bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE RIBONUCLEOPROTEIN NATURE OF LARGE PARTICLES IN THE MEIOSPORANGIA OF ALLOMYCES
Authors: Rorem Edward S. , Machlis Leonard 
Published: May 2004

Particles averaging 3 to 4 µ in diameter, which are called chromospheres and fill the immature meiosporangia of the watermold Allomyces, were isolated and analyzed. The preparations were obtained by repeated centrifugations or by passage of the homogenate into a column of sand saturated with oleic acid, followed by selective elution of the chromospheres with alternate layers of oleic acid and an aqueous solution.
The chromospheres contain approximately 12 per cent RNA, no DNA, and 60 per cent protein. It was concluded that they are pure or nearly pure ribonucleoprotein. Analysis of meiosporangia with chromospheres and after the chromospheres have disappeared showed no significant change in RNA or free amino acids. It was concluded that chromosphere disappearance is a fragmentation into small granules.
The relation of chromospheres to postmeiotic chromospheres and nuclear caps is discussed. Speculation as to the function of these bodies is presented.
THE CELL IN STARVATION: PHYSIOLOGICAL AND CHEMICAL OBSERVATIONS
Authors: Cohen Adolph I. 
Published: May 2004

Observations made on Amoeba proteus during total inanition revealed the following changes:
Dry weight declined progressively, but at a decreasing rate to about 45 per cent of the initial levels when determined in surviving members of a dying population. Protein fell to about 70 per cent of the initial level. A hexane-alcohol extractable component fell during early starvation then rose to about its initial absolute level in the dying cells. While initially most of this component is probably lipide, it is not certain that other materials are not extracted during cell degeneration.
Survival as a function of cell size was studied. No advantage in survival was apparent for any size class. Nucleate cell "halves" likewise showed no survival time differential, unlike a highly significant decrease in the survival of enucleate portions. The maintenance of the initial variance about the mean population weight (after hexane-alcohol extraction) during starvation, likewise supports the idea that survival depends largely on concentration parameters.
AN ELECTRON MICROSCOPE STUDY OF THE CYTOLOGY OF THE PROTOZOAN EUPLOTES PATELLA
Authors: Roth L. E. 
Published: May 2004

1. Structurally the "sensory bristles" in Euplotes patella are typical cilia, but no ciliary rootlets connect their bases.
2. The "neuromotor fibrils" are composed of filaments 21 mµ in diameter. At the point of junction of the filaments with the peripheral ciliary fibrils a granular structure 65 to 90 mµ in diameter is seen which has dense central and peripheral zones separated by a less dense layer. Information on the interconnection of organelles is expanded.
3. A system of subpellicular fibrils is described. The external fibrillar system described by others could not be found.
4. The motorium is shown to be a mass of intertwining rootlet filaments.
5. The micronucleus is shown to have a spongy, dense material in a less dense material, all of which is surrounded by a double-layered membrane.
6. The double-layered macronuclear membrane contains annuli whose outside diameter is 70 mµ; the macronuclear bodies are sometimes closely applied to the membrane. In the macronuclear reorganization bands, the solution plane is a fine network, while the reconstruction plane is devoid of structure at the level of resolution observed.
7. The mitochondria are composed of tubules, only occasionally oriented, usually embedded in a surrounding material of lower density.
8. Microbodies whose diameters are 250 to 350 mµ are frequently observed in close association with mitochondrial surfaces.
9. The food vacuoles, contractile vacuoles, and ciliary vacuoles are bounded by single-layered membranes. In the food vacuoles, the bacteria are surrounded by membranes individually or in small groups.
10. Cytoplasmic rods localized in the oral region, and cytoplasmic granules dispersed at random, are described. No typical ergastoplasm, endoplasmic reticulum, or Golgi material was observed.
THE ACTION OF EXCESS OF VITAMIN A ALCOHOL ON THE FINE STRUCTURE OF RAT DERMAL FIBROBLASTS
Authors: Daniel Mary R. , Dingle J. T. , Glauert Audrey M. , Lucy J. A. 
Published: May 2004

Rat dermal fibroblasts were grown as monolayers, and changes in the fine structure of the cells that occurred during 12 hr incubation in a medium containing protein and excess of retinol (vitamin A alcohol) were studied by electron microscopy.
There is little change during the first 6 hr, although some of the nuclei have highly convoluted membranes. During the subsequent 3 hr, there is some disorganization of the mitochondrial cristae; the cisternae of the rough-surfaced endoplasmic reticulum diminish in number; and the amount of smooth membranous material and free ribosomes increases. There is a rapid decline in the respiratory activity of the cells after 6 hr exposure to the vitamin. It is concluded that the primary action of excess of retinol is to cause alterations in the membranes of the cells and that these alterations affect the functions of the mitochondria and endoplasmic reticulum.
Biochemical and Cytological Changes Accompanying Growth and Differentiation in the Roots of Zea mays
Authors: Lund H. A. , Vatter A. E. , Hanson J. B. 
Published: May 2004

The apical meristem of the root affords an excellent material with which to study changes in cellular components accompanying growth and differentiation. The ontogeny of cytoplasmic particles can be followed, since the younger cells are constantly dividing and reforming new cytoplasm. Electron microscope pictures of these newly formed cells reveal a dense background of microsomal granules and small, thin walled vesicles of the endoplasmic reticulum. Two types of mitochondria are noted and, as the cells enlarge, mitochondria regarded as immature can no longer be seen, but only mitochondria with well developed cristae. The development of these cristae was found to be associated with an increase in respiration of the tissue as well as with increased rates of oxidation and phosphorylation of isolated mitochondria. As the cells grow and mature, the mitochondria make up an increasing percentage of the total cytoplasmic protein, and this increase probably accounts to a great extent for the increase in tissue respiration. Concomitantly, there is a decrease in microsomal granules.
All these changes have been verified by electron microscope pictures of cells in situ, chemical analysis of isolated particulates, and metabolic studies of tissue and isolated fractions.
An Electron Microscope Study of Lampbrush Chromosomes
Authors: Lafontaine Jean G. , Ris Hans 
Published: May 2004

Lampbrush chromosomes were isolated from germinal vesicles of oocytes from Necturus maculatus, Triturus viridescens, Pseudotriton montanus and Rana pipiens.
After treatment of isolated nuclei with 10 per cent sucrose, chromosomes free of nuclear sap are obtained for examination in either the light microscope or in the electron microscope. For electron microscopy the chromosomes were prepared either by Anderson's critical-point procedure or were embedded in methacrylate and sectioned.
The evidence presented in favor of the view that the loops, axis, and the chromomeres of lampbrush chromosomes are formed by two chromonemata is based on the following observations:
1. Treatment of isolated chromosomes with 0.002 M KCN loosens the structure of the loops, and a more or less coiled organization is then observed in most of them with the light microscope. At the electron microscope level, each loop consists of a bundle of microfibrils. The latter are 500 A in diameter, and their complex arrangement within the loops is best studied in stereoscopic preparations.
2. Treatment of chromosomes with 0.002 M KCN also unravels the "chromomeric" regions of the axis. A fibrillar organization then becomes visible in the light microscope. In the electron microscope, wide strands are seen within some chromomeres; their diameter corresponds closely to that of the chromonemata forming the loops associated with the same chromomeres. In thin transverse sections of isolated chromosomes, no special structure is visible in the axial region except random profiles of fibrils similar to those seen in the loops of the same preparations.
3. Two strands sometimes connect adjacent chromomeres. Where gaps exist along the axis, after stretching of the chromosomes, a loop occasionally straddles the break and returns to a chromomere on each side.
Histochemical Demonstration of Protein-Bound Alpha-Acylamido Carboxyl Groups
Authors: Barrnett Russell J. , Seligman Arnold M. 
Published: May 2004

A method has been developed to demonstrate the alpha-acylamido carboxyl groups of protein, taking advantage of the fact that acylamido carboxyl groups are converted to ketonic carbonyls by the action of acetic anhydride and absolute pyridine. The method utilizes deparaffinized sections of tissues fixed in a variety of fixatives. Following the conversion of carboxyls to the methyl ketones, the latter are stained with 2-hydroxy-3-naphthoic acid hydrazide.
Control experiments have indicated that methylation of carboxyls prevented staining, as did carbonyl reagents after the carboxyls were transformed to methyl ketones. Leucofuchsin did not stain the ketonic carbonyls, and only elastic tissue stained with 2-hydroxy-3-naphthoic acid hydrazide without the previous use of the catalyzed reaction with anhydride.
A brief survey of the reaction on various tissues of the albino rat was made, and the effects of various fixatives were assayed. Of particular interest were certain sites, such as acidophiles of the anterior pituitary gland, where an intense reaction occurred. The possibility exists that certain specific proteins rich in terminal acylamido carboxyl groups, by virtue of their protein side chains or low molecular weight, may be demonstrated by this method.
The Fine Structure of Endothelium of Large Arteries
Authors: Buck R. C. 
Published: May 2004

Endothelium of large arteries from several species was studied in thin sections with the electron microscope. Before sacrifice, some animals received an intravenous injection of colloidal thorium dioxide which was visualized in the sections. Surface replicas were prepared by carbon evaporation on either frozen-dried endothelium or on endothelium dried by sublimation of naphthalene with which the tissue had been impregnated. Cell boundaries, stained with silver, were observed in sections and also from the surface by stripping off the inner part of the endothelium.
In addition to the usual cytoplasmic organelles, the endothelial cells showed certain characteristic features, namely, large invaginated pockets communicating with the arterial lumen, numerous much smaller vesicular structures immediately under the plasma membrane and apparently also communicating with the lumen, and inclusions, into which injected thorium particles were incorporated. Intercellular boundaries appeared as regular double membranes in thin sections, and they were outlined by a double row of silver granules after silver staining. No evidence was obtained of permeation of intracellular spaces by colloidal thorium.
A Cytochemical Study on the Pancreas of the Guinea Pig
Authors: Siekevitz Philip , Palade George E. 
Published: May 2004

Microsomes were isolated from the pancreas of starved and fed guinea pigs. In the first case, the gland was removed from animals starved for 48 hours; in the second, the pancreas was excised 1 hour after the beginning of a meal that ended a fast of 48 hours. These are referred to below as fed animals. In both cases the tissue was homogenized in 0.88 M sucrose and the microsomes obtained by centrifuging the mitochondrial supernatant at 105,000 g for 60 minutes.
In starved animals the content of the endoplasmic reticulum of the exocrine cells and the content of the microsomes were found to be of low or moderate density. In fed guinea pigs the cavities of the reticulum frequently contained dense intracisternal granules and the microsomes were distinguished by a content of high density sometimes in the form of recognizable intracisternal granules.
In starved animals, the microsomes were found to account for 5 to 20 per cent of the trypsin-activatable proteolytic activity and ribonuclease activity of the whole cell, whereas in fed animals they contained uniformly almost 30 per cent of these activities.
In fed animals the dense, cohesive content of the microsomes (intracisternal granules) could be isolated by breaking up the microsomes with dilute (0.1 per cent) deoxycholate solutions and separating microsomal subfractions by differential centrifugation. The specific enzymatic activities of a heavy microsomal subfraction rich in intracisternal granules were almost equal to those of isolated purified zymogen granules. The ribonucleoprotein particles attached to the microsomal membranes could be isolated by the same technique and found also to exhibit some of the same enzymatic activities. Corresponding subfractions isolated from the microsomes of starved animals were considerably less active.
The relevance of these findings for the synthesis and intracellular transport of protein in the exocrine cell of the pancreas is discussed.
Structural Alterations in Nerve Fibers Produced by Hypotonic and Hypertonic Solutions
Authors: Robertson J. David 
Published: May 2004

In sections of KMnO4-fixed, developing mouse sciatic nerves, the central gap of mesaxons in myelinating fibers is normally closed with close apposition of the outside ∼20 A dense strata of the two ∼75 A Schwann cell membranes. The two combined outside strata make the intraperiod line bisecting each myelin lamella. The ∼150 A mesaxon is elaborated spirally around the axon in either a right hand or left hand spiral, and its inside (cytoplasmic) ∼20 A strata in apposition form the major dense lines of myelin. In hypotonic solutions the lamellae of adult frog sciatic myelinated fibers split apart along the outside membrane strata apposed at the intraperiod line throughout the spiral. Under similar conditions the inside (cytoplasmic) strata of the membranes, in apposition at the major dense lines, do not separate. The ∼150 A membranous structure resulting from this is called an "internal compound membrane."
The double membranes of normal and control frog sciatic unmyelinated fibers have a central gap ∼100 to 150 A wide. After soaking in 4 to 10 times normal strength Ringer solution or 10 N sucrose-Ringer solution, this gap closes and a membranous structure ∼150 A wide resembling developing mouse mesaxons results. This is designated by the term "external compound membrane." The latter membranes resemble internal compound membranes, but their central dense zones, each consisting of two apposed outside membrane strata, are less dense.
Intracellular Amounts of Nucleic Acids and Protein During Pollen Grain Growth in Tradescantia
Authors: Woodard John W. 
Published: May 2004

The rapid growth, large organelles, and synchronous development of T. paludosa pollen grains make them ideal subjects for cytochemical analysis. A microphotometric study of the nucleoli, chromosomes, and cytoplasm fixed at daily intervals during pollen grain maturation indicated that:
1. DNA (Feulgen) synthesis in the generative nucleus occurred during the first third of interphase, while the DNA content of the vegetative nucleus remained unchanged.
2. Throughout development, changes in RNA (azure B) content, in general, paralleled changes in protein (NYS1, Millon) content in each organelle of the vegetative cell. Initially, the RNA and protein of all organelles increased up to mid interphase, when chromosomal and nucleolar fractions began to decline despite a continued increase in cytoplasmic RNA and protein. At least 24 hours before anthesis, the vegetative nucleolus had disappeared and chromosomal protein and RNA of the vegetative nucleus were apparently in rapid decline. Such a system offered an opportunity to study the role of the nucleus, especially the nucleolus, in RNA and protein metabolism in the cytoplasm, by noting what cytoplasmic processes could and could not continue at a time when nuclear mechanisms were absent or minimal. It was found that at least 2 fundamental processes continued during this period: both RNA and protein accumulated in the cytoplasm at a rapid rate.
It was concluded that the nucleus is not the sole source of cytoplasmic RNA, for the data suggest that there are at least 2 separate and independent, or remotely dependent synthesizing systems, one nuclear and the other cytoplasmic. It is evident that nuclear influence on cytoplasmic synthesis need be neither direct nor immediate.
Cytological Effects of Prefixation Treatment
Authors: Hungerford David A. , DiBerardino Marie 
Published: May 2004

The effects produced by prefixation treatments on cells in metaphase from 10-day mouse fetuses and from several embryonic stages of the frog were investigated. The technical value of some of these pretreatments is noted.
Pretreatment with isotonic solutions (both ionic and non-ionic in the case of the mouse, ionic only in the frog) generally produced a similar effect, viz., chromosomal swelling with little effect on the spindle. A notable exception is provided by frog embryos preceding the neurula stage; spindle disorganization without chromosomal swelling was produced by pretreatment in isotonic modified Niu-Twitty solution, containing no divalent cations.
Pretreatment with hypotonic solutions (both ionic and non-ionic in the case of the mouse, ionic only in the frog) generally produced several major effects, viz., despiralization of chromosomes, chromatid separation, and spindle disorganization. The conclusion is drawn from the mouse data that, in order to produce these effects, pretreating solutions must be of low osmotic pressure. Low ionic strength alone (e.g., isotonic sucrose solutions) is not sufficient.
As differentiation of frog embryos progressed, pretreatments either of longer duration or with solutions of increasing degrees of hypotonicity were required to produce comparable intensities of the same effects.
Many of the effects on metaphases produced by hypotonic pretreatment of frog embryos were reversible by subsequent exposure to isotonic solutions.
The significance of results presented here is discussed briefly with respect to some current considerations of the macromolecular structure of chromosomes.
An Electron Microscope Study of Smooth Muscle in Pregnant Uterus of the Rabbit
Authors: Shoenberg C. F. 
Published: May 2004

In the smooth muscle of the rabbit uterus one type of myofilament can be found; this is about 50 A thick.
In the sarcoplasmic reticulum there are smooth walled vesicles and many vesicles with particles attached. It is suggested that these particles may correspond to the ribonucleoprotein-containing particles of Palade and Siekevitz. The diameter of the particles is 250 A. There are also unattached particles some of which may be glycogen.
The membranes of the muscle cells and the connective tissue lying between them are described.
Spermatogenesis in Animals as Revealed by Electron Microscopy
Authors: Yasuzumi G. , Tanaka Hiroaki 
Published: May 2004

This paper reports an electron microscope study of typical and atypical spermatogenesis in the pond snail, Cipangopaludina malteata.
In the typical spermatid the nucleus undergoes profound changes as development proceeds, affecting both its form and internal fine structure. A large number of roughly parallel, dense filaments, arranged along the long axis of the nucleus, fuse with each other to form in the end the homogeneous helical body characteristic of the head of the adult spermatozoa. The nebenkern is apparently mitochondrial in nature and, in its early development, is similar to that of insects except that it appears as a double structure from the beginning. As differentiation proceeds, the mitochondria lose their membranes, and the residual, now denuded cristae, reorganize to give a parallel radial arrangement. In the last stages of development, the nebenkern derivations become applied to the sheath of the middle piece in a compact helical fashion.
In the development of the atypical spermatozoa, the nucleus fails to differentiate and simply shrinks in volume until only a remnant, devoid of DNA, is left. The cytoplasm shows numerous vesicles containing small Feulgen-positive bodies, 80 to 130 mµ in diameter. These vesicles plus contents increase in number as spermatogenesis proceeds. The "head" structure of the atypical spermatozoa consists of a bundle (7 to 17) of tail flagella, each with a centriole at its anterior end. The end-piece of the atypical form appears brush-like and is made up of the free ends of the several flagella.
The Relation between the Axial Complex of Meiotic Prophase Chromosomes and Chromosome Pairing in a Salamander (Plethodon cinereus)
Authors: Moses Montrose J. 
Published: May 2004

An investigation of the structure of meiotic chromosomes from primary spermatocytes of two salamanders, Plethodon cinereus and Desmognathus fusca, has been made using correlated light and electron microscopy. Feulgen squashes were compared with stained sections and these related to adjacent thin sections in the electron microscope. A transition from the familiar cytological preparation to the electron image was thus effected.
A linear complex consisting of three parallel strands has been observed with the electron microscope, passing along the central axis of primary spermatocyte chromosomes. The complex is similar to that found in comparable chromosomes from at least a dozen animal species. The structure in Plethodon is described in detail.
Synapsis has been positively identified as the stage of meiotic prophase at which the complex occurs. Thus the complex is a part of bivalent chromosomes. It has not been seen in other stages or other divisions and is thus thought to be exclusively of synaptic occurrence. The term synaptinemal complex is suggested for the entire structure.
By virtue of the material condensed around it, the complex is also seen in the light microscope where it appears as a fine, densely Feulgen-positive central core along the chromosome. The complex is thus closely associated with DNA, if not at least in part, composed of it.
In the stages studied, homologous chromosomes are not always completely paired. The lateral elements of the complex separate and follow the single chromosome axes at these points. The central element disappears and thus may be a phenomenon of pairing. It is concluded that the lateral elements of the synaptinemal complex may more correctly be a "core" of the single meiotic prophase chromosome, possibly being concerned with its linear organization.