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J P Roy

Publications and source records attributed to J P Roy.

12 recordsLinked to original sources
PubMed1992

H chain V region sequences of three human monoclonal IgM with anti-myelin-associated glycoprotein activity.

The amino acid sequence corresponding to the V region H chain gene used by three monoclonal IgM directed to the myelin-associated glycoprotein (MAG) is presented. They all belonged to the VHIII variability subgroup, but each may well represent a new member of this family inasmuch as their homology with previously sequenced VHIII genes was less than 80%. Strikingly, there was no greater homology between the H chain V regions of the anti-MAG IgM. Partial amino acid sequence data indicated that these V regions were joined to as yet unidentified DH segments; however, two H chains used very similar DH, possibly indicating that this sequence was involved in the fine specificity of the IgM for MAG. All H chains included a JHIV region. These data, together with results obtained from the sequence of the three kappa L chains of the same IgM molecules (Mihaesco, E., H. Ayadi, N. Congy, M. C. Gendron, J. P. Roy, H. Heyermann, B. Frangione, and J. C. Brouet. 1989. J. Biol. Chem. 264:21481), indicate that the repertoire of VL and VH gene segments used by anti-MAG IgM is quite diverse, in contrast to previous structural data obtained for other human monoclonal IgM autoantibodies. Possibly, these differences reflect distinct pathogenesis.

Amino Acid Sequence↗
PubMed1992

Disparity sensitivity of neurons in monkey extrastriate area MST.

We tested the disparity sensitivity of neurons from the medial superior temporal area (MST) in awake behaving monkeys. While the monkey looked at a fixation spot on a screen in front of it, random dot stimuli moved in the preferred direction of the cell under study, and the disparity of the dots made the stimuli appear to move in a frontoparallel plane in front of, on, or behind the screen. Over 90% of the 272 neurons studied were sensitive to the disparity of the visual stimulus. Of those disparity-sensitive cells, 95% were most responsive either to near stimuli (stimuli with crossed disparities appearing to move in front of the screen) or to far stimuli (stimuli with uncrossed disparities appearing to move behind the screen). In a smaller sample of the disparity-sensitive cells, we found cells whose preferred direction of stimulus motion reversed as the disparity of the stimulus reversed. For example, a cell that responded best to rightward motion for near stimuli responded best to leftward motion for far stimuli. We found that 40% of the disparity-sensitive cells had this disparity-dependent direction selectivity. This disparity-dependent direction selectivity was maintained over the entire range of speeds tested (6-56 degrees/sec). We tested whether the disparity sensitivity of the neurons indicated the distance of the stimulus from the screen where the monkey was fixating (relative depth) or the distance of the stimulus from the monkey (absolute depth) by having the monkey fixate at different depths in front of or behind the screen. For most MST neurons, the changes in vergence did not alter the disparity response, indicating that the disparity sensitivity of these neurons conveyed information on depth relative to the plane of fixation. We conclude that the disparity characteristics of cells in the dorsomedial MST are those expected of a system serving primarily coarse rather than fine stereopsis. The correlation between disparity selectivity and direction selectivity in these neurons, as well as their other properties, suggests a role in signaling the direction of self-motion of the observer through the environment.

Animals↗
PubMed1990

The role of disparity-sensitive cortical neurons in signalling the direction of self-motion.

Movement of an observer through the environment generates motion on the retina. This optic flow provides information about the direction of self-motion, but only if it contains differential motion of elements at different depths. If the observer tracks a stationary object while moving in a direction different from his line of sight, the images of objects in the foreground and in the background move in opposite directions. We have found neurons in the cerebral cortex of monkeys that prefer one direction of motion when the disparity of a stimulus corresponds to foreground motion and prefer the opposite direction when the disparity corresponds to background motion. We propose that these neurons contribute a signal about the direction of self-motion.

Animals↗
PubMed1990

A new extra sequence at the amino terminal of a mu heavy chain disease protein (DAG).

The primary structure of a human mu heavy chain (DAG) protein is described. The native protein is a circular decamer with a molecular weight (Mr) of 500 kDa, each decamer being constituted of the constant domains C mu 2, C mu 3 and C mu4 and interlinked by 15 disulfide bridges. At its NH2-terminal each monomeric chain starts with an "extra sequence". The amino acid sequence of this segment is Arg-Gln-Ser-Asp-Asp-Pro-Val-Leu-Arg-Gly-Thr-Thr-Val-Pro-Val-Thr-Glu and its reinitiation point is located at Val223 (Gal numbering), at the beginning of C mu 2. This sequence has no homology with any other protein included in the present databases.

Amino Acid Sequence↗
PubMed1989

Multiple mutations in the variable region of the kappa light chains of three monoclonal human IgM with anti-myelin-associated glycoprotein activity.

Human monoclonal IgM having an antibody activity directed to myelin-associated glycoprotein have distinctive features. Amino-terminal sequence of light and heavy chains from 6 IgM kappa that we have previously studied indicated that heavy chains belong to the VHIII subgroup, whereas light chains belong to 3 different subgroups of variability (V kappa I 2, V kappa II 1, and V kappa IV 3). We report here the complete sequence of the variable domain of 3 L chains: 2 V kappa IV and 1 V kappa II subgroups. Strikingly an unusually high degree of mutations clustered in the complementarity-determining regions (CDR) 1 and CDR 3 was found and the variable regions were joined to three different JK segments. Amino acid substitutions did not yield similar sequence in the CDRs suggesting that the kappa chains had no predominant role in the unique binding activity of these IgM or alternatively they are directed against different epitopes. Data are consistent with the previously reported lack of easily demonstrated public idiotopes common to anti-myelin-associated glycoprotein IgM. The pathogenesis of these IgM autoantibodies is most likely different from that of previously studied monoclonal rheumatoid factors or cold agglutinins where a genetic restriction of L or H chains or both has been observed.

Amino Acid Sequence↗
PubMed1985

The amino acid sequence of a lambda light chain presenting abnormal physicochemical and antigenic features.

The amino acid sequence of the light chain of a human monoclonal IgA1 (Mem) was established, in part by analogy with already known sequences. By homology its variable part was shown to belong to the V lambda I subgroup while the isotype-associated amino acid residues characterized it as Mcg+, Kern+ and Oz-. The normal primary structure of this chain was in contrast to its abnormal physical and antigenic properties: (a) its apparent molecular mass estimated by SDS/polyacrylamide gel electrophoresis, by gel filtration chromatography and by gradient ultracentrifugation was found to be lower by approximately equal to 10% than the values (23.5 kDa) of 'normal' light chain used as controls; (b) the lambda I chain Mem, when tested in native state was not antigenically reactive. These abnormalities were reverted when the chain was treated with 8 M urea. These data suggest that the abnormal behaviour of lambda I chain Mem is at a conformational level.

Amino Acid Sequence↗
PubMed1979

The surgical separation of pygopagous twins.

A set of female pygopagous twins was successfully separated. Preparation for the main operative procedure and the surgical anatomy encountered are described in details.

Anal Canal↗
PubMed1978

Effect of metergoline on delayed response in cats and its relation to the metabolism of dopamine and serotonin in neostriatal and mesolimbic neurons.

In cats the effect of Metergoline (Liserdol, Farmitalia) was investigated on the performance of a delayed response task and was related to the associated changes in the concentrations of dopamine, nonadrenaline and serotonin in the brain. Metergoline (14 microgram/kg/day, i.m.) administered during the first 10 days of the training significantly decreased response latencies at delay periods of 0, 3, 9 and 27 sec without significantly affecting the number of errors. Biochemical assays showed that the improved performance correlated with the increased dopamine content of limbic structures and the decreased serotonin content in all brain structures. The concentrations of dopamine in the neostriatum remain unchanged. Response latencies and the number of errors in cats treated with Metergoline were significantly different from those in animals treated with L-DOPA (30 mg/kg/day) probably relfecting the specific biochemical disturbance induced by the two drugs. These results suggest an inhibitory influence of serotoninergic pathways on areas like the meso-limbic system retaining high concentrations of dopamine.

Animals↗
PubMed1975

[Emphysematous cholecystitis: presentation of two clinical cases].

Emphysematous cholecystitis is relatively rare: in 1971 the cumulative total of cases reported in the world literature was 115. Two cases seen in the period 1967 to 1972 can be added. The features of these two cases, and those described in the literature support the view that emphysematous cholecystitis results from a primary obliterative endarteritis and a secondary proliferation of microorganisms.

Aged↗