Depolarization of membrane potential and the smooth muscle contraction by isothiocyanatobenzyl imidazoline in guinea-pig stomach circular muscle

Isothiocyanatobenzyl imidazoline (IBI) produces characteristic slowly developing contraction of many smooth muscle preparations including the circular smooth muscle of the guinea-pig stomach. Changes in the membrane potential were recorded intracellularly, and the muscle contraction induced by IBI was investigated. IBI at 100 micromol/l slowly produced a sustained depolarization of the membrane with a maximum change of approximately 15 mV. This depolarization could not be blocked by 1-hyoscyamine, 100 nmol/l. An imidazoline analogue, oxymetazoline at 1 micromol/l, did not change the resting membrane potential as observed after IBI. Significant membrane depolarization after IBI still occurred in Ca2+-free medium. During IBI-induced depolarization, sudden reduction of Na+ to 30 mmol/l in the medium reduced the depolarization slightly. IBI-induced depolarization was additive with that produced by 20 mmol/l K+ in the medium. In the presence of tetraethylammonium chloride or levcromakalim or nifedipine, IBI continued to depolarize the membrane although functional pharmacological experiments showed that the contractile effects of IBI were significantly inhibited by 30 micromol/l levcromakalim and abolished by 100 nmol/l nifedipine. At 100 micromol/l phentolamine (reported by others as an inhibitor of ATP-sensitive potassium channels) completely blocked IBI-induced contraction. Phentolamine (30 micromol/l) blocked the contractile effects of IBI by 50%. On the other hand, S(-)-Bay K 8644, a voltage-dependent calcium channel activator, was additive with the contractile response of IBI. These results indicated that IBI produced membrane depolarization and contraction of the guinea-pig stomach circular muscle, by a mechanism not involving muscarinic receptors or alpha-adrenoceptors. Even though levcromakalim, an ATP-sensitive potassium channel opener, could not inhibit IBI-induced depolarization, the ATP-sensitive potassium channel and the voltage-dependent calcium channel may be intrinsically linked with the action of IBI.     

A role for exposed mannosylations in presentation of human therapeutic self-proteins to CD4+ T lymphocytes

Several therapeutic self-proteins elicit immune responses when administered to patients. Such adverse immune responses reduce drug efficacy. To induce an immune response, a protein must interact with different immune cells, including antigen-presenting cells, T cells, and B cells. Each cell type recognizes distinct immunogenic patterns on antigens. Mannose-terminating glycans have been identified as pathogen-associated molecular patterns that are essential for internalization of microbes by antigen-presenting cells, leading to presentation. Here, we have investigated the importance of exposed mannosylation on an immunogenic therapeutic self-protein, procoagulant human factor VIII (FVIII). Administration of therapeutic FVIII to hemophilia A patients induces inhibitory anti-FVIII antibodies in up to 30% of the cases. We demonstrate that entry of FVIII into human dendritic cells (DC) leading to T cell activation, is mediated by mannose-terminating glycans on FVIII. Further, we identified macrophage mannose receptor (CD206) as a candidate endocytic receptor for FVIII on DC. Saturation of mannose receptors on DC with mannan, and enzymatic removal of mannosylated glycans from FVIII lead to reduced T cell activation. The interaction between FVIII and CD206 was blocked by VWF, suggesting that, under physiological conditions, the intrinsic mannose-dependent immunogenicity of FVIII is quenched by endogenous immunochaperones. These data provide a link between the mannosylation of therapeutic self-proteins and their iatrogenic immunogenicity. Such a link would be of special relevance in the context of replacement therapy where mechanisms of central and peripheral tolerance have not been established during ontogeny because of the absence of the antigen.     

Modulation of neural responses in inferotemporal cortex during the interpretation of ambiguous photographs

Ambiguous images are interpreted in the context of biases about what they might be; these biases and the behavioral consequences induced by them may influence the processing of images. In this report, we examine neural responses in inferotemporal cortex (IT) during the interpretation of ambiguous photographs created by morphing between two photographs. Monkeys classified different images as being one of two choices and learned to classify most of the samples correctly. For one image (the ambiguous sample) reward was administered randomly for either possible choice, and the monkeys were free to classify that image based on their own interpretation, with no learning possible. The ambiguous samples were not classified randomly: the monkey interpreted the samples differently during different sessions. The interpretation of the ambiguous sample was, in turn, highly correlated with the normalized response of individual neurons in IT to the ambiguous sample. If an ambiguous sample was interpreted as a particular choice during a session, the response to that ambiguous sample more closely resembled the response to that choice. Identical ambiguous images were interpreted differently during different sessions, and neural responses reflected the differing interpretations of the image during that session. The relationship between the interpretation of the image and neural responses strengthened over the course of a session because neural responses shifted to more closely resemble the response to the initial interpretation of the image. The data support a flexible representation of visual stimuli in higher visual areas.     

Safety & efficacy of single subconjunctival triamcinolone 5 mg depot vs topical loteprednol post cataract surgery: less drop cataract surgery

AIM: To do a randomized prospective interventional study for comparing the effects of a single subconjunctival triamcinolone acetonide (SCTA) injection to tapering topical loteprednol in patients undergoing phacoemulsification surgery under topical anesthesia. METHODS: A total of 400 patients were randomized into 2 groups; Group A (200 patients) received 5 mg SCTA at the end of surgery and topical ketorolac tromethamine (0.5%) with ofloxacin (0.3%) combination for 3wk. Group B (200 patients) received tapering topical loteprednol etabonate (0.5%) along with ofloxacin (0.3%) and ketorolac tromethamine (0.5%) for 3wk. Outcomes evaluated were intraocular pressure (IOP), anterior chamber cells/flare and macular oedema postoperatively at 1, 6 and 12wk. RESULTS: Baseline parameters were almost similar in both the groups. No statistical difference was seen between the preoperative and postoperative IOP values for Group A (P=0.82) and Group B (P=0.61) and postoperative IOP values in between both groups (P=0.14) at 1wk. Incidence of cells/flare postoperative was statistically not significant (P=0.82) in both groups at all follow up visits. Postoperative macular oedema was not observed at any follow up visit. CONCLUSION: SCTA appears to be an effective alternative to prolong postoperative topical steroid use.     

Propensity-matched analysis of association between preoperative anemia and in-hospital mortality in cardiac surgical patients undergoing valvular heart surgeries

Introduction:

Anaemia is associated with increased post-operative morbidity and mortality. We retrospectively assess the relationship between preoperative anaemia and in-hospital mortality in valvular cardiac surgical population.

Materials and Methods:

Data from consecutive adult patients who underwent valvular repair/replacement at our institute from January 2010 to April 2014 were collected from hospital records. Anaemia was defined according to WHO criteria (hemoglobin <13g/dl for males and <12g/dl for females). 1:1 matching was done for anemic and non-anemic patients based on propensity for potentially confounding variables. Logistic regression was used to evaluate the relationship between anaemia and in-hospital mortality. MatchIt package for R software was used for propensity matching and SPSS 16.0.0 was used for statistical analysis.

Results:

2449 patients undergoing valvular surgery with or without coronary artery grafting were included. Anaemia was present in 37.1% (33.91% among males & 40.88% among females). Unadjusted OR for mortality was 1.6 in anemic group (95% Confidence Interval [95% CI] – 1.041-2.570; p=0.033). 1:1 matching was done on the basis of propensity score for anaemia (866 pairs). Balancing was confirmed using standardized differences. Anaemia had an OR of 1.8 for mortality (95% CI- 1.042 to 3.094, P=0.035). Hematocrit of < 20 on bypass was associated with higher mortality.

Conclusion:

Preoperative anaemia is an independent risk factor associated with in-hospital mortality in patients undergoing valvular heart surgery.     

Common variable immunodeficiency is associated with defective functions of dendritic cells

Common variable immunodeficiency (CVID) is characterized by hypogammaglobulinemia and defects in T-cell functions that could be primary or secondary. We addressed whether CVID is associated with impairment in the dendritic cell (DC) compartment, as DCs play a central role in the development of adaptive immunity. We demonstrate that DCs from CVID patients display severely perturbed differentiation, maturation, and function, and express markedly reduced levels of the costimulatory molecules that are critical for T-cell stimulation. Patients' DCs induced weak proliferation of allogeneic T cells and produced significantly low amounts of interleukin-12 (IL-12) upon CD40 signaling. Multiple defects in the immune system, including malfunctioning of DCs, appear to be prominent features of CVID patients. Impairment in both the innate and adaptive compartments of the immune system may thus cumulatively account for the inability of CVID patients to eradicate pathogens through conventional immune pathways, thus resulting in an increased risk for recurrent bacterial infections.     

Structural determinants of agonist-induced signaling and regulation of the angiotensin AT1 receptor

Angiotensin II (Ang II) regulates aldosterone secretion by stimulating inositol phosphate production and Ca(2+) signaling in adrenal glomerulosa cells via the G(q)-coupled AT(1) receptor, which is rapidly internalized upon agonist binding. Ang II also binds to the heptahelical AT(2) receptor, which neither activates inositol phosphate signaling nor undergoes receptor internalization. The differential behaviors of the AT(1) and AT(2) receptors were analyzed in chimeric angiotensin receptors created by swapping the second (IL2), the third (IL3) intracellular loops and/or the cytoplasmic tail (CT) between these receptors. When transiently expressed in COS-7 cells, the chimeric receptors showed only minor alterations in their ligand binding properties. Measurements of the internalization kinetics and inositol phosphate responses of chimeric AT(1A) receptors indicated that the CT is required for normal receptor internalization, and IL2 is a determinant of G protein activation. In addition, the amino-terminal portion of IL3 is required for both receptor functions. However, only substitution of IL2 impaired Ang II-induced ERK activation, suggesting that alternative mechanisms are responsible for ERK activation in signaling-deficient mutant AT(1) receptors. Substitution of IL2, IL3, or CT of the AT(1A) receptor into the AT(2) receptor sequence did not endow the latter with the ability to internalize or to mediate inositol phosphate signaling responses. These data suggest that the lack of receptor internalization and inositol phosphate signal generation by the AT(2) receptor is a consequence of its different activation mechanism, rather than the inability of its cytoplasmic domains to couple to intracellular effectors.