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51.
Valera E Sánchez-Martín FJ Ferrer-Montiel AV Messeguer A Merino JM 《Neurochemistry international》2008,53(5):148-154
N-Methyl-d-aspartate (NMDA) receptors play a critical role in the brain stimulating synaptic plasticity and mediating neurodegeneration; a neuroprotective role has also been described, but its molecular mechanisms in hippocampus are under study. Here, we report that in primary cultures of rat hippocampal neurons exposure to low micromolar NMDA concentrations are neuroprotective against excitotoxic insults, while high micromolar NMDA concentrations provoke neuronal death. Molecular analysis reveals that a toxic concentration of NMDA induced a transient phosphorylation of cAMP-response element-binding protein (pCREB) in 2 min that rapidly decreased below basal levels. In contrast, a nontoxic NMDA concentration gave up to longer (20 min) rise of pCREB, suggesting that neuroprotection could be associated to a relatively prolonged presence of pCREB in the neurons. In support of this tenet, rolipram, an inhibitor of phosphodiesterase IV that increases the levels of cAMP and pCREB, protected against NMDA-induced neuronal death. Similar results were obtained with dibutyrate-cAMP (a cAMP analogue with membrane permeability) that also abrogated NMDA excitotoxicity. Conversely, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinoline sulfonamide (H89), an inhibitor of protein kinase A (PKA), that prevents the formation of pCREB induced by nontoxic NMDA concentrations, reverted the neuroprotection achieved by preincubation of low micromolar NMDA concentrations. These results substantiate the notion that induction of pCREB via PKA plays an important role in NMDA-mediated neuroprotection. 相似文献
52.
Nicolas Grammel Kvitka Pankevych Julia Demydchuk Klaus Lambrecht Hans-Peter Saluz Hans Krügel 《European journal of biochemistry》2002,269(1):347-357
Nourseothricins (syn. Streptothricins), a group of nucleoside peptides produced by several streptomycete strains, contain a poly beta-lysine chain of variable length attached in amide linkage to the amino sugar moiety gulosamine of the nucleoside portion. We show that the nourseothricin-producing Streptomyces noursei contains an enzyme (NpsA) of an apparent M(r) 56,000 that specifically activates beta-lysine by adenylation but does not bind to it as a thioester. Cloning and sequencing of npsA from S. noursei including its flanking DNA regions revealed that it is closely linked to the nourseothricin resistance gene nat1 and some other genes on the chromosome possibly involved in nourseothricin biosynthesis. The deduced amino-acid sequence revealed that NpsA is a stand-alone adenylation domain with similarity to the adenylation domains of nonribosomal peptide synthetases (NRPS). Further analysis revealed that S. noursei contains a beta-lysine binding enzyme (NpsB) of about M(r) 64,100 which can be loaded by NpsA with beta-lysine as a thioester. Analysis of the deduced amino-acid sequence from the gene (npsB) of NpsB showed that it consists of two domains. The N-terminal domain of approximately 100 amino-acid residues has high similarity to PCP domains of NRPSs whereas the 450-amino-acid C-terminal domain has a high similarity to epimerization (E)-domains of NRPSs. Remarkably, in this E-domain the conserved H-H-motif is changed to H-Q, which suggests that either the domain is nonfunctional or has a specialized function. The presence of one single adenylating beta-lysine activating enzyme in nourseothricin-producing streptomycete and a separate binding protein suggests an iteratively operating NRPS-module catalyses synthesis of the poly beta-lysine chain. 相似文献
53.
Summary A study of fossils in thin sections of a sample from the uppermost Krol E Member in the Mussoorie Hills of the Lesser Himalaya,
India, proves the existence of morphologically differentiated calcified sponges within the Precambrian-Cambrian boundary time
interval. The sponges, described as Mussooriella kroli n.g., n.sp. and Maldeotaina composita n.g., n.sp. indicate the presence of different organization grades at the Precambrian-Cambrian interval. Mussooriella had a calcareous skeleton consisting of skeletal elements composed of an inner laminated part and a distinct peripheral layer
with knobs. Maldeotaina is characterized by a stromatoporoid-grade growth pattern following a thalamid-grade pattern. The stromatoporoidgrade part
of the skeletons reminds strongly on skeletal elements common in labechiid Ordovician and younger stromatoporoids. Maldeotaina also shows criteria of Early Cambrian fossils, originally described as stromatoporoids and later excluded from this group
and transferred to archaeocyaths. These similarities point to an Early Cambrian age of the fossil-bearing horizon in the topmost
Krol E Member. Growth cavities with crypts indicate that the sponges might have contributed to the formation of small metazoan
reefs-like structures.
Although the study is based on limited material and many interpretations are still tentative, a thorough documentation of
the preliminary results seems reliable considering the high potential of the fossils of the upper Krol Formation important
source in understanding of early metazoan differentiation. 相似文献
54.
Extracellular proteases produced by Scytalidium thermophilum, grown on microcrystalline cellulose, were most active at pH 6.5–8 and 37–45 °C when incubated for 60 min. Highest protease activity was at day 3 where endoglucanase activity was low. Protease activity measurements with and without the protease inhibitors, p-chloromercuribenzoate, PMSF, antipain, E-64, EDTA and pepstatin A, suggest production of thiol-containing serine protease and serine proteases. Endoglucanase and Avicel-adsorbable endoglucanase activity in culture medium was not significantly affected by protease inhibitors. 相似文献
55.
Victòria Marfâ Enric Mele Jean Michael Vassal Joaquima Messeguer 《In vitro cellular & developmental biology. Plant》2002,38(4):310-315
Summary To determine the degree of insect resistance in transgenic plants, different bioassays are used which typically use either
whole plant or small pieces of leaves or stems of transgenic plants, following culture under greenhouse conditions. An in vitro insect-feeding bioassay is presented which permits the infestation of transgenic plantlets with newly hatched larvae from
the striped stem borer. The bioassay consists of the germination of rice seeds in vitro using Murashige and Skoog medium in test tubes, and then infestation of each 3–4 cm long seedling with one neonate larva
obtained from surfacesterilized eggs of Chilo suppressalis. The infested in vitro plantlets are kept in culture rooms at 25°C for several days and then the seedling damage and the growth of the larvae are
analyzed. Senia (japonica variety) homozygous transgenic rice plants were used for these experiments. The plants were transformed
with either the cry1B or the maize proteinase inhibitor (mpi) genes. Both genes confer resistance to Chilo suppressalis. With non-transformed plants the larvae grew and developed normally, feeding on the small rice plantlets. In contrast, with
cry1B plants, the neonate larvae died during the first days of the infestation. These plantlets recovered completely and developed
similarly to the non-infested control plants. With transgenic plants transformed with the mpi gene, the neonate larvae did not die but grew more slowly compared with the controls. Thus, this in vitro insect-feeding bioassay is a rapid and easy method to detect the resistance of cry and mpi transgenic plants to stem borers such as Chilo suppressalis. 相似文献
56.
57.
The 3'-orf protein of human immunodeficiency virus 2 shows sequence homology with the bel3 gene of the human spumaretrovirus 总被引:10,自引:0,他引:10
The primary amino acid sequence within a domain of 89 residues of the central part of the 3'-orf protein (p27 3'-orf) of human immunodeficiency virus (HIV-2) shares homology with the middle and carboxy-terminal portion of the bel3 gene product of human spumaretrovirus (HSRV). In addition, a limited region of the tat protein of HIV-2 but not HIV-1 shows a 28% degree of homology to the deduced protein sequence of the bel1 gene product of HSRV. Comparison between the viral sequences suggests that the 3'-orf and bel1 gene product of HSRV could serve similar functions to those in HIV-2. 相似文献
58.
59.
The growing number of reports on the effective cargo delivery by cell-penetrating peptides (CPPs) has extensively widened our knowledge about the mechanisms involved in CPP-mediated delivery. However, the data available on the internalization mode of CPP–cargo complexes are often conflicting and/or equivocal. Moreover, the intracellular trafficking of CPP–cargo complexes is, to date, relatively unexplored resulting in only minimal information about what is really happening to the complexes inside the cell. This review focuses on defining the endocytic pathways engaged in the transduction of CPP–cargo complexes and seeks to determine the extent of different endocytic routes required for effective uptake. In addition, the intracellular pathways utilized during the trafficking and sorting of CPP–cargo complexes as well as the ultimate fate of the complexes inside cells will be discussed. 相似文献
60.