bluuebunny/crossref_metadata_2025 huggingface dataset:
CYTOCHEMISTRY OF PHOSPHATASES OF THE SARCOPLASMIC RETICULUM
Authors: Engel A. G. , Tice Lois W.
Published: May 2004

A microsomal fraction was isolated from rabbit psoas muscle by a modification of Muscatello's method. The fraction contained a Mg-dependent ATPase which had a pH optimum of 7.5. Activity was further stimulated by addition of Na or K or other monovalent cations to the reaction mixture, but synergistic activation by Na and K, and ouabain inhibition, could not be demonstrated. The enzyme hydrolyzed only ATP (adenosine triphosphate) and ITP (inosine triphosphate) at appreciable rates, but Na or K stimulated activity only when ATP was used as substrate. Activity was inhibited by Ca and by low concentrations of Na deoxycholate, and was sensitive to inhibition by thiol group reagents. The enzyme could be distinguished from another enzyme, also present in the fraction, which was Ca-activated, and which exhibited a wider substrate specificity, different pH activation characteristics, lower specific activity, lack of stimulation by Na or K, and less sensitivity to inhibition by deoxycholate and by thiol group reagents. These findings formed the basis for demonstration of the Mg-dependent ATPase in situ.
CYTOCHEMISTRY OF PHOSPHATASES OF THE SARCOPLASMIC RETICULUM
Authors: Tice Lois W. , Engel A. G.
Published: May 2004

The distribution of the Mg-dependent ATPase associated with a microsomal fraction of rabbit psoas muscle was studied histochemically and its localization in relation to the vesicles of the fraction and to the structure of intact fixed muscle was determined. Although enzyme activity was retained after fixation in hydroxyadipaldehyde and in glyoxal, it was lost after fixation in glutaraldehyde or after 4 hr fixation in formaldehyde. Activity was optimally demonstrated when incubations were conducted at 17°C, in media containing 125 mM Trismaleate buffer, pH 7.5, 5 mM ATP, 4 mM MgCl2, and 1 mM Pb(NO3)2. After such incubations, activity was present throughout the sarcoplasmic reticulum, but was absent from the T system. Activation by Na or K could not be demonstrated histochemically. However, the other biochemical properties of the enzyme in the isolated vesicles and in intact muscle were similar with respect to Mg dependence, substrate specificity, inhibition by Ca, N-ethyl maleimide, p-hydroxymercuribenzoate, and lack of inhibition by ouabain.
BASAL BODIES OF BACTERIAL FLAGELLA IN PROTEUS MIRABILIS
Authors: van Iterson Woutera , Hoeniger Judith F. M. , van Zanten Eva Nijman
Published: May 2004

Years ago (16, 18, 19), in a study of shadowed preparations of Proteus vulgaris that had been autolyzed in the cold, the observation was made that the flagella arose from basal bodies. However, recently (3, 7, 24, 33) doubt has been cast on the conclusion that the flagella of bacteria emerge from sizable basal bodies. This problem has, therefore, been reinvestigated with actively developing cultures of Proteus mirabilis, the cell walls of which had been expanded slightly by exposure to penicillin. Two techniques were applied: ultramicrotomy, and negative staining of whole mount preparations. This paper deals with the thin sections of bacteria after the usual fixation technique had been altered slightly: the cells were embedded in agar prior to their fixation and further processing. The flagella then remained attached to the cells and were seen to extend between the cell wall and the plasma membrane. Occasionally, the flagella appeared to be anchored in the cell by means of a hook-shaped ending. In sections of cells rich in cytoplasm, the basal bodies are particularly difficult to visualize due to their small size (25 to 45 mµ) and the lack of properties that would enable one to distinguish them from the ribonucleoprotein structures; in addition, their boundary appears to be delicate. However, when the cytoplasm is sparse in the cells, either naturally or as a result of osmotic shocking in distilled water, the flagella can be observed to emerge from rounded structures approximately 25 to 45 mµ wide. Contrary to a previous suggestion (21), the flagella do not terminate in the peripheral sites of reduced tellurite, i.e. the chondrioids. The observations in this part of the study agree with those described in the following paper (15) dealing with negatively stained preparations.
BASAL BODIES OF BACTERIAL FLAGELLA IN PROTEUS MIRABILIS
Authors: Hoeniger Judith F. M. , van Iterson Woutera , van Zanten Eva Nijman
Published: May 2004

This paper investigates further the question of whether the flagella of Proteus mirabilis emerge from basal bodies. The bacteria were grown to the stage of swarmer differentiation, treated lightly with penicillin, and then shocked osmotically. As a result of this treatment, much of the cytoplasmic content and also part of the plasma membrane were removed from the cells. When such fragmented organisms were stained negatively with potassium phosphotungstate, the flagella were found to be anchored—often by means of a hook—in rounded structures approximately 50 mµ wide, thus confirming Part I of our study. In these rounded structures a more brilliant dot was occasionally observed, which we interpret as being part of the basal granule. A prerequisite for the demonstration of the basal granules within the cells was, however, the removal of both the cytoplasm and the plasma membrane from their vicinity. In some experiments, the chondrioids were "stained" positively by the incorporation into them of the reduced product of potassium tellurite. The chondrioids were here observed to be more or less circular areas from which rodlike structures extended. The chondrioids adhered so firmly to the plasma membrane that they were carried away with it during its displacement by osmotic shocking, while the basal bodies were left behind. This observation disproves our previous suggestion that the flagella might terminate in the chondrioids. The basal bodies often occur in pairs, which suggest that they could be self-reproducing particles.
A "MICROTUBULE" IN A BACTERIUM
Authors: van Iterson Woutera , Hoeniger Judith F. M. , van Zanten Eva Nijman
Published: May 2004

A study of the anchorage of the flagella in swarmers of Proteus mirabilis led to the incidental observation of microtubules. These microtubules were found in thin sections and in whole mount preparations of cells from which most of the content had been released by osmotic shock before staining negatively with potassium phosphotungstate (PTA). The microtubules are in negatively stained preparations about 200 A wide, i.e. somewhat thicker than the flagella (approximately 130 A). They are thus somewhat thinner than most microtubules recorded for other cells. They are referred to as microtubules because of their smooth cylindrical wall, or cortex, surrounding a hollow core which is readily filled with PTA when stained negatively. Since this is probably the first time that such a structure is described inside a bacterium, we do not know for certain whether it represents a normal cell constituent or an abnormality, for instance of the type of "polysheaths" (16).
FINE STRUCTURAL CHANGES IN UTERINE SMOOTH MUSCLE AND FIBROBLASTS IN RESPONSE TO ESTROGEN
Authors: Ross Russell , Klebanoff Seymour J.
Published: May 2004

The fine structure of the estrogen-primed uterus was examined in two series of rats, with emphasis upon the alterations in smooth muscle cells and fibroblasts. The first series of animals were mature animals that were sacrificed at diestrus or estrus. The second series consisted of prepubertal rats (57–70 g) that received subcutaneous injections of estradiol-17 ß in 20% alcohol. Four groups of animals received the hormone twice daily for 3 days for a total dose of 0.06, 0.6, 6.0, or 60.0 µg, respectively. An estrogenic response was observed in all groups as indicated by an increase in uterine weight. Control groups consisted of either untreated animals or animals receiving 20% alcohol. All animals were sacrificed on the 4th day. The fibroblasts and smooth muscle cells in the controls were similar to their counterparts in the mature animal in diestrus. They were small, contained relatively little rough endoplasmic reticulum, and the connective tissue cells appeared like fibrocytes. All of the estrogen-treated animals were similar in appearance and were comparable to their counterparts in the mature animal in estrus. Both the smooth muscle cells and the fibroblasts were increased in size, demonstrated a marked enlargement and dilation of ergastoplasmic cisternae, and contained increased numbers of attached and free cytoplasmic ribosomes. The presence of an extensive rough endoplasmic reticulum in the smooth muscle cells of the stimulated uterus is in marked contrast to the appearance of these cells in other tissues. These observations correlate with previous biochemical studies by other workers, in which estrogens have been shown to promote the synthesis of uterine RNA, collagen, and noncollagenous protein, and suggest that smooth muscle cells may participate in the synthesis of connective tissue proteins.
POLARIZED LIGHT OBSERVATIONS ON STRIATED MUSCLE CONTRACTION IN A MITE
Authors: Aronson John F.
Published: May 2004

Contraction of individual sarcomeres within the living mite Tarsonemus sp. was observed by polarized light microscopy. In unflattened animals the usual range of contraction was such that the minimum sarcomere length approximated the length of the A region, and the maximum sarcomere length was about twice the length of the A region. The central sarcomeres of the dorsal metapodosomal muscles were observed in detail. The A band length increased slightly with increasing sarcomere length since the regression of I region length on sarcomere length had an average slope of 0.91. When the A band length in a sarcomere which was shortening was compared with the length when the same sarcomere lengthened, no significant difference was seen. The A band of each sarcomere seemed to act as a not too rigid limit to further shortening; this agreed with the reversible shortening of a muscle in which the A band had been experimentally shortened. An H region was visible at long sarcomere lengths and was not visible at short sarcomere lengths, even when the muscle was actively shortening. The rate of change of H region length with sarcomere length suggested that I filament length may increase as sarcomere length increases. Despite this effect and the small increase in A length with sarcomere length, the results are considered to be consistent with a model in which shortening occurs by the relative movement of A and I filaments, with little or no change in length of either set of filaments. Sarcomere shortening was clearly associated with an increase in the retardation of the A region.
QUANTITATIVE ANALYSIS OF CELL PROLIFERATION AND DIFFERENTIATION IN THE CORTEX OF THE POSTNATAL MOUSE CEREBELLUM
Authors: Fujita Setsuya
Published: May 2004

The generation cycle of germinative cells (external matrix cells) in the external granular layer of the cerebellar cortex of the 10-to 11-day-old mouse was studied by radioautography following repeated injections of H3-thymidine. The generation time is 19 hr, presynthetic time 8.5 hr, DNA-synthetic time 8 hr, postsynthetic time 2 hr, and mitotic time 0.5 hr. These proliferating cells occupy the outer half of the external granular layer and make up the external matrix layer. Neuroblasts are differentiated from the external matrix cell, migrate out from the layer and accumulate in the inner half of the external granular layer to form the external mantle layer. The transit time of the neuroblasts in the external mantle layer is 28 hr. Thereafter, they migrate farther into the molecular layer and the internal granular layer. By means of long-term cumulative labeling, the rate of daily production of neuroblasts from the external matrix cell is studied in quantitative terms. It becomes clear that the entire population of the inner granule neurons arises postnatally in the external granular layer between 1 and 18 days of age and that 95% of them is produced between postnatal days 4 and 15. Finally, the fate of the cells in the external granular layer at its terminal stage was studied by marking the cells with H3-thymidine during 15–16 days of life and following their subsequent migration and developmental changes up to 21 days of life. Comparison of radioautographs taken before and after the migration disclosed that the external matrix cells give rise to a small number of neuroglia cells. This finding revealed their multipotential nature.
PREPARATION FROM HUMAN SERUM OF AN ALPHA-ONE PROTEIN WHICH INDUCES THE IMMEDIATE GROWTH OF UNADAPTED CELLS IN VITRO
Authors: Holmes Richard
Published: May 2004

An alpha-one protein is separated from human serum on a microbead column. This nondialyzable protein induces the immediate growth of unadapted cells placed in chemically defined Medium A2 + APG. HeLa, conjunctiva and human heart cells, which stop growing if the protein is removed, continue to grow only if the protein is returned or the cells are permitted to adapt to the defined medium. A 90–120 day period is required for adaptation. The spreading and growth of fully adapted cells is also stimulated by the addition of the protein. As little as 0.4 µg per ml of medium is effective. The protein analyzed by paper, starch, and discontinuous acrylamide gel electrophoresis appears to be a single component. The protein is periodate-Schiff positive and readily binds small molecules which are removed, without loss of biological activity, by precipitating the protein in 50% saturated ammonium sulfate. The protein is adsorbed on the microbead column as a complex with the beta lipoprotein fraction of human serum; it cannot be separated from bovine or equinesera by this method; and it is not identical with fetuin. Its biological response is not duplicated by insulin, carbamyl phosphate, putrescine, or linoleic acid.
EFFECTS OF TEMPERATURE ON GROWTH RATE OF CULTURED MAMMALIAN CELLS (L5178Y)
Authors: Watanabe I. , Okada S.
Published: May 2004

L5178Y cells were cultured in vitro at various temperatures. When the cells were in the exponential growth phase, the cells were in the "steady state of growth," i.e., the fraction of cells in the G1, S, G2, and M stages and the durations of each stage were constant. The life cycle analysis of the cells in the steady state of growth demonstrated that the G1 stage and the S stage were affected the most by variation of temperature, and suggested that these two stages have considerable influence on the growth rate of the L5178Y cells. The calculated activation energies were positive in each stage of the life cycle, whereas the entropies of activation were negative throughout. The possible significance of these findings in our search for the regulatory mechanisms of cell growth is discussed.
LYSOSOMES IN LYMPHOID TISSUE
Authors: Bowers William E. , de Duve Christian
Published: May 2004

Differential centrifugation and density gradient isopycnic centrifugation have been used to fractionate homogenates of rat spleen and, in a few experiments, of rat thymus and cervical lymph nodes. The fractions have been analyzed for proteins, DNA, RNA, cytochrome oxidase, esterase, and up to 11 acid hydrolases. The results obtained indicate that the hydrolases are associated, at least largely, with cytoplasmic particles of lysosomal nature, and suggest further that these particles belong to two, and possibly three, distinct populations, perhaps reflecting the cellular heterogeneity of the tissues. The populations are identified as: (a) the L19 population, the most important group, containing all 12 hydrolases and characterized by a modal density of about 1.19 in a sucrose—0.2 M KCl gradient; (b) the L15 population with a modal density of 1.15, a group of apparently incomplete lysosomes containing cathepsin D and a few other enzymes, but very poor in, or entirely devoid of, several acid hydrolases, including cathepsins B and C; (c) the L30 population, comprising all 12 enzymes and banding together with the nuclei at a density of 1.30 or higher. Lack of success in separating the latter group from the nuclei renders its significance unclear.
ELECTRON MICROSCOPE RADIOAUTOGRAPHY AS A QUANTITATIVE TOOL IN ENZYME CYTOCHEMISTRY
Authors: Salpeter Miriam M.
Published: May 2004

Tritiated diisopropylfluorophosphate (DFP) was used to phosphorylate acetylcholinesterase (AChase) in the motor end plate of mouse sternomastoid muscle, and its distribution within the end plate was evaluated quantitatively by electron microscope radioautography. With the use of emulsion layers whose sensitivity to tritium had been calibrated, the density of AChase in different components of the end plate was calculated. The AChase was primarily localized (85%) in the junctional fold region. The concentration of AChase there was more than 20,000 active sites per cubic micron of tissue. The resolution of the technique was not sufficient to determine whether there was some AChase in the nerve end bulb; however, if there is any there, the concentration must be less than 10% of that at the junctional fold region.
OCTAGONAL NUCLEAR PORES
Authors: Gall Joseph G.
Published: May 2004

Negative staining of isolated nuclear envelopes by phosphotungstate shows that the nuclear pores are octagonal rather than circular. Pores of the same shape and approximately the same width, 663 ± 5 A, were demonstrated in the newt, Triturus, the frog, Rana, and the starfish, Henricia. The outer and inner diameters of the annulus associated with each pore are respectively greater and less than the width of the pore itself. For this reason surface views of the envelope, unless negatively stained, fail to show the true dimensions of the pores.
A LIGHT AND ELECTRON MICROSCOPE STUDY OF LONG-TERM ORGANIZED CULTURES OF RAT DORSAL ROOT GANGLIA
Authors: Bunge Mary Bartlett , Bunge Richard P. , Peterson Edith R. , Murray Margaret R.
Published: May 2004

Dorsal root ganglia from fetal rats were explanted on collagen-coated coverslips and carried in Maximow double-coverslip assemblies for periods up to 3 months. These cultured ganglia were studied in the living state, in stained whole mounts, and in sections after OsO4 fixation and Epon embedment. From the central cluster of nerve cell bodies, neurites emerge to form a rich network of fascicles which often reach the edge of the carrying coverslip. The neurons resemble their in vivo counterparts in nuclear and cytoplasmic content and organization; e.g., they appear as "light" or "dark" cells, depending on the amount of cytoplasmic neurofilaments. Satellite cells form a complete investment around the neuronal soma and are themselves everywhere covered by basement membrane. The neuron-satellite cell boundary is complicated by spinelike processes arising from the neuronal soma. Neuron size, myelinated fiber diameter, and internode length in the cultures do not reach the larger of the values known for ganglion and peripheral nerve in situ (30). Unmyelinated and myelinated nerve fibers and associated Schwann cells and endoneurial and perineurial components are organized into typical fascicles. The relationship of the Schwann cell and its single myelinated fiber or numerous unmyelinated fibers and the properties of myelin, such as lamellar spacing, mesaxons, Schmidt-Lanterman clefts, nodes of Ranvier, and protuberances, mimic the in vivo pattern. It is concluded that cultivation of fetal rat dorsal root ganglia by this technique fosters maturation and long-term maintenance of all the elements that comprise this cellular community in vivo (except vascular components) and, furthermore, allows these various components to relate faithfully to one another to produce an organotypic model of sensory ganglion tissue.
CYTOLOGICAL STUDIES OF ORGANOTYPIC CULTURES OF RAT DORSAL ROOT GANGLIA FOLLOWING X-IRRADIATION IN VITRO
Authors: Masurovsky Edmund B. , Bunge Mary Bartlett , Bunge Richard P.
Published: May 2004

Long-term organotypic cultures of rat dorsal root ganglia were exposed to a single 40 kR dose of 184 kvp X-rays and studied in the living and fixed states by light or electron microscopy at 1–14 day intervals thereafter. Within the first 4 days following irradiation, over 30% of the neurons display chromatolytic reactions (eccentric nuclei, peripheral dispersal of Nissl substance, central granular zone) as well as abnormal nucleolar changes and dissociation of ribosomes from endoplasmic reticulum cisternae. Some satellite cells undergo retraction or acute degeneration, leaving only basement membrane to cover the neuron in these areas. 8 days after irradiation, neurons also exhibit (a) areas in which ribosomes are substantially reduced, (b) regions of cytoplasmic sequestration, (c) extensive vacuolization of granular endoplasmic reticulum and Golgi complex, and (d) diversely altered mitochondria (including the presence of ribosome-like particles or association with abnormal glycogen and lipid deposits). Nucleolar components become altered or reoriented and may form abnormal projections and ringlike configurations. Sizeable areas of the neuronal soma are now denuded of satellite cells; underlying these areas, nerve processes are found abnormally invaginated into the neuronal cytoplasm. By the 14th day following irradiation, most neurons display marked degenerative changes including extensive regions of ribosome depletion, sequestration, vacuolization, autolysis, and, in some areas, swirls of filaments, myelin figures, and heterogeneous dense bodies. These observations demonstrate that X-irradiation produces profound cytopathological changes in nervous tissue isolated from the host and that many of these changes resemble the effects of radiation on nervous tissue in vivo.
CYTOLOGICAL STUDIES OF ORGANOTYPIC CULTURES OF RAT DORSAL ROOT GANGLIA FOLLOWING X-IRRADIATION IN VITRO
Authors: Masurovsky Edmund B. , Bunge Mary Bartlett , Bunge Richard P.
Published: May 2004

Under suitable conditions rat dorsal root ganglia differentiate and myelinate in culture, providing an organotypic model of the ganglion (8). Mature cultures of this type were irradiated with a 40 kR dose of 184 kvp X-rays and, after daily observation in the living state, were fixed for light and electron microscopy. Within 24 hr after irradiation, numerous Schwann cells investing unmyelinated axons acutely degenerate. The axons thus denuded display little change. Conversely, few ultrastructural changes develop in Schwann cells investing myelinated axons until after the 4th day. During the 4–14 day period, these Schwann cells and their related myelin sheaths undergo progressive deterioration. Associated axons decrease in diameter but are usually maintained. Myelin deterioration begins as a nodal lengthening and then progresses along two different routes. In intact Schwann cells, fragmentation of myelin begins in a pattern reminiscent of Wallerian degeneration, but its slow breakdown thereafter suggests metabolic disturbances in these Schwann cells. The second pattern of myelin deterioration, occurring after complete degeneration of the related Schwann cell, involves unusual configurational changes in the myelin lamellae. Atypical repeating periods are formed by systematic splitting of lamellae at each major dense line with further splitting at the intraperiod line (Type I) or by splitting in the region of every other intraperiod line (Type II); some sheaths display a compact, wavy, inner zone and an abnormally widened lamellar spacing peripherally (Type III). Extensive blebbing of myelin remnants characterizes the final stages of this extracellular myelin degradation. These observations provide the first description of ultrastructural changes produced by ionizing radiation in nerve fascicles in vitro.
THE SARCOPLASMIC RETICULUM AND ITS ASSOCIATION WITH THE T SYSTEM IN AN INSECT
Authors: Hagopian Martin , Spiro David
Published: May 2004

The fine structure of the sarcoplasmic reticulum and the transverse tubular system of the femoral muscle of the cockroach, Leucophaea maderae, was studied after prefixation in glutaraldehyde, postfixation in osmium tetroxide, and embedding in Epon. The sarcoplasmic reticulum in this muscle reveals features not previously reported. The sarcoplasmic reticulum is abundant, consisting mainly of a fenestrated envelope which surrounds each myofibril at all levels in the sarcomere. This sarcoplasmic reticulum envelope is continuous transversally as well as longitudinally along the myofibrils. Dyadic junctions are formed by a single T system element which contacts the unfenestrated sarcoplasmic reticulum of adjacent myofibrils in an alternating manner at the ends of the A band. At the dyads, regularly spaced thickenings of the sarcoplasmic reticulum membranes bordering the dyadic spaces are noted. These thickenings, however, do not contact the T tubule membrane. Typical dyadic contacts also are seen between the cell surface membrane and sarcoplasmic reticulum. Z line-like material is seen in contact with the membranes of the cell surface and longitudinal branches of the T systems.
CHOLINESTERASE ACTIVITY OF NODAL AND INTERNODAL REGIONS OF MYELINATED NERVE FIBERS OF FROG
Authors: Brzin Miro , Dettbarn Wolf-D.
Published: May 2004

The distribution of cholinesterase (Ch-esterase) in isolated myelinated fibers of the frog has been investigated. Quantitative microgasometric measurements have confirmed the previous histochemical observations. Both approaches indicate that in frog nerve fibers acetylcholinesterase (ACh-esterase) is the only or the predominant enzyme when selective inhibitors and different substrates are used: acetylcholine (ACh), butyrylcholine, and acetyl-B-methylcholine (Mecholyl). By means of the microgasometric technique, a significant difference in ACh-esterase activity between axons isolated from ventral (37.2 ± 1.7 µmole x 10-5 ACh/mm2/hr) and dorsal roots (2.0 ± 0.9 µmole x 10-5 ACh/mm2/hr) was found. In the region of the node of Ranvier the enzyme activity (50.4 ± 4.4 µmole x 10-5 ACh/mm2/hr) appears to be considerably higher than in the internodal area (36.6 ± 2.1 µmole x 10-5 ACh/mm2/hr). The findings are discussed in relation to the theory of saltatory conduction and the ACh system.
A STUDY OF NEWT MITOTIC CHROMOSOMES BY NEGATIVE STAINING
Authors: Barnicot N. A.
Published: May 2004

A method is described for bursting single, selected mitotic cells on a fluid surface. Cells from cultures of newt heart tissue were burst on dilute solutions containing potassium and sodium with and without added calcium and also on dilute calcium chloride solution. The material was negatively stained with uranyl acetate or sometimes with ammonium molybdate or sodium phosphotungstate. The bodies of chromatids spread on NaCl/KCl solutions showed many parallel fibers about 150 A in diameter. Loops with a complex nodular structure were observed projecting from the sides and ends of chromatids. In calcium-containing solutions there was evidence of fiber coagulation; the chromatid body was more compact and laterally projecting fibers tended to be pulled out straight. Especially in the absence of calcium the chromosomal fibers had a nodular form and appeared to be composed of irregularly folded fibrillar elements. The question as to whether chromosomal fibers, which range in diameter from about 50 to 300 A, consist of single, folded threads or of two or more adjacent subunits is discussed.
METABOLIC AND MORPHOLOGICAL OBSERVATIONS ON THE EFFECT OF SURFACE-ACTIVE AGENTS ON LEUKOCYTES
Authors: Graham R. C. , Karnovsky M. J. , Shafer A. W. , Glass E. A. , Karnovsky Manfred L.
Published: May 2004

Morphological and metabolic observations have been made on the effects of endotoxin, deoxycholate, and digitonin (at less than 50 µg/ml) on polymorphonuclear leukocytes and mononuclear cells. The agents stimulate the respiration and glucose oxidation of these cells in a manner similar to that seen during phagocytosis. Electron microscopy revealed no morphological changes with the first two agents, but dramatic membrane changes were seen in the case of digitonin. Here tubular projections of characteristic size and shape formed on and split off the membrane. All the agents stimulated uptake of inulin, but efforts to demonstrate increased pinocytosis by electron microscopy have not so far succeeded, probably due to limitations in present experimental techniques.
SPERMIOGENESIS IN WILD TYPE AND IN A MALE STERILITY MUTANT OF DROSOPHILA MELANOGASTER
Authors: Shoup Jane Rearick
Published: May 2004

Spermiogenesis in the translocation heterozygote T (1; 2H) 25(20) y l 25/FM6 has been studied with the electron microscope and compared with that in wild type males. It appears that the genetic lesion in the male sterility mutant is associated primarily with a failure in differentiation of the head. In wild type flies, the spermatid nucleus assumes a conchoidal shape; chromatin accumulates along the convex surface. Adjacent to the concave surface a large bundle of microtubules runs parallel to the long axis of the spermatid. A single row of microtubules is juxtaposed against the convex surface of the head. As differentiation proceeds, the nucleus elongates, chromatin condenses, and the nucleus is compacted to a final diameter of about 0.3 µ. In the sterile mutant the spermatid nucleus has an irregular or wedge-shaped profile and no concavity is formed, nor is the bundle of microtubules observed. The row of microtubules, however, is usually present around the periphery. The change from lysine-rich to arginine-rich histone in mature wild type sperm does not occur in the sterile male. The substructure of the axial filament and mitochondrial derivatives, however, are similar to those in wild type.
STUDIES ON PROTEIN UPTAKE BY ISOLATED TUMOR CELLS
Authors: Ryser Hugues J.-P.
Published: May 2004

Fixation of 131I-serum albumin by Ehrlich ascites tumor cells in suspensions and sarcoma S-180 monolayers was measured under experimental conditions. Anaerobic incubation and inhibitors of the oxidative metabolism critically restricted the range of glucose concentrations capable of supporting cell life; in glucose concentrations higher than 10-2 M, Ehrlich cells suffered from their own acid production; in concentrations 10-2 M, lower than they underwent damage by starvation. Both types of damage were accompanied by increased albumin fixation unrelated to pinocytosis. Different procedures recommended to enhance the uptake of infectious viral RNA by animal cells in culture were tested for their ability to increase albumin uptake. They enhanced the penetration of both albumin and vital dyes and decreased the viability of cell populations. Their effect, therefore, is related to cell damage. It was postulated that reversible damage to cells favors RNA infection by leading to abnormal uptake processes and by decreasing intracellular digestion. This abnormal uptake is different from pinocytosis and also from the massive fixation of albumin to dead cells. The latter phenomenon is due to adsorption by intracellular sites exposed by disruption of the cell membrane. Polycations are able to induce all three forms of fixation depending on the experimental conditions.
ULTRASTRUCTURE OF THE SHOOT APEX OF CHENOPODIUM ALBUM AND CERTAIN OTHER SEED PLANTS
Authors: Gifford Ernest M. , Stewart Kenneth D.
Published: May 2004

The ultrastructure of cells of the vegetative shoot apices is described for Chenopodium album, Kalanchoë blossfeldiana and K. laxiflora, Bryophyllum daigremontianum, Nicotiana rustica, and N. tabacum (Maryland Mammoth), and Ginkgo biloba. A less intensive study was made of the last three listed. The structures and organelles usually associated with meristematic cells were observed: dictyosomes, plastids (in various stages of development), mitochondria, endoplasmic reticulum (ER), vacuoles, lipid droplets, and plasmalemma. In addition, spherosome-like structures were observed in all zones of the shoot apices. Also, multivesicular bodies were observed in C. album and B. daigremontianum. Ribosome density is greater in cells of the flank meristem. Proplastids, plastids with prolamellar bodies, or grana have a differential distribution in the apex, characteristic for a particular species. Confirmation could not be given to the concept that vacuoles arise as a series of local dilations in long extensions of the so called "smooth ER." The tonoplast and ER are distinguishable at the time of inception of a vacuole, although the tonoplast may arise from the ER. Rapid growth of a vacuole and/or fusion with other vacuoles may result in irregularly shaped prevacuoles. No vacuoles were observed to originate from cisternae of dictyosomes in the species studied.
BONE FORMATION INDUCED IN MOUSE THIGH BY CULTURED HUMAN CELLS
Authors: Anderson H. Clarke , Coulter P. R.
Published: May 2004

Cultured FL human amnion cells injected intramuscularly into cortisone-conditioned mice proliferate to form discrete nodules which become surrounded by fibroblasts. Within 12 days, fibroblastic zones differentiate into cartilage which calcifies to form bone. Experiments were conducted to test the hypothesis that FL cells behave as an inductor of bone formation. In the electron microscope, FL cells were readily distinguished from surrounding fibroblasts. Transitional forms between the two cell types were not recognized. Stains for acid mucopolysaccharides emphasized the sharp boundary between metachromatic fibroblastic and cartilaginous zones and nonmetachromatic FL cells. 35S was taken up preferentially by fibroblasts and chondrocytes and then deposited extracellularly in a manner suggesting active secretion of sulfated mucopolysaccharides. FL cells showed negligible 35S utilization and secretion. FL cells, labeled in vitro with thymidine-3H, were injected and followed radioautographically, during bone formation. Nuclear label of injected FL cells did not appear in adjacent fibroblasts in quantities sufficient to indicate origin of the latter from FL cells. The minimal fibroblast nuclear labeling seen may represent reutilization of label from necrotic FL cells. It is suggested that FL cells injected into the mouse thigh induced cartilage and bone formation by host fibroblasts.
STUDIES OF SPERMATOGENESIS IN THE HEPATICAE
Authors: Carothers Zane B. , Kreitner Gerald L.
Published: May 2004

Spermatids of the liverwort Marchantia polymorpha were shown by analysis of thin-sections to contain a four-layered organelle, the Vierergruppe, lying between the flagellar bases above and a subjacent mitochondrial body. The uppermost layer consists of parallel tubules structurally similar to those of the axoneme. Some of the tubules extend beyond the four-layered region to form a long ribbon-like appendage. The second layer consists of low, vertical, membranous fins connected by numerous short links to the tubules above. The third layer, limited above and below by two horizontal membranes, consists of vertical partitions, apparently continuous with the fins. The fourth and lowermost layer consists of narrow parallel tubules aligned beneath alternate partitions. The long axes of the lower three layers are parallel to each other and lie at an angle of 48° to the tubule axis of the uppermost stratum. A graphic representation of a three-dimensional scale model interpreting organelle structure is given. The Vierergruppe supersedes Dreiergruppe interpretation in most if not all of the bryophytes studied to date.
THE LOCALIZATION OF ACETYLCHOLINESTERASE AT THE AUTONOMIC NEUROMUSCULAR JUNCTION
Authors: Robinson Peter M. , Bell Christopher
Published: May 2004

Acetylcholinesterase has been localized at the autonomic neuromuscular junction in the bladder of the toad (Bufo marinus) by the Karnovsky method. High levels of enzyme activity have been demonstrated in association with the membranes of cholinergic axons and the adjacent membranes of the accompanying Schwann cells. The synaptic vesicles stained in occasional cholinergic axons. After longer incubation times, the membrane of smooth muscle cells close to cholinergic axons also stained. Axons with only moderate acetylcholinesterase activity or with no activity at all were seen in the same bundles as cholinergic axons, but identification of the transmitter in these axons was not possible.
INTERCELLULAR COMMUNICATION AND TISSUE GROWTH
Authors: Loewenstein Werner R. , Kanno Yoshinobu
Published: May 2004

Intercellular communication was examined with intracellular electrical techniques in primary and transplanted rat liver cancers. Normal liver cells communicate rather freely with each other through permeable junctional membranes. Cancer liver cells show no communication at all; their surface membrane is a strong barrier to diffusion all around the cell. Cancer cells induce alterations in membrane permeability in normal liver cells; communication among the latter is markedly reduced when cancer cells grow near them.
INTERCELLULAR COMMUNICATION AND TISSUE GROWTH
Authors: Loewenstein Werner R. , Penn Richard D.
Published: May 2004

Intercellular communication was examined in regenerating rat liver and urodele skin, two tissues of fast but normal growth. In both, cellular communication is in general as good as in their respective normal intact state. This stands in striking contrast to the lack of cellular communication in tissues with cancerous growth. Upon wounding of the urodele skin, the normally permeable junctional membranes of cells near the wound border seal themselves off, thereby insulating the interiors of the communicated cell systems from the exterior. When the cells of two opposing borders make mechanical contact in the course of wound closure, communication between them ensues within 30 min. Within this period all cell movement also ceases ("contact inhibition"). The possible implications of these findings in the control of tissue growth are discussed.
PARTICLE ARRANGEMENTS IN PROPLASTIDS OF TRITICUM VULGARE L. SEEDLINGS
Authors: Bartels Paul G. , Weier T. Elliot
Published: May 2004

Particles having ribosome-like characteristics are described in proplastids of dark-grown wheat seedlings as the membranes of the prolamellar body become transformed, under the influence of light, into grana and fret membranes. Three arrangements of particles were noted: (1) a random distribution of discrete particles; (2) particles occurring in helices or parallel rows; and (3) particles arranged in rough squares with six to eight particles per side. It is possible that the third type of particle is a cross-section of long parallel rods. A particle ranges in size from 170 to 220 A, those of group three being somewhat smaller. The particulates vary from diamond shaped with smooth surfaces to circular with irregular surfaces. These particles have the characteristics of ribosomes as visualized by the electron microscope: they are preserved by glutaraldehyde and osmium tetroxide, they stain intensely with uranyl acetate, and are digested by RNase. Their properties do not coincide with those of viruses, smog-induced particles, stromacenter particles, or phytoferritin. They are frequently adjacent to membranes but never attached to membranes. The involvement of ribosomes in membrane development is discussed.
SYNTHESIS OF RNA IN MAMMALIAN CELLS DURING MITOSIS AND INTERPHASE
Authors: King Donald W. , Barnhisel M. L.
Published: May 2004

Chinese hamster cells in the mitotic and G1 phases of the growth cycle were incubated for 30 or 60 min in suspension tissue culture and pulse-labeled with tritiated uridine. After appropriate chases, washes, and extractions, it was found that all incorporation into the nucleic acid may be accounted for by those cells in interphase. An average of 410 counts was found for incorporation into the cell population (approximately 2.0 x 105 cells) of which over 80% of the cells was initially in mitosis. The increasing number of cells leaving mitosis and entering interphase during the 30 min incubation was theoretically able to account for 470 counts. In addition, short-pulse labeling experiments have shown a consistent linear relationship between the percentage of cells in division and the incorporation of the isotope, which strongly suggests that, if 100% of the cells were in mitosis, the counts would be essentially zero. Thus, the entire label may be attributed to those cells in interphase where portions of the chromosomal material are known to be already extended.
NUCLEOLAR AND NUCLEAR RNA SYNTHESIS DURING THE CELL LIFE CYCLE IN MONKEY AND PIG KIDNEY CELLS IN VITRO
Authors: Showacre Jane L. , Cooper W. G. , Prescott D. M.
Published: May 2004

The incorporation of 5-3H-uridine and 5-3H-cytidine into nucleolar and nonnucleolar RNA in the nucleus of monkey and pig kidney cells was measured in vitro during the cell life cycle. Time-lapse cinematographic records were made of cells during asynchronous exponential proliferation, in order to identify the temporal position of individual cells in relation to the preceding mitosis. Immediately following cinematography, cells were labeled with uridine-3H and cytidine-3H for a short period, fixed, and analyzed by radioautography. Since the data permit correlation of the rate of RNA labeling with the position of a cell within the cycle, curves could be constructed describing the rate of RNA synthesis over the average cell cycle. RNA synthesis was absent in early telophase, and rose very abruptly in rate in late telophase and in very early G1 in both the nucleus and the reconstituting nucleolus. Thereafter, through the G1 and S periods the rate of nuclear RNA synthesis rose gradually. When we used a 10-min pulse, there was no detectable change in the rate for nucleolar RNA labeling in monkey kidney cells during G1 or S. When we used a 30-min labeling time, the rate of nucleolar RNA labeling rose gradually in pig kidney cells. With increasing time after mitosis, the data became more variable, which may, in part, be related to the variation in generation times for individual cells.
MICRONUCLEAR RNA SYNTHESIS IN PARAMECIUM CAUDATUM
Authors: Rao M. V. Narasimha , Prescott David M.
Published: May 2004

In a generation time of 8 hr in Paramecium caudatum, the bulk of DNA synthesis detected by thymidine-3H incorporation takes place in the latter part of the cell cycle. The micronuclear cycle includes a G1 of 3 hr followed by an S period of 3–3½ hr. G2 and division occupies the remaining period of the cycle. Macronuclear RNA synthesis detected by 5'-uridine-3H incorporation is continuous throughout the cell cycle. Micronuclear RNA synthesis is restricted to the S period. Ribonuclease removes 80–90% of the incorporated label. Pulse-chase experiments showed that part of the RNA is conserved and released to the cytoplasm during the succeeding G1 period.
REVERSIBLE DEGRADATION OF POLYRIBOSOMES IN CHANG CELLS CULTURED IN A GLUTAMINE-DEFICIENT MEDIUM
Authors: Eliasson Eva , Bauer G. Eric , Hultin Tore
Published: May 2004

The effects of temporary glutamine deficiency on the protein and nucleic acid metabolism of Chang's liver cells in suspension cultures have been studied. It was observed that cells maintained in a glutamine-free medium showed a reduced incorporation of labeled precursors into protein and RNA. At the same time, the activity of the ribosomes and the proportion of polyribosomal aggregates in cell extracts diminished. These effects were reversed when the glutamine content of the medium was restored. The restoration of a normal rate of amino acid incorporation by intact cells as well as by cell-free systems was time dependent, and took place within a few hours after glutamine addition without preceding increase in the prevailing low rate of RNA synthesis. The addition of actinomycin D at concentrations that strongly inhibited the RNA metabolism of the cells did not prevent the increase in protein synthesis or the reappearance of polyribosomal aggregates. These facts suggest that the restoration of protein synthesis in the cells after glutamine starvation was not dependent on a production of new messenger RNA. The experimental data are consistent with the hypothesis that previously synthesized messenger RNA, preserved in the cells in a stable form, was brought into action in response to the reestablishment of an adequate cellular environment.
ENZYME-LABELED ANTIBODIES FOR THE LIGHT AND ELECTRON MICROSCOPIC LOCALIZATION OF TISSUE ANTIGENS
Authors: Nakane Paul K. , Pierce G. Barry
Published: May 2004

Enzymes, either acid phosphatase or horseradish peroxidase, were conjugated to antibodies with bifunctional reagents. The conjugates, enzymatically and immunologically active, were employed in the immunohistochemical localization of tissue antigens utilizing the reaction product of the enzymatic reaction as the marker. Tissues reacted with acid phosphatase-labeled antibodies directed against basement membrane were stained for the enzyme with Gomori's method, and those reacted with peroxidase-labeled antibody were stained with Karnovsky's method. The reaction products of the enzymes localized in the basement membrane. Unlike the preparations of the fluorescent antibody technique, enzyme-labeled antibody preparations were permanent, could be observed with an ordinary microscope, and could be examined with the electron microscope. In the latter, specific localization of antibody occurred in the basement membrane and in the endoplasmic reticulum of cells known to synthesize basement membrane antigens. The method is sensitive because of the amplifying effect of the enzymatic activity. The ultrastructural preservation and localization were better with acid phosphatase-labeled antibody than with peroxidase-labeled antibody, but acid phosphatase conjugated antibody was unstable and difficult to prepare. Peroxidase-antibody conjugates were stable and could be stored for several months at 4°C, or indefiniely in a frozen state.
LIPID SYNTHESIS, INTRACELLULAR TRANSPORT, STORAGE, AND SECRETION
Authors: Stein Olga , Stein Yechezkiel
Published: May 2004

A time sequence study of intracellular movement of labeled lipid in the liver was carried out on fasted and ethanol-treated rats injected with either palmitate-3H or glycerol-3H by electron microscopic radioautography. The elimination of water-soluble lipid precursors during specimen preparation was checked and found to be complete. The labeled lipid product in the tissue was identified as mostly triglyceride. A dehydration procedure was adapted to minimize the loss of lipid during specimen preparation. At 2 min after injection, the earliest time interval studied, both precursors were found to have penetrated the liver cells, and the label was found over both rough and smooth elements of the endoplasmic reticulum, which is the site of glyceride esterification. From 5 min on, in fasted and especially in ethanol-treated rats, the label was seen also over lipid droplets 0.5–2.0 µ in diameter, which represent "storage lipid" (slowly turning over compartment). Mitochondria became labeled mostly at later time intervals after injection. From 10 min on, concentration of label was seen over the Golgi apparatus, containing small osmiophilic particles. Association of label with groups of particles in smooth-surfaced vesicles and vacuoles in and near the Golgi apparatus and in the vicinity of the sinusoidal border was seen, both after palmitate-3H and glycerol-3H. It is proposed that these particles represent lipoproteins which are formed in the endoplasmic reticulum, "processed" in the Golgi apparatus, and transported in vacuoles to the sinusoid surface to be discharged into the circulation.
STUDIES ON CELL DEFORMABILITY
Authors: Weiss Leonard
Published: May 2004

The nonlethal procedure of incubation in EDTA solution makes the peripheral regions of ascites sarcoma 37 cells more easily deformable, as reflected in measurements of the decreased amount of negative pressure required to suck out standard hemispherical bulges from the cells into micropipettes. The facilitation of deformability was abolished after reincubation of cells in calcium-containing saline, and this mechanical parameter was partially restored to normal after reincubation in magnesium-containing saline; the mechanical effect of EDTA treatment is, therefore, thought to be due mainly to the removal of calcium from the cell periphery. As EDTA treatment produces no detectable change in cellular electrophoretic mobility, it is concluded that peripheral calcium must be bound to anionic sites deeper than about 10 A from the cellular hydrodynamic slip plane. The data are discussed with emphasis on the view that they should not be extrapolated freely to other cell types.