Marked Changes In Shape Research Articles

The mode of rabbit platelet shape change and aggregation induced by theonezolide-A, a novel polyketide macrolide, isolated from the Okinawan marine sponge <I>Theonella</I> sp.

Theonezolide-A (TZ-A), a novel polyketide macrolide, isolated from the Okinawan marine sponge Theonella sp., caused a marked platelet shape change at low concentrations (0.2-0.6 microM). Increasing concentrations of TZ-A to 6 microM or more caused shape change followed by a small but sustained aggregation. In a Ca(2+)-free solution, TZ-A-induced aggregation was markedly inhibited, although the marked shape change was still observed. Aggregation stimulated by TZ-A increased in a linear fashion with increasing Ca2+ concentrations from 0.1 to 3.0 mM. Furthermore TZ-A markedly enhanced 45Ca2+ uptake into platelets. Aggregation induced by TZ-A was inhibited by Arg-Gly-Asp-Ser, an inhibitor of fibrinogen binding to glycoprotein IIb-IIIa, H-7 and staurosporine, protein kinase C inhibitors, or genistein and tyrphostin A23, protein tyrosine kinase inhibitors, whereas shape change was blocked by genistein and tyrphostin A23. H-7 or staurosporine did not affect the TZ-A-induced shape change. These results suggest that TZ-A-induced platelet shape change is not dependent on external Ca2+, whereas TZ-A-induced aggregation is caused by an increase in Ca2+ permeability of the plasma membrane. It is also suggested that both aggregation and shape change induced by TZ-A are associated with protein phosphorylation by protein kinase C and tyrosine kinase.

Effects of hypotonic and hypoionic media on drug pumping by P‐glycoprotein expressed in epithelial and nonepithelial cell lines

The effects of anisotonic and anisoionic media on the drug-pumping function of P-glycoprotein (Pgp) were studied in epithelial and nonepithelial cells. We used HT-29 colon cells (HT-29/Pgp-) induced to express Pgp and MDR phenotype (HT-29/Pgp+) and NIH3T3 (3T3/Pgp-) cells which were stably transfected with human MDR1 DNA (3T3/Pgp+). Intracellular concentrations of rhodamine 123 (R-123) preloaded into cells were monitored as a function of time by fluorescence imaging microscopy, while cells were superfused with media of different tonicity and/or ionic strength. Efflux was analyzed by a single exponential decay function. In all media tested efflux was considerably higher in Pgp+ than Pgp- cells. In both HT-29 and 3T3 cells loaded with dye in isotonic conditions, dye efflux was not significantly different whether it was measured in isoionic-isotonic (130 mM NaCl, 300 mOsm), hypoionic-isotonic (87 mM NaCl), or hypoionic-hypotonic (200, 150, or 100 mOsm) media throughout the entire experiment or whether the media were changed during the experiment. Similar results were obtained when cells were preincubated and preloaded with dye under hypotonic conditions. Under extreme hypotonic and hypoionic challenge (changing from 130 mM NaCl-300 mOsm to 43 mM NaCl-100 mOsm medium), 3T3 cells, but not HT-29 cells, underwent marked shape and size changes which reduced R-123 cell-associated fluorescence. The changes were most conspicuous in Pgp+ cells, possibly reflecting a Pgp effect on the osmotic or osmoregulatory properties of the cells. However, drug-pumping activity remained essentially unimpaired even under the most extreme hypotonic/hypoionic conditions.

Expression and regulation of basic fibroblast growth factor mRNA levels in mouse osteoblastic MC3T3-E1 cells.

Basic fibroblast growth factor (bFGF) is a potent mitogen for bone cells and is a constituent of the bone matrix. We have found that osteoblastic MC3T3-E1 cells expressed bFGF mRNA transcript of 4.5 kilobases (kb). We examined factors that regulate the expression of bFGF mRNA and protein in MC3T3-E1 cells. Treatment of MC3T3-E1 cells with bFGF (10 nM) for 4-48 h induced another 7-kb bFGF transcript at 4 h. Treatment of MC3T3-E1 cells with TGF beta (10 ng/ml) also induced the 7-kb transcript of bFGF mRNA. In contrast, heparin, parathyroid hormone, and interleukin-1 had no effect on bFGF mRNA. Western blot analyses revealed that MC3T3-E1 cells produced a 24-kDa bFGF protein, which was increased by TGF beta. Immunofluorescence showed that bFGF protein was localized to the cytoplasm in serum-deprived MC3T3-E1 cells. Treatment of these cultures with medium containing fetal calf serum or TGF beta caused increased cytoplasmic staining for bFGF and marked shape change. Furthermore, in the cells treated with TGF beta there was both nuclear and cytoplasmic staining for the protein. These data demonstrate that bFGF mRNA and protein are expressed in osteoblastic cells and are regulated by treatment with TGF beta and bFGF. Production of bFGF may be important as an autocrine and paracrine mediator of bone cell replication, differentiation, and function.

Retinoic acid negatively regulates β4 integrin expression and suppresses the malignant phenotype in a Lewis lung carcinoma cell line

Retinoic acid (RA) is a potent inhibitor of the malignant phenotype and of tumour cell growth. We observed that in vitro RA treatment of a highly metastatic lung carcinoma cell line (C87) induced a marked reduction in the amount of the beta 4 integrin subunit. The downregulation of this adhesion molecule was assessed by immunofluorescence, immunoprecipitation, and northern analysis. In order to investigate the effects of RA on the malignant phenotype in C87 cells we performed morphological and functional analysis after RA treatment. We found that RA was able to produce marked changes in C87 cell shape, increasing the number of flat cells (90% of the total cell population), and significantly inhibiting the malignant and invasive phenotype of C87 cells. RA treatment suppressed their clonogenic potential in soft agar (control, 20 +/- 5; RA, 0), and strongly reduced their chemotactic and chemoinvasive capacity (chemotaxis: control, 231 +/- 5; RA, 28 +/- 0; chemoinvasion: control, 132 +/- 11; RA = 2 +/- 1). FACS analysis and cell count, however, indicated that RA reduced the growth of C87 cells only partially. After 72 h of treatment we observed only a 10% reduction in the S phase fraction of the cell population. Finally, the reduced lung colony-forming ability, observed after i.v. injection of RA-treated cells (lung foci/animal: RA-treated cells, 1 +/- 0.1; untreated, 8.5 +/- 0.8), further supports the conclusion that in this murine lung carcinoma cell line a marked reduction in the expression of the beta 4 integrin subunit is associated with a marked inhibition of the malignant phenotype.

Okadaic acid induces marked shape change of human platelets.

Okadaic acid (OA) induced marked shape changes of human platelets but neither granule secretion nor increase in [Ca2+]i occurred. Morphological changes induced by OA were unique and different from those observed with thrombin mainly in two respects. One is that the pseudopods formed by OA treatment were longer and straighter than those by thrombin. The other is that no granule centralization was observed with OA-treatment, although central condensation of cytofilaments was observed as was with thrombin. The immunocytochemical analysis employing anti-myosin antibody revealed that myosin was distributed in the elongated pseudopods. Since OA induced phosphorylation of the 20-kDa myosin light chain (MLC20) corresponding to the change in shape of platelets but did not induce phosphorylation of the 47-kDa protein (pleckstrin) (Higashihara M. et al. FEBS Lett. 307:206-210, 1992), these results suggest that phosphorylation of MLC20 plays an important role in OA-induced unique morphological changes of platelets.

Further observations on ischaemic suppression of motor units in human soleus muscle: A single case study

Changes in action potentials (APs) of human soleus motor units (MUs), that occur during ischaemia produced by thigh compression, were studied in five experiments on one subject. In each experiment, a well-isolated AP of a low threshold MU was recorded by a needle electrode beginning with ischaemia onset up to the final MU block. All registered low-threshold MUs responded to Achilles tendon jerks throughout their life cycle. The block of low-threshold MUAps either coincided with or preceded complete tendon reflex loss (min 25 of ischaemia). Low-threshold MUAPs were suppressed in two phases. During the first phase of MUAP slowing, beginning with ischaemia onset up to min 17-22, MUAP amplitude decreased, while MUAP area remained approximately unchanged. During the second phase, MUAP area as well as MUAP amplitude decreased, and in 2-5 min MUAP failed. More ischaemia-resistant high-threshold MUAPs were recorded after the population of low-threshold Mus was blocked. Some high-threshold MUAPs deteriorated similarly to low-threshold MUAPs. Others were blocked abruptly, without any marked changes in shape. It is likely that early extinction of low-threshold MUs contributes to the effect of the stretch reflex suppression during ischaemia. It is suggested that the pattern of MUAP changes during ischaemia in different MUs is related to their degree of aerobic metabolism.

Nuclear pore complex antigens delineate nuclear envelope dynamics in vegetative and conjugating Saccharomyces cerevisiae.

In the yeast Saccharomyces cerevisiae, the nucleus undergoes dramatic shape changes during mitosis and mating. We have studied nuclear envelope dynamics during the processes of mitosis and conjugation using nuclear pore complexes as a marker for the nuclear envelope in wild-type cells and several cell-division-cycle (cdc) mutants. Three monoclonal antibodies are described that recognize nuclear pore complex-related antigens in S. cerevisiae. One of these antibodies, RL1, has been extensively characterized by Gerace and colleagues and recognizes nuclear pore complexes in mammalian and amphibian cells. By indirect immunofluorescence of yeast cells, all three antibodies yield a discontinuous nuclear rim stain. All three react with multiple nuclear-enriched proteins in immunoblots, including the nucleoporin protein encoded by the NSP1 gene. When the antibodies were used in immunofluorescence experiments on mating cells, the nuclear pore complex staining pattern proved to be a sensitive indicator of nuclear fusion. Nuclei with closely apposed spindle pole bodies and unfused nuclear envelopes could be readily distinguished. Marked shape changes were observed in nuclei during fusion and segregation of the diploid nucleus into the zygotic bud. In cdc14 and cdc15 mutants that arrest late in mitosis, the elongated nuclear envelope extension that stretches between daughter nuclei during telophase was preserved. In cytokinesis-defective mutants (cdc3, cdc10, cdc11 and cdc12), the elongated nuclear envelope was usually resolved into two daughter nuclei in the absence of cytokinesis. These results indicate that nuclear envelope division is mechanically distinguishable from chromosome segregation, nucleolar segregation and cytokinesis.

Stimulatory effect of phospholipase A 2 treatment on glucose utilization in human erythrocytes

We examined whether modification of membrane phospholipids of human erythrocytes by hydrolysis with phospholipase A 2 (PLA 2 from bee venom) would affect glucose utilization, chosen as a typical model of intracellular metabolism, and, if so, intended to clarify the mechanism of the alteration of glycolysis. Treatment of erythrocytes with PLA 2 induced a marked shape change (i.e., crenation) and significantly increased the rate of lactate production from glucose. Available evidence indicated that there is no relevance of this cell-shape change to the alteration of glycolysis. The lack of a detectable effect of papain treatment on glycolysis in PLA 2-treated cells suggested that the increase in glycolysis by PLA 2 treatment might not be caused by the conformational change of band-3 protein through modulation of membrane phospholipids. The result of the measurement of lactate production in the presence and absence of ouabain did not support the idea that hydrolysis of phospholipids by PLA 2 treatment makes plasma membranes leaky to Na + and consequently enhances glycolysis through activation of Na + K +- ATPase . The action of PLA 2 on glycolysis was abolished by extraction of free fatty acids in the cell membrane with bovine serum albumin. Loading erythrocytes with free fatty acid (oleic acid, linoleic acid, or arachidonic acid) caused a significant increase in glycolysis. Analysis of glycolytic intermediates suggested that the enhancement of glycolysis was induced by activation of 6-phosphofructokinase. The data, thus, indicate that treatment of human erythrocytes with PLA 2 significantly accelerates glucose utilization and suggest that the stimulation of glycolysis is caused by activation of 6-phosphofructokinase through liberation of free fatty acids of membrane phospholipids by PLA 2.

Quantitative regional curvature analysis: Validation in animals of a method for assessing regional ventricular remodelling in ischemic heart disease

Recent studies show the impact of left ventricular shape and remodelling on patient prognosis. This mandates the development of quantitative methods for measuring shape. Quantitative regional curvature analysis (QRCA) was developed to quantitate shape on a regional basis so that measurements would not be constrained to assessment of only global shape and would, therefore be applicable to ischemic heart disease. To validate QRCA, eleven dogs were instrumented with coronary occluders and radiopaque markers on the epicardium and endocardium to provide fiducial points for calculation of shape, motion and thickening. These parameters were measured in the anterior and inferior walls, at rest, during left anterior descending occlusion and finally during circumflex occlusion. QRCA showed increased curvature (increased globularity) in each wall when thickening and motion deteriorated during occlusion. The most marked shape changes occurred in the inferior wall whereas the most marked deterioration of function was detected by wall thickening measurements of the anterior wall. Thus, QRCA detects regional ventricular shape disorders coincident with regional dysfunction induced by ischemia. These changes show regional heterogeneity and demonstrate the potential importance of this measurement as opposed to simple, global measures of shape. QRCA is, therefore, suitable for monitoring acute changes of shape that occur during acute ischemia.

Quantitative regional curvature analysis: Validation in animals of a method for assessing regional ventricular remodelling in ischemic heart disease

Recent studies show the impact of left ventricular shape and remodelling on patient prognosis. This mandates the development of quantitative methods for measuring shape. Quantitative regional curvature analysis (QRCA) was developed to quantitate shape on a regional basis so that measurements would not be constrained to assessment of only global shape and would, therefore be applicable to ischemic heart disease. To validate QRCA, eleven dogs were instrumented with coronary occluders and radiopaque markers on the epicardium and endocardium to provide fiducial points for calculation of shape, motion and thickening. These parameters were measured in the anterior and inferior walls, at rest, during left anterior descending occlusion and finally during circumflex occlusion. QRCA showed increased curvature (increased globularity) in each wall when thickening and motion deteriorated during occlusion. The most marked shape changes occurred in the inferior wall whereas the most marked deterioration of function was detected by wall thickening measurements of the anterior wall. Thus, QRCA detects regional ventricular shape disorders coincident with regional dysfunction induced by ischemia. These changes show regional heterogeneity and demonstrate the potential importance of this measurement as opposed to simple, global measures of shape. QRCA is, therefore, suitable for monitoring acute changes of shape that occur during acute ischemia.

Isolation of flavodoxin in isoforms from a macroalga Porphyra umbilicalis and a conformational change on dissociation of flavin

In Porphyra umbilicalis the 2Fe-2S ferredoxin that is the predominant low potential electron transfer protein is accompanied by small amounts of two flavodoxins, in ca 5:1 ratio. These are of the long chain group ( M r 21 000) and contain one FMN per molecule. The absorption spectrum of the major isoform exhibited maxima at 274, sh 283, sh 291; 381; 464, sh 490 nm and under anaerobic conditions the flavodoxin was reduced via a blue semiquinone to the hydroquinone. On dissociation of the flavin both isoforms underwent a marked change in shape from approximately globular to an extended conformation. Nevertheless, the apoflavodoxin would reassociate readily with FMN, but not riboflavin or FAD, to reform the flavodoxin. The major flavodoxin differed from cyanobacterial flavodoxins in possession of a higher proline content, and in this respect and also in behaviour on flavin dissociation it was similar to the flavodoxin from another red alga Chondrus crispus.

Calyculin‐A increases the level of protein phosphorylation and changes the shape of 3T3 fibroblasts

Calyculin-A, an inhibitor of type 1 and 2A phosphatases, was applied extracellularly to 3T3 fibroblasts. At 0.1 microM, calyculin-A caused a marked increase in protein phosphorylation in both the cytosolic and insoluble cellular fractions. This effect was independent of external Ca2+. An immunoprecipitate, formed with an antibody to myosin, contained several cytoskeletal components. Increased phosphorylation following treatment with calyculin-A was observed in vimentin, the 20-kD myosin light chain, and an unidentified 440-kD component. An enhanced level of vimentin phosphorylation was found in intermediate filament preparations from treated cells. Calyculin-A also caused marked shape changes of 3T3 cells. Within minutes after addition of calyculin-A (0.1 microM) cells became rounded and lost attachment to the substratum. Stress fibers, intermediate filaments, and microtubules, prominent in the attached control cells, were not evident in the rounded cells. Shape changes were reversible and after removal of calyculin-A the rounded cells attached to the substratum, resumed a flattened shape, and were active mitotically. In the cells treated with calyculin-A an unusual "ball-like" structure was observed with transmission electron microscopy. This unique structure was 2-3 microM in diameter and was located close to the nucleus. The use of calyculin-A adds further support to the idea that cell shape is controlled, at least in part, by concerted actions of a kinase-phosphatase couple.

Induction of M-phase entry of prophase-blocked mouse oocytes through microinjection of okadaic acid, a specific phosphatase inhibitor

We report that a specific inhibitor of types 1 and 2A phosphatases, okadaic acid (OA), induces germinal vesicle break down (GVBD) and chromosome condensation when microinjected into denuded mouse oocytes maintained in prophase block by analogs of cAMP, inhibitors of phosphodiesterase, or a tumor-promoting phorbol ester. GVBD and chromosome condensation are also observed when incompetent oocytes are similarly injected with OA, this effect being dependent on the oocyte diameter. Marked changes in cell shape, cytoskeletal organization, and chromosome condensation with abnormal or abortive spindle formation are associated with such injections. The polar body is not formed. These results led to the conclusions that in mouse oocytes, OA acts distal to both the cAMP-modulated pathway involved in meiotic arrest and the inhibitory action exerted by tumor-promoting phorbol esters.

Tumor Necrosis Factor Alters Cytoskeletal Organization and Barrier Function of Endothelial Cells

Treatment of human umbilical cord vein endothelial cells with tumor necrosis factor results in marked changes in cell shape and cytoskeletal organization. After 4 h of treatment, these cells loose reciprocal contacts with the formation of intercellular gaps. This retraction reaches a maximum after 6 h when most stress fibers staining for F-actin disappear and vinculin becomes diffused in the cytoplasm. Such changes spontaneously reverse after 24 h in the presence of tumor necrosis factor or after 2 h of incubation in fresh medium. After treatment with tumor necrosis factor, endothelial monolayers become permeable to albumin because of gaps that form between cells. Normal human serum, plasma alpha 1-proteinase inhibitor and an anti-inflammatory peptide that decrease synthesis of platelet-activating factor inhibit the changes induced by tumor necrosis factor. Furthermore, receptor antagonists of platelet-activating factor have the same effect. These findings suggest that platelet-activating factor is a secondary mediator responsible for the changes in cell shape and cytoskeletal organization, and for the leakiness of endothelial monolayers.

Characterization and Fibrinolytic Properties of Human Omental Tissue Mesothelial Cells. Comparison With Endothelial Cells

It has been reported that omental fat tissue is a good source of human microvascular endothelial cells. By characterization we demonstrate that the epitheloid cells isolated from omental tissue are not endothelial cells, but mesothelial cells. They contain abundant cytokeratins 8 and 18, which are absent in endothelial cells, and vimentin. No staining with the endothelial-specific antibodies EN-4 and PAL-E is observed. A faint and diffuse staining of von Willebrand factor (vWF) is seen in mesothelial cells, whereas microvascular endothelial cells from subcutaneous fat display vWF in distinct granular structures. Human peritoneal mesothelium produces plasminogen activator-dependent fibrinolytic activity, which is essential in the resolution of fibrous exudates and may therefore be important in preventing the formation of fibrous peritoneal adhesions. This fibrinolytic activity is plasminogen activator-dependent, but has not been fully characterized. We report here that human omental tissue mesothelial cells in vitro produce large amounts of tissue-type plasminogen activator (t-PA), together with type 1 and 2 plasminogen activator inhibitor (PAI-1 and PAI-2). PAI-1 is predominantly secreted into the culture medium, whereas the major part of PAI-2 is found in the cells. No urokinase-type plasminogen activator is detected. On stimulation with the inflammatory mediator tumor necrosis factor (TNF), at least a threefold decrease in t-PA antigen is observed, together with an increase in both PAI-1 and PAI-2. TNF also induces a marked change in cell shape. Whereas TNF and bacterial lipopolysaccharide (LPS) have similar effects on the production of PA inhibitor by human endothelial cells, LPS has no or only a relatively small effect on the fibrinolytic properties of mesothelial cells. The decreased fibrinolytic activity induced by the cytokine TNF may impair the natural dissolution of fibrin deposits at the peritoneum in the presence of an inflammatory reaction.

Characterization and fibrinolytic properties of human omental tissue mesothelial cells. Comparison with endothelial cells

It has been reported that omental fat tissue is a good source of human microvascular endothelial cells. By characterization we demonstrate that the epitheloid cells isolated from omental tissue are not endothelial cells, but mesothelial cells. They contain abundant cytokeratins 8 and 18, which are absent in endothelial cells, and vimentin. No staining with the endothelial-specific antibodies EN-4 and PAL-E is observed. A faint and diffuse staining of von Willebrand factor (vWF) is seen in mesothelial cells, whereas microvascular endothelial cells from subcutaneous fat display vWF in distinct granular structures. Human peritoneal mesothelium produces plasminogen activator-dependent fibrinolytic activity, which is essential in the resolution of fibrous exudates and may therefore be important in preventing the formation of fibrous peritoneal adhesions. This fibrinolytic activity is plasminogen activator-dependent, but has not been fully characterized. We report here that human omental tissue mesothelial cells in vitro produce large amounts of tissue-type plasminogen activator (t-PA), together with type 1 and 2 plasminogen activator inhibitor (PAI-1 and PAI-2). PAI-1 is predominantly secreted into the culture medium, whereas the major part of PAI-2 is found in the cells. No urokinase-type plasminogen activator is detected. On stimulation with the inflammatory mediator tumor necrosis factor (TNF), at least a threefold decrease in t-PA antigen is observed, together with an increase in both PAI-1 and PAI-2. TNF also induces a marked change in cell shape. Whereas TNF and bacterial lipopolysaccharide (LPS) have similar effects on the production of PA inhibitor by human endothelial cells, LPS has no or only a relatively small effect on the fibrinolytic properties of mesothelial cells. The decreased fibrinolytic activity induced by the cytokine TNF may impair the natural dissolution of fibrin deposits at the peritoneum in the presence of an inflammatory reaction.

An AES study of the initial oxidation of Ni(110) and the influence of Al in clean NiAl

The Interaction of oxygen with Ni(110) at room temperature has been Investigated by AES for oxygen exposures from 10 to 1000 langmulr. Particular attention has been directed to the M2,3VV, L2VV and L3VV Auger transitions in N1 and the neighbouring satellite features. The M2, 3VV is shifted down in energy and undergoes marked changes in shape whereas the L2VV and L3VV are not shifted significantly. The major change in the L3VV is the reduction in Intensity of only one of the two components that comprise this feature. Satellite features 6 eV below both the M2,3VV and L3VV transitions are identified and attributed to 3-hole final states. The Ni L3VV transition has also been examined In NiAl and found to be narrower and shifted down In energy by 2.2 eV as compared with this transition for clean Ni.

Microinjection of p34 cdc2 kinase induces marked changes in cell shape, cytoskeletal organization, and chromatin structure in mammalian fibroblasts

We have examined the effects of elevating the intracellular levels of p34 cdc2 kinase by microinjection into living mammalian cells. These studies reveal rapid and dramatic changes in cell shape with cells becoming round and losing the bulk of their cell-substratum contact. Such effects were induced at all times in the cell cycle except at S phase and were fully reversible at S phase or mitosis. Similar results were obtained with the homogeneous catalytic subunit of p34 cdc2 kinase or p34 cdc2 kinase associated with cyclin B. These alterations were accompanied by a marked reduction in interphase microtubules without the spindle formation, actin microfilament redistribution, and premature chromatin condensation. Although these changes closely mimic the events occurring during early phases of mitosis, p34 cdc2 kinase-injected cells were not induced to pass further into division. These data provide detailed evidence that p34 cdc2 kinase plays a major prerequisite role in the rearrangement of cellular structures associated with mammalian cell mitosis.

Membrane deformability and the capacity for shape change in the erythrocyte

Erythrocytes must have the capacity to undergo marked membrane deformation and shape changes in order to circulate through capillaries and respond to a range of shear stresses. To study the interrelationships between membrane deformability and the capacity for shape transformation, we created rigid membranes using several agents and then examined the ability of these erythrocytes with rigid membranes to undergo amphipath-induced shape change. We have previously shown that wheat germ agglutinin (WGA) and a monoclonal antibody to glycophorin A (R-10) cause membrane rigidity as measured by ektacytometry. Experiments were therefore designed to produced comparably rigid membranes using WGA, R-10, and diamide, and then to test the ability of lysophosphatidylcholine to produce echinocytes, and primaquine to produce stomatocytes. We found that diamide treatment substantially blocked both types of shape change. In contrast, R-10 binding did not impair either primaquine- or lysophosphatidylcholine- induce shape change. Further, WGA blocked echinocyte transformation, as previously reported, but not stomatocytosis. Using reduced and unreduced gel electrophoresis and Triton extraction, we compared the biochemical changes associated with WGA-, diamide-, and R-10-induced rigidity, and found them to be different. We conclude that not all rigid cells are incapable of shape change, and therefore that decreased membrane deformability is not predictive of impaired capacity for shape change.

Cell membrane and volume changes during red cell development and aging.

This paper provides a summary of our understanding of cell membrane and volume changes during red cell development and aging. Cytoskeletal structures which include microtubules and microfilaments appear to play key roles in the genesis of the anucleate reticulocyte from its nucleated precursor cell, as well as in the early stages of reticulocyte development. The maturation of reticulocyte into red cell is accompanied by marked changes in cell shape and extensive remodeling of the membrane skeleton, resulting in the mature red cell acquiring a highly deformable yet remarkably stable membrane. The volume and cell density heterogeneity seen for circulating red cells also appears to be the result of the membrane changes that occur during reticulocyte maturation. Following its genesis from reticulocyte, the mature red cell undergoes further membrane and volume changes during its life span of 120 days. While it is clear that surface area loss, decrease in cell volume and cell surface modifications leading to binding of immunoglobulins accompany red cell aging, the cardinal cellular modification responsible for the removal of senescent red cells from the circulation is yet to be defined.