Structure and diversity of the Mesozoic wood genus Xenoxylon in Far East Asia: implications for terrestrial palaeoclimates

Although the faunal elements of Far East Asian Mesozoic terrestrial biota have attracted much attention in recent years, their palaeoecology remains poorly known. In particular, features of the palaeoclimate are highly controversial. To address this point we used the Mesozoic fossil wood Xenoxylon , a genus recognized as an indicator of wet temperate biotopes and which is common in the area during the Carnian–Maastrichtian interval. We re-appraised bibliographic data and gathered new data for Xenoxylon in the Mesozoic of Far East Asia. This demonstrated that previous taxonomic approaches to the genus have been so far idiosyncratic. We examined the anatomical diversity of morphogenus Xenoxylon in Far East Asia and compared it to that of samples from Europe. This indicates that in an area centred on north-eastern China, Xenoxylon reached a level of anatomical diversity unmatched elsewhere in the world. We hypothesize that this diversity witnesses the persistence of palaeoecological conditions particularly suitable for Xenoxylon and that a wet temperate climate prevailed over most of the area throughout the Carnian–Maastrichtian interval. It is in this setting that the famous Jehol Biota probably evolved.     

Maintenance of rat taste buds in primary culture

The differentiated taste bud is a complex end organ consisting of multiple cell types with various morphological, immunocytochemical and electrophysiological characteristics. Individual taste cells have a limited lifespan and are regularly replaced by a proliferative basal cell population. The specific factors contributing to the maintenance of a differentiated taste bud are largely unknown. Supporting isolated taste buds in culture would allow controlled investigation of factors relevant to taste bud survival. Here we describe the culture and maintenance of isolated rat taste buds at room temperature and at 37 degrees C. Differentiated taste buds can be sustained for up to 14 days at room temperature and for 3-4 days at 37 degrees C. Over these periods individual cells within the cultured buds maintain an elongated morphology. Further, the taste cells remain electrically excitable and retain various proteins indicative of a differentiated phenotype. Despite the apparent health of differentiated taste cells, cell division occurs for only a short period following plating, suggesting that proliferating cells in the taste bud are quickly affected by isolation and culture.     

Spontaneous excitatory postsynaptic currents in crayfish neuromuscular junctions in the absence and presence of serotonin and 3,4-diaminopyridine

Summary Spontaneous excitatory postsynaptic currents (sEPSCs) were recorded under voltage clamp in short fibres (l0.6mm) from opener muscles and the contractor epimeralis muscle of small crayfish. From the amplitude distributions of sEPSCs which could be approximated by a Gaussian function, a mean amplitudeã= –1.16 nA±0.28 (SE) was found for sEPSCs in 16 fibres of the claw opener voltage clamped toE=–60 mV (19–22 °C). In the opener of the first walking leg and in the contractor epimeralis muscleã=s-1.1 nA±0.21 (SE;n= 6, –100 mVE–60 mV, 5–10 °C) andã= –2.0 nA±0.2 (SE;n=4, E=–60 mV, 19–22 °C) were obtained. On average about 300–500 synaptic channels were estimated to open during a sEPSC. Giant sEPSCs (gsEPSCs) were also observed. The amplitudes of gsEPSCs were up to 14 times larger than the amplitude of an average normal sEPSC. Moreover, the lifetime of gsEPSCs was up to about 3 times longer than that of sEPSCs. Like sEPSCs, gsEPSCs could not be abolished by 0.1 mol/l tetrodotoxin. The rate at which sEPSCs and gsEPSCs occurred could be markedly enhanced by serotonin (1 mol/l) and 3,4-diaminopyridine (1 mol/l)Abbreviations sEPSCs spontaneous excitatory postsynaptic currents - gsEPSCs giant spontaneous excitatory postsynaptic currents - sIPSCs spontaneous inhibitory postsynaptic currents - gsIPSCs giant spontaneous inhibitory postsynaptic currents - 5-HT 5-hydroxytryptamine - 3,4-DAP 3,4-diaminopyridine - time constant of exponential decay of sEPSCs or gsEPSCs - t _B50 lifetime of sEPSCs or gsEPSCs given by the width of these currents at 50% of their amplitude; ã amplitude of sEPSCs or gsEPSCs - i current amplitude evoked by opening of single glutamate-activated channels - z number of channels open at the peak of an average sEPSC This investigation was supported by the Deutsche Forschungsgemeinschaft. Project Fi 305/1-3     

Central projections of the frontal organ of Rana pipiens,as demonstrated by the anterograde transport of horseradish peroxidase

Summary The central projections of the frontal organ of Rana pipiens are more widespread, and more similar to those of the epiphysis, than previously realized. Fibers labeled with horseradish peroxidase were traced to the amygdala, the epiphysis, the pretectal region, and several nuclear areas of the mesencephalic and diencephalic central gray. When peroxidase reaction product was carefully distinguished from neuromelanin by means of polarization microscopy, no unequivocally labeled cell bodies of centrifugal fibers could be found.Supported by NIH grants GM-09181, EY-02083, and by BRSG RR-05357 awarded by the Biomedical Research Grant Program, Division of Research Resources, N.I.H.     

AIFM1 is a component of the mitochondrial disulfide relay that drives complex I assembly through efficient import of NDUFS5

The mitochondrial intermembrane space protein AIFM1 has been reported to mediate the import of MIA40/CHCHD4, which forms the import receptor in the mitochondrial disulfide relay. Here, we demonstrate that AIFM1 and MIA40/CHCHD4 cooperate beyond this MIA40/CHCHD4 import. We show that AIFM1 and MIA40/CHCHD4 form a stable long‐lived complex in vitro, in different cell lines, and in tissues. In HEK293 cells lacking AIFM1, levels of MIA40 are unchanged, but the protein is present in the monomeric form. Monomeric MIA40 neither efficiently interacts with nor mediates the import of specific substrates. The import defect is especially severe for NDUFS5, a subunit of complex I of the respiratory chain. As a consequence, NDUFS5 accumulates in the cytosol and undergoes rapid proteasomal degradation. Lack of mitochondrial NDUFS5 in turn results in stalling of complex I assembly. Collectively, we demonstrate that AIFM1 serves two overlapping functions: importing MIA40/CHCHD4 and constituting an integral part of the disulfide relay that ensures efficient interaction of MIA40/CHCHD4 with specific substrates.