Short‐term survival and movements of Atlantic sharpnose sharks captured by hook‐and‐line in the north‐east Gulf of Mexico

Ultrasonic telemetry was used to compare post‐release survival and movements of Atlantic sharpnose sharks Rhizoprionodon terraenovae in a coastal area of the north‐east Gulf of Mexico. Ten fish were caught with standardized hook‐and‐line gear during June to October 1999. Atlantic sharpnose sharks were continuously tracked after release for periods of 0·75 to 5·90 h and their positions recorded at a median interval of 9 min. Individual rate of movement was the mean of all distance and time measurements for each fish. Mean ± s.e . individual rate of movement was 0·45 ± 0·06 total lengths per second (L_T s^?1) and ranged from 0·28 to 0·92 L_T s^?1 over all fish. Movement patterns did not differ between jaw and internally hooked Atlantic sharpnose sharks. Individual rate of movement was inversely correlated with bottom water temperature at capture (r² = 0·52, P ≤ 0·05). No consistent direction in movement was detected for Atlantic sharpnose sharks after release, except that they avoided movement towards shallower areas. Capture‐release survival was high (90%), with only one fish not surviving, i.e. this particular fish stopped movement for a period of 10 min. Total rate of movement was total distance over total time (m min^?1) for each Atlantic sharpnose shark. Mean total rate of movement was significantly higher immediately after release at 21·5 m min^?1 over the first 1·5 h of tracking, then decreased to 11·2 m min^?1 over 1·5–6 h, and 7·7 m min^?1 over 3–6 h (P ≤ 0·002), which suggested initial post‐release stress but quick recovery from capture. Thus, high survival (90%) and quick recovery indicate that the practice of catch‐and‐release would be a viable method to reduce capture mortality for R. terraenovae.     

Evaluation of swimming performance for fish passage of longnose dace Rhinichthys cataractae using an experimental flume

The swimming performance of longnose dace Rhinichthys cataractae, the most widely distributed minnow (Cyprinidae) in North America, was assessed in relation to potential passage barriers. The study estimated passage success, maximum ascent distances and maximum sprint speed in an open‐channel flume over a range of water velocities and temperatures (10·7, 15·3 and 19·3° C). Rhinichthys cataractae had high passage success (95%) in a 9·2 m flume section at mean test velocities of 39 and 64 cm s^–1, but success rate dropped to 66% at 78 cm s^–1. Only 20% of fish were able to ascend a 2·7 m section with a mean velocity of 122 cm s^–1. Rhinichthys cataractae actively selected low‐velocity pathways located along the bottom and corners of the flume at all test velocities and adopted position‐holding behaviour at higher water velocities. Mean volitional sprint speed was 174 cm s^–1 when fish volitionally sprinted in areas of high water velocities. Swimming performance generally increased with water temperature and fish length. Based on these results, fishways with mean velocities <64 cm s^–1 should allow passage of most R. cataractae. Water velocities >100 cm s^–1 within structures should be limited to short distance (<1 m) and structures with velocities ≥158 cm s^–1 would probably represent movement barriers. Study results highlighted the advantages of evaluating a multitude of swimming performance metrics in an open‐channel flume, which can simulate the hydraulic features of fishways and allow for behavioural observations that can facilitate the design of effective passage structures.     

Do viscous forces affect survival of marine fish larvae? Revisiting the ‘safe harbour’ hypothesis

Aquatic organisms physically interact with the water that surrounds them, and this interaction is fundamental in shaping many aspects of their biology. General characteristics of the hydrodynamic interactions between organisms and the flow around them can be captured by the dimensionless Reynolds number (Re), depicting the ratio between inertial and viscous forces operating on the organism. The characteristic flow regime of larval fish that cruise at slow speeds is a regime of low Re, where viscous forces dominate. In this study, we experimentally test the ‘safe harbour’ hypothesis, which proposes that increasing larval body size facilitates an ‘escape’ from the detrimental effects of low Re. Larval gilthead seabream (Sparus aurata) were reared during early ontogeny under artificially manipulated water viscosities to expose larvae to low Re regimes. Larval survival decreased significantly with increasing water viscosity, and increased with increasing standard length. Surviving larvae exceeded the mean length of mortalities by ~1 mm, on average. Our findings provide direct experimental support for the ‘safe harbour’ hypothesis, indicating that marine larvae incur a fitness cost when operating under low Re conditions. Moreover, the results highlight the need to recognize the hydrodynamic environment when considering the a-biotic characteristics that may influence organismal performance and fitness.     

Growth inhibition of dinoflagellate algae in shake flasks: Not due to shear this time!

Large scale algae cultures present interesting challenges in that they exhibit characteristics of typical bacterial and animal cell cultures. One current commercial food additive, docosahexaenoic acid (DHA), is produced using the dinoflagellate algae, Crypthecodinium cohnii. Like animal cell culture, the perceived sensitivity of algae culture to hydrodynamic forces has potentially limited the agitation and aeration applied to these systems. However, the high density cultivation of C. cohnii required for an economically feasible process inevitably results in high oxygen demand. In this study, we demonstrated what first appeared to be a problem with shear sensitivity in shake flasks is most probably a mass transfer limitation. We subsequently demonstrated the limit of chronic and rapid energy dissipation rate, EDR, that C. cohnii cells can experience. This limit was determined using a microfluidic device connected in a recirculation loop to a stirred tank bioreactor, which has been previously used to repeatedly expose animal cells to high levels of EDR. Inhibition of cell growth was observed when C. cohnii cells were subjected to an EDR of 5.9 × 10⁶ W/m³ with an average frequency of 0.2/min or more. This level of EDR is sufficiently high that C. cohnii can withstand typically encountered hydrodynamic forces in bioprocesses. This result suggests that at least one dinoflagellate algae, C. cohnii, is quite robust with respect to hydrodynamic forces and the scale‐up of process using this type of algae should be more concerned with providing sufficient gas transfer given the relatively high oxygen demand. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

EFFECTS OF LIGHT AND TEMPERATURE ON GROWTH,NITRATE UPTAKE,AND TOXIN PRODUCTION OF TWO TROPICAL DINOFLAGELLATES: ALEXANDRIUM TAMIYAVANICHII AND ALEXANDRIUM MINUTUM (DINOPHYCEAE)1

The two tropical estuarine dinoflagellates, Alexandrium tamiyavanichii Balech and A. minutum Halim, were used to determine the ecophysiological adaptations in relation to their temperate counterparts. These species are the two main causative organisms responsible for the incidence of paralytic shellfish poisoning (PSP) in Southeast Asia. The effects of light (10, 40, 60, and 100 μmol photons·m^?2·s^?1) and temperature (15, 20, and 25°C) on the growth, nitrate assimilation, and PST production of these species were investigated in clonal batch cultures over the growth cycle. The growth rates of A. tamiyavanichii and A. minutum increased with increasing temperature and irradiance. The growth of A. tamiyavanichii was depressed at lower temperature (20°C) and irradiance (40 μmol photons·m^?2·s^?1). Both species showed no net growth at 10 μmol photons·m^?2·s^?1 and a temperature of 15°C, although cells remained alive. Cellular toxin quotas (Q_t) of A. tamiyavanichii and A. minutum varied in the range of 60–180 and 10–42 fmol PST·cell^?1, respectively. Toxin production rate, R_tox, increased with elevated light at both 20 and 25°C, with a pronounced effect observed at exponential phase in both species (A. tamiyavanichii, r²=0.95; A. minutum, r²=0.96). Toxin production rate also increased significantly with elevated temperature (P<0.05) for both species examined. We suggest that the ecotypic variations in growth adaptations and toxin production of these Malaysian strains may reveal a unique physiological adaptation of tropical Alexandrium species.     

The effect of spine postures on the hydrodynamic drag in Epinephelus ongus larvae

Laboratory behavioural observation and computational fluid dynamics (CFD) analysis were conducted to examine whether the movement of the elongated dorsal and pelvic spines changed the hydrodynamic drag in white‐streaked grouper Epinephelus ongus larvae. The behavioural observation in the tank revealed that the larvae extended the dorsal and pelvic spines during passive transport and retracted during swimming; the angles of the dorsal and pelvic spines in relation to the anteroposterior axis were larger during the passive transport (mean ± s.d . = 28·84 ± 14·27 and 20·35 ± 15·05°) than those during the swimming (mean ± s.d . = 2·59 ± 5·55 and 0·32 ± 6·49°). The CFD analysis indicated that the relative hydrodynamic drag acting on the larvae was approximately 1·25 times higher when the spines were extended (passive transport) than when the spines were retracted (swimming), suggesting that the E. ongus larvae have an ability to adjust their hydrodynamic drag depending on the behavioural context.     

Antimicrobial activity of honey from the stingless bee Trigona carbonaria determined by agar diffusion,agar dilution,broth microdilution and time‐kill methodology

Aims: The aim of this study was to determine the spectrum of antimicrobial activity of 11 samples of stingless bee honey compared to medicinal, table and artificial honeys. Methods and Results: Activity was assessed by agar diffusion, agar dilution, broth microdilution and time‐kill viability assays. By agar dilution, minimum inhibitory concentration (MIC) ranges were 4% to >10% (w/v) for Gram‐positive bacteria, 6% to >16% (w/v) for Gram‐negative bacteria and 6% to >10% (w/v) for Candida spp. By broth microdilution, all organisms with the exception of Candida albicans and Candida glabrata were inhibited at ≤32% (w/v). Geometric MIC (w/v) means for stingless bee honeys ranged from 7·1% to 16·0% and were 11·7% for medicinal honey and 26·5% for table honey. Treatment of organisms with 20% (w/v) stingless bee honey for 60 min resulted in decreases of 1–3 log for Staphylococcus aureus, >3 log for Pseudomonas aeruginosa and <1 log for C. albicans. Similar treatment with each control honey resulted in decreases of <1 log for all organisms. Conclusions: Stingless bee honey has broad‐spectrum antibacterial activity although activity against Candida was limited. Stingless bee honey samples varied in activity and the basis for this remains to be determined. Significance and Impact of the Study: Stingless bee honey had similar activity to medicinal honey and may therefore have a role as a medicinal agent.     

PHOTOMOVEMENT RESPONSES OF PORPHYRIDIUM PURPUREUM1

The influence of light quality on positive phototopotaxis by the gliding, unicellular red alga Porphyridium purpureum was obtained using interference filters. Cells exposed to 3 × 10^?7 mol · m²· s^?1 of various wavelengths for 72 h showed maximum topotaxis at 420 and 440 nm. The lower threshold for positive, movement was approximately 5 × 10^?8 mol · m^?2· s^?1. Random movement occurred at nonactinic wavelengths, and no movement occurred in the dark. Cell motility appeared to be unaffected by light polarity, suggesting that the photoreceptor(s) for topotaxis and photokinesis are randomly oriented.     

Melatonin does not affect the black pigment migration in the crab Neohelice granulata

N-acetyl-5-methoxytryptamine or melatonin is a multifunctional molecule. The main physiological function, at least in vertebrates, is to transduce to the animal the photoperiodic information and regulate rhythmic parameters. But studies have also observed the action of this molecule on pigment migration in ectothermic vertebrates. Thus the aim of this paper was to investigate in vivo and in vitro the influence of melatonin on the pigment migration in melanophores of the crab Neohelice granulate. Injections of melatonin (2 × 10⁻⁹ moles · crab⁻¹) at 07:00 h or 19:00 h did not affect (p > 0.05) the circadian pigment migration of the melanophores in constant darkness. Additionally no significant pigment migration (p > 0.05) was verified in normal and eyestalkless crabs injected with melatonin (10⁻¹⁰–10⁻⁷ moles · crab⁻¹) during the day or night. In the ^{in vitro} assay, the response of melanophores to the pigment-dispersing hormone in eyestalkless crabs injected with melatonin (2 × 10⁻⁹ moles · crab⁻¹) 1 and 12 hours before the observations did not differ (p > 0.05) from the control group (injected with physiological solution). These results suggest that melatonin does not act as a signaling factor for pigment dispersion or aggregation in the melanophores of N. Granulate.     

Diverse migratory histories of Japanese Trachidermus and Cottus species (Cottidae) as inferred from otolith microchemistry

The migratory histories of Japanese freshwater sculpins, one Trachidermus and four Cottus species, were studied by examining strontium (Sr) and calcium (Ca) concentrations in their otoliths using wavelength dispersive X‐ray spectrometry on an electron microprobe. The Sr : Ca ratios in the otoliths changed with salinity of the habitat. The otoliths of Cottus nozawae showed consistently low Sr : Ca ratios, with an average of 3·37 × 10^?3 from the core to the edge, suggesting a freshwater resident life cycle. In contrast, the otolith Sr : Ca ratios for Trachidermus fasciatus and Cottus kazika changed along the life history transects possibly in accordance with their migration patterns from sea to fresh water. The ratios of T. fasciatus and C. kazika averaged 5·4 × 10^?3 and 5·3 × 10^?3 respectively, in the otolith region from the core to the points 450–890 μm, and changed to the lower levels, averaging 2·0 × 10^?3 and 2·7 × 10^?3, in the outer otolith region. These data suggest that both the species have a catadromous life cycle. The otoliths of Cottus hangiongensis had low Sr : Ca ratios in the two regions from the core to the points 15–30 μm and the points 415–582 μm to the edge, averaging 2·0 × 10^?3 and 1·9 × 10^?3, with significantly higher ratios in the narrow area between these regions, averaging 4·6 × 10^?3. Similar ontogenetic changes in otolith Sr : Ca ratios were found in the otoliths of Cottus amblystomopsis, suggesting their amphidromous life cycle. These findings suggest that otolith Sr : Ca ratios reflect individual life histories and that Japanese Trachidermus and Cottus species have diverse migratory histories.     

Physicochemical studies on xylinan (acetan). III. Hydrodynamic characterization by analytical ultracentrifugation and dynamic light scattering

A laboratory-made sample of the polysaccharide xylinan (acetan) has been further characterized with respect to (i) purity, (ii) molar mass and polydispersity, and (iii) gross conformation by a combination of hydrodynamic measurements (sedimentation velocity and equilibrium analytical ultracentrifugation, viscometry, and dynamic light scattering) in aqueous NaCl (I = 0.10 mol·L⁻¹). Sedimentation velocity diagrams recorded using Schlieren optics revealed highly pure material sedimenting as a single boundary [s^o_20.w = 9.5 ± 0.7) S; k_s = (273 ± 112) mL/g]. The hypersharp nature of these boundaries is symptomatic of a polydisperse and highly nonideal (in the thermodynamic sense) system. Low speed sedimentation equilibrium in the analytical ultracentrifuge using Rayleigh interference optics and two different types of extrapolation procedure (involving point and whole-cell molar masses) gave a weight average molar mass M_w of (2.5 ± 0.5) × 10⁻⁶ g·mol⁻¹ and also a second virial coefficient, B = (2.8 ± 0.7) × 10⁻⁴ mL·mol·g⁻², both values in good agreement with those from light scattering-based procedures (Part II of this series). A dynamic Zimm plot from dynamic light scattering measurements gave a z-average translational diffusion coefficient D^o_20.w = (3.02 ± 0.05) × 10⁻⁸ cm²·s⁻¹ and the concentration-dependence parameter k_D = (370 ± 15) mL/g. Combination of s^o_20.w with D^o_20.w via the Svedberg equation gave another estimate for M_w of ≅ 2.4 × 10⁶ g/mol, again in good agreement. Both the Wales-van Holde ratio (k_s/[η]) ≅ 0.4 (with [η] = (760 ± 77) mL/g) and the ρ-parameter (ratio of the radius of gyration from static light scattering to the hydrodynamic radius from dynamic light scattering) as ρ > 2.0 all indicate an extended conformation for the macromolecules in solution. These findings, plus Rinde-type simulations of the sedimentation equilibrium data are all consistent with the interpretation in terms of a unimodal wormlike coil model performed earlier. © 1996 John Wiley & Sons, Inc.     

Effect of inotropic agents on the calcium binding to isolated cardiac sarcolemma

Ca²⁺ binding to fragmented sarcolemma isolated from canine heart was measured by an ultracentrifugation technique. Two classes of binding site with dissociation constants of 2.0 · 10^?5 and 1.2 · 10^?3 M were identified. The capacities of the high- and low-affinity sites were 15 and 452 nmol/mg, respectively. These sites were not affected by treatment with neuraminidase. The effects of various cations and drugs on Ca²⁺ binding were studied. All cations tested inhibited Ca²⁺ binding with the following order of potency: trivalent > divalent > monovalent cations. The order of potency for the monovalent ions was: Na⁺ > K⁺ > Li⁺ ? Cs⁺ and for the divalent and trivalent ions: La³⁺ ? Mn²⁺ > Sr²⁺ ? Ba²⁺ > Mg²⁺. 1 · 10^?3 M caffeine and 1 · 10^?8 M ouabain increased the capacity of the low-affinity sites to 1531 and 837 nmol/mg, respectively. 1 · 10^?7 M verapamil, acidosis (pH 6.4), 1^?10^?5 M Mn²⁺ and 1 · 10^?4 M ouabain depressed the capacity of the low-affinity sites to a range of 154–291 nmol/mg. The dissociation constants of the high- and low-affinity sites and the capacity of the high-affinity sites were not affected by these agents.     

Postprocessing microflora of commercial attieke (a fermented cassava product) produced in the south of Côte d'Ivoire

The distribution and presence of hygiene indicator and pathogenic micro‐organisms in 375 samples of attieke marketed in Côte d'Ivoire, and their roles in the food poisoning were evaluated. Microbiological analyses were carried out, which included the total viable bacteria, coliforms, Escherichia coli, Staphylococcus aureus, Salmonella, Bacillus spores, fungi and Clostridium perfringens. The results revealed that the viable bacteria counts ranged from 2·2 ± 1·2 × 10⁵ to 3·4 ± 1·4 × 10⁶ CFU g^?1, while the yeasts and the moulds counts ranged, respectively, from 2·4 ± 0·12 × 10⁴ to 9·8 ± 0·4 × 10⁵ CFU g^?1 and 1·3 ± 0·7 × 10¹ to 1·7 ± 0·7 × 10² CFU g^?1. Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Citrobacter freundi, Enterobacter amnigenus, Citrobacter youngae, Enterobacter aerogenes, Klebsiella pneumoniae, Serratia marcescens, Enterobacter agglomerans and Klebsiella oxytoca were the bacteria isolated, and Rhizopus spp., Mucor spp., Thamnidium spp., Fusarium spp., Moniliella spp. the fungi. Escherichia coli, Clostridium perfringens and Salmonella spp. were not found. The occurrence of some bacteria and fungi illustrate that attieke collected in Côte d'Ivoire markets may act as a reservoir of pathogenic micro‐organisms for human.

Significance and Impact of Study

This study demonstrates the great need to carry out microbiological tests frequently on attieke and even more the need to apply correct HACCP system during the production. Attieke is especially a well‐known product in West Africa; hence, it is extremely important to ensure an adequate microbiological quality to guarantee consumers health. Overall, the study highlighted the need for effective communication on microbiological food risks, proper instruction and supervision in food‐handling procedures, greater education on food safety risks.     

Isolation and regeneration of protoplasts from Porphyra dentata and Porphyra crispata

Large numbers of protoplasts (10⁶ to 3·2 × 10⁷ per gram fresh weight) were routinely isolated from two Taiwanese species of Porphyra: P. dentata and P. crispata. Intermediate and final forms of regeneration were observed, including swollen cells, monospore-like cells, filaments, callus-like structures and bladelets. Regeneration of leafy plants was achieved from protoplasts of P. crispata, whereas only conchocelis-like filaments were regenerated from protoplasts of P. dentata. In this latter species, conchosporangia and monosporangia appeared on the filaments upon cultivation at 25 °C. The variability in regenerative patterns is discussed.     

PRIMARY PRODUCTION OF CRUSTOSE CORALLINE RED ALGAE IN A HIGH ARCTIC FJORD1

Crustose coralline algae occupied ～1%–2% (occasionally up to 7%) of the sea floor within their depth range of 15–50 m, and they were the dominant encrusting organisms and macroalgae beyond 20 m depth in Young Sound, NE Greenland. In the laboratory, oxygen microelectrodes were used to measure net photosynthesis (P) versus downwelling irradiance (E_d) and season for the two dominant corallines [Phymatolithon foecundum (Kjellman) Düwel et Wegeberg 1996 and Phymatolithon tenue (Rosenvinge) Düwel et Wegeberg 1996] representing> 90% of coralline cover. Differences in P‐E_d curves between the two species, the ice‐covered and open‐water seasons, or between specimens from 17 and 36 m depth were insignificant. The corallines were low light adapted, with compensation irradiances (E_c) averaging 0.7–1.8 μmol photons·m ^{? 2}·s ^{? 1} and light adaptation (E_k) indices averaging 7–17 μmol photons·m ^{? 2}·s ^{? 1}. Slight photoinhibition was evident in most plants at irradiances up to 160 μmol photons·m ^{? 2}·s ^{? 1}. Photosynthetic capacity (P_m) was low, averaging 43–67 mmol O₂·m ^{? 2} thallus·d ^{? 1} (～250–400 g C·m ^{? 2} thallus·yr ^{? 1}). Dark respiration rates averaged ～5 mmol O₂·m ^{? 2} thallus·d ^{? 1}. In ice covered periods, E_d at 20 m depth averaged ～1 μmol photons·m ^{? 2}·s ^{? 1}, with daily maxima of 2–3 μmol photons·m ^{? 2}·s ^{? 1}. During the open water season, E_d at 20 m depth averaged ～7 μmol photons·m ^{? 2}·s ^{? 1} with daily maxima of ～30 μmol photons·m ^{? 2}·s ^{? 1}. Significant net primary production of corallines was apparently limited to the 2–3 months with open water, and the small contribution of corallines to primary production seems due to low P_m values, low in situ irradiance, and their relatively low abundance in Young Sound.     

Effects of thymol and diphenyliodonium chloride against Campylobacter spp. during pure and mixed culture in vitro

Aims: To determine if the purported deaminase inhibitors diphenyliodonium chloride (DIC) and thymol reduce the growth and survivability of Campylobacter. Methods and Results: Growth rates of Campylobacter jejuni and Camp. coli were reduced compared to unsupplemented controls during culture in Muellar–Hinton broth supplemented with 0·25 μmol DIC or thymol ml^?1 but not with 0·01 μmol monensin ml^?1 or 1% ethanol. Recovery of Camp. jejuni and Camp. coli was reduced >5 log₁₀ CFU from controls after 24 h pure culture in Bolton broth supplemented with 0·25 or 1·0 μmol DIC ml^?1 or with 1·0 μmol thymol ml^?1. Similarly, each test Campylobacter strain was reduced >3 log₁₀ CFU from controls after 24 h mixed culture with porcine faecal microbes in Bolton broth supplemented with 0·25 or 1·0 μmol DIC ml^?1 or with 1·0 μmol thymol ml^?1. Treatments with 0·25 μmol thymol ml^?1, 0·01 μmol monensin ml^?1 or 1% ethanol were less effective. Ammonia production during culture or incubation of cell lysates was reduced by 0·25 or 1·0 μmol DIC ml^?1 but only intermittently reduced, if at all, by the other treatments. Conclusions: Diphenyliodonium chloride and thymol reduced growth, survivability and ammonia production of Camp. jejuni and Camp. coli. Significance and Impact of the Study: Results suggest a potential physiological characteristic that may be exploited to develop interventions.     

Peptones from diverse sources: pivotal determinants of bacterial growth dynamics

Aims: In view of the major problems encountered by microbiologists in obtaining reproducible data on growth dynamics in complex media, we studied the effects of different peptones made from different biological sources and produced by numerous manufacturers. Methods and Results: Peptones (including casein, gelatin, meat, soy and yeast) were assessed as a constituent of the pre‐enrichment broth buffered peptone water (BPW). Generation times (g) and yields of Salmonella serovar Typhimurium were significantly affected by the type of peptone employed with yeast peptones generating yields of 7·04 × 10⁹ CFU ml^?1 and gelatin peptones producing 0·81 × 10⁹ CFU ml^?1. Medium sterilization was also found to have significant effects (P = 0·000) upon subsequent bacterial growth. Filter sterilization of BPW media produced lower generation times compared with those obtained after sterilization by autoclaving. Finally, it was observed that some peptones which produced good growth when inoculated with healthy organisms, showed relatively poor growth when inocula were sublethally injured by heating. Conclusions: Variation in peptone as a constituent of BPW has a significant effect on growth and enumeration of bacteria. Significance and Impact of the Study: Increased consideration with respect to culture media may significantly improve bacterial growth and experimental reproducibility.     

Influence of culture vessel characteristics and agitation rate on gaseous exchange,hydrodynamic stress,and growth of embryogenic cork oak (<Emphasis Type="BoldItalic">Quercus suber</Emphasis> L.) cultures

Somatic embryogenesis can be induced in the leaves of cork oak (Quercus suber L.) trees. The use of this propagation system in multivarietal forestry requires the mass production of cloned plants at low cost. Investigations were made into the influence of three types of Erlenmeyer flask and three orbiting speeds (60, 110, and 160 rpm) on oxygen transfer rate (K_L a), the shear force index (SFI), biomass production, and the proliferation of embryogenic clumps (EMCs) in cultures during the proliferation phase. K_L a varied between 0.11 and 1.47 h⁻¹ without biomass production being limited by oxygen availability. The EMCs grew even in hypoxic conditions, although the suppression of gaseous exchange strongly reduced biomass production. Cultures with different levels of hydrodynamic stress and SFI values (1.4·10⁻³–8.8·10⁻³ cm min⁻¹) were obtained. Proliferation rates of EMCs increased with agitation rate and the SFI. The largest number of EMCs was obtained in baffled flasks agitated at 160 rpm (K_L a of 1.47 h⁻¹, and SFI of 8.8·10⁻³ cm min⁻¹) with mild hydrodynamic stress enhancing growth. Biomass production increased with agitation and hydrodynamic stress, but only when the SFI value was below 5·10⁻³ cm min⁻¹. The greatest biomass production was obtained in smooth 100 ml flasks agitated at 160 rpm. The differentiation of embryos was favoured by the lowest K_L a (0.11 h⁻¹) and SFI (1.40·10³ cm min⁻¹) values, achieved using these flasks when agitated at 60 rpm.     

Zinc and salinity effects on membrane transport in Chara connivens

Pressure-probe measurements showed that the pressure relaxation of internodal cells of the freshwater alga Chara connivens slowed considerably when 1–5 mol m^?3 Zn²⁺, or more especially Zn²⁺ and 75 mol m^?3 NaCl, were present in the medium for periods of 1 h or longer. These results indicate that the water permeability of the Chara membrane is decreased by Zn²⁺, and that this effect is enhanced by 75 mol m^?3 NaCl. Specific values taken after 375 min exposure were: 5 mol m^?3 Zn²⁺ and 75 mol m^?3 NaCl caused the half-time for bulk water movement to increase from 7·8±2·3 to 79·5±5·4s, corresponding to a decrease in the hydraulic conductivity (Lp) from (13·0±3·3) × 10^?7 m s^?1 mPa^?1 to (1·25±0·23) × 10^?7 m s^?1 MPa^?1 (mean±S.D., n= 10). These changes are not seen in the presence of NaCl alone, and to a reduced extent in the presence of 5 mol m^?3Zn²⁺ alone (after 375 min, Lp was (2·4±0·1) × 10^?7 m s^?1 MPa^?1, mean±S.D., n = 6). Ca²⁺ cannot substitute for Zn²⁺, but seems to competitively inhibit Zn²⁺. There was another, kinetically distinct effect of Zn²⁺: the ingress of Na⁺ within 15 min of exposure to 75 mol m^?3 NaCl is halved by the presence of 1–5 mol m^?3 Zn²⁺, although internal osmolality is little changed by Zn²⁺. In spite of this, Zn²⁺ does not exert the long-term protection against NaCl that has been reported for Ca²⁺. Depending on the concentration of Zn²⁺ and the duration of the exposure, the effects on water permeability were fully or partly reversible within 24–48 h. The mechanism of these changes is difficult to identify. One possibility is a zinc-induced restriction of trans-membrane channels to give single-file channels which can be blocked by salt.     

A comparison of two global positioning system devices for team-sport running protocols

The comparability and reliability of global positioning system (GPS) devices during running protocols associated with team-sports was investigated. Fourteen moderately-trained males completed 690 m of straight-line movements, a 570 m change of direction (COD) course and a 642.5 m team-sport simulated circuit (TSSC); on two occasions. Participants wore a FieldWiz GPS device and a Catapult MinimaxX S4 10-Hz GPS device. Typical error of measurement (TE) and coefficient of variation (CV%) were calculated between GPS devices, for the variables of total distance and peak speed. Reliability comparisons were made within FieldWiz GPS devices, between sessions. Small TE were observed between FieldWiz and Catapult GPS devices for total distance and peak speed during straight-line (16.9 m [2%], 1.2 km·h⁻¹ [4%]), COD (31.8 m [6%], 0.4 km·h⁻¹ [2%]) and TSSC protocols (12.9 m [2%], 0.5 km·h⁻¹ [2%]), respectively, with no significant mean bias (p > 0.05). Small TE were also observed for the FieldWiz GPS device between sessions (p > 0.05) for straight-line (9.6 m [1%], 0.2 km·h⁻¹ [1%]), COD (12.8 m [2%], 0.2 km·h⁻¹ [1%]) and TSSC protocols (6.9 m [1%], 0.6 km·h⁻¹ [2%]), respectively. Data from the FieldWiz GPS device appears comparable to established devices and reliable across a range of movement patterns associated with team-sports.