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1.
Subsequent to observations that pulmonary responses to antigen challenge are of different magnitudes in sensitized rats that are anesthetized with different drugs, we conducted studies to test whether the alterations in responses were due to changes in airway responsiveness to cholinergic or serotonergic challenge, opioid-receptor mediated events, or changes in mast cell mediator release. Immunoglobulin E-sensitized rats anesthetized with ketamine/urethan had larger changes in lung resistance and plasma histamine after pulmonary antigen challenge compared with rats anesthetized with fentanyl-droperidol. Blockade of opioid receptors with naloxone did not affect the responses. In unsensitized rats, airway responses to aerosolized methacholine were similar for the two anesthetics, indicating unchanged smooth muscle responsiveness; however, airway responses to intravenous serotonin were enhanced by ketamine and ablated by droperidol. We conclude that ketamine- and droperidol-induced alterations of pulmonary allergic responses are due to changes in sensitivity to serotonin and in mast cell mediator release. We speculate that mast cell mediator release may be modulated by a serotonin receptor-linked mechanism. 相似文献
2.
Changes in gas exchange characteristics and water use efficiency of mangroves in response to salinity and vapour pressure deficit 总被引:12,自引:0,他引:12
Summary Measurements were made of the photosynthetic gas exchange properties and water use efficiency of 19 species of mangrove in 9 estuaries with different salinity and climatic regimes in north eastern Australia and Papua New Guinea. Stomatal conductance and CO2 assimilation rates differed significantly between species at the same locality, with the salt-secreting species, Avicennia marina, consistently having the highest CO2 assimilation rates and stomatal conductances. Proportional changes in stomatal conductance and CO2 assimilation rate resulted in constant and similar intercellular CO2 concentrations for leaves exposed to photon flux densities above 800 mol·m-2·s-1 in all species at a particular locality. In consequence, all species at the same locality had similar water use efficiencies. There were, however, significant differences in gas exchange properties between different localities. Stomatal conductance and CO2 assimilation rate both decreased with increasing salinity and with increasing leaf to air vapour pressure deficit (VPD). Furthermore, the slope of the relationship between assimilation rate and stomatal conductance increased, while intercellular CO2 concentration decreased, with increasing salinity and with decreasing ambient relative humidity. It is concluded from these results that the water use efficiency of mangroves increases with increasing environmental stress, in this case aridity, thereby maximising photosynthetic carbon fixation while minimising water loss.Contribution No. 459 from the Australian Institute of Marine Science 相似文献
3.
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.
相似文献
4.
D.L. Clough 《Life sciences》1984,35(19):1937-1946
Vanadate (VO4?3) produces a positive inotropic effect in rats and also promotes diuresis as well as natriuresis. Although the mechanism(s) of these effects is uncertain, in the kidney, VO4?3 may act through inhibition of (Na++K+)-ATPase activity, whereas in the heart, other or additional mechanisms are likely. Under the assay conditions used in the present study, microsomal (Na++K+)-ATPase activities from rat kidney cortex and medulla were inhibited to a greater extent than was left ventricular (Na++K+)-ATPase activity over a range of VO4?3 concentrations. The apparent dissociation constant for left ventricular (Na++K+)-ATPase (10.95 ± 1.26 × 10?7M VO4?3) was significantly greater than that of (Na++K+)-ATPase from the cortex (3.46±0.96×10?7 M VO4?3) or the medulla (3.32±0.7×10?7M VO4?3, N=6, P<.05) whereas there were no significant differences between the effects of VO4?3 on (Na++K+)-ATPase from the cortex and medulla. The greater inhibition by VO4, of (Na++K+)-ATPase from the cortex relative to that of the left ventricle, occurred over a range of Na+ and K+ concentrations, and K+ enhanced the inhibition by VO4?3 to a greater extent for (Na++K+)-ATPase from the cortex than the left ventricle. These results suggest that renal (Na++K+)-ATPase is more sensitive than left ventricular (Na++K+)-ATPase to inhibition by VO4?3 and would, therefore, be more likely to be modulated 相似文献
5.
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.
相似文献
6.
7.
Digestion of haemoglobin by schistosomes: 35 years on 总被引:5,自引:0,他引:5
Adult schistosomes obtain nutrients by digesting haemoglobin, which they obtain from ingested host red blood cells. Here John Dalton, Angela Smith, Karen Clough and Paul Brindley argue that a cathepsin L proteinase recently identified in their laboratory as the predominant cysteine proteinase activity of Schistosoma mansoni may play the leading role in haemoglobin digestion. They discuss the importance of elucidating the roles of both cathepsin B and cathepsin L in the digestion of haemoglobin, since both should be considered important targets to which novel schistosomicidal agents could be directed. 相似文献
8.
The establishment of 3 specified-pathogen-free marmosets (Callithrix jacchus) during the period May 1969 to January 1973 is described. A brief history of the conventional breeding colony from which the animals were derived is given and hysterotomy and hand-rearing techniques are described. 相似文献
9.
Photosynthetic Adaptation of Solanum dulcamara L. to Sun and Shade Environments: II. Physiological Characterization of Phenotypic Response to Environment 下载免费PDF全文
Photosynthetic and growth properties of Solanum dulcamara L. were studied under controlled environments. The 200 experimentally tested plants were clonal replicates of five field-collected individuals, three from fully exposed habitats and two from deeply shaded habitats. After 4 weeks of growth in one of eight environmental treatments, each plant was measured for leaf adaxial and abaxial conductance to water vapor, specific leaf weight, chlorophyll per square decimeter of leaf, photosynthetic unit size, light-saturated photosynthetic rate, total leaf area, and total leaf, stem, and root dry weights. Changes in light level influenced photosynthesis and growth of each plant more than changes in water availability or temperature. It is strongly suggested that the primary adaptive response of the tested individuals to changes in levels of light involves the regulation of leaf thickness. 相似文献
10.
The radiological prevalence of Paget''s disease was studied in 14 towns. Routine radiographs showed that the disease was present in 5.4% of people aged 55 years and over. The disease was more prevalent in men than in women at all ages, and the prevalence increased with age. The three Lancashire towns studied (Preston, Bolton, and Blackburn) had higher rates than elsewhere. This probably reflects a real geographical variation in the prevalence of Paget''s disease in England and Wales. 相似文献