bluuebunny/crossref_metadata_2025 huggingface dataset:
Experiments on the Action of Mordants: I. ‘Single-bath’ Mordant Dyeing
Authors: Baker John R.
Published: April 2021

Aluminium sulphate was chosen as the simplest mordant, and purpurine (1,2,4-hydroxyanthraquinone) as the simplest dye suitable for use in experiments with mordants.

It was shown by a series of experiments that a solution containing about 16 atoms of aluminium to each molecule of purpurine has special properties. A section already dyed with an aluminium/purpurine solution till chromatin is dark and cytoplasm lightly tinged, is in equilibrium with such a solution : that is to say, it neither takes up more dye nor loses any part of what it already holds. If the proportion of dye to mordant is increased, the section will take up more of the dye ; if the proportion of the mordant to the dye is increased, the section will lose part or all of the dye it held.

The experiments described in the paper, taken in conjunction with existing knowledge of the behaviour of aluminion ions in solution and of their capacity to form chelate compounds with anthraquinonoid dyes, afford a basis for the following theory of single-bath mordant dyeing by aluminium/purpurine.

One purpurine ion chelates with one hydrated aluminium ion to form a complex ion with double positive charge; this is attracted to sites of negative charge in the tissues, such as the phosphoric groups of the nucleic acids. Electrostatic attraction is replaced by covalent bonds, resistant to solution by neutral ethanol. In extraction (‘differentiation’) by the mordant, the dye partitions itself between the tissue/mordant complex on one hand and the dissolved mordant on the other.
An Electron Microscope Study of Bacteria in the Oocytes and Follicle Cells of Blatta orientalis
Authors: Gresson R. A. R. , Threadgold L. T.
Published: April 2021

The bacteria present in the oocytes and follicle cells of Blatta orientalis Linn, were studied by means of electron microscopy. Bacteria are present in the follicle cells surrounding young oocytes, from where they invade the peripheral ooplasm. Each bacterium in an oocyte soon becomes surrounded by a system of membrane-like structures that form an outer covering. Later the bacteria congregate at the poles of the oocyte. An oval body was visible in one electron micrograph; this probably represents a stage in the life-history of the organism.
Tropical Ester Wax 1960
Authors: Steedman H. F.
Published: April 2021

A modification of the standard ester wax 1960 is given which enables sections to be cut at a room temperature of 170 to 37° C (62·6° to 98 6° F). The melting-point of tropical ester wax is 50° C. Ribboning and flattening of sections is good, from 1 to 10 p.
The Structure and Mode of Functioning of the Reproductive Organs of Tritonia hombergi (Gastropoda Opisthobranchia)
Authors: Thompson T. E.
Published: April 2021

Routine observations on Tritonia hombergi Cuvier dredged from an area off the south coast of the Isle of Man indicate that the species has an annual life-cycle similar to that of many dorid nudibranchs.

The ovotestis communicates with the anterior genital mass through numbers of collecting tubules which unite to form a stout hermaphrodite duct. This duct functions as a vesicula seminalis in adult specimens; spermatozoa stored here are physiologically immature. The hermaphrodite duct bifurcates to form male and female ducts; the region of the bifurcation forms a valve ensuring that oocytes shall not enter the purely male regions of the genital system during oviposition. The male duct is the glandular and muscular vas deferens which connects with the base of the protrusible penis. The oviduct opens into the lumen of the mucus-gland. A region of convoluted tubules close to the point of the opening of the oviduct into the mucus-gland is the albumen-gland. The bursa copulatrix is a blind tubular invagination of the lateral body-wall which in mature specimens stores spermatozoa received at copulation. There are thus three external genital openings.

Copulation is almost invariably reciprocal, the penis of each individual being inserted into the bursa copulatrix of the other. Secretions from the glandular linings of the bursa and of the vas deferens render spermatozoa exchanged at copulation physiologically mature; they are active and capable of fertilizing oocytes.

At oviposition oocytes are expelled from the ovotestis and transported by cilia to the main hermaphrodite duct. They then travel (through the dense masses of spermatozoa in this duct) along a narrow longitudinal ciliated tract of lining epithelium; this phenomenon was clearly observed in vivisected individuals. At the hermaphrodite valve the oocytes are deflected into the oviduct and are carried by cilia into the mucusgland. In the lumen of this organ they meet active ‘foreign’ spermatozoa which have made their way from the bursa copulatrix. The oocytes and spermatozoa are now conducted along a tortuous predetermined ciliary path through the albumen-gland (where the primary egg-cases are secreted and where fertilization occurs), and then through the peripheral tubules of the mucus-gland (where successive mucous coats are added). The completed egg-string is expelled through the external female aperture and forms a ribbon which is attached to the substratum by pressure of the parent’s foot upon it. Active spermatozoa may be observed moving within the primary egg-cases for some days after oviposition.
A Morphological and Histochemical Study of Oogenesis in the Gall-fly Cynips folii
Authors: Kraińska M.
Published: April 2021

In the ovariole of Cynips, cell groups that have arisen in the initial period of oogenesis, presumably from one gonial cell, differentiate into the oocyte and 12 nurse cells (which constitute the nutritive chamber). The oocyte remains connected with the nurse cells by a strand of cytoplasm; the whole group acts as a physiological unit till the completion of vitellogenesis. Ribonucleoproteins are synthesized in the nurse cells and transmitted to the oocyte. The latter produces no detectable RNA.

There is no morphological evidence of any interchange of material between the nuclei or nucleoli and the cytoplasm of the oocyte or nurse cells.

Protein yolk components appear in the oocyte around the RNA inflow from the nurse cells. They associate with mucopolysaccharides, which appear in the same territory, to form carbohydrate-protein complexes. The synthesis of lipid yolk starts in the posterior part of the undifferentiated cell group and occurs subsequently only in the oocyte.

Nurse cells never penetrate inside the oocyte in normal undamaged ovarioles. They shrink and disintegrate outside the ovariole after completion of their life-cycle.

The anterior part of the oocyte develops into the egg pedicel with a terminal extension in which most of the glycogen of the cell is accumulated; the protein spheres in this extension are different from the protein yolk of the main part of the oocyte. The precursors of these protein spheres arise in the cytoplasm of the common cell group before the onset of yolk formation.

The function of the follicular epithelium is secretion of the egg envelope, which is of epicuticular nature. The penetration of material from the haemolymph to the oocyte occurs mainly through the cells of the nutritive chamber. The contribution of the follicular epithelium to this process seems to be of minor importance, at any rate in the early stages.
A Cytological and Histochemical Study of the Stria Vascularis of the Guinea-pig’s Ear
Authors: Chou John T. Y.
Published: April 2021

The cells of the stria vascularis of the guinea-pig have been studied morphologically and histochemically. The stria vascularis consists of three layers of cells with bloodcapillaries. Apart from some yellowish pigments, the only cytoplasmic inclusions seen in the living cells and in the fixed materials are numerous rod-shaped mitochondria and spherical lipid globules. The mitochondria are about 1 ·5; μ in length with a diameter of 0 ·8; they contain phospholipid. The lipid globules are about 1 ·0 μ to 1 ·5 μ in diameter; they contain phospholipid and a small amount of cerebroside.

The cytoplasm of these cells contains a small amount of diffused phospholipid and cerebroside.
The Nerve-net of Metridium senile: Artifacts and the Nerve-net
Authors: Batham E. J. , Pantin C. F. A. , Robson E. A.
Published: April 2021

The present paper follows an account of the structure of the nervous system of Metridium, senile (L.). Conflicting statements about the actinian nervous system in the earlier literature made it necessary to assess the results of previous workers critically. Several of their methods have now been repeated and compared with our results after using more specific techniques. The criteria for distinguishing nerve-cells from non-nervous elements in actinians are discussed. Mesogloeal fibres, amoebocytes, nematocyst threads, and muscle-fibres may on occasion be confused with nerve-cells, and deteriorating nerve-cells may also have a misleading appearance. Gross artifacts may be reduced by the use of special staining methods, and on the basis of this work the results of several earlier authors have been re-interpreted. It is concluded that the nervous system in the mesenteries and column of Metridium follows the epithelial layers and does not penetrate the mesogloea.
A Comparative Histological Study of the Tube-feet of two Regular Echinoids
Authors: Nichols David
Published: April 2021

The histology of the suckered and peristomial tube-feet of the two regular echinoids Cidaris cidaris (Cidaroida) and Echinus esculentus (Diadematoida) is described; of these orders the Cidaroida is the more primitive. The suckered tube-feet of both urchins have a connective-tissue sheath the fibres of which branch extensively before inserting at the disk, and in which are embedded numerous spicules, enlarged distally to form a supporting skeleton of the disk. A series of levator muscles, separate from the retractors of the stem, raise the centre of the disk during adhesion, and this activity also probably squeezes mucus from a series of glands opening at the disk surface. In Cidaris a second series of glands, goblet cells in the disk epithelium, are operated by special short muscle-fibres running between them; these cells and the muscles are absent in Echinus. In Cidaris sensory cells are apparently scattered over the entire disk surface, whereas in Echinus they appear to be mainly concentrated in a ring round the disk periphery. The peristomial tube-feet of both urchins are not suckered; the levator muscles are absent, and the disk, supported by a less complex calcareous skeleton, contains mainly sensory cells and mucous glands. The possible derivation of the diadematoid, clypeasteroid, and spatangoid tube-foot plans from that of the cidaroid is discussed. The differences in ornamentation of the regions of the test which bear the tube-feet are discussed functionally, the main conclusion being that a tube-foot whose activity is at all angles to the test requires a wider base than one whose activity is mainly perpendicular; this is shown to be the case in spatangoids also. A respiratory function for Stewart’s organs in the Cidaroida is suggested.
Histological Changes in the Gut of Mitopus morio (Phalangiida) during Protein Digestion
Authors: Phillipson John
Published: April 2021

The description of the gross morphology of the gut of Mitopus morio agrees with Kastner’s (1933) description for Opilio parietinus De Geer except that 4 pairs of lateral openings lead from the mid-gut into the diverticula and not 3 as previously recorded. The two main types of diverticular cell in M. morio are digestive and secretory. There is thus agreement with the structures present in spiders, scorpions, and other harvest-spiders. The mid- and hind-gut epithelia both possess a single cell-type. That of the midgut is absorptive and digestive, whereas that of the hind-gut secretes a membrane round the faeces to form a pellet. During protein metabolism some extracellular digestion occurs in the lumina of the diverticula and mid-gut. The necessary enzyme or enzymes are produced by the diverticular secretory cells and are replenished within 24 h. Extracellular digestion is followed by partial or complete intracellular digestion in the diverticular digestive cells, which then cut off either digestive cell apices, containing partially digested protein globules, or digestive cell faeces which contain excretory material. Further digestion of the protein globules of the digestive cell apices occurs in the mid-gut cells, which then produce mid-gut cell faeces that are voided with the digestive cell faeces and indigestible food remnants.
A Comparison of the Nervous Systems of two Sea-Anemones, Calliactis parasitica and Metridium senile
Authors: Robson Elaine A.
Published: April 2021

The properties of the actinian nervous system are known mainly from physiological experiments on Calliactis parasitica (Couch), and from histological work on Metridium senile (L.). The structure of the nerve-net in the mesenteries of Calliactis is now shown to resemble in general that in Metridium. Methylene blue stains a network of bipolar cells over the retractor muscle, together with sense-cells, and unlike Metridium, multipolar nerve-cells. The nerve-net over the radial surface of the mesentery is similarly much sparser. The distribution of nerve-cells and sense-cells in the column also resembles that in Metridium.

Experiments on Metridium show that as in Calliactis, the rate of conduction in the mesenteries is greater than in other parts of the anemone. The column, including the sphincter region, conducts more slowly. It is thus shown that the presence of a well- developed nerve-net over the retractors is associated with the development of fast tracts in the through-conduction system, and of rapid, facilitated contractions of the retractor muscles, in both species of anemone.
Structural Changes in the Gills, Intestine, and Kidney of Etroplus tnaculatus (Teleostei) adapted to different Salinities
Authors: Virabhadrachari V.
Published: April 2021

There is an increase in the number of the so-called ‘chloride cells’ in the gill epithelium with increasing salinity of the medium. In 75% and 100% sea-water the ‘chloride cells’ exhibit a change in structure, in that they become more granular and acquire an apical vacuole. There is also a general decrease in the number of mucous cells with increasing salinity of the medium of adaptation.

The glomerulus tends to become smaller in the fishes adapted to high salinity as compared to the fresh-water fish. There is also a deposition of pigment around the nucleus and an indication of some changes in the nucleus of the kidney tubule cells in fishes adapted to 100% sea-water.

In the intestine, adaptation to high salinities results in an increase in the nuclear size of the columnar epithelial cells, an increase in the number of flask-shaped cells, and a considerable increase in the thickness occupied by the tunica propria.
Lipids in the Human Oocyte
Authors: Guraya Sardul Singh
Published: April 2021

The cytoplasm of the human oocyte contains two categories of lipid bodies that are here called and Lt for the sake of brevity. The Lj granules and spheres consist of phospholipids and triglycerides. The La bodies occur as aggregations of granules or fenestrated plates, consisting of phospholipids. The yolk granules are made up of phospholipids, proteins, and carbohydrates.
Principles and Technique of Fluorescence Microscopy
Authors: Young M. R.
Published: April 2021

Interest in fluorescence microscopy has greatly increased in recent years. Technical considerations have to some extent prevented even wider application of the various fluorescence techniques now available for microscopical study of biological specimens. This paper outlines the basic requirements for optimal image quality, for the benefit of biologists and others who may not be conversant with the optical principles involved. The central problem of illumination is reviewed in some detail, and an assessment given of the two methods in current use, namely the bright-field and dark-field systems. Ratios of fluorescent to activating light received by the objective aperture, given by the two systems, have been compared, and measurements have been made of their relative light-concentrating power.

Available light sources and their suitability for the excitation of fluorescence are discussed, with the problems of selecting appropriate light filters for use with the alternative systems of illumination.

It is concluded that the dark-field system has decided advantages in practice and in theory for the following reasons:

The dark-field condenser serves as an efficient primary filter, contributing to a black background and hence good contrast.

The equivalent focal length is less than that of the bright-field condenser and it concentrates energy in a smaller area; this compensates in part for the loss of energy inevitably caused by the central stop.

It permits the use of wide-band primary filters of maximum transmission because contrast in the fluorescent image is affected only by a weak superimposed dark-field image produced in the object-plane by scattered residual activating light passed by the primary filter. With blue-light activation the visible dark-field image is effectively eliminated by means of a weak blue-absorbing secondary filter.

The loss of contrast due to veiling glare is minimized.

A rational layout for fluorescence microscopy and methods for accurate alignment of the microscope in the vertical and horizontal positions are described. Factors influencing the choice of suitable objectives and eyepieces and some details of methods for mounting specimens are given.
The Connective-Tissue Sheath of the Nervous System of Locusta migratoria: an Electron Microscope Study
Authors: Ashhurst Doreen E. , Chapman J. A.
Published: April 2021

The sheath is composed of an outer non-cellular layer, the neural lamella, and an inner layer of sheath cells. The neural lamella possesses a large number of collagen fibrils arranged in layers with differing orientations. The sheath cells are flattened on the inner surface of the lamella and the cytoplasm contains lipochondria, mitochondria, and small amounts of endoplasmic reticulum.
Cytological and biochemical studies of anucleolate Xenopus larvae
Authors: Wallace H.
Published: April 2021

A larval lethal mutant of Xenopus laevis lacks true nucleoli but possesses analogous intranuclear organelles, here termed blobs, which are smaller and more numerous than nucleoli. Cytochemical tests reveal that blobs (like nucleoli) contain ribonucleic acid (RNA), arginine, and alkaline phosphatase, but probably no Feulgen-positive material. Anucleolate larvae are deficient in cytoplasmic RNA. By biochemical methods the nucleic acid content of anucleolate embryos is found to be normal at the tail-bud stage, but does not increase after this. By the time they hatch, anucleolate larvae are deficient in both RNA and deoxyribonucleic acid (DNA). The implications of this and related mutations on the formation and function of the nucleolus are considered. The term ‘blob’ is justified in that it would be misleading to regard such organelles as nucleoli produced by normally latent organizers.
The uptake of dyes by extracted phospholipids and cerebrosides
Authors: Byrne Jennifer M.
Published: April 2021

It was found that basic dyes were without exception taken up by lecithin, cephalin, and sphingomyelin, while the typical acid dyes were not taken up by any of the phospholipids. However, the weakly acidic dyes aurantia, eosin Y, eosin SS, and erythrosin were taken up by all phospholipids, although to a smaller extent than the basic dyes.

Basic dyes were taken up by cerebrosides, but to a smaller extent than by the phospholipids. The basic metachromatic dyes gave a strongly metachromatic reaction with cerebrosides. None of the acid dyes tried was taken up by cerebroside.

The direct observation that basic dyes were taken up less strongly by cerebrosides than by phospholipids was confirmed by spectrophotometric readings.

Basic dyes were found to be insoluble in olive oil, with the exception of Bismarck brown, neutral red, acridine orange, Nile blue, and chrysoidine. The acid dyes tried were without exception insoluble in olive oil.

Oleic acid took up all basic dyes and some acid dyes.

It is suggested that a chemical reaction is at least in part responsible for the uptake of basic dyes by conjugated lipids.
Experiments on fixation for electron microscopy I.Unbuffered osmium tetroxide
Authors: Malhotra S. K.
Published: April 2021

The effect of fixation with a simple solution of osmium tetroxide in distilled water was studied by electron microscopy. Exocrine cells of the pancreas and cells of the proximal tubule of the kidney of the mouse were used as test-objects. Partially prepolymerized methacrylate was used for embedding. There did not appear to be any marked disorganization of the cell inclusions. The appearance of the inclusions in the electron micrographs was similar to what is generally seen after fixation with the buffered osmium tetroxide solution of Palade.
A study of the intestinal epithelium of the goldfish Carassius auratus: its normal structure, the dynamics of cell replacement, and the changes induced by salts of cobalt and manganese
Authors: Vickers T.
Published: April 2021

The normal structure of the intestine of the goldfish is described, with special attention to the character of the mucosal epithelium.

The rate of epithelial replacement has been determined by the use of colchicine, and found to vary between 6 days for the upper intestine and 9 day’s for the lower parts. The colchicine data have also been used to determine the duration of a normal mitosis, which has been found to be between 2 and 3 h.

Cobaltous and manganous salts have been shown to cause a considerable but transient increase in the level of mucification which can be ascribed to the formation of new mucous cells; although there sometimes appears to be formation of mucoid substances in the principal cells, there is no evidence that these cells undergo transformation into goblet cells or that goblet cells ever become principal cells after they have lost their secretion.

It is suggested that mitosis in the intestine produces cells initially capable of both modes of differentiation, and that the effect of the metal ions is to increase temporarily the likelihood of mucous differentiation.
Observations on histological methods involving the use of phosphotungstic and phosphomolybdie acids, with particular reference to staining with phosphotungstic acid /haematoxylin
Authors: Bulmer D.
Published: April 2021

An attempt has been made to elucidate some of the factors involved in differential staining of tissues with Mallory’s phosphotungstic acid /haematoxylin, and to find out how far these factors are applicable to other histological methods in which phosphotungstic or phosphomolybdic acid is used. Sections have been subjected to various pretreatments to find whether specific chemical groupings are responsible for any of the staining reactions, but the results obtained are not always easy to interpret.

The most important single factor in determining the staining reaction of a tissue material with PTAH appears to be its relative permeability to the two colour-complexes of the PTAH mixture. The red complex, of larger molecular size, penetrates collagen; muscle-fibres are penetrated mainly by the smaller blue complex, while red bloodcorpuscles fixed with formaldehyde are not penetrated by either. The staining reactions of muscle and red blood-corpuscles can be altered by a methylation procedure, by treatment with performic acid or formic acid, or by mild alkaline hydrolysis; but this appears to be due to alteration of permeability rather than to chemical alteration of any specific dye-binding groups. The effects of blocking reactions indicate that the binding of both complexes is to basic groups in the tissues, though it is possible that hydroxyl groups and carboxyl groups may also be involved.

It appears that similar factors control the differential staining with other techniques which involve the use of complex acids (Baker, 1958), and that the chemical specificities which have been claimed for some of them are not well founded.
The relation between the Nissl and Sudan black pictures of the motor neurones of the spinal cord of the adult horse, with special reference to the cytoplasmic inclusions
Authors: Perbøll Ove
Published: April 2021

The motor neurones of the spinal cord of the horse, fixed in neutral formaldehydecalcium, embedded in paraffin, and sectioned, are easily coloured with Sudan black dissolved in propylene glycol or in tertiary butanol. No procedure for ‘unmasking’ lipids is necessary.

Any effect due to electropolar bonds are excluded by blocking and extraction procedures. The true lysochrome effect is confirmed by the removal of the colour by lipid solvents and the absence of stable sudanophilia and of background colouring. No brown colour suggestive of decomposition products is seen, and this is further confirmed by absorption spectra of the Sudan black solutions.

The structures revealed are in the main identical with those of ordinary Nissl preparations made, for instance, by Einarson’s chromalum/gallocyanin stain. In addition, however, structures closely similar to ordinary Nissl bodies are seen in the axon hillock and in the axon. This suggests that in these situations Sudan black colours corpuscles that are lacking in ribonucleic acid (presumably endoplasmic reticulum devoid of ribosomes).

The nature of the lipids revealed by Sudan black in these cells has not been determined histochemically. Extraction in pyridine either before or after fixation had no definite effect on the colouring of the Nissl bodies or of the nucleus.

The histochemical recognition of lipids in the cytoplasmic network of neurones has recently been reported by David and Brown (1961). The present paper supports the findings of these authors. Different material and methods were used, but the colouring agents were the same.
Histochemical differentiation of the basement membrane of the mouse seminiferous tubule
Authors: Baillie A. H.
Published: April 2021

The ground substance of the testis of the albino mouse is PAS-positive but not meta-chromatic, and probably highly aggregated. The basement of the seminiferous tubules is intensely PAS-positive, metachromatic, and possibly not so highly aggregated.

The reactivity of the ground substance to the PAS reaction and toluidine blue is tentatively ascribed to the presence of chondroitin sulphate C: this compound, previously known to contain N acetyl-galactosamine, glucuronic acid, tyrosine and tryptophane, is associated with arginine.

The genesis of the basement membrane of the seminiferous tubule is shown to include the formation of a sheath of atypical elongated fibroblasts, the secretion of a PAS positive, metachromatic substance associated with arginine between this sheath and the seminiferous tubule, the appearance of mitochondria in the cells of the sheath, and lastly, the acquisition of alkaline phosphatase by these fibroblasts and its spread to the intervening ground substance. These changes are thought to be related to the structural and nutritional requirements of the seminiferous tubules.

In its intense positive reaction to PAS and in its metachromasy, the basement membrane of the seminiferous tubule agrees with the ground substance adjacent to sites of active protein metabolism, such as growing tumours, embryonic organs, hair follicles, and skin.
The cuticle of cysticerci of Taenia saginata, T. hydatigena, and T. pisiformis
Authors: Siddiqui E. H.
Published: April 2021

The structure of the cuticle of the cysticerci of 3 species of Taenia was studied by means of optical and electron microscopy. In all 3 species the cuticle is composed of 3 layers and covered with hair-like processes. The middle layer, which comprises the bulk of the cuticle, varies in thickness from head to bladder, but there are no differences in thickness between the species studied. The hairs are composed of a core representing an extension of the middle layer and are covered by a continuation of the outer layer. The arrangement of these hairs varies in the species studied.
Experiments on fixation for electron microscopy 4. The sodium veronal buffer
Authors: Malhotra S. K.
Published: April 2021

Michaelis’s sodium acetate /sodium veronal buffer is generally used for holding the pH of fixing solutions for electron microscopy at about pH 7·3 to 7·5. The acetate, however, has no buffering action on the alkaline side of neutrality. Experiments were therefore made to study the effect on preservation of cellular constituents when sodium acetate is omitted from Palade’s (or its variants) and Luft’s fluids. Exocrine cells of the pancreas, convoluted tubule cells of the kidney, and the testes of the mouse were used as test-objects, n-butyl methacrylate (generally partially prepolymerized) and epikote 812 were used for embedding. The preservation visualized in the micrographs did not seem to suggest any marked differences in the quality of fixation from that produced by fixation in Palade’s and Luft’s fluids. However, there is some evidence that comparable micrographs could be produced by fixation in simple solutions of OsO4 in distilled water and subsequent embedding in suitable media.
A histochemical study of the Golgi apparatus or ‘acroblast’ of the spermatid of the snail, Helix aspersa
Authors: Bradbury S. , Meek G. A.
Published: April 2021

The acroblast of Helix spermatids is a duplex structure: it consists of an ‘externum’ (which appears dark by positive phase-contrast microscopy and becomes impregnated with osmium) enclosing a region called the ‘internum’.

Histochemical studies show the externum to be composed principally of phospholipid and to contain glycolipid, alkaline phosphatase, and an enzyme which splits thiamine pyrophosphate. The internum contains neutral mucopolysaccharide. Ribonucleic acid and acid phosphatase are not present in the acroblast.

These histochemical results suggest a homology between the invertebrate acroblast and the Golgi apparatus in vertebrate cells.
The sensory neurones and sensilla in the abdomen and thorax of the blowfly larva
Authors: Osborne M. P.
Published: April 2021

The peripheral nervous system in the Phormia larva consists of bipolar neurones that end in specialized sensilla, and bipolar or multipolar neurones with ramifying distal processes. The former are associated with the cuticular sensilla and chordotonal organs. The latter (a) constitute a sub-epidermal nerve-plexus with processes that occasionally run over skeletal muscles, (b) innervate specifically orientated strands of connective tissue, the longitudinal, vertical, and ventral stretch receptors, and (c) innervate the tracheal epithelium, imaginai buds and associated pedicels, and the nerve-sheaths.
Thiamine pyrophosphatase, acid phosphatase, and alkaline phosphatase in the neurones of Helix aspersa
Authors: Nancy J. Lane
Published: April 2021

All three phosphatases have been found to be localized mainly in the cortices of bodies which have the distribution, size, and shape of the ‘blue’ and yellow lipid globules. Colouring neurone preparations with the lysochrome Sudan IV, either before or after incubation for thiamine pyrophosphatase or acid phosphatase activity, shows a sudano-phil reaction in the medullary spaces surrounded by the cortices that hydrolyse both phosphates. It is concluded that the acid phosphatase and thiamine pyrophosphatase activities, which in vertebrates are present in the lysosomes and Golgi lamellae respectively, are mainly found, in these invertebrate neurones, in the phospholipid lamellae which form the externa of certain of the lipid globules present in the cytoplasm.
The tegument and associated structures of Fasciola hepatica
Authors: Threadgold L. T.
Published: April 2021

The cuticle of light microscopy is shown by electron microscopy to be a surface layer of protoplasm which is an extension of areas of nucleated protoplasm lying deep in the parenchyma. The cuticle therefore exists at two levels. The external level is syncytial, consisting of plateaux separated by branching valleys. This level contains apical pinocytotic vesicles, numerous mitochondria, endoplasmic membranes, large basal and other vacuoles, and dense spines. Tube-like evaginations from the base of the external level connect it to the individual areas of flask-shaped protoplasm which compose the internal level. Each of these areas of protoplasm contains a nucleus, great numbers of mitochondria, some vacuoles and diffuse inclusions, and the Golgi bodies.

The histochemistry and function of the cuticle is discussed in the light of this new knowledge of cuticular ultrastructure, and a comparison is made between the cuticle of Cestoda and Trematoda.
The nerve-net of a swimming anemone, Stomphia coccinea
Authors: Robson Elaine A.
Published: April 2021

The nervous system of this anemone has been examined in an attempt to study the pacemaker system, previously thought to be localized in the median zone of the column. No clear-cut nerve-ring has been found. The whole column, however, is characterized by the presence of large multipolar nerve-cells in the endoderm, to which pacemaker activity is provisionally attributed. There are several thousand of these cells and their neurites connect with those of other nerve-cells and sense-cells in the column, and with the mesenteric nerve-nets. The column nerve-net, of which the multipolars form part, conducts slowly and fatigues easily. Present physiological evidence from Stomphia and other coelenterates does not invalidate the suggestion that the multipolar cells may also function as a pacemaker system.

Other features of the nervous and sensory systems are very like those of other anemones (e.g. Calliactis, Metridium). The column, mesenteries, and oral and pedal disks are briefly described; much information is still lacking. As expected, sense-cells are aggregated along the angles of the mesenteries except in the pharynx. Their neurites connect with the column nerve-net, and with the mesenteric nerve-nets. A well-developed network of bipolar nerve-cells on the retractor surface may be regarded as a rapid through-conduction tract. As in Metridium and Calliactis the radial nerve-net on the opposite face of the mesentery is similar but much sparser. The ectodermal surface of the oral disk, as described by the Hertwigs, shows a criss- cross network of bipolar nerve-cells together with radial rows of small multipolar nerve-cells above the septa. These might perhaps have a proprioceptive function. In the endoderm of the pedal disk, sense-cells are numerous but nerve-cells few. These features are discussed only in so far as they may be related to the swimming behaviour of Stomphia.
An electron microscopical study of the innervation and sarcoplasmic reticulum of the fibrillar flight muscle of Drosophila melanogaster
Authors: Ahmad Shafiq S.
Published: April 2021

The peripheral nerves of Drosophila are of the ‘tunicated’ type; their mesaxons are derived from several independent invaginations of the lemnoblast plasma membrane and possess septate desmosomes.

Fine branches of the nerves and tracheoles penetrate deeply into the fibres of the flight muscle and draw the sarcolemma in with them. The myoneural junctions occur on the invaginated portions of the sarcolemma. The axons shed their lemnoblastic elements and become closely apposed to the muscle plasma membranes at the junctions.

The sarcoplasmic reticulum of the flight muscle seems to consist mainly of the extensive infoldings of the sarcolemma and their processes, as in Tenebrio. ‘Dyads’ formed by the association of isolated vesicles with the membranous infoldings are present in Drosophila. Most of these ‘dyads’ seem to be in register with the myofibrils, two pairs being associated with each sarcomere.
The union of protein and nucleic acid in the living cell and its demonstration by osmium staining
Authors: Wigglesworth V. B.
Published: April 2021

The greater part of the osmium tetroxide that is reduced and bound by living cells in neutral solution is taken up by unsaturated lipids. The protein in mitochondria, muscle-fibres, connective tissue, red blood cells, See., takes up a smaller amount of osmium; but the basic proteins that are combined with DNA and RNA in the chromosomes, nucleoli, and cytoplasm do not react: their reactive groups are presumably held in salt linkages with the phosphate residues of the nucleic acids.

If the cells are exposed to an acid medium (0.001 M acetic acid or saturated carbonic acid) these salt linkages are weakened, and chromosomes and cytoplasmic nucleoprotein will now take up large amounts of osmium and stain intensely with ethyl gallate. This effect of hydrogen ion concentration is reversible within the living cell.

By the application of a series of blocking reagents it is concluded that the chief reactive groups on the proteins are the guanidino group of arginine, the e-amino group of lysine, the iminazole group of histidine, and the pyrrolidine group of proline. Tryptophane and cystein, though highly reactive, are perhaps less important quantitatively.
Studies on the receptors in the cerebral vesicle of the ascidian tadpole. 2. The ocellus
Authors: Dilly Noel
Published: April 2021

Electron microscope observations of the photoreceptor of the tadpole larva of Ciona intestinalis show the ocellus to consist of about 10 cells. It is made up of 3 parts: a pigment cup, a lens system, and a retina. A single cup-shaped cell filled with membrane-bound pigment granules lies between the lens and the retinal cells. Part of the lens cell is contained within its concavity. The pigment granules are arranged to keep stray light from falling upon the photoreceptor endings.

The lens system has 3 lens vesicles arranged in a line along the main axis of the pigment cup cell. The spherical vesicles are usually contained within a single cell. Each vesicle is separated from the rest of the lens cell cytoplasm by a single-layered sphere of mitochondria. No membrane separates the vesicle contents from the rest of the lens cell cytoplasm.

The retinal cells lie above the dorsal arm of the pigment cup cell, and have tubular processes that pass through it to end as piles of membranes closely applied to the lens cell. Morphologically the photoreceptor units of the ascidian tadpole closely resemble the visual cells of the vertebrates, the piled photoreceptor membrane corresponding to the outer segment of the vertebrate rod cell and the tubular part to the connecting piece of a retinal rod.
The fine structure of certain secretory cells in the optic tentacles of the snail, Helix aspersa
Authors: Lane Nancy J.
Published: April 2021

In Helix aspersa, the cytoplasm of the collar cells that surround the tentacular ganglion contains spheroidal granules of low electron density (α-bodies), and β-bodies that contain electron-dense vesicles within the size range of elementary neurosecretory granules. Mitochondria and lamellar Golgi complexes are also present. Mitochondria, a-bodies, fibrils, objects resembling multivesicular bodies, and moderately electrondense granules are found in the lengthy processes into which the collar cells are drawn out.

One process of each bipolar collar cell seems to merge into the tentacular ganglion. This consists of neurones with processes that contain mitochondria, vesicles of various sizes, filaments, and electron-dense granules similar to elementary neurosecretory granules.

The lateral cells that line the dermo-muscular sheath encasing the optic tentacles contain in their cytoplasm an endoplasmic reticulum with many ribosomes, mitochondria, Golgi complexes, and many electron-lucent globules. These globules seem to be elaborated by the lamellar Golgi bodies. There are also electron-dense inclusions, which may be lysosomes, that are scattered sparsely between the other globules and cytoplasmic components. All these structural details are similar to those found in some mucus-secreting cells.

The possible nature and origin of the tentacular secretory cells are discussed.
Further observations on the secretory cells in the optic tentacles of Helix, with special reference to the results of vital staining
Authors: Lane Nancy J.
Published: April 2021

When the collar cells or the lateral cells in the tentacles of Helix aspersa are stained with neutral red and other vital dyes, uptake of the dyes occurs chiefly in the lipoidal β-bodies. Janus green B and dahlia are taken up by the mitochondria.

In vitally-coloured preparations, no ‘peri-nuclear bodies’ are present in the collar and lateral oval cells, such as were previously found in these cells after post-osmication for 14 days. Fixed preparations of similar cells, post-osmicated for different periods, indicate that the peri-nuclear dictyosomes are artifacts due to over-impregnation with osmium.

In addition to the lateral oval and lateral processed cells, which lie at intervals along the inner surface of the dermo-muscular sheath in Helix, unicellular calcium glands are found, lying immediately beneath the epithelial surface; these are far more numerous in H. pomatia than in H. aspersa. They contain granules of a calcium salt suspended in a matrix of mucopolysaccharide, and apparently produce the whitish mucoid secretion that is extruded on to the surface of the tentacles when the animal is disturbed. There is no evidence to suggest that the lateral cells are concerned in the production of this mucoid secretion.
Sheaths of the motor axons of the crab Carcinus
Authors: Horridge G. A. , Chapman R. A.
Published: April 2021

In crab leg nerves, the largest axons, which are the motor axons usually isolated for physiological experiments, have a sheath structure which is different from that in medium sized and smaller axons of the same nerve or of any other described nerves. Axons with a diameter over 20 μ have (a) an outer sheath, about 5 μ. thick, of wellspaced layers of alternating glial cell cytoplasm and extracellular fibrous material, formed from fewer cells than there are layers, and (b) an inner sheath of elongated cells which creep along the axon longitudinally and interdigitate where they meet, as seen 2 or 3 times round the outside of the membranes of axons in cross-section. Therefore, possible channels between inner glial cells are elongated and few. On these structural grounds, together with physiological evidence, they seem unlikely to be preferred pathways of diffusion of ions in crab axons. Smaller axons have simple sheaths; some occur in groups within a fibrous sheath; the thinnest axons frequently occur in bundles and have no glial cell membrane in contact with them.
The coelomocytes of the terebellid polychaete Amphitrite johnstoni
Authors: Phillips Dales R.
Published: April 2021

The coelomocytes of the terebellid polychaete Amphitrite johnstoni Malmgren are phagocytic and accumulate oil, glycogen, and β-carotene. They also contain haemoglobin, which is transformed to haematin by ageing cells. It is to haematin that the brown colour of some worms is due. The quantity of haemoglobin in the coelomocytes is about half that in the blood. The coelomocytes increase in number in summer during early growth of the gametes, and decrease before spawning. Measurement of the quantities of coelomocytes and of gametes, and quantitative determinations of oil and glycogen suggest that the principal function of the coelomocytes is the supply of nutrients for the gametes.
An electron microscopical study of isolated mitochondrial membranes treated with osmium tetroxide, potassium permanganate, and formaldehyde
Authors: Deutsch K. , Krause W. , Rosenthal S.
Published: April 2021

An investigation of isolated mitochondrial membranes, fixed with osmium tetroxide, potassium permanganate, or formaldehyde, shows that a great number of small particles are attached to their surfaces. Sections of specimens fixed in potassium permanganate or osmium tetroxide appear to confirm these findings. An attempt has been made to compare these particles with the ‘elementary particles’ described by Fernández-Morán and by Green, and also with particles revealed by negative staining of mitochondrial membranes, as reported by Stoeckenius. Specimens fixed with formaldehyde, whether isolated mitochondria or material fixed in bulk, show very poor contrast in electron micrographs.
The yolk-nucleus in the oocytes of Anabas scandens (Teleostei)
Authors: Gopal Dutt N. H.
Published: April 2021

The yolk-nucleus appears as an organelle in contact with the nucleus in the early oocyte. It is spherical and appears in fixed preparations to be composed of 3 con- centric zones. Histochemical tests indicate that it contains RNA, lipid, sulphydryl groups, carbohydrate, and certain amino-acids. It assumes a reticulate form before it finally merges with the peripheral cytoplasm. Circumstantial evidence suggests that the yolk-nucleus may be involved indirectly in vitellogenesis.
A silver-Schiff reaction for cytological studies : light microscope observations
Authors: Bryan John H. D.
Published: April 2021

A method is presented in which a complex metal-ion (ammoniacal silver) is sub- stituted for leuco-basic fuchsin in the well-known Schiff reaction for aldehydes. The reagent is reduced to metallic silver by tissue aldehydes and submicroscopic particles of the metal are deposited at the reactive sites. When the reagent is used in the Feulgen reaction chromosomes may be ‘stained’ in a specific manner to show the localization of deoxyribonucleic acid. For such a purpose, fixation should be carried out with acetic acid and alcohol mixtures rather than with solutions containing formalin or dichromate ; these latter substances preserve more of the tissue lipids and thus complicate the issue by producing cytoplasmic staining (plasmal reaction).
A silver-aldehyde reaction for studies of chromosome ultrastructure
Authors: Bryan John H. D. , Brinkley Bill R.
Published: April 2021

A method is presented for the visualization of structures containing deoxyribonucleic acid at the electron microscope level. This is achieved by the substitution of an ammoniacal silver reagent for leucobasic fuchsin in a Feulgen-like procedure. Tissue aldehydes reduce this reagent to metallic silver, which is deposited at the reactive sites in the form of fine particles. The particles range in size from about 4 m/x downwards to below the resolving power of the microscope used. 3 fixatives have been investigated (buffered osmium tetroxide, formalin, glutaraldehyde) and the special problems encountered with each fixative are discussed. Detailed considerations regarding the preparation and handling of this somewhat unstable staining solution have been described previously (Bryan, 1964).

Results obtained from an application of this procedure in an investigation of the ultrastructure of polytene chromosomes are also reported in detail. The fibrillar nature of these chromosomes is depicted more clearly following staining than in preparations resulting from the employment of the more conventional methods in current use. The fibrils are clearly delineated by silver particles and may be grouped into 2 classes. Thus, the finest fibrils are of about 4 mµ, diameter and they are usually associated in pairs to form units of about 10 mµ diameter. Although there is a predominant orientation of the fibrils composing individual bands, the nature of the association of the 10 mµ units which results in this is not clear. Evidence for the occurrence of similar fibrils in chromatin of interphase nuclei of mammalian origin is also presented.

Taken together, the results of the various experiments suggest that this silver procedure may be used to advantage in a wide variety of investigations concerning the ultrastructure of chromosomes and chromatin.