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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Serum concentrations of 25-hydroxyvitamin D (25-OHD), 24,25-dihydroxyvitamin D [24,25-(OH)2D], and 1 alpha, 25-dihydroxyvitamin D [1, 25-(OH)2D] were measured in 30 ambulatory adult epileptic patients during long-term anticonvulsant treatment with phenytoin, phenobarbital, or carbamazepine. For the entire group, serum 24,25-(OH)2D was decreased (p less than 0.0005) as compared to normal subjects to a mean value of 0.7 +/- 0.1 (SEM) ng/ml. However, serum 1, 25-(OH)2D was increased at 50 +/- 7 pg/ml (p less than 0.025). Serum 25-OHD declined insignificantly to 19 +/- 3 ng/ml. All three drugs caused a significant reduction of serum 24,25-(OH)2D concentrations. A significant decrease in serum 25-OHD was observed only for the phenobarbital-treated patients. Serum 1, 25-(OH)2D was high in patients receiving phenytoin or carbamazepine but not in those taking phenobarbital. The findings suggest that while various anticonvulsant drugs appear to exert different effects on vitamin D metabolism, a universal finding is diminished serum 24,25-(OH)2D. The results support the notion that 24,25-(OH)2D deficiency may play an important role in the pathogenesis of anticonvulsant-induced osteomalacia.
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PMID:Decreased serum 24,25-dihydroxyvitamin D concentration during long-term anticonvulsant therapy in adult epileptics. 698 22

In man as well as in experimental animals progressive renal failure is associated with a decrease in the fractional reabsorption (FR) of inorganic phosphate (Pi). This response has been considered as an adaptation phenomenon and generally attributed to an increase in parathyroid hormone (PTH) secretion. One report indicates that in chronic thyroparathyroidectomized (TPTX) dogs treated with large doses of vitamin D progressive renal failure can also be associated with a fall in FRPi. However, in this latter study the concomittant administration of vitamin D could have accounted for the observed decrease in FRPi. In our study we investigated whether or not chronic reduction in renal mass leads to a similar decrease in maximal net tubular Pi reabsorption per volume of glomerular filtrate (maximal TRPi/ml GF) in the presence and absence of PTH and without pharmacological supplementation in vitamin D. Male rats were either TPTX or sham-operated (intact). One and two weeks later the animals of both groups were either subtotally nephrectomized (NX) in two stages or sham-operated (control). Four weeks after the second renal operation, the glomerular filtration rate (GFR) and the reabsorption of Pi were determined by clearance methodology under acute sodium chloride and Pi infusion, that is, at endogenous and increased plasma Pi concentrations ([Pi]Pl.). Thus maximal TRPi/ml GFR could be determined. In rats with intact parathyroid glands GFR was 1.56 +/- 0.10 (mean +/- SEM) and 0.54 +/- 0.10 ml/min in control and NX respectively, whereas maximal TRPi/ml GF was 2.24 +/- 0.07 in control and 1.57 +/- 0.18 mumol/ml (P less than 0.005) in NX. In TPTX rats GFR was 1.66 +/- 0.27 and 0.62 +/- 0.06 ml/min in control and NX respectively, whereas maximal TRPi/ml GF was 3.80 +/- 0.20 in control and 2.95 +/- 0.13 mumol/ml (P less than 0.005) in NX. The marked decrease in maximal TRPi/ml GF observed in TPTX after subtotal NX could not be ascribed to any consistent change in plasma calcium. Our study provides conclusive evidence that the decrease in maximal TRPi/ml GF in response to renal mass reduction can occur to the same degree in the presence or absence of PTH.
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PMID:Parathyroid hormone-independent adaptation of the renal handling of phosphate in response to renal mass reduction. 708 83

An experimental infant developed to meet the specific nutritional needs of very-low-birth-weight infants was evaluated by 96-hour balance studies in ten preterm infants (birth weight: 1,130 to 1,530 gm). The formula contained 23.2 gm/liter of protein (whey protein/casein ratio, 60:40), 44.1 gm/liter of fat (50% medium-chain triglycerides) and 85.0 gm/liter of carbohydrate (50% lactose, 50% Polycose), and provided relatively higher amounts of calcium, phosphorus, vitamin D, and electrolytes than are in human milk. All infants were fed 150 ml/kg/day (120 calories/kg/day) by intermittent gavage. Balance studies were carried out nine days following establishment of oral intake. The mean (+/- SEM) nutrient retention rates revealed by balance studies in these infants (calcium, 170 +/- 4 mg/kg/day; phosphorus, 78 +/- 3 mg/kg/day; nitrogen, 426 +/- 8 mg/kg/day; sodium, 1.4 +/- 0.1 mEq/kg/day) were comparable to normal fetal accretion rates. The mean (+/- SEM) fat absorption was 92.5 +/- 0.9%. No clinical intolerances or biochemical abnormalities were observed, and adequate postnatal growth was achieved in all infants. The diet proved to be nutritionally advantagaeous and safe for very-low-birth-weight infants.
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PMID:Nutritional balance studies in very-low-birth-weight infants: enhanced nutrient retention rates by an experimental formula. 740 7

1. A radioimmunoassay of 25,26-dihydroxycholecalciferol has been developed with an antiserum raised in a sheep, tritiated 1,25-dihydroxycholecalciferol as tracer and synthetic 25,26-dihydroxycholecalciferol as standard. The metabolite was purified from serum extracts by Sephadex LH 20 and high-pressure liquid chromatography; recovery was monitored with biologically generated, tritiated 25,26-dihydroxycholecalciferol. 2. The mean +/- SEM concentration of 25,26-dihydroxycholecalciferol in serum from 18 healthy subjects was 587 +/- 65 pmol/l. Seven Asian patients with osteomalacia due to vitamin D deficiency had very low or undetectable (< 96--231 pmol/l) circulating 25,26-dihydroxycholecalciferol concentrations. 3. The metabolite was detectable in the sera from seven anephric patients (mean 262 +/- 43 pmol/l), indicating that extrarenal sites for the 26-hydroxylation of 25-hydroxycholecalciferol exist in man. 4. A strong positive correlation between the concentrations of 25-hydroxycholecalciferol and those of 25,26-dihydroxycholecalciferol in serum was obtained. Thus it appears that in man the production of this dihydroxy metabolite of vitamin D depends on the concentration of its precursor, 25-hydroxycholecalciferol.
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PMID:Determination of circulating 25,26-dihydroxycholecalciferol in man by radioimmunoassay. 742 93

We investigated the homeostatic compensation for the lower cutaneous synthesis of vitamin D in heavily melanized persons. Vitamin D2 (50,000 IU) was administered in a single oral dose to 24 young adults, 12 blacks and 12 whites, matched for age, gender, and socioeconomic status. We also included a group of eight healthy elderly white adults as representatives of a population with a nonracial mechanism for decreased cutaneous vitamin D synthesis. Plasma determinants were performed under basal conditions and at 6, 10, and 24 hours after vitamin D intake. Basal 25-hydroxyvitamin D (25-OH-D) levels were significantly lower in blacks (12.5 +/- 2.2 ng/ml (mean +/- SEM)) and in elderly whites (19.2 +/- 1.9 ng/ml), compared with young whites (30.2 +/- 3.0 ng/ml (p < 0.0001)); levels of basal 1,25-dihydroxyvitamin D (1,25(OH)2 -D) did not differ between groups. The vitamin D blood curve was similar between groups after the oral vitamin D2 load. Increases in 25-OH-D were 91.7 +/- 15.9% in blacks, 18.8 +/- 5.2% in young whites, and 28.6 +/- 6.9 in elderly whites; 1,25(OH)2-D levels increased slightly and did not differ between groups, although in blacks the change over time was significant (p < 0.05). As a whole, the study populations exhibited a strong relation between basal and peak 25-OH-D (r = -0.80; p < 0.001). Levels of intact parathyroid hormone and serum calcium of blacks and young whites did not differ within or between groups throughout the test.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Compensation for the interracial variance in the cutaneous synthesis of vitamin D. 759 30

The incidence of nutritional rickets in the southern part of Argentina is 8-12 times higher than in the rest of the country. Winter 25(OH)D serum levels in normal population of southern areas are lower than in central and northern areas. To elucidate these differences, we compared the photoconversion of provitamin D3 (7-DHC) to previtamin D3 in two cities: Ushuaia (latitude 55 degrees S) and Buenos Aires (34 degrees S). Ampules containing 7-DHC were exposed to sunlight one day in the middle of each month either from 10:30 a.m. to 2:30 p.m. or from 8:00 a.m. to 5:00 p.m. The percentages of photoproducts formed were determined by high performance liquid chromatography (HPLC). Previous studies have proved that this is a valid model to assess "in vitro" the photoproduction of vitamin D3 in human skin. Previtamin D3 + vitamin D3 formed in Ushuaia were less (p < 0.02) than those found in Buenos Aires during all seasons: summer, (X +/- SEM) 6.4 +/- 0.8% vs. 13.2 +/- 1.8%; autumn, 1.2 +/- 0.7% vs. 6.3 +/- 1.3%; winter, 0.8 +/- 0.7% vs. 3.6 +/- 0.7%; spring, 3.4 +/- 0.5% vs. 9.1 +/- 1.1%. The photoproducts produced from 10:30 a.m. to 2:30 p.m. were similar for each month and latitude to those formed when the ampules were exposed from 8:00 a.m. to 5:00 p.m. We conclude that in Ushuaia there is a prolonged "vitamin D winter" during which cutaneous synthesis of vitamin D is absent, leading to lower serum values of 25(OH)D and contributing to the higher incidence of rickets.
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PMID:Solar ultraviolet B radiation and photoproduction of vitamin D3 in central and southern areas of Argentina. 761 Sep 24

To evaluate the effect of abstinence on bone mass and bone mineral metabolism in chronic alcoholics, a 2 year longitudinal follow-up study was carried out in a group of 30 chronic alcoholic males who started a rehabilitation program. Lumbar and femoral bone mineral density (BMD) and serum levels of osteocalcin and 25-hydroxyvitamin D were measured at entry and after 1 and 2 years in all patients. Circulating cortisol and parathyroid hormone were measured in 14 and 6 patients, respectively, at entry and every year. Testosterone was measured in 18 patients at entry and after 1 year. At entry, lumbar BMD was significantly lower in alcoholics (1.06 +/- 0.03 g/cm2) than in age-matched healthy men (1.22 +/- 0.03 g/cm2; p < 0.001). Circulating osteocalcin and vitamin D levels were also significantly lower in alcoholics than in controls. Lumbar and femoral neck BMD increased in alcoholics after 2 years of abstinence (lumbar BMD, mean +/- SEM, 1.06 +/- 0.03 to 1.10 +/- 0.04 g/cm2, p < 0.05; femoral BMD, 0.82 +/- 0.02 to 0.84 +/- 0.02 g/cm2; p < 0.02). Moreover, lumbar BMD increased in alcoholics (2.9 +/- 1.4%) and decreased in controls (-1.1 +/- 0.2%; p < 0.02). Femoral BMD also increased in alcoholics (2.8 +/- 1.0%) but the expected mean decrease of -0.92% was found in healthy age-matched males. Baseline low osteocalcin levels (5.1 +/- 0.6 ng/ml) increased after 1 year (8.6 +/- 0.5 ng/ml, p < 0.001) and 2 years of abstinence (9.5 +/- 0.7 ng/ml, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Bone mass improves in alcoholics after 2 years of abstinence. 781 7

Vitamin D may protect against colorectal cancer by reducing cell proliferation and inducing differentiation. By contrast, epidermal growth factor (EGF) stimulates cell proliferation and may encourage gastrointestinal mucosal healing. This study investigated the effect of a synthetic vitamin D analogue, calcipotriol, and EGF on human rectal epithelial cell proliferation in patients with familial adenomatous polyposis (FAP). In addition, a new technique to measure the cell cycle time is described. Sigmoidoscopic biopsy specimens were obtained from 14 patients with FAP. Tissue was established in organ culture, with or without the addition of EGF (n = 8), or calcipotriol (n = 6). Proliferation was determined using (a) metaphase arrest to measure the crypt cell production rate, (b) native mitotic index, and (c) the growth fraction using PC10 antibody. EGF receptor expression was shown using a polyclonal antibody AP12E. Calcipotriol reduced crypt cell production rate by 52% from mean (SEM) 5.29 (1.18) to 2.56 (0.80) cells/crypt/hour (p < 0.01) and EGF increased crypt cell production rate by 102% from 3.62 (0.59) to 7.33 (0.90) cells/crypt/hour (p < 0.05), and this tissue expressed the EGF receptor. The growth fraction was 48.40 (4.0)%, and the native mitotic index 1.08 (0.14)%. The cell cycle time was estimated as 94.5 hours and the time for mitosis as one hour. Thus, calcipotriol and EGF have divergent effects on human rectal mucosal proliferation.
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PMID:Divergent effects of epidermal growth factor and calcipotriol on human rectal cell proliferation. 782 12

Bisphosphonates seem to be effective as antiresorptive agents in the prevention and treatment of osteoporosis. However, the optimal dose and route of administration as well as the specific effects on cortical or trabecular bone have not been clarified. To compare pamidronate (APD) with fluoride (F) in the therapy of postmenopausal osteoporosis, 32 osteoporotic women were treated for 2 years either with APD (30 mg as a single intravenous infusion over 1 h every 3 months, n = 16, mean age 65 years) or with fluoride orally (20-30 mg F/day, n = 16, mean age 67 years) in an open study. Both groups received 1 g calcium and 1000 U vitamin D per day, but no estrogens or other drugs acting on bone. Both groups showed the same initial mean number of fractures per patient (2.8 and 2.7). Bone densitometry was performed every 6 months at three sites: lumbar spine and hip with dual-energy X-ray absorptiometry (BMD), distal forearm with single photon absorptiometry and lumbar spine with quantitative computed tomography. Biochemical assessment was performed in blood and urine every 3 months. Lumbar BMD (g/cm2, mean +/- SEM) increased from 0.632 (+/- 0.030) at time 0 to 0.696 (+/- 0.028) at 24 months in the APD group (p < 0.001), and from 0.684 (+/- 0.025) to 0.769 (+/- 0.028) in the fluoride group (p < 0.001). Femoral neck BMD increased significantly from 0.558 (+/- 0.025) to 0.585 (+/- 0.025) (p < 0.01) in the APD group, whereas it did not change in the fluoride group.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Two years' effectiveness of intravenous pamidronate (APD) versus oral fluoride for osteoporosis occurring in the postmenopause. 800 44

Cryptomys hottentotus has no access to dietary or endogenous sources of cholecalciferol (D3). Serum concentrations of calcifediol (25(OH)D3) were undetectable (< 5 ng/ml) and calcitriol (1,25(OH)2D3), although detectable in plasma, was at a low concentration (31.40 (SEM 3.06 pg/ml). Despite their naturally impoverished vitamin D status, these animals exhibited highly efficient mineral absorption processes (Ca apparent fractional absorption efficiency, AFA (%) 95.33 (SEM 1.36); inorganic P (P(i)) AFA (%) 93.49 (SEM 0.81)). Furthermore, plasma mineral content was tightly regulated (Ca 2.57 (SEM 0.08) mmol/l; Mg 1.23 (SEM 0.05) mmol/l; P(i) 2.12 (SEM 0.15) mmol/l). Mode of uptake in C. hottentotus was unlike that in other D3-replete mammals. First, passive (rather than active) uptake occurred in the traditional site of active Ca absorption (with serosal:mucosal (S:M) ratios in the duodenum of 1.32 (SEM 0.13)), and the only site of active Ca uptake was the hindgut (caecum S:M 3.35 (SEM 0.46); proximal colon S:M 2.13 (SEM 0.30)). Despite the presence of active uptake in these hindgut regions, their overall contribution to the daily rate of mineral absorption was small (9.53 (SEM 1.27)%). These underground inhabitants rely upon highly efficient, passive mineral uptake. This is adequate to meet their mineral requirements and maintain mineral homeostasis in the absence of vitamin D.
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PMID:Passive uptake in the small intestine and active uptake in the hindgut contribute to the highly efficient mineral metabolism of the common mole-rat, Cryptomys hottentotus. 801 10


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