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Markus Grabenbauer Kurt Sätzler Eveline Baumgart H. Dariush Fahimi 《Cell biochemistry and biophysics》2000,32(1-3):37-49
Peroxisomes in the human hepatoblastoma cell line, HepG2, exhibit distinct alterations of shape, size, and distribution, dependent
on culture conditions (cell density, duration in culture, and presence of specific growth factors). Although many cells with
elongated tubular peroxisomes are present in thinly seeded cultures, spherical particles forming large focal clusters are
found in confluent cultures. The authors have analyzed the ultrastructure and the spatial relationship of peroxisomes of HepG2
cells at different stages of differentiation, using three-dimensional (3D)-reconstruction of ultrathin serial sections, and
electronic image processing. Cells were prepared for immunofluorescence using different antibodies against peroxisomal matrix
and membrane proteins, as well as for electron microscopy after the alkaline 3,3′-diaminobenzidine staining for catalase.
The results indicate that the tubular peroxisomes, which can reach a length of several microns, are consistently isolated,
and never form an interconnected peroxisomal reticulum. At the time of disappearance of tubular peroxisomes, rows of spherical
peroxisomes, arranged like beads on a string, are observed, suggesting fission of tubular ones. In differentiated confluent
cultures, clusters of several peroxisomes are seen, which, by immunofluorescence, appear as large aggregates, but after 3D
reconstruction consist of single spherical and angular peroxisomes without interconnections. The majority of such mature spherical
peroxisomes (but not the tubular ones) exhibit tail-like, small tubular and vesicular attachments to their surface, suggesting
a close functional interaction with neighboring organelles, particularly the endoplasmic reticulum, which is often observed
in close vicinity of such peroxisomes. 相似文献
73.
INFLUENCE OF UV-B RADIATION ON NITROGEN UTILIZATION BY A NATURAL ASSEMBLAGE OF PHYTOPLANKTON 总被引:2,自引:0,他引:2
Juliette Fauchot† Michel Gosselin Maurice Levasseur Behzad Mostajir Claude Belzile Serge Demers Suzanne Roy Piedad Zulema Villegas 《Journal of phycology》2000,36(3):484-496
A 7‐day mesocosm experiment was conducted in July 1996 to investigate the effects of ambient UV‐B radiation (UVBR) exclusion and two UVBR enhancements above ambient levels on NO3?, NH4+ and urea utilization in a natural plankton community (<240 μm) from the Lower St. Lawrence Estuary. The phytoplankton community was dominated by diatoms during the first 3 days and, afterward, by flagellates and dinoflagellates. The results of 4‐h incubations just below the water surface show that, compared with ambient UVBR conditions, UVBR exclusion generally increased NO3?, NH4+, and urea uptakes. During the last 4 days of the experiment, the percent increase in the specific uptake rate of urea under excluded UVBR conditions varied between 17% and 130% and was a linear function of the ambient UVBR dose removed. During the first 3 days, the phytoplankton community dominated by diatoms was able to withstand UVBR enhancements without any perceptible effect on nitrogen uptake. However, during the post‐diatom bloom period, UVBR enhancements resulted in decreases in NO3?, NH4+, and urea uptake compared with ambient UVBR conditions. The reduction of urea uptake under UVBR enhancements during the last 3 days varied between 23% and 64% and was linearly related to the enhanced UVBR dose. However, the different UVBR treatments did not affect the internal organic nitrogen composition (internal urea, free amino acids, and proteins) of the phytoplankton community experiencing vertical mixing in the mesocosms. The discrepancy between short‐term uptake measurements at the surface and long‐term effects in the mesocosms emphasizes the importance of vertical mixing on UVBR effects in natural ecosystems. This suggests that an increase in ambient UVBR would have a minimal effect on nitrogen utilization by natural phytoplankton assemblages if these are vertically mixed. 相似文献
74.
Sanam Sadreddini Behzad Baradaran Ali Aghebati-Maleki Sevil Sadreddini Dariush Shanehbandi Ali Fotouhi Leili Aghebati-Maleki 《Journal of cellular physiology》2019,234(6):8541-8549
Among the main promising systems to triggering therapeutic antitumor immunity is the blockade of immune checkpoints. Immune checkpoint pathways regulate the control and eradication of infections, malignancies, and resistance against a host of autoantigens. Initiation point of the immune response is T cells, which have a critical role in this pathway. As several immune checkpoints are initiated by ligand–receptor interactions, they can be freely blocked by antibodies or modulated by recombinant forms of ligands or receptors. Antibodies against cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) were the first immunotherapeutics that achieved the US Food and Drug Administration approval. Preliminary clinical results with the blockers of additional immune checkpoint proteins, such as programmed cell death protein 1 (PD-1) indicate extensive and different chances to boost antitumor immunity with the objective of conferring permanent clinical effects. This study provides an overview of the immune checkpoint pathways, including CTLA-4, PD-1, lymphocyte activation gene 3, T-cell immunoglobulin and mucin domain 3, B7-H3, and diacylglycerol kinase α and implications of their inhibition in the cancer therapy. 相似文献
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76.
Courboulès Justine Vidussi Francesca Soulié Tanguy Mas Sébastien Pecqueur David Mostajir Behzad 《Aquatic Ecology》2021,55(2):647-666
Aquatic Ecology - To investigate the responses of a natural microbial plankton community of coastal Mediterranean waters to warming, which are still poorly known, an in situ mesocosm experiment was... 相似文献
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Dariush Shokri Mohammad Rabbani Khorasgani Milad Mohkam Seyed Masih Fatemi Younes Ghasemi Asghar Taheri-Kafrani 《Probiotics and antimicrobial proteins》2018,10(1):34-42
The emergence of antibiotic-resistant and food-spoilage microorganisms has renewed efforts to identify safe and natural alternative agents of antibiotics such as probiotics. The aim of this study was the isolation of lactobacilli as potential probiotics from local dairy products with broad antibacterial and anti-biofilm activities against antibiotic-resistant strains of Pseudomonas aeruginosa and determination of their inhibition mechanism. Antibiotic susceptibility and classification of acquired resistance profiles of 80 P. aeruginosa strains were determined based on Centers for Disease Control and Prevention (CDC) new definition as multidrug-resistant (MDR), extensively drug-resistant (XDR), and pan-drug-resistant (PDR) followed by antibacterial assessment of lactobacilli against them by different methods. Among the 80 P. aeruginosa strains, 1 (1.3%), 50 (62.5%), and 78 (97.5%) were PDR, XDR, and MDR, respectively, and effective antibiotics against them were fosfomycin and polymyxins. Among 57 isolated lactobacillus strains, two strains which were identified as Lactobacillus fermentum using biochemical and 16S rDNA methods showed broad inhibition/killing and anti-biofilm effects against all P. aeruginosa strains. They formed strong biofilms and had bile salts and low pH tolerance. Although investigation of inhibition mechanism of these strains showed no bacteriocin production, results obtained by high-performance liquid chromatography (HPLC) analysis indicated that their inhibitory effect was the result of production of three main organic acids including lactic acid, acetic acid, and formic acid. Considering the broad activity of these two L. fermentum strains, they can potentially be used in bio-control of drug-resistant strains of P. aeruginosa. 相似文献
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