Biomedical subjects

L Wen

Publications and source records attributed to L Wen.

At least 73 records · Page 4Linked to original sources

PubMed1998

Induction of insulitis by glutamic acid decarboxylase peptide-specific and HLA-DQ8-restricted CD4(+) T cells from human DQ transgenic mice.

Insulin-dependent diabetes mellitus in humans is linked with specific HLA class II genes, e.g., HLA-DQA1*0301/ DQB1*0302 (DQ8). To investigate the roles of HLA-DQ8 molecules and glutamic acid decarboxylase (GAD) in disease development, we generated DQ8(+)/I-Abo transgenic mice expressing functional HLA-DQ8 molecules and devoid of endogenous mouse class II. DQ8(+)/I-Abo mice produced antigen-specific antibodies and formed germinal centers after immunization with GAD65 peptides. Two GAD peptide-specific (247-266 and 509-528), DQ8 restricted Th1 CD4(+) T cell lines, were generated from immunized DQ8(+)/I-Abo mice. They induced severe insulitis after adoptive transfer into transgene positive (but not negative) mice who were treated with a very low dose of streptozotocin that alone caused no apparent islet pathology. In addition to CD4, islet mRNA from these mice also showed expression of CD8, IFNgamma, TNFalpha, Fas, and Fas ligand. Our data suggest that a mild islet insult in the presence of HLA-DQ8 bearing antigen-presenting cells promotes infiltration of GAD peptide reactive T cells into the islet.

Animals↗

PubMed1998

The expression in vivo of a second isoform of pT alpha: implications for the mechanism of pT alpha action.

A second isoform of pT alpha, "pT alpha(b)," is derived from the pT alpha locus by tissue-specific, alternative splicing. pT alpha(b) is coexpressed in the thymus with the previously characterized form of pT alpha (which we term pT alpha(a)) and is also expressed in peripheral cells without pT alpha(a). While pT alpha(a) acts to retain most TCR beta-chains intracellularly, pT alpha(b) permits higher levels of cell surface TCR beta expression and facilitates signaling from a CD3-TCR beta complex.

Alternative Splicing↗

PubMed1998

The role of lymphocyte subsets in accelerated diabetes in nonobese diabetic-rat insulin promoter-B7-1 (NOD-RIP-B7-1) mice.

B7-1 transgene expression on the pancreatic islets in nonobese diabetic (NOD) mice leads to accelerated diabetes, with >50% of animals developing diabetes before 12 wk of age. The expression of B7-1 directly on the pancreatic beta cells, which do not normally express costimulator molecules, converts the cells into effective antigen-presenting cells leading to an intensified autoimmune attack. The pancreatic islet infiltrate in diabetic mice consists of CD8 T cells, CD4 T cells, and B cells, similar to diabetic nontransgenic NOD mice. To elucidate the relative importance of each of the subsets of cells, the NOD-rat insulin promoter (RIP)-B7-1 animals were crossed with NOD.beta2microglobulin -/- mice which lack major histocompatibility complex class I molecules and are deficient in peripheral CD8 T cells, NOD.CD4 -/- mice which lack T cells expressing CD4, and NOD.muMT -/- mice which lack B220-positive B cells. These experiments showed that both CD4 and CD8 T cells were necessary for the accelerated onset of diabetes, but that B cells, which are needed for diabetes to occur in normal NOD mice, are not required. It is possible that B lymphocytes play an important role in the provision of costimulation in NOD mice which is unnecessary in the NOD-RIP-B7-1 transgenic mice.

Adoptive Transfer↗

PubMed1998

Ultra-Low velocity zones near the core-mantle boundary from broadband PKP precursors

Short- and long-period precursors of the PKP phase were used to study an ultra-low velocity zone (ULVZ) near the core-mantle boundary beneath the Western Pacific. Synthetic seismograms were computed from a hybrid method, which handles seismic wave propagation through two-dimensional complex structures. Long-period precursors were explained by Gaussian-shaped ULVZs of 60 to 80 kilometers height with P velocity drops of at least 7 percent over 100 to 300 kilometers. Short-period precursors suggest the presence of smaller scale anomalies accompanying these larger Gaussian-shaped structures. These fine structures may be areas of partial melt caused by vigorous small-scale convection or the instability of a thermal boundary layer at the mantle's base, or both.

Journal Article↗

PubMed1998

Primary gamma delta cell clones can be defined phenotypically and functionally as Th1/Th2 cells and illustrate the association of CD4 with Th2 differentiation.

The division of CD4+ alpha beta T cells into Th1 and Th2 subsets has become an established and important paradigm. The respective activities of these subsets appear to have profound effects on the course of infectious and autoimmune diseases. It is believed that specific programs of differentiation induce the commitment of an uncommitted Th0 precursor cell to Th1 or Th2. A component of these programs is hypothesized to be the nature of MHC-peptide antigen presentation to the alpha beta T cell. It has heretofore remained uncertain whether a Th1/Th2 classification likewise defines, at the clonal level, gamma delta T cells. Such cells do not, as a general rule, express either CD4 or CD8 alpha beta, and they do not commonly recognize peptide-MHC. In this report, gamma delta cell clones are described that conform strikingly to the Th1/Th2 classification, both by cytokine expression and by functional activities of the clones in vitro and in vivo. Provocatively, both the gamma delta cell clones and primary gamma delta cells in vivo showed a strong association of the Th2 phenotype with CD4 expression. These results are discussed with regard to the immunoregulatory role that is increasingly emerging for gamma delta cells.

Amino Acid Sequence↗

PubMed1998

NMR studies of internal dynamics of serine proteinase protein inhibitors: Binding region mobilities of intact and reactive-site hydrolyzed Cucurbita maxima trypsin inhibitor (CMTI)-III of the squash family and comparison with those of counterparts of CMTI-V of the potato I family.

Serine proteinase protein inhibitors follow the standard mechanism of inhibition (Laskowski M Jr, Kato I, 1980, Annu Rev Biochem 49:593-626), whereby an enzyme-catalyzed equilibrium between intact (I) and reactive-site hydrolyzed inhibitor (I*) is reached. The hydrolysis constant, Khyd, is defined as [I*]/[I]. Here, we explore the role of internal dynamics in the resynthesis of the scissile bond by comparing the internal mobility data of intact and cleaved inhibitors belonging to two different families. The inhibitors studied are recombinant Cucurbita maxima trypsin inhibitor III (rCMTI-III; Mr 3 kDa) of the squash family and rCMTI-V (Mr approximately 7 kDa) of the potato I family. These two inhibitors have different binding loop-scaffold interactions and different Khyd values--2.4 (CMTI-III) and 9 (CMTI-V)--at 25 degrees C. The reactive-site peptide bond (P1-P1') is that between Arg5 and Ile6 in CMTI-III, and that between Lys44 and Asp45 in CMTI-V. The order parameters (S2) of backbone NHs of uniformly 15N-labeled rCMTI-III and rCMTI-III* were determined from measurements of 15N spin-lattice and spin-spin relaxation rates, and [1H]-15N steady-state heteronuclear Overhauser effects, using the model-free formalism, and compared with the data reported previously for rCMTI-V and rCMTI-V*. The backbones of rCMTI-III [(S2) = 0.71] and rCMTI-III* [(S2) = 0.63] are more flexible than those of rCMTI-V [(S2) = 0.83] and rCMTI-V* [(S2) = 0.85]. The binding loop residues, P4-P1, in the two proteins show the following average order parameters: 0.57 (rCMTI-III) and 0.44 (rCMTI-III*); 0.70 (rCMTI-V) and 0.40 (rCMTI-V*). The P1'-P4' residues, on the other hand, are associated with (S2) values of 0.56 (rCMTI-III) and 0.47 (rCMTI-III*); and 0.73 (rCMTI-V) and 0.83 (rCMTI-V*). The newly formed C-terminal (Pn residues) gains a smaller magnitude of flexibility in rCMTI-III* due to the Cys3-Cys20 crosslink. In contrast, the newly formed N-terminal (Pn' residues) becomes more flexible only in rCMTI-III*, most likely due to lack of an interaction between the P1' residue and the scaffold in rCMTI-III. Thus, diminished flexibility gain of the Pn residues and, surprisingly, increased flexibility of the Pn' residues seem to facilitate the resynthesis of the P1-P1' bond, leading to a lower Khyd value.

Amino Acid Sequence↗

PubMed1998

[Intraperitoneal transplantation of isolated hepatocytes of the pig: the implantable bioartificial liver].

The general aim is to prepare a bioartificial liver to treat acute hepatic failure using allo- and xenogeneic hepatocytes, immunoprotected by macroencapsulation and transplanted into the peritoneal cavity. The goal of this study was to prepare a large amount of isolated porcine hepatocytes, to encapsulate them within biocompatible membranes for transplant in allo- and xenogeneic combinations and to examine the viability and functionality of the cells 6 weeks later. Hepatocyte isolation was performed in 12 kg pigs (n = 15) by dissociation of the liver with collagenase D (1 g) without oxygenation. Encapsulation of the hepatocyte suspension (10(7)/mL) was performed in hydrogel membranes AN69; hollow fibers (2 m x 0.8 mm) and flaskes (1.8 cm), and transplanted to Yucatan pigs (n = 4) and Lewis rats (n = 12). Six weeks later, they were removed to study the cell viability by histological examination, and the production of albumin by immunonephelometry. The rate of isolated hepatocytes was 38 +/- 5 x 10(9)/mL by liver of pig and the mean viability was 93 +/- 2%. Six weeks after transplantation, hepatocytes were viable, organized in lobules, and showed conserved albumin production. The same results were observed for allogenic and xenogeneic combinations. In conclusion, this method of liver dissociation allowed for preparation of a large amount of isolated hepatocytes from a single pig liver, theoretically sufficient to treat a patient with acute liver failure. Hydrogel membranes were well tolerated and allowed immunoprotection without immunosuppression. Transplanted hepatocytes remained functional. This work is an important step in progress toward clinical application.

Animals↗

PubMed1998

Encapsulated xenogeneic hepatocytes remain functional after peritoneal implantation despite immunization of the host.

BACKGROUND/AIMS: Xenogeneic hepatocytes encapsulated in semipermeable membranes could be used in the future for the treatment of acute liver failure and congenital liver defects. However, host immune response could affect the viability and function of transplanted cells. The purpose of this study was to investigate the immunological consequences of intraperitoneal implantation of encapsulated xenogeneic hepatocytes and their effects. METHODS: Recipient Lewis rats received 2 x 10(7) human hepatocytes encapsulated in semipermeable hydrogel-based hollow fibers, 2 x 10(7) free human hepatocytes or 2 x 10(7) encapsulated Lewis rat hepatocytes. The presence of human albumin in rat sera was assessed by Western blot and the presence of anti-human hepatocytes and anti-human albumin antibodies by ELISA. RESULTS: Anti-hepatocyte antibodies were detected on the 7th day, and their level increased progressively on days 21 and 28 in rats grafted with encapsulated or free human hepatocytes. Anti-albumin antibodies were detected on day 7 and increased progressively in rats grafted with encapsulated human hepatocytes, but were not detected in the other groups. No immune complexes or complement components of donor origin were detected by immunofluorescence in the recipients' tissues. Despite immunization of the host, encapsulated xenogeneic hepatocytes survived and produced albumin, whereas free hepatocytes had been lysed. CONCLUSION: Transplantation of encapsulated xenogeneic hepatocytes resulted in immunization of the host with production of anti-hepatocyte and anti-albumin antibodies. However, hepatocytes could be efficiently protected by the membrane and remained viable and functional during the study.

Animals↗

PubMed1998

Determination of serotypes of astroviruses by reverse transcription-polymerase chain reaction and homologies of the types by the sequencing of Japanese isolates.

Human standard astroviruses, serotypes 1 to 7, and 35 Japanese isolates were typed by reverse transcription and polymerase chain reaction (RT-PCR) with serotype-specific primers for the first time. The results were identical with those obtained by enzyme immunoassay with serotype-specific polyclonal antibodies, a method which has already been reported. RT-PCR with serotype-specific primers is useful for epidemiological studies of astroviruses where serotype-specific polyclonal antibodies are not available. Two parts of the capsid region, N terminus and C terminus, were sequenced. Serotypes differed in those regions. The N terminus differed less than the C terminus between serotypes. Both the N terminus and C terminus were similar intraserotypically with the exception of serotype-4 isolates which could be divided into A and B subgroups on the basis of their C terminus sequences, which were not known previously.

Amino Acid Sequence↗

PubMed1998

[Color Doppler monitoring the utero-placental-fetal circulation variety of normal pregnancy and intrauterine growth retardation].

OBJECTIVE: To study the utero-placental-fetal circulation (UPFC) in normal pregnancy and intrauterine growth retardation (IUGR) cases. METHODS: Color doppler ultrasound was used to detect UPFC in 150 second and third trimester pregnant women, of which 89 cases were normal pregnancy and 58 cases were IUGR. 3 cases were IUGR with chronic renal failure. Hemodynamical value of the umbilical artery (UmA), umbilical vein (UmV) and uterine artery (UtA) were examined directly. The indices included time average velocity (TAV), pulsatility index (PI), resistance index (RI), systolic/diastolic (S/D) ratio, blood flow volume (Q). The maternal serum estriol (E3), human placental lactogen (HPL) and plasma thromboxane B2 (TXB2)/6-keto-PGF1 alpha (6-KP) were measured simultaneously. RESULTS: The result shows that in normal pregnancy group UPFC is abundant gradually with increasing gestational age. In IUGR group 92.53% of cases showed that TAV and Q of UmA, UmV markedly decreased and PI, RI and S/D ratio of UmA elevated at 20 weeks of gestation. There were significant difference between the two groups, maternal serum E3, HPL level in IUGR group were significantly lower than that of the normal pregnancy group, 6-KP level reduced, and TXB2/6-KP ratio significantly increased. CONCLUSION: Using color doppler ultrasound examining hemodynamical changes of UmA, UmV and UtA could observe UPFC function directly. It is one of the best method to early diagnose and predict the prognosis of IUGR.

Adult↗

PubMed1998

[Study on relativity between oxygen free radical and thromboxane B2, 6-keto-PGF1 alpha during ligustrazine treatment of intrauterine growth retardation].

OBJECTIVE: To study the pathophysiological changes and effective treatment of intrauterine growth retardation (IUGR). METHODS: Eighty-five cases with normal pregnancy and 58 IUGR women maternal red blood cell superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), serum lipid peroxide (LPO) and thromboxane B2 (TXB2), 6-keto-PGF1 alpha(6KP) were examined. IUGR group was divided into Ligustrazine group (LIG, 47 cases) and amino acid group (AAG, 11 cases) and treated accordingly. RESULTS: In IUGR group, LPO increased and SOD, GSH-Px activity, 6KP value decreased abnormally, TXB2/6KP ratio significantly increased, which was negative correlated with SOD, GSH-Px activity and positive correlated with LPO level markedly. After treatment, all the changes were improved and almost reached normal range. The fetal outcome showed that the total effective rate was 95.7% in LIG, markedly higher than that in AAG (81.8%, P < 0.05), there was significant difference between LIG and AAG. CONCLUSIONS: The balance of body oxidate/antioxidate system was disturbed and the uteroplacental-fetal circulation was obstracted in IUGR. Ligustrazine could inhibit oxygen free radical, rise SOD, GSH-Px activity, regulate TXA2/PGI2 balance, promote fetal growth.

6-Ketoprostaglandin F1 alpha↗

PubMed1998

[Pathogenetic study of femoral head necrosis caused by cortical steroid].

OBJECTIVE: To study cortical steroid caused femoral head necrosis. METHODS: We designed an experimental animal model of femoral head necrosis through cortical steroid administration. Lipid analyses of blood samples were made and examined specimens from livers and femoral heads were studied with HE, TEM methods. RESULTS: Cortical steroid resulted in dearrangement of fat metabolism, lipid change of liver and hyperlipemia. CONCLUSION: The pathogenesis of femoral head necrosis is due to fatty degeneration of osteocytes.

Animals↗

PubMed1998

[Histological and electron microscopic study of rotator cuff tear].

OBJECTIVE: To understand the changes of rotator cuff during tear and observe the pathologic and ultramicroscopic structure of rotator cuff. METHOD: Histological and ultra thin slides of samples of 36 cases of rotator cuff were made. RESULT: The degeneration of rotator cuff happened in synovium side, and then extended to the middle and deep sides of tendon. The deep side of cuff tendon could degenerate without synovium. The repair of tendon could be achieved with two types of healing. CONCLUSION: It would be difficult to achieve full repair when complete tear and deep side tear occurred to the rotator cuff.

Adult↗

PubMed1998

[Cloning and sequencing of adenovirus type 7 vaccine strain 76.5-87 mu fragment].

Adenovirus 7(Ad7) vaccine strain has been used more than 30 years in US army recruits for prevention of Ad7 infection and has been proven to be safe and effective. Recent years more attention has been paid to exploring the possibilities of using it for gene therapy or making recombinant vaccine. In order to construct adenovirus 7 vector, Ad 7 vaccine strain 76.5-87 mu fragment was cloned and sequenced. The fragment contains 3,557 bp which encodes 6 proteins of E3 region, namely 12.1 kD, 19.2 kD, 20.1 kD, 20.5 kD, 10.3 kD and partial of 15.2 kD. Nucleotide sequences of all these proteins show a high homology with the corresponding region of human adenovirus prototype strain Ad 7(Ad 7p) and Ad 7h(the homology of nucleotide sequence of the 6 proteins is more than 97.2%). The equivalent of ORF 16.1 kD in Ad7p and Ad7h was mutation due to a base pair deletion. The region corresponding to ORF 7.7 kD in Ad7p was missing in Ad7v due to a deletion. The results should be helpful to the construction of Ad7v vectors.

Adenovirus E3 Proteins↗

PubMed1998

[Construction of adenovirus type 7(vaccine strain) vector and expression of beta-galactosidase gene].

Human adenovirus type 7 DNA was extracted from purified virus cultured in WI-38 cells. The essential fragment (68-100 mu) of Ad7 DNA was used for constructing a non-defective Ad7 vector termed as pAd7 delta E3. The vector was characterized by a deletion at the E3 region that contains a multicloning site for the insertion of foreign genes. A helper-independent adenovirus type 7-beta-galactosidase recombinant was established. The recombinant contains the beta-galactosidase gene flanked by CMV early promoter and SV40 poly A signal. The constructed recombinant virus showed efficient capacity in expressing the foreign gene, beta-galactosidase.

Adenovirus E3 Proteins↗

PubMed1997

Gamma delta T-cell help in responses to pathogens and in the development of systemic autoimmunity.

Mice rendered deficient in alpha beta T-cells by single-gene knockout mutation show enhanced levels of autoantibody formation and even some symptoms of autoimmune disease. This is remarkable given that most experimental studies heretofore have indicated that the development of autoimmune disease is highly multigenic, requiring the complementary actions of multiple loci. The basis of the phenomenon in alpha beta T-cell-deficient mice appears to be the provision of help to B-cells by other cells, including gamma delta T-cells. Perhaps surprisingly, gamma delta T-cell help seems quite efficacious, particularly after infection, when it can culminate in the formation of germinal centers. Furthermore, two independent sets of studies reviewed here indicate that significant levels of self-reactive IgG can also be provoked by gamma delta T-cells independent of germinal center formation. The task ahead is to integrate this pathway into the physiologic immune responses to healthy individuals, immunocompromised individuals, and newborns.

Animals↗

PubMed1997

Color Doppler monitoring of changes of utero-placental-fetal circulation in normal pregnancy and intrauterine growth retardation.

The utero-placental-fetal circulation (UPFC) of 150 subjects during second and third trimester was examined by using color Doppler. Of them 89 were normal woman and 58 were patients with intrauterine growth retardation IUGR). Our results showed that UPFC was increased gradually during normal pregnant period. In IUGR patients it was revealed that TAV and Q of UmA, UmV and UtA decreased at 20th week of gestation, especially after 30th week. PI, RI and S/D ratio of UmA were increased, but TAV, Q of UmA and UmV were markly reduced, so was UtA. PI were increased, but the changes of RI, S/D ratio in UtA were not significant. Hemodynamical findings of UmA, UmV and UtA were abnormal in 92.53% of IUGR patients. Only 81.03% present abnormal S/D ratio of UmA (P < 0.01) and the difference was statistically significant. Maternal serum E3, HPL level in IUGR were significantly lower than that of the normal. 6KP level was reduced, TXB2/6KP ratio was significantly increased. TXB2/6KP ratio was markedly related with TAV, Q of UmA, UmV and UtA. Our results suggested that using color doppler ultrasound for examination of hemodynamical changes of UmA, UmV and UtA could revealed UPFC function directly. It is one of the best methods for monitoring IUGR and might be used for early diagnosis of IUGR. The main pathophysiological changes of IUGR were UPFC obstruction and placental disfunction.

Adult↗

PubMed1997

Endothelin-1 induces liver vasoconstriction through both ETA and ETB receptors.

BACKGROUND/AIMS: We investigated which endothelin receptors mediate the vasoconstrictive effects of endothelin-1 on liver circulation. METHODS: An isolated perfused rat liver model in recirculation was used. RESULTS: The perfusion of 10(-10) M endothelin-1 had no significant influence on the liver flow, whereas 10(-9) M endothelin-1 induced significant vasoconstriction, with flow dropping from 3.20 +/- 0.34 to 1.48 +/- 0.28 ml. min-1.g-1 liver tissue (p < 0.01 vs controls). The liver flow was interrupted following the perfusion of 10(-8) M endothelin-1. Sarafatoxin C and BQ 3020, two agonists of ETB receptor, had vasoconstrictive effects in this model. Sarafatoxin C decreased the liver flow in a dose-dependent manner, from 3.32 +/- 0.21 to 2.18 +/- 0.20, 1.60 +/- 0.09, and 1.01 +/- 0.06 ml.min-1. g-1, respectively, with 10(-9) M, 10(-8) M, and 10(-7) M. While BQ 123, an antagonist of ETA receptor, or BQ 788, an antagonist of ETB receptor, partially reversed the effect of 10(-9) M endothelin-1, the simultaneous administration of BQ 123 and BQ 788 completely reversed these effects. CONCLUSIONS: These results indicate that the vasoconstrictive effects of endothelin-1 on the liver circulation are mediated through both ETA and ETB receptors.

Animals↗