Silver-catalyzed direct conversion of epoxides into cyclopropanes using N-triftosylhydrazones

Epoxides, as a prominent small ring O-heterocyclic and the privileged pharmacophores for medicinal chemistry, have recently represented an ideal substrate for the development of single-atom replacements. The previous O-to-C replacement strategy for epoxides to date typically requires high temperatures to achieve low yields and lacks substrate range and functional group tolerance, so achieving this oxygen-carbon exchange remains a formidable challenge. Here, we report a silver-catalyzed direct conversion of epoxides into trifluoromethylcyclopropanes in a single step using trifluoromethyl N-triftosylhydrazones as carbene precursors, thereby achieving oxygen-carbon exchange via a tandem deoxygenation/[2 + 1] cycloaddition. The reaction shows broad tolerance of functional groups, allowing routine cheletropic olefin synthesis in a strategy for the net oxygen-carbon exchange reaction. The utility of this method is further showcased with the late-stage diversification of epoxides derived from bioactive natural products and drugs. Mechanistic experiments and DFT calculations elucidate the reaction mechanism and the origin of the chemo- and stereoselectivity.

Easy and Accessible Synthesis of Cannabinoids from CBD

Cannabidiol (CBD), a prominent phytocannabinoid found in various Cannabis chemotypes, is under extensive investigation for its therapeutic potential. Moreover, because it is nonpsychoactive, it can also be utilized as a functional ingredient in foods and supplements in certain countries, depending on its legal status. From a chemical reactivity point of view, CBD can undergo conversion into different structurally related compounds both during storage and after the consumption of CBD-based products. The analytical determination of these compounds is of paramount concern due to potential toxicity and the risk of losing the active ingredient (CBD) title. Consequently, the complete stereoselective total synthesis of representative CBD-derived compounds has become a matter of great interest. The synthesis of pure CBD-derived compounds, achievable in a few synthetic steps, is essential for preparing analytical standards and facilitating biological studies. This paper details the transformation of the readily available CBD into Δ8-THC, Δ9-THC, Δ8-iso-THC, CBE, HCDN, CBDQ, Δ6-iso-CBD, and 1,8-cineol cannabinoid (CCB). The described protocols were executed without the extensive use of protecting groups, avoiding tedious purifications, and ensuring complete control over the structural features.

Sigma receptor and aquaporin modulators: chiral resolution, configurational assignment, and preliminary biological profile of RC752 enantiomers

The key role of chiral small molecules in drug discovery programs has been deeply investigated throughout last decades. In this context, our previous studies highlighted the influence of the absolute configuration of different stereocenters on the pharmacokinetic, pharmacodynamic and functional properties of promising Sigma receptor (SR) modulators. Thus, starting from the racemic SR ligand RC752, we report herein the isolation of the enantiomers via enantioselective separation with both HPLC and SFC. After optimization of the eco-sustainable chiral SFC method, both enantiomers were obtained in sufficient amount (tens of mg) and purity (ee up to 95%) to allow their characterization and initial biological investigation. Both enantiomers a) displayed a high affinity for the S1R subtype (Ki = 15.0 ± 1.7 and 6.0 ± 1.2 nM for the (S)- and (R)-enantiomer, respectively), but only negligible affinity toward the S2R (> 350 nM), and b) were rapidly metabolized when incubated with mouse and human hepatic microsomes. Furthermore, the activity on AQP-mediated water permeability indicated a different functional profile for the enantiomers in terms of modulatory effect on the peroxiporins gating.

Electrifying Friedel-Crafts Intramolecular Alkylation toward 1,1-Disubstituted Tetrahydronaphthalenes

In this work, we successfully employed electrochemical conditions to promote a Hofer-Moest, intramolecular Friedel-Crafts alkylation sequence. The reaction proceeds under mild conditions, employing carboxylic acids as starting materials. Notably, the electrochemical process performed in batch was adapted to a continuous flow electrolysis apparatus to provide a significant improvement. This catalyst-free, electrochemical approach produces an array of tetrahydronaphthalenes that could be used for API synthesis.

Iridium Acylnitrenoid-Initiated Biomimetic Cascade Cyclizations: Stereodefined Access to Polycyclic δ-Lactams

Ring-fused azacyclic compounds are important building units in the synthesis of biorelevant natural products, pharmaceutical agents, and molecular materials. Herein, we present a new approach to these condensed azacycles by a biomimetic cascade cyclization of arylalkenyl dioxazolones. This cascade reaction was found to proceed with excellent stereoselectivity and a high functional group tolerance. The substrate scope of arylalkenyl dioxazolones turned out to be highly flexible and extendable to additional terminating subunits, such as heteroaryl and alkynyl moieties. This biomimetic cyclization was elucidated to be initiated by an intramolecular transfer of the in situ generated electrophilic Ir-acylnitrenoid to the tethered olefinic double bond, leading to a key N-acylaziridine intermediate, which is in turn reacted with pendant (hetero)arenes or alkynes in a highly regio- and stereoselective manner to produce ring-fused azacyclic compounds.

NLRP3 monomer functional dynamics: From the effects of allosteric binding to implications for drug design

The protein NLRP3 and its complexes are associated with an array of inflammatory pathologies, among which neurodegenerative, autoimmune, and metabolic diseases. Targeting the NLRP3 inflammasome represents a promising strategy for easing the symptoms of pathologic neuroinflammation. When the inflammasome is activated, NLRP3 undergoes a conformational change triggering the production of pro-inflammatory cytokines IL-1β and IL-18, as well as cell death by pyroptosis. NLRP3 nucleotide-binding and oligomerization (NACHT) domain plays a crucial role in this function by binding and hydrolysing ATP and is primarily responsible, together with conformational transitions involving the PYD domain, for the complex-assembly process. Allosteric ligands proved able to induce NLRP3 inhibition. Herein, we examine the origins of allosteric inhibition of NLRP3. Through the use of molecular dynamics (MD) simulations and advanced analysis methods, we provide molecular-level insights into how allosteric binding affects protein structure and dynamics, remodelling of the conformational ensembles populated by the protein, with key reverberations on how NLRP3 is preorganized for assembly and ultimately function. The data are used to develop a Machine Learning model to define the protein as Active or Inactive, only based on the analysis of its internal dynamics. We propose this model as a novel tool to select allosteric ligands.

Ceftazidime/avibactam-resistant meropenem-susceptible KPC-producing Klebsiella pneumoniae: analysis of cases and evaluation of in-vitro activity of fosfomycin-containing combinations

BACKGROUND

Little is known regarding outcomes and optimal therapeutic regimens of infections caused by KPC-producing Klebsiella pneumoniae (KPC-Kp) resistant to ceftazidime/avibactam (CZA) and susceptible to meropenem (MEM). Although in-vitro susceptible to MEM, the possibility of developing MEM resistance overtime is a concern. We described the clinical characteristics of patients with colonization/infection due to KPC-variant with a focus on the in-vitro activity of fosfomycin (FOS)-containing combinations.

MATERIALS/METHODS

Patients with colonization/infection due to KPC-variant were included. FOS susceptibility was performed by agar dilution method. Synergistic activity of FOS-based combinations was evaluated by gradient strip-agar diffusion method. The emergence of in-vitro MEM resistance was also tested.

RESULTS

Eleven patients were included, 8 with infection [4 ventilator-associated pneumonia, 4 bloodstream infections], 3 with colonization. A previous therapy with CZA was administered to all the patients (mean cumulative duration 23 days). All subjects with infection received meropenem, in monotherapy (n=4) or with amikacin (n=2) or fosfomycin (n=2) and achieved clinical cure. A new CZA-susceptible and MEM-resistant KPC-Kp strain was subsequently isolated in 3 patients (27.3%). Meropenem/vaborbactam (MVB) showed high in-vitro activity, while FOS+MEM combination was synergistic in 40% of cases. In-vitro resistance to MEM was observed, with maintenance of CZA resistance.

DISCUSSION

Detection of KPC-variant may occur within the same patient, especially if CZA has been previously administered. Although clinical success has been obtained with carbapenems, the emergence of MEM resistance is a concern. Fosfomycin plus meropenem is synergistic and may represent a valuable combination option for KPC-variant, while MVB may be considered in monotherapy.

IMPORTANCE

The detection of KPC-variants in an endemic setting for KPC-Kp represents a worryingly emerging condition. The optimal therapeutic approach is still unknown and the development of meropenem resistance is a concern, which may finally lead to a therapeutic failure in the clinical practice. In these cases, the addition of fosfomycin to meropenem or a more potent antibiotic such as meropenem/vaborbactam may represent valuable therapeutic options.

Conformational Behavior of SARS-Cov-2 Spike Protein Variants: Evolutionary Jumps in Sequence Reverberate in Structural Dynamic Differences

SARS-CoV-2 has evolved rapidly in the first 3 years of pandemic diffusion. The initial evolution of the virus appeared to proceed through big jumps in sequence changes rather than through the stepwise accumulation of point mutations on already established variants. Here, we examine whether this nonlinear mutational process reverberates in variations of the conformational dynamics of the SARS-CoV-2 Spike protein (S-protein), the first point of contact between the virus and the human host. We run extensive microsecond-scale molecular dynamics simulations of seven distinct variants of the protein in their fully glycosylated state and set out to elucidate possible links between the mutational spectrum of the S-protein and the structural dynamics of the respective variant, at global and local levels. The results reveal that mutation-dependent structural and dynamic modulations mostly consist of increased coordinated motions in variants that acquire stability and in an increased internal flexibility in variants that are less stable. Importantly, a limited number of functionally important substructures (the receptor binding domain, in particular) share the same time of movements in all variants, indicating efficient preorganization for functional regions dedicated to host interactions. Our results support a model in which the internal dynamics of the S-proteins from different strains varies in a way that reflects the observed random and non-stepwise jumps in sequence evolution, while conserving the functionally oriented traits of conformational dynamics necessary to support productive interactions with host receptors.

Five waves of COVID-19 pandemic in Italy: results of a national survey evaluating the impact on activities related to arrhythmias, pacing, and electrophysiology promoted by AIAC (Italian Association of Arrhythmology and Cardiac Pacing)

BACKGROUND

The subsequent waves of the COVID-19 pandemic in Italy had a major impact on cardiac care.

METHODS

A survey to evaluate the dynamic changes in arrhythmia care during the first five waves of COVID-19 in Italy (first: March-May 2020; second: October 2020-January 2021; third: February-May 2021; fourth: June-October 2021; fifth: November 2021-February 2022) was launched.

RESULTS

A total of 127 physicians from arrhythmia centers (34% of Italian centers) took part in the survey. As compared to 2019, a reduction in 40% of elective pacemaker (PM), defibrillators (ICD), and cardiac resynchronization devices (CRT) implantations, with a 70% reduction for ablations, was reported during the first wave, with a progressive and gradual return to pre-pandemic volumes, generally during the third-fourth waves, slower for ablations. For emergency procedures (PM, ICD, CRT, and ablations), recovery from the initial 10% decline occurred in most cases during the second wave, with some variability. However, acute care for atrial fibrillation, electrical cardioversions, and evaluations for syncope showed a prolonged reduction of activity. The number of patients with devices which started remote monitoring increased by 40% during the first wave, but then the adoption of remote monitoring declined.

CONCLUSIONS

The dramatic and profound derangement in arrhythmia management that characterized the first wave of the COVID-19 pandemic was followed by a progressive return to the volume of activities of the pre-pandemic periods, even if with different temporal dynamics and some heterogeneity. Remote monitoring was largely implemented during the first wave, but full implementation is needed.

Oxo-Rhenium-Mediated Allylation of Furanoside Derivatives: A Computational Study on the Mechanism and the Stereoselectivity

Properly substituted tetrahydrofuran (THF) rings are important building blocks in the synthesis of many natural metabolites. Having reliable procedures to control the stereoselectivity at the THF core while decorating it with different substituents is a fundamental requirement to achieve and fulfill the complexity of nature. We recently reported a new chemical approach to control the stereochemistry in the alkylation and arylation of furanoside derivatives by using a rhenium(V) complex to form an intermediate oxo-carbenium species able to react with proper soft nucleophiles. Here, we describe theoretical calculations, performed at the DFT B3LYP level, to disclose the important mechanistic features which regulate the entire catalytic cycle of the reaction of mono- and disubstituted furanosides with allyltrimethylsilane catalyzed by Re(O)Cl₃(OPPh₃)(Me₂S). Moreover, the key factors governing the allylation step were investigated, confirming that the stereoselectivity, which is independent of the anomeric configuration of starting acetal, mainly arises from the orientation of the substituent at C-4, with only marginal contribution of the substituent at C-5. Finally, puckering Cremer–Pople parameters were used to take trace of the structural modifications throughout the catalytic cycle.

Highly Stereoselective Glycosylation Reactions of Furanoside Derivatives via Rhenium (V) Catalysis

A novel approach for the formation of anomeric carbon-functionalized furanoside systems was accomplished through the employment of an oxo-rhenium catalyst. The transformation boasts a broad range of nucleophiles including allylsilanes, enol ethers, and aromatics in addition to sulfur, nitrogen, and hydride donors, able to react with an oxocarbenium ion intermediate derived from furanosidic structures. The excellent stereoselectivities observed followed the Woerpel model, ultimately providing 1,3-cis-1,4-trans systems. In the case of electron-rich aromatic nucleophiles, an equilibration occurs at the anomeric center with the selective formation of 1,3-trans-1,4-cis systems. This anomalous result was rationalized through density functional theory calculations. Different oxocarbenium ions such as those derived from dihydroisobenzofuran, pyrrolidine, and oxazolidine heterocycles can also be used as a substrate for the oxo-Re-mediated allylation reaction.

An In-Depth Computational Study of Alkene Cyclopropanation Catalyzed by Fe(porphyrin)(OCH3) Complexes. The Environmental Effects on the Energy Barriers

Iron porphyrin methoxy complexes, of the general formula [Fe(porphyrin)(OCH₃)], are able to catalyze the reaction of diazo compounds with alkenes to give cyclopropane products with very high efficiency and selectivity. The overall mechanism of these reactions was thoroughly investigated with the aid of a computational approach based on density functional theory calculations. The energy profile for the processes catalyzed by the oxidized [Fe^III(Por)(OCH₃)] (Por = porphine) as well as the reduced [Fe^II(Por)(OCH₃)]^- forms of the iron porphyrin was determined. The main reaction step is the same in both of the cases, that is, the one leading to the terminal-carbene intermediate [Fe(Por)(OCH₃)(CHCO₂Et)] with simultaneous dinitrogen loss; however, the reduced species performs much better than the oxidized one. Contrarily to the iron(III) profile in which the carbene intermediate is directly obtained from the starting reactant complex, the favored iron(II) process is more intricate. The initially formed reactant adduct between [Fe^II(Por)(OCH₃)]^- and ethyl diazoacetate (EDA) is converted into a closer reactant adduct, which is in turn converted into the terminal iron porphyrin carbene [Fe(Por)(OCH₃)(CHCO₂Et)]^-. The two corresponding transition states are almost isoenergetic, thus raising the question of whether the rate-determining step corresponds to dinitrogen loss or to the previous structural and electronic rearrangement. The ethylene addition to the terminal carbene is a downhill process, which, on the open-shell singlet surface, presents a defined but probably short-living diradicaloid intermediate, though other spin-state surfaces do not show this intermediate allowing a direct access to the cyclopropane product. For the crucial stationary points, the more complex catalyst [Fe(2)(OCH₃)], in which a sterically hindered chiral bulk is mounted onto the porphyrin, was investigated. The corresponding computational data disclose the very significant effect of the porphyrin skeleton on the reaction energy profile. Though the geometrical features around the reactive core of the system remain unchanged, the energy barriers become much lower, thus revealing the profound effects that can be exerted by the three-dimensional organic scaffold surrounding the reaction site.

Overriding ortho selectivity by template assisted meta-C–H activation of benzophenones

A regioselective meta-C–H activation strategy for benzophenone was successfully developed by overriding the inherent ketone-directed ortho-selectivity.

Comparative effectiveness of novel oral anticoagulants for atrial fibrillation: evidence from pair-wise and warfarin-controlled network meta-analyses

INTRODUCTION

Novel oral anticoagulants have been tested against warfarin for atrial fibrillation, yet no direct comparison is available. We thus aimed to perform pair-wise (direct) and warfarin-adjusted network (i.e. indirect) meta-analyses of novel oral anticoagulants for atrial fibrillation.

METHODS

Databases were searched for randomized warfarin-controlled trials of novel anticoagulants for non-valvular atrial fibrillation. The primary end-point was long-term stroke/systemic embolism. Odds ratios (95% intervals) were computed with RevMan and WinBUGS.

RESULTS

Seven trials (52701 patients) were included, focusing on apixaban, dabigatran, edoxaban and rivaroxaban. Pair-wise meta-analysis showed that after a weighted average of 23 months these novel anticoagulants lead to significant reductions in the risk of stroke/systemic embolism (odds ratio=0.81 [0.71-0.92], I2=23%) and all cause death (odds ratio=0.88 [0.82-0.95], I2=0%) in comparison to warfarin. Network meta-analysis showed that apixaban and dabigatran proved similarly superior to warfarin in preventing stroke/systemic embolism (odds ratio=0.78 [0.62-0.96] for apixaban vs warfarin; odds ratio=0.66 [0.52-0.84] for high-dose dabigatran vs warfarin; odds ratio for apixaban vs high-dose dabigatran=1.17 [0.85-1.63]), but apixaban was associated with fewer major bleedings (odds ratio=0.73 [0.57-0.93]) and drug discontinuations (odds ratio=0.64 [0.52-0.78]) than dabigatran. Rivaroxaban did not reduce stroke/systemic embolism (odds ratio=0.87 [0.71-1.07]) or major bleedings in comparison to warfarin (odds ratio=0.87 [0.71-1.07]) and was associated with more major bleedings in comparison to apixaban (odds ratio=1.52 [1.19-1.92]). Data for edoxaban were inconclusive.

CONCLUSIONS

Novel oral anticoagulants appear as a very promising treatment option for atrial fibrillation.

Nucleoside triphosphate diphosphohydrolases role in the pathophysiology of cognitive impairment induced by seizure in early age

Studies have shown that seizures in young animals lead to later cognitive deficits. There is evidence that long-term potentiation (LTP) and long-term depression (LTD) might contribute to the neural basis for learning and memory mechanism and might be modulated by ATP and/or its dephosphorylated product adenosine produced by a cascade of cell-surface transmembrane enzymes, such as E-NTPDases (ecto-nucleoside triphosphate diphosphohydrolases) and ecto-5'-nucleotidase. Thus, we have investigated if hippocampal ecto-nucleotidase activities are altered at different time periods after one episode of seizure induced by kainic acid (KA) in 7 days old rats. We also have evaluated if 90 day-old rats previously submitted to seizure induced by KA at 7 days of age presented cognitive impairment in Y-maze behavior task. Our results have shown memory impairment of adult rats (Postnatal day 90) previously submitted to one single seizure episode in neonatal period (Postnatal day 7), which is accompanied by an increased ATP hydrolysis in hippocampal synaptosomes. The metabolism of ATP evaluated by HPLC confirmed that ATP hydrolysis was faster in adult rats treated with KA in neonatal period than in controls. Surprisingly, the mRNA and protein levels as seen by PCR and Western blot, respectively, were not altered by the KA administration in early age. Since we have found an augmented hydrolysis of ATP and this nucleotide seems to be important to LTP induction, we could assume that impairment of memory and learning observed in adult rats which have experienced a convulsive episode in postnatal period may be a consequence of the increased ATP hydrolysis. These findings correlate the purinergic signaling to the cognitive deficits induced by neonatal seizures and contribute to a better understanding about the mechanisms of seizure-induced memory dysfunction.

Hydroxystearic acid effects on CDC2/histone H1 kinase activity in C108 carcinoma cells

HSA at appropriate concentrations shows cytostatic and/or cytotoxic effects on murine Lewis carcinoma cell line C108. The cytostatic effect is mediated by an arrest in the cell cycle machinery, with accumulation of cells in G2-M. The combination of enzymatic assays, cell cycle kinetics studies and immunoprecipitation shows that HSA causes to a certainty an accumulation of cells in the M phase, while a similar effect in G2 has still to be demonstrated. It also inhibits histone H1 kinase activity up to 95% of that of mitotic cells, having as a direct or indirect target the cdc2 complex.

In vitro effects of hydroxystearic acid on the proliferation of HT29 and I407 cells

The in vitro effects of hydroxystearic acid on the proliferation of human colon carcinoma cells (HT29) and human embryonic intestine cells (I407) were examined and compared to previous results obtained in murine C108 lung carcinoma cells. The cells were cultured in the presence, or in the absence, of hydroxystearic acid and tested for cell proliferation and viability; the distribution of cells in the cell cycle was evaluated by flow cytometry. Results show that hydroxystearic acid is also an inhibitor of human cell proliferation, and not only of murine C108 cells. Differently from C108 cells, which upon treatment with hydroxystearic acid accumulate in G2-M phases, hydroxystearic acid-treated HT29 cells increase significantly in numbers in G0-G1; I407, embryonic cells used as a control, when treated show only a slight increase in G0-G1.

[Variations of blood flow in pulmonary veins caused by electric stimulation in total atrioventricular block]

It was suggested that Doppler study of pulmonary venous flow (PVF) in combination with mitral flow is useful to evaluate ventricular function. In order to investigate the utility of PVF study in patients with total A-V block treated with pacemaker DDD, we performed transesophageal echocardiography pulsed Doppler of PVF and mitral flow in 12 patients. We measured the following parameters in PVF: peak systolic velocities (S1 and S2), peak diastolic velocity (D) reversal atrial flow diastolic deceleration time. In mitral flow we measured: E wave, A wave and deceleration time of E. We compared our results with the same patients with pacemaker inhibited. In patients with total A-V block with pacemaker inhibited we reported one systolic wave of PVF, a larger D wave with a shortened deceleration time. The PVA seems to disappear. Transmitral flow slowed a higher E wave in patients A-V block with pacemaker inhibited. In patients with total A-V block stimulated by DDD pacemaker we restored the atrioventricular sequentialty; therefore electric stimulation determines the onset of S1 peak and the reduction of S2 peak and the systematic presence of the atrial-pulmonary regurgitant wave.

[Transesophageal echocardiography in the assessment of patients with atrial fibrillation and stroke]

Cardiac evaluation of stroke or transient ischemic attack (TIA) patients includes transthoracic and transesophageal echocardiography to identify potential cardiac source of embolism. In the present study transesophageal echocardiography was performed in 53 consecutive patients with non valvular atrial fibrillation and a previous embolic stroke. All patients were referred to our department because of an episode of atrial fibrillation. They all underwent computed tomography (CT) scan: 31 patients had a positive scan whereas 22 had a negative scan with a positive history of TIA diagnosed from a neurologist during hospitalization. In the group of 31 patients with a positive scan 9 patients with no history of a previous ischemic attack were found. The transesophageal echocardiography was performed in all the study subjects: 7 patients had a thrombus in the left atrial appendage, 2 patients had a thrombus in the right atrium. Spontaneous echo contrast was reported in 15 patients. Evaluating the interatrial septum we observed a patent foramen ovale in 4 patients, a defect in 2 patients and a fossa ovalis aneurysm in 3 patients. The mitral valve analysis showed a leaflet prolapse in 3 patients. The entire thoracic aorta was imaged in each patient: in 12 an abnormal atherosclerotic plaque was found. Transesophageal echocardiography is an important component of the comprehensive evaluation of potential sources of embolism in patients with ischemic cerebral attack and nonrheumatic atrial fibrillation.

Symptomatic achievements with diuretics in congestive heart failure

The short-term clinical efficacies of furosemide, 25 mg/day, and torasemide, 10 mg/day, have been compared in 2 groups of 12 patients with severe heart failure. In each group there were similar numbers of patients in whom heart failure was due to coronary heart disease, high blood pressure, or idiopathic dilated cardiac myopathy. The design of the study was open and the diuretics were added to baseline treatment with digoxin. Treatment for 8 days with the 2 loop diuretics resulted in similar substantial and significant improvements in symptoms and exercise tolerance as judged by the increase in total body oxygen consumption, and reductions in radiographic evidence of pulmonary congestion and in right heart filling pressure as judged from the jugular venous pressure wave. The results of this short-term comparative study confirm that furosemide and torasemide are equally efficacious in inducing substantial improvements in the clinical status of patients in severe heart failure.

[Effects of left bundle branch block on pulmonary vein and transmitral flow]

Doppler evaluation of pulmonary venous flow (PVF) and of mitral flow (MF) can be useful to understand left ventricular function. It is well known that left bundle branch block (LBBB) can influence ventricular function. The aim of the present study was to evaluate the role of LBBB induced by ventricular pacing on cardiac performance. We performed transesophageal echocardiography (TEE) in 10 patients affected by sick sinus syndrome (SSS) treated with a permanent pacemaker (VDD modality). We evaluated PVF and MF and compared the pattern from the same patients in sinus rhythm and during cardiac pacing. We observed an increase in the reversal flow in the pulmonary vein during atrial contraction. The diastolic flow of pulmonary vein increased during cardiac pacing. The MF showed an increase in deceleration time. Our results suggest that LBBB is associated with a reduction in ventricular function. This phenomenon induce a higher contribution of atrial contraction to ventricular function.

Influence of hydroxystearic acid on in vitro cell proliferation

Lipid peroxidation products have recently been proposed among the possible regulators of tumour cell growth. According to our current working hypothesis, the greatly diminished content of such products in tumour cells might relieve the inhibition of cell growth thus leading to uncontrolled proliferation. Hydroperoxy- and hydroxy derivatives of long chain fatty acids have been identified and determined in normal and tumour cells. Among these, hydroxystearic acid (HSA) has been shown to have a different cytostatic and cytotoxic effect when administered to murine lung carcinoma cells or to human colon tumour cells. It interferes with cell cycle kinetics, blocking the murine cells in G2-M and the human ones in G0-G1. The molecular target of HSA in both cell lines has been shown to be the cdc2 kinase complex. The results so far obtained in tumour as long as in normal highly proliferating cells do not exclude a potential future use of this class of compounds as selective anti tumour drugs.

Identification of the peroxidation product hydroxystearic acid in Lewis lung carcinoma cells

Whole cell lipids were extracted from the Lewis lung carcinoma in vitro line C108. The fatty acids were derivatized to methylesters in order to identify endogenous oxidized derivatives by gasmass spectroscopy. The presence of 9-hydroxystearic acid and 10-hydroxystearic acid was thus evidenced for the first time in cultured mammalian cells. Moreover a linear correlation was found between the concentration of these products expressed as percentage of total fatty acid methylesters and the cell density in tissue culture flasks. This finding suggests an involvement of hydroxystearic acid in cellular functions related to the cell density in monolayer cultures.

Oxy-radical metabolism and control of tumour growth

1. The content of oxy-radical scavenging enzymes is decreased in Morris hepatomas in a fashion which is inversely related with the growth rate of the tumour. 2. Hepatoma microsomal membranes are more resistant than normal rat liver membranes to lipid peroxidation induced in vitro by organic hydroperoxides or superoxide radicals. 3. In tumour membranes the most relevant rate-limiting factor of peroxidation is the low availability of polyunsaturated fatty acids (PUFA). Besides lipids, some proteins (particularly cytochrome P-450) act as controlling factors of peroxidation. 4. Tumour microsomes are more ordered and less fluid than liver microsomes. The latter, exposed to superoxide radical attack, exhibit chemical (fatty acid composition) and physical (molecular order) properties that are similar to those of transformed cell membranes. 5. These data indicate an aberration in the oxy-radical metabolism of cancer cells, and a sequence of events is hypothesized that could drive the transformed cell towards uncontrolled proliferation.

Fluorescence investigation of the sex steroid binding protein of rabbit serum: steroid binding and subunit dissociation

The relationship between steroid binding and protein subunit interactions of rabbit sex steroid binding protein (rSBP) has been studied by steady-state and time-resolved fluorescence spectroscopy. The high-affinity (Ka approximately 10(8) M-1 at 4 degrees C), fluorescent estrogen d-1,3,5(10),6,8-estrapentaene-3,17 beta-diol [dihydroequilenin (DHE)] was used as a fluorescent probe of the steroid-binding site. Perturbation of the binding site with guanidinium chloride (Gdm.Cl) was monitored by changes in the steady-state fluorescence anisotropy of DHE as well as by changes in fluorescence quenching of DHE with acrylamide. The results of acrylamide quenching at 11 degrees C show that, while between 0 and 1 M Gdm.Cl the steroid-binding site is completely shielded from bulk solvent, there is decreased DHE binding. To study the subunit-subunit interactions, rSBP was covalently labeled with dansyl chloride in the presence of saturating 5 alpha-dihydrotestosterone (DHT), which yielded a dansyl-conjugated protein that retained full steroid-binding activity. The protein subunit perturbation was monitored by changes in the steady-state fluorescence anisotropy of the dansyl group. At 11 degrees C, the dansyl anisotropy perturbation, reflecting changes in global and segmental motions of the dimer protein, occurs at concentrations of Gdm.Cl above 1 M. The Gdm.Cl titration in the presence of steroids with equilibrium association constants less than 10(8) M-1 shows a plateau near 3 M Gdm.Cl at 11 degrees C; at this Gdm.Cl concentration, no DHE is bound. No plateau is observed at 21 degrees C. At higher Gdm.Cl concentrations, the dansyl fluorescence anisotropy decreases further and shows no steroid dependence. Recovery of steroid-binding activity (assayed by saturation binding with [3H]DHT), under renaturation conditions, is dependent on both steroid concentration and affinity. Both unlabeled and dansyl-labeled protein recovery the same amount of activity, and according to fluorescence anisotropy, dansyl-labeled rSBP re-forms a dimer upon dilution below 1 M or removal of Gdm.Cl. From the steroid requirement for recovery of steroid-binding activity, it appears that a conformational template is required for the dimeric protein to re-form a steroid-binding site with native-like properties.

[A study of the nurses quitting Legnano Hospital USSL 70]

Reasons why nurses left a general Hospital were analyzed through a questionnaire sent to all nurses who abandoned their position over the last 5 years (218). 50.6% of these nurses do not live in Lombardy region. 127 (57.7%) answered the questionnaire. 35% of whom answered the questionnaire would get back to work in the hospital. The main reason for hospital leave is related to family reasons (children and parents) for registered nurses and to shift work state enrolled nurses. Low salary is the main problem for 21-30 years old nurses. According to nurses who answered the questionnaire, more efficient recruitment and retention strategies should include higher salaries, riqualification of the profession in general and improvement of working conditions and organization.

Lipid peroxidation and physical properties of smooth and rough hepatoma microsomes

Smooth and rough endoplasmic reticulum of two Morris hepatomas, the slow growing 9618A and the fast growing 3924A, have been isolated, and their biochemical composition, supramolecular organization, and response to the action of peroxidative agents have been studied. Cytochrome P450 content and lipid availability are the limiting factors of their peroxidizability. The hemoprotein content is reduced about 80% in hepatoma 9618A and is virtually absent in hepatoma 3924A. The peroxidizability decreases with increasing growth rate of the tumor. The protein, phospholipid, and cholesterol content, the fatty acid composition as well as the double bond index, and the saturated and unsaturated fatty acid content are reported. Differences have been found between normal liver and tumors and between the fractions within a given tumoral tissue. The molecular order, as determined by fluorescence anisotrophy decay of DPH, increases in total microsomes and in the smooth fraction going from liver 9618A to 3924A, whereas for the rough fraction it is the same in liver and hepatoma 9618A; in 3924A it increases of about 30%. Fluidity decreases in total microsomes going from liver to 3924A, to 9618A. In both the purified fractions it decreases with increasing deviation of the tumor.

Lipid peroxidation in cancer cells: chemical and physical studies

Our studies on the biochemical composition and the structural organization of smooth and rough endoplasmic reticulum isolated from Morris hepatomas 9618A and 3924A confirm the results obtained employing the total microsomal fraction. We have definitely established the following facts: (1) Tumor subcellular organelles exhibit the very low degree of peroxidizability that has been shown to be related to the growth rate of the tumor. (2) Associated with such a low susceptibility to peroxidation are (a) changed lipid composition of cellular membranes, whose content in polyunsaturated fatty acid is markedly decreased, and (b) changed static and dynamic properties of the membrane. Previously it was also found that cellular oxy-radical scavenging enzymes are markedly reduced. From these data, it is possible to infer that tumor membranes are altered structurally and functionally in part as the result of an oxy-radical-induced damage that occurs in vivo under conditions of oxygen toxicity. This seems to be supported by recent findings that the spontaneous increase in growth rate of the originally very slow-growing Morris hepatoma 9618A results also in the loss of cytochrome P-450 (an important intramembraneous propagator of lipid peroxidation) as well as of C20:4 and C22:6. Studies performed by GLC and GC-MS on the fatty acid residues of phospholipids of rat liver microsomes show the presence of C20:3-OH and C18:1-OH, but no hydroxyl derivatives of low molecular weight aldehydes. The hydroxyl derivatives of arachidonic acid and linoleic acid are present in much smaller amounts in the microsomes isolated from H9618A and H3924A.

Lipid peroxidation in tumour cells

Several studies point to the existence of a disturbance in the metabolism of the reactive species of oxygen in cancer cells. Based on this evidence, and in particular on a characteristic behaviour of tumour membrane lipids, namely their growth-related resistance to oxy-radical-induced peroxidation, a sequence of events is outlined that could hypothetically drive the transformed cell to an uncontrolled proliferation. The proposed scheme is also conceived as a framework for further in vivo investigations of the complex biological phenomena of tumour cell growth and invasion in more integrated and kinetically controlled cellular systems.

Tryptophan interactions of gramicidin A' channels in lipids: a time-resolved fluorescence study

The evolution of the incorporation of cation transport channels into lysolecithin micelles by gramicidin A was followed by measuring the ns time-resolved fluorescence of the tryptophan residues. In all samples, the tryptophan fluorescence could be resolved into three exponentially decaying components. The three decay times ranged from 6 to 8 ns, 1.8 to 3 ns, and 0.3 to 0.8 ns, depending on the emission wavelength. The fractional fluorescence of each component changed with incubation time. The long lifetime component had a reduced contribution to the total fluorescence while the short decay time component increased. The fluorescence spectra could be resolved into three distinct fluorescent components having maxima at 340 nm, 330 nm and 323 nm after 90 min of incubation, and 335 nm, 325 nm and 320 nm after 24 h of incubation. These maxima were, respectively, associated with the long, medium and short decay components. The fluorescence decay behaviour was interpreted as representing three families of tryptophans, the short lifetime component being due to a stacking interaction between tryptophan residues. The variation with incubation time suggests a two-step process in the channel-lipid organization. The first is associated with the conformational change of the polypeptide as it takes up a left-handed helical head-to-head dimer structure in the lipid. The second step is proposed to involve changes originating from membrane assembly and intermolecular interactions between channels as they form hexameric clusters.

O2-dependent lipid peroxidation does not affect the molecular order in hepatoma microsomes

Microsomal membranes from rat liver and from the fast-growing Morris hepatoma 3942A have been peroxidized to different extents and the order parameter of the membranes measured by fluorescence depolarization of the probe 1,6-diphenyl-1,3,5-hexatriene. The data have been analysed by applying a mathematical approach that takes into account simultaneously static and dynamic fluorescence parameters. It appears that tumour membranes are more ordered than the control and their order parameter does not increase with greater exposure to the action of O2 radicals in contrast to liver membranes. The fatty acid composition of the membrane lipids has been studied under different experimental conditions and correlated to the behaviour of the physical parameter.

Isolation and enzymatic characterization of the plasmalemma from bovine spermatozoa

An improved method for the isolation of pure plasma and acrosomal membranes from bull spermatozoa is presented. Plasma membranes were isolated from the spermatozoa of bulls of different breeds, and some enzymatic activity, such as (Na+-K+) ATPase, Ca++ ATPase, Mg++ ATPase, alkaline and acidic phosphatases were assayed. Such enzymatic activity levels differ noticeably from those published by other authors, whose preparations were probably contaminated by other cellular components. Highly statistically significant differences of these activities have been found among the several breeds.

Interactions of ubiquinones with membrane models

The effect of the insertion of coenzyme Q10 and some of its shorter chain homologues in membrane models (Reverse Micelles, Small Unilamellar Vesicles and Liposomes) has been studied by NMR and IR spectroscopies. By 1H-NMR we have found that the stretched conformation of the isoprenoid side-chain observed in solution is maintained in membrane models. Interaction between the quinonoid moiety of the Q's and the phosphatidic groups of the phospholipids has been evidenced by 31P-NMR. A large effect of this interaction on the water microdynamics and distribution around the charged groups of the phospholipids has been observed by measurements of 1H and 2H relaxation times and by infrared spectra. The 13C-NMR spectra of the backbone of the acyl chains of phospholipids does not seem to be influenced to a noticeable extent by the presence of the Q's.

Supramolecular organization of lysophosphatidylcholine-packaged Gramicidin A

Heat derived gramicidin A'/L-alpha-lysophosphatidylcholine complexes were separated on a sucrose gradient to form two fractions: Fraction A which had an approximately constant Gramicidin A' to phospholipid ratio of 8 to 10 lipid molecules per Gramicidin A' molecule and Fraction B which had a larger but variable ratio. Fluorescence and circular dichroism studies confirmed Fraction A to be a lipid-incorporated channel state. Electron microscopic studies, using uranyl acetate negative staining, showed fraction A to be a membranous state with the formation of bilayer vesicles, that is, the interaction of peptide and phospholipid micelles causes the lipid to reorganize into a bilayer structure. Freeze-fracture replicas of the channel incorporated state demonstrated the presence of a supramolecular organization of particles exhibiting a tendency to form rows with a 50-60 A periodicity along the row and with 70-80 A distance between rows. An idealized working model for the incorporated state is presented.

Gramicidin A induces lysolecithin to form bilayers

Heat-induced association of Gramicidin A with lysolecithin micelles results in the formation of lipid bilayer structures. The capacity of the Gramicidin A peptide to transform the lysolecithin lipid structure from micelle to bilayer is considered in terms of molecular packing mechanisms and relevance to membrane processes in general. The resulting lipid-bilayer-packaged channel system has particular usefulness in characterizing channel structure and mechanism.

Intermolecular interactions of gramicidin A' transmembrane channels incorporated into lysophosphatidylcholine lipid systems

Fluorescence studies are reported on gramicidin A' incorporated into lysophosphatidylcholine phospholipid structures. The shift in the emission maximum during incorporation and the quenching of fluorescence by I- and by acrylamide of the incorporated state obtained after prolonged heating are consistent with the presence of the channel state comprised of two single-stranded beta 6 -helices associated head-to-head (formyl end-to-formyl end). The quantum yield for the incorporated state, when gramicidin A' is within the lipid matrix, is very low and indicates the occurrence of intermolecular Trp-Trp interactions. Possible interactions between channels within the lipid matrix are discussed utilizing Trp-Trp contacts.

Ubiquinones: stereochemistry and biological implications

Proton NMR and 13C-NMR studies on the configuration of CoQn homologues show that the polyisoprenoid side-chain is in the all-trans configuration and confers a higher degree of rigidity to the quinones with respect to the acyl-chains of the phospholipids within the membrane bilayer. The quinonoid ring appears to be specifically involved in the redox function of the coenzyme while the side-chain length only affects the lipophilicity of the molecule. LIS data show that the ring strongly interacts with metals as a consequence of the high pi-electron density on the carbonyls that is somewhat larger on the carbonyl oxygen to alpha to the isoprenoid chain.