Vase‐shaped microfossils from the Tonian Callison Lake Formation of Yukon,Canada: taxonomy,taphonomy and stratigraphic palaeobiology

Vase‐shaped microfossils (VSMs), interpreted as the remains of testate amoebae, are found in late Tonian sedimentary rocks around the world. Here we explore the taxonomy, taphonomy and stratigraphical occurrence of VSMs from the Callison Lake Formation of the Coal Creek inlier, Yukon, Canada. Found in silicified black shale horizons and stromatolitic dolostone, sedimentological data suggest these VSMs inhabited a series of marine embayments characterized by lagoonal and/or shelf interior depositional environments. The fossiliferous strata have recently been dated with Re–Os geochronology at c. 753–740 Ma, which indicates they are not only coeval with diverse VSM assemblages described in the Chuar Group of Grand Canyon, Arizona, but also provides supportive evidence for the early diversification of eukaryotic clades prior to the Sturtian age Snowball Earth event (c. 717–660 Ma). Petrographic examination of well‐preserved specimens reveal taxa comparable to those from the Chuar Group, as well as two previously undescribed species. Species overlapping with Chuar Group VSMs are Bonniea dacruchares, Bonniea pytinaia, Cycliocyrillium simplex, Cycliocyrillium torquata, Melanocyrillium hexodiadema and Palaeoarcella athanata. New taxa described here are Bonniea makrokurtos and Cycliocyrillium rootsi. Energy dispersive x‐ray spectroscopic data reveal that the Callison Lake microfossils are preserved through a variety of taphonomic pathways, including silicification, infilling, authigenic mineralization and dolomitization. We explore the utility of M. hexodiadema as a latest Tonian biostratigraphical marker and examine the role of Callison Lake sequence stratigraphy as a control on the distribution and abundance of VSMs in the Coal Creek inlier and other global sedimentary successions.     

Calcium/calmodulin-dependent protein kinase II expression in motor neurons: Effect of axotomy

Although Ca²⁺/calmodulin-dependent (CaM) protein kinase II isoforms are present in the nervous system in high amounts, many aspects of in vivo expression, localization, and function remain unexplored. During development, CaM kinase IIα and IIβ are differentially expressed. Here, we examined CaM kinase II isoforms in Sprague-Dawley rat sciatic motor neurons before and after axotomy. We cut the L4-5 spinal nerves unilaterally and exposed the proximal nerve stumps to a fluoroprobe, to retrogradely label the neurons of origin. Anti-CaM kinase IIβ antibody showed immunoreactivity in motor neurons, which decreased to low levels by 4 days after axotomy. We found a similar response by in situ hybridization with riboprobes. The decrease in expression of mRNA and protein was confined to fluorescent motor neurons. For CaM kinase IIα, in situ hybridization showed that the mRNA was in sciatic motor neurons, with a density unaffected by axotomy. However, these neurons were also enlarged, suggesting an up-regulation of expression. Northern blots confirmed an mRNA increase. We were unable to find CaM kinase IIα immunoreactivity before or after axotomy in sciatic motor neuron cell bodies, suggesting that CaM kinase IIα is in the axons or dendrites, or otherwise unavailable to the antibody. Using rats with crush lesions, we radiolabeled axonal proteins being synthesized in the cell body and used two-dimensional polyacrylamide gel electrophoresis with Western blots to identify CaM kinase IIα as a component of slow axonal transport. This differential regulation and expression of kinase isoforms suggests separate and unique intracellular roles. Because we find CaM kinase IIβ down-regulates during axonal regrowth, its role in these neurons may be related to synaptic transmission. CaM kinase IIα appears to support axonal regrowth. © 1997 John Wiley & Sons, Inc. J Neurobiol 33: 796–810, 1997     

Inositol(3,4)bisphosphate and inositol(1,3)bisphosphate in GH4 cells--evidence for complex breakdown of inositol(1,3,4)trisphosphate

Analysis of inositol bisphosphates in GH4 cells labelled with [3H]myo-inositol shows that these cells contain three detectable inositol bisphosphates: inositol(1,4)bisphosphate, and two novel inositol bisphosphates. These latter inositol bisphosphates were degraded by periodate oxidation, borohydride reduction and alkaline phosphatase dephosphorylation; each yielded single non-cyclic alditols, ribitol and threitol, indicating that they must be respectively inositol(1,3)bisphosphate and inositol(3,4) bisphosphate. These two inositol bisphosphates are putative breakdown products of inositol(1,3,4)trisphosphate, and their occurrence suggests a complex route of hydrolysis of inositol(1,3,4)trisphosphate in intact cells.     

Impacts of invasion by <Emphasis Type="Italic">Dreissena polymorpha</Emphasis> (Pallas, 1771) on the performance of macroinvertebrate assessment tools for eutrophication pressure in lakes

Aquatic ecosystems are experiencing increasing disturbance from multiple stressors caused by anthropogenic activities. The potential for multiple stressors to modify each others’ impacts is not well understood. Legislation such as the EU Water Framework Directive (WFD) requires the development of tools to assess human impacts in aquatic systems that incorporate ecological elements, such as macroinvertebrates. Nutrient enrichment and invasive species are major threats to freshwater systems. The invasive zebra mussel Dreissena polymorpha is a conspicuous invader in freshwater aquatic systems in Europe and North America, and has been linked to drastic changes in macroinvertebrate communities and lake ecology. In 31 lake sites varying in nutrient pressure and in the presence or absence of D. polymorpha we tested three ecological quality assessment tools based on macroinvertebrate assemblages (% Sensitive Taxa to Total Phosphorus (TP), TP Score and Indicator Taxa Metric) and two basic ecological metrics. There were highly significant changes in macroinvertebrate diversity, structure, and composition associated with the invasion by D. polymorpha. While the three metrics performed consistently well in non-invaded systems, they lost explanatory power for eutrophication pressure in invaded systems. Our results suggest that metrics may need to be developed separately for invaded and non-invaded systems, and that the interaction between alien species and nutrient enrichment requires further investigation.     

B.M.A. Planning Unit Survey of General Practice 1969

A postal survey of 776 principals representative of general practice in Britain is described. Doctors working in health centres are compared both with colleagues in other group practices and with doctors who have no group practice allowance. Young doctors are mainly in group practice, especially health centres; the proportion of doctors who are not in groups is diminishing steadily, and they are mainly older. With some notable exceptions health centres provide most space, equipment, and staff; group practitioners in privately-owned premises spend more of their money on their practices, more often use appointment systems, and tend to make more efficient use of premises and staff. Overall, however, the picture is still one of general practice geared to the needs of practitioners working alone. Premises with space for sophisticated organization and for future teaching needs are unusual.Scotland, the North of England, and Wales have fewer young doctors. Average lists are higher in the North of England, and less money is invested in practice premises.Young doctors look for modern premises and the tools and staff for the job. If their career expectations are to be met the tremendous improvements made in some practices must be extended rapidly to the remainder.