A paragenetic perspective on integration of RNA silencing into the epigenome and its role in the biology of higher plants.

We describe features of RNA silencing and associated epigenetic imprints that illustrate potential roles for RNA interference (RNAi) in maintenance and transmission of epigenetic states between cells, throughout a plant, and perhaps even across sexual generations. Three types of transgenes can trigger RNAi of homologous endogenous plant genes: (1) "sense" transgenes that overexpress translatable transcripts, (2) inverted repeat (IR) transgenes that produce double-stranded RNA (dsRNA), and (3) antisense transgenes. Each mode of RNAi produces a different characteristic developmental silencing pattern. Single-copy transgenes are sufficient for sense-RNAi and antisense-RNAi, but not inverted repeat-RNAi. A single premature termination codon dramatically attenuates sense-RNAi, but it has no effect on antisense or inverted repeat-RNAi. We report here that antisense transgenes altered by removal of nonsense codons generate silencing patterns characteristic of sense-RNAi. Duplication of a sense overexpression transgene results in two types of epigenetic events: (1) complete loss of silencing and (2) altered developmental pattern of silencing. We also report that duplicating only the transgene promoter results in complete loss of silencing, whereas duplicating only transcribed sequences produces the second class, which are vein-based patterns. We infer that the latter class is due to systemic RNA silencing signals that interact with certain epigenetic states of the transgene to imprint it with information generated at a distance elsewhere in the plant.

Chloroplast transformation in Euglena gracilis: splicing of a group III twintron transcribed from a transgenic psbK operon.

The Escherichia coli aadA gene product, which confers resistance to spectinomycin and streptomycin, has been widely used as a dominant selectable marker for chloroplast transformation of Chlamydomonas and tobacco. An aadA transformation cassette was adapted for expression in Euglena gracilis chloroplasts by replacing the Chlamydomonas promoter and 3' untranslated region (UTR) with the E. gracilis psbA promoter and 3' UTR. Transgenic DNA was introduced into E. gracilis chloroplasts by biolistic transformation. Streptomycin- and spectinomycin-resistant colonies were obtained, which screened positively for the presence of the transforming vector by PCR amplification. Although integration of the transforming DNA into the chloroplast genome was not detected, transforming DNA was stably maintained in the chloroplast as an episomal element during continuous selection on antibiotics. The aadA cassette was also inserted into a transformation vector which contained the independently expressed psbK operon from either E. gracilis or a closely related species, E. stellata. The psbK operon contained at least two group III introns and a group III twintron, was highly expressed, and was only 1.5 kb in length. In transgenic E. gracilis chloroplasts, a truncated E. stellata psbK operon was transcribed, and the resultant pre-mRNA was accurately spliced. This system should allow the first direct analysis of group II and group III intron-splicing mechanisms. In addition, it could prove useful in the study of many other Euglena transcription and processing events.

Comparison of psbK operon organization and group III intron content in chloroplast genomes of 12 Euglenoid species.

A novel mixed operon has been identified in the photosynthetic protist E. gracilis. The genes for psbK, ycf12, psaM, and trnR are co-transcribed. The resulting tetracistronic transcripts are processed through endonucleolytic cleavage of the intergenic spacers and intron splicing to form three mature monocistronic mRNAs and a tRNA. A group III twintron and a group III intron are located in psbK. Another group III intron is found in ycf12. The psbK operon has been cloned by PCR amplification from nine related Euglenoid species. In each species, the gene order and content of the psbK operon is conserved. The psbK operons contain phylogenetically conserved eubacterial promoter, translational, and 3' processing elements. Intron content varies significantly from species to species. Based on a comparison of the intron content with the results of phylogenetic analysis, group III intron evolution within the Euglenoid lineage is much more complex than previously believed.

Characterization of the glnK-amtB operon of Azotobacter vinelandii.

To determine whether in Azotobacter vinelandii the PII protein influences the regulation of nif gene expression in response to fluxes in the ammonium supply, the gene encoding PII was isolated and characterized. Its deduced translation product was highly similar to PII proteins from other organisms, with the greatest degree of relatedness being exhibited to the Escherichia coli glnK gene product. A gene designated amtB was found downstream of and was contranscribed with glnK as in E. coli. The AmtB protein is similar to functionally characterized ammonium transport proteins from a few other eukaryotes and one other prokaryote. glnK and amtB comprise an operon. Attempts to isolate a stable glnK mutant strain were unsuccessful, suggesting that glnK, like glnA, is an essential gene in A. vinelandii. amtB mutants were isolated, and although growth on limiting amounts of ammonium was similar in the mutant and wild-type strains, the mutants were unable to transport [14C]methylammonium.

A maturase-encoding group III twintron is conserved in deeply rooted euglenoid species: are group III introns the chicken or the egg?

The fourth intron of the Euglena gracilis chloroplast photosystem II gene, psbCi4, is a 1,605-bp twintron composed of two group III introns and a coding locus for a 458-aa polypeptide, mat1, located in the internal intron. psbCi4 homologs have been identified in seven euglenoids, including E. myxocylindracea, E. viridis, E. deses, E. pisciformis, Cryptoglena pigra, Eutreptia sp., and Lepocinclis beutschlii. All of the species examined contain both the group III twintron and the mat1 locus, revealing a more widespread occurrence of group III introns than previously known. The L. beutschlii mat1 locus is interrupted by two novel mini-group II introns of 224 and 258 nt, the smallest group II introns yet identified. Reverse transcriptase polymerase chain reaction analysis confirmed the splicing boundaries of the external and internal E. myxocylindracea, E. viridis, and E. deses introns as well as the novel L. beutschlii mat1 introns. As determined by comparative phylogenetic analysis, group III introns contain a structural homolog of group II intron domain VI. The mat1 loci encode peptide motifs characteristic of group II intron maturases. A group III intron-encoded protein whose predicted sequence is similar to group II intron-encoded maturases and a bona fide domain VI within group III introns are compelling evidence for a common ancestor of group II and group III introns.

Impact of particulate contamination in crystalloid cardioplegic solutions: studies by scanning and transmission electron microscopy.

The amount of particulate matter present in Bretschneider's cardioplegic solution (HTK) was assessed by laser-mediated particle counting. Permissible levels of contaminant particles with a distribution of diameters between 0.2 and 20 microns were found. A significant further increase in the particle count was observed when the fluid was administered for clinical use, which resulted in the additional release of particles from, for example, the infusion kit, which included an in-line filter with pores of 270 microns. Filtration of the HTK solution by a terminal inline filter (0.2 micron) significantly reduced the number of particles. In order to determine the chemical composition and the potential hazards of the particulate material we used scanning electron microscopy in combination with energy dispersive X-ray analysis and transmission electron microscopy to examine specimens taken from heart tissue obtained from Göttinger minipigs after cardioplegia and from humans undergoing mitral valve replacement after cardioplegia and reperfusion. Particles of various diameters were found either to be plugging coronary capillaries, to be adherent to the endothelial layer, or to be engulfed by polymorphonuclear (PMN) granulocytes, which appeared to be activated. Some of the PMN granulocytes were apparent in the endothelial layer. It is recommended, therefore, that a terminal in-line filter (0.2 micron) should be routinely used.

Alternative lead positioning in the right ventricular outflow tract in transvenous implantation of ICDs.

Pacing and sensing failure in apical right ventricular coil electrode PCD implantation due to ventricular scars or aneurysma may force the implanting surgeon to switch to more invasive procedures such as subxyphoidal pericardiotomy or thoracotomy for epimyocardial corkscrew electrode and for epicardial patch application. In order to avoid this more invasive operation in the most severely impaired patients, right ventricular outflow tract positioning of the RV electrode is suggested as an alternative RV electrode site for implantation. A study of four cases shows that this occasional procedure is a practicable method to avoid more invasive techniques. Excellent pacing, sensing, and defibrillation characteristics were obtained and application is relatively simple.

Sequential bilateral lung transplantation for pulmonary alveolar microlithiasis.

Lung transplantation has been successfully used in the treatment of patients with end-stage pulmonary disease and adequate cardiac function. We report about a 32-year-old man with pulmonary alveolar microlithiasis who underwent sequential bilateral lung transplantation. Preoperative hemodynamic studies revealed severe pulmonary hypertension; the right ventricular ejection fraction was 0.27. Eighteen months postoperatively, he continues to do well with normalized pulmonary and cardiac function and without clinical or histopathologic signs of graft rejection.

Endothelial damage of the venous graft in CABG. Influence of solutions used for storage and rinsing on endothelial function.

A significant proportion of early graft occlusions after aortocoronary revascularization using autologous saphenous vein grafts (SVG) are due to mechanical and/or metabolic or biochemical endothelial lesions. The morphological examination of the endothelium, usually carried out using light microscopy or by various types of scanning electron microscopy (SEM), does not give any indication of the functioning of the endothelium (E). Functionally intact E is capable of producing endothelium-derived relaxing factor (EDRF); a practicable in vitro test is the relaxation of pre-contracted vein segments (VS) in response to acetylcholine (ACh) application. To study the effect of the solution used to rinse and store the SVG between removal and implantation on the functional characteristics of the E, we performed in vitro tests on macroscopically intact VS removed from the saphenous vein of 30 male patients who underwent elective CABG surgery. Isolated VS rings were incubated for 60 min in heparinized whole blood (HWB), Bretschneider's cardioplegic solution (HTK), human albumin solution (HAS), or Ringer's solution (RS) and compared with the results obtained immediately after the removal of untreated control samples (C) taken from the same patients. After equilibration in carbogen aerated Krebs-Henseleit solution and precontraction by 3 x 10(-7) M noradrenaline (NE), relaxation induced by 10(-6) M ACh was measured. Only the samples stored in HWB (13.4 +/- 0.4 mN) showed similar maximal contractions with NE to those in the control group (14.4 +/- 0.5 mN), i.e. all those segments which showed both contractions with NE and relaxation with ACh.(ABSTRACT TRUNCATED AT 250 WORDS)

Low-output syndrome after heart surgery: is a monotherapy with phosphodiesterase-III inhibitors feasible? A comparative study of amrinone and enoximone.

In order to determine whether the primary use of a phosphodiesterase-III (PDE) inhibitor as monotherapy for severe cardiac low-output states (LOS) is in fact practicable, we investigated the haemodynamic effects of amrinone and enoximone in a prospective randomized study. After elective CABG, AVR, or MVR, patients with cardiac LOS were given amrinone (n = 10) or enoximone (n = 9). Following bolus saturation (1.0-2.0 mg/kg [XA = 1.4] or 0.5-1 mg/kg [XE = 0.9] in total), a dose of 5-10 microgram/kg/min was given by infusion. The standard monitoring program included discontinuous haemodynamic measurements (Swan-Ganz) over a maximum time period of 48 hours, arterial and venous blood-gas analyses, and clinical chemistry. The preoperative clinical and haemodynamic status of the enoximone (E) group (55% CABG patients; MPAP 27 +/- 2.5 mmHg, PCWP 20 +/- 2.9 mmHg, PVR 201 +/- 35 dyn.s.cm-5) was considerably worse than that of the amrinone (A) group (70% CABG patients; MPAP 23 +/- 2.3 mmHg, PCWP 16 +/- 3.5 mmHg, PVR 153 +/- 28 dyn.s.cm-5). Both PDE inhibitor preparations led to a significant increase in cardiac index (from 1.9 +/- 0.1 to 2.5 +/- 0.12 L/min/m2 (A) and from 1.98 +/- 0.1 to 2.6 +/- 0.18 L/min/m2 (E) within 30 minutes, accompanied by a simultaneous decrease in filling pressures and vascular resistances. For up to 2 hours, 3/10 (A) and 2/9 (E) patients required additional positive inotropic support with adrenaline. There were no significant differences between the two groups at any time.(ABSTRACT TRUNCATED AT 250 WORDS)

[The concept of lung and heart-lung preservation within the scope of multiple organ procurement]. / Konzept zur Lungen- und Herz-Lungen-Präservation im Rahmen der Multiorganentnahme.

Preservation of the lung is still one of the most challenging problems, because due to limited procurement time not all organs available can be used. The most common procurement technique is flush perfusion of the pulmonary artery system. Alternative methods in clinical use are either the autologous working heart-lung preparation or donor core-cooling (DCC). The own concept presented here, modified to the special demands of multi-organ-procurement, combines DCC and interstitial equilibration adapted to intracellular ion concentration. DCC is induced by extracorporeal circulation (ECC) using a transportable heart lung machine including a highly effective cooling system: cooling circuit based on two parallel heat exchangers with ice-water cooling produced by a high-pressure overflow of a low-temperature ice block (-40 degrees C). While cooling by ECC stepwise hemodilution is achieved by priming volume and incorporation of the cardioplegic solution (Bretschneider-HTK). The aim of equilibration is to lower the extracellular levels of sodium and calcium, and to increase the level of potassium. Additionally, the buffer capacity of donor blood is increased by the incorporated histidine-buffer system (alpha-stat). To avoid donor organ edema the time of ECC should be as short as possible. Using our system donor organ temperatures below 10 degrees C are reached within less than 30 min. In addition to ECC, lung surface cooling is achieved by external overflow with cold arterial blood (internal mammary artery). Besides lung preservation the main advantage of this concept is the profound precooling of all visceral organs before their individual flush perfusion.

Chronic beta 1-adrenoceptor antagonist treatment sensitizes beta 2-adrenoceptors, but desensitizes M2-muscarinic receptors in the human right atrium.

1. In 64 patients undergoing coronary artery bypass grafting the effects of chronic beta 1-adrenoceptor antagonist (metoprolol, atenolol, bisoprolol) treatment on right atrial beta-adrenoceptor and muscarinic M2-receptor number and functional responsiveness were investigated. 2. The beta 1-adrenoceptor antagonists increased right atrial beta 1-adrenoceptor number, did not affect beta 2-adrenoceptor number, and decreased muscarinic M2-receptor number. 3. Concomitantly, activation of right atrial adenylate cyclase by 10 microM GTP, 10 microM isoprenaline and 1 microM forskolin was enhanced and inhibition by 100 microM carbachol was diminished. 4. On isolated, electrically driven right atria the beta 1-adrenoceptor-mediated positive inotropic effect of noradrenaline was - even with beta 1-adrenoceptor number increased - not altered, while the beta 2-adrenoceptor-mediated effect of procaterol was markedly enhanced. However, the carbachol-induced negative inotropic effect was decreased. 5. It is concluded that chronic beta 1-adrenoceptor antagonist treatment increases beta 1-adrenoceptor number and concomitantly sensitizes beta 2-adrenoceptor function, but desensitizes muscarinic M2-receptor function in the human heart.

Muscarinic cholinoceptors in the human heart: demonstration, subclassification, and distribution.

In human atrial and ventricular myocardium, the muscarinic cholinoceptor (M-cholinoceptor) populations were characterized by means of radioligand binding (with [N-methyl-3H]-scopolamine ([3H]-NMS) as the ligand) and functional experiments (negative inotropic effect of carbachol on isolated electrically driven right atrial and left papillary muscle preparations). (1) Binding of [3H]-NMS to human atrial and ventricular membranes was rapid, reversible and saturable (KD-values: 0.5-1.0 nmol/l). The maximal number of [3H]-NMS binding sites, however, was approximately 2.5-fold higher in right and left atrial membranes (200-250 fmol [3H]-NMS specifically bound/mg protein) than in right and left ventricular membranes (80-100 fmol/mg protein). (2) M-cholinoceptor antagonists inhibited [3H]-NMS binding to right atrial and left ventricular membranes with steep, monophasic competition curves indicating interaction with a single class of binding sites. In both tissues the order of potency was: atropine greater than AF-DX 116 greater than hexahydrosiladifenidol (HHSiD) greater than pirenzepine. (3) On isolated electrically driven right atrial and left papillary muscle preparations (with force of contraction enhanced by 10(-5) mol/l isoprenaline), carbachol (10(-8)-10(-4) mol/l) caused concentration-dependent decreases in force of contraction; the pD2-value for carbachol was 6.65 +/- 0.09 (n = 8, atria) and 6.62 +/- 0.08 (n = 10, papillary muscles). In both tissues M-cholinoceptor antagonists antagonized the negative inotropic effect of carbachol with an order of potency: atropine greater than AF-DX 116 greater than HHSiD greater than pirenzepine, identical to that obtained in radioligand binding experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

[Diagnosis and therapy of acute traumatic aortic rupture]. / Dignostik und Therapie der akuten traumatischen Aortenruptur.

Aortic transection is defined as complete or partial dehiscence of the aortic wall layers. Aortic transections are seen in 16% of all lethal traffic accidents. The quality of the first emergency care outside hospital and the organization of rescue systems result in an increasing number of patients (espec. with life-threatening multiple injuries incl. atypical aortic lesions) reaching a trauma-center. Guide-lines for surgical indications are: 1. emergency-operation in case of symptomatic transection incl. simultaneous surgery of concommitant lesions. 2. Urgent operation following primary hemodynamic stabilisation in cases of isolated or asymptomatic transection. 3. In cases of concommitant lesions with surgical priority, delayed operation of asymptomatic transection. The perioperative letality claims up to 20%. Next of operative complication paraplegia remains the most deleterious problem. Despite different methods of protection on the spinal cord the incidence of paraplegia persists in the range of 5-10%.

[Catheter break in an implantable central venous infusion system with embolization in the pulmonary artery]. / Katheterbruch eines implantierbaren zentralvenösen Infusionssystems mit Embolisation in die Arteria pulmonalis.

A central venous catheter with a subcutaneous infusion port was implanted for chemotherapy into a 64-year-old woman with gastric lymphoma. Six weeks later, two weeks after a trivial trauma with hyperextension of the shoulder joint, it was found that the catheter had broken and its tip portion had embolized into the pulmonary artery: it was retrieved without difficulty via the femoral vein. This event suggests that pressure between clavicle and first rib can cause material fatigue in a silicon catheter. Such catheters should therefore not be implanted via the subclavian vein.

Survival after heart and coronary-artery penetration by an air-rifle projectile.

Gunshot injuries of the heart are extremely rare thoracic traumas in Europe during peacetime. Concomitant lesions of the coronary arteries occur in less than 5%. This case reports on a 26-year-old man who was shot with an air rifle at short range. On admission the patient showed signs of pericardial tamponade. Emergency thoracotomy was performed and a frontal cardiac lesion was found in the distal third of the anterior descending branch of the left coronary artery. The bullet crossed the cavum of the left ventricle and remained in the posterior wall in the subepicardial layer adjacent to the posterior descending coronary branch. Under the conditions of extracorporeal circulation we removed the bullet, repaired both ventricle walls using patches in sandwich technique, and bypassed the coronary lesion by single aortocoronary venous graft. No signs of myocardial infarction could be detected by ECG. The follow-up after 3 years shows no cardiac problems and normal stress tolerance. This case report proves that even air rifle shots, which in general are considered to be harmless, may result in life-threatening injuries. For the severity of the injury are decisive the kinetic energy at the muzzle as well as configuration and type of the bullet.

Myocardial beta-adrenoceptor changes in heart failure: concomitant reduction in beta 1- and beta 2-adrenoceptor function related to the degree of heart failure in patients with mitral valve disease.

In patients suffering from end-stage congestive cardiomyopathy, cardiac beta 1-adrenoceptor function is markedly reduced, whereas cardiac beta 2-adrenoceptor function is nearly normal. To determine whether beta 1-adrenoceptor function is impaired in heart failure selectively, beta 1- and beta 2-adrenoceptor density and functional responsiveness in the right and left atria and the left papillary muscles from patients with mitral valve disease (functional class III to IV) were studied. In all three tissues concomitantly beta 1- and beta 2-adrenoceptor density gradually declined when the degree of heart failure increased from functional class III to IV. This decrease in beta 1- and beta 2-adrenoceptor density was accompanied by similar decreases in the contractile response of isolated electrically driven right atrial and left ventricular papillary muscles to beta-adrenergic agonists. It is concluded that a decrease in cardiac beta-adrenoceptor function is a general phenomenon in heart failure, and its extent is related to the degree of heart failure. However, in contrast to congestive cardiomyopathy, in mitral valve disease the decrease in cardiac beta-adrenoceptor function is due to a concomitant decrease in beta 1- and beta 2-adrenoceptors.

Subtype-selective up-regulation of human saphenous vein beta 2-adrenoceptors by chronic beta-adrenoceptor antagonist treatment.

To study beta-adrenoceptor antagonist-induced changes in human vascular beta-adrenoceptors, we determined the effects of chronic treatment with different beta-adrenoceptor antagonists without intrinsic sympathomimetic activity (ISA) on beta 2-adrenoceptor density (assessed by (-)-[125I]-iodopindolol binding) in human saphenous vein membranes obtained from patients undergoing coronary artery bypass grafting. In patients chronically treated with the non-selective beta-adrenoceptor antagonists propranolol or sotalol, the density of saphenous vein beta 2-adrenoceptors was significantly higher than in control (i.e. patients not treated with beta-adrenoceptor antagonists), whereas in patients chronically treated with the selective beta 1-adrenoceptor antagonists metoprolol or bisoprolol it was not different from control. It is concluded that beta-adrenoceptor antagonists without ISA increase human saphenous vein beta 2-adrenoceptors in a subtype-selective fashion.

[Femoro-axillary bypass--a rarely used form of revascularization in occlusions of the supra-aortic vessels]. / Der femoro-axillare Bypass--eine selten genutzte Revaskularisationsform bei Verschlüssen supraaortaler Gefässe.

Revascularization of central occluded supraaortic vascular branches is more and more successfully done by extra-anatomic junction to the nearest other supraaortic vessel. In case of extreme stenosis of all supraaortic donor vessels intrathoracic surgery may be excluded in poor risk patients. The only possibility of extra-anatomic junction remains connection to iliaco-femoral vessels according to the well known femoro-axillary bypass. Showing two typical cases, this method is demonstrated proving its importance in elective and emergency surgery. The first patient (67 yrs. of age) showed an acute complete ischemia of the right arm due to obstruction of the subclavian artery distal of the origin of the truncus brachiocephalicus. Emergency operation was performed, and revascularization was achieved by femoro-axillary bypass because of biological inoperability to all other orthopic procedures. The second case is of a 66 yrs. old patient with abdominal aortic aneurysm and multiple stenoses of the supraaortic vessels. The abdominal aortic aneurysm was electively operated upon, and during the same operation the cerebral circulation was hemodynamically improved by performing a femoro-subclavian bypass. In considering these two cases, indications, risks and benefits of extra-anatomic revascularization procedures are discussed.