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排序方式: 共有771条查询结果,搜索用时 15 毫秒
71.
Müller SP Bartels I Stein W Emons G Gutensohn K Köhler M Legler TJ 《Transfusion》2008,48(11):2292-2301
BACKGROUND: Noninvasive fetal RHD genotyping might become a valuable tool in decision making on antenatal Rh prophylaxis, which is currently in routine practice for all D? pregnancies in several countries. This study provides a large‐scale validation study of this technology to address questions concerning feasibility and applicability of its introduction into clinical routine. STUDY DESIGN AND METHODS: Real‐time polymerase chain reaction (PCR) targeting RHD Exons 5 and 7 was applied for the detection of fetal‐specific RHD sequences in maternal plasma. A total of 1113 women in 6 to 32 weeks (median, Week 25) of pregnancy were recruited. All of them were serologically typed as D? according to current German guidelines. DNA was extracted via a spin‐column method and a novel automated approach using magnetic tips. Real‐time PCR results were compared with postnatal serology and discrepancies further elucidated by DNA sequencing from a newborn's buccal swab. RESULTS: Sensitivities of fetal RHD genotyping were 99.7 percent (spin columns) and 99.8 percent (magnetic tips), thus comparable with serology (99.5%). The detection of weak D variants was more reliable by real‐time PCR. Specificities of fetal RHD genotyping were 99.2 percent (spin columns) and 98.1 percent (magnetic tips), which is lower than serology (>99.7%). Automation achieved significantly higher yields of cell‐free fetal DNA. CONCLUSION: This prospective clinical trial revealed that routine determination of the fetal D status from maternal plasma is feasible. Noninvasive fetal RHD genotyping can be considered as sensitive as the traditional postnatal serologic assay. 相似文献
72.
Visual identification of bacterially contaminated red cells 总被引:1,自引:0,他引:1
There have been increasing numbers of reports of transfusion-acquired Yersinia enterocolitica bacteremia (including several fatal cases). Fifteen units of whole blood were inoculated with various concentrations of Y. enterocolitica serotype 0:3 and processed into AS-3 preserved red cells (RBCs). Consistent growth of the organism was found at inoculum concentrations greater than or equal to 10 colony-forming units per mL. In all 13 units of RBCs that supported the growth of Y. enterocolitica, a darkening in color (due to hemolysis and a decrease in pO2) was observed in the bag. The attached sample segments, which were sealed from the main unit, remained sterile and did not darken. This color change was apparent in all the contaminated units by Day 35, which was 1.5 to 2 weeks after the bacteria were first detected in cultures of the blood. Hence, by comparison of the color of the segment tubing with that of the unit itself, units grossly contaminated with Y. enterocolitica can be identified prior to transfusion. Moreover, review of photographs on file at the Centers for Disease Control revealed this dramatic color change in 2 units of blood that caused transfusion-transmitted sepsis (Enterobacter agglomerans and an unidentified gram-negative bacillus, not Yersinia sp.), which demonstrated that the color change was not limited to Y. enterocolitica. This method of visual identification of contaminated units of blood could decrease the incidence of posttransfusion bacterial sepsis. 相似文献
73.
Effects of cholinergic modulation on responses of neocortical neurons to fluctuating input 总被引:1,自引:0,他引:1
Neocortical neurons in vivo are spontaneously active and intracellular
recordings have revealed strongly fluctuating membrane potentials arising
from the irregular arrival of excitatory and inhibitory synaptic
potentials. In addition to these rapid fluctuations, more slowly varying
influences from diffuse activation of neuromodulatory systems alter the
excitability of cortical neurons by modulating a variety of potassium
conductances. In particular, acetylcholine, which effects learning and
memory, reduces the slow alterhyperpolarization, which contributes to spike
frequency adaptation. We used whole-cell patch-clamp recordings of
pyramidal neurons in neocortical slices and computational simulations to
show, first, that when fluctuating inputs were added to a constant current
pulse, spike frequency adaptation was reduced as the amplitude of the
fluctuations was increased. High- frequency, high-amplitude fluctuating
inputs that resembled in vivo conditions exhibited only weak spike
frequency adaptation. Second, bath application of carbachol, a cholinergic
agonist, significantly increased the firing rate in response to a
fluctuating input but minimally displaced the spike times by < 3 ms,
comparable to the spike jitter observed when a visual stimulus is repeated
under in vivo conditions. These results suggest that cholinergic modulation
may preserve information encoded in precise spike timing, but not in
interspike intervals, and that cholinergic mechanisms other than those
involving adaptation may contribute significantly to cholinergic modulation
of learning and memory.
相似文献
74.
P. K. Sibley J. Legler D. G. Dixon D. R. Barton 《Archives of environmental contamination and toxicology》1997,32(3):274-284
In this study, we assessed the acute and chronic toxicity
of sediments contaminated by bleached kraft pulp mill effluent (BKME).
Sediments were collected in August 1991 and 1992, and May 1993 from eight
stations exposed directly to the effluent and from four reference sites.
Acute toxicity was determined for five macroinvertebrates (Hyalella
azteca, Daphnia magna, Chironomus riparius, Hexagenia spp., and
Tubifex tubifex) using pore water, elutriate, and bulk sediment
exposures. Chronic toxicity was assessed using C. tentans and H.
azteca (growth and survival) and D. magna and T. tubifex
(reproduction) in bulk sediment exposures. Mortality declined with decreasing
proximity to the outfall; acute toxicity (>20% mortality after 48 h)
was observed at the two stations closest to the outfall (300 and 400 m). At
300 m, pore water was consistently more toxic than elutriate or bulk sediment
phases, resulting in 100% mortality for all invertebrates except
T. tubifex (23%). Elutriate exposures were toxic to C.
riparius (88%), D. magna (54%), and
Hexagenia (47%), but not H. azteca. Bulk sediments
were toxic to Hexagenia (100%) and D. magna
(88%), but not to C. riparius or H. azteca. In chronic
tests, mortality in H. azteca and T. tubifex was highest at
300 and 400 m, indicating that toxicity observed in the short-term aqueous
exposures adequately predicted long-term toxicity in bulk sediments. In both
acute and chronic tests, mortality was significantly correlated with the
concentration of extractable organic chlorines (EOCl) in the sediment, with
LC50 values ranging from 4500 to 5500 mg EOCl/kg organic carbon. Growth of
C. tentans larvae was depressed at 300 and 400 m in August 91 but
enhanced in May 93 relative to the reference sites. Growth of H.
azteca also declined near the outfall in August 91 sediments and was
approximately one half that observed in 92/93 sediments; however, growth did
not differ among stations in 92 or 93. Reproductive output in D.
magna (neonates) and T. tubifex (cocoons) was highest at 300 and
400 m. In T. tubifex, the number of hatched young was lowest at these
stations. This study provides evidence that toxicity may occur in sediments
exposed to BKME, and emphasizes the need to incorporate sediment toxicity
bioassessment as part of efforts directed toward remedial action in the pulp
and paper industry.
Received: 28 May 1996/Revised: 17 September 1996 相似文献
75.
76.
77.
78.
T.J. Legler J.H. Maas V. Blaschke M. Malekan H. Ohto R. Lynen N. Bustami D.W.M. Schwartz W.R. Mayr M. Kohler S. Panzer 《Transfusion》1998,38(5):434-440
BACKGROUND: Weak D phenotypes involve a quantitative variation of D. The genomic basis in weak D has been disputed, however. STUDY DESIGN AND METHODS: Five sequence-specific polymerase chain reactions (SSP- PCRs) on exons 2, 5, and 7 of the RHD gene were evaluated in 248 white and 98 Japanese blood donors and compared with the results obtained by amplification of intron 4 and serology. All methods and SSP-PCR testing on the 3′ non-coding region of the RHD gene were applied to the genotyping of 94 DNA samples derived from individuals expressing weak D phenotypes. RESULTS: Concordant results were obtained with all genotyping and phenotyping methods in testing 201 D-positive and 145 D- negative donors. Four of 94 weak D samples were typed as D-negative by amplification of intron 4 and SSP-PCR on exon 5. Phenotyping with monoclonal antibodies revealed a DVI category in one of these cases and DFR phenotype in three of these cases. One weak D sample, which reacted like normal D-positive cells with all applied monoclonal antibodies, was typed falsely negative by SSP-PCR on exon 5 because of a point mutation at nucleotide 667 (T–>G) that resulted in a Phe223Val amino acid substitution. In this individual, heterozygosity was found at two other amino acid positions (Glu233Gln and Val238Met) by restriction fragment length polymorphism analysis. CONCLUSION: Genetic diversity in weak D phenotypes is rare. Only 1 of 90 true weak D phenotypes (1.1%) had a genetic variation in testing on seven gene regions of the RHD gene. 相似文献
79.
Ross AA; Cooper BW; Lazarus HM; Mackay W; Moss TJ; Ciobanu N; Tallman MS; Kennedy MJ; Davidson NE; Sweet D 《Blood》1993,82(9):2605-2610
Although peripheral blood stem cell collections (PBSC) are thought to have less tumor involvement than bone marrow (BM), the incidence of circulating tumor cells in patients with breast cancer has not been widely investigated. We prospectively investigated the incidence and viability of tumor cell involvement in PBSC and BM collections from breast cancer patients undergoing high-dose chemotherapy/hematopoietic stem cell transplantation. Paired samples of PBSC and BM from 48 patients were analyzed using an immunocytochemical technique that detects one epithelial-derived tumor cell per 5 x 10(5) mononuclear cells. Immunostained tumor cells were detected in 9.8% (13/133) PBSC specimens from 9/48 (18.7%) patients and in 62.3% (38/61) BM specimens from 32/48 (66.7%) patients, a significantly higher rate than in PBSC (P < .005). The geometric mean concentration of tumor cells in contaminated PBSC specimens was 0.8/10(5) mononuclear cells (range 0.33 to 2.0/10(5)) compared with 22.9/10(5) mononuclear cells in BM (range 1 to 3,000/10(5), P < .0001). In culture experiments, clonogenic tumor colonies grew in 21/26 immunocytochemically positive specimens. No tumor colony growth was detected in 30/32 immunocytochemically negative specimens. Immunocytochemical detection of tumor involvement in BM and PBSC correlated significantly with in vitro clonogenic growth (P < .0001). We conclude that PBSC contain fewer tumor cells than paired BM specimens from patients with advanced breast cancer and that these tumor cells appear to be capable of clonogenic growth in vitro. 相似文献
80.
Invasion of erythrocytes by Plasmodium falciparum malaria parasites: evidence for receptor heterogeneity and two receptors 总被引:19,自引:0,他引:19
Plasmodium falciparum malaria parasites with different capabilities of invading sialic acid-deficient erythrocytes were identified. Thai-2 parasites cultured in Tn erythrocytes invaded neuraminidase-treated and Tn erythrocytes twice as efficiently as Thai-2 parasites cultured in normal erythrocytes and seven to ten times more efficiently than a cloned line of Camp parasites cultured in normal erythrocytes. All three parasite lines required sialic acid for optimal invasion, but Thai-2 parasites cultured in Tn erythrocytes invaded neuraminidase- treated erythrocytes with 45% efficiency whereas Camp parasites invaded neuraminidase-treated erythrocytes with less than 10% efficiency. P falciparum malaria parasites probably possess two receptors: one that binds to a sialic acid-dependent ligand and another that binds to a sialic acid-independent ligand. Parasites may differ in the quantity or affinity of their receptors for the sialic acid-independent ligand. 相似文献