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Background: Hereditary cerebellar ataxias (HCA) and hereditary spastic paraplegias (HSP) are two groups of neurodegenerative disorders that usually present with progressive gait impairment, often leading to permanent disability. Advances in genetic research in the last decades have improved their diagnosis and brought new possibilities for prevention and future treatments. Still, there is great uncertainty regarding their global epidemiology. Summary: Our objective was to assess the global distribution and prevalence of HCA and HSP by a systematic review and meta-analysis of prevalence studies. The MEDLINE, ISI Web of Science and Scopus databases were searched (1983-2013) for studies performed in well-defined populations and geographical regions. Two independent reviewers assessed the studies and extracted data and predefined methodological parameters. Overall, 22 studies were included, reporting on 14,539 patients from 16 countries. Multisource population-based studies yielded higher prevalence values than studies based primarily on hospitals or genetic centres. The prevalence range of dominant HCA was 0.0-5.6/105, with an average of 2.7/105 (1.5-4.0/105). Spinocerebellar ataxia type 3 (SCA3)/Machado-Joseph disease was the most common dominant ataxia, followed by SCA2 and SCA6. The autosomal recessive (AR) HCA (AR-HCA) prevalence range was 0.0-7.2/105, the average being 3.3/105 (1.8-4.9/105). Friedreich ataxia was the most frequent AR-HCA, followed by ataxia with oculomotor apraxia or ataxia-telangiectasia. The prevalence of autosomal dominant (AD) HSP (AD-HSP) ranged from 0.5 to 5.5/105 and that of AR-HSP from 0.0 to 5.3/105, with pooled averages of 1.8/105 (95% CI: 1.0-2.7/105) and 1.8/105 (95% CI: 1.0-2.6/105), respectively. The most common AD-HSP form in every population was spastic paraplegia, autosomal dominant, type 4 (SPG4), followed by SPG3A, while SPG11 was the most frequent AR-HSP, followed by SPG15. In population-based studies, the number of families without genetic diagnosis after systematic testing ranged from 33 to 92% in the AD-HCA group, and was 40-46% in the AR-HCA, 45-67% in the AD-HSP and 71-82% in the AR-HSP groups. Key Messages: Highly variable prevalence values for HCA and HSP are reported across the world. This variation reflects the different genetic make-up of the populations, but also methodological heterogeneity. Large areas of the world remain without prevalence studies. From the available data, we estimated that around 1:10,000 people are affected by HCA or HSP. In spite of advances in genetic research, most families in population-based series remain without identified genetic mutation after extensive testing.

In this study a comparison between two different methods for measuring the susceptibility of Giardia lamblia trophozoites to metronidazole and albendazole is performed. Modifications of Meloni's method, based on the loss of adherence of parasites to surfaces, and the Hill method, based on the loss of parasite division capacity, are compared. A logistic model was used to calculate the inhibitory concentrations IC(10), IC(50) and IC(90) that were further compared using the respective standard errors. The results obtained, after contact of parasites with the antiparasitic drugs for 24h, show that the adherence method is more sensitive than the multiplication method for low and moderate inhibitory concentrations of albendazole. Conversely for metronidazole the multiplication method seems to be more sensitive for high inhibitory concentrations of the drug. For screening the IC(50), both methods seem to be effective, however, the inhibition of adherence method have even better performance for the benzimidazole like drugs.

Methamphetamine (Meth) neurotoxicity upon the mesencephalic dopaminergic systems was demonstrated in the adult, both in humans and in experimental models. In the rat, the development and maturation of the dopaminergic systems is accomplished during the first month of postnatal life, a period of particular vulnerability to environmental influences. In this study, the effect of Meth exposure during the first month of life was assessed in the nigrostriatal dopaminergic system of the rat. For this purpose, Wistar rat litters were culled to 8 pups, retaining preferentially 4 males and 4 females, which, in the day following birth (postnatal day 1, PND1), were randomly attributed to either the Meth or control group. Meth-groups were administered 10 mg of (+)-methamphetamine hydrochloride/kg body weight/day, subcutaneously, twice daily, from PND1 until PND29; control groups received isovolumetric doses of saline. Animals were sacrificed at PND30. Males exposed to Meth during the first month of life had increased tyrosine hydroxylase (TH) activity both in the caudate-putamen and substantia nigra. Males also had increased nigral TH mRNA levels, as assessed by in situ hybridization. These effects did not exist in females. These results support the evidence that Meth exposure during the first month of life in the rat has a gender-specific stimulatory effect upon the maturation of TH, the key enzyme for dopamine biosynthesis in the nigrostriatal dopaminergic system.

A project for studying the prevalence of hereditary ataxias (HA) and familial spastic paraplegias (FSP) in Portugal was set up in 1993. The ascertainment of patients in previous prevalence studies relied mainly on the information of hospital admissions and out-patient contacts with the neurology and other related departments at central hospitals covering the whole region surveyed. Many patients might be overlooked if large populations were studied using this method, since registers at central hospitals are very incomplete and for most part not yet computerized. On the other hand HA and FSP are rare diseases appearing in family clusters, and it would be unreasonable to undertake a sample survey based upon a suitable frame of the Portuguese population. Therefore we decided to carry out a two-phase prevalence survey at district level, involving the collaboration of all physicians working in the district health institutions and the population, in the screening of eligible subjects in phase 1. All subjects screened as positive were examined by a neurologist in phase 2. This method provided a direct estimate of false positives and false negatives were all patients also examined in phase 2, who came to our knowledge using other sources of information. The prevalence of hereditary ataxias and spastic paraplegias in the pilot district was 6.4 per 100,000 inhabitants. The sensitivity of the screening procedure was 81.2% and the predictive value of a positive screening was 25%. Considering the geographically circumscribed district nature of the populations to be studied, the comprehensive sources of case identification used and the high adherence of the health professionals involved, we believe that this method can be widely used, particularly in countries with similar health care services.

Importance Epidemiological data on hereditary cerebellar ataxia (HCA) and hereditary spastic paraplegia (HSP) are scarce. Objective To present the prevalence and distribution of HCA and HSP in Portugal. Design and Setting Population-based, nationwide, systematic survey, from January 1, 1994, through April 15, 2004, in Portugal. Participants Multiple sources of information were used (review of clinical files, active collaboration of neurologists and geneticists, and investigation of affected families), but the main source was active collaboration of general practitioners. Patients were examined by the same team of neurologists, using homogeneous inclusion criteria. The clinical data were registered, and all families were genetically tested. Results Overall, 1336 patients from a population of 10 322 million were diagnosed as having HCA or HSP, a prevalence of 12.9 per 100 000 population. Hereditary cerebellar ataxia was more prevalent (prevalence, 8.9 per 100 000 population; 5.6 for dominant and 3.3 for recessive ataxias) than HSP (prevalence, 4.1 per 100 000 population; 2.4 for dominant and 1.6 for recessive). Machado-Joseph disease (spinocerebellar ataxia type 3) (prevalence, 3.1 per 100 000 population), Friedreich ataxia (prevalence, 1.0 per 100 000 population), and ataxia with oculomotor apraxia (prevalence, 0.4 per 100 000 population) were the most frequent HCAs. Spastic paraplegia types 4 (prevalence, 0.91 per 100 000 population), 3 (prevalence, 0.14 per 100 000 population), and 11 (prevalence, 0.26 per 100 000 population) were the most prevalent HSPs. Conclusions and Relevance This population-based survey covered all the Portuguese territory and mobilized most general practitioners and health centers. To our best knowledge, this survey was the largest ever performed for HCA and HSP. Prevalence of autosomal dominant ataxias was high, particularly for Machado-Joseph disease (spinocerebellar ataxia type 3). The genetic cause has not been identified in 39.7% of the patients studied.

By 2002 Portugal had one of the highest mortality rates due to cerebrovascular diseases among the European Countries. Meanwhile, several strategies have been adopted to improve prevention and treatment in the acute phase, amongst which the Stroke Code. The purpose of this study is to describe how this measure has been used and its outcome as part of a prospective community based study of stroke/TIA incidence in Northern Portugal.Between 1st October 2009 and 30th September 2010 all strokes occurred in patients registered at Western Porto, Mirandela and Vila Pouca de Aguiar health centres have been recorded. For cases ascertainment multiple sources of information were used, including the WEB, letter, e-mail and Alert P1, as well as systematic searches on databases provided by the entities involved in this study: hospital emergency, discharge records, diagnosis procedures, death certificates, Stroke Code admissions and health centre emergency records.Six hundred strokes were recorded in a population of 241 000 (incidence rate of 250 / 100 000 person-years) and 434 were first-ever-in-the-lifetime (180 / 100 000). There were 72 Stroke Code calls and in 66.7% of them a stroke was confirmed. Considering the criteria for Stroke Code call (age = 80 years, functional independency, the stroke signs/symptoms, and time after episode = 3 hours), only 15.9% patients "could" have access to it. Of those who used the Stroke Code, only 56.3% fulfilled the criteria. Considering all patients fulfilling Stroke Code criteria, 96.3% that used prehospital Stroke Code were inpatients, as well as 83.3% that used intra/interhospital Stroke Code and 64.0% of the remainder; this trend is also present in patients with ischaemic stroke submitted to fibrinolysis, 77.3%, 36.4% and 17.4%, respectively. A high post-stroke Rankin was more frequent among Stroke Code users (70.3% vs. 35.3%), but they exhibit more often the three stroke signs/symptoms (44.0% vs. 16.2%). After adjusting for age, sex and number of signs, the risk of a more severe post-stroke Rankin is not significantly different among patients using the prehospital Stroke Code (OR = 2.9, 95% CI: 0.8 - 10.2).The criteria for accessing the Stroke Code are currently restrictive. Though the Stroke Code is accessed in case of more severe patient's conditions, the proportion of patients treated with fibrinolysis is relatively high in comparison with other studies.Introdução: Em 2002 Portugal detinha uma das mais altas taxas de mortalidade por doenças cerebrovasculares entre os países europeus. Várias estratégias foram adoptadas para melhorar a prevenção da doença e o seu tratamento na fase aguda, entre as quais a criação da Via Verde do Acidente Vascular Cerebral. O objectivo deste trabalho é descrever a utilização e resultados desta estratégia no contexto de um registo prospectivo comunitário na Região Norte de Portugal. Material e Métodos: Foram registados todos os AVCs ocorridos entre 1 de Outubro de 2009 e 30 de Setembro de 2010 nos utentes inscritos no agrupamento de centros de saúde do Porto Ocidental e nos de Mirandela e Vila Pouca de Aguiar. Para a detecção de casos utilizaram-se múltiplas fontes de informação: notificação via WEB, e-mail, Alerta P1 e pesquisas sistemáticas em registos disponibilizados pelas entidades envolvidas - urgências hospitalares, listas de altas, procedimentos de diagnóstico, óbitos, Via Verde do Acidente Vascular Cerebral e serviço de atendimento de situações urgentes. Resultados: Ocorreram 600 AVCs em 241 000 habitantes (taxa de incidência de 250 / 100 000), dos quais 434 foram primeiros na vida (180 / 100 000). Foram registados 72 acessos à Via Verde do Acidente Vascular Cerebral, dos quais 66,7% foram diagnosticados como AVC. Considerando os quatro critérios de activação (idade ≤ 80 anos, independência funcional, sinais/sintomas do AVC e tempo após episódio ≤ 3 horas), só 15,9% dos doentes a poderiam utilizar e, dos utilizadores, apenas 56,3% satisfaziam esses critérios. Dos doentes com critérios de activação, foram internados 96,3% pela VV pré-hospitalar, 83,3% pela VV intra/inter-hospitalar e 64,0% dos restantes; a fibrinólise foi realizada em 77,3%, 36,4% e 17,4% dos doentes com enfarte cerebral, respectivamente. O Rankin pós- AVC é mais grave nos utilizadores da VV pré-hospitalar (70,3% vs. 35,3%), mas estes apresentam mais assiduamente os três sinais/ sintomas de AVC (44,4% vs. 16,2%). Ajustando para a idade, sexo e número de sinais, o risco de incapacidade grave pós-AVC não é significativamente diferente no acesso pela VV pré-hospitalar (RP = 2,9; IC 95%: 0,8 - 10,2), bem como a taxa de letalidade. Conclusões: Os critérios para activação da Via Verde do Acidente Vascular Cerebral são muito restritivos. Embora esta seja mais vezes accionada em situações clínicas graves, a proporção de doentes que realizou fibrinólise é relativamente alta em comparação com outros estudos.

Background: Changes in meteorological parameters have been associated with cardiovascular mortality and stroke. The high incidence of stroke in Portugal may be modelled by short- or long-term weather changes whose effect may be different across stroke types and severity. Methods: Data include all patients with a first-ever-in-a-lifetime stroke registered in a population of 86,023 residents in the city of Porto from October 1998 to September 2000. Specific stroke types were considered and ischaemic stroke (IS) subtype was defined according to the Oxfordshire Community Stroke Projet classification and the Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria. Information on daily temperature, humidity and air pressure was obtained from the National Meteorological Office. The Poisson distribution was used to model the daily number of events as a function of each weather parameter measured over different hazard periods, and the binomial model to contrast effects across subgroups. Differential effects of meteorological parameters and hazard periods upon stroke occurrence and outcome were analysed in a stepwise model. Results: Among the 462 patients registered, 19.6% had a primary intracerebral haemorrhage (PICH) and 75.3% an IS. Among patients with IS, 21.6% were total anterior circulation infarcts (TACIs), 19.8% partial anterior circulation infarcts (PACIs), 19.5% posterior circulation infarcts (POCIs) and 39.1% were lacunar infarcts (LACIs). The aetiology of IS was large artery atherosclerosis in 6.9%, cardioembolism in 23.3% and small artery occlusion in 35.6%. The incidence of PICH increased by 11.8% (95% CI: 3.8–20.4%) for each degree drop in the diurnal temperature range in the preceding day. The incidence of IS increased by 3.9% (95% CI: 1.6–6.3%) and cardioembolic IS by 5.0% (95% CI: 0.2–10.1%) for a 1°C drop in minimum temperature in the same hazard period. The incidence of TACIs followed the IS pattern while for PACIs and POCIs there were stronger effects of longer hazard periods and no association was found for LACIs. The relative risk of a fatal versus a non-fatal stroke increased by 15.5% (95% CI: 6.1–25.4%) for a 1°C drop in maximum temperature over the previous day. Conclusions: Outdoor temperature and related meteorological parameters are associated with stroke occurrence and severity. The different hazard periods for temperature effects and the absence of association with LACIs may explain the heterogeneous effects of weather on stroke occurrence found in community-based and hospital admission studies. Emergency services should be aware that specific weather conditions are more likely to prompt calls for more severe strokes.

The purpose of this study was to identify patterns in Portuguese television advertisements and interpret changes in the portrayal of gender roles using data collected 7 years apart: 1996 and 2003. We grouped 11 attributes of the central figure displayed in 623 evening commercials using a k-means cluster procedure. There were 4 distinct groups of advertisements that emerged, 2 of them characterizing a predominantly male central figure and the other 2 a female central figure. The overall increase in women portrayed in advertisements from 1996 (32.9%) to 2003 (40.8%) is reflected in a shift toward an increase of advertisements with a female central figure in the typically male “narrator” cluster. Practical implications of these findings are discussed.

Background and Purpose— There are no community-based studies on the incidence of transient ischemic attacks (TIAs) in Portugal. This study was designed to determine TIA incidence and the risk of stroke occurrence in rural and urban populations in northern Portugal. Methods— All suspected first-ever TIAs occurring between October 1998 and September 2000 in 18 677 residents in a rural municipality and 86 023 living in the city of Porto were entered into a population-based registry. Standard definitions and comprehensive sources of information were used for identification of patients who were followed up at 3 and 12 months after the TIA. Results— During a 24-month period, 141 patients with a first-ever TIA were registered, 36 in rural and 104 in urban areas. The vascular territory was carotid in 66.7% of the patients, vertebrobasilar in 29.1%, and undetermined in 4.3%. The overall crude annual incidence rate per 1000 was 0.67 (95% CI, 0.45 to 1.04), 0.61 (95% CI, 0.38 to 1.01) for rural, and 0.96 (95% CI, 0.43 to 2.33) for urban populations. The risk of stroke within the first 7 days of the index event was 12.8% (95% CI, 7.3 to 18.3), reaching 21.4% (95% CI, 14.6 to 28.1) at 1 year. Three factors were associated with stroke occurrence within 120 days after TIA: patients’ age ≥65 years and an episode in the carotid distribution lasting ≥3 hours. Conclusions— The incidence of TIA in northern Portugal, particularly in rural populations, ranks among the highest reported in community-based studies, following closely the stroke incidence trend (ACINrpc). Early recognition of TIA by patients and physicians is crucial for effective stroke prevention.

Background and Purpose— Mortality statistics indicate that Portugal has the highest stroke mortality in Western Europe. Data on stroke incidence in Northern Portugal, the region with the highest mortality, are lacking. This study was designed to determine stroke incidence and case fatality in rural and urban populations in Northern Portugal. Methods— All suspected first-ever-in-a-lifetime strokes occurring between October 1998 and September 2000 in 37 290 residents in rural municipalities and 86 023 living in the city of Porto were entered in a population-based registry. Standard definitions and comprehensive sources of information were used for identification of patients who were followed-up at 3 and 12 months after onset of symptoms. Results— During a 24-month period, 688 patients with a first-ever stroke were registered, 226 in rural and 462 in urban areas. The crude annual incidence was 3.05 (95% CI, 2.65 to 3.44) and 2.69 per 1000 (95% CI, 2.44 to 2.93) for rural and urban populations, respectively; the corresponding rates adjusted to the European standard population were 2.02 (95% CI, 1.69 to 2.34) and 1.73 (95% CI, 1.53 to 1.92). Age-specific incidence followed different patterns in rural and urban populations, reaching major discrepancy for those 75 to 84 years old, 20.2 (95% CI, 16.1 to 25.0) and 10.9 (95% CI, 9.0 to 12.8), respectively. Case fatality at 28 days was 14.6% (95% CI, 10.2 to 19.3) in rural and 16.9% (95% CI, 13.7 to 20.6) in urban areas. Conclusions— Stroke incidence in rural and urban Northern Portugal is high compared to that reported in other Western Europe regions. The high official mortality in our country, which could be explained by a relatively high incidence, was not because of a high case fatality rate.

Background: Neurological and cognitive sequelae resulting from cardiac arrest (CA), despite their potential personal and social impact, are usually not considered as major outcome measures in long-term analysis of survivors. The aim of this study is to analyze the contribution of neuropsychological testing and cerebral imaging to the development of a long-term classification of neurological impairment. Patients and methods: A total of 19 patients admitted over a 3 years period in an eight-bed intensive care unit of a tertiary care hospital with a diagnosis of CA were alive and attended a 6-month follow-up consultation. Eleven of these patients agreed to participate in this study carried out between 1 and 3 years after CA. Patients were classified using the Cerebral Performance Categories (CPC), neurological examination, detailed cognitive testing and computerized tomography (CT) scan with qualitative and quantitative imaging analysis. Results: Six of the 11 patients had good cerebral performance. Verbal and visuo-spatial short-term memory scores were associated with CPC. All patients with at least moderate cerebral disability had abnormal verbal memory test results compared with only one survivor with CPC 1; visuo-spatial short-term memory was abnormal in four moderately affected survivors and normal in those with CPC 1. The bicaudate ratio evaluated in the CT scan was correlated with the verbal memory score while the III ventricle diameter correlated with the executive functions score, suggesting involvement of different brain areas in these functions. Conclusions: Neuropsychological and CT scan measurements are proxy measures of long-term impairment of CA survivors, providing a dichotomized global evaluation of CA survivors in close agreement with CPC.

The effects of gender, age and school grade on several career exploration dimensions measured by the Career Exploration Survey were investigated. Subjects were high school students facing an imminent career decision. Regression analyses indicated that sex and grade-level were the most significant and prevailing individual characteristics related to the adolescents’ career exploration behaviours, reactions and beliefs. Implications for career exploration interventions are discussed., JNICT -Junta Nacional de Investigação Científica e Tecnológica(PSU436-92), info:eu-repo/semantics/publishedVersion

Summary Our purpose was to study the role of the expression of P-glycoprotein (Pgp) and glutatione S transferase-pi (GST pi) in predicting the response to chemotherapy, relapse-free interval, and survival of patients with synovial sarcoma (SS). Thirty-seven cases of primary SS, without regional lymph node or distant metastases, were studied. There were 17 females and 20 males, ranging in age from 7 to 81 years (median, 31 years) with tumors located in the lower extremity (n =24) upper extremity (n =5) and trunchus (n =8). The cases were retrospectively studied without knowledge of clinical course to compare the immunohistochemical expression of Pgp and GST-pi, flow cytometry parameters (ploidy and % of cells in S+G2 phases), and PCNA and Ki-67 labeling of primary tumors before any therapy, with that observed in local recurrences and metastases after chemotherapy. The relationship of the aforementioned parameters with clinicopathological features (gender, age, and histoblood group of the patients, size, location, histological subtype, TNM stage, and clinical response to chemotherapy of the tumors) was also evaluated. Results revealed that Pgp and GST-pi were expressed in 29.7% and 40.5% of the cases, respectively. In 48.6% of the tumors there was expression of at least one of the drug resistance markers. The markers were coexpressed in 25.0% of the tumors. The prevalence of Pgp expression was lower, but not significantly, in stage I-II (17.6%) than in stage III (40.0%) tumors, and also in cases without clinical progression (16.7%), than in cases with (36.0%). No such differences were observed for GST-pi expression. Pgp and GST-pi expressions were significantly associated with biphasic SS and were particularly noticeable in solid/glandular areas of biphasic SSe The expression of the drug resistance markers was not significantly associated with gender, age, and histo-blood group of the patients, dimension, location, and proliferative activity of the tumors; it was also not significantly related to relapse-free interval and survival of the patients. The expression of Pgp and GST-pi was not significantly associated either to response to chemotherapy or influenced by chemotherapy. We conclude that Pgp and GST-pi expressions are not good predictors response to of the chemotherapy in patients with localized SSe Other drug resistance mechanisms may be active in SS

Information about the intent to emigrate was collected for a sample of 960 adolescents living in the northern region of Portugal. This question was part of a detailed questionnaire designed to assess specific issues concerning social representations of migration-namely, information, attitude, and fields of representation. Using information about the sociodemographic characteristics and the components of social representation mentioned above, our aim was to identify the independent predictors underlying the adolescent's intent to emigrate. Due to the great number of factors involved in the analysis, we conducted a preliminary selection of independent predictors within each of the aforementioned components and created a global index describing their importance. The findings indicate that, among all components of a social representation, attitude and representation of detachment and adaptation are the most important predictors of intent to emigrate. The relatively poor ability of sociodemographic variables to predict a future emigration does not mean that they are not important, but rather that they are more likely to condition attitude, the strongest predictor of a future emigration in the northern region of Portugal. The implication of these findings for handling intervening migration policies is discussed.

Methamphetamine (Meth) is an illicit substance known to interfere with catecholaminergic systems and a popular recreational drug among young adult women, that is, in gestational age. Tyrosine hydroxylase (TH), the rate-limiting enzyme of the synthetic pathway of catecholamines, is a good marker to assess potential effects of Meth in catecholaminergic (particularly in dopaminergic) systems. In the rat, prolonged neonatal Meth exposure altered several dopaminergic markers (TH activity and gene expression) in substantia nigra pars compacta (SN) and in caudate-putamen (TH activity) when animals matured. However, it was never verified whether gestational exposure to Meth might compromise TH enzyme in the pups during the neonatal immature periods. The present study was designed to address this issue by analyzing TH gene expression, measured by in situ hybridization in SN and ventral tegmental area (VTA), dopaminergic areas that are well characterized as target areas for Meth, and in rats prenatally exposed to this psychostimulant. To this end, dated pregnant Wistar rat dams received 5 mg Meth hydrochloride/kg body weight/day. It was administered subcutaneously from gestational day 8 until 22. The control group was pair-fed and saline injected, using the same experimental protocol as for Meth-treated dams. On the day of birth (postnatal day 0, PND 0), litters were culled to 8 pups, sex-balanced whenever possible, and were followed until the day of sacrifice (PND 7, 14, or 30). Meth treatment differentially affected TH mRNA levels in VTA and SN, in an age- and gender-dependent manner. Thus, TH mRNA levels were decreased in the VTA of PND 7 and PND 14 females gestationally exposed to Meth; this effect was not evident in males or on PND 30. TH mRNA levels also tend to decrease in SN of PND 14 females gestationally exposed to Meth. Collectively, the present results indicated that gestational Meth exposure affects TH gene expression in the postnatal life, a phenomenon that appears to be transient, since it is no longer evident by the end of the first month of life in the rat.

In this study, the association between the acute toxicity of 15 compounds to Daphnia magna, expressed as 24- and 48-h LC50 values, and the corresponding oral LD50 values for the rat was tested. Since there was evidence of a strong relationship between the two species, the sample was extended to 54 cases by including the values for acute toxicity to D. magna and rat of more chemicals published by other authors. Thus, a total of 54 data points were further used to ascertain the relationship between the acute toxicity of chemical compounds to D. magna and that to the rat. To summarize its validity, the D. magna test is more specific than sensitive as an indicator of toxicity to the rat. When it is used with a chemical that has a high probability of being very toxic to D. magna (LC50< 0.22 mg/L), the test provides considerable information if it is positive, virtually giving evidence of toxicity to the rat (with a probability of 0.83). On the other hand, a negative test (D. magna LC50>0.22 mg/L) has a probability of correctly assigning nontoxicity to the rat equal to 0.74. This study and results published by other authors provide good evidence of the applicability of using invertebrate tests as prescreening methods, thus considerably reducing the number of mammals required in toxicity testing. http://www.sciencedirect.com/science/article/B6WDM-45F556G-25/1/121bce1063111e232b88e96d482edccd