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Biomedical subjects

S Edelstein

Publications and source records attributed to S Edelstein.

At least 91 records · Page 5Linked to original sources
PubMed1978

Synthesis of 1 alpha-hydroxy[7-3H]cholecalciferol and its metabolism in the chick.

1. 1 alpha-Hydroxy[7-3H]cholecalciferol (specific radioactivity of 2-Ci/mmol) was synthesized, and its metabolism in chicks studied. 2. 1 alpha-Hydroxy[7-3H]cholecalciferol was metabolized very rapidly in the chick to 1 alpha,25-dihydroxy[7-3H]cholecalciferol and to a metabolite less polar than 1 alpha-hydroxycholecalciferol. Intestine exhibited highest accumulation of 1 alpha-25-dihydroxy[7-3H]cholecalciferol, and liver exhibited highest accumulation of the non-polar metabolite. 3. Tissue uptake of 1 alpha-hydroxy[7-3H]cholecalciferol and its metabolites in chicks that were dosed continuously for 16 days with 1 alpha-hydroxy[7-3H]cholecalciferol did not exceed by very much that observed in tissues obtained from chicks that were dosed with a single injection of 1 alpha-hydroxy[7-3H]cholecalciferol 24 h before killing, except for liver and kidney. 4. Lowest accumulation of metabolites was noted in muscle and bone, and for the latter, highest uptake of 1 alpha,25-dihydroxy[7-3H]cholecalciferol was noted in the epiphysial periosteum and the metaphysis. 5. Formation of 1 alpha,24,25-trihydroxy[7-3H]cholecalciferol was not observed in the chicks that were dosed continuously with 1 alpha-hydroxy[7-3H]cholecalciferol, despite the fact that plasma calcium and phosphorus were normal and despite the presence of renal 24-hydroxylase activity. 6. The vitamin D status of the chicks did not appear to affect the metabolic profile of the administered 1 alpha-hydroxy[7-3H]cholecalciferol.

Animals↗
PubMed1978

The parotid gland: a new target organ for vitamin D action.

Radioactively labelled cholecalciferol was administered continuously to rats which were fed a vitamin D-deficient diet. It has been possible to show that all the metabolites of the cholecalciferol which normally occur in known target tissues of vitamin D are present in the parotid gland, and the pattern resembled that obtained for the kidney, a known target tissue for vitamin D action. The accumulation of cholecalciferol metabolites in the parotid gland was shown to be functional, as a calcium-binding protein was found to be present in the gland, possessing similar properties to the renal vitamin D-dependent calcium-binding protein.

Animals↗
PubMed1978

Vitamin D metabolism and expression in rats fed on low-calcium and low-phosphorus diets.

1. Cholecalciferol, radioactively labelled with both (14)C and (3)H, was administered weekly for 7 weeks to rats that had been depleted of vitamin D for 4 weeks before repletion with the radioactive vitamin. This permitted measurement of the steady-state effect on vitamin D metabolism of low-calcium and low-phosphorus regimens, as compared with a normal mineral intake. These dietary manoeuvres were carried out during the last 3 weeks of repletion. Cholecalciferol, 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol were determined in plasma, intestine, kidney and bone. Ca(2+)-binding-protein content was measured in intestine and kidneys of comparable animals. 2. In rats on the low-calcium diets, 1,25-dihydroxycholecalciferol concentration was elevated in plasma, bone, kidney and intestine, and intestinal Ca(2+)-binding protein was increased to over twice the concentration found in the control animals. 3. The low-phosphorus regimens led to a decrease in plasma phosphate and 1,25-dihydroxycholecalciferol in all tissues studied, for the latter to the point where it was undetectable in plasma and bone. Intestinal and renal concentrations of Ca(2+)-binding protein were unchanged in the low-phosphate-intake group and decreased in the very-low-phosphate-intake group. 4. It is concluded that in the rat, unlike in the chick, hypophosphataemia is not associated with a stimulation of the production of 1,25-dihydroxycholecalciferol or its expression in the synthesis of Ca(2+)-binding protein. Therefore the plasma phosphate concentration does not appear to be directly involved in the regulation of the functional metabolism of vitamin D.

Animals↗
PubMed1978

Involvement of cholecalciferol metabolism in birds in the adaptation of calcium absorption to the needs during reproduction.

1. The metabolism of calcium and cholecalciferol in quail (Coturnix coturnix japonica) and chicken (Gallus domesticus) during maturation was correlated to gonadal activity and plasma oestrogen levels. 2. Birds with undeveloped ovaries (immature), developed ovaries but not laying (mature), and after laying 3-8 eggs (laying), were used in the first series. 3. Birds in which egg production had been arrested by Nicarbazin, were used in the second series. 4. Plasma 17 beta-oestradiol and calcium were elevated in the mature bird, with no further change in the laying bird. Kidney 25-hydroxycholecalciferol-1-hydroxylase and intestinal calcium-binding protein increased slightly in the mature bird, whereas they were grossly elevated in the laying bird. 5. Calcium and phosphorus absorption were markedly elevated in the laying bird. 6. No changes were noted in plasma 25-hydroxycholecalciferol, at any stage of maturation. 7. During the arrest of egg production by Nicarbazin, 17 beta-oestradiol level, calcium concentration of plasma, and medullary bone were maintained. Kidney 25-hydroxy-cholecalciferol-1-hydroxylase, intestinal calcium-binding protein and absorption of calcium were strikingly reduced. 8. The results suggest that changes in calcium absorption and cholecalciferol metabolism during maturation in birds are not directly affected by gonadal hormones; they appear to represent an adaptation to the increased calcium needs due to medullary bone formation and, more importantly, to the large losses of calcium imposed by shell formation.

Adaptation, Physiological↗
PubMed1977

Decreased oral colonization of Streptococcus mutans during aging of Sprague-Dawley rats.

The colonization by streptomycin-resistant Streptococcus mutans strains of the teeth of conventional and ex-germfree Sprague-Dawley rats of various ages fed either a high-sucrose or a high-glucose diet was studied. Bacterial colonization occurred with increasingly greater difficulty as the rats became older. This was observed in studies of the implantation of the test organism after oral inoculation with different cell numbers as well as its transmission between infected and uninfected rats. With rat fed sucrose diet, the effect of age could not be demonstrated until they were age 3 months or older; the results from rats fed a glucose diet suggest that changes may already have occurred early after weaning. Changes in susceptibility to colonization during aging manifested themselves as a decrease in the proportions of rats which became infected as well as lower population levels in infected rats. The possible mechanism(s) involved as well as the possible significance of the findings was discussed.

Aging↗
PubMed1977

Relationship between the populations of Streptococcus mutans in the mouth and feces of conventional Sprague-Dawley rats.

The relationship between oral and fecal S mutans populations has been studied in rats fed high sucrose or glucose diet. All molar teeth were extracted either prior to or following oral challenge with strain 6715. In certain instances this procedure was supplemented with amputation of the incisors and disinfection of the remaining incisor surface area with iodine solution. The results suggest that in rats the colonization of S mutans on the teeth is required for its presence in the intestinal canal as well as the mouth. The significance of the observations has been discussed.

Animals↗
PubMed1976

Some characteristics of new tissue-binding proteins for metabolites of vitamin D other than 1,25-dihydroxyvitamin D.

Protein(s) have been found in a wide range of tissues which have a high affinity for 25-hydroxycholecalciferol. Of the tissues examined only erythrocytes do not have this protein. The properties of the protein have been examined and it has been found that the association constatns range from 2 - 10(9) to 5 - 10(9) M-1 and the sedimentation constants between 5.0 and 6.0 S. It was not possible to distinguish the proteins from the different tissues by their S values, mobility on gel electrophoresis or behaviour on ion-exchange chromatography. These techniques were all used, however, to show that the tissue 25-hydroxycholecalciferol binding protein is distinct from the main plasma binding protein for this steroid and from the intestinal 1,25-dihydroxycholecalciferol-binding protein. A protein has been in the plasma of rachitic animals but not of normals, which is apparently indistinguishable from this new tissue 25-hydroxycholecalciferol-binding protein. The steroid specificity of this new binding protein has been shown to be dependent upon a C-25 hydroxyl group, and an intact conjugated double bond system. Possible functions for this protein have been briefly discussed.

Animals↗
PubMed1976

Maternal-perinatal interrelationships of vitamin D metabolism in rats.

In pregnant rats it has been possible to show that the distribution of cholecalciferol metabolites in their fetuses reflects the distribution of these metabolites in the blood. In these experiments, pregnant rats were maintained on a vitamin D deficient diet but were supplemented with radiolabelled cholecalciferol. The metabolites found were 25-hydroxycholecalciferol and 24,25-dihydroxycholecalciferol and, to a lesser extent, cholecalciferol. 1,25-Dihydroxycholecalciferol was not detected in fetal tissues, despite the ability of fetal kidney homogenates to hydroxylate 25-hydroxycholecalciferol in C-1. Kidney homogenates of newborn pups were found to possess marked activity of 25-hydroxycholecalciferol-24-hydroxylase, which was retained even in hypocalcemic pups born to pregnant rats that were fed a low-calcium diet. Injection of radiolabeled cholecalciferol to newborn pups resulted in the formation of 25-hydroxycholecalciferol and 24,25-dihydroxycholecalciferol. 1,25-Dihydroxycholecalciferol was not detected. Tissues thought of as target organs for vitamin D (in pregnant rats), namely, intestine, kidney and bone, were found to contain none or very little 1,25-dihydroxycholecalciferol. Mammary glands obtained from lactating rats were found to contain mainly the unchanged vitamin.

Animals↗
PubMed1975

Response of renal calcium-binding protein. Independence of kidney vitamin D hydroxylation.

Dietary calcium and dietary phosphorus restriction were studied in chicks fed either cholecalciferol or 1alpha-hydroxycholecalciferol. Intestinal calcium absorption and calcium-binding protein of 1alpha-hydroxycholecalciferol-treated chicks remained unchanged under dietary calcium restriction, but increased under dietary phosphorus restriction. Kidney calcium-binding protein was not altered by dietary caclium restriction in chidks treated with either cholecalciferol or 1alpha-hydroxycholecalciferol, but increased under dietary phosphorus restriction independent of the vitamin D source. In contrast to the intestine, calcium-binding activity of the kidney was found to be poorly related to the calcium-binding protein concentration. It is suggested that kidney calcium-binding protein is regulated by a mechanism different from that of intestinal calcium-binding protein, and that its concentration in renal tissue is related to renal caclium excretion or plasma calcium level.

Animals↗