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Biomedical subjects

B Garat

Publications and source records attributed to B Garat.

5 recordsLinked to original sources
PubMed1987

Antibody heterogeneity: theoretical and experimental evaluation of a simple procedure to describe differing affinities in hapten binding reactions.

Heterogeneity in antibody binding affinity for hapten is easily and comprehensibly described by plotting the histogram of delta r, the change in the fraction of occupied active sites, vs the logarithm of the concn of free ligand. Computer simulations of binding reactions revealed that multimodal histograms occur only if differences in affinity are greater than 10-fold. Otherwise, the delta r histogram closely approximates a normal distribution, the variance of which increases with increasing heterogeneity. In biochemical experiments delta r histograms successfully detected mixtures of anti-DNP antibodies of varying affinities as well as changes between early and late anti-DNP immune responses in rabbits immunized with or without Freund's complete adjuvant.

Animals↗
PubMed1985

Presence of a membrane bound pyroglutamyl amino peptidase degrading thyrotropin releasing hormone in rat brain.

In the present work we studied the pattern of degradation of [3H-Pro]-TRH by soluble and membrane fractions from rat brain. Demonstration of the membrane bound or soluble nature of the activities was obtained by comparing their distribution to that of lactate dehydrogenase and by looking at the effect of NaCl washes on the membrane fractions. We observed that the pyroglutamyl amino peptidase activity detected in brain homogenates is a result of two different enzymes. One of them is a soluble enzyme previously characterized, that needs DTT and EDTA for its expression, is inhibited by SH-blocking agents such as iodoacetamide and utilizes p-glu-beta-naphtylamide as a substrate. The other one, a membrane enzyme, is inhibited by chelating agents such as EDTA and DTT, is not affected by iodoacetamide and does not degrade p-glu-beta-naphtylamide. The later presents some specificity towards TRH as shown by competition experiments with TRH analogs. We were able to corroborate that the post proline cleaving enzyme acting on TRH is a soluble enzyme. In membranes we demonstrated also the presence of a post-proline dipeptidyl aminopeptidase. The membrane bound pyroglutamidase activity is a potential new source of L-his-L-pro-diketopiperazine in brain. The presence of a TRH degrading enzyme in membrane fractions is of particular importance in searching an inactivation mechanism of this peptide once it is released into the synaptic cleft.

Aminopeptidases↗