Primary and secondary olfactory centres in human ontogeny.

The olfactory centres are the evolutionary oldest and most conservative area of the telencephalon. Olfactory deficiencies are involved in a large spectrum of neurologic disorders and neurodegenerative diseases. The growing interest in human olfaction has been also been driven by COVID-19-induced transitional anosmia. Nevertheless, recent data on the human olfactory centres concerning normal histology and morphogenesis are rare. Published data in the field are mainly restricted to classic studies with non-uniform nomenclature and varied definitions of certain olfactory areas. While the olfactory system in model animals (rats, mice, and more rarely non-human primates) has been extensively investigated, the developmental timetable of olfactory centres in both human prenatal and postnatal ontogeny are poorly understood and unsystemised, which complicates the process of analysing human material, including medical researches. The main purpose of this review is to provide and discuss relevant morphological data on the normal ontogeny of the human olfactory centres, with a focus on the timetable of maturation and developmental cytoarchitecture, and with special reference to the definitions and terminology of certain olfactory areas.

New data on the internal organs of a frozen Yukagir bison mummy (Bison priscus Bojanus, 1827), Yakutia, Russia.

The paper presents the first morphological description of the internal organs of a frozen corpse of the steppe bison Bison priscus (Bojanus, 1827) from the Holocene of northern Yakutia. Necropsy revealed that most of the internal organs, including the brain, heart with the main vessels, and reproductive system were well preserved. It demonstrated that the anatomy of this bison was close to that of the genera Bos and Bison. Trauma or pathological changes in the organs were not detected. The cause of death of the bison remains unknown.

[Development of the Human Olfactory Bulbs in the Prenatal Ontogenesis: an Immunochistochemical Study with Markers of Presynaptic Terminals (anti-SNAP-25, -Synapsin-I, -Synaptophysin)].

We provide the data of the olfactory bulbs (OB) development in the human fetuses on the stages from 8 week to birth. Immunochistochemical markers of presynaptic terminals (anti-SNAP-25, -synapsin-I, -synaptophysin) were used to evaluate the maturation of the OB. Differentiation of the OB layers begins from periphery, which implicitly evidences that growth of the olfactory nerves fibers induses not only anatomical differentiation of the OB, but also differentiation of its functional layers. The sites of the developing glomerulus are revealed using the immunochistochemical prosedure on the stage before distinct glomerulus can be identified with common histological procedure. OB conductive system demonstrates immunoreactivity with the antibodies to the presynaptic proteins on the all stages from 10-11 weeks of fetus development. Four stages of the OB development are described. All functional layers of the OB are mature at the 22-weeks stage. Further differentiation of the OB neuroblasts, including lamina formation of the internal granular leyer, glomerular layer development, OB growth continue after 20-22 weeks stage until 38-40 weeks of the fetus develoment. Patterns of the immunoreactivity with antibodies to SNAP-25, synapsin-I and synaptophysin are completely appropriate to those of adult's OB on the 38-40 weeks of the prenatal development. Complete maturity of the human OB is achived at 38-40 weeks of the prenatal development.

[Immunohistochemical study of human fetal vomerona structures the nasal septum, by applying neuron-specific beta3-tubulin antibodies].

The functioning of Jacobson's or vomeronasal organ (VNO) in man is the subject-matter of discussion today. It is generally taken that VNO as an anatomic structure also remains in the adult; however, its receptor apparatus still degenerates in the fetal stage of ontogenesis. Nevertheless, the data available in the literature on the time and specific features of degenerative changes in the human fetal VNO are conflicting and ambiguous. The authors examined the human fetal nasal septum from the 8th week of development to birth, by applying the traditional histological procedures and neuron-specific beta3-tubulin antibodies. An immunohistochemical study could first show the receptor apparatus of the human fetal VNO at weeks 8-26 of development. The immunohistochemical study on a series of sections could reveal the regularities of spatial receptor distribution depending on the time of fetal development. In addition, the developed human fetal vomeronasal nerve and ganglion at weeks 8-26 were described, in human fetuses at weeks 8-26. The neuron-specific marker test has shown the nerve fibers departing directly from the VNO wall, which is inconsistent with the data available in the literature on vomeronasal nerve degeneration in this sign just after the 18th week of development.

Development of the olfactory bulbs in human fetuses (an immunohistochemical study).

An immunohistochemical study of the olfactory bulb (OB) in human fetuses was performed. Immunohistochemical markers for nervous system-specific protein complexes S-100 and SNAP-25 were used. At 20-22 weeks of development, the development of cells expressing protein S-100 was greater in the OB than in the neocortex (the areas of the gyrus rectus and the gyrus orbitalis longitudinalis internus). These quantitative differences indicate heterochronicity in glial differentiation in the OB and cerebral cortex. Immunopositive reactions for SNAP-25 were for the first time detected at the periphery of the OB and in glomeruli in human fetuses at 15-16 and 20-22 weeks of development. Immunohistochemical staining of the OB with antibodies to SNAP-25 indicated that the human olfactory system cannot function prior to 20-22 weeks of development. In the OB of fetuses at 28-29 weeks of development, the intensity of the immunohistochemical reaction showed topological differences. The reaction with antibodies to SNAP-25 in the OB of full-term fetuses was similar to the reaction in the OB of adult humans. The results of these immunohistochemical studies using the reaction for the protein complex SNAP-25 in fetuses of different ages suggest the that the primary olfactory center in humans starts to function no earlier than the 30th week of development.