bluuebunny/crossref_metadata_2025 huggingface dataset:
PHAGOCYTOSIS BY THE CELLULAR SLIME MOLD POLYSPHONDYLIUM PALLIDUM DURING GROWTH AND DEVELOPMENT
Authors: Githens S. , Karnovsky M. L.
Published: May 2004

The phagocytic ability of amoebae of the cellular slime mold Polysphondylium pallidum, grown in shaken suspension, was examined. An established quantitative assay of the uptake of polystyrene (PS) beads was shown to be valid for this organism. The kinetics of phagocytosis were determined, and estimates of the concentration of PS beads necessary to achieve half-maximal phagocytic velocity (Kp), as well as the maximal velocity itself (Vpmax), were made. Comparison with previously published data on Acanthamoeba and guinea pig leukocytes suggested that the P. pallidum amoebae had the lowest Kp, while the leukocytes had the highest Vpmax. Beads approximately 1 µm in diameter appeared to be the optimal size for ingestion. Simultaneously with phagocytosis, comparable numbers of beads accumulated at the cell surface; this accumulation did not occur when phagocytosis was inhibited. Phagocytosis was depressed by protein in the medium, by increased osmolarity, and by inhibitors of aerobic metabolism. Starvation-initiated development, leading to encystment, was shown to affect the capacity of the cells to phagocytize, mainly by progressively decreasing the time span over which the cells ingested particles at a constant initial rate.
ZINC REQUIREMENT FOR DNA REPLICATION IN STIMULATED HUMAN LYMPHOCYTES
Authors: Williams Richard O. , Loeb Lawrence A.
Published: May 2004

The requirement for Zn++ in DNA replication by phytohemagglutinin-stimulated human lymphocytes was studied. When 6 µM o-phenanthroline, a chelator with a high affinity for Zn++, is added to cultures of stimulated lymphocytes a nearly complete inhibition of thymidine incorporation results within a few hours. In contrast, the incorporation of uridine is only slightly reduced and the incorporation of leucine is unaffected. m-Phenanthroline, a nonchelating analogue, does not alter the rate of thymidine incorporation even when present in 10-fold greater amounts than o-phenanthroline. The inhibition of thymidine incorporation by o-phenanthroline could be entirely reversed by the addition of Zn++ to the cultures, or could be prevented by the prior addition of either Zn++ or Ni++. All other divalent cations tested were incapable of reversing the o-phenanthroline inhibition of thymidine incorporation.
CONTRAST BETWEEN THE ENVIRONMENTAL pH DEPENDENCIES OF PROPHASING AND NUCLEAR MEMBRANE FORMATION IN INTERPHASE-METAPHASE CELLS
Authors: Obara Yoshitaka , Yoshida Hiroshi , Chai Lee S. , Weinfeld Herbert , Sandberg Avery A.
Published: May 2004

In Chinese hamster Don cells, fusion of an interphase cell with a metaphase cell resulted either in prophasing of the interphase nucleus, including loss of the nuclear envelope (NE), or in the formation of a double membrane around the metaphase chromosomes. Only one of these phenomena occurred in a given interphase-metaphase (I–M) binucleate cell. At pH 7.4, there was about an equal probability that either event could occur amongst the population of I–M cells. The effect of pH changes in the medium containing the fused cells was examined. At pH 6.6, prophasing was the predominant event; at pH 8.0, membrane formation predominated. It was found that the rate of progression of a mononucleate cell from G2 to metaphase was appreciably faster at pH 6.6 than at pH 8.0. Conversely, the progression from metaphase to G1 was faster at pH 8.0 than at pH 6.6. These results with the mononucleate cells strengthen the hypothesis that structural changes in I–M cells are reflections of normal mitotic phenomena. Additional evidence for this hypothesis was produced by electron microscope examination after direct fixation in chrom-osmium. The double membrane around the chromosomes of the I–M cell was indistinguishable from the normal NE. The results obtained by varying the pH of the medium containing the fused cells provide an indication that disruption or formation of the NE of Don cells depends on the balance reached between disruptive and formative processes.
EFFECTS OF TRYPSIN DIGESTION ON FLAGELLAR STRUCTURES AND THEIR RELATIONSHIP TO MOTILITY
Authors: Summers Keith E. , Gibbons I. R.
Published: May 2004

Flagellar axonemes isolated from sea urchin sperm were digested with trypsin for various time periods. The course of digestion was monitored turbidimetrically and was found to take two different courses depending on the presence or absence of ATP in the digestion mixture. It was found that ATP induced active disintegration of the axonemes after slight digestion. Samples of the digested axonemes were examined with the electron microscope to determine the effects of trypsin digestion on the substructures of the axonemes. The rate at which trypsin sensitized the axonemes to ATP paralleled the rate at which it damaged the radial spokes and the nexin links, while the dynein arms were removed much more slowly. The results suggest that inactive dynein arms form cross bridges between the adjacent doublet tubules in digested axonemes, and that when activated by the addition of ATP, they induce an active shearing force between adjacent doublets. The radial spokes and the nexin links are not directly involved in the production of mechanical force, but they may participate in regulating the sliding between tubules to produce a propagated bending wave.
MITOCHONDRIAL BIOGENESIS DURING DIFFERENTIATION OF ARTEMIA SALINA CYSTS
Authors: Schmitt H. , Grossfeld H. , Littauer U. Z.
Published: May 2004

Mitochondria isolated from cysts of Artemia salina (brine shrimp) were found to be devoid of cristae and to possess a low respiratory capability. Hydration of the cysts induces marked biochemical and morphological changes in the mitochondria. Their biogenesis proceeds in two stages. The first stage is completed within 1 h and is characterized by a rapid increase in the respiratory capability of the mitochondria, their cytochrome oxidase, cytochrome b, cytochrome c and perhaps some morphological changes. In the second stage there is an increase in the protein-synthesizing capacity of the mitochondria as well as striking changes in mitochondrial morphology leading to the formation of cristae.
ANALYSIS OF THE SCHEDULE OF DNA REPLICATION IN HEAT-SYNCHRONIZED TETRAHYMENA
Authors: Jeffery William R. , Frankel Joseph , de Bault Lawrence E. , Jenkins Leslie M.
Published: May 2004

The temporal schedule of DNA replication in heat-synchronized Tetrahymena was studied by autoradiographic and cytofluorometric methods. It was shown that some cells, which were synchronized by selection of individual dividing cells or by temporary thymidine starvation, incorporated [3H]thymidine into macronuclei in a periodic fashion during the heat-shock treatment. It was concluded that supernumerary S periods occurred while cell division was blocked by high temperature. The proportion of cells which initiated supernumerary S periods was found to be dependent on the duration of the heat-shock treatment and on the cell cycle stage when the first heat shock was applied. Cytofluorometric measurements of Feulgen-stained macronuclei during the heat-shock treatment indicated that the DNA complement of these cells was substantially increased and probably duplicated during the course of each S period. Estimates of DNA content also suggested that the rate of DNA synthesis progressively declined during long heat-shock treatments. These results indicate that the mechanism which brings about heat-induced division synchrony is not an interruption of the process of DNA replication. Further experiments were concerned with the regulation of DNA synthesis during the first synchronized division cycle. It was shown that participation in DNA synthesis at this time increased as more cells were able to conclude the terminal S period during the preceding heat-shock treatment. It is suggested that a discrete period of time is necessary after the completion of DNA synthesis before another round of DNA synthesis can be initiated.
MANGANESE STIMULATES ADHESION AND SPREADING OF MOUSE SARCOMA I ASCITES CELLS
Authors: Rabinovitch Michel , de Stefano Mary Jo
Published: May 2004

Adhesion of Sarcoma I cells (SaI) to untreated or to serum-treated glass was examined by layering 51Cr-labeled cells on the substrate for 20 min at 34°C and determining the glass-bound radioactivity after the monolayers were rinsed. Adhesion to untreated glass proceeded in sodium chloride-imidazole-potassium medium (SIK) without added divalent cations, whereas SaI adhered maximally to the serum-coated substrate only in the presence of 50 µM or more Mn. Divalent Mg, Ca, Co, Ni, or Zn were inactive or minimally active. Mn-stimulated adhesion was sharply temperature dependent, reversible upon removal of Mn, and inhibited by Ca as well as by cytochalasin B, vinblastine, or tetracaine. Adhesion of SaI in SIK did not ensue when cells or the coated substrate were pretreated with Mn and washed in SIK before the adhesion assays. Microscope observations showed that Mn induced the formation of cell processes, ruffles, and veils, and that SaI spread on the uncoated or serum-coated substrate when exposed to Mn. Cells withdrew veils and processes and rounded up when postincubated in Mn-free medium. Formation of cell processes and spreading was inhibited by cytochalasin B, vinblastine, or tetracaine. Manganese-induced adhesion seems to require the participation of microtubules and microfilaments and may be mediated by an effect of Mn on Ca fluxes. The results support the role of cell processes and spreading in cell-to-substrate adhesion.
MICROTUBULES: EVIDENCE FOR 13 PROTOFILAMENTS
Authors: Tilney Lewis G. , Bryan Joseph , Bush Doris J. , Fujiwara Keigi , Mooseker Mark S. , Murphy Douglas B. , Snyder Daniel H.
Published: May 2004

When microtubules are fixed in glutaraldehyde in the presence of tannic acid and thin sections cut, the subunit structure of the microtubule is readily observed without the need of image reinforcement. Seven types of microtubules were analyzed: those in the heliozoan axoneme, the mitotic apparatus, the contractile axostyle, repolymerized microtubules derived from the chick brain, the central pair in flagella, and the A tubules of flagella and the basal body. In all cases microtubules were composed of 13 equally spaced protofilaments. The B tubules in flagella and the basal body appear to be composed of 11 subunits. The connections of the B to the A and the C to the B are described. A model of a microtubule is presented.
HORMONE SECRETION BY CELLS DISSOCIATED FROM RAT ANTERIOR PITUITARIES
Authors: Hopkins Colin R. , Farquhar Marilyn G.
Published: May 2004

A new procedure has been developed for dissociating anterior pituitary tissue and producing a viable suspension of single cells. The procedure involves incubation of small tissue blocks in 1 mg/ml trypsin (15 min), followed by incubation in 8 µg/ml neuraminidase and 1 mM EDTA (15 min), followed by mechanical dispersion. Cell yields are ∼55%, based on recovered DNA. By electron microscopy five types of secretory cells (somatotrophs, mammotrophs, thyrotrophs, gonadotrophs, and corticotrophs) plus endothelial and follicular cells can be identified and are morphologically well preserved up to 20 h after dissociation. Throughout this period, the cells incorporate linearly [3H]leucine into protein for up to 4 h at a rate 90% greater than hemipituitaries, and they synthesize, transport intracellularly, and release the two major pituitary secretory products, growth hormone and prolactin. Immediately after dissociation the cells' ability to respond to secretogogues (high K+ and dibutyryl cyclic AMP) is impaired, but after a 6–12-h culture period, the cells apparently recover and discharge 24% and 52%, respectively, of their content of prelabeled growth hormone over a 3-h period in response to these two secretogogues. This represents a stimulation of 109% and 470% over that released by cells incubated in control medium. The results demonstrate that function and morphologic integrity are preserved in this cell system. Therefore it is suitable for the study of various aspects of pituitary secretion and its control.
PHOTOTAXIS IN CHLAMYDOMONAS REINHARDTII
Authors: Stavis Robert L. , Hirschberg Rona
Published: May 2004

Parameters which distinguish phototaxis from random motility in Chlamydomonas reinhardtii have been defined with quantitative assays. The phototactic responses in photosynthetic, mixotrophic, and heterotrophic cultures were highest during exponential growth and declined rapidly as the cultures entered stationary phase. In contrast, random motility was relatively constant throughout growth. Phototaxis and motility also differ in their sensitivity to azide and antimycin A. Both of these drugs inhibited phototaxis within 5 min, but motility was unaffected for at least 30 min. Phototaxis and motility have different ion requirements. Optimum motility was observed in the presence of either Ca++ or Mg++; phototaxis required Ca++ and either K+ or NH4+. Photosynthesis is not required for phototaxis, since phototaxis was not inhibited by dichlorophenyldimethyl urea, and a mutant lacking chlorophyll was phototactic.
ANIONIC SITES OF HUMAN ERYTHROCYTE MEMBRANES
Authors: Nicolson Garth L. , Painter Richard G.
Published: May 2004

The effects of affinity-purified antispectrin γ-globulins on the topographic distribution of anionic residues on human erythrocytes membranes was investigated using collo ida iron hydroxide labeling of mounted, fixed, ghost membranes. Antispectrin γ-globulins were sequestered inside ghosts by hemolysis and the ghosts were incubated for 30 min at 37°C and then fixed with glutaraldehyde. The topographic distribution of colloidal iron hydroxide clusters on ghosts incubated with low (<0.05 mg/ml) or high (>5–10 mg/ml concentrations of sequestered antispectrin was dispersed, but the distribution at intermediate concentrations (0.1–5 mg/ml) was highly aggregated. The aggregation of colloidal iron hydroxide binding sites was time and temperature dependent and required the sequestering of cross-linking antibodies (antispectrin Fab could not substitute for γ-globulin antibodies) inside the ghosts. Prior glutaraldehyde fixation or fixation at the time of hemolysis in antispectrin solutions prevented the antispectrin-induced colloidal iron site aggregation. The antispectrin reacted exclusively at the inner ghost membrane surface and the colloidal iron hydroxide bound to N-acetylneuraminic acid residues on the outer membrane surface which are overwhelming on the sialoglycoprotein glycophorin. These results were interpreted as evidence for a structural transmembrane linkage between the inner surface peripheral protein spectrin and the integral membrane component glycophorin.
LOCALIZATION AND PROPERTIES OF THE CHOLINESTERASE IN CRUSTACEAN MUSCLE
Authors: Spielholz Neil I. , Van der Kloot William G.
Published: May 2004

Cholinesterase (ChE) activity is present in crustacean muscle extracts. However, since acetylcholine (ACh) is not a neuromuscular transmitter in these animals, the role and exact localization of ChE was unknown.

The histochemical localization of the enzyme was studied in whole muscle and in the sarcoplasmic reticulum fraction of the extract, 50-µm frozen sections of glutaraldehyde-fixed crayfish tail flexor muscle were incubated with acetylthiocholine (ATC) as substrate, and examined under the electron microscope. After some modifications in published techniques, dense deposits were found associated with the sarcolemma, sarcolemmal invaginations, and transverse tubules. No deposits were found in 10-4 M eserine, or if butyrylthiocholine (BTC) was substituted for ATC. The vesicles in the sarcoplasmic reticulum fraction which demonstrate the activity must represent minced bits of these membranes.

Using a spectrophotometric method, the kinetics of the crustacean muscle enzyme was compared to the acetylcholinesterase (AChE) on mammalian red blood cells and in the lobster ventral nerve cord. Surprisingly, and contrary to previous reports, the crustacean muscle enzyme did not demonstrate substrate inhibition. While a number of similarities to AChE were found, this lack of substrate inhibition makes questionable an unequivocal similarity with classical AChE.
ISOLATION AND PROPERTIES OF THE PLASMA MEMBRANE OF KB CELLS
Authors: Charalampous F. C. , Gonatas N. K. , Melbourne A. D.
Published: May 2004

Plasma membranes from KB cells were isolated by the method of latex bead ingestion and were compared with those obtained by the ZnCl2 method. Optimal conditions for bead uptake and the isolation procedure employing discontinuous sucrose gradient centrifugation are described. All steps of preparative procedure were monitored by electron microscopy and specific enzyme activities. The plasma membrane fraction obtained by both methods is characterized by the presence of the Na+ + K+-activated ATPase and 5'-nucleotidase, and contains NADPH-cytochrome c reductase and cytochrome b5. The latter two enzymes are also present in lower concentrations in the microsomal fraction. Unlike microsomes which are devoid of the Na+ + K+-activated ATPase and which contain only traces of 5'-nucleotidase activity, the plasma membrane fraction contains only trace amounts of the rotenone-insensitive NADH-cytochrome c reductase but no cytochrome P-450, both of which are mainly microsomal components. Morphologically the plasma membrane fraction isolated by the latex bead method is composed of vesicles of 0.1–0.3 µm in diameter. On the basis of the biochemical and morphological criteria presented, it is concluded that the plasma membrane fraction isolated by the above methods are of high degree of purity.
THE DEPRESSION OF PHAGOCYTOSIS BY EXOGENOUS CYCLIC NUCLEOTIDES, PROSTAGLANDINS, AND THEOPHYLLINE
Authors: Cox Joyce P. , Karnovsky Manfred L.
Published: May 2004

The effects of agents that elevate intracellular cyclic adenosine 3',5'-monophosphate (cAMP) have been studied with respect to phagocytosis by guinea pig polymorphonuclear leukocytes. The investigation depends upon the use of a precise method for following ingestion. Theophylline, dibutyryl cAMP, and prostaglandins inhibited the phagocytosis of starch particles. The inhibitions caused by prostaglandins E1, E2, and F2α (PGE1, PGE2, and PGF2α) were synergistic with that due to theophylline. Inhibition by PGA1 and PGA2 was not. At equal concentrations the order of increasing inhibition of phagocytosis (assayed at 10 min) by the prostaglandins was PGE1 < PGF2α < PGE2 < PGA1 = PGA2. Our results are consistent with the hypothesis that increased intracellular levels of cAMP impair the phagocyte's ability to ingest particles. The mechanism of the inhibition has not been defined. The increment in oxidation of [1-14C]glucose to 14CO2 that normally accompanies phagocytosis was found to be depressed in the presence of PGE1 or theophylline, together or individually as expected from the inhibition of phagocytosis. Paradoxically, oxygen consumption although depressed by theophylline or PGE1 plus theophylline, was stimulated by PGE1 alone.
THE SYNTHESIS AND TURNOVER OF RAT LIVER PEROXISOMES
Authors: Lazarow Paul B. , de Duve Christian
Published: May 2004

The subcellular distribution of the biosynthetic intermediates of catalase was studied in the livers of rats receiving a mixture of [3H]leucine and [14C]δ-aminolevulinic acid by intraportal injection. Postnuclear supernates were fractionated by a one-step gradient centrifugation technique that separates the main subcellular organelles, partly on the basis of size, and partly on the basis of density. Labeled catalase and its biosynthetic intermediates were separated from the gradient fractions by immunoprecipitation, and the distributions of radioactivity were compared with those of marker enzymes. The results show that catalase protein is synthesized outside the peroxisomes, but rapidly appears in these particles, mostly still in the form of the first hemeless biosynthetic intermediate. Addition of heme and completion of the catalase molecule take place within the peroxisomes. During the first 15 min after [3H]leucine administration, more than half of the newly formed first intermediate was recovered in the supernatant fraction, where it was found to exist as an aposubunit of about 60,000 molecular weight.
METHODS FOR GENTLE, DIFFERENTIAL HEATING OF PART OF A SINGLE LIVING CELL
Authors: Nicklas R. Bruce
Published: May 2004

The fabrication and use of resistance wire microheaters is described and the results obtainable with cells are illustrated. The microheaters permit localized warming of a small area, wherever desired, within a single living cell. This is directly shown by the production of localized structural changes in the mitotic spindle. Thus in this case, subcellular areas respond independently to the local temperature. The method is applicable to a variety of cellular processes, providing clues to cellular control mechanisms.
MACROMOLECULAR SYNTHESES RELATED TO THE REPRODUCTIVE CYST OF TETRAHYMENA PATULA
Authors: Gabe P. R. , de Bault L. E.
Published: May 2004

Macromolecular syntheses in encysted Tetrahymena patula were studied using Feulgen fluorescence cytophotometry, autoradiography, and inhibitors of RNA and protein synthesis. Cycloheximide significantly depressed protein synthesis and D-actinomycin effectively blocked RNA synthesis. Under these conditions, the cells within the cyst were unable to divide. Both cytophotometric measurements and autoradiographic data with tritiated thymidine show that DNA synthesis does not occur during the encystment divisions. Excysted cells placed in nutrient broth medium showed a prolonged generation time after the first cell growth cycle, and by the third generation the mean DNA content per cell was almost triple that of starved excysted cells. These findings indicate that (a) the encystment divisions require RNA and protein synthesis, which are apparently effected through turnover, (b) the encystment division cycles occur in the absence of DNA synthesis, and (c) excysted cells placed in culture medium may go through more than one DNA replication per cell cycle.
CONTROL OF 5S RNA SYNTHESIS DURING EARLY DEVELOPMENT OF ANUCLEOLATE AND PARTIAL NUCLEOLATE MUTANTS OF XENOPUS LAEVIS
Authors: Miller Leo
Published: May 2004

Ribosomes of all eukaryotes contain a single molecule of 5S, 18S, and 28S RNA. In the frog Xenopus laevis the genes which code for 18S and 28S RNA are located in the nucleolar organizer, but these genes are not linked to the 5S RNA genes. Therefore the synthesis of the three ribosomal RNAs provides a model system for studying interchromosomal aspects of gene regulation. In order to determine if the synthesis of the three ribosomal RNAs are interdependent, the relative rate of 5S RNA synthesis was measured in anucleolate mutants (o/o), which do not synthesize any 18S or 28S RNA, and in partial nucleolate mutants (pl-1/o), which synthesize 18S and 28S RNA at 25% of the normal rate. Since the o/o and pl-1/o mutants have a complete and partial deletion of 18S and 28S RNA genes respectively, but the normal number of 5S RNA genes, they provide a unique system in which to study the dependence of 5S RNA synthesis on the synthesis of 18S and 28S RNA. Total RNA was extracted from embryos labeled during different stages of development and analyzed by polyacrylamide gel electrophoresis. Quite unexpectedly it was found that 5S RNA synthesis in o/o and pl-1/o mutants proceeds at the same rate as it does in normal embryos. Furthermore, 5S RNA synthesis is initiated normally at gastrulation in o/o mutants in the complete absence of 18S and 28S RNA synthesis.
A SCANNING ELECTRON MICROSCOPE STUDY OF SURFACE FEATURES OF VIRAL AND SPONTANEOUS TRANSFORMANTS OF MOUSE BALB/3T3 CELLS
Authors: Porter Keith R. , Todaro George J. , Fonte Virginia
Published: May 2004

Cells of the mouse line Balb/3T3 as well as three virus-induced transformants and two spontaneous transformants grown in vitro have been studied for their topography by scanning electron microscopy. The parent cell in confluent culture closely resembles an endothelial cell in its form and in the structure of its association with adjacent cells. The tumorigenic transformants produced by SV40, murine sarcoma virus, or polyoma viruses are fusiform to pleomorphic and distinctly different from the cell of origin. They show relatively smooth surfaces except for blebs and marginal microvilli. Perhaps most surprising is the similarity they bear to one another. This is made the more singular by the very different form shown by the tumorigenic transformants of spontaneous origin. One of these, S2-4, possesses a thickened rather than the lamellar form of the parent A31 cell and is covered by long microvilli and many spherical blebs. The other, TuT3, more closely resembles the cell of origin but shows extensive ruffling at its margins. All transformants grow without evidence of contact inhibition.

The significance of the surface morphologies and the factors influencing cell form are discussed.
PRODUCTION AND RELEASE OF A LOCUS-SPECIFIC RIBONUCLEOPROTEIN PRODUCT IN POLYTENE NUCLEI OF DROSOPHILA HYDEI
Authors: Derksen J. , Berendes H. D. , Willart E.
Published: May 2004

A specific, 0.1–0.3-µm large ribonucleoprotein complex consisting of a central core with stalklike extensions on top of which 280–320-Å ribonucleoprotein particles are situated is found in an experimentally activated chromosome region, 2–48C, of the polytene chromosomes of Drosophila hydei. Alkaline hydrolysis, RNAse digestion, and uranyl-EDTA-lead staining indicated the ribonucleoprotein character of the 280–320-Å particles, whereas the central core seems to be devoid of RNA.

The characteristic complexes are present in the nucleoplasm and at the nuclear membrane, but absent from the cytoplasm. It is suggested that the large RNP complexes are the specific products of the puff at 2–48C. Complexes similar to the ones described have not been observed in any other region of the polytene salivary gland chromosomes of this species.
QUANTITATIVE AUTORADIOGRAPHIC STUDY OF LABELED RNA IN RABBIT OPTIC NERVE AFTER INTRAOCULAR INJECTION OF [3H]URIDINE
Authors: Gambetti Pierluigi , Autilio-Gambetti Lucila , Shafer Brenda , Pfaff LaDorna
Published: May 2004

The distribution of labeled RNA in the optic nerve of the rabbit was studied by quantitative ultrastructural autoradiography after the intraocular injection of [3H]uridine. The highest density of silver grains related to [3H]RNA (27–40 grains/100 µm2) was found in glial cell perikarya; a slightly lower density was present in the glial nuclei (19–20 grains/100 µm2). Axons (4–5 grains/100 µm2) and myelin (2–3 grains/100 µm2) had the lowest grain densities. 74–83% of all counted grains were located outside the axons. By comparing the grain density distribution over the axon with that expected in the case of an exclusive labeling of the surrounding myelin and glial cell processes, it was concluded that the axons contained a number of grains representing [3H]RNA significantly higher than that expected to scatter from myelin and glial processes. Most of these grains were concentrated at the periphery of the axon and were not related to axonal mitochondria.
ASSOCIATION OF THE ALKALINE PHOSPHATASE OF RABBIT POLYMORPHONUCLEAR LEUKOCYTES WITH THE MEMBRANE OF THE SPECIFIC GRANULES
Authors: Bretz Ursula , Baggiolini Marco
Published: May 2004

The localization of alkaline phosphatase in the specific granules of rabbit polymorphonuclear leukocytes was investigated. The results obtained suggest very strongly that alkaline phosphatase is a component of the granule membrane. The enzyme remains attached to the membrane upon disruption of the granules by the use of detergents or by hypotonic shock and subsequent extraction with sodium sulfate, and can be isolated together with fragments of the granule membrane by isopycnic equilibration. Treatment of the granules with high amounts of Triton-X-100, sodium deoxycholate, or hexadecyltrimethylammonium bromide releases the enzyme in soluble form. In polymorphonuclear leukocyte homogenates, lysis of the granules is needed in order to render alkaline phosphatase fully accessible to substrates. This suggests that the catalytic site of the enzyme is exposed at the inner face of the granule membrane.
Nuclear-Cytoplasmic Relationships in Human Cells in Tissue Culture
Authors: Goldstein Lester , Micou Julie
Published: May 2004

The movement of ribonucleic acid (RNA) from nucleus to cytoplasm has been studied, by autoradiographic techniques, in cells of the human amnion grown in tissue culture.

Cells were exposed to cytidine-H3 for 1 hour after which time only the RNA of the nuclei was labelled. After this 1 hour exposure the cells were placed in a medium containing an excess amount of unlabelled cytidine. Periodically, cells from this medium were fixed. Autoradiographs showed that there was a progressive movement of the label from nucleus to cytoplasm, such that after 24 hours essentially all the label was in the RNA of the cytoplasm.

A study of the incorporation of the cytidine-H3 in deoxyribonucleic acid (DNA), in the same population of cells at the same times, indicated that the presence of excess amounts of unlabelled cytidine almost instantaneously inhibited further utilization of cytidine-H3.

It is concluded that RNA moves from nucleus to cytoplasm as a complex polynucleotide structure.
Nucleoprotein Changes in Plant Tumor Growth
Authors: Rasch Ellen , Swift Hewson , Klein Richard M.
Published: May 2004

Tumor cell transformation and growth were studied in a plant neoplasm, crown gall of bean, induced by Agrobacterium rubi. Ribose nucleic acid (RNA), deoxyribose nucleic acid (DNA), histone, and total protein were estimated by microphotometry of nuclei, nucleoli, and cytoplasm in stained tissue sections. Transformation of normal cells to tumor cells was accompanied by marked increases in ribonucleoprotein content of affected tissues, reaching a maximum 2 to 3 days after inoculation with virulent bacteria. Increased DNA levels were in part associated with increased mitotic frequency, but also with progressive accumulation of nuclei in the higher DNA classes, formed by repeated DNA doubling without intervening reduction by mitosis. Some normal nuclei of the higher DNA classes (with 2, 4, or 8 times the DNA content of diploid nuclei) were reduced to diploid levels by successive cell divisions without intervening DNA synthesis. The normal relation between DNA synthesis and mitosis was thus disrupted in tumor tissue. Nevertheless, clearly defined DNA classes, as found in homologous normal tissues, were maintained in the tumor at all times.
Electron Microscope Observations of the Melanocyte of the Human Epidermis
Authors: Charles Arwyn , Ingram John T.
Published: May 2004

Using standard osmium fixation and methacrylate embedding techniques, a study has been made of the melanocyte of human biopsy skin removed under general and local anaesthesia. Melanogenesis was easily observable in the melanocytes, but immature pigment granules were rarely seen in the Malpighian cells. The passage of melanin from melanocyte to Malpighian cell—cytocrine secretion—is thought to have been observed. Phagocytes near the dermal-epidermal junction seem to have their pigment granules in vacuoles, rather than surrounded directly by the cytoplasmic matrix as in the melanocytes. This, together with the failure to observe "effete" melanocytes, prompts the suggestion that the phagocytes are melanocytes which have migrated from the epidermis into the dermis.

A melanin granule is shown with alternating dark and lighter transverse striations, concerning which structure little can at present be said.
Some Chemical Properties of Isolated Pea Nucleoli
Authors: Stern Herbert , Johnston F. B. , Setterfield G.
Published: May 2004

Isolated nuclei and nucleoli of ungerminated pea embryos have been analyzed chemically for their content of DNA, RNA, zinc, iron, phosphorus, and protein sulfhydryl groups. The values obtained cannot be considered to represent the whole of the living nucleolar body as an undetermined amount of material is extracted from nucleoli in the course of their isolation. Only negligible amounts of DNA have been found in the isolated nucleoli; most of the DNA released on disruption of nuclei appears in a fraction showing very few structures under the light microscope. RNA is more concentrated in the nucleolus than in the nucleus or cytoplasm, but since nucleolar protein is 6 per cent of nuclear and less than 1 per cent of cytoplasmic protein, the total amount of nucleolar RNA is comparatively small. None of the other components listed occurs in high concentration in either nucleus or nucleolus.
Mitochondria
Authors: Pappas George D. , Brandt Philip W.
Published: May 2004

Some of the mitochondria in the free-living giant ameba Pelomyxa carolinensis (Chaos chaos) exhibit unusual and strikingly complex morphological patterns. A study of serial sections of these mitochondria reveals that the patterns are formed by the organization and packing of minute villi (cristae mitochondriales). The form of the individual villus is a regular soft zigzag (or wave) with a bulbous enlargement at each point of inflection ("elbow") on the wave. The pattern of the mitochondria may become increasingly complex as a result of branching and fusing of the wavy villi. Densely packed fibrillar material is sometimes present in the stroma of the mitochondria.
Mitochondria
Authors: Brandt Philip W. , Pappas George D.
Published: May 2004

This study has demonstrated that in the ameba, Pelomyxa carolinensis Wilson (Chaos chaos L.) the limiting membranes of mitochondria and postdivision nuclei are often continuous. The morphological relationship may be functional in that it permits an exchange of material resulting directly or indirectly in an increased enzyme content of the mitochondria. It is suggested that through a series of progressive foldings of its envelope, the nucleus may be a site of formation of mitochondria.
Histochemical and Autoradiographic Studies on the Effects of Aging on the Mucopolysaccharides of the Periosteum
Authors: Tonna Edgar A. , Cronkite Eugene P.
Published: May 2004

An autoradiographic study was made using S35-sulfate for the localization, distribution, and variation in the mucopolysaccharide content of the femoral periosteum of rats from birth to old age. The mucopolysaccharides were also studied histochemically, using toluidine blue O, Rinehart and Abu'l-Haj's colloidal iron method, and the periodic acid-Schiff reaction, before and after hyaluronidase treatment.

Autoradiograms revealed the uptake of S35 particularly in the vicinity of the preosseous zone and adjacent osteoblasts. This labelling was highest at the period of rapid bone growth. With increasing age, the S35 uptake became progressively less. The preosseous zone showed γ-metachromatic staining at all ages after treatment with toluidine blue. Active osteoblasts were mostly orthochromatic, however, ß-metachromasia was exhibited at a later age. Abundant amounts of intra- and extracellular mucopolysaccharides of both the acid and neutral type were demonstrated in the periosteum.

S35 uptake and γ-metachromasia show the presence of sulfated mucopolysaccharides, of which chondroitin sulfate predominates in the preosseous zone. Since S35 uptake is high in active osteoblasts, the inability to demonstrate metachromasia in osteoblasts may indicate either that chondroitin sulfate is liberated as fast as it is being produced, or that it may be present within the cells in a precursor form not detectable by histochemical methods.
A Quantitative Estimation of the Uptake of Two New Electron Stains by the Cytoplasmic Membrane of Ram Sperm
Authors: Silvester N. R. , Burge R. E.
Published: May 2004

From microdensitometer measurements on electron micrographs of sectioned sperm heads it has been found that the electron stains, triiodobenzoyl chloride, and triiodophenylisocyanate, increase the image contrast of the cell membrane above its immediate background by about 40 per cent and 70 per cent respectively, while the nucleus remains unstained. Assumptions based on current electron scattering theory have been used to deduce the uptake by weight of the stains in terms of the density of the nucleus, which was estimated from complementary measurements made with the interference microscope and electron microscope. The uptake of the stains was found to be about 7 per cent and 12 per cent by weight respectively. It is suggested that the method used in this work could be applied generally for the density measurement of cell structures unresolved by the light microscope.
In Vitro Studies of the Metabolism of Tissue Slices
Authors: Cascarano Joseph , Zweifach Benjamin W.
Published: May 2004

The use of tetrazolium salts for metabolic studies has been dismissed on the basis of their poor penetration into fresh tissue slices. In view of the fact that the penetration of these compounds can be visualized, it was felt that knowledge of the factors involved would be important. Factors, known to influence the penetration of oxygen, were examined with respect to the tetrazolium salts. The penetration of tetrazolium salt into tissue slices was a regular and predictable phenomenon. It was found that decreasing the metabolism of the cells in the slice substantially increased the penetration of these compounds, while increases in metabolism, by addition of substrate (such as succinate) to the incubating medium, considerably decreased their penetration. Increasing concentrations of the salt in the medium resulted in greater but limited penetration. It is our belief that the metabolism of tissue slices can be effectively studied with the aid of the tetrazolium salts, the portion of the population of cells participating in any reaction being accurately established by measuring the depth of the zone of reduced dye.
Differents aspects du fer dans l'organisme
Authors: Bessis Marcel , Breton-Gorius Janine
Published: May 2004

On voit des molécules de ferritine apparaitre dans le cytoplasme des cellules réticulaires au cours de la digestion des érythrocytes, autour des stromas phagocytés.

Cette ferritine s'accumule en amas dans lesquels entrent d'autres substances, en particulier des lipides, provenant aussi des stromas globulaires et qui apparaissent sous forme myélinique.

Souvent la ferritine se dispose d'une manière cristalline. Parfois la ferritine et l'apoferritine alternent dans ces cristaux. Parfois l'hémosidérine contient des cristaux qui semblent bien être de l'apoferritine pure.

L'injection de sels de fer donne lieu à l'apparition de ferritine dans les cellules réticulaires. Dans les conditions de nos expériences, la plus grande partie du fer injecté était sous forme de ferritine dans un délai de 3 jours. Un aspect intermédiaire entre celui du fer injecté et celui de la ferritine a été trouvé. Dans le cas des injections de saccharate de fer ce sont de fines aiguilles; dans le cas des injections de lactate de fer, il s'agit de masses fibreuses.
The Structure of the Mitochondrial Membrane: Inferences from Permeability Properties
Authors: Tedeschi Henry
Published: May 2004

Mitochondria possess a semipermeable membrane with properties similar to the cell membrane. Despite the presence of a limiting membrane, mitochondria swell approximately 4 to 5 times their original volume without lysis or loss of internal solute. For this reason, it has been argued that the membrane might be convoluted. The present kinetic study of the permeability of isolated mitochondria was undertaken to clarify this question. A photometric method described previously was used.

In the case of highly lipid soluble penetrants, the results suggest that neither the permeability nor the surface area available for penetration varies significantly during considerable swelling. These results may be interpreted to mean that the mitochondrial membrane is convoluted. For highly polar compounds, the permeability of the membrane also remains unchanged during swelling, but the surface area available to penetration increases. These results may be interpreted to mean that in this latter case, the surface of the convolutions becomes available only after they are unfolded by swelling.

The simplest model that can explain the permeability properties of this membrane consists of a bimolecular lipid layer where the inner monomolecular layer is convoluted.
Basic Proteins of Plant Nuclei during Normal and Pathological Cell Growth
Authors: Rasch Ellen , Woodard John W.
Published: May 2004

Histone proteins were studied by microphotometry of plant tissue sections stained with fast green at pH 8.1. For comparative purposes the Feulgen reaction was used for deoxyribose nuclei acid (DNA); the Sakaguchi reaction for arginine; and the Millon reaction for estimates of total protein.

Analysis of Tradescantia tissues indicated that amounts of nuclear histone fell into approximate multiples of the gametic (egg or sperm) quantity except in dividing tissues, where amounts intermediate between multiples were found. In differentiated tissues of lily, corn, onion, and broad bean, histones occurred in constant amounts per nucleus, characteristic of the species, as was found also for DNA. Unlike the condition in several animal species, the basic proteins of sperm nuclei in these higher plants were of the histone type; no evidence of protamine was found.

In a plant neoplasm, crown gall of broad bean, behavior of the basic nuclear proteins closely paralleled that of DNA. Thus, alterations of DNA levels in tumor tissues were accompanied by quantitatively similar changes in histone levels to maintain the same Feulgen/fast green ratios found in homologous normal tissues.
The Structure of Rhodospirillum rubrum
Authors: Hickman Donald D. , Frenkel Albert W.
Published: May 2004

Cells from serial cultures of R. rubrum, grown anaerobically in the light, were harvested at intervals from ½ to 15 days and sectioned for electron microscopy by conventional methods.

Cells of this species possess a multilayered outer envelope, and the external cell surface is differentiated into ridges extending parallel or obliquely to the long axis of the cell.

Cells from very young cultures resemble non-photosynthetic bacteria and contain only a granular cytoplasm, scattered high-density particles, and low-density areas corresponding to the chromatin areas observed by light microscopy. They contain neither the chromatophores nor the lamellar systems assumed by previous investigators to be characteristic of this species when grown anaerobically in the light.

Chromatophores appear in cells from cultures older than about 12 hours, while systems of paired lamellae appear along with the chromatophores in cells from cultures older than about 8 days. Divergent opinions concerning the occurrence of chromatophores or lamellae in this species can be resolved on the basis of the age of cultures used in previous studies.

Other changes occurring in cells from cultures of increasing age include the appearance of granular and reticulate cytoplasmic bodies and vacuoles, extension of the chromatin areas, and the appearance of a single membrane enclosing several chromatophores.
Structure and Photochemical Activity of Chlorophyll-Containing Particles from Rhodospirillum rubrum
Authors: Frenkel Albert W. , Hickman Donald D.
Published: May 2004

Comparative studies on isolated chromatophores and on sectioned cells of the photosynthetic bacterium Rhodospirillum rubrum confirm the assumption expressed in earlier investigations that the photochemically active chromatophores isolated from disrupted cells represent structural chlorophyll-bearing components of the protoplast.

Actively growing cells from light-grown cultures about 12 hours old do not release chromatophores when disrupted in dilute buffers, but do release smaller, chlorophyll-containing structures about 25 mµ in diameter. Sections of such cells do not reveal chromatophores, but contain in the ground cytoplasm numerous particles somewhat smaller in size than the 25 mµ chlorophyll-containing particles released from disrupted cells. Similar particles are obtained by the sonication of isolated chromatophores obtained from cells of 1-day-old cultures.

The small, subchromatophore particles described here appear to be functionally complete units which are photochemically active in photo-oxidation, photoreduction, and photophosphorylation, and it is postulated that they represent the basic biochemical and structural components of the chromatophore.
Permeability and Structural Characteristics of Isolated Nuclei from Chaetopterus Eggs
Authors: Merriam R. W.
Published: May 2004

The germinal vesicle of the mature Chaetopterus egg is invested by an envelope which can be seen in electron micrographs to contain "pores" in its bilaminar structure. While under continuous microscopic observation, individual germinal vesicles were isolated in various test solutions by an extremely gentle method. Repeated measurements of nuclear diameter and of optical path differences with an interference microscope provided data on changes in mass after isolation. It was found that bovine serum albumin can readily penetrate the nuclear envelope of the isolated nucleus and that there are soluble elements which rapidly diffuse out. A relatively non-diffusible mass is lost at a much slower rate, the proportion of soluble to non-diffusible mass being dependent on the ionic environment. Calcium and manganese increase the proportion of the non-diffusible mass at the expense of the soluble components, while potassium decreases it.

The shape and size of the isolated nucleus is at least partially dependent on the non-diffusible mass of its interior. Digestion with trypsin causes a complete structural collapse and loss of the non-diffusible elements, along with disappearance of the nucleolus. The nucleus shrinks and becomes wrinkled. A small residual mass is left which is probably associated with the nuclear envelope. Digestion with RNase or DNase causes no detectable effect on the isolated nucleus.

Micromanipulation of the isolated nucleus consistently indicates that there are strands emanating from the nucleus. They may be up to several hundred microns long, are structurally strong, and are not destroyed by trypsin, RNase, or DNase. Electron micrographs of thin sections of intact cells show that the germinal vesicle is highly irregular in outline with complex evaginations extending into the cytoplasm. With the light microscope the isolated nucleus looks spherical and smooth and no emanating strands can be seen. The nature of the strands is not known.
Cytoplasmic Membranes and the Nuclear Membrane in the Flagellate Trichonympha
Authors: Grimstone A. V.
Published: May 2004

The structure of the nuclear and cytoplasmic membranes of Trichonympha, a complex flagellate, has been studied in the electron microscope. The nuclear membrane consists of two 70 A membranes, penetrated by numerous pores. Small (100 A) granules occur on the outer surface, around the rims of the pores. Granule-bearing membranes, only 30 to 40 A thick, form long, ribbon-shaped sacs, with 100 A granules on their outer surface. They apparently form close to the nucleus, from which they probably derive their granules. Smooth membranes occur in the parabasal bodies, which consist of stacks of 70 A membranes, joined at their edges in pairs to form flattened sacs. These can inflate and form cytoplasmic vesicles. A protein fibre is applied laterally to the pile of sacs. New sacs, replacing those lost by inflation, appear to form by a process involving the granular membranes, and there may be a transformation of one into the other. Starving eliminates granular membranes and results in a failure in the formation of new parabasal sacs. Refeeding reverses these effects. A parabasal body is a steady-state system, in which the rates of loss and gain of sacs are normally approximately equal. Parabasal bodies resemble the Golgi apparatus.