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991.
992.
Tomasek JJ Gabbiani G Hinz B Chaponnier C Brown RA 《Nature reviews. Molecular cell biology》2002,3(5):349-363
During the past 20 years, it has become generally accepted that the modulation of fibroblastic cells towards the myofibroblastic phenotype, with acquisition of specialized contractile features, is essential for connective-tissue remodelling during normal and pathological wound healing. Yet the myofibroblast still remains one of the most enigmatic of cells, not least owing to its transient appearance in association with connective-tissue injury and to the difficulties in establishing its role in the production of tissue contracture. It is clear that our understanding of the myofibroblast its origins, functions and molecular regulation will have a profound influence on the future effectiveness not only of tissue engineering but also of regenerative medicine generally. 相似文献
993.
Gritsenko OM Koudan EV Mikhailov SN Ermolinsky BS Van Aerschot A Herdewijn P Gromova ES 《Nucleosides, nucleotides & nucleic acids》2002,21(11-12):753-764
Affinity modification of EcoRII DNA methyltransferase (M x EcoRII) by DNA duplexes containing oxidized 2'-O-beta-D-ribofuranosylcytidine (Crib*) or 1-(beta-D-galactopyranosyl)thymine (Tgal*) residues was performed. Cross-linking yields do not change irrespective of whether active Crib* replaces an outer or an inner (target) deoxycytidine within the EcoRII recognition site. Chemical hydrolysis of M x EcoRII in the covalent cross-linked complex with the Tgal*-substituted DNA indicates the region Gly268-Met391 of the methylase that is likely to interact with the DNA sugar-phosphate backbone. Both specific and non-specific DNA interact with the same M x EcoRII region. Our results support the theoretically predicted DNA binding region of M x EcoRII. 相似文献
994.
Miyamoto T Iwasaki H Reizis B Ye M Graf T Weissman IL Akashi K 《Developmental cell》2002,3(1):137-147
We demonstrate here that "promiscuous" expression of myeloid or lymphoid genes precedes lineage commitment in hematopoiesis. Prospectively purified single common myeloid progenitors (CMPs) coexpress myelo-erythroid but not lymphoid genes, whereas single common lymphoid progenitors (CLPs) coexpress T and B lymphoid but not myeloid genes. Genes unrelated to the adopted lineage are downregulated in bipotent and monopotent descendants of CMPs and CLPs. Promiscuous gene expression does not alter the biological potential of multipotent progenitors: CMPs with an activated endogenous M lysozyme locus yield normal proportions of myelo-erythroid colonies, and CLPs expressing the pre-T cell receptor alpha gene differentiate into normal numbers of B cells. Thus, the accessibility for multiple myeloid or lymphoid programs promiscuously may allow flexibility in fate commitments at these multipotent stages. 相似文献
995.
A. Ben-Amotz Shaul Yatziv Mordechai Sela Simon Greenberg Boris Rachmilevich Masha Shwarzman Ze'ev Weshler 《Radiation and environmental biophysics》1998,37(3):187-193
Attempts were made to evaluate 709 children (324 boys and 385 girls) who had been exposed long-term to different doses of
radiation during and after the Chernobyl accident and had moved to Israel between 1990 and 1994. Upon arrival, all of them
underwent a check-up for most common clinical disorders and were then divided into three groups according to their residences
(distance from the reactor) and the level of irradiation exposure: no radiation, <5 Ci/m2, and >5 Ci/m2, respectively. Blood serum analyses for total carotenoids, retinol, α-tocopherol and oxidized conjugated dienes in 262 of the children showed increased HPLC levels of conjugated dienes, indicating
increased levels of oxidation of in vivo blood lipids in children from the contaminated areas. The levels were higher in girls
than in boys. Some 57 boys and 42 girls were given a basal diet with a diurnal supplementation of 40 mg natural 9-cis and all-trans equal isomer mixture β-carotene in a capsulated powder form of the alga Dunaliella bardawil, for a period of 3 months. Blood serum analyses were regularly conducted before supplementation to determine the baseline
effect of radiation exposure to the children, after 1 and 3 months of natural β-carotene supplementation. After supplementation, the levels of the oxidized conjugated dienes decreased in the children's
sera without any significant changes in the level of total carotenoids, retinol or α-tocopherol. Other common blood biochemicals were within the normal range for all tests and no statistical differences before
or after supplementation of β-carotene were noted. High pressure liquid chromatography (HPLC) analyses for carotenoids in the blood detected mainly oxycarotenoids,
and to a lesser extent, all-trans β-carotene, α-carotene, but not 9-cis β-carotene. The results suggest that irradiation increases the susceptibility of lipids to oxidation in the Chernobyl children
and that natural β-carotene may act as an in vivo lipophilic antioxidant or radioprotector.
Received: 20 March 1998 / Accepted in revised form: 1 August 1998 相似文献
996.
997.
Elena I. Deryugina Boris Ratnikov Edward Monosov Tanya I. Postnova Richard DiScipio Jeffrey W. Smith Alex Y. Strongin 《Experimental cell research》2001,263(2):209
We evaluated cellular mechanisms involved in the activation pathway of matrix prometalloproteinase-2 (pro-MMP-2), an enzyme implicated in the malignant progression of many tumor types. Membrane type-1 matrix metalloproteinase (MT1-MMP) cleaves the N-terminal prodomain of pro-MMP-2 thus generating the activation intermediate that then matures into the fully active enzyme of MMP-2. Our results provide evidence on how a collaboration between MT1-MMP and integrin αvβ3 promotes more efficient activation and specific, transient docking of the activation intermediate and, further, the mature, active enzyme of MMP-2 at discrete regions of cells. We show that coexpression of MT1-MMP and integrin αvβ3 in MCF7 breast carcinoma cells specifically enhances in trans autocatalytic maturation of MMP-2. The association of MMP-2′s C-terminal hemopexin-like domain with those molecules of integrin αvβ3 which are proximal to MT1-MMP facilitates MMP-2 maturation. Vitronectin, a specific ligand of integrin αvβ3, competitively blocked the integrin-dependent maturation of MMP-2. Immunofluorescence and immunoprecipitation studies supported clustering of MT1-MMP and integrin αvβ3 at discrete regions of the cell surface. Evidently, the identified mechanisms appear to be instrumental to clustering active MMP-2 directly at the invadopodia and invasive front of αvβ3-expressing cells or in their close vicinity, thereby accelerating tumor cell locomotion. 相似文献
998.
Irina V. Solovei Boris I. Joffe Tetsua Hori Philippa Thomson Shigeki Mizuno Herbert C. Macgregor 《Chromosoma》1998,107(3):184-188
The arrangement of chromosomes in the elongated sperm nuclei of chicken was studied using fluorescence in situ hybridization
with probes specific for telomeres of all chromosomes, a microchromosome, the long arm of chromosome 6, the large heterochromatic
block on the Z-chromosome, and the same heterochromatic block plus subtelomeric sites on macrochromosomes 1–4. The positions
of all probes vary from one sperm to another. No order in chromosome arrangement is apparent. It is suggested that large chromosome
size and small chromosome number correlate with constant positions of chromosomes and vice versa. Based on the known quantity
of repetitive units of the repeat on the Z-chromosome, the degree of compaction of chromatin in the chicken sperm nucleus
is estimated as ca 0.7 Mb/μm. As judged from the length of the heterochromatic region of the Z-chromosome at the lampbrush
stage, the total length of the Z-chromosome in mature sperm is 2.5–4 times that of the sperm nucleus.
Received: 15 December 1997; in revised form: 24 March 1998 / Accepted: 14 April 1998 相似文献
999.
The nervous system of three species of the Temnocephalida has been studied using the GAIF method (which in small flatworms mostly reveals sensory catecholaminergic neurons). These species represent the evolution from the primitive “turbellarian-like” temnocephalids to the most specialised ones with tentacles and a sucker. The numbers and positions of GAIF-positive neurons are invariant within each species and do not change from hatching to full maturity. A characteristic unpaired neuron contributing to the innervation of the anterior margin of the body is present in all species: such a cell has previously been found only in marine Thalassovortex tyrrhenicus (Dalyellidae) which confirms close relationships between these taxa. Our series of species shows (i) a reduction in number of GAIF-positive perikarya associated with the lateral cords and reduction of GAIF-positive innervation on the ventral side of the body, which is probably related to the loss of ciliary locomotion (the shift to passive hunting and looping locomotion) and (ii) reinforcement of the GAIF-positive innervation of the anterior end of the body which begins to play an important role in capturing the prey. The retention of the medial unpaired neuron and nearly identical sets of GAIF-positive neurons in Diceratocephala boschmai and Craspedella pedum (rather different in morphology) give the first indication (in the Plathelminthes) of persistence of homologous neurons through significant evolutionary transformations of the organs they innervate. 相似文献
1000.
Boris M. Hogema Jos C. Arents Rechien Bader Kevin Eijkemans Hiromi Yoshida Hideyuki Takahashi Hiroji Aiba & Pieter W. Postma 《Molecular microbiology》1998,30(3):487-498
The main mechanism causing catabolite repression in Escherichia coli is the dephosphorylation of enzyme IIAGlc , one of the enzymes of the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS). The PTS is involved in the uptake of a large number of carbohydrates that are phosphorylated during transport, phosphoenolpyruvate (PEP) being the phosphoryl donor. Dephosphorylation of enzyme IIAGlc causes inhibition of uptake of a number of non-PTS carbon sources, a process called inducer exclusion. In this paper, we show that dephosphorylation of enzyme IIAGlc is not only caused by the transport of PTS carbohydrates, as has always been thought, and that an additional mechanism causing dephosphorylation exists. Direct monitoring of the phosphorylation state of enzyme IIAGlc also showed that many carbohydrates that are not transported by the PTS caused dephosphorylation during growth. In the case of glucose 6-phosphate, it was shown that transport and the first metabolic step are not involved in the dephosphorylation of enzyme IIAGlc , but that later steps in the glycolysis are essential. Evidence is provided that the [PEP]–[pyruvate] ratio, the driving force for the phosphorylation of the PTS proteins, determines the phosphorylation state of enzyme IIAGlc . The implications of these new findings for our view on catabolite repression and inducer exclusion are discussed. 相似文献