Untersuchungen zu Dynamik und Sauerstoffverbrauch des isolierten,spontan schlagenden Froschherzens

Zusammenfassung Mit Hilfe einer früher beschriebenen Meßkammer wurde bei 27 isolierten, spontan schlagenden Froschherzen Sauerstoffverbrauch, Schlagvolumen und Frequenz im Zeitraum von 1 Std registriert. In weiteren drei Versuchen wurde das dynamische Verhalten des Herzen im völligen Sauerstoffmangel untersucht. Dabei wurden folgende Ergebnisse gefunden:1. Nach Verbringen in die Meßkammer steigert das isolierte Froschherz bei auxotoner Tätigkeit mit konstanter Ausgangsbelastung spontan sein Schlagvolumen von einem niedrigen Anfangswert auf einen Maximalwert im Bereich von durchschnittlich 250 mm³ (=18 cm Wasser systolischer Druck), der in der folgenden Zeit beibehalten wird und relativ unabhängig von der Größe des Herzens ist.2. Dieser Maximalwert des Schlagvolumens sinkt bei zunehmendem Sauerstoffmangel infolge Verbrauchs aus einer anfänglich sauerstoffgesättigten Nährlösung nur sehr verzögert und langsam ab. Er beträgt nach 40–60 min bei einem Sauerstoffverbrauch von annähernd Null durchschnittlich noch 86% seiner Maximalhöhe.3. Die anfängliche Steigerung des Schlagvolumens tritt auch bei von vornherein bestehendem totalen Sauerstoffmangel ein. In diesem Fall sinkt das Schlagvolumen bald nach Erreichen des Maximalwerts langsam wieder ab. Die Frequenz liegt von Anfang an um ungefähr 30% tiefer und sinkt rascher ab. Das Minutenvolumen weist gegenüber den Versuchen mit Sauerstoffsättigung entsprechend niedrigere Werte auf.Die seit langem bekannte relative Sauerstoffunabhängigkeit des Froschherzens wird durch diese Versuche erneut bestätigt und für das spontan schlagende Herz präzisiert. Es wird gefolgert, daß diese relative Unabhängigkeit die quantitative Bestimmung des Sauerstoffverbrauchs methodisch erschwert. Die dabei möglichen Fehlerquellen und ihre Berücksichtigung werden diskutiert.Mit 3 TextabbildungenMit Hilfe der Deutschen Forschungsgemeinschaft durchgeführt.     

Impaired sodium excretion, decreased glomerular filtration rate and elevated blood pressure in endothelin receptor type B deficient rats

The renal endothelin (ET) system, particularly the ET type B receptor, has been implicated in the regulation of sodium excretion and glomerular filtration rate (GFR). We analyzed kidney morphology and function in a rat strain characterized by complete absence of a functional ETB receptor. Due to Hirschsprung's disease limiting lifetime in these rats, studies were performed in 23-day-old rats. Kidney size and morphology (glomerular and interstitial matrix content, glomerular size and cell density and intrarenal vascular morphology) were normal in ETB-deficient rats. There were also no evidence of altered kidney cell cycle regulation in these rats. GFR was significantly lower, by 72% (P<0.001), in homozygous ETB-deficient rats than in wild-type rats. Fractional sodium excretion was likewise markedly reduced by 84% in homozygous ETB-deficient rats (P<0.001 versus wild-type rats). Treatment with the specific epithelial sodium channel blocker amiloride led to a much higher increase in fractional sodium excretion in ETB-deficient rats (934.2+/-73% in ETB-deficient rats versus 297+/-20% in wild-type rats, expressed as percentage of corresponding placebo treated control; P<0.001). Mean arterial blood pressure was elevated by 7.9 mmHg in homozygous ETB-deficient rats (P<0.05 versus wild-type rats). Our study demonstrates that ETB-deficiency causes early onset kidney dysfunction characterized by a markedly reduced sodium excretion, decreased GFR, and slightly elevated blood pressure. The complete absence of the ETB receptor causes in the kidney--in contrast to the colon--a functional rather than a developmental, neural crest cell dependent disease, since kidney morphology was normal in ETB-deficient rats. The much higher increase in the fractional sodium excretion in ETB-deficient rats after pharmacological blockade of the epithelial sodium channel indicates that the decreased fractional sodium excretion in ETB-deficient rats is most probably due to a lack of the inhibitory property of the ETB receptor on the epithelial sodium channel activity.     

Central nervous system inflammatory response after cerebral infarction as detected by magnetic resonance imaging

Brain inflammation contributes to the tissue injury caused by ischemic stroke. Macrophages as the most abundant inflammatory cell population in stroke lesions can be visualized using ultrasmall superparamagnetic iron oxide (USPIO) as a cell-specific contrast agent for magnetic resonance imaging (MRI). The aim of our present study was to delineate the inflammatory response during experimental cerebral infarction by means of USPIO-enhanced MRI and to correlate the spatial distribution of USPIO-induced MR signal alterations with cellular infiltration and iron deposition. To this end USPIOs were administered to Wistar rats 5 days after photothrombotic cerebral infarction. MR imaging at 7 T performed 24 h later displayed a rim-like signal loss around the infarction in the USPIO treated animals. On histological brain sections obtained from the same animals after MRI the distribution of iron and ED1+ phagocytes was in full spatial agreement with the signal loss seen on T2*-weighted images. Our study validates USPIO-enhanced MRI as an important tool for the noninvasive visualization of brain inflammation in stroke and other CNS pathologies.     

CXCR4-transgene expression significantly improves marrow engraftment of cultured hematopoietic stem cells

Hematopoietic stem cells (HSCs) lose marrow reconstitution potential during ex vivo culture. HSC migration to stromal cell-derived factor (SDF)-1 (CXCL12) correlates with CXC chemokine receptor 4 (CXCR4) expression and marrow engraftment. We demonstrate that mobilized human CD34+ peripheral blood stem cells (CD34+ PBSCs) lose CXCR4 expression during prolonged culture. We transduced CD34+ PBSCs with retrovirus vector encoding human CXCR4 and achieved 18-fold more CXCR4 expression in over 87% of CD34+ cells. CXCR4-transduced cells yielded increased calcium flux and up to a 10-fold increase in migration to SDF-1. Six-day cultured CXCR4-transduced cells demonstrated significant engraftment in nonobese diabetic/severe combined immunodeficient mice under conditions in which control transduced cells resulted in low or no engraftment. We conclude that transduction-mediated overexpression of CXCR4 significantly improves marrow engraftment of cultured PBSCs.     

The water jet as a new tool for endoprosthesis revision surgery--an in vitro study on human bone and bone cement

In revision surgeries of endoprostheses, the interface between implant and bone cement or bone must be loosened. Conventional tools have many disadvantages because of their size and limited range. Taking advantage of the selective and athermic cutting process, a plain water jet is already used in order to cut soft tissues. This study investigates the possibilities of both a plain and an abrasive water jet as cutting tools for revision surgery. Samples of the mid-diaphysis of human femora and bone cement (CMW3) were cut with a plain water jet (PWJ) and an abrasive water jet (AWJ) at two different jet-to-surface angles (30 degrees,90 degrees ) and at five different pressure levels (30, 40, 50, 60, 70 MPa). For a PWJ a selective pressure range was identified, where only bone cement was cut. Injecting a bio-compatible abrasive (lactose) to the jet stream resulted in significantly higher cut depths in both materials. Material removal in bone was significantly less at the smaller jet-to-surface angle for both techniques. No clear selectivity between bone and bone cement was observed for application of the AWJ. However, the material removal rate was significantly higher for bone cement than for bone at all pressure levels. The results indicate that an AWJ might be an alternative tool for cement removal. The possibility for localised cutting at interfaces could be an advantage for revision of a non-cemented prosthesis.     

Skill needs for nurses in their role as health informatics professionals: a survey in the context of global health informatics education

In the process of developing global health informatics education, a common understanding of educational outcomes is required. Therefore, an educational framework for health informatics professionals is desirable to support student mobility, trans-national and borderless education. Nurses form a significant part of the health workforce and need to be properly educated for their roles in health informatics. To ascertain their perceptions of needs and priorities, we developed a web-based questionnaire and surveyed Australian nurses on the preferred knowledge/skills set for health informatics professionals. Among others, the questionnaire is based on the International Medical Informatics Association's (IMIA) set of recommendations on education and IMIA's scientific map. Benner's five levels of competencies were applied to measure the degree of competency required for each skill/knowledge. Altogether, 82 Australian nurses completed the questionnaire. The nurses' perceived degree of competency required for a total of 74 specific skills and knowledge in five skill categories is presented in this paper as well as the overall results for each of the five categories. Further, significant differences between the nurses' primary roles and primary interest in health informatics are discussed. The development of a comprehensive health informatics education framework needs to take into account nurses as well as other health professionals. Repeating the survey in other countries and for various professions is essential to develop an international educational framework.     

Human acute pancreatitis: Its pathogenesis in the light of immunocytochemical and ultrastructural findings in acinar cells

Summary Human acute pancreatitis results from an autodigestive process frequently associated with alcohol abuse, gall stone disease and shock. Peripancreatic fat necrosis was identified as one of the earliest visible lesions, whereas acinar cell necrosis and haemorrhage were regarded as secondary changes. To examine the alterations in acinar cells in more detail, their enzyme content and fine structural features were studied immunocytochemically using antisera against -amylase, lipase, trypsin, chymotrypsin and pancreatic stone protein, and electronmicroscopically in pancreatic tissues from patients with severe acute pancreatitis. Peripheral acinar cells in the immediate vicinity of fat necrosis were found to be heavily degranulated, while acinar cells at some distance of necrosis fully retained their enzyme content. Other frequent changes of the acinar cells included cuboidal transformation, loss of microvilli, increased occurrence of autophagosomes, and formation of enlarged acinar lumina. As there was no apparent cell membrane leakage or rupture of duct lumina, it is concluded that the acinar cells adjacent to fat necrosis release their granules by undirected basolateral extrusion. The findings thus suggest that one of the basic defects in acute pancreatitis is the uncontrolled release of enzymes from peripheral acinar cells into the interstitial space which, in turn, presumably by the action of lipase, leads to autodigestive fat necrosis.Dedicated to Prof. Dr. G. Seifert on the occasion of his 65th birthdayPresented in part at the Second International Symposium on the Classification of Pancreatitis, Marseille, 1984, and at the Meeting of the European Pancreatic Club, Manchester, 1985     

Impaired Ca-signaling in astrocytes from the Ts16 mouse model of Down syndrome

The trisomy 16 mouse model of Down syndrome has been used to compare calcium (Ca)-homeostasis and Ca-signaling in astrocytes from trisomic mice and from diploid littermates. Ratio calcium-imaging of Fura-2/AM loaded primary astroglial cultures prepared from the hippocampus shows that resting Ca levels are on average significantly higher in trisomic than in the control astrocytes (280 vs. 120 nM). Serotonin (3 μM) and glutamate (30–300 μM) evoked transient Ca-increases from 400 to 600 nM in euploid but from only 20 to 150 nM in trisomic astrocytes. Imaging of ATP-driven Ca-accumulation in cellular organelles revealed a significantly stronger uptake of Ca in trisomic astrocytes that might buffer cytosolic Ca-increases. Our results demonstrate major disturbances in Ca-signaling in trisomic astrocytes that are likely to be of pathophysiological relevance.     

Factors influencing active avoidance behavior in rats with ventromedial hypothalamic lesions

Ventromedial hypothalamic lesioned rats maintained at preoperative body weight received an equal number of shocks while emitting significantly fewer responses than controls in a lever-pressing free-operant avoidance paradigm, and performed as well as unoperated animals in lever-pressing and shuttle box (both 1- and 2-way) discriminated avoidance tasks. The failure of VMH lesions to facilitate performance in the 2-way avoidance paradigm was probably the result of a ceiling effect. With the exception of the simple one-way avoidance task, obese lesioned rats were markedly impaired in the acquisition of all active avoidance behavior, but escape behavior was not affected. When tested in a free-operant paradigm, the avoidance performance of well trained lesioned animals varied inversely with body weight. As obese rats displayed lower flinch thresholds to shock than controls and similar levels of activity and responding as lean lesioned animals, it was concluded that their impaired avoidance behavior was not due to changes in sensitivity or mobility. The possible relation to other VMH lesion- and/or obesity-induced deficits is discussed.