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41.
R Kneen NG Pham T Solomon TM Tran TT Nguyen BL Tran J Wain NP Day TH Tran CM Parry NJ White 《Canadian Metallurgical Quarterly》1998,27(4):845-850
PURPOSE: To review the University of Florida experience in treating ependymomas, analyze prognostic factors, and provide treatment recommendations. METHODS AND MATERIALS: Forty-one patients with ependymoma and no metastases outside the central nervous system received postoperative radiotherapy with curative intent between 1966 and 1989. Ten patients had supratentorial lesions, 22 had infratentorial lesions, and 9 had spinal cord lesions. All patients had surgery (stereotactic biopsy, subtotal resection, or gross total resection). Most patients with high-grade lesions received radiotherapy to the craniospinal axis. Low-grade intracranial lesions received more limited treatment. Spinal cord lesions were treated using either partial spine or whole spine fields. RESULTS: Of 32 intracranial tumors, 21 recurred, all at the primary site; no spinal cord tumors recurred. Overall 10-year survival rates were 51% (absolute) and 46% (relapse-free); by tumor site: spinal cord, 100%; infratentorial, 45%; supratentorial, 20% (p = 0.002). On multivariate analysis, tumor site was the only factor that influenced absolute survival (p = 0.0004); other factors evaluated included grade, gender, age, duration of symptoms, resection extent, primary tumor dose, treatment field extent, surgery-to-radiotherapy interval, and days under radiotherapy treatment. CONCLUSIONS: Patients with supratentorial or infratentorial tumors receive irradiation, regardless of grade. Craniospinal-axis fields are used when spinal seeding is radiographically or pathologically evident. Spinal cord tumors are treated using localized fields to the primary site if not completely resected. Failure to control disease at the primary site remains the main impediment to cure. 相似文献
42.
Genetic variation among malaria parasites has important consequences with regard to drug resistance, pathogenicity, immunity, transmission, and speciation. In this regard, malaria parasites have been shown to display a high degree of inter- and intra-species genetic divergence. The nuclear genomes of Plasmodium falciparum, Plasmodium yoelii, and Plasmodium gallinaceum are vastly divergent yet share a similar codon usage and total A/T content of approximately 82%. This is in contrast to other primate-specific species including P. vivax which have an A/T content of approximately 67%. To assess the effects of this evolutionary divergence on the conservation of gene content, organization, and codon usage in the mitochondrial DNA (mtDNA) of malaria parasites, we have cloned and sequenced the mitochondrial genome of Plasmodium vivax, and compared it with the mtDNAs of P. falciparum, P. yoelii, and P. gallinaceum. The P. vivax mitochondrial genome was found to be 5990 base pairs in length, and displayed a gene organization identical to that of P. falciparum, P. yoelii, and P. gallinaceum. Furthermore, there was a remarkable 90% conservation of sequence identity between the mitochondrial genomes of all four species. As an example of intra-species conservation, comparison of mtDNAs from two independently cloned P. falciparum isolates, Malay Camp and C10, revealed only a single nucleotide substitution. A/T content of the P. vivax mitochondrial genome was found to be identical to other species of Plasmodium, hence, we have postulated that the mitochondrial genomes of malaria parasites were refractory to the evolutionary shifts in nucleotide content seen among the nuclear genomes of malaria parasites. Among different Plasmodium species, the second position of mitochondrial codons were found to be the least prone to substitutions and displayed a significant bias in pyrimidines. These aspects of mitochondrial codon usage were distinct from the nuclear genome and may reflect functional aspects of decoding by the mitochondrial translational system. 相似文献
43.
NJ Watkins A Gottschalk G Neubauer B Kastner P Fabrizio M Mann R Lührmann 《Canadian Metallurgical Quarterly》1998,4(12):1549-1568
The eukaryotic nucleolus contains a large number of small nucleolar RNAs (snoRNAs) that are involved in preribosomal RNA (pre-rRNA) processing. The H box/ACA-motif (H/ACA) class of snoRNAs has recently been demonstrated to function as guide RNAs targeting specific uridines in the pre-rRNA for pseudouridine (psi) synthesis. To characterize the protein components of this class of snoRNPs, we have purified the snR42 and snR30 snoRNP complexes by anti-m3G-immunoaffinity and Mono-Q chromatography of Saccharomyces cerevisiae extracts. Sequence analysis of the individual polypeptides demonstrated that the three proteins Gar1p, Nhp2p, and Cbf5p are common to both the snR30 and snR42 complexes. Nhp2p is a highly basic protein that belongs to a family of putative RNA-binding proteins. Cbf5p has recently been demonstrated to be involved in ribosome biogenesis and also shows striking homology with known prokaryotic psi synthases. The presence of Cbf5p, a putative psi synthase in each H/ACA snoRNP suggests that this class of RNPs functions as individual modification enzymes. Immunoprecipitation studies using either anti-Cbf5p antibodies or a hemagglutinin-tagged Nhp2p demonstrated that both proteins are associated with all H/ACA-motif snoRNPs. In vivo depletion of Nhp2p results in a reduction in the steady-state levels of all H/ACA snoRNAs. Electron microscopy of purified snR42 and snR30 particles revealed that these two snoRNPs possess a similar bipartite structure that we propose to be a major structural determining principle for all H/ACA snoRNPs. 相似文献
44.
BACKGROUND/AIMS: A link between abuse and irritable bowel syndrome (IBS) has been reported in outpatients but remains controversial. No population-based studies have investigated this issue. The aim of this study was to determine the prevalence of abuse and its association with symptoms in a representative community sample. METHODS: An age- and sex-stratified random sample of residents of Olmsted County, Minnesota ranging in age from 30 to 49 years was mailed a valid self-report symptom questionnaire. Abuse was assessed by standard published criteria. RESULTS: Of the 919 responders (74%), the age-adjusted prevalence of any abuse was 41% in women and 11% in men, resulting in an age- and sex-adjusted prevalence of 26%. Symptoms of IBS, dyspepsia, and frequent heartburn were reported by 14%, 23%, and 12%, respectively. There was a significant association between IBS and sexual abuse, emotional or verbal abuse, and abuse in childhood and adulthood. Similarly, dyspepsia and heartburn were both significantly associated with abuse. In the population, 31% had visited a physician for gastrointestinal symptoms; the odds of visiting a physician were highest in those reporting abuse in adulthood and childhood. CONCLUSIONS: Self-reported abuse is common in middle-aged subjects; those who report abuse are more likely to have symptoms consistent with IBS, dyspepsia, or heartburn and to visit a physician for bowel symptoms. 相似文献
45.
A Nighorn NJ Gibson DM Rivers JG Hildebrand DB Morton 《Canadian Metallurgical Quarterly》1998,18(18):7244-7255
The nitric oxide (NO)-cGMP signaling system is thought to play important roles in the function of the olfactory system in both vertebrates and invertebrates. One way of studying the role of NO in the nervous system is to study the distribution and properties of NO synthase (NOS), as well as the soluble guanylyl cyclases (sGCs), which are the best characterized targets of NO. We study NOS and sGC in the relatively simple and well characterized insect olfactory system of the hawkmoth, Manduca sexta. We have cloned Manduca sexta nitric oxide synthase (MsNOS) and two sGCs (MsGCalpha1 and MsGCbeta1), characterized their basic biochemical properties, and studied their expression in the olfactory system. The sequences of the Manduca genes are highly similar to their mammalian homologs and show similar biochemical properties when expressed in COS-7 cells. In particular, we find that MsGC functions as an obligate heterodimer that is stimulated significantly by NO. We also find that MsNOS has a Ca2+-sensitive NO-producing activity similar to that of mammalian neuronal NOS. Northern and in situ hybridization analyses show that MsNOS and the MsGCs are expressed in a complementary pattern, with MsNOS expressed at high levels in the antennae and the MsGCs expressed at high levels in a subset of antennal lobe neurons. The expression patterns of these genes suggest that the NO-sGC signaling system may play a role in mediating communication between olfactory receptor neurons and projection neurons in the glomeruli of the antennal lobe. 相似文献
46.
D. E. Spahr K. Friedrich J. M. Schultz R. S. Bailey 《Journal of Materials Science》1990,25(10):4427-4439
Microstructure and fracture mechanical behaviour of injection-moulded, longer glass fibrereinforced polypropylene (Verton* aspect ratio 320) were studied as a function of fibre volume fraction and compared to that of shorter fibre-filled polypropylene (aspect ratio 70). Toughness was measured using instrumented notched lzod and falling weight impact tests, as well as compact tension specimens. It was found that the addition of longer fibres generally increased the toughness of the material, although more significant increases were seen in the impact tests than were seen in the compact tension test. For the latter results, a correlation between toughness improvement and microstructural details was performed on the basis of the microstructural efficiency concept, a semi-empirical approach of the formK
c,C = (a* +nR)K
c,M, where,K
c,C andK
c,M are the fracture toughnesses of the composite and the matrix, respectively,a* is a matrix stress correction factor,n is a scaling parameter andR is a fibre reinforcement effectiveness factor. The latter corrects for differences in the composite microstructures, and incorporates effective fibre orientation factors, layering of injection moulded parts, and fibre volumes in the different layers.Nomenclature
a
crack length
-
a
*
matrix toughness correction factor
-
A
cross-sectional area
-
B
thickness of the sample plaques
-
C
thickness of the composite core regions
-
E
peak
energy adsorbed up to the maximum force in the impact load-displacement curve
-
E
t
tensile modulus
-
F
max
maximum force in impact force-displacement curves
-
f
p
fibre orientation factor
-
f
pe
effective orientation factor
-
f
pe,C
effective orientation parameter, core region
-
f
pe, s
effective orientation parameter, surface region
-
F
critical load in the tensile test load-displacement curves
-
K
c
critical stress intensity factor/fracture toughness
-
K
L
fracture toughness of the composite materials
-
K
d
dynamic fracture toughness
-
K
L
fracture toughness of the matrix
-
L
test with crack parallel to the mould filling direction
-
M
microstructural efficiency factor
-
n
scaling parameter for reinforcement effectiveness factor (energy absorbtion ratio)
-
R
reinforcement effectiveness factor
-
S
thickness of the composite surface regions
- T
test with crack perpendicular to the mould filling direction
-
V
f
fibre volume fraction
-
V
m
matrix volume fraction (= 1 —V
f)
-
W
specimen width
-
W
f
fibre weight fraction
-
W
m
matrix weight fraction (= 1 —W
f)
-
X
n
number average fibre length
-
X
v
volume average fibre length
-
Y(a/ W)
polynomial correction for compact tension specimens
-
variable in effective orientation factor formula
-
variable in effective orientation factor formula
- B
strain to break
- c
density of the composite
- f
fibre density
- m
matrix density
- F
fracture strength
-
fibre angle with respect to a reference direction 相似文献
47.
Rasheed A. Bailey Derek L. Beahm I. Martha Skerrett 《International journal of molecular sciences》2021,22(5)
Glycine is an amino acid with unique properties because its side chain is composed of a single hydrogen atom. It confers conformational flexibility to proteins and conserved glycines are often indicative of protein domains involving tight turns or bends. All six beta-type connexins expressed in human epidermis (Cx26, Cx30, Cx30.3, Cx31, Cx31.1 and Cx32) contain a glycine at position 12 (G12). G12 is located about halfway through the cytoplasmic amino terminus and substitutions alter connexin function in a variety of ways, in some cases altering protein interactions and leading to cell death. There is also evidence that alteration of G12 changes the structure of the amino terminus in connexin- and amino acid- specific ways. This review integrates structural, functional and physiological information about the role of G12 in connexins, focusing on beta-connexins expressed in human epidermis. The importance of G12 substitutions in these beta-connexins is revealed in two hereditary skin disorders, keratitis ichthyosis and erythrokeratodermia variabilis, both of which result from missense mutations affecting G12. 相似文献
48.
The decomposition of 1,2-dichloroethane on polycrystalline copper has been studied using a microreactor. The reaction is found to have an activation energy of 81±5 kJ mol–1 generating gaseous ethene and chemisorbed chlorine. The reaction terminates on completion of a monolayer of chemisorbed chlorine and is followed by a much slower reaction. The rate limiting step is thought to be C2H4Cl2(phys)C2H4Cl(ads)+Clads The reaction is compared with a UHV study of the same molecule on Cu(l 11) and the possibility of a negative ion transition state is discussed. 相似文献
49.
G. J. Boudreaux A. V. Bailey V. W. Tripp 《Journal of the American Oil Chemists' Society》1972,49(3):200-201
The use of a pseudo contact shift reagent, (Eu[fod]3), to obtain simplified NMR spectra of a typical long chain monounsaturated fatty acid methyl ester, methyl petroselinate,
is described. Spectra were obtained in which individual methylene groups are identifiable from their splitting patterns. Non-equivalent
splitting patterns were observed for the methine protons with varying amounts of reagent used. The effect of concentration
of the shift reagent on the chemical shift is discussed.
Presented in part at the Meeting of the Gulf Coast Instrumental Analysis Group, Houston, October 1971.
S. Market. and Nutr. Res. Div., ARS, USDA 相似文献
50.
A new method is presented for determining thecis/trans isomer content of edible vegetable oils. The intensities of Raman lines near 1656 and 1670 cm−1 are associated with thecis andtrans configuration, respectively. A precision of ca. 1% can be obtained in thecis/trans isomer analysis of binary mixtures of methyl esters and triglycerides of monoenes and dienes and of hydrogenated vegetable
oils. The spectroscopic data also provide the iodine value of vegetable oils or isolated fractions with precision for a single
determination of ca. 1%.
Presented at the AOCS meeting, Houston, May 1971.
W. Market. Nutr. Res. Div., ARS, USDA. 相似文献