Non-fermi-liquid scaling in Ce(Ru0.5Rh)2Si2.

We study the temperature and field dependence of the magnetic and transport properties of the non-Fermi-liquid (NFL) compound Ce(Ru0.5Rh0.5)2Si2. For fields H less, similar0.1 T the results suggest that the observed NFL behavior is disorder driven. For higher fields, however, magnetic and transport properties are dominated by the coupling of the conduction electrons to critical spin fluctuations. The temperature dependence of the susceptibility as well as the scaling properties of the magnetoresistance are in very good agreement with the predictions of recent dynamical mean-field theories of Kondo alloys close to a spin-glass quantum critical point.

Effect of cholesterol on apolipoprotein A-I binding to lipid bilayers and emulsions.

The effects of cholesterol (Chol) on the interaction of apolipoprotein A-I (apoA-I) with phospholipid bilayer vesicles and lipid emulsions were investigated. ApoA-I bound to phosphatidylcholine (PC) vesicles with higher affinity and lower capacity compared to triglyceride-PC emulsions. An increase in surface Chol in triglyceride-PC emulsions decreased the binding capacity without changing the binding affinity. In contrast, addition of Chol to PC vesicles caused a marked increase in capacity and decrease in affinity for apoA-I binding. ApoA-I caused a large release of entrapped aqueous dye, calcein, from PC vesicles, whereas this apoA-I-induced leakage was relatively small in the vesicles containing Chol. The incorporation of phosphatidylethanolamine into the vesicles also exerted effects similar to those of Chol on apoA-I binding and calcein leakage. The shifts of fluorescence emission maximum of dansyl lysine, probing the surface region of membranes, indicated that Chol as well as phosphatidylethanolamine increased the headgroup space of the vesicles. The binding maximum of apoA-I was closely correlated with the emission maximum of dansyl lysine, not with the fluorescence anisotropy of I-[4-(trimethylamino)phenyl]phenylhexatriene, suggesting that the binding capacity of apoA-I to the bilayer surface was modulated by the headgroup space rather than the acyl chain fluidity. These results show that Chol affects the bilayer surface so as to allow more apoA-I to bind to bilayers and may suggest the possibility of the interaction of apoA-I with Chol-enriched membrane domains.

Morphogenesis of the photoreceptive site and development of the electrical responses in the butterfly genital photoreceptors during the pupal period.

This paper describes the process of morphogenesis of the photoreceptive site of the butterfly genital photoreceptors. Associated development of the electrical responses is also described. The photoreceptor is a sensory neuron whose cell body is located in the genitalia and has a photoreceptive site of the phaosome-type. This consists of the distal processes and the tubular membranes, which protrude from the tip of distal processes. Phaosome morphogenesis was studied using electron microscopy. The results indicate that morphogenesis occurs in the latter half of the pupal period and that the process is divided into five phases. First, the tubular membranes appear as small membrane protrusions (phase I). The short tubular membranes emerge from several portions of the cell body forming several membrane clusters (phase II). The clusters then collect to form a small phaosome. Short distal processes become evident (phase III). The phaosome volume increases, mainly due to the extensive elongation and bifurcation of both tubular membranes and distal processes (phase IV). Phase V achieves final adult morphology. The photoreceptors of phase II are already able to produce spikes in response to light stimulation, although the sensitivity was about one tenth of the adult. The sensitivity increase occurred in parallel with the increase in the phaosome volume.

Ultrastructure of the extraocular photoreceptor in the genitalia of a butterfly, Papilio xuthus.

This paper describes the ultrastructure of a sensory neuron found in the extraocular photoreceptive site on the butterfly genitalia. Our previous studies have shown that there are two pairs of the photoreceptive sites in a butterfly (four per individual). Each photoreceptive site is recognizable by a transparent area in the pigmented cuticle of the genitalia. From the nerve that extends from the transparent cuticle to the last abdominal ganglion, a sustained train of single unit spikes can be recorded in response to a light flash. The single unit spikes disappear when the transparent cuticle is covered, thus indicating that a single photoreceptor exists close to it. Here, we examined complete serial semithin sections of plastic-embedded photoreceptive sites of both male and female, and observed an ovoid structure close to the transparent cuticle. The structure contained the cell body of a sensory neuron whose axon was in the nerve branch from which the photoresponse had been recorded. Further electron microscopy revealed that the cell body extended a few distal processes that protrude tubular membrane from the tip, forming a structure resembling the phaosome (from Greek; phaos = light, some = body) which was first described in the earthworm dermal photoreceptors. The sensory neuron was also found in a surgically isolated nerve-photoreceptor preparation that responded to the light. We therefore propose that the phaosome-containing sensory neuron is the butterfly genital photoreceptor.