Ionic Coulomb blockade and the determinants of selectivity in the NaChBac bacterial sodium channel.

Mutation-induced transformations of conductivity and selectivity in NaChBac bacterial channels are studied experimentally and interpreted within the framework of ionic Coulomb blockade (ICB), while also taking account of resonant quantised dehydration (QD) and site protonation. Site-directed mutagenesis and whole-cell patch-clamp experiments are used to investigate how the fixed charge Qf at the selectivity filter (SF) affects both valence selectivity and same-charge selectivity. The new ICB/QD model predicts that increasing ∣Qf∣ should lead to a shift in selectivity sequences toward larger ion sizes, in agreement with the present experiments and with earlier work. Comparison of the model with experimental data leads to the introduction of an effective charge Qf∗ at the SF, which was found to differ between Aspartate and Glutamate charged rings, and also to depend on position within the SF. It is suggested that protonation of the residues within the restricted space of the SF is important in significantly reducing the effective charge of the EEEE ring. Values of Qf∗ derived from experiments on divalent blockade agree well with expectations based on the ICB/QD model and have led to the first demonstration of ICB oscillations in Ca2+ conduction as a function of the fixed charge. Preliminary studies of the dependence of Ca2+ conduction on pH are qualitatively consistent with the predictions of the model.

Decreased diffusion capacity on lung function testing in asymptomatic patients with systemic lupus erythematosus does not predict future lung disease.

BACKGROUND: In a previous study performed 9 ± 3.6 years ago, 74 asymptomatic patients with systemic lupus erythematosus (SLE) and/or antiphospholipid syndrome (APS) underwent lung function testing. A significantly low diffusion capacity (DLCO) ranging from 45% to 70% was recorded in 28 of the 74 (37.8%) patients who were all free of respiratory symptoms. AIM: The aim of this report is to assess the clinical importance and the predictive value of a low DLCO in asymptomatic patients with SLE or APS. METHODS: Asymptomatic patients with SLE and/or APS who were found to have a low DLCO in the previous study were contacted. Of the 28 patients, 15 were recruited and reevaluated in the current study (SLE with APS (n = 7), SLE without APS (n = 7); primary APS (n = 1)). A full history, physical examination, nail bed capillaroscopy, current laboratory tests and full lung function tests including DLCO were performed. RESULTS: During a surveillance period of 9 ± 3.6 years, none of the patients developed lung disease. Diffusion capacity corrected for alveolar volume (DLCO/VA) improved in the study group during this period from 60.4% ± 7.0 to 76.1% ± 11.2 (p < 0.0001). Lung function tests including total lung capacity (TLC) and forced expiratory volume in one second (FEV1) remained within normal limits. Capillaroscopy studies did not reveal changes compatible with scleroderma in any of the patients. CONCLUSION: Low DLCO findings on lung function testing does not have a positive predictive value for the development of future lung disease in patients with SLE, with or without APS, who are free of respiratory symptoms. Our results suggest that a finding of low DLCO in asymptomatic patients with SLE, with or without APS, does not necessarily require further evaluation and imaging and may improve spontaneously over time. Further studies in a larger group of patients are needed to validate these findings.

Energetics of discrete selectivity bands and mutation-induced transitions in the calcium-sodium ion channels family.

We use Brownian dynamics (BD) simulations to study the ionic conduction and valence selectivity of a generic electrostatic model of a biological ion channel as functions of the fixed charge Q(f) at its selectivity filter. We are thus able to reconcile the discrete calcium conduction bands recently revealed in our BD simulations, M0 (Q(f)=1e), M1 (3e), M2 (5e), with a set of sodium conduction bands L0 (0.5e), L1 (1.5e), thereby obtaining a completed pattern of conduction and selectivity bands vs Q(f) for the sodium-calcium channels family. An increase of Q(f) leads to an increase of calcium selectivity: L0 (sodium-selective, nonblocking channel) → M0 (nonselective channel) → L1 (sodium-selective channel with divalent block) → M1 (calcium-selective channel exhibiting the anomalous mole fraction effect). We create a consistent identification scheme where the L0 band is putatively identified with the eukaryotic sodium channel The scheme created is able to account for the experimentally observed mutation-induced transformations between nonselective channels, sodium-selective channels, and calcium-selective channels, which we interpret as transitions between different rows of the identification table. By considering the potential energy changes during permeation, we show explicitly that the multi-ion conduction bands of calcium and sodium channels arise as the result of resonant barrierless conduction. The pattern of periodic conduction bands is explained on the basis of sequential neutralization taking account of self-energy, as Q(f)(z,i)=ze(1/2+i), where i is the order of the band and z is the valence of the ion. Our results confirm the crucial influence of electrostatic interactions on conduction and on the Ca(2+)/Na(+) valence selectivity of calcium and sodium ion channels. The model and results could be also applicable to biomimetic nanopores with charged walls.

Multi-ion conduction bands in a simple model of calcium ion channels.

We report self-consistent Brownian dynamics simulations of a simple electrostatic model of the selectivity filters (SF) of calcium ion channels. They reveal regular structure in the conductance and selectivity as functions of the fixed negative charge Qf at the SF. With increasing Qf, there are distinct regions of high conductance (conduction bands) M0, M1, M2 separated by regions of almost zero-conductance (stop-bands). Two of these conduction bands, M1 and M2, are related to the saturated calcium occupancies of P = 1 and P = 2, respectively and demonstrate self-sustained conductivity. Despite the model's limitations, its M1 and M2 bands show high calcium selectivity and prominent anomalous mole fraction effects and can be identified with the L-type and RyR calcium channels. The non-selective band M0 can be identified with a non-selective cation channel, or with OmpF porin.

Self-consistent analytic solution for the current and the access resistance in open ion channels.

A self-consistent analytic approach is introduced for the estimation of the access resistance and the current through an open ion channel for an arbitrary number of species. For an ion current flowing radially inward from infinity to the channel mouth, the Poisson-Boltzmann-Nernst-Planck equations are solved analytically in the bulk with spherical symmetry in three dimensions, by linearization. Within the channel, the Poisson-Nernst-Planck equation is solved analytically in a one-dimensional approximation. An iterative procedure is used to match the two solutions together at the channel mouth in a self-consistent way. It is shown that the current-voltage characteristics obtained are in good quantitative agreement with experimental measurements.

Anaesthetic management of parturients with hereditary haemorrhagic telangiectasia for caesarean section.

Hereditary haemorrhagic telangiectasia, also known as Osler-Weber-Rendu disease, is a vascular disorder characterized by multiple mucocutaneous and visceral arteriovenous malformations. There is little in the literature about the anaesthetic management of parturients with this condition. We report the anaesthetic management for caesarean section of two such parturients. One patient, with significant pulmonary involvement, received neuraxial anaesthesia for caesarean delivery. The second patient had general anaesthesia because investigations could not rule out neurological involvement. We review and discuss the anaesthetic considerations for obstetric patients with hereditary haemorrhagic telangiectasia.

Sjögren's syndrome - not just Sicca: renal involvement in Sjögren's syndrome.

OBJECTIVE: To present a case of severe interstitial nephritis with proteinuria in primary Sjögren's syndrome (pSS) and review the literature regarding renal disease and its management in pSS, aiming to suggest recommendations for treatment. METHODS: A search of MEDLINE (PubMed) was performed for review articles and case reports using the MESH terms: Sjögren syndrome; renal disease; interstitial nephritis (IN); glomerulonephritis (GN). RESULTS: We describe a rare case of pSS presenting with hypokalaemic tetraparesis and proteinuria due to severe IN, successfully treated with high-dose steroids and azathioprine. Reviewing the literature, we identified 180 reported cases of renal involvement in pSS (selected based on the European criteria for pSS), 89 of which underwent renal biopsies revealing IN in 49 cases, GN in 33 samples, and both IN and GN in seven. Eighteen studies reported treatment experience of renal disease in 32 pSS cases. Seventeen patients were treated with corticosteroids and cyclophosphamide, and 15 patients received only steroids with improvement in the majority of cases. CONCLUSION: The present case, as well as the limited number of reports in the literature, suggest that renal involvement, including IN, in pSS may improve with immunosuppressive therapy. Further studies are required to determine indications for and dosages of immunosuppressive treatment in patients with renal involvement of pSS.

Maternal factors implicated in fetal bradycardia after combined spinal epidural for labour pain.

BACKGROUND AND OBJECTIVE: Combined spinal epidural analgesia is effective for fast relief of severe labour pain but has been associated with worrisome decreases in fetal heart rate. Since the reasons for this phenomenon remain elusive, some anaesthesiologists may abstain from using this technique. We postulated that factors unrelated to the neuraxial technique could play a role in the decrease in fetal heart rate. To our knowledge, no prospective study has previously looked into this possibility. METHODS: We collected prospective data on 223 consecutive patients who received combined spinal epidural analgesia (123) or epidural analgesia (100). Maternal blood pressure, analogue pain scores, exogenous infusion of oxytocin, cervical dilatation, maternal age, parity and ethnicity were collected and correlated with the occurrence of decreases in fetal heart rate post combined spinal epidural. RESULTS: Univariate analysis showed a correlation between the incidence of fetal bradycardia and higher maternal pain scores, older maternal age, and combined spinal epidural analgesia. Multivariate analysis revealed that only pain scores and maternal age were independent predictors of fetal bradycardia post neuraxial blockade. CONCLUSIONS: Maternal pain scores and older maternal age are factors unrelated to the neuraxial technique that are independent predictors of fetal bradycardia after neuraxial analgesia for labour.

Pulmonary dysfunction in systemic lupus erythematosus and anti-phospholipid syndrome patients.

OBJECTIVE: To assess and compare parameters of pulmonary function in systemic lupus erythematosus (SLE) and anti-phospholipid syndrome (APS) patients. METHODS: Consecutive patients (n = 74) who were free of respiratory symptoms were divided into four groups: 1) SLE (n = 23); 2) SLE with anti-phospholipid antibodies (aPL) (n = 18); 3) SLE with APS (n = 20); and 4) primary APS (PAPS) (n = 13). Pulmonary function testing, single breath diffusion capacity of carbon monoxide (DLCO/SB) and echocardiography studies were performed. Induced sputum cytology was analysed. RESULTS: Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and DLCO were significantly reduced in SLE compared to PAPS patients (p = 0.039; p = 0.017; p = 0.029, respectively). Elevated pulmonary arterial pressure was observed in two patients with SLE and aPL and in two with SLE and APS. Lymphocyte and eosinophil counts in induced sputum showed no significant differences; however, a trend towards lower CD4 counts in SLE vs. PAPS was noted (p = 0.086), while in patients with both SLE and APS, a low CD4/CD8 ratio was seen. Patients with APS were older than patients without APS (47.12+/-14.86 vs. 34.29+/-12.6, p = 0.0001), while SLE patients were younger than PAPS patients (38.19+/-14.68 vs. 48.53+/-13.97, p = 0.023). CONCLUSION: Abnormal pulmonary functions tests were detected frequently in asymptomatic patients with SLE or PAPS. Although SLE patients were younger, pulmonary function was significantly more impaired in SLE as compared to PAPS patients.

Vaccination against influenza in rheumatoid arthritis: the effect of disease modifying drugs, including TNF alpha blockers.

OBJECTIVE: To assess the efficacy and safety of vaccination against influenza virus in patients with rheumatoid arthritis, with special emphasis on the effect of disease modifying antirheumatic drugs (DMARDs), including tumour necrosis factor alpha (TNFalpha) blockers. METHODS: 82 rheumatoid patients and 30 healthy controls were vaccinated with a split-virion inactivated vaccine containing 15 mug haemagglutinin (HA) per dose of each of B/Hong Kong/330/2001 (HK), A/Panama/2007/99 (PAN), and A/New Caledonian/20/99 (NC). Disease activity was assessed by tender and swollen joint count, morning stiffness, evaluation of pain, Health Assessment Questionnaire, ESR, and C reactive protein on the day of vaccination and six weeks later. Haemagglutination inhibiting (HI) antibodies were tested by a standard WHO procedure. Response was defined as a fourfold or more rise in HI antibodies six weeks after vaccination, or seroconversion in patients with a non-protective baseline level of antibodies (<1/40). Geometric mean titres (GMT) were calculated to assess the immunity of the whole group. RESULTS: Six weeks after vaccination, a significant increase in GMT for each antigen was observed in both groups, this being higher in the healthy group for HK (p=0.004). The percentage of responders was lower in rheumatoid patients than healthy controls (significant for HK). The percentage of responders was not affected by prednisone or any DMARD, including methotrexate, infliximab, and etanercept. Indices of disease activity remained unchanged. CONCLUSIONS: Influenza virus vaccine generated a good humoral response in rheumatoid patients, although lower than in healthy controls. The response was not affected by the use of prednisone or DMARDs.

Spinal anesthesia for a patient with type I sialidosis undergoing abdominal surgery.

Type I and II sialidosis are autosomal recessively inherited glycoprotein storage disorders. Until now, there has been no published reports of patients with these conditions requiring anesthesia. We present the case of a 31-year-old male afflicted with type I sialidosis who underwent a surgical jejunostomy. Regional (spinal) anesthesia was carried out uneventfully. We discuss the anesthetic challenges posed by patients with type I and II sialidosis. Airway assessment and management is particularly crucial.

Noise-induced escape on time scales preceding quasistationarity: New developments in the Kramers problem.

Noise-induced escape from the metastable part of a potential is considered on time scales preceding the formation of quasiequilibrium within that part of the potential. It is shown that, counterintuitively, the escape flux may then depend exponentially strongly, and in a complicated manner, on time and friction. (c) 2001 American Institute of Physics.

Neurotoxicity after spinal anaesthesia induced by serial intrathecal injections of magnesium sulphate. An experimental study in a rat model.

We have previously demonstrated in a rat model that the lumbar intrathecal injection of 0.02 ml 6.3% magnesium sulphate, a concentration iso-osmolar with rat plasma, produces a state of spinal anaesthesia and general sedation which reversed completely after 6 h, without evidence of neurotoxicity, immediately or during the week thereafter. Using the same model and five groups of six animals in each, we administered the same volume and concentration of magnesium sulphate and compared its clinical effects with those of 0.02 ml 12.6% magnesium sulphate, 0.02 ml 2% lignocaine and 0.02 ml 0.9% sodium chloride solution, given as a series of 15 injections on alternate days for a period of 1 month. The animals were then killed and their spinal cords and meninges examined histologically. No significant differences were noted in the times of onset, durations of sensory and motor blockade and the times to full recovery throughout the entire period of 1 month's observation in the animals receiving intrathecal 6.3% magnesium sulphate. In the group receiving 12.6% magnesium sulphate, the time of onset of sensory and motor blockade was shorter and the duration of both parameters was significantly longer than in the former group. Full clinical recovery and resumption of normal eating and drinking took place in both groups throughout the entire series of 15 successive intrathecal injections. Identical, mild, uniform histopathological changes in the spinal cord were seen in all the five groups, including the group in which only the intrathecal catheter was implanted. The complete recovery and benign consequences of repeated intrathecal injections of iso-osmolar magnesium sulphate in a rat model indicate a lack of neurotoxicity and provide an impetus for further trials in larger animal species, before initial clinical trials of this substance, given intrathecally, in humans.

0.6 T magnetic resonance imaging of the orbit.

Magnetic resonance (MR) imaging of the orbit was performed with a 0.6 T superconducting imaging system in 100 patients with normal orbits who were being evaluated for brain pathology and in 21 additional patients with a variety of orbital lesions to determine the efficacy of MR imaging in displaying orbital abnormalities. Usually, MR studies were performed using a multislice technique with multiple spin-echo pulse sequences and 30, 60, and 90 msec echo times and 500, 1500, and 2000 msec repetition times. Using section thicknesses of about 8 mm, imaging was performed in the transaxial, coronal, and sagittal projections. Pixel size was 0.9 X 1.8 mm, and the examination took about 30 min. The MR findings were compared with computed tomographic (CT) findings in all cases. Either combined axial and coronal studies of 5-mm-thick sections or a thin axial study of 1-mm-thick sections followed by reformatting techniques to obtain multiplanar images was used. Contrast enhancement was used in the CT studies. Both MR and CT clearly demonstrated the soft-tissue abnormality in all cases except two, in which MR failed to detect the abnormality. In one, MR failed to detect a small retrobulbar hemorrhage that occurred after a surgical procedure for retinal detachment. In the second case, rather extensive calcification in the posterior choroidal layers and lens was not detected by MR imaging. In several other cases, MR provided information beyond that obtained with CT. MR has the advantage of providing exquisite anatomic detail in multiplanar images, and it appears to be more sensitive than CT in detecting small, subacute and chronic hemorrhage within soft-tissue masses in the orbit and in detecting ischemia of the globe. CT is superior to MR imaging in portraying fine bone detail.

Prevalence of diabetes mellitus in southern Wisconsin.

The prevalence of known cases of diabetes was ascertained from patient records in an 11-county area in Wisconsin in July 1979 to June 1980. The prevalence in the noninstitutionalized population was found to be 1%. Prevalence rates rose from 0.5 cases per 1000 population in the first decade of life to 44.7 cases per 1000 population in the eighth decade. The highest rates were found in the nursing home population. Males had higher age-adjusted rates than females. No difference in prevalence was found between persons living in metropolitan or nonmetropolitan counties. Determination of prevalence by these methods is a rapid and inexpensive means of ascertainment of known cases of diabetes.

Lesch-Nyhan disease: clinical experience with nineteen patients.

The clinical phenotype in Lesch-Nyhan disease has been analyzed in 19 patients studied in hospital. In each case the diagnosis was made on the basis of inactivity of the enzyme hypoxanthine guanine phosphoribosyltransferase in erythrocyte lysates. All had hyperuricemia, and the presence of 'orange sand' in the diaper was a prominent early complaint. All had self-mutilative behavior, of which the most characteristic form was biting the fingers or lips. All had the neurological syndrome of spasticity and choreoathetoid involuntary movements. All but one had less-than-normal intelligence.