There is a well-known controversy among scientific societies regarding the recommendation to screen for thyroid dysfunction (TD) during pregnancy. Although several studies have shown an association between maternal subclinical hypothyroidism and/or hypothyroxinemia with obstetric problems and/or neurocognitive impairment in the offspring, there is only limited evidence on the possible positive effects of thyroxine (T 4 ) treatment in such cases. Despite the scarcity of this evidence, there is a widespread agreement among clinicians on the need for treatment of clinical hypothyroidism during pregnancy and the risks that could arise due to therapeutic abstention. As maternal TD is a quite prevalent condition, easily diagnosed and for which an effective and safe treatment is available, some scientific societies have proposed to assess thyroid function during the first trimester of pregnancy and ideally before week 10 of gestational age. Given the physiologic changes of thyroid function during pregnancy, hormone assessment should be performed using trimester-specific reference values ideally based on locally generated data as geographic variations have been detected. Screening of TD should be based on an initial determination of TSH performed early during the first trimester and only if abnormal should it be followed by either a free or total T 4 measurement. Furthermore, adequate iodine supplementation during pregnancy is critical and if feasible it should be initiated before the woman attempts to conceive.

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The Junin virus is the agent of hemorrhagic Argentine fever. It was isolated in 1958 by Parodi et al. (1) from a human being. It has been tentatively classified as a member of Arboviruses by its biological and epidemiological features.In order to confirm its classification it is necessary to know in more detail its properties, size and the chemical nature of its nucleic acid.Junin virus reproduces not only in new born mouse brain, but also in guinea pigs in which case it is possible to observe a viremia till the death of the animal. Therefore, we used infected guinea pig plasma for our studies. Materials and Methods Virus. Plasma from guinea pigs infected with Junin virus, strain XJwith several passages in guinea pigs and mice was used.The dilutions of the virus were made in steril isotonic phosphate buffer pH 7.4 with 2% of inactivated normal rabbit serum, 1000 U/ml. penicillin and 100 ug/ml, streptomycin, in every ease, if not otherwise stated. The infected plasma was prepared by inoculation of guinea pigs (200--250grs. weight) with a 10 -3 dilution of virus in a dose of 0.2 ml. by intramuscular route. Eleven days after the inoculation they were bled and the blood collected with heparin.

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