Hironori Iwasaki

1. The demand for natural alternatives to antibiotic growth promoters in poultry has led to growing interest in bioactive compounds, such as polysaccharides derived from algae. This study evaluated the effects of algae (Spirulina platensis)-derived polysaccharides (ADP) on growth performance, blood profiles, carcase characteristics, meat quality, amino acid composition and antioxidant status in broilers.2. A total of 320, 1-d-old Ross 308 mixed-sex broilers were randomly allocated to one of the five dietary treatments; a control diet (0% ADP) and diets supplemented with 0.15%, 0.30%, 0.45% and 0.60% of ADP. Each treatment included four replicates containing 16 birds each. The feeding trial was conducted over 42 d and was divided into three phases, including starter (1-14 d), grower (15-28 d) and finisher (29-42 d).3. Dietary inclusion of ADP at 0.30% significantly improved body weight gain and feed conversion ratio during the finisher (1.77 kg and 1.71, respectively) and overall (2.82 kg and 1.56, respectively) periods. There were no adverse effects observed on haematological, serum biochemistry or carcase characteristics.4. Supplementation with 0.45-0.60% ADP reduced cooking loss to 34-40% and improved meat cohesiveness by about 5%. Its inclusion elevated the levels of key amino acids, such as threonine, histidine, isoleucine, arginine and glutamic acid in the breast muscle. Additionally, ADP linearly increased hepatic antioxidant enzyme activities, including total superoxide dismutase (317.60-337.12 U/mg protein), glutathione peroxidase (39.98-48.70 U/mg protein), catalase (7.09-7.71 U/mg protein) and decreased malondialdehyde concentrations (0.63-0.68 nmol/mg protein) demonstrating enhanced oxidative status. These improvements were attributed to the prebiotic and antioxidant properties of Spirulina-derived polysaccharides, which enhance nutrient utilisation, maintain gut integrity and strengthen redox balance.5. This study provides preliminary evidence that polysaccharides derived from S. platensis, particularly at 0.30-0.45%, can be used as safe and effective feed additives in broiler diets. These compounds have the potential to enhance performance, oxidative stability and certain aspects of meat quality without adverse effects.

In higher plants, multiple copies of the cysteine synthase gene are present for cysteine biosynthesis. Some of these genes also have the potential to produce various kinds of β-substitute alanine. In the present study, we cloned a 1275-bp cDNA for cytosolic O-acetylserine(thiol)lyase (cysteine synthase) (Cy-OASTL) from Leucaena leucocephala. The purified protein product showed a dual function of cysteine and mimosine synthesis. Kinetics studies showed pH optima of 7.5 and 8.0, while temperature optima of 40 and 35 °C, respectively, for cysteine and mimosine synthesis. The kinetic parameters such as apparent K_m, k_cat were determined for both cysteine and mimosine synthesis with substrates O-acetylserine (OAS) and Na₂S or 3-hydroxy-4-pyridone (3H4P). From the in vitro results with the common substrate OAS, the apparent k_cat for Cys production is over sixfold higher than mimosine synthesis and the apparent K_m is 3.7 times lower, suggesting Cys synthesis is the favored pathway.

We identified a nitidine- (NTD-) accumulating organelle and evaluated the net cytotoxicity of accumulated NTD. To evaluate tumor cell selectivity of the drug, we evaluated its selective cytotoxicity against 39 human cancer cell lines (JFCR39 panel), and the profile was compared with those of known anticancer drugs. Organelle specificity of NTD was visualized using organelle-targeted fluorescent proteins. Real-time analysis of cell growth, proliferation, and cytotoxicity was performed using the xCELLigence system. Selectivity of NTD in the JFCR39 panel was evaluated. Mitochondria-specific accumulation of NTD was observed. Real-time cytotoxicity analysis suggested that the mechanism of NTD-induced cell death is independent of the cell cycle. Short-term treatment indicated that this cytotoxicity only resulted from the accumulation of NTD into the mitochondria. The results from the JFCR39 panel indicated that NTD-mediated cytotoxicity resulted from unique mechanisms compared with those of other known anticancer drugs. These results suggested that the cytotoxicity of NTD is only induced by its accumulation in mitochondria. The drug triggered mitochondrial dysfunction in less than 2 h. Similarity analysis of the selectivity of NTD in 39 tumor cell lines strongly supported the unique tumor cell specificity of NTD. Thus, these features indicate that NTD may be a promising antitumor drug for new combination chemotherapies.

Isoprene emission from plants is very sensitive to environmental temperature both at short‐term and long‐term scales. Our previous study demonstrated suppression of isoprene emission by cold temperatures in a high emitting tropical tree Ficus septica and revealed a strong correlation of emission to isoprene synthase (IspS) protein levels. When challenged with decreasing daily temperatures from 30 to 12 °C, F. septica completely stopped isoprene emission at 12 °C, only to recover on the second day after re‐exposure to 30 °C. Here, we explored this regulation of isoprene emission in response to environmental temperature by a comprehensive analysis of transcriptome data, gene expressions and metabolite pools of the 2‐C‐methyl‐D‐erythritol 4‐phosphate (MEP) pathway. MEP pathway genes and metabolites dynamics did not support substrate‐level limitations as major control over observed basal emission, but transcriptome data, network inferences and putative regulatory elements on IspS promoter suggested transcriptional regulation of IspS gene through circadian rhythm and phytohormone signalling processes. Expression levels of 29 genes involved in these pathways were examined by quantitative real‐time PCR. We propose that temperature controls over basal isoprene emission at a time‐scale of hours to few days are regulated by phytohormone‐mediated transcriptional modulation of IspS gene under synchronization by the circadian clock.