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At least 703 records · Page 39Linked to original sources
PubMed2005

Immunohistochemical analyses on albumin and immunoglobulin in acute hypertensive mouse kidneys by "in vivo cryotechnique".

The purpose of this study is to visualize topographical changes of serum proteins, albumin and immunoglobulin, passing through mouse glomerular capillary loops and their reabsorption in renal proximal tubules by immunohistochemistry in combination with our "in vivo cryotechnique". The "in vivo cryotechnique" was performed on left mouse kidneys under normotensive, experimentally acute hypertensive and heart-arrest conditions. The cryofixed tissues by the technique were routinely processed for freeze-substitution. Serial deparaffinized sections were stained with hematoxylin-eosine and immunostained with anti-mouse albumin, immunoglobulin G (IgG), kappa or lambda light chain and IgG1 heavy chain antibodies. Under the normotensive and heart-arrest conditions, albumin and IgG were clearly immunolocalized in blood vessels and slightly in apical cytoplasmic parts of some proximal tubules. Under the acute hypertensive condition, the albumin and kappa or lambda light chains, but not IgG1 heavy chain, were strongly immunolocalized in the apical cytoplasm of almost all proximal tubules. This study is the first in vivo visualization for glomerular passage of serum proteins and their transtubular absorption. Thus, the "in vivo cryotechnique" with freeze-substitution can be used for clarifying not only the functional morphology of living animal cells, but also in situ immunohistochemical localization of their components.

Acute Disease↗
PubMed1981

The effect of right ventricular filling on the pressure-volume relationship of ejecting canine left ventricle.

Acute shifts in the pressure-volume relationship of the left ventricle occur under several conditions. One potential mechanism for this phenomenon is ventricular interdependence, that is, the influence of right ventricular filling on the left ventricle. This mechanism was studied in an isolated cross-circulated ejecting canine heart preparation with balloons sewn into both right and left ventricles and connected to volumetric chambers allowing continuous and accurate simultaneous measurement of right and left ventricular pressures and volume. Sets of left ventricular pressure-volume loops were obtained under a variety of right ventricular volumes. Experiments were repeated with and without the pericardium. Both diastole and systole were studied. We show that in the pericardium-free heart working over a normal range of volumes, the right ventricle exerts little influence on left ventricular pressure. With the pericardium present, there is a small but significant effect of right ventricular volume on left ventricular pressure during systole and diastole. Over a wider range of volumes imposed in the arrested heart, the right ventricle does influence left ventricular pressure even without the pericardium. Thus we have demonstrated that ventricular interdependence is not likely to lead to large acute pressure-volume shifts, either during diastole or systole, except in the presence of considerably above normal right ventricular volumes.

Animals↗
PubMed2003

The effect of duration of deep hypothermic circulatory arrest in infant heart surgery on late neurodevelopment: the Boston Circulatory Arrest Trial.

OBJECTIVES: Despite the technical advantages of total circulatory arrest for vital organ support during infant heart surgery, many centers have moved away from its use because of the demonstrated effects of circulatory arrest of long duration on neurodevelopmental outcomes. Our goal was to determine the functional form of the association between duration of circulatory arrest and risk of neurodevelopmental dysfunction. METHODS: From 1988 to 1992, in a single-center trial, infants with d-transposition of the great arteries underwent the arterial switch operation after random assignment to circulatory arrest or low-flow bypass. The alpha-stat method was used, and hematocrit on bypass was maintained at 20%. Developmental, neurologic, and speech outcomes were assessed at 8 years of age in 155 of 160 eligible children (97%). Outcomes selected for analysis were Full-Scale, Verbal, and Performance IQ, Reading and Mathematics Composite, time to complete the Grooved Pegboard (dominant hand), and the Mayo Test for Apraxia. RESULTS: Nonparametric regression and piecewise linear models indicated that neurodevelopmental outcomes were generally not adversely affected unless the duration of circulatory arrest exceeded a threshold of 41 minutes (95% 1-sided lower confidence limit of 32 minutes). CONCLUSIONS: We found that the effect of duration of total circulatory arrest on later neurodevelopmental outcomes is nonlinear, with little influence at shorter durations and with steadily worsening outcomes after longer durations of circulatory arrest. Because the effects of duration of circulatory arrest may vary according to diagnosis, age at surgery, and other bypass and perioperative variables, this study cannot ascertain a universally "safe" duration of total circulatory arrest.

Boston↗
PubMed2006

Implantation of cryopreserved mitral allograft into the tricuspid position in an experimental study in sheep: technical aspects of implantation and immediate results evaluated by epicardial echocardiography.

AIMS: Cryopreserved mitral allograft valve (MAV) offers theoretical advantages over conventional mechanical or biological prostheses in tricuspid position, especially in infectious endocarditis patients. MAV processing and tricuspid valve (TV) replacement in a sheep model is described. METHODS AND RESULTS: In 20 adult sheep, MAV were harvested, processed and cryopreserved. One month later, recipient's TV were excised and the MAVs were transplanted into the tricuspid position in 13 sheep, under general anaesthesia, via a right thoracotomy, with an extracorporeal circulation (ECC) and cardioplegic heart arrest. Both MAV papillary muscles were anchored into the right ventricular wall by transmural stitches and the MAV anulus was sewn into the recipient's tricuspid anulus. After weaning from ECC, the anatomy and function of the MAV in the tricuspid position was assessed by epicardial echocardiography. The average duration of the ECC was 58 minutes (42-88), the cardioplegic heart arrest was 36 minutes (28-45). Weaning from EEC was always uneventful. Right atrial & pulmonary artery pressure measurements and epicardial echocardiography documented good function of all MAVs. CONCLUSION: MAV remained mechanically strong enough for implantation into the tricuspid position. Reproducible technique of MAV transplantation into the tricuspid position with excellent early postoperative haemodynamic performance was developed.

Animals↗
PubMed1975

Coronary responses to dilating substances and competitive inhibition by theophylline in the isolated perfused guinea pig heart.

Coronary dilation induced by infusion of adenosine, adenine nucleotides, dipyridamole, and papaverine was quantitated in the spontaneously beating isolated perfused guinea pig heart. Theophylline antagonized the effects of all the substances tested. The inhibition proved to be reversible and of a competititve type. Single injections of ADP and ATP induced flow increases which were more rapid in onset and of greater magnitude than those due to equimolar amounts of adenosine. Lowering the perfusate temperature prolonged coronary responses to ADP and ATP more than those to adenosine. Papaverine produced greater maximal dilation than adenosine. Theophylline inhibited papaverine-induced dilation less effectively than dilating responses to adenosine and other compounds. In the potassium arrested heart, the dilation caused by compound D 600 and papaverine was sensitive to the perfusate calcium concentration but that due to adenosine was unaffected. Dipyridamole, which was equipotent to adenosine in the non-arrested hear, became less potent than adenosine in the arrested heart. The results favour the view that all of the substances tested induce coronary dilation per se and that their effects are not mediated by adenosine. The dilator response to papaverine is assumed to be the result of two effects, one of which is inhibited by theophylline, the other by high extracellular calcium.

Adenine Nucleotides↗
PubMed1989

Basal metabolic energy requirements of polarized and depolarized arrest in rat heart.

Basal energy requirements of polarized [tetrodotoxin (TTX), 25 microns] and depolarized [potassium (K), 20 mM] arrested hearts were studied by continuously measuring myocardial oxygen consumption (MVO2) during 60 min of normothermic arrest in isolated Langendorff-perfused rat hearts. TTX, a fast sodium channel blocker, was used to produce polarized arrest because of its specificity and reversibility. MVO2 was significantly lower in the polarized (TTX) group at all time points, a typical difference occurring 30 min after arrest (0.070 +/- 0.005 vs. 0.109 +/- 0.006 ml O2.min-1.g dry wt-1, P less than 0.001). Coronary flow was lower in the polarized group (14.3 +/- 1.4 vs. 28.4 +/- 2.2 ml.min-1.g dry wt-1, P less than 0.001, data at 30 min of arrest), but flow-restricted studies showed basal MVO2 to be independent of variation in coronary flow within this range. Recovery of function was similar in both groups. Ventricular pressure during cardiac arrest was lower in the polarized group (5.5 +/- 1.2 vs. 10.3 +/- 1.3 mmHg, P less than 0.01, data at 30 min of arrest), implying reduced myocardial wall tension and a lower intracellular calcium concentration. These results suggest that polarized arrest can decrease myocardial metabolic demands below that of depolarized arrest. A plausible mechanism is a reduction in myocardial wall tension caused by decreased calcium influx mediated by the Na-Ca exchanger.

Animals↗
PubMed1989

Hemoglobin solutions in experimental cardioplegia.

The addition of stroma-free hemoglobin solution to a standard St. Thomas Hospital cardioplegic solution significantly protected the heart from ischemic damage compared to the effect of the same solution without added hemoglobin. An experimental model of rat heart cardioplegia and transplantation comprising heart arrest for three hours at 20 degrees C was used. The number of hearts performing strong contractions after cardioplegia with iso-oncotic oxyhemoglobin prior to transplantation was close to the results with histidine-buffered cardioplegic solution according to Bretschneider. Comparative biochemical model experiments in vitro confirmed that the positive effect of oxyhemoglobin was due predominantly to its buffering capacity. The role of oxygen transport to tissues by hemoglobin was limited only to the first minutes of cardioplegia since neither recirculation nor reoxygenation took place in the present experimental setting.

Animals↗