bluuebunny/crossref_metadata_2025 huggingface dataset:
THE FEEDING MECHANISM OF AVIAN MALARIAL PARASITES
Authors: Aikawa Masamichi , Hepler Peter K. , Huff Clay G. , Sprinz Helmuth
Published: May 2004

Electron microscope studies of the erythrocytic forms, including gametocytes and asexual schizonts, of the protozoa Plasmodium fallax, P. lophurae, and P. cathemerium, have revealed a "cytostome," a specialized organelle of the pellicular membrane which is active in the ingestion of host cell cytoplasm. In material fixed in glutaraldehyde and postfixed in OsO4, the cytostome appears in face view as a pore limited by two dense circular membranes and having an inside diameter of approximately 190 mµ. In cross-section, the cytostome is a cavity bounded on each side by two dense segments corresponding to the two dense circles observed in face view; its base consists of a single unit membrane. In the process of feeding, the cytostome cavity enlarges by expansion of its membrane, permitting a large quantity of red cell cytoplasm to come into contact with the cytostome wall. Subsequent digestion of erythrocyte cytoplasm occurs exclusively in food vacuoles which emanate from the cytostome invagination. As digestion progresses, the food vacuoles initially stain more densely and there is a marked build-up of hemozoin granules. In the final stage of digestion, a single membrane surrounds a cluster of residual pigment particles and very little of the original host cell cytoplasm remains. The cytostome in exoerythrocytic stages of P. fallax has been observed only in merozoites and does not seem to play the same role in the feeding mechanism.
ELECTRON MICROSCOPE STUDIES ON SOMA-SOMATIC INTERNEURONAL JUNCTIONS IN THE CORPUS PEDUNCULATUM OF THE WOOD ANT (FORMICA LUGUBRIS ZETT.)
Authors: Landolt Alex M. , Ris Hans
Published: May 2004

1. The corpora pedunculata of the wood ant (Formica lugubris Zett.) contain densely packed neuron perikarya which are separated by ultrathin glial sheaths. 2. These glial sheaths are occasionally interrupted by round holes with an average surface area of 2.64 µ2. The holes are designated glial windows since they represent intracellular gaps of glial cytoplasm. 3. The glial windows allow soma-somatic interneuronal junctions. Of all adjacent neurons in a selected neuron pool, only 42% were interconnected by such junctions. 4. The intercellular space at the soma-somatic junctions has an average diameter of 30 A; occasionally, it is collapsed and an external compound membrane ensues. The junctional membranes are characterized by the presence of a subunit pattern of cross-directional electron-opaque lines with a 50- to 70-A periodicity. 5. Morphological signs of chemical transmission are absent in these junctions. On the other hand, there is a striking similarity in structural organization between soma-somatic junctions and electrical synapses described in other species. Therefore, it is suggested that these cell contacts of the ant's "cerebral cortex" are another form of electrical junction. 6. The close proximity of the junctions to the cell nucleus is noted. Its significance could not be ascertained. 7. The suggestion is made that glial windows may have dynamic properties and may intervene in the regulation of interneuronal transfer of information.
STUDIES ON INSULIN BIOSYNTHESIS
Authors: Bauer G. Eric , Lindall Arnold W. , Dixit Padmaker K. , Lester Gordon , Lazarow Arnold
Published: May 2004

Islet tissue from the goosefish (Lophius piscatorius) was incubated in the presence of leucine-H3. The tissue was then separated into subcellular fractions and the radioactivity determined in total acid alcohol-soluble proteins, insoluble proteins, and insulin. At any time, microsomal protein had a higher activity than secretion granule protein. Pulse-chase experiments further suggest the microsomes as primary sites of protein synthesis. The data are evidence for microsomal synthesis of insulin and for its subsequent transfer into the secretion granules.
URIDINE-5-H3 RADIOAUTOGRAPHY OF THE HUMAN SEX CHROMATIN BODY
Authors: Comings David E.
Published: May 2004

To obtain an estimate of the rate of RNA synthesis by the heterochromatic sex chromatin body, human female fibroblasts were labeled with uridine-5-H3 and radioautographed. The number of grains over the sex chromatin body was compared with the number of grains over a comparable area of euchromatin. The ratio was 0.37. When corrected for the higher content of DNA per unit area in heterochromatin, the maximum rate of RNA synthesis by the DNA of the sex chromatin body was approximately 18% of the rate of RNA synthesis by a comparable amount of euchromatin DNA. The rate of RNA synthesis by the sex chromatin body did not increase significantly with partial despiralization of this chromatin at prophase.
THE LOSS OF PHENOTYPIC TRAITS BY DIFFERENTIATED CELLS
Authors: Abbott Joan , Holtzer Howard
Published: May 2004

Observations were made on the behavior of chondrocytes grown under various conditions in vitro. The chondrocytes in 10-day embryonic chick vertebrae were grown as cultures of intact vertebrae, as pellets of chondrocytes liberated from their matrix, and as monodispersed cells plated out on plasma clots. Cartilage matrix was stained metachromatically with toluidine blue. Radioautographs were made of incorporated H3-thymidine, H3-proline, and S35-sulfate to determine the extent of DNA synthesis, collagen synthesis, and chondroitin sulfate synthesis, respectively. Chondrocytes in intact vertebrae or in pellets are rounded and actively synthesizing chondroitin sulfate and collagen. There is little DNA synthesis by cells in either vertebrae or pellets. Chondrocytes grown as monodisperse cells rapidly cease synthesizing cytologically detectable chondroitin sulfate and are induced to synthesize DNA and divide. There is a change in the shape of these chondrocytes from a rounded to a more stellate condition which accompanies the shift in metabolic activity. Conversely, when the cells attain a certain cell density, they reacquire a rounded shape, cease dividing, and again synthesize chondroitin sulfate. Clusters of chondrocytes synthesize more chondroitin sulfate than isolated chondrocytes. It is concluded that most chondrocytes synthesizing chondroitin sulfate do not concurrently synthesize DNA. Interaction between associated chondrocytes is important in inducing and maintaining chondroitin sulfate synthesis in genetically determined chondrocytes. Failure of interaction between chondrocytes leads to DNA synthesis and cell multiplication.
STUDIES ON THE MECHANISM OF HORMONAL INDUCTION OF ALKALINE PHOSPHATASE IN HUMAN CELL CULTURES
Authors: Griffin Martin J. , Cox Rody P.
Published: May 2004

Increased alkaline phosphatase activity is induced in certain epithelial cell cultures by hormones with adrenal glucocorticoid activity or their analogues such as prednisolone (ΔI-hydrocortisone). Enzyme induction occurs in two distinct phases. During the first 12 hr after the addition of prednisolone, there is a small increase in alkaline phosphatase levels. After 15 to 24 hr, the enzyme activity shows a sudden, marked linear rise, reaching a maximum at 60 to 80 hr. Puromycin blocks enzyme induction immediately, even when added during the period of rapid increase of enzyme. Actinomycin D blocks induction when added no later than 8 hr after the addition of prednisolone. On the other hand, Actinomycin D added during the phase of rapid enzyme induction has no effect for at least 12 hr. These findings suggest that de novo protein synthesis is involved in prednisolone induction of alkaline phosphatase and that the RNA messenger for this enzyme is relatively stable.
RADIATION-STIMULATED DNA SYNTHESIS IN CULTURED MAMMALIAN CELLS
Authors: Rasmussen R. E. , Painter R. B.
Published: May 2004

A type of DNA synthesis in mammalian cells that is stimulated by ultraviolet light has been studied by means of radioautography and density gradient centrifugation. The characteristics of this synthesis are: (a) it is not semiconservative; (b) it is enhanced by the presence of 5-bromodeoxyuridine in the DNA molecule; (c) the degree of stimulation is dose dependent; (d) there is less variability in the rate of incorporation of H3-thymidine during this synthesis than during normal DNA synthesis; (e) it occurs in cells that are not in the normal DNA synthesis phase (G1 and G2 cells). This kind of synthesis has been found in cultured cell lines from five different species; however, in some strains, the presence of bromouracil in the DNA is required before it can be demonstrated by radioautography.
INCORPORATION OF NUCLEOTIDES INTO NUCLEI OF FIXED CELLS BY DNA POLYMERASE
Authors: von Borstel R. C. , Prescott D. M. , Bollum F. J.
Published: May 2004

The enzyme calf thymus polymerase requires denatured or single-stranded DNA as a primer for DNA synthesis and is inactive on native DNA preparations. The enzyme and tritium-labeled deoxyribonucleoside triphosphates were incubated with alcohol-fixed and Carnoy-fixed tissue preparations to see if primer DNA could be found in several types of cells undergoing DNA synthesis. In all cases, low-pH controls were prepared for comparison. Priming activity was not found in nuclei that had been fixed in alcohol. Priming activity was found in cell nuclei that had been fixed with an acid fixative or had been treated at a low pH prior to treatment with the enzyme reaction mixture.
THE INCORPORATION OF TRITIUM FROM THYMIDINE INTO PROTEINS OF THE MOUSE
Authors: Bryant B. J.
Published: May 2004

Tritium from methyl-H3-thymidine was found to be incorporated into proteins in mice. This incorporation in the mouse as a whole represented between 1 and 10% of the injected tritium. Tritiated water was not an intermediate. Transmethylation reactions are proposed as a means whereby certain amino acids might have acquired the tritium from thymidine at some stage of its catabolism. The initial (2 hr) ratios of DNA to protein tritium activities per milligram of wet tissue ranged from 5 in two tissues of low DNA synthetic activity (pancreas, liver) to 35 to 40 in two tissues of high DNA synthetic activity (spleen, small intestine). Labeled nuclear protein was coincident with labeled DNA in nuclei, where it constituted less than 2.5% of the total tritium. The significance of the findings is discussed.
THE IN VIVO PROTEIN SYNTHETIC ACTIVITIES OF FREE VERSUS MEMBRANE-BOUND RIBONUCLEOPROTEIN IN A PLASMA-CELL TUMOR OF THE MOUSE
Authors: Kuff E. L. , Hymer W. C. , Shelton E. , Roberts N. E.
Published: May 2004

Cytoplasmic extracts of the transplantable RPC-20 plasma-cell tumor were fractionated by sucrose density gradient centrifugation. Four major fractions were distinguished: (a) microsomes and mitochondria; (b) membrane-free polyribosomes; (c) free monomeric ribosomes; and (d) soluble fraction. The fractions were analyzed for RNA and lipid phosphorus, and their particulate components were characterized by electron microscopy. Particular attention was paid to the problem of membrane contamination of the free polyribosome fraction. It was shown that this contamination was small in relation with the total content of ribosomes in the fraction, and that it consisted primarily of smooth-surfaced membranes which were not physically associated with the polyribosomes themselves. In vivo incorporation studies were carried out by injecting tumor-bearing animals intravenously with leucine-C14, removing the tumors at various times thereafter, and determining the distribution of protein radioactivity among the gradient-separated cytoplasmic fractions. The free polyribosome and the microsome-mitochondria fractions constituted active centers for protein synthesis. It was shown that nascent protein of the free polyribosome fractions was not associated significantly with the contaminating membranes. The kinetics of labeling during incorporation times up to 11 min suggested that protein synthesized on the free polyribosomes was rapidly transferred in vivo to the soluble fraction of the cell, while protein synthesized by the microsomes and mitochondria remained localized within these elements. It was estimated that the free polyribosome fraction and the microsome-mitochondria fraction accounted for approximately equal proportions of the total cytoplasmic protein synthesis in vivo.
THE MICROCRYSTALLINE STRUCTURE OF CELLULOSE IN CELL WALLS OF COTTON, RAMIE, AND JUTE FIBERS AS REVEALED BY NEGATIVE STAINING OF SECTIONS
Authors: Heyn A. N. J.
Published: May 2004

With a new technique of negative staining of sections, it has been possible to observe directly, in ultrathin sections under the electron microscope, the original microcrystalline and microfibrillar structure of cellulose as it occurs in living cells. This method has advantages over the study of isolated fibers used so far by others, in that the original arrangement of microfibrils is better preserved, and their collapse into larger fibrillar units is prevented. With this method, the cell walls of ramie, jute, and cotton fibers have been studied. The size (diameter, 25 to 40 A) and the longitudinal periodicity observed in the single microfibrils and the orientation and spatial arrangement of the microcrystallite within the microfibrils are found to correspond with the latest models derived by others from data obtained by indirect methods such as X-ray diffraction. The microfibril size of about 35 A, found by measuring these structures in sections, agrees with the latest conclusions reached by others in recent work with isolated fibrils.
INCORPORATION OF TRITIUM-LABELED THYMIDINE AND LYSINE INTO CHROMOSOMES OF CULTURED HUMAN LEUKOCYTES
Authors: Cave Mac Donald
Published: May 2004

The incorporation of thymidine-H3 and lysine-H3 into human leukocyte chromosomes was studied in order to determine the temporal relationships between the syntheses of chromosomal deoxyribonucleic acid and chromosomal protein. The labeled compounds were incorporated into nuclei of interphase cells. Label from both precursors became apparent over the chromosomes of dividing cells. Incorporation of thymidine-H3 occurred during a restricted period of midinterphase (S) which was preceded by a nonsynthetic period (G1) and followed by a nonsynthetic period (G2). Incorporation of lysine-H3 into chromosomal protein occurred throughout interphase. Grain counts made over chromosomes of dividing cells revealed that the rate of incorporation of lysine-H3 into chromosomal protein differed during various periods of interphase. The rate of incorporation was diminished during G1. During early S period the rate of incorporation increased, reaching a peak in late S. The high rate continued into G2. Thymidine-H3 incorporated into DNA was distributed to mitotic chromosomes of daughter cells in a manner which has been referred to as a "semi-conservative segregation." No such semi-conservative mechanism was found to affect the distribution of lysine-H3 to the mitotic chromosomes of daughter cells. Therefore, it is concluded that synthesis of chromosomal protein and its distribution to chromosomes of daughter cells are not directly influenced by synthesis and distribution of the chromosomal DNA with which the protein is associated.
THE FINE STRUCTURE OF GIARDIA MURIS
Authors: Friend Daniel S.
Published: May 2004

Giardia is a noninvasive intestinal zooflagellate. This electron microscope study demonstrates the fine structure of the trophozoite of Giardia muris in the lumen of the duodenum of the mouse as it appears after combined glutaraldehyde and acrolein fixation and osmium tetroxide postfixation. Giardia muris is of teardrop shape, rounded anteriorly, with a convex dorsal surface and a concave ventral one. The anterior two-thirds of the ventral surface is modified to form an adhesive disc. The adhesive disc is divided into 2 lobes whose medial surfaces form the median groove. The marginal grooves are the spaces between the lateral crests of the adhesive disc and a protruding portion of the peripheral cytoplasm. The organism has 2 nuclei, 1 dorsal to each lobe of the adhesive disc. Between the anterior poles of the nuclei, basal bodies give rise to 8 paired flagella. The median body, unique to Giardia, is situated between the posterior poles of the nuclei. The cytoplasm contains 300-A granules that resemble particulate glycogen, 150- to 200-A granules that resemble ribosomes, and fusiform clefts. The dorsal portion of the cell periphery is occupied by a linear array of flattened vacuoles, some of which contain clusters of dense particles. The ventrolateral cytoplasm is composed of regularly packed coarse and fine filaments which extend as a striated flange around the adhesive disc. The adhesive disc is composed of a layer of microtubules which are joined to the cytoplasm by regularly spaced fibrous ribbons. The plasma membrane covers the ventral and lateral surfaces of the disc. The median body consists of an oval aggregate of curved microtubules. Microtubules extend ventrally from the median body to lie alongside the caudal flagella. The intracytoplasmic portions of the caudal, lateral, and anterior flagella course considerable distances, accompanied by hollow filaments adjacent to their outer doublets. The intracytoplasmic portions of the anterior flagella are accompanied also by finely granular rodlike bodies. No structures identifiable as mitochondria, smooth endoplasmic reticulum, the Golgi complex, lysosomes, or axostyles are recognized.
STUDIES ON THE FUNCTION OF INTRACELLULAR RIBONUCLEASES
Authors: Utsunomiya Takeshi , Roth Jay S.
Published: May 2004

Polysome and ribosome preparations from normal rat liver and from a series of transplantable rat hepatomas of different growth rates were compared. All the hepatomas had a significantly higher percentage of RNA in a polysome preparation than did the normal liver, and the polysome preparations from the tumors, with the exception of the Dunning hepatoma which has a high lipid content, gave a greater yield of RNA and protein per gram of wet tissue than the liver did. Heavier polysomes were considerably less prevalent in the tumors than in the liver, and the tumors contained a larger proportion of monomer and dimer ribosomes than the liver did. Evidence is presented that the increased monomer and dimer ribosome population of the hepatomas studied is not an artifact of preparation, but represents the true intracellular distribution. Ribosomes from normal liver and Morris 5123-D hepatoma were readily dissociated by 20 min' treatment with 1.0 mM EDTA, but ribosomes from the Dunning, Novikoff ascites, and McCoy MDAB hepatomas were little affected by such treatment. With higher concentrations of EDTA, the ribosomes from the Novikoff ascites and McCoy MDAB hepatomas broke down and did not form specific subunits as did ribosomes from liver and the Morris 5123-D hepatoma but rather gave rise to a variety of small degradation products. This behavior is ascribed to a higher RNase content of the Novikoff and McCoy MDAB hepatomas. Dunning hepatoma ribosomes were resistant to 4 mM EDTA.
QUANTITATIVE STUDY OF MITOCHONDRIA IN RAT LIVER
Authors: Glas Ulla , Bahr Gunter F.
Published: May 2004

The dry mass, wet mass, and volume of mitochondria of normal rat liver were determined, as well as nitrogen content and concentration. A scheme of multiple approaches to these quantities was devised, permitting comparison of values obtained by independent methods. The following basic values are considered highly accurate: Mean dry mass, 13.6 x 10-14 g; mean wet mass, 51.8 x 10-14 g; mean volume, 0.43 µ3; nitrogen content, 1.75 x 10-14 g The work emphasizes the fact that in mitochondria the quantities, mass, and volume occur in logarithmic-normal distributions.
NUCLEOSIDE PHOSPHATASE AND CHOLINESTERASE ACTIVITIES IN DORSAL ROOT GANGLIA AND PERIPHERAL NERVE
Authors: Novikoff Alex B. , Quintana Nelson , Villaverde Humberto , Forschirm Regina
Published: May 2004

In dorsal root ganglia and peripheral nerve of the rat and other species, nucleoside phosphatase and unspecific cholinesterase reaction products are found in the plasma membranes and spaces between them at two sites: (1) Schwann cell-axon interfaces and mesaxons of unmyelinated fibers, and (2) sheath cell-perikaryon interfaces and interfaces between adjacent sheath cells. Acetylcholinesterase reaction product is found in the perikaryon (within the endoplasmic reticulum) and the axon (axoplasmic surface). Nucleoside phosphatase reaction product is also found in the numerous vacuoles at the surface of perineurium cells, ganglion sheath cells, and cells surrounding some ganglion blood vessels. Nucleoside phosphatase activities in the sections fail to respond, in the manner described for "transport ATPase," to diisopropylphosphofluoridate, sodium and potassium ions, and ouabain. Nucleoside diphosphates are hydrolyzed more slowly than triphosphates in unmyelinated fibers, and are not hydrolyzed at the perikaryon surface. Nucleoside monophosphates are either not hydrolyzed or hydrolyzed very slowly. In contrast to these localizations, which are believed to demonstrate sites of enzyme activity, it is considered likely that diffusion artifacts account for the nucleoside phosphatase reaction product frequently found along the outer surfaces of myelinated fibers and within vacuoles at the Schwann cell surfaces of these fibers. The diffuse reaction product seen in basement membranes of ganglion and nerve may also be artifact.
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.
ELECTRON MICROSCOPY OF THE TISSUE MAST CELL
Authors: Smith Douglas E. , Lewis Yevette S.
Published: May 2004

Electron microscopy was carried out on sections through tissue mast cells from the peritoneal fluid of rats and hamsters, either untreated, x-irradiated, or injected with toluidine blue, protamine sulfate, or stilbamidine. Mast cells from untreated animals have large nuclei and are filled with densely packed, cytoplasmic granules. The latter possess a distinct boundary and an internal structure which is reticular or vacuolar in nature. Between the granules are found elongate mitochondria and endoplasmic reticulum. Mitochondria often appear also in groups in granule-free areas adjacent to the nucleus. Nuclear and cell membranes of an apparent double nature are found. After treatment with toluidine blue, protamine sulfate, and stilbamidine the granules are surrounded by clear areas and are widely separated from one another; the endoplasmic reticulum is more conspicuous. The internal structure of the granule is unchanged. In the mast cells from x-irradiated animals there is an apparent coalescence of granules which is attented by a loss of intragranular structure. The findings are discussed in relation to other work on the structure and function of mast cells.
THE ROLE OF WATER IN THE STRUCTURE OF PERIPHERAL NERVE MYELIN
Authors: Finean J. B.
Published: May 2004

In the study of the drying kinetics of nerve fibres, at least five "phases" of water evaporation can be distinguished. A consideration of the accompanying changes in low-angle x-ray diffraction patterns permits a tentative identification of the "phases" and a quantitative interpretation of the data in terms of the water distribution in nerve fibres. These results suggest that the myelin sheath of frog sciatic nerve contains 40 to 50 per cent water, and it is suggested further that the greater part of this water is "organised" in relation to the hydrophilic groups of the lipide and protein components.
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.
ELECTRON MICROSCOPY OF THE AVIAN RENAL GLOMERULUS
Authors: Pak Poy R. K. F. , Robertson J. S.
Published: May 2004

Electron microscopy of sections of chicken glomeruli shows them to possess a large central cell mass, occupying the hilum and the centre of the glomerulus, and continuous with the adventitia of the afferent and efferent arterioles. The glomerular capillaries form a much simpler system than in mammals and are spread over the surface of the central cell mass. Between the capillaries the mass is limited externally by the major component of the glomerular capillary basement membrane, which continues over the surface of the mass from one capillary to the next. Projections of the central cell mass characteristically form the support for glomerular capillaries, and smaller knobs of the central mass may project actually into the lumen of the capillaries, but always carry a layer of endothelial cytoplasm before them. They are never in direct contact with blood. The basement membrane of the glomerular capillary loop has a central dense layer and two lateral less dense layers as in mammals. The central dense layer is continuous with similar appearing dense material in the intercellular spaces of the adventitiae of the arterioles, and also with that of the central cell mass. The two less dense layers can also be traced into direct continuity with the less dense regions of this intercellular substance. The endothelial cytoplasm is spread as a thin sheet over the inner surface of the capillary basement membrane, and shows scattered "pores" resembling those described in mammals. Epithelial cells with interlacing pedicels are at least as prominent as those in mammals. Bowman's capsular membrane also possesses three layers similar to but less wide than those of the capillary basement membrane, and all three layers can be traced into continuity with the dark and light regions of the intercellular material of the adventitial cells of the arterioles, and beyond them with that of the central cell mass. At the hilum Bowman's capsular membrane also fuses with the capillary basement membrane.
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.
THE BASE OF THE PROXIMAL CONVOLUTED TUBULE CELLS OF RAT KIDNEY
Authors: Ruska Helmut , Moore Dan H. , Weinstock John
Published: May 2004

The three dimensional arrangement of the compartments on the base of proximal convoluted tubule cells of rat kidney is described. An extracellular basal labyrinth is found to be enclosed by these compartments. The compartments with their mitochondria and the basal labyrinth are regarded as forming a functional unit. It is supposed that this basal unit serves for excretion of reabsorbed fluid from the cell into the labyrinth and for the development of hydrostatic pressure in the labyrinth to overcome the capillary pressure and to pass the reabsorbed fluid into the blood stream.
ELECTRON MICROSCOPE STUDY OF MAMMALIAN CARDIAC MUSCLE CELLS
Authors: Moore Dan H. , Ruska Helmut
Published: May 2004

The cellular theory of heart muscle is supported by a detailed description of the intercalary discs. The discs are adjacent plasma membranes separated by an interspace while the sarcolemma appears as plasma membrane, interspace plus basement membrane of the interstitium. The nucleus of the cell is closely associated with the entire cell by way of the endoplasmic reticulum. Transversely it connects the outer nuclear membrane at the level of the Z and M bands with the contractile material and the sarcolemma. Longitudinally it connects the outer nuclear membrane with the plasmalemma at the intercalated discs. The description of the spiral attachment of the endoplasmic reticulum on the outer nuclear membrane supplements earlier observations on the helicoidal structure of the heart muscle cell. Plasma membranes and endoplasmic reticulum are considered to be carriers of membrane potentials and to conduct excitation.
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.
HISTOLOGY AND CYTOCHEMISTRY OF HUMAN SKIN
Authors: Montagna William
Published: May 2004

1. Various amounts of ß-glucuronidase activity may be found in all of the cutaneous appendages.

2. In the epidermis, the basal layer and the Malpighian layer contain a moderate amount of it, but a band of cells, including the stratum granulosum and the cells immediately above it, is rich in ß-glucuronidase.

3. The cells of the duct of eccrine sweat glands have moderately strong enzyme activity, but those in the secretory coil are strongly reactive; small and large reactive granules are crowded in the reactive cytoplasm.

4. The cells of the secretory coil of the apocrine glands contain more ß-glucuronidase than any other cutaneous appendage.

5. In the sebaceous glands, a very strong concentration of enzyme activity is found in the undifferentiated peripheral cells, a smaller amount of it is found in the differentiating cells.

6. In active hair follicles, the largest amount of ß-glucuronidase is found in the outer root sheath and in the bulb. In the outer sheath, the strongest concentration is found around the level of the keratogenous zone of the cortex. The dermal papilla is strongly reactive. In quiescent hair follicles, the outer root sheath has a moderate amount of enzyme concentration, but the dermal papilla is unreactive.

7. In the dermis, the fibroblasts in the papillary layer, the smooth muscle cells of the arrectores pilorum and the tunica media of arteries, and the fat cells all exhibit enzyme activity. Mast cells show a great concentration of ß-glucuronidase.
MUCOPOLYSACCHARIDES PRODUCED IN TISSUE CULTURE
Authors: Grossfeld Henry , Meyer Karl , Godman Gabriel , Linker Alfred
Published: May 2004

1. A method of mass tissue culture has been devised by which, in a relatively short period of time, samples large enough for chemical isolation of mucopolysaccharides can be obtained.

2. Chemical isolation of acid mucopolysaccharides from mass cultures of human fetal skin, human fetal bone, bovine fetal skin, and rat subcutaneous tissue has been carried out. It has been found that the fibroblasts of each of these tissues produce in tissue culture more than one mucopolysaccharide, namely, hyaluronic acid, and a chondroitin sulfate.

3. The chondroitin sulfate produced by fibroblasts of the above tissues in tissue culture was not fully sulfated. The possible significance of this finding is discussed.
INTRACELLULAR LOCALIZATION OF ENZYMES IN SPLEEN
Authors: Eichel Herbert J. ,   With the Technical Assistance of Jeanne Hagan
Published: May 2004

1. The intracellular distribution of nitrogen, DPNH cytochrome c reductase, succinic dehydrogenase, and cytochrome c oxidase has been studied in fractions derived by differential centrifugation from rat and guinea pig spleen homogenates.

2. In the spleens of each species, the nuclear fraction accounted for 40 to 50 per cent of the total nitrogen content of the homogenate, and the mitochondrial, microsome, and supernatant fractions contained about 8, 12, and 30 per cent of the total nitrogen, respectively.

3. Per mg. of nitrogen, DPNH cytochrome c reductase was concentrated in the mitochondria and microsomes of both rat and guinea pig spleens. Seventy per cent of the total DPNH cytochrome c reductase activity was recovered in these two fractions. The reductase activity associated with the nuclear fraction was lowered markedly by isolating nuclei from rat spleens with the sucrose-CaCl2 layering technique. The lowered activity was accompanied by the recovery of about 90 per cent of the homogenate DNA in the isolated nuclei, indicating that little, if any, of the reductase is present in spleen cell nuclei.

4. Per mg. of nitrogen, succinic dehydrogenase was concentrated about 10-fold in the mitochondria of rat spleen, and 65 per cent of the total activity was recovered in this fraction.

5. Cytochrome c oxidase was concentrated, per mg. of nitrogen, in the mitochondria of both rat and guinea pig spleens. The activity associated with the nuclear fraction was greatly diminished when this fraction was isolated from rat spleens by the sucrose-CaCl2 layering technique. Only 50 to 70 per cent of the total cytochrome c oxidase activity of the original homogenates was recovered among the four fractions from both rat and guinea pig spleens, while the specific activities of reconstructed homogenates were only 55 to 75 per cent of those of the original whole homogenates. This was in contrast to the results with DPNH cytochrome c reductase and succinic dehydrogenase where the recovery of total enzyme activity approached 100 per cent, and the specific activities of reconstructed homogenates equalled those of the original homogenates. The recovery of cytochrome c oxidase was greatly improved when only the nuclei were separated from rat spleen homogenates.

6. Data were presented comparing the concentrations (ratio of activity per mg. of nitrogen of the fraction to activity per mg. of nitrogen of the homogenate) of DPNH cytochrome c reductase in mitochondria and microsomes derived from different organs of different animals.

7. Data were presented comparing the activities per mg. of nitrogen of DPNH cytochrome c reductase in homogenates from several organs of various animals.
MORPHOLOGY OF THE OMMATIDIA OF THE COMPOUND EYE OF LIMULUS
Authors: Miller William H.
Published: May 2004

The sensory portion of the ommatidium of the compound eye of Limulus has been studied with the electron microscope. In axial longitudinal section the rhabdom appears to be made up of small polygons, and in transverse section the rhabdom appears as a banded structure of dark lines. Thus in three dimensions the rhabdom resembles a honeycomb composed of tubular units, the long axes of which lie in transverse planes and are oriented perpendicular to the retinula cell's contours. The tubular units, which are about 140 mµ in diameter in Limulus (70 mµ in diameter in the spider and Scutigera), are microvilli of the borders of the retinula cells. The walls of these microvilli are continuous with fine linear structures (membranes) in the cytoplasm of the retinula cells.

In transverse sections of the ommatidium oval bodies interpreted as mitochondria are observed in an annular zone at the tips of the rhabdom's rays. These mitochondria, which are 2 to 10 µ in diameter, are crowded with irregular closed outlines about 100 mµ in diameter.

Possible functions of components of the ommatidium are discussed.
PHOTORECEPTOR STRUCTURES
Authors: Wolken J. J. , Capenos J. , Turano A.
Published: May 2004

The eyes of three eye mutants of Drosophila melanogaster were fixed and thin sections studied for its structural detail in the electron microscope. Each ommatidium was found to have seven retinula cells with an equal number of rhabdomeres (visual units). The rhabdomeres average 1.2 µ in diameter and 60 µ in length. Each rhabdomere consists of osmium-fixed dense bands averaging 120 A in thickness, and with less dense interspaces 200 to 400 A. There is an average of 23 dense bands or 46 interfaces per micron within the rhabdomere. The rhabdomere as we have presented it is a single structure of packed rods or tubes. The "fine structure" within the rhabdomere is similar to that observed by electron microscopy for the retinula of the house fly, and to the retinal rods of the vertebrate eye, and to the chloroplasts of plant cells in a variety of animal and plant photoreceptor structures. In addition, the radial arrangements within the ommatidium of radially unsymmetrical units, the rhabdomeres, is probably related to the analysis of polarized light in the insect eye.
THE NISSL SUBSTANCE OF LIVING AND FIXED SPINAL GANGLION CELLS
Authors: Deitch Arline D. , Moses Montrose J.
Published: May 2004

Living chick spinal ganglion neurons grown for 19 to 25 days in vitro were photographed with a color-translating ultraviolet microscope (UV-91) at 265, 287, and 310 mµ. This instrument was unique in permitting rapid accumulation of ultraviolet information with minimal damage to the cell.

In the photographs taken at 265 mµ of the living neurons, discrete ultraviolet-absorbing cytoplasmic masses were observed which were found to be virtually unchanged in appearance after formalin fixation. These were identical with the Nissl bodies of the same cells seen after staining with basic dyes. The correlation of ultraviolet absorption, ribonuclease extraction, and staining experiments with acid and basic dyes confirmed the ribonucleoprotein nature of these Nissl bodies in the living and fixed cells.

No change in distribution or concentration of ultraviolet-absorbing substance was observed in the first 12 ultraviolet photographs of a neuron, and it is concluded that the cells had not been subjected to significant ultraviolet damage during the period of photography.

On the basis of these observations, as well as previous findings with phase contrast microscopy, it is concluded that Nissl bodies preexist in the living neuron as discrete aggregates containing high concentrations of nucleoprotein.