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‣ Targeted disruption of the mouse Stat3 gene leads to early embryonic lethality

Takeda, Kiyoshi; Noguchi, Koichi; Shi, Wei; Tanaka, Takashi; Matsumoto, Makoto; Yoshida, Nobuaki; Kishimoto, Tadamitsu; Akira, Shizuo
Fonte: The National Academy of Sciences of the USA Publicador: The National Academy of Sciences of the USA
Tipo: Artigo de Revista Científica
Publicado em 15/04/1997 Português
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451.23344%
Signal transducer and activator of transcription (STAT) proteins have been shown to mediate biological actions in response to cytokines. Stat3, a member of the STAT family, is activated by a variety of cytokines, including the interleukin 6 family of cytokines, leptin, granulocyte colony-stimulating factor, and epidermal growth factor. To address the biological function of Stat3, we generated mice deficient in Stat3 by gene targeting. No viable Stat3-deficient mice could be obtained from heterozygote intercross. Analysis of embryos at several gestation times revealed that Stat3-deficient embryos showed a rapid degeneration between embryonic days 6.5 and 7.5, although they developed into the egg cylinder stage until embryonic day 6.0. These results demonstrate that Stat3 is essential for the early development of mouse embryos.

‣ In situ molecular association of dystrophin with actin revealed by sensitized emission immuno-resonance energy transfer

Root, Douglas D.
Fonte: The National Academy of Sciences of the USA Publicador: The National Academy of Sciences of the USA
Tipo: Artigo de Revista Científica
Publicado em 27/05/1997 Português
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451.23344%
A novel method was developed to detect molecular associations of dystrophin with actin in cryostat muscle tissue sections by combining resonance energy transfer technology with immunohistochemical techniques. This method takes advantage of the long phosphorescent lifetime of terbium chelates, a property that enables the accurate determination of energy transfer in biological tissues by lifetime measurements of sensitized emission. After a brief excitation pulse, terbium chelates emit for milliseconds after the intrinsically high autofluorescence of biological specimens has decayed to negligible levels. Rat skeletal muscle tissue sections were labeled with both anti-dystrophin monoclonal antibody conjugated to a terbium-based resonance energy transfer donor and anti-actin tetramethylrhodamine phalloidin as an acceptor. Resonance energy transfer between the two probes indicated that the distance separating the probes is within 10 nm (about the size of an IgG2b antibody molecule). The fraction of antibodies that participated in resonance energy transfer was estimated to be 80–90% because of the close agreement between the quenching of donor phosphorescence and the efficiency of resonance energy transfer revealed by lifetime measurements of sensitized emission by tetramethyl-rhodamine phalloidin. Sensitized emission was detectable only when both anti-dystrophin antibody and tetramethyl-rhodamine phalloidin were present. These results indicate that actin and dystrophin are closely associated within the cell. This method is potentially applicable to the investigation of many types of intracellular associations.

‣ Construction of hybrid proteins that migrate retrogradely and transynaptically into the central nervous system

Coen, Laurent; Osta, Rosario; Maury, Martine; Brûlet, Philippe
Fonte: The National Academy of Sciences of the USA Publicador: The National Academy of Sciences of the USA
Tipo: Artigo de Revista Científica
Publicado em 19/08/1997 Português
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451.23344%
The nontoxic proteolytic C fragment of tetanus toxin (TTC peptide) has the same ability to bind nerve cells and be retrogradely transported through a synapse as the native toxin. We have investigated its potential use as an in vivo neurotropic carrier. In this work we show that a hybrid protein encoded by the lacZ–TTC gene fusion retains the biological functions of both proteins in vivo—i.e., retrograde transynaptic transport of the TTC fragment and β-galactosidase enzymatic activity. After intramuscular injection, enzymatic activity could be detected in motoneurons and connected neurons of the brainstem areas. This strategy could be used to deliver a biological activity to neurons from the periphery to the central nervous system. Such a hybrid protein could also be used to map synaptic connections between neural cells.