Changes in the treatment strategy following intracoronary pressure wire in a contemporaneous real-life cohort of patients with intermediate coronary stenosis. Results from a nationwide registry

BACKGROUND

Intracoronary pressure wire is useful to guide revascularization in patients with coronary artery disease.

AIMS

To evaluate changes in diagnosis (coronary artery disease extent), treatment strategy and clinical results after intracoronary pressure wire study in real-life patients with intermediate coronary artery stenosis.

METHODS

Observational, prospective and multicenter registry of patients in whom pressure wire was performed. The extent of coronary artery disease and the treatment strategy based on clinical and angiographic criteria were recorded before and after intracoronary pressure wire guidance. 12-month incidence of MACE (cardiovascular death, non-fatal myocardial infarction or new revascularization of the target lesion) was assessed.

RESULTS

1414 patients with 1781 lesions were included. Complications related to the procedure were reported in 42 patients (3.0 %). The extent of coronary artery disease changed in 771 patients (54.5 %). There was a change in treatment strategy in 779 patients (55.1 %) (18.0 % if medical treatment; 68.8 % if PCI; 58.9 % if surgery (p < 0.001 for PCI vs medical treatment; p = 0.041 for PCI vs CABG; p < 0.001 for medical treatment vs CABG)). In patients with PCI as the initial strategy, the change in strategy was associated with a lower rate of MACE (4.6 % vs 8.2 %, p = 0.034).

CONCLUSIONS

The use of intracoronary pressure wire was safe and led to the reclassification of the extent of coronary disease and change in the treatment strategy in more than half of the cases, especially in patients with PCI as initial treatment.

Development, equivalence study, and normative data of version B of the Spanish-language Free and Cued Selective Reminding Test

INTRODUCTION

The Free and Cued Selective Reminding Test (FCSRT) is widely used for the assessment of verbal episodic memory, mainly in patients with Alzheimer disease. A Spanish-language version of the FCSRT and normative data were developed within the NEURONORMA project. Availability of alternative, equivalent versions is useful for following patients up in clinical settings. This study aimed to develop an alternative version of the original FCSRT (version B) and to study its equivalence to the original Spanish-language test (version A), and its performance in a sample of healthy individuals, in order to develop reference data.

METHODS

We evaluated 232 healthy participants of the NEURONORMA-Plus project, aged between 18 and 90. Thirty-three participants were assessed with both test versions using a counterbalanced design.

RESULTS

High intra-class correlation coefficients (between 0.8 and 0.9) were observed in the equivalence study. While no significant differences in performance were observed in total recall scores, free recall scores were significantly lower for version B.

CONCLUSIONS

These preliminary results suggest that the newly developed FCSRT version B is equivalent to version A in the main variables tested. Further studies are necessary to ensure interchangeability between versions. We provide normative data for the new version.

Impact of COVID-19 on ST-segment elevation myocardial infarction care. The Spanish experience

Introduction and objectives

The COVID-19 outbreak has had an unclear impact on the treatment and outcomes of patients with ST-segment elevation myocardial infarction (STEMI). The aim of this study was to assess changes in STEMI management during the COVID-19 outbreak.

Methods

Using a multicenter, nationwide, retrospective, observational registry of consecutive patients who were managed in 75 specific STEMI care centers in Spain, we compared patient and procedural characteristics and in-hospital outcomes in 2 different cohorts with 30-day follow-up according to whether the patients had been treated before or after COVID-19.

Results

Suspected STEMI patients treated in STEMI networks decreased by 27.6% and patients with confirmed STEMI fell from 1305 to 1009 (22.7%). There were no differences in reperfusion strategy (> 94% treated with primary percutaneous coronary intervention in both cohorts). Patients treated with primary percutaneous coronary intervention during the COVID-19 outbreak had a longer ischemic time (233 [150-375] vs 200 [140-332] minutes, P < .001) but showed no differences in the time from first medical contact to reperfusion. In-hospital mortality was higher during COVID-19 (7.5% vs 5.1%; unadjusted OR, 1.50; 95%CI, 1.07-2.11; P < .001); this association remained after adjustment for confounders (risk-adjusted OR, 1.88; 95%CI, 1.12-3.14; P = .017). In the 2020 cohort, there was a 6.3% incidence of confirmed SARS-CoV-2 infection during hospitalization.

Conclusions

The number of STEMI patients treated during the current COVID-19 outbreak fell vs the previous year and there was an increase in the median time from symptom onset to reperfusion and a significant 2-fold increase in the rate of in-hospital mortality. No changes in reperfusion strategy were detected, with primary percutaneous coronary intervention performed for the vast majority of patients. The co-existence of STEMI and SARS-CoV-2 infection was relatively infrequent.

Development, equivalence study, and normative data of version B of the Spanish-language Free and Cued Selective Reminding Test

INTRODUCTION

The Free and Cued Selective Reminding Test (FCSRT) is widely used for the assessment of verbal episodic memory, mainly in patients with Alzheimer disease. A Spanish version of the FCSRT and normative data were developed within the NEURONORMA project. Availability of alternative, equivalent versions is useful for following patients up in clinical settings. This study aimed to develop an alternative version of the original FCSRT (version B) and to study its equivalence to the original Spanish test (version A), and its performance in a sample of healthy individuals, in order to develop reference data.

METHODS

We evaluated 232 healthy participants of the NEURONORMA-Plus project, aged between 18 and 90. Thirty-three participants were assessed with both versions using a counterbalanced design.

RESULTS

High intra-class correlation coefficients (between 0.8 and 0.9) were observed in the equivalence study. While no significant differences in performance were observed in total recall scores, free recall scores were significantly lower for version B.

CONCLUSIONS

These preliminary results suggest that the newly developed FCSRT version B is equivalent to version A in the main variables tested. Further studies are necessary to ensure interchangeability between versions. We provide normative data for the new version.

Review of difficult airway management in thoracic surgery

The management of difficult airway (DA) in thoracic surgery is more difficult due to the need for lung separation or isolation and frequent presence of associated upper and lower airway problems. We performed an article review analysing 818 papers published with clinical evidence indexed in Pubmed that allowed us to develop an algorithm. The best airway management in predicted DA is tracheal intubation and independent bronchial blockers guided by fibroscopy maintaining spontaneous ventilation. For unpredicted DA, the use of videolaryngoscopes is recommended initially, and adequate neuromuscular relaxation (rocuronium/sugammadex), among other maneuvers. In both cases, double lumen tubes should be reserved for when lung separation is absolutely indicated. Finally, extubation should be a time of maximum care and be performed according to the safety measures of the Difficult Arway Society.

Evolution of regional oxygen saturation in the peri-operative of thoracic surgery and its relationship with central venous saturation

OBJECTIVE

To study the relationship between the values of SvcO2 and SrcO2 in lung resection with one lung ventilation (OLV) and changes in these variables and mean arterial pressure (MAP) and arterial oxygen saturation (SpO2) during the perioperative period.

MATERIAL AND METHODS

Prospective, observational study of 25 patients in whom pulmonary resection was performed with OLV. The values of MAP, SpO2, SvO2, and SrcO2 were recorded at 6 different times: 1)baseline; 2)double-lung ventilation before the OLV (VBP1); 3)during OLV; 4)after double-lung ventilation (VBP2); 5)30minutes after surgery, and 6)6hours after surgery.

RESULTS

The SrcO2 showed a significant increase from baseline to starting ventilation (65.72±9.05% vs 70.44±7.24%; P<.01). There were no significant changes in their values at the different intraoperative times. Post-operatively, as in the case of the SvcO2, a significant decrease (P<.001) of its value compared with the previous value was observed.

CONCLUSIONS

SrcO2 showed a significant increase after induction of anaesthesia and initiation of mechanical ventilation compared to baseline, and a significant decrease at the end of surgery after extubation in the immediate postoperative period. Being a tissue monitoring, non-invasive technique and with continuous values it can alert the clinician of changes in the ratio of oxygen consumption (VO2) to oxygen delivery (DO2) at times of greatest risk, such as OLV, extubation, and the early postoperative period.

Infrapopliteal arterial occlusive disease in elderly men: a population based study

AIM

The aim of this paper was to determine prevalence, cardiovascular risk factors and association with coronary heart disease (CHD) of isolated infrapopliteal arterial disease in old-adult men.

DESIGN

cross-sectional; participants: population-based sample of 699 men aged 55 to 74 years, measurements: cardiovascular history and risk factors, electrocardiogram, segmental pressures and velocity waveforms in lower limbs.

RESULTS

Peripheral arterial occlusive disease (PAOD) was observed in 13.4% subjects, of whom 39.4% (37 patients) had isolated infrapopliteal PAOD. Of these, 11 (29.7%) patients were symptomatic. Isolated infrapopliteal PAOD was significantly associated with increased age, smoking, diabetes and hypertriglyceridemia. Subjects with extended PAOD differed from those with isolated infrapopliteal PAOD in increased tobacco exposure, higher levels of LDL and lower levels of HDL cholesterol. Association between PAOD and CHD was almost always significant (odds ratio from 1.8 to 3.4) irrespective of PAOD topographic pattern and symptom characteristics of CHD subjects.

CONCLUSION

Isolated infrapopliteal PAOD is a frequent asymptomatic disorder in old-adult men, clearly associated with both symptomatic and asymptomatic CHD. In contrast to an expected risk factor profile biased by clinical practice, these subjects only differed from those with PAOD significantly extended to proximal arteries in their smoking exposition and a more atherogenic lipid profile.

[Spanish Society of Anaesthesia (SEDAR) guidelines for pre-anaesthesia checking procedures]

We present this document as a guide to preparing a specific institutional pre-anaesthesia checklist, as recommended in the Helsinki declaration on patient safety in anaesthesiology. Also, the recently recommended WHO "safe surgery check-list" includes a check-list for anaesthesia. A working group was established in accordance with the charter of the Spanish Society of Anaesthesiology and Resuscitation (Sociedad Española de Anestesiología y Reanimación [SEDAR]). The new patient safety culture introduced into medicine, and the recommendations of European anaesthesia societies has led us to design and update protocols in order to improve results in this important part of our speciality. We have prepared these recommendations or guidelines using, as examples, updates of pre-anaesthesia check-lists by other American (ASA), British, or Canadian societies of anaesthesia. With that aim, we enlisted the help of anaesthesia ventilator experts and the participation and advice of experienced anaesthesiologists from all parts of Spain. After various corrections and modifications, the document was available at www.sedar.es, so that any anaesthesiologist could propose any correction, or give their opinion. Finally, these guidelines have been approved by the SEDAR Board of Directors, before it was sent for publication in this journal. The aims of this document are to provide: a guideline applicable to all anaesthesia machines, a descriptive pre-anaesthesia check-list that include everything necessary for the anaesthesia procedure, and a resumed check-list to be available in all the anaesthesia machines or other equivalent, but prepared for each institution, which should include anaesthetic equipment and drugs. So, in order to ensure the aims and requirements of the European Board of Anaesthesiology, the European Society of Anaesthesiology, and the WHO are met, each institution should have a protocol for checking equipment and drugs. These guidelines are applicable to any anaesthesia equipment, enabling every institution to develop their own checking protocols, adapted to their anaesthesia machines and their procedures. With the consent of the SEDAR, this group will collaborate with anaesthesia machines providers in order to develop specific checklists for each of their models that will be available at www.sedar.es.

Autophagy, and BiP level decrease are early key events in retrograde degeneration of motoneurons

Disconnection of the axon from the soma of spinal motoneurons (MNs) leads either to a retrograde degenerative process or to a regenerative reaction, depending on the severity and the proximity to the soma of the axonal lesion. The endoplasmic reticulum (ER) is a continuous membranous network that extends from the nucleus to the entire cytoplasm of the neuronal soma, axon and dendrites. We investigated whether axonal injury is sensed by the ER and triggers the activation of protective mechanisms, such as the unfolded protein response (UPR) and autophagy. We found early (at 3 days) accumulation of beclin1, LC3II and Lamp-1, hallmarks of autophagy, in both degenerating MNs after spinal root avulsion and in non-degenerating MNs after distal nerve section, although Lamp-1 disappeared by 5 days only in the former. In contrast, only degenerating MNs presented early activation of IRE1α, revealed by an increase of the spliced isoform of Xbp1 and accumulation of ATF4 in their nucleus, two branches of the UPR, and late BiP downregulation in association with cytoskeletal and organelle disorganization. We conclude that BiP decrease is a signature of the degenerating process, as its overexpression led to an increase in MN survival after root avulsion. Besides, Bcl2 is strongly implicated in the survival pathway activated by BiP overexpression.

[Postoperative nausea and vomiting and opioid-induced nausea and vomiting: guidelines for prevention and treatment]

Postoperative nausea and vomiting (PONV) causes patient discomfort, lowers patient satisfaction, and increases care requirements. Opioid-induced nausea and vomiting (OINV) may also occur if opioids are used to treat postoperative pain. These guidelines aim to provide recommendations for the prevention and treatment of both problems. A working group was established in accordance with the charter of the Sociedad Española de Anestesiología y Reanimación. The group undertook the critical appraisal of articles relevant to the management of PONV and OINV in adults and children early and late in the perioperative period. Discussions led to recommendations, summarized as follows: 1) Risk for PONV should be assessed in all patients undergoing surgery; 2 easy-to-use scales are useful for risk assessment: the Apfel scale for adults and the Eberhart scale for children. 2) Measures to reduce baseline risk should be used for adults at moderate or high risk and all children. 3) Pharmacologic prophylaxis with 1 drug is useful for patients at low risk (Apfel or Eberhart 1) who are to receive general anesthesia; patients with higher levels of risk should receive prophylaxis with 2 or more drugs and baseline risk should be reduced (multimodal approach). 4) Dexamethasone, droperidol, and ondansetron (or other setrons) have similar levels of efficacy; drug choice should be made based on individual patient factors. 5) The drug prescribed for treating PONV should preferably be different from the one used for prophylaxis; ondansetron is the most effective drug for treating PONV. 6) Risk for PONV should be assessed before discharge after outpatient surgery or on the ward for hospitalized patients; there is no evidence that late preventive strategies are effective. 7) The drug of choice for preventing OINV is droperidol.

Cardiac rupture and tamponade during ventriculography

Left ventricular free wall rupture after a myocardial infarction is a complication which is unusually seen during ventriculography. We present the case of a patient who developed a cardiac rupture and tamponade captured on ventriculography.

Late gadolinium-enhanced cardiovascular magnetic resonance identifies patients with standardized definition of ischemic cardiomyopathy: A single centre experience

BACKGROUND

Definition of ischemic cardiomyopathy (IC) is not always obvious, which is why new criteria based on prognosis and the extent of the coronary artery disease (CAD) have been proposed. In the present study, we assess the capability of late gadolinium-enhanced cardiovascular magnetic resonance (CMR) for predicting IC as determined by standardized criteria previously reported.

METHODS AND RESULTS

123 patients with heart failure (HF) and left ventricular (LV) systolic dysfunction, underwent both late gadolinium-enhanced CMR and coronary angiography 37/123 (30%) of patients were assigned to the IC group and 86/123 (70%) to the non-IC group. Subendocardial late gadolinium enhancement (LGE) was found in 35/37 (94%) of patients in the IC group, whereas only 12/86 (14%) had this distribution in the non-IC group (p<0.001). There was a significant positive correlation between the extent of subendocardial LGE and that of the CAD as determined by the CAD Prognostic Index (r=0.78, p<0.01), the number of coronary stenoses > or = 50% (r=0.76, p<0.01) and the number of coronary stenoses of any percentage (r=0.70, p<0.01).

CONCLUSION

In patients with HF and LV systolic dysfunction presence of subendocardial LGE makes an excellent indicator of underlying significant CAD, and the extent of the LGE correlates with the severity of the disease. It is therefore appealing as a method for diagnosing IC.

Hydrolase and glycosynthase activity of endo-1,3-beta-glucanase from the thermophile Pyrococcus furiosus

Pyrococcus furiosus laminarinase (LamA, PF0076) is an endo-glycosidase that hydrolyzes beta-1,3-glucooligosaccharides, but not beta-1,4-gluco-oligosaccharides. We studied the specificity of LamA towards small saccharides by using 4-methylumbelliferyl beta-glucosides with different linkages. Besides endo-activity, wild-type LamA has some exo-activity, and catalyzes the hydrolysis of mixed-linked oligosaccharides (Glcbeta4Glcbeta3Glcbeta-MU (Glc = glucosyl, MU = 4-methylumbelliferyl)) with both beta-1,4 and beta-1,3 specificities. The LamA mutant E170A had severely reduced hydrolytic activity, which is consistent with Glu170 being the catalytic nucleophile. The E170A mutant was active as a glycosynthase, catalyzing the condensation of alpha-laminaribiosyl fluoride to different acceptors. The best condensation yields were found at pH 6.5 and 50 degrees C, but did not exceed 30%. Depending on the acceptor, the synthase generated either a beta-1,3 or a beta-1,4 linkage.

[Prognostic factors of early morbidity and mortality after lung transplantation]

OBJECTIVES

Despite years of experience with lung transplantation, the rate of perioperative mortality remains high. The objective of this study was to look at our experience in the early postoperative period following lung transplantation in an effort to identify possible pre-, intra- and postoperative risk factors associated with mortality.

PATIENTS AND METHODS

A retrospective study of 68 consecutive patients receiving lung transplants over a period of 56 months. The conditions that led to transplantation were obstructive disease (40%), interstitial disease (33%) and suppurative disease (27%). Pre-, intra- and postoperative characteristics of donors and recipients were analyzed for their relation to morbidity and mortality. Statistical studies were done using SPSS 10.0 software. A p-value less than.05 was considered significant. Univariate analysis identified variables associated with the incidence of mortality in the postoperative recovery unit, and the variables with statistically significant associations were entered into multivariate analysis, using a logistic regression model to calculate odds ratio (OR) and 95% confidence intervals (CI).

RESULTS

No donor variables correlated with mortality. Patients with suppurative lung disease had a lower mortality rate (0% vs 30%; P = 0.04). Mortality was related to ischemic time longer than 300 minutes (OR = 2) and the use of extracorporeal circulation (OR = 4). A PaO2/FiO2 ratio less than 150 during the first 24 hours following transplantation (OR = 5) and reoperation due to bleeding (OR = 12) were the variables showing the highest correlations with mortality during the early postoperative period.

CONCLUSIONS

The mortality rate during the early postoperative period in our series was 22%. The survival rate was better in patients with suppurative lung disease. Bleeding that required reoperation and early graft dysfunction (defined in part by a PaO2/FiO2 ratio less than 150 during the first 24 hours) were the variables that best predicted death in the early postoperative period following lung transplantation.

Essential catalytic role of Glu134in endo-β-1,3-1,4-d-glucan 4-glucanohydrolase fromB. licheniformisas determined by site-directed mutagenesis

Site-directed mutagenesis experiments designed to identify the active site of Bacillus licheniformis endo-beta-1,3-1,4-D-glucan 4-glucanohydrolase (beta-glucanase) have been performed. Putative catalytic residues were chosen on the basis of sequence similarity analysis to viral and eukaryotic lysozymes. Four mutant enzymes were expressed and purified from recombinant E. coli and their kinetics analysed with barley beta-glucan. Replacement of Glu134 by Gln produced a mutant (E134Q) that retains less than 0.3% of the wild-type activity. The other mutants, D133N, E160Q and D179N, are active but show different kinetic parameters relative to wild-type indicative of their participation in substrate binding and transition-state complex stabilization. Glu134 is essential for activity; it is comprised in a region of high sequence similarity to the active site of T4 lysozyme and matches the position of the general acid catalyst. These results strongly support a lysozyme-like mechanism for this family of Bacillus beta-glucan hydrolases with Glu134 being the essential acid catalyst.

Oligosaccharide synthesis by coupled endo-glycosynthases of different specificity: a straightforward preparation of two mixed-linkage hexasaccharide substrates of 1,3/1,4-beta-glucanases

Glycosynthases are engineered glycosidases which are hydrolytically inactive yet efficiently catalyse transglycosylation reactions of glycosyl fluoride donors, and are thus promising tools for the enzymatic synthesis of oligosaccharides. Two endo-glycosynthases, the E134A mutant of 1,3/1,4-beta-glucanase from Bacillus licheniformis and the E197A mutant of cellulase Cel7B from Humicola insolens, were used in coupled reactions for the stepwise synthesis of hexasaccharide substrates of 1,3/1,4-beta-glucanases. Because the two endo-glycosynthases show different specificity, towards laminaribiosyl and cellobiosyl donors, respectively, the target hexasaccharides were prepared by condensation of the corresponding disaccharide building blocks through sequential addition of the glycosynthases in a "one-pot" process. Different strategies were used to achieve the desired transglycosylation between donor and acceptor in each step, and to prevent unwanted elongation of the first condensation product and polymerization (self-condensation) of the donor: 1) selection of disaccharide donors differing in the configuration of the hydroxyl substituent normally acting as acceptor, 2) temporary protection of the polymerizable hydroxyl group of the donor, or 3) addition of an excess of acceptor to decrease the probability that the donor can act as an acceptor. The best procedure involved the condensation of alpha-lactosyl or 4II-O-tetrahydropyranyl-alpha-cellobiosyl fluorides with alpha-laminaribiosyl fluoride, catalyzed by E197A Cel7B, to give tetrasaccharide fluorides, which were then the donors for in situ condensation with methyl beta-cellobioside catalyzed by E134A 1,3/1,4-beta-glucanase. After isolation, the final hexasaccharides Gal/beta4Glcbeta4Glcbeta3Glcbeta4Glcbeta4Glcbeta-OMe and Glcbeta4Glcbeta4Glcbeta3Glcbeta4Glcbeta4-Glcbeta-OMe were obtained in 70-80% overall yields.

Mechanism of the family 1 beta-glucosidase from Streptomyces sp: catalytic residues and kinetic studies

The Streptomyces sp. beta-glucosidase (Bgl3) is a retaining glycosidase that belongs to family 1 glycosyl hydrolases. Steady-state kinetics with p-nitrophenyl beta-D-glycosides revealed that the highest k(cat)/K(M) values are obtained with glucoside (with strong substrate inhibition) and fucoside (with no substrate inhibition) substrates and that Bgl3 has 10-fold glucosidase over galactosidase activity. Reactivity studies by means of a Hammett analysis using a series of substituted aryl beta-glucosides gave a biphasic plot log k(cat) vs pK(a) of the phenol aglycon: a linear region with a slope of beta(lg) = -0.8 for the less reactive substrates (pK(a) > 8) and no significant dependence for activated substrates (pK(a) < 8). Thus, according to the two-step mechanism of retaining glycosidases, formation of the glycosyl-enzyme intermediate is rate limiting for the former substrates, while hydrolysis of the intermediate is for the latter. To identify key catalytic residues and on the basis of sequence similarity to other family 1 beta-glucosidases, glutamic acids 178 and 383 were changed to glutamine and alanine by site-directed mutagenesis. Mutation of Glu178 to Gln and Ala yielded enzymes with 250- and 3500-fold reduction in their catalytic efficiencies, whereas larger reduction (10(5)-10(6)-fold) were obtained for mutants at Glu383. The functional role of both residues was probed by a chemical rescue methodology based on activation of the inactive Ala mutants by azide as exogenous nucleophile. The E178A mutant yielded the beta-glucosyl azide adduct (by (1)H NMR) with a 200-fold increase on k(cat) for the 2,4-dinitrophenyl glucoside but constant k(cat)/K(M) on azide concentration. On the other hand, the E383A mutant with the same substrate gave the alpha-glucosyl azide product and a 100-fold increase in k(cat) at 1 M azide. In conclusion, Glu178 is the general acid/base catalyst and Glu383 the catalytic nucleophile. The results presented here indicate that Bgl3 beta-glucosidase displays kinetic and mechanistic properties similar to other family 1 enzymes analyzed so far. Subtle differences in behavior would lie in the fine and specific architecture of their respective active sites.

Isolation and characterization of a thermostable endo-beta-glucanase active on 1,3-1,4-beta-D-glucans from the aerobic fungus talaromyces emersonii CBS 814.70

A novel endoglucanase active on 1,3-1,4-beta-D-glucans was purified to apparent homogeneity from submerged cultures of the moderately thermophilic aerobic fungus Talaromyces emersonii CBS 814.70. The enzyme is a single subunit glycoprotein with M(r) and pI values of 40.7 +/- 0.3 kDa and 4.4, respectively, and an estimated carbohydrate content of 77% (w/w). The purified beta-glucanase displayed activity over broad ranges of pH and temperature, yielding respective optima values of pH 4.8 and 80 degrees C. This enzyme was markedly thermostable with 15% of the original activity remaining after incubation for 15 min at 100 degrees C. Substrate specificity studies revealed the identity of the enzyme to be a 1,3-1,4-beta-D-glucanase. Identical K(m) values (13.38 mg.ml(-1)) were obtained with lichenan and BBG, while the V(max) value with lichenan (142.9 IU.mg(-1)) was approximately twice the value obtained with BBG (79.3 IU.mg(-1)). Time-course hydrolysis of barley-beta-glucan did not proceed linearly with respect to time indicating an 'endo' or more processive action for the enzyme. HPAEC fractionation of the products of hydrolysis yielded a range of oligosaccharides, with cellobiose, cellotriose and cellotetraose being the predominant oligosaccharide products.

Relationship of obesity distribution and peripheral arterial occlusive disease in elderly men

OBJECTIVE

To examine the relationships between total body fatness and abdominal fat distribution with peripheral arterial disease.

DESIGN

Cross-sectional.

SUBJECTS

Population-based sample of 708 men aged 55-74.

MEASUREMENTS

Body mass index (BMI) to estimate total body fatness and waist-to-hip ratio for abdominal fat distribution; peripheral arterial disease defined by ankle/brachial index <0.9; cardiovascular risk factors.

RESULTS

Peripheral arterial disease was observed in 13.4% of subjects. BMI did not correlate with peripheral arterial disease, whereas an increased waist-to-hip ratio over 0.966 (median value) doubled the prevalence of arterial disease. After controlling for smoking, diabetes, hypertension, high-density lipoprotein cholesterol and triglycerides, increased waist-to-hip ratio was independently associated with peripheral arterial disease (odds ratio 1.68; 95% confidence interval 1.05-2.70).

CONCLUSION

Abdominal fat distribution, but not total body fatness, is associated with peripheral arterial occlusive disease, independently of concurrent cardiovascular risk factors.

Presteady-state kinetics of Bacillus 1,3-1,4-beta-glucanase: binding and hydrolysis of a 4-methylumbelliferyl trisaccharide substrate

In the present study the first stopped-flow experiments performed on Bacillus 1,3-1,4-beta-glucanases are reported. The presteady-state kinetics of the binding of 4-methylumbelliferyl 3-O-beta-cellobiosyl-beta-D-glucoside to the inactive mutant E134A, and the wild-type-catalysed hydrolysis of the same substrate, were studied by measuring changes in the fluorescence of bound substrate or 4-methylumbelliferone produced. The presteady-state traces all showed an initial lag phase followed by a fast monoexponential phase leading to equilibration (for binding to E134A) or to steady state product formation (for the wild-type reaction). The lag phase, with a rate constant of the order of 100 s(-1), was independent of the substrate concentration; apparently an induced-fit mechanism governs the formation of enzyme-substrate complexes. The concentration dependencies of the observed rate constant of the second presteady-state phase were analysed according to a number of reaction models. For the reaction of the wild-type enzyme, it is shown that the fast product formation observed before steady state is not due to a rate-determining deglycosylation step. A model that can explain the observed results involves, in addition to the induced fit, a conformational change of the productive ES complex into a form that binds a second substrate molecule in a non-productive mode.

Long-lived glycosyl-enzyme intermediate mimic produced by formate re-activation of a mutant endoglucanase lacking its catalytic nucleophile

The mutant E134A 1,3-1,4-beta-glucanase from Bacillus licheniformis, in which the catalytic nucleophilic residue has been removed by mutation to alanine, has its hydrolytic activity rescued by exogenous formate in a concentration-dependent manner. A long-lived alpha-glycosyl formate is detected and identified by (1)H-NMR and matrix-assisted laser desorption ionization-time-of-flight-MS. The intermediate is kinetically competent, since it is, at least partially, enzymically hydrolysed, and able to act as a glycosyl donor in transglycosylation reactions. This transient compound represents a true covalent glycosyl-enzyme intermediate mimic of the proposed covalent intermediate in the reaction mechanism of retaining glycosidases.

Bacterial 1,3-1,4-beta-glucanases: structure, function and protein engineering

1,3-1,4-beta-Glucanases (or lichenases, EC 3.2.1.73) hydrolyse linear beta-glucans containing beta-1,3 and beta-1,4 linkages such as cereal beta-glucans and lichenan, with a strict cleavage specificity for beta-1,4 glycosidic bonds on 3-O-substituted glucosyl residues. The bacterial enzymes are retaining glycosyl hydrolases of family 16 with a jellyroll beta-sandwich fold and a substrate binding cleft composed of six subsites. The present paper reviews the structure-function aspects of the enzymatic action including mechanistic enzymology, protein engineering and X-ray crystallographic studies.

Pancreatitis induces HSP72 in the lung: role of neutrophils and xanthine oxidase

The aim of this work was to evaluate the systemic Hsp72 expression in rat lung and liver in vivo in a model of acute pancreatitis and investigate the possible involvement of xanthine oxidase and neutrophils in this process. Pancreatitis was induced by intraductal administration of 5% sodium taurocholate and samples of lung and liver were obtained 1 and 3 h later. In some groups of rats circulating xanthine oxidase was inhibited with oxypurinol, and neutrophil recruitment was blocked with a monoclonal antibody against P-selectin. Hsp72 expression was assessed by means of Western blot and immunohistochemistry. Results showed Hsp72 induction in lung, but not in liver, shortly after pancreatitis. Hsp72-induced expression was located in bronchial epithelium, alveolar macrophages, infiltrating neutrophils, and blood vessels. Oxypurinol and the antibody against P-selectin prevented pancreatitis-induced lung Hsp72 overexpression suggesting that Hsp72 induction is mediated by neutrophil infiltration into the lungs.

Protein-carbohydrate interactions defining substrate specificity in Bacillus 1,3-1,4-beta-D-glucan 4-glucanohydrolases as dissected by mutational analysis

The carbohydrate-binding site of Bacillus macerans 1,3-1, 4-beta-D-glucan 4-glucanohydrolase has been analyzed through a mutational analysis to probe the role of protein-carbohydrate interactions defining substrate specificity. Amino acid residues involved in substrate binding were proposed on the basis of a modeled enzyme-substrate complex [Hahn, M., Keitel, T., and Heinemann, U. (1995) Eur. J. Biochem. 232, 849-859]. The effects of the mutations at 15 selected residues on catalysis and binding were determined by steady-state kinetics using a series of chromogenic substrates of different degree of polymerization to assign the individual H-bond and hydrophobic contributions to individual subsites in the binding site cleft. The glucopyranose rings at subsites -III and -II are tightly bound by a number of H-bond interactions to Glu61, Asn24, Tyr92, and Asn180. From k(cat)/K(M) values, single H-bonds account for 1.8-2.2 kcal mol(-)(1) transition-state (TS) stabilization, and a charged H-bond contributes up to 3.5 kcal mol(-)(1). Glu61 forms a bidentated H-bond in subsites -III and -II, and provides up to 6.5 kcal mol(-)(1) TS stabilization. With a disaccharide substrate that fills subsites -I and -II, activation kinetics were observed for the wild-type and mutant enzymes except for mutations on Glu61, pointing to an important role of the bidentate interaction of Glu61 in two subsites. Whereas removal of the hydroxyl group of Tyr121, initially proposed to hydrogen-bond with the 2OH of Glcp-I, has essentially no effect (Y121F mutant), side-chain removal (Y121A mutant) gave a 100-fold reduction in k(cat)/K(M) and a 10-fold lower K(I) value with a competitive inhibitor. In subsite -IV, only a stacking interaction with Tyr22 (0.7 kcal mol(-)(1) TS stabilization) is observed.

From beta-glucanase to beta-glucansynthase: glycosyl transfer to alpha-glycosyl fluorides catalyzed by a mutant endoglucanase lacking its catalytic nucleophile

Removal of the catalytic nucleophile Glu134 of the retaining 1,3-1,4-beta-glucanase from Bacillus licheniformis by mutation to alanine yields an enzyme with no glycosidase activity. The mutant is able to catalyze the regio- and stereospecific glycosylation of alpha-laminaribiosyl fluoride with different glucoside acceptors through a single-step inverting mechanism. The main advantage of the mutant as glycosylation catalyst with respect to the kinetically controlled transglycosylation using the wild-type enzyme is that the reaction products cannot be hydrolyzed by the mutant enzyme, and glycosylation yields rise to 90%.

Expeditious synthesis of a new hexasaccharide using transglycosylation reaction catalyzed by Bacillus (1-->3),(1-->4)-Beta-D-glucan 4-glucanohydrolase

Enzymatic hydrolysis of barley (1-->3),(1-->4)-beta-D-glucan using a recombinant (1-->3),(1-->4)-beta-glucanase from Bacillus licheniformis gives Glc beta 4Glc beta 3Glc isolated after acetylation in 49% yield. Conventional treatment produced the corresponding beta-fluoride which was carefully de-O-acetylated. A transglycosylation reaction with this substrate, catalyzed by the title enzyme, gave Glc beta 4Glc beta 3Glc beta 4Glc beta 4Glc beta 3Glc in 20% yield.

Probing the mechanism of Bacillus 1,3-1,4-beta-D-glucan 4-glucanohydrolases by chemical rescue of inactive mutants at catalytically essential residues

The role of the key catalytic residues Glu134 and Glu138 in the retaining 1,3-1,4-beta-glucanase from Bacillus licheniformis is probed by a chemical rescue methodology based on enzyme activation of inactive mutants by the action of added nucleophiles. While Glu134 was proposed as the catalytic nucleophile on the basis of affinity labeling experiments, no functional proof supported the assignment of Glu138 as the general acid-base catalyst. Alanine replacements are prepared by site-directed mutagenesis to produce the inactive E138A and E134A mutants. Addition of azide reactivates the mutants in a concentration-dependent manner using an activated 2, 4-dinitrophenyl glycoside substrate. The chemical rescue operates by a different mechanism depending on the mutant as deduced from 1H NMR monitoring and kinetic analysis of enzyme reactivation. E138A yields the beta-glycosyl azide product arising from nucleophilic attack of azide on the glycosyl-enzyme intermediate, thus proving that Glu138 is the general acid-base residue. Azide activates the deglycosylation step (increasing kcat), but it also has a large effect on a previous step (as seen by the large decrease in KM, the increase in kcat/KM, and the pH dependence of activation), probably increasing the rate of glycosylation through Bronsted acid catalysis by enzyme-bound HN3. By contrast, azide reactivates the E134A mutant through a single inverting displacement to give the alpha-glycosyl azide product, consistent with Glu134 being the catalytic nucleophile. Formate as an exogenous nucleophile has no effect on the E138A mutant, whereas it is a better activator of E134A than azide. Although the reaction yields the normal hydrolysis product, a transient compound was detected by 1H NMR, tentatively assigned to the alpha-glycosyl formate adduct. This is the first case where a nonmodified sugar gives a long-lived covalent intermediate that mimics the proposed glycosyl-enzyme intermediate of retaining glycosidases.

Synthesis of aryl 3-O-beta-cellobiosyl-beta-D-glucopyranosides for reactivity studies of 1,3-1,4-beta-glucanases

A series of substituted aryl beta-glycosides derived from 3-O-beta-cellobiosyl-D-glucopyranose with different phenol-leaving group abilities as measured by the pKa of the free phenol group upon enzymatic hydrolysis has been synthesised. Aryl beta-glycosides with a pKa of the free phenol leaving group > 5 were prepared by phase-transfer glycosidation of the per-O-acetylated alpha-glycosyl bromide with the corresponding phenol, whereas the 2,4-dinitrophenyl beta-glycoside was obtained by condensation of 1-fluoro-2,4-dinitrobenzene with the partially acetylated trisaccharide followed by acid de-O-acetylation. The aryl beta-glycosides have been used for reactivity studies of the wild-type Bacillus licheniformis 1,3-1,4-beta-D-glucan 4-glucanohydrolase. The Hammett plot log kcat versus pKa is biphasic with an upward curvature at low pKa values suggesting a change in transition-state structure depending on the aglycon.

Mechanism of Bacillus 1,3-1,4-beta-D-glucan 4-glucanohydrolases: kinetics and pH studies with 4-methylumbelliferyl beta-D-glucan oligosaccharides

The carbohydrate binding site of Bacillus licheniformis 1,3-1,4-beta-D-glucan 4-glucanohydrolase was probed with a series of synthetic 4-methylumbelliferyl beta-D-glucan oligosaccharides (1a-e). The title enzyme is a retaining endo-glycosidase that has an extended carbohydrate binding site composed of four glucopyranosyl binding subunits on the non-reducing end from the scissile glycosidic bond, plus two or three subsites on the reducing end. Subsites -II to -IV have a stabilizing effect on the enzyme-substrate transition state complex in the rate-determining step leading to a glycosyl-enzyme intermediate, with subsite -III having a larger effect (-3.5 kcal mol-1). Since KM values decrease from the mono- to the tetrasaccharide, part of the effect is due to ground stabilization of the Michaelis complex. On the other hand, the chromophoric trisaccharide 1c and the homologous nonchromogenic tetrasaccharide 2b, which locates a glucopyranosyl unit in subsite +I, have almost identical KM values, the difference in reactivity being a consequence of an 18-fold increase of kcat for 2b. Therefore, interactions between subsite +I and the substrate appear to be mainly used to lower the energy of the transition state in the glycosylation step, rather than in the stabilization of the Michaelis complex. Finally, the pH dependence of the kinetic parameters for the hydrolysis of 1c, and the pH-dependent enzyme inactivation by a water-soluble carbodiimide (EAC) suggest two essential groups with pKa values of 5.5 and 7.0 in the free enzyme. The latter value is shifted up to 1.5 pH units upon binding of substrate in the non-covalent enzyme-substrate complex.

[Hemodynamic and respiratory changes during lung transplant]

OBJECTIVE

To study the hemodynamic and gasometric changes observed during lung transplantation, and discuss the differences between unilateral (ULT) and sequential bilateral lung transplantation (SBLT).

PATIENTS AND METHODS

We enrolled 13 consecutive patients (8 ULT and 5 SBLT). Gasometric and hemodynamic readings, including right ventricular (RV) function measured as ejection fraction through a catheter, were recorded at the different phases of surgery. ANOVA and Neumann Keuls tests were used for statistical analysis.

RESULTS

During ULT no significant changes in RV function were seen and gasometric alterations stayed within clinically tolerable limits. No significant hemodynamic or gasometric changes were observed during the first implantation during SBLT, although there was a significant increase in pulmonary artery pressure as cardiac index decreased, as well as significant depression of RV function and hypoxemia during reperfusion and ventilation of the first lung transplanted. Extracorporeal circulation was needed in one case.

CONCLUSIONS

During SBLT, selective reperfusion and ventilation of the first transplanted lung is a moment of great hemodynamic and ventilatory instability. Exhaustive monitoring of RV function is essential for adequate management.

Mutational analysis of the major loop of Bacillus 1,3-1,4-beta-D-glucan 4-glucanohydrolases. Effects on protein stability and substrate binding

The carbohydrate-binding cleft of Bacillus licheniformis 1,3-1, 4-beta-D-glucan 4-glucanohydrolase is partially covered by the surface loop between residues 51 and 67, which is linked to beta-strand-(87-95) of the minor beta-sheet III of the protein core by a single disulfide bond at Cys61-Cys90. An alanine scanning mutagenesis approach has been applied to analyze the role of loop residues from Asp51 to Arg64 in substrate binding and stability by means of equilibrium urea denaturation, enzyme thermotolerance, and kinetics. The DeltaDeltaGU between oxidized and reduced forms is approximately constant for all mutants, with a contribution of 5.3 +/- 0.2 kcal.mol-1 for the disulfide bridge to protein stability. A good correlation is observed between DeltaGU values by reversible unfolding and enzyme thermotolerance. The N57A mutant, however, is more thermotolerant than the wild-type enzyme, whereas it is slightly less stable to reversible urea denaturation. Mutants with a <2-fold increase in Km correspond to mutations at residues not involved in substrate binding, for which the reduction in catalytic efficiency (kcat/Km) is proportional to the loss of stability relative to the wild-type enzyme. Y53A, N55A, F59A, and W63A, on the other hand, show a pronounced effect on catalytic efficiency, with Km > 2-fold and kcat < 5% of the wild-type values. These mutated residues are directly involved in substrate binding or in hydrophobic packing of the loop. Interestingly, the mutation M58A yields an enzyme that is more active than the wild-type enzyme (7-fold increase in kcat), but it is slightly less stable.