Targeted inactivation of hypocretin receptors in dopaminergic and noradrenergic systems alters brain activity in wakefulness

Since the discovery of hypocretins/orexins (Hcrt/Ox) in 1998, several narcoleptic mouse models, such as Hcrt-KO, Hcrtrl-KO, Hcrtr2-KO and double receptors KO mice, and orexin-ataxin transgenic mice were generated. The available Hcrt mouse models do not allow the dissection of the specific role of Hcrt in each target region. Dr. Anne Vassalli generated loxP-flanked alleles for each Hcrt receptor, which are manipulated by Cre recombinase to generate mouse lines with disrupted Hcrtrl or Hcrtr2 (or both) in cell type-specific manner. The role of noradrenaline (NA) and dopamine (OA) in ttie regulation of vigilance states is well documented. The purpose of this thesis is to explore the role of the Hcrt input into these two monoaminergic systems. Chronic loss of Hcrtrl in NA neurons consolidated paradoxical sleep (PS), and altered wakefulness brain activity in baseline, during the sleep deprivation (SD), and when mice were challenged by a novel environment, or exposed to nest-building material. The analysis of alterations in the sleep EEG delta power showed a consistent correlation with the changes in the preceding waking quality in these mice. Targeted inactivation of Hcrt input into DA neurons showed that Hcrtr2 inactivation present the strongest phenotype. The loss of Hcrtr2 in DA neurons caused modified brain activities in spontaneous wakefulness, during SD, and in novel environmental conditions. In addition to alteration of wakefulness quality and quantity, conditional inactivation of Hcrtr2 in DA neurons caused an increased in time spent in PS in baseline and a delayed and less complete PS recovery after SD. In the first 30 min of sleep recovery, single (i.e. for Hcrtrl or Hcrtr2) conditional knockout receptor mice had opposite changes in delta activity, including an increased power density in the fast delta range with specific inactivation of Hcrtr2, but a decreased power density in the same range with specific inactivation of Hcrtrl in DA cells. These studies demonstrate a complex impact of Hcrt receptors signaling in both NA and DA system, not only on quantity and quality of wakefulness, but also on PS amount regulation as well as on SWS delta power expression. -- Depuis la découverte des hypocrétines/orexines (Hcrt/Ox) en 1998, plusieurs modèles de souris, narcoleptiques telles que Hcrt-KO, Hcrtr2-KO et récepteurs doubles KO et les souris transgéniques orexine-ataxine ont été générés. Les modèles de souris Hcrt disponibles ne permettaient pas la dissection du rôle spécifique de l'Hcrt dans chaque noyau neuronal cible. Notre laboratoire a généré des allèles loxP pour chacun des 2 gènes codant pour les récepteurs Hcrtr, qui sont manipulés par recombinase Cre pour générer des lignées de souris avec Hcrtrl inactivé, ou Hcrtr2 inactivé, (ou les deux), spécifiquement dans un type cellulaire particulier. Le rôle de la noradrénaline (NA) et la dopamine (DA) dans la régulation des états de vigilance est bien documentée. Le but de cette thèse est d'étudier le rôle de l'afférence Hcrt dans ces deux systèmes monoaminergiques au niveau de l'activité cérébrale telle qu'elle apparaît dans l'électroencéphalogramme (EEG). Mon travail montre que la perte chronique de Hcrtrl dans les neurones NA consolide le sommeil paradoxal (PS), et l'activité cérébrale de l'éveil est modifiée en condition spontanée, au cours d'une experience de privation de sommeil (SD), et lorsque les souris sont présentées à un nouvel environnement, ou exposées à des matériaux de construction du nid. Ces modifications de l'éveil sont corrélées à des modifications de puissance de l'activité delta du sommeil lent qui le suit. L'inactivation ciblée des Hcrtrs dans les neurones DA a montré que l'inactivation Hcrtr2 conduit au phénotype le plus marqué. La perte de Hcrtr2 dans les neurones DA mène à des modification d'activité cérébrale en éveil spontané, pendant SD, ainsi que dans des conditions environnementales nouvelles. En plus de l'altération de la qualité de l'éveil et de la quantité, l'inactivation conditionnelle de Hcrtr2 dans les neurones DA a provoqué une augmentation du temps passé en sommeil paradoxal (PS) en condition de base, et une reprise retardée et moins complète du PS après SD. Dans les 30 premières minutes de la récupération de sommeil, les modèles inactivés pour un seul des récepteurs (ie pour Hcrtrl ou Hcrtr2 seulement) montrent des changements opposés en activité delta, en particulier une densité de puissance accrue dans le delta rapide avec l'inactivation spécifique de Hcrtr2, mais une densité de puissance diminuée dans cette même gamme chez les souris inactivées spécifiquement en Hcrtrl dans les neurones DA. Ces études démontrent un impact complexe de l'inactivation de la neurotransmission au niveau des récepteurs d'Hcrt dans les deux compartiments NA et DA, non seulement sur la quantité et la qualité de l'éveil, mais aussi sur la régulation de quantité de sommeil paradoxal, ainsi que sur l'expression de la puissance delta pendant le sommeil lent.

The Aldosterone/Renin Ratio as a Diagnostic Tool for the Diagnosis of Primary Hypoaldosteronism in Newborns and Infants.

BACKGROUND/AIMS: Primary hypoaldosteronism is a rare inborn disorder with life-threatening symptoms in newborns and infants due to an aldosterone synthase defect. Diagnosis is often difficult as the plasma aldosterone concentration (PAC) can remain within the normal range and thus lead to misinterpretation and delayed initiation of life-saving therapy. We aimed to test the eligibility of the PAC/plasma renin concentration (PRC) ratio as a tool for the diagnosis of primary hypoaldosteronism in newborns and infants. Meth ods: Data of 9 patients aged 15 days to 12 months at the time of diagnosis were collected. The diagnosis of primary hypoaldosteronism was based on clinical and laboratory findings over a period of 12 years in 3 different centers in Switzerland. To enable a valid comparison, the values of PAC and PRC were correlated to reference methods. RESULTS: In 6 patients, the PAC/PRC ratio could be determined and showed constantly decreased values <1 (pmol/l)/(mU/l). In 2 patients, renin was noted as plasma renin activity (PRA). PAC/PRA ratios were also clearly decreased. The diagnosis was subsequently genetically confirmed in 8 patients. CONCLUSION: A PAC/PRC ratio <1 pmol/mU and a PAC/PRA ratio <28 (pmol/l)/(ng/ml × h) are reliable tools to identify primary hypoaldosteronism in newborns and infants and help to diagnose this life-threatening disease faster. © 2015 S. Karger AG, Basel.

Responding to Young People's Health Risks in Primary Care: A Cluster Randomised Trial of Training Clinicians in Screening and Motivational Interviewing.

OBJECTIVE: To evaluate the effectiveness of a complex intervention implementing best practice guidelines recommending clinicians screen and counsel young people across multiple psychosocial risk factors, on clinicians' detection of health risks and patients' risk taking behaviour, compared to a didactic seminar on young people's health. DESIGN: Pragmatic cluster randomised trial where volunteer general practices were stratified by postcode advantage or disadvantage score and billing type (private, free national health, community health centre), then randomised into either intervention or comparison arms using a computer generated random sequence. Three months post-intervention, patients were recruited from all practices post-consultation for a Computer Assisted Telephone Interview and followed up three and 12 months later. Researchers recruiting, consenting and interviewing patients and patients themselves were masked to allocation status; clinicians were not. SETTING: General practices in metropolitan and rural Victoria, Australia. PARTICIPANTS: General practices with at least one interested clinician (general practitioner or nurse) and their 14-24 year old patients. INTERVENTION: This complex intervention was designed using evidence based practice in learning and change in clinician behaviour and general practice systems, and included best practice approaches to motivating change in adolescent risk taking behaviours. The intervention involved training clinicians (nine hours) in health risk screening, use of a screening tool and motivational interviewing; training all practice staff (receptionists and clinicians) in engaging youth; provision of feedback to clinicians of patients' risk data; and two practice visits to support new screening and referral resources. Comparison clinicians received one didactic educational seminar (three hours) on engaging youth and health risk screening. OUTCOME MEASURES: Primary outcomes were patient report of (1) clinician detection of at least one of six health risk behaviours (tobacco, alcohol and illicit drug use, risks for sexually transmitted infection, STI, unplanned pregnancy, and road risks); and (2) change in one or more of the six health risk behaviours, at three months or at 12 months. Secondary outcomes were likelihood of future visits, trust in the clinician after exit interview, clinician detection of emotional distress and fear and abuse in relationships, and emotional distress at three and 12 months. Patient acceptability of the screening tool was also described for the intervention arm. Analyses were adjusted for practice location and billing type, patients' sex, age, and recruitment method, and past health risks, where appropriate. An intention to treat analysis approach was used, which included multilevel multiple imputation for missing outcome data. RESULTS: 42 practices were randomly allocated to intervention or comparison arms. Two intervention practices withdrew post allocation, prior to training, leaving 19 intervention (53 clinicians, 377 patients) and 21 comparison (79 clinicians, 524 patients) practices. 69% of patients in both intervention (260) and comparison (360) arms completed the 12 month follow-up. Intervention clinicians discussed more health risks per patient (59.7%) than comparison clinicians (52.7%) and thus were more likely to detect a higher proportion of young people with at least one of the six health risk behaviours (38.4% vs 26.7%, risk difference [RD] 11.6%, Confidence Interval [CI] 2.93% to 20.3%; adjusted odds ratio [OR] 1.7, CI 1.1 to 2.5). Patients reported less illicit drug use (RD -6.0, CI -11 to -1.2; OR 0·52, CI 0·28 to 0·96), and less risk for STI (RD -5.4, CI -11 to 0.2; OR 0·66, CI 0·46 to 0·96) at three months in the intervention relative to the comparison arm, and for unplanned pregnancy at 12 months (RD -4.4; CI -8.7 to -0.1; OR 0·40, CI 0·20 to 0·80). No differences were detected between arms on other health risks. There were no differences on secondary outcomes, apart from a greater detection of abuse (OR 13.8, CI 1.71 to 111). There were no reports of harmful events and intervention arm youth had high acceptance of the screening tool. CONCLUSIONS: A complex intervention, compared to a simple educational seminar for practices, improved detection of health risk behaviours in young people. Impact on health outcomes was inconclusive. Technology enabling more efficient, systematic health-risk screening may allow providers to target counselling toward higher risk individuals. Further trials require more power to confirm health benefits. TRIAL REGISTRATION: ISRCTN.com ISRCTN16059206.

Premature Discontinuation of Randomized Trials in Critical and Emergency Care: A Retrospective Cohort Study.

OBJECTIVES: Randomized clinical trials that enroll patients in critical or emergency care (acute care) setting are challenging because of narrow time windows for recruitment and the inability of many patients to provide informed consent. To assess the extent that recruitment challenges lead to randomized clinical trial discontinuation, we compared the discontinuation of acute care and nonacute care randomized clinical trials. DESIGN: Retrospective cohort of 894 randomized clinical trials approved by six institutional review boards in Switzerland, Germany, and Canada between 2000 and 2003. SETTING: Randomized clinical trials involving patients in an acute or nonacute care setting. SUBJECTS AND INTERVENTIONS: We recorded trial characteristics, self-reported trial discontinuation, and self-reported reasons for discontinuation from protocols, corresponding publications, institutional review board files, and a survey of investigators. MEASUREMENTS AND MAIN RESULTS: Of 894 randomized clinical trials, 64 (7%) were acute care randomized clinical trials (29 critical care and 35 emergency care). Compared with the 830 nonacute care randomized clinical trials, acute care randomized clinical trials were more frequently discontinued (28 of 64, 44% vs 221 of 830, 27%; p = 0.004). Slow recruitment was the most frequent reason for discontinuation, both in acute care (13 of 64, 20%) and in nonacute care randomized clinical trials (7 of 64, 11%). Logistic regression analyses suggested the acute care setting as an independent risk factor for randomized clinical trial discontinuation specifically as a result of slow recruitment (odds ratio, 4.00; 95% CI, 1.72-9.31) after adjusting for other established risk factors, including nonindustry sponsorship and small sample size. CONCLUSIONS: Acute care randomized clinical trials are more vulnerable to premature discontinuation than nonacute care randomized clinical trials and have an approximately four-fold higher risk of discontinuation due to slow recruitment. These results highlight the need for strategies to reliably prevent and resolve slow patient recruitment in randomized clinical trials conducted in the critical and emergency care setting.

EEG as an Indicator of Cerebral Functioning in Postanoxic Coma.

Postanoxic coma after cardiac arrest is one of the most serious acute cerebral conditions and a frequent cause of admission to critical care units. Given substantial improvement of outcome over the recent years, a reliable and timely assessment of clinical evolution and prognosis is essential in this context, but may be challenging. In addition to the classic neurologic examination, EEG is increasingly emerging as an important tool to assess cerebral functions noninvasively. Although targeted temperature management and related sedation may delay clinical assessment, EEG provides accurate prognostic information in the early phase of coma. Here, the most frequently encountered EEG patterns in postanoxic coma are summarized and their relations with outcome prediction are discussed. This article also addresses the influence of targeted temperature management on brain signals and the implication of the evolution of EEG patterns over time. Finally, the article ends with a view of the future prospects for EEG in postanoxic management and prognostication.

Harmonization of training and assessment of medical specialists in physical and rehabilitation medicine across Europe - The contribution of the UEMS Board of Physical and Rehabilitation Medicine

Background.- The main goals of the European Board of Physical and Rehabili-tation Medicine (EBPRM), founded in 1991 as the third speciality board of theUnion of European Medical Specialists (UEMS), are to harmonize pre-graduate,post-graduate and continuous medical education in physical and rehabilitationmedicine (PRM) all over Europe. The harmonization of curricula of the medi-cal specialities and the assessment of medical specialists has become one of thepriorities of the UEMS and its working groups to which the EBPRM contributes.Action.- The EBPRM will continue to promote a specific minimal undergraduatecurriculum on PRM including issues like disability, participation and handicapto be taught all over Europe as a basis for general medical practice. The EBPRMwill also expand the existing EBPRM postgraduate curriculum into a detailedcatalogue of learning objectives. This catalogue will serve as a tool to boostharmonization of the national curricula across Europe as well as to structurethe content of the MCQ examination. It would be a big step forward towardsharmonization of European PRM specialist training if an important number ofcountries would use the certifying MCQ examination of the Board as a part ofthe national assessments for PRM specialists.

Timing of visual stimuli in V1 and V5/MT: fMRI and TMS

Time perception is used in our day-to-day activities. While we understand quite well how our brain processes vision, touch or taste, brain mechanisms subserving time perception remain largely understudied. In this study, we extended an experiment of previous master thesis run by Tatiana Kenel-Pierre. We focused on time perception in the range of milliseconds. Previous studies have demonstrated the involvement of visual areas V1 and V5/MT in the encoding of temporal information of visual stimuli. Based on these previous findings the aim of the present study was to understand if temporal information was encoded in V1 and extrastriate area V5/MT in different spatial frames i.e., head- centered versus eye-centered. To this purpose we asked eleven healthy volunteers to perform a temporal discrimination task of visual stimuli. Stimuli were presented at 4 different spatial positions (i.e., different combinations of retinotopic and spatiotopic position). While participants were engaged in this task we interfered with the activity of the right dorsal V1 and the right V5/MT with transcranial magnetic stimulation (TMS). Our preliminary results showed that TMS over both V1 and V5/MT impaired temporal discrimination of visual stimuli presented at specific spatial coordinates. But whereas TMS over V1 impaired temporal discrimination of stimuli presented in the lower left quadrant, TMS over V5/MT affected temporal discrimination of stimuli presented at the top left quadrant. Although it is always difficult to draw conclusions from preliminary results, we could tentatively say that our data seem to suggest that both V1 and V5/MT encode visual temporal information in specific spatial frames.

Impact of maternity care policy in Catalonia: a retrospective cross-sectional study of service delivery in public and private hospitals

Background: As a result of the growing number of interventions that are now performed in the context of maternity care, health authorities have begun to examine the possible repercussions for service provision and for maternal and neonatal health. In Spain the Strategy Paper on Normal Childbirth was published in 2008, and since then the authorities in Catalonia have sought to implement its recommendations. This paper reviews the current provision of maternity care in Catalonia. Methods: This was a descriptive study. Hospitals were grouped according to their source of funding (public or private) and were stratified (across four strata) on the basis of the annual number of births recorded within their respective maternity service. Data regarding the distribution of obstetric professionals were taken from an official government survey of hospitals published in 2010. The data on obstetric interventions (caesarean, use of forceps, vacuum or non-specified instruments) performed in 2007, 2010 and 2012 were obtained by consulting discharge records of 44 public and 20 private hospitals, which together provide care in 98% of all births in Catalonia. Proportions and confidence intervals were calculated for each intervention performed in all full-term (3742 weeks) singleton births. Results: Analysis of staff profiles according to the stratification of hospitals showed that almost all the hospitals had more obstetricians than midwives among their maternity care staff. Public hospitals performed fewer caesareans [range between 19.20% (CI 18.84-19.55) and 28.14% (CI 27.73-28.54)] than did private hospitals [range between 32.21% (CI 31.78-32.63) and 39.43% (CI 38.98-39.87)]. The use of forceps has decreased in public hospitals. The use of a vacuum extractor has increased and is more common in private hospitals. Conclusions: Caesarean section is the most common obstetric intervention performed during full-term singleton births in Catalonia. The observed trend is stable in the group of public hospitals, but shows signs of a rise among private institutions. The number of caesareans performed in accredited public hospitals covers a limited range with a stable trend. Among public hospitals the highest rate of caesareans is found in non-accredited hospitals with a lower annual number of births.

Impact of maternity care policy in Catalonia: a retrospective cross-sectional study of service delivery in public and private hospitals

Background: As a result of the growing number of interventions that are now performed in the context of maternity care, health authorities have begun to examine the possible repercussions for service provision and for maternal and neonatal health. In Spain the Strategy Paper on Normal Childbirth was published in 2008, and since then the authorities in Catalonia have sought to implement its recommendations. This paper reviews the current provision of maternity care in Catalonia. Methods: This was a descriptive study. Hospitals were grouped according to their source of funding (public or private) and were stratified (across four strata) on the basis of the annual number of births recorded within their respective maternity service. Data regarding the distribution of obstetric professionals were taken from an official government survey of hospitals published in 2010. The data on obstetric interventions (caesarean, use of forceps, vacuum or non-specified instruments) performed in 2007, 2010 and 2012 were obtained by consulting discharge records of 44 public and 20 private hospitals, which together provide care in 98% of all births in Catalonia. Proportions and confidence intervals were calculated for each intervention performed in all full-term (3742 weeks) singleton births. Results: Analysis of staff profiles according to the stratification of hospitals showed that almost all the hospitals had more obstetricians than midwives among their maternity care staff. Public hospitals performed fewer caesareans [range between 19.20% (CI 18.84-19.55) and 28.14% (CI 27.73-28.54)] than did private hospitals [range between 32.21% (CI 31.78-32.63) and 39.43% (CI 38.98-39.87)]. The use of forceps has decreased in public hospitals. The use of a vacuum extractor has increased and is more common in private hospitals. Conclusions: Caesarean section is the most common obstetric intervention performed during full-term singleton births in Catalonia. The observed trend is stable in the group of public hospitals, but shows signs of a rise among private institutions. The number of caesareans performed in accredited public hospitals covers a limited range with a stable trend. Among public hospitals the highest rate of caesareans is found in non-accredited hospitals with a lower annual number of births.

The determinants of capital intensity in Japan and the U.S

We estimate the determinants of capital intensity in Japan and the US, characterized by striking different paths. We augment an otherwise standard Constant Elasticity of Substitution (CES) model with demand-side considerations, which we find especially relevant in the US. In this augmented setting, the elasticity of substitution between capital and labor is placed around 0.85 in Japan, and 0.30 in the US. We also find evidence of biased technical change, which is capital-saving in Japan but labor-saving in the US. These differences help us explain the diverse experience in the capital deepening process of these economies, and lead us to conclude that demand-side drivers may also be relevant to account for different growth experiences. A close look at the nature of technological change is also needed before designing one-size-fits-all industrial, economic growth, and/or labor market policies.

Ion pair-dispersive liquid-liquid microextraction of trace amount of rhodium ion in water and road dust samples prior to flame atomic absorption spectrometry determination

A simple ion pair-dispersive liquid-liquid microextraction method was proposed for preconcentration trace amounts of rhodium. An ion association complex of RhCl4- and tetradecyldimetylbenzylamonium was extracted into cholorobenzene. The volume and the type of extractive and dispersive solvents, the extraction time and the pH of the aqueous solutions were optimized. The calibration curve was linear in the range of 0.6-500 ng mL-1 of rhodium. The limit of detection was 0.10 ng mL-1 in initial solution and preconcentration factor was 40. The proposed method was successfully applied to the extraction and determination of rhodium in road dust and water samples.

Imaging and Characterisation of Dirt Particles in Pulp and Paper

Dirt counting and dirt particle characterisation of pulp samples is an important part of quality control in pulp and paper production. The need for an automatic image analysis system to consider dirt particle characterisation in various pulp samples is also very critical. However, existent image analysis systems utilise a single threshold to segment the dirt particles in different pulp samples. This limits their precision. Based on evidence, designing an automatic image analysis system that could overcome this deficiency is very useful. In this study, the developed Niblack thresholding method is proposed. The method defines the threshold based on the number of segmented particles. In addition, the Kittler thresholding is utilised. Both of these thresholding methods can determine the dirt count of the different pulp samples accurately as compared to visual inspection and the Digital Optical Measuring and Analysis System (DOMAS). In addition, the minimum resolution needed for acquiring a scanner image is defined. By considering the variation in dirt particle features, the curl shows acceptable difference to discriminate the bark and the fibre bundles in different pulp samples. Three classifiers, called k-Nearest Neighbour, Linear Discriminant Analysis and Multi-layer Perceptron are utilised to categorize the dirt particles. Linear Discriminant Analysis and Multi-layer Perceptron are the most accurate in classifying the segmented dirt particles by the Kittler thresholding with morphological processing. The result shows that the dirt particles are successfully categorized for bark and for fibre bundles.

Effects of thermal environment and supplementation levels on the physiological parameters of moxotó goats in confined and semi-confined rising systems

The objective of this work was to determine the effect of environmental variables and supplementation levels on physiological parameters of Moxotó goats in confined and semi-confined rising systems, in the Brazilian semi-arid region. The semi-confined individuals were kept on a grass based diet during the day and arrested in the end of the afternoon. The confined animals were kept in a management center, receiving two diets composed by forage cactus and maniçoba hay into two different levels (0.5 and 1.5% of the body weight). Inside the management center and in the external environment the environmental comfort parameters were set high during the afternoon period characterizing a situation of thermal discomfort for the animals. During the morning the semi-confined animals presented an average respiratory frequency (69.5 mov min-1) and rectal temperature (39.5 ºC) higher than the confined ones (62.6 mov min-1 and 39.0 ºC, respectively). The confined and semi-confined animals were able to maintain their rectal temperature within normal limits, with increase in the cardiac beatings rate and respiratory frequency. The greater percentage of the used supplementations (1.5%) seemed to increase rectal temperature in the two studied rising systems.

On the etiology of an outbreak of winter dysentery in dairy cows in Brazil

Winter dysentery (WD) is a seasonal infectious disease described worldwide that causes a marked decrease in milk production in dairy cows. In the Northern hemisphere, where the disease is classically recognized, bovine coronavirus (BCoV) has been assigned as a major etiologic agent of the disease. Nonetheless, in the Southern hemisphere, an in-deep etiological survey on WD cases had not been carried out. This study aimed to survey for BCoV by nested-RT-PCR, rotavirus by polyacrylamide gel electrophoresis (PAGE) and ELISA, bacteria by classical bacteriological methods and PCR for virulence factors and parasites by sugar flotation test on fecal samples of 21 cows from a farm during an outbreak of WD in São Paulo state, Southeastern Brazil. BCoV was detected in all 21 samples, while rotavirus was detected in two symptomatic cows. Escherichia coli, Yersinia intermedia, Providencia rustigianii Proteus penneri, Klebsiella terrigena and Enterobacter aglomerans were detected in samples from both asymptomatic and healthy cows in different associations. The study of E. coli virulence factors revealed that the strains isolated were all apathogenic. Cysts of Eimeria sp. and eggs of Strongyloidea were detected at low numbers in four of the symptomatic cows, with one co-infestation. These results suggest BCoV as the main etiologic agent of the cases of WD in Brazil, a conclusion that, with the clinical and epidemiological patterns of the disease studied herein, match those already described elsewhere. These findings give basis to the development of preventive measures and contribute to the understanding of the etiology of WD.

Parasitism level by helminths and weight gain of calves kept in organic and conventional grazing

Sustainable production is a principle in which we must meet the needs of the present without compromising the capacity of future generations. Despite the successful development of pesticides against endo and ectoparasites found in domestic ruminants, these parasites are still the major problem of the herbivore production system. The purpose of this study was to know the population of gastrintestinal parasites and their influence on weight gain of calves kept in organic and conventional grazing. Thus, organic and conventional calves were randomly selected in 2008 and 2009. The fecal egg count (FEC) indentified the following genders of helminths: Haemonchus, Trichostrongylus, Oesophagostomum, Cooperia, Strongyloides, Trichuris and oocysts of Eimeria. There was no significant difference (p>0.05) between FEC in organic and conventional animals. Calves younger than 6 months showed significant higher infection (p<0.05) than calves between 7 and 12 months of age. The weight gain observed during the study was of 327g/day and 280g/day for conventional and organic systems animals, respectively. Consequently, the combination of sustainable practices of grazing associated with the selective application of anthelmintics may be a feasible alternative for nematode control in a conventional system and in transition to an organic one.