Ultrasmall MnSe Nanoparticles as T1-MRI Contrast Agents for In Vivo Tumor Imaging.

Magnetic resonance imaging (MRI) has excellent potential in the clinical monitoring of tumors because it can provide high-resolution soft tissue imaging. However, commercial contrast agents (CAs) used in MRI still have some problems such as potential toxicity to the human body, low relaxivity, and a short MRI acquisition window. In this study, ultrasmall MnSe nanoparticles are synthesized by living Staphylococcus aureus cells. The as-prepared MnSe nanoparticles are monodispersed with a uniform particle size (3.50 ± 0.52 nm). Due to the ultrasmall particle size and good water solubility, the MnSe nanoparticles exhibit in vitro high longitudinal relaxivity properties (14.12 ± 1.85 mM-1·s-1). The CCK-8 colorimetric assay, histological analysis, and body weight results show that the MnSe nanoparticles do not have appreciable toxicity on cells and organisms. Besides, the MnSe nanoparticles as T1-MRI CAs offer a long MRI acquisition window to tumor imaging (∼7 h). This work provides a promising T1-MRI CA for clinical tumor imaging and a good reference for the application of functional MnSe nanoparticles in the biomedicine field.

Manganese (II) chloride leads to dopaminergic neurotoxicity by promoting mitophagy through BNIP3-mediated oxidative stress in SH-SY5Y cells.

BACKGROUND: Manganese overexposure can induce neurotoxicity, lead to manganism and result in clinical manifestations similar to those of parkinsonism. However, the underlying molecular mechanism is still unclear. This study demonstrated that MnCl2 induces mitophagy and leads to neurotoxicity by promoting BNIP3-mediated reactive oxygen species (ROS) generation. METHODS: Human neuroblastoma SH-SY5Y cells were used throughout our experiments. Cell viability was detected by cell proliferation/toxicity test kits. Mitochondrial membrane potential was measured by flow cytometry. ROS generation was detected using a microplate reader. Protein levels were evaluated by Western blot. Transmission electron microscopy was used to evaluate mitochondrial morphology. Co-immunoprecipitation was used to verify the interaction between BNIP3 and LC3. RESULTS: MnCl2 led to loss of mitochondrial membrane potential and apoptosis of SH-SY5Y cells by enhancing expression of BNIP3 and conversion of LC3-I to LC3-II. Moreover, MnCl2 reduced expression of the mitochondrial marker protein TOMM20 and promoted interaction between BNIP3 and LC3. The results also indicated that a decrease in BNIP3 expression reduced the mitochondrial membrane potential loss, attenuated apoptosis and reduced mitochondrial autophagosome formation in SH-SY5Y cells after MnCl2 treatment. Finally, we found that manganese-induced ROS generation could be reversed by the antioxidant N-acetyl cysteine (NAC) or silencing BNIP3 expression. CONCLUSIONS: BNIP3 mediates MnCl2-induced mitophagy and neurotoxicity in dopaminergic SH-SY5Y cells through ROS. Thus, BNIP3 contributes to manganese-induced neurotoxicity by functioning as a mitophagy receptor protein.

Low-Dose Radiation Exposure with 56MnO2 Powder Changes Gene Expressions in the Testes and the Prostate in Rats.

To investigate the biological effects of internal exposure of radioactive 56MnO2 powder, the major radioisotope dust in the soil after atomic bomb explosions, on male reproductive function, the gene expression of the testes and the prostate was examined. Ten-week-old male Wistar rats were exposed to three doses of radioactive 56MnO2 powder (41-100 mGy in whole body doses), stable MnO2 powder, or external 60Co γ-rays (2 Gy). Animals were necropsied on Days 3 and 61 postexposure. The mRNA expressions of testicular marker protein genes and prostatic secretory protein genes were quantified by Q-RT-PCR. On Day 3 postexposure, the testicular gene expressions of steroidogenesis-related enzymes, Cyp17a1 and Hsd3b1, decreased in 56MnO2-exposed groups. Germ cell-specific Spag4 and Zpbp mRNA levels were also reduced. On postexposure Day 61, the Cyp11a1 gene expression became significantly reduced in the testes in the group exposed to the highest dose of 56MnO2, while another steroidogenesis-related StAR gene mRNA level reduced in the 60Co γ-rays group. There were no differences in Spag4 and Zpbp mRNA levels among groups on Day 61. No histopathological changes were observed in the testes in any group following exposure. Expression in the prostatic protein genes, including CRP1, KS3, and PSP94, significantly decreased in 56MnO2-exposed groups as well as in the 60Co γ-rays group on Day 61 postexposure. These data suggest that the internal exposure to 56MnO2 powder, at doses of less than 100 mGy, affected the gene expressions in the testis and the prostate, while 2 Gy of external γ-irradiation was less effective.

Patch Testing With an Extended Metal Allergen Series at the Massachusetts General Hospital (2006-2017).

BACKGROUND: Reports of patch test data with an extended metal series that includes rare metals are limited. OBJECTIVE: The aims of the study were to analyze and report patch testing results from an extended metal series, examine associations with sex and age, and highlight concomitant metal reactions. METHODS: This study is a retrospective review of 150 patients referred for suspected metal allergy from January 1, 2007, to December 31, 2016. RESULTS: The most common indications for evaluation referral were those having symptoms after implantation of a metal device (55.3%) and those with a history and concern of metal allergy before implantation of a metal device (22.0%). One or more positive patch test reactions were observed in 87 patients (58.0%). Metals with the highest frequencies were nickel sulfate 2.5% (26.2%), gold sodium thiosulfate 0.5% (23.0%), gold sodium thiosulfate 2.0% (20.7%), palladium chloride 2.0% (19.6%), cobalt chloride 1.0% (12.0%), and manganese chloride 2.0% (10.1%). Of the 45 metals tested, 15 caused no patch test reactions. Female patients were more likely to be sensitized to nickel, gold, and palladium (P < 0.05). Younger patients (≤40 years) had higher reaction rates to nickel, mercury, palladium, and cobalt. Concomitant reactions of the top metals (nickel, palladium, gold, and cobalt) were statistically associated bidirectionally (P < 0.05), except for cobalt and gold. CONCLUSIONS: Allergy to metals, including those not included in standard series, may be more prevalent than previously suspected. Results may help guide future testing for suspected metal allergy, although future studies are warranted.

Secretogranin III upregulation is involved in parkinsonian toxin-mediated astroglia activation.

Environmental neurotoxins such as paraquat (PQ), manganese, and 1-1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) are associated with a higher risk of Parkinson's disease (PD). These parkinsonian toxins exert certain common toxicological effects on astroglia; however, their role in the regulatory functions of astroglial secretory proteins remains unclear. In a previous study, we observed that secretogranin II (SCG2) and secretogranin III (SCG3), which are important components of the regulated secretory pathway, were elevated in PQ-activated U118 astroglia. In the current study, we used the parkinsonian toxins dopamine (DA), active metabolite of MPTP (MPP+), MnCl2, and lipopolysaccharide (LPS) as inducers, and studied the potential regulation of SCG2 and SCG3. Our results showed that all the parkinsonian toxins except LPS affected astroglial viability but did not cause apoptosis. Exposure to DA, MPP+, and MnCl2 upregulated glial fibrillary acidic protein (GFAP), a marker for astrocyte activation, and stimulated the levels of several astrocytic-derived factors. Further, DA, MPP+, and MnCl2 exposure impeded astroglial cell cycle progression. Moreover, the expression of SCG3 was elevated, while its exosecretion was inhibited in astroglia activated by parkinsonian toxins. The level of SCG2 remained unchanged. In combination with our previous findings, the results of this study indicate that SCG3 may act as a cofactor in astrocyte activation stimulated by various toxins, and the regulation of SCG3 could be involved in the toxicological mechanism by which parkinsonian toxins affect astroglia.

[An investigation of occupational exposure to welding fume, manganese, and manganese compounds in a large container manufacturing enterprise].

Objective: To investigate the current status of the occupational hazards of welding fume, manganese, and manganese compounds in the welding environment of a large container manufacturing enterprise, as well as the status of occupational health examination of workers, and to provide a basis for improving the welding environment of this enterprise. Methods: In August 2016, July 2017, and August 2018, convenience sampling was used to perform an on-site occupational hygiene survey of the welding workshop for three consecutive years, and welding fume, manganese and, manganese compounds (counted as manganese dioxide) were measured for their workplace exposure concentrations and exposure levels in workers. A comprehensive analysis was performed for the results of occupational health examination. Results: Welding fume, manganese, and manganese compounds in the welding environment gradually increased from 2016 to 2018 (χ(2)(trend)=5.14 and 5.54, P<0.05). The maximum over-standard rate of concentration-short term exposure limit was 43.3% (13/30) for welding fume and 40.0% (12/30) for manganese and its compounds, and the maximum over-standard rate of time-weighted average concentration was 26.7% (8/30) for welding fume and 23.3% (7/30) for manganese and its compounds. Abnormalities were observed in the occupational health examination of welding workers in 2016-2018, among which respiratory system abnormalities (cough, expectoration, and wheezing), nervous system abnormalities (dizziness, fatigue, sleep disorders, amnesia, hyperhidrosis, and palpitations), and electrocardiogram abnormalities (bundle conduction block) had an incidence rate of above 10.0%, and the incidence rate of abnormalities on posterior-anterior X-ray high-kV chest radiograph was close to 8.9% (30/336) . Conclusion: There is severe exposure to welding fume, manganese, and manganese compounds among workers in this enterprise, which cause great hazards to the health of workers. It is necessary to strengthen occupational health management, take measures to improve the welding environment, and enhance occupational disease prevention.

Composition-Tunable Ultrasmall Manganese Ferrite Nanoparticles: Insights into their In Vivo T1 Contrast Efficacy.

The development of a highly efficient, low-toxicity, ultrasmall ferrite nanoparticle-based T1 contrast agent for high-resolution magnetic resonance imaging (MRI) is highly desirable. However, the correlations between the chemical compositions, in vitro T1 relaxivities, in vivo nano-bio interactions and toxicities remain unclear, which has been a challenge in optimizing the in vivo T1 contrast efficacy. Methods: Ultrasmall (3 nm) manganese ferrite nanoparticles (MnxFe3-xO4) with different doping concentrations of the manganese ions (x = 0.32, 0.37, 0.75, 1, 1.23 and 1.57) were used as a model system to investigate the composition-dependence of the in vivo T1 contrast efficacy. The efficacy of liver-specific contrast-enhanced MRI was assessed through systematic multiple factor analysis, which included the in vitro T1 relaxivity, in vivo MRI contrast enhancement, pharmacokinetic profiles (blood half-life time, biodistribution) and biosafety evaluations (in vitro cytotoxicity testing, in vivo blood routine examination, in vivo blood biochemistry testing and H&E staining to examine the liver). Results: With increasing Mn doping, the T1 relaxivities initially increased to their highest value of 10.35 mM-1s-1, which was obtained for Mn0.75Fe2.25O4, and then the values decreased to 7.64 m M-1s-1, which was obtained for the Mn1.57Fe1.43O4 nanoparticles. Nearly linear increases in the in vivo MRI signals (ΔSNR) and biodistributions (accumulation in the liver) of the MnxFe3-xO4 nanoparticles were observed for increasing levels of Mn doping. However, both the in vitro and in vivo biosafety evaluations suggested that MnxFe3-xO4 nanoparticles with high Mn-doping levels (x > 1) can induce significant toxicity. Conclusion: The systematic multiple factor assessment indicated that the MnxFe3-xO4 (x = 0.75-1) nanoparticles were the optimal T1 contrast agents with higher in vivo efficacies for liver-specific MRI than those of the other compositions of the MnxFe3-xO4 nanoparticles. Our work provides insight into the optimization of ultrasmall ferrite nanoparticle-based T1 contrast agents by tuning their compositions and promotes the translation of these ultrasmall ferrite nanoparticles for clinical use of high-performance contrast-enhanced MRI.

Tau folding and cytotoxicity of neuroblastoma cells in the presence of manganese oxide nanoparticles: Biophysical, molecular dynamics, cellular, and molecular studies.

Manganese oxide nanoparticles (Mn2O3 NPs) have been widely used in the medical and biological applications. However, few studies have been undertaken to investigate the cytotoxicity of Mn2O3 NPs against nervous system. Herein, we studied the toxicity of Mn2O3 NPs against tau protein and neuroblastoma cells (SH-SY5Y) in vitro. Circular dichroism (CD) spectroscopy, fluorescence spectroscopy, molecular docking, and molecular dynamic studies were used to explore the conformational changes of protein. The cell-based experiments, such as viability, activation of caspases-3/9, apoptosis, and gene (Bax and Bcl-2) expression assays were performed in vitro. Spectroscopic methods and molecular dynamic studies revealed that Mn2O3 NPs can fold the structure of tau toward a more packed structure. The Mn2O3 NPs also decreased the cell viability in a dose-dependent manner. Indeed, caspase-3 and caspase-9 activation, Bax/Bcl-2 ratio elevation and apoptosis induction were observed after exposure of SH-SY5Y to Mn2O3 NPs. In conclusion, tau folding and cytotoxicity against SH-SY5Y cells may be involved in adverse effects induced by Mn2O3 NPs.

Internal exposure to neutron-activated 56Mn dioxide powder in Wistar rats-Part 2: pathological effects.

To fully understand the radiation effects of the atomic bombing of Hiroshima and Nagasaki among the survivors, radiation from neutron-induced radioisotopes in soil and other materials should be considered in addition to the initial radiation directly received from the bombs. This might be important for evaluating the radiation risks to the people who moved to these cities soon after the detonations and probably inhaled activated radioactive "dust." Manganese-56 is known to be one of the dominant radioisotopes produced in soil by neutrons. Due to its short physical half-life, 56Mn emits residual radiation during the first hours after explosion. Hence, the biological effects of internal exposure of Wistar rats to 56Mn were investigated in the present study. MnO2 powder was activated by a neutron beam to produce radioactive 56Mn. Rats were divided into four groups: those exposed to 56Mn, to non-radioactive Mn, to 60Co γ rays (2 Gy, whole body), and those not exposed to any additional radiation (control). On days 3, 14, and 60 after exposure, the animals were killed and major organs were dissected and subjected to histopathological analysis. As described in more detail by an accompanying publication, the highest internal radiation dose was observed in the digestive system of the rats, followed by the lungs. It was found that the number of mitotic cells increased in the small intestine on day 3 after 56Mn and 60Co exposure, and this change persisted only in 56Mn-exposed animals. Lung tissue was severely damaged only by exposure to 56Mn, despite a rather low radiation dose (less than 0.1 Gy). These data suggest that internal exposure to 56Mn has a significant biological impact on the lungs and small intestine.

Continuous infusion of manganese improves contrast and reduces side effects in manganese-enhanced magnetic resonance imaging studies.

The ability to administer systemically high doses of manganese as contrast agent while circumventing its toxicity is of particular interest for exploratory MRI studies of the brain. Administering low doses either repeatedly or continuously over time has been shown to enable the acquisition of satisfactory MRI images of the mouse brain without apparent side effects. Here we have systematically compared the obtained MRI contrast and recorded potential systemic side effects such as stress response and muscle strength impairment in relation to the achieved contrast. We show in mice that administering MnCl2 via osmotic infusion pumps allows for a side-effect free delivery of a high cumulative dose of manganese chloride (480mg/kg bodyweight in 8 days). High contrast in MRI was achieved while we did not observe the weight loss or distress seen in other studies where mice received manganese via fractionated intraperitoneal injections of lower doses of manganese. As the normal daily conduct of the mice was not affected, this new manganese delivery method might be of particular use to study brain activity over several days. This may facilitate the phenotyping of new transgenic mouse models, the study of chronic disease models and the monitoring of changes in brain activity in long-term behavioral studies.

Attenuation of Combined Nickel(II) Oxide and Manganese(II, III) Oxide Nanoparticles' Adverse Effects with a Complex of Bioprotectors.

Stable suspensions of NiO and Mn3O4 nanoparticles (NPs) with a mean (±s.d.) diameter of 16.7±8.2 and 18.4±5.4 nm, respectively, purposefully prepared by laser ablation of 99.99% pure nickel or manganese in de-ionized water, were repeatedly injected intraperitoneally (IP) to rats at a dose of 2.5 mg/kg 3 times a week up to 18 injections, either alone or in combination. A group of rats was injected with this combination with the background oral administration of a "bio-protective complex" (BPC) comprising pectin, vitamins A, C, E, glutamate, glycine, N-acetylcysteine, selenium, iodide and omega-3 PUFA, this composition having been chosen based on mechanistic considerations and previous experience. After the termination of injections, many functional and biochemical indices and histopathological features (with morphometric assessment) of the liver, spleen, kidneys and brain were evaluated for signs of toxicity. The Ni and Mn content of these organs was measured with the help of the atomic emission and electron paramagnetic resonance spectroscopies. We obtained blood leukocytes for performing the RAPD (Random Amplified Polymorphic DNA) test. Although both metallic NPs proved adversely bio-active in many respects considered in this study, Mn3O4-NPs were somewhat more noxious than NiO-NPs as concerns most of the non-specific toxicity manifestations and they induced more marked damage to neurons in the striatum and the hippocampus, which may be considered an experimental correlate of the manganese-induced Parkinsonism. The comparative solubility of the Mn3O4-NPs and NiO-NPs in a biological medium is discussed as one of the factors underlying the difference in their toxicokinetics and toxicities. The BPC has attenuated both the organ-systemic toxicity and the genotoxicity of Mn3O4-NPs in combination with NiO-NPs.

Melatonin inhibits manganese-induced motor dysfunction and neuronal loss in mice: involvement of oxidative stress and dopaminergic neurodegeneration.

Excessive manganese (Mn) induces oxidative stress and dopaminergic neurodegeneration. However, the relationship between them during Mn neurotoxicity has not been clarified. The purpose of this study was to investigate the probable role of melatonin (MLT) against Mn-induced motor dysfunction and neuronal loss as a result of antagonizing oxidative stress and dopaminergic neurodegeneration. Mice were randomly divided into five groups as follows: control, MnCl2, low MLT + MnCl2, median MLT + MnCl2, and high MLT + MnCl2. Administration of MnCl2 (50 mg/kg) for 2 weeks significantly induced hypokinesis, dopaminergic neurons degeneration and loss, neuronal ultrastructural damage, and apoptosis in the substantia nigra and the striatum. These conditions were caused in part by the overproduction of reactive oxygen species, malondialdehyde accumulation, and dysfunction of the nonenzymatic (GSH) and enzymatic (GSH-Px, superoxide dismutase, quinone oxidoreductase 1, glutathione S-transferase, and glutathione reductase) antioxidative defense systems. Mn-induced neuron degeneration, astrocytes, and microglia activation contribute to the changes of oxidative stress markers. Dopamine (DA) depletion and downregulation of DA transporter and receptors were also found after Mn administration, this might also trigger motor dysfunction and neurons loss. Pretreatment with MLT prevented Mn-induced oxidative stress and dopaminergic neurodegeneration and inhibited the interaction between them. As a result, pretreatment with MLT significantly alleviated Mn-induced motor dysfunction and neuronal loss. In conclusion, Mn treatment resulted in motor dysfunction and neuronal loss, possibly involving an interaction between oxidative stress and dopaminergic neurodegeneration in the substantia nigra and the striatum. Pretreatment with MLT attenuated Mn-induced neurotoxicity by means of its antioxidant properties and promotion of the DA system.

Manganese oxidation state as a cause of irritant patch test reactions.

BACKGROUND: Manganese chloride (MnCl2) 2.5% is included in the extended metals patch test series to evaluate patients for contact hypersensitivity to this metal salt. OBJECTIVES: The objective of this study was to prospectively determine the rate of allergic and irritant patch test reactions to MnCl2 (Mn(II)), Mn2O3 (Mn(III)), and KMnO4 (Mn(VII)) in a cohort of patients undergoing patch testing. METHODS: Fifty-eight patients were patch tested with MnCl2, Mn2O3, and KMnO4, each at 2.5% in petrolatum. Patch readings were taken at 48, and 72 or 96 hours, and scored using standard methods. Cultured monolayers of keratinocytes (KCs) were exposed to MnCl2, Mn2O3, and KMnO4 in aqueous culture medium, and cell survival and cytokine release were studied. CONCLUSIONS: MnCl2 caused irritant patch test reactions in 41% of the cohort, whereas Mn2O3 and KMnO4 caused a significantly lower rate of irritant reactions (both 3%). No allergic morphologies were observed. Similarly, in cultured KC monolayers, only MnCl2 was cytotoxic to KC and induced tumor necrosis factor α release.The oxidation state of manganese used for patch testing affects the irritancy of this metal salt, as Mn(II) caused an unacceptably high rate of irritant reactions in a cohort of patients. In vitro studies confirmed these clinical data, as only Mn(II) was cytotoxic to cultured monolayers of KC.

Understanding the metabolic fate and assessing the biosafety of MnO nanoparticles by metabonomic analysis.

Recently, some types of MnO nanoparticle (Mn-NP) with favorable imaging capacity have been developed to improve the biocompatible profile of the existing Mn-based MRI contrast agent Mn-DPDP; however, the overall bio-effects and potential toxicity remain largely unknown. In this study, (1)H NMR-based metabolic profiling, integrated with traditional biochemical analysis and histopathological examinations, was used to investigate the absorption, distribution, metabolism, excretion and toxicity of Mn-NPs as candidates for MRI contrast agent. The metabolic responses in biofluids (plasma and urine) and tissues (liver, spleen, kidney, lung and brain) from rats could be divided into four classes following Mn-NP administration: Mn biodistribution-dependent, time-dependent, dose-dependent and complicated metabolic variations. The variations of these metabolites involved in lipid, energy, amino acid and other nutrient metabolism, which disclosed the metabolic fate and biological effects of Mn-NPs in rats. The changes of metabolic profile implied that the disturbance and impairment of biological functions induced by Mn-NP exposure were correlated with the particle size and the surface chemistry of nanoparticles. Integration of metabonomic technology with traditional methods provides a promising tool to understand the toxicological behavior of biomedical nanomaterials and will result in informed decision-making during drug development.

Ocular integrity following manganese labeling of the visual system for MRI.

Injection of manganese into the eye will enhance the contrast of visual system neuronal pathways imaged by MRI (MEMRI). The present study was undertaken to determine the effect of a range of MnCl2 doses upon the integrity of various ocular structures. Anesthetized mice received ocular anterior chamber injections of 50-500 nmol of MnCl2. One week later, the eyes were fixed, embedded in paraffin, sectioned, and stained with hematoxylin and eosin. Additional animals received 50 nmol of MnCl2 injected into the anterior chamber and were later imaged using T1-weighted 7T MRI. Following 500 and 300nmol MnCl2, the corneal stroma and endothelium were degenerated, the anterior chamber contained a dense fibrin matrix with extensive inflammatory cell infiltration, a plaque often formed on the anterior lens, and significant retinal degeneration was observed. Following 100nmol MnCl2, retinal preservation of ocular structures was significantly better than at higher doses. In addition, there was no difference from vehicle control retina in cell counts within the ganglion cell layer, or in the width of the inner nuclear layer or outer nuclear layer. Also, there was no difference in the thickness of the inner plexiform layer. However, there was thinning of the peripheral outer plexiform layer, as well as in the outer segment layer. Visual system elements labeled in MRI of mice that received 100nmol MnCl2 included the retina, optic nerve, lateral geniculate nucleus, and superior colliculus. The preservation of ganglion cell layer cell counts and inner plexiform layer thickness following 100nmol MnCl2 suggests there was negligible injury to RGCs following this dose. These results support using 100nmol MnCl2 in mouse eyes for in vivo assessment of the integrity of RGC projections to target neurons in the brain.

Mn-citrate and Mn-HIDA: intermediate-affinity chelates for manganese-enhanced MRI.

In this study we investigated two manganese chelates in order to improve the image enhancement of manganese-enhanced MRI and decrease the toxicity of free manganese ions. Since both MnCl2 and a low-affinity chelate were associated with a slow continuous decrease of cardiac functions, we investigated intermediate-affinity chelates: manganese N-(2-hydroxyethyl)iminodiacetic acid (Mn-HIDA) and Mn-citrate. The T1 relaxivity values for Mn-citrate (4.4 m m⁻¹ s⁻¹) and Mn-HIDA (3.3 m m⁻¹ s⁻¹) in artificial cerebrospinal fluid (CSF) were almost constant in a concentration range from 0.5 to 5 m m at 37 °C and 4.7 T. In human plasma, the relaxivity values increased when the concentrations of these Mn chelates were decreased, suggesting the presence of free Mn²âº bound with serum albumin. Mn-HIDA and Mn-citrate demonstrated a tendency for better contractility when employed with an isolated perfused frog heart, compared with MnCl2. Only minimal changes were demonstrated after a venous infusion of 100 m m Mn-citrate or Mn-HIDA (8.3 µmol kg⁻¹ min⁻¹) in rats and a constant heart rate, arterial pressure and sympathetic nerve activity were maintained, even after breaking the blood-brain barrier (BBB). Mn-citrate and Mn-HIDA could not cross the intact BBB and appeared in the CSF, and then diffused into the brain parenchyma through the ependymal layer. The responses in the supraoptic nucleus induced by the hypertonic stimulation were detectable. Therefore, Mn-citrate and Mn-HIDA appear to be better choices for maintaining the vital conditions of experimental animals, and they may improve the reproducibility of manganese-enhanced MRI of the small nuclei in the hypothalamus and thalamus.

Effect of divalent metals on the neuronal proteasomal system, prion protein ubiquitination and aggregation.

The role of normal cellular prion protein (PrP) remains to be fully elucidated; however, the protein is crucial for the infection and progression of prion diseases. Recent evidence indicates that PrP is a metalloprotein since the octapeptide repeat sequences in the protein have high affinity for various divalent cations and the binding sites appear to play a role in the pathogenesis of prion diseases. In our present study, we tested several divalent metals including manganese and cadmium and determined their effects on protein degradation and protein aggregation in mouse neuronal cells expressing PrP. Cadmium was more neurotoxic than manganese following 24h exposure. Manganese did not show any significant effect on the inhibition of proteasomal activity or formation of high molecular weight ubiquitinated PrPs. Interestingly, treatment with cadmium profoundly inhibited proteasomal activity, which resulted in greatly increased formation of high molecular weight ubiquitinated PrPs. Immunohistochemical analysis also revealed a dramatic increase in formation of oligomers after cadmium treatment. Cadmium also increased the formation of ubiquitinated PrP, but it did not lead to the formation of proteinase-K resistant PrP. Collectively, our results show that a divalent metal, cadmium affects proteasomal function and PrP aggregation, which promote neurotoxicity.

Tolerance and efficacy of tribasic manganese chloride in growing broiler chickens.

These studies were designed to determine the relative bioavailability and tolerance of tribasic Mn chloride (TBMC) for growing broiler chickens. In experiment 1, birds were fed a basal diet (starter, 102 ppm; grower, 209 ppm) or the basal diet supplemented with 3,600, 4,500, or 5,400 ppm Mn from either TBMC or manganese sulfate (MnSO(4)), and BW, feed intake, and plasma Mn were measured. In experiments 2 and 3, diets included the basal diet (45 and 43 ppm Mn, respectively) and the basal diet supplemented with graded levels of either TBMC or MnSO(4) ranging from 30 to 240 ppm Mn. Body weight and feed intake were measured and tibia, bile, and liver were collected for mineral analysis; heart samples were taken for manganese superoxide dismutase activity, protein, and relative mRNA abundance. In experiment 1, BW differed among treatments, with higher Mn leading to lower BW (P < 0.05). Birds from all treatments showed higher plasma Mn than birds fed the basal diet. Birds supplemented with the highest level of MnSO(4) had the highest level of plasma Mn (P < 0.05). In experiment 2, tibia and liver Mn increased with higher dietary Mn regardless of source (P < 0.05). Liver Mn increased up to the 60 ppm diets whereas Mn in the tibia was highest with the 130 ppm diets. Bile Mn increased with increasing dietary Mn, but these differences were not significant. In experiment 3, manganese superoxide dismutase activity, protein, and relative mRNA abundance were not affected by diet. The calculated bioavailabilities of TBMC and MnSO(4) did not differ significantly (P > 0.20). Together, these results indicate that TBMC is as effective as and better tolerated than MnSO(4) and that supplementing Mn at the lowest level used in this study may be sufficient for normal development of broiler chickens.

Impact of repeated topical-loaded manganese-enhanced MRI on the mouse visual system.

PURPOSE: Optic nerve degeneration in diseases such as glaucoma and multiple sclerosis evolves in months to years. The use of Mn(2+)-Enhanced Magnetic Resonance Imaging (MEMRI) in a time-course study may provide new insights into the disease progression. Previously, we demonstrated the feasibility of using a topical administration for Mn(2+) delivery to the visual system. This study is to evaluate the impact of biweekly or monthly repeated Mn(2+) topical administration and the pH levels of the Mn(2+) solutions for MEMRI on the mouse visual pathway. METHODS: Using groups of mice, the MEMRI with an acidic or pH neutralized 1 M MnCl(2) solution was performed. To evaluate the feasibility of repeated MEMRIs, topical-loaded MEMRI was conducted biweekly seven times or monthly three times. The enhancement of MEMRI in the visual system was quantified. After repeated MEMRIs, the corneas were examined by optical coherence tomography. The retinal ganglion cells (RGCs) and optic nerves were examined by histology. RESULTS: All mice exhibited consistent enhancements along the visual system following repeated MEMRIs. The acidic Mn(2+) solution induced a greater MEMRI enhancement as compared with a neutral pH Mn(2+) solution. Significant 20% RGC loss was found after three biweekly Mn(2+) inductions, but no RGC loss was found after three monthly Mn(2+) treatments. The corneal thickness was found increased after seven biweekly topical-loaded MEMRI. CONCLUSIONS: Acidic Mn(2+) solutions enhanced the uptake of Mn(2+) observed on the MEMRI. Increasing the time intervals of repeated Mn(2+) topical administration reduced the adverse effects caused by MEMRI.