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31.
Dr. Stefan B. Cajander M. P. Hugin Peter Kristensen Aaron J. W. Hsueh 《Cell and tissue research》1989,257(1):1-8
Summary The observation that tissue-type plasminogen activator (tPA) activity increased dramatically in preovulatory follicles has led to the hypothesis that plasminogen activation is causally related to follicle rupture. With immunohistochemistry, we have studied the appearance of tPA in ovaries of immature rats induced to ovulate and in adult cycling rats. Treatment of immature female rats with a single dose of pregnant mare serum gonadotropin (PMSG) induced follicular maturation. A subsequent human chorionic gonadotropin (hCG) injection resulted in follicle rupture 12–14 h later. PMSG treatment alone did not induce appearance of tPA-immunoreactive cells in any ovarian compartment. After hCG stimulation, however, theca cells, granulosa cells, and oocytes of pre- and postovulatory follicles displayed distinct tPA immunoreactivity. Fibroblastlike cells in the theca layers and tunica albuginea of the follicle apex also demonstrated localized cytoplasmic tPA reactivity. In addition to tPA synthesis in preovulatory follicles, hCG also induced tPA staining in the theca (but not granulosa) layers of non-ovulatory follicles. At 24 h after hCG treatment, there was a marked tPA staining in developing corpora lutea, ovulated ova, and oviductal epithelium. Ovaries from regularly cycling adult rats displayed a similar ovulation-related pattern of tPA immunostaining. The appearance of tPA in different cell types of the preovulatory follicle and in the fibroblast-like cells at the follicle apex, strengthens the hypothesis of a direct involvement of tPA in follicle rupture. Presence of tPA in postovulatory oocytes, cumulus cells, and surrounding oviductal epithelium may also indicate a role for tPA in the transfer of eggs in the oviduct.This work was supported by NIH Research Grants HD-14084; 12303 相似文献
32.
Summary The ultrastructural and transmitter development of lumbar sympathetic ganglia was studied in embryonic day-6 through-18 chick embryos. At embryonic day 6, ganglia are populated by two morphologically distinct types of neuronal cells and Schwann cell precursors. The neuronal populations basically comprise a granule-containing cell and a developing principal neuron. Granule-containing cells have, an irregularly shaped or oval nucleus with small clumps of chromatin attached to the inner nuclear membrane and numerous large (up to 300 nm) membrane-limited granules. Developing principal neurons display a more rounded vesicular nucleus with evenly distributed chromatin, prominent nucleoli, more developed areas of Golgi complexes, and rough endoplasmic reticulum and large dense-core vesicles up to 120 nm in diameter. There are granule-containing cells with fewer and smaller granules which still display the nucleus typical for granule-containing cells. These granule-containing cells may develop toward developing principal neurons or the resting state of granule-containing cells found in older ganglia. Both granule-containing cells and developing principal neurons proliferate and can undergo degeneration. At embryonic day 9 there are far more developing principal neurons than granule-containing cells. Most granule-containing cells have very few granules. Mitotic figures and signs of cell degeneration are still apparent. Synapse-like terminals are found on both developing principal neurons and granule-containing cells. Ganglionic development from embryonic day 11 through 18 comprises extensive maturation of developing principal neurons and a numerical decline of granule-containing cells. Some granule-containing cells with very few and small granules still persist at embryonic day 18. The mean catecholamine content per neuron increases from 0.044 femtomol at embryonic day 7 to 0.22 femtomol at embryonic day 15. Concomitantly, there is a more than 6-fold increase in tyrosine hydroxylase activity. Adrenaline has a 14% share in total catecholamines at embryonic day 15. Somatostatin levels are relatively high at embryonic day 7 (1.82 attomol per neuron) and are 10-fold reduced by embryonic day 15. Our results suggest the presence of two morphologically distinct sympathetic neuronal precursors at embryonic day 6: one with a binary choice to become a principal neuron or to die, the other one, a granule-containing cell, which alternatively may develop into a principal neuron, acquire a resting state or die. 相似文献
33.
Dopamine Receptor Stimulation Does Not Affect Phosphoinositide Hydrolysis in Slices of Rat Striatum 总被引:3,自引:3,他引:0
The effect of dopamine receptor stimulation on the accumulation of labelled inositol phosphates in rat striatal slices under basal and stimulated conditions was examined following preincubation with [3H]inositol. Incubation of striatal slices with the selective D-1 agonist SKF 38393 or the selective D-2 agonist LY 171555 for 5 or 30 min did not affect the basal accumulation of labelled inositol mono-, bis-, tris-, and tetrakisphosphate. Resolution by HPLC of inositol trisphosphate into inositol-1,3,4-tris-phosphate and inositol-1,4,5-trisphosphate isomers revealed that under basal conditions dopamine did not influence the accumulation of inositol-1,4,5-trisphosphate. Depolarisation evoked by KCl, or addition of the muscarinic receptor agonist carbachol, produced a marked increase in the accumulation of labelled inositol phosphates in both the presence and absence of lithium. Addition of dopamine did not reduce the ability of KCl or carbachol to increase inositol phospholipid hydrolysis. In the presence of lithium, dopamine (100 microM) enhanced KCl-stimulated inositol phospholipid hydrolysis, but this effect appears to be mediated by alpha 1 adrenoceptors because it was blocked by prazosin. SKF 38393 (10 microM) or LY 171555 (10 microM) also did not affect carbachol-stimulated inositol phospholipid hydrolysis. These data, in contrast to recent reports, suggest that striatal dopamine receptors do not appear to be linked to inositol phospholipid hydrolysis. 相似文献
34.
Summary LiCl, a well-known vegetalising agent, interferes with the commitment of stem cells to nerve cells and nematocytes in Hydra attenuata. Treatment with 20 mM LiCl inhibits commitment to nerve cells, treatment with 1 mM LiCl inhibits commitment to nematocytes. However, LiCl does not prevent stem cells committed to the nematocyte pathway from dividing and differentiating into nests of nematocytes. Following LiCl treatment, determination to nerve cells and nematocytes is triggered again. Commitment to nerve cells is strongly stimulated within the first 3 h following pulse treatment with LiCl if the animals have been fed immediately prior to treatment. In Hydra exposed to LiCl for 10 days the stem cell density is reduced by at least 90% of the initial value, and nematocytes are almost completely missing, whereas the density of nerve cells is within the normal range in animals with normal morphology. Animals which developed a transverse constriction in the middle of the body axis contain a 1.7-fold higher nerve cell density in the lower part than is observed in control animals. 相似文献
35.
The effect of NAD(P) and analogs of this nucleotide on nitrogenase activity in Rhodospirillum rubrum has been studied. Addition of NAD+ to nitrogen fixing Rsp. rubrum leads to inhibition of nitrogenase. NADP+ has the same effect but NADH or analogs modified in the nicotinamide portion do not cause inhibition. In contrast to ammonium
ions, addition of NAD+ leads to inhibition of nitrogenase in cells that have been N-starved under argon. The inhibitory effect of NAD+ is more pronounced at lower light intensities. Addition of NAD+ also leads to inhibition of glutamine synthetase, a phenomenon also occurring when “switchoff” is produced by the addition
of effectors such as ammonium ions or glutamine. It is also shown that NAD+ is taken up by Rsp. rubrum cells. 相似文献
36.
Juliane Plieth Frauke Rininsland Manfred Schlösser David N. Cooper Jochen Reiss 《Human genetics》1992,88(3):283-287
Summary In Central Europe, the F508 deletion accounts for approximately 75% of mutations in the cystic fibrosis transmembrane conductance regulator gene causing cystic fibrosis. The remainder comprise a large number of individually infrequent mutations whose detection requires a disproportionately large effort. However, a sizeable proportion of non-F508 mutations have been found to cluster within exon 11. We have taken advantage of this clustering to detect a total of five previously described point mutations present on 26/72 (36%) non-F508 chromosomes by polymerase chain reaction/direct sequencing of exon 11. These exon 11 mutations were then subjected to single-strand conformation polymorphism (SSCP) analysis, which was shown (i) to discriminate reliably between mutant and wildtype alleles and (ii) to generate reproducible mutation-specific band patterns. This analysis thus represents the first attempt to assess SSCP analysis retrospectively, and serves to illustrate the potential of this screening technique in diagnostic medicine. 相似文献
37.
Stefan Jansson Eran Pichersky Roberto Bassi Beverley R. Green Masahiko Ikeuchi Anastasios Melis David J. Simpson Michael Spangfort L. Andrew Staehelin J. Philip Thornber 《Plant Molecular Biology Reporter》1992,10(3):242-253
We propose a nomenclature for the genes encoding the chlorophylla/b-binding proteins of the light-harvesting complexes of photosystem I and II. The genes encoding LHC I and LHC II polypeptides
are namedLhca1 throughLhca4 andLhcb1 throughLhcb6, respectively. The proposal follows the general format recommended by the Commision on Plant Gene Nomenclature. We also present
a table for the conversion of old gene names to the new nomenclature. 相似文献
38.
Rhizome dynamics and resource storage in Phragmites australis 总被引:6,自引:1,他引:5
Wilhelm Granéli Stefan E. B. Weisner Mark D. Sytsma 《Wetlands Ecology and Management》1992,1(4):239-247
Seasonal changes in rhizome concentrations of total nonstructural carbohydrates (TNC), water soluble carbohydrates (WSC), and mineral nutrients (N, P and K) were monitored in two Phragmites australis stands in southern Sweden. Rhizome biomass, rhizome length per unit ground area, and specific weight (weight/ length ratio) of the rhizomes were monitored in one of the stands.Rhizome biomass decreased during spring, increased during summer and decreased during winter. However, changes in spring and summer were small (< 500 g DW m-2) compared to the mean rhizome biomass (approximately 3000 g DW m–2). Winter losses were larger, approximately 1000 g DW m-2, and to a substantial extent involved structural biomass, indicating rhizome mortality. Seasonal changes in rhizome length per unit ground area revealed a rhizome mortality of about 30% during the winter period, and also indicated that an intensive period of formation of new rhizomes occurred in June.Rhizome concentrations of TNC and WSC decreased during the spring, when carbohydrates were translocated to support shoot growth. However, rhizome standing stock of TNC remained large (> 1000 g m–2). Concentrations and standing stocks of mineral nutrients decreased during spring/ early summer and increased during summer/ fall. Only N, however, showed a pattern consistent with a spring depletion caused by translocation to shoots. This pattern indicates sufficient root uptake of P and K to support spring growth, and supports other evidence that N is generally the limiting mineral nutrient for Phragmites.The biomass data, as well as increased rhizome specific weight and TNC concentrations, clearly suggests that reloading of rhizomes with energy reserves starts in June, not towards the end of the growing season as has been suggested previously. This resource allocation strategy of Phragmites has consequences for vegetation management.Our data indicate that carbohydrate reserves are much larger than needed to support spring growth. We propose that large stores are needed to ensure establishment of spring shoots when deep water or stochastic environmental events, such as high rhizome mortality in winter or loss of spring shoots due to late season frost, increase the demand for reserves. 相似文献
39.
40.
Stefan Schlatt Gerhard F. Weinbauer Eberhard Nieschlag 《Cell and tissue research》1991,265(2):203-209
Summary Inhibin-like immunoreactivity was detected by immunocytochemistry in the pituitaries of untreated male crab-eating macaques (cynomolgus monkey) and rhesus monkeys, in rhesus monkeys actively immunized against FSH, and in one orchidectomized crab-cating macaque. Localizations were performed by the immunogold-silver staining with 5-nm colloidal gold-conjugated second or third antibodies and by the alkaline phosphatase-anti-alkaline-phosphatase technique. Two different inhibin-specific antisera, raised against the -subunit or the entire inhibin molecule, provided identical staining patterns. Positive label was confined to the pars distalis of the pituitary and occurred exclusively in the cytoplasm of morphologically different cell types throughout the pars distalis in all pituitaries. Staining was most prominent in clusters of chromophobic cells. The presence of inhibin-like activity in the pituitary of an orchidectomized monkey with undetectable serum inhibin levels suggests that inhibin is produced within the pituitary gland. Co-localization studies for the -subunits of the gonadotropic hormones revealed that on average 82% of the gonadotropes were bihormonal. Using the same protocol, co-localization of inhibin-like activity with gonadotropin-like immunoreactivity revealed only a small degree of common distribution (<15%). Inhibinpositive cells were frequently in close proximity to gonadotropic cells and, thus, paracrine effects of inhibin on gonadotropin-synthesizing cells are conceivable. 相似文献