The Review of Current Knowledge on Neutrophil Gelatinase-Associated Lipocalin (NGAL).

Neutrophil gelatinase-associated lipocalin (NGAL) is a 25-kDa protein that is secreted mostly by immune cells such as neutrophils, macrophages, and dendritic cells. Its production is stimulated in response to inflammation. The concentrations of NGAL can be measured in plasma, urine, and biological fluids such as peritoneal effluent. NGAL is known mainly as a biomarker of acute kidney injury and is released after tubular damage and during renal regeneration processes. NGAL is also elevated in chronic kidney disease and dialysis patients. It may play a role as a predictor of the progression of renal function decreases with complications and mortality due to kidney failure. NGAL is also useful in the diagnostic processes of cardiovascular diseases. It is highly expressed in injured heart tissue and atherosclerostic plaque; its serum concentrations correlate with the severity of heart failure and coronary artery disease. NGAL increases inflammatory states and its levels rise in arterial hypertension, obesity, diabetes, and metabolic complications such as insulin resistance, and is also involved in carcinogenesis. In this review, we present the current knowledge on NGAL and its involvement in different pathologies, especially its role in renal and cardiovascular diseases.

Melatonin Treatment in Kidney Diseases.

Melatonin is a neurohormone that is mainly secreted by the pineal gland. It coordinates the work of the superior biological clock and consequently affects many processes in the human body. Disorders of the waking and sleeping period result in nervous system imbalance and generate metabolic and endocrine derangements. The purpose of this review is to provide information regarding the potential benefits of melatonin use, particularly in kidney diseases. The impact on the cardiovascular system, diabetes, and homeostasis causes melatonin to be indirectly connected to kidney function and quality of life in people with chronic kidney disease. Moreover, there are numerous reports showing that melatonin plays a role as an antioxidant, free radical scavenger, and cytoprotective agent. This means that the supplementation of melatonin can be helpful in almost every type of kidney injury because inflammation, apoptosis, and oxidative stress occur, regardless of the mechanism. The administration of melatonin has a renoprotective effect and inhibits the progression of complications connected to renal failure. It is very important that exogenous melatonin supplementation is well tolerated and that the number of side effects caused by this type of treatment is low.

Changes of the clock gene expression in central and peripheral organs of common carp exposed to constant lighting conditions.

In both mammals and fish, the circadian system is composed of oscillators that function at the cellular, tissue, and system levels and show the cyclic expression of clock genes. The organization and functioning of the biological clock in fish has not yet been characterized in detail, therefore, in the present study, an extensive analysis of the rhythmic expression of the main components of the biological clock in the central and peripheral organs of common carp was performed. The diurnal changes in clock gene expression were determined with respect to the subjective light cycle in fish exposed to constant light or darkness. It was found that the pattern of expression of clock, bmal, per and cry genes in carp was highest in the brain, pituitary gland, and retina. The peak clock and bmal expression was phase aligned with the lights off, whereas both per genes show similar phasing with acrophase close to light onset. The expression of cry genes varied depending on the type of tissue and the subtype of gene. The diurnal changes in the expression of clock genes demonstrates that, in particular, the expression of the clock in the retina shows endogenous oscillations independent of the influence of light. The data suggest that in carp, the time-varying expression of individual genes allows for a diverse and tissue-specific response to secure oscillations with variable phase and period.

Modeling Bilingual Lexical Processing Through Code-Switching Speech: A Network Science Approach.

The study of code-switching (CS) speech has produced a wealth of knowledge in the understanding of bilingual language processing and representation. Here, we approach this issue by using a novel network science approach to map bilingual spontaneous CS speech. In Study 1, we constructed semantic networks on CS speech corpora and conducted community detections to depict the semantic organizations of the bilingual lexicon. The results suggest that the semantic organizations of the two lexicons in CS speech are largely distinct, with a small portion of overlap such that the semantic network community dominated by each language still contains words from the other language. In Study 2, we explored the effect of clustering coefficients on language choice during CS speech, by comparing clustering coefficients of words that were code-switched with their translation equivalents (TEs) in the other language. The results indicate that words where the language is switched have lower clustering coefficients than their TEs in the other language. Taken together, we show that network science is a valuable tool for understanding the overall map of bilingual lexicons as well as the detailed interconnections and organizations between the two languages.

Corrigendum: Modeling Bilingual Lexical Processing Through Code-Switching Speech: A Network Science Approach.

[This corrects the article DOI: 10.3389/fpsyg.2021.662409.].

The effects of temperature on the proxies of visual detection of Danio rerio larvae: observations from the optic tectum.

Numerous studies have indicated that temperature improves the visual capabilities of different ectotherms, including a variety of fish species. However, none of these studies has directly tested whether elevated temperature extends the visual detection distance - the distance from which a visual stimulus is detected. To test this hypothesis, we investigated the effect of temperature on the visual detection distance of zebrafish (Danio rerio) larvae by measuring the largest distance from a moving target that induced a neural response in the optic tectum. We applied advanced methods of functional calcium imaging such as selective plane illumination microscopy in combination with a miniature OLED screen. The screen displayed an artificial, mobile prey, appearing in the visual field of the larvae. We performed experiments in three temperature treatments (18, 23 and 28°C) on transgenic fish expressing a fluorescent probe (GCaMP5G) that changes intensity in response to altered Ca2+ concentrations in the nerves in the optic tectum. Based on the obtained data, we also measured three additional parameters of the neural response in the optic tectum, each being a proxy of sensitivity to changes in the stimulus movement. We did not confirm our hypothesis, since the visual detection distance shortened as the temperature increased. Moreover, all of the three additional parameters indicated a negative effect of the temperature on the speed of the neural response to the stimuli. However, the obtained results could be explained not only by worse visual capabilities at the elevated temperature, but also by the differences in the visual field and in turn, the retinotopic location of the visual stimulus between the temperature treatments, since the stimulus in the experiments moved horizontally rather than forward and backward from the fish's eye.

Kairomone-like activity of bile and bile components: A step towards revealing the chemical nature of fish kairomone.

Despite the efforts of a number of research groups worldwide, we still have a poor understanding of the chemical nature of the fish kairomones which induce defensive morphology, life history and behavior in their planktonic prey. Bile excreted by foraging fish play a crucial role in their signaling systems. Using high-performance liquid chromatography (HPLC), we revealed the presence of primary and secondary bile acids and bile salts in fish-conditioned water, similar as in carp bile. Upon exposure to either fish bile or commercially acquired bile salts, Daphnia demonstrated similar changes in life history and behavior as when exposed to fish kairomones. The synergic effect of the injured Daphnia alarm substance with fish bile on Daphnia life history is similar to the adaptive effect of the same alarm substance combined with fish kairomones. This strongly supports the view that fish bile or selected bile acids/salts may be responsible for the biological activity of kairomones.

Morphological deformation of Daphnia magna embryos caused by prolonged exposure to ibuprofen.

The effect of chronic exposure of freshwater cladoceran Daphnia magna to low, environmentally relevant concentrations i.e 4 µgL-1of ibuprofen (a nonsteroidal anti-inflammatory drug) in a laboratory experiment was studied. We observed the key life history traits of first and fifth generation individuals: age and size at first reproduction, number of first clutch eggs and individual growth rate. Moreover, chosen molecular/subcellular markers of experimental animals stress response such as triglyceride content, heat shock proteins (HSP) expression and DNA:RNA ratio were collected. Overall, chronic exposure to ibuprofen had no significant effect on the molecular markers nor on the life history parameters of the Daphnia. It did, however, caused lethal morphological deformities in embryos and juvenile daphnids. Depending on the clonal affiliation, exposure to a low dosage of ibuprofen over five generations resulted in the deformation of ∼3%-∼10% of the first clutch of offspring. Also, up to 90% of females carried at least one deformed embryo. This is the first time that research has revealed such an effect of ibuprofen on D. magna.

Dexamethasone affects day/night development and function of thymus-derived T regulatory cells.

Thymus-derived T regulatory (tTregs) cells play a crucial role in the maintenance of tolerance and immune homeostasis. Mechanisms and factors regulating tTreg development and function are widely investigated, but to a large degree still remain unclear. Our previous findings demonstrated that, in physiological conditions, the development and suppressive function of tTregs demonstrated day/night rhythmicity, which correlated with the concentration of plasma corticosterone and the expression of glucocorticoid receptors. In this study we ask whether synthetic glucocorticoids commonly used to inhibit excessive activity of the immune system, can modulate the development and suppressive function of tTregs in vivo depending on the time of administration. Young C57BL/6 male and female mice were injected intraperitoneally with a single dose of dexamethasone at two time points of the day: 7.00-8.00 a.m. and 7.00-8.00 p.m. The experimental can be used to indicate on the potentially expected positive or adverse side effects and can constitute also a good model for the assessment of the effects of long-term therapy. The results of our studies demonstrated the increase of the percentage of tTregs at both time points in male mice, but only in the evening in females. The suppressive activity of tTregs increased independently on the day time of in female mice, but in the morning only in males. We concluded that in the condition of dexamethasone supplementation, the elevated suppressive potential of tTregs is balanced by the induction apoptosis in order to prevent excessive suppression.

Daily Profiles of Neuropeptides, Catecholamines, and Neurotransmitter Receptors in the Chicken Pineal Gland.

The avian pineal gland is one of three central biological clocks that contain all the components of a circadian system: a photoreceptive input, oscillator, and rhythmically secreted melatonin (MEL) as an effector. The biosynthesis of MEL is regulated by the neurotransmitters noradrenaline (NA), vasoactive intestinal peptide (VIP), and pituitary adenylate cyclase-activating polypeptide (PACAP). The aim of the present study was to characterize the daily profile of neurotransmitters and their receptors in the pineal gland of male Hy-Line chickens housed under controlled light (12:12 light:dark) conditions. The pineal glands were isolated from 16-day-old birds every 2 h over a 24-h period, immediately after decapitation. The catecholamine content was measured using HPLC with electrochemical detection, whereas expression of VIP and PACAP was measured using quantitative real-time PCR (RT-qPCR) assays and Western blotting. Expression of the neurotransmitter receptors was also measured using RT-qPCR. We found daily changes in NA content, with elevated nocturnal levels, whereas the NA receptor was expressed in antiphase. Although we did not observe daily changes in VIP and PACAP protein levels, we found prominent diurnal changes in the expression of the Vip and Pacap genes. We also detected precursors of NA, 3,4-dihydroxy-L-phenylalanine (DOPA), and dopamine (DA) in the pineal glands, in addition to the DA metabolites. Our results provide the first evidence that the pineal gland itself may synthetize the neurotransmitters needed to regulate MEL biosynthesis.

Avian biological clock - Immune system relationship.

Biological rhythms in birds are driven by the master clock, which includes the suprachiasmatic nucleus, the pineal gland and the retina. Light/dark cycles are the cues that synchronize the rhythmic changes in physiological processes, including immunity. This review summarizes our investigations on the bidirectional relationships between the chicken pineal gland and the immune system. We demonstrated that, in the chicken, the main pineal hormone, melatonin, regulates innate immunity, maintains the rhythmicity of immune reactions and is involved in the seasonal changes in immunity. Using thioglycollate-induced peritonitis as a model, we showed that the activated immune system regulates the pineal gland by inhibition of melatonin production at the level of the key enzyme in its biosynthetic pathway, arylalkylamine-N-acetyltransferase (AANAT). Interleukin 6 and interleukin 18 seem to be the immune mediators influencing the pineal gland, directly inhibiting Aanat gene transcription and modulating expression of the clock genes Bmal1 and Per3, which in turn regulate Aanat.

Daily profiles of melatonin synthesis-related indoles in the pineal glands of young chickens (Gallus gallus domesticus L.).

The aim of the present study was to characterize the daily profiles of melatonin synthesis-related indoles in the pineal glands of male Hy-Line chickens hatched in the winter and reared under controlled light (L:D 12:12) conditions. The pineal glands were isolated from 16-day-old birds immediately after decapitation every 2h over a 24-h period. The indole contents were measured using HPLC with fluorescence detection. According to the obtained data, in chicken pineal glands tryptophan occurred at the highest level among the investigated compounds, showing rhythmical, daily changes with decreased levels during the scotophase. Rhythmical fluctuations were also observed for all studied tryptophan derivatives, except serotonin, 5-hydroxyindole acetic acid and 5-hydroxytryptophol. The highest levels of 5-hydroxytryptophan, N-acetylserotonin and melatonin were observed during the night, whereas the highest levels of 5-methoxytryptophol and 5-methoxyindoleacetic acid were observed during the day. The most interesting results concerned serotonin and the associated oxidative deamination products. The serotonin content did not exceed 5% of all investigated indoles, suggesting that there is no reserve pool of this indoleamine in the chicken pineal gland and that the activity of aromatic L-amino acid decarboxylase might be an important factor of melatonin synthesis regulation. In contrast to serotonin, 5-hydroxyindole acetic acid occurred at high levels in the investigated pineal gland, suggesting intensive oxidative deamination and explaining the observed low content of this indoleamine.

Day/night changes of thymus-deriving natural regulatory T cell development and function.

Activity of the immune system shows day/night rhythmicity. Changes in the migration and biological activities of immune cells are strongly regulated by the HPA axis. Another mechanism governing the level of the immune response is based on the suppressive activity of natural regulatory T cells CD4+CD25+Foxp3+ (nTregs) which play a crucial role in the maintenance of self-tolerance and immune homeostasis. The aim of our study was to answer the question: are nTregs changing their development and suppressive activity according to day/night cycle? We demonstrated the effect of day time on nTreg distribution in the thymus and their suppressive potential to inhibit the proliferation of activated responder T cells.

Detection and identification of potentially toxic cyanobacteria in Polish water bodies.

The main goal of this study was to determine the distribution of potentially toxic cyanobacteria in 39 selected Polish water bodies. From the water bodies with blooms and also from those in which blooms were not visible 87 samples were investigated. For the first time samples from ponds localized in villages with high agricultural activities were included. Lakes for which microcystin concentrations had been determined before were included as a reference for the research. The detection of cyanobacteria was conducted by microscopic observation as well as by PCR amplification of the rpoC1 gene fragment. Cyanobacteria were present in 75 out of 87 samples. The presence of potentially toxic cyanobacteria was detected by amplification of the mcyB and mcyE genes, which are involved in the biosynthesis of microcystins. Both genes were detected in 7 out of 9 blooms investigated. In the case of samples collected from water bodies in which blooms were not observed, the mcyB and mcyE genes were detected in 20 out of 36. In order to identify the cyanobacteria occurring in selected reservoirs, 16S plus ITS clone libraries were constructed. The method allowed distinguishing 18 different genotypes. After sequence analysis, cyanobacteria belonging to genera Microcystis, Planktothrix, Anabaena, Pseudanabaena, Synechocystis, Synechococcus and Woronichinia were identified. Results confirmed the usefulness of the rpoC1 and mcy genes for monitoring water bodies and detection of potentially toxic cyanobacteria. Application of molecular markers allowed detecting potentially toxic cyanobacteria before the bloom was visible. This is the first comprehensive study concerning cyanobacteria present in different types of Polish water bodies performed using molecular markers.

Photoperiod-related changes in hormonal and immune status of male Siberian hamsters, Phodopus sungorus.

Previously we have demonstrated that in Siberian hamsters some immune measures, especially the development of experimentally evoked peritonitis, varied in a photoperiod- and gender-dependent manner. The aim of the present study was to investigate whether the photoperiod-related differences in the activity of inflammation-involved immune cells are in this species attributed to the changes in the pineal gland function and/or hormonal status. Male hamsters housed in short day (SD), compared with those from long day (LD) conditions, exhibited significantly reduced plasma testosterone concentration and elevated cortisol and melatonin levels, the latter resulting from increased activity of hydroxyindole-O-methyltransferase (HIOMT). In LD hamsters but not in those from SD, an intraperitoneal (i.p.) injection of zymosan evoked a well-pronounced peritonitis expressed by increased free radical (ROS) production by peritoneal leukocytes (PTLs) stimulated in vitro with PMA. ROS production by these cells was additionally stimulated by both in vivo and in vitro treatment with melatonin and the latter was partially reversed by melatonin receptor antagonist luzindole. To conclude, in Siberian hamsters melatonin seems to exert rather immunostimulatory than anti-inflammatory effect, therefore other mechanisms, e.g. immunosuppressive effect of glucocorticoids, may underlay the compromised immune status observed in SD in this species.

Diurnal differences in melatonin effect on intracellular Ca2+ concentration in chicken spleen leukocytes in vitro.

Melatonin plays a pleiotropic role in the immune system of mammals and birds. Endogenous and exogenous melatonin modulates lymphocyte proliferation via specific MT(1), MT(2) and Mel(1c) membrane receptors, although the mechanisms behind this process are poorly understood. The diurnal changes in the expression and function of melatonin membrane receptors within the immune system have so far received little attention. We investigated the day/night differences in melatonin membrane receptor mRNA expression in chicken lymphoid organs and cultured splenocytes and examined the in vitro effect of melatonin and 2-iodomelatonin on the intracellular Ca(2+) concentration ([Ca(2+)](i)) in chicken splenocytes. In whole organs, expression of all subtypes of Mel membrane receptors was observed, and the level did not change significantly with the time of day. Interestingly, we observed a significant increase in the expression of the transcripts of all receptor subtypes in cultured splenocytes isolated at night compared with cells obtained during the day. In chicken spleen leukocytes isolated during the day, melatonin and 2-iodomelatonin increased [Ca(2+)](i), with only 2-iodomelatonin being effective in the 'night' cells. Luzindole modulated the [Ca(2+)](i) increase caused by melatonin receptor agonists: it potentiated the stimulatory effect of melatonin during the day, but counteracted that evoked by 2-iodomelatonin at night. The results of this study demonstrate that melatonin can induce changes in [Ca(2+)](i) in chicken spleen leukocytes that should modulate proliferation. The effect of melatonin on [Ca(2+)](i) is less pronounced at night, possibly caused by receptor desensitization.

Functional MT1 and MT2 melatonin receptors in mammals.

Melatonin, dubbed the hormone of darkness, is known to regulate a wide variety of physiological processes in mammals. This review describes well-defined functional responses mediated through activation of high-affinity MT1 and MT2 G protein-coupled receptors viewed as potential targets for drug discovery. MT1 melatonin receptors modulate neuronal firing, arterial vasocon-striction, cell proliferation in cancer cells, and reproductive and metabolic functions. Activation of MT2 melatonin receptors phase shift circadian rhythms of neuronal firing in the suprachiasmatic nucleus, inhibit dopamine release in retina, induce vasodilation and inhibition of leukocyte rolling in arterial beds, and enhance immune responses. The melatonin-mediated responses elicited by activation of MT1 and MT2 native melatonin receptors are dependent on circadian time, duration and mode of exposure to endogenous or exogenous melatonin, and functional receptor sensitivity. Together, these studies underscore the importance of carefully linking each melatonin receptor type to specific functional responses in target tissues to facilitate the design and development of novel therapeutic agent.

Season- and gender-dependent changes in the immune function of Siberian hamsters (Phodopus sungorus).

OBJECTIVES: Siberian hamsters are photoperiodic animals exhibiting seasonality of reproduction and other physiological functions. Thus, the influence of photoperiod on the in vitro activity of selected immune cells from male and female hamsters challenged with peritoneal inflammation was examined. METHODS: Animals were housed for 8-10 weeks in LD (L:D=18:6) or SD (L:D=6:18). Peritoneal leukocytes (PTLs) and splenocytes were isolated form male and female and testicular macrophages (TMs) from male hamsters, intact or challenged with zymosan-induced peritonitis. PTL and TM activity was assessed by the level of reactive oxygen species (ROS) measured with the use of flow cytometry and splenocyte activity -- by the spontaneous and mitogen-stimulated proliferation measured with the use of 3H-tymidine incorporation test. RESULTS: Results obtained indicate that the immune system of Siberian hamsters is highly sexually dimorphic. Experimentally evoked peritonitis developed differently in males and females: only in LD male hamsters an increase in PTL activity was observed after zymosan treatment. Also, in LD males, PTL activity was higher in LD than in SD. Developing peritonitis exerted in these animals a stimulatory effect on splenocyte proliferation but had no influence on cells residing in the immune privileged testes. Splenocyte proliferation, both spontaneous and PHA-stimulated, depended on the photoperiod studied: in LD it was significantly higher than in SD in animals of both sexes. CONCLUSIONS: Innate immunity of Siberian hamsters studied on the peritoneal inflammation model, seems to be gender- and photoperiod dependent. Moreover, local inflammation may affect other lymphoid organs but does not influence immune-privileged sites.

Intracellular second messengers involved in melatonin signal transduction in chicken splenocytes in vitro.

The pineal hormone melatonin exhibits immunomodulatory activity well documented in mammals and birds. The mechanism of melatonin action within the immune system is, however, poorly understood. In mammalian immune cells in vitro, melatonin acts mainly as an antiapoptotic, oncostatic and antiproliferative agent, and these effects are exerted via specific receptors or are related to its free radical scavenging activity. In previous studies we have found that in short-term chicken splenocyte cultures in vitro melatonin stimulated basil proliferation and inhibited that stimulated with phytohemagglutinin, a T-cell mitogen. This paper is devoted to the involvement of membrane receptors, previously characterised by us as MT2 (Mel(1b)) and Mel(1c) subtypes, in the above mentioned melatonin effects in chicken splenocyte cultures. For this purpose, in present study a nonselective melatonin receptor antagonist, luzindole, and the selective MT2 blocker, 4P-PDOT, were used. The effect of melatonin on second messengers, cyclic adenosine-3',5'-monophosphate (cAMP) and inositol-1,4,5-trisphosphate (IP(3)), involved in the regulation of proliferation, was examined. We have found that the stimulation of proliferation occurs via Mel(1c) receptor and is associated with the changes in intracellular second messengers concentration: a decrease in cAMP and an increase in IP(3). In contrast, in mitogen-activated splenocytes, melatonin-induced inhibition of proliferation is mediated by MT2 receptors and is related to cAMP accumulation, as well as a decrease in IP(3). In conclusion, we have demonstrated that the stimulatory and inhibitory effect of melatonin on chicken splenocytes in vitro, dependent on the magnitude of cell stimulation, resulted from two different subtypes of membrane receptors.