iMPI: portable human-sized magnetic particle imaging scanner for real-time endovascular interventions

Minimally invasive endovascular interventions have become an important tool for the treatment of cardiovascular diseases such as ischemic heart disease, peripheral artery disease, and stroke. X-ray fluoroscopy and digital subtraction angiography are used to precisely guide these procedures, but they are associated with radiation exposure for patients and clinical staff. Magnetic Particle Imaging (MPI) is an emerging imaging technology using time-varying magnetic fields combined with magnetic nanoparticle tracers for fast and highly sensitive imaging. In recent years, basic experiments have shown that MPI has great potential for cardiovascular applications. However, commercially available MPI scanners were too large and expensive and had a small field of view (FOV) designed for rodents, which limited further translational research. The first human-sized MPI scanner designed specifically for brain imaging showed promising results but had limitations in gradient strength, acquisition time and portability. Here, we present a portable interventional MPI (iMPI) system dedicated for real-time endovascular interventions free of ionizing radiation. It uses a novel field generator approach with a very large FOV and an application-oriented open design enabling hybrid approaches with conventional X-ray-based angiography. The feasibility of a real-time iMPI-guided percutaneous transluminal angioplasty (PTA) is shown in a realistic dynamic human-sized leg model.

TIP - Training of Intensive medical support in the case of a Pandemic

The COVID-19 pandemic has led to a short-term sharp increase in the demand for auxiliary staff in emergency rooms and intensive care units. Against this background student tutors of the Medical Faculty Erlangen have developed a training concept. The aim was to familiarize students in the clinical section quickly and effectively with skills that are particularly important in a clinical assignment as (student) assistant in the care of corona patients (e.g.: personal protective equipment, intubation assistance, arterial blood collection, assessment of blood gas values and ventilation parameters). In a blended learning concept, learning materials were prepared in advance and then implemented and deepened in a presence phase. The selection of learning materials and the low supervision ratio (1:2) made it possible to realize an internally differentiated approach. The offer met with great interest among students of all clinical semesters and was evaluated very positively. The skills learned can be applied widely even independently of a pandemic.

[Obstructive sleep apnea syndrome in the setting of Gorlin-Goltz syndrome]

Goltz-Gorlin syndrome is a rare autosomal dominant hereditary disease associated with a high rate of spontaneous mutation. Diagnosis is based on clinically defined major and minor criteria. The disease is caused by a gene mutation locating to chromosome 9q22-31. We report on a young Goltz-Gorlin syndrome patient with obstructive sleep apnea syndrome. Due to intolerance to continuous positive airway pressure (CPAP) therapy and in order to avoid a tracheotomy, we opted for an alternative therapy comprising interdisciplinary multi-level surgery.

Combining quantitative trait loci and heterogeneous microarray data analyses reveals putative candidate pathways affecting mastitis in cattle

Mastitis is a frequent disease and considerable problem for the global dairy industry. Identification of solutions leading to the development of new control strategies is therefore of high importance. In this study, we have integrated genomic data from genome-wide association mapping in cattle with transcriptomic data from microarray studies of several mastitis pathogens and host species in vitro and in vivo. To identify significant candidate pathways directly and indirectly involved in the immune response to mastitis, ingenuity pathway analysis (ipa) and database for annotation, visualization and integrated discovery bioinformatic (david) were applied. Several candidate pathways were found. Of great interest are IL-17 and IL-8 signalling pathways, responsible for the recruitment and migration of inflammatory cells into tissue during inflammation and infection. These results may emphasize further functional studies for identification of factors contributing to resistance to mastitis pathogens in cattle.

Host-response patterns of intramammary infections in dairy cows

Many different bacterial species have the ability to cause an infection of the bovine mammary gland and the host response to these infections is what we recognize as mastitis. In this review we evaluate the pathogen specific response to the three main bacterial species causing bovine mastitis: Escherichia coli, Streptococcus uberis and Staphylococcus aureus. In this paper we will review the bacterial growth patterns, host immune response and clinical response that results from the intramammary infections. Clear differences in bacterial growth pattern are shown between bacterial species. The dominant pattern in E. coli infections is a short duration high bacteria count infection, in S. aureus this is more commonly a persistent infection with relative low bacteria counts and in S. uberis a long duration high bacteria count infection is often observed. The host immune response differs significantly depending on the invading bacterial species. The underlying reasons for the differences and the resulting host response are described. Finally we discuss the clinical response pattern for each of the three bacterial species. The largest contrast is between E. coli and S. aureus where a larger proportion of E. coli infections cause potentially severe clinical symptoms, whereas the majority of S. aureus infections go clinically unnoticed. The relevance of fully understanding the bovine host response to intramammary infection is discussed, some major gaps in our knowledge are highlighted and directions for future research are indicated.

Cyclin H is targeted to the nucleus by C-terminal nuclear localization sequences

Cdk-activating kinase (CAK) is a trimeric complex consisting of cdk7, cyclin H, and MAT1, which activates the cell-cycle-regulating cdks through T loop phosphorylation. In addition, other substrates of the CAK complex have been identified when CAK is assembled with the TFIIH core proteins, thereby regulating transcription and nucleotide excision repair. Little is known about the regulation of the CAK complex through cyclin H. In this study we further analyzed cyclin H regulation and identified two basic clusters in the C terminus of the protein as putative nuclear localization sequences (NLSs). Fusion constructs of full-length and truncated cyclin H sequences demonstrated the functionality of the NLSs. A peptide-binding assay revealed that at least one NLS interacts with the nuclear import receptors importin alpha/beta. Phosphorylation in the vicinity of the NLSs by cyclin C/cdk8 or protein kinase CK2, however, does not influence the nuclear translocation of cyclin H.

Specific localization of the catalytic subunits of protein kinase CK2 at the centrosomes

The protein kinase CK2 holoenzyme is composed of two regulatory beta subunits and two catalytic alpha or alpha' subunits. Although experimental evidence for involvement of the enzyme in the regulation of cell proliferation is accumulating, the exact mechanism of its action is still unclear. The subcellular localization of the enzyme may be a key to its function. We have recently shown that the CK2 holoenzyme is tightly associated with the Golgi complex and the endoplasmic reticulum. Centrosomes, which organize spindle formation during the cell cycle and microtubule cytoskeleton formation and, thereby, the location and orientation of different organelles in the cell, are in close vicinity to the Golgi complex. Because several kinases and phosphatases have been described to regulate the functions of the centrosome, we analysed the association of CK2 with these organelles. Using biochemical cell fractionation and coimmunoprecipitation, we never found the holoenzyme but only the catalytic alpha subunits associated with the centrosome. These data were confirmed by immunoelectron microscopy. Thus, the present data point to a particular role of the catalytic alpha and alpha' subunit of protein kinase CK2, which may be different from their roles in the holoenzyme.

Use of Relibase for retrieving complex three-dimensional interaction patterns including crystallographic packing effects

Relibase is a database system that has been specially designed to handle protein-ligand data. Included within Relibase is a tool that can be used to systematically analyse protein-ligand interaction patterns specified by three-dimensional (3D) constraints, revealing favorable combinations of interacting functional groups and their preferred interaction geometries. This paper describes the Relibase 3D query tools, including novel extensions (Relibase+) for handling crystallographic packing effects. Examples illustrating the broad range of functionality for defining 3D interaction patterns and the application of such queries in drug design comprise carbonyl-carbonyl interactions, zinc binding site environments, and ligand-ligand interactions in the crystal packing.

Contractile function of rat myocardium is less susceptible to hypoxia/reoxygenation after acute infarction

In this study we tested the hypothesis that induction of heat shock proteins (HSPs) and antioxidant enzymes is a compensatory mechanism, which preserves the contractility of the surviving myocardium after acute myocardial infarction. For this purpose, mechanical function of isolated rat papillary muscles was tested 15 h after experimental myocardial infarction and sham operation, respectively. Contractility of the preparations was compared to the expression of HSP25, HSP72, and glutathione peroxidase activity (GSH-Px) at normoxia and during hypoxia/reoxygenation. At normoxic conditions, rates of isometric contraction and, in particular, of relaxation were significantly higher after acute myocardial infarction than after sham operation. Improved relaxation rates were reflected in 2- to 3-fold higher heat shock protein levels in papillary muscles from rats with myocardial infarction compared to sham operated animals. During hypoxia/reoxygenation, the rates of contraction and relaxation were better preserved after myocardial infarction than after sham surgery. Recovery of relaxation rates during reoxygenation was associated with increased HSP25 levels and enhanced GSH-Px activity after myocardial infarction. In conclusion, heat shock proteins exert a beneficial effect on cardiac muscle relaxation after acute myocardial infarction. Enhanced heat shock protein expression and GSH-Px activity may protect the contractile function of the surviving myocardium against the damaging influence of hypoxia/reoxygenation during the early post-infarct period.

Localization of individual subunits of protein kinase CK2 to the endoplasmic reticulum and to the Golgi apparatus

The protein kinase CK2 is composed of two catalytic alpha- or alpha'- and two regulatory beta-subunits. In mammalian cells there is ample evidence for the presence of individual CK2 subunits beside the holoenzyme. By immunofluorescence studies using peptide antibodies which allow us to detect the CK2alpha-, alpha'- and beta-subunits we found all three subunits to be co-localized with a 58 KDa Golgi protein which is specific for the Golgi complex. Subfractionation studies using dog pancreas cells revealed the presence of all three subunits of CK2 at the smooth endoplasmic reticulum (sER)/Golgi fraction whereas the rough endoplasmic reticulum (rER) harboured only the catalytic alpha- and alpha'-subunits. We found that the microsomal preparation from dog pancreas cells contained CK2 which phosphorylated a CK2 specific synthetic peptide and which was heparin sensitive. Furthermore, we could immunoprecipitate the CK2alpha-subunit that exhibited a kinase activity which phosphorylated a CK2 specific substrate and which was heparin sensitive. Protease digestion experiments revealed that the CK2 subunits were located on the cytosolic side of the rER and the sER/Golgi complex. Thus, we could demonstrate an asymmetric distribution of the CK2 subunits at the rER and sER/Golgi complex. Since the CK2alpha- and alpha'-subunits exhibit a substrate specificity which is different from the CK2 holoenzyme one might speculate that the asymmetric distribution of the CK2 holoenzyme and the CK2 catalytic subunits may have regulatory functions.

Quadruple pads approach for external cardioversion of atrial fibrillation

This study examined the alternative of transthoracic quadruple pads shock delivery of two simultaneous 360-J shocks to convert refractory AF in patients failing standard external cardioversion. Forty-six patients (mean age 58 +/- 11 years, 23 men) with chronic AF (duration 14 +/- 17 months, range 1-60 months) were included. The left atrial diameter was 47 +/- 7 mm. The left ventricular ejection fraction was 59 +/- 11%. Antiarrhythmic drugs had failed to convert 44 (96%) of these patients. All patients underwent conventional external transthoracic cardioversion with pads applied in the antero-apical position using energy settings of 200 and 360 J, consecutively. In all patients who failed conventional cardioversion, quadruple pads were applied. Quadruple pads consisted of four pads, two in the antero-posterior position and two in a second apex-posterior position. Standard cardioversion to sinus rhythm was successful in 19 (41%) patients after use of a single 200-J shock and an additional 8 (17%) after a single 360-J shock. The total success rate was 58% after conventional cardioversion. The quadruple pads were successful in 14 (74%) of the remaining 19 patients. Four of the five patients who failed the quadruple pads approach subsequently also failed internal cardioversion. Thus, the cardioversion success rate was increased from 48% using the conventional approach to 89% using the quadruple pads approach. Quadruple pads external cardioversion is highly effective in converting chronic AF refractory to standard shock protocols to sinus rhythm. Moreover, the failure of the quadruple pads approach seems to predict poor response to internal cardioversion.

Myocardial adrenergic dysfunction in rats with transgenic, human renin-dependent hypertension

OBJECTIVES

We investigated cardiac function in rats transgenic for the human renin and angiotensinogen genes (TGR) to test the hypothesis that elevated local angiotensin II precipitates adrenergic dysfunction and abnormal contractile function.

METHODS

Hearts from TGR and Sprague-Dawley control rats, aged 6 weeks, were studied using the Langendorff model and papillary muscle preparations (n = 6-10 per group). Incremental isoproterenol (1 - 1000 nmol/l) and external Ca2+-concentrations (0.75-6.0 mmol/l) were tested. Cardiac protein and mRNA expression levels were determined by Western blot and RNAase protection assay.

RESULTS

TGR rats showed left ventricular hypertrophy (54%), higher blood pressures (76 mmHg), and elevated plasma renin activity (seven-fold) compared to controls (P < 0.01). The effect of isoproterenol on TGR rat systolic and diastolic left ventricular performance was decreased in both in-vitro models compared to controls (two- to threefold, P < 0.01). TGR rat papillary muscles showed impaired force generation with abnormal basal and Ca2+-dependent relaxation. Gialpha2 and Gialpha3 protein levels were increased (20-30%) and SERCA2a and adenylyl cyclase protein levels were decreased (23 and 37%, respectively) in TGR hearts compared to controls, while Gsalpha or beta1 and beta2-receptor levels were unchanged. Cardiac angiotensin converting enzyme and atrial natriuretic peptide mRNA levels were increased more than four-fold in TGR with no differences for the angiotensin type1 receptor, beta1-receptor, SERCA2a, phospholamban, adenylyl cyclase V and angiotensinogen genes.

CONCLUSIONS

TGR rat hearts develop severe adrenergic dysfunction with decreased adenylyl cyclase and abnormal intracellular Ca2+-homeostasis. Our findings emphasize angiotensin II as a major risk factor promoting early functional decline in cardiac hypertrophy. The data may have implications for patients with activating polymorphisms of the renin-angiotensin system and support the need for an early therapeutic intervention.

Mechanically induced potentials in rat atrial fibroblasts depend on actin and tubulin polymerisation

When atrial tissue contracts, mechanically induced potentials (MIPs) are generated in fibroblasts, presumably by activation of a non-selective cation conductance Gns. Non-stimulated atrial fibroblasts had a mean (+/-SD) membrane potential (Em) of -22 +/- 2 mV and an input resistance of 510 +/- 10 MS. MIP amplitude (AMIP) was 38+/-4 mV when current injection had polarised Em to Vm = -50 mV. The slope of the function relating AMIP to Vm can be regarded as a mechanosensitive factor (Xms) that describes the relative increase in Gns during a MIP. Putative involvement of cytoskeletal fibres in activation of Gns was studied by delivering drugs from the intracellular recording microelectrode. Destabilisation of F-actin by 0.2 mM cytochalasin D reduced AMIP from 38 to 16 mV and Xms from 5 to 1.8. Destabilisation of tubulin with 0.2 mM colchicine reduced AMIP to 21 mV and Xms to 2.1. The combination colchicine plus cytochalasin D reduced AMIP to 9 mV and Xms to 1.4. Promoting F-actin stability with exogenous adenosine 5'-triphosphate (ATP) increased AMIP and Xms and attenuated the effects of cytochalasin D. Similarly, facilitation of tubulin stability with guanosine 5'-triphosphate (GTP) or taxol increased AMIP and Xms and attenuated the effects of colchicine. The results suggest that transfer of mechanical energy from the deformed fibroblast surface to the Gns channel protein depends on intact F-actin and tubulin fibres.

Combined treatment with ramipril and metoprolol prevents changes in the creatine kinase isoenzyme system and improves hemodynamic function in rat hearts after myocardial infarction

Beneficial effects of monotherapy with ACE inhibitors or beta-blockers on hemodynamic function after myocardial infarction are well known. Until now, the effects of combined treatment on cardiac function and energy metabolism have been poorly described. This study examines the effects of combined ramipril and metoprolol treatment on the creatine kinase (CK) system and hemodynamic function in rats after infarction. Wistar rats with experimental infarction were randomized for treatment with ramipril (R), metoprolol (M), combined treatment (MR), or placebo (P). Sham-operated (SO) animals served as controls. After 6 weeks, we assayed for CK isoenzymes and performed hemodynamic measurements. In P versus SO, left ventricular systolic pressures (dp/dt(max) and dp/dt(min)) diminished, whereas left ventricular end-diastolic pressure (LVEDP) increased. Decreased total CK activity and mitochondrial CK isoenzyme, increased CK-MB, and increased CK-BB isoenzymes were measured in P versus SO. With infarct size < or =45%, mitochondrial CK increased in M and R versus P. Combined treatment had an additional enhancing effect on mitochondrial CK isoenzyme level versus M and R, decreased LVEDP versus P, as well as increased dp/dt(max) and dp/dt(min) versus R. These results provide evidence of an interaction between normalization of energy metabolism and improvement in cardiac function due to a combination of ACE inhibition and beta blockade after myocardial infarction.

Myocardial contractility after infarction and carnitine palmitoyltransferase I inhibition in rats

Inhibition of carnitine palmitoyltransferase I with etomoxir increases sarcoplasmic reticulum Ca(2+)-transport and V(1) isomyosin expression. To test whether etomoxir attenuates contractile dysfunction after myocardial infarction, we compared the contractility of papillary muscles from etomoxir- and placebo-treated rats 6 weeks after infarction. Etomoxir induced cardiac hypertrophy in animals with small infarctions, and enhanced compensatory heart growth at large infarct size. Contractile function of papillary muscles from etomoxir-treated rats was improved particularly in animals with small infarctions. Thus, induction of mild cardiac hypertrophy by etomoxir in rats with small infarctions may be beneficial for myocardial performance.

Oxygen radical system in chronic infarcted rat heart: the effect of combined beta blockade and ACE inhibition

In vitro experiments suggest that beta blockade and angiotensin-converting enzyme (ACE) inhibition may protect the failing heart by reduction of myocardial oxidative stress. To test this hypothesis in an in vivo model, the beta blocker metoprolol (350 mg) and the ACE inhibitor ramipril (1 mg) were given either alone or in combination to rats (per kilogram body weight per day) for 6 weeks after myocardial infarction. Left ventricular end-diastolic pressure (LVEDP), contractile function of papillary muscles, enzymatic antioxidative defense (indicated by the activities of the superoxide dismutase isoenzymes and glutathione peroxidase), and the extent of lipid peroxidation were studied. Placebo-treated rats showed cardiac hypertrophy, increased LVEDP, lower rates of contraction and relaxation, as well as a deficit in the myocardial antioxidative defense associated with increased lipid peroxide levels, when compared with sham-operated animals. Combined beta blockade and ACE inhibition improved the antioxidative defense, reduced hypertrophy and LVEDP, and enhanced rates of contraction. Thus prolonged beta blockade and ACE inhibition after infarction may decrease myocardial oxidative stress and thereby could be beneficial in heart failure.

Mechano-electric feedback in right atrium after left ventricular infarction in rats

Left ventricular myocardial infarction (MI) can lead to alterations in hemodynamic load conditions, thereby inducing right atrial hypertrophy and dilatation associated with phenotypic modulation of cardiomyocytes, electrical abnormalities, rhythm disturbances, and atrial fibrillation. However, there is limited information on the electrophysiological basis for these events. We investigated whether atrial stretch in the setting of chronic MI modulates the electrophysiological properties of cardiomyocytes via "mechano-electric feedback", providing a mechanism for atrial arrhythmia after ventricular infarction. Five weeks after left ventricular MI (n=37), action potentials (AP) were measured in right atrial tissue preparations using a current clamp scheme, and compared to sham-operated rats (SO, n=10). Contractile activity was recorded at a preload of 1 mN, and sustained stretch was applied via a micrometer. In SO, stretch of 1.75 mN shortened repolarization at 50% and prolonged it at 90%. In MI, mechanically-induced electrical alterations were observed at a significantly lower level of stretch than in SO (0.19 mN). Sustained stretch in MI prolonged AP at 90% repolarization giving rise to stretch-activated depolarizations (SAD) near 90% repolarization (SAD90). When reaching threshold for premature APs, electrical phenomena similar to atrial fibrillations were seen in some preparations. Moreover, we observed APs with prolonged duration at 25%, 50%, and 90% repolarization where stretch induced SAD near 50%. Gadolinium used at a concentration to inhibit stretch-activated channels (40microM) suppressed mechanically-induced electrical events. In conclusion, increased susceptibility after MI to mechanical stretch may predispose atrial cardiomyocytes to arrhythmia. These mechano-electrical alterations are sensitive to gadolinium suggesting involvement of stretch-activated ion channels.

Effects of metoprolol and ramipril on action potentials after myocardial infarction in rats

The effects of chronic treatment with the beta-adrenoceptor antagonist metoprolol, the angiotensin converting enzyme inhibitor ramipril, their combination, or placebo on action potential configuration 6 weeks after myocardial infarction in rats were studied. Action potentials were measured in isolated left ventricular posterior papillary muscles and compared with action potentials from a sham operated group without infarction. After infarction, the action potential amplitude was reduced and this phenomenon was partially reversed by metoprolol- and ramipril-treatment. Prolonged repolarisation after infarction compared to sham operated animals was additionally delayed after metoprolol treatment. Thus, metoprolol extends the refractory period, which may counteract tachyarrhythmia.

Mechanoelectric feedback after left ventricular infarction in rats

BACKGROUND

Myocardial infarction can lead to electrical abnormalities and rhythm disturbances. However, there is limited data on the electrophysiological basis for these events. Since regional contraction abnormalities feature prominently in infarction, we investigated whether stretch of myocardium from the infarction borderzone can modulate the electrophysiological properties of cardiomyocytes via mechanoelectric feedback providing a mechanism for post-infarction arrhythmia.

METHODS

Five weeks after experimental myocardial infarction (MI) in rats due to ligation of the left coronary artery (n = 26) or after sham operation (SO, n = 16), action potentials (AP) were measured in left ventricular preparations from the infarction borderzone. Sustained stretch was applied via a micrometer.

RESULTS

Preparations from MI generated spontaneous electrical and contractile activity. Cardiomyocytes from MI had a comparable AP amplitude, a more negative resting membrane potential, and a prolonged AP duration (APD) when compared to SO. In SO, stretch of 150 microns increased the APD90. This was associated with stretch activated depolarizations near APD90 (SAD-90). In MI, significantly lower stretch, of only 20 microns, elicited SAD-90s, or SADs near APD50 (SAD-50). Stretch-induced events were suppressed by gadolinium, at a concentration (40 microM) normally used to inhibit stretch-activated channels.

CONCLUSION

After MI, SADs are generated in the infarction borderzone at lower degrees of stretch. Increased sensitivity of the membrane potential of cardiac myocytes to mechanical stimuli may contribute to the high risk of arrhythmia after infarction. These SADs may involve the opening of stretch-activated channels.

Thalidomide inhibits angiogenesis in embryoid bodies by the generation of hydroxyl radicals

Thalidomide is a teratogen with anti-angiogenic properties and causes stunted limb growth (dysmelia) during human embryogenesis. The molecular mechanisms of thalidomide action in embryopathy are currently unknown. Using the endothelial-specific antigen platelet endothelial cell adhesion molecule-1 and confocal laser scanning microscopy we have demonstrated that thalidomide exerts anti-angiogenic effects on the development of capillary structures in embryoid bodies differentiated from murine embryonic stem cells. Consequently, in thalidomide-treated embryoid bodies the diffusion properties of the tissue were deteriorated. Thalidomide raised reactive oxygen species (ROS), as revealed using 2'7'-dichlorodihydrofluorescein diacetate (H(2)DCF-DA) as an indicator. A comparable ROS generation was achieved with the thalidomide hydrolysis product phthaloyl glutamic acid (PGA), but not with phthalimide (PI), the major component of thalidomide. ROS formation by thalidomide was inhibited by the hydroxyl radical scavengers mannitol and 2-mercaptoethanol. After coadministration of either 2-mercaptoethanol or mannitol with thalidomide the anti-angiogenic effects of thalidomide were abolished and the diffusion properties of the tissue were restored to the control values. In summary, our data suggest that thalidomide exerts its anti-angiogenic properties via the generation of toxic hydroxyl radicals, which impair vasculogenesis and angiogenesis during embryoid body development.

Mechanically induced potentials in fibroblasts from human right atrium

It has been shown that cardiac fibroblasts of the human heart are electrically non-excitable and mechanosensitive. The resting membrane potential of these cells is -15.9+/-2.1 mV and the membrane resistance is 4.1+/-0.1 G[Omega]. Rhythmic contractions of the myocardium associated with stretch of the surrounding tissue produce reversible changes in the membrane potential of cardiac fibroblasts. These mechanically induced potentials (MIPs) follow the rhythm of myocardial contractions. Simultaneous recording of the action potential of cardiomyocytes and MIPs of cardiac fibroblasts demonstrates a delay of 40.0+/-0.4 ms after the action potential before the appearance of the MIP. Contraction produces a MIP which is more positive or more negative than the reversal potential - the membrane potential due to current injection at which the MIP reverses its direction. Regardless of the initial orientation of the MIP, intracellular polarization increases the amplitude towards the reversal potential if the background MIP had depolarized the membrane or away from the reversal potential if the initial background MIP had hyperpolarized the membrane. Artificial intracellular polarization changed the amplitude but not the frequency of the MIP. The pool of electrically non-excitable mechanosensitive cells, which change their electrical activity during contraction and relaxation of the heart, may play a role in the mechano-electrical feedback mechanism which has to be taken into account in the normal function of the heart as well as in pathological processes.

Decreased susceptibility of contractile function to hypoxia/reoxygenation in chronic infarcted rat hearts

Cardiac hypertrophy is associated with modifications in Ca2+ transport processes, enzymes of energy metabolism and antioxidant capacity. It is unknown whether these changes occur in infarct-induced hypertrophy with regard to an altered susceptibility to ischemia/reperfusion injury. We examined changes in sarcoplasmic reticulum (SR) Ca2+ transport, creatine kinase (CK) system, and the antioxidant enzymes glutathionperoxidase (GSH-Px) and superoxide dismutase (SOD) in rats 6 weeks after infarction due to coronary ligation (MI). Phenotypic modifications v sham operation (SHAM) were related to the contractile response of hypertrophied papillary muscle to hypoxia/reoxygenation for 30 min each. Under aerobic conditions we observed in MI v SHAM: decreases in isometric contraction and relaxation rate, a reduced Vmax-equivalent of sarcomeric shortening, a faster twitch-to-twitch decay of post-rest potentiation (PRC) which correlated closely to the decrease in SR Ca2+ uptake (-25%), a decrease in CK activity (-20%), reduced CK-MI and CK-MM, increased CK-MB and CK-BB, and enhanced activities of SOD (40%) and GSH-Px (50%). During hypoxia, an initial increase in peak force (PF) was followed by a slower PF decline in MI v SHAM. Reoxygenation caused a recovery of PF to approximately 30% in both groups; rates of contraction and relaxation recovered better in MI. In SHAM but not MI, twitch-to-twitch decay of PRC was accelerated after reoxygenation v aerobic control. The results suggest that adaptive changes in SR Ca2+ handling, CK isoenzymes and antioxidant enzymes may contribute to higher resistance against reduced oxygen supply and reoxygenation in hypertrophy due to MI.

p53 autoantibodies in patients with urological tumours

OBJECTIVE

To determine the presence of p53 serum antibodies in patients with clinically well-defined urological cancer using a new enzyme-linked immunosorbent assay (ELISA).

PATIENTS AND METHODS

The study included 73 patients with prostatic cancer, 72 with transitional cell carcinoma of the urinary tract, 37 with renal cell cancer and 16 controls with a benign disease, all of whom were tested using the ELISA for p53 autoantibodies. The specific reaction of the ELISA (positive p53 antibody titre) was confirmed by Western Blot analysis.

RESULTS

Thirteen patients with cancer and one control patient (7.6% overall) were positive for p53 autoantibodies. The sensitivity of the test was low, whereas the specificity was remarkably high. Surprisingly, 9 of the 13 p53-positive patients died within a median of 3.7 months (range 2-6) and the one positive control patient died of undetected lung cancer. There was no significant correlation of p53 antibody positivity with clinical stage or tumour-specific differences.

CONCLUSIONS

The expression of p53 autoantibody seems to be a very late but significant event in urological tumour development, with the worst outcome (tumour-specific death) within a few weeks of developing positivity. In histopathologically heterogeneous tumour entities, p53 autoantibodies might be independent prognostic factors in patients with urological cancers.

The embryoid body as a novel in vitro assay system for antiangiogenic agents

Tumor progression necessitates the induction of blood vessels that converge upon the tumor and enhance the diffusibility of oxygen and nutrients. Approaches to treat cancer by antiangiogenic therapy are therefore straightforward, and there is a great need for suitable in vitro systems to test antiangiogenic agents. In the present study, embryoid bodies (EBs) differentiated from totipotent mouse embryonic stem (ES) cells and cultivated using the spinner flask technique are introduced as an in vitro system for antiangiogenesis research. ES cells effectively differentiated endothelial cells within the three-dimensional tissue of EBs. The total area of capillary-like structures, which were positive for CD31 (platelet endothelial cell adhesion molecule, PECAM-1), was assessed by confocal laser scanning microscopy and image analysis of a series of optical sections. Endothelial differentiation occurred between Day 4-5 and Day 8 of EB development. Within 7 days, 100% of EBs contained capillary-like structures. Suramin, tamoxifen, tetrahydrocortisol, and a combination of tetrahydrocortisol and heparin were tested for their antiangiogenic capacity in the EB system and were found to efficiently inhibit endothelial differentiation. Diffusion studies of a 10-kd 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF)-dextran and the fluorescent, amphiphilic agent doxorubicin in avascular and vascularized EBs revealed that the endothelial structures formed functional vessels that facilitated diffusion. The diffusion coefficient D for doxorubicin was 296 x 10(-9) cm2 s(-1) in vascularized 8-day-old EBs, ie, about 10-fold larger than in avascular 3-day-old EBs (18 x 10(-9) cm2 s(-1)) and EBs treated with suramin (14 x 10(-9) cm2 s(-1)), tamoxifen (13.5 x 10(-9) cm2 s(-1)), and tetrahydrocortisol/heparin (18.5 x 10(-9) cm2 s(-1)). Consequently, avascular EBs treated with antiangiogenic agents developed central necrosis, which was absent in vascularized EBs. Our findings indicate that EBs are a suitable in vitro model system to study the effects of antiangiogenic agents in a three-dimensional tissue context. Furthermore, EBs provide a unique model to investigate the diffusion of anticancer agents in a tissue in both the avascular and vascularized states.