In vivo toxicity evaluation of a polyoxotungstate nanocluster as a promising contrast agent for computed tomography

In this study, we demonstrate for the first time, that a discrete metal-oxo cluster α-/β-K₆P₂W₁₈O₆₂ (WD-POM) exhibits superior performance as a computed tomography (CT) contrast agent, in comparison to the standard contrast agent iohexol. A toxicity evaluation of WD-POM was performed according to standard toxicological protocols using Wistar albino rats. The maximum tolerable dose (MTD) of 2000 mg/kg was initially determined after oral WD-POM application. The acute intravenous toxicity of single WD-POM doses (1/3, 1/5, and 1/10 MTD), which are at least fifty times higher than the typically used dose (0.015 mmol W kg^-1) of tungsten-based contrast agents, was evaluated for 14 days. The results of arterial blood gas analysis, CO-oximetry status, electrolyte and lactate levels for 1/10 MTD group (80% survival rate) indicated the mixed respiratory and metabolic acidosis. The highest deposition of WD-POM (0.6 ppm tungsten) was found in the kidney, followed by liver (0.15 ppm tungsten), for which the histological analysis revealed morphological irregularities, although the renal function parameters (creatinine and BUN levels) were within the physiological range. This study is the first and important step in evaluating side effects of polyoxometalate nanoclusters, which in recent years have shown a large potential as therapeutics and contrast agents.

Measuring pharmacovigilance knowledge and attitudes among healthcare sciences students: development and validation of a universal questionnaire

OBJECTIVE

Pharmacovigilance education and reporting of adverse drug reactions (ADRs) are important competencies that healthcare sciences students should develop before completing their studies and entering clinical practice. Since students frequently lack adequate knowledge in this area and fail to recognize the importance of ADRs monitoring and reporting, the aim of this study was to develop and validate a unique and reliable instrument for assessing health sciences students' knowledge and attitudes toward pharmacovigilance and ADRs reporting.

SUBJECTS AND METHODS

A cross-sectional observational study was conducted from February to July 2021 to examine students' knowledge and attitudes toward pharmacovigilance activities. Students of medicine, dentistry, pharmacy, and nursing science of three faculties in the Autonomous Province of Vojvodina, Serbia were examined. A total of 211 of them completed the specially designed, three-section questionnaire (Demographic data section, Pharmacovigilance Knowledge test, PVKT, and Pharmacovigilance Attitude Questionnaire, PVAQ). The questionnaire was posted on the Google Forms platform, and the link was distributed to respondents via the official websites and social networks of all three faculties.

RESULTS

Findings demonstrated good psychometric properties and reliability of the questionnaire. Six questions were removed from the PVKT after item analyses. After excluding these items, the calculated ordinal alpha of the final version of the PVKT, which included 14 items, was good (αord = 0.83), as were other statistical indicators. PVAQ reliability testing also revealed great performance of this questionnaire-calculated ordinal alpha for two PVAQ subscales was excellent (αord = 0.91, for both scales).

CONCLUSIONS

This questionnaire has favorable validity and reliability in assessing healthcare sciences students' knowledge and attitudes toward pharmacovigilance and ADRs reporting.

COVID-19 associated pulmonary embolism with D-dimer values within the referent range: a case report and review of the literature

OBJECTIVE

COVID-19 is associated with an increased incidence of pulmonary embolism (PE). Elevated D-dimer levels are linked to an increased risk of PE and poor clinical outcome. We reported a case of PE in a COVID-19 patient with normal D-dimer levels and conducted a review of the literature on the subject.

CASE REPORT

A 38-year-old man with no prior comorbidities returned to the COVID-19 outpatient clinic 36 hours after being discharged from the hospital, where he had been treated for COVID-19 pneumonia. He reported a sudden feeling of dyspnea and chest pain. The physical examination was unremarkable. No new changes were detected on the chest X-ray. D-dimer and cardiac-specific markers values were within the referent range. The patient underwent an urgent computerized tomography pulmonary angiography which revealed signs of bilateral arterial thrombosis. He was treated with a therapeutic dose of low molecular weight heparin and discharged after 15 days, with a recommendation to use a direct oral anticoagulant.

CONCLUSIONS

Healthcare professionals should be aware that PE can occur as a late complication of COVID-19. Clinical suspicion of PE should lead physicians to use additional diagnostic methods to confirm or rule out PE, even if D-dimer levels are within the referent range.

[Early results in the surgical treatment of Crawford type IV thoracoabdominal aneurysms]

OBJECTIVE

The aim of the study was to present the outcome of surgical treatment of patients with thoracoabdominal aortic aneurysm Crawford type IV, operated on between January 2001 and April 2004.

METHODS

This study included 42 subsequent patients (40 males, 2 females, age 41-76 years). All patients underwent ultrasonography, angiography, computed tomography or magnetic resonance imaging (MRI). Surgical treatment was performed under combined anaesthesia (continuous thoracic epidural analgesia and general endotracheal anaesthesia). In two patients thoracophrenolumbotomy was performed at the level of X rib, while others were operated through left lumbotomy after the extra pleural resection of XI rib. We did not perform any spinal cord protection procedures in this type of aneurysm. Reconstruction included interposition of Dacron graft in 20 patients, aortobiiliac bypass in 18, and aortobifemoral bypass in 4 patients with different varieties of visceral branches reimplantation.

RESULTS

Thirty-days mortality was 31% (13 patients, two of them intraoperatively). Causes of death were: pulmonary embolism--in 1 patient; haemorrhage--in 2; myocardial infarction--in 4 (two intraoperative); acute renal failure--in 2; multisystem organ failure (MSOF)--in 4 patients. Respiratory failure dominated in all cases of MSOF. One patient with acute renal failure had paraplegia also, and that was the only case of neurological complication in whole group. All female patients (2), all patients with ruptured aneurysm (4), acute myocardial infarction (4) and acute renal failure (2) have died. Advanced age (over 70 years) and the need for extensive operative procedure with bifurcated graft use significantly influenced their mortality (p < 0.01 and p < 0.05 respectively).

CONCLUSIONS

Surgical treatment of thoracoabdominal aortic aneurysm Crawford IV type was successful in 69% of our patients. There was no need for spinal cord protection measures, and extra peritoneal approach with XI rib resection under the combined anaesthesia was preferred.

[Acute transfusion-related lung injury]

Transfusion Related Acute Lung Injury (TRALI) is the most serious, potentially lethal, transfusion reaction caused by anti leukocyte antibodies carried passively into recipient's circulation by transfused haemoproduct. It is manifested most frequently within first four hours after transfusion of allogenous haemoproduct containing anti leukocyte antibodies. It is characterized with symptoms and signs of acute respiratory distress syndrome. This rare, but severe transfusion reaction with mortality rate of around 10% is often misdiagnosed, since TRALI signs are assigned to other clinical conditions. Thus, an education for timely recognition and urgent care of TRALI should be initiated.

[Acute hemolytic transfusion reaction]

Alloogenous blood and/or corresponding haemoproduct transfusion is an efficient and relatively safe supportive treatment. Despite the fact that pre transfusion investigation of both patients and donors ensure high degree of safety of this type of treatment, occurrence of adverse haemotherapy effects is possible and often unpredictable. Acute haemolytic transfusion reaction occur as a consequence of immune conflict between red blood cell membrane agents and specific antibodies present in plasma. Since it is impossible to completely avoid the occurrence of transfusion reactions, wherein acute transfusion haemolytic reaction present a serious, possibly life threatening complication, it is an imperative to continue to improve the knowledge on pathogenesis mechanisms leading to complications associated with these reaction and to define the most efficient therapeutical modalities.

Electrophysiological characterization of "giant" cells in stratum radiatum of the CA3 hippocampal region

Whole cell patch-clamp recording and intracellular staining with biocytin allowed the morphological and electrophysiological characterization of "giant" cells, studied in stratum (st.) radiatum of the CA3 region in 17- to 21-day-old rat hippocampal slices. These neurons had extensive dendritic arborization, a triangular soma, and a bipolar vertical orientation with axons directed to the pyramidal layer or extended into the st. oriens. Giant cells had significantly higher input resistance and shorter action potentials compared with CA3 pyramidal cells. Evoked action potentials were typically followed by an afterdepolarizing potential (ADP). During depolarizing current injection, most (80%) of recorded giant cells displayed a regular firing pattern (maximum steady-state firing rate, approximately 30 Hz) characterized by a modest early accommodation, whereas irregular firing was observed in the remaining 20% of giant cells. Hyperpolarizing current pulses induced a slow inward rectification of the electrotonic voltage responses, blocked by 2 mM external Cs(+). N-methyl-D-aspartate (NMDA) and non-NMDA-mediated excitatory postsynaptic currents (EPSCs) measured under voltage clamp were distinguished on the basis of their voltage dependence and sensitivity to specific NMDA and non-NMDA glutamate receptor blockers. Non-NMDA EPSCs possessed a linear current-voltage relationship. EPSCs elicited by st. lucidum stimulation were reversibly reduced (mean, 23%) by the group II metabotropic glutamate receptor agonist (2S, 1'R, 2'R, 3'R)-2-(2,3-dicarboxyl-cyclopropyl)-glycine (DCG-IV, 1 microM). GABA(A)-mediated postsynaptic currents were subject to paired-pulse depression that was inhibited by the GABA(B) antagonist CGP 55845A (5 microM). We conclude that CA3 giant cells represent a particular class of hippocampal neuron located in st. radiatum that shares only some morphological and physiological properties with principal cells.

Medium afterhyperpolarization and firing pattern modulation in interneurons of stratum radiatum in the CA3 hippocampal region

Stratum (st.) radiatum interneurons represent a heterogeneous class of hippocampal cells with as yet poorly characterized physiological properties. Intracellular staining with biocytin, in situ hybridization, and patch-clamp recording have been combined to investigate the morphological and electrophysiological properties of these cells in the CA3 hippocampal region in young rats [postnatal days 10 to 21 (P10-21)]. Labeled cells presented a heterogeneous morphology with various soma shapes, often found multipolar, and dendritic arborizations confined to st. radiatum. The passive membrane properties of these st. radiatum interneurons showed instead no significant differences between P10 and P21. Low resting potential, high-input resistance, and short time constants characterized CA3 st. radiatum interneurons, which were silent at rest. Action potentials, elicited by brief current pulses, were lower and shorter than in pyramidal cells and followed by a Ca(2+)-dependent medium-duration afterhyperpolarizing potential (mAHP). Prolonged depolarizing current injection generated trains of action potentials that fired at constant frequency after a slight accommodation. The maximum steady-state firing rate was 31 +/- 4 (SD) Hz. Hyperpolarizing current pulses revealed a prominent inward rectification characterized by a "sag," followed by a depolarizing rebound that triggered action potentials. Sag and anodal brake excitation were blocked by Cs(+), suggesting that they were mediated by a hyperpolarization-activated cation conductance (I(h)). In the presence of tetrodotoxin and tetraethylammonium, biphasic tail currents were elicited in voltage clamp after a depolarizing step inducing Ca(2+) influx. Tail currents presented a fast Ca(2+)-activated and apamin-sensitive component (I(AHP)) and were further reduced by carbachol. The presence of I(AHP) was consistent with the high expression level of the apamin-sensitive SK2 subunit transcript in CA3 st. radiatum interneurons as detected by in situ hybridization. Different pharmacological agents were shown to affect the afterhyperpolarizing potential as well as the firing properties of st. radiatum interneurons. Exposure to Ca(2+)-free solutions mainly affected the late phase of repolarization and strongly reduced the mAHP. The mAHP was also attenuated by carbachol and by apamin, suggesting it to be partly mediated by I(AHP). Reduction of the mAHP increased the interneuron firing frequency. In conclusion, st. radiatum interneurons of CA3 hippocampal region represent a class of nonpyramidal cells with action potentials followed by an AHP of relatively short duration, partially generated by apamin and carbachol-sensitive conductances involved in the regulation of the cell firing rate.

Intracellular calcium stores modulate miniature GABA-mediated synaptic currents in neonatal rat hippocampal neurons

The whole-cell configuration of the patch clamp technique was used to record miniature gamma-aminobutyric acidA (GABAA) receptor-mediated currents (in tetrodotoxin, 1 microM and kynurenic acid 1 mM) from CA3 pyramidal cells in thin hippocampal slices obtained from postnatal (P) day (P6-9) old rats. Switching from a Ca2+-containing to a nominally Ca2+-free medium (in which Ca2+ was substituted with Mg2+, in the presence or in the absence of 100 microM EGTA) did not change significantly the frequency or amplitude of miniature events. Superfusion of thapsigargin induced a concentration-dependent increase in frequency but not in amplitude of tetrodotoxin-resistant currents that lasted for the entire period of drug application. Mean frequency ratio (thapsigargin 10 microM over control) was 1.8+/-0.5, (n = 9). In nominally Ca2+-free solutions thapsigargin was ineffective. When bath applied, caffeine (10 mM), reversibly reduced the amplitude of miniature postsynaptic currents whereas, if applied by brief pressure pulses, it produced an increase in frequency but not in amplitude of spontaneous GABAergic currents. Superfusion of caffeine (10 mM) reversibly reduced the amplitude of the current induced by GABA (100 microM) indicating a clear postsynaptic effect on GABAA receptor. Superfusion of ryanodine (30 microM), in the majority of the cells (n = 7) did not significantly modify the amplitude or frequency of miniature events. In two of nine cells it induced a transient increase in frequency of miniature postsynaptic currents. These results indicate that in neonatal hippocampal neurons, mobilization of calcium from caffeine-ryanodine-sensitive stores facilitates GABA release.

Facilitation of miniature GABAergic currents by ruthenium red in neonatal rat hippocampal neurons

The whole cell configuration of the patch-clamp technique was used to study the modulation gamma-aminobutyric acid (GABA)-mediated postsynaptic currents by ruthenium red in CA3 hippocampal neurons in slices obtained from postnatal (P) days P6-P10 old rats. In the presence of kynurenic acid (1 mM), ruthenium red (100 microM) completely blocked stimulus-elicited GABA-mediated postsynaptic currents and reduced by 50% the amplitude of the spontaneous ones. Ruthenium red (100 microM) increased the frequency but not the amplitude of miniature GABAergic currents recorded in the presence of tetrodotoxin (1 microM) and kynurenic acid (1 mM), an effect that was prevented by heparin (100 microM). Ruthenium red did not modify the kinetics of miniature postsynaptic currents and the currents induced by exogenous application of GABA (10 microM) in the presence of tetrodotoxin, suggesting that its action was presynaptic in origin. The effects of ruthenium red on quantal GABA release was independent of external calcium. In a nominally Ca2+-free solution the potentiating effect induced by this polyvalent cation on miniature postsynaptic currents was still present. Intracellular calcium stores were not involved in ruthenium red action, because this polyvalent cation was able to facilitate miniature currents also in the presence of thapsigargin (10-20 microM). These results indicate that ruthenium red has a dual action on GABA release from GABAergic interneurons: it reduces the amplitude of spontaneous events and increases the frequency of miniature currents. The former effect is calcium-dependent, whereas the latter is calcium independent.