scholarly journals Microtubules and control of macronuclear ‘amitosis’ in Paramecium

1980 ◽  
Vol 44 (1) ◽  
pp. 135-151
Author(s):  
J.B. Tucker ◽  
J. Beisson ◽  
D.L. Roche ◽  
J. Cohen
Keyword(s):  
Spatial Relationship ◽  
Longitudinal Axis ◽  
Nuclear Shape ◽  
Dorsal Cortex ◽  
Spatially Correlated ◽  
Sliding Mechanism ◽  
Intranuclear Microtubules ◽  
Oriented Parallel ◽  
And Control ◽  
Macronuclear Division

The ‘amitotic’ division of the macronucleus during binary fission in P. tetraurelia includes a detailed sequence of shape changes that are temporally coordinated with the adoption of a series of well-defined positions and orientations inside the cell. The deployment of nucleoplasmic microtubules that is spatially correlated with the shaping ritual is more complex and precise than has been reported previously. Macronuclear division is not amitotic. It is not a simple constriction into two halves. As a dividing macronucleus starts to elongate it becomes dorsoventrally flattened against the dorsal cortex of the organism and assumes an elliptical shape. Concurrently, an elliptical marginal band of intranuclear microtubules assembles that has the same spatial relationship to nuclear shape as the marginal microtubules assembles that has the same spatial relationship to nuclear shape as the marginal microtubule bands of certain elliptical vertebrate blood cells have to cell shape. The band breaks down as further elongation occurs and the nucleus adopts the shape of a straight and slender sausage. Most of the intranuclear microtubules assemble as elongation starts and break down shortly after elongation is completed; the majority are oriented parallel to the longitudinal axis of the nucleus throughout elongation. Some of them are attached to nucleoli and are coated with granules which are almost certainly derived from the cortices of nucleoli. The peripheral concentration, interconnexion, orientation, and overlapping arrangement of microtubules, and the reduction in microtubule number per nuclear cross-section as elongation proceeds at a rate of about 40 micrometers min-1, are all compatible with the provision of a microtubule sliding mechanism as the main skeletal basis for elongation. There are indications that this mechanism is augmented by anchorage and/or active propulsion of nucleoli that may perhaps facilitate fairly equitable segregation of chromosomal material to daughter nuclei.

Abnormal microtubule deployment during defective macronuclear division in a Paramecium mutant

1980 ◽  
Vol 44 (1) ◽  
pp. 153-167
Author(s):  
J. Cohen ◽  
J. Beisson ◽  
J.B. Tucker
Keyword(s):  
Plasma Membrane ◽  
Binary Fission ◽  
Cell Cortex ◽  
Paramecium Tetraurelia ◽  
Wild Type ◽  
Dorsal Cortex ◽  
Irregular Shapes ◽  
Anterior Dorsal ◽  
Sliding Mechanism ◽  
Macronuclear Division

The tam 8 mutant of Paramecium tetraurelia is a representative of a class of mutants characterized by abnormal nuclear divisions during binary fission and the failure of trichocysts to attach to the plasma membrane. Compared with wild-type organisms the following abnormalities occur in tam 8 individuals. (I) The spherical interphase macronucleus is not positioned near the oral apparatus; it is randomly located in the cytoplasm of interfission organisms. (2) The macronucleus does not migrate towards the anterior dorsal cortex as its division starts, nor is it dorsally and subcortically positioned as it elongates. (3) Elongating macronuclei exhibit variable and irregular shapes. (4) This elongation is delayed and reduced. (5) Longitudinally oriented microtubules assemble in the nucleoplasm of dividing macronuclei but their spatial deployment is abnormal. (6) Unequal segregation of micronuclei between daughter organisms occurs during binary fission. The abnormal arrangement of nucleoplasmic microtubules provides support for the proposal that a microtubule sliding mechanism is involved during the elongation of dividing macronuclei. The extent to which macronuclear division may be controlled by the cell cortex is considered in relation to tthe pleiotropic effects of the tam 8 mutation.

scholarly journals Fabrication of Mesostructured Silica and Titania Rods on Substrates by Using Polycarbonate Membranes

2010 ◽  
Vol 2010 ◽  
pp. 1-4 ◽  
Author(s):  
Norihiro Suzuki ◽  
Yusuke Yamauchi
Keyword(s):  
Electron Microscope ◽  
Longitudinal Axis ◽  
Sem Images ◽  
One Pot ◽  
Polycarbonate Membrane ◽  
Entire Area ◽  
Transmission Electron ◽  
Polycarbonate Membranes ◽  
Fibrous Morphology ◽  
Oriented Parallel

By using the polycarbonate membrane a template, mesoporous silica rods are fabricated on a silicon substrate in one pot. From scanning electron microscope (SEM) images, the creation of fibrous morphology is confirmed over the entire area. The diameter of the obtained rods is consistent with that of the template. Transmission electron microscope (TEM) images revealed that the tubular mesochannels are uniaxially oriented parallel to the longitudinal axis of the silica rods. The mesoporous titania rods with anatase crystalline frameworks are also fabricated.

A novel approach to radiographic detection of bucco-palatal/lingual dilacerations: A preliminary study with ImageJ

2021 ◽  
pp. 095441192110307
Author(s):  
Samed Satir ◽  
Muhammed Hilmi Buyukcavus ◽  
Kaan Orhan
Keyword(s):  
Longitudinal Axis ◽  
Control Group ◽  
Single Root ◽  
Novel Approach ◽  
Significant Difference ◽  
Spectrum Feature ◽  
Group 2 ◽  
Imagej Software ◽  
And Control ◽  
Control Group Group

The purpose of our study is to determine whether bucco-palatal/lingual (BPL) root dilacerations (RD), especially in single root teeth, can be determined using the ImageJ program through only one periapical radiography. Extracted teeth without any RD ( n = 8) were determined as the control group (Group 1) and with RD in apical 1/3 part at least 20° with the longitudinal axis in the BPL direction ( n = 8) as the study group (Group 2). With the help of a simple holder system prepared, digital periapical radiographs of all teeth were taken in an anteroposterior position. Histogram analysis of all periapical radiographs was performed using the spectrum feature of ImageJ software. It was aimed to make a dilaceration analysis by comparing the groups using mean, standard deviation, minimum, maximum, and bin width values. As a result of the Mann-Whitney U test, all mean and maximum values showed a statistically significant difference between the study and control groups ( p < 0.05). This pilot study revealed that the ImageJ software can be used to diagnose BPL dilaceration in the apical 1/3 part of the root. It is important for dentists and patients that it can contribute to limiting the radiation dose to which patients will be exposed.

The Structure and Development of the Spermatozoon of Aspiculuris Tetraptera (Nematoda)

1967 ◽  
Vol 2 (4) ◽  
pp. 537-544
Author(s):  
D. L. LEE ◽  
A. O. ANYA
Keyword(s):  
Longitudinal Axis ◽  
Mature Spermatozoon ◽  
Abundant Cytoplasm ◽  
Oriented Parallel ◽  
Aspiculuris Tetraptera

The mature spermatozoon of Aspiculuris tetraptera has a distinct head-like structure and a tail-like structure. The tail contains a long mitochondrion which extends from within the head almost to the posterior end of the tail. Two bundles of microtubules oriented parallel to the longitudinal axis also extend the length of the tail on either side of the mitochondrion. The head of the spermatozoon contains abundant cytoplasm but no nucleus. The DNA of the spermatozoon is in the tail-like structure where it is associated with an electron-dense sheath and the two bundles of microtubules. The head can put out pseudopodia and it is suggested that they may be involved in locomotion or may be acrosome-like. The tail, which structurally resembles a motile appendage, has not been seen to move. This spermatozoon differs markedly in its structure from all others which have been described.

scholarly journals How the cosmic web induces intrinsic alignments of galaxies

2014 ◽  
Vol 11 (S308) ◽  
pp. 437-442 ◽  
Author(s):  
S. Codis ◽  
Y. Dubois ◽  
C. Pichon ◽  
J. Devriendt ◽  
A. Slyz
Keyword(s):  
Gravitational Lensing ◽  
Theoretical Calculations ◽  
Future Generation ◽  
Wide Field ◽  
Imaging Data ◽  
Weak Gravitational Lensing ◽  
Spatially Correlated ◽  
Hydrodynamical Simulation ◽  
Good Proxy ◽  
And Control

AbstractIntrinsic alignments are believed to be a major source of systematics for future generation of weak gravitational lensing surveys like Euclid or LSST. Direct measurements of the alignment of the projected light distribution of galaxies in wide field imaging data seem to agree on a contamination at a level of a few per cent of the shear correlation functions, although the amplitude of the effect depends on the population of galaxies considered. Given this dependency, it is difficult to use dark matter-only simulations as the sole resource to predict and control intrinsic alignments. We report here estimates on the level of intrinsic alignment in the cosmological hydrodynamical simulation Horizon-AGN that could be a major source of systematic errors in weak gravitational lensing measurements. In particular, assuming that the spin of galaxies is a good proxy for their ellipticity, we show how those spins are spatially correlated and how they couple to the tidal field in which they are embedded. We will also present theoretical calculations that illustrate and qualitatively explain the observed signals.

scholarly journals Secondary organic aerosol enhanced by increasing atmospheric oxidizing capacity in Beijing-Tianjin-Hebei (BTH), China

2019 ◽  
Author(s):  
Tian Feng ◽  
Shuyu Zhao ◽  
Naifang Bei ◽  
Jiarui Wu ◽  
Suixin Liu ◽  
...  
Keyword(s):  
Air Pollution ◽  
Secondary Organic Aerosol ◽  
Action Plan ◽  
Spatial Relationship ◽  
Pollution Prevention ◽  
Organic Aerosol ◽  
Temporal Variations ◽  
Sensitivity Studies ◽  
Distribution Studies ◽  
And Control

Abstract. The implementation of the Air Pollution Prevention and Control Action Plan in China since 2013 has profoundly altered the ambient pollutants in the Beijing-Tianjin-Hebei region (BTH). Here we show observations of substantially increased O3 concentration (about 30 %) and a remarkable increase in the ratio of organic carbon (OC) to elemental carbon (EC) in BTH during the autumn from 2013 to 2015, revealing an enhancement in atmospheric oxidizing capacity (AOC) and secondary organic aerosol (SOA) formation. To explore the impacts of increasing AOC on the SOA formation, a severe air pollution episode from 3 to 8 October 2015 with high O3 and PM2.5 concentrations is simulated using the WRF-Chem model. The model performs reasonably well in simulating the spatial distributions of PM2.5 and O3 concentrations over BTH and the temporal variations of PM2.5, O3, NO2, OC, and EC concentrations in Beijing compared to measurements. Sensitivity studies show that the change in AOC substantially influences the SOA formation in BTH. A sensitivity case characterized by a 31 % O3 decrease (or 36 % OH decrease) reduces the SOA level by about 30 % and the SOA fraction in total organic aerosol by 17 % (from 0.52 to 0.43). Spatially, the SOA decrease caused by reduced AOC is ubiquitous in BTH, but the spatial relationship between SOA concentrations and the AOC is dependent on the SOA precursor distribution. Studies on SOA formation pathways further show that, when the AOC is reduced, the SOA from oxidation, partitioning of semi-volatile POA and co-emitted intermediate volatile organic compounds (VOCs) decreases remarkably, followed by those from anthropogenic and biogenic VOCs. Meanwhile, the SOA decrease in the irreversible uptake of glyoxal and methylglyoxal on aerosol surfaces is negligible.

scholarly journals CENTROSOMES AND MICROTUBULES DURING MEIOSIS IN THE MUSHROOM BOLETUS RUBINELLUS

1971 ◽  
Vol 50 (3) ◽  
pp. 737-745 ◽  
Author(s):  
David J. McLaughlin
Keyword(s):  
Electron Microscope ◽  
Longitudinal Axis ◽  
Spindle Pole ◽  
Middle Part ◽  
Prophase I ◽  
Cytoplasmic Microtubules ◽  
Oriented Parallel ◽  
Relationship Of ◽  
The Relationship

The double centrosome in the basidium of Boletus rubinellus has been observed in three planes with the electron microscope at interphase preceding nuclear fusion, at prophase I, and at interphase I. It is composed of two components connected by a band-shaped middle part. At anaphase I a single, enlarged centrosome is found at the spindle pole, which is attached to the cell membrane. Microtubules mainly oriented parallel to the longitudinal axis of the basidium are present at prefusion, prophase I and interphase I. Cytoplasmic microtubules are absent when the spindle is present. The relationship of the centrosome in B. rubinellus to that in other organisms and the role of the cytoplasmic microtubules are discussed.

267 DIFFERENCES IN BULL SPERM NUCLEAR SHAPE BETWEEN FLOW-SORTED AND NON-SORTED SPERM USING FOURIER HARMONIC ANALYSIS

2009 ◽  
Vol 21 (1) ◽  
pp. 231
Author(s):  
J. R. Schindler ◽  
R. L. Monson ◽  
K. L. Willenburg ◽  
J. J. Parrish
Keyword(s):  
Longitudinal Axis ◽  
Sperm Nucleus ◽  
Sperm Head ◽  
Nuclear Shape ◽  
Harmonic Amplitude ◽  
Head Shape ◽  
Hoechst 33342 ◽  
Fourier Harmonic ◽  
Frozen Semen ◽  
Sorting Process

The objective of the study was to evaluate sperm nuclear shape in sex-sorted and non-sorted semen using Fourier Harmonic Amplitudes (FHA). Frozen semen was obtained from a single commercially available source. Mature bulls (n = 15) from the same breed with an average age of 4.42 ± 2.08 years were collected and the semen was either frozen or X-chromosome sorted using a flow cytometer and then frozen. Frozen straws were transported to the lab and analyzed for FHA. Briefly, straws were thawed and cells were incubated with 1.6 μm Hoechst 33342. Cells were then washed, fixed, dried to a slide and analyzed for nuclear head shape. Harmonic amplitudes 0 to 5 (HA0–HA5), derived from FHA, were previously shown to be an accurate, objective, and repeatable measure of sperm nuclear shape. HA0 describes the overall nuclear size of the sperm, whereas HA1 describes the anterior head, HA2 the length of the sperm along the longitudinal axis, and HA3 to 5 the distal, post-nuclear curvature of the sperm head. Each unit of semen was evaluated for motility and FHA. There was a significant decrease in motility in the sorted group (77 ± 1% v. 54 ± 3%; P < 0.0001). Multivariate ANOVA showed that there were differences between the sorted and non-sorted groups in HA1 to 4 (P < 0.02). Harmonic amplitude means ± SD (microns) for sorted and non-sorted treatments are as follows: HA1 (0.117 ± 0.003 v. 0.109 ± 0.003), HA2 (1.087 ± 0.005 v. 1.063 ± 0.005), HA3 (0.139 ± 0.003 v. 0.130 ± 0.003), and HA4 (0.201 ± 0.004 v. 0.191 ± 0.004), respectively. The nuclear shape of X-sorted sperm is longer and more pinched in both the anterior and posterior head. Interestingly there was no difference in HA0 (P = 0.119) indicating that the overall size of the sperm head is not affected by the sorting process. The differences in harmonic amplitudes may be due to the size and a restricted location of the X v. Y chromosome in the sperm nucleus.

Modeling and Control of the Lithographic Offset Color Printing Process Using Artificial Neural Networks

1994 ◽  
Vol 116 (2) ◽  
pp. 274-276 ◽  
Author(s):  
Ming-Shong Lan ◽  
P. Lin ◽  
J. Bain
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Process Model ◽  
Spatial Relationship ◽  
Printing Process ◽  
Modeling And Control ◽  
Color Printing ◽  
Artificial Neural ◽  
Flow Effects ◽  
And Control

This paper investigates the use of artificial neural networks (ANNs) for modeling and control of the lithographic offset color printing process. The color controller consists of two ANNs; the controller network, which learns an inverse model of the process, takes a set of desired colors as input and generates a set of ink key settings, while the model network learns a forward model of the process through which the controller network can be adapted by using the error backpropagation method. We use three-layer networks with “local” connections between neurons of adjacent layers for the process model as well as for the controller; the architectures address the spatial relationship of multiple inking zones and consider the crosswise ink flow effects existing in the printing process.

Chromoplasts in Rosa rugosa: Development and Chemical Characterization of Tubular Elements

1976 ◽  
Vol 31 (7-8) ◽  
pp. 456-460d ◽  
Author(s):  
Hans-Gunter Wuttke
Keyword(s):  
Fine Structure ◽  
Chemical Composition ◽  
Cross Section ◽  
Early Stage ◽  
Chemical Characterization ◽  
Longitudinal Axis ◽  
Rosa Rugosa ◽  
Polarizing Microscopy ◽  
Oriented Parallel

Abstract 1. Development and fine structure of the chromoplasts in hips of Rosa rugosa have been in­ vestigated by electron and polarizing microscopy. 2. The chromoplasts develop from chloroplasts. During disorganization of the thylakoid system characteristic strutures become visible: ‘oblique’ grana, U-shaped thylakoids, and occassionally ‘thylakoid teeth’ as well as thylakoid anastomoses. - In this early stage, tubules appear in the plastid matrix. They are sometimes connected with membranes, especially with thylakoids. 3. In ripe hips the chromoplasts are packed with tubules. These chromoplast tubules, which attain lengths of up to at least 1.5 μm, are non-ramified and lie parallel to each other. Their diameter is variable, with a mean of 18 nm. They are polygonal in cross-section with electron-dense walls and electron-transparent cores. Association of ellipsoidal osmiophilic globules with the tubules can often be seen. Irregularly swollen remnants of former thylakoids are found in connection with these tubules. In spindle-shaped chromoplasts, the tubules are oriented parallel to the longitudinal axis. Positive birefringence and positive dichroism are observed. 4. The chemical composition of tubule fractions has been analyzed. The tubules contain appreciable amounts of carotenoids, phospho- and glycolipids, and proteins. 5. The origin and development of the tubules is discussed. It appears likely that reorganization of part of the thylakoid system and synthesis of carotenoids are involved in the formation of tubules. 6. The plastids in the yellow autumn leaves of Rosa rugosa contain globules but not tubules.

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