Cell surface vitamin D-binding protein (GC-globulin) is acquired from plasma.

Vitamin D-binding protein (DBP) is an abundant plasma protein. The observation of immunodetectable, cell-associated DBP on peripheral blood mononuclear cells and placental cytotrophoblasts had presented the question of the origin, function, and precise subcellular localization of cell-associated DBP. Using anti-human DBP F(ab')2 with fluorescence-activated cytometric analysis and immunogold electron microscopy, we detected DBP on the plasmalemma of U937 cells, a monoblastic, histiocytic cell line grown in media supplemented with fetal calf serum (FCS). DBP was then removed from FCS by actin affinity chromatography followed by anti-DBP immunoaffinity chromatography. U937 cells in this DBP-free medium exhibited nearly identical growth rates to cells grown in medium containing native FCS. However, in contrast to cells grown with native FCS, those grown for seven to eight generations with DBP-free FCS exhibited less cell-surface DBP as quantified by fluorescence-activated cytometric analysis (73% decrease) and immunoelectron microscopy (88% decrease). DBP mRNA could not be detected in U937 cells, placental tissues, freshly prepared resting and stimulated B and T lymphocytes, or lymphocyte-derived cell lines by Northern analysis. In addition, using the sensitive reverse transcriptase/polymerase chain reaction assay no DBP fragments were detectable in U937 cells. We conclude that U937 cell-associated DBP is exogenously derived from plasma and is located on the plasmalemma. Based upon this conclusion, we postulate that specific binding sites for DBP may exist on the plasma membranes of certain cell types.

The metabolism of ceramic and non-ceramic forms of uranium dioxide after deposition in the rat lung.

Ceramic and non-ceramic forms of uranium dioxide, produced industrially, were administered to rats either by inhalation or as an aqueous suspension which was injected directly into the pulmonary region of the lungs. The results showed that: 1 both materials should be assigned to inhalation class Y as defined by the International Commission on Radiological Protection; 2 whilst the translocation of uranium to the blood for the non-ceramic UO2 was about twice that obtained for the ceramic form, the two dioxides were unlikely to be differentiated on the basis of their lung retention kinetics; 3 the distribution of uranium amongst body tissues and the relationship between systemic content and cumulative urinary excretion indicated that it was transported in the hexavalent form; 4 in addition to air sampling procedures, lung radioactivity counting measurements could be used to advantage for assessing occupational exposures; 5 the exposure limits should be based on radiation dose rather than chemical toxicity.

Metabolism of uranium in the rat after inhalation of two industrial forms of ore concentrate: the implications for occupational exposure.

Aerosols produced from two commercially available ore concentrates in which the uranium was present essentially in the one as ammonium diuranate (ADU) and in the other as uranium octoxide (U3O8) were administered to rats. The results show that: 1 uranium in the ADU bearing material was cleared rapidly from the lungs, mainly to the blood, such that the retention kinetics were similar to those for a class D (highly transportable) compound as defined by ICRP; 2 uranium in the U3O8 bearing material was removed from the lungs principally by mechanical processes, the retention kinetics in this case being similar to those defined for a class Y (poorly transportable) compound; 3 for both materials the distribution of uranium amongst body tissues and the fraction of the systemic content excreted in urine were similar to those obtained after the injection of soluble hexavalent compounds; 4 for workers potentially exposed to both these materials, urine monitoring and lung radioactivity counting measurements should be used in addition to air sampling procedures for assessing the intake of uranium. 5 intakes of the ADU bearing material should be restricted to those permitted for short-term exposures on the basis of chemical toxicity, whereas those for the U3O8 bearing material should be governed by radiation dose.

Metabolism of an industrial uranium trioxide dust after deposition in the rat lung.

UNLABELLED: Uranium trioxide, produced industrially, was administered to rats either by inhalation or direct injection of an aqueous suspension into the lungs. THE RESULTS: show that uranium was cleared rapidly from the lungs, mainly to the blood; show that distribution of uranium among body tissues, and the fraction of the systemic content excreted in urine, was similar to that obtained for other transportable hexavalent uranium compounds; suggest that urine monitoring data would be of more value than lung radioactivity counting measurements for assessing occupational human exposure; indicate that for setting exposure limits by inhalation the uranium trioxide should be considered a highly transportable compound. Thus intakes by workers should be restricted to those recommended for short-term exposures and not those based on an annual limit.

Metabolism of some industrial uranium tetrafluorides after deposition in the rat lung.

UNLABELLED: Two commercially produced natural uranium tetrafluorides were administered to rats either by inhalation or direct injection into the lungs. THE RESULTS: show that, for both materials uranium is cleared rapidly from the lungs, much of it to the blood, show that the distribution of uranium amongst body tissues, and the fraction of the systemic content excreted in urine, is similar to that obtained after the administration of U(VI) bicarbonate, show that the transportability of uranium is much greater than in previously reported studies with other preparations of uranium tetrafluoride, suggest that lung radioactivity counting measurements would be of limited value for interpreting human exposures, indicate that for setting exposure limits these tetrafluorides should be considered moderately transportable compounds (ICRP inhalation class W).

Unusual pulmonary reactions to oily propyliodone (Dionosil) in bronchography.

Severe reactions to oily propyliodone are rare. Side-effects are usually mild and self-limiting. Three cases are reported of early pulmonary reactions, the cause of which may be a chemical pneumonitis or possibly an allergic response to one of the components of the contrast medium. There was a good response to corticosteroid therapy in all three patients.

Antacid-induced osteomalacia and nephrolithiasis.

A 36-year-old woman suffered from bone pain, muscle weakness, and renal stones after prolonged ingestion of antacids for esophageal reflux. Investigation disclosed hypophosphatemia, hypercalciuria, and osteomalacia by bone biopsy. All symptoms and abnormal laboratory findings reversed with a regimen of oral phosphate supplementation and cessation of antacid intake.

Hypercalcaemia in adolescent tetraplegic patients: case report and review.

The paper presents the case history of a 15-year-old boy with traumatic tetraplegia who developed hypercalcaemia within 6 weeks of injury. The condition was initially controlled by the infusion of intravenous fluids in large amounts and by the administration of calcitonin. After 3 weeks, calcitonin became ineffective. Eventually the hypercalcaemia responded to cortisone administered in low dosage. The endocrinologic implications of this observation are discussed.