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Biomedical subjects

R Bouillon

Publications and source records attributed to R Bouillon.

At least 289 records · Page 16Linked to original sources
PubMed1988

Diabetes and low Ca-P diet have opposite effects on adult and fetal bone mineral metabolism.

The effect of diabetes on maternal bone mineral metabolism and fetal mineralization was studied in nonpregnant and pregnant BB rats fed two diets (0.85% calcium-0.7% phosphorus and 0.2% calcium-phosphorus). Non-pregnant female diabetic rats had normal total bone mineral content (BMC), despite decreased trabecular bone volume density (TBVD). Nondiabetic rats on the low calcium-phosphorus diet showed decreased TBVD, signs of increased bone turnover, and decreased BMC; plasma 1,25-dihydroxyvitamin D3 [1,25 (OH)2D3] was increased and urinary calcium excretion was decreased. A similar response was observed in diabetic rats with a further decrease in TBVD. Nondiabetic 21-day pregnant rats on high and low calcium-phosphorus diets had higher 1,25(OH)2D3 than nonpregnant rats (98 vs. 58 and 328 vs. 147 pg/ml, respectively). Maternal BMC did not change during pregnancy but was decreased by the low calcium-phosphorus diet; fetal mineral content was not influenced by the low calcium-phosphorus regime. No increase in 1,25(OH)2D3 was observed in pregnant diabetic rats (57 vs. 52 and 112 vs. 128 pg/ml in high and low calcium-phosphorus diet groups). Fetal mineralization was severely impaired in diabetes but was not further decreased by the low calcium-phosphorus diet. Thus nonpregnant diabetic rats respond normally to a low calcium-phosphorus diet, but pregnant diabetic rats do not show increased 1,25(OH)2D3 levels due to impairment of fetal mineralization.

Amniotic Fluid↗
PubMed1988

1,25(OH)2D3 and Ca-binding protein in fetal rats: relationship to the maternal vitamin D status.

The autonomy and functional role of fetal 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] were investigated in nondiabetic and diabetic BB rats fed diets containing 0.85% calcium-0.7% phosphorus or 0.2% calcium and phosphorus and in semistarved rats on the low calcium-phosphorus diet. The changes in maternal and fetal plasma 1,25(OH)2D3 were similar: the levels were increased by calcium-phosphorus restriction and decreased by diabetes and semistarvation. Maternal and fetal 1,25(OH)2D3 levels were correlated (r = 0.80; P less than 0.001). The vitamin D-dependent calcium-binding proteins (CaBP9K and CaBP28K) were measured in multiple maternal and fetal tissues and in the placenta of nondiabetic, diabetic, and calcium-phosphorus-restricted rats. The distributions of CaBP9K and CaBP28K in the pregnant rat were similar to that of the growing rat. The increased maternal plasma 1,25(OH)2D3 levels in calcium-phosphorus-restricted rats were associated with higher duodenal CaBP9K and renal CaBPs, but placental CaBP9K was not different. In diabetic pregnant rats, duodenal CaBP9K tended to be lower, while renal CaBPs were normal; placental CaBP9K was decreased. No significant changes in CaBP levels were observed in fetuses of low calcium-phosphorus diet rats or fetuses of diabetic rats. The results indicate that in the rat fetal 1,25(OH)2D3 depends on maternal 1,25(OH)2D3 or on factors regulating maternal 1,25(OH)2D3. The lack of changes in fetal CaBP in the presence of altered fetal plasma 1,25(OH)2D3 levels confirms earlier data showing that 1,25(OH)2D3 has a limited hormonal function during perinatal development in the rat.

Animals↗
PubMed1988

Role of group-specific component (vitamin D binding protein) in clearance of actin from the circulation in the rabbit.

The possible role of group specific component (Gc) (vitamin D-binding protein) in the clearance of cellular actin entering the circulation was examined with 125I-labeled Gc and actin injected into a rabbit model. Although filamentous F-actin is depolymerized primarily by plasma gelsolin, greater than or equal to 90% 125I-actin injected in either monomeric G- or F-form became complexed eventually with Gc (1:1 molar ratio). Clearance of Gc complexes was much faster (greater than 90% within 5 h) than that of native Gc (t1/2 = 17.2 h). Nephrectomy did not significantly alter the clearance of either Gc or actin. Since Gc complexes are dramatically increased in situations of tissue necrosis such as in fulminant hepatic failure, the current results suggest a crucial role for Gc in sequestration and clearance of released cellular actin.

Actins↗
PubMed1988

Mineral metabolism and bone mass at peripheral and axial skeleton in diabetes mellitus.

Bone mineral content (BMC), mineral homeostasis, and diabetes control were evaluated in 31 Caucasian insulin-dependent diabetic patients (disease duration 18.3 +/- 7.7 yr, mean +/- SD) with normal kidney function. To evaluate bone mass, we performed radiogrammetry and single- and dual-photon absorptiometry. In women, a significantly lower mean BMC was found in the distal radius, at a mixed trabecular-cortical (P less than .01) and a cortical (P less than .05) site, as well as in the lumbar spine (P less than .02). In diabetic men, mean BMC was significantly reduced at the trabecularcortical (P less than .01) and cortical (P less than .05) sites of the radius but not in the lumbar spine. When expressed as densities (i.e., BMC/width or lumbar BMC/area), only the BMC/width at the radius cortical area was significantly reduced in women (P less than .05). The results of the radiogrammetry showed a larger endosteal diameter in the diabetic women, resulting in a significantly lower cortical thickness (P less than .05). Diabetic men did not show abnormalities on radiogrammetry. Diabetic patients had diminished serum calcium and phosphorus concentrations (P less than .001), whereas serum parathyroid, 25-hydroxyvitamin D3, and concentrations of both total and free 1,25-dihydroxyvitamin D3 were normal. No correlation between parameters of diabetes control (HbA1, insulin dose, and triglycerides) or calcium-regulating hormones and BMC were found. These data confirm that, despite large overlap of individual values, mean bone mass at the peripheral skeleton is significantly decreased in diabetic patients. Moreover, we report that the BMC of the lumbar spine is significantly reduced in female diabetic patients.

Adult↗
PubMed1988

Renal responses to calcium deprivation in young rabbits.

To evaluate the renal adaptations to dietary Ca deprivation, young growing female albino rabbits were fed a Ca-deficient diet for 8 consecutive days while they were housed in metabolism cages. Urinary Ca excretion rates decreased markedly within 24 h of Ca deprivation, reached a nadir by day 5, and remained low thereafter. Concomitantly, urinary P excretion increased. The hypocalciuria during the 8-day study was accounted for by an increased tubular reabsorption of Ca. Urinary cyclic AMP excretion was increased on the first day of Ca deprivation. Plasma immunoreactive parathyroid hormone and calcitriol concentrations were elevated after 8 days of Ca deprivation. Conversely, plasma calcifediol concentrations were decreased. We conclude that there are rapidly induced, appropriate renal homeostatic adaptations to dietary Ca deprivation in the rabbit and suggest that increases in endogenous plasma parathyroid hormone concentration, in part, play a role in mediating these changes.

Animals↗
PubMed1988

Renal responses to phosphorus deprivation in young rabbits.

To evaluate the renal adaptations to dietary P deprivation, young growing female rabbits were fed a P-deficient diet for 10 consecutive days while they were housed in metabolism cages. Urinary Ca excretion rates increased markedly within 24 h of P deprivation, remained high for each of the 10 days that dietary P was low, and returned to control values within 24 h of consuming a normal-P feed. The hypercalciuria was attributable to both an increased filtered load and decreased tubular reabsorption of Ca. Urinary P excretion rates decreased gradually in response to a low P diet and reached a nadir only after 9 days of deprivation. Urinary P excretion rates recovered to control values within 24 h of feeding a normal-P diet. Increased tubular reabsorption of P alone accounted for the hypophosphaturia. Plasma P concentration was reduced significantly after 10 days of dietary P deprivation, and this was associated with a significant increase in plasma calcitriol concentration. We conclude that dietary P deprivation in the rabbit effects the hypophosphatemia, hypophosphaturia, and hypercalciuria that characterize this condition in rats, dogs, and humans. Furthermore, the elevation in plasma calcitriol concentration that has been observed with dietary P deprivation in healthy rats and humans also occurs in the laboratory rabbit.

Absorption↗
PubMed1987

Autosomal dominant hypophosphataemia with elevated serum 1,25 dihydroxyvitamin D and hypercalciuria.

A 14-year-old boy presented with the clinical and radiological features of rickets. Serum inorganic phosphate levels were constantly low, whereas serum calcium and parathyroid hormone levels were within the normal range. Laboratory investigation did not show any evidence for vitamin-D deficiency, chronic renal insufficiency, Fanconi syndrome, tubular acidosis, hepatic disease or intestinal malabsorption. A family study comprising 34 members over four generations revealed 10 other individuals to be affected and the mode of inheritance to be autosomal dominant. In addition to hypophosphataemia and normocalcaemia, the disease is characterized by elevated serum 1,25 dihydroxyvitamin D levels and hypercalciuria. This hereditary syndrome of renal hypophosphataemia differs from the common familial X-linked hypophosphataemia and the recently described autosomal recessive hypophosphataemic rickets with hypercalciuria by its dominant mode of inheritance; it differs from hypophosphataemic non-rachitic bone disease by the elevated serum 1,25 dihydroxyvitamin D levels and hypercalciuria.

Adolescent↗
PubMed1987

Calcium, vitamin D-endocrine system, and parathyroid hormone in black and white males.

The serum and urinary calcium, 25-hydroxyvitamin D (25OHD), 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), and parathyroid hormone (PTH) were studied in healthy black and white males living in Belgium, and the results were compared to data in blacks of similar age living in Zaïre. Dietary calcium and vitamin D were estimated in a sub-sample of blacks and whites examined in Belgium. Compared to whites (9.51 +/- 0.28 mg%) serum calcium was somewhat lower in blacks (9.26 +/- 0.27 mg% in Belgium; 9.19 +/- 0.48 mg% in Zaïre). The 24 hour urinary calcium excretion averaged 215.0 +/- 16.7 mg% in whites and was higher (P less than 0.05 or less) than in blacks (115 +/- 71 mg% in Belgium; 36 +/- 33 mg% in Zaïre). The serum 25OHD levels were similar in whites and blacks evaluated in Zaïre, both being higher (P less than 0.05 or less) than in blacks living in Belgium. In the latter blacks, an inverse correlation was observed between the 25OHD level and the duration of the stay in a temperate climate. Parathyroid hormone levels were slightly higher in blacks living in Belgium than in the other two groups of subjects. The serum levels of 1,25(OH)2D3 and human vitamin D-binding protein were similar in the three groups of subjects. Dietary calcium averaged 541 +/- 152 mg/day in blacks and was significantly (P less than 0.001) less than in whites (1,203 +/- 508 mg/day), whereas no significant difference was observed in dietary vitamin D intake between blacks and whites. It is concluded that calcium intake is low in blacks but stimulation of parathyroid hormone and 1,25(OH)2D3 required to achieve normocalcemia does not occur.

25-Hydroxyvitamin D 2↗
PubMed1987

Parathyroid hormone-stimulated calcium absorption in cTAL from vitamin D-deficient rabbits.

Cortical thick ascending limbs of Henle's loop were dissected from the kidneys of chronically vitamin D-deficient or -replete rabbits and perfused in vitro. Unidirectional transepithelial calcium fluxes from lumen to bath were measured with 45Ca. The tubules were bathed in a solution containing 150 mM sodium and perfused with a solution containing 60 mM sodium to simulate conditions in the cortical thick ascending limb in vivo. Transepithelial voltages were equal across tubules from vitamin D-deficient and -replete rabbits. Likewise, baseline and parathyroid hormone-stimulated calcium fluxes were the same in tubules from the two groups. Because calcidiol and calcitriol were undetectable in the serum of the vitamin D-deficient rabbits, we suggest that neither of these endogenous vitamin D metabolites is essential in the regulation of calcium absorption in this portion of the rabbit nephron.

Absorption↗
PubMed1987

Immunological and clinical observations in diabetic kidney graft recipients pretreated with total-lymphoid irradiation.

In a feasibility study, twenty patients with end-stage diabetic nephropathy were treated with fractionated total-lymphoid irradiation (TLI, mean dose 25 Gy), before transplantation of a first cadaveric kidney. During radiotherapy, only one patient had a serious side effect (bone marrow depression). After transplantation four patients died (one of a myocardial infarction, one of ketoacidosis, and two of infections occurring during treatment of rejection crises). One graft was lost because of chronic rejection. The other 15 patients have a functioning graft (mean follow-up 24 months) and receive low-dose prednisone alone (less than 10 mg/day, n = 11) or in conjunction with cyclosporine (n = 4) as maintenance immunosuppressive therapy. A favorable clinical outcome after TLI (no, or only one, steroid-sensitive rejection crisis) was significantly correlated with a high pre-TLI helper/suppressor lymphocyte ratio, a short interval between TLI and the time of transplantation, and the occurrence of functional suppressor cells early after TLI. The most striking immunological changes provoked by TLI consisted of a long-term depression of the mixed lymphocyte reaction and of the phytohemagglutinin, and Concanavalin A or pokeweed-mitogen-induced blastogenesis. A rapid and complete recovery of the natural killer cell activity was observed after TLI. A permanent inversion of the OKT4+ (T helper/inducer) over OKT8+ (T suppressor/cytotoxic) lymphocyte ratio was provoked by a decrease of the OTK4+ subpopulation, together with a supranormal recovery of the OKT8+ lymphocytes. A majority of the latter lymphocytes did also express the Leu 7 and the Leu 15 phenotype.

Adult↗
PubMed1987

Plasma vitamin D-binding protein and free 1,25-dihydroxyvitamin D3 index in pregnant ewes and their fetuses in the last month of gestation.

A radioimmunoassay for ovine vitamin D-binding protein (DBP) has been developed. This assay can also effectively measure DBP in goat plasma. A suitable ovine DBP antiserum raised in a rabbit produced a single monospecific line of precipitation when reacted against purified sheep DBP and sheep plasma. The preliminary purification of 125I-labelled ovine DBP was carried out using adsorption chromatography, and the final purification immediately before addition to the assay tubes was achieved by high-pressure liquid chromatography. Displacement of 125I-labelled ovine DBP by dilutions of sheep and goat plasma or standard DBP gave parallel curves, and only weak competition was observed with calf and pig plasma. The assay detected as little as 26 pmol DBP/l with intra- and interassay coefficients of variation of 3 and 14% respectively. The mean plasma concentration of DBP in nine pregnant sheep (110-120 days of gestation) was 8.7 +/- 0.3 (S.E.M.) mumol/l. These levels were significantly (P less than 0.02; paired t-test) higher than those in matched fetal plasma (6.7 +/- 0.4 mumol/l) obtained in utero through a catheter in a carotid artery. Plasma DBP concentrations in pregnant sheep were also significantly (P less than 0.02) higher than in five normal non-pregnant sheep (6.8 +/- 0.5 mumol/l). The mean concentrations of total 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) in maternal and fetal plasma were 92.0 +/- 8.7 pmol/l and 152.5 +/- 18.0 pmol/l respectively (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗