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Biomedical subjects

S Tan

Publications and source records attributed to S Tan.

At least 199 records · Page 11Linked to original sources
PubMed1990

[Reoperation of tetralogy of Fallot long after correction with aortic homograft: a case report].

Late results in the surgery for congenital heart disease repaired with external conduit have not yet been fully elucidated. We experienced a reoperation of tetralogy of Fallot (TF) that was previously repaired with an aortic homograft pretreated with beta-propiolactone for the reconstruction of right ventricular outflow tract. Ten years after correction of TF, right ventricular failure developed due to the regurgitation of tricuspid valve. At reoperation tricuspid annuloplasty was performed, and the valve of aortic homograft was also replaced with xenograft because of its uncertain durability. However, the resected valve had pliability with least degenerative change macroscopically. The postoperative course was smooth. The case was a rare one of late reoperation of TF due to the tricuspid valve regurgitation, and the case also indicated unexpected long durability of the valve cusp of the aortic homograft.

Adult↗
PubMed1990

Rewarming after cardiopulmonary bypass--a comparison of two methods.

Patients returning to the Intensive Care Unit following cardiac surgery with cardiopulmonary bypass are almost always hypothermic despite having been rewarmed prior to termination of bypass. The study compared the effect of an overhead radiant heat source with a reflective metallised blanket. Both groups received warmed humidified gases. Rectal, tympanic membrane and great toe temperatures were measured. Patients nursed under the radiant heat source had higher temperatures at the end of the study period as compared to those nursed with conventional means (p less than 0.05).

Aged↗
PubMed1990

[Key grafts in emergency aortocoronary bypass surgery].

We evaluated relations with operative results of emergency aortocoronary bypass grafting to severity of residual stenotic lesion after surgery in patients with impending myocardial infarction or acute myocardial infarction. Mortality in patients with residual stenotic lesion whose score more than 15 is 66%. Mortality in patients with residual stenotic lesion whose score less than 15 is 5%, excluding patients died with noncardiac cause. Four of 6 patients (66%) with residual stenotic lesion whose score more than 5 have residual angina after the operation. None of fourteen patients with residual stenotic lesion whose score less than 5 has residual angina after the operation. In theory, we could save their lives with only one graft in 76% patients and cure their angina with less than 2 grafts in 72% patients. These grafts are key grafts.

Aged↗
PubMed1989

Purification of an acidic plastocyanin from Microcystis aeruginosa.

Plastocyanin and cytochrome c-553 are two functionally equivalent electron carriers in the photosynthetic chain of cyanobacteria. Microcystis aeruginosa, a unicellular cyanobacterium which grows well at a high pH (8.6) and which was not known to possess plastocyanin, has been studied for its ability to synthesize plastocyanin in culture media with and without Cu. In the absence of Cu, an acidic cytochrome c-553 alone was isolated. With the inclusion of 2 microM Cu, cytochrome c-553 synthesis was partially suppressed and an acidic plastocyanin was isolated. A newly developed procedure, using high concentrations of ammonium sulfate to fractionate water-soluble proteins on Sephacryl S-200 was successfully used to isolate and concentrate the plastocyanin, thus allowing it to be further purified to homogeneity. This protein has an isoelectric point of 4.8 which is similar to the pI value reported for other acidic plastocyanins from higher plants and green algae. Its N-terminal sequence of the first 15 amino acids has been determined; 9 of these amino acids are identical to those in the sequence of the basic plastocyanin from Anabaena variabilis.

Amino Acid Sequence↗
PubMed1989

Effects of the NMDA antagonists CPP and MK-801 on delayed conditional discrimination.

N-methyl-D-aspartate (NMDA) receptor/channel antagonists have previously been shown to impair spatial working memory and hippocampal long-term potentiation. The present experiment investigated the effects of a variety of doses of NMDA antagonists on a working memory task in rats involving an auditory delayed conditional discrimination. Signal detection analysis and an exponential memory decay model were used to extract independent measures of stimulus discriminability and rate of forgetting. A competitive NMDA antagonist, (CPP, 0.33, 1.0, 10.0 mg/kg, IP) produced a reduction in discriminability which was linearly related to log dose, but which was only clear at the 10 mg/kg dose. Rate of forgetting was not increased by any dose. Similar results were obtained with a non-competitive antagonist (MK-801, 0.1, 0.33 mg/kg, IP). These data suggest that doses of NMDA receptor channel antagonists sufficient to disrupt hippocampal long-term potentiation and radial arm maze performance will also disrupt delayed conditional discrimination. The effect on delayed conditional discrimination is due to a disruption of stimulus discriminability and not to an increased rate of forgetting. The extent to which these effects relate to the reported changes in hippocampal long-term potentiation and radial arm maze performance remains to be determined.

Animals↗
PubMed1989

Expertise and configural coding in face recognition.

Diamond & Carey (1986) have argued that expertise in face recognition depends on the ability to code configural properties in addition to isolated features. We tested this hypothesis in two experiments by comparing the effect of inversion on recognition of 'own race' (high expertise) and 'other race' (low expertise) faces. Use of configural information should be associated with a larger inversion effect than use of isolated features, and therefore inversion should produce a larger recognition decrement for own race than for other race faces. In Expt 1 there was a larger inversion effect in reaction times for recognition of own race faces than other race faces, for both European and Chinese subjects (ceiling effects made interpretation of accuracy difficult). In Expt 2 a larger own race inversion effect was found for recognition accuracy, when test face pairs were randomly selected, but not when they were matched on isolated features. Our results are largely consistent with the hypothesis that expertise is associated with greater use of configural information in faces.

Adolescent↗
PubMed1989

Monocyte antigen CD14 is a phospholipid anchored membrane protein.

A cDNA clone encoding the human monocyte antigen CD14 was isolated by transient expression in COS cells of a cDNA library prepared from phorbol diester-treated HL60 cells. RNA blot analysis showed abundant expression of a single mRNA species in mature monocytes and an increased expression of the mRNA following induction of differentiation in leukemic cell lines. The DNA blot hybridization pattern was consistent with a single-copy gene. The predicted amino acid sequence lacks the characteristic transmembrane domain and stop transfer motif of conventionally anchored membrane proteins. COS cells transfected with the CD14 cDNA released virtually all CD14 protein in soluble form following treatment with glycosyl phosphatidylinositol-specific phospholipase C, and CD14 immunoreactivity was absent from the affected monocytes of a patient with paroxysmal nocturnal hemoglobinuria (PNH). The data show that, to the limit of experimental sensitivity, all monocyte CD14 is joined to the plasma membrane by a phosphatidylinositol phospholipid.

Amino Acid Sequence↗
PubMed1988

Interactions of purified transcription factors: binding of yeast MAT alpha 1 and PRTF to cell type-specific, upstream activating sequences.

Pheromone receptor transcription factor (PRTF) and MAT alpha 1 are protein transcription factors that are involved in the regulation of the alpha-specific genes in Saccharomyces cerevisiae. We have expressed MAT alpha 1 as a fusion protein in Escherichia coli and purified it from inclusion bodies in milligram quantities. The MAT alpha 1 protein was obtained after specific cleavage of the fusion protein. Quantitative band shift electrophoresis was used to determine the equilibrium dissociation constants that describe the multicomponent binding equilibrium between the PRTF and MAT alpha 1 proteins, and alpha-specific STE3 upstream activating sequence (UAS) DNA. The dissociation constant for the complex of PRTF and the a-specific UAS of STE2 was also measured and found to be 5.9 X 10(-11) M, only three times less than that for the PRTF-STE3 UAS complex. Analyses of these complexes by DNase I footprinting demonstrate that the PRTF binding site is confined to the palindromic P-box sequence in the case of the STE3 UAS, but extends symmetrically from this central region to cover 28 bp for the STE2 UAS. When MAT alpha 1 is bound to the PRTF-STE3 complex, the region of DNA protected is enlarged to that seen for the PRTF-STE2 complex. Our results using these two purified factors in vitro suggest that PRTF has nearly the same affinity for a- and alpha-specific UAS elements and that transcriptional activation requires a particular conformational state for the PRTF-DNA complex which occurs in the PRTF-STE2 and MAT alpha 1-PRTF-STE3 complexes, but not in the PRTF-STE3 complex.

Base Sequence↗
PubMed1988

Isolation of water-soluble cytochromes from cyanobacteria by adsorption chromatography.

A simple procedure using ammonium sulfate to fractionate water-soluble cytochromes c553 and c550 on Sephacryl S-200 gel is described. The usefulness of this procedure has been studied using the crude extracts of mesophilic cyanobacteria. It was found that almost all the cytochromes were adsorbed on to the gel at 2.34 M ammonium sulfate and were eluted at decreasing salt concentrations. The cytochromes were free of interfering phycobiliproteins and thus were suitable for the study of isoelectric points. It was also found that this procedure allowed a clear separation of the cytochromes based on their hydrophobicities. The order of elution was cytochrome c553, then cytochrome c550, indicating that c550 is more hydrophobic than c553. All these results show that this procedure provides both a simplified and an efficient purification of the cytochromes and insight into their surface properties. The cytochromes of Microcystis aeruginosa were purified to homogeneity using this procedure and other existing ones. Homogeneous cytochromes c553 and c550 were chromatographed on Sephacryl S-200 at 1.75 M (NH4)2SO4 and found to elute in the same order as reported earlier for the cytochromes in the crude extracts. In addition, cytochrome c550 was found to be more heat resistant and less water soluble than cytochrome c553.

Acrylic Resins↗
PubMed1988

Effect of low- and high-fat intakes on the hormonal milieu of premenopausal women.

To compare the influence of low- and high-fat diets on hormone metabolism, we studied six premenopausal women over two complete menstrual cycles. After an initial 7-10 d dietary adjustment subjects were randomly assigned to either low- (25% of calories) or high-fat (46% of calories) diets. The diets were isocaloric and similar in proportions of protein, polyunsaturated:saturated fatty acid ratio, fiber, and cholesterol. All subjects completed both diets in a crossover experimental design. Fasting blood and 24-h urine samples were collected every other day. No significant differences in plasma luteinizing hormone, progesterone, prolactin, estrone (E1), and estradiol-17 beta (E2) or in urinary E1, E2, and estriol were observed. Prolactin secretion in response to thyrotropin-releasing hormone stimulation was also unchanged. Dietary fat may influence breast-cancer incidence by modulating the hormonal environment; however, an increase in short-term fat intake from 28 to 51 g/1000 kcal did not lead to substantial differences in the hormonal milieu.

Adult↗
PubMed1987

Fluorescence light microscopy of F-actin in retinal rods and glial cells.

The actin cytoskeleton of rod photoreceptors and glial cells in toad retina has been directly viewed using fluorescence microscopy of cells labeled with a potent phallotoxin that specifically binds to F-actin. The three-dimensional organization of this cytoskeletal protein consists of actin filaments, which course through the inner segment and end at the tips of the calycal processes surrounding the base of the outer segment. A transverse layer of actin staining is also observed at the base of rod outer segments in the region where new discs are formed. At the level of the external limiting membrane, evidence has been found for rings of actin within the glial cells that surround the photoreceptors. These actin rings form a structural meshwork in which photoreceptor cells are embedded.

Actins↗