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991.
The objective of this work was to characterize tumor cell locomotion in response to chemotactic stimulation using a dual-micropipet assay. The assay involves two micropipets. An individual A2058 human melanoma cell was retained, without pressure gradient, in a pipet of approximately 14 micrometers i.d. A solution of type IV collagen, chosen as the chemotactic source, was placed in another pipet (approximately 10 micrometers o.d.) with zero pressure at the pipet tip. The smaller pipet was then inserted into the larger one containing the melanoma cell. The initial chemoattractant concentration (C0) and the distance between the tip of the small pipet and the cell surface (delta) provided a gradient (C0/delta) for tumor cell locomotion toward stimulation. This novel assay provides a direct measure of cell movement: cyclic pseudopod protrusion (Lp) and subsequent cell locomotion (Lc). The influences of different adhesion substrates on cell locomotion were also studied. The peak length in Lp precedes the highest locomotion velocity (dLc/dt) by an apparent lag time. C0/delta influences pseudopod protrusion frequency (fp) and dLc/dt, but not significantly on Lp. Substrate adhesions affect dLc/dt, but apparently not Lp or fp. In conclusion, pseudopod protrusion and substrate adhesion are two necessary but mutually independent factors in tumor cell locomotion. dLc/dt correlates with changes in C0/delta, which is in significant correlation with fp but not Lp. 相似文献
992.
993.
We have determined the full sequence of the ribosomal DNA intergenic spacer (IGS) of the swimming crab, Charybdis japonica, by long PCR for the first time in crustacean decapods. The IGS is 5376 bp long and contains two nonrepetitive regions separated
by one long repetitive region, which is composed mainly of four subrepeats (subrepeats I, II, III, and IV). Subrepeat I contains
nine copies of a 60-bp repeat unit, in which two similar repeat types (60 bp-a and 60 bp-b) occur alternatively. Subrepeat
II consists of nine successive repeat units with a consensus sequence length of 142 bp. Subrepeat III consists of seven copies
of another 60-bp repeat unit (60 bp-c) whose sequence is complementary to that of subrepeat I. Immediately downstream of subrepeat
III is subrepeat IV, consisting of three copies of a 391-bp repeat unit. Based on comparative analysis among the subrepeats
and repeat units, a possible evolutionary process responsible for the formation of the repetitive region is inferred, which
involves the duplication of a 60-bp subrepeat unit (60 bp-c) as a prototype.
Received: 13 April 1999 / Accepted: 2 August 1999 相似文献
994.
The murine homolog (Mph) of human herpesvirus entry protein B (HveB) mediates entry of pseudorabies virus but not herpes simplex virus types 1 and 2
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A mouse member of the immunoglobulin superfamily, originally designated the murine poliovirus receptor homolog (Mph), was found to be a receptor for the porcine alphaherpesvirus pseudorabies virus (PRV). This mouse protein, designated here murine herpesvirus entry protein B (mHveB), is most similar to one of three related human alphaherpesvirus receptors, the one designated HveB and also known as poliovirus receptor-related protein 2. Hamster cells resistant to PRV entry became susceptible upon expression of a cDNA encoding mHveB. Anti-mHveB antibody and a soluble protein composed of the mHveB ectodomain inhibited mHveB-dependent PRV entry. Expression of mHveB mRNA was detected in a variety of mouse cell lines, but anti-mHveB antibody inhibited PRV infection in only a subset of these cell lines, indicating that mHveB is the principal mediator of PRV entry into some mouse cell types but not others. Coexpression of mHveB with PRV gD, but not herpes simplex virus type 1 (HSV-1) gD, inhibited entry activity, suggesting that PRV gD may interact directly with mHveB as a ligand that can cause interference. By analogy with HSV-1, envelope-associated PRV gD probably also interacts directly with mHveB during viral entry. 相似文献
995.
Ryu JR Jin BS Suh MJ Yoo YS Yoon SH Woo ER Yu YG 《Biochemical and biophysical research communications》1999,265(3):625-629
Peptides derived from gp41 effectively block the gp41-mediated cell fusion or HIV infection. A 36-mer (naDP178), 51-mer (C51) and 27-mer peptide (C27) from the membrane proximal region of gp41 have been examined their interaction modes with the coiled-coil motif of gp41 presented in thioredoxin (Trx-N) or the bacterially expressed ectodomain of gp41 (Ec-gp41ec). All of these peptides effectively inhibited the gp41-mediated membrane fusion, however, they showed distinct interaction modes with Ec-gp41ec or Trx-N. C51 peptide bound tightly to Trx-N, and it increased the solubility of Ec-gp41ec. naDP178 showed very weak binding affinity to Trx-N, however, it effectively solubilized Ec-gp41ec. In contrast, C27 peptide showed significant binding to Trx-N; however, it did not affect the solubility of Ec-gp41ec. These interaction modes of C-peptides were assumed to be related to their different inhibitory mechanism against gp41-mediated cell fusion. 相似文献
996.
997.
Effects of dopamine on the membrane permeability transition, thioredoxin reductase activity, production of free radicals and oxidation of sulfhydryl groups in brain mitochondria and the Ca2+ uptake by Na+-Ca2+ exchange and sulfhydryl oxidation in brain synaptosomes were examined. The brain mitochondrial swelling and the fall of transmembrane potential were altered by pretreatment of dopamine in a dose dependent manner. Depressive effect of dopamine on mitochondrial swelling was reversed by 10 g/ml catalase, and 10 mM DMSO. The activities of thioredoxin reductase in intact or disrupted mitochondria were decreased by dopamine (1-100 M), 25 M Zn2+ and 50 M Mn2+. Dopamine-inhibited enzyme activity was reversed by 10 g/ml SOD and 10 g/ml catalase. Pretreatment of dopamine decreased Ca2+ transport in synaptosomes, which was restored by 10 g/ml SOD and 10 mM DMSO. Dopamine (1-100 M) in the medium containing mitochondria produced superoxide anion and hydrogen peroxide, while its effect on nitrite production was very weak. The oxidation of sulfhydryl groups in mitochondria and synaptosomes were enhanced by dopamine with increasing incubation times. Results suggest that dopamine could modulate membrane permeability in mitochondria and calcium transport at nerve terminals, which may be ascribed to the action of free radicals and the loss of reduced sulfhydryl groups. 相似文献
998.
Lee Gap Ryol Kim Se Nyun Noguchi Kohei Park Sang Dai Hong Seung Hwan Cho-Chung Yoon S. 《Molecular and cellular biochemistry》1999,195(1-2):77-86
Expression of the RI regulatory subunit of protein kinase A type I is increased in human cancer cell lines, in primary tumors, in cells after transformation, and in cells upon stimulation of growth. Ala99 (the pseudophosphorylation site) of human RI was replaced with Ser (RI-p) for the structure-function analysis of RI. MCF-7 hormone- dependent breast cancer cells were transfected with an expression vector for the wild-type RI or mutant RI-p. Overexpression of RI-P resulted in suppression of protein kinase A type II, the isozyme of type I kinase, production of kinase exhibiting reduced cAMP activation, and inhibition of cell growth showing an increase in G0/G1 phase of the cell cycle and apoptosis. The wild-type RI overexpression had no effect on protein kinase A isozyme distribution or cell growth. Overexpression of protein kinase A type II regulatory subunit, RII, suppressed RI and protein kinase A type I and inhibited cell growth. These results show that the growth of hormone-dependent breast cancer cells is dependent on the functional protein kinase A type I. 相似文献
999.
Defective Glucose Transport Across Brain Tissue Barriers: A Newly Recognized Neurological Syndrome 总被引:6,自引:0,他引:6
Klepper J Wang D Fischbarg J Vera JC Jarjour IT O'Driscoll KR De Vivo DC 《Neurochemical research》1999,24(4):587-594
Impaired glucose transport across brain tissue barriers causes infantile seizures, developmental delay and acquired microcephaly. Since the first report in 1991 (De Vivo et al, NEJM, 1991) 17 patients have been identified with the glucose transporter protein syndrome (GTPS). The diagnostic feature of the syndrome is an unexplained hypoglycorrhachia in the clinical setting of an infantile epileptic encephalopathy. We review our clinical experience by highlighting one illustrative case: a 6-year old girl who presented at age 2 months with infantile seizures and hypoglycorrhachia. The CSF/blood glucose ratio was 0.33. DNA sequencing identified a missense mutation in exon 7 (C1108T). Erythrocyte GLUT1 immunoreactivity was normal. The time course of 3-0-methyl-glucose (3OMG) uptake by erythrocytes of the patient was 46% that of mother and father. The apparent Km was similar in all cases (2–4 mmol/L), but the apparent Vmax in the patient was only 28% that of the parents (500 versus 1,766 fmol/s/106RBC; p < 0.004). In addition, a 3-month trial of oral thioctic acid also benefited the patient and increased the Vmax to 935 fmol/s/106 RBC (p < 3 × 10–7). Uptake of dehydroascorbic acid by erythrocytes of the patient was impaired to the same degree as that of 3OMG (Vmax was 38% of that of the mother's), which supports previous observations of GLUT1 being multifunctional. These studies confirm the molecular basis of the GTPS and the multifunctional role of GLUT1. The need for more effective treatment is compelling. 相似文献
1000.