The Mesozoic and Cenozoic motion of Adria (central Mediterranean): a review of constraints and limitations

This paper presents kinematic analysis on the motion of Adria, which is the continental mass that bridges Africa and Europe in the central Mediterranean. Palaeomagnetic data show a general coherence between the motion of Adria and Africa since the Late Paleozoic. This mutual motion, for the period from 120 Ma and the present, is verified by comparing inferred palaeolatitudes from relatively stable parts of Adria (Apulia, Gargano, Istria, and the Southern Alps) and the Hyblean Plateau, with latitudinal changes that are calculated from the motion of Africa with respect to hotspots. Additional constraints on the motion of Adria are provided from the Late Paleozoic-Early Mesozoic passive margin of Adria in the Ionian Sea. The seismic structure of the floor of the Ionian Sea resembles the structure of the oceanic crust in marginal back-arc basins, suggesting that it formed as a small ocean basin. Furthermore, the Ionian lithosphere in the Calabrian arc has been subjected to rapid rollback, which commonly occurs only when the subducting slab is made of oceanic lithosphere. This oceanic domain marks the Pennian-Triassic to Jurassic plate boundary between Adria and Africa, suggesting that a small amount of independent motion between Adria and Africa took place at that time. Since the Jurassic, Adria and Africa have shared a relatively coherent motion path. (C) 2004 Lavoisier SAS. All rights reserved.

Firing properties and connectivity of neurons in the rat lateral central nucleus of the amygdala

Using whole cell recordings from acute slices of the rat amygdala, we have examined the physiological properties of and synaptic connectivity to neurons in the lateral sector of the central amygdala (CeA). Based on their response to depolarizing current injections, CeA neurons could be divided into three types. Adapting neurons fired action potentials at the start of the current injections at high frequency and then showed complete spike-frequency adaptation with only six to seven action potentials evoked with suprathreshold current injections. Late-firing neurons fired action potentials with a prolonged delay at threshold but then discharged continuously with larger current injections. Repetitive firers discharged at the start of the current injection at threshold and then discharged continuously with larger current injections. All three cells showed prolonged afterhyperpolarizations (AHPs) that followed trains of action potentials. The AHP was longer lasting with a larger slow component in adapting neurons. The AHP in all cell types contained a fast component that was inhibited by the SK channel blocker UCL1848. The slow component, not blocked by UCL1848, was blocked by isoprenaline and was significantly larger in adapting neurons. Blockade of SK channels increased the discharge frequency in late firers and regular-spiking neurons but had no effect on adapting neurons. Blockade of the slow AHP with isoprenaline had no effect on any cell type. All cells received a mixed glutamatergic and GABAergic input from a medial pathway. Electrical stimulation of the lateral (LA) and basolateral (BLA)nuclei evoked a large monosynaptic glutamatergic response followed by a disynaptic inhibitory postsynaptic potential. Activation of neurons in the LA and BLA by puffer application of glutamate evoked a small monosynaptic response in 13 of 55 CeA neurons. Local application of glutamate to the CeL evoked a GABAergic response in all cells. These results show that at least three types of neurons are present in the CeA that can be distinguished on their firing properties. The firing frequency of two of these cell types is determined by activation of SK channels. Cells receive a small input from the LA and BLA but may receive inputs that course through these nuclei en route to the CeA.

Transgenic expression of a viral oncoprotein exclusively in K14(+) epithelial cells results in peripheral but not central CD8 T cell tolerance

The role of thymic versus peripheral epithelial cells in the negative selection of the peptide-specific CD8 T cell repertoire is still largely unresolved. We have generated TCRb chain transgenic mice in which 20–35% of peripheral CD8 T cells recognize an epitope from a viral, nuclear oncoprotein (human papillomavirus type 16 E7) in the context ofMHC class I, H-2Db. When T cells from these transgenic mice develop through the thymus of a second transgenic mouse expressing E7 from a keratin 14 promoter, no major perturbation to thymic T cell development is observed over a 7 month period. In contrast, peripheral CD8 T cell responses in these same mice (E7TCRxK14E7 double transgenic) become reduced over time. This data suggests that peripheral tolerance mechanisms predominate over thymic negative selection in controlling CD8 T cell responses to this epithelial, nuclear oncoprotein.

The central pathway of primary olfactory axons is abnormal in mice lacking the N-CAM-180 isoform

Although N-CAM has previously been implicated in the growth and fasciculation of axons, the development of axon tracts in transgenic mice with a targeted deletion of the 180-kD isoform of the neural cell adhesion molecule (N-CAM-180) appears grossly normal in comparison to wild-type mice. We examined the organization of the olfactory nerve projection from the olfactory neuroepithelium to glomeruli in the olfactory bulb of postnatal N-CAM-180 null mutant mice. Immunostaining for olfactory marker protein revealed the normal presence of fully mature primary olfactory neurons within the olfactory neuroepithelium of mutant mice. The axons of these neurons form an olfactory nerve, enter the nerve fiber layer of the olfactory bulb, and terminate in olfactory glomeruli as in wild-type control animals. The olfactory bulb is smaller and the nerve fiber layer is relatively thicker in mutants than in wild-type mice. Previous studies have revealed that the plant lectin Dolichos biflorus agglutinin (DBA) clearly stains the perikarya and axons of a subpopulation of primary olfactory neurons. Thus, DBA staining enabled the morphology of the olfactory nerve pathway to be examined at higher resolution in both control and mutant animals. Despite a normal spatial pattern of DBA-stained neurons within the nasal cavity, there was a distorted axonal projection of these neurons onto the surface of the olfactory bulb in N-CAM-180 null mutants. In particular, DBA-stained axons formed fewer and smaller glomeruli in the olfactory bulbs of mutants in comparison to wild-type mice. Many primary olfactory axons failed to exit the nerve fiber layer and contribute to glomerular formation. These results indicate that N-CAM-180 plays an important role in the growth and fasciculation of primary olfactory axons and is essential for normal development of olfactory glomeruli. (C) 1997 John Wiley & Sons, Inc.

Super-Yangian double and its central extension

We introduce the super-Yangian double DY(h over bar), [gl(m/n)] and its central extension DY(h over bar)[gl(m/n)]. We give their defining relations in terms of current generators and obtain Drinfeld co-multiplication. (C) 1997 Elsevier Science B.V.

A Century of Change in Coral Reef Status in Southeast and Central Pacific: Polynesia Mana Node, Cook Islands, French Polynesia, Kiribati, Niue, Tokelau, Tonga, Wallis and Futuna

The Polynesia Mana Node of the southeast and central Pacific contains 7 independent or autonomous countries or territories with only 6,000 km2 of land on 347 islands, but surrounded by 12 million km2 of EEZ. These seas contain 13,000 km2 of coral reefs as the main natural ecosystem providing food resources and opportunities for development, especially for tourism and pearl culture for 500,000 inhabitants. During the 19th and first half of the 20th centuries, there was major exploitation by the colonial powers of mother-of-pearl oysters for the button industry, as well as guano, sandalwood and trepang. The Polynesian people were largely involved in a subsistence economy and all coral reefs and lagoons were healthy. During the last two decades of the 20th, all countries experienced rapid development and urbanization, rising populations, and some increased agriculture. These developments were limited to a few islands of each country (i.e. 15 islands amongst the 347) with resulting degradation of the coral reefs around these sites. The other islands remained mostly uninhabited and pristine, and continued with a subsistence economy. Generally, there was more damage to the coral reefs through natural events such as cyclones and coral bleaching, than by human activities. There is however, an urgent need to combat the threats on some islands from increased sedimentation, over-fishing, dredging and nutrient pollution.