Apoptose dans le sperme éjaculé: Revue

It has become clear in recent years that programmed cell death occurs spontaneously in the cycle of the seminiferous epithelium. Although apoptosis is a key phenomenon in the control of sperm production, the existence and role of apoptosis in ejaculated sperm cells remain controversial. Apoptosis — as determined by DNA fragmentation and ultrastructural analysis — is abnormally frequent in the sperm cells of the ejaculate of sterile men. In this review, we discuss the possible origins of DNA damage in ejaculated human spermatozoa and the consequences of this DNA damage when apoptotic spermatozoa are used for ICSI. Percentages of DNA fragmentation in human ejaculated sperm are correlated with fertilization rates after IVF or ICSI assay. Detection of DNA fragmentation in human sperm could provide additional information about the biochemical integrity of sperm and may be used in future studies for fertilization failures not explained by conventional sperm parameters. However, the analysis of new markers of apoptosis (Fas, ANNEXINE V) and molecular mechanisms is now necessary to assess the role of apoptosis in human ejaculated sperm cells.     

Apoptose et spermatogenèse

Onset of spermatogenesis is associated with a wave of apoptosis, which limits its efficacy during the first cycles in most mammals. After the first cycles, the actual efficacy of spermatogenesis always remains below the theoretical yield. Among the germinal cells, spermatogonia are the main targets of physiological apoptosis. This physiological apoptosis partly depends on the relationships between germ cells and Sertoli cells. The impact of the Sertoli cell/germ cell number ratio on the efficacy of spermatogenesis is well accepted, the concept of density-dependent regulation in the seminiferous tubule was proposed in the early eighties. Since the steps of spermatogenesis require a continuous progression of the cell cycle rather than an arrest, germ cells might therefore be more sensitive to apoptosis. This may also lead to severe disturbances between proliferation and cell death. The first experiments designed to elucidate the mechanisms of germ cell apoptosis were based on hormonal deprivation or cryptorchidism. However, the link between hormonal or cellular action and cell survival remained to be established. Analysis of signal transduction pathways involved in germ cell apoptosis and their regulation were the next steps. The involvement of bcl-2 family genes has been confirmed, although the expression of some of its members remains more controversial. Data derived from overexpression of some genes (Bcl-2, Bcl-xl) or resulting from gene inactivation (Bax) at the testicular level have highlighted the role of these genes in the control of germ cell apoptosis and have also provided some evidence for the strict requirement for density-dependent regulation of spermatogenesis. More recently, variations in the pattern of expression of these genes or proteins helped to explain some of the discrepancies in the literature. The place of the Fas/Fas ligand system during the first cycle of spermatogenesis remains a matter of debate, with controversies concerning the precise site of expression of this oncogene and its receptor. Conversely, its role in the testis after chemotoxic or radiotoxic treatments is well established. However, the normal fertility of animals with a spontaneous inactivation of Fas or Fas L genes does not support a physiological role of these factors during spermatogenesis. While factors involved in TNF/TNF R1 (Tumor Necrosis Factor) are under study, some data have been reported concerning the role of TRAIL (TNFalpha Related Apoptosis Inducing Ligand) and its active or decoy receptors in the testis. Among the oncogenes which may modulate the apoptotic process, Kit/Stem Cell Factor is particularly interesting, as Kit is expressed in some germ cells and Leydig cells, whereas SCF is expressed by Sertoli cells. Its impact during gonadal development and in the survival and proliferation of differentiated spermatogonia has been clearly established. Using a transgenic mice model, in which the Kit gene was inactivated by the insertion of a nls-lacZ sequence in its first exon, we showed that one single copy of the gene was unable to sustain physiological spermatogenesis and fertility in male mice. Our results also suggest that the Kit gene might be expressed at different steps of spermatogenesis, with different signal transduction pathways and biological actions. Finally, analysis of the signal transduction pathways involved in testicular apoptosis and their mechanisms of control is one of the key steps to a better understanding of both impairment of spermatogenesis and the pathogenesis of certain germ cell tumours.     

Facteurs impliqués dans le remodelage de la chromatine au cours de la spermiogenèse

Round spermatids are post-meiotic cells with a haploid genome contained in a nucleus, with a structure initially similar to that of the somatic cell nucleus. During spermatogenesis, the spermatid nucleus undergoes drastic remodelling during which it first elongates and then condenses into the very specific and tightly packaged structure of the sperm nucleus. During this remodelling dthe histones are replaced by transition proteins, which, in turn, are replaced by protamines, the specific nuclear proteins of the spermatozoa. Immediately prior to their replacement, the histones are hyperacetylated. The first part of our work was to precisely characterise the changes in histone acetylation during murine spermatogenesis. We have shown that the core histones H2A, H2B, H3 and H4 are hyperacetylated in the elongating spermatids. We have also shown that these changes in acetylation are associated with degradation of the enzymes responsible for histone deacetylation, histone deacetylases or HDACs, while histone acetyl transferases are still present in these cells. The histone acetylation pattern was also investigated during human spermatogenesis, revealing that histone hyperacetylation in the nucleus of elongating spermatids, which appears to be conserved during the course of evolution, also occurs during human spermatogenesis. Moreover, our data obtained from the testes of men with severely altered spermatogenesis, including SCO syndromes (Sertoli Cells Only Syndromes), show that a global hyperacetylation of the Sertoli cell nuclei is associated with an absence of meiotic and post-meiotic cells. This suggests that the global histone acetylation variations observed during spermatogenesis are part of a signalling pathway involving germ cell — Sertoli cell communication. Altogether, these data provide a basis for a better understanding of the mechanisms and identification of the factors involved in post-meiotic remodelling of chromatin.     

Synthèse d'ARN dans le chondriome au cours de la spermiogenèse chez la Drosophile

Résumé L'incorporation d'uridine-³H dans l'ARN nucléaire et dans l'ARN mitochondrial est détectée à l'aide de l'autoradiographie à haute résolution au cours de la spermiogenèse chez la Drosophile.Le marquage apparaît simultanément sur le noyau et sur le chondriome jusqu'au début de la condensation de la chromatine. Le nebenkern, qui caractérise un des premiers stades de la spermiogenèse, est le territoire cellulaire le plus radioactif. La synthèse de l'ARN nucléaire cesse au cours de la condensation de la chromatine. Pendant ce temps, le marquage des dérivés mitochondriaux se poursuit; il persiste jusqu'à leur complète transformation en paracristal. Ces observations mettent en évidence une synthèse autonome d'ARN par les mitochondries à la fin de la spermiogenèse.

---

Autonomous mitochondrial RNA synthesis during spermiogenesis in Drosophila

Summary The incorporation of ³H-uridine into nuclear and mitochondrial RNA has been followed by electron microscope autoradiography during spermiogenesis in Drosophila.Nuclei and mitochondria are simultaneously labeled up to the beginning of the chromatin condensation. The nebenkern, characteristic of the first stages of spermiogenesis, is the most radioactive cellular component. During chromatin condensation, nuclear RNA synthesis ceases, but mitochondrial derivatives continue to be significantly labeled up to their complete paracrystalline transformation. These data show an autonomous RNA synthesis by mitochondria at the end of spermiogenesis.

Ce travail a bénéficié de l'aide du C.N.R.S. (E.R.A. 174), de la D.R.M.E. (contrat 70/414) et du C.E.A. (participation à l'achat de molécules marquées).     

Nature et évolution des protéines basiques au cours de la spermiogenèse chez Pleurodeles waltlii Michah., Amphibien urodèle

Résumé La spermatogenèse du Triton Pleurodeles waltlii a été étudiée au moyen de techniques cytochimiques et autoradiographiques. Les phénomènes spermiogénétiques ont été divisés en six stades caractéristiques en fonction de la forme du noyau et de l'évolution des structures extranucléaires: cou et filament de soutien de la queue.Les protéines basiques du noyau du spermatozoïde sont du type protamine, tandis que certaines structures extranucléaires se montrent riches en protéines basiques libres. Les transitions depuis les histones de type somatique présentes dans les jeunes spermatides I et II jusqu'aux protamines du spermatozoïde mûr par l'intermédiaire d'histones enrichies en arginine, montrent des phénomènes intéressants.La première transition depuis les histones de type somatique riches en lysine vers les histones enrichies en arginine est progressive. Elle se produit au cours des stades III et IV. Un gradient apparaît dans le noyau depuis la base vers le sommet. Au même moment, les protéines basiques libres apparaissent dans le cou.La perte des histones enrichies en arginine puis leur substitution par des protamines au niveau des noyaux des spermatides V est beaucoup plus brutale, elle intéresse tout le noyau. Ce dernier montre de même une disparition complète des acides aminés soufrés. Au même moment, les protéines basiques apparaissent dans la queue, de même que des acides aminés soufrés.Toutes ces observations plaident en faveur d'une origine nucléaire possible de certains composants de ces structures extranucléaires originales et riches en protéines basiques libres.

---

Nature and development of the basic proteins during the spermiogenesis in Pleurodeles waltlii michah., urodele amphibian

Summary The spermiogenesis of the newt Pleurodeles waltlii has been studied with cytochemical and autoradiographical methods. The process of spermiogenesis has been divided into six characteristic steps in relation with the nuclear shape and the evolution of the extranuclear structures: the neck and the supporting filament of the tail.The nuclear basic proteins of the spermatozoon are of protamine type while the well developed extra-nuclear structures show a free basic proteins rich content. The transition from early spermatids somatic type histone to the mature sperm protamine via arginine-rich histone and the appearance of the free basic proteins in the tail show different interesting features. The first transition from the somatic rich lysine histone to the arginine rich histone which occurs at the spermatid III and IV steps, is gradual. A gradient appears in the nuclei from the base to the apex. Concurrently the free basic proteins appear in the neck. The loss of the arginine rich histone and its substitution by protamine in the spermatid V is more sudden and affects all the nuclei without a gradient, the sulfhydryl group content of the nuclei also disappear. At the same time, the basic protein of the tail appear as well as the sulfhydryl group.All these results are discussed in view of the hypothetical nuclear origin of these very unusual extranuclear basic proteins.

---

---

Equipe de Recherche associée au C.N.R.S. Cytologie Ultrastructurale No. 129.

---

Avec la collaboration technique de Melle F. de Sallier Dupin et de M. B. Morille.     

Aspects moléculaires de la spermatogenèse: la réparation post-réplication de l’ADN et le système ubiquitine

Ubiquitin is a ubiquitous and highly conserved protein of 76 amino acid residues, that can be covalently attached to cellular acceptor proteins through a multi-step enzymatic pathway. Mono- or poly-ubiquitination of proteins can lead to protein degradation or modification of protein activity. The ubiquitin system is essential to all eukaryotic cells. Many components of the complex ubiquitin system show remarkable evolutionary conservation, from yeast to mammalian species. Interestingly, during gametogenesis, many specialized and important aspects of the ubiquitin system become apparent. TheHR6B gene is a mammalian, autosomal homolog of theSaccharomyces cerevisiae geneRAD6 encoding a ubiquitin-conjugating enzyme.RAD6 in yeast is required for a variety of cellular functions, including sporulation, DNA repair, and mutagenesis. Male infertility inHR6B knockout mice is associated with impairment of spermatogenesis. Components of the ubiquitin system appear to be involved in different steps and processes during gametogenesis, including control of meiosis, and reorganization of chromatin structure.     

Les éléments cytoplasmiques au cours de la spermiogenèse du TritonPleurodeles waltlii Michah

Résumé L'origine et la morphogenèse des différents éléments de l'acrosome du spermatozode dePleurodeles waltlii ont été suivies et décrites depuis le tout début de la spermiogenèse. La formation de la vésicule acrosomienne et son évolution en une coiffe acrosomienne se fait selon le schéma classique. Son extrémité apicale se différencie tardivement en un bouton terminal et un crochet. Les trois parties de la coiffe diffèrent dans leur composition et leur structure fine.Les volumineux et complexes éléments situés sous la coiffe acrosomienne: axe, baguette puis manchon périphérique et manchon moyen, sont dépourvus de polysaccharides. Leur origine est envisagées. Ils sont comparés aux éléments situés dans l'espace sous-acrosomien des spermatozodes des autres vertébrés.

---

The cytoplasmic elements during spermiogenesis in the triturusPleurodeles waltlii MichahI. Acrosome genesis

Summary The origin and the morphogenesis of the acrosome different parts ofPleurodeles spermatozoon, have been investigated and described from the early beginning spermiogenesis process. The acrosomal vesicle and acrosomal cap formation take place according to the classical scheme. The acrosomal anterior tip cap late differentiate in a blunt terminal knob and a hook. The three cap parts differ in their composition and fine structure.The large and complicated structure stretching under the acrosomal cap: axis, peripheral muff and middle muff, are devoided of polysaccharides; their origin is discussed. They are compared with the subacrosomal components lying in the other vertebrates spermatozoon subacrosomal space.

Equipe de Recherche Associée au C.N.R.S., E.R.A. n^o 129.     

Les éléments cytoplasmiques au cours de la spermiogenèse du TritonPleurodeles waltlii Michah

Summary The development of the different components of thePleurodeles spermatozoon neck region have been investigated and described from the early beginning spermiogenesis process. In some cases their origine is not well defined. Some dictyosomes remain in a constant relationship with the pericentriolar granule and the two different rings, even after they had left the acrosomal region.The development of the neck in a deep postnuclear niche, does not seem related with the centrioles. The nuclear origine of some basic proteins of the neck is discussed in relation to the close correspondence between their appearance and the substitution of the lysine rich histone by the arginine rich histone in the nuclear. The various morphologic signs of transit at the nuclear envelope level have been investigated. The ways along which some materials is eventually transferred out of the nucleus remained an open question. ThePleurodeles spermatid neck region is compared with the same region of the insect and mammalian sperm.Some components of thePleurodeles young spermatids display common characters with the mammalian chromatoid body. Their development are fairly similar. Thus the Urodele spermatid seems to posses a chromatoîd body like most other vertebrate spermatids.

Equipe de Recherche Associée au C.N.R.S., E.R.A. n^o 129.     

Diminution de la capacité de surfusion au cours de l'embryogenèse et du développement larvaire chez un coléoptère

Potential cold resistance of non-diapause eggs and first instar larvae of Osmoderma eremita (Coleoptera, Cetoniidae, Trichiinae) during embryogenesis and post-embryonic growth was assessed by measuring individual supercooling points (SCP): sterile eggs had a mean SCP of −24.3 ± 2.0 °C; fertilized newly laid eggs a mean SCP of −23.4 ± 3.2 °C and eggs about to hatch a mean SCP of −9.2 ± 2.9 °C. Water absorption by fertilized eggs is a necessary requirement for the development of the embryo and results in an increase in weight and water content: fertilized newly laid eggs had a mean fresh weight of 10.687 ± 1.072 mg and a mean water content (expressed as a percentage of the dry weight) of 79.5 ± 10.83%; eggs about to hatch had a mean fresh weight of 19.127 ± 3.183 mg and a mean water content of 250.10 ± 74.15%. The ex-ovo larvae, hatched 30 days after oviposition, had a mean SCP of −10.1 ± 3.6 °C (no significant difference with eggs about to hatch) and had gained in weight (24.845 ± 3.911 mg) and in water content (499.72 ± 55.49%). Feeding 1st instar larvae had a decreased supercooling ability (mean SCP = −5.7 ± 0.4 °C) whereas their mean fresh weight (99.858 ± 53.091 mg) and mean water content (665.83 ± 82.74%) increased. The eggs and larvae of O. eremita are freezing intolerant. Before overwintering, all larvae switch to being freezing tolerant and can survive ice formation in their tissues and body fluids, whereas their mean SCP stays at around −5 °C. However, recent experiments in the winter of 1996 have shown that frozen larva mortality does occur at temperatures lower than about −12 °C.     

Place des troubles de la spermatogenèse dans l’hypofertilité masculine

According to Thonneauet al., (1991), 14% of couples are subfertile. In at least 59% of the cases, a male factor was involved. This indicates that 8% (14% × 59%) of men are hypofertile. Since several causes can induce male infertility and because of the heterogeneous criteria and classifications used in the literature, the percentage of each etiologic factor has not been very precisely established. In a population of 2072 consecutive patients we identified an alteration of spermatogenesis in 52% of the cases. This indicates that about 4% of men might have a spermatogenic problem. The spermatogenic insufficiency was isolated in 43% of the cases (i.e. 23% of the total population) or associated with post-testicular causes of male infertility (infectious/inflammatory; autoimmune; obstructive) in 57% of the cases (i.e. 30% of the total population studied). An etiologic factor is clinically identified for 64% of the patients presenting with a spermatogenic insufficiency. The most relevant risk factors linked to spermatogenic alteration were history of mumps orchitis (OR [IC95%]=14,6 [3,4–62,3]), history of radiotherapy-chemotherapy (OR=14,7 [3,4–63,2]). These situations were found with a low frequency (1,4% and 1,3% of the cases respectively) but provoked a spermatogenic alteration in a large majority of cases (92,9% and 92,3% respectively). On the other hand, varicoceles (OR=3,7 [2,9–4,8]) and troubles in testicular descend (OR=2,9 [2,3–3,7]), were more frequent (20,6% and 20,1% of the cases respectively), but less frequently associated with spermatogenic insufficiency (in 73,7 and 69,6% of the cases).     

La spermatogenèse et l'ovogenèse de Lepisma (Thermobia) domestica. Hétéropycnose dans un sexe homogametique

Sans résumé     

Les ultrastructures nucléaires de la Noctiluque (Dinoflagellé libre) au cours de la sporogenèse

The trophozoït of Noctiluca miliaris has a large nucleus (30 ) with several nucleoli of considerable size that contain DNA fibrillae lying in the interspaces. — Before and during the first sporogenetic divisions, the nucleoli disintegrate, releasing towards the cytoplasma numerous groups of ribonucleic granules passing through the nuclear ampullae. At the end of the sporulation, there are no nucleoli visible in the nuclei and no ampullae. — The nucleoplasm diminishes, as the DNA filaments are built up, to form the meshes of a network which limit the masses of chromatic material that take the shape of chromosomes characterized by regular fibrillar arches, at the 8–16 nuclei stage. In their centre, there is an axial structure which remains intact during the chromosomal segregation; its function during mitosis seems to be important: supplementary layers of arches appear at this level. — The progressive condensation of the chromosomes is correlated to the sporogenetic evolution of the nuclei, not to the different phases of the mitotic cycle. — The karyokinesis is brought about, during early stages, by mere splitting of the chromatic mass and of its envelope, and later one by separation into two lots of chromosomes. The segregation of these chromosomes is effected by partial intervention and growth of the envelope of the nucleus; there is no centromeric structure visible. At the end of divisions, the nucleus is almost entirely formed by its chromosomes. — The nucleolar structure, the karyokinesis, the structure of the nuclear envelope and the chromosomal cycle show the particularly high evolution of Noctiluca, within the Dinoflagellata.     

Anomalies postnatales du développement de la spermatogenèse associées aux troubles de la migration testiculaire

Cryptorchidism, a non-descended testis in its physiological intrascrotal location, is one of the most frequent congenital anomalies of the male genital system. The mechanisms of the normal descent of the testis are still unclear. Several etiological hypotheses have been proposed for cryptorchidism. Cryptorchidism is associated with a greater risk of testis cancer, and is also a cause of impairment in sperm parameters and fertility in the adult age. In this article, we review the cellular and hormonal events occurring from birth to puberty in isolated cases of congenital cryptorchidism that will later, in adulthood, alter both spermatogenesis and fertility.     

Lamine C2 et spermatogenèse

Lamin A/C are intermediate filaments present in nucleus. Their roles are numerous and laminopathies are issued from LMNA gene mutations. In male germ cells, this protein family is only represented by lamin C2. The results obtained in male mice show the importance of these filaments in male meiosis and suggest the existence of a new male infertility domain involving this intermediate filament and its associated proteins.     

Recherches cytochimiques sur la présence de certaines hydrolases au cours de la cytocinèse chez les plantes supérieures

Résumé Les granulations qui constituent les structures les plus primitives de la plaque cellulaire contiennent des enzymes hydrolytiques caractéristiques pour les sphérosomes de la cellule végétale; la plupart de ces enzymes sont présentes dans les lysosomes de la cellule animale. Dans les granulations de la plaque cellulaire nous avons constaté l'activité des enzymes suivantes: estérases non spécifiques, lipases, phosphatases acide et alcaline, aryl-sulfatase, désoxyribonucléase acide et probablement-glucuronidase. Le caractère chimique et morphologique de ces granulations, ainsi que leur équipement enzymatique correspondent aux sphérosomes.Dans la littérature les images de la cytocinèse au microscope électronique étant divergentes, le problème de l'origine et de la nature des granulations en question ne peut pas être pour le moment totalement résolu.

---

Zusammenfassung Die Körnchen, die die ursprünglichen Strukturen der Zellplatte bilden, enthalten die hydrolytischen Enzyme, die für die Sphärosomen der pflanzlichen Zelle und meistens für die Lysosomen der tierischen Zelle charakteristisch sind. Es sind die folgenden Enzyme: Esterasen (nicht spezifisch), Lipasen, saure Phosphatase, Aryl-sulfatase, saure Desoxyribonuklease und-Glukuronidase. Außerdem enthalten diese Körnchen die alkalische Phosphatase. Der morphologische und chemische Charakter dieser Körnchen und ihr enzymatischer Inhalt entsprechen den Sphärosomen.Wegen großer Unterschiede der in der Literatur vorhandenen Beschreibungen der Zellplatte in elektronenmikroskopischen Bildern kann das Problem der Entstehung und der Natur dieser Körnchen zur Zeit nicht völlig entschieden werden.

     

Étude de la décomposition de la matière organique dans le sol au moyen de carbone radioactif

Conclusions Par l'emploi de substrats radioactifs, il a été possible de montrer que le glucose, le ray-grass tel quel, la fraction soluble, les hemicelluloses et la fraction cellulosique du ray-grass ne sont pas, dans les conditions expérimentales appliquées, entièrement transformés en CO₂ dans le sol après une période de deux mois.La décomposition du glucose est plus rapide que celle des hemicelluloses et celle-ci est plus rapide que celle de la fraction cellulosique. Pour le glucose et pour la fraction cellulosique, 11% et 15% respectivement ne se retrouvent pas sous forme de C¹⁴O₂ tandis que pour la fraction soluble, pour les hemicelluloses et pour le ray-grass tel quel, c'est près de 20% qui ne sont pas oxydés en CO₂.La décomposition de chacun de ces substrats radioactifs donne encore lieu à la production de produits organiques radioactifs que l'on trouve dans la fraction des substances solubles, dans la fraction groupant l'- et le -humus et dans l'humine. La radioactivité de cette dernière fraction est du même ordre de grandeur que la somme des deux autres fractions.Travail effectué sous les auspices de l'Institut pour l'Encouragement de la Recherche Scientifique dans l'Industrie et l'Agriculture (I.R.S.I.A.).     

Rétablissement du cytoplasme et de la force motrice au cours de la restauration de la cyclose chezNitella après irradiation

Résumé En irradiant (500 kR) une fraction seulement du volume cellulaire de la cellule internodale deNitella, il est possible de distinguer au cours des phénomènes de restauration du mouvement cytoplasmique ceux qui dépendent de Pendoplasme (observation de la cyclose dans la zone protégée) et ceux qui dépendent de l'ectoplasme siège de la force motrice (observation de la cyclose dans la zone irradiée).Dans la zone protégée, la vitesse de la fraction endoplasmique irradiée se rétablit en fonction du temps suivant une équation du second ordre. L'augmentation du volume irradié diminue la rapidité du premier des deux processus de restauration et la quantité d'endoplasme qui reste altérée s'accroît.Dans la zone irradiée, le courant cytoplasmique est suspendu; il ne reprend que 4 minutes après le traitement alors que la couche chloroplastique se réorganise. Le glissement des inclusions qu'il charrie se fait un certain temps par saccades. La vitesse de la fraction endoplasmique protégée y augmente régulièrement témoignant ainsi du rétablissement de la force motrice. Le rétablissement a lieu suivant un schéma analogue à celui de Pendoplasme irradié sauf que ce phénomène y est plus rapide et que la force motrice du moins pendant les premières heures se rétablit intégralement. Ces résultats sont discutés (rôle des groupes SH, effet indirect d'empoisonnement, nature des lésions) et comparés à ceux obtenus pour des cellules irradiées in toto.

---

Cytoplasm and motive force separated recovery during the re-establishment of the gyclosis in irradiatedNitella cells

Summary In these experiments onNitella internodal cells, only a fraction of the cellular volume is irradiated (by 500 kR). The restoring of the endoplasm (by measurement of the cyclosis in the shielded zone) and the restoring of the ectoplasm where the motive force is generated (by measurement of the cyclosis in the irradiated zone) can be examinated separately during the recovery of the cytoplasmic streaming.In the shielded zone, the plot on a semi-logarithmic scale of a typical rate of streaming-time curve shows that the speed of the irradiated endoplasm. increases again according to a second order equation. With increasing irradiated cellular volume, there are a gradual slowing down of the first processus of restauration and an increase of the definitively altered fraction of the endoplasm.In the irradiated zone, the cytoplasmic streaming stopped completely. About 4 minutes after the treatment, when the chloroplasts layer is reorganising, it exhibits a tendency to flow again. The carried inclusions slide then in jerks during several minutes. The rate of the protected fraction of the endoplasm increases regularly, proving the recovery of the motive force. An analysis of this processus versus time shows that it can be exprimed by a second order equation as that of the irradiated endoplasm. But it is faster and the motive force resumes until full recovery (at least during the first hours).These results are discussed (importance of SH-groups, indirect poisoning effect, kind of lesions) and compared with those observed in completely irradiated cells.