Physiological regeneration of the digestive parenchyma in Convoluta convoluta and Oxyposthia praedator (Turbellaria,Acoela)

Autoradiography has been applied to two acoel turbellarians, Convoluta convoluta and Oxyposthia praedator, to determine the distribution and fate of proliferative cells. In C. convoluta, mitotic figures and nuclei that labelled with [³H]thymidine could be observed in the peripheral parenchyma but not in the middle zone of the central parenchyma. The time required for regeneration of physiologically competent digestive cells was about 10–15 days. In O. praedator, mitotic figures (in metaphase and telophase) were observed in the peripheral parenchyma while none were found in the epidermis either in untreated animals or after treatment with colchicine. Mitotic figures were found only rarely in the central parenchyma and only in its marginal zone. Autoradiographs of O. praedator demonstrated [³H]thymidine incorporation into both the nuclei and the cytoplasm of peripheral parenchymal cells. In the central parenchyma, no nuclei with primary labelling were observed. The digestive parenchyma of the acoels is regarded as a unique histological system involving both specialized cells of the central parenchyma and stem cells located in the peripheral parenchyma.     

An ultrastructural and cytochemical study of the digestive system in Oxyposthia praedator (Turbellaria,Acoela)

The central parenchyma in Oxyposthia praedator consists of multifunctional cells. These cells digest food material intracellularly, can effect extracellular digestion through release of digestive enzymes by cell lysis and clasmatosis, and synthesize reserve nutritional substances.     

Organisation of the nervous system in the Acoela: an immunocytochemical study

In order to broaden the information about the organisation of the nervous system in taxon Acoela, an immunocytochemical study of an undetermined Acoela from Cape Kartesh, Faerlea glomerata, Avagina incola and Paraphanostoma crassum has been performed. Antibodies to 5-HT and the native flatworm neuropeptide GYIRFamide were used. As in earlier studies, the pattern of 5-HT immunoreactivity revealed an anterior structure composed mainly of commissures, a so-called commissural brain. Three types of brain shapes were observed. No regular orthogon was visualised. GYIRFamide immunoreactive cell clusters were observed peripherally to the 5-HT immunoreactive commissural brain. Staining with anti-GYIRFamide revealed more nerve processes than did staining with anti-FMRFamide. As no synapomorphies were found in the organisation of the nervous system of the Acoela and that of the Platyhelminthes, the results support the view that the Acoela is not a member of the Platyhelminthes.     

Morphofunctional study of the statocyst of the cuban crayfishprocambarus cubensis

After replacing sand, a natural component of the endogenous otolithic apparatus of the Cuban crayfishProcamabrus cubensis by particles of reducible iron and subsequent exposure of the animals to a constant magnetic field, the following changes were noted in their behavior: during the first 24 h the motor activity of the animals increased and was accompanied by frequent strong beats of antennulae on water; animals tried to go away from the magnet attached to the aquarium wall and to hide in a shelter; by the day 10–12, there appeared signs of adaptation to the action of magnet; the animals spent most time near the wall with the magnet and were clinging close to it. If the magnet was moved the animals not only slipped to their side but also rotated around their longitudinal axis. The eyestalks also started moving. After molt and repeated introduction of reduced iron particles into the statocysts, a negative reaction to magnet was practically absent, and the crayfish preferred staying near the magnet. Study of structural organization of the statocysts under a scanning electron microscope showed that the iron particles in the otolithic apparatus of the crayfish are covered with a thinner layer of glycocalyx as compared to control animals whose otolithic apparatus is composed of sand grains. Besides, the otolithic apparatus of the experimental animals is a loose formation, unlike the dense glycocalyx rich in conglomerate in control animals.     

Morphofunctional study of the statocyst of the Cuban crayfish Procambarus cubensis

After replacing sand, a natural component of the endogenous otolithic apparatus of the Cuban crayfishProcamabrus cubensis by particles of reducible iron and subsequent exposure of the animals to a constant magnetic field, the following changes were noted in their behavior: during the first 24 h the motor activity of the animals increased and was accompanied by frequent strong beats of antennulae on water; animals tried to go away from the magnet attached to the aquarium wall and to hide in a shelter; by the day 10—12, there appeared signs of adaptation to the action of magnet; the animals spent most time near the wall with the magnet and were clinging close to it. If the magnet was moved the animals not only slipped to their side but also rotated around their longitudinal axis. The eyestalks also started moving. After molt and repeated introduction of reduced iron particles into the statocysts, a negative reaction to magnet was practically absent, and the crayfish preferred staying near the magnet. Study of structural organization of the statocysts under a scanning electron microscope showed that the iron particles in the otolithic apparatus of the crayfish are covered with a thinner layer of glycocalyx as compared to control animals whose otolithic apparatus is composed of sand grains. Besides, the otolithic apparatus of the experimental animals is a loose formation, unlike the dense glycocalyx rich in conglomerate in control animals.     

Morphofunctional organization of reserve stem cells providing for asexual and sexual reproduction of invertebrates

Published and original data indicating evolutionary conservation of the morphofunctional organization of reserve stem cells providing for asexual and sexual reproduction of invertebrates are reviewed. Stem cells were studied in representatives of five animal types: archeocytes in sponge Oscarella malakhovi (Porifera), large interstitial cells in colonial hydroid Obelia longissima (Cnidaria), neoblasts in an asexual race of planarian Girardia tigrina (Platyhelmintes), stem cells in colonial rhizocephalans Peltogasterella gracilis, Polyascus polygenea, and Thylacoplethus isaevae (Arthropoda), and colonial ascidian Botryllus tuberatus (Chordata). Stem cells in animals of such diverse taxa feature the presence of germinal granules, are positive for proliferating cell nuclear antigen, demonstrate alkaline phosphatase activity (a marker of embryonic stem cells and primary germ cells in vertebrates), and rhizocephalan stem cells express the vasa-like gene (such genes are expressed in germline cells of different metazoans). The self-renewing pool of stem cells is the cellular basis of the reproductive strategy including sexual and asexual reproduction.     

Cell wall organization of cortical parenchyma of angiosperms observed by the freeze etching technique

Cell wall organization of the parenchyma in the primary tissue of 3 angiosperms ofPopulus nigra var.italica Koehne,Morus bombycis Koidz. andPhaseolus vulgaris var.humilis Alef. was investigated by the freeze etching technique. The walls of these parenchyma cells have a crossed polylamellate structure, although a variety of fibrillar angles are found between 2 lamellae adjacent to one another. On the basis of this evidence, this paper discusses whether the growth of parenchyma cell walls can be interpreted by a simple multinet growth hypothesis.     

Morphofunctional characteristics of the endosteum

Basing on the literature data analysis, modern notions concerning endosteum structure, its connections with the bone and bone marrow are presented. Participation of the endosteum in processes of osteogenesis and resorption, as well as its changes with ageing are discussed.     

Monograph of the solenofilomorphidae (Turbellaria: Acoela)

Morphological studies of eleven new species in the family permitted reconstruction of progressive evolutionary lines, and this strongly implies progressive evolutionary lines for other acoela. Solenofilomorpha funilis n. sp., Myopea crassula n. g. n. sp., M. latafaucium n. sp., Fusantrum rhammiphorum n. g. n. sp. and Endocincta punctata n. g. n. sp. are described from the coast of South Carolina, U.S.A., and S. guaymensis n. sp. is described from the Gulf of California. Five additional unnamed species from the U. S. Pacific Coast, Sweden and Tunisia are briefly described. Two species groupings were based on correlation between two different arrangements of pharynx muscles and trio arrangements of antrum muscles and further correlations with lesser characters. The membership of the two groupings in a single family make it clear that evolution proceeded by addition of structures to a less complex common ancestor. Functional and behavioral considerations support the evolutionary path drawn from morphology. Distinctive statocyst structure, ciliary interconnections and sperm morphology shared by acoels show them to have a common ancestry, but clearly different pharynges and male structures cannot be consistent with evolution by reductions. A common ancestor of low complexity has probably given rise to several partly parallel evolutionary lines which together form the structurally diverse Acoela. The history of acoel systematics is also briefly summarized.     

Morphofunctional Differentiation in the Liver

The purpose of these experiments was to determine whether materials physically present in, and modifying the activity of, the reticuloendothelial (RE) cells could influence selected metabolic functions in hepatic parenchyma, and modify the overall regenerative growth in partially resected livers. Induction of tyrosine transaminase by endotoxin or cortisone, and repression, of either endogenous or hormonally induced glyconeogenesis by the toxin, progressed as well in partially hepatectomized animals as in normal mice. The uptake, binding and association of ³H-cortisone with its receptors was largely uninfluenced by partial hepatectomy.
In doses that stimulate the RE function, administration of either bacterial endotoxin or cortisone resulted in a delayed burst of ³H-thymidine incorporation in regenerating livers. In, higher doses, cortisone lowered DNA synthesis associated with regeneration. Celite or bentonite also retarded the onset of DNA formation after partial hepatectomy. Moreover, the regenerative growth was almost completely eliminated in animals which had been rendered tolerant to bacterial endotoxin prior to surgery. Post-operative administration of bovine somatotropin, or phagocytosis of latex particles, however, did not influence the increased ³H-thymidine incorporation associated with the regenerative growth. These results are discussed as a model to explore possible intercellular co-operation regulating a variety of cellular responses.