Protocolized reduction of non-resuscitation fluids versus usual care in septic shock patients (REDUSE): a randomized multicentre feasibility trial

BACKGROUND/PURPOSE

Non-resuscitation fluids constitute the majority of fluid administered for septic shock patients in the intensive care unit (ICU). This multicentre, randomized, feasibility trial was conducted to test the hypothesis that a restrictive protocol targeting non-resuscitation fluids reduces the overall volume administered compared with usual care.

METHODS

Adults with septic shock in six Swedish ICUs were randomized within 12 h of ICU admission to receive either protocolized reduction of non-resuscitation fluids or usual care. The primary outcome was the total volume of fluid administered within three days of inclusion.

RESULTS

Median (IQR) total volume of fluid in the first three days, was 6008 ml (interquartile range [IQR] 3960-8123) in the restrictive fluid group (n = 44), and 9765 ml (IQR 6804-12,401) in the control group (n = 48); corresponding to a Hodges-Lehmann median difference of 3560 ml [95% confidence interval 1614-5302]; p < 0.001). Outcome data on all-cause mortality, days alive and free of mechanical ventilation and acute kidney injury or ischemic events in the ICU within 90 days of inclusion were recorded in 98/98 (100%), 95/98 (98%) and 95/98 (98%) of participants respectively. Cognition and health-related quality of life at six months were recorded in 39/52 (75%) and 41/52 (79%) of surviving participants, respectively. Ninety out of 134 patients (67%) of eligible patients were randomized, and 15/98 (15%) of the participants experienced at least one protocol violation.

CONCLUSION

Protocolized reduction of non-resuscitation fluids in patients with septic shock resulted in a large decrease in fluid administration compared with usual care. A trial using this design to test if reducing non-resuscitation fluids improves outcomes is feasible.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT05249088, 18 February 2022. https://clinicaltrials.gov/ct2/show/NCT05249088.

Systematic review and literature appraisal on methodology of conducting and reporting critical-care echocardiography studies: a report from the European Society of Intensive Care Medicine PRICES expert panel

Background

The echocardiography working group of the European Society of Intensive Care Medicine recognized the need to provide structured guidance for future CCE research methodology and reporting based on a systematic appraisal of the current literature. Here is reported this systematic appraisal.

Methods

We conducted a systematic review, registered on the Prospero database. A total of 43 items of common interest to all echocardiography studies were initially listed by the experts, and other “topic-specific” items were separated into five main categories of interest (left ventricular systolic function, LVSF n = 15, right ventricular function, RVF n = 18, left ventricular diastolic function, LVDF n = 15, fluid management, FM n = 7, and advanced echocardiography techniques, AET n = 17). We evaluated the percentage of items reported per study and the fraction of studies reporting a single item.

Results

From January 2000 till December 2017 a total of 209 articles were included after systematic search and screening, 97 for LVSF, 48 for RVF, 51 for LVDF, 36 for FM and 24 for AET. Shock and ARDS were relatively common among LVSF articles (both around 15%) while ARDS comprised 25% of RVF articles. Transthoracic echocardiography was the main echocardiography mode, in 87% of the articles for AET topic, followed by 81% for FM, 78% for LVDF, 70% for LVSF and 63% for RVF. The percentage of items per study as well as the fraction of study reporting an item was low or very low, except for FM. As an illustration, the left ventricular size was only reported by 56% of studies in the LVSF topic, and half studies assessing RVF reported data on pulmonary artery systolic pressure.

Conclusion

This analysis confirmed sub-optimal reporting of several items listed by an expert panel. The analysis will help the experts in the development of guidelines for CCE study design and reporting.

Correction to: A decade of progress in critical care echocardiography: a narrative review

The original version of this article unfortunately contained a mistake.

Fabricated facial rash - an unusual presentation of factitious disorder

Patients with factitious disorder typically present with signs or symptoms suggesting a medical problem, but which transpire to be self-induced or fabricated. Repeated investigations and treatments are often carried out to no avail before this possibility is considered. In this case, a 51-year-old female presented to the oral and maxillofacial surgery unit with toothache and a facial rash. Following admission to hospital a range of investigations were performed, and a tooth was extracted. Judicious attention by nursing staff led to the discovery that the patient had been applying make-up to mimic a skin rash. This concern was raised with the patient and she admitted falsifying the rash. Although this patient may have been experiencing pain, by applying make-up in this manner she sought to exaggerate the severity of her condition and as a result underwent potentially unnecessary procedures. This case provides a reminder that the possibility of factitious disorder should be considered in cases where patients present with symptoms or signs which appear fabricated or self-inflicted, defy anatomical or physiological principles, or do not correlate with the history. Thorough history taking is essential, and access to electronic care records may be informative. Psychiatric follow-up is recommended, but not all patients are willing to engage with this process.

Preoperative abnormalities in serum sodium concentrations are associated with higher in-hospital mortality in patients undergoing major surgery

BACKGROUND

Abnormal serum sodium concentrations are common in patients presenting for surgery. It remains unclear whether these abnormalities are independent risk factors for postoperative mortality.

METHODS

This is a secondary analysis of the European Surgical Outcome Study (EuSOS) that provided data describing 46 539 patients undergoing inpatient non-cardiac surgery. Patients were included in this study if they had a recorded value of preoperative serum sodium within the 28 days immediately before surgery. Data describing preoperative risk factors and serum sodium concentrations were analysed to investigate the relationship with in-hospital mortality using univariate and multivariate logistic regression techniques.

RESULTS

Of 35 816 (77.0%) patients from the EuSOS database, 21 943 (61.3%) had normal values of serum sodium (138-142 mmol litre(-1)) before surgery, 8538 (23.8%) had hyponatraemia (serum sodium ≤137 mmol litre(-1)) and 5335 (14.9%) had hypernatraemia (serum sodium ≥143 mmol litre(-1)). After adjustment for potential confounding factors, moderate to severe hypernatraemia (serum sodium concentration ≥150 mmol litre(-1)) was independently associated with mortality [odds ratio 3.4 (95% confidence interval 2.0-6.0), P<0.0001]. Hyponatraemia was not associated with mortality.

CONCLUSIONS

Preoperative abnormalities in serum sodium concentrations are common, and hypernatraemia is associated with increased mortality after surgery. Abnormalities of serum sodium concentration may be an important biomarker of perioperative risk resulting from co-morbid disease.

Platelet shedding of CD40L is regulated by matrix metalloproteinase-9 in abdominal sepsis

BACKGROUND AND OBJECTIVES

Platelet-derived CD40L is known to regulate neutrophil recruitment and lung damage in sepsis. However, the mechanism regulating shedding of CD40L from activated platelets is not known. We hypothesized that matrix metalloproteinase (MMP)-9 might cleave surface-expressed CD40L and regulate pulmonary accumulation of neutrophils in sepsis.

METHODS

Abdominal sepsis was induced by cecal ligation and puncture (CLP) in wild-type and MMP-9-deficient mice. Edema formation, CXC chemokine levels, myeloperoxidase levels, neutrophils in the lung and plasma levels of CD40L and MMP-9 were quantified.

RESULTS

CLP increased plasma levels of MMP-9 but not MMP-2. The CLP-induced decrease in platelet surface CD40L and increase in soluble CD40L levels were significantly attenuated in MMP-9 gene-deficient mice. Moreover, pulmonary myeloperoxidase (MPO) activity and neutrophil infiltration in the alveolar space, as well as edema formation and lung injury, were markedly decreased in septic mice lacking MMP-9. In vitro studies revealed that inhibition of MMP-9 decreased platelet shedding of CD40L. Moreover, recombinant MMP-9 was capable of cleaving surface-expressed CD40L on activated platelets. In human studies, plasma levels of MMP-9 were significantly increased in patients with septic shock as compared with healthy controls, although MMP-9 levels did not correlate with organ injury score.

CONCLUSIONS

Our novel data propose a role of MMP-9 in regulating platelet-dependent infiltration of neutrophils and tissue damage in septic lung injury by controlling CD40L shedding from platelets. We conclude that targeting MMP-9 may be a useful strategy to limit acute lung injury in abdominal sepsis.

Hemodynamics and jugular venous oxygen saturation during carotid endarterectomy: a comparison between general and locoregional anesthesia

AIM

To study hemodynamic and blood oxygenation changes in patients undergoing carotid endarterectomy (CEA) under general (GA) or locoregional (LRA) anesthesia.

METHODS

Prospective non-randomized study including 50 patients undergoing CEA (31 men, mean age 72 (range 50-84) years-old under GA (N.=23) or LRA (N.=27). Systemic blood pressure, ECG, venous oxygen saturation in the ipsilateral jugular bulb and pulse-oximetry were monitored. Blood-gas analysis was done from blood obtained from the radial artery and ipsilateral jugular vein.

RESULTS

Pulse rate and systemic systolic blood pressure were higher in LRA compared to the GA before, during and after cross clamping (P<0.05). Seven GA patients required dopamine-infusion to maintain systolic blood pressure >120 mmHg. Jugular venous saturation was initially identical in both groups, but decreased significantly upon cross clamping in LRA compared to GA (P<0.05). This difference remained at least 3 minutes after cross clamp release (P<0.05).

CONCLUSION

Patients under LRA seem to have increased sympathetic activity compared to patients under GA, as expressed by higher pulse rates and systolic blood pressures. Jugular venous saturation was lower during clamping of LRA patients. The differences were small and concur with the near-equality findings in studies analysing the clinical outcome.

Soluble CD40L (CD154) is increased in patients with shock

OBJECTIVE

Recent data suggest that soluble CD40L (sCD40L) plays an important role in murine sepsis. The aim of the present study was to determine plasma levels of CD40L in critically ill patients with systemic inflammatory response syndrome (SIRS) and shock, with and without sepsis.

DESIGN

A prospective observational one-centre cohort study in a mixed-bed ICU of an university hospital. Fifty-three consecutive patients fulfilling the criteria for SIRS with shock as well as seven age-matched controls were included. ELISA was used to determine sCD40L in the plasma.

RESULTS

The level of sCD40L in plasma from healthy controls was 0.18 ± 0.03 ng/ml. It was found that sCD40L levels were significantly higher in patients with non-septic shock (0.72 ± 0.18 ng/ml) and septic shock (0.50 ± 0.1 ng/ml). However, the levels of sCD40L were not different between these two groups of patients, or in those with low and high APACHE scores.

CONCLUSION

Our data show that sCD40L is increased in patients with shock from septic and non-septic etiologies. However, further studies are needed to delineate the functional significance of sCD40L in the clinical outcome in shock patients.

Comparison of new clinical and scintigraphic algorithms for the diagnosis of pulmonary embolism

Since the publication of the modified Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) criteria for the diagnosis of pulmonary embolism (PE), new clinical and scintigraphic diagnostic algorithms (the McMaster clinical criteria, the PisaPED simplified scintigraphic grading and the Miettinen logistic regression analysis) have been reported although the results have not been reproduced in other sites. Ventilation-perfusion lung scintigraphy was performed in 238 consecutive patients with a provisional diagnosis of PE. Scans were reported as normal/very low, low, intermediate or high probability for PE using standardized criteria. Each patient received a clinical grading of probability of PE as low, moderate or high using the McMaster clinical criteria. Using the PisaPED criteria (an alternate simplified scintigraphic grading system using the perfusion scan alone) each scan was also graded as normal/near normal, abnormal but not PE, or abnormal and PE. Using the logistic regression algorithm of Miettinen each scan received a numerical probability of PE. Frequencies for differing levels of probability of PE varied widely between the various algorithms. Cross tabulations revealed correlation of the standardized criteria with the Miettinen grading but not with the McMaster or the PisaPED gradings. We were unable to reproduce similar results using the McMaster clinical grading or the PisaPED simplified scintigraphic grading although the Miettinen logistic regression formula gave comparable results. New algorithms are not automatically transferable to new environments.

Plasma cytokines do not reflect expression of pro- and anti-inflammatory cytokine mRNA at organ level after cardiopulmonary bypass in neonatal pigs

BACKGROUND

Plasma concentrations of inflammatory markers are increased in response to the trauma of cardiac surgery and cardiopulmonary bypass (CPB). It is, however, unknown whether the plasma cytokine levels and cytokine mRNA expression at organ level reflect each other.

METHODS

Twenty-six piglets (17-19 days) were allocated to the sham-group (sternotomy only, n = 13) or to the CPB-group (sternotomy, 120 min CPB procedure with 60-min aortic cross-clamp, n = 13). The pigs were observed for 0.5 h or 4 h post-CPB. Plasma levels of IL-1beta, IL-6, IL-8 and IL-10 and mRNA expression of TNF-alpha, IL-1beta, IL-6, IL-8, IL-10 and iNOS in organs were registered with concomitant changes in oxygenation index (OI) and expiratory nitric oxide (NO).

RESULTS

In pigs killed 0.5 h post-CPB there was a significant increase in IL-10 mRNA in the lungs and kidneys compared with the sham-group. IL-1beta mRNA was detectable in the kidneys and lungs of the CPB-pigs, while IL-6 mRNA was up regulated only in lungs. In pigs killed 4 h post-CPB a significantly higher IL-6 mRNA was found in heart tissue and a lower IL-10 mRNA was found in lungs of CPB pigs compared with the sham-group. There was a concomitant significant increase in OI and increased plasma IL-8 and IL-10 concentrations in the CPB-pigs compared with the sham-pigs.

CONCLUSION

The cytokine mRNA expression pattern was very different for the pigs killed already 0.5 h after the CPB procedure compared with the pigs killed 4 h post-CPB. The plasma cytokine levels poorly reflected mRNA expression of the pro- and anti-inflammatory cytokines.

Quasi-periodic substructure in the microvessel endothelial glycocalyx: a possible explanation for molecular filtering?

The luminal surface of endothelial cells is lined with the glycocalyx, a network structure of glycoproteins probably 50 to 100 nm thick. It has been suggested that a relatively regular fibre-matrix structure may be responsible for the ultrafiltration properties of microvascular walls, both when the endothelium is continuous and when it is fenestrated. Positive structural evidence demonstrating an underlying periodicity in the glycocalyx has been hard to obtain. Here we present structural analysis of glycocalyx samples prepared in a variety of ways for electron microscopy. Using computed autocorrelation functions and Fourier transforms of representative areas of the electron micrograph images, we show that there is an underlying three-dimensional fibrous meshwork within the glycocalyx with characteristic spacings of about 20 nm. Together with a fibre diameter consistent with our observations of about 10-12 nm, the 20-nm spacing provides just the size regime to account satisfactorily for the observed molecular filtering; the observations are consistent with the fibre matrix model. We also show that the fibrous elements may occur in clusters with a common intercluster spacing of about 100 nm and speculate that this may reveal organisation of the glycocalyx by a quasi-regular submembranous cytoskeletal scaffold.

Freunds adjuvant alone is antiatherogenic in apoE-deficient mice and specific immunization against TNFalpha confers no additional benefit

TNFalpha participates in the pathogenesis of atherosclerosis. The effect of immunization against TNFalpha on development of advanced vascular lesions in atherosclerosis-susceptible apoE-deficient mice was investigated. At 5-7 weeks of age, animals received immunization with either Freunds adjuvant and a recombinant antigenic TNFalpha molecule (TNF106), Freunds adjuvant alone, or no immunization. All mice received a Western-type high-fat diet for 12 weeks. Aortic sinus lesion area was determined by microscopic morphometry, the total aortic arch cholesterol content was determined by gas chromatography, and antibodies against TNFalpha, malondialdehyde-modified low density lipoprotein, or heat shock protein 60, were assessed by ELISAs. Immunization with TNF106 induced high-titered circulating antibodies against TNFalpha (n=23), and these antibodies were not detected in mice immunized with Freunds adjuvant alone (n=22), or in non-immunized control animals (n=25). After 12 weeks, the atherosclerotic lesion size was significantly reduced in immunized animals, whether they had been immunized with TNF106 or Freunds adjuvant alone, and the total lesional cholesterol content was decreased in mice immunized with TNF106. There were no correlations between circulating antibody titers and plaque size, total aortic arch cholesterol content, or plasma lipid levels, respectively. Administration of Freunds adjuvant alone can thus reduce formation of mature atherosclerotic lesions in apoE-deficient mice and this response is not modified by specific immunization against TNFalpha.

Precipitated withdrawal following codeine administration is dependent on CYP genotype

The role of metabolic polymorphism in the development of physical dependence to codeine was assessed in cytochrome P450 2D2 (CYP2D2) deficient Dark Agouti and CYP2D2 intact Sprague-Dawley rats by assessment of the severity of naloxone precipitated withdrawal after codeine and morphine administration. Plasma morphine concentrations after codeine were significantly higher (P<0.01) in Sprague-Dawley than in Dark Agouti rats with metabolic ratios of 0.71 +/- 0.27 and 0.07 +/- 0.04, respectively. Withdrawal after codeine resulted in significantly greater hypothermia (3.5-4 degrees C, P<0.0001) in Sprague-Dawley animals compared to the other groups. Body weight loss was similar for all groups ranging from 6.2 +/- 0.4 to 8.2 +/- 0.6 g. When strain and treatment data were combined, a relationship between body temperature and plasma morphine concentration could be described by the inverse Hill equation (r(2)=0.76, EC(50)=556 +/- 121 ng/ml, n=2.9 +/- 1.5). These data indicate that dependence and withdrawal after codeine administration are dependent on its bioconversion to morphine.

A-band architecture in vertebrate skeletal muscle: polarity of the myosin head array

Despite extensive knowledge of many muscle A-band proteins (myosin molecules, titin, C-protein (MyBP-C)), details of the organization of these molecules to form myosin filaments remain unclear. Recently the myosin head (crossbridge) configuration in a relaxed vertebrate muscle was determined from low-angle X-ray diffraction (Hudson et al. (1997), J Mol Biol 273: 440-455). This showed that, even without C-protein, the myosin head array displays a characteristic polar pattern with every third 143 A-spaced crossbridge level particularly prominent. However, X-ray diffraction cannot determine the polarity of the crossbridge array relative to the neighbouring actin filaments; information crucial to a proper understanding of the contractile event. Here, electron micrographs of negatively-stained goldfish A-segments and of fast-frozen, freeze-fractured plaice A-bands have been used to determine the resting myosin head polarity relative to the M-band. In agreement with the X-ray data, the prominent 429 A-spaced striations are seen outside the C-zone, where no non-myosin proteins apart from titin are thought to be located. The head orientation is with the concave side of the curved myosin heads (containing the entrance to the ATP-binding site) facing towards the M-band and the convex surface (containing the actin-binding region at one end) facing away from the M-band.

Modulation of cisplatin cytotoxicity and cisplatin-induced DNA cross-links in HepG2 cells by regulation of glutathione-related mechanisms

Glutathione (GSH), glutathione S-transferase (GST), and glutathione conjugate export pump (GS-X pump) have been shown to participate collectively in the detoxification of many anticancer drugs, including cisplatin. Identification and regulation of the rate-limiting step in the overall system for cisplatin detoxification is of crucial importance for sensitization of human tumor cells to cisplatin. In this study, the GSH content, GST activity, and GS-X pump activity were regulated separately to examine effects of the regulation on cisplatin cytotoxicity and cisplatin-induced DNA interstrand cross-links (ICL) in HepG2 cells. Seventy-percent depletion of GSH by buthionine sulfoximine (BSO) and 50% increase of GSH by monoethyl GSH ester (GSHe) potentiated and decreased cisplatin cytotoxicity, respectively. This was reflected by a significant decrease and increase of their respective IC(50) values by 62 and 107%. Cisplatin-induced ICL was also potentiated by depletion of GSH by BSO and decreased by enrichment of GSH by GSHe, as shown by a 125% increase and a 34% decrease of cross-linked DNA compared with control samples exposed to cisplatin alone (p = 0.008 and 0.03, respectively). On the other hand, inhibition of GST and GS-X pump by ethacrynic acid, quercetin, tannic acid, and indomethacin at concentrations that inhibited activities of GST and GS-X pump by more than 50% had no significant effects on cisplatin cytotoxicity and cisplatin-induced DNA ICL in these cells. The results showed that of the parameters measured, intracellular GSH seems to be the rate-limiting factor, and its regulation would provide a more promising strategy for sensitization of human liver tumor cells to cisplatin.

Endogenous morphine is produced in response to cardiopulmonary bypass in neonatal pigs

BACKGROUND

Cardiopulmonary bypass (CPB) is associated with a systemic inflammatory response. Endogenous morphine production has previously been demonstrated in humans after cardiac surgery with CPB. It has been hypothesized that morphine plays a role as an anti-inflammatory mediator in the systemic inflammatory response. The aim of this study was to investigate if the CPB procedure in itself elicits an endogenous morphine production in neonatal pigs.

METHODS

Endogenous morphine production was measured in arterial blood in piglets exposed to sternotomy alone (sham group, n=10) or sternotomy and CPB (n=10). Blood samples were obtained immediately after the induction of anaesthesia, at the end of CPB and 4 h later. Morphine in arterial blood was detected by radioimmunoassay and confirmed by gas chromatography mass spectrometry.

RESULTS

Animals undergoing CPB showed detectable endogenous morphine concentrations immediately after CPB, with increased concentrations postoperatively. There was no measurable morphine production in the sham operated pigs.

CONCLUSION

The CPB procedures elicits an endogenous morphine production in neonatal pigs. This morphine response is analogous to the previously demonstrated response in patients subjected to cardiac surgery and CPB.

A new model for evaluation of thrombosis and ischaemia/reperfusion injury

BACKGROUND

The purpose of the present study was to describe infarct size and platelet accumulation when reperfusion injury was combined with a thrombogenic lesion in the coronary artery. The left anterior descending artery was damaged in 11 pigs and subsequently occluded proximal to the lesion for 50 min, followed by 4 h of reperfusion.

RESULTS

The infarct size/area at risk was 40 (35 63)%. Infarct size correlated with troponin-T-3 h (p=0.85, p<0.002), but not with creatine kinase-3 h. Platelet aggregation decreased by 34% (p<0.01) at 15 min of reperfusion, but returned to baseline. Platelet accumulation in the left ventricle was significantly higher in the area at risk (194 (157-206)%) compared to the right ventricle (137 (120-142)%); p<0.05).

CONCLUSION

A decreased platelet reactivity and increased accumulation of platelets in the area at risk indicates that activated platelets become entrapped in the myocardium. Troponin-T was a better marker of myocardial damage than creatine kinase in this in vivo model with pigs.

Plaque pathology and coronary thrombosis in the pathogenesis of acute coronary syndromes

Coronary atherosclerosis is by far the most frequent cause of ischemic heart disease and plaque disruption with superimposed thrombosis is the main cause of the acute coronary syndromes of unstable angina, myocardial infarction, and sudden coronary death. Therefore, for event-free survival, the vital question is not why atherosclerosis develops but rather why, after years of indolent growth, it suddenly becomes complicated by life-threatening thrombosis. Therefore, we have to focus on plaque composition and vulnerability to rupture and plaque thrombogenicity rather than on plaque size and stenosis severity. The risk for plaque disruption depends more on plaque vulnerability (plaque type) than on degree of stenosis (plaque size). Lipid-rich and soft plaques are more vulnerable and prone to rupture than collagen-rich and hard plaques. They are also highly thrombogenic after disruption because of high content of tissue factor. There seems to be three major determinants of a plaque's vulnerability to rupture: 1) the size and consistency of the lipid-rich atheromatous core, 2) the thickness of the fibrous cap covering the core, and 3) ongoing inflammation and repair processes within the fibrous cap. Lipid accumulation, cap thinning, lack of smooth muscle cells (smc), and macrophage-related inflammation destabilize plaques, making them vulnerable to rupture. In contrast, smc-related healing and repair processes stabilize plaques, protecting them against disruption. Plaque size or stenosis severity tell nothing about a plaque's vulnerability. Many vulnerable plaques are invisible angiographically due to their small size and compensatory vascular remodeling.

Intravenous magnesium reduces infarct size after ischemia/reperfusion injury combined with a thrombogenic lesion in the left anterior descending artery

Experimental studies have demonstrated that intravenous magnesium (Mg) can protect the ischemic myocardium and has an antithrombotic effect. In patients with myocardial infarction, the reperfusion injury is complicated by the presence of a thrombogenic area in the affected coronary artery that may cause repetitive thrombus formation and embolization. We investigated the effect of Mg on infarct size in a randomized study in pigs. Myocardial infarction was induced by a 50-minute mechanical occlusion of the left anterior descending artery combined with an arterial injury, which stimulated a dynamic thrombus formation with emboli shedding on reperfusion. Magnesium sulfate (6 mmol/20 min plus 3 mmol/h) or saline was started at 30 minutes after coronary occlusion. Real-time ventricular pressure-volume loops were generated from the left ventricle by using a microtip pressure manometer and a conductance catheter. Platelet accumulation in the myocardium was evaluated by using 111In-labeled platelets. After 4 hours of reperfusion, the infarct size/area at risk ratio in the placebo group was 46+/-0.06% (n=8) compared with 22+/-0.07% (n=6) in the Mg-treated animals (P=0. 03). Ejection fraction decreased significantly in the control group but not in the Mg-treated animals (P=0.03). Platelet accumulation in the myocardium did not change significantly between the Mg- and placebo-treated animals (placebo group, 191+/-19%; Mg group, 177+/-29%; NS). The present study demonstrates that intravenous Mg infusion is able to reduce infarct size by >50% and preserve the ejection fraction in this model where ischemia/reperfusion injury was evaluated in the presence of a thrombogenic area in the nutrient artery.

Liver regeneration after partial hepatectomy is non-uniform: flow cytometric bromodeoxyuridine incorporation and cell cycle studies in a porcine model

The rate of hepatocyte regeneration at different anatomical locations of the remnant liver after partial hepatectomy was assessed in porcine hepatocytes by bromodeoxyuridine (BrdUr) incorporation and cell cycle kinetics using flow cytometric analysis. Partial hepatectomy was performed in five Yorkshire pigs. A single intravenous injection of BrdUr at 50 mg/kg was administered on the 2nd post-operative day and the animals were sacrificed 1 h later. The remnant liver tissue was harvested and divided into four equal zones, from the liver periphery towards the surgical cut-edge. Biopsy samples were obtained from the centre of each of these zones and similarly from identical anatomical locations in two control pigs that had undergone sham surgery. Hepatocyte nucleus suspension was prepared, double labelled with anti-BrdUr and propidium iodide and analysed by a flow cytometer. The cells in S-phase was used as the parameter to measure the regeneration status. A gradient increase in S-phase from the periphery to the cut edge was observed in all five pigs that had undergone partial hepatectomy. The percentage of S-phase cells in all four zones from the hepatectomy group was significantly higher when compared with that in the controls. Liver regeneration after partial hepatectomy was not uniform but was greatest adjacent to the surgical cut edge and decreased towards the periphery of the liver.

Myosin crossbridge configurations in equilibrium states of vertebrate skeletal muscle. Heads swing axially or turn upside-down between resting and rigor

The positions and orientations of the myosin heads in relaxed, active, rigor and S1-labelled fish muscle are being determined by analysis both of electron micrographs and of low-angle X-ray diffraction patterns. The X-ray analysis of resting muscle makes use of the head shape defined from the study of S1 crystals, with variable head configurational parameters being used on each of the three different 3-fold symmetric 14.3 nm-spaced 'crowns' of myosin heads within the 42.9 nm axial repeat of the myosin filaments. Diffraction patterns were stripped using CCP13 fibre diffraction software. Searches and optimisation were carried out using simulated annealing and local refinement procedures to give a 'best fit' relaxed structure with a crystallographic R-factor of about 4%. It had heads oriented all the same way up (i.e. with similar rotations around their own long axes) on the myosin filament, but with a small range of axial tilts. Head configuration in rigor fish muscle is being determined by X-ray diffraction and electron microscopy of normal rigor muscle and of skinned muscle soaked with extrinsic myosin S1. Computed 3-D reconstructions of acto-S1 using X-ray amplitudes and phases from electron microscopy are informative and help to analyse the X-ray diffraction data that extend axially to about 1 nm resolution. An ambiguity is the axial direction of the observed resting myosin head array relative to the known polarity of the actin filaments. One polarity would give little axial displacement (2-3 nm) between opposite ends of the resting and rigor heads, and in this case the heads would need to rotate around their own long axes by about 115 degrees to make a rigor attachment. The other (preferred) filament polarity would provide considerable axial swinging (14-15 nm) between the two states. We are attempting to define the absolute polarity of the resting muscle myosin head array using electron microscopy and image processing either of cryo-sections or of replicas from shadowed, freeze-fractured, rapidly frozen fish muscle fibres.

A practical technique of colour image analysis: applications in experimental research

Commercially available colour image analysers are relatively expensive. We describe a cheaper alternative developed by the Department of Experimental Surgery, Singapore General Hospital using an assembly of optical and computer equipment commonly available in the research laboratory. This manual colour imaging system is comparable to the commercial model in terms of functional capabilities and accuracy, except that it takes a longer time to process and analyse images and is unable to measure colour density. However, it is capable of not only analysing microscopic images of stained histological tissue sections but also X-ray images and images of large pathological specimens. In the case of commercial models, different systems have to be used to analyse images from different types of specimens. This system was developed in 1987 and has since been used successfully in a number of experimental studies. It has been applied to the measurement of parameters defining eye anatomical configuration, delineating the extent of tissue necrosis and fibrosis after therapeutic treatment and surgery, the development of new bone formation in fracture healing and to quantitative studies in liver regeneration. Due to its accuracy, low cost and versatility, this system should be within the means of even the most modest research laboratory.