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There is an ongoing discussion on the influence of surface-modifications on the toxicity of commercial particulate materials and how alterations in physical-chemical properties of surfaces impact toxicity. Titanium dioxide (TiO 2 ) is a poorly soluble particulate material of significant socioeconomic importance that largely exists as surface-modified particle-types in commerce. The observed toxicological effects of TiO 2 are primarily due to particle effects rather than substance chemistry, as such TiO 2 is commonly considered to be a poorly soluble low toxicity (PSLT) particle. This review provides an overview of the effect of surface modifications on the pulmonary and oral toxicity of commercial TiO 2 particles with emphasis on in vivo studies with appropriate controls, and where both surface modified and untreated materials are present in the same study. Published literature findings involving pulmonary and oral exposures to surface modified TiO 2 particles were reviewed and evaluated for quality and commercial relevance. Suitable publications involving animal studies were identified and summarized. Several studies were identified that have evaluated commercially-relevant surface-modified forms of titanium dioxide with appropriate data quality and with direct comparison to untreated counterparts. Hydrophilic inorganic surface modifications including silica, alumina/alumina hydroxide depositions have been tested along with common hydrophilic and hydrophobic-organic surface treatments. The results for both pigmentary and nanoscale materials demonstrate similar behaviour and indicate limited impact of particle size, surface chemistry, surface charge and surface wettability on observed pulmonary or oral toxicity effects. The low intrinsic toxicity of the TiO 2 base particle and evaluated surface modifications may account for the observed outcomes. A few published studies have drawn different conclusions; however, these were either not conducted using commercial TiO 2 samples (with surface coatings), had several confounding variables to investigate, or were carried out using mouse strains. The differences in experimental designs are described. The identified pulmonary and oral toxicity studies largely indicate that surface modifications and particle size alone have little or no impact on the lung toxicity of TiO 2 particles, following pulmonary exposures when all constituent materials are comprised of chemicals of low specific toxicity particles. In addition, based upon the results of 2 oral toxicity studies, one with surface treated TiO 2 particles (OECD 408) and one without surface treated (OECD 407) TiO 2 particles, there appears to have been no adverse impact on toxicity with the surface-coated material, as both studies produced no adverse effects at the very high doses tested., (Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.)

The primary crystallite size of titania powder relates to its properties in a number of applications. Transmission electron microscopy was used in this interlaboratory comparison (ILC) to measure primary crystallite size and shape distributions for a commercial aggregated titania powder. Data of four size descriptors and two shape descriptors were evaluated across nine laboratories. Data repeatability and reproducibility was evaluated by analysis of variance. One-third of the laboratory pairs had similar size descriptor data, but 83% of the pairs had similar aspect ratio data. Scale descriptor distributions were generally unimodal and were well-described by lognormal reference models. Shape descriptor distributions were multi-modal but data visualization plots demonstrated that the Weibull distribution was preferred to the normal distribution. For the equivalent circular diameter size descriptor, measurement uncertainties of the lognormal distribution scale and width parameters were 9.5% and 22%, respectively. For the aspect ratio shape descriptor, the measurement uncertainties of the Weibull distribution scale and width parameters were 7.0% and 26%, respectively. Both measurement uncertainty estimates and data visualizations should be used to analyze size and shape distributions of particles on the nanoscale.

Six pigment-grade (pg) or ultrafine (uf)/nanoscale (anatase and/or rutile) titanium dioxide (TiO2) particulates were evaluated for in vivo genotoxicity (OECD 474 Guidelines) in male and female rats by two different laboratories. All test materials were robustly characterized. The BET surface areas of the pg and uf samples ranged from 7 to 17 m(2)/g and 50 to 82 m(2)/g respectively. The materials were assessed for induction of micronuclei and toxicity in bone marrow by analyzing peripheral blood reticulocytes (RETs) by flow cytometry. Single oral gavage doses of 500, 1000 or 2000 mg/kg body weight (bw) of each material were implemented with concurrent negative (water) and positive controls (cyclophosphamide). Approximately 48 and 72 h after exposure, blood samples were collected and 20,000 RETs per animal were analyzed. For each of the six tests, there were no biologically or toxicologically relevant increases in the micronucleated RET frequency in any TiO2 exposed group at either time point at any dose level. In addition, there were a lack of biologically relevant decreases in %RETs among total erythrocytes. All six TiO2 test substances were negative for in vivo genotoxicity effects; however, it is noted that the exposure to target tissues was likely negligible. One pigment grade and one ultrafine material each were evaluated for potential systemic exposure/uptake from the gastrointestinal tract by analysis of TiO2 into blood and liver. No significant increases in TiO2 over controls were measured in blood (48 or 72 h) or liver (72 h) following exposures to 2000 mg/kg bw TiO2. These data indicate that there was no absorption of the test material from the gastrointestinal tract into the blood circulation and the lack of genotoxic effects is therefore attributed to a lack of exposure due to the inability of the test material to migrate from the gastrointestinal tract into the blood and then into target tissues., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Six different commercial forms and sizes of titanium dioxide particles were tested in separate developmental toxicity assays. The three pigment-grade (pg) or 3 ultrafine (uf)/nanoscale (anatase and/or rutile) titanium dioxide (TiO2) particle-types were evaluated for potential maternal and developmental toxicity in pregnant rats by two different laboratories. All studies were conducted according to OECD Guideline 414 (Prenatal Developmental Toxicity Study). In addition, all test materials were robustly characterized. The BET surface areas of the pg and uf samples ranged from 7 to 17 m(2)/g and 50-82 m(2)/g respectively (see Table 1). The test substances were formulated in sterile water. In all of the studies, the formulations were administered by oral gavage to time-mated rats daily beginning around the time of implantation and continuing until the day prior to expected parturition. In 3 of the studies (uf-1, uf-3, & pg-1), the formulations were administered to Crl:CD(SD) rats beginning on gestation day (GD) 6 through GD 20. In 3 additional studies (uf-2, and pg-2, pg-3 TiO2 particles), the formulations were administered to Wistar rats beginning on GD 5 through 19. The dose levels used in all studies were 0, 100, 300, or 1000 mg/kg/day; control group animals were administered the vehicle. During the in-life portions of the studies, body weights, food consumption, and clinical observations before and after dosing were collected on a daily basis. All dams were euthanized just prior to expected parturition (GD 21 for Crl:CD(SD) rats and GD 20 for Wistar rats). The gross necropsies included an examination and description of uterine contents including counts of corpora lutea, implantation sites, resorptions, and live and dead fetuses. All live fetuses were sexed, weighed, and examined externally and euthanized. Following euthanasia, fresh visceral and head examinations were performed on selected fetuses. The fetal carcasses were then processed and examined for skeletal alterations. There was no evidence of maternal or developmental toxicity at any dose level tested in any of the six studies. Based on these results, the no-observed-adverse-effect level (NOAEL) for titanium dioxide was 1000 mg/kg/day, the highest administered dose, in both the Sprague-Dawley (Crl:CD(SD) and Wistar rat strains., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Introduction: Pulmonary regurgitation (PR) following surgery of the right ventricular outflow tract (RVOT) is not innocent and leads to significant right heart dysfunction over time. Recent studies have demonstrated that percutaneous valves can be implanted in conduit free outflow tracts with good outcomes., Objectives: To evaluate in patients with severe PR--anticipated to require future pulmonary valve replacement--the feasibility and safety of pre-stenting dilated non-stenotic patched conduit-free right ventricular outflow tracts before excessive dilation occurs, followed by percutaneous pulmonary valve implantation (PPVI)., Patients and Methods: Twenty seven patients were evaluated, but only 23 were deemed suitable based on the presence of an adequate retention zone ≤ 24 mm defined by semi-compliant balloon interrogation of the RVOT. A 2 step procedure was performed: first the landing zone was prepared by deploying a bare stent, followed 2 months later by valve implantation., Results: RVOT pre-stenting with an open cell bare metal stent (Andrastent XXL range) was performed at a median age of 13.0 years (range: 6.0-44.9) with a median weight of 44.3 kg (range: 20.0-88.0). Ninety six percent (22/23) of patients proceeded to PPVI a median of 2.4 months (range: 1.4-3.4) after initial pre-stent placement. Twenty one Melody valves and one 26 mm Edwards SAPIEN™ valve were implanted. Complications consisted of embolization of prestent (n = 1), scrunching (n = 4) and mild stent dislocation (n = 2). During follow-up, no stent fractures were observed and right ventricular dimensions decreased significantly., Conclusions: Post-surgical conduit-free non-stenotic RVOT with free pulmonary regurgitation can be treated percutaneously with a valved stent if anatomical (predominantly size) criteria are met. In experienced hands, the technique is feasible with low morbidity., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

The common Z mutant (Glu342Lys) of alpha(1)-antitrypsin results in the formation of polymers that are retained within hepatocytes. This causes liver disease whilst the plasma deficiency of an important proteinase inhibitor predisposes to emphysema. The Thr114Phe and Gly117Phe mutations border a surface cavity identified as a target for rational drug design. These mutations preserve inhibitory activity but reduce the polymerisation of wild-type native alpha(1)-antitrypsin in vitro and increase secretion in a Xenopus oocyte model of disease. To understand these effects, we have crystallised both mutants and solved their structures. The 2.2 A structure of Thr114Phe alpha(1)-antitrypsin demonstrates that the effects of the mutation are mediated entirely by well-defined partial cavity blockade and allows in silico screening of fragments capable of mimicking the effects of the mutation. The Gly117Phe mutation operates differently, repacking aromatic side chains in the helix F-beta-sheet A interface to induce a half-turn downward shift of the adjacent F helix. We have further characterised the effects of these two mutations in combination with the Z mutation in a eukaryotic cell model of disease. Both mutations increase the secretion of Z alpha(1)-antitrypsin in the native conformation, but the double mutants remain more polymerogenic than the wild-type (M) protein. Taken together, these data support different mechanisms by which the Thr114Phe and Gly117Phe mutations stabilise the native fold of alpha(1)-antitrypsin and increase secretion of monomeric protein in cell models of disease.

Mutations in the LMNA gene, which encodes nuclear lamins A and C by alternative splicing, can give rise to Emery-Dreifuss muscular dystrophy. The mechanism by which lamins A and C separately contribute to this molecular phenotype is unknown. To address this question we examined ten LMNA mutations exogenously expressed as lamins A and C in COS-7 cells. Eight of the mutations when expressed in lamin A, exhibited a range of nuclear mislocalisation patterns. However, two mutations (T150P and delQ355) almost completely relocated exogenous lamin A from the nuclear envelope to the cytoplasm, disrupted nuclear envelope reassembly following cell division and altered the protein composition of the mid-body. In contrast, exogenously expressed DsRed2-tagged mutant lamin C constructs were only inserted into the nuclear lamina if co-expressed with any EGFP-tagged lamin A construct, except with one carrying the T150P mutation. The T150P, R527P and L530P mutations reduced the ability of lamin A, but not lamin C from binding to emerin. These data identify specific functional roles for the emerin-lamin C- and emerin-lamin A- containing protein complexes and is the first report to suggest that the A-type lamin mutations may be differentially dysfunctional for the same LMNA mutation.

We have identified a novel omega-hydroxy-alkanedicarboxylic acid, ESP 55016, that favorably alters serum lipid variables in obese female Zucker (fa/fa) rats. ESP 55016 reduced serum non-HDL-cholesterol (non-HDL-C), triglyceride, and nonesterified fatty acid levels while increasing serum HDL-C and beta-hydroxybutyrate levels in a dose-dependent manner. ESP 55016 reduced fasting serum insulin and glucose levels while also suppressing weight gain. In primary rat hepatocytes, ESP 55016 increased the oxidation of [(14)C]palmitate in a dose- and carnitine palmitoyl transferase-I (CPT-I)-dependent manner. Furthermore, in primary rat hepatocytes and in vivo, ESP 55016 inhibited fatty acid and sterol synthesis. The "dual inhibitor" activity of ESP 55016 was unlikely attributable to the activation of the AMP-activated protein kinase (AMPK) pathway because AMPK and acetyl-CoA carboxylase (ACC) phosphorylation states as well as ACC activity were not altered by ESP 55016. Further studies indicated the conversion of ESP 55016 to a CoA derivative in vivo. ESP 55016-CoA markedly inhibited the activity of partially purified ACC. The activity of partially purified HMG-CoA reductase was not altered by the xenobiotic-CoA. These data suggest that ESP 55016-CoA favorably alters lipid metabolism in a model of diabetic dyslipidemia in part by initially inhibiting fatty acid and sterol synthesis plus enhancing the oxidation of fatty acids through the ACC/malonyl-CoA/CPT-I regulatory axis.

We recently identified mutations in the fukutin related protein (FKRP) gene in patients with congenital muscular dystrophy type 1C (MDC1C) and limb girdle muscular dystrophy type 2I (LGMD2I). The sarcolemma of these patients typically displays an immunocytochemical reduction of alpha-dystroglycan. In this report we extend these observations and report a clear correlation between the residual expression of alpha-dystroglycan and the phenotype. Three broad categories were identified. Patients at the severe end of the clinical spectrum (MDC1C) were compound heterozygote between a null allele and a missense mutation or carried two missense mutations and displayed a profound depletion of alpha-dystroglycan. Patients with LGMD with a Duchenne-like severity typically had a moderate reduction in alpha-dystroglycan and were compound heterozygotes between a common C826A (Leu276Ileu) FKRP mutation and either a missense or a nonsense mutation. Individuals with the milder form of LGMD2I were almost invariably homozygous for the Leu276Ile FKRP mutation and showed a variable but subtle alteration in alpha-dystroglycan immunolabeling. Our data therefore suggest a correlation between a reduction in alpha-dystroglycan, the mutation and the clinical phenotype in MDC1C and LGMD2I which supports the hypothesis that dystroglycan plays a central role in the pathogenesis of these disorders.

Context: Over the past 15 years the causative genes of several inherited muscular dystrophies have been identified. These genes encode sarcolemmal, extracellular matrix, sarcomeric, and nuclear envelope proteins. Although the post-translational processing of muscle proteins has a significant role in their correct assembly and function, these processes have not been shown to be primarily involved in the pathogenesis of muscular dystrophies until recently. In the past 18 months, four different forms of inherited muscular dystrophy in human beings have been associated with mutations in genes encoding for putative glycosyltransferases. Aberrant glycosylation of alpha-dystroglycan, an external membrane protein expressed in muscle, brain, and other tissues, is a common feature in these disorders. alpha-dystroglycan is highly glycosylated, its sugar components varying in different tissues and controlling its interaction with extracellular matrix partners. Disrupted glycosylation of alpha-dystroglycan results in a loss of these interactions, giving rise to both progressive muscle degeneration and abnormal neuronal migration in the brain., Starting Point: Kevin Campbell and colleagues have recently demonstrated that patients with muscle-eye-brain disease (MEB) and Fukuyama congenital muscular dystrophy (FCMD), as well as the myodystrophy (myd) mouse, have an abnormally glycosyated form of alpha-dystroglycan (Nature 2002; 418: 417-22 and 422-25). The abnormally glycosylated protein did not bind to three of its extracellular matrix ligands, laminin alpha2 chain, agrin, and neurexin. The investigators also showed that a neuronal migration disorder occurs in both the myd mouse and in a brain-restricted alpha-dystroglycan knock-out mouse that is similar to that seen in patients with MEB and FCMD. These results identify alpha-dystroglycan as having an essential role in both muscle and brain development and function., Where Next: Emphasis is moving away from identifying the protein components of the muscle fibre that are involved in muscular dystrophies towards the post-translational processing of proteins and the enzymes involved in these modifications. This opens up new avenues of research. Abnormal glycosylation of alpha-dystroglycan may underlie other as yet uncharacterised forms of muscular dystrophy and neuronal migration disorders.

The spatio-temporal distribution of intracellular, free calcium ions, [Ca2+]i, induced in human myotubes by electrical stimulation typically showed a relatively large increase of [Ca2+]i in the vicinity of the plasmalemma. The similarity of this distribution, with that observed after the application of caffeine, and the lack of any effect of lanthanum, strongly suggest that the main source of Ca2+ participating in the electrically induced transient is the sarcoplasmic reticulum. Aneurally cultured human myotubes therefore display a 'skeletal muscle type' coupling between membrane depolarization and calcium release. However, the relatively slow time course of the electrically induced transients compared to rat and mouse myotubes, together with the inability of Ca2+ released from the sarcoplasmic reticulum to activate the contractile machinery, implies that aneurally cultured human myotubes achieve only a limited degree of differentiation. The relevance this may have to an apparent delay between the electrically induced rise in intranuclear Ca2+ relative to cytosolic Ca2+ remains to be determined but, at this stage of differentiation, there appears to be some form of barrier to free diffusion between the two cellular compartments.

Natural infestations of the cattle tick Boophilus microplus, levels of the buffalo fly Haematobia irritants exigua and faecal nematode egg concentrations (Bunostomum phlebotomum, Cooperia spp., Haemonchus placei, Oesophagostomum radiatum and Trichostrongylus axei) were assessed in 221 Belmont Red calves during the post-weaning period, when the animals were between 9 and 18 months of age. In addition, the 98 males of this group were challenged with B. microplus larvae on two separate occasions. There were strong positive correlations among replicate assessments of the same parasite. Field tick counts and tick counts following deliberate challenge were strongly correlated, and both showed negative correlations with post-weaning weight gain. There was a weak positive correlation between buffalo fly counts and post-weaning weight gain. There was a negative correlation between total worm egg count and weight gain. Among worm species, only the effect of O. radiatum on weight gain was significant. Cattle with bovine major histocompatibility (BoLA) antigens W6.1 and W7 had significantly fewer ticks than cattle lacking these antigens. Cattle with BoLA antigens W7 and CA36 had lower concentrations of nematode eggs in their faeces than cattle lacking these BoLA antigens.

We have performed molecular mechanical calculations on intercalation complexes of actinomycin D with a series of base-paired hexanucleoside pentaphosphates; d(GCGCGC)2, d(GCCGGC)2, d(GCATGC)2, d(GCTAGC)2 and d(ATGCAT)2. Our results are in good agreement with previous experimental work on sequence selectivity. The results provide a rationalization for the strong preference of actinomycin D to intercalate on the 3' side of guanine residues, consistent with previously proposed models. Finally, the computed structures for d(ATGCAT)2-actinomycin D complexes have been compared with two-dimensional nuclear magnetic resonance nuclear Overhauser effect experimental results. To our knowledge, this is the first extensive comparison of molecular mechanical model structures for a drug-DNA complex with experimental solution phase data. We find generally good agreement between our computational models and the experimental solution phase structures.

Two consecutive calf crops consisting of 141 three-quarters Brahman/one-quarter Shorthorn cattle were assessed for resistance to the Australian cattle tick Boophilus microplus in May, July and October 1983. Although the level of expressed resistance to artificial infestation varied considerably between seasons, the animals maintained very similar rankings for resistance in all three seasons, and the repeatability of tick resistance ranged from 0.59 to 0.82. The cattle were typed for 30 bovine class I lymphocyte antigens. Antigens W6 and CA31 were associated with susceptibility to artificial tick infestation but none of the other lymphocyte antigens showed strong associations with resistance or susceptibility.

The relationship between the inhalation exposure concentration of talc and the resulting lung burdens and histologic lesions was studied using groups of 20 F344/Crl rats and 20 B6C3F mice (10 male and 10 female) exposed to one of three concentrations of asbestos-free talc for 6 hr/day, 5 days/week for 4 weeks. Controls were exposed to filtered air using the same schedule. The pulmonary retention of talc and the development of pulmonary pathology were evaluated. The mass median aerodynamic diameter (MMAD) of the talc aerosol was 3.0 microns with a geometric standard deviation (sigma g) of 1.9. The mean exposure concentrations for rats were 0, 2.3, 4.3, and 17 mg talc/m3. Lung burdens in rats averaged 0, 0.07, 0.17, and 0.72 mg talc/g lung after the 20-day inhalation exposure; thus, the amount retained in the lung per unit of exposure concentration increased with increasing concentration. Mean exposure concentrations for the mice were 0, 2.2, 5.7, and 20.4 mg of talc/m3, which resulted in lung burdens of 0, 0.10, 0.29, and 1.0 mg talc/g lung; thus, the relationship between exposure concentration and the amount retained in the lung was approximately constant. Lung burdens from this study were used to project lung burdens that would result from longer exposures of rodents and man. No clinical signs were observed in the rats or mice prior to sacrifice 24 hr after the last exposure day. Histologic alterations in lung tissue consisted of only a modest, diffuse increase of talc-containing, free macrophages within alveolar spaces in both rat and mouse groups exposed to the highest level of talc for 20 days. A model simulating chronic talc inhalation exposure of rats and mice predicted lung burdens of 2-3 mg talc/g lung (wet wt) if animals were exposed to 17 mg talc/m3 for 2 years, and deposition and clearance of talc were unchanged by continued exposure. A potential limitation in this modeling is that if clearance of talc is delayed by continued exposure, the accumulated talc lung burdens would be higher than those projected by the simulation model. Humans exposed to aerosols of respirable talc are projected to accumulate much higher lung burdens than would occur in rodents exposed to the same aerosol, because humans have a higher estimated deposition fraction and slower estimated clearance of the deposited talc dust. Equilibrium lung burdens of greater than or equal to 2 mg talc/g lung were predicted for human exposures at or near the TLV for talc.