Direct evidence for a colchicine-induced impairment in the mobility of membrane components

Colchicine increases hepatic alkaline phosphatase activity

In vivo administration of colchicine increases the activity of alkaline phosphatase significantly in the livers of rats. Prior treatment with cycloheximide prevented the induction of the enzyme by colchicine suggesting that de novo protein synthesis was essential for the effect of colchicine on alkaline phosphatase activity. Bilateral adrenalectomy did not affect the response of alkaline phosphatase following the administration of colchicine. This indicates that the rise in the level of alkaline phosphatase in liver caused by colchicine is not secondary to the release of glucocorticoids.

Smooth muscle sensitization induced by colchicine: is it an in vitro property of antitubulin agents?

Colchicine 0.1 microgram/ml induces a reversible increase of guinea-pig isolated ileum contractions (50 to 60% of maximal contractions) to acetylcholine, nicotine and PGE2. At 1 microgram/ml, it induces an irreversible increase of similar contractions to acetylcholine and 5-hydroxytryptamine. Low concentrations of indomethacin are able to reduce or even to abolish this increase. This smooth muscle sensitization could be related to the ability of colchicine to stimulate prostaglandin biosynthesis. Vinblastine has been described to induce a similar in vitro sensitization of guinea-pig isolated ileum. This effect might be also a non-specific property of antitubulin agents. The relationships between such an in vitro sensitization and the clinical effects of colchicine, including diarrhea, remain unclear.

Inhibition of the rapid movement of optically detectable axonal particles colchicine and vinblastine

The rapid saltatory motion of intra-axonal particles detected by dark-field microscopy in myelinated axons isolated from sciatic nerves of adult Xenopus laevis was inhibited by colchicine or vinblastine at a concentration of larger than or equal to 0.1 mM. Both the predominant somatopetal transport and the somatofugal transport of these round particles were inhibited. The reduction in numbers of moving particles was apparent first in the juxtanodal portions of the isolated axons within about 1 h. No particles could be detected moving by 3-5 h after application of the colchicine or vinblastine. During the phase of partial inhibition, those particles that were still progressing along the axon did so at apparently normal velocities while they were in motion, but remained stationary increasingly frequently and for progressively longer periods. Colchicine or vinblastine at a concentration of less than or equal to 10 micronM caused no observable inhibition within 4 h of application. Colchicine at a concentration of larger than or equal to 10 mM caused local accumulation of round particles, and vinblastine at a concentration of larger than or equal to 2.5 mM caused fragmentation of rod-shaped organelles, believed to be mitochondria. Electron microscopy of nerve fibers treated with 5 mM colchicine showed a progressive loss of microtubules from the axoplasm, such that approximately 70% of the microtubules had disappeared after 4h.

Membrane anomalies of neoplastic cells

Neoplastic cells exhibit numerous membrane anomalies. Those involving the plasma membrane have attracted the greatest attention, although ample evidence indicates that the membranes of mitochondria, endoplasmic reticulum and lysosomes are also profoundly implicated. The information on these topics is briefly reviewed and it is concluded that of the multiple membrane anomalies observed, those responsible for high aerobic lactate production, abnormal plasma membrane transport and release of hydrolytic enzymes may figure prominently in malignant behaviour, i.e. invasiveness and metastasis. It is proposed that the membrane polymorphism of neoplastic cells can be explained in terms of the Changeux membrane lattice hypothesis. In particular it is suggested that the concerted behaviour of tumor cell membranes might deviate from normal due to one or more of the following processes: (a) insertion of a new protein (or lipid); (b) alteration of existing proteins (or lipids); (c) change in the proportion of phospholipid; (d) change in the proportion of glycolipid; (e) change in the proportion of cholesterol; (f) change in the steady-state of membrane ligands. The validity of this proposal is evaluated in terms of recent advances in membrane molecular biology.

Effect of colchicine and vinblastine on crayfish neuromuscular junction

1. The effect of the microtubule disrupting agents colchicine and vinblastine was studied on crayfish excitatory neuromuscular transmission. 2. Colchicine, in concentrations of 1-3 mM, brought about a decrease in the amplitudes of intracellularly recorded excitatory junctional potentials (ejps). Vinblastine, in concentrations of 0.08-0.32 mM, increased the amplitudes of ejps. 3. Drug-induced alterations in ejp amplitude resulted from changes in quantal content of the excitattory nerve as determined by extracellular recording. The effect could not be explained by changes in quantal size. 4. The effect of colchicine and vinblastine does not appear to be related to an action on microtubules.

Functional and structural changes in mammalian sympathetic neurones following colchicine application to post-ganglionic nerves

1. The effects of post-ganglionic colchicine application on neurones of the guinea-pig superior cervical ganglion were studied with intracellular recording and electron microscopy. 2. Local colchicine application for 30 min to one of the major post-ganglionic nerves caused several electrophysiological changes after 4-7 days in many neurones whose axons run in this nerve. These changes include: (a) a reduction in the amplitude of synaptic potentials elicited by supramaximal preganglionic stimulation; (b) a decrease in the number of preganglionic fibres innervating individual neurones; (c) the development of regenerative responses in dendrites; and (d) the failure of antidromic action potentials to fully invade the neuronal soma. These functional changes occurred in the absence of impaired impulse conduction or axon degeneration, and were not observed in nearby neurones whose axons ran in an untreated post-ganglionic nerve. The effects of colchicine are similar to the changes produced by axotomy. 3. Counts of synapses in thin sections from the region of the ganglion where the affected neurones were located showed a reduction, compared to the number of synapses in other regions of the colchicine treated ganglia, or normal control ganglia. This finding indicates that synaptic depression after colchicine treatment, like that after axotomy, is due primarily to a loss of synaptic contacts from the dendrites of affected nerve cells. Unusual profiles containing numerous vesicular and tubular organelles frequently seen after interruption of the axons were also observed in thin sections after colchicine treatment. 4. The similarity of the electrophysiological and ultrastructural effects of colchicine treatment and axon interruption offers further support for the view that synaptic contacts on sympathetic neurones are normally regulated by an interaction of the neuronal soma with its axonal extension to the periphery.

Surface architecture of the plant cell: biogenesis of the cell wall, with special emphasis on the role of the plasma membrane in cellulose biosynthesis

Cell wall structure and biogenesis in the unicellular green alga, Oocystis apiculata, is described. The wall consists of an outer amorphous primary layer and an inner secondary layer of highly organized cellulosic microfibrils. The primary wall is deposited immediately after cytokinesis. Golgi-derived products contribute to this layer. Cortical microtubules underlie the plasma membrane immediately before and during primary wall formation. They function in maintaining the elliptical cell shape. Following primary wall synthesis, Golgi-derived materials accumulate on the cell surface to form the periplasmic layer. This layer functions in the deposition of coating and cross-linking substances which associate with cellulosic microfibrils of the incipient secondary wall. Secondary wall microfibrils are assembled in association with the plasma membrane. Freeze-etch preparations of untreated, living cells reveal linear terminal complexes in association with growing cellulosic microfibrils. These complexes are embedded in the EF fracture face of the plasma membrane. The newly synthesized microfibril lies in a groove of the outer leaflet of the plasma membrane. The groove is decorated on the EF fracture face by perpendicular structures termed "ridges". The ridges interlink with definitive rows of particles associated withe PF fracture face of the innter leaflet of the plasma membrane. These particles are termed "granule bands", and they function in the orientation of the newly synthesized microfibrils. Microfibril development in relation to a coordinated multienzyme complex is discussed. The process of cell wall biogenesis in Oocystis is compared to that in higher plants.

Membranes of Tetrahymena. IV. Isolation and characterization of temperature-responsive smooth and rough microsomal subfractions

Temperature-responsive microsomes of the ciliate protozoan Tetrahymena have been originally fractionated by step centrifugation on two-layered, Mg2+-containing sucrose gradients. Three fractions have been obtained, which are termed smooth I, smooth II and rough according to the appearance of the membrane vesicles upon electron-microscopy. Smooth I, smooth II, and rough microsomes exhibit RNA/protein ratios of 0.09, 0.20, and 0.34; their phospholipid/protein ratios and their neutral lipid/phospholipid ratios were 0.52, 0.43 and 0.25, and 0.17, 0.18 and 0.13, respectively. All three fractions contain equivalent, low succinic dehydrogenase and 5'-nucleotidase activities. Glucose-6-phosphatase and acid phosphatase are more concentrated in smooth I membranes than in rough membranes. The reverse is true for ATPase. The smooth II membranes occupy an intermediate position except that their ATPase activity is the lowest of the three fractions. The specific activities of these enzymes of the three microsomal fractions are compared to those of homogenates of whole cells. Thin-layer chromatography reveals a very similar polar and nonpolar lipid pattern of the three microsomal fractions. The major phospholipid compounds are phosphatidlethanolamine, glycerideaminoethylphosphonate and phosphatidylcholine, while diglycerides, an unknown NL-compound, and triglycerides are the major apolar lipids. Gas liquid chromatography shows that the fatty acids are mainly even-numbered ranging between C12 and C18. The smooth I, smooth II and rough membranes contain 65.2, 69.3 and 72.7% unsaturated fatty acids in their polar lipids, whereas only 52.7, 49.7 and 48.3% unsaturated acids are found in their apolar lipids, respectively. The fatty acids are more unevenly distributed among the individual polar lipids than in the apolar ones.

Colchicine administration to mice: a metabolic and ultrastructural study

A single injection of colchicine has been administered to normal albino mice, and the metabolic effects as well as the hepatic ultrastructural changes resulting from this treatment have been studied at various time intervals. A marked decrease in circulating triglyceride levels was evident 4 hours after colchicine injection and was maximum after 11 hours. It coincided with a marked increase in hepatic triglyceride content. Twenty hours after colchicine administration, plasma triglyceride levels and hepatic triglyceride content had returned to normal values. Similar changes in the levels of circulating proteins were observed although their magnitude was less than that observed for triglycerides. Ultrastructurally, colchicine treatment resulted in the virtual disappearance of the microtubules from the hepatocytes, and in the appearance of many clusters of vesicles containing very low density lipoprotein-like particles which eventually transformed into lipid droplets. These ultrastructural alterations were also completely reversible, the reversibility coinciding with the morphological reappearance of microtubules. Finally, colchicine treatment resulted in marked metabolic changes that are interpreted as representing an attempt, by the organism, to keep adequate energy sources during the period of lack of circulating triglycerides.

Reversal of morphological differentiation of mouse neuroblastoma cells by mitosis-inhibitors and anesthetics

Differentiated mouse neuroblastoma cells (C 1300) were exposed to various mitosis-inhibitors (vinblastine, colchicine and griseofulvin) and substances with anesthetic action (lidocaine, tetracaine, chlorpromazine and sodium dodecyl sulphate). All the drugs caused rapid retraction of the neurites, which was reversible in all cases but for sodium dodecyl sulphate, and showed a sigmoid dose-response relationship. The two groups of substances caused morphologically similar effects in that the microtubules disappeared and the intracellular orientation was lost. The order of potency of the anesthetics corresponded to their efficiency to cause nerve-block and antihemolysis as reported by others. Colchicine, griseofulvin, lidocaine and chlorpromazine were tested for effects of agglutination of undiffentiated cells. They inhibited agglutination at doses that were only slightly higher than those causing neurite retraction. The possibility of a close relationship between the cell membrane and microtubule system will be considered.

A reduction in energy-dependent amino acid transport by microtubular inhibitors in Ehrlich ascites tumor cells

Vincristine, other periwinkle alkaloids, and colchicine partially inhibit the energy dependent transport of alpha-aminoisobutyric acid in Ehrlich ascites tumor cells. The properties of this phenomenon were characterized in detail for vincristine. Maximum depression of the steady-state intracellular alpha-aminoisobutyric acid level was achieved with a vincristine concentration of less than 0.5 muM. The inhibitory effect of vincristine increases as the extracellular alpha-aminoisobutyric acid concentration is increased reaching a maximum, however, of only approximately to 25% at a level of 5 mM, leaving a large gradient for alpha-aminoisobutyric acid across the cell membrane. Vincristine produced an asymmetrical uptake rate, while increasing the efflux of alpha-aminoisobutyric acid. Inhibition of net alpha-aminoisobutyric acid transport by vincristine was partially reversible (approximately to 40%). Colchicine (50 muM) reduced the steady-state alpha-aminoisobutyric acid level by 30%, an effect that was not reversible. Inhibition by vinleurosine and vinrosidine was comparable to that of vincristine. Addition of glucose to the medium resulted in a small, but significant, decrease in the inhibitory effects of both vincristine and colchicine. The data indicate that these agents inhibit a small component of the uphill transport of alpha-aminoisobutyric acid in Ehrlich ascites tumor cells. The inhibitory effect of vincristine cannot be attributed to an increase in the passive permeability of the cell membrane to this agent. Rather, the data along with other studies from this laboratory suggest that vincristine reduces the energy-dependent transport of alpha-aminoisobutyric acid by either inhibiting cellular energy metabolism or by inhibiting cellular energy metabolism or by inhibiting the coupling of energy-metabolism to the transport of this amino acid and raises the possibility that cellular microtubules play a role in these processes.

Modulation of the distribution of plasma membrane intramembranous particles in contact-inhibited and transformed cells

The intrinsic organization of the plasma membrane differs in normal and transformed cells. With the technique of freeze fracture and electron microscopy contact inhibited 3T3 cells have been shown to contain aggregated plasma membrane intramembranous particles, while transformed cells demonstrate a uniform particle distribution. The distribution of intramembrous particles in transformed cells can be affected by colchicine or vinblastine which induces a dose- and time-dependent particle aggregation. These observations suggest that microtubules and other membrane-associated colchicine-sensitive proteins probably influence the distribution of intrinsic membrane proteins and intramembranous particles in nucleated mammalian cells. An aggregated particle distribution has been observed in 3T3 cells or colchicine-treated transformed cells frozen in media, phosphate-buffered saline or following brief exposure to glycerol, sucrose or dimethyl sulfoxide containing solutions, independent of whether specimens were rapidly frozen from 37 degrees C, room temperature or 4 degrees C incubations. Cells briefly stabilized in 1% formaldehyde yields similar patterns of particle distribution as cells rapidly frozen in media or cryoprotectants. Glutaraldehyde fixation of cells, however, appears to alter the fracturing process in these cells, as visualized by an altered fracture face appearance, decreased numbers of particles, and no particle aggregates. Differences in membrane organization between normal and transformed cells have therefore been demonstrated using a series of preparative methods and colchicine and vinblastine have been shown to modulate intramembranous particle distribution in transformed 3T3 cells.

Evidence for endocytotic uptake of cobra neurotoxin in mouse skeletal muscle

An isolated 3H-labelled neurotoxin from Naja naja siamensis binds irreversibly to the extensor digitorum longus muscle of the mouse in vitro. The binding consists of an adsorption to cholinergic receptors and of a slower temperature sensitive binding mechanism. The slow binding is markedly stimulated by the presence of cationic proteins (protamine, histone and polylysine) and is blocked at low temperature (+4 degrees C). Vinblastine and colchicine inhibit the stimulatory effect of protamine on the slow binding. Unlabelled neurotoxin blocks the adsorption binding but fails to affect the slow binding. The results suggest that the slow binding of neurotoxin is not associated with the presence of cholinergic receptors but is the result of endocytotic uptake into the muscle cell. Unless properly recognized this uptake will give a considerable overestimate of the number of cholinergic receptors present in the muscle.

Prophase chromosome movements in living house cricket spermatocytes and their relationship to prometaphase, anaphase and granule movements

Chromosome and granule movements in meiotic prophase and prometaphase have been studied by time-lapse cinemicrography in live spermatocytes of the house cricket, Acheta domesticus. Chromosome movements in prophase cells, up to one hour or more before breakdown of the nuclear envelope, are described. These movements are frequent but saltatory; are based mostly at chromosome ends but also at kinetochores; occur in very intimate association with the inside of the nuclear envelope; are directed towards and away from the extranuclear centres (centrioles); tend weakly to accumulate bivalents round the two centres and reach a velocity of 0.65 micron/sec. Saltatory movements in granules associated with extranuclear asters are remarkably similar to basic characteristics to the intranuclear chromosome movements. Surprisingly, the chromosome movements (and those granules) are reversably blocked by colcemid (but not lumi-colcemid), and yet occur in the apparent absence of an intranuclear envelope. However, kinetochore movements in very early prometaphase are similar in velocity and other respects to prophase movements; later prometaphase movements are clearly slower, and those of anaphase very much slower still. -The prophase movements suggest a two component model for motion: a non-microtubule, linear force producer together withrotubules with a skeletal, orientational role. Arguably, both these components are also necessary for chromosome movements in prometaphase and anaphase.

Colchicine-induced inhibition of lipoprotein and protein secretion into the serum and lack of interference with secretion of biliary phospholipids and cholesterol by rat liver in vivo

Rats were injected with colchicine and the secretion of triglycerides into the serum was studied for 90 min after injection of [(14)C]palmitic acid and Triton WR 1339. The release of labeled and chemically determined triglyceride was reduced to about 20-30% of control values. The effect of colchicine on serum triglyceride levels was not dependent on the presence of Triton and was similar in males and females and in fed and fasted rats. The effect was dose dependent and was reversible 6-7 h after injection of 0.05 mg/100 g body weight. Colchicine inhibited also the release of labeled proteins into the serum but did not affect the amount of [(3)H]leucine incorporated into liver proteins. Within 4 h of colchicine treatment there was an 80% fall in serum very low density lipoproteins (VLDL), a 30% fall in serum high density lipoproteins (HDL), and no change in the d > 1.21 protein level, but reduction in the appearance of labeled proteins was encountered in all serum fractions. Colchicine had no effect on the rate of bile flow and on the secretion of phospholipids and cholesterol into the bile. In the hepatocyte there was accumulation of Golgi-derived secretory vesicles, containing nascent VLDL particles; these vesicles were seen also in the vicinity of the sinusoidal cell surface, but the space of Disse contained few or no VLDL particles. There was an apparent reduction in microtubules and some increase in microfilaments. It is suggested that microtubules affect the secretion of lipoproteins and proteins into the serum by maintaining the organization of the plasma membrane required for its fusion with secretory vesicles. The lack of effect of colchicine on biliary lipid secretion indicates that the latter is not dependent on vesicular transport.