The abdominal ganglion of Aplysia brasiliana: A comparative morphological and electrophysiological study,with notes on A. dactylomela

The ultrastructure and electrophysiological properties of neurons in the abdominal (visceral) ganglion of the marine opisthobranch gastropod Aplysia brasiliana have been investigated to determine whether this preparation compares favorably with the well studied A. californica for neurobiological research. In general, the topography, morphology and physiological characteristics, including synaptic connections, of neurons in this ganglion are quite similar to those of A. californica. There is close correspondence between the two animals in terms of each of the identified cells or neuronal clusters in the ganglion, including the presence of the cell L10 (interneuron I) in A. brasiliana which makes synaptic connections comparable with those in A. californica. New follower cells of this interneuron have been found in A. brasiliana. This species offers some advantages in that the connective tissue surrounding the ganglion is thinner and more transparent, making cell identification and penetration easier. A. brasiliana appears to exhibit the behaviors of A. californica that have been used in previous functional analyses of neural circuits. In addition, this species swims and exhibits a ?burrowing”? activity less commonly seen in A. californica. The rich repertoire of behaviors and accessibility of large identifiable and functionally interconnected neurons makes this species of Aplysia an excellent model preparation for future neurobiological studies. Similar, less thorough, investigations of the abdominal ganglion of A. dactylomela indicate that this species is also very similar to A. californica in terms of the identified cells in the abdominal ganglion.     

Isolation of a photoactive photosynthetic reaction center-core antenna complex from Heliobacillus mobilis

A photoactive reaction center-core antenna complex was isolated from the photosynthetic bacterium Heliobacillus mobilis by extraction of membranes with Deriphat 160c followed by differential centrifugation and sucrose density gradient ultracentrifugation. The purified complex contained a Mr 47,000 polypeptide(s) that bound both the primary donor (P800) and approximately 24 antenna bacteriochlorophylls g. Time-resolved fluorescence emission spectroscopy indicated that the antenna bacteriochlorophylls g are active in energy transfer to P800, exhibiting a decay time of 25 ps. The complex contained 1.4 menaquinones, 9 Fe, and 3 labile S2- per P800. The complex was photoactive with an exponential decay time of 14 ms for P800+ yet showed no EPR-detectable Fe-S center signal in the g less than or equal to 2.0 region, either by chemical reduction to -600 mV or by illumination of reduced samples. The complex is similar to photosystem I of oxygen-evolving photosynthetic systems in that both the primary donor and a core antenna are bound to the same pigment-protein complex.     

Growth of Clostridium perfringens in cooked chili during cooling

U.S. Department of Agriculture regulations require that brick chili be cooled from 48.9 degrees C to 4.4 degrees C within 2 h of cooking, but processors may not always be able to comply. Studies were conducted to evaluate the extent of bacterial multiplication resulting from outgrowth of germinated Clostridium perfringens spores experimentally inoculated into chili and incubated at various temperatures. Inoculated samples were heated (75 degrees C for 20 min) to activate spores, quickly equilibrated, and held at one of five desired temperatures for 6 h. No growth was observed for C. perfringens in samples held at 26.7 degrees C and below for 6 h, but growth was observed by 6 h in samples held at 32.2 degrees C and after 2 h in samples held at temperatures between 37.8 degrees C and 48.9 degrees C. Using isothermal growth data, we developed a simple model for predicting the growth of bacteria with time under exponential cooling conditions. The model predicts both the lag phase and the numbers of bacteria at specific times during the growth phase. It was developed by using isothermal growth data and tested by using temperature-varying growth data from experiments with spores of C. perfringens in chili. Actual data agreed closely with predicted results. The results should be useful for evaluating the hazard potential for growth of C. perfringens in chili.     

N1-acetylspermidine is not a substrate for N-acetylspermidine deacetylase

The specificity of N-acetylspermidine deacetylase from rat liver for the two naturally occurring forms of monoacetylated spermidine was studied. N8-Acetylspermidine is the preferred substrate in vitro for this enzyme, and, in fact, N1-acetylspermidine did not undergo deacetylation under the conditions used in this study. Thus N8-acetylspermidine is the more appropriate substrate for assaying N-acetylspermidine deacetylase activity.     

Effect of purine derivatives, papaverine hydrochloride, and imidazole on enterotoxin formation by Clostridium perfringens type A

The percentage sporulation and enterotoxin specific activity were improved for all of five Clostridium perfringens strains, and numbers of heat-resistant spores were improved for four of five strains by replacing proteose peptone with peptone in Duncan-Strong (DS) medium. When raffinose replaced starch in DS, peptone was superior to proteose peptone in increasing percentage sporulation, numbers of heat-resistant spores, and enterotoxin formation for four of five strains. Enterotoxin levels for a strain varied when different lots of the same peptone were used. Additional experiments were conducted with three C. perfringens strains grown in DS medium with peptone. Enterotoxin specific activity was increased for three strains by adding papaverine (hydrochloride crystalline), for two strains by adding each of caffeine and 3-isobutyl-l-methylxanthine, for one strain by adding each of theophylline, 6-mercaptopurine, and 2-amino-6-mercaptopurine, and for none of the strains by adding imidazole. When enterotoxin formation was improved for a strain by one of the compounds, percentage sporulation increased, but growth decreased. Effective compounds also increased numbers of heat-resistant spores for strains H6 and R42, but slightly or not at all for strain E13. The action of these compounds was concentration dependent, with the optimal concentration differing between compounds and between strains grown in the presence of the same compound.     

Rapid quantitative analysis of a gibberellin-sterol inhibitor using high-performance liquid chromatographic cartridge columns

A rapid, sensitive, and economical chemical analysis of the triazole, gibberellin-inhibitor, paclobutrazol (PP333, [(2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4 triazol-1-yl) pentan-3-ol]) was sought, featuring high-performance liquid chromatography (HPLC) as the final quantitation step. Three C₁₈-reverse phase columns (conventional, 250×4.6 mm; cartridge type, 125×4.6 mm; and minicolumn, 33×4.6 mm) were evaluated for their performance in HPLC separation and quantitation of PP333 applied to soil and plant foliage. The 125-mm Whatman Partisil 5 ODS-3 cartridge column was superior to the standard 250-mm DuPont Zorbax ODS unit, and provided enhanced resolution and reduced solvent consumption, analysis time, and cost. A Perkin-Elmer Pecosphere 3×3C-C₁₈ cartridge system was also superior to the 125-mm column with respect to these parameters. Although this minicolumn necessitated an additional purification step prior to HPLC analysis, its exceptionally fast analysis time and recovery period coupled with a high degree of sensitivity rendered it the most superior unit. This HPLC technology provided an efficient means of assaying for PP333 in large-scale experiments dealing with the chemical's absorption, translocation, and physiological response.