Vol 164, No 2 (2026)

The article is devoted to one of the prominent representatives of the scientific histological school of Academician Alexey A. Zavarzin — the distinguished Soviet histologist, Doctor of Sciences in Biology, Professor Alexander A. Braun (1904–1984). From 1931 to 1950, after graduating from Leningrad University and completing postgraduate training at the Department of Histology, he worked at higher education institutions and research institutes in Leningrad. By the late 1930s, Alexander A. Braun had become one of the country’s leading histologists. Owing to developments in biology and medicine in the late 1940s, he was forced to leave Leningrad. From 1950 to 1972, Braun headed departments of histology at medical universities in Kyrgyzstan (Frunze) and Tajikistan (Dushanbe). His scientific research was devoted to problems of comparative and evolutionary histology, issues of intertissue correlations, the relationships between epithelium and connective tissue, the features of morpho- and histogenesis, as well as to the identification of patterns of reparative histogenesis. Based on comparative studies of vertebrate skin, Braun identified patterns of evolutionary transformation of the integument, in particular demonstrating parallelism in the dermal structure of fish and aquatic mammals. He described features of the morphofunctional organization of the thyroid gland in various mammals and the dynamics of its seasonal changes. Together with Mikhailov, Braun outlined and implemented approaches to synthesizing Zavarzin’s theory of parallelism in tissue evolution and Khlopin’s theory of divergent tissue evolution. They proposed that tissue evolution in phylogeny proceeds through parallelism of their divergent changes. Braun developed an original classification of post-traumatic organ regeneration patterns in vertebrates. Studies of regeneration under high-altitude conditions demonstrated that relocation of animals from lowland to highland environments reduces their adaptive and reparative capacities, and that wound healing in such conditions proceeds significantly more slowly. As adaptation to high-altitude conditions occurs, resistance to damaging factors and reparative potential are restored. The results of Alexander A. Braun’s research became a fundamental basis for adaptive medicine. He established a major scientific histological school that continues to develop the outlined research directions to this day.

The notochord represents a defining synapomorphy of the phylum Chordata, serving as the primary axial skeleton and a crucial embryonic organizer. This review systematizes current concepts regarding the evolutionary origin, molecular mechanisms of morphogenesis, and structural–functional organization of the notochord. Major evolutionary hypotheses — dorsoventral inversion and aboral dorsalization — are examined and compared in the context of vertebrate body plan formation.

The hierarchical gene regulatory network underlying notochord development is described in detail, with emphasis on the central role of the transcription factor TBXT (Brachyury) and the Wnt/PCP, Hedgehog, and Notch signaling pathways. Molecular and cellular mechanisms of convergent extension, formation of the perinotochordal sheath, and cellular vacuolization — processes that generate turgor pressure and mechanical stiffness — are analyzed. Particular attention is given to notochord formation in humans, from the stage of the notochordal plate to its postnatal transformation into the nucleus pulposus of the intervertebral discs.

The clinical relevance of residual progenitor cell populations within the nucleus pulposus expressing the markers Tie2 and GD2 is discussed. Their role in maintaining homeostasis within the avascular intervertebral disc, the association between depletion of this cell pool and the development of degenerative spinal disorders, and their potential applications in regenerative medicine are considered. The review also addresses issues related to the molecular diagnosis of chordoma as a tumor of notochordal origin.

This review summarizes and systematizes published data on the normal (typical and variant) anatomy of the human right atrium.

Most researchers agree that the right atrium consists of the sinus venarum cavarum, the atrial body, the right atrial appendage, and the vestibule of the tricuspid valve with the cavotricuspid isthmus. The dimensions and shape of the atrial body and appendage exhibit individual and typological variability; however, in the reviewed scientific sources, no data were found regarding the dependence of these parameters on sex or age. Various patterns of the internal surface features of the right atrial walls have been described, but existing classifications are largely based on subjective criteria, which reduces their accuracy and reproducibility. The true interatrial septum is represented only by the floor and the limbus of the fossa ovalis rather than the entire medial wall of the atrium. In 15%–35% of heart specimens from patients who died of noncardiac causes, an interatrial communication is present anterior to the fossa ovalis. A review of the scientific data showed that publications on the anatomy of the normal human right atrium are, for the most part, devoted to individual aspects of the structure of its parts and components, whereas comprehensive studies of the typological and variant anatomy of the walls and subdivisions of this cardiac chamber are few. Studies aimed at developing features of the normal structure of the right atrium, substantiated from the standpoint of morphometry and ontogeny and based on the methodology of evidence-based anatomy, are currently relevant.

BACKGROUND: Accurate prediction of neonatal birth weight using ultrasound fetometry remains a relevant challenge in modern perinatology. Despite numerous studies in this field, a gap persists in defining the optimal combination of fetometric parameters required for precise estimation of fetal birth weight, which substantially affects timely diagnosis of intrauterine growth restriction.

AIM: To determine the contribution of individual fetometric parameters to predicting neonatal birth weight and to develop an optimal fetal weight estimation model based on comprehensive analysis of ultrasound measurement data.

METHODS: This retrospective study used data from 5161 full-term neonates and 8022 fetal ultrasound examinations. The dataset included neonates with complete clinical information for the main fetometric parameters available. The observation period covered the interval from the first ultrasound examination to delivery. The primary endpoint was neonatal birth weight measured at birth. To assess parameter contributions, descriptive and correlation analyses, multiple linear regression, quantile regression with coefficients reported to three decimal places, and machine-learning methods (Random Forest and XGBoost) were applied. Additionally, principal component analysis was performed to derive a general fetal growth factor, enabling integration of multiple fetometric measurements into a single composite indicator that more reliably reflects overall fetal size and is more closely associated with birth weight.

RESULTS: Abdominal circumference showed the strongest correlation with birth weight (r = 0.820), whereas femur length and head circumference demonstrated correlations of r = 0.620 and r = 0.540, respectively. Multiple regression including these three parameters yielded R² = 0.730. Quantile regression showed that the coefficient for abdominal circumference increased at the upper weight quantile (β = 23.500 at τ = 0.900) compared with the median (β = 18.900 at τ = 0.500). Machine-learning methods confirmed the dominant role of abdominal circumference in birth weight prediction (feature importance 50%–55%). Principal component analysis indicated that the first principal component, interpreted as a general size measure, explained 78% of the variance and was highly correlated with birth weight (r = 0.850).

CONCLUSION: These findings indicate that abdominal circumference is the most informative fetometric parameter for predicting fetal birth weight, whereas femur length provides complementary information by reflecting skeletal growth. Head circumference contributes minimally. The combined use of classical statistical approaches and machine-learning algorithms supports prioritizing accurate measurement of abdominal circumference and femur length when estimating fetal weight.

BACKGROUND: Soft tissue injuries constitute a substantial proportion of musculoskeletal damage and are frequently associated with complications related to immune response dysregulation, including secondary infections and delayed wound healing. Understanding systemic alterations in immune organs, particularly the spleen, is essential for developing strategies aimed at optimizing regeneration and preventing complications. Although the role of Bcl-2 (B-cell lymphoma 2) protein in the regulation of apoptosis is well established, data on its expression in the spleen following soft tissue injury remain limited. Most studies focus on local wound-site changes, whereas systemic effects, especially in lymphoid organs, have been insufficiently investigated.

AIM: To investigate changes in the number of Bcl-2-positive lymphocytes in different zones of the splenic white pulp in rats after soft tissue injury of the thigh using immunohistochemical and morphometric analysis.

METHODS: The study was performed on male outbred white rats weighing 180–200 g. Mechanical thigh injury comparable in kinetic energy to a 5.6-mm caliber bullet wound was induced using a specialized device (under ether anesthesia). Animals were euthanized by decapitation. Spleen specimens measuring 0.5 × 1.5 cm were collected at 1, 3, 7, and 14 days after injury for morphometric and immunohistochemical examination. Tissue sections were stained with hematoxylin and eosin. Immunohistochemistry was performed to detect cells expressing the antiapoptotic protein Bcl-2, T lymphocytes (CD3), and B lymphocytes (CD19), with Mayer’s hematoxylin nuclear counterstaining. Statistical analysis was conducted in R software (version 4.3.2) using the packages dplyr, tidyr, car, rstatix, pwr, ggplot2, and ggpubr.

RESULTS: Mechanical thigh injury in rats led to changes in the number of Bcl-2-positive lymphocytes in various splenic zones. A transient decrease in these cells was observed at 1 and 3 days post-injury, likely associated with lymphocyte migration to peripheral tissues, followed by gradual restoration and even increased Bcl-2 expression in the spleen by day 14.

CONCLUSION: An increase in Bcl-2-positive lymphocytes reflects a systemic immune response to local soft tissue injury of the thigh. This response may contribute to host defense against infections but could potentially delay wound healing when excessively activated. The association between local and systemic immune responses underscores the important regulatory role of the spleen and justifies further investigation to optimize therapeutic strategies for injury management.

BACKGROUND: Macrophages represent a heterogeneous cell population with diverse origins, phenotypic characteristics, and functional properties. In the brain, resident macrophages are associated with barrier structures, including the meninges, blood vessels, and choroid plexus. Anti-CD68/macrosialin antibodies are commonly used to identify macrophages. Published data and experimental experience indicate a low degree of conservation of this protein, necessitating the use of species-specific antibodies and careful selection of primary reagents for macrophage detection in laboratory rodent tissues.

AIM: To perform a comparative analysis of macrophage detection in rats using rabbit polyclonal anti-CD68 antibodies and mouse monoclonal antibodies of the ED1 clone.

METHODS: Brain sections obtained from Wistar rats (n = 6) were examined; heart and liver sections from the same strain served as controls. CD68/macrosialin-positive macrophages were identified using mouse monoclonal antibodies (clone ED1) and rabbit polyclonal antibodies in various immunohistochemical staining protocols.

RESULTS: Both antibody types specifically detected brain macrophages in three locations: the pia mater, vascular walls, and the choroid plexus. Rabbit polyclonal antibodies demonstrated higher intensity of specific staining compared with mouse monoclonal antibodies, with no nonspecific binding observed. The use of mouse monoclonal antibodies required heat-induced antigen retrieval and blocking reagents within the staining protocol.

CONCLUSION: Comparative analysis of macrophage detection in rat brain sections using antibodies of different origins and clonality demonstrated that rabbit polyclonal antibodies provide reliable macrophage labeling using a simpler immunohistochemical protocol compared with mouse monoclonal antibodies. Therefore, rabbit polyclonal antibodies may be recommended as a useful alternative for CD68/macrosialin staining in rat tissue sections.

BACKGROUND: Tissue macrophages play a key role in regulating hepatic tissue homeostasis. At the same time, they represent a heterogeneous population of cells in terms of both phenotypic and functional characteristics.

AIM: To characterize the immunophenotype of rat liver macrophages using the phagocytic activity marker CD68 and the microglial marker Iba-1.

METHODS: Liver and brain samples from Wistar rats (n = 8) were used. Double immunohistochemical staining was performed using antibodies against CD68 and Iba-1 (ionized calcium-binding adapter molecule 1). Specimens were analyzed using confocal laser scanning microscopy.

RESULTS: Iba-1-positive cells identified in the specimens corresponded to interstitial macrophages and Kupffer cells. CD68- positive macrophages were detected along hepatic sinusoidal capillaries and between hepatocytes. Co-expression of CD68 and Iba-1 was observed in Kupffer cells in the liver and in perivascular macrophages in the brain, but not in perivascular macrophages localized in the portal triads or in the interlobular connective tissue.

CONCLUSION: The colocalization of Iba-1 and CD68 in brain perivascular macrophages and the absence of their co-expression in hepatic interstitial macrophages indicate organ-specific phenotypic features of perivascular phagocytes.