Irregular sleep–wake cycle associated with malignant brain tumor in an adolescent

Sleep and Biological Rhythms - We report an adolescent case of malignant brain tumor who presented with an irregular sleep–wake cycle as the first significant clinical symptom. The patient...     

Genomic imprinting in mammals: an interplay between chromatin and DNA methylation?

Most imprinted loci have key regulatory elements that are methylated on only one of the parental chromosomes. For several of these 'differentially methylated regions', recent studies establish that the unmethylated chromosome has a specialized chromatin organization that is characterized by nuclease hypersensitivity. The novel data raise the question of whether specific proteins and associated chromatin features regulate the allele-specificity of DNA methylation at these imprinting control elements.     

The interplay between chromosome stability and cell cycle control explored through gene–gene interaction and computational simulation

Chromosome stability models are usually qualitative models derived from molecular-genetic mechanisms for DNA repair, DNA synthesis, and cell division. While qualitative models are informative, they are also challenging to reformulate as precise quantitative models. In this report we explore how (A) laboratory experiments, (B) quantitative simulation, and (C) seriation algorithms can inform models of chromosome stability. Laboratory experiments were used to identify 19 genes that when over-expressed cause chromosome instability in the yeast Saccharomyces cerevisiae. To better understand the molecular mechanisms by which these genes act, we explored their genetic interactions with 18 deletion mutations known to cause chromosome instability. Quantitative simulations based on a mathematical model of the cell cycle were used to predict the consequences of several genetic interactions. These simulations lead us to suspect that the chromosome instability genes cause cell-cycle perturbations. Cell-cycle involvement was confirmed using a seriation algorithm, which was used to analyze the genetic interaction matrix to reveal an underlying cyclical pattern. The seriation algorithm searched over 10¹⁴ possible arrangements of rows and columns to find one optimal arrangement, which correctly reflects events during cell cycle phases. To conclude, we illustrate how the molecular mechanisms behind these cell cycle events are consistent with established molecular interaction maps.     

Cell cycle–related metabolism and mitochondrial dynamics in a replication-competent pancreatic beta-cell line

Cell replication is a fundamental attribute of growth and repair in multicellular organisms. Pancreatic beta-cells in adults rarely enter cell cycle, hindering the capacity for regeneration in diabetes. Efforts to drive beta-cells into cell cycle have so far largely focused on regulatory molecules such as cyclins and cyclin-dependent kinases (CDKs). Investigations in cancer biology have uncovered that adaptive changes in metabolism, the mitochondrial network, and cellular Ca²⁺ are critical for permitting cells to progress through the cell cycle. Here, we investigated these parameters in the replication-competent beta-cell line INS 832/13. Cell cycle synchronization of this line permitted evaluation of cell metabolism, mitochondrial network, and cellular Ca²⁺ compartmentalization at key cell cycle stages. The mitochondrial network is interconnected and filamentous at G1/S but fragments during the S and G2/M phases, presumably to permit sorting to daughter cells. Pyruvate anaplerosis peaks at G1/S, consistent with generation of biomass for daughter cells, whereas mitochondrial Ca²⁺ and respiration increase during S and G2/M, consistent with increased energy requirements for DNA and lipid synthesis. This synchronization approach may be of value to investigators performing live cell imaging of Ca²⁺ or mitochondrial dynamics commonly undertaken in INS cell lines because without synchrony widely disparate data from cell to cell would be expected depending on position within cell cycle. Our findings also offer insight into why replicating beta-cells are relatively nonfunctional secreting insulin in response to glucose. They also provide guidance on metabolic requirements of beta-cells for the transition through the cell cycle that may complement the efforts currently restricted to manipulating cell cycle to drive beta-cells through cell cycle.     

Do ATP and UTP involve cGMP in positive inotropism on rat atria?

ATP and UTP induced a dual inotropic effect in rat left atria: first a decrease and then an increase in contractile tension were observed. PPADS, an antagonist of P2X receptors, inhibited positive inotropism induced by ATP and alpha,beta-meATP. Chiefly, we investigated intracellular mechanisms responsible for the positive inotropism. We tested cromakalim and glibenclamide, an activator and an inhibitor, respectively, of ATP-sensitive K(+) channels. These compounds did not influence the effects of ATP. IBMX, a phosphodiesterase inhibitor, and H-7, an inhibitor of protein kinase C and cAMP-dependent protein kinase, did not modify the inotropic effects of ATP. Instead, H-8, an inhibitor of cAMP- and cGMP-dependent protein kinases, strongly inhibited the positive effects of both ATP and UTP, suggesting the possible involvement of cGMP in the inotropism. Also, LY 83583, an inhibitor of cGMP production, reduced positive inotropism by alpha,beta-meATP, ATP and UTP. Moreover, 8-Br-cGMP (50 microM), a stable analogue of cGMP, inhibited positive inotropism by all nucleotides. Lastly, we determined intracellular cGMP levels by RIA; the cyclic nucleotide increased during positive inotropism induced by ATP and UTP. The results regarding positive inotropism suggest that: (a) ATP acts through P2X receptors, while UTP may act by P2X, but also through PPADS-insensitive receptors; and (b) changes in intracellular cGMP concentration are involved in this inotropic effect.     

Leaf succulence determines the interplay between carboxylase systems and light use during Crassulacean acid metabolism in Kalanchöe species

The photosynthetic physiology of Crassulacean acid metabolism was investigated in two Kalancho? species with differing leaf succulence. The magnitude of CAM was higher for the more succulent leaves of K. daigremontiana, compared to the less succulent leaves of K. pinnata. High succulence was related to low mesophyll conductance: K. pinnata was able to maximize diurnal carbon gain by the C(3) pathway, whereas increased succulence is associated with a higher commitment to the CAM cycle in K. daigremontiana. The Rubisco specificity factor, tau, determining selectivity for CO(2) over O(2), was similar for both species (approximately 88), and lower than that of Spinacea (approximately 95), but in contrast to C(4) plants, the Rubisco K(mCO(2)) (determined independently) was also lower in Kalancho? spp. than in spinach. Differences in light use were related to the nature of the sink strength in each Phase of CAM, with PEPC activity resulting in low electron transport rates. Decarboxylation was marked by high, non-saturated rates of electron transport, with Rubisco activity and activation state increasing in both species during the course of the light period. The degree of succulence, and extent of CAM activity, was associated with a progressive inhibition of PSII photochemistry and potential Rubisco activity during the night in both species. Rubisco could be 'woken up' more rapidly in K. pinnata, whereas 45 min light acclimation was required for full recovery of electron transport and Rubisco activity in K. daigremontiana. Leaf morphology therefore seems to alter the expression of and dependence on CAM, but also the extent of co-regulation of carboxylase networks and light use capacity.     

Metabolic pathways in the periphery and brain: Contribution to mental disorders?

The association between mental disorders and diabetes has a long history. Recent large-scale, well-controlled epidemiological studies confirmed a link between diabetes and psychiatric illnesses. The scope of this review is to summarize our current understanding of this relationship from a molecular perspective. We first discuss the potential contribution of diabetes-associated metabolic impairments to the etiology of mental conditions. Then, we focus on possible shared molecular risk factors and mechanisms. Simple comorbidity, shared susceptibility loci, and common pathophysiological processes in diabetes and mental illnesses have changed our traditional way of thinking about mental illness. We conclude that schizophrenia and affective disorders are not limited to an imbalance in dopaminergic and serotoninergic neurotransmission in the brain. They are also systemic disorders that can be considered, to some extent, as metabolic disorders.     

Delineating the complex mechanistic interplay between NF-κβ driven mTOR depedent autophagy and monocyte to macrophage differentiation: A functional perspective

Autophagy is an extremely essential cellular process aimed to clear redundant and damaged materials, namely organelles, protein aggregates, invading pathogens, etc. through the formation of autophagosomes which are ultimately targeted to lysosomal degradation. In this study, we demonstrated that mTOR dependent classical autophagy is ubiquitously triggered in differentiating monocytes. Moreover, autophagy plays a decisive role in sustaining the process of monocyte to macrophage differentiation. We have delved deeper into understanding the underlying mechanistic complexities that trigger autophagy during differentiation. Intrigued by the significant difference between the protein profiles of monocytes and macrophages, we investigated to learn that autophagy directs monocyte differentiation via protein degradation. Further, we delineated the complex cross-talk between autophagy and cell-cycle arrest in differentiating monocytes. This study also inspects the contribution of adhesion on various steps of autophagy and its ultimate impact on monocyte differentiation. Our study reveals new mechanistic insights into the process of autophagy associated with monocyte differentiation and would undoubtedly help to understand the intricacies of the process better for the effective design of therapeutics as autophagy and autophagy-related processes have enormous importance in human patho-physiology.     

Sticholysin I–membrane interaction: An interplay between the presence of sphingomyelin and membrane fluidity

Sticholysin I (St I) is a pore-forming toxin (PFT) produced by the Caribbean Sea anemone Stichodactyla helianthus belonging to the actinoporin protein family, a unique class of eukaryotic PFT exclusively found in sea anemones. As for actinoporins, it has been proposed that the presence of sphingomyelin (SM) and the coexistence of lipid phases increase binding to the target membrane. However, little is known about the role of membrane structure and dynamics (phase state, fluidity, presence of lipid domains) on actinoporins' activity or which regions of the membrane are the most favorable platforms for protein insertion. To gain insight into the role of SM on the interaction of St I to lipid membranes we studied their binding to monolayers of phosphatidylcholine (PC) and SM in different proportions. Additionally, the effect of acyl chain length and unsaturation, two features related to membrane fluidity, was evaluated on St I binding to monolayers. This study revealed that St I binds and penetrates preferentially and with a faster kinetic to liquid-expanded films with high lateral mobility and moderately enriched in SM. A high content of SM induces a lower lateral diffusion and/or liquid-condensed phases, which hinder St I binding and penetration to the lipid monolayer. Furthermore, the presence of lipid domain borders does not appear as an important factor for St I binding to the lipid monolayer.     

Evidence for an Ester Linkage between Lignin and Glucuronic Acid in Lignin–Carbohydrate Complexes by DDQ-Oxidation

The effects of ethanol feeding on the tryptophan-niacin metabolism were investigated in rats. Male rats of the Wistar strain (3 weeks old) were fed with a 20% casein diet and 15% ethanol ad libitum for 56 days. Urine samples were collected every week during the experimental period. Urinary excretion of N¹-methylnicotinamide (MNA) was always higher in the ethanol-fed group than in the control group, but urinary excretion of its oxidized metabolites N¹-methyl-2-pyridone-5-carboxamide (2-Py) and N¹-methyl-4-pyridone-3-carboxamide (4-Py) was always lower. Therefore, the ratio of (2-Py + 4-Py)/MNA excretion was lower in the ethanol-fed group than in the control group. The rats were killed on day 57 and liver enzyme activities involved in the tryptophan-niacin metabolism were also measured. Tryptophan oxygenase, kynureninase, nicotinamide mononucleotide adenylyltransferase, NAD⁺ synthetase, and nicotinamide methyltransferase activities were similar in both groups, but, 2-Py-forming MNA oxidase and 4-Py-forming MNA oxidase activities in the ethanol-fed group were 43% and 18% of the control, respectively. Therefore, the increase in MNA excretion and the decrease in the ratio of (2-Py + 4-Py)/MNA excretion might be attributed to the inhibition of the two MNA oxidase activities by ethanol feeding. Furthermore, it happened to be found that this excretion ratio also increased with growth up to nine weeks and this change was attributed to the increased reaction MNA → 4-Py with growth.     

Decreased glutamine synthetase,increased citrulline–nitric oxide cycle activities,and oxidative stress in different regions of brain in epilepsy rat model

To understand their role in epilepsy, the nitric oxide synthetase (NOS), argininosuccinate synthetase (AS), argininosuccinate lyase (AL), glutamine synthetase (GS), and arginase activities, along with the concentration of nitrate/nitrite (NOx), thiobarbituric acid reactive substances (TBARS), and total antioxidant status (TAS), were estimated in different regions of brain in rats subjected to experimental epilepsy induced by subcutaneous administration of kainic acid (KA). The short-term (acute) group animals were killed after 2 h and the long term (chronic) group animals were killed after 5 days of single injection of KA (15 mg/kg body weight). After decapitation of rats, the brain regions were separated and in their homogenates, the concentration of NOx, TBARS and TAS and the activities of NOS, AS, AL, arginase and glutamine synthetase were assayed by colorimetric methods. The results of the study demonstrated the increased activity of NOS and formation of NO in acute and chronic groups epilepsy. The activities of AS and AL were increased and indicate the effective recycling of citrulline to arginine. The activity of glutamine synthetase was decreased in acute and chronic groups of epilepsy compared to control group and indicate the modulation of its activity by NO in epilepsy. The activity of arginase was not changed in acute group; however it was decreased in chronic group and may favor increased production of NO in this condition. The concentration TBARS were increased and TAS decreased in acute and chronic groups of epilepsy and supports the oxidative stress in epilepsy.     

Immunoglobulin G transport increases in an in vitro blood–brain barrier model with amyloid-β and with neuroinflammatory cytokines

Immunotherapies are a promising strategy for the treatment of neurological diseases such as Alzheimer's disease (AD), however, transport of antibodies to the brain is severely restricted by the blood–brain barrier (BBB). Furthermore, molecular transport at the BBB is altered in disease, which may affect the mechanism and quantity of therapeutic antibody transport. To better understand the transport of immunotherapies at the BBB in disease, an in vitro BBB model derived from human induced pluripotent stem cells (iPSCs) was used to investigate the endocytic uptake route of immunoglobulin G (IgG). In this model, uptake of fluorescently labeled IgGs is a saturable process. Inhibition of clathrin-mediated endocytosis, caveolar endocytosis, and macropinocytosis demonstrated that macropinocytosis is a major transport route for IgGs at the BBB. IgG uptake and transport were increased after the addition of stimuli to mimic AD (Aβ_1–40 and Aβ_1–42) and neuroinflammation (tumor necrosis factor-α and interleukin-6). Lastly, caveolar endocytosis increased in the AD model, which may be responsible for the increase in IgG uptake in disease. This study presents an iPSC-derived BBB model that responds to disease stimuli with physiologically relevant changes to molecular transport and can be used to understand fundamental questions about transport mechanisms of immunotherapies in health and neurodegenerative disease.     

Does nitrogen fertilization have an impact on the trade-off between willow growth and defensive secondary metabolism?

The effect of nitrogen fertilization on the phytomass production, shoot length and leaf secondary phenolics in nine Salix myrsinifolia clones was investigated. Cuttings taken from 1-year-old and 2-year-old shoot parts of field cultivated clones were grown at three concentrations of nitrogen (7, 150 and 300 ppm) in a greenhouse for one growing season. The willow clones differed significantly in phytomass yield and secondary phenolics content. Nitrogen fertilization affected significantly the growth and secondary metabolism of willow clones. In most clones, the addition of nitrogen from a sub-optimum concentration (7 ppm) to an optimum concentration (150 ppm) appeared to reduce the amounts of salicortin, chlorogenic acid and unknown salicylate and increased shoot phytomass, but a supraoptimum nitrogen concentration (300 ppm) resulted in highly variable growth and secondary phenolic responses. A significantly negative correlation between leaf phytomass and amount of total phenolics at sub-optimum and optimum N-treatments indicates trade-off between growth and secondary metabolism in willow clones at these treatments. However, the leaf phytomass:total amount of phenolics ratio varied significantly among clones, and in all clones it was not significantly lower at sub-optimum N-treatment than at optimum N-treatment.     

A tribute to Ulrich Heber (1930–2016) for his contribution to photosynthesis research: understanding the interplay between photosynthetic primary reactions,metabolism and the environment

Upon high light excitation in photosynthetic bacteria, various triplet states of pigments can accumulate leading to harmful effects. Here, the generation and lifetime of flash-induced carotenoid triplets (³Car) have been studied by observation of the quenching of bacteriochlorophyll (BChl) fluorescence in different strains of photosynthetic bacteria including Rvx. gelatinosus (anaerobic and semianaerobic), Rsp. rubrum, Thio. roseopersicina, Rba. sphaeroides 2.4.1 and carotenoid- and cytochrome-deficient mutants Rba. sphaeroides Ga, R-26, and cycA, respectively. The following results were obtained: (1) ³Car quenching is observed during and not exclusively after the photochemical rise of the fluorescence yield of BChl indicating that the charge separation in the reaction center (RC) and the carotenoid triplet formation are not consecutive but parallel processes. (2) The photoprotective function of ³Car is not limited to the RC only and can be described by a model in which the carotenoids are distributed in the lake of the BChl pigments. (3) The observed lifetime of ³Car in intact cells is the weighted average of the lifetimes of the carotenoids with various numbers of conjugated double bonds in the bacterial strain. (4) The lifetime of ³Car measured in the light is significantly shorter (1–2 μs) than that measured in the dark (2–10 μs). The difference reveals the importance of the dynamics of ³Car before relaxation. The results will be discussed not only in terms of energy levels of the ³Car but also in terms of the kinetics of transitions among different sublevels in the excited triplet state of the carotenoid.     

Aging and urinary control: Alterations in the brain–bladder axis

Age-associated alterations in bladder control affect millions of older adults, with a heavy burden added to families both economically and in quality of life. Therapeutic options are limited with poor efficacy in older adults, lending to a growing need to address the gaps in our current understanding of urinary tract aging. This review summarizes the current knowledge of age-associated alterations in the structure and function of the brain–bladder axis and identifies important gaps in the field that have yet to be addressed. Urinary aging is associated with decreased tissue responsiveness, decreased control over the voiding reflex, signaling dysfunction along the brain–bladder axis, and structural changes within the bladder wall. Studies are needed to improve our understanding of how age affects the brain–bladder axis and identify genetic targets that correlate with functional outcomes.