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Science ; 365(6460): 1441-1445, 2019 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-31604272


Surveys have shown that super-Earth and Neptune-mass exoplanets are more frequent than gas giants around low-mass stars, as predicted by the core accretion theory of planet formation. We report the discovery of a giant planet around the very-low-mass star GJ 3512, as determined by optical and near-infrared radial-velocity observations. The planet has a minimum mass of 0.46 Jupiter masses, very high for such a small host star, and an eccentric 204-day orbit. Dynamical models show that the high eccentricity is most likely due to planet-planet interactions. We use simulations to demonstrate that the GJ 3512 planetary system challenges generally accepted formation theories, and that it puts constraints on the planet accretion and migration rates. Disk instabilities may be more efficient in forming planets than previously thought.

Vet Rec ; 137(11): 266-9, 1995 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-7502465


The aim of this study was to control endemic contagious agalactia due to Mycoplasma agalactiae in a semi-extensive goat herd by means of vaccination with an inactivated vaccine. Groups of 400 goats were vaccinated one month before and three months after parturition (group A), one month before and four months after parturition (group B), and two months and one month before and three months after parturition (group C). The experiment continued over six lactations and natural infections were monitored clinically, immunologically and microbiologically. After the sixth lactation there were no significant clinical differences between these two groups and group C. The levels of growth-inhibiting antibodies ranged from 1:20 to 1:80 in groups A and B and from 1:40 to 1:160 in group C. The numbers of goats excreting mycoplasmas decreased to a greater extent in group C than in groups A and B. A natural infection induced an outbreak of contagious agalactia in group B. An experimental infection with 10(6) cfe affected seven of 10 goats in group A (two seriously) and two goats in group C moderately. It is recommended that three doses of vaccine should be administered before, and one dose after each parturition, and that the herd should be kept isolated in order to control the disease.

Vacinas Bacterianas/administração & dosagem , Doenças das Cabras/prevenção & controle , Infecções por Mycoplasma/veterinária , Mycoplasma/imunologia , Animais , Anticorpos Antibacterianos/sangue , Feminino , Doenças das Cabras/epidemiologia , Doenças das Cabras/imunologia , Cabras , Esquemas de Imunização , Incidência , Leite/microbiologia , Infecções por Mycoplasma/epidemiologia , Infecções por Mycoplasma/imunologia , Infecções por Mycoplasma/prevenção & controle , Fatores de Tempo , Vacinas de Produtos Inativados/administração & dosagem
Anal Biochem ; 200(1): 176-9, 1992 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-1595892


A stopped-flow FIA adaptation of the classical Ellman's colorimetric procedure for the measurement of acetylcholinesterase or cholinesterase activity is described. The samples are injected into a flow analytical system which is provided with an electronic timer and an electrovalve in order to stop the flow when the sample is inside the measurement cell. In this way, the absorbance-time relationship is obtained with a savings of sample, time, and reagents.

Acetilcolinesterase/sangue , Butirilcolinesterase/sangue , Acetiltiocolina/química , Ácido Ditionitrobenzoico/química , Humanos , Concentração de Íons de Hidrogênio , Indicadores e Reagentes , Análise Espectral , Temperatura
J Bacteriol ; 174(2): 646-9, 1992 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-1309530


Assays of CDP-glycerol:poly(glycerophosphate) glycerophosphotransferase (CGPTase) (EC in membranes isolated from Bacillus subtilis 168 wild type and 11 strains bearing conditional lethal thermosensitive mutations in tagB, tagD, or tagF revealed that CGPTase deficiency was associated only with mutant tagF alleles. In vitro, thermosensitivity of CGPTase strongly suggests that the structural gene for this enzyme is tagF. We discuss apparent discrepancies between biochemical evidence favoring a membrane location for TagF and a previous report that suggested a cytoplasmic location based on sequence analysis.

Bacillus subtilis/genética , Parede Celular/química , Genes Bacterianos , Fosfotransferases/genética , Ácidos Teicoicos/biossíntese , Transferases (Outros Grupos de Fosfato Substituídos) , Bacillus subtilis/química , Bacillus subtilis/enzimologia , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Parede Celular/enzimologia , Óperon , Fosfotransferases/fisiologia
J Gen Microbiol ; 137(4): 921-8, 1991 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-1649892


A biochemical analysis was undertaken of thermosensitive mutants of Bacillus subtilis 168 harbouring mutations in several tag genes, involved in the synthesis of the major wall teichoic acid, poly(glycerol phosphate), poly(groP). Incorporation of a pulse of [2-3H]glycerol into whole cells, following shift to the restrictive growth temperature, was used to assess synthesis of this polymer and to seek evidence of accumulation of a specific precursor. The rate of incorporation into poly(groP) was strongly decreased in all mutants; glycerol uptake was diminished by 80% or more for a strain harbouring mutation tagB1 (formerly tag-1) and one bearing tagD11 (formerly tag-11). The pool of CDP-glycerol (CDP-gro), a specific precursor of poly(groP), was increased, relative to the wild-type, for all mutations except tagD11, where the pool of CDP-gro was reduced. Cytoplasmic extracts, assayed at the permissive temperature for glycerol-3-phosphate cytidylyltransferase (gro-PCT), the enzyme synthesizing CDP-gro, revealed wild-type activities for all mutations except tagD11. Gro-PCT activity in the latter strain was 100-fold lower and, unlike that in all other mutant strains, highly thermolabile. This thermosensitivity suggests that tagD encodes gro-PCT. The identification, in a gene encoding a poly(groP)-specific enzyme, of a mutation conferring a thermosensitive growth phenotype renders explicit the conclusion that synthesis of this teichoic acid is essential for the growth of B. subtilis.

Bacillus subtilis/genética , Mutação , Nucleotidiltransferases/genética , Ácidos Teicoicos/metabolismo , Bacillus subtilis/enzimologia , Bacillus subtilis/crescimento & desenvolvimento , Genes Bacterianos , Genes Letais , Glicerol/metabolismo , Substâncias Macromoleculares , Nucleotidiltransferases/metabolismo , Solubilidade , Especificidade por Substrato , Temperatura