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Biomedical subjects

S M Chang

Publications and source records attributed to S M Chang.

At least 127 records · Page 7Linked to original sources
PubMed1991

Presynaptic effects of melatonin on norepinephrine release and uptake in rat pineal gland.

The effect of melatonin injection on norepinephrine (NE) turnover rate in rat pineal gland was estimated from the decline of tissue NE levels after the injection of the tyrosine hydroxylase inhibitor alpha-methyl-p-tyrosine. The administration of a single injection of 300 micrograms/Kg of melatonin at the beginning of the scotophase induced, 3 hr later, a significant decrease of pineal NE turnover. The possible direct effect of melatonin on pineal NE release was examined in vitro. Exposure of rat pineal explants previously loaded with 3H-NE to 10(-8)-10(-6) M melatonin decreased significantly 3H-NE release triggered by 60 mM K+. This activity of melatonin was revealed only in pineals excised at night (0000 and 0400, i.e., at the fourth or eighth hours of darkness) and not in those excised in the middle (1400) or late light phase of the daily photoperiod (2000). Melatonin did not modify the spontaneous pineal 3H-NE efflux. Melatonin decreased 3H-NE uptake at a low NE concentration (0.5 microM) in a dose-dependent manner (IC50 identical to 10(-10) M). A kinetic analysis of the pineal NE uptake process indicated that melatonin augmented both Vmax and Km of transmitter uptake. These results suggest that endogenously released melatonin may be a regulatory signal for rat pineal sympathetic synapses.

Analysis of Variance↗
PubMed1991

Malignant papillary cystic tumor of the pancreas: report of a case and review of the literature.

Papillary cystic tumor of the pancreas almost always occurs in young female patient and metastasis is extremely rare although local recurrence may occur. Prognosis is excellent and the tumor can be considered to be curable by surgery. Reported here is an unusual case of malignant papillary cystic tumor of the pancreas that occurred in a 51 Y/O man with metastasis to bilateral inguinal soft tissue at the time of diagnosis. Beside distal pancreatectomy, subtotal gastrectomy and excision of the inguinal masses were also performed because of the presence of a separate tumor in the lesser sac, which was unrelated to the pancreas. Immunohistochemical staining for NSE was positive in tumor cells. However, electron microscopy failed to reveal neurosecretory or zymogen granules but there were abundant mitochondria, rough endoplasmic reticulum and annulate lamellae. These findings show that a ductal origin is more likely in our case but the hypothesis of an origin from a primitive cell capable of acinar, ductal or endocrine differentiation should also be considered.

Carcinoma, Papillary↗
PubMed1990

Fibroblast-mediated acceleration of human epithelial tumor growth in vivo.

Transformed fibroblasts coinoculated with epithelial cells accelerated the growth and shortened the latency period of human epithelial tumors in athymic mice. Addition of NbF-1 fibroblasts caused epithelial tumors to grow from five marginally tumorigenic or "nontumorigenic" (nontumor-forming) human tumor cell lines or strains: PC-3 (prostate), WH (bladder), MDA-436 (breast), and cells derived from the ascites fluids of patients with metastatic renal pelvic or prostate cancers. Evidence for the human and epithelial nature of these experimental tumors was provided by histologic, immunohistochemical, Southern and dot-blot hybridization, and cytogenetic analyses. Transformed fibroblasts induced predominantly carcinosarcomas, whereas nontumorigenic fibroblasts (NIH 3T3) and lethally irradiated transformed fibroblasts induced exclusively carcinomas. The fibroblast-epithelial interaction appears to occur bidirectionally and does not result from cell fusion. Because coculture experiments in vitro did not demonstrate an increased cell proliferation, it appears that undefined host factors can influence tumor growth. This tumor model may be useful in drug-screening programs and in mechanistic studies of factors regulating human tumor growth and progression.

Animals↗
PubMed1990

Dietary intake and observed activity of stunted and non-stunted children in Kingston, Jamaica. Part II: Observed activity.

It is generally believed that activity levels are reduced in poorly nourished children. This may conserve energy, but may have a detrimental effect on mental development. However there are few data which support this hypothesis. No previous studies were found which looked at the activity levels of stunted children. In this study we modified the time and motion observation methods of Torun (1984) by using recording periods of 1 instead of 10 min. This significantly reduced the estimated time spent by young children in moderate and vigorous activities. Four hours of observing young children while they were awake, using the modified method, produced highly reliable data. The activity levels of a subsample of children described in part I were observed. The children were aged 12-24 months and were observed for 4 h on 2 d. Seventy-eight stunted children (height less than -2 SD of median, NCHS) were compared with 26 non-stunted children (height greater than -1 SD). The stunted children were significantly less active than the non-stunted children, although the difference in activity rating was small (3.4 per cent). They spent more time in light activities (P less than 0.001) and less time in moderate or vigorous activities (P less than 0.01). Both groups slept a similar amount. Using Torun's values for the energy cost of activities it appears unlikely that the reduced activity would conserve energy to a great extent, but it may still be of biological importance, since it is comparable to the energy cost of growth at this age. Activity levels increased with age but were not significantly related to weight for height.(ABSTRACT TRUNCATED AT 250 WORDS)

Child, Preschool↗
PubMed1989

Co-inoculation of tumorigenic rat prostate mesenchymal cells with non-tumorigenic epithelial cells results in the development of carcinosarcoma in syngeneic and athymic animals.

Co-inoculation of NbF-I and NbE-I s.c. into either adult male syngeneic rats or athymic nude mice induced the development of tumors that resembled carcinosarcoma on histopathologic evaluation. These tumors were composed of a mixture of adenocarcinoma and fibrosarcoma and were induced by the mixtures of NbF-I and NbE-I cells at a ratio ranging from 0.001 to 3.2; inoculation of NbF-I alone resulted in the development of fibrosarcoma. Flow-cytometric analysis showed that the epithelial cells subcloned from the carcinosarcoma had a DNA profile like that of their parental cell line and remained non-tumorigenic. When co-inoculated with the tumorigenic fibroblasts in syngeneic hosts, however, the subcloned epithelial cells again formed carcinosarcomas. Our results indicate that cell fusion between epithelial cells and fibroblasts is an unlikely explanation for tumorigenicity. We propose that prostatic fibroblasts exert a directive influence on their adjacent epithelial cells through a paracrine mechanism that determines epithelial growth and tumorigenicity in vivo.

Animals↗
PubMed1989

Infection of bovine cells of embryonic origin by amphotropic retroviral vectors.

Two amphotropic-based mouse retroviral vectors carrying the neomycin-resistance gene were used to infect four bovine cell lines. Two cell lines, bovine kidney and spleen cells, were refractory to the infection while two independent bovine cells of apparent embryonic origin were infected by the amphotropic retroviral vectors at a measurable titer. Southern blot analysis reveals the presence of neomycin-resistance gene in the G418-resistant bovine cells. The results demonstrate the successful transfer of a gene to bovine cells of embryonic origin using a murine retroviral vector system.

Animals↗
PubMed1989

Interaction between prostatic fibroblast and epithelial cells in culture: role of androgen.

We have established and characterized two cell lines from the ventral prostate gland of normal Nb rats: NbE-1 (prostatic epithelial) and NbF-1 (prostatic fibroblast) cell lines. To identify the direct mitogenic action of dihydrotestosterone (DHT), we incubated these cell lines alone and together (in the presence and absence of cell contact) with various concentrations of DHT (0.1-10,000 ng/ml) for 24-72 h and assayed for the rate of DNA synthesis and the total number of cells in tissue culture at specified time periods. Results demonstrate that the primary target for DHT mitogenic action is the prostatic fibroblasts. DHT inhibited the growth of prostatic epithelial cells by themselves, but stimulated prostatic epithelial cell growth when the epithelial cells were cocultured with prostatic fibroblasts. Furthermore, the cell-conditioned medium obtained from either the fibroblast or the epithelial cells stimulated in an autocrine or a paracrine manner the growth of prostatic cells in culture. These results are consistent with the concept that DHT stimulates the growth of prostatic epithelial cells indirectly via its direct mitogenic action on the prostatic fibroblasts. Because epithelial cells are the cell type principally responsible for converting testosterone to DHT, and the fibroblasts respond to the mitogenic action of DHT, our results support the concept that tight metabolic cooperation exists between prostatic epithelial and fibroblast cells. These data are in agreement with previous in vivo studies in which we have demonstrated that androgen receptors in the mesenchyme are obligatory for androgen-induced prostate growth and development.

Acid Phosphatase↗
PubMed1989

A retrovirus vector which transduces a functional estrogen receptor gene at high efficiency.

A high titer retroviral vector containing the cDNA of human estrogen receptor (hER) was generated and used to transfer the hER gene into the rat 208F cell line. Southern blot analysis showed the integration of the provirus to be at a unique site and that the provirus was intact in the genome of recipient cells. The expression of the integrated hER gene in the infected rat cells was detected by Northern blot analysis and by a functional assay in which the hER gene product stimulated the production of a chloramphenicol acetyl transferase gene under the control of an estrogen-responsive element. These experiments demonstrate the feasibility of using a retroviral vector system to introduce a functional ER gene into cultured cells lacking this receptor.

Animals↗
PubMed1989

Waldenström's macroglobulinemia with unilateral massive pleural effusion: report of a case.

One rare case of Waldenström's macroglobulinemia with massive right-sided pleural effusion is reported. A 66-year-old woman was admitted to our hospital because of exertional dyspnea and chronic cough of three months' duration. Chest X-ray examination showed massive right-sided pleural effusion. Routine blood examination revealed severe anemia. Sternal bone marrow aspirate revealed a hypercellular marrow with replacement of 50% of the normal hematopoietic cells by a spectrum of lymphoid cells, including small lymphocytes, a few plasma-cytoid lymphocytes and immature plasma cells. The diagnosis was confirmed by serum protein electrophoresis and immunoglobulin assay. The effect of chemotherapy was satisfactory in the first two years as pleural effusion subsided completely and the marrow returned to near normal. But, the response was poor during the last 6 months. She died about 4 years after her first admission.

Aged↗
PubMed1989

The first isolate of Tatumella ptyseos in Malaysia.

Tatumella ptyseos, the type species for the genus Tatumella, is a newly established member of the Family Enterobacteriaceae. It is a Gram-negative, oxidase negative, fermentative rod that grows on Mac Conkey agar. This first isolate was obtained from the blood culture of a neonate having neonatal jaundice with presumed sepsis. The organism was in vitro sensitive to Gentamicin, Chloramphenicol, Cotrimoxazole and Ampicillin. The patient was treated with Ampicillin and Gentamicin and recovered uneventfully.

Anti-Bacterial Agents↗
PubMed1988

Expression of human adenosine deaminase in murine hematopoietic cells.

Multiple replication-defective retrovirus vectors were tested for their ability to transfer and express human adenosine deaminase in vitro and in vivo in a mouse bone marrow transplantation model. High-titer virus production was obtained from vectors by using both a retrovirus long terminal repeat promoter and internal transcriptional units with human c-fos and herpes virus thymidine kinase promoters. After infection of primary murine bone marrow with one of these vectors, human adenosine deaminase was detected in 60 to 85% of spleen colony-forming units and in the blood of 14 of 14 syngeneic marrow transplant recipients. This system offers the opportunity to assess methods for increasing efficiency of gene transfer, for regulation of expression of foreign genes in hematopoietic progenitors, and for long-term measurement of the stability of expression in these cells.

Adenosine Deaminase↗
PubMed1988

Prostatic carcinogenesis evoked by cellular interaction.

Inoculation of tumorigenic prostatic stroma and nontumorigenic prostatic epithelia into the subcutaneous space of syngeneic rats induced the development of carcinosarcoma. The induced tumors, which were composed of a mixture of adenocarcinoma and fibrosarcoma, were androgen responsive. This model offers a novel mechanism for prostatic carcinogenesis in which prostatic fibroblasts determine epithelial growth, androgen responsiveness, and tumorigenicity. Our results emphasize the potential importance of an epigenetic pathway in prostatic carcinogenesis.

Androgens↗