Inhibition of the sodium–calcium exchanger via SEA0400 altered manganese‐induced T1 changes in isolated perfused rat hearts

Manganese (Mn²⁺)‐enhanced MRI (MEMRI) provides the potential for the in vivo evaluation of calcium (Ca²⁺) uptake in the heart. Recent studies have also suggested the role of the sodium–calcium (Na⁺–Ca²⁺) exchanger (NCX) in Mn²⁺ retention, which may have an impact on MEMRI signals. In this study, we investigated whether MEMRI with fast T₁ mapping allowed the sensitive detection of changes in NCX activity. We quantified the dynamics of the Mn²⁺‐induced T₁ changes in isolated perfused rat hearts in response to SEA0400, an NCX inhibitor. The experimental protocol comprised 30 min of Mn²⁺ perfusion (wash‐in), followed by a 30‐min wash‐out period. There were three experimental groups: 1, NCX inhibition by 1 µ m SEA0400 during Mn²⁺ wash‐in only (SEAin, n = 6); 2, NCX inhibition by 1 µ m SEA0400 during Mn²⁺ wash‐out only (SEAout, n = 6); 3, no NCX inhibition during both wash‐in and wash‐out to serve as the control group (CNTL, n = 5). Rapid T₁ mapping at a temporal resolution of 3 min was performed throughout the perfusion protocol using a triggered saturation–recovery Look–Locker sequence. Our results showed that NCX inhibition during Mn²⁺ wash‐in caused a significant increase in relaxation rate (R₁) at the end of Mn²⁺ perfusion. During the wash‐out period, NCX inhibition led to less reduction in R₁. Further analysis of Mn²⁺ content in myocardium with flame atomic absorption spectroscopy was consistent with the MRI findings. These results suggest that Mn²⁺ accumulation and retention in rat hearts are, in part, dependent on NCX activity. Hence, MEMRI may provide an imaging method that is also sensitive to changes in NCX activity. Copyright © 2012 John Wiley & Sons, Ltd.     

Assessing manganese efflux using SEA0400 and cardiac T1‐mapping manganese‐enhanced MRI in a murine model

The sodium–calcium exchanger (NCX) is one of the transporters contributing to the control of intracellular calcium (Ca²⁺) concentration by normally mediating net Ca²⁺ efflux. However, the reverse mode of the NCX can cause intracellular Ca²⁺ concentration overload, which exacerbates the myocardial tissue injury resulting from ischemia. Although the NCX inhibitor SEA0400 has been shown to therapeutically reduce myocardial injury, no in vivo technique exists to monitor intracellular Ca²⁺ fluctuations produced by this drug. Cardiac manganese‐enhanced MRI (MEMRI) may indirectly assess Ca²⁺ efflux by estimating changes in manganese (Mn²⁺) content in vivo, since Mn²⁺ has been suggested as a surrogate marker for Ca²⁺. This study used the MEMRI technique to examine the temporal features of cardiac Mn²⁺ efflux by implementing a T₁‐mapping method and inhibiting the NCX with SEA0400. The change in ¹H₂O longitudinal relaxation rate, ΔR₁, in the left ventricular free wall, was calculated at different time points following infusion of 190 nmol/g manganese chloride (MnCl₂) in healthy adult male mice. The results showed 50% MEMRI signal attenuation at 3.4 ± 0.6 h post‐MnCl₂ infusion without drug intervention. Furthermore, treatment with 50 ± 0.2 mg/kg of SEA0400 significantly reduced the rate of decrease in ΔR₁. At 4.9–5.9 h post‐MnCl₂ infusion, the average ΔR₁ values for the two groups treated with SEA0400 were 2.46 ± 0.29 and 1.72 ± 0.24 s^?1 for 50 and 20 mg/kg doses, respectively, as compared to the value of 1.27 ± 0.28 s^?1 for the control group. When this in vivo data were compared to ex vivo absolute manganese content data, the MEMRI T₁‐mapping technique was shown to effectively quantify Mn²⁺ efflux rates in the myocardium. Therefore, combining an NCX inhibitor with MEMRI may be a useful technique for assessing Mn²⁺ transport mechanisms and rates in vivo, which may reflect changes in Ca²⁺ transport. Copyright © 2009 John Wiley & Sons, Ltd.     

Development of manganese‐enhanced magnetic resonance imaging of the rostral ventrolateral medulla of conscious rats: Importance of normalization and comparison with other regions of interest

Spinally projecting neurons in the rostral ventrolateral medulla (RVLM) are believed to contribute to pathophysiological alterations in sympathetic nerve activity and the development of cardiovascular disease. The ability to identify changes in the activity of RVLM neurons in conscious animals and humans, especially longitudinally, would represent a clinically important advancement in our understanding of the contribution of the RVLM to cardiovascular disease. To this end, we describe the initial development of manganese‐enhanced magnetic resonance imaging (MEMRI) for the rat RVLM. Manganese (Mn²⁺) has been used to estimate in vivo neuronal activity in other brain regions because of both its paramagnetic properties and its entry into and accumulation in active neurons. In this initial study, our three goals were as follows: (1) to validate that Mn²⁺ enhancement occurs in functionally and anatomically localized images of the rat RVLM; (2) to quantify the dose and time course dependence of Mn²⁺ enhancement in the RVLM after one systemic injection in conscious rats (66 or 33 mg/kg, intraperitoneally); and (3) to compare Mn²⁺ enhancement in the RVLM with other regions to determine an appropriate method of normalization of T₁‐weighted images. In our proof‐of‐concept and proof‐of‐principle studies, Mn²⁺ was identified by MRI in the rat RVLM after direct microinjection or via retrograde transport following spinal cord injections, respectively. Systemic injections in conscious rats produced significant Mn²⁺ enhancement at 24 h (p < 0.05). Injections of 66 mg/kg produced greater enhancement than 33 mg/kg in the RVLM and paraventricular nucleus of the hypothalamus (p < 0.05 for both), but only when normalized to baseline scans without Mn²⁺ injection. Consistent with findings from our previous functional and anatomical studies demonstrating subregional neuroplasticity, Mn²⁺ enhancement was higher in the rostral regions of the RVLM (p < 0.05). Together with important technical considerations, our studies support the development of MEMRI as a potential method to examine RVLM activity over time in conscious animal subjects.     

Myocardial infarction quantification with Manganese‐Enhanced MRI (MEMRI) in mice using a 3T clinical scanner

Manganese (Mn²⁺) was recognized early as an efficient intracellular MR contrast agent to assess cardiomyocyte viability. It had previously been used for the assessment of myocardial infarction in various animal models from pig to mouse. However, whether Manganese‐Enhanced MRI (MEMRI) is also able to assess infarction in the acute phase of a coronary occlusion reperfusion model in mice has not yet been demonstrated. This model is of particular interest as it is closer to the situation encountered in the clinical setting. This study aimed to measure infarction volume taking TTC staining as a gold standard, as well as global and regional function before and after Mn²⁺ injection using a clinical 3T scanner. The first step of this study was to perform a dose‐response curve in order to optimize the injection protocol. Infarction volume measured with MEMRI was strongly correlated to TTC staining. Ejection fraction (EF) and percent wall thickening measurements allowed evaluation of global and regional function. While EF must be measured before Mn²⁺ injection to avoid bias introduced by the reduction of contrast in cine images, percent wall thickening can be measured either before or after Mn²⁺ injection and depicts accurately infarct related contraction deficit. This study is the first step for further longitudinal studies of cardiac disease in mice on a clinical 3T scanner, a widely available platform. Copyright © 2010 John Wiley & Sons, Ltd.     

Manganese‐enhanced MRI (MEMRI) via topical loading of Mn2+ significantly impairs mouse visual acuity: a comparison with intravitreal injection

Manganese‐enhanced MRI (MEMRI) with topical loading of MnCl₂ provides optic nerve enhancement comparable to that seen by intravitreal injection. However, the impact of this novel and non‐invasive Mn²⁺ loading method on visual function requires further assessments. The objective of this study is to determine the optimal topical Mn²⁺ loading dosage for MEMRI and to assess visual function after MnCl₂ loading. Intravitreal administration was performed to compare the two approaches of MnCl₂ loading. Twenty‐four hours after topical loading of 0, 0.5, 0.75, and 1 M MnCl₂, T₁‐weighted, T2‐weighted, diffusion tensor imaging and visual acuity (VA) assessments were performed to determine the best topical loading dosage for MEMRI measurements and to assess the integrity of retinas and optic nerves. Mice were perfusion fixed immediately after in vivo experiments for hematoxylin and eosin and immunohistochemistry staining. Topical loading of 1 M MnCl₂ damaged the retinal photoreceptor layer with no detectable damage to retina ganglion cell layers or prechiasmatic optic nerves. For the topical loading, 0.75 M MnCl₂ was required to see sufficient enhancement of the optic nerve. At this concentration the visual function was significantly affected, followed by a slow recovery. Intravitreal injection (0.25 μL of 0.2 M MnCl₂) slightly affected VA, with full recovery a day later. To conclude, intravitreal MnCl₂injection provides more reproducible results with less adverse side‐effects than topical loading. Copyright © 2014 John Wiley & Sons, Ltd.     

Fractionated manganese-enhanced MRI

We investigated the use of manganese-enhanced MRI (MEMRI) with fractionated doses as a way to retain the unique properties of manganese as a neuronal contrast agent while lessening its toxic effects in animals. First, we followed the signal enhancement on T1-weighted images of the brains of rats receiving 30 mg/kg fractions of MnCl2 . 4H2O every 48 h and found that the signal increased in regions with consecutive fractionated doses and ultimately saturated. Second, we used T1 mapping to test whether the amount of MRI-visible manganese that accumulated depended on the concentration of manganese in the fractions. For a fixed cumulative dose of 180 mg/kg MnCl2 . 4H2O, increasing fraction doses of 6 x 30 mg/kg, 3 x 60 mg/kg, 2 x 90 mg/kg and 1 x 180 mg/kg produced progressively shorter T1 values. The adverse systemic health effects, including complications at the injection site and poor animal well-being, also rose with the fraction dose. Thus, fractionated MEMRI can be used to balance the properties of manganese as a contrast agent in animals against its toxic effects.     

Regional specificity of manganese accumulation and clearance in the mouse brain: implications for manganese‐enhanced MRI

Manganese‐enhanced MRI has recently become a valuable tool for the assessment of in vivo functional cerebral activity in animal models. As a result of the toxicity of manganese at higher dosages, fractionated application schemes have been proposed to reduce the toxic side effects by using lower concentrations per injection. Here, we present data on regional‐specific manganese accumulation during a fractionated application scheme over 8 days of 30 mg/kg MnCl₂, as well as on the clearance of manganese chloride over the course of several weeks after the termination of the whole application protocol supplying an accumulative dose of 240 mg/kg MnCl₂. Our data show most rapid accumulation in the superior and inferior colliculi, amygdala, bed nucleus of the stria terminalis, cornu ammonis of the hippocampus and globus pallidus. The data suggest that no ceiling effects occur in any region using the proposed application protocol. Therefore, a comparison of basal neuronal activity differences in different animal groups based on locally specific manganese accumulation is possible using fractionated application. Half‐life times of manganese clearance varied between 5 and 7 days, and were longest in the periaqueductal gray, amygdala and entorhinal cortex. As the hippocampal formation shows one of the highest T₁‐weighted signal intensities after manganese application, and manganese‐induced memory impairment has been suggested, we assessed hippocampus‐dependent learning as well as possible manganese‐induced atrophy of the hippocampal volume. No interference of manganese application on learning was detected after 4 days of Mn²⁺ application or 2 weeks after the application protocol. In addition, no volumetric changes induced by manganese application were found for the hippocampus at any of the measured time points. For longitudinal measurements (i.e. repeated manganese applications), a minimum of at least 8 weeks should be considered using the proposed protocol to allow for sufficient clearance of the paramagnetic ion from cerebral tissue. Copyright © 2012 John Wiley & Sons, Ltd.     

Infusion-based manganese-enhanced MRI: a new imaging technique to visualize the mouse brain

Manganese-enhanced magnetic resonance imaging is a technique that employs the divalent ion of the paramagnetic metal manganese (Mn²⁺) as an effective contrast agent to visualize, in vivo, the mammalian brain. As total achievable contrast is directly proportional to the net amount of Mn²⁺ accumulated in the brain, there is a great interest in optimizing administration protocols to increase the effective delivery of Mn²⁺ to the brain while avoiding the toxic effects of Mn²⁺ overexposure. In this study, we investigated outcomes following continuous slow systemic infusion of manganese chloride (MnCl₂) into the mouse via mini-osmotic pump administration. The effects of increasing fractionated rates of Mn²⁺ infusion on signal enhancement in regions of the brain were analyzed in a three-treatment study. We acquired whole-brain 3-D T1-weighted images and performed region of interest quantitative analysis to compare mean normalized signal in Mn²⁺ treatments spanning 3, 7, or 14 days of infusion (rates of 1, 0.5, and 0.25 μL/h, respectively). Evidence of Mn²⁺ transport at the conclusion of each infusion treatment was observed throughout the brains of normally behaving mice. Regions of particular Mn²⁺ accumulation include the olfactory bulbs, cortex, infralimbic cortex, habenula, thalamus, hippocampal formation, amygdala, hypothalamus, inferior colliculus, and cerebellum. Signals measured at the completion of each infusion treatment indicate comparable means for all examined fractionated rates of Mn²⁺ infusion. In this current study, we achieved a significantly higher dose of Mn²⁺ (180 mg/kg) than that employed in previous studies without any observable toxic effects on animal physiology or behavior.     

Accurate identification of myocardial viability after myocardial infarction with novel manganese chelate‐based MR imaging

We developed a novel manganese (Mn²⁺) chelate for magnetic resonance imaging (MRI) assessment of myocardial viability in acute and chronic myocardial infarct (MI) models, and compared it with Gadolinium‐based delay enhancement MRI (Gd³⁺‐DEMRI) and histology. MI was induced in 14 rabbits by permanent occlusion of the left circumflex coronary artery. Gd³⁺‐DEMRI and Mn²⁺ chelate‐based delayed enhancement MRI (Mn²⁺ chelate‐DEMRI) were performed at 7 days (acute MI, n = 8) or 8 weeks (chronic MI, n = 6) after surgery with sequential injection of 0.15 mmol/kg Gd³⁺ and Mn²⁺ chelate. The biodistribution of Mn²⁺ in tissues and blood was measured at 1.5 and 24 h. Blood pressure, heart rate (HR), left ventricular (LV) function, and infarct fraction (IF) were analyzed, and IF was compared with the histology. The Mn²⁺ chelate group maintained a stable hemodynamic status during experiment. For acute and chronic MI, all rabbits survived without significant differences in HR or LV function before and after injection of Mn²⁺ chelate or Gd³⁺ (p > 0.05). Mn²⁺ chelate mainly accumulated in the kidney, liver, spleen, and heart at 1.5 h, with low tissue uptake and urine residue at 24 h after injection. In the acute MI group, there was no significant difference in IF between Mn²⁺ chelate‐DEMRI and histology (22.92 ± 2.21% vs. 21.79 ± 2.25%, respectively, p = 0.87), while Gd³⁺‐DEMRI overestimated IF, as compared with histology (24.54 ± 1.73%, p = 0.04). In the chronic MI group, there was no significant difference in IF between the Mn²⁺ chelate‐DEMRI, Gd³⁺‐DEMRI, and histology (29.50 ± 11.39%, 29.95 ± 9.40%, and 29.00 ± 10.44%, respectively, p > 0.05), and all three were well correlated (r = 0.92–0.96, p < 0.01). We conclude that the use of Mn²⁺ chelate‐DEMRI is reliable for MI visualization and identifies acute MI more accurately than Gd³⁺‐DEMRI.     

MEMRI and tumors: a method for the evaluation of the contribution of Mn(II) ions in the extracellular compartment

The purpose of the work was to set‐up a simple method to evaluate the contribution of Mn²⁺ ions in the intra‐ and extracellular tumor compartments in a MEMRI experiment. This task has been tackled by “silencing” the relaxation enhancement arising from Mn²⁺ ions in the extracellular space. In vitro relaxometric measurements allowed assessment of the sequestering activity of DO2A (1,4,7,10‐tetraazacyclododecane‐1,7‐diacetic acid) towards Mn²⁺ ions, as the addition of Ca‐DO2A to a solution of MnCl₂ causes a drop of relaxivity upon the formation of the highly stable and low‐relaxivity Mn‐DO2A. It has been proved that the sequestering ability of DO2A towards Mn²⁺ ions is also fully effective in the presence of serum albumin. Moreover, it has been shown that Mn‐DO2A does not enter cell membranes, nor does the presence of Ca‐DO2A in the extracellular space prompt migration of Mn ions from the intracellular compartment. On this basis the in vivo, instantaneous, drop in SE% (percent signal enhancement) in T₁‐weighted images is taken as evidence of the sequestration of extracellular Mn²⁺ ions upon addition of Ca‐DO2A. By applying the method to B16F10 tumor bearing mice, T₁ decrease is readily detected in the tumor region, whereas a negligible change in SE% is observed in kidneys, liver and muscle. The relaxometric MRI results have been validated by ICP‐MS measurements. Copyright © 2015 John Wiley & Sons, Ltd.     

Testing the calcium hypothesis of aging in the rat hippocampus in vivo using manganese-enhanced MRI

In this study, we noninvasively tested the hypothesis that Mn²⁺-enhanced magnetic resonance imaging (MEMRI) is sensitive to age-related changes in Ca²⁺ influx occurring in the hippocampal region CA1. Uptake of Mn²⁺, an MRI contrast agent and Ca²⁺ surrogate with low cellular efflux rates (days to weeks), was measured in longitudinal MEMRI studies involving 2 separate groups of male Long-Evans rats: one group was studied at 2.5 and 7 months of age, whereas the other was studied at 7 and 19 months of age. Separate or combined analysis revealed that the extent of Mn²⁺ accumulation in CA1 significantly increased with age (p < 0.05). These results provide first-time in vivo confirmation of the calcium hypothesis of aging and justify future longitudinal studies combining MEMRI with behavioral testing to investigate mechanisms of age-related cognitive decline.     

Interaction of divalent metal ions with poly(riboinosinic acid)

Methods of differential UV and visible spectroscopy are used to study the interaction of Mg²⁺, Ca²⁺, Mn²⁺ and Cu²⁺ ions with four (4×I)‐ and single‐stranded poly I in solutions with 1 mol·l^–1 Na⁺. Up to concentrations of about 0.1 mol·l^–1 Mt²⁺, Mg²⁺ and Ca²⁺ ions do not bind to heteroatoms of hypoxanthine of 4×I. Cu²⁺ ions interact with N7 and/or N1 and possibly with O6 through the water molecule of the hydrate shell of the ion. It is likely that the interaction with O6 causes enolization of the hypoxanthine, N1 deprotonation and, as a result, this leads to the melting of the four‐stranded helix. In single‐stranded chains, Cu²⁺ ions induce the formation of compact particles which have the effective radii r_e ≈ 100 Å. The Mn²⁺‐induced differential spectra are similar to those observed in the presence of Cu²⁺ ions but in the case of Mn²⁺ they occur at concentrations about two orders of magnitude higher. In contrast to the positive cooperativity of the Cu²⁺ binding to bases of single‐stranded poly I, their interaction with 4×I has the negative cooperativity.     

Lingo‐1 Inhibited by RNA Interference Promotes Functional Recovery of Experimental Autoimmune Encephalomyelitis

Lingo‐1 is a negative regulator of myelination. Repairment of demyelinating diseases, such as multiple sclerosis (MS)/experimental autoimmune encephalomyelitis (EAE), requires activation of the myelination program. In this study, we observed the effect of RNA interference on Lingo‐1 expression, and the impact of Lingo‐1 suppression on functional recovery and myelination/remyelination in EAE mice. Lentiviral vectors encoding Lingo‐1 short hairpin RNA (LV/Lingo‐1‐shRNA) were constructed to inhibit Lingo‐1 expression. LV/Lingo‐1‐shRNA of different titers were transferred into myelin oligodendrocyte glycoprotein‐induced EAE mice by intracerebroventricular (ICV) injection. Meanwhile, lentiviral vectors carrying nonsense gene sequence (LVCON053) were used as negative control. The Lingo‐1 expression was detected and locomotor function was evaluated at different time points (on days 1,3,7,14,21, and 30 after ICV injection). Myelination was investigated by luxol fast blue (LFB) staining.LV/Lingo‐1‐shRNA administration via ICV injection could efficiently down‐regulate the Lingo‐1 mRNA and protein expression in EAE mice on days 7,14,21, and 30 (P < 0.01), especially in the 5 × 10⁸ TU/mL and 5 × 10⁹ TU/mL LV/Lingo‐1‐shRNA groups. The locomotor function score in the LV/Lingo‐1‐shRNA treated groups were significantly lower than the untreated or LVCON053 group from day 7 on. The 5 × 10⁸ TU/mL LV/Lingo‐1‐shRNA group achieved the best functional improvement (0.87 ± 0.11 vs. 3.05 ± 0.13, P < 0.001). Enhanced myelination/remyelination was observed in the 5 × 10⁷, 5 × 10⁸, 5 × 10⁹ TU/mL LV/Lingo‐1‐shRNA groups by LFB staining (P < 0.05, P < 0.01, and P < 0.05).The data showed that administering LV/Lingo‐1‐shRNA by ICV injection could efficiently knockdown Lingo‐1 expression in vivo, improve functional recovery and enhance myelination/remyelination. Antagonism of Lingo‐1 by RNA interference is, therefore, a promising approach for the treatment of demyelinating diseases, such as MS/EAE. Anat Rec, 297:2356–2363, 2014. © 2014 Wiley Periodicals, Inc.     

Manganese‐enhanced MRI optic nerve tracking: effect of intravitreal manganese dose on retinal toxicity

The aim of this study was to provide data on the dose dependence of manganese‐enhanced MRI (MEMRI) in the visual pathway of experimental rats and to study the toxicity of MnCl₂ to the retina. Sprague–Dawley rats were intravitreally injected with 2 μL of 0, 10, 25, 50, 75, 100, 150 and 300 mm MnCl₂, respectively_. The contrast‐to‐noise ratio (CNR) of MEMRI for optic nerve enhancement was measured at different concentrations of MnCl₂. Simultaneously, the toxicity of manganese was evaluated by counting retinal ganglion cells and by retinal histological examination using light microscopy and transmission electron microscopy. The CNR increased with increasing concentration of MnCl₂ up to 75 mm . Retinal ganglion cell densities were reduced significantly when the concentration of MnCl₂ in the intravitreal injection was equal to or greater than 75 mm . Increasing numbers of ribosomes in retinal ganglion cells were first detected at 25 mm of MnCl₂. The retinal toxicity of MnCl₂ at higher concentration also included mitochondrial pathology and cell disruption of retinal ganglion cells, as well as abnormalities of photoreceptor and retinal pigment epithelium cells. It can be concluded that intravitreal injection of MnCl₂ induces retinal cell damage that appears to start from 25 mm . The concentration of MnCl₂ should not exceed 25 mm through intravitreal injection for visual pathway MEMRI in the rat. Copyright © 2012 John Wiley & Sons, Ltd.     

Kinetic Peculiarities of Ethylene Polymerization over Homogeneous Bis(imino)pyridine Fe(II) Catalysts with Different Activators

Summary: Method of polymerization inhibition by radioactive carbon monoxide (¹⁴CO) has been used to determine the number of active centers (C_P) and propagation rate constant (k_P) for ethylene polymerization with homogeneous complex 2,6‐(2,6‐(Me)₂C₆H₃NCMe)₂C₅H₃NFeCl₂ (LFeCl₂), activated with methylalumoxane (MAO) or Al(i‐Bu)₃. With both activators the rate profile of polymerization was unstable: high activity [0.8 × 10³–1.5 × 10³ kg PE per (mol_Fe · h · atm) at 35 °C] of the initial period sharply decreases (sevenfold in 10 min). In the beginning of polymerization with the catalysts LFeCl₂/MAO and LFeCl₂/Al(i‐Bu)₃, the C_P values were found to be 8 and 41% of total Fe‐complex content in catalysts, respectively, and decreased 1.5–2‐fold in 9 min. As polymerization proceeds, the k_P value for LFeCl₂/MAO system decreases from 5 × 10⁴ to 1.5 × 10⁴ L · (mol · s)⁻¹ LFeCl₂/MAO, and for LFeCl₂/Al(i‐Bu)₃ system from 2.6 × 10⁴ to 0.82 × 10⁴ L · (mol · s)⁻¹. Data on the effect of polymerization time on polyethylene molar mass distribution are presented. Basing on the obtained results it was suggested that highly reactive, but unstable centers, dominating at short polymerization times, produce low‐molar‐mass polyethylene, while polyethylene with higher molar mass is produced by less active (low k_P) and more stable centers.

Data showing change in molar mass distribution of polyethylene with polymerization time.     

Immunologic induction of reticulum cell sarcoma: donor-type lymhomas in the graft-versus-host model

The aim of this study was to investigate malignant lymphomas of donor origin induced in F₁ mice undergoing a chronic graft-versus-host reaction (GVHR) after injection of parental strain spleen cells. A total of 3 × 10⁸ or 4 × 10⁸ C57BL/10 spleen cells were administered to 7—8-week-old H-2 incompaltible (C57BL/10 × HTG)F₁ hybrids either as single or fractionated i.p. injections. Recipients were killed at intervals ranging from 1 month to 1 year after the first injection and their lymphoid cells typed for host-derived and donor-derived histocompatibility antigens. In 49 % of the 88 GVH F₁ mice, cells failed to be killed by a hyperimmune serum against HTG (H-2^g) but reacted normally with antisera to C57BL/10(H-2^b) and, in the 9 cases tested, to theta-C3H. The conclusion that the lymphoid cells of these mice were derived from donor cells was supported by the finding that these amimals lacked immunoglobulins bearing host-derived Ig^a allotype in their serum. Forty-three percent of the GVH F₁ mice developed reticulum cell sarcomas (RCS), 32 % revealed hyperplasticlymphoreticular tissue, and 25 % showed no grossly abnormal changes. Mice with donor-typelymphoid tissues were found in all three groups; 50 % of the 38 RCS detected were donor-type neoplasms. The induction of donor-type RCS during the GVHR strengthens the concept of lymphomagenesis through persistent stimulation with antigen(s).     

A Genome‐Wide Search for Type 2 Diabetes Susceptibility Genes in an Extended Arab Family

Twenty percent of people aged 20 to 79 have type 2 diabetes (T2D) in the United Arab Emirates (UAE). Genome‐wide association studies (GWAS) to identify genes for T2D have not been reported for Arab countries. We performed a discovery GWAS in an extended UAE family (N = 178; 66 diabetic; 112 healthy) genotyped on the Illumina Human 660 Quad Beadchip, with independent replication of top hits in 116 cases and 199 controls. Power to achieve genome‐wide significance (commonly P = 5 × 10^?8) was therefore limited. Nevertheless, transmission disequilibrium testing in FBAT identified top hits at Chromosome 4p12‐p13 (KCTD8: rs4407541, P = 9.70 × 10^?6; GABRB1: rs10517178/rs1372491, P = 4.19 × 10^?6) and 14q13 (PRKD1: rs10144903, 3.92 × 10^?6), supported by analysis using a linear mixed model approximation in GenABEL (4p12‐p13 GABRG1/GABRA2: rs7662743, P_adj‐agesex = 2.06 × 10^?5; KCTD8: rs4407541, P_adj‐agesex = 1.42 × 10^?4; GABRB1: rs10517178/rs1372491, P_adj‐agesex = 0.027; 14q13 PRKD1: rs10144903, P_adj‐agesex = 6.95 × 10^?5). SNPs across GABRG1/GABRA2 did not replicate, whereas more proximal SNPs rs7679715 (P_adj‐agesex = 0.030) and rs2055942 (P_adj‐agesex = 0.022) at COX7B2/GABRA4 did, in addition to a trend distally at KCTD8 (rs4695718: P_adj‐agesex = 0.096). Modelling of discovery and replication data support independent signals at GABRA4 (rs2055942: P_{adj‐agesex‐combined} = 3 × 10^?4) and at KCTD8 (rs4695718: P_{adj‐agesex‐combined} = 2 × 10^?4). Replication was observed for PRKD1 rs1953722 (proxy for rs10144903; P_adj‐agesex = 0.031; P_{adj‐agesex‐combined} = 2 × 10^?4). These genes may provide important functional leads in understanding disease pathogenesis in this population.     

Semiconducting Oligo‐(Aryleneethynylene)s with Coplanarity of Main Chain and Tetrathiafulvalene (TTF) Side Chains: Synthesis,Self‐Assembly,and Conductive Properties

Two oligo‐(aryleneethynylene)s, with coplanarity of main chain and tetrathiafulvalene (TTF) side chains, have been prepared and characterized. The X‐ray diffractions (XRDs) show that their π‐extended coplanar backbones can form continuous π‐stacking. For the two oligomers, one stacks in the inter‐digitation packing mode; another stacks in the end‐to‐end packing mode. Cyclic voltammetries reveal that the two oligomers have almost the same reversible electroactive properties. The TTF units of the two oligomers can be oxidized to TTF ^{. 1+} by Fe(bpy)₃(PF₆)₃ (bpy = 2,2′‐bipyridine). The band gaps, deduced from UV‐Vis absorption spectra, are 1.92 and 2.03 eV, respectively. The conductivities of the two oligomers are 1 × 10^?5 and 6 × 10^?8 S · cm^?1 at room temperature. The charge transfer (CT) complexes of the oligomers and tetracyanoquinodimethane (TCNQ) exhibit higher conductivity up to 0.2 S · cm^?1.

     

The distribution of Mn2+ in rabbit eyes after topical administration for manganese-enhanced MRI

Purpose: To analyze the distribution of Mn²⁺ in rabbit eyes after topical administration of Mncl₂ for manganese-enhanced MRI. Methods: Forty-eight Chinese white rabbits were divided into three groups. In group 1 (n = 4), the baseline concentration of Mn²⁺ in aqueous, vitreous and serum samples were analyzed. In group 2 and 3, the rabbits received one topical instillation (20 μL) of Mncl₂ (1 mol•L^-1). In group 2 (n = 40), aqueous, vitreous and serum samples were collected and analyzed at predetermined time points (0.5, 1, 2, 4, 6, 12, 24, 48, 72 and 168 hours postdose). Assays were performed using inductively coupled plasma-mass spectrometer (ICP-MS). In group 3 (n = 4), after topical administration of Mncl₂, dynamic manganese-enhanced MRI (MEMRI) was performed at predetermined time points. The signal-to-noise ratio (SNR) was calculated to evaluate the enhancements of eyes. Results: After topical administration, the maximum concentrations of Mn²⁺ in the aqueous and vitreous samples were 11.1641 ± 0.7202 (2 hours) and 1.5622 ± 0.1567 (12 hours). In group 3, the maximum enhancement of aqueous humor (SNR = 108.81 ± 10.65) appeared at 2 hours postdose, whereas, no significant changes were detected in vitreous. Conclusion: Mn²⁺ could distribute into aqueous humor rapidly after topical administration of Mncl₂, whereas, the concentration of Mn²⁺ in vitreous body fluctuated in a narrow range over the course. The uptake of Mn²⁺ in retina may involve several different pathways.     

Orotracheal manganese‐enhanced MRI (MEMRI): An effective approach for lung tumor detection

Lung cancer is a primary cause of cancer deaths worldwide. Timely detection of this pathology is necessary to delay or interrupt lung cancer progression, ultimately resulting in a possible better prognosis for the patient. In this context, magnetic resonance imaging (MRI) is especially promising. Ultra‐short echo time (UTE) MRI sequences, in combination with gadolinium‐based contrast agents, have indeed shown to be especially adapted to the detection of lung neoplastic lesions at submillimeter precision. Manganese‐enhanced MRI (MEMRI) increasingly appears to be a possible effective alternative to gadolinium‐enhanced MRI. In this work, we investigated whether low‐dose MEMRI can effectively target non‐small‐cell lung cancer in rodents, whilst minimizing the potential toxic effect of manganese. Both systemic and orotracheal administration modalities allowed the identification of tumors of submillimeter size, as confirmed by bioluminescence imaging and histology. Equivalent tumor signal enhancements and contrast‐to‐noise ratios were observed with orotracheal administration using 20 times lower doses compared with the more conventional systemic route. This finding is of crucial importance as it supports the observation that higher performances of contrast agents can be obtained using an orotracheal administration route when targeting lung diseases. As a consequence, lower concentrations of contrast media can be employed, reducing the dose and potential safety issues. The non‐detectable accumulation of ionic manganese in the brain and liver following orotracheal administration observed in vivo is extremely encouraging with regard to the safety of the orotracheal protocol with low‐dose Mn²⁺ administration. To our knowledge, this is the first time that a study has clearly allowed the high‐precision detection of lung tumor and its contours via the synergic employment of a strongly T₁‐weighted MRI UTE sequence and ionic manganese, an inexpensive contrast agent. Overall, these results support the growing interest in drug and contrast agent delivery via the airways to target and diagnose several diseases of the lungs.