Giant input neurons of the mushroom body: intracellular recording and staining in the cockroach

Covalent complexes of nucleic acids and proteins are widespread among viruses. Covalent complexes of RNA and proteins are proposed to exist in eukaryotic cells. The goal of this work was to obtain specific antibodies to the covalent linkage unit (CLU) between virus RNA and protein to search cellular RNA-protein complexes. Antibodies were generated by direct immunization of a rabbit with the BSA-coupled EMC virus RNA-VPg complex. By a dot-blot immunoassay and immunofluorescent microscopy it was found that the antibodies specifically recognize both EMC virus RNA-VPg and synthetic CLU-containing compounds. Thus, a fraction of the antibodies was directed to CLU.     

Mushroom bodies of the cockroach: activity and identities of neurons recorded in freely moving animals

This article describes novel attributes of the mushroom bodies of cockroaches revealed by recording from neurons in freely moving insects. The results suggest several hitherto unrecognized functions of the mushroom bodies: extrinsic neurons that discriminate between imposed and self-generated sensory stimulation, extrinsic neurons that monitor motor actions, and a third class of extrinsic neurons that predict episodes of locomotion and modulate their activity depending on the turning direction. Electrophysiological units have been correlated with neurons that were partially stained by uptake of copper ions and silver intensification. Neurons so revealed correspond to Golgi-impregnated or Lucifer yellow-filled neurons and demonstrate that their processes generally ascend to other areas of the protocerebrum. The present results support the idea of multiple roles for the mushroom bodies. These include sensory discrimination, the integration of sensory perception with motor actions, and, as described in the companion article, a role in place memory.     

Fiber Bragg grating cryogenic temperature sensors

Temperature sensing to as low as 80 K was demonstrated with 1.55-μm fiber Bragg gratings. The gratings were bonded on substrates to increase sensitivity, and a shift of the reflection wavelength was measured. The temperature sensitivity was 0.02 nm/K at 100 K when an aluminum substrate was used and 0.04 nm/K at 100 K when a poly(methyl methacrylate) substrate was used. These values are smaller than those at room temperature because of the nonlinearity of both the thermal expansion and the thermo-optic effect. Extension to the liquid helium temperature is also discussed.     

Bragg gratings in multimode and few-mode optical fibers

Bragg gratings in optical fibers in multimode propagation are investigated experimentally and theoretically. Bragg gratings formed in optical fibers in multimode propagation show multiple reflection peaks or multiple transmission dips in the reflection or transmission spectra, respectively. For standard graded-index multimode fiber, the number of reflection peaks of a Bragg grating depends on excitation condition of propagating modes. The number of reflection peaks of a Bragg grating at around 1.55 μm is 19 for highly multimode excitation and 3-4 for lower order mode excitation. We analyze the phase-matching conditions of the propagating modes and identify half of the reflection peaks as the reflection to the same mode and the rest as the reflection to the neighboring modes. In dispersion-shifted fiber, a Bragg grating at around 0.8 μm in three-mode propagation shows three reflection peaks in the reflection spectrum. The temperature dependence of each reflection peak is similar to that of a conventional Bragg grating in single-mode fiber. Polarization dependence measured on a Bragg grating in multimode graded-index fiber is negligible. An advantage of Bragg gratings in multimode fiber (MMF) and the applications are discussed     

Computer control of fiber Bragg grating spectral characteristicsusing a thermal head

We present a new technique for arbitrarily controlling the temperature distribution in fiber Bragg gratings (FBG's) to control their spectral characteristics. A thermal head consisting of a microheater array, driven with computer control signals is used as a controlling device. Various spectral characteristics including a chirped grating and a transmission filter are demonstrated using a single unchirped grating. An effective improvement in response time constant of thermal control was observed on bonding of the fiber grating to thermal head (18 ms), in comparison to that without bonding (40 ms). The measured results did not show any hysterisis. Reliability studies of this technique are also reported. The same technique is further used for the dual wavelength operation of an Er-doped fiber laser     

Multiple-order stokes pulse generation by nitrogen-laser-pumped fiber Raman laser

A multimode silica-core fiber Raman laser was pumped by a compact Blumlein-type nitrogen laser. Four orders of Stokes pulses were obtained in the range of 341-359 nm at 280 MW/cm²fiber input. All the Stokes pulses were expanded by modal dispersion. The threshold of each Stokes pulse was measured and the energy transfer to the next order was observed. Conditions for efficient conversion to the required-order Stokes pulse are discussed.     

Mushroom bodies of the cockroach: their participation in place memory

Insects and other arthropods use visual landmarks to remember the location of their nest, or its equivalent. However, so far, only olfactory learning and memory have been claimed to be mediated by any particular brain region, notably the mushroom bodies. Here we describe the results of experiments that demonstrate that the mushroom bodies of the cockroach (Periplaneta americana), already shown to be involved in multimodal sensory processing, play a crucial role in place memory. Behavioral tests, based on paradigms similar to those originally used to demonstrate place memory in rats, demonstrate a rapid improvement in the ability of individual cockroaches to locate a hidden target when its position is provided by distant visual cues. Bilateral lesions of selected areas of the mushroom bodies abolish this ability but leave unimpaired the ability to locate a visible target. The present results demonstrate that the integrity of the pedunculus and medial lobe of a single mushroom body is required for place memory. The results are comparable to the results obtained from hippocampal lesions in rats and are relevant to recent studies on the effects of ablations of Drosophila mushroom bodies on locomotion.     

Short-wavelength stimulated Raman scattering in a silica fiberpumped by an XeBr excimer laser

A UV-grade silica optical fiber was pumped by a 281.8-nm XeBr excimer laser. The first Stokes spectrum was observed at 285 nm. The spectral width was one-half of that of the spontaneous Raman spectrum. A numerical analysis of stimulated Raman scattering which includes two-photon absorption loss is presented. The Raman gain coefficient, determined by an analysis of the nonlinearity observed in the Stokes output, was 1.8×10^-5 cm/MW. The analysis also indicates that two-photon absorption is a more important loss factor than linear attenuation. The short wavelength limit of net amplification by stimulated Raman scattering is estimated to be 272 nm     

Topography of four classes of Kenyon cells in the mushroom bodies of the cockroach

The authors compared 218 black and 68 white nursing home patients with dementia for differences in the prevalence, recognition, and treatment of depression. There were no racial differences in depressive symptoms, but whites were significantly more likely to receive a diagnosis of "possible depression" and there were few racial differences in clinical, social, or demographic factors associated with depression. Depression was often unrecognized and undertreated in both racial groups; several depression instruments developed for use in dementia had good reliability and validity among blacks; and there were no significant differences in depressive symptoms or diagnosis between U.S.-born and Caribbean-born black patients. The absence of any appreciable interracial or intraracial differences in depression symptoms or diagnoses may reflect uniformity in nursing home selection criteria or lessening of mood differences that may have existed before admission.