The interplay of increased urea synthesis and reduced ammonia production in the African lungfish Protopterus aethiopicus during 46 days of aestivation in a mucus cocoon

This study was undertaken to test the hypothesis that the rate of urea synthesis in Protopterus aethiopicus was up-regulated to detoxify ammonia during the initial phase of aestivation in air (day 1-day 12), and that a profound suppression of ammonia production occurred at a later phase of aestivation (day 35-day 46) which eliminated the need to sustain the increased rate of urea synthesis. Fasting apparently led to a greater rate of nitrogenous waste excretion in P. aethiopicus in water, which is an indication of increases in production of endogenous ammonia and urea probably as a result of increased proteolysis and amino acid catabolism for energy production. However, 46 days of fasting had no significant effects on the ammonia or urea contents in the muscle, liver, plasma and brain. In contrast, there were significant decreases in the muscle ammonia content in fish after 12, 34 or 46 days of aestivation in air when compared with fish fasting in water. Ammonia was apparently detoxified to urea because urea contents in the muscle, liver, plasma and brain of P. aethiopicus aestivated for 12, 34 or 46 days were significantly greater than the corresponding fasting control; the greatest increases in urea contents occurred during the initial 12 days. There were also significant increases in activities of some of the hepatic ornithine-urea cycle enzymes from fish aestivated for 12 or 46 days. Therefore, contrary to a previous report on P. aethiopicus, our results demonstrated an increase in the estimated rate of urea synthesis (2.8-fold greater than the day 0 fish) in this lungfish during the initial 12 days of aestivation. However, the estimated rate of urea synthesis decreased significantly during the next 34 days. Between day 35 and day 46 (12 days), urea synthesis apparently decreased to 42% of the day 0 control value, and this is the first report of such a phenomenon in African lungfish undergoing aestivation. On the other hand, the estimated rate of ammonia production in P. aethiopicus increased slightly (14.7%) during the initial 12 days of aestivation as compared with that in the day 0 fish. By contrast, the estimated rate of ammonia production decreased by 84% during the final 12 days of aestivation (day 35-day 46) compared with the day 0 value. Therefore, it can be concluded that P. aethiopicus depended mainly on increased urea synthesis to ameliorate ammonia toxicity during the initial phase of aestivation, but during prolonged aestivation, it suppressed ammonia production profoundly, eliminating the need to increase urea synthesis which is energy-intensive.     

Identification of kinetin and kinetin riboside in coconut (Cocos nucifera L.) water using a combined approach of liquid chromatography-tandem mass spectrometry, high performance liquid chromatography and capillary electrophoresis

Kinetin (free base and riboside), which was assumed by many scientists to be a synthetic cytokinin plant growth hormone, has been detected for the first time in the endosperm liquid of fresh young coconut fruits ("coconut water"). To facilitate the study, we developed a sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the identification and quantification of kinetin and kinetin riboside in purified coconut water extract sample. Following a solid-phase extraction of cytokinins in coconut water using C18 columns, the samples were further purified by Oasis MCX columns and analyzed by LC-MS/MS for kinetin and kinetin riboside. Detection by mass spectrometry was carried out using selected reaction monitoring (SRM) mode, by identifying the putative kinetin and kinetin riboside based on their characteristic fragments. Based on a signal-to-noise ratio of 3, the limits of detection in SRM mode were 0.02 microM and 0.005 microM for kinetin and kinetin riboside, respectively. Furthermore, optimal conditions for a baseline chromatographic separation of 18 cytokinin standards by high performance liquid chromatography (HPLC) were developed. The HPLC method had been employed for the confirmation and further fractionation of kinetin in coconut water extracts. The confirmation and fractionation of kinetin riboside was carried out using a further modified HPLC program due to the presence of other interfering material(s) in the sample matrix. Finally, fractions of putative kinetin and kinetin riboside collected from HPLC eluate of coconut water sample were further authenticated by independent capillary zone electrophoresis (CZE) experiment.     

High frequency production of embryos from liquid flask cultures of oilseed rape

As part of the program to scale-up the production of artificial seeds of winter oilseed rape, Brassica napus ssp. oleifera, we established a liquid flask culture system that enables the high frequency production of freely suspended embryos. As many as 4000 embryos could be obtained from 1 mL packed-cell-volume of cells. For initiation of liquid flask cultures, four different types of callus tissues were used. Among them, the most embryogenic cell suspension cultures were obtained from spontaneous callus developed on the surface of secondary embryos precultured in medium supplemented with 2,4-dichlorophenoxyacetic acid (4.52 muM) and kinetin (0.46 muM) (type B callus). Growth curves of the cell suspension were determined and the cell suspension was able to grow in medium without plant growth regulators. Embryos were observed to developed directly from the cells without going through an obvious callus phase. When subcultured to agar medium containing 44.38 muM benzylaminopurine, about 43% of the embryos developed into plants. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 231-238, 1997.     

Changes in lipid profiles in the developing haustorium of oil palm seeds

Germinated oil palm seeds were placed in special trays in the field and at different intervals the haustoria were harvested. Changes in haustorial lipids were followed until the eighth week after germination. The moisture content decreased while the lipids increased. The haustorial fatty acid profile was similar to that of the palm kernel. Changes in fatty acid composition at different weeks after germination were observed. The major haustorial lipids were triacylglycerols; free fatty acids and diacylglycerols were also present     

An Air‐Stable Densely Packed Phosphorene–Graphene Composite Toward Advanced Lithium Storage Properties

Phosphorene, monolayer or few‐layer black phosphorus (BP), has recently triggered strong scientific interest for lithium/sodium ion batteries (LIBs/SIBs) applications. However, there are still challenges regarding large‐scale fabrication, poor air stability. Herein, we report the high‐yield synthesis of phosphorene with good crystallinity and tunable size distributions via liquid‐phase exfoliation of bulk BP in formamide. Afterwards, a densely packed phosphorene–graphene composite (PG‐SPS, a packing density of 0.6 g cm^?3) is prepared by a simple and easily up‐scalable spark plasma sintering (SPS) process. When working as anode materials of LIBs, PG‐SPS exhibit much improved first‐cycle Coloumbic efficiency (60.2%) compared to phosphorene (11.5%) and loosely stacked phosphorene–graphene composite (34.3%), high specific capacity (1306.7 mAh g^?1) and volumetric capacity (256.4 mAh cm^?3), good rate capabilities (e.g., 415.0 mAh g^?1 at 10 A g^?1) as well as outstanding long‐term cycling life (91.9% retention after 800 cycles at 10 A g^?1). Importantly, excellent air stability of PG‐SPS over the 60 days observation in maintaining its high Li storage properties can be achieved. On the contrary, 95.2% of BP in PG sample was oxidized after only 10 days exposure to ambience, leading to severe degradation of electrochemical properties.     

Cycloart-24-ene-26-ol-3-one,a New Cycloartane Isolated from Leaves of Aglaia exima Triggers Tumour Necrosis Factor-Receptor 1-Mediated Caspase-Dependent Apoptosis in Colon Cancer Cell Line

Plants in the Meliaceae family are known to possess interesting biological activities, such as antimalaral, antihypertensive and antitumour activities. Previously, our group reported the plant-derived compound cycloart-24-ene-26-ol-3-one isolated from the hexane extracts of Aglaia exima leaves, which shows cytotoxicity towards various cancer cell lines, in particular, colon cancer cell lines. In this report, we further demonstrate that cycloart-24-ene-26-ol-3-one, from here forth known as cycloartane, reduces the viability of the colon cancer cell lines HT-29 and CaCO-2 in a dose- and time-dependent manner. Further elucidation of the compound’s mechanism showed that it binds to tumour necrosis factor-receptor 1 (TNF-R1) leading to the initiation of caspase-8 and, through the activation of Bid, in the activation of caspase-9. This activity causes a reduction in mitochondrial membrane potential (MMP) and the release of cytochrome-C. The activation of caspase-8 and -9 both act to commit the cancer cells to apoptosis through downstream caspase-3/7 activation, PARP cleavage and the lack of NFkB translocation into the nucleus. A molecular docking study showed that the cycloartane binds to the receptor through a hydrophobic interaction with cysteine-96 and hydrogen bonds with lysine-75 and -132. The results show that further development of the cycloartane as an anti-cancer drug is worthwhile.     

Design,synthesis, and SAR of N-((1-(4-(propylsulfonyl)piperazin-1-yl)cycloalkyl)methyl)benzamide inhibitors of glycine transporter-1

The design, synthesis, and structure–activity relationships (SAR) of a series of N-((1-(4-(propylsulfonyl)piperazin-1-yl)cycloalkyl)methyl)benzamide inhibitors of glycine transporter-1 (GlyT-1) are described. Optimization of the benzamide and central ring components of the core scaffold led to the identification of a GlyT-1 inhibitor that demonstrated in vivo activity in a rodent cerebral spinal fluid (CSF) glycine model.     

Thalidomide decreases intrahepatic resistance in cirrhotic rats

Increased intrahepatic resistance (IHR) within cirrhotic liver is caused by increased endotoxemia, cytokines tumor necrosis factor-α (TNF-α), vasoconstrictor thromboxane A₂ (TXA₂), and disrupted microvasculatures. We evaluated the effects of thalidomide-related inhibition of TNF-α upon the hepatic microcirculation of cirrhosis in rats. Portal venous pressure (PVP), hepatic TNF-α, expression of thromboxane synthase (TXS), and leukocyte common antigen (LCA) were measured in bile-duct-ligated (BDL) rats receiving 1 month of thalidomide (BDL-thalido rats). Portal perfusion pressure (PPP), IHR, and hepatic TXA₂ production were measured in the isolated liver perfusion system. Intravital microscopy was used to examine hepatic microvascular disruptions. In BDL-thalido rats, PVP, PPP, IHR, hepatic TXA₂ and TNF-α, hydroxyproline content, expression of TXS and LCA, and LPS-induced leukocyte recruitment were significantly decreased. Conversely, hepatic microvascular density and perfused sinusoids were significantly increased. Thalidomide decreased PVP and IHR by reducing hepatic TXA₂ and improving hepatic microvascular disruptions in rats with biliary cirrhosis.     

DNA aptamers bind specifically and selectively to (1 → 3)-β-d-glucans

(1 → 3)-β-d-Glucans are structural cell wall components of fungi, plants, and some bacteria and have been linked with human respiratory symptoms following aerosol exposure. A clear interpretation of the health impact of (1 → 3)-β-d-glucans is limited by the high cost and uncertainties associated with current glucan quantitation methods. The objective of this research is to develop DNA aptamers for the measurement of (1 → 3)-β-d-glucans. Aptamers are synthetic DNA functional binding molecules that fold into unique conformations, allowing them to bind specifically to their target. Through the in vitro selection process SELEX, we have produced aptamers that are able to bind with sub-micromolar affinity to curdlan, a linear unbranched form of (1 → 3)-β-d-glucans. These aptamers display high selectivity to curdlan and do not bind to non-(1 → 3)-β-d-polysaccharides, suggesting specificity for the β-(1 → 3)-glycosidic linkage. The aptamers produced here will enable the production of more cost-effective, less ambiguous assays for the environmental measurement of (1 → 3)-β-d-glucans.