Search PubMed⌕ Search

Biomedical subjects

T H Chang

Publications and source records attributed to T H Chang.

At least 73 records · Page 4Linked to original sources
PubMed1991

Long term and large-scale cultivation of human hepatoma Hep G2 cells in hollow fiber bioreactor. Cultivation of human hepatoma Hep G2 in hollow fiber bioreactor.

Long-term and large scale cultivation of an anchorage-dependent cell line using an industrial scale hollow fiber perfusion bioreactor is described. Hep G2 cells (a human hepatoma cell line) were cultivated in an Acusyst-P (Endotronic) with a total fiber surface area of 7.2 m2 6 x 1.2m2) to produce Hep G2 crude conditioned medium (CCM). Pretreatment of the cellulose acetate hollow fibers with collagen enhances the attachment of the anchorage-dependent cells. We have succeeded in growing the Hep G2 cells in an antibiotics- and serum-free IMDM medium, supplemented with 50 micrograms/ml of Hep G2 CCM protein at inoculation. The Hep G2 cells replicate and secrete CCM protein in quantities comparable to those produced in DMEM containing 10% fetal calf serum (FCS). The highest CCM protein productivity during the 80-day cultivation was 1.1 g/day with a total of 30 g of protein accumulated. Hep G2 CCM (20-40 micrograms protein/ml) was comparable to or even better than 10% FCS in supporting the growth of Molt-4 (a human T leukemia cell line) and FO (a mouse myeloma cell line) cells in vitro. The availability of this large amount of Hep G2 CCM will aid the further purification and characterization of growth factor(s) which could be used as serum substituents.

Carcinoma, Hepatocellular↗
PubMed1991

Preparation of radioiodinated secretin for radioimmunoassay.

Radioiodination of synthetic human secretin on its N-terminal histidyl residue was not difficult when a greater amount of Chloramine T and a longer reaction time were employed to achieve better incorporation of 125I. The radioiodinated tracer for an optimal radioimmunoassay required purification. The combination of Sep-pak C18 Cartridge and high performance liquid chromatography for the purification of 125I-secretin in our study revealed that the Sep-pak cartridge was a preliminary step in removing unlabeled radioactive iodide, the reactant, and labeled materials unadsorbed to the cartridge. The eluate eluted from the Sep-pak containing high radioactivity and high immunoreactivity to the antibody were selected for further purification by HPLC which eliminated undesirable radiolabeled substances with lower immunoreactivity. The purified radiolabeled secretin was used in developing a sensitive radioimmunoassay.

Humans↗
PubMed1990

Specific erythrocyte binding is an additional nutrient acquisition system for Trichomonas vaginalis.

Specific receptor-mediated binding by Trichomonas vaginalis of human erythrocytes was demonstrated. The ability of live parasites to internalize erythrocytes was also documented. In vitro growth assays during lipid-free and iron-limiting conditions that do not support the survival of T. vaginalis organisms showed that purified erythrocyte lipids and hemoglobin were each able to provide lipids and/or hemoglobin iron for trichomonal growth and multiplication. Parasites bound hemoglobin in a highly specific receptor-mediated fashion, and only the homologous unlabeled hemoglobin, but not lactoferrin and transferrin, competed with iodinated hemoglobin binding. Two antibody-crossreactive surface proteins of the parasites were identified as adhesins, and antibody to the individual adhesins inhibited T. vaginalis recognition and binding of erythrocytes. Finally, patient sera possessed antibody to the adhesins, showing the immunogenic nature and in vivo relevance of the trichomonad proteins during infection.

Animals↗
PubMed1990

Characterization of Trichomonas vaginalis haemolysis.

The haemolytic activity of live Trichomonas vaginalis organisms was investigated. Optimal haemolysis of human erythrocytes was observed at a parasite to erythrocyte ratio of 1:5 during a 2 h incubation period. No haemolytic activity was detected in concentrated culture supernatants after overnight growth of trichomonads or when parasites were separated from erythrocytes by a 3 microns filter, suggesting a contact-dependent mechanism for haemolysis. The haemolytic activity was temperature-dependent and maximal haemolysis occurred at 37 degrees C. Treatment of trichomonads with metronidazole reduced levels of haemolysis by greater than 50%. Maximal haemolysis occurred at the pH range of the vagina during trichomoniasis. N-alpha-tosyl-L-lysyl-chloromethyl ketone and iodoacetamide, inhibitors of trichomonad cysteine proteinases, reduced the haemolytic activity of live parasites.

Animals↗
PubMed1990

Identification of five putative yeast RNA helicase genes.

The RNA helicase gene family encodes a group of eight homologous proteins that share regions of sequence similarity. This group of evolutionarily conserved proteins presumably all utilize ATP (or some other nucleoside triphosphate) as an energy source for unwinding double-stranded RNA. Members of this family have been implicated in a variety of physiological functions in organisms ranging from Escherichia coli to human, such as translation initiation, mitochondrial mRNA splicing, ribosomal assembly, and germinal line cell differentiation. We have applied polymerase chain reaction technology to search for additional members of the RNA helicase family in the yeast Saccharomyces cerevisiae. Using degenerate oligonucleotide primers designed to amplify DNA fragments flanked by the highly conserved motifs V L D E A D and Y I H R I G, we have detected five putative RNA helicase genes. Northern and Southern blot analyses demonstrated that these genes are single copy and expressed in yeast. Several members of the RNA helicase family share sequence identity ranging from 49.2% to 67.2%, suggesting that they are functionally related. The discovery of such a multitude of putative RNA helicase genes in yeast suggests that RNA helicase activities are involved in a variety of fundamentally important biological processes.

Amino Acid Sequence↗
PubMed1990

[Large-scale production of monoclonal antibodies using hollow fiber bioreactor].

Development of large-scale monoclonal antibody production using industrial scale hollow fiber bioreactor is described. Hybridoma cell lines H505AC and A306AA were cultivated in the hollow fiber perfusion bioreactor with a total fiber surface area of 7.2 m2 (6 x 1.2 m2) to produce anti-hepatitis B surface antigen (anti-HBsAg) monoclonal antibody IgM and anti-alpha-fetal protein (anti-AFP) monoclonal antibody IgG. The highest anti-HBsAg IgM productivity obtained during 49 days cultivation of H505AC was 0.135 g/day and the total accumulated IgM was 1.90 g. Results from the cultivation of A306AA in the hollow fiber module for 23 days showed the highest anti-AFP IgG productivity and the total accumulated IgG were 0.672 g/day and 7.21 g, respectively.

Animals↗
PubMed1990

The effect of birth order in twins on fetal umbilical blood gas and apgar score.

Although recent reports have revealed no difference in perinatal mortality between a set of twins, more sensitive means other than perinatal mortality are necessary to evaluate differences in twins. This study examined differences between 34 twin pairs with respect to Apgar score, umbilical venous and arterial blood gas, and acid-base data. The parameters were measured in paired samples and compared with the paired t test and Fisher's exact probability test. The most coherent findings were a higher umbilical venous PO2 and umbilical arterial PO2 in twin A. Their differences were not due to the route of delivery, interval between twins, presentation or chorionicity. The data suggest that the second-born twin has potentially greater susceptibility to hypoxia and trauma.

Apgar Score↗
PubMed1990

Supplemental vitamin A prevents the tumor-induced defect in wound healing.

To test our hypothesis that supplemental vitamin A would mitigate the impaired healing that occurs in tumor-bearing animals, six groups of C3H mice, eight per group, eating a standard commercial mouse chow ad libitum that supports normal growth, reproduction, and longevity were innoculated with 200,000 C3HBA cells. When tumors measured approximately 6 mm in diameter, the mice were anesthesized and wounded (dorsal skin incisions and subcutaneous polyvinyl alcohol sponges). Twenty-four hours later, two groups (one continued on the chow and the other started on the chow supplemented with 150,000 IU vitamin A/kg chow) underwent local tumor irradiation; two groups, one ingesting the chow, the other the vitamin A supplemented chow, were started on cyclophosphamide therapy; two groups, one ingesting the chow, the other the vitamin A supplemented chow, received neither local tumor irradiation nor cyclophosphamide therapy. An additional two groups ingesting the chow, one group neither innoculated with tumor nor wounded, the other wounded by not innoculated, served as controls. Wound breaking strength and sponge reparative collagen accumulation (assessed by hydroxyproline proline measurement) were used as indicators of wound healing. The mice were killed 12 days after wounding. Tumor presence decreased wound breaking strength and sponge hydroxyproline content; these effects were largely negated by supplemental vitamin A. Local tumor irradiation diminished the adverse effect of tumor on sponge reparative collagen content but to a lesser extent than the supplemental vitamin A. Supplemental vitamin A added to the irradiation effect on healing but irradiation did not add to the vitamin A effect. Cyclophosphamide, a systemic radiomimetic anti-tumor agent, did not alter the impaired wound healing of the tumor-bearing mice. Supplemental vitamin A mitigated the impaired wound healing in the cyclophosphamide-treated tumor-bearing mice. Supplemental vitamin A also moderated the effects of wounding, tumor, and tumor therapies (local irradiation and cyclophosphamide) on the increase in adrenal size, leukopenia, thrombocytopenia, and thymic involution (except the last was not moderated in the cyclophosphamide-treated tumor-bearing rats). The splenic enlargement in the untreated tumor-bearing wounded rats and in those treated with cyclophosphamide was lessened by supplemental vitamin A. We hypothesize that these anti-stress effects of vitamin A underlie, in part, its action in mitigating the impaired wound healing of tumor-bearing mice, including those treated by local irradiation or cyclophosphamide. These findings have implications for the care of patients with malignant tumors.

Animals↗
PubMed1990

Characterization of monoclonal antibody binding site to the polymorphic length of hepatitis B surface antigen synthesized in a cell-free system.

A combination of two modern biological techniques, hybridoma and recombinant DNA, was described to screen and characterize a monoclonal antibody binding site. Three monoclonal antibodies, M27, M9 and M01 recognizing to a specific domain of the hepatitis B virus surface antigen (HBsAg), were determined by their ability to immunoprecipitate the in vitro synthesized HBsAg in a polymorphic length. Results indicated that the M9 and M01 both recognize the S region of surface antigen while the M27 binds to the pre-S2 region of surface antigen.

Animals↗
PubMed1989

Reduction of difluoromethylornithine-induced thrombocytopenia in rats with ornithine while maintaining antitumor activity.

The purpose of this study was to evaluate the effect of a concomitant infusion of ornithine on the difluoromethylornithine (DFMO)-induced thrombocytopenia and antitumor activity. Male Fischer 344 rats with either a transplantable fibrosarcoma or Ward colon tumor were given a 12-day continuous infusion of DFMO (2000 mg/kg/day) alone or with ornithine. The dose of ornithine was defined as the molar ratio to DFMO. A continuous infusion of DFMO significantly reduced circulating platelet counts to 5-16% of the control. Concomitant ornithine treatment at a molar ratio of 0.2-0.5 resulted in protection of the rat from thrombocytopenia while the antiproliferative activity of DFMO against the fibrosarcoma or Ward colon tumor was unaffected. At a higher ornithine: DFMO molar ratio (0.7), the DFMO-induced inhibition of tumor growth was blocked. Tissue polyamine levels suggest a different sensitivity of tumor and normal tissue to DFMO. Concomitant ornithine resulted in a greater increase in the polyamine levels of normal tissues, compared with the tumor. These results suggest that ornithine can selectively inhibit DFMO-induced thrombocytopenia while not affecting the antitumor activity.

Animals↗
PubMed1989

The production of polyclonal and monoclonal antibodies in mice using novel immunization methods.

Two novel immunization methods (intrasplenic and intra-inguinal lymph node) have been developed for the production of polyclonal and monoclonal antibodies in mice. Freund's complete adjuvant and antigen were mixed in the ratio of 1:2 (v/v). Various concentrations of human serum albumin (HSA) were used as antigen. No primary immune response was induced with 0.1 microgram of HSA in either of the methods studied. Intrasplenic immunization resulted in the strongest primary immune responses using all other doses of HSA. The primary immune response induced by intrasplenic immunization with 0.5 microgram of HSA was higher than any response induced by subcutaneous immunization with various doses of HSA. Inguinal lymph node immunization was less effective than intrasplenic immunization but better than subcutaneous immunization with 1-50 micrograms of HSA. Comparisons were also made of the efficacy of different adjuvants when inducing primary immune responses with 1 microgram of HSA. Freund's complete adjuvant resulted in a much stronger response than Freund's incomplete adjuvant and alum. Both intrasplenic and inguinal lymph node immunization using 1-5 micrograms of HSA were able to induce strong primary immune responses. Secondary immunization with either method or intravenous injection 3 days before fusion resulted in a higher frequency of specific monoclonal antibodies.

Adjuvants, Immunologic↗
PubMed1989

A very small viral double-stranded RNA.

UmV is a double-stranded RNA (dsRNA) virus of the corn fungal pathogen Ustilago maydis. UmV has no infectious cycle. Some UmV subtypes have viral dsRNAs encoding secreted toxins that kill sensitive cells of the same species and related species. There are three viral subtypes, P1, P4 and P6, which differ in the specificity of their secreted killer toxins. Each has three size classes of dsRNA: H (heavy), M (medium) and L (light). The L segments of UmV are unique in being derived from one end of the larger M segments. We have sequenced P1 L and placed it at the 3' end of the P1 M1 plus strand. In their overlapping regions, these dsRNAs are identical in sequence. In vitro translation of P1 M1 results in a peptide whose size is consistent with its being encoded by the non-L region of M1. P1 L is a very small dsRNA of 355 bp. It has no long open reading frames and produces no detectable in vitro translation product. The sequence of P1 L suggests that it is derived by a process unique among dsRNA viruses: replication and packaging of the 3' end fragment of a processed mRNA.

Base Sequence↗
PubMed1989

Routine pretreatment evaluation in cervical carcinoma.

A review of 573 previously untreated patients with invasive cervical carcinoma was undertaken to determine the significance of the routine pretreatment performance of chest x-ray, intravenous pyelography (IVP), cystoscopy and sigmoidoscopy. Chest x-ray was performed in 570 patients (99.5%), IVP in 514 (89.7%), cystoscopy, 502 (87.6%) and sigmoidoscopy, 496 (86.6%). The overall yield of tumor-related abnormalities demonstrated in chest x-ray, IVP, cystoscopy and sigmoidoscopy was 1.8%, 9.1%. 6.4% and 1.2% respectively. The chest x-ray findings changed the initial clinical stage in 1.3% of cases, IVP in 4.2%, cystoscopy in 4.0% and sigmoidoscopy in 0.6%. There were 5 instances of bladder involvement and 5 of bullous edema of the bladder found in patients originally classified as having stage I or stage II disease. Thus, to omit cystoscopy may not be so safe in patients with stage I and stage II diseases. We suggest that chest x-ray, IVP and cystoscopy should be performed as part of staging in all patients with cervical carcinoma, however, sigmoidoscopy can be reserved for those initially diagnosed to have advanced disease or symptomatic patients.

Carcinoma↗
PubMed1988

Polyamine-directed preferential nutritional repletion of normal tissues in tumor-bearing hosts.

Our previous study demonstrated that total parenteral nutrition (TPN) increases erythrocyte (RBC) polyamines selectively in cancer patients but not in non-cancer patients, suggesting that these changes may relate to tumor presence. We therefore studied the possible relationship between RBC polyamine levels and potential tumor growth induced by TPN. In addition, we attempted to control tumor growth during TPN with alpha-difluoromethylornithine (DFMO), a suicide inhibitor of ornithine decarboxylase (ODC), in a fibrosarcoma-bearing rat model. Rats in a control group received chow ad libitum for 3 weeks and their tumors grew exponentially. A restricted intake (RI) tumor-bearing group received 8 g chow per day per rat; this produced malnourished rats in which tumor growth significantly slowed. The third group (RI----TPN) received the RI diet for 2 weeks and TPN for 1 week, which resulted in an increase in tumor growth. The last group (RI----TPN + DFMO) received a 2-week RI regimen and 1-week TPN plus DFMO regimen, which inhibited tumor growth to the level of the RI group due to the addition of DFMO (1 g/kg/day). Although the addition of TPN to the RI regimen markedly increased tumor ODC activity, as well as tumor putrescine and RBC putrescine levels, the addition of DFMO to the RI----TPN regimen entirely abolished these increases. Despite DFMO treatment, liver ODC activity in RI----TPN + DFMO group was unaffected. The plasma albumin level, an indicator of host nutrition, of the RI----TPN + DFMO group was significantly higher than that of the RI group. Liver, spleen, kidney and total body weights of the RI----TPN or RI----TPN + DFMO group were significantly higher than those of the RI group. These results indicate that TPN can enhance tumor growth in malnourished hosts and that the addition of DFMO to TPN can effectively control this TPN-enhanced tumor growth, leading to preferential nutritional repletion of the host.

Animals↗
PubMed1988

RNA11 protein is associated with the yeast spliceosome and is localized in the periphery of the cell nucleus.

The yeast rna mutations (rna2 through rna10/11) are a set of temperature-sensitive mutations that result in the accumulation of pre-mRNAs at the nonpermissive temperature. Most of the yeast RNA gene products are involved in and essential for mRNA splicing in vitro, suggesting that they code for components of the splicing machinery. We tested this proposal by using an in vitro-synthesized RNA11 protein to complement the temperature-sensitive defect of the rna11 extract. During the in vitro complementation, the input RNA11 protein was associated with the 40S spliceosome and a 30S complex, suggesting that the RNA11 protein is indeed a component of the spliceosome. The formation of the RNA11-associated 30S complex did not require any exogenous RNA substrate, suggesting that this 30S particle is likely to be a preassembled complex involved in splicing. The RNA11-specific antibody inhibited the mRNA splicing in vitro, confirming the essential role of the RNA11 protein in mRNA splicing. Finally, using the anti-RNA11 antibody, we localized the RNA11 protein to the periphery of the yeast nucleus.

Antibodies, Fungal↗
PubMed1988

[Continuous production of anti-hepatitis B surface antigen monoclonal antibody in hollow fiber perfusion bioreactor].

Hybridoma cell line H440Ac was cultivated continuously in hollow fiber perfusion bioreactor for fifty days to produce anti-hepatitis B surface antigen (anti-HBsAg) monoclonal antibody. A total of 90 mg anti-HBsAg antibody was produced in the hollow fiber bioreactor with 1000 cm2 membrane surface area. The collected production medium has an average antibody concentration of 0.45 mg/ml with a high concentration of 2.3 mg/ml. This compares with 0.016 and 1.1 mg/ml antibody concentration as collected from spinner flask and mouse ascites. The purity of the produced antibody is 0.085, 0.0028 and 0.026 mg antibody per mg of total harvested protein in the culture media produced from the hollow fiber bioreactor, spinner flasks and mouse ascites, respectively.

Animals↗
PubMed1986

A new method for biliary tract reconstruction for primary bile duct stones.

Twelve patients with repeated episodes of jaundice and infection due to primary biliary duct stones were treated by interposing a 50-cm segment of the jejunum between the proximal common duct below the liver and the first portion of the duodenum. The interposed jejunum was positioned in a retrogastric position. There were no postoperative deaths, and laboratory data indicate no alteration in gastric secretion, gastrin levels, or barium reflux into the liver. After a mean follow-up period of 11.67 months, there was no need for further operations in these patients, all of whom had had previous multiple episodes of cholangitis and biliary colic.

Adult↗