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Litman GW; Rast JP; Shamblott MJ; Haire RN; Hulst M; Roess W; Litman RT; Hinds- Frey KR; Zilch A; Amemiya CT 《Molecular biology and evolution》1993,10(1):60-72
Immunoglobulins are encoded by a large multigene system that undergoes
somatic rearrangement and additional genetic change during the development
of immunoglobulin-producing cells. Inducible antibody and antibody-like
responses are found in all vertebrates. However, immunoglobulin possessing
disulfide-bonded heavy and light chains and domain-type organization has
been described only in representatives of the jawed vertebrates. High
degrees of nucleotide and predicted amino acid sequence identity are
evident when the segmental elements that constitute the immunoglobulin gene
loci in phylogenetically divergent vertebrates are compared. However, the
organization of gene loci and the manner in which the independent elements
recombine (and diversify) vary markedly among different taxa. One striking
pattern of gene organization is the "cluster type" that appears to be
restricted to the chondrichthyes (cartilaginous fishes) and limits
segmental rearrangement to closely linked elements. This type of gene
organization is associated with both heavy- and light-chain gene loci. In
some cases, the clusters are "joined" or "partially joined" in the germ
line, in effect predetermining or partially predetermining, respectively,
the encoded specificities (the assumption being that these are expressed)
of the individual loci. By relating the sequences of transcribed gene
products to their respective germ-line genes, it is evident that, in some
cases, joined-type genes are expressed. This raises a question about the
existence and/or nature of allelic exclusion in these species. The
extensive variation in gene organization found throughout the vertebrate
species may relate directly to the role of intersegmental
(V<==>D<==>J) distances in the commitment of the individual
antibody-producing cell to a particular genetic specificity. Thus, the
evolution of this locus, perhaps more so than that of others, may reflect
the interrelationships between genetic organization and function.
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The chain of lymph-nodes in the rat mesentery was isolated and the preparation was perfused via cannulae in the superior mesenteric vessels. The perfusate consisted of serum to which labelled lymphocytes had usually been added. The entry of radioactively labelled lymphocytes from the blood vessels into the lymph-nodes was studied by scintillation counting and autoradiography. It was observed that: (1) In the perfused node labelled lymphocytes localized in and around post-capillary venules in the paracortex as they do early after i.v. injection. (2) The number of lymphocytes which entered the node was directly proportional to the concentration in the perfusate over the range studied. The proportion of cells retained in the node varied considerably around a mean of 11% of lymphocytes reaching it. (3) The isolated lymph-node released few if any lymphocytes into the effluent (venous) perfusate. (4) Large lymphocytes migrated into isolated lymph-nodes slightly more readliy than did small lymphocytes. (5) Unlike intact cells isolated lymphocyte membranes did not adhere to specialized vascular endothelium. 相似文献
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Lymphocytes were exposed in vitro to either trypsin or neuraminidase. The ability of the treated cells to migrate into tissues was measured (a) by i.v. injection into intact recipients and (b) by vascular perfusion through an isolated lymph-node preparation. The localization of trypsinized cells in the lymph-nodes of recipients was deficient when compared to untreated lymphocytes and there was a surplus of trypsinized cells in the blood. Trypsinized cells migrated into the isolated nodes in reduced numbers. By contrast, neuraminidase treated lymphocytes were markedly deficient in the blood of recipients early after injection; their localization in the spleen and lymph-nodes was also deficient but they were in surplus in the liver. Moreover they migrated into the isolated nodes in slightly increased numbers. By 24 hr after injection the perturbed localization pattern produced by either enzyme was partly restored to normal. In conclusion, trypsin interfered with the capacity of lymphocytes to migrate into lymph-nodes but neuraminidase did not; the latter promoted the hepatic sequestration of cells and the reduced localization in the blood and tissues was a consequence of this. The hypothesis that lymphocytes adhere to specialized endothelia in lymph-nodes because of specific glycoside sequences on their surface lacks experimental support. 相似文献
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Pharmawati M Yan G Sedgley R Finnegan PM 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2004,109(8):1694-1701
The inheritance of chloroplast DNA (cpDNA) in Leucadendron species was studied by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) analysis. A total of 100 progeny from five interspecific crosses involving seven parental species were tested, and all progeny exhibited the cpDNA restriction fragment pattern of the female parent, indicating that cpDNA in Leucadendron is maternally inherited. PCR-RFLP was also employed to study cpDNA variation among 21 Leucadendron species. Parsimony analysis using a heuristic search resulted in a phylogenetic tree that showed limited agreement to the taxonomic classification of Leucadendron species, based on morphological characteristics. The incongruence between cpDNA phylogenetic and taxonomic groupings in Leucadendron may be due to reticulate evolution involving a combination of hybridization and introgression, convergent evolution and/or lineage sorting at the interspecific, intersubsectional and intersectional levels. 相似文献
6.
Structural basis of the rind disorder oleocellosis in Washington navel orange (Citrus sinensis L. Osbeck) 总被引:2,自引:0,他引:2
Oleocellosis, a physiological rind disorder of citrus fruit, is an unattractive surface blemish caused by phytotoxic effects of released rind oils. The development of oleocellosis in Washington navel orange (Citrus sinensis L. Osbeck) was examined by following a time sequence of surface symptoms and microscopic rind changes. The two natural causes of oleocellosis were simulated: mechanical damage to the fruit and transfer of rind oil between fruit. Mechanical fruit injury resulted in rupture of the epidermis above oil glands. Released surface oil appeared to infiltrate the rind via the ruptured epidermis resulting in rapid degeneration of cortical, but not epidermal, cell contents. Oil application to the rind surface produced a more severe blemish than did mechanical damage. The oil appeared to diffuse through the cuticle causing degeneration of the contents of all cell layers, including the epidermis. Loss of membrane integrity was detected within 30 min, followed by cell content degeneration and cell collapse. The resulting blemish, characterized by rind collapse and darkening, developed substantially within 3 d and was attributed to the cellular damage. 相似文献
7.
The study was conducted to identify the self-incompatibility mechanism in Eucalyptus globulus ssp. globulus. Controlled self- and cross-pollinations were conducted on individual flowers from three mature trees that had self-incompatibility levels of 76, 99.6 and 100%. Flowers were harvested at 4, 6 and 8 weeks after pollination. Embryology was investigated by bright field microscopy on material harvested at 4 and 6 weeks after pollination. Fertilization had taken place at 4 weeks after pollination with zygotes and free nuclear endosperm visible. There was a greater proportion of healthy, fertilized ovules in the cross- compared with the self-pollination treatment, and approx. half the ovules examined from both pollen treatments were not fertilized or were degenerating. By 6 weeks after pollination a few zygotes were starting to divide. The number of healthy, fertilized ovules was still greater in the cross-pollination treatment, but the number of healthy fertilized ovules was lower in both treatments compared with 4 weeks after pollination, and many ovules were degenerating. Fertilized ovules were significantly larger than non-fertilized or degenerating ovules and this difference was detectable by eye at 6 and 8 weeks after pollination. The mechanism of self-incompatibility appears to have both late pre- and post-zygotic components. 相似文献
8.
Asenstorfer RE Morgan AL Hayasaka Y Sedgley M Jones GP 《Phytochemical analysis : PCA》2003,14(3):150-154
A new method has been developed for the isolation and rapid identification of anthocyanins from two floricultural crops based on the use of high-voltage paper electrophoresis with bisulphite buffer. Using this method, anthocyanin pigments were successfully purified as their negatively charged bisulphite-addition compounds from crude extracts of plant tissue. In conjunction with liquid chromatography-electrospray mass spectrometry, the method enabled the anthocyanins from the flowers of two Banksia species and the leaves of two Acacia species to be identified. The Banksia flowers contained both cyanidin and peonidin-based pigments, while the Acacia leaves contained cyanidin and delphinidin derivatives. 相似文献
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Ainsley Phillip J. Hammerschlag Freddi A. Bertozzi Terry Collins Graham G. Sedgley Margaret 《Plant Cell, Tissue and Organ Culture》2001,67(3):221-226
Adventitious shoots were regenerated from immature cotyledons of four almond cultivars (`Ne Plus Ultra', `Nonpareil', `Carmel' and `Parkinson'). Open-pollinated fruit were collected from orchard-grown trees 100–115 days after full bloom. The proximal ends of the cotyledons were excised and the embryonic axes discarded. The effects of different concentrations of thidiazuron (TDZ) and indole-3-butyric acid (IBA) and the presence or absence of light for the first 7 days of culture were determined. Shoot regeneration rates were highest for cotyledons cultured for 8 weeks on Murashige and Skoog (MS) basal medium containing TDZ (10.0 M), followed by 4 weeks on medium without plant growth regulators. Regeneration levels were further improved if cotyledons were maintained in darkness for the first 7 days. IBA (0.5 M) significantly reduced the development of adventitious shoots. The frequency of cotyledons that developed adventitious shoots under the optimum tested conditions for `Ne Plus Ultra', `Nonpareil', `Carmel', and `Parkinson' were 80.0%, 73.3%, 100.0% and 86.7%, respectively. 相似文献
10.
Amegilla spp. (Hymenoptera: Anthophoridae) have been suggested as potential native Australian alternative to overseas used bumblebees (Bombus spp.) for pollination of tomato in greenhouses. In this study, we investigate the effectiveness of Amegilla chlorocyanea Cockerell as a greenhouse pollinator of tomato, Lycopersicon esculentum Mill. We show that (1) a single buzz by a female increases tomato weight by 11% compared with pollination by using an industrial pollination wand, (2) multiple buzzes increase tomato weight compared with a single buzz, and (3) unlimited flower visits lead to an increase in fruit weight of 21% compared with wand pollination. These results are comparable with those achieved by bumblebee pollination and demonstrate that A. chlorocyanea is a valid alternative to bumblebees for greenhouse tomato pollination in Australia. 相似文献