D3 Absorption Research Articles

Potential and Metabolic Impacts of Double Enrichments of Docosahexaenoic Acid and 25-Hydroxy Vitamin D3 in Tissues of Broiler Chickens

BackgroundChicken may be enriched with 25-hydroxy D3 [25(OH)D3] and docosahexaenoic acid (DHA) to enhance the dietary intake of the public. ObjectivesTwo experiments (Expt.) were conducted to determine the potential and metabolic impacts of enriching both DHA and 25(OH)D3 in the tissues of broiler chickens. MethodsIn Expt. 1, 144 chicks (6 cages/treatment and 6 birds/cage) were fed a corn–soybean meal basal diet (BD), BD + 10,000 IU 25(OH)D3/kg [BD + 25(OH)D3], BD + 1% DHA-rich Aurantiochytrium (1.2 g DHA/kg; BD + DHA), or BD + 25(OH)D3+DHA for 6 wk. In Expt. 2, 180 chicks were fed the BD, BD + DHA-rich microalgal oil (1.5–3.0 g DHA/kg, BD + DHA), BD + DHA + eicosapentaenoic acid (EPA)-rich microalgae (0.3–0.6 g EPA/kg, BD + DHA + EPA), BD + DHA + 25(OH)D3 [6000 to 12,000 IU/kg diet; BD + DHA + 25(OH)D3], and BD + DHA + EPA + 25(OH)D3 for 6 wk. ResultsSupranutrition of these 2 nutrients resulted in 57–62 mg DHA and 1.9–3.3 μg of 25(OH)D3/100 g of breast or thigh muscles. The DHA enrichment was independent of dietary EPA or 25(OH)D3, but that of 25(OH)D3 in the liver was decreased (68%, P < 0.05) by dietary DHA in Expt. 1. Compared with BD, BD + 25(OH)D3 enhanced (P < 0.05) gene expression related to D3 absorption (scavenger receptor class B type 1 and Niemann-pick c1 like 1) in the liver and D3 degradation (cytochrome P450 24A1) in the breast, and decreased mRNA or protein concentrations of vitamin D binding protein in the adipose tissue or thigh muscle. Supranutrition of DHA decreased mRNA concentrations of lipid metabolism-related genes (fatty acid desaturase 1,2, ELOVL fatty acid elongase 5, fatty acid desaturase 2, fatty acid synthase, and sterol regulatory element-binding protein 1). ConclusionsBoth DHA and 25(OH)D3 were enriched in the muscles up to meeting 50%–100% of the suggested intakes of these nutrients by consuming 2 servings of 100 g of fortified chicken. The enrichments altered gene expression related to lipid biosynthesis and vitamin D transport or storage.

A Comparison and Safety Evaluation of Micellar versus Standard Vitamin D3 Oral Supplementation in a Randomized, Double-Blind Human Pilot Study.

The aim of this pilot study was to evaluate and compare bioavailability and safety of two Vitamin D3 formulations (softgels) in healthy adults, at single daily doses of 1000 and 2500 IU, over a 60-day period. A total of 69 participants were initially screened for eligibility in a double-blind randomized study with a four-arm parallel design; 35 participants were randomized to treatment groups: (1) standard Vitamin D3 1000 IU (STD1000), (2) micellar Vitamin D3 1000 IU (LMD1000), (3) standard Vitamin D3 2500 IU (STD2500), and (4) micellar Vitamin D3 2500 IU (LMD2500). Serum Vitamin D concentrations were determined through calcifediol [25(OH)D] at baseline (=before treatment), at day 5, 10, and 15 (=during treatment), at day 30 (=end of treatment), and at day 45 and 60 (=during follow-up/post treatment). Safety markers and minerals were evaluated at baseline and at day 30 and day 60. The pharmacokinetic parameters with respect to iAUC were found to be significantly different between LMD1000 vs. STD1000: iAUC(5-60): 992 ± 260 vs. 177 ± 140 nmol day/L; p < 0.05, suggesting up to 6 times higher Vitamin D3 absorption of LMD when measured incrementally. During follow-up, participants in the LMD1000 treatment group showed approx. 7 times higher Vitamin D3 concentrations than the STD1000 group (iAUC(30-60): 680 ± 190 vs. 104 ± 91 nmol day/L; p < 0.05). However, no significant differences were found between the pharmacokinetics of the higher dosing groups STD2500 and LMD2500. No significant changes in serum 1,25(OH)2D concentrations or other biochemical safety markers were detected at day 60; no excess risks of hypercalcemia (i.e., total serum calcium > 2.63 mmol/L) or other adverse events were identified. LMD, a micellar delivery vehicle for microencapsulating Vitamin D3 (LipoMicel®), proved to be safe and only showed superior bioavailability when compared to standard Vitamin D at the lower dose of 1000 IU. This study has clinical trial registration: NCT05209425.

Photoprotective Steering of Previtamin D3 Photochemistry by Phenylalanine in Solution

Provitamin D3 is the biological precursor to naturally formed vitamin D3 in humans, and its conversion is initiated via photoexcitation by near ultraviolet light. Following an initial photolysis, the primary intermediate, known as previtamin D3, is prone to light-induced isomerization or recyclization, which creates byproducts that limit the desired final thermal conversion to vitamin D3. The branching of the photochemical reaction is highly wavelength-dependent, whereby excitation toward the blue edge of the provitamin D3 absorption spectrum tends to terminate the reaction with the most undesired tachysterol byproduct and the lowest previtamin D3 concentration. In this work, the influence of introducing the natural amino acid phenyalanine as an excitation energy donor to the photochemical reaction is investigated. We find that the incorporation of phenylalanine into provitamin D3 solution results in greater intermediate concentrations and prolonged lifetimes of the desired previtamin D3 while simultaneously reducing the final concentration of tachysterol when exposing the solution to wavelengths at the blue edge of the provitamin D3 spectrum. The results, coupled with quantum chemical analysis, suggest that phenylalanine indeed helps to funnel energy from shorter wavelengths more effectively into the provitamin D3 precursor, while simultaneously screening those wavelengths from direct excitation, which otherwise leads to enhanced concentrations of tachysterol byproduct at the expense of previtamin D3.

Sex-Specific Catabolic Metabolism Alterations in the Critically Ill following High Dose Vitamin D.

Pharmacological interventions are essential for the treatment and management of critical illness. Although women comprise a large proportion of the critically ill, sex-specific pharmacological properties are poorly described in critical care. The sex-specific effects of vitamin D3 treatment in the critically ill are not known. Therefore, we performed a metabolomics cohort study with 1215 plasma samples from 428 patients from the VITdAL-ICU trial to study sex-specific differences in the metabolic response to critical illness following high-dose oral vitamin D3 intervention. In women, despite the dose of vitamin D3 being higher, pharmacokinetics demonstrated a lower extent of vitamin D3 absorption compared to men. Metabolic response to high-dose oral vitamin D3 is sex-specific. Sex-stratified individual metabolite associations with elevations in 25(OH)D following intervention showed female-specific positive associations in long-chain acylcarnitines and male-specific positive associations in free fatty acids. In subjects who responded to vitamin D3 intervention, significant negative associations were observed in short-chain acylcarnitines and branched chain amino acid metabolites in women as compared to men. Acylcarnitines and branched chain amino acids are reflective of fatty acid B oxidation, and bioenergesis may represent notable metabolic signatures of the sex-specific response to vitamin D. Demonstrating sex-specific pharmacometabolomics differences following intervention is an important movement towards the understanding of personalized medicine.

Using food fortification to improve vitamin D bioaccessibility and intakes.

Vitamin D intakes and status are low in many countries due to seasonal UVB exposure variation and the fact that few foods are naturally vitamin D rich. Data modelling studies show that vitamin D intakes increase with food fortification, and countries with mandatory fortification policies have higher vitamin D intakes and status compared to countries without. While many foods can be vitamin D fortified, vitamin D bioavailability differs depending on fortification methods, food structure and composition. Randomised controlled trials (RCT) report that vitamin D2 bioavailability varies between foods, whereas vitamin D3 is bioavailable from many foods. In vitro studies suggest that altering the lipid composition of fortified foods increases vitamin D3 absorption. Olive oil increased vitamin D3 absorption during in vitro digestion compared to other dietary oils. Additionally, when vitamin D3 was incorporated into micelles formed from in vitro digestion of olive oil, more vitamin D3 was absorbed compared to other dietary oils. However, in a human postprandial study, a preformed vitamin D3 micelle dairy drink did not increase vitamin D3 absorption, and a vitamin D3 olive dairy drink increased vitamin D3 absorption in vitamin D insufficient participants only. Action is urgently needed to improve vitamin D intakes and status worldwide. Food fortification improves vitamin D intakes; however, fortification strategies unique to each country are needed. This review will synthesise the literature describing data modelling and intervention trials that assess the safety and efficacy of vitamin D fortification strategies, and those manipulating food composition to alter vitamin D bioavailability from fortified foods. Additionally, RCT examining the impact of vitamin D fortification strategies on vitamin D intakes and status over time are reviewed.

Line formation of He I D3 and He I 10 830 Å in a small-scale reconnection event

Context. Ellerman bombs (EBs) and UV bursts are small-scale reconnection events that occur in the region of the upper photosphere to the chromosphere. It has recently been discovered that these events can have emission signatures in the He I D3 and He I 10 830 Å lines, suggesting that their temperatures are higher than previously expected. Aims. We aim to explain the line formation of He I D3 and He I 10 830 Å in small-scale reconnection events. Methods. We used a simulated EB in a Bifrost-generated radiative magnetohydrodynamics snapshot. The resulting He I D3 and He I 10 830 Å line intensities were synthesized in 3D using the non-local thermal equilibrium (non-LTE) Multi3D code. The presence of coronal extreme UV (EUV) radiation was included self-consistently. We compared the synthetic helium spectra with observed raster scans of EBs in He I 10 830 Å and He I D3 obtained at the Swedish Solar Telescope with the TRI-Port Polarimetric Echelle-Littrow Spectrograph. Results. Emission in He I D3 and He I 10 830 Å is formed in a thin shell around the EB at a height of ∼0.8 Mm, while the He I D3 absorption is formed above the EB at ∼4 Mm. The height at which the emission is formed corresponds to the lower boundary of the EB, where the temperature increases rapidly from 6 × 103 K to 106 K. The synthetic line profiles at a heliocentric angle of μ = 0.27 are qualitatively similar to the observed profiles at the same μ-angle in dynamics, broadening, and line shape: emission in the wing and absorption in the line core. The opacity in He I D3 and He I 10 830 Å is generated through photoionization-recombination driven by EUV radiation that is locally generated in the EB at temperatures in the range of 2 × 104 − 2 × 106 K and electron densities between 1011 and 1013 cm−3. The synthetic emission signals are a result of coupling to local conditions in a thin shell around the EB, with temperatures between 7 × 103 and 104 K and electron densities ranging from ∼1012 to 1013 cm−3. This shows that both strong non-LTE and thermal processes play a role in the formation of He I D3 and He I 10 830 Å in the synthetic EB/UV burst that we studied. Conclusions. In conclusion, the synthetic He I D3 and He I 10 830 Å emission signatures are an indicator of temperatures of at least 2 × 104 K; in this case, as high as ∼106 K.

Personalise vitamin D3 using physiologically based pharmacokinetic modelling.

Plasma concentration of vitamin D3 metabolite 25‐hydroxyvitamin D3 (25(OH)D3) is variable among individuals. The objective of this study is to establish an accurate model for 25(OH)D3 pharmacokinetics (PKs) to support selection of a suitable dose regimen for an individual. We collated vitamin D3 and 25(OH)D3 plasma PK data from reported clinical trials and developed a physiologically‐based pharmacokinetic (PBPK) model to appropriately recapitulate training data. Model predictions were then qualified with 25(OH)D3 plasma PKs under vitamin D3 and 25(OH)D3 dose regimens distinct from training data. From data exploration, we observed the increase in plasma 25(OH)D3 after repeated dosing was negatively correlated with 25(OH)D3 baseline levels. Our final model included a first‐order vitamin D3 absorption, a first‐order vitamin D3 metabolism, and a nonlinear 25(OH)D3 elimination function. This structure explained the apparent paradox. Remarkably, the model accurately predicted plasma 25(OH)D3 following repeated dosing up to 1250 μg/d in the test set. It also made sensible predictions for large single vitamin D3 doses up to 50,000 μg in the test set. Model predicts 10 μg/d regimen may be ineffective for achieving sufficiency (plasma 25(OH)D3 ≥ 75 nmol/L) for a severely deficient individual (baseline 25(OH)D3 = 10 nmol/L), and it might take the same person over 200 days to reach sufficiency at 20 μg/d dose. We propose to personalize vitamin D3 supplementation protocol with this PBPK model. It would require measuring 25(OH)D3 baseline levels, which is not routinely performed under the current UK public health advice.Study Highlights WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? Vitamin D PK exhibits substantial inter‐individual variability. Different officially recommended daily doses are confusing.​ WHAT QUESTION DID THIS STUDY ADDRESS? Is the UK’s recommended 10 µg daily dose sufficient? Should everyone be given same dose?​ WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE? Our model accurately predicts plasma 25(OH)D under daily oral administration of vitamin D3. The 10 µg daily vitamin D3 dose is insufficient for prophylaxis (plasma 25(OH)D at 75 nmol/L).​ HOW MIGHT THIS CHANGE DRUG DISCOVERY, DEVELOPMENT, AND/OR THERAPEUTICS? Combining blood test to measure 25(OH)D baseline with this PBPK model will help inform dosage selection and select follow‐up date to improve effectiveness of Hypovitaminosis D treatment.

Milk protein complexation enhances post prandial vitamin D3 absorption in rats.

This study investigated the effect of complexation with whey and casein protein, respectively, on post prandial absorption of vitamin D3. For this purpose, Sprague-Dawley rats (n = 78) were administered 840 IU vitamin D3 dissolved in ethanol and either (i) complexed with whey protein isolate (protein : vitamin ration 2 : 1), (ii) complexed with caseinate (protein : vitamin ration 2 : 1), or (iii) provided in a water solution. Serum concentrations of vitamin D3, 25-hydroxyvitamin D3 and 24,25-dihydroxyvitamin D3 were measured before and 2, 3, 4, 5, 6, 7, 8, and 10 hours after administration of vitamin D3. Significant effects of complexation on serum concentrations of vitamin D3, 25-hydroxyvitamin D3 and 24,25-dihydroxyvitamin D3 were demonstrated. Complexation with whey protein isolate resulted in the fastest and highest absorption of vitamin D3 while an effect of complexation with caseinate was evident but more modest and non-significant. In conclusion, the study demonstrates that complexation with milk proteins is an efficient strategy to enhance bioaccessibility of vitamin D3.

Thermal enhancement of the green luminescence of Tb3+ ion generated by ground state thermal population

Abstract Here a strategy was proposed to realize the thermal enhancement of the green luminescence of Tb3+ ion through ground state thermal population. The 5D4-7F5 emission line of Tb3+ ion was observed under the excitation of a commonly used 405 nm laser diode for the first time, to the best of our knowledge. Its intensity was found to increase by ten times upon increasing the temperature from 343 to 783 K. Moreover, this change law was in good accordance with the Boltzmann distribution. It was confirmed that the thermal population of the 7F5 state at the expense of the depopulation of the 7F6 ground state, namely the ground state thermal equilibrium, should be responsible for this uncommon phenomenon. For comparison, the Xe lamp was also used to directly excite the 7F6 -5D3 absorption line of Tb3+ ion. In this case, the 5D4-7F5 emission line of Tb3+ ion was also observed. Different from the former case, this line decreased monotonously upon increasing the temperature over the experimental range. The reason for this change law was also discussed.

Chromospheric condensations and magnetic field in a C3.6-class flare studied via He I D3 spectro-polarimetry

Context. Magnetic reconnection during flares takes place in the corona, but a substantial part of flare energy is deposited in the chromosphere. However, high-resolution spectro-polarimetric chromospheric observations of flares are very rare. The most used observables are Ca II 8542 Å and He I 10830 Å. Aims. We aim to study the chromosphere during a C3.6 class flare via spectro-polarimetric observations of the He I D3 line. Methods. We present the first SST/CRISP spectro-polarimetric observations of He I D3. We analyzed the data using the inversion code HAZEL, and estimate the line-of-sight velocity and the magnetic field vector. Results. Strong He I D3 emission at the flare footpoints, as well as strong He I D3 absorption profiles tracing the flaring loops are observed during the flare. The He I D3 traveling emission kernels at the flare footpoints exhibit strong chromospheric condensations of up to ∼60 km s−1 at their leading edge. Our observations suggest that such condensations result in shocking the deep chromosphere, causing broad and modestly blueshifted He I D3 profiles indicating subsequent upflows. A strong and rather vertical magnetic field of up to ∼2500 G is measured in the flare footpoints, confirming that the He I D3 line is likely formed in the deep chromosphere at those locations. We provide chromospheric line-of-sight velocity and magnetic field maps obtained via He I D3 inversions. We propose a fan-spine configuration as the flare magnetic field topology. Conclusions. The He I D3 line is an excellent diagnostic to study the chromosphere during flares. The impact of strong condensations on the deep chromosphere has been observed. Detailed maps of the flare dynamics and the magnetic field are obtained.

A Randomised, Cross-Over Study to Estimate the Influence of Food on the 25-Hydroxyvitamin D₃ Serum Level after Vitamin D₃ Supplementation.

Vitamin D3 is known to be liposoluble and its release could be a factor limiting the rate of absorption. It was presumed that the presence of fat could favor absorption of vitamin D3. However, as bioavailability is related not only to the active molecules but also to the formulations and excipients used, the optimization of the pharmaceutical form of vitamin D3 is also important. The objective of this study was to evaluate if there is a food effect on absorption when a high dose of vitamin D3 is completely solubilized in an oily solution. In the present cross-over study, 88 subjects were randomized and received a single dose of 50,000 IU of vitamin D3 in fasting state or with a standardized high-fat breakfast. Assessment of serum concentrations of 25 hydroxyvitamin D3 (25(OH)D3) was performed three, five, seven, 14, 30 and 60 days after supplementation. In fed and fast conditions, the 25(OH)D3 serum concentrations were significantly higher than the baseline value three days after administration and remained significantly higher during the first month. No significant difference between fasting vs. fed conditions was observed. It is therefore concluded that the vitamin D3 absorption from an oily solution was not influenced by the presence or absence of a meal.

Prospective, Randomized, Double-Blind, Parallel-Group, Comparative Effectiveness Clinical Trial Comparing a Powder Vehicle Compound of Vitamin D With an Oil Vehicle Compound in Adults With Cystic Fibrosis.

There is little consensus on the most efficacious vehicle substance for vitamin D supplements. Fat malabsorption may impede the ability of patients with cystic fibrosis (CF) to absorb vitamin D in an oil vehicle. We hypothesized that vitamin D contained in a powder vehicle would be absorbed more efficiently than vitamin D contained in an oil vehicle in patients with CF. In this double-blind, randomized controlled trial, hospitalized adults with CF were given a one-time bolus dose of 100,000 IU of cholecalciferol (D3) in a powder-based or oil-based vehicle. Serum D3, 25-hydroxyvitamin D, and parathyroid hormone concentrations were analyzed at 0, 12, 24, and 48 hours posttreatment. The area under the curve for serum D3 and the 12-hour time point were also assessed as indicators of D3 absorption. This trial was completed by 15 patients with CF. The median (interquartile range) age, body mass index, and forced expiratory volume in 1 second were 23.7 (19.9-33.2) years, 19.9 (18.6-22.6) kg/m2, and 63% (37%-80%), respectively. The increase in serum D3 and the area under the curve was greater in the powder group ( P = .002 and P = .036, respectively). Serum D3 was higher at 12 hours in the powder group compared with the oil group ( P = .002), although levels were similar between groups by 48 hours. In adults with CF, cholecalciferol is more efficiently absorbed in a powder compared with an oil vehicle. Physicians should consider prescribing vitamin D in a powder vehicle in patients with CF to improve the absorption of vitamin D from supplements.

Variability of solar UV-B irradiance: in situ monitoring and model calculation of the vitamin D synthetic capacity of sunlight

The prediction of the biological effects of solar radiation on human health, in particular involving terrestrial level of solar ultraviolet (UV) radiation, requires the development of an adequate methodological strategy for remote sensing. To date, it is well understood that, in appropriate doses, UV radiation is beneficial for people, specifically due to the production of vitamin D3 in the skin from its precursor 7-dehydrocholesterol. But as far as excessive UV exposure causes acute and chronic health effects, in most cases biological activity of solar UV radiation is calculated by weighting solar UV spectra with International Commission on Illumination (CIE) erythemal action spectrum. Yet the beneficial vitamin D synthetic capacity of sunlight cannot be correctly estimated in this way because of the significant difference between the erythemic and vitamin D synthesis action spectra. With due regard to the essential role of vitamin D3 for human health, in this article we examine the possibility of simplified estimation in situ of provitamin D3 photoconversion into previtamin D3 from the UV absorption spectra of an in vitro model of vitamin D synthesis upon exposure to sunlight. A large-scale linear correlation (R = 0.99) was found on a clear summer day between the concentration of accumulated previtamin D3 and maximum absorbance decline in the initial provitamin D3 absorption spectrum. However, long-term observations showed a poorer (R = 0.77) correlation, and a source of ambiguity of such indirect estimation of previtamin D3 concentration is discussed in detail. In addition, we propose a reliable algorithm for the direct calculation of previtamin D3 accumulation using solar UV spectra as input data to the reaction model of previtamin D photosynthesis and demonstrate the critical dependence of previtamin D3 accumulation on stratospheric ozone, season, latitude and cloudiness. The comparison of experimental and simulation data conforms to recent findings on Europe's darker atmosphere in the UV-B and implicates the practical certainty of the presented algorithm for the calculation of the vitamin D synthetic capacity from the remotely sensed solar spectra.

Chromospheric Activity in Dwarf and Evolved Late A‐ and Early F‐Type Stars

Chromospheric activity in late A- and early F-type field stars of luminosity classes III through V has been investigated using the helium D3 absorption feature. This feature shows a detection boundary near b - y = 0.19 (B - V = 0.29). This color index corresponds to a dividing line in activity levels as determined from the C II λ1335 chromospheric emission line. On the red side of this boundary, stars exhibit strong or moderately strong C II emission and strong or moderately strong D3 absorption. However, on the blue side, D3 absorption does not conclusively appear, while several stars show moderately strong C II emission. The data suggest that D3 is sensitive to the boundary at B - V = 0.29, but they also suggest limitations in the use of D3 as an activity indicator in the late A-type stars. To within observational errors, the D3 boundary appears at the same color index for the full range of luminosity classes explored, in contradiction with some acoustic energy calculations. In addition, the strength of D3 absorption shows no significant trend with luminosity class or the Stromgren δc1 index, with a wide range of activity levels at a given luminosity or surface gravity.

Vitamin D Absorption, Plasma Concentration and Urinary Excretion of 25-Hydroxyvitamin D in Nephrotic Syndrome

Nephrotic syndrome (NS) is commonly associated with vitamin D deficiency. Urinary losses of the protein-bound intermediary metabolite of this vitamin is thought to contribute to the deficiency state. The role of possible changes, if any, of vitamin D absorption has not been investigated previously in NS. We determined intestinal absorption of vitamin D3 as well as plasma concentration and urinary excretion of 25-hydroxyvitamin D3 in rats with puromycin aminonucleoside-induced NS. In vivo recirculating perfusion technique was employed at 100 and 600 nM perfusate concentrations. The results were compared with those obtained in animals receiving placebo injections provided with either free access to food (normal controls) or those pair-fed with their NS counterparts (pair-fed group). The NS group showed heavy proteinuria and hypoalbuminemia. In addition, the NS group exhibited marked urinary losses and significantly reduced plasma concentration of 25-hydroxyvitamin D. The rate of vitamin D3 absorption (given as nmol/100 cm/min) at 100 nM perfusate concentration in the NS group (0.161 +/- 0.029) was not significantly different from those obtained in the pair-fed group (0.202 +/- 0.058) and the normal control group (0.143 +/- 0.053). Likewise, no significant difference was found in the rats of vitamin D absorption at 600 nM concentration among the NS (1.073 +/- 0.383), pair-fed (0.955 +/- 0.229), and normal control (0.756 +/- 0.314) groups. Accordingly, intestinal absorption of vitamin D appears to be unaffected by the presence of experimental NS and as such the associated vitamin D deficiency can be managed by enteral supplementation.

Bone Disease in Chronic Childhood Cholestasis II. Better Absorption of 25-OH Vitamin D than Vitamin D in Extrahepatic Biliary Atresia

Infants with extrahepatic biliary atresia (EHBA) commonly develop rickets in infancy, whereas long-term survivors with EHBA commonly develop osteopenia with increasing age. We evaluated baseline vitamin D (D2 and D3), 25-OH vitamin D2 and D3, 1,25(OH)2 vitamin D, bone mineral content, and vitamin D2 and 25-OH vitamin D3 absorption in six infants and children (age 4-22 mo) with EHBA whose portoenterostomy failed to produce bile flow (group 1) and five infants and children (age 10/12 to 8-4/12 y) with EHBA whose portoenterostomy repair led to good postoperative bile flow (group 2). Baseline serum vitamin D2 and D3 were undetectable in all subjects in group 1 despite supplements of 2500-5000 IU/day, whereas all group 2 subjects given supplements (doses 400-5000 IU/d) had measurable levels. Baseline serum 25-OH vitamin D was less than 15 ng/mL in five of six (three with rickets) in group 1, whereas only one in group 2 had concentrations less than 15 ng/mL. A significantly blunted rise of vitamin D2 above baseline and reduced area under the absorption curve after 1000 IU/kg vitamin D2 were found in group 1 patients compared to group 2 (both p less than 0.01), and five pediatric controls (both p less than 0.01). The peak change and area under the absorption curve for serum 25-OH vitamin D3 from baseline after 10 micrograms/kg 25-OH vitamin D3 were significantly reduced for group 1 (both at least p less than 0.05) and group 2 compared to controls (both p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The vertical structure of arch filament systems in solar emerging flux regions

The paper studies the vertical velocity of arch filaments in emerging flux regions by measuring their proper motion near the limb in H-alpha filtergrams and their radial velocity near the disk center in H-alpha spectrograms. Both show that arch filaments rise at a velocity between 10 and 15 km/s. The possible mechanisms producing this high velocity are discussed. None of them is satifactory, but it appears that the unloading of the arches by outflow must play a role. From the strength of H-alpha emission and D3 absorption, the temperature of arch filaments is estimated at 6000-15,000 K and the density at 10 to the 11th-12th/cu cm.

Effects of chlorothiazide on 1,25-dihydroxyvitamin D3, parathyroid hormone, and intestinal calcium absorption in the rat.

Previous studies have shown that thiazide diuretic agents reverse secondary hyperparathyroidism and reduce circulating 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and intestinal calcium absorption rates in patients with idiopathic hypercalciuria of the renal-leak variety. We have investigated whether thiazides can reverse the secondary increase in serum parathyroid hormone (PTH) and 1,25(OH)2D3 levels or intestinal calcium absorption induced by feeding rats a diet low in calcium (LCD, 0.02% calcium) but adequate in phosphorus and vitamin D. We found that LCD increased circulating immunoreactive PTH [chow vs. LCD, 0.52 +/- 0.06 vs. 1.06 +2- 0.1 (SE) ng/ml, P less than 0.001], 1,25(OH)2D3 (chow vs. LCD, 101 +/- 15 vs. 325 +/- 38 pg/ml, P less than 0.001), calcium uptake by everted gut sacs from duodenum, ileum, and descending colon, and net calcium absorption by descending colon studied in Ussing chambers in vitro. Chlorothiazide (CTZ) prevented the increase in PTH during LCD (chow + CTZ vs. LCD + CTZ, 0.69 +/- 0.07 vs. 0.73 +/- 0.06, NS) but not the increase in 1,25(OH)2D3 (chow + CTZ vs. LCD + CTZ, 88 +/- 10 vs. 277 +/- 31, P less than 0.002) or intestinal calcium transport. The drug caused no change in serum 1,25(OH)2D3 or intestinal calcium absorption in rats fed normal chow. In rats given exogenous 1,25(OH)2D3 to stimulate intestinal calcium absorption, CTZ reduced urine calcium excretion greatly but did not alter intestinal calcium absorption.

Hormonal regulation of phosphate transport in the differentiating chick small intestine.

The intestine is the prime target organ of vitamin D where the sterol, by virtue of its active metabolite 1,25-dihydroxy-vitamin D3, promotes calcium and inorganic phosphate (Pi) absorption (for review see Wasserman, 1981).

Intestinal absorption of vitamin D sterols: Differential absorption into lymph and portal blood in the rat

Radiolabeled vitamin D sterols (5 nmol) were administered intraduodenally (in fat emulsion) into conscious rats with mesenteric lymph fistula and portal vein cannulation. The rats were kept for 4 h in restraining cages, and lymph and blood samples were collected at half-hour intervals. Vitamin D3 was absorbed mostly into the mesenteric lymph (6.5% of administered dose vs. < 1%/4 h into the portal blood). 1,25-Dihydroxyvitamin D3 was absorbed mainly into the portal blood (~7%/4 h and only 1.6%/4 h into the mesenteric lymph). 25-Hydroxyvitamin D3 had a similar rate of absorption into the lymph and portal vein (5%/4h and 7%/4 h, respectively). Vitamin D3 absorption started after 2 h, whereas the more hydroxylated metabolites were more rapidly absorbed and appeared in the lymph and portal blood within the first half-hour. In the lymph the vitamin D sterols were transported mainly on chylomicrons and lipoproteins (> 50%), whereas in blood less than 20% were associated with plasma lipoproteins. In rats where lymph was not diverted, the increment of lymphatic contribution was observed in plasma levels for all vitamin D sterols. The absorbed sterols in lymph and blood were mostly unchanged with the exception of 25-hydroxyvitamin D3, about one-third of which underwent esterification during absorption into the mesenteric lymph. We conclude that 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3, in particular, are absorbed directly into portal blood independent of fat absorption, and thus may be prescribed as oral supplements in most patients with fat malabsorption.