Biomedical subjects

M C Maurel

Publications and source records attributed to M C Maurel.

24 records · Page 2Linked to original sources

PubMed1992

Immunochemical study of equine chorionic gonadotropin (eCG/PMSG): antigenic determinants on alpha- and beta-subunits.

In the present study we have established an immunochemical mapping of equine Chorionic Gonadotropin (eCG/PMSG) using three monoclonal antibodies (mAbs), namely the antibodies ECG01, E10 and D7, raised against the native hormone. These antibodies do not bind to reduced, alkylated hormone, suggesting that they recognize discontinuous rather than continuous epitopes. We have also assessed the reactivity of mAbs towards human CG, and ovine, porcine, equine and bovine LH and FSH. The antigenic determinant recognized by ECG01 is localized on the alpha-subunit of equine gonadotropins and of human CG and LH. The epitopes recognized by E10 and D7 mAbs appear to be very similar and are present on the beta-subunit of eCG and of LHs from all species tested, except hLH, as well as on porcine and equine FSHs. Attempts to specify the amino-acid residues involved in these epitopes suggest that ECG01 mAb might preferentially bind to residues around position 70 whereas the region around disulfide bridges Cys-88-Cys-90 might be involved in the epitopes recognized by D7 and E10 mAbs. Topographical relationships of epitopes show that ECG01 mAb never binds to eCG simultaneously with either D7 or E10 mAbs. Furthermore, simultaneous binding of D7 and E10 mAbs on eCG could not be achieved. Thus, these three epitopes appear to be closely located on the surface of eCG. Finally, ECG01 mAb inhibits eCG binding to LH and FSH receptors, suggesting that its antigenic site is closely related to hormone-receptor interaction site(s).

Animals↗

PubMed1990

Chemical structure of a prebiotic analog of adenosine.

Upon heating a dry mixture of ribose and adenine, condensation products are formed. They were identified as isomers of N6-ribosyl-adenine (Fuller, Sanchez and Orgel, 1972). Due to the current interest in nucleotide analogs as potential constituents of primitive RNA catalysts, the products were further characterized by mass spectroscopy and proton NMR. Our results fully substantiate the previous proposals.

Adenosine↗

PubMed1988

Evidence for tertiary structure in natural single stranded RNAs in solution.

Binding isotherms (20 degrees C) of ethidium bromide to a number of tRNA species at various ionic strengths indicate that i) the number ni of intercalation sites is high 7 to 11 per molecule, in the low salt form III, but small, 2 to 1, at high Mg2+ or Na+ when form I predominates. ii) modification of tRNA at strategic positions for 3D folding prevents full expression of intercalation restriction iii) maximal restriction is obtained at salt concentrations higher than needed for full conversion to form I. It is inferred that restriction, which is not observed with bihelical RNA (or DNA), requires the native tRNA 3D structure but also some physical coupling between the region of 3D folding and bihelical arms. Ribosomal RNAs, some viral RNAs, mRNA from sheep mammary gland as well as the random copolymers Poly UG, Poly AUG, Poly AUCG all exhibit intercalation restriction. Hence 3D folding of the polyribonucleotide chains appears to be a feature common to single-stranded RNAs when free in solution under physiological conditions.

DNA↗

PubMed1987

A highly sensitive microtitre plate enzyme immunoassay for oestradiol-17 beta.

A specific and sensitive solid-phase microtitre plate enzyme-linked immunosorbent assay for oestradiol-17 beta (E2) is described. After coating with an IgG anti-E2 fraction, we used E2-6-carboxymethyl-oxime-beta-galactosidase in a competitive binding assay and revealed the bound activity with a fluorogenic substrate. Two methods for the competitive binding assay were tested: (1) a classical one (method A) defined as a 'two-step competition' because the E2 sample was first incubated alone, and then E2-beta-galactosidase conjugate was added; (2) and a new one (method B) also performed in two steps but in which the E2 sample was evaporated to dryness. The detection limit of method A was 100 pg/ml (9 pg/well). Method B was more sensitive since 1 pg/ml (0.3 pg/well) was statistically different from 0 pg/ml. Specificity was equivalent with both methods while precision was better in B. Thus, this new method may be able to measure very low levels of oestradiol-17 beta in, for example, the blood of domestic mammals.

Binding, Competitive↗

PubMed1987

Catalysis by a prebiotic nucleotide analog of histidine.

A ribosylated derivative of adenine, N6 ribosyl adenine, likely to have formed under prebiotic synthesis conditions, is shown to be as active as histidine in the model reaction of p-nitrophenyl acetate hydrolysis. This property widens the range of reactions accessible to RNA catalysis.

Adenosine↗

PubMedDate not supplied

Relationship between peri-oestrus progesterone levels and time of ovulation by echography in pigs and influence of the interval between ovulation and artificial insemination (AI) on litter size.

Two methods for the determination of ovulation were compared to one ultrasonography performed 5 times a day. Time of ovulation by echography was 40 +/- 5.8 h (mean +/- SD) after the onset of oestrus. Preovulatory LH rise (two blood samples per day) began near the onset of oestrus but, in our conditions, this parameter could not be used to predict ovulation. The basal level of progesterone (two blood samples per day) was determined with a non-linear model, the timing when progesterone rose more than one SD (0.3 ng x mL(-1)) coincided with the timing of ovulation determined by echography (R2 = 0.98). This method was efficient and was used in a field trial to measure the consequences of the variability of the interval between Al and ovulation on litter size. The interval between Al and ovulation had an effect on litter size; litter size decreased by one piglet when this interval increased by 10h.

Animals↗