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31.
Presence or absence of N-acetylneuraminic acid (Neu5Ac) can change a
sialylated glycoprotein's serum half-life and possibly its function. We
evaluated the linearity, sensitivity, reproducibility, and accuracy of a
HPAEC/PAD method to determine its suitability for routine simultaneous
analysis of Neu5Ac and N-glycolylneuraminic acid (Neu5Gc). An effective
internal standard for this analysis is 3-deoxy-d-glycero-d-
galacto-2-nonulosonic acid (KDN). We investigated the effect of the Au
working electrode recession and determined that linear range and
sensitivity were dependent on electrode recession. Using an electrode that
was 350 &mgr;m recessed from the electrode block, the minimum detection
limits of Neu5Ac, KDN, and Neu5Gc were 2, 5, and 2 pmol, respectively, and
were reduced to 1, 2, and 0.5 pmol using a new electrode. The response of
standards was linear from 10 to 500 pmol (r2>0.99) regardless of
electrode recession. When Neu5Ac, KDN, and Neu5Gc (200 pmol each) were
analyzed repetitively for 48 h, area RSDs were <3%. Reproducibility was
unaffected when injections of glycoprotein neuraminidase and acid
digestions were interspersed with standard injections. Area RSDs of Neu5Ac
and Neu5Gc improved when the internal standard was used. We determined the
precision and accuracy of this method for both a recessed and a new working
electrode by analyzing Neu5Ac and Neu5Gc contents of bovine fetuin and
bovine and human transferrins. Results were consistent with published
values and independent of the working electrode. The sensitivity,
reproducibility, and accuracy of this method make it suitable for direct
routine analysis of glycoprotein Neu5Ac and Neu5Gc contents.
相似文献
32.
Microbiological Hazards of Household Toilets: Droplet Production and the Fate of Residual Organisms 总被引:4,自引:3,他引:4 下载免费PDF全文
Large numbers of bacteria and viruses when seeded into household toilets were shown to remain in the bowl after flushing, and even continual flushing could not remove a persistent fraction. This was found to be due to the adsorption of the organisms to the porcelain surfaces of the bowl, with gradual elution occurring after each flush. Droplets produced by flushing toilets were found to harbor both bacteria and viruses which had been seeded. The detection of bacteria and viruses falling out onto surfaces in bathrooms after flushing indicated that they remain airborne long enough to settle on surface throughout the bathroom. Thus, there is a possibility that a person may acquire an infection from an aerosol produced by a toilet. 相似文献
33.
Asian elephants (Elephas maximus) are an endangered species. Their future survival depends on intensive conservation and management, based on in‐depth knowledge of particular populations. Molecular genetic methods, especially microsatellite analysis through noninvasive sampling, provides an effective means of obtaining such information. The use of tri‐ and tetranucleotide microsatellite markers is advantageous in noninvasive sampling through dung analysis. Here we describe the isolation and characterization of five tri‐ and tetranucleotide markers in the Asian elephant. All five loci were found to be polymorphic in a sample of 20 Asian elephants from Sri Lanka. 相似文献
34.
Tina Jaskoll Haiming Chen Yan Min Zhou Dingwen Wu Michael Melnick 《BMC developmental biology》2001,1(1):5-6
Background
The regulation of programmed cell death is critical to developmental homeostasis and normal morphogenesis of embryonic tissues. Survivin, a member of the inhibitors of apoptosis protein (IAP) family primarily expressed in embryonic cells, is both an anti-apoptosis and a pro-survival factor. Since our previous studies have demonstrated the importance of apoptosis during embryonic submandibular salivary gland (SMG) development, we postulated that survivin is a likely mediator of SMG epithelial cell survival. 相似文献35.
36.
Photodynamic treatment of herpes simplex virus type 1-infected hamster embryo fibroblasts (LSH strain) with a low concentration of proflavine (0.08 mug/10(5) cells per ml), a 3-9-diamine acridine dye, inhibited production not only of infectious progeny but also of virion particles. However, there was no appreciable inhibition of viral or cellular DNA synthesis, even when the infected cells were repeatedly exposed to this low concentration of dye and light during the replication cycle of the virus. It thus appears that photodynamic treatment of infected cells interferes with the processes involved in virus maturation. 相似文献
37.
38.
Jennifer Pastorini Michael R.J. Forstner Robert D. Martin Don J. Melnick 《Journal of molecular evolution》1998,47(1):32-41
The New World monkeys are divided into two main groups, Callitrichidae and Cebidae. Callimico goeldii shares traits with both the Cebidae and the Callitrichidae. Recent morphological phyletic studies generally place Callimico as the most basal member of the Callitrichidae. In contrast, genetic studies (immunological, restriction fragment, and sequence
data) have consistently placed Callimico somewhere within the Callitrichidae, not basal to this clade. A DNA sequence data set from the terminal 236 codons of the
mitochondrial ND4 gene and the tRNAHis, tRNASer, and tRNALeu genes was generated to clarify the position of Callimico. The sequences of 887 base pairs were analyzed by maximum-parsimony, neighbor-joining, and maximum-likelihood methods. The
results of these various methods are generally congruent and place Callimico within the Callitrichidae between the marmosets (Callithrix and Cebuella) and the tamarins (Saguinus and Leontopithecus). Combined analyses of all suitable nuclear and mitochondrial gene sequences confirm the position of Callimico between the marmosets and the tamarins. As available molecular evidence indicates that Callimico is more closely related to the marmosets than to the tamarins, a reconsideration of the morphological evidence in light of
the consensus tree from DNA sequence analyses is warranted. The marmosets and tamarins share four morphological characters
(loss of the third molar, loss of the hypocone, reduced body size, reproductive twinning). Dwarfism may have evolved repeatedly
among the Callitrichidae. It is well-known that the loss of a character can occur many times independently. The reproduction
of marmosets and tamarins is extremely specialized and it is difficult to imagine that this complex and unique twinning system
evolved separately in marmosets and tamarins. However, it is possible that a secondary reversal to single offspring took place
in Callimico.
Received: 20 March 1997 / Accepted: 17 December 1997 相似文献
39.
The observation that increased muscular activity leads to muscle hypertrophy is well known, but identification of the biochemical and physiological mechanisms by which this occurs remains an important problem. Experiments have been described (5, 6) which suggest that creatine, an end product of contraction, is involved in the control of contractile protein synthesis in differentiating skeletal muscle cells and may be the chemical signal coupling increased muscular activity and the increased muscular mass. During contraction, the creatine concentration in muscle transiently increases as creatine phosphate is hydrolyzed to regenerate ATP. In isometric contraction in skeletal muscle for example, Edwards and colleagues (3) have found that nearly all of the creatine phosphate is hydrolyzed. In this case, the creatine concentration is increased about twofold, and it is this transient change in creatine concentration which is postulated to lead to increased contractile protein synthesis. If creatine is found in several intracellular compartments, as suggested by Lee and Vissher (7), local changes in concentration may be greater then twofold. A specific effect on contractile protein synthesis seems reasonable in light of the work of Rabinowitz (13) and of Page et al. (11), among others, showing disproportionate accumulation of myofibrillar and mitochondrial proteins in response to work-induced hypertrophy and thyroxin-stimulated growth. Previous experiments (5, 6) have shown that skeletal muscles cells which have differentiated in vitro or in vivo synthesize myosin heavy-chain and actin, the major myofibrillar polypeptides, faster when supplied creatine in vitro. The stimulation is specific for contractile protein synthesis since neither the rate of myosin turnover nor the rates of synthesis of noncontractile protein and DNA are affected by creatine. The experiments reported in this communication were undertaken to test whether creatine selectively stimulates contractile protein synthesis in heart as it does in skeletal muscle. 相似文献
40.
A mitochondrial DNA phylogeny of African clawed frogs: phylogeography and implications for polyploid evolution 总被引:1,自引:0,他引:1
Evans BJ Kelley DB Tinsley RC Melnick DJ Cannatella DC 《Molecular phylogenetics and evolution》2004,33(1):197-213
The African clawed frogs (Silurana and Xenopus), model organisms for scientific inquiry, are unusual in that allopolyploidization has occurred on multiple occasions, giving rise to tetraploid, octoploid, and dodecaploid species. To better understand their evolution, here we estimate a mitochondrial DNA phylogeny from all described and some undescribed species. We examine the timing and location of diversification, and test hypotheses concerning the frequency of polyploid speciation and taxonomy. Using a relaxed molecular clock, we estimate that extant clawed frog lineages originated well after the breakup of Gondwana, about 63.7 million years ago, with a 95% confidence interval from 50.4 to 81.3 million years ago. Silurana and two major lineages of Xenopus have overlapping distributions in sub-Saharan Africa, and dispersal-vicariance analysis suggests that clawed frogs originated in central and/or eastern equatorial Africa. Most or all extant species originated before the Pleistocene; recent rainforest refugia probably acted as "lifeboats" that preserved existing species, rather than "species pumps" where many new successful lineages originated. We estimate that polyploidization occurred at least six times in clawed frogs. 相似文献