Protection by acidotic pH and fructose against lethal injury to rat hepatocytes from mitochondrial inhibitors, ionophores and oxidant chemicals

The importance of mitochondrial ATP formation and extracellular acidosis was evaluated in hepatocyte suspensions after different toxic treatments. Acidotic pH was protective against cell killing from all toxic treatments examined except for pronase, a toxic protease. Fructose, a substrate for glycolytic ATP formation, provided good protection against toxicity from cyanide, oligomycin, t-butyl hydroperoxide, menadione and cystamine. Protection by fructose against CCCP, gramicidin and Br-A23187 required oligomycin. This indicated that these ionophores were causing cytotoxicity by uncoupling oxidative phosphorylation. Fructose provided little protection against pronase and HgCl2, the latter compound being a potent inhibitor of glycolysis. In conclusion, disruption of mitochondrial ATP formation was a common event contributing to the toxicity of chemical oxidants and ionophores. Acidotic pH was generally protective under these conditions of impaired ATP generation.

R- and S-wave amplitude changes with acute anterior transmural myocardial ischemia. Correlations with left ventricular filling pressures

The value of R- and S-wave amplitude changes as electrocardiographic (ECG) markers of myocardial ischemia and dysfunction was evaluated using coronary angioplasty as a model of acute transmural ischemia and ST segment elevation. Hemodynamic data and 12-lead ECGs were recorded at baseline and during coronary occlusion in 34 patients with left anterior descending artery angioplasty. In the precordial leads V1 through V4, the sum of R-wave amplitude increased in 17 patients, was unchanged in ten, and decreased in seven; the sum of S-wave amplitude decreased in 33 patients (including two patients with complete loss of S wave) and increased in one. Mean R-wave change was 2.7 +/- 6.2 mm, mean S-wave change was -12.9 +/- 9.0 mm, and mean precordial ST elevation was 12.5 +/- 8.7 mm. Absolute R-wave change correlated directly with ST elevations (p = .013), while S-wave change correlated inversely (p less than .007). Only ST elevations correlated with changes in pulmonary capillary wedge pressure (PW) (p less than .007). In the precordial lead with maximum ST elevations, only R-wave changes correlated with ST elevations (p = .002), and both R-wave changes and ST elevations correlated with changes in PW (R:p = .027; ST:p = .007). The presence of large increases in R waves or decreases in S wave, or of high-magnitude ST elevations identified patients with the highest elevations in PW. In conclusion, decreases in S waves and, less commonly, increases in R waves are seen with diagnostic ST elevations and may have some limited clinical value. The correlation between magnitude of acute anterior ST elevations and changes in left ventricular filling pressures may have important clinical consequence.

Toxic injury from mercuric chloride in rat hepatocytes

The relationship between cytosolic free Ca2+, mitochondrial membrane potential, ATP depletion, pyridine nucleotide fluorescence, cell surface blebbing, and cell death was evaluated in rat hepatocytes exposed to HgCl2. In cell suspensions, 50 microM HgCl2 oxidized pyridine nucleotides between 1/2 and 2 min, caused ATP depletion between 2 and 5 min, and produced an 89% loss of cell viability after 20 min. Rates of cell killing were identical in high (1.2 mM) and low (2.6 microM) Ca2+ buffers. Cytosolic free Ca2+ was determined in 1-day cultured hepatocytes by ratio imaging of Fura-2 employing multiparameter digitized video microscopy. In high Ca2+ medium, HgCl2 caused a 3-4-fold increase of free Ca2+ beginning after 6-7 min, but free Ca2+ did not change in low Ca2+ medium. Bleb formation occurred after about 4-5 min in both buffers prior to any increase of free Ca2+. Subsequently, in high Ca2+ medium, blebs became hot spots of free Ca2+ (greater than 600 nM). After about 2 min of exposure to HgCl2, rhodamine 123 fluorescence redistributed from mitochondrial to cytosolic compartments signifying collapse of the mitochondrial membrane potential. The results taken together demonstrate that bleb formation, ATP depletion, and the onset of cell death are not dependent on an increase of cytosolic free Ca2+. HgCl2 toxicity appears to be a consequence of inhibition of oxidative phosphorylation leading to ATP depletion and cell death.

Assessment of Fura-2 for measurements of cytosolic free calcium

Fura-2 has become the most popular fluorescent probe with which to monitor dynamic changes in cytosolic free calcium in intact living cells. In this paper, we describe many of the currently recognized limitations to the use of Fura-2 in living cells and certain approaches which can circumvent some of these problems. Many of these problems are cell type specific, and include: (a) incomplete hydrolysis of Fura-2 acetoxymethyl ester bonds by cytosolic esterases, and the potential presence of either esterase resistant methyl ester complexes on the Fura-2/AM molecule or other as yet unidentified contaminants in commercial preparations of Fura-2/AM; (b) sequestration of Fura-2 in non-cytoplasmic compartments (i.e. cytoplasmic organelles); (c) dye loss (either active or passive) from labeled cells; (d) quenching of Fura-2 fluorescence by heavy metals; (e) photobleaching and photochemical formation of fluorescent non-Ca2+ sensitive Fura-2 species; (f) shifts in the absorption and emission spectra, as well as the Kd for Ca2+ of Fura-2 as a function of either polarity, viscosity, ionic strength or temperature of the probe environment; and (g) accurate calibration of the Fura-2 signal inside cells. Solutions to these problems include: (a) labeling of cells with Fura-2 pentapotassium salt (by scrape loading, microinjection or ATP permeabilization) to circumvent the problems of ester hydrolysis; (b) labeling of cells at low temperatures or after a 4 degrees C pre-chill to prevent intracellular organelle sequestration; (c) performance of experiments at lower than physiological temperatures (i.e. 15-33 degrees C) and use of ratio quantitation to remedy inaccuracies caused by dye leakage; (d) addition of N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) to chelate heavy metals; (e) use of low levels of excitation energy and high sensitivity detectors to minimize photobleaching or formation of fluorescent non-Ca2+ sensitive forms of Fura-2; and (f) the use of 340 nm and 365 nm (instead of 340 nm and 380 nm) for ratio imaging, which diminishes the potential contributions of artifacts of polarity, viscosity and ionic strength on calculated calcium concentrations, provides a measure of dye leakage from the cells, rate of Fura-2 photobleaching, and can be used to perform in situ calibration of Fura-2 fluorescence in intact cells; however, use of this wavelength pair diminishes the dynamic range of the ratio and thus makes it more sensitive to noise involved in photon detection. Failure to consider these potential problems may result in erroneous estimates of cytosolic free calcium.(ABSTRACT TRUNCATED AT 400 WORDS)

Calcium and pH in anoxic and toxic injury

The critical events that lead to the transition from reversible to irreversible injury remain unclear. Studies are reviewed that have suggested that a rise in cytosolic free Ca2+ initiates plasma membrane bleb formation and a sequence of events that leads ultimately to cell death. In recent studies, we have measured changes in cytosolic free Ca2+, mitochondrial membrane potential, cytosolic pH, and cell surface blebbing in relation to the onset of irreversible injury and cell death following anoxic and toxic injury to single hepatocytes utilizing multiparameter digitized video microscopy (MDVM). MDVM is an emerging new technology that permits single living cells to be labeled with multiple probes whose fluorescence is responsive to specific cellular parameters of interest. Fluorescence images specific for each probe are collected over time, and then digitized and stored. Image analysis and processing then permits quantitation of the spatial distribution of the various parameters within the single living cells. Our results indicate the following: (1) formation of plasma membrane blebs accompanies all types of injury in hepatocytes; (2) cell death is a rapid event, initiated by rupture of a plasma membrane bleb, and is coincident with the onset of irreversible injury; (3) an increase of cytosolic free Ca2+ is not the stimulus for bleb formation or the final common pathway leading to cell death; (4) a decrease of mitochondrial membrane potential precedes loss of cell viability; (5) cytosolic pH falls by more than 1 pH unit during chemical hypoxia. This acidosis protects against the onset of cell death.

Pancreatic cystadenoma. A clinicopathologic study

A retrospective study of 19 patients with pancreatic cystadenoma included 15 patients with microcystic and 4 with mucinous cystadenomas. The typical clinical presentation was that of an elderly woman with an upper abdominal mass. An association with diabetes mellitus and extrapancreatic malignant disease was noted. Total tumor resection provided the best chance of cure and removed the risk of compression of adjacent organs and, in mucinous cystadenomas, the risk of malignant transformation.

Swelling, reductive stress, and cell death during chemical hypoxia in hepatocytes

In rat hepatocytes, we examined the relationship between cell volume, bleb formation, and loss of cell viability during chemical hypoxia with KCN plus iodoacetic acid. In hypotonic media (150-200 mosmol/kgH2O), cells swelled to a greater extent during chemical hypoxia than in isotonic media, but rates of cell killing were identical. Sucrose (300 mM) added to isotonic media prevented early cell swelling but actually accelerated cell killing. In contrast, mannitol (300 mM) improved cell survival but did not prevent cell swelling. Bleb formation occurred regardless of buffer tonicity. The antioxidants desferrioxamine and cyanidanol but not superoxide dismutase +/- catalase delayed lethal cell injury. Cell killing was greater during aerobic compared with anaerobic chemical hypoxia. Hydroperoxide formation was measured using a dichlorofluorescin assay and was accelerated during aerobic but not anaerobic chemical hypoxia. The results indicate that cell swelling is not the driving force for bleb formation or lethal cell injury. We conclude that "reductive stress" caused by respiratory inhibition favors formation of toxic oxygen species and may contribute to lethal cell injury during intermittent or incomplete oxygen deprivation.

Role of Na+/H+ exchange by interferon-gamma in enhanced expression of JE and I-A beta genes

The rapid transductional sequences initiated by interferon-gamma (IFN-gamma) on binding to its receptor regulate functional and genomic responses in many cells but are not well defined. Induction of macrophage activation is an example of such functional and genomic changes in response to IFN-gamma. Addition of IFN-gamma to murine macrophages, at activating concentrations, produced rapid (within 60 seconds) alkalinization of the cytosol and a concomitant, rapid influx of 22Na+. Amiloride inhibited the ion fluxes and the accumulation of specific messenger RNA for two genes induced by IFN-gamma (the early gene JE and the beta chain of the class II major histocompatibility complex gene I-A). The data indicate that IFN-gamma initiates rapid exchange of Na+ and H+ by means of the Na+/H+ antiporter and that these amiloride-sensitive ion fluxes are important to some of the genomic effects of IFN-gamma.

Relationship of cytosolic ion fluxes and protein kinase C activation to platelet-derived growth factor induced competence and growth in BALB/c-3T3 cells

Platelet-derived growth factor (PDGF) and other agents that activate protein kinase C (PKC) rapidly alter cytosolic pH (pHi) and intracellular free calcium ([Ca++]i) in BALB/c-3T3 fibroblasts. To define whether changes in pHi or [Ca++]i are linked to PDGF-stimulated mitogenesis, these parameters were assessed in control and PKC depleted fibroblasts. PDGF addition to BALB/c-3T3 fibroblasts resulted in transient acidification of the cytoplasm followed by prolonged cytosolic alkalinization. Exposure of cells to 12-tetradecanoylphorbol-13-acetate (TPA), a phorbol ester that activates PKC, resulted in cytosolic alkalinization without prior acidification. Overnight incubation with 600 nM TPA decreased the total cell PKC histone phosphorylating activity in BALB/c-3T3 fibroblasts by greater than 90%. In PKC-deficient fibroblasts, TPA, and PDGF-induced alkalinization was abolished. In addition, the transient drop in pHi seen initially in control cells treated with PDGF is sustained to the point where pHi is fully 0.6-0.7 pH units below control cell values for up to 30 minutes. PDGF increased [Ca++]i threefold; this transient rise in [Ca++]i was only minimally affected (less than 15%) by lowering of the extracellular calcium level with ethylene glycol bis(b-aminoethyl ether)0 N,N,N' tetraacetic acid (EGTA) or blocking calcium influx with CoCl2. In contrast, 8-(diethylamine)-octyl-3,4,5-trimethoxybenzoate (TMB-8), an agent thought to inhibit calcium release from intracellular stores, substantially inhibited the rise in [Ca++]i caused by PDGF. TPA and 1-oleoyl-2-acetylglycerol (OAG) increased [Ca++]i but in contrast to PDGF this effect was blocked by pretreatment of cells with EGTA or CoCl2. In PKC-deficient fibroblasts, PDGF still increased [Ca++]i and stimulated DNA synthesis as effectively as in controls. TPA and OAG however, no longer increased [Ca++]i. The continued ability of PDGF to stimulate DNA synthesis in the face of sustained acidification and the absence of PKC activity suggests that cytosolic alkalinization and PKC activation are not essential for PDGF-induced competence in BALB/c-3T3 fibroblasts.

Platelet-derived growth factor and angiotensin II cause increases in cytosolic free calcium by different mechanisms in vascular smooth muscle cells

Platelet-derived growth factor (PDGF) and angiotensin II (AII) are thought to mediate their biological effects in vascular smooth muscle cells (VSMCs) by causing alterations in cytosolic free calcium ([ Ca2+]i). In this study we examine the pathways by which PDGF and AII alter [Ca2+]i in VSMCs. Addition of PDGF resulted in a rapid, transient, concentration-dependent increase in [Ca2+]i; this rise in [Ca2+]i was blocked completely by preincubation of cells with ethylene glycol-bis (beta-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA) or CoCl2, by the voltage-sensitive Ca2+-channel antagonists verapamil or nifedipine, by 12-O-tetradecanoylphorbol-13-acetate (TPA), or by pertussis toxin. AII also caused an increase in [Ca2+]i; however, AII-stimulated alterations in [Ca2+]i displayed different kinetics compared with those caused by PDGF. Pretreatment of cells with 8-(diethylamine)-octyl-3,4,5-trimethyoxybenzoate hydrochloride (TMB-8), almost totally inhibited AII-induced increases in [Ca2+]i. EGTA or CoCl2 only slightly diminished AII-stimulated increases in [Ca2+]i. Nifedipine, verapamil, TPA, and pertussis toxin pretreatment were without effect on AII-induced increases in [Ca2+]i. PDGF and AII both stimulated increases in total inositol phosphate accumulation, although the one-half maximal concentration (ED50) for alterations in [Ca2+]i and phosphoinisitide hydrolysis differed by a factor of 10 for PDGF (3 X 10(-10) M for Ca2+ vs. 2.5 X 10(-9) M for phosphoinositide hydrolysis), but they were essentially identical for AII (7.5 X 10(-9) M for Ca2+ vs. 5.0 X 10(-9) M for phosphoinositide hydrolysis). PDGF stimulated mitogenesis (as measured by [3H]-thymidine incorporation into DNA) in VSMCs with an ED50 similar to that for PDGF-induced alterations in phosphoinositide hydrolysis. PDGF-stimulated mitogenesis was blocked by pretreatment of cells with voltage-sensitive Ca2+ channel blockers, TPA, or pertussis toxin. These results suggest that PDGF and AII cause alterations in [Ca2+]i in VSMCs by at least quantitatively distinct mechanisms. PDGF binding activates a pertussis-toxin-sensitive Ca2+ influx into cells via voltage-sensitive Ca2+ channels (blocked by EGTA, verapamil, and nifedipine), as well as stimulating phosphoinositide hydrolysis leading to release of Ca2+ from intracellular stores. AII-induced alterations in [Ca2+]i are mainly the result of phosphoinositide hydrolysis and consequent entry of Ca2+ into the cytoplasm from intracellular stores. Our data also suggest that changes in [Ca2+]i caused by PDGF are required for PDGF-stimulated mitogenesis.

A laboratory evaluation of standard leakage tests for surgical & examination gloves

Analysis of leakage tests for surgical and examination gloves is reported. Six widely applicable tests were evaluated, using samples from 16 glove manufacturers. Various techniques for inducing sub-millimeter holes were developed and employed for creating test holes in a wide variety of gloves. The prescribed tests were performed and the results compared to calculations of expected sensitivities. In general, there was reasonable agreement between calculation and measurement (within about a factor of 2), although there were some exceptions. Minimum detectable hole sizes, before the holes were stretched by the tests, were generally in the range of 25-100 microns in diameter. Theoretical predictions of minimum detectable hole sizes for the various tests ranged from about 100-200 microns (in the stretched condition). Because of inherent limitations of the test protocols, it is clear that much larger holes can go undetected under certain circumstances, especially in examination gloves. Some test procedures had important procedural ambiguities; some tests were patently impossible to perform. All tests had inherent limitations resulting in sensitivities that varied from glove to glove or that were quite nonuniform over the surface of the glove being tested or both.

Social class and risk factors for coronary heart disease in the Federal Republic of Germany. Results of the baseline survey of the German Cardiovascular Prevention Study (GCP)

The relationship between social class and seven important risk factors for coronary heart disease has been evaluated utilising data from the German Cardiovascular Prevention Study baseline survey. Of German residents aged 25 to 69 years, 16,430 were randomly selected from both the six intervention regions and the Federal Republic of Germany to undergo the screening procedures between 1984 and 1986. Among males the prevalence of cigarette smoking and lack of physical activity was associated with social class. For females, overweight and physical activity demonstrated a strong social gradient. No relationship existed between social class and hypercholesterolaemia. The prevalence of Type A behaviour was significantly higher for the upper social classes. The number of CHD risk factors per study subject increased with decreasing social class. Predicted cardiovascular mortality was clearly higher for the lower social class among males in general and for females younger than 60 years. These findings point to the need for risk factor intervention strategies focusing more on the lower social classes in order to achieve more adequate prevention of coronary heart disease.

The TGF-alpha precursor expressed on the cell surface binds to the EGF receptor on adjacent cells, leading to signal transduction

The 50 amino acid form of TGF-alpha is cleaved from a conserved integral membrane glycoprotein by a protease that, in many tumor cells, appears to be limiting. To test whether the membrane-bound precursor has biological activity in the absence of processing, we introduced amino acid substitutions at the proteolytic cleavage sites. BHK cells transfected with expression vectors containing these altered sequences do not secrete detectable levels of mature TGF-alpha into the medium, but express high levels of proTGF-alpha at the cell surface. Coincubation of these BHK cells with A431 cells demonstrates that membrane-bound proTGF-alpha may bind to EGF receptors on the surface of contiguous cells, induce receptor autophosphorylation, and thereby produce a rapid rise in A431 intracellular calcium levels. Thus, proTGF-alpha can be biologically active in the absence of processing, a fact that may have implications for the integral membrane precursors of related growth factors.

Intracellular pH during "chemical hypoxia" in cultured rat hepatocytes. Protection by intracellular acidosis against the onset of cell death

The relationships between extracellular pH (pHo), intracellular pH (pHi), and loss of cell viability were evaluated in cultured rat hepatocytes after ATP depletion by metabolic inhibition with KCN and iodoacetate (chemical hypoxia). pHi was measured in single cells by ratio imaging of 2',7'-biscarboxy-ethyl-5,6-carboxyfluorescein (BCECF) fluorescence using multiparameter digitized video microscopy. During chemical hypoxia at pHo of 7.4, pHi decreased from 7.36 to 6.33 within 10 min. pHi remained at 6.1-6.5 for 30-40 min (plateau phase). Thereafter, pHi began to rise and cell death ensued within minutes, as evidenced by nuclear staining with propidium iodide and coincident leakage of BCECF from the cytoplasm. An acidic pHo produced a slightly greater drop in pHi, prolonged the plateau phase of intracellular acidosis, and delayed the onset of cell death. Inhibition of Na+/H+ exchange also prolonged the plateau phase and delayed cell death. In contrast, monensin or substitution of gluconate for Cl- in buffer containing HCO3- abolished the pH gradient across the plasma membrane and shortened cell survival. The results indicate that intracellular acidosis after ATP depletion delays the onset of cell death, whereas reduction of the degree of acidosis accelerates cell killing. We conclude that intracellular acidosis protects against hepatocellular death from ATP depletion, a phenomenon that may represent a protective adaptation against hypoxic and ischemic stress.

Calcium dependence of bleb formation and cell death in hepatocytes

Calcium dependence of bleb formation and cell death was evaluated in rat hepatocytes following ATP depletion by metabolic inhibition with KCN and iodoacetate ('chemical hypoxia'). Cytosolic free Ca2+ was measured in single cells by ratio imaging of Fura-2 fluorescence using multiparameter digitized video microscopy. Cells formed surface blebs within 10 to 20 minutes after chemical hypoxia and most cells lost viability within an hour. An increase of cytosolic free Ca2+ was not required for bleb formation to occur. One to a few minutes prior to the onset of cell death, free Ca2+ increased rapidly in high Ca2+ buffer (1.2 mM) but not in low Ca2+ buffer (less than 1 microM). In either buffer, the rate of cell killing was the same. As the onset of cell death was approached in both high and low Ca2+ buffers, Fura-2 began to leak from the cells at an accelerating rate indicating rapidly increasing plasma membrane permeability. In high Ca2+ buffer, cytosolic free Ca2+ increased in parallel with dye leakage. No regional changes in cytosolic free Ca2+ were observed during this metastable period of increased membrane permeability. In many experiments, actual rupture of cell surface blebs could be observed which led to micron-size discontinuities of the cell surface and cell death. We conclude that a metastable period characterized by increasing plasma membrane permeability marked the onset of cell death in cultured hepatocytes which culminated in rupture of a cell surface bleb. An increase of cytosolic free Ca2+ was not required for the metastable state to develop or cell death to occur.

Extracellular acidosis delays onset of cell death in ATP-depleted hepatocytes

A fluorometric assay using propidium iodide total fluorescence was utilized to quantitate cell viability in hepatocyte suspensions continuously. For viable hepatocytes exposed to KCN, fluorescence was linearly proportional to lactate dehydrogenase release and to nuclear labeling by propidium iodide. In KCN-treated hepatocytes, iodoacetate eliminated the protective effect of the fed state and fructose against the onset of cell death. A model of cell death with KCN and iodoacetate was developed to mimic the ATP depletion of anoxia. This "chemical hypoxia" was used to investigate the role of pH in cell death. At pH 7.4, cell viability decreased to 10% after 120 min, whereas at pH 5.5-7.0, cell viability was 65-85%, nearly the same as normoxic cells. During chemical hypoxia under acidotic conditions, a return of pH to 7.4 resulted in a rapid acceleration of cell killing, a "pH paradox." Inhibition of Na+-H+ exchange increased survival, whereas promoting exchange of intracellular Cl- for extracellular HCO3- potentiated cell killing. Monensin, a Na+-H+ ionophore, potentiated cell killing at pH 7.4 but not at pH 6.2. The results show that extracellular acidosis markedly protects against cell killing after ATP depletion, an effect that appears mediated through cytoplasmic acidification.

Biochemical and functional responses stimulated by platelet-activating factor in murine peritoneal macrophages

Platelet-activating factor (PAF) is a potent stimulant of leukocytes, including macrophages. To analyze the mechanisms of its effects upon macrophages, we determined whether macrophages bear specific surface receptors for PAF. By competitive radioactive binding assays, we determined two classes of specific receptors to be present on purified membranes derived from murine peritoneal macrophages (one having a Kd of approximately 1 X 10(-10) M and one a Kd of approximately 2 X 10(-9) M). When the macrophages were incubated with PAF, rapid formation of several inositol phosphates including inositol 1,4,5-trisphosphate and inositol 1,3,4,5-tetrakisphosphate were observed. PAF also elevated intracellular levels of calcium to 290 +/- 27% of basal levels which were 82.7 +/- 12 nM. Increases in calcium were observed first in submembranous areas of the macrophages. PAF also led to increases of 1,2-diacylglycerol of approximately 200 pmol/10(7) cells. A characteristic pattern of enhanced protein phosphorylation, similar to that initiated by both phorbol 12,13-myristate and lipopolysaccharide, was observed and involved enhanced phosphorylation of proteins of 28, 33, 67, and 103 kD. The half-maximal dose of PAF for initiating all the above effects was approximately 5 X 10(-9) M. PAF also initiated significant chemotaxis of the cells; the half-maximal dose for this effect was approximately 1 X 10(-11) M. Taken together, these observations suggest that murine mononuclear phagocytes bear specific membrane receptors for PAF and that addition of PAF leads to generation of break-down products of polyphosphoinositides, subsequent changes in intracellular calcium and protein phosphorylation, and chemotaxis.

Inhibition of early platelet-derived growth factor responses in BALB/c-3T3 cells by interferon

Stimulation of total inositol phosphate production, alteration of cytosolic free calcium [( Ca++]i), vinculin disruption from adhesion plaques, and DNA synthesis caused by PDGF were examined in normal and INF pretreated density arrested BALB/c-3T3 fibroblasts. In normal cells, PDGF caused an increase in total inositol phosphates, a rapid, transient increase in [Ca++]i, disappearance of vinculin from adhesion plaques, and stimulation of DNA synthesis. Pretreatment of cells with INF inhibited PDGF-stimulated increases in [Ca++]i, vinculin disruption from adhesion plaques, and DNA synthesis, but had no effect on PDGF-induced increase in total inositol phosphate levels. These findings suggest that INF prevents entry of quiescent BALB/c-3T3 cells into G1 by inhibiting PDGF-induced release of Ca++ from intracellular stores.

Irreversible injury in anoxic hepatocytes precipitated by an abrupt increase in plasma membrane permeability

Using low-light digitized video microscopy, the onset, progression, and reversibility of anoxic injury were assessed in single hepatocytes isolated from fasted rats. Cell-surface bleb formation occurred in three stages over 1-3 h after anoxia. Stage I was characterized by formation of numerous small blebs. In stage II, small blebs enlarged by coalescence and fusion to form a few large terminal blebs. Near the end of stage II, cells began to swell rapidly, ending with the apparent breakdown of one of the terminal blebs. Breakdown of the bleb membrane initiated stage III of injury and was coincident with a rapid increase of nonspecific permeability to organic cationic and anionic molecules. On reoxygenation, stages I and II were fully reversible, and plasma membrane blebs were resorbed completely within 6 min of reoxygenation without loss of viability. Stage III, however, was not reversible, and no morphological changes occurred on reoxygenation. The results indicate that onset of cell death owing to anoxia is a rapid event initiated by a sudden increase of nonspecific plasma membrane permeability caused by rupture of a terminal bleb. Anoxic injury is reversible until this event occurs.

Chloral hydrate disrupts mitosis by increasing intracellular free calcium

In examining how chloral hydrate affects mitosis, we found that extracellular application of 0.1% chloral hydrate produced an abrupt rise in cytosolic free Ca2+. Digitized fluorescence microscopy of Fura-2-loaded, mitotic and interphase PtK cells revealed that Ca2+ rose 15 s after chloral hydrate application, peaked within 1 min at a concentration two- to sevenfold above the basal level and then slowly dropped. Bathing cells in 0.1% chloral hydrate caused metaphase spindles to shorten, starting in 1–2 min, and inhibited spindle elongation without affecting chromosome-to-pole movement during anaphase, as determined by phase-contrast observation of living cells. Spindle elongation and chromosome movement were unaffected by intracellular injection of 7.5% chloral hydrate. Extensive mitotic microtubule breakdown occurred after cells were bathed for 7 min in 0.1% chloral hydrate, while interphase microtubules were unaffected as determined by immunofluorescence. The chloral hydrate-induced microtubule breakdown and metaphase spindle shortening were prevented by 10 mM-CoCl2, which has previously been shown to block Ca2+ influx and to stabilize microtubules in vitro. These results imply that disruption of mitotic spindle function and structure by chloral hydrate is due to a rise in cytosolic free Ca2+, and also indicate that mitotic microtubules are more Ca2+-labile than interphase microtubules.

Calcium-induced assembly of adherens junctions in keratinocytes

Extracellular calcium concentration has been shown to control the stratification of cultured keratinocytes, presumably by regulation of formation of desmosomes. Previous studies have shown that keratinocytes cultured in medium containing 0.1 mM Ca++ form loose colonies without desmosomes. If the Ca++ is raised to 1 mM, desmosomes are assembled and the distribution of keratin filaments is altered. We have examined the disposition of vinculin and actin in keratinocytes under similar conditions. Using immunofluorescence microscopy we show that raising [Ca++] in the medium dramatically alters the distribution of vinculin and actin and results in the formation of adherens-type junctions within 15 min after switching to high calcium medium. Borders of cells at the edge of colonies, which are not proximal to other cells, are not affected, while cells in the interior of the colony form junctions around their periphery. Attachment plaques in keratinocytes grown in low calcium medium are located at the ventral plane of the cell, but junctions formed after switching to high calcium are not, as demonstrated by interference reflection microscopy. In cells colabeled with antibodies against vinculin and desmoplakin, vinculin-containing adherens junctions were visible before desmosomal junctions when cells were switched to high calcium. Although newly formed vinculin-containing structures in high calcium cells, like desmosomes, colocalize with phase-dense structures, superimposition of video fluorescence images using digitized fluorescence microscopy indicates that adherens junctions and desmosomes are discrete structures. Adherens junctions, like desmosomes, may play an essential role in controlling stratification of keratinocytes.

Effects of bacterial lipopolysaccharide on the hydrolysis of phosphatidylinositol-4,5-bisphosphate in murine peritoneal macrophages

LPS and lipid A initiated enhanced hydrolysis of PIP2 in macrophages. When murine peritoneal macrophages were labeled with [2-3H]myoinositol and stimulated with either LPS or lipid A, a rapid (within 10 sec) rise in Ins(1,4,5)P3 was observed. The breakdown pattern of Ins(1,4,5)P3 was complex; this included breakdown of Ins(1,4,5)P3 and formation of Ins(1,3,4,5)P4 (approximately 10 to 30 sec), and ultimately formation of Ins(1,3,4)P3 (approximately 60 sec). Within 10 sec after treatment, LPS caused an average increase of about fourfold to fivefold in Ins(1,4,5)P3, which declined over 5 min. When the total isomers of InsP3 were measured, levels rose about twofold in response to LPS or to lipid A and remained elevated for as long as 5 min. Lipid A, in the concentration range of 0.1 to 10 micrograms/ml, induced elevated intracellular levels of Ca2+ as quantified by fluorescence with Quin 2 or with Fura 2. When single, adherent Fura 2-loaded macrophages were treated with lipid A, basal levels of calcium rose over 10 sec from approximately 55 nM to almost 600 nM. LPS, paradoxically, did not cause such substantial increases in intracellular calcium (i.e., increases of approximately 26 nM) when judged by Fura 2 fluorescence. LPS treatment led to enhanced phosphorylation of a characteristic set of proteins, similar to those induced by stimulating protein kinase C (PKC) with phorbol myristate acetate as previously reported. The enhanced phosphorylation of pp28, pp33, and pp67 in macrophages was evident by 15 min and optimal by 30 min. Taken together, these observations indicate that LPS and lipid A cause increased breakdown of phosphatidylinositol 4,5-bisphosphate, which led to enhanced intracellular levels of calcium and also to enhanced protein phosphorylation, presumably mediated by PKC. The data thus suggest that one major intracellular signal transduction mechanism, initiated by LPS and lipid A in macrophages, is the rapid breakdown of PIP2.

Effects of bacterial lipopolysaccharide on the hydrolysis of phosphatidylinositol-4,5-bisphosphate in murine peritoneal macrophages

LPS and lipid A initiated enhanced hydrolysis of PIP2 in macrophages. When murine peritoneal macrophages were labeled with [2-3H]myoinositol and stimulated with either LPS or lipid A, a rapid (within 10 sec) rise in Ins(1,4,5)P3 was observed. The breakdown pattern of Ins(1,4,5)P3 was complex; this included breakdown of Ins(1,4,5)P3 and formation of Ins(1,3,4,5)P4 (approximately 10 to 30 sec), and ultimately formation of Ins(1,3,4)P3 (approximately 60 sec). Within 10 sec after treatment, LPS caused an average increase of about fourfold to fivefold in Ins(1,4,5)P3, which declined over 5 min. When the total isomers of InsP3 were measured, levels rose about twofold in response to LPS or to lipid A and remained elevated for as long as 5 min. Lipid A, in the concentration range of 0.1 to 10 micrograms/ml, induced elevated intracellular levels of Ca2+ as quantified by fluorescence with Quin 2 or with Fura 2. When single, adherent Fura 2-loaded macrophages were treated with lipid A, basal levels of calcium rose over 10 sec from approximately 55 nM to almost 600 nM. LPS, paradoxically, did not cause such substantial increases in intracellular calcium (i.e., increases of approximately 26 nM) when judged by Fura 2 fluorescence. LPS treatment led to enhanced phosphorylation of a characteristic set of proteins, similar to those induced by stimulating protein kinase C (PKC) with phorbol myristate acetate as previously reported. The enhanced phosphorylation of pp28, pp33, and pp67 in macrophages was evident by 15 min and optimal by 30 min. Taken together, these observations indicate that LPS and lipid A cause increased breakdown of phosphatidylinositol 4,5-bisphosphate, which led to enhanced intracellular levels of calcium and also to enhanced protein phosphorylation, presumably mediated by PKC. The data thus suggest that one major intracellular signal transduction mechanism, initiated by LPS and lipid A in macrophages, is the rapid breakdown of PIP2.

Epidermal growth factor stimulates the rapid accumulation of inositol (1,4,5)-trisphosphate and a rise in cytosolic calcium mobilized from intracellular stores in A431 cells

Exposure of A431 human epidermoid carcinoma cells to epidermal growth factor (EGF), bradykinin, and histamine resulted in a time- and concentration-dependent accumulation of the inositol phosphates (InsP) inositol monophosphate, inositol bisphosphate, and inositol trisphosphate (InsP3). Maximal concentrations of EGF (316 ng/ml; approximately 50 nM), bradykinin (1 microM), and histamine (1 mM) resulted in 3-, 6-, and 3-fold increases, respectively, in the amounts of inositol phosphates formed over a 10-min period. The K0.5 values for stimulation were approximately 10 nM, 3 nM, and 10 microM for EGF, bradykinin, and histamine, respectively. EGF and bradykinin stimulated the rapid accumulation of the two isomers of InsP3, Ins(1,3,4)P3, and Ins(1,4,5)P3 as determined by high performance liquid chromatography analysis; maximal accumulation of Ins(1,4,5)P3 occurred within 15 s. EGF and bradykinin also stimulated a rapid (maximal levels attained within 30 s after addition of hormone) and a sustained 4- and 6-fold rise, respectively, in cytosolic free Ca2+ levels as measured by Fura-2 fluorescence. EGF and bradykinin also produced a rapid, although transient, 3- and 5-fold increase, respectively, in cytosolic free Ca2+ after chelation of extracellular Ca2+ with 3 mM EGTA. These data are consistent with the idea that EGF elevates intracellular Ca2+ levels in A431 cells, at least in part, as a result of the rapid formation of Ins(1,4,5)P3 and the consequential release of Ca2+ from intracellular stores.

Blebbing, free Ca2+ and mitochondrial membrane potential preceding cell death in hepatocytes

Cell surface 'blebbing' is an early consequence of hypoxic and toxic injury to cells. A rise in cytosolic free Ca2+ has been suggested as the stimulus for bleb formation and the final common pathway to irreversible cell injury. Here, using digitized low-light video microscopy, we examine blebbing, cytosolic free Ca2+, mitochondrial membrane potential and loss of cell viability in individual cultured hepatocytes. Unexpectedly, we found that after 'chemical hypoxia' with cyanide and iodoacetate, cytosolic free Ca2+ does not change during bleb formation or before loss of cellular viability. Cell death was precipitated by a sudden breakdown of the plasma membrane permeability barrier, possibly caused by rupture of a cell surface bleb.

Platelet-derived growth factor-induced alterations in vinculin distribution in porcine vascular smooth muscle cells

Exposure of porcine vascular smooth muscle cells to platelet-derived growth factor (PDGF; 18-180 ng/ml) but not epidermal growth factor (EGF; 30 ng/ml), somatomedin C (SmC; 30 ng/ml), or insulin (10 microM), results in a rapid, reversible, time- and concentration-dependent disappearance of vinculin staining in adhesion plaques; actin-containing stress fibers also become disrupted following exposure of cells to PDGF. Disappearance of vinculin staining from adhesion plaques is also caused by 12-O-tetradecanoyl-phorbol-13-acetate (TPA; 200-400 nM), though the time course of the disappearance of vinculin staining under these conditions takes longer than in cells exposed to PDGF. The PDGF-induced removal of vinculin from adhesion plaques was inhibited in a concentration-dependent fashion by 8-(N,N-diethylamino) octyl-3,4,5-trimethoxybenzoate (TMB-8; 0.25-4 microM) and leupepetin (2-300 microM), and by n-alpha-tosyl-L-lysine chloromethylketone (TLCK; 100 microM) and trifluoperazine (TFP; 2.5 microM). Addition of PDGF to vascular smooth muscle cells caused a rapid, transient increase in cytosolic free calcium, from a basal resting level of 146 +/- 6.9 nM (SEM, n = 62) to 414 +/- 34 nM (SEM, n = 22) as determined using the calcium-sensitive indicator Fura-2 and Digitized Video Microscopy. This increase in cellular calcium preceded the disappearance of vinculin from adhesion plaques and was partially blocked by pretreatment of cells with TMB-8 but not leupeptin. This rise in cytosolic free calcium was found to occur in approximately 80% of the sample population and displayed both spatial and temporal subcellular heterogeneity. Exposure of cells to TPA (100 nM) did not result in a change in cytosolic free calcium. Both PDGF (20 ng/ml) and TPA (100 nM) caused cytosolic alkalinization which occurred after PDGF-induced disruption of vinculin from adhesion plaques, as determined using the pH-sensitive indicator BCECF and Digitized Video Microscopy. PDGF stimulated DNA synthesis and vinculin disruption in a similar dose-dependent fashion. Both could be inhibited by leupeptin or TMB-8. These results suggest that 1) exposure of vascular smooth muscle cells to PDGF is associated with the disruption of vinculin from adhesion plaques, 2) PDGF-induced vinculin disruption is regulated by an increase in cytosolic calcium (but not cytosolic alkalinization), and involves proteolysis; 3) activation of protein kinase C also causes vinculin removal from adhesion plaques but by a calcium-independent mechanism, and 4) the cellular response to PDGF-stimulated increases in cytosolic free calcium is heterogeneous.(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of deoxyribonucleic acid distribution in noncleaving oocytes from patients undergoing in vitro fertilization

The purpose of this study was to describe the quantity and distribution of deoxyribonucleic acid (DNA) in oocytes that did not fertilize or did fertilize and failed to cleave, from patients who underwent in vitro fertilization. Patients were selected with at least one cleaving egg, so that the sperm population was known to be fertile, and failure of fertilization or cleavage in the remaining oocytes could be attributed to nonspermatozoan factors. The noncleaving oocytes were classified into five categories, the majority of which (71%) lacked a polar body and any morphologically identifiable nucleus or germinal vesicle. Three general defects were found: failure to replicate the DNA properly; failure to package the DNA properly; and failure to organize the nuclear material properly after sperm penetration. It is concluded that either altered stimulation protocols or altered in vitro maturation conditions are needed to increase the average number of normal embryos available for transfer.

Identification of the cellular mechanisms responsible for platelet-derived growth factor induced alterations in cytoplasmic vinculin distribution

Exposure of quiescent density arrested BALB/c-3T3 cells (clone A31) to platelet-derived growth factor (PDGF; 6-12 ng/ml) results in a rapid, reversible, time- and dose-dependent removal of vinculin from adhesion plaques (Herman and Pledger, 1985). Potential cellular mechanisms involved in PDGF-induced removal of vinculin from adhesion plaques were examined. Removal of vinculin from adhesion plaques following exposure of cells to PDGF was temperature dependent, occurred in many fibroblast cell lines, and could be mimicked by 12-tetradecanoyl phorbol-13-acetate (TPA; 5-125 nM) or melittin (0.35 microM). Unlike the effect of PDGF, TPA- or melittin-induced vinculin disruption was not reversible. The removal of vinculin from adhesion plaques was inhibited by trifluoroperazine (TFP; 2.5 microM). 8-(N,N-diethylamino) octyl-3,4,5-trimethoxy benzoate (TMB-8; 1.0 microM), mepacrine (220 microM), n-alpha-p-tosyl-L-lysine chloromethylketone (TLCK; 100 microM), phenylmethoxysulphonylfluoride (PMSF; 500 microM), and epsilon-aminocaproic acid (epsilon-ACA; 100 microM); however, amiloride (100 microM), A23187 (20 microM), and chloroquine (1 mM) were unable to inhibit this effect. Melittin disruption of vinculin was inhibited by (in order of decreasing effectiveness) mepacrine greater than TMB-8 greater than TFP greater than leupeptin greater than PMSF, whereas A23187 and amiloride had no effect. The return of vinculin to adhesion plaques following PDGF treatment required de novo mRNA transcription and protein synthesis and was associated with PDGF-stimulated synthesis of vinculin. The observation that both PDGF- and melittin-induced removal of vinculin from adhesion plaques is inhibited by mepacrine suggests that phospholipase activation may be an early and important step in PDGF-induced disruption of vinculin from adhesion plaques. In addition, TFP, TMB-8 and protease inhibitor inhibition of both the PDGF and melittin effects on vinculin distribution, coupled with the finding that TPA can mimic the PDGF or melittin response, suggests that Ca2+, calmodulin, protein kinase C, and/or proteolysis may play an important role(s) in the removal of vinculin from adhesion plaques following PDGF addition. The lack of effect of A23187 addition on vinculin distribution suggests that alterations in cellular Ca2+ is necessary but not sufficient for vinculin removal from adhesion plaques.

[Instrumental esophageal perforation--its treatment and results]

The number of oesophagus perforations has increased considerably with the increase in endoscopic, diagnostic and therapeutic procedures. 46 instrumental oesophagus perforations have been observed between 1973 and 1984. The youngest patient was a 2-year-old girl with a benign oesophagus stenosis and the eldest was an 89-year-old man with a neoplasm of the cardia. The average age was 62 years. 26 patients were treated conservatively; 20 patients were treated surgically. In 2 cases the oesophagus was diverted at the cervical level and the cardia detached. 8 months later this was successfully reconstructed. 9 out of 43 patients died. In every case, the cause of death were cardio-pulmonal complications accompanying general sepsis.

[Esophagus perforation--treatment and results]

Esophageal perforation is most often caused by instrumental lesion during endoscopy. Mortality is still high; underlying malignant disease, septic complications and cardiopulmonary problems are endangering the patient. In small perforation with poor clinical symptoms, conservative treatment (i.e. antibiotics, gastric suction, parenteral nutrition) should be considered. We could treat in this way more than 50% of our cases. On the other hand, some patients require agressive surgical procedures, e.g. cervical esophagostomy gastrostomy and disconnection of esophageal continuity.

Binding and internalization of heparin by vascular smooth muscle cells

Previous work from our laboratory has demonstrated that heparin specifically inhibits the proliferation of vascular smooth muscle cells in vivo and in vitro. In this paper, we examine the binding and mode of internalization of heparin by smooth muscle cells. For these studies, radiolabeled and fluoresceinated (FITC) heparin probes were synthesized that retained their antiproliferative capacity. Binding of 3H-heparin to these cells occurs via specific, high-affinity binding sites (Kd = 10(-9) M, 100,000 binding sites per cell). Approximately 80% of the heparin bound to the cell surface was shed into the culture medium within 2 hr. The heparin that was left on the cell surface was internalized with biphasic kinetics. Approximately 50% of the bound material was internalized within 2 hr. After this initial rapid uptake, the rate slowed substantially, with the remaining heparin requiring 1-2 days to be internalized. Binding and uptake of FITC heparin was monitored using video image intensification fluorescence microscopy. When smooth muscle cells were exposed to FITC heparin at 4 degrees C, a diffuse surface staining pattern was observed. After warming the cells to 37 degrees C, intensely fluorescent vesicles were seen superimposed over the diffuse surface staining within 2 min. After 15 min at 37 degrees C, numerous large punctate vesicles were seen inside the cell. After 2 hr these vesicles had concentrated in the perinuclear region. This pattern of uptake, when considered along with the presence of specific, high-affinity binding sites and the initial rapid uptake of 3H-heparin, suggests that heparin enters smooth muscle cells by both receptor-mediated and other endocytic pathways.

Platelet-derived growth factor-induced alterations in vinculin and actin distribution in BALB/c-3T3 cells

Exposure of BALB/c-3T3 cells (clone A31) to platelet-derived growth factor (PDGF) results in a rapid time- and dose-dependent alteration in the distribution of vinculin and actin. PDGF treatment (6-50 ng/ml) causes vinculin to disappear from adhesion plaques (within 2.5 min after PDGF exposure) and is followed by an accumulation of vinculin in punctate spots in the perinuclear region of the cell. This alteration in vinculin distribution is followed by a disruption of actin-containing stress fibers (within 5 to 10 min after PDGF exposure). Vinculin reappears in adhesion plaques by 60 min after PDGF addition while stress fiber staining is nondetectable at this time. PDGF treatment had no effect on talin, vimentin, or microtubule distribution in BALB/c-3T3 cells; in addition, exposure of cells to 5% platelet-poor plasma (PPP), 0.1% PPP, 30 ng/ml epidermal growth factor (EGF), 30 ng/ml somatomedin C, or 10 microM insulin also had no effect on vinculin or actin distribution. Other competence-inducing factors (fibroblast growth factor, calcium phosphate, and choleragen) and tumor growth factor produced similar alterations in vinculin and actin distribution as did PDGF, though not to the same extent. PDGF treatment of cells for 60 min followed by exposure to EGF (0.1-30 ng/ml for as long as 8 h after PDGF removal), or 5% PPP resulted in the nontransient disappearance of vinculin staining within 10 min after EGF or PPP additions; PDGF followed by 0.1% PPP or 10 microM insulin had no effect. Treatment of cells with low doses of PDGF (3.25 ng/ml), which did not affect vinculin or actin organization in cells, followed by EGF (10 ng/ml), resulted in the disappearance of vinculin staining in adhesion plaques, thus demonstrating the synergistic nature of PDGF and EGF. These data suggest that PDGF-induced competence and stimulation of cell growth in quiescent fibroblasts are associated with specific rapid alterations in the cellular organization of vinculin and actin.

A time-lapse video image intensification analysis of cytoplasmic organelle movements during endosome translocation

Vital fluorescence staining has been used in conjunction with time-lapse video image intensification microscopy to analyze the distribution and movement of endosomes, lysosomes, and mitochondria in cultured rat ovarian granulosa cells. Exposure of 5-d granulosa cell cultures to pyrene-concanavalin A (P-Con A) or 3,3'-dioctadecylindocarbocyanine-labeled low-density lipoprotein (dil-LDL) at 4 degrees C results in the formation of randomly distributed endosomes 10 min after warming to 37 degrees C that exhibit saltatory motion for 20 min. If granulosa cells are labeled at 4 degrees C with both P-Con A and dil-LDL and warmed to 37 degrees C, both ligands are found within the same endosomes which migrate centripetally to the cell center where label accumulates within phase-dense structures by 60 min. The initial endosome saltations occur over short distances (mean distance = 4.6 micron) with a mean velocity of 0.03 micron/s. Endosome saltations then cease and are followed by a gradual centriptal migration of endosomes to the cell center where they accumulate and fuse with phase-dense structures. The second phase of movement involves a continuous, unidirectional migration of endosomes over distances ranging from 5 to 40 micron at a mean velocity of 0.05 micron/s. Lysosomes were simultaneously visualized as acridine orange-staining, phase-dense structures in control cells and cells exposed to fluorescent ligands. In untreated cells, lysosomes are dispersed throughout the cytoplasm and undergo bidirectional saltations covering a mean distance of 8.7 micron with a mean velocity of 0.3 micron/s. Lysosomes redistribute centripetally to the perinuclear region of the cell by saltatory movement within 20 min of exposure to ligand. Mitochondria were visualized with the fluorescent dye rhodamine 123 in granulosa cells labeled with P-Con A and were found to redistribute to the cell center coincident with endosomes. The microtubule-disrupting agent nocodazole was found to inhibit lysosome saltations and all phases of endosome movement. Taxol, a microtubule-stabilizing agent, partially impaired lysosome movement and led to a redistribution of lysosomes into linear aggregates surrounding the nucleus. Taxol was also found to inhibit endosome movement. The data indicate that (a) endosome movement proceeds initially by saltation and later by a nonsaltatory centripetal migration in association with mitochondria, that (b) lysosomes and endosomes undergo a temporally distinct but spatially similar change in cytoplasmic distribution, and that (c) microtubules are required for the directed translocation of endosomes and lysosomes towards the cell center.

Microtubule regulation of cell surface receptor topography during granulosa cell differentiation

A possible role for cytoplasmic microtubules in modulating lectin binding site topography has been examined during the hormone-directed differentiation of rat ovarian granulosa cells in vitro. Indirect immunofluorescence staining with anti-tubulin antibodies indicates that undifferentiated cultured granulosa cells contain a network of microtubules which radiate from the cell center to the cell periphery. Cultures induced to differentiate by a three day treatment with 1 microgram/ml prolactin exhibit a marginal distribution of microtubules and a centrally-located primary cilium. Prolactin enhances the incidence of granulosa cells containing a primary cilium from 9% in undifferentiated cultures to 53% in hormone-treated cultures. The pattern of lectin binding site redistribution induced by Concanavalin A (Con A) is also modified by prolactin treatment. In contrast to undifferentiated cells, which randomly endocytose fluorescein Con A, granulosa cells exposed to prolactin respond to fluorescein Con A by forming central surface caps to a greater extent (75%) than undifferentiated controls (25%). Double label fluorescence microscopy and transmission electron microscopy on Con A labeled cells show that caps form at central cell surface sites which contain the primary cilium. Disruption of cytoplasmic microtubules by colchicine, in undifferentiated granulosa cells, results in the formation of cell surface caps upon Con A addition. These data suggest that cytoplasmic microtubules modulate the topography of lectin bindings sites which is subject to hormonal control during the in vitro differentiation of ovarian granulosa cells.

In vivo and in vitro studies on the role of HMW-MAPs in taxol-induced microtubule bundling

The involvement of high molecular weight microtubule-associated proteins (HMW-MAPs) in the process of taxol-induced microtubule bundling has been studied using immunofluorescence and electron microscopy. Immunofluorescence microscopy shows that HMW-MAPs are released from microtubules in granulosa cells which have been extracted in a Triton X-100 microtubule-stabilizing buffer (T-MTSB), unless the cells are pretreated with taxol. 1.0 microM taxol treatment for 48 h results in microtubule bundle formation and the retention of HMW-MAPs in these cells upon extraction with T-MTSB. Electron microscopy demonstrates that microtubules in control cytoskeletons are devoid of surface structures whereas the microtubules in taxol-treated cytoskeletons are decorated by globular particles of a mean diameter of 19.5 nm. The assembly of 3 X cycled whole microtubule protein (tubulin plus associated proteins) in vitro in the presence of 1.0 microM taxol, results in the formation of closely packed microtubules decorated with irregularly spaced globular particles, similar in size to those observed in cytoskeletons of taxol-treated granulosa cells. Microtubules assembled in vitro in the absence of taxol display prominent filamentous extensions from the microtubule surface and center-to-center spacings greater than that observed for microtubules assembled in the presence of taxol. Brain microtubule protein was purified into 6 s and HMW-MAP-enriched fractions, and the effects of taxol on the assembly and morphology of these fractions, separately or in combination, were examined. Microtubules assembled from 6 s tubulin alone or 6 s tubulin plus taxol (without HMW-MAPs) were short, free structures whereas those formed in the presence of taxol from 6 s tubulin and a HMW-MAP-enriched fraction were extensively crosslinked into aggregates. These data suggest that taxol induces microtubule bundling by stabilizing the association of HMW-MAPs with the microtubule surface which promotes lateral aggregation.