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151.
J. Xu D. M. Gooler A. S. Feng 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1996,178(4):435-445
Single-unit recordings were made from 143 neurons in the frog (Rana p. pipiens) inferior colliculus (IC) to investigate how free-field sound direction influenced neural responses to sinusoidal-amplitude-modulated (SAM) tone and/or noise. Modulation transfer functions (MTFs) were derived from 3 to 5 sound directions within 180° of frontal field. Five classes of MTF were observed: low-pass, high-pass, band-pass, multi-pass, and all-pass. For 64% of IC neurons, the MTF class remained unchanged when sound direction was shifted from contralateral 90° to ipsilateral 90°. However, the MTFs of more than half of these neurons exhibited narrower bandwidths when the loudspeaker was shifted to ipsilateral azimuths. There was a decrease in the cut-off frequency for neurons possessing low-pass MTFs, an increase in cut-off frequency for neurons showing high-pass MTFs, or a reduction in the pass-band for neurons displaying bandpass MTFs. These results suggest that sound direction can influence amplitude modulation (AM) frequency tuning of single IC neurons.Since changes in periodicity of SAM tones alter both the temporal parameters of sounds as well as the sound spectrum, we examined whether directional effects on spectral selectivity play a role in shaping the observed direction-dependent AM selectivity. The directional influence on AM selectivity to both SAM tone and SAM noise was measured in 62 neurons in an attempt to gain some insight into the mechanisms that underlie directionally-induced changes in AM selectivity. Direction-dependent changes in the shapes of the tone and noise derived MTFs were different for the majority of IC neurons (55/62) tested. These data indicate that a spectrally-based and a temporally-based mechanism may be responsible for the observed results.Abbreviations
AM
amplitude modulation
-
CF
characteristic frequency
-
DI
direction index
-
FR
isointensity frequency response
-
GABA
gamma-aminobutyric acid
-
IC
inferior colliculus
-
ICc
central nucleus of the inferior colliculus
-
ITD
interaural time difference
-
MTF
modulation transfer function
-
PSTH
peri-stimulus time histogram
-
SAM
sinusoidal-amplitude-modulated
-
SC
synchronization coefficient
-
CN
cochlear nucleus 相似文献
152.
Vibrio hollisae strains isolated recently from patients in various locations were examined for the presence of the thermostable direct hemolysin gene (tdh) using nucleic acid hybridization and polymerase chain reaction assays. The results were consistent with the previous finding that all strains of V. hollisae carry the tdh gene. In contrast, the tdh gene has been detected in a minority of strains for other Vibrio species (V. parahaemolyticus, V. cholerae non-O1, and V. mimicus). Detailed phylogenetic analysis showed that the tdh genes of the non-V. hollisae species were very closely related to each other and that the tdh gene of V. hollisae was distantly related to the tdh genes of the non-V. hollisae species. These results and the proposed insertion sequence-mediated tdh transfer mechanism suggest that the tdh gene may have been maintained stably in V. hollisae and that the tdh genes of the non-V. hollisae species may have been involved in recent horizontal transfer. 相似文献
153.
芸苔属青菜(Brassica chinensis)与紫菜苔(B. cam pestrisvar. purpurea)的花粉经低温水合、热激、渗激三步程序,分离出大量具萌发能力的脱外壁花粉,脱外壁率可高达60% 以上。在含有碳源与氮源及Roberts培养基盐成分的碱性PEG 培养基中,首次使芸苔属脱外壁花粉萌发,萌发率可达33% ~41% 。在扫描电镜下观察了花粉脱外壁与萌发的过程。讨论了不同植物花粉脱外壁的方法与花粉壁生物学特点的对应关系,以及外壁对花粉萌发的可能作用 相似文献
154.
从嗜热蓝藻优雅粘囊藻(Myxosarcina concinna Printz.)中分离到具有放氧活性的藻胆体-类囊体膜复合物。它的吸收峰位于680、628、490、438和420 nm ,在低离子强度(0.1~0.4 m ol/L)磷酸缓冲液中的664 nm 荧光发射峰随离子强度的降低而升高,718 nm 荧光发射峰与此相反(77 。K,Ex= 580 nm )。当把游离的藻胆体和已解离去藻胆体的类囊体膜在蔗糖磷酸缓冲液中重组时,随时间延长(0~60 m in),718 nm 荧光发射峰逐渐升高,685 nm 荧光发射峰逐渐下降(77 。K,Ex = 580 nm ),表明藻胆体与类囊体之间的解离和结合对光能传递的影响 相似文献
155.
Haruko Ogawa Ako Hijikata Maho Amano Kyoko Kojima Hisako Fukushima Ineo Ishizuka Yoshie Kurihara Isamu Matsumoto 《Glycoconjugate journal》1996,13(4):555-566
The oligosaccharide structures ofCry j I, a major allergenic glycoprotein ofCryptomeria japonica (Japanese cedar, sugi), were analysed by 400 MHz1H-NMR and two-dimensional sugar mapping analyses. The four major fractions comprised a series of biantennary complex type N-linked oligosaccharides that share a fucose/xylose-containing core and glucosamine branches including a novel structure with a nongalactosylated fucosylglucosamine branch.Rabbit polyclonal anti-Cry j I IgG antibodies cross-reacted with three different plant glycoproteins having the same or shorter N-linked oligosaccharides asCry j I. ELISA and ELISA inhibition studies with intact glycoproteins, glycopeptides and peptides indicated that both anti-Cry j I IgGs and anti-Sophora japonica bark lectin II (B-SJA-II) IgGs included oligosaccharide-specific antibodies with different specificities, and that the epitopic structures against anti-Cry j I IgGs include a branch containing 1–6 linked fucose and a core containing fucose/xylose, while those against anti-B-SJA-II IgGs include nonreducing terminal mannose residues. The cross-reactivities of human allergic sera to miraculin andClerodendron Trichotomum lectin (CTA) were low, and inhibition studies suggested that the oligosaccharides onCry j I contribute little or only conformationally to the reactivity of specific IgE antibodies.Abbreviations
Cry j I
a major allergenic glycoprotein ofCryptomeria japonica
- B-SJA-II
Sophora japonica bark lectin II
- CTA
Clerodendron trichotomum lectin
- TFMS
trifluoromethanesulfonic acid
- HRP
horseradish peroxidase 相似文献
156.
Heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins) serve to transduce information from agonist-bound receptors to effector enzymes or ion channels. Current models of G protein activation-deactivation indicate that the oligomeric GDP-bound form must undergo release of GDP, bind GTP and undergo subunit dissociation, in order to be in active form (GTP bound subunits and free dimers) and to regulate effectors. The effect of receptor occupation by an agonist is generally accepted to be promotion of guanine nucleotide exchange thus allowing activation of the G protein. Recent studies indicate that transphosphorylation leading to the formation of GTP from GDP and ATP in the close vicinity, or even at the G protein, catalysed by membrane-associated nucleoside diphosphate kinase, may further activate G proteins. This activation is demonstrated by a decreased affinity of G protein-coupled receptors for agonists and an increased response of G protein coupled effectors. In addition, a phosphorylation of G protein subunits and consequent phosphate transfer reaction resulting in G protein activation has also been demonstrated. Finally, endogenously formed GTP was preferentially effective in activating some G proteins compared to exogenous GTR The aim of this report is to present an overview of the evidence to date for a transphosphorylation as a means of G protein activation (see also refs [1 and 2] for reviews). (Mol Cell Biochem 157: 593, 1996)Recipient of Servier Investigator Award 相似文献
157.
C. F. MUSIL 《Plant, cell & environment》1996,19(9):1017-1027
Two D. sinuata populations, established from the same seed batch, were cultured concurrently under ambient (2.5–8.9 kj m?2 d?1) and enhanced (4.7–11.4 kj m?2 d?1) ultraviolet-B radiation for two consecutive generations. The two populations, designated low- and high-UV-B cultivars, were each grown for an additional generation under both UV-B fluences at different alignments. Differences in plant performance were examined between UV-B treatments (immediate UV-B effects), cultivars (accumulated UV-B effects), alignments and their interactions. Accumulated UV-B had a greater effect on plant performance than immediate UV-B. The former induced earlier reproductive effort, substantial (up to 35%) reductions in dry mass (stems, leaves and reproductive organs), decreased stem and inflorescence production, and diminished steady-state fluorescence yields, chlorophyll a concentrations, pollen tube growth and germination of seeds set. The latter caused only diminished non-photochemical quenching, reduced chlorophyll a, soluble sugar and starch concentrations, decreased pollen germination, and increased carotenoid contents. Interactions between UV-B fluence level and alignment occurred for all measured dry mass parameters, leaf area, photosynthetic pigment and soluble sugar concentrations, and germination success of seeds set. These results indicate altered DNA integrity rather than an indirect UV-B effect of photomorphogenic origin. 相似文献
158.
Shun Hirota Margareta Svensson-Ek Pia Ädelroth Nobuhito Sone Thomas Nilsson Bo G. Malmström Peter Brzezinski 《Journal of bioenergetics and biomembranes》1996,28(6):495-501
The time course of absorbance changes following flash photolysis of the fully-reduced carboxycytochrome oxidase fromBacillus PS3 in the presence of O2 has been followed at 445, 550, 605, and 830 nm, and the results have been compared with the corresponding changes in bovine cytochrome oxidase. The PS3 enzyme has a covalently bound cytochromec subunit and the fully-reduced species therefore accommodates five electrons instead of four as in the bovine enzyme. In the bovine enzyme, following CO dissociation, four phases were observed with time constants of about 10 s, 30 s, 100 s, and 1 ms at 445 nm. The initial, 10-s absorbance change at 445 nm is similar in the two enzymes. The subsequent phases involving hemea and CuA are not seen in the PS3 enzyme at 445 nm, because these redox centers are re-reduced by the covalently bound cytochromec, as indicated by absorbance changes at 550 nm. A reaction scheme consistent with the experimental observations is presented. In addition, internal electron-transfer reactions in the absence of O2 were studied following flash-induced CO dissociation from the mixed-valence enzyme. Comparisons of the CO recombination rates in the mixed-valence and fully-reduced oxidases indicate that more electrons were transferred from hemea
3 toa in PS3 oxidase compared to the bovine enzyme. 相似文献
159.
E. A. Walker J. P. Ride S. Kurup V. E. Franklin-Tong M. J. Lawrence F. C. H. Franklin 《Plant molecular biology》1996,30(5):983-994
The S
3 allele of the S gene has been cloned from Papaver rhoeas cv. Shirley. The sequence predicts a hydrophilic protein of 14.0 kDa, showing 55.8% identity with the previously cloned S
1 allele, preceded by an 18 amino acid signal sequence. Expression of the S
3 coding region in Escherichia coli produced a form of the protein, denoted S3e, which specifically inhibited S3 pollen in an in vitro bioassay. The recombinant protein was ca. 0.8 kDa larger than the native stigmatic form, indicating post-translational modifications in planta, as was previously suggested for the S1 protein. In contrast to other S proteins identified to date, S3 protein does not appear to be glycosylated. Of particular significance is the finding that despite exhibiting a high degree of sequence polymorphism, secondary structure predictions indicate that the S1 and S3 proteins may adopt a virtually identical conformation. Sequence analysis also indicates that the P. rhoeas S alleles share some limited homology with the SLG and SRK genes from Brassica oleracea. Previously, cross-classification of different populations of P. rhoeas had revealed a number of functionally identical alleles. Probing of western blots of stigma proteins from plants derived from a wild Spanish population which contained an allele functionally identical to the Shirley S
3 allele with antiserum raised to S3e, revealed a protein (S
3
s) which was indistinguishable in pI and M
r from that in the Shirley population. A cDNA encoding S
3
s was isolated, nucleotide sequencing revealing a coding region with 99.4% homology with the Shirley-derived clone at the DNA level, and 100% homology at the amino acid level. 相似文献
160.