Phospholipid and cholesterol differences amongst leukemic cell types with special reference to hairy cell leukemia: a preliminary report.

Whole cell cholesterol and phospholipid content was determined for ten patients with hairy cell leukemia (HCL) and 15 patients with chronic lymphocytic leukemia (CLL). Malignant cells from HCL patients contained 0.412 mumol/10(8) whole cells is compared to 0.177 mumol/10(8) whole cells for CLL cells; the total phospholipid concentrations were 0.746 and 0.469 mumol/10(8) whole cells respectively (p less than 0.001). Phospholipid sub-types were determined by thin-layer chromatography. The percentages of sphingomyelin (HCL-16.2%, CLL-8.2%) and phosphatidylcholine (HCL-46.0%, CLL-55.1%) differed significantly between the two diseases (p less than 0.05, respectively). The novel finding in our study is that HCL cells are enriched two- to three-fold in sphingomyelin (expressed on a mumol/g protein basis) at the expense of phosphatidylcholine when compared to Cll cells (a PC/SM ratio of 2.9 in HCL compared to 6.5 in CLL). Increases in the total amount of cholesterol and phospholipid as well as in the selective portions of the individual phospholipids could reflect and, possibly, result in the unique membrane architecture of the hairy cell.

Comparison between the cellular proteins of hairy cell leukemia and the leukemic phase of other lymphoproliferative diseases.

Cellular proteins from malignant cells of the leukemic phase of hairy cell leukemia and other lymphoproliferative diseases characterized by immunological markers were evaluated by sodium dodecyl sulfate gradient-polyacrylamide gel electrophoresis. The protein patterns from eight patients with hairy cell leukemia were essentially identical. The protein patterns from eight patients with chronic lymphocytic leukemia, seven patients with acute lymphocytic leukemia, and four patients with poorly differentiated lymphocytic lymphoma were examined and did not demonstrate a consistent pattern within each disease. The protein patterns of one patient each with T-cell malignant lymphoma, lymphoblastic lymphoma, or acute monocytic leukemia were also examined. The protein pattern for hairy cell leukemia is distinctly different from that of all the other diseases studied; differences were distinct even within and between immunological subtypes.

Preparation and characterization of plasma membrane-enriched fractions from rat pancreatic islets.

Methods have been developed for the isolation on a semi-micro scale of a plasma membrane-enriched fraction from rat islets of Langerhans. An important feature of these experiments is the use of 125I-labeled wheat germ agglutinin as a specific probe for plasma membrane-containing fractions. The partly purified plasma membrane fraction had a density in sucrose of about 1.10 and was enriched in the activities of 5'-nucleotidase, alkaline phosphatase, sodium-potassium, and magnesium-dependent ATPase and adenylate cyclase. It contained only very low levels of acid phosphatase, cytochrome c oxidase, insulin, and RNA. Further purification was hampered by the relatively small amounts of fresh plasma membrane material that could be obtained from 16-24 rats in each experiment. When islets were prelabeled with radioactive fucose, the plasma membrane-enriched fraction contained radioactivity at a four- to fivefold higher specific acivity than the whole islet homogenate. Sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis of plasma membrane-enriched fractions pooled from several experiments revealed a distinctive pattern of protein bands as compared with other less pure fractions. With respect to rapidity, apparent specificity, and easy reversibility of the labeling of the plasma membrane fraction, 125I-wheat germ agglutinin provides a highly useful tool for the detection of microgram quantities of plasma membrane components which should be applicable to many other systems as well.

Biosynthesis of insulin and glucagon: a view of the current state of the art.

It is now well established that insulin biosynthesis proceeds through a precursor molecule, proinsulin. This single polypeptide chain form has been identified as a ribosomal product in the microsomal fraction from islet tissues. The newly synthesized peptide chain, after folding and thiol oxidation, is transferred to the Golgi apparatus where it begins to undergo proteolytic processing to insulin and packaging into secretory granules. The secretion from the cells of significant amounts of newly synthesized material by exocytosis begins only one hour or more after biosynthesis and this process is regulated by several factors, including glucose. Foci of current attention discussed in this paper include (1) the possible existence of larger precursor forms than proinsulin, especially short-lived biosynthetic transients with extended NH2-termini analogous to the recently described immunoglobulin L chain and proparathyroid hormone precursors; (2) the large-scale production of insulin by chemical or genetic engineering approaches; (3) isolation of beta-cell plasma membranes; (4) regulatory mechanisms for the biosynthesis and secretion of insulin, the possible role of mRNA modification in this process, and effects of somatostatin on insulin biosynthesis and secretion; (5) studies on the secretion, metabolism and clinical usefulness of the proinsulin C-peptide; (6) finally, the biosynthesis of glucagon and other peptide hormones and the general significance of precursor forms.

Effect of ascorbic acid on ACTH-induced cyclic AMP formation and steroidogenesis in isolated adrenal cells of vitamin E-deficient rats.

Isolated adrenal cells from Vitamin E-deficient and control rats were prepared by a trypsin digestion method. Cyclic adenosine 3',5'-monophosphate (cyclic AMP) formation was studied in response to adrenocorticotropin (ACTH) in the presence and absence of ascorbate by measuring the conversion of prelabeled adenosine 5'-triphosphate [14C]ATP to cyclic [14C]AMP. Ascorbate (0.5 mM) inhibited ACTH-induced cyclic [14C]AMP formation in adrenal cells isolated from Vitamin E-deficient rats but had no effect in the control cells. The inhibitory effect of ascorbate on ACTH-induced cyclic AMP formation in Vitamin E-deficient rats decreased as the concentration of ACTH increased. In Vitamin E-deficient rats ascorbate inhibited ACTH-induced cyclic [14C]AMP formation after 30 min of incubation. There was no further significant accumulation of cyclic [14C]AMP at 60 min or 120 min although in the absence of ascorbate cyclic [14C]AMP continued to be formed. The in vitro addition of alpha-tocopherol reduced the inhibition of ACTH-induced cyclic [14C]AMP formation by ascorbate in Vitamin E-deficient rats. These studies suggest that alpha-tocopherol and ascorbate may affect ACTH-induced cyclic AMP formation through interaction with the membrane-bound enzyme adenylate cyclase.

Heterogeneity of human very low density lipoproteins by gel filtration chromatography.

Very low density lipoproteins were separated by gel filtration on Sepharose 4B. A decrease in mean particle diameter and flotation rate was seen with increasing elution volumes. The smaller lipoproteins had relatively more protein and phospholipid and less triglyceride than the larger ones. No differences were noted in the relative contents of the various phospholipids or partial glycerides between small and large lipoproteins. Fatty acid patterns of triglycerides and cholesteryl esters were also similar for the various lipoproteins. Relatively more lecithin containing linoleoyl acyl groups was found in smaller lipoproteins of some subjects. More of the protein of smaller lipoproteins was apo-LDL protein. Apo-HDL peptide was lost from the very low density lipoprotein as a consequence of the gel filtration.