scholarly journals Kinetochores capture astral microtubules during chromosome attachment to the mitotic spindle: direct visualization in live newt lung cells.

1990 ◽  
Vol 111 (3) ◽  
pp. 1039-1045 ◽  
Author(s):  
J H Hayden ◽  
S S Bowser ◽  
C L Rieder
Keyword(s):  
Light Microscopy ◽  
Mitotic Spindle ◽  
Dynamic Instability ◽  
Lung Cells ◽  
Polar Regions ◽  
Clear Area ◽  
Chromosome Attachment ◽  
Initial Interaction ◽  
Favorable Conditions ◽  
First Time

When viewed by light microscopy the mitotic spindle in newt pneumocytes assembles in an optically clear area of cytoplasm, virtually devoid of mitochondria and other organelles, which can be much larger than the forming spindle. This unique optical property has allowed us to examine the behavior of individual microtubules, at the periphery of asters in highly flattened living prometaphase cells, by video-enhanced differential interference-contrast light microscopy and digital image processing. As in interphase newt pneumocytes (Cassimeris, L., N. K. Pryer, and E. D. Salmon. 1988. J. Cell Biol. 107:2223-2231), centrosomal (i.e., astral) microtubules in prometaphase cells appear to exhibit dynamic instability, elongating at a mean rate of 14.3 +/- 5.1 microns/min (N = 19) and shortening at approximately 16 microns/min. Under favorable conditions the initial interaction between a kinetochore and the forming spindle can be directly observed. During this process the unattached chromosome is repeatedly probed by microtubules projecting from one of the polar regions. When one of these microtubules contacts the primary constriction the chromosome rapidly undergoes poleward translocation. Our observations on living mitotic cells directly demonstrate, for the first time, that chromosome attachment results from an interaction between astral microtubules and the kinetochore.

scholarly journals The nuclear-mitotic apparatus protein is important in the establishment and maintenance of the bipolar mitotic spindle apparatus.

1992 ◽  
Vol 3 (11) ◽  
pp. 1259-1267 ◽  
Author(s):  
C H Yang ◽  
M Snyder
Keyword(s):  
Mitotic Spindle ◽  
Polar Regions ◽  
Mitotic Apparatus ◽  
Structural Support ◽  
Microtubule Motors ◽  
Interphase Cells ◽  
Spindle Apparatus ◽  
Nuclear Mitotic Apparatus ◽  
Multicellular Organisms ◽  
First Time

The formation and maintenance of the bipolar mitotic spindle apparatus require a complex and balanced interplay of several mechanisms, including the stabilization and separation of polar microtubules and the action of various microtubule motors. Nonmicrotubule elements are also present throughout the spindle apparatus and have been proposed to provide a structural support for the spindle. The Nuclear-Mitotic Apparatus protein (NuMA) is an abundant 240 kD protein that is present in the nucleus of interphase cells and concentrates in the polar regions of the spindle apparatus during mitosis. Sequence analysis indicates that NuMA possesses an unusually long alpha-helical central region characteristic of many filament forming proteins. In this report we demonstrate that microinjection of anti-NuMA antibodies into interphase and prophase cells results in a failure to form a mitotic spindle apparatus. Furthermore, injection of metaphase cells results in the collapse of the spindle apparatus into a monopolar microtubule array. These results identify for the first time a nontubulin component important for both the establishment and stabilization of the mitotic spindle apparatus in multicellular organisms. We suggest that nonmicrotubule structural components may be important for these processes.

Petalomonas sphagnophila (Euglenophyta, Petalomonadales), a new euglenophyte species for Russia

2016 ◽  
Vol 50 ◽  
pp. 112-119
Author(s):  
D. A. Kapustin ◽  
D. A. Philippov ◽  
I. V. Sokolova ◽  
E. S. Gusev
Keyword(s):  
Light Microscopy ◽  
Original Publication ◽  
Raised Bog ◽  
Vologda Region ◽  
First Time

Petalomonas sphagnophila has been found for the first time in Russia from the Shichengskoe raised bog (Vologda Region). Morphology of the species is studied by means of light microscopy and illustrated by original micrographs. The data on its taxonomy, ecology and distribution are given. The name P. sphagnophila was not validly published because no type was indicated in the original publication (Christen, 1962), so we are validating the name by indicating its holotype. P. polytaphrena Skuja, nom. inval. is treated as a synonym of P. sphagnophila. Currently, thirty species of the genus Petalomonas, including P. sphagnophila, are known from Russia.

scholarly journals Motile kinetochores and polar ejection forces dictate chromosome position on the vertebrate mitotic spindle

1994 ◽  
Vol 124 (3) ◽  
pp. 223-233 ◽  
Author(s):  
CL Rieder ◽  
ED Salmon
Keyword(s):  
Mitotic Spindle ◽  
Constant Velocity ◽  
Molecular Mechanisms ◽  
Dynamic Instability ◽  
Microtubule Dynamic ◽  
Pole Motion ◽  
Microtubule Motors ◽  
Chromosome Position ◽  
Pulling Forces

We argue that hypotheses for how chromosomes achieve a metaphase alignment, that are based solely on a tug-of-war between poleward pulling forces produced along the length of opposing kinetochore fibers, are no longer tenable for vertebrates. Instead, kinetochores move themselves and their attached chromosomes, poleward and away from the pole, on the ends of relatively stationary but shortening/elongating kinetochore fiber microtubules. Kinetochores are also "smart" in that they switch between persistent constant-velocity phases of poleward and away from the pole motion, both autonomously and in response to information within the spindle. Several molecular mechanisms may contribute to this directional instability including kinetochore-associated microtubule motors and kinetochore microtubule dynamic instability. The control of kinetochore directional instability, to allow for congression and anaphase, is likely mediated by a vectorial mechanism whose magnitude and orientation depend on the density and orientation or growth of polar microtubules. Polar microtubule arrays have been shown to resist chromosome poleward motion and to push chromosomes away from the pole. These "polar ejection forces" appear to play a key role in regulating kinetochore directional instability, and hence, positions achieved by chromosomes on the spindle.

scholarly journals Structural Transitions at Microtubule Ends Correlate with Their Dynamic Properties in Xenopus Egg Extracts

2000 ◽  
Vol 149 (4) ◽  
pp. 767-774 ◽  
Author(s):  
Isabelle Arnal ◽  
Eric Karsenti ◽  
Anthony A. Hyman
Keyword(s):  
Dynamic Instability ◽  
Dynamic Properties ◽  
Microtubule Assembly ◽  
Two Dimensional ◽  
Egg Extracts ◽  
Xenopus Egg ◽  
Xenopus Egg Extracts ◽  
First Time ◽  
The Relationship ◽  
Dynamic Populations

Microtubules are dynamically unstable polymers that interconvert stochastically between growing and shrinking states by the addition and loss of subunits from their ends. However, there is little experimental data on the relationship between microtubule end structure and the regulation of dynamic instability. To investigate this relationship, we have modulated dynamic instability in Xenopus egg extracts by adding a catastrophe-promoting factor, Op18/stathmin. Using electron cryomicroscopy, we find that microtubules in cytoplasmic extracts grow by the extension of a two- dimensional sheet of protofilaments, which later closes into a tube. Increasing the catastrophe frequency by the addition of Op18/stathmin decreases both the length and frequency of the occurrence of sheets and increases the number of frayed ends. Interestingly, we also find that more dynamic populations contain more blunt ends, suggesting that these are a metastable intermediate between shrinking and growing microtubules. Our results demonstrate for the first time that microtubule assembly in physiological conditions is a two-dimensional process, and they suggest that the two-dimensional sheets stabilize microtubules against catastrophes. We present a model in which the frequency of catastrophes is directly correlated with the structural state of microtubule ends.

scholarly journals Petal and Sepal Epidermal Micromorphology of Six Lathyrus Taxa (Fabaceae) and their Systematic Value

2012 ◽  
Vol 40 (1) ◽  
pp. 35 ◽  
Author(s):  
Hüseyin CILDIR ◽  
Ahmet KAHRAMAN ◽  
Musa DOGAN
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Light Microscopy ◽  
Glandular Trichomes ◽  
Systematic Significance ◽  
Trichome Types ◽  
First Time ◽  
Scanning Electron

In this study, the epidermal types and their distribution on dorsal and lateral petals, the trichome types and their density on sepals of Lathyrus chloranthus, L. digitatus, L. laxiflorus subsp. laxiflorus, L. roseus subsp. roseus, L. sativus, and L. tuberosus, belonging to sections Lathyrus, Lathyrostylis, Pratensis, and Orobon of the genus Lathyrus in Turkey were investigated using light microscopy (LM) and scanning electron microscopy (SEM), and the systematic significance of these characters was evaluated. These taxa, except L. sativus, are studied for the first time under aspects of the petal and sepal micromorphology. Three major epidermal types were recognized on the petal: tabular rugose striate cells (TRS), areolate cells with more or less striations (AS), and papillose conical striate cells (PCS). TRS and AS were further subdivided into three subtypes. TRS was found on the dorsal and lateral petals of L. chloranthus, L. sativus, and L. tuberosus: the dorsal petals of L. roseus subsp. roseus and the lateral petals of L. laxiflorus subsp. laxiflorus, while AS was present on the dorsal and lateral petals of L. digitatus and the lateral petals of L. roseus subsp. roseus. PCS was found only on the dorsal petals of L. digitatus. Three main types of trichomes on the sepal were observed: peltate glandular, capitate glandular, and nonglandular trichomes. The capitate glandular and nonglandular trichomes were further subdivided into three subtypes. The peltate glandular trichomes were present only in L. chloranthus, but absent in the others. The capitate glandular trichomes were found in L. chloranthus, L. laxiflorus subsp. laxiflorus, L. roseus subsp. roseus, and L. tuberosus. The nonglandular trichomes were always present in L. chloranthus and L. laxiflorus subsp. laxiflorus. The present results show that the petal and sepal micromorphology can be used in delimitation of the taxa based on petal and sepal micromorphology.

scholarly journals Molecular-level evidence for marine aerosol nucleation of iodic acid and methanesulfonic acid

2021 ◽  
Author(s):  
An Ning ◽  
Ling Liu ◽  
Lin Ji ◽  
Xiuhui Zhang
Keyword(s):  
Molecular Level ◽  
Methanesulfonic Acid ◽  
Field Studies ◽  
Nucleation Mechanism ◽  
Polar Regions ◽  
Atmospheric Conditions ◽  
Iodic Acid ◽  
Quantum Chemical Approach ◽  
Marine Areas ◽  
First Time

Abstract. Both iodic acid (HIO3, IA) and methanesulfonic acid (CH3S(O)2OH, MSA) have been identified by field studies as important precursors of new particle formation (NPF) in marine areas. However, the mechanism of NPF in which IA and MSA are jointly involved is still unclear. Hence, we investigated the IA-MSA nucleation system under different atmospheric conditions and uncovered the corresponding nucleating mechanism at a molecular level for the first time using quantum chemical approach and Atmospheric Cluster Dynamics Code (ACDC). The findings showed that MSA can stabilize IA clusters via both hydrogen and halogen bonds. Moreover, the joint nucleation rate of IA-MSA system is significantly higher than that of IA self-nucleation, particularly in relatively cold marine regions with sparse IA and rich MSA. For the IA-MSA nucleation mechanism, in addition to self-nucleation of IA, the IA-MSA-involved clusters can also directly participate in the nucleation process, and their contribution is particularly prominent in the polar regions with rich MSA and sparse IA. The IA-MSA nucleation mechanism revealed in this work may help to elucidate some missing sources of marine NPF.

scholarly journals Pollen morphology of the Balkan-Carpathian endemic Campanula lingulata Waldst. & Kit. (Campanulaceae)

2016 ◽  
pp. 75-82
Author(s):  
Marina Macukanovic-Jocic ◽  
Snezana Jaric
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Light Microscopy ◽  
Endemic Species ◽  
Pollen Morphology ◽  
Average Length ◽  
Pollen Grains ◽  
Polar Axis ◽  
First Time ◽  
Scanning Electron

Palynomorphological characteristics of Campanula lingulata, the Balkan-Carpathian endemic species growing in Serbia, have been investigated using light microscopy and scanning electron microscopy for the first time, in order to provide some information helpful for a better understanding of the taxonomic position of this species within the genus, as well as to contribute to the pollen atlas of Serbian apiflora. The pollen grains are radially symmetrical, isopolar, 3-zonoporate and medium-sized monads oblate-sphaeroidal in shape. Mean of the polar axis (P) is 27.6?1.9 ?m, while the average length of the equatorial axis (E) is 28.8?1.6 ?m. The apertures are operculate. The sculpturing pattern of the exine is microre?ticulate-microechinatae. The exine surface is covered with evenly distributed supratectal spinules of variable length and sparse granules. The longest supratectal spinules are 0.64?0.05 ?m in length and the smallest sculptural elements are less than 0.2 ?m high. The microechinae density per sample area of 5 ?m x 5 ?m averages 17.4?2.4.

Patterns of Abnormal Myogenesis in Human Cleft Palates

1994 ◽  
Vol 31 (5) ◽  
pp. 345-350 ◽  
Author(s):  
Steven R. Cohen ◽  
Lynn L. Chen ◽  
Alphonse R. Burdi ◽  
Carroll-Ann Trotman
Keyword(s):  
Light Microscopy ◽  
Cleft Palate ◽  
Muscle Fiber ◽  
Soft Palate ◽  
Crown Rump Length ◽  
Levator Veli Palatini ◽  
Myotube Formation ◽  
Preliminary Study ◽  
Mesenchymal Condensation ◽  
First Time

To test the hypothesis that soft palate muscles are abnormal in cleft palate, we compared soft palate morphogenesis in fetuses with cleft palate (n=4) to age-matched (n=3) and nonmatched (n=1) control specimens. The morphologic status of all soft palate and masticatory structures were classified into one of six stages based on the level of histogenesis. At 54 mm crown-rump length (CRL), the levator veli palatini (L), palatopharyngeus (PP), and palatoglossus (PG) in cleft subjects demonstrated mesenchymal condensation into myoblastic fields, lagging behind the control specimens (97 mm CRL), which displayed definitive fields of myoblasts and myotube formation. In the 175 mm and 225 mm cleft and the 170 mm and 192 mm control specimens, muscular morphology was similar and had reached its postnatal appearance for the tensor veli palatini (175 m only) and L, PP, PG (225 mm only). Muscle fiber directions were, however, disoriented and disorganized, especially close to the medial epithelial edge of the cleft. The levator veli palatini, could not be distinguished as a discrete muscle in the cleft specimens, and what we believed to be the PP and PG seemed “normal” at the level of light microscopy, but malpositioned in a superior direction. This preliminary study demonstrates for the first time that early myogenesis in cleft palates differs from normal.

scholarly journals 2-(2-(4-Methoxyphenyl)-4,9-dimethyl-7-oxo-7H-furo[2,3-f]chromen-3-yl)acetic Acid

Molbank ◽  
10.3390/m1304 ◽  
2021 ◽  
Vol 2021 (4) ◽  
pp. M1304
Author(s):  
Boris V. Lichitsky ◽  
Andrey N. Komogortsev ◽  
Valeriya G. Melekhina
Keyword(s):  
Acetic Acid ◽  
High Resolution Mass Spectrometry ◽  
13C Nmr Spectroscopy ◽  
Acid Moiety ◽  
Acidic Media ◽  
New Approach ◽  
Multicomponent Condensation ◽  
Reaction Proceeds ◽  
Initial Interaction ◽  
First Time

For the first time, we describe a new approach towards the synthesis of previously unknown 2-(2-(4-methoxyphenyl)-4,9-dimethyl-7-oxo-7H-furo[2,3-f]chromen-3-yl)acetic acid. The presented method is based on the multicomponent condensation of 5-hydroxy-4,7-dimethyl-2H-chromen-2-one, 4-methoxyphenylglyoxal and Meldrum’s acid. It was shown that the studied reaction proceeds in two steps including the initial interaction of starting materials in MeCN and the final formation of furylacetic acid moiety in acidic media. The structures of the obtained compound were established by 1H, 13C-NMR spectroscopy and high-resolution mass spectrometry.

scholarly journals Dependence of the critical Richardson number on the temperature gradient in the mesosphere

2018 ◽  
Author(s):  
Michael N. Vlasov ◽  
Michael C. Kelley
Keyword(s):  
Temperature Gradient ◽  
Atmospheric Turbulence ◽  
Gravity Waves ◽  
Wind Shear ◽  
Richardson Number ◽  
Buoyancy Force ◽  
Dynamic Instability ◽  
Critical Richardson Number ◽  
Vertical Accelerations ◽  
First Time

Abstract. Maximum upper atmospheric turbulence results in the mesosphere from convective and/or dynamic instabilities induced by gravity waves. For the first time, by comparing the vertical accelerations induced by wind shear and the buoyancy force, it is shown that the critical Richardson number Ric can be estimated. Dynamic instability is developed for Ri 

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