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51.
52.
Murata Yoshiyuki; Fujita Masashi; Nakatani Takuya; Obi Ichiro; Kakutani Tadaaki 《Plant & cell physiology》1998,39(4):452-457
Characteristics of Ca2+-binding on the plasma membrane of barleymesophyll cells were studied by a microelec-trophoretic method.The results indicated that Na+ ions could cause nonspecificreduction but not specific reduction in the total amount ofCa2+ bound to the plasma membrane of (salt-tolerant) barleymesophyll cells. (Received October 13, 1997; Accepted January 23, 1998) 相似文献
53.
Tetsuji Sato 《Histochemistry and cell biology》1998,109(4):359-367
The detailed distribution and heterogeneity of various immunocompetent cells were characterized in the normal adrenal gland
of the rat, with special emphasis on major histocompatibility complex (MHC) class II-expressing cells and macrophages. All
adrenals contained at least two different populations of cells reactive with the dendritic cell or the macrophage antibodies.
These cells were clearly distinguished from adrenal parenchymal cells by their morphology and location. The majority of dendritic
cells were immunoreactive for the MHC class II (Ia) antigen (MRC OX6) and/or the dendritic cell antibodies (MRC OX62), and
negative for the macrophage antibodies (ED1, ED2, and/or MRC OX42), whereas the main population of macrophages was immunonegative
for the former antibodies and positive for the latter. The OX62-positive cells and the OX42-labeled cells occurred exclusively
throughout the medulla. The cellular density of dendritic cells in the adrenal cortex was significantly higher than that of
macrophages. Double-immunoperoxidase staining for ED1 and OX6 revealed that positively stained cells could be classified into
the following categories: ED1+OX6+, ED1+OX6−, and ED1−OX6+. More then 40% of OX6+ cells were immunoreactive for ED1 in the zona glomerulosa, while approximately 15%, 20%, and 30% of OX6+ cells were positive for ED1 in the zona fasciculata, zona reticularis and medulla, respectively. ED1+ED2− cells were more frequently detected in the zona glomerulosa than in other adrenal zones. Only a few ED1−ED2+ cells were located in the zona glomerulosa, whereas a large number of them were found in the zona fasciculata. In the zona
reticularis and medulla, ED1+ED2+, ED1+ED2−, and ED1−ED2+ cells were detected in the ratio 2:1:3. Our rsults suggest that dendritic cells and macrophages mature during their migration
within the adrenal gland. These immunocompetent cells may contribute to a paracrine regulation of adrenal function under physiological
conditions.
Accepted: 3 November 1997 相似文献
54.
Tetsuji Yamashita Pierre Hakizimana Siva Wu Ahmed Hassan Stefan Jacob Jamshid Temirov Jie Fang Marcia Mellado-Lagarde Richard Gursky Linda Horner Barbara Leibiger Sara Leijon Victoria E. Centonze Per-Olof Berggren Sharon Frase Manfred Auer William E. Brownell Anders Fridberger Jian Zuo 《PLoS genetics》2015,11(9)
Nature’s fastest motors are the cochlear outer hair cells (OHCs). These sensory cells use a membrane protein, Slc26a5 (prestin), to generate mechanical force at high frequencies, which is essential for explaining the exquisite hearing sensitivity of mammalian ears. Previous studies suggest that Slc26a5 continuously diffuses within the membrane, but how can a freely moving motor protein effectively convey forces critical for hearing? To provide direct evidence in OHCs for freely moving Slc26a5 molecules, we created a knockin mouse where Slc26a5 is fused with YFP. These mice and four other strains expressing fluorescently labeled membrane proteins were used to examine their lateral diffusion in the OHC lateral wall. All five proteins showed minimal diffusion, but did move after pharmacological disruption of membrane-associated structures with a cholesterol-depleting agent and salicylate. Thus, our results demonstrate that OHC lateral wall structure constrains the mobility of plasma membrane proteins and that the integrity of such membrane-associated structures are critical for Slc26a5’s active and structural roles. The structural constraint of membrane proteins may exemplify convergent evolution of cellular motors across species. Our findings also suggest a possible mechanism for disorders of cholesterol metabolism with hearing loss such as Niemann-Pick Type C diseases. 相似文献
55.
56.
Gordon H. Sato J. Denry Sato Tetsuji Okamoto Wallace L. McKeehan David W. Barnes 《In vitro cellular & developmental biology. Animal》2010,46(7):590-594
Lack of tissue-specific differentiated functions of cells in tissue culture, once thought to be due to “dedifferentiation”,
was shown to be due to selective overgrowth of fibroblasts by a series of simple experiments that challenged the prevailing
dogma. Following this insight, enrichment culture techniques (alternate animal and culture passage) were designed to give
functionally differentiated tumor cells selective advantage over the fibroblasts. These experiments resulted in the derivation
of a large number of functionally differentiated clonal strains of a range of cell types, providing the final point of destruction
of the dogma of “dedifferentiation.” Instead, the hypothesis was proposed that cells in culture accurately represent cells
in vivo, but without the complex in vivo environment. With the development of hormonally defined media and its combination
with functionally differentiated clonal cell lines, this concept has been strengthened and the potential of tissue culture
studies has been greatly augmented. Hormonally defined media allow the culture of cell types that cannot be grown in conventional,
serum-supplemented media. These approaches demonstrate that hormonal responses and dependencies can be discovered in culture.
Following this thinking and the discovery of hormonal dependencies of cancer cells has led to a new rationale for therapy.
Tissue culture and cell technology continue to play an important role in solving human health problems. 相似文献
57.
Detailed features of genomic DNA methylation have been revealed by recent genome-wide analyses on several model organisms.
An unexpected feature conserved among plants and some animals is the presence of DNA methylation within transcribed genes.
For understanding the controlling mechanisms of the enigmatic genic methylation, genetic and genomic approaches using Arabidopsis
may be effective. 相似文献
58.
Visual opsins bind 11-cis retinal at an orthosteric site to form rhodopsins but increasing evidence suggests that at least some are capable of binding an additional retinoid(s) at a separate, allosteric site(s). Microspectrophotometric measurements on isolated, dark-adapted, salamander photoreceptors indicated that the truncated retinal analog, β-ionone, partitioned into the membranes of green-sensitive rods; however, in blue-sensitive rod outer segments, there was an enhanced uptake of four or more β-ionones per rhodopsin. X-ray crystallography revealed binding of one β-ionone to bovine green-sensitive rod rhodopsin. Cocrystallization only succeeded with extremely high concentrations of β-ionone and binding did not alter the structure of rhodopsin from the inactive state. Salamander green-sensitive rod rhodopsin is also expected to bind β-ionone at sufficiently high concentrations because the binding site is present on its surface. Therefore, both blue- and green-sensitive rod rhodopsins have at least one allosteric binding site for retinoid, but β-ionone binds to the latter type of rhodopsin with low affinity and low efficacy. 相似文献
59.
60.
Gonzalez-Begne M Nakamoto T Nguyen HV Stewart AK Alper SL Melvin JE 《The Journal of biological chemistry》2007,282(48):35125-35132
Cl(-) influx across the basolateral membrane is a limiting step in fluid production in exocrine cells and often involves functionally linked Cl(-)/HCO(3)(-) (Ae) and Na(+)/H(+) (Nhe) exchange mechanisms. The dependence of this major Cl(-) uptake pathway on Na(+)/H(+) exchanger expression was examined in the parotid acinar cells of Nhe1(-/-) and Nhe2(-/-) mice, both of which exhibited impaired fluid secretion. No change in Cl(-)/HCO(3)(-) exchanger activity was detected in Nhe2-deficient mice. Conversely, Cl(-)/HCO(3)(-) exchanger activity increased nearly 4-fold in Nhe1-deficient mice, despite only minimal or any change in mRNA and protein levels of the anion exchanger Ae2. Acetazolamide completely blocked the increase in Cl(-)/HCO(3)(-) exchanger activity in Nhe1-null mice suggesting that increased anion exchange required carbonic anhydrase activity. Indeed, the parotid glands of Nhe1(-/-) mice expressed higher levels of carbonic anhydrase 2 (Car2) polypeptide. Moreover, the enhanced Cl(-)/HCO(3)(-) exchange activity was accompanied by an increased abundance of Car2.Ae2 complexes in the parotid plasma membranes of Nhe1(-/-) mice. Anion exchanger activity was also significantly reduced in Car2-deficient mice, consistent with an important role of a putative Car2.Ae2 HCO(3)(-) transport metabolon in parotid exocrine cell function. Increased abundance of this HCO(3)(-) transport metabolon is likely one of the multiple compensatory changes in the exocrine parotid gland of Nhe1(-/-) mice that together attenuate the severity of in vivo electrolyte and acid-base balance perturbations. 相似文献