bluuebunny/crossref_metadata_2025 huggingface dataset:
IMMUNO-ELECTRON MICROSCOPE ANALYSIS OF THE SURFACE LAYERS OF THE UNFERTILISED SEA URCHIN EGG
Authors: Baxandall Jane , Perlmann P. , Afzelius B. A.
Published: May 2004

The immunological properties of the surface layers of Paracentrotus lividus eggs have been studied further by using ferritin-labelled antibody to localise specific antigenic sites. In order to detect a wider spectrum of antigenic determinants, several antisera against egg and jelly substance have been employed in combination with absorption procedures using lyophilised antigen. This use of absorbed antisera was made feasible by adding ferritin label in a second antiserum layer of ferritin-anti-γ-globulin. Eggs were treated with antibody for short periods to detect antigenic sites without incurring structural changes (shown in previous paper) resulting from long antibody treatment. Unspecific ferritin uptake, found in pinocytotic vesicles and yolk granules, is considered in relation to yolk formation. The jelly layer, found to be immunologically heterogeneous, included one component interacting with antijelly γ-globulin and one with antiegg γ-globulin. The vitelline membrane proved to be rich in egg antigens (heat-stable and heat-labile). The role of this layer in specificity of fertilisation, parthenogenetic activation, and the possibility of being analogous to a basement membrane are discussed. Few antigenic sites were found on the plasma membrane with antiegg γ-globulin. This γ-globulin resulted in some specific labelling of cortical granules and its action is considered in relation to the permeability properties of the egg.
MICROSCOPIC DETERMINATION OF BONE PHOSPHORUS BY QUANTITATIVE AUTORADIOGRAPHY OF NEUTRON-ACTIVATED SECTIONS
Authors: Vincent Jacques , Haumont Stanislas , Roels Joseph
Published: May 2004

Longitudinal sections of human cortical bone were submitted to thermal neutrons. γ-ray spectra were recorded repeatedly during 15 days following irradiation. They showed that Na24 is predominant as early as 3 hours after activation and that all the γ-emitters have decayed on the 15th day. When the γ-rays have disappeared, ß-rays are still produced by the sections. It was proved by the absorption curve in aluminium that all these ß-rays are issued from the P32 induced in the sections by activation of P31. Therefore autoradiograms registered 15 days after activation reveal the distribution of P32 in the sections. γ-ray spectra and ß-ray absorption curves of neutron activated sections of ivory demonstrated a mineral composition similar to that of bone. Autoradiograms of ivory sections activated for various times were used to establish the relation between the optical density of the autoradiograms and the radioactivity in P32. When the bone autoradiograms are compared with the ivory standards of known radioactivity, the optical densities of single osteons (Haversian systems), can be related to their phosphorus contents. Autoradiograms and microradiograms of the same sections were examined side by side. The least calcified osteons, that contain 80 per cent of the calcium of the fully calcified osteons, also contain about 80 per cent of the phosphorus of the fully mineralized osteons. It is concluded that the Ca:P ratio remains constant while mineralization of bone tissue is being completed.
STUDIES ON THE BIOCHEMISTRY AND FINE STRUCTURE OF SILICA SHELL FORMATION IN DIATOMS
Authors: Reimann B. E. F. , Lewin Joyce C. , Volcani B. E.
Published: May 2004

An electron microscope study on the cell wall of the diatom Cylindrotheca fusiformis was carried out using stereoscopic and sectioning techniques. Material prepared by an enzyme treatment or by a mechanical method showed that the wall consists of two major components: a silica shell and organic material. Vapor of hydrofluoric acid was employed to remove the silica and thereby reveal the arrangement of the organic material. An attempt was made to increase the contrast of the organic component by "staining." Uranylacetate not only increased the electron opacity of the organic material but also apparently decreased the electron opacity of the silica shell. In ultrathin sections of complete cells, the structure as revealed by stereoscopy could be confirmed and extended. Every part of the silica shell is tightly enclosed by organic material. In the valve region the silica enclosed in this way is located between other layers of organic material. The whole cell wall is surrounded by a mucilaginous substance which stains with ruthenium red.
AN ELECTRON MICROSCOPE STUDY OF CULTURED RAT SPINAL CORD
Authors: Bunge Richard P. , Bunge Mary Bartlett , Peterson Edith R.
Published: May 2004

Explants prepared from 17- to 18-day fetal rat spinal cord were allowed to mature in culture; such preparations have been shown to differentiate and myelinate in vitro (61) and to be capable of complex bioelectric activity (14–16). At 23, 35, or 76 days, the cultures were fixed (without removal from the coverslip) in buffered OsO4, embedded in Epon, sectioned, and stained for light and electron microscopy. These mature explants generally are composed of several strata of neurons with an overlying zone of neuropil. The remarkable cytological similarity between in vivo and in vitro nervous tissues is established by the following observations. Cells and processes in the central culture mass are generally closely packed together with little intervening space. Neurons exhibit well developed Nissl bodies, elaborate Golgi regions, and subsurface cisternae. Axosomatic and axodendritic synapses, including synaptic junctions between axons and dendritic spines, are present. Typical synaptic vesicles and increased membrane densities are seen at the terminals. Variations in synaptic fine structure (Type 1 and Type 2 synapses of Gray) are visible. Some characteristics of the cultured spinal cord resemble infrequently observed specializations of in vivo central nervous tissue. Neuronal somas may display minute synapse-bearing projections. Occasionally, synaptic vesicles are grouped in a crystal-like array. A variety of glial cells, many apparently at intermediate stages of differentiation, are found throughout the otherwise mature explant. There is ultrastructural evidence of extensive glycogen deposits in some glial processes and scattered glycogen particles in neuronal terminals. This is the first description of the ultrastructure of cultured spinal cord. Where possible, correlation is made between the ultrastructural data and the known physiological properties of these cultures.
SOME OBSERVATIONS ON THE FINE STRUCTURE OF THE LATERAL LINE ORGAN OF THE JAPANESE SEA EEL LYNCOZYMBA NYSTROMI
Authors: Hama Kiyoshi
Published: May 2004

The fine structure of the lateral line organ of the Japanese sea eel Lyncozymba nystromi has been studied with the electron microscope. The sensory epithelium of the lateral line organ consists of a cluster of two major types of cells, the sensory hair cells and the supporting cells. The sensory cell is a slender element with a flat upper surface provided with sensory hairs, Two different types of synapses are distinguished on the basal surface of the receptor cell. The first type is an ending without vesicles and the second type is an ending with many vesicles. These are presumed to correspond to the afferent and the efferent innervations of the lateral line organ. The fine structure of the supporting cells and the morphological relationship between the supporting cells and the receptor cells were observed. The possible functions of the supporting cells are as follows: (a) mechanical and metabolic support for the receptor cell; (b) isolation of the individual receptor cell; (c) mucous secretion and probably cupula formation; (d) glial function for the intraepithelial nerve fibers. Both myelinated and unmyelinated fibers were found in the lateral line nerve. The mode of penetration of these fibers into the epithelium was observed.
CYTOCHEMICAL LOCALIZATION OF ACID PHOSPHATASES IN EUGLENA GRACILIS
Authors: Sommer Joachim R. , Blum Jacob J.
Published: May 2004

The localization of induced and constitutive acid phosphatase activity in Euglena was studied by light and electron microscopy, using two different cytochemical methods. Cells grown in high phosphate medium have constitutive acid phosphatase activity in three regions: in the Golgi complex, around the paramylum bodies, and in the peri-reservoir vesicles. Cells that have formed an induced acid phosphatase by exposure to a phosphate-deficient medium have, in addition to the constitutive activity localized exactly as in the uninduced cell, a strong activity in the pellicle. The induced activity is not uniformly distributed over the pellicle, but is localized at the notch of each pellicle complex, near a group of about four fibrils and near a characteristic vesicle of the endoplasmic reticulum. In the cytostome, where fission begins during division, there is an alternation of large and small pellicle complexes, both of which have induced phosphatase activity. A similar alternation is seen over the entire pellicle of dividing cells.
LOCALIZATION OF THE SUCCINIC DEHYDROGENASE SYSTEM IN ESCHERICHIA COLI USING COMBINED TECHNIQUES OF CYTOCHEMISTRY AND ELECTRON MICROSCOPY
Authors: Sedar Albert W. , Burde Ronald M.
Published: May 2004

The activity of the succinic dehydrogenase system was studied in Escherichia coli utilizing combined techniques of cytochemistry and electron microscopy. Organisms were incubated in a medium containing tetranitro-blue tetrazolium (TNBT) which served as an electron acceptor. Enzymatic activity, as evidenced by the deposition of aggregates of TNBT-formazan, was found associated with the site of the plasma membrane of the bacterium.
THE FINE STRUCTURE OF THE NUCLEOLUS DURING MITOSIS IN THE GRASSHOPPER NEUROBLAST CELL
Authors: Stevens Barbara J.
Published: May 2004

The behavior of the nucleolus during mitosis was studied by electron microscopy in neuroblast cells of the grasshopper embryo, Chortophaga viridifasciata. Living neuroblast cells were observed in the light microscope, and their mitotic stages were identified and recorded. The cells were fixed and embedded; alternate thick and thin sections were made for light and electron microscopy. The interphase nucleolus consists of two fine structural components arranged in separate zones. Concentrations of 150 A granules form a dense peripheral zone, while the central regions are composed of a homogeneous background substance. Observations show that nucleolar dissolution in prophase occurs in two steps with a preliminary loss of the background substance followed by a dispersal of the granules. Nucleolar material reappears at anaphase as small clumps or layers at the chromosome surfaces. These later form into definite bodies, which disappear as the nucleolus grows in telophase. Evidence suggests both a collecting and a synthesizing role for the nucleolus-associated chromatin. The final, mature nucleolar form is produced by a rearrangement of the fine structural components and an increase in their mass.
STRUCTURE OF THE MITOTIC SPINDLE IN L STRAIN FIBROBLASTS
Authors: Krishan Awtar , Buck Robert C.
Published: May 2004

The mitotic spindle of L strain fibroblasts, fixed with glutaraldehyde followed by osmium tetroxide, contains many 150- to 180-A tubules. They appear first in the cytoplasm. They extend from the centrospheres to the kinetochores, and from one centrosphere to the other. Only occasionally can points of continuity between the spindle tubules and the tubules of the centrioles be observed. The chromosomal insertion is by a means of a thin dense plate of the kinetochore. The total number of continuous spindle tubules is between 500 and 600. Occasionally, tubules appear paired. At anaphase, short lengths of individual spindle tubules possess a coating of a substance of high density midway between the poles. These parts of the spindle tubules aggregate to form irregular groups, comprising the stem-body, and, by becoming aligned into a plate, they form the mid-body.
THE INFLUENCE OF PRECURSOR POOL SIZE ON MITOCHONDRIAL COMPOSITION IN NEUROSPORA CRASSA
Authors: Luck David J. L.
Published: May 2004

The chemical composition of mitochondria obtained from exponentially growing Neurospora can be varied by addition of choline or amino acids to the culture medium. The variation affects the phospholipid to protein ratio, and the density of mitochondria as determined by isopycnic centrifugation in sucrose gradients. These variations have been observed in biochemical mutant strains as well as wild type cultures. In a choline-requiring strain, two levels of choline supplementation to the medium have been defined: a low choline concentration just adequate to support maximal logarithmic growth, and a high choline concentration which permits maximal incorporation of radioactive choline into cellular lipids. Mitochondria isolated from cultures growing at the low choline concentration have one-half the phospholipid to protein ratio of those from high choline cultures, and their density is significantly higher. Artificial mixtures of the two types of mitochondria can be resolved into two populations by isopycnic centrifugation. The concentration of cytochromes (measured by mitochondrial difference spectra) and of malate and succinate dehydrogenases (measured by enzyme activity) were the same in both types of mitochondria, on a protein basis. The results suggest that during growth of the mitochondrial mass, the incorporation of phospholipid and protein components can vary independently. Direct kinetic measurements did indeed show that choline, added to a culture growing at low choline concentration, was incorporated into mitochondrial lipids at a rate faster than the incorporation of protein. The mitochondrial phospholipid to protein ratio can also be influenced by the level of leucine supplementation to a leucine-requiring mutant, so that with leucine concentrations above those required for maximal exponential growth, mitochondria of increasing density and decreasing phospholipid to protein ratio are produced. Additions of choline or amino acids to the minimal medium of wild type cultures influence mitochondrial composition in a manner directly comparable to that observed in biochemical mutant strains. The results suggest that mitochondrial composition, in general, is determined by rates of incorporation of the two major components, phospholipid and protein; that these rates can vary independently in response to precursor concentration in the culture medium; and that they normally operate at a precursor (substrate) concentration below saturation level.
FORMATION OF MITOCHONDRIA IN NEUROSPORA CRASSA
Authors: Luck David J. L.
Published: May 2004

The choline concentration used in the growth medium influences the density of mitochondria produced by the chol-1 mutant of Neurospora. Isopycnic centrifugation in sucrose gradients can be used to determine the density of mitochondria, and can resolve into two populations, mitochondria derived from a mixture of cells grown at low (1 µg/ml choline chloride) and high (10 µg/ml choline chloride) choline levels. In an experiment in which cells are shifted from low to high choline growth conditions, mitochondria obtained after varying time periods show a gradual decrease in density tending toward the level typical of high choline mitochondria. Over a 90-minute period of observation, during which time there is an increase of mitochondrial protein mass of ∼ 50 per cent over that initially present, the mitochondria change density as a single population. These results are consistent with the view that mitochondria grow by random accretion of new lecithin into existing mitochondrial structures, and also that the mitochondrial population increases by division.
INTRANUCLEAR AND CYTOPLASMIC ANNULATE LAMELLAE IN TUNICATE OOCYTES
Authors: Kessel R. G.
Published: May 2004

Electron microscope studies were made on various tunicate oocytes at different stages of growth and development. Both the inner and outer lamellae of the perforated nuclear envelope demonstrate considerable blebbing activity. The blebs of the inner lamella detach into the nucleoplasm where they undergo a special type of fusion process resulting in the formation of numerous, usually single, differentiated annulate lamellae of various lengths. The blebbing of the outer layer of the nuclear envelope contributes to the vesicular and granular endoplasmic reticulum characteristically present in the ooplasm and perhaps to the differentiation of cytoplasmic annulate lamellae as well. Cytoplasmic stacks of annulate lamellae frequently have ribosomes associated with them. In addition, granular accumulations are sometimes observed around or between the annuli. The morphological evidence suggests that, at least in many cases, the annuli in the annulate lamellae are patent.
IONIC EFFECTS ON LIGNIFICATION AND PEROXIDASE IN TISSUE CULTURES
Authors: Lipetz Jacques , Garro Anthony J.
Published: May 2004

Crown-gall tumor tissue cultures release peroxidase into the medium in response to the concentration of specific ions in the medium. This release is not due to diffusion from cut surfaces or injured cells. Calcium, magnesium, and ammonium were, in that order, most effective in increasing peroxidase release. The enzyme was demonstrated cytochemically on the cell walls and in the cytoplasm. Cell wall fractions, exhaustively washed in buffer, still contained bound peroxidase. This bound peroxidase could be released by treating the wall fractions with certain divalent cations or ammonium. The order of effectiveness for removing the enzyme from the washed cell walls is: Ca++ ≈ Sr++ > Ba++ > Mg++ > NH4+. These data support the thesis presented that specific ions can control the deposition of lignin on cell walls by affecting the peroxidase levels on these walls.
STUDIES OF THE ULTRASTRUCTURE AND RIBOSOMAL ARRANGEMENTS OF THE PLEUROPNEUMONIA-LIKE ORGANISM A5969
Authors: Maniloff Jack , Morowitz Harold J. , Barrnett Russell J.
Published: May 2004

Thin-section electron microscopy, together with isolation of cellular organelles by differential centrifugation and chemical analysis, has been used to investigate the ultrastructure of the avian pleuropneumonia-like organism A5969. Each cell (approximate diameter 5500 A) was surrounded by a 150 A plasma membrane. In the center of the cell was an unbounded area, granular in appearance and containing the cell's DNA. The periphery of the cell contained granules of several different sizes and densities. The most dense particles (150 A) corresponded to the 78S ribosomes. These particles exhibited two predominant arrangements: (a) sometimes they showed cubic packing; (b) most arrays, however, were consistent with cylindrical arrangements of approximately 50 particles. Bundles of up to 18 arrays were observed. Structured blebs have been found protruding from the surface of log phase cells.
THE MECHANISM OF COLCHICINE INHIBITION OF MITOSIS
Authors: Taylor Edwin W.
Published: May 2004

H3-colchicine of high specific activity (2.5 curies per mM) was prepared in order to study the mechanism of colchicine inhibition of mitosis in cultures of human cells, strain K.B. No direct effects on the duration of the cell cycle or macromolecular synthesis were demonstrable at a concentration of colchicine which completely inhibited mitosis. The radioactive compound was bound to the cells at a rate proportional to colchicine concentration. The binding appeared to be reversible since the radioactivity of the cells reached a maximum value for a given concentration and was slowly lost after resuspension of the cells in fresh medium. A suitable exposure to colchicine produced accumulation of metaphase-blocked mitoses after the colchicine was removed from the medium. An exposure of 6 to 8 hours at 10-7 M was sufficient to block essentially all the cells in metaphase, thus indicating that colchicine is bound to the majority of interphase cells. The data are in quantitative agreement with a mechanism involving reversible binding of colchicine to a set of cellular sites. Based on the correlation between the time of first appearance of blocked mitoses and the radioactivity per cell, it is suggested that if a critical fraction (3 to 5 per cent) of the sites are complexed, the cell is unable to form a functional mitotic spindle.
AN UNUSUAL CONFIGURATION OF THE GOLGI COMPLEX IN PIGMENT-PRODUCING "TEST" CELLS OF THE OVARY OF THE TUNICATE, STYELA
Authors: Kessel R. G. , Beams H. W.
Published: May 2004

The test cell in the ovary of the tunicate Styela contains a large and robust Golgi complex which demonstrates a regional structural differentiation. In one of the regions, branching of the lamellae occurs resulting in a honeycomb or lattice-type arrangement. Small, dense granules or homogeneous material of moderate density may be present within certain of the Golgi cisternae. The close association, or continuity in some cases, between elements of the Golgi complex and immature forms of pigment suggests that the Golgi complex in these cells is involved in pigment formation. These relationships are shown and discussed in terms of possible functional significance.
BIOSYNTHESIS OF COLLAGEN AND NON-COLLAGEN PROTEIN DURING DEVELOPMENT OF THE CHICK CORNEA
Authors: Coleman John R. , Herrmann Heinz , Bess Barbara
Published: May 2004

The relationship between the rates of increase of corneal protein fractions and incorporation of labeled precursors has been examined during embryonic and early posthatching development of the chick corneal stroma. Non-collagen protein increased gradually from 9 through 20 days of incubation. Collagen accumulated approximately logarithmically through the 19th day, the most rapid rate occurring between 13 and 20 days of incubation. The rates at which labeled amino acids are incorporated into collagen in vivo and in vitro undergo marked changes during the last week of embryonic development, corresponding closely to the rate of collagen accumulation in vivo; whereas incorporation into non-collagen protein changes much less markedly. Changes in the rate of incorporation of precursors into collagen are not due to changes in the rate of conversion of collagen from the soluble to insoluble form, or to changes in the endogenous amino acid pool size. Chick embryo corneal stroma collagen turns over very slowly, if at all. Non-collagen protein turns over more rapidly. An increase in cell number, as indicated by DNA content, does not account for the increased rate of collagen synthesis between the 9th and 16th day of incubation. It is concluded that the observed changes in collagen synthesis reflect changing activities in the individual cornea fibroblasts. These activities are comparable in the intact tissue in vivo and in isolated corneas in vitro.
THE FINE STRUCTURE OF DIFFERENTIATING SIEVE TUBE ELEMENTS
Authors: Bouck G. Benjamin , Cronshaw James
Published: May 2004

The developmental sequences leading to the formation of mature sieve tube elements were studied in pea plants by electron microscopy. From this study it has been found that the peripheral layer of cytoplasm in the mature element is composed of flattened cisternae which are apparently derived from a tubular form of endoplasmic reticulum (ER) and possibly the nuclear envelope. These flattened cisternae, designated in this report as sieve tube reticula, are attached perpendicularly to the wall surface and are oriented in a predominantly longitudinal direction. Cisternae of the sieve tube reticulum are frequently associated with the slime in mature elements, and tubular ER may be associated with slimelike material in the developing sieve tube element. During differentiation mitochondria become reduced in size and chloroplasts either fail to develop stroma and grana lamellae or lose them early in development. In agreement with other workers it is found that the sieve plate pores appear to be plugged with a finely fibrous material, presumably "slime." Nacreous wall formation is well established before reorganization of cytoplasmic components. Microtubules are prevalent during these early stages, but are lost as the element matures.
A STRUCTURAL STUDY OF RAT LIVER RIBOSOMES
Authors: Dass C. M. S. , Bayley S. T.
Published: May 2004

Polyribosomes, ribosomes, and ribosomal subunits were prepared from rat liver using sodium deoxycholate and a variety of ionic media. They were examined in the electron microscope, mainly as negatively or positively stained preparations, and in the analytical ultracentrifuge. The polyribosomes consist of up to twelve or more ribosomes linked by a fine strand, 10 to 15 A in diameter, probably of RNA. The ribosomes are approximately spherical with diameters of 250 to 300 A, and are estimated to be about 50 per cent porous. Possibly because of their high protein content, whole ribosomes show no cleavage furrows. Ribosomes were dissociated in phosphate buffer and the subunits separated on sucrose density gradients containing 10 per cent formalin. Three classes of subunit were obtained with sedimentation coefficients of 71S, 50S, and 31S respectively. The smallest, 31S subunit is about 250 A long by 100 A wide. The largest subunits appear to be clusters of smaller particles. It is estimated from their linear dimensions in electron micrographs that the whole 83S ribosome could contain up to six 31S subunits, or their equivalent.
AUTORADIOGRAPHIC STUDY OF SUGAR AND AMINO ACID ABSORPTION BY EVERTED SACS OF HAMSTER INTESTINE
Authors: Kinter William B. , Wilson T. Hastings
Published: May 2004

Autoradiographs were prepared from frozen sections of everted sacs of hamster jejunum which had been incubated in vitro with C14- or H3-labeled sugars and amino acids. When such tissue was incubated in 1 mM solutions of L-valine or L-methionine, columnar absorptive cells at tips of villi accumulated these amino acids to concentrations ranging from 5 to 50 millimoles per liter of cells. Quantitative data were obtained by microdensitometry of C14 autoradiographs. Similar, though less striking, results were obtained with the sugars: galactose, 3-0-methylglucose, α-methylglucoside, and 6-deoxyglucose. In all cases the marked "step-up" in concentration occurred near the brush border of the cell, and a "step-down" in concentration occurred at the basal pole of the cell. Known inhibitors of intestinal absorption, e.g., phlorizin in the case of sugars, blocked the concentrative step at the luminal border of the absorptive cell. It is inferred from these data that active transport systems for sugars and amino acids reside in the brush border region of the cell. Additional evidence suggests that the basal membrane of the cell may be the site of both a diffusion barrier and a weak transport system directed into the cell.
THE ULTRASTRUCTURE OF COTYLEDONARY TISSUE FROM GOSSYPIUM HIRSUTUM L. SEEDS
Authors: Yatsu Lawrence Y.
Published: May 2004

Quiescent cottonseeds stored in a dry, anaerobic situation for over a year have been shown to contain cells whose contents are ultrastructurally similar to those of normal, fully hydrated plant cells. Plastids, mitochondria, and nuclei of the cells of cotyledon tissue in dry seeds possess normal-looking double membranes even under conditions of extreme desiccation. Previous reports have indicated on the basis of light microscopic work, that the cells of certain dry seeds do not possess nuclear membranes or mitochondria. The cells of the dry cottonseed do contain these structures, however. Dictyosomes have not been observed in the spongy parenchymal cells of the cotyledon tissue; it is suggested that they are concerned with translocation and/or utilization of material. The storage materials in the cells, protein and oil, are contained in vacuolar areas enclosed by a single membrane.
SOME OBSERVATIONS ON THE PERMEABILITY OF MITOCHONDRIA TO SUCROSE
Authors: Tedeschi Henry
Published: May 2004

In experiments carried out with sucrose-isolated rat liver mitochondria, C14-sucrose seems to penetrate most of the mitochondrial space rapidly, whereas it seems to penetrate the remainder relatively slowly. However, taking into account the wide size distribution found in isolated preparations, these rates have been found consistent with the kinetics expected from the assumption of a single compartment per mitochondrion. These data cannot be readily interpreted on the basis of two mitochondrial spaces, one highly permeable, and another relatively impermeable to sucrose.
NUCLEIC ACIDS OF CHLOROPLASTS AND MITOCHONDRIA IN SWISS CHARD
Authors: Kislev Naomi , Swift Hewson , Bogorad Lawrence
Published: May 2004

Nucleic acids in young leaves of Swiss chard have been studied by light and electron microscope techniques. Leaf DNA has also been characterized by density gradient centrifugation and shown to contain a minor band of higher guanine plus cytosine (GC) content, presumably attributable to chloroplasts. The chloroplasts were faintly stained by the Feulgen reaction; radioautography demonstrated the incorporation of tritiated thymidine in the cytoplasm and in some nuclei. The Feulgen stainability and most of the radioactivity were removable with DNase. Under the electron microscope, both mitochondria and chloroplasts were found to contain filamentous and particulate components within the matrix areas. The morphology of the filamentous component was dependent on the fixation, being partially clumped after OSO4 or formalin, but finely filamentous after Kellenberger fixation. The filaments were stainable with uranyl acetate, and were extractable with DNase following formalin fixation under conditions in which nuclear DNA was also extracted. The particulate component, after formalin fixation and uranyl staining, was prominent in chloroplasts from young leaves, but was only sparsely distributed in mitochondria. The stainability was removed with ribonuclease. We have concluded that chloroplasts and mitochondria of Swiss chard possess a filamentous component that contains DNA, probably responsible for both cytoplasmic thymidine incorporation and the minor band in CsCl centrifugation. A particulate ribosome-like component that contains RNA is also present.
ELECTRON MICROSCOPE AND X-RAY DIFFRACTION STUDIES ON A HOMOLOGOUS SERIES OF SATURATED PHOSPHATIDYLCHOLINES
Authors: Elbers P. F. , Ververgaert P. H. J. T.
Published: May 2004

Three homologous saturated phosphatidylcholines were studied by electron microscopy after tricomplex fixation. The results are compared with those obtained by x-ray diffraction analysis of the same and some other homologous compounds, in the dry crystalline state and after tricomplex fixation. By electron microscopy alternating dark and light bands are observed which are likely to correspond to phosphatide double layers. X-Ray diffraction reveals the presence of lamellar structures of regular spacing. The layer spacings obtained by both methods are in good agreement. From the electron micrographs the width of the polar parts of the double layers can be derived directly. The width of the carboxylglycerylphosphorylcholine moiety of the layers is found by extrapolating the x-ray diffraction data to zero chain length of the fatty acids. When from this width the contribution of the carboxylglyceryl part of the molecules is subtracted, again we find good agreement with the electron microscope measurements. An attempt has been made to account for the different layer spacings measured in terms of orientation of the molecules within the double layers.
STUDIES ON THE INTRACELLULAR DIGESTIVE PROCESS IN MAMMALIAN TISSUE CULTURE CELLS
Authors: Gordon Gerald B. , Miller Leonard R. , Bensch Klaus G.
Published: May 2004

DNA-protein coacervates containing colloidal gold particles were readily phagocytized by strain L fibroblasts. During the subsequent digestion process, the gold particles served as markers which permitted the demonstration of the evolution of digestive vacuoles to multivesicular bodies and finally to dense bodies. Acid phosphatase and esterolytic activity was present in these structures. The hydrolytic enzymes were apparently brought to the phagocytotic vacuoles in small vesicles originating in the Golgi region. These vesicles entered the vacuoles prior to the digestion of the coacervates and the appearance of positive cytochemical reactions. The cytoplasmic dense bodies frequently merged with the phagocytotic vacuoles. This was demonstrated by prelabeling the dense bodies with colloidal iron prior to phagocytosis of the coacervates. In addition, evidence is presented for the interrelationship of the phagocytotic and autophagic pathways.
MORPHOLOGICAL AND BIOCHEMICAL CORRELATES OF CEREBRAL MICROSOMES
Authors: de Balbian Verster F. , Sellinger O. Z. , Harkin J. C.
Published: May 2004

Microsomal fractions, both homogeneous in appearance and functionally operative, were isolated from a homogenate of rat cerebral cortex by fractionation in water. The preparations thus obtained contain the membranous elements of the endoplasmic reticulum, synaptic vesicles, and ribosomes. Esterase, ATPase, and glutamine synthetase were found to be present and fully functional in the microsomal fractions isolated in water. The contamination of the water-isolated microsomal fractions by mitochondria and lysosomes was found to be considerably lower than in microsomal pellets isolated in sucrose. The contamination by nerve ending particles, as judged by electron microscopy and by the levels of soluble lactic dehydrogenase entrapped in the cytoplasm of the particles, was also low. Most of the contamination by mitochondria and nerve ending particles could be removed by treatment of the microsomal pellet with 150 mM NaCl. Resistant to elution by this treatment is the lysosomal contamination as well as microsomal esterase and ATPase. Glutamine synthetase, on the other hand, was almost totally solubilized. Microsomal preparations isolated in water are also shown to contain amounts of protein, RNA, phospholipid, and ganglioside comparable to those found in microsomal preparations isolated in sucrose.
DEVELOPMENTAL CHANGES IN THE STRUCTURE OF THE SYNAPSE ON THE MYELINATED CELL BODIES OF THE CHICKEN CILIARY GANGLION
Authors: Hess Arthur
Published: May 2004

Electron micrographs, stained Epon-embedded sections, and silver stains of the ciliary ganglion of chickens 19 days prehatched, 4 days, 5 weeks, 6 months, and 1 to 2 years of age were studied. The majority of ganglion cells are large neurons; smaller cells are restricted to a dorsal, distal part of the ganglion. The following description applies to the large neurons. Three to twenty lamellae of loose, semicompact, and compact myelin ensheathe virtually every neuron. All these types of myelin form the sheath of a single neuron. The lamellae greatly increase in number and in compactness during the period between the 19-day embryo and the 4-day-old chick. During the period between the 4-day chick and the adult chicken, the myelin becomes only slightly thicker and denser. The calyx is a large synaptic terminal encircling virtually every neuron in the ganglion up to 5 weeks of age. At 6 months of age, the calyx appears to break up; only about half the number of neurons in the ganglion have this large terminal, while the remaining neurons have numerous relatively small, boutonlike synapses. This rather remarkable transformation in the structure of the calyx is virtually complete in the 1- to 2-year-old chickens. In these older chickens all the cells have boutons, and calyces are no longer present. The entering preterminal fiber, the calyx, the neuron, and the axon hillock can all have myelin lamellae on them. It is possible that this entire complex is effectively insulated by the myelin sheath. No synaptic discs or fusion of the membranes of the preterminal fiber and the postganglionic neuron are seen. The chick ciliary ganglion cells are the only myelinated neurons so far described which receive synapses. The neurons in the small-cell part of the ganglion do not have calyces and are not ensheathed by myelin lamellae at any age.
THE LOCALIZATION OF MYOFIBRILLAR ATPASE ACTIVITY IN THE FLIGHT MUSCLES OF THE BLOWFLY, CALLIPHORA ERYTHROCEPHALA
Authors: Tice Lois W. , Smith David S.
Published: May 2004

The distribution of ATPase activity in the asynchronous flight muscles of Calliphora erythrocephala (Diptera) was studied at a fine structural level, using preparations of teased fibers, both unfixed and after brief fixation in hydroxyadipaldehyde, incubated in a medium for the histochemical demonstration of myosin or actomyosin ATPase. In relaxed fibrils, activity was found confined to the A bands and was absent from the H zones as well as from the Z and I band regions. At high magnification, deposits of final product, lead phosphate, appeared primarily related to the thick filaments, or to short lateral extensions from them. Evidence was gathered which indicated that this enzyme activity was that of a triphosphatase which did not act on dinucleoside or non-nucleoside substrates.
QUANTITATIVE TRITIUM AUTORADIOGRAPHY OF MAMMALIAN CHROMOSOMES
Authors: Stubblefield Elton
Published: May 2004

A technique has been developed that allows repeated autoradiographs to be made of the isotope distribution in the chromosomes of a single cell. A series of 10 separate autoradiographs were made of a Chinese hamster diploid male metaphase cell which had been labeled with tritiated thymidine during the first 15 minutes of its DNA synthesis period in the previous interphase. Each autoradiograph had low grain densities above the chromosomes so that quantitation was feasible. The separate autoradiographs were photographically combined into a single composite in which grain images were converted to lines oriented at right angles to the chromosome axis. The line densities were then measured with a recording microdensitometer to yield graphs reflecting the isotope distribution along each chromosome. The area under each graph was directly proportional to the total number of grains counted above the corresponding chromosome in the 10 separate autoradiographs. The distribution of isotope along the chromosomes was different for each chromosome, and in some cases homologs also differed in their early labeling patterns.
AN ELECTRON MICROSCOPE STUDY OF LYMPHATIC TISSUE IN RUNT DISEASE
Authors: Weiss Leon , Aisenberg Alan C.
Published: May 2004

The thymus, spleen, and lymph nodes were studied in runt disease induced by a graft of intravenously injected homologous splenic cells into newborn rats and mice. Adult Long-Evans cells (70 x 106) were injected into Sprague-Dawley rats. Adult DBA cells (7 x 106) were injected into C57BL/6 mice. Runted rats were sacrificed at 14 to 28 days of age; mice at 10 to 20 days. The thymic cortex is depleted of small lymphocytes. Those remaining are severely damaged and phagocytized. Evidence of damage includes swelling of mitochondria, myelin figure formation, margination of chromatin, and sharp angulation in nuclear contour. Large numbers of macrophages are present. Epithelial-reticular cells which envelop small cortical blood vessels are often retracted, with the result that the most peripheral layer in the thymic-blood barrier suffers abnormally large gaps. Lymphocytes of the periarterial lymphatic sheaths of spleen and of the cortex of lymph nodes are reduced in number and damaged. Vast numbers of plasma cells and many lymphocytes are evident throughout lymph nodes, in the periarterial lymphatic sheaths, and in the marginal zone and red pulp of the spleen. Plasma cells are of different sizes, the larger having dilated sacs of endoplasmic reticulum. Lymphocytes are small to medium in size. They contain, in varying quantity, ribosomes and smooth membrane-bounded cytoplasmic vesicles approximately 350 to 500 A in diameter. Most plasma cells and lymphocytes are damaged and many of these are phagocytized. Many lymphocytes in lymph nodes, however, show no evidence of damage. Reticular cells and other fixed cells of the connective tissues seldom appear affected. Thus, the major cell types reacting in runt disease are lymphocytes, plasma cells, and histiocytes or macrophages. It appears, therefore, that both the delayed and immediate types of sensitivity play a part in this disease.
THE EFFECT OF CALCIUM WITHDRAWAL ON THE STRUCTURE AND FUNCTION OF THE TOAD BLADDER
Authors: Hays Richard M. , Singer Bayla , Malamed Sasha
Published: May 2004

Previous reports have indicated that calcium is necessary to support active sodium transport by the toad bladder, and may be required as well in the action of vasopressin on both toad bladder and frog skin. The structure and function of the toad bladder has been studied in the absence of calcium, and a reinterpretation of the previous findings now appears possible. When calcium is withdrawn from the bathing medium, epithelial cells detach from one another and eventually from their supporting tissue. The short-circuit current (the conventional means of determining active sodium transport) falls to zero, and vasopressin fails to exert its usual effect on short-circuit current and water permeability. However, employing an indirect method for the estimation of sodium transport (oxygen consumption), it is possible to show that vasopressin exerts its usual effect on Qoo2 when sodium is present in the bathing medium. Hence, it appears that the epithelial cells maintain active sodium transport when calcium is rigorously excluded from the bathing medium, and continue to respond to vasopressin. The failure of conventional techniques to show this can be attributed to the structural alterations in the epithelial layer in the absence of calcium. These findings may provide a model for the physiologic action of calcium in epithelia such as the renal tubule.
CORRELATED MORPHOLOGICAL AND PHYSIOLOGICAL STUDIES ON ISOLATED SINGLE MUSCLE FIBERS
Authors: Brandt Philip W. , Reuben John P. , Girardier Lucien , Grundfest Harry
Published: May 2004

Single fibers isolated from walking leg muscles of crayfish have 8- to 10-µ sarcomeres which are divided into A, I, and Z bands. The H zone is poorly defined and no M band is distinguishable. Changes in the width of the I band, accompanied by change in the overlap between thick and thin myofilaments, occur when the length of the sarcomere is changed by stretching or by shortening the fiber. The thick myofilaments (ca. 200 A in diameter) are confined to the A band. The thin myofilaments (ca. 50 A in diameter) are difficult to resolve except in swollen fibers, when they clearly lie between the thick filaments and run to the Z disc. The sarcolemma invaginates at 50 to 200 sites in each sarcomere. The sarcolemmal invaginations (SI) form tubes about 0.2 µ in diameter which run radially into the fiber and have longitudinal side branches. Tubules about 150 A in diameter arise from the SI and from the sarcolemma. The invaginations and tubules are all derived from and are continuous with the plasma membrane, forming the transverse tubular system (TTS), which is analogous with the T system of vertebrate muscle. In the A band region each myofibril is enveloped by a fenestrated membranous covering of sarcoplasmic reticulum (SR). Sacculations of the SR extend over the A-I junctions of the myofibrils, where they make specialized contacts (diads) with the TTS. At the diads the opposing membranes of the TTS and SR are spaced 150 A apart, with a 35-A plate centrally located in the gap. It appears likely that the anion-permselective membrane of the TTS which was described previously is located at the diads, and that this property of the diadic structures therefore may function in excitation-contraction coupling.
CYTOLOGICAL AND CYTOCHEMICAL STUDIES OF GREEN MONKEY KIDNEY CELLS INFECTED IN VITRO WITH SIMIAN VIRUS 40
Authors: Love Robert , Fernandes Mario V.
Published: May 2004

Cytological and cytochemical studies of green monkey kidney cells infected with SV40 virus indicated that the type of lesion produced was influenced by the multiplicity of infection and that the lesions appeared later and progressed more slowly when the inoculum was diluted. The earliest change consisted of enlargement of ribonucleoprotein-containing spherules in the nucleolus (nucleolini). This was followed by rarefaction, with or without condensation, of the chromatin and the appearance of one or more homogeneous masses of inclusion material containing DNA, RNA, and non-histone protein which eventually filled the nucleus. In some instances the chromatin appeared to be directly transformed into inclusion material. In the later stages of infection, the ribonucleoprotein of the nucleolini was no longer stainable and material resembling the nucleoprotein of the intranuclear inclusions was found in the nucleolar vacuoles and in the cytoplasm. The nucleic acids in the inclusions were stained by toluidine blue, toluidine blue-molybdate, the Feulgen stain, and by methyl green. The stainable material was extractable by nuclease digestion or by hot trichloroacetic acid. Green or yellowish green staining by acridine orange was apparently due to binding of dye by protein and not by nucleic acids since the staining reaction was not reduced by extraction of nucleic acids by hot trichloroacetic acid. Extraction with pepsin in combination with ribonuclease or deoxyribonuclease removed practically all the inclusions from the cells; consequently they could not be stained with acridine orange. The cytochemical studies suggest that the use of pepsin together with nuclease is not a meaningful technique.
DIFFERENTIATION AND PROLIFERATION OF EMBRYONIC MAST CELLS OF THE RAT
Authors: Combs J. W. , Lagunoff D. , Benditt E. P.
Published: May 2004

Histochemical reactions and radioautography were used to investigate the sequence of mast cell development in rat embryos. Mast cells arise ubiquitously in and are confined to the loose connective tissue in the embryo. The alcian blue-safranin reaction distinguishes between weakly sulfated and strongly sulfated mucopolysaccharides by a shift from alcian blue to safranin staining. Based on this reaction and morphologic characteristics, four stages were identified. Stage I mast cells are lymphocyte-like cells with cytoplasmic granules which invariably stain blue with the alcian blue-safranin reaction. In Stage II cells the majority of granules are alcian blue-positive, but some safranin-positive granules have appeared. Stage III mast cells are distinguished by a majority of safranin-positive cytoplasmic granules; some alcian blue-positive granules still remain. Stage IV cells contain only safranin-positive granules. Thymidine-H3 uptake and identification of mitotic figures indicates that mast cells in Stages I and II comprise a mitotic pool while those in Stages III and IV are mitotically inactive. The pattern of S35O4 incorporation and the sequence of appearance of histochemically identifiable mast cell constituents corroborates division of the proliferation and differentiation of embryonic mast cells into the four stages described above. The process of formation of mast cell granules is interpreted as reflecting the synthesis and accumulation of a heparin precursor in alcian blue positive granules followed by the synthesis and accumulation of highly N-sulfated heparin along with mast cell chymase and finally histamine in safranin-positive granules.