Influence of drying treatment on three Sargassum species 2. Protein extractability, in vitro protein digestibility and amino acid profile of protein concentrates

The effects of different drying treatments (oven- andfreeze-drying) on protein extractability of three subtropical brownseaweeds, Sargassum hemiphyllum, S. henslowianum and S. patens, as well as in vitro protein digestibility and amino acid profileof their protein concentrates (PCs) were investigated. When comparedwith freeze-drying, oven-drying not only improved significantly (p <0.05, two-way ANOVA, Tukey-HSD) the protein extractability of thethree Sargassum species but also the protein quality (in vitroprotein digestibility) of their PCs. Therefore, oven-drying was found to bemore suitable for protein extraction of brown seaweeds. The relationshipsbetween the protein extractability and total phenolic content in seaweedsand between in vitro protein digestibility and total phenolic contentin PCs were also discussed.     

Sulfated polysaccharides from brown seaweeds Saccharina japonica and Undaria pinnatifida: isolation, structural characteristics, and antitumor activity

During the last decade brown seaweeds attracted much attention as a source of polysaccharides, namely laminarans, alginic acids, and sulfated polysaccharides—fucoidans, with various structures and biological activities.In this study, sulfated polysaccharides were isolated from brown seaweeds Saccharina japonica (formerly named Laminaria) and Undaria pinnatifida and their antitumor activity was tested against human breast cancer T-47D and melanoma SK-MEL-28 cell lines.The sulfated polysaccharide form S. japonica was highly branched partially acetylated sulfated galactofucan, built up of (1→3)-α-l-fucose residues. The sulfated polysaccharide from U. pinnatifida was partially acetylated highly sulfated galactofucan consisting of (1→3)- or (1→3);(1→4)-α-l-fucose residues.Fucoidans from S. japonica and U. pinnatifida distinctly inhibited proliferation and colony formation in both breast cancer and melanoma cell lines in a dose-dependent manner. These results indicated that the use of sulfated polysaccharides from brown seaweeds S. japonica and U. pinnatifida might be a potential approach for cancer treatment.     

Mesoherbivores reduce net growth and induce chemical resistance in natural seaweed populations

Herbivory on marine macroalgae (seaweeds) in temperate areas is often dominated by relatively small gastropods and crustaceans (mesoherbivores). The effects of these herbivores on the performance of adult seaweeds have so far been almost exclusively investigated under artificial laboratory conditions. Furthermore, several recent laboratory studies with mesoherbivores indicate that inducible chemical resistance may be as common in seaweeds as in vascular plants. However, in order to further explore and test the possible ecological significance of induced chemical resistance in temperate seaweeds, data are needed that address this issue in natural populations. We investigated the effect of grazing by littorinid herbivorous snails (Littorina spp.) on the individual net growth of the brown seaweed Ascophyllum nodosum in natural field populations. Furthermore, the capacity for induced resistance in the seaweeds was assessed by removing herbivores and assaying for relaxation of defences. We found that ambient densities of gastropod herbivores significantly reduced net growth by 45% in natural field populations of A. nodosum. Seaweeds previously exposed to grazing in the field were less consumed by gastropod herbivores in feeding bioassays. Furthermore, the concentration of phlorotannins (polyphenolics), which have been shown to deter gastropod herbivores, was higher in the seaweeds that were exposed to gastropod herbivores in the field. This field study corroborates earlier laboratory experiments and demonstrates that it is important to make sure that the lack of experimental field data on marine mesoherbivory does not lead to rash conclusions about the lack of significant effects of these herbivores on seaweed performance. The results strongly suggest that gastropods exert a significant selection pressure on the evolution of defensive traits in the seaweeds, and that brown seaweeds can respond to attacks by natural densities of these herbivores through increased chemical resistance to further grazing.     

Effect of different conditioning treatments on total phenolic content and antioxidant activities in two Sargassacean species: Comparison of the frondose Sargassum muticum (Yendo) Fensholt and the cylindrical Bifurcaria bifurcata R. Ross

The effects of different conditioning treatments (fresh, freezing, freeze‐drying, oven‐drying and greenhouse‐drying) on the total phenolic content (TPC) and antioxidant activities of two brown algae, Sargassum muticum and Bifurcaria bifurcata, were investigated and compared. Phenolic compounds were extracted in a methanol/water (50:50) solution, and TPC was measured by the colorimetric Folin‐Ciocalteu assay. Antioxidant activity was assessed by the DPPH (2, 2‐diphenyl‐1‐picrylhydrazyl) radical scavenging assay and the β‐carotene bleaching method. The dried seaweeds showed lower phenolic contents and lower antioxidant capacities than the fresh and frozen ones, which suggests that the phenolic content and antioxidant activities are decreased by the drying treatments, especially, oven‐ and greenhouse‐drying. Relationships between TPC, antioxidant properties and conditioning treatments are discussed.     

SEASONALITY OF SELECTED NUTRITIONAL CONSTITUENTS OF EDIBLE DELMARVA SEAWEEDS

Edible seaweeds have not been thoroughly explored for food, medicinal, or industrial purposes in the United States. This study compared selected proximate constituents of three edible seaweed species (Ulva lactuca L., Fucus vesiculosus L., and Gracilaria tikvahiae McLachan) at two sites for possible future development as a food crop on the Delmarva Peninsula. Sampling was conducted bimonthly at Chincoteague Memorial Park, Virginia, and Indian River Inlet, Delaware, from 2005 to 2008. Proximate constituents of moisture, ash, dietary fiber, proteins, and fat were measured seasonally and calorific values were calculated. Data were analyzed using correlation, paired samples t‐tests and one‐ and two‐way ANOVA. Significant variations in the proximate constituents were found among seasons, species, and between sites. The brown seaweed (Fucus) at both sites had higher fiber, fat, and ash (mineral) content than the green (Ulva) or the red (Gracilaria). Ulva and Gracilaria had higher protein content than Fucus. Seaweeds from Delaware had more fat, ash, and protein than from Virginia, potentially because of the more polluted, nutrient rich environment at the Delaware site. Positive correlations between seaweed fat and protein content may indicate an increase in the synthesis of both components under optimal growth conditions. Species' physiology differences and the water quality at the two sites likely impacted proximate constituent values. This study contributed new information to the existing body of knowledge in the areas of nutrition and ecology of seaweeds and their potential as a cash crop.     

FATTY ACIDS,AMINO ACIDS,MINERAL CONTENTS,AND PROXIMATE COMPOSITION OF SOME BROWN SEAWEEDS1

This study was conducted to create a nutritional database on brown seaweeds and to popularize their consumption and utilization in Iran. The fatty acid contents, amino acids profiles, and certain mineral elements composition of some brown seaweeds, Padina pavonica (L.) Thivy, Dictyota dichotoma (Huds.) J. V. Lamour., and Colpomenia sinuosa (Mert. ex Roth) Derbés et Solier were determined. Total lipid content ranged from 1.46 ± 0.38 to 2.94 ± 0.94 g · 100 g^?1dry weight (dwt), and the most abundant fatty acids were C16:0, C18:1, C20:4 ω6, and C20:5 ω3. The unsaturated fatty acids predominated in all species and had balanced sources of ω3 and ω6 acids. Highest total polyunsaturated fatty acid (PUFA) levels occurred in C. sinuosa. The protein content of D. dichotoma was 17.73 ± 0.29 g · 100 g^?1dwt, significantly higher than the other seaweeds examined. Among amino acids essential to human nutrition, methionine (Met; in D. dichotoma and P. pavonica) and lysine (Lys; in C. sinuosa) were present in high concentrations. The crude fiber content varied by 9.5 ± 11.6 g · 100 g^?1dwt in all species. Chemical analysis indicated that ash content was between 27.02 ± 0.6 and 39.28 ± 0.7 g · 100 g^?1dwt, and that these seaweeds contained higher amounts of both macrominerals (7,308–9,160 mg · 100 g^?1dwt; Na, K, Ca) and trace elements (263–1,594 mg · 100 g^?1dwt; Fe, Ni, Mn, Cu, Co) than have been reported for edible land plants. C. sinuosa had the highest amount of Ca, Fe, and a considerable content of Na was measured in P. pavonica.     

Phycological research in the development of the Chinese seaweed industry

The term seaweed industry is employed in a broad sense and includes production both of commercial seaweeds such as Laminaria and Porphyra by phycoculture and of processed seaweed products, such as algin, agar and carrageenan.Before the founding of the People's Republic, China had a very insignificant seaweed industry, producing small quantities of the purple laver Porphyra and the glueweed Gloiopeltis by the primitive rock-cleaning method and the kelps Laminaria and Undaria by the primitive stone-throwing method, both aiming at enhancing the growth of the wild seaweeds. Also, a small quantity of agar was manufactured by the traditional Japanese method of gelling, freezing, thawing and drying the product. The small production was not sufficient to meet the demand of the Chinese people who for ages have appreciated seaweeds and their products for food. Therefore, large quantities of seaweeds and seaweed products had to be imported from various countries, for instance, Eucheuma and Gracilaria from Indonesia and other southeastern Asian countries, Laminaria and agar from Japan, even Porphyra from the USA. Annual Laminaria import from Japan generally amounted to over 10 000 tons and in some years approached 20 000–30 000 tons. Some quantities of the glueweed Gloiopeltis and the vermifuge weed Digenea simplex were exported, mainly to Japan.Since the founding of the People's Republic of China in October, 1949, China has exerted efforts to build up a self-supporting seaweed industry. Now after a lapse of 30-some years, a sizable seaweed industry has been developed. China is now able to produce by phycoculture more than one million tons of fresh seaweeds, including Laminaria, Undaria, Porphyra, Eucheuma, Gracilaria etc. and several thousand tons of seaweed extracts, including algin, agar, carrageenan, mannitol and iodine. At present, China still imports some quantities of seaweeds and seaweed products from various countries but is able to produce sufficient quantities to meet the people's need and even to export some quantities of the seaweeds Laminaria, Undaria and Porphyra and the seaweed products algin and mannitol.At the Tenth International Seaweed Symposium, I presented a paper on the Marine Phycoculture of China, in which I emphasized on the methods of cultivation (Tseng 1981b). Therefore I would like to take this opportunity to supplement the last lecture by presenting a paper on the role of phycological research in the development of China's seaweed industry.     

Antioxidant activities and phenolics content of eight species of seaweeds from north Borneo

The antioxidant activity of eight edible species of Malaysian North Borneo seaweeds obtained from Sabah waters (Kudat, Tanjung Aru and Semporna) consisting of three red seaweeds (Eucheuma cottonii, E. spinosum and Halymenia durvillaei), two green seaweeds (Caulerpa lentillifera and C. racemosa) and three brown seaweeds (Dictyota dichotoma, Sargassum polycystum and Padina sp.) were determined. Methanol and diethyl ether were used as extraction solvent. The antioxidant activities were determined by two methods, TEAC (trolox equivalent antioxidant capacity) and FRAP (ferric reducing antioxidant power) assays. The total phenolic content of the extract was determined according to the Folin–Ciocalteu method and results were expressed as phloroglucinol equivalents. The methanolic extracts of green seaweeds, C. lentillifera and C. racemosa, and the brown seaweed, S. polycystum showed better radical-scavenging and reducing power ability, and higher phenolic content than the other seaweeds. The TEAC and FRAP assays showed positive and significantly high correlation (R ² = 0.89). There was a strong correlation (R ² = 0.96) between the reducing power and the total phenolic content of the seaweeds methanolic dry extracts. These seaweeds could be potential rich sources of natural antioxidants.     

Amino acid composition, protein content and calculation of nitrogen-to-protein conversion factors for 19 tropical seaweeds

The use of nitrogen‐to‐protein conversion factors (N‐Prot factors) is the most practical way of determining protein content. The accuracy of protein determination by this method depends on the establishment of N‐Prot factors specific to individual species. Experimental data are needed to allow the use of this methodology with seaweeds. The present study was designed to characterize the amino acid composition and to establish specific N‐Prot factors for six green, four brown and nine red marine algae. Mean values for individual amino acids tended to be similar among the three groups, but some differences were found. Green algae tended to show lower percentages of both aspartic acid and glutamic acid than the other two groups of algae. The percentages of both lysine and arginine were higher in red algae, while brown algae tended to show more methionine than green and red algae. The actual protein content of the species, based on the sum of amino acid residues, varied from 10.8% (Chnoospora minima, brown algae) to 23.1% (Aglaothamnion uru‐guayense, red algae) of the dry weight. Nitrogen‐to‐protein conversion factors were established for the species studied, based on the ratio of amino acid residues to total nitrogen, with values ranging from 3.75 (Cryptonemia seminervis, red algae) to 5.72 (Padina gymnospora, brown algae). The relative importance of non‐protein nitrogen is greater in red algae, and consequently lower N‐Prot factors were calculated for these species (average value 4.59). Conversely, protein nitrogen content in both green and brown algae tends to be higher, and average N‐Prot factors were 5.13 and 5.38, respectively. An overall average N‐Prot factor for all species studied of 4.92 ± 0.59 (n = 57) was established. This study confirms that the use of the traditional factor 6.25 is unsuitable for seaweeds, and the use of the N‐Prot factors proposed here is recommended.     

Microbiology and storage life of fresh edible seaweeds

Samples of two edible seaweeds, Palmaria palmata and Ulva rigida, were stored at 4 °C after harvesting, and their microbial flora were measured over a period of two weeks, using food control methods. The results showed a low level of mesophilic aerobes, fungi and yeasts throughout the storage period, whether the seaweeds were unwashed, or washed with seawater, and there was a satisfactory retention of physical characteristics. Seaweeds washed with tap water degraded in less than one week.     

Production, use and fate of Chilean brown seaweeds: re-sources for a sustainable fishery

Chile is an important producer of brown seaweeds representing 10% of world supply. Landings of Chilean kelp fluctuated between 40,000 t.year⁻¹ in the early ‘80s to 250,000 t.year⁻¹ more recently. Commercialized algae come from natural populations and no mass-cultures of involved species have been established. Four species of brown algae are commercially collected in the country: Lessonia trabeculata, L. nigrescens, Macrocystis pyrifera and M. integrifolia. Since 2000, the demand of alginate sources and food for cultivated abalones dramatically raised the harvesting of these species. Direct evaluations of Lessonia spp. and Macrocystis standing-stocks were made along 700 km of coast in northern Chile. Lessonia spp. estimated populations exceed 900,000 t, whereas M. integrifolia does not exceed 300 t. The insights provided indicate that sustainability of Chilean kelp subjected to intense harvesting would require management programs including the following bio-ecological recommendations: (1) to harvest the entire plant including the holdfast; (2) to harvest plants larger than 20 cm in diameter; (3) to harvest plants sparsely, selecting mayor specimens; (4) rotation of harvesting areas; and (5) for Macrocystis, to cut the canopy 1–2 m from the surface. They must be implemented in a National Program of Kelp Management, elaborated by government, scientists, fisherman, and industry.     

Contents of ultraviolet-absorbing substances in two color morphs of the photosymbiotic ascidian Didemnum molle

The contents of mycosporine-like amino acids (MAAs) were compared in the two color morphs (dark-gray and brown colonies) of the tropical ascidian Didemnum molle (Herdman, 1886), which harbors the photosymbiotic prokaryote Prochloron. The colonies of each color morph were exclusively distributed in shallow reef lagoons at the different sites. Spectroscopic and chromatographic analyses showed that the Prochloron cell density and MAA concentration in the dark-gray colonies were an estimated 1.4 and 2.4 times higher, respectively, than in the brown colonies. The significant difference in MAA contents between the color morphs was primarily due to the difference in shinorine contents (p < 0.01, Mann–Whitney U-test). The high concentration of MAAs in the dark-gray colonies may provide better conditions for Prochloron cells, compared to the brown colonies with lower MAA concentrations.     

Interaction of Mercuric Ions with Different Marine Algal Species

The use of different seaweeds such as Sargassum sp., Turbinaria conoides, and Ulva sp. in removing mercury(II) from aqueous solutions were investigated. The initial experimental runs, conducted at different equilibrium pH conditions, demonstrated that brown seaweeds outperformed green seaweed in Hg(II) biosorption at all pH conditions. In particular, at pH 5, maximum biosorption capacities of 170.3 and 145.8 mg/g were recorded for the brown seaweeds T. conoides and Sargassum sp., respectively, compared with 138.4 mg/g for the green seaweed Ulva sp. Isotherm data were modeled and interpreted using the Langmuir, Freundlich, Redlich-Peterson, and Toth models, with the latter described the Hg(II) isotherms with high correlation coefficients and low % error values. The kinetic data indicate the rapidity of the biosorption process, with the equilibrium achieved within 90 min. Several models, including the Elovich, pseudo-first-order, and pseudo-second-order models, were examined for their suitability with the present data; the correlation coefficient and % error values, along with better prediction of equilibrium uptake values, favored the pseudo-first-order model. The desorption experiments were highly successful for T. conoides biomass with 0.05 M HCl, whereas for the other two seaweeds, 0.05 M HCl resulted in high biomass weight loss. Reusing T. conoides biomass in three successive sorption-desorption cycles resulted in only 8.8% reduction in Hg(II) biosorption capacity compared with its original uptake.     

Rapid determination of nucleosides,nucleobases and free amino acids in brown seaweeds using ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry

In this study the contents of nucleosides, nucleobases and free amino acids (FAAs) in common brown seaweeds Saccharina japonica, Sargassum pallidum, S. fusiforme, S. thunbergii and S. muticum from major production areas in China were determined by ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-TQ-MS). The total contents of nucleosides and nucleobases varied from 48.46 to 4,105.00 μg g^?1. Among the five seaweeds, levels of nucleosides and nucleobases in S. japonica were higher than the other species. The contents of ribonucleosides in these brown seaweeds were higher than those of deoxynucleosides. Uridine was the predominant constituent in all samples while 2′-deoxycytidine was the least in most samples. FAAs contents ranged from 0.14 to 22.76 mg g^?1. Among the five seaweeds, levels of FAAs in S. muticum were higher than the other species. Essential amino acids accounted for 3.26–51.49 % of total FAAs contents in different species. Glutamic acid was the major constituent in most samples. Four non-protein amino acids, γ-aminobutyric acid, taurine, hydroxyproline and citrulline, were found in the seaweed samples. Furthermore, principal component analysis (PCA) showed that chemical profiles of nucleosides, nucleobases and FAAs in S. pallidum and S. fusiforme were different from S. muticum, S. thunbergii and S. japonica. Common brown seaweeds could be promising natural sources for future industrial research into nucleosides, nucleobases and FAAs with potential benefits for human health.     

Seasonal patterns of nucleic acid concentrations and amino acid profiles of Parapenaeus longirostris (Crustacea, Decapoda): relation to growth and nutritional condition

The present work describes the seasonal changes in nucleic acid concentrations and amino acid profiles in the muscle of juvenile Parapenaeus longirostris and their relation to growth and nutritional condition. RNA content varied significantly between seasons, being the highest values attained in spring and the lowest in winter (p < 0.05). Similar results were obtained with RNA:protein and RNA:DNA ratios. In respect to total amino acid content (TAA), a significant increase from winter to spring was observed (p < 0.05) and the major essential amino acids (EAA) were arginine, histidine and leucine. Within non-essential amino acids (NEAA) glutamic acid, aspartic acid, glycine and proline were dominant. From winter to spring, a significant variation in NEAA content occurred (26.8; p < 0.05), mainly due to the significant increase of glutamic acid (79.1) and serine (66.7) (p < 0.05). EAA content did not vary significantly between seasons (p > 0.05). In opposition, during this period a significant decrease in the free amino acid content (FAA) was observed (p < 0.05); a higher percentage of decrease was attained in free non-essential (FNEAA – 42.9) in comparison to free essential amino acids (FEAA – 40.2). The significant increase in RNA and TAA contents from winter to spring may be related with protein synthesis. On the other hand, the lowest values obtained in winter may be due to a reduction in feeding activity; in this period the muscle protein must be progressively hydrolysed, which is evident with the higher FAA content. The liberated amino acids enter FAA pool and become available for energy production. In conclusion, it was evident that the seasonal cycle in activities such as feeding and growth with nucleic acids and amino acid analyses was noticed.     

Influence of light and nitrogen on the phlorotannin content of the brown seaweeds Ascophyllum nodosum and Fucus vesiculosus

Phlorotannins, C-based defence compounds in brown seaweeds, show a high degree of spatial and temporal variation within seaweed species. One important model explaining this variation is the Carbon Nutrient Balance Model (CNBM), which states that the relative supply of carbon and limiting nutrients will determine the level of defence compounds in plants. Nitrogen is often considered to be the limiting nutrient for marine macroalgal growth and the CNBM thus predicts that when the carbon:nitrogen ratio is high, photosynthetically fixed carbon will be allocated to production of phlorotannins. In the present study, we evaluated the effects of light (i.e. carbon) and nitrogen on the phlorotannin content of two intertidal brown seaweeds, Ascophyllum nodosum and Fucus vesiculosus. This was done in an observational field study, as well as in a manipulative experiment where plants from habitats with different light regimes were subjected to different nitrogen and light treatments, and their phlorotannin content was measured after 14 days. The results showed that there was a negative relationship between tissue nitrogen and phlorotannin content in natural populations of F. vesiculosus, but not in A. nodosum. In the short term, the phlorotannin content in both algal species was not affected by changes in nitrogen availability. Exposure to sunlight had a positive effect on the phlorotannin content in natural populations of both algal species but, in the manipulative experiment, only F. vesiculosus showed a rapid response to changes in light intensities. Plants subjected to sunlight contained higher phlorotannin content than shaded plants. In conclusion, the results imply that nitrogen availability explains some of the natural variation in the phlorotannin content of F. vesiculosus, but the light environment has greater importance than nitrogen availability in predicting the phlorotannin content of each species.     

Modelling the Effects of Debranching and Microwave Irradiation Treatments on the Properties of High Amylose Corn Starch by Using Response Surface Methodology

Response surface methodology was applied to determine the effects of pullulanase debranching, microwave irradiation time (2–4 min) and power (20–100%) on resistant starch (RS) formation and in-vitro glycemic index (GI) values in high amylose corn starch, Hylon VII. Starch:water (1:10) suspensions were cooked and autoclaved, debranched with pullulanase (1000 PUN/g; 1500 U/kg starch) at 60 °C and then different microwave-storing cycles and drying (oven or freeze drying) processes were applied. In order to describe the relationship between the dependent and independent variables (microwave power and irradiation time), the response values were fitted by first order polynomial regression models. Significance analysis showed that microwave irradiation time had significant effect on RS content and GI value of the samples treated with one cycle of microwave-storing prior to freeze-drying. Microwave power had significant factor on the GI value of the samples that were oven-dried after one cycle of microwave-storing. Solubility and water binding capacity values of all heat treated samples were higher than those of native starch. On the other hand, RVA viscosity values were lower than native starch for oven-dried samples. Water binding capacity, solubility and final viscosity values of the freeze-dried samples were higher than those of oven-dried ones.     

Variations in the alginate content and composition of Durvillaea antarctica and D. willana from southern New Zealand

The brown seaweeds Durvillaea antarctica andD. willana are dominant components of the lowerlittoral and upper sublittoral of exposed rocky shoresin southern New Zealand. Tissue samples of bothspecies, harvested from a site on the south-east coastof South Island over a period of 2 years, wereanalysed for alginate content and composition.Individuals of both species were further separatedinto different blade (lamina and palm) and stipe(cortex and medulla) fractions to assess variationwithin the thallus. On average the alginate contentand frequency of mannuronic acid (F_m) was higherin D. antarctica than in D. willana. Blades contained more alginate than stipes, laminaeand stipes were rich in mannuronic acid whereasholdfasts were rich in guluronic acid. Variations incomposition are considered to reflect the functionaldifferences of the tissue, giving flexibility to bladeand stipe and rigidity to the holdfast. Despitefluctuations in content and composition betweencollection times no seasonal trends in eithercomponent were apparent.     

Use of freeze-dried microalgae for rearing gilthead seabream, Sparus aurata L., larvae. II. Biochemical composition

The objectives of this study were to test whether freeze-dried microalgae are nutritionally adequate for rearing rotifers as food for gilthead seabream larvae. The elemental composition (C, N, H) and fatty acid composition were analysed in larvae of gilthead seabream, Sparus aurata L., rotifers Brachionus plicatilis and Brachionus rotundiformis and freeze-dried microalgae Nannochloropsis oculata. Four larval feeding treatments were tested: (A) larvae fed rotifers cultivated with freeze-dried microalgae and daily addition of freeze-dried microalgae to the larval tanks; (B) larvae fed rotifers cultivated with freeze-dried microalgae and daily addition of live microalgae to the larval tanks; (C) larvae fed rotifers cultivated with freeze-dried microalgae, without addition of microalgae to the larval tank and (D) larvae fed rotifers cultivated with live microalgae and daily addition of live microalgae to the larval tanks. No significant differences were observed between the biochemical composition of larvae with treatment A (with freeze-dried microalgae) and the composition of larvae in treatment D that were obtained with the acceptable methods for culture systems (with live microalgae).     

Influence of acoustic stimulation on the circadian and ultradian rhythm of premature infants

The aim of the present study was to evaluate the development of the circadian rhythm of the salivary cortisol in premature infants and its correlation with the onset of the sleep–activity behavior pattern during the first 3 weeks of life under controlled light:dark conditions. Furthermore, we investigated the influence of acoustic stimulation by audiotaped lullabies or the maternal voice on the cortisol values and long-term sleep–activity patterns. The study was a block-randomized, prospective clinical trial with a study population of 62 preterm neonates (30?<?37 gestational age). We compared two study groups who listened either to music or to the maternal voice (music: N?=?20; maternal voice: N?=?20) with a matched control group (N?=?22). The acoustic stimulation took place every evening between 20:00 and 21:00?h for 30?min over a period of 2 weeks. The cortisol values and activity–rest behavior of the neonates were determined during the first 3 weeks of life on the 1st, 7th and 14th day. Actigraphic monitoring was used to record the activity pattern continuously over 24?h and a validated algorithm for neonates was used to estimate sleep and wakefulness. The saliva samples were obtained 10?min before and 10?min after the acoustic interventions for the study groups. Additionally, saliva samples were obtained from the control group seven times over a 24-h period (20:00, 21:00, 01:00, 05:00, 08:00, 13:00 and 17:00?h). The cortisol data were analyzed by fast Fourier transformation to assess periodic characteristics and frequencies. Hierarchical linear modeling was further performed for the statistical analysis. Results: The cortisol rhythm analysis indicated a circadian rhythm pattern for only one premature infant, all others of the neonates showed no circadian or ultradian rhythm in cortisol. Cortisol level of the premature neonates was significantly higher during the first day of the study period at night-time (median: 17.1?nmol/L, IQR?=?9.7–24.4?nmol/L) than on days 7 (median: 9.6?nmol/L, IQR?=?4.7–14.6?nmol/L; Tukey-HSD, z?=?4.12, p?<?0.001) and 14 (IQR?=?5.8–13.7?nmol/L; Tukey-HSD, z?=?2.89, p?<?0.05). No significant effect of acoustic stimulation was observed on the cortisol concentration and sleep–wake behavior. The activity–sleep rhythm of preterm neonates was dominated by ultradian rhythm patterns with a prominent period length of 4?h (30.5%). Activity frequencies of neonates were also significantly higher overnight on the first study day (mean: 329?±?185.1?U) than of night seven (mean: 260.2?±?132.4?U; Tukey-HSD, z?=?2.50, p?<?0.05). Quiet-activity patterns increased, whereas high-activity patterns decreased during the observation period. Average sleep time increased significantly during the study time from day 1 to day 7 (Tukey-HSD, z?=?2.51, p?<?0.05). In conclusion, premature infants showed higher cortisol levels – without a circadian rhythmicity – and higher activity frequencies in the first days after birth which may reflect an adaptation process of neonates after birth. Cortisol concentrations and the activity patterns were not influenced by music interventions.