bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron Microscope Study of DNA-Containing Plasms
Authors: Kellenberger Edouard , Ryter Antoinette , Séchaud Janine 
Published: May 2004

The nucleoids of Escherichia coli, independently of the physiological state of the bacteria, are shown to be preserved as a fine-stranded fibrillar nucleoplasm by an OsO4 fixation under defined conditions: acetate-veronal buffer pH 6, presence of Ca++ and amino acids, stabilization with uranyl-acetate before dehydration. The same fixation procedure applied to the DNA of vegetative phage reveals a pool of homogeneous fibrillar structure very similar to the nucleoplasm. The "versene test," which produces a coarse coagulation of these plasms, emphasizes the similar behaviour of the pool and the nucleoids.
The heads of mature phage are preserved in their true polyhedral shape by the standard fixation procedure, although they may be badly distorted when fixed under different conditions. Lanthanum nitrate and uranyl-acetate are shown to increase markedly the contrast of both phage and cytoplasm.
The consequences of the fibrillar structure of the genetic material are discussed in relation to the probable division process.
The Cytochemical Localization of Oxidative Enzymes
Authors: Scarpelli D. G. , Hess R. , Pearse A. G. E. 
Published: May 2004

Cytochemical methods involving metal chelation of the formazan of an N-thiazol-2-yl tetrazolium salt are described for the localization of diphosphopyridine nucleotide diaphorase (DPND) and triphosphopyridine nucleotide diaphorase (TPND) in mitochondria. These methods utilize the reduced coenzymes DPNH or TPNH as substrate. The reaction involves a direct transfer of electrons from reduced coenzyme to the respective diaphorase which in turn transfers the electrons to tetrazolium salt, reducing it to the insoluble formazan. Competition for electrons by preferential acceptors in the respiratory chain was prevented by various inhibitors. In the presence of respiratory inhibitors the rate of tetrazolium reduction was markedly increased. The greatest reduction was observed when amytal was used.
Sites of diaphorase activity appeared as deposits of blue-black metal formazan chelate measuring 0.2 to 0.3 µ in diameter. Small mitochondria contained 2 deposits, while larger ones contained up to 6.
Considerable differences were observed in the rate of tetrazolium reduction and cellular localization of diaphorase activity when DPNH was used as substrate as compared to TPNH. In each instance DPNH was oxidized more rapidly by tissues than TPNH. These findings support the concept that the oxidation of coenzymes I and II is mediated through separate diaphorases.
Adenosinetriphosphatase Activity in the Cell Membranes of Kidney Tubule Cells
Authors: Spater Herman W. , Novikoff Alex B. , Masek Bertha 
Published: May 2004

This cytochemical study demonstrates high levels of apparent ATPase activity in the infolded cell membranes of the proximal tubules (dog, rat, human, mouse, monkey, and opossum) and ascending loops of Henle (dog, rat, human and, to a variable degree, mouse). Electron microscopy has shown (see Rhodin (1)) that these membranes separate adjacent cells where they interlock with one another by multiple cytoplasmic lamellae containing oriented mitochondria. The significance of the high ATPase activity is considered in relation to possible movements of the membranes and to "active transport" believed to occur there.
In the rat, enzyme activity in the proximal tubule membranes does not survive formol-calcium fixation, and it is therefore necessary to use unfixed sections for its demonstration. However, in edematous rats with experimental nephrosis (induced by the injection of aminonucleoside or with antikidney serum) marked ATPase activity is exhibited in these membranes even after formol-calcium fixation.
When proximal tubule or Henle loop cells of the dog acquire an altered metabolism, as indicated by accumulated lipide spheres or by "droplets," the infolded ATPase-rich membranes are no longer demonstrable.
Structure and Mode of Formation of the Nucleolus in Meristematic Cells of Vicia faba and Allium cepa
Authors: Lafontaine J. G. 
Published: May 2004

Interphase nucleoli from Vicia faba and Allium cepa meristematic cells are roughly classified into two categories: (a) those that commonly show a rather homogeneous texture (except for small light spaces of various sizes) and frequently contain dense particles 140 A in diameter; (b) those found more frequently in Vicia characterized by a very sharp boundary between a dense outer cortex and a much lighter central core. The dense particles are not found in such nucleoli. In Allium the boundary is more irregular and dense particles are sometimes observed in the outer layer. Many nucleoli show a structure intermediate between these two types. They are characterized by a gradient of increasing density from the center to the periphery and occasionally contain dense 140 A granules.
During interphase, certain nucleoli are closely associated with segments of chromatin strands which undoubtedly represent nucleolar organizing regions.
The dense 140 A granules are followed during the mitotic cycle. In Allium, they are first seen in loose clusters between arms of late anaphase chromosomes where they become more concentrated in early telophase. The substance within which they are scattered slowly increases in density during that time until finally, the particles are limited to small bodies of distinctive character. Evidence is presented suggesting that these small prenucleolar bodies fuse during telophase to give rise to the mature interphase nucleoli.
Similar events are described in Vicia material except that a coating of dense substance appears around telophase chromosomes before the formation of prenucleolar bodies.
Fine Structure and Function in Stentor polymorphus
Authors: Randall J. T. , Jackson Sylvia Fitton 
Published: May 2004

The fine structure of the ciliate Stentor has been studied by means of the electron microscope and the results have been correlated with observations made on the living organism by means of light microscopy; special reference has been made to structural features which may be responsible for contraction and extension in Stentor.
Descriptions have been given of the structure of the macronucleus, the vacuolated cytoplasm, mitochondria and the pellicle; a detailed study has also been made of the adoral membranelles. About 250 membranelles encircle the peristomal cap and each is composed of 3 rows of cilia, with 20 to 25 cilia in each row; a fibrillar root system connected with the membranelles depends into the endoplasm for about 20 µ and each is essentially in the shape of a fan, the terminal ends of each root bifurcating to connect to neighbouring roots. The membranelles thus form a cohesive unit and this morphological arrangement may have a bearing on the motion and coordination of the whole system.
Two structural features extending throughout the length of the animal have been identified per cortical stripe in the body wall of Stentor; first, km fibres lying just beneath the pellicle are composed of stacks of fibrillar sheets and are identical with the birefringent fibres observed in the living animal. The individual fibrils of the sheets are in turn connected to the kinetosomes of the body cilia; thus the km fibres are homologous to kinetodesmata. Secondly, M bands lie beneath the km fibres and form an interconnected system in contact with the surrounding vacuolated cytoplasm; the thickness of the M bands is greatest at the base of a contracted animal. The contractile and extensile properties of these organelles have been discussed in the light of experimental results and theoretical considerations.
RETARDATION OF PERIPHERAL NERVE MYELINATION IN MICE TREATED WITH INHIBITORS OF CHOLESTEROL BIOSYNTHESIS
Authors: Rawlins Frank A. , Uzman Betty G. 
Published: May 2004

The effect of two inhibitors of cholesterol biosynthesis, triparanol and AY 9944, on peripheral nerve myelination, was studied. Suckling mice were intraperitoneally injected with both drugs on 3 consecutive days and were sacrificed 6 hr after the last injection; others were suckled by an injected mother and sacrificed at 2½ days of age. A single mouse which had been injected with both drugs at 1, 2, and 3 days of age was sacrificed 2 wk after the last injection.
Membranous and crystalline intracytoplasmic inclusions were observed in the Schwann cells of the sciatic nerves of all the experimental animals. Both the number of unmyelinated single axons and the number of myelin lamellae around each myelinating axon in the sciatic nerves were recorded for treated mice and of mice suckled by treated mothers.
The sciatic nerve of the experimental mice contained a larger proportion of unmyelinated single axons and smaller numbers of myelin lamellae around the myelinating axons, when compared with age-matched controls. The results suggest that a decrease of endogenous cholesterol in suckling mice may affect peripheral nerve myelination in two ways: by retarding the "triggering" of myelination in unmyelinated axons and by decreasing the rate of myelination already in progress.
LONG-TERM ORGAN CULTURE OF THE SALAMANDER HEART
Authors: Millhouse Edward W. , Chiakulas John J. , Scheving Lawrence E. 
Published: May 2004

Beating salamander hearts were maintained in tissue culture for periods ranging from 1 to 6 months. After 1, 3, or 6 months of culture, six hearts, along with six control hearts, were fixed for electron microscopy.
In control tissue, the sarcoplasmic reticulum usually demonstrated the normal pattern of paired, linearly arranged membranes, although in some cases, the reticulum showed a variation from these membranes to a series of small vesicles. There was no evidence of a T-system of tubules in any of the material examined. Desmosome-Z band complexes were observed in almost all sections of both control and experimental material. A possible role of these complexes in the excitation-contraction mechanism is discussed.
In 3 month cultured material, alterations in normal myofibrillar pattern occurred. Small segments of myofibrils branched from one Z band to join the Z band of an adjacent myofibril, or appeared to be fraying out into the sarcoplasm. In 6 month cultured material, myofibrils were fragmented into short segments from which myofilaments frayed out into the sarcoplasm. This filamentous material may be remnants of myofilaments.
Despite the morphological changes in myofibrils, the heart pulsation rate, established at the beginning, was maintained throughout the culture period. It is suggested that the alterations, observed in the experimental material, occurred in elements not essential for heart beat maintenance, or that these alterations have not yet progressed to a critical point of affecting the heart beat.
STUDIES ON SEEDS
Authors: Mollenhauer Hilton H. , Totten Clara 
Published: May 2004

At least two kinds of lipid vesicles are present in pea and bean cotyledons which can be recognized at seed maturity on the basis of whether they do or do not interassociate into lipid vesicle sheets. Those that do interassociate into sheets are also characterized by (a) their association with plastids or plasma membranes during dormancy, and (b) the unique transformation into flattened saccules that they undergo during the first few days of seed germination. These interassociated (or composite) lipid vesicles have been found in only a few seeds and may be restricted to certain classes of plants and/or certain states of cellular development.
Lipid vesicle-to-saccule transformation is predominantly confined to the germinating seed. However, some lipid vesicle-derived saccules are already present in some cells even before the seed reaches maturity. These partially transformed vesicles and saccules remain unchanged over dormancy, and then resume their transformation when the seed is germinated. This suggests that some stages of seed germination are already underway before the seed reaches maturity and are only resumed at seed germination.
The lipid vesicles that do not interassociate into sheets (i.e., the simple lipid vesicles) are present in all tissues at all states of cellular development. These vesicles do not undergo any conspicuous structural changes during development.
The Fibrinogen Molecule: Its Size, Shape, and Mode of Polymerization
Authors: Hall Cecil E. , Slayter Henry S. 
Published: May 2004

Improved electron micrographs of the shadow-cast bovine fibrinogen molecule have been obtained establishing its general morphology and dimensions in the dry state. It consists of a linear array of 3 nodules held together by a very thin thread which is estimated to have a diameter of from 8 to 15 A, though it is not clearly resolved. The two end nodules are alike but the center one is slightly smaller. Measurements of shadow lengths indicate that nodule diameters are in the range 50 to 70 A. The length of the dried molecule is 475 ± 25 A.
Adopting the molecular volume from previous physical chemical data and the general morphological features and length from electron microscopy, we calculate the diameters of the end nodules to be 65 A and the center one as 50 A. The model of the molecule so obtained is consistent with the electron microscopical observations and the data from physical chemistry.
The intermediate polymers formed when fibrinogen is activated with thrombin were also examined and found to be end-to-end aggregates of altered fibrinogen molecules which shrink in length during the process. Intermediate polymer lengths are from 1000 to 5000 A.
The nodular nature of fibrinogen, its shrinkage and end-to-end aggregation on polymerization permits us to deduce an explanation for the system of cross-bands previously observed in stained fibrin fibrils.
The Origin and Fate of Annulate Lamellae in Maturing Sand Dollar Eggs
Authors: Merriam R. W. 
Published: May 2004

Electron micrograph evidence is presented that the nuclear envelope of the mature ovum of Dendraster excentricus is implicated in a proliferation of what appear as nuclear envelope replicas in the cytoplasm. The proliferation is associated with intranuclear vesicles which apparently coalesce to form comparatively simple replicas of the nuclear envelope closely applied to the inside of the nuclear envelope. The envelope itself may become disorganized at the time when fully formed annulate lamellae appear on the cytoplasmic side and parallel with it.
The concept of interconvertibility of general cytoplasmic vesicles with most of the membrane systems of the cytoplasm is presented.
The structure of the annuli in the annulate lamellae is shown to include small spheres or vesicles of variable size embedded in a dense matrix.
Dense particles which are about 150 A in diameter are often found closely associated with annulate lamellae in the cytoplasm. Similar structures in other echinoderm eggs are basophilic. In this species, unlike other published examples, the association apparently takes place in the cytoplasm only after the lamellae have separated from the nucleus. If 150 A particles are synthesized by annulate lamellae, as their close physical relationship suggests, then in this species at least the necessary synthetic mechanisms and specificity must reside in the structure of annulate lamellae.
Fine Structure of Bacillus subtilis
Authors: Tokuyasu Kiyoteru , Yamada Eichi 
Published: May 2004

The fine structure of Bacillus subtilis has been studied by observing sections fixed in KMnO4, OsO4, or a combination of both. The majority of examinations were made in samples fixed in 2.0 per cent KMnO4 in tap water. Samples were embedded in butyl methacrylate for sectioning.
In general, KMnO4 fixation appeared to provide much better definition of the boundaries of various structures than did OsO4. With either type of fixation, however, the surface structure of the cell appeared to consist of two components: cell wall and cytoplasmic membrane. Each of these, in turn, was observed to have a double aspect. The cell wall appeared to be composed of an outer part, broad and light, and an inner part, thin and dense. The cytoplasmic membrane appeared (at times, under KMnO4 fixation) as two thin lines.
In cells fixed first with OsO4 solution, and then refixed with a mixture of KMnO4 and OsO4 solutions, the features revealed were more or less a mixture of those revealed by each fixation alone.
A homogeneous, smooth structure, lacking a vacuole-like space, was identified as the nuclear structure in a form relatively free of artifacts.
Two unidentified structures were observed in the cytoplasm when B. subtilis was fixed with KMnO4. One a tortuous, fine filamentous element associated with a narrow light space, was often found near the ends of cells, or attached to one end of the pre-spore. The other showed a special inner structure somewhat similar to cristae mitochondriales.
The Ingestion of Proteins and Colloidal Materials by Columnar Absorptive Cells of the Small Intestine in Suckling Rats and Mice
Authors: Clark Sam L. 
Published: May 2004

Proteins and colloidal materials, administered orally to suckling rats and mice, were ingested by columnar absorptive cells of the jejunum and ileum, but not of the duodenum. Bovine gamma globulin and ovalbumin were identified in the apical cytoplasm by staining with fluorescent antibody; trypan blue, Evans blue, saccharated iron oxide, and colloidal gold were detected intracellularly by their color, specific staining, and appearance in the electron microscope. Each substance was segregated in membrane-enclosed vacuoles, apparently part of a system of potentially interconnecting vacuoles and tubules in the apical cytoplasm which is continuous in places with the apical cell membrane. We postulate that ingestion of foreign materials was accomplished by pinocytosis, that is, by invagination of the apical cell membrane to form vacuoles containing material from the intestinal lumen.
Approximately 18 days after birth columnar absorptive cells lost the ability to ingest proteins and colloids, and no longer contained large vacuoles and numerous tubules. At this age rats and mice lose the ability to absorb antibodies from the intestine in an immunologically intact form, and we conclude that cellular ingestion is part of the mechanism of absorption of intact proteins in suckling animals. Particulate fat apparently is absorbed in both newborn and adult animals by micropinocytosis. Thus adult animals may not have lost the capacity for pinocytosis, but rather have become selective as to what substances provoke it.
Cortisone acetate, administered subcutaneously to rats 8 to 10 days old alters the columnar absorptive cells within 72 hours so that they resemble the cells in adult animals and no longer ingest proteins.
Cytological Studies of the Nematocysts of Hydra
Authors: Chapman George B. , Tilney Lewis G. 
Published: May 2004

Entire hydras or tentacles were prepared for electron microscopy as described in the preceding paper.
The stenotele capsule has been observed to be composed of an external membrane, a thick chitinous or keratin layer, and an inner membrane. A sac-like extension of the capsular wall into the capsule bears spines and stylets on its inner surface and evagination of this structure occurs on discharge. Profiles of tubular or membranous structures often are seen within the capsules of resting stenoteles. These structures are presumably related to the external filament. The spines often reveal a flattened aspect which suggests that at least some of them might more accurately be called "vanes." A cnidocil has been found to accompany each stenotele.
This study revealed several aspects of the developmental stages of stenoteles: A vacuole is formed which is nearly surrounded by the nematocyte nucleus. The vacuole content changes in density and a capsular wall is formed at the periphery of the vacuole. Tubules differentiate from the capsular matrix, and spines and stylets develop somewhat later. An operculum is formed from the nematocyte cytoplasm.
Rapid Cytochemical Identification of Phagosomes in Various Tissues of the Rat and their Differentiation from Mitochondria by the Peroxidase Method
Authors: Straus Werner 
Published: May 2004

1. Granules characterized by their ability to segregate foreign proteins (phagosomes) were identified in the cells of many rat organs after intravenous administration of horseradish peroxidase, by using the conventional test with benzidine for the histochemical detection of peroxidase. The largest numbers of phagosomes were identified in kidney and liver. Considerable numbers were observed cytochemically in pancreas, prostate, epididymis, thymus, spleen, bone marrow, small intestine, heart, pituitary, and mouse mammary carcinoma.
2. The variation in size of the phagosomes ranging from the limit of microscopic visibility up to 5 µ diameter, previously described for kidney, was also observed to occur in many of the other organs. The average size of the phagosomes in different organs was also different, the phagosomes of the liver, for example being on the average smaller than those of the kidney, pancreas, and prostate.
3. In squash preparations of kidney and liver, the phagosomes appeared often in curved rows following the course of the cell membranes of epithelial cells. In several other organs, they appeared aggregated in cells located in the vicinity of blood or lymphatic vessels or capillaries.
4. After injection of peroxidase directly into the brain of a rabbit, a striking concentration of peroxidase was observed in phagosomes of endothelial cells of capillaries and vessels, surrounding the site of injection. It was suggested that this localization may offer an explanation for the so called blood-brain barrier.
5. The cytochemical peroxidase method was applied to smears of isolated fractions of kidney and liver. Only the isolated phagosomes, but not the isolated nuclei, mitochondria, and microsomes, reacted with benzidine after administration of peroxidase. The contamination of conventionally prepared nuclear, mitochondrial, and microsomal fractions of kidney and liver with phagosomes of different sizes was observed. By correlating the cytochemical peroxidase test of smears of isolated fractions with the colorimetric determination of peroxidase, acid phosphatase, and cytochrome oxidase in the same fractions, the differentiation of the phagosomes from mitochondria and other cell granules was facilitated.
6. The marked difference in the osmotic properties of phagosomes and mitochondria, detectable after treatment with 70 per cent alcohol, and the difference in their affinities towards basic fuchsin, made it possible to differentiate the phagosomes from the mitochondria. It was found by this simple procedure that kidney cells of normal rats contain a large number of phagosomes ranging in size from 0.5 to 3 µ, whereas liver cells of normal rats contain relatively few phagosomes of this size but many smaller ones (0.2 to 0.5 µ diameter). These increased in size after treatment of the rats with horseradish peroxidase.