bluuebunny/crossref_metadata_2025_split huggingface dataset:
ELECTRON MICROSCOPY OF CARTILAGE AND BONE MATRIX AT THE DISTAL EPIPHYSEAL LINE OF THE FEMUR IN THE NEWBORN INFANT
Authors: Robinson Robert A. , Cameron D. A. 
Published: May 2004

An examination of the fine structure of cartilage and bone matrix at the distal epiphyseal line of the femur of a newborn infant has revealed the following information.
Cartilage matrix is composed of a network of widely spaced fibers without obvious periodic banding. Calcification is first seen about the level of the third chondrocyte capsule distal to the furthest penetration of the capillaries. It starts as a haphazard deposition of crystals which have no obvious relationship to the location of the fibers. The process of calcification is completed before ossification commences but the central zone of matrix remains only partly mineralized.
Bone matrix is formed over a bar of calcified cartilage. Fibers, recognizable as collagen, are deposited in a loose network in a narrow zone between the osteoblasts and cartilage. These fibers are 2 to 5 times as wide as the fibers in epiphyseal cartilage. Calcification then begins in the osteoid, crystals being first laid down irregularly on or close to the fibers. As they increase in number, the crystals tend to line up along the fibers and eventually are arranged so that the periodicity of the underlying collagen is emphasized. In such an area the fibers are more tightly packed than when uncalcified.
There is no change observed in the calcified cartilage at this level.
The extracellular matrices of this epiphyseal cartilage and bone can be distinguished from one another in the electron microscope.
"MICROBODIES" AND THE PROBLEM OF MITOCHONDRIAL REGENERATION IN LIVER CELLS
Authors: Rouiller C. , Bernhard W. 
Published: May 2004

The cytoplasm of the hepatic cell contains, besides the well known organelles, microbodies, characterized by a single membrane, a finely granular matrix, and average dimensions below those of mitochondria.
Microbodies, rare in normal cells, become more numerous in regenerative livers and in various pathological conditions. In these cases, they either evolve towards degenerative forms or else show structural modifications corresponding to transitional forms between them and mitochondria. This suggests to us that the microbodies can be precursors of mitochondria.
MITOCHONDRIAL STRUCTURE IN SITES OF STEROID SECRETION
Authors: Belt W. Duane , Pease Daniel C. 
Published: May 2004

1. Mitochondria of the adrenal gland, corpus luteum, theca interna and granulosa of the graafian follicle, interstitial cells of the testis, and placenta of the rat have been studied with the electron microscope.
2. In most sites of steroid secretion, the internal structure of the mitochondria is in the form of tubular reflections of the internal mitochondrial membrane, rather than plate-like cristae.
3. The mitochondria of the adrenal gland have a highly variable size, even within a single cell; they may reach 2 to 3 µ in diameter, and are nearly filled with tubules.
4. It is suggested that while mitochondria in many places have a tubular component, those in the adrenal gland are highly specialized by virtue of their giant size and their internal structure.
A POSSIBLE MECHANISM FOR THE MORPHOGENESIS OF LAMELLAR SYSTEMS IN PLANT CELLS
Authors: Hodge A. J. , McLean J. D. , Mercer F. V. 
Published: May 2004

A mechanism for the formation of lamellar systems in the plant cell has been proposed as a result of electron microscope observations of young and mature cells of Nitella cristata and the plastids of Zea mays in normal plants, developing plants, and certain mutant types. The results are compatible with the concept that lamellar structures arise by the fusion or coalescence of small vesicular elements, giving rise initially to closed double membrane Structures (cisternae). In the chloroplasts of Zea, the cisternae subsequently undergo structural transformations to give rise to a compound layer structure already described for the individual chloroplast lamellae.
During normal development, the minute vesicles in the young chloroplast are aggregated into one or more dense granular bodies (prolamellar bodies) which often appear crystalline. Lamellae grow out from these bodies. In fully etiolated leaves lamellae are absent and the prolamellar bodies become quite large, presumably because of inhibition of the fusion step which appears to require chlorophyll. Lamellae develop rapidly on exposure of the plant to light, and subsequent development closely parallels that seen under normal conditions. The plastids of white and very pale green mutants of Zea similarly lack lamellae and contain only vesicular elements. A specialized peripheral zone immediately below the double limiting membrane in Zea chloroplasts appears to be responsible for the production of vesicles. These may be immediately converted to lamellae under normal conditions, but accumulate to form a prolamellar body if lamellar formation is prevented, as in the case of etiolation and chlorophyll-deficient mutation, or when the rate of lamellar formation is slower than that of the production of precursor material (as appears to be the case in the early stages of normal development).
CYTOCHEMICAL STUDIES OF MITOCHONDRIA
Authors: Siekevitz Philip , Watson Michael L. 
Published: May 2004

1. Mitochondria isolated from rat liver were disrupted with 0.3 per cent deoxycholate and a number of subfractions were isolated from this preparation by differential centrifugation.
2. The protein N, RNA and phospholipide content, as well as the succinoxidase, cytochrome c oxidase, adenylate kinase, and DPNH-cytochrome c reductase of these fractions were determined.
3. Two of these subfractions, found to consist of mitochondrial membranes (2), contained ∼ 12 per cent of the protein N and ∼ 35 per cent of the phospholipide of the whole mitochondria and accounted for ∼ 70 per cent of the succinoxidase and cytochrome c oxidase activity of the original mitochondrial preparation. There was no discernible adenylate kinase, DPNH-cytochrome c reductase, or phosphorylating activities in these fractions, nor could they oxidize other substrates of the Krebs's cycle.
4. The most active fraction (60 minutes at 105,000 g pellet) had a higher phospholipide/protein value than the whole mitochondria and showed a seven-to elevenfold concentration of succinoxidase and cytochrome c oxidase activities.
5. Evidence has been given to indicate that the various components of the succinoxidase complex are present in this membrane fraction in the same relative proportions as in the whole mitochondria.
6. The implications of these findings are discussed.
ELECTRON MICROSCOPIC AND HISTOCHEMICAL OBSERVATIONS OF MUSCLE DEGENERATION AFTER TOURNIQUET
Authors: Moore Dan H. , Ruska Helmut , Copenhaver Wilfred M. 
Published: May 2004

As an experimental model for the different forms of muscle degeneration, injury caused by 2 hours' ischemia has been studied from 20 minutes to 16 hours after release of the tourniquet.
Discoid degeneration developed in stretched fibers by dissolution of the I bands (Z substances and actin). The discs represented the Q bands (A-H-A). In fibers which passively maintained contraction lengths during degeneration, the Z substances were dissolved, but the continuity of the fibrils was preserved, since the filaments are continuous over all sarcomeres under these conditions. Mitochondria and the tubules of the endoplasmic reticulum swelled, ruptured, and disintegrated. Granular degeneration developed in fibers where mitochondria were abundant. Unstretched degenerating fibers with few mitochondria gave a homogeneous or hyaline appearance. The different forms of degeneration therefore were dependent on the status of stretch and the fiber type. The extent of degeneration was not a function of time after ischemia, there being both nearly normal and severely damaged fibers at 20 minutes and 16 hours after the release of tourniquets. When degeneration occurred, however, the basic alterations were the same in all fibers; there was mitochondrial and reticular swelling, dissolution of the Z substances, and finally disintegration of the contractile material. Some damage developed in the sarcolemmas and capillaries.
The mitochondrial disintegration was not linked with inactivation of the succinic dehydrogenase system.
LYTIC ACTIVITIES IN RENAL PROTEIN ABSORPTION DROPLETS
Authors: Miller Fritz , Palade George E. 
Published: May 2004

The digestive cycle following reabsorption of hemoglobin by cells of the proximal convoluted tubules in mouse kidney and the uptake of ferritin by glomerular mesangial cells in the kidney of normal and nephrotic rats were investigated by electron microscopical histochemical procedures.
Mouse kidneys, sampled at closely spaced time points between 1 to 48 hours after intraperitoneal injection of hemoglobin, and rat (normal and nephrotic) kidneys, sampled at 30 minutes, 2 hours, and 48 hours after intravenous injection of ferritin, were fixed in glutaraldehyde, cut at 50 µ on a freezing microtome, incubated for acid phosphatase and thiolacetate-esterase, and postfixed in OsO4. Satisfactory preservation of fine structure permitted the localization of the enzymatic reaction products on cell structures involved in uptake and digestion of exogenous proteins. The latter were identified either by their density (hemoglobin) or their molecular structure (ferritin).
It was found that lysosomal enzymic activities and incorporated exogenous proteins occur together in the same membrane-bounded structures. In the cells of the proximal convolution, lytic activities become demonstrable within 1 hour after hemoglobin injection, appear first in apical vacuoles filled with hemoglobin, and persist in fully formed protein absorption droplets. At the end of the lytic cycle (∼48 hours post injection), the cells have an increased population of polymorphic bodies which exhibit lytic activities. In smaller numbers, identical bodies occur in controls. It is concluded that they represent remnants of previous digestive events.
The means by which the resorptive vacuoles acquire hydrolytic activities remain unknown. Fusion of newly formed vacuoles with residual bodies was not seen, and hemoglobin incorporation into such bodies was only occasionally encountered. Acid phosphatase activity was found sometimes in the Golgi complex, but enzyme transport from the complex to the resorbing vacuoles could not be established. Autolytic vacuoles containing mitochondria or mitochondrial remnants were frequently found during the early stages of hemoglobin resorption, but no definite conclusions about the mechanism involved in the segregation of endogenous material were obtained.
In nephrotic rats ferritin was segregated in membrane-bounded bodies mainly in the mesangial cells and to a lesser extent in epithelial and endothelial cells. Most of these sites were marked by the reaction products of acid phosphatase and organophosphorus-resistant esterase and therefore identified as lysosomes connected with the digestion of incorporated exogenous proteins.
THE STRUCTURE OF THE SMOOTH MUSCLE FIBRES IN THE BODY WALL OF THE EARTHWORM
Authors: Hanson Jean 
Published: May 2004

1. The structure of the smooth muscle fibres in the longitudinal muscle coat of the body wall of Lumbricus terrestris has been investigated by phase contrast light microscopy and electron microscopy.
2. The muscle fibre is ribbon-shaped, and attached to each of its two surfaces is a set of myofibrils. These are also ribbon-shaped, and they lie with their surfaces perpendicular to the surfaces of the fibre, and their inner edges nearly meeting in the middle of the fibre. These fibrils are oriented at an angle to the fibre axis, and diminish greatly in width as they approach the edge of the fibre. The orientation of the set of fibrils belonging to one surface of the fibre is the mirror image of that of the set belonging to the other surface; thus, when both sets are in view in a fibre lying flat on one face, the fibre exhibits double oblique striation. A comparison of extended and contracted fibres indicates that as the fibre contracts, the angle made between fibre and fibril axes increases (e.g. from 5 to 30°) and so does the angle made between the two sets of fibrils (e.g. from 10 to 60°).
3. The myofibril, throughout its length, contains irregularly packed filaments, commonly 250 A in diameter, which are parallel to its long axis and remain straight in contracted muscles. Between them is material which probably consists of much finer filaments. Thus A and I bands are absent.
4. Bound to one face of each fibril, but not penetrating inside it, is a regularly spaced series of transverse stripes. They are of two kinds, alternating along the length of the fibril, and it is suggested that they are comparable to the Z and M lines of a cross-striated fibril. The spacing of these stripes is about 0.5 µ ("Z" to "Z") in extended muscles, and 0.25 µ in contracted muscles. A bridge extends from each stripe across to the stripeless surface of the next fibril.
The Nucleolus and Parachromatin of the Ascites Tumor Cell
Authors: Love Robert 
Published: May 2004

1. A method is described for distinguishing the ribonucleoproteins of the nucleolus and parachromatin of ascitic tumor cells of the mouse.
2. In these cells the transfer of ribonucleoprotein from the nucleus to the cytoplasm can occur in two ways. (a) At the end of prophase the nucleolus separates from the chromosomes and nucleolar fragments are released into the cytoplasm. (b) During prophase the parachromatin is aggregated to form parachromatin bodies which are discharged into the cytoplasm, where they can be detected during metaphase, anaphase, and telophase.
3. A metachromatic form of RNA is demonstrable, and may be synthesized, in close relation to the chromosomes during prophase, metaphase, and anaphase. During telophase the distribution of metachromatic RNA changes, the chromatin loses its metachromasia, and intranuclear metachromatic parachromatin becomes evident.
ELECTRON MICROSCOPY OF STRUCTURAL DETAIL IN FROZEN BIOLOGICAL SPECIMENS
Authors: Steere Russell L. 
Published: May 2004

A procedure is described whereby preshadowed replicas can be obtained from frozen biological specimens which have been cut and then etched by sublimation of the ice from their surfaces. Electron micrographs showing details of the internal structure of plant virus crystals are presented to demonstrate the values of the procedure. Crystals of purified tobacco ringspot virus and squash mosaic virus and some portions of turnip yellow mosaic virus crystals have been shown to exhibit hexagonal packing. Sections through in situ crystals of tobacco mosaic virus show the rods to be parallel within each layer and arranged in a square net as viewed end on. Individual rods in each layer of the latter measure 300 mµ in length and are somewhat tilted with respect to the rods of adjacent layers. This results in the formation of a herring-bone appearance when a crystal is cut perpendicular to its hexagonal face.
It is suggested that the procedure outlined here might well serve to supplement other procedures for the preparation of many cytological specimens for electron microscopy.
A CHROMATOGRAPHIC STUDY OF HYDROLYSIS IN THE FEULGEN NUCLEAL REACTION
Authors: Woods Philip S. 
Published: May 2004

In a study on Feulgen hydrolysis of frozen-dried alcohol-fixed lily anthers, a chromatographic technique was developed to analyze the acid hydrolysate for some of the degradation products of nucleic acid. Hydrolysis was accomplished by 10 per cent perchloric acid at 20°C., and a typical hydrolysis time-Feulgen intensity curve was obtained, with maximum staining occurring at 19 hours. Microphotometric measurements indicated that the amount of stain per nucleus was no different from amount in nuclei fixed and hydrolyzed by more conventional procedures.
Uracil-containing material (from ribonucleic acid) was almost completely separated from thymine-containing material (deoxyribonucleic acid) of tissue sections by acid treatment for 1½ hours. Adenine (purines), as the base, was effectively all removed from the deoxyribonucleic acid at the time of optimum hydrolysis. Detectable amounts of thymine-containing material appeared in the hydrolysate shortly after the onset of hydrolysis; and the amount increased rapidly with increased hydrolysis time. At the time of optimum hydrolysis approximately two-thirds of the total deoxyribonucleic acid thymine was lost. The removal of these thymine-containing fragments was linear with respect to time during the first 24 hours and occurred at a relatively high rate. Removal after 24 hours was also linear but was at a markedly lower rate. These results would suggest that two kinds of deoxyribonucleic acid exist in lily anthers; an acid-labile fraction amounting to approximately three-fourths of the total, and an acid-resistant fraction making up the remainder. In the Feulgen procedure much of the labile fraction is lost by the time of optimum hydrolysis and is not stained; most of the stable fraction remains in the tissue and is stained. In light of these findings the use of the Feulgen method as a means of determining cytochemically relative amounts of deoxyribonucleic acid in nuclei by measuring their Feulgen dye content was discussed.
THE FINE STRUCTURE OF NUCLEI DURING SPERM MATURATION IN THE LOCUST
Authors: Gibbons I. R. , Bradfield J. R. G. 
Published: May 2004

1. In the heads of maturing sperm of a locust the chromatin becomes arranged in a highly regular manner so as to produce many parallel lines about 60 A thick in longitudinal section and contiguous polygons in transverse section.
2. This configuration appears after fixation in osmium tetroxide, formaldehyde, or acetic acid; intermediate stages in its development are illustrated.
3. These electron micrographs are interpreted to mean that, during sperm maturation, the chromatin becomes formed into sheets and then into tubes running parallel with the long axis.
4. In the mature sperm head we have been unable so far to detect this structure. This may be because the chromatin becomes so compact during the shrinkage of the nucleus which occurs during formation of the mature sperm.
THE NUTRITION OF ANIMAL TISSUES CULTIVATED IN VITRO
Authors: Morgan Joseph F. , Morton Helen J. 
Published: May 2004

1. The amino acid requirements of freshly explanted chick embryonic heart tissues cultivated in completely synthetic media have been determined, employing a nutritional depletion technique. Arginine, histidine, lysine, tyrosine, tryptophan, phenylalanine, cystine, methionine, threonine, leucine, and valine were found to be essential. Serine, isoleucine, glycine, and glutamine were found to be non-essential. Glutamic acid, aspartic acid, α-alanine, proline, and hydroxyproline were found to be inhibitory in this test system.
2. A total amino acid level of approximately 100 mg. per cent was found to be optimal and DL-amino acids were found to be non-toxic, unless used in high concentrations.
3. A comparison has been made of the amino acid requirements of various types of tissue cultures, of the chick, and of man and certain differences in these requirements have been discussed.
AN ELECTRON MICROSCOPE STUDY OF THE MORPHOLOGY AND DISTRIBUTION OF THE INTRACYTOPLASMIC "VIRUS-LIKE" PARTICLES OF EHRLICH ASCITES TUMOR CELLS
Authors: Adams W. Robert , Prince Alfred M. 
Published: May 2004

Electron microscope studies of eight different sublines of Ehrlich ascites tumor cells which had not, as far as could be determined, come in contact with any known virus, revealed dense particles measuring approximately 55 to 70 mµ in diameter, both within and attached to the wall of cytoplasmic vesicles identified as the endoplasmic reticulum.
All tumor sublines contained significant numbers of particles and revealed no qualitative or quantitative differences in particle morphology or distribution.
It is concluded that these structures are a constant morphological component of the Ehrlich ascites tumor and that they probably do not represent contaminating virus. Their morphology and distribution are described, and the possible interpretations of their significance are discussed.
AUTORADIOGRAPHIC STUDIES OF THE UTILIZATION OF S35-SULFATE BY THE CHICK EMBRYO
Authors: Johnston Perry M. , Comar Cyril L. 
Published: May 2004

From studies of autoradiograms of various developmental stages of the chick embryo containing S35 given us sulfate it was determined that as early as Stages 3+ and 4 there is a selective utilization or accumulation of sulfate by the various parts. The earliest accumulation site is the axial portion of the primitive streak and the floor of the groove. Later S35 was found in the head process, Hensen's node, notochord, amniocardiac vesicle, wall of the omphalomesenteric vein, endocardium, subendocardial jelly, mesenchyme destined to become cartilage, basement membrane area of the gut, and a mucopolysaccharide layer formed on the free surface of the stomach.
The early notochordal localizations of S35 coincide with the region in which a thin ring of chondroitin sulfate is subsequently laid down. However, it is apparent that there is an intracellular accumulation of inorganic sulfate by the chondroitin-forming cells prior to the time they produce sufficient chondroitin sulfate to be demonstrable histochemically.
It was interesting to note that the endocardium appears to concentrate sulfate that later apparently finds its way into the subendocardial jelly.
The fact that those mesenchymal cells which later form chondroblasts begin to utilize sulfate selectively before histological differentiation is apparent was determined.
In addition, the presence of sulfate-containing substances in the forming basement membrane of the gut would seem to indicate that sulfate is important in the histological differentiation of this membrane.
ELECTRON MICROSCOPE STUDY OF THE VITELLINE BODY OF SOME SPIDER OOCYTES
Authors: Sotelo J. Roberto , Trujillo-Cenóz Omar 
Published: May 2004

The structure of the vitelline nuclei of Lycosidae and Thomisidae was described as follows: Vitelline nuclei are constituted of two parts: (a) a peripheral layer (vitelline body cortex), and (b) a central core. The vitelline body cortex is demonstrated to be formed by many cisternae of the endoplasmic reticulum among which mitochondria and Golgi elements are intermingled. The central core is made up mainly of a special type of body described under the name of "capsulated body." Capsulated bodies comprise a capsular layer, limited by a membrane, and two central masses called "geminated masses," each one limited by a double membrane. Irregular masses of closely packed vesicles are found in some cases among the capsulated bodies and free vesicles are present in large numbers.
The optical properties of the vitelline body cortex compared with the electron microscope findings lead us to the concept that this layer is a "composite body" according to Weiner's theory.