Epithelial supporting cells can differentiate into outer hair cells and Deiters' cells in the cultured organ of Corti

The organ of Corti is a complex structure containing a single row of inner hair cells (IHCs) and three rows of outer hair cells (OHCs), supported respectively by one row of inner phalangeal cells and three rows of Deiters' cells. When fetal rat organ of Corti explants are cultured, supernumerary OHCs and supernumerary Deiters' cells are produced, without any additional cell proliferation. Analysis of semi- and ultrathin sections revealed that supernumerary OHCs are produced at the distal edge of the organ of Corti. Quantitative analysis of cell types present in the organ of Corti demonstrates that when the number of OHCs increases: (i) the total number of cells remains constant; (ii) the number of Deiters' cells increases; (iii) the number of tectal cells decreases and of Hensen's cells decreases. Using specific HC markers, i.e. jagged2 (Jag2) and Math1, we showed that in addition to existing OHCs, supernumerary OHCs, tectal cells and Hensen's cells expressed these markers in embryonic day 19 organ of Corti explants after 5 days in vitro. The results of this study suggest that Hensen's cells retain the capacity to differentiate into either tectal cells, which differentiate into OHCs, or into undertectal cells which differentiate into Deiters' cells. Received 15 May 2002; received after revision 18 July 2002; accepted 7 August 2002 RID="*" ID="*"Corresponding author.     

Évolution du contrôle cérébelleux sur l'activité unitaire spontanée du noyau de Deiters chez le jeune Lapin

Summary The inhibitory cerebellar control of the spontaneous firing of Deiters' neurones has been demonstrated from the early post natal hours in the rabbit.     

GABA in the caudate nucleus: A possible synaptic transmitter of interneurons

Summary Microiontophoretic application of GABA and its antagonist, picrotoxin, altered focal potentials evoked in the caudate nucleus by stimulation near the recording site to a much greater extent than potentials elicited by stimulation of afferent pathways, suggesting that GABA is a transmitter of interneurons in this nucleus.This study was supported by funds from the Veterans Administration and by NIH research grant No. 06820.We thank Kathleen Downes and Clifford Smathers for their assistance.     

Cellular maintenance of nuclear protein homeostasis

The accumulation and aggregation of misfolded proteins is the primary hallmark for more than 45 human degenerative diseases. These devastating disorders include Alzheimer’s, Parkinson’s, Huntington’s, and amyotrophic lateral sclerosis. Over 15 degenerative diseases are associated with the aggregation of misfolded proteins specifically in the nucleus of cells. However, how the cell safeguards the nucleus from misfolded proteins is not entirely clear. In this review, we discuss what is currently known about the cellular mechanisms that maintain protein homeostasis in the nucleus and protect the nucleus from misfolded protein accumulation and aggregation. In particular, we focus on the chaperones found to localize to the nucleus during stress, the ubiquitin–proteasome components enriched in the nucleus, the signaling systems that might be present in the nucleus to coordinate folding and degradation, and the sites of misfolded protein deposition associated with the nucleus.     

La teneur du noyau cellulaire en acide désoxyribonucléique à travers les organes,les individus et les espèces animales

Summary Techniques are described for the isolation of nuclei from animals cells and for the determination of the desoxyribonucleic acid content for each nucleus. These techniques have already been used in order to study a few mammalian species. From the first results (especially in calf, ox and bull), it seems to appear that the nucleus of the somatic cells contains constantly the same amount of desoxyribonucleic acid, whatever tissue and animal we studied within the same species; and this amount is just the double of that of the haploid cells (spermatozoa) in the same animal. This result constitutes a strong argument, from the analytical point of view, for the theory according to which the desoxyribonucleic acid is considered to be the substrate of the hereditary characters of the species.     

Differential displacement of cells from the median eminence into the arcuate nucleus during puberty. Effects of melatonin administration

A displacement of catecholaminergic-positive and catalase-containing cells from the median eminence into the arcuate nucleus at puberty has been described previously. This study reports on the displacement phenomena after postnatal administration of melatonin. Catalase-positive cells undergo a delayed displacement from the median eminence into the arcuate nucleus. However, part of this cell population lags behind within the median eminence. This differential reaction of cell displacement by catalase-positive cells is considered as a special reaction of these cells to melatonin administration.     

Differential displacement of cells from the median eminence into the arcuate nucleus during puberty. Effects of melatonin administration

Summary A displacement of catecholaminergic-positive and catalase-containing cells from the median eminence into the arcuate nucleus at puberty has been described previously. This study reports on the displacement phenomena after postnatal administration of melatonin. Catalase-positive cells undergo a delayed displacement from the median eminence into the arcuate nucleus. However, part of this cell population lags behind within the median eminence. This differential reaction of cell displacement by catalase-positive cells is considered as a special reaction of these cells to melatonin administration.     

Organization of the mammalian red nucleus and its interconnections with the cerebellum.

The red nucleus in monkeys and rats consists of a magnocellular, rubrospinal portion which receives its cerebellar information from the nucleus interpositus, and a parvocellular, rubroolivary portion which receives cerebellar afferents from the nucleus lateralis. Distinct interpositorubrospinal and dentatorubroolivary projections are therefore common to these 2 species.     

Microtubule dynamics alter the interphase nucleus

Microtubules are known to drive chromosome movements and to induce nuclear envelope breakdown during mitosis and meiosis. Here we show that microtubules can enforce nuclear envelope folding and alter the levels of nuclear envelope-associated heterochromatin during interphase, when the nuclear envelope is intact. Microtubule reassembly, after chemically induced depolymerization led to folding of the nuclear envelope and to a transient accumulation of condensed chromatin at the site nearest the microtubule organizing center (MTOC). This microtubule-dependent chromatin accumulation next to the MTOC is dependent on the composition of the nuclear lamina and the activity of the dynein motor protein. We suggest that forces originating from simultaneous polymerization of microtubule fibers deform the nuclear membrane and the underlying lamina. Whereas dynein motor complexes localized to the nuclear envelope that slide along the microtubules transfer forces and/or signals into the nucleus to induce chromatin reorganization and accumulation at the nuclear membrane folds. Thus, our study identified a molecular mechanism by which mechanical forces generated in the cytoplasm reshape the nuclear envelope, alter the intranuclear organization of chromatin, and affect the architecture of the interphase nucleus.     

Organization of the mammalian red nucleus and its interconnections with the cerebellum

Summary The red nucleus in monkeys and rats consists of a magnocellular, rubrospinal portion which receives its cerebellar information from the nucleus interpositus, and a parvocellular, rubroolivary portion which receives cerebellar afferents from the nucleus lateralis. Distinct interpositorubrospinal and dentatorubroolivary projections are therefore common to these 2 species.     

Dopamine-β-hydroxylase activity in stroke-prone spontaneously hypertensive rats

Summary Dopamine--hydroxylase (DBH) activity was higher in the serum, the mesenteric artery and the cerebral cortex of 4-week-old stroke-prone spontaneously hypertensive rats (SHRSP), and lower in the nucleus tractus solitarii than it was in spontaneously hypertensive rats (SHR).The authors wish to thank Prof. Masao Sano (Nagoya University) for his aid in dissecting the nucleus tractus solitarii and the locus coeruleus.     

A simple interspike interval analyzer for study of neuronal spike trains

Summary A simple, low cost interspike interval analyzer for the analysis of trains of nerve impulses is described. The analyzer is built with readily available integrated circuits and has been used to analyze spike trains in the lateral vestibular nucleus of cats.Acknowledgment. This research is supported in part by Higher Degrees and Research Grant No. 158/363 to J.C.H. from the University of Hong Kong.     

Aminergic innervation of the hypothalamo-hypophyseal system in Gambusia sp. (Teleost, Poecilidae) studied by two fluorescence techniques]

Using fluorescence techniques (Falck-Hillarp, de La Torre and Surgeon) 2 paired groups of perikarya were observed in the hypothalamus of Gambusia, one in the nucleus recessus lateralis (NRL) and the other in the nucleus recessus posterioris (NRP). No fluorescent neuron could be detected in the nucleus recessus preopticus (NRPO) nor in the nucleus lateralis tuberis (NLT). Fluorescent aminergic fibers demonstrated in the rostral neurohypophysis and in the neurointermediate lobe might originate from the NRL. These two techniques are complementary, but the last one, more rapidly performed, appears promising.     

Association of intermediate filaments with other cell organelles in carcinoid tumor of the colon

Summary Carcinoid tumor of the colon was studied in electron microscope. In cytoplasm, prominent intermediate-sized filaments were seen frequently attaching to nucleus and mitochondria. Direct contacts of intermediate filaments with secretory granules were not observed.Acknowledgments. The skilful technical assistance of Ms Tuire Koro is gratefully acknowledged. — This study was supported by grants from the Finnish Medical Research Council, Finnish Culture Foundation and J.K. Paasikivi Foundation for Cancer Research.     

Friedrich Miescher Prize awardee lecture review. A conserved family of nuclear export receptors mediates the exit of messenger RNA to the cytoplasm

The distinguishing feature of eukaryotic cells is the segregation of RNA biogenesis and DNA replication in the nucleus, separate from the cytoplasmic machinery for protein synthesis. As a consequence, messenger RNAs (mRNAs) and all cytoplasmic RNAs from nuclear origin need to be transported from their site of synthesis in the nucleus to their final cytoplasmic destination. Nuclear export occurs through nuclear pore complexes (NPCs) and is mediated by saturable transport receptors, which shuttle between the nucleus and cytoplasm. The past years have seen great progress in the characterization of the mRNA export pathway and the identification of proteins involved in this process. A novel family of nuclear export receptors (the NXF family), distinct from the well-characterized family of importin β-like proteins, has been implicated in the export of mRNA to the cytoplasm. Received 23 January 2001; received after revision 12 April 2001; accepted 12 April 2001     

Reciprocal connections between substantia nigra and medullary reticular formation in the rat

Summary Electrophysiological analysis shows reciprocal connections between substantia nigra and medullary reticular formation (nucleus reticularis giganto celullaris). The nigro-reticular connection appears to be monosynaptic, as shown by antidromic activation, and comprises an ipsi and a contralateral component. Its effect is mainly inhibitory. The reticulonigral component produces mainly excitatory effects and includes fibres from nucleus giganto celullaris and nucleus parvocelullaris in the medullary reticular formation.This work was aided by a grant from CONICIT (projecto 31.26.S1-0412).     

Nuclear blebs in oocytes of the fishClarias batrachus

Summary Large nuclear blebs have been observed in oocytes of the fish,Clarias batrachus. The bleb, which contains nucleoplasm, is finally extruded from the nucleus. The extruded body is DNase-sensitive, and it implies that some amount of DNA is extruded from the nucleus of these oocytes.Acknowledgments. We are thankful to Dr. R.K. Sharan, Department of Zoology, Patna University, for providing laboratory facilities, and to Dr V.G. Jhingran and Dr P.V. Dehadrai of ICAR for their keen interest in the work.     

Arginine-rich cell penetrating peptides: from endosomal uptake to nuclear delivery

Delivery of macromolecules into living cells by arginine-rich cell penetrating peptides (AR-CPPs) is an important new avenue for the development of novel therapeutic strategies. However, to date the mechanism of this delivery remains elusive. Recent data implicate endocytosis in the internalization of AR-CPPs and their macromolecular cargo and also indicate limited delivery of macromolecules into the cell cytoplasm and nucleus. Different types of endocytosis – clathrin-dependent endocytosis, raft/caveolin-dependent endocytosis and macropinocytosis – are all implicated in the uptake of AR-CPPs and their cargo into different cells. Cationic AR-CPPs dramatically increase uptake of conjugated molecules through efficient binding to surface proteoglycans. Whether this increase in binding can assure delivery of a sufficient amount of functionally active macromolecules into the cytoplasm and nucleus or whether there is a specific mechanism by which AR-CPPs facilitate the escape of conjugated cargo from endosomes remains to be understood. Received 30 June 2005; received after revision 9 August 2005; accepted 30 August 2005     

The influence of peripheral or central administration of ondansetron on stress-induced gastric ulceration in rats

Ondansetron (0.08, 0.15 or 0.3 mg/kg) injected s.c., every 12h with the fourth dose given 0.5 h before experiments, dose-dependently lessened gastric glandular mucosal ulceration produced by cold-restraint stress for 2h. When given intracerebrally (i.c.) (0.1, 0.5 or 1g), using the same treatment regimen, infusion of ondansetron 1 g into the nucleus amygdaloideus centralis decreased stress-evoked ulcers; in contrast, injection of the same dose into the nucleus accumbens intensified these lesions. The associated stress-induced stomach wall mast cell degranulation was unaffected by all s.c. or i.c. doses of ondansetron. Pretreatment with disodium cromoglycate i.p. alone, or concurrently with ondansetron s.c., prevented not only ulceration but also mast cell degranulation. 5-Hydroxytryptamine₃ receptor antagonism appears to inhibit stress-evoked ulcers mainly by blocking the peripheral effects of the amine after its release from the gastric mucosal mast cells.