bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effects of Ultraviolet Irradiation on Uncleaved Eggs of Xenopus laevis
Authors: Gurdon J. B. 
Published: April 2021

ABSTRACT
The effects are described of ultraviolet (u.v.) irradiation upon the eggs of Xenopus laevis. The results obtained apply to fertilized eggs and also to unfertilized eggs into which blastula nuclei have been transplanted. Eggs were irradiated up to 20 min after laying, for periods varying from 15 to 50 sec.
The egg nucleus is completely inactivated by small doses of u.v. If fertilized eggs are used this gives rise to haploids, which the use of a nuclear marker has shown to be androgenetic. After irradiation the egg nucleus descends towards the centre of the egg, and comes to lie adjacent to the transplanted or sperm nucleus. At the first mitosis, however, it does not fuse but remains as a pycnotic clump in the centre of the spindle. Soon after this it disappears, without disintegrating into visible fragments. The transplanted or sperm nucleus appears to be unaffected by the irradiation and death of the egg nucleus.
The egg cytoplasm does not appear to be damaged, even after doses of u.v. which are considerably more than sufficient to kill the egg nucleus. The main reasons for this belief are that haploids obtained by other means develop no better than those obtained by u.v. An increase of u.v. treatment from 30 to 80 sec results in no increase in abnormalities sustained.
The jelly is broken down and the vitelline membrane weakened. This enables the egg to be penetrated by a micropipette without causing damage or preventing healing.
This investigation was undertaken to facilitate the analysis of nuclear transplantation experiments in Xenopus. The increased penetrability of eggs is of technical value for this purpose. The interpretation of these experiments is greatly facilitated by the knowledge that the egg cytoplasm need not be damaged by the u.v. and that the egg nucleus is completely inactivated so as not to interfere with the development of the egg.
The Electron Microscopy of the ‘Golgi Apparatus’ in the Purkinje Cells of Owls
Authors: Malhotra S. K. , Meek G. A. 
Published: April 2021

ABSTRACT
The classical site of the ‘Golgi apparatus’, the Purkinje cells of the cerebellum of owls, has been examined by electron microscopy. The greater part of the cytoplasm consists of aggregates of closely packed granular membranes of endoplasmic reticulum. The objects described by Dalton and Felix in electron micrographs and called by them the Golgi apparatus are rarely seen in these preparations. It seems likely that the ‘Golgi apparatus’ of this cell as seen in the optical microscope is formed by the de- position of silver or osmium on the membranes of the endoplasmic reticulum, which form a network throughout the cytoplasm of this cell.
The Early Post-moult Cuticle in Buthus
Authors: Krishnakumaran A. 
Published: April 2021

ABSTRACT
The cuticle of the scorpion, Buthus tamulus, has been studied at the early postmoult stage. There is a distinct two-layered epicuticle, which is non-chitinous, and a procuticle consisting of a chitin/protein complex. Polyphenols, phenolase, and sulphur are present at this stage. Quinones and groups containing sulphur seem to play a part in the subsequent hardening of the cuticle.
The Histology of the Neurosecretory System of the Adult Female Desert Locust, Schistocerca gregaria
Authors: Highnam K. C. 
Published: April 2021

ABSTRACT
The pars intercerebralis of the brain of the desert locust contains about 2,400 cells in two groups, which stain with chrome-haematoxylin-phloxin and with paraldehydefuchsin. On the basis of differences in size and staining reactions, four types of cell, called A-, B-, C-, and D-cells may be differentiated. The A- and B-cells produce different kinds of material; they are not thought to be stages in a secretory cycle. The C- and D-cells are probably not neurosecretory. The corpora cardiaca are divided into two regions. One part stores neurosecretory material from the pars intercerebralis and the other is glandular in appearance. Material discharged from the A- and B-cells in the immature female passes along the nervi corporis cardiaci I to the anterior parts of the corpora cardiaca. The mature female is characterized by the presence of very much larger amounts of material in the corpora cardiaca, in the nervi corporis cardiaci I, and in the A-cells of the pars intercerebralis. The significance of this larger amount of material with respect to neurosecretory cell activity is discussed.
A Comparative Histochemical Study of the ‘Golgi Apparatus’
Authors: Malhotra S. K. 
Published: April 2021

ABSTRACT
The purpose of this investigation was to find out the responses of Golgi’s net in the neurones of vertebrates to various dyes and histochemical reagents, and to compare these responses with those given by the ‘dictyosomes’ of the cells of invertebrates. Dictyosomes are regarded by many cytologists as the homologue of Golgi’s net. The young oocyte of Limnaea stagnalis was chosen as a cell that possesses typical dictyosomes, which have recently been examined by histochemical methods.
The object that presents the characteristic Golgi pictures in the neurones of vertebrates is essentially different, not only in ultrastructure but also in its chemical composition, from those that represent in life the ‘dictyosomes’ of invertebrates. The dictyosomes of the oocyte react positively to tests for phospholipid and cerebroside, whereas Golgi’s net is negative to these tests. Tests for arginine and for ribonucleic acid are positive for Golgi’s net, but not for the dictyosomes of the oocyte. The dictyosomes are intensely stained by Rawitz’s inversion staining technique and also by acid fuchsine (Metzner) and by iron haematoxylin, but these techniques do not show the net in the neurones of vertebrates. Golgi’s net is resistant to embedding in paraffin after fixation in Clarke’s (Carnoy’s) fluid, but the dictyosomes are not. Neutral red is taken up during life by the object representing the dictyosomes, but not by the net of Golgi.
The Iridophores of the Echinoid Diadema antillarum
Authors: Millott Norman , Manly Brenda M. 
Published: April 2021

ABSTRACT
The blue pattern seen when the skin of Diadema antillarum is viewed by reflected light is due to iridophores. The quality of their blueness varies with the background provided by neighbouring chromatophores.
Microdissection reveals that they consist of gelatinous plates contained in a fibrous and cellular capsule. The study of fixed preparations shows that the plates are sheathed and that their structure is greatly altered by fixation which distorts, disrupts, or dissolves them.
The structure of the iridophores bears little resemblance to the description of the so-called ‘eyes’ of D. setosum given by Sarasin and Sarasin, with which they appear to correspond.
Examination of their optical properties indicates that Rayleigh scattering by the colloidal contents is the most likely cause of their colour.
Coloration of the Golgi-Nissl Network in a Vertebrate Neurone by Sudan Black
Authors: Malhotra S. K. 
Published: April 2021

ABSTRACT
Though it is generally considered that the cytoplasmic inclusions, commonly described as ‘Golgi apparatus’, contain phospholipid, the routine histochemical tests for lipid do not reveal the apparatus in the neurone of vertebrates. A technique for colouring the apparatus in the neurones of vertebrates with Sudan black is described in this paper.
A New Automatic Machine for staining Histological Sections
Authors: Dilworth S. 
Published: April 2021

ABSTRACT
A machine is described for the automatic staining of sections of tissue, mounted on microscope slides. It is narrow and compact, and can be placed along the back of a bench or on a shelf. Although for the present purpose the machine is designed to accommodate up to 26 tanks, any number less than this may be used. A rack holding 30 slides is attached to a carrier, which then conveys it through the various solutions, according to a predetermined programme.
A Study of the so-called ‘Chloride-Secretory’ Cells of the Gills of Teleosts
Authors: Vickers T. 
Published: April 2021

ABSTRACT
The histology of the gills of a normally freshwater teleost, the guppy (Lebistes reticulatus), has been studied after the fish had been subjected to various concentrations of sodium chloride. Cells similar to those identified by previous workers as ‘chloride- secretory cells’ develop in response to adaptation to hypertonic salt solutions, and the number and character of the cells can be related to the salt load and to the degree of adaptation of the fish to it. The cytology of these cells has been shown to be consistent with their supposed function. In fish which are not fully adapted to the salt load, these cells show signs of the formation of mucous materials, and under extreme conditions they may undergo transformation into goblet cells. This may provide an explanation of the failure of Bevelander (1935, 1936) to find any specialized cells other than mucous cells on the teleost gill.
The staining of nervous elements by the Bodian method I. The influence of factors preceding impregnation
Authors: Williams Terry 
Published: April 2021

ABSTRACT
The stainability of neural elements is determined during the various stages of tissue preparation which precede impregnation.
The hypothesis (Romanes, 1950) that variations in the physiological state of the neurones at the time of fixation might influence the stain was examined. Feeding and anaesthesia did not influence the staining of gastric nerve fibres under the conditions of the experiments.
A study was made of fixing fluids for Bodian staining. A picric-acetic-alcohol mixture and alcoholic Bouin were convenient and effective, each being superior to formaldehyde-acetic-alcohol. For overnight fixation formaldehyde solution neutralized with calcium carbonate was satisfactory, but where prolonged fixation is permissible formaldehyde neutralized with excess of magnesium carbonate gave superior results.
Attention was drawn to the probability that the final stain could be improved by ‘pretreatment’ of mounted sections before silvering. Dewaxed sections were treated individually with 27 substances from a variety of chemical groups to determine the effects on subsequent Bodian staining. Nitric and sulphuric acids, formaldehyde solution neutralized with magnesium carbonate, methyl alcohol, and perhaps sodium carbonate contribute in different ways towards better preparations. In particular pretreatment with nitric acid suppresses the background stain, especially in smooth muscle; sulphuric acid increases the number of fine nerve fibres displayed, and methyl alcohol facilitates the staining (in formaldehyde-fixed tissues) of nerve fibres that are otherwise difficult to demonstrate, such as those in the renal cortex, which are almost certainly post-ganglionic sympathetic fibres.
Neurosecretory cells in the optic tentacles of certain pulmonates
Authors: Lane Nancy J. 
Published: April 2021

ABSTRACTCells considered to be neurosecretory have been observed in the optic tentacles of certain stylommatophoran pulmonates. Such cells are divisible into three distinct types, of which those called the ‘collar’ cells surround the central digitate ganglion and eye. The other two types, the ‘lateral oval’ and the ‘lateral processed’ cells, lie laterally in the tentacle, on the inner edge of the outer dermo-muscular sheath. All three cell-types have branching dendritic processes, containing granules. The dendrites of the collar and of the lateral cells apparently extend from the cell-body to the surface of the epithelium. The axonal processes of all three types are thick and contain granules.The ground cytoplasm of these cells is scarcely visible owing to the great number of homogeneous, spheroidal granules that are present. The granules are sudanophil, and the ones in the collar cells contain phospholipid (probably cerebroside as well). All three types of cells contain a much smaller number of lipid droplets, with sudanophil and osmiophil externum and sudanophobe and osmiophobe internum; these are dispersed through the cytoplasm. Special ‘perinuclear bodies’, also binary in structure, are present in the collar cells and lateral oval cells.Cells of the types described in this paper have not been found in other sub-classes of the Gastropoda, nor in the Basommatophora, but only in the pulmonate order, Stylommatophora. They appear to form an area of active neurosecretion in the re-tractile tentacles of these animals.
A modification to the Huxley ultramicrotome
Authors: Mcgee-Russell S. M. , Roberts F. H. , Jacobs J. K. 
Published: April 2021

ABSTRACT
The mechanism of advance of the Huxley ultramicrotome was modified by the addition of appropriate gearing to facilitate the routine preparation of ½ to 2 μ sections for phase contrast or interference microscopy as an adjunct to the study of thin adjacent sections by electron microscopy. The plate depicts the nature of the modification.
An investigation of the anomalous staining of chromatin by the acid dyes, methyl blue and aniline blue
Authors: Mckay R. B. 
Published: April 2021

ABSTRACT
Methyl blue and aniline blue, though acid dyes, stain the chromatin of the spermatogenetic cells of the mouse (especially of the primary spermatocytes) strongly. Extraction of the basiphil nucleic acid constituents from the chromatin causes loss of this property, while destruction of acidophilia in the protein constituents does not. It has been concluded that the dyes interact with the nucleic acids. Further, they appear to react with both DNA and RNA in the chromatin, although they show no affinity for the cytoplasm of the exocrine cells in sections of pancreas, which is rich in RNA.
The mechanism of the reaction has not been fully elucidated, although apparently the dyes do not behave as basic dyes towards the nucleic acids, and the interaction is non-ionic. Methyl blue and aniline blue stain strongly other ‘acidic’ substrates, such as cellulose and nitrocellulose, and attempts have been made to relate the staining of nucleic acids to the staining of these substrates, particularly cellulose; for the staining properties of this substrate have been intensively investigated elsewhere. No satisfactory correlation, however, has been obtained, for nitrocellulose has been found to be less strongly stained at pH 3·0 than at pH 7·1, while the reverse is true for cellulose. Further, only one of 3 direct cotton dyes used appears to have any affinity for the chromatin of the spermatogenetic cells. Direct cotton dyes have large flat molecules with a high degree of conjugation. It is suggested that these characteristics are essential for interaction with nucleic acids, and also that the molecule must be reasonably compact.
Finally, it has been shown that methyl blue, aniline blue, and 3 direct cotton dyes of the azo type have no ability to stain the glycogen in liver cells, yet glycogen is very closely related to cellulose.
The control of dragline spinning in the garden spider
Authors: Wilson R. S. 
Published: April 2021

ABSTRACT
A study of the tarsal claws, the spinning apparatus, and other factors affecting dragline spinning has been made using certain orb-web spiders, principally Araneus diadematus. The structure of the tarsal claws suggests that they are incapable of smoothly controlling the speed at which the silk thread is extracted, although they can grip and release the thread quickly.
Evidence is presented that smooth control of spinning is achieved through the interaction of the intra-abdominal pressure and the control valve which lies in the silk duct. The intra-abdominal pressure is shown to be equivalent to from 3 to 4 cm of mercury, and to be responsible for moving the fluid silk out of the gland and up the duct. The experimental results also suggest that the control valve regulates the amount of fluid silk available for spinning as a thread and that it also acts as the functional spinning orifice, its aperture controlling the diameter of the thread spun.
The fine structure of the cortical layers in Paramecium aurelia
Authors: Stewart John M. , Muir Alan R. 
Published: April 2021

ABSTRACT
Paramecia have been cultured in 5 % iron-dextran solution for several days, but under the present experimental conditions do not appear to synthesize the iron-storage protein ferritin.
High resolution electron micrographs were obtained of the outer ‘pellicular’ and inner ‘peribasal’ membranes of the cortical layer in Paramecium aurelia; both membranes proved to be triple-layered unit membranes, each having two osmiophilic layers 2 to 3 mμ thick separated by a space of 3 mμ- The outer membrane of the cilium has the same structure as, and is continuous with, the pellicular membrane. This fact is thought to be of significance with regard to antigen studies.
Modifications to the Gomori acid phosphatase technique for controlled-temperature frozen sections
Authors: Bitensky Lucille 
Published: April 2021

ABSTRACT
The preservation of inert lysosomes in tissue sections depends on the use of the controlled-temperature freezing-sectioning technique. The Gomori procedure for acid phosphatase produces considerable disintegration of these unfixed sections. This disintegration is not due to incubation in the acid medium nor to the rinsing either in dilute acetic acid or in distilled water, but to the treatment with the solution of ammonium sulphide. It is suggested that for this solution there should be substituted a saturated aqueous solution of hydrogen sulphide gas, which does not cause such cellular deformation. Another improvement involves the deletion of the rinse in acetic acid, because this might render soluble some of the specific precipitate in sections showing minimal acid phosphatase activity.
The form of bivalent chromosomes in newt oocytes at first metaphase of meiosis
Authors: Watson I. D. , Callan H. G. 
Published: April 2021

ABSTRACT
Lampbrush chromosomes in the ovarian oocytes of newts are associated as bivalents. Some connexions between lampbrush chromosomes are chiasmata; others are known to be fusions of gene products; yet others, namely reflected, centromere, and telomere fusions, do not appear to be due simply to the fusion of gene products. Whether chiasmata are involved in reflected, centromere, and telomere fusions cannot be decided from examination of the chromosomes at the lampbrush stage. Bivalents from oocytes at first meiotic metaphase were therefore studied. The oocytes of newts reach first meiotic metaphase after ovulation, whilst they are free in the coelome. Reflected, centromere, and the great majority of telomere fusions do not persist to first meiotic metaphase: thus chiasmata are not involved in them.
In oocyte bivalents of Triturus helveticus chiasmata are not restricted in their distribution, whereas in spermatocyte bivalents of this species chiasmata are proterminally localized. In oocyte bivalents of 3 subspecies of T. cristatus chiasmata are procentrically localized, whereas in spermatocyte bivalents of these subspecies chiasmata are not restricted in their distribution.
Thus in T. helveticus meiosis in the female sex is mainly responsible for genetic recombination, whereas in T. cristatus the situation is reversed. We conclude that to base genetical and evolutionary inferences on information drawn from the meiosis of one sex only is unjustified, and we doubt the validity of the claim that chiasma localization has arisen so as to restrict genetic recombination.
The fine structure of the membranes which cover the egg of the grasshopper, Melanoplus differentialis, with special reference to the hydropyle
Authors: Slifer Eleanor H. , Sekhon Sant S. 
Published: April 2021

ABSTRACT
Electron-microscope studies have shown that the epicuticle of the hydropyle consists of 2 layers. The inner is complexly folded and the outer consists of a meshwork of fine fibrils which fills the spaces between the folds. The endocuticle is laminated, penetrated by pore canals, and contains many wax-canal filaments. The filaments are especially abundant immediately before diapause.
During diapause a dense, homogeneous layer is present at the outer surface of the hydropyle. It is absent before diapause and discontinuous or absent in eggs which are developing without diapause, or after diapause has been prevented or broken. The results confirm the conclusions, based on earlier studies, that the hydropyle is waterproofed by a waxy coating during diapause and that this material is absent or discontinuous in eggs which are developing.
The vitelline membrane is an excessively thin, dense layer which lies below the chorion and lines the micropyles. It is less resistant at the posterior end of the egg than elsewhere. During development it is incorporated into the cuticle, which is secreted by the serosa. It is now believed that the ‘resistant endochorion’ described earlier for this species is identical with the vitelline membrane which Salt described in 1952 for the eggs of Melanoplus bivittatus.
Morphological variability and its physiological origin in oocyte nuclei of the crested newt
Authors: Macgregor H. C. 
Published: April 2021

ABSTRACT
The effects of hypophysectomy and of subcutaneous injection of gonadotrophin upon whole oocytes, oocyte nuclei, and lampbrush chromosomes of the newt Triturus cristatus carnifex have been studied.
Hypophysectomy leads to a reduced rate of incorporation of 32P into the whole oocytes and oocyte nuclei. Large, yolky oocytes are more severely affected than are small oocytes lacking yolk. Hypophysectomy also leads to decreased stiffness of oocyte nuclear sap, change in the number and character of free granules in the nuclear sap, and alteration in the size of certain objects occurring at specific sites on the lampbrush chromosomes.
Injection of mammalian gonadotrophin leads to an increased rate of uptake of 3aP into the cytoplasm and nuclei of yolky oocytes. Gonadotrophin treatment also leads to increased stiffness of oocyte nuclear sap, decrease in the number and/or the size of free granules in the nuclear sap, reduction in size of the giant loops of chromosomes X, XI, and XII, and changes at the axial granule loci of chromosome I and the sphere loci of chromosomes V and VIII.
Each of the features mentioned above varies in nature from one animal to another. This inconstancy, which is superimposed upon stable genetic characteristics and upon those developmental changes which normally accompany oocyte growth, is now shown to reflect differences in the physiological states of the ovaries of different newts.
The cuticle and associated structures of Podura aquatica at the moult
Authors: Noble-Nesbitt J. 
Published: April 2021

ABSTRACT
At the beginning of a moult a foam secretion appears between the epidermal cell surface and the old cuticle. This secretion is involved only with the lifting away of the old cuticle and formation of the exuvial space. A granular secretion then appears in the exuvial space. The granules contain inactive moulting enzymes, which become active only after the completion of the new cuticulin layer, and then digest the soft parts of the old cuticle. The rest of the new cuticle is laid down extracellularly and in lamellae below the cuticulin layer. The sculpturing of the new cuticle occurs under the influence of the epidermal cells. Subsequent hardening of certain areas of the new cuticle involves disruption of the lamellae and complete reorganization. Setae are formed early and rapidly, but nervous connexions with the old setae are maintained until just before ecdysis. Muscle insertions into the new cuticle are formed early, but attachment to the old cuticle is retained until ecdysis. The cuticulin layer is involved in the formation of the new attachments.