Localization of Endo-Oligopeptidase (EC 3.4.22.19) in the Rat Nervous Tissue

The subcellular and regional distribution of endo-oligopeptidase (EC 3.4.22.19), an enzyme capable of generating enkephalin by single cleavage from enkephalin-containing peptides, was determined by an enzymatic assay using metorphamide and by immunochemical techniques in the CNS of the rat. The rat CNS contains a membrane-associated form of endo-oligopeptidase, an enzyme predominantly associated with the soluble fraction of brain homogenates. Subcellular fractionation showed that approximately 17% of the total activity of the enzyme is associated with membrane fractions including synaptosomes. Synaptosomal membranes were prepared from neocortex, striatum, hypothalamus, medulla, spinal cord, and cerebellum. The amount of EC 3.4.22.19 activity solubilized by 3-[( 3-cholamidopropyl]dimethylammonio)-1-propanesulfonate from synaptosomal membranes was similar in neocortex, striatum, and hypothalamus, being three- to 10-fold greater than in spinal cord, cerebellum, and medulla. A polyclonal antibody exhibiting high affinity for endo-oligopeptidase was raised in rabbits against the purified rat brain enzyme and used to localize endo-oligopeptidase by Western blotting and by immunoperoxidase techniques. A strong band corresponding to the Mr of EC 3.4.22.19 was found in solubilized proteins obtained from synaptosomal membranes prepared from hypothalamus, neocortex, and striatum when subjected to Western blotting. The immunohistochemical localization of endo-oligopeptidase indicated that the immunoreactivity was confined to gray matter in regions known to be rich in peptide-containing neurons such as the striatum. In the cerebellum, a region poor in peptides, no staining could be detected. The nonuniform distribution of endo-oligopeptidase in rat brain suggests a role in neurotransmitter processing in the CNS.     

Multiple Bacteriocin Production by Leuconostoc mesenteroidesTA33a and Other Leuconostoc/Weissella Strains

Leuconostoc (Lc.) mesenteroides TA33a produced three bacteriocins with different inhibitory activity spectra. Bacteriocins were purified by adsorption/desorption from producer cells and reverse phase high-performance liquid chromatography. Leucocin C-TA33a, a novel bacteriocin with a predicted molecular mass of 4598 Da, inhibited Listeria and other lactic acid bacteria (LAB). Leucocin B-TA33a has a predicted molecular mass of 3466 Da, with activity against Leuconostoc/Weissella (W.) strains, and appears similar to mesenterocin 52B and dextranicin 24, while leucocin A-TA33a, which also inhibited Listeria and other LAB strains, is identical to leucocin A-UAL 187. A survey of other known bacteriocin-producing Leuconostoc/Weissella strains for the presence of the three different bacteriocins revealed that production of leucocin A-, B- and C-type bacteriocins was widespread. Lc. carnosum LA54a, W. paramesenteroides LA7a, and Lc. gelidum UAL 187-22 produced all three bacteriocins, whereas W. paramesenteroides OX and Lc. carnosum TA11a produced only leucocin A- and B-type bacteriocins. Received: 11 April 1997 / Accepted: 10 June 1997     

Guaraná (Paullinia cupana) as a commercial crop in Brazilian Amazonia

Guaraná (Paullinia cupana) is a woody vine or sprawling shrub native to the central Amazon Basin. The seeds are commercially produced on some 6,000 ha in the state of Amazonas near Manaus. The principal article of commerce is an amber-colored, carbonated soft drink. It is also widely used as a high caffeine stimulant and in local medicines. The plant is monoecious and is damaged by a number of diseases, the most severe being anthracnose. Prospects are excellent for greatly expanded international markets.     

Synthesis and structure-activity relationship of 2-(aminoalkyl)-2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine derivatives: a novel series of 5-HT(2A/2C) receptor antagonists. Part 2.

Following the programme started at Janssen Research Foundation searching for 5-HT(2A/2C) antagonists, we now report on the synthesis of a series of substituted 2-(Dimethylaminomethyl)-2,3,3a,8-tetrahydrodibenzo[c,f]isoxazolo[2,3-a]azepine derivatives. The 5-HT(2A), 5-HT(2C) and H(1) receptor affinities as well as the mCPP antagonistic activity of the compounds synthesised is described.     

Suppression of the rotifer Polyarthra remata by the omnivorous copepod Tropocyclops extensus: predation or competition

Indirect evidence from observations in the field suggested thata common and often abundant cyclopoid copepod, Tropocyclopsextensus, despite its small size (0.5 mm) and largely algaldiet, is an important predator of the rotifer Polyarthra remata.Laboratory experiments showed that copepodids and adults, butnot nauplii, markedly suppressed the population growth of thisrotifer. The suppression could be attributed entirely to predation,rather than to exploitative competition for shared food resourcesor to interference. Mortality rates predicted from a separatefeeding-rate experiment weresufficient to account for the declinein population size observed in the Tropocyclops treatment ofculture experiments. Also, monitoring the availability of cryptomonadfood in treatments with and without Tropocyclops throughoutthese experiments showed that cryptomonad densities always remainedhigh and were just as high or significantly higher in the copepodtreatments. Furthermore, direct videographic observations ofP. remata from cultures with and without Tropocyclops demonstratedno significant differences in swimming velocity, tendency todeviate from a straight-line path, or frequency and length ofspontaneous escape responses. Per capita ingestion rates ofT. extensus on P. remata varied from 2 to 8 day^-1, were significantlyhigher for adult females than adult males or copepodids V, andincreased significantly with rotifer density. A tendency ofcopepods to have higher ingestion rates on young than adultrotifers was not significant. Copepods cultured since birthwith cryptomonads and P. remata ate significantly fewer rotifersthan those cultured only with cryptomonads; this may be explainedby a more sated condition of the former and provided no evidencefor the idea that previous experience with this rotifer mightincrease predation efficiency. The results show that T. extensusin natural communities has the potential to deplete naturalpopulations of susceptible rotifer prey. Accordingly, it mayshift the species structure of rotifer assemblages in favourof resistant species, and provide selection pressure for avoidanceresponses.     

Characterization of a light-dependent glutamate synthase activity in Chlamydomonas reinhardtii

Photosynthetically active vesicles prepared from Chlamydomonas reinhardtii retained a light-dependent glutamate synthase activity which was highly specific for 2-oxoglutarate (K_m=2.1 mM) and L-glutamine (K_m=0.9 mM) as amido group acceptor and donor respectively. This activity was inhibited by azaserine, p-hydroxymercuribenzoate and 3-(p-chlorophenyl)-1,1-dimethyl urea.Light-dependent synthesis of glutamate was also obtained by coupling Chlamydomonas photosynthetic particles to purified ferredoxin-glutamate synthase, using ascorbate and 2,6-dichlorophenol-indophenol as electron donor. This system was also specific for 2-oxoglutarate (K_m=1 mM) and L-glutamine (K_m=0.8 mM) as substrates, and was stimulated by dithioerythritol. Azaserine and p-hydroxymercuribenzoate, but not 3-(p-chlorophenyl)-1,1-dimethyl urea, inhibited the reconstituted activity; high concentrations of 2-oxoglutarate were inhibitory.Abbreviations A Absorbance - CCP p-Trichlorometoxi-carbonylcyanide-phenylhydrazone - Chl Chlorophyll - CMU 3-(p-Chlorophenyl)-1,1-dimethyl urea - DPIP 2,6-Dichlorophenol-indophenol - DTE Dithioerythritol - MSX L-Methionine, D-L, sulfoximine - MV Methyl viologen     

Hydrolysis of sunflower oil by means of hydrophobic membrane with lipolytic activity

Polytetrafluoroethylene (PTFE) membranes of different porosity were used for lipase from Rhizopus immobilization. The immobilized enzyme applied to sunflower oil hydrolysis achieved the activity of 1228 U/m² of the membrane area and the half-life time was calculated to be 7 days.     

On the solution of mathematical models of herd immunity in human helminth infections

The general solution of the mathematical model of herd immunity to human helminth infections recently proposed by Anderson and May [3] is obtained. The numerical solution of a more accurate biological model is indistinguishable from the corresponding exact solution of a more tractable mathematical model. Computer simulations of some particular cases of this model support the notion that both ecological and immunological factors determine the observed convex patterns of age-prevalence and age-intensity curves of human helminth infections.This work was made thanks to the advise and support of Dr. Robert M. May while the author was Postdoctoral Fellow at Princeton University     

Nutrient transfer between the root zones of soybean and maize plants connected by a common mycorrhizal mycelium

The objective of the study was to determine whether nutrient fluxes mediated by hyphae of vesicular-arbuscular mycorrhizal (VAM) fungi between the root zones of grass and legume plants differ with the legume's mode of N nutrition. The plants, nodulating or nonnodulating isolines of soybean [ Glycine max (L.) Merr.], were grown in association with a dwarf maize ( Zea mays L.) cultivar in containers which interposed a 6-cm-wide root-free soil bridge between legume and grass container compartments. The bridge was delimited by screens (44 μm) which permitted the passage of hyphae, but not of roots and minimized non VAM interactions between the plants. All plants were colonized by the VAM fungus Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe. The effects of N input to N-sufficient soybean plants through N₂-fixation or N-fertilization on associated maize-plant growth and nutrition were compared to those of an N-deficient (nonnodulating, unfertilized) soybean control. Maize, when associated with the N-fertilized soybean, increased 19% in biomass, 67% in N content and 77% in leaf N concentration relative to the maize plants of the N-deficient association. When maize was grown with nodulated soybean, maize N content increased by 22%, biomass did not change, but P content declined by 16%. Spore production by the VAM fungus was greatest in the soils of both plants of the N-fertilized treatment. The patterns of N and P distribution, as well as those of the other essential elements, indicated that association with the N-fertilized soybean plants was more advantageous to maize than was association with the N₂-fixing ones.     

Calcium transport sensitive to ruthenium red in cytochrome oxidase vesicles reconstituted with mitochondrial proteins

We describe a calcium transport that is sensitive to ruthenium red in liposomes reconstituted with mitochondrial extracts. This system is able to build an internally negative membrane potential, which allows the electrogenic influx of Ca²⁺ and Sr²⁺. Proteins with molecular weights higher than 35 kDa were incorporated to the vesicles, and enhanced the accumulation of the cation in an energy-dependent fashion.