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S F Chiu

Publications and source records attributed to S F Chiu.

7 recordsLinked to original sources
PubMed1996

Hyperglycemia induced activation of type-1 protein phosphatase activator (kinase FA) in perfused human placenta.

We report the identification of type-1 protein phosphatase activating factor (kinase FA), a unique biologic mediator for both insulin and epidermal growth factors in the human placenta. The activity of kinase F, was found to be extremely labile in the unperfused placenta. Fresh term placentas lost more than 50% of the total kinase FA activity within 6 hours when exposed to air of incubated in medium but not perfused. In contrast, the activity of kinase FA was stable when the human term placenta was dually perfused. This indicates that placental dual perfusion is a useful method for studying protein phosphorylation-dephosphorylation involved in signal transduction. When fresh placentas were perfused with media containing glucose at 141 +/- 10, 242 +/- 12 and 436 +/- 20 mg/dL, kinase FA activity was stimulated several-fold in a glucose concentration-dependent manner when compared with control levels at delivery. The results suggest that hyperglycemia-mediated activation may represent a previously unknown control mechanisms for the regulation of protein kinase FA. The results also suggest that human placental perfusion is a good in vitro system for studying signal transduction mechanisms involved in hormonal actions and metabolic regulation.

Analysis of Variance↗
PubMed1994

Chorionic villi sampling: laboratory experience with 4,000 consecutive cases.

Experience with 4,000 consecutive CVS cases shows that 1) the combination of both the direct and culture methods greatly reduces false diagnoses and maternal cell contamination; 2) the time interval between the sampling procedure and processing of villus specimens influences the quality of direct preparations; 3) maternal cell contamination (MCC) can be minimized with dissection of CVS specimens. We have compiled a large volume of confined placental mosaicism (CPM) cases to serve as a resource in interpreting mosaic cytogenetic findings. It was noted that, in up to 92% of the mosaic cases, the abnormal cell line was confined to the placenta. The frequency of true chromosomal mosaicism was 0.2%, and is not different from that for amniocentesis.

Cells, Cultured↗
PubMed1992

Simultaneous monitoring of pituitary hormone secretion and gene expression within individual cells.

We have recently developed a method to simultaneously quantitate the level of gene expression and the level of secretion of a peptide from individual cells. Our approach has been to combine the reverse hemolytic plaque assay sequentially with in situ hybridization. We present data to show how we have used the pituitary lactotroph as a model to demonstrate the power of this technique. However, we are particularly excited about the potential application of this strategy to approach a broad spectrum of questions regarding the cellular and molecular mechanisms that regulate the coupling of peptide secretion and gene expression at the single cell level. The method can be used in any system in which an appropriate antibody for the reverse hemolytic plaque assay and probes complementary to the mRNA of interest are available.

Animals↗
PubMed1991

Measurement of peptide secretion and gene expression in the same cell.

A combined reverse hemolytic plaque-in situ hybridization assay was developed to allow analysis of the relationship between peptide secretion and gene expression within individual cells. We used the pituitary lactotroph as a model system, but this strategy should be widely applicable. It can be used to test hypotheses regarding if and when peptide secretion and gene expression are coupled in any system in which antibodies to the secreted peptide and probes complementary to the mRNA are available. Using the mRNA hybridization signal to identify certain cell types, this method may also be useful in further studies on the biochemical mechanism of peptide secretion. In addition, questions regarding whether a cell known to secrete a given peptide contains other specific mRNAs and the relationship between these mRNAs and the secretion of the peptide can be studied using this strategy. We found striking heterogeneity among lactotrophs in both gene expression and PRL secretion and a lack of correlation of these parameters within individual lactotrophs under every treatment examined. We also present the first direct visualization and quantitation of the percentage of nonsecreting PRL mRNA-containing cells after estradiol treatment and in the presence or absence of the PRL secretagogue, TRH. Finally, we found that in ovariectomized rats, nonsecreting lactotrophs exhibited significantly higher levels of PRL mRNA than lactotrophs that were actively secreting PRL during the assay.

Animals↗