Variability in the measurement of hERG potassium channel inhibition: effects of temperature and stimulus pattern

INTRODUCTION: In vitro evaluation of drug effects on hERG K(+) channels is a valuable tool for identifying potential proarrhythmic side effects in drug safety testing. Patch-clamp recording of hERG K(+) current in mammalian cells can accurately evaluate drug effects, but the methodology has not been standardized, and results vary widely. Our objective was to evaluate two potential sources of variability: the temperature at which recordings are performed and the voltage pulse protocol used to activate hERG K(+) channels expressed in HEK293 cells. METHODS: A panel of 15 drugs that spanned a broad range of potency for hERG inhibition and pharmacological class was evaluated at both room and near-physiological temperatures using several patch-clamp voltage protocols. Concentration-response analysis was performed with three stimulus protocols: 0.5- and 2-s step pulses, or a step-ramp pattern. RESULTS: Block by 2 of the 15 drugs tested, d,l-sotalol (antiarrhythmic) and erythromycin (antibiotic), was markedly temperature sensitive. hERG inhibition measured using a 2-s step-pulse protocol underestimated erythromycin potency compared with results obtained with a step-ramp protocol. Using conservative acceptance criteria and the step-ramp protocol, the IC(50) values for hERG block differed by less than twofold for 15 drugs. DISCUSSION: Data obtained at near-physiological temperatures using a step-ramp pattern are highly repeatable and provide a conservative safety evaluation of hERG inhibition.     

Proton magnetic resonance spectroscopy: normal findings in the cerebellar hemisphere in childhood

BACKGROUND: The cerebellar hemispheres (CER) are different from the supratentorial white and gray matter embryologically, in cytoarchitecture, and probably in metabolic activity. Proton magnetic resonance spectroscopy ((1)H MRS) can provide a noninvasive biochemical analysis of this region. OBJECTIVE: To study, with (1)H MRS, metabolite concentrations in CER as a function of age and compare these metabolic data with those of parietoccipital white matter (PO WM) in healthy children. MATERIALS AND METHODS: Using single-voxel (1)H MRS, we studied 37 volunteers (3-18 years) with normal MRI scans of the brain. (1)H MRS was performed using the PRESS technique in CER and PO WM. The NAA/Cr, Cho/Cr, NAA/H(2)O, Cr/H(2)O, and Cho/H(2)O ratios were analyzed as a function of age. Metabolic data from these regions were compared. RESULTS: The NAA/Cr ratio tended to increase with age in CER. Mean NAA/Cr and Cho/Cr ratios were found to be lower in CER than in PO WM. Mean NAA/H(2)O, Cr/H(2)O, and Cho/H(2)O ratios in CER were higher than in the PO WM. CONCLUSION: Our data confirm the regional variations between CER and PO WM metabolite ratios, and demonstrate a tendency of age-dependent change of the NAA/Cr ratio in CER. The creatine concentration was significantly higher in the cerebellum than in the PO WM.     

Cerebral venous sinus thrombosis in a neonate due to factor V Leiden deficiency

A case is described of cerebral venous sinus thrombosis due to factor V Leiden deficiency that occurred in the neonatal period, presenting with seizures. Diagnosis was based on ultrasonography, Doppler ultrasound (US) and magnetic resonance imaging (MRI). The aetiology was only recognized after blood-clotting tests, antithrombin III, C and S protein levels and factor V Leiden were studied. This situation was treated with intravenous heparin controlled by activated partial thromboplastin time (APTT). MRI angiography and Doppler US were important in the follow-up. It is important to assess periodically the neurological development of the baby and to prevent situations such as dehydration or severe infection, which can precipitate further thrombotic events. Molecular genetics allowed the identification of this trait in other family members. CONCLUSION: In every newborn with a thrombotic episode, coagulation studies must be performed, including testing for activated protein C (APC) resistance. Doppler US flow measurement and the MRI studies provide the best tools for diagnosis and follow-up. Heparin should be given to double the initial individual APTT. It is important to prevent any risk situation such as dehydration or severe infection, which could lead to a recurrence of a thrombotic episode. Regular assessment of the child's neurodevelopment is an important aspect of further care.     

Neuropsychological performance and regional cerebral blood flow in obsessive-compulsive disorder

Convergent findings from neuropsychological and neuroimaging studies have suggested that neural dysfunction in frontal-subcortical circuits may play a central role in the pathophysiology of obsessive-compulsive disorder (OCD). To further examine the relationship between these two sets of findings we investigated both neuropsychological functions and regional cerebral blood flow (rCBF) in a combined study. Fourteen unmedicated patients fulfilling DSM-IV criteria for OCD and 14 healthy controls matched for age, gender, handedness, and education were assessed on neuropsychological tests that included Trail Making Test (TMT), Rey Complex Figure Test (RCF) (copy and 5-min recall), Verbal Fluency Test (VFT), and Wisconsin Card Sorting Test (WCST). rCBF was studied with 99 mTc-hexamethyl-propyleneamine-oxime (HMPAO) single photon emission computed tomography (SPECT). Patients performed more poorly than controls (P<.05) on RCF (copy), VFT, and WCST (perseverative errors). Spearman's correlations indicated that severity of OCD correlated inversely with performance on the RCF (copy and recall scores) and positively with rCBF in the right thalamus. Positive correlations were observed between nonperseverative errors (WCST) and rCBF in frontal areas and anterior cingulate. Perseverative errors (WCST) correlated negatively with rCBF in the right thalamus. These findings are consistent with most previously published studies and suggest neural dysfunctions in the frontal-subcortical circuits probably more pronounced in the right hemisphere. They also extend the existing research, showing associations between deficits in cortical-subcortical circuitry and performance on neuropsychological tests of controlled attention and visuospatial functions.     

Relationship between the chest radiograph, regional lung function studies, exercise tolerance, and clinical condition in cystic fibrosis

This study evaluated the accuracy of the interpretation of the chest film in delineating localised abnormalities of ventilation and perfusion, as well as the overall severity of airways obstruction, exercise tolerance, and clinical condition in children with cystic fibrosis. Radiographic findings in various regions of the chest film were compared with the functional values obtained with regional lung function tests which evaluated the arrival and disappearance of boluses of radioactive nitrogen given by inhalation and infusion. While the more severely affected areas on the chest radiograph were found to correlate with similar regions on the lung function tests, as did overall scores, errors occurred in some cases if the x-ray film alone was used as a judge of regional physiological derangement. In addition the degree of airways obstruction, the exercise tolerance on a cycle ergometer, and clinical grading, each correlated significantly with the radiographic score. We conclude that the chest radiograph is a good indicator of the overall severity of the lung disease and that it correlates well with exercise tolerance and clinical condition in cystic fibrosis.     

Hepatic scintigraphy in management of infants and children with liver disease

Scintiscans of liver and spleen using technetium 99m sulphur colloid in 15 infants with extrahepatic biliary atresia and 11 infants with severe obstructive jaundice (7 with genetic deficiency of alpha 1-antitrypsin) showed similar hepatic size, pattern of isotope uptake, and splenic abnormality with no distinguishing features. In 37 older children with a variety of liver disorders, the scan was invaluable in showing filling defects in five instances. Selenomethionine was taken up not only by the two filling defects due to hepatoblastoma but also in a haemangioendothelioma. In the remaining patiens liver scanning confirmed hepatic abnormality and the necessity for more specific invasive diagnostic investigations.     

Cardiac Tamponade,Sever Hypothyroidism and Acute Respiratory Distress Syndrome (ARDS) with COVID-19 Infection

A 21-years-old with Down syndrome presented with respiratory distress. Initial investigations revealed a cardiac tamponade. On further evaluation, he had positive coronavirus disease-2019 (COVID-19), severe chest infection and severe hypothyroidism. He responded well to urgent pericardiocentesis, levothyroxine, hydrocortisone and tocilizumab.