Ventilatory response to adjuvant arthritis in the rat

This study examined ventilation in rats with arthritis induced by Mycobacterium butyricum. It was found that, 19 days after inoculation, the minute ventilation of arthritic rats breathing air was about two-fold higher than that of control animals. This increase resulted from an increase both in respiratory frequency and in tidal volume. Air-CO2 mixtures continued to stimulate ventilation in arthritic rats, and the minute ventilation of these animals on breathing 5 or 7% CO2 exceeded that of controls. The results are consistent with the hypothesis that arthritic rats hyperventilate and contribute to the validation of adjuvant arthritis as an animal model of chronic pain.     

The amphioxus (Branchiostoma floridae) genome contains a highly diversified set of G protein-coupled receptors

Background

When natural hybridization occurs at sites where the hybridizing species differ in abundance, the pollen load delivered to the rare species should be predominantly from the common species. Previous authors have therefore proposed a hypothesis on the direction of hybridization: interspecific hybrids are more likely to have the female parent from the rare species and the male parent from the common species. We wish to test this hypothesis using data of plant hybridizations both from our own experimentation and from the literature.

Results

By examining the maternally inherited chloroplast DNA of 6 cases of F1 hybridization from four genera of plants, we infer unidirectional hybridization in most cases. In all 5 cases where the relative abundance of the parental species deviates from parity, however, the direction is predominantly in the direction opposite of the prediction based strictly on numerical abundance.

Conclusion

Our results show that the observed direction of hybridization is almost always opposite of the predicted direction based on the relative abundance of the hybridizing species. Several alternative hypotheses, including unidirectional postmating isolation and reinforcement of premating isolation, were discussed.     

Aerobic fitness and performance in elite female futsal players

Despite its growing popularity, few studies have investigated specific physiological demands for elite female futsal. The aim of this study was to determine aerobic fitness in elite female futsal players using laboratory and field testing. Fourteen female futsal players from the Venezuelan National team (age =21.2±4.0 years; body mass =58.6±5.6 kg; height =161±5.0 cm) performed a progressive maximal treadmill test under laboratory conditions. Players also performed a progressive intermittent futsal-specific field test for endurance, the Futsal Intermittent Endurance Test (FIET), until volitional fatigue. Outcome variables were exercise heart rate (HR), VO₂, post-exercise blood lactate concentrations ([La]b) and running speeds (km · h^-1). During the treadmill test, VO₂max, maximal aerobic speed (MAS), HR and peak [La]b were 45.3±5.6 ml · kg^-1 · min^-1, 12.5±1.77 km · h^-1, 197±8 beats · min^-1 and 11.3±1.4 mmol · l^-1, respectively. The FIET total distance, peak running velocity, peak HR and [La]b were 1125.0±121.0 m, 15.2±0.5 km · h^-1, 199±8 beats · min^-1 and 12.5±2.2 mmol · l^-1, respectively. The FIET distance and peak speed were strongly associated (r= 0.85-87, p < 0.0001) with VO₂max and MAS, respectively. Peak HR and [La]b were not significantly different between tests. Elite female futsal players possess moderate aerobic fitness. Furthermore, the FIET can be considered as a valid field test to determine aerobic fitness in elite level female futsal players.     

Paradoxical signal transduction in neurobiological systems

Information processing in neurobiological systems is commonly thought to rely on the assessment of a signal-to-noise ratio as the key mechanism of signal detection; it assumes and requires that both signal and noise are concurrently available. An alternative theory holds that detection proceeds by the system appreciating any instantaneous input by the input’s departure from the moving average of past activity. The evidence reviewed here suggests that this latter transduction mechanism provides a unique, formal account of the highly dynamic, neuroadaptative plasticity (i.e., tolerance, dependence, sensitization) that ensues upon μ-opioid receptor activation. The mechanism would appear already to operate with the receptor-G protein coupling that occurs upon agonist binding to μ-opioid receptors, and also with highly integrated responses such as whole-organism analgesia. The mechanism may perhaps operate ubiquitously with further neuronal and non-neuronal, cell surface, and intracellular-signaling systems, and may govern the experience-dependent regulation of synaptic strength. The transduction mechanism defines a continuously evolving process; the process’s most peculiar feature is that it makes any input generate not one but two outcomes that are paradoxical, or opposite in sign.     

Drug treatments to reduce excitotoxicity in vivo: a potential for α 2-adrenoceptor antagonists?

Summary. It is hypothesized that the locus coeruleus-noradrenergic system controls compensatory and repair mechanisms in the CNS, and that its dysfunction is a critical factor in the progression of central neurodegenerative diseases. Pharmacological activation of locus coeruleus neurons can be achieved with α ₂-adrenoceptor antagonists, and such compounds are protective in vivo in some models of brain injury where excitotoxicity is thought to be a causative factor. To further explore this neuroprotective potential, the effects of a 7-day treatment with the α ₂-antagonists, (+)-efaroxan and (±)-idazoxan, were evaluated in rats undergoing a unilateral lesioning of the striatum with the excitotoxin, quinolinic acid. The α ₂-antagonist treatments reduced both the ipsiversive circling response to apomorphine and the deficit of choline acetyltransferase in the lesioned animals. To elucidate the mechanisms underlying this neuroprotective effect, a modulation of the extracellular levels of amino acids within the striatum was investigated using in vivo microdialysis. Intrastriatal injection of quinolinic acid increased taurine and tyrosine levels by 2–2.5 fold, while most other amino acids were not significantly altered; the effect of (+)-efaroxan on these changes is being investigated. Further research is required to identify which of several possible mechanisms is involved in the neuroprotective action of α ₂-antagonists in vivo. Received August 31, 1999 Accepted September 20, 1999     

SPRIT: Identifying horizontal gene transfer in rooted phylogenetic trees

Background  

Phylogenetic trees based on sequences from a set of taxa can be incongruent due to horizontal gene transfer (HGT). By identifying the HGT events, we can reconcile the gene trees and derive a taxon tree that adequately represents the species' evolutionary history. One HGT can be represented by a rooted Subtree Prune and Regraft (RSPR) operation and the number of RSPRs separating two trees corresponds to the minimum number of HGT events. Identifying the minimum number of RSPRs separating two trees is NP-hard, but the problem can be reduced to fixed parameter tractable. A number of heuristic and two exact approaches to identifying the minimum number of RSPRs have been proposed. This is the first implementation delivering an exact solution as well as the intermediate trees connecting the input trees.