bluuebunny/crossref_metadata_2025 huggingface dataset:
AN ELECTRON MICROSCOPE STUDY OF YOLK FORMATION DURING OOGENESIS IN LEBISTES RETICULATUS GUPPYI
Authors: Droller Michael J. , Roth Thomas F.
Published: May 2004

The present investigation describes the fine structural changes that occur during proteid yolk formation in the developing oocytes of the guppy (Lebistes reticulatus), an ovoviviparous teleost. These changes suggest the operation of a number of different intra- and extraoocyte processes that may account for the synthesis and deposition of the proteid yolk. Early in oogenesis, the egg's Golgi systems proliferate and begin to disclose an electron-opaque content. Numerous 70-mµ diameter vesicles apparently pinch off from the Golgi systems, transport this material through the egg, and probably then fuse to form a crenate, membrane-limited yolk droplet. At the same time, the rough-surfaced endoplasmic reticulum accumulates a flocculent substance that differs in appearance from the Golgi content. Smooth vesicles, presumably derived from the ER, then coalesce to form a second type of intraoocyte yolk droplet. These dissimilar, separately derived droplets subsequently fuse, thus combining the materials that constitute the intraoocyte contribution to the proteid yolk. Somewhat later in development, the egg appears to ingest extracellular material via 75-mµ diameter bristle-coated micropinocytotic pits and vesicles. These structures apparently fuse to form tubules which then coalesce into large yolk droplets. At a later stage, bristle-coated micropinocytotic vesicles of 100 mµ diameter presumably take up a material that is then probably immediately deposited into a second type of proteid yolk droplet. It is postulated that these two different micropinocytotic structures are specifically involved with the selective uptake of dissimilar extracellular proteid materials.
THE SYNTHESIS OF DNA, RNA, AND NUCLEAR PROTEIN IN NORMAL AND TUMOR STRAIN CELLS
Authors: Seed John
Published: May 2004

Interferometric and photometric measurements have been made on HeLa cells, a strain of cells originally derived from a human carcinoma. From a study of the relations between successive physical measurements on individual cells, it was confirmed that, whereas the net syntheses of nuclear RNA and nuclear protein are closely associated during interphase, they are dissociated from DNA replication to a significant extent. These results on nuclear metabolism agree with others previously reported in cell strains derived from tumors; they contrast with results from freshly prepared normal cells, where the net syntheses of DNA, nuclear RNA, and protein are closely associated during interphase. Cytoplasmic measurements on HeLa cells showed that much of the net synthesis of cytoplasmic RNA is associated with DNA replication as in normal cells, and they failed to detect transfer from the nucleus of a stable RNA component synthesized independently from DNA replication. In auxiliary experiments, an inhibition of the onset of DNA synthesis was produced by a dose of X-rays; under these conditions it was shown that the major part of the accumulation of nuclear protein was independent of DNA replication and that the accumulation of nuclear RNA was equivalent to or slightly less than that of nuclear protein. About half the accumulation of cytoplasmic RNA was inhibited when DNA synthesis was blocked.
ORIGIN OF GRANULES IN POLYMORPHONUCLEAR LEUKOCYTES
Authors: Bainton Dorothy Ford , Farquhar Marilyn G.
Published: May 2004

The origin, nature, and distribution of polymorphonuclear leukocyte (PMN) granules were investigated by examining developing granulocytes from normal rabbit bone marrow which had been fixed in glutaraldehyde and postfixed in OsO4. Two distinct types of granules, azurophil and specific, were distinguished on the basis of their differences in size, density, and time and mode of origin. Both types are produced by the Golgi complex, but they are formed at different stages of maturation and originate from different faces of the Golgi complex. Azurophil granules are larger (∼800 mµ) and more dense. They are formed only during the progranulocyte stage and arise from the proximal or concave face of the Golgi complex by budding and subsequent aggregation of vacuoles with a dense core. Smaller (∼500 mµ), less dense specific granules are formed during the myelocyte stage; they arise from the distal or convex face of the Golgi complex by pinching-off and confluence of vesicles which have a finely granular content. Only azurophil granules are found in progranulocytes, but in mature PMN relatively few (10 to 20%) azurophils are seen and most (80 to 90%) of the granules present are of the specific type. The results indicate that inversion of the azurophil/specific granule ratio occurs during the myelocyte stage and is due to: (a) reduction of azurophil granules by multiple mitoses; (b) lack of new azurophil granule formation after the progranulocyte stage; and (c) continuing specific granule production. The findings demonstrate the existence of two distinct granule types in normal rabbit PMN and their separate origins from the Golgi complex. The implications of the observations are discussed in relationship to previous morphological and cytochemical studies on PMN granules and to such questions as the source of primary lysosomes and the concept of polarity within the Golgi complex.
TRANSFORMATION OF MONOCYTES IN TISSUE CULTURE INTO MACROPHAGES, EPITHELIOID CELLS, AND MULTINUCLEATED GIANT CELLS
Authors: Sutton Jerry S. , Weiss Leon
Published: May 2004

The sequential transformation of chicken monocytes into macrophages, epithelioid cells, and multinucleated giant cells in vitro was studied by electron microscopy after fixation and embedment in situ. The following changes occur. In the nucleus, margination of chromatin, evident in monocytes, decreases in later forms. Nucleoli become more complex and nuclear pores increase in number. In cytoplasm, a progressive increase in volume of the ectoplasm and endoplasm occurs in culture. Lysosomes increase in number and size prior to phagocytosis. During phagocytosis (most active from 1 to 3 days of culture) lysosome depletion occurs. Lysosomes are present in greatest number and show maximal structural variation in the epithelioid and young giant cells. Aging giant cells lose lysosomes. All stages possess variably large quantities of rough-surfaced endoplasmic reticulum and free ribosomes. The Golgi apparatus, small in monocytes, increases in size and complexity. Massive accumulations of lysosomes within the Golgi apparatus of macrophages and epithelioid cells suggest that lysosomes originate there. In giant cells, multiple Golgi regions occur, often ringing the nuclei. Monocytes and macrophages have few mitochondria. Mitochondria of epithelioid cells are larger, more numerous, and may have discontinuous outer membranes. Mitochondria are most numerous in giant cells where they increase with age and become polymorphous. Cytoplasmic filaments are approximately 50 to 60 A in diameter and of indeterminate length. They occur both singly and in bundles which touch cytoplasmic vesicles and mitochondria. Few filaments occur in monocytes and macrophages. A large increase in the number of filaments occurs in epithelioid cells, where filaments (90 to 100 A) surround the cytocentrum as a distinctive annular bundle often branching into the cytoplasm. The greatest concentration of filaments occurs in aged giant cells. Pseudopodia are always present. They are short and filiform in monocytes and giant cells, and broad, with abundant micropinocytotic vesicles, in macrophages and epithelioid cells. At every stage, the cell membrane contains dense cuplike structures. These may represent the membranous residue of lysosomes which have discharged to the outside, analogous to merocrine secretion. Contiguous epithelioid cells display elaborate cytoplasmic interdigitation. In places, the plasma membranes break down and epithelioid cells fuse to form giant cells.
THE NUCLEOIDS OF RAT LIVER CELL MICROBODIES
Authors: Tsukada Hideyuki , Mochizuki Yohichi , Fujiwara Seiki
Published: May 2004

The nucleoids of microbodies of rat liver cells were isolated in a highly homogeneous and pure state, by treating the microbody-rich fraction, prepared from 10% polyvinylpyrrolidone-0.25 M sucrose homogenate, with Triton X-100. Three treatments with 0.1% detergent were enough to render the nucleoids free from contamination with mitochondria, microsomes, lysosomes, and intact microbodies. Electron microscopically, the nucleoids were found to consist of parallel bundles of highly dense hollow tubules, the outer and inner diameters of which are approximately 150 and 50 A, respectively. Ten tubules are arranged around a longitudinal space 190 x 200 A in width. The nucleoids thus show a honeycomb appearance in the cross-plane and a parallel-packed structure in the longitudinal plane. Biochemically, the nucleoids were found to bear only urate oxidase among probably microbody-enzymes, and they might be the only cytoplasmic particles of rat liver cells in which the enzyme locates. Urate oxidase activity, on a unit protein basis, of the nucleoid preparation is approximately 380 times as high as that of the whole homogenate, and is almost comparable with that of a commercial type I enzyme preparation. No enzymes of mitochondrial, microsomal, and lysosomal origins were detected in the nucleoids. The fine structure of the nucleoids is described in detail, and a probable schematic diagram is presented.
SOME ASPECTS OF THE STRUCTURAL ORGANIZATION OF THE MYOFIBRIL AS REVEALED BY ANTIBODY-STAINING METHODS
Authors: Pepe Frank A.
Published: May 2004

From observations of fluorescent antibody staining and antibody staining in electron microscopy, evidence is presented for the following: (a) Direct contact of the actin and myosin filaments occurs at all stages of contraction. This results in inhibition of antibody staining of the H-meromyosin portion of the myosin molecule in the region of overlap of the thin and thick filaments. (b) Small structural changes occur in the thick filaments during contraction. This leads to exposure of antigenic sites of the L-meromyosin portion of the myosin molecule. The accessibility of these antigenic sites is dependent upon the sarcomere length. (c) The M line is composed of a protein which is weakly bound to the center of the thick filament and is not actin, myosin, or tropomyosin. (d) Tropomyosin as well as actin is present in the I band. (e) If actin or tropomyosin is present in the Z line, it is masked and unavailable for staining with antibody.
A FIBER APPARATUS IN THE NUCLEUS OF THE YEAST CELL
Authors: Robinow C. F. , Marak J.
Published: May 2004

The structure and mode of division of the nucleus of budding yeast cells have been studied by phase-contrast microscopy during life and by ordinary microscopy after Helly fixation. The components of the nucleus were differentially stained by the Feulgen procedure, with Giemsa solution after hydrolysis, and with iron alum haematoxylin. New information was obtained in cells fixed in Helly's by directly staining them with 0.005% acid fuchsin in 1% acetic acid in water. Electron micrographs have been made of sections of cells that were first fixed with 3% glutaraldehyde, then divested of their walls with snail juice, and postfixed with osmium tetroxide. Light and electron microscopy have given concordant information about the organization of the yeast nucleus. A peripheral segment of the nucleus is occupied by relatively dense matter (the "peripheral cluster" of Mundkur) which is Feulgen negative. The greater part of the nucleus is filled with fine-grained Feulgen-positive matter of low density in which chromosomes could not be identified. Chromosomes become visible in this region under the light microscope at meiosis. In the chromatin lies a short fiber with strong affinity for acid fuchsin. The nucleus divides by elongation and constriction, and during this process the fiber becomes long and thin. Electron microscopy has resolved it into a bundle of dark-edged 150 to 180 A filaments which extends between "centriolar plaques" that are attached to the nuclear envelope.
ELECTRON MICROSCOPE STUDIES ON THE ACTIVE ACCUMULATION OF SR++ BY RAT-LIVER MITOCHONDRIA
Authors: Greenawalt John W. , Carafoli Ernesto
Published: May 2004

Electron-opaque granules are deposited in isolated rat-liver mitochondria concomitant with the energy-linked accumulation of Sr++ by these organelles. High temperature microincineration (600°C) of thin sections of mitochondria containing different amounts of Sr++ shows that a clear qualitative correlation exists between the number of inorganic residues remaining after incineration and the amount of Sr++ translocated into the mitochondria. By loading the mitochondria with consecutive pulses of small amounts of Sr++ ("multiple-pulse" loading), very early stages of granule formation can be detected; the first detectable deposits are seen closely associated with the cristae. The evidence presented supports the hypothesis that mineral deposition following or during the in vitro accumulation of ions by mitochondria occurs, at least initially, at sites on these membranes and not as nonspecific precipitates in the mitochondrial matrix. The large number of electron-opaque deposits (100 to 200) seen in single thin sections of individual mitochondria having accumulated intermediate levels of Sr++ clearly exceeds the number of normal dense granules in rat-liver mitochondria, indicating that the normal matrix granules per se do not constitute sites essential for deposition. At the highest levels of Sr++ uptake studied in the multiple-pulse loading experiments, needlelike deposits are seen, a result which suggests that the structural form ("crystallinity") of the mineral deposits may be determined by the rate of accumulation.
CYTOPLASMIC GRANULE FORMATION IN MYELOCYTES
Authors: Fedorko Martha E. , Hirsch James G.
Published: May 2004

The intracellular flow of tritiated lysine as revealed by electron microscope radioautography was studied in heterophilic myelocytes of rabbit marrow. Label over the Golgi complex rose to a maximum of 37% of total cytoplasmic grains 30 min after initial exposure to the tracer and fell to 11% after 3 to 4 hr of incubation. Coincident with decrease in label over the Golgi complex, grain counts over granules rose to 32% after 3 to 4 hr. The time sequence of incorporation and flow of tritiated lysine and the per cent distribution of label was similar in bone marrow myelocytes under in vivo and in vitro conditions. The results demonstrate a function of the Golgi complex in incorporating or packaging certain basic amino acids or proteins into cytoplasmic granules of heterophilic myelocytes.
ULTRASTRUCTURAL ORGANIZATION OF CILIA AND BASAL BODIES OF THE EPITHELIUM OF THE CHOROID PLEXUS IN THE CHICK EMBRYO
Authors: Doolin Paul F. , Birge Wesley J.
Published: May 2004

Ultrastructural studies were performed on normal and abnormal cilia and basal bodies associated with the choroidal epithelium of the chick embryo. Tissues were prepared in each of several fixatives including: 1% osmium tetroxide, in both phosphate and veronal acetate buffers; 2% glutaraldehyde, followed by postfixation in osmium tetroxide; 1% potassium permanganate in veronal acetate buffer. Normal cilia display the typical pattern of 9 peripheral doublets and 2 central fibers, as well as a system of 9 secondary fibers. The latter show distinct interconnections between peripheral and central fibers. Supernumerary fibers were found to occur in certain abnormal cilia. The basal body is complex, bearing 9 transitional fibers at the distal end and numerous cross-striated rootlets at the proximal end. The distal end of the basal body is delimited by a basal plate of moderate density. The tubular cylinder consists of 9 triple fibers. The C subfibers end at the basal plate, whereas subfibers A and B continue into the shaft of the cilium. The 9 transitional fibers radiate out from the distal end of the basal body, ending in bulblike terminal enlargements which are closely associated with the cell membrane in the area of the basal cup. One or 2 prominent basal feet project laterally from the basal body. These structures characteristically show several dense cross-bands and, on occasion, are found associated with microtubules.
A STUDY OF THE NUCLEOLAR MATERIAL IN SCIARA COPROPHILA
Authors: Gabrusewycz-Garcia Natalia , Kleinfeld Ruth G.
Published: May 2004

In the polytene chromosomes of Sciara coprophila, in addition to a nucleolus, large numbers of nucleolarlike structures or micronucleoli are formed. A detailed mapping localized the nucleolar organizer at one end of the X chromosome and revealed that approximately 18% of the bands of each chromosome are potentially capable of producing micronucleoli. Most of these sites are in regions known from a previous study to show asynchronous DNA replication: DNA puffs and certain heterochromatic regions. Micronucleoli are rarely found in association with bulbs. The RNA metabolism of the polytene chromosomes during late fourth instar was studied using radioautographic techniques. Isolated glands were incubated in tritiated uridine for 10 to 30 min, and radioautographs were made of squash preparations. Despite the wide range of variation found among different larval cultures, the following pattern was observed. Just prior to and at the beginning of DNA puff formation, a period of intense extrachromosomal nucleolar and micronucleolar RNA synthesis occurs. After maximal development of the DNA puffs, the synthesis of extrachromosomal RNA is at a low point, while incorporation into bulbs and DNA puffs remains high. With the onset of the prepupal stage, all nuclear RNA synthesis ceases.
STUDIES ON THE FUNCTION OF INTRACELLULAR RIBONUCLEASES
Authors: Utsunomiya Takeshi , Roth Jay S.
Published: May 2004

The RNase activity and properties of ribosome and polysome preparations from normal rat liver and some hepatomas have been examined. Polysome and ribosome preparations from the Novikoff, McCoy MDAB, and Dunning hepatomas had considerably higher specific RNase activity than corresponding preparations from normal rat liver, Novikoff ascites, or Morris 5123 hepatomas. The optimum pH of the RNase was approximately 8.5 for all samples tested, and the samples showed no evidence of latent RNase activity when treated with 3 M sodium chloride, EDTA, urea, or p-chloromercuribenzenesulfonic acid. The RNase activity appeared to be associated principally with breakdown products and/or subunits smaller than 80S. In the presence of Mg++ ions, subunits could reaggregate to form monomer ribosomes indistinguishable from the natural products, but some of the reassociated ribosomes could contain RNase activity which had been bound to the smaller particles. Similar results were obtained with spermine. In the hepatomas, evidence was obtained for the preexistence of considerable amounts of the smaller, RNase-containing subunits in the cell. When a small amount of crystalline bovine pancreatic RNase was added to partly dissociated ribosomes, the RNase was found only in association with the smaller subunits, and little or no enzyme was taken up by ribosomes or polysomes. The results have led to the conclusion that RNase is not a normal constituent of the ribosome or polysome, but that RNase may become associated with these particulates if dissociation and reassociation take place. Some implications of these findings for the stability of messenger RNA and for the mechanism of its breakdown are discussed.
RELATIONSHIP BETWEEN RNA SYNTHESIS, CELL DIVISION, AND MORPHOLOGY OF MAMMALIAN CELLS
Authors: Studzinski George P. , Ellem Kay A. O.
Published: May 2004

Logarithmically growing HeLa cell monolayers were treated with a range of concentrations of puromycin aminonucleoside (AMS). The effects of AMS were studied by the following means: microscope examination of treated cells; enumeration of the cell number using an electronic particle counter; analyses for DNA, RNA, and protein content; incorporation of P32 and H3-thymidine into nucleic acids; and fractionation of nucleic acids by column chromatography. Taking the rate of incorporation of the isotopic precursor as a measure of nucleic acid synthesis, it was found that concentrations of the inhibitor which had a rapid effect on the rate of cell division inhibited the synthesis of all types of nucleic acids and of protein, but depressed ribosomal RNA synthesis most markedly. Lower concentrations of AMS selectively inhibited ribosomal RNA and, to a lesser extent, transfer RNA synthesis. Partial inhibition of ribosomal RNA synthesis with low doses had no effect on the rate of cell division within the period studied (3 generation times). The cell content of RNA returned to normal when the inhibitor was removed.
GRANULES ASSOCIATED WITH THE CHLOROPLAST LAMELLAE OF PORPHYRIDIUM CRUENTUM
Authors: Gantt E. , Conti S. F.
Published: May 2004

Small granules with a diameter of approximately 350 A are attached to the chloroplast lamellae of the red alga Porphyridium cruentum. To some extent, their size depends on the culture conditions and the age of the cell. It was possible to preserve the granules only with aldehyde prefixation. It can be seen that fixed or negatively stained granules are comprised of smaller subunits. The granules are arranged regularly on the lamellae in repeating rows with a center-to-center granule distance of 400 to 500 A. Attempts at characterization of these chloroplast granules revealed that they are resistant to hydrolysis by ribonuclease and appear to be structurally unaffected by methanol-acetone extraction. Because of their close association with the chloroplast lamellae, they are considered as possible sites of phycobilin concentration. This possibility is supported by two observations: when the phycobilins are removed, the granules disappear; and, when the chlorophyll and stainable membrane portions are selectively removed, the phycobilins and granules are still present. It was found that all other marine red algae examined had granules which were associated with the chloroplast lamellae.
A SIMPLE FREEZE-FRACTURE REPLICATION METHOD FOR ELECTRON MICROSCOPY
Authors: Bullivant Stanley , Ames Adelbert
Published: May 2004

A simple method to achieve results similar to the freeze-etching technique of Moor et al. (1961) is described. The frozen tissue is cut under liquid nitrogen with a razor blade outside the evaporator rather than inside with a cooled microtome. The conditions of the experiment do not favor sublimation, and it is proposed that the structure of the replica be explained by local faults in the cleavage plane which leaves structures, such as membranes, standing above the ice. Micrographs of replicas of glycerol-protected frozen small intestine of mouse prepared by the method are presented and the structural details they show are discussed. The problem of vapor-deposited contamination is discussed. It is concluded that this is a practical method for obtaining electron micrographs that are relatively free of artifact, and that further improvements may be expected from the use of rapidly frozen fresh tissue and a clean vacuum system, possibly of the ion-pumped type.
FINE STRUCTURAL LOCALIZATION OF ACETYLCHOLINESTERASE IN ELECTROPLAQUE OF THE ELECTRIC EEL
Authors: Bloom Floyd E. , Barrnett Russell J.
Published: May 2004

The electroplaques composing the electric organ of the eel, Electrophorus electricus, have been utilized for the dual purpose of demonstrating the subcellular sites of acetylcholinesterase activity and as a model for comparison of the several cytochemical methods available. Fresh tissue and tissue fixed by immersion in formalin, hydroxyadipaldehyde, or glutaraldehyde was reacted with the Cu-thiocholine method, the Cu-ferrocyanide thiocholine method, or the thiolacetic acid (TAA) method using Pb, Ag, or Au as capture reagents. Controls were obtained by omission of substrate, or by addition to complete media of varying concentrations of different cholinesterase inhibitors. Reactions were run at 0–5°C at a pH range of 5.0–7.1 for 0.25 to 120 min. Regardless of the capture metal, the localization obtained with TAA as substrate was identical with that observed with acetylthiocholine, the majority of precipitate being deposited on or near the external innervated surface of the plaque and within the tubulovesicular organelles opening onto the innervated surface. Both of the thiocholine methods and the Pb-TAA method showed reaction product in synaptic vesicles of the nerve endings innervating the plaque which was uninhibitable by 10-4 M physostigmine. All methods also showed some inhibitor-sensitive deposition of reaction product in the mucoid material forming the immediate extracellular environment of the innervated surface.
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 STRUCTURE OF THE PRIMARY EPIDERMAL CELL WALL OF AVENA COLEOPTILES
Authors: Bayley S. T. , Colvin J. R. , Cooper F. P. , Martin-Smith Cecily A.
Published: May 2004

The primary walls of epidermal cells in Avena coleoptiles ranging in length from 2 to 40 mm. have been studied in the electron and polarizing microscopes and by the low-angle scattering of x-rays. The outer walls of these cells are composed of multiple layers of cellulose microfibrils oriented longitudinally; initially the number of layers is between 10 and 15 but this increases to about 25 in older tissue. Where epidermal cells touch, these multiple layers fuse gradually into a primary wall of the normal type between cells. In these radial walls, the microfibrils are oriented transversely. Possible mechanisms for the growth of the multilayered outer wall during cell elongation are discussed.
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.
STUDIES ON THE ENDOPLASMIC RETICULUM
Authors: Porter Keith R. , Palade George E.
Published: May 2004

Several types of striated muscle have been examined by the technics of electron microscopy and the findings in myotome fibers of Amblystoma larvae, the sartorius, and cardiac muscle of the rat are reported on in some detail. Particular attention has been given to structural components of the interfibrillar sarcoplasm and most especially to a finely divided, vacuolar system known as the sarcoplasmic reticulum. This consists of membrane-limited vesicles, tubules, and cisternae associated in a continuous reticular structure which forms lace-like sleeves around the myofibrils. It shows a definable organization which repeats with each sarcomere of the fiber so that the entire system is segmented in phase with the striations of the associated myofibrils. Details of these repetitive patterns are presented diagrammatically in Text-figs. 1, 2, and 3 on pages 279, 283, and 288 respectively. The system is continuous across the fiber at the H band level and largely discontinuous longitudinally because of interruptions in the structure at the I and Z band levels. The structure of the system relates it to the endoplasmic reticulum of other cell types. The precise morphological relation of the reticulum to the myofibrils, with specializations opposite the different bands, prompts the supposition that the system is functionally important in muscle contraction. In this regard it is proposed that the membrane limiting the system is polarized like the sarcolemma and that the corresponding potential difference is utilized in the intracellular distribution of the excitatory impulse.
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 FORM BIREFRINGENCE OF LAMELLAR SYSTEMS CONTAINING THREE OR MORE COMPONENTS
Authors: Thornburg Wayne
Published: May 2004

Equations are derived which predict the form birefringence of lamellar systems containing three or more components. These equations may be found useful in interpreting the birefringence of biological specimens and in testing certain theories about the structure of natural membranes.
Iron Particles in Normal Erythroblasts and Normal and Pathological Erythrocytes
Authors: Bessis Marcel C. , Breton-Gorius Janine
Published: May 2004

Iron-containing granules (40 to 100 A in diameter), in groups or isolated, are present in normal erythroblasts, normoblasts, reticulocytes, and certain pathological erythrocytes. Similar granules are present in macrophages and have been noted in the stroma of erythrocytes following phagocytosis and hemolysis by macrophages. Incorporation of the granules from the macrophage into erythroblasts is presented as a process similar to pinocytosis. The presence of the iron-containing granules within the erythroid cells parallels hemoglobin synthesis.
NUCLEAR CHANGES DURING SPERMIOGENESIS IN A PULMONATE SNAIL
Authors: Rebhun Lionel I.
Published: May 2004

Changes in both external form and internal arrangement of nuclear material have been investigated in the differentiation of the sperm of the pulmonate snail, Otala lactea. Sperm head differentiation begins with a flattening of the previously spherical nucleus and a thickening of the nuclear envelope covering the anterior and posterior surfaces of that nucleus. Tail filaments can be seen in the cytoplasm at this time. At a slightly later period the mitochondria begin to form the tail filament sheath and at this time the nucleus begins to elongate in a direction parallel to the future axis of the sperm. At the same time the nuclear material begins to orient itself at right angles to the nuclear surface which lines the pit occupied by the centriole. As nuclear elongation proceeds, this orientation of nuclear substance takes on the appearance of 60 A thick sheets bent in a direction parallel to the sperm axis. Soon the sheets fill the entire nucleus. The nucleus then begins to twist along its axis so that it starts to take on the mature, flame-shaped form. At this time the flat sheets begin to disappear and in the mature sperm head they are no longer visible (see Text-fig. 2 B).
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.
COLLAGEN BIOSYNTHESIS
Authors: Woessner J. Frederick , Gould Bernard S.
Published: May 2004

Quantitative studies of collagen formation by chick embryonic lung tissue grown in media deficient in, or completely lacking, ascorbic acid have been carried out. Cell growth and collagen formation in such cultures can proceed almost normally in media lacking ascorbic acid. Ascorbic acid in combination with whole embryo extract, dialyzed media, or synthetic mixture number 703 was found to have no appreciable effect on cell growth or total collagen formation. This is in marked contrast to the almost total failure of collagen formation in scorbutic animals and suggests that for slow collagen biosynthesis as distinct from more prolific collagen-producing systems, ascorbic acid plays an indirect role.
MICROKINETOSPHERES AND VP SATELLITES OF PINOCYTIC CELLS OBSERVED IN TISSUE CULTURES OF GEY'S STRAIN HELA WITH PHASE CONTRAST CINEMATOGRAPHIC TECHNIQUES
Authors: Rose George G.
Published: May 2004

By tissue culture methods and with the use of phase contrast, interference color contrast, and time-lapse cinematographic equipment, the activity of a cytoplasmic organoid, termed the microkinetosphere, has been followed and correlated with pinocytosis. A transformation of several microkinetospheres by coherence and coalescence into the solitary VP satellite was observed in cells undergoing pinocytosis in serum nutrients. A correlation of both of these structures to cytoplasmic organoids described by others, notably with the electron microscope, and a hypothesis on the nature of the microkinetosphere and its transformation was presented.
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.