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The alpha-like globin gene cluster in rabbits contains embryonic zeta-
globin genes, an adult alpha-globin gene, and theta-globin genes of
undetermined function. The basic arrangement of genes, deduced from
analysis of cloned DNA fragments, is 5'-zeta 0-zeta 1-alpha 1-theta 1- zeta
2-zeta 3-theta 2-3'. However, the pattern of restriction fragments
containing zeta- and theta-globin genes varies among individual rabbits.
Analysis of BamHI fragments of genomic DNA from 24 New Zealand white
rabbits revealed eight different patterns of fragments containing
zeta-globin genes. The large BamHI fragments containing genes zeta 0 and
zeta 1 are polymorphic in length, whereas a 1.9-kb fragment containing the
zeta 2 gene and the 3.5-kb fragment containing the zeta 3 gene do not vary
in size. In contrast to this constancy in the size of the restriction
fragments, the copy number of the zeta 2 and zeta 3 genes does vary among
different rabbits. No length polymorphism was detected in the BamHI
fragments containing the theta-globin genes, but again the copy number
varies for restriction fragments containing the theta 2 gene. The alpha 1-
and theta 1-globin genes are located in a nonpolymorphic 7.2-kb BamHI
fragment. The combined data from hybridization with both zeta and theta
probes shows that the BamHI cleavage pattern does not vary within the
region 5'-alpha 1-theta 1- zeta 2-zeta 3-theta 2-3', but the pattern
genomic blot-hybridization patterns for the progeny of parental rabbits
with different zeta-globin gene patterns shows that the polymorphic
patterns are inherited in a Mendelian fashion. Two different haplotypes
have been mapped based on the genomic blot-hybridization data. The
variation in the alpha-like globin gene cluster in the rabbit population
results both from differences in the copy number of the duplication block
containing the zeta-zeta-theta gene set and from the presence or absence of
polymorphic BamHI sites.
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Assignment of orthologous relationships among mammalian alpha-globin genes by examining flanking regions reveals a rapid rate of evolution 总被引:1,自引:0,他引:1
In order to study the relationships among mammalian alpha-globin genes, we
have determined the sequence of the 3' flanking region of the human alpha 1
globin gene and have made pairwise comparisons between sequenced
alpha-globin genes. The flanking regions were examined in detail because
sequence matches in these regions could be interpreted with the least
complication from the gene duplications and conversions that have occurred
frequently in mammalian alpha-like globin gene clusters. We found good
matches between the flanking regions of human alpha 1 and rabbit alpha 1,
human psi alpha 1 and goat I alpha, human alpha 2 and goat II alpha, and
horse alpha 1 and goat II alpha. These matches were used to align the
alpha-globin genes in gene clusters from different mammals. This alignment
shows that genes at equivalent positions in the gene clusters of different
mammals can be functional or nonfunctional, depending on whether they
corrected against a functional alpha-globin gene in recent evolutionary
history. The number of alpha-globin genes (including pseudogenes) appears
to differ among species, although highly divergent pseudogenes may not have
been detected in all species examined. Although matching sequences could be
found in interspecies comparisons of the flanking regions of alpha- globin
genes, these matches are not as extensive as those found in the flanking
regions of mammalian beta-like globin genes. This observation suggests that
the noncoding sequences in the mammalian alpha-globin gene clusters are
evolving at a faster rate than those in the beta-like globin gene clusters.
The proposed faster rate of evolution fits with the poor conservation of
the genetic linkage map around alpha-globin gene clusters when compared to
that of the beta-like globin gene clusters. Analysis of the 3' flanking
regions of alpha-globin genes has revealed a conserved sequence
approximately 100-150 bp 3' to the polyadenylation site; this sequence may
be involved in the expression or regulation of alpha-globin genes.
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4.
Starved Tetrahymena thermophila cells that are unable to mount an effective heat shock response selectively degrade their rRNA. 总被引:11,自引:8,他引:3 下载免费PDF全文
Tetrahymena thermophila cells that had been shifted from log growth to a non-nutrient medium (60 mM Tris) were unable, during the first few hours of starvation, to mount a successful heat shock response and were killed by what should normally have been a nonlethal heat shock. An examination of the protein synthetic response of these short-starved cells during heat shock revealed that whereas they were able to initiate the synthesis of heat shock proteins, it was at a much reduced rate relative to controls and they quickly lost all capacity to synthesize any proteins. Certain pretreatments of cells, including a prior heat shock, abolished the heat shock inviability of these starved cells. Also, if cells were transferred to 10 mM Tris rather than 60 mM Tris, they were not killed by the same heat treatment. We found no abnormalities in either heat shock or non-heat shock mRNA metabolism in starved cells unable to survive a sublethal heat shock when compared with the response of those cells which can survive such a treatment. However, selective rRNA degradation occurred in the nonsurviving cells during the heat shock and this presumably accounted for their inviability. A prior heat shock administered to growing cells not only immunized them against the lethality of a heat shock while starved, but also prevented rRNA degradation from occurring. 相似文献
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Out of Africa and back again: nested cladistic analysis of human Y chromosome variation 总被引:18,自引:3,他引:15
Hammer MF; Karafet T; Rasanayagam A; Wood ET; Altheide TK; Jenkins T; Griffiths RC; Templeton AR; Zegura SL 《Molecular biology and evolution》1998,15(4):427-441
We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544
individuals from Africa, Asia, Europe, Oceania, and the New World.
Phylogenetic analyses of these nine sites resulted in a tree for 10
distinct Y haplotypes with a coalescence time of approximately 150,000
years. The 10 haplotypes were unevenly distributed among human populations:
5 were restricted to a particular continent, 2 were shared between Africa
and Europe, 1 was present only in the Old World, and 2 were found in all
geographic regions surveyed. The ancestral haplotype was limited to African
populations. Random permutation procedures revealed statistically
significant patterns of geographical structuring of this paternal genetic
variation. The results of a nested cladistic analysis indicated that these
geographical associations arose through a combination of processes,
including restricted, recurrent gene flow (isolation by distance) and range
expansions. We inferred that one of the oldest events in the nested
cladistic analysis was a range expansion out of Africa which resulted in
the complete replacement of Y chromosomes throughout the Old World, a
finding consistent with many versions of the Out of Africa Replacement
Model. A second and more recent range expansion brought Asian Y chromosomes
back to Africa without replacing the indigenous African male gene pool.
Thus, the previously observed high levels of Y chromosomal genetic
diversity in Africa may be due in part to bidirectional population
movements. Finally, a comparison of our results with those from nested
cladistic analyses of human mtDNA and beta-globin data revealed different
patterns of inferences for males and females concerning the relative roles
of population history (range expansions) and population structure
(recurrent gene flow), thereby adding a new sex-specific component to
models of human evolution.
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7.
Vaccination of channel catfish with either of two serotypes of the parasitic ciliate Ichthyophthirius multifiliis conferred protection against challenge infection by either serotype. Fish were vaccinated by intracoelomic injection with live theronts of isolate G5 (serotype D) or isolate G12 (a new serotype), which express different surface immobilisation antigens. Vaccination with live G12 theronts conferred complete protection against subsequent challenge by both serotypes while vaccination with G5 theronts elicited only partial protection against both serotypes. Vaccination with trophont lysates did not protect against challenge infection. Sera from vaccinated fish were tested in immobilisation assays, ELISAs, and Western blots. Serum antibodies recognised only immobilisation antigens of the serotype used for vaccination in immobilisation assays or on Western blots. No antigens common to both serotypes were identified by Western blots. In contrast, serum antibodies bound antigens in cell lysates from both serotypes by ELISA, demonstrating that antibodies recognising both serotypes are produced in response to infection, which presumably confer observed cross-serotype protection. 相似文献
8.
In vitro response of Ichthyophthirius multifiliis to sera from immune channel catfish 总被引:1,自引:0,他引:1
T. G. Clark H. W. Dickerson † J. B. Gratzek † R. C. Findly 《Journal of fish biology》1987,31(SA):203-208
Sera from channel catfish rendered immune to the protozoan pathogen Ichthyophthirius multifiliis were screened for activity against live parasites. Cells in the infective stage (tomites) were incubated in doubling dilutions of immune and pre-immune sera from fish that had been immunized by exposure to sublethal infections. When examined by light microscopy, tomites were found to agglutinate in the presence of immune sera. While the stength of individual sera varied, agglutination of cells occurred at dilutions as high as 1:128. Cells showed little tendency to agglutinate in pre-immune sera, and virtually no effects were seen with dilutions of pre-immune sera greater than 1:16. Agglutination was usually accompanied by release of mucus from cells, and while tomites appeared to be immobilized, their cilia continued to beat. Low dilutions of immune sera appeared to be toxic. Similar effects on tomites were seen with rabbit antisera prepared against Ichthyophthirius cilia. The involvement of humoral antibodies in agglutination and protective immunity is discussed. 相似文献
9.
L da Silva Lopes RB Marques HB Fernandes S da Silva Pereira MC Ayres MH Chaves FR Almeida 《Journal of biomedical science》2012,19(1):68-6
ABSTRACT: BACKGROUND: The mechanisms of the antinociceptive activity of () epicatechin (EPI), a compound isolated from the hydroalcoholic fraction of Combreum leprosum Mart & Eicher. METHODS: were assessed in the model of chemical nociception induced by glutamate (20 mumol/paw). To evaluate the mechanisms involved, the animals , male Swiss mice (25-30 g), received EPI (50 mg/kg p.o.) after pretreatment with naloxone (2 mg/kg s.c. opioid antagonist), glibenclamide (2 mg/kg s.c. antagonist K + channels sensitive to ATP), ketanserin (0.3 mg/kg s.c. antagonist of receptor 5-HT2A), yoimbine (0.15 mg/kg s.c. alpha2 adrenergic receptor antagonist), pindolol (1 mg/kg s.c. 5-HT1a/1b receptor antagonist), atropine (0.1 mg/kg s.c. muscarinic antagonist) and caffeine (3 mg/kg s.c. adenosine receptor antagonist), ondansetron (0.5 mg/kg s.c. for 5-HT3 receptor) and L-arginine (600 mg/kg i.p.). RESULTS: The antinociceptive effect of EPI was reversed by pretreatment with naloxone and glibenclamide, ketanserin, yoimbine, atropine and pindolol, which demonstrates the involvement of opioid receptors and potassium channels sensitive to ATP, the serotoninergic (receptor 5HT1A and 5HT2A), adrenergic (receptor alpha 2) and cholinergic (muscarinic receptor) systems in the activities that were observed. The effects of EPI, however, were not reversed by pretreatment with caffeine, L-arginine or ondansetron, which shows that there is no involvement of 5HT3 receptors or the purinergic and nitrergic systems in the antinociceptive effect of EPI. In the Open Field and Rotarod test, EPI had no significant effect, which shows that there was no central nervous system depressant or muscle relaxant effect on the results. CONCLUSIONS: This study demonstrates that the antinociceptive activity of EPI in the glutamate model involves the participation of the opioid system, serotonin, adrenergic and cholinergic. 相似文献
10.
H. Y. Sun J. Noe J. Barber R. S. Coyne D. Cassidy-Hanley T. G. Clark R. C. Findly H. W. Dickerson 《Applied and environmental microbiology》2009,75(23):7445-7452
Endosymbiotic bacteria were identified in the parasitic ciliate Ichthyophthirius multifiliis, a common pathogen of freshwater fish. PCR amplification of DNA prepared from two isolates of I. multifiliis, using primers that bind conserved sequences in bacterial 16S rRNA genes, generated an ∼1,460-bp DNA product, which was cloned and sequenced. Sequence analysis demonstrated that 16S rRNA gene sequences from three classes of bacteria were present in the PCR product. These included Alphaproteobacteria (Rickettsiales), Sphingobacteria, and Flavobacterium columnare. DAPI (4′,6-diamidino-2-phenylindole) staining showed endosymbionts dispersed throughout the cytoplasm of trophonts and, in most, but not all theronts. Endosymbionts were observed by transmission electron microscopy in the cytoplasm, surrounded by a prominent, electron-translucent halo characteristic of Rickettsia. Fluorescence in situ hybridization demonstrated that bacteria from the Rickettsiales and Sphingobacteriales classes are endosymbionts of I. multifiliis, found in the cytoplasm, but not in the macronucleus or micronucleus. In contrast, F. columnare was not detected by fluorescence in situ hybridization. It likely adheres to I. multifiliis through association with cilia. The role that endosymbiotic bacteria play in the life history of I. multifiliis is not known.The ciliate Ichthyophthirius multifiliis is an obligate parasite of freshwater fish that infects epithelia of the skin and gills. The life cycle of I. multifiliis consists of three stages: an infective theront, a parasitic trophont, and a reproductive tomont. Infection is initiated by invasion of the skin and gills by free-swimming, 40-μm-long, pyriform-shaped theronts that burrow several cell layers deep into epithelial tissue of the skin and gills and rapidly differentiate into trophonts. Trophonts feed on epithelial cells and grow into 500- to 800-μm-diameter cells, causing extensive damage to skin and gills, which in severe infections results in mortality (10-12). After feeding for 5 to 7 days, trophonts leave the host, form encysted tomonts, and undergo up to 10 cell divisions over 18 to 24 h, producing as many as 103 daughter cells, which exit the cyst as infective theronts to reinitiate the life cycle. I. multifiliis is ciliated at all stages (9).DNA sequencing of the I. multifiliis genome at the J. Craig Venter Institute unexpectedly revealed that bacterial DNA sequences, including sequences with homology to Rickettsia, were present in the DNA preparations (R. S. Coyne, 2009 [http://www.jcvi.org/cms/research/projects/ich/overview]). The origin of these sequences was unclear, but they represented evidence for either horizontal gene transfer into the I. multifiliis genome (17, 27) or the presence of intracellular bacteria. No previous evidence suggested the presence of intracellular bacteria in I. multifiliis, even though the fine structure of I. multifiliis theronts and trophonts has been examined by transmission electron microscopy (10-12). Intracellular or endosymbiotic bacteria, however, are commonly found in protists, and about 200 ciliate species are known to harbor intracellular bacteria (13, 15). Sonneborn and Preer in their classic studies on endosymbionts in Paramecium characterized a number of different endosymbionts, including “killers,” named for their ability to kill uninfected strains of Paramecium. Cytoplasmic endosymbionts in Paramecium now include Caedibacter taeniospiralis (Gammaproteobacteria), and Pseudocaedibacter conjugates, Tectibacter vulgaris, and Lyticum flagellatum (Alphaproteobacteria). Macronuclear endosymbionts include the Alphaproteobacteria, Holospora caryophila, and Caedibacter caryophila, which can also infect the cytoplasm (4, 16, 22, 26). The roles these endosymbionts play in protists are not well understood.The presence of sequences with homology to bacterial genomes prompted us to determine if I. multifiliis contained endosymbionts, or if these sequences represented evidence for horizontal gene transfer into the I. multifiliis genome. Our identification of the same two endosymbionts, in two different isolates of I. multifiliis, suggests that endosymbionts are common in I. multifiliis. However, the physiological relationships between I. multifiliis and its resident endosymbionts are unclear. It is not known if the endosymbionts contribute to the growth of I. multifiliis, if they contribute to the severity or pathogenicity of infection, or if they provide their host with any selective advantage, as occurs with Paramecium containing killer particles (4). It has not been determined if they influence the immune response of fish infected with I. multifiliis. It is possible that they may simply be parasites of this parasitic ciliate. 相似文献