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排序方式: 共有177条查询结果,搜索用时 31 毫秒
1.
A composite transposon 3'' to the cow fetal globin gene binds a sequence specific factor. 总被引:2,自引:2,他引:0
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Two unusual sequence organizations were found within the beta-globin locus of the cow. Each was a composite, consisting of closely linked Alu-type repeats with a short stretch of genomic non-repetitive sequence, called a lagan, sandwiched between. One lagan was found 3' to the fetal globin gene, while the second lay between the adult globin gene and a globin pseudogene. Southern blot analysis indicated that both lagans appeared twice within the cow haploid genome, with the second copies lying outside the cow beta-globin locus. One of these non-globin locus homologues was cloned and subjected to sequence analysis. Comparison of the DNA sequence data showed that the lagan-Alu composite was transposed as a unit. The lagan 3' to the cow fetal globin gene contains the recognition site for a sequence specific DNA binding factor. This factor was present in extracts from fetal, but not from adult cow tissues. 相似文献
2.
L.A. Lugo-Roman P.J. Rico R. Sturdivant R. Burks & T.L. Settle 《Journal of medical primatology》2010,39(1):41-49
Background This study aimed at determining the cumulative effect of daily anesthesia, using two drug regimens, over hematological and biochemical parameters.
Methods Blood samples were obtained from rhesus monkeys 20 minutes after intramuscular administration of ketamine or ketamine/medetomidine combination for three consecutive days and results were evaluated to determine their effect on hematological and serum biochemistry values. Statistical significance of drug, day, and interaction of these two variables were evaluated.
Results Drug effect resulted in a dramatic increase of aspartate aminotransferase and creatine kinase values. Day effect resulted in decreases of RBC, HCT, Hgb, and alkaline phosphatase but an increase of other biochemical parameters evaluated. The drug/day interaction effect was found to be –significant for RBC, platelets, aspartate aminotransferase, alanine aminotransferase, and creatine kinase values.
Conclusion The results of our study suggest a cumulative effect of serial anesthesia and should be an important consideration when interpreting hematology and serum biochemistry in rhesus macaques. 相似文献
Methods Blood samples were obtained from rhesus monkeys 20 minutes after intramuscular administration of ketamine or ketamine/medetomidine combination for three consecutive days and results were evaluated to determine their effect on hematological and serum biochemistry values. Statistical significance of drug, day, and interaction of these two variables were evaluated.
Results Drug effect resulted in a dramatic increase of aspartate aminotransferase and creatine kinase values. Day effect resulted in decreases of RBC, HCT, Hgb, and alkaline phosphatase but an increase of other biochemical parameters evaluated. The drug/day interaction effect was found to be –significant for RBC, platelets, aspartate aminotransferase, alanine aminotransferase, and creatine kinase values.
Conclusion The results of our study suggest a cumulative effect of serial anesthesia and should be an important consideration when interpreting hematology and serum biochemistry in rhesus macaques. 相似文献
3.
Although three neurokinin receptors (NK-1, NK-2, NK-3) have been identified by radioligand binding assays, only the NK-1 and NK-3 types have been found in smooth muscle bioassays. In this study, evidence is presented demonstrating functional NK-2 type receptors in the guinea pig gallbladder (GPGB). The potencies of the following neurokinins were determined in the GPGB and the guinea pig ileum (GPI): substance P (SP), physalaemin (PH), eledoisin (EL), substance K (SK) and kassinin (KA). ED50 values were determined by linear regression analysis of the dose-related increases in the force generated by each peptide. In the GPI, the rank order of potency was SP = PH = EL greater than SK = KA, indicating NK-1 selectivity. In the GPGB, the relative potencies were SK greater than KA greater than EL much greater than PH greater than SP, which is similar to that reported for the NK-2 receptor in radioligand binding assays. These findings demonstrate the NK-2 receptor tissue selectivity of the GPGB. 相似文献
4.
Mechanisms of depletion of substance P by capsaicin 总被引:2,自引:0,他引:2
Capsaicin is a neurotoxin that can deplete sensory nerves of their content of substance P and interfere with certain sensory functions, such as responses of animals to noxious heat stimuli. In adult guinea pigs, a species that is susceptible to the effects of capsaicin on both substance P content and sensory function, capsaicin induces selective depletion of substance P from dorsal root ganglia and the dorsal spinal cord, sites of the cell bodies and central terminals of primary afferent neurons, respectively. As the onset of thermal analgesia in guinea pigs precedes depletion of substance P, direct neural actions of capsaicin probably account for its effects on sensory function. Capsaicin interferes with the retrograde transport of nerve growth factor (NGF) to the cell bodies of sensory nerves. Decreased availability of NGF at the site of neural protein synthesis leads to decreased synthesis of substance P. After failure of synthesis of substance P, the content of the peptide in sensory nerves gradually decreases until depletion occurs. 相似文献
5.
R K Moyzis D C Torney J Meyne J M Buckingham J R Wu C Burks K M Sirotkin W B Goad 《Genomics》1989,4(3):273-289
The distribution of interspersed repetitive DNA sequences in the human genome has been investigated, using a combination of biochemical, cytological, computational, and recombinant DNA approaches. "Low-resolution" biochemical experiments indicate that the general distribution of repetitive sequences in human DNA can be adequately described by models that assume a random spacing, with an average distance of 3 kb. A detailed "high-resolution" map of the repetitive sequence organization along 400 kb of cloned human DNA, including 150 kb of DNA fragments isolated for this study, is consistent with this general distribution pattern. However, a higher frequency of spacing distances greater than 9.5 kb was observed in this genomic DNA sample. While the overall repetitive sequence distribution is best described by models that assume a random distribution, an analysis of the distribution of Alu repetitive sequences appearing in the GenBank sequence database indicates that there are local domains with varying Alu placement densities. In situ hybridization to human metaphase chromosomes indicates that local density domains for Alu placement can be observed cytologically. Centric heterochromatin regions, in particular, are at least 50-fold underrepresented in Alu sequences. The observed distribution for repetitive sequences in human DNA is the expected result for sequences that transpose throughout the genome, with local regions of "preference" or "exclusion" for integration. 相似文献
6.
The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
相似文献
7.
Nancy C. Tuchman Romi L. Burks Christopher A. Call John Smarrelli 《Freshwater Biology》2004,49(2):191-198
1. Zebra mussels aggregate to form dense colonies where, depending on the flow rate, individuals in different vertical locations within the colony may experience restricted food availability. 2. Using 32P‐labelled Chlamydomonas angulosa, we found ingestion rates of individual mussels located at the surface to exceed those in the bottom of a 6 cm thick colony by up to 75%. 3. Higher velocities (10 and 20 cm s?1) increased algal delivery to the colony's middle layer (2–4 cm depth), subsequently increasing ingestion rates to equal those in the surface layer, while increasing ingestion only for the smallest mussels in the bottom (4–6 cm). 4. At all vertical locations within the colonies, smaller mussels showed higher ingestion rates per unit mass than larger mussels, particularly at higher flow rates. 相似文献
8.
Enrichment and visualization of small replication units from cultured mammalian cells 总被引:1,自引:0,他引:1
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DNA from cultured Chinese hamster cells has been fractionated to yield a population of DNA enriched for replicating molecules. Molecules containing replication structures were analyzed by electron microscopy, and replicon size was estimated. The enrichment procedure takes advantage of single-stranded regions characteristic of replicating molecules, and the greater affinity of mercuric ion for single-stranded rather than native DNA. After interaction with low concentrations of HgCl2, DNA with bound mercury is separated from the bulk of the DNA by virtue of its increased buoyant density in an isopycnic Cs2SO4 gradient. When DNA from cells labeled with [3H]thymidine for 45 s is interacted with HgCl2 and banded in Cs2SO4, the DNA with the highest specific activity is found in a dense region of the gradient. The high specific activity DNA behaves kinetically like nascent DNA since the radioactivity can be chased into main band if the cells are incubated for a further 2 h in excess unlabeled thymidine. Electron microscope analysis of the DNA in the enriched fraction confirmed that it contains a substantial fraction of molecules with replication structures. The level of enrichment is about 25-fold compared to unfractionated DNA or DNA taken from the main band of the Hg++/Cs2SO4 gradient. Of the replicating molecules visualized, 85% possessed a single replication structure. All molecules with multiple replication forms contained replicon sizes less than 5 micron, ranging from 0.2 to 4.5 micron. Replicon size was determined by measuring the distance from the center of one replication structure to the center of the adjacent replication structure on the same molecule. The replicons observed in this study are far smaller than can be detected by DNA fiber autoradiography and are in the same size range as the very small replication units reported in embryonic systems. 相似文献
9.
Burks Oakley II Sheldon S. Miller Roy H. Steinberg 《The Journal of membrane biology》1978,44(3-4):281-307
Summary We have studied the hyperpolarizing, electrogenic pump located on the apical membrane of the retinal pigment epithelium (RPE) in anin vitro preparation of bullfrog RPE-choroid. Changes in RPE [K+]
i
alter the current produced by this pump. Increasing [K+]
o
in the solution perfusing thebasal membrane increases RPE [K+]
i
(measured with a K+-specific microelectrode), and also depolarizes theapical membrane. This depolarization is due to a decrease in electrogenic pump current flowing across the apical membrane resistance, since it is abolished when the pump is inhibited by apical ouabain, by cooling the tissue, or by 0mm [K+]
o
outside the apical membrane. Removal of Cl– from the solution perfusing the basal membrane abolishes the K+-evoked apical depolarization by preventing the entry of K+ (as KCl) into the cell. We conclude that the increase in [K+]
i
causes the decrease in pump current. This result is consistent with the finding that [K+]
i
is a competitive inhibitor of the Na+–K+ pump in red blood cells.It is possible that the light-evoked changes in [K+]
o
in the distal retina could alter RPE [K+]
i
, and thus could affect the pump from both sides of the apical membrane. Any change in pump current is likely to influence retinal function, since this pump helps to determine the composition of the photoreceptor extracellular space. 相似文献
10.
Motility effects of opioid peptides in dog intestine 总被引:1,自引:0,他引:1
Six opioid peptides, like morphine, were found to produce dose-dependent contractions of dog isolated intestine when administered as intraarterial boluses. The increases in incidence and amplitude of intestinal contractions were antagonized by naloxone. The rank order of potency of the opioid agonists tested was D-Ala2-met-enkephalinamide greater than D-Ala2-leu-enkephalinamide greater than met-enkephalin greater than beta-endorphin 1-31 greater than morphine greater than morphiceptin greater than dynorphin 1-13. The contractions induced by two opioid agonists displayed differential sensitivity to blockade by tetrodotoxin (TTX). Met-enkephalin was barely affected by concentrations of TTX that markedly reduced responses to morphiceptin. Some portion of the motility effect of metenkephalin may be exerted directly on intestinal smooth muscle. 相似文献