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Biomedical subjects

L Chang

Publications and source records attributed to L Chang.

At least 361 records · Page 20Linked to original sources
PubMed1986

Childhood erythroleukemia. Studies on pathogenesis using colony assays.

Marrow hematopoiesis was examined in two infants with erythroleukemia (EL) using cell culture colony assays. At diagnosis, marrow from both yielded normal to increased numbers of granulocytic colonies (CFU-C), erythroid bursts (BFU-E), and mixed colonies (CFU-GEMM), which contrasted sharply with the reduced growth in eight other newly diagnosed patients with acute leukemia. BFU-E proliferation and hemoglobinization proceeded normally in culture and was entirely erythropoietin-dependent. CFU-C colony cellular composition showed normal granulopoiesis in various stages of development. Despite low numbers of morphologically recognizable blasts in the aspirates, they were readily identified in a blast colony assay because of their high plating efficiency and high index of self-renewal on replating. Blast cells in all cultures had myeloblastic morphology, were peroxidase positive, and expressed the granulocytic-specific My-1 antigen. Monosomy 7 was seen in fresh and cultured blast cells but not in lymphocytes, indicating a clonal proliferation. After chemotherapy-induced remission, blast colonies and monosomy 7 could no longer be detected. It appears that the integrity and function of the normal hematopoietic progenitor pool were preserved in these patients with EL. The abnormal myeloblastic proliferation was expressed actively in colony assays and was useful diagnostically in these cases because marrow morphology was nondiagnostic. In these patients, EL seems to be a misnomer since the findings are suggestive of acute myeloblastic leukemia with secondary erythroid and granulocytic hyperplasia.

Bone Marrow↗
PubMed1986

A crossed polaroid-pinhole device.

The study describes the use of a pinhole device in which the light-absorbing area surrounding the holes is varied by polarizing filters. The study demonstrates that a pinhole aperture of 1.6-1.8 mm in diameter with polaroids crossed at 90 degrees will allow a visual acuity equal to or better than 20/40 in the face of refractive errors of 1, 2, and 3 diopters. The study next evaluates the effects of pinholes of different sizes and the polarizing components crossed at angles less than 90 degrees. The study concludes by showing that polaroids crossed at between 75 degrees and 85 degrees allow a greater depth of focus, a larger visual field, and greater illumination than traditional pinhole devices.

Humans↗
PubMed1985

Does phenobarbital protect against trimethyltin-induced neuropathology of limbic structures?

Because of the similarity in the pattern of limbic sites damaged by both compounds, it has been suggested that trimethyltin (TMT) may be an excitotoxin like kainic acid (KA). KA produces seizures which eventually result in neuronal damage similar to that found in epilepsy. Anticonvulsants reduce both the seizures and pathology associated with KA. Because TMT may also produce seizures, we undertook to determine whether or not some of the TMT-induced limbic neuropathology could result from seizure activity. To do this, a single dose of TMT chloride (either 7.5 or 15 mg/kg) was given per os to rats, and then phenobarbital (30 mg/kg) was administered subcutaneously in repeated doses. Treatment with phenobarbital did not prevent pathologic changes in the hippocampus, dentate gyrus, and pyriform or prepyriform cortex. Since phenobarbital did not protect against TMT-induced neuronal damage, as it has been reported by others to protect against KA-induced damage, the present findings suggest that these two toxicants probably produce hippocampal pathology via different mechanisms and that the TMT-induced pathologic changes do not require sustained electrical seizure activity.

Animals↗
PubMed1985

Histopathology of microvenous repair.

The histopathology of microvascular repair was investigated in the femoral vein of the rat. Previous microvascular repair studies have primarily involved arteries, giving little insight to similar processes in veins. In our study, 36 rats with an average weight of 440 gm were randomly assigned to experimental groups of 1 hour, 24 hours, 2 weeks, and 4 weeks after repair. Histological evaluation of the suture site included the use of light, scanning electron, and transmission electron microscopy. Endothelial loss was observed in all 1-hour specimens. Extensive inflammatory response appeared in 2-hour specimens. Re-endothelialization of the intima was achieved in all animals by the 2-week time interval. At 4 weeks, the animals exhibited evidence of medial regeneration of smooth muscle cells. This was predominantly occurring between adjacent suture sites. Minimal subintimal hyperplasia was localized at the suture site itself in both 2- and 4-week specimens.

Animals↗
PubMed1985

Purification and characterization of high-affinity cyclic adenosine 5'-monophosphate phosphodiesterases from human acute myelogenous leukemic cells.

Soluble, high-affinity cyclic adenosine 3':5'-monophosphate (cyclic AMP) phosphodiesterases extracted from blast cells of patients with acute myelogenous leukemia have been characterized by physical, kinetic, and immunological criteria and fractionated to a high degree of purity. Procedures used in this study were similar to those used to purify the high-affinity enzyme from dog kidney. Two forms of high-affinity enzyme were found in blast cells. Form A was similar to the known type IV phosphodiesterases, including those of normal lymphocytes and monocytes. It showed a molecular weight near 60,000, a rate of hydrolysis of cyclic AMP 7 to 10 times that of cyclic guanosine 3':5'-monophosphate (cyclic GMP), competitive inhibition by cyclic GMP for cyclic AMP hydrolysis, and identical immunoreactivity by Western transfer analysis. This enzyme form was purified to apparent homogeneity by physical criteria but showed a low maximum velocity relative to other phosphodiesterase forms. A second, different form of high-affinity phosphodiesterase (Form B) was also resolved and partially purified. By comparison with Form A, this enzyme eluted from diethylaminoethyl cellulose at slightly lower ionic strength, had a lower molecular weight, appeared specific for cyclic AMP as substrate, showed no inhibition of cyclic AMP hydrolysis by cyclic GMP, and displayed no immunological cross-reactivity to the Mr 60,000 enzyme. Neither enzyme form was activated by calmodulin or proteolysis, whereas both showed comparable inhibition by 6,7-dimethoxy-1-veratrylisoquinoline, 1-methyl-3-isobutylxanthine, and 1,3-dimethylxanthine.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1985

The origin and innervation of the adductor pollicis muscle.

A gross dissection of twenty human adductor pollicis muscles indicated an extensive origin of both the transverse and oblique heads. The origins included the second, third, and fourth metacarpal bones and the capitate, trapezoid, and trapezium bones. Soft tissue origins included intermetacarpal ligaments and the anterior fascia of palmar interosseous muscles. An interfascicular dissection of the deep branch of the ulnar nerve within the substance of the adductor pollicis muscle revealed three distinct patterns of terminal branching to the transverse and oblique heads, and to the first dorsal interosseous muscle.

Hand↗
PubMed1984

The dorsal tegmental nucleus: an axoplasmic transport study.

The afferent and efferent connections of the dorsal tegmental nucleus (DTN) were studied in the rat using axoplasmic transport techniques. Horseradish peroxidase (HRP) and Fast Blue were injected stereotaxically into either pars centralis or pars ventromedialis of the DTN, two subdivisions of the nucleus with distinctive connections. The pars centralis is reciprocally connected with the ipsilateral lateral mammillary and interpeduncular nuclei; these projections constitute the major afferent and efferent systems of the DTN. Commissural fibers from the corresponding pars centralis and intrinsic fibers systems are massive and form a complex fiber meshwork within the subnucleus. The prepositus hypoglossi nucleus (ipsilateral) and supragenualis nuclei (bilateral) also project to the pars centralis. Smaller numbers of afferent fibers arise from the lateral habenular nucleus, the posterior hypothalamus and the brainstem reticular formation. The pars ventromedialis of the DTN receives diverse inputs which include the septal nuclei, diagonal band of Broca, preoptic area, anterior and lateral hypothalamus, lateral and medial habenular nuclei, medial mammillary nucleus and many nuclei of the brainstem reticular formation. Based on the differences of connections and cytoarchitecture between the pars centralis and the pars ventromedialis, the pars ventromedialis may be an entity separate from the dorsal tegmental nucleus.

Animals↗
PubMed1982

The natural history of colorectal carcinoma in adolescents.

The symptoms, histology, extent, and course of disease of 24 adolescents with colorectal carcinoma who were admitted to St. Jude Children's Hospital between 1964 and 1980 are presented. Twenty of the patients were referred between October 1974 and June 1980. Most patients presented with vague abdominal complaints. Twenty-one of the 24 patients had poorly differentiated mucin-producing adenocarcinoma. Extensive disease at diagnosis and unresponsiveness to medical management was reflected in the eight-month median survival from diagnosis. Only two of the 24 patients survive free of disease 15 and 130 months from diagnosis. Two other patients survive with disease at four and 24 months.

Adenocarcinoma, Mucinous↗
PubMed1982

Peripheral blood blast cell progenitors in human preleukemia.

Progenitors of blast cell colonies have been identified in acute leukemia. The peripheral blood of 18 of 25 patients with preleukemic states yielded low numbers of blast cell colonies, and the colony-forming cells were in an active proliferative state when assessed using short-term exposure to tritiated thymidine. The clinical significance of blast cell colonies is uncertain, but we suggest that further analysis of this cultural abnormality may lead to a better understanding of mechanisms and management in preleukemia.

Adolescent↗
PubMed1981

The effects of cyclophosphamide, azathioprine, and 6-mercaptopurine on oocyte and follicle number in C57BL/6N mice.

Cyclophosphamide, azathioprine and 6-mercaptopurine were studied for oocyte and follicle toxicity in a murine ovarian toxicity assay system. Seven days after a single treatment with cyclophosphamide (100 mg/kg ip), 63% of the primordial follicles and 0% of the growing or large follicles and their oocytes were destroyed in four week old C57BL/6N mice. Treatment with azathioprine (100 mg/kg/day ip x 9 days) or 6-mercaptopurine (100 mg/kg/day ip x 9 days) suppressed weight gain and increased mortality but had no effect on the number of oocytes or follicles in these mice. These data are consistent with previous observations on the effects of cyclophosphamide, azathioprine and 6-mercaptopurine on human ovarian toxicity. This suggests that the murine ovarian toxicity assay system may be useful in evaluating xenobiotics, including drugs, for human ovarian toxicity.

Animals↗
PubMed1980

Primary malignant tumors of the stomach in children.

Primary malignant tumors of the stomach are rare in children. During the years 1952--1977, eight children were seen at Childrens Hospital of Los Angeles with primary malignant tumors of the stomach. The patients were between the ages of 20 mo and 17 hr and included 5 males and 3 females. The series consisted of 3 malignant lymphomas, 2 adenocarcinomas, 2 leiomyosarcomas, and 1 rhabdomyosarcoma of the stomach. Three patients are living and five are dead. Clinical histories, treatment and pathologic findings are described along with a review of the literature and recommendations for the management of primary gastric malignancies in children.

Adenocarcinoma↗
PubMed1979

Glucose effect on respiration: possible mechanism for capacitation in guinea pig spermatozoa.

Guinea pig sperm respiration was determined in minimal capacitation medium (MCM) with different energy sources. The ZO2 observed for spermatozoa suspended in media containing pyruvate and lactate was 35.7 +/- 5.9, pyruvate alone, 27.9 +/- 3.8 and D-glucose alone 3.4 +/- 1.1. When D-glucose was added to spermatozoa rapidly respiring in media containing pyruvate as the only exogenous energy source, an immediate suppression in respiration was observed. Further reduction was caused by continued addition of D-glucose. Fructose and mannose also produced a suppression in respiratory rate. However, lactose, fucose, sucrose, L-glucose, and galactose did not alter the respiratory rate. The suppression of respiration by metabolizable sugars is paralleled by a suppression of acrosome reaction in guinea pig spermatozoa. The possibility that suppression of respiration is the mechanism for retardation of capacitation and the subsequent acrosome reaction by D-glucose and other metabolizable sugars is suggested.

Animals↗