Plenty of rooftops with few neighbours occupied by young breeding Yellow-legged Gulls (Larus michahellis): Does this occur at the expense of their health condition?

Gulls, as largely flexible opportunistic individuals, have been increasingly breeding in many cities around the world, but it is still unclear whether urban habitats are of equal or higher quality than traditional natural habitats or represent an ecological trap with immediate reproductive benefits but longer-term detrimental consequences to health. Here we present a study of breeding parameters (nest density, egg dimensions, clutch size, hatching success and adult body condition) and physiological parameters (erythrocyte sedimentation rate, heterophil/lymphocyte ratio, haemoglobin concentration and measurements of oxidative stress) as indicators of the general health condition of Yellow-legged Gull Larus michahellis adults and chicks from natural and urban colonies. Yellow-legged Gulls in the largest urban area (Porto) laid smaller eggs and clutches, showed a significantly lower occurrence of inflammatory processes in chicks, and showed a slower early chick growth than in the natural colony of Deserta. This suggests that urban gulls might be facing important trade-offs between the advantages of breeding in lower density urban colonies, with fewer intraspecific interactions and a lower disease transmission probability, and the disadvantages of having an anthropogenic diet usually lower in nutritional value.     

Energy cost of walking and gait instability in healthy 65- and 80-yr-olds.

This study tested whether the lower economy of walking in healthy elderly subjects is due to greater gait instability. We compared the energy cost of walking and gait instability (assessed by stride to stride changes in the stride time) in octogenarians (G80, n = 10), 65-yr-olds (G65, n = 10), and young controls (G25, n = 10) walking on a treadmill at six different speeds. The energy cost of walking was higher for G80 than for G25 across the different walking speeds (P < 0.05). Stride time variability at preferred walking speed was significantly greater in G80 (2.31 +/- 0.68%) and G65 (1.93 +/- 0.39%) compared with G25 (1.40 +/- 0.30%; P < 0.05). There was no significant correlation between gait instability and energy cost of walking at preferred walking speed. These findings demonstrated greater energy expenditure in healthy elderly subjects while walking and increased gait instability. However, no relationship was noted between these two variables. The increase in energy cost is probably multifactorial, and our results suggest that gait instability is probably not the main contributing factor in this population. We thus concluded that other mechanisms, such as the energy expenditure associated with walking movements and related to mechanical work, or neuromuscular factors, are more likely involved in the higher cost of walking in elderly people.     

Isolation and characteristics of a wheatbran-degrading Butyrivibrio from human faeces

Screening over 100 isolates from human faeces for cellulolytic activity led to the isolation of a weakly cellulolytic anaerobic, curved, motile bacterium which produced H₂, lactate and butyrate from wheatbran. The mol% of G + C in the DNA was 39–42. These properties, together with the Gram-positive cell wall ultrastructure and SDS-PAGE profile, are consistent with the genus Butyrivibrio. The isolate is believed to be the most active wheatbran-degrading bacterium so far described.     

Cloned DNA probes distinguish endemic and exotic Entomophaga grylli fungal pathotype infections in grasshopper life stages

Entomophaga grylli is a fungal pathogen of grasshoppers and at least three pathotypes are recognized world-wide. Pathotypes 1 and 2 are endemic to North America while the Australian pathotype 3 had been released into two field sites in North Dakota between 1989 and 1991. Grasshoppers were collected over the summer at the field sites in 1992 and assessed for pathotype infection by cloned DNA probe analysis. The three most predominant grasshopper species that were infected ( Melanoplus sanguinipes, M. bivittatus and Camnula pellucida ) were assessed for pathotype infection with respect to their life stages (nymphal instars and adult males and females). Pathotype 1 predominantly infected grasshoppers in the subfamilies Oedipodinae and Gomphocerinae and pathotype 2 predominantly infected grasshoppers in the subfamily Melanoplinae. Early-instar M. sanguinipes and M. bivittatus had higher pathotype 2 infection frequencies, while late-instar and adult C. pellucida had higher pathotype 1 infection frequencies. Cross-infection by the pathotypes did occur in up to 3% of the individuals, on a per species basis, and primarily in later instar and adult grasshoppers. Pathotype 3 infections occurred in later instar and adults of the three grasshopper species. Infection of grasshoppers by E. grylli pathotypes is discussed with reference to the fungal life cycles.     

Effect of Amiloride on the Taste of NaCl, Na-gluconate and KCl in Humans: Implications for Na+ Receptor Mechanisms

Sodium-salt transduction in many species may be mediated byboth apical and submucosal ion channels on the taste receptorcell membrane. The apical ion channel is blockable by the diureticamiloride, whereas the submucosal pathway is not. Sodium saltswith small anions, such as NaCl, can stimulate submucosal aswell as apical ion channels; sodium salts with large anions,such as Na-gluconate, activate primarily the apical channels.In humans, reports on the effects of amiloride on the tasteof NaCl are conflicting and no data exist on the effects ofamiloride on organic sodium salts. In the present experiment,subjects gave magnitude estimates of the total intensity andof each of the basic taste qualtities for NaCl, Na-gluconateand KCl. Five concentrations of each of these stimuli were presentedto the anterior tongue following distilled water adaptationand after amiloride treatment. There was a significant decreasein the total taste intensity of NaCl and Na-gluconate afteramiloride, but no effect on KCl. The saltiness of all threesalts was unaffected, but amiloride decreased the preceivedsourness of the sodium salts. KCl sourness was unaffected byamiloride. There was a proportionately larger effect of amilorideon Na-gluconate than on Nacl, which is consistent with a largerrole for the apical ion channel in Na-gluconate transduction.However, an appreciable amiloride-insensitive component is presentfor both NaCl and Na-gluconate, suggesting that an amiloride-insensitivepathway also plays a role in the transduction of both sodiumsalts. These data support the hypothesis that an amiloride-sensitivetransduction component exists in humans, but suggest that itis considerably smaller than in many other species.     

Location by fluorescence microscopy of glycosidases and a xylanase in the anaerobic gut fungi Caecomyces communis,Neocallimastix frontalis,and Piromyces rhizinflata

-d-Glucosidase, -d-fucosidase -d-xylosidase, and -cellobiopyranosidase activities in Caecomyces communis, Neocallimastix frontalis, and Piromyces rhizinflata, located with fluorescent conjugates, occur throughout the whole thallus as from zoospore germination and disappear before sporulation. -d-Galactosidase and -l-arabinopyranosidase activities are low or nonexistent. A xylanase, detected by indirect immunofluorescence, was observed at the surface of the vegetative cells, vesicles, or rhizoids. Cross-reactions prove the existence of analogies in structure among the enzymes of these anaerobic gut fungi.