Cell Death Associated with Abnormal Mitosis Observed by Confocal Imaging in Live Cancer Cells

Phenanthrene derivatives acting as potent PARP1 inhibitors prevented the bi-focal clustering of supernumerary centrosomes in multi-centrosomal human ...

Tel-Aviv University

The frontal ganglion (FG) is part of the insect stomatogastric nervous system and is found in most insect orders. Previous work has shown that in the desert locust, Schistocerca gregaria, the FG constitutes a major source of innervation to the foregut. In an in vitro preparation, isolated from all descending and sensory inputs, the FG spontaneously generated rhythmic multi-unit bursts of action potentials that could be recorded from all its efferent nerves. The consistent endogenous FG rhythmic pattern indicates the presence of a central pattern generator network. We found the appearance of in vitro rhythmic activity to be strongly correlated with the physiological state of the donor locust. A robust pattern emerged only after a period of saline superfusion, if the locust had a very full foregut and crop, or if the animal was close to ecdysis. Accordingly, haemolymph collected at these stages inhibited an ongoing rhythmic pattern when applied onto the ganglion. We present this novel central pattern generating system as a basis for future work on the neural network characterisation and its role in generating and controlling behaviour.

The locust frontal ganglion: a central pattern generator network controlling foregut rhythmic motor patterns.

In the desert locust, Schistocerca gregaria, the frontal ganglion (FG) plays a key role in control of foregut movements, and constitutes a source of innervation to the foregut dilator muscles. In this work we studied the generation and characteristics of FG motor outputs in two distinct and fundamental behaviours: feeding and moulting. The FG motor pattern was found to be complex, and strongly dependent on the locust's physiological and behavioural state. Rhythmic activity of the foregut was dependent on the amount of food present in the crop; animals with food in their crop demonstrated higher FG burst frequency than those with empty crop. A very full gut inhibited the FG rhythm altogether. When no feeding-related foregut pattern was observed, the FG motor output was strongly correlated with the locust's ventilation pattern. This ventilation-related rhythm was dominant in pre-moulting locusts. During the moult, synchronization with the ventilation pattern can be transiently switched off, revealing the endogenous (feeding-related) FG pattern. This presumably happens during vigorous air swallowing, and could also be induced experimentally. Our findings suggest that the FG central pattern generator can be modulated to generate a variety of motor outputs under different physiological conditions and behavioural contexts.

The role of the frontal ganglion in locust feeding and moulting related behaviours.

The locust frontal ganglion (FG) constitutes a major source of innervation to the foregut dilator muscles and thus plays a key role in control of foregut movements. This paper reviews our recent studies on the generation and characteristics of FG motor outputs in two distinct and fundamental locust behaviors: feeding and molting. In an in vitro preparation, isolated from all descending and sensory inputs, the FG was spontaneously active and generated rhythmic multi-unit bursts of action potentials, which could be recorded from all efferent nerves. Thus the FG motor pattern is generated by a central pattern generator within the ganglion. Intracellular recordings suggest that only a small fraction (10-20%) of the FG 100 neurons demonstrate rhythmic activity. The FG motor output in vivo was relatively complex, and strongly dependent on the locust's physiological and behavioral state. Rhythmic activity of the foregut was found to depend on the amount of food present in the crop; animals with full crop demonstrated higher FG burst frequency than those with empty crop. At the molt, the FG generates a distinct motor pattern that could be related to air-swallowing behavior.

The locust frontal ganglion: a multi-tasked central pattern generator.

Although locust feeding has been well studied, our understanding of the neural basis of feeding-related motor patterns is still far from complete. This paper focuses on interactions between the pattern of rhythmic movements of the mouth appendages, governed by the suboesophageal ganglion (SOG), and the foregut movements, controlled by the frontal ganglion (FG), in the desert locust. In vitro simultaneous extracellular nerve recordings were made from totally isolated ganglia as well as from fully interconnected SOG-FG and brain-SOG-FG preparations. SOG-confined bath application of the nitric oxide donor, SNP, or the phosphodiesterase antagonist, IBMX, each followed by the muscarinic agonist pilocarpine, consistently induced robust fictive motor patterns in the SOG. This was observed in both isolated and interconnected preparations. In the brain-SOG-FG configuration the SOG-confined modulator application had an indirect excitatory effect on spontaneous FG rhythmic activity. Correlation between fictive motor patterns of the two ganglia was demonstrated by simultaneous changes in burst frequency. These interactions were found to be brain-mediated. Our results indicate the presence of intricate neuromodulation-mediated circuit interactions, even in the absence of sensory inputs. These interactions may be instrumental in generating the complex rhythmic motor patterns of the mandibles and gut muscles during locust feeding or ecdysis-related air swallowing.

Interactions of suboesophageal ganglion and frontal ganglion motor patterns in the locust.

Gap junctions (GJs) belong to one of the most conserved cellular structures in multicellular organisms. They probably serve similar functions in all Metazoa, providing one of the most common forms of intercellular communication. GJs are widely distributed in embryonic cells and tissues and have been attributed an important role in development, modulating cell growth and differentiation. These channels have been also implicated in mediating electrical synaptic signaling; Coupling through GJs is now accepted as a major pathway that supports network behavior and contributes to physiological rhythms. Here we focus on the physiology and molecular biology of GJs in a recently established model for the study of rhythm-generating networks and their role in behavior: the frontal ganglion (FG) of the desert locust, Schistocerca gregaria. Four novel genes of the invertebrate GJs (innexin) gene family were found to be expressed in the FG: Sg-inx1, Sg-inx2, Sg-inx3 and Sg-inx4. Immunohistochemistry revealed that some of the neurons in the FG express at least one innexin protein, INX1. We also established the presence of functional gap junction proteins in the FG and demonstrated functional electrical coupling between the neurons in the FG. This study forms the basis for further investigation of the role of GJs in network development and behavior.

Innexin genes and gap junction proteins in the locust frontal ganglion.

Studies of sensorineural hearing loss have long suggested that survival of spiral ganglion neurons (SGNs) depends on trophic support provided by their peripheral targets, the inner hair cells (IHCs): following ototoxic drugs or acoustic overexposure, IHC death is rapid whereas SGN degeneration is always delayed. However, recent noise-trauma studies show that SGNs can die even when hair cells survive, and transgenic mouse models show that supporting cell dysfunction can cause SGN degeneration in the absence of IHC pathology. To reexamine this issue, we studied a model of IHC loss that does not involve noise or ototoxic drugs. Mice lacking the gene for the high-affinity thiamine transporter (Slc19a2) have normal cochlear structure and function when fed a regular (thiamine-rich) diet. However, dietary thiamine restriction causes widespread, rapid (within 10 d) loss of IHCs. Using this model, we show that SGNs can survive for months after IHC loss, indicating that (1) IHCs are not necessary for neuronal survival, (2) neuronal loss in the other hearing loss models is likely due to effects of the trauma on the sensory neurons or other inner ear cells, and (3) that other cells, most likely supporting cells of the organ of Corti, are the main source of SGN survival factors. These results overturn a long-standing dogma in the study of sensorineural hearing loss and highlight the importance of cochlear supporting cells in neuronal survival in the adult inner ear.

Inner hair cells are not required for survival of spiral ganglion neurons in the adult cochlea.

Stroma cells and extracellular matrix (ECM) components provide the pivotal microenvironment for tumor development. The study aimed to evaluate the importance of the pancreatic stroma for tumor development.

Involvement of host stroma cells and tissue fibrosis in pancreatic tumor development in transgenic mice.

Fibrosis is the main complication of muscular dystrophies. We identified collagen triple helix repeat containing 1 (Cthrc1) in skeletal and cardiac muscles of mice, representing Duchenne and congenital muscle dystrophies (DMD and CMD, respectively), and dysferlinopathy. In all of the mice, Cthrc1 was associated with high collagen type I levels; no Cthrc1 or collagen was observed in muscles of control mice. High levels of Cthrc1 were also observed in biopsy specimens from patients with DMD, in whom they were reversibly correlated with that of Î²-dystroglycan, whereas collagen type I levels were elevated in all patients with DMD. At the muscle sites where collagen and Cthrc1 were adjacent, collagen fibers appeared smaller, suggesting involvement of Cthrc1 in collagen turnover. Halofuginone, an inhibitor of Smad3 phosphorylation downstream of the transforming growth factor-Î² signaling, reduced Cthrc1 levels in skeletal and cardiac muscles of mice, representing DMD, CMD, and dysferlinopathy. The myofibroblasts infiltrating the dystrophic muscles of the murine models of DMD, CMD, and dysferlinopathy were the source of Cthrc1. Transforming growth factor-Î² did not affect Cthrc1 levels in the mdx fibroblasts but decreased them in the control fibroblasts, in association with increased migration of mdx fibroblasts and dystrophic muscle invasion by myofibroblasts. To our knowledge, this is the first demonstration of Cthrc1 as a marker of the severity of the disease progression in the dystrophic muscles, and as a possible target for therapy.

Yael Zilberstein

Imaging Unit,
Sackler Faculty of Medicine,
Imaging Unit, Sackler Faculty of Medicine

Tel-Aviv University

Cell Death Associated with Abnormal Mitosis Observed by Confocal Imaging in Live Cancer Cells

Yael Zilberstein

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Tel-Aviv University

Cell Death Associated with Abnormal Mitosis Observed by Confocal Imaging in Live Cancer Cells

Imaging Unit,
Sackler Faculty of Medicine,
Imaging Unit, Sackler Faculty of Medicine