Thermal energetics of the New-Guinean moss-forest rat (Rattus niobe) in comparison with other tropical murid rodents.

The thermal energetics of rodents from cool, wet tropical highlands are poorly known. Metabolic rate, body temperature and thermal conductance were measured in the moss-forest rat, Rattus niobe (Rodentia), a small murid endemic to the highlands of New Guinea. These data were evaluated in the context of the variation observed in the genus Rattus and among tropical murids. In 7 adult R. niobe, basal metabolic rate (BMR) averaged 53.6±6.6mLO2h(-1), or 103% of the value predicted for a body mass of 42.3±5.8g. Compared to other species of Rattus, R. niobe combines a low body temperature (35.5±0.6°C) and a moderately low minimal wet thermal conductance cmin (5.88±0.7mLO2h(-1)°C(-1), 95% of predicted) with a small size, all of which lead to reduced energy expenditure in a constantly cool environment. The correlations of mean annual rainfall and temperature, altitude and body mass with BMR, body temperature and cmin were analyzed comparatively among tropical Muridae. Neither BMR, nor cmin or body temperature correlated with ambient temperature or altitude. Some of the factors which promote high BMR in higher latitude habitats, such as seasonal exposure to very low temperature and short reproductive season, are lacking in wet montane tropical forests. BMR increased with rainfall, confirming a pattern observed among other assemblages of mammals. This correlation was due to the low BMR of several desert adapted murids, while R. niobe and other species from wet habitats had a moderate BMR.

Spontaneous pre-stimulus fluctuations in the activity of right fronto-parietal areas influence inhibitory control performance.

Inhibitory control refers to the ability to suppress planned or ongoing cognitive or motor processes. Electrophysiological indices of inhibitory control failure have been found to manifest even before the presentation of the stimuli triggering the inhibition, suggesting that pre-stimulus brain-states modulate inhibition performance. However, previous electrophysiological investigations on the state-dependency of inhibitory control were based on averaged event-related potentials (ERPs), a method eliminating the variability in the ongoing brain activity not time-locked to the event of interest. These studies thus left unresolved whether spontaneous variations in the brain-state immediately preceding unpredictable inhibition-triggering stimuli also influence inhibitory control performance. To address this question, we applied single-trial EEG topographic analyses on the time interval immediately preceding NoGo stimuli in conditions where the responses to NoGo trials were correctly inhibited [correct rejection (CR)] vs. committed [false alarms (FAs)] during an auditory spatial Go/NoGo task. We found a specific configuration of the EEG voltage field manifesting more frequently before correctly inhibited responses to NoGo stimuli than before FAs. There was no evidence for an EEG topography occurring more frequently before FAs than before CR. The visualization of distributed electrical source estimations of the EEG topography preceding successful response inhibition suggested that it resulted from the activity of a right fronto-parietal brain network. Our results suggest that the fluctuations in the ongoing brain activity immediately preceding stimulus presentation contribute to the behavioral outcomes during an inhibitory control task. Our results further suggest that the state-dependency of sensory-cognitive processing might not only concern perceptual processes, but also high-order, top-down inhibitory control mechanisms.

Incidência natural e biologia de Trichogramma atopovirilia Oatman & Platner, 1983 (Hymenoptera, Trichogrammatidae) em ovos de Anticarsia gemmatalis Hübner, 1818 (Lepidoptera, Noctuidae)

Trichogramma atopovirilia Oatman & Platner is an egg parasitoid of the corn earworm Helicoverpa zea (Boddie) (Lepidoptera, Noctuidae), and has recently been collected from eggs of Anticarsia gemmatalis Hübner on soybeans. In order to evaluate the suitability of A. gemmatalis eggs as hosts of T. atopovirilia, field surveys were conducted in 1999 and 2000 on corn and soybeans, and a colony of the parasitoid was established in laboratory. At 25 ºC, development from oviposition to emergence lasted nine days and a sex-ratio of 0.58 (females:males) was obtained. Females lived significantly longer (11.4 days) when kept in ovipositional activity, than in the absence of host eggs (6.6 days). Total fecundity averaged 104.5 parasitized eggs, resulting in the emergence of 138.3 descendents. Mean daily fecundity was highest (30 eggs/female) on the first day. Oviposition continued until one day before the death of the females, however 70% of the eggs were laid during the first four days after emergence. A female-biased progeny was produced during the first three days of oviposition, whereas further ovipositions were male-biased. Females lived significantly longer when exposed to host eggs in comparison to females deprived of eggs. The results show that eggs of A. gemmatalis are suitable for the development of T. atopovirilia, and this parasitoid should be considered in future programs of biological control of the velvetbean caterpillar.

Loss of interactions with ants under cold climate in a regional myrmecophilous butterfly fauna

Aim Specialized mutualistic clades may revert and thus increase their autonomy and generalist characteristics. However, our understanding of the drivers that trigger reductions in mutualistic traits and of the consequences for the tolerance of these species to various environmental conditions remains limited. This study investigates the relationship between the environmental niche and the degree of myrmecophily (i.e. the ability to interact with ants) among members of the Lycaenidae. Location The western Swiss Alps. Methods We measured the tolerance of Lycaenidae species to low temperatures by comparing observations from a random stratified field sampling with climatic maps. We then compared the species-specific degree of myrmecophily with the species range limits at colder temperatures while controlling for phylogenetic dependence. We further evaluated whether the community-averaged degree of myrmecophily increases with temperature, as would be expected in the case of environmental filters acting on myrmecophilous species. Results Twenty-nine Lycaenidae species were found during sampling. Ancestral state reconstruction indicated that the 24 species of Polyommatinae displayed both strong myrmecophily and secondary loss of mutualism; these species were used in the subsequent statistical analyses. Species with a higher degree of ant interaction were, on average, more likely to inhabit warmer sites. Species inhabiting the coldest environments displayed little or no interaction with ants. Main conclusions Colder climates at high elevations filter out species with a high degree of myrmecophily and may have been the direct evolutionary force that promoted the loss of mutualism. A larger taxon sampling across the Holarctic may help to distinguish between the ecological and evolutionary effects of climate.

Thermogenic response to an oral glucose load in man: comparison between young and elderly subjects.

To investigate the effect of age and change in body composition on the increase in energy expenditure consecutive to the ingestion of a 75-g glucose load, respiratory exchange measurements were performed on 24 subjects, 12 elderly (mean +/- SEM, 73 +/- 1 yr) and 12 young (25 +/- 1 yr). The body weight was comparable, 62 +/- 2 kg in the elderly group vs 61 +/- 3 in the young, but the body fat content of the elderly group was significantly greater than that of the young (29 +/- 2% vs 19 +/- 2%, p less than 0.001). The elderly group presented a slight glucose intolerance according to the World Health Organization (WHO) criteria, with a 120-min plasma glucose of 149 +/- 9 mg/dl (p less than 0.005 vs young). The postabsorptive resting energy expenditure (REE) was 0.83 +/- 0.03 kcal/min in the elderly group vs 0.98 +/- 0.04 in the young (p less than 0.02); this decrease of 15% was mainly related to the decrease in fat free mass (FFM) in the elderly group, which averaged 14%. The difference was not significant when REE was expressed per kg FFM. The glucose-induced thermogenesis (GIT) expressed as percent of energy content of the load was 6.2 +/- 0.6% in the elderly group and 8.9 +/- 0.9% in the young (p less than 0.05). It is concluded that the glucose-induced thermogenesis is decreased in elderly subjects. However, when expressed per kg FFM, the increment in energy expenditure (EE), in response to the glucose load, is not different in elderly subjects, suggesting that the decrease of thermogenesis may be attributed to the age-related decrease in FFM.

Hypotensive effect of the active fragment derived from factor XII is mediated by an activation of the plasma kallikrein-kinin system.

Plasma protein fraction (PPF) contaminated by factor XII active fragment (XIIf) may cause hypotensive reactions when infused to patients. This study was planned to assess in conscious normotensive rats whether the blood pressure response to the factor XIIf is mediated by an activation of the plasma kallikrein-kinin system or by stimulation of prostaglandin synthesis. To test whether the factor XIIf-induced blood pressure fall is due partially to an enhanced generation of vasodilating prostaglandins, the blood pressure effect of XIIf (1 microgram i.v.) was investigated 15 min after treatment with indomethacin (5 mg i.v.), an inhibitor of cyclo-oxygenase. Factor XIIf reduced mean blood pressure similarly in indomethacin- and vehicle-treated rats (-23 +/- 4 mmHg, n = 5, and -23 +/- 5 mmHg, n = 4, respectively). Other rats received factor XIIf 15 min after depletion of circulating prekallikrein by the administration of dextran sulfate. Thirty minutes after a 0.25 mg i.v. dose of this agent, plasma prekallikrein activity averaged 0.12 +/- 0.015 mumol/min/ml (n = 6) as compared to 2.48 +/- 0.31 mumol/min/ml in control rats (n = 4, P less than .001). Factor XIIf decreased mean blood pressure by only 4 +/- 2 mm Hg in rats pretreated with dextran sulfate. Thus, it was possible to blunt the acute hypotensive effect of factor XIIf by depleting circulating prekallikrein, but not by inhibiting prostaglandin production. This strongly suggests that the blood pressure effects of factor XIIf is mediated by a stimulation of the plasma kallikrein-kinin system.

Correlative light and electron microscopy in parasite research.

The interaction of a parasite and a host cell is a complex process, which involves several steps: (1) attachment to the plasma membrane, (2) entry inside the host cell, and (3) hijacking of the metabolism of the host. In biochemical experiments, only an event averaged over the whole cell population can be analyzed. The power of microscopy, however, is to investigate individual events in individual cells. Therefore, parasitologists frequently perform experiments with fluorescence microscopy using different dyes to label structures of the parasite or the host cell. Though the resolution of light microscopy has greatly improved, it is not sufficient to reveal interactions at the ultrastructural level. Furthermore, only specifically labeled structures can be seen and related to each other. Here, we want to demonstrate the additional value of electron microscopy in this area of research. Investigation of the different steps of parasite-host cell interaction by electron microscopy, however, is often hampered by the fact that there are only a few cells infected, and therefore it is difficult to find enough cells to study. A solution is to profit from low magnification, hence large overview, and specific location of the players by fluorescence labels in a light microscope with the high power resolution and structural information provided by an electron microscope, in short by correlative light and electron microscopy.

Fat oxidation and adiposity in prepubertal children: exogenous versus endogenous fat utilization.

Fat balance plays an important role in fat mass regulation. The mechanisms by which fat intake and fat oxidation are controlled are poorly understood. In particular, no data are available on the origin, i.e. exogenous (meal intake) or endogenous (adipose tissue lipolysis), of fat oxidized during the postprandial period in children and the proportion between these two components. In this study we tested the hypothesis that there is a relationship between adiposity and the oxidative fate of fat taken with a mixed meal in a group of 15 children with a wide range of fat mass (9-64%). The combination of stable isotope analysis ([13C] enriched fatty acids added to a mixed meal) and indirect calorimetry allowed us to differentiate between the exogenous and endogenous resting fat oxidation rate over the 9-h postprandial period. During the 9 hours of the postprandial period, the children oxidized an amount of fat comparable to that ingested with the meal [26.8 (+/-2.31) g vs. 26.4 (+/-2.3) g, respectively, P = ns]. On average, exogenous fat oxidation [2.99 (+/-3.0) g/9 h] represented 10.8% (+/-0.9) of total fat oxidation. Endogenous fat oxidation, calculated as the difference between total fat oxidation and exogenous fat oxidation, averaged 23.4 (+/-1.9) g/9 h and represented 88.2% (+/-0.9) of total fat oxidation. Endogenous fat oxidation as well as exogenous fat oxidation were highly correlated to total fat oxidation (r = 0.83, P < 0.001; r = 0.84, P < 0.001, respectively). Exogenous fat oxidation expressed as a proportion of total fat oxidation was directly related to fat mass (r = 0.56, P < 0.03), while endogenous fat oxidation expressed as a proportion of total fat oxidation was inversely related (r = -0.57, P < 0.03) to the degree of adiposity. The enhanced exogenous fat oxidation observed when adiposity increases in the dynamic phase of obesity may be viewed as a protective mechanism to prevent further increase in fat mass and hence to maintain fat oxidation at a sufficient rate when the body is exposed to a high amount of dietary fat, as typically encountered in obese children.

Intérêt du bleu de méthylène dans la chirurgie de l'hyperparathyroïdism primaire [Methylene blue in surgery of primary hyperparathyroidism]

Is surgery for primary hyperparathyroidism easier when methylene blue (MB) is given preoperatively? This retrospective study compares the durations of interventions for primary hyperparathyroidism carried out after i.v. MB administration to those when no MB was given. Over a period of 20 years (June 1976 to December 1996), 175 consecutive patients (56 men and 119 women, with ages ranging from 16 to 92, mean 59.6) were operated upon for primary hyperparathyrodism; 55 were operated before February 1986--the period when BM was introduced routinely, and 120 after. Thirty-two other patients were excluded from the study: 14 had had a previous cervicotomy and 18 another procedure in addition to the parathyroidectomy (usually on the thyroid gland), two conditions which prolonged the time devoted to parathyroid identification and excision. Preoperative calcemia averaged 2.97 mmol/L (2.34 to 4.59) and mean preoperative PTH was equal to 2.6 times the upper normal limit (0.5 to 24.1). Both groups were similar for as age, sex, preoperative calcium and PTH, and histologies. Methylene blue was administered intravenously (5 mg/kg diluted in 500 cc of 5% glucose) over a period of time of one hour starting two hours prior to surgery. All 175 procedures were performed by two surgeons and duration of surgery was recorded from the anesthesiologist's notes. There were 149 adenomas (85%), 24 hyperplasias (14%), a combination of both in two, and unspecified in two others. Except for a case of acute lower back pain synchronous to the injection of the dye (which was immediately stopped), MB was well tolerated. Mean duration for the 55 interventions performed without MB was 68 minutes (35 to 140, median 60), compared to 49 minutes for the 120 procedures carried out after MB had been given (20 to 155, median 45). Differences in operative, times were highly significant (p < 10(-6) and represented a gain of time of 27%. Surgery for primary hyperparathyroidism was significantly shorter when it was preceded by the administration of MB, a dye which facilitates the identification of pathologic parathyroid gland(s).

Fick's law adapted to cationic diffusion in a semi-infinite solid: application to spinel megacrystals

In alkaline lavas, the chemical zoning of megacrystals of spinel is due to the cationic exchange between the latter and the host lava. The application of Fick's law to cationic diffusion profiles allows to calculate the time these crystals have stayed in the lava. Those which are in a chemical equilibrium were in contact with the lava during 20 to 30 days, whereas megacrystals lacking this equilibrium were in contact only for 3 or 4 days. The duration of the rise of an ultrabasic nodule in the volcanic chimney was calculated by applying Stokes' law.

The genus Aloe L. (Xanthorrhoeaceae) in Djibouti

The Horn of Africa is rich in succulent plants, yet the flora in some parts of the region remains under-explored, owing largely to political instability and inaccessibility. The Republic of Djibouti is a relatively small, politically stable country where botanical studies continue to identify new species records and new taxa. Here, we focus on the genus Aloe L. (Xanthorrhoeaceae subfamily Asphodeloideae) in Djibouti. Recent field surveys resulted in five new species records for the country (A. rigens Reynolds & Bally, A. macrocarpa Tod., A. eumassawana Carter, Gilbert & Sebsebe, A. ericahenriettae McCoy and A. djiboutiensis McCoy), in addition to the three taxa included in treatment for the Flora of Djibouti (Aloe trichosantha A.Berger, A. aff. trichosantha and A. mcloughlinii Christian). We present notes on the determination distribution and habitats of the nine Aloe species recorded in Djibouti.

Energetic and metabolic cost of growth in Gambian infants.

The aim of the study was to measure the energy used for growth of healthy fullterm and breast-fed Gambian infants. The weight gain (WG) of 14 infants (mean age +/- SEM 17 +/- 1 d, weight 3.581 +/- 0.105 kg) was measured over a 2-week period; the energy intake (EI) from breast milk was assessed for 24 h in the middle of the study period by weighing the infant before and after each breast-feed. On the same day, sleeping energy expenditure (SEE) and respiratory quotient (RQ) were measured for 30 min on five occasions through the 24-h period. EI averaged 502 +/- 25 kJ/kg.d, and SEE 230 +/- 6 kJ/kg.d; thus, an average of 272 kJ/kg.d were available for physical activity and the energy stored for growth. The total energy spent by infants while sleeping and for periods of physical activity was calculated to be 1.7 x SEE. The mean RQ measured on five occasions averaged 0.879 +/- 0.009. SEE was correlated with WG (r = 0.747, P less than 0.005), with a slope of the regression line of 5.5 kJ/g; this value can be considered as an estimate of the energy spent for new tissue synthesis in the resting infant. The efficiency of weight gain was lower in this study (67%) than in studies conducted on fast-growing preterm infants or children recovering from malnutrition.

Evaluation par des médecins installés de l'efficacité antihypertensive de la débrisoquine, de la méthyldopa et du propranolol [Evaluation by practicing physicians of the antihypertensive efficacy of debrisoquin, methyldopa and propranolol]

The antihypertensive effect of debrisoquine (20 mg/day), methyldopa (100 mg/day) and propranolol (160 mg/day) was compared to that obtained with a placebo in a controlled trial carried out by a group of 14 internists. Forty-eight patients with uncomplicated essential hypertension were included. Mefruside (25 mg/day) was first given alone for 6 weeks ("open phase" of the trial) and to this diuretic was then added in double-blind fashion and randomized sequence a placebo or an active drug. Each of the 4 blind phases lasted 4 weeks. At the end of the "open phase", blood pressure in seated position averaged 168/111 +/- 19.6/13.5 mm Hg (mean +/- SD). A significant blood pressure decrease was observed after 4 weeks of treatment with the placebo as well as with the investigated compounds. With the placebo blood pressure was reduced to 158/102 +/- 19.6/13.5 mm Hg (p less than 0.001). The magnitude of the additional blood pressure decrease induced by the active drugs was relatively small and varied from 4 (debrisoquine) to 10 mm Hg (methyldopa, p less than 0.01) for the systolic and from 3 (debrisoquine, p less than 0.05) to 5 mm Hg (propranolol, p less than 0.05) for the diastolic. The percentage of patients with systolic pressure of less than or equal to 140 mm Hg and with diastolic pressure of less than 90 mm Hg during administration of either drug was not greater than 40 to 20% respectively. Propranolol appeared to be better tolerated than the other antihypertensive agents. These rather disappointing blood pressure results suggest that the efficacy of antihypertensive agents in private practice cannot be extrapolated from studies carried out in specialized hypertension clinics.