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排序方式: 共有934条查询结果,搜索用时 15 毫秒
1.
Coronary artery bypass grafts: visualization with MR imaging 总被引:1,自引:0,他引:1
2.
Digital radiography of subtle pulmonary abnormalities: an ROC study of the effect of pixel size on observer performance 总被引:3,自引:0,他引:3
Forty conventional radiographs with examples of mild interstitial infiltrates and subtle pneumothoraces and 40 normal studies of the chest were selected and digitized, with pixel sizes of 1.0, 0.5, 0.2, and 0.1 mm. Observer performance tests were carried out using receiver operating characteristic analysis. Conventional radiographs and digitized images were compared. The results indicate that, in such cases, diagnostic accuracy increases significantly as the pixel size is reduced, at least to the 0.1-mm level. We conclude that, for digital systems using screen-film or similar image receptors, use of a pixel size substantially larger than 0.1 mm may result in some loss of diagnostic accuracy. 相似文献
3.
4.
J M Pearl H Laks D C Drinkwater A Meneshian S M Martin M Curzan P A Chang 《The Annals of thoracic surgery》1992,54(6):1144-1150
Blood cardioplegia is considered by many to be the preferred solution for myocardial protection. Proposed benefits include the ability to deliver oxygen and the ability to maintain metabolic substrate stores. However, the decreased capacity of blood to release oxygen at hypothermic conditions as well as the presence of deleterious leukocytes, platelets, and complement may limit complete functional recovery. Fluosol is an asanguineous solution with the ability to bind and release oxygen linearly at low temperatures. Neonatal piglet hearts (24 to 48 hours old) were excised and supported on an isolated, blood-perfused working heart model. After baseline stroke-work index was determined, hearts were arrested with either normocalcemic blood cardioplegia (group 1, n = 8) or normocalcemic Fluosol cardioplegia (group 2, n = 8). Cold cardioplegia was administered at 45 mm Hg every 20 minutes for 2 hours. Hearts were then reperfused with whole blood. Functional recovery, expressed as percent of control stroke-work index, was determined 60 minutes after reperfusion at left atrial pressures of 3, 6, 9, and 12 mm Hg. Functional recovery at 60 minutes was similar between group 1 (95%, 93%, 93%, 88%) and group 2 (100%, 94%, 94%, 95%) at left atrial pressures of 3, 6, 9, and 12 mm Hg, respectively. Mean lactate consumption 5 minutes after reperfusion was significantly greater (p = 0.0001) in group 1 (31.8 +/- 6.3 micrograms.min-1 x g-1) than in group 2 (-0.59 +/- 0.1 microgram.min-1 x g-1), indicating superior metabolic recovery in the blood cardioplegia hearts. Edema formation, as determined both by water content (group 1, 81.10%; group 2, 81.63%) and by electron microscopy, was not significantly different between groups.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
5.
Amenorrheic athletes have been found to have a lower vertebral bone mineral density (BMD) than matched groups of eumenorrheic athletes. This study reports changes in BMD over a 15.5 month period in athletes who regained menses, athletes who remained amenorrheic, and athletes with regular cycles. The BMD was measured at two sites on the radius and at the lumbar vertebrae (L-1 through L-4), using single- and dual-photon densitometry, respectively. Changes in vertebral BMD were significant for the amenorrheic group (+6.3%), but not for cyclic women (-0.3%). A slight increase in radial density at S-1 and S-2 was not significant for either group. Two athletes who remained amenorrheic during this period continued to lose bone (-3.4%). We conclude that resumption of menses was the primary factor for the significant increase in the vertebral BMD of the formerly amenorrheic athletes. 相似文献
6.
Y chromosome microdeletions, in azoospermic or near-azoospermic subjects, are located in the AZFc (DAZ) subregion 总被引:9,自引:2,他引:9
Submicroscopic deletions of the Y chromosome and polymorphisms of the
androgen receptor (AR) gene in the X chromosome have been observed in men
with defective spermatogenesis. To further define the subregions/genes in
the Y chromosome causing male infertility and its relationship to
polymorphisms of the AR polyglutamine tract, we screened the genomic DNA of
202 subfertile males and 101 healthy fertile controls of predominantly
Chinese ethnic origin. Y microdeletions were examined with 16
sequence-tagged site (STS) probes, including the RBM and DAZ genes,
spanning the AZFb and AZFc subregions of Yq11, and related to the size of
trinucleotide repeat encoding the AR polyglutamine tract. Y microdeletions
were detected and confirmed in three out of 44 (6.8%) of azoospermic and
three out of 86 (3.5%) severely oligozoospermic patients. No deletions were
detected in any of the patients with sperm counts of >0.5 x 10(6)/ml,
nor in any of the 101 fertile controls. All six affected patients had
almost contiguous Y microdeletions spanning the entire AZFc region
including the DAZ gene. The AZFb region, containing the RBM1 gene, was
intact in five of the six subjects. Y deletions were not found in those
with long AR polyglutamine tracts. Our study, the first in a Chinese
population, suggest a cause and effect relationship between Y
microdeletions in the AZFc region (possibly DAZ), and azoospermia or
near-azoospermia. Y microdeletions and long AR polyglutamine tracts appear
to be independent contributors to male infertility.
相似文献
7.
Catt SL; Sakkas D; Bizzaro D; Bianchi PG; Maxwell WM; Evans G 《Molecular human reproduction》1997,3(9):821-825
Controlling the sex of offspring by the separation of X and Y
chromosome-bearing spermatozoa using flow cytometry has been reported as a
clinical technique aiding prevention of X-linked diseases. Although this
technique has resulted in several hundred normal births in animals and at
least one human birth, there is still concern over its genetic safety due
to the involvement of two potentially mutagenic agents: UV light and the
fluorochrome dye, Hoechst 33342 (H33342). Human spermatozoa, particularly
those considered abnormal, may be more likely to suffer DNA damage
following exposure to mutagenic agents, compared with other mammalian
species. The stability of normal fresh and decondensed human spermatozoa
were examined after exposure to a range of levels of UV and H33342
staining, using an assay that detects endogenous nicks in the DNA of
spermatozoa. The stability of abnormal and normal, fresh and frozen-thawed
human spermatozoa was examined following UV laser, H33342 staining and flow
cytometry treatments utilizing the same assay. There was an increase in the
presence of endogenous nicks when spermatozoa were decondensed compared
with fresh spermatozoa. There was no increase in the incidence of nicks in
any group of spermatozoa after UV and fluorochrome exposure compared with
controls without exposure.
相似文献
8.
Winberg JO; Hammami-Hauasli N; Nilssen O; Anton-Lamprecht I; Naylor SL; Kerbacher K; Zimmermann M; Krajci P; Gedde-Dahl T Jr; Bruckner-Tuderman L 《Human molecular genetics》1997,6(7):1125-1135
Dystrophic epidermolysis bullosa (EBD) is a clinically heterogeneous skin
disorder, characterized by abnormal anchoring fibrils (AF) and loss of
dermal-epidermal adherence. EBD has been linked to the COL7A1 gene at
chromosome 3p21 which encodes collagen VII, the major component of the AF.
Here we investigated two unrelated EBD families with different clinical
phenotypes and novel combinations of recessive and dominant COL7A1
mutations. Both families shared the same recessive heterozygous 14 bp
deletion at the exon-intron 115 boundary of the COL7A1 gene. The deletion
caused in-frame skipping of exon 115 and the elimination of 29 amino acid
residues from the pro-alpha1(VII) polypeptide chain. As a result,
procollagen VII was not converted to collagen VII and the C-terminal NC-2
propeptide which is normally removed from the procollagen VII prior to
formation of the anchoring fibrils was retained in the skin. All affected
individuals also carried missense mutations in exon 73 of COL7A1 which lead
to different glycine- to-arginine substitutions in the triple-helical
domain of collagen VII. Combination of the deletion mutation with a G2009R
substitution resulted in a mild phenotype. In contrast, combination of the
deletion with a G2043R substitution led to a severe phenotype. The G2043R
substitution was a de novo mutation which alone caused a mild phenotype.
Thus, different combinations of dominant and recessive COL7A1 mutations can
modulate disease activity of EBD and alter the clinical presentation of the
patients.
相似文献
9.
Khai Lai Monica Rencken Barbara L. Drinkwater Charles H. Chesnut III 《Calcified tissue international》1993,53(4):225-228
Summary The purpose of this study was to determine whether bone mineral density (BMD) measurements at the lumbar spine and femoral neck provided comparable information to women planning to use that knowledge to help them make a decision about hormone replacement therapy. Eighty-eight healthy Caucasian women, aged 44–59 and within 0 to 5 years of menopause, participated in the study. BMD measurements were performed at the lumbar spine (L1-L4) and the femoral neck by dual energy X-ray absorptiometry (DXA). Criteria suggested by the National Osteoporosis Foundation were used to categorize women as at risk for osteoporosis, bone density more than one standard deviation (SD) below the young adult mean, or as low risk, bone density at or above this level. The re that 46 women would be classified into the low risk category on the basis of spinal BMD alone. However, 28 of these 46 women would fall into the at risk category when the femoral neck BMD was measured. Sixty-one percent of women informed they were at low risk on the basis of spinal BMD would be considered at risk based on femoral neck BMD. When femoral neck BMD was used as the primary risk indicator, 14% of the women classified as low risk would be at risk if spinal BMD were added. These results suggest that both lumbar spine and proximal femur measurements should be made when women are using bone density measurements as an aid in deciding whether or not to use hormone therapy in their postmenopausal years. 相似文献
10.