Paleomagnetic evidence for the evolution of Meso- to Neo-proterozoic glaciogenic rocks in central-eastern Brazil

Paleomagnetic studies on basic dikes in the eastern São Francisco Craton which have isotopic ages of 1.0–1.1 Ga, define an apparent polar wander path for South America over this time interval. The data indicate that the São Francisco Craton was at paleolatitudes between 40° and 65° at the time of emplacement of these dikes. Neo-Proterozoic sedimentary glaciogenic rocks, the Macaúbas Group, Bebedouro Formation, Ibiá Formation and Carandai Formation, crop out in central-eastern Brazil. An age of about 1.0 Ga has been proposed for these glacial deposits. Paleogeographical reconstructions of South America show a continental movement coherent with paleoenvironmental models proposed for the Macaúbas Group and suggest that the glacial period may have occurred between 1.01 and 1.08 Ga.     

An animal model for the measurement of acute tolerance to ethanol

An apparatus is described for the measurement of acute tolerance to ethanol in small animals. Male, Sprague-Dawley rats were trained on the apparatus to leap to a descending platform to avoid being shocked. After an i.p. injection of 2 g/kg ethanol, the rats were tested repeatedly on the apparatus, and the plasma ethanol concentration was measured after each trial. The results demonstrated that the jumping ability of the rats was significantly more impaired during the ascending portion of the plasma ethanol curve than during the descending portion of the curve. Furthermore, it was demonstrated that the improvement in jumping ability during the descending portion of the curve was not dependent on a lowered plasma ethanol concentration. In a second experiment, the possibility of practice effects was eliminated by measuring the jumping ability and plasma ethanol concentration in one group of rats on the ascending portion of the plasma ethanol curve and in another group on the descending portion of the curve. A significant improvement in jumping ability was again observed during the descending portion of the curve, even though the plasma ethanol concentrations of the two groups were comparable. The development of acute tolerance to ethanol was thus demonstrated in both experiments.     

Direct and indirect bacterial killing functions of neutrophil defensins in lung explants

Studies of the antimicrobial activity of neutrophil defensins have mostly been carried out in microbiological media, and their effects on the host defense in physiological conditions are unclear. We examined 1) the antibacterial activity of defensins in physiological media with and without lung tissue present, 2) the effect of defensins on hydrogen peroxide (H(2)O(2)) production by lung tissue that had been exposed to bacteria, and 3) the effect of diphenyleneiodonium (DPI), an inhibitor of reactive oxygen species formation, on the antibacterial activity of defensins in the presence of lung tissue. Defensins were incubated with Escherichia coli or Pseudomonas aeruginosa in the absence or presence of primary cultured mouse lung explants. Defensins reduced bacterial counts by approximately 65-fold and approximately 25-fold, respectively, at 48 h; bacterial counts were further decreased by approximately 600-fold and approximately 12,000-fold, respectively, in the presence of lung tissue. Defensins induced H(2)O(2) production by lung tissue, and the rate of killing of E. coli by defensins was reduced by approximately 2,500-fold in the presence of 10 microM DPI. We conclude that defensins exert a significant antimicrobial effect under physiological conditions and that this effect is enhanced in the presence of lung tissue by a mechanism that involves the production of reactive oxygen species.     

The development of new triazole based inhibitors of tumor necrosis factor-alpha (TNF-alpha) production

4-Aryl-5-pyridyl and 4-aryl-5-pyrimidyl based inhibitors of TNF-alpha production, which contain a novel triazole 5-member heterocyclic core, are described. Many pyridyl triazoles containing either an alkyl ether or a substituted aryl side chain on the triazole core showed sub-micromolar activity against LPS-induced TNF-alpha, while pyrimidyl triazoles containing an ethoxymethyl side chain exhibited even better inhibitory activity. Secondary screening data are presented for the pyrimidyl triazoles. Triazole 14e combined excellent potency with good oral bioavailability in the rat.     

Growth and metabolism in the embryonic white-spotted bamboo shark, Chiloscyllium plagiosum: comparison with embryonic birds and reptiles

Birds and reptiles have been important models for studying the energetics of embryonic development. Studies on these groups reveal three metabolic patterns: an exponential increase in metabolism with embryo age, a sigmoidal increase with age, or a sigmoidal increase followed by a decrease before hatching. Models developed to explain avian metabolic patterns and developmental costs partition total costs between growth and maintenance. To test the generality of these models, we examined embryonic energetics of the oviparous white-spotted bamboo shark Chiloscyllium plagiosum. Oviparous sharks must actively ventilate during development, which could increase their development costs relative to birds and reptiles. Our results demonstrated that bamboo shark embryos have a peaked metabolic pattern and sigmoidal increase in body mass similar to ratites, crocodilians, and some turtles. The total cost of development was higher in bamboo sharks than in reptiles and many birds. However, calculations reveal that the high cost of bamboo shark development can be explained by the relatively long incubation time rather than the additional cost of muscular movement. Finally, an avian model can reasonably describe shark embryonic metabolism, suggesting that movement costs do not significantly alter the metabolic pattern during development.     

A life history model for the San Francisco Estuary population of the Chinese mitten crab, <Emphasis Type="Italic">Eriocheir sinensis</Emphasis> (Decapoda: Grapsoidea)

First discovered in San Francisco Bay in 1992, the Chinese mitten crab,Eriocheir sinensis, has become established over hundreds of km² of the San Francisco Estuary. Ecological and economic impacts of this invasive species motivated our search for a greater understanding of the crabs life history as an important step in better management and control. Data for this life history model comes from the authors research and scientific literature. Juvenile crabs migrate from the Estuary into fresh water where they develop into adults. Environmental signals may stimulate gonad development that is followed by a downstream migration beginning at the end of summer. Mating occurs after the crabs reach saline water. Embryos are carried until hatching, and the larvae undergo five zoeal stages before settlement. Our model projects rates of development at various temperatures and growth increments, supports a minimum of 2 years in low salinity or freshwater habitat, and predicts that most California mitten crabs are at least 3 years old before becoming sexually mature. Environmental factors strongly influence the timing and duration of the crabs life stages, and are discussed in the context of a gradient of development times for worldwide populations of this important invasive species.     

The ontogeny of contractile performance and metabolic capacity in a high-frequency muscle

High-performance muscles such as the shaker muscles in the tails of western diamond-backed rattlesnakes (Crotalus atrox) are excellent systems for studying the relationship between contractile performance and metabolic capacity. We observed that shaker muscle contraction frequency increases dramatically with growth in small individuals but then declines gradually in large individuals. We tested whether metabolic capacity changed with performance, using shaker muscle contraction frequency as an indicator of performance and maximal activities of citrate synthase and lactate dehydrogenase as indicators of aerobic and anaerobic capacities, respectively. Contraction frequency increased 20-fold in 20-100-g individuals but then declined by approximately 30% in individuals approaching 1,000 g. Mass-independent aerobic capacity was positively correlated with contractile performance, whereas mass-independent anaerobic capacity was slightly but negatively correlated with performance; body mass was not correlated with performance. Rattle mass increased faster than the ability to generate force. Early in ontogeny, shaker muscle performance appears to be limited by aerobic capacity, but later performance becomes limited equally by aerobic capacity and the mechanical constraint of moving a larger mass without proportionally thicker muscles. This high-performance muscle appears to shift during ontogeny from a metabolic constraint to combined metabolic and mechanical constraints.