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Biomedical subjects

Y Zhou

Publications and source records attributed to Y Zhou.

At least 793 records · Page 44Linked to original sources
PubMed1995

[Swallowing pattern in skeletal Class III malocclusion].

In this research, we compared the swallowing pattern in 33 normal occlusion adults with that in 29 skeletal Class III malocclusion adults, using computerized videofluoscopy. We found that: 1) in skeletal Class III malocclusion patients, the tongue, the hyoid bone and the mandible were in much lower position than those in normal people at postural position. The gap separation between the upper and lower lip was much larger. So was the space between the upper and lower molars. During swallowing, the tongue tip moved upward and backward, and continually moved back along with the backward movement of the tongue dorsum. This was the typical tongue retraction swallowing pattern in Class III malocclusion. The lips kept separation during deglutition, so did the molar region. 2) Abnormal swallowing pattern in skeletal Angle Class III patients was the adaptable change with the dentoalveolar disharmony, while the long time abnormal swallowing could change dentoalveolar structure.

Adolescent↗
PubMed1995

[Effect of cholecystokinin on prolactin release and its action mechanism in the rats].

The effect of cholecystokinin octapeptide (CCK-8) on the release of prolactin (PRL) in male rats were studied in vivo and in vitro. CCK-8 at the concentrations (microgram) of 0.05 and 0.5 was injected into the third cerebral ventricle (3rd, V. I) of conscious rats, outfitted with chronic 3rd. V. and jugular cannulae, a significant increase in resting secretion and restraint stress-induced release of PRL were observed. The effects of CCK-8 at the concentration of 0.05 microgram were stronger than those of 0.5 microgram. To determine if CCK-8 would exert any direct action on anterior pituitary, CCK-8 of 0.05, 0.5, 1.00 microgram were added to the medium of dispersed anterior pituitary cell, and caused dose-dependent increase of PRL secretion. To study a mechanism of intracellular signal transduction in the action of CCK-8, the levels of cAMP and [Ca2+] in the medium were measured. Intracellular Ca2+ concentration of disperse anterior pituitary cell was significantly elevated by CCK-8 (2 x 10(-4) mol/L), but CCK-8 (10(-8)-10(-6) mol/L) did not change intracellular cAMP content. The results indicate that CCK-8 stimulate prolactin release at both sites of hypothalamic and anterior pituitary and the mechanism of stimulating effects of CCK-8 might be mediated by [Ca2+] but not cAMP.

Animals↗
PubMed1994

The novel behaviour of interactions between Ni2+ ion and human or bovine serum albumin.

We discovered a series of novel behaviours of interactions between Ni2+ ion and human or bovine serum albumin. Our results indicated that there exist two closely neighbouring identical prior binding sites in the binding of human or bovine serum albumin with Ni2+ ions, not only one. It is very likely that, after the binding of the first Ni2+ ion, an induced slow conformational transition happens, which leads to the binding of the second Ni2+ ion and shows itself as a hysteretic effect for a process of non-enzymic protein binding with metal ions. As the concentrations of the 1:1 (molar ratio of Ni2+ ion to protein) system increase, an increasing hypochromic effect is observed. Such a hypochromic effect has not been reported previously; however, it is in accord with the mechanism of dipole-dipole interactions between the electric dipole transition moments of chromophores.

Animals↗
PubMed1994

Characterization of the activating region of Escherichia coli catabolite gene activator protein (CAP). I. Saturation and alanine-scanning mutagenesis.

It has been proposed that the surface loop consisting of amino acid residues 152 to 166 of the catabolite gene activator protein (CAP) of Escherichia coli makes direct protein-protein contact with RNA polymerase at the lac promoter. In this work, we have used targeted saturation mutagenesis of codons 152 to 166 of the gene encoding CAP, followed by a screen, to isolate more than 200 independent mutants of CAP defective in transcription activation but not defective in DNA binding. All isolated single-substitution mutants map to just eight amino acid residues; 156, 157, 158, 159, 160, 162, 163 and 164. We propose that these residues define the full extent of the epitope on CAP for the proposed CAP-RNA polymerase interaction. In addition, we have constructed alanine substitutions at each position from residue 152 to 166 of CAP, and we have analyzed the effects on transcription activation at the lac promoter and on DNA binding. Alanine substitution of Thr158 results in an approximately eightfold specific defect in transcription activation. In contrast, alanine substitution of no other residue tested results in a more than twofold specific defect in transcription activation. We conclude that, for Thr158, side-chain atoms beyond C beta are essential for transcription activation at the lac promoter, and we propose that Thr158 OH7 gamma makes direct contact with RNA polymerase in the ternary complex of lac promoter, CAP and RNA polymerase. We conclude further that for no residue other than Thr158 are side-chain atoms beyond C beta essential for transcription activation at the lac promoter.

Alanine↗
PubMed1994

Characterization of the activating region of Escherichia coli catabolite gene activator protein (CAP). II. Role at Class I and class II CAP-dependent promoters.

CAP-dependent promoters can be divided into classes based on the position of the DNA site for CAP. In class I CAP-dependent promoters, the DNA site for CAP is located upstream of the DNA site for polymerase; the DNA site for CAP can be located at various distances from the transcription start point, provided that the DNS site for CAP and the DNA site for RNA polymerase are on the same face of the DNA helix. In class II CAP-dependent promoters, the DNA site for CAP overlaps the DNA site for RNA polymerase, replacing the -35 determinants for binding of RNA polymerase. In previous work, we have shown that a surface loop consisting of amino acid residues 152 to 166 of CAP is essential for transcription activation at the best-characterized class I CAP-dependent promoter, the lac promoter, and we proposed that this surface loop makes direct protein-protein contact with RNA polymerase in the ternary complex of lac promoter, CAP, and RNA polymerase. Here, we show that the surface loop consisting of amino acid residues 152 to 166 is essential for transcription activation at other class I CAP-dependent promoters and at a class II CAP-dependent promoter. We show further that the effects of alanine substitutions of residues 152 to 166 are qualitatively identical at the lac promoter and other class I CAP-dependent promoters, but are different at a class II CAP-dependent promoter. We propose that the surface loop consisting of residues 152 to 166 makes identical molecular interactions in transcription activation at all class I CAP-dependent promoters, irrespective of distance between the DNA site for CAP and the transcription start point, but makes a different set of molecular interactions in transcription activation at class II CAP-dependent promoters.

Alanine↗
PubMed1994

Cloning and expression of the gene encoding the porcine NADPH oxidase light-chain subunit (p22-phox).

In previous studies, we showed that interleukin-4 (IL-4) suppressed porcine (p) macrophage superoxide production and that the mechanism of suppression involved down-regulation of the superoxide-generating enzyme NADPH oxidase heavy-chain 91-kDa subunit mRNA (gp91-phox) expression. In order to examine the effect of IL-4 on expression of the gene encoding the porcine NADPH oxidase light-chain 22-kDa subunit (p22-phox), we cloned the p22-phox cDNA from a macrophage library. The p22-phox cDNA is 786 bp in length and contains a 576-bp open reading frame which predicts a primary translation product of 192 amino acids (aa). Comparison of the porcine and human 22-phox cDNAs showed a high degree of similarity between the two species in their nucleotide (85%) and deduced aa (83%) sequences. as well as in their hydropathy profiles. Notable features, including a high proline content and an iron-coordinating His94, are conserved in both the porcine and human 22-Phox. A single species of mRNA of about 1 kb was detected in macrophages. The mRNA levels remained unchanged in cells treated with lipopolysaccharide (LPS) or with IL-4 at various concentrations from 0-50 ng/ml. Prolonged treatment with LPS or IL-4 did not enhance the effect of these substances on p22-phox mRNA expression. The effect of IL-4 on p22-phox mRNA expression was also compared with another immunosuppressive cytokine, transforming growth factor-beta 1 (TGF beta 1). No change in mRNA expression was found in the cells with or without TGF beta 1 treatment. The results indicated that the heavy and light chains of NADPH oxidase are independently regulated by IL-4 in macrophages.

Amino Acid Sequence↗
PubMed1994

Enhanced tumor cell growth suppression by an N-terminal truncated retinoblastoma protein.

The retinoblastoma (RB) gene encodes a nuclear phosphoprotein of 928 amino acids (pRB). Thus far, much effort in RB research has been focused on both the viral oncoprotein-binding domains and the C-terminal domain, whereas little is known about the N-terminal moiety of the protein. We report here that an N-terminal truncated RB protein of approximately 94 kDa (pRB94) exerts more potent cell growth suppression as compared to the full-length pRB protein in a diversity of tumor cell lines examined, including those having a normal endogenous RB gene. Tumor cells transfected with the pRB94-expressing plasmids displayed multiple morphological changes frequently associated with cellular senescence and/or apoptosis. They failed to enter S phase and rapidly died. The pRB94 expressed in recipient tumor cells had a longer half-life than the full-length pRB protein and tended to remain in an active un- or hypophosphorylated form. Since it has also been found that N-terminal truncated RB proteins often accumulated in growth-arrested and/or differentiated tumor cells, we suggest that N-terminal truncation of pRB may be one of the cellular mechanisms modulating the RB protein function in cell-cycle control.

Animals↗
PubMed1994

The functional subunit of a dimeric transcription activator protein depends on promoter architecture.

In Class I CAP-dependent promoters, the DNA site for CAP is located upstream of the DNA site for RNA polymerase. In Class II CAP-dependent promoters, the DNA site for CAP overlaps the DNA site for RNA polymerase, replacing the -35 site. We have used an 'oriented heterodimers' approach to identify the functional subunit of CAP at two Class I promoters having different distances between the DNA sites for CAP and RNA polymerase [CC(-61.5) and CC(-72.5)] and at one Class II promoter [CC(-41.5)]. Our results indicate that transcription activation at Class I promoters, irrespective of the distance between the DNA sites for CAP and RNA polymerase, requires the activating region of the promoter-proximal subunit of CAP. In striking contrast, our results indicate that transcription activation at Class II promoters requires the activating region of the promoter-distal subunit of CAP.

Bacterial Proteins↗
PubMed1994

Chiral derivatizing reagents for drug enantiomers bearing hydroxyl groups.

This review extensively summarizes and critically evaluates the recent research on the indirect resolution technique for enantiomeric alcohols. Twenty-one chiral derivatizing reagents divided in seven types, including chiral acids, activated acids, chloroformates, isocyanates, carbonyl nitriles, oxazolidin-2-ones and lactones, are described. The derivatization methods of the various chiral reagents, the liquid chromatography separation systems, the detection systems used for the diastereomeric derivatives of alcohols as well as their limitations and the prospects of the indirect resolution technique for the future are thoroughly discussed. This paper aims to instruct the application of a particular chiral reagent and the technical approach to be used and should be beneficial to the development of an indirect resolution method for enantiomeric alcohols as well as to the biomedical investigation of the differences between the antipodes of chiral alcohols.

Alcohols↗
PubMed1994

Purification of recombinant human granulocyte-macrophage colony-stimulating factor from the inclusion bodies produced by transformed Escherichia coli cells.

Recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF), produced as inclusion bodies in genetically transformed Escherichia coli cells was purified to homogeneity by a three-step chromatographic procedure involving hydrophobic interaction, ion exchange and gel filtration. Each purification step is reproducible and well suited for process-scale operations. The purification process also leads to a significant decrease in DNA and endotoxin levels in the final product. Of the three gel media used, Phenyl Sepharose 6 FF (high sub) was most effective in reducing the DNA content (by a factor of ca. 2000) while Superdex 75 prep grade was more effective for removing endotoxins (reduction factor ca. 15). The recovery of purified rhGM-CSF was 35% by enzyme-linked immunosorbent assay and 70% by a biological assay method. The overall purification factor obtained was about 4.6, which is in the range of those reported for recombinant proteins produced in E. coli as inclusion bodies. The purified rhGM-CSF is an acidic protein (pI = 5.4) and has a specific activity of ca. 3.3 x 10(7) units/mg, which is in excellent agreement with that reported for its natural counterpart. Its monomer molecular mass of 14,605, as determined by electrospray mass spectrometry, corresponds exactly to the mass calculated from its cDNA sequence. Its amino acid composition and partial NH2-terminal sequence (up to seventeen residues) are also identical with those reported for this protein. These and other results confirm the identity of the purified rhGM-CSF with its natural counterpart. However, the results also showed that it is apparently heterogeneous from its NH2-terminal side as it is composed of three polypeptides having Met, Ala and Pro as the NH2-terminal residues in which the intact Met analogue accounts for 60% for the mixture. This heterogeneity does not seem to have any biological significance since the specific activity of the purified rhGM-CSF is identical with that of its natural counterpart.

Amino Acid Sequence↗
PubMed1994

Effect of low- and intermediate-purity clotting factor therapy on progression of human immunodeficiency virus infection in congenital clotting disorders. Transfusion Safety Study Group.

Low- and intermediate-purity clotting-factor therapies are believed to accelerate human immunodeficiency virus (HIV) progression in hemophiliacs through adverse immune effects of the other plasma proteins in the preparations. To investigate this postulate, we evaluated data from six clinical centers that observed persons with congenital factor deficiencies at 6-month intervals. The present analysis is based on HIV-infected subjects who received intermediate purity factor VIII or factor IX concentrates, or cryoprecipitate. For long-term outcome, we classified 374 subjects by the type and amount of treatment during our first year of observation, and determined the subsequent rate of progression to a CD4 count less than 200 cells/microL. A second analysis of this group used a repeated-measures, random-effect model that allowed for individual differences in CD4 decline. Finally, we compared short-term rates of change in CD4 count in each treatment interval of 525 subjects with the type and amount of factor therapy received in the same interval. There was no overall or dose-related deleterious effect of any form of treatment on CD4 trend. The CD4 decrease was less when cryoprecipitate was administered alone or combined with concentrate, but not significantly so. Our results counter the assertion that low- and intermediate-purity products accelerate the rate of CD4 decrease in HIV-1-infected hemophiliacs.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Waiting for radiotherapy in Ontario.

PURPOSE: Waiting lists for radiotherapy are a fact of life at many Canadian cancer centers. The purpose of this study was to provide a detailed description of the magnitude of the problem in Ontario. METHODS AND MATERIALS: The interval between diagnosis and initiation of radiation treatment was calculated for all patients receiving primary radiotherapy for carcinoma of the larynx, cervix, lung, and prostate at seven Ontario cancer centers between 1982 and 1991. The interval between surgery and initiation of postoperative radiotherapy for breast cancer was also calculated over the same period. The intervals between diagnosis and referral (t1), between referral and consultation (t2), and between consultation and initiation of radiotherapy (t3), were analyzed separately to determine where delay occurred. RESULTS: Median waiting times between diagnosis and initiation of radical treatment for carcinoma of the larynx, carcinoma of the cervix, nonsmall cell lung cancer, and carcinoma of the prostate were 30.3 days, 27.2 days, 27.3 days, and 93.3 days, respectively. The exceptional interval between diagnosis and treatment of prostate cancer was due to much longer delays between diagnosis and referral. The median waiting time between diagnosis and initiation of postoperative radiotherapy for breast cancer was 61.4 days and the median time between the completion of surgery and initiation of postoperative radiotherapy was 57.8 days. There were significant intercenter variations in median waiting times, but in every situation the median waiting time in Ontario as a whole increased steadily between 1982 and 1991. Median waiting times from diagnosis to the start of curative treatment for laryngeal cancer, cervical cancer, nonsmall cell lung cancer, and prostate cancer increased by 178.7%, 105.6%, 158.3%, and 62.9%, respectively. Waiting time from completion of surgery to initiation of postoperative radiotherapy for breast cancer increased by 102.7%. Most of the increase in treatment delay was found in the interval between consultation and initiation of radiotherapy. CONCLUSIONS: The Committee on Standards of the Canadian Association of Radiation Oncologists recommends that the interval between referral and consultation should not exceed 2 weeks and that the interval between consultation and initiation of radiotherapy should also not exceed 2 weeks. The majority of patients treated in Ontario met both those standards in 1982, but by 1991 few patients received care within the prescribed intervals.

Breast Neoplasms↗
PubMed1994

Imaging with ion beams and laser postionization.

We investigate the use of a liquid metal ion gun (LMIG) combined with multiphoton resonance ionization of sputtered atoms and/or molecules to acquire mass-selected images with submicrometer spatial resolution. Images from several model systems are presented including those of an In grid, and of patterned surfaces of benzo[a]pyrene and tryptophan thin films. Since postionization for these systems yields ionization efficiencies that are considerably higher than those achieved with secondary ion mass spectrometry (SIMS), spatial resolution of 2600 A for molecular species could be achieved while static conditions were maintained. Cooling of the sample to < 210 K was shown to be essential for molecular systems since the number of thermally evaporating molecules overwhelms the number of sputtered molecules at room temperature. Other details necessary to incorporate laser postionization into a time-of-flight SIMS instrument using a pulsed LMIG source are also discussed.

Benzo(a)pyrene↗
PubMed1994

1H NMR and spin-labeled EPR studies on the interaction of calmodulin with jujuboside A.

Jujuboside A (JuA), an effective component of sanzaoren, a Chinese herbal medicine, is a noncompetitive inhibitor of calmodulin (CaM). The interaction of JuA with CaM has been investigated with 1H NMR and spin-labeled EPR spectroscopies. The 1H NMR experiments showed that JuA has two kinds of binding sites on CaM: one locates in the N-terminus, the other locates in the C-terminal region of the polypeptide chain. The EPR studies on 3-maleimido-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl labeled CaM (spin-labeled CaM) revealed that each CaM molecule can bind at least two JuA molecules. Binding of JuA affects the environments of some lysine residues (most likely Lys-74 and Lys-94), suggesting that JuA binds to CaM through hydrophobic interaction.

Amino Acid Sequence↗
PubMed1994

Enzymatic properties of carboxyl-terminally truncated prohormone convertase 1 (PC1/SPC3) and evidence for autocatalytic conversion.

Previous studies have shown that the prohormone convertase 1 (PC1, or SPC3), a member of the new eukaryotic subtilisin-like proteinase family, undergoes a series of proteolytic processing events during its biosynthesis. The first cleavage, of the amino-terminal prosegment, is probably involved in enzyme activation, while the secondary cleavages at the carboxyl terminus are of unknown significance and occur mainly in cells possessing a regulated secretory pathway. In this work, we found that 87-kDa PC1, a homogeneous recombinant protein, could spontaneously convert to 74- and 66-kDa forms in vitro. Limited digestion of 87-kDa PC1 using chymotrypsin and trypsin could also generate 74- and 66-kDa-like PC1s, which were enzymatically active against the fluorogenic peptide carbobenzoxy-Arg-Tyr-Lys-Arg-aminomethylcoumarin. The 74/66-kDa PC1 generated by spontaneous conversion was purified away from the 87-kDa form and enzymatically characterized. Compared to the 87-kDa form, 74/66-kDa PC1 was more active but less stable. In addition, 74/66-kDa PC1 exhibited a narrower pH optimum (between 5.0 and 5.5) and was activated by higher concentrations of calcium. Carboxyl-terminally truncated PC1 also appeared to be more sensitive to certain protease inhibitors than 87-kDa PC1. Taken together, our results suggest that autocatalysis could be involved in carboxyl-terminal cleavages of PC1. These carboxyl-terminal cleavages of PC1 result in alterations in certain PC1 properties and may therefore possess potential significance with respect to prohormone processing.

Amino Acid Sequence↗
PubMed1994

The neuroendocrine polypeptide 7B2 is an endogenous inhibitor of prohormone convertase PC2.

The subtilisin-like prohormone convertase PC2 and the polypeptide 7B2 (an intracellularly cleaved protein of unknown function) are both selectively present in the regulated secretory pathway of neurons and endocrine cells. Here we demonstrate that intact recombinant 7B2 is a potent inhibitor of PC2 and prevents proPC2 cleavage in vitro, whereas the 7B2 cleavage product is virtually inactive. The PC2-related proteinase PC1/PC3 is not inhibited by 7B2. Furthermore, the carboxyl-terminal half of the 7B2 protein sequence is distantly related to the so-called potato inhibitor I family (which includes subtilisin inhibitors). Our findings indicate that 7B2 is a physiological inhibitor of PC2 and may provide alternative avenues for the manipulation of peptide hormone levels.

Amino Acid Sequence↗
PubMed1994

Further characterization of retinoblastoma gene-mediated cell growth and tumor suppression in human cancer cells.

We have transfected the osteosarcoma cell line Saos2 and the bladder carcinoma cell line 5637 with additional retinoblastoma (RB) expression plasmids. The RB-reconstituted Saos2 and 5637 cells showed only slightly lower ratios of cells undergoing DNA synthesis compared to their parental RB- tumor cells, and there were no noticeable changes in cell morphology. Furthermore, we have isolated long-term RB+ clones from Saos2, 5637, and the retinoblastoma cell line WERI-Rb27 after transfection/transduction with a RB expression plasmid or retrovirus. These clones were similar to their parental cell lines in terms of morphology and growth rates, and they all expressed functional RB protein (p110RB) as evidenced by its potential of phosphorylation, simian virus 40 large tumor antigen binding, and nuclear tethering. No mutation or deletion of the exogenous RB gene was detectable by PCR and single-strand conformation polymorphism analysis. In addition, either the individual or pooled RB+ clones did form malignant tumors in nude mice but usually with a longer latency period and lower frequency. Such tumors also retained normal RB expression, suggesting that at least a portion of the RB-reconstituted tumor cells were still tumorigenic. This phenomenon is referred to by us as tumor suppressor resistance (TSR).

Animals↗