Occurrence and evolutionary origins of polyploids in the clubmoss genus Diphasiastrum (Lycopodiaceae).

Two polyploid taxa are commonly recognized in the genus Diphasiastrum, D. wightianum from Asia and D. zanclophyllum from South Africa and Madagascar. Here we present results from Feulgen DNA image densitometry analyses providing the first evidence for the polyploid origin of D. zanclophyllum. Also reported for the first time are data confirming that D. multispicatum and D. veitchii, representing the putative parent lineages of D. wightianum, are diploids. Phylogenetic analyses of the nuclear regions RPB2, LEAFY and LAMB4 reveal that putative tetraploid accessions are of allopolyploid origin. Diphasiastrum zanclophyllum shows close relationship to the North American taxon D. digitatum on the maternal side, but the paternal relationship is less clear. Two accessions from Asia, both inferred to be polyploid, have D. veitchii as the maternal parent, whereas the paternal paralogs show relationships to D. multispicatum and D. tristachyum, respectively. None of these parental combinations have previously been hypothesized.

Sevoflurane improves myocardial ischaemic tolerance in a closed-chest porcine model.

AIMS: Volatile anaesthetics prevent experimental myocardial ischaemia-reperfusion injury (I/R) in several species, but this finding is partially inconsistent with clinical evidence. Some experimental models may not accurately represent the complex signal transduction pathways triggered by volatile anaesthetics. We therefore investigated sevoflurane I/R prevention in vivo in a porcine model with greater likeness to human physiology than models previously used and compared it with neutral anaesthetic. METHODS AND RESULTS: Myocardial infarct size [IS/AAR] was compared in three groups of pigs (N=35) randomised to Control anaesthesia (pentobarbital infusion, n=12), sevoflurane inhalation alone (end-tidal concentration 3.2%) (Sevo, n=9), or both Combined (n=14), throughout ischaemia and reperfusion. Anterior/septal myocardial infarcts resulted from distal LAD coronary artery occlusion by balloon catheter for 45 min followed by 120 min of reperfusion. [IS/AAR] was measured in tetrazolium-stained heart slices after standardised image processing with computer-assisted planimetry. Measurements included full invasive monitoring. Control animals developed infarction in 55.0 +/- 3.9% (SEM) of the area at risk, Sevo in 17.5 +/- 4.4% (P=0.0002), and Combined with pentobarbital in 24.3 +/- 3.8% (P=0.0001) of the AAR, sevoflurane reducing infarct size significantly (68% and 60%, respectively). CONCLUSIONS: Sevoflurane markedly decreased myocardial infarct size after prolonged coronary occlusion in a porcine model. In addition to novel sevoflurane cardioprotection in the closed-chest model, which is more comparable to normal human hearts than models previously used, sevoflurane cardioprotection is substantiated in the juvenile intact organism. The perspectives underline recommending volatile anaesthetics in risk patients and in cardiac surgery.

Does the pre-ischaemic administration of sevoflurane reduce myocardial stunning? A porcine experimental model.

BACKGROUND: In a porcine model, the cardioprotective effect of sevoflurane was studied with regard to the preservation of myocardial contractility (myocardial stunning) after a myocardial ischaemic insult. METHODS: Twenty-seven pigs were randomized to receive either a dual 4% sevoflurane inhalation period as a supplement to pentobarbital anaesthesia or pentobarbital anaesthesia only before a 15-min ischaemic insult on the left anterior descending coronary artery. The ischaemic period was followed by 180 min of reperfusion. Myocardial contractility was assessed by myocardial sonomicrometry. RESULTS: A significant difference was found between the sevoflurane group and the control group at 5 min of reperfusion. However, subsequently, there was no overall difference between the two groups. CONCLUSION: Sevoflurane administered as a pre-ischaemic bolus does not provide long-term improvement of the myocardial contractility. However, it can be speculated that sevoflurane may induce an early improvement in contractility.

Pre-occlusion ischaemia, not sevoflurane, successfully preconditions the myocardium against further damage in porcine in vivo hearts.

BACKGROUND: Sevoflurane is proposed to possess important tissue protective effects based on experimental ischaemia-reperfusion studies from models with collateral coronary flow, unlike that of the normal human or the porcine heart. The objective was to evaluate the infarct-reducing capability of pre-ischaemic sevoflurane inhalation on myocardial infarct size in a porcine model. METHODS AND MATERIALS: The study comprised 33 pigs under pentobarbital anaesthesia. Animals were divided into three groups: control (CON), sevoflurane intervention (SEVO) and ischaemic preconditioning (IP). The distal left anterior descending coronary artery was occluded for 40 min with a percutaneous coronary intervention catheter. Before occlusion, group IP underwent two 5-min ischaemia cycles, whereas SEVO received two 5-min sevoflurane 4%v/v inhalation cycles. Animals were reperfused for 150 min. We then measured risk area (AAR) and infarct size (IS) after tetrazolium staining. The [IS/AAR-ratio] was calculated. Haemodynamics and transthoracic tissue-Doppler echocardiography were monitored. RESULTS: Control animals developed a myocardial infarction in 46.4 (+/- 6.2)% (mean +/- SEM) of the AAR. Both SEVO and IP groups had infarction mitigated, to 34.4 (5.7)% and 23.1 (5.3)%, respectively; however, only in the IP group was this significant. No significant differences between groups with respect to AAR, haemodynamics or echocardiographic variables were found. CONCLUSION: Pre-ischaemic sevoflurane was found to reduce the extent of myocardial necrosis, but the change was not significant, whereas IP reduced IS by 50% (P= 0.038). Cardioprotection is species related and no previous results from porcine models have found sevoflurane to reduce IS. Anaesthetic washout, insufficient exposure or collateral coronary blood supply, dissimilar to human, may account for positive results in rodent models.

Evaluation of a novel method for measuring tissue blood flow and gases.

In clinical practice a method for assessment of tissue vitality is a sought-after tool. We have developed a new sensor principle, which is able to register changes in tissue concentration of O2 and tissue flow. The technique is based on diffusion of inert gases and mass spectrometer detection of gaseous metabolites. It was hypothesized that the new sensor could register changes in vital parameters after induction and release of an ischaemic insult to muscular tissue. The sensor performance was evaluated in ten anaesthetized pigs subjected to local muscular ischaemia. Preliminary data from this study indicate the validity of registered hypoxia and reduction in tissue flow as a consequence of compromised blood supply. It was concluded that although precise calibration of the technique is not yet established, it holds promise as a technique that can be used to monitor changes in tissue vitality.

A secondary hybrid zone between diploid Dactylorhiza incarnata ssp. cruenta and allotetraploid D. lapponica (Orchidaceae).

Secondary hybrid zones are not uncommon in Dactylorhiza, but knowledge of ecological and evolutionary consequences of hybridization are scarce. Here, we assess interploidal gene flow and introgression in a hybrid zone between diploid Dactylorhiza incarnata ssp. cruenta (2n = 2x = 40) and its putative allotetraploid derivative D. lapponica (2n = 4x = 80). Photometric quantification of DNA content and morphology confirmed that triploids are abundant in sympatric populations in our study area. Allozyme segregation patterns in D. lapponica supported an allopolyploid origin, although unbalanced genotypes suggested rare pairings between homoeologous chromosomes. Photometric data and chromosome counts suggest backcrossing between the triploid hybrid and D. lapponica, and hence some hybrid fertility. Triploids are morphologically more similar to the tetraploids than the diploids, maybe owing to the hybrid origin of both triploids and tetraploids. The diploids and tetraploids were not more similar in the parapatric populations compared to when they occur in allopatry. This indicates that backcrossing rarely leads to introgression, or alternatively that allopatric populations are not isolated enough to prevent influx of pollen from the other species. Despite some evidence of backcrossing, our study gives few indications that widespread hybridization entails local breakdown of species boundaries. Rather, the hybrid zone may be a transient phenomenon due to intensive mowing, resulting in the opening of habitats and hence bringing the parental species into close contact.

Dietary fish oil reduces microvascular thrombosis in a porcine experimental model.

Microvascular thrombosis plays a significant role in the pathophysiology of ischaemic reperfusion injury. A fish oil-supplemented diet containing n-3 polyunsaturated fatty acids (PUFA) reduces thromboxane A(2) (TxA(2)) synthesis and, thus, vasoconstriction and platelet aggregation. The aim of this study was to elucidate whether n-3 PUFA in a porcine model of ischaemia and reperfusion injury 1) inhibit accumulation of platelets and fibrinogen in ischaemia-reperfusion injured tissue, 2) prolong the bleeding time, and 3) inhibit TxA(2) synthesis. Nine pigs were fed a standard diet supplemented with 7 g n-3 PUFA/day for 3 weeks. Nine pigs on the standard diet served as controls. Unilateral myocutaneous flaps were exposed to ischaemia for a period of 6 hours. Contralateral flaps were nonischaemic. Tissue contents of radioactive-labelled platelets and fibrinogen were measured after 4 hours of reperfusion. Platelet count, serum TxB(2), and the cutaneous bleeding time were measured before and after 3 weeks of diet. In the fish oil group, the accumulation of platelets was significantly reduced in all the myocutaneous flaps, except in the ischaemic skin part, when compared to control animals. Fibrinogen was significantly reduced in nonischaemic flaps, but not in ischaemic flaps. After the feeding period, the level of TxB(2) was significantly lowered in the fish oil group (p<0.01). No difference in the bleeding time was observed. Thus, dietary supplementation with n-3 PUFA inhibits the formation of microvasculatory thrombosis in this model.