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51.
Dalit Ben-Yosef Anat Talmor Lior Shwartz Yosef Granot Ruth Shalgi 《Molecular reproduction and development》1998,49(2):176-185
Fertilization in invertebrates results in tyrosine (Tyr) phosphorylation of several egg proteins. However, the involvement of Tyr phosphorylation in mediating mammalian egg activation has not yet been investigated. Using an antibody specific for phosphotyrosine (P-Tyr), immunoblotting, and densitometric analysis, we found that maturation of the oocyte is accompanied by a generalized increase in the P-Tyr content of almost all egg proteins detected. After sperm penetration, 5 of the 17 protein bands detected demonstrated a small increase in their P-Tyr content, while at the pronuclear (PN) stage the signal was markedly reduced. Ionomycin emulated the changes observed at fertilization in most protein bands detected, demonstrating a small increase in their P-Tyr content within 15 min of exposure. Analysis of the involvement of the tyrosyl-phosphorylated, mitogen-activated protein (MAP) kinase during meiosis revealed comigration of the phosphotyrosyl bands with the protein and a good correlation with its enzyme activity. Maturation was accompanied by an increase in MAP kinase activity. The activity dropped partially after sperm penetration and furthermore later at the PN stage. A larger quantity accompanied by a more significant change in the P-Tyr content implies for extracellular regulated kinase (ERK) 2 being the dominant isoform present in the rat egg. Our results indicate that fertilization in mammals involves changes in activity of protein tyrosine kinases (PTKs) or in the balance between PTKs and protein tyrosine phosphatases. The single, ionomycin-induced Ca2+ rise is sufficient to imitate fertilization-induced changes in MAP kinase activity, as well as in tyrosine phosphorylation of other proteins within the egg. Mol. Reprod. Dev. 49:176–185, 1998. © 1998 Wiley-Liss, Inc. 相似文献
52.
The ability to expand normal pancreatic islet
β cells in culture would significantly advance
the prospects of cell therapy for diabetes. A
number of growth factors can stimulate limited
islet cell replication, however other factors may
exist which are more effective β-cell-specific
mitogens. The search for novel β-cell growth
factors has been hampered by the lack of a β-cell-specific proliferation assay. We developed a
simple and sensitive assay for β-cell growth factors
based on a conditionally-transformed
mouse β-cell line (βTC-tet). These cells express
the SV40 T antigen (Tag) oncoprotein under
control of the tetracycline (Tc) operon regulatory
system. In the presence of Tc, Tag expression
is tightly shut off and the cells undergo
complete growth arrest. Here we show that the
growth-arrested cells can proliferate in
response to growth factors in the absence of Tag. Using this assay, a number of growth factors
previously shown to be mitogenic to a
mixed islet cell population were found to
induce proliferation of pure β cells. We conclude
that growth-arrested βTC-tet cells can be
employed in a survey of factors from various
sources for identifying novel factors with β-cell
mitogenic activity. 相似文献
53.
Dalit Roth Rosenberg Markus Haber Joshua Goldford Maya Lalzar Dikla Aharonovich Ashraf Al-Ashhab Yoav Lehahn Daniel Segrè Laura Steindler Daniel Sher 《Environmental microbiology》2021,23(8):4295-4308
In the oceans and seas, environmental conditions change over multiple temporal and spatial scales. Here, we ask what factors affect the bacterial community structure across time, depth and size fraction during six seasonal cruises (2 years) in the ultra-oligotrophic Eastern Mediterranean Sea. The bacterial community varied most between size fractions (free-living (FL) vs. particle-associated), followed by depth and finally season. The FL community was taxonomically richer and more stable than the particle-associated (PA) one, which was characterized by recurrent ‘blooms’ of heterotrophic bacteria such as Alteromonas and Ralstonia. The heterotrophic FL and PA communities were also correlated with different environmental parameters: the FL population correlated with depth and phytoplankton, whereas PA bacteria were correlated primarily with the time of sampling. A significant part of the variability in community structure could, however, not be explained by the measured parameters. The metabolic potential of the PA community, predicted from 16S rRNA amplicon data using PICRUSt, was enriched in pathways associated with the degradation and utilization of biological macromolecules, as well as plastics, other petroleum products and herbicides. The FL community was enriched in predicted pathways for the metabolism of inositol phosphate, a potential phosphorus source, and of polycyclic aromatic hydrocarbons. 相似文献
54.
Ocean acidification, resulting from rising atmospheric carbon dioxide concentrations, is a pervasive stressor that can affect many marine organisms and their symbionts. Studies which examine the host physiology and microbial communities have shown a variety of responses to the ocean acidification process. Recently, several studies were conducted based on field experiments, which take place in natural CO2 vents, exposing the host to natural environmental conditions of varying pH. This study examines the sea anemone Anemonia viridis which is found naturally along the pH gradient in Ischia, Italy, with an aim to characterize whether exposure to pH impacts the holobiont. The physiological parameters of A. viridis (Symbiodinium density, protein, and chlorophyll a+c concentration) and its microbial community were monitored. Although reduction in pH was seen to have had an impact on composition and diversity of associated microbial communities, no significant changes were observed in A. viridis physiology, and no microbial stress indicators (i.e., pathogens, antibacterial activity, etc.) were detected. In light of these results, it appears that elevated CO2 does not have a negative influence on A. viridis that live naturally in the site. This suggests that natural long-term exposure and dynamic diverse microbial communities may contribute to the acclimation process of the host in a changing pH environment. 相似文献