Citations

Monolayer cell cultures of macrophages, monocytes, myoblasts, and density-inhibited and transformed fibroblasts form and release cell surface membrane vesicles following exposure to formaldehyde, related low-molecular-weight aldehydes, and disulfide blocking agents. Vesicles have a unique composition of proteins and lipids. They show enrichment of cholesterol and sphingomyelin content and a seven-to tenfold enrichment of 5′-nucleotidase activity. Vesicles also contain intramembranous particles and show a trilamellar unit membrane and no ultrastructural evidence of contamination with other cytoplasmic organelles. The technique is proposed as a novel method for isolating plasma membrane vesicles from cells in culture.

Data are presented to explain discrepancies in the literature involving the in vitro binding of steroid receptor complexes to isolated nuclei and chromatin. The type of binding in vitro of the progesterone-receptor complex to nuclei, chromatin, or DNA of hen organs is largely determined by the ionic strength of the medium. Low ionic conditions (0.01 to 0.05 molar potassium chloride) result in a nonspecific, nonsaturable binding, while high ionic conditions (0.15 to 0.20 molar potassium chloride) create a tissue-specific, saturable binding. Pure DNA binds the steroid receptor complex extensively in low salt but very little in the higher salt conditions.

Hormones and purine nucleosides and nucleotides induced cultured bone cells to transform transiently from a spherical to a stellate shape. Cytochalasin B also induced the transformation. The change was blocked by colchicine and vinblastine, but not by lumicolchicine or cycloheximide. This morphologic transformation may provide a dynamic model of hormone action and bone cell modulation in vitro.

The quantities of immunoglobulin E (IgE) antibodies to grass or ragweed allergens were measured by an immunoabsorption in the serums of patients sensitive to one of these allergens. IgE antibodies to grass or ragweed allergens accounted for means of 30 and 29 percent of the total IgE protein. After the ragweed pollination season, the levels of serum IgE antibodies to ragweed allergens rose dramatically and in postpollination serums they accounted for 39 percent of the total IgE protein with a range from 13 to 50 percent.

Evidence from several model systems suggests that nonhistone chromosomal proteins may regulate gene expression in eukaryotic cells. The data indicate that the synthesis of new species of nonhistone chromosomal proteins as well as modifications of preexisting nonhistone chromosomal proteins are involved in the control of transcription. However, from the vast number of proteins included in this class, it is apparent that, in addition to regulating the transcription of defined genome loci, the nonhistone chromosomal proteins include enzymes that have a general function, proteins that are involved in determining the structure of chromatin, as well as proteins that serve as recognition sites for binding of regulatory macromolecules. The presence of a nucleoplasmic pool of nonhistone chromosomal proteins which may exchange with the chromatin has also been reported ( 89 ). While it is clear that the nonhistone chromosomal proteins play a key role in the regulation of gene expression, the exact manner in which they interact with the genome to initiate, modify, or augment the transcription of specific RNA molecules remains to be resolved.

Dopamine-β-hydroxylase activity is released into the blood with catecholamines from the adrenal medulla and sympathetic nerves. This enzyme activity has been measured in the blood of 317 normal children and 227 normal adults. A significant sibling-sibling correlation of serum dopamine-β-hydroxylase values was found in the 94 sibling pairs tested. Frequency distributions of serum enzyme values in both children and adults suggest the existence of two populations with regard to serum activity of this enzyme.

Dopamine-β-hydroxylase activity accumulated above a ligature on biopsy samples of normal human sural nerves incubated in vitro. The rate of accumulation indicated that this enzyme was transported distally at a velocity of 2 millimeters per hour. Axoplasmic transport of dopamine-β-hydroxylase was greatly reduced in sural nerves from a few patients with peripheral neuropathies.

In a rare myopathy muscle fibers contained myriad lipid-filled vacuoles. Homogenates of the patient's muscle oxidized fatty acids more slowly than normal (11 controls). Addition of carnitine increased the oxidation rate with the patient's muscle to the level attained by the controls with carnitine. In five separate muscle samples from the patient the mean carnitine level was less than 20 percent of that observed in 42 controls. Carnitine palmityl transferase and palmityl thiokinase levels in the patient's muscles were not depressed. The present case represents the first recognized instance of carnitine deficiency in human skeletal muscle.

Serum immunoreactive parathyroid hormone (IPTH) is normal in patients with X-linked hypophosphatemic rickets who are not treated with phosphate salts. Phosphate raises IPTH in these patients. Endogenous IPTH does not influence the existing defect in tubular reabsorption of phosphate in male patients.