Reduction in Histone H3 Acetylation and Chromatin Remodeling in Corneas of Alloxan-Induced Diabetic Rats.

PURPOSE: To evaluate acetylation of histone H3, chromatin remodeling, nuclear size and shape, DNA ploidy, and distribution of nucleolus organizing regions (NORs) in corneal epithelial and stromal cells of diabetic and nondiabetic rats. METHODS: Diabetes was induced by a single intraperitoneal injection of alloxan. All diabetic rats (n = 20) included in the study had 4 weeks of moderate-to-severe hyperglycemia (plasma glucose levels >400 mg/dL). Acetylated histone H3 levels were quantified in corneal tissue using a colorimetric assay. Chromatin remodeling, nuclear sizes (area/perimeter) and shapes (circularity), and DNA ploidies were evaluated from Feulgen-stained tissue sections using video image analysis. Distributions of NORs were studied in tissue sections impregnated with silver ions. Ophthalmic clinical parameters, including corneal sensitivity, were investigated. Twenty nondiabetic rats were used as controls. RESULTS: Acetylation of histone H3 was reduced in the corneas of the diabetic rats. Nuclei in corneal epithelial cells of diabetic rats compacted chromatin, increased in size, modified their shapes, and elevated DNA ploidy. The only nuclear change observed in the corneal stromal cells of diabetic rats was chromatin decompaction. The size of the silver-stained NOR did not differ between the study samples. The corneal sensitivity in diabetic rats was 51.8% lower than that in nondiabetic rats. CONCLUSIONS: The results of this study show that alloxan-induced diabetes altered the histone H3 acetylation pattern and compromised the chromatin supraorganization in corneal tissue/cells. Continued research is needed to understand the clinical and morphofunctional significance of changes in corneal cell nuclei of diabetic individuals.

Effects of chronic malnourishment and aging on the ultrastructure of pyramidal cells of the dorsal hippocampus.

OBJECTIVES: Malnourishment (M) produces permanent alterations during the development of the CNS and might modify the aging process. In pyramidal neurons (PN) of the hippocampus, which are associated with learning and memory performance, few studies have focused on changes at the subcellular level under chronic malnutrition (ChM) in young (Y, 2 months old) and aged (A, 22 months old) rats. The present work evaluated the extent to which ChM disrupts organelles in PN of the dorsal hippocampus CA1 as compared to controls (C). METHODS: Ultrastructural analysis was performed at 8000× and 20 000× magnification: Nucleus eccentricity and somatic, cytoplasmic, and nuclear areas were measured; and in the PN perikaryon, density indices (number of organelles/cytoplasmic area) of Golgi membrane systems (GMS, normal, and swollen), mitochondria (normal and abnormal), and vacuolated organelles (lysosomes, lipofuscin granules, and multivesicular bodies (MVB)) were determined. RESULTS: The density of abnormal mitochondria, swollen GMS, and MVB increased significantly in the AChM group compared to the other groups. The amount of lipofuscin was significantly greater in the AChM than in the YChM groups - a sign of oxidative stress due to malnutrition and aging; however, in Y animals, ChM showed no effect on organelle density or the cytoplasmic area. An increased density of lysosomes as well as nucleus eccentricity was observed in the AC group, which also showed an increase in the cytoplasmic area. DISCUSSION: Malnutrition produces subcellular alterations in vulnerable hippocampal pyramidal cells, and these alterations may provide an explanation for the previously reported deficient performance of malnourished animals in a spatial memory task in which aging and malnutrition were shown to impede the maintenance of long-term memory.

Lung tumors masquerading as desquamative interstitial pneumonia (DIP): report of 7 cases and review of the literature.

Malignant tumors in the lung (both primary and metastatic) rarely may be associated with markedly discohesive tumor cells, resulting in airspace filling reminiscent of "desquamative interstitial pneumonia" (DIP) on histopathology evaluation. A peculiar aspect of this growth pattern is the relatively bland appearance of the tumor cells, in many cases simulating benign alveolar macrophages at scanning magnification. We searched the Charles Carrington Memorial consultation files in the Department of Laboratory Medicine and Pathology at Mayo Clinic Arizona for instances of malignant tumors in lung simulating DIP, from 1992 to 2011. We identified 7 cases involving transbronchial biopsies, needle core samples, or resected lung specimens. Clinical, histopathologic, and immunohistochemical analyses of these 7 patients were performed, including detailed morphometric analysis of the individual tumor cells using calibrated measurement tools on digital images. We compared the results with those of a control group of 4 patients with benign DIP-macrophage reactions in smoking-related lung disease. The study group comprised 5 male and 2 female patients, 48 to 86 years in age (median: 67 y). The radiologic findings included lobar consolidation, localized ground-glass opacities, and 1 or more nodules. None of the patients had typical bilateral infiltrates of DIP. Microscopically, the lung parenchyma was dominated by the presence of prominent tumor cells filling alveolar spaces. Four patients had primary lung carcinoma (adenocarcinoma), whereas 3 had metastases from other sites, including a melanoma. Immunohistochemical staining studies were performed on 6 of 7 cases to establish the diagnosis. Nuclear diameter, cytoplasmic diameter, and nuclear/cytoplasmic (N/C) ratios in patient and control groups were compared using the Wilcoxon rank sum test. No significant difference in the diameters of nucleus and cytoplasm between cases and control groups (P=0.3447 and 0.7055, respectively) was seen, and only a marginally significant difference in N/C ratios (P=0.0890) was seen. A more complex analysis, generalized estimating equation analysis, showed a significant difference in N/C ratio between the 2 groups (P=0.0278). A "DIP-growth pattern" of malignant tumors in the lung is presented. Although the N/C ratio differences approached statistical significance when compared with controls, the key to diagnosis is the recognition of the malignant cytology of the tumor nuclei. Immunohistochemical studies (keratin or other markers) are helpful in establishing an accurate diagnosis in this setting.

c-Fos-activated synthesis of nuclear phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] promotes global transcriptional changes.

c-Fos is a well-recognized member of the AP-1 (activator protein-1) family of transcription factors. In addition to this canonical activity, we previously showed that cytoplasmic c-Fos activates phospholipid synthesis through a mechanism independent of its genomic AP-1 activity. c-Fos associates with particular enzymes of the lipid synthesis pathway at the endoplasmic reticulum and increases the Vmax of the reactions without modifying the Km values. This lipid synthesis activation is associated with events of differentiation and proliferation that require high rates of membrane biogenesis. Since lipid synthesis also occurs in the nucleus, and different phospholipids have been assigned transcription regulatory functions, in the present study we examine if c-Fos also acts as a regulator of phospholipid synthesis in the nucleus. Furthermore, we examine if c-Fos modulates transcription through its phospholipid synthesis activator capacity. We show that nuclear-localized c-Fos associates with and activates PI4P5K (phosphatidylinositol-4-monophosphate 5-kinase), but not with PI4KIIIß (type IIIß phosphatidylinositol 4-kinase) thus promoting PtdIns(4,5)P2 (phosphatidylinositol 4,5-bisphosphate) formation, which, in turn, promotes transcriptional changes. We propose c-Fos as a key regulator of nuclear PtdIns(4,5)P2 synthesis in response to growth signals that results in c-Fos-dependent transcriptional changes promoted by the newly synthesized lipids.

Volumen nuclear de hepatocitos de hígados sometidos a un factor estimulante humoral en ratones isogénicos linea IOR / Nuclear volume of hepatocytes in livers subjected to a humoral stimulating factor in isogenic rats, IOR line

Se estudió el comportamiento del volumen nuclear de los hepatocitos en 14 muestras del lóbulo medio de hígados de ratones isogénicos IOR que fueron sometidos a tres dosis de citosol de hígado regenerativo al inicio del experimento. Las muestras fueron tomadas durante ocho días con frecuencia de doce horas. El corte se dividió en zonas proximal, medial y distal al hilio. Se aplico el método morfométrico para la determinación del volumen nuclear de los hepatocitos a partir de su diámetro mayor y menor. Los resultados mostraron que los valores más altos del volumen nuclear esta en la zona proximal al hilio, aunque en todas las zonas existen diferencias significativas entre los valores obtenidos en la primera mitad de tiempo del experimento respecto a la parte final, con marcada orientación a decrecer lo que puede ser debido a la presencia de factores humorales estimulantes en el citosol regenerativo(AU)

We studied the behavior of the nuclear volume of hepatocytes in 14 samples of the middle lobe of isogenic rats liver IOR that were subjected to three doses of regenerating liver cytosol at the beginning of the experiment. Samples were taken during eight days with a frequency of twelve hours. The incision was divided into the proximal, medial and distal to the ileum zones. The Morphometric method was applied to determine the nuclear volume of hepatocytes from its major and minor diameter. The results showed that the highest values of the nuclear volume are located in the proximal zone to the ileum, although in all zones there are significant differences between the values obtained in the first half of the experiment in relation to the final part, with marked orientation to decrease what can be due to the presence of stimulant humoral factors in the regenerative cytosol(AU)

Volumen nuclear de hepatocitos de hígados sometidos a un factor estimulante humoral en ratones isogénicos linea IOR / Nuclear volume of hepatocytes in livers subjected to a humoral stimulating factor in isogenic rats, IOR line

Se estudió el comportamiento del volumen nuclear de los hepatocitos en 14 muestras del lóbulo medio de hígados de ratones isogénicos IOR que fueron sometidos a tres dosis de citosol de hígado regenerativo al inicio del experimento. Las muestras fueron tomadas durante ocho días con frecuencia de doce horas. El corte se dividió en zonas proximal, medial y distal al hilio. Se aplico el método morfométrico para la determinación del volumen nuclear de los hepatocitos a partir de su diámetro mayor y menor. Los resultados mostraron que los valores más altos del volumen nuclear esta en la zona proximal al hilio, aunque en todas las zonas existen diferencias significativas entre los valores obtenidos en la primera mitad de tiempo del experimento respecto a la parte final, con marcada orientación a decrecer lo que puede ser debido a la presencia de factores humorales estimulantes en el citosol regenerativo

We studied the behavior of the nuclear volume of hepatocytes in 14 samples of the middle lobe of isogenic rats liver IOR that were subjected to three doses of regenerating liver cytosol at the beginning of the experiment. Samples were taken during eight days with a frequency of twelve hours. The incision was divided into the proximal, medial and distal to the ileum zones. The Morphometric method was applied to determine the nuclear volume of hepatocytes from its major and minor diameter. The results showed that the highest values of the nuclear volume are located in the proximal zone to the ileum, although in all zones there are significant differences between the values obtained in the first half of the experiment in relation to the final part, with marked orientation to decrease what can be due to the presence of stimulant humoral factors in the regenerative cytosol

Nuclear structure of Trypanosoma cruzi.

The presence of nucleus in living organisms characterizes the Eukaryote domain. The nucleus compartmentalizes the genetic material surrounded by a double membrane called nuclear envelope. The nucleus has been observed since the advent of the light microscope, and sub-compartments such as nucleoli, diverse nuclear bodies and condensed chromosomes have been later recognized, being part of highly organized and dynamic structure. The significance and function of such organization has increased with the understanding of transcription, replication, DNA repair, recombination processes. It is now recognized as consequence of adding complexity and regulation in more complex eukaryotic cells. Here we provide a description of the actual stage of knowledge of the nuclear structure of Trypanosoma cruzi. As an early divergent eukaryote, it presents unique and/or reduced events of DNA replication, transcription and repair as well as RNA processing and transport to the cytosol. Nevertheless, it shows peculiar structure changes accordingly to the cell cycle and stage of differentiation. T. cruzi proliferates only as epimastigote and amastigote stages, and when these forms differentiate in trypomastigote forms, their cell cycle is arrested. This arrested stage is capable of invading mammalian cells and of surviving harsh conditions, such as the gut of the insect vector and mammalian macrophages. Transcription and replication decrease during transformation in trypomastigotes implicating large alterations in the nuclear structure. Recent evidences also suggest that T. cruzi nucleus respond to oxidative and nutritional stresses. Due to the phylogenetic proximity with other well-known trypanosomes, such as Trypanosoma brucei and Leishmania major, they are expected to have similar nuclear organization, although differences are noticed due to distinct life cycles, cellular organizations and the specific adaptations for surviving in different host environments. Therefore, the general features of T. cruzi nuclear structure regarding unique characteristics of this protozoan parasite will be described.

Spermatogonial morphology and kinetics during testis development in mice: a high-resolution light microscopy approach.

Despite the knowledge of spermatogonial biology in adult mice, spermatogonial development in immature animals has not been fully characterized. Thus, the aim of this study was to evaluate the ontogeny of the morphological development of the spermatogonial lineage in C57BL/6 mouse testis, using high-resolution light microscopy. Spermatogonial morphology, chronology, and absolute number were determined for different ages postpartum (pp). The morphology of spermatogonia in immature mice was similar to that of adult spermatogonia, although their nuclear diameter was slightly smaller. The A(1) spermatogonia were first observed on day 2 pp, and only 24 h later, differentiating type A(3) and A(4) spermatogonia were observed in the seminiferous cords. This result indicated a shortening of the spermatogonial phase for immature mice of about ∼2.5 days when compared with adult mice and suggests that gonocytes and/or A(1) spermatogonia could directly become A(4) spermatogonia, skipping the developmental sequence of type A spermatogonia. These A(4) spermatogonia are functional as they develop into type B spermatogonia by day 5 pp. At day 8 pp, while differentiation to spermatocytes begins, the A(und) spermatogonia reach their maximal numbers, which are maintained through adulthood. The various details of the spermatogonial behavior in immature normal mice described in this study can be used as a baseline for further studies under experimental or pathological conditions.

Alteraciones en las características morfométricas del riñón de ratas albinas machos provocadas por la ingestión crónica de etanol desde la adolescencia / Alterations in the morphometric features of kidney of male albino rats provoked by chronic ingestion of ethanol from the adolescence

En el presente trabajo se pretendió determinar las variaciones que sobre las características morfométricas del riñón provoca la ingestión crónica de etanol en ratas adolescentes, para lo cual se utilizaron 42 ratas albinas machos de 30 días de nacidas con las cuales se conformaron dos grupos de 21 animales cada uno y con tiempos de tratamiento de tres y cinco meses y con estos, dos subgrupos: experimental y control. A las ratas experimentales se les suministró etanol a dosis de 5 g/kg de peso corporal mediante cánula intraesofágica. A las controles se les administró agua en lugar de etanol, en iguales condiciones. Se emplearon cortes histológicos coloreados con técnica PAS y se estudiaron las porciones contorneadas de los túbulos proximales y distales. Se calculó el área de sección transversal tubular y se midieron los volúmenes nucleares de las células de ambos túbulos. Se comprobó que las ratas experimentales mostraron volúmenes nucleares menores que las controles. El grupo experimental mostró valores de áreas de sección transversal de los túbulos renales mayores que los controles, siendo estos valores superiores en los túbulos proximales en las ratas de cinco meses, y los distales en las ratas de tres meses. Se concluyó que en la muestra estudiada el alcoholismo crónico iniciado en la adolescencia provocó variaciones morfométricas en los túbulos proximales y distales del riñón(AU)

Present paper allowed us to determine the variations exerted by the chronic ingestion of ethanol from the adolescence on the kidney morphometric features in 42 male albino rats of 30 days born divided into two groups of 21 animal each and with the treatment times of three and five months and with these 42 animals into two subgroups: one of experimental type and other as control. The experimental rats received ethanol at 5 g/kg doses according to the body weight using an intraesophageal cannula. The control ones received water instead of ethanol in similar conditions. We used histological sections stained with PAS technique to study the outlined portions of the proximal and distal tubules. The tubular transversal section area was estimated measuring the nuclear volumes of cells in both tubules. It was demonstrated that the experimental rats showed higher values of the transversal section of renal tubules higher than the control ones, where these values were superior in proximal tubules in the five months old rats and the distal ones in the three months old. We conclude that in study sample the chronic alcoholism started during adolescence provoked morphometric variations in proximal and distal tubules of kidney(AU)

Fractal dimension of chromatin is an independent prognostic factor for survival in melanoma.

BACKGROUND: Prognostic factors in malignant melanoma are currently based on clinical data and morphologic examination. Other prognostic features, however, which are not yet used in daily practice, might add important information and thus improve prognosis, treatment, and survival. Therefore a search for new markers is desirable. Previous studies have demonstrated that fractal characteristics of nuclear chromatin are of prognostic importance in neoplasias. We have therefore investigated whether the fractal dimension of nuclear chromatin measured in routine histological preparations of malignant melanomas could be a prognostic factor for survival. METHODS: We examined 71 primary superficial spreading cutaneous melanoma specimens (thickness > or = 1 mm) from patients with a minimum follow up of 5 years. Nuclear area, form factor and fractal dimension of chromatin texture were obtained from digitalized images of hematoxylin-eosin stained tissue micro array sections. Clark's level, tumor thickness and mitotic rate were also determined. RESULTS: The median follow-up was 104 months. Tumor thickness, Clark's level, mitotic rate, nuclear area and fractal dimension were significant risk factors in univariate Cox regressions. In the multivariate Cox regression, stratified for the presence or absence of metastases at diagnosis, only the Clark level and fractal dimension of the nuclear chromatin were included as independent prognostic factors in the final regression model. CONCLUSION: In general, a more aggressive behaviour is usually found in genetically unstable neoplasias with a higher number of genetic or epigenetic changes, which on the other hand, provoke a more complex chromatin rearrangement. The increased nuclear fractal dimension found in the more aggressive melanomas is the mathematical equivalent of a higher complexity of the chromatin architecture. So, there is strong evidence that the fractal dimension of the nuclear chromatin texture is a new and promising variable in prognostic models of malignant melanomas.

Alteraciones en las características morfométricas del riñón de ratas albinas machos provocadas por la ingestión crónica de etanol desde la adolescencia / Alterations in the morphometric features of kidney of male albino rats provoked by chronic ingestion of ethanol from the adolescence

En el presente trabajo se pretendió determinar las variaciones que sobre las características morfométricas del riñón provoca la ingestión crónica de etanol en ratas adolescentes, para lo cual se utilizaron 42 ratas albinas machos de 30 días de nacidas con las cuales se conformaron dos grupos de 21 animales cada uno y con tiempos de tratamiento de tres y cinco meses y con estos, dos subgrupos: experimental y control. A las ratas experimentales se les suministró etanol a dosis de 5 g/kg de peso corporal mediante cánula intraesofágica. A las controles se les administró agua en lugar de etanol, en iguales condiciones. Se emplearon cortes histológicos coloreados con técnica PAS y se estudiaron las porciones contorneadas de los túbulos proximales y distales. Se calculó el área de sección transversal tubular y se midieron los volúmenes nucleares de las células de ambos túbulos. Se comprobó que las ratas experimentales mostraron volúmenes nucleares menores que las controles. El grupo experimental mostró valores de áreas de sección transversal de los túbulos renales mayores que los controles, siendo estos valores superiores en los túbulos proximales en las ratas de cinco meses, y los distales en las ratas de tres meses. Se concluyó que en la muestra estudiada el alcoholismo crónico iniciado en la adolescencia provocó variaciones morfométricas en los túbulos proximales y distales del riñón

Present paper allowed us to determine the variations exerted by the chronic ingestion of ethanol from the adolescence on the kidney morphometric features in 42 male albino rats of 30 days born divided into two groups of 21 animal each and with the treatment times of three and five months and with these 42 animals into two subgroups: one of experimental type and other as control. The experimental rats received ethanol at 5 g/kg doses according to the body weight using an intraesophageal cannula. The control ones received water instead of ethanol in similar conditions. We used histological sections stained with PAS technique to study the outlined portions of the proximal and distal tubules. The tubular transversal section area was estimated measuring the nuclear volumes of cells in both tubules. It was demonstrated that the experimental rats showed higher values of the transversal section of renal tubules higher than the control ones, where these values were superior in proximal tubules in the five months old rats and the distal ones in the three months old. We conclude that in study sample the chronic alcoholism started during adolescence provoked morphometric variations in proximal and distal tubules of kidney

Memantine prevents cardiomyocytes nuclear size reduction in the left ventricle of rats exposed to cold stress.

OBJECTIVES: Memantine is an N-methyl-d-aspartate (NMDA) glutamate receptor antagonist used to treat Alzheimer's disease. Previous studies have suggested that receptor blockers act as neuroprotective agents; however, no study has specifically investigated the impact that these drugs have on the heart. We sought to evaluate the effects of memantine on nuclear size reduction in cardiac cells exposed to cold stress. METHOD: We used male EPM-Wistar rats (n=40) divided into 4 groups: 1) Matched control (CON); 2) Memantine-treated rats (MEM); 3) Rats undergoing induced hypothermia (IH) and 4) Rats undergoing induced hypothermia that were also treated with memantine (IHM). Animals in the MEM and IHM groups were treated by oral gavage administration of 20 mg/kg/day memantine over an eight-day period. Animals in the IH and IHM groups were submitted to 4 hours of hypothermia in a controlled environment with a temperature of -8 degrees C on the last day of the study. RESULTS: The MEM group had the largest cardiomyocyte nuclear size (151 +/- 3.5 microm(3) vs. CON: 142 +/- 2.3 microm(3); p<0.05), while the IH group had the smallest mean value of nuclear size. The nuclear size of the IHM group was preserved (125 +/- 2.9 microm(3)) compared to the IH group (108 +/- 1.7 microm(3); p<0.05). CONCLUSION: Memantine prevented the nuclear size reduction of cardiomyocytes in rats exposed to cold stress.

Memantine prevents cardiomyocytes nuclear size reduction in the left ventricle of rats exposed to cold stress

OBJECTIVES: Memantine is an N-methyl-d-aspartate (NMDA) glutamate receptor antagonist used to treat Alzheimer's disease. Previous studies have suggested that receptor blockers act as neuroprotective agents; however, no study has specifically investigated the impact that these drugs have on the heart. We sought to evaluate the effects of memantine on nuclear size reduction in cardiac cells exposed to cold stress. METHOD: We used male EPM-Wistar rats (n=40) divided into 4 groups: 1) Matched control (CON); 2) Memantine-treated rats (MEM); 3) Rats undergoing induced hypothermia (IH) and 4) Rats undergoing induced hypothermia that were also treated with memantine (IHM). Animals in the MEM and IHM groups were treated by oral gavage administration of 20 mg/kg/day memantine over an eight-day period. Animals in the IH and IHM groups were submitted to 4 hours of hypothermia in a controlled environment with a temperature of - 8ºC on the last day of the study. RESULTS: The MEM group had the largest cardiomyocyte nuclear size (151 ± 3.5 μm³ vs. CON: 142 ± 2.3 μm³; p<0.05), while the IH group had the smallest mean value of nuclear size. The nuclear size of the IHM group was preserved (125 ± 2.9 μm³) compared to the IH group (108 ± 1.7 μm³; p<0.05). CONCLUSION: Memantine prevented the nuclear size reduction of cardiomyocytes in rats exposed to cold stress.

Cold stress effects on cardiomyocytes nuclear size in rats: light microscopic evaluation / Efeitos do estresse pelo frio sobre o tamanho nuclear do cardiomiócito em ratos: avaliação por microscopia de luz

INTRODUÇÃO: Hipotermia corporal induzida e resfriamento do miocárdio são métodos efetivos em relação à proteção domiocárdio durante cirurgias cardíacas e isquemia. É descrito na literatura que a exposição a temperaturas extremamente baixas causa comprometimentos de miofilamentos e de cristas mitocondriais em cardiomiócitos, entretanto, nenhum estudo analisou os efeitos do estresse pelo frio no tamanho do núcleo dos cardiomiócios. OBJETIVOS: Analisar os efeitos do estresse agudo pelo frio sobre o tamanho do núcleo dos cardiomiócitos. MÉTODOS: O estudo foi realizado em ratos Wistar adultos, pesando 300-310g (n=20). Os ratos foram divididos em dois grupos: 1) Controle (CON) e; 2) Hipotermia induzido (IH). Os animais do grupo IH foram expostos a uma temperatura controlada de -8ºC, durante 4 horas uma única vez. Foi realizada análise histológica de fígados e glândulas adrenais para examinar a condição de estresse. O tamanho do núcleo dos cardiomiócitos foi examinado por três investigadores independentes com o mesmo critério padronizado e posteriormente analisado pelo coeficiente de correlação de Bartko (R>0,75=concordância positiva). Teste t de Student foi aplicado. O nível de significância foi considerado como P<0,05. RESULTADOS: O grupo exposto ao estresse pelo frio apresentou maior depleção de lipídio nas glândulas adrenais (P<0,05) e de glicogênio no fígado (P<0,05). O grupo induzido à hipotermia mostrou menor volume do núcleo de seus cardiomiócitos (108 + 1,7 µm³; P<0,05), reduziu em 76 por cento comparado ao grupo controle (142 + 2,3 µm³). Correlação de Bartko: CON=0,44; IH=0,96, a variação entre a média dos grupos foi significativamente diferente. CONCLUSÃO: Esses resultados sugerem que a exposição ao estresse agudo pelo frio induz redução do núcleo dos cardiomiócitos em ratos.

INTRODUCTION: Total body induced hypothermia and myocardial cooling are effective methods regarding myocardial protection during heart surgery and ischemia. It is described in previous studies that extreme low temperature exposure causes mitochondrial cristae and myofilament disarrangement in cardiomyocytes, however, no investigation has analyzed the effects of cold stress on nuclear size of cardiomyocytes. OBJECTIVES: To evaluate the effects of acute cold stress exposure on the nuclear size of cardiomyocytes in rats. METHODS: The experimental study procedures were performed on 300-310g adult male Wistar rats. Rats (n=20) were divided into two groups: 1) Control (CON) and; 2) Induced hypothermic (IH) group. Animals of IH group were exposed during 4 hours once at a controlled temperature of - 8ºC. It was performed histological analysis of liver and adrenal gland to examine the stress condition of animals. Cardiomyocytes nucleus size were examined by three independent investigators with the same and standardized criteria and analyzed by Bartko's intra-class correlation coefficient (R>0.75 = positive concordance). Student's t test was applied. The significance level was set at P<0.05. RESULTS: The induced hypothermic group presented higher lipid depletion in adrenal gland cells (P<0.05) and higher glycogen depletion in liver glycogen (P<0.05). The experimental group showed lower cardiomyocytes nuclear volume (108 + 1.7 µm³; P<0.05), it decreased in 76 percent compared to the control group (142 + 2.3 µm³). Bartko's correlation: CON=0.44; IH=0.96, variation analysis between group's means differences was significant. CONCLUSION: These data suggest that acute cold stress exposure induces cardiomyocytes nucleus size reduction in rats.

Cold stress effects on cardiomyocytes nuclear size in rats: light microscopic evaluation.

INTRODUCTION: Total body induced hypothermia and myocardial cooling are effective methods regarding myocardial protection during heart surgery and ischemia. It is described in previous studies that extreme low temperature exposure causes mitochondrial cristae and myofilament disarrangement in cardiomyocytes, however, no investigation has analyzed the effects of cold stress on nuclear size of cardiomyocytes. OBJECTIVES: To evaluate the effects of acute cold stress exposure on the nuclear size of cardiomyocytes in rats. METHODS: The experimental study procedures were performed on 300-310 g adult male Wistar rats. Rats (n=20) were divided into two groups: 1) Control (CON) and; 2) Induced hypothermic (IH) group. Animals of IH group were exposed during 4 hours once at a controlled temperature of - 8 degrees C. It was performed histological analysis of liver and adrenal gland to examine the stress condition of animals. Cardiomyocytes nucleus size were examined by three independent investigators with the same and standardized criteria and analyzed by Bartko's intra-class correlation coefficient (R>0.75 = positive concordance). Student's t test was applied. The significance level was set at P<0.05. RESULTS: The induced hypothermic group presented higher lipid depletion in adrenal gland cells (P<0.05) and higher glycogen depletion in liver glycogen (P<0.05). The experimental group showed lower cardiomyocytes nuclear volume (108 + 1.7 microm(3); P<0.05), it decreased in 76% compared to the control group (142 + 2.3 microm(3)). Bartko's correlation: CON=0.44; IH=0.96, variation analysis between group's means differences was significant. CONCLUSION: These data suggest that acute cold stress exposure induces cardiomyocytes nucleus size reduction in rats.