This study uniquely describes all steps of the risk assessment process for the use of one specific nanomaterial (nanosilica) in food products. The aim was to identify gaps in essential knowledge and the difficulties and uncertainties associated with each of these steps. Several food products with added silica (E551) were analyzed for the presence, particle size and concentration of nanosilica particles, using experimental analytical data, and the intake of nanosilica via food was estimated. As no information is available on the absorption of nanosilica from the gastrointestinal tract, two scenarios for risk assessment were considered. The first scenario assumes that the silica is absorbed as dissolved silica, while the second scenario assumes that nanosilica particles themselves are absorbed from the gastrointestinal tract. For the first scenario no adverse effects are expected to occur. For the second scenario there are too many uncertainties to allow proper risk assessment. Therefore, it is recommended to prioritize research on how nanosilica is absorbed from the gastrointestinal tract.

The aim of this study was to develop a method for spermatogonial stem cell transplantation into the bovine testis. Five-month-old Holstein-Friesian calves were used and half of the calves were hemicastrated to allow autologous transplantation and the other half were used for homologous transplantation. Approximately 20 g of each testis was used for cell isolation. On average 10 6 cells per gram of testis containing about 70% type A spermatogonia were isolated. The cells were frozen in liquid nitrogen until transplantation. Testes were irradiated locally with 10-14 Gy of Xrays to deplete endogenous spermatogenesis. At 2 months after irradiation, cells (approximately 10 × 10 6 ) were injected into the rete testis through a long injection needle (18 gauge), using ultrasonography and an ultrasound contrast solution. At 2.5 months after transplantation, calves were castrated and samples of testes were taken for histological examination. After 2.5 months in the irradiated non-transplanted control testes, only 45% of the tubules contained type A spermatogonia. However, after autologous spermatogonial transplantation, > 80% of the tubule cross-sections contained type A spermatogonia. In addition, only 20% of the tubules of the control testes contained spermatocytes and, except for a few tubules (5%) with round spermatids, no more advanced germ cells were found. After autologous spermatogonial transplantation, about 60% of the tubules contained spermatocytes; 30% contained spermatids and in about 15% of tubules spermatozoa were found. No improvement in spermatogonial repopulation was found after homologous transplantation. The results of this study demonstrate, for the first time, successful autologous transplantation of bovine spermatogonial stem cells resulting in a complete regeneration of spermatogenesis.

The PEGylation of gold nanorods resulted in a prolongation of the blood clearance and the highest organ exposure in the spleen. In view of the time frame (up to 48 h) of the observed presence in blood circulation, PEGylated gold nanorods can be considered to be promising candidates for therapeutic and diagnostic imaging purposes.

effects and pharmacokinetic profile of a long-term continuous rate infusion of racemic ketamine in healthy conscious horses. J. vet. Pharmacol. Therap. 29,[477][478][479][480][481][482][483][484][485][486][487][488] Ketamine (KET) possesses analgesic and anti-inflammatory activity at subanesthetic doses, suggesting a benefit of long-term KET treatment in horses suffering from pain, inflammatory tissue injury and/or endotoxemia. However, data describing the pharmacodynamic effects and safety of constant rate infusion (CRI) of KET and its pharmacokinetic profile in nonpremedicated horses are missing. Therefore, we administered to six healthy horses a CRI of 1.5 mg/kg/h KET over 320 min following initial drug loading. Cardiopulmonary parameters, arterial blood gases, glucose, lactate, cortisol, insulin, nonesterified fatty acids, and muscle enzyme levels were measured, as were plasma concentrations of KET and its metabolites using liquid chromatographytandem mass spectrometry (LC-MS/MS). Levels of sedation and muscle tension were scored. Respiration and heart rate significantly increased during the early infusion phase. Glucose and cortisol significantly varied both during and after infusion. During CRI all horses scored 0 on sedation. All but one horse scored 0 on muscle tension, with one mare scoring 1. All other parameters remained within or close to physiological limits without significant changes from pre-CRI values. The mean plasma concentration of KET during the 1.5 mg/kg/h KET CRI was 235 ng/mL. The decline of its plasma concentration-time curve of both KET and norketamine (NKET) following the CRI was described by a twocompartmental model. The metabolic cascade of KET was NKET, hydroxynorketamine (HNK), and 5,6-dehydronorketamine (DHNK). The KET median elimination half-lives (t 1/2a and t 1/2b ) were 2.3 and 67.4 min, respectively. The area under the KET plasma concentration-time curve (AUC), elimination was 76.0 lgAEmin/mL. Volumes of C 1 and C 2 were 0.24 and 0.79 L/kg, respectively. It was concluded that a KET CRI of 1.5 mg/kg/h can safely be administered to healthy conscious horses for at least 6 h, although a slight modification of the initial infusion rate regimen may be indicated. Furthermore, in the horse KET undergoes very rapid biotransformation to NKET and HNK and DHNK were the major terminal metabolites.(Paper

Thrombophlebitis is a well-known complication of the use of long-term in-dwelling catheters. In humans, catheter material has been shown to strongly influence the occurrence of thrombophlebitis. In the horse, the influence of catheter material has been studied in healthy experimental animals, but information on the relative importance of this factor is lacking. To investigate which factors have most impact on the frequency of jugular vein thrombosis in post-surgical colic horses, a clinical study was performed on 38 animals. Horses were randomly divided into two groups. In one group a polytetrafluoroethylene catheter was used, in the other a polyurethane catheter. Both groups were clinically monitored and screened for signs of thrombophlebitis. Seven out of 38 horses developed thrombophlebitis. The type of catheter material used had no influence on thrombophlebitis development. Dwell time was significantly longer in horses that developed thrombophlebitis compared with those that did not. There was no relationship between the occurrence of thrombophlebitis and underlying disease or surgical treatment, suggesting that the general state of debilitation these horses experienced was the most important determinant for the development of thrombophlebiris. This was further stressed by the fact that seven horses developed thrombophlebitis of the contralateral vein that had been used for the induction of anaesthesia (this incidence is much higher than in horses anaesthetized for elective surgery). It is concluded that the state of debilitation is the most important determining factor for the occurrence of thrombophlebitis after the use of long-term in-dwelling intravenous catheters. This makes a substantial reduction of the incidence of thrombophlebitis difficult, but some progress can be made by consequently restricting dwell time.

Nanotechnology applications already on the market or in development promise great benefits for humans as well as the environment. Simultaneously, the pressure to advance the development of fast methods for evaluating the potential risks of increased human exposure to nanomaterials is augmented. One way forward would be to enhance the role of in vitro toxicity studies in risk assessment procedures of nanomaterials. However, to maximize the use of in vitro assays for this purpose, their values and limitations need to be revealed. Even in risk assessment frameworks for regular chemicals, in vitro studies play a minor role. A comparative analysis of published in vitro data with nanomaterials demonstrates that there are a number of issues that need resolving before in vitro studies can play a role in the risk assessment of nanomaterials.

Immunotoxicity is defined as the toxicological effects of xenobiotics including pharmaceuticals on the functioning of the immune system and can be induced in either direct or indirect ways. Direct immunotoxicity is caused by the effects of chemicals on the immune system, leading to immunosuppression and subsequently to reduced resistance to infectious diseases or certain forms of nongenotoxic carcinogenicity.In vitro testing has several advantages over in vivo testing, such as detailed mechanistic understanding, species extrapolation (parallelogram approach), and reduction, refinement, and replacement of animal experiments. In vitro testing for direct immunotoxicity can be done in a two-tiered approach, the first tier measuring myelotoxicity. If this type of toxicity is apparent, the compound can be designated immunotoxic. If not, the compound is tested for lymphotoxicity (second tier). Several in vitro assays for lymphotoxicity exist, each comprising specific functions of the immune system (cytokine production, cell proliferation, cytotoxic T-cell activity, natural killer cell activity, antibody production, and dendritic cell maturation). A brief description of each assay is provided. Only one assay, the human whole blood cytokine release assay, has undergone formal prevalidation, while another one, the lymphocyte proliferation assay, is progressing towards that phase.Progress in in vitro testing for direct immunotoxicity includes prevalidation of existing assays and selection of the assay (or combination of assays) that performs best. To avoid inter-species extrapolation, assays should preferably use human cells. Furthermore, the use of whole blood has the advantage of comprising multiple cell types in their natural proportion and environment. The so-called "omics" techniques provide additional mechanistic understanding and hold promise for the characterization of classes of compounds and prediction of specific toxic effects. Technical innovations such as high-content screening and high-throughput analysis will greatly expand the opportunities for in vitro testing.

-Ketamine is widely used in equine anaesthesia. Beside its anaesthetic and analgesic properties, ketamine possesses a cytokine-modulating activity. However, to date, no data are available regarding the inhibitory effect of ketamine on the cytokine response in horses. In horses, cytokines such as tumour necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) play a pivotal role in the pathogenesis of equine endotoxaemia following gastrointestinal disorders. Hence, the objective of this study was to assess the influence of ketamine on LPS-induced TNF-α and IL-6 formation in an equine macrophage cell line (eCAS cells). The results demonstrate a cytokinemodulating activity of ketamine in an equine cell line, suggesting a beneficial role for ketamine in the treatment of equine endotoxaemia. ketamine / cytokine / equine endotoxaemia / eCAS