scholarly journals Traction force on a kinetochore at metaphase acts as a linear function of kinetochore fiber length

1982 ◽  
Vol 93 (2) ◽  
pp. 374-382 ◽  
Author(s):  
TS Hays ◽  
D Wise ◽  
ED Salmon
Keyword(s):  
Fiber Length ◽  
Traction Force ◽  
Time Lapse ◽  
Resultant Force ◽  
Microtubule Assembly ◽  
Γ Irradiation ◽  
Average Value ◽  
Length Relationship ◽  
Balance Of Forces ◽  
The Individual

We are investigating the relation between the force pulling a kinetochore poleward and the length of the corresponding kinetochore fiber. It was recognized by Ostergren in 1950 (Hereditas 36:1-19) that the metaphase position of a chromosome could be achieved by a balance of traction forces were proportional to the distance from kinetochore to pole. For the typical chromosome (i.e., a meiotic bivalent or mitotic chromosome) with a single kinetochore fiber extending to each pole, the resultant force (RF) would equal zero when the chromosome lay at the midpoint between the two poles. For special chromosomes that have unequal numbers of kinetochore fibers extending towards opposite poles. For special chromosomes that have unequal numbers of kinetochore fibers extending towards opposite poles. For special chromosomes that have unequal numbers of kinetochore fibers extending towards opposite poles, Ostergren's proposal suggests that RF = 0 when the chromosome is shifted closer to the pole toward which the greater number of kinetochore fibers are pulling. We have measured the force-length relationship in living spindles by analyzing the metaphase positions of experimentally generated multivalent chromosomes having three or four kinetochore fibers. Multivalent chromosomes of varied configurations were generated by γ-irradiation of nymphs of the grasshopper melanoplus differentialis, and their behavior was analyzed in living first meiotic spermocytes. The lengths of kinetochore fibers were determined from time-lapse photographs by measuring the kinetochore-to-pole distances for fully congressed chromosomes just before the onset of anaphase. In our analysis, force (F) along a single kinetochore fiber is expressed by: F = kL(exp), where k is a length-independent proportionality constant, L represents the kinetochore fiber length, and exp is an unknown exponent. The RF on a chromosome is then given by: RF = σk(i)L(i)(exp), where kinetochore fiber lengths in opposite half- spindles are given opposite sign. If forces on a metaphase chromosome are at equilibrium (RF = 0), then for asymmetrical orientations of multivalents we can measure the individual kinetochore fiber lengths (L(i)) and solve for the exponent that yields a resultant force of zero. The value of the exponent relates how the magnitude of force along a kinetochore fiber varies with its length. For six trivalents and one naturally occurring quadrivalent we calculated an average value of exp = 1.06 +/- 0.18. This result is consistent with Ostergren's hypothesis and indicates that the magnitude of poleward traction force along a kinetochore fiber is directly proportional to the length of the fiber. Our finding suggests that the balance of forces along a kinetochore fiber may be a major factor regulating the extent of kinetochore microtubule assembly.

scholarly journals Differential roles of microtubule assembly and sliding in proplatelet formation by megakaryocytes

Blood ◽  
2005 ◽  
Vol 106 (13) ◽  
pp. 4076-4085 ◽  
Author(s):  
Sunita R. Patel ◽  
Jennifer L. Richardson ◽  
Harald Schulze ◽  
Eden Kahle ◽  
Niels Galjart ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Average Rate ◽  
Blood Platelets ◽  
Time Lapse ◽  
Microtubule Assembly ◽  
Alternative Mechanism ◽  
Differentiated Cells ◽  
Continuous Polymerization ◽  
Regulatory Complex ◽  
Green Fluorescent

Megakaryocytes are terminally differentiated cells that, in their final hours, convert their cytoplasm into long, branched proplatelets, which remodel into blood platelets. Proplatelets elongate at an average rate of 0.85 μm/min in a microtubule-dependent process. Addition of rhodamine-tubulin to permeabilized proplatelets, immunofluorescence microscopy of the microtubule plus-end marker end-binding protein 3 (EB3), and fluorescence time-lapse microscopy of EB3–green fluorescent protein (GFP)–expressing megakaryocytes reveal that microtubules, organized as bipolar arrays, continuously polymerize throughout the proplatelet. In immature megakaryocytes lacking proplatelets, microtubule plus-ends initiate and grow by centrosomal nucleation at rates of 8.9 to 12.3 μm/min. In contrast, plus-end growth rates of microtubules within proplatelets are highly variable (1.5-23.5 μm/min) and are both slower and faster than those seen in immature cells. Despite the continuous assembly of microtubules, proplatelets continue to elongate when net microtubule assembly is arrested. One alternative mechanism for force generation is microtubule sliding. Triton X-100–permeabilized proplatelets containing dynein and its regulatory complex, dynactin, but not kinesin, elongate with the addition of adenosine triphosphate (ATP) at a rate of 0.65 μm/min. Retroviral expression in megakaryocytes of dynamitin (p50), which disrupts dynactindynein function, inhibits proplatelet elongation. We conclude that while continuous polymerization of microtubules is necessary to support the enlarging proplatelet mass, the sliding of overlapping microtubules is a vital component of proplatelet elongation.

scholarly journals Size control models of Saccharomyces cerevisiae cell proliferation.

1982 ◽  
Vol 2 (4) ◽  
pp. 361-368 ◽  
Author(s):  
A E Wheals
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Proliferation ◽  
Critical Size ◽  
Transition Probability ◽  
Size Control ◽  
Time Lapse ◽  
Growth Conditions ◽  
Yeast Cells ◽  
Cycle Times ◽  
The Individual

By using time-lapse photomicroscopy, the individual cycle times and sizes at bud emergence were measured for a population of saccharomyces cerevisiae cells growing exponentially under balanced growth conditions in a specially constructed filming slide. There was extensive variability in both parameters for daughter and parent cells. The data on 162 pairs of siblings were analyzed for agreement with the predictions of the transition probability hypothesis and the critical-size hypothesis of yeast cell proliferation and also with a model incorporating both of these hypotheses in tandem. None of the models accounted for all of the experimental data, but two models did give good agreement to all of the data. The wobbly tandem model proposes that cells need to attain a critical size, which is very variable, enabling them to enter a start state from which they exit with first order kinetics. The sloppy size control model suggests that cells have an increasing probability per unit time of traversing start as they increase in size, reaching a high plateau value which is less than one. Both models predict that the kinetics of entry into the cell division sequence will strongly depend on variability in birth size and thus will be quite different for daughters and parents of the asymmetrically dividing yeast cells. Mechanisms underlying these models are discussed.

MAKING AN ALGORITHM FOR CONTROLLING THE INDIVIDUAL DRIVE OF THE DRIVING WHEELS OF A TRANSPORT AND TECHNOLOGICAL MODULE

2020 ◽  
pp. 10-15
Author(s):  
SHUTENKO VLADIMIR V. ◽  
Keyword(s):  
Power Distribution ◽  
Rotation Speed ◽  
Traction Force ◽  
Microprocessor System ◽  
Movement Trajectory ◽  
Microprocessor Control ◽  
Microprocessor Control System ◽  
The Individual ◽  
Mathematical Relationships ◽  
Technological Module

Improving the traction properties of mobile power tools is one of the most important tasks of modern tractor construction. The use of transport-technological modules (TTM) helps to solve this problem, but to ensure the best indicators of fuel economy and stabilization of a machine-and-tractor unit (MTU), the TTM driving wheels should be driven individually, which can be ensured by a microprocessor control system. Therefore, the study goal is to make an algorithm for controlling the driving wheels of the TTM, which will ensure the best characteristics of a MTU. To achieve this goal, the authors used mathematical modeling and graph-analytical methods. They are necessary for stating the main relationships and setting algorithm conditions that will optimize a tractor’s traction force and power consumption, as well as stabilize its movement trajectory. The operation of the microprocessor system consists in obtaining data from external sensors and determining the actual speed, skidding and direction of travel. The microprocessor system compares these parameters with ideal conditions, described with mathematical relationships, and based on the developed algorithm, corrects the rotation speed and power distribution between the driving wheels of a TTM.

scholarly journals 3D Imaging of Indentation Damage in Bone

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2533
Author(s):  
Tristan Lowe ◽  
Egemen Avcu ◽  
Etienne Bousser ◽  
William Sellers ◽  
Philip Withers
Keyword(s):  
Traumatic Event ◽  
Time Lapse ◽  
Bone Microstructure ◽  
Three Dimensions ◽  
Aging Populations ◽  
Deformation Plasticity ◽  
Indentation Tests ◽  
Crack Blunting ◽  
Indentation Methods ◽  
The Individual

Bone is a complex material comprising high stiffness, but brittle, crystalline bio-apatite combined with compliant, but tough, collagen fibres. It can accommodate significant deformation, and the bone microstructure inhibits crack propagation such that micro-cracks can be quickly repaired. Catastrophic failure (bone fracture) is a major cause of morbidity, particularly in aging populations, either through a succession of small fractures or because a traumatic event is sufficiently large to overcome the individual crack blunting/shielding mechanisms. Indentation methods provide a convenient way of characterising the mechanical properties of bone. It is important to be able to visualise the interactions between the bone microstructure and the damage events in three dimensions (3D) to better understand the nature of the damage processes that occur in bone and the relevance of indentation tests in evaluating bone resilience and strength. For the first time, time-lapse laboratory X-ray computed tomography (CT) has been used to establish a time-evolving picture of bone deformation/plasticity and cracking. The sites of both crack initiation and termination as well as the interconnectivity of cracks and pores have been visualised and identified in 2D and 3D.

scholarly journals Profiling of Individual Desulfo-Glucosinolate Content in Cabbage Head (Brassica oleracea var. capitata) Germplasm

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1860 ◽  
Author(s):  
Shiva Ram Bhandari ◽  
Juhee Rhee ◽  
Chang Sun Choi ◽  
Jung Su Jo ◽  
Yu Kyeong Shin ◽  
...  
Keyword(s):  
Significant Variation ◽  
The Other ◽  
Glucosinolate Content ◽  
Breeding Programs ◽  
Average Value ◽  
Hydrolysis Products ◽  
Coefficients Of Variation ◽  
Anti Cancer ◽  
The Individual ◽  
Different Origins

Individual glucosinolates (GSLs) were assessed to select cabbage genotypes for a potential breeding program. One hundred forty-six cabbage genotypes from different origins were grown in an open field from March to June 2019; the cabbage heads were used for GSL analyses. Seven aliphatics [glucoiberin (GIB), progoitrin (PRO), epi-progoitrin (EPI), sinigrin (SIN), glucoraphanin (GRA), glucoerucin (GER) and gluconapin (GNA)], one aromatic [gluconasturtiin (GNS)] and four indolyl GSLs [glucobrassicin (GBS), 4-hydroxyglucobrassicin (4HGBS), 4-methoxyglucobrassicin (4MGBS), neoglucobrassicin (NGBS)] were found this study. Significant variation was observed in the individual GSL content and in each class of GSLs among the cabbage genotypes. Aliphatic GSLs were predominant (58.5%) among the total GSLs, followed by indolyl GSL (40.7%) and aromatic GSLs (0.8%), showing 46.4, 51.2 and 137.8% coefficients of variation, respectively. GIB, GBS and NGBS were the most common GSLs found in all genotypes. GBS was the most dominant GSL, with an average value of 3.91 µmol g−1 (0.79 to 13.14 µmol g−1). SIN, GIB, PRO and GRA were the other major GSLs, showing average values of 3.45, 1.50, 0.77 and 0.62 µmol g−1, respectively. The genotypes with relatively high contents of GBS, SIN, GIB and GRA warrant detailed studies for future breeding programs since the hydrolysis products of these GSLs have several anti-cancer properties.

Distribution Characteristics and Risk Evaluation of Cd and Hg in Sediments on the Zhenjiang Ancient Canal River

2013 ◽  
Vol 726-731 ◽  
pp. 296-300
Author(s):  
Zhi Gang Chen ◽  
An Ping Wei ◽  
Xiao Hong Zhou
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Heavy Metal Contamination ◽  
Risk Index ◽  
Potential Ecological Risk ◽  
Middle Part ◽  
Average Value ◽  
Heavy Metal Element ◽  
Individual Potential ◽  
The Individual

The purpose of this paper is to study the speciation and contents of two types of heavy metals (Cd and Hg) in the sediments in Power Bridge (D1) and Nanshui Bridge (N2) in the middle part of the Ancient Canal in Zhenjiang. The relationship between the speciation of these heavy metals and their environmental factors were described. Morerover, the ecological hazard and trace to the source of these two types of heavy metals was also determined preliminarily. The results showed that (1) the main heavy metal contamination in the sediments of Power Bridge and Nanshui Bridge is Cd, and the average value is 20 mg/Kg, 17 mg/Kg, respectively, which were higher than environmental background value;(2) The peak value of Hg and Cd were near equilibrium in the 0.1-0.2m depth of Sediments; (3) Calculate the individual potential ecological risk index in the sediments of heavy metal element of two sample points both quantity of contents are Cd>Hg. And visible ecological threat of heavy metals were from Cd. After removing the Cd value, the RI value showed that ecological harm index basically below mild ecological harm degree.

Laminar Counterflow Exchangers: An Approximate Account of Wall Resistance and Variable Transfer Coefficients

1972 ◽  
Vol 94 (4) ◽  
pp. 391-396 ◽  
Author(s):  
R. A. Seban ◽  
T. C. Hsieh ◽  
R. Greif
Keyword(s):  
Graphical Form ◽  
Exact Results ◽  
Parallel Plates ◽  
Transfer Coefficients ◽  
Usual Definition ◽  
Average Value ◽  
Overall Heat Transfer Coefficient ◽  
Adequate Accuracy ◽  
Definition Of ◽  
The Individual

There is considered the calculation of the average value of the overall heat-transfer coefficient for counterflow between parallel plates or in concentric tubes when the flows are laminar and the thermal entry lengths for one or both streams extend over a significant part of the exchanger length. It is shown that if this length is at least less than the total length for one of the fluids, the average value of the overall coefficient can be calculated with adequate accuracy from the average values of the individual coefficients by means of the usual definition of the overall coefficient. When both thermal entry lengths exceed the exchanger length, then a special calculation is needed to obtain suitable average overall values. This result is given in graphical form and supported by more exact results from the literature and as obtained here.

187. The effect of subclinical mastitis on the solids-not-fat content of milk

1938 ◽  
Vol 9 (2) ◽  
pp. 182-184 ◽  
Author(s):  
S. J. Rowland ◽  
M. Zein-El-Dine
Keyword(s):  
Subclinical Mastitis ◽  
Fat Content ◽  
Average Value ◽  
The Individual ◽  
Very High

The solids-not-fat content (expressed as a percentage of fat-free milk) has been determined for 247 samples of milk from the individual quarters of sixty-two cows. The samples were also examined bacteriologically for the presence of mastitis streptococci and 121 were found to be infected, 114 uninfected, and twelve “doubtful”.The solids-not-fat content of the uninfected samples varied from 8·24 to 10·28 and of the infected samples from 4·26 to 9·92. For the uninfected samples of the Shorthorn, Friesian, Ayrshire and Guernsey breeds it averaged 9·36, 9·11, 9·82 and 9·83 respectively, but in the infected samples only 8·44, 8·38, 8·28 and 9·49%.Of the 247 samples, 36 % were below 8·80 in solids-not-fat content. Of 121 infected samples, 63% were below while of the 114 uninfected samples only 9% were below this standard. Hence 88% of the samples below 8·80 were infected samples, thus showing that subclinical mastitis accounts for a very high percentage of samples low in solids-not-fat content. In these samples the average value for solids-not-fat was 7·93%. The few uninfected samples that were low in solids-not-fat averaged 8·56%.

scholarly journals Financial health of agricultural enterprises in the organic farming sector

2011 ◽  
Vol 59 (7) ◽  
pp. 91-96 ◽  
Author(s):  
Ivana Brožová
Keyword(s):  
Organic Farming ◽  
Financial Indicators ◽  
Financial Health ◽  
Organic Farms ◽  
Conventional Agriculture ◽  
Agricultural Enterprises ◽  
Average Value ◽  
Organic Farm ◽  
The Individual ◽  
Legal Entities

The present research was aimed at evaluating the economic performance of organic farm enterprises (legal entities) in the Czech Republic on the basis of their production base and financial health. The evaluation was carried out by means of specific financial indicators. The results recorded in the organic farming sector were confronted with those of the conventional agriculture. It stemmed from the analysis that conventionally farming legal entities, as opposed to the organically farming ones, tend to have higher average assets per hectare of farmland. Secondly, as for the structure of assets, fixed assets prevail substantially over current assets. Organic farms, on the contrary, have a significantly higher average value of external financial resources per hectare of farmland. In order to evaluate the financial health of organic farms, their economic results were used; firstly in absolute value (including per hectare calculation) and then within the individual ratios. The analysis showed that 84.4 % farms of the sample were profitable as long as subsidies were included in the yields. While excluding subsidies from the calculations, an overwhelming majority of enterprises (95.3 %) recorded a loss. Comparing the per hectare economic results, higher average profit rates were recorded for organic farms. Furthermore, financial health of the enterprises was analyzed by means of selected indicator ratios. Concrete results, including the respective commentaries, can be found in the present paper too.

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