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1.
J.G. Roddick 《Phytochemistry》1974,13(1):9-25
The literature relating to chemical, biochemical and biological aspects of the steroidal glycoalkaloid, α-tomatine, is reviewed. The alkaloid, which can be used as a starting compound for the synthesis of steroidal hormones, is toxic to a wide range of living organisms. The significance of tomatine to plants which elaborate it is discussed and some possible uses of the compound are mentioned. 相似文献
2.
Conversion of phosphatidylglycerol to lyso(bis)phosphatidic acid by alveolar macrophages 总被引:1,自引:0,他引:1
We report here studies of the synthesis of lyso(bis)phosphatidic acid [L(b)PA] by normal and BCG-elicited rabbit alveolar macrophages. This study was prompted by our earlier observations that 1) alveolar macrophages did not synthesize L(b)PA de novo despite its abundance in these cells, 2) BCG-elicited cells contained only one-quarter the amount of L(b)PA as normal cells, and 3) the turnover of arachidonate in L(b)PA led to hydroxyeicosatetraenoic acid and leukotriene synthesis. We found that exogenous phosphatidylglycerol (PG) was specifically converted to L(b)PA by both types of cells although BCG-elicited cells had only one-quarter the synthetic capacity of normal cells. Other phospholipids were found to become cell associated but were not significantly metabolized. Both glycerol moieties and the phosphate were incorporated into the product L(b)PA. However, substitution of the ester with an alkyl linkage in position 1 blocked the conversion of PG to L(b)PA. Most of the alkylphosphatidylglycerol was converted to phosphatidylcholine and phosphatidylethanolamine. This result implied that catabolism of the acyl group in position 1 was essential for L(b)PA synthesis. Because alveolar macrophages are present in a surfactant-rich milieu, we suggest that surfactant provides a source of PG for macrophage synthesis of L(b)PA in situ. It is interesting that the surfactants from rabbits challenged with BCG have a significant decrease in PG content. 相似文献
3.
Fruits of tomato incorporated [2-14C]mevalonic acid lactone into the steroidal glycoalkaloid α-tomatine. Young fruits showed the greatest alkaloid-synthesizing ability but this decreased as the fruits developed. Analysis of sap exuded from fruit stalks and also application of[4-14C]cholesterol to leaves confirmed that tomatine is not transported into fruits from vegetative organs. Accumulation of this alkaloid in fruits thus appears entirely due to synthesis. Excised fruits of all developmental stages degraded injected [14C]tomatine and rates were directly related to fruit age. The pattern of accumulation/decline in fruit tomatine may be explicable on the basis of changing capacity for synthesis/degradation during development. Label from injected [14C]tomatine was present mainly in chlorophylls and carotenoids where it increased with time as that in tomatine decreased. The significance of the relationship between tomatine disappearance and carotenoid development is briefly discussed. The aglycone tomatidine was not detected in green fruits but a Δ16-5α-pregnenolone-like compound was. 相似文献
4.
J. G. Roddick 《Planta》1971,102(2):134-139
Summary The steroidal alkaloid tomatine did not enhance elongation of oat coleoptile and first internode sections, or of wheat coleoptile sections. Higher concentrations of the alkaloid inhibited elongation and interacted antagonistically with IAA. Although 10-4 M tomatine alone did not influence elongation of oat coleoptile sections, it did reduce growth response to exogenous IAA. Tomatine concentrations less than 10-4 M did not influence response to IAA. The auxin activity of tomatine, reported by Vendrig, was therefore not confirmed. 相似文献
5.
We have broadly defined the DNA regions regulating esterase6 activity in
several life stages and tissue types of D. melanogaster using P-
element-mediated transformation of constructs that contain the esterase6
coding region and deletions or substitutions in 5' or 3' flanking DNA.
Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and
the primary sequences regulating its activity lie between -171 and -25 bp
relative to the translation initiation site: deletion of these sequences
decrease activity approximately 20-fold. Hemolymph activity is also
modulated by four other DNA regions, three of which lie 5' and one of which
lies 3' of the coding region. Of these, two have positive and two have
negative effects, each of approximately twofold. Esterase6 activity is
present also in two male reproductive tract tissues; the ejaculatory bulb,
which is another ancestral activity site, and the ejaculatory duct, which
is a recently acquired site within the melanogaster species subgroup.
Activities in these tissues are at least in part independently regulated:
activity in the ejaculatory bulb is conferred by sequences between -273 and
-172 bp (threefold decrease when deleted), while activity in the
ejaculatory duct is conferred by more distal sequences between -844 and
-614 bp (fourfold decrease when deleted). The reproductive tract activity
is further modulated by two additional DNA regions, one in 5' DNA (-613 to
-284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to
+2731 bp; threefold decrease when deleted) that probably overlaps the
adjacent esteraseP gene. Collating these data with previous studies
suggests that expression of EST6 in the ancestral sites is mainly regulated
by conserved proximal sequences while more variable distal sequences
regulate expression in the acquired ejaculatory duct site.
相似文献
6.
Nucleotide variation at the hypervariable esterase 6 isozyme locus of Drosophila simulans 总被引:2,自引:0,他引:2
Esterase 6 (Est-6/EST6) is polymorphic in both Drosophila melanogaster and
D. simulans for two common allozyme forms, as well as for several other
less common variants. Parallel latitudinal clines in the frequencies of the
common EST6-F and EST6-S allozymes in these species have previously been
interpreted in terms of a shared amino acid polymorphism that distinguishes
the two variants and is subject to selection. Here we compare the sequences
of four D. simulans Est-6 isolates and show that overall estimates of
nucleotide heterozygosity in both coding and 5' flanking regions are more
than threefold higher than those obtained previously for this gene in D.
melanogaster. Nevertheless, the ratio of replacement to exon silent-site
polymorphism in D. simulans is less than the ratio of replacement to silent
divergence between D. simulans and D. melanogaster, which could be the
result of increased efficiency of selection against replacement
polymorphisms in D. simulans or to divergent selection between the two
species. We also find that the amino acid polymorphisms separating EST6- F
and EST6-S in D. simulans are not the same as those that separate these
allozymes in D. melanogaster, implying that the shared clines do not
reflect shared molecular targets for selection. All comparisons within and
between the two species reveal a remarkable paucity of variation in a
stretch of nearly 400 bp immediately 5' of the gene, indicative of strong
selective constraint to retain essential aspects of Est-6 promoter
function.
相似文献
7.
Roots of Acer pseudoplatanus seedlings grown in liquid nutrient medium contained much lower levels of both free and bound abscisic acid than did leaves. The levels of free abscisic acid were similar in young expanding and of mature leaves, but lower in older senscing leaves. Growing plants under long days or short days did not influence the levels of free and bound abscisic acid in leaves. However, under both long days and short days, levels of bound abscisic acid were lower at the end of the dark period than 8 h later during the light period. Phaseic acid was also detected during the light period but never at the end of the dark period.Abbreviations ABA
abscisic acid
- PA
phaseic acid
- SD
short day
- GLC
gas-liquid chromatography
- LD
long day 相似文献
8.
9.
10.
Ilkovski B Cooper ST Nowak K Ryan MM Yang N Schnell C Durling HJ Roddick LG Wilkinson I Kornberg AJ Collins KJ Wallace G Gunning P Hardeman EC Laing NG North KN 《American journal of human genetics》2001,68(6):1333-1343
Nemaline myopathy (NM) is a clinically and genetically heterogeneous disorder characterized by muscle weakness and the presence of nemaline bodies (rods) in skeletal muscle. Disease-causing mutations have been reported in five genes, each encoding a protein component of the sarcomeric thin filament. Recently, we identified mutations in the muscle alpha-skeletal-actin gene (ACTA1) in a subset of patients with NM. In the present study, we evaluated a new series of 35 patients with NM. We identified five novel missense mutations in ACTA1, which suggested that mutations in muscle alpha-skeletal actin account for the disease in approximately 15% of patients with NM. The mutations appeared de novo and represent new dominant mutations. One proband subsequently had two affected children, a result consistent with autosomal dominant transmission. The seven patients exhibited marked clinical variability, ranging from severe congenital-onset weakness, with death from respiratory failure during the 1st year of life, to a mild childhood-onset myopathy, with survival into adulthood. There was marked variation in both age at onset and clinical severity in the three affected members of one family. Common pathological features included abnormal fiber type differentiation, glycogen accumulation, myofibrillar disruption, and "whorling" of actin thin filaments. The percentage of fibers with rods did not correlate with clinical severity; however, the severe, lethal phenotype was associated with both severe, generalized disorganization of sarcomeric structure and abnormal localization of sarcomeric actin. The marked variability, in clinical phenotype, among patients with different mutations in ACTA1 suggests that both the site of the mutation and the nature of the amino acid change have differential effects on thin-filament formation and protein-protein interactions. The intrafamilial variability suggests that alpha-actin genotype is not the sole determinant of phenotype. 相似文献