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Biomedical subjects

H Zhao

Publications and source records attributed to H Zhao.

At least 541 records · Page 30Linked to original sources
PubMed1994

[The diagnosis and surgical treatment of Leriches syndrome: an analysis of 16 cases].

The authors report 16 cases of atherosclerotic obliteration of the terminal abdominal aorta seen in the period of 1987-1991. Early diagnosis can be made by using color doppler, and angiography and DSA are very important to determinate the clinical patterns and occlusive locations. A/B Index is also valuable in the diagnosis and treatment. Clinically, it should be differentiated from orthopedic, neurologic and urologic diseases, surgical procedure varies with occlusive location, clinical patterns, general status, and conditions of the affected blood vessels. Follow-up found that Y type aorto-femoral bypass get the best result with one-year unobstructed rate of 100% in all cases, and five-year cumulative unobstructed rate of 75%. The outcome of auxiliary-femoral bypass grafts were the least satisfactory, with the five-year cumulative unobstructed rate of only 34%. Comprehensive therapy should be adopted to improve the long-term cumulative unobstructed rate.

Adult↗
PubMed1994

Application of internal fixation in the treatment for tuberculosis of the spine.

This is a study of 18 patients who had surgical treatment for spinal tuberculosis. All patients were admitted with the spinal tuberculosis and treated with a combination of anterior debridement and bone graft with posterior internal fixation using the Luque or Dick technique. The patients were able to walk within a few days postoperation. Three to seven years follow-ups show no recurrence, kyphosis and/or solid fusion.

Adolescent↗
PubMed1994

Radiofrequency current catheter ablation of the left atrioventricular accessory pathways with paroxysmal supraventricular tachycardia.

Seventy patients with left atrioventricular accessory pathways and paroxysmal supraventricular tachycardia (PSVT) underwent radiofrequency catheter ablation (RFCA). The success rate was 94.3%. Among these patients, 26 had manifest preexcitation syndrome, and 44 had concealed preexcitation. Eighteen patients with concealed preexcitation underwent coronary sinus (CS) pacing, and delta wave appeared in 15. The keys to successful RFCA were correct positioning of the radiofrequency (RF) catheter tip, A/V amplitude ratio, AV interval (in sinus rhythm) and VA interval (during SVT or ventricular pacing). After 1-14 months of follow-up, two patients had supraventricular tachycardia (SVT) recurrence.

Adolescent↗
PubMed1994

On the analysis of the pathophysiology of Chediak-Higashi syndrome. Defects expressed by cultured melanocytes.

BACKGROUND: The Chediak-Higashi syndrome (CHS) is a disorder that affects the synthesis and/or maintenance of storage/secretory granules in various types of cells. Lysosomes of leukocytes and fibroblasts, dense bodies of platelets, azurophilic granules of neutrophils and melanosomes of melanocytes are generally larger in size and irregular in morphology, indicating that a common pathway in storage organellogenesis is affected in patients with CHS. EXPERIMENTAL DESIGN: A pure line of melanocytes has been established using a 2 cm2 shave biopsy from a child with CHS. This 4-week-old male patient had oculocutaneous albinism and expressed neutropenia, impaired platelet function, and no natural killer cell activity. The cultured CHS melanocytes were analyzed for cell biological and biochemical aberrancies. RESULTS: Cultured melanocytes demonstrated some large and/or complexed melanosomes that resembled those observed in melanocytes from ultrastructural sections of the biopsy. Cytoplasmic localization of tyrosinase, tyrosinase-related protein-1 and granulophysin (a 40 kilodalton membrane protein originally identified as a component in dense bodies of platelets) demonstrated a prominent perinuclear accumulation. The basal synthesis of melanin and the activity levels of tyrosine hydroxylase, dihydroxyphenylalanine (DOPA) oxidase, or DOPAchrome tautomerase were comparable to control Caucasian melanocytes in culture. However, melanin synthesis as well as the catalytic activities of tyrosinase were not dramatically upregulated in CHS melanocytes by the addition of isobutyl methylxanthine and cholera toxin in the growth medium when parameters were assayed in cell lysates. In contrast, when assays were performed using live cells, tyrosine hydroxylase demonstrated dramatic upregulation. Medium conditioned by CHS melanocytes demonstrated phenylthiourea-inhibitable tyrosinase activity. Melanocyte lysates and conditioned medium analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and DOPA staining showed an extra, approximately 100 kilodalton soluble protein band with DOPA positivity and tyrosinase immunoreactivity. In addition to tyrosinase, one of three lysosomal enzymes assayed (beta-glucuronidase) was aberrantly secreted into the medium. CONCLUSIONS: These results demonstrate that melanocytes cultured from CHS express a defect in the structure and/or function of the melanosome and abnormal trafficking of some cellular proteins.

Cell Line↗
PubMed1993

Evolution of an enzyme activity: crystallographic structure at 2-A resolution of cephalosporinase from the ampC gene of Enterobacter cloacae P99 and comparison with a class A penicillinase.

The structure of the class C ampC beta-lactamase (cephalosporinase) from Enterobacter cloacae strain P99 has been established by x-ray crystallography to 2-A resolution and compared to a class A beta-lactamase (penicillinase) structure. The binding site for beta-lactam (penicillinase) structure. The binding site for beta-lactam antibiotics is generally more open than that in penicillinases, in agreement with the ability of the class C beta-lactamases to better bind third-generation cephalosporins. Four corresponding catalytic residues (Ser-64/70, Lys-67/73, Lys-315/234, and Tyr-150/Ser-130 in class C/A) lie in equivalent positions within 0.4 A. Significant differences in positions and accessibilities of Arg-349/244 may explain the inability of clavulanate-type inhibitors to effectively inactivate the class C beta-lactamases. Glu-166, required for deacylation of the beta-lactamoyl intermediate in class A penicillinases, has no counterpart in this cephalosporinase; the nearest candidate, Asp-217, is 10 A from the reactive Ser-64. A comparison of overall tertiary folding shows that the cephalosporinase, more than the penicillinase, is broadly similar to the ancestral beta-lactam-inhibited enzymes of bacterial cell wall synthesis. On this basis, it is proposed that the cephalosporinase is the older of the two beta-lactamases, and, therefore, that a local refolding in the active site, rather than a simple point mutation, was required for the primordial class C beta-lactamase to evolve to the class A beta-lactamase having an improved ability to catalyze the deacylation step of beta-lactam hydrolysis.

Binding Sites↗
PubMed1993

Gap junction communication modulates [Ca2+]i oscillations and enzyme secretion in pancreatic acini.

Global (all cells in an acinus) and focal (1-2 out of 10-15 cells) stimulation of pancreatic acini with bombesin or t-butyloxycarbonyl-Tyr(SO3)-Nle-Gly-Tyr-Asp-2-phenylethyl ester (CCKJ) together with modulation of gap junction (GJ) permeability by octanol and NO2- was used to study the role of GJ permeability in controlling [Ca2+]i oscillations and enzyme secretion. GJ permeability was quantitated by measuring fluorescence recovery after photobleaching. Octanol at 0.5 mM markedly reduced, whereas 15 mM NO2- increased GJ permeability. Focal application of bombesin caused synchronized oscillations in the entire acinus, whereas global stimulation resulted in asynchronous oscillations. Increasing GJ permeability with NO2- had no effect on bombesin-evoked [Ca2+]i oscillations. Octanol inhibited ongoing oscillations evoked by focal or global bombesin stimulation. However, when GJ were blocked prior to stimulation, subsequent global stimulation with bombesin induced long-lasting oscillations in all cells. Re-establishing GJ communication for as little as 37.5 s conferred GJ dependence on the order and time of [Ca2+]i spiking evoked by global bombesin stimulation. Focal and global stimulation with CCKJ gave different patterns of [Ca2+]i oscillations. However, in contrast to bombesin, inhibition of GJ with octanol had no effect on oscillations induced by global CCKJ stimulation. Increasing GJ permeability with NO2- synchronized CCKJ-stimulated oscillations by equalizing the amplitude and increasing the frequency in all cells within an acinus. These observations suggest that amplitude and frequency of [Ca2+]i oscillations can be regulated independently of each other, and that GJ permeable molecules modulate the frequency of [Ca2]i oscillation in an agonist-specific manner. Regardless of the agonist, increasing the frequency of oscillations by modulation of GJ permeability correlated with an increased enzyme secretion.

Animals↗
PubMed1993

A novel programed frameshift expresses the POL3 gene of retrotransposon Ty3 of yeast: frameshifting without tRNA slippage.

Most retroviruses and retrotransposons express their pol gene as a translational fusion to the upstream gag gene, often involving translational frameshifting. We describe here an unusual translational frameshift event occurring between the GAG3 and POL3 genes of the retrotransposon Ty3 of yeast. A +1 frameshift occurs within the sequence GCG AGU U (shown as codons of GAG3), encoding alanine-valine (GCG A GUU). Unlike other programed translational frameshifts described, this event does not require tRNA slippage between cognate or near-cognate codons in the mRNA. Two features distal to the GCG codon stimulate frameshifting. The low availability of the tRNA specific for the "hungry" serine codon, AGU, induces a translational pause required for frameshifting. A sequence of 12 nt distal to the AGU codon (termed the Ty3 "context") also stimulates the event.

Amino Acid Sequence↗
PubMed1993

Ca(2+)-dependent kinase and phosphatase control inositol 1,4,5-trisphosphate-mediated Ca2+ release. Modification by agonist stimulation.

A permeable cell system in which Ca2+ release can be evoked by inositol 1,4,5-trisphosphate (IP3) or agonist stimulation was used to study the regulation of Ca2+ release by Ca2+ itself. At low concentrations, Ca2+ activated IP3-mediated Ca2+ release (IMCR) with half-maximal effect at about 15 nM. At high concentrations, Ca2+ inhibited IMCR giving rise to a biphasic [Ca2+] dependence of IMCR. The activation of IMCR by Ca2+ appears to be mediated by a kinase, probably the Ca(2+)-and calmodulin-dependent protein kinase (CaMKII). Thus, the activation required MgATP, completely blocked at 0 degrees C, required Ca2+, and was inhibited by the CaMKII inhibitors KT5926 and KN62. The inhibition of IMCR seems to be mediated by a protein phosphatase, probably the Ca(2+)-dependent protein phosphatase 2B. Hence, the inhibition required Ca2+, was prevented by the general protein phosphatase inhibitor pyrophosphate and by the immunosuppressants cyclosporin A and FK506, but not by okadaic acid or VO4(2-), and was modified by chelating agents such as EGTA. Stimulation with agonists modified the activities of the kinase and phosphatase to make the release independent of [Ca2+]. This appears to be due to an increase in the apparent affinity for Ca2+ in stimulating IMCR and inhibition of the phosphatase. We suggest that agonist-dependent modification of the kinase/phosphatase activity ratio can be the biochemical pathway responsible for regulation of Ca2+ release and in turn [Ca2+]i oscillations.

Adenosine Triphosphate↗
PubMed1993

Relative binding free energy calculations of DNA to daunomycin and its 13-dihydro analogue.

We present the results of thermodynamic integration/molecular dynamics on the 13-dihydrodaunomycin.d(CGTACG) complex and 13-dihydrodaunomycin in vacuo based on the GROMOS force field. The objective is to calculate the binding free energy differences between two complexes--13-dihydrodaunomycin.d(CGTACG) and daunomycin.d(CGTACG). The results are in agreement with the experimental data, i.e. the theoretical binding free energy difference of 13-dihydrodaunomycin.d(CGTACG) and daunomycin.d(CGTACG) is 2.1 +/- 1.6 kcal/mol which accords well with the experimental value of 0.6 kcal/mol. The free energy contributions of different interactions and different groups have also been analysed.

DNA↗
PubMed1993

Predictors of assistive technology abandonment.

Technology abandonment may have serious repercussions for individuals with disabilities and for society. The purpose of this study was to determine how technology users decide to accept or reject assistive devices. Two hundred twenty-seven adults with various disabilities responded to a survey on device selection, acquisition, performance, and use. Results showed that 29.3% of all devices were completely abandoned. Mobility aids were more frequently abandoned than other categories of devices, and abandonment rates were highest during the first year and after 5 years of use. Four factors were significantly related to abandonment--lack of consideration of user opinion in selection, easy device procurement, poor device performance, and change in user needs or priorities. These findings suggest that technology-related policies and services need to emphasize consumer involvement and long-term needs of consumers to reduce device abandonment and enhance consumer satisfaction.

Adult↗
PubMed1993

Assignment of fatty acid-beta-oxidizing syntrophic bacteria to Syntrophomonadaceae fam. nov. on the basis of 16S rRNA sequence analyses.

After enrichment from Chinese rural anaerobic digestor sludge, anaerobic, sporing and nonsporing, saturated fatty acid-beta-oxidizing syntrophic bacteria were isolated as cocultures with H2- and formate-utilizing Methanospirillum hungatei or Desulfovibrio sp. strain G-11. The syntrophs degraded C4 to C8 saturated fatty acids, including isobutyrate and 2-methylbutyrate. They were adapted to grow on crotonate and were isolated as pure cultures. The crotonate-grown pure cultures alone did not grow on butyrate in either the presence or the absence of some common electron acceptors. However, when they were reconstituted with M. hungatei, growth on butyrate again occurred. In contrast, crotonate-grown Clostridium kluyveri and Clostridium sticklandii, as well as Clostridium sporogenes, failed to grow on butyrate when these organisms were cocultured with M. hungatei. The crotonate-grown pure subcultures of the syntrophs described above were subjected to 16S rRNA sequence analysis. Several previously documented fatty acid-beta-oxidizing syntrophs grown in pure cultures with crotonate were also subjected to comparative sequence analyses. The sequence analyses revealed that the new sporing and nonsporing isolates and other syntrophs that we sequenced, which had either gram-negative or gram-positive cell wall ultrastructure, all belonged to the phylogenetically gram-positive phylum. They were not closely related to any of the previously known subdivisions in the gram-positive phylum with which they were compared, but were closely related to each other, forming a new subdivision in the phylum. We recommend that this group be designated Syntrophomonadaceae fam. nov.; a description is given.

Bacteria, Anaerobic↗
PubMed1993

Smyth chicken melanocyte autoantibodies: cross-species recognition, in vivo binding, and plasma membrane reactivity of the antiserum.

Smyth line (SL) chickens, which develop a depigmenting disorder similar to human vitiligo, produce circulating anti-melanocyte antibodies (Austin, L.M. et al., (1992) The detection of melanocyte autoantibodies in the Smyth chicken model for vitiligo. Clin. Immunol. Immunopathol., 64:112-120). In order to characterize these autoantibodies, we studied the reactivity of cultured chicken, mouse, and human melanocytes, as well as frozen sections of chicken feather follicles and embryonic eyes, against SL serum, employing indirect immunofluorescence. Light Brown Leghorn (LBL) serum was used as a negative control. Chicken (SL and LBL), mouse, and human melanocytes exhibited greater fluorescence with SL serum than with LBL serum (up to a 1:60,000 dilution). The fluorescent pattern was predominant along the perimeter of the cells, suggesting plasma membrane staining. Fluorescence-activated flow cytometry analysis and immunocytochemical localization at the ultrastructural level using intact chicken cells supported this hypothesis. Melanocytes were readily stained in cryosections of regenerating feather follicles and embryonic eyes incubated with SL, but not LBL, serum. In addition, amelanotic melanocytes in albino chicken feathers reacted with SL serum. SL serum also preferentially stained cells emigrating from cultured avian neural tubes and within the dermis of the proliferative germ of regenerating feather follicles suggesting that melanoblasts express the antigens. We conclude that Smyth line serum contains melanocyte autoantibodies that cross-react with mouse and human melanocytes, are able to bind to pigment cells within tissues, and recognize antigens expressed in the cytoplasm and on the surface of melanocytes and melanoblasts.

Animals↗
PubMed1993

Three downstream sites repress transcription of a Ty2 retrotransposon in Saccharomyces cerevisiae.

Transcription of Ty1 and Ty2 retrotransposons of the yeast Saccharomyces cerevisiae is modulated by multiple downstream regulatory sites. Both transposon families include a positively acting site within the transcribed region which resembles a higher eukaryotic enhancer. We have demonstrated the existence of a repression site distal to the enhancer of the Ty2-917 element. Here we describe experiments investigating the internal structure of this site. We show that this 200-bp region includes three distinct repression sites which we term DRSI (downstream repression site I), DRSII, and DRSIII. Individually each site causes almost twofold repression, and together the sites repress eightfold. Unexpectedly, when the entire region encompassing the DRS sites is moved outside the transcription unit, it acts as a qualitatively positively acting element. In this context the DRS sites still repress transcription, since eliminating them increases transcription further. That the region can activate transcription implies that it includes activation sites in addition to the three repression sites. The change from qualitatively negatively acting to positively acting must reflect a change in the relative effects of the multiple positive and negative sites; when moved outside the transcription unit, the activators predominate. Importantly, DRSII and DRSIII repress transcription autonomously when inserted upstream of a heterologous promoter activated by the transcriptional activator GCN4, showing that they are indeed transcriptional repression sites.

Base Sequence↗
PubMed1993

Contribution of melanogenic proteins to the heterogeneous pigmentation of human melanocytes.

Human melanocytes from individuals with different skin types, as well as from the skin of the same individual, are heterogeneous in their melanin content. This heterogeneity may be attributed to differences in the activity and expression of the three melanogenic proteins: tyrosinase and tyrosinase-related proteins 1 and 2 (gp75 and DOPAchrome tautomerase, respectively), which in turn are affected by certain regulatory factors. Established melanocyte strains that exhibited intrinsic melanogenic heterogeneity could be separated into subpopulations according to density and melanin content by Percoll density gradient centrifugation. The least melanotic subpopulation consisted of melanocytes that contained an active tyrosinase enzyme and a low amount of melanin. Tyrosinase activity and the quantities of tyrosinase enzyme, tyrosinase-related protein-1 and DOPAchrome tautomerase gradually increased with increased melanin content and Percoll density of the isolated melanocyte subpopulations. We have found a direct correlation between melanin content, tyrosinase activity and the expression of the three melanogenic proteins in melanocyte strains established from different skin types. Addition of the two epidermal cytokines, tumor necrosis factor-alpha or interleukin-1 alpha, to cultures of human melanocytes from different skin types caused decreased proliferation, tyrosinase activity and expression of tyrosinase, tyrosinase-related protein-1 and DOPAchrome tautomerase. Similar results were obtained when Percoll-derived melanocyte subpopulations were treated with tumor necrosis factor-alpha and interleukin-1 alpha. These results indicate that the variation in melanin content in human melanocytes is due to differences in the activity and expression of the melanogenic proteins, which are influenced by autocrine and paracrine factors.

Cell Separation↗
PubMed1993

Alteration of crystallin polypeptides in rat lenses during the development of galactose-induced cataract.

Some striking differences in relative polypeptide abundance of crystallins were observed in normal and galactose-induced cataractous lenses of rat by means of SDS-PAGE. In the cataractous lenses a prominent band appeared at about 25 kDa and the aA chain increased markedly, whereas the relative amount of the 31 kDa band decreased substantially. These alterations are similar to the changes observed during the incubation of young mouse lenses in glucose-free medium.

Animals↗
PubMed1993

[Antigen analysis of McAb E4B7D5 directed against outer envelope of Leptospira interrogans serovar lai by SDS-PAGE and immunoblot].

McAb E4B7D5 was prepared by hybridoma technology in BALB/c mice immunized to outer envelope of Leptospira interrogans serovar lai. This McAb agglutinated specifically with all the 13 serovars of Icterohaemorrhagiae serogroup in MAT test at high titres and protected the guinea pigs against the attack of virulent strain (017) of serovar lai. SDS-PAGE and immunoblot were used to analyse the reaction of the outer envelopes of the five strains of Leptospira (Leptospira interrogans Icterohaemorrhagiae serogroup, serovar lai, 017 and 601 stains; L. interrogans Hebdomadis serogroup, hebdomadis serovar strain 156; L. interrogans Australis serogroup australis serovar strain 620; biflexa leptospira patoc serovar strain Patoc I; with McAb E4B7D5. Results indicated that this McAb E4B7D5 recognized specifically 34.5 kd and 39.5 kd outer envelope proteins of serovar lai, strain 017 and 601, so it might be an immunoprotective McAb directed against Leptospira interrogans serovar lai. It was suggested that 34.5 kd and 39.5 kd outer envelope proteins of serovar lai recognized specifically by McAb E4B7D5 might be immunoprotective antigens.

Animals↗