Biomedical subjects

L Du

Publications and source records attributed to L Du.

At least 91 records · Page 5Linked to original sources

PubMed1997

Nitric oxide synthase activity in arterial tissues of cirrhotic rats.

The changes in the activities of constitutive nitric oxide (NO) synthase (cNOS) and inducible NOS (iNOS) were investigated in arterial tissues of CCl4-induced cirrhotic adult SD rats. The aortic tissue homogenate were prepared in normal and cirrhotic rats. NOS activity was measured by conversion of 3H-arginine to 3 H-citrulline. The activities of cNOS and iNOS were calculated in terms of presence or absence of Ca2+. The results showed that activities of total NOS, cNOS and iNOS in arterial tissues were all increased significantly in cirrhotic rats as compared with those in normal controls. There was a significant positive correlation between the activities of total NOS and cGMP content in cirrhotic arterial tissues.

Animals↗

PubMed1997

Conservation of fimbriae and the hemagglutinating adhesin HA-Ag2 among Porphyromonas gingivalis strains and other anaerobic bacteria studied by epitope mapping analysis.

Monoclonal antibodies characterized as antifimbria and anti-HA-Ag2 were used in immunoblotting to examine the antigenic distribution of fimbriae and HA-Ag2 among a collection of human and animal Porphyromonas strains and human Prevotella and Bacteroides strains. The results showed that fimbrial and HA-Ag2 antigenic structures are peculiar to the species Porphyromonas gingivalis.

Animals↗

PubMed1997

Fimbriae and the hemagglutinating adhesin HA-Ag2 mediate adhesion of Porphyromonas gingivalis to epithelial cells.

The mechanisms by which Porphyromonas gingivalis, a gram-negative anaerobic bacterium, is pathogenic for the periodontium remain largely hypothetical. Invasion of host tissues by P. gingivalis is believed to require adhesion of the bacterium to host cells. The aim of this study was to use monoclonal antibodies (MAbs) to characterize the bacterial cell surface component(s) acting as a ligand binding to a receptor on epithelial cells. Surface antigens of P. gingivalis ATCC 33277 were obtained as a glass bead-EDTA extract (GBE), and antiserum against the GBE was produced in rabbits. Epithelial cell membrane proteins (ECMP) were prepared from a homogenate of the SK-MES-1 cell line with Triton X-100. The antigen/ligand profile of GBE was resolved by crossed immunoaffinity electrophoresis by using ECMP in the first-dimension gel. The migration of one immunoprecipitate (IP) was retarded, indicating a ligand-receptor interaction between a surface antigen of P. gingivalis and a complementary binding site on the epithelial cell membrane. The corresponding IP in the GBE/anti-GBE immunoelectrophoresis profile was excised from replicate gels to immunize mice for production of MAbs specific for the bacterial ligand. Five MAbs were obtained and tested for reactivity with GBE in immunoblots and for inhibition of the interaction between GBE and ECMP. Immunoblots revealed polypeptides at 28, 42, 43, and 49 kDa. Inhibition tests were positive for all five MAbs. These results are conclusive evidence that the MAbs recognize functional epitopes involved in the adherence of P. gingivalis to epithelial cells and that the adhesins are likely associated with fimbriae and the hemagglutinating adhesin HA-Ag2.

Adhesins, Bacterial↗

PubMed1997

[Determination and analysis of masticatory performance of unilateral free-end removable partial denture].

In this study, the changes of masticatory performance of 30 cases (18 males, 12 females) wearing unilateral free-end removable partial dentures were studied before wearing, 1 week, 1 month and 3 months after wearing by using the light absorption method and peanuts as test food. The results showed: 1. The masticatory performance before wearing unilateral free-end removable partial denture was predominantly lower than that of normal control group. The more teeth lost, the lower unilateral masticatory performance was observed. When the number of lost teeth was few, patients compensated and maintained their masticatory performance before swallowing. 2. The masticatory performance was gradually improved with wearing denture period increasing. 3. Factors relating to the masticatory performance were sex, the extent of alveolar bone resorption and age. Except sex, the extent of alveolar bone resorption and age factors were negative correlative with the masticatory performance; However the number of occlusal units lost, chewing habit and the kinds of denture base materials had no relation to the masticatory performance.

Adult↗

PubMed1997

[A probe into rehabilitating occlusion of majority teeth missing].

It is generally to be found that decrease of occlusal vertical dimension, worn occlusive surface of remaining teeth without opposite teeth and loss of intercusping position (ICP), etc. in the patients with majority teeth missing. In western countries, fixed restorations (including implant dentures) are routinely used for the patients with majority teeth missing in order to rehabilitate occlusion. The authors applied occlusal theory, combining with the clinical facilities and used one-piece casting base and functional impression technique for rehabilitation of occlusion. The purpose of this article was to summarize clinical experiences, to explore the relative problems concerning rehabilitation for patients with majority teeth missing.

Aged↗

PubMed1996

cDNA cloning of the murine Pex gene implicated in X-linked hypophosphatemia and evidence for expression in bone.

The recently identified human PEX gene apparently encodes for a neutral endopeptidase that is mutated in patients with X-linked hypophosphatemia. The 3' and 5' ends of the coding region of PEX have not been cloned, nor has the tissue expression of the gene been identified. Here we report the isolation and characterization of the complete open reading frame of the mouse Pex gene and the demonstration of its expression in bone. Mouse Pex cDNA is predicted to encode a protein of 749 amino acids with 95% identity to the available human PEX sequence and significant homology to members of the membrane-bound metalloendopeptidase family. Northern blot analysis revealed a 6.6-kb transcript in bone and in cultured osteoblasts from normal mice that was not detectable in samples from the Hyp mouse, the murine homolog of human X-linked hypophosphatemia. Pex transcripts were, however, detectable in Hyp bone by RT-PCR amplification. Of particular interest, a cDNA clone from rat incisor shows 93% sequence identity to the 5' end of Pex cDNA, suggesting that Pex may be expressed in another calcified tissue, the tooth. The association of impaired mineralization of bone and teeth and disturbed renal phosphate reabsorption with altered expression of Pex suggests that the Pex gene product may play a critical role in these processes.

Amino Acid Sequence↗

PubMed1996

A hyperphosphorylated form of the large subunit of RNA polymerase II is associated with splicing complexes and the nuclear matrix.

A hyperphosphorylated form of the largest subunit of RNA polymerase II (pol IIo) is associated with the pre-mRNA splicing process. Pol IIo was detected in association with a subset of small nuclear ribonucleoprotein particle and Ser-Arg protein splicing factors and also with pre-mRNA splicing complexes assembled in vitro. A subpopulation of pol IIo was localized to nuclear "speckle" domains enriched in splicing factors, indicating that it may also be associated with RNA processing in vivo. Moreover, pol IIo was retained in a similar pattern following in situ extraction of cells and was quantitatively recovered in the nuclear matrix fraction. The results implicate nuclear matrix-associated hyperphosphorylated pol IIo as a possible link in the coordination of transcription and splicing processes.

Animals↗

PubMed1996

The bryostatins inhibit growth of B16/F10 melanoma cells in vitro through a protein kinase C-independent mechanism: dissociation of activities using 26-epi-bryostatin 1.

Bryostatin 1 is a potential cancer chemotherapeutic agent in Phase II clinical trials, with positive responses observed for malignant melanoma, among other tumors. The bryostatins are known to be potent ligands for protein kinase C (PKC), functioning as partial antagonists. In the present study, we explore the mechanism by which the bryostatins inhibit growth to B16/F10 mouse melanoma cells in vitro. Three experimental approaches suggest that the growth inhibition is independent of PKC. First, we characterized in detail the translocation and down-regulation of the PKC isozymes alpha, delta, and epsilon in response to phorbol ester and bryostatin 1 in these cells. Although the dose-response curves obtained for the translocation-activation of PKC isozymes showed good correlation with the growth-enhancing activity of phorbol 12-myristate 13-acetate, for no PKC isozyme was there a good correlation with the growth-inhibitory activity of bryostatin 1. Second, inhibition PKC, inhibited the growth of the B16/F10 melanoma cell lines with potency similar to that of bryostatin 1. We confirmed here that 26-epi-bryostatin 1 showed 60-fold reduced affinity for PKC and 30-60-fold reduced potency to translocate and downregulate PKC isozymes compared with bryostatin 1. We presumed that the principal toxicity of bryostatin 1 reflects its interaction with PKC, and we would thus predict that epi-bryostatin 1 would be less toxic. Indeed, we found at least 10-fold reduced toxicity of 26-epi-bryostatin 1 in C57BL/6 mice compared with bryostatin 1. We conclude that the growth inhibition of the bryostatins, at least in this system, does not result from interaction with PKC. As exemplified by 26-epi-bryostatin 1, this insight permits the design of analogues with comparable growth inhibition to bryostatin 1 but with reduced toxicity.

Animals↗

PubMed1996

Fine genetic mapping of the Hyp mutation on mouse chromosome X.

The hypophosphatemic (Hyp) mouse is the murine homolog of hypophosphatemic vitamin-D-resistant rickets (HYP) in human. Despite extensive investigations in the Hyp mouse, the pathophysiology of this X-linked dominant disorder remains unclear. As a first step toward cloning the Hyp gene, we have generated a high-resolution linkage map in the vicinity of the Hyp locus using two independent backcross panels segregating the Hyp mutation, one generated from an interspecific mating between C57BL/6J-Hyp/Hyp and Mus spretus and the other from an intrasubspecific mating between C57BL/6J-Hyp/Hyp and Mus musculus castaneus. Linkage analyses in 1101 backcross progeny using a total of 23 DNA markers favor the following gene order from the centromere: DXMitl3-(DXMit11, DXMit34)-(DXMit36, Alas2)-(Hyp, DXMit8O)-DXMi198-(DXMit28, DXMit33, DXMit7O)-Pdhal-DXMit2O. This study has localized Hyp to a region of approximately 1 cM flanked by the proximal markers DXMit36 and Alas2 and the distal marker DXMit98. One microsatellite marker, DXMit8O, was found to be very tightly linked to Hyp, as it was nonrecombinant with Hyp among all the progeny of both backcrosses corresponding to 1101 meioses.

Animals↗

PubMed1996

The scotopic electroretinogram of macaque after retinal ganglion cell loss from experimental glaucoma.

PURPOSE: This study describes the dark-adapted electroretinograms (ERGs) of macaque monkeys with severe visual field defects and substantial retinal ganglion cell loss as a consequence of long-standing ocular hypertension. METHODS: Monocular experimental glaucoma was produced by argon laser trabeculoplasty, and visual fields were assessed with behavioral static perimetry. Electroretinographic responses to brief ganzfeld flashes under fully dark-adapted conditions were recorded using DTL fiber electrodes in anesthetized animals. The authors quantified retinal layer thickness and cell loss in 1-micron radial sections and inspected optic nervous under the light microscope. RESULTS: At the lowest intensities, a sensitive negative component of the scotopic ERG, which normally peaks approximately 200 msec after stimulus onset, was present in the control eyes but was reduced greatly or was virtually absent in the experimental eyes of monkeys with severe visual field loss. A previously unreported sensitive positive component of the scotopic ERG remained in both eyes. In the control eyes, the positive component gave rise to a sharp peak approximately 120 msec after stimulus onset, but in the experimental eyes, because of the absence of the more delayed sensitive negative potential, it was sustained, lasting as long as 700 msec. Scotopic a- and b-waves and oscillatory potentials in the experimental eyes were not consistently different from control eyes. Ganglion cell and optic nerve loss in the experimental eyes was substantial, and there was little other obvious retinal damage. CONCLUSIONS: A sensitive negative component is reduced or absent from the dark-adapted ERGs of macaque monkeys with severe visual field defects and substantial retinal ganglion cell loss as a consequence of long-standing ocular hypertension.

Animals↗

PubMed1995

Involvement of cytochrome P450 in oxime production in glucosinolate biosynthesis as demonstrated by an in vitro microsomal enzyme system isolated from jasmonic acid-induced seedlings of Sinapis alba L.

An in vitro enzyme system for the conversion of amino acid to oxime in the biosynthesis of glucosinolates has been established by the combined use of an improved isolation medium and jasmonic acid-induced etiolated seedlings of Sinapis alba L. An 8-fold induction of de novo biosynthesis of the L-tyrosine-derived p-hydroxybenzylglucosinolate was obtained in etiolated S. alba seedlings upon treatment with jasmonic acid. Formation of inhibitory glucosinolate degradation products upon tissue homogenization was prevented by inactivation of myrosinase by addition of 100 mM ascorbic acid to the isolation buffer. The biosynthetically active microsomal enzyme system converted L-tyrosine into p-hydroxyphenylacetaldoxime and the production of oxime was strictly dependent on NADPH. The Km and Vmax values of the enzyme system were 346 microM and 538 pmol per mg of protein per h, respectively. The nature of the enzyme catalyzing the conversion of amino acid to oxime in the biosynthesis of glucosinolates has been subject of much speculation. In the present paper, we demonstrate the involvement of cytochrome P450 by photoreversible inhibition by carbon monoxide. The inhibitory effect of numerous cytochrome P450 inhibitors confirms the involvement of cytochrome P450. This provides experimental documentation of similarity between the enzymes converting amino acids into the corresponding oximes in the biosynthesis of glucosinolates and cyanogenic glycosides.

Carbon Monoxide↗

PubMed1995

Resiniferatoxin-amide and analogues as ligands for protein kinase C and vanilloid receptors and determination of their biological activities as vanilloids.

The naturally occurring diterpene resiniferatoxin (RTX) is an ultrapotent analogue of capsaicin. Acting on polymodal afferent neurons, RTX induces a generally similar pattern of responses as does capsaicin. However, the two compounds, as well as other vanilloid derivatives, display different relative potencies for different responses. In the present study, we examined the vanilloid-like activities of two new derivatives, the amide analogue of RTX and phorbol 12,13-dibenzoate 20-homovanillylamide. Structurally, RTX-amide resembles capsaicin more closely than does RTX, and after cleavage of the amide bond the resulting amine would be predicted to not bind to protein kinase C in contrast to resiniferonol 9,13,14-orthophenylacetate, the parent diterpene of RTX. In contrast to our expectations the binding potency of the RTX-amide for the vanilloid receptor present in rat spinal cord was 450-fold lower than that of RTX (Ki values for the RTX-amide and RTX were 10.4 +/- 0.7 nM and 23.1 +/- 3.2 pM, respectively). In the case of phorbol 12,13-dibenzoate 20-homovanillylamide, there was a further loss of affinity for the vanilloid receptor compared with RTX; nonetheless, the Ki (8.56 +/- 0.61 microM) was comparable with that of capsaicin (5.31 +/- 0.37 microM). Computer fitting of the binding data yielded Hill coefficient values of 2.25 +/- 0.03, 2.33 +/- 0.03, and 1.84 +/- 0.05 for RTX, RTX-amide, and phorbol 12,13-dibenzoate 20-homovanillylamide, respectively, indicating that both new compounds induced apparent positive cooperativity among vanilloid binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Transcription-dependent redistribution of the large subunit of RNA polymerase II to discrete nuclear domains.

A subpopulation of the largest subunit of RNA polymerase II (Pol II LS) is located in 20-50 discrete subnuclear domains that are closely linked to speckle domains, which store splicing proteins. The speckle-associated fraction of Pol II LS is hyperphosphorylated on the COOH-terminal domain (CTD), and it is highly resistant to extraction by detergents. A diffuse nucleoplasmic fraction of Pol II LS is relatively hypophosphorylated on the CTD, and it is easily extracted by detergents. In transcriptionally active nuclei, speckle bound hyperphosphorylated Pol II LS molecules are distributed in irregularly shaped speckle domains, which appear to be interconnected via a reticular network. When transcription is inhibited, hyperphosphorylated Pol II LS and splicing protein SC35 accumulate in speckle domains, which are transformed into enlarged, dot-like structures lacking interconnections. When cells are released from transcriptional inhibition, Pol IIO and SC35 redistribute back to the interconnected speckle pattern of transcriptionally active cells. The redistribution of Pol II and SC35 is synchronous, reversible, and temperature dependent. It is concluded that: (a) hyperphosphorylation of Pol II LS's CTD is a better indicator of its tight association to discrete subnuclear domains than its transcriptional activity; (b) during states of transcriptional inhibition, hyperphosphorylated Pol II LS can be stored in enlarged speckle domains, which under the light microscope appear to coincide with the storage sites for splicing proteins; and (c) Pol II and splicing proteins redistribute simultaneously according to the overall transcriptional activity of the nucleus.

Amanitins↗

PubMed1995

[Time course of the effect of electroacupuncture on immunomodulation of normal rat].

Lymphocyte proliferation of splenocytes induced by concanavalin A (Con A) and the induction of IL-2 production test were used to study the effects of acupuncture on immunomodulation by stimulation of Zusanli (ST 36) and Lanwei (Extra 33) points of the rat's left leg. It was observed that the lymphocyte proliferation of splenocytes was increased in EA groups of 3 days (p < 0.05) 5 days (p < 0.001) and 7 days (P < 0.05). The parabolical curve could be found by currilinear regression (R2 = 0.9901). EA groups of 3 days and 5 days had a significantly increased induction of IL-2 production (P < 0.05). These results will be helpful to choose an optimal time for clinical treatment.

Animals↗

PubMed1995

Effect of alteration of the heterocyclic nucleus of ILV on its isoform selectivity for PKC. Palladium catalyzed route to benzofuran analogues of ILV.

A palladium catalyzed route for the preparation of several benzofuran analogues of the PKC activator indolactam V (ILV) is described together with the ability of these compounds to activate the isoforms of PKC. The benzofuran analogues of ILV are shown to activate PKC with a slightly different pattern of isotype selectivity than ILV or 7-n-octyl-ILV. Moreover, in an examination of the effect of stereochemistry at the C-14 center of the teleocidins on PKC binding activity, a clear preference for R-stereochemistry at the C-14 center was found, thus providing additional verification of previously published structural correlations between the families of PKC activators.

Benzofurans↗

PubMed1995

[A study on human dental embryology in an endemic high fluorosis region].

In a high endemic fluorosis area in Guizhou, China, 40 human fetuses delivered by induced abortion during the 5th-8th month of gestation were utilized to study dental embryonic samples under transmission electron microscope (TEM). Compared with normal controls, ultrastructure findings in the ameloblast cell organs include swelling of mitochondria, enlargement of SER, increase in RNA granules and RER. This study suggests that the irregularities of the collagenous fibers and crystallites are due to the maldevelopment of the ameloblast Tome's processes, which explains the mechanism of motteled enamel.

Ameloblasts↗

PubMed1995

[The use of the Ho: YAG laser in arthroscopic surgery].

From May 1993 to April 1994 we had performed 72 cases (total 84 joints) of arthroscopic operations with holmium laser. It included 12 bilateral knees, and single joints in the shoulder, elbow, wrist and ankle. We performed partial menisectomy, chondroplasy, partial synovectomy and lateral retinacular release. The energy used was from 1 to 12kJ depending the complexity of the operations. All these cases had been followed up 6 to 16 months. The function of the joints was good, only two cases had joint effusion. The rate of good and excellent results was 97%.

Adolescent↗

PubMed1995

[Studies on theory and models of systemic conservation of animal and poultry genetic resources. II. Simulation experiment of systemic conservation of animal and poultry genetic resources].

Tribolium castaneum simulation and computer simulation proved the feasibility and rationality of Systemic Conservation of Animal and Poultry Genetic Resources (SCAPGR) theory and the biological meaning of the SCAPGR mathematical models. It also demonstrated that the right effective population size should be maintained and gene flow among populations should be controlled and adequate selecting method and mating system should determined according to population genetic characters of gene conserved in the SCAPGR population.

Animals↗