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Typical preparation of seed samples for infrared (IR) microspectroscopy involves imbibition of the seed for varying time periods followed by cryosectioning. Imbibition, however, may initiate germination even at 4° C with associated changes in the chemistry of the sample. We have found that it is possible to section seeds that are sufficiently hard, such as soybeans, on a standard laboratory microtome without imbibition. The use of dry sectioning of unimbibed seeds is reported here, as well as a comparison of different mounting media and modes of analysis. Glycerol, Tissue-Tek, and ethanol were used as mounting media, and the quality of the resulting spectra was assessed. Ethanol was the preferred mountant, because it dried quickly with no residue and thus did not interfere with the spectrum of interest. Analysis in transmission mode using barium fluoride windows to hold the samples was compared with transmission-reflection analysis with sections mounted on special infrared-reflecting slides. The two modes of analysis performed well in different regions of the spectrum. The mode of analysis (transmission vs. transmission-reflection) should be based on the components of greatest interest in the sample. 相似文献
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ADOLFO AMZQUITA ALBERTINA P. LIMA ROBERT JEHLE LINA CASTELLANOS
SCAR RAMOS ANDREW J. CRAWFORD HERBERT GASSER WALTER H
DL 《Biological journal of the Linnean Society. Linnean Society of London》2009,98(4):826-838
Evolutionary divergence in behavioural traits related to mating may represent the initial stage of speciation. Direct selective forces are usually invoked to explain divergence in mate‐recognition traits, often neglecting a role for neutral processes or concomitant differentiation in ecological traits. We adopted a multi‐trait approach to obtain a deeper understanding of the mechanisms behind allopatric divergence in the Amazonian frog, Allobates femoralis. We tested the null hypothesis that geographic distance between populations correlates with genetic and phenotypic divergence, and compared divergence between mate‐recognition (acoustic) and ecological (coloration, body‐shape) traits. We quantified geographic variation in 39 phenotypic traits and a mitochondrial DNA marker among 125 individuals representing eight populations. Geographic variation in acoustic traits was pronounced and tracked the spatial genetic variation, which appeared to be neutral. Thus, the evolution of acoustic traits tracked the shared history of the populations, which is unexpected for pan‐Amazonian taxa or for mate‐recognition traits. Divergence in coloration appeared uncorrelated with genetic distance, and might be partly attributed to local selective pressures, and perhaps to Batesian mimicry. Divergence in body‐shape traits was low. The results obtained depict a complex evolutionary scenario and emphasize the importance of considering multiple traits when disentangling the forces behind allopatric divergence. ©2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 826–838. 相似文献
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Twelve biologically active derivatives of vitamin B(12) (cyanocobalamin) have been synthesized in which spacers were attached to the ribose-5'-hydroxyl group of vitamin B(12). Their potential to act as oral delivery agents for proteins, nanospheres, or immunogens using the vitamin B(12) uptake system was evaluated by determining their affinity for intrinsic factor (IF) and non-IF. The ribose-5'-hydroxyl group of vitamin B(12) was activated through the use of 1,1'-carbonyldiimidazole (CDI), 1,1'-carbonyldi(1,2, 4-triazole) (CDT), or di(1-benzotriazolyl) carbonate (DBTC). Subsequent addition of an aminoalkane, diaminoalkane, or alkane diacid dihydrazide gave rise to vitamin B(12) derivatives suitable for attachment to various proteins, peptides, or nanospheres to enable oral delivery utilizing the vitamin B(12) uptake system. The ribose-5'-carbamate derivatives were found to possess similar affinity for intrinsic factor as that of the e-monocarboxylic acid of vitamin B(12). The affinity for non-IF was similar to cyanocobalamin or even higher for some of the smaller derivatives. Polysciences nanoparticles derivatized with vitamin B(12) 5'-carbamate adipic dihydrazide into CaCo-2 cells showed significantly higher levels of transport of the particles, when compared to unmodified particles. 相似文献
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The genomes of homeothermic (warm-blooded) vertebrates are mosaic
interspersions of homogeneously GC-rich and GC-poor regions (isochores).
Evolution of genome compartmentalization and GC-rich isochores is
hypothesized to reflect either selective advantages of an elevated GC
content or chromosome location and mutational pressure associated with the
timing of DNA replication in germ cells. To address the present controversy
regarding the origins and maintenance of isochores in homeothermic
vertebrates, newly obtained as well as published nucleotide sequences of
the insulin and insulin-like growth factor (IGF) genes, members of a
well-characterized gene family believed to have evolved by repeated
duplication and divergence, were utilized to examine the evolution of base
composition in nonconstrained (flanking) and weakly constrained (introns
and fourfold degenerate sites) regions. A phylogeny derived from amino acid
sequences supports a common evolutionary history for the insulin/IGF family
genes. In cold- blooded vertebrates, insulin and the IGFs were similar in
base composition. In contrast, insulin and IGF-II demonstrate dramatic
increases in GC richness in mammals, but no such trend occurred in IGF- I.
Base composition of the coding portions of the insulin and IGF genes across
vertebrates correlated (r = 0.90) with that of the introns and flanking
regions. The GC content of homologous introns differed dramatically between
insulin/IGF-II and IGF-I genes in mammals but was similar to the GC level
of noncoding regions in neighboring genes. Our findings suggest that the
base composition of introns and flanking regions is determined by
chromosomal location and the mutational pressure of the isochore in which
the sequences are embedded. An elevated GC content at codon third positions
in the insulin and the IGF genes may reflect selective constraints on the
usage of synonymous codons.
相似文献
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Jackson NC Carroll PV Russell-Jones DL Sönksen PH Treacher DF Umpleby AM 《American journal of physiology. Endocrinology and metabolism》2000,278(2):E226-E233
During critical illness glutamine deficiency may develop. Glutamine supplementation can restore plasma concentration to normal, but the effect on glutamine metabolism is unknown. The use of growth hormone (GH) and insulin-like growth factor I (IGF-I) to prevent protein catabolism in these patients may exacerbate the glutamine deficiency. We have investigated, in critically ill patients, the effects of 72 h of treatment with standard parenteral nutrition (TPN; n = 6), TPN supplemented with glutamine (TPNGLN; 0.4 g x kg(-1) x day(-1), n = 6), or TPNGLN with combined GH (0.2 IU. kg(-1). day(-1)) and IGF-I (160 microg x kg (-1) x day(-1)) (TPNGLN+GH/IGF-I; n = 5) on glutamine metabolism using [2-(15)N]glutamine. In patients receiving TPNGLN and TPNGLN+GH/IGF-I, plasma glutamine concentration was increased (338 +/- 22 vs. 461 +/- 24 micromol/l, P < 0.001, and 307 +/- 65 vs. 524 +/- 71 micromol/l, P < 0.05, respectively) and glutamine uptake was increased (5.2 +/- 0.5 vs. 7.4 +/- 0.7 micromol x kg(-1) x min(-1), P < 0.05 and 5.2 +/- 1.1 vs. 7.6 +/- 0.8 micromol x kg(-1) x min(-1), P < 0.05). Glutamine production and metabolic clearance rates were not altered by the three treatments. These results suggest that there is an increased requirement for glutamine in critically ill patients. Combined GH/IGF-I treatment with TPNGLN did not have adverse effects on glutamine metabolism. 相似文献
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Clunes MT Lindsay SL Roussa E Quinton PM Bovell DL 《Journal of molecular histology》2004,35(4):339-345
The localisation of the vacuolar proton pump (V-H+ -ATPase) and the enzyme carbonic anhydrase II (CAII) was investigated in the human eccrine sweat gland employing standard immunohistochemical techniques after antigen retrieval using microwave heat treatment and high pressure. The high-pressure antigen retrieval unmasked the presence of V-H+ -ATPase in the clear cells of the secretory coil, with a distribution similar to that previously observed for CAII. However, the dark cells were unreactive to both antibodies. In addition, heat and high-pressure antigen retrieval demonstrated the presence of CAII in the apical zone of luminal cells of the reabsorptive duct, a location not previously reported. The localisation of V-H+ -ATPase and CAII in the secretory coil clear cells suggests that the formation of HCO3- and H+ by carbonic anhydrase II and the transport of H+ by V-H+ -ATPase may play an role in sweat fluid secretion. Their presence at the apex of the duct cells indicates involvement in ductal ion reabsorption. 相似文献
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Intrinsic factor (IF) was first identified as a component of the gastric mucosa that reacted with an extrinsic factor, later discovered to be vitamin B12 (VB12). IF has been extensively characterized, and its cloned cDNA used to produce sufficient IF to produce high quality antibodies, and to elucidate its 3-dimensional structure bound to cobalamin (Cbl, VB12). The absorption of the IF–Cbl complex involves internalization by endocytosis, incorporation into multivesicular/lysosomal bodies, release of Cbl by lysosomal proteolysis and pH effects, with subsequent binding to transcobalamin (TC). Hereditary IF deficiency is rare, consistent with the need for IF to absorb Cbl, a vitamin essential for cell replication. When mutations occur, they are most often associated with loss of function, but some mutations occur outside the coding region. The IF-mediated intestinal uptake of Cbl has been harnessed for use as a transporter for peptides, proteins and even nanoparticles. Nanoparticle (NP) technology has produced Cbl-coated NPs that can incorporate peptides (insulin, IgG) that can be absorbed orally to function as hormones and antibodies in rodent models, but these systems are not yet ready for clinical use. 相似文献