On the Neural Crest of the Lamprey Embryo

Development ◽  
1956 ◽  
Vol 4 (4) ◽  
pp. 358-375
Author(s):  
D. R. Newth
Keyword(s):  
Neural Crest ◽  
Early Stage ◽  
The Other ◽  
Embryonic Tissue ◽  
Critical Step ◽  
Other Hand ◽  
Vertebrate Embryo ◽  
Common Ancestors

The neural crest is an embryonic tissue found only in craniate vertebrates, but important in the embryogenesis of all of them in which it has been studied. It may be assumed to be of great antiquity and, indeed, to have been present in the latest common ancestors of cyclostomes and gnathostomes, its acquisition having been an early and critical step in the evolution of the craniates. It follows that its properties in living cyclostomes have a twofold interest. It is possible that it is here in one or more ways ‘primitive’, and that its study will reveal something of an early stage in the evolution of the vertebrate embryo. On the other hand, the presumptive fate of the crest in cyclostomes may differ from that of the crest in higher vertebrates for another reason. For certain structures in gnathostomes that are of crest origin, in particular elements of the cartilaginous visceral skeleton, are only doubtfully homologous with their cyclostome analogues.

Two deoxyribonucleases from Novikoff ascites hepatoma cells

1968 ◽  
Vol 46 (9) ◽  
pp. 1121-1129 ◽  
Author(s):  
Peter M. K. Ip ◽  
Shan-Ching Sung
Keyword(s):  
Actinomycin D ◽  
Early Stage ◽  
Maximum Activity ◽  
The Other ◽  
Average Chain Length ◽  
Ascites Hepatoma ◽  
Dnase Digestion ◽  
Other Hand ◽  
Acid Dnase ◽  
Sulfhydryl Compounds

Two DNases have been isolated and separated from Novikoff ascites hepatoma by ammonium sulfate fractionation and have been further purified by chromatography on ion-exchange columns of DEAE types.The partially purified acid DNase is free of any measurable RNase activity, while the partially purified alkaline DNase preparation still exhibits RNase activity.The alkaline DNase requires sulfhydryl compounds for maximum activity, whereas the acid DNase does not. Both DNases require Mg2+ ions for maximum activity. EDTA strongly inhibits the alkaline DNase activity and the inhibition can be reversed by the addition of Mg2+ ions. On the other hand, EDTA activates the acid DNase either in the presence or in the absence of Mg2+.Sarkomycin inhibits the alkaline DNase but does not inhibit the acid DNase. Actinomycin D and heparin inhibit both DNase activities.The products of the alkaline DNase digestion consist of four deoxymononucleotides as well as higher oligonucleotides, all terminating in 5′-phosphate. The alkaline DNase seems to exhibit an endonucleolytic mode of attack in the early stage of hydrolysis with a subsequent exonucleolytic action. However, the possibility of contamination by an unknown exonuclease cannot be ruled out. On the other hand, the products of the acid DNase digestion consist mainly of oligonucleotides with average chain length larger than 8 units all terminating in 3′-phosphate. No mononucleotides can be detected. This suggests that the acid DNase is a typical endonuclease and possesses no detectable exonuclease activity.The acid DNase preferentially attacks linkages of the type dPupGp, whereas the preferential linkage(s) for the alkaline DNase has not been established.

The Organisation of African Unity: A Progress Report

1966 ◽  
Vol 4 (2) ◽  
pp. 135-153 ◽  
Author(s):  
John Markakis
Keyword(s):  
Present State ◽  
Early Stage ◽  
Progress Report ◽  
The Other ◽  
African Unity ◽  
Other Hand

The Organisation of African Unity is now three years old. In view of the nature of both its scope and its goals, it would obviously be premature to attempt an evaluation of this organisation at such an early stage. On the other hand, the O.A.U. has grown precociously since its birth in May 1963, and the time is ripe for a description of its rapidly multiplying organs, and for some preliminary observations of the multifarious activity in which they have been engaged. To state that the O.A.U. is still in the cradle stage of its development is to emphasise the obvious. It is hardly surprising also that it should suffer the pains of growth, which are likely to be rather severe in the case of a scheme so ambitiously conceived. These facts must be kept in mind while reviewing the O.A.U. at its present state of development.

scholarly journals Identification of Chemical Toxicity Using Ontology Information of Chemicals

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Zhanpeng Jiang ◽  
Rui Xu ◽  
Changchun Dong
Keyword(s):  
Combinatorial Chemistry ◽  
Early Stage ◽  
Prediction Method ◽  
Previous Method ◽  
The Other ◽  
New Drugs ◽  
Chemical Toxicity ◽  
Synthetic Compounds ◽  
Limited Knowledge ◽  
Other Hand

With the advance of the combinatorial chemistry, a large number of synthetic compounds have surged. However, we have limited knowledge about them. On the other hand, the speed of designing new drugs is very slow. One of the key causes is the unacceptable toxicities of chemicals. If one can correctly identify the toxicity of chemicals, the unsuitable chemicals can be discarded in early stage, thereby accelerating the study of new drugs and reducing the R&D costs. In this study, a new prediction method was built for identification of chemical toxicities, which was based on ontology information of chemicals. By comparing to a previous method, our method is quite effective. We hope that the proposed method may give new insights to study chemical toxicity and other attributes of chemicals.

An extension of Maxwell’s theory of pin-jointed frameworks by M. W. Crofton, F.R.S

1989 ◽  
Vol 43 (1) ◽  
pp. 53-56 ◽  
Keyword(s):  
Early Stage ◽  
The Other ◽  
Other Hand ◽  
Railway System ◽  
The One

At an early stage of Maxwell’s researches into the theory of plane ‘triangulated’ frameworks whose bars or ‘pieces’ arc connected together by pin-joints he derived a relation between the number of bars, joints and supports, respectively, that was necessary if the forces throughout, due to imposed loads, were to be found by simple statics (1). Those researches were stimulated by the needs of engineers to determine the general and detailed proportions of the then novel iron frameworks, especially for bridges for the developing railway system. Rigidity or stiffness to imposed loads was implied by Maxwell’s criterion. Violation of the criterion would, on the one hand, result in a mechanism whereby the bars would be capable of motion and, on the other hand, in a framework with excess stiffness. Moreover, the latter would be capable of having unknown forces introduced into its bars by, say, malpractice during construction, that would then be additional to those caused by eventual loading; that is, it could be self-strained.

scholarly journals Notes on the Development of the Neural Crest in the Head of Mus musculus

Development ◽  
1953 ◽  
Vol 1 (4) ◽  
pp. 393-398
Author(s):  
Bengt Källén
Keyword(s):  
Neural Crest ◽  
Mus Musculus ◽  
The Other ◽  
The Third ◽  
Other Hand ◽  
Viii Level ◽  
Cranial Ganglia ◽  
The One

The relations between the neural crest on the one hand and the neuromeres and their precursors the proneuromeres on the other hand have never been fully described. Many authors have, however, shown that the cranial ganglia lie level with every second neuromere, so that ganglion V lies level with neuromere VII, ganglion VII–VIII level with neuromere IX, and ganglion IX–X level with neuromere XI (Bergquist, 1952). The neuromeres develop in a rostro-caudal wave, which is preceded by a similar wave of proneuromeres—formations of approximately the same appearance but relatively larger (Källén & Lindskog, 1953). The first proneuromere directly corresponds to neuromeres I–II, the second to neuromeres III–IV, the third to neuromere V; and in the rhombencephalon each proneuromere also corresponds to two neuromeres.

Nouns in σις and -τύς in Homer

Antichthon ◽  
1968 ◽  
Vol 2 ◽  
pp. 15-31 ◽  
Author(s):  
G.P. Shipp
Keyword(s):  
Western Europe ◽  
Early Stage ◽  
The Other ◽  
Considerable Importance ◽  
Greek Language ◽  
Verbal Nouns ◽  
Language And Thought ◽  
Other Hand ◽  
Secondary Type

The study of verbal nouns in Homer is of considerable importance for the understanding of the development of Greek language and thought and hence of methods of expression in the languages of Western Europe. Verbal nouns function primarily in much the same way as verbs, i.e. they express the same ideas as do verbs, and on the other hand they play similar parts in the structure of the sentence to other nouns. From this second aspect there evolves the tendency to particular reference, the ‘concrete’ use. The two functions of verbal nouns are a commonplace of semantic studies. In English we can say (1) in the building of houses=when one is building houses, (2) he came out of the building, and, in the plural, an important step, these buildings are to be demolished. The suffix -ing would be the nearest equivalent to -σις, capable like it of construction from any verb. The particular interest of nouns in -σις and -τύς in Homer is that the secondary type of use is still very rare, for example these nouns hardly ever occur in the plural, and thus the development of the ‘concrete’ use can be observed at a very early stage. The only functionally similar nouns in Homer, of types still in ‘free’ use, are those in -θμóς and -σἰη, which for reasons of space will be mentioned only incidentally, as their use impinges on that of the two other classes.

THE NATURE OF FIRE AND ITS COMPLICATIONS: THEOPHRASTUS' DE IGNE 1–10

2010 ◽  
Vol 53 (1) ◽  
pp. 47-97
Author(s):  
MARLEIN VAN RAALTE
Keyword(s):  
Early Stage ◽  
Formal Analysis ◽  
The Other ◽  
Other Hand ◽  
Simple Body ◽  
Fire Characteristics ◽  
Alter Ego ◽  
The Way

Abstract This article offers a running commentary on De igne 1–10 (with text and translation). The way in which Theophrastus sets out to ascribe to the simple body of fire characteristics of terrestrial, burning fire, and only gradually dismisses his focus on fire (and its alter ego of heat) as a principle seems to indicate an early stage of his thought. On the other hand, a formal analysis of the text shows that the argument bears an unmistakably Theophrastean stamp. Finally it is argued that it cannot be inferred from De igne that Theophrastus adhered to the Aristotelian concept of aithêr, and that it is also very unlikely that he did so. The relevant passages from Theophrastus' botanical treatises and Metaphysics confirm this picture. Even the quite explicit testimonies from Philoponus and Julian seem to allow of an interpretation that does not involve Theophrastus having adopted this Aristotelian concept.

scholarly journals Cosmology, Chemistry, and Aristotle’s Elemental Powers

Phronimon ◽  
2018 ◽  
Vol 19 ◽  
Author(s):  
Brad Berman
Keyword(s):  
The Other ◽  
Critical Step ◽  
Other Hand ◽  
Simple Body ◽  
The One

Aristotle employs the simple bodies, or elements, in two rather different scientific contexts, each of which highlights some of their qualities at the expense of others. On the one hand, he uses the elements in the service of cosmology, where their natural motions are imperative to drafting an architectural plan of the cosmos. On the other hand, he uses them in the service of chemistry, where their heat, coldness, dryness, and moistness are decisive in securing accounts of elemental transformation and the generation of composite bodies. Two families of interpretive proposals for the formal principles of Aristotle’s elements have been advanced accordingly. One family of interpretations construes the form of a simple body in terms of its cosmological characterisation, while a second construes that form in terms of the simple body’s chemical characterisation instead. A critical step in bridging that interpretive divide is thus to bridge the underlying divide between Aristotle’s cosmological and chemical characterisations of the sublunary elements. It is that latter task that I set out to accomplish in the present paper. I argue that the hot and the cold are efficient causes, respectively, of the light and the heavy, and further, that the moistness of elemental water and air explains the intermediary natural positions of those elements relative to earth and fire in Aristotle’s idealised cosmic landscape. In this way, Aristotle’s chemical characterisation of the elements is shown to ground his cosmological characterisation of them

The ECB's policy under the presidency of Mario Draghi: a curse or a blessing for Europe?

2020 ◽  
Vol 17 (2) ◽  
pp. 171-182
Author(s):  
Peter Bofinger
Keyword(s):  
Monetary Policy ◽  
Central Bank ◽  
European Central Bank ◽  
Early Stage ◽  
Financial System ◽  
The Other ◽  
European Central ◽  
Other Hand ◽  
Threatening Situation

The paper discusses the monetary policy of the European Central Bank (ECB) under the presidency of Mario Draghi. It first shows the serious mistakes made under his predecessor, Jean-Claude Trichet, during which period the ECB destabilized rather than stabilized. Draghi, on the other hand, embarked on a more expansive course immediately after taking office, thereby securing the existence of the euro in a very threatening situation. In 2014, he then identified the deflationary risks for the eurozone at an early stage and successfully countered them with massive bond purchases. The undesirable developments for the financial system and especially the banks predicted by his critics, who are to be found primarily among German economists, have not materialized.

THE CAUSE OF INCOMPATIBILITY BETWEEN BARLEY AND RYE

1945 ◽  
Vol 23c (1) ◽  
pp. 1-15 ◽  
Author(s):  
W. P. Thompson ◽  
Dorothy Johnston
Keyword(s):  
Early Stage ◽  
Embryo Sac ◽  
The Other ◽  
Abnormal Development ◽  
Barley Embryo ◽  
The Third ◽  
Other Hand ◽  
Hybrid Embryo ◽  
Viable Seeds ◽  
Antipodal Cells

When common barley is pollinated by common rye fertilization takes place normally but no viable seeds are produced. The immediate cause of the failure is abnormal development of the hybrid endosperm and particularly of the endospermic nuclei, which from an early stage are of immense size and are always few in number. No cells are ever formed in the endosperm. It collapses on the fifth or sixth day after pollination and disintegrates. The hybrid embryo, on the other hand, although it grows more slowly than the pure barley embryo from the third day, remains normal and healthy in appearance long after the endosperm has become very abnormal or has completely collapsed. The behaviour of the maternal tissues of crossed material is similar to that of selfed material, and rules out the theory of somatoplastic incompatibility. The behaviour of the antipodal cells of the embryo sac is not sufficiently different from normal to be of significance.

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