Positional information and pattern regulation in Hydra. Dynamics of regions at the boundary

Development ◽  
1975 ◽  
Vol 33 (2) ◽  
pp. 499-510
Author(s):  
J. Hicklin ◽  
A. Hornbruch ◽  
L. Wolpert
Keyword(s):  
Positional Information ◽  
Boundary Region ◽  
The Times ◽  
Pattern Regulation ◽  
Cut Surface

The dynamics of boundary regions have been investigated mainly by axial grafting and with the emphasis on the head end. The time to lesist inhibition of head-end formation and the ability to inhibit head-end formation have been assayed under a variety of conditions. The times increase with distance from the head end. The times required by a boundary region to acquire the inhibitory properties of a head end are longer than those required to acquire resistance to inhibition. Determination of a head end is faster at a cut surface and at higher temperatures. The results are discussed in terms of a model involving two gradients. Some anomalous results are reported.

scholarly journals Positional information and pattern regulation in hydra: formation of the foot end

Development ◽  
1973 ◽  
Vol 30 (3) ◽  
pp. 727-740
Author(s):  
J. Hicklin ◽  
L. Wolpert
Keyword(s):  
Positional Information ◽  
Basal Disc ◽  
Time Required ◽  
Pattern Regulation

The time required for foot end formation increases with distance from the foot end. Using lateral grafting it was shown that both the peduncle and basal disc could induce a proximal axis when grafted into the gastric region. The time for foot end determination was shown to be about 4 h at the proximal end of the gastric region and to increase towards the head end. In general the determination of the foot end is similar to that of the head end.

The interaction of the organizing regions in hydra and its possible relation to the role of the cut end in regeneration

Development ◽  
1974 ◽  
Vol 31 (3) ◽  
pp. 541-555 ◽  
Author(s):  
Stuart A. Newman
Keyword(s):  
Cell Division ◽  
Pattern Formation ◽  
Positional Information ◽  
Regenerative Process ◽  
Basal Disc ◽  
Model Based ◽  
Pattern Regulation ◽  
Cut Surface

Regeneration in hydra does not necessarily involve cell division, so that the problem of pattern regulation is essentially one of finding the processes by which a given population of cells are assigned appropriate functions in the correct positions. The restoration and nature of the organizers or ‘dominant regions’ must also be explained. Lateral transplants of the two different organizer tissues (hypostome and basal disc) into the digestive regions of host animals unexpectedly antagonize one another's inductive ability, suggesting that the heretofore separately studied distal and proximal developmental fields may in fact be interconnected. A model based on this idea, incorporating the extinction results with classical findings, leads to the hypothesis of a role for leakage from the cut surface as a trigger for the regenerative process. This is tested using a ligature technique in which the cut surface is minimized when the hypostome is removed, and the degree of regeneration is found to be significantly lowered, in agreement with prediction. These results are discussed in relation to ‘positional information’ and ‘special substance’ models for pattern formation.

Positional information and pattern regulation in hydra: enzyme profiles

Development ◽  
1975 ◽  
Vol 33 (4) ◽  
pp. 853-867
Author(s):  
Najma Zaheer Baquer ◽  
Patricia McLean ◽  
Amata Hornbruch ◽  
L. Wolpert
Keyword(s):  
Pentose Phosphate Pathway ◽  
Citrate Synthase ◽  
Positional Information ◽  
Pentose Phosphate ◽  
Basal Region ◽  
Redox Systems ◽  
Metabolic Pattern ◽  
Alternative Pathways ◽  
Redox States ◽  
Pattern Regulation

Certain key enzymes of alternative pathways of glucose metabolism, of amino acid metabolism and of redox systems have been measured in hydra and this profile compared with mammalian differentiated tissues with a view to locating pathways of specific importance in hydra. There was a marked constant proportionality in the major part of the enzymes investigated, the profile suggested a metabolic pattern geared to utilization of amino acids as a carbon source for biosynthesis and energy production and to the production and conservation of pyruvate. The importance of conversion to ionized forms was noted. The most notable specific proportion changes were the exceptionally low lactate dehydrogenase, malic enzyme and the relatively high citrate synthase. The proximal-distal gradients in hydra were examined and these gradients suggested a switch to a more anaerobic type of metabolism and an elevation of the pentose phosphate pathway as the basal region was approached. Measurements of the formation of 14CO2 from specifically labelled glucose provided additional evidence for the functional activity and polarity of the pentose phosphate pathway in hydra. The effect of oligomycin, which can reverse polarity in hydra, had a significant effect on gradients of enzymes eliminating all except that observed for G6P dehydrogenase. The profile suggested a movement towards a more anaerobic type of metabolism, in keeping with the known biochemical action of this inhibitor. It is suggested that redox states and/or phosphorylation states may be featured in the positional information of cells in hydra.

IX. Contributions to terrestrial magnetism.—No. IV

1843 ◽  
Vol 133 ◽  
pp. 113-143 ◽  
Keyword(s):  
Pacific Ocean ◽  
West Coast ◽  
China Seas ◽  
North West ◽  
The North ◽  
The Pacific ◽  
The Pacific Ocean ◽  
The Times ◽  
The China Seas

In the present number of these Contributions, I resume the consideration of Captain Sir Edward Belcher’s magnetic observations, of which the first portion, viz. that of the stations on the north-west coast of America and adjacent islands, was discussed in No. II. The return to England of Her Majesty’s ship Sulphur by the route of the Pacific Ocean, and her detention for some months in the China Seas, have enabled Sir Edward Belcher to add magnetic determinations at thirty-two stations to those at the twenty-nine stations previously recorded. In the notice of the earlier observations, a provisional coefficient was employed in the formula for the temperature corrections of the results with the intensity needles, as no experiments had then been made for the determination of their individual co­efficients. As soon therefore as Sir Edward Belcher had completed the observation of the times of vibration of those needles at Woolwich, as the concluding station of the series made with them, Lieut. Riddell, R. A. undertook the determination of their several coefficients, which was performed in the manner and with the results described in the subjoined memorandum.

scholarly journals Drying of green bean and okra under solar energy

2011 ◽  
Vol 17 (2) ◽  
pp. 199-205 ◽  
Author(s):  
İbrahim Doymaz
Keyword(s):  
Green Bean ◽  
Chi Square ◽  
Sun Drying ◽  
Constant Rate ◽  
Thin Layer Drying ◽  
Rate Period ◽  
Drying Models ◽  
Drying Curves ◽  
The Times

In this study, sun drying behaviours of green bean and okra were investigated. Drying experiments were conducted in Iskenderun-Hatay, Turkey. The drying study showed that the times taken for drying of green bean and okra from the initial moisture contents of 89.5% and 88.7% (w.b.) to final moisture content of around 15?0.5% (w.b.) were 60 and 100 h in open sun drying, respectively. The constant rate period is absent in drying curves. The drying process took place in the falling rate period. The drying data were fitted to thirteen thin-layer drying models. The performance of these models was investigated by comparing the determination of coefficient (R2), reduced chi-square (c2) and root mean square error (RMSE) between the observed and predicted moisture ratios. Estimations by Approximation of diffusion (for green bean) and Midilli et al. models (for okra) were in good agreement with the experimental data obtained.

scholarly journals On the determination of the difference of longitude, by means of the magnetic telegraph. By Elias Loomie, Esq., in a letter to Lieut.-Col. Sabine, R. A., For. Sec. R. S. Communicated by Lieut.-Col. Sabine, R. A., For. Sec. R. S

1851 ◽  
Vol 5 ◽  
pp. 787-789
Keyword(s):  
New York ◽  
Usual Manner ◽  
Series Of Experiments ◽  
The Difference ◽  
The Times ◽  
The Right ◽  
Time Pieces ◽  
Right Ascension ◽  
Source Of Error

The writer first refers to a series of experiments made under the direction of Professor Bache, for the determination of the difference of longitude between New York, Philadelphia and Washington, by means of the magnetic telegraph. By this series of experiments he considers it established that, by means of Morse’s telegraph, two clocks distant from each other 200 miles, can be compared together with the same precision as if they were placed side by side; and that the difference of longitude of two places can be determined with the same precision as the relative error of the clocks. These results were so satisfactory that Professor Bache determined to pro­secute them more extensively, and during the past summer comparisons have been made between New York and Cambridge observatory near Boston. The plan of operation this season was more matured than during the former. The comparisons were all made between a solar chronometer at Cambridge and a sidereal clock at New York. At ten o’clock in the evening, the two observatories having been put in telegraphic communication, when the seconds hand of the solar chronometer came round to 60 s , a signal was given at Cambridge, by pressing the key of the telegraph-register; at the same instant a click was heard at New York, and the time was recorded according to the sidereal clock. At the end of 10 s a second signal was given, which was also recorded at New York; at the end of another 10 s a third signal was given, and so on for sixty seconds. The Cambridge astronomer then commenced beating seconds by striking the key of the telegraph-register in coincidence with the beats of his chronometer. The New York astronomer compared the signals received with the beats of his clock, and waited for a coincidence. When the beats were sensibly synchronous the time was recorded, and the astronomer waited six minutes for another coincidence of beats. The Cambridge astronomer continued beating seconds for fifteen minutes , during which time the New York observer was sure of two coincidences, and might obtain three. When these were concluded, the New York astronomer in the same manner gave signals for one minute at intervals of 10 s , and then beat seconds for fifteen minutes, during which time the Cambridge astronomer obtained four or five coincidences upon his chronometer. This mode of comparison was practised every night, and it is considered that the uncertainty in the comparison of the time-pieces cannot exceed two or three hundredths of a second on any night; and in a series of comparisons the error may be regarded as entirely eliminated. Another mode of comparison which was practised is that of telegraphing star transits. A list of stars which culminate near our zenith at intervals of five or six minutes was prepared, and the observers, both at New York and Cambridge, were furnished with a copy. They then proceeded as follows: Cambridge selected two stars from the list, which we wall call A and B, and struck the key of his register at the instant when the star A passed each of the seven wires of his transit. These signals were heard at New York, and the times recorded. Cambridge then observed the transit of star B in the ordinary manner without telegraphing. New York then observed the transit of star A on his meridian in the usual manner; and struck his key at the instant the star B passed each of the seven wires of his transit, which signals were heard and recorded at Cambridge. The difference of longitude between New York and Cambridge is nearly twelve minutes, affording ample time for all these observations. Thus New York obtained upon his own clock the times of transit of star A over the meridians of Cambridge and New York; and Cambridge obtained upon his chronometer the times of transit of star B over the same meridians. The difference of these times gives the difference of longitude independent of the right ascension of the stars. Both observers then reversed the axis of their transit instruments; Cambridge selected a second pair of stars from the list, and the same series of observations was repeated as with the first pair. The error of collimation was thus eliminated, and by confining the observations to stars within about five degrees of the zenith, the influence of azimuthal error was avoided. The level being read at every reversal, the correction for it was applied by computation. In this manner it is hoped to eliminate every possible source of error, except that which arises from the personal habits of the observers. In order to eliminate this error, a travelling observer worked for a time at Cambridge and compared with the Cambridge astronomer; then came to New York and compared with the New York astronomer; then returned to Cambridge again, and so on as often as was thought necessary. Finally, at the conclusion of the campaign all the observers were to meet at Cambridge and make a general comparison of their modes of observation.

Load on Osseointegrated Fixation of a Transfemoral Amputee during a Fall: Determination of the Time and Duration of Descent

2010 ◽  
Vol 34 (4) ◽  
pp. 472-487 ◽  
Author(s):  
Laurent Alain Frossard
Keyword(s):  
Fall Detection ◽  
Protective Mechanism ◽  
Protective Device ◽  
Transfemoral Amputee ◽  
Automated Algorithm ◽  
Measurement Session ◽  
Transfemoral Amputees ◽  
The Times ◽  
Automated Methods

Mitigation of fall-related injuries for populations of transfemoral amputees fitted with a socket or an osseointegrated fixation is challenging. Wearing a protective device fitted within the prosthesis might be a possible solution, provided that issues with automated fall detection and time of deployment of the protective mechanism are solved. The first objective of this study was to give some examples of the times and durations of descent during a real forward fall of a transfemoral amputee that occurred inadvertently while attending a gait measurement session to assess the load applied on the residuum. The second objective was to present five semi-automated methods of detection of the time of descent using the load data. The load was measured directly at 200 Hz using a six-channel transducer. The average time and duration of descent were 242 ± 42 ms (145–310 ms) and 619 ± 42 ms (550–715 ms), respectively. This study demonstrated that the transition between walking and falling was characterized by times of descent that occurred sequentially. The sensitivity and specificity of an automated algorithm might be improved by combining several methods of detection based on the deviation of the loads measured from their own trends and from a template previously established.

scholarly journals UKRAINIAN REVOLUTION AND STATE FORMATION: ON ISSUE OF THE PERIODIZATION AND CHRONOLOGY OF NATIONAL LIBERATION STRUGGLE OF THE EARLY 20th CENTURY

2018 ◽  
pp. 4-12
Author(s):  
Pavlo Hai-Nyzhnyk
Keyword(s):  
20Th Century ◽  
State Formation ◽  
Political History ◽  
National Liberation ◽  
Historical Processes ◽  
Chronological Period ◽  
History Of ◽  
Liberation Struggle ◽  
The Times

The controversial issue of periodization of the political history of Ukraine at the beginning of the 20th century, including the period of the National liberation struggle and Ukrainian State entities during 1917–1922 is considered. Scientists and experts have not yet reached a consensus not only on determining the place, role and character of the Hetmanate in 1918 in the latest Ukrainian past, but also about the periodization of the Ukrainian political history of the 20th century, defi nition of the term and chronological boundaries of the Ukrainian Revolution and Ukrainian statehood, etc. The issute of the periodization of the National liberation struggle of the Ukrainian people from the beginning of the 20th century, the aspiration and purpose of which was to gain and assert its own statehood, had several main schemes, models and periodizations in the national historiography. However, disputes over defi nitions not only of the chronological framework of this historical path, but also of the interpretations and characteristics of its individual days, periods, and stages are still ongoing in the scientifi c community. It is up to me, that the times from 1917 to 1922 should be defi ned as one of the days of the Ukrainian political history of the 20th century, namely: The Day “National Liberation Struggle and Ukrainian State Formation (1917–1922 biennium)”. This title was due to historical processes and components, that took place in the specifi ed chronological period, the logic of interrelated events, factors and circumstances, objective signs of fl uidity, similarity and diversity of periods, the identity of the causal eff ects of both internal and external circumstances and infl uences, interconnectedness of cultural, social, ideological and political, and state-evolutionary factors of nation-wide signifi cance, the regularity of the beginning and end of the national-political breakdown, holding otvorchyh eff orts and organized struggle for their own rights to self-determination of Nation-Ukrainian people. It is the author’s conception of the periodization of this era, that would be discussed in this essay

scholarly journals Molecular Clock and Phylogeny ofAnophelesspecies of the subgenusNyssorhynchus(Diptera: Culicidae)

2018 ◽  
Author(s):  
Richard Hoyos-López
Keyword(s):  
Molecular Markers ◽  
Molecular Clock ◽  
Phylogenetic Hypothesis ◽  
Bayesian Approaches ◽  
Natural Group ◽  
Phylogenetic Studies ◽  
The Times

AbstractThe main Phylogenetic hypothesis supporting the Myzorhynchella section as a natural group, but the sections Albimanus and Argyritarsis, do not present clearly resolved relationships, nor is it possible to recover the monophyly of both sections, even within these sections ofNyssorhynchus; it has not been possible identify the relationships between the species that make up these taxonomic subdivisions (Sallum, 2000, Sallum, 2002, Bourke, 2011, Foster, 2013). This lack of resolution has been attributed to the effect of few species for phylogenetic studies, making difficult the determination of monophyly of many groups, subgroups and complexes within sections Albimanus and ArgyritarsisWe infer the phylogeny of the subgenusNyssorhynchusthrough the sequences characterized for the molecular markers ND6, COI-Barcode, White and CAD, in addition we calculate the times of divergence for the main lineages corresponding to the sections Albimanus, Argyritarsis and Myzorhynchella using Bayesian approaches.

Nucleic acid and protein synthesis and pattern regulation in hydra

Development ◽  
1969 ◽  
Vol 21 (1) ◽  
pp. 55-70
Author(s):  
S. G. Clarkson
Keyword(s):  
Protein Synthesis ◽  
Dna Synthesis ◽  
Experimental Approach ◽  
Direct Evidence ◽  
Animal Cells ◽  
Rna And Protein Synthesis ◽  
Metabolic Activities ◽  
Time Required ◽  
Pattern Regulation

In a previous paper (Clarkson, 1969) data were presented which indicate that hypostome determination is accompanied by a large and rapid burst of RNA synthesis, a slight stimulation of protein synthesis, and no increase in DNA synthesis. More direct evidence concerning the relative importance of these metabolic activities in hypostome determination is reported in this paper. The experimental approach made use of the transplantation test of Webster & Wolpert (1966) in conjunction with some inhibitors of DNA, RNA and protein synthesis, the rationale being that if these metabolic activities play important roles in the determination of the hypostome, then their inhibition would be expected to have severe effects on the time required for this process. Regarding the inhibitors, hydroxyurea (HU) inhibits DNA synthesis in a variety of animal cells without altering rates of formation of RNA or protein (Young & Hodas, 1964; Yarbro, Kennedy & Barnum, 1965; Schwartz, Garofalo, Sternberg & Philips, 1965).

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