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81.
Enrico Gobbato John F. Marsh Tatiana Vernié Ertao Wang Fabienne Maillet Jiyoung Kim J. Benjamin Miller Jongho Sun S. Asma Bano Pascal Ratet Kirankumar S. Mysore Jean Dénarié Michael Schultze Giles E.D. Oldroyd 《Current biology : CB》2012,22(23):2236-2241
Download : Download video (88MB) 相似文献
82.
Manoj K Gupta Damir J Illich Andrea Gaarz Matthias Matzkies Filomain Nguemo Kurt Pfannkuche Huamin Liang Sabine Classen Michael Reppel Joachim L Schultze Jürgen Hescheler Tomo Šarić 《BMC developmental biology》2010,10(1):1-19
Background
The C-terminal Eps15 homology domain-containing protein 1 (EHD1) is ubiquitously expressed and regulates the endocytic trafficking and recycling of membrane components and several transmembrane receptors. To elucidate the function of EHD1 in mammalian development, we generated Ehd1 -/- mice using a Cre/loxP system.Results
Both male and female Ehd1 -/- mice survived at sub-Mendelian ratios. A proportion of Ehd1 -/- mice were viable and showed smaller size at birth, which continued into adulthood. Ehd1 -/- adult males were infertile and displayed decreased testis size, whereas Ehd1 -/- females were fertile. In situ hybridization and immunohistochemistry of developing wildtype mouse testes revealed EHD1 expression in most cells of the seminiferous epithelia. Histopathology revealed abnormal spermatogenesis in the seminiferous tubules and the absence of mature spermatozoa in the epididymides of Ehd1 -/- males. Seminiferous tubules showed disruption of the normal spermatogenic cycle with abnormal acrosomal development on round spermatids, clumping of acrosomes, misaligned spermatids and the absence of normal elongated spermatids in Ehd1 -/- males. Light and electron microscopy analyses indicated that elongated spermatids were abnormally phagocytosed by Sertoli cells in Ehd1 -/- mice.Conclusions
Contrary to a previous report, these results demonstrate an important role for EHD1 in pre- and post-natal development with a specific role in spermatogenesis. 相似文献83.
A rich vertebrate fauna is described from the Middle Muschelkalk (Anis, Triassic) north of Gottingen, West-Germany. Completely preserved juvenile fishes ofEosemionotus vogeli Fritsch 1906 occur besides teeth of selachians, scales and some bones of actinopterygians and actinistians and bones of nothosaurs. Genus and species ofEosemionotus vogeli is described and redefined. These findings and search in the literature demonstrate that a rich vertebrate fauna existed in the sea of the Middle Muschelkalk; the contrary is accepted generally. 相似文献
84.
85.
Hubert H. Felle Éva Kondorosi Ádám Kondorosi Michael Schultze 《The Plant journal : for cell and molecular biology》1998,13(4):455-463
Using ion-selective microelectrodes, the basis of Nod factor-induced changes in the plasma membrane potential was analysed by measuring the extracellular free concentrations of Ca2+, K+, H+ and Cl– in the root hair zone of alfalfa. After addition of the Rhizobium meliloti Nod factor NodRm-IV(C16:2,S) at a concentration of 0.1 μM, a decrease in [Ca2+] was observed first, which was followed after a few seconds by an increase of [Cl–], by an alkalinization, and then by a delayed increase of [K+], all of which were transient changes. Simultaneously with the appearance of Cl– ions in the root hair zone, a decrease in cytosolic [Cl–] was measured. It was concluded that the depolarization was caused by temporary short-circuiting of the proton pump through the rapid release of Cl– ions along their steep electrochemical gradient. Since under resting conditions the driving force for K+ ions was inwardly directed, their release was delayed until their driving force was inverted. This indicates that K+ serves as a charge balance that eventually stops depolarization and initiates repolarization. Since the decrease in [Ca2+] was observed seconds before the increase in [Cl–] and the depolarization, it is argued that Ca2+ entering into the cell does not cause the depolarization directly, but might initiate it by triggering the activation of an anion channel that then releases the chloride ions. The observations that the Ca2+ ionophore A23187 mimicks the Nod factor response, and that the Ca2+ channel antagonist nifedipine inhibits this response, support the idea that Ca2+ plays a primary role in the transduction of the Nod signal in alfalfa. 相似文献
86.
87.
Haematopoietic stem cells are capable of developing colonies of differentiated granulocytes in a semi-stable agar environment under corresponding experimental conditions. Number and size of aggregations developing from a single stem cell in each case called "in culture Colony Forming Unit (CFU-c)" enable conclusions to be made about the functional ability of the cultivated human or animal bone marrow. The method is applied in investigating the kinetics in the haematopoietic system and, in addition, it is used for diagnostics, therapy and control of the course in haematological diseases as well as to check the proliferous ability of cryopreserved bone marrow cells. As to the standardization of the procedure the instability of the active principle of the foetal calf serum as well as the essential colony stimulating factor represent limiting items at present. 相似文献
88.
The proliferation of hepatocytes in the liver of 3-week-old rats has been investigated by autoradiographic methods. This investigation is a continuation of earlier work on the same topic (Schultze & Maurer, 1972; 1973). 21 days after birth, 102 rats received a single injection of 3H-TdR. the percentage of labelled mitoses was then determined 1 hr later and at various times throughout the interval up to 12 days after application of 3H-TdR. In agreement with earlier work, a first peak of labelled mitoses was found 7 hr after 3H-TdR injection. the area under the peak indicates an S phase duration of 8 hr. In addition a second very broad peak of labelled mitoses was found between 2 and 12 days after pulse labelling. the analysis of the results leads to the conclusion that the hepatocytes of the 3-week-old rat have a growth fraction close to 1 and a doubling time of 6–7 days. This is at variance with earlier results of Post, Huang & Hoffman (1963) and Grisham (1969) who had derived a value of 21.5 hr for the duration of the cell cycle and a value of only 0. 1–0.2 for the growth fraction of the hepatocytes. 相似文献
89.
The mechanism of action of the alkaloid vincristine (VCR) has been investigated in vitro on HeLa cells in culture and in vivo on jejunal crypt cells of the mouse. The in vitro experiments with HeLa cells show that VCR affects not only mitotic but also interphase cells. The VCR-affected cells first continue their passage through the cell cycle undisturbed but after reaching mitosis they are arrested in metaphase. This agrees well with the results obtained by Madoc-Jones & Mauro (1968) and Madoc-Jones (1973) on synchronized cell cultures. Until now there has been no investigation of the mechanism of action of VCR in vivo. This is due to the absence of a suitable technique for synchronization in vivo. The present study is based on a method which permits the assessment of the VCR sensitivity as a function of the cell age without synchronization in the usual sense. The jejunal crypt epithelium of the normal mouse was double labelled with 3H- and 14C-thymidine (TdR) in such a way as to produce a narrow subpopulation of crypt cells with a maximum age difference of 1 hr. On autoradiographs these cells can be distinguished by their characteristic labelling from other cells. As this ‘pseudo’-synchronized subpopulation passes through the cycle the effect of VCR can be studied, i.e. one can analyse the effect in well-defined time intervals of the cycle. The results show that the effect of VCR is the same in vivo as in vitro. The crypt cells which are affected by VCR in interphase continue their passage through the cycle, but upon entering mitosis they are arrested in metaphase. VCR has, at the concentration used in the present study, no effect on the duration of the S and G2 phases. The necrotic cells seen after VCR application are formed from arrested metaphases. 相似文献
90.
Proton nuclear magnetic resonance assignments and structural characterization of an intramolecular DNA triplex. 总被引:3,自引:0,他引:3
Two-dimensional 1H n.m.r. spectroscopy has been used to study the 31-base DNA oligonucleotide 5'-dAGAGAGAACCCCTTCTCTCTTTTTCTCTCTT-3', which folds to form a stable intramolecular triplex in solution at acidic pH. This structure is considerably more difficult to assign than short B-DNA duplexes and requires new assignment methods. The assignment strategy and assignments of almost all of the exchangeable and nonexchangeable resonances are presented. Seven base triplets and one Watson-Crick base-pair form the core of the structure and are connected by a four C and four T loop at either end. The second pyrimidine "strand" (bases 24 to 31) in this intramolecular pyrimidine-purine-pyrimidine triplex binds via Hoogsteen base-pairs in the major groove and is parallel to the purine "strand" (bases 1 to 8). Analysis of the sugar puckers reveals that, contrary to widely accepted belief, the triplex sugars are not predominantly in the N-type (close to C3'-endo) conformation. Except for some of the C nucleotides, all sugars are predominantly S-type (close to C2'-endo). Thus, the duplex DNA does not assume N-type sugar conformations to accommodate a third strand in the major groove. A preliminary model of the triplex structure is presented. 相似文献