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Glucocorticoids are used during glioblastoma treatment to prevent the cerebral edema effect surrounding normal brain tissue. The aim of our study was to investigate the long-term effects of multiple administrations of glucocorticoids onto the glycosylated components (proteoglycans and glycosaminoglycans) of normal brain extracellular matrix and the glucocorticoid receptor (GR, Nr3c1 ) in an experimental model in vivo . Two-month-old male C57Bl/6 mice (n = 90) were injected intraperitoneally with various doses of dexamethasone (DXM) (1; 2.5 mg/kg) for 10 days. The mRNA levels of the GR, proteoglycans core proteins, and heparan sulfate metabolism-involved genes were determined at the 15th, 30th, 60th, and 90th days by a real-time RT-PCR. The glycosaminoglycans content was studied using dot blot and staining with Alcian blue. A DXM treatment increased total GAG content (2-fold), whereas the content of highly sulfated glycosaminoglycans decreased (1.5-2-fold). The mRNA level of the heparan sulfate metabolism-involved gene Hs3St2 increased 5-fold, the mRNA level of Hs6St2 increased6-7-fold, and the mRNA level of proteoglycan aggrecan increased 2-fold. A correlation analysis revealed an association between the mRNA level of the GR and the mRNA level of 8 of the 14 proteoglycans-coding and 4 of the 13 heparan sulfate metabolism-involved genes supporting GR involvement in the DXM regulation of the expression of these genes. In summary, multiple DXM administrations led to an increase in the total GAG content and reorganized the brain extracellular matrix in terms of its glycosylation pattern.

Objective: At the histological and ultramicroscopic level, compare biopsy specimens of donor heart under standard (up to 240 min) and extended (more than 240 min) periods of pharmaco-cold preservation., Material and Methods: Biopsy specimens of the left atrium of donor hearts: group 1 - 8 samples after transportation with pharmaco-cold preservation of the graft in Bretschneider solution (Dr. Franz Köhler Chemie GmbH, Germany) up to 240 min, (Me 140), and group 2 - 5 samples after an extended pharmaco-cold period (more than 240 min; Me 375) were examined using light microscopy of semi-thin sections and transmission electron microscopy, followed by stereological and statistical analysis., Results: A comparative study of the myocardium of donor hearts revealed stereotypical dystrophic changes in cardiomyocytes. Semi-thin sections demonstrated a mosaic pattern of myocardial parenchyma in both groups, caused by contracture and less pronounced lytic changes in myocytes, which were accompanied by stromal edema without statistically significant differences according to stereological studies. Ultrathin sections of the perinuclear zones of cardiomyocytes visualized reduction and focal damage to myofibrils and mitochondria in combination with pronounced autophagy; at the same time, with a shorter duration of the pharmaco-cold period, the stereological indicators of cardiomyocyte organelles indicated a relatively better supply of myofibrils with mitochondria., Conclusion: The results obtained suggest a sufficiently high degree of preservation of the tissue and ultrastructural organization of donor hearts with prolonged (more than 240 min) pharmaco-cold ischemia to restore adequate cardiac activity after heart transplantation.

Chemotherapy with temozolomide (TMZ) is an essential part of anticancer therapy used for malignant tumors (mainly melanoma and glioblastoma); however, the long-term effects on patient health and life quality are not fully investigated. Considering that tumors often occur in elderly patients, the present study was conducted on long-term (4 months) treatment of adult Wistar rats (9 months old, n=40) with TMZ and/or dexamethasone (DXM) to investigate potential behavioral impairments or morphological and molecular changes in their brain tissues. According to the elevated plus maze test, long-term use of TMZ affected the anxiety of the adult Wistar rats, although no significant deterioration of brain morphology or cellular composition of the brain tissue was revealed. The expression levels of all studied heparan sulfate (HS) proteoglycans (HSPGs) (syndecan-1, syndecan-3, glypican-1 and HSPG2) and the majority of the studied chondroitin sulfate (CS) proteoglycans (CSPGs) (decorin, biglycan, lumican, brevican, neurocan aggrecan, versican, Cspg4/Ng2, Cspg5 and phosphacan) were not affected by TMZ/DXM, except for neurocan and aggrecan. Aggrecan was the most sensitive proteoglycan to TMZ/DXM treatment demonstrating downregulation of its mRNA and protein levels following TMZ (-10-fold), DXM (-45-fold) and TMZ-DXM (-80-fold) treatment. HS content was not affected by TMZ/DXM treatment, whereas CS content was decreased 1.5-2.5-fold in the TMZ- and DXM-treated brain tissues. Taken together, the results demonstrated that treatment of adult Wistar rats with TMZ had long-term effects on the brain tissues, such as decreased aggrecan core protein levels and CS chain content and increased anxiety of the experimental animals., Competing Interests: The authors declare that they have no competing interests., (Copyright: © Strokotova et al.)

Glioblastoma (GB) is an aggressive cancer with a high probability of recurrence, despite active chemoradiotherapy with temozolomide (TMZ) and dexamethasone (DXM). These systemic drugs affect the glycosylated components of brain tissue involved in GB development; however, their effects on heparan sulfate (HS) remain unknown. Here, we used an animal model of GB relapse in which SCID mice first received TMZ and/or DXM (simulating postoperative treatment) with a subsequent inoculation of U87 human GB cells. Control, peritumor and U87 xenograft tissues were investigated for HS content, HS biosynthetic system and glucocorticoid receptor (GR, Nr3c1 ). In normal and peritumor brain tissues, TMZ/DXM administration decreased HS content (5-6-fold) but did not affect HS biosynthetic system or GR expression. However, the xenograft GB tumors grown in the pre-treated animals demonstrated a number of molecular changes, despite the fact that they were not directly exposed to TMZ/DXM. The tumors from DXM pre-treated animals possessed decreased HS content (1.5-2-fold), the inhibition of HS biosynthetic system mainly due to the -3-3.5-fold down-regulation of N-deacetylase/N-sulfotransferases ( Ndst1 and Ndst2 ) and sulfatase 2 ( Sulf2 ) expression and a tendency toward a decreased expression of the GRalpha but not the GRbeta isoform. The GRalpha expression levels in tumors from DXM or TMZ pre-treated mice were positively correlated with the expression of a number of HS biosynthesis-involved genes ( Ext1/2 , Ndst1/2 , Glce , Hs2st1 , Hs6st1/2 ), unlike tumors that have grown in intact SCID mice. The obtained data show that DXM affects HS content in mouse brain tissues, and GB xenografts grown in DXM pre-treated animals demonstrate attenuated HS biosynthesis and decreased HS content.

In the treatment of coronary heart disease, the most promising approach for replacing lost contractile elements involves obtaining cardiomyocytes through cardiac differentiation of pluripotent cells. The objective of this study is to develop a technology for creating a functional layer of cardiomyocytes derived from iPSCs, capable of generating rhythmic activity and synchronous contractions. To expedite the maturation of cardiomyocytes, a renal subcapsular transplantation model was employed in SCID mice. Following explantation, the formation of the cardiomyocyte contractile apparatus was assessed using fluorescence and electron microscopy, while the cytoplasmic oscillation of calcium ions was evaluated through visualization using the fluorescent calcium binding dye Fluo-8. The results demonstrate that transplanted human iPSC-derived cardiomyocyte cell layers, placed under the fibrous capsules of SCID mouse kidneys (for up to 6 weeks), initiate the development of an organized contractile apparatus and retain functional activity along with the ability to generate calcium ion oscillations even after removal from the body.

Intensive adjuvant radiotherapy (RT) is a standard treatment for glioblastoma multiforme (GBM) patients; however, its effect on the normal brain tissue remains unclear. Here, we investigated the short-term effects of multiple irradiation on the cellular and extracellular glycosylated components of normal brain tissue and their functional significance. Triple irradiation (7 Gy*3 days) of C57Bl/6 mouse brain inhibited the viability, proliferation and biosynthetic activity of normal glial cells, resulting in a fast brain-zone-dependent deregulation of the expression of proteoglycans (PGs) (decorin, biglycan, versican, brevican and CD44). Complex time-point-specific (24-72 h) changes in decorin and brevican protein and chondroitin sulfate (CS) and heparan sulfate (HS) content suggested deterioration of the PGs glycosylation in irradiated brain tissue, while the transcriptional activity of HS-biosynthetic system remained unchanged. The primary glial cultures and organotypic slices from triple-irradiated brain tissue were more susceptible to GBM U87 cells' adhesion and proliferation in co-culture systems in vitro and ex vivo. In summary, multiple irradiation affects glycosylated components of normal brain extracellular matrix (ECM) through inhibition of the functional activity of normal glial cells. The changed content and pattern of PGs and GAGs in irradiated brain tissues are accompanied by the increased adhesion and proliferation of GBM cells, suggesting a novel molecular mechanism of negative side-effects of anti-GBM radiotherapy.

Adjuvant chemotherapy with temozolomide (TMZ) is an intrinsic part of glioblastoma multiforme (GBM) therapy targeted to eliminate residual GBM cells. Despite the intensive treatment, a GBM relapse develops in the majority of cases resulting in poor outcome of the disease. Here, we investigated off-target negative effects of the systemic chemotherapy on glycosylated components of the brain extracellular matrix (ECM) and their functional significance. Using an elaborated GBM relapse animal model, we demonstrated that healthy brain tissue resists GBM cell proliferation and invasion, thereby restricting tumor development. TMZ-induced [especially in combination with dexamethasone (DXM)] changes in composition and content of brain ECM proteoglycans (PGs) resulted in the accelerated adhesion, proliferation, and invasion of GBM cells into brain organotypic slices ex vivo and more active growth and invasion of experimental xenograft GBM tumors in SCID mouse brain in vivo . These changes occurred both at core proteins and polysaccharide chain levels, and degradation of chondroitin sulfate (CS) was identified as a key event responsible for the observed functional effects. Collectively, our findings demonstrate that chemotherapy-induced changes in glycosylated components of brain ECM can impact the fate of residual GBM cells and GBM relapse development. ECM-targeted supportive therapy might be a useful strategy to mitigate the negative off-target effects of the adjuvant GBM treatment and increase the relapse-free survival of GBM patients., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Tsidulko, Shevelev, Khotskina, Kolpakova, Suhovskih, Kazanskaya, Volkov, Aidagulova, Zavyalov and Grigorieva.)

Adjuvant chemoradiotherapy is a standard treatment option for glioblastoma multiforme (GBM). Despite intensive care, recurrent tumors developed during the first year are fatal for the patients. Possibly contributing to this effect, among other causes, is that therapy induces changes of polysaccharide heparan sulfate (HS) chains in the cancer cells and/or tumor microenvironment. The aim of this study was to perform a comparative analysis of heparanase (HPSE) expression and HS content in different normal and GBM brain tissues. Immunohistochemical analysis revealed a significant decrease of HPSE protein content in the tumor (12-15-fold) and paratumorous (2.5-3-fold) GBM tissues compared with normal brain tissue, both in cellular and extracellular compartments. The relapsed GBM tumors demonstrated significantly higher intertumor and/or intratumor heterogeneity of HPSE and HS content and distribution compared with the matched primary ones (from the same patient) ( n = 8), although overall expression levels did not show significant differences, suggesting local deterioration of HPSE expression with reference to the control system or by the treatment. Double immunofluorescence staining of various glioblastoma cell lines (U87, U343, LN18, LN71, T406) demonstrated a complex pattern of HPSE expression and HS content with a tendency towards a negative association of these parameters. Taken together, the results demonstrate the increase of intratumor heterogeneity of HPSE protein in relapsed GBM tumors and suggest misbalance of HPSE expression regulation by the adjuvant anti-GBM chemoradiotherapy.

Chondroitin sulfate proteoglycans (CSPGs) are important components of brain extracellular matrix (ECM), although their contribution in gliomagenesis remains underinvestigated. Here, both chondroitin sulfate (CS) content/distribution and expression of a number of CSPG core proteins were studied in glioblastoma multiforme (GBM) tumours with different prognosis (n = 40) using immunohistochemistry and RT-PCR analysis. Survival rates for clinically different patient groups were compared using the Kaplan-Meier analysis and univariate Cox model. CS content was increased in 60-65% of studied GBM tumours and distributed heterogeneously, mainly at perinecrotic and perivascular zones rather than tumour cells with specific morphology. CS accumulation, especially in the tumour extracellular matrix, was positively associated with the proliferative activity of GBM cells according to theKi67 index (p < 0.01) but revealed no significant association with age or sex of the patients, tumour localisation, relapse or disease outcome. The increase in CS content in GBM tumours was accompanied by upregulation of decorin (1.5-fold), biglycan (3-fold) and serglycin (2-fold) expression (p < 0.05), while only decorin expression level was negatively associated with the overall survival rate of the GBM patients (p < 0.05). These results demonstrate a contribution of CS to high intratumoural heterogeneity of GBM and suggest CS content and decorin expression for further investigation as potential microenvironmental glycomarkers/targets for GBM diagnostics and treatment.

Histological and immunohistochemical studies require high-quality paraffin blocks, where proper fixation of tissue samples with formalin is a key point. However, in some cases, the possibility to preserve biological samples prior to the formalin fixation or to use deposited tissues from biobanks is important. RNA-stabilizing reagent RNALater represents a potential option, but its suitability for pathological and immunohistochemical studies remains underinvestigated. Here, comparative study of formalin-fixed tissues and those had undergone preservation with RNALater was performed for different SCID mice tissues (brain, liver, kidney, and lung) using histological staining (hematoxylin-eosin and Weigert-van Gieson) or immunostaining for b-actin, glial fibrillary acidic protein, and glycosaminoglycan chondroitin sulfate. It was shown that RNALater preservation for 7-14 days was suitable for histological characterisation of mouse lung tissue, whereas all other tissues demonstrated some changes. Immunoreactivity of all the studied tissues was affected to a different extent, and the observed changes were detected at the 7th day already and continued to get worse by the 14th day. Overall, RNALater preservation affects immunogenicity of normal mouse tissues (brain, liver, kidney, and lung) making them unsuitable for immunohistochemistry. Some tissues retain their morphology (lung tissue) or demonstrate moderate changes (brain, liver, kidney), suggesting a restricted suitability of the RNALater-preserved tissues for histological analysis.

We performed a complex morphological study of samples of different types of unstable atherosclerotic plaques obtained from 33 men with occlusive coronary atherosclerosis, who underwent coronary artery endarterectomy during coronary artery bypass surgery. In the samples, expression of MMP-2 and MMP-9, collagen IV, CD31, CD34, factor VIII, and actin of smooth muscle cells was evaluated by morphometric and immunohistochemical methods. The maximum expression of MMP-9 was found in unstable plaques of the lipid type, where it 1.4- and 1.24-fold surpassed the corresponding levels in plaques of the inflammatory-erosive and degenerative-necrotic types. Unstable plaques of the degenerative-necrotic type are characterized by the most intensive expression of collagen IV in comparison with plaques of the inflammatory-erosive and lipid types (by 2.8 and 2.2 times, respectively). The maximum neovascularization was detected in inflammatory-erosive plaques, which was confirmed by enhanced expression of CD31 and CD34 markers in comparison with plaques of the lipid (by 7.6 and 18.95 times, respectively) and degenerative-necrotic (by 31.1 and 39.8 times) types.

Temozolomide (TMZ) is a conventional chemotherapy drug for adjuvant treatment of glioblastoma multiforme (GBM), often accompanied by dexamethasone (DXM) to prevent brain oedema and alleviate clinical side effects. Here, we aimed to investigate an ability of the drugs to affect normal brain tissue in terms of proteoglycan (PG) composition/content in experimental rat model in vivo . Age- and brain zone-specific transcriptional patterns of PGs were demonstrated for 8, 60, and 120 days old rats, and syndecan-1, glypican-1, decorin, biglycan, and lumican were identified as the most expressed PGs. DXM treatment affected both PG core proteins expression (mainly syndecan-1, glypican-1, decorin, biglycan, lumican, versican, brevican, and NG2) and heparan sulphate (HS)/chondroitin sulphate (CS) content in organotypic brain slice culture ex vivo and experimental animals in vivo in a dose-dependent manner. TMZ treatment did not result in the significant changes in PG core proteins expression both in normal rat brain hippocampus and cortex in vivo (although generics did), but demonstrated significant effects onto polysaccharide HS/CS content in the brain tissue. The effects were age- and brain zone-specific and similar with the age-related PGs expression changes in rat brain. Combination of TMZ with DXM resulted in the most profound deterioration in PGs composition and content in the brain tissue both at core protein and glycosaminoglycan levels. Taken together, the obtained results demonstrate that conventional anti-glioblastoma therapy affects proteoglycan structure and composition in normal brain tissue, potentially resulting in deterioration of brain extracellular matrix and formation of the favourable tumorigenic niche for the expansion of the residual glioma cells. During the TMZ chemotherapy, dose and regimen of DXM treatment matter, and repetitive low DXM doses seem to be more sparing treatment compared with high DXM dose(s), which should be avoided where possible, especially in combination with TMZ.

We performed a complex morphological analysis of atherosclerotic plaques obtained from 68 men with coronary atherosclerosis during coronary bypass surgery with endarterectomy. The expression of MMP-2 and MMP-9, collagen IV, CD31, CD34, factor VIII, and of smooth muscle cell actin was measured in the samples by morphometric and immunohistochemical methods. The expression of MMP-2 and MMP-9 as well as the intensity of neoangiogenesis estimated by the expression of CD31, CD34, and factor VIII in unstable plaques was significantly higher than in stable ones. Immunohistochemical analysis showed more intensive collagen IV expression in stable plaques. The observed differences in immunohistochemical phenotypes of stable and unstable atherosclerotic plaques reflect peculiarities of morphogenesis of atherosclerotic foci in the coronary arteries determining their further development.

Aim: to investigate diagnostically significant for atherosclerotic plaques (ASP) of various types parameters of activity of matrix metalloproteinases (MMP-3, MMP-7, MMP-9) in homogenates, as well as tissue expression of MMP-2, MMP-9 and collagen type IV., Materials and Methods: We included in this study 54 men with coronary atherosclerosis without acute coronary syndrome who underwent coronary artery bypass surgery with endarterectomy. In the obtained samples we determined levels of MMP-3, MMP-7, and MMP-9 (by enzyme immunoassay), as well as tissue expression of antibodies to MMP-2, MMP-9 and collagen type IV., Results: In unstable plaques we observed increased activity of MMP-7 and MMP-9, significant increase of tissue expression of MMP-2 and MMP-9, and decreased expression of type IV collagen. Of three types of unstable ASP the highest tissue expression of MMP-9 was found in plaques of lipid type compared with plaques of necrotic and inflammatory-erosive types. Expression of type IV collagen predominated in plaques of necrotic type., Conclusion: The data obtained allows us to speak about tissue expression of collagen as the marker of fibrous cap stability; the presence of metalloproteinases in necrotic detritus, collagen fibers, and cellular elements can characterize an ASP as unstable or being in the transitional structural state. The immunohistochemical method helps to detect structural elements that characterize instability in various types of ASP.

Glycosaminoglycans are major components of brain extracellular matrix (ECM), although heparan sulfate (HS) contribution in brain physiology and carcinogenesis remains underinvestigated. This study examined HS content and distribution in glioblastoma multiforme (GBM) tissues in the context of potential molecular mechanisms underlying its deregulation in brain tumours. Totally, 42 tissue samples and paraffin-embedded tissues for 31 patients with different prognosis were investigated. HS expression was demonstrated in 50-55% of the GBM tumours by immunohistochemistry (IHC), while almost no HS content was detected in the surrounding paratumourous brain tissues. Heterogeneous HS distribution in the HS-positive tumours was more related to the necrosis or glandular-like brain zones rather than glioma cells with high or low Ki-67 index. According the Kaplan-Meier curves, HS accumulation in glioma cells was associated with low relapse-free survival (RS) of the GBM patients (p < 0.05) and was likely to be due to the increased transcriptional activity of HSPG core proteins (syndecan-1, 2-3 fold; glypican-1, 2,5 fold; perlecan/HSPG2, 13-14 fold). Activation of perlecan/HSPG2 expression correlated with the patients' survival according Kaplan-Meier (p = 0.0243) and Cox proportional-hazards regression (HR = 3.1; P(Y) = 0.03) analyses, while up-regulation of syndecan-1 and glypican-1 was not associated with the patients survival. Taken together, the results indicate that increase of HS content and up-regulation of perlecan/HSPG2 expression in glioblastoma tissues contribute to tumour development through the transformation of brain extracellular matrix into tumour microenvironment, and represent negative prognostic factors for glioblastoma progression.

Heparan sulfate (HS) is an important component of the extracellular matrix and cell surface, which plays a key role in cell-cell and cell-matrix interactions. Functional activity of HS directly depends on its structure, which determined by a complex system of HS biosynthetic enzymes. During malignant transformation, the system can undergo significant changes, but for glioma, HS biosynthesis has not been studied in detail. In this study, we performed a comparative analysis of the HS biosynthetic system in human gliomas of different grades. RT-PCR analysis showed that the overall transcriptional activity of the main HS biosynthesis-involved genes ( EXT1 , EXT2 , NDST1 , NDST2 , GLCE , HS2ST1 , HS3ST1 , HS3ST2 , HS6ST1 , HS6ST2 , SULF1 , SULF2 , HPSE ) was decreased by 1.5-2-fold in Grade II-III glioma ( p < 0.01) and by 3-fold in Grade IV glioma (glioblastoma multiforme, GBM) ( p < 0.05), as compared with the para-tumourous tissue. The inhibition was mainly due to the elongation (a decrease in EXT1/2 expression by 3-4-fold) and 6- O -sulfation steps (a decrease in 6OST1/2 expression by 2-5-fold) of the HS biosynthesis. Heparanase ( HPSE ) expression was identified in 50% of GBM tumours by immunostaining, and was characterised by a high intratumoural heterogeneity of the presence of the HPSE protein. The detected disorganisation of the HS biosynthetic system in gliomas might be a potential molecular mechanism for the changes of HS structure and content in tumour microenvironments, contributing to the invasion of glioma cells and the development of the disease., Competing Interests: The authors declare no conflict of interest.

Neuron-glial antigen 2 (NG2, also known as CSPG4) and hyaluronic acid receptor CD44 are chondroitin sulphate proteoglycans actively involved in brain development and its malignant transformation. Here, we aimed to compare prognostic significances of NG2, CD44 and Ki-67 expression in glioblastoma multiforme patients. Totally, 45 tissue samples and 83 paraffin-embedded tissues for 75 patients were analysed. The prognostic values of the genes were analysed using Kaplan-Meier survival curves. Grade III gliomas showed 2-fold difference in NG2 expression between anaplastic astrocytoma and oligoastrocytoma (10.1 ± 3.5 and 25.5 ± 14.5, respectively). For grade IV gliomas, upregulated NG2 expression (21.0 ± 6.8) was associated with poor glioblastoma multiforme prognosis (overall survival < 12 months) compared with glioblastoma multiforme patients with good prognosis (4.4 ± 3.2; overall survival > 12 months). Multivariate survival analysis using Cox proportional hazards model confirmed that high NG2 expression was associated with low survival of the patients (hazard ratio: 3.43; 95% confidence interval: 1.18-9.93; p = 0.02), whereas age (hazard ratio: 1.02; 95% confidence interval: 0.96-1.09; p = 0.42), tumour resection (hazard ratio: 1.03; 95% confidence interval: 0.98-1.08; p = 0.25) and sex (hazard ratio: 0.62; 95% confidence interval: 0.21-1.86; p = 0.40) did not show significant association with prognosis. Although the positive correlation was shown for NG2 and CD44 expression in the glioblastomas (Pearson coefficient = 0.954), Kaplan-Meier and multivariate survival analyses did not revealed a significant association of the increased CD44 expression (hazard ratio: 2.18; 95% confidence interval: 0.50-9.43; p = 0.30) or high Ki-67 proliferation index (hazard ratio: 1.10; 95% confidence interval: 1.02-1.20; p = 0.02) with the disease prognosis. The results suggest that upregulation of NG2/CSPG4 rather than changes in CD44 or Ki-67 expression is associated with low overall survival in glioblastoma multiforme patients, supporting NG2/CSPG4 as a potential prognostic marker in glioblastoma.

Surgical correction of complicated congenital heart disease in infants is terminated by postischemic reperfusion of myocardium accompanied with closure of more than 20% microvessels in the coronary bed by edematous endothelial cells, their bleb-like fragments, and aggregates of the blood formed elements. Degradation of the transmission capacity of the coronary microvessels developed in parallel with moderation of activity of the antiradical protection enzymes and positively correlated with the level of LPO secondary products, whose elevation during the surgery stages was not reduced by catalase activation.

Similarity of the structural characteristics of perfusion capacity of right-atrial and left-ventricular capillaries of the dog heart in health were detected, the capillaries differing significantly by size and by the majority of the morphometrical values. Exposure of animals to hypothermia induces different ultrastructural responses of the capillaries in two compartments of the heart: the perfusion characteristics of the right atrium deteriorate and the morphometrical parameters of endotheliocytes change, while in the left ventricle the population composition of endothelial cells changes significantly (the percentage of cells of the main type reduces, while the share of dark cells increases).

Cardiosurgical stress initiates endothelial injury of the colliquation necrosis type (without activating coagulation necrosis) in coronary capillaries of infants aged under 1 year. The dark cells exhibited high tolerance to operation stress in the presence of labile ultrastructural response of endothelial cells of the main and light types. The percentage of dark cells does not change during surgical intervention, which is a sign predicting a favorable course of the postoperative period.

In patients with chronic myocardial tissue hypoxia irrespective of the disease (Fallot's tetralogy, coronary disease) factors of cardiosurgical stress initiate a drop of secretory production in coronary capillary endothelium and obstruction of the intravascular space by blood cells. In children the peak of exocytosis of secretory granules coincides with the period of aortic occlusion, while in adults it is attained at the stage of reperfusion.

A combination of pharmacological and cold cardioplegia in with hypothermia without perfusion in open-heart surgery guarantee the reversible character of shifts in energy and free radical balance in the myocardium. However, this procedure can impair coronary micricirculation due to structural and functional changes in microvessel endothelium. Our results demonstrate that new cytoprotective approaches are extremely needed for cardiac protection during surgery.

Ultrastructure of myocardial microvessels was examined during surgical correction of congenital heart disease (ventricular septal defect) under conditions of cold and pharmacological low-potassium cardioplegia without perfusion. Addition of calcium antagonist verapamil to cardioplegic solution prevented postischemic damage to vascular and perivascular structures occurring during reperfusion and body temperature rise.

Ultrastructural changes in endothelial cells (EC) of myocardial capillaries were studied in 24 dogs which underwent hypothermia without perfusion. Biopsy specimens for electron microscopy were taken from the left ventricle of each dog in the control group, during anesthesia (prior to active cooling), and at the end of moderate (28-30 degrees ) and deep (22-24 degrees ) artificial body cooling. The following morphological types of the EC were identified both in the control group and in all test groups: those with moderately dense cytoplasm, light, dark, and irreversibly damaged cells. Dark cells showed increased numbers of plasmalemmal vesicles and appeared to be more transport-specialized as opposed to other types. In all stages of the experiment the amount of dark cells continuously increased (to 23.80, 34.62, and 47.17%, respectively). On cooling to 28-30 degrees, subcellular manifestation of reduced synthetic activity of organelles (nucleus, Golgi complex, and rough endoplasmic reticulum) was observed in all types of the EC. These changes persisted, or even increased, at the end of deep hypothermia. The transport activity of the EC changed differently in three experimental groups in all cell types. Micropinocytotic activity increased under spontaneous mild hypothermia (34-35 degrees ) during anesthesia and tended to decrease with subsequent artificial lowering of the temperature to 22-24 degrees. These ultrastructural changes seem to make up an integral part of the process of capillary endothelium adaptation to body surface cooling, and they might contribute to the development of tolerance to subsequent ischemic exposure during cardiac arrest., (Copyright 1999 Academic Press.)