Spermatogénèse et Paraplégie

In this article, the paraplegics’ possibilities for procreation will be examined. A first chapter will deal with the testicle functioning along with the study of hormonal measuring and testicle histology (study involving 100 patients). As a result, it appears that, after a testicle biopsy, there is a testicle lesion of neurological origin that is sometimes irreversible. On the contrary, the endocrinal testicle lesions have proved reversible under stimulation or spontaneously. A second chapter will deal with the different techniques to obtain an ejaculation and the semen analysis. The techniques that were used being: massage by vibrator, electroejaculation, ejaculation through pharmacological stimulation. The study focuses on 124 ejaculatory tests among which 64 forward ejaculations (52%) and 4 bachward ejaculations (3%) were obtained. The resulting semen analysis revealed a spermatozoon count greater than 20 millions per millilitre (that is 51,5%) and smaller than 5 millions in 11 cases (16%).     

Stress et Spermatogénèse

Stress, which originates in the brain, can influence spermatogenesis hormonally or via the nervous system. The hormonal route commences with the central secretion of Corticotrophin-Releasing Factor, leading to a fall in LHRH production, a decrease in Leydig cell LH receptors and a decrease in 17 a hydroxylase activity. Thus, in the case of major, prolonged stress, testosterone secretion falls, which in turn affects spermatogenesis. However, given that the testosterone threshold required for normal seminiferous epithelium function is significantly less than the mean circulating level of this hormone, the importance of low intensity stress remains unknown. The nervous route involves catecholaminergic fibres which, in the testis, innervate the Highmore corpus, the vessels, the area adjacent to the Leydig cells, and the basement membrane of seminiferous tubules. The experimental destruction of these fibres leads a regression of the seminiferous epithelium. Moreover, the experimental ablation of the rat anterior neocortex leads to changes in spermatogenesis. Therefore, given that the endocrine system does not seem to be involved in these changes, these results indicate that the highest level of the nervous system may participate in the controlling the germinal epithelium which, all things considered, would tend to support psychosomatic influences. However, given that the number of spermatozoa varies significantly between ejaculate and independantly of the level of testosterone secretion necessary for normal spermatogenesis, it may be hypothesized that it is only when sperm production is low that temporary stress, in aggravating the situation, becomes deleterious to spermatogenesis. Since, under normal conditions, such periods are short, the role of the influence of stress on spermatogenesis can only be relative. Nevertheless, if variations occur during permanently low sperm production, the likelihood of negative effects is increased. Consequently, the impact of stress or psychological factors on spermatogenesis might well depend upon particular circumstances.     

L'histogenèse régénératrice chez les phoronidiens

Summary The regeneration (organogenesis was studied by Emig, 1972 a, b) of Phoronida can be divided into three phases: the first one, cicatrisation, is characterized by a provisional mesodermal scar-tissue, later the old epidermis cover this scar-tissue. The regenerating blastema, second phase, takes place by cellular dedifferentiation processes; each germ layer (ectoderm, mesoderm, endoderm) regenerates itself from its own elements. One exception only seems to be oesophagel regeneration by metaplasia of the prestomacal cells during the asexual reproduction. The differentiation of the amputated structures (third phase) appears submitted to the inductive influence of the mesoderm and to the trophic action of the nervous system (especially the epithelial plexus). The polarity in regeneration sets a problem in Phoronida.

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Ce travail a été effectué dans le cadre du contrat L. A. n 41 au C. N. R. S.     

Les relations ontogenèse-phylogenèse:Applications paléontologiques

After a short historical introduction, the principal notions used to study the connections between ontogeny and phylogeny are desribed. The three fondamental standards (shape, age, size) upon which are made ontogenetic comparisons are defined and discussed.The different ontogenetic heterochronies are described and illustrated with concrete paleontological examples. Successively are studied:u

1. -dwarfirsm and giantism which are particularcases;
2. -the 4 types of heterochrony which affect somatic development (neoteny and acceleration) or sexual maturation (hypermorphosis and progenesis);
3. -the innovations which are a fast appearence of a new character and their associations with the 4 elementary heterochronies.

The heterochronies are connected with phylogeny. This leads to the definition of two fondamental tendancies: paedomorphosis and peramorphosis; the terms proterogenesis and palingenesis are redefined. To conclude, this study is inserted in a more wider context that shows the importance of ontogenetic knowledge to understand numerous evolutif processes (tempos in evolution, demographic strategies, cladism).     

L'analyse et la synthèse en systématique végétale

Analysis and synthesis have been widely used in systematics since, at least, the XIXth Century. Even now, the four major authors (Cronquist, Dahlgren, Takhtajan, Thorne) of angiosperm systems use “synthetic” to qualify their classifications. This word — synthetic or synthesis — has many different meanings that can create ambiguity. Among these meanings, is there one that can be justifiably used to define biological classifications? Although much more than the following applications can be found in the botanical literature, this paper will mainly deal with six meanings which are still in use in contemporary systematics. A synthetic classification has been understood as a classification built upward, from the lower to the higher categories. If we define synthesis as the operation that starts with elements and proceeds to a whole, then upward classification could be viewed as a synthesis in which the concept of hierarchy plays a primordial role, a role that is not initially a part of synthesis. Moreover, synthesis cannot replace all classificatory processes, and other criteria of taxa must be used in addition to synthesis Historically, synthesis has replaced analysis; the latter being employed by Linnaeus in his sexual system. Indeed, Linnaeus used a divisive method in producing his classification; and since division was seen as synonymous to analysis and recognized as a method that led to artificial taxa, leading French taxonomists Adanson, Lamarck and A.-L. de Jussieu among others, rejected analysis and viewed their classifications as synthetic, i.e., based on the natural method. Therefore, a system of value took place: natural was better than artificial, synthesis better than analysis. Reinforcing the importance of synthesis was the belief in a concept widely accepted at the end of the XVIIIth Century: that of continuity. Linking groups and forming a continuum was a procedure eminently synthetic. Such a procedure, known as “chaining”, produced series or sequences of taxa. Analysis was used solely to express the idea of dichotomous or analytical keys, a Lamarckian innovation that enabled taxonomists to identify plants. But whether classifications are built from lower to higher categories (a synthesis of taxa) or from higher to lower categories (an analysis of taxa), another simultaneous, concomitant movement is implied: with the latter, a synthesis of characters, with the former, an analysis of characters. Therefore, a synthetic classification is nevertheless an analytical classification.Basing groups on resemblance instead of difference, results in yet another application of synthesis. This application is probably due to the analogy with “composition”. Already, a separation between resemblance and difference among characters is an analysis. More important, still, is that at a certain rank some characters are used to join whereas, at another rank, they separate. Thus, depending on ranks and taxa, characters are applied in a synthetic or analytical procedure. Here also, other criteria are needed to support group delimitation.In connection with the upward (synthetic) movement in classifying taxa, the use of a great number of characters was also considered to be synthesis. This has been a recurring theme in taxonomy over the last two centuries and was sometimes seen as the Gilmourian approach to classification. When would we be justified to talk about synthesis? After how many characters? In fact, it is not the number of characters that matters but how characters are handled. The use of many characters has been closely linked to the idea of natural groups and its joining with synthesis seems to derive from the association of “natural” and “synthetic”.Synthetic classifications equally imply the common idea that they must represent a résumé of information stemming from all biological fields or disciplines. If classifications portray evolution, as many systematists suggest, then it cannot be just a résumé. And one must first decide what classifications are about: a controversial subject among different schools of thought in taxonomy. This explains another meaning attached to synthesis. Biological classifications have been said to be a synthesis or résumé of two types of information: that of similarity and that of phylogeny. Anagenesis is sometimes viewed as incremental to classification and makes up for a third type of information. Even though taxonomists would (for once!) agree that a classification should be based on phenetic, cladogenetic and anagenetic data, such a classification cannot qualify as a synthesis since it is not a composition and does not meet the definition given above (an operation that starts with elements and goes on to a whole). It is impossible to represent these three types of data together in one classification scheme; they express three, sometimes irreducible, points of view. For such a classification, the word “eclectic” is preferable and closer to reality.The use of synthesis as one term of the dialectical movement has made hesitant steps in taxonomy. Indeed, the two opposed theses that evolve into the synthesis are hardly met in classification and the “dialectical” synthesis promulgated by a few taxonomists can be referred back to synthesis as a résumé.Is classification synthetic because it appears to be based on inductive procedures, as it is sometimes implied by different authors who link deduction and analysis (stemming from downward classification)? In logic, synthesis is sometimes (and questionably so) associated with deduction. Moreover, synthesis cannot follow from induction which deals, for example, with the universality of characters. In that sense, there is no composition and so no synthesis. Thus, although induction has been part of classification, it is not a synthetic method.Apart from the ambiguity originating from the multiple meanings of the word “synthesis” in the context of taxonomy, synthetic classifications do not fully express all the complexity and procedures that lead to it. Actually, a classification is as much a synthesis as an analysis. Both methods are complementary, and should not be opposed as is sometimes the case. This opposition was implicit in the debate between Linneans and Jussieans, surrounding the development of the natural method. If one wants to use “synthetic”, then one should be explicit about its meaning. Taxonomists should also be aware of the incompleteness of synthesis in constructing a classification and should be careful not to create a system of value based upon philosophical ground. They should always prefer a complementary mode of thinking when feasible, instead of an “either-or” approach.     

Imagerie de la néoangiogenèse en médecine nucléaire

The formation of new vessels, a process referred to as neoangiogenesis, is one of the key pathophysiological mechanisms in the development and progression of cancer. It contributes to tumour growth and dissemination of neoplastic cells and can determine response or resistance to anticancer therapies. It involves different signaling pathways including the vascular endothelial growth factor (VEGF) pathway and integrins, which are also preferred targets for the development of antiangiogenic therapies. Changes in the microvasculature induced by antiangiogenic treatments occur before morphological changes can be detected with conventional imaging approaches. The development of molecular tools enabling an assessment of these targets before initiating therapy, or early detection of response or recurrence during or following treatment is essential for the close monitoring of antiangiogenic treatments. These outstanding needs call for the development of specific probes enabling the characterization of the molecules and pathways involved. This review summarizes the major signaling pathway involved in promoting tumor neoangiogenes is, the different radiotracers recently developed in preclinical and clinical settings, as well as their potential use in humans in order to improve the management of patients treated with antiangiogenic treatments.     

Les complications orthopédiques de l’ostéogenèse imparfaite

Osteogenesis imperfecta is a genetic disease characterized by bone frailty. It is generally caused by an abnormal production of collagen, which is the main fibrous protein of the bone. Collagen is also present in the skin, tendons, the sclera of the eye and dentin. The most frequent manifestation of osteogenesis imperfecta is the occurrence of multiple fractures without major trauma. Severity and timing of the attack varies widely: some patients sustain a significant number of fractures during early childhood which may have a serious impact on growth, while others will have some fractures separated by a few years. In all cases, the bone strength improves in adulthood. The bone fractures cause pain and bone deformities sometimes result in a smaller size. Scoliosis is frequent and associated with painful vertebral collapses. We present a case of osteogenesis imperfecta in a 40-year-old adult and we describe the various orthopaedic complications of the disease, stressing the role of bone scintigraphy in the diagnosis and monitoring of these complications.     

Analyse de la fécondation par la parthénogénèse expérimentale

Sans résumé     

Agents anticholinestérasiques et tératogénèse axiale chez l'embryon de Caille

Résumé Une étude conduite avec des organophosphorés (OP), des carbamates (C) et un produit à groupements oxamides (GO) permet d'établir une corrélation entre l'inhibition des activités cholinestérasiques et l'expression des anomalies de l'axe vertébral chez l'embryon de Caille japonaise. L'action anticholinestérasique des divers composés est étudiée in vitro et in vivo. In vitro, les cholinestérases embryonnaires sont surtout sensibles aux carbamates alors qu'avec les organophosphorés — et notamment avec ceux qui nécessitent une activation métabolique —, des concentrations élevées n'aboutissent qu'à des inhibitions partielles des activités enzymatiques envisagées. In vivo, des produits étudiés, seuls le malathion (OP) et l'ambénonium (GO) se montrent inactifs (ou faiblement actifs) vis-à-vis des cholinestérases. Bien qu'assez fortement embryotoxiques, ces deux poisons ne se révèlent pas tératogènes. Les autres produits, administrés à des doses tératogènes, inhibent toujours très fortement les activités cholinestérasiques. L'association satisfaisante existant entre l'inhibition des cholinestérases et l'expression des malformations axiales est confirmée par l'usage de doses croissantes de parathion (OP) et de néostigmine (C).Les anomalies du bec et des pattes, ne se manifestant qu'avec le dicrotophos (OP) et l'ésérine (C), n'apparaissent pas, quant à elles, reliées à l'inactivation des cholinestérases, puisqu'elles ne sont pas relevées avec des composés aussi actifs à l'égard de ces enzymes que le parathion (OP), la néostigmine (C) et le démécarium (C).

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Anticholinesterase agents and axial teratogenesis in quail embryos

Summary The results of an investigation made with organo-phosphorous compounds (OP), carbamates (C), and a compound including oxamide groups (GO), indicate that spine anomalies in Japanese quail embryos are linked with cholinesterase inhibition. The blocking effect of these various compounds on cholinesterases has been examined both in vitro and in vivo.In vitro, the embryonic cholinesterases are particularly sensitive to carbamates, whereas high concentrations of organo-phosphorous compounds-and especially those which need to be activated at the level of metabolism-block only part of the relevant activities of the enzyme.In vivo, among the products examined, only malathion (OP) and ambenonium (GO) were found to be inactive (or having little effect) so far as cholinesterases are concerned. Although they appeared rather strongly embryotoxic, these two poisons did not prove teratogenic. A strong inhibition of cholinesterase activities was noticed in all cases, when applying the other compounds at teratogenic doses.The close relationship between the inhibition of cholinesterases and the appearance of axial abnormalities is confirmed by using increasing doses of parathion (OP) and neostigmine (C).Beak and leg malformations were brought about only by dicrotophos and eserine, and did not prove to be linked with cholinesterase inhibition, since they were not observed with compounds having a high activity towards these enzymes, such as parathion (OP), neostigmine (C) and demecarium (C).

Travail dédié à la mémoire du professeur W. Landauer     

Les bases cytologiques de la théorie du ≪crossing-over≫: Étude sur la spermatogénèse et l'ovogénèse des calliphorinae

Sans résumé     

La spermatogénèse du lézard (Lacerta muralis lin.)

Sans résumé     

Nouveaux essais de Parthénogenèse expérimentale chez les Vertébrés inférieurs

Sans résumé     

Etude de la cholangiogénèse chez le foetus humain

Résumé Les auteurs, étudiant les régions périportales et centrolobulaires des foies d'un embryon et de quatre foetus humains, tendent à préciser quelques aspects de la formation des canaux biliaires intrahépatiques. Ils apportent ainsi une nouvelle contribution à la théorie hépatogène de la cholangiogénèse intrahépatique.

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Summary The present study describes the fine structure of tubules surrounded by parenchymal or biliary epithelial cells at the margin of the centrolobular or portal spaces. The hepatogenic theory of intrahepatic cholangiogenesis is discussed.

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Travail subventionné par le «Fonds National Suisse de la Recherche Scientifique», requête N 3731.

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Avec la collaboration technique de Mlles J. Braeutigam et M.-M. Bertholet et de Mme M. Schreyer.     

Etude de la cholangiogénèse chez le foetus humain

Résumé Les auteurs, étudiant les diverses cellules épithéliales rencontrées dans la région périportale du foie foetal humain, décrivent deux types d'éléments qui possèdent des caractères ultrastructuraux intermédiaires entre ceux de la cellule épithéliale biliaire et ceux de l'hépatocyte.Ils décrivent un type cellulaire à cytoplasme et noyau fortement denses, différents de ceux que l'on observe dans les «dark cells» de Steiner et coll. (1962b).

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Summary The fine structure of the different cells at the margin of the portal spaces was investigated in the foetal human liver. Two types of cells intermediate between biliary epithelial and parenchymal elements were described.In addition, a type of cell in which both the cytoplasm and nucleus are electron-dense was observed. This element is different from the dark cell of Steiner et al. (1962b).

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Travail subventionné par le «Fonds National Suisse de la Recherche Scientifique», requête N 3731.

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Avec la collaboration technique de Mme M. Schreyer et de Mlle M.-M. Bertholet.