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Studies of proteins that inhibit tissue factor activity have generally been conducted using either an extracted tissue homogenate ("thromboplastin") or tissue factor protein reconstituted into phospholipid vesicles rather than with tissue factor expressed in cell membranes (its physiological environment). In the present study, a human fibroblast cell strain was used to evaluate the effects of lipoprotein associated coagulation inhibitor (LACI), placental anticoagulant protein (PAP), and apolipoprotein A-II (apo A-II) on human tissue factor in cell membranes. LACI was tested from 7.8 to 500 pmol/L on fibroblasts cultured at cell densities ranging from 3,500 to 9,925 cells/well, and caused a progressive inhibition of tissue factor activity. PAP was tested from 3.9 nmol/L to 1 mumol/L at cell densities ranging from 4,500 to 15,400 cells/well and caused up to 83% inhibition of tissue factor activity. Inhibition by these proteins appeared to be influenced by cell density as well as whether the cells were intact or disrupted. Apo A-II, up to 1 mumol/L, did not inhibit the tissue factor activity of intact or disrupted fibroblasts at any cell density examined even though it did inhibit the activity of tissue factor in phospholipid vesicles. Of these inhibitors of tissue factor-dependent activation of factor X, LACI was the most effective in suppressing the generation of factor Xa activity. The effects obtained with apo A-II are clearly dependent on the nature of the tissue factor preparation with which it is tested. The disparity between the inhibitory effect of apo A-II on the activity of tissue factor reconstituted into lipid vesicles and the absence of effect on the activity of tissue factor remaining in cell membranes serves to reemphasize the necessity of reexamining results obtained with model systems using as nearly physiological reagents as possible. 相似文献
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Myosin VIIA gene: heterogeneity of the mutations responsible for Usher syndrome type IB 总被引:8,自引:1,他引:8
Levy G; Levi-Acobas F; Blanchard S; Gerber S; Larget-Piet D; Chenal V; Liu XZ; Newton V; Steel KP; Brown SD; Munnich A; Kaplan J; Petit C; Weil D 《Human molecular genetics》1997,6(1):111-116
Usher syndrome is recognized as the most frequent cause of hereditary
deaf-blindness. Usher syndrome type I (USH1), the most severe form of the
disease, is characterized by profound congenital sensorineural deafness,
constant vestibular dysfunction, and retinitis pigmentosa of prepubertal
onset. This form is genetically heterogeneous and five loci (USH1A-E) have
been mapped thusfar. However, only the gene responsible for USH1 B (which
accounts for approximately 75% of USH1 cases) has been characterized. It
encodes a long-tailed unconventional myosin, myosin VIIA, with a predicted
2215 amino acid sequence. Primers covering the complete myosin VIIA coding
sequence as well as the 3' non coding sequence were designed, allowing
direct sequence analysis of each of the 48 coding exons and flanking splice
sites in seven patients affected by USH1. Four novel mutations were thereby
identified. The possibility should now be considered of a sequence-based
prenatal diagnosis in some of the families affected by this very severe
form of Usher syndrome.
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Evolutionary silencing of the human elastase I gene (ELA1) 总被引:6,自引:0,他引:6
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Amare Kadam PS Ghule P Jose J Bamne M Kurkure P Banavali S Sarin R Advani S 《Cancer Genetics and Cytogenetics》2004,150(1):33-43
Although retinoblastoma (Rb) is initiated as a result of biallelic inactivation of the RB1 gene, additional genetic events (M3) in tumor cells are indicative of their role in the full transformation of retinal cells. We investigated the constitutional genetic instability by fragile site (FS) expression studies and checked its relationship with loci of tumor cytogenetics in a series of 36 retinoblastoma patients (34 nonfamilial and 2 familial cases). Tumor cytogenetics revealed -13/+13, del/t(13)(q14) (50%), +1/del/t(1p/q) (65%), +6/i(6p) (60%), and del(16)(q13)/(q22 approximately q23) (60%). Conventional cytogenetics in leukocytes revealed constitutional del(13q14) in five unilateral Rb (URB) and one trilateral Rb (TRB). Constitutional del(16)(q22) and t(6;12) were also identified in two cases. Constitutional FS analysis showed a significant increase in the cellular fragility, with high prevalence at 13q14, 3p14, 6p23, 16q22 approximately q23, and 13q22 loci in retinoblastoma patients (P<0.05). Patients with constitutional del(13)(q14) demonstrated higher fragility than those with normal constitution. A strong correlation between loci of constitutional FSs and loci of recurrent chromosomal abnormalities in tumors strengthen and support the proposal that FS loci present as inherent genomic instability in retinoblastoma. The chromosomal changes and resultant genetic mutations, along with RB1 mutation events, probably contribute synergistically to the development and progression of Rb malignancy. Implementation of fluorescence in situ hybridization to nonfamilial Rb on a large scale (113 cases) could detect constitutional RB1 deletion in 12.3% of cases, with equally higher incidence in URB (14.7%) and bilateral Rb (13.6%), demonstrating that the true prevalence of patients with predisposition to RB1 mutation in sporadic URB is definitely higher in our populations. Also, higher incidence of constitutional RB1 deletion mosaicism in unilateral than in bilateral Rb indicates that the constitutional genetic mosaicism in URB should be given serious consideration during genetic counseling. 相似文献