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Biomedical subjects

M F Holick

Publications and source records attributed to M F Holick.

At least 163 records · Page 9Linked to original sources
PubMed1985

Detection and developmental changes of the 1,25-(OH)2-D3 receptor concentration in mouse skin and intestine.

We investigated [3H]1,25-dihydroxyvitamin D3-specific binding activity in fetal, neonatal, and adult mouse skin to determine (a) during which stage in development the skin develops the capacity to respond to this hormone and (b) whether the hormone binding activity changed during development and maturation. A macromolecule with properties similar to those of the chick intestinal 1,25-dihydroxyvitamin D3 receptor was detected in the skin and intestine of mouse pups at 17 days of fetal life. 1,25-Dihydroxyvitamin D3-specific binding activity from both tissues sedimented on linear sucrose gradients at 3.5-3.7S and eluted from DNA cellulose at 0.22 M KCl. At earlier stages of fetal life (12-14 days) receptor-like activity was detected in cytosols prepared from whole-mouse fetuses. 1,25-Dihydroxyvitamin D3-specific binding activity was quantitated in the skin and intestine throughout development using a chromatin binding assay. Scatchard analysis of saturation binding data showed that the concentration of binding activity in skin increased rapidly after birth and reached a maximum when the mice were 10-19 days old. By contrast, the binding activity that was detected in the fetal and neonatal whole intestine remained low until the mice were weaned. The affinity (Kd) of the binding activity was similar in skin and intestine at all ages studied. It is concluded that 1,25-dihydroxyvitamin D3-specific binding activity appears in both skin and intestine of the mouse prior to birth and increases in these two tissues during different stages in development.

Animals↗
PubMed1985

Aging decreases the capacity of human skin to produce vitamin D3.

An evaluation of surgically obtained skin (age range, 8-92 yr) revealed that there is an age-dependent decrease in the epidermal concentrations of provitamin D3 (7-dehydrocholesterol). To ascertain that aging indeed decreased the capacity of human skin to produce vitamin D3, some of the skin samples were exposed to ultraviolet radiation and the content of previtamin D3 was determined in the epidermis and dermis. The epidermis in the young and older subjects was the major site for the formation of previtamin D3, accounting for greater than 80% of the total previtamin D3 that was produced in the skin. A comparison of the amount of previtamin D3 produced in the skin from the 8- and 18-yr-old subjects with the amount produced in the skin from the 77- and 82-yr-old subjects revealed that aging can decrease by greater than twofold the capacity of the skin to produce previtamin D3. Recognition of this difference may be extremely important for the elderly, who infrequently expose a small area of skin to sunlight and who depend on this exposure for their vitamin D nutritional needs.

Adolescent↗
PubMed1985

Isolation and structural identification of 1,25-dihydroxyvitamin D3 produced by cultured alveolar macrophages in sarcoidosis.

Hypercalcemia and hypercalciuria in sarcoidosis are thought to result from the endogenous overproduction of an active vitamin D metabolite. We employed primary cultures of pulmonary alveolar macrophages from two patients with biopsy-proven pulmonary sarcoidosis and a recent or current clinical abnormality in calcium metabolism to synthesize in vitro a 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]-like metabolite from 25-hydroxyvitamin D3 (25OHD3). The macrophage metabolite cochromatographed with [3H]1,25-(OH)2D3 on normal phase and reverse phase high performance liquid chromatography and was bound with high affinity by the chick intestinal receptor for 1,25-(OH)2D3. On UV spectroscopy, the metabolite possessed the carbon-5,7,10 (19) cis-triene chromophore characteristic of a vitamin D sterol. Electron impact mass spectrometry of trimethylsilyl ether derivatives of the metabolite revealed a mass fragmentation pattern similar to that of the trimethylsilyl ether derivative of authentic 1,25-(OH)2D3. The incubation of cultured macrophages from two patients with idiopathic pulmonary fibrosis and two with scleroderma with [3H]25OHD3 did not result in production of a metabolite with the chromatographic identity of 1,25-(OH)2D3. These data indicate that the metabolite of 25OHD3 synthesized by sarcoid macrophages in vitro is 1,25-(OH)2D3 and that the macrophage is a synthetic source of the sterol metabolite in sarcoidosis.

Adult↗
PubMed1984

1 alpha,25-dihydroxyvitamin D3 induces maturation of the human monocyte cell line U937, and, in association with a factor from human T lymphocytes, augments production of the monokine, mononuclear cell factor.

The monocyte factor, interleukin 1, or other factors homologous with interleukin 1, modulates functions of a variety of cells, including T and B lymphocytes, synovial cells, and chondrocytes. We have reported that a human monocyte cell line, U937, produces interleukin 1 when incubated with a soluble factor from lectin-stimulated T lymphocytes. We have also shown that U937 cells have a specific cytosolic receptor for 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25[OH]2D3). We now report that 1 alpha,25(OH)2D3(10(-11)-10(-10) M) induces maturational changes in the U937 cells similar to those produced by conditioned medium from lectin-stimulated T lymphocytes (increase in Fc receptors and OKM1 binding and decrease in proliferation), but does not induce monokine production as measured by mononuclear cell factor activity. 1 alpha,25(OH)2D3 is 200-300-fold more effective than 25-hydroxyvitamin D3, which is consistent with the known biological potency of these vitamin D3 metabolites. 1 alpha,25(OH)2D3 and the lymphokine together markedly augment maturational effects and, in addition, augment monokine production. The specificity of the interaction is further demonstrated by the lack of augmentation of monokine production with 1 beta,25-dihydroxyvitamin D3 in the presence of lymphokine. These interactions of a classical hormone and the hormonelike product(s) of the immune system with U937 cells serve as a model for human monocyte/macrophage differentiation and suggest a role for these interactions in some aspects of inflammation.

Antigens, Surface↗
PubMed1983

A parathyroid hormone inhibitor in vivo: design and biological evaluation of a hormone analog.

A synthetic analog of bovine parathyroid hormone (bPTH), [tyrosine-34] bPTH-(7-34)NH2, was found to inhibit parathyroid hormone action in vivo. When the analog and parathyroid hormone were infused simultaneously to rats at a molar ratio of 200 to 1, the analog inhibited the excretion of urinary phosphate and adenosine 3',5'-monophosphate. When infused alone at the same dose rate, the analog was devoid of agonist activity. The compound was prepared by following design principles developed for inhibitors of parathyroid hormone, and is believed to be the first antagonist of parathyroid hormone that is effective in vivo.

Amino Acid Sequence↗
PubMed1983

A simple method for generation of antibodies with specificity for 1,25-dihydroxyergocalciferol and 1,25-dihydroxycholecalciferol.

A simple method for production of antisera with high affinity and selectivity for 1 alpha, 25-dihydroxyergocalciferol and 1 alpha, 25-dihydroxychole-calciferol is described. 1 alpha-Hydroxy-25,26,27-trisnorcholecalciferol-24-oic acid was coupled directly to bovine serum albumin. Rabbits immunized with this conjugate rapidly produced antibodies that bound 3H-1 alpha,-25-dihydroxycholecalciferol with high affinity and demonstrated nearly equal reactivity with 1 alpha, 25-dihydroxyergocalciferol and poor reactivity with 25-hydroxycholecalciferol; 24,25-dihydroxycholecalciferol; 25,26-dihydroxycholecalciferol; and 1 beta,25-dihydroxycholecalciferol. The use of one of these antisera has led to the development of a specific assay for 1 alpha,25-dihydroxyergocalciferol and 1 alpha,25-dihydroxycholecalciferol in human serum.

Animals↗
PubMed1983

A multiresponse parathyroid hormone assay: an inhibitor has agonist properties in vivo.

Vitamin D-deficient rats subjected to thyroparathyroidectomy (TPTX) were used to evaluate in vivo the biological properties of native bovine parathyroid hormone (bPTH) and chemically synthesized fragments and analogues of the hormone on several parameters of hormone action: calcium and phosphorus fluxes, generation of cyclic adenosine 3',5'-monophosphate (cAMP), and the metabolism of 25-hydroxyvitamin D3 [25(OH)D3]. Vitamin D-deficient rats, after TPTX or sham operation, were intravenously infused with a nutrient containing 7.5 mM CaCl2 for 30 h. During the last 7 h, PTH or one of its analogues was infused intravenously at rates between 0.04 and 20 nmol/h. One hour after the start of the peptide infusion, tritiated 25(OH)D3 was injected. Urine was collected hourly for phosphate and cAMP determinations and, at the end of the experiment, blood was obtained to determine the relative accumulation of tritiated 1,25-dihydroxyvitamin D3 ([3H]1,25(OH)2D3). Infusion of bPTH-(1--84), bPTH-(1--34), human (h)PTH-(1--34), or [Nle8, Nle18, Tyr34]bPTH-(1--34) amide was accompanied by a comparable dose-dependent decrease in plasma phosphate and a dose-dependent increase in plasma calcium and [3H]-1,25(OH)2D3, and urinary excretion of phosphate and cAMP. An evaluation of [Nle8, Nle18, Tyr34]bPTH-(3--34) amide, a potent inhibitor of PTH action in vitro in the renal adenylate cyclase assay, revealed that the analogue possessed weak agonist properties in vivo. The analogue increased excretion of both cAMP and phosphate in the urine, decreased plasma phosphate levels, and increased the accumulation of [3H]-1,25(OH)2D3 in the plasma. This multiparameter model system should aid in the elucidation of the in vivo biological effects of PTH and its analogues.

Animals↗
PubMed1983

Specific high-affinity receptors for 1,25-dihydroxyvitamin D3 in human peripheral blood mononuclear cells: presence in monocytes and induction in T lymphocytes following activation.

Human peripheral blood monocytes have high affinity binding sites for 1,25-(OH)2D3 (Kd 0.14 nM, sedimentation coefficient 3.7S). Resting human peripheral blood T lymphocytes, however, do not have a demonstrable 1,25-(OH)2D3 receptor. After activation with phytohemagglutinin the T cells exhibit the receptor within 24 h, and this expression is blocked by cycloheximide. The receptor in activated T lymphocytes has a sedimentation coefficient of 3.7S and a high affinity (Kd 0.10 nM) for the ligand.

Calcitriol↗
PubMed1982

Measurement of circulating vitamin D in man.

An assay for vitamin D consisting of high-pressure liquid chromatography (HPLC) and ultraviolet (UV) absorbance detection has been developed and used to measure circulating vitamin D concentrations in human subjects during summer and winter and after deliberate exposure to ultraviolet radiation. Extracts of 2-4 ml of serum were initially fractionated on silica Sep-Pak cartridges followed by reverse-phase HPLC and finally quantitated by UV-absorbance during straight-phase HPLC. Using these methods, we determined the normal range for circulating vitamin D in Boston subjects to be less than 0.5 ng/ml to 25 ng/ml (n = 30); subjects sampled during summer months had higher concentrations of vitamin D than those sampled during winter months. In subjects exposed to a single quantitative dose of ultraviolet radiation (UVR), large transient increases in circulating vitamin D3 were observed. Concentrations rose 30-50 fold over the first days after exposure before returning to basal levels by one week.

Adult↗
PubMed1982

Spectral character of sunlight modulates photosynthesis of previtamin D3 and its photoisomers in human skin.

The photosynthesis of previtamin D3 from 7-dehydrocholesterol in human skin was determined after exposure to narrow-band radiation or simulated solar radiation. The optimum wavelengths for the production of previtamin D3 were determined to be between 295 and 300 nanometers. When human skin was exposed to 295-nanometer radiation, up to 65 percent of the original 7-dehydrocholesterol content was converted to previtamin D3. In comparison, when adjacent skin was exposed to simulated solar radiation, the maximum formation of previtamin D3 was about 20 percent. Major differences in the formation of lumisterol3, and tachysterol3 from previtamin D3 were also observed. It is concluded that the spectral character of natural sunlight has a profound effect on the photochemistry of 7-dehydrocholesterol in human skin.

Cholecalciferol↗
PubMed1982

Increased skin pigment reduces the capacity of skin to synthesise vitamin D3.

To determine the effect of increased skin pigment on the cutaneous production of vitamin D3, circulating vitamin D concentrations were determined in two lightly pigmented Caucasian and three heavily pigmented Negro volunteers after exposure to a single standard dose of ultraviolet radiation (UVR). Exposure of Caucasian subjects to 1 minimal erythemal dose of UVR greatly increased serum vitamin-D concentrations by up to 60-fold 24-48 h after exposure, whereas this dose did not significantly change serum vitamin-D concentrations in Negro subjects. Re-exposure of one Negro subject to a dose of UVR six times larger than the standard dose increased circulating vitamin D to concentrations similar to those recorded in Caucasian subjects after exposure to the lower dose. These results indicate that increased skin pigment can greatly reduce the UVR-mediated synthesis of vitamin D.

Black People↗