The participation of the adrenal and thyroid in fat metabolism in hypophysectomized baboons (Papio ursinus)

Zusammenfassung 1. Im Gegensatz zum Hund entwickelt sich beim Pavian keine Fettleber nach Hypophysektomie oder Thyreoidektomie oder nach einer Kombination dieser beiden Eingriffe.2. Thyroxin wirkt als Antagonist hemmend auf die Fettbildung, die durch Cortison beim hypophysektomierten Pavian angeregt wird.3. Starke Leberverfettung entsteht bei hypophysektomierten Pavianen nach gleichzeitiger Entziehung von Cortison und Thyroxin.     

Stem-cell-based therapy and lessons from the heart

The potential usefulness of human embryonic stem cells for therapy derives from their ability to form any cell in the body. This potential has been used to justify intensive research despite some ethical concerns. In parallel, scientists have searched for adult stem cells that can be used as an alternative to embryonic cells, and, for the heart at least, these efforts have led to promising results. However, most adult cardiomyocytes are unable to divide and form new cardiomyocytes and would therefore be unable to replace those lost as a result of disease. Basic questions--for example, whether cardiomyocyte replacement or alternatives, such as providing the damaged heart with new blood vessels or growth factors to activate resident stem cells, are the best approach--remain to be fully addressed. Despite this, preclinical studies on cardiomyocyte transplantation in animals and the first clinical trials with adult stem cells have recently been published with mixed results.     

Strigolactone inhibition of shoot branching

A carotenoid-derived hormonal signal that inhibits shoot branching in plants has long escaped identification. Strigolactones are compounds thought to be derived from carotenoids and are known to trigger the germination of parasitic plant seeds and stimulate symbiotic fungi. Here we present evidence that carotenoid cleavage dioxygenase 8 shoot branching mutants of pea are strigolactone deficient and that strigolactone application restores the wild-type branching phenotype to ccd8 mutants. Moreover, we show that other branching mutants previously characterized as lacking a response to the branching inhibition signal also lack strigolactone response, and are not deficient in strigolactones. These responses are conserved in Arabidopsis. In agreement with the expected properties of the hormonal signal, exogenous strigolactone can be transported in shoots and act at low concentrations. We suggest that endogenous strigolactones or related compounds inhibit shoot branching in plants. Furthermore, ccd8 mutants demonstrate the diverse effects of strigolactones in shoot branching, mycorrhizal symbiosis and parasitic weed interaction.     

Stereocilin-deficient mice reveal the origin of cochlear waveform distortions

Although the cochlea is an amplifier and a remarkably sensitive and finely tuned detector of sounds, it also produces conspicuous mechanical and electrical waveform distortions. These distortions reflect nonlinear mechanical interactions within the cochlea. By allowing one tone to suppress another (masking effect), they contribute to speech intelligibility. Tones can also combine to produce sounds with frequencies not present in the acoustic stimulus. These sounds compose the otoacoustic emissions that are extensively used to screen hearing in newborns. Because both cochlear amplification and distortion originate from the outer hair cells-one of the two types of sensory receptor cells-it has been speculated that they stem from a common mechanism. Here we show that the nonlinearity underlying cochlear waveform distortions relies on the presence of stereocilin, a protein defective in a recessive form of human deafness. Stereocilin was detected in association with horizontal top connectors, lateral links that join adjacent stereocilia within the outer hair cell's hair bundle. These links were absent in stereocilin-null mutant mice, which became progressively deaf. At the onset of hearing, however, their cochlear sensitivity and frequency tuning were almost normal, although masking was much reduced and both acoustic and electrical waveform distortions were completely lacking. From this unique functional situation, we conclude that the main source of cochlear waveform distortions is a deflection-dependent hair bundle stiffness resulting from constraints imposed by the horizontal top connectors, and not from the intrinsic nonlinear behaviour of the mechanoelectrical transducer channel.