Conjugate feedback induced suppression and generation of oscillations in the Chua circuit: experiments and simulations

We study the suppression (amplitude death) and generation of oscillations (rhythmogenesis) in the Chua circuit using a feedback term consisting of conjugate variables (conjugate feedback). When the independent Chua circuit (without feedback) is placed in the oscillatory domain, this conjugate feedback induces amplitude death in the system. On the contrary, introducing the conjugate feedback in the system exhibiting fixed point behavior results in the generation of rhythms. Furthermore, it is observed that the dynamics of the Chua circuit could be tuned efficiently by varying the strength of this feedback term. Both experimental and numerical results are presented.

Depressive disorder moderates the effect of the FTO gene on body mass index

There is evidence that obesity-related disorders are increased among people with depression. Variation in the FTO (fat mass and obesity associated) gene has been shown to contribute to common forms of human obesity. This study aimed to investigate the genetic influence of polymorphisms in FTO in relation to body mass index (BMI) in two independent samples of major depressive disorder (MDD) cases and controls. We analysed 88 polymorphisms in the FTO gene in a clinically ascertained sample of 2442 MDD cases and 809 controls (Radiant Study). In all, 8 of the top 10 single-nucleotide polymorphisms (SNPs) showing the strongest associations with BMI were followed-up in a population-based cohort (PsyCoLaus Study) consisting of 1292 depression cases and 1690 controls. Linear regression analyses of the FTO variants and BMI yielded 10 SNPs significantly associated with increased BMI in the depressive group but not the control group in the Radiant sample. The same pattern was found in the PsyCoLaus sample. We found a significant interaction between genotype and affected status in relation to BMI for seven SNPs in Radiant (P<0.0057), with PsyCoLaus giving supportive evidence for five SNPs (P-values between 0.03 and 0.06), which increased in significance when the data were combined in a meta-analysis. This is the first study investigating FTO and BMI within the context of MDD, and the results indicate that having a history of depression moderates the effect of FTO on BMI. This finding suggests that FTO is involved in the mechanism underlying the association between mood disorders and obesity.

Niflumic acid blocks native and recombinant T-type channels

Voltage-dependent calcium channels are widely distributed in animal cells, including spermatozoa. Calcium is fundamental in many sperm functions such as: motility, capacitation, and the acrosome reaction (AR), all essential for fertilization. Pharmacological evidence has suggested T-type calcium channels participate in the AR. Niflumic acid (NA), a non-steroidal anti-inflammatory drug commonly used as chloride channel blocker, blocks T-currents in mouse spermatogenic cells and Cl(-) channels in testicular sperm. Here we examine the mechanism of NA blockade and explore if it can be used to separate the contribution of different Ca(V)3 members previously detected in these cells. Electrophysiological patch-clamp recordings were performed in isolated mouse spermatogenic cells and in HEK cells heterologously expressing Ca(V)3 channels. NA blocks mouse spermatogenic cell T-type currents with an IC(50) of 73.5 µM, without major voltage-dependent effects. The NA blockade is more potent in the open and in the inactivated state than in the closed state of the T-type channels. Interestingly, we found that heterologously expressed Ca(V)3.1 and Ca(V)3.3 channels were more sensitive to NA than Ca(V)3.2 channels, and this drug substantially slowed the recovery from inactivation of the three isoforms. Molecular docking modeling of drug-channel binding predicts that NA binds preferentially to the extracellular face of Ca(V)3.1 channels. The biophysical characteristics of mouse spermatogenic cell T-type currents more closely resemble those from heterologously expressed Ca(V)3.1 channels, including their sensitivity to NA. As Ca(V)3.1 null mice maintain their spermatogenic cell T-currents, it is likely that a novel Ca(V)3.2 isoform is responsible for them.

Identification of a disulfide bridge essential for structure and function of the voltage-gated Ca(2+) channel α(2)δ-1 auxiliary subunit

Voltage-gated calcium (Ca(V)) channels are transmembrane proteins that form Ca(2+)-selective pores gated by depolarization and are essential regulators of the intracellular Ca(2+) concentration. By providing a pathway for rapid Ca(2+) influx, Ca(V) channels couple membrane depolarization to a wide array of cellular responses including neurotransmission, muscle contraction and gene expression. Ca(V) channels fall into two major classes, low voltage-activated (LVA) and high voltage-activated (HVA). The ion-conducting pathway of HVA channels is the α(1) subunit, which typically contains associated β and α(2)δ ancillary subunits that regulate the properties of the channel. Although it is widely acknowledged that α(2)δ-1 is post-translationally cleaved into an extracellular α(2) polypeptide and a membrane-anchored δ protein that remain covalently linked by disulfide bonds, to date the contribution of different cysteine (Cys) residues to the formation of disulfide bridges between these proteins has not been investigated. In the present report, by predicting disulfide connectivity with bioinformatics, molecular modeling and protein biochemistry experiments we have identified two Cys residues involved in the formation of an intermolecular disulfide bond of critical importance for the structure and function of the α(2)δ-1 subunit. Site directed-mutagenesis of Cys404 (located in the von Willebrand factor-A region of α(2)) and Cys1047 (in the extracellular domain of δ) prevented the association of the α(2) and δ peptides upon proteolysis, suggesting that the mature protein is linked by a single intermolecular disulfide bridge. Furthermore, co-expression of mutant forms of α(2)δ-1 Cys404Ser and Cys1047Ser with recombinant neuronal N-type (Ca(V)2.2α(1)/β(3)) channels, showed decreased whole-cell patch-clamp currents indicating that the disulfide bond between these residues is required for α(2)δ-1 function.

Effects of the new immunosuppressive agents on the occurrence of malignancies after renal transplantation

INTRODUCTION

The risk of malignancies in renal transplant recipients is considerably greater than in the general population. The purpose of the present study was to investigate the effects on the appearance of malignancies of 3 immunosuppressive periods: azathioprine (AZA), cyclosporine (CsA), and tacrolimus (TAC).

PATIENTS AND METHODS

This study included 1029 first renal transplant recipients of mean age at transplantation of 44.6±14.9 years with a mean follow-up of 95.6±84.2 months. Initial immunosuppression was AZA-based (n=198), CsA-based (n=524), and TAC (n=307). A total of 280 recipients were also treated with mycophenolate mofetil or mycophenolic acid.

RESULTS

There were 157 patients (15.3%) who displayed≥1 malignancy; there were 95 skin (9.2%) and 74 (7.8%) non-skin malignancies with presentations at 74±62 and 107±77 months, respectively (P=.003). The skin malignancies included squamous cell carcinomas (n=41), basal cell carcinomas (n=41), Kaposi sarcomas (n=7), and melanomas (n=4). Among the solid tumors, lymphoproliferative disorders (n=15), digestive tract (n=14), kidney and urinary tract (n=11), lung (n=10), and breast (n=3) carcinomas. The cumulative incidences at 5, 10, and 15 years were 6%, 10%, and 18% for skin and 3%, 7%, and 14% for non-skin malignancies, respectively. Multivariate analysis showed that age at transplant in years (P=.000) and male gender (P=.000) were the only variables associated with skin malignancies; age at transplant in years (P=.004) and treatment with OKT3 (P=.000) were associated with non-skin malignancies. Malignancies were the cause of death in 18% of recipients who died with functioning grafts.

CONCLUSION

Malignancies are an important cause of morbidity and mortality among renal transplant recipients. The new immunosuppressive agents do not increase the risk of malignancies. Special surveillance is needed for older, male recipients.

Civilian and military trauma: does civilian training prepare surgeons for the battlefield?

The management of trauma patients continues to be a major focus of resident training. The purpose of this review is to compare the mechanism and distribution of injuries in civilian and military trauma and to ascertain whether we are optimally preparing surgeons for the injuries seen on the battlefield. We performed a retrospective 5-year review of all trauma admissions to our urban trauma center (TC). We then compared this data with that recently acquired from Operation Iraqi Freedom (OIF). There were 7732 trauma patients seen during that time at our TC with 9.8 per cent sustaining gunshot wounds. Of those, 26 per cent sustained a gunshot wound to the thorax, and injuries to the abdomen and pelvis were sustained in 28.5 per cent. In total, truncal trauma accounted for 55 per cent of the injuries. Extremity injuries occurred in just 31 per cent. Data from OIF show the mechanism and distribution of injuries to be quite different. Improvised explosive devices accounted for greater than 50 per cent of the injuries in OIF. Truncal injuries accounted for just 14 per cent of the injuries seen and extremity injuries accounted for, a significant, 56 per cent of all the injuries observed. The civilian experience with gunshot wounds often focuses on truncal trauma, yet the military data show a need for knowledge of devastating injuries to the extremity. This divergent experience may be even more salient in the future as the battlefield is brought closer to home through domestic terrorism and the line is blurred between military and civilian trauma.

Civilian and Military Trauma: Does Civilian Training Prepare Surgeons for the Battlefield?

The management of trauma patients continues to be a major focus of resident training. The purpose of this review is to compare the mechanism and distribution of injuries in civilian and military trauma and to ascertain whether we are optimally preparing surgeons for the injuries seen on the battlefield. We performed a retrospective 5-year review of all trauma admissions to our urban trauma center (TC). We then compared this data with that recently acquired from Operation Iraqi Freedom (OIF). There were 7732 trauma patients seen during that time at our TC with 9.8 per cent sustaining gunshot wounds. Of those, 26 per cent sustained a gunshot wound to the thorax, and injuries to the abdomen and pelvis were sustained in 28.5 per cent. In total, truncal trauma accounted for 55 per cent of the injuries. Extremity injuries occurred in just 31 per cent. Data from OIF show the mechanism and distribution of injuries to be quite different. Improvised explosive devices accounted for greater than 50 per cent of the injuries in OIF. Truncal injuries accounted for just 14 per cent of the injuries seen and extremity injuries accounted for, a significant, 56 per cent of all the injuries observed. The civilian experience with gunshot wounds often focuses on truncal trauma, yet the military data show a need for knowledge of devastating injuries to the extremity. This divergent experience may be even more salient in the future as the battlefield is brought closer to home through domestic terrorism and the line is blurred between military and civilian trauma.

Haemolytic anaemia and renal failure associated with antibodies to trimethoprim and sulfamethoxazole

AIM

The aim of this study was to support a clinical diagnosis of drug-induced immune haemolytic anaemia (DIIHA).

BACKGROUND

DIIHA is rare and has only been described twice with the antibiotic combination of trimethoprim (TMP) and sulfamethoxazole (SMX).

METHODS/MATERIALS

Serologic tests for drug antibodies were performed using methods previously published by our laboratory.

RESULTS

A 44-year-old woman experienced body aches, chills, chest pressure, nausea and a rash while receiving TMP-SMX; a week later her haemoglobin was low and she was in renal failure. At the hospital, the direct antiglobulin test (DAT) was positive (C3 only) and the serum reacted with all red blood cells (RBCs) by the gel method only (TMP-SMX is present in the RBC diluent used for the gel method). At the Red Cross immunohaematology laboratory, the patient's serum was reactive in the presence of TMP-SMX (haemolysis and positive antiglobulin test), pure TMP (positive antiglobulin test using anti-IgG only) and pure SMX (haemolysis and positive antiglobulin test using both anti-IgG and anti-C3). The patient was treated with transfusions and haemodialysis and was discharged after a week in stable condition.

CONCLUSION

We describe a patient who appeared to have haemolytic anaemia and renal failure associated with antibodies to both TMP and SMX.

Outcomes of multidrug-resistant tuberculosis among binational cases in El Paso, Texas

In the United States, multidrug-resistant tuberculosis (MDR-TB) is more commonly seen among foreign-born patients. We report outcomes for 46 patients with MDR-TB who were born in Mexico and treated along the United States-Mexico border. According to our definition, 30 were cured, 3 showed treatment failure, 3 died, and 10 abandoned treatment. Multidrug-resistant tuberculosis can be successfully treated on an ambulatory basis.

Mycophenolate acid vs mycophenolate mofetil therapy

BACKGROUND

Mycophenolate mofetil (MMF) is included in the basic immunosuppression regimen in heart transplantation (HTx). Classically, the mycophenolic acid (MPA) concentration has not been considered to provide clinical information.

OBJECTIVE

To perform a comparative analysis of MMF dosage and MPA concentration and their effect on post-HTx renal function.

PATIENTS AND METHODS

Sixty patients underwent HTx between January 2007 and April 2009, and were followed up at 4 scheduled visits in 6 months. The standard MMF dose was 1000 mg/12 h, with adjustment according to clinical criteria. The MPA concentration was determined using an enzyme-multiplied immunoassay (EMIT 2000; Siemens Healthcare Diagnostics Inc, Deerfield, Illinois), without change in dosage. The correlation between mean MMF dosage and MPA concentrations at all visits vs renal function values was analyzed using serum creatinine concentration, creatinine clearance (CrCl; Modification of Diet in Renal Disease), and glomerular filtration rate (GFR; Cockcroft-Gault formula).

RESULTS

Mean (SD) patient age was 50 (13) years, and 45 of 60 (75.4%) were men. Pre-HTx values were as follows: creatinine concentration, 1.13 (0.47) mg/dL; CrCl, 81.59 (36.84) mL/min/1.73 m2; and GFR, 77.46 (30.60) mL/min. In the first 6 months post-HTx, significant negative correlations were observed between mean MPA concentration and creatinine concentration (r=.42; P=.001), CrCl (r=-.36; P=.01), and GFR (r=-.45; P=.001). No correlation was observed with mean MMF dosage.

CONCLUSION

There are important differences in the relationship of MPA concentration vs MMF dosage and post-HTx renal function. Although studies with a larger number of patients are needed, treatment guided by MPA concentration seems reliable for evaluation of renal function.