bluuebunny/crossref_metadata_2025_split huggingface dataset:
CELL JUNCTIONS IN AMPHIBIAN SKIN
Authors: Farquhar Marilyn G. , Palade George E. 
Published: May 2004

Cell junctions have been investigated in the amphibian epidermis, a stratified squamous epithelium, and compared to those described previously in simple columnar epithelia of mammalian cavitary organs.
In adult frogs and toads, and in larvae approaching metamorphosis, belts of membrane fusion or zonulae occludentes of considerable depth are regularly found between adjoining cells of the outermost layer of the stratum corneum, binding the cells together into a continuous, uninterrupted sheet. Another set of occluding zonules appears in the second cornified layer (when such a layer is present), and a third set usually occurs in the outermost layer of the stratum granulosum. Specialized elements described as "modified" and "composite" desmosomes are encountered along the lateral and basal aspects, respectively, of the cornified cells; ordinary desmosomes and maculae occludentes (i.e., spots of membrane fusion) are found in all other strata. The usual 200 A intercellular gap is generally maintained between the cells of the stratum germinativum at the basal ends of the intercellular spaces. Hence, the intercellular spaces of the epidermis form a largely continuous network, closed to the external medium and open to the dermal interstitia. The situation is comparable to that found in columnar epithelia, except that the intercellular spaces are much more extensive, and an extracellular subcompartment (or two) apparently exists in the stratum corneum and between the latter and the stratum granulosum. The last subcompartment is usually filled with a dense substance, probably derived from discharged secretory granules. The tripartite junctional complex characteristic of lumen-lining epithelia (i.e., a zonula occludens followed by a zonula adhaerens, and desmosome) is seen only in early larvae; in adults and in larvae approaching metamorphosis, the occluding zonule is followed directly by a series of modified desmosomes.
Interpreted in the light of current physiological data, these findings suggest that the diffusion of water, ions, and small, water-soluble molecules is impeded along the intercellular spaces of the epidermis by zonulae occludentes while it is facilitated from cell to cell within the epidermis by zonulae and maculae occludentes.
A CORRELATED HISTOCHEMICAL AND ELECTRON MICROSCOPIC STUDY OF THE INTRANUCLEAR CRYSTALLINE AGGREGATES OF ADENOVIRUS (RI-APC VIRUS) IN HELA CELLS
Authors: Bloch David P. , Morgan Councilman , Godman Gabriel C. , Howe Calderon , Rose Harry M. 
Published: May 2004

HeLa cells in tissue cultures infected with types 3, 4, or 7 of adenovirus (RI-APC virus) were studied in order to correlate certain histochemical and electron microscopic findings.
Adjacent thin (ca. 0.05 µ) and thick (2–4 µ) sections of osmium-fixed, methacrylate-embedded cells were cut; by mapping the sections the same cells could be identified with both the electron and the light microscope.
Intranuclear crystalline aggregates seen with the electron microscope to be composed of ordered arrays of viral particles were found by means of the Feulgen reaction to contain DNA. DNA is therefore assumed to be a constituent of the viral particle. The virus appeared to develop from an osmiophilic Feulgen-negative matrix. Displacement of nuclear chromatin occurred during this process.
A Feulgen-azure staining method was found to permit clear distinction between viral and nuclear (host) DNA in thick sections.
EFFECTS OF IONIC STRENGTH OF IMMERSION MEDIUM ON THE STRUCTURE OF PERIPHERAL NERVE MYELIN
Authors: Finean J. B. , Millington P. F. 
Published: May 2004

A study of the effects of hypertonic solutions on the structure of peripheral nerve myelin reveals an expansion rather than a contraction of the layer spacing. This suggests the absence of "free" water between the myelin layers.
Hypotonic solutions bring about a change in radial repeat period from 171 A to 250 to 270 A.
These findings are of significance in relation to the structure of myelin.
SOME ASPECTS OF THE METABOLISM OF SULFATE-S35 AND CALCIUM-45 IN THE METAPHYSES OF IMMATURE RATS
Authors: Dziewiatkowski Dominic D. , Bronner Felix , Di Ferrante Nicola , Archibald Reginald M. 
Published: May 2004

Weanling rats were given 2 mg. of 17-ß-estradiol benzoate at weekly intervals for 4 weeks. Twenty-four hours after each intraperitoneal injection of the estrogen 100 µc. of S35-sulfate or 11 µc. of Ca45 was similarly injected. The animals were sacrificed 24 hours after the last dose of isotopes.
An effect of estradiol benzoate on calcium metabolism was deduced from the observation that the concentration of calcium in some tissues of the treated rats was higher than the concentration in the tissues of untreated rats.
Alkaline extracts of the distal metaphyses of femurs from the estradiol-treated and from control rats, given S35-sulfate, were shown by chromatography on an anion exchange resin to contain from 9 to 22 per cent of the S35 as inorganic sulfate. From similar bone samples, 6 to 21 per cent of the S35 was removed by decalcification with sodium versenate. Most of the remaining S35 was associated with uronic acid and hexosamine; on paper chromatograms and paper electrophoretograms S35 was shown to be part of material which migrated and was metachromatic in the same way as purified chondroitin sulfate.
Autoradiograms of the proximal ends of tibiae from the animals given estradiol benzoate showed that both the S35 and Ca45 were deposited in the metaphyses in strata. The arrangement of the strata of S35, however, was different from the arrangement of the strata of Ca45. This difference in arrangement is interpreted as indicating that most of the S35 in the metaphysis was derived from the chondroitin sulfate of the cartilage plate which the metaphysis had replaced.
THE ELECTRON MICROSCOPY OF THE HUMAN HAIR FOLLICLE
Authors: Birbeck M. S. C. , Mercer E. H. 
Published: May 2004

1. The presumptive cortical cells of hair in the undifferentiated matrix of the bulb contain mitochondria, agranular vesicles, and many small dense R.N.P. particles, but no keratin, pigment granules, or endoplasmic reticulum.
2. In the mid-bulb region intercellular adhesion is limited to small localised areas. Intercellular gaps are common and the cell surfaces are irregularly convoluted. The melanocyte processes penetrate the cell gaps. The relation between their pigment-bearing tips and the involutions of the cell membranes suggests an active phagocytosis of the tips.
3. Fibrous keratin first appears in loose parallel strands of fine filaments (ca. 60 A diameter) in the mid-bulb. The filaments, the long mitochondria, and elongated nucleus are all parallel to the long axis of the cell and the axis of the follicle.
4. At the level of the constriction of the bulb and above, a dense amorphous substance appears between the fine filaments and apparently acts as adhesive cement. The bundles of filaments now form well defined fibrils. The packing of the filaments within the fibrils is in places hexagonal and elsewhere in the form of "whorls."
5. At higher levels further filaments and interfilamentous cement are added together and the whole cytoplasmic space becomes packed with fibrils which finally condense to massive blocks of keratin. The residual cellular material occupies the interstices.
6. The addition of the interfilamentous substance is regarded as an essential factor in keratinisation. Keratin is considered to be a complex made of fine filaments (α-filaments) embedded in an amorphous substance (γ-keratin) which has the higher cystine content.
7. The wide-angle fibre-type x-ray pattern is thought to be due to scattering by the fine α-filaments and some low angle lateral spacings to the filament-plus-cement structure.
THE ELECTRON MICROSCOPY OF THE HUMAN HAIR FOLLICLE
Authors: Birbeck M. S. C. , Mercer E. H. 
Published: May 2004

1. During the early differentiation of the cuticle the cell membranes smooth out and the cells become closely attached over most of their surface. The change seems to be due to a layer of cement which forms between them. The plasma membranes also increase in density.
2. The decreased membrane activity of the cuticle cells may prevent a phagocytosis of the melanocyte processes and thus account for the non-pigmentation of the cuticle.
3. The flattening and imbrication of the cuticle may possibly be explained by a zipper-like spread of cell contacts.
4. Keratinisation of the cuticle occurs at a late stage in its development; the keratin formed is an amorphous type, similar to the γ-fraction of the cortex which is produced at a similar level.
5. Keratinisation is accompanied by the formation of complex intercellular layers similar to structures observed in the inner root sheath (see Part 3).
6. In the final stage of keratinisation the remaining cytoplasm condenses with the result that the cell is divided into a laminated structure with an outer keratinised layer and an inner layer, which is insoluble in keratinolytic solvents.
EXPERIMENTALLY INDUCED CHROMOSOME ABERRATIONS IN PLANTS
Authors: Kihlman B. A. , Merz T. , Swanson C. P. 
Published: May 2004

The discovery of Lilly and Thoday, that the presence of potassium cyanide (KCN) increases the production of chromosome aberrations by x-rays in anoxia, but has no effect on the production of chromosome aberrations by x-rays in air, was confirmed.
In the presence of cyanide, the effect of a given dose of x-rays in nitrogen was found to be even greater than the effect of the same dose of x-rays in air. The cyanide effect on x-ray breakage in nitrogen was obtained at cyanide concentrations as low as 2 x 10–5 M. The breakage obtained after the combined x-ray-cyanide treatments was of the x-ray type, as evidenced by the distribution of breaks within and between the chromosomes.
A number of other heavy metal complexing agents as well as some other compounds were tested for their ability to increase x-ray breakage in nitrogen and air. Of these compounds only cupferron proved to be effective.
The results are discussed and it is concluded that the increased x-ray breakage in the presence of cyanide or cupferron cannot be due to an accumulation of peroxides. Instead it is suggested that the cyanide effect may be due to a complex formation between the active agents and heavy metals, presumably iron, within the chromosomes. The consequences of this hypothesis on the concept of the "oxygen effect," are discussed.
THE FINE STRUCTURE OF THE CELLS IN MOUSE SARCOMA 37 ASCITIC FLUIDS
Authors: Epstein M. A. 
Published: May 2004

The tumour cells and the reaction cells in Sarcoma 37 ascitic fluids have been studied in thin sections with the electron microscope. The reaction cells were either leucocytes or much larger acidophilic peritoneal cells of the same dimensions as the tumour cells; the peritoneal cells formed as much as 20 per cent of the large cell population.
The fine structure of the cells is described and some new observations recorded. It has been found that the cell membrane of eosinophil granulocytes has a laminated composition and the characteristic granules of these cells a double limiting membrane. The pores in the double nuclear membrane of the peritoneal cells have been observed to have a fine line running across them. In the tumour cells, a rounded granular body with a central dense area has been found in the region of the centrosome; these cells were also seen to contain rows of parallel smooth surfaced cisternae lying 150 mµ apart similar to those hitherto only observed in spermatids. There was a feltwork of fine filaments in the cytoplasm of the centrosome region of the tumour cells.
The cytoplasmic fine structure underlying the basophilia of the tumour cells and the acidophilia of the peritoneal cells is compared and discussed.
Submicroscopic Changes of the Nerve Endings in the Adrenal Medulla after Stimulation of the Splanchnic Nerve
Authors: De Robertis Eduardo , Ferreira Alberto Vaz 
Published: May 2004

The nerve endings of the adrenal medulla of the rabbit were studied under the electron microscope in the normal condition and after prolonged electrical stimulation of the splanchnic nerve. With a stimulus of 100 pulses per second for 10 minutes, there is an increase in the number of synaptic vesicles in the nerve ending. The mean number is of 82.6 vesicles per square micron in the normal and of 132.7 per square micron in the stimulated glands. With a stimulus of 400 pulses per second for 10 minutes, there is a considerable depletion of synaptic vesicles and other changes occur in the nerve endings. The mean number of vesicles is of 29.2 per square micron.
These results are interpreted as indicative of an increased activity of the ending in one case, and as a diminished activity and fatigue of the synaptic junction in the other.
ACTION OF MITOCHONDRIAL DNAASE I IN DESTROYING THE CAPACITY OF ISOLATED CELL NUCLEI TO FORM GELS
Authors: Dounce Alexander L. , O'Connell Marguerite P. , Monty Kenneth J. ,   With the Technical Assistance of Joan C. W. West
Published: May 2004

1. DNA prepared from non-gelable rat liver nuclei isolated in the presence of disrupted mitochondria at pH 6.0, has been compared with DNA obtained from gelable nuclei isolated at pH 4.0. The DNA of the non-gelable nuclei is partially depolymerized relative to the DNA of the gelable nuclei.
2. It has been found that sufficiently small quantities of crystallized DNAase I can cleave a very large part of the DNA of gelable nuclei isolated at pH 4 from the residual protein of these nuclei without causing extensive depolymerization of the DNA. At the same time the gelable nuclei are rendered non-gelable.
3. Partially purified DNAase II can also render gelable nuclei isolated at pH 4 non-gelable, and in so doing presumably also cleaves the DNA from the residual protein of the nuclei.
4. Mitochondrial DNAase I appears to be the enzyme responsible to a large extent for the cleavage of DNA from the residual protein of gelable rat liver cell nuclei with concomitant destruction of the gel-forming capability of these nuclei, when the nuclei are subjected to the action of disrupted mitochondria at pH 6.0 during the isolation procedure.
5. Mitochondrial DNAase II does not appear to exert appreciable action on nuclei during the course of isolation of the nuclei at pH 6.0 in the presence of disrupted mitochondria.
6. It is probable that DNAase I is not the sole enzyme responsible for destroying the gelability of nuclei isolated at pH 6.0 in the presence of disrupted mitochondria. Protease may be involved.
7. Sodium dodecyl sulfate at pH 6.0–6.3 cleaves the DNA of isolated gelable nuclei from the residual protein of these nuclei over a period of 2 to 3 hours. At pH 7.0–7.5, however, there is negligible cleavage over a period of 96 hours.
8. If non-gelable nuclei are isolated at pH 6.0 in the presence of disrupted mitochondria, DNA subsequently can be removed from them by the use of detergent at pH values ranging from 6.0–7.5 without the necessity of incubation in the detergent solution, since the DNA had already been detached from the residual protein by the action of the mitochondrial enzyme system during isolation of the nuclei.
SPERMATOGENESIS IN ANIMALS AS REVEALED BY ELECTRON MICROSCOPY
Authors: Yasuzumi G. , Ishida Hiroshi 
Published: May 2004

The submicroscopic structure of the maturing spermatid nucleus of the grasshopper, Gelastorrhinus bicoler de Haan, has been studied in thin tissue sections by electron microscopy.
In the early spermatid the nucleus appears dense with no clearly resolvable fine structure. In the advanced spermatid with a conical-shaped nucleus, the karyoplasm begins to show a fibrillar structure. At subsequent stages, the elongated spermatid nucleus displays in cross-sections a hexagonal honeycomb pattern and in longitudinal sections an array of parallel lines, 70 A in diameter and spaced 100 to 220 A apart.
As differentiation of the spermatid proceeds further, the space between the lines becomes narrower and narrower until it can no longer be resolved.
AN ANALYSIS OF MYOGENESIS BY THE USE OF FLUORESCENT ANTIMYOSIN
Authors: Holtzer Howard , Marshall John M. , Finck Henry 
Published: May 2004

Antibodies against myosin of adult chicken skeletal muscle were labelled with fluorescein and used as staining reagents to analyze the development of trunk myoblasts in the chick embryo. Myoblasts from the brachial myotomes were studied in three ways: (a) Specimens were fixed, sectioned, and stained with iron-hematoxylin. (b) Living myoblasts, and myoblasts prepared by glycerol extraction, were teased and examined by phase contrast microscopy. (c) Embryo trunks were treated with fluorescent antimyosin or with a control solution of fluorescent normal globulin, and were examined by fluorescence and phase contrast microscopy. Both glycerol-extracted and fixed materials were used.
Cross-striated myofibrils appeared first in stage 16 to 17 embryos in the series studied by antimyosin staining and fluorescence microscopy. Striated myofibrils appeared first in stage 18 to 19 embryos, in the series stained by iron-hematoxylin, and at stage 22 to 23, in the series studied by glycerol extraction and phase contrast microscopy. In each series, myofibrils without apparent cross-striations were detected shortly before cross-striations were observed. Specific staining by antimyosin occurred only in differentiating myoblasts. Within the myoblasts antimyosin staining was confined to the A bands of the slender myofibrils.
The following observations suggest that the first delicate striated structure to appear in the early 3 day myoblast was remarkably mature: (1) The sarcomere pattern both in length and in internal detail, was similar to that of adult muscle. (2) The distribution of myosin, as revealed by antimyosin staining, was the same in the embryonic as in the mature myofibril. (3) Glycerol-extracted myoblasts contracted vigorously on exposure to ATP. The changes in sarcomere band pattern were indistinguishable from those occurring during contraction of adult muscle induced by ATP. (4) ATP contraction was blocked by prior antimyosin staining in embryonic myoblasts as in mature muscle.
It is suggested that the early myofibril grows laterally as a thin sheet associated with the sarcolemma, and that growth in length occurs in the growth tips of the elongating myoblast.
THE GOLGI APPARATUS IN NEURONS AND EPITHELIAL CELLS OF THE COMMON LIMPET PATELLA VULGATA
Authors: Lacy Dennis 
Published: May 2004

1. In view of widely diverse views held about the identity and structure of the Golgi apparatus in neurons of Mollusca, particularly gastropods, a study has been made on neurons of the common limpet, Patella vulgata, both by light and electron microscopy. A report is given also of observations made on epithelial cells of Patella by electron microscopy.
2. As revealed by Kolatchev's method, the Golgi apparatus in neurons consists basically of black filaments lying to one side of the nucleus. The filaments generally anastomose to form networks of various complexity. Rarely some cells contain only discrete filaments. Associated with some of the filaments is a weakly osmiophilic substance identified as archoplasm. Kolatchev's method also revealed spheroidal bodies (neutral red bodies, "lipochondria," etc.).
3. It has not been possible to demonstrate the Golgi apparatus using either iron-haematoxylin or Sudan black.
4. Examination of Kolatchev's preparations by electron microscopy has revealed that some of the Golgi filaments consist of chromophilic and chromophobic components. The chromophilic component consists of dense lamellae.
5. After fixation in buffered osmium tetroxide solution and examination by electron microscopy, it has been concluded that (a) the chromophilic component of the Golgi apparatus corresponds to a system of paired membranes (which usually enclose an inner dense substance), (b) the chromophobic component corresponds to a substance lying within small dilations of the paired membrane, and (c) the archoplasm corresponds to numerous small vesicles.
6. The paired membranes branch, anastomose, and can often be traced back to a common source. They are interpreted as lamelliform folds, and occasionally tubular processes, of essentially a single Golgi membrane. In cells containing a Golgi network it is suggested that the membrane extends through the whole of the apparatus in such a way that the substance it encloses may be regarded as being in a continuous phase.
7. Epithelial cells of Patella contain a juxtanuclear Golgi apparatus with an ultrastructure similar to that described for neurons.
AN INTEGRATED MORPHOLOGICAL AND BIOCHEMICAL STUDY OF A PURIFIED PREPARATION OF THE SUCCINATE AND DPNH OXIDASE SYSTEM
Authors: Ball Eric G. , Barrnett Russell J. 
Published: May 2004

Electron micrographs of a purified succinate and DPNH oxidase system prepared from heart muscle reveal that it has a vesicular appearance and is membranous in nature. In keeping with its vesicular appearance is the fact that light scattering by this preparation shows marked changes as the molarity of the suspending medium is altered. Treatment of this preparation with 0.5 per cent deoxycholate solutions removes a large part of the lipide material, which comprises almost half of the dry weight of the preparation. The residue, which still contains the "core" of the cytochrome electron transmitter system, as shown by spectroscopic and enzymatic experiments, is still structured and is membranous in morphological appearance.
It is concluded that the enzyme preparation is largely composed of fragmented mitochondrial membranes, and some of the consequences of the localization of the succinate and DPNH oxidase systems in or on these membranes are discussed.
ELECTRON MICROSCOPIC OBSERVATIONS OF THE OLFACTORY MUCOSA AND OLFACTORY NERVE
Authors: de Lorenzo A. J. 
Published: May 2004

The olfactory receptor cell is characterized by a distal process (the dendrite) which terminates in the olfactory passage as the olfactory rod. The olfactory rod is provided with numerous cilia which are similar in structure to those seen in other tissues. The central processes of the bipolar cell constitute the fila olfactoria.
The cytoplasmic organelles of the sustentacular cell are concentrated at the apical and basal ends of the cell with a paucity of cytoplasmic elements in the region of the nucleus.
The plasma membrane of the supporting cell forms a mesaxon for both the dendrite and axon of the bipolar cell. Terminal bars are present in the epithelial cells.
The axons constituting the fila olfactoria form fascicles which are ensheathed by mesaxons of adjacent Schwann cells. Thus the olfactory neurons are ensheathed throughout their course by the membranes of sustentacular and Schwann cells.
Observations of the olfactory mucosa with the electron microscope are discussed with respect to recent electrophysiological studies.
THE FINE STRUCTURAL ORGANISATION OF ROUS TUMOUR CELLS
Authors: Epstein M. A. 
Published: May 2004

The fibroblast-like tumour cells of Rous sarcomata have been studied in thin sections with the electron microscope.
A description is given of the fine structure of the cells which includes some features not hitherto recorded. The tightly packed piles of smooth cisternae usually found only in the centrosome region have been observed, in individual Rous cells, in two separate areas of cytoplasm at opposite poles of the nucleus. Continuity between the perinuclear space and the lumen of rough surfaced cisternae of the endoplasmic reticulum has frequently been found; a similar continuity between the cisternae and the exterior of the cell has also been seen. In some cases, the cell membrane has been shown to have an unbroken connection with the outer nuclear membrane through continuity with the limiting membranes of elements of the endoplasmic reticulum.
These findings are discussed.