Prolonged changes in hormonal homeostasis after brief circulatory arrest in the small intestine

It has been established that temporary cessation of blood circulation in the rat small intestine induces alterations in the levels of thyroid and glucocorticoid hormones. These alterations are of the wavy character and can be traced up to 2 weeks after the operation that correlates with duration of previously found functional biochemical, and morphological changes.     

The dynamic changes in autophagy activity and its role in lung injury after deep hypothermic circulatory arrest

Deep hypothermic circulatory arrest (DHCA) can cause acute lung injury (ALI), and its pathogenesis mimics ischaemia/reperfusion (I/R) injury. Autophagy is also involved in lung I/R injury. The present study aimed to elucidate whether DHCA induces natural autophagy activation and its role in DHCA‐mediated lung injury. Here, rats were randomly assigned to the Sham or DHCA group. The sham group (n = 5) only received anaesthesia and air intubation. DHCA group rats underwent cardiopulmonary bypass (CPB) followed by the DHCA procedure. The rats were then sacrificed at 3, 6 and 24 h after the DHCA procedure (n = 5) to measure lung injury and autophagy activity. Chloroquine (CQ) was delivered to evaluate autophagic flux. DHCA caused lung injury, which was prominent 3–6 h after DHCA, as confirmed by histological examination and inflammatory cytokine quantification. Lung injury subsided at 24 h. Autophagy was suppressed 3 h but was exaggerated at 6 h. At both time points, autophagic flux appeared uninterrupted. To further assess the role of autophagy in DHCA‐mediated lung injury, the autophagy inducer rapamycin and its inhibitor 3‐methyladenine (3‐MA) were applied, and lung injury was reassessed. When rapamycin was administered at an early time point, lung injury worsened, whereas administration of 3‐MA at a late time point ameliorated lung injury, indicating that autophagy contributed to lung injury after DHCA. Our study presents a time course of lung injury following DHCA. Autophagy showed adaptive yet protective suppression 3 h after DHCA, as induction of autophagy caused worsening of lung tissue. In contrast, autophagy was exaggerated 6 h after DHCA, and autophagy inhibition attenuated DHCA‐mediated lung injury.     

Subcellular reorganization of cardiomyocytes during and after temporary experimental hypothermic circulatory arrest

Ultrastructure of cardiomyocytes of the left ventricle has been studied in dogs during the experiments, performed with a general external cooling, prolonged circulatory arrest, as well as during long term periods after the operation. In the experiment without cooling it is not possible to restore hemodynamics after 30 min of total ischemia. In cardiomyocytes severe, sometimes irreversible lytic lesions are registered. Opposite to this, by the end of one hour's cardiac arrest under total cooling up to 24-22 degrees C, changes in ultrastructure of cardiomyocytes are minimal. This is proved by a stabilizing action of hypothermia to membranous, fibrillar and even labile granular cellular components. More manifested changes occur in cells after restoration of the cardiac activity and worming, though even at this stage certain morphological signs of partial restoration of synthetic processes are noted. By the third day after the operation ultrastructure of cardiomyocytes is fully normalized at an essential hypertrophy and hyperplasia of protein synthesis organels and lysosomes. Thus, under conditions of aperfusional hypothermia (24-22 degrees C) and cardiac arrest, produced with pharmacological cooling, cardiomyocytes safely survive one hour's total ischemia, presenting their ability to intracellular regeneration in full.     

pH-dependent changes in mitochondrial membrane structure

The pH-dependent changes in structure of submitochondrial vesicles prepared from rat liver have been investigated by a variety of structural probes. The main changes are: (a) the volume of the vesicles as assessed by electron microscopy and packed volume is dependent upon pH, being a minimum at pH 5. Between pH 5 and pH 9 the changes are reversible; (b) the accompanying light-scattering changes are also sensitive to divalent cations; (c) the binding characteristics of 8-anilinonaphthalene-1-sulfonic acid indicate pH-dependent changes in the amount of net charge on the membrane; (d) above pH 4, circular dichroism spectra show alterations characteristic of changes in quaternary protein structure; (e) below pH 4, infrared studies indicate changes in protein secondary conformation are also taking place. From these results, the nature and limits of conformational (molecular) and configurational (morphological) changes in mitochondrial membranes following changes in H⁺ activity are better defined. In the physiological range, pH-dependent conformational changes are confined to reversible changes in quaternary structure resulting from alterations in membrane charge.     

Astrocyte swelling leads to membrane unfolding, not membrane insertion

The mechanisms mediating the release of chemical transmitters from astrocytes are the subject of intense research. Recent experiments have shown that hypotonic conditions stimulate the release of glutamate and ATP from astrocytes, but a mechanistic understanding of this process is not available. To determine whether hypotonicity activates the process of regulated exocytosis, we monitored membrane capacitance by the whole-cell patch-clamp technique whilst a hypotonic medium was applied to cultured astrocytes. If exocytosis is triggered under hypotonic conditions, as it is following increases in cytosolic calcium, a net increase in membrane surface area, monitored by measuring the whole-cell membrane capacitance, is expected. Simultaneous measurements of cell size and whole-cell membrane conductance and surface area demonstrated that hypotonic medium (210 mOsm for 200 s) resulted in an increase in membrane conductance and in the swelling of cultured astrocytes by an average of 40%, as monitored by cell cross-sectional area, but without any corresponding change in membrane surface area. As we have demonstrated that capacitance measurements have the sensitivity to detect increases in cell surface area as small as 0.5%, we conclude that cell swelling occurs via an exocytosis-independent mechanism, probably involving the unfolding of the plasma membrane.     

Bacitracin-induced changes in bacterial plasma membrane structure

Bacitracin interacts with the plasma membranes of gram-positive and gram-negative bacteria to produce morphological changes which appear as rods, 25–35 nm in diameter, and of variable length, in freeze fractured preparations.     

Rewarming from severe accidental hypothermia with circulatory arrest

This case report demonstrates successful cardiopulmonary and cerebral resuscitation (CPCR) of a young male explored 15 hours following a suicide attempt (carbamazepine intoxication) in deep hypothermia (19 degrees C) with circulatory arrest. An extracorporeal circuit was used to rewarm the patient's blood. Weaning from extracorporeal circulation (ECC) was successful and without complications as was recovery from multiorgan dysfunction, severe rhabdomyolysis and carbamazepine intoxication. An excellent outcome was achieved without any neurological deficit at the time of discharge from the hospital.     

Lindane-induced modifications to membrane lipid structure: Effect on membrane fluidity after subchronic treament

Chronic lindane intoxication by injecting subcutaneously the toxicant, resulted in an altered lipid pattern in rat ventral prostate membranes. An increase of membrane fluidity was also observed using a fluorescence polarization technique. Whenin vitro experiments were carried out with both treated and untreated rats, an interesting lack of parallelism was found, which could indicate the development of a resistance to membrane disordering by lindane. The observed changes in cholesterol and phospholipid composition are also consistent with the hypothesis that lindane perturbs the lipid matrix of membranes, possibly inducing complex compensatory changes in the membrane lipid composition.     

Functional consequences of sphingomyelinase-induced changes in erythrocyte membrane structure

Inflammation enhances the secretion of sphingomyelinases (SMases). SMases catalyze the hydrolysis of sphingomyelin into phosphocholine and ceramide. In erythrocytes, ceramide formation leads to exposure of the removal signal phosphatidylserine (PS), creating a potential link between SMase activity and anemia of inflammation. Therefore, we studied the effects of SMase on various pathophysiologically relevant parameters of erythrocyte homeostasis. Time-lapse confocal microscopy revealed a SMase-induced transition from the discoid to a spherical shape, followed by PS exposure, and finally loss of cytoplasmic content. Also, SMase treatment resulted in ceramide-associated alterations in membrane–cytoskeleton interactions and membrane organization, including microdomain formation. Furthermore, we observed increases in membrane fragility, vesiculation and invagination, and large protein clusters. These changes were associated with enhanced erythrocyte retention in a spleen-mimicking model. Erythrocyte storage under blood bank conditions and during physiological aging increased the sensitivity to SMase. A low SMase activity already induced morphological and structural changes, demonstrating the potential of SMase to disturb erythrocyte homeostasis. Our analyses provide a comprehensive picture in which ceramide-induced changes in membrane microdomain organization disrupt the membrane–cytoskeleton interaction and membrane integrity, leading to vesiculation, reduced deformability, and finally loss of erythrocyte content. Understanding these processes is highly relevant for understanding anemia during chronic inflammation, especially in critically ill patients receiving blood transfusions.