bluuebunny/crossref_metadata_2025 huggingface dataset:
CARDIOLIPIN CONTENT OF WILD TYPE AND MUTANT YEASTS IN RELATION TO MITOCHONDRIAL FUNCTION AND DEVELOPMENT
Authors: Jakovcic S. , Getz G. S. , Rabinowitz M. , Jakob H. , Swift H.
Published: May 2004

The phospholipid composition of various strains of the yeast, Saccharomyces cerevisiae, and several of their derived mitochondrial mutants grown under conditions designed to induce variations in the complement of mitochondrial membranes has been examined. Wild type and petite (cytoplasmic respiratory deficient) yeasts were fractionated into various subcellular fractions, which were monitored by electron microscopy and analyzed for cytochrome oxidase (in wild type) and phospholipid composition. 90% or more of the phospholipid, cardiolipin was found in the mitochondrial membranes of wild type and petite yeast. Cardiolipin content differed markedly under various growth conditions. Stationary yeast grown in glucose had better developed mitochondria and more cardiolipin than repressed log phase yeast. Aerobic yeast contained more cardiolipin than anaerobic yeast. Respiration-deficient cytoplasmic mitochondrial mutants, both suppressive and neutral, contained less cardiolipin than corresponding wild types. A chromosomal mutant lacking respiratory function had normal cardiolipin content. Log phase cells grown in galactose and lactate, which do not readily repress the development of mitochondrial membranes, contained as much cardiolipin as stationary phase cells grown in glucose. Cytoplasmic mitochondrial mutants respond to changes in the glucose concentration of the growth medium by variations in their cardiolipin content in the same way as wild type yeast does under similar growth conditions. It is concluded that cardiolipin content of yeast is correlated with, and is a good indicator of, the state of development of mitochondrial membrane.
STRUCTURAL DIFFERENTIATION OF STACKED AND UNSTACKED CHLOROPLAST MEMBRANES
Authors: Goodenough Ursula W. , Staehelin L. Andrew
Published: May 2004

Wild-type chloroplast membranes from Chlamydomonas reinhardi exhibit four faces in freeze-etchreplicas: the complementary Bs and Cs faces are found where the membranes are stacked together; the complementary Bu and Cu faces are found in unstacked membranes. The Bs face carries a dense population of regularly spaced particles containing the large, 160 ± 10 A particles that appear to be unique to chloroplast membranes. Under certain growth conditions, membrane stacking does not occur in the ac-5 strain. When isolated, these membranes remain unstacked, exhibit only Bu and Cu faces, and retain the ability to carry out normal photosynthesis. Membrane stacking is also absent in the ac-31 strain, and, when isolated in a low-salt medium, these membranes remain unstacked and exhibit only Bu and Cu faces. When isolated in a high-salt medium, however, they stack normally, and Bs and Cs faces are produced by this in vitro stacking process. We conclude that certain particle distributions in the chloroplast membrane are created as a consequence of the stacking process, and that the ability of membranes to stack can be modified both by gene mutation and by the ionic environment in which the membranes are found.
COMPOSITION OF CELLULAR MEMBRANES IN THE PANCREAS OF THE GUINEA PIG
Authors: Meldolesi J. , Jamieson J. D. , Palade G. E.
Published: May 2004

The subcellular components involved in the synthesis, transport, and discharge of secretory proteins in the guinea pig pancreatic exocrine cell have been isolated from gland homogenates by differential and gradient centrifugation. They include rough and smooth microsomes derived respectively from the rough endoplasmic reticulum and Golgi periphery, a zymogen granule fraction consisting mainly of mature zymogen granules and a smaller population of condensing vacuoles, and a plasmalemmal fraction. Membrane subfractions were obtained from the particulate components by treatment with mild (pH 7.8) alkaline buffers which extract the majority (>95%) of the content of secretory proteins, allowing the membranes to be recovered from the extracting fluid by centrifugation. The purity of the fractions was assessed by electron microscopy and by assaying marker enzymes for cross-contaminants. The rough and smooth microsomes were essentially free of mitochondrial contamination; the smooth microsomes contained <15% rough contaminants. The zymogen granule fraction and its derived membranes were free of rough microsomes and contained <3% contaminant mitochondria. The plasmalemmal fraction was heterogeneous as to origin (deriving from basal, lateral, and apical poles of the cell) and contained varying amounts of adherent fibrillar material arising from the basement membrane and terminal web. The lipid and enzymatic composition of the membrane fractions are described in the following reports.
COMPOSITION OF CELLULAR MEMBRANES IN THE PANCREAS OF THE GUINEA PIG
Authors: Meldolesi J. , Jamieson J. D. , Palade G. E.
Published: May 2004

A comparative study of the enzymic activities of membrane fractions derived from guinea pig pancreatic homogenates has yielded the following results: Rough microsomal membranes (derived from the rough ER) have the reductase activities of the two microsomal electron transport systems but lack enzyme activities of Golgi-type (TPPase) and plasmalemmal-type (5'-nucleotidase, ß-leucyl naphthylamidase, Mg-ATPase). Smooth microsomal membranes (derived primarily from the Golgi complex), zymogen granule membranes, and plasmalemmal fractions possess overlapping enzyme activities of plasmalemmal type, in different relative concentrations for each fraction. In addition, the smooth microsomal membranes exhibit TPPase and ADPase activity and share with rough microsomes the reductase activities of the two electron transport chains. Taken together with recent data on the lipid composition of the same fractions (2), these results indicate that the membranes of the pancreatic exocrine cell are chemically and functionally distinct, and hence do not mix with one another during the transport of secretory products.
MORPHOLOGICAL CORRELATES OF INCREASED COUPLING RESISTANCE AT AN ELECTROTONIC SYNAPSE
Authors: Pappas George D. , Asada Y. , Bennett M. V. L.
Published: May 2004

Close appositions between axonal membranes are present in the septum between adjacent axonal segments of the septate or lateral giant axons of the crayfish Procambarus. In sections the closely apposed membranes appear separated by a space or gap. The use of lanthanum indicates that there may be structures connecting the apposed membranes. The apparent gap is actually a network of channels continuous with the extracellular space. Adjacent axonal segments are electrotonically coupled at the septa. The coupling resistance is increased by mechanical injury of an axon, immersion in low Cl- solutions, and immersion in low Ca++ solutions, followed by a return to normal physiological solution. Septa at which coupling resistance had been measured were examined in the electron microscope. The induced increases in coupling resistance are associated with separation of the junctional membranes (with the exception of the moderate increases during immersion in low Ca++ solutions). Schwann cell processes are present between the separated axonal membranes. When nerve cords in low Cl- solutions are returned to normal physiological solution, coupling, i.e., electrotonic synapses. A model of an electrotonic synapse is proposed in which tween axonal membranes are again found. The association between the morphological and physiological findings provides further evidence that the junctions are the sites of electrotonic coupling, i.e., electrotonic, synapses. A model of an electrotonic synapse is proposed in which intercytoplasmic channels not open to the extracellular space are interlaced with a hexagonal network of extracellular channels between the apposed junctional membranes.
STUDIES OF THE TRIAD
Authors: Franzini-Armstrong Clara
Published: May 2004

Ferritin and Imferon molecules were introduced as tracers inside "skinned" muscle fibers to test which part of the triadic junction gap is freely exchangeable with the sarcoplasm. At least 50% of the T-system surface is freely accessible from the sarcoplasm. Of the remainder, 30% of the total T-system surface is covered by the junctional feet, and 20% in the center of the junction may or may not be accessible. The possibility is discussed that the triadic junction may not function as an electrical coupling.
FINE STRUCTURAL AND RADIOAUTOGRAPHIC OBSERVATIONS ON DENSE PERINUCLEAR CYTOPLASMIC MATERIAL IN TADPOLE OOCYTES
Authors: Eddy E. M. , Ito Susumu
Published: May 2004

Dense fibrous material is first seen in association with mitochondria in tadpole oogonia but is most prominent in oocytes during the extended first meiotic prophase when it aggregates into dense bodies in the perinuclear cytoplasm. The origin of this material has been attributed to 350-A nuclear granules which form cytoplasmic streamers of fibrous material upon passage through nuclear pores. This has commonly been interpreted as the transfer of ribonucleoprotein to the cytoplasm for storage. However, cytochemical reactions for nucleic acids have indicated an absence of detectable RNA in this dense material, and the results of radioautographic studies with labeled uridine, thymidine, or actinomycin D argue against the presence of nucleic acids. When sites of incorporation of tritiated amino acids were radioautographically localized, an appreciable number of silver grains were present over the dense bodies. Uptake of certain amino acids occurs fairly promptly but the degree of labeling levels off after about 6 hr, suggesting a rapid turnover of the material in the dense bodies. Attention is drawn to the similarity of the dense bodies to structures present in germ cells of a number of other species, and possible functions of the dense bodies in germ cell differentiation are considered.
SARCOPLASMIC RETICULUM AND T TUBULES IN DIFFERENTIATING RAT SKELETAL MUSCLE
Authors: Kelly A. M.
Published: May 2004

An electron microscope study has been made of the distribution of membrane couplings between the sarcoplasmic reticulum (SR) and either the plasmalemma or the T tubules in fetal and neonatal rat intercostal muscle. Within primitive muscle cells at 12 days of gestation, the SR forms both simple and specialized membrane junctions with the plasmalemma; caveolae are very few, and T tubules are not detected. Undifferentiated cells neighbor muscle cells. Occasionally these cells contain subsurface couplings between the endoplasmic reticulum and plasmalemmae. Possible relationships between these couplings and the peripheral couplings of muscle cells are discussed. By 15–18 days of gestation, caveolae and beaded T tubules, comparable to those of cultured muscle, develop; T tubules lie along-side myofibrils and are rarely transverse. SR couples both to T tubules and to plasmalemmae during this period. T tubules with lineal profiles appear after further development and their orientation transverse to A–I junctions becomes increasingly evident. Membrane couplings between SR and T tubules also increase in number, whereas the incidence of peripheral coupling declines rapidly Evidence suggests that peripheral couplings are swept into myotubes as caveolae proliferate and T tubules form. SR thus appears to initially couple with the plasmalemma and then to await T tubular growth. This contrasts with the developmental pattern described in cultured chick muscle in which peripheral couplings are not reported and T tubules with diads and triads occur at very primitive stages of muscle differentiation.
INHIBITION OF EMPTYING OF SKELETAL MUSCLE CELL SEGMENTS BY ADENINE NUCLEOTIDES AND POLYVALENT CATIONS
Authors: Comissiong E. A. , Stanley D. W. , Hultin H. O.
Published: May 2004

A correlation had previously been established between actomyosin content of homogenized skeletal muscle cell segments as determined by extraction in strong salt solution and the ability of those segments to empty when extracted with buffered water. In this study, we examined the ability of certain compounds to inhibit the process of emptying. Adenosine triphosphate (ATP) and adenosine diphosphate (ADP), which dissociate actomyosin, inhibited the process of emptying, while adenosine monophosphate (AMP) which does not dissociate actomyosin, did not. We conclude that the formation of actomyosin is a necessary prerequisite for emptying and not just a secondary effect. Polyvalent cations were also found to inhibit emptying. The inhibition was reversible by washing with a solution of NaCl-histidine or with chelating agents, ethylenediaminetetraacetate (EDTA) and ethylene-glycol-bis(ß-amino-ethyl ether) tetraacetic acid (EGTA). A factor(s) solubilized from aged muscle functions as an inhibitory agent; the suggestion is made that this factor(s) may be a polyvalent cation.
TRANSPORT OF VIRAL RNA IN KB CELLS INFECTED WITH ADENOVIRUS TYPE 2
Authors: Raskas Heschel J. , Okubo Case K.
Published: May 2004

Messenger RNA transport was studied in KB cells infected with the nuclear DNA virus adenovirus type 2. Addition of 0.04 µg/ml of actinomycin completes the inhibition of ribosome synthesis normally observed late after infection and apparently does not alter the pattern of viral RNA synthesis: Hybridization-inhibition experiments indicate that similar viral RNA sequences are transcribed in cells treated or untreated with actinomycin. The polysomal RNA synthesized during a 2 hr labeling period in the presence of actinomycin is at least 60% viral specific. Viral messenger RNA transport can occur in the absence of ribosome synthesis. When uridine-3H is added to a late-infected culture pretreated with actinomycin, viral RNA appears in the cytoplasm at 10 min, but the polysomes do not receive viral RNA-3H until 30 min have elapsed. Only 25% of the cytoplasmic viral RNA is in polyribosomes even when infected cells have been labeled for 150 min. The nonpolysomal viral RNA in cytoplasmic extracts sediments as a broad distribution from 10S to 80S and does not include a peak cosedimenting with 45S ribosome subunits. The newly formed messenger RNA that is ribosome associated is not equally distributed among the ribosomes; by comparison to polyribosomes, 74S ribosomes are deficient at least fivefold in receipt of new messenger RNA molecules.
LYSOZYME IN EPIPHYSEAL CARTILAGE
Authors: Kuettner K. E. , Eisenstein R. , Soble L. W. , Arsenis C.
Published: May 2004

The localization of chick embryonic lysozyme was determined by two techniques: by studying the rate of release from the tissue during sequential enzymatic digestion and by immunocytochemistry. Both techniques indicate that, in this tissue, lysozyme is primarily extra-cellular. Cartilage lysozyme was isolated and partially characterized and found to be identical with egg white lysozyme in its immunologic and enzymatic behavior. In addition, a method for the isolation of large numbers of viable chondrocytes is described.
THE DISTRIBUTION OF SPINDLE MICROTUBULES DURING MITOSIS IN CULTURED HUMAN CELLS
Authors: McIntosh J. Richard , Landis Story C.
Published: May 2004

WI-38 and HeLa cells in mitosis have been selected from fixed monolayer cultures and serially sectioned for electron microscopy. Sections perpendicular to the spindle axis permit counting of the number of microtubules at each position on the spindle axis and hence the preparation of tubule distribution profiles. Errors intrinsic to this method are discussed. The changes in the tubule distributions from one mitotic stage to another provide evidence concerning the behavior of the spindle tubules during mitosis. The ratio of the number of tubules passing the chromosomes on the metaphase plate to the maximum number in each half spindle is about 1/2. This ratio changes little in early anaphase, and then decreases in late anaphase at about the same time that a zone of increased tubule number develops at the middle of the interzone. The region where the stem bodies form contains about 3/2 the number of tubules seen elsewhere in the interzone. This ratio is almost constant as the mid-body forms in telophase and then increases to 2/1 in early interphase before the final stages of cytokinesis occur.
RELATIONSHIPS BETWEEN NUCLEIC ACID SYNTHETIC PATTERNS AND ENCYSTMENT IN AGING UNAGITATED CULTURES OF ACANTHAMOEBA CASTELLANII
Authors: Rudick V. L.
Published: May 2004

Changes in the levels of DNA and RNA syntheses have been studied in unagitated cultures of Acanthamoeba castellanii during the phases of logarithmic multiplication (LM) and population growth deceleration (PGD). Pulse-labeling experiments show that the rate of DNA synthesis decreases at the same time that DNA per cell is known to drop by 50%. The drop in DNA content has been explained by demonstrating with hydroxyurea that the majority of LM amebas can replicate once when DNA synthesis is inhibited and, therefore, must be in G2, whereas the PGD amebas cannot multiply in the presence of inhibitor and, therefore, must be in G1. The inhibition of DNA synthesis in LM or PGD cells has been shown to induce encystment. The rate of RNA synthesis, as illustrated by pulse-labeling experiments, increases 25% in late LM-early PGD while RNA per cell increases 75%. The rate of synthesis then decreases 65%. The majority of accumulated RNA has been demonstrated to be ribosomal by disc electrophoresis. By using actinomycin D at different stages during the RNA build-up, the ability of the amebas to encyst has been shown to depend on the presence of this RNA. The observations on DNA and RNA are discussed with respect to the occurrence of cysts in the cultures during PGD.
THICK FILAMENTS IN VASCULAR SMOOTH MUSCLE
Authors: Devine Carrick E. , Somlyo Andrew P.
Published: May 2004

Two sets of myofilaments were demonstrated after incubation of strips of rabbit portal-anterior mesenteric vein under moderate stretch in a physiological salt solution. Thick filaments had a mean diameter of 18 nm and reached a maximum length of 1.4 µm with a mean length of 0.61 µm. In transverse sections, 2.5–5 nm particles were resolved as subunits of the thick filaments. Thin filaments had an average diameter of 8.4 nm and generally conformed to the structure believed to represent actin filaments in smooth and striated muscles. In the areas of maximum concentration there were 160–328 thick filaments/µm2 and the lowest ratio of thin to thick filaments was 12:1. Thick filaments were present in approximately equal numbers in vascular smooth muscle relaxed by theophylline, in Ca++-free solution, or contracted by norepinephrine. The same preparatory procedures used with vascular smooth muscle also enabled us to visualize thick filaments in guinea pig and rabbit taenia coli and vas deferens.
THE EFFECT OF PROTEIN SYNTHESIS INHIBITION ON THE ENTRY OF MESSENGER RNA INTO THE CYTOPLASM OF SEA URCHIN EMBRYOS
Authors: Hogan Brigid , Gross Paul R.
Published: May 2004

Emetine is a potent inhibitor of protein synthesis in sea urchin embryos. At a concentration of the drug that rapidly inhibits protein synthesis in blastulae by 95%, uridine incorporation into RNA continues for more than 1 hr and presumptive histone messenger RNA is synthesized and transported into the cytoplasm where it is apparently associated with polyribosomes. Possible explanations of this result and its implications for the "informasome" theory of messenger transport in embryonic cells are discussed.
STUDIES OF MEMBRANE FORMATION IN TETRAHYMENA PYRIFORMIS
Authors: Nozawa Yoshinori , Thompson Guy A.
Published: May 2004

A method has been devised to fractionate cells of Tetrahymena pyriformis, yielding pure or highly enriched preparations of cilia, cilia-associated soluble material, pellicles, mitochondria, microsomes, and postmicrosomal supernatant. The method prevents the destructive action of lipolytic enzymes commonly associated with this organism. Analysis of the membrane lipids of these fractions reveals significant differences in lipid composition. Most noteworthy are the high concentrations of phosphonolipid and tetrahymanol in the surface membranes.
NUCLEOLI OF DIPLOID CELL STRAINS
Authors: Phillips Stephanie G. , Phillips David M.
Published: May 2004

Nucleoli of cultured Chinese hamster or mouse cells in early passages had a loosely reticular substructure. Within the reticulum small, irregularly shaped, light fibrillar zones occurred which were contiguous with denser fibrillar zones. These denser zones appeared to be connected in some places to the particulate material which composed the mass of the nucleolus. Generally, electron-transparent spaces separated the particulate zones from the fibrillar areas. Treatment with toyocamycin, an agent which is reported to cause a blockage in the processing of ribosomal RNA, greatly inhibited the accumulation of newly synthesized RNA in the cytoplasm, as monitored by radioautography. Toyocamycin treatment caused the gradual disappearance of the granules from the particulate region of the nucleoli, and resulted ultimately in the nucleoli appearing homogeneously fibrillar. Actinomycin D treatment, which inhibited virtually all RNA synthesis, caused a segregation, and finally a disaggregation, of nucleolar components.
MORPHOLOGICAL AND BIOCHEMICAL CHARACTERISTICS OF GLYCOGEN PARTICLES ISOLATED FROM RABBIT POLYMORPHONUCLEAR LEUKOCYTES
Authors: Wanson Jean-Claude , Tielemans Louis
Published: May 2004

The fine structure of ascitic cells, consisting of 87–92% heterophil, 5–10% eosinophil leukocytes, and 3% macrophages, is well preserved by glutaraldehyde-osmium tetroxide fixation only when the osmolality of the fixative is appropriately balanced. The ß-glycogen particles, 35–45 mµ in diameter, are found either as large accumulations in the perinuclear region or in a dispersed form in peripheral cytoplasm. In the heterophils, they are embedded in a coarse-grained ground substance. Extraction and purification of the glycogen were performed by differential precipitation-centrifugation. Yield (35% recovery), purity (4% protein contamination), and preservation of a high sedimentation coefficient (240S) represent the main advantages of the proposed procedure. The analysis of the profile of the sedimentation curve, together with an analysis of the particle size measurements and of particle fine structure, leads to the conclusion that the ß-particles form a homogeneous population with a gaussian distribution curve. Each particle consists of smaller units which increase in number with increasing size, the largest ones taking on the appearance of small rosettes. The glycogen particles of the microsomal fraction, still loaded with phosphorylase, were submitted to a synthetic activity by incubation in the presence of glucose-l-phosphate. The analysis of the particle growth shows that particles of all sizes respond equally well.
The Fibrinogen Molecule: Its Size, Shape, and Mode of Polymerization
Authors: Hall Cecil E. , Slayter Henry S.
Published: May 2004

Improved electron micrographs of the shadow-cast bovine fibrinogen molecule have been obtained establishing its general morphology and dimensions in the dry state. It consists of a linear array of 3 nodules held together by a very thin thread which is estimated to have a diameter of from 8 to 15 A, though it is not clearly resolved. The two end nodules are alike but the center one is slightly smaller. Measurements of shadow lengths indicate that nodule diameters are in the range 50 to 70 A. The length of the dried molecule is 475 ± 25 A.

Adopting the molecular volume from previous physical chemical data and the general morphological features and length from electron microscopy, we calculate the diameters of the end nodules to be 65 A and the center one as 50 A. The model of the molecule so obtained is consistent with the electron microscopical observations and the data from physical chemistry.

The intermediate polymers formed when fibrinogen is activated with thrombin were also examined and found to be end-to-end aggregates of altered fibrinogen molecules which shrink in length during the process. Intermediate polymer lengths are from 1000 to 5000 A.

The nodular nature of fibrinogen, its shrinkage and end-to-end aggregation on polymerization permits us to deduce an explanation for the system of cross-bands previously observed in stained fibrin fibrils.
The Origin and Fate of Annulate Lamellae in Maturing Sand Dollar Eggs
Authors: Merriam R. W.
Published: May 2004

Electron micrograph evidence is presented that the nuclear envelope of the mature ovum of Dendraster excentricus is implicated in a proliferation of what appear as nuclear envelope replicas in the cytoplasm. The proliferation is associated with intranuclear vesicles which apparently coalesce to form comparatively simple replicas of the nuclear envelope closely applied to the inside of the nuclear envelope. The envelope itself may become disorganized at the time when fully formed annulate lamellae appear on the cytoplasmic side and parallel with it.

The concept of interconvertibility of general cytoplasmic vesicles with most of the membrane systems of the cytoplasm is presented.

The structure of the annuli in the annulate lamellae is shown to include small spheres or vesicles of variable size embedded in a dense matrix.

Dense particles which are about 150 A in diameter are often found closely associated with annulate lamellae in the cytoplasm. Similar structures in other echinoderm eggs are basophilic. In this species, unlike other published examples, the association apparently takes place in the cytoplasm only after the lamellae have separated from the nucleus. If 150 A particles are synthesized by annulate lamellae, as their close physical relationship suggests, then in this species at least the necessary synthetic mechanisms and specificity must reside in the structure of annulate lamellae.
Fine Structure of Bacillus subtilis
Authors: Tokuyasu Kiyoteru , Yamada Eichi
Published: May 2004

The fine structure of Bacillus subtilis has been studied by observing sections fixed in KMnO4, OsO4, or a combination of both. The majority of examinations were made in samples fixed in 2.0 per cent KMnO4 in tap water. Samples were embedded in butyl methacrylate for sectioning.

In general, KMnO4 fixation appeared to provide much better definition of the boundaries of various structures than did OsO4. With either type of fixation, however, the surface structure of the cell appeared to consist of two components: cell wall and cytoplasmic membrane. Each of these, in turn, was observed to have a double aspect. The cell wall appeared to be composed of an outer part, broad and light, and an inner part, thin and dense. The cytoplasmic membrane appeared (at times, under KMnO4 fixation) as two thin lines.

In cells fixed first with OsO4 solution, and then refixed with a mixture of KMnO4 and OsO4 solutions, the features revealed were more or less a mixture of those revealed by each fixation alone.

A homogeneous, smooth structure, lacking a vacuole-like space, was identified as the nuclear structure in a form relatively free of artifacts.

Two unidentified structures were observed in the cytoplasm when B. subtilis was fixed with KMnO4. One a tortuous, fine filamentous element associated with a narrow light space, was often found near the ends of cells, or attached to one end of the pre-spore. The other showed a special inner structure somewhat similar to cristae mitochondriales.
The Effect of Extended Anaerobic Treatments on the Chromosomes of Vicia faba
Authors: Merz Timothy
Published: May 2004

The effects of extended anaerobic treatments on Vicia faba lateral root-tip chromosomes were determined. It was observed that aberrations resulted from these treatments, and that the frequency varied from root to root as well as from experiment to experiment. It was suggested that the inconsistency observed might be due to variation in the abilities of different roots to produce energy via fermentation routes. If this were true, an inhibition of fermentation would result in a more consistent aberration frequency. A fermentation inhibitor, NaF, was used in combination with extended anaerobic treatments. The observed frequency of aberrations after the combined treatments was generally higher and considerably less variable. Although other hypotheses might account for the NaF effect, the hypothesis most compatible with the evidence is that the effect is due to energy deprivation. The experimental results are discussed in terms of the aforementioned effect and in terms of three alternative hypotheses for the production of chromosomal aberrations as a consequence of a lack of energy. It is concluded that damage might result from a build-up of normal cellular compounds to abnormally high concentrations which would act directly or indirectly on the chromosomes, from the breakdown of DNA as an energy source, or simply as a result of the fact that the chromosome needs energy to remain intact.
The Ingestion of Proteins and Colloidal Materials by Columnar Absorptive Cells of the Small Intestine in Suckling Rats and Mice
Authors: Clark Sam L.
Published: May 2004

Proteins and colloidal materials, administered orally to suckling rats and mice, were ingested by columnar absorptive cells of the jejunum and ileum, but not of the duodenum. Bovine gamma globulin and ovalbumin were identified in the apical cytoplasm by staining with fluorescent antibody; trypan blue, Evans blue, saccharated iron oxide, and colloidal gold were detected intracellularly by their color, specific staining, and appearance in the electron microscope. Each substance was segregated in membrane-enclosed vacuoles, apparently part of a system of potentially interconnecting vacuoles and tubules in the apical cytoplasm which is continuous in places with the apical cell membrane. We postulate that ingestion of foreign materials was accomplished by pinocytosis, that is, by invagination of the apical cell membrane to form vacuoles containing material from the intestinal lumen.

Approximately 18 days after birth columnar absorptive cells lost the ability to ingest proteins and colloids, and no longer contained large vacuoles and numerous tubules. At this age rats and mice lose the ability to absorb antibodies from the intestine in an immunologically intact form, and we conclude that cellular ingestion is part of the mechanism of absorption of intact proteins in suckling animals. Particulate fat apparently is absorbed in both newborn and adult animals by micropinocytosis. Thus adult animals may not have lost the capacity for pinocytosis, but rather have become selective as to what substances provoke it.

Cortisone acetate, administered subcutaneously to rats 8 to 10 days old alters the columnar absorptive cells within 72 hours so that they resemble the cells in adult animals and no longer ingest proteins.
Cytological Studies of the Nematocysts of Hydra
Authors: Chapman George B. , Tilney Lewis G.
Published: May 2004

Entire hydras or tentacles were prepared for electron microscopy as described in the preceding paper.

The stenotele capsule has been observed to be composed of an external membrane, a thick chitinous or keratin layer, and an inner membrane. A sac-like extension of the capsular wall into the capsule bears spines and stylets on its inner surface and evagination of this structure occurs on discharge. Profiles of tubular or membranous structures often are seen within the capsules of resting stenoteles. These structures are presumably related to the external filament. The spines often reveal a flattened aspect which suggests that at least some of them might more accurately be called "vanes." A cnidocil has been found to accompany each stenotele.

This study revealed several aspects of the developmental stages of stenoteles: A vacuole is formed which is nearly surrounded by the nematocyte nucleus. The vacuole content changes in density and a capsular wall is formed at the periphery of the vacuole. Tubules differentiate from the capsular matrix, and spines and stylets develop somewhat later. An operculum is formed from the nematocyte cytoplasm.
Rapid Cytochemical Identification of Phagosomes in Various Tissues of the Rat and their Differentiation from Mitochondria by the Peroxidase Method
Authors: Straus Werner
Published: May 2004

1. Granules characterized by their ability to segregate foreign proteins (phagosomes) were identified in the cells of many rat organs after intravenous administration of horseradish peroxidase, by using the conventional test with benzidine for the histochemical detection of peroxidase. The largest numbers of phagosomes were identified in kidney and liver. Considerable numbers were observed cytochemically in pancreas, prostate, epididymis, thymus, spleen, bone marrow, small intestine, heart, pituitary, and mouse mammary carcinoma.

2. The variation in size of the phagosomes ranging from the limit of microscopic visibility up to 5 µ diameter, previously described for kidney, was also observed to occur in many of the other organs. The average size of the phagosomes in different organs was also different, the phagosomes of the liver, for example being on the average smaller than those of the kidney, pancreas, and prostate.

3. In squash preparations of kidney and liver, the phagosomes appeared often in curved rows following the course of the cell membranes of epithelial cells. In several other organs, they appeared aggregated in cells located in the vicinity of blood or lymphatic vessels or capillaries.

4. After injection of peroxidase directly into the brain of a rabbit, a striking concentration of peroxidase was observed in phagosomes of endothelial cells of capillaries and vessels, surrounding the site of injection. It was suggested that this localization may offer an explanation for the so called blood-brain barrier.

5. The cytochemical peroxidase method was applied to smears of isolated fractions of kidney and liver. Only the isolated phagosomes, but not the isolated nuclei, mitochondria, and microsomes, reacted with benzidine after administration of peroxidase. The contamination of conventionally prepared nuclear, mitochondrial, and microsomal fractions of kidney and liver with phagosomes of different sizes was observed. By correlating the cytochemical peroxidase test of smears of isolated fractions with the colorimetric determination of peroxidase, acid phosphatase, and cytochrome oxidase in the same fractions, the differentiation of the phagosomes from mitochondria and other cell granules was facilitated.

6. The marked difference in the osmotic properties of phagosomes and mitochondria, detectable after treatment with 70 per cent alcohol, and the difference in their affinities towards basic fuchsin, made it possible to differentiate the phagosomes from the mitochondria. It was found by this simple procedure that kidney cells of normal rats contain a large number of phagosomes ranging in size from 0.5 to 3 µ, whereas liver cells of normal rats contain relatively few phagosomes of this size but many smaller ones (0.2 to 0.5 µ diameter). These increased in size after treatment of the rats with horseradish peroxidase.
A Cytochemical Study of the Stem Cell Concept in Specimens of a Human Ovarian Tumor
Authors: Bader Saul
Published: May 2004

The amounts of DNA in interphase nuclei were compared with the amounts of DNA in metaphase and anaphase figures in Feulgen-stained tissue sections of 5 specimens of the human ovarian papillary serous adenocarcinoma. The relative amounts of DNA per cell were determined by cytophotometric measurements of interphase nuclei at a single wavelength and of mitotic figures by the two wavelength method.

The 5 specimens conformed to the stem cell concept of cell proliferation since anaphase distributions of amounts of DNA were restricted to a narrow range of DNA values indicating the successful mitosis of a single cell type (stem cell) out of several cell types whose presence were suggested by the wide spread of interphase and metaphase values. In addition, the data indicated that, in some instances, only the amounts of DNA in anaphase figures can reliably identify the stem cell. Changes in the frequency of dividing cells having doubled amounts of DNA, and/or the presence of cells resulting from endoreduplication can distort the interphase distribution of amounts of DNA and thus give rise to a modal DNA interphase value which is not the same as the DNA value of the stem cell (anaphase figures).
Submicroscopic Changes in Visual Cells of the Rabbit Induced by Iodoacetate
Authors: Lasansky Arnaldo , De Robertis Eduardo
Published: May 2004

Alterations produced by iodoacetate in visual cells have been studied under the electron microscope. Lesions of the outer segments of the rods are visible as early as 3 hours after a single injection of 20 mg. iodoacetate per kg. body weight. After 6 hours the changes are more marked and consist then of disorganization, vesiculation, and lysis of the rod sacs. The inner segments of most rod cells show swelling and vacuolization of the matrix, the endoplasmic reticulum, and the Golgi complex. The mitochondria of the ellipsoid show a tendency to disintegrate. In some inner segments the changes consist primarily in an increase in density of the matrix and deposition of a granular material. The rod synapses are also affected, showing lysis of the synaptic vesicles and alterations of the synaptic membrane.

With a second injection of 20 mg. iodoacetate per kg. body weight, all these changes become more marked and lead to complete destruction of the rod cells.

The cones seem more resistant than the rods. A single injection produces no visible changes in the outer or inner segments of the cones. At cone synapses, however, there are changes consisting of fusion of synaptic vesicles and other membranous material to form large concentric membranes characteristic of myelin figures. A second dose of the drug causes complete destruction of the cone cells.

All these, and other submicroscopic changes, are discussed in relation to various hypotheses put forward to explain the mode of action of iodoacetate on visual cells. The pronounced alterations of submicroscopic intracellular membranes suggest that the locus of action of iodoacetate may be a component widely dispersed throughout the visual cells and related, in some way, to the maintenance of these lipoprotein structures.
Cytophotometric Study of Deoxyribonucleic Acid in Cortisone-Treated Rat Hepatocytes
Authors: Lowe Charles U. , Box Harold , Venkataraman P. R. , Sarkaria D. S.
Published: May 2004

Rats were treated by intramuscular injection with cortisone acetate, 25 mg./day for 5 days. Small pieces of liver obtained from treated and normal animals were squashed on a microscope slide so as to obtain many areas only a single cell in thickness. After Feulgen staining to demonstrate DNA, optical density was measured using a projection technique.

In both the normal and treated animals the nuclei were easily segregated in three ploidy classes, diploid, tetraploid, and octaploid, depending upon Feulgen intensity. In all three classes, the absorbence of nuclei from cortisone-treated animals was approximately 20 per cent lower than the normal. These data were interpreted to indicate that a change in DNA content had been induced by cortisone administration. These findings are comparable to data obtained from similar animals using chemical methods for the determination of DNA.
Macronuclear Duplication in the Ciliated Protozoan Euplotes
Authors: Gall Joseph G.
Published: May 2004

The ribbon-like macronucleus of Euplotes eurystomus pinches in half amitotically at each cell division. Several hours before the actual division two lightly staining duplication bands (reorganization bands) appear at the ends of the nucleus and approach each other slowly, finally meeting near the middle. Distal to the bands, that is, in regions through which the bands have already passed, the concentration of DNA (Feulgen) and "histone" (alkaline fast green) is greater than in the central zone. These facts suggest the hypothesis that DNA-histone synthesis takes place in a sequential fashion starting at the tips of the nucleus and proceeding to the middle. That this hypothesis is correct is shown by autoradiographic and photometric observations. Tritium-labelled thymidine is incorporated only in a limited region immediately distal to the bands. The average amount of Feulgen dye bound by the nucleus rises as the duplication bands approach each other, and is double the presynthesis value by the time the bands meet. A similar rise in the alkaline fast green dye is seen in duplicating nuclei, although no completely post-synthesis values were obtained in this study. The quantitative data are consistent with the assumption that the macronucleus contains a number of DNA-histone "units," presumably chromosomes, each of which duplicates once and only once.
C14 Assays and Autoradiographic Studies on the Rooster Comb
Authors: Balazs Endre A. , Szirmai John A. , Bergendahl Gudrun
Published: May 2004

The distribution of C14 was studied in various parts of the rooster comb following treatment with testosterone. The value of gas-phase assay of C14 in tissue has been demonstrated and the results compared with those of autoradiographic studies on the same tissue.

The results of these experiments showed that androgen treatment significantly increases the rate of incorporation of C14 in various parts of the comb. The specific activity of carbon in the comb, cornea, and liver differed, depending on which precursor, viz. glucose-6-C14, glucose-1-C14, and glucuronolactone-U-C14, was administered. The highest values were obtained after the administration of glucose-6-C14; glucuronolactone-U-C14 gave the lowest specific activity.

The specific activity of carbon in different parts of the comb showed considerable variation. Carbon assay of serial sections of the comb cut at various planes showed that the specific activity of carbon was highest in the mucoid layer. Both C14 assays and autoradiograms indicate that C14 is also present in other parts of the comb. As seen in autoradiography, the concentration of C14 was highest in the epithelium, in the blood vessel walls, and in the avascular collagenous tissue. These results, and indications from previous studies, suggest that the high specific activity of carbon in the mucoid layer is due mainly to the presence of C14-labelled hyaluronic acid. Autoradiograms and PAS staining suggest that a significant amount of C14 is also incorporated into the glycoproteins associated with the collagen fibers.
The Relation between Protein Synthesis and Lipide Accumulation in L Strain Cells and Ehrlich Ascites Cells
Authors: King Donald W. , Socolow Edward L. , Bensch Klaus G.
Published: May 2004

It has long been known that fat accumulates in old injured cells both in tissue culture and in many mammalian disease states. The use of L cells grown in suspension tissue culture permitted the opportunity to study conditions in which lipide accumulation could be retarded or accelerated.

These cultures exhibit a three-phase growth curve which is similar to that previously found with bacteria and consists of a lag period, logarithmic growth period, and stationary period. Daily aliquots were removed from cultures going through these phases and protein and cholesterol content correlated with cell division.

It was found that L cells gradually accumulated lipide in the cell concurrent with retardation of cell division and protein synthesis. Conversely old lipide-laden cells, placed in fresh media and encouraged to active division with net protein synthesis progressed from a high to a low lipide/cell ratio over a period of 2 to 4 days. An amino acid analogue p-fluorophenylalanine and a mitotic inhibitor, colchicine, also markedly increased the lipide/cell ratio. Similar results were found in in vitro experiments with Ehrlich ascites cells.
The Occurrence of Intercellular Bridges in Groups of Cells Exhibiting Synchronous Differentiation
Authors: Fawcett Don W. , Ito Susumu , Slautterback David
Published: May 2004

A previous electron microscopic study of the cat testis revealed that spermatids derived from the same spermatogonium are joined together by intercellular bridges. The present paper records the observation of similar connections between spermatocytes and between spermatids in Hydra, fruit-fly, opossum, pigeon, rat, hamster, guinea pig, rabbit, monkey, and man. In view of these findings, it is considered likely that a syncytial relationship within groups of developing male germ cells is of general occurrence and is probably responsible for their synchronous differentiation. When clusters of spermatids, freshly isolated from the germinal epithelium are observed by phase contrast microscopy, the constrictions between the cellular units of the syncytium disappear and the whole group coalesces into a spherical multinucleate mass. The significance of this observation in relation to the occurrence of abnormal spermatozoa in semen and the prevalence of multinucleate giant cells in pathological testes is discussed.

In the ectoderm of Hydra, the clusters of cnidoblasts that arise from proliferation of interstitial cells are also connected by intercellular bridges. The development of nematocysts within these groups of conjoined cells is precisely synchronized.

Both in the testis of vertebrates and the ectoderm of Hydra, a syncytium results from incomplete cytokinesis in the proliferation of relatively undifferentiated cells. The intercellular bridges between daughter cells are formed when the cleavage furrow encounters the spindle remnant and is arrested by it. The subsequent dissolution of the spindle filaments establishes free communication between the cells. The discovery of intercellular bridges in the two unrelated tissues discussed here suggests that a similar syncytial relationship may be found elsewhere in nature where groups of cells of common origin differentiate synchronously.
The Metabolism of Chromosomal Ribonucleic Acid in Drosophila Salivary Glands and its Relation to Synthesis of Desoxyribonucleic Acid
Authors: McMaster-Kaye Rachel , Taylor J. Herbert
Published: May 2004

Incorporation of adenine-8-C14 into chromosomal nucleic acids of Drosophila salivary glands has been observed with the autoradiographic technique. RNA-C14 and DNA-C14 were detected as the fractions extractable by ribonuclease digestion and resistant to ribonuclease, respectively. Extractions with desoxyribonuclease and acids were also used to identify the nucleic acids.

Time-course curves were determined from grain counts. RNA-C14 concentration reached a maximum in 2 hours, and decreased after the 4th hour. DNA-C14 concentration reached its maximum within 8 hours, and showed no decreases during a 48-hour experiment.

In the latter part of the period of observation, morphological differentiation of the gland occurred, the decrease in RNA-C14 became very rapid, and a large increase in DNA-C14 was observed. Marked decrease in RNA-C14 and increase in DNA-C14 were detectable in a few hours when isotope was administered shortly before visible differentiation of the gland.

Measurements of nuclear size indicated no significant decreases in RNA-C14 amount prior to the period of differentiation. During this later period, a large decrease in RNA-C14 amount occurs suddenly, and the same amount of C14 is added simultaneously to the DNA fraction, as expected if RNA-C14 is utilized in the synthesis of DNA.
An Electron Microscope Study of Myelin Figures
Authors: Stoeckenius Walther
Published: May 2004

In the electron microscope, thin sections of OsO4-fixed myelin figures from the phospholipide fraction of human brain show a pattern of parallel dark lines with a repeating period of about 40 A. It is shown that the dark lines probably represent the reaction product of OsO4 with double bonds in the fatty acid chains, thereby marking the central portion of one bimolecular lamella. The addition of globin results in dense lines 25 to 50 A wide that cover the surface of the myelin figures. When such a figure consists of only two bimolecular leaflets of lipide covered with globin, the structure shows striking similarity to the image of cell membranes in fixed tissue sections. A hypothetical schema is given of the molecular structure of the figure, and the distribution of OsO4 in it.