Biomedical subjects

D A Yeats

Publications and source records attributed to D A Yeats.

3 recordsLinked to original sources

PubMed1992

Analysis of differentially expressed genes in retinitis pigmentosa retinas. Altered expression of clusterin mRNA.

The molecular and cellular processes underlying photoreceptor degeneration in retinitis pigmentosa (RP) are unknown. We have investigated gene expression in diseased retinas using differential hybridization screening of a retinal cDNA library with probes derived from normal and RP retinal RNA. Most differential clones detected corresponded to transcripts absent from the dystrophic state, including e.g. opsin. However, one clone was noticeably increased in RP in comparison with the control: partial sequencing showed it encoded clusterin. Increased expression of clusterin has been identified in several cases of tissues undergoing apoptosis (programmed cell death), and our finding suggests that the degenerative changes in advanced RP may represent another example of apoptosis, possibly with common causative mechanisms.

Adult↗

PubMed1990

Cationic factors affecting phospholipase activities from human lung.

1. The effects of varying H+ and other cation concentrations on phospholipase activity were investigated on two particulate fractions from human lung, corresponding to the mitochondrial and microsomal fractions. 2. Three 14C-labelled substrates, arachidonyl-phosphatidylcholine (PC), -phosphatidylethanolamine (PE) and -phosphatidylinositol (PI) were used. 3. For two substrates, PE and PI, hydrolysis was maximal at pH 6, with either subcellular fraction. 4. Hydrolysis of all three substrates was strongly inhibited by EDTA and EGTA (10-25 mM). Addition of 2,2-dipyridyl, o-phenanthroline, 8-hydroxyquinoline or desferrioxamine (10 microM-1 mM) did not inhibit but often increased hydrolysis of all substrates. 5. Addition of Zn2+, as ZnCl2, (10 microM-1 mM) inhibited PE and PI, but not PC, hydrolysis. 6. The phospholipase activities from human lung appear to be dependent on Ca2+ for maximal activity and to be inhibited by other metal ions including Zn2+.

Calcium↗

PubMed1989

Phospholipases A2 and C of human lung; subcellular distribution and substrate selectivity.

The phospholipase activities of cell-free extracts of human lung were studied using sn-2-arachidonoyl phospholipids. Samples of human lung obtained during surgery were homogenized and separated by centrifugation into three fractions: P1, containing mitochondrial and lysosomal marker enzymes; P2, with microsomal enzymes; and S2, with cytosolic enzymes. The highest phospholipase activities were in the microsomal fraction, using any of the three substrates, [14C]arachidonoylphosphatidylcholine (PC), [14C]arachidonoylphosphatidylethanolamine (PE) and [14C]arachidonoylphosphatidylinositol (PI). From PC and PE, only free arachidonic acid was formed, suggesting the presence of a phospholipase A2 (PLA2)-like activity. From PI, two metabolites were produced, diacylglycerol and arachidonic acid, suggesting the presence of a PI-specific PLC activity. Rates of hydrolysis were highest for PI, followed by PE and then PC. Hydrolysis of [14C]arachidonoyl-PC was compared to that of [14C]oleoyl-PC and found to be similarly distributed and of comparable velocity. The distribution and relative activities of phospholipases in rat lung homogenates were very similar to those in human lung.

Animals↗