Search PubMed⌕ Search

Biomedical subjects

J Chang

Publications and source records attributed to J Chang.

At least 415 records · Page 23Linked to original sources
PubMed1992

Management of ophthalmic complications of facial nerve palsy.

Six stages--supportive care (with or without tarsorrhaphy), planning for facial reanimation, lower eyelid and lateral canthal resuspension, passive upper eyelid reanimation, dynamic eyelid reanimation, and soft tissue repositioning--should be considered in the management of the ophthalmic complications of facial nerve palsies. Each stage should be considered in order, although action in each stage may not be appropriate for all patients. In addition, after appropriate consideration, two or more staged procedures may be performed at the same time. Treatment may be held at any stage in which the cornea is compensated and the patient is comfortable and happy. By employing this staged approach, the surgeon has a method of organizing therapy in a logical fashion, and the patient is offered a set of reassuring goals, which combine to make the treatment plan more effective.

Eyelid Diseases↗
PubMed1991

Acute toxicity of amine-boranes and related derivatives in mice.

Three boron derivatives, i.e. trimethylamine-carbomethoxyborane, tetrakis-mu-(trimethylamine-boranecarboxylato)-bis(trimethylamine- carboxyborane)-dicopper(II), and N,N-dimethyl-n-octadecylamine borane were evaluated for acute toxicity in male mice, at 1, 2 or 5 x their therapeutic dose in rodents for pharmacological activity. Based on organ weights, clinical chemistry, hematopoietic parameters and tissue morphology, the trimethylamine-carbomethoxyborane was shown to be free of toxicity. The dicopper(II) complex and N,N-dimethyl-n-octadecylamine borane demonstrated slight toxicity with marginal disturbance in hepatic and kidney morphology. The dicopper(II) complex may cause marginal myocardial damage and the N,N-dimethyl-n-octadecylamine borane caused elevations in cholic acid. All three derivatives demonstrated reductions in hematocrit.

Animals↗
PubMed1991

Determination of ML-1035 enantiomers in plasma by chiral high-performance liquid chromatography.

ML-1035, is a gastroprokinetic agent structurally related to metoclopramide. Because ML-1035 contains an asymmetric chiral sulphoxide moiety, a chiral HPLC method has been developed to separate and quantitate its R- and S-enantiomers in plasma. The ML-1035 enantiomers present in plasma are extracted with dichloroethane under alkaline conditions, the extract evaporated to dryness and reconstituted in the mobile phase. Samples are chromatographed on a Chiralcel OD HPLC column with hexane-absolute ethanol (1% TEA) (1:1, v/v) as the mobile phase. The enantiomers of the unchanged drug are determined by fluorescence measurement (ex: 310 nm, em: 350 nm). The method provides a linear response for both enantiomers over a concentration range of 25 (limit of determination) to 2500 ng ml-1 with correlation coefficients of 0.9987 or greater. The inter-assay precision is 9.5% or less and the accuracy ranges from 93.9 to 103.4% of the theoretical value. The method is used to determine the plasma concentrations of the R- and S-enantiomers following oral and intravenous administration of R- or S-enantiomers to dogs. The method is also adapted to measure enantiomer levels from in vitro reaction mixtures so that the possibility of metabolic inversion may be assessed. The data suggest that no significant level of inversion between the enantiomers occurred either in vivo or in vitro.

Animals↗
PubMed1991

In vitro IgE production by interleukin 4-stimulated human peripheral blood mononuclear cells is suppressed by rapamycin.

Rapamycin (RAPA) is a new immunosuppressant which is 50-fold to 100-fold more potent than cyclosporin A (CyA) in inhibiting cellular immune responses and allograft rejection in animal models of organ transplantation. The drug's effect on in vitro IgE synthesis by interleukin (IL)4-stimulated human peripheral blood mononuclear cells was examined and compared with CyA's effect in this study. RAPA was found to be about 100-fold more potent than CyA in inhibiting IgE synthesis. Its inhibitory effect on IgE production was significant if it was added to the culture before Day 6 of a 14-day culture. The suppression was accompanied by the inhibitory effect on cell proliferation and on IgE-binding factor (IgE-BF) production. IL2 was able to partially reverse CyA- but not RAPA-induced inhibition of IgE production. Commercial B cell growth factor (cBCGF) was not able to reverse either RAPA- or CyA-induced suppression of IgE synthesis. The strong inhibitory effect of RAPA in IgE synthesis may be useful in certain clinical applications where overproduction of pathogenic IgE is a key issue. RAPA can also be used as a tool to dissect the regulation of IgE production.

Cell Division↗
PubMed1991

Long-term marrow cultures: in vitro purging of leukaemic cells.

After induction and consolidation chemotherapy, patients with acute myeloid leukaemia (AML) usually achieve clinical remission. However, leukaemic cells, although not readily apparent, persist in most patients since the remissions cannot be sustained without further cytoreductive measures. To eradicate residual disease after induction chemotherapy, various treatment options (particularly allogeneic bone marrow transplantation) have been used. Autologous bone marrow transplantation (ABMT) can also lead to long-term survival, presumably due to the eradication or control of residual disease, but this occurs in only about 50% of cases transplanted. Relapse in the other patients occurs as a consequence of leukaemic cells surviving the conditioning regimen and/or the infusion of leukaemic cells present in the autografted bone marrow. In attempts to decrease the relapse rates after ABMT, chemical or immunological methods for in vitro purging of the harvested bone marrow cells to remove residual leukaemia have been used: the effectiveness of these procedures is unproven. This chapter describes the biology of long-term bone marrow cultures (LTBMC). How the biological differences between normal and leukaemic cells in LTBMC can be exploited to encourage the growth of normal haemopoietic cells at the expense of leukaemic cells, and how these cultured cells can be used in ABMT are discussed. The survival of patients after LTBMC/ABMT and the low relapse rate indicate that this is a useful therapeutic approach in the treatment of patients with leukaemia.

Bone Marrow↗
PubMed1991

High dose combination chemotherapy with ifosfamide, cyclophosphamide or cisplatin, mitomycin C and mustine with autologous bone marrow support in advanced non-small cell lung cancer. A phase I/II study.

Twenty-three patients with advanced NSCLC were treated with high dose chemotherapy using four agents and autologous bone marrow reinfusion. Ten patients received two bolus doses of cyclophosphamide (maximum tolerated total dose 10 G m-2), ifosfamide as a 24 h infusion (11 G m-2) followed by mitomycin C (70 mg m-2) as a subsequent 24 h infusion and mustine as two boluses (total dose 30 mg m-2). Another 13 patients received the same agents except cisplatin was substituted for cyclophosphamide, two doses (total dose 100 mg m-2) being given in a 24 h period. The median time of recovery to greater than or equal to 20,000 platelets was 21 days and of neutropaenia greater than or equal to 500 was 12-15 days. Unusual non-haematological toxicity e.g. cardiomyopathy, colitis, veno occlusive disease was not noted, all patients being given regular selenium and other trace elements. Three patients died in the first 2 weeks. There were five complete responses (22%) and 12 partial responses (52%) with four patients (2CR, 2PR) still alive at 27, 48, 73 and 82 weeks. The patient's Karnofsky performance in the cisplatin regimen improved over pretreatment values when compared a month after the end of treatment. The high dose regimen was associated with a high (74%) response rate, but with an overall median survival of only 6 months. The regimen has no advantage over conventional doses with the same agents in patients with metastatic NSCLC.

Adult↗
PubMed1991

Regulation of human lymphocyte proliferation by a tumour cell-derived DNA fraction.

A suppressor activity was isolated and partially purified from culture supernatant of human myeloid leukaemic cell line HL-60 by ion-exchange chromatography, HPLC and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). This activity was capable of suppressing proliferation of mitogen-stimulated normal human lymphocytes in a dose-dependent manner. The suppressor activity was identified as DNA by its typical absorbance at 260 nm, and by its susceptibility to DNase digestion. The DNA with suppressive activity was found to be double-stranded with the molecular weight range between 0.6 and 1.5 kb. This DNA material did not have cytotoxic activity and did not alter interleukin-2 receptor expression. Cell cycle analysis has suggested that DNA molecules could interact with lymphocytes to arrest the stimulated lymphocytes in the G1 phase, apparently preventing the cells from entering into the proliferating S phase.

Cell Cycle↗
PubMed1991

In vitro assessment of marrow 'stem cell' and stromal cell function in aplastic anaemia.

An in vitro model system is described that allows separate assessment of 'stem cell' and stromal cell function in aplastic anaemia (AA). Seven patients with non-severe AA, who had responded to immunosuppressive therapy and had haematological evidence of residual marrow function, were studied. Of these, three with otherwise typical AA had an acquired clonal cytogenetic marker. Purified bone marrow haemopoietic progenitors labelled with CD34 monoclonal antibody were positively selected using the fluorescence activated cell sorter (FACS) from both normal subjects and from patients with AA. The generative capacity of the CD34 positive cells was assessed by monitoring the output of granulocyte/macrophage colony forming cells (CFU-GM) in the non-adherent layer after inoculation onto irradiated performed long-term marrow culture (LTBMC) stromas. Stromal function in AA was assessed by inoculating CD34 positive cells from normal bone marrow onto performed irradiated stromas from patients with AA. Haemopoietic cell ('stem cell') function in AA was assessed by inoculating CD34 positive cells from AA patients onto confluent irradiated normal marrow stromas. Using these crossover/LTBMC experiments, all patients exhibited severe defects in haemopoietic cell function with normal functioning stroma. The proportion of CD34 positive cells present in bone marrow from these patients was reduced compared with controls, they comprised fewer small primitive 'blast-like' cells which in normal bone marrow are known to possess marrow repopulating ability, and demonstrated reduced clonogenic potential in short-term colony assays.

Adult↗
PubMed1991

Post consolidation therapy for adult patients with acute myeloid leukaemia.

One hundred and sixteen adult patients aged 14-73 with previously untreated acute myeloid leukaemia received induction and consolidation chemotherapy with daunorubicin, cytosine arabinoside and thioguanine. Two novel approaches to post consolidation therapy have been investigated. Patients aged 50 years or less who had no suitable matched allogeneic donor were considered for autologous bone marrow transplantation (BMT) using bone marrow which had been cultured in vitro for 14 d. Patients over the age of 50 years with normal bone marrow cellularity and peripheral blood count were treated with a single oral dose of busulphan 100 mg/m2 (without BMT rescue) 3 months following the completion of consolidation therapy. Eighty-seven patients (75%) achieved a complete remission. Of 70 patients who completed consolidation therapy, 40 were aged less than or equal to 50 years and 30 were greater than 50 years. Forty-three patients went on to receive post consolidation therapy in first CR (autologous BMT 12, allogeneic BMT 7, busulphan therapy 24). The event-free survival at 4 years was 47% for autologous BMT, 34% for allogeneic BMT and 45% for busulphan-treated patients. The survival for the older cohort of patients who received post consolidation therapy with single dose busulphan therapy was encouraging, and this agent should be considered for future post consolidation strategies.

Acute Disease↗
PubMed1991

Clostridium difficile infection in adult hamsters.

Diarrhea was encountered in a group of adult female golden Syrian hamsters (Mesocricetus auratus) used for titrating the scrapie agent. Ninety percent of the cases occurred in animals over 210 days old even though animals of all age groups lived in the colony concurrently. The cause of diarrhea was investigated in both uninoculated animals and those receiving greater than a limiting dilution of scrapie infectivity, i.e., animals that were not expected to contract the experimental scrapie disease. Three forms of diarrhea were observed. The most commonly encountered was profuse and watery. A chronic form presented with semiformed, thin fecal material smearing the retroperitoneal region. Hemorrhagic diarrhea was observed rarely. Mortality was high among animals with acute watery or hemorrhagic diarrhea. Animals with semiformed soft stools were dehydrated, had a roughened hair-coat, and hunched back. Cardinal lesions were necrosis, inflammation, and mucosal hyperplasia of the cecum and colon and cholangiohepatitis with amyloid deposition. Diffuse renal amyloidosis was present in chronic cases. Toxigenic, cytotoxin B-positive Clostridium difficile was isolated from a majority of affected animals. Cytotoxin B was also present in cecal homogenates of diarrheic animals with C. difficile. The pathological and microbiologic findings indicated a typhlitis and colitis in adult hamsters that was associated with C. difficile infection.

Animals↗
PubMed1991

Removal of intrinsic enamel stains with vital bleaching and modified microabrasion.

This study utilized a vital bleaching agent as well as an enamel microabrasion compound with low hydrochloric acid concentration to remove intrinsic stains on the facial surfaces of anterior teeth. In addition, scanning electron microscopic analyses of enamel from extracted teeth compared the etching pattern of the commercial compound used in this study to 18% hydrochloric acid. Type 1 and Type 2 etch patterns were observed with 18% hydrochloric acid after 5 and 20 seconds, respectively. Milder and more diffuse etch patterns were observed with the enamel microabrasion compound. A conservative form of treatment to remove intrinsic stains would employ the use of a vital bleaching agent, followed by an enamel microabrasion compound.

Acid Etching, Dental↗
PubMed1990

The hematopoietic defect in aplastic anemia assessed by long-term marrow culture.

Thirty-two patients with aplastic anemia (AA) have been studied using the long-term bone marrow culture (LTBMC) system. Of these patients, 26 had been treated with immunosuppressive therapy including antilymphocyte globulin (ALG) with or without androgens or high-dose methyl prednisolone. The remaining six patients either required no treatment or were studied before therapy was begun. Thirty-one of 32 patients (96%) had defective hematopoiesis in LTBMC with little or no evidence for the generation of primitive progenitor cells. The only exception was a patient with spontaneous recovery of aplasia in whom the defect was less marked. Crossover LTBMC experiments were performed in 23 cases by inoculating (1) patient marrow hematopoietic cells that had been depleted of adherent cells onto preformed, irradiated, normal stromas to assess the proliferative capacity of the hematopoietic cells, and (2) normal marrow hematopoietic cells that were depleted of adherent cells onto preformed, irradiated stromas from patients with AA to assess stromal function. Results of these experiments demonstrated a hematopoietic defect in all patients that was independent of the degree of hematologic recovery after ALG therapy. Only one patient had a probable stromal defect and this coexisted with a defect in the regenerative capacity of hematopoietic cells. We conclude that LTBMC is a sensitive method for detecting and defining the hematopoietic failure in AA. We suggest that the defective hematopoiesis present in all patients studied may be important in the pathogenesis of clonal evolution in AA.

Adolescent↗
PubMed1990

Comparative gastrointestinal enzyme activity and activation of the promutagen 2,6-dinitrotoluene in male CD-1 mice and male Fischer 344 rats.

Comparative intestinal nitroreductase, azo reductase, beta-glucuronidase, dechlorinase and dehydrochlorinase activities in young male Fischer 344 rats and young male CD-1 mice were measured in vitro while the comparative biotransformation of 2,6-dinitrotoluene to mutagenic metabolites was determined in vivo. The mice, which exhibit a high spontaneous incidence of hepatomas, had markedly greater nitroreductase activity and metabolized significantly more 2,6-dinitrotoluene to mutagenic metabolites than did Fischer 344 rats, which show a low incidence of liver tumors. Results of this study indicate that species differences in the incidence of hepatomas may be influenced by microbial flora and/or the biotransformation of xenobiotics in the G.I. tract.

Animals↗
PubMed1990

Stromal cells in haemopoiesis.

Stromal cells of the bone marrow can provide the growth-promoting and differentiation-inducing molecules which are necessary for haemopoiesis. While the nature of these stimuli is largely unknown, the development of haemopoietic cells in association with stromal cells requires intimate cell contact. Molecules of the extracellular matrix, such as heparan sulphate, are able to bind growth factors and in this way the stromal cells may form microenvironmental niches which preferentially promote development of multipotent and committed cells along discrete lineages. Cells from some patients with acute and chronic myeloid and lymphoid leukaemias are defective in their ability to interact with stromal cells and consequently cannot survive in stromal cell-mediated long-term marrow cultures. We have exploited this phenomenon to obtain normal haemopoietic cells from patients with leukaemia, and to use these cells for successful autografting in patients with acute and chronic myeloid leukaemias.

Animals↗
PubMed1990

Lack of response of bone marrow, in vitro, to growth factors in congenital neutropenia.

Severe congenital neutropenia has a poor outlook. In vitro clonogenic assays using recombinant growth factors may improve understanding of the underlying pathogenetic mechanisms and identify those in whom growth factors might be clinically useful. Marrow from a boy with congenital neutropenia was cultured with a variety of recombinant growth factors. The results show that the neutropenia did not result from a lack of myeloid progenitors but that these progenitors could not produce mature neutrophils. Bone marrow transplantation is being considered as the most likely approach to correct neutropenia.

Agranulocytosis↗
PubMed1990

Growth of normal versus leukemic bone marrow cells in long term culture from acute lymphoblastic and myeloblastic leukemias.

The ability of the in vitro long-term bone marrow culture (LTBMC) system to impair the survival of leukemic cells and to enhance the growth of normal progenitors has been studied. Bone marrow cells from 19 acute lymphoblastic leukemia (ALL) and 30 acute myeloid leukemia (AML) patients at diagnosis were grown in LTBMC for 4-10 weeks. In half of the cases the leukemic population declined down to undetectable levels and was replaced by putative normal hemopoietic precursors, both in ALL and in AML. In the remaining cases, leukemic cells persisted throughout the culture time and few if any normal hemopoietic cells were detected. These data led us to extend to the lymphoid compartment the previous observation of decreasing leukemic myeloid blasts in LTBMC. The potential of such cultures as an in vitro purging system for autologous bone marrow transplantation in selected poor-prognosis lymphoid malignancies should be explored, as has been done for acute and chronic myeloid leukemias.

Bone Marrow↗