FERNANDO ERTHAL

In the marine realm, the interpretation of taphofacies relies heavily on how oceanographic and sedimentary conditions affect the preservation state of fossils. Several taphonomic variables either covary with depth or are directly influenced by depth. Facies‐level factors rather than broad, basin‐scale parameters influence the taphonomic profile of mollusc death assemblages according to actualistic and experimental evidence. To determine the possible relation between depth and the taphonomic conditions of multiple species of bivalve remains, we used seven samples gathered over a comprehensive bathymetric gradient (from 7 to 150 m below mean sea level; topmost 10‐ to 20‐cm layer, roughly corresponding to the taphonomically active zone). We selected samples from predominantly muddy facies on the southern Brazilian shelf (SBS). The taphonomic damage profile (TDP) was measured using site samples based on a standard taphonomic analysis (categorical scoring system) of shells and fragments larger than 4 mm, to identify site damage patterns. Restricting the sedimentary grain size (samples from fine sediments) enabled the determination of the variation in damage with depth among the samples. Constrained analysis of proximities (CAP) revealed that up to 46{%} of the taphonomic variation observed was related to variation in depth (with approximately 28{%} unexplained by environmental factors). Part of the unexplained fraction was due to the effect of temporal mixing, which is predictable along large‐scale patches but is inversely linked to the TDP. Our results show that taphonomic analysis, considering large spatial scales in recent environments, can explain the variations present in shell beds that formed during distinct time periods of the evolution of a Quaternary sedimentary basin.

Copyright © 2017, SEPM (Society for Sedimentary Geology). Fossil assemblages are expected to be time-averaged as a result of biological and physical processes that mix skeletal remains. Our quantitative understanding of time-averaging derives primarily from actualistic studies, in which direct numerical dating of individual specimens is used to assess the scale and structure of age mixing in death assemblages (incipient fossil assemblages). Here we examine the age, and the time-averaging of Mactra shells (Bivalvia: Mollusca) gathered from surface mixed siliciclastic-bioclastic sands at three sites on a passive-margin subtropical shelf (the Southern Brazilian Shelf; ∼ 33°S). Sixty Mactra specimens were individually dated using amino acid racemization (AAR) calibrated using radiocarbon ages (n=15). The time-averaging and the total age variability was based on a Bayesian approach that integrates the estimation errors and uncertainties derived from the posterior distribution associated with the AAR calibration average model. The 14C-calibrated AAR ages, pooled across all three sites, are strongly right-skewed with 97{%} of the individual mollusk shell age estimates ranging from 0 to 6 cal kyr BP. The magnitude of time-averaging varied inversely with the water depth, from {\textless} 15 yr at the deepest site (21 m) up to 1020-1250 yr at the shallowest site (7 m). The substantial variation in the temporal resolution across nearby sites, which are located in a seemingly homogenous depositional setting, indicates the presence of notable (if cryptic) spatial heterogeneities in local sedimentation, production, and exhumation, all increasing with water depth.

The South America southern coast exhibits many outcrops with abundant shell beds, from the Pleistocene through the Recent. How much biological information is preserved within these shell beds? Or, what is the actual probability a living community has to leave a fossil record corresponding to these shell deposits? Although ecological and biogeographical aspects might had been pointed, considering these temporal scales, up to the moment there is no taphonomically-oriented studies available. Quantitative comparisons between living (LAs), death (DAs) and fossil assemblages (FAs) are important not only in strictly taphonomic studies, but have grown a leading tool for conservation paleobiology analysis. Comparing LAs, DAs and FAs from estuaries and lagoons in the Rio Grande do Sul Coastal Plain makes possible to quantitatively understand the nature and quantity of biological information preserved in fossil associations in Holocene lagoon facies. As already noted by several authors, spatial scale parts the analysis, but we detected that the FAs reflects live ones, rather than dead ones, as previously not realized. The results herein obtained illustrates that species present in DA are not as good preserved in recent (Holocene) fossil record as originally thought. Strictly lagoon species are most prone to leave fossil record. The authors consider that the fidelity pattern here observed for estuarine mollusks to be driven by (i) high temporal and spatial variability in the LAs, (ii) spatial mixing in the DA and (iii) differential preservation of shells, due to long residence times in the taphonomically active zone. © 2013 by the Sociedade Brasileira de Paleontologia.

Molluscan shell accumulations (shell beds) are very common in shallow marine and estuarine environments in South America and also on the continental shelf between Argentina and southern Brazil. The development of these shell beds is restricted to the Quaternary, and can provide a great opportunity for taphonomic studies, which are rare in this geographic location. This study investigates the influence of environmental processes on the destruction of biological remains in a subtropical lagoonal setting by describing the taphonomic signatures occurring in the mollusk shells from the Tramandaí Lagoon, northeastern Rio Grande do Sul State, Brazil. This lagoon system originated during the regressive phase that followed a transgressive maximum at 6.0-6.5 ka BP. The taphonomic variables (fragmentation, margin modification, surface alteration, hinge fine scale alteration and corrosion degree) and their damage states were recorded for 1000 shells of Erodona mactroides. The shells were recovered from two outcrops 8 km apart. 14 C-AMS dating were performed on the shells of E. mactroides from those outcrops, which yielded similar ages (from 1060 to 1490 cal yrs BP). The ages would indicate that the Tramandaí Lagoon occupied a larger area and must have been subjected to very rapid progradation towards its present position. Several taphonomic variables, such as fragmentation, surface alteration, and corrasion extent and oxidation, presented significant differences (p {\textless} 0.01) between the two outcrops. This may be due to some natural variation of the estuarine and lagoonal environments or differences within the taphonomically active zone (TAZ). Dissolution seems to be a leading taphonomic agent in lagoonal environments. The shells from the two outcrops are within the TAZ and, due to intense dissolution, they will most likely leave no geological record. © 2013 Elsevier Ltd and INQUA.

In this work was investigated the effect of pre-treatment with (PhSe) 2 and (PhTe) 2 on chemical seizure and 4-aminopyridine-induced lethality in mice. Additionally, lipid peroxidation levels of whole brain after treatment with 4-aminopyridine and effect of pre-treatment with (PhSe) 2 and (PhTe) 2 on these levels were investigated. Mice were pre-treated with (PhSe) 2 or (PhTe) 2 (50, 100, or 150 $μ$mol/kg) 30 min before 4-aminopyridine (12 mg/kg) administration. The treatment with 4-aminopyridine caused a significant incidence of seizures (clonic, tonic) and death. Pre-treatment with (PhSe) 2 and (PhTe) 2 significantly increased the latency for clonic and tonic seizures, and prevented 4-aminopyridine-induced death. Significantly, the pre-treatment with (PhSe) 2 or (PhTe) 2 increased the latency for clonic seizures in a dose-dependent manner. Additionally, a significant increase was observed in the brain lipid peroxidation level after treatment with 4-aminopyridine, which was significantly inhibited by pre-treatment with 150 $μ$mol/kg (PhSe) 2 or (PhTe) 2 . These results demonstrate that (PhSe) 2 and (PhTe) 2 counteract the harmful effects of 4-aminopyridine. It is possible that this effect results from modulation of the redox state of N-methyl-d-aspartate receptors and/or of Ca 2+ channel activity with subsequent alteration in neurotransmitter release. Importantly, this study provides evidence for anticonvulsant and antioxidant properties of (PhSe) 2 and (PhTe) 2′ which indicates a neuroprotective activity of these compounds.

Objectives: To evaluate the potential role of oxidative stress in the evolution of cervical cancer, including its pre-malignant states. Design and methods: Erythrocytes thiobarbituric acid reactive substances (TBARS) levels, plasma vitamin C and thiol content and total blood $δ$-ALA-D levels were estimated in 46 untreated cervical cancer and pre-malignant patients and in 46 age-sex-matched controls. Results: Erythrocytes from patients, regardless of disease state, pre-malignant (low squamous intraepithelial lesion-LSIL and high squamous intraepithelial lesion-HSIL) or cancer, showed a significant 2-3 times increase in TBARS levels (P {\textless} 0.01). Plasma vitamin C was lower in the carcinoma group (P {\textless} 0.01). The reactivation index of $δ$-aminolevulinate dehydratase ($δ$-ALA-D) was higher in the patient group, when compared to control (P {\textless} 0.01). Conclusion: LSIL, HSIL or cervical cancer can be associated with changes in 3 indicators of oxidative stress: increase in erythrocyte TBARS, ALA-D reactivation index and a decrease in vitamin C content, that may play an important role in carcinogenesis. © 2005 The Canadian Society of Clinical Chemists. All rights reserved.