Power-law eigenstates of a regular Vicsek fractal with hierarchical interactions.
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Journal Article↗
Biomedical subjects
Z Lin
Publications and source records attributed to Z Lin.
Platelet hyperfunction exists in both acute non-haemorrhagic and haemorrhagic stroke.
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Acute Disease↗
tert.-butyl hydroperoxide-mediated DNA base damage in cultured mammalian cells.
tert.-Butyl hydroperoxide has been utilized to study the effect of oxidative stress on living cells; however, its effect on DNA bases in cells has not been characterized. In the present work, we have investigated DNA base damage in mammalian cells exposed to this organic hydroperoxide. SP2/0 derived murine hybridoma cells were treated with 4 concentrations of tert.-butyl hydroperoxide for varying periods of time. Chromatin was isolated from treated and control cells and subsequently analyzed by gas chromatography-mass spectrometry with selected-ion monitoring for DNA base damage. Quantification of damaged DNA bases was achieved by isotope-dilution mass spectrometry. The amounts of 8 products were significantly higher than control levels in cells treated with tert.-butyl hydroperoxide at a concentration range of 0.01-0.1 mM. At concentrations from 1.0 to 10 mM, product formation was inhibited and the amounts of products were similar to those in control cells. The bimodal nature of the dose-response may be qualitatively analogous to previous reports of bimodal killing of E. coli bacteria by hydrogen peroxide. The nature of the identified DNA base lesions suggests the involvement of the hydroxyl radical in their formation. tert.-Butyl hydroperoxide is known to produce the tert.-butoxyl radical in reactions with metal ions. However, it is unlikely that the tert.-butoxyl radical produces these DNA lesions. It is suggested that DNA base damage arises from tert.-butyl hydroperoxide-mediated oxidative stress in cells, resulting in formation of hydroxyl radicals in close proximity to DNA. The inhibition of product formation at high concentrations of tert.-butyl hydroperoxide may be explained by the scavenging of tert.-butoxyl radical by tert.-butyl hydroperoxide resulting in inhibition of oxidative stress. The plausibility of the scavenging mechanism was evaluated with a mathematical simulation of the dose-response for DNA damage in solutions containing hydrogen peroxide. The simulation model predicted a bimodal dose-response which agreed qualitatively with the results in this study and with other in vivo and in vitro studies reported in the literature.
Animals↗
Thrombospondin 3 is a developmentally regulated heparin binding protein.
The thrombospondins (TSPs) are a growing family of cell surface and extracellular matrix molecules composed of multiple repeating elements. Thrombospondin 3 is a recently described member that possesses the calcium binding Type 3 repeats, has 4 epidermal growth factor receptor-like Type 2 repeats, a complete absence of the complement-like Type 1 repeats, and a distinct N terminus that has no significant homology to the other TSPs. Metabolic labeling and immunoprecipitation analysis of cells transfected with a TSP3 expression vector revealed it to be an oligomeric heparin binding protein present in both the cell layer and medium. Finally, a combination of in situ hybridization and immunocytochemistry demonstrated TSP3 to be expressed in a temporal and spatial manner during murine embryogenesis, especially in the gut, cartilage, lung, and central nervous system.
Amino Acid Sequence↗
Conformational rearrangements required of the V3 loop of HIV-1 gp120 for proteolytic cleavage and infection.
HIV gp120 is specifically cleaved at a single site in the V3 loop between Arg315 and Ala316 by thrombin. Previous observations by others have indicated that binding to CD4 enhances the rate of V3 loop cleavage, and that this cleavage is a prerequisite for HIV infection. Other observations also suggest that the cleavage site is in a type II beta-turn centered at Pro313-Gly314. However, our docking experiments indicate that this conformation cannot dock to thrombin and other trypsin-like serine proteases. Thus, based on the thrombin-bound conformation of peptide substrates, we propose that CD4 binding, at a site remote from the V3 loop, induces and stabilizes a trans to cis isomerization of the highly conserved residue Pro313, and that this conformational shift is a prerequisite for cleavage by a 'thrombin-like' cellular protease and subsequent infection.
Binding Sites↗
Sequential appearance of muscle-specific proteins in myoblasts as a function of time after cell division: evidence for a conserved myoblast differentiation program in skeletal muscle.
Based on the assumption that a conserved differentiation program governs the assembly of sarcomeres in skeletal muscle in a manner analogous to programs for viral capsid assembly, we have defined the temporal and spatial distribution of 10 muscle-specific proteins in mononucleated myoblasts as a function of the time after terminal cell division. Single cells in mitosis were identified in monolayer cultures of embryonic chicken pectoralis, followed for selected time points (0-24 h postmitosis) by video time-lapse microscopy, and then fixed for immunofluorescence staining. For convenience, the myoblasts were termed x-h-old to define their age relative to their mitotic "birthdate." All 6 h myoblasts that emerged in a mitogen-rich medium were desmin+ but only 50% were positive for a alpha-actin, troponin-I, alpha-actinin, MyHC, zeugmatin, titin, or nebulin. By 15 h postmitosis, approximately 80% were positive for all of the above proteins. The up-regulation of these 7 myofibrillar proteins appears to be stochastic, in that many myoblasts were alpha-actinin+ or zeugmatin+ but MyHC- or titin- whereas others were troponin-I+ or MyHC+ but alpha-actinin- or alpha-actin-. In 15-h-old myoblasts, these contractile proteins were organized into nonstriated myofibrils (NSMFs). In contrast to striated myofibrils (SMFs), the NSMFs exhibited variable stoichiometries of the sarcomeric proteins and these were not organized into any consistent pattern. In this phase of maturation, two other changes occurred: (1) the microtubule network was reorganized into parallel bundles, driving the myoblasts into polarized, needle-shaped cells; and (2) the sarcolemma became fusion-competent. A transition from NSMFs to SMFs took place between 15 and 24 h (or later) postmitosis and was correlated with the late appearance of myomesin, and particularly, MyBP-C (C protein). The emergence of one, or a string of approximately 2 mu long sarcomeres, was invariably characterized by the localization of myomesin and MyBP-C to their mature positions in the developing A-bands. The latter group of A-band proteins may be rate-limiting in the assembly program. The great majority of myoblasts stained positively for desmin and myofibrillar proteins prior to, rather than after, fusing to form myotubes. This sequential appearance of muscle-specific proteins in vitro fully recapitulates myofibrillar assembly steps in myoblasts of the myotome and limb bud in vivo, as well as in nonmuscle cells converted to myoblasts by MyoD. We suggest that this cell-autonomous myoblast differentiation program may be blocked at different control points in immortalized myogenic cell lines.
Animals↗
Simple method of purification of Escherichia coli heat-labile enterotoxin and cholera toxin using immobilized galactose.
A simple method for purification of heat-labile enterotoxin produced by enterotoxigenic Escherichia coli and for purification of cholera toxin using immobilized D-galactose column is described. A single run of column chromatography yielded homogeneous toxin as demonstrated by sodium dodecyl sulfate polyacrylamide slab gel electrophoresis.
Bacterial Toxins↗
Specific detection of a verotoxin 2 variant, VT2vp1, by a bead-enzyme-linked immunosorbent assay.
A bead-enzyme-linked immunosorbent assay to specifically detect a Verotoxin 2 variant, VT2vp1, was developed. The sensitivity of the bead-ELISA was 200 pg/ml of the purified VT2vp1 and it did not react with 20 ng/ml of the purified VT2. The specificity of the bead-ELISA was examined with 107 strains of Verocytotoxin-producing Escherichia coli that include VT1-, VT2-, VT2vha-, VT2vhb- and VT2vp1-producing E. coli, and only VT2vp1-producing E. coli that were confirmed by VT2vp1-specific polymerase chain reaction gave positive results. It was noted that all 58 VT2vp1-producing E. coli strains were from pigs, but not from cows and humans.
Animals↗
Identification of a partition region carried by the plasmid QpH1 of Coxiella burnetii.
Coxiella burnetii is an intracellular bacterial pathogen which causes Q fever in humans and other animals. Most of the isolates found carry plasmids which share considerable homology. Unfortunately all of these plasmids remain cryptic. Initial attempts to look for secreted or membrane proteins encoded by these plasmids using TnphoA mutagenesis revealed an open reading frame on the EcoRI-fragment C of the plasmid QpH1. Upstream DNA sequencing of the TnphoA insertions revealed a deduced peptide sequence with homology to the SopA protein which is encoded by the F plasmid in Escherichia coli. Maxicell analysis showed that fragment C encoded two proteins: one was 43.5 kDa in size and designated QsopA, and a second was 38 kDa in size. These proteins are similar in molecular weight to the SopA and SopB proteins, which are essential components of the partition mechanism of the F plasmid. The region appears to be conserved in plasmids QpRS, QpDV, and QpDG, but is absent in a plasmidless isolate in which plasmid sequences have integrated into the chromosomal DNA. Complementation studies demonstrated that fragment C has a plasmid partitioning function and can restore maintenance stability of the partition-defective mini-F plasmid. These data suggest that fragment C carries the plasmid partition region of the plasmid QpH1.
Amino Acid Sequence↗
Interregional migration and interindustry labour mobility in Canada: a simultaneous approach.
"This paper argues that interindustry labour mobility and interregional migration are simultaneously determined processes. It estimates a bivariate probit model of migration and mobility [using data for Canada] and concludes that the interindustry mobility of labour is dominated by the availability of employment hours, and that wage differentials are a statistically significant, but small, determinant of interregional migration.... Since interindustry mobility is much larger in magnitude than interregional migration, quantity constraints in labour markets are of central importance to the adaptive capacity of the economy." (SUMMARY IN FRE)
Americas↗
[A genetic study of adult polycystic kidney disease].
The 3'HVR has been considered as the most useful probe in making the linkage analysis of adult polycystic kidney disease (APKD). We examined three APKD families using this probe. Their polymorphism information was then computed for linkage study using LINKAGE package and computer programme HOMOG for homogeneity test. One family was defined as non PKD 1, because the disease locus was failed to show linkage to the 3'HVR marker. Of the other two families, one can still not be identified as non PKD1, but had distinguishable meiotic recombinations, another was in favour of linkage to 3'HVR and therefore judged to be PKD1. The presence of genetic heterogeneity could significantly reduce the value of linked probe analysis as a tool for gene diagnosis of APKD.
Adolescent↗
Corneal topographic analysis in patients with cataract.
We studied the corneal curvature of 161 eyes in 101 patients, aged from 50 to 80 years (mean: 63 years), with senile cataract using the Topographic Modeling System (TMS) preoperatively. The results revealed that mean surface asymmetry index (SAI) was 0.36 and mean surface regularity index (SRI) 0.79. Simulated keratometry reading (Sim K) was 44.46 D, and 43.56 D. Minimum K reading was 42.60 D. The same patterns of corneal topography in both eyes were 50% in 60 patients who had binocular examination. Astigmatism less than 1 D was 23% in 161 corneas. Corneal patterns included round (21.2%), oval 16.1%), symmetric and asymmetric bow-tie (22.2%), and irregular (40.4%). SRI and SAI of the irregular pattern were statistically higher than those of the round, oval and bow-tie patterns in our patients (P < 0.01 and P < 0.05). The results of our study determined that the cornea of eye with senile cataract preoperatively is not a perfect spherocylinder. It is asymmetrically aspheric, with less curvature peripherally than centrally.
Aged↗
[Mapping of face and extremity skin cleavage lines in Chinese adult cadavers].
On fresh Chinese adult cadavers, which were obtained within 6 hours of sudden death, multiple skin holes of 1 cm apart were made with a conical steel punch of a diameter of 5 mm. Chinese ink was dipped into the wounds, which presently appeared to be rhomboid slits. Mapping of the directions of these rhomboid slits gave rise to cleavage lines of that area. This paper presents the skin cleavage lines of the face and extremities in Chinese adult cadavers.
Adult↗
The clinical analysis of secondary glaucoma following posterior chamber intraocular lens implantation.
We present 14 patients with secondary glaucoma following the implantation of a posterior chamber intraocular lens (IOLs). All patients were unilateral glaucoma, which developed within 1 month following the IOL implantation in 10 cases, and from 1 to 3 years in 4 cases. The angle of anterior chamber was open in 8 patients, and close in 6 ones. Seven patients required treatment of antiglaucomatous medicine; 4 patients underwent laser iridectomy and 3 patients required antiglaucoma surgery. The results showed that the corrected visual acuity was more than 0.5 in 28% of the patients before antiglaucoma treatment and in 50% of the patients after treatment. The main cause of poor vision is glaucomatous optic nerve atrophy. It suggests that it is important to find glaucoma early.
Adolescent↗
[Glucocorticoid cataract and intraocular lens implantation].
13 cases (21 eyes) of patients with glucocorticoid cataract due to topical or systemical administration of dexamethasone or prednisone were reported. The patients comprised 10 men and 3 women, averaging 34 years of age (ranged from 11 to 64 years). Average time of administrating glucocorticoid was 7.1 years (ranged from 6 months to thirty years). The clinical type was posterior subcapsular cataract (PSC). After the treatment of discontinuation of the glucocorticoid drugs, cataract was not improved. 7 cases (11 eyes) of the patients underwent extracapsular cataract extraction and posterior chamber intraocular lens implantation. In 91.1% of the eyes, the postoperative corrected visual acuity achieved 0.5 or better, and 88.9% of the ECCE eyes achieved the same level. There were no significant differences between them. The study shows that posterior chamber intraocular lens implantation is an effective way for glucocorticoid cataract.
Adolescent↗
[Comparison of corneal topography and keratometer in patients with cataract preoperatively and postoperatively].
The comparison of corneal topography with keratometer in 200 patients (278 eyes) was made. The results revealed that Sim K values of corneal topography were 44.22D and 44.26D, mean diopters of keratometer were 44.16D and 44.23D in 150 eyes of 116 patients with cataract preoperatively. There was no significant difference between Sim K values of topography and diopters of keratometer (P > 0.05). The Sim K values of the topography were 46.37D and 43.06D and diopters of keratometer were 46.09D and 42.88D in 90 eyes of 67 patients who received cataract extraction with IOL implantation or second IOL implantation. No significance was found in results between Sim K values and diopters of keratometer in patients postoperatively (P > 0.05). Our investigation demonstrated that Sim K values of corneal topography were in agreements with diopters of keratometer in patients with cataracts preoperatively or postoperatively. However, corneal topography has great values in diagnosis of corneal diseases, traumatic astigmatism, severe non-rule stigmatisms, in which keratometer is often useless.
Adolescent↗
[Repair of soft tissue defects of hand with pudendo-femoral skin flaps].
Soft tissue defects of the hand have been repaired with free pudendo-femoral skin flaps in 13 patients. The results are quite satisfactory in all cases. The flaps are thin with little fat to interfere with post-operative appearance. The donor sites are well-hidden and can be primarily closed with no functional disturbances. Hence the ideal donor site for soft tissue defects of the hand.
Adolescent↗
[Computer assisted studies on the structural requirements for the mutagenicity in Salmonella reversion assay for organophosphorus pesticides].
Computer assisted molecular fragment evaluation (CAMFE) program has been established and applied to the data set analysis of the mutagenicity of 59 organophosphorus pesticides (OPPs) in Salmonella reversion assay. The results favour the hypothesis that the mutagenic properties of OPPs lie in their alkylation to DNA mainly by the molecular fragments containing methyl groups rather than those containing ethyl groups. Oxygen atom in phosphoryl group may prompt the mutagenic ability induced by OPPs; However, the mutagenic ability may be decreased by sulfur atom, the substitute of oxygen atom at the same site in PPs structure. It was suggested that, among the most relevant fragments, the methoxyphosphinyl group appears as the common structural subunit responsible for the activities detected in the Salmonella reversion assay, while the ethyl thionophosphinyl group appears as the descriptor of negative results.
Insecticides↗