Partial purification of polyphenol oxidase from Chinese cabbage Brassica rapa L

Polyphenol oxidase (PPO) was purified and characterized from Chinese cabbage by ammonium sulfate precipitation and DEAE-Toyopearl 650M column chromatography. Substrate staining of the crude protein extract showed the presence of three isozymic forms of this enzyme. The molecular weight of the purified enzyme was estimated to be approximately 65 kDa by gel filtration on Toyopearl HW-55F. On SDS-PAGE analysis, this enzyme was composed of a subunit molecular weight of 65 kDa. The optimum pH was 5.0, and this enzyme was stable at pH 6.0 but was unstable below pH 4.0 or above pH 7.0. The optimum temperature was 40 degrees C. Heat inactivation studies showed temperatures >40 degrees C resulted in loss of enzyme activity. PPO showed activity to catechol, pyrogallol, and dopamine (K(m) and V(max) values were 682.5 mM and 67.6 OD/min for catechol, 15.4 mM and 14.1 OD/min for pyrogallol, and 62.0 mM and 14.9 OD/min for dopamine, respectively). The most effective inhibitor was 2-mercaptoethanol, followed in decreasing order by ascorbic acid, glutathione, and L-cysteine. The enzyme activity of the preparation was maintained for 2 days at 4 degrees C but showed a sudden decreased after 3 days.     

Salsolinol is present in the bovine posterior pituitary gland and stimulates the release of prolactin both in vivo and in vitro in ruminants

The aims of the present study were to determine whether salsolinol (SAL), a dopamine-related compound, is present in the bovine posterior pituitary (PP) gland, and to clarify the effect of SAL on the secretion of prolactin (PRL) in ruminants. SAL was detected in extract of bovine PP gland using high-pressure liquid chromatography with electrochemical detection (HPLC-EC). A single intravenous (i.v.) injection of SAL (5 and 10mg/kg body weight) significantly and dose-dependently stimulated the release of PRL in goats (P<0.05). Plasma PRL levels reached a peak 10min after the injection, then gradually returned to basal values in 60-80min. The PRL-releasing pattern was similar to that in response to sulpiride (a dopamine receptor antagonist). The intracerebroventricular (i.c.v.) injection of 1mg of SAL had no significant effect on the release of PRL in calves, however, 5mg significantly stimulated the release (P<0.05) with peak values reached 30-40min after the injection. Moreover, SAL significantly stimulated the release of PRL from cultured bovine anterior pituitary cells at doses of 10(-6) and 10(-5)M, compared to control cells (P<0.05). Taken together, our data clearly show that SAL is present in extract of the PP gland of ruminants, and has PRL-releasing activity both in vivo and in vitro. Therefore, this endogenous compound is a strong candidate for the factor having PRL-releasing activity that has been previously detected in extract of the bovine PP gland.     

Differences in oxygen and carbon stable isotope ratios between hatchery and wild pink salmon fry

We examined differences in otolith oxygen (δ¹⁸O_otolith) and carbon (δ¹³C_otolith) stable isotope ratios between hatchery and wild pink salmon fry. The δ¹⁸O_otolith values of hatchery and wild fry were ?7.7 ± 0.2 ‰ and ?8.3 ± 0.3 ‰ (1σ), respectively. This difference reflected differences in temperature conditions experienced by each fry. The δ¹³C_otolith values of hatchery and wild fry were ?19.2 ± 0.3 ‰ and ?11.1 ± 1.8 ‰ (1σ), respectively. The lower δ¹³C_otolith values of hatchery fry were probably related to their intake of artificial diets. Discriminant analysis of δ¹⁸O_otolith and δ¹³C_otolith values demonstrated a highly significant difference between hatchery and wild fry with 95.8 % classification accuracy. Therefore, analysis of δ¹⁸O_otolith and δ¹³C_otolith precipitated in the fry stage may be useful for discriminating the origin of returning adult pink salmon. The discrimination method for returning adult fish would provide important information for evaluating the effect of hatchery release and their impact on the wild population.     

Allelopathic potential and an allelopathic substance in mango leaves

The present study was aimed to determine the allelopathic potential of mango (Mangifera indica L.) leaves and to identify allelopathic substances in the leaves. The aqueous methanol extracts of mango leaves inhibited seedling growth of garden cress, radish, rapeseed, foxtail fescue and crabgrass, and the inhibitory effects increased with the increasing extract concentration, suggesting that mango leaves may contain allelopathic substances. The extract was then purified by several chromatographic runs through a bioassay-directed fractionation, and an growth inhibitory substance was isolated and identified by spectral data as methyl-3,4,5-trihydroxybenzoate (methyl gallate). Methyl gallate at the concentration of 10 mM inhibited 98.6% and 99.8% of root and shoot growth of garden cress relative to the control, respectively, and 94.4% and 49.3% of those of foxtail fescue, respectively. The concentrations of methyl gallate required for 50% growth inhibition (I₅₀) on garden cress roots and shoots were 3.9 and 3.3 mM, and those on foxtail fescue roots and shoots were 1.5 and 9.5 mM, respectively. It is the first report of an allelopathic substance in mango leaves and allelopathic activity of methyl gallate. Therefore, the mango leaves may have potential as a soil additive material for the weed management options.     

Purification and characterization of two anionic trypsins from the hepatopancreas of carp

SUMMARY: Two trypsins, designated as trypsin A and trypsin B, have been purified from the hepatopancreas of carp. The purification procedures consisted of ammonium sulfate fractionation, and chromatographies on DEAE-Sephacel, Ultrogel AcA54 and Q-Sepharose. Trypsin A was purified to homogeneity with the molecular mass of approximately 28 kDa, while trypsin B gave two close bands of 28.5 kDa and 28 kDa on sodium dodecylsulfate polyacrylamide gel electrophoresis both under reducing and non-reducing conditions. On native-PAGE, both trypsin A and trypsin B showed a single band. Trypsin A and trypsin B revealed optimum temperature of 40°C and 45°C, respectively, and shared the same optimum pH 9.0 using Boc-Phe-Ser-Arg-MCA as substrate. Both enzymes were effectively inhibited by trypsin inhibitors and their susceptibilities were similar. The NH₂-terminal amino acid sequences of trypsin A and trypsin B were determined to 37th and 40th amino acid residue, respectively. Their sequences were very homologous, but not identical to that of a trypsin-type serine proteinase from carp muscle and these of other trypsins. Immunoblotting test using the antibody raised against trypsin A cross-reacted with trypsin B positively.     

Analysis of the role of forest,biomass policy legislation and other factors that may affect the future of Kenya’s forests: Use of Japanese forestry as a model

Forests are one of the most important ecosystems on earth that require careful management, conservation, and sustainable exploitation. As countries have their own guideline systems, each may learn and borrow from one another’s experience. One of such countries is Japan, which has elaborate forest policies, and rich in forest cover (67%) with its forest history dating many years back. On the other hand, Kenya, with a forest cover of just 7% and its policies demonstrating notable weaknesses, has a lot to learn from Japan. Therefore, we have attempted to do a comparative analysis of forest policies, technologies, and management practices between Kenya and Japan. Results indicate that Kenya’s forest policies do not place adequate emphasis on silvicultural practices and the establishment of forest plantations, and rarely focus on sustainable biomass utilization—factors that contributed significantly to forest growth and development in Japan. Additionally, policy legislation, revision, and implementation have not been given the deserved priority in Kenya. We conclude that Kenyan forest policy would benefit from both revision and thorough implementation. We also discuss the role of indirect factors such as economic growth and availability of nonwood-based energy sources in the future of Kenya’s forests.     

The soil seed bank of the threatened plant <Emphasis Type="Italic">Magnolia stellata</Emphasis> is subordinate to the emergence of current-year seedlings

We studied seed bank formation of the threatened star magnolia, Magnolia stellata, to examine the early stage of regeneration. Forty-five seedling plots (2 × 2 m), each including a soil-sampling quadrat (40 × 40 cm), were established randomly under or around the crowns of mature M. stellata trees. Seeds of M. stellata were collected from each quadrat to a depth of 5 cm. Only four seeds of M. stellata were found (0.56 seeds/m²) and all were located under mature crowns. Current-year seedlings were abundant in water channels, on moss, or under mature crowns, suggesting that the seeds may require wet soil conditions for germination. Magnolia stellata seeds show considerable germination below the crowns of mature trees in the year following masting, while some seeds remain dormant in the soil. Considering the soil seed bank and the current-year seedling bank of M. stellata, a frequent supply of seed is essential for the regeneration of this species. Thus, it is important to maintain mature trees in addition to promoting seed production.     

Integrating what and when across the primate medial temporal lobe

Episodic memory or memory for the detailed events in our lives is critically dependent on structures of the medial temporal lobe (MTL). A fundamental component of episodic memory is memory for the temporal order of items within an episode. To understand the contribution of individual MTL structures to temporal-order memory, we recorded single-unit activity and local field potential from three MTL areas (hippocampus and entorhinal and perirhinal cortex) and visual area TE as monkeys performed a temporal-order memory task. Hippocampus provided incremental timing signals from one item presentation to the next, whereas perirhinal cortex signaled the conjunction of items and their relative temporal order. Thus, perirhinal cortex appeared to integrate timing information from hippocampus with item information from visual sensory area TE.