bluuebunny/crossref_metadata_2025 huggingface dataset:
CHANGES IN FINE STRUCTURE AND ACID PHOSPHATASE LOCALIZATION IN RAT THYROID CELLS FOLLOWING THYROTROPIN ADMINISTRATION
Authors: Wetzel Bruce K. , Spicer Samuel S. , Wollman Seymour H.
Published: May 2004

Shortly after the administration of 1/40 unit thyrotropin to rats, 24 hours post-hypophysectomy, the following sequence of changes has been observed within thyroid follicular epithelial cells: (1) the appearance of apical cell surface activity consisting of pseudopods projecting into the follicular lumen; (2) apparent phagocytic engulfment of colloid droplets lacking indications of acid phosphatase activity; (3) close association and probable fusion of newly formed colloid droplets and dense granules, the latter cytochemically positive for acid phosphatase activity; (4) the appearance of presumptive acid phosphatase activity within colloid droplets; and, (5) further colloid droplet changes, viz., basipetal migration and decrease in size, accompanied by an increase in density and in demonstrable acid phosphatase activity. These changes appeared to represent the resorption and degradation of follicular colloid. Comparable results were obtained using intact and more heavily stimulated animals. Colloid biosynthesis was tentatively visualized in these cells as a separate mechanism involving small vesicles prominent in the Golgi region and beneath the apical plasma membrane of some, but not all, thyroid follicular cells in each specimen.
INCORPORATION OF H3-THYMIDINE INTO CHLOROPLAST DNA OF MARINE ALGAE
Authors: Steffensen Dale M. , Sheridan William F.
Published: May 2004

The chloroplasts of three genera of marine algae, Dictyota, Padina, and Bryopsis, were labeled with tritiated-thymidine for various time periods during culture in "Erd-Schreiber's" solution. Autoradiographs were prepared from both smeared and sectioned material. They revealed that almost all of the radioactivity was in the cytoplasm and associated with the chloroplasts, as detected in the overlying silver halide crystals. Deoxyribonuclease, ribonuclease, and hot trichloracetic acid treatments indicated that the loss of radioactivity corresponded to the removal of DNA and not RNA. Quantitative studies of silver grain distribution suggested that the radioactivity of the labeled DNA originated from the edge of the pyrenoids on either side in the longitudinal direction of Bryopsis chloroplasts. Nuclei did not incorporate H3-thymidine even though cells were dividing rapidly in the three genera examined. It is postulated that the enzyme, thymidine kinase, is absent as a coding sequence of nuclear DNA in algae, but is present in chloroplast DNA. When the chloroplasts of Dictyota and Padina in various stages of division were scored for labeling, there appeared to be a DNA synthesis period, analogous to S period in cell division. This chloroplast-labeling period occurred just previous to fission. Many of the criteria seem to have been satisfied to establish the self-reproducing and semi-autonomous nature of chloroplasts, especially when combined with the chemical, genetic, and morphological evidence.
LOCALIZATION OF A BASIC PROTEIN IN THE MYELIN OF VARIOUS SPECIES WITH THE AID OF FLUORESCENCE AND ELECTRON MICROSCOPY
Authors: Kornguth Steven Edward , Anderson John Walberg
Published: May 2004

In this study, alanine was shown to be the N-terminal amino acid of a basic protein of low molecular weight that was isolated from either human or guinea pig brain. Antibodies prepared against the guinea pig protein were labeled with either fluorescein or ferritin. Studies with the labeled antibodies showed that an immunohistochemically similar protein is found in the myelin sheaths of central and peripheral nervous tissues of chicken and frog and a variety of mammalian species. Loss of integrity of the myelin during processing was shown to enhance markedly the antigen-antibody reaction.
THE INTRACELLULAR LOCALIZATION OF PITUITARY THYROTROPIC HORMONE
Authors: Greenspan Francis S. , Hargadine Judy R.
Published: May 2004

The intracellular localization of a bovine anterior pituitary preparation of thyroid-stimulating hormone (TSH) was studied in guinea pigs and dogs. The preparation was administered intravascularly or applied directly to tissue sections. TSH was detected by an indirect technique utilizing bovine TSH antiserum and fluorescein-labeled anti-rabbit globulin; the presence of TSH in the tissue was indicated by fluorescence when the tissue was examined under the microscope with an ultraviolet light source. After either intravascular administration or direct application of the TSH preparation, striking fluorescence was found in the nuclei of the thyroid cells and to a lesser degree in the nuclei of retro-orbital fat tissue and kidney tubules in both species studied. A little fluorescence was also seen in spleen tissue. No fluorescence was noted in comparable tissues removed from control animals injected with bovine albumin or globulin or when the tissues were treated with the fluorescein-labeled globulin alone. Fluorescence was also noted in the nuclei of adrenal cells treated with unabsorbed antiserum, but this was greatly diminished when antiserum absorbed with crystalline ACTH was used. The positive reactions were all markedly decreased when the tissues were treated with antisera absorbed with the original TSH preparation. Fluorescence was noted in the cytoplasm of pituitary tissue from both treated and control animals, suggesting a cross-reaction between the bovine pituitary antisera and guinea pig or dog hypophysis. The indirect technique seems to be highly satisfactory for demonstration of the pitiutary hormone within the cell. In addition, the demonstration of immunologically active anterior pituitary TSH bound to cell nuclei offers a clue to the site of action of this hormone.
RADIATION EFFECTS ON THE GROWTH RATE AND CELL POPULATION KINETICS OF ACTIVELY GROWING AND DORMANT ROOTS OF TRADESCANTIA PALUDOSA
Authors: Van't Hof Jack , Sparrow A. H.
Published: May 2004

Actively growing and dormant roots of Tradescantia paludosa were exposed to x-rays to compare the radiosensitivity of an actively proliferating tissue with that of one which is not active but is potentially proliferative. The level of effect was ascertained by the degree of change in the rate of root growth 4 days after exposure. Cell population kinetics were measured in control and in irradiated roots to determine whether or not a change was produced either in the number of proliferating cells or in the mitotic cycle duration which was sufficient to explain the altered rate of root growth. Nuclear volumes were also measured to provide an estimate of the relative total target size in actively growing vs. dormant roots. Tritiated thymidine was used to measure the cycle duration and the proportion of cells synthesizing DNA. The results showed that 184 and 305 r respectively were required to reduce the linear root growth rate to 37 per cent of that of the control for actively growing and dormant roots. Mitotic cycle duration, measured 4 days after x-ray exposure, was the same as in the control. The number of proliferating cells, however, was reduced. The rate of cell production in the irradiated roots was reduced to approximately one-half that of the controls. The average nuclear volumes of active and dormant roots were 733 and 491 µ3 respectively; thus the difference in the number of roentgens required to reduce growth to 37 per cent of that of the control can be attributed to the different average nuclear volumes. Therefore, the experiments suggest that part if not most of the differences in sensitivity between an actively dividing and an essentially non-dividing meristematic cell population resides in their different average nuclear volumes. Thus the law of Bergonie and Tribondeau needs to be reinterpreted, since the basic reason for the differences is secondary to whether or not the meristematic cells are proliferating.
THE CELL GENERATION CYCLE OF THE ELEVEN-DAY MOUSE EMBRYO
Authors: Atlas M. , Bond V. P.
Published: May 2004

The incorporation of tritiated thymidine into the DNA of erythroblasts, primitive ependymal cells, and mesenchymal cells of 11-day mouse embryos was studied by radioautography at different times between 25 minutes and 18 hours after injection intraperitoneally. There was no labeling of mitotic figures until 1 hour after injection. Following this, mitotic figures were labeled for about 5.5 hours in primitive ependymal cells and mesenchymal cells, and for a longer period in erythroblasts. The percentage of the labeled primitive ependymal cells at various times after injection indicate a periodic migration into and out of the mitotic zone. The cell generation cycle of primitive ependymal cells and mesenchymal cells is similar to some kinds of adult cells. The cycle of the erythroblasts is more like that of the cells of aging mice.
ANTIGEN-INDUCED CHANGES IN LYMPHOID CELL HISTONES
Authors: Black Maurice M. , Ansley Hudson R.
Published: May 2004

An acute effect of antigens on the nuclear histones of mouse thymocytes was investigated by means of cytophotometric measurements of thymocytes stained with ammoniacal-silver (A-S) and with fast green (FG). In addition, the DNA content was measured in terms of Feulgen staining. In terms of such staining it appeared that nuclei of control thymocytes contain a greater amount of nuclear histones and a higher histone/DNA ratio than do renal cell nuclei from the same animal. Within 1 hour after the injection of antigen the thymocyte nuclei appear to lose approximately 32 per cent and 20 per cent, respectively, of A-S and FG stainable nuclear proteins, while the Feulgen staining remains unchanged. Since the renal cell nuclei show no antigen-induced change in histone staining, the histone staining and histone/DNA ratios were found to be similar in the thymocytes and renal cells of the antigen-injected mice. The antigen-induced loss of thymocyte histones was also found to be associated with a change in the color of the A-S staining, from yellowish brown to black. This and other findings suggest that thymocyte nuclei contain an antigen-labile, lysine-rich histone. The implication of these observations in regard to the phenomenon of immunological competence is discussed and the need for continued investigation indicated.
AN INVESTIGATION BY ELECTRON MICROSCOPY OF THE NUCLEOSIDE PHOSPHATASE ACTIVITY OF AMPHIBIAN AND MAMMALIAN ERYTHROCYTES
Authors: Tooze J.
Published: May 2004

Amphibian and mammalian blood was washed in isotonic saline, fixed in glutaraldehyde, and then stained in the ATPase medium of Wachstein and Meisel. The blood cells were subsequently postfixed in osmium tetroxide, embedded in epoxy resins, and studied by electron microscopy. The plasma membranes of amphibian erythrocytes, from the newt Triturus cristatus and the frog Rana esculenta, were stained after incubation in media containing ATP or ADP as substrates, but were unstained after incubation in media containing AMP or sodium ß-glycerophosphate. The addition of 0.001 M ouabain to ATP-containing media did not inhibit the staining of the plasma membranes, but the omission of Mg++ ions from the medium inhibited staining. The plasma membranes of rat and rabbit erythrocytes were never stained after incubation in any of the media used.
PROTEIN UPTAKE IN THE OOCYTES OF THE CECROPIA MOTH
Authors: Stay Barbara
Published: May 2004

The formation of yolk spheres in the oocyte of the cecropia moth, Hyalophora cecropia (L.), is known immunologically to result largely from uptake of a sex-limited blood protein. Recent electron microscope analyses of insect and other animal oocytes have demonstrated fine structural configurations consistent with uptake of proteins by pinocytosis. An electron microscope analysis of the cecropia ovary confirms the presence of similar structural modifications. With the exception of two apparently amorphous layers, the basement lamella on the outer surface of the follicular epithelium and the vitelline membrane on the inner, there is free access of blood to the oocyte surface between follicle cells. Dense material is found in the interfollicular cell space and adsorbed to the outer surface of the much folded oocyte membrane. Pits in the oocyte membrane and vesicles immediately under it are lined with the same dense material not unlike the yolk spheres in appearance. Introduction of ferritin into the blood of a developing cecropia moth and its localization adsorbed to the surface of the oocyte, and within the vesicles and yolk spheres of the oocyte cortex, is experimental evidence that the structural modifications of the oocyte cortex represent stages in the pinocytosis of blood proteins which arrive at the oocyte surface largely by an intercellular route. Small tubules attached to the yolk spheres are provisionally interpreted as a manifestation of oocyte-synthesized protein being contributed to the yolk spheres.
THE INTRAEPIDERMAL INNERVATION OF THE SNOUT SKIN OF THE OPOSSUM
Authors: Munger Bryce L.
Published: May 2004

The intraepidermal innervation of the snout skin of the opossum has been studied with the light and electron microscope. Numerous large nerve fibers loose their myelin sheath in the superficial dermis and pass into the epidermis. The basement membranes of the epidermis and Schwann cell become continuous at the point of entry of the neurite into the epidermis. Within the epidermis, the neurite is associated with a specialized secretory epidermal cell, termed a Merkel cell. This cell has many secretory granules apposed to the neurite. The Merkel cells are epidermal cells since they have desmosomes between them and adjacent epidermal cells. The neurite in the stratum spinosum is enveloped by Schwann cells in a manner analogous to the Schwann cell investment of unmyelinated neurites. In the upper stratum spinosum the nerve fiber evidences changes which can be interpreted as degenerative. The Merkel cell-neurite complex is interpreted as representing a sensory receptor unit.
THE DISTRIBUTION WITHIN THE BRAIN OF FERRITIN INJECTED INTO CEREBROSPINAL FLUID COMPARTMENTS
Authors: Brightman Milton W.
Published: May 2004

From 10 minutes to 3½ hours after the intraventricular injection into rats of 15 to 100 mg of ferritin, an appreciable fraction of the protein, visualized electron microscopically, traverses the ependymal epithelium by diffusing along the dense intercellular substance of the luminal open junction and thence, by circumventing discrete intercellular fusions which partition rather than seal the interspace. These partitions shunt additional protein into the cell, where ferritin is transported within pinocytotic vesicles to the lateral and basal plasma-lemma and, presumably, back into the interspace again. The basal interspace is irregularly distended by pools of moderately dense "filler" within which ferritin accumulates. The larger fraction of protein enters the ependyma by pinocytosis and is eventually segregated within membrane-enclosed organelles such as vacuoles, multivesicular bodies, and dense bodies, where the molecules may assume a crystalline packing. As a result of the accumulation of ferritin within these inclusions and within filler substance, only a small amount of protein remains to enter the underlying parenchyma. Presentation of ferritin to prefixed cells leads to a random dispersion of free cytoplasmic ferritin. This artifactual distribution in both prefixed and postfixed cells is concurrent with disruption of cell membranes.
THE SARCOPLASMIC RETICULUM, THE T SYSTEM, AND THE MOTOR TERMINALS OF SLOW AND TWITCH MUSCLE FIBERS IN THE GARTER SNAKE
Authors: Hess Arthur
Published: May 2004

Twitch and slow muscle fibers, identified morphologically in the garter snake, have been examined in the electron microscope. The transverse tubular system and the sarcoplasmic reticulum are separate entities distinct from each other. In twitch fibers, the tubular system and the dilated sacs of the sarcoplasmic reticulum form triads at the level of junction of A and I bands. In the slow fibers, the sarcoplasmic reticulum is severely depleted in amount and the transverse tubular system is completely absent. The junctional folds of the postsynaptic membrane of the muscle fiber under an "en grappe" ending of a slow fiber are not so frequent or regular in occurrence or so wide or so long as under the "en plaque" ending of a twitch fiber. Some physiological implications of these differences in fine structure of twitch and slow fibers are discussed. The absence of the transverse tubular system and reduction in amount of sarcoplasmic reticulum, along with the consequent disposition of the fibrils, the occurrence of multiple nerve terminals, and the degree of complexity of the post junctional folds of the sarcolemma appear to be the morphological basis for the physiological reaction of slow muscle fibers.
THE NUCLEOLI IN MITOTIC DIVISIONS OF MAMMALIAN CELLS IN VITRO
Authors: Hsu T. C. , Arrighi Frances E. , Klevecz Robert R. , Brinkley B. R.
Published: May 2004

In a number of mammalian cell strains nucleoli persisted through mitosis. This phenomenon was especially pronounced in several cell lines derived from Chinese hamster tissues. All the methods employed, including radioautography with tritiated uridine, cytochemical stains (methyl green-pyronin and azure B), fluorescent microscopy (coriphosphine O), ribonuclease digestion, and electron microscopy, demonstrated that the bodies identified as persistent nucleoli in the mitotic stages had the same characteristics as did the nucleoli in the interphase. Persistent nucleoli may attach to the chromosomes or may be free in the cytoplasm. In cells where no persistent nucleoli as such were noted, nucleolar material was observed to attach to the chromosomes in shapeless masses which moved with the chromosomes during anaphase. At least a portion of the nucleolar material was included in the daughter nuclei, presumably for immediate use for protein synthesis after cell division.
THE FINE STRUCTURE OF MITOSIS IN RAT THYMIC LYMPHOCYTES
Authors: Murray Raymond G. , Murray Assia S. , Pizzo Anthony
Published: May 2004

The fine structure of rat thymic lymphocytes from early prophase to late telophase of mitosis is described, using material fixed at pH 7.3 either in 1 per cent OsO4 or in glutaraldehyde followed by 2 per cent OsO4. The structure of the centriolar complex of interphase thymocytes is analyzed and compared with that of centrioles during division. The appearance of daughter centrioles is the earliest clearly recognizable sign of prophase. Daughter centrioles probably retain a secondary relation to the primary centriole, while the latter appears to be related, both genetically and spatially, to the spindle apparatus. The nuclear envelope persists in recognizable form to help reconstitute the envelopes of the daughter nuclei. Ribosome bodies (dense aggregates of ribosomes) accumulate, beginning at late prophase, and are retained by the daughter cells. Cytokinesis proceeds by formation of a ribosome-free plate at the equator with a central plate of vesicles which may coalesce to form the new plasma membrane of the daughter cells. Stages in the formation of the midbody are illustrated.
MICROSPECTROPHOTOMETRY OF CYTOCHROMES IN THE SINGLE CELL AT ROOM AND LIQUID NITROGEN TEMPERATURES
Authors: Thorell B. , Chance B. , Legallais V.
Published: May 2004

By increasing further the sensitivity of microspectrophotometry, it is now possible to measure, under favorable conditions, the smaller absorption bands of the respiratory pigments of single cells in the visible region of the spectrum. A considerable aid in the distinction between cytochromes is afforded by liquid nitrogen microspectrophotometry. Under favorable conditions, the height of the peaks is increased over 8-fold at low temperatures. In diploid yeast, characteristically sharpened components not resolvable at room temperature are observed at low temperature; and in pentaploid yeast, a hitherto unrecognized pigment is observed at 583 mµ. These preliminary results indicate the feasibility and the value of low temperature microspectrophotometry of biological materials.
THE OCCURRENCE AND STRUCTURE OF MICROBODIES
Authors: Afzelius Björn A.
Published: May 2004

Livers from chickens, rats, mongrel dogs, Dalmatian dogs, and man have been examined in the electron microscope in order to compare the microbodies with the known content of uricase. It is concluded that microbodies with inclusion are present in rats, mongrel dogs, and, although the inclusion generally is smaller, in Dalmatian dogs. The inclusion has a characteristic structural appearance. These species (rat, dog) have uricase. Chickens and man lack both the enzyme uricase and the microbody inclusion. This evidence and that from previously published electron micrographs in the literature on microbodies support the notion of a positive correlation between uricase and microbodies with an inclusion. It is recommended that the term "uricosome" be used for such microbodies that have an inclusion of the appearance here described.
REVERSIBLE AND IRREVERSIBLE CHANGES IN THE FINE STRUCTURE OF NERVOUS TISSUE DURING OXYGEN AND GLUCOSE DEPRIVATION
Authors: deF. Webster Henry , Ames Adelbert
Published: May 2004

Rabbit retinas were fixed for electron microscopy immediately after removing the eye and after incubations in a control medium and in three different deprivation media that were identical with the control except for the omission of glucose, oxygen, or both. A systematic comparison was made of the electron microscopic appearance of the different retinas with particular attention to four regions: rod inner segments, rod synapses, bipolar cell bodies, and ganglion cell myelinated axons. Retinas fixed after 1 hour of incubation in the control medium appeared virtually identical with those fixed immediately after ocular removal. Retinas deprived of oxygen and glucose for only 3 minutes showed generalized swelling of mitochondria and alterations in the structure of the synapses with loss of synaptic vesicles. Extending the combined deprivation caused further mitochondrial swelling and synaptic changes and also led to progressive swelling of the Golgi membranes and the granular endoplasmic reticulum. All these changes were almost completely reversible for up to 20 minutes but were irreversible by 30 minutes, at which time multiple discontinuities had appeared in cell and organelle membranes. Anoxia alone produced alterations similar to those found after somewhat shorter periods of the combined deprivation, whereas glucose withdrawal produced only minor changes. These electron microscopic results correlate quite well with previously reported electrophysiological measurements.
ELECTRON MICROSCOPIC EXAMINATION OF THE SITES OF NUCLEAR RNA SYNTHESIS DURING AMPHIBIAN EMBRYOGENESIS
Authors: Karasaki Shuichi
Published: May 2004

The site of H3-uridine incorporation and the fate of labeled RNA during early embryo-genesis of the newt Triturus pyrrhogaster were studied with electron microscopic autoradiography. Isolated ectodermal and mesodermal tissues from the embryos were treated in H3-uridine for 3 hours and cultured in cold solution for various periods before fixation with OsO4 and embedding in Epon. At the blastula stage, the only structural component of the nucleus seen in electron micrographs is a mass of chromatin fibrils. At the early gastrula stage, the primary nucleoli originate as small dense fibrous bodies within the chromatin material. These dense fibrous nucleoli enlarge during successive developmental stages by the acquisition of granular components 150 A in diameter, which form a layer around them. Simultaneously larger granules (300 to 500 A) appear in the chromatin, and they fill the interchromatin spaces by the tail bud stage. Autoradiographic examination has demonstrated that nuclear RNA synthesis takes place in both the nucleolus and the chromatin, with the former consistently showing more label per unit area than the latter. When changes in the distribution pattern of radioactivity were studied 3 to 24 hours after immersion in isotope at each developmental stage, the following results were obtained. Labeled RNA is first localized in the fibrous region of the nucleolus and in the peripheral region of chromatin material. After longer culture in non-radioactive medium, labeled materials also appear in the granular region of the nucleolus and in the interchromatin areas. Further incubation gives labeling in cytoplasm.
ON THE DIFFERENTIAL RESPONSE OF SARCOPLASM AND MYOPLASM TO DENERVATION IN FROG MUSCLE
Authors: Muscatello Umberto , Margreth Alfredo , Aloisi Massimo
Published: May 2004

Electron microscopic evidence is presented that the early response to denervation ("simple atrophy") of the semitendinosus m. of the frog is characterized by a greater prominence of the sarcoplasmic reticulum and by the presence, in the interfibrillar spaces, of mitochondria which are more numerous and smaller than in normal muscle. In contrast with the dynamic changes of the sarcoplasmic structural components, the myofibrils showed a progressive decrease in diameter after denervation and throughout the period studied. By carrying out tissue fractionation experiments, the yield of microsome-protein was found significantly greater in the denervated muscles, as compared with the contralateral controls, in this initial stage. Under the conditions attending the overdevelopment of the sarcoplasmic reticulum (SR), denervated semitendinosus m. incorporated valine-C14 into proteins more actively than the control pairs. The denervated muscles also showed an increase in the number of freely scattered and membrane-bound ribosomes and of polyribosomes, suggesting a more active synthesis of the SR membranes. Pronounced atrophy of the myofibrils, disorganization of the SR, and an increased number of ribonucleoprotein particles lying in the enlarged interfibrillar spaces were the main ultrastructural features of "degenerative atrophy" in frog muscle in the late periods after denervation. The probably adaptive character of the early changes occurring on denervation of frog muscle is discussed.
CELL POPULATION KINETICS OF EXCISED ROOTS OF PISUM SATIVUM
Authors: Van't Hof Jack
Published: May 2004

The cell population kinetics of excised, cultured pea roots was studied with the use of tritiated thymidine and colchicine to determine (1) the influence of excision, (2) the influence of sucrose concentration, (3) the average mitotic cycle duration, and (4) the duration of mitosis and the G1, S, and G2 periods of interphase.1 The results indicate that the process of excision causes a drop in the frequency of mitotic figures when performed either at the beginning of the culture period or after 100 hours in culture. This initial decrease in frequency of cell division is independent of sucrose concentration, but the subsequent rise in frequency of division, after 12 hours in culture, is dependent upon sucrose concentration. Two per cent sucrose maintains the shortest mitotic cycle duration. The use of colchicine indicated an average cycle duration of 20 hours, whereas the use of tritiated thymidine produced an average cycle duration of 17 hours.
PRODUCTION AND CHARACTERIZATION OF MULTIPLE-LAYERED POPULATIONS OF ANIMAL CELLS
Authors: Kruse Paul F. , Miedema Ed
Published: May 2004

Dense populations containing 129 x 106 Jensen sarcoma, 134 x 106 DON Chinese hamster, 28.9 x 106 WI-38 human diploid, 61.8 x 106 HEp-2 human carcinoma, and 67.4 x 106 WISH human amnion cells were produced from dilute inocula, 0.85 to 5.33 x 106, in 7 to 8 days in a perfusion system using replicate T-60 flasks. Perfusion rates as high as 560 ml medium/day/T-60 were required to maintain pH (to ca ±0.1 unit) and adequate nutrient supplies. The cell densities encountered are described by the term "monolayer equivalents" (M.E.), defined as number of cells per culture divided by number of cells in a monolayer. The M.E.'s for T-60 cultures containing unusually dense populations of 40 x 106 WI-38 and 250 x 106 DON cells (9-day perfusion) were 5 and 17, respectively, and numbers of cells in illustrations of stained cross-sections of membranes from these cultures were in excellent agreement. Threshold M.E.'s exist below which proliferation is the chief cellular activity and above which one or more cell functions may predominate even though proliferation persists. Cellular nutrition and metabolism may change with changes in M.E., as illustrated in different patterns of glutamic acid, proline, and glycine utilization or production in dense vs. dilute WI-38 cell populations. The results indicated that the role of contact inhibition phenomena in arresting cellular proliferation was diminished in perfusion system environments.
ISOLATION OF SKELETAL MUSCLE NUCLEI
Authors: Edelman Jean C. , Edelman P. Michael , Knigge Karl M. , Schwartz Irving L.
Published: May 2004

A method employing aqueous media for isolation of nuclei from rat skeletal muscle is described. The technique involves (a) mincing and then homogenizing in a 0.32 M sucrose-salt solution with a Potter-Elvehjem type homogenizer using a Delrin (an acetal resin) pestle and a carefully controlled, relatively large pestle-to-glass clearance, (b) filtering through fiberglass and stainless steel screens of predetermined mesh size to remove myofibrils and connective tissue, and (c) centrifuging in a 2.15 M sucrose-salt solution containing 0.7 mM ATP. Electron and phase-contrast microscopic observations show that the nuclei are intact, unencumbered by cytoplasmic tags, and possess well preserved distinct nucleoli, nucleoplasm, and nuclear membranes. Cytoplasmic contamination is minimal and mainly mitochondrial. Chemical assays of the nuclear fraction show that the DNA/protein and RNA/DNA ratios are comparable to those obtained in other tissues. These ratios, as well as the low specific activity obtained for cytochrome c oxidase and the virtual absence of myofibrillar ATPase, indicate a high degree of purity with minimal mitochondrial and myofibrillar contamination. The steps comprising the technique and the reasons for their selection are discussed.
THE FINE STRUCTURE OF THE NUCLEOLUS IN MITOTIC DIVISIONS OF CHINESE HAMSTER CELLS IN VITRO
Authors: Brinkley B. R.
Published: May 2004

The nucleolus of Chinese hamster tissue culture cells (strain Dede) was studied in each stage of mitosis with the electron microscope. Mitotic cells were selectively removed from the cultures with 0.2 per cent trypsin and fixed in either osmium tetroxide or glutaraldehyde followed by osmium tetroxide. The cells were embedded in both prepolymerized methacrylate and Epon 812. Thin sections of interphase nucleoli revealed two consistent components; dense 150-A granules and fine fibrils which measured 50 A or less in diameter. During prophase, distinct zones which were observed in some interphase nucleoli (i.e. nucleolonema and pars amorpha) were lost and the nucleoli were observed to disperse into smaller masses. By late prophase or prometaphase, the nucleoli appeared as loosely wound, predominantly fibrous structures with widely dispersed granules. Such structures persisted throughout mitosis either free in the cytoplasm or associated with the chromosomes. At telophase, those nucleolar bodies associated with the chromosomes became included in the daughter nuclei, resumed their compact granular appearance, and reorganized into an interphase-type structure.
STUDIES ON FINE STRUCTURE AND CYTOCHEMICAL PROPERTIES OF ERYTHROPHORES IN SWORDTAIL, XIPHOPHORUS HELLERI, WITH SPECIAL REFERENCE TO THEIR PIGMENT GRANULES (PTERINOSOMES)
Authors: Matsumoto Jiro
Published: May 2004

The fine structure and the composition of pteridine pigments of erythrophores in adults of the swordtail fish, Xiphophorus helleri, were studied by means of cytochemistry, paper chromatography, ionophoresis, centrifugal fractionation, and electron microscopy. It was found that water-soluble pigments of erythrophores consisted exclusively of pteridine derivatives including large amounts of drosopterin, isodrosopterin, neodrosopterin, and moderate amounts of sepiapterin. While these substances were responsible for red pigmentation, moderate quantities of colorless pteridines, biopterin, Rana-chrome 3, xanthopterin, isoxanthopterin, and others, were also detectable. The ultrastructure of the erythrophore is characterized by numerous pigment granules and a well developed tubular endoplasmic reticulum. The former consist of a three-layered limiting membrane and inner lamellae which appear to be whorl-like due to a concentric arrangement of parallel membranes. All of the mentioned pteridines are primarily contained in this organelle which is designated, accordingly, "pterinosome." The possible functions of erythrophores and pterinosomes are discussed in the light of their structure and pigmentary constitution.
THE FINE STRUCTURE OF THE NUCLEI OF TETRAHYMENA PYRIFORMIS THROUGHOUT THE CELL CYCLE
Authors: Flickinger Charles J.
Published: May 2004

The fine structure of the nuclei of logarithmically growing Tetrahymena pyriformis, strain HSM, was studied at 30-minute intervals throughout the cell cycle. Organisms were selected at similar stages of cytokinesis by means of a braking pipette, incubated, fixed in OsO4, and embedded in agar to facilitate subsequent preparation for electron microscopy. Aggregates of micronuclear chromatin underwent a decrease in density and number with a concomitant increase in size throughout interphase. There were no impressive changes in macronuclear morphology. It was found possible to estimate a cell's progress through interphase by observation of micronuclear morphology, but attempts to correlate changes in fine structure with periods of DNA synthesis were unsuccessful.
PLATELET PHAGOCYTOSIS AND AGGREGATION
Authors: Movat Henry Z. , Weiser William J. , Glynn Michael F. , Mustard James F.
Published: May 2004

The addition of latex particles to native (no anticoagulant) or citrated human platelet-rich plasma (PRP), or to a once-washed platelet suspension causes platelet aggregation. This aggregation is associated with phagocytosis of the latex particles by the platelets and appears to be due to release of adenosine diphosphate (ADP) from the platelets. Adenosine and adenosine monophosphate, which are known to inhibit platelet aggregation induced by ADP, also block that induced by latex. These compounds do not prevent the phagocytosis of latex particles by the platelet. The addition of iodoacetate and 2,4-dinitrophenol in appropriate concentrations to the PRP, prior to the addition of the latex, blocks platelet aggregation and phagocytosis. This is also true for the chelating agent ethylenediaminetetraacetate (EDTA). Platelets left in contact with latex for a sufficient period of time show loss of their granules. Leucocytes phagocytose both latex and platelets that had themselves phagocytosed latex. It is concluded that phagocytosis of latex particles by platelets resembles that by white cells, and that in both processes metabolic changes appear to be involved.
FINE STRUCTURE OF THE MYOEPITHELIUM OF THE ECCRINE SWEAT GLANDS OF MAN
Authors: Ellis Richard A.
Published: May 2004

The secretory coils of glutaraldehyde-osmium tetroxide-fixed and Epon-Araldite-embedded eccrine sweat glands from the palms of young men were studied with the electron microscope. The myoepithelial cells lie on the epithelial side of the basement membrane and abut other epithelial elements directly. The irregularly serrated base of the cell has dense thickenings along the plasma membrane which alternate with zones bearing pits; the smooth apical surface lacks dense thickenings, is studded with pits, and conjoined to secretory cells by occasional desmosomes. Masses of myofilaments, 50 A in diameter, fill most of the cell and are associated with irregular dense zones. In cross-section the arrangement of the myofilaments seems identical with that of the I band of striated muscle, and the dense zone has typical Z band structure. A few microtubules and cytoplasmic cores bearing profiles of the endoplasmic reticulum, filamentous mitochondria, and glycogen granules penetrate the fibrillar masses and run parallel to the oriented myofilaments. In the perinuclear zone, Golgi membranes, rough- and smooth-surfaced elements of the endoplasmic reticulum, mitochondria, glycogen, microtubules, lipid, pigment, and dense granules are variable components in the cytoplasm. The interrelationships of the myoepithelial cells with the secretory cells suggest that the former may act as regulators, controlling the flow of metabolites to the secretory epithelium.
RIBONUCLEIC ACID AND PROTEIN SYNTHESIS IN MITOTIC HELA CELLS
Authors: Johnson Terry C. , Holland John J.
Published: May 2004

HeLa cells arrested in mitosis were obtained in large numbers, with only very slight interphase cell contamination, by employing the agitation method of Terasima and Tolmach, and Robbins and Marcus. Protein synthesis and RNA synthesis were almost completely suppressed in mitotic cells. Active polyribosomes were nearly absent in mitotic cells as compared with interphase cells treated in the same way. Cell-free protein synthesis and RNA polymerase activity were also greatly depressed in extracts of metaphase cells. The deoxyribonucleoprotein (DNP) of condensed chromosomes from mitotic cells was less efficient as a template for Escherichia coli RNA polymerase than was DNP from interphase cells, although isolated DNA from both sources was equally active as a primer. Despite very poor endogenous amino acid incorporation by extracts of metaphase cells, polyuridylate stimulated phenylalanine incorporation by a larger factor in mitotic cell extracts than it did in interphase cell extracts. These results suggest that RNA synthesis is suppressed in mitotic cells because the condensed chromosomes cannot act as a template, and that protein synthesis is depressed at least in part because messenger RNA becomes unavailable to ribosomes. This conclusion was supported by the demonstration that cells arrested in metaphase supported multiplication of normal yields of poliovirus, thereby showing that the mitotic cell is capable of considerable synthesis of RNA and protein.
EFFECTS OF ARGININE DEPRIVATION, ULTRAVIOLET RADIATION, AND X-RADIATION ON CULTURED KB CELLS
Authors: Lane Nancy J. , Novikoff Alex B.
Published: May 2004

Cultured KB cells (derived from a human oral carcinoma) grown in monolayers were injured by one of three agents: starvation by arginine deprivation or treatment with high doses of either ultraviolet radiation or x-radiation. The different agents produced changes in nucleolar structure and varying accumulations of triglyceride and glycogen. All three agents produced an increase in number and size of lysosomes. These were studied in acid phosphatase preparations, viewed by both light and electron microscopy, and, occasionally, in vital dye, esterase, and aryl sulfatase preparations. Ultrastructurally, alterations in lysosomes suggested that "residual bodies" developed in a variety of ways, i.e., from the endoplasmic reticulum, multivesicular bodies, or autophagic vacuoles. Following all three agents the endoplasmic reticulum assumed the form of "rough" or "smooth" whorls, and, after two of the agents, arginine deprivation or ultraviolet radiation, it acquired cytochemically demonstrable acid phosphatase activity. Near connections between the endoplasmic reticulum and lysosomes raise the possibility that in KB cells, at least when injured, the endoplasmic reticulum is involved in the formation of lysosomes and the transport of acid phosphatase to them.
ANOMALOUS CONTRACTION OF INVERTEBRATE STRIATED MUSCLE
Authors: Stephens R. E.
Published: May 2004

The phenomenon of A band shortening or contraction has been investigated in glycerinated myofibrils of Pecten irradians, Homarus americanus, Cambarus virilis, and Limulus polyphemus through the techniques of ultraviolet microbeam inactivation and polarization microscopy. With the former method, it has been shown that these muscles, even though exhibiting the shortening effect, contract in a manner consistent with only the sliding filament model. Intrinsic birefringence studies have indicated no significant changes in mass distribution or orientation within the shortened A bands. Except in the case of Limulus muscle, the shortening effect was seen only in contraction under tension. The magnitude of this anomalous phenomenon was dependent upon glycerination time and has been duplicated in rabbit psoas muscle through brief trypsin treatment. A band shortening could not be observed in glutaraldehyde-fixed muscle or in myofibrils glycerinated for only short periods. It has been concluded that the phenomenon of A band contraction is an artifact induced by the glycerination procedure, possibly through weakening of the sarcomere structure. However, the fact that the A band shortens under tension rather than lengthens poses an interesting paradox.
LYSOSOMES IN THE RAT SCIATIC NERVE FOLLOWING CRUSH
Authors: Holtzman Eric , Novikoff Alex B.
Published: May 2004

Peripheral nerves undergoing degeneration are favorable material for studying the types, origins, and functions of lysosomes. The following lysosomes are described: (a) Autophagic vacuoles in altered Schwann cells. Within these vacuoles the myelin and much of the axoplasm which it encloses in the normal nerve are degraded (Wallerian degeneration). The delimiting membranes of the vacuoles apparently form from myelin lamellae. Considered as possible sources of their acid phosphatase are Golgi vesicles (primary lysosomes), lysosomes of the dense body type, and the endoplasmic reticulum which lies close to the vacuoles. (b) Membranous bodies that accumulate focally in myelinated fibers in a zone extending 2 to 3 mm distal to the crush. These appear to arise from the endoplasmic reticulum in which demonstrable acid phosphatase activity increases markedly within 2 hours after the nerve is crushed. (c) Autophagic vacuoles in the axoplasm of fibers proximal to the crush. The breakdown of organelles within these vacuoles may have significance for the reorganization of the axoplasm preparatory to regeneration. (d) Phagocytic vacuoles of altered Schwann cells. As myelin degeneration begins, some axoplasm is exposed. This is apparently engulfed by the filopodia of the Schwann cells, and degraded within the phagocytic vacuoles thus formed. (e) Multivesicular bodies in the axoplasm of myelinated fibers. These are generally seen near the nodes of Ranvier.
INCREASED NUMBERS OF ANNULATE LAMELLAE IN MYOCARDIUM OF CHICK EMBRYOS INCUBATED AT ABNORMAL TEMPERATURES
Authors: Merkow Leonard , Leighton Joseph
Published: May 2004

Annulate lamellae have been observed in the myocardium of 18-day-old chick embryos maintained at the normal temperature of 100°F and at 90°F during the last week of incubation. An increased number of annulate lamellae was observed in heart muscle of embryos incubated at 90°F. This is probably caused by a persistent production of these organelles, since annulate lamellae are present in greater frequency than in 11-day-old embryos incubated at 100°F. In the hypertrophic hearts of 18-day-old embryos incubated at 90°F, the annulate lamellae were associated with a net increase of protein content and an elevated concentration of myocardial glycogen. It is suggested that the increased number of annulate lamellae is a sequela of reduced environmental temperature during incubation.
ULTRASTRUCTURAL INTERRELATIONSHIPS OF NERVE PROCESSES AND SMOOTH MUSCLE CELLS IN THREE DIMENSIONS
Authors: Thaemert J. C.
Published: May 2004

The muscularis externa of the intestinal wall of frogs was fixed in osmium tetroxide, embedded in Vestopal-W, serially sectioned for electron microscopy, and stained with uranyl acetate. A method to obtain individually mounted and properly positioned serial sections is described. The three-dimensional techniques used during the course of this investigation demonstrate that it is possible to examine carefully relatively large areas of tissue on individual serial sections with the electron microscope and subsequently to construct montages of electron micrographs of pertinent areas from each section. Several carefully rendered interrelationships of nerve processes and smooth muscle cells in three dimensions are exhibited and described. Recent studies of other neuro-effector relationships are discussed in relation to the present status of the nature and organization of the autonomic nervous system in visceral organs.
REDUNDANT MYELIN SHEATHS AND OTHER ULTRASTRUCTURAL FEATURES OF THE TOAD CEREBELLUM
Authors: Rosenbluth Jack
Published: May 2004

Some of the myelin sheaths in the cerebellum of normal adult toads exhibit extensive evaginations of their full thickness. These redundant flaps of myelin are collapsed; i.e., they contain no axon and have no lumen. They extend away from the parent axonal myelin sheaths and tend to enfold other myelinated fibers or granule cell perikarya, producing bizarre configurations of myelin and what appear to be partially or completely myelinated cell bodies. In some instances, only the redundant flap of myelin appears in the plane of section, and its attachment to an axonal myelin sheath in another plane is only inferred. Single lamellae of myelin also tend to invest cerebellar granule cells and other processes, and these too appear to fold on themselves producing two- or four-layered segments. It is suggested that there are two phases of myelinogenesis: an initial "wrapping" phase, followed by a prolonged second phase during which internodes of myelin increase in both length and girth by a process other than wrapping, and that the occurrence of redundant myelin sheaths may reflect overgrowth of myelin during the second phase. Observations on the general organization of the toad cerebellum and on the ultrastructural cytology of its layers are also presented.
MICROTUBULES IN THE MICROSPIKES AND CORTICAL CYTOPLASM OF ISOLATED CELLS
Authors: Taylor A. C.
Published: May 2004

In thin sections through microspikes extending from the surface of isolated cells, a core has been seen which may contain microtubular elements. The differences between these and microtubules seen elsewhere in the cytoplasm are attributed to their rapid growth and exposed location which make them especially vulnerable to injury by preparative treatment. In support of this view it is shown that cytoplasmic microtubules may be altered or even destroyed by exposing the cells to changes in osmotic pressure. Associated with these straight microtubules in the cytoplasm were also found solid microfilaments. The form of these components and their location and alignment in portions of cells which are under tension or in motion suggest that they function in the structural support of the cell and its microspikes and in the transmission of tension in the cytoplasm. A second type of microtubule, smaller in diameter and tortuous in form, was also seen in certain cells and is presumed, from its shape, to have little to do with cytoplasmic support.
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 replicating embryo human cell cultures. From a study of the relations between successive physical measurements on individual cells, it was found that the net syntheses of DNA, nuclear RNA, nuclear protein, and cytoplasmic RNA are closely associated during interphase. Additional measurements of DNA and cytoplasmic RNA on freshly prepared replicating monkey kidney cells gave similar results. In auxiliary experiments with embryo human cells, an inhibition of the onset of DNA synthesis (produced by a dose of X-rays) was found to block the majority of the accumulation of nuclear protein and RNA and about half the accumulation of cytoplasmic RNA. These results are consistent with others previously reported in dividing cell cultures freshly prepared from normal tissues.