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1.
Metabolism of linoleic acid by prostaglandin endoperoxide synthase from adult and fetal blood vessels 总被引:2,自引:0,他引:2
Linoleic acid (18:2) is converted by prostaglandin endoperoxide synthase in particulate fractions and homogenates of fetal calf aorta to its 9- and 13-hydroperoxy metabolites. These intermediates are then either dehydrated to the corresponding oxo compounds or reduced to monohydroxy products. Alternatively, the hydroperoxyoctadecadienoic acids can be converted to epoxyhydroxyoctadecenoic acids, which are hydrolyzed to trihydroxy metabolites by epoxide hydrolases present in both particulate and cytosolic fractions from aorta. Linoleic acid (Km, 442 microM) is a much poorer substrate for prostaglandin endoperoxide synthase than is arachidonic acid (20:4) (Km, 48 microM). However, the oxygenation of 18:2 by particulate fractions from aorta is linear with time for at least 5 min, whereas the oxygenation of 20:4 is linear for only 15 s. Arachidonic acid strongly inhibits the conversion of 18:2 to monohydroxy (ID50, 10 microM) and trihydroxy (ID50, 140 microM) products. Linoleic acid has a similar, but much weaker effect on the formation of 6-oxoprostaglandin F1 alpha from 20:4. Substantial amounts of both the monohydroxy (9-hydroxy-10, 12-octadecadienoic acid and 13-hydroxy-9,11-octadecadienoic acid) and trihydroxy (9,10,11-trihydroxy-12-octadecenoic acid, 9,10,13-trihydroxy-11-octadecenoic acid and 9,12,13-trihydroxy-10-octadecenoic acid) metabolites of 18:2 were shown by gas chromatography-mass spectrometry to be formed from endogenous substrate during incubation of slices of fetal calf aorta in physiological medium. This raises the possibility that some of these products or their hydroperoxy precursors may have some biological significance. 相似文献
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Matthew L. Knope Clifford W. Morden Vicki A. Funk Tadashi Fukami 《Journal of Biogeography》2012,39(7):1206-1216
Aim To estimate the rate of adaptive radiation of endemic Hawaiian Bidens and to compare their diversification rates with those of other plants in Hawaii and elsewhere with rapid rates of radiation. Location Hawaii. Methods Fifty‐nine samples representing all 19 Hawaiian species, six Hawaiian subspecies, two Hawaiian hybrids and an additional two Central American and two African Bidens species had their DNA extracted, amplified by polymerase chain reaction and sequenced for four chloroplast and two nuclear loci, resulting in a total of approximately 5400 base pairs per individual. Internal transcribed spacer sequences for additional outgroup taxa, including 13 non‐Hawaiian Bidens, were obtained from GenBank. Phylogenetic relationships were assessed by maximum likelihood and Bayesian inference. The age of the most recent common ancestor and diversification rates of Hawaiian Bidens were estimated using the methods of previously published studies to allow for direct comparison with other studies. Calculations were made on a per‐unit‐area basis. Results We estimate the age of the Hawaiian clade to be 1.3–3.1 million years old, with an estimated diversification rate of 0.3–2.3 species/million years and 4.8 × 10?5 to 1.3 × 10?4 species Myr?1 km?2. Bidens species are found in Europe, Africa, Asia and North and South America, but the Hawaiian species have greater diversity of growth form, floral morphology, dispersal mode and habitat type than observed in the rest of the genus world‐wide. Despite this diversity, we found little genetic differentiation among the Hawaiian species. This is similar to the results from other molecular studies on Hawaiian plant taxa, including others with great morphological variability (e.g. silverswords, lobeliads and mints). Main conclusions On a per‐unit‐area basis, Hawaiian Bidens have among the highest rates of speciation for plant radiations documented to date. The rapid diversification within such a small area was probably facilitated by the habitat diversity of the Hawaiian Islands and the adaptive loss of dispersal potential. Our findings point to the need to consider the spatial context of diversification – specifically, the relative scale of habitable area, environmental heterogeneity and dispersal ability – to understand the rate and extent of adaptive radiation. 相似文献
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Summary Plant cell suspension cultures producing secondary metabolites have been permeabilized for product release by electroporation. The two cell cultures studied, i.e. Thalictrum rugosum and Chenopodium rubrum, require about 5 and 10 kV cm–1, respectively, for complete permeabilization (release of all the intracellularly stored product). The number of electrical pulses and capacitance used had a relatively limited effect on product release while the viability of the cells was strongly influenced by the latter. Conditions for complete product release resulted in total loss of viability of the cells after treatment. The release of product from immobilized cells was also achieved by electroporation. Cells entrapped in alginate required less voltage for permeabilization than free or agarose entrapped cells. 相似文献
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Cyclic amplification and selection of targets (CASTing) for the myogenin consensus binding site. 总被引:47,自引:18,他引:29 下载免费PDF全文
The consensus binding site for the muscle regulatory factor myogenin was determined from an unbiased set of degenerate oligonucleotides using CASTing (cyclic amplification and selection of targets). Stretches of totally random sequence flanked by polymerase chain reaction priming sequences were mixed with purified myogenin or myotube nuclear extracts, DNA-protein complexes were immunoprecipitated with an antimyogenin antibody, and the DNA was amplified by polymerase chain reaction. Specific binding was obtained after four to six cycles of CASTing. The population of selected binding sites was then cloned, and a consensus was determined from sequencing individual isolates. Starting from a pool with 14 random bases, purified myogenin yielded a consensus binding site of AACAG[T/C]TGTT, while nuclear extracts retrieved the sequence TTGCACCTGTTNNTT from a pool containing 35 random bases. The latter sequence is consistent with that predicted from combining an E12/E47 half-site (N[not T]CAC) with the purified myogenin half-site ([T/C] TGTT). The presence of paired E boxes in many of the sequences isolated following CASTing with nuclear extracts proves that myogenin can bind cooperatively with other E-box-binding factors. 相似文献
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Studies on the functional morphology of rat ocular vessels with scanning electron microscopy 总被引:1,自引:0,他引:1
R Funk 《Acta anatomica》1986,125(4):252-257
Tests are still lacking about the suitability of scanning electron microscopy (SEM) of vascular resin casts to show different functional states of peripheral blood vessels. With the aid of a vitalmicroscopic device, we tried to elaborate a vascular casting method using the model of the albino rat iris vasculature. Functional variations of the vasculature were induced by local application of epinephrine to one eye using the untreated fellow eye as a control. It was found that if our modification of Araldite plastic is injected via a systemic access and without preceding rinsing with fixatives or salt solutions there is a good correlation between the vessel diameters seen in SEM of resin casts and the vessel diameters found in the vitalmicroscopic observations. Thus, this method appears also suitable for studying the effect of vasoactive substances. 相似文献
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An autonomous N-terminal transactivation domain in Fos protein plays a crucial role in transformation. 总被引:4,自引:1,他引:3 下载免费PDF全文
To date, three functional domains have been defined in c-Fos and v-Fos proteins and have been shown to play a role in transactivation: the leucine zipper mediating hetero-dimerization, the basic DNA contact site, and a C-terminally located transactivation domain (C-TA) harbouring the HOB1 and HOB2 motifs. While the bZip region, consisting of the leucine zipper and the DNA contact site, is indispensable for transformation, the C-TA domain is not required and is actually altered by internal deletions in the FBR-MuSV. We now show that the N-terminal regions of c-Fos and v-Fos contain a second transactivation domain (N-TA). A functionally crucial motif within the N-TA domain, termed NTM, was pinpointed to a approximately 25 amino acid stretch around positions 60-84 which is highly conserved in FosB. Analysis of LexA fusion proteins showed that the N-TA domains of both c-Fos and FosB function in an autonomous fashion in both fibroblasts and yeast. Most importantly, deletion of the NTM motif impairs the transforming properties of v-Fos. Apart from the bZip region, the N-TA domain is the only functional domain required for transformation by v-Fos, at least when its expression is driven by the strong FBR-MuSV-LTR promoter. 相似文献
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A study was designed to measure the Toxoplasma gondii-specific IgM and IgG antibody responses of opossums inoculated with tachyzoites of the temperature-sensitive mutant of T. gondii, ts-4, and to examine its persistence in the tissues. Four young opossums seronegative for anti-Toxoplasma gondii IgM and IgG antibodies immediately after capture and 4 wk later were injected subcutaneously with 1.8 x 10(6) ts-4 tachyzoites; a fifth opossum (also seronegative) received an injection of saline only. Serum was collected weekly and titered by modified direct agglutination for anti-Toxoplasma gondii IgM and IgG. IgM titers were detectable from week 1 to week 6 postinoculation (PI). IgG was measurable by week 3 and remained high for 30 wk PI when the opossums were killed and examined. The control opossum did not develop a specific antibody response. At necropsy major lesions were not found. No anti-Toxoplasma gondii IgG was detected in serum collected from mice injected with tissues prepared from the opossums at necropsy, and no T. gondii was found on impression smears made at necropsy from these mice. Modified direct agglutination performed with or without 0.2 M 2-mercaptoethanol worked well for measuring specific IgM and IgG antibodies in experimentally infected opossums. 相似文献