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961.
J. Tougaard 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1996,178(5):669-677
The temporal integration of the A1 auditory receptor of two species of noctuid moths (Lepidoptera, Noctuidae) was investigated. Tympanal nerve spikes were recorded while stimulating the ear with broad band clicks. Thresholds were measured for single clicks, pairs of clicks with a separation of 1–20 ms, and trains of up to 8 clicks at separations of 1–2 ms. The average threshold for single clicks was 52.9 dB peSPL (SD 1.7 dB, n = 40) for Noctua pronuba and 50.1 dB peSPL (SD 4.0 dB, n = 27) for Spodoptera littoralis. The thresholds for double clicks with a 1 ms separation were lower than the thresholds for single clicks. The difference decreased as the separation between the clicks was increased. The results were fully consistent with an energy detector model (a leaky integrator with an exponential decay) with a time constant of about 4 ms.The results are compared to previously published results with pure tone intensity/duration trading. A common underlying mechanism is suggested, based on the passive electric properties of the receptor cell membrane.It is suggested, that the time constant revealed in the present study characterizes auditory receptors in general, and is related to the short time constants in vertebrate audition.Abbreviations
peSPL
peak equivalent sound pressure level
-
SD
standard deviation
-
time constant 相似文献
962.
Masashi Yamada Toshihiko Ikeuchi Saburo Aimoto Dr. Hiroshi Hatanaka 《Neurochemical research》1996,21(7):815-822
PC12h-R cell, a subclone of PC12 cells, exhibited a neuron-like phenotype, including neurite outgrowth and increased acetylcholinesterase
activity, in response to epidermal growth factor (EGF) as well as nerve growth factor (NGF). We examined the mechanism by
which EGF induced the neuronal differentiation in PC12h-R cells. The EGF-induced neuronal differentiation of PC12h-R cells
was not blocked by K252a, whereas that induced by NGF was. EGF induced sustained tyrosine phosphorylation of the EGF receptor
in PC12h-R cells, but not in the parent PC12h cells, which do not show neuronal differentiation in response to EGF. In addition,
the rate of EGF-induced down-regulation of the EGF receptor in PC12h-R cells was decreased compared with that in PC12h cells.
Furthermore, we found that the duration of EGF-induced tyrosine phosphorylation of the EGF receptor in PC12h-R cells was similar
to that of NGF-induced tyrosine phosphorylation of p140
trkA in PC12h cells. The EGF-induced phosphorylation of the EGF receptor in PC12h cells was less sustained than that of p140
trkA by NGF in PC12h cells. These findings suggested that the EGF-induced neuronal differentiation of PC12h-R cells is due to
the sustained activation of the EGF receptor, resulting from the decreased down-regulation of the EGF receptor and that the
duration of the receptor tyrosine kinase activity determines the cellular responses of PC12 cells. We concluded that sustained
activation of the receptor tyrosine kinase induces neuronal differentiation, although transient activation promotes proliferation
of PC12 cells.
Special issue dedicated to Dr. Hans Thoenen. 相似文献
963.
Nefiracetam is a novel pyrrolidone derivative which attenuates scopolamine-induced learning and post-training consolidation
deficits. Given that apomorphine inhibits passive avoidance retention when given during training or in a defined 10–12h post-training
period, we evaluated the ability of nefiracetam to attenuate amnesia induced by dopaminergic agonism. A step-down passive
avoidance paradigm was employed and nefiracetam (3 mg/kg) and apomorphine (0.5 mg/kg) were given alone or in combination during
training and at the 10–12h post-training period of consolidation. Co-administration of nefiracetam and apomorphine during
training or 10h thereafter produced no significant anti-amnesic effect. However, administration of nefiracetam during training
completely reversed the amnesia induced by apomorphine at the 10h post-training time and the converse was also true. These
effects were not mediated by a dopaminergic mechanism as nefiracetam, at millimolar concentrations, failed to displace either
[3H]SCH 23390 or [3H]spiperone binding from D1 or D2 dopamine receptor subtypes, respectively. It is suggested that nefiracetam augments molecular processes in the early stages
of events which ultimately lead to consolidation of memory. 相似文献
964.
Linker insertion analysis of the FimH adhesin of type 1 fimbriae in an Escherichia coli fimH-null background 总被引:2,自引:0,他引:2
Mark A. Schembri Lars Pallesen Hugh Connell David L. Hasty Per Klemm 《FEMS microbiology letters》1996,137(2-3):257-263
Abstract The gene encoding the Escherichia coli FimH adhesin of type 1 fimbriae has been subjected to linker insertion mutagenesis. Amino acid changes were introduced at a number of positions spanning the entire sequence in order to probe the structure-function relationship of the FimH protein. The effect of these mutations on the ability of bacteria to express a D-mannose binding phenotype was assessed in a fimH null mutant (MS4) constructed by allelic exchange in the E. coli K-12 strain PC31. Mutations mapping at amino acid residues 36, 58 and 279 of the mature FimH protein were shown to completely abolish binding to D-mannose receptors. Differences in the level of fimbriation were also observed as a result of some of the mutations in the fimH gene. These mutants may prove useful in dissecting receptor-ligand interactions by defining regions of the FimH protein that are important in erythrocyte binding. 相似文献
965.
Complete development of Cryptosporidium parvum in MDBK cells 总被引:1,自引:0,他引:1
Isabel Villacorta Dirk de Graaf Gerard Charlier Johan E. Peeters 《FEMS microbiology letters》1996,142(1):129-132
Abstract Sporozoites of Cryptosporidium parvum excysted in vitro from bovine oocysts were incubated with monolayers of Madin-Darby bovine kidney cells. The extent of parasite colonisation was monitored by light microscopy and immunofluorescence. Electron microscopy confirmed the complete development and replication of C. parvum within Madin-Darby bovine kidney cells. 相似文献
966.
Tonia S. Agin J. Robert Cantey Edgar C. Boedeker Marcia K. Wolf 《FEMS microbiology letters》1996,144(2-3):249-258
Abstract A number of enteric pathogens, including enteropathogenic (EPEC) and enterohemorrhagic (EHEC) Escherichia coli , Hafnia alvei , a strain of Citrobacter freundii , and rabbit EPEC strain RDEC-1 cause attaching-effacing (AE) lesions in the gut mucosa. These bacteria have a pathogenicity cassette (locus of enterocyte effacement or LEE) containing the eaeA gene. This gene encodes intimin, an outer membrane protein required for production of AE lesions. RDEC-1, a non-invasive enteropathogen in young rabbits, produces AE lesions morphologically indistinguishable from lesions caused by human AE bacterial strains. The RDEC-1 example of E. coli diarrhea in rabbits is an important model for studying the pathogenesis of AE bacteria in a natural infection and for analyzing specific roles of the components of LEE. In order to better understand the role of intimin in the development of AE lesions, a portion of DNA within RDEC-1 LEE, containing the eaeA gene and an upstream open reading frame (ORF), was sequenced. The RDEC-1 eaeA gene shared 87%, 92%, and 93% DNA sequence identity and > 80% amino acid sequence identity with the eaeA genes of C. freundii biotype 4280, EHEC O157:H7, and EPEC O127:H6, respectively. The carboxy-terminal 280 amino acid residues of intimin has 80%, 56%, and 54% identity with C. freundii , EHEC O157:H7, and EPEC O127:H6 intimins, respectively. The predicted protein encoded by the upstream ORF (156 amino acids) shares 95%, 97%, and 99% amino acid identity with predicted proteins from C. freundii , EHEC O157:H7, and EPEC O127:H6, respectively. The high degree of sequence homology of the ORF and the eaeA gene of RDEC-1 with those of other AE bacteria suggests an evolutionary relationship of LEE and supports and facilitates the use of the RDEC-1 model for studying the role of LEE in pathogenesis. 相似文献
967.
Kazuhito Hisatsune Seiichi Kondo Takehiro Iguchi Teruyo Ito Keiichi Hiramatsu 《Microbiology and immunology》1996,40(9):621-626
Structural and serological studies were performed with the lipopolysaccharide (LPS) expressed by Escherichia coli K12 strains No. 30 and No. 64, into which cosmid clones derived from Vibrio cholerae O1 NIH 41 (Ogawa) and NIH 35A3 (Inaba) had been introduced, respectively. The two recombinant strains, No. 30 (Ogawa) and No. 64 (Inaba), produced LPS that included, in common, the O-polysaccharide chain composed of an α(1 → 2)-linked N-(3-deoxy-L -glycero-tetronyl)-D -perosamine (4-amino-4,6-dideoxy-D -manno-pyranose) homopolymer attached to the core oligosaccharide of the LPS of E. coli K12. Structural analysis revealed the presence of N-(3-deoxy-L -glycero-tetronyl)-2-O-methyl-D -perosamine at the non-reducing terminus of the O-polysaccharide chain of LPS from No. 30 (Ogawa) but not from No. 64 (Inaba). Serological analysis revealed that No. 30 (Ogawa) and No. 64 (Inaba) LPS were found to share the group antigen factor A of V. cholerae O1. They were distinguished by presence of the Ogawa antigen factor B [co-existing with relatively small amounts of the Inaba antigen factor (c)] in the former LPS and the Inaba antigen factor C in the latter LPS. It appears, therefore, that No. 30 (Ogawa) and No. 64 (Inaba) have O-antigenic structures that are fully consistent with the AB(c) structure for the Ogawa and the AC structure for the Inaba O-forms of V. cholerae O1, respectively. Thus, the present study clearly confirmed our previous finding that the Ogawa antigenic factor B is substantially related to the 2-O-methyl group at the non-reducing terminus of the α(1 → 2)-linked N-(3-deoxy-L -glycero-tetronyl)-D -perosamine homopolymer that forms the O-polysaccharide chain of LPS of V. cholerae O1 (Ogawa). 相似文献
968.
969.
Sequence analysis within the unique long segment of the bovine herpesvirus 1 (BHV-1) genome previously identified an open reading frame (ORF), designated UL2, whose deduced polypeptide of 204 amino acids contained a consensus uracil-DNA glycosylase (UDGase) signature sequence. To determine whether the BHV-1 UL2 ORF product has UDGase activity, we positioned the UL2 sequence downstream of the T7 promoter on the vector pET-28b(+) and expressed it in Escherichia coli. Upon induction with isopropyl β-D -thiogalactopyranoside these cells produced a 23-kDa protein, the molecular mass of which was in accordance with the prediction from the nucleotide sequence. A one-step purification procedure using nickel-chelating affinity chromatography resulted in a homogeneous preparation of this protein, which displayed specific UDGase activity in an in vitro enzyme assay. These results provide evidence that the BHV-1 UL2 gene does encode a UDGase. 相似文献
970.
We previously demonstrated that tumor necrosis factor-α (TNF-α) induces rapid human neutrophil apoptosis. In this paper, we examined which of the TNF receptors, p55 kDa TNF receptor (55-R) or p75 kDa TNF receptor (75-R), or both are involved in this process using specific rabbit antisera. Antibodies to 55-R (anti55-R) or 75-R (anti75-R) alone did not induce neutrophil apoptosis. Further addition of cycloheximide and anti-rabbit immunoglobulin to anti55-R but not to anti75-R accelerated apoptosis, although anti75-R augmented the capacity of anti55-R to do so. These results suggest that 55-R is a prerequisite for TNF-α induced neutrophil apoptosis. 相似文献