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Biomedical subjects

W Luo

Publications and source records attributed to W Luo.

At least 37 records · Page 2Linked to original sources
PubMed2001

Biological organization of hydroxyapatite crystallites into a fibrous continuum toughens and controls anisotropy in human enamel.

Enamel forms the outer surface of teeth, which are of complex shape and are loaded in a multitude of ways during function. Enamel has previously been assumed to be formed from discrete rods and to be markedly aniostropic, but marked anisotropy might be expected to lead to frequent fracture. Since frequent fracture is not observed, we measured enamel organization using histology, imaging, and fracture mechanics modalities, and compared enamel with crystalline hydroxyapatite (Hap), its major component. Enamel was approximately three times tougher than geologic Hap, demonstrating the critical importance of biological manufacturing. Only modest levels of enamel anisotropy were discerned; rather, our measurements suggest that enamel is a composite ceramic with the crystallites oriented in a complex three-dimensional continuum. Geologic apatite crystals are much harder than enamel, suggesting that inclusion of biological contaminants, such as protein, influences the properties of enamel. Based on our findings, we propose a new structural model.

Anisotropy↗
PubMed2001

[X-linked recessive Charcot-Marie-Tooth disease and Cx32 gene mutation].

OBJECTIVE: To study the Cx32 gene mutation in a X-linked recessive Charcot-Marie-Tooth disease (CMTXR) family. METHODS: Mutation analysis of Cx32 was screened by polymerase chain reaction single strand conformation polymorphism (PCR-SSCP) combined with DNA direct sequencing in 4 patients, 9 unaffected family members and 50 unrelated normal individuals. RESULTS: Arg15Gln mutation was found in 4 patients and 3 unaffected family members. CONCLUSION: The mutation of Cx32 can also cause CMTXR. Using PCR-SSCP combined with DNA direct sequencing can make gene diagnosis to CMTXR that is caused by Cx32 mutation.

Adult↗
PubMed2001

[Antigen receptor V beta gene usage of T lymphocytes in diseased thyroids in patients with autoimmune thyroid diseases].

OBJECTIVE: To explore the patterns of TCR V beta gene families and the preferentially used V beta genes in intrathyroidal T lymphocytes (ITL) of patients with Graves disease and Hashimoto thyroiditis. METHODS: Thyroid tissues of 12 patients with Graves disease, and 15 patients with Hashimotos thyroiditis were used for RNA extraction. Then, the RNA was used as templates for RT-PCR with a panel of primers including 24 oligonucleotides specific for TCR V beta gene families as upstream primers and one oligonucleotide specific for C beta as downstream primer. The amplified products were subjected to electrophoresis in agarose gels and observed under UV light. The positive expression of TCR V beta gene was identified by comparing the products with the size of the designed V beta genes. The matched peripheral blood samples of 5 Graves patients, 5 Hashimoto thyroiditis patients and 7 normal subjects were also obtained and used as controls. RESULTS: In 24 TCR V beta gene families tested for each individual sample, their average expressions were 5.3 +/- 1.2 and 13.4 +/- 3.0 in thyroid specimens of patients with Graves disease and Hashimoto thyroiditis, respectively, while those in the matched peripheral blood lymphocytes of the above two groups and normal controls were 23.0 +/- 1.0, 22.2 +/- 1.3 and 22.4 +/- 1.7, respectively. In addition, some of the TCR V beta genes such as V beta 3, V beta 5 and V beta 8 were more frequently used by intrathyroidal lymphocytes of Graves disease. CONCLUSIONS: These data indicate the oligoclonality of the intrathyroidal T cell populations in patients with Graves disease. Also, those of the preferentially used TCR V beta genes can be regarded as molecular targets for specific immune intervention. In contrast, the loss of restriction of TCR V beta gene utilization exists in Hashimoto thyroiditis, which may be related to the recruitment of T lymphocytes in thyroid glands through this mechanism.

Adult↗
PubMed2001

[Inhibitory effects of beta-carotene on hepatic cancer cell line SMMC-7721].

The inhibitory effect of beta-carotene on the proliferation of hepatic cancer was studied. Cells from a hepatic cancer cell line SMMC-7721 were incubated in culture media with 20, 40 and 80 mumol/L beta-carotene for 12, 24 and 48 h respectively. MTT test, Trypan blue exclusion test and DNA gel electrophoresis were used. The results of MTT test revealed that beta-carotene (20-80 mumol/L) could inhibit the proliferation of SMMC-7721 cells in a dose-dependent manner. DNA gel electrophoresis showed that the apoptosis of hepatic cancer cells could be induced by beta-carotene (40 mumol/L). It is concluded that the proliferation of hepatic cancer cells inhibited by beta-carotene, probably through interfering DNA metabolism and inducing cell apoptosis.

Antineoplastic Agents, Phytogenic↗
PubMed2001

[The research and development of computer workstation for Bayer Clinitek urine analyzer].

Computerization and networking is the developing trend of modern medical instruments. This paper describes the research and development work of computer workstation for Bayer Clinitek urine analyzer, including the system designing, hardware composing and software programming. The system can receive analyzing data automatically, manage sample database, print sample report and share data via the network, etc.

Computer Communication Networks↗
PubMed2001

[Preliminary study of the facial nerve regeneration in the chamber: the influence of myelin basic protein].

OBJECTIVE: To study the role of exogenous myelin basic protein(MBP) in neural repairment. METHODS: Adult New Zealand rabbits were employed in vivo preparation. A 12 microL nerve growth chamber was created by suturing the proximal and distal stumps of a transected facial never (FN) trunk into a tube. The regenerated nerves within the chambers were dissected and fixed for histological studies with light microscope at 4, 6 and 8 weeks respectively following the surgery. RESULTS: Morphological analysis of nerves showed no difference between the MBP and control group in the size of the regeneration FN within the chambers, diameters of myelinated axons, thickness of myelin sheath and number of myelin axons grew into the distal end of chamber at 4 weeks. At 6 and 8 weeks after operation, the MBP group showed a more mature-appearance regenerative nerve comparing to control group. Especially, the enhancement of maturation in the regeneration axons was very noticeable at 6 weeks. CONCLUSION: The study showed that pharmacological administration of exogenous MBP within a chamber at the time of entubational nerve repair enhances regeneration of myelinated axons across the sectioned ends of FN.

Animals↗
PubMed2001

[Analysis of the contents of Zn, Cu, Fe, Mn and Ni in suxiaoweiningchongji].

The contents of Zn, Cu, Fe, Mn and Ni in five groups of Suxiaoweiningchongii were determined by AAS. The results showed that he Fe content is the highest and Cu is the lowest, and the reduced order of contents from highest to lowest is Fe to Zn to Mn to Ni to Cu. The relationship between the trace elements in Suxiaoweiningchongji and the curative effect was discussed.

Copper↗
PubMed2000

Improved experimental limits on the production of magnetic monopoles.

We present new limits on low mass accelerator-produced pointlike Dirac magnetic monopoles trapped and bound in matter surrounding the D0 collision region of the Tevatron at Fermilab (experiment E-882). In the context of a Drell-Yan mechanism, we obtain cross section limits for the production of monopoles with magnetic charge values of 1, 2, 3, and 6 times the minimum Dirac charge of the order of picobarns, some 100 times smaller than found in similar previous Fermilab searches. Mass limits inferred from these cross section limits are presented.

Journal Article↗
PubMed2000

A single site (Ser16) phosphorylation in phospholamban is sufficient in mediating its maximal cardiac responses to beta -agonists.

Phospholamban (PLB) can be phosphorylated at Ser(16) by cyclic AMP-dependent protein kinase and at Thr(17) by Ca(2+)-calmodulin-dependent protein kinase during beta-agonist stimulation. A previous study indicated that mutation of S16A in PLB resulted in lack of Thr(17) phosphorylation and attenuation of the beta-agonist stimulatory effects in perfused mouse hearts. To further delineate the functional interplay between dual-site PLB phosphorylation, we generated transgenic mice expressing the T17A mutant PLB in the cardiac compartment of the null background. Lines expressing similar levels of T17A mutant, S16A mutant, or wild-type PLB in the null background were characterized in parallel. Cardiac myocyte basal mechanics and Ca(2+) kinetics were similar among the three groups. Isoproterenol stimulation was associated with phosphorylation of both Ser(16) and Thr(17) in wild-type PLB and Ser(16) phosphorylation in T17A mutant PLB, whereas there was no detectable phosphorylation of S16A mutant PLB. Phosphorylation of Ser(16) alone in T17A mutant PLB resulted in responses of the mechanical and Ca(2+) kinetic parameters to isoproterenol similar to those in wild-type myocytes, which exhibited dual-site PLB phosphorylation. However, those parameters were significantly attenuated in the S16A mutant myocytes. Thus, Ser(16) in PLB can be phosphorylated independently of Thr(17) in vivo, and phosphorylation of Ser(16) is sufficient for mediating the maximal cardiac responses to beta-adrenergic stimulation.

Amino Acid Substitution↗
PubMed2000

A tuftelin-interacting protein (TIP39) localizes to the apical secretory pole of mouse ameloblasts.

Enamel biomineralization is a complex process that involves interactions between extracellular matrix proteins. To identify proteins interacting with tuftelin, a potential nucleator of enamel crystallites, the yeast two-hybrid system was applied to a mouse tooth expression library and a tuftelin-interacting protein (TIP) was isolated for further characterization. Polyclonal antibodies were prepared against two recombinant variants of this protein. Both antibodies identified a major protein product in tooth organs at 39 kDa, and this protein has been called TIP39. Northern analysis showed TIP39 messenger RNA in multiple organs, a pattern similar to that of tuftelin messenger RNA. In situ hybridization of mandibles of 1-day-old mice detected TIP39 RNA in secretory ameloblasts and odontoblasts. Immunolocalization of TIP39 and tuftelin in cultured ameloblast-like cells showed that these two proteins colocalize. Within the developing tooth organ, TIP39 and tuftelin immunolocalized to the apical pole of secretory ameloblasts (Tomes' processes) and to the newly secreted extracellular enamel matrix. TIP39 amino acid sequence appears to be highly conserved with similarities to proteins in species as diverse as yeast and primates. Available sequence data and the findings reported here suggest a role for TIP39 in the secretory pathway of extracellular proteins.

Ameloblasts↗
PubMed2000

Characterization of spiroiminodihydantoin as a product of one-electron oxidation of 8-Oxo-7,8-dihydroguanosine.

[reaction: see text] Further oxidation of the common DNA lesion 8-oxo-7,8-dihydroguanosine by one-electron oxidants such as IrCl6(2-), Fe(CN)6(3-), or SO4-* leads to two major products, depending upon reaction conditions. In nucleosides at pH 7, 22 degrees C, the principal product is shown herein to be a spiroiminodihydantoin nucleoside, as a diastereomeric mixture, that can be characterized by NMR, ESI-MS/MS, and independent synthesis.

Crystallography, X-Ray↗
PubMed2000

Enamel biomineralization defects result from alterations to amelogenin self-assembly.

Enamel formation is a powerful model for the study of biomineralization. A key feature common to all biomineralizing systems is their dependency upon the biosynthesis of an extracellular organic matrix that is competent to direct the formation of the subsequent mineral phase. The major organic component of forming mouse enamel is the 180-amino-acid amelogenin protein (M180), whose ability to undergo self-assembly is believed to contribute to biomineralization of vertebrate enamel. Two recently defined domains (A and B) within amelogenin appear essential for this self-assembly. The significance of these two domains has been demonstrated previously by the yeast two-hybrid system, atomic force microscopy, and dynamic light scattering. Transgenic animals were used to test the hypothesis that the self-assembly domains identified with in vitro model systems also operate in vivo. Transgenic animals bearing either a domain-A-deleted or domain-B-deleted amelogenin transgene expressed the altered amelogenin exclusively in ameloblasts. This altered amelogenin participates in the formation an organic enamel extracellular matrix and, in turn, this matrix is defective in its ability to direct enamel mineralization. At the nanoscale level, the forming matrix adjacent to the secretory face of the ameloblast shows alteration in the size of the amelogenin nanospheres for either transgenic animal line. At the mesoscale level of enamel structural hierarchy, 6-week-old enamel exhibits defects in enamel rod organization due to perturbed organization of the precursor organic matrix. These studies reflect the critical dependency of amelogenin self-assembly in forming a competent enamel organic matrix and that alterations to the matrix are reflected as defects in the structural organization of enamel.

Amelogenesis↗
PubMed2000

Measuring dew formation and its threshold value for net radiation loss on top leaves in a paddy rice crop by using the dewball: a new and simple instrument.

In a field experiment on dew formation in tropical paddy rice, the threshold value for the nocturnal net radiative loss required for dew formation was investigated during 23 nights from February to April 1994. The onset and cessation of dew were visually observed on both the top leaves of a rice crop and on a glass sphere, the "dewball", installed in the field 1.0 m above the ground. The threshold value for the nocturnal net radiative loss (Rn,thresh) necessary for dew formation on the ball was deduced from the maximum zenith angle on the ball surface reached by the dew formed. Rn,thresh was found to be linearly related to the nightly minimum vapour-pressure deficit. This linear relationship as well as the Penman-Monteith equation (an energy-balance approach) were used to predict both the time of dew onset and the duration of dew on the ball. These predicted values agreed well with the observed results. Dew duration and time of dew onset on the ball were well correlated. During most nights, dew began to form on the top leaf surfaces at almost the same time as it reached the zenith angle of 60 degrees on the ball. A linear relationship was found between the observed daily duration of dew on the top leaf surfaces of the rice crop and the estimated time when dew reached the zenith angle of 60 degrees on the ball. This relationship gave as accurate an estimation of dew duration on the top leaf surface of the rice crop as did the Penman-Monteith combination equation. This study showed that the dewball is a potentially useful device for observing dew formation.

Models, Theoretical↗