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181.
Wild type rat lens main intrinsic protein (MIP) and MIP mutated (F73I, F75L) to resemble the glycerol facilitator of Escherichia coli in the region of the NPA1 box were used to investigate the topology of MIP in the membrane of Spodoptera frugiperda (Sf21) cells using the baculovirus expression system and expression in mouse erythroid leukaemia cells (MEL C88). Differential fixation for staining was used, with paraformaldehyde for externally exposed antigenic sites, and acetone for both externally and internally exposed protein antigenic sites. Immunofluorescence using antibodies to synthetic MIP peptides showed that wild type MIP had a six transmembrane topography. The N- and C-termini were intracellular in both expression systems, and both NPA boxes were found to be extracellular. These results show that residues around the NPA1 box can influence the folding of the MIP in the membrane, and provide structural evidence for the poor water transport properties of MIP, as the NPA boxes lie outside the plane of the membrane. 相似文献
182.
Influence of initial pH on hydrogen production from cheese whey 总被引:1,自引:0,他引:1
Batch experiments were conducted to investigate the effect of initial pH, between 5 and 10, on fermentative hydrogen production from crude cheese whey (87.5% (v/v) by Clostridium saccharoperbutylacetonicum). Hydrogen was produced over the range of pH studied. The hydrogen production rate and yield peaked at an initial pH 6 and then steadily decreased as the pH increased. The highest rate and yield were 28.3 ml h−1 and 7.89 mmol g−1 lactose, respectively. Sugar consumption was unaffected between pH 5 and 9 and remained at 97%. All final pHs were acidic and increased alongside the initial pH. There was no correlation between the initial pH and the fermentation time; the times were shorter (50–52 h) between pH 6 and 8, and longer (62–82 h) outside this range. A modified Gompertz equation adequately described fermentative hydrogen production from cheese whey. The respective maximum hydrogen production rate and hydrogen potential at an optimal pH of 6 were 47.07 ml h−1 and 1432 ml. Lag phase times were much longer at acidic pHs than at alkaline pHs. 相似文献
183.
Ethanol exerts biphasic effects on behavior, stimulant at low doses and depressant at higher doses. In the present study we used two mouse genetic models to investigate the relationships among activating and depressant responses to alcohol. The first model was a panel of nine isogenic genotypes. FAST and SLOW mice, selectively bred for high and low ethanol-induced motor activation, respectively, were used as a second model. We used loss of righting reflex to assess initial sensitivity and acute functional tolerance to a hypnotic dose of ethanol (3 g/kg, 20% v/v). Blood ethanol concentration at the onset of loss of righting reflex was used as an estimate of initial sensitivity, while the difference between concentration values at the recovery and loss of righting represented an acute functional tolerance score. Mean initial sensitivity and acute functional tolerance values of the nine strains were correlated with a previously obtained measure of ethanol-induced locomotor activation. Activation correlated significantly with both initial sensitivity ( r g = 0.80; P < 0.05) and acute functional tolerance ( r g = 0.77; P < 0.05). Thus, inbred genotypes that were activated more by a low dose of ethanol were also more sensitive to and developed more acute tolerance to a high dose. FAST mice had initial sensitivity values similar to those of SLOW mice, but developed more pronounced tolerance, indicating that ethanol-induced activation and acute functional tolerance may be regulated by some common genetic mechanisms. In summary, these results supported a genetic association between ethanol-induced activation and rapid development of tolerance. 相似文献
184.
Norbert Meyer Jan W Dallinga Sarah Janine Nuss Edwin JC Moonen Joep JBN van Berkel Cezmi Akdis Frederik Jan van Schooten Günter Menz 《Respiratory research》2014,15(1)
Background
Several classifications of adult asthma patients using cluster analyses based on clinical and demographic information has resulted in clinical phenotypic clusters that do not address molecular mechanisms. Volatile organic compounds (VOC) in exhaled air are released during inflammation in response to oxidative stress as a result of activated leukocytes. VOC profiles in exhaled air could distinguish between asthma patients and healthy subjects. In this study, we aimed to classify new asthma endotypes by combining inflammatory mechanisms investigated by VOC profiles in exhaled air and clinical information of asthma patients.Methods
Breath samples were analyzed for VOC profiles by gas chromatography–mass spectrometry from asthma patients (n = 195) and healthy controls (n = 40). A total of 945 determined compounds were subjected to discriminant analysis to find those that could discriminate healthy from asthmatic subjects. 2-step cluster analysis based on clinical information and VOCs in exhaled air were used to form asthma endotypes.Results
We identified 16 VOCs, which could distinguish between healthy and asthma subjects with a sensitivity of 100% and a specificity of 91.1%. Cluster analysis based on VOCs in exhaled air and the clinical parameters FEV1, FEV1 change after 3 weeks of hospitalization, allergic sensitization, Junipers symptoms score and asthma medications resulted in the formation of 7 different asthma endotype clusters. We identified asthma clusters with different VOC profiles but similar clinical characteristics and endotypes with similar VOC profiles, but distinct clinical characteristics.Conclusion
This study demonstrates that both, clinical presentation of asthma and inflammatory mechanisms in the airways should be considered for classification of asthma subtypes.Electronic supplementary material
The online version of this article (doi:10.1186/s12931-014-0136-8) contains supplementary material, which is available to authorized users. 相似文献185.
M.James C. Crabbe 《FEMS microbiology letters》1988,56(1):71-77
Abstract Yeast-like blastosporic growth, lowered levels of isopenicillin N synthetase and deacetoxycephalosporin C synthetase/hydroxylase, and lowered antibiotic production were induced in Cephalosporium acremonium strain C.O. 728 by inclusion of cysteine or glutathione in the growth medium. These effects were similar to those observed under normal conditions with strain M 8650/4, which had higher levels of glutathione reductase and protein disulphide reductase than strain C.O. 728. The addition of cytochalasins A and B slightly increased yeast-like growth in C.O. 728, although levels of biosynthetic enzyme activity and antibiotic secretion were not significantly affected. The Ca2+ ionophore A23187 inhibited C.O. 728 growth, slowed penicillin secretion into the medium, and totally inhibited cephalosporin secretion. These results show that maintenance of Ca2+ levels and the absence of thiols are important for antibiotic production in Cephalosporium acremonium . 相似文献
186.
The nucleotide sequences of the cow epsilon 2 and epsilon 4 globin genes
were determined. The sequences were 95% identical. These genes arose via a
four-gene block duplication that also gave rise to the bovine fetal (gamma)
and adult (beta) genes. Their deduced amino acid sequences are unlike any
previously reported fetal or adult globins; rather, comparison to other
mammalian globin genes indicates that they are embryonic in nature. The
sequence data indicate that these two genes have converted each other
during evolution. Pairwise comparison to the corresponding goat genes shows
greater similarity between paralogues than between more directly related
orthologues. This is in direct contrast to the situation between the cow
and goat fetal and adult genes. These observations suggest that the
frequency of DNA conversion or the fixation of conversion events may vary
in different locations of the cow beta-globin cluster.
相似文献
187.
Statistical methods of DNA sequence analysis: detection of intragenic recombination or gene conversion 总被引:32,自引:4,他引:28
Simple but exact statistical tests for detecting a cluster of associated
nucleotide changes in DNA are presented. The tests are based on the linear
distribution of a set of s sites among a total of n sites, where the s
sites may be the variable sites, sites of insertion/deletion, or
categorized in some other way. These tests are especially useful for
detecting gene conversion and intragenic recombination in a sample of DNA
sequences. In this case, the sites of interest are those that correspond to
particular ways of splitting the sequences into two groups (e.g., sequences
A and D vs. sequences B, C, and E-J). Each such split is termed a
phylogenetic partition. Application of these methods to a well-documented
case of gene conversion in human gamma-globin genes shows that sites
corresponding to two of the three observed partitions are significantly
clustered, whereas application to hominoid mitochondrial DNA
sequences--among which no recombination is expected to occur--shows no
evidence of such clustering. This indicates that clustering of
partition-specific sites is largely due to intragenic recombination or gene
conversion. Alternative hypotheses explaining the observed clustering of
sites, such as biased selection or mutation, are discussed.
相似文献
188.
Human responses to propionic acid. I. Quantification of within- and between-participant variation in perception by normosmics and anosmics 总被引:4,自引:3,他引:1
The objective of this study was to fully characterize normosmic perception
of stimuli expected to cause widely varying degrees of olfactory and nasal
trigeminal stimulation and to directly evaluate the possible role of
olfactory nerve stimulation in nasal irritation sensitivity. During each of
four identical test sessions, four anosmic and 31 normosmic participants
were presented with a range of concentrations extending from peri-threshold
for normosmics to supra- threshold for anosmics. For each session, odor (O)
and nasal irritation (NI) sensitivities were summarized in terms of the
concentrations required to produce four sensation levels ('iso-response'
concentrations). Within-participant variation in these iso-response
concentrations was < 10-fold for 95% of normosmics, for both O and NI.
For O but not NI, these apparent fluctuations in sensitivity were largely
accounted for by the uncertainty surrounding the iso-response
concentrations calculated for each session. Anosmics exhibited minimal
within- and between-participant variation in NI and required, for all but
the highest perceptual level, a higher concentration than almost all
normosmics. Between-participant variation, expressed in terms of 90%
confidence interval widths, was approximately 0.5 log units for both O and
NI for the highest perceptual level, but increased to approximately 0.8 and
1.8 log units, respectively, for the lowest (peri- threshold) level. Our
findings suggest that: (i) most apparent variation over time in O
sensitivity is actually a reflection of the uncertainty surrounding
estimates of sensitivity obtained for each session; (ii) within- and
between-participant variation in O sensitivity is far less than is commonly
reported; and (iii) low to moderate levels of NI in normosmics are the
result of relatively weak trigeminal stimulation combined with much greater
olfactory activation.
相似文献
189.
Regier JC; Fang QQ; Mitter C; Peigler RS; Friedlander TP; Solis MA 《Molecular biology and evolution》1998,15(9):1172-1182
Evolution and phylogenetic utility of the period gene are explored through
sequence analysis of a relatively conserved 909-bp fragment in 26
lepidopteran species. Taxa range from tribes to superfamilies, primarily
within the putative clade Macrolepidotera plus near outgroups, and include
both strongly established and problematic groupings. Their divergence dates
probably range from the late Cretaceous through much of the Tertiary.
Comparisons within the same set of closely related species show that amino
acid substitutions in period occur 4.9 and 44 times as frequently as they
do in two other nuclear genes--dopa decarboxylase and elongation factor-1
alpha, respectively. In contrast, rates of observed synonymous substitution
are within 60% of each other for these three genes. Synonymous changes in
period approach saturation by the family level, whereas nonsynonymous and
amino acid divergences across the Macrolepidoptera are less than half the
maximal values reported for this gene. Phylogenetic analyses of period
strongly supported groupings at the family level and below. In contrast to
previous analyses at this level with other nuclear genes, much of the
information lies in nonsynonymous change. Relationships up to the
superfamily level were recovered with decreasing effectiveness, and little,
if any, signal was apparent regarding relationships among superfamilies.
This could reflect rapid radiation of the superfamilies, however, rather
than saturation in the period locus; thus, period, in combination with
other genes, remains a plausible candidate for approaching the difficult
problems of lepidopteran family and superfamily relationships.
相似文献
190.
Multiple haplotypes from each of three nuclear loci were isolated and
sequenced from geographic populations of the American oyster, Crassostrea
virginica. In tests of alternative phylogeographic hypotheses for this
species, nuclear gene genealogies constructed for these haplotypes were
compared to one another, to a mitochondrial gene tree, and to patterns of
allele frequency variation in nuclear restriction site polymorphisms
(RFLPs) and allozymes. Oyster populations from the Atlantic versus the Gulf
of Mexico are not reciprocally monophyletic in any of the nuclear gene
trees, despite considerable genetic variation and despite large allele
frequency differences previously reported in several other genetic assays.
If these populations were separated vicariantly in the past, either
insufficient time has elapsed for neutral lineage sorting to have achieved
monophyly at most nuclear loci, or balancing selection may have inhibited
lineage extinction, or secondary gene flow may have moved haplotypes
between regions. These and other possibilities are examined in light of
available genetic evidence, and it is concluded that no simple explanation
can account for the great variety of population genetic patterns across
loci displayed by American oysters. Regardless of the source of this
heterogeneity, this study provides an empirical demonstration that
different sequences of DNA within the same organismal pedigree can have
quite different phylogeographic histories.
相似文献