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  • 1
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The pulmonary veins of albino Wistar rats were studied by means of light and electron microscopy. The media of larger veins consists of cardiac muscle fibers which extend until the vessels attain about 100 μ in diameter. This coat consists of external longitudinal fibers and internal circular fibers. The vasa vasorum are well developed and the capillaries show pseudofenestrations. The numerous adrenergic and cholinergic nerve endings do not form typical motor end-plates as seen in skeletal muscles. The ultrastructure of these media muscle fibers is similar to that of rat hearts. The smooth muscle layer of larger pulmonary veins is not continuous as it is in smaller veins where it forms cushions. Comparisons of albino rats and other rodents reveal striking differences.Action potential shape and propagation velocity (0.5-1.2 m/s) along the myocardial coat of the pulmonary vein were similar to those observed in the left atrium and so was their sensitivity to locally applied acetylcholine. The physiological direction of propagation in rat pulmonary veins is toward the lung. This finding lends support to the hypothesis of a rhythmic, valve-like action of the striated musculature of the pulmonary venous wall during the systole and a possible role in the capacitance of the pulmonary circulation.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 81 (1973), S. 149-151 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Warming of exponentially growing T. pyriformis to 34°C results in severe inhibition of nucleotide pool formation. The utilization of the pool for stable RNA synthesis is poorly affected at the high temperature. It thus appears that the synthesis and processing of ribosomal RNA precursors are not primarily impaired at 34°C.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 1 (1981), S. 469-483 
    ISSN: 0886-1544
    Keywords: microtubules ; nucleation ; mitosis ; nocodazole ; immunocytochemistry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The reassembly of microtubules is described in mitotic cells after release from nocodazole-induced block. The formation of microtubules was followed by light microscopic immunocytochemical staining using the PAP method, combined with to-luidine blue staining of the chromatin. The light microscopic observations on whole cells were compared with ultrastructural observations on thin sections. This step is essential to ascertain complete destruction of microtubules during the nocodazole treatment and to correlate immunocytochemical staining with the presence of microtubules.Removal of nocodazole (10 or 1 μg/ml) after a sufficiently long incubation to induce a complete disappearance of microtubules resulted in the appearance of tubulin staining specifically associated with the centromeres and with one or two isolated points in the cytoplasm. Electron microscopy confirmed that the staining was due to the massive accumulation of small microtubules at the kinetochores and centrosomes. Kinetochore nucleation was seen only in association with condensed metaphase-stage chromosomes and not with the less-condensed prophase chromosomes.In a second type of experiment cells were allowed to enter mitosis in the presence of an incompletely active concentration of nocodazole (0.1 μg/ml). The construction of the mitotic spindle was arrested; however, short microtubules were assembled at the kinetochores and centrosomes.These experiments demonstrate that in living mitotic PTK2 cells the kinetochores, as well as the centrosomes, exert a nucleating action on tubulin assembly.The further elongation of microtubules after removal of nocodazole was seen to occur preferentially along axes between the centrosomes and the kinetochores. This resulted in the construction of normal metaphases that evolved through anaphase and telophase. We have attempted to formulate a hypothesis that may explain the oriented assembly that seems to be essential in the construction of the spindle.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 105-113 
    ISSN: 0886-1544
    Keywords: video-microscopy ; colloidal gold ; immunocytochemistry ; microtubules ; receptors ; saltatory motion ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We describe a new approach to probe the molecular biology of the living cell that uses small colloidal gold particles coupled to specific ligands. They are visualized in cells by bright-field, video enhanced contrast microscopy. We describe the basic aspects of the technique and provide examples of applications to intracellular motility, cell membrane dynamics, receptor translocation, internalization, and intracellular routing. We also provide examples of the use of this approach in immunospecific labelling of cells and tissue sections.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 20-28 
    ISSN: 0886-1544
    Keywords: proliferation ; large T antigen ; peripheral nervous system ; cytoskeleton ; microtubules ; myelination ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Schwann cells (SC), the myelinating cells of the peripheral nervous system, show a remarkable capacity to switch from a differentiated state to a proliferative state both during development and peripheral nerve regeneration. In order to better understand the regulatory mechanisms involved with this change we are studying a Schwann cell line transfected with the SV-40 large T gene (TSC). Serum-free medium combined with elevating intra-cellular cAMP levels produced a slower proliferating TSC whose morphology changed from pleiomorphic to process bearing, reminiscent of primary SC in culture. This change was abrogated by colcemid but was unaltered by cytochalasin D, indicating a major role for microtubules. Ultrastructural studies demonstrated numerous microtubules in the cellular extensions which correlated with strong immunocytochemical staining for tubulin in the processes. Analysis of cytoskeletal fractions from the treated cells revealed a greater proportion of tubulin in the polymerized state compared with untreated cells which closely resembled the distribution in primary SC. The cytoskeletal changes observed in the TSC as a result of elevating the intra-cellular cAMP levels may reflect the earliest cellular changes in the induction of myelination. © 1994 Wiley-Liss, Inc.
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  • 6
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Lovastatin (LOV), a hydroxy-methylglutaryl-coenzyme A (HMGCoA) reductase competitive inhibitor, blocks epidermal growth factor (EGF) -  or prostaglandin F2α (PGF2α) - induced mitogenesis in confluent resting Swiss 3T3 cells. This inhibition occurs even in the presence of insulin, which potentiates the action of these mitogens in such cells. LOV exerts its effect in a 2-80 μM concentration range, with both mitogens attaining 50% inhibition at 7.5 μM. LOV exerted its effect within 0-8 h following mitogenic induction. Mevanolactone (10-80 μM) in the presence of LOV could reverse LOV inhibition within a similar time period. LOV-induced blockage of PGF2α response is reflected in a decrease in the rate of cell entry into S phase. Neither cholesterol, ubiquinone, nor dolichols of various lengths could revert LOV blockage. In EGF- or PGF2α-stimulated cells, LOV did not inhibit [3H]leucine or [3H]mannose incorporation into proteins, while tunicamycin, an inhibitor of N′ glycosylation, prevented this last phenomenon. Thus, it appears that LOV exerts its action neither by inhibiting unspecific protein synthesis nor by impairing the N′ glycosylation process. These findings strongly suggest that either EGF or PGF2α stimulations generate early cell cycle signals which induce mevalonate formation, N′ glycoprotein synthesis, and proliferation. The causal relationship of these events to various mechanisms controlling the onset of DNA synthesis is also discussed. © 1995 Wiley-Liss, Inc.
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  • 7
    ISSN: 0192-253X
    Keywords: Somatic embryogenesis ; temperature-sensitive mutant ts11 ; chitinase ; carrot (Daucus carota L.) ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: At the nonpermissive temperature, somatic embryos of the temperature-sensitive (ts) carrot (Daucus carota L.) cell variant ts11 only proceed beyond the globular embryo stage in the presence of medium conditioned by wild-type cells. The causative component in the conditioned medium has been identified as an acidic 32 kD endochitinase. An antiserum raised against the 32 kD chitinase detected this protein in culture medium from ts11 embryo cultures grown at the permissive temperature as well as at the nonpermissive temperature. No difference in biochemical characteristics or in effect on ts11 embryo development could be detected between the 32 kD chitinase purified from wild-type cultures and the chitinase from ts11 cultures grown at the permissive or at the nonpermissive temperature. Compared to the amount present in a ts11 embryo culture at the permissive temperature, a reduction in the amount of 32 kD chitinase was observed during the temperature-sensitive period at the nonpermissive temperature. These results imply that the arrested embryo phenotype of ts11 is not the result of a structural difference in its 32 kD chitinase, but is the result of a transient decrease in the amount of 32 kD chitinase present. Morphological observations indicate that the ts11 phenotype is pleiotropic and also affects the cell wall of nonembryogenic cells. © 1995 Wiley-Liss, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 23 (1989), S. 349-356 
    ISSN: 0148-7280
    Keywords: FSH ; ovary ; amphibian ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In the fully grown Bufo arenarum oocyte, carbohydrate breakdown during the autumn-winter season is accomplished mainly through the glycolytic pathway followed by the krebs cycle. During the breeding season (spring-summer), carbohydrates are used mainly through the pentose phosphate cycle and through the variant of the Krebs cycle known as the glutamic aspartic cycle.The metabolism operating in the oocytes was determined using the following paramenters: 1) the capacity of isolated mitochondria to oxidize citrate and fumarate; 2) the enzymatic activities of phosphofructokinase (PEK) and glucose-6-phosphate dehydrogenase (G-6-PDH); and 3) cirate and ATP compartmentalization.The present paper shows that follicle-stimulating hormone (FSH) would be one of the factors responsible for summer metabolism, since ovary fractios obtained from winter specimens treated with the hormone acquired the metabolic characteristics corresponding to oocytes obtained from breeding-season animals from dose-response, and response in the function of time curves, it could be assumed that the optimum doses and times were 0.1 μg FSH/ml of incubation medium and 30 min treatment, respecitively.The metabolic effect of FSH upon oocytes could be mediaated by the adenylate cyclase cAMP system, since treatment of ovric fractions with cAMP 10-3 M reproduced the effects obtained with the hormone. In addition, 0.02 mg/ml tetracyline proved to block the effect of FSH. A direct metabolic action of FSH on body cavity oocytes (without follicle cells) was observed when submitting these oocytes to the same hormonal treatment.
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  • 9
    ISSN: 1040-452X
    Keywords: Chick embryos ; Organogenesis ; δ-crystallin gene ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Extracellular signals are likely to be involved in the control of growth and differentiation during embyrogenesis of vertebrates. These signals include, among others, several members of the insulin family: insulin-like growth factor (IGF)-I, IGF-II, and insulin. In the chick embryo, maternal IGF-I is stored in the yolk. In addition, the embryonic IGF-I gene is expressed very early and in late development in multiple tissues. We have used reverse-transcribed (RT) RNA and amplification by the polymerase chain reaction (PCR) to detect IGF-I gene expression. IGF-I was preferentially expressed in cephalic regions during late neurulation and early organogenesis. During late organogenesis, in some tissues, such as the eye lens, IGF-I gene expression is compartmentalized to a subset of cells, the epithelial cells. In these lens cells, IGF-I stimulates transcription of the δ-crystallin gene. Competence to respond to IGF-I exists in multiple cell types, since, based on binding studies, receptors for IGF-I are widespread in the gastrulating and neurulating embryo. Target tissues in which an autocrine/paracrine role for IGF-I appears more likely are the developing eye lens and retina, which are avascular organs rich in IGF-I receptors. In late development, IGF-I may have an additional endocrine role, with an impact on the general growth of the chick embryo. In embryos developed ex ovo, that show growth retardation after day 10 of embyrogenesis, IGF-I serum levels are very low. By day 8, expression of IGF-I mRNA in these embryos is markedly reduced in multiple tissues. Future studies in which IGF-I and its receptor are overexpressed or abolished should clarify the function of this growth factor in development. © 1993 Wiley-Liss, Inc.
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  • 10
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Pancreatic ducts of young posthatching Rana temporaria tadpoles are the main component of the developing pancreas. At this stage (free-swimming tadpoles with internal gills), duct cells display a high degree of development of basal and lateral outfoldings of the cell membrane with extensive interdigitation, and numerous mitochondria are present throughout the cytoplasm. Wide intercellular spaces also exist, sometimes forming canaliculi-like structures. Since these traits are characteristic of cells engaged in osmotic regulation, we suggest the possibility that this temporary duct system participates in such control. Duct cells in tadpoles with well-developed hindlegs have diminished interdigitation, and mitochondria are localized apically. © 1993 Wiley-Liss, Inc.
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