Search PubMed⌕ Search

Biomedical subjects

S Chang

Publications and source records attributed to S Chang.

At least 343 records · Page 19Linked to original sources
PubMed1987

Experimental vitreous replacement with perfluorotributylamine.

Perfluorotributylamine, a liquid fluorochemical used in artificial blood substitution, was evaluated for potential application as a vitreous substitute having heavier density than saline. It was injected into the vitreous of 38 rabbit eyes after mechanical vitrectomy or gas compression of the vitreous with perfluoropropane. The eyes were observed for periods of up to five months. Clinically the liquid occupied the lower vitreous space but gradually dispersed into smaller fluorochemical droplets. In the upper vitreous clusters of cells appeared within three to four weeks which precipitated on the posterior lens surface and in the cortical vitreous. In eyes with experimental retinal detachment perfluorotributylamine had physical properties which provided mechanical retinal tamponade. Its interfacial tension prevented passage through iatrogenic retinal breaks. Histopathologic findings showed irregularly shaped defects in the outer segment disks as early as two days after vitreous replacement. These changes appeared to reverse if perfluorotributylamine was removed after two days. The cellular response in the vitreous consisted primarily of monocyte-derived macrophages capable of ingesting fluorochemical (foam cells).

Animals↗
PubMed1987

Low viscosity liquid fluorochemicals in vitreous surgery.

Low viscosity liquid fluorocarbons have physical properties potentially useful as intraoperative adjuncts during vitreous surgery for complicated retinal detachments. These substances are optically clear, have specific gravity greater than that of water, and interfacila tension properties similar to those of silicone oil. In four patients who had complicated retinal detachments I used perfluorotributylamine and perfluorodecalin during vitreous surgery. Two giant retinal tears were flattened intraoperatively without turning the patient into the prone position. In two patients with severe proliferative vitreoretinopathy, perfluorotributylamine allowed adequate retinal tamponade and avoided a posterior retinotomy for internal drainage of subretinal fluid. Endophotocoagulation was applied.

Adolescent↗
PubMed1987

Effects of retinoic acid on the growth and morphology of hamster tracheal epithelial cells in primary culture.

Hamster tracheal epithelial cells were grown in primary culture on a collagen gel substrate in hormone-supplemented serum-free Ham's F12 medium with 10(-8) M retinoic acid (RA+), or without retinoic acid (RA-). On days 1 and 2, the colonies were composed of large (secretory) cells and lesser numbers of small (basal) cells; ciliated cells were rare. At these times, cell number, thymidine incorporation, and total labelling indices (small and large cells, combined) were similar in RA+ and RA- cultures, but the large cells became flat in RA- medium on day 2. On days 3-5, thymidine incorporation and total labelling indices were less in RA- than RA+ cultures, and on days 4-6, cell numbers were decreased in RA- cultures. On day 3, the large cells of the RA- colonies had flattened further and clusters of small basal cells had formed. On day 4, the RA+ colonies were composed of densely-packed cuboidal secretory cells, small basal cells were inconspicuous; the total labelling index was about 27%. The RA- colonies were composed of large flat secretory cells and numerous small basal cells which were clustered in groups; the total labelling index was about 7%. Since large and small cells could be discriminated by size in RA- colonies, a labelling index was generated based on cell size. On days 2, 3 and 4, the labelling index of the small basal cells in the RA- colonies was 44%, 43% and 24% respectively, whereas the labelling index of the large secretory cells fell rapidly over the same period (56%, 14% and 2%). On days 5 and 6, the cuboidal secretory cells in the RA+ cultures had differentiated further and the cells were stratified focally. Some new ciliated cells had formed on day 6. In RA- cultures, mucous granules were not observed in the large flat cells and ciliated cells were not seen. The total labelling indices were 11% and 0.35% in RA+ cultures, and 0.5% and 0.25% in RA- cultures on days 5 and 6, respectively. The study shows that the target cell for vitamin A in the hamster tracheal epithelium is the secretory (mucous) cell. When retinoic acid was deficient, the secretory cells flattened and their capacity to divide was greatly diminished. Since the basal cells continued to replicate when the secretory cells did not, the population density of the basal cells increased disproportionally, which could be interpreted erroneously as a "basal cell hyperplasia".(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Isotopic characterisation of kerogen-like material in the Murchison carbonaceous chondrite.

Isotopic data for C, H and N in acid-resistant residues from carbonaceous chondrites show substantial variability during stepwise pyrolysis and/or combustion. After subtraction of contributions due apparently to inorganic C grains, of probably circumstellar origin, considerable isotopic variability remains, attributable to the kerogen-like organic fraction. That variability may be interpreted in terms of three or four distinct components, based on C, H and N isotopes. The relative proportions of those components vary significantly from sample to sample. The different isotopic components are tentatively identified in terms of specific chemical/structural moieties within the kerogen-like material. This combination of chemical, structural and isotopic information suggests a complex for meteoritic organic matter. At least three components within the organic populations as a whole still carry a signature of apparently interstellar D-enrichment. Part, at least, of the interstellar carrier consisted of reactive entities, not solely polymers.

Carbon↗
PubMed1987

Management of intraocular foreign bodies.

Thirty-five consecutive cases of perforating ocular injuries with retained intraocular foreign body (IOFB) are examined in this retrospective study. Of the 35 cases with injuries, 30 (86%) were due to metallic foreign bodies. Of these, 25 (83%) involved foreign bodies of ferromagnetic origin. Magnetic extraction in combination with pars plana vitrectomy (or when possible, magnetic extraction alone) was successfully used to remove these foreign bodies. Even in cases where posterior vitrectomy is indicated, magnetic extraction allows good control of the foreign body during removal minimizing surgical trauma and the subsequent postoperative inflammatory response.

Eye Foreign Bodies↗
PubMed1987

Extension of neurites on axons is impaired by antibodies against specific neural cell surface glycoproteins.

We have developed an in vitro assay which measures the ability of growth cones to extend on an axonal substrate. Neurite lengths were compared in the presence or absence of monovalent antibodies against specific neural cell surface glycoproteins. Fab fragments of antibodies against the neural cell adhesion molecule, NCAM, have an insignificant effect on the lengths of neurites elongating on either an axonal substrate or a laminin substrate. Fab fragments of polyclonal antibodies against two new neural cell surface antigens, defined by mAb G4 and mAb F11, decrease the lengths of neurites elongating on an axonal substrate, but have no effect on the lengths of neurites elongating on a laminin substrate. G4 antigen is related to mouse L1, while F11 antigen appears to be distinct from all known neural cell surface glycoproteins. Our results suggest that the G4 and F11 antigens help to promote the extension of growth cones on axons.

Animals↗
PubMed1987

Weight loss, cortisol levels, and dexamethasone suppression in major depressive disorder.

Appetite and/or weight loss are integral, albeit not necessary, symptoms of depression. We explored the contribution of diminished appetite and/or weight loss ascertained by history to the hypothalamic-pituitary-adrenocortical (HPA) axis dysregulation in 120 patients with primary major depressive disorder. Significant positive relationship for both appetite and weight loss with cortisol levels in plasma and cerebrospinal fluid (CSF) were observed. Plasma cortisol levels were consistently higher in patients who noted both appetite and weight loss as opposed to patients without appetite or weight loss. Depressed patients with weight loss showed higher rates of dexamethasone-nonsuppression. Age and severity of depression influenced but did not eliminate the significance of the findings, suggesting that weight loss accounts in part for the HPA-axis function changes observed in depression.

Adult↗
PubMed1987

alpha-Amylase gene of Streptomyces limosus: nucleotide sequence, expression motifs, and amino acid sequence homology to mammalian and invertebrate alpha-amylases.

The nucleotide sequence of the coding and regulatory regions of the alpha-amylase gene (aml) of Streptomyces limosus was determined. High-resolution S1 mapping was used to locate the 5' end of the transcript and demonstrated that the gene is transcribed from a unique promoter. The predicted amino acid sequence has considerable identity to mammalian and invertebrate alpha-amylases, but not to those of plant, fungal, or eubacterial origin. Consistent with this is the susceptibility of the enzyme to an inhibitor of mammalian alpha-amylases. The amino-terminal sequence of the extracellular enzyme was determined, revealing the presence of a typical signal peptide preceding the mature form of the alpha-amylase.

Amino Acid Sequence↗
PubMed1987

Processing of the initiation methionine from proteins: properties of the Escherichia coli methionine aminopeptidase and its gene structure.

Methionine aminopeptidase (MAP) catalyzes the removal of amino-terminal methionine from proteins. The Escherichia coli map gene encoding this enzyme was cloned; it consists of 264 codons and encodes a monomeric enzyme of 29,333 daltons. In vitro analyses with purified enzyme indicated that MAP is a metallo-oligopeptidase with absolute specificity for the amino-terminal methionine. The methionine residues from the amino-terminal end of the recombinant proteins interleukin-2 (Met-Ala-Pro-IL-2) and ricin A (Met-Ile-Phe-ricin A) could be removed either in vitro with purified MAP enzyme or in vivo in MAP-hyperproducing strains of E. coli. In vitro analyses of the substrate preference of the E. coli MAP indicated that the residues adjacent to the initiation methionine could significantly influence the methionine cleavage process. This conclusion is consistent, in general, with the deduced specificity of the enzyme based on the analysis of known amino-terminal sequences of intracellular proteins (S. Tsunasawa, J. W. Stewart, and F. Sherman, J. Biol. Chem. 260:5382-5391, 1985).

Amino Acid Sequence↗
PubMed1987

Structural and genetic analyses of a par locus that regulates plasmid partition in Bacillus subtilis.

The Bacillus plasmid pLS11 partitions faithfully during cell division. Using a partition-deficient plasmid vector, we randomly cloned DNA fragments of plasmid pLS11 and identified the locus that regulates plasmid partition (par) by cis complementation in Bacillus subtilis. The cloned par gene conferred upon the vector plasmid a high degree of segregational stability. The par locus was mapped to a 167-base-pair segment on pLS11, and its nucleotide sequence was determined. The cloned par fragment regulated the partition of several different Bacillus replicons, and it only functioned in cis; it did not contain the replication function nor elevate the plasmid copy number in B. subtilis. The expression of par was orientation specific with respect to the replication origin on the same plasmid. We propose that the pLS11-derived par functions as a single-stranded site that interacts with other components involved in plasmid partition during cell division.

Bacillus subtilis↗
PubMed1987

Diagnosis and treatment of mixed mania.

In a study of 19 manic patients, the authors found that eight suffered from mixed mania, a condition in which depressive symptoms are found in the context of classic manic features. The presence of a mixed manic state predicted at least a slower and possibly a poor response to lithium therapy. The authors suggest that the delineation of a subgroup of mixed manic patients might help to identify potential lithium-resistant patients.

Adult↗
PubMed1987

Differentiation of tracheal mucociliary epithelium in primary cell culture recapitulates normal fetal development and regeneration following injury in hamsters.

Hamster tracheal epithelial cells were grown in primary culture for 8 days on a collagen gel substrate, in hormone-supplemented serum-free medium (Ham's F-12). On Days 1-3 in culture, the colonies were composed of a monolayer of poorly-differentiated flattened cells. Most of these were large cells which appeared to be altered secretory (mucous) cells. On Days 4 and 5, many of the epithelial cells were cuboidal. The rough endoplasmic reticulum was moderately developed, and mucous granules were seen at the cell apices. Preciliated and newly formed ciliated cells were observed on Day 6, and a differentiated mucociliary epithelium was established by Day 7 in culture. The study shows that in the hamster tracheal epithelium, the stages of normal fetal development and regeneration following injury, which have been characterized previously in vivo, are recapitulated in vitro. Formation of a mucociliary tracheal epithelium occurs within 7 days in vito and in vitro.

Animals↗
PubMed1987

Maintenance of plasma triglyceride-lowering through use of low-dose fish oils in the diet.

The ingestion of large doses of fish oil may be associated with a marked reduction in plasma triglyceride concentrations. The present study was a preliminary evaluation of whether a lower maintenance dose of fish oils in hyperlipidemic patients would be sufficient to sustain therapeutic effects already achieved on higher dosage over a prior period of three months or longer. For the purposes of this study, 10 or 16g/day of fish oil (LipitacR) was defined as high dosage, 6g/day as medium dosage and 3g/day as low dosage. Five subjects entered on high dosage and were subsequently evaluated on medium and then on low dosage at intervals of six weeks. Five subjects entered on medium dosage and were evaluated after six weeks on low dosage. Seven of the subjects entered with a significant degree of hypertriglyceridemia while the remainder had hypercholesterolemia. Subjects entering with background triglyceride concentrations in excess of 2mmol/l showed reduced triglyceride concentrations at all dose levels, while two subjects with entry triglycerides in excess of 10mmmol/l experienced further improvement in plasma triglycerides when comparing medium with low dosage, or high with medium dosage. Low dose fish oil appears to have potential as a form of maintenance therapy in the management of moderate degrees of hypertriglyceridemia.

Adult↗