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31.
2-Phenylethylamine (PEA) was measured in rabbit brain by gas-liquid chromatography. D-Amphetamine sulfate (0.65 mg/Kg) initially reduced brain PEA levels to one-third of its usual content (30 min) and subsequently doubled brain PEA (4 hr). Brain PEA levels were reduced (30 min) and subsequently increased (ten-fold at 4 hr) by D-amphetamine sulfate (13 mg/Kg); tolerance to these two effects was observed in rabbits treated for three days with D-amphetamine. Methylphenidate HCl (30 mg/Kg) but not L-amphetamine sulfate (0.65 mg/Kg and 13 mg/Kg) induced a small, non-significant lowering of brain PEA (30 min) followed by a marked augmentation (4 hr) of brain PEA content. D-Amphetamine (30 min or 4 hr prior) increased the recovery of labeled PEA from the brain of rabbits injected intraventricularly with labeled phenylalanine, and reduced the recovery of labeled PEA after its intraventricular injection, suggesting that D-amphetamine accelerates both the synthesis and the disposition of brain PEA. Pretreatment with α-methyldopa (which depletes PEA and other brain amines) or with α-methyldopa hydrazine (which selectively reduces brain PEA content by inhibiting decarboxylase in peripheral tissues only) markedly reduced the CNS effects of D-amphetamine (behavioral stimulation in mice and rabbits, anti-convulsant effect in mice); these decarboxylase inhibitors enhanced the amphetamine-like effects induced by PEA in mice pretreated with a monoamine oxidase inhibitor. The ability of PEA depleters to selectively block the stimulant effects of D-amphetamine, together with the close structural and pharmacological similarities between amphetamine and PEA, and marked influence of amphetamine administration upon PEA brain levels, synthesis and metabolism, suggest to us that many of the central actions of amphetamine may be mediated by endogenous PEA. 相似文献
32.
Molecular evolutionary dynamics of cytochrome b in strepsirrhine primates: the phylogenetic significance of third-position transversions 总被引:3,自引:2,他引:1
DNA sequences of the complete cytochrome b gene are shown to contain robust
phylogenetic signal for the strepsirrhine primates (i.e., lemurs and
lorises). The phylogeny derived from these data conforms to other molecular
studies of strepsirrhine relationships despite the fact that uncorrected
nucleotide distances are high for nearly all intrastrepsirrhine
comparisons, with most in the 15%-20% range. Cytochrome b sequences support
the hypothesis that Malagasy lemuriforms and Afro-Asian lorisiforms each
comprise clades that share a sister- group relationship. A study (Adkins
and Honeycutt 1994) of the cytochrome c oxidase subunit II (COII) gene
placed one Malagasy primate (Daubentonia) at the base of the strepsirrhine
clade, thereby suggesting a diphyletic Lemuriformes. The reanalysis of COII
third- position transversions, either alone or in combination with
cytochrome b third-position transversions, however, yields a tree that is
congruent with phylogenetic hypotheses derived from cytochrome b and other
genetic data sets.
相似文献
33.
In rabbits, Δ9-tetrahydrocannabinol (Δ9-THC) increased the recovery of labeled 2-phenylethylamine (PEA) from brain following its intraventricular administration. Δ9-THC also enhanced the excitatory effect of iontophoretic PEA on cortical unit potentials. Although Δ9-THC induced sedation in mice, the subsequent injection of reserpine induced transient excitement. Low doses of PEA, which do not significantly alter the behavior of mice, induced marked excitement in mice pretreated with Δ9-THC. In mice treated with pargyline, Δ9-THC induced excitement (instead of sedation); this excitement was increased by PEA and reduced by phenylethanolamine. These results suggest that Δ9-THC inhibits the disposition of PEA. Since endogenous PEA may be one of the adrenergic ergotropic modulators, it may play a role in the euphoriant effect of marihuana. 相似文献
34.
The effect of relaxed functional constraints on the photosynthetic gene rbcL in photosynthetic and nonphotosynthetic parasitic plants 总被引:1,自引:0,他引:1
The photosynthetic gene rbcL has been lost or dramatically altered in some
lineages of nonphotosynthetic parasitic plants, but the dynamics of these
events following loss of photosynthesis and whether rbcL has sustained
functionally significant changes in photosynthetic parasitic plants are
unknown. To assess the changes to rbcL associated with the loss of
functional constraints for photosynthesis, nucleotide sequences from
nonparasitic and parasitic plants of Scrophulariales were used for
phylogeny reconstruction and character analysis. Plants in this group
display a broad range of parasitic abilities, from photosynthetic
("hemiparasites") to nonphotosynthetic ("holoparasites"). With the
exception of Conopholis (Orobanchaceae), the rbcL locus is present in all
parasitic plants of Scrophulariales examined. Several holoparasitic genera
included in this study, including Boschniakia, Epifagus, Orobanche, and
Hyobanche, have rbcL pseudogenes. However, the holoparasites Alectra
orobanchoides, Harveya capensis, Harveya purpurea, Lathraea clandestina,
Orobanche corymbosa, O. fasciculata, and Striga gesnerioides have intact
open reading frames (ORFs) for the rbcL gene. Phylogenetic hypotheses based
on rbcL are largely in agreement with those based on sequences of the
nonphotosynthetic genes rps2 and matK and show a single origin of
parasitism, and loss of photosynthesis and pseudogene formation have been
independently derived several times in Scrophulariales. The mutations in
rbcL in nonparasitic and hemiparasitic plants would result in largely
conservative amino acid substitutions, supporting the hypothesis that
functional proteins can experience only a limited range of changes, even in
minimally photosynthetic plants. In contrast, ORFs in some holoparasites
had many previously unobserved missense substitutions at functionally
important amino acid residues, suggesting that rbcL genes in these plants
have evolved under relaxed or altered functional constraints.
相似文献
35.
Alternative splicing and protein function 总被引:1,自引:0,他引:1
AD?Neverov II?Artamonova RN?Nurtdinov D?Frishman MS?GelfandEmail author AA?Mironov 《BMC bioinformatics》2005,6(1):266
Background
Alternative splicing is a major mechanism of generating protein diversity in higher eukaryotes. Although at least half, and probably more, of mammalian genes are alternatively spliced, it was not clear, whether the frequency of alternative splicing is the same in different functional categories. The problem is obscured by uneven coverage of genes by ESTs and a large number of artifacts in the EST data. 相似文献36.
The components of hard tissues including dentin, enamel, cementum, bone and other calcified deposits, and mature and immature collagen pose problems for identification in routine hematoxylin and eosin (H & E) stained sections. Use of combinations of stains can demonstrate the components of hard tissues and soft tissues distinctly. We assessed the efficacy of the Verde Luz-orange G-acid fuchsin (VOF) stain for differentiating hard and soft connective tissues and compared results with other histochemical staining techniques. Eighty tissue sections comprising developing tooth (30), ossifying fibroma (30) and miscellaneous pathologies (20) expected to contain varying types of calcified tissues were stained with H & E, VOF, and Masson's trichrome (MT). In developing tooth, VOF demonstrated better differentiation of hard tissues, while it was comparable to MT for ossifying fibroma and miscellaneous pathologies. The intensity of staining was greater with VOF than with the other stains studied. VOF stains hard tissue components distinctly and gives good contrast with the surrounding connective tissue. VOF is comparable to MT, but has added advantages including single step staining, rapid and easy procedures, and it distinguishes the maturity of the tissues. 相似文献
37.
The method of affinity coelectrophoresis was used to study the binding of
nine representative glycosaminoglycan (GAG)-binding proteins, all thought
to play roles in nervous system development, to GAGs and proteoglycans
isolated from developing rat brain. Binding to heparin and non-neural
heparan and chondroitin sulfates was also measured. All nine
proteins-laminin-1, fibronectin, thrombospondin-1, NCAM, L1, protease
nexin-1, urokinase plasminogen activator, thrombin, and fibroblast growth
factor-2-bound brain heparan sulfate less strongly than heparin, but the
degree of difference in affinity varied considerably. Protease nexin-1
bound brain heparan sulfate only 1.8- fold less tightly than heparin
(Kdvalues of 35 vs. 20 nM, respectively), whereas NCAM and L1 bound heparin
well (Kd approximately 140 nM) but failed to bind detectably to brain
heparan sulfate (Kd>3 microM). Four proteins bound brain chondroitin
sulfate, with affinities equal to or a few fold stronger than the same
proteins displayed toward cartilage chondroitin sulfate. Overall, the
highest affinities were observed with intact heparan sulfate proteoglycans:
laminin-1's affinities for the proteoglycans cerebroglycan (glypican-2),
glypican-1 and syndecan-3 were 300- to 1800-fold stronger than its affinity
for brain heparan sulfate. In contrast, the affinities of fibroblast growth
factor-2 for cerebroglycan and for brain heparan sulfate were similar.
Interestingly, partial proteolysis of cerebroglycan resulted in a >400-
fold loss of laminin affinity. These data support the views that (1)
GAG-binding proteins can be differentially sensitive to variations in GAG
structure, and (2) core proteins can have dramatic, ligand-specific
influences on protein-proteoglycan interactions.
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