Biomedical subjects

Y Le Maho

Publications and source records attributed to Y Le Maho.

At least 19 recordsLinked to original sources

PubMed2004

Long-term effects of flipper bands on penguins.

Changes in seabird populations, and particularly of penguins, offer a unique opportunity for investigating the impact of fisheries and climatic variations on marine resources. Such investigations often require large-scale banding to identify individual birds, but the significance of the data relies on the assumption that no bias is introduced in this type of long-term monitoring. After 5 years of using an automated system of identification of king penguins implanted with electronic tags (100 adult king penguins were implanted with a transponder tag, 50 of which were also flipper banded), we can report that banding results in later arrival at the colony for courtship in some years, lower breeding probability and lower chick production. We also found that the survival rate of unbanded, electronically tagged king penguin chicks after 2-3 years is approximately twice as large as that reported in the literature for banded chicks.

Animal Identification Systems↗

PubMed2004

Effects of fasting and refeeding on jejunal morphology and cellular activity in rats in relation to depletion of body stores.

BACKGROUND: Intestinal mucosa atrophy following a period of starvation characterized by the mobilization of fat stores for energy expenditure (phase II) worsen after a long fast marked by an increase in protein catabolism (phase III). However, the morphology of the jejunum is completely restored after 3 days of refeeding. The aim of this study was to determine the mechanisms involved in the rapid jejunal restoration following the critical phase III. METHODS: Jejunal structure was observed through conventional and environmental scanning electron microscopy, whilst cellular dynamics were studied using classical optic microscopy tools and immunohistochemistry. RESULTS: Mucosal structural atrophy during fasting proved to worsen over the two phases. During phase II, apoptosis is still present at the tip of the villi, the number of mitosis in crypts showed a 30% decrease and a transient drop in cell migration is observed. During phase III, however, an 85% rise in mitosis was noticed along with an increase in cell migration and the disappearance of apoptotic cells at the villus tips. This increased cell renewal continues after food ingestion. CONCLUSIONS: Starved rats appeared to be in a phase of energy sparing in phase II, with depressed cellular events in the intestinal mucosa. In phase III, however, the preservation of functional cells and the early increase in crypt cell proliferation should prepare the mucosa to refeeding and could explain why jejunal repairs are complete after 3 days of refeeding following either phase II or phase III.

Animals↗

PubMed2004

Adjustments of gastric pH, motility and temperature during long-term preservation of stomach contents in free-ranging incubating king penguins.

Male king penguins are able to store undigested food in their stomach for up to 3 weeks during their incubation fast, which evidently implies some modification of their digestive process. Using small electronic recorders, we studied the change in gastric pH, motility and temperature during the first week of food storage. The pH could be maintained at values as high as 6 throughout the incubation fast, a pH that is unfavourable for avian gastric proteinase activity. Gastric motility was never completely inhibited but could be markedly reduced. Stomach temperature was maintained at around 38 degrees C. The fact that stomach temperature of incubating birds did not show a daily rhythmic fluctuation as seen in non-breeding birds could be due to temperature constraints on embryo development. Thus the present study demonstrates substantial adjustments of pH and gastric motility in incubating king penguins, which may contribute to the inhibition of digestive gastric processes.

Analysis of Variance↗

PubMed2004

Heart rate and energetics of free-ranging king penguins (Aptenodytes patagonicus).

The main objective of this study was to determine heart rate (fh) and the energetic costs of specific behaviours of king penguins while ashore and while foraging at sea during their breeding period. In particular, an estimate was made of the energetic cost of diving in order to determine the proportion of dives that may exceed the calculated aerobic dive limit (cADL; estimated usable O2 stores/estimated rate of oxygen consumption during diving). An implanted data logger enabled fh and diving behaviour to be monitored from 10 free-ranging king penguins during their breeding period. Using previously determined calibration equations, it was possible to estimate rate of oxygen consumption (VO2) when the birds were ashore and during various phases of their foraging trips. Diving behaviour showed a clear diurnal pattern, with a mixture of deep (>40 m), long (>3 min) and shallow (<40 m), short (<3 min) dives from dawn to dusk and shallow, short dives at night. Heart rate during dive bouts and dive cycles (dive + post-dive interval) was 42% greater than that when the birds were ashore. During diving, fh was similar to the 'ashore' value (87+/-4 beats min(-1)), but it did decline to 76% of the value recorded from king penguins resting in water. During the first hour after a diving bout, fh was significantly higher than the average value during diving (101+/-4 beats min(-1)) and for the remainder of the dive bout. Rates of oxygen consumption estimated from these (and other) values of fh indicate that when at sea, metabolic rate (MR) was 83% greater than that when the birds were ashore [3.15 W kg(-1) (-0.71, +0.93), where the values in parentheses are the computed standard errors of the estimate], while during diving bouts and dive cycles, it was 73% greater than the 'ashore' value. Although estimated MR during the total period between dive bouts was not significantly different from that during dive bouts [5.44 W kg(-1) (-0.30, +0.32)], MR during the first hour following a dive bout was 52% greater than that during a diving bout. It is suggested that this large increase following diving (foraging) activity is, at least in part, the result of rewarming the body, which occurs at the end of a diving bout. From the measured behaviour and estimated values of VO2, it was evident that approximately 35% of the dives were in excess of the cADL. Even if VO2 during diving was assumed to be the same as when the birds were resting on water, approximately 20% of dives would exceed the cADL. As VO2 during diving is, in fact, that estimated for a complete dive cycle, it is quite feasible that VO2 during diving itself is less than that measured for birds resting in water. It is suggested that the regional hypothermia that has been recorded in this species during diving bouts may be at least a contributing factor to such hypometabolism.

Analysis of Variance↗

PubMed2002

The heart rate/oxygen consumption relationship during cold exposure of the king penguin: a comparison with that during exercise.

This study investigated whether exposure to low ambient temperature could be used as an alternative to exercise for calibrating heart rate (fH) against rate of oxygen consumption ((O(2))) for subsequent use of fH to estimate (O(2)) in free-ranging animals. Using the relationship between the oxygen pulse (OP, the amount of oxygen used per heart beat) and an index of body condition (or nutritional index, NI), a relationship between fH and (O(2)) was established for resting king penguins exposed to a variety of environmental temperatures. Although there was a small but significant increase in the OP above and below the lower critical temperature (-4.9 degrees C), there was no difference in the relationship obtained between the OP and body condition (NI) obtained above or below the lower critical temperature. These results were then compared with those obtained in a previous study in which the relationship between fH and (O(2)) had been established for king penguins during steady-state exercise. The relationship between OP and NI in the present study was not significantly different from the relationship between resting OP and NI in the previous study. However, the relationship was different from that between active OP and NI. We conclude that, at least for king penguins, although thermoregulation does not affect the relationship between resting OP and NI, temperature cannot be used as an alternative to exercise for calibrating fH against (O(2)) for subsequent use of fH to estimate (O(2)) in free-ranging animals.

Animals↗

PubMed2002

Buoyancy and maximal diving depth in penguins: do they control inhaling air volume?

Using a newly developed data logger to measure acceleration, we demonstrate that free-ranging king and Adélie penguins only beat their flippers substantially during the first part of descent or when they were presumed to be chasing prey at the bottom of dives. Flipper beating stopped during the latter part of ascent: at 29+/-9 % (mean +/- S.D.) of dive depth (mean dive depth=136.8+/-145.1 m, N=425 dives) in king penguins, and at 52+/-20 % of dive depth (mean dive depth=72.9+/-70.5 m, N=664 dives) in Adélie penguins. Propulsive swim speeds of both species were approximately 2 m s(-1) during dives; however, a marked increase in speed, up to approximately 2.9 m s(-1), sometimes occurred in king penguins during the passive ascending periods. During the prolonged ascending, oblique ascent angle and slowdown near the surface may represent one way to avoid the potential risk of decompression sickness. Biomechanical calculations for data from free-ranging king and Adélie penguins indicate that the air volume of the birds (respiratory system and plumage) can provide enough buoyancy for the passive ascent. When comparing the passive ascents for shallow and deep dives, there is a positive correlation between air volume and the depth of the dive. This suggests that penguins regulate their air volume to optimize the costs and benefits of buoyancy.

Air↗

PubMed2001

Feeding behaviour of free-ranging penguins determined by oesophageal temperature.

Sea birds play a major role in marine food webs, and it is important to determine when and how much they feed at sea. A major advance has been made by using the drop in stomach temperature after ingestion of ectothermic prey. This method is less sensitive when birds eat small prey or when the stomach is full. Moreover, in diving birds, independently of food ingestion, there are fluctuations in the lower abdominal temperature during the dives. Using oesophageal temperature, we present here a new method for detecting the timing of prey ingestion in free-ranging sea birds, and, to our knowledge, report the first data obtained on king penguins (Aptenodytes patagonicus). In birds ashore, which were hand-fed 2-15 g pieces of fish, all meal ingestions were detected with a sensor in the upper oesophagus. Detection was poorer with sensors at increasing distances from the beak. At sea, slow temperature drops in the upper oesophagus and stomach characterized a diving effect per se. For the upper oesophagus only, abrupt temperature variations were superimposed, therefore indicating prey ingestions. We determined the depths at which these occurred. Combining the changes in oesophageal temperatures of marine predators with their diving pattern opens new perspectives for understanding their foraging strategy, and, after validation with concurrent applications of classical techniques of prey survey, for assessing the distribution of their prey.

Animals↗

PubMed2001

Restoration of the jejunal mucosa in rats refed after prolonged fasting.

To investigate the importance of body fuel depletion on gut rehabilitation after food deprivation, we compared the kinetics of jejunal mucosa alteration and restoration in rats that were refed after reaching different stages in body fuel depletion. Rats (P2) were refed while still in the so-called phase II, where body protein utilization is minimized, whereas rats (P3) were refed when they had reached the stage of increasing protein utilization (phase III). There was a significant decrease in total mass of intestine (P2, -30%; P3, -40%) and jejunal mucosa (P2, -52%; P3, -60%), as well in the size of the crypts (P2, -15%; P3, -36%) and villi (P2, -37%; P3, -55%). Structural changes of the mucosa included disappearance of some villi and a reduction in the size and number of crypts. Despite the larger morphological alterations in P3, the restoration of mucosa was as fast and complete after only 3 days of refeeding for both P2 and P3 rats. The respective roles of the mitosis pressure and of the lamina propria dynamics were studied. The rapid reversibility of the gut mucosal alterations due to fasting might constitute an integrative process.

Animals↗

PubMed2001

Are non-migrant white storks (Ciconia ciconia) able to survive a cold-induced fast?

Northwestern European populations of White Storks (Ciconia ciconia) have been restored by settling young birds which, after having been maintained captive for 3 years, do not migrate when released. Since they are still supplied with food, the question we address here is how settled White Storks would cope with a fast resulting from a cold spell if food were no longer available. We therefore measured daily body mass loss, nitrogen excretion and daily energy expenditure under natural photoperiod and climatic conditions in six captive White Storks exposed to 5 days of food deprivation during winter. Daily ambient temperature ranged between -10 and 17 degrees C. After an initial decrease in both daily body mass loss and nitrogen excretion during the first day of fasting, these two parameters stabilized at low values. Lipids were the main fuel energy source (91%) and body proteins accounted for the remainder (9%). The rate of CO(2) production, measured with the doubly labeled water method, decreased significantly (P<0.001) during fasting when compared to the ad libitum value. Our data show that the metabolic adjustments of White Storks facing starvation are similar to those found in birds well-adapted to long-term fasting. From the determination of lipid and protein stores and of lipid and protein depletion rates, we conclude that White Storks would be able to survive at least during 4 weeks, a period of time twice as long as the duration of cold spells usually occurring in the Alsace region.

Acclimatization↗

PubMed2001

A new technique for monitoring the behaviour of free-ranging Adélie penguins.

Measurement of the time allocation of penguins at sea has been a major goal of researchers in recent years. Until now, however, no equipment has been available that would allow measurement of the aquatic and terrestrial behaviour of an Antarctic penguin while it is commuting between the colony and the foraging grounds. A new motion detector, based on the measurement of acceleration, has been used here in addition to current methods of inferring behaviour using data loggers that monitor depth and speed. We present data on the time allocation of Adélie penguins (Pygoscelis adeliae) according to the different types of behaviours they display during their foraging trips: walking, tobogganing, standing on land, lying on land, resting at the water surface, porpoising and diving. To illustrate the potential of this new technique, we compared the behaviour of Adélie penguins during the chick-rearing period in a fast sea-ice region and an ice-free region. The proportion of time spent standing, lying on land and walking during foraging trips was greater for penguins in the sea-ice region (37.6+/-13.3% standing, 21.6+/-15.6% lying and 5.9+/-6.3% walking) than for those in the ice-free region (12.0+/-15.8 % standing, 0.38+/-0.60% lying and 0 % walking), whereas the proportion of time spent resting at the water surface and porpoising was greater for birds in the ice-free region (38.1+/-6.4% resting and 1.1+/-1.1% porpoising) than for those in the sea-ice region (3.0+/-2.3% resting and 0% porpoising; means +/- s.d., N=7 for the sea-ice region, N=4 for the ice-free region). Using this new approach, further studies combining the monitoring of marine resources in different Antarctic sites and the measurement of the energy expenditure of foraging penguins, e.g. using heart rates, will constitute a powerful tool for investigating the effects of environmental conditions on their foraging strategy. This technique will expand our ability to monitor many animals in the field.

Animals↗

PubMed2000

Determining body fuels of wintering mallards.

Measuring body lipids and proteins of wild animals such as mallards is essential to determine the impact of the environment on their body condition. A major difficulty, however, is that biochemical analysis of carcass is tedious and therefore cannot be applied at a large scale. The main objective of this study was therefore to find out if simple measurements can be used as indices of total body lipids and proteins. Four classes of lipid and protein indices, derived on a 'source' group, were defined according to their complexity and condition of application (field or laboratory). Accuracy of the indices was evaluated on an independent group, of which the body composition calculated from indices was compared to carcass analysis. In live birds, body mass was an accurate and convenient predictor for both lipid and protein masses. If carcasses are available, extensive analysis provides a higher accuracy for body lipids only. This can be simply obtained through multiple regressions using abdominal fat mass and/or dry body mass.

Animals↗

PubMed2000

Seabirds as monitors of upper-ocean thermal structure. King penguins at the Antarctic polar front, east of Kerguelen sector.

The main objective of this work was to assess the potential of diving birds to monitor the hydrographic features near the Antarctic polar front. We compared the temperature/depth profiles recorded by instrumented King penguins Aptenodytes patagonicus at Kerguelen Islands (South Indian Ocean) with the oceanographic and remote sensing (satellite) data available for the same area during the same season. The birds were equipped with time/depth/temperature recorders or Argos transmitters. In addition, two birds were instrumented (of which one successfully) both with a time/depth/temperature recorder and an Argos transmitter. King penguins foraged as far as 400 km from the coast, in water masses with a vertical temperature structure characteristic of the region just south of the polar front. The temperature/depth profiles recorded throughout the dives (up to 270 m) revealed a pronounced thermocline. A three-dimensional distribution of water temperature was reconstructed. Comparison with previous hydrographic data shows a high correlation. Instrumented predators may therefore usefully and cheaply complement the database provided by conventional hydrographic surveys and remote sensing, especially in distant and rough areas such as the Southern Ocean.

Animals↗

PubMed1999

Intersexual differences in the diving behaviour of foraging subantarctic cormorant (Phalacrocorax albiventer) and Japanese cormorant (P. filamentosus).

Cormorants feed by feet-propelled diving. How cormorants optimize foraging is of a particular interest in relation to the understanding of the feeding strategies of diving birds, as well as within the debate about cormorants' impact on sustainable resources. Using microdata loggers that recorded diving depth, we investigated the foraging strategy of males and females of subantarctic cormorants, which inhabit cold regions, and of Japanese cormorants, which live in the northern temperate zone. For both species, males and females daily spent the same amount of time submerged, and apparently captured the same amount of fish. However, males dived deeper and longer, which could be explained by their 15-20% larger body mass and may minimize potential competition for food.

Animals↗

PubMed1999

Precise monitoring of porpoising behaviour of Adélie penguins determined using acceleration data loggers.

A new method using acceleration data loggers enabled us to measure the porpoising behaviour of Adélie penguins (Pygoscelis adeliae), defined as a continuous rapid swimming with rhythmic serial leaps. Previous hydrodynamic models suggested that leaping would be energetically cheaper when an animal swims continuously at depths of less than three maximum body diameters below the water surface. In the present study, free-ranging Adélie penguins leapt at a mean speed of 2.8 m s(-)(1) above the predicted threshold speed (0.18-1. 88 m s(-)(1)). Wild penguins reduced drag by swimming deeper (0.91 m) and did not swim continuously within the high-drag layer while submerged. This indicates that previous calculations may be incomplete. Moreover, leaps represented an average of only 3.8 % of the total distance travelled during the porpoising cycle, which would make energy savings marginal. Among the six penguins used in our study, two did not porpoise and three porpoised for less than 7 min, also indicating that this behaviour was not important during travel to and from foraging sites, as has been previously suggested. Birds mainly porpoised at the start and end of a trip. One explanation of porpoising might be an escape behaviour from predators.

Animals↗

PubMed1997

Brown fat thermogenesis in rats fed high-fat diets enriched with n-3 polyunsaturated fatty acids.

OBJECTIVE: To examine the possible involvement of an increase in diet-induced thermogenesis from brown adipose tissue (BAT) in the n-3 polyunsaturated fatty acids (n-3 PUFA) induced limitation of the development of white fat pads during high-fat feeding. DESIGN: Rats fed for four weeks on a low-fat/high-carbohydrate diet (C group) or high-fat diet without n-3 PUFA (REF group), with eicosapentaenoic acid (EPA group), with docosahexaenoic acid (DHA group) or with a mixture of these two fatty acids (MIX group). MEASUREMENTS: Epididymal and retroperitoneal fat pad mass, BAT composition, Guanosine 5'-diphosphate (GDP) binding and uncoupling protein (UCP) content were measured in the five groups of rats. RESULTS: The masses of retroperitoneal and epididymal white fat pads were lower in the groups fed n-3 PUFA than in the C and REF groups. The total BAT GDP binding was 1.6 times higher in the MIX and EPA groups than in the REF group. The BAT from the EPA group presented an enrichment in mitochondria compared to the C and REF groups whereas the BAT from the DHA and REF groups presented a hyperplasia and an increase in thermogenic activity of the mitochondria compared to the C group. The higher thermogenic activity of BAT was observed in the MIX group and is due to hyperplasia and to an increase in thermogenic activity of mitochondria. CONCLUSIONS: n-3 PUFA induce a marked stimulation of BAT thermogenic activity without changes in the UCP content compared to a high-fat diet without n-3 PUFA. The mixture of EPA and DHA has the more pronounced effect while EPA and DHA seem to act in synergy on BAT thermogenesis via different mechanisms.

Adipose Tissue↗

PubMed1996

Ventromedial hypothalamic lesions prevent the fasting-induced changes in day-night pattern of locomotor activity.

The time-course of day-night organization of running wheel activity during prolonged fasting was studied in rats, with or without electrolytic lesions in the ventromedial hypothalamus (VMH). For each individual, dates were referenced to the metabolic transition from lipid to protein utilization in late fasting; this was estimated by daily weighing. In fasted sham-operated controls, daytime activity increased progressively over the fast. This fasting-induced rise in diurnal activity was not due to daily handling, since it was observed also in non-handled (fasted) controls. The pattern of the increase in sham-operated rats differed between 2-hour periods (8-10 h to 18-20 h). The distribution of nocturnal activity was also modified during food deprivation: nocturnal activity in late fasting increased in the 20-22 h period and concomitantly decreased in the two 4-6 h and 6-8 h periods. By contrast, VMH lesions markedly limited and delayed the rise in diurnal running activity, irrespective of the 2-hour period. They prevented any significant change in nocturnal activity pattern over the fast. In fasted sham-operated rats, the data may be interpreted as a phase-advance of the nocturnal pattern of locomotor activity, concomitant with the increase of activity during daytime. These changes were suppressed by the VMH lesions. This suggests that the fasting-induced changes in the day-night pattern of locomotor activity are centrally mediated by a neuronal circuit involving the ventromedial hypothalamus.

Animals↗

PubMed1996

Food deprivation modifies fatty acid partitioning and beta-oxidation capacity in rat liver.

The involvement of lipids under starvation conditions in the shift from the phase of protein sparing (phase II) to the phase of increased protein breakdown (phase III) has been investigated. Plasma and liver were sampled from fed and unfed rats at two distinct stages which were characterized according to the changes in specific loss in daily body mass and nitrogen excretion. In the two groups of food-deprived rats corresponding to phases II and III, the liver concentration of triglycerides (micromol/g) was significantly lower, that of cholesterol significantly higher and that of the other lipid classes was moderately affected compared with concentrations in fed rats. Hepatic phospholipids had significantly higher concentrations (mol/100 mol) of 22:6(n-3) in food-deprived rats than in fed rats. Triglycerides had significantly higher concentrations of stearic and arachidonic acids in livers of both groups of food-deprived rats compared with fed rats. The total activity of carnitine palmitoyl transferase [mmol/(min x liver)] was 48% higher in rats studied at the end of phase II than in fed rats but was similar in fed rats and in rats studied at the beginning of phase III. The total activity of fatty acyl-CoA oxidase was 73% lower only in rats studied at the beginning of phase III when compared with fed rats. Our results indicate that during food deprivation the change in the rate of protein utilization is associated with important qualitative and quantitative alterations of hepatic lipids and oxidative capacity of fatty acids. These modifications appear to be related to the change from a preferential use of lipids to a preferential utilization of proteins.

3-Hydroxybutyric Acid↗

PubMed1996

Gastrointestinal tract protein synthesis and mRNA levels for proteolytic systems in adult fasted rats.

We studied protein turnover in the gastrointestinal tract of adult fasted rats, since the mechanisms responsible for protein wasting in these tissues are poorly understood. Protein mass of stomach, small intestine, and colon decreased by 14-29 and 21-49% after 1 and 5 days of fasting, respectively. The fractional rate of in vivo protein synthesis (ks) was approximately 34% lower in the stomach after 1 and 5 days of fasting due to decreased capacity for protein synthesis (Cs). In small intestine and colon, ks was not different after 1 day, but was approximately 26% lower on day 5, mainly because of a reduction in Cs. Thus protein wasting in the stomach is primarily mediated by decreased protein synthesis but not in small intestine and colon during short-term fasting. To determine which proteolytic systems may be activated in the gut, we measured mRNA levels for critical components of the lysosomal (cathepsins B and D), Ca(2+)-activated (m-calpain), and ubiquitin-dependent (ubiquitin, 14-kDa ubiquitin-conjugating enzyme E2, and C8, and C9 proteasome subunits) proteolytic pathways. mRNA levels for most of these components increased during fasting, suggesting that a coordinated activation of multiple proteolytic systems contributed to intestinal protein wasting.

Animals↗