A Plastic Clock: How Circadian Rhythms Respond to Environmental Cues in Drosophila

Circadian clocks synchronize the physiology and behavior of most animals with the day to night cycle. A fundamental property of the molecular pacemakers generating circadian rhythms is their self-sustained nature: they keep oscillating even under constant conditions, with a period close to, but not exactly, 24 h. However, circadian pacemakers have to be sensitive to environmental cues to be beneficial. They need to be reset every day to keep a proper phase relationship with the day to night cycle, and they have to be able to adjust to seasonal changes in day length and temperature. Here, we review our current knowledge of the molecular and neural mechanisms contributing to the plasticity of Drosophila circadian rhythms, which are proving to be remarkably sophisticated and complex.     

Mechanism of gain modulation at single neuron and network levels

Gain modulation, in which the sensitivity of a neural response to one input is modified by a second input, is studied at single-neuron and network levels. At the single neuron level, gain modulation can arise if the two inputs are subject to a direct multiplicative interaction. Alternatively, these inputs can be summed in a linear manner by the neuron and gain modulation can arise, instead, from a nonlinear input–output relationship. We derive a mathematical constraint that can distinguish these two mechanisms even though they can look very similar, provided sufficient data of the appropriate type are available. Previously, it has been shown in coordinate transformation studies that artificial neurons with sigmoid transfer functions can acquire a nonlinear additive form of gain modulation through learning-driven adjustment of synaptic weights. We use the constraint derived for single-neuron studies to compare responses in this network with those of another network model based on a biologically inspired transfer function that can support approximately multiplicative interactions.     

Genetic and phenotypic studies of the dark-like mutant mouse

The dark-like (dal) mutant mouse has a pleiotropic phenotype that includes dark dorsal hairs and reproductive degeneration. Their pigmentation phenotype is similar to Attractin (Atrn) mutants, which also develop vacuoles throughout the brain. In further characterizing the testicular degeneration of dal mutant males, we found that they had reduced serum testosterone and developed vacuoles in their testes. Genetic crosses placed dal upstream of the melanocortin 1 receptor (Mc1r) and downstream of agouti, although dal suppressed the effect of agouti on pigmentation but not body weight. Atrn(mg-3J) and dal showed additive effects on pigmentation, testicular vacuolation, and spongiform neurodegeneration, but transgenic overexpression of Attractin-like-1 (Atrnl1), which compensates for loss of ATRN, did not rescue dal mutant phenotypes. Our results suggest dal and Atrn function in the same pathway and that identification of the dal gene will provide insight into molecular mechanisms of vacuolation in multiple cell types.     

Control of cultivation processes for recombinant protein production: a review

The current state-of-the-art in control of cultivation processes for recombinant protein production is examined including the quantitative knowledge that can be activated for this purpose and the measurement techniques that can be employed for control at industrial manufacturing sites.     

Co-transplantation of bFGF-expressing amniotic epithelial cells and neural stem cells promotes functional recovery in spinal cord-injured rats

We have previously demonstrated that amniotic epithelial cells (AECs) can enhance survival and neural differentiation of neural stem cells (NSCs) when co-cultured in basal media. In addition, the presence of basic fibroblast growth factor (bFGF) enhances this AEC function. The aim of the present study was to extend those findings and investigate whether AECs modified with the bFGF gene will also enhance NSCs survival and neural differentiation in vivo and promote repair of the injured spinal cord. Female Wistar rats were used for a contusive spinal cord injury (SCI) model. Contusive SCIs were induced using a weight-drop device at levels T9-T11. Seven days following contusion, rats received grafts of NSCs only, NSCs with AECs/pLEGFP-hbFGF, or NSCs with AECs/pLEGFP-C1 into the injured region. Significant locomotor improvement was observed in the NSCs/AECs co-graft group beginning at 3 weeks compared with the NSCs or NaCl only groups. These results were confirmed and extended in an electrophysiological analysis. An immunohistological analysis revealed that AECs/pLEGFP-hbFGF promoted the survival (vs NaCl group: 194+/-9.17 vs 103.6+/-13.05) and neural differentiation (vs NaCl group: 14.24+/-1.11 vs 7+/-0.63) of co-transplanted NSCs. We also confirmed that AECs could promote the survival of host neurons. These results suggest that AECs/pLEGFP-hbFGF improve the NSCs survival and differentiation microenvironment and may be useful as a source of sustained trophic supported to improve NSCs differentiation into neurons in vivo. These findings suggest that a cograft of AECs/pLEGFP-hbFGF and NSCs may have benefits for SCI.     

Contuse lesion of the rat spinal cord of moderate intensity leads to a higher time-dependent secondary neurodegeneration than severe one. An open-window for experimental neuroprotective interventions

Secondary neurodegeneration takes place in the surrounding tissue of spinal cord trauma and modifies substantially the prognosis, considering the small diameter of its transversal axis. We analyzed neuronal and glial responses in rat spinal cord after different degree of contusion promoted by the NYU Impactor. Rats were submitted to vertebrae laminectomy and received moderate or severe contusions. Control animals were sham operated. After 7 and 30 days post surgery, stereological analysis of Nissl staining cellular profiles showed a time progression of the lesion volume after moderate injury, but not after severe injury. The number of neurons was not altered cranial to injury. However, same degree of diminution was seen in the caudal cord 30 days after both severe and moderate injuries. Microdensitometric image analysis demonstrated a microglial reaction in the white matter 30 days after a moderate contusion and showed a widespread astroglial reaction in the white and gray matters 7 days after both severities. Astroglial activation lasted close to lesion and in areas related to Wallerian degeneration. Data showed a more protracted secondary degeneration in rat spinal cord after mild contusion, which offered an opportunity for neuroprotective approaches. Temporal and regional glial responses corroborated to diverse glial cell function in lesioned spinal cord.     

Bioindication of chemical and hydromorphological habitat characteristics with benthic macro-invertebrates based on Artificial Neural Networks

This study aims to enhance the discussion about the usefulness of Artificial Neural Networks and specific input relevance detection for water quality assessment. The focus is on the development of neural modelling techniques initiating further research on predictor selection for bioindication. We tested the predictability of abiotic variables and quality indices BOD₅, conductivity, NH₃-N, NH₄-N, NO₂-N, NO₃-N, N_total, oxygen, pH-value, P_total, water temperature, chemical and morphological water quality class and saprobic index by means of benthic macro-invertebrates on 51 sampling sites of nine small streams in Central Germany. The results show that General Regression Neural Networks and modified Multi-Layer-Perceptrons can successfully be applied for modelling and predicting ecological and environmental data because of their ability to solve non-linear and multidimensional problems. Nevertheless, Linear Neural Networks have been proved suitable in some cases. Particularly, stepwise method, genetic algorithms and sensitivity analysis can be used to reduce the complexity of data sets in a reasonable way by detecting important predictors. In many cases the prediction accuracy even increases. In addition, using only the presence of species instead of their abundance provides mostly better results, simpler models and an easier collection of data. Thus, complex systems can be illustrated in easily surveyed models with low measuring and computing effort. We claim that the identification of indicator species and the assessment of complex anthropogenic impacts can be improved substantially and managed more efficiently using the neural-based approach. It is predestinated for bioindication, particularly with regard to aquatic ecosystems.     

Advanced glycation end products regulate anabolic and catabolic activities via NLRP3‐inflammasome activation in human nucleus pulposus cells

Intervertebral disc degeneration is widely recognized as a cause of lower back pain, neurological dysfunction and other musculoskeletal disorders. The major inflammatory cytokine IL‐1β is associated with intervertebral disc degeneration; however, the molecular mechanisms that drive IL‐1β production in the intervertebral disc, especially in nucleus pulposus (NP) cells, are unknown. In some tissues, advanced glycation end products (AGEs), which accumulate in NP tissues and promote its degeneration, increase oxidative stress and IL‐1β secretion, resulting in disorders, such as obesity, diabetes mellitus and ageing. It remains unclear whether AGEs exhibit similar effects in NP cells. In this study, we observed significant activation of the NLRP3 inflammasome in NP tissues obtained from patients with degenerative disc disease compared to that with idiopathic scoliosis according to results detected by Western blot and immunofluorescence. Using NP cells established from healthy tissues, our in vitro study revealed that AGEs induced an inflammatory response in NP cells and a degenerative phenotype in a NLRP3‐inflammasome‐dependent manner related to the receptor for AGEs (RAGE)/NF‐κB pathway and mitochondrial damage induced by mitochondrial reactive oxygen species (mtROS) generation, mitochondrial permeability transition pore (mPTP) activation and calcium mobilization. Among these signals, both RAGE and mitochondrial damage primed NLRP3 and pro‐IL‐1β activation as upstream signals of NF‐κB activity, whereas mitochondrial damage was critical for the assembly of inflammasome components. These results revealed that accumulation of AGEs in NP tissue may initiate inflammation‐related degeneration of the intervertebral disc via activation of the NLRP3 inflammasome.     

异氟烷对小鼠神经干细胞BDNF/Caspase3 及Notch信号相关基因表达的影响

目的:探讨异氟烷对小鼠神经干细胞的BDNF、Caspase3及Notch信号相关基因表达的影响。方法:给予体外培养的新生小鼠海马神经干细胞不同浓度异氟烷处理,实验分为对照组和异氟烷处理组(ISO1.0,ISO1.5),其中异氟烷组细胞分别给予1.0MAC和1.5 MAC两个浓度的异氟烷处理2小时,对照组给予O_2处理2小时,随后置于培养箱正常培养24小时后收集细胞,提取细胞RNA检测BDNF,Caspase3及Notch相关基因(Notch2、Notch 3和Hes5)的m RNA水平变化。结果:与对照组相比,(1)异氟烷组小鼠神经干细胞的功能基因BDNF m RNA水平下调,凋亡相关基因Caspase3的m RNA水平上调;(2)异氟烷组神经干细胞的Notch2和Notch3受体m RNA表达下调,Notch信号通路靶基因Hes5的m RNA水平也明显下调;(3)异氟烷对神经干细胞的作用具有剂量依赖性,浓度越高对神经干细胞BDNF、Caspase3及Notch信号相关基因表达的影响越大。结论:异氟烷可能通过抑制小鼠神经干细胞的Notch信号通路,下调BDNF的m RNA表达,上调Caspase3的m RNA水平,影响神经干细胞的正常功能。     

Neuromuscular degenerative effects of Ankaferd Blood Stopper® in mouse sciatic nerve model

Purpose: Ankaferd Blood Stopper^® (ABS), a licenced medicinal herbal extract, is commonly used as an effective topical haemostatic agent. This study is designed to investigate whether topical ABS application may cause peripheral nerve degeneration and neuromuscular dysfunction in a mouse sciatic nerve model.

Methods: Twenty mice were randomly divided into two groups; an ABS treated experimental group and a saline-treated control group. Left sciatic nerves were treated with 0.3?ml of ABS in the experimental group and 0.3?ml of sterile saline in the control group for 5?min. Peripheral nerve degeneration and neuromuscular dysfunction were evaluated by behavioural tests, electrophysiological analysis and weight ratio comparison of target muscles.

Results: The motor function, assessed by the sciatic function index, was significantly impaired in ABS-treated animals as compared to the animals treated with saline. Motor coordination, evaluated with the rotarod test, was significantly decreased (–42%) in ABS-treated animals compared to the saline-treated animals. The degree of pain, assessed by the reaction latency to thermal stimuli (hot-plate test), was significantly prolonged (313%) in ABS-treated mice when compared to the saline-treated mice. ABS-treated mice showed a significant reduction in motor nerve conduction velocity (MNCV) (–52%) and the compound muscle action potential (CMAP) (–47%); however, it significantly prolonged onset latency (23%). The gastrocnemius muscles weight ratio of the ABS group was considerably lower than that of the control group.

Conclusions: These findings demonstrate that ABS triggers peripheral nerve degeneration and functional impairment and, thus promotes a deterioration of sciatic nerves.