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51.
Robert Y. Kanterman Christian C. Felder Douglas E. Brenneman Alice L. Ma Sandra Fitzgerald Julius Axelrod 《Journal of neurochemistry》1990,54(4):1225-1232
The alpha 1-adrenergic receptor has been shown to mediate the release of arachidonic acid in FRTL5 thyroid cells and MDCK kidney cells. In primary cultures of spinal cord cells, norepinephrine stimulated release of arachidonic acid (from neurons only) and turnover of inositol phospholipids (from neurons and glia) via alpha 1-adrenergic receptors. These two responses were dissociated by treatment with phorbol ester and pertussis toxin, which inhibited production of inositol phosphates with no appreciable effect on release of arachidonic acid. Extracellular calcium was required for release of arachidonic acid, but not for production of inositol phosphates. The calcium channel blockers nifedipine and verapamil inhibited release of arachidonic acid only. However, 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8), a compound that blocks intracellular calcium release, diminished production of inositol phosphates, but had little effect on release of arachidonic acid. These results suggest that alpha 1-adrenergic receptors couple to release of arachidonic acid in primary cultures of spinal cord cells by a mechanism independent of activation of phospholipase C, possibly via the activation of phospholipase A2. 相似文献
52.
Summary Filamentous actin in the apices of growing hyphae of the oomyceteSaprolegnia ferax is distributed such that it could compensate for weakness in the expanding apical cell wall and thus play a role in morphogenesis of the tip. The tapered extensible portion of the hyphal tip where the cell wall is plastic contains a cap of actin which differs in organization from the actin in subapical, inextensible regions of the hypha. Rapidly growing hyphae which are expected to have a longer plastic cell wall region contain longer actin caps. Furthermore, the weakest point in the hyphal apex, demonstrated by osmotic shock-induced bursting, was within the taper where the wall is plastic but never in the extreme apex where actin was most densely packed and presumably the strongest. Treatment of hyphae with cytochalasin E/dimethyl sulphoxide induced rapid changes in actin caps. Cap disruption was accompanied by transient growth rate increases, subsequent rounding and swelling of apices and a shift of osmotically induced burst points closer to the apex. These correlated changes are consistent with a role for the actin cap in tip morphogenesis. The association between regions of plasticity in the apical cell wall, the extent of the actin cap, the location of the weakest point in the apex and the effects of damage to the actin cap suggest that the cap functions to support the apex in regions where the cell wall is weak.Abbrevations CE
cytochalasin E
- DMSO
dimethyl sulphoxide
- RP
rhodamine phalloidin
Dedicated to the memory of Professor Oswald Kiermayer 相似文献
53.
Sandra Afione Luciano Debeljuk Adriana Seilicovich Daniel Pisera Mercedes Lasaga María del Carmen Díaz Beatriz Duvilanski 《Peptides》1990,11(6):1065-1068
In the present work we examined the effect of the neutralization of endogenous substance P by the administration of an anti-substance P serum (ASPS) on GABA concentration in the anterior pituitary in hyperprolactinemic conditions induced by 5-hydroxytryptophan or by grafting anterior pituitaries. ASPS reduced the increase in the anterior pituitary GABA concentration induced by hyperprolactinemia. In vitro experiments showed that substance P inhibited K+-evoked GABA efflux from hypothalamic fragments and decreased GABA concentration in the anterior pituitary but ASPS increased it. Our results demonstrate that substance P modifies hypothalamic GABA release and anterior pituitary GABA concentration and suggest that an interaction exists between substance P and GABA. 相似文献
54.
Increased Neostriatal Tyrosine Hydroxylation During Stress: Role of Extracellular Dopamine and Excitatory Amino Acids 总被引:2,自引:0,他引:2
Abstract: We examined the regulation of neostriatal tyrosine hydroxylation during acute stress, testing the hypothesis that excitatory amino acids (EAAs) contribute to the stress-evoked increase in dopamine (DA) synthesis. Dialysis probes implanted into neostriatum permitted delivery of drugs and sampling of extracellular fluid. Rats were exposed to 30 min of intermittent tail shock during infusion of an inhibitor of aromatic amino acid decarboxylase (AAAD), NSD-1015 (100 µM), and DOPA was measured in the dialysate. Tail shock was applied beginning either 15 min after the onset of NSD-1015 treatment (the initial rate of DOPA accumulation) or 75 min after the onset of treatment (when DOPA had approached steady state). Tail shock increased the steady-state levels of extracellular DOPA in neostriatum (+40%). However, there was no change in the initial rate of DOPA accumulation unless animals also received the D2 receptor antagonist eticlopride (50 nM), in which case an increase was observed (+228%). The impact of tail shock on the steady-state level of DOPA was attenuated by the D2 agonist quinpirole (100 µM), or by 2-amino-5-phosphonovalerate (APV) (100 µM) or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (100 µM), EAA antagonists acting at NMDA or d ,l -α-amino-3-hydroxy-5-methyl-4-isoxazole-4-propionate (AMPA) receptors, respectively. These data suggest that acute stress normally has little effect on tyrosine hydroxylation in neostriatum due to the inhibitory influence of DA in the extracellular fluid. However, when that influence is absent (e.g., during extended inhibition of DOPA decarboxylation or blockade of DA receptors), stress increases tyrosine hydroxylation via EAAs acting on NMDA and AMPA receptors. Thus, EAAs released from corticostriatal projections may stimulate DA synthesis and thereby restore dopaminergic activity under conditions in which the availability of DA for release has been compromised. 相似文献
55.
The life cycle of the red alga Porphyra purpurea alternates between two morphologically distinct phases: a shell-boring, filamentous sporophyte and a free-living, foliose gametophyte. From a subtracted cDNA library enriched for sporophyte-specific sequences, we isolated a cDNA encoding an unusual elongation factor 1 (EF-1) that is expressed only in the sporophyte. A second EF-1 gene that is expressed equally in the sporophyte and the gametophyte was isolated from a genomic library. These are the only EF-1 genes detectable in P. purpurea. The constitutively expressed gene encodes and EF-1 very similar to those of most eukaryotes. However, the sporophyte-specific EF-1 is one of the most divergent yet described, with nine insertions or deletions ranging in size from 1 to 26 amino acids. This is the first report of a developmental stage-specific EF-1 outside of the animal kingdom and suggests a fundamental role for EF-1 in the developmental process. 相似文献
56.
57.
Microtubule-associated proteins (MAPs) regulate microtubule stability and play critical roles in neuronal development and the balance between neuronal plasticity and rigidity. MAP1a (HGMW-approved symbol MAP1A) stabilizes microtubules in postnatal axons. We describe human MAP1a's genomic organization and deduced cDNA and amino acid sequences. MAP1a is a single-copy gene spanning 10.5 kb. MAP1a coding sequence is contained in five exons. Translation begins in exon 3. Human MAP1a contains 2805 amino acids (predicted molecular weight 306.5 kDa) and is slightly larger than rat MAP1a (2774 amino acids). Like rat and bovine MAP1a, human MAP1a contains conserved tubulin binding motifs in the amino-terminal region. The carboxy-terminal portion contains a conserved pentadecapeptide that is present in the light chain portion of rat and bovine MAP1a/LC2 polyprotein. We show that human MAP1a gene expression occurs almost exclusively in the brain and that there is approximately 10-fold greater gene expression in adult brain compared to fetal brain. Strong, interspecies conservation between human and rat MAP1a cDNA and amino acid sequences indicates important relationships between MAP1a's function and its primary amino acid sequence. 相似文献
58.
The inheritance of obesity has been analyzed in an intercross between the lean 129/Sv mouse strain and the obesity-prone EL/Suz mouse strain. The weights of three major fat pads were determined on 4-month-old mice, and the sum of these weights, divided by body weight, was used as an adiposity index. The strategy of selective DNA pooling was used as a primary screen to identify putative quantitative trait loci (QTLs) affecting adiposity index. DNA pools representing the leanest 15% and fattest 15% of the F2 progeny were compared for differential allelic enrichment using widely dispersed microsatellite variants. To evaluate putative QTLs, individual genotyping and interval mapping were employed to estimate QTL effects and assess statistical significance. One QTL affecting adiposity index, which accounted for 12.3% of phenotypic variance in gender-merged data, was mapped to the central region of Chromosome (Chr) 7. The QTL allele inherited from EL conferred increased adiposity. A second QTL that accounts for 6.3% of phenotypic variance was identified on Chr 1 nearD1Mit211.At both QTLs, the data are consistent with dominant inheritance of the allele contributing to obesity. The possible relationships between these QTLs and previously described obesity QTLs, major obesity mutations, and candidate genes are discussed. 相似文献
59.
Sandra Irene Pitta-Alvarez Ana María Giulietti 《In vitro cellular & developmental biology. Plant》1995,31(4):215-220
Summary
Brugmansia candida hairy roots, obtained by infection withAgrobacterium rhizogenes LBA 9402, exhibit, after subculturing in liquid media, a tendency towards dedifferentiation. It has been found that the following
strategies can be applied to inhibit this dedifferentiation and preserve normal root morphology: (a) lowering both the mineral
and sucrose concentration in the media employed so as to diminish osmotic stress (a condition to which these roots appear
to be particularly susceptible); (b) employing antiauxins in appropriate concentrations; and (c) maintaining the hairy roots
on solid media prior to use in production processes in liquid media. The first strategy suggested does not favor alkaloid
productivity, but in this case a two-step method could be attempted: biomass with normal root morphology could be obtained
in a first stage using low sucrose concentrations, and in a second stage, sucrose could be increased in order to achieve higher
productivity. In all the clones ofB. candida obtained, alkaloid production was biased towards scopolamine. 相似文献
60.
Abstract. The Argentine Chaco is a mosaic of grassland and open forest habitats maintained by natural disturbance activities such as fire. Since the introduction of domestic livestock and other human activities, the balance of this mosaic has been significantly altered, both in plant species and structural composition. This study focuses on the impact of such changes on the diversity of ground-dwelling arthropods within semi-arid Chaco forest. Quantitative measures of habitat structure and arthropod diversity were taken in forest areas previously subjected to grazing, logging and ploughing. Results indicated that arthropod diversity was smaller on sites with reduced structural complexity, with marked changes in arthropod family composition. The habitat components relating to plant architectural and vertical diversity were particularly influential on arthropod diversity. The guild size ratio of predatory to non-predatory arthropods also differed significantly between habitats suggesting a change in the resource base available to some groups. The latter suggests a shift in the functional organisation of the forest ecosystem which could have important repercussions for the diversity of other trophic levels. 相似文献