Ingestion of Bt rice pollen does not reduce the survival or hypopharyngeal gland development of Apis mellifera adults.

Because of its ecological and economic importance, the honey bee Apis mellifera is commonly used to assess the environmental risk of insect-resistant, genetically modified plants. In the present study, feeding-exposure experiments were used to determine whether pollen from transgenic rice harms A. mellifera worker bees. In 1 experiment, the survival and mean acinus diameter of hypopharyngeal glands of adult bees were similar when bees were fed on pollen from Bt rice lines or from a non-Bt rice line, but bee survival was significantly reduced when they received pollen that was mixed with potassium arsenate as a positive control. In a second experiment, bee survival and hypopharyngeal gland development were not reduced when adult bees were fed on non-Bt pollen and a sucrose solution supplemented with Cry2A at 400 µg/g, Cry1C at 50 µg/g, or bovine serum albumin (BSA) at 400 µg/g, but bee survival and hypopharyngeal gland development were reduced when the diet was supplemented with soybean trypsin inhibitor as a positive control. In both experiments, the uptake of Cry proteins by adult bees was confirmed. Overall, the results indicate that the planting of Bt rice lines expressing Cry2A or Cry1C protein poses a negligible risk to A. mellifera worker bees. Environ Toxicol Chem 2017;36:1243-1248. © 2016 SETAC.

Hexavalent chromium affects sperm motility by influencing protein tyrosine phosphorylation in the midpiece of boar spermatozoa.

Hexavalent chromium reportedly induces reproductive toxicity and further inhibits male fertility in mammals. In this study, we investigated the molecular mechanism by which hexavalent chromium affects motility signaling in boar spermatozoa in vitro. The results indicated that Cr(VI) decreased sperm motility, protein phosphorylation, mitochondrial membrane potential (ΔΨm) and metabolic enzyme activity starting at 4µmol/mL following incubation for 1.5h. Notably, all parameters were potently inhibited by 10µmol/mL Cr, while supplementation with the dibutyryl-cAMP (dbcAMP) and the 3-isobutyl-1-methylxanthine (IBMX) prevented the inhibition of protein phosphorylation. Interestingly, high concentrations of Cr (>10µmol/mL) increased the tyrosine phosphorylation of some high-molecular-weight proteins in the principle piece but decreased that in the middle piece associated with an extreme reduction of sperm motility. These results suggest that chromium affects boar sperm motility by impairing tyrosine phosphorylation in the midpiece of sperm by blocking the cAMP/PKA pathway in boar sperm in vitro.

A fluorescence-based hydrolytic enzyme activity assay for quantifying toxic effects of Roundup® to Daphnia magna.

Daphnia magna is a widely used model organism for aquatic toxicity testing. In the present study, the authors investigated the hydrolytic enzyme activity of D. magna after exposure to toxicant stress. In vivo enzyme activity was quantified using 15 fluorogenic enzyme probes based on 4-methylumbelliferyl or 7-amino-4-methylcoumarin. Probing D. magna enzyme activity was evaluated using short-term exposure (24-48 h) to the reference chemical K2 Cr2 O7 or the herbicide formulation Roundup®. Toxicant-induced changes in hydrolytic enzyme activity were compared with changes in mobility (International Organization for Standardization standard 6341). The results showed that hydrolytic enzyme activity was quantifiable as a combination of whole body fluorescence of D. magna and the fluorescence of the surrounding water. Exposure of D. magna to lethal and sublethal concentrations of Roundup resulted in loss of whole body enzyme activity and release of cell constituents, including enzymes and DNA. Roundup caused comparable inhibition of mobility and alkaline phosphatase activity with median effective concentration values at 20 °C of 8.7 mg active ingredient (a.i.)/L to 11.7 mg a.i./L. Inhibition of alkaline phosphatase activity by Roundup was lowest at 14 °C and greater at 20 °C and 26 °C. The results suggest that the fluorescence-based hydrolytic enzyme activity assay (FLEA assay) can be used as an index of D. magna stress. Combining enzyme activity with fluorescence measurements may be applied as a simple and quantitative supplement for toxicity testing with D. magna.

Decreased pain threshold and enhanced synaptic transmission in the anterior cingulate cortex of experimental hypothyroidism mice.

BACKGROUND: Thyroid hormones are essential for the maturation and functions of the central nervous system. Pain sensitivity is related to the thyroid status. However, information on how thyroid hormones affect pain processing and synaptic transmission in the anterior cingulate cortex (ACC) is limited. Nociceptive threshold and synaptic transmission in the ACC were detected in the experimental hypothyroidism (HT) mice. RESULTS: HT was induced by methimazole and potassium perchlorate in distilled drinking water for 4 weeks. The threshold of pain perception to hot insults, but not mechanical ones, decreased in hypothyroid mice. After treatment with tri-iodothyronine (T3) or thyroxine (T4) for 2 weeks, thermal pain threshold recovered. Electrophysiological recordings revealed enhanced glutamatergic synaptic transmission and reduced GABAergic synaptic transmission in the ACC. Supplementation with T3 or T4 significantly rescued this synaptic transmission imbalance. In the same model, HT caused the up-regulation of the GluR1 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor and NR2B-containing N-methyl-D-aspartate receptors, but it down-regulated γ-aminobutyric acid A receptors in the ACC. Supplementation with T3 or T4 notably recovered the levels of above proteins. CONCLUSIONS: These results suggest that HT promotes hypersensitivity to noxious thermal, and that supplementation with T3 or T4 rescues the imbalance between excitatory and inhibitory transmission in the ACC.

Development and survival of Orius insidiosus (Say) nymphs on encapsulated bee pollen-based diet in a Tier-I toxicity assay.

The insidious flower bug, Orius insidiosus (Say) (Heteroptera: Anthocoridae) is an important surrogate species for assessing potential effects of plant-incorporated protectants (PIPs) on nontarget heterotrophic predators. In this study, a continuous dietary exposure system was optimized by assessing the effect of diet composition and age on the survival and development of nymphs of O. insidiosus. Greater than 85% control survival and an acceptable rate of development from nymph hatching to adult was achieved using 5-d-old nymphs at test initiation and a bee pollen-based diet supplemented with 25% Ephestia eggs. There was an unacceptable level of mortality (>40%) and/or a significantly prolonged development time when nymphs were <5 d old at test initiation. When 5-d-old nymphs were fed a bee pollen diet containing 25% Ephestia eggs and 100 µg/g potassium arsenate, time-dependent mortality was observed with a median lethal time (LT50) of 4.4 d and 100% mortality was observed after 10 d of feeding, indicating the effectiveness of the test system to detect adverse effects by dietary exposure. It is recommended that well-defined 5-d-old nymphs and an encapsulated bee pollen-based diet containing 25% ground Ephestia eggs be used in a Tier-I dietary feeding exposure assay for detecting potential effects of PIPs on O. insidiosus nymphs.

Supplemental selenium alleviates the toxic effects of excessive iodine on thyroid.

As excessive iodine intake is associated with a decrease of the activities of selenocysteine-containing enzymes, supplemental selenium was hypothesized to alleviate the toxic effects of excessive iodine. In order to verify this hypothesis, Balb/C mice were tested by giving tap water with or without potassium iodate and/or sodium selenite for 16 weeks, and the levels of iodine in urine and thyroid, the hepatic selenium level, the activities of glutathione peroxidase (GSHPx), type 1 deiodinase (D1), and thyroid peroxidase (TPO) were assayed. It had been observed in excessive iodine group that hepatic selenium, the activities of GSHPx, D1, and TPO decreased, while in the groups of 0.2 mg/L, 0.3 mg/L and 0.4 mg/L supplemental selenium, the urinary iodine increased significantly. Compared with the group of excessive iodine intake alone, supplemental selenium groups had higher activities of GSHPx, D1, and TPO. We could draw the conclusion that supplemental selenium could alleviate toxic effect of excessive iodine on thyroid. The optimal dosage of selenium ranges from 0.2 to 0.3 mg/L which can protect against thyroid hormone dysfunction induced by excessive iodine intake.

Effects of selenium on chromium (VI)-induced hepatotoxicity in adult rats.

Chromium, a major environmental pollutant, is known for its wide toxic manifestations. The present experiment pertains to the protective role of selenium (Se) against K(2)Cr(2)O(7)-induced hepatotoxicity. Female Wistar rats were divided into four groups of six each: group I served as controls which received standard diet; group II received in drinking water K(2)Cr(2)O(7) alone (700 ppm); group III received both K(2)Cr(2)O(7) and Se (0.5 Na(2)SeO(3) mg/kg of diet); group IV received Se (0.5 mg/kg of diet) for 3 weeks. Exposure of rats to chromium promoted oxidative stress with an increase in malondialdehyde (MDA) and a decrease in glutathione (GSH) levels. A decrease in glutathione peroxidase (GPx) and an increase in superoxide dismutase (SOD) and catalase (CAT) activities were observed. Se supplementation to the diet of group III improved all the parameters cited above. Yet, plasma transaminases (AST and ALT), lactate dehydrogenase (LDH) activities, cholesterol, triglycerides (TG) and low density lipoprotein-cholesterol (LDL-C) levels increased, while high density lipoprotein-cholesterol (HDL-C) decreased. Co-administration of Se to the diet of group III restored hepatic markers to near-normal values. The biochemical results confirmed the histopathological findings. Therefore, our investigation revealed that Se was effective in preventing K(2)Cr(2)O(7)-induced hepatotoxicity.

Properties of a new mouthrinse for patients receiving radiation therapy.

INTRODUCTION: Patients receiving radiation therapy due to oral cancer develop complications such as hyposalivation, mucositis, oral infections, dental hypersensitivity and caries. Mouthrinses can alleviate some of these problems. AIMS AND OBJECTIVES: To investigate the in vitro antimicrobial properties and cytotoxicity of an experimental mouthrinse. METHODS: The mouthrinse contained 30% hexylene glycol (glycerine), 7% potassium nitrate and 0.025% sodium fluoride. The minimal inhibitory concentration (MIC) of these ingredients and the mixture was determined for C. albicans, S. aureus and S. mutans over 24 hours at different concentrations. The MICs of two commercial mouthrinses, Corsodyl and Plax, were also determined using the same organisms. All mouthrinses were then tested to determine the percentage kill over 1, 2, and 3 minutes. RESULTS: The MICs for hexylene glycol were 10%, 30% and 10% for C. albicans, S. aureus and S. mutons respectively. Potassium nitrate and sodium fluoride had no antimicrobial effects. The MIC of Corsodyl was 0.016 mg/ml for all the test organisms. The MIC for Plax varied from 0.0002 mg/ml to 0.001 mg/ml. The kill rates for all mouthrinses were acceptable, with no statistical differences between them. The experimental mouthrinse was not toxic to human oesophageal SCC cells after 1 minute exposure. At the time of the experiment, the costs of a similar quantity of the experimental mouthrinse, Corsodyl and Plax were R5.24, R30.00 and R10.00 respectively. CONCLUSIONS: The experimental mouthrinse was cost-effective and proved to have an antimicrobial effect and could be used safely to alleviate oral infections, desensitize teeth, improve oral hygiene and control dental caries in cancer patients after radiation therapy.

Sudden bilateral sensorineural hearing loss as an unusual consequence of accidental ingestion of potassium hydroxide.

OBJECTIVE: To discuss the possible etiopathogenetic mechanism of inner ear damage induced by the ingestion of potassium hydroxide (KOH). CLINICAL PRESENTATION AND INTERVENTION: We report the case of a 37-year-old patient with sudden bilateral sensorineural hearing loss after accidental ingestion of a KOH solution. The first ear, nose and throat examination disclosed only mild edema of the upper airways. He was treated in the intensive care unit and prescribed high-dose steroids, proton pump inhibitors and sucralfate for 2 weeks. Unfortunately, there was no recovery of the hearing loss, and no audiogram changes were noticed after 12 months of follow-up. CONCLUSION: After exploring the possible etiopathogenetic mechanism involved, the authors believe that in this case, a transient severe hemodynamic imbalance can actually be considered to be the most reliable explanation for the inner ear damage and subsequent onset of permanent bilateral sensorineural hearing loss.

Genotoxic effects of chromium(VI) and cadmium(II) in human blood lymphocytes using the electron microscopy in situ end-labeling (EM-ISEL) assay.

Evaluation of genotoxic effects of potassium chromate (K2CrO4) and cadmium chloride (CdCl2) was carried out in human blood lymphocytes in vitro as measured by the electron microscopy in situ end-labeling (EM-ISEL). EM-ISEL was used to assess DNA single-strand breaks (SSBs) expressed as number of immunogold particles per microm2 of chromatin at both chromosomal and nuclear DNA levels. Human lymphocytes were cultured in supplemented RPMI medium for 72 h including treatment for 2 h with K2CrO4 (0-150 microM), CdCl2 (0-150 microM) or methyl methanesulfonate (500 microM) as a positive control. Quantification of SSBs by EM-ISEL showed that both compounds are genotoxic agents at non-cytotoxic concentrations. This study brings new information on the utility of EM-ISEL for the evaluation of genotoxicity and confirms the genotoxic effects induced by chromium and cadmium.

Toxicity and carcinogenicity of acidogenic or alkalogenic diets in rats; effects of feeding NH(4)Cl, KHCO(3) or KCl.

The effects of diet-induced acid-base disturbances were examined in 4-week, 13-week and 18-month toxicity studies, and in a 30-month carcinogenicity study. Rats were fed a natural ingredient diet (controls), supplemented with 2% or 4% KHCO(3) (base-forming diets), or with 1% or 2.1% NH(4)Cl (acid-forming diets). Additional controls were fed 3% KCl (neutral diet providing K(+) and Cl(-) in amounts equimolar to those in the 4% KHCO(3) diet and the 2.1% NH(4)Cl diet, respectively). NH(4)Cl induced the expected metabolic acidosis, as shown by decreased base excess in blood, decreased urinary pH and increased urinary net acid excretion. KHCO(3) induced the opposite effects. KCl did not affect the acid-base balance. Clinical condition and death rate were not affected. The feeding of high levels of each salt resulted in growth retardation and increased water intake and urinary volume. Plasma potassium and urinary potassium excretion were increased with KHCO(3) and KCl. Plasma chloride was increased with NH(4)Cl, but not with KCl. Urinary calcium and phosphate excretion were increased with NH(4)Cl, but there were no indications that bone minerals were involved (weight, calcium content and fat free solid of the femur were not affected). Standard haematological and clinical chemistry parameters were not affected. Kidney weights were increased with 2.1% NH(4)Cl. Hypertrophy of the adrenal zona glomerulosa occurred with KHCO(3), KCl and NH(4)Cl, due to chronic stimulation of the adrenal cortex by either K(+) or by NH(4)Cl-induced acidosis. An early onset (from week 13) of oncocytic tubules was noted in the kidneys of rats fed KHCO(3) and, after 30 months, the incidence of this lesion was much higher than the background incidence in ageing controls. No progression to oncocytomas was noted. KCl showed only slight effects on the early onset of oncocytic tubules (from 18 months). In contrast, the severity of nephrosis and the incidence of oncocytic tubules were decreased with 2.1% NH(4)Cl, suggesting a protective effect of acidosis. The feeding of KHCO(3) resulted in hyperplasia, papillomas and carcinomas of the urinary bladder. With KCl only a slight increase in proliferative urothelial lesions was noted. Apart from these (pre-)neoplastic lesions in the urinary bladder there were no treatment-related differences in tumour response among the groups. We concluded that most of the observed changes represent physiological adaptations to the feeding of acid- or base-forming salts. Remarkable effects noted with KHCO(3), and to a far lesser extent with KCl, consisted of renal oncocytic tubules and (pre-)neoplastic lesions of the urinary bladder epithelium. NH(4)Cl-induced chronic metabolic acidosis was not associated with dissolution of alkaline bone salts in rats. Finally, a protective effect of chronic acidosis on tumour development was not found.

Pharmacokinetics and toxicity of bromide following high-dose oral potassium bromide administration in healthy Beagles.

The pharmacokinetics of a multidose regimen of potassium bromide (KBr) administration in normal dogs was examined. KBr was administered at 30 mg/kg p.o. q 12 h for a period of 115 days. Serum, urine, and cerebrospinal fluid (CSF) bromide (BR) concentrations were measured at the onset of dosing, during the accumulation phase, at steady-state, and after a subsequent dose adjustment. Median elimination half-life and steady-state serum concentration were 15.2 days and 245 mg/dL, respectively. Apparent total body clearance was 16.4 mL/day/kg and volume of distribution was 0.40 L/kg. The CSF:serum BR ratio at steady-state was 0.77. Dogs showed no neurologic deficits during maintenance dosing but significant latency shifts in waves I and V of the brainstem auditory evoked response were evident. Following a subsequent dose adjustment, serum BR concentrations of approximately 400 mg/dL were associated with caudal paresis in two dogs. Estimated half-life during the accumulation phase was shorter than elimination half-lives reported in other studies and was likely related to dietary chloride content. The range of steady-state concentrations achieved suggests individual differences in clearance and bioavailability between dogs. The described protocol reliably produced serum BR concentrations that are required by many epileptic patients for satisfactory seizure control.

Cytotoxicity of a trial resin composite liner containing TiK2F6 on rat dental pulp cells.

The aim of this study was to assess the toxicological responses of a resin composite containing TiK2F6 and NaF in rat dental pulp cells. Trial resin composite liners were made, containing 3 wt% fluorides (TiK2F6 or NaF). These specimens were immersed in 5 ml of cell culture medium supplemented at 37 degrees C for 24 hours. The eluates were used for the experiments. We judged the cytotoxicity of the samples by the cell viability. The original elute solution was serially diluted and then the medium was exchanged for the dilute medium. The cell viability at 1, 2 or 5 days after commencement of re-culturing was calculated. The viability of cells in the eluate from the resin composite liners containing TiK2F6 and NaF decreased with time. The cytotoxicity of TiK2F6 was weaker than that of NaF at all times.

Interfacial reactions of osteoblasts to dental and implant materials.

Scanning electron microscopy was used to study the response of osteoblasts to various surfaces including ceramics and glasses as well as steel and titanium. Hydroxylapatite, tricalcium phosphate, bioglass, steel, and titanium supported cell adhesion. However, the toxic effects of the In-Ceram (Vita, Bad Säckingen, Germany), and feldspar ceramic and glaze were severe enough to cause verrucous necrosis that was identifiable after 2 days of culture. After 10 days in culture only the peripheral portions of these specimens were still occupied by cells; the cells in the central portion of the circular specimens had succumbed to necrosis. It was concluded that scanning electron microscopy is useful in identifying the response of cells to materials. Pathologic changes are not recognizable if they are limited to the internal structure of the cell, but readily discernible when they impinge on the morphologic integrity of the cell surface.