Some Observations on the Vertical Migrations of the Dinoflagellate Prorocentrum micans Ehrenberg in the Lim Fjord (Northern Adriatic)

Tokom 48-satnog razdoblja praćena je vertikalna distribucija dinoflagelata Prorocentrum micans Ehrenberg u odnosu na dnevne promjene intenziteta svjetla, te vertikalnu raspodjelu važnijih hranjivih soli (nitrata i fosfata). Uzorci vode za biološke i fizikalno-kemijske analize uzimani su na postaji u Limskom kanalu u 4-satnim vremenskim intervalima, na dubinama od 0 do 13 metara. Rezultati indiciraju da P. micans migrira za najjače insolacije na dubinu od 5 metara (gdje se u periodu od 8 do 12 sati primjećuje izrazito povećanje gustoće stanica u odnosu na ostale istraživane dubine). Smanjivanjem intenziteta svjetla, primjećuju se migracije te vrste u dublje slojeve (10—13 m). Pretpostavlja se da su ta gibanja bila povezana sa nešto višim koncentracijama fosfata, hranjive soli, za koju se smatra da limitira primarnu proizvodnju u vodama sjevernog Jadrana. Nitrati su u toku istraživane periode bili nađeni u količinama višim od onih koje bi se mogle smatrati graničnima za primarnu proizvodnju, a za razliku od fosfata, najviše koncentracije nitrata bile su općenito nađene u površinskim slojevima.Diurnal vertical migration of the dinoflagellate Prorocentrum micans Ehrenberg was investigated under field conditions in relation to the underwater light field, and the vertical distribution of nutrients (phosphates and nitrates). Water samples were taken in the Lim Fjord at 4-hour intervals over a 48 hr period. Samples were collected from 0, 2, 5, 7, 10 and 13-m depths for microscopical analysis of the species present, and at 0, 5, 10 and 13 m for other physical and chemical measurements. The changes in the vertical distribution of P. micans cell densities during the investigation show a periodicity, indicating that the dinoflagellate is capable of undergoing diel vertical migrations. Results indicated that P. micans »avoids« surface layers and accumulates at 5-m depth during the daylight intensities (Figs. 2, 3, 4). During the night, with the lowering of light intensities, the algae migrated to the deeper portions of the water colum (10—13 m). It is hypothesized that this downward movement is related to the availability of phosphate, a nutrient considered limiting phytoplankton production in the Northern Adriatic. Nitrate occurred at concentrations considered non-limiting throughout the water column, and in contrast to phosphate, higher concentrations were found in the upper layers (Figs. 2 and 3)

Some Observations on the Vertical Migrations of the Dinoflagellate Prorocentrum micans Ehrenberg in the Lim Fjord (Northern Adriatic)

Tokom 48-satnog razdoblja praćena je vertikalna distribucija dinoflagelata Prorocentrum micans Ehrenberg u odnosu na dnevne promjene intenziteta svjetla, te vertikalnu raspodjelu važnijih hranjivih soli (nitrata i fosfata). Uzorci vode za biološke i fizikalno-kemijske analize uzimani su na postaji u Limskom kanalu u 4-satnim vremenskim intervalima, na dubinama od 0 do 13 metara. Rezultati indiciraju da P. micans migrira za najjače insolacije na dubinu od 5 metara (gdje se u periodu od 8 do 12 sati primjećuje izrazito povećanje gustoće stanica u odnosu na ostale istraživane dubine). Smanjivanjem intenziteta svjetla, primjećuju se migracije te vrste u dublje slojeve (10—13 m). Pretpostavlja se da su ta gibanja bila povezana sa nešto višim koncentracijama fosfata, hranjive soli, za koju se smatra da limitira primarnu proizvodnju u vodama sjevernog Jadrana. Nitrati su u toku istraživane periode bili nađeni u količinama višim od onih koje bi se mogle smatrati graničnima za primarnu proizvodnju, a za razliku od fosfata, najviše koncentracije nitrata bile su općenito nađene u površinskim slojevima.Diurnal vertical migration of the dinoflagellate Prorocentrum micans Ehrenberg was investigated under field conditions in relation to the underwater light field, and the vertical distribution of nutrients (phosphates and nitrates). Water samples were taken in the Lim Fjord at 4-hour intervals over a 48 hr period. Samples were collected from 0, 2, 5, 7, 10 and 13-m depths for microscopical analysis of the species present, and at 0, 5, 10 and 13 m for other physical and chemical measurements. The changes in the vertical distribution of P. micans cell densities during the investigation show a periodicity, indicating that the dinoflagellate is capable of undergoing diel vertical migrations. Results indicated that P. micans »avoids« surface layers and accumulates at 5-m depth during the daylight intensities (Figs. 2, 3, 4). During the night, with the lowering of light intensities, the algae migrated to the deeper portions of the water colum (10—13 m). It is hypothesized that this downward movement is related to the availability of phosphate, a nutrient considered limiting phytoplankton production in the Northern Adriatic. Nitrate occurred at concentrations considered non-limiting throughout the water column, and in contrast to phosphate, higher concentrations were found in the upper layers (Figs. 2 and 3)

Phytoplankton Bloom in the Northern Adriatic - Dominant Groups and Species during the Spring-Summer Period 1988.

Daje se osvrt na sastav dominantnih grupa i vrsta fitoplanktona u vodama sjevernog Jadrana tijekom perioda »cvjetanja« u proljetno-ljetnom razdoblju 1988. godine. Razmatraju se neke ekološke karakteristike sredine, koje bi mogle imati utjecaj na sastav fitoplanktonske zajednice, te na razvitak specifičnog oblika »cvjetanja«, praćenog tvorbom sluzavih agregata.During the late spring-summer period 1988 an exceptional phytoplankton bloom, accompanied by mucous aggregates formation occurred in the whole of the northern Adriatic region. Nanoplankton dominated the phytoplankton community, while within the microplankton, diatoms (Chaetoceros sp., Rhizosolenia fragilissima, Leptocylindrus danicus, Nitzschia delicatissima compl., Skeletonema costatum) were dominant. The long-term investigation data indicate nanoplankton blooms, as well as di- noflagellate dominance in the late spring period, when the phytoplankton bloom 1988 was determined. An analysis of oceanographic data for the period of initial bloom phase 1988 show unusual values. Salinity was lowered to 16 X 10-3, while all the nutrient concentrations were exceptionally high (Tab. 2). Surface water temperature was higher than usually by about 2”C. On the base of literature data, it is hypothesized that the observed shift in the phytoplankton community structure with appearance of diatoms bloom 1988 could be related to the unusually high nutrient concentrations, originating from freshwater inflows, especially those of the Po river, in the vicinity of which the bloom began

Direct Separation of Clopidogrel Enantiomers by Reverse-Phase Planar Chromatography Method Using beta-Cyclodextrin as a Chiral Mobile Phase Additive

A simple and rapid TLC method using beta-cyclodextrin as a chiral mobile phase additive (CMPA) was developed for direct separation of S-clopidogrel and its impurity R-clopidogrel. The influence of different factors (stationary phases, organic modifiers, chiral selectors and their concentrations in the mobile phase, and optimal saturation time of the chamber) on enantioseparation was studied. The best resolution of clopidogrel enantiomers was achieved on Polygram (R) cel 300 Ac-10% plates using isopropanol-0.5 mM beta-cyclodextrin (6: 4, v/v) as mobile phase in TLC chamber previously equilibrated with the mobile phase for 20 min. The spots were detected under UV light and using iodine vapours. The method enables rapid separation of clopidogrel enantiomers and can be successfully used in control of stereoselective synthesis of clopidogrel and in control of its purity. Finally, the molecular modelling of the inclusion complexes between the analytes and alpha-, beta-, and gamma-cyclodextrin was performed to investigate the mechanism of the enantiorecognition

QSAR studies and design of new analogs of vitamin E with enhanced antiproliferative activity on MCF-7 breast cancer cells

Vitamin E is group of natural antioxidants comprised of tocopherols and tocotrienols. Structural analogs of vitamin E exhibit selective antiproliferative activity that has been intensively studied over the last decade in various cancer cells (MCF-7, MDA-MB-231, LNCaP, PC-3, A549, K562, Jurkat). 2D- and 3D-QSAR studies were applied on a series of 30 derivatives of tocopherols, tocotrienols and chromane with antiproliferative activity in MCF-7 breast cancer cell line. All molecular structures were previously optimized using ab initio Hartree-Fock/3-21 G method. Partial Least Square Regression analysis was used to develop 2D- and 3D-QSAR model. Statistical parameters: R-2 = 0.798, Q(2) = 0.772, R-pred(2) = 0.685 (2D-QSAR) and R-2 = 0.960, Q(2) = 0.830, R-pred(2) = 0.649 (3D-QSAR) indicated on good predictive power of both models. Based on the applied QSAR studies were identified molecular determinant with the greatest influence on the antiproliferative activity and designed novel compounds with enhanced activity against MCF-7 breast cancer cells