Zn–0.8Mg–0.2Sr (wt.%) Absorbable Screws—An In-Vivo Biocompatibility and Degradation Pilot Study on a Rabbit Model

In this pilot study, we investigated the biocompatibility and degradation rate of an extruded Zn–0.8Mg–0.2Sr (wt.%) alloy on a rabbit model. An alloy screw was implanted into one of the tibiae of New Zealand White rabbits. After 120 days, the animals were euthanized. Evaluation included clinical assessment, microCT, histological examination of implants, analyses of the adjacent bone, and assessment of zinc, magnesium, and strontium in vital organs (liver, kidneys, brain). The bone sections with the implanted screw were examined via scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). This method showed that the implant was covered by a thin layer of phosphate-based solid corrosion products with a thickness ranging between 4 and 5 µm. Only negligible changes of the implant volume and area were observed. The degradation was not connected with gas evolution. The screws were fibrointegrated, partially osseointegrated histologically. We observed no inflammatory reaction or bone resorption. Periosteal apposition and formation of new bone with a regular structure were frequently observed near the implant surface. The histological evaluation of the liver, kidneys, and brain showed no toxic changes. The levels of Zn, Mg, and Sr after 120 days in the liver, kidneys, and brain did not exceed the reference values for these elements. The alloy was safe, biocompatible, and well-tolerated.     

Mitochondrial complex I inhibition in cerebral cortex of immature rats following homocysteic acid-induced seizures

The major finding of the present study concerns the marked decrease of respiratory chain complex I activity in the cerebral cortex of immature rats following seizures induced by bilateral intracerebroventricular infusion of dl-homocysteic acid (600 nmol/side). This decrease was already evident during the acute phase of seizures (60-90 min after infusion) and persisted for at least 20 h after the seizures. It was selective for complex I since activities of complex II and IV and citrate synthase remained unaffected. Inhibition of complex I activity was not associated with changes in complex I content. Based on enhanced lipoperoxidation and decreased aconitase activity, it can be postulated that oxidative modification is most likely responsible for the observed inhibition. Mitochondrial respiration, as well as cortical ATP levels remained in the control range, apparently due to excess capacity of the complex I documented by energy thresholds. On the other hand, the enhanced production of reactive oxygen species by inhibited complex I was observed in mitochondria from HCA-treated animals. The decrease of complex I activity was substantially attenuated when animals were treated with substances providing an anticonvulsant effect and also with selected free radical scavengers. We can assume that inhibition of complex I may elicit enhanced formation of reactive oxygen species and contribute thus to neuronal injury demonstrated in this model.     

In vitro and in vivo examination of cardiac troponins as biochemical markers of drug-induced cardiotoxicity

Cardiac troponin T (cTnT) and troponin I (cTnI) are becoming acknowledged as useful biochemical markers of drug-induced cardiotoxicity. In this study we examined the release kinetics of cTnT and cTnI using an in vitro model of isolated rat neonatal ventricular cardiomyocytes (NVCM, 72h treatment with 0.1-3microM of daunorubicin) and compared it with data from a rabbit model of chronic anthracycline-induced cardiomyopathy in vivo (3mg/kg of daunorubicin weekly, 10 weeks). In cell-culture media, the cTnI and cTnT concentrations were concentration- and time-dependently increasing in response to daunorubicin exposure and were negatively exponentially related to cardiomyocyte viability. With 3microM daunorubicin, the relative increase of AUC of cTnT and cTnI was 2.4- and 5.3-fold higher than the increase of LDH activity, respectively. In rabbits, the daunorubicin-induced cardiomyopathy was associated with progressive increase of both cTnT and cTnI. Although the correlation between cTnT and cTnI cumulative release (AUCs) was found (R=0.81; P<0.01) and both cardiac troponins corresponded well with the echocardiographically-assessed systolic dysfunction (R=0.83 and 0.81 for cTnT and cTnI, respectively; P<0.001), the first significant increase in cTnI levels was observed earlier (at a cumulative daunorubicin dose of 200mg/m(2)) than with cTnT (350mg/m(2)). In conclusion, our study has confirmed cTnT and cTnI as very sensitive and specific markers of anthracycline-induced cardiotoxicity. The troponins can become not only the bridge between the clinical and experimental studies of drug-induced cardiotoxicity but also the linkage between the preclinical experiments in vitro and in vivo.     

Thyroid autoimmunity occurs more frequently in women with breast cancer compared to women with colorectal cancer and controls but it has no impact on relapse-free and overall survival

The aim of the study was to compare the prevalence of autoimmune thyroid diseases (AITD) in patients with breast and colorectal cancer and controls and to evaluate the impact of AITD on the outcome of patients with breast cancer. Serum levels of TSH (thyroid-stimulating hormone), FT4 (free thyroxine), TPOAb (antibodies to thyroid peroxidase), TgAb (antibodies to thyroglobulin), selenium and prolactin were investigated in 210 randomly chosen women (89 with breast cancer and 72 with colorectal cancer after breast or abdominal surgery and 49 controls without oncological diseases). Eighty-four women with breast cancer were followed for a median of 136.0 months. The prevalence of positive titres of TPOAb (>60 kIU.l(-1)) was higher in the women with breast cancer as compared to positive titres in women with colorectal cancer and the controls (29.8 vs. 12.5 and 12.2%, respectively, P=0.016 and 0.036, respectively). Similarly, the prevalence of clinical, ultrasound and laboratory documented AITD was higher in women with breast cancer as compared to that in women with colorectal cancer and the controls (35.7 vs. 18.1 and 16.3%, respectively, P=0.014 and 0.029, respectively). We did not find any prognostic significance of FT4, TSH, TgAb, TPOAb, prolactin and the presence of AITD on relapse-free and overall survival among women with breast cancer. A negative prognostic significance of body mass index and serum levels of selenium on relapse-free survival was found. In conclusion, the prevalence of euthyroid AITD was higher in women with breast cancer as compared to euthyroid AITD in women with colorectal cancer and controls. The presence of AITD did not have an impact on the outcome of women with breast cancer.     

Inhibitory Effect of Fluoranthene on Photosynthetic Processes in Lichens Detected by Chlorophyll Fluorescence

The effect of increasing concentration (0.01, 1 and 5 mg l⁻¹) of fluoranthene (FLT) and the duration of exposure (12, 24, 36, 48 and 60 h) on the chlorophyll fluorescence parameters (F ₀, F _V/F _M, Φ_II and (F _M⁻ F _S)/F _S) of symbiotic algae in thalli of two foliose lichens Lasallia pustulata and Umbilicaria hirsuta was investigated. Also the FLT concentration in thalli of both lichen species and the proportion of symbiotic algae (photobionts) in thalli was studied. The results obtained demonstrated that the applied concentration of FLT (1 and 5 mg l⁻¹) affected primary photochemical processes of photosynthesis of algae in both lichen species. The F ₀ values increased and the F _V/F _M and Φ_II values decreased. The fluoranthene content in thallus of both lichen species was increased with increasing FLT concentration in the environment. Chlorophyll fluorescence parameters showed different sensitivity to the content of FLT in Lasallia pustulata and Umbilicaria hirsuta, respectively. Higher sensitivity, detected in U. hirsuta, can be related to its diverse anatomical structure (higher portion of symbiotic algae in thalli) and to the different (nearly 2.5 times higher) content of FLT after exposure.     

Seizures induced in immature rats by homocysteic acid and the associated brain damage are prevented by group II metabotropic glutamate receptor agonist (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate

The present study has examined the anticonvulsant and neuroprotective effect of group II metabotropic glutamate receptor (mGluR) agonist (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate (2R,4R-APDC) in the model of seizures induced in immature 12-day-old rats by bilateral intracerebroventricular infusion of dl-homocysteic acid (DL-HCA, 600 nmol/side). For biochemical analyses, rat pups were sacrificed during generalized clonic-tonic seizures, approximately 45-50 min after infusion. Comparable time intervals were used for sacrificing the pups which had received 2R,4R-APDC. Low doses of 2R,4R-APDC (0.05 nmol/side) provided a pronounced anticonvulsant effect which was abolished by pretreatment with a selective group II mGluR antagonist LY341495. Generalized clonic-tonic seizures were completely suppressed and cortical energy metabolite changes which normally accompany these seizures were either normalized (decrease of glucose and glycogen) or markedly reduced (an accumulation of lactate). EEG recordings support the marked anticonvulsant effect of 2R,4R-APDC, nevertheless, this was only partial. In spite of the absence of obvious motor phenomena, isolated spikes or even short periods of partial ictal activity could be observed. Isolated spikes could also be seen in some animals after application of 2R,4R-APDC alone, reflecting most likely subclinical proconvulsant activity of this agonist. The neuroprotective effect of 2R,4R-APDC was evaluated after 24 h and 6 days of survival following DL-HCA-induced seizures. Massive neuronal degeneration, as revealed by Fluoro-Jade B staining, was observed in a number of brain regions following infusion of DL-HCA alone (seizure group), whereas 2R,4R-APDC pretreatment provided substantial neuroprotection. The present findings support the possibility that group II mGluRs are a promising target for a novel approach to treating epilepsy.