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Biomedical subjects

Y Zhao

Publications and source records attributed to Y Zhao.

At least 163 records · Page 9Linked to original sources
PubMed2001

Dynamic contact forces on leukocyte microvilli and their penetration of the endothelial glycocalyx.

We develop a theoretical model to examine the combined effect of gravity and microvillus length heterogeneity on tip contact force (F(m)(z)) during free rolling in vitro, including the initiation of L-, P-, and E-selectin tethers and the threshold behavior at low shear. F (m)(z) grows nonlinearly with shear. At shear stress of 1 dyn/cm(2), F(m)(z) is one to two orders of magnitude greater than the 0.1 pN force for gravitational settling without flow. At shear stresses > 0.2 dyn/cm(2) only the longest microvilli contact the substrate; hence at the shear threshold (0.4 dyn/cm(2) for L-selectin), only 5% of microvilli can initiate tethering interaction. The characteristic time for tip contact is surprisingly short, typically 0.1-1 ms. This model is then applied in vivo to explore the free-rolling interaction of leukocyte microvilli with endothelial glycocalyx and the necessary conditions for glycocalyx penetration to initiate cell rolling. The model predicts that for arteriolar capillaries even the longest microvilli cannot initiate rolling, except in regions of low shear or flow reversal. In postcapillary venules, where shear stress is approximately 2 dyn/cm(2), tethering interactions are highly likely, provided that there are some relatively long microvilli. Once tethering is initiated, rolling tends to ensue because F(m)(z) and contact duration will both increase substantially to facilitate glycocalyx penetration by the shorter microvilli.

Animals↗
PubMed2001

Expression of matrix metalloproteinase (MMP-1) and tissue inhibitor of MMP in serosal tissue of intraperitoneal organs and adhesions.

OBJECTIVE: To compare expression of matrix metalloproteinase (MMP-1) and tissue inhibitor of MMP (TIMP-1) in serosal tissue of intraperitoneal organs and adhesions. DESIGN: Prospective and cross-sectional study. SETTING: Academic research centers. PATIENT(S): Patients undergoing abdominal or pelvic surgery. INTERVENTION(S): MMP-1 and TIMP-1 expression. MAIN OUTCOME MEASURE(S): Expression of messenger ribonucleic acid (mRNA) and protein was measured by using quantitative reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay. RESULT(S): Serosal tissue of intraperitoneal organs and adhesions express MMP-1 and TIMP-1 mRNA and protein at levels that are consistently varied with 10- to 10,000-fold and 2- to 10-fold higher TIMP, mRNA and protein, respectively. Parietal peritoneum, fallopian tubes and ovaries express higher MMP-1 mRNA levels compared with uterus and adhesions; the lowest expression is found in small and large bowels, subcutaneous tissue. and omentum. Expression of TIMP-1 mRNA was less variable; the highest level was found in the uterus and the lowest in subcutaneous tissue and small bowels. There was less variability in MMP-1 and TIMP-1 protein content than mRNA expression; ovaries and adhesions contained the highest MMP-1 and TIMP-1 levels, respectively, and peritoneum contained the lowest. The MMP-1 and TIMP-1 content and ratios further indicate limited MMP-1 proteolytic activity. Although tissues from premenopausal women express more MMP-1 and TIMP-1, expression did not differ by sex or age. CONCLUSION(S): Because MMP-1 and TIMP-1 expression varies consistently among the serosal tissues of peritoneal organs and adhesions, and because tissue injury alters their expression, site-specific variations in expression of these substances may predispose a particular organ to develop more adhesions.

Abdomen↗
PubMed2001

Learning impairments and motor dysfunctions in adult Lhx5-deficient mice displaying hippocampal disorganization.

Lhx5 is a member of the LIM homeobox gene family that regulates development of the nervous system. Adult mice generated with a mutation in Lhx5 were found to display absent or disorganized hippocampal neuroanatomy. The pyramidal cell layer in Ammon's horn and the granule cell layer in the dentate gyrus were absent or poorly defined in the hippocampus of adult Lhx5 knockout mice. Behavioral phenotyping of Lhx5 null mutants detected deficits on learning and memory tasks, including the Barnes maze spatial learning task, spontaneous alternation recognition memory, and contextual and cued fear conditioning. General health, neurological reflexes, and sensory abilities appeared to be normal in Lhx5 knockout mice. Motor tests showed impaired performance on some measures of motor activity, coordination, balance, and gait. These results reveal functional outcomes of Lhx5 gene deletion on the integrity of hippocampal neuroanatomy and behavior in the adult mouse.

Animals↗
PubMed2001

Prevention of brick tea fluorosis in rats with low-fluoride brick tea on laboratory observation.

To test whether low-fluoride brick tea can prevent the occurrence of fluorosis, rats had access only to a specially prepared low-fluoride brick tea for 1 year. The daily fluoride intake, fluoride metabolism, tissue distribution and development of tooth fluorosis were observed at 4-monthly intervals, at the end of months 4, 8 and 12, respectively. Rats drinking ordinary brick tea (F- 503.5 mg/kg) served as control. The daily intake of fluoride in the ordinary brick tea group was 0.3 mg, and this group developed dental fluorosis characterized as brown and white horizontal marks at the end of month 8, and white chalky dental fluorosis developed at the end of month 12. The total incidence was 75%. In contrast, the daily fluoride intake of the low-fluoride brick tea (F- 210 mg/kg) group was 0.19 mg, and this group did not develop any signs of dental fluorosis. Fluoride distribution was mainly retained in the bone tissue, and about half of the absorbed fluoride was excreted via urine and feces. The results suggest that this low-fluoride brick tea did not induce fluorosis in rats and can be used as an effective control measure for humans.

Age Factors↗
PubMed2001

Simultaneous determination of SU5416 and its phase I and phase II metabolites in rat and dog plasma by LC/MS/MS.

SU5416, Z-3-[(2,4-dimethylpyrrol-5-yl)methylidenyl]-2-indolinone, is a cytostatic substance in development as an anti-angiogenic agent. SU5416 has several phase I and phase II metabolites including SU9838, SU6595, SU6689, 5'-hydroxy glucuronide of SU5416 and 5'-acyl glucuronide of SU5416. In order to support the preclinical studies, a liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) method for simultaneous determination of SU5416 and its metabolites in rat and dog plasma was developed. This method is fast, simple, sensitive (LOQ=2.0 ng/ml), reproducible and has a wide linear range (2.0-5000 ng/ml for SU5416, 2.0-2000 ng/ml for SU6689 and 2.0-1000 ng/ml for SU9838 and SU6595). This method was applied to rat and dog plasma samples obtained from pharmacokinetic and toxicokinetic studies.

Angiogenesis Inhibitors↗
PubMed2001

A DNA damage-induced p53 serine 392 kinase complex contains CK2, hSpt16, and SSRP1.

Phosphorylation of the human p53 protein at Ser-392 has been shown to be responsive to UV but not gamma irradiation. Here we describe identification and purification of a mammalian UV-activated protein kinase complex that phosphorylates Ser-392 of p53 in vitro. This kinase complex contains casein kinase 2 (CK2) and the chromatin transcriptional elongation factor FACT (a heterodimer of hSpt16 and SSRP1). In vitro studies show that FACT alters the specificity of CK2 in the complex such that it selectively phosphorylates p53 over other substrates including casein. In addition, phosphorylation by the kinase complex enhances p53 activity. These results thus provide a potential mechanism for p53 activation by UV irradiation.

Amino Acid Sequence↗
PubMed2001

Inhibition of melanosome transfer from melanocytes to keratinocytes by lectins and neoglycoproteins in an in vitro model system.

We propose that some of the critical molecules involved in the transfer of melanosomes from melanocytes to keratinocytes include plasma membrane lectins and their glycoconjugates. To investigate this mechanism, co-cultures of human melanocytes and keratinocytes derived from neonatal foreskins were established. The process of melanosome transfer was assessed by two experimental procedures. The first involved labeling melanocyte cultures with the fluorochrome CFDA. Labeled melanocytes were subsequently co-cultured with keratinocytes, and the transfer of fluorochrome assessed visually by confocal microscopy and quantitatively by flow cytometry. The second investigative approach involved co-culturing melanocytes with keratinocytes, and processing the co-cultures after 3 days for electron microscopy to quantitate the numbers of melanosomes in keratinocytes. Results from these experimental approaches indicate significant transfer of dye or melanosomes from melanocytes to keratinocytes that increased with time of co-culturing. Using these model systems, we subsequently tested a battery of lectins and neoglycoproteins for their effect in melanosome transfer. Addition of these selected molecules to co-cultures inhibited transfer of fluorochrome by approximately 15-44% as assessed by flow cytometry, and of melanosomes by 67-93% as assessed by electron microscopy. Therefore, our results suggest the roles of selected lectins and glycoproteins in melanosome transfer to keratinocytes in the skin.

Cell Membrane↗
PubMed2001

'VIT1', a novel gene associated with vitiligo.

To define genes associated with the pigmentary disorder vitiligo, gene expression was compared in non-lesional melanocytes cultured from three vitiligo patients and from three control melanocyte cultures by differential display. A basic local alignment search tool search did not reveal homology of six differentially expressed cDNA fragments to previously identified expressed sequence tags; thus, one was used to screen a melanocyte cDNA library. The underlying VIT1 gene maps to chromosome 2p16. The 3' portion of the VIT1 message is complementary to the 3' end of hMSH6 mRNA, enabling the formation of RNA-RNA hybrids, which may interfere with G/T mismatch repair function. Moreover, the aligned cDNA sequence revealed an open reading frame identical to a hypothetical protein expressed in brain, with a similarity to Drosophila calmodulin, and containing a zinc-finger motif partially identical to N-recognin. Expression of ORF mRNA was confirmed for multiple skin cell types, suggesting its importance for skin physiology.

Adult↗
PubMed2001

Keratinocytes play a role in regulating distribution patterns of recipient melanosomes in vitro.

Melanosomes in keratinocytes of Black skin are larger and distributed individually whereas those within keratinocytes of Caucasian skin are smaller and distributed in clusters. This disparity contributes to differences in skin pigmentation and photoprotection, but the control of these innate distribution patterns is poorly understood. To investigate this process, cocultures were established using melanocytes and keratinocytes derived from different racial backgrounds and were examined by electron microscopy. Melanosomes transferred to keratinocytes were categorized as individual or in various clusters. Melanosome size was also determined for individual and clustered melanosomes. Results indicate that, in our model system, melanosomes in keratinocytes from different racial backgrounds show a combination of clustered and individual melanosomes. When keratinocytes from dark skin were cocultured with melanocytes from (i) dark skin or (ii) light skin, however, recipient melanosomes were individual versus clustered in (i) 77% vs 23% and (ii) 64% vs 36%, respectively. In contrast, when keratinocytes from light skin were cocultured with melanocytes from (iii) dark skin or (iv) light skin, recipient melanosomes were individual versus clustered in (iii) 34% vs 66% and (iv) 39% vs 61%, respectively. These results indicate that recipient melanosomes, regardless of origin, are predominantly distributed individually by keratinocytes from dark skin, and in membrane-bound clusters by those from light skin. There were also differences in melanosome size from dark or light donor melanocytes. Melanosome size was not related to whether the melanosomes were distributed individually or clustered, however, in cocultures. These results suggest that regulatory factor(s) within the keratinocyte determine recipient melanosome distribution patterns.

Black People↗
PubMed2001

Abnormal translocation of tyrosinase and tyrosinase-related protein 1 in cutaneous melanocytes of Hermansky-Pudlak Syndrome and in melanoma cells transfected with anti-sense HPS1 cDNA.

Hermansky-Pudlak syndrome is an autosomal recessive disorder characterized by oculocutaneous albinism, a bleeding disorder, and, in some patients, ceroid storage and progressive lung disease. Although Hermansky-Pudlak syndrome exhibits locus heterogeneity, most patients have mutations in the HPS1 gene. Melanocytes in the basal epithelial layer of skin from patients with different mutations in the HPS1 gene exhibited occasional large complexes containing dihydroxyphenylalanine-positive cisterna and 50 nm vesicles. To characterize the role of the HPS1 protein in cells, human HPS1 cDNA was transfected into pigmented SK-MEL-188 melanoma cells (M-188) in either the sense (S-188) or the antisense (A-188) orientation. Expression of the 79 kDa HPS1 protein (in M-188 and S-188 cells) or lack of expression (in A-188 cells) was confirmed by Western blotting using two HPS1-protein-specific polyclonal antibodies. Significant reduction in expression of HPS1 protein in A-188 cells resulted in a significant decrease in tyrosinase activity and melanin content compared with M-188 and S-188 cells using an intact cell assay for tyrosinase. In contrast, tyrosinase activities in cell lysates of M-188, S-188, and A-188 cells were not significantly different. Knockout of HPS1 protein expression in A-188 cells caused both tyrosinase and tyrosinase-related protein 1 to be localized to large granular complexes in the cell cytosol and dendrites. Electron microscope analysis of the A-188 cells revealed that absence of HPS1 protein resulted in the deposition of dihydroxyphenylalanine reaction products (i.e., tyrosinase) confined to large membrane-bound structures with limiting membranes. We conclude that lack of HPS1 protein expression results in mistranslocation of tyrosinase and tyrosinase-related protein 1 to large granular complexes rather than melanosomes, compromising melanin synthesis.

Cells, Cultured↗
PubMed2001

Keratin 14 point mutations at codon 119 of helix 1A resulting in different epidermolysis bullosa simplex phenotypes.

Epidermolysis bullosa simplex is a heterogeneous group of inherited bullous disorders due to mutations in keratins 5 and 14. We report two different mutations in keratin 14 at codon 119 of the helix initiation peptide, each with different phenotypic expression. One, a sporadic case that clinically resembles Dowling-Meara epidermolysis bullosa simplex, resulted from conversion of methionine to threonine (M119T). The other, a multigeneration family with the Koebner phenotype, resulted from a previously unreported methionine to valine substitution (M119V). We suggest that loss of hydrophobicity during conversion of methionine to threonine is responsible for the more severe presentation of the first family, whereas maintenance of the hydrophobic nature of the amino acid with conversion to valine resulted in a less severe variant of epidermolysis bullosa simplex. Although most prior mutations in the highly conserved boundary motif of the alpha-helix have resulted in the Dowling-Meara subtype, our findings confirm that it is not always possible to predict the epidermolysis bullosa simplex severity on the basis of the location of the mutation along the keratin polypeptide. The specific amino acid substitution may be more critical in some cases.

Adolescent↗
PubMed2001

Familial koilonychia.

A 2-year-old boy with flat and spoon-shaped nail plates was referred to us. His mother had noticed that his fingernails were quite soft when he was born. After 2 months, the nails became flat or spoon-shaped; the toenail plates also became rough and flat. Systemic examination revealed nothing unusual. All his fingernail plates were quite thin, and had concave surfaces; the distal edges of some nail plates were rough and darkened (Fig. 1). His great, second and middle toenails on both sides showed the same abnormalities as the fingernails. Routine laboratory tests were normal; serum levels of iron, zinc, calcium, and magnesium were within normal limits. Repeated microscopic examination and culture of fungi from both fingernails and toenails were negative. Histologic examination of the distal edges of some of his fingernail plates was basically normal. When checking members of the family, we noticed that the boy's mother and maternal grandmother had similar nail problems (out of 14 members of three generations), although no systemic or other skin disorders were noticed. All the fingernails of the boy's mother were lusterless and concave with darkening of the distal edges (Fig. 2). All her toenails were rough, lusterless, and brown; some of them had longitudinal ridges. His maternal grandmother had light brown colored fingernail plates with concave profiles (Fig. 3), and dark brown or even blackish colored toenails. Both the mother and maternal grandmother acknowledged that their nails were abnormal from early childhood. Repeated microscopic examination and culture of fungi from both fingernails and toenails were negative. Several distal portions of the nail plates were collected for histologic examination. The fingernail plates of the boy's mother showed numerous parakeratotic cells in the middle zone, and those of his maternal grandmother showed diffuse parakeratotic cells; melanin granules were not found in those nail plates that were checked. Taken together, a diagnosis of familial koilonychia was established.

Child, Preschool↗
PubMed2001

Differential activation of migration by hypoxia in keratinocytes isolated from donors of increasing age: implication for chronic wounds in the elderly.

Chronic wound healing conditions are often observed in elderly patients with poor tissue oxygenation. Impaired re-epithelialization is a hallmark of these wounds, which is seen in both clinical studies and in our animal models of impaired healing. To investigate the pathogenic mechanism of chronic wounds, we studied the effect of hypoxia on migration of keratinocytes isolated from human donors of increasing age. Keratinocytes from elderly donors had depressed migratory activity when exposed to hypoxia, as opposed to an increase in migration in young cells. Analysis of underlying biochemical changes demonstrated a differential activation of matrix metalloproteinases by hypoxia in keratinocytes isolated from the young and the old. Matrix metalloproteinases-1 and -9 and tissue inhibitor of matrix metalloproteinase-1 were strongly upregulated by hypoxia in young cells, whereas no induction was observed in aged cells. Furthermore, transforming growth factor-beta 1 signaling appears to be involved in the keratinocyte differential response to hypoxia, as transforming growth factor-beta type I receptor was upregulated by hypoxia in young cells, while there was no induction in aged cells. Transforming growth factor-beta neutralizing reagents blocked hypoxia-induced matrix metalloproteinase-1, matrix metalloproteinase-9 expression, and hypoxia-induced cell migration as well. Our results suggest that an age-related decrease in response to hypoxia plays a crucial part in the pathogenesis of retarded re-epithelialization in wound.

Adult↗
PubMed2001

Molecular prenatal diagnosis in families with fetal mitochondrial trifunctional protein mutations.

OBJECTIVES: To evaluate the feasibility of molecular prenatal diagnosis in families with mitochondrial trifunctional protein (TFP) mutations and prospectively study the effects of fetal genotype on pregnancy outcome. TFP catalyzes the last 3 steps in mitochondrial long-chain fatty acid oxidation. STUDY DESIGN: We performed molecular prenatal diagnosis in 9 pregnancies, 8 in 6 families with isolated long-chain 3-hydroxyacyl-coenzyme A dehydrogenase (LCHAD) deficiency and one in a family with complete TFP deficiency. Analyses were performed on chorionic villous samples in 7 pregnancies and on amniocytes in 2. RESULTS: Molecular prenatal diagnosis successfully identified the fetal genotype in all 9 pregnancies. Two fetuses were affected, and both pregnancies were terminated by family decision. Two other fetuses had normal genotype and 5 others were heterozygotes. These 7 pregnancies were uncomplicated, and all the offspring are alive and apparently healthy. Genotypes of the aborted fetuses and neonates were confirmed by molecular analysis and enzymatic assays. CONCLUSIONS: Molecular prenatal diagnosis is possible and valid in guiding management of pregnancies in families with known TFP defects. Women heterozygous for TFP alpha-subunit mutations who carry fetuses with wild-type or heterozygous genotypes have uncomplicated pregnancies.

Amniocentesis↗
PubMed2001

alpha-Adducin gene and essential hypertension in China.

Adducin is a membrane skeletal protein that is involved in the regulation of membrane ion transport and cellular signal transduction. Essential hypertension has been linked to alpha-adducin gene locus, and association of a polymorphism of the gene has been found in some studies, but results of linkage or association studies on alpha-adducin gene are controversial among different populations. This study was designed to examine the linkage between alpha-adducin gene locus and essential hypertension and to reveal the relationship between an alpha-adducin gene polymorphism (Gly460Trp) and essential hypertension in a Chinese population. For the linkage study, one hundred and six Chinese nuclear families were recruited, including 417 hypertensive patients in all 474 individuals. Those samples were genotyped at D4S412 and D4S3038. The distances between the two microsatellite markers and the alpha-adducin gene locus are less than 3cM. Parametric, non-parametric linkage (NPL) analyses using the GENEHUNTER software were carried out. Sib transmission-dise- quilibrium test (S-TDT), as well as transmission-disequilibrium test (TDT). was also implemented with TDT/S-TDT Program 1.1. Serum levels of uric acid, creatinine, blood urea nitrogen (BUN), fasting glucose and lipids were determined as phenotypes. In an association study, 138 hypertensive and 121 normotensive subjects were genotyped at Gly460Trp of the alpha-adducin gene to examine a possible association between this polymorphism and blood pressure or other phenotypes. We fail to find the linkage between the two markers and essential hypertension by parametric, NPL analysis or TDT/S-TDT study. With the use of the simple association and the multivariate logistic regression analyses, we also fail to reveal a significant association between the Gly460Trp polymorphism in alpha-adducin gene and the blood pressure variation, or blood biochemical indices studied. The frequency of the 460Trp allele in Chinese (46-48%) is similar to that found in Japanese (54-60%) while the allele frequency is less common in Caucasian (13%-23%). These findings suggest that in our Chinese population, alpha-adducin 460Trp variant may not play an important role in the etiology of EH. And the negative results of linkage and TDT/ S-TDT further supports this conclusion.

Adult↗
PubMed2001

Overexpression of MnSOD protects murine fibrosarcoma cells (FSa-II) from apoptosis and promotes a differentiation program upon treatment with 5-azacytidine: involvement of MAPK and NFkappaB pathways.

Stable transfection of neomycin and human manganese superoxide dismutase (MnSOD2) expression plasmids into a murine fibrosarcoma cell line (FSa-II) was previously done in our laboratory. Treatment with 10 microM 5-azacytidine induced apoptosis in the control cell line (NEO), whereas the MnSOD-overexpressing cell line (SOD-H) demonstrated differentiated-appearing morphology. The levels of the myogenic transcription factor, MyoD, and the muscle-specific marker, alpha-actin, were increased over time with 5-azacytidine treatment in the SOD-H cell line. Nuclear transcription factor NFkappaB was activated in the SOD-H cell line, whereas inhibition of NFkappaB activation reduced the levels of MyoD and alpha-actin. Members of mitogen-activated protein kinase pathway and the Raf1/MEK/ERK cascade were shown to play a positive role in this event. Overexpression of MnSOD not only can protect cells from the toxic effects of 5-azacytidine, but can also promote the fibrosarcoma cells to enter a differentiation program.

Actins↗