Scolicia and its producer in shallow-marine deposits of the Miocene Chenque Formation (Patagonia,Argentina): functional morphology and implications for understanding burrowing behavior

Abstract

Scolicia is one of the most conspicuous trace fossils in lower shoreface deposits of the Miocene Chenque Formation of Patagonia, Argentina. This ichnotaxon consists of horizontal, sinuous or meandering trace fossils with a laminated backfill and two parallel strings located at the base. Abundant body fossils attributed to Brisaster iheringi occur in close association to these trace fossils. The echinoids are very well preserved, and most of the specimens have some areas with their spines attached in life position. In particular, preservation of the subanal tufts of spines, associated to isopores (which are interpreted as being associated to funnel building tube feet), supports the interpretation that these organisms are the producers of Scolicia isp. A shaft connecting the burrow with the sediment-water interface was not observed in vertical sections of the excavations, although on bedding plane surfaces, some small circular tube outlets are recognized. However, the great diversity and abundance of ichnofossils co-occurring in these deposits may preclude adequate identification of vertical structures. These deposits provide an excellent opportunity to integrate trace fossil data, body fossil information and observations from modern analogues in order to perform a morpho-functional analysis of Scolicia.     

Influence of metabolic equilibrium on erythrocyte deformability in diabetes mellitus

Red blood cell filtration test (Reid's test) was performed in 23 diabetic patients and in 10 normal subjects and it was related to metabolic equilibrium. Results showed an increase of filtration time in diabetics when compared to controls (35.1' +/- 2.3; M +/- SEM vs 22.2' +/- 0.7, p less than 0.001) and a significant correlation to cholesterol (178.7 mg% +/- 8.9, r = 0.40, p less than 0.05), triglycerides (131.3 mg% +/- 20.6, r = 0.72, p less than 0.001) and to glycosylated hemoglobin (10.7% +/- 0.5, r = 0.60, p less than 0.01) in diabetic patients. No correlation was observed in control subjects. The values of red blood cells filtration time observed in diabetics suggest that an altered erythrocyte deformability in diabetic patients can play an important role in peripheral hypoxia and therefore in diabetic microangiopathy.     

Vertical water column resource partitioning by a ciliated protozoan population under stratified conditions in the northern Adriatic

The vertical distribution of the ciliated protozoan stock, potentialprey and potential predators were repeatedly sampled over twodiurnal cycles at an eutrophic site off the Po River delta duringsummer when the water column was strongly stratified. A subsurfaceciliated protozoan maximum (SCPM) was associated with a subsurfacenanoplankton chlorophyll maximum (SCM), which was located belowthe pycnocline at the nutricline. A subsurface oxygen maximumindicated that the SCM resulted from in situ growth. The associatedSCPM appeared to result from the interaction of two primaryfactors: (i) the availability of a high prey biomass (i.e. nanoplankton)and (ii) low grazing pressure from potential predators (i.e.macrozooplankton).     

Cole-Moore superposition and kinetic models for the potassium conductance of nerve fiber membranes

Restrictions imposed by “Cole-Moore superposition” on a class of models for the potassium conductance of nerve fiber membranes are studied. The models studied assume that: (1) different potassium transfer sites on the membrane are not coupled; (2) each site is characterized by a set of states |α>, α = 0, …, N, each of energy E_α, and degeneracy, r_α. (3) The time dependence is described by kinetic equations.It is rigorously shown that: (a) there is superposition if, and only if, in going from one equilibrium state to another, the system passes only through equilibrium states. (b) Condition (a) is satisfied only if: (i) the energy levels are equally spaced, (ii) the state |n> is [N!/n!(N-n)!]-fold degenerate, and (iii) only transitions between nearest neighbor levels are allowed.     

Immune mechanisms in alcoholic liver disease

Growing evidence indicates that inflammatory reactions play an important role in the pathogenesis of alcoholic liver disease (ALD). The implication of immunity in fueling chronic inflammation in ALD has emerged from clinical and experimental evidence showing the recruitment and the activation of lymphocytes in the inflammatory infiltrates of ALD and has received further support by the recent demonstration of a role of Th17 lymphocytes in alcoholic hepatitis. Nonetheless, the mechanisms by which alcohol triggers adaptive immune responses are still incompletely characterized. Patients with advanced ALD show a high prevalence of circulating IgG and T-lymphocytes towards epitopes derived from protein modification by hydroxyethyl free radicals (HER) and end-products of lipid peroxidation. In both chronic alcohol-fed rats and heavy drinkers the elevation of IgG against lipid peroxidation-derived antigens is associated with an increased production of pro-inflammatory cytokines/chemokines and with the severity of histological signs of liver inflammation. Moreover, CYP2E1-alkylation by HER favors the development of anti-CYP2E1 auto-antibodies in a sub-set of ALD patients. Altogether, these results suggest that allo- and auto-immune reactions triggered by oxidative stress might contribute to fuel chronic hepatic inflammation during the progression of ALD.     

Microplankton diversity indices as indicators of eutrophication in the northern adriatic sea

Phytoplankton community diversity indices are used to characterize the effects of eutrophication in the Northern Adriatic Sea. A derived Shannon diversity frequency spectrum provided a single biological quantification which allowed an interpretation of temporal and regional differences and which can also be used to evaluate future changes in species diversity. The data base comprised a 4+ year time series involving 300 taxa.     

Factors affecting the saturation assay of cyclic AMP in biological systems

Nonspecific (blank) effects interfering with the saturation analysis of cyclic AMP may be mediated either through the primary reaction between cyclic AMP and the binding protein or on the efficacy of the separation procedure. It is not normally permissible to substract blank values, measured at zero concentration of added nucleotide from the measurement of unknowns since the magnitude of the correction may vary with different nucleotide concentrations. Response curves should be set up in equivalent concentrations of the particular blank extract in every assay.     

Biochemical evidence for chemical and/or topographic differences in the lipoperoxidative processes induced by CCl4 and iron

Isolated rat hepatocytes, treated with CCl4 or ADP-Fe3+ complex show an enhanced lipid peroxidation and a decreased glucose 6-phosphatase activity. Lipid peroxidation is much more stimulated by ADP-Fe3+ or Fe3+ than by CCl4, when the metal and the haloalkane are used at a similar concentration. Increasing rates of lipid peroxidation in the different experimental conditions do not correlate with the degree of glucose 6-phosphatase inactivation, which is produced by CCl4 and not by a similar amount of ferric iron. In the case of iron, its intracellular concentration must be higher to give the enzyme inactivation exerted by CCl4. Higher intracellular levels of iron are reached when the metal is added to the cell suspension together with ADP. Under these conditions there is inactivation of glucose 6-phosphatase. Possible mechanisms accounting for a different enzyme sensitivity to iron and CCl4 are discussed.