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At least 19 recordsLinked to original sources
PubMed1976

Brbiturate spindle activity in the association cortex of the cat and its relation to spindle activity in the somatosensory system.

(1) Spontaneous barbiturate spindle activity was recorded simultaneously from nucleus ventralis poster-lateralis (VPL) of the thalamus, from the corresponding projection site in the primary somatosensory cortex (SI) and from the lateral (LAT) and middle suprasylvian (SSM) gyri. (2) Barbiturate spindles occurred more frequently in LAT and SSM than in the somatosensory cortex. Spindles in LAT and SSM were of longer duration than SI spindles while the intraspindle frequency was higher in spindles from the latter areas. The amplitude of the spindle waves was significantly higher in LAT and SSM than in SI. The largest spindle waves were recorded from the anterior part of LAT and SSM. (3) Barbiturate spindles recorded at various interelectrode distances were cross-correlated. In LAT and SSM the cross-correlation coefficients remained high up to an interelectrode distance of 4-5 mm while spindles recorded at this distance in SI gave low coefficients when cross-correlated. (4) Extensive removal of the somatosensory cortex had no effect on spindle formation in LAT or SSM. Furthermore, cutting of the cortico-cortical connections between two recording sites in either of these gyri produced no reduction in spindle wave synchrony between the recording sites. (5) Spindles in the VPL-SI only rarely started simultaneously with spindles in LAT and SSM. Those few coincident spindles which occurred were cross-correlated. The cross-correlation coefficients were invariably low suggesting that no wave synchrony existed between spindles in the VPL-SI system and those in the LAT and SSM.

Animals↗
PubMed1979

Micromanipulation studies of chromosome movement. I. Chromosome-spindle attachment and the mechanical properties of chromosomal spindle fibers.

We have used micromanipulation to study the attachment of chromosomes to the spindle and the mechanical properties of the chromosomal spindle fibers. Individual chromosomes can be displaced about the periphery of the spindle, in the plane of the metaphase plate, without altering the structure of the spindle or the positions of the nonmanipulated chromosomes. From mid-prometaphase through the onset of anaphase, chromosomes resist displacement toward either spindle pole, or beyond the spindle periphery. In anaphase a chromosome can be displaced either toward its spindle pole or laterally, beyond the periphery of the spindle; however, the chromosome resists displacement away from the spindle pole. When an anaphase half-bivalent is displaced toward its spindle pole, it stops migrating until the nonmanipulated half-bivalents reach a similar distance from the pole. The manipulated half-bivalent then resumes its poleward migration at the normal anaphase rate. No evidence was found for mechanical attachments between separating half-bivalents in anaphase. Our observations demonstrate that chromosomes are individually anchored to the spindle by fibers which connect the kinetochores of the chromosomes to the spindle poles. These fibers are flexible, much less extensible than the chromosomes, and are to pivot about their attachment points. While the fibers are able to support a tensile force sufficient to stretch a chromosome, they buckle when subjected to a compressive force. Preliminary evidence suggests that the mechanical attachment fibers detected with micromanipulation correspond to the birefringent chromosomal spindle fibers observed with polarization microscopy.

Animals↗
PubMed1975

Pressure-induced depolymerization of spindle microtubules. I. Changes in birefringence and spindle length.

Changes in birefringence retardation (BR) and length of Chaetopterus meiotic metaphase-arrested spindles produced by increased hydrostatic pressure were observed with polarized-light microscopy using a newly developed optical pressure chamber. Increased pressure produced rapid, reversible decreases in spindle BR and length. Pressures of 3,500 psi or higher at 22 degrees C caused complete disappearance of spindle BR within 3 min. Up to 6,000 psi, the rates of both BR decay and spindle shortening increased progressively with increasing pressure. At 6,000 psi or above, the BR decreased rapidly but there was no evidence of spindle shortening. The general observations are consistent with results of earlier classical experiments on effects of pressure on mitosis, and with experiments that used colchicine or low temperature as microtubule-depolymerizing agents. The kinetics of spindle depolymerization and repolymerization showed two phases: an initial phase of rapid decreases or increase in half-spindle microtubule BR; and a second phase of nearly constant BR during which most of the spindle shortening or growth occurs. BR is assumed to be directly related to the number of microtubules in a spindle cross section. It is hypothesized that microtubules in the spindle have different stabilities depending on the attachment of nonattachment of their ends. This hypothesis is used to explain the two phases of spindle depolymerization and repolymerization as well as several other observations.

Animals↗
PubMed1978

Evoked K-complexes and cardiovascular responses to spindle-synchronous and spindle-asynchronous stimulus clicks during NREM sleep.

The hypothesis that the functional role of the sleep spindle is to preserve sleep by inhibiting sensory input (Yamadori 1971) was examined. Series of 44 dB, 10 msec, 1000 c/sec 'clicks' were presented to 12 subjects at a 30-sec ISI during stage 2 sleep either during spindle bursts (i.e. spindle-synchronous clicks) or during interburst periods (i.e. spindle-asynchronous clicks). Contrary to the spindle inhibitory hypothesis, cortical EEG and cardiovascular responses showed no evidence of spindle 'suppression'. Evoked K-complexes were potentiated by the spindle-synchronous stimulation. A second study with 7 subjects replicated this result and extended the finding to include stage 3--4 sleep. It was suggested that the potentiation of evoked K-complexes was due to phasic reductions in inhibitory action during sleep spindles resulting in increased transmission of sensory events or, perhaps, an increase in the lability of certain EEG response systems.

Adolescent↗
PubMed1978

[Orientation of the cleavage spindles in pulmonate mollusks. I. The role of the form of the blastomeres in 2d cleavage spindle orientation].

In the normal two-celled embryos of various pulmonate molluscs, the orientation of spindles characteristic of metaanaphase is being frequently established gradually, in the process of transition from pro- to metaphase accompained by the growth of spindle and asters. The typical growth of contact zone between the blastomeres of the common pond snail embryos was inhibited to a different extent under their cultivation after the 1 cleavage division in the calcium-free media or after trypsinization. At the same time the orientation of meta-anaphase spindles was markedly affected (as judged by an angle alpha between the spindle axis and the plane of contact zone in the equatorial projection). When analyzing the model distributions of the angles between the two spindle axes (in the same projection), it was shown that the empirical distributions of these angles corresponded to the principle of stochastic combination of two alpha. A conclusion is drawn that the orientation of one spindle does not depend on that of another but the position of each of them depends on the size of the contact zone and, hence, on the general form of the adjacent blastomere region. Some other processes determining the spindle orientation are discussed.

Anaphase↗
PubMed1978

[Orientation of the cleavage spindles in pulmonate mollusks. II. The role of the architecture of the intercellular contacts in III and IV cleavage spindle orientation].

In the normal development of pulmonate molluscs, the variety of orientations of the III and IV cleavage spindles markedly reduces in the process of transition from pro- to meta- and anaphase. Even prior to the completion of spindle growth in these cleavage divisions the external faces of blastomeres become asymmetrical due to intercellular interactions but the whole system of external intercellular contacts (edges) is characterized by a certain symmetry. This symmetry coincides partially or fully with that of the system of definitive spindles. In the artificially obtained four-celled common pond snail embryos with the chain-like position of blastomeres, the III cleavage spindles were oriented at right angles to the polar axis, rather than in parallel with it (as in the normal development). The eight-celled embryos with symmetrical external faces of macromeres were also obtained. The variety of orientation of the IV cleavage definitive spindles in such embryos was markedly widened and in the macromeres with inverse asymmetry the inversion of the sign of declination of the spindles was observed. The spindle orientation depends, thus, on the form of adjacent region of the external face. This form as a whole is determined by the mutual position of blastomeres, curvature of surface and relative length of the face edges.

Anaphase↗
PubMed1976

[Muscle spindles in denervated and reinnervated m. soleus of the rat. I. Changes in number, distribution and length of muscle spindles].

After a transient or permanent unilateral denervation of the soleus muscle of the rat the number, distribution and length of muscle spindles were determined. The results were compared with those of the contralateral innervated muscle and with the data received from investigating soleus muscles of normal uninjured rats. Denervation (with or without reinnervation) reduces the number of muscle spindles by nearly 50%. The typical uniform distribution of muscle spindles in the muscle remains almost unchanged. The remaining muscle spindles grow longer. The same findings are observed in the contralateral still innervated muscles, too. Consequently a comparison of the denervated (reinnervated) muscle exclusively with its contralateral muscle does not show different counts of muscle spindles. Therefore in such investigations the contralateral muscle is of dubious value as a mean of control. As regards number, distribution and length of muscle spindles there exist only small differences between the various strains of rats.

Animals↗
PubMed1975

Pressure-induced depolymerization of spindle microtubules. II. Thermodynamics of in vivo spindle assembly.

The present experiments were designed to test whether the simple equilibrium assembly model proposed by Inoué could predict variations in spindle microtubule assembly in response to changes in hydrostatic pressure as it does for changes in temperature. The results were also analyzed according to a model based on nucleated condensation polymerization since this recently appears to be the mechanism by which purified brain microtubules are assembled in vitro. Equilibrium birefringence (BR) of the meiotic metaphase-arrested spindle was measured in vivo as a function of hydrostatic pressure and temperature in Chaetopterus oocytes using a miniature microscope pressure chamber. Increasing pressure in steps to 3,000 psi at temperatures below 22 degrees C did produce decreases in spindle equilibrium BR predictable directly from the simple equilibrium model of spindle assembly. Thermodynamic analysis of the pressure data yielded a value of delta V congruent to 400 ml/mol of polymerizing unit. Theoretical curves based on the nucleated condensation model can also be made to fit the data, but semilog plots of the dependence of the equilibrium constant versus pressure and versus reciprocal temperature are biphasic, suggesting that either the size of the polymerizing unit changes or more than one equilibrium constant governs the assembly reaction. That the same value of delta V, 90 ml/mol, was estimated from both the majority of the spindle BR data and data for the assembly of neural microtubules in vitro supports the possibility that spindle microtubules are assembled by a nucleated condensation mechanism.

Animals↗
PubMed1979

Actin in spindles of Haemanthus katherinae endosperm. II. Distribution of actin in chromosomal spindle fibres, determined by analysis of serial sections.

We have studied the arrangements of actin-containing filaments in 13 bundles of kinetochore microtubules in glycerinated, heavy meromyosin-treated Haemanthus endosperm cells: 7 bundles were in a cell at anaphase, and 6 were in a cell at metaphase. Actin-containing filaments were present in each of the 13 bundles of kinetochore microtubules: they were in amongst the microtubules in the bundle and seemed to be associated with the microtubules. Actin-containing filaments in each bundle seemed to terminate at the kinetochores. Actin-containing filaments associated with the kinetochore microtubules were of consistent polarity (the arrowheads pointed towards the kinetochores) whereas those associated with other microtubles and those not associated with microtubules did not have consistent polarity (some pointed towards the spindle pole, others pointed away from it). Roughly, there were as many individual stretches of actin-containing filaments identified per bundle of kinetochore microtubules as there were microtubules which terminated at the kinetochore. These data suggest that actin-containing filaments in spindles have a functional role. We used 2 glycerination procedures in our studies (one for each cell), and neither seemed to disrupt the basic microtubule arrangements: the arrangements of spindle microtubules seen after glycerination of Haemanthus endosperm were identical to those described previously by others in non-glycerinated glutaraldehyde-fixed Haemanthus endosperm. Thus we argue that spindle structure is not disrupted by the procedures, and therefore that the arrangements of actin-containing filaments are not artifacts of the glycerination procedures. The only difference between microtubules in glycerinated cells and microtubules in untreated cells is that there seem to be fewer in the glycerinated cells. The possible role of actin-containing filaments in the spindle is discussed.

Actins↗
PubMed1975

Behavior of spindles and spindle plaques in the cell cycle and conjugation of Saccharomyces cerevisiae.

The interdependence of spindle plaque with other aspects of cell division and conjugation in Saccharomyces cerevisiae has been investigated. Three forms of the spindle plaque appear sequentially before the formation of the complete, intranuclear spindle. The single plaque is present initially in the mitotic cycle; it becomes transformed into a satellite-bearing single plaque during the latter part of G1. Subsequently, plaque duplication yields the double plaque characteristic of the early phase of budding, which coincides with the period of chromosome replication (S). The eventual separation of these plaques to form a complete spindle, with a single plaque at each pole, is nearly coincident with the completion of S. The form of the plaque differs in two independent cases of G1 arrest: the single plaque is found in a cell in stationary arrest of growth, whereas a cell arrested by mating factors in preparation for conjugation contains a satellite-bearing single plaque. The latter form is retained during zygote formation, where it serves as the initial site of fusion of each prezygotic nuceus with the other. This fusion results in the formation of a single zygotic nucleus with a satellite-bearing single plaque, which is subsequently transformed into a double plaque as the zygote buds. The double plaque is situated adjacent to the site of bud emergence in both vegetative cells and zygotes.

Cell Division↗
PubMed1976

Spindle birefringence of isolated mitotic apparatus: further evidence for two birefringent spindle components.

We studied sea-urchin zygote mitotic apparatus (MA) isolated in hexylene glycol, transferred immediately to a glycerol-dimethylsulphoxide medium, and stored for 2 weeks at room temperature. Treatment with 0-5 M KC1 caused loss of 45% of the birefringence, but microtubules remained intact (as seen electron microscopically in glutaraldehyde-fixed MA), and tubulin was not extracted (as determined by polyacrylamide gel electrophoresis). These results suggest that a non-tubulin component which is extracted by the KC1 contributes 45% of the MA birefringence. Further evidence for this conclusion came from indirect immunofluorescence experiments. Non-extracted (control) MA were fixed with formaldehyde and reacted with antibody against tubulin; there was intense staining of the spindle fibres and astral rays. Electron microscopically, however, microtubules were not present in formaldehyde-fixed MA. Since formaldehyde fixation caused breakdown of microtubules but the tubulin remained in the MA (as judged by reaction with antibodies) we suggest that after microtubule breakdown the tubulin remains in the MA because it is bound to a peri-microtubule spindle component (which we call 'substance gamma'). When KCl-extracted MA were fixed with formaldehyde and reacted with antibody against tubulin there was very little staining of spindle fibres and astral rays. Electron microscopically, formaldehyde caused microtubule breakdown, and since the tubulin is lost from formaldehydefixed, KC1-extracted MA (as judged by reaction with antibodies), we suggest that the tubulin-binding component, substance gamma, is extracted by the 0-5 M KC1. Pressure treatment caused the asters not to stain with antibody against tubulin, suggesting that the stability of substance gamma is different in different regions of the mitotic apparatus.

Animals↗
PubMedDate not supplied

An automatic spindle analysis and detection system based on the evaluation of human ratings of the spindle quality.

An evaluation of the spindle quality ranked by experienced human raters is described. The pattern discriminating criteria obtained from this evaluation are used for an automatic system based on the complex demodulation method. The performance of this automatic system is compared with both the human visual scoring and with a second automatic system employing phaselocked loop techniques. The performance of the complex demodulation is satisfactory. It also detects spindles buried in slow waves. It is not sensitive to the age of the subject. This method opens possibilities for research of either temporal or chemical (drugs etc.) effects on the characteristics of rhythmic activity, without being hampered by the arbitrary EEG jargon "alpha" or "sigma".

Adult↗
PubMed1976

A spindle cell varient of thymic carcinoid tumor. A clinical, histologic, and fine structural study with emphasis on its distinction from spindle cell thymoma.

We describe the clinical, histologic, and fine structural features of two thymic carcinoid tumors that had a major spindle cell component, and present the reason for classifying our two cases as variants of thymic carcinoid tumors. These tumors pursued an aggressive clinical course, demonstrated histologic features such as vascular invasion and mitotic activity, ultrastructurally contained numerous dense-core granules, and lacked prominent tonofilaments and well-formed desmosomes. Radiotherapy, even for apparently encapsulated cases, may be indicated for this aggressive mediastinal neoplasm, which can be clearly separated from the thymoma by clinical, histologic, and fine structural criteria.

Adult↗
PubMed1978

Analysis of the distribution of spindle microtubules in the diatom Fragilaria.

The spindle of the colonial diatom Fragilaria contains two distinct sets of spindle microtubules (MTs): (a) MTs comprising the central spindle, which is composed of two half-spindles interdigitated to form a region of "overlap"; (b) MTs which radiate laterally from the poles. The central spindles from 28 cells are reconstructed by tracking each MT of the central spindle through consecutive serial sections. Because the colonies of Fragilaria are flat ribbons of contiguous cells (clones), it is possible, by using single ribbons of cells, to compare reconstructed spindles at different mitotic stages with minimal intercellular variability. From these reconstructions we have determined: (a) the changes in distribution of MTs along the spindle during mitosis; (b) the change in the total number of MTs during mitosis; (c) the length of each MT (measured by the number of sections each traverses) at different mitotic stages; (d) the frequency of different classes of MTs (i.e., free, continuous, etc.); (e) the spatial arrangement of MTs from opposite poles in the overlap; (f) the approximate number of MTs, separate from the central spindle, which radiate from each spindle pole. From longitudinal sections of the central spindle, the lengths of the whole spindle, half-spindle, and overlap were measured from 80 cells at different mitotic stages. Numerous sources of error may create inaccuracies in these measurements; these problems are discussed. The central spindle at prophase consists predominantly of continuous MTs (pole to pole). Between late prophase and prometaphase, spindle length increases, and the spindle is transformed into two half-spindles (mainly polar MTs) interdigitated to form the overlap. At late anaphase-telophase, the overlap decreases concurrent with spindle elongation. Our interpretation is that the MTs of the central spindle slide past one another at both late prophase and late anaphase. These changes in MT distribution have the effect of elongating the spindle and are not involved in the poleward movement of the chromosomes. Some aspects of tracking spindle MTs, the interaction of MTs in the overlap, formation of the prophase spindle, and our interpretation of rearrangements of MTs, are discussed.

Cell Cycle↗
PubMed1979

Chromosome movement and spindle birefringence in locally heated cells: interaction versus local control.

A microheater was used to produce a temperature gradient within the mitotic spindle of living cells. The slope of the temperature gradient was estimated from thermal conductivity calculations and confirmed by measurements of spindle birefringence and by experiments on striated muscle. When the microheater was placed at one spindle pole or at one group of kinetochores, the gradient was steep enough to cause a large difference in birefringence between the two half-spindles, but the velocity of chromosome movement in anaphase was nearly the same in the warmer and cooler half-spindles. When the heater was shifted from the pole toward the interzone, the average velocity of chromosome movement increased approximately two-fold but was, again, nearly uniform in the two half-spindles. The rate of spindle elongation was especially sensitive to the site of heating, increasing ten-fold when the heater was shifted from the pole to the interzone. Regardless of heater position, the rate of chromosome movement was determined largely by the temperature of the coolest spindle region--chromosomes in the warmer half-spindle moved more slowly than expected from estimates of the temperature in that region. Since the microheater produces a substantial temperature gradient within the spindle, the near uniformity of chromosome velocity in both half-spindles must be due to some biological property of the spindle. Two very different explanations for the results are considered the most likely. According to one explanation, the near uniformity of velocity in both half-spindles is determined by the structure of the interpolar spindle, while changes in velocity involve force producers located both in the half-spindles and in the interzone. On the other explanation, the velocity is nearly the same in both half-spindles because the force producers are located exclusively in the interzone (Margolis et al., 1978).

Anaphase↗