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51.
52.
Chromosomal DNA from 23 closely related, pathogenic strains of Escherichia
coli was digested and probed for the insertion sequences IS1, IS2, IS4,
IS5, and IS30. Under the assumption that elements residing in DNA
restriction fragments of the same apparent length are identical by descent,
parsimony analysis of these characters yielded a unique phylogenetic tree.
This analysis not only distinguished among bacterial strains that were
otherwise identical in their biochemical characteristics and enzyme
electrophoretic mobilities, but certain aspects of the topology of the tree
were consistent across several unrelated insertion elements. The
distribution of IS elements was then reexamined in light of the inferred
phylogenetic relationships to investigate the biological properties of the
elements, such as rates of insertion and deletion, and to discover apparent
recombinational events. The analysis shows that the pattern of distribution
of insertion elements in the bacterial genome is sufficiently stable for
epidemiological studies. Although the rate of recombination by conjugation
has been postulated to be low, at least two such events appear to have
taken place.
相似文献
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Velocity, force, power, and Ca2+ sensitivity of fast and slow monkey skeletal muscle fibers 总被引:1,自引:0,他引:1
Fitts Robert H.; Bodine Sue C.; Romatowski Janell G.; Widrick Jeffrey J. 《Journal of applied physiology》1998,84(5):1776-1787
In this study,we determined the contractile properties of single chemically skinnedfibers prepared from the medial gastrocnemius (MG) and soleus (Sol)muscles of adult male rhesus monkeys and assessed the effects of thespaceflight living facility known as the experiment support primatefacility (ESOP). Muscle biopsies were obtained 4 wk before andimmediately after an 18-day ESOP sit, and fiber type was determined byimmunohistochemical techniques. The MG slow type I fiber wassignificantly smaller than the MG type II, Sol type I, and Sol type IIfibers. The ESOP sit caused a significant reduction in the diameter oftype I and type I/II (hybrid) fibers of Sol and MG type II and hybridfibers but no shift in fiber type distribution. Single-fiber peak force(mN and kN/m2) was similarbetween fiber types and was not significantly different from valuespreviously reported for other species. The ESOP sit significantlyreduced the force (mN) of Sol type I and MG type II fibers. Thisdecline was entirely explained by the atrophy of these fiber typesbecause the force per cross-sectional area (kN/m2) was not altered. Peakpower of Sol and MG fast type II fiber was 5 and 8.5 times that of slowtype I fiber, respectively. The ESOP sit reduced peak power by 25 and18% in Sol type I and MG type II fibers, respectively, and, for theformer fiber type, shifted the force-pCa relationship to the right,increasing the Ca2+ activationthreshold and the free Ca2+concentration, eliciting half-maximal activation. The ESOP sit had noeffect on the maximal shortening velocity(Vo) of anyfiber type. Vo ofthe hybrid fibers was only slightly higher than that of slow type Ifibers. This result supports the hypothesis that in hybrid fibers theslow myosin heavy chain would be expected to have a disproportionatelygreater influence onVo. 相似文献
55.
Background
Fairy shrimps (Anostraca), tadpole shrimps (Notostraca), clam shrimps (Spinicaudata), algae (primarily filamentous blue-green algae [cyanobacteria]), and suspended organic particulates are dominant food web components of the seasonally inundated pans and playas of the western Mojave Desert in California. We examined the extent to which these branchiopods controlled algal abundance and species composition in clay pans between Rosamond and Rogers Dry Lakes. We surveyed branchiopods during the wet season to estimate abundances and then conducted a laboratory microcosm experiment, in which dried sediment containing cysts and the overlying algal crust were inundated and cultured. Microcosm trials were run with and without shrimps; each type of trial was run for two lengths of time: 30 and 60 days. We estimated the effect of shrimps on algae by measuring chlorophyll content and the relative abundance of algal species.Results
We found two species of fairy shrimps (Branchinecta mackini and B. gigas), one tadpole shrimp (Lepidurus lemmoni), and a clam shrimp (Cyzicus setosa) in our wet-season field survey. We collected Branchinecta lindahli in a pilot study, but not subsequently. The dominant taxa were C. setosa and B. mackini, but abundances and species composition varied greatly among playas. The same species found in field surveys also occurred in the microcosm experiment. There were no significant differences as a function of experimental treatments for either chlorophyll content or algal species composition (Microcoleus vaginatus dominated all treatments).Conclusions
The results suggest that there was no direct effect of shrimps on algae. Although the pans harbored an apparently high abundance of branchiopods, these animals had little role in regulating primary producers in this environment. 相似文献56.
M Kale R Ramsey-Goldman S Bernatsky MB Urowitz D Gladman PR Fortin M Petri E Yelin S Manzi S Edworthy O Nived S-C Bae D Isenberg A Rahman JG Hanly C Gordon S Jacobsen E Ginzler DJ Wallace GS Alarcón MA Dooley L Gottesman K Steinsson A Zoma J-L Senécal S Barr G Sturfelt L Dreyer L Criswell J Sibley JL Lee AE Clarke 《Arthritis research & therapy》2012,14(Z3):A15
57.
Sharon J. Marks Niall R. Moore Mo L. Clark Boyd JG Strauss T. Derek R. Hockaday 《Obesity (Silver Spring, Md.)》1996,4(1):1-7
Increased visceral adipose tissue is thought to contribute to impaired glucose tolerance. We studied 10 men with non-insulin dependent diabetes (NIDDM) before and after a 12-week intervention study using dexfenfluramine. Subjects had a mean body mass index (BMI) of 26.4 ± 1.7 kg\m2 and had an abdominal distribution of body fatness (waist-to hip ratio >0.9). Anthropometric indices, biochemistry, macronutrient intake from 7-day food records as well as a euglycaemic glucose clamp and magnetic resonance imaging (MRI) were performed at week 0 and week 12. Abdominal adipose tissue area measured by MRI was reduced from 854 ± 270 cm2 to 666 ± 231 cm2 (p=0.003) due mainly to a selective 32% reduction in visceral fat area from 484 ± 230 cm2 to 333 ± 72 cm2 (p=0.002). Insulin sensitivity improved from 0.29 ± 0.13 [min?1 (mU/L)] to 0.54 ± 0.21 [min?1 (mU/L)] (p=0.01) and C-peptide levels reduced from 0.77 ± 0.24 μmol/L to 0.58 ± 0.15 μmol/L (p=0.002). The reductions in fasting glucose and glycated haemoglobin failed to achieve significance. Fasting total cholesterol and triglyceride levels significantly reduced (p=<0.001 and p=0.021 respectively). There was a reduction in total energy intake (p=0.005) due to a significant reduction in calories obtained from fat (p<0.001). Thus dexfenfluramine was shown to be a useful adjunct therapy for the reduction of visceral fat in abdominally-obese men with NIDDM with an associated improvement in insulin sensitivity. 相似文献
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59.
At the early onset of the 20th century, several studies already reported that the gray matter was implicated in the histopathology of multiple sclerosis
(MS). However, as white matter pathology long received predominant attention in this disease, and histological staining techniques
for detecting myelin in the gray matter were suboptimal, it was not until the beginning of the 21st century that the true extent and importance of gray matter pathology in MS was finally recognized. Gray matter damage was
shown to be frequent and extensive, and more pronounced in the progressive disease phases. Several studies subsequently demonstrated
that the histopathology of gray matter lesions differs from that of white matter lesions. Unfortunately, imaging of pathology
in gray matter structures proved to be difficult, especially when using conventional magnetic resonance imaging (MRI) techniques.
However, with the recent introduction of several more advanced MRI techniques, the detection of cortical and subcortical damage
in MS has considerably improved. This has important consequences for studying the clinical correlates of gray matter damage.
In this review, we provide an overview of what has been learned about imaging of gray matter damage in MS, and offer a brief
perspective with regards to future developments in this field. 相似文献
60.