Partial purification and characterization of a factor from a cloned thymic epithelium cell line

The culture supernatant from a cloned line of thymic epithelium (TEPI) is shown to enhance the response of thymocytes to alloantigen as measured by cell-mediated lympholysis. The supernatant has no effect on the spleen cell response to alloantigen as measured by cell-mediated lysis and does not contain interleukin 1, interleukin 2, interleukin 3, or interferon-gamma activity. The activity is shown to have an apparent m.w. of 160,000 by Sephacryl S-200 gel permeation chromatography, to have an isoelectric point of 6.5, and to elute from DEAE-Sepharose at 0.07 M NaCl.     

The role of cysteine oxidation in the thermal inactivation of T4 lysozyme

Wild-type T4 lysozyme contains unpaired cysteine residues at positions 54 and 97. To investigate the role these residues play in the thermal inactivation of the wild-type, we constructed a double mutant with these cysteines replaced with valine and serine. This molecule, T4 lysozyme (C54V/C97S), is more stable than the wild-type to inactivation at 70 degrees C at pH 6.5 and 8.0. Guanidine hydrochloride reactivation experiments and SDS-PAGE on the inactivated products show that the wild-type is susceptible to varying degrees of oxidative damage, depending on buffer conditions, while the cysteine-minus mutant inactivates only by other pathways. The products of thermal, oxidative inactivation of the wild-type are disulfide-linked oligomers. The dependence of inactivation rate on temperature suggests that the formation of these aggregates depends on prior thermal unfolding of the T4 lysozyme molecule.     

Odorant-stimulated phosphoinositide signaling in mammalian olfactory receptor neurons

Recent evidence has revived interest in the idea that phosphoinositides (PIs) may play a role in signal transduction in mammalian olfactory receptor neurons (ORNs). To provide direct evidence that odorants indeed activate PI signaling in ORNs, we used adenoviral vectors carrying two different fluorescently tagged probes, the pleckstrin homology (PH) domains of phospholipase Cδ1 (PLCδ1) and the general receptor of phosphoinositides (GRP1), to monitor PI activity in the dendritic knobs of ORNs in vivo. Odorants mobilized PI(4,5)P₂/IP₃ and PI(3,4,5)P₃, the substrates and products of PLC and PI3K. We then measured odorant activation of PLC and PI3K in olfactory ciliary-enriched membranes in vitro using a phospholipid overlay assay and ELISAs. Odorants activated both PLC and PI3K in the olfactory cilia within 2 s of odorant stimulation. Odorant-dependent activation of PLC and PI3K in the olfactory epithelium could be blocked by enzyme-specific inhibitors. Odorants activated PLC and PI3K with partially overlapping specificity. These results provide direct evidence that odorants indeed activate PI signaling in mammalian ORNs in a manner that is consistent with the idea that PI signaling plays a role in olfactory transduction.     

Biophysical Underpinnings of the Repeat Length Dependence of Polyglutamine Amyloid Formation

There are now 10 expanded CAG repeat diseases in which both disease risk and age of onset are strongly dependent on the repeat length of the polyglutamine (polyQ) sequence in the disease protein. Large, polyQ-rich inclusions in patient brains and in cell and animal models are consistent with the involvement of polyQ aggregation in the disease mechanism. This possibility is reinforced by studies showing strong repeat length dependence to the aggregation process, qualitatively mirroring the repeat length dependence of disease risk. Our understanding of the underlying biophysical principles that mediate the repeat length dependence of aggregation, however, is far from complete. A previous study of simple polyQ peptides showed that N*, the size of the critical nucleus that controls onset of aggregation, decreases from unfavorable tetramer to favorable monomer over the range Q₂₃ to Q₂₆. These data, however, do not explain why, for all peptides exhibiting N* ∼ 1, spontaneous aggregation rates continue to increase with increasing repeat length. Here we describe a novel kinetics analyses that maps out the nonlinear dependence with repeat length of a nucleation efficiency term that is likely related to aspects of nucleus structure. This trend accounts for why nucleus size increases to tetrameric at repeat lengths of Q₂₃ or below. Intriguingly, both aggregation and age of onset trend with repeat length in similar ways, exhibiting large changes per added Gln at low repeat lengths and small changes per added Gln at relatively long repeat lengths. Fibril stability also increases with repeat length in a nonlinear fashion.     

Kontrolle der Eiablage der Brachfliege (Leptohylemyia coarctata Fallén) als Voraussetzung für die Befallsprognose und Bekämpfung

Study of bean plants infected by tabacco mosaic virus and potato X virus was performed. Virus infection of bean plants induced the injury of structural state of photosynthetic apparatus, viz., the a/b chlorophyll ratio decreased and the main photosynthetic membrane lipid monogalactosyl diacylglycerol degradation took place with parallel accumulation of intermediate compound suggested to perform a signal function. Phospholipid and free sterol content increase pointed out on the changes of the membrane fluidity and permeability. Accumulation of sulphoquinovosyl diacylglycerol in infected plants evidences the probability of latter to play important roles in adaptive reactions of photosynthetic apparatus.     

Comparative morphology of cotylephores in Platystacus and Solenostomus: modifications of the integument for egg attachment in skin-brooding fishes

External skin brooding evolved independently in several groups of fishes. Cotylephores, sites for the attachment of developing embryos, occur within the fused pelvic fins of the ghost pipefishes, Solenostomus, on the ventral surface of the South American catfish, Platystacus, and on other aspredinid cattfishes of the tribe Aspredini. Cotylephores are transient outgrowths of tissue that occur only on brooding fish. They consist of a pedicle that extends from the abdomen or fin and terminates in an apical calyx. The calyx supports and adheres to the egg envelope that encloses the developing embryo. The pedicle of the catfish cotylephore is a single, large structure (1615 ± 23.25 μm), while those of ghost pipefishes are small and branched (687 ± 3.89 μm; number of branches: 26 ± 0.63). In both instances, a simple cuboidal epithelium, whose cells bear microplicae, encloses an extensive connective tissue core that contains large blood vessels that ramify into a capillary plexus in the calyx. Cotylephores of Platystacus are more heavily vascularized than those of Solenostomus and contain 34.77% more blood vessel surface area at the calyx, to which the egg envelope adheres. In addition to their role in attachment, cotylephores may function in embryonic maintenance through the exchange of gas across the egg envelope, mediated by female circulatory vessels within the cotylephore calyx. Comparisons of morphology and development suggest that cotylephores are the result of convergent evolution of a reproductive adaptation. This revised version was published online in July 2006 with corrections to the Cover Date.