Search PubMed⌕ Search

Biomedical subjects

M Picard

Publications and source records attributed to M Picard.

At least 37 records · Page 2Linked to original sources

Early age thermal conditioning immediately reduces body temperature of broiler chicks in a tropical environment.

Early age thermal conditioning (TC) durably improves resistance of broilers to heat stress and reduces body temperature (Tb). Three experiments on broiler chicks were conducted to evaluate the effects of TC at 5 d of age on Tb variation measured by thermometer between 4 and 7 d of age, under a tropical environment. Because manipulation of chickens to measure Tb with a thermometer may increase Tb, a preliminary experiment on 13 3-to-4-wk-old male broilers compared Tb measured by telemetry to Tb measured in the terminal colon during three successive periods at 22, 33, and 22 degrees C. During heat exposure, Tb rapidly increased by 0.9 degrees C and plateaued over 24 h. During the last period, seven of the broilers rapidly reduced Tb to a plateau lower than the initial Tb, although six broilers exhibited more variable Tb. Measurement by thermometer underestimated on average core Tb by 0.28 degrees C at 22 degrees C and by 0.57 degrees C at 33 degrees C, whereas Tb recorded by telemetry was not affected by manipulation of the chickens. TC reduced Tb 24 h later in the three experiments. Compared to unexposed control chicks (N), 12 h of TC at 40 degrees C did not significantly reduce Tb at 7 d of age, although 24 h did. TC at 38 and 40 degrees C over 24 h significantly reduced Tb variation from 4 to 7 d of age compared to N chicks, whereas 36 degrees C did not. Withdrawing feed from the chicks for 2 h prior to measurement did not significantly reduce Tb at 4 and 7 d of age, but Tb reduction due to TC was greater in fed chicks (0.28 degrees C) than in chicks without feed (0.05 degrees C). Early age thermal conditioning at 38 to 40 degrees C at 5 d of age for 24 h reduced body temperature of 7-d-old male broilers.

Adaptation, Physiological↗

On the importance of early reflections for speech in rooms.

This paper presents the results of new studies based on speech intelligibility tests in simulated sound fields and analyses of impulse response measurements in rooms used for speech communication. The speech intelligibility test results confirm the importance of early reflections for achieving good conditions for speech in rooms. The addition of early reflections increased the effective signal-to-noise ratio and related speech intelligibility scores for both impaired and nonimpaired listeners. The new results also show that for common conditions where the direct sound is reduced, it is only possible to understand speech because of the presence of early reflections. Analyses of measured impulse responses in rooms intended for speech show that early reflections can increase the effective signal-to-noise ratio by up to 9 dB. A room acoustics computer model is used to demonstrate that the relative importance of early reflections can be influenced by the room acoustics design.

Adult↗

Early-age thermal conditioning reduces uncoupling protein messenger RNA expression in pectoral muscle of broiler chicks at seven days of age.

Early-age thermal conditioning (TC) by exposing young chicks to 40 C for 24 h reduces body temperature (Tb) and has been showed by others to improve long-term resistance of broilers to heat stress. Uncoupling oxidative phosphorylation in pectoral muscle mitochondria might be related to heat production. Fertile eggs were hatched under video control, and 161 pedigree chicks froml2 sires and 22 dams were immediately allocated to two groups (T, a group composed of 81 chicks exposed to TC at 5 d of age, and N, a control group of 80 nonexposed chicks). Body weights and Tb were measured at 2 and 7 d of age. Five pairs (one N and one T) of full sib chicks from families that exhibited the largest difference of Tb variation from 2 to 7 d of age between the two treatments were chosen for pectoral muscle sampling. Avian uncoupling protein (avUCP) messenger RNA expression was measured by reverse transcript-PCR coupled to southern blot in the pectoral muscle of 7-d-old broiler chicks. At 7 d of age, there were no BW differences between treatments and Tb was significantly reduced by TC (-0.13 C on average). Heritability of Tb variation between 2 and 7 d was 0.38 +/- 0.20 (SE) for T chicks and 0.35 +/- 0.17 for N chicks without a significant genetic correlation between the two environments. Expression of avUCP mRNA was significantly (85%) lower in T chicks than in N chicks. Uncoupling protein mRNA expression in pectoral muscle and Tb are quickly adjusted in broiler chicks 24 h after early thermal conditioning.

Adaptation, Physiological↗

Sequential feeding can increase activity and improve gait score in meat-type chickens.

This study investigated the short- and long-term effects of sequential feeding by alternating low-and high-lysine diets during the day on growth, gait score (GS), and behavior in broilers. From Days 2 to 12, 6 pens of 10 birds were assigned to control treatment and fed a standard normal lysine diet (NL) (ME = 3,250 kcal/kg, CP = 23%, Lys = 1.19%) and six pens of 10 birds were assigned to the sequential treatment and fed a low-lysine diet (LL) (Lys = 0.85%) for half of the day and NL for the other half of the day. From Days 13 to 21, all groups were fed NL, and from Days 21 to 42, they were fed a grower diet. Sequential (S) chicks were lighter than Control chicks at Days 13 (304 +/- 6 vs. 378 +/- 7 g) and 42 (2,588 +/- 31 vs. 2,714 +/- 10 g) and had better leg condition at Day 42 (mean GS = 1.6 +/- 0.1 vs. 2.1 +/- 0.1, P < or = 0.05). During a day of S feeding, S birds ate less and wasted more LL than NL. Sequential birds spent less time standing and more time lying idle when fed LL than when fed NL. Sequential birds spent more time eating than Control birds, and they gradually increased the number of pecks in the litter during a sequential feeding day. The results suggest a major effect of food composition on behavior. Sequential feeding could be a means of decreasing leg problems in broilers.

Animals↗

Akt activation preserves cardiac function and prevents injury after transient cardiac ischemia in vivo.

BACKGROUND: The serine-threonine kinase Akt is activated by several ligand-receptor systems previously shown to be cardioprotective. Akt activation reduces cardiomyocyte apoptosis in models of transient ischemia. Its role in cardiac dysfunction or infarction, however, remains unclear. METHODS AND RESULTS: We examined the effects of a constitutively active Akt mutant (myr-Akt) in a rat model of cardiac ischemia-reperfusion injury. In vivo gene transfer of myr-Akt reduced infarct size by 64% and the number of apoptotic cells by 84% (P<0.005 for each). Ischemia-reperfusion injury decreased regional cardiac wall thickening as well as the maximal rate of left ventricular pressure rise and fall (+dP/dt and -dP/dt). Akt activation restored regional wall thickening and +dP/dt and -dP/dt to levels seen in sham-operated rats. To better understand this benefit, we examined the effects of myr-Akt on hypoxic cardiomyocyte dysfunction in vitro. myr-Akt prevented hypoxia-induced abnormalities in cardiomyocyte calcium transients and shortening. Akt activation also enhanced sarcolemmal expression of Glut-4 in vivo and increased glucose uptake in vitro to the level seen with insulin treatment. CONCLUSIONS: Akt activation exerts a powerful cardioprotective effect after transient ischemia that probably reflects its ability to both inhibit cardiomyocyte death and improve function of surviving cardiomyocytes. Akt may represent an important nodal target for therapy in ischemic and other heart disease.

Adenoviridae↗

Do broiler chicks have a cognitive representation of food quality?. Appetitive, behavioural and ingestive responses to a change in diet quality.

It has been observed that when a new diet formulation, or a new batch of the same diet formulation, is presented to poultry, there is a transitory suppression of feeding. It appears that the birds do not recognise the food as being edible, or classify it as being 'unknown'. In order to understand more about food recognition and rejection, the aim of this experiment was to determine whether cognitive processes are involved. Sixteen groups of four broiler chicks were used, and were fed a low quality diet in their home pens. The groups of chicks were trained to run a winding maze to gain access to a high quality diet in a test trough for 15min per day. When training was completed, the feed in the test trough for eight of the groups was changed to that which they received in the home pen, while the other eight groups received no change as a control. Time to traverse the runway did not show an immediate decrease on the day after the change (P>0.05) as would be expected if the birds used a cognitive comparison to determine speed of approach to the test trough. However, the experimental groups were significantly slower compared to the control groups after 4 days (P<0.05). The behaviour observed on the day of the change was indicative of frustration with more scratching and hurried movements shown (P<0.05), and less pecking at feed (P<0.01). Food consumption was lower for experimental groups compared to control groups on all days from the day of change onward (P<0.001). It was concluded that although there was no definitive evidence for the presence of a cognitive representation of food, this may have been due in part to the testing of groups of birds rather than individuals, and the way in which food quality is perceived. The occurrence of behaviours indicative of frustration suggest that a cognitive expectation may have been present.

Journal Article↗

Chicken leptin: properties and actions.

Chicken leptin cDNA shows a high homology to mammalian homologous, with an expression localized in the liver and adipose tissue. It is noteworthy, that the hepatic expression is most likely associated with the primary role that this organ plays in lipogenic activity in avian species. As in mammals, chicken leptin expression is regulated by hormonal and nutritional status. This regulation is tissue-specific and with a high sensitivity in the liver compared to adipose tissue. The blood leptin levels are regulated by the nutritional state with high levels in the fed state compared to the fasted state. The recombinant chicken leptin markedly inhibits food intake as reported in mammals, suggesting the presence of an hypothalamic leptin receptor. The chicken leptin receptor has been identified and all functional motifs are highly conserved compared to mammalian homologous. Chicken leptin receptor is expressed in the hypothalamus but also in other tissues such as pancreas, where leptin inhibits insulin secretion and thus may have a key role in regulating nutrient utilization in this species.

Adipose Tissue↗

Genome quality control: RIP (repeat-induced point mutation) comes to Podospora.

RIP (repeat-induced point mutation) is a silencing process discovered in Neurospora crassa and so far clearly established only in this species as a currently occurring process. RIP acts premeiotically on duplicated sequences, resulting in C-G to T-A mutations, with a striking preference for CpA/TpG dinucleotides. In Podospora anserina, an RIP-like event was observed after several rounds of sexual reproduction in a strain with a 40 kb tandem duplication resulting from homologous integration of a cosmid in the mating-type region. The 9 kb sequenced show 106 C-G to T-A transitions, with 80% of the replaced cytosines located in CpA dinucleotides. This led to the alteration of at least six genes, two of which were unidentified. This RIP-like event extended to single-copy genes between the two members of the repeat. The overall data show that the silencing process is strikingly similar to a light form of RIP, unaccompanied by C-methylation. Interestingly, the N. crassa zeta-eta sequence, which acts as a potent de novo C-methylation RIP signal in this species, is weakly methylated when introduced into P. anserina. These results demonstrate that RIP, at least in light forms, can occur beyond N. crassa.

Ascomycota↗

Concept, development, administration, and analysis of a certifying examination in echocardiography for physicians.

In 1993, the American Society of Echocardiography appointed a committee to develop an objective examination in echocardiography. In 1995, a pilot of this examination was administered, with operational examinations offered each year from 1996 to 1999. This report describes the development of the examination, including its underlying philosophy, the test itself, and the scoring process, and includes results from the first 4 examinations. To date, 1266 physicians have taken the examination, and roughly 60% of those have passed. The number of echocardiograms performed or interpreted each week had the largest effect on examination scores; the effects of both the amount of training and the practice discipline were small but significant. The evolution of the original committee and new directions for the testing organization are also discussed.

Certification↗

eEF1A Controls ascospore differentiation through elevated accuracy, but controls longevity and fruiting body formation through another mechanism in Podospora anserina.

Antisuppressor mutations in the eEF1A gene of Podospora anserina were previously shown to impair ascospore formation, to drastically increase life span, and to permit the development of the Crippled Growth degenerative process. Here, we show that eEF1A controls ascospore formation through accuracy level maintenance. Examination of antisuppressor mutant perithecia reveals two main cytological defects, mislocalization of spindle and nuclei and nuclear death. Antisuppression levels are shown to be highly dependent upon both the mutation site and the suppressor used, precluding any correlation between antisuppression efficiency and severity of the sporulation impairment. Nevertheless, severity of ascospore differentiation defect is correlated with resistance to paromomycin. We also show that eEF1A controls fruiting body formation and longevity through a mechanism(s) different from accuracy control. In vivo, GFP tagging of the protein in a way that partly retains its function confirmed earlier cytological observation; i.e., this factor is mainly diffuse within the cytosol, but may transiently accumulate within nuclei or in defined regions of the cytoplasm. These data emphasize the fact that the translation apparatus exerts a global regulatory control over cell physiology and that eEF1A is one of the key factors involved in this monitoring.

Alleles↗

Early age thermal conditioning and a dual feeding program for male broilers challenged by heat stress.

The effects of early age thermal conditioning (TC) and dual feeding on responses of male broilers to a thermal challenge at 34 d of age are reported. Three hundred chicks were randomly divided into two equal groups. One group was exposed to thermal conditioning (38 C, 42% relative humidity for 24 h) at the age of 5 d, and the other group was not exposed. From 11 to 41 d of age, temperature was diurnally cyclic: 26 C (1600 to 0900 h) and 30 C (0900 to 1600 h). From Day 19, a factorial (2 x 2, TC x diet) experiment was conducted using eight pens of six broilers per treatment. Diets were control diet and dual feeding of a high protein fraction (1600 to 0900 h) and an energy-rich fraction (0900 to 1600 h). Growth and feed efficiency were slightly enhanced (+4%) by thermal conditioning and slightly reduced (-4%) by dual feeding. Mortality during thermal challenge was reduced by both factors. [In not conditioned chicks (N), 31 fed a control grower diet (NG) and 12 on a dual feeding program (NDF) died; in thermal conditioned chicks (T), 18 fed a control grower diet (TG) and 11 on a dual feeding program (TDF) died.] Before the thermal challenge period, body temperature (Tb) was consistently reduced in T. During the thermal challenge period, Tb was reduced by thermal conditioning and dual feeding. Measured at the age of 32 d, Tb gave an estimation of the ability of the chickens to cope with heat stress 2 d later. Pectoral mass was increased in TG, whereas the liver and the gizzard were significantly heavier in TDF and NDF. These results suggest that thermal conditioning at 5 d of age induces a consistent metabolic change in broiler males. The dual feeding program might have induced transitory effects on heat production during the heat stress.

Adaptation, Physiological↗

Performance of pureline broiler breeders fed two levels of vitamin E.

Reported in this paper is an experiment designed to evaluate responses of two commercial broiler dam purelines (A and B) continuously fed 10 or 300 IU of vitamin E/kg from 168 to 441 d of age. Prior to Day 168, all pullets were fed diets containing 10 IU of vitamin E/kg. During the early laying period, percentage hen-day ovulations and percentage hen-day normal egg production were similar for both lines and diets. During the latter part of the laying cycle, there were differences between lines for these traits (A > B), as well as for BW and egg weight for which line differences were reversed (A < B). Also during this period, percentage hen-day ovulations and percentage hen-day normal egg production differed between diets (300 > 10 IU/kg). These differences between diets were consistent with the greater number of females that entered lay and higher hen-housed egg production of the 300- than 10-IU/kg group. Although during the laying cycle all females received a fixed amount of feed, BW gains were greater for Line B than A and for the 300- than the 10-IU/kg level of vitamin E. Heterophil (H):lymphocyte (L) ratios, percentage livability, and relative asymmetries of shank length and diameter were similar among groups. Pullets from Line B and those fed the higher level of vitamin E exhibited more fear than their counterparts. Head shaking did not differ between vitamin E levels; however, there was a line-by-time of day interaction for this behavior. The 30-fold difference in dietary vitamin E was reflected by a 15-fold difference in plasma vitamin E levels in both lines. For vitamin E level in the yolk, however, there was a line-by-diet interaction. The interaction resulted from no difference between lines at the 10 IU/kg level and differences of 10- and 6+-fold in Lines B and A at the 300 IU/ kg level, respectively. Overall, responses to continuous feeding of vitamin E at these levels were influenced by genetic stock, age, duration of feeding, and measurement criteria.

Age Factors↗

Time structure of behavioral patterns related to feed pecking in chicks.

Nonrandom time patterns of pecking acts by 16 chicks were detected using the software Theme during three videotaped pecking sessions (M, C, and A). At 15 days of age pecking session, M (mash) was recorded when chicks ate a mash diet. Pecking session C (change) at 16 or 17 days of age was recorded immediately after the change of the diet to pellets presented either as regular cylinders (P) to eight chicks, or as semiovoid (Po) to eight other chicks. Pecking session A (adapted) was recorded 5 or 6 days after adaptation to P and Po. Successful (consumatory) pecks were 72%, 52%, and 61% of all pecks for sessions M, C, and A, respectively. The head of the chicks remained in a steady position between two consecutive pecks for a longer period during C (65% of the time) than M and A (54%). During C, the pecking rate was less for P (0.54 pecks/s) than for Po (0.79 pecks/s). Two consistent time patterns involving four acts frequently observed were: head rotation (or exploratory peck)-->head in steady position-->consumatory peck-->head in steady position with jaw movements. Time intervals within a pattern were stable throughout sessions. However, the proportion of synchronized (included in a pattern) vs. nonsynchronized (not included in a pattern) acts decreased immediately after the change of feed form (session C). These results suggest that pecking at feed is composed of two distinct sets of acts: consistently organized patterns little affected by the form of the pecked particles and nonsynchronized acts that may be involved in sensory information.

Aging↗

Early locomotor behaviour in genetic stocks of chickens with different growth rates.

Reduction in exercise increases the occurrence of lameness in meat-type chickens. Locomotor activity is dramatically reduced during the finishing period in chickens from fast-growing genetic types compared to slow-growing genetic types, but it is not known whether this difference is already present during the starting period and may be influenced by genetic factors. In order to define the effect of genetic origin on early locomotor behaviour, exercise was compared from 1 to 22 days of age in two meat-type chicken stocks differing in growth rate: male broilers (B) which grow fast and are often lame, and male "label rouge" chickens (L) which grow slowly and are rarely lame.Time budget (lying, standing, drinking, eating, walking) was measured by scanning in six repetitions of five birds (density=2.5 birds/m(2)) at 1, 8, 15 and 17 days of age. Standing bouts were analysed by focal sampling at 2-3, 6-7, 13-14 and 20-21 days of age.B chicks spent less time standing than L chicks at 15 days of age (B=13+/-2%, L=24+/-1%, P<0.01) and 17 days of age, and spent more time lying at 17 days of age (B=73+/-3%, L=60+/-4%, P<0.05).The major part (74%) of the total active time observed by focal sampling was linked to feeding activity. At 2 and 3 days, the activity of B chicks was half that of L chicks during standing bouts (duration of walking per bout: 19+/-4 s for B; 45+/-4 s for L, P<0.05). The activity observed by focal sampling during non-feeding bouts at 20-21 days was significantly correlated with the corresponding data recorded at 2-3 days in the same chicks in the B stock but not in the L stock.We concluded that (1) both B and L genetic stocks have the same overall activity during the first 3 days of age (scanning) but they exhibit different organisation and composition of standing bouts (focal sampling). (2) Genetic factors are probably involved in the expression of locomotor behaviour in very young chicks. (3) The correlations between the levels of activity at early and later ages suggest that selection of young mobile broiler chicks might increase activity at a later age and might therefore reduce the occurrence of leg abnormalities.

Journal Article↗

ami1, an orthologue of the Aspergillus nidulans apsA gene, is involved in nuclear migration events throughout the life cycle of Podospora anserina.

The Podospora anserina ami1-1 mutant was identified as a male-sterile strain. Microconidia (which act as male gametes) form, but are anucleate. Paraphysae from the perithecium beaks are also anucleate when ami1-1 is used as the female partner in a cross. Furthermore, in crosses heterozygous for ami1-1, some crozier cells are uninucleate rather than binucleate. In addition to these nuclear migration defects, which occur at the transition between syncytial and cellular states, ami1-1 causes abnormal distribution of the nuclei in both mycelial filaments and asci. Finally, an ami1-1 strain bearing information for both mating types is unable to self-fertilize. The ami1 gene is an orthologue of the Aspergillus nidulans apsA gene, which controls nuclear positioning in filaments and during conidiogenesis (at the syncytial/cellular transition). The ApsA and AMI1 proteins display 42% identity and share structural features. The apsA gene complements some ami1-1 defects: it increases the percentage of nucleate microconidia and restores self-fertility in an ami1-1 mat+ (mat-) strain. The latter effect is puzzling, since in apsA null mutants sexual reproduction is quite normal. The functional differences between the two genes are discussed with respect to their possible history in these two fungi, which are very distant in terms of evolution.

Amino Acid Sequence↗

Vitamin E and immune responses of broiler pureline chickens.

Immunological responses of cockerels fed diets containing either 10 or 300 mg/kg of vitamin E were measured in three commercial broiler nuclear lines designated as A, B, and C. All cockerels were fed the 10 mg/kg diet to 91 d of age, at which time half were continued on that diet and the other half were fed a diet supplemented to contain 300 mg/kg of vitamin E. Sixteen days after feeding the diets, cutaneous basophil hypersensitivity (CBH), which is an in vivo, cell-mediated immune response, was determined as the increase in toe-web skin thickness 24 h after an injection with phytohemagglutinin-P (PHA-P). Twenty-two days after feeding the diets, heterophils and lymphocytes were enumerated. At this time cockerels were also inoculated intravenously with 0.1 mL of 0.25% SRBC. The injection with SRBC was repeated 27 d later. Six and 20 d after each injection, antibody titers were determined. Mercaptoethanol-resistant (IgG) and mercaptoethanol-sensitive (IgM) antibodies were also measured in the secondary titers. The ratio of heterophils to lymphocytes increased, and CBH response was depressed by feeding the higher vitamin E diet. For cockerels of Lines A and B, the higher level of vitamin E maintained primary and secondary SRBC antibody levels, whereas for Line C, levels were depressed. The effect of the higher vitamin E diet on IgG and IgM was also stock-dependent. The enhanced heterophil:lymphocyte ratio from feeding vitamin E suggests an improved phagocytic ability of the immune system. Relative asymmetries for toe-web skin thickness and shank length were similar for the three lines.

Animals↗

Subacute NO generation induced by Alzheimer's beta-amyloid in the living brain: reversal by inhibition of the inducible NO synthase.

Glial activation contiguous to deposits of amyloid peptide (Abeta) is a characteristic feature in Alzheimer's disease. We performed complementary in vitro and in vivo experiments to study the extent, kinetics, and mechanisms of microglial generation of nitric oxide (NO) induced by challenge with Abeta. We showed that Abeta fibrils dose-dependently induced a marked release of stable metabolites of NO in vivo that was strikingly similar regarding extent and temporal profile to the one in the parallel designed microglial cell culture experiments. However, costimulation with interferon gamma, which was a prerequisite for Abeta-induced NO generation in vitro, was not required in vivo, demonstrating that factors are present in the living brain that activate glial cells synergistically with Abeta. Therefore, in Alzheimer's disease, deposits of Abeta fibrils alone may be sufficient to induce a chronic release of neurotoxic microglial products, explaining the progressive neurodegeneration associated with this disease. Our observation that systemic administration of selective iNOS inhibitors abolishes Abeta-induced NO generation in vivo may have implications for therapy of Alzheimer's disease.

Amyloid beta-Peptides↗

Maintenance and integrity of the mitochondrial genome: a plethora of nuclear genes in the budding yeast.

Instability of the mitochondrial genome (mtDNA) is a general problem from yeasts to humans. However, its genetic control is not well documented except in the yeast Saccharomyces cerevisiae. From the discovery, 50 years ago, of the petite mutants by Ephrussi and his coworkers, it has been shown that more than 100 nuclear genes directly or indirectly influence the fate of the rho(+) mtDNA. It is not surprising that mutations in genes involved in mtDNA metabolism (replication, repair, and recombination) can cause a complete loss of mtDNA (rho(0) petites) and/or lead to truncated forms (rho(-)) of this genome. However, most loss-of-function mutations which increase yeast mtDNA instability act indirectly: they lie in genes controlling functions as diverse as mitochondrial translation, ATP synthase, iron homeostasis, fatty acid metabolism, mitochondrial morphology, and so on. In a few cases it has been shown that gene overexpression increases the levels of petite mutants. Mutations in other genes are lethal in the absence of a functional mtDNA and thus convert this petite-positive yeast into a petite-negative form: petite cells cannot be recovered in these genetic contexts. Most of the data are explained if one assumes that the maintenance of the rho(+) genome depends on a centromere-like structure dispensable for the maintenance of rho(-) mtDNA and/or the function of mitochondrially encoded ATP synthase subunits, especially ATP6. In fact, the real challenge for the next 50 years will be to assemble the pieces of this puzzle by using yeast and to use complementary models, especially in strict aerobes.

Adenosine Triphosphatases↗