Effects of Temperature and Crude Oil Composition on Petroleum Biodegradation

The biodegradability of seven different crude oils was found to be highly dependent on their composition and on incubation temperature. At 20 C lighter oils had greater abiotic losses and were more susceptible to biodegradation than heavier oils. These light crude oils, however, possessed toxic volatile components which evaporated only slowly and inhibited microbial degradation of these oils at 10 C. No volatile toxic fraction was associated with the heavier oils tested. Rates of oil mineralization for the heavier oils were significantly lower at 20 C than for the lighter ones. Similar relative degradation rates were found with a mixed microbial community, using CO2 evolution as the measure, and with a Pseudomonas isolate from the Arctic, using O2 consumption as the measure. The paraffinic, aromatic, and asphaltic fractions were subject to biodegradation. Some preference was shown for paraffin degradation, especially at low temperatures. Branched paraffins, such as pristane, were degraded at both 10 and 20 C. At best, a 20% residue still remained after 42 days of incubation. Oil residues generally had a lower relative percentage of paraffins and higher percentage of asphaltics than fresh or weathered oil.     

Specific affinity labelling of tubulin with bromocolchicine

Bromocolchicine, synthesized by substituting tho N-acetyl moiety of colchicine with a reactive bromoacetyl group, was found to be an affinity label for tubulin. Binding of [³H]colchicine to tubulin was competitively and irreversibly inhibited by bromocolchicine with a K_i value of 2.3 × 10^?5m. The affinity label could not be displaced by precipitating the protein with trichloroacetic acid and is thus covalently bound. Autoradiographs of brain high-speed supernatant proteins after their electrophoretic separation on sodium dodecyl sulphate/polyacrylamide gels showed that [³H]bromocolchicine reacted with four proteins, of which tubulin was one.Labelling of two of these proteins could be prevented by pretreatment of the brain extracts with α-bromoacetic acid, after which 70% of the covalently bound label was specifically located in the tubulin band. Up to 1.6 mol of affinity label could be bound per mol of tubulin, while under our experimental conditions 1 mol of protein bound irreversibly only 0.2 mol of [³H]colchicine. Autoradiography of sodium dodecyl sulphate/urea-polyacrylamide gels, which separate the subunits of tubulin, showed about 30% [³H] bromocolchicine bound to the α-subunit of tubulin and 70% to tho β-subunit.The irreversible binding site of colchicine was localized to the α-subunit, as labelling of only this subunit was inhibited by colchicine at high affinity label concentrations. At lower concentrations, colchicine inhibited the labelling of both subunits.Bromoacetic acid did not inhibit the reaction of the affinity label with the tubulin subunits, but increased the inhibition of [³H]bromocolchicine binding at lower concentrations of the affinity label in brain extracts preincubated with cold colchicine. This is interpreted to show a conformational change which takes place in the two subunits of tubulin upon binding of colchicine and results in the exposure of some of the binding sites of [³H]bromocolchicine to bromoacetic acid.     

Distribution of Hydrocarbon-Utilizing Microorganisms and Hydrocarbon Biodegradation Potentials in Alaskan Continental Shelf Areas

Hydrocarbon-utilizing microorganisms were enumerated from Alaskan continental shelf areas by using plate counts and a new most-probable-number procedure based on mineralization of ¹⁴C-labeled hydrocarbons. Hydrocarbon utilizers were ubiquitously distributed, with no significant overall concentration differences between sampling regions or between surface water and sediment samples. There were, however, significant seasonal differences in numbers of hydrocarbon utilizers. Distribution of hydrocarbon utilizers within Cook Inlet was positively correlated with occurrence of hydrocarbons in the environment. Hydrocarbon biodegradation potentials were measured by using ¹⁴C-radiolabeled hydrocarbon-spiked crude oil. There was no significant correlation between numbers of hydrocarbon utilizers and hydrocarbon biodegradation potentials. The biodegradation potentials showed large seasonal variations in the Beaufort Sea, probably due to seasonal depletion of available nutrients. Non-nutrient-limited biodegradation potentials followed the order hexadecane > naphthalene pristane > benzanthracene. In Cook Inlet, biodegradation potentials for hexadecane and naphthalene were dependent on availability of inorganic nutrients. Biodegradation potentials for pristane and benzanthracene were restricted, probably by resistance to attack by available enzymes in the indigenous population.     

Molecular identification and reconstitution of depolarization-induced exocytosis monitored by membrane capacitance

Regulated exocytosis of neurotransmitters at synapses is fast and tightly regulated. It is unclear which proteins constitute the "minimal molecular machinery" for this process. Here, we show that a novel technique of capacitance monitoring combined with heterologous protein expression can be used to reconstitute exocytosis that is fast (<0.5 s) and triggered directly by membrane depolarization in Xenopus oocytes. Testing synaptic proteins, voltage-gated Ca2+ channels, and using botulinum and tetanus neurotoxins established that the expression of a Ca2+ channel together with syntaxin 1A, SNAP-25, and synaptotagmin was sufficient and necessary for the reconstitution of depolarization-induced exocytosis. Similar to synaptic exocytosis, the reconstituted release was sensitive to neurotoxins, modulated by divalent cations (Ca2+, Ba2+, and Sr2+) or channel (Lc-, N-type), and depended nonlinearly on divalent cation concentration. Because of its improved speed, native trigger, and great experimental versatility, this reconstitution assay provides a novel, promising tool to study synaptic exocytosis.     

A low molecular weight copper chelator crosses the blood-brain barrier and attenuates experimental autoimmune encephalomyelitis

Increasing evidence suggests that enhanced production of reactive oxygen species (ROS) activates the MAP kinases, c-Jun N-terminal protein kinase (JNK) and mitogen-activated protein kinase MAPK (p38). These phosphorylated intermediates at the stress-activated pathway induce expression of matrix metalloproteinases (MMPs), leading to inflammatory responses and pathological damages involved in the etiology of multiple sclerosis (MS). Here we report that N-acetylcysteine amide (AD4) crosses the blood-brain barrier (BBB), chelates Cu(2+), which catalyzes free radical formation, and prevents ROS-induced activation of JNK, p38 and MMP-9. In the myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, oral administration of AD4 drastically reduced the clinical signs, inflammation, MMP-9 activity, and protected axons from demylination damages. In agreement with the in vitro studies, we propose that ROS scavenging by AD4 in MOG-treated animals prevented MMP's induction and subsequent damages through inhibition of MAPK pathway. The low toxicity of AD4 coupled with BBB penetration makes this compound an excellent potential candidate for the therapy of MS and other neurodegenerative disorders.     

Functional interaction of syntaxin and SNAP-25 with voltage-sensitive L- and N-type Ca2+ channels.

We have used an electrophysiological assay to investigate the functional interaction of syntaxin 1A and SNAP-25 with the class C, L-type, and the class B, N-type, voltage-sensitive calcium channels. Co-expression of syntaxin 1A with the pore-forming subunits of the L- and N-type channels in Xenopus oocytes generates a dramatic inhibition of inward currents (>60%) and modifies the rate of inactivation (tau) and steady-state voltage dependence of inactivation. Syntaxin 1-267, which lacks the transmembrane region (TMR), and syntaxin 2 do not modify channel properties, suggesting that the syntaxin 1A interaction site resides predominantly in the TMR. Co-expression of SNAP-25 significantly modifies the gating properties of L- and N-type channels and displays modest inhibition of current amplitude. Syntaxin 1A and SNAP-25 combined restore the syntaxin-inhibited N-type inward current but not the reduced rate of inactivation. Hence, a distinct interaction of a putative syntaxin 1A-SNAP-25 complex with the channel is apparent, consistent with the formation of a synaptosomal SNAP receptors (SNAREs) complex. The in vivo functional reconstitution: (i) establishes the proximity of the SNAREs to calcium channels; (ii) provides new insight into a potential regulatory role for the two SNAREs in controlling calcium influx through N- and L-type channels; and (iii) may suggest a pivotal role for calcium channels in the secretion process.     

Legionella contamination of dental-unit waters

Volume 61, no. 4, p. 1211, column 2, line 40: this sentence should read as follows. "The viable-culture methods for Legionella sp. detection, however, often fail, and the Centers for Disease Control and Prevention has turned, when necessary, to PCR for epidemiological investigations of Legionnaires' disease and Pontiac fever (19)." Line 46: "(6)" should read "(11)." [This corrects the article on p. 1208 in vol. 61.].     

Barley aleurone cells contain two types of vacuoles. Characterization Of lytic organelles by use of fluorescent probes

Light microscopy was used to study the structure and function of vacuoles in living protoplasts of barley (Hordeum vulgare cv Himalaya) aleurone. Light microscopy showed that aleurone protoplasts contain two distinct types of vacuole: the protein storage vacuole and a lysosome-like organelle, which we have called the secondary vacuole. Fluorescence microscopy using pH-sensitive fluorescent probes and a fluorogenic substrate for cysteine proteases showed that both protein storage vacuoles and secondary vacuoles are acidic, lytic organelles. Ratio imaging showed that the pH of secondary vacuoles was lower in aleurone protoplasts incubated in gibberellic acid than in those incubated in abscisic acid. Uptake of fluorescent probes into intact, isolated protein storage vacuoles and secondary vacuoles required ATP and occurred via at least two types of vanadate-sensitive, ATP-dependent tonoplast transporters. One transporter catalyzed the accumulation of glutathione-conjugated probes, and another transported probes not conjugated to glutathione.