Peripheral blood monocytes were isolated from normal human donors by separation on a continuous Percoll gradient and adherence to yield preparations of blood monocytes with a high degree of purity (greater than 99%). The monocytes were incubated in vitro with medium alone or with multilamellar liposomes that contained either a lipophilic derivative of muramyl dipeptide, muramyl tripeptide (MTP-...

Culture of spleen cells from strain 2 guinea pigs with Jurkat interleukin-2 (IL-2) resulted in the induction of lymphokine-activated killer (LAK) cells. Maximum LAK activity was induced using 5000 pmol of IL-2. Incubation of spleen cells with IL-2 for as little as 8 h resulted in detectable LAK activity. LAK cell activity was transient and could be stimulated by adding back IL-2. LAK cell activ...

The subcellular localization of a heparan sulfate degrading endoglycosidase, heparanase, was studied in human neutrophils. Unstimulated cells were disrupted by nitrogen cavitation and fractionated on a Percoll density gradient into three components, separating the plasma membranes, specific granules, and azurophilic granules. Heparanase activity was measured by gel filtration analysis of 35S-la...

Mitochondria were isolated from nodules of cowpea (Vigna unguiculata (L). Walp.) and purified on a Percoll gradient. They were only slightly contaminated by bacteroids (an average of 3.5%), and had low lipoxygenase activity. Compared to mitochondria from hypocotyls the nodule mitochondria had similar O(2) uptake rates and respiratory control ratios. The ADP/O ratios for both preparations were 1...

We previously reported that 125I-labeled epidermal growth factor is processed intracellularly to acidic macromolecules in Rat-1 fibroblasts. The present study defines the precursor-product relationship and localization of the processing steps to subcellular organelles by the use of a single isoelectric species of 125I-epidermal growth factor and Percoll gradient fractionation. The native pI 4.5...

Phagocytic functions of rat alveolar macrophages (AM) following intraperitoneal injection of conagenin (CNG) and of AM sub-populations fractionated by Percoll discontinuous gradient centrifugation were investigated. Phagocytosis of opsonized-sheep red blood cells (SRBC) following in vitro incubation with CNG showed a significant increase in a higher density of AM (fraction IV). In addition, pha...

Lysosomal cystine transport is a carrier-dependent process that, in isolated lysosomes, is stimulated by proton gradients, membrane potential, and millimolar concentrations of divalent cations. The importance of these regulatory factors in vivo is not well established. Polyamines were found to stimulate cystine transport in Percoll gradient purified rat liver lysosomes with spermidine greater t...

Pancreatic islet B cells from Sprague-Dawley and Fisher 344 rats aged 3-27 months were separated from A and D cells by centrifugation over a linear percoll density gradient, and incubated in vitro with various concentrations of glucose and somatostatin. Elevation of glucose concentration in the incubation medium from 2.6 to 16.7 mM provokes an insulin secretory response that is independent of r...

Cytotoxic T lymphocytes have been thought to lyse cellular targets in the past by a calcium-dependent pathway. This notion was recently supported by the identification and purification of a pore-forming protein (perforin) from the granules of these cell types. Here, we show that perforin is absent from a number of cell lines that nevertheless display vigorous cytolytic activity toward target ce...

Although endosomal proteolysis has been reported (e.g. for peptide hormones and lysosomal enzymes), lysosomes are believed to be the main site of degradation in the endocytic pathway. We have studied the separate roles of lysosomes and prelysosomal endocytic organelles in the degradation of ovalbumin in J774 cells. The ovalbumin was labelled with 125I-tyramine cellobiose (125I-TC-ova). The labe...