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Biomedical subjects

T Chang

Publications and source records attributed to T Chang.

At least 37 records · Page 2Linked to original sources
PubMed2000

Enhanced allograft survival induced by posttransplant donor spleen cell infusion occurs via a mechanism that is distinct from the mechanism of enhancement by donor bone marrow.

BACKGROUND: Our previous studies have shown that the ability of donor bone marrow to augment skin graft survival in antithymocyte serum (ATS)-treated recipients is dependent on the presence of functional CD95-ligand (Fas-ligand) molecules on donor cells. Because donor spleen cells can augment graft survival to a similar degree in the same model, we investigated whether the donor spleen cell effect was also dependent on the presence of CD95-ligand on donor cells and CD95 on recipient cells. METHODS: Mutant mice bearing defects in the expression of CD95 (lpr mutation) and CD95-ligand (gld mutation) were used as recipients and cell donors, respectively. Recipients were injected with rabbit ATS on days -1 and +2, and then were injected with 5x10(7) spleen cells on day +7. Skin graft survival was compared and correlated with the use of mutant mice as recipients and cell donors. RESULTS: The combination of ATS and infusions of wild-type [median survival (MST)=44 days, P=0.0004] and gld (mutant CD95-ligand, MST=37 days, P=0.02) donor spleen cells enhanced C3H graft survival, compared with (C57BL/6 x A)F1 recipients treated with ATS alone (MST=27 days). Furthermore, C57BL/6 lpr (CD95-deficient) strain recipients treated with ATS and donor spleen cells demonstrated enhanced B10.D2(R107) strain skin graft survival (MST=44 days, P=0.003), compared with C57BL/6 lpr recipients treated with ATS alone (MST=31 days). Wild-type C57BL/6 recipients treated in the same manner also exhibited an extension of graft survival (MST=64 days) versus controls treated with ATS alone (MST=31 days). CONCLUSION: The data demonstrate that the ability of donor spleen cells to augment allograft survival is not dependent on the CD95/CD95-ligand pathway; therefore the deletion of allospecific cells by donor spleen cells may be induced via a pathway other than deletion by donor bone marrow cells.

Animals↗
PubMed2000

Developmentally regulated expression of a peptide:N-glycanase during germination of rice seeds (Oryza sativa) and its purification and characterization.

Peptide:N-glycanase (PNGase; EC 3.5.1.52) activity was detected in dormant rice seeds (Oryza sativa) and the imbibed rice grains. Time-course studies revealed that the enzyme activity remained almost constant until about 30 h after imbibition in both of endosperm- and embryo tissue-containing areas, and started to increase only in growing germ part, reached a peak at about 3-day stage, followed by a gradual decrease concomitant with a sharp increase in the coleoptile. The specific activity increased about 6-fold at about 3-day stage. PNGase was purified to electrophoretic homogeneity from the extracts of germinated rice seeds at 24 h, and the apparent molecular weight of the purified enzyme, estimated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), was about 80,000. The purified enzyme was designated PNGase Os to denote its origin. The N-terminal sequence of the 10 residues was determined to be SYNVASVAGL. The purified PNGase Os in SDS-PAGE appeared as a rather broad band, consistent with the presence of multiple glycoforms as indicated by chromatographic behavior on a Sephadex G-75 column. PNGase expressed in coleoptile under anoxia condition was also purified, and both of the purified enzymes were found to exhibit very similar, if not identical, electrophoretic mobility in SDS-PAGE. PNGase Os exhibited a broad pH-activity profile with an optimum of 4-5 and, interestingly, was significantly inactivated by K(+) and Na(+) at near the physiological concentration, 100 mM. These results are discussed in relation to other work.

Amidohydrolases↗
PubMed2000

Glycoprotein Ib-binding protein from the venom of Deinagkistrodon acutus--cDNA sequence, functional characterization, and three-dimensional modeling.

Agkicetin-C, a potent glycoprotein Ib antagonist from the venom of the Chinese pit viper, Deinagkistrodon acutus, has been purified and characterized (5). It is a disulfide-linked heterodimer containing subunits of 132 and of 123 amino acid residues. Herein, the complete amino acid sequences were resolved by cloning and nucleotide sequencing of the cDNAs. The sequences of its subunits are homologous to those of other snake venom proteins of the C-type (Ca2+-dependent) lectin superfamily. A three-dimensional model of agkicetin-C was constructed based on the crystal structure of habu coagulation factor IX/X-binding protein. By careful alignment of all the related sequences available and comparing the 3D-model of agkicetin-C with structures of other homologous proteins of different functions, some variable residues of agkicetin-C were identified, which possibly are responsible for the specificity of this distinct subtype of the C-type lectin-like venom proteins.

Amino Acid Sequence↗
PubMed1999

Initial characterization of the complement activating compounds in extracts of smokeless tobacco.

Aqueous extracts of smokeless tobacco (ST) have been shown to be potent activators of complement. However, the mechanisms by which smokeless tobacco activates complement are not well understood. This study was undertaken to identify the complement activating compounds in ST extracts. The approximate molecular size of the activating agent(s) in smokeless tobacco was determined by dialyzing aqueous extracts of loose leaf chewing tobacco (1S1), dry snuff (1S2), and moist snuff (1S3). Following dialysis (total dilution effect of 1:10(9)), using a membrane with a molecular weight retention limit of 12-14 kDa, all extracts retained full capacity to activate serum complement as determined by a hemolytic assay. Fractionation of the extracts by gel filtration chromatography revealed that the complement activating agents in ST were high molecular weight compounds that eluted between 400 kDa and the void volume (1500 kDa) of a Sephacryl S300 column. The high molecular weight complement-activating peak was isolated and found to be a more potent complement activator than the unfractionated extract. The chemical nature of the complement activating compounds was determined by subjecting the extracts to boiling for 30 min, an organic extraction with chloroform/methanol 2:1, or treatment with a DNAse/RNAse enzyme cocktail. None of these treatments destroyed the capacity of ST extracts to activate complement, suggesting that the activating agents may be carbohydrate-like. Finally, an extraction protocol designed to remove polyphenols significantly diminished the complement activating capacity of the ST extracts. These results clearly demonstrate that the complement activating substances in smokeless tobacco extracts may be large (>400 kDa) polyphenol-containing compounds (i.e. tannins). Identification of this agent(s) will be important for distinguishing the mechanism of smokeless tobacco-induced complement activation.

Complement Activation↗
PubMed1999

Donor cell induced CD69 expression and intracellular IL-2 and IL-4 production by peripheral blood lymphocytes isolated from kidney transplant recipients.

Flow cytometry assays, which measure CD69 activation and intracellular cytokine production, have been used to measure peripheral blood lymphocyte (PBL) responses to in vitro antigen exposure. In the present study, we show that, in healthy individuals and immunosuppressed kidney transplant recipients, CD69 expression and intracellular cytokine production by peripheral blood T cells compare favorably to thymidine uptake as a measure of PBL response to alloantigen in mixed leukocyte culture (MLC). Heparinized whole blood from 23 healthy individuals was incubated for 24-48 h with 3rd party allogeneic monocytes; blood from twelve kidney transplant recipients was incubated with monocytes from their kidney donor and with monocytes from unrelated individuals. The percentage of T cells expressing surface CD69 or intracellular IL-2 or IL-4 was determined by 3-color flow cytometry. We identified 5 donor-specific response patterns in our kidney transplant group. One transplant recipient was hyporesponsive; his cells did not express CD69 or produce IL-2 in response to either donor or 3rd party allogeneic cells. All other transplant recipients expressed CD69 and IL-2 in response to 3rd party allogeneic cells. Two had no response to donor cells (donor-specific hyporesponsiveness), three had donor-specific anergy (CD69 expression without cytokine production in response to donor cells), five had a donor-specific Thl response (CD69 expression and IL-2 production in response to donor cells), and one had a donor-specific Th2 response (CD69 expression and IL-4 but not IL-2 production in response to donor cells). Rapid measures of donor-specific hyporesponsiveness such as CD69 activation antigen expression and intracellular cytokine production may prove valuable in monitoring lymphocyte function and aid in the long-term management of kidney transplant recipients.

Antigens, CD↗
PubMed1999

Safety of Neoral conversion in maintenance renal transplant patients: A one-year, double-blind study. NOVARTIS OLN-353 Study Group.

BACKGROUND: Despite the improved pharmacokinetic characteristics of Neoral, some centers have encountered difficulty with the conversion of some patients from Sandimmune to Neoral and have reported precipitation of toxicity and rejection. METHODS: We conducted a randomized, double-blind, parallel-group, multicenter prospective study of stable maintenance renal transplant patients to compare the safety and tolerability of converting from Sandimmune to Neoral (N = 132) versus continuing Sandimmune (N = 130). Patients were studied for one year. The cyclosporine (CsA) dose was adjusted as necessary to maintain site-specific trough whole blood levels. RESULTS: During the study, dose adjustments were frequent in both groups: 67% Neoral versus 65% Sandimmune patients. At study completion, the mean trough CsA levels were comparable; the dose change-from-baseline did not differ statistically between groups. Fewer Neoral (87.1%) than Sandimmune (95.4%) patients reported adverse events, and serious adverse events were comparable. Adverse events related to CsA were not more common in the Neoral group. Renal function measures also implied comparability of the two treatments. Three Neoral versus five Sandimmune patients experienced acute rejection; two Neoral versus five Sandimmune patients experienced chronic graft dysfunction. Two septic deaths occurred in the Neoral group. No grafts were lost. CONCLUSIONS: With careful monitoring, conversion of maintenance renal transplant patients to Neoral can be safely accomplished.

Adult↗
PubMed1999

Correction of the contracted eye socket and orbitozygomatic hypoplasia using postauricular skin flap and temporal fascial flap.

The authors corrected a contracted eye socket and orbitozygomatic hypoplasia simultaneously, secondary to previous surgery and radiotherapy. A one-stage surgical reconstruction was undertaken using both a postauricular skin flap and a temporal fascial flap, which were rotated for eye socket reconstruction and bone graft coverage. Hydroxyapatite was inserted as an onlay bone graft substitute to enlarge the orbitozygomatic region. The authors' experience with 12 patients resulted in contours that were satisfying and encouraging. f1

Adolescent↗
PubMed1999

Surgical reconstruction of the contracted eye socket and orbitozygomatic hypoplasia in a one-stage operation.

To correct the contracted eye socket and orbitozygomatic hypoplasia simultaneously secondary to previous surgery and radiotherapy, we employed a one-stage surgical reconstruction that used a postauricular skin flap and temporal fascial flap, which were rotated for eye socket reconstruction and bone graft coverage. Hydroxyapatite was inserted as an onlay bone graft substitute to enlarge the orbitozygomatic region. In our 12-case experience the results were satisfying and encouraging with minor complications, which are presented.

Adolescent↗
PubMed1999

Canine pancreatic juice stimulates the release of secretin and pancreatic secretion in the dog.

A secretin-releasing factor (SRF) was found in canine pancreatic juice that increases plasma secretin and stimulates pancreatic secretion in rats, suggesting that a positive feedback mechanism may be involved in the regulation of pancreatic secretion. In the present study, we investigated to determine whether or not SRF releases endogenous secretin and stimulates exocrine pancreatic secretion in conscious dogs. Fresh pancreatic juice was collected from four dogs by intravenous administration of secretin at 0.5 microg. kg(-1). h(-1) and CCK at 0.2 microg. kg(-1). h. The juice was boiled for 10 min at 100 degrees C. Experiments were carried out in phase I of spontaneous cycle of interdigestive pancreatic secretion. The testing solutions were infused intraduodenally in separate experiments: NaHCO3 solution (0.1 M, 4.5 ml/min, 60 min), a corn oil (Lipomul, 2 ml/min, 10 min), boiled pancreatic juice (BPJ, 4.5 ml/min, 60 min), and mixture of BPJ and Lipomul. Pancreatic secretion of fluid and bicarbonate was significantly increased by either BPJ or a mixture of BPJ and Lipomul (34- and 31-fold or 41- and 38-fold, respectively). Plasma secretin level also significantly increased by 164.7 +/- 13.4% and 223.1 +/- 35.0%, respectively, from basal concentration of 1.7 +/- 0.5 pM. In contrast, neither bicarbonate solution nor Lipomul influenced the plasma secretin level or pancreatic secretion. In addition, when Lipomul was incubated with BPJ, no fatty acid was produced. Thus the increased pancreatic secretion in the dog infused with a combination of BPJ and Lipomul was caused by SRF in BPJ, which released endogenous secretin. Moreover, the increases by BPJ of both plasma secretin level and bicarbonate secretion were completely blocked by intravenous administration of an antisecretin antibody in these dogs. The observations suggest that SRF in pancreatic juice exerts a positive feedback effect on exocrine pancreatic secretion that is mediated by the release of secretin in the interdigestive state in dogs.

Animals↗
PubMed1999

Curriculum renewal and a process of care curriculum for teaching clerkship students.

BACKGROUND AND OBJECTIVES: A school-wide curriculum renewal led to a new clerkship curriculum that teaches core family practice competencies by focusing on the process of care in generalist practice. The organizing framework consists of five prototypic visits and their encounter tasks: 1) new problem visit, 2) checkup visit, 3) chronic illness visit, 4) psychosocial problem visit, and 5) behavioral change visit. METHODS: The seminars occur at the beginning of the rotation and use active learning techniques. Evaluation includes student perceptions of the seminars and teachers and student performance on a clinical performance examination (CPX). RESULTS: Students rated the usefulness of the seminars and the seminar leaders' teaching behaviors favorably. The CPX checklist scores showed that students could perform most of the behaviors expected for each prototypic visit. The students listed the appropriate encounter tasks nearly half of the time when describing what tasks they tried to accomplish during the CPX cases. The students listed concrete behaviors just over 50% of the time. CONCLUSIONS: The students learned the material presented in the seminars and applied it during the CPX. Students can do most of the behaviors but do not seem to describe the tasks as abstractly as faculty. These results come from one class cohort in one medical school, so the generalizability is limited until further work, including other learners, confirms these findings.

Attitude of Health Personnel↗
PubMed1999

Effects of microwave heating on systemic and local infiltrating lymphocytes in patients with chronic limb lymphedema.

OBJECTIVES: To observe the characteristics of lymphocyte phenotypes in systemic and local skin and to evaluate the effects of microwave heating and bandaging treatment on chronic limb lymphedema. METHODS: Totally 27 patients with lymphedema and 10 normal subjects were examined with alkaline phosphatase-anti-alkaline phosphatase (APAAP) and avidin-biotin-peroxidase (ABC) immunohistochemistry for the observation of systemic lymphocyte phenotypes and inflammatory cell infiltration of skin tissues. RESULTS: In the peripheral blood of patients with chronic limb lymphedema, the number of CD4 T lymphocytes and the ratio of CD4/CD8 decreased, while the number of CD8 T lymphocytes increased. Obvious dermal perivascular infiltration of T lymphocytes was also observed. After two courses of microwave heating and bandaging treatment, the number of CD4 T lymphocytes augmented and the decreased CD4/CD8 ratio returned to normal, and the number of CD8 T lymphocytes reduced. The perivascular T lymphocyte infiltration in the dermis resolved and the number of macrophages elevated. CONCLUSION: Microwave heating and bandaging treatment can regulate the imbalance of systemic and local immunity in patients with chronic lymphedema.

Adolescent↗
PubMed1998

Identification of free deaminated sialic acid (2-keto-3-deoxy-D-glycero-D-galacto-nononic acid) in human red blood cells and its elevated expression in fetal cord red blood cells and ovarian cancer cells.

Chemical studies have shown the occurrence of the deaminated sialic acid 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (KDN) in paired samples of blood obtained from mothers and newborns of healthy human individuals. Most of the KDN was found in red blood cells, although low levels were detected in mononuclear cells. No N-glycolylneuraminic acid was detected. Unexpectedly, nearly all of the KDN in fetal cord and matched maternal red blood cells was present as the free sugar and comparatively little occurred conjugated or as cytidine 5'-KDN phosphate. The amount of free KDN in fetal newborn red blood cells was 2.4-fold higher than in red blood cells from the mothers or from healthy nonpregnant women. Free KDN was also identified in normal human ovaries, in ovarian tumors, and in ascites cells obtained from ovarian cancer patients. Importantly, as in fetal cord red blood cells, a distinguishing feature of KDN expression in ovarian tumor cells was an elevated level of free KDN compared with normal controls. A positive correlation was found between an increase in the ratio of free KDN/N-acetylneuraminic acid in ovarian adenocarcinomas and the stage of malignancy. This was particularly evident in tumor cells isolated from the ascites fluid. The central importance of these new findings is 2-fold. First, they show that free KDN is a minor but ubiquitous sialic acid in human red blood cells and that its elevated expression in red blood cells from fetal cord blood compared with maternal red blood cells may be developmentally related to blood cell formation during embryogenesis. Second, the enhanced expression of KDN in ovarian cancer cells suggests that this sialic acid, like the alpha2,8-linked polysialic acid glycotope, may be an oncofetal antigen in these tumors and thus could be an "early warning" signal for onset of disease and/or a marker for detection of recurrence of disease. These new findings highlight the importance of elucidating the role that KDN and KDN-containing glycoconjugates may play in normal development and malignancy.

Adenocarcinoma↗
PubMed1998

The C-terminal segment is essential for maintaining the quaternary structure and enzyme activity of the nitric oxide forming nitrite reductase from Achromobacter cycloclastes.

We have constructed and expressed a series of mutated nitrite reductase (NIR) mutants based on the sequence of NIR from Achromobacter cycloclastes. Deleting a pentapeptide, an undecapeptide, or a heptadecapeptide from the C-terminus of NIR resulted in a series of C-terminal deletion mutated proteins designated as NIR-5, NIR-11, and NIR-17, respectively. A C-terminally extended mutated protein, NIR+8, was also produced, which contains an extra octapeptide attached to the C-terminus of the wild-type NIR. An SDS-PAGE system using tris-tricine buffer could retain the native NIR in its trimeric form, thus offering a convenient method to check the quaternary structure of NIR analogs. By using this system it was found that NIR-5 was maintained as trimer and retained 72% of wild-type enzyme activity. However, both NIR-11 and NIR-17 behaved as monomers in the SDS-PAGE and lost all their enzyme activity. Although NIR+8 maintained its trimeric structure it was enzymatically inactive. These results clearly indicate that the C-terminal undecapeptide is essential for maintaining the quaternary structure as well as the full enzymatic activity, as expected from the X-ray crystallography studies.

Alcaligenes↗
PubMed1998

Mouse brain potassium channel beta1 subunit mRNA: cloning and distribution during development.

The pore-forming alpha subunits of voltage-gated potassium channels in neurons and other excitable cells are expressed in association with accessory beta subunits. These subunits both promote insertion of channel complexes into surface membranes and influence their electrophysiological properties. As part of an effort to understand the regulation of voltage-gated potassium channels during development, we cloned the mouse homolog of the rat Kvbeta1 potassium channel subunit. Kvbeta1 subunits are known to associate preferentially with Shaker (Kv1)-related alpha subunits. We then used a digoxigenin-tagged cRNA probe and in situ hybridization techniques to visualize the appearance of Kvbeta1 mRNA transcripts during late embryonic and early neonatal development of the mouse brain. We detected Kvbeta1-specific labeling of cells in hippocampus, cerebral cortex, caudate putamen, colliculus, and cerebellum. In hippocampus, we observed Kvbeta1 mRNA in CA3 pyramidal neurons at the earliest time examined, embryonic day 16 (E16). Between E16 and postnatal day 7 (P7), cell labeling increased uniformly across the pyramidal neurons of Ammon's horn (CA1, CA2, and CA3). Subsequently, between P7 and P22, regional differences characteristic of mature hippocampus appeared-intense labeling of neurons in CA3 and CA1, and less in CA2. In cortex, labeling of cells in the subplate and cortical plate layers was observed at E16. During development, the intensity of this labeling increased, and labeled cells persisted into the adult stage in the deep cortical layer (VIb) formed from subplate neurons. Additional labeling of scattered solitary cells in cortical layers II-VIa emerged between P3 and P7 and was prominent in mature cortex. In caudate putamen, Kvbeta1-labeled cells were observed at P1 and were restricted to the lateral and rostral half of the caudate. During development, labeling expanded caudally and medially and eventually filled the mature caudate putamen. In colliculus, a small population of inferior colliculus cells showed labeling at P7, and additional labeling of scattered cells appeared during development. In superior colliculus, labeling was observed only in the adult deep gray layer. In cerebellum, intense labeling was observed in Purkinje cells at all stages between P1 and adult. Labeling was also seen in granule neurons in the external granule layer at early postnatal stages and in the inner granule layer beginning at P7.

Amino Acid Sequence↗
PubMed1998

Smokeless tobacco extracts activate complement in vitro: a potential pathogenic mechanism for initiating inflammation of the oral mucosa.

The use of smokeless tobacco has been linked to an increased incidence of inflammation of the buccal and gingival mucosa. However, the mechanisms by which smokeless tobacco initiates inflammation are not well understood. The complement cascade is a ubiquitous source of proinflammatory molecules and can be activated rapidly by a wide variety of agents. Therefore, the effect of smokeless tobacco on complement was investigated as a potential pathogenic mechanism for triggering inflammation of the oral mucosa. Aqueous extracts of loose leaf chewing tobacco (1S1), dry snuff (1S2), and moist snuff (1S3), added to normal human serum, depleted complement hemolytic activity in a dose-dependent manner. Experiments utilizing sera deficient in one specific complement component indicated that the smokeless tobacco-induced depletion of hemolytic activity was due largely to consumption of C3. Furthermore, assays designed to test the activity of the alternative pathway of complement clearly showed that all three extracts depleted the hemolytic activity of this pathway. Finally, all three smokeless tobacco extracts activated the alternative pathway since significantly elevated levels of the cleavage fragments iC3b and Bb were detected in extract-treated serum. High quantities of the classical pathway cleavage fragment C4d also were detected in serum treated with moist snuff (1S3). The results clearly demonstrate that smokeless tobacco extracts activate the alternative pathway and also suggest some measure of classical pathway activation. Activation of complement by smokeless tobacco may be a mechanism for initiating inflammation of the oral mucosa.

Complement Activation↗
PubMed1998

A prospective study of bone mineral density change in Taiwan.

In 1989, a cross-sectional study was carried out in Lin-Kou Township, Taiwan, to determine the distribution of bone mineral density (BMD) in the lumbar spine of Chinese people. Lumbar spine BMD was measured using dual-photon absorptiometry in 404 healthy volunteers (266 women and 138 men, aged 15 to 83 years). In 1994-1995, 318 of the same volunteers were reexamined for the present study. Except for there being fewer males and smokers present, there were no significant differences between the second survey respondents and nonrespondents. Spine BMD decreased at over 1% per year in Chinese women over age 50, which was somewhat higher than reported for caucasian women. Since there was a loss of BMD in Chinese women after their 20s, a case can be made for starting preventive activities for female adolescents. There were no differences in the mean BMD change rates among the different age groups of Chinese men. Baseline BMD, menopause, and weight change were associated with the lumbar spine BMD change rates in Chinese women. Body mass index was the only variable significantly associated with BMD change in Chinese men. The rate of BMD change was not associated with diet.

Absorptiometry, Photon↗