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  • 1
    Electronic Resource
    Electronic Resource
    Electron microscopic stereology of capillary endothelial cells and cardiomyocytes in artificially arrested canine hearts (1999)
    Springer
    Medical electron microscopy 32 (1999), S. 151-160 
    Details
    ISSN: 1437-773X
    Keywords: Key words Heart ; Ultrastructure ; Capillaries ; Endothelium ; Stereology ; Cardioplegic solutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In open heart surgery and transplantation, sufficient structural preservation of the myocardium immediately following cardioplegic arrest is a precondition for overcoming ischemia and for resumption of postischemic function. Therefore, we compared the protective effect of three clinically applied cardioplegic solutions with fibrillating and beating hearts using structural criteria. Left ventricular samples were taken from (1) beating, or (2) fibrillating or arrested hearts following coronary perfu-sion with (3) St. Thomas' Hospital solution, (4) histidine tryptophane ketoglutalate (HTK) (Custodiol), or (5) University of Wisconsin (UW) solution and fixed by immersion. Ultrastructural differences in the swelling of capillary endothelial cells and myocytes were quantitatively evaluated using stereological methods. Endothelial cells were somewhat more swollen after St. Thomas perfusion than those in beating and fibrillating hearts. HTK-arrested hearts showed significantly lower values for cellular edema than beating hearts. UW perfusion resulted in the (significantly) lowest degree of endothelial cell edema. Edematous changes in myocytes were significantly greater in St. Thomas-arrested hearts than in UW- or HTK-arrested hearts. Cardiomyocyte edema in beating and fibrillating hearts was comparable to that in St. Thomas-perfused hearts. Thus, the stereol-ogical analysis revealed significant differences between cardioplegic solutions in structural preservation of myocardial ultrastructure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007950050022
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  • 2
    Electronic Resource
    Electronic Resource
    Occurrence and prevention of contraction bands in Purkinje fibres, transitional cells and working myocardium during global ischaemia (1990)
    Springer
    Virchows Archiv 417 (1990), S. 463-471 
    Details
    ISSN: 1432-2307
    Keywords: Purkinje fibres ; Transitional cells ; Working myocardium ; Global ischaemia ; Ultrastructure ; Contraction state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Contraction bands usually occur in the intramural working myocardium following post-ischaemic reperfusion. In the subendocardium, however, they are found during ischaemia. Thus, we ascertained the contraction states of Purkinje fibres, transitional cells, subendocardial and intramural parts of the working myocardium during 30 min global ischaemia at 25° C. The effects with and without myocardial protection were compared. At the onset of pure ischaemia contraction bands are completely lacking in all cell types. During pure ischaemia contraction bands are found in all subendocardial cell types but not in the intramural working myocardium. A peak of pathological contraction states is found in the intramural working myocardium at the onset (0 min), in the subendocardial working myocardium at 10 min, in the transitional cells and Purkinje fibres at 30 min of pure ischaemia. Histidine-, tryptophan-, ketoglutarate-enriched (HTK) cardioplegia prevents contraction bands completely at the onset of ischaemia and prevents both contraction bands and pathological contraction states during ischaemia almost completely. Striking differences in the physiological contraction states are seen only in the working myocardium: HTK cardioplegia brings about dominance of relaxation during ischaemia. These findings may be due mainly to the effects of global ischaemia on the one hand and to catecholamines, calcium and oxygen on the other.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01625725
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of ischaemia and preservation on the ultrastructure of the bronchiolar epithelium (1996)
    Springer
    Virchows Archiv 429 (1996), S. 109-118 
    Details
    ISSN: 1432-2307
    Keywords: Lung-transplantation pathology ; Bronchi-epithelium ; Ischaemia ; Mitochondrial swelling ; Scanning electron microscopy ; Transmission electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In ten cases of clinical human single-lung transplantation, the nontransplanted Euro-Collins-preserved contralateral lungs were examined using electron microscopy to determine the effects of ischaemia on the bronchiolar epithelium. Existing structural damage at the time of transplantation was characterized using this approach, and nine nonpreserved canine single lungs were also investigated to identify the impact of ischaemia. The study revealed a significant correlation between the duration of ischaemia and the mitochondrial surface-to-volume ratio, which can serve as a morphometric criterion for mitochondrial damage, in canine lungs. However, this correlation was not found in the human donor lungs. Further examination of human donor lungs showed slight to moderate damage to the endoplasmic reticulum and nuclear chromatin. In addition, various degrees of damage to mitochondrial structure, ranging from inconspicuous to severe, were found. The mitochondrial surface-to-volume ratio can be considered to be a suitable criterion for the quantification of ischaemic damage of the bronchiolar epithelium under experimental conditions. Ultrastructural analysis of human donor lungs revealed intact bronchiolar epithelial cell structures at the time of transplantation, reflecting adequate organ preservation with Euro-Collins solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192433
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  • 4
    Electronic Resource
    Electronic Resource
    The surface to volume ratio of mitochondria, a suitable parameter for evaluating mitochondrial swelling (1990)
    Springer
    Virchows Archiv 416 (1990), S. 305-315 
    Details
    ISSN: 1432-2307
    Keywords: Myocardial ultrastructure ; Mitochondrial swelling ; Stereology ; Correlations of structural parameters ; Cardiac arrest and global ischaemia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cellular changes occuring in the left ventricular myocardium during ischaemia after different methods of cardiac arrest have been evaluated by morphological and morphometric parameters: volume densities of mitochondria (VVMi), sarcoplasm (VVSp), myofibrils (VVMf), surface densities of mitochondria (SVMi). The surface to volume ratio of mitochondria (SVratioMi) has been used as an independent parameter of mitochondrial swelling. Since ischaemic swelling of myocardial cells increases the volume of the reference space and ischaemic swelling of mitochondria decreases the free sarcoplasm, VVMi and VVSp cannot be considered as reliable indicators of the degree of oedema. SVMi/VVMf remains nearly constant after different forms of cardiac arrest, demonstrating the integrity of mitochondrial outer membranes. The inverse linear ratio between SVratioMi and the mean mitochondrial volume indicates that the increase in mitochondrial volume is achieved by surface smoothing. Loss of matrix structure and fragmentation of cristae occur at an SVratioMi of about 5.8, cristolysis at 5.5 to 5.6 and amorphous matrix densities at an SVratioMi of less than 5.5 μm2/μm3. The SVratioMi is a suitable parameter for evaluating mitochondrial swelling both at the onset and during global myocardial ischaemia, independent of the method of cardiac arrest used. It serves as an indicator of the state of structural preservation of mitochondria during ischaemia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01605291
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrastructural effects induced by global ischaemia on the AV node compared with the working myocardium (1990)
    Springer
    Virchows Archiv 416 (1990), S. 317-328 
    Details
    ISSN: 1432-2307
    Keywords: AV nodal cells ; Working myocardium ; Cardiac arrest and global ischaemia ; HTK cardioplegia ; Qualitative and quantitative ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cardiac conduction system is considered to be particularly resistant to ischaemia. Nevertheless, following open heart surgery with short periods of ischaemia disturbances in AV conduction or ventricular arrhythmia have been reported. We compared the ultrastructure of AV node and working myocardium following 30 min global ischaemia at 25° C, during pure ischaemia and with HTK cardioplegia qualitatively and morphometrically. After 30 min of pure ischaemia, interstitial and intracellular oedema together with considerable changes in organelles in AV nodes predominate over mainly cellular oedema in working myocardium. Sometimes irregular overcontractions of sarcomeres occur in the AV node, though very seldom in working myocardium. In pure ischaemia, mitochondrial swelling is comparable in both types of tissue. Following HTK cardioplegia and 30 min ischaemia, cellular oedema and mitochondrial swelling are significantly reduced in AV nodal cells and working myocardium, but remain more extensive in the AV nodes. Irregularities in the contractile state of sarcomeres are not observed. The extent of the ultrastructural alterations corresponds to the degree of metabolic change in the working myocardium. Thus, despite considerable differences during pure ischaemia and HTK cardioplegia, ultrastructurally the AV nodal cells do not display a greater resistance to ischaemia than working myocardium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01605292
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  • 6
    Electronic Resource
    Electronic Resource
    The ultrastructural effects of global ischaemia on Purkinje fibres compared with working myocardium: A qualitative and morphometric investigation on the canine heart (1991)
    Springer
    Virchows Archiv 418 (1991), S. 17-25 
    Details
    ISSN: 1432-2307
    Keywords: Purkinje fibres ; Ischaemia tolerance ; Qualitative and quantitative ultrastructure ; Cardioplegia ; Arrhythmias
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary During open heart surgery, reperfusion-induced arrhythmias arising after short periods of ischaemia may originate from subendocardial Purkinje fibres. We investigated the ultrastructure of these fibres during 30 min of global ischaemia at 25° C. The effects both with myocardial protection (HTK cardioplegia) and without it (pure ischaemia) were compared qualitatively and morphometrically. After 30 min pure ischaemia overcontraction of sarcomeres, hypercontraction and contraction bands, together with considerable changes in organelles, predominate over cellular oedema. In Purkinje fibres, both cellular and mitochondrial swelling were significantly increased within this 30-min time period from the onset of pure ischaemia. In contrast, following HTK cardioplegia and 30 min ischaemia, cellular and mitochondrial swelling remain moderate and over-contractions are almost entirely lacking. This means that despite remarkable differences between pure ischaemia and HTK cardioplegia in the degree of protection attained it is clear that, compared with the working myocardium, subendocardial Purkinje fibres do not display a higher resistance to early global ischaemia. Further investigations of this sensitivity of Purkinje fibres to global ischaemia and certain drugs may bring about new insights into myocardial protection and pharmacotherapy of arrhythmias.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01600240
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  • 7
    Electronic Resource
    Electronic Resource
    Gastric Fundectomy in the Rat: Effects on Mineral and Bone Metabolism, with Emphasis on the Gastrin–Calcitonin–Parathyroid Hormone–Vitamin D Axis (1998)
    Springer
    Calcified tissue international 63 (1998), S. 433-441 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Gastric fundectomy — Hypergastrinemia — Calciotropic hormones — Bone — Mineral homeostasis.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. In humans, gastric surgery results in in osteopenia via mechanisms that are insufficiently understood; surgery-induced changes in the hormonal axes involving the stomach, thyroid, and the parathyroids may play a role. To study this in more detail, we evaluated calcium (Ca), magnesium (Mg), and phosphorus (P) metabolism as well as physical, chemical, and histomorphometric bone parameters in rats rendered hypergastrinemic by fundectomy (FX). In independent experiments, the response to an oral Ca challenge was investigated in intact rats versus FX, and in thyroidectomized versus thyroid-intact FX rats. Sixteen weeks following FX, body weight was approximately 80% that of sham-operated controls. In urine, P excretion was elevated fivefold, the pH was significantly decreased, and cAMP excretion was elevated as compared with controls; serum parathyroid hormone (PTH), calcitonin, 25OHD, Ca, Mg, and P were normal; gastrin and 1,25(OH)2D were elevated. On the basis of bone ash mineral content, FX rats developed significant osteopenia, and histomorphometry indicated only slightly elevated bone turnover and mineralization. Following oral Ca, thyroid-intact FX rats developed hypercalcemia, serum gastrin decreased, and calcitonin increased significantly; in thyroidectomized FX rats, calcitonin remained at baseline levels although there was a similar degree of hypercalcemia; PTH decreased during the hypercalcemic period in both groups. Serum gastrin did not correlate with calcitonin or PTH, and in multivariate regression analysis the only predictor of serum 1,25(OH)2D was urinary phosphorus. It was concluded that in the FX rat (1) osteopenia is not caused by intestinal Ca malabsorption, vitamin D, Ca deficiency, or secondary hyperparathyroidism; (2) osteopenia may be related to PTH-independent urinary hyperexcretion of P, followed by a rise of serum 1,25(OH)2D; (3) the existence of endocrine axes among gastrin, calcitonin, and PTH cannot be substantiated. FX osteopenia appears to be related to gastric acid abolition, and the reactive hypergastrinemia probably stabilizes the mass and turnover of bone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900553
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  • 8
    Electronic Resource
    Electronic Resource
    Postprandial hyperinsulinaemia, insulin resistance and inappropriately high phosphaturia are features of younger males with idiopathic calcium urolithiasis: Attenuation by ascorbic acid supplementation of a test meal (1997)
    Springer
    Urological research 25 (1997), S. 49-58 
    Details
    ISSN: 1434-0879
    Keywords: Idiopathic calcium urolithiasis ; Test meal Hyperinsulinaemia ; Insulin resistance ; Inappropriate phosphaturia ; Ascorbic acid effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In idiopathic recurrent calcium urolithiasis (RCU) the state of insulin and carbohydrate metabolism, and relationships to minerals such as phosphate, are insufficiently understood. Therefore, in two groups of males with RCU (n = 30) and healthy controls (n = 8) the response to an oral carbohydrate- and calcium-rich test meal was studied with respect to glucose, insulin, and C-peptide in peripheral venous blood (taken before and up to 180 min post-load), and phosphate and glucose in fasting and post-load urine. In one RCU group (n = 16) the meal was supplemented with ascorbic acid (ASC; 5 mg/kg body weight). The mean age (RCU 29, RCU + ASC 30, controls 27 years) and mean body mass index [RCU 24.4, RCU + ASC 25.0, controls 24.0 kg/m2] were similar. Insulin resistance (synonymous sensitivity of peripheral organs to insulin) was calculated from insulin serum concentration, as was also integrated insulin, C-peptide, and glucose. Untreated stone patients (RCU) developed hyperinsulinaemia between 60 and 120 min post-load, increased integrated insulin, and insulin resistance (P ≤ 0.05 vs controls)., whereas the rise of C-peptide and glycaemia (absolute and integrated values) was only of borderline significance. Fasting phosphaturia was low in both RCU subgroups vs controls; however, phosphaturia in untreated RCU rose in response to the meal, contrasting sharply with a decrease in controls. ASC supplementation of the meal (in the RCU + ASC subgroup) normalized insulin, failed to normalize postload phosphaturia, but reduced post-load glucosuria and urinary pH significantly (mean pH values 5.55 vs 5.93 in untreated RCU, controls 5.50). Postprandial urinary oxalate, calcium, protein, and supersaturation products were not changed. The postprandial changes in phosphaturia and insulin sensitivity were inversely correlated (n = 38,r = -0.44,P = 0.007). It was concluded that in younger RCU males: (1) postprandial hyperinsulinaemia, the failure to reduce phosphaturia and —within limits — glucosuria, appropriately, as well as poor urine acidification are important features of the metabolism; (2) these phenomena are probably caused by insulin resistance of organs, the kidney included; and (3) the addition of a supraphysiological dose of ASC to a meal, the subsequent abolition of hyperinsulinaemia, and the restoration of normal urine acidification suggest that this antioxidant is capable of counteracting some preexisting basic abnormality of cell metabolism in RCU.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00941906
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  • 9
    Electronic Resource
    Electronic Resource
    Magnesium, citrate, magnesium citrate and magnesium-alkali citrate as modulators of calcium oxalate crystallization in urine: observations in patients with recurrent idiopathic calcium urolithiasis (1999)
    Springer
    Urological research 27 (1999), S. 117-126 
    Details
    ISSN: 1434-0879
    Keywords: Key words Magnesium ; Citrate ; Alkali ; Calcium oxalate crystallization ; Artificial and postprandial urine ; Idiopathic calcium urolithiasis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of magnesium (Mg) and citrate on the metastable limit of calcium oxalate (CaOx) solubility (synonym: tolerable oxalate TO) were examined in artificial urine and in postprandial urine of male patients with idiopathic calcium urolithiasis (ICU). In artificial urine increasing pH, Mg and citrate elevate TO, decrease CaOx supersaturation only marginally, but elevate considerably free citrate; the effect of Mg alone was small in comparison with citrate alone, and the effects of both substances appeared additive. In ICU patients, matched for sex, age and CaOx supersaturation to non-stone-forming controls, TO was decreased (mean values 0.33 vs. 0.52 mM/l in controls, P 〈 0.05). Additional significant (P 〈 0.05) differences were found between ICU and controls: the former exhibited increased CaOx crystal growth, decreased crystal agglomeration time, a more acidic urinary pH, increased concentrations of free calcium and free Mg, and decreased free oxalate and free citrate. After ingestion of a urine-acidifying test meal, or this meal supplemented with either neutral Mg citrate or Mg-alkali citrate, by three groups of male ICU patients, matched for age and CaOx supersaturation, only the last-named preparation evoked an increase in TO and a decrease in crystal diameter, while the normally occurring pH decline from fasting urine was virtually abolished, and the ratios urinary Mg/citrate and calcium/citrate tended towards low values. In contrast, Mg citrate increased crystal agglomeration time, while changes in the other parameters were only insignificant. The crystals formed in urine were CaOx di- and monohydrate (by electron microscopy), and energy dispersive X-ray analysis showed calcium peaks exclusively. However, chemical analysis of crystals verified the presence not only of oxalate and calcium, but also of Mg, phosphate, citrate, and urate; moreover, these crystal constituents seemed to be influenced by Mg citrate and Mg-alkali citrate in different ways. It was concluded that (1) Mg and citrate are effectors of TO in artificial and natural urine; (2) in ICU, low TO and other disturbed CaOx crystallization parameters appear related to the prevailing low urinary pH and low free citrate; (3) Mg-alkali citrate inhibits CaOx crystallization, probably via actions of the citrate, but not the Mg. Because of the eminent role of Mg in human health and ICU, further studies on crystallization after oral intake of Mg in the form of citrate are warranted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002400050097
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  • 10
    Electronic Resource
    Electronic Resource
    Ascorbic acid in idiopathic recurrent calcium urolithiasis in humans – does it have an abettor role in oxalate, and calcium oxalate crystallization? (2000)
    Springer
    Urological research 28 (2000), S. 167-177 
    Details
    ISSN: 1434-0879
    Keywords: Key words Ascorbic acid ; Load studies ; Plasma and urinary oxalate ; Urinary oxalate/glycolate ; Calcium oxalate crystallization ; ASC stability in urine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The role of ascorbic acid (ASC) in the pathophysiology of renal calcium stones is not clear. We evaluated ASC in blood and urine of fasting male patients with idiopathic calcium urolithiasis (ICU) and healthy volunteers. Using smaller subgroups, we also evaluated their response to exogenous ASC [either intravenous or oral ASC (5 mg/kg bodyweight)] administered together with an oxalate-free test meal. The influence of ASC on calcium oxalate crystallization, the morphology of crystals at urinary pH 5, 6 and 7, and the effect of increasing duration of urine incubation on urinary oxalate at these pHs, without and with addition of ASC, were studied too. In normo- and hypercalciuric ICU, blood and urinary ASC from fasting patients remained unchanged, but the slope of the regression line of urinary ASC versus urinary oxalate was steeper than in the controls; the plasma ASC half-life did not differ between controls, normo- and hypercalciuric ICU; the ASC-supplemented meal caused an increase in the integrated plasma oxalate in the normocalciuric subgroup versus controls. In normo- and hypercalciuric ICU urinary oxalate, the oxalate/glycolate ratio, and calcium oxalate supersaturation were increased, but urinary glycolate was unchanged. In the controls, oral ASC did not affect calcium oxalate crystallization, while in ICU, ASC inhibited crystal growth. In control urine calcium oxalate dihydrate and calcium oxalate monohydrate develops, while in ICU urine only the former crystal type develops. In vitro oxalate neoformation from ASC did not occur. It was concluded that (1) under normal conditions an abettor role of ASC for renal stones is not recognizable, (2) in ICU, urinary oxalate excess unrelated to degradation of exogenous ASC is exhibited, and that this is most likely unrelated to an initial increase in oxalate biosynthesis, and (3) ASC appears to modulate directly calcium oxalate crystallization in ICU, although the true mode of action is still not known.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002400000101
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