Characterization of a glucuronyltransferase: neolactotetraosylceramide glucuronyltransferase from rat brain

The properties of a rat brain glucuronyltransferase, which is presumed to be associated with the biosynthesis of the HNK-1 epitope on sulfoglucuronyl glycolipids, are described. The enzyme required divalent cations for reaction, with maximal activity at 10mm Mn²⁺, and exhibited a dual optimum at pH 4–5 and pH 6 depending upon the buffer used, with the highest activity at pH 4.5 in MES buffer. This enzyme strictly recognized the Gal1-4GlcNAc terminal structure, and was highly specific for neolacto (type 2) glycolipids as acceptor. The enzyme was localized specifically in the brain, and was barely detected in other issues, including the thymus, spleen, liver, kidney, lung, and sciatic nerve fibres. Phosphatidylinositol and phosphatidylserine increased the enzymatic reaction 4.4- and 2.3-fold, respectively, whereas phosphatidylcholine slightly decreased the rate.Abbreviations GlcA glucuronic acid - Lc-PA₁₄ lactotetraose-phenyl-C₁₄H₂₉ - nLc-PA₁₄ neolactotetraose-phenyl-C₁₄H₂₉ - nLcOse₄-Cer neolactotetraosylceramide - NP-40 Nonidet P-40 - PC phosphatidylcholine - PE phosphatidylethanolamine - PI phosphatidylinositol - PS phosphatidylserine - SGGL sulfoglucuronyl glycolipid     

Dynamics of cockroach ocellar neurons

The incremental responses from the second-order neurons of the ocellus of the cockroach, Periplaneta americana, have been measured. The stimulus was a white-noise-modulated light with various mean illuminances. The kernels, obtained by cross-correlating the white-noise input against the resulting response, provided a measure of incremental sensitivity as well as of response dynamics. We found that the incremental sensitivity of the second-order neurons was an exact Weber-Fechner function; white-noise-evoked responses from second-order neurons were linear; the dynamics of second-order neurons remain unchanged over a mean illuminance range of 4 log units; the small nonlinearity in the response of the second-order neuron was a simple amplitude compression; and the correlation between the white-noise input and spike discharges of the second-order neurons produced a first-order kernel similar to that of the cell's slow potential. We conclude that signal processing in the cockroach ocellus is simple but different from that in other visual systems, including vertebrate retinas and insect compound eyes, in which the system's dynamics depend on the mean illuminance.     

Visual interneurons in the lobula complex of the fleshfly,Boettcherisca peregrina

Summary The physiology and morphology of visual interneurons in the lobula complex of the fleshfly,Boettcherisca peregrina, were studied using intracellular recordings and intracellular cobalt stainings, respectively. Using responses to movements of a spot of light and on-off stimuli at single positions, we classified the interneurons into five physiological groups ON, OFF, ON-OFF, nondirectional motion sensitive (NDM) and directional motion sensitive (DM) neurons. They could be further divided into four morphological types, depending on the location and extent of their dendrites and terminal branches.     

The Receptor Potential of the Taste Cell of the Rat

The electrical responses of the taste cell of the rat to chemical stimuli were studied by means of microelectrode techniques. Although large positive potential changes in the taste cell were usually elicited by taste stimuli, the response was a small negative potential change with respect to surrounding tissues if the microelectrode was thrust deeply into the taste bud. Both FeCl₃ and cocaine produced a positive change in the steady potential. If this new potential is larger than a certain equilibrium potential, reversal of the polarity of the potential change caused by a taste stimulus is observed. Gamma-aminobutyric acid and acetylcholine had no effect on the receptor steady potential nor on the receptor responses elicited by taste stimuli.     

Detection of Antibody-Coated Bacteria in Expectorated Sputum for Diagnosis of Lower Respiratory Infections

We evaluated antibody-coated bacteria (ACB) in expectorated sputum to discriminate contaminating or colonizing organisms from true pathogens. We examined 60 expectorated sputum samples from 51 patients with lower respiratory infections (chronic obstructive pulmonary disease 25, pneumonia 20, purulent tracheobronchitis 6). All samples were examined with quantitative culture and immunofluorescent demonstration of ACB. From the results of quantitative culture, we divided specimens into pathogen-isolated and pathogen-free samples. Among pathogen-isolated samples, in which we isolated accepted pathogenic organisms at ≥ 10⁷ colony-forming units per ml, 16 of 23 samples were ACB-positive (69.5%). In contrast, among pathogen-free samples, in which we isolated accepted pathogens at < 10⁷ colony forming units per ml or only upper respiratory flora, only 3 of 37 samples were ACB-positive (8.1%). The ACB-positive rate was significantly higher in pathogen-isolated than in pathogen-free samples (P < 0.001). Consequently, detecting ACB in expectorated sputum shows good potential as another criterion for distinguishing contaminating or colonizing organisms from true pathogens.     

PCR method for genotyping and zygosity-testing of RasH2 transgenic mice.

In short-term carcinogenicity testing using CB6F1-TgrasH2 mice, sibling nonTgrasH2 mice are used as a negative control. However, selection of TgrasH2 and nonTgrasH2 mice has been performed by PCR with only transgene specific primers by the conventional method. Therefore, the conventional method involves the risk of false negative results due to reaction failure, and contamination with TgrasH2 mice in the control mice group. Based on the nucleotide sequence information around the pre-integration site, we developed a genotyping method for distinguishing not only TgrasH2 mice (hemizygous for the Tg allele) but also nonTgrasH2 (homozygous for the nonTg allele) in a positive manner.     

Proteins and Carbohydrates in Xylem Sap from Squash Root

The xylem sap from squash roots was collected from the cut surfaceof stems, and the proteins and carbohydrates in the sap wereanalyzed. The sap contained 18.6 µg ml^–1 proteinand the major polypeptides were as follows: 1) two polypeptides,of 75 and 40 kDa, with high-mannose glycans, the levels of whichincreased for about 24 h after cutting and then decreased; 2)a 32-kDa polypeptide, which appeared soon after cutting, disappearedand then reappeared again 48–64 h after cutting; and 3)a 19-kDa and a 14-kDa polypeptide, which were present constitutively.The carbohydrates contained in the xylem sap were fractionatedinto 80% ethanol-soluble and -insoluble material, and whichwere analyzed by high-performance liquid chromatography, gaschromatography and enzymatic mathods. The former fraction containedconsiderable amounts of myo-inositol and fructose as free sugarsand oligosaccharides composed mainly of galactose, arabinoseand glucose. The latter contained polysaccharides composed mainlyof uronic acids, galactose and arabinose. The possible significanceof these substances, which may mediate the interactions betweenthe root and the aerial organs, is discussed. (Received April 20, 1992; Accepted July 4, 1992)     

Receptive field of the stemmata in the swallowtail butterflyPapilio

Summary Receptive fields of individual retinular cells in the stemmata ofPapilio xuthus L. were examined electrophysiologically, and the receptive field of the complete stemmatal system was reconstructed (Fig. 8).In stemmata I-IV, proximal retinular cells have narrow receptive fields (acceptance angles of = 1.7–5 °, Fig. 5) and small inclinations of the visual axes (inclinations of = 0.7–1.5 °, Fig. 2) with respect to the axis of the stemma, while distal ones have wide fields ( =7–13 °, Fig. 5) and large inclinations of the visual axes ( = 5–10 °, Fig. 3). In stemmata V and VI, both proximal and distal retinular cells have wide receptive fields ( = 7–26 °, Fig. 6) and have large inclinations of their visual axes ( = 9–19 °) with respect to the axis of the stemma except for one proximal cell ( = 0 °) (Fig. 4).The spatial properties of distal and proximal retinular cells, combined with the finding that distal cells are homogeneous in the spectral sensitivity while proximal ones are heterogeneous (Ichikawa and Tateda 1980), suggest that the distal cells may be concerned largely with the detection of objects and proximal cells are involved with the discrimination of the color and shape of the detected objects.