Efficacy and safety of intravenous levosimendan compared with dobutamine in severe low-output heart failure (the LIDO study): a randomised double-blind trial

BACKGROUND

Levosimendan, a novel calcium sensitiser, improves myocardial contractility without causing an increase in myocardial oxygen demand. We compared the effects of levosimendan and dobutamine on haemodynamic performance and clinical outcome in patients with low-output heart failure.

METHODS

Patients were recruited into a multicentre, randomised, double-blind, double-dummy, parallel-group trial. Under continuous haemodynamic monitoring, an initial loading dose of levosimendan of 24 microg/kg was infused over 10 min, followed by a continuous infusion of 0.1 microg kg(-1) min(-1) for 24 h. Dobutamine was infused for 24 h at an initial dose of 5 microg kg(-1) min(-1) without a loading dose. The infusion rate was doubled if the response was inadequate at 2h. The primary endpoint was the proportion of patients with haemodynamic improvement (defined as an increase of 30% or more in cardiac output and a decrease of 25% or more in pulmonary-capillary wedge pressure) at 24 h. Analyses were by intention to treat.

FINDINGS

103 patients were assigned levosimendan and 100 dobutamine. The primary haemodynamic endpoint was achieved in 29 (28%) levosimendan-group patients and 15 (15%) in the dobutamine group (hazard ratio 1.9 [95% CI 1.1-3.3]; p=0.022). At 180 days, 27 (26%) levosimendan-group patients had died, compared with 38 (38%) in the dobutamine group (0.57 [0.34-0.95]; p=0.029).

INTERPRETATION

In patients with severe, low-output heart failure, levosimendan improved haemodynamic performance more effectively than dobutamine. This benefit was accompanied by lower mortality in the levosimendan group than in the dobutamine group for up to 180 days.

Three-dimensional reconstitution of embryonic cardiomyocytes in a collagen matrix: a new heart muscle model system

A method has been developed for culturing cardiac myocytes in a collagen matrix to produce a coherently contracting 3-dimensional model heart tissue that allows direct measurement of isometric contractile force. Embryonic chick cardiomyocytes were mixed with collagen solution and allowed to gel between two Velcro-coated glass tubes. During culture, the cardiomyocytes formed spontaneously beating cardiac myocyte-populated matrices (CMPMs) anchored at opposite ends to the Velcro-covered tubes through which they could be attached to a force measuring system. Immunohistochemistry and electron microscopy revealed a highly organized tissue-like structure of alpha-actin and alpha-tropomyosin-positive cardiac myocytes exhibiting typical cross-striation, sarcomeric myofilaments, intercalated discs, desmosomes, and tight junctions. Force measurements of paced or unpaced CMPMs were performed in organ baths after 6-11 days of cultivation and were stable for up to 24 h. Force increased with frequency between 0.8 and 2.0 Hz (positive "staircase"), increasing rest length (Starling mechanism), and increasing extracellular calcium. The utility of this system as a test bed for genetic manipulation was demonstrated by infecting the CMPMs with a recombinant beta-galactosidase-carrying adenovirus. Transduction efficiency increased from about 5% (MOI 0.1) to about 50% (MOI 100). CMPMs display more physiological characteristics of intact heart tissue than monolayer cultures. This approach, simpler and faster than generation of transgenic animals, should allow functional consequences of genetic or pharmacological manipulation of cardiomyocytes in vitro to be studied under highly controlled conditions.

The ETS domain protein pointed-P2 is a target of MAP kinase in the sevenless signal transduction pathway

The fate of the R7 photoreceptor cell in the developing eye of Drosophila is controlled by the Sevenless (Sev) receptor tyrosine kinase. Sev activates a highly conserved signal transduction cascade involving the proteins Ras1 and Raf and the Rolled/mitogen-activated protein (Rl/MAP) kinase. Here we show that the ETS domain protein encoded by the P2 transcript of the pointed (pnt) gene is a nuclear target of this signalling cascade which acts downstream of Rl/MAP kinase. The PntP2 protein is phosphorylated by Rl/MAP kinase in vitro at a single site and this site is required for its function in vivo. Furthermore, we present genetic and biochemical data suggesting that MAP kinase controls neural development through phosphorylation of two antagonizing transcription factors of the ETS family, Yan and PntP2.

The regulation of the calcium conductance of cardiac muscle by adrenaline

1. The effect of adrenaline on the Ca-dependent slow inward current, Is, of mammalian cardiac muscle has been investigated by the voltage-clamp method. The mechanism of the increase in the conductance, gs, was analysed on the basis of a kinetic scheme (Hodgkin & Huxley, 1952) applicable to this system. 2. The rate constants alphad and betad, of activation of gs were not influenced by adrenaline, although the limiting conductance, gs, was greatly increased. 3. Reduction of [Ca]o from 1-8 to 0-2 mM decreased the amplitude of inward tail currents when gs was fully activated; however, the relative decrease of the current amplitude was the same with and without adrenaline. The reversal potential, ER, of Is was not changed by the drug. This indicates that the catecholamine has no influence on the selectivity of these conductance channels. 4. An increase in the number of functional conductance channels by adrenaline is discussed as a possible mechanism for the increase in Gs.

A study of the ion selectivity and the kinetic properties of the calcium dependent slow inward current in mammalian cardiac muscle

1. A voltage-clamp method combining a single surcose gap and two intracellular micro-electrodes was used to measure membrane currents in ventricullar myocardial fibres. 2. The adequacy of the voltage-clamp method is demonstrated by comparing the total current, It, across the gap with the voltage difference, delta V, between the two intracellular micro-electrodes, i.e. another independent way of measuring membrane currents. With both current measurements the slow inward current, Is, shows the same voltage- and time-dependences. 3. The sensitivity of the slow inward current to variation in external Ca and Na concentrations was investigated systematically. The reversal potential of the slow inward current was sensitive to variation of both ion species. 4. From the reversal potential measurements relative permeabilities of the conductance channels of the slow inward current were estimated as PCa/PNa approximately 1/0-01 and PCa/PK approximately 1/0-01 by means of the constant field equation. 5. The activation and inactivation kinetics of the slow inward current were explored in detail and related to the plateau of the action potential.

The effect of the internal sodium concentration on calcium fluxes in isolated guinea-pig auricles

1. Calcium efflux from guinea-pig auricles followed saturation kinetics when [Ca](o) and [Na](o) were changed while the ratio [Ca](o)/[Na](o) (2) was kept constant. The Michaelis constant, K(m) (Ca+Na) = 40 mM, suggests that a hypothetical carrier system, responsible for sodium-calcium exchange, is far from saturation with the inside concentrations of these ions.2. [Na](i) was altered in the auricles between 12.5 and 60 mM/kg fibre water while total cellular calcium concentration ([Ca](t)) at the beginning of the influx period was not significantly different in the various groups of preparations.3. (45)Ca influx increased appreciably with increasing [Na](i). (45)Ca influx from sodium-poor solution corresponded to an almost equal increase in [Ca](t), while [Ca](t) did not change much in preparations loaded with (45)Ca in Tyrode solution. When the sodium-activated fraction of calcium influx was plotted against [Na](i) (2) the resulting curve indicated saturation with K(m) (Na) = 3500 (mM [Na](i))(2) and maximal influx rate, J(i, max) (Ca') = 1.35 mM/kg wet weight x 10 min.4. When the preparations were re-equilibrated for various times in normal Tyrode solution after [Na](i) had been increased, both the sodium-activated component of calcium influx and [Na](i) (2) decreased with approximately the same rate constants.5. Calcium efflux from auricles with high [Na](i) was increased when it was measured in Tyrode solution while the efflux in sodium-poor solution was inhibited.6. Auricles with increased [Na](i) showed a positive inotropic contractile response.7. The main conclusion reached by these experiments is that calcium influx is affected by [Na](i) in a way which is compatible with a carrier-mediated sodium-calcium exchange system.

Increase in myocardial Gi-proteins in heart failure

The contractile response and myocardial content of Gi-proteins were examined in cardiac preparations from explanted hearts of four different patients with end-stage heart failure. Three patients had idiopathic dilated cardiomyopathy and one patient had inflammatory heart disease. Preparations from patients with idiopathic dilated cardiomyopathy showed reduced contractile response to the cAMP-increasing agent isoprenaline and an increase in myocardial Gi-proteins, compared with preparations from non-failing hearts. Therefore it is conceivable that an increase in myocardial Gi-proteins is causally related to heart failure due to idiopathic dilated cardiomyopathy. In the preparation from the patient with inflammatory heart disease the contractile response to isoprenaline was not reduced and likewise content of Gi-proteins was not changed.

The Ets transcription factors encoded by the Drosophila gene pointed direct glial cell differentiation in the embryonic CNS

The Drosophila gene pointed (pnt) encodes two putative transcription factors (P1 and P2) of the Ets family, which in the embryonic CNS are found exclusively in glial cells. Loss of pnt function leads to poorly differentiated glial cells and a marked decrease in the expression of the neuronal antigen 22C10 in the MP2 neurons, which are known to interact intimately with the pntP1-expressing longitudinal glial cells. Ectopic expression of pntP1 RNA forces additional CNS cells to enter the glial differentiation pathway. Interestingly, the additional glial-like cells are often flanked by cells that ectopically express the neuronal antigen 22C10. Therefore, both the pnt loss-of-function as well as the gain-of-function phenotype suggest that glial cells are able to induce 22C10 expression on neighboring neurons. This was further verified by cell transplantation experiments. Thus, pnt is not only required but also sufficient for several aspects of glial differentiation.

Increased expression of cardiac phosphatases in patients with end-stage heart failure

Type 1 phosphatase activity was increased in membrane vesicles from failing human ventricles compared with non-failing controls. Likewise, expression of the mRNA encoding for type 1 phosphatase was enhanced by 37%. The present study provides evidence that alterations of phosphatase activity coincide with end-stage heart failure. Thus, enhanced activity of phosphatases may be causally related to heart failure and/or may aggravate the well known decreased cardiac responsiveness to positive inotropic agents in end-stage heart failure.

Functional ethanol tolerance in Drosophila

In humans, repeated alcohol consumption leads to the development of tolerance, manifested as a reduced physiological and behavioral response to a particular dose of alcohol. Here we show that adult Drosophila develop tolerance to the sedating and motor-impairing effects of ethanol with kinetics of acquisition and dissipation that mimic those seen in mammals. Importantly, this tolerance is not caused by changes in ethanol absorption or metabolism. Rather, the development of tolerance requires the functional and structural integrity of specific central brain regions. Mutants unable to synthesize the catecholamine octopamine are also impaired in their ability to develop tolerance. Taken together, these data show that Drosophila is a suitable model system in which to study the molecular and neuroanatomical bases of ethanol tolerance.

Activity of cAMP-dependent protein kinase and Ca2+/calmodulin-dependent protein kinase in failing and nonfailing human hearts

OBJECTIVES

A hallmark of human heart failure is prolonged myocardial relaxation. Although the intrinsic mechanism of phospholamban coupling to the Ca(2+)-ATPase is unaltered in normal and failed human hearts, it remains possible that regulation of phospholamban phosphorylation by cAMP-dependent mechanisms or other second messenger pathways could be perturbed, which may account partially for the observed dysfunctions of the sarcoplasmic reticulum (SR) associated with this disease.

METHODS

cAMP-dependent protein kinase (PKA) and Ca2+/calmodulin-dependent protein kinase II (CaM kinase) were characterized initially by DEAE-Sepharose chromatography in hearts from patients with end-stage dilated cardiomyopathy. We measured the activity of PKA and CaM kinase in left ventricular tissue of failing (idiopathic dilated cardiomyopathy; ischemic heart disease) and nonfailing human hearts.

RESULTS

Basal PKA activity was not changed between failing and nonfailing hearts. One major peak of CaM kinase activity was detected by DEAE-Sepharose chromatography. CaM kinase activity was increased almost 3-fold in idiopathic dilated cardiomyopathy. In addition, hemodynamical data (left ventricular ejection fraction, cardiac index) from patients suffering from IDC positively correlate with CaM kinase activity.

CONCLUSIONS

Increased CaM kinase activity in hearts from patients with dilated cardiomyopathy could play a role in the abnormal Ca2+ handling of the SR and heart muscle cell.

Increased messenger RNA level of the inhibitory G protein alpha subunit Gi alpha-2 in human end-stage heart failure

In human heart failure the positive inotropic and cAMP-elevating effects of both beta-adrenoceptor agonists and phosphodiesterase inhibitors are diminished. This has been explained at least in part by an increase in the inhibitory signal-transducing G protein (Gi) and unchanged stimulatory G protein (Gs). In the present study we determined the mRNA expression pattern of the alpha subunits of Gi-1, Gi-2, Gi-3, and Gs in myocardial tissue samples of patients undergoing heart transplantation. Northern blot analysis of total RNA extracted from left ventricles with 32P-labeled cDNAs demonstrated expression of Gi alpha-2, Gi alpha-3, and Gs alpha mRNA. In contrast, Gi alpha-1 mRNA was not detectable. To investigate whether the increased ratio of Gi/Gs might be due to altered gene expression, we compared mRNA levels of Gi alpha-2, Gi alpha-3, and Gs alpha in left ventricular myocardium from failing hearts with idiopathic dilated cardiomyopathy (n = 8) and ischemic cardiomyopathy (n = 6) and from nonfailing hearts from transplant donors (n = 8). Compared with nonfailing control hearts, the Gi alpha-2 mRNA was increased by 75 +/- 26% (p less than 0.05) in idiopathic dilated cardiomyopathy hearts and 90 +/- 26% (p less than 0.05) in ischemic cardiomyopathy hearts. Gi alpha-3 and Gs alpha mRNA levels were similar in the three groups. The results suggest that as in other mammalian species, Gi alpha-2 and Gi alpha-3 mRNA are the predominant Gi alpha mRNA subtypes in human ventricular myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Inotropic drugs and their mechanisms of action

This report describes various old and new positive inotropic drugs with respect to their mechanisms of action. Drugs with established cardiotonic effects include cardiac glycosides, beta 1-adrenergic agents, glucagon, histamine and the methylxanthines. New agents discussed are prenalterol, beta 2- and alpha-adrenergic drugs, amrinone and sulmazole. Prenalterol is a beta 1-adrenergic agent. Beta 2-adrenergic drugs, amrinone and sulmazole, combine a positive inotropic and a vasodilator effect. The latter resemble theophylline and other methylxanthines in that they appear to act mainly as phosphodiesterase inhibitors with a subsequent increase in cyclic adenosine monophosphate (cAMP). The mechanism of the positive inotropic effect of alpha-adrenergic stimulating agents (for example, phenylephrine) is unknown. It is independent of the cAMP system and is not accompanied by changes in frequency.

Endotoxin and cytokines induce direct cardiodepressive effects in mammalian cardiomyocytes via induction of nitric oxide synthase

In patients with septic shock or inflammatory cardiac diseases like myocarditis myocardial contractility is depressed. These patients have elevated circulating levels of bacterial endotoxins (lipopolysaccharides, LPS) and pro-inflammatory cytokines like interleukin-1 beta (IL-alpha 1 beta) or tumor necrosis factor-alpha (TNF-alpha). It is not clear, whether LPS and/or cytokines have direct inotropic effects on cardiomyocytes and whether these effects are mediated via the L-arginine-nitric oxide synthase (NOS) pathway as demonstrated in vascular smooth muscle cells. Therefore, we examined the direct effects of LPS. IL-1 beta and TNF-alpha on contractility and cGMP content in isolated guinea-pig ventricular cardiomyocytes. Furthermore, the influence of the NOS inhibitor NG-nitro-L-arginine (L-NNA) and dexamethasone on these effects was studied as well as inducible NOS (iNOS) protein expression. LPS (1000 ng/ml), IL-1 beta (25 ng/ml) and TNF-alpha (100 ng/ml) decreased contractility by 48%, 55% and 65% and augmented cGMP content by 135%, 88% or 70% after long-term treatment (18 h) in cardiomyocytes, without altering contractility or cGMP content after short-term treatment (30 min). These effects were blocked by L-NNA (100 microM) and dexamethasone (3 microM). Furthermore iNOS protein was expressed in LPS- and cytokine-treated cardiomyocytes. These findings demonstrate that LPS. IL-1 beta and TNF-alpha have direct negative inotropic effects on cardiomyocytes, which are accompanied by an increase in cGMP content. These effects are mediated via de novo synthesis of a myocardial iNOS. The direct negative inotropic effects of endotoxins and cytokines on cardiomyocytes may in part contribute to the contractile dysfunction observed in patients with septic shock or inflammatory cardiac diseases.

Muscarinic and beta-adrenergic regulation of heart rate, force of contraction and calcium current is preserved in mice lacking endothelial nitric oxide synthase

Nitric oxide (NO) is an ubiquitous signaling molecule produced from L-arginine by NO synthase (NOS). In the vasculature, NO mediates parasympathetic endothelium-dependent vasodilation. NO may also mediate the parasympathetic control of myocardial function. This is supported by the observations that NOS3, the endothelial constitutive NOS, is expressed in normal cardiac myocytes from rodents and human, and NOS and/or guanylyl cyclase inhibitors antagonize the effect of muscarinic agonists on heart rate, atrio-ventricular conduction, contractility and L-type calcium current. Here we examine the autonomic regulation of the heart in genetically engineered mice deficient in NOS3 (NOS3-KO). We show that the chronotropic and inotropic responses to both beta-adrenergic and muscarinic agonists were unaltered in isolated cardiac tissue preparations from NOS3-KO mice, although these mice have a defective parasympathetic regulation of vascular tone. Similarly, beta-adrenergic stimulation and muscarinic inhibition of the calcium current did not differ in cardiac myocytes from NOS3-KO mice and those from wild-type mice. RT-PCR did not demonstrate upregulation of other NOS isoforms. Similarly, Gi/Go proteins and muscarinic receptor density were unaltered. These data refute the idea that NOS3 is obligatory for the normal autonomic control of cardiac muscle function.

EGF receptor signaling induces pointed P1 transcription and inactivates Yan protein in the Drosophila embryonic ventral ectoderm

The induction of different cell fates along the dorsoventral axis of the Drosophila embryo requires a graded activity of the EGF receptor tyrosine kinase (DER). Here we have identified primary and secondary target genes of DER, which mediate the determination of discrete ventral cell fates. High levels of DER activation in the ventralmost cells trigger expression of the transcription factors encoded by ventral nervous system defective (vnd) and pointed P1 (pntPl). Concomitant with the induction of pntP1, high levels of DER activity lead to inactivation of the Yan protein, a transcriptional repressor of Pointed-target genes. These two antagonizing transcription factors subsequently control the expression of secondary target genes such as otd, argos and tartan. The simultaneous effects of the DER pathway on pntP1 induction and Yan inactivation may contribute to the definition of the border of the ventralmost cell fates.

Effects of alpha-adrenoceptor stimulation with phenylephrine in the presence of propranolol on force of contraction, slow inward current and cyclic AMP content in the bovine heart

The mechanism of the cyclic AMP-independent positive inotropic effect of cardiac alpha-adrenoceptor stimulation was studied by analyzing the effects of phenylephrine on force of contraction, calcium-dependent slow action potentials and the slow inward current (Isi) in bovine ventricular trabeculae. The preparations were electrically driven at 0.3 Hz in the presence of propranolol 1 mumol 1(-1). Phenylephrine increased the force of contraction in a concentration-dependent manner (maximum about 200% of control at 30 mumol 1(-1). The effect was surmountably antagonized by phentolamine. The positive inotropic effect of phenylephrine was accompanied by a concentration-dependent increase in time to peak force and occurred without any detectable increase in cyclic adenosine 3',5'-monophosphate (cyclic AMP) levels. The positive inotropic effect of phenylephrine was accompanied by an increase in action potential duration both at 20% and 90% repolarization. Calcium-dependent slow action potentials were also prolonged by phenylephrine and there was a distinct increase in the maximal rate of depolarization (dV/dtmax) of these slow potentials. These effects were also completely reversible on washing and surmountably blocked by phentolamine. However, the increase in dV/dtmax was smaller than that of isoprenaline in concentrations producing similar inotropic effects. Voltage-clamp experiments with the single sucrose-gap method showed that the phenylephrine-induced increase in force of contraction was associated not only with an increase in peak slow calcium inward current, Isi max, but also with a delay in the inactivation of Isi. Outward currents were not detectably altered by phenylephrine. It is concluded that the alpha-adrenoceptor mediated, cyclic AMP-independent positive inotropic effects of phenylephrine in bovine cardiac muscle are associated with an increase in slow inward current. Additionally, the amount of calcium influx during excitation is probably increased by a delay in the inactivation of Isi. Both effects can explain the phenylephrine-produced prolongation of the action potential, and probably contribute to the positive inotropic effect of alpha-adrenoceptor stimulation. However, as the effect on dV/dtmax is smaller than that of isoprenaline, other (still unknown) mechanisms may also be involved.

Genetic dissection of pointed, a Drosophila gene encoding two ETS-related proteins

The Drosophila gene pointed (pnt) is required for the differentiation of a number of tissues during embryogenesis, including the ventral ectoderm, the nervous system, the tracheal system and certain muscle fibers. The phenotypes associated with strong pointed alleles are reflected by a complex pointed expression pattern during embryogenesis. Two promoters, P1 and P2, separated by some 50 kb of genomic sequences, direct the transcription of two different transcript forms, encoding two different proteins related to the ETS family of transcription factors. To assess the individual functions of the two different pointed protein forms, we have generated new pointed alleles affecting either the P1 or the P2 transcript, termed P1 and P2 alleles, respectively. Genetic analysis reveals partial heteroallelic complementation between certain pointed P1 and P2 alleles. Surviving trans-heterozygous flies have rough eyes, abnormal wings and halters, suggesting a requirement for pointed function during their imaginal disc development. Further genetic analysis demonstrates that expression of a given pointed P2 allele depends on trans-acting transcriptional regulatory sequences. We have identified two chromosomal domains with opposite regulatory effects on the transcriptional activity of the pointed P2 promoter, one trans-activates and the other trans-represses pointed P2 expression. By deletion mapping we were able to localize these control regions within the 5' region of the pointed P2 transcript.

Alpha-adrenoceptor-mediated positive inotropic effect of phenylephrine in isolated human ventricular myocardium

In isolated human ventricular myocardium the alpha-adrenoceptor agonist phenylephrine had a positive inotropic effect in preparations from 9 of 14 patients. This effect was seen in the presence of the beta-adrenoceptor-blocking agent propranolol but was nearly abolished by the alpha-adrenoceptor blocking agent prazosin. In contrast to the beta-adrenoceptor-mediated positive inotropic effect, the effect of phenylephrine was accompanied by a prolongation of the isometric contraction. The results suggest that alpha-adrenoceptors exist in human ventricular myocardium.

Prevalence of genotypes 1 and 2 of bovine viral diarrhea virus in Lower Saxony, Germany

The aim of this study was to find whether an antigenic drift had occurred in Lower Saxony in the past 40 years. For this, the genetic diversity of bovine viral diarrhea virus (BVDV) isolates mainly from Lower Saxony was estimated by RT-PCR and sequencing of a 420 bp fragment of the E2 glycoprotein gene. Sixty-one field virus isolates collected during routine diagnostics between 1960 and 2000 in Lower Saxony, Northern Germany, were analyzed. Phylogenetic analysis allowed discrimination of genotypes BVDV 1 and 2. Excepting two isolates, which were of BVDV type 2, most of the isolates were classified as BVDV type 1. This group could be further subdivided into four subgroups and one disparate isolate. Independent of the year of isolation and geographical localization, 54 isolates clustered in two subtypes (BVDV subtypes 1b and 1d). Only one isolate was classified as BVDV type 1a, thus being similar to the North American NADL strain, and to the vaccine strain Oregon C24V, which was extensively used for vaccination in Germany. The remaining isolates belonged to new clusters tentatively designated as BVDV subtypes 1g and 1f. To compare the cluster designation with that of other studies, phylogenetic analysis of representatives of each of the subgroups based on the 5' untranslated region (5'UTR) was performed. It grouped the viruses similarly. The results indicate that the BVDV population seems to be relatively stable over 40 years in Lower Saxony.

Radioimmunochemical quantification of Gi alpha in right and left ventricles from patients with ischaemic and dilated cardiomyopathy and predominant left ventricular failure

An increase of Gi alpha-related pertussis toxin substrates has been observed in the failing myocardium. In order to quantify the protein expression of Gi alpha directly, we developed a fast radioimmunoassay using the iodinated synthetic peptide 125I-KENLKDCGLF. beta-adrenoceptors were studied with 125I-cyanopindolol binding for comparison. Immunoblot experiments using recombinant G-protein alpha-subunits showed that DS4 immunostained the G-protein alpha-subunits with a rank order of potency rGi alpha 1 = rGi alpha 2 > rGo alpha >> rGi alpha 3. The G-protein alpha-subunits recognized by DS4 in human ventricular membranes comigrated with rGi alpha 1 and rGi alpha 2. The radioimmunoassay had a sensitivity of 2.5 micrograms/ml transducin alpha with an interassay variation of less than 10%. The non-labelled peptide selectively competed with the myocardial 40 kDa membrane protein for binding to the antiserum DS4. Radioimmunochemical quantification of Gi alpha from cardiac membranes showed that in left ventricular membranes (LV) from dilated cardiomyopathy (DCM), there was an increase of Gi alpha by 138.5% when related to mg protein and 135% when related to 3H-ouabain binding sites as membrane marker. In LV from ischaemic cardiomyopathy (ICM), the increase was smaller (58.4%) when related to mg protein compared to the increase of Gi alpha when related to 3H-ouabain binding sites as membrane marker (155% v NF). In contrast, in the right ventricles (RV) there was no increase of Gi alpha in ICM or DCM. The numbers of beta-adrenoceptors were reduced in RV and LV of both, ICM and DCM. It is concluded that the radioimmunoassay may become an important tool for studying the expression of Gi alpha-protein levels and changes thereof in pathological conditions. The amount of immunodetectable Gi alpha-proteins is increased in failing LV due to DCM and ICM but not in RV, while beta-adrenoceptor down-regulation occurred in RV and LV in both conditions. These findings might indicate that the liability of the LV but not of RV to express Gi alpha-proteins may be increased in predominant LV heart failure. Alternatively, the underlying mechanism, e.g. sympathetic activation, may be regulated locally in the failing heart producing different changes in adjacent chambers.

Natrialba magadii virus phiCh1: first complete nucleotide sequence and functional organization of a virus infecting a haloalkaliphilic archaeon

The double-stranded (ds)DNA virus phiCh1 infects the haloalkaliphilic archaeon Natrialba magadii. The complete DNA sequence of 58 498 bp of the temperate virus was established, and the probable functions of 21 of 98 phiCh1-encoded open reading frames (ORFs) have been assigned. This knowledge has been used to propose functional modules each required for specific functions during virus development. The phiCh1 DNA is terminally redundant and circularly permuted and therefore appears to be packaged by the so-called headful mechanism. The presence of ORFs encoding homologues of proteins involved in plasmid replication as well as experimental evidence indicate a plasmid-mediated replication strategy of the virus. Results from nanosequencing of virion components suggest covalent cross-linking of monomers of at least one of the structural proteins during virus maturation. A comparison of the phiCh1 genome with the partly sequenced genome of Halobacterium salinarum virus phiH revealed a close relationship between the two viruses, although their host organisms live in distinct environments with respect to the different pH values required for growth.