Management of patients with left main stem stenosis in Iceland 2010–2020: PCI or CABG?

Introduction

Coronary artery bypass surgery (CABG) has been standard treatment for patients with left main coronary artery disease (LMCAD) but percutaneous coronary intervention (PCI) is a good alternative in selected patients.

Our purpose was to evaluate the prevalence of LMCAD in Iceland, the impact of background factors on treatment choices, and treatment changes in recent years with respect to current guidelines.

Methods

This retrospective, population-based study analyzed data from the SCAAR-SWEDEHEART database. Patients with significant LMCAD on coronary angiography in Iceland 2010–2020, without previous history of CABG or contraindication for surgery were enrolled. Survival analysis was estimated with Kaplan-Meier and COX regression analysis for investigating the association between survival time and predictor variables.

Findings

Of 702 patients with LMCAD, 195 were treated with PCI, 460 with CABG and 47 with medical treatment only. The widest age range was in the PCI group and the mean age was highest in the medical therapy only group (p<0.001). Patients with LMCAD and either three vessel disease or heart valve disease were most often treated with CABG (76.1% and 84.4%, p<0.001).The majority of patients with LMCAD only were treated with PCI, as were patients with STEMI or cardiogenic shock (67.1% and 70.0%, p<0.001). The proportion of patients treated with PCI increased from 19.8% in 2010–2015 to 42.7% in 2016–2020. There was no significant difference in survival between PCI and CABG (p=0.41).

Conclusions

In patients with LMCAD the main factors that affect treatment choice are age, anatomical complexity and acuteness. Treatment choice appears to be in keeping with current guidelines. There is no significant difference in long term survival between PCI and CABG groups but the groups are different. There has been a significant increase in patients treated with PCI in recent years.

Funding Acknowledgement

Type of funding sources: None.

Efficacy and safety of memantine in children with autism spectrum disorder: Results from three phase 2 multicenter studies

Three phase 2 trials were conducted to assess the efficacy and long-term safety of weight-based memantine extended release (ER) treatment in children with autism spectrum disorder. MEM-MD-91, a 50-week open-label trial, identified memantine extended-release treatment responders for enrollment into MEM-MD-68, a 12-week randomized, double-blind, placebo-controlled withdrawal trial. MEM-MD-69 was an open-label extension trial in which participants from MEM-MD-68, MEM-MD-91, and open-label trial MEM-MD-67 were treated ⩽48 weeks with memantine extended release. In MEM-MD-91, 517 (59.6%) participants were confirmed Social Responsiveness Scale responders at week 12; mean Social Responsiveness Scale total raw scores improved two to three times a minimal clinically important difference of 10 points. In MEM-MD-68, there was no difference between memantine and placebo on the primary efficacy parameter, the proportion of patients with a loss of therapeutic response (defined as ⩾10-point increase from baseline in Social Responsiveness Scale total raw score). MEM-MD-69 exploratory analyses revealed mean standard deviation improvement in Social Responsiveness Scale total raw score of 32.4 (26.4) from baseline of the first lead-in study. No new safety concerns were evident. While the a priori-defined efficacy results of the double-blind trial were not achieved, the considerable improvements in mean Social Responsiveness Scale scores from baseline in the open-label trials were presumed to be clinically important.

Boronic Acid for the Traceless Delivery of Proteins into Cells

The use of exogenous proteins as intracellular probes and therapeutic agents is in its infancy. A major hurdle has been the delivery of native proteins to an intracellular site of action. Herein, we report on a compact delivery vehicle that employs the intrinsic affinity of boronic acids for the carbohydrates that coat the surface of mammalian cells. In the vehicle, benzoxaborole is linked to protein amino groups via a "trimethyl lock." Immolation of this linker is triggered by cellular esterases, releasing native protein. Efficacy is demonstrated by enhanced delivery of green fluorescent protein and a cytotoxic ribonuclease into mammalian cells. This versatile strategy provides new opportunities in chemical biology and pharmacology.

Selective Inhibition of Collagen Prolyl 4-Hydroxylase in Human Cells

Collagen is the most abundant protein in animals. Its overproduction is associated with fibrosis and cancer metastasis. The stability of collagen relies on post-translational modifications, the most prevalent being the hydroxylation of collagen strands by collagen prolyl 4-hydroxylases (CP4Hs). Catalysis by CP4Hs enlists an iron cofactor to convert proline residues to 4-hydroxyproline residues, which are essential for the conformational stability of mature collagen. Ethyl 3,4-dihydroxybenzoate (EDHB) is commonly used as a "P4H" inhibitor in cells, but suffers from low potency, poor selectivity, and off-target effects that cause iron deficiency. Dicarboxylates of 2,2'-bipyridine are among the most potent known CP4H inhibitors but suffer from a high affinity for free iron. A screen of biheteroaryl compounds revealed that replacing one pyridyl group with a thiazole moiety retains potency and enhances selectivity. A diester of 2-(5-carboxythiazol-2-yl)pyridine-5-carboxylic acid is bioavailable to human cells and inhibits collagen biosynthesis at concentrations that neither cause general toxicity nor disrupt iron homeostasis. These data anoint a potent and selective probe for CP4H and a potential lead for the development of a new class of antifibrotic and antimetastatic agents.

Creating site-specific isopeptide linkages between proteins with the traceless Staudinger ligation

Site-specific isopeptide linkages between the ε-amino group of a lysine residue in one protein and a carboxyl group in another are central to ubiquitin-mediated protein degradation and other cellular processes. These linkages are inaccessible with common recombinant DNA techniques. Here, we describe a method to link two proteins by an authentic isopeptide bond. The method unites three techniques at the forefront of molecular biology. An azidonorleucine residue is installed at a desired site in a substrate protein by nonnatural amino acid incorporation, and a phosphinothioester is installed at the C terminus of a pendant protein by expressed protein ligation. Then, the traceless Staudinger ligation is used to link the substrate and pendant proteins via an isopeptide bond. This method facilitates the study of otherwise intractable protein structure-function relationships.

Diazo groups endure metabolism and enable chemoselectivity in cellulo

We introduce a stabilized diazo group as a reporter for chemical biology. ManDiaz, which is a diazo derivative of N-acetylmannosamine, is found to endure cellular metabolism and label the surface of a mammalian cell. There its diazo group can undergo a 1,3-dipolar cycloaddition with a strained alkyne, providing a signal comparable to that from the azido congener, ManNAz. The chemoselectivity of diazo and alkynyl groups enables dual labeling of cells that is not possible with azido and alkynyl groups. Thus, the diazo group, which is approximately half the size of an azido group, provides unique opportunities for orthogonal labeling of cellular components.

Intrinsic site-selectivity of ubiquitin dimer formation

The post-translational modification of proteins with ubiquitin can take on many forms, including the decoration of substrates with polymeric ubiquitin chains. These chains are linked through one of the seven lysine residues in ubiquitin, with the potential to form a panoply of linkage combinations as the chain length increases. The ensuing structural diversity of modifications serves a variety of signaling functions. Still, some linkages are present at a much higher level than others in cellulo. Although ubiquitination is an enzyme-catalyzed process, the large disparity of abundancies led us to the hypothesis that some linkages might be intrinsically faster to form than others, perhaps directing the course of enzyme evolution. Herein, we assess the kinetics of ubiquitin dimer formation in an enzyme-free system by measuring the rate constants for thiol-disulfide interchange between appropriate ubiquitin variants. Remarkably, we find that the kinetically expedient linkages correlate with those that are most abundant in cellulo. As the abundant linkages also appear to function more broadly in cellulo, this correlation suggests that the more accessible chains were selected for global roles.

Diazo compounds for the bioreversible esterification of proteins

A diazo compound is shown to convert carboxylic acids to esters efficiently in an aqueous environment. The basicity of the diazo compound is critical: low basicity does not lead to a reaction but high basicity leads to hydrolysis. This reactivity extends to carboxylic acid groups in a protein. The ensuing esters are hydrolyzed by human cellular esterases to regenerate protein carboxyl groups. This new mode of chemical modification could enable the key advantages of prodrugs to be translated from small-molecules to proteins.

Organocatalysts of oxidative protein folding inspired by protein disulfide isomerase

Organocatalysts derived from diethylenetriamine effect the rapid isomerization of non-native protein disulfide bonds to native ones. These catalysts contain a pendant hydrophobic moiety to encourage interaction with the non-native state, and two thiol groups with low pKa values that form a disulfide bond with a high E°' value.

Cytotoxicity of paclitaxel in breast cancer is due to chromosome missegregation on multipolar spindles

The blockbuster chemotherapy drug paclitaxel is widely presumed to cause cell death in tumors as a consequence of mitotic arrest, as it does at concentrations routinely used in cell culture. However, we determine here that paclitaxel levels in primary breast tumors are well below those required to elicit sustained mitotic arrest. Instead, cells in these lower concentrations of drug proceed through mitosis without substantial delay and divide their chromosomes on multipolar spindles, resulting in chromosome missegregation and cell death. Consistent with these cell culture data, most mitotic cells in primary human breast cancers contain multipolar spindles after paclitaxel treatment. Contrary to the previous hypothesis, we find that mitotic arrest is dispensable for tumor regression in patients. These results demonstrate that mitotic arrest is not responsible for the efficacy of paclitaxel, which occurs because of chromosome missegregation on highly abnormal, multipolar spindles. This mechanistic insight may be used to improve selection of future antimitotic drugs and to identify a biomarker with which to select patients likely to benefit from paclitaxel.

The sigma-1 receptor is enriched in postsynaptic sites of C-terminals in mouse motoneurons. An anatomical and behavioral study

The sigma-1 receptor regulates various ion channel activity and possesses protein chaperone function. Using an antibody against the full sequence of the sigma-1 receptor we detected immunostaining in wild type but not in knockout mice. The receptor was found primarily in motoneurons localized to the brainstem and spinal cord. At the subcellular level the receptor is restricted to large cholinergic postsynaptic densities on the soma of motoneurons and is colocalized with the Kv2.1 potassium channel and the muscarinic type 2 cholinergic receptor. Ultrastructural analysis of the neurons indicates that the immunostained receptor is located close but separate from the plasma membrane, possibly in subsurface cisternae formed from the endoplasmic reticulum (ER), which are a prominent feature of cholinergic postsynaptic densities. Behavioral testing on a rotorod revealed that Sigma-1 receptor knockout mice remained on the rotorod for significantly less time (a shorter latency period) compared to the wild type mice. Together these data indicate that the sigma-1 receptor may play a role in the regulation of motor behavior.

Glutamate modulation of GABA transport in retinal horizontal cells of the skate

Transport of the amino acid GABA into neurons and glia plays a key role in regulating the effects of GABA in the vertebrate retina. We have examined the modulation of GABA-elicited transport currents of retinal horizontal cells by glutamate, the likely neurotransmitter of vertebrate photoreceptors. Enzymatically isolated external horizontal cells of skate were examined using whole-cell voltage-clamp techniques. GABA (1 mM ) elicited an inward current that was completely suppressed by the GABA transport inhibitors tiagabine (10 microM) and SKF89976-A (100 microM), but was unaffected by 100 microM picrotoxin. Prior application of 100 microM glutamate significantly reduced the GABA-elicited current. Glutamate depressed the GABA dose-response curve without shifting the curve laterally or altering the voltage dependence of the current. The ionotropic glutamate receptor agonists kainate and AMPA also reduced the GABA-elicited current, and the effects of glutamate and kainate were abolished by the ionotropic glutamate receptor antagonist 6-cyano-7-nitroquinoxaline. NMDA neither elicited a current nor modified the GABA-induced current, and metabotropic glutamate analogues were also without effect. Inhibition of the GABA-elicited current by glutamate and kainate was reduced when extracellular calcium was removed and when recording pipettes contained high concentrations of the calcium chelator BAPTA. Caffeine (5 mM) and thapsigargin (2 nM), agents known to alter intracellular calcium levels, also reduced the GABA-elicited current, but increases in calcium induced by depolarization alone did not. Our data suggest that glutamate regulates GABA transport in retinal horizontal cells through a calcium-dependent process, and imply a close physical relationship between calcium-permeable glutamate receptors and GABA transporters in these cells.

Inducible resistance to oxidant stress in the protozoan Leishmania chagasi

Leishmania sp. protozoa are introduced into a mammalian skin by a sandfly vector, whereupon they encounter increased temperature and toxic oxidants generated during phagocytosis. We studied the effects of 37 degrees C "heat shock" or sublethal menadione, which generates superoxide and hydrogen peroxide, on Leishmania chagasi virulence. Both heat and menadione caused parasites to become more resistant to H(2)O(2)-mediated toxicity. Peroxide resistance was also induced as promastigotes developed in culture from logarithmic to their virulent stationary phase form. Peroxide resistance was not associated with an increase in reduced thiols (trypanothione and glutathione) or increased activity of ornithine decarboxylase, which is rate-limiting in trypanothione synthesis. Membrane lipophosphoglycan increased in size as parasites developed to stationary phase but not after environmental exposures. Instead, parasites underwent a heat shock response upon exposure to heat or sublethal menadione, detected by increased levels of HSP70. Transfection of promastigotes with L. chagasi HSP70 caused a heat-inducible increase in resistance to peroxide, implying it is involved in antioxidant defense. We conclude that leishmania have redundant mechanisms for resisting toxic oxidants. Some are induced during developmental change and others are induced in response to environmental stress.

Short report: regulation of inducible heat shock protein 70 genes in Leishmania chagasi

Eukaryotic and prokaryotic cells undergo an increase in heat shock proteins, including hsp70, during exposure to environmental stress and during some developmental changes. In trypanosomatid protozoa such as Leishmania sp. that cycle between poikilothermic vectors and mammalian hosts, this heat shock response occurs at programmed times in the parasite's life cycle. The increase in heat shock proteins in mammalian cells is initiated by an increased rate of transcription, resulting in greater amounts of total hsp70 RNA and protein. In contrast, we found a dramatic increase in hsp70 RNA during growth of Leishmania chagasi promastigotes from logarithmic to stationary phase in liquid culture, which was not accompanied by an increased amount of hsp70 protein. Furthermore, there was a 1.8-fold increase in hsp70 protein induced by exposure of L. chagasi to superoxide, but this was not associated with an increase in hsp70 RNA. We conclude that in contrast to higher eukaryotes, the amount of hsp70 protein produced by Leishmania sp. is not regulated by the steady state level of total hsp70 RNA.

N-tert-butyl-alpha-phenylnitrone: a free radical trap with unanticipated effects on diaphragm function

The spin trap N-tert-butyl-alpha-phenylnitrone (PBN) has a high avidity for free radical species and hence functions as an antioxidant in many biological systems. As such, we hypothesized that PBN would have powerful antioxidant effects on muscle function. We examined the effects of PBN on directly stimulated in vitro (37 degrees C) rat diaphragm. First, a dose-response curve for the effects of PBN on force frequency (n = 8) was established by comparing PBN-treated muscle strips (0.01-10 mM) with time- and stimulus-matched control strips. Second, the effect of 1.0 mM PBN on muscle endurance (n = 8) was established. Our findings were as follows. 1) Compared with baseline, peak twitch and low-frequency muscle tensions increased in a dose-dependent fashion, with peak effects at 1.0 mM PBN. 2) Muscle function at all stimulation frequencies was depressed at doses above 1.0 mM PBN. 3) Complete inhibition at 10 mM PBN was reversed with caffeine administration or washout. 4) During early fatigue, 1.0 mM PBN facilitated force. However, endurance time decreased in the PBN-treated group. We conclude that PBN has direct reversible dose-dependent effects on diaphragm function. However, facilitation of low-frequency forces and the lack of fatigue-attenuating properties suggest that PBN has atypical antioxidant effects on muscle function.

Response of Leishmania chagasi promastigotes to oxidant stress

At the onset of infection, Leishmania promastigotes are phagocytized by mammalian macrophages. They must survive despite exposure to toxic oxidants such as hydrogen peroxide (H2O2) and superoxide (.O2-) generated during phagocytosis. We investigated the effects of these oxidants on Leishmania chagasi promastigotes and promastigote mechanisms for oxidant resistance. According to spin trapping and electron paramagnetic resonance spectrometry, .O2- could be generated by exposure of promastigotes to the redox-cycling compound menadione. Incubation in either menadione or H2O2 caused a concentration-dependent loss of promastigote viability. However, incubation in sublethal concentrations of H2O2 or menadione caused a stress response in promastigotes. This oxidant-induced response was associated with an increase in the amount of heat shock protein hsp70. Induction of a stress response by exposure of promastigotes either to heat shock or to sublethal oxidants (H2O2 or menadione) caused promastigotes to become more resistant to H2O2 toxicity. Sublethal menadione also caused promastigotes to become more virulent in a BALB/c mouse model of leishmaniasis. We previously correlated H2O2 cytotoxicity for promastigotes with the formation of hydroxyl radical (.OH) from H2O2. However, according to electron paramagnetic resonance spectrometry, the increase in H2O2 resistance after exposure to sublethal oxidants was not associated with diminished generation (i.e., scavenging) of .OH. These data suggest that there is a cross-protective stress response that occurs after exposure of L. chagasi promastigotes to heat shock or to sublethal H2O2 or .O2-, exposures that also occur during natural infection. This response results in increased resistance to H2O2 toxicity and increased virulence for a mammalian host.

Acquisition of iron from transferrin and lactoferrin by the protozoan Leishmania chagasi

Leishmania chagasi, the cause of South American visceral leishmaniasis, requires iron for its growth. However, the extent to which different iron sources can be utilized by the parasite is not known. To address this question, we studied acquisition of iron from lactoferrin and transferrin by the extracellular promastigote form of L. chagasi during growth in vitro. A promastigote growth medium based on minimal essential medium supplemented with iron-depleted serum supported promastigote growth only after the addition of exogenous iron. The addition of 8 microM iron chelated to lactoferrin or hemin resulted in normal promastigote growth. Ferritransferrin also supported promastigote growth, but only after a considerable lag. Promastigotes grown in all three iron sources generated similar amounts of hydroxyl radical upon exposure to hydrogen peroxide, indicating that none of these protected parasites against generation of this toxic radical. Promastigotes were able to take up 59Fe chelated to either transferrin or lactoferrin, although uptake from 59Fe-lactoferrin occurred more rapidly. 59Fe uptake from either 59Fe-transferrin or 59Fe-lactoferrin was inhibited by a 10-fold excess of unlabeled ferrilactoferrin, ferritransferrin, apolactoferrin, apotransferrin, or iron nitrilotriacetate but not ferritin or bovine serum albumin. There was no evidence for a role for parasite-derived siderophores or proteolytic cleavage of ferritransferrin or ferrilactoferrin in the acquisition of iron by promastigotes. Thus, L. chagasi promastigotes can acquire iron from hemin, ferrilactoferrin, or ferritransferrin. This capacity to utilize several iron sources may contribute to the organism's ability to survive in the diverse environments it encounters in the insect and mammalian hosts.

[Distance diagnosis of skin diseases]

During a period of eight weeks in late 1989, doctors in general practice in Kirkenes brought 27 dermatological patients to a studio at the local hospital. Video images were transmitted via a two-way telephone and video network, which enabled the patient and the doctor in Kirkenes to consult a specialist in dermatology in Tromsø. All the patients received written information before the consultation. Anamnestic information and clinical manifestations were presented from the studio at Kirkenes sykehus. The dermatologist diagnosed the disease and prescribed treatment from the studio at the hospital in Tromsø. The technical equipment satisfied our demands for remote diagnostics in dermatology. All the patients were positive to remote consultations.