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M Joffre

Publications and source records attributed to M Joffre.

52 records · Page 3Linked to original sources
PubMed1984

Electrophysiological study of single Leydig cells freshly isolated from rat testis. I. Technical approach and recordings of the membrane potential in standard solution.

Single Leydig cells were isolated from rat testis by a collagenase digestion procedure and purified through a 21,000 g self generated densities gradient of 35% Percoll. A method including collagen and fibronectin was proposed to attach freshly prepared Leydig cells to the bottom of plastic Petri dishes. Four hours after the isolation of the cells, it was simultaneously possible to determine their membrane potential by a standard electrophysiological technique using intracellular microelectrodes and to judge cellular integrity by direct microscopic observations. In standard Earle's solution, changes of membrane potentials appeared to be biphasic. On 198 impaled cells, 18 +/- 1 S after the impalement was effective, the membrane potential reached a most negative value (MP1) (-37.6 +/- 0.7 mV), followed by a gradual depolarization to a steady state (MP2) (-25.1 +/- 0.6 mV) which remained constant for a few minutes. In standard Earle's solution, the membrane resistance was low or decreasing towards the most negative potential, then it increased towards the steady potential. At this state, the average value of the cell input resistance was 65.9 +/- 6.0 M omega (n = 16). No action potential was observed either in standard Earle's solution or under a depolarizing current state. It was concluded that the electrophysiological characteristics of the Leydig cell are similar to those of fibroblasts and macrophages, three types of cells with the same mesenchymal origin, present in the interstitial tissue of the rat testis. But the resting potential of the Leydig cell is higher and this secreting cell does not elicit hyperpolarizing oscillations at the steady state, under mechanical or electrical stimuli.

Animals↗
PubMed1984

Electrophysiological study of single Leydig cells freshly isolated from rat testis. II. Effects of ionic replacements, inhibitors and human chorionic gonadotropin on a calcium activated potassium permeability.

Changes in the membrane potential of isolated Leydig cells produced by modified ionic solutions were investigated in vitro either by a total change of the bathing medium (procedure P1) or by a flush of the solution around the impaled cell (procedure P2). In standard Earle's solution, the impalement of 198 cells by a glass microelectrode was accompanied by an hyperpolarization (MP1 = -37.6 +/- 0.7 mV) (means +/- S.E.M.) followed by a gradual depolarization to a steady state potential (MP2 = -25.1 +/- 0.6 mV) (Joffre et al. 1984). Experiments with K modified media (P1) showed that MP2, and to a greater extend MP1, were dependent on the external K. A tenfold increase of K decreased MP2 by 16 mV and MP1 by 25 mV. When the extracellular Cl was reduced (P1) by substituting Cl with a less permeant anion, MP2 was unchanged and MP1 was significantly decreased. A transient depolarization of MP2 occurred when a low Cl medium was flushed (P2). An equimolar Na replacement by choline chloride (P1) did not change MP1 or MP2, during the first 10 min. It suppressed MP1 and decreased MP2 after a 15 min exposure. MP1 reappeared and MP2 increased after the restoration of the normal Na solution (P1 and P2). The modification of external Ca from 0 to 3.6 mM (P1) increased both MP1 and MP2. MP1 was never cancelled in 0 mM Ca. In 18 mM Ca, MP1 was suppressed and MP2 decreased. Restoration of 1.8 mM Ca was rapidly accompanied by the MP1 reappearance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1977

Relationship between testicular blood flow, testosterone secretion and spermatogenic activity in young and adult wild red foxes (Vulpes vulpes).

Testicular capillary blood flow (TCBF) was measured by the radioactive inert gas clearance technique throughout the reproductive life of young adult foxes and was related to the spermatogenic and androgenic activities of the testis. Mean (+/-S.E.M.) blood flow (ml min-1 g-1) was maximal in January in adults during the mating period (0-65 +/- 0-03), and in pubertal animals (0-62 +/- 0-04). At this time spermatozoa were observed in the testes of all animals, but testicular weight and circulating testosterone levels were lower in the pubescent foxes than in the adults. TCBF was minimal during immaturity (0-29 +/- 0-03) and during the resting period of the adult (0-12 +/- 0-01). These values were associated with a low testosterone level and with the multiplication of gonocytes in the young or with the seasonal very low spermatogenic activity in the adult. During the prepubertal period, TCBF slowly increased and was accompanied by testicular growth. In the adult, in September, TCBF rapidly increased without changes of testicular size and then slowly increased as the testes enlarged. High plasma testosterone concentrations occurred later. During the period of testicular regression, TCBF, testicular size, spermatogenic and androgenic activities decreased together.

Aging↗
PubMed1975

An angiographic study of the fox testis in various stages of sexual activity.

The arteries and veins of the fox testis were studied using an angiographic technique. The postnatal development of the testis involved only minor modification of the vasculature. In the non-breeding season both the arteries and veins of the adult fox testis undergo extensive spiralization which completely disappears during the breeding season. When the sequence of morphological changes in blood vessels are related to available data on changes in testicular size, blood flow and connective tissue content, it is obvious that the vascular spiralization is passive and related to shrinkage of the organ and dose not primarily influence the testicular blood flow.

Angiography↗
PubMedDate not supplied

Testicular capillary blood flow in the impubertal lamb and the ram during the breeding and non-breeding seasons.

The testicular capillary blood flow was measured by the 133Xenon clearance technique in the Ile-de-France lambs and rams in Spring and Autumn. Anaesthetized animals were maintained in the supine position and 133Xe was injected into the testicle through the scrotal skin. In the adult, the blood-flow (ml/min./100 g) depended upon the season: 8.3 +/- 1.0 vs 12.7 +/- 0.7 in May and October (P less than 0.001). In the impubertal lamb (50 days old) regardless of the period of the year, the blood flow was the same as in the adult in the breeding season (11.4 +/- 1.2 vs 12.7 +/- 0.7). In prepubertal lambs (120 days old) the rapid increase in testicular weight was not correlated with an increase in the blood flow (9.4 +/- 0.7).

Animals↗
PubMedDate not supplied

Cyclic AMP- and calcium-activated chloride currents in Leydig cells isolated from mature rat testis.

Using the whole-cell recording technique, we have investigated some properties of the membrane currents induced by depolarization of Leydig cells isolated from mature rat testis. Internal perfusions with cyclic AMP or calcium induce currents which reveal the properties of the cyclic AMP-activated and calcium-activated chloride conductances. Both currents are sensitive to EC1 displacement and are similarly affected by SITS and DIDS, two stilbene-derived chloride channel blockers. However, at the resting membrane potential, the cyclic AMP-dependent, not the calcium dependent conductance, is activated. We discuss the involvement of these results in the physiology of the Leydig cells.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗