Increased Hippocampal Afterdischarge Threshold in Ketogenic Diet is Accompanied by Enhanced Kynurenine Pathway Activity

The efficacy of a ketogenic diet (KD) in controlling seizure has been shown in many experimental and clinical studies, however, its mechanism of action still needs further clarification. The major goal of the present study was to investigate the influence of the commercially available KD and caloric restriction (CR) on the hippocampal afterdischarge (AD) threshold in rats, and concomitant biochemical changes, specifically concerning the kynurenine pathway, in plasma and the hippocampus. As expected, the rats on the KD showed higher AD threshold accompanied by increased plasma β-hydroxybutyrate level compared to the control group and the CR rats. This group presented also lowered tryptophan and elevated kynurenic acid levels in plasma with similar changes in the hippocampus. Moreover, the KD rats showed decreased levels of branched chain amino acids (BCAA) and aromatic amino acids (AAA) in plasma and the hippocampus. No regular biochemical changes were observed in the CR group. Our results are analogous to those detected after single administrations of fatty acids and valproic acid in our previous studies, specifically to an increase in the kynurenine pathway activity and changes in peripheral and central BCAA and AAA levels. This suggests that the anticonvulsant effect of the KD may be at least partially associated with those observed biochemical alternations.

     

Paracellular and transcellular migration of metastatic cells through the cerebral endothelium

Breast cancer and melanoma are among the most frequent cancer types leading to brain metastases. Despite the unquestionable clinical significance, important aspects of the development of secondary tumours of the central nervous system are largely uncharacterized, including extravasation of metastatic cells through the blood‐brain barrier. By using transmission electron microscopy, here we followed interactions of cancer cells and brain endothelial cells during the adhesion, intercalation/incorporation and transendothelial migration steps. We observed that brain endothelial cells were actively involved in the initial phases of the extravasation by extending filopodia‐like membrane protrusions towards the tumour cells. Melanoma cells tended to intercalate between endothelial cells and to transmigrate by utilizing the paracellular route. On the other hand, breast cancer cells were frequently incorporated into the endothelium and were able to migrate through the transcellular way from the apical to the basolateral side of brain endothelial cells. When co‐culturing melanoma cells with cerebral endothelial cells, we observed N‐cadherin enrichment at melanoma‐melanoma and melanoma‐endothelial cell borders. However, for breast cancer cells N‐cadherin proved to be dispensable for the transendothelial migration both in vitro and in vivo. Our results indicate that breast cancer cells are more effective in the transcellular type of migration than melanoma cells.     

Synthesis and in Vitro Antimicrobial Activity Screening of New 3‐Acetyl‐2,5‐disubstituted‐1,3,4‐oxadiazoline Derivatives

Thirteen new 3‐acetyl‐2,5‐disubstituted‐1,3,4‐oxadiazoline derivatives were synthesized from corresponding hydrazide‐hydrazones of isonicotinic acid in the reaction with acetic anhydride. The obtained compounds were identified with the use of spectral methods (IR, ¹H‐NMR, ¹³C‐NMR, MS). In vitro antimicrobial activity screening of synthesized compounds against a panel of bacteria and fungi revealed interesting antibacterial and antifungal activity of tested 1,3,4‐oxadiazoline derivatives, which is comparable to that of commonly used antimicrobial agents.     

Control of the blood–brain barrier function in cancer cell metastasis

Cerebral metastases are the most common brain neoplasms seen clinically in the adults and comprise more than half of all brain tumours. Actual treatment options for brain metastases that include surgical resection, radiotherapy and chemotherapy are rarely curative, although palliative treatment improves survival and life quality of patients carrying brain‐metastatic tumours. Chemotherapy in particular has also shown limited or no activity in brain metastasis of most tumour types. Many chemotherapeutic agents used systemically do not cross the blood–brain barrier (BBB), whereas others may transiently weaken the BBB and allow extravasation of tumour cells from the circulation into the brain parenchyma. Increasing evidence points out that the interaction between the BBB and tumour cells plays a key role for implantation and growth of brain metastases in the central nervous system. The BBB, as the tightest endothelial barrier, prevents both early detection and treatment by creating a privileged microenvironment. Therefore, as observed in several in vivo studies, precise targetting the BBB by a specific transient opening of the structure making it permeable for therapeutic compounds, might potentially help to overcome this difficult clinical problem. Moreover, a better understanding of the molecular features of the BBB, its interrelation with metastatic tumour cells and the elucidation of cellular mechanisms responsible for establishing cerebral metastasis must be clearly outlined in order to promote treatment modalities that particularly involve chemotherapy. This in turn would substantially expand the survival and quality of life of patients with brain metastasis, and potentially increase the remission rate. Therefore, the focus of this review is to summarise the current knowledge on the role and function of the BBB in cancer metastasis.     

Light microscopy and scanning electron microscopy studies on the reduction of the tongue microstructures in the white stork (Ciconia ciconia,Aves)

The structure of the tongue in the white stork (Ciconia ciconia) is observed macroscopically and under light and scanning electron microscopy. Our observations of the tongue reveal a rare terminal reduction of the size of the tongue and microstructures of the lingual mucosa among the investigations of birds published so far. The short, triangular tongue with a pointed tip is approximately 2.5 cm long in the adult and is situated in the caudal part of the oral cavity close to the laryngeal prominence. On the dorsal surface of the tongue, no typical mucosa microstructures like lingual papillae, median groove or lingual prominence are observed. The main structure of the tongue is composed of rostral part of hyoid apparatus, that is, entoglossal cartilage connects with basihyoid. Very thin mucosa is composed of fibrous connective tissue covered with orthokeratinized epithelium. No lingual glands and muscles are observed in the lamina propria of mucosa. Even though the triangular shape of the tongue in the white stork is typical for birds, the inner structure of the reduced organ is composed only of flat cartilagineous entoglossum of hyoid apparatus. During feeding behaviour of the white stork, the food transportation in oral cavity called cranio‐inertial transport is undoubtedly affected by structural reduction of the tongue.     

Free and Cell Wall-Bound Polyamines under Long-Term Water Stress Applied at Different Growth Stages of ×Triticosecale Wittm

Background

Long-stemmed and semi-dwarf cultivars of triticale were exposed to water stress at tillering, heading and anthesis stage. Quantitative determination of free and cell wall-bound polyamines, i.e. agmatine, cadaverine, putrescine, spermidine and spermine, was supplemented with an analysis of quantitative relationships between free and cell wall-bound polyamines.

Results

The content of free and cell wall-bound polyamines varied depending on the development stage, both under optimal and water stress conditions. Drought-induced increase in free agmatine content was observed at all developmental stages in long-stemmed cultivar. A depletion of spermidine and putrescine was also reported in this cultivar, and spermidine was less abundant in semi-dwarf cultivar exposed to drought stress at the three analyzed developmental stages. Changes in the content of the other free polyamines did not follow a steady pattern reflecting the developmental stages. On the contrary, the content of cell wall-bound polyamines gradually increased from tillering, through heading and until anthesis period.

Conclusion

Water stress seemed to induce a progressive decrease in the content of free polyamines and an accumulation of cell wall-bound polyamines.     

Gamma irradiation induced apoptotic changes in the chromatin structure of human erythroleukemia K562 cells

Exponentially growing human erythroleukemia K562 cells were synchronized by centrifugal elutriation prior to and after Co⁶⁰ γ-irradiation (4 Gy). Forward scatter flow cytometry used for size analysis revealed the increase of an early apoptotic cell population ranging from lower (0.05 C-value) to higher DNA content (∼1 C) as the cells progressed through the S phase. The increase in cellular DNA content expressed in C-values correlated with apoptotic chromatin changes manifested as many small apoptotic bodies in early S phase and larger but less numerous disintegrated apoptotic bodies in late S phase. Most significant changes after exposure to γ-irradiation took place in early S phase resulting in an increase of nuclear size by more than 50%. Cell fractions containing irradiated cells showed enhanced growth arrest at 2.4 C-value, which was accompanied by apoptosis. Apoptotic cell cycle arrest near to the G₁/G₀ checkpoint and apoptotic changes indicate that the radiation resistance of K562 cells is related to the bypass of the early stage of the p53 apoptotic pathway. Apoptotic changes in chromatin structure induced by γ-irradiation indicate that these injury-specific changes can be identified and distinguished from chromatin changes induced by UV radiation or heavy metals.     

Engineering a customizable antibacterial T6SS‐based platform in Vibrio natriegens

Bacterial pathogens are a major risk to human, animal, and plant health. To counteract the spread of antibiotic resistance, alternative antibacterial strategies are urgently needed. Here, we construct a proof‐of‐concept customizable, modular, and inducible antibacterial toxin delivery platform. By engineering a type VI secretion system (T6SS) that is controlled by an externally induced on/off switch, we transform the safe bacterium, Vibrio natriegens, into an effective antibacterial weapon. Furthermore, we demonstrate that the delivered effector repertoire, and thus the toxicity range of this platform, can be easily manipulated and tested. We believe that this platform can serve as a foundation for novel antibacterial bio‐treatments, as well as a unique tool to study antibacterial toxins.