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191.
Hypervariable Region of Human Immunoglobulin Heavy Chains 总被引:5,自引:0,他引:5
J. DONALD CAPRA 《Nature: New biology》1971,230(10):61-63
THE variable regions of human immunoglobulin light chains contain three areas of unusually high variability1–4. Similar hypervariable regions have been postulated for human heavy chains5, 6, but there are no amino-acid sequence data to support this idea. These hypervariable regions are particularly interesting because they may be the areas of the immunoglobulin molecule involved in antibody complementarity.We have made use of the recent observation that a variable region subclass of heavy chains is characterized by an unblocked amino-terminal residue7 and of the availability of automated sequencing techniques8, 9 to study this question in detail with additional heavy chain sequences. 相似文献
192.
A molecular phylogeny and revised higher‐level classification for the leaf‐mining moth family Gracillariidae and its implications for larval host‐use evolution 下载免费PDF全文
193.
Outbred 7-week old male Wistar rats were exposed for 21 days to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) via the drinking water and N7-methyl deoxyguanosine 3'-monophosphate (N7-MedGp) levels in DNA from the pyloric mucosa (target tissue) and white blood cells (wbc: non-target tissue) were determined by 32P-postlabelling. Exposure to MNNG resulted in the non-linear, dose-related formation of N7-medGp in both tissues. Adduct levels in the pyloric mucosa were determined to be 1058, 5.4 and 1.1 μmole N7-medGp mole-1 deoxyguanosine 3'-monophosphate (dGp) after exposure to 4.1, 0.62 and 0.006 mg MNNG kg-1 day-1 respectively whereas adduct levels in the wbc DNA were lower at 5.2, 0.52 and 0.68 μmoles N7-medGp mole-1 dGp after exposure to 4.1, 0.62 and 0.062 mg MNNG kg-1 day-1 respectively. In addition, the persistence of N7-medGp was investigated. Loss of adduct occurred rapidly, with a decrease of 87 and 97% respectively in target tissue and wbc DNA by 48 h after cessation of 4.1 mg MNNG kg-1 day-1 exposure; 14 days post-MNNG treatment, however, N7-medGp was still detectable (0.46 μmole N7-medGp mole-1 dGp) in pyloric mucosal DNA. The quantitation of N7-medGp after exposure to low doses of carcinogen, i.e. 0.006 mg MNNG kg-1 day-1, approaching environmentally relevant levels has not been previously reported, and indicates that the 32P-postlabelling assay developed here possesses sufficient sensitivity to quantitate N7- medGp in human DNA arising from environmental exposure to methylating agents. 相似文献
194.
Abstract A new subgenus and species, Glyptomorpha (Zanporiu) egyptiaca from Egypt, Arabia, Yemen and Pakistan are described and illustrated. G. Zanporia differs from G. Glyptomorpha in the form of the scapus and the lengh of the ovipositor. The status of Teraturus Kokujev is reconsidered and it is proposed that it should be treated as a subgenus of Glyptomorpha Holmgren, The relationship of Glyptomorpha to Rhadinobracon Szépligeti and Victoroviella Tobias is also discussed. 相似文献
195.
Rapid indexing of the sunblotch disease of avocados using a complementary DNA probe to avocado sunblotch viroid 总被引:1,自引:0,他引:1
PETER PALUKAITIS ‡ REW G. RAKOWSKI DONALD McE. ALEXANDER† ROBERT H. SYMONS 《The Annals of applied biology》1981,98(3):439-449
A routine procedure has been established for the sensitive and specific detection of avocado sunblotch viroid in partially purified nucleic acid extracts of avocado leaves by hybridisation analysis with 32P-complementary DNA prepared against the purified viroid. Avocado sunblotch viroid was shown to be present in 12 avocado trees that had indexed positive in a biological test for sunblotch disease but was absent from 10 trees that indexed negative. The complete correlation between sunblotch disease and the presence of viroid indicates that the complementary DNA hybridisation assay procedure can be used for the indexing of sunblotch disease. The overall procedure of leaf extraction and hybridisation analysis can be completed in 5 days and is to be compared with up to 2 yr required for indexing by biological methods. The level of avocado sunblotch viroid in partially purified nucleic acid extracts of a number of different sources of sunblotch infected avocado leaves was found to vary 10 000-fold from 0.2% to 2 × 10-5% by weight. The lower limit of detectability of the viroid by the hybridisation assay is considered to be about 10-5% by weight; this is at least 103 times more sensitive than the detection of the viroid by polyacrylamide gel electrophoresis of the leaf nucleic acid extracts followed by staining. 相似文献
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198.
DONALD D. STULL 《American anthropologist》2008,110(2):271-274
199.
SYNOPSIS. Macronuclei of Paramecium primaurelia were isolated and examined by scanning electron microscopy. These nuclei consisted of a closely packed array of chromatin bodies measuring ~ 0.2 μm in diameter. We estimated there were ~ 30,000 such bodies/macronucleus, 20 times more than the number of unit genome equivalents. This suggests that a unit genome is physically shared by several chromatin bodies. 相似文献
200.