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71.
J. M. Clyne J. A. Running M. Stempien R. S. Stephens H. Akhavan-Tafti A. P. Schaap M. S. Urdea 《Luminescence》1989,4(1):357-366
With an estimated 3–4 million new cases per year, human infections from Chlamydia trachomatis are probably the most prevalent sexually transmitted disease (STD) in the United States. Diagnosis of Chlamydia is usually conducted by tissue culture methods. Direct immunofluorescence and ELISA tests have become available, but there remains a need for a test with better specificity and sensitivity. In response to this need, we have developed a rapid DNA hybridization assay using synthetic oligonucleotide probes to detect the presence of the Chlamydia trachomatis specific 7.4 kb plasmid. The assay involves solution phase hybridization of unlabelled probes, rapid capture of the probe-target duplex onto a microtitre dish surface, a new signal amplification technique that employs chemically cross-linked oligonucleotides, and an alkaline phosphatase labelled probe. Signal is obtained by reacting the labelled probe-target complex with an enzyme triggerable dioxetane substrate. Detection of the chemiluminescent output is performed either with a luminometer or by exposure to instant film. All 15 serovars of Chlamydia trachomatis react positively while organisms known to co-inhabit the human urogenital tract react negatively. 相似文献
72.
Crustacean and cheliceratan hemocyanins (oxygen-transport proteins) and
insect hexamerins (storage proteins) are homologous gene products, although
the latter do not bind oxygen and do not possess the copper- binding
histidines present in the hemocyanins. An alignment of 19 amino acid
sequences of hemocyanin subunits and insect hexamerins was made, based on
the conservation of elements of secondary structure observed in X-ray
structures of two hemocyanin subunits. The alignment was analyzed using
parsimony and neighbor-joining methods. Results provide strong indications
for grouping together the sequences of the 2 crustacean hemocyanin
subunits, the 5 cheliceratan hemocyanin subunits, and the 12 insect
hexamerins. Within the insect clade, four methionine- rich proteins, four
arylphorins, and two juvenile hormone-suppressible proteins from
Lepidoptera, as well as two dipteran proteins, form four separate groups.
In the absence of an outgroup sequence, it is not possible to present
information about the ancestral state from which these proteins are
derived. Although this family of proteins clearly consists of homologous
gene products, there remain striking differences in gene organization and
site of biosynthesis of the proteins within the cell. Because studies on
18S and 12S rRNA sequences indicate a rather close relationship between
insects and crustaceans, we propose that hemocyanin is the ancestral
arthropod protein and that insect hexamerins lost their copper-binding
capability after divergence of the insects from the crustaceans.
相似文献
73.
74.
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
75.
The aim of this experiment was to evaluate the effects of an intracerebroventricular (icv) injection of prostaglandin E1 (PGE1) on the sympathetic activation and the thermogenic changes in rats with acute lesions of the ventromedial hypothalamus (VMH). Four groups of six Sprague-Dawley male rats were anesthetized with ethyl-urethane. The firing rate of the sympathetic nerves innervating the interscapular brown adipose tissue (IBAT) and the colonic and IBAT temperatures were monitored both before and after one of the following treatments: 1) VMH lesion plus icv injection of PGE1 (500 ng); 2) VMH lesion plus icv injection of saline; 3) sham lesion plus icv injection of PGE1; and 4) sham lesion plus icv injection of saline. PGE1 induced an increase in the firing rate of IBAT nerves and the colonic and IBAT temperatures. These effects were reduced by VMH lesion. The findings indicate that acute lesions of the VMH reduce the effects of PGE1 and seem to suggest a possible role played by the VMH in the control of the sympathetic activation and the thermogenic changes during PGE1 hyperthermia. 相似文献
76.
TD Smith KP Bhatnagar CJ Bonar KL Shimp MP Mooney MI Siegel 《American journal of physical anthropology》2003,122(3):301-301
77.
78.
Satellite Evidence of Phenological Differences Between Urbanized and Rural Areas of the Eastern United States Deciduous Broadleaf Forest 总被引:6,自引:0,他引:6
Michael A. White Ramakrishna R. Nemani Peter E. Thornton Steven W. Running 《Ecosystems》2002,5(3):260-273
We used a 10-year record (1990–99) of composited and cloud-screened reflectances from the Advanced Very High Resolution Radiometer
(AVHRR) to test for phenological differences between urban and rural areas in the eastern United States deciduous broadleaf
forest (DBF). We hypothesized that well-documented urban heat island effects would be associated with alterations in temperature-sensitive
vegetation phenology. Our objectives were thus (a) to investigate possible differences in the start of the growing season
(SOS) and end of the growing season (EOS) between the urban and DBF land covers, (b) to investigate related differences in
greenness amplitude and fractional cover, and (c) to develop a generalized additive model (GAM) to predict the spatial variation
of observed differences. By analyzing individual 1° latitude by 1° longitude blocks, we found that, on average, urbanization
is associated with a growing season expansion of 7.6 days. Most of this effect is caused by an earlier SOS in urban areas.
In all cases, urban regions had lower fractional cover and greenness amplitude. The GAM model failed to produce a viable model
for differences in EOS, probably because it is dominated by photoperiod controls with only a minor temperature impact. SOS
differences were predicted with an accuracy of about 2.4 days, with a GAM consisting of smoothed functions of mean annual
average temperature, urban fractional cover, and the urban vs DBF greenness amplitude difference. We speculate that evidence
of a phenological response to warming indicates that global warming, without reduction in DBF vegetation cover and greenness
amplitude, may increase carbon sequestration in mesic deciduous forests.
Received 6 June 2001; accepted 23 October 2001. 相似文献
79.
This paper looked at the leaf architecture characteristics of Vachellia tortilis to determine if either there is or not an effect of the tropic line on plants. Vachellia tortilis leaves were sampled along a national road (N1) in Limpopo province. Sampling points were set 10 km apart away from the Tropic of Capricon in opposite directions. Leaf morphology revealed that leaves of V. tortilis are bipinnately compound with alternate arrangement. The venation pattern of the pinnules was eucamptodromus and brochidodromous with imperfect reticulation. Areoles were imperfect and pentagonal or irregular in shape. 相似文献
80.
Arctic and boreal ecosystems of western North America as components of the climate system 总被引:7,自引:0,他引:7