bluuebunny/crossref_metadata_2025_split huggingface dataset:
PEPTIDASE DISTRIBUTION IN LYMPHATIC TISSUE
Authors: Doyle William L. 
Published: May 2004

The lymphatic tissue of the rabbit contains a labile peptidase as measured by the hydrolysis of alanylglycine. Some characteristics of the enzyme were determined. This enzyme increases in amount when the numbers of macrophages in the tissue are increased and it is also present in the extracellular fluid in high concentration. The extracellular fluid value for this activity is calculated to be about 8 times the value for serum. Based on a correlation between the types of cells present and the amount of peptidase found in the tissue the following relative activities are assigned to the tissue components per unit volume: lymphocytes 1.0, tissue fluid 11.0, serum 1.4, phagocytes (macrophages) 30.0, reticular cells 12.0. The amount of chloride space varied from 35 to 55 per cent.
The relative amounts of acid phosphatase per unit volume in the same elements were calculated to be: lymphocytes 1.0, tissue fluid 0, phagocytes 20.0, and reticular cells 4.0.
Analysis of the distribution of peptidase was facilitated by simultaneous determination of acid phosphatase whose primary localization in one cell type was known.
The over-all contribution of lymphocytes to the labile peptidase content of lymphatic tissue is relatively minor and was not found to exceed 5 per cent of the average value for the entire nodular tissue. In the absence of large numbers of macrophages the intercellular fluid of the nodule accounts for half or more of the peptidase content of the nodules.
CYTOLOGICAL STUDIES ON THE ANTIMETABOLITE ACTION OF 2,6-DIAMINOPURINE IN VICIA FABA ROOTS
Authors: Setterfield George , Duncan Robert E. 
Published: May 2004

At a concentration of 9.6 x 10–5 M, 2,6-diaminopurine (DAP) completely inhibited cell enlargement, cell division, and DNA synthesis (determined by microphotometric measurement of Feulgen dye) in Vicia faba roots.
Inhibition of cell enlargement was partially reversed by adenine, guanine, xanthine, adenosine, and desoxyadenosine. Guanine and the nucleosides gave the greatest reversal, suggesting that one point of DAP action upon cell enlargement is a disruption of nucleoside or nucleotide metabolism, possibly during pentosenucleic acid synthesis.
DAP inhibited cell division by preventing onset of prophase. At the concentrations used it had no significant effect on the rate or appearance of mitoses in progress. Inhibition of entrance into prophase was not directly due to inhibition of DNA synthesis since approximately half of the inhibited nuclei had the doubled (4C) amount of DNA. Adenine competitively reversed DAP inhibition of cell division, giving an inhibition index of about 0.5. Guanine gave a slight reversal while xanthine, hypoxanthine, adenosine, and desoxyadenosine were inactive. A basic need for free adenine for the onset of mitosis was suggested by this reversal pattern.
Meristems treated with DAP contained almost no nuclei with intermediate amounts of DNA, indicating that DAP prevented the onset of DNA synthesis while allowing that underway to reach completion. The inhibition of DNA synthesis was reversed by adenine, adenosine, and desoxyadenosine although synthesis appeared to proceed at a slower rate in reversals than in controls. Inhibition of DNA synthesis by DAP is probably through nucleoside or nucleotide metabolism.
A small general depression of DNA content of nuclei in the reversal treatments was observed. This deviation from DNA "constancy" cannot be adequately explained at present although it may be a result of direct incorporation of DAP into DNA.
The possible purine precursor, 4-amino-5-imidazolecarboxamide gave no reversal of DAP inhibition of cell elongation and cell division and only a slight possible reversal of inhibition of DNA synthesis.
The Use of OsO4 Fixative for Feulgen-Stained Preparations
Authors: Rudzinska Maria A. 
Published: May 2004

OsO4 has many advantages over Carnoy's fixative mixture for the Feulgen nuclear staining in the protozoan Tokophrya infusionum.
While Carnoy's fluid used prior to the Feulgen reaction produces shrinkage of the macronucleus and coarse clumping of its chromatin bodies, OsO4 preserves faithfully the size and shape of the macronucleus and its chromatin material.
This finding seems to be of special importance in view of the fact that electron microscopy relies on OsO4 fixation. The satisfactory preservation of structured detail in Feulgen-stained preparations is of importance for the correlation of histochemical and morphological information.
THE FINE STRUCTURE OF NEUROMUSCULAR JUNCTIONS AND THE SARCOPLASMIC RETICULUM OF EXTRINSIC EYE MUSCLES OF FUNDULUS HETEROCLITUS
Authors: Reger James F. 
Published: May 2004

The extrinsic eye muscles of the killifish (F. heteroclitus) were fixed in OSO4 (pH 7.6) and subsequently dehydrated, embedded, and sectioned for electron microscopy. The fine structures of neuromuscular junctions and of sarcoplasmic reticulum were then observed.
The neuromuscular junction consists of the apposition of axolemma (60 to 70 Å) and sarcolemma (90 to 100 Å), with an intervening cleft space of 200 to 300 Å, forming a synaptolemma 400 to 500 Å thick. The terminal axons contain synaptic vesicles, mitochondria, and agranular reticulum. The subsynaptic sarcolemma lacks the infolding arrangement characteristic of neuromuscular junctions from other vertebrate skeletal muscle, making them more nearly like that of insect neuromuscular junctions. A comparison between the folded and non-folded subsynaptic membrane types is made and discussed in terms of comparative rates of acetylcholine diffusion from the synaptic cleft and resistances of the clefts and subsynaptic membranes. The sarcoplasmic reticulum consists of segmentally arranged, membrane-limited vesicles and tubular and cisternal elements which surround individual myofibrils in a sleeve-like arrangement. Triadic differentiation occurs at or near the A-I junction. Unit sleeves span the A and I bands alternately and consist of closed terminal cisternae interconnected across the A and I bands by tubular cisternae. The thickness of the sarcoplasmic membranes increases from 30 to 40 Å in intertriadic regions to 50 to 70 Å at the triads. The location of the triads is compared with previously described striated muscle from Ambystoma larval myotomes, cardiac and sartorius muscles of the albino rat, mouse limb muscle, chameleon lizard muscle, and insect muscle, with reference to their possible role in intracellular impulse conduction.
THE ULTRASTRUCTURE OF THE Z DISC IN SKELETAL MUSCLE
Authors: Knappeis G. G. , Carlsen F. 
Published: May 2004

This electron microscopic study deals with the structure of the Z disc of frog's skeletal muscle, with special regard to the I filaments—whether they pass through the Z disc or terminate at it. In most longitudinal sections the I filaments terminate as rod-like projections on either side of the Z disc, one I filament on one side lying between two I filaments on the opposite side. This indicates that the I filaments are not continuous through the Z disc. The rod-like projections are often seen to consist of filaments (denoted as Z filaments) which meet at an angle.
In cross-sections through the Z region the I filaments and Z filaments form tetragonal patterns. The I filaments are situated in the corners of the squares; the oblique Z filaments form the sides of squares. The tetragonal pattern formed by the Z filaments is rotated 45 degrees with respect to the tetragons formed by the I filaments on both sides of Z. This structural arrangement is interpreted to indicate that each I filament on one side of the Z disc faces the center of the space between four I filaments on the opposite side of Z and that the interconnection is formed by four Z filaments.
JUNCTIONAL COMPLEXES IN VARIOUS EPITHELIA
Authors: Farquhar Marilyn G. , Palade George E. 
Published: May 2004

The epithelia of a number of glands and cavitary organs of the rat and guinea pig have been surveyed, and in all cases investigated, a characteristic tripartite junctional complex has been found between adjacent cells. Although the complex differs in precise arrangement from one organ to another, it has been regularly encountered in the mucosal epithelia of the stomach, intestine, gall bladder, uterus, and oviduct; in the glandular epithelia of the liver, pancreas, parotid, stomach, and thyroid; in the epithelia of pancreatic, hepatic, and salivary ducts; and finally, between the epithelial cells of the nephron (proximal and distal convolution, collecting ducts). The elements of the complex, identified as zonula occludens (tight junction), zonula adhaerens (intermediary junction), and macula adhaerens (desmosome), occupy a juxtaluminal position and succeed each other in the order given in an apical-basal direction.
The zonula occludens (tight junction) is characterized by fusion of the adjacent cell membranes resulting in obliteration of the intercellular space over variable distances. Within the obliterated zone, the dense outer leaflets of the adjoining cell membranes converge to form a single intermediate line. A diffuse band of dense cytoplasmic material is often associated with this junction, but its development varies from one epithelium to another.
The zonula adhaerens (intermediate junction) is characterized by the presence of an intercellular space (∼200 A) occupied by homogeneous, apparently amorphous material of low density; by strict parallelism of the adjoining cell membranes over distances of 0.2 to 0.5 µ; and by conspicuous bands of dense material located in the subjacent cytoplasmic matrix.
The desmosome or macula adhaerens is also characterized by the presence of an intercellular space (∼240 A) which, in this case, contains a central disc of dense material; by discrete cytoplasmic plaques disposed parallel to the inner leaflet of each cell membrane; and by the presence of bundles of cytoplasmic fibrils converging on the plaques.
The zonula occludens appears to form a continuous belt-like attachment, whereas the desmosome is a discontinuous, button-like structure. The zomula adhaerens is continuous in most epithelia but discontinuous in some. Observations made during experimental hemoglobinuria in rats showed that the hemoglobin, which undergoes enough concentration in the nephron lumina to act as an electron-opaque mass tracer, does not penetrate the intercellular spaces beyond the zonula occludens. Similar observations were made in pancreatic acini and ducts where discharged zymogen served as a mass tracer. Hence the tight junction is impervious to concentrated protein solutions and appears to function as a diffusion barrier or "seal." The desmosome and probably also the zonula adhaerens may represent intercellular attachment devices.
THE EFFECT OF ENUCLEATION ON THE DPN LEVEL OF AMEBA
Authors: Cohen Adolph I. 
Published: May 2004

1. Amebae contain DPN at levels of from 1 to 4 x 10–13 moles per cell.
2. Following enucleation, nucleate and enucleate halves continue to have equal DPN contents over the six day period studied. Similarly, starving whole amebae maintain their DPN level over this period.
3. No reduced DPN could be detected in these aerobic animals. This remained true for whole amebae and for nucleate and enucleate halves over 5 days of starvation.
4. A method is described for the preparation and rapid separation of nucleate and enucleate ameba halves, based on a response of amebae to light.
ISOLATION AND PROPERTIES OF LIVER CELL NUCLEOLI
Authors: Monty K. J. , Litt M. , Kay E. R. M. , Dounce A. L. 
Published: May 2004

1. The significance of the term nucleolus has been discussed.
2. A detailed method for the isolation of nucleoli from already isolated rat or cat liver nuclei has been presented.
3. The presence of DNA in isolated liver cell nucleoli has been indicated by histochemical methods.
4. The percentages of DNA and RNA in the isolated nucleoli have been determined by chemical analysis.
5. The specific activities of aldolase, arginase, and catalase have been determined for two subnuclear fractions and for the isolated nucleoli of rat and cat liver, and the relative amounts of these enzymes in the same subnuclear fractions and nucleoli of rat liver have been measured.
6. The significance of the above findings has been discussed and consideration has been given to what types of isolated nuclei might best serve as starting material for the isolation of nucleoli.
7. A new hypothesis has been presented that nucleoli of the liver cell type may function primarily in furnishing (directly or indirectly) templates for the synthesis of the particular enzymes that must govern the chemistry of mitosis.
AN ELECTRON MICROSCOPE STUDY OF SPERMATID DIFFERENTIATION IN THE TOAD, BUFO ARENARUM HENSEL
Authors: Burgos Mario H. , Fawcett Don W. 
Published: May 2004

The differentiation of the spermatids of Bufo arenarum has been described from a study of electron micrographs of thin sections of testis.
The development of the acrosome from the Golgi complex takes place in much the same manner as in mammalian spermatogenesis but no acrosome granule is formed.
A perforatorium is described for the first time in this species. It is formed by a convergence of dense filaments that arise between the nuclear membrane and the head cap.
During maturation of the spermatid the chromatin undergoes striking physicochemical alterations. Fine chromatin granules uniformly dispersed in the karyoplasm are replaced by larger and larger aggregates and these ultimately coalesce to form a very dense sperm head.
Two centrioles of cylindrical form are situated very near the base of the sperm head. The longitudinal fibrils of the tail flagellum take origin from one, and the dense fibrous substance of the undulating membrane is closely related to the other.
Phase contrast cinematographic observations on the swimming movements of living toad sperm, when considered in relation to the fine structural components of the tail, suggest that there is a contractile component in the undulating membrane as well as in the axial fibrils.
The differences in the structure of mammalian and amphibian sperm tails are discussed in relation to differences in the character of their movements.
ELECTRON MICROSCOPY OF GROWING OOCYTES OF RANA PIPIENS
Authors: Kemp Norman E. 
Published: May 2004

1. In the cytoplasm of oocytes of stage Y0, prior to the appearance of yolk, one observes a few scattered profiles of endoplasmic reticulum and numerous filamentous mitochondria, usually distributed at random but sometimes clustered. As the nuclear membrane begins to bulge outward, small granules and short rods appear in the perinuclear cytoplasm and endoplasmic reticulum becomes more prominent throughout the cytoplasm.
2. Coincident with the appearance of the first yolk platelets, which are deposited in a narrow peripheral ring within the endoplasm at stage Y1, protoplasmic processes, the microvilli, push out all over the surface of the oocyte. At the same time follicle cells pull away but remain attached to the oocyte at some points through finger-like processes which interdigitate with neighboring microvilli. It is estimated that the microvilli increase the absorptive area of the surface to about thirty-five times that of a simple sphere. Just beneath the microvillous layer is the basal protoplasm of the cortex, now containing tiny granules probably synthesized from newly absorbed raw materials. Cortical granules appear and become aligned below the basal layer on the external border of the endoplasm. Both the cortical granules and the yolk platelets measure up to 1 µ in diameter at this stage.
3. By stage Y3 (yolk filling peripheral three-fourths of cytoplasm), the basal layer of the cortex is folded so that it appears in section as alternating ridges and valleys. The microvilli now extend from the summits of the cortical ridges. Small, ring-shaped granules are abundant in the cortex. Cortical granules have increased to 2 µ in diameter.
4. Yolk platelets continue to be synthesized around the cortical granules and in the subjacent endoplasm. The largest platelets measured in the interior cytoplasm at stage Y4 (cytoplasm filled with yolk) were 3.7 µ wide by 5.8 µ long. Pigment granules increase in size from 0.15 µ in diameter at stage Y3 to 0.30 µ in diameter at stage Y4.
THE STRUCTURE OF INSECT VIRUS PARTICLES
Authors: Smith Kenneth M. 
Published: May 2004

Thin sections have been cut of the virus particles from four types of insect virus diseases: cytoplasmic polyhedroses of lepidopterous larvae, a nuclear polyhedrosis of Tipula paludosa (Diptera), a granulosis from Melanchra persicariae (Lepidoptera), and a new virus disease without polyhedra from T. paludosa.
The cytoplasmic polyhedral viruses are thought to have composite particles in some cases. The shape and enveloping membranes of the different virus particles are compared. In the new virus disease of T. paludosa some of the virus particles appear to be empty; inclusion bodies surrounded by complicated membranes are also demonstrated.
UPTAKE AND TRANSFER OF PARTICULATE MATTER FROM THE PERITONEAL CAVITY OF THE RAT
Authors: Odor D. Louise 
Published: May 2004

1. Colloidal mercuric sulfide or thorium dioxide injected intraperitoneally passes into the cytoplasm of the mesothelium of the mesentery and of the diaphragm as early as 15 to 30 minutes after the injection.
2. Between 15 minutes and 12½ hours the number of particles within the mesothelial cells increases as the time between injection and termination of the experiment is lengthened.
3. The particulate matter is usually localized in the cytoplasm within clear vacuoles or bodies having a relatively dense matrix.
4. A greater quantity of the absorbed material is commonly observed within the cytoplasm of the diaphragmatic than of the mesenteric mesothelium.
THE GOLGI ZONE OF THE RAT SPERMATID AND ITS ROLE IN THE FORMATION OF CYTOPLASMIC VESICLES
Authors: Clermont Yves 
Published: May 2004

Electron microscopic study of the Golgi zone of the rat spermatids revealed two main types of vesicular structures: flat vesicles generally accumulated in stacks and spheroidal vesicles of various sizes. The Golgi zone of young spermatids showed a predominance of flat vesicles and small spherical vesicles, while the "residual" Golgi zone of the maturing spermatids displayed an increased number of large spherical vesicles and thus became increasingly vacuolated in appearance.
The images presented were suggestive of a transformation of the flat vesicles into spherical vesicles by fragmentation and dilatation and also of a passage of the spherical vesicles from the Golgi zone to the surrounding cytoplasm.
THE ULTRASTRUCTURE OF STRIATED MUSCLE AT VARIOUS SARCOMERE LENGTHS
Authors: Spiro David 
Published: May 2004

1. Rest and equilibrium length muscle sarcomeres are composed of thin filaments (actin) which traverse the sarcomeres from the Z membranes up to the H band; at this level the filaments are considerably thicker and less numerous.
2. Shortening of muscle is associated with a transformation of thin into thick filaments in the A band.
3. These observations are discussed in terms of interaction of actin and myosin to form a supercoiled structure as the basis of contraction.
INFOLDED BASAL PLASMA MEMBRANES FOUND IN EPITHELIA NOTED FOR THEIR WATER TRANSPORT
Authors: Pease Daniel C. 
Published: May 2004

Epithelia noted for their water transport have been studied by electron microscopy with particular emphasis upon basal specializations. Epithelia of the submaxillary gland, choroid plexus, and ciliary body are described in this article, and compared with previous observations on the kidney.
The basal surface of all these epithelia is tremendously expanded by folds which penetrate deeply into the cytoplasm. In the submaxillary gland this is particularly notable in cells of the serous alveoli and in the secretory ducts. In these instances the folds have a fairly regular distribution and have a marked tendency to turn back upon themselves and so form repeating S-shaped patterns. In the choroid plexus the penetrating basal folds are limited to the lateral regions of each ependymal cell where they blend with the intercellular membranes that are also folded. In the epithelium of the ciliary body it is the inner layer that is specialized. The surface adjacent to the cavity of the eye penetrates irregularly, nearly through the full depth of the cell layer. The exposed surface is, in a fundamental sense, the basal surface of this epithelial layer.
It is apparent that the pattern of folding is quite distinctive in the different epithelia. Therefore, the specializations should be regarded as analogous rather than homologous.
Topographic considerations presumably limit the manner in which basal cell surfaces might be expanded. Penetrating folds would seem to represent almost the only possible solution.
ASPECTS OF CILIARY FINE STRUCTURE IN EUPLOTES PATELLA
Authors: Roth L. E. 
Published: May 2004

1. The functional unity of cirri and membranelles can result structurally only from extensions of the ciliary membrane.
2. The pellicle is composed of an outer pellicular membrane and an inner cytoplasmic membrane.
3. The ciliary rootlets are composed of numerous filaments 120 A in diameter with central areas of low density. They have no periodic structure.
4. The ciliary membrane is a double-layered structure continuous with the pellicular membrane. The cilia show the typical arrangement of nine double, peripheral and two single, central fibrils. All fibrils pass into the basal region, the peripheral ones joining with the rootlet filaments, while the central fibrils from the extreme proximal position of the basal region turn back toward the pellicle and appear to unite just beneath the cytoplasmic membrane.
5. The cilia (300 mµ diameter) taper at their tips to a diameter at least as small as 50 mµ. At a diameter of about 150 mµ, the fibrils begin to show a reduction in number.
6. The central ciliary fibrils may determine the possible directions of ciliary beat. These fibrils show an intrafibrillar structure in their basal portion, which involves regularly spaced 40 A granules.
7. These observations on Euplotes, together with the other evidence cited, are consistent with the hypothesis that ciliary motion is produced by the contraction of the peripheral fibrils, while the central fibrils perhaps determine the plane in which the cilia can bend.
STUDIES ON THE CORNEA. II. THE FINE STRUCTURE OF DESCEMET'S MEMBRANE
Authors: Jakus Marie A. 
Published: May 2004

Descemet's membrane, previously thought to be "structureless," has been found to be characterized by a fine structure of great regularity. Sections perpendicular to the plane of the membrane surface appeared to be cross-striated, with narrow dark bands separated by wide light bands traversed by fine filaments. Tangential sections showed a two-dimensional array of dark nodes and thin internodal filaments which connected each node with the six others around it to form a hexagonal figure. The average distance between nodes, and between the dark bands in transverse sections, was about 1070 A; the width of the nodes was about 270 A; and the width of the connecting filaments was less than 100 A. This pattern has been found in all species of Descemet's membrane so far examined, although it appeared to be better developed in some forms than in others. So far as is known, it has not been observed in any other type of tissue.
The differentiation of Descemet's membrane has been followed in the chick embryo. It appeared late and developed slowly but showed the characteristic fine structure from the time it could be clearly identified.
The evidence for placing Descemet's membrane in the collagen class of proteins is strongly supplemented by the results obtained from x-ray diffraction examination by Rougvie and Bear.