Morphine and Enkephalins Potently Inhibit [3H]Noradrenaline Release from Rat Brain Cortex Synaptosomes: Further Evidence for a Presynaptic Localization of μ-Opioid Receptors

Synaptosomes prepared from rat cerebral cortex and labeled with [3H]noradrenaline (NA) were superfused with calcium-free Krebs-Ringer-bicarbonate medium and exposed to 10 mM K+ plus 0.1 mM Ca2+ so that [3H]NA release was induced. 6,7-Dihydroxy-N,N-dimethyl-2-aminotetralin (TL-99) strongly inhibited synaptosomal K+-induced [3H]NA release (EC50 = 5-10 nM) by activating alpha 2-adrenoceptors. Release was also inhibited (maximally by 40-50%) by morphine (EC50 = 5-10 nM), [Leu5]enkephalin (EC50 = approximately 300 nM), [D-Ala2,D-Leu5]enkephalin (DADLE), and Tyr-D-Ala-Gly-(NMe)Phe-Gly-ol (DAGO) (EC50 values = approximately 30 nM). In contrast to the mu-selective opioid receptor agonists morphine and DAGO, the highly delta-selective agonist [D-Pen2,D-Pen5]enkephalin (1 microM) did not affect [3H]-NA release. Furthermore, the inhibitory effect of DADLE, an agonist with affinity for both delta- and mu-opioid receptors, was antagonized by low concentrations of naloxone. The findings strongly support the view that, like alpha 2-adrenoceptors, mu-opioid receptors mediating inhibition of NA release in the rat cerebral cortex are localized on noradrenergic nerve terminals.     

Local movements and population size of European eels,Anguilla anguilla,in a small lake in southwestern Spain

Synopsis Radio telemetry was used to study the movements of European eels,Anguilla anguilla, in a small (1.2 ha) lake in southwestern Spain in March and April, 1985. Observations were taken on the locations of 7 eels at least once each 2 h for a combined total of 1713 h. The size of individual activity regions varied from 2700 to 1300 m². Eels covered a larger area at night than during the day, with an average of 23% and 42% of the activity region used during the day and night respectively. Average distance moved between observations was significantly greater at night than in the day. Eels tracked during rainy and cloudy weather were more active during the day and used a larger total area than did those tracked during drier, more stable weather. The standing crop of eels was estimated to be about 77 kg ha^–1.     

ASSESSING NORTHERN ELEPHANT SEAL FEEDING HABITS BY STOMACH LAVAGE

Stomach lavaging was used to study the feeding habits of northern elephant seals ( Mirounga angustirostris ) found on San Miguel Island, California, during the spring of 1984. Fifty-nine elephant seals were chemically immobilized with an intramuscular injection of ketamine hydrochloride. Once immobilized, an animal's stomach was intubated, filled with 3–4 liters of water to create a slurry of the undigested food items, and evacuated into a collection device. The stomachs of 57 (96.6%) of the animals lavaged contained identifiable parts of prey. Twenty-nine different food items were identified, 12 of which have not been previously reported as prey of the northern elephant seal: two teleost fish, Coryphaenoides acrolepis (Pacific rattail) and another unidentified macrourid; two crustaceans, Pasiphaea pacifica (glass shrimp) and Euphausia sp.; six squid, Abraliopsis felis, Gonatus berryi, Histioteuthis dofleini, Cranchia scabra, Taonius pavo, and Galiteuthis sp. and two octopi, Octopus dofleini and Octopus rubescens.     

Influence of Nitrogen Fertilizers on Growth, Spore Production and Germination, and Biocontrol Potential of Trichoderma and Gliocladium

The mycelial weight of eight out of nine isolates of Trichoderma spp. and Gliocladium virens increased in media supplemented with 2000 mg/l of nitrogen (N) from the fertilizers NH₄Cl, NaNO₃, and a commercial 20–20–20. In general, the greatest increase in growth (up to 311 %) occurred with 20–20–20. The extent of growth was similar with either NH₄Cl or NaNO₃, but was less than that with 20–20–20. Measured by radial development on agar surfacesgrowth of isolates was either not affected or was constricted by supplemental fertilizers. Production of conidia by six out of eight isolates was stimulated by 20–20–20 but not by NH₄Cl or NaNO₃. Germination of conidia of all isolates, generally was high (> 85 %) on amended and nonamended agar. Chlamydospore formation by three Trichoderma isolates in liquid media was not affected by fertilizers. Antagonism or overgrowth of the pathogen Rhizoctonia solani by Trichoderma isolates in culture was reduced appreciably by NaNO₃, but was not affected by NH₄Cl or 20–20–20. Addition of 20–20–20 to natural soil did not reduce further the survival of R. solani caused by germling preparations of six out of seven Trichoderma isolates. However, reduction in survival of the pathogen caused by a T. hamatum isolate was stimulated further (45 %) by the fertilizer.     

Growth determinations for unattached bacteria in a contaminated aquifer.

Growth rates of unattached bacteria in groundwater contaminated with treated sewage and collected at various distances from the source of contamination were estimated by using frequency of dividing cells and tritiated-thymidine uptake and compared with growth rates obtained with unsupplemented, closed-bottle incubations. Estimates of bacterial generation times [(In 2)/mu] along a 3-km-long transect in oxygen-depleted (0.1 to 0.7 mg of dissolved oxygen liter-1) groundwater ranged from 16 h at 0.26 km downgradient from an on-land, treated-sewage outfall to 139 h at 1.6 km and correlated with bacterial abundance (r2 = 0.88 at P less than 0.001). Partitioning of assimilated thymidine into nucleic acid generally decreased with distance from the contaminant source, and one population in heavily contaminated groundwater assimilated little thymidine during a 20-h incubation. Several assumptions commonly made when frequency of dividing cells and tritiated-thymidine uptake are used were not applicable to the groundwater samples.     

Mammalian folylpoly-gamma-glutamate synthetase. 3. Specificity for folate analogues

A variety of folate analogues were synthesized to explore the specificity of the folate binding site of hog liver folylpolyglutamate synthetase and the requirements for catalysis. Modifications of the internal and terminal glutamate moieties of folate cause large drops in on rates and/or affinity for the protein. The only exceptions are glutamine, homocysteate, and ornithine analogues, indicating a less stringent specificity around the delta-carbon of glutamate. It is proposed that initial folate binding to the enzyme involves low-affinity interactions at a pterin and a glutamate site and that the first glutamate bound is the internal residue adjacent to the benzoyl group. Processive movement of the polyglutamate chain through the glutamate site and a possible conformational change in the protein when the terminal residue is bound would result in tight binding and would position the gamma-carboxyl of the terminal glutamate in the correct position for catalysis. Steric limitations imposed on the internal glutamate residues that loop out and additional steric constraints imposed by binding of different pterin moieties would be expected to effect slight conformational changes in the protein and/or the terminal glutamate and would explain the decrease in on rate and catalytic rate with increased polyglutamate chain length, and the differential effect of one-carbon substitution on the catalytic rate with polyglutamate derivatives. The 4-amino substitution of folate increases the on rate for monoglutamate derivatives but severely impairs catalysis with diglutamate derivatives. Pteroylornithine derivatives are the first potent and specific inhibitors of folylpolyglutamate synthetase to be identified and may act as analogues of reaction intermediates.(ABSTRACT TRUNCATED AT 250 WORDS)     

Three-dimensional reconstruction of a human metaphase chromosome from electron micrographs

A complete human metaphase chromosome has been reconstructed from a series of electron microscopical projections obtained by tilting the specimen stage at 3 degree intervals from –60 to +60 degrees. The reconstructed structure is about 3.0 m long, 1.6 m wide, and 0.8 m thick. The mass distribution was fairly homogeneous within the chromatids and neither a hollow nor a dense core was observed. The distribution and course of fibers observed are most consistent with a looping model of chromosome structure.     

Physiological Significance of the Alcohol Dehydrogenase Polymorphism in Larvae of Drosophila

This study deals with biochemical and metabolic-physiological aspects of the relationship between variation in in vivo alcohol dehydrogenase activity and fitness in larvae homozygous for the alleles Adh71k, AdhF, AdhS, of Drosophila melanogaster, and for the common Adh allele of Drosophila simulans. The Adh genotypes differ in the maximum oxidation rates of propan-2-ol into acetone in vivo. There are smaller differences between the Adh genotypes in rates of ethanol elimination. Rates of accumulation of ethanol in vivo are negatively associated with larval-to-adult survival of the Adh genotypes. The rank order of the maximum rates of the ADHs in elimination of propan-2-ol, as well as ethanol, is ADH-71k greater than ADH-F greater than ADH-S greater than simulans-ADH. The ratio of this maximum rate to ADH quantity reveals the rank order of ADH-S greater than ADH-F greater than ADH-71k greater than simulans-ADH, suggesting a compensation for allozymic efficiency by the ADH quantity in D. melanogaster.Our findings show that natural selection may act on the Adh polymorphism in larvae via differences in rates of alcohol metabolism.     

Aging alterations in the modulation of central dopaminergic cilioinhibition by etorphine in the marine mussel,Mytilus edulis: Decrease in the inhibition of presynaptic dopamine release

1. This report further demonstrates that etorphine influences presynaptic dopamine release, which in turn centrally modulates peripheral cilioinhibition. 2. In older animals cilioinhibition has become enhanced due to a lack of responsiveness to endogenous opioids which results in greater dopamine release, causing a higher level of cilioinhibition as demonstrated by challenging the visceral ganglia with etorphine or destroying the dopaminergic component with 6-hydroxydopamine. 3. Only the central cilioinhibitory, not the peripheral inhibitory response, mechanism appears to be altered in older animals. Thus, the alteration appears in the central integrative mechanisms involved with regulating ciliary activity. 4. The KCl-stimulated release of dopamine is unaltered in both young and old organisms, whereas the opiate inhibition of the KCl-stimulated release of dopamine is reduced in older organisms. Thus, the aging-associated alteration is associated with a specific process. 5. The reduction of opioid influence and the resulting enhanced cilioinhibitory activity may make the organisms more susceptible to environmental stress.