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A palaeocommunity of large Conichnus conicus, a conical, cone-in-cone shaped burrow, created by sea anemones, occurs in medium-grained, crossbedded, well-sorted sandstone in the middle part of the Cretaceous Guneri Member of the Bhuj Formation in India. The trace fossil Conichnus is considered to be a common element of the Skolithos ichnofacies and is interpreted to reflect equilibrium movement in response to substrate aggradation. In the present study, three different varieties of Conichnus conicus are distinguished based on morphology and internal fabric. Community dynamics and burrowing behavior are revealed by inter-burrow relationships, burrow initiation levels and sedimentology. Three types of behavior are envisaged: retrusive equilibrium, protrusive equilibrium response, and escape behavior. Palaeocommunity dynamics show that the tracemakers consisted of only adult organisms that initiated burrows during neap tides and are adapted to feed effectively during weak flow conditions. The occurrence of Conichnus palaeocommunity in the Guneri Member indicates the tidal conditions in a fully marine setting. Results presented herein may aid in the understanding of palaeocommunity dynamics in other shallow marine sequences. 相似文献
3.
A Amar S F Radka S L Holbeck S J Kim B S Nepom K Nelson G T Nepom 《Journal of immunology (Baltimore, Md. : 1950)》1987,138(11):3986-3990
Bgl II restriction endonuclease digestion of genomic DNA from lymphoblastoid cell lines homozygous for HLA DR and DQ serological specificities, followed by hybridization with a DQ alpha cDNA probe, identified a genomic polymorphism characterized by two reciprocal patterns, one associated with DR 3, 5 and 8 and the other with DR 1, 2, 4, 7, and 9. The former pattern corresponded precisely to the reactivity of monoclonal antibody SFR20-DQ alpha 5, shown by Western blotting to react with isolated alpha-chains, but not with beta-chains. Additional variants of the DQ alpha genes were identified by using a locus-specific oligonucleotide probe for the DQ alpha gene, indicating differences among the DQ alpha 5-negative set of alleles. This analysis defines a set of DQ alpha allelic markers that are distinct from the well-established DQ serologic specificities DQw1, 2, 3 or "blank." Although most DQ alpha 5+ cells carry the DRw52 specificity associated with the DR beta 2 gene, analysis of DQ alpha polymorphisms on DR5, DQw1; DR8, DQw1; and DRw13, DQw1 cells verified that this DQ alpha family of alleles was not invariably linked to the DR beta 2 locus. 相似文献
4.
HLA-DP and HLA-DO genes in presumptive HLA-identical siblings: structural and functional identification of allelic variation 总被引:1,自引:0,他引:1
A Amar G T Nepom E Mickelson H Erlich J A Hansen 《Journal of immunology (Baltimore, Md. : 1950)》1987,138(6):1947-1953
We analyzed HLA class II genomic polymorphisms in three families in which bone marrow transplantation was performed between individuals presumed to be HLA identical, but in which unexplained mixed lymphocyte culture reactivity was observed. These families were characterized by classical HLA serology, MLC, and DP typing. In each family, a pair of "HLA-identical" siblings demonstrated a small proliferative response in bidirectional MLC. Southern blotting analysis performed with cDNA probes for DQ alpha, DP alpha, and DP beta identified DP genomic differences in each case. Hybridization of Bgl II-digested genomic DNA with a DP alpha cDNA probe revealed three prominent polymorphic fragments (7.7, 5.8, and 3.7 kb), which discriminated between presumptive identical siblings and indicated crossover events within HLA. Similarly, hybridization of SstI-digested genomic DNA with a DP beta cDNA probe, although resulting in a more complex pattern, identified DP genomic disparity between the presumed HLA identical siblings. Hybridization of SstI-digested DNA from two families with evidence of DP recombination was performed by using an oligonucleotide probe specific for the newly described HLA class II gene DO beta. Two major polymorphic fragments, at 6.2 and 3.3 kb, segregated in these families and localized the crossovers flanking the DO beta gene between the DQ and DP loci. The contribution of the antigenic differences marked by these HLA DP and DO DNA polymorphisms to allorecognition in MLR and in graft-vs-host disease are discussed. 相似文献
5.
The qualitative distribution and quantitative estimates of nitrogenase (EC 1.7.99.2), glutamine synthetase (EC 6.3.1.2), phycoerythrin and ribulose 1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) were studied in the cyanobacterium Nostoc residing in internal cephalodia of the tripartite lichen Nephroma arcticum L. Polyclonal antisera, raised in rabbit against the proteins, and goat anti-rabbit IgG conjugated to 10 nm gold were used as probes to detect the antigens by transmission electron microscopy. Western blot analyses demonstrated the monospecificity of the antisera. Nitrogenase was localized in heterocysts, with vegetative cells showing a label intensity comparable to the background. Distribution of the antigen within the heterocysts was uniform. Glutamine synthetase labelling was very low, but appeared to be distributed in both cell types. An intense phycoerythrin labelling was associated with the thylakoid region of the vegetative cells, whereas a much lower labelling was observed in the heterocyst. No significant differences were found between cyanobionts in younger and older cephalodia except for the nitrogenase labelling, which was higher in heterocysts of the cyanobiont in younger cephalodia. Most of the ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) label was present in vegetative cells. The Rubisco label was pronounced in the carboxysomes, whereas the label in the cytoplasm, on a unit area basis, was much lower. Heterocysts showed a label intensity similar to that of the vegetative cell cytoplasm. In Nostoc of the bipartite lichen Peltigera canina L., the Rubisco protein showed a comparable distribution pattern, but the average number of carboxysomes per vegetative cell was about 4 times higher. 相似文献
6.
The isolation,characterization and application in the Triticeae of a set of wheat RFLP probes identifying each homoeologous chromosome arm 总被引:8,自引:0,他引:8
P. J. Sharp S. Chao S. Desai M. D. Gale 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1989,78(3):342-348
Summary To investigate the use of RFLP analysis in the Triticeae, a set of low copy number probes has been isolated from a wheat cDNA library. The probes identify each of the 14 homoeologous chromosome arms of wheat as determined by analysis of DNA fragments hybridizing to the probes in aneuploid lines of Chinese Spring. These probes can be used in RFLP analyses both for the assignment of homoeology of alien chromosomes or arms added to wheat, and for the determination of chromosome dosage in wheat aneuploids. Different chromosomes from various Triticeae species can therefore be followed in a wheat genetic background using a single technique. The potential uses of the set in facilitating the transfer of alien segments into wheat are outlined. 相似文献
7.
PACAP, a VIP-like peptide, in neurons of the esophagus. 总被引:1,自引:0,他引:1
R Uddman A Luts A Absood A Arimura M Ekelund H Desai R H?kanson G Hambreaus F Sundler 《Regulatory peptides》1991,36(3):415-422
The lower esophagus of guinea-pig, cat, sheep and man was analyzed for pituitary adenylate cyclase activating peptide (PACAP), a novel vasoactive intestinal peptide (VIP)-like peptide, using immunocytochemistry and radioimmunoassay. PACAP-immunoreactive nerve fibers were numerous in the longitudinal and circular muscle layers of sheep and man, moderate in numbers in cat, while being few in the esophagus of guinea-pig. A few PACAP-immunoreactive nerve cell bodies and numerous nerve fibers were seen in the myenteric ganglia of the esophagus of cat, sheep and man. In the lower esophagus of cat, sheep and man all PACAP-containing nerve cell bodies and nerve fibers stored VIP. The results of radioimmunoassay of PACAP in extracts of specimens from man were in good agreement with the immunocytochemical findings. High performance liquid chromatography revealed one major peak of PACAP-like immunoreactivity in extracts of human esophagus. We suggest that neuronal PACAP may serve to modulate motor activity and secretion in the lower esophageal sphincter region. 相似文献
8.
9.
Possible Involvement of Phage-Like Structures in Antagonism of Cowpea Rhizobia by Rhizobium trifolii
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A reduction in the viability of cowpea rhizobia was observed when Rhizobium trifolii IARI and cowpea Rhizobium strain 3824 were inoculated together in soil. The reduction in number of cowpea rhizobia in soil was found to be associated with the reduction in number of nodules per plant and retardation in plant growth. An antimicrobial substance was isolated from R. trifolii which, on electron microscopic investigation, demonstrated the presence of several phage-like structures. 相似文献
10.
Nitrate metabolism in the cyanobacterium Anabaena cycadeae: Regulation of nitrate uptake and reductase by ammonia 总被引:2,自引:0,他引:2
Suvendra N. Bagchi Upendra N. Rai Amar N. Rai Hriday N. Singh 《Physiologia plantarum》1985,63(3):322-326
Nitrogen regulation of nitrate uptake and nitrate reductase (EC 1.7.99.4) was studied in the cyanobacterium Anabaena cycadeae Reinke and its glutamine auxotroph. Development of the nitrate uptake system preceded, and was independent of, the development of the nitrate reductase system. The levels of both systems were several-fold higher in the glutamine auxotroph lacking glutamine synthetase (EC 6.3.1.2) than in the wild type strain having normal glutamine synthetase activity. The nitrate uptake system was found to be NH4-repressible and the nitrate reductase system NO3 − -inducible. NH4 + was the initial repressor signal for the uptake process which was involved in the control of the NO3 − inducible reductase system. 相似文献