Biomedical subjects

J L Connat

Publications and source records attributed to J L Connat.

22 records · Page 2Linked to original sources

PubMed1986

Metabolism of [3H]ecdysone by isolated tissues of the female ixodid tick Amblyomma hebraeum (Ixodoidea; Ixodidae).

Malpighian tubules, gut, ovaries and carcasses of the adult female tick Amblyomma hebraeum were incubated in vitro in the presence of 2 microM [3H]ecdysone. Organs and media were separately extracted after 6, 24 and 48 h incubations and the patterns of ecdysone metabolites were analyzed by HPLC. Esterase-susceptible apolar metabolites similar to the AP2 already described in the soft tick Ornithodoros moubata and thus presumably corresponding to the same conjugates (C-22 esters with fatty acids) were rapidly produced in all tissues investigated. They were mainly found within the organs but they were also released into the medium to some extent. By contrast, less apolar metabolites corresponding to the AP1 esters were mainly found in the media. Malpighian tubules and gut were the most active organs regarding the conversion of ecdysone into 20-hydroxyecdysone (20E). However, only low quantities of 20E were formed, reaching respectively 12.5% and 11.6% of the total metabolites after 48 h incubations. In the carcass and in the ovary the formation of 20E was only a minor pathway (1.7% and 3.1% of the total metabolites after 48 h). In ovaries we observed a massive conversion of ecdysone into 3-epiecdysone, which (as in insects) presumably proceeded through the intermediate formation of 3-dehydroecdysone. These two compounds were identified among the metabolites by CI/D mass spectrometry. The 3-epimer was released into the media, in contrast with the AP2 which were essentially stored within ovaries. Epimerization was also realized to some extent by carcasses, and again the epimer was released into the culture media. The different pathways are compared with those found in other tick species and in insects, and the significance of the various metabolites is discussed.

Animals↗

PubMed1984

Metabolism of ecdysteroids during the vitellogenesis of the tick Ornithodoros moubata (Ixodoidea, Argasidae): accumulation of apolar metabolites in the eggs.

The fate of injected [3H]ecdysone [( 3H]E) and 20-hydroxy-[3H]ecdysone [( 3H]20E) has been investigated in the female tick Ornithodoros moubata (Murray, 1877; sensu Walton, 1962). When injected into fed mated vitellogenic females, [3H]E is converted into [3H]20E and two apolar classes of metabolites, AP1 and AP2. Injected [3H]20E is directly converted into AP1 and AP2. AP2 is incorporated into the ovaries in a high proportion and at the end of the vitellogenic cycle represents about 25% of the total label recovered from the animal. The fate of labeled hormones injected into virgin females which perform an abortive vitellogenic cycle is quite similar. However, the ovaries incorporated less of the AP2 products. Ovaries of mated females cultured in vitro in the presence of [3H]E are able to produce [3H]20E and AP2. AP2 is incorporated, while [3H]20E is mainly found in the medium. Ovaries of virgin females presented a slower rate of transformation and of incorporation of the label. Labeled AP2 is recovered in freshly laid eggs and AP1 in the females after oviposition. AP1 and AP2 can produce [3H]20E, [3H]E, and other minor polar peaks when submitted to hydrolysis by esterase. It is concluded that the female O. moubata possesses a special enzymatic mechanism for transformation of ecdysteroids into apolar products and for selective incorporation of AP2 into the ovaries. These products are present in the freshly laid eggs and could play a role during embryogenesis.

Animals↗

PubMedDate not supplied

Calcitonin gene-related peptide innervation and binding sites in rat aorta during development.

Indirect immunohistochemistry performed on whole mounts of arch and thoracic part of the rat aorta at six developmental stages (from embryonic day 17 to 6 months, in males and females) revealed that calcitonin gene-related peptide (CGRP) innervation is highest in the arch. The highest density of innervation is found at the three first postnatal ages investigated (day 1, day 3 and 5 weeks; 2.6 +/- 0.6 intercepts/mm in the arch at 1 day); however, all values are low compared to other arteries. The innervation grows from a few short isolated fibres in the embryo to a more complex meshwork in older animals. No striking differences were noticed between males and females. Autoradiographic studies were performed on serial sections at several levels of the aorta but did not reveal binding sites for CGRP in the vascular wall. This might be due to the technique which does not allow visualization of low density of binding sites, or to binding sites of weak affinity. We discuss the possible importance of CGRP in rat aortic smooth muscle development.

Aging↗

PubMedDate not supplied

CGRP innervation and receptors during aging of male and female hepatic rat portal veins.

Calcitonin gene-related peptide (CGRP) innervation and binding sites were studied on hepatic portal veins of male and female rats from 19 days to 22 months of age. CGRP containing nerve fibers were present both in adventitial and medial nerve plexuses, closely apposing to or penetrating into the muscular layers. The density of CGRP innervation was estimated on whole mount preparations and compared during aging. In females, aging did not affect the number of fibers per unit length, although the vessel circumference decreased after 6 months of age. In males, the vessel circumference remained constant during aging, while the density of innervation significantly decreased. Whatever the age or sex of the animals was, no CGRP binding sites were found on portal veins sections by autoradiography. CGRP had no effect on spontaneous contractions of perfused portal veins. The difference observed in the evolution of CGRP innervation density between males and females suggests that CGRP innervation in the rat portal vein may be influenced by gonadal steroids during aging.

Age Distribution↗