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71.
Jeffery R. Cook Barbara E. Crute Laura M. Patrone Joseph Gabriels Maureen E. Lane Robert G. van Buskirk 《In vitro cellular & developmental biology. Plant》1989,25(10):914-922
Summary We have analyzed the ability of the physical substratum to modulate both the ultrastructural and protein synthetic characteristics
of the Madin-Darby canine kidney (MDCK) renal cell line. When MDCK cells were seeded on Millipore Millicell CM microporous
membrane cell culture inserts they demonstrated a more columnar organization with an increase in cell density sixfold greater
than the same cells seeded on conventional plastic substrata. After 1 wk postseeding on the microporous membrane a partial
basal lamina was noted, with a contiguous basement membrane being apparent after 2 wk. One-dimensional sodium dodecyl sulfate
gel electrophoresis was used to analyze detergent-solubilized proteins from MDCK cells maintained on plastic substrata vs.
microporous membranes. When proteins were pulse-labeled with [35S]methionine, a 55 kDa protein was evident in the cytosolic extract of cells grown on collagen, laminin, and nontreated plastic
substrata; but this labeled protein was not evident in similar extracts from cells grown on collagen and laminin-coated microporous
membranes. To test if the polarized, basement-membrane secreting phenotype of the MDCK cells could be generated on a microporous
membrane without pretreatment with any extracellular matrix (ECM) components, cells were seeded on the Millipore Millicell
HA (cellulosic) microporous membrane. This type of substrata does not need a coating of ECM components for cell attachment.
A partial basement membrane was formed below cells where the basal surface of the cell was planar, but not in areas where
the cell formed large cytoplasmic extensions into the filter. This led us to the conclusion that the microporous nature of
the substrata can dictate both ultrastructural and protein synthetic activities of MDCK cells. Furthermore, we suggest that
both the planar nature of the basal surface and the microporosity of the substrate are corequisites for the deposition of
the basement membrane. 相似文献
72.
The ultrastructure of the mature spermatozoa and spermatogenesis of the bivalve Scrobicularia plana are described. Support cells extend from the basal lamina to the lumen of the testis and are laterally connected to the germinal epithelium. Germ cells present intercellular bridges and flagella since the spermatogonial stage. While spermatogonia and spermatocytes appear connected to support cells by desmosome-like junctions, elongated spermatids are held at the acrosomal region by support cell finger-like processes. During spermiogenesis, the acrosomal vesicle differentiates from a golgian saccule and then migrates to the nuclear apex. A microtubular manchette arising from centrioles surrounds the acrosomal vesicle, the nucleus, and the mitochondria at the time these three organelles start their elongation, disappearing after that. The mature spermatozoon of S. plana lacks a distinct midpiece because the mitochondria extend from the region of the pericentriolar complex along the nucleus anteriorly for approximately 1.4 μm. The features of this bivalve type of modified spermatozoon are compared with those of other animal groups having similar modifications. 相似文献
73.
Bruna Tadolini Diana Fiorentini Laura Landi Luciana Cabrini 《Free radical research》1989,5(4):245-252
To find experimental conditions to selectively study the propagation phase of lipoperoxidation we studied the lipoperoxidation, catalyzed by FeCl2, of liposomes in a buffering condition where Fe2+ autoxidation and oxygen active species generation does not occur. Liposomes from egg yolk phosphatidylcholine. prepared by vortex mixing, do not oxidize Fe2+: on the contrary they oxidize Fe2+ when prepared by ultrasonic irradiation. Dimyristoyl phosphatidylcholine liposomes prepared by ultrasonic irradiation do not oxidize Fe2+. During sonication polyunsaturated fatty acid residues autoxidize and lipid hydroperoxides (LOOH) are generated. Only when LOOH are present in the liposimes Fe2+ oxidizes and its rate of oxidation depends on the amount of LOOH in the assay. The reaction results in the generation of both LOOH and thiobarbituric acid reactive material (TBAR): it is inhibited by butylated hydroxytoluene and has a acidic pH optimum; it is not inhibited by catalase and OH' scavengers. The reaction studied. thus, appears to be the chain branching and propagation phase of lipoperoxidation. When we studied the dependence of Fe2+ oxidation, LOOH and TBAR generation on FeCl2 concentration, we observed that at high FeCl2 concentrations the termination phase of lipoperoxidation was prevalent. Thus. by selecting the appropriate FeCl2 concentration the proposed experimental system allows study of either the propagation or the termination phase of lipoperoxidation. 相似文献
74.
75.
Physella heterostropha size distributions and densities were measured in Pen Branch delta, a thermally altered swamp of the Savannah River, South Carolina. During cessation of thermal input, measurements were taken in a highly impacted area and more natural area. Of the three substrates sampled, logs, small woody material and benthos, snail density was highest on small pieces of submerged wood and < 20% of the snails on logs were out of the water. Following resumption of thermal input, snail density was four times higher on logs than previously measured. Snails responded to elevated water temperatures by congregating in a narrow band slightly above the water. Snail size did not appear to affect their response. However, the thermal history of the snails influenced their behaviour and survival rates. Logs may be a potential refuge for snails when water temperature are greater greater than 38°C. However, our results indicate that long-term survival in this manner may be impossible. 相似文献
76.
Duplication of an Xp segment that includes the ZFX locus causes sex inversion in man 总被引:6,自引:6,他引:0
Gerd Scherer Werner Schempp Carlo Baccichetti Elisabetta Lenzini Franca Dagna Bricarelli Laura Doria Lamba Carbone Ulrich Wolf 《Human genetics》1989,81(3):291-294
Summary Two 46,XY females with tandem duplications of an X short arm segment were studied by cytogenetic and Southern blot analysis. The results show that the duplicated segment in each case included the Xp21.2–Xp22.2 interval, resulting in a double dose of ZFX on the single active X chromosome. The results from our two cases, in conjunction with those reported by other workers, lead us to conclude that the duplication is the reason for the sex inversion. If ZFY and ZFX are indeed sex-determining gene loci, these findings favour a model of sex determination characterized by antagonistic interaction between these genes. 相似文献
77.
A single cDNA encodes two isoforms of stathmin, a developmentally regulated neuron-enriched phosphoprotein 总被引:6,自引:0,他引:6
V Doye F Soubrier G Bauw M C Boutterin L Beretta J Koppel J Vandekerckhove A Sobel 《The Journal of biological chemistry》1989,264(21):12134-12137
Stathmin, a 19-kDa neuron-enriched soluble phosphoprotein, has been recently proposed as an ubiquitous intracellular relay for the diverse extracellular signals regulating cell proliferation, differentiation, and functions through various second messenger pathways (Sobel, A., Boutterin, M.C., Beretta, L., Chneiweiss, H., Doye, V., and peyro-Saint-Paul, H. (1989) J. Biol. Chem. 264, 3765-3772). Internal sequences of the protein from rat brain were determined after purification by two-dimensional polyacrylamide gel electrophoresis, electrotransfer onto Immobilon, and in situ proteolysis. Oligonucleotide mixtures based on these sequences were used to clone a cDNA for stathmin from a rat PC12 cell lambda gt 10 library. The deduced amino acid sequence reveals partial homologies with the coiled coil structural regions of several intracellular matrix phosphoproteins. Using this cDNA as a probe, we show that the expression of stathmin mRNA parallels that of the protein during brain ontogenesis, reaching a maximum at the neonatal stage. In vitro translation of the derived cRNA yielded all the known molecular forms of stathmin, namely its alpha and beta isoforms in their unphosphorylated and phosphorylated states. Thus, a single cDNA codes for both biologically relevant isoforms of the protein, indicating that they differ by co- or post-translational modifications. 相似文献
78.
Ian A. Graham Laura M. Smith Christopher J. Leaver Steven M. Smith 《Plant molecular biology》1990,15(4):539-549
The cucumber malate synthase (MS) gene, including 1856 bp of 5 non-trnascribed sequence, has been transferred into Petunia (Mitchell) and Nicotiana plumbaginifolia plants using an Agrobacterium binary vector. The transferred gene is found in variable copy number in different transformants, and is stably transmitted in each case as a single Mendelian character. Transgene mRNA accumulates in the seedling during the first three days of germination, then declines in amount as the cotyledons emerge from the seed. The decline is more pronounced in light-grown seedlings than in dark-grown seedlings. Expression of the MS transgene is also detected at a low level in petals of transformed Petunia plants. In these respects the pattern of MS gene expression is similar in cucumber and in trnasformed plants, showing that the transferred DNA fragment contains a functional MS gene. A 1076 bp fragment of 5 sequence was linked to the -glucuronidase reporter gene and transferred into Nicotiana, where it was shown to direct temporal and spatial patterns of expression similar to that of the complete MS gene. However, histochemical localisation of -glucuronidase activity demonstrated that the chimaeric gene is expressed not only in cotyledons of transgenic plants, but also in endosperm and some hypocotyl cells during early germination. The relevance of these findings to the control of malate synthase gene expression is discussed. 相似文献
79.
D. Sanglard I. Beretta M. Wagner O. K ppeli A. Fiechter 《Biocatalysis and Biotransformation》1990,4(1):19-28
The genes for the alkane-inducible monooxygenase system of the yeast Candida tropicalis, namely a cytochrome P450alk (P450alk) and a NADPH cytochrome P450 oxidoreductase (NCPR) gene, were transferred in Saccharomyces cerevisiae. The P450alk gene was expressed in this host with the help of the yeast alcohol dehydrogenase I (ADHI) promoter and terminator, whereas the NCPR gene could be expressed with its own structural elements. The presence of P450alk in S. cerevisiae microsomal fractions resulted in a new acquired lauric acid terminal hydroxylation activity. Moreover, the same activity, coupled with the appearance of 12-hydroxylauric acid derivatives, could be obtained by the addition of lauric acid to intact cells expressing P450alk. The coordinate expression of the P450alk and NCPR genes in S. cerevisiae elevated the turnover rate of the P450alk monooxygenase activity about 2-fold. 相似文献
80.
Modulation of ζ-Protein Kinase C by Cyclic AMP in PC12 Cells Occurs Through Phosphorylation by Protein Kinase A 总被引:1,自引:1,他引:0
Marie W. Wooten M. Lamar Seibenhener Laura H. Matthews Guisheng Zhou Elaine S. Coleman 《Journal of neurochemistry》1996,67(3):1023-1031
Abstract: Although cyclic AMP (cAMP) has been reported to cross talk with the protein kinase C (PKC) system, effects of elevated intracellular cAMP on the activities of specific PKC isoforms have not been studied. We report findings from a permeabilized cell assay that was used to examine changes in the activity of the atypical PKC isoforms brought about by exposure of PC12 cells to agents that elevate intracellular cAMP. We found that increases in intracellular cAMP led to rapid stimulation of atypical PKC activity, 40–70% above control, for a sustained period of time, a response that occurred independent of the phorbol 12-myristate 13-acetate (PMA)-sensitive PKC isoforms. Changes in intracellular cAMP levels resulted in a dose-dependent redistribution of ζ-PKC to the cytoplasm with a concomitant increase in the phosphorylation state of the enzyme. Incubation of purified ζ-PKC with increasing concentrations of PKA likewise caused a twofold increase in the phosphorylation state of ζ-PKC. In contrast to the positive effect that PKA-mediated phosphorylation had on the activity of ζ-PKC, the enzyme displayed reduced binding to ras when phosphorylated. Taken together, these findings are consistent with the hypothesis that protein phosphorylation of PKC acts as a positive effector of its enzyme activity and may serve as a negative modulator for interaction with other proteins. 相似文献