Sections of nuclei of oocytes, showing one or more of these heterochromosomes, from safranin-gentian preparations.
In addition to this, in one-half of the spermatid nuclei there is a condensed mass of chromatin which is evidently the derivative of the odd chromosome of the spermatogonia and spermatocytes (figs.
It was interesting to find here and there in this material whole cysts in which the nuclei were like those described by Paulmier ('99) for Anasa tristis (plate XIII, fig.
There is no synizesis and no polarized or bouquet stage, but the nuclei of all of the spermatocytes contain a continuous spireme throughout the growth stage.
Next to the secondary spermatogonia are cysts of young spermatocytes, whose nuclei show a continuous spireme and an elongated deeply staining chromatin rod which is the odd chromosome (fig.
The size of the heterochromosome pair varies considerably at different times in the growth period, and in some nuclei (fig.
One of the four nuclei resulting from the second division again dividing to form the pairing-nuclei in either mate, while the other 3 nuclei degenerate.
The aggregation of matter round thenuclei by gravitation would have no such tendency; no more than a perfect balance would of itself have a tendency to move about its fulcrum, or a falling stone to deviate from its vertical course.
The existence of the fire-mist and nuclei are assumptions only, and the way by which he tries to account for rotatory motion is clearly erroneous.
Like a good chemist, previous to analysis, the author first throws all matter into a state of solution; but granting him his fire-mist and nuclei in the midst, how or whence came this condition and arrangement of nature?
Then the rupture of the crust and the emergence of the nuclei of continents.
The wide level bottom of the Laurentian sea was broken up and thrown into those bold ridges which were to constitute the nuclei of the existing continents.
The period was characterised also by the great interest taken in cytology, following upon the pioneer work of Hertwig, van Beneden and others on the behaviour of the nuclei in fertilisation and maturation.
These nuclei had accordingly the same significance as the nuclei of plants, and deserved the same name of cytoblasts or cell-generators.
These specific nuclear substances, different for each cell, are accumulated also in the nuclei of the germinal substance, constituting what Rignano calls the central zone of development.
The division of nuclei was observed by Coste in 1846.
Müller himself had not only recognised the cellular nature of the notochord, but had observed the cells of the vitreous humour, fat cells and pigment cells, and even the nuclei of cartilage cells.
Müller seems to have been the first actually to prove that it forms by division the nuclei of the first two segmentation spheres.
He held, however, that the nuclei multiplied endogenously and not by division.
Other nuclei were in many cases present in the cell, round which young cells could be seen to develop, in exactly the same manner as in plants.
He considered the nuclei to be anucleate cells, and the same view was taken by Kölliker in 1843.
Several nuclei might be formed in this way in a single cell.
It is not uncommon for needles, hair-pins, and the like to form nuclei for incrustations.
Poland, which has large nuclei of German populations, after having been enslaved, claims the right to enslave populations, which are more cultured, richer and more advanced.
Also other nuclei of population have been detached without reason.
In ordinary circumstances the abundant free nuclei demonstrable in the plasmodium afford the only evidence of cellular organization.
From the physiological point of view it is perfectly clear that Cobra-venom especially affects the bulbar centres, and particularly the nuclei of origin of the pneumogastric nerve.
The muscular nuclei become distorted, appear long or angular, and assume the aspect of myoblasts (sarcoblastic muscle cells).
The nuclei are opaque, the nucleoli swollen and broken up.
Death is always preceded by a period of asphyxia, indicating that the bulbar nuclei of the pneumogastric nerve have become affected.
There ought to result a morphogenetic chaos according to the theory of real “evolutio” carried out by nuclear division, if the positions of the single nuclei were fundamentally changed with regard to one another (Fig.
It is from this phenomenon of nuclear union as the main character of fertilisation that almost all theories of heredity assume their right to regard the nuclei of the sexual cells as the true “seat” of inheritance.
Thus in the egg of Diptera, the two nuclei which are first separated by division from the segmentation nucleus, form the sexual cells, and this proves that they receive the germ-plasm of the segmentation nucleus unchanged.
It is now generally admitted that, in the Vascular Cryptogams, as also in Mosses and Liverworts, the bodies of the spermatozoids are formed by the nuclei of the cells from which they arise.
In this way each resulting daughter-nucleus receives an equal supply of halves, and it therefore appears that the two nucleimust be completely identical.
But the complexity of the whole organism is not represented in the molecular structure of the idioplasm of any single nucleus, but by that of all the nuclei present at any one time.
But however this may be, the assumed attraction between the conjugating nuclei certainly cannot depend upon the molecular structure of their germ-plasm, which is the same in both, but it must be due to some accessory circumstance.
It is conceivable that all somatic nuclei may contain 211 some germ-plasm II.
But now we can hardly give to the body of the egg-cell a higher significance than that of the common nutritive soil of the twonuclei which conjugate in fertilization.
A little later, however, two nuclei may be found in the protoplasm.
One of the nuclei which grows into the pollen tube is known as the sperm nucleus.
The nuclei in the tube in (3) are the sperm nuclei.
Two nuclei are found (n, n') at this stage of its growth.
When the pollen grain germinates, the nuclei enter the threadlike growth (this growth is called the pollen tube; see Figure).
Nevertheless, it is possible to get around the random behavior of an individual nucleus by dealing statistically with large numbers of nuclei of a particular radioactive isotope.
The three basic modes of radioactive decay are the emission of alpha, beta and gamma radiation: Alpha--Unstable nuclei frequently emit alpha particles, actually helium nuclei consisting of two protons and two neutrons.
In fusion, according to nuclear theory, when the nuclei of light atoms like hydrogen are joined, the mass of the fused nucleus is lighter than the two original nuclei; the loss is expressed as energy.
The signification of these facts is as follows: as soon as, in the course of development, the conjugated nuclei divide again into two cells, as in Figs.
Moreover, although of the same size, the nuclei which become conjugated are evidently of unequal strength; the energies of one or the other predominate later on in the embryo, and still later in man.
Moreover, the different organs of the body may receive their energies from different parts of the conjugated nuclei in different degrees.
Their nuclei become applied against each other and each exchanges half its substance with the other as in the preceding case, so that the final result is the same.
These masses of grey matter, taken together, are the basal nuclei of the brain.
The reason why the basal lamina is here small is because it contains the nuclei of no cranial nerves.
For in the medulla are found the nerve nuclei which preside over the facial, laryngeal and pharyngeal muscles.
On transverse sections no difference between the olivary nucleibeyond that which occurs in healthy persons could be found; the asymmetry was ascertainably one of prominence only.
Some of the cells of the anterior horn were swollen and the nuclei eccentric; chromatolysis had occurred in many of them.
These larger cells have a granular protoplasm with large nuclei and are obviously actively secreting.
These nuclei are often referred to as "dust particles," but it is recognized that a vast proportion of them are very much more minute than the dust that worries housewives.
As we have seen, the existence of nuclei in the air serves to explain why, when the conditions of temperature and humidity are right, moisture condenses in the tiny droplets that constitute clouds.
The number of nuclei is so great that, as Humphreys has pointed out, even if all the water vapor in a volume of humid air was condensed upon them, the size of each drop would remain very small.
It is supposed that, like drops, they require nuclei on which to condense, but this matter has not been fully investigated.
An instrument for determining approximately the number of dust particles or condensation nuclei per unit volume in a sample of air.
These bundles are generally marked by the possession of nuclei, especially in their cortical parts, which become no doubt the nuclei of the nerve sheath, and, in the neighbourhood of the ganglia, of nerve cells.
Such a centre of growth is frequently called a blastema, and consists of a mass of closely packed nuclei which have arisen by the growth-activity of the nuclei in the neighbourhood.
The centrosome now divides, the membranes of both nuclei disappear, and a spindle is formed.
In other Arthropodan eggs the cleavage is on the so-called centrolecithal type, in which the dividing nuclei pass to the cortex of the ovum, and the surface of the ovum becomes indented with grooves corresponding to each nucleus.
The other product of the dividing yolk-nuclei remains in the yolk, in readiness for the next division.
The object with which these two minute and simple organisms are produced is to fuse with one another and give rise to one resultant uninucleated (for the nuclei fuse) organism or cell, which is called the zygote.
The nuclear division of cleavage is usually at first a rhythmical process; all the nuclei divide simultaneously, and periods of nuclear activity alternate with periods of rest.
In the mouse the subsequent events are as follow:--Both pronuclei assume the resting form, the chromatin being distributed over the nuclear network, and the nuclei come to lie side by side in the centre of the egg.
One of these is epithelial in character, while the other has the form of a network of protoplasm, withnuclei at the nodes.
As the science of magnetohydrodynamics had progressed, the effect had become more and more controllable, enabling scientists to force the nuclei of hydrogen, for instance, closer and closer together.
Now, suppose a man had a pair of tweezers small enough to pick up a single molecule of lithium hydride and pinch the two nuclei together.
There still were to be seen piles of earth that marked where at least seven great communal houses had formed nuclei for a numerous people.
It stains the nuclei and blood plates, but does not alter the shape of the red cells.
Thus, the nuclei are stained violet, the cell protoplasm a much paler and warmer violet, the fibrous tissues pink, and red blood corpuscles orange or brick red.
The red corpuscles are slightly stained, while the nuclei of the white corpuscles are stained a bright crimson, and the “blood plates” a deep pink colour.
The nuclei of the leucocytes may be stained rapidly in a couple of minutes in a one per cent.
It picks out the nuclei and axis cylinders of nerves, stains cell protoplasm slightly, and the fibrous elements scarcely at all.
The tissue must be very thoroughly washed in running water to remove all traces of osmic acid, and then stained for a couple of days in borax carmine to demonstrate the nuclei and axis cylinders.
Hæmatoxyline stains the nuclei of the cells a beautiful violet colour, and also tints, more or less lightly, the cell protoplasm and the fibrous elements.
Thus hæmatoxyline stains the nuclei and rapidly growing parts of the tissue, leaving the formed material, as a rule, much more lightly tinted.
In this way the eosinophile granules of the leucocytes and the red corpuscles, are stained by the eosine, while the nuclei of the leucocytes are stained by the methyl blue.
The nerve cells and their processes are stained a deep slate colour, as are the nuclei of the connective tissue cells, while the ground work of the neuroglia is faintly stained and of a neutral grey tint.
Here they might have gathered in a nucleus and, collecting other fragments to it, form a small planet, were it not that the gaps were frequent enough to preventnuclei of sufficient size arising anywhere.
For had they arisen from already more or less complete nuclei these could not have borne to one another the general comensurate relation of mean motions existent to-day.
Their laminæ in fragments, and the nuclei entire, are, in consequence, often evacuated along with the urine in considerable numbers.
And these minutenuclei constitute a proximate animal principle, possessing such well marked characters as to justify us in regarding them as peculiar in their nature, and essential to the composition of the pus globule.
It is a very intimate form of nourishment; for it appears that in general the nuclei themselves of the two cells are shared and in part exchanged.
The situation then is that there are two nuclei of the same size and both charged with chromatin of the same general character, in close proximity, and waiting to fuse with each other.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "nuclei" in a variety of sentences. We hope that you will now be able to make sentences using this word.
