A comparative evaluation of the performance of full-scale high-rate methane biofilter (HMBF) systems and flow-through laboratory columns.

Methane biofilter (MBF) technology, a cost effective method to control atmospheric emission of CH4, is usually developed as a passively aerated system to control low-volume point-source emissions such as those from landfills with gas collection systems. Actively aerated high-rate methane biofilter (HMBF) systems are designed to overcome the shortcomings of passively aerated systems by ensuring the entire filter bed is utilized for CH4 oxidation. Flow-through column experiments point to the fact that CH4 oxidation rates of actively aerated systems could be several times higher than that of passively aerated systems. However, reports of the performance of field HMBF systems are not available in literature. Furthermore, there are no studies that demonstrate the possibility of using laboratory data in the design and operation of field systems. The current study was conducted to fill this research gap and involve a comparative study of the performance of laboratory columns to field performance of a HMBF system using solution gas produced at an oil battery site as the CH4 source. The actively aerated column studies confirmed past results with high CH4 oxidation rates; one column received air at two injection points and achieved an oxidation rate of 1417 g/m3/d, which is the highest reported value to date for compost-filled columns. Subsequent studies at a specially designed field HMBF filled with compost showed a higher oxidation rate of 1919 g/m3/d, indicating the possibility of exceeding the high CH4 oxidation rates observed in the laboratory. The achievement of observed field oxidation rates being higher than those in the laboratory is attributed to the capability of maintaining higher temperatures in field HMBFs. Furthermore, results show that field HMBFs could operate at lower than stoichiometric air to CH4 ratios, and lower retention times than that of laboratory columns. Results indicated that laboratory columns may not truly represent field behavior, and said results could only be used in the preliminary design of field HMBFs.

Brain targeted transcranial administration of diazepam and shortening of sleep latency in healthy human volunteers.

Application of medicated oils on scalp had been practiced for centuries in the Ayurvedic system of medicine in diseases associated with the central nervous system. It is possible that the effectiveness of the therapy may be a result of targeted delivery of active compounds to the brain transcranially. Evidence also comes from two previous studies with positive results on brain targeted transcranial delivery of methadone base and diazepam on rat models. Possibility of transcranial drug delivery was investigated in healthy human volunteers using electroencephalography techniques by assessing the ability of transcranially administered diazepam in bringing about ß activity in the electroencephalographic wave patterns and shortening of the sleep latency period. Non polar drug molecules dissolved in a non-aqueous sesame oil based vehicle is a significant feature in the transcranial dosage design. The study was under taken in two phases. In the Phase-I study scalp application of a single dose of 2 mg/3 ml of the oil was employed and in the Phase-II study repeat application of three doses 24 h apart were employed. Sleep latency changes were monitored with Multiple Sleep Latency Tests with 5 naps employing the standard electroencephalography, electroocculography and electromyography electrodes. Sleep onset was identified with the first epoch of any sleep stage non rapid eye movement 1, 2, 3, 4 or rapid eye movement using electroencephalography, electroocculography and electromyography criteria. In both phases of the study there was significant reduction in the sleep latencies. It was much more pronounced in the Phase-II study. None of the subjects however displayed beta activity in the electroencephalography. Sleep latency reduction following scalp application in both the phases are suggestive of transcranial migration of diazepam molecules to the receptor sites of the nerve tissue of the brain eliciting its pharmacological effect of sedation. Transcranial brain targeted dosage design is therefore feasible.

Neurophysiological findings in patients 1 year after snake bite induced neurotoxicity in Sri Lanka.

Snake bite causes significant morbidity and mortality in Sri Lanka. Snake venoms contain neurotoxins that block neuromuscular junction transmission. Presynaptic neurotoxicity most commonly causes destruction of nerve terminals with recovery by regrowth, whilst postsynaptic neurotoxicity usually involves competition at the acetylcholine receptor. The aim of this study was to investigate whether there were long-term clinical or neurophysiological changes in snake bite survivors 1 year after their envenoming. Detailed neurophysiological tests and clinical examinations were performed on 26 snake bite victims who had presented with neurotoxicity 12 months previously, and their results were compared with controls recruited from the same communities. Significant differences were observed in some nerve conduction parameters in some snake bite victims compared with controls, predominantly in those thought to have elapid bites, including prolongation of sensory, motor and F-wave latencies and reduction of conduction velocities. There was no evidence of any residual deficits in neuromuscular junction transmission. These results suggest a possible demyelinating type polyneuropathy. None of the cases or controls had abnormalities on clinical examination. This is one of the few studies to report possible long-term neurological damage following systemic neurotoxicity after snake bite. The clinical significance of these neurophysiological abnormalities is uncertain and further studies are required to investigate whether the abnormalities persist and to see whether clinical consequences develop.

Acute small fibre sensory neuropathy: another variant of Guillain-Barré syndrome?

Six patients who presented with acute sensory neuropathy were studied. All patients underwent detailed clinical assessment along with electrophysiological tests and relevant laboratory investigations. All patients had acute onset numbness, reaching the peak deficit within 4 weeks. Four of them had associated burning dysaesthesia. An antecedent illness was reported in four; diarrhoea in three, and urinary tract infection in one. The neurological examination disclosed normal muscle strength, symmetric glove and stocking type sensory loss for pain and temperature, normal proprioception, and vibration senses with normal or brisk tendon reflexes. Analysis of CSF demonstrated albuminocytological dissociation in all. Routine motor and sensory nerve conduction studies were normal. Sympathetic skin responses were also normal except for the lower limbs in one patient. Stool cultures for Campylobacter jejuni were negative. The outcome was favourable. Burning dysaesthesia disappeared within 4 months. Numbness and objective sensory loss tended to persist longer. The clinical features and normal routine nerve conduction studies, which assess large diameter nerve fibre function, indicate small sensory fibre dysfunction in the group. Their presentation and CSF findings would fit into the diagnosis of sensory Guillain-Barré syndrome. The current study suggests that acute small fibre sensory neuropathy (ASFSN) is another clinical entity which could perhaps be included in the heterogeneous range of Guillain-Barré syndrome.

Structure-activity relationship studies of discodermolide and its semisynthetic acetylated analogs on microtubule function and cytotoxicity.

PURPOSE: Discodermolide, a natural product from the marine sponge Discodermia dissoluta, has been previously described as an antimitotic agent with microtubule hyperstabilizing properties similar to those of paclitaxel (Taxol). The clinical success of paclitaxel has led to a growing interest in novel antimitotic compounds and the elucidation of their structure-activity characteristics. Analogs of discodermolide were prepared by acetylation of the hydroxyl groups at carbons 3, 7, 11 and/or 17 and tested for biological activity in human tumor cells to determine the structural requirements for tubulin interaction and cytotoxic effects. METHODS: A549 human lung adenocarcinoma cells were incubated with discodermolide, or its acetylated analogs, and examined for their effects on microtubule architecture, cytotoxicity. and perturbations of the cell cycle. To confirm their direct interaction with tubulin. analogs were assayed for their ability to induce the polymerization of purified bovine brain tubulin. RESULTS: Acetylation of discodermolide at the C-7 hydroxyl group potentiated the cytotoxicity of the molecule to A549 cells, whereas acetylation at the C-3 hydroxyl group had little effect on the cytotoxicity of the parent or C-7-acetylated compounds. The acetylation of the hydroxyl groups at the C-11 and C-17 positions severely abrogated the cytotoxicity of the molecule. Cell cycle analysis by flow cytometry revealed that the more cytotoxic analogs caused the accumulation of cells in the G2/M phase, a mechanism previously reported for discodermolide. All discodermolide analogs with IC50 values below 1000 nM exhibited microtubule effects to varying degrees in cultured A549 cells, yet only the most cytotoxic promoted the polymerization of purified tubulin. CONCLUSIONS: Although the parent compound was more effective at polymerizing purified tubulin, acetylation of the C-3 or C-3 and C-7 hydroxyl groups improved its cytotoxicity in whole cells suggesting that acetylation either enhances accumulation of the molecules within cells or imparts a secondary cytotoxic quality not present in the discodermolide molecule. The study reported here is the first to provide information on the structure-activity relationships of discodermolide using human tumor cells and analogs produced by semisynthetic modification of natural discodermolide.

Acetylated analogues of the microtubule-stabilizing agent discodermolide: preparation and biological activity.

A series of eight discodermolide acetates have been prepared using natural (+)-discodermolide and evaluated for in vitro cytotoxicity against the cultured murine P-388 leukemia cells. The acetylated analogues showed a significant variation of cytotoxicity and suggested the importance of C-11 and C-17 hydroxyl groups for potency. The preparation and structure elucidation of the new analogues are described.

Sterols of the marine sponge Petrosia weinbergi: implications for the absolute configurations of the antiviral orthoesterols and weinbersterols.

The marine sponge Petrosia weinbergi was found to contain isofucosterol and clionasterol as its major sterols. The rare cyclopropyl sterol (24S,28S)-24,28-methylenestigmast-5-en-3beta-ol, previously detected as only 0.07% of the total sterols of a pelagophytic alga Pulvinaria sp., made up 6.6% of the total sterols. These sterols are believed to be the biosynthetic precursors of the antiviral orthoesterols and weinbersterols found in the same sponge. Based on the side chains of the isolated sterols, the absolute configurations of the antiviral steroid side chains are assigned to be (24R,28S)- for orthoesterol B, (24R)- for orthoesterol C, and (24S,28S)- for weinbersterols A and B.

Secobatzellines A and B, two new enzyme inhibitors from a deep-water Caribbean sponge of the genus Batzella.

Secobatzelline A (1), a new batzelline natural analogue, and secobatzelline B (2), a likely artifact formed during the isolation procedure, have been isolated from a deep-water marine sponge of the genus Batzella. Secobatzellines A and B inhibited the phosphatase activity of calcineurin, and secobatzelline A inhibited the peptidase activity of CPP32. Both compounds showed in vitro cytotoxicity against P-388 and A-549 cell lines. The isolation and structure elucidation of secobatzellines A (1) and B (2) are described.

Discorhabdin P, a new enzyme inhibitor from a deep-water Caribbean sponge of the genus Batzella.

Discorhabdin P (1), a new discorhabdin analogue, has been isolated from a deep-water marine sponge of the genus Batzella. Discorhabdin P (1) inhibited the phosphatase activity of calcineurin and the peptidase activity of CPP32. It also showed in vitro cytotoxicity against P-388 and A-549 cell lines. The isolation and structure elucidation of discorhabdin P (1) are described.

The microtubule-stabilizing agent discodermolide competitively inhibits the binding of paclitaxel (Taxol) to tubulin polymers, enhances tubulin nucleation reactions more potently than paclitaxel, and inhibits the growth of paclitaxel-resistant cells.

The lactone-bearing polyhydroxylated alkatetraene (+)-discodermolide, which was isolated from the sponge Discodermia dissoluta, induces the polymerization of purified tubulin with and without microtubule-associated proteins or GTP, and the polymers formed are stable to cold and calcium. These effects are similar to those of paclitaxel (Taxol), but discodermolide is more potent. We confirmed that these properties represent hypernucleation phenomena; we obtained lower tubulin critical concentrations and shorter polymers with discodermolide than paclitaxel under a variety of reaction conditions. Furthermore, we demonstrated that discodermolide is a competitive inhibitor with [3H]paclitaxel in binding to tubulin polymer, with an apparent Ki value of 0.4 microM. Multidrug-resistant human colon and ovarian carcinoma cells overexpressing P-glycoprotein, which are 900- and 2800-fold resistant to paclitaxel, respectively, relative to the parental lines, retained significant sensitivity to discodermolide (25- and 89-fold more resistant relative to the parental lines). Ovarian carcinoma cells that are 20-30-fold more resistant to paclitaxel than the parental line on the basis of expression of altered beta-tubulin polypeptides retained nearly complete sensitivity to discodermolide. The effects of discodermolide on the reorganization of the microtubules of Potorous tridactylis kidney epithelial cells were examined at different times. Intracellular microtubules were reorganized into bundles in interphase cells much more rapidly after discodermolide treatment compared with paclitaxel treatment. A variety of spindle aberrations were observed after treatment with both drugs. The proportions of the different types of aberration were different for the two drugs and changed with the length of drug treatment.

beta-Amyloid-mediated inhibition of redox activity (MTT reduction) is not an indicator of astroglial degeneration.

The reduction in 3-[4,5-dimethylthiazol]-2,5-diphenyltetrazolium bromide (MTT) to a coloured formazan compound by cultured cells has been extensively used as an in vitro model for understanding neurobiological mechanisms involved in amyloid beta-protein (A beta-mediated cell death. In primary cultures of astrocytes, very low concentrations of aggregated A beta 1-4C, but not A beta 4C-1, produced a significant inhibition in the reduction of the dye MTT. This inhibitory response was rapid and persisted as long as A beta 1-4C was present in the culture medium. Such a severe reduction in cell redox activity for days failed to cause death of astroglial cells, measured in terms of trypan blue uptake and lactate dehydrogenase release. Interleukin-1 beta (IL-1 beta), which is known to attenuate excitotoxic neurodegeneration, had no effect on A beta 1-4C-induced inhibition of MTT reduction. These results suggest that even though inhibition of MTT reduction represents an early indicator of the A beta 1-4C mediated cell injury, without other corroborating evidence, it should not be used as a measure of cell death.

A new cytotoxic sterol methoxymethyl ether from a deep water marine sponge Scleritoderma sp. cf. paccardi.

24(R)-Methyl-5 alpha-cholest-7-enyl 3 beta-methoxymethyl ether (1), a new sterol ether, has been isolated from a deep-water marine sponge Scleritoderma sp. cf. paccardi. Compound 1 exhibited in vitro cytotoxicity against the cultured murine P-388 tumor cell line with an IC50 of 2.3 micrograms/mL. The isolation and structure elucidation of 1 by NMR spectroscopy is described.

Discodermolide, a cytotoxic marine agent that stabilizes microtubules more potently than taxol.

Computer-assisted structure analysis indicated (+)-discodermolide, a polyhydroxylated alkatetraene lactone marine natural product, was an antimitotic compound, and we confirmed this prediction. Previous work had shown an accumulation of discodermolide-treated cells in the G2/M portion of the cell cycle, and we have now found that discodermolide arrests Burkitt lymphoma cells in mitosis. Discodermolide-treated breast carcinoma cells displayed spectacular rearrangement of the microtubule cytoskeleton, including extensive microtubule bundling. Microtubule rearrangement that occurred with 10 nM discodermolide required 1 microM taxol. Discodermolide had equally impressive effects on tubulin assembly in vitro. Near-total polymerization occurred at 0 degree C with tubulin plus microtubule-associated proteins (MAPs) under conditions in which taxol at an identical concentration was inactive. Without MAPs and/or without GTP, tubulin assembly was also more vigorous with discodermolide than with taxol under every reaction condition examined. Discodermolide-induced polymer differed from taxol-induced polymer in that it was completely stable at 0 degree C in the presence of high concentrations of Ca2+. In a quantitative assay designed to select for agents more effective than taxol in inducing assembly, discodermolide had an EC50 value of 3.2 microM versus 23 microM for taxol.

Ophirapstanol trisulfate, a new biologically active steroid sulfate from the deep water marine sponge Topsentia ophiraphidites.

Ophirapstanol trisulfate [1], a new steroid trisulfate related to sokotrasterol trisulfate was isolated from a deep water marine sponge Topsentia ophiraphidites. Compound 1 exhibited significant inhibition in the guanosine diphosphate/G-protein RAS exchange assay. The structure elucidation of 1 and ophirapstanol [2] by nmr spectroscopy is described.

Hamacanthins A and B, new antifungal bis indole alkaloids from the deep-water marine sponge, Hamacantha sp.

Hamacanthin A [1] and hamacanthin B [2] are two bioactive dihydropyrazinonediylbis(indole) alkaloids isolated from a new species of deep-water marine sponge, Hamacantha sp. The hamacanthins are growth inhibitors of Candida albicans and Cryptococcus neoformans. Isolation and structure elucidation of 1 and 2 by nmr spectroscopy are described.

Discobahamins A and B, new peptides from the Bahamian deep water marine sponge Discodermia sp.

Discobahamin A [1] and discobahamin B [2] are two bioactive peptides isolated from a new species of the Bahamian deep water marine sponge Discodermia. The discobahamins are inhibitors of the growth of Candida albicans, and the isolation and structure elucidation of 1 and 2 by nmr and chemical methods is described.

Immunosuppression by discodermolide.

In summary, discodermolide, a novel, marine-derived compound, is a potent in vitro and in vivo immunosuppressive agent. Discodermolide blocks cellular proliferation in lymphoid and nonlymphoid cells. This blocking action is not due to cytotoxicity. Blockage of cell proliferation by discodermolide appears to occur at the G2/M interface of the cell cycle, similar to that observed with other types of antiproliferative drugs (i.e., doxorubicin). The cell cycle block appears to be reversible, as cells recover normal cycling patterns within 48 h after removal of the compound. Additional work with this compound is targeted towards determining the exact nature of discodermolide's mitotic block and is currently under way.