bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
The Striated Musculature of Blood Vessels
Authors: Karrer H. E. 
Published: May 2004

The musculature of small lung veins, of the thoracic portion of the inferior vena cava, and of other thoracic veins of the mouse have been studied in the electron microscope. Tissues were fixed in 1 per cent osmium tetroxide buffered with veronal, to which either sodium chloride or sucrose had been added. Methacrylate or araldite served as embedding matrices. Phosphotungstic acid or uranyl acetate was used to stain some of the preparations. Thin sections were examined in a Siemens and Halske Elmiskop Ib electron microscope.
The entire musculature of the veins examined was of the striated type. It represents a variety of cardiac muscle, characterized by centrally located nuclei, typical mitochondria, and narrow I bands. Many I bands cannot be recognized at all. H and M bands are likewise indistinct. There is a double array of primary and secondary myofilaments. Mitochondria are large and numerous and contain many cristae. The endoplasmic reticulum consists of longitudinal tubules which run through the whole sarcomeres and bypass Z bands, and of transverse tubules which accompany Z bands. Some "triads," located at Z levels, consist of flattened vacuoles flanked by such transverse tubules. Small vesicles located at Z bands, close to the nucleus, and beneath the plasma membrane may represent still other portions of the reticulum.
Studies on the Mitotic Apparatus of the Sea Urchin by Means of Antigen-Antibody Reactions in Agar
Authors: Went Hans A. 
Published: May 2004

The primary purpose of the experiments reported in this paper was to gain information on the molecular origin of the mitotic apparatus. Antisera were prepared against unfertilized sea urchin (Strongylocentrotus purpuratus) egg antigens and mitotic apparatus antigens. These were permitted to react with various antigen solutions in Ouchterlony agar gel diffusion plates, and the resultant precipitation patterns analysed. The results revealed that the mitotic apparatus contains probably no more than two antigens (precursor-1 component and precursor-2 component) and that these are shared by the unfertilized egg. Absorption and fractionation techniques indicated that in the unfertilized egg the precursor-1 component is present both as a "soluble" protein and as an insoluble form tenaciously associated with intracellular structural elements. A survey of dividing and non-dividing tissues for the precursor-1 component revealed that it was restricted to tissues in which mitotic activity could be detected microscopically.
No immunochemical relationship could be detected between the mitotic apparatus and proteins extracted, by various methods, from the lantern muscle.
Chemical and Morphological Studies of Bacterial Spore Formation
Authors: Young I. Elizabeth , Fitz-James Philip C. 
Published: May 2004

The development of both the spore and parasporal protein crystal of Bacillus cereus var. alesti was followed using chemical and cytological techniques. The changes which led to the formation of the fore-spore were similar to those already described for Bacillus cereus. However, adjacent to the developing fore-spore a small inclusion became discernible in phase contrast. This protein inclusion during its growth was differentiated from the chromatin and lipid-containing inclusions by sequential staining techniques.
During spore and crystal formation no net synthesis of either nucleic acid was detected. Tracer studies with radioactive phosphorus confirmed that the spore chromatin was derived from that in the vegetative cell. These same studies also indicated that a turnover of ribonucleic acid occurred during the sporulation process.
During their formation both the spore and crystal incorporated methionine-35S from the medium and from cellular material into a bound form. Sequential extractions with alkali and with alkaline-thioglycollate reagent revealed that the solubility characteristics of the mature crystal were possibly related to the presence of intermolecular disulphide bonds which developed after the major synthesis of the crystal was complete.
The synthetic nature of sporogenesis and crystal formation is discussed with reference to the concept of "endotrophic" sporulation.
REGULATION OF PHOSPHOENOLPYRUVATE CARBOXYKINASE AND TYROSINE TRANSAMINASE IN HEPATOMA CELL CULTURES
Authors: van Rijn Han , Bevers Marinus M. , van Wijk Roeland , Wicks Wesley D. 
Published: May 2004

The ability of N6, O2'-dibutyryl cyclic AMP (DBcAMP) to regulate a number of metabolic events in four lines of cultured rat hepatomas has been examined. Although dexamethasone induces tyrosine transaminase in all four lines, DBcAMP induces this enzyme normally only in H35 cells. A slight increase in transaminase activity was seen with MH1C1 cells and HTC cells, but no effect was detectable in RLC cells. In contrast, phosphoenolpyruvate carboxykinase activity is increased by both agents in H35 and MH1C1 cells, but neither had any effect in HTC or RLC cells.
DBcAMP caused a rapid inhibition of the growth rate and DNA synthesis and an increase in protein content in both H35 and MH1C1 cells but not in HTC or RLC cells. The effect of DBcAMP on DNA synthesis in MH1C1 cells could be reversed by deoxycytidine as is also the case with H35 cells.
The resistance of HTC and RLC cells to DBcAMP was not due to reduced uptake or deacylation as judged by studies with [3H]DBcAMP. The cyclic nucleotide appears to enter the cells by passive diffusion as the intracellular concentration approaches that in the medium within 30–60 min. Possible explanations for the differential responses observed are discussed.
THE EFFECTS OF PARATHYROID HORMONE, COLCHICINE, AND CALCITONIN ON THE ULTRASTRUCTURE AND THE ACTIVITY OF OSTEOCLASTS IN ORGAN CULTURE
Authors: Holtrop Marijke E. , Raisz Lawrence G. , Simmons Hollis A. 
Published: May 2004

The ultrastructure of osteoclasts was examined in fetal rat bones after stimulation or inhibition of resorption in culture. A central ruffled border area completely encircled by a clear zone was considered to represent the resorbing system of the cell. The proportion of ruffled border and clear zone in osteoclast cross sections was compared with changes in bone resorption as measured by the release of previously incorporated radioactive calcium (45Ca). In control cultures 55% of the osteoclast cross sections showed an area closely apposed to bone and this consisted mainly of clear zone; only 11% showed ruffled borders. Treatment with parathyroid hormone (PTH) increased 45Ca release, increased the frequency of finding areas closely apposed to bone (79%), and markedly increased the frequency of the ruffled border area (64%).
Colchicine given concurrently with PTH decreased the number of osteoclasts. Colchicine or calcitonin treatment after PTH stimulation decreased the proportion of ruffled border area significantly by 1 h; this was followed by a decrease in 45Ca release. These inhibited osteoclasts resembled osteoclasts from control, unstimulated cultures, suggesting that the cells had returned to their inactive state.
Colchicine-treated osteoclasts also showed a loss of microtubules and a massive accumulation of 100 Å filaments, suggesting that synthesis of microtubular subunits had increased.
THE NATURE OF HYPOTHALAMO-NEUROHYPOPHYSEAL NEUROSECRETION IN THE RAT
Authors: Kent Christine , Williams M. A. 
Published: May 2004

The nature of hypothalamo-neurohypophyseal neurosecretion was examined in the rat by means of intraventricular injections of tritiated amino acids. Quantitation of autoradiographs was used at the light microscope level to study the sites of synthesis of proteins and their time of arrival in the neural lobe. Electron microscope autoradiographs were used to study the labeling of neural lobe tissue. It was concluded that the great majority of the labeled material was translocated inside dense-cored granules and was probably composed mostly of neurophysins.
The effect of ether anesthesia was also examined. It was found to remove the dense cores from about 20% of the granules in the neural lobe tissue, a process accompanied by the loss of most of their labeled material. The mechanism of the ether effect is discussed and compared to the normal secretion process.
THE LYSOSOME PERIPHERY: BIOCHEMICAL AND ELECTROKINETIC PROPERTIES OF THE TRITOSOME SURFACE
Authors: Gersten Douglas M. , Kimmerer Thomas W. , Bosmann H. Bruce 
Published: May 2004

Normal rat liver lysosomes were isolated by the technique of loading with Triton WR-1339. Purity of the preparation was monitored with marker enzymes; a high enrichment in acid hydrolases was obtained in the tritosome fraction. In 0.0145 M NaCl, 4.5% sorbitol, 0.6 mM NaHCO3, pH 7.2 at 25°C the tritosomes had an electrophoretic mobility of -1.77 ± 0.02 µm/s/V/cm, a zeta potential of 23.2 mV, a surface charge of 1970 esu/cm2, and 33,000 electrons per particle surface assuming a tritosome diameter of 5 x 10-7 m. Treatment of the tritosomes with 50 µg neuraminidase/mg tritosome protein lowered the electrophoretic mobility of the tritosome to -1.23 ± 0.02 µm/s/V/cm under the same conditions and caused the release of 2.01 µg sialic acid/mg tritosome protein. Treatment of the tritosomes with hyaluronidase did not affect their electrophoretic mobility, while trypsin treatment elevated the net negative electrophoretic mobility of the tritosomes. Tritosome electrophoretic mobilities indicated a homogeneous tritosome population and varied greatly with ionic strength of the suspending media. pH vs. electrophoretic mobility curves indicated the tritosome periphery to contain an acid-dissociable group which likely represents the carboxyl group of N-acetylneuraminic acid; this was not conclusively proven, however, since the tritosomes lysed below a pH of 4 in the present system. Total tritosome carbohydrate (anthrone-positive material as glucose equivalents) was 0.19 mg/mg tritosome protein while total sialic acid was 3.8 µg (11.4 nmol)/mg tritosome protein.
A tritosome "membrane" fraction was prepared by osmotic shock, homogenization, and sedimentation. Approximately 25% of the total tritosome protein was present in this fraction. Analysis by gas-liquid chromatography and amino acid analyzer showed the following carbohydrate composition of the tritosome membrane fraction (in microgram per milligram tritosome membrane protein): N-acetylneuraminic acid, 14.8 ± 3; glucosamine, 24 ± 3; galactosamine, 10 ± 2; glucose, 21 ± 2; galactose, 26 ± 2; mannose, 31 ± 5; fucose, 7 ± 1; xylose, 0; and arabinose, 0. The results indicate that the tritosome periphery is characterized by external terminal sialic acid residues and an extensive complement of glycoconjugates. Essentially all the tritosome N-acetylneuraminic acid is located in the membrane and about 53% of it is neuraminidase susceptible.
GENETIC CONTROL OF MITOCHONDRIAL THYMIDINE KINASE IN HUMAN-MOUSE AND MONKEY-MOUSE SOMATIC CELL HYBRIDS
Authors: Kit Saul , Leung Wai-Choi 
Published: May 2004

Distinctive thymidine (dT) kinase molecular forms are present in mouse, human, and monkey mitochondria. Disk polyacrylamide gel electrophoresis (disk PAGE) analyses have shown that the mitochondrial-specific dT kinases differ from cytosol dT kinases in relative electrophoretic mobilities (Rm). Furthermore, the mouse mitochondrial dT kinase differs in Rm value from primate mitochondrial dT kinases. The mouse and primate cytosol dT kinases can also be distinguished.
Disk PAGE analyses have been carried out on the cytosol and mitochondrial dT kinases of human-mouse (WIL-8) and monkey-mouse (mK·CVIII) somatic cell hybrids in order to learn whether the mitochondria of the hybrid cells contained murine mitochondrial-specific, primate mitochondrial-specific, or both dT kinases. WIL-8 cells were derived from cytosol dT kinase-negative, mitochondrial dT kinase-positive mouse fibro blasts and from cytosol dT kinase-positive, mitochondrial dT kinase-positive human embryonic lung cells; they contained mostly mouse chromosomes and a few human chromosomes, including the determinant for human cytosol dT kinase. The mK·CVIII cells were derived from cytosol dT kinase-negative, mitochondrial dT kinase-positive mouse kidney cells and from cytosol dT kinase-positive, mitochondrial dT kinase-positive monkey kidney cells; they contained mostly mouse chromosomes and a few monkey chromosomes, including the determinant for monkey cytosol dT kinase. Disk PAGE analyses demonstrated that the mitochondria of human-mouse and monkey-mouse somatic cell hybrids contained the mouse-specific mitochondrial dT kinase but not the human- or monkey-specific mitochondrial dT kinase. These findings suggest that primate cytosol and mitochondrial thymidine kinase genes are coded on different chromosomes.
CONCOMITANT EFFECTS OF INSULIN ON SURFACE MEMBRANE CONFORMATION AND POLYSOME PROFILES OF SERUM-STARVED BALB/C 3T3 FIBROBLASTS
Authors: Evans R. Blair , Morhenn Vera , Jones Albert L. , Tomkins Gordon M. 
Published: May 2004

By scanning and transmission electron microscopy we have shown that insulin rapidly reversed changes in surface membrane conformation and polysome profile induced by the transfer of actively growing Balb/c 3T3 fibroblasts from a serum-containing to a serum-free medium. Morphometric analysis of polysome profiles revealed a 94% aggregation of total f ribosomes during logarithmic growth. This figure fell to 78% after 18 h of serum starvation. The number of f ribosomes per unit area of cytoplasm also fell. 1 h of insulin treatment restored aggregation to 92% and increased the number of f ribosomes per unit area of cytoplasm by 22%.
Scanning electron microscopy of logarithmically growing cells revealed an abundance of surface microvilli, whereas serum starvation promoted a smooth surface with few microvilli. After 1 h of insulin treatment, microvilli reappeared with a distribution and subcellular organization characteristic of exponential growth.
This study shows the combined and rapid effect of insulin on the regulation of polysome formation and the promotion of a specific surface membrane conformation in cultured cells. The observations are consistent with the knowledge that insulin, acting on the surface membrane, can influence such parameters as membrane transport, and the rates of protein and RNA synthesis.
NUCLEAR GENE DOSAGE EFFECTS ON MITOCHONDRIAL MASS AND DNA
Authors: Grimes Gary W. , Mahler Henry R. , Perlman Philip S. 
Published: May 2004

In order to assess the effect of nuclear gene dosage on the regulation of mitochondria we have studied serial sections of a set of isogenic haploid and diploid cells of Saccharomyces cerevisiae, growing exponentially in the absence of catabolite repression, and determined the amount of mitochondrial DNA per cell.
Mitochondria accounted for 14% of the cytoplasmic and 12% of the total cellular volume in all cells examined regardless of their ploidy or their apparent stage in the cell cycle. The mean number of mitochondria per cell was 22 in the diploid and 10 in the haploids. The volume distribution appeared unimodal and identical in haploids and diploids. The mitochondrial DNA accounted for 12.6 ± 1.2% and 13.5 ± 1.3% of the total cellular DNA in the diploid and haploid populations, respectively. These values correspond to 3.6 x 10-15 g, 2.2 x 109 daltons, or 44 genomes (50 x 106 daltons each) per haploid and twice that per diploid cell. On this basis, the average mitochondrion in these cells contains four mitochondrial genomes in both the haploid and the diploid.
CHANGES IN THE DNA SYNTHESIS PATTERN OF PARAMECIUM WITH INCREASED CLONAL AGE AND INTERFISSION TIME
Authors: Smith-Sonneborn Joan , Klass Michael 
Published: May 2004

The clonal age in paramecia refers to the total number of vegetative divisions a clone has undergone since its origin at autogamy (self-fertilization).
As clonal age increases, the interfission time usually increases. The DNA synthesis pattern of cells of different ages was compared by autoradiographic analysis of the DNA synthesis of synchronized cells at various time intervals during the cell cycle (from one division to the next). The study showed that the G1 period (the lag in DNA synthesis post division) was constant, irrespective of interfission time or clonal age; but the duration of the DNA synthesis period increased with increased interfission time or clonal age. Therefore, we have shown for the first time that the G1 period is fixed, and the S period is increased in a eukaryotic unicellular organism as a function of interfission time and clonal age.