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Regulation of gap junction coupling in the developing neocortex 总被引:4,自引:0,他引:4
In the developing mammalian, neocortex gap junctions represent a transient, metabolic, and electrical communication system.
These gap junctions may play a crucial role during the formation and refinement of neocortical synaptic circuitries. This
article focuses on two major points. First, the influence of gap junctions on electrotonic cell properties will be considered.
Both the time-course and the amplitude of synaptic potentials depend,inter alia, on the integration capabilities of the postsynaptic neurons. These capabilities are, to a considerable extent, determined
by the electrotonic characteristics of the postsynaptic cell. As a consequence, the efficacy of chemical synaptic inputs may
be crucially affected by the presence of gap junctions.
The second major topic is the regulation of gap junctional communication by neurotransmitters via second messenger pathways.
The monoaminergic neuromodulators dopamine, nordrenaline, and serotonin reduce gap junction coupling via activation of two
different intracellular signaling cascades—the cAMP/protein kinase A pathway and the IP3/Ca2+/protein kinase C pathway, 013 respectively. In addition, gap junctional
communication seems to be modulated by the nitric oxide (NO)/cGMP system. Since NO production can be stimulated by glutamate-induced
calcium influx, the NO/cGMP-dependent modulation of gap junctions might represent a functional link between developing glutamatergic
synaptic transmission and the gap junctional network. Thus, it might be of particular importance in view of a role of gap
junctions during the process of circuit formation. 相似文献
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Margarete Traiser Bernd Diener Dietmar Utesch Franz Oesch 《In vitro cellular & developmental biology. Animal》1995,31(4):266-273
Summary In primary monocultures of adult rat liver parenchymal cells (PC), the activities of the xenobiotic metabolizing enzymes microsomal
epoxide hydrolase (mEHb), soluble epoxide hydrolase (sEH), glutathione S-transferases (GST), and phenolsulfotransferase (ST) were reduced after 7
d to values below 33% of the initial activities. Furthermore, the gap junctional intercellular communication (GJIC), measured
after microinjection by dye transfer, decreased from 90% on Day 1 to undetectable values after 5 d in monoculture. Co-culture
of PC with nonparenchymal rat liver epithelial cells (NEC) increased (98% on Day 1) and stabilized (82% on Day 7) the homotypic
GJIC of PC. Additionally, most of the measured xenobiotic metabolizing enzyme activities were well stabilized over 1 wk in
co-culture. Because GJIC is one of several mechanisms playing an important role in cell differentiation, the importance of
GJIC for the stabilization of xenobiotic metabolizing enzymes in PC was investigated. PC in monoculture were, therefore, treated
with 2% dimethyl sulfoxide (DMSO), a differentiation promoting factor, and 1,1,1-trichloro-2,2,-bis (p-chlorophenyl) ethane
(DDT) (10 μg/ml), a liver tumor promotor and inhibitor of GJIC, was given to co-cultures of PC with NEC. DMSO significantly
stabilized (68% on Day 7), while DDT significantly inhibited (8% on Day 7) homotypic GJIC of PC in the respective culture
systems. In contrast, the activities of mEHb, sEH, GST, and ST were not affected in the presence of DMSO or DDT. These results lead to the assumption that the differentiation
parameters measured in this study (i.e., homotypic GJIC and the activities of xenobiotic metabolizing enzymes) are independently
regulated in adult rat liver PC. 相似文献
158.
A. Quesada-Chanto A. S.-Afschar F. Wagner 《Applied microbiology and biotechnology》1994,41(4):378-383
With a cell concentration of 125 g dry biomass 1–1 and a dilution rate of 0.1 h–1,Propionibacterium acidipropionici produces 30 g propionic acid 1–1 from sugar with a productivity of 3 g 1–1 h–1. The yield of propionic acid is approx. 0.36–0.45 g propionic acid g–1 sucrose and is independent of the dilution rate and cell concentration. Acetic acid is an unwanted by-product in the production of propionic acid. The concentration of acetic acid only increases slightly when the cell concentration is increased. A two-stage fermentation process was developed for the conversion of sugar or molasses of various types to propionic acid and vitamin B12. By fermentation of blackstrap molasses (from sugar beet and sugar cane) in the first fermentation stage 17.7 g propionic acid 1–1 with a yield of 0.5 g propionic acid g–1 carbohydrate was produced with a dilution rate of 0.25 h–1. In the second stage 49 mg vitamin B12 1–1 was produced at a dilution rate of 0.03 h–1. 相似文献
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Molecular chaperones cooperate with PIM1 protease in the degradation of misfolded proteins in mitochondria. 总被引:23,自引:6,他引:17 下载免费PDF全文
ATP dependent proteolytic degradation of misfolded proteins in the mitochondrial matrix is mediated by the PIM1 protease and depends on the molecular chaperone proteins mt-hsp70 and Mdj1p. Chaperone function is essential to maintain misfolded proteins in a soluble state, a prerequisite for their degradation by PIM1 protease. In the absence of functional mt-hsp70 or Mdj1p misfolded proteins either remain associated with mt-hsp70 or form aggregates and thereby are no longer substrates for PIM1 protease. Mdj1p is shown to regulate the ATP dependent association of an unfolded polypeptide chain with mt-hsp70 affecting binding to as well as release from mt-hsp70. These findings establish a central role of molecular chaperone proteins in the degradation of misfolded proteins by PIM1 protease and thereby demonstrate a functional interrelation between components of the folding machinery and the proteolytic system within mitochondria. 相似文献