Showing papers by "Rockefeller University published in 1974"

Secretion of plasminogen activator by stimulated macrophages

Abstract: Cultured thioglycollate-stimulated peritoneal macrophages synthesize, accumulate, and continuously release high levels of plasminogen activators for at least 4 days whereas cultures of unstimulated macrophages do not; the higher specific catalytic activity of released vs. cell-associated enzyme suggests that the plasminogen activators are actively secreted. The major macrophage plasminogen activator is a serine protease of mol wt 48,000, and thus resembles the comparable enzyme released by virally transformed fibroblasts. Macrophages release a second plasminogen activator of mol wt 28,000 that is also a serine enzyme. The secretion products released by stimulated and unstimulated macrophages have been compared by SDS-polyacrylamide gel electrophoresis after chemical labeling with 3H-DFP or biosynthetic labeling with 14C-amino acids. These procedures show that some proteins are formed in both cultures, whereas others are uniquely secreted by each type of macrophage. The serine enzymes released by the two kinds of macrophages differ in specificity and electrophoretic mobility.

Connections of the median and dorsal raphe nuclei in the rat: an autoradiographic and degeneration study.

Abstract: Ascending and descending projections from the median and dorsal raphe nuclei of the midbrain were mapped in the albino rat, using reduced-silver stains after lesions or the autoradiographic technique following injections of tritiated proline. In all major respects the two techniques gave the same results. The majority of the ascending projections sweep ventrally from the raphe nuclei, then curve rostrally to course through the ventral tegmentum and into the medial forebrain bundle (MFB). Others radiate through the mesencephalic reticular formation (RF) and central grey, turning ventrally at the posterior thalamic border to enter the subthalamus. From the MFB, fibers branch into the hypothalamus, preoptic areas, anterior amygdala and olfactory tubercle, while some fibers enter the fornix or the stria terminalis. Many fibers continue rostrally in the MFB, joining the diagonal bands of Broca to reach the septal nuclei or, further rostrally, the cingulum bundle. Fibers in the cingulum bundle turn caudally around the genu of the corpus callosum, some branching into the cell-free layers of the pregenual cortex. Runing caudally, then curving around the splenium, the cingulum bundle projection sprays out into the subiculum and in some cases a projection into the hippocampus is seen. Other ascending projections include one to the habenular nuclei through the fasciculus retroflexus. Projections to the mediodorsal, parafascicular and reuniens nuclei of the thalamus were also noted. Descending projections were observed to the dorsal tegmental nucleus and locus coeruleus and diffusely to the pontine reticular formation and caudal central grey. No projections were seen below the level of the facial nerve nucleus and none were observed to the cerebellum, caudal raphe nuclei or cranial nerve nuclei.

Identification of a novel cell type in peripheral lymphoid organs of mice. II. Functional properties in vitro.

Abstract: Several properties of lymphoid dendritic cells in situ have been determined, and contrasted to information previously established for lymphocytes and mononuclear phagocytes. Dendritic cells are not found in newborn mice, and their concentration in both spleen and mesenteric lymph node does not reach adult levels until 3–4 wk of age. Dendritic cells largely disappear from adherent populations following administration of steroids (2.5 mg hydrocortisone acetate s.c.) and ionizing radiation (Do of 100 rads for Co60). Splenic dendritic cells can originate from precursors located in both bone marrow and spleen itself, probably the red pulp. The mature splenic population does not actively divide (pulse labeling index with [3H]thymidine of 1.5–2.5%), but does turnover at substantial rate, 10+% of the total pool per day. The influx of new cells appears to be derived from a proliferating precursor compartment, but the mechanism for efflux or turnover is not known. Dendritic cells in spleen and node undergo little or moderate increase in numbers during development of a primary immune response. These in vivo characteristics, taken together, further distinguish dendritic cells as a novel cell type, distinct from mononuclear phagocytes and lymphocytes.

Protein degradation in cultured cells. II. The uptake of chloroquine by rat fibroblasts and the inhibition of cellular protein degradation and cathepsin B1.

Abstract: The degradation of cellular proteins in fibroblasts, both those of rapid and those of slow turnover rates, was inhibited by low concentrations of chloroquine or neutral red in the medium. Cells inhibited by chloroquine can be inhibited further by fluoride. Chloroquine was taken up by the fibroblasts and the concentration in the cells reached several hundred times that in the medium. Isopycnic fractionation studies showed that within the cells the chloroquine was concentrated in the lysosomes, and that these chloroquine-containing lysosomes had a lower equilibrium density than the lysosomes of untreated cells. Chloroquine, at concentrations attained inside the lysosomes, inhibited cathepsin B1 but not cathepsin D. It is concluded that chloroquine impairs the breakdown of cellular proteins after these have entered the lysosome system, probably through inhibition of cathepsin B1.

In vitro synthesis and secretion of lysozyme by mononuclear phagocytes

Abstract: Pure cultures of three types of mononuclear phagocytes-mouse peritoneal macrophages, unstimulated or after thioglycollate stimulation, and human monocytes-synthesize and secrete large amounts of lysozyme in vitro. The macrophage lysozyme is indistinguishable from authentic lysozyme in its ability to lyse M. lysodeikticus, inhibition by specific antisera, a similar size of 14,000 and cationic charge. Lysozyme secretion in culture is characterized by a large net increase in total lysozyme, 4-20-fold in 3 h, 75-95% of which is in the medium, and its continued extracellular accumulation over at least 2 wk in culture. Lysozyme is the major (14)C-labeled protein secreted into the medium by both unstimulated and thioglycollate-stimulated macrophages and the 0.75-1 microg produced per 1 x 10(6) cells/day represents 0.5-2.5% of the total cell protein. Lysozyme is a cell-specific marker for mononuclear phagocytes and the PMN, which contains preformed enzyme, since it is absent in lymphoid cells and a variety of fibroblast and epithelioid cell lines. Lysozyme production is also a useful measure of mononuclear phagocyte cell number. The rate of lysozyme production and secretion is remarkably constant for all cell types under a variety of culture conditions. Production by the mouse macrophage increases threefold on the 2nd day in culture and then remains linear with time. Production is optimal at a relatively low serum concentration, but can be maintained, in the absence of serum, in lactalbumin hydrolysate or, at a reduced level in basal media. The production and secretion of lysozyme are independent of the production of macrophage acid hydrolases. Net increase and secretion of lysozyme occur under conditions where acid hydrolases like N-acetyl beta-glucosaminidase, beta-glucuronidase, beta-galactosidase, and cathepsin D are neither accumulated nor secreted. Massive phagocytosis of latex particles has no effect on lysozyme production and secretion. Lysozyme production can be rapidly inhibited by treatment with cycloheximide (0.4 microg/ml) whereas inhibition of its production by colchicine (10(-6) M) occurs only after a lag period of more than 8 h, and is probably due to a secondary effect. These results show that mouse macrophages provide a simple in vitro system to measure lysozyme secretion and its control. These studies also indicate the possible importance of mononuclear phagocytes in the secretion of a variety of biologically active products and in the modification of their environment.

The telencephalon, diencephalon, and mesencephalon of the canary, Serinus canaria, in stereotaxic coordinates

Abstract: A stereotaxic atlas of the telencephalon, diencephalon and mesencephalon of the canary, Serinus canaria, was prepared for use in anatomical and behavioral experiments. Canaries have a complex vocal and behavioral repertoire many of whose components are under hormonal control in the male, and are therefore useful for many physiological and anatomical experiments. They are available commercially, breed easily in captivity, are quite hardy and respond well to anesthetic and surgical procedures. The atlas consists of 30 frontal plates from the frontal pole to the level of the motor nucleus of the trigeminus. One sagittal plate is included for reference purposes. Six birds (three males and three females) with marking lesions were used to make the atlas. Their brains were embedded in albumin-gelatin media, cut at 50 and 25μ and stained with cresyl violet for cell bodies, Weil stain for myelinated fibers and the Fink-Schneider method for unmyelinated fibers. Plates were drawn from the cresyl violet series and labeled using all three stains. The completed atlas was tested for accuracy by making 12 small lesions in a number of predetermined discrete loci in several birds and evaluating their placement. Eleven of these lesions were found to be within the targeted structure. The results of this test, combined with the results of experiments in over 50 birds, have shown the atlas to be accurate in 80% of all cases.

Pinocytosis in fibroblasts: Quantitative studies in vitro

Abstract: Horseradish peroxidase (HRP) was used as a marker to determine the rate of ongoing pinocytosis in several fibroblast cell lines. The enzyme was interiorized in the fluid phase without evidence of adsorption to the cell surface. Cytochemical reaction product was not found on the cell surface and was visualized only within intracellular vesicles and granules. Uptake was directly proportional to the administered concentration of HRP and to the duration of exposure. The rate of HRP uptake was 0.0032–0.0035% of the administered load per 106 cells per hour for all cells studied with one exception: L cells, after reaching confluence, progressively increased their pinocytic activity two- to fourfold. After uptake of HRP, L cells inactivated HRP with a half-life of 6–8 h. Certain metabolic requirements of pinocytosis were then studied in detail in L cells. Raising the environmental temperature increased pinocytosis over a range of 2–38°C. The Q10 was 2.7 and the activation energy, 17.6 kcal/mol. Studies on the levels of cellular ATP in the presence of various metabolic inhibitors (fluoride, 2-desoxyglycose, azide, and cyanide) showed that L cells synthesized ATP by both glycolytic and respiratory pathways. A combination of a glycolytic and a respiratory inhibitor was needed to depress cellular ATP levels as well as pinocytic activity to 10–20% of control values, whereas drugs administered individually had only partial effects. In spite of the availability of an accurate quantitative assay for fluid and solute uptake, the function of pinocytosis in tissue culture cells remains unknown.

INDUCTION OF MACROPHAGE PLASMINOGEN ACTIVATOR BY ENDOTOXIN STIMULATION AND PHAGOCYTOSIS : Evidence for A Two-Stage Process

Abstract: The injection of thioglycollate medium into the peritoneal cavity of the mouse induces high levels of macrophage fibrinolytic activity due to the production and secretion of a plasminogen activator, a trypsinlike serine protease, which is absent in unstimulated macrophages. Intraperitoneal injection of endotoxin or mineral oil can stimulate only a fraction (<10%) of the fibrinolytic activity of thioglycollate cells, similar to the partial stimulation (<10%) seen 1-2 days after phagocytosis of latex or SRBC by unstimulated macrophages. The endotoxin-stimulated macrophages contain and release relatively low levels of plasminogen activator, but these primed cells can be triggered to produce and secrete high levels of enzyme, by phagocytosis of latex. Under conditions where the plasminogen activator is induced and secreted, there are no effects on the production and/or release of lysozyme or intracellular acid hydrolases, Discovery of a two-stage procedure for inducing macrophage plasminogen activator made it possible to study the role of cell priming and phagocytosis separately. Endotoxin was a more effective priming agent, weight for weight, than lipid A:BSA complex. Secretion of the plasminogen activator was induced only by thioglycollate, or endotoxin and latex. In situ fibrinolysis was induced by these agents and mineral oil, BCG, and fetal calf serum, in decreasing order of effectiveness. Phagocytosis of latex in all cases except thioglycollate stimulation, increased fibrinolytic activity from three- to sixfold. Latex and a variety of other particles such as M. lysodeikticus, aggregated gamma-globulin and immune complexes showed dose-dependent stimulation of fibrinolysis by endotoxin-primed macrophages. Although the initial phagocytic trigger was not specific for the substance employed, the ability to induce a sustained response depended on the persistence of the phagocytized particle within the cell. Fibrinolysis and secretion of plasminogen activator continued at high levels for at least 9 days after uptake of latex, a nondigestible particle, whereas plasminogen activator was secreted only transiently after ingestion of rapidly digested M. lysodeikticus. The induction of plasminogen activator secretion provides a mechanism by which the activated macrophage can exert a selective effect on its extracellular environment.

Effect of Verapamil on the Sinoatrial and Atrioventricular Nodes of the Rabbit and the Mechanism by Which it Arrests Reentrant Atrioventricular Nodal Tachycardia

Abstract: The effects of verapamil, an antiarrhythmic drug that apparently blocks slow inward currents, were studied on the isolated, superfused sinoatrial (SA) and atrioventricular (AV) nodes of the rabbit heart with intracellular microelectrodes. Verapamil decreased the rate of spontaneous impulse initiation by the SA node. This effect could be overcome with epinephrine. Concomitantly, verapamil decreased the amplitude of SA node action potentials without reducing maximum diastolic potential. The peak of the action potential fell well short of reversal after exposure to the drug. Verapamil had similar effects on the action potentials of the upper and middle AV nodal regions, reducing action potential amplitude so that the overshoot vanished without significantly reducing maximum diastolic potential. Action potentials of fibers in the lower region of the AV node were not affected as greatly. Verapamil slowed conduction of atrial impulses through the AV node; such slowing increased when the atrial rate increased. Verapamil also prolonged the effective refractory period of the AV node, thus slowing or blocking conduction of premature impulses. Verapamil prevented AV nodal reentry and initiation of atrial tachycardia by causing premature impulses to block rather than to conduct with the delay needed to initiate reentry. Verapamil had no effect on the rate of depolarization, action potential amplitude, or maximum diastolic potential of atrial or His bundle fibers. The results are consistent with the hypotheses that fibers in the SA and AV nodes show slow response activity, that the slow response plays a crucial role in causing certain cardiac arrhythmias, and that drugs that block the slow response are therefore antiarrhythmic.

Morphometric data on the endothelium of blood capillaries

Abstract: Local differentiations within the endothelium of both muscular (diaphragm, myocardium) and visceral (pancreas, jejunal villi) capillaries have been studied in rats on sectioned and freeze-cleaved preparations. Four distinct parts have been recognized in the endothelial cells of all these vessels on the basis of subcellular components present in each part and on the basis of variations in the local frequency of plasmalemmal vesicles: (a) the parajunctional zone, (b) the peripheral zone, (c) the organelle region, and (d) the nuclear region. Our data indicate that ∼16, ∼7.0, and 8.5% of the endothelial cytoplasmic volume (in the peripheral zone) is accounted for by vesicles, their content, and their membranes, respectively. The average density of vesicular openings per µm2 is 78 in diaphragm, 89 in myocardium, 25 in pancreas, and 10 in jejunal mucosa capillaries. The frequency of fenestrae is 1.7 times as high in jejunal (26/µm2) as in pancreatic capillaries (15/µm2), the corresponding fractional areas being ∼9.5 and ∼6%, respectively, of the endothelial surface. Intercellular spaces occupy a relatively small area (∼0.08 to 0.2%) of the inner endothelial surface.

A Pragmatic Description of Early Language Development

Abstract: Language acquisition involves more than learning the abstract structures of linguistic competence The child also has to learn how to use linguistic structures appropriately In this paper, the speech act is proposed as the unit of analysis for studying the pragmatics of early child language The results of a study of children's uses of single-word utterances are reported, and the data are analyzed in terms of “primitive speech acts”

Belief and the basis of meaning

Abstract: A theory of radical interpretation gives the meanings of all sentences of a language, and can be verified by evidence available to someone who does not understand the language. Such evidence cannot include detailed information concerning the beliefs and intentions of speakers, and therefore the theory must simultaneously interpret the utterances of speakers and specify (some of) his beliefs. Analogies and connections with decision theory suggest the kind of theory that will serve for radical interpretation, and how permissible evidence can support it.

Cytochemistry of golgi fractions prepared from rat liver

Abstract: Cytochemical tests for several marker enzymes were applied to liver tissue and to the three Golgi fractions (GF1, GF2, GF3) separated by the procedure of Ehrenreich et al. from liver homogenates of alcohol-treated rats. 5'-Nucleotidase (AMPase) reaction product was found in all three fractions but in different locations: It occurred along the inside of the membrane of VLDL-filled vacuoles in GF1 and GF2, and along the outside of the cisternal membranes in GF3. In the latter it was restricted to the dilated cisternal rims and was absent from the cisternal centers. The AMPase activity found in the fractions by biochemical assay is therefore indigenous to Golgi components and is not due to contamination by plasma membrane. Acid phosphatase (AcPase) reaction product was detected within lysosomal contaminants in GF1 and within many VLDL-filled vacuoles in GF1 and GF2, indicating that AcPase activity is due not only to contaminating lysosomes, but also to enzyme indigenous to Golgi secretory vacuoles. G-6-Pase reaction product was present in GF3 and within contaminating endoplasmic reticulum fragments, but not in other fractions. Thiamine pyrophosphatase (TPPase) was localized to some of the VLDL-filled vacuoles and cisternae in GF1 and GF2, and was not found in the cisternae in GF3. The results demonstrate the usefulness of cytochemical methods in monitoring the fractionation procedure: They have (a) allowed a reliable identification of contaminants, (b) made possible a distinction between indigenous and contaminating activities, and (c) shown, primarily by the results of the TPPase test, that the procedure achieves a meaningful subfractionation of Golgi elements, with GF1 and GF3, representing primarily trans-Golgi elements from the secretory Golgi face, and GF3 consisting largely of cis-Golgi components from the opposite face.

Studies on dispersed pancreatic exocrine cells. I. Dissociation technique and morphologic characteristics of separated cells.

Abstract: A procedure for dissociation of the guinea pig pancreas into individual cells is described which employs enzymatic digestion with pure collagenase, chymotrypsin, and hyaluronidase, utilizes an interposed chelation of divalent cations by EDTA, and is terminated by gentle shearing. Yields of cells are 50–60%, based on DNA recovered. The population comprises ∼95% exocrine cells, the remainder consisting of endocrine, duct, and vascular endothelial cells. The exocrine cells, though spherical, retain the structural attributes of their in situ counterparts, including differentiation of the plasmalemma into zones corresponding to the former apical and basal plasmalemma, polarized distribution of organelles indicated by fields of zymogen granules in the cytoplasm underlying the former apex, central location of the Golgi complex, and placement of the rough endoplasmic reticulum and nucleus in the former basal pole of the cell. Electron microscope study of the effects of individual treatments used during dissociation indicates that digestion of basement membrane and collagen is solely due to collagenase activity and that separation of desmosomes (and possibly of zonulae adherentes) results only from exposure to low [Ca++] and EDTA and is not effected by the enzymes used. Gap junctions are resistant to enzymes and EDTA; tight junctions resist enzyme treatment but undergo rearrangement upon exposure to EDTA. Both junctions require mechanical shear for complete cell separation. Neither chymotrypsin nor hyaluronidase produces visible alterations in stromal or junctional elements. Dissociation requires the concerted action of enzymes, chelation of divalent cations, and mechanical shear, since the individual treatments are alone ineffective.

Effect of Verapamil on the Normal Action Potential and on a Calcium Dependent Slow Response of Canine Cardiac Purkinje Fibers

Abstract: The effect of verapamil on normal sodium (Na)-dependent and slow calcium (Ca)-dependent action potentials recorded from canine cardiac Purkinje fibers was studied. The Ca-dependent slow response was obtained in fibers exposed to solutions in which all NaCl was replaced by tetraethylammonium chloride and in which Ca ranged from 4 mM to 16.2 mM. Verapamil (0.25-2 mg/liter) had little or no effect on the upstroke of the normal action potential, but such concentrations of verapamil suppressed rhythmic activity and depressed excitability in fibers that showed Ca-dependent slow responses. Spontaneous activity and rhythmic activity evoked by long depolarizing pulses were depressed. Verapamil decreased the amplitude and the upstroke velocity and shifted the threshold potential toward zero in fibers that showed Ca-dependent slow responses. The effectiveness of verapamil varied with the level of Ca; 0.25 mg/liter of verapamil was as effective in suppressing activity in fibers exposed to 4 mM Ca as was 2 mg/liter of verapamil in fibers exposed to 16.2 mM Ca. Although verapamil did not alter the upstroke of the normal Nadependent action potential, it did depress the plateau and prolong the action potential of fibers exposed to normal Tyrode's solution.

Electric Communication: Functions in the Social Behavior of Eigenmannia Virescens

Abstract: Eigenmannia virescens was observed in aquaria in Guyana, South America, during the non-breeding and breeding seasons. Agonistic behavior was described and correlated with electrical activity. Variations in the electric discharges play important roles in agonistic behavior as displays given during attack and retreat. Although descriptions of sexual behavior are not complete, certain electrical signals also appear to be used in courtship. The role of electrical signals in agonistic behavior of Eigemnannia were studied by (1) an analysis of the behavior of fish in dominant and subordinate roles, (2) an analysis of the simultaneous occurrence of electrical displays and motor actions, (3) an analysis of preceding actions of one fish and following actions of the other fish, and (4) analysis of responses to artificial electrical stimuli. These studies indicate that at least three classes of electric signals are important in communication among Eigenmannia: the normal discharge, Interruptions, and Rises. The normal discharge. The normal discharge of Eigenmannia virescens is species-distinctive in the area where this study was conducted. Playback of recorded signals and presentation of sinusoidal electrical stimuli, indicates that the normal discharge particularly the fundamental frequency of the normal discharge (240 to 600 Hz)- is used in species recognition. Males and females overlap extensively in their discharge frequency, and males do not appear to distinguish the electric discharges of males from those of females. Interruptions. Interruptions are brief cessations of the electric discharge. They are most often 20 to 40 msec in duration during agonistic interactions whereas they are often 60 to 80 msec when given by males during interactions with females during the breeding season. Interruptions are usually given in bouts where a bout is any group of Interruptions separated by less than 1.5 seconds. Interruptions are given almost exclusively by dominant fish. They are given at the same time as Attacks, Threats, and No Action, but rarely during Retreat. Bouts with many Interruptions are more likely to be associated with Attacks, and less likely with No Action, than are bouts containing only a few Interruptions. Interruptions correlate with motivation to Attack, and the number of Interruptions in a bout correlates with the probability of attack. Interruptions in one fish are followed by Retreat and No Action in the other fish, thus they appear to be an effective threat display. Interruptions with long durations are given at high repetition rates by male Eigenmannia in the presence of females during the breeding season, thus they may play a role in courtship. Rises. A Rise is an increase in discharge frequency followed by a decrease to the resting frequency. Rises lasting less than two seconds (Short Rises) are often given by dominant fish in agonistic interactions, most often at the same time as Attacks or Threats. They are given rarely. Long Rises (longer than two seconds) are given predominantly by subordinate fish in agonistic interactions. They are given simultaneous with Retreat and No Action and are thus an indicator of submissive behavior. Long Rises in one fish are followed by Attacks, Threats, Approaches, and by No Action in the other. During the breeding season, females, in the presence of males, often give long series of frequency modulations of unknown significance.

Effects of concanavalin A on mouse peritoneal macrophages. I. Stimulation of endocytic activity and inhibition of phago-lysosome formation.

Abstract: Concanavalin A (Con A) binds to saccharide residues on the mouse peritoneal macrophage plasma membrane and stimulates extensive pinocytic interiorization of the membrane. The overall pinocytic rate is increased 3.5–4.5 times by the addition of Con A, and the surface marker enzyme adenosine triphosphatase can be identified histochemically in association with the cytoplasmic vesicles generated after exposure of the cells to Con A. Once formed, these pinocytic vesicles may persist for several days and fail to show morphologic evidence of fusion with primary or preformed secondary lysosomes. There is no apparent effect on the capacity of the macrophage to ingest either latex particles or IgG-coated SRBC administered either simultaneously with or subsequent to the Con A.

Properties of plasminogen activators formed by neoplastic human cell cultures

Abstract: A series of human cell lines has been examined for fibrinolysis in culture. The sera that are activating for fibrinolysis by human cells are mouse, monkey, human, horse, and bovine. Individual human sera show considerable variation in the ability to activate fibrinolysis. In common with other neoplastic or transformed mammalian and avian cell cultures, human cell lines of neoplastic origin produce substantial amounts of plasminogen activator. Several cultures of nonmalignant origin also produce plasminogen activator, whereas cultures obtained from trypsinized human embryos, or from human embryonic skin do not. The human melanoma plasminogen activators are of two kinds: a major component with a mol wt of 50,000, and a minor species with a mol wt of approximately 60,000. Both are DFP sensitive, serine proteases.

Cryoprotectant-induced redistribution of intramembranous particles in mouse lymphocytes.

Abstract: This study demonstrates, by freeze fracture, clustering of intramembranous particles caused by cryoprotectant treatment of intact unfixed mouse lymphoid cells. Both T and B cells react in a similar fashion, while similar clustering of particles is not observed in some other cell types. The intramembranous particles can be aggregated by incubating unfixed cells in glycerol or dimethylsulfoxide (DMSO) before freezing. The aggregation phenomenon is dependent on the length of time of exposure and the concentration of the cryoprotectants. Further, the cells remain viable and the cryoprotectant-induced clustering is completely reversible. Prefixation of glycerol-treated cells with glutaraldehyde prevents the formation of these particle clusters, and unfixed nonglycerinated cells show no clusters. Thin sections of cells exposed to glycerol or DMSO without previous fixation exhibit bizarre membrane alterations and numerous other degenerative changes. These observations stress the importance of prefixation of lymphoid cells before exposure to glycerol or DMSO, as well as indicate that the membrane characteristics of certain cell types may be probed by glycerol treatment of unfixed cells.

Segmental response of the macrophage plasma membrane to a phagocytic stimulus

Abstract: for the segments of macrophage membrane to which they are attached, we have studied the effect of phagocytosis of latex particles and opsonized pneumococci on these membrane associated RBCs. Our data show that these RBCs are attached to functionally active membrane segments since they are ingested when rabbit anti-mouse RBC IgG is added to the medium and that phagocytosis of latex and of opsonized pneumococci does not stimulate the ingestion of membrane-attached RBCs. Thus, ingestion of one particle does not trigger generalized phagocytosis of all particles attached to the cell's plasma membrane. These findings suggest that the phagocytic stimulus is confined to the segment of the cell's plasma membrane immediately adjacent to the particle being ingested.