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Biomedical subjects

P George

Publications and source records attributed to P George.

At least 73 records · Page 4Linked to original sources
PubMed1993

Rapid detection of infectious mononucleosis-associated heterophile antibodies by a novel immunochromatographic assay and a latex agglutination test.

A novel immunochromatographic assay, the CARDS O.S. MONO test (Pacific Biotech, San Diego, Calif.), and a latex agglutination test, the Infectious Mononucleosis Kit (Unipath Ltd., Hampshire, United Kingdom) were compared with the Paul-Bunnell-Davidsohn test. Of the 957 serum specimens studied, 78 were positive and 879 were negative by the Paul-Bunnell-Davidsohn test. After discrepancies were resolved by determining Epstein-Barr virus serology, the sensitivities of the CARDS O.S. MONO test and the Infectious Mononucleosis Kit were 91.0 and 96.2%, respectively, and both tests had a specificity and a positive predictive value of 100% and a negative predictive value and overall agreement of greater than 99%. The results show that both tests can accurately detect infectious mononucleosis-associated heterophile antibodies.

Adolescent↗
PubMed1992

Study of O-glycan sialylation in C6 cultured glioma cells: regulation of a beta-galactoside alpha 2,3 sialyltransferase activity by Ca2+/calmodulin antagonists and phosphatase inhibitors.

We have demonstrated that the alpha 2,3 sialyltransferase (alpha 2,3 ST) from C6 cultured glioma cells was inhibited in vivo by W-7 and related Ca2+/Calmodulin (Ca/CaM) antagonists while protein kinase C effectors had no effect. Dephosphorylation of alpha 2,3 ST by the wide specificity alkaline phosphatase led to inactivation indicating that the enzyme is phosphorylated. The serine/threonine protein phosphatase inhibitors okadaic acid and Calyculin A led also to an inhibition of alpha 2,3 ST activity. In addition, Ca/CaM antagonists and phosphatase inhibitors led both to an inhibition of a alpha 2,3 sialoglycoprotein from C6 glioma cells as demonstrated with lectin affinity blotting. A concerted regulatory mechanism with phosphorylation/dephosphorylation of alpha 2,3 ST is then postulated.

Animals↗
PubMed1991

Study of O-glycan sialylation in C6 cultured glioma cells: evidence for post-translational regulation of a beta-galactoside alpha 2,3 sialyltransferase activity by N-glycosylation.

We have studied the Gal beta 1-3GalNAc-R alpha 2,3 sialyltransferase from C6 glioma cells transferring Neu5Ac from CMP-Neu5Ac onto O-glycans of glycoproteins. Using synchronized C6 glioma cells, we showed that the alpha 2,3 sialyltransferase activity was inhibited by tunicamycin to a greater extend than DNA and protein biosynthesis suggesting inhibition of N-glycosylation of this enzyme. Additional demonstration of N-glycosylation of the alpha 2,3 sialytransferase was provided through ConA-Sepharose binding. Treatment of partially purified alpha 2,3 sialytransferase by peptide-N-glycosidase F showed a significative inhibition demonstrating that N-glycan moiety is required for complete activity of the C6 glioma cell alpha 2,3 sialyltransferase.

Animals↗
PubMed1990

Antithrombin Rouen-IV 24 Arg----Cys. The amino-terminal contribution to heparin binding.

A variant antithrombin with reduced heparin affinity was shown by mass spectrometry sequencing and DNA amplification to have a substitution of a cysteine for an arginine at residue 24. The position of Arg-24 can be fixed within a 12 A radius from the bridge at Cys-21. This is compatible with findings in the homologous protease nexin-1 which indicate an extension of the binding site of heparin from the D-helix to under the adjacent amino-terminal pole.

Adult↗
PubMed1990

DNA analysis using polymerase chain reactions in the families of children with cystic fibrosis.

The results of our experience in DNA analysis in cystic fibrosis families using polymerase chain reaction (PCR) is reported. Of the first 10 families studied, seven were fully informative using the probe KM19 and PCR. In the remaining three families, Southern blotting analysis and the probe pXV2c were required before full information was obtained in two and partial information in the other family. The methods used, the current place of PCR and the clinical relevance of DNA analysis are discussed.

Blotting, Southern↗
PubMed1990

Effect of retinoic acid on two glycosyltransferase activities in C6 cultured glioma cells.

1. Activity of two glycosyltransferases was studied in retinoic acid-treated C6 cultured glioma cells. 2. The beta-galactoside alpha 2,3-sialyltransferase transferring N-acetylneuramin onto the O-glycans residues of glycoproteins was activated up to twice after chronic treatment (from 24 to 96 hr) with all-trans retinoic acid. 3. No effect was observed for shorter treatments. 4. On the opposite, the N-glycan galactosyltransferase activity remained unchanged whatever the length of retinoic acid treatment was. 5. The activatory effect was not dependent on isomery, as all-trans and 13-cis retinoic acid isomers were both activators of the C6 glioma cell sialyltransferase. 6. Measurement of adhesion of retinoic acid-treated cells using labelled plasma membranes showed an enhancement of adhesion in correlation with enhancement of sialyltransferase activity.

Animals↗
PubMed1990

Selectivity for omega-receptor subtypes as a strategy for the development of anxiolytic drugs.

The names omega 1-, omega 2-, and omega 3-receptor subtypes have recently been proposed to replace the nomenclature of BZ1, BZ2 and BZp receptors in order to avoid a nomenclature exclusively linked to the benzodiazepine (BZ) structure or to a regional localization. The multiplicity of pharmacological actions of currently available anxiolytics may be due to their lack of selectivity for omega-receptor subtypes. The idea that a receptor-subtype selective drug will offer a more specific therapeutic profile is widely accepted. In the field of preferential anxiolytic or hypnotic drugs, imidazopyridines represent a new chemical and therapeutic class possessing selectivity for omega-receptor subtypes. Of these, alpidem (6-chloro-2-(4-chloro-phenyl)-N,N-dipropylimid-azo[1,2-a] pyridine-3-acetamide) behaves preferentially as an anxiolytic drug in both animal models and man. Receptor-binding studies using alpidem either as a displacer or as a radioligand indicate that the compound has a high affinity for omega 1- and for omega 3- but not for omega 2-receptors. In the human brain, the binding of [3H]-alpidem to omega 1- and omega 3-receptors occurs with a Kd of 1.67 nM and 0.33 nM respectively. The binding of [3H]-alpidem to omega 1-receptors in the rat cerebral cortex with a Kd of 1.5 nM is enhanced by GABA, and in contrast to anxiolytics of the benzodiazepine type, is unaffected by chloride ions and pentobarbital. In conclusion, the affinity of alpidem for the omega 1-receptor is allosterically influenced by the activation of the GABAA receptor but not by other components of the same receptor complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Hypermutability of CpG dinucleotides in the propeptide-encoding sequence of the human albumin gene.

An electrophoretically slow albumin variant was detected with a phenotype frequency of about 1:1000 in Sweden and was also found in a family of Scottish descent from Kaikoura, New Zealand, and in five families in Tradate, Italy. Structural study established that the major variant component was arginyl-albumin, in which arginine at the -1 position of the propeptide is still attached to the processed albumin. A minor component with the amino-terminal sequence of proalbumin was also present as 3-6% of the total albumin. After amplification of the gene segment encoding the prepro sequence of albumin, specific hybridization of DNA to an oligonucleotide probe encoding cysteine at position -2 indicated the mutation of arginine at the -2 position to cysteine (-2 Arg----Cys). This produced the propeptide sequence Arg-Gly-Val-Phe-Cys-Arg. This was confirmed by sequence analysis after pyridylethylation of the cysteine. This mutation produces an alternate signal peptidase cleavage site in the variant proalbumin precursor of arginyl-albumin giving rise to two possible products, arginyl-albumin and the variant proalbumin. Another plasma from Bremen had an alloalbumin with a previously described substitution (1 Asp----Val), which also affects propeptide cleavage. Hypermutability of two CpG dinucleotides in the codons for the diarginyl sequence may account for the frequency of mutations in the propeptide. Mutation at these two sites results in a series of recurrent proalbumin variants that have arisen independently in diverse populations.

Amino Acid Sequence↗
PubMed1990

Effect of desipramine on a glycoprotein sialyltransferase activity in C6 cultured glioma cells.

The tricyclic antidepressant desipramine, when added to culture medium, gave rise in C6 rat glioma cells to a decrease of the activity of the enzyme asialofetuin sialyltransferase. The inhibition was dose and time dependent and was observed in both multiplying cells and cells blocked with 2 mM thymidine or depletion of amino acids. This inhibition was rather specific to the sialyltransferase, as under the conditions where this enzyme was inhibited up to 70%, other enzymes such as dolichol phosphate mannose synthetase, glutamine synthetase, and glycerol phosphate dehydrogenase remained unaffected. This inhibition was not reversed after removal of desipramine from the medium and was not observed by direct addition of desipramine to the sialyltransferase incubation assay. Under the same conditions, W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide], which is known to be a potent calmodulin antagonist and an inhibitor of calmodulin-dependent kinases, gave the same concentration-dependent inhibition profile of sialyltransferase as desipramine, whereas H-7 [1-(5-isoquinolinylsulfonyl)-2-methylpiperazine], which is an inhibitor of protein kinase C and cyclic nucleotide-dependent kinases, had no effect. So, it is suggested that desipramine inhibits the sialyltransferase activity in C6 glioma cells through a calmodulin-dependent system.

Animals↗
PubMed1990

Indium-111 labelled granulocyte scanning to detect inflammation in the lungs of patients with chronic sputum expectoration.

Thirty eight patients with chronic sputum expectoration underwent indium-111 labelled granulocyte lung scanning and measurement of whole body loss of indium-111 labelled granulocytes. Twenty four patients had radiologically proved bronchiectasis and 14 had mucus hypersecretion without radiological evidence of bronchiectasis. None was having an acute exacerbation at the time of the scan. The median 24 hour volume of sputum expectorated was 17 (range 2-175) ml. The 24 hour volume of purulent sputum was 5 (0-142) ml; six patients expectorated mucoid sputum only. Twenty one of the 38 patients had a positive granulocyte lung scan. All nine patients expectorating more than 20 ml purulent sputum in 24 hours had positive lung scans and all had lost more than 19% of the indium-111 from the body after five to seven days. Of the six patients with mucoid sputum, only one had a positive scan and these subjects lost only 6-11% of the indium-111 in five to seven days. The percentage loss of indium-111 from the body correlated with 24 hour purulent sputum volume (r = 0.41, n = 38, p less than 0.001) and total elastolytic activity in 24 hour sputum (r = 0.54, n = 14, p less than 0.01). The loss of indium-111 was not related to the extent of bronchiectasis when purulent sputum volume was allowed for. Indium-111 labelled granulocyte scanning provides a sensitive and objective method for detecting inflammation in the lungs and should help to improve understanding of chronic bronchial sepsis and possibly treatment in selected cases.

Adult↗
PubMed1989

Evidence for an O-glycan sialylation system in brain. Characterization of a beta-galactoside alpha 2,3-sialyltransferase from rat brain regulating the expression of an alpha-N-acetylgalactosaminide alpha 2,6-sialyltransferase activity.

We present evidence for the existence in rat brain of several sialyltransferases able to sialylate sequentially asialofetuin. [14C]Sialylated glycans of asialofetuin were analyzed by gel filtration. Three types of [14C]sialylated glycans were synthesized: N-glycans and monosialylated and disialylated O-glycans. The varying effects of N-ethylmaleimide, lysophosphatidylcholine (lysoPtdCho) and trypsin, were helpful in the identification of these different sialyltransferases. One of them, selectively inhibited by N-ethylmaleimide, was identified as the Neu5Ac alpha 2----3Gal beta 1----3GalNAc-R:alpha 2----6 sialyltransferase previously described [Baubichon-Cortay, H., Serres-Guillaumond, M., Louisot, P. and Broquet, P. (1986) Carbohydr. Res. 149, 209-223]. This enzyme was responsible for the synthesis of disialylated O-glycans. LysoPtdCho and trypsin selectively inhibited the enzyme responsible for the synthesis of monosialylated O-glycan. N-ethylmaleimide, lysoPtdCho and trypsin did not inhibit Neu5Ac transfer onto N-glycans, giving evidence for three different molecular species. To identify the enzyme responsible for monosialylated O-glycan synthesis, we used another substrate: Gal beta 1----3GalNAc--protein obtained after galactosylation of desialylated ovine mucin by a GalNAc-R:beta 1----3 galactosyltransferase from porcine submaxillary gland. This acceptor was devoid of N-glycans and of NeuAc in alpha 2----3 linkages on the galactose residue. When using N-ethylmaleimide we obtained the synthesis of only one product, a monosialylated structure. After structural analysis by HPLC on SAX and SiNH2 columns, we identified this product as Neu5Ac alpha 2----3Gal beta 1----3GalNAc. The enzyme leading to synthesis of this monosialylated O-glycan was identified as a Gal beta 1----3GalNAc-R:alpha 2----3 sialyltransferase. When using lysoPtdCho and trypsin, sialylation was completely abolished, although the Neu5Ac alpha 2----3Gal beta 1----3GalNAc-R:alpha 2----6 sialyltransferase was not inhibited. We provided thus evidence for the interpendence between the two enzymes, the alpha 2----3 sialyltransferase regulates the alpha 2----6 sialyltransferase activity since it synthesizes the alpha 2----6 sialyltransferase substrate.

Animals↗
PubMed1989

Retention deficits produced in monkeys with reversible cold lesions in the prestriate cortex.

Cryodes were implanted over the prelunate and fusiform gyri in 4 monkeys. The intention was to block the prestriate projection to the inferotemporal cortex (IT). Cooling this cortex produced deficits that were completely reversed by removing the cold. The deficits appeared in the recall of visual discriminations that were learned prior to the application of the cold, but new discriminations were learned during cooling at the same rate as in control animals. This closely resembles the results of ablation experiments in this same cortex. There was no deficit when cooling this area on a delayed match-to-sample (DMS) task that required the animals to hold visual information over delays of 10 or 45 s. However, performance was close to chance during cooling when the delays were 6 min. With this long delay, when cooling was done separately at sample when the stimulus is received, or at match when the information is recalled, a significant deficit occurred only at match. The results are consistent with the suggestion that this area is involved in retrieval of visual information from long-term memory.

Animals↗
PubMed1989

Different reactivity of two brain sialyltransferases towards sulfhydryl reagents. Evidence for a thiol group involved in the nucleotide-sugar binding site of the NeuAc alpha 2-3Gal beta 1-3GalNAc alpha(2-6)sialyltransferase.

We have studied the amino-acid residues involved in the catalytic activity of two distinct brain sialyltransferases acting on fetuin and asialofetuin. These two enzymes were strongly inhibited by N-bromosuccinimide, a specific blocking reagent for tryptophan residues. This result suggests the involvement of such residues in the catalytic process of the two sialyltransferases. Furthermore, chemical modifications by various sulfhydryl reagents led to a strong inhibition of the fetuin sialyltransferase while the asialofetuin sialyltransferase was only slightly inhibited. For a more thorough understanding of the thiol inactivation mechanism of the fetuin sialyltransferase, we studied in more detail the reactivity of this enzyme with NEM (N-ethylmaleimide), an irreversible reagent. The time-dependent inactivation followed first-order kinetics and these kinetic data afforded presumptive evidence for the binding of 1 mol NEM per mol of enzyme. Only CMP-NeuAc protected the enzyme against NEM inactivation effectively. MnCl2 did not enhance the protective effect of CMP-NeuAc. The modifications of the fetuin sialyltransferase kinetic parameters by NEM showed a competitive mechanism between NEM and CMP-NeuAc. The results suggest the involvement of a sulfhydryl residue in or near the nucleotide-sugar binding site of the fetuin sialyltransferase (but we could not excluded that CMP-NeuAc binding may induce a change in conformation of the protein, leading to a decreased accessibility of this thiol group located near the nucleotide-sugar binding site). This SH group is essential to the enzyme activity, which is not the case for the asialofetuin sialyltransferase.

Animals↗
PubMed1989

Noninvasive measurement of microvascular permeability to small solutes.

Quantification of microvascular permeability to diffusible hydrophilic solutes has received little attention in a clinical setting, probably because of a lack of noninvasive techniques. We describe a gamma camera technique which measures the clearance of 99Tcm-DTPA from the intravascular to extravascular space in extra-renal regions of interest over the lumbar region, the tissues within which being predominantly skin and muscle. This regional clearance (PSr), normalized to 100 ml of tissue, represents the permeability-capillary surface area (PS) product, a classical concept for describing solute transfer across the capillary. We found a mean value in 14 patients with normal renal function of 1.0 (S.D. 0.2) ml/min/100 ml of tissue, which is broadly similar to values anticipated from published values of 51Cr-EDTA extraction fraction (in a single pass) in human skeletal muscle and resting muscle plasma flow. The technique also generates the plasma volume (tPV) within this subrenal tissue, which we found to be 5.0 (2.0) ml/100 ml. In an attempt to reproduce an index of extraction fraction we also calculated the ratio PSr:tPV and this was 0.23 (0.08) min-1. This approach could prove useful in a variety of clinical settings.

Capillary Permeability↗
PubMed1989

Filtration fraction.noninvasive measurement with Tc-99m DTPA and changes induced by angiotensin-converting enzyme inhibition in hypertension.

Using a recently described new technique, individual kidney filtration fraction was measured from the first 3 min of the Tc-99m DTPA renogram in a series of 11 subjects without evidence of renal disease and in 23 patients with hypertension. Fourteen of these hypertensives had angiographic evidence of renal artery stenosis (RAS) but only 2 had proven renovascular hypertension (RVH). In addition, renal blood flow (RBF), expressed as a fraction of cardiac output, was measured from the first pass time activity curves following bolus injection of Tc-99m DTPA, and individual kidney glomerular filtration rate (IKGFR) was measured from the subsequent plasma Tc-99m DTPA clearance and renographic divided function. An estimation of filtration fraction based on these measurements of RBF and IKGFR correlated rather poorly with that directly based on the renogram, although both showed directionally similar changes in the hypertensive patients following inhibition of angiotensin-converting enzyme (ACE) with captopril. Filtration fraction by both estimates fell significantly after ACE inhibition in patients with RAS and essential hypertension, while RBF increased. IKGFR showed no change in essential hypertension or in hypertensive patients with RAS but fell sharply in 3 renal units in 2 patients with RVH. This renographic method for measuring filtration fraction is worthy of further elaboration and might be a simple and useful discriminator of RVH in a hypertensive population.

Adult↗