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Biomedical subjects

Y Pan

Publications and source records attributed to Y Pan.

At least 181 records · Page 10Linked to original sources
PubMed1996

Fluoride analysis of apatite crystals with a central planar OCP inclusion: concerning the role of F- ions on apatite/OCP/apatite structure formation.

To study the roles of F- ions in the formation of apatite crystals embedding octacalcium phosphate (OCP) lamella in the center of apatite (Ap), a range of the Ap/OCP/Ap lamellar-mixed crystals were synthesized under various concentrations of fluoride ion (F-) from 0. 1-1.0 ppm at pH 6.5 and 37 degrees C. The products were analyzed for the F- incorporation, F- distribution, and the amount of OCP and Ap by chemical analysis, X-ray diffraction (XRD), electron probe microanalysis (EPMA), and nuclear magnetic resonance (NMR) techniques. The F- content and the amount of apatite in the crystalline product increased with an increase in the F- concentration in solution, whereas the amount of OCP and the yield of total product decreased. EPMA indicated that F- ions are distributed in the crystals almost homogeneously. The combined analysis suggested that a low-substituted fluoridated hydroxyapatite (FHAp) grew on a small amount of F--containing OCP or on a surface-reaction layer of OCP, which has accumulated a small amount of F-. The roles of F- ions were hypothesized as the reduction of the growth rate and/or the critical thickness in the a*-axis direction of OCP, the enhancement of hydrolysis of OCP, and the activation of the growth of FHAp, resulting in thinner OCP lamella and thicker apatite lamella in the a*-axis direction with an increase in F- concentration.

Apatites↗
PubMed1996

Tetraploid or near-tetraploid clones characterized by two 8;21 translocations and other chromosomal abnormalities in two patients with acute myeloblastic leukemia.

Acute myeloblastic leukemia (AML) with tetraploidy is rare. There have been only six such cases studied with banding techniques in the literature. Two were diagnosed as having AML-M2 and found to have similar near-tetraploid karyotypes with t(8;21) and missing Y chromosomes. We report two further cases of AML with tetraploid or near-tetraploid clones characterized by two t(8;21) and other chromosomal changes. Their cytogenetic findings were compatible with the diagnosis of AML-M2. Giant and bizarre blasts were seen on bone marrow (BM) smears from both cases. Immunologically, the blasts express CD2, CD15, and HLA-DR in case 1 and CD2 and CD65 in case 2. Cytogenetic studies on BM cells at diagnosis revealed that both cases had three related abnormal clones besides a normal one: 46,XY,t(8;21) (2%)/46,idem,add(7)(q31)(6.8%)/92, idem x 2 (80.6%) for case 1; and 46,XX,t(8;21)(13.4%)/47, idem,+4 (46.3%)/94,idem x 2 (39.1%) for case 2. Flow cytometric analysis displayed two cell populations in the former: one was in the diploid range and the other was in the tetraploid range. The patients did not obtain complete remissions and survived four and six months, respectively. These results indicate that tetraploid or near-tetraploid clones are secondary events which are associated with t(8;21) leukemia and may be associated with poor prognostic significance.

Adult↗
PubMed1996

Identification of two mutations in a compound heterozygous child with dihydrolipoamide dehydrogenase deficiency.

An infant girl with elevated blood lactate, pyruvate, and plasma branched-chain amino acids was diagnosed with dihydrolipoamide dehydrogenase (E3; dihydrolipoamide: NAD+ oxidoreductase, EC 1.8.1.4) deficiency. Activities of the pyruvate dehydrogenase complex and E3 from patient were 26 and 2% of controls in blood lymphocytes, and 11 and 14% in cultured skin fibroblasts, respectively. Western blot analysis demonstrated that the amount of E3 protein in fibroblasts from the patient and her father was about half of controls, while Northern blot analysis showed normal amounts of E3 RNA. DNA sequencing of cloned full-length E3 cDNAs from the patient revealed two mutations in separate alleles. One is a single base insertion of an extra adenine in the last codon of the leader peptide sequence (TAC-->TAAC) leading to a nonsense mutation which results in the premature termination of the precursor E3 polypeptide (Y35X). The other is a missense mutation due to substitution of guanine for adenine, causing an Arg-->Gly substitution at amino acid 460 of the mature protein (R460G) which triggers the loss of E3 activity probably by structural change in the E3 dimer. DNA sequencing of E3 cDNAs from the parents demonstrated that the nonsense mutation was inherited from the father and the missense mutation was inherited from the mother.

Alleles↗
PubMed1996

Methionine-containing peptides can be used as methionine sources for protein accretion in cultured C2C12 and MAC-T cells.

Twenty-two methionine-containing di- to octapeptides were evaluated for their ability to be a source of methionine to support protein accretion in C2C12 myogenic and MAC-T bovine mammary epithelial cells. The cell cultures were incubated for 72 h at 37 degrees C in a humidified environment of 90% air: 10% CO2 for C2C12 cells or 95% air: 5% CO2 for MAC-T cells. The basal medium contained methionine-free Dulbecco's modified Eagle's medium and 6% desalted fetal bovine serum. Treatments included basal medium, the basal medium supplemented with one of the 22 methionine-containing peptides, or the basal medium supplemented with free L-methionine. Methionine-containing peptides with the exception of glycylmethionine and prolylmethionine in C2C12 cells were able to support protein accretion with responses ranging from 29.1 to 123.3% of the response of L-methionine. Dipeptides with methionine at the N-terminus promoted greater (P < 0.0001) protein accretion than dipeptides with methionine at the C-terminus. Stimulation of protein accretion by seven pairs of dipeptides with methionine at either the C- or the N-terminus was linearly (P < 0.0001) related to the hydrophobicity of the dipeptides. These results indicate that C2C12 myogenic and MAC-T mammary epithelial cells have the ability to utilize methionine-containing peptides as sources of methionine to support protein accretion.

Amino Acid Sequence↗
PubMed1996

[Influence of green tea polyphenols varnish on saliva]

This study observed the inhibitory effect of green tea polyphenols varnish on the activity of humman saliva.We found 0.78 and 1.56mg/ml green tea polyphenols varnish is the best.We also observed the release of green tea polyphenols from liquid varnish is more than that from membraniform vanish.The release quantities of green tea polyphenols from membraniform is limited,suggest the influence of green tea polyphenols varnish on the activity of human saliva is small.

Journal Article↗
PubMed1996

[Experimental study on human glioma SHG44 treated by HSV-tk gene therapy].

The paper reports the construction of retroviral vector pLNTK carrying HSV-tk gene driven by PGK promoter and the successful transfer into human glioma cell SHG44. The in vitro study confirmed that ayclovir (ACV) sensitive level of the gene-transferred glioma cell (SHGLNTK) was 1,000 times that of SHG44. 3H-TdR incorporation confirmed that the DNA replication in SHGLNTK was considerably suppressed when treated with ACV. The in vivo study confirmed that ACV could suppress tumor formation of the SHGLNTK cells. In situ gene transfer treatment of nude mice carrying SHG44 tumor showed good therapeutic results. Such treatment may be used as an innovative method for brain tumor therapy.

Acyclovir↗
PubMed1996

[DNA contents and cycle analysis of porcine burn wounds treated with growth factors].

Wound healing is a complex biologic process in which peptide growth factors play a very important role. The object of this research was to study the effects of recombinant human epidermal growth factors (rh-EGF) and acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFGF) and bovine brain extract (bBE) on porcine partial-thickness burn wound healing. The biopsies were taken for determination of DNA contents and cell DNA cycle with the aid of flow cytometry and histological observation. The results showed that more extensive reepithelization and greater thickness of epidermis exhibited in growth factor treated wounds, and DNA contents and percent of S phase of cell DNA cycle were also higher in those groups treated with growth factors. The results suggested that repeated topical application of rh-EGF, aFGF, bFGF and bBE accelerated epithelial healing of burn wounds, and it may be helpful in clinical practice.

Animals↗
PubMed1996

[Topographic stereoscopic measurements of optic disc in early primary open angle glaucoma].

OBJECTIVE: To search a sensitive parameter for the early diagnosis of primary open angle glaucoma (POAG). METHOD: A system of computerized image analysis was used to acquire images of the optic nerve head of patients with POAG, suspect glaucoma (SG) and of normal persons. Each of these groups contained 31 eyes of 31 cases. The mean relative depths of disc rim and cup at different areas in the optic nerve head were measured. All these patients were followed up for four to six months, and the changes of the mean depths of every sector were compared between each pair of the three groups with statistic analysis. RESULTS: The mean depth of the neural rim and cup of each sector and that of total rim and total cup of POAG and SG patients were all deeper than that of normal controls. The mean depths of neural rim of the superior sector, inferior sector and the total rim area of POAG were deeper than that of SG patients. Compared to their first measurements, the changes of mean depths of neural rim of superior sector and total neural rim area of POAG patients were more prominent than that of normal controls and SG. We also compared the relative depth of the total rim area in the different areas in the optic nerve head with other two dimensional optic disc parameters such as cup/disc ratio, etc. CONCLUSION: Our study suggests that three-dimensional stereoscopic measurement of the surface of optic nerve head and follow-up be of paramount importance in the early diagnosis of POAG patients.

Adult↗
PubMed1995

Fluorescence image cytometry for measurement of nuclear DNA content in surgical pathology.

A study was made on various methodological aspects of fluorescence image cytometry (FICM) for measurement of nuclear DNA content by using CCD cameras attached to an epifluorescence microscope. Cell nuclei of paraffin-embedded specimens from mouse tissues and human prostate carcinomas were isolated and stained with 4'-6-diamidino-2-phenylindole (DAPI). We found that fluorescence fading, lamp stability, and the homogeneity of the illumination can easily be controlled. A camera with a signal-to-noise ratio of 53 dB gave a slightly more precise measurement than did a 46-dB camera. The linearity of the analysis results was very good. The coefficient of variation of mouse kidney standard cells in the DNA histograms was about 5% and 7.4% in histograms of prostate carcinoma biopsies. Stained cell nuclei can be stored for long periods at -20 degrees C without impairment of quality. Comparative measurements of ploidy by FICM and flow cytometry confirmed the accuracy of the FICM analyses. Thus, FICM appears to be an easy method for quantifying the DNA content of visually inspected cell nuclei in surgical pathology.

Animals↗
PubMed1995

The minor form alpha' chain from lamprey fibrinogen is rapidly crosslinked during clotting.

Lampreys have two genes for the alpha chains of fibrinogen, the second of which encodes a minor form with a carboxyl-terminal domain homologous to the carboxyl-terminal domains of beta and gamma chains. Initially, we referred to the alternative chain as alpha-II; we now use the designation alpha' in order to facilitate reference to crosslinked dimers. Antisera raised to synthetic peptides based on the cDNA sequence confirmed that the alpha' chain was present in fibrinogen prepared directly from plasma. The same antibodies were used to determine the size and properties of the carboxyl-terminal domain after its release by mild tryptic digestion, a fragment of apparent molecular weight 35,000-40,000 being produced. Unlike fragment D generated in the same digestions, the alpha' fragment did not bind to Gly-Pro-Arg or Gly-Val-Arg peptide affinity columns. During clotting under conditions where factor XIII is active, the alpha' chains became crosslinked very much more rapidly than ordinary alpha chains, the principal product being an apparent dimer, but smaller amounts of higher multimers being detectable. The crosslinking was inhibited by various amines, as well as by peptides that prevent polymerization.

Amino Acid Sequence↗
PubMed1995

Mapping of chromosomal gains and losses in prostate cancer by comparative genomic hybridization.

Comparative genomic hybridization (CGH) allows detection of chromosomal imbalances in whole genomes in a comprehensive manner. With this approach, ten cases of prostate cancer (seven primary tumors and three metastases) were analyzed. Frequent chromosomal gains detected by CGH involved chromosome arms 7q, 8q, 9q, and 16p, and chromosomes 20 and 22, as well as frequent losses of chromosome arms 16q and 18q, in at least three of the ten cases. Overrepresentation of chromosome arm 9q has not been described in published reports. The CGH data were compared with results of a loss of heterozygosity (LOH) study, in which complete allelotyping was performed in the same prostate tumors with 74 different polymorphic markers. In general, a high concordance between the CGH and LOH results was observed (92%). Tumors revealing discrepancies by CGH and LOH analysis were investigated further by interphase cytogenetics, and the resulting picture regarding the genomic alterations is discussed in detail.

Chromosome Aberrations↗
PubMed1995

Hepatitis C virus type I(1a) in northern China.

Twenty-four patients with hepatitis C virus (HCV) antibody from the Chinese North Western province of Jilin were further analysed by the immunoblot assay-2 (RIBA-2), reverse transcription-polymerase chain reaction (RT-PCR) for serum HCV RNA detection, and direct sequence-genotyping. Good concordance was found between the original second generation HCV antibody ELISA, RIBA-2, and serum HCV RNA. The occurrence of genotype I (1a), a genotype not previously reported in China, is described in 5(20.8%) of 24 cases, in association with genotypes II(1b) and III(2a) which were found in 16(66.7%) and 3(12.5%) of 24 cases, respectively. Imported blood products were unlikely to be the source of infection with genotype I (1a) but could not be definitively ruled out.

Base Sequence↗
PubMed1995

Expression of serum albumin and of alphafetoprotein in murine normal and neoplastic primitive embryonic structures.

Alphafetoprotein (AFP), a major serum protein synthesized during the embryo-fetal and postnatal period (in the yolk sac, then in the liver), is also an oncoprotein. The intracellular presence of AFP and of serum albumin (SA) in normal and neoplastic neural crest and neural tube derivatives was previously demonstrated. In this work we have studied the comparative expression of AFP and SA in primitive neuroectoblastic structures of mouse embryos (6 and 7 days "post coitum") and mouse teratocarcinomas (derived from the PCC4 cell line). Using immunofluorescence technique, antibodies to SA gave a positive reaction in embryos of 7 days, while AFP was not detected during this period. By mRNA in situ hybridization, SA mRNA gave a strong signal in both 6 and 7 day embryos, whereas AFP mRNA gave a weak signal only in 7-day embryos. The distribution of SA and AFP and their mRNAs was investigated in primitive neuroectoblastic structures of the teratocarcinomas by in situ hybridization and immunostaining. Only SA protein was detectable by immunostaining. SA mRNA gave a strong signal in differentiating structures as well as in undifferentiated cell clusters. AFP mRNA was observed only in differentiating structure. Dot-blot hybridization indicated that the level of SA transcripts was at least 6-fold higher than that of AFP transcripts in the teratocarcinomas investigated. In teratocarcinoma-bearing mice injected intraperitoneally with 125I-radiolabeled SA and AFP, significant accumulations of both SA and AFP were demonstrated in the tumors, SA being about 3-fold higher than that of AFP after normalization to quantity of uptake in liver. External in vivo photoscanning confirmed this relationship of accumulated radiolabeled proteins. The last observation could be useful in vivo for diagnosis of teratocarcinoma. We conclude that the expression of SA relative to AFP and the external cellular uptake of SA relative to AFP are similar in normal embryonic developing tissues and in the corresponding morphologically neoplastic tissues of the teratocarcinomas. The same SA:AFP relationship constitutes an oncofetal marker of primitive neuroectoblastic structures.

Animals↗
PubMed1995

Quantitative and dynamic MRI of neuroprotection in experimental stroke.

Experimental studies of stroke in animal models have traditionally relied on histological endpoints for the measurement of neuroprotection. In this study, we used in vivo and dynamic MRI to quantify the neuroprotective effects of the non-competitive NMDA antagonist MK801. Four hours of occlusion followed by 6 h of reperfusion was performed in a rabbit model of focal cerebral ischemia. Spin-echo T2-weighted (T2W) MRI was used to quantify ischemic lesion volumes. Hemispheric measurements of perfusion deficits were assessed by using dynamic susceptibility-contrast MRI to map the first-pass transit of injected GdDTPA. Histological correlates of infarction were quantified using tetrazolium staining. Animals treated with 2 mg/kg MK801 infused immediately post-occlusion (n = 6) were compared with untreated controls (n = 8). T2W MRI scans obtained after 6 h of reperfusion showed high-intensity lesions in the ischemic basal ganglia and cortex. MK801-treated animals showed significantly decreased lesion volumes compared to untreated controls (7.3 +/- 3.2% treated vs 20.7 +/- 4.8% control, p < 0.05). Lesion volumes measured with MRI were significantly correlated with tetrazolium-defined infarct volumes (r = 0.766, p = 0.004). Dynamic MRI demonstrated the phenomenon of delayed hypoperfusion in the ischemic hemisphere during the late reperfusion phase; relative cerebral blood volume (rCBV) was 45.2 +/- 10.3% in untreated animals. MK801 slightly improved these deficits although the differences did not reach statistical significance (rCBV = 77.0 +/- 9.7%, p = 0.128).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

31P-19F rotational-echo, double-resonance nuclear magnetic resonance experiment on fluoridated hydroxyapatite.

This work demonstrates 31P-19F rotational-echo, double-resonance nuclear magnetic resonance (REDOR NMR), a simple experiment used to measure 31P-19F dipolar couplings. 19F-observed 31P-19F REDOR NMR of fluorapatite revealed the 31P-19F connectivities. 31P-observed 31P-19F REDOR NMR determined the nearest 31P-19F distance in fluorapatite. The application on fluoride-treated hydroxyapatite, the principal inorganic constituent of dental enamel and dentine, showed the formation of fluorohydroxyapatite with a surface coverage of less than one unit-cell layer.

Apatites↗
PubMed1995

Proposed structure of the A domains of factor VIII by homology modelling.

We have predicted a structure for the three A domains of blood coagulation factor VIII by virtue of their homology to blue copper-binding proteins. This structure, consisting of six beta-barrels, is arranged in a triangular configuration with a single type II copper-binding site linking the A1 and A3 domains.

Amino Acid Sequence↗
PubMed1995

Properties of Rab5 N-terminal domain dictate prenylation of C-terminal cysteines.

Rab5 is a Ras-related GTP-binding protein that is post-translationally modified by prenylation. We report here that an N-terminal domain contained within the first 22 amino acids of Rab5 is critical for efficient geranylgeranylation of the protein's C-terminal cysteines. This domain is immediately upstream from the "phosphate binding loop" common to all GTP-binding proteins and contains a highly conserved sequence recognized among members of the Rab family, referred to here as the YXYLFK motif. A truncation mutant that lacks this domain (Rab5(23-215) fails to become prenylated. However, a chimeric peptide with the conserved motif replacing cognate Rab5 sequence (MAYDYLFKRab5(23-215) does become post-translationally modified, demonstrating that the presence of this simple six amino acid N-terminal element enables prenylation at Rab5's C-terminus. H-Ras/Rab5 chimeras that include the conserved YXYLFK motif at the N-terminus do not become prenylated, indicating that, while this element may be necessary for prenylation of Rab proteins, it alone is not sufficient to confer properties to a heterologous protein to enable substrate recognition by the Rab geranylgeranyl transferase. Deletion analysis and studies of point mutants further reveal that the lysine residue of the YXYLFK motif is an absolute requirement to enable geranylgeranylation of Rab proteins. Functional studies support the idea that this domain is not required for guanine nucleotide binding since prenylation-defective mutants still bind GDP and are protected from protease digestion in the presence of GTP gamma S. We conclude that the mechanism of Rab geranylgeranylation involves key elements of the protein's tertiary structure including a conserved N-terminal amino acid motif (YXYLFK) that incorporates a critical lysine residue.

Alkyl and Aryl Transferases↗