Developmental regulation of the effects of fibroblast growth factor-2 and 1-octanol on neuronogenesis: implications for a hypothesis relating to mitogen-antimitogen opposition.

Neocortical neurons arise from a pseudostratified ventricular epithelium (PVE) that lies within the ventricular zone (VZ) at the margins of the embryonic cerebral ventricles. We examined the effects of fibroblast growth factor-2 (FGF-2) and 1-octanol on cell output behavior of the PVE in explants of the embryonic mouse cerebral wall. FGF-2 is mitogenic and 1-octanol antimitogenic in the PVE. Whereas all postmitotic cells migrate out of the VZ in vivo, in the explants some postmitotic cells remain within the VZ. We refer to these cells as the indeterminate or I fraction, because they neither exit from the VZ nor reenter S phase as part of the proliferative (P) fraction. They are considered to be either in an extremely prolonged G(1) phase, unable to pass the G(1)/S transition, or in the G(0) state. The I fate choice is modulated by both FGF-2 and 1-octanol. FGF-2 decreased the I fraction and increased the P fraction. In contrast, 1-octanol increased the I fraction and nearly eliminated the P fraction. The effects of FGF-2 and 1-octanol were developmentally regulated, in that they were observed in the developmentally advanced lateral region of the cerebral wall but not in the medial region.

Continuity with ganglionic eminence modulates interkinetic nuclear migration in the neocortical pseudostratified ventricular epithelium.

Cells of the pseudostratified ventricular epithelium (PVE) undergo interkinetic nuclear migration whereby position of cell soma with nucleus is systematically dependent upon cell cycle phase. We examined if the interkinetic nuclear migration in the neopallial PVE is influenced by tissue continuity with the ganglionic eminence (GE) of the basal forebrain in explants from embryonic day 13 mice. We found that when continuity between the neopallial wall and the GE is intact, some neopallial PVE cells discontinue interkinetic nuclear migration following S-phase and upon entry into G2-phase. The somata and nuclei of those cells shift outward from the S-phase zone toward the subventricular and the intermediate zones. The outward migration of post-S-phase cells is observed only in the lateral region of the cerebral wall, which is closely adjacent to the GE, but not in the medial region, and only when tissue continuity with GE is maintained. We suggest that the outward moving PVE cells seed the secondary proliferative population (SPP) and that exit of the SPP seeding cells occurs in G2-phase. The phenomenon recapitulates similar migratory behavior of neopallial PVE cells in vivo and appears to represent a "choice" between two opposing options available to post-S-phase cells of the PVE. The choice appears to be imposed by mechanisms dependent upon continuity with the GE. We conclude that GE, and/or other adjacent basal forebrain structures, modulates interkinetic nuclear migration in the neopallial PVE.

Stable operation of a 300-m laser interferometer with sufficient sensitivity to detect gravitational-wave events within our galaxy.

TAMA300, an interferometric gravitational-wave detector with 300-m baseline length, has been developed and operated with sufficient sensitivity to detect gravitational-wave events within our galaxy and sufficient stability for observations; the interferometer was operated for over 10 hours stably and continuously. With a strain-equivalent noise level of h approximately 5x10(-21)/sqrt[Hz], a signal-to-noise ratio of 30 is expected for gravitational waves generated by a coalescence of 1.4M-1.4M binary neutron stars at 10 kpc distance. We evaluated the stability of the detector sensitivity with a 2-week data-taking run, collecting 160 hours of data to be analyzed in the search for gravitational waves.

Complicated hereditary spastic paraplegia with peripheral neuropathy, optic atrophy and mental retardation.

An 8-year old girl with a not previously described type of complicated hereditary spastic paraplegia (HSP) is presented. Spasticity in her lower limbs had already been recognized during infancy and worsened progressively. Severe delay in mental development was observed. Peripheral neuropathy and optic atrophy developed at 5 years of age. On brain magnetic resonance imaging, an abnormally thin corpus callosum was observed. Involvement of the fasciculus gracilis was suggested by somatosensory evoked potentials. To our knowledge, there has been no reported case of complicated HSP with peripheral neuropathy, optic atrophy and mental retardation so far. We postulate that our patient is a sporadic case of not previously described complicated HSP.

Sequence of neuron origin and neocortical laminar fate: relation to cell cycle of origin in the developing murine cerebral wall.

Neurons destined for each region of the neocortex are known to arise approximately in an "inside-to-outside" sequence from a pseudostratified ventricular epithelium (PVE). This sequence is initiated rostrolaterally and propagates caudomedially. Moreover, independently of location in the PVE, the neuronogenetic sequence in mouse is divisible into 11 cell cycles that occur over a 6 d period. Here we use a novel "birth hour" method that identifies small cohorts of neurons born during a single 2 hr period, i.e., 10-20% of a single cell cycle, which corresponds to approximately 1.5% of the 6 d neuronogenetic period. This method shows that neurons arising with the same cycle of the 11 cycle sequence in mouse have common laminar fates even if they arise from widely separated positions on the PVE (neurons of fields 1 and 40) and therefore arise at different embryonic times. Even at this high level of temporal resolution, simultaneously arising cells occupy more than one cortical layer, and there is substantial overlap in the distributions of cells arising with successive cycles. We demonstrate additionally that the laminar representation of cells arising with a given cycle is little if at all modified over the early postnatal interval of histogenetic cell death. We infer from these findings that cell cycle is a neuronogenetic counting mechanism and that this counting mechanism is integral to subsequent processes that determine cortical laminar fate.

Proliferative behavior of the murine cerebral wall in tissue culture: cell cycle kinetics and checkpoints.

Cerebral wall from embryonic day 13 mice was cultured in a three-dimensional collagen matrix in defined, serum-free medium. The cerebral wall retained its normal architecture, including the radial glial fiber system, for up to 19 h in culture. The cell cycle was initially blocked at the S/G2/M and the G1/S phase transitions, resulting in a transient synchronization of the proliferative cells. The transient blockades correspond, we suggest, to the G2 checkpoint and G1 restriction point, adaptive mechanisms of normal proliferative cells. The blocks were relieved within a few hours of explantation with restoration of the interkinetic nuclear migration and flow of cells through the cycle phases. The duration of the reestablished cell cycle and those of G1, S, and combined G2-M phases were estimated to be 19.2, 6.3-8.3, 8.8, and 2.0-4.0 h, respectively. The leaving (Q) fraction of the cycle (0.64) was twice the in vivo value. Two-thirds of the Q fraction cells remained in the ventricular epithelium, resulting in a substantially low growth fraction of 0.73 compared with 1.0 in vivo. The embryonic murine cerebral explant, cultured in minimum essential medium, should be favorable for studies of cycle modulatory actions of cell external influences such as growth factors or neurotransmitters.

A gradient in the duration of the G1 phase in the murine neocortical proliferative epithelium.

Neuronogenesis in the neocortical pseudostratified ventricular epithelium (PVE) is initiated rostrolaterally and progresses caudo-medially as development progresses. Here we have measured the cytokinetic parameters and the fractional neuronal output parameter, Q, of laterally located early-maturing regions over the principal embryonic days (E12-E15) of neocortical neuronogenesis in the mouse. These measures are compared with ones previously made of a medial, late-maturing portion of the PVE. Laterally, as medially, the duration of the neuronogenetic interval is 6 days and comprises 11 integer cell cycles. Also, in both lateral and medial areas the length of G1 phase (TG1) increases nearly 4-fold and is the only cell cycle parameter to change. Q progresses essentially identically laterally and medially with respect to the succession of integer cell cycles. Most importantly, from E12 to E13 there is a steeply declining lateral to medial gradient in TG1. The gradient is due both to the lateral to medial graded stage of neuronogenesis and to the stepwise increase in TG1 with each integer cycle during the neuronogenetic interval. To our knowledge this gradient in TG1 of the cerebral PVE is the first cell biological gradient to be demonstrated experimentally in such an extensive proliferative epithelial sheet. We suggest that this gradient in TG1 is the cellular mechanism for positionally encoding a protomap of the neocortex within the PVE.

Regulation of normal proliferation in the developing cerebrum potential actions of trophic factors.

We review here a computational model of neocortical histogenesis based upon experiments in the developing cerebral wall of the mouse. Though based upon experiments in mouse, commonalities of developmental history and structure of neocortex across mammalian species suggest that the principles which support this model will be generally applicable to neocortical evolution and development across species. In its scope the model spans the successive histogenetic events: cell proliferation, cell migration, and the positioning of cell somata in neocortical layers following migration. Neurons are produced in a pseudostratified epithelium (PVE) which lines the ventricular cavaties of the embryonic cerebrum. The parameters which determine the rate and total number of neurons produced in the PVE are (1) the size of the founder population, (2) the number of integer cell cycles executed by the founder population and its progeny in the course of the neuronogenetic interval, (3) the growth fraction, and (4) the fraction of cells which exits the cycle (Q fraction) with each integer cycle. There is a systematic relationship between the integer cycle of origin and the sequence of cell migration, position in the cortex, and the extent to which a set of postmigratory neurons will be diluted in the cortex by the combined effects of tissue growth and cell death. Variation across species in the number of integer cell cycles as a function of the rate of progression of Q may be expected to modulate profoundly the total numbers of neurons that are produced but not the relative proportions of neurons assigned to the major neocortical layers.

Lanthanide ions for the first non-enzymatic formation of adenosine 3',5'-cyclic monophosphate from adenosine triphosphate under physiological conditions.

Adenosine 3',5'-cyclic monophosphate (cAMP) is formed from adenosine triphosphate at pH 8 and 50 degrees C by use of lanthanide ions. Pr3+ and La3+ are the most active. The cAMP formation is more efficient at higher pH, where the mixture is made homogeneous by the addition of beta-cyclodextrin. The potential functioning of lanthanide ions as the catalytic center of an artificial adenylate cyclase is indicated.

Oxygen-independent photocleavage of DNA by xanthene dyes.

Plasmid DNA has been efficiently photocleaved by a series of xanthene dyes in the absence of molecular oxygen. The cleavage by fluorescein proceeds mostly via its singlet excited state.

Isolated aplasia of the anterior pituitary as a cause of congenital panhypopituitarism. Case report.

We document a male infant with congenital panhypopituitarism as detected at birth, in whom the adenohypophysis was totally absent by magnetic resonance imaging and all the anterior pituitary hormones were undetectable. His neurohypophysis was, by contrast, identified ectopically at the median eminence and antidiuretic hormone was appropriately secreted.