Word Finder - nuclei

definition

The core, central part of something, around which other elements are assembled.

definition

An initial part or version that will receive additions.

example

This collection will form the nucleus of a new library.

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The massive, positively charged central part of an atom, made up of protons and neutrons.

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A large membrane-enclosed organelle found in eukaryotic cells which contains genetic material.

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A ganglion, cluster of many neuronal bodies where synapsing occurs.

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The central part of a syllable, most commonly a vowel.

Nuclei are everywhere present.

Miss Nichols fi -ids that it occurs very soon after the germination of the spore in Cc sinus, but no fusion of cells or migration of nuclei was to be observed.

This view is still maintained by those who differentiate two acts of fertilization within the embryo-sac, and regard that of the egg by the first male-cell, as the true or generative fertilization, and that of the polar nuclei by the second male gamete as a vegetative fertilization which gives a stimulus to development in correlation with the other.

The idea of the endosperm as a second subsidiary plant is no new one; it was suggested long ago in explanation of the coalescence of the polar nuclei, but it was then based on the assumption that these represented male and female cells, an assumption for which there was no evidence and which was inherently improbable.

The full number is restored in the fusion of the male and female nuclei in the process of fertilization, and remains until the formation of the cells from which the spores are derived in the new generation.

The so-called zoospore of Vaucheria is a coenocyte covered over with paired cilia corresponding in position to nuclei lying below.

In coenocytic forms the zoospores would seem to arise simultaneously, probably because many nuclei are already present.

All investigation goes to show that an essential part of sexual union is the fusion of the two nuclei concerned.

It is interesting to know, on the authority of Oltmanns, that when the oosphere is forming in the oogonium of Vaucheria, there is a retrocession of all the included nuclei but one.

It would seem that in some cases the nuclei of the gametes remain distinct in the zygospore for a considerable time after conjugation.

It would seem that eight nuclei primarily arise in all Fucaceae, and that a number corresponding to the number of oospheres subsequently formed is reserved, the restbeing discharged to the periphery, where they may be detected at a late stage.

It is singular that in the last-named species two nuclei occur regularly in the spermatium.

In the latter case, and especially where the union is with a special auxiliary cell, it is of importance to know what happens to the nuclei of the fusing cells.

Schmitz was of opinion that in the cases of open union there occurred a fusion of nuclei similar to that which occurs in the sexual union of two cells.

As is well known, the dividing nuclei of the cells of the sporophyte generation of the higher plants exhibit a double number of chromosomes, while the dividing nuclei of the cells of the gametophyte generation exhibit the single number.

Starting from a widely diffused nebula, more or less uniform, we find that, in consequence of gravitational instability, it will tend to condense about a number of nuclei.

As the nuclei grow by the attraction of matter they begin to be capable of retaining the lighter gases, and atmospheres of hydrogen and helium are formed.

The most recent works (Vejdovsky, Mend), however, appear to show that nuclei of a structure and mode of division almost typical are to be found in some of the largest bacteria.

This product is largely derived from the nuclei of the leucocytes, which contain large quantities of the nucleo-proteids, of which uric acid is a decomposition product.

Evidence has lately been adduced of the existence of numerous nuclei in the pollen-tubes of the Araucarieae, and it seems probable that in this as in several other respects this family is distinguished from other members of the Coniferales.

Blackman, who also succeeded in showing that the nuclei of the sporophyte generation contain twice as many chromosomes as the nuclei of the gametophyte.

Other observers have in recent years demonstrated a similar relation in other genera between the number of chromosomes in the nuclei of the two generations.

In the process of fertilization the two male generative nuclei, accompanied by the pollen-tube nucleus and that of the stalk-cell, pass through an open pit at the apex of the pollen-tube into the protoplasm of the ovum.

After fertilization the nucleus of the egg divides, the first stages of karyokinesis being apparent even before complete fusion of the male and female nuclei has occurred.

The result of this is the production of four nuclei, which eventually take up a position at the bottom of the ovum and become separated from one another by vertical cellwalls; these nuclei divide again, and finally three tiers of cells are produced, four in each tier.

In certain species of Gnetum described by Karsten the megaspore contains a peripheral layer of protoplasm, in which scattered nuclei represent the female reproductive cells; in Gnetum Gnemon a similar state of things exists in the upper half of the megaspore, while the lower half agrees with the megaspore of Welwitschia in being full of prothallus-tissue, which serves merely as a reservoir of food.

In Gnetum Gnemon, as described by Lotsy, a mature embryo-sac contains in the upper part a large central vacuole and a peripheral layer of protoplasm, including several nuclei, which take the place of the archegonia of Ephedra; the lower part of the embryo-sac, separated from the upper by a constriction, is full of parenchyma.

The megaspore becomes filled with the female prothallus, the formation of cell-walls commencing at the pointed end of the spore, where from the first the nuclei are more numerous, and later extending to the base.

All the bishops in a coenobium were subject to the abbot; but besides the bishop in the monastic families, every tuath or tribe had its own bishop. The church in Ireland having been evolved out of the monastic nuclei already described the tribe bishop was an episcopal development of a somewhat later period.

For purposes of defence early settlers naturally chose elevated ground, frequently a hill with precipitous sides, and these early citadels became in many parts of the world the nuclei of large cities which grew up on the surrounding lower ground.

The segmentation is peculiar, and leads to the formation of a solid gastrula, consisting of a cortex of ectoderm nuclei surrounding a central endodermal mass, which is exposed at one point - the blastopore.

After analyzing individual transformants, nucleoplasmin was shown to successfully target aequorin to nuclei.

Greater ionizing radiation from the Sun during those times also tends to produce more nuclei in the atmosphere for cloud condensation.

In all cases tumor cells were relatively small and showed monomorphic or pleomorphic nuclei, prominent nucleoli, and ill-defined cytoplasm.

H Be able to attribute this decrease in activity to a corresponding decrease in the number of unstable nuclei.

A powerful electromagnet causes the nuclei of atoms (particularly hydrogen in water molecules) to align magnetically.

Several neutrons are also produced which may go on to strike the nuclei of other atoms causing further fission.

Infection also involves motor cortex, hypothalamus, and globus pallidus, brainstem nuclei, reticular formation, cerebellar roof nuclei, and vermis.

Basically, the Hydrogen nuclei fuse together in a series of reactions to form Helium nuclei and energy.

If sufficiently energetic, the created hadrons can undergo further interactions, making yet new hadrons and disrupting more nuclei.

Due to their narrow spectral lines, they also act as a high-resolution probe of gas kinematics in outflow regions and active galactic nuclei.

In contrast, the DNA in somatic nuclei is not fully neutralized by histones.

Early in 1932 James Chadwick discovered the neutron, a particle in the nuclei of most atoms.

The paraventricular nuclei produce mostly oxytocin and the supraoptic mostly vasopressin although both hormones may also be produced by the other type of nuclei.

The nuclei of the cells show pleomorphism, with variation in size, shape and chromatin staining pattern.

The high kinetic energies are needed to overcome the repulsion of the two positive nuclei.

He uses high-resolution solid-state detectors to make precision measurements on the gamma rays emitted by radioactive nuclei.

What is the nature of the massive dusty torus believed to surround Active Galactic Nuclei?

Tetanus has been reported to induce lesions in the vagal nuclei, while locally applied toxin may lead to excessive vagal nuclei, while locally applied toxin may lead to excessive vagal activity.

The body is covered externally by a chitinous cuticle which is a product of the subjacent epidermic layer in which no cell limits can be detected though nuclei are scattered through it.