Discovery and spectroscopy of the young jovian planet 51 Eri b with the Gemini Planet Imager.

Directly detecting thermal emission from young extrasolar planets allows measurement of their atmospheric compositions and luminosities, which are influenced by their formation mechanisms. Using the Gemini Planet Imager, we discovered a planet orbiting the ~20-million-year-old star 51 Eridani at a projected separation of 13 astronomical units. Near-infrared observations show a spectrum with strong methane and water-vapor absorption. Modeling of the spectra and photometry yields a luminosity (normalized by the luminosity of the Sun) of 1.6 to 4.0 × 10(-6) and an effective temperature of 600 to 750 kelvin. For this age and luminosity, "hot-start" formation models indicate a mass twice that of Jupiter. This planet also has a sufficiently low luminosity to be consistent with the "cold-start" core-accretion process that may have formed Jupiter.

Epidemiological and serological study of hepatitis A virus outbreaks in France: a comparison between immunoadherence and radioimmunoassay.

An epidemiological study and the simultaneous evaluation of anti-HAV antibody using radio immunoassay (RIA) and immunoadherence hemagglutination assay (IAHA) was performed during three hepatitis A epidemics in the Tours area (France). Fifty-seven sera from 35 subjects with viral hepatitis type A and 16 sera from nine children who did not develop any clinical signs of hepatitis were studied. The more explosive epidemic occurred in an institution for mentally retarded children (attack rate 68%). The two major outbreaks observed were due to the introduction of the institutions of individuals infected with hepatitis A virus. Two out of three of the index cases had a seafood dinner three to four weeks before onset of jaundice. Sera taken one week after jaundice were always found to be anti-HAV positive by both RIA and IAHA, and sera taken more than three days before the appearance of jaundice were negative by both methods. Sera taken at the peak of the transaminase elevation were anti-HAV positive by RIA but only one out of two were positive by IAHA. The anti-HAV titre by RIA increased from the time of the appearance of jaundice and the highest titres, over 1/20000 were seen only after several months. Observations of subjects in close contact with patients who seroconverted without any manifestation of hepatitis, confirmed the existence of clinically mute infections.

Hepatitis A diagnosis in man: radioimmunoassay for hepatitis A antigen detection in faeces.

A new radioimmunoassay (RIA) procedure using a double-sandwich technique was developed for the detection of hepatitis A antigen (HAV) in crude faecal extracts for patients involved in three outbreaks of type A hepatitis. Stools were obtained from 24 residents suffering from acute hepatitis A and from six children who remained asymptomatic throughout the epidemic. In addition, the HAV detection was performed in sera from 13 patients with hepatitis. HAV was detected in stools as early as five days before and as late as five days after the onset of jaundice. In this procedure, positive activity was only found in stools from patients with type A hepatitis, but not in negative controls. HAV was not detected in acute-phase sera. The double-sandwich RIA test used appears to be a reliable test for the large-scale screening of HAV in stool samples from patients suffering from type A hepatitis.

[The identification of hepatitis A virus in faeces. Diagnosis and epidemiological value (author's transl)]. / Identification du virus del'hépatite A dans les selles. Intérêt diagnostique et épidémiologique.

During 1976, two hepatitis A epidemics in institutions enabled the authors to study the presence of the virus in the faeces during the course of the disease. After concentration of feacal extracts in polyethyleneglycol 6000, virions were observed by immune electron microscopy. Among 13 stool extracts examined, 11 proved positive. The two negative extracts were samples collected one month after the onset of clinical symptoms and signs. The samples richest in particles were those collected during the preicteric phase of the disease. In those cases in which samples were collected during jaundice, the viral concentration was lower. The limit of detection was a period of five days after the onset of jaundice. Thus, examination for hepatitis A virus in the faeces by electron microscopy may be used to obtain an aetiological diagnosis at the beginning of the disease. In one of the patients, a study of the kinetics of the appearance of antibodies was possible. From the time of onset of jaundice, the presence of specific antibodies was noted, reaching a maximum after two months. In the children's institution, no cases of hepatitis A were seen among those entrants who had received an injection of standard polyvalent gammaglobulin at the time of admission.