Sbk2, a Newly Discovered Atrium-Enriched Regulator of Sarcomere Integrity

BACKGROUND

Heart development relies on tight spatiotemporal control of cardiac gene expression. Genes involved in this intricate process have been identified using animals and pluripotent stem cell-based models of cardio(myo)genesis. Recently, the repertoire of cardiomyocyte differentiation models has been expanded with iAM-1, a monoclonal line of conditionally immortalized neonatal rat atrial myocytes (NRAMs), which allows toggling between proliferative and differentiated (ie, excitable and contractile) phenotypes in a synchronized and homogenous manner.

METHODS

In this study, the unique properties of conditionally immortalized NRAMs (iAMs) were exploited to identify and characterize (lowly expressed) genes with an as-of-yet uncharacterized role in cardiomyocyte differentiation.

RESULTS

Transcriptome analysis of iAM-1 cells at different stages during one cycle of differentiation and subsequent dedifferentiation identified ≈13 000 transcripts, of which the dynamic changes in expression upon cardiomyogenic differentiation mostly opposed those during dedifferentiation. Among the genes whose expression increased during differentiation and decreased during dedifferentiation were many with known (lineage-specific) functions in cardiac muscle formation. Filtering for cardiac-enriched low-abundance transcripts, identified multiple genes with an uncharacterized role during cardio(myo)genesis including Sbk2 (SH3 domain binding kinase family member 2). Sbk2 encodes an evolutionarily conserved putative serine/threonine protein kinase, whose expression is strongly up- and downregulated during iAM-1 cell differentiation and dedifferentiation, respectively. In neonatal and adult rats, the protein is muscle-specific, highly atrium-enriched, and localized around the A-band of cardiac sarcomeres. Knockdown of Sbk2 expression caused loss of sarcomeric organization in NRAMs, iAMs and their human counterparts, consistent with a decrease in sarcomeric gene expression as evinced by transcriptome and proteome analyses. Interestingly, co-immunoprecipitation using Sbk2 as bait identified possible interaction partners with diverse cellular functions (translation, intracellular trafficking, cytoskeletal organization, chromatin modification, sarcomere formation).

CONCLUSIONS

iAM-1 cells are a relevant and suitable model to identify (lowly expressed) genes with a hitherto unidentified role in cardiomyocyte differentiation as exemplified by Sbk2: a regulator of atrial sarcomerogenesis.

Cardiovascular magnetic resonance-derived left ventricular mechanics-strain, cardiac power and end-systolic elastance under various inotropic states in swine

BACKGROUND

Cardiovascular magnetic resonance (CMR) strain imaging is an established technique to quantify myocardial deformation. However, to what extent left ventricular (LV) systolic strain, and therefore LV mechanics, reflects classical hemodynamic parameters under various inotropic states is still not completely clear. Therefore, the aim of this study was to investigate the correlation of LV global strain parameters measured via CMR feature tracking (CMR-FT, based on conventional cine balanced steady state free precession (bSSFP) images) with hemodynamic parameters such as cardiac index (CI), cardiac power output (CPO) and end-systolic elastance (Ees) under various inotropic states.

METHODS

Ten anaesthetized, healthy Landrace swine were acutely instrumented closed-chest and transported to the CMR facility for measurements. After baseline measurements, two steps were performed: (1) dobutamine-stress (Dobutamine) and (2) verapamil-induced cardiovascular depression (Verapamil). During each protocol, CMR images were acquired in the short axisand apical 2Ch, 3Ch and 4Ch views. MEDIS software was utilized to analyze global longitudinal (GLS), global circumferential (GCS), and global radial strain (GRS).

RESULTS

Dobutamine significantly increased heart rate, CI, CPO and Ees, while Verapamil decreased them. Absolute values of GLS, GCS and GRS accordingly increased during Dobutamine infusion, while GLS and GCS decreased during Verapamil. Linear regression analysis showed a moderate correlation between GLS, GCS and LV hemodynamic parameters, while GRS correlated poorly. Indexing global strain parameters for indirect measures of afterload, such as mean aortic pressure or wall stress, significantly improved these correlations, with GLS indexed for wall stress reflecting LV contractility as the clinically widespread LV ejection fraction.

CONCLUSION

GLS and GCS correlate accordingly with LV hemodynamics under various inotropic states in swine. Indexing strain parameters for indirect measures of afterload substantially improves this correlation, with GLS being as good as LV ejection fraction in reflecting LV contractility. CMR-FT-strain imaging may be a quick and promising tool to characterize LV hemodynamics in patients with varying degrees of LV dysfunction.

Cardiovascular magnetic resonance feature tracking in pigs: a reproducibility and sample size calculation study

Cardiovascular magnetic resonance feature tracking (CMR-FT) is a novel technique for non-invasive assessment of myocardial motion and deformation. Although CMR-FT is standardized in humans, literature on comparative analysis from animal models is scarce. In this study, we measured the reproducibility of global strain under various inotropic states and the sample size needed to test its relative changes in pigs. Ten anesthetized healthy Landrace pigs were investigated. After baseline (BL), two further steps were performed: (I) dobutamine-induced hyper-contractility (Dob) and (II) verapamil-induced hypocontractility (Ver). Global longitudinal (GLS), circumferential (GCS) and radial strain (GRS) were assessed. This study shows a good to excellent inter- and intra-observer reproducibility of CMR-FT in pigs under various inotropic states. The highest inter-observer reproducibility was observed for GLS at both BL (ICC 0.88) and Ver (ICC 0.79). According to the sample size calculation for GLS, a small number of animals could be used for future trials.

[Refeeding syndrome during alcohol detoxification]

Refeeding syndrome (RS) can occur when malnourished patients are reintroduced to carbohydrates. The symptoms are caused by a combination of electrolyte shifts and fluid retention. Symptoms are wide-ranging; some patients may suffer from harmless muscle cramps, others from more severe neurological and cardiological symptoms that can even lead to death. Although alcohol dependence is a risk factor for the development of RS, little attention is being given to this problem in addiction treatment. In this article we report a case of RS that occurred during alcohol detoxification. We also present the results of a pilot study on the incidence of RS during the alcohol detoxification of 12 patients.

Is enhancing cGMP-PKG signalling a promising therapeutic target for heart failure with preserved ejection fraction?

Heart failure with preserved ejection fraction, i.e. HFpEF, is highly prevalent in ageing populations, accounting for more than 50 % of all cases of heart failure in Western societies, and is closely associated with comorbidities such as obesity, diabetes and arterial hypertension. However, all large multicentre trials of potential HFpEF treatments conducted to date have failed to produce positive outcomes. These disappointing results suggest that a 'one size fits all' strategy may be ill-suited to HFpEF and support the use of tailored, personalised therapeutic approaches with specific treatments designed for specific comorbidity-related HFpEF phenotypes. The accumulation of a multitude of cardiovascular comorbidities over time leads to increased systemic inflammation, oxidative stress and coronary microvascular endothelial inflammation, eventually resulting in degradation of cyclic guanosine monophosphate (cGMP) via multiple pathways, thereby reducing protein kinase G (PKG) activity. The importance of cGMP-PKG pathway modulation is supported by growing evidence that suggests that this pathway may be a promising therapeutic target, evidence that is mainly based on its role in the phosphorylation of the giant cytoskeletal protein titin. This review will focus on the preclinical and early clinical evidence in the field of cGMP-enhancing therapies and PKG activation.

Mild hypothermia induces incomplete left ventricular relaxation despite spontaneous bradycardia in pigs

AIM

Mild hypothermia (MH) decreases left ventricular (LV) end-diastolic capacitance. We sought to clarify whether this results from incomplete relaxation.

METHODS

Ten anaesthetized pigs were cooled from normothermia (NT, 38 °C) to MH (33 °C). LV end-diastolic pressure (LVPed), volume (LVVed) and pressure-volume relationships (EDPVRs) were determined during stepwise right atrial pacing. LV capacitance (i.e. LVVed at LVPed of 10 mmHg, LV VPed10) was derived from the EDPVR. Pacing-induced changes of diastolic indices (LVPed, LVVed and LV VPed10) were analysed as a function of (i) heart rate and (ii) the ratio between diastolic time interval (t-dia) and LV isovolumic relaxation constant τ, which was calculated using a logistic fit (τL ) and monoexponential fit with zero asymptote (τZ ) and nonzero asymptote (τNZ ).

RESULTS

Mild hypothermia decreased heart rate (85 ± 4 to 68 ± 3 bpm), increased τL (22 ± 1 to 57 ± 4 ms), τZ (26 ± 2 to 56 ± 5 ms) and τNZ (41 ± 1 to 96 ± 5 ms), decreased t-dia/τ ratios, and shifted the EDPVR leftwards compared to NT (all P < 0.05). During NT, pacing at ≥140 bpm shifted the EDPVR progressively leftwards. During MH, relationships between diastolic indices and heart rate were shifted towards lower heart rates compared to NT. However, relationships between diastolic indices and t-dia/τ during NT and MH were superimposable.

CONCLUSION

We conclude that the loss of LV end-diastolic capacitance during MH can be explained at least in part by slowed LV relaxation. MH thereby is an example of incomplete LV relaxation at a spontaneous low heart rate. Caution may be advised, when heart rate is increased in patients treated with MH.

PexLoc-Parallel excitation using local encoding magnetic fields with nonlinear and nonbijective spatial profiles

With the recent proposal of using magnetic fields that are nonlinear by design for spatial encoding, new flexibility has been introduced to MR imaging. The new degrees of freedom in shaping the spatially encoding magnetic fields (SEMs) can be used to locally adapt the imaging resolution to features of the imaged object, e.g., anatomical structures, to reduce peripheral nerve stimulation during in vivo experiments or to increase the gradient switching speed by reducing the inductance of the coils producing the SEMs and thus accelerate the imaging process. In this work, the potential of nonlinear and nonbijective SEMs for spatial encoding during transmission in multidimensional spatially selective excitation is explored. Methods for multidimensional spatially selective excitation radiofrequency pulse design based on nonlinear encoding fields are introduced, and it is shown how encoding ambiguities can be resolved using parallel transmission. In simulations and phantom experiments, the feasibility of selective excitation using nonlinear, nonbijective SEMs is demonstrated, and it is shown that the spatial resolution with which the target distribution of the transverse magnetization can be realized varies locally. Thus, the resolution of the target pattern can be increased in some regions compared with conventional linear encoding. Furthermore, experimental proof of principle of accelerated two-dimensional spatially selective excitation using nonlinear SEMs is provided in this study.

The induction of mild hypothermia improves systolic function of the resuscitated porcine heart at no further sympathetic activation

AIM

Mild hypothermia (MH) after cardiac arrest attenuates hypoxic brain injury and improves survival. As MH increases contractility in normal hearts, we hypothesized that MH improves cardiovascular function after cardiac arrest.

METHODS

In 16 anaesthetized pigs (64 ± 2 kg), ventricular fibrillation was induced electrically for 5 min. At 10 min after resuscitation and return of spontaneous circulation (ROSC), pigs were assigned to normothermia (NT, 38°C, n = 8) or MH (33°C, n = 8, intravascular cooling).

RESULTS

At ROSC 6 h vs. baseline, heart rate (HR) was unchanged in NT, but decreased in MH. Cardiac output (CO, l min(-1)) decreased in MH (3.5 ± 0.2 vs. 5.5 ± 0.4, P < 0.05) more than in NT (4.8 ± 0.4 vs. 5.7 ± 0.4, P = ns). Mixed venous oxygen saturation decreased in NT (56 ± 2 vs. 66 ± 3%, P < 0.05), but remained constant in MH (64 ± 2 vs. 65 ± 2%) due to a 35% decrease of whole body oxygen consumption. Left ventricular (LV) dP/dt(max) (mmHg s(-1)) decreased in NT (1163 ± 97 vs. 1665 ± 134, P < 0.05), but was preserved in MH (1602 ± 102 vs. 1603 ± 96), whereas LV relaxation was profoundly slowed during MH. Pressure-volume analysis confirmed improved LV systolic function during MH, but also demonstrated decreased LV end-diastolic distensibility, which was further potentiated by right atrial pacing at baseline HR. MH did not increase plasma catecholamine levels. Spectral analysis of heart rate variability revealed reduced sympathetic activation during MH.

CONCLUSION

The induction of MH after cardiac resuscitation improves systolic myocardial function without further sympathetic activation. A reduced metabolism during MH outweighs a decreased CO and thereby acts favourably on systemic oxygen supply/demand balance.

Cardiac function during mild hypothermia in pigs: increased inotropy at the expense of diastolic dysfunction

AIM

The induction of mild hypothermia (MH; 33 degrees C) has become the guideline therapy to attenuate hypoxic brain injury after out-of-hospital cardiopulmonary resuscitation. While MH exerts a positive inotropic effect in vitro, MH reduces cardiac output in vivo and is thus discussed critically when severe cardiac dysfunction is present in patients. We thus assessed the effect of MH on the function of the normal heart in an in vivo model closely mimicking the clinical setting.

METHODS

Ten anaesthetized, female human-sized pigs were acutely catheterized for measurement of pressure-volume loops (conductance catheter), cardiac output (Swan-Ganz catheter) and for vena cava inferior occlusion. Controlled MH (from 37 to 33 degrees C) was induced by a vena cava inferior cooling catheter.

RESULTS

With MH, heart rate (HR) and whole body oxygen consumption decreased, while lactate levels remained normal. Cardiac output, left ventricular (LV) volumes, peak systolic and end-diastolic pressure and dP/dt(max) did not change significantly. Changes in dP/dt(min) and the time constant of isovolumetric relaxation demonstrated impaired active relaxation. In addition, MH prolonged the systolic and shortened the diastolic time interval. Pressure-volume analysis revealed increased end-systolic and end-diastolic stiffness, indicating positive inotropy and reduced end-diastolic distensibility. Positive inotropy was preserved during pacing, while LV end-diastolic pressure increased and diastolic filling was substantially impaired due to delayed LV relaxation.

CONCLUSION

MH negatively affects diastolic function, which, however, is compensated for by decreased spontaneous HR. Positive inotropy and a decrease in whole body oxygen consumption warrant further studies addressing the potential benefit of MH on the acutely failing heart.

ACS, myocardial bridging, Tako-tsubo syndrome and mitral regurgitation

Isolated systolic compression of the mid portion of the left anterior descending artery (LAD) by a bridge of overlying cardiac muscle is an infrequent but well-recognised angiographic anomaly that is often considered harmless. The long-term prognosis appears to be excellent, but occasional reports of patients with angina pectoris, myocardial infarction and sudden death indicate that this is not always true. The prevalence of the anomaly in the normal population is unknown, but the incidence is low and ischaemic events are rare. Tako-tsubo-like left ventricular dysfunction syndrome (TTS) is characterised by ischaemia, anterior ST-segment elevation, no significant coronary artery disease and reversible ampulla-like left ventricular ballooning in postmenopausal females after emotional or physical stress. Dynamic left ventricular outflow tract (LVOT) obstruction is a rare but potentially fatal complication of acute anterior wall infarction. We present a patient with an acute coronary syndrome (ACS) with ST-segment elevation in the anterior leads, transient TTS and transient LVOT obstruction with systolic anterior motion (SAM) of the mitral valve and severe mitral regurgitation. This is the first report of myocardial bridging associated with TTS, and the first report of TTS associated with dynamic LVOT obstruction with SAM and mitral regurgitation.

Ischemic preconditioning. Experimental facts and clinical perspective

Brief periods of non-lethal ischemia and reperfusion render the myocardium more resistant to subsequent ischemia. This adaption occurs in a biphasic pattern: the first being active immediately and lasting for 2-3 hrs (early preconditioning), the second starting at 24 hrs until 72 hrs after the initial ischemia (delayed preconditioning) and requiring genomic activation with de novo protein synthesis. Early preconditioning is more potent than delayed preconditioning in reducing infarct size; delayed preconditioning also attenuates myocardial stunning. Early preconditioning depends on the ischemia-induced release of adenosine and opioids and, to a lesser degree, also bradykinin and prostaglandins. These molecules activate G-protein coupled receptors, initiate the activation of KATP channels and generation of oxygen radicals, and stimulate a series of protein kinases with essential roles for protein kinase C, tyrosine kinases and members of the MAP kinase family. Delayed preconditioning is triggered by a similar sequence of events, but in addition essentially depends on eNOS-derived NO. Both early and pharmacological preconditioning can be pharmacologically mimicked by exogenous adenosine, opioids, NO and activators of protein kinase C. Newly synthetized proteins associated with delayed preconditioning comprise iNOS, COX-2, manganese superoxide dismutase and possibly heat shock proteins. The final mechanism of protection by preconditioning is yet unknown; energy metabolism, KATP channels, the sodium-proton exchanger, stabilisation of the cytoskeleton and volume regulation will be discussed. For ethical reasons, evidence for ischemic preconditioning in humans is hard to provide. Clinical findings that parallel experimental ischemic preconditioning are reduced ST-segment elevation and pain during repetitive PTCA or exercise tests, a better prognosis of patients in whom myocardial infarction was preceded by angina, and reduced serum markers of myocardial necrosis after preconditioning protocols during cardiac surgery with cardiac arrest. The most promising approach to apply principles of ischemic preconditioning therapeutically appears to be the pharmacological recruitment of delayed protection, as recently demonstrated with intravenous nitroglycerine in patients undergoing PTCA 24 hrs later.

No involvement of nitric oxide in the limitation of beta-adrenergic inotropic responsiveness during ischemia

We tested whether or not endogenous nitric oxide (NO) attenuates beta-adrenergic inotropic responsiveness during normoperfusion or moderate myocardial ischemia. In 13 anesthetized pigs with a cannulated left anterior descending (LAD) coronary artery, the maximal contractile responses to intracoronary dobutamine and calcium were assessed during normoperfusion and at the end of a 90-min period of moderate ischemia (50% reduction in coronary arterial inflow) without (group 1, n = 6) and with (group 2, n = 7) prior inhibition of NO synthesis [30 mg/kg iv N(omega)-nitro-L-arginine (L-NNA)]. Contractile function was assessed by a regional work index (sonomicrometry, micromanometry, mm. mmHg). In groups 1 and 2 during normoperfusion, the maximal increase of the work index was greater with calcium than with dobutamine. At the end of ischemia in group 1, the baseline work index was decreased by approximately 50%, and the subsequent maximal increase of the work index with dobutamine, but not with calcium, was reduced compared with normoperfusion. In group 2 during normoperfusion, L-NNA did not alter the maximal increases of the work index with dobutamine or calcium. At the end of ischemia, the baseline work index was reduced by 64%, and the subsequent maximal increases of the work index with both dobutamine and calcium were reduced compared with normoperfusion; however, the response to calcium was still greater than that to dobutamine. We conclude that endogenous NO does not limit beta-adrenergic inotropic responsiveness in normoperfused or moderately ischemic porcine myocardium.

Linear and non-linear dynamics of heart rate variability in brain dead organ donors

Recent studies outlined linear and non-linear dynamics in heart rate variability; however, their physiological origin is still unknown. The present study investigated the impact of cerebral function on linear and non-linear dynamics in heart rate variability. Electrocardiograms from seven brain dead organ donors and seven healthy volunteers were analyzed. Atropine was used in healthy volunteers to adjust their heart rate to that of the donors. As compared to healthy volunteers without atropine, the linear dynamics of heart rate variability, determined by time and frequency domain analyses, were significantly reduced in healthy volunteers with atropine and, to an even greater extent, in donors. Atropine tended to increase the complexity and non-linearity of heart rate variability in healthy volunteers, as determined by the correlation dimension D and the largest Lyapunov exponent L, respectively (D = 9.43 +/- 2.93 vs. 7.65 +/- 0.97 and L = 0.525 +/- 0.099 vs. 0.504 +/- 0.047 bits.beat-1; both NS), while these indices were significantly reduced in donors by 19.5 +/- 12.8% and 15.0 +/- 11.7%, respectively (D = 6.16 +/- 0.98 and L = 0.428 +/- 0.059 bits.beat-1; both p < 0.05 vs. volunteers). Thus, loss of cerebral function reduces both linear and non-linear components of heart rate variability.

Progressive loss of perfusion-contraction matching during sustained moderate ischemia in pigs

It is unclear whether perfusion-contraction matching (PCM) is maintained during prolonged myocardial ischemia. In 27 anesthetized pigs, left anterior descending coronary arterial inflow was reduced to decrease an anterior work index (WI) at 5 min of hypoperfusion by 40% and then maintained at this level for 12 or 24 h. With 12 h of hypoperfusion, the myocardium remained viable in 6 of 7 pigs (with triphenyltetrazolium chloride; TTC) and with 24 h of hypoperfusion in 5 of 11 pigs (TTC, histology). The reduction in WI to 62 +/- 4 and 62 +/- 3% of baseline in the two groups was matched to the reduction of transmural blood flow (TBF; microspheres) at 5 min of hypoperfusion, averaging 59 +/- 4 and 60 +/- 2% of baseline. With prolonged hypoperfusion, WI decreased to 30 +/- 5% at 12 h and 18 +/- 3% at 24 h; TBF remained unchanged (53 +/- 4 and 54 +/- 4%). The added calcium concentration required for the half-maximal increase in WI increased from 121 +/- 25 microg/ml blood at baseline to 192 +/- 26 microg/ml blood at 12 h of hypoperfusion. Thus, with hypoperfusion for 24 h, PCM is progressively lost, and calcium responsiveness is reduced.

Less afterload sensitivity in short-term hibernating than in acutely ischemic and stunned myocardium

Short-term hibernating myocardium is characterized by reduced contractile function during persistent moderate ischemia, the recovery of metabolic parameters, and the absence of necrosis. To study the afterload dependence of regional wall excursion in short-term hibernating myocardium, in 11 enflurane-anesthetized swine the left anterior descending coronary artery was cannulated and hypoperfused for 90 min to reduce anterior systolic wall thickening (WT, sonomicrometry) by 60%. Under control conditions, at 5 and 90 min ischemia the descending thoracic aorta was acutely constricted to increase left ventricular (LV) pressure by 30 mmHg. Under control conditions, increased LV pressure resulted in decreased WT [i.e., a negative slope of the relationship between WT and LV end-systolic pressure: -11.2 +/- 4.2 (SD) microm/mmHg]. This slope was further significantly decreased at 5 min ischemia (-26.5 +/- 8.8 microm/mmHg) but returned toward control values in short-term hibernating myocardium at 90 min ischemia (-17.2 +/- 6.6 microm/mmHg). At 30 min reperfusion, the slope was once more significantly decreased (-27.8 +/- 8.1 microm/mmHg). In conclusion, WT in short-term hibernating myocardium is less afterload dependent than in acutely ischemic and reperfused myocardium.

Enhanced reduction of myocardial infarct size by combined ACE inhibition and AT(1)-receptor antagonism

The effects of the angiotensin-converting-enzyme inhibitor (ACEI) ramiprilat, the angiotensin II type 1 receptor antagonist (AT(1)A) candesartan, and the combination of both drugs on infarct size (IS) resulting from regional myocardial ischaemia were studied in pigs. Both ACEI and AT(1)A reduce myocardial IS by a bradykinin-mediated process. It is unclear, however, whether the combination of ACEI and AT(1)A produces a more pronounced IS reduction than each of these drugs alone. Forty-six enflurane-anaesthetized pigs underwent 90 min low-flow ischaemia and 120 min reperfusion. Systemic haemodynamics (micromanometer), subendocardial blood flow (ENDO, microspheres) and IS (TTC-staining) were determined. The decreases in left ventricular peak pressure by ACEI (by 9+/-2 (s.e. mean) mmHg), AT(1)A (by 11+/-2 mmHg) or their combination (by 18+/-3 mmHg, P<0.05 vs ACEI and AT(1)A, respectively) were readjusted by aortic constriction prior to ischaemia. With placebo (n=10), IS averaged 20.0+/-3.3% of the area at risk. IS was reduced to 9.8+/-2.6% with ramiprilat (n=10) and 10.6+/-3.1% with candesartan (n=10). Combined ramiprilat and candesartan (n=10) reduced IS to 6.7+/-2.1%. Blockade of the bradykinin-B(2)-receptor with icatibant prior to ACEI and AT(1)A completely abolished the reduction of IS (n=6, 22.8+/-6.1%). The relationship between IS and ischaemic ENDO with placebo was shifted downwards by each ACEI and AT(1)A and further shifted downwards with their combination (P<0.05 vs all groups); icatibant again abolished such downward shift. The combination of ACEI and AT(1)A enhances the reduction of IS following ischaemia/reperfusion compared to a monotherapy by either drug alone; this effect is mediated by bradykinin.

Inconsistent relation of MAPK activation to infarct size reduction by ischemic preconditioning in pigs

The importance of the activation of mitogen-activated protein kinases (MAPK) for the cardioprotection achieved by ischemic preconditioning (IP) is still controversial. We therefore measured infarct size and p38, extracellular signal-regulated kinase (ERK), and c-Jun NH(2)-terminal kinase (JNK) MAPK phosphorylation (by biopsies) in enflurane-anesthetized pigs. After 90 min low-flow ischemia and 120 min reperfusion, infarct size averaged 18.3 +/- 12.4 (SD)% (group 1, n = 14). At similar subendocardial blood flows, IP by 10 min ischemia and 15 min reperfusion (group 2, n = 14) reduced infarct size to 6.2 +/- 5.1% (P < 0.05). An inconsistent increase in p38, ERK, and p54 JNK phosphorylation (by Western blot) was found during IP; p46 JNK phosphorylation increased with the subsequent reperfusion. At 8 min of the sustained ischemia, p38, ERK, and p54 JNK phosphorylation were increased with no difference between groups (medians: p38: 207% of baseline in group 1 vs. 153% in group 2; ERK: 142 vs. 144%; p54 JNK: 171 vs. 155%, respectively). MAPK phosphorylation and reduction of infarct size by IP were not correlated, thus not supporting the concept of a causal role of MAPK in mediating cardioprotection by IP.

Endogenous nitric oxide and myocardial adaptation to ischemia

Ischemic myocardium does not inevitably undergo necrosis but rather can survive through downregulation of contractile function, ie, "hibernate." To study the role of endogenous NO in this adaptation, 41 enflurane-anesthetized swine were subjected to 90 minutes of moderate left anterior descending coronary artery hypoperfusion and assigned to placebo (P), to 30 mg/kg N(G)-nitro-L-arginine (L-NNA) IV to inhibit NO synthase, or to aortic constriction (AO) to match the increased left ventricular pressure observed with L-NNA. During normoperfusion, a regional myocardial external work index (WI, mm Hg. mm, sonomicrometry and micromanometry) was reduced with L-NNA (from 326+/-27 [SEM] to 250+/-19, P<0.05) but increased with AO (from 321+/-16 to 363+/-19, P<0.05 versus L-NNA). At 10 minutes of ischemia, WI was lower with L-NNA (109+/-10, P<0.05) than P (180+/-22) and AO (170+/-11) and did not change further at 85 minutes of ischemia. Relationships between WI and transmural myocardial blood flow and oxygen consumption were shifted rightward by L-NNA versus P and AO at both 10 and 85 minutes of ischemia. The maximal increment in calcium-activated external work was not different during normoperfusion among groups but was decreased during ischemia with L-NNA. L-NNA transiently increased myocardial contractile calcium sensitivity along with systemic pressure but reduced it during ongoing ischemia. The free-energy change of ATP hydrolysis after an early ischemic decrease recovered toward baseline values in all groups, and necrosis was absent after 2 (triphenyltetrazolium chloride staining) or 8 (histology) hours of reperfusion. Thus, endogenous NO contributes to hibernation by reducing oxygen consumption and preserving calcium sensitivity and contractile function without an energy cost during ischemia.

No involvement of endogenous nitric oxide in classical ischemic preconditioning in swine

Endogenous nitric oxide (NO) is involved in the protection by classical ischemic preconditioning (IP) against ischemia-induced arrhythmias in anesthetized dogs. Furthermore, NO triggers and mediates protection against infarction and stunning in delayed IP in conscious rabbits. Up to now it is unclear whether or not endogenous NO is also involved in the protection against infarction by classical IP in vivo. In 45 enflurane-anesthetized swine, severe left anterior descending coronary artery hypoperfusion for 90 min followed by 2 h of reperfusion resulted in an infarct size (IS, triphenyl tetrazolium chloride-staining) of 20.5+/-5.4% (S.E.M.) of the area at risk. Inhibition of NO synthase by l -nitro arginine (l -NA, 30 mg/kg i.v.) increased left ventricular (LV) peak pressure from 93+/-3 to 120+/-1 mmHg (P<0.05), but did not alter IS (22.4+/-5. 6%). With aortic constriction to match the increase in LV peak pressure with l -NA, IS was unchanged (18.1+/-5.1%). IP by 10 min ischemia and 15 min reperfusion preceding the 90 min target ischemia reduced IS to 2.0+/-0.8% (P<0.05 v. non-preconditioned groups). This reduction of IS by IP was not affected by l -NA (1.3+/-0.9%, P<0.05 v. non-preconditioned groups). Area at risk and myocardial blood flow (microspheres) during ischemia were not different among groups. Relationships between IS and subendocardial blood flow with l -NA or aortic constriction, respectively, were not different from that with placebo, but were significantly shifted downwards by IP with and without l -NA. Thus, endogenous NO does not alter infarct size development per se and is not involved in the protection against infarction by classical IP in pigs in vivo.

Unique cardioprotective action of the new calcium antagonist mibefradil

BACKGROUND

Mibefradil is a calcium antagonist with few negative inotropic effects at therapeutic concentrations.

METHODS AND RESULTS

The effect of mibefradil on infarct size (IS) was compared with those of placebo, amlodipine, and verapamil in 64 anesthetized pigs. In placebo pigs, after 90 minutes of ischemia and 120 minutes of reperfusion, IS (by triphenyl tetrazolium chloride staining) was 15.3+/-10.8% (SD) of the area at risk. Mibefradil (0.60 mg/kg IV) reduced heart rate and left ventricular (LV) pressure, and IS was 1. 9+/-3.9% (P<0.05 versus placebo). Verapamil (0.15 mg/kg IV) also decreased heart rate, LV pressure, and IS (6.1+/-4.2%, P<0.05 versus placebo). Amlodipine (0.20 mg/kg IV) did not alter heart rate, LV pressure, or IS (9.9+/-5.4%, P=NS versus placebo). When heart rate was maintained constant by left atrial pacing and LV pressure was adjusted to that of the placebo group by an intra-aortic balloon, mibefradil still decreased IS (3.8+/-3.0%, P<0.05 versus placebo), but verapamil did not (11.6+/-8.3%, P=NS versus placebo). With glibenclamide infusion, mibefradil no longer reduced IS (13.1+/-4.3% versus 17.8+/-5.6% with glibenclamide alone, P=NS).

CONCLUSIONS

The IS-limiting effect of mibefradil, in contrast to that of verapamil, was not dependent on favorable hemodynamics but was abolished by glibenclamide, suggesting a direct cardioprotective action of mibefradil.

Impact of resting and ischemic blood flow on infarct probability in ischemic preconditioning--a new approach to infarct size-blood flow data by logistic regression

The linear regression analysis of infarct size (IS) v ischemic myocardial blood flow (MBF) does not account for the heterogeneity of MBF and infarcted tissue; moreover, it cannot assess a blood flow threshold for infarction (MBFT) accurately, as with ischemic preconditioning (IP) the close relationship between ischemic MBF and IS otherwise observed is lost. Finally, the impact of resting blood flow on myocardial infarction cannot be considered in such analysis. Therefore, in a retrospective data analysis of 32 enflurane-anaesthetized swine undergoing 90 min severe ischemia and 120 min reperfusion without (CON, n = 12) or with IP induced by either 3 (IP3, n = 8) or 10 min ischemia (IP10, n = 12) and 15 min reperfusion, a MBFT was assessed by logistic regression (LR) in individual tissue pieces. MBFT was arbitrarily defined as that ischemic MBF (microspheres) at which infarct probability was 0.2, derived from the ratio of infarcted (n = 141, TTC) to all tissue samples (n = 684). The duration of the preconditioning ischemia and MBF both at rest and during the sustained ischemia were significant predictors of infarct probability. Ischemic MBFT at an infarct probability of 0.2, was 0.089 +/- 0.023 ml/min/g in CON. MBFT was decreased to 0.051 +/- 0.03 ml/min/g with IP3 (P < 0.05 v CON) and further to 0.004 +/- 0.037 ml/min/g with IP10 (P < 0.05 v CON, IP3). Corresponding to the leftward shift of MBFT, the relationships between infarct probability and MBF were shifted in parallel by IP with no change in their slopes.

Ischemic preconditioning in pigs: a graded phenomenon: its relation to adenosine and bradykinin

BACKGROUND

A threshold concept for ischemic preconditioning (IPc) has been proposed. It is unclear, however, whether IPc, above a certain threshold, is an all-or-nothing or a graded phenomenon.

METHODS AND RESULTS

In 71 enflurane-anesthetized swine, severe left anterior descending coronary artery hypoperfusion for 90 minutes followed by 2 hours of reperfusion resulted in an infarct size (IS, by triphenyltetrazolium chloride) of 16.7+/-3.4% (SEM) of the area at risk. IPc by 2 minutes of low-flow ischemia and 15 minutes of reperfusion before the 90-minute target ischemia did not reduce IS (21.9+/-7.0%). IS was decreased to 9.0+/-2.6% (P<0.05) by 3 minutes of IPc and reduced further to 1.9+/-0.9% (P<0.05) by 10 minutes of IPc. The interstitial adenosine concentration (microdialysis, high-performance liquid chromatography) was unchanged with 2 and 3 minutes of IPc but increased with 10 minutes of IPc (by 573+/-144%). The interstitial bradykinin concentration (microdialysis, radioimmunoassay) remained unchanged with 2 minutes of IPc but increased to a similar extent with 3 minutes (by 198+/-32%) and 10 minutes (by 224+/-30%) of IPc. The IS reduction by 3 minutes of IPc was abolished by blockade of the bradykinin B2 receptor with intracoronary HOE 140 (16.6+/-4.3%) but not with intracoronary infusion of adenosine deaminase (8.4+/-2.5%, P<0.05). HOE 140, however, did not affect the IS reduction (3.5+/- 1.1%, P<0.05) by 10 minutes of IPc. Combined infusion of HOE 140 and adenosine deaminase abolished the IS reduction by 10 minutes of IPc (15.4+/-6.7%).

CONCLUSIONS

IS reduction by IPc is a graded phenomenon. Whereas bradykinin is essential during preconditioning ischemia of shorter duration, adenosine is more important during preconditioning ischemia of longer duration.

Relation of olfactory event-related potentials to changes in stimulus concentration

OBJECTIVE

The aim of this study was to investigate the influence of odorant concentration on the olfactory event-related potential (OERP).

METHODS

OERP were evaluated in 8 men and 8 women (17-34 years of age) in response to 4 concentrations of vanillin (7, 28, 56 and 84% v/v). Sixteen presentations of each concentration (stimulus duration 200 ms, interval 40 s, flow 81/min) were applied in a randomized order. EEG recordings were made at 3 midline sites (pos. Fz, Cz, Pz). Amplitudes and latencies of four peaks were measured (latencies in ms at Pz after stimulation with 84% v/v vanillin): P1 (277), N1 (348), P2 (412) and P3 (496). Statistical analysis was performed with MANOVAs ('concentration', 'recording site' = within-subject-factors; 'age' as covariate).

RESULTS

With increasing stimulus concentration amplitudes became significantly larger; this was most pronounced for P3 (P1N1: F = 2.90, P < 0.05; N1P2: F = 5.15, P < 0.01; N1P3: F = 35.7, P < 0.001; P3: F = 38.6; P < 0.001). Correspondingly, latencies shortened with increasing concentrations (P1: F = 25.2; N1: 17.51; P2: 14.8; P3: 13.4; all P < 0.001). While there was no correlation between OERP amplitudes and butanol odor detection thresholds, latencies were the shorter the lower the subjects' thresholds (coefficients of correlations for peak latencies at Cz for 84% v/v: P1 rl5 = -0.59; N1 rl5 = 0.58; P2 r15 = -0.55; P3 r15 = -0.45).

CONCLUSIONS

The results indicated that both OERP amplitudes and latencies are related to the concentration of olfactory stimuli. They also suggested that latencies exhibit a stronger relation to changes in stimulus intensity compared to OERP amplitudes.

Prevention of ischemic preconditioning only by combined inhibition of protein kinase C and protein tyrosine kinase in pigs

In rabbits, inhibition of either protein kinase C or protein tyrosine kinase abolishes the infarct size reduction achieved by ischemic preconditioning. In pigs, however, inhibition of protein kinase C does not attenuate ischemic preconditioning. The present study tested whether inhibition of protein tyrosine kinase alone or in combination with inhibition of protein kinase C interferes with ischemic preconditioning in pigs. In 29 enflurane-anesthetized pigs, the LAD was cannulated and perfused from an extracorporeal circuit. Protein tyrosine kinase and protein kinase C were inhibited by continuous intracoronary infusion of genistein (5x10(-6) mol/l) and staurosporine (10(-7) mol/l), respectively. Subendocardial blood flow (ENDO) was measured with microspheres. Infarct size was analysed by TTC staining (% of LV area at risk) following 90 min low-flow ischemia and 120 min reperfusion. In the presence of genistein, 90 min ischemia at an ENDO of 0.06+/-0.01 (+/-s.e.m.) ml/min/g resulted in an infarct size of 16.7+/-4.2% (n=8). With genistein, ischemic preconditioning by 10 min ischemia and 15 min reperfusion still reduced infarct size to 6.5+/-2.7% (ENDO: 0.05+/-0. 01 ml/min/g, n=7, P<0.05). In the presence of both genistein and staurosporine, infarct size following 90 min ischemia was 14.1+/-3. 6% (ENDO: 0.06+/-0.01 ml/min/g, n=7). With genistein and staurosporine, ischemic preconditioning no longer reduced infarct size significantly (11.5+/-3.1%, ENDO: 0.06+/-0.01 ml/min/g, n=7). The effective attenuation of ischemic preconditioning only by simultaneous inhibition of both, protein kinase C and protein tyrosine kinase, suggests a complex signal cascade involving both protein kinases.

A new simple method for conservation and demonstration of body sections for teaching clinically oriented courses in gross anatomy

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No prevention of ischemic preconditioning by the protein kinase C inhibitor staurosporine in swine

The delay of infarct size development by ischemic preconditioning involves the activation of protein kinase C in rats and rabbits. In dogs the role of protein kinase C in ischemic preconditioning is controversial. We investigated whether or not the activation of protein kinase C is a prerequisite for ischemic preconditioning in swine. Swine were used, since they are large mammals and since infarct development in this species, due to the lack of an innate collateral circulation, is similar to that in humans. In 20 enflurane-anesthetized swine, the proximal left anterior descending coronary artery was cannulated and perfused from an extracorporeal circuit. The impact of continuous intracoronary infusion of 10(-7) mol/L staurosporine, a potent protein kinase C inhibitor, on global and regional myocardial function (sonomicrometry), subendocardial blood flow (ENDO, microspheres), and infarct size (IS, triphenyltetrazolium chloride staining after 120 minutes of reperfusion) was analyzed. Staurosporine (10(-7) mol/L) abolished the 1.6-fold increase in coronary arterial resistance in response to 10(-6) mol/L IC 4 beta-phorbol 12-myristate 13-acetate, a potent protein kinase C activator. In the presence of staurosporine, 90 minutes of low-flow ischemia at an ENDO of 0.05 +/- 0.04 (mean +/- SD) mL.min-1.g-1 resulted in an IS of 12.5 +/- 8.6% (n = 10) of the area at risk. Also, in the presence of staurosporine, ischemic preconditioning by a cycle of 10 minutes of low-flow ischemia followed by 15 minutes reperfusion before the 90 minutes sustained ischemic period (ENDO, 0.05 +/- 0.03 mL.min-1.g-1) reduced IS to 3.3 +/- 3.4% (n = 10, P < .05). The protein kinase C inhibitor staurosporine does not prevent ischemic preconditioning in swine.

No attenuation of ischaemic preconditioning by the calcium antagonist nisoldipine

In anaesthetized dogs, intracoronary infusion of calcium prior to a prolonged ischaemic period reduced infarct size, thereby mimicking the protective effects of ischaemic preconditioning and suggesting that an increase in the intracellular calcium concentration might be an important mechanism underlying this phenomenon. The aim was to determine whether pretreatment with the calcium antagonist nisoldipine attenuates the reduction in infarct size achieved by ischaemic preconditioning. In 10 enflurane-anaesthetized pigs serving as controls (group 1), the inflow into the cannulated left anterior descending coronary artery was reduced (low-flow ischaemia) to achieve a 90% reduction in an anterior myocardial work index (sonomicrometry) for 90 min. In 11 pigs (group 2), a cycle of 10 min of low-flow ischaemia and 15 min of reperfusion (preconditioning) preceded the prolonged ischaemia. In groups 3 (n = 9) and 4 (n = 7), nisoldipine was administered by intravenous infusion (500 ng/kg/min) starting 40 min prior to and then throughout a protocol identical to that of groups 1 and 2, respectively. Subendocardial blood flow was measured with radiolabelled microspheres. Infarct size (% area at risk) was determined by triphenyltetrazolium staining in all pigs after 120 min of reperfusion. Subendocardial blood flow in the area at risk was similar in all four groups (group 1: 0.09 +/- 0.04 ml/min/g; group 2: 0.05 +/- 0.03; group 3: 0.09 +/- 0.03; group 4: 0.07 +/- 0.03). Group 2 had reduced infarct size when compared with group 1 (2.6 +/- 3.0% v 12.4 +/- 8.7%, P = 0.004), and there was a trend for a reduction in infarct size following nisoldipine treatment (group 3: 10.2 +/- 7.1%, group 4: 1.6 +/- 2.8%, P = 0.01). Thus administration of nisoldipine in pigs tended to decrease infarct size, and did not abolish the cardioprotection afforded by ischaemic preconditioning.

Calcium responsiveness in regional myocardial short-term hibernation and stunning in the in situ porcine heart. Inotropic responses to postextrasystolic potentiation and intracoronary calcium

BACKGROUND

We tested the hypothesis that decreased calcium responsiveness is responsible for the reduction in contractile function in regional hibernating and stunned myocardium in situ.

METHODS AND RESULTS

In 19 anesthetized swine, the left anterior descending coronary artery flow was reduced to decrease anterior myocardial work index (sonomicrometry) by approximately 60%. During 90 minutes of hypoperfusion, creatine phosphate recovered (as determined by biopsy specimens and bioluminescence) and no necrosis developed (as determined by staining with triphenyl tetrazolium chloride). In 10 swine, changes in the intracellular calcium concentration were induced by systematic variation of the postextrasystolic time interval at a constant prematurity. In 9 additional swine, a graded IC calcium infusion was performed. Under control conditions, anterior myocardial work increased with a fully compensated postextrasystolic time interval from 380+/-93 (mean+/-SD) to 523+/-98 mm Hg . mm. IC calcium infusion increased anterior myocardial work under control conditions from 356+/-85 to a maximum of 428+/-93 mm Hg . mm. Although the maximal responses were decreased during postextrasystolic potentiation (222+/-68 versus 523+/-98 mm Hg . mm) and calcium infusion (176+/-32 versus 428+/-93 mm Hg . mm) after 90 minutes of ischemia, the relationships between increases in anterior myocardial work and, respectively, postextrasystolic time interval and IC calcium were not different. The same was true after 30 minutes of reperfusion.

CONCLUSIONS

Both regional hibernating myocardium and stunned myocardium in situ are characterized by a decrease in overall myocardial calcium responsiveness; however, there appears to be no significant myocardial desensitization to calcium.

Involvement of endogenous adenosine in ischaemic preconditioning in swine

Adenosine release and the subsequent activation of adenosine receptors are involved in ischaemic preconditioning in dogs and rabbits. In the present study, we investigated whether adenosine also mediates ischaemic preconditioning in swine. Swine were used since, due to the lack of an innate collateral circulation, infarct development in this species most closely resembles that observed in humans. In 36 enflurane-anaesthetized swine the impact of increased adenosine breakdown with exogenous porcine adenosine deaminase (5 IU/ml blood/min) on global and regional myocardial function (sonomicrometry), subendocardial blood flow (ENDO, microspheres) and infarct size (IS, triphenyl tetrazolium chloride staining following 90 min ischaemia and 120 min reperfusion) were analysed. Low-flow ischaemia for 90 min at an ENDO of 0.09 +/- 0.04 (mean +/- SD) ml/min/g caused an IS of 13.2 +/- 9.7% (n = 8) of the area at risk. Ischaemic preconditioning by a cycle of 10 min low-flow ischaemia followed by 15 min reperfusion prior to the 90-min ischaemic period (ENDO = 0.06 +/- 0.03 ml/min/g) reduced IS to 2.6 +/- 3.0% (n = 11, P < 0.05). The interstitial adenosine concentration (microdialysis) increased from 1.60 +/- 0.87 nmol/ml to above 10 microM during ischaemia; with intracoronary adenosine deaminase, the interstitial adenosine concentration fell from 1.65 +/- 0.23 to 0.12 +/- 0.07 nmol/ml and did not increase during ischaemia. Adenosine deaminase per se did not alter IS after 90 min ischaemia (n = 7, ENDO = 0.08 +/- 0.04 ml/min/g, IS = 12.1 +/- 6.9%) but abolished the beneficial effect of ischaemic preconditioning (n = 10, ENDO = 0.06 +/- 0.03 ml/min/g, IS = 8.8 +/- 5.8%). For any given ENDO, IS was significantly reduced in the ischaemic preconditioned group compared with the other three groups. Global and regional myocardial function were comparable among all groups of swine. We conclude that endogenous adenosine mediates ischaemic preconditioning also in swine.

Regional short-term myocardial hibernation in swine does not involve endogenous adenosine or KATP channels

Short-term hibernating myocardium is characterized by reduced contractile function during persistent ischemia, the recovery of metabolism over time, a recruitable inotropic reserve, and the lack of necrosis. The mechanisms underlying myocardial hibernation are unclear. The present study addressed the role of endogenous adenosine and that of activation of ATP-dependent potassium (KATP) channels. In 22 enflurane-anesthetized swine, coronary inflow was reduced to decrease regional myocardial work (W, measured by sonomicrometry) by 60-70% at 5 min of ischemia; this flow reduction has previously been shown to be compatible with the development of myocardial hibernation. Systemic hemodynamics, W, subendocardial blood flow (measured by microspheres), and the myocardial creatine phosphate content (measured by biopsies, mumol/g wet wt) were measured under control conditions and during 90 min of ischemia, with an intracoronary dobutamine infusion during the last 5 min of ischemia. The impact of endogenous adenosine was eliminated by infusion of intracoronary adenosine deaminase (ADA), and the impact of activation of KATP channels by glibenclamide. Creatine phosphate content recovered in the placebo-treated swine (n = 8, 3.8 +/- 1.9 to 5.8 +/- 2.0 mumol/g wet wt) as well as in swine receiving ADA (n = 7, 4.1 +/- 1.2 to 6.0 +/- 1.7 mumol/g wet wt) or glibenclamide (n = 7, 2.8 +/- 1.3 to 6.7 +/- 1.6 mumol/g wet wt) when ischemia was prolonged from 5 to 85 min. At the end of 90 min of ischemia, W increased during intracoronary dobutamine in all three groups to a comparable extent, and myocardial necrosis was absent in all three groups of swine.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraischemic preconditioning. Increased tolerance to sustained low-flow ischemia by a brief episode of no-flow ischemia without intermittent reperfusion

Ischemic preconditioning (IP) and myocardial hibernation (MH) are both adaptive phenomena during acute myocardial ischemia, characterized by preserved myocardial viability and attenuated alterations of energy metabolism. Recent data from isolated buffer-perfused rabbit hearts pointed to a further link between IP and MH, in that an initial stimulus of no-flow ischemia was required to permit the development of MH during subsequent sustained low-flow ischemia. In the present study, we therefore investigated in the in situ pig heart whether a brief episode of no-flow ischemia enhances the myocardial tolerance to subsequent sustained low-flow ischemia. By blocking ATP-dependent potassium channels, we attempted to further determine whether such increased tolerance to ischemia is related to IP or MH, since blockade of ATP-dependent potassium channels abolishes the cardioprotection achieved by IP but not by MH. In 8 enflurane-anesthetized pigs serving as controls (group 1), the inflow into the cannulated left anterior descending coronary artery was reduced to achieve a 90% reduction in the anterior myocardial work index (sonomicrometry) for 90 minutes. In 15 pigs (group 2), a 10-minute no-flow ischemic episode preceded 80 minutes of sustained ischemia at a blood flow reduction identical to that in pigs of group 1. In 8 additional pigs (group 3), glibenclamide was administered before the 10-minute no-flow ischemic episode. In all pigs after 120 minutes of reperfusion, infarct size (IS, percentage of area at risk) was determined by triphenyltetrazolium chloride staining. In group 2, IS was reduced (6.8 +/- 6.0% [mean +/- SD], P < .05) when compared with groups 1 (13.2 +/- 9.8%) and 3 (16.7 +/- 8.3%).(ABSTRACT TRUNCATED AT 250 WORDS)

Encoding of frequency of occurrence by aphasia patients: attentional or linguistic deficit?

Frequency-encoding performance of aphasic patients and control subjects was studied in order to test Grober's (1984) hypothesis that aphasic patients are not deficient in the encoding of frequency of events. Experiment 1 compared patients and controls on four types of list: spoken words, visual words, images of objects, and abstract figures. Experiment 2 varied semantic and phonological similarity among the words in one list. Both experiments found differences between the groups, and differences between conditions. The deterioration in patients tended to be greater for linguistic than for nonlinguistic material (experiment 1), and was strongly enhanced by semantic similarity (experiment 2). Results are better explained by a linguistic deficit than by an attentional capacity account of aphasia.

Family participation during resuscitation: an option

We began to question the fairness of a policy to exclude close family members from the treatment room during attempted resuscitation of cardiac arrest victims in 1982 after 13 of 18 surviving relatives (72%) who were surveyed about their experiences during the attempted resuscitation of a family member responded that they would have liked to have been present during the resuscitation. We report the results of a program instituted at that time that allowed selected family members to be present during resuscitation efforts. Family members were asked by a chaplain or nurse if they wished to be present in the resuscitation room, and those accepting were accompanied by a supporting emergency staff member who explained the milieu of the code room. None of the participants interfered with resuscitation efforts. Seventy persons who participated were later contacted by one of the chaplains and asked to complete a survey form. Forty-four of 47 respondents (94%) who had been present during resuscitation believed that they would participate again. Thirty-six (76%) thought that adjustment to the death or grieving was facilitated by their witnessing the resuscitation; 30 (64%) felt that their presence was beneficial to the dying family member. We conclude that lay person may wish to be with family members who may be dying even though resuscitation efforts are being made, and that it is reasonable to inquire about this wish. This experience has assisted the grieving process for many and has not interrupted or adversely affected medical efforts at resuscitation.

Accurate T2 NMR images

We present a method for producing accurate calculated T2 nuclear magnetic resonance (NMR) images. A modified Carr-Purcell-Meiboom-Gill pulse sequence is used to obtain a series of images with progressive T2 dependence. This image series is then analyzed pixel by pixel to generate a T2 and initial signal strength image. Tests performed using four samples of known T2 indicate accuracies of better than 9%.

Trifluorothymidine versus adenine arabinoside in the treatment of herpes simplex keratitis

Trifluorothymidine (TFT) and adenine arabinoside (ara-A) are effective antiviral drugs with a very low toxicity for the cornea. In our study no difference between these 2 drugs in antiviral activity was noted. The average healing time for TFT was 11-14 days and for ara-A 10-54 days. These data differ markedly from those of other studies. This was the result of the use of additional criteria for healing of the lesion. Not only absence of fluorescein staining of the cornea but also the absence of oedema and cystic changes in the epithelium over the previous ulcer were considered criteria for healing. In addition to clearly defined healing criteria and the healing time we found the interval between the first symptoms and the commencement of the therapy of greatest importance in the clinical evaluation of antiviral drug efficacy. An effort was made to approximate this relationship for TFT and ara-A mathematically.