The ontogeny of the neuro-insular complexes (NIC) and the islets innervation in human pancreas has not been studied in detail. Our aim was to describe the developmental dynamics and distribution of the nervous system structures in the endocrine part of human pancreas. We used double-staining with antibodies specific to pan-neural markers [neuron-specific enolase (NSE) and S100 protein] and to hormones of pancreatic endocrine cells. NSE and S100-positive nerves and ganglia were identified in the human fetal pancreas from gestation week (gw) 10 onward. Later the density of S100 and NSE-positive fibers increased. In adults, this network was sparse. The islets innervation started to form from gw 14. NSE-containing endocrine cells were identified from gw 12 onward. Additionally, S100-positive cells were detected both in the periphery and within some of the islets starting at gw 14. The analysis of islets innervation has shown that the fetal pancreas contained NIC and the number of these complexes was reduced in adults. The highest density of NIC is detected during middle and late fetal periods, when the mosaic islets, typical for adults, form. The close integration between the developing pancreatic islets and the nervous system structures may play an important role not only in the hormone secretion, but also in the islets morphogenesis.

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Reptiles are a rare model object for space research. However, some reptile species demonstrate effective adaptation to spaceflight conditions. The main scope of this review is a comparative analysis of reptile experimental exposure in weightlessness, demonstrating the advantages and shortcomings of this model. The description of the known reptile experiments using turtles and geckos in the space and parabolic flight experiments is provided. Behavior, skeletal bones (morphology, histology, and X-ray microtomography), internal organs, and the nervous system (morphology, histology, and immunohistochemistry) are studied in the spaceflight experiments to date, while molecular and physiological results are restricted. Therefore, the results are discussed in the scope of molecular data collected from mammalian (mainly rodents) specimens and cell cultures in the parabolic and orbital flights and simulated microgravity. The published data are compared with the results of the gecko model studies after the 12–44.5-day spaceflights with special reference to the unique peculiarities of the gecko model for the orbital experiments. The complex study of thick-toed geckos after three spaceflights, in which all geckos survived and demonstrated effective adaptation to spaceflight conditions, was performed. However, future investigations are needed to study molecular mechanisms of gecko adaptation in space.

The aim of the investigation was to study the distribution of S100-positive cells in the islets of Langerhans of human pancreas during prenatal and early postnatal development, as well as in adult humans.Materials and Methods. using antibodies to S100 protein, to main hormones produced in the islets of Langerhans in human pancreas (insulin, glucagon and somatostatin), and to neuron-specific enolase (NSE) we carried out an immunohistochemical analysis of human pancreatic samples. The samples were taken from adults without pancreatic diseases, from patients with type 2 diabetes mellitus, as well as from fetuses and newborns.Results. Two types of S100-positive cells can be found in human islets of Langerhans starting from gestation week 15-16: cells located on islet periphery, and cells situated inside an islet. Cells located on periphery are flattened and have small amount of cytoplasm. These cells have long processes extending mainly along periphery. The cells located inside islets are oval-or round-shaped, and generally have no processes.Conclusion. In an early fetal period in islets of Langerhans of human pancreas, two types of S100-positive cells appear, they being different in their structure. The cells on periphery are similar morphologically to glial cells. The cells inside islets are no different in their structure from other endocrine cells. Two types of S100-positive cells can be suggested to be of importance both in islet morphology, and in the regulation of hormones expressed by endocrine cells.