proposed for this disorder.

Allopurinol↗
PubMed1979

Familial idiopathic hypercalciuria.

The frequency of hypercalciuria was determined in the families of nine hypercalciuric patients with idiopathic hypercaliuria who formed recurrent calcium oxalate renal stones. Idiopathic hypercalciuria occurred in 26 of 73 relatives, in three consecutive generations of two families and in two successive generations of four other families. Multiple siblings or children of the probands were affected in three families. Nineteen of 44 first-degree relatives (43 per cent) had idiopathic hypercalciuria, as compared to seven of 29 (29 per cent) other relatives; there was no relation to age or sex. Renal stones were formed by 19 of the 44 first-degree relatives but by none of the others; nine of the 19 were women. We conclude that there is a familial form of hypercalciuria, which appears to be transmitted as an autosomal dominant trait. Stone disease is frequent in first-degree relatives, and affects both sexes equally.

Adult↗
PubMed1979

Urinary saturation measurements in calcium nephrolithiasis.

Urinary saturation with respect to calcium oxalate monohydrate was measured in 111 consecutive patients with calcium nephrolithiasis. Each patient also was evaluated by a detailed conventional metabolic protocol. Patients with idiopathic hypercalciuria produced abnormally oversaturated urine more frequently than normal subjects and normocalciuric patients, but normocalciuric patients had unexpectedly high levels of urine saturation. Measuring levels of calcium concentration, oxalate concentration, or the chemical concentration product of calcium and oxalate in urine did not predict oversaturation. During thiazide treatment, saturation level tended to fall if it was initially elevated, whether the patient was hypercalciuric or not. Patients whose urine was not remarkably oversaturated showed no tendency to elaborate even less saturated urine during thiazide treatment; instead, the average calcium oxalate saturation level remained constant. Direct urine saturation measurements can detect a small but significant number of normocalciuric patients who have marked oversaturation with respect to calcium oxalate and appear to benefit from treatment.

Calcium↗