Studies on the nature and excretion of biliary copper in man

1. Gall-bladder bile was obtained at cholecystectomy from seven patients who had been given [64Cu]cupric acetate intravenously.

2. Studies using dialysis and Sephadex gel filtration indicated that most of the 64Cu in the bile was in a heat-stable complex of molecular weight exceeding 50 000. The remaining biliary 64Cu was in a low-molecular-weight component.

3. Above pH 4, 64Cu could not readily be removed from the macromolecular complex either by excess carrier copper ions, by d-penicillamine or by EDTA.

4. Absorption of 64Cu from 64Cu-labelled bile injected intraduodenally into rats was significantly less than from [64Cu]cupric acetate similarly injected.

5. These observations suggest that limitation of an entero-hepatic circulation of copper by a biliary macromolecule which differs from caeruloplasmin, may be a significant factor in copper homeostasis in man.

Antigen-induced stimulation of glucosamine incorporation by guinea pig peritoneal macrophages in delayed hypersensitivity

The interaction between sensitized lymphocytes and specific antigen occurring in delayed hypersensitivity causes bystander macrophages to undergo a variety of light-microscopic, ultrastructural, and biochemical changes, which are reflected in alterations in cell movement and intercellular contacts. Since such alterations involve functions of the cell periphery, we postulated that metabolic changes in this polysaccharide-rich zone would accompany the expression of delayed hypersensitivity. We here demonstrate that the incorporation of radioactive glucosamine by peritoneal macrophages into TCA-precipitable, membrane-associated material is regularly enhanced when these are cultured in the presence of specific antigen and nonadherent cells (lymphocytes) primed for delayed hypersensitivity. Lymphocytes from unsensitized animals, or from animals immunized so as to form antibody but not delayed hypersensitivity, do not stimulate such incorporation. Antigen-induced glucosamine incorporation is maximal at 2 or 3 days of culture and is not observed earlier; it may be elicited with as little as 0.1 microg/ml PPD, and affords an exceedingly reproducible and sensitive index of delayed hypersensitivity. Radioautographic studies indicate that nearly all plastic adherent cells (90% macrophages) incorporate glucosamine and that grains are concentrated in the regions of the perinuclear zone and cell membrane. Subcellular fractionation indicates that nearly 30% of counts and the highest specific activity are associated with the membrane-rich microsomal fraction; the microsomal distribution of counts increases in both absolute and relative terms when macrophages are cultured in the presence of specific antigen and sensitized lymphocytes. Taken together, these data indicate that a sizable fraction of incorporated glucosamine is localized to the vicinity of the cell periphery but lack sufficient resolution to determine whether this material is associated with the cell membrane itself or with the extramembranous cell coat. This last possibility is of particular interest since we have previously shown that macrophage cell coat material is lost or altered as a consequence of an interaction between sensitized lymphocytes and specific antigen.

Enzymic depolymerization of macromolecular heparin as a factor in control of lipoprotein lipase activity

Macromolecular heparin from rat skin shows poor lipoprotein lipase-releasing activity in vivo and is a potent inhibitor of rat-heart lipoprotein lipase in vitro. Rat-skin heparin is depolymerized by incubation with the 100,000 x g supernatant from a sonicated homogenate of rat small intestine. The depolymerized products, fractionated by gel filtration, range from inhibitors to activators of lipoprotein lipase as molecular size decreases. Depolymerized rat heparin in the same molecular size range as commercial heparin from pig intestinal mucosa has about two-thirds the activity of the commercial preparation, both in vivo and in vitro.

Intestinal uptake of macromolecules: effect of oral immunization

Animals were orally immunized with horseradish peroxidase and bovine serum albumin, and absorption of these antigens was studied. In comparison with controls, a consistent and significant decrease in peroxidase uptake was noted in both germ-free and conventional rats immunized with peroxidase; a similar decrease in serum albumin uptake was also noted in animals immunized with serum albumin. There was no difference in the uptake of an unrelated macromolecule. These observations suggest that local immunization interferes specifically with the intestinal uptake of macromolecular antigens.

Macromolecular absorption. Mechanism of horseradish peroxidase uptake and transport in adult and neonatal rat intestine

The immature small intestine of neonatal mammals is permeable to gamma globulins as a source of passive immunity. Allegedly, macromolecular absorption ceases when the epithelial cell membrane matures. However, some evidence exists that adult animals retain a limited capacity to transport antigenic and biologically active quantities of large molecules. In this study, the mechanism of absorption of the tracer protein, horseradish peroxidase (HRP), was tested in neonatal and adult rat gut sacs. Transport into serosal fluid was quantitated by enzymatic assay and monitored morphologically by histochemical techniques. A greater transport of HRP was noted in the adult jejunum compared to adult ileum and neonatal intestine. Morphologically, the uptake mechanism in adult intestine was similar to the endocytosis previously reported in neonatal animals Like other endocytotic processes, HRP uptake in adult rats is an energy-dependent process as determined by metabolic inhibitors and temperature-controlled studies. An understanding of the mechanism whereby macromolecules are bound to intestinal membranes and engulfed by them is necessary before the action of physiologic macromolecules such as enterotoxins can be appreciated.

Transcapillary exchange of protein-bound hormones from the bloodstream into the tissue fluid

The transcapillary exchange of protein-bound for measuring this exchange are discussed. methods to the study of the transcapillary described, and the usefulness of the methods for a study of transcapillary exchange of protein-bound steroid hormones considered. ligands and methods useful The application of these exchange of thyroxine is

Aryl hydrocarbon hydroxylase and polycyclic hydrocarbon tumorigenesis: effect of the enzyme inhibitor 7,8-benzoflavone on tumorigenesis and macromolecule binding

Aryl hydrocarbon hydroxylase is present and is inducible in mouse skin. 7,8-Benzoflavone, an inhibitor of the enzyme, markedly inhibits tumorigenesis by 7,12-dimethylbenz(a)anthracene, but has either no effect on or stimulates benzo(a)pyrene tumorigenesis. Thus, the role of aryl hydrocarbon hydroxylase appears highly specific for each polycyclic hydrocarbon, in respect to detoxification and/or activation of the hydrocarbon to a carcinogenic form. In parallel studies, we found that 7,8-benzoflavone significantly reduces the amount of 7,12-dimethylbenz(a)anthracene binding to mouse skin DNA, RNA, and protein, and the binding of benzo(a)pyrene to RNA and protein of mouse skin. 7,8-Benzoflavone exhibited a markedly lesser effect on the binding of benzo(a)pyrene to DNA.

Effect of some triphenylethylenes on oestradiol binding in vitro to macromolecules from uterus and anterior pituitary

The effects of a series of triphenylethylenes (I.C.I. 46,474, I.C.I. 47,699 and clomiphene isomers A and B) on oestradiol binding to receptors from rat, rabbit and mouse uteri and rat anterior pituitary were studied. Binding of oestradiol to receptors from uteri was inhibited competitively by I.C.I. 46,474. Receptors from uteri of the three species and from rat anterior pituitary have very similar affinities for oestradiol and the four triphenylethylenes. The order of activity of the triphenylethylenes as inhibitors of oestradiol binding is: clomiphene B > I.C.I. 46,474 > I.C.I. 47,699 > clomiphene A. Some correlations are made with the activity of the compounds in vivo.