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Biomedical subjects

Z Zhao

Publications and source records attributed to Z Zhao.

At least 127 records · Page 7Linked to original sources
PubMed2000

[Expression of type X collagen in condylar cartilage during mandibular protrusion].

OBJECTIVE: This study was designed to detect type X collagen expression, at both gene and protein levels, in condylar cartilage during mandibular protrusion triggered by functional appliance. METHODS: One hundred SD rats with age of 5 weeks were selected and divided into 5 experimental groups (n = 5) and 5 control groups (n = 5). Animals in experimental groups were imposed with bite-jumping appliances which caused identical magnitude of mandibular protrusion. The animals of experimental groups, together with their matched controls, were sacrificed 3, 7, 14, 21 and 30 days after the appliance insertion. 6 microns sections were cut from TMJ through the sagittal plane. In situ hybridization and immunohistochemical analysis were performed to detect the expression of type X collegen mRNA transcription and its protein synthesis. RESULTS: 1. Intensive staining of type X collegen mRNA was found to distribute within the whole area of hypertrophic zone, a sharp contrast to the control groups which showed very little or no staining. 2. Type X collegen protein synthesis, which was highlighted by immunofluoscent staining, was found to spread over the whole hypertrophic zone, compared to the controls that demonstrated a very little staining. CONCLUSION: Expression of type X collagen in condylar cartilage indicates the onset of endochondral ossification in condyle in response to mandibular protrusion provoked by functional appliances.

Animals↗
PubMed2000

[The analysis of the changes of tongue shape and position, hyoid position in Class II, division 1 malocclusion treated with functional appliances (FR-I)].

OBJECTIVE: The objective of this study is to analyze the changes of tongue shape and position, hyoid position with FR-I therapy in class II, division 1 malocclusion. METHODS: 12 patients with class II, division 1 malocclusion treated with FR-I appliance(8 male, 4 female, average 11 years old) were chosen. The acceptable standard of this experiment was an horizontal growth pattern with normal maxilla, retracted mandible and short lower facial height. The average period of treatment was about 8 months. The assessment was made from a lateral cephalogram taken in habitual occlusion before and after treatment. The shapes and sizes of tongue can be measured from the occlusal films with template. These seven lines from six angles of 30 degrees which can be marked in millimeter. Fig 2 showed the reference points and lines: Is1 (the incisal margin of the lower incisors), Mc (the tip of the distobuccal cusp of the lower fist molar), V(the most caudal point on the shadow of the soft palate or its projection onto the reference line). Is1 connected Mc by a straight line extended to V to form the reference lines. After the lines were constructed, the middle point between Is1 and V was called O, and a perpendicular line was constructed from it to the palate contour. The baseline of the template was coincided with the constructed reference line, and the vertical line intersected the reference line at O. The template was placed over the constructed lines, and the exact measurements of the root, the dorsum and the tip of tongue were taken. This was done along the seven constructed lines, and the measurement gived a relative size of the tongue(e.g. the size related to the oral cavity). RESULTS: After treatment, the shape of tongue changed as a result of the increase of oral cavity. There was a tendency that the position of the tongue shifted forwarded and the tip of tongue lied further forward. At the same time, the position of hyoid moved forward in a horizontal dimension and downward in a vertical dimension. CONCLUSION: It confirms that the therapeutic mechanism of FR-I is to induce an anterior shift of mandible and lead to a forward position of tongue, hyoid and cervical soft tissue, which modify the saggital relationship of jaws. The shape of tongue changes due to the increase of oral cavity.

Child↗
PubMed2000

[The preliminary analysis on the changes of the oral functional space in Class II division 1 malocclusion after triggered by functional appliance].

OBJECTIVE: The purpose of this paper is to study the area changes of the oral functional space in the patients with Angle's Class II division 1 malocclusion after triggered by FR-I functional appliances. METHODS: Twenty patients with Angle's Class II division 1 malocclusion were selected, and the patients were selected by the standards of an horizontal growth pattern with normal maxilla, retracted mandible and short lower facial height. All patients were triggered by FR-I functional appliances and achieved the Angle's Class I occlusion after treatments. The average periods of the treatments were about 9 months. The assessments were made from the lateral cephalograms taken in centric occlusion before and after treatments. The upper and behind borders of the oral functional space are hard palate and soft palate, the forward border is the lingual side of upper and lower incisors, the lower border is the line between apex of lower incisor and lower first molar. The graphics from the lateral cephalogram were painted and input into the computer by scaner, which were measured by special software. Self-controls of individuals before and after treatments were used in statistic analysis. RESULTS: The paired-samples t test confirmed the oral functional space was enlarged after triggered by FR-I functional appliance, which was induced by obviously increased mandibular body and ramus, anterior lower facial height and posterior facial height. At the same time, the angle of Y axis increased and the upper incisor inclined lingually, but the inclining angle of lower incisor was not obvious. CONCLUSION: Enlarged oral functional space facilitates the development of the maxilla, mandible and alveolar bones and consummates the functions of oral and jaw system. This study aids the design and application of FR-I functional appliance.

Adolescent↗
PubMed2000

[The design, functions and clinic applications of lip bumper].

OBJECTIVE: This paper introduced the principle of design, methods of fabrication, indications and functions of lip bumper, and advocated the application of lip bumper in orthodontic clinic. METHODS: Two typical cases treated with lip bumper were introduced. Some notices and experiences of applying lip bumpers were summed up. RESULTS: There were following functions of lip bumper: as a space maintainer, Fränkel effect, headgear effect, post-maxillary expansion retention, derotation of molars, and combined using with headgear. CONCLUSION: The advantages of lip bumper are inclusions of a wide range of indication, wearing for 24 hours per day, easily fabricating and prefabricating, comfortable and hidden for patients.

Child↗
PubMed2000

[Study on the mechanism of pulmonary edema after seawater drowning in rabbit].

To study the mechanism of pulmonary edema after seawater drowning (PE-SWD), the indexes of blood-gas and acid-base in rabbits artery blood were measured by the blood-gas analyser. The activity of Na(+)-K(+)-ATPase, cytochrome oxidase(CYTO) and alkaline phospharase(ALP) in the lungs were measured and analysed by computer image system. C-fos mRNA and Fos protein in the lungs were respectively determined by situ hybrioization and immunohisto chemical techniques. The distribution of phospholipid and Ca2+ of rabbits lungs was quantitatively analysed by ultrastructural location method. The results showed that, five parameters of PaO2, oxygen saturation(SaO2), pH, actual bicarbonite(AB) and base excess(BE) and the activity of Na(+)-K(+)-ATPase and CYTO decreased remarkably in PE-SWD. Both c-fos mRNA and Fos protein expression in pulmonary epithelial cells in PE-SWD were significantly elevated compared with the normal controls(P < 0.01). The phospholipids products in the pulmonary alveolar type II epithelial cells were decreased, however, the Ca2+ precipitate pellets inside the lung capillary endothelial cells and the pulmonary alveolar type I and II epithelial cells increased obviously. The arthors suggest that the injuny action of the seawater, hypoxia and metabolic acidosis may be the mian three mechanisms of the pulmonary edema induced seawater drowning. The lowering activity of Na(+)-K(+)-ATPase and CYTO in the lungs and calcium overload in the cells are not only evil consequence resulted from above three factors, but also the importent causes leading to the worse of PE-SWD. The transmiting line of Ca(2+)-fos may be also a key link to bring about the worse of PE-SWD.

Acidosis↗
PubMed2000

[Nickel cation biosorping studies by yeast with dimethylglyoxime spectrophotometry].

The beer yeast as the biosorbent of Ni2+ is studied. Nickel cation was determined by dimethylglyoxime spectrophotometry. The adsorbed quantity is larger at pH = 6. The equilibrium time was 60 minutes. Salinity and Ca2+, Mg2+ have no significant effect on the biomaterial uptake. Higher the equilibrium concentration(c) is, larger the adsorbed quantity(q) of yeast is. In addition, relations between c and q were fitted with followed equations: 1/q = 0.340 + 0.0753 x 1/c, r = 0.995; lgq = 3.989 + 0.789 lgc, r = 0.995. So we concluded that the models of adsorption are fitted with Langmuir and Freundlich isotherm adsorption equation.

Adsorption↗
PubMed1999

Upregulation of lysyl oxidase in vascular smooth muscle cells by cAMP: role for adenosine receptor activation.

Lysyl oxidase (LO) is a key participant in the accumulation of insoluble fibers of elastin and collagen by virtue of its role in the initiation of the covalent cross-linkages between and within individual molecules comprising these fibers. In view of the essential role played by LO in the accumulation of the fibrotic components of occlusive arterial lesions in atherosclerosis, identification of the signaling molecules which can affect the expression of the LO gene in vascular smooth muscle is of considerable interest. In the present report, we describe evidence for the role of the second messenger, cAMP, in the modulation of the levels of LO in vascular smooth muscle cells. Elevated intracellular cAMP induces the transcription of the LO gene, as revealed by Northern blot analysis and nuclear run on assays. Transient transfection experiments performed with the wild-type LO promoter and with this promoter mutated at a consensus CREB site, located within the region -100 to -93 base pairs relative to the start of transcription, indicate that cAMP-induced transcriptional activation is partially due to the presence of this CREB site within the promoter. Activation of stimulatory adenosine receptors in vascular smooth muscle cells with 5'-N-ethylcarboxamido adenosine (NECA) increases cAMP, LO mRNA, and enzyme activity. These findings point to the importance of cAMP signaling, potentially initiated by a variety of physiological agents, in the upregulation of LO expression in vascular smooth muscle cells.

Adenosine-5'-(N-ethylcarboxamide)↗
PubMed1999

Ectopic purinergic sensitivity develops at sites of chronic nerve constriction injury in rat.

The possibility that ectopic purinergic sensitivity develops following peripheral nerve injury was investigated in chronic constriction injury (CCI). Spontaneous firing of A-fibers originated from the injury site or from sensory endings of afferents in the contralateral sciatic nerve. ATP injected intravenously excited most of the injured fibers whereas none of the contralateral afferents responded to ATP. The ATP-induced effect was blocked by the P2 receptor antagonist reactive blue 2, but not the P1 receptor antagonist aminophylline. Neither the alpha-adrenoreceptor antagonist phentolamine nor the cyclooxygenase inhibitor indomethacin attenuated the ATP-evoked effect. We conclude that a novel ectopic purinergic sensitivity mediated by P2 receptors develops at sites of the CCI of nerves in the rat, which may contribute to neuropathic pain.

Adenosine Triphosphate↗
PubMed1999

Direct cloning of cell differential expression genes with full-length by a new strategy based on the multiple rounds of 'long distance' polymerase chain reaction and magnetic beads mediated subtraction.

The paper described a new cDNA subtractive cloning strategy. This strategy was based on the 'cap-finder' method, 'long distance' polymerase chain reaction (PCR), streptavidin magnetic beads mediated subtraction, and spin column chromatography. When PCR products were resolved on agarose gel after three rounds of subtraction, the 'single gene difference' group displayed a predominantly enriched band, but the 'multiple gene difference' group did not display any apparent difference. Of 200 clones inserted with 0.7-2 kb fragments from the 'multiple gene difference' group, 50% were identified to be new sequences and 35% were known. Of 100 new sequences, 35% contained coding regions and 75% were confirmed by dot-blotting to be differentially expressed by genes of the target cell. The results suggested that this strategy might be very efficient for full-length cloning of differentially expressed genes of the cell.

Cloning, Molecular↗
PubMed1999

Stages in iron storage in the ferritin of Escherichia coli (EcFtnA): analysis of Mössbauer spectra reveals a new intermediate.

Iron uptake into the nonheme ferritin of Escherichia coli (EcFtnA) and its site-directed variants have been investigated by Mössbauer spectroscopy. EcFtnA, like recombinant human H chain ferritin (HuHF), oxidized Fe(II) at a dinuclear ferroxidase center situated at a central position within each subunit. As with HuHF, Mössbauer subspectra observed between 1 min and 24 h after Fe(II) addition were assigned to Fe(III) monomers, "c", mu-oxo-bridged dimers, "b", and clusters, "a", the latter showing magnetically split spectra, "d", at 4.1 K. Like those of HuHF, the mu-oxo-bridged dimers were formed at the ferroxidase centers. However, the analysis also revealed the presence of a new type of dimer, "e" (QS1 = 0.38 mm/s, IS1 = 0.51 mm/s and QS2 = 0.72 mm/s, IS2 = 0.50 mm/s), and this was also assigned to the ferroxidase center. Dimers "b" appeared to be converted to dimers "e" over time. Subspectra "e" became markedly asymmetric at temperatures above 90 K, suggesting that the two Fe(III) atoms of dimers "e" were more weakly coupled than in the mu-oxo-bridged dimers "b", possibly due to OH- bridging. Monomeric Fe(III), giving relaxation spectra "c", was assigned to a unique site C that is near the dinuclear center. In EcFtnA all three iron atoms seemed to be oxidized together. In contrast to HuHF, no Fe(III) clusters were observed 24 h after the aerobic addition of 48 Fe(II) atoms/molecule in wild-type EcFtnA. This implies that iron is more evenly distributed between molecules in the bacterial ferritins, which may account for its greater accessibility.

Alanine↗
PubMed1999

Trinucleotide CGG repeat in the FMR1 gene in Chinese mentally retarded patients.

The fragile X syndrome of mental retardation is related to the number of trinucleotide CGG repeats at the 5'-untranslated region of the FMR1 gene located on the X-chromosome. We have studied X-chromosomes from 649 unaffected Chinese subjects and 324 patients with mild mental retardation. All study subjects were unrelated. The CGG repeat number was analysed by electrophoresis of a polymerase chain reaction followed by gel transfer and hybridisation with a 32P-labeled (CCG)5 probe. The DNA samples having detectable CGG expansion were further analysed by Southern blot analysis with probe StB12.3 after restriction digestion by EcoR I and Eag I. For the unaffected Chinese subjects, a different distribution pattern of CGG allele size from Caucasians was observed. It was a bimodal pattern and the CGG repeat number ranged from 19 to 54. The most common CGG repeat allele was 29 compared with 30 in Caucasians. The second mode appeared at 36 repeats. There was mild statistical difference in the repeat patterns between the mentally retarded patients and unaffected subjects, although the essential features were similar. Among the mentally retarded patients, one male had an unmethylated full mutation and one female had a full mutation. The fragile X prevalence was 0.6%, which is lower than two previous studies in Chinese mentally retarded patients utilising cytogenetic analysis. Our results indicate that a large-scale screening program would be worthwhile to determine the prevalence of the fragile X syndrome in the Chinese population.

China↗
PubMed1999

Characterization of the murine A1 adenosine receptor promoter, potent regulation by GATA-4 and Nkx2.5.

Adenosine acts via A1 adenosine receptors (A1ARs) in the heart and brain to potently influence mammalian physiology. A1ARs are expressed very early in embryonic development, and A1ARs are among the earliest expressed G protein coupled receptors in the heart and brain. To understand the biologic basis of A1AR expression, a genomic fragment containing the murine A1AR promoter was cloned. Reporter assay studies using DDT1 MF2 cells that express A1ARs revealed that 500 base pairs of the proximal A1AR promoter contained essential elements for A1AR gene expression. Transgenic mice with A1AR proximal promoter coupled with the beta-galactosidase reporter gene had heavy labeling of the brain and atria, consistent with normal patterns of A1AR expression. Within the proximal A1AR promoter, putative binding sites for cardiac transcription factors GATA and Nkx2.5 were identified. Co-expression studies revealed that GATA-4 and Nkx2.5 could individually drive A1AR promoter activity and act synergistically to activate A1AR expression. These observations suggest that embryonic A1AR expression involves activation of the A1AR promoter by GATA-4 and Nkx2.5.

Animals↗
PubMed1999

Characterization of the mouse A3 adenosine receptor gene: exon/intron organization and promoter activity.

In a previous study, we reported the expression of A3 adenosine receptor mRNA in rat vascular smooth muscle cells (VSMC) and demonstrated that its levels affect the intracellular concentration of cAMP. In the current study, we isolated the mouse A3 adenosine receptor (A3AR) gene, characterized its structure, and defined its promoter activity in VSMC. The mouse A3AR gene fragment available to us has 3 kb of coding sequences, composed of two exons separated by a single intron, and 2.3 kb of 5' noncoding region. The promoter region lacks "TATA" and "CAAT" boxes, but contains an initiator consensus sequence. In accordance with Northern blot analysis of A3AR mRNA, transient transfection experiments showed that the promoter activity of this fragment was significant in VSMC and astrocytes and high in mast cells. The characterization of the mouse A3 adenosine receptor gene and insight into its promoter region will allow further studies to determine the physiological importance of its transcriptional regulation in different tissues.

Animals↗
PubMed1999

Lack of enhancer function in mammals is unique to oocytes and fertilized eggs.

Previous studies have shown that the lack of novel coactivator activity in mouse oocytes and one-cell embryos (fertilized eggs) renders them incapable of utilizing Gal4:VP16-dependent enhancers (distal elements) but not promoters (proximal elements) in regulating transcription. This coactivator activity first appears in two- to four-cell embryos coincident with the major activation of zygotic gene expression. Here we show that whereas oocytes and fertilized eggs could utilize Sp1-dependent promoters, they could not utilize Sp1-dependent enhancers, although they showed promoter repression, which is a requirement for delineating enhancer function. In contrast, both Sp1-dependent promoters and enhancers were functional in two- to four-cell embryos. Furthermore, the same embryonic stem cell mRNA that provided the coactivator activity for Gal4:VP16-dependent enhancer function also provided Sp1-dependent enhancer function in oocytes. Therefore, the coactivator activity appears to be a requirement for general enhancer function. To determine whether the absence of enhancer function is a unique property of oocytes or a general property of other terminally differentiated cells, transcription was examined in terminally differentiated hNT neurons and their precursors, undifferentiated NT2 stem cells. The results showed that both cell types could utilize enhancers and promoters. Thus, in mammals, the lack of enhancer function appears to be unique to oocytes and fertilized eggs, suggesting that it provides a safeguard against premature activation of genes prior to zygotic gene expression during development.

Animals↗
PubMed1999

Kinetic comparison of the catalytic domains of SHP-1 and SHP-2.

The phosphatase activity of SH2-containing protein tyrosine phosphatase (SHP) is inhibited by its SH2 domains and C-terminal tail. In order to determine the inhibitory effects of the SH2 domains and C-terminal tail, we have expressed and purified the catalytic domains of SHP-1 and SHP-2, and the SH2 domain truncated SHP-1 and SHP-2. We have then measured their kinetic parameters using p-nitrophenyl phosphate (p-NPP) and phosphotyrosine (pY) as substrates under the same experimental conditions. The results indicate that the pH-dependent profiles of SHP-1 and SHP-2 are mainly determined by their catalytic domains. Both enzymes have maximum activity at pH 5.0. In addition, the phosphatase activity of different forms of SHP-1 and SHP-2 decreases as the salt concentration increases. Without SH2 domains, both SHP-1 and SHP-2 are no longer inhibited by their C-terminal tails. However, the C-terminal tail of SHP-1 can further prevent the salt inhibition of the phosphatase activity. Under the same experimental conditions, the catalytic domain of SHP-1 is two times more active than the catalytic domain of SHP-2.

Binding Sites↗
PubMed1999

Collision-induced dissociation of protonated MK-0991: novel ring opening of a cyclic hexapeptide in the gas phase.

Electrospray ionization tandem mass spectrometry was applied to probe the collision-induced dissociation (CID) of protonated MK-0991 {(4R,5S)-5-[(2-aminoethyl)amino]-N(2)-(10, 12-dimethyl-1-oxotetradecyl)-4-hydroxy-L-ornithyl-L-threonyl-trans -4- hydroxy-L-prolyl-(S)-4-hydroxy-(4-hydroxyphenyl)-L-threonyl-threo-3-h ydroxy-L-or-nithyl-trans-3-hydroxy-L-proline cyclic (6-1)-peptide} in the gas phase; MK-0991 is a newly developed, broad-spectrum pneumocandin antifungal drug. The study showed that protonated MK-0991 (m/z 1094) undergoes specific ring opening under the CID conditions to form two protonated linear peptides at m/z 1076 and 1034. This is different from the commonly observed ring opening of a cyclic peptide that occurs by the cleavage of the N-acyl bonds in many places on the peptide backbone. The structures of the two linear peptides were elucidated on the basis of their tandem mass spectra. The results strongly indicate that the specific ring opening of MK-0991 is affected by the ethylenediamine side-chain formed from the modification of one of the ornithine amino acids in this cyclic hexapeptide.

Anti-Bacterial Agents↗
PubMed1999

Level of sustained entorhinal activity at study correlates with subsequent cued-recall performance: a functional magnetic resonance imaging study with high acquisition rate.

Functional magnetic resonance imaging (fMRI) with high acquisition rate was performed during the intentional memorizing of words to specify which medial temporal lobe structure is important in determining what words are subsequently remembered in a cued-recall test and to characterize the time course of activation in that structure. Functional images of six healthy young subjects were analyzed by two subject- and voxel-wise statistics: First, to identify brain areas transiently engaged in encoding of words, brain activity during memorizing visually presented words and watching a fixation cross was compared by a Kolmogorov-Smirnov statistic (KS-test). Second, to identify brain areas whose activity correlates with memory encoding success, a Kendall's correlation was calculated between signal intensity at study and performance in a subsequent cued-recall test. Averaged signal intensities were plotted as a function of time to depict the time course of brain activity detected by both statistical tests. The level of slowly modulated, sustained activity in Brodmann area 28 (entorhinal cortex) did not respond transiently as study words appeared, but did correlate positively with subsequent test performance. More left than right activity in Brodmann area 45 (dorso-lateral prefrontal cortex) and bilateral activity in Brodmann area 44 (premotor cortex) exhibited transient hemodynamic responses that did not show any relation to subsequent memory performance. Thus, the study identified a novel pattern of slowly modulated brain activity in human entorhinal cortex that may represent a declarative memory encoding state whose level predicts whether experiences will be remembered or forgotten.

Adult↗