Bridging the Gap Between Salmon Spawner Abundance and Marine Nutrient Assimilation by Juvenile Salmon: Seasonal Cycles and Landscape Effects at the Watershed Scale

Ecosystems - Anadromous Pacific salmon are semelparous, and resource subsidies from spawning adults (marine-derived nutrients, or MDN) benefit juvenile salmonids rearing in freshwater. However, it...     

Interaction of vasomotor and exocrine neurons in bullfrog paravertebral sympathetic ganglia

A 2 min sample of an intracellular recording of in vivo synaptic activity from a vasomotor C-neuron in a bullfrog sympathetic ganglion was converted to a series of stimulus pulses. This physiologically derived activity was used to stimulate preganglionic C-fibres of similar ganglia studied in vitro. Intracellular recordings were made from exocrine B-cells within the ganglia. Although they do not receive fast, nicotinic synaptic input from preganglionic C-fibres, B-cell excitability was profoundly increased by stimulation of C-fibres with physiologically derived activity. Also, subthreshold depolarizing current pulses that failed to generate action potentials in B-cells under control conditions almost always generated action potentials whilst C-fibres were activated. These effects were attenuated or prevented by the luteinizing hormone releasing hormone antagonist, [D-pyro-Glu1,D-Phe2,D-Trp3,6]-LHRH (70 microM). The physiological release of luteinizing hormone releasing hormone from C-fibres therefore causes an interaction between vasomotor and exocrine outflow within a paravertebral sympathetic ganglion.     

Ethical issues in medical research in the developing world: a report on a meeting organised by Fondation Mérieux

This paper reports on a multidisciplinary meeting held to discuss ethical issues in medical research in the developing world. Many studies, including clinical trials, are conducted in developing countries with a high burden of disease. Conditions under which this research is conducted vary because of differences in culture, public health, political, legal and social contexts specific to these countries. Research practices, including standards of care for participants, may vary as a result. It is therefore not surprising that ethical issues emerge. This meeting sought to identify and discuss these issues from the perspectives of the many actors in such research, including community representatives, with a view to finding ethical and pragmatic solutions to these issues. Dialogue between these actors was also promoted, with a view to identifying the need to develop such dialogue in future.
Drawing from the experiences of the speakers, the colloquium attempted to outline some answers to several key questions characterising the field today. Experiences related to epidemiologic research, vaccine trials, drug trials, diagnostic tests and to some fundamental ethical issues in health research. Speakers were from different countries, disciplines and professions. The meeting provided a forum for consultation and debate between different ethics actors. Both encouraging findings and challenges emerged.     

Protection by oral vaccination of mice with an avirulent live strain of Salmonella typhimurium]

Before determining the quantity of mouse intestinal secretory IgA after oral vaccination, we have tried to find the best conditions of immunization with an avirulent S. typhimurium strain given by oral route. The results show the superiority of the live vaccin with respect to the heat-killed one.     

fMRI evidence for a dual process account of the speed-accuracy tradeoff in decision-making

Background

The speed and accuracy of decision-making have a well-known trading relationship: hasty decisions are more prone to errors while careful, accurate judgments take more time. Despite the pervasiveness of this speed-accuracy trade-off (SAT) in decision-making, its neural basis is still unknown.

Methodology/Principal Findings

Using functional magnetic resonance imaging (fMRI) we show that emphasizing the speed of a perceptual decision at the expense of its accuracy lowers the amount of evidence-related activity in lateral prefrontal cortex. Moreover, this speed-accuracy difference in lateral prefrontal cortex activity correlates with the speed-accuracy difference in the decision criterion metric of signal detection theory. We also show that the same instructions increase baseline activity in a dorso-medial cortical area involved in the internal generation of actions.

Conclusions/Significance

These findings suggest that the SAT is neurally implemented by modulating not only the amount of externally-derived sensory evidence used to make a decision, but also the internal urge to make a response. We propose that these processes combine to control the temporal dynamics of the speed-accuracy trade-off in decision-making.     

Unlocking the ring: Occurrence and development of the uninterrupted intrabullar septum in Canidae

The maned wolf, Chrysocyon brachyurus, and some of the earliest canids are known for the peculiar ring-like shape of their intrabullar septum (an incomplete bony partition in the auditory bulla). In attempt to understand the origin of this character state, the auditory bullae in adult and juvenile dried skulls of 28 species of living Caninae were examined with a special emphasis on the occurrence of a ring-like (uninterrupted) septum. In addition to C. brachyurus, this morphology was invariably found in the bush dog, Speothos venaticus, what makes the presence of the uninterrupted septum the first osteological synapomorphy supporting the Chrysocyon–Speothos clade recently revealed by molecular systematics.The canine juvenile morphologies indicate that the intrabullar septum is ring-like at its early developmental stage. As ontogeny progresses, the septum resorbs differentially, depending on taxon, to become horseshoe- or crescent-like. By this transformation of the initially ring-like septum, Caninae seem to ontogenetically parallel a trend found in the phylogeny of Hesperocyoninae, an extinct canid group. The reverse recapitulation occurs, however, in the evolution of Caninae themselves, with their most-derived members having a least-resorbed septum. This implies that the ontogenetic criterion cannot be used for inference of the polarity of septal character states within the Caninae. The evolution of the canine intrabullar septum could have involved a series of heterochronies towards increasingly paedomorphic states in several lineages of the tribe Canini.New data were also obtained on the bone composition of the canid intrabullar septum. While the dorsal septum is entotympanic, the ventral one is in fact ectotympanic in adult Caninae. This compound structure results from penetration of the ventral entotympanic sinus into the ectotympanic.     

Intestinal absorption and metabolism of retinoyl beta-glucuronide in humans, and of 15-[14C]-retinoyl beta-glucuronide in rats of different vitamin A status

In order to prove the hypothesis that humans and animals with adequate vitamin A status do not absorb and metabolize orally administered all-trans retinoyl β-glucuronide, unlabeled retinoyl glucuronide (0.1 mmol) was orally dosed to fasting well-nourished young men. Neither retinoyl glucuronide nor retinoic acid, a possible metabolite, appeared in the blood within 12 h after ingestion. Next, radiolabeled all-trans 15-[¹⁴C]-retinoyl β-glucuronide was chemically synthesized by a new procedure, and fed orally to rats of different vitamin A status. Analysis of blood and other tissues 5 or 24 h after the dose, showed the presence of radioactivity ( 0.5%) in the blood of vitamin A deficient rats, but not in sufficient rats. Livers of all rats contained small, but detectable amounts (0.3 to 1.1% of the dose) of radioactivity. The accumulation of radioactivity in the liver was highest in deficient rats. Analysis of the retinoids showed that the radioactivity in serum and liver was due to retinoic acid formed from retinoyl glucuronide. Within 24 h after the dose, 31 to 40% of the administered radioactivity was excreted in the feces, and 2 to 4.7% of the dose was excreted in the urine. Results of the present studies show that oral administration of retinoyl β-glucuronide did not give rise to detectable changes in blood retinoyl glucuronide and/or retinoic acid concentrations in humans or rats with adequate vitamin A status.