PubMed Health⌕ Search

Biomedical subjects

S Palmer

Publications and source records attributed to S Palmer.

At least 145 records · Page 8Linked to original sources
PubMed1991

Listeria meningitis and paté.

Listeria meningitis occurred in a 63 year old man who was in complete haematological remission following chemotherapy for acute myeloid leukaemia. The patient had followed Department of Health advice to immunocompromised patients and had avoided soft cheeses, cook-chill meals, and salads. He had, however, recently eaten paté produced in Belgium. This was no longer available for examination but a coincidental survey of paté in the Cardiff area found Listeria monocytogenes in 16 out of 73 samples. Paté should be included in the list of foods to be avoided by immunocompromised patients.

Food Microbiology↗
PubMed1990

A modified quantitative whole blood clot lysis method for general laboratory analysis of fibrinolysis.

Because fibrinolysis is now recognized as an important factor in hypercoagulable states, we have developed and characterized an easily performed, rapid, and quantitative screening test that assesses a patient's fibrinolytic activity. This modification of the dilute whole blood clotting time (DWBCT) counts the number of intact erythrocytes released from the clot formed in samples obtained before and after the application of a venous occlusion cuff. Samples were corrected for the plasma volume changes that occurred during venous occlusion. This test was performed on nine healthy volunteers. Specimens were diluted 1:1 with PBS, rapidly clotted with thrombin and incubated at 37 C. Starting thirty minutes after the thrombin was added and then at twenty minute intervals until 110 minutes, the number of RBCs released from the clot were counted using a Coulter S Plus counter. There were consistently more RBCs released at each time period after venous occlusion (p less than 0.001). Aliquots were also obtained for measuring PAI activity and TPA levels. PAI activity was lower post-cuff at every point (p less than 0.001). TPA level was higher at every point (p less than 0.001) post-cuff. The addition of exogenous TPA, activated protein C, or anti-PAI antibodies increased the amount of clot lysis; while the addition of anti-TPA antibodies and EACA each prevented the post-cuff increase. Unlike the euglobulin lysis time (ELT) this modified DWBCT (mDWBCT) measures the patients intact fibrinolytic system, including PAI and erythrocytes, in a quantitative fashion. Unlike either the ELT or the DWBCT the mDWBCT can be performed within two hours, so results are rapidly available for clinical decisions. These studies have demonstrated an easily performed, inexpensive, quantitative screening test of a patient's overall fibrinolytic system that reacts appropriately to pharmacologic manipulations.

Aminocaproic Acid↗
PubMed1990

Regulation of bombesin-stimulated inositol 1,4,5-trisphosphate generation in Swiss 3T3 fibroblasts by a guanine-nucleotide-binding protein.

The stimulation of inositol phosphate generation by bombesin and GTP analogues was studied in Swiss 3T3 cells permeabilized by electroporation. Bombesin-stimulated inositol phosphate generation is potentiated by guanosine 5'-[gamma-thio]triphosphate (GTP[S]) and inhibited by guanosine 5'-[beta-thio]diphosphate at all peptide concentrations tested, with no change in the EC50 value (concn. giving half-maximal response) for the agonist. Kinetic analysis showed that, although bombesin-stimulated [3H]InsP3 generation in [3H]inositol-labelled cells was rapid (maximal by 5-10 s), the response to GTP[S] alone displayed a distinct lag time of 20-30 s. This lag time was significantly decreased by the addition of bombesin, suggesting that in this system agonist-stimulated GTP/GDP exchange occurs. In addition, bombesin-stimulated generation of Ins(1,4,5)P3 mass at 10 s was enhanced by GTP[S] in the absence of a nucleotide response alone, a result consistent with this proposal. Pretreatment of the cells with phorbol 12-myristate 13-acetate (PMA) resulted in a dose-dependent inhibition of bombesin-, but not GTP[S]-, stimulated inositol phosphate generation. Furthermore, although PMA pretreatment did not affect the lag time for InsP3 formation in response to GTP[S] alone, the degree of synergy between bombesin and the nucleotide was severely decreased at early time points. The results therefore demonstrate that the high-affinity bombesin receptor is coupled via a G-protein to phospholipase C in a manner consistent with a general model for receptor-G-protein interactions and that this coupling is sensitive to phosphorylation by protein kinase C.

Animals↗
PubMed1990

Mass measurement of inositol 1,4,5-trisphosphate and sn-1,2-diacylglycerol in bombesin-stimulated Swiss 3T3 mouse fibroblasts.

Two specific and selective assays were used to measure changes in the mass of Ins(1,4,5)P3 and sn-1,2-diacylglycerol in bombesin-stimulated Swiss 3T3 cells. The results demonstrate that the increase in Ins(1,4,5)P3 was extremely rapid, but transient, returning to basal levels by 30 s. In contrast, the increase in sn-1,2-diacylglycerol was biphasic: the first phase mirrored the transient Ins(1,4,5)P3 response, whereas the second phase was sustained and occurred in the absence of elevated Ins(1,4,5)P3. The possible source of the second phase of diacylglycerol is discussed.

Adenosine Triphosphate↗
PubMed1989

Mass measurement of inositol phosphates.

This review summarises the methods available for the mass measurement of inositol phosphates, i.e., use of radioactive inositol lipid precursors, optical techniques, gas chromatography, mass spectrometry, nuclear magnetic resonance, fast atom bombardment and assays specific for Ins(1,4,5)P3. Examples of the use of each method, its sensitivity, advantages and drawbacks are given.

Animals↗
PubMed1989

The Ins(1,4,5)P3 binding site of bovine adrenocortical microsomes: function and regulation.

Adrenocortical microsomes possess a single population of Ins(1,4,5)P3-specific binding sites [IC50 5.9 +/- 0.9 nM; Palmer, Hughes, Lee & Wakelam (1988) Cell. Signalling 1, 147-156]. Competition studies showed that Ins(1:2-cyclic,4,5)P3 exhibits a 21-fold lower affinity for the site than Ins(1,4,5)P3 (IC50 124 +/- 16 nM). The affinity of the binding sites for Ins(1,4,5)P3 was not influenced by the non-hydrolysable GTP analogues GTP gamma S and Gpp[NH]p or by preincubation of the binding protein with a preparation of partially purified protein kinase C in the presence of ATP and TPA (12-O-tetradecanoylphorbol 13-acetate). These observations are discussed with reference to the identify and function of the Ins(1,4,5)P3 binding site.

Adrenal Cortex↗
PubMed1989

Point mutations in the dihydrofolate reductase-thymidylate synthase gene as the molecular basis for pyrimethamine resistance in Plasmodium falciparum.

The dihydrofolate reductase-thymidylate synthase (DHFR-TS) bifunctional complex from pyrimethamine-sensitive (3D7) and drug-resistant (HB3 and 7G8) clones from Plasmodium falciparum was purified to homogeneity. A modified sequence of purification steps with a 10-formylfolate affinity column at its center, allows the isolation of the enzyme complex with a 10-fold higher yield than previously reported, irrespective of the pyrimethamine resistance of the parasites. Titration of the homogenous DHFR-TS complex with the inhibitor revealed a 500-fold lower affinity of the enzyme from clone 7G8 for the drug than found with the enzyme from clone 3D7. Direct comparison of the homogenous enzyme preparations on SDS-PAGE revealed no difference in the molecular mass of the DHFR-TS from the 3 clones, nor could a reproducible difference be detected in the peptide patterns obtained after digesting the DHFR-TS complex with various proteases. The amplification of segments from the DHFR-TS coding region of the 3 clones and 7 isolates of P. falciparum by polymerase chain reaction resulted in fragments of the predicted length without any size heterogeneity. The DNA sequence of the DHFR coding region from FCR-3, 3D7, HB3 and 7G8 differs in a total of 4 nucleotides. One point mutation changes amino acid residue 108 from threonine (FCR-3) or serine (3D7) to asparagine (HB3 and 7G8). The presence of asparagine-108 appears to be the molecular basis of pyrimethamine resistance of HB3 and 7G8. The degree of resistance is associated with a point mutation affecting the codon for amino acid 51 in 7G8.

Animals↗
PubMed1989

Development of a novel, Ins(1,4,5)P3-specific binding assay. Its use to determine the intracellular concentration of Ins(1,4,5)P3 in unstimulated and vasopressin-stimulated rat hepatocytes.

The binding of [3H]Ins(1,4,5)P3 to bovine adrenocortical microsomes has been shown to be rapid, reversible and saturable. The microsomal preparation contained a single population of high affinity sites (KD = 6.82+/-2.3 nM, Bmax = 370+/-38 fmol/mg protein). The binding site was shown to exhibit positional specificity with respect to inositol trisphosphate binding, i.e. Ins(2,4,5)P3 was able to compete with [3H]Ins(1,4,5)P3 whereas Ins(1,3,4)P3 was not. Ins(1,3,4,5)P4 showed a similar affinity for the receptor as Ins(2,4,5)P3 whereas the other inositol phosphates tested, ATP, GTP and 2,3-DPG, were poor competitors. [3H]Ins(1,4,5)P3-binding was independent of free Ca2+ concentrations. The adrenocortical microsomal preparation has been incorporated into an assay which has been used to determine the basal and vasopressin-stimulated content of neutralised acid extracts of rat hepatocytes. Intracellular concentrations of Ins(1,4,5)P3 were calculated to be 0.22+/-0.15 microM basal and 2.53+/-1.8 microM at peak stimulation. This assay provides a simple, specific and quantitative method for the measurement of Ins(1,4,5)P3 concentrations in the picomolar range.

Adrenal Cortex↗