Spatial and Temporal Variations in the Species Composition of Bycatch Collected During a Striped Mullet (Mugil cephalus) Survey

We examined the variations in species composition of bycatch collected in an annual spawning-season survey of striped mullet, Mugil cephalus, in Tampa Bay and Charlotte Harbor, FL. Bycatch was defined as all species captured with the collection gear other than the target species, M. cephalus. Variations between habitat types, between months, and between years in the species composition of bycatch captured 1993-96 in this ongoing survey were examined using a nonparametric analysis of variance based on Bray-Curtis similarities. Mugil cephalus was the dominant species collected in both study areas, representing 16%-100% of the annual catch. Lagodon rhomboides and Arius felis were the most abundant bycatch species in Tampa Bay, and A. felis and Mugil curema were the most abundant bycatch species in Charlotte Harbor. Archosargus probatocephalus, Sciaenops ocellatus, and Cynoscion nebulosus composed the majority of the remaining bycatch species collected. Bycatch species composition was not significantly different between months, although indices of species richness (Margalef\u27s index, d), species diversity (Shannon index, H\u27 ), and evenness (Pielou\u27s index, J\u27) declined from fall to winter in each year. Species composition differed significantly between riverine and bay habitats and between habitats with and without bottom vegetation (seagrass). Samples from seagrass habitats had more L. rhomboides, A. probatocephalus, and S. ocellatus, and samples from habitats without seagrass had more A. felis. Indices of species richness, diversity, and evenness were lowest in 1996 as a result of increased catches of M. cephalus and decreased occurrence of bycatch in survey samples. The implementation of the Florida net ban in 1995 may have brought about this increased abundance of M. cephalus and concomitant decrease in the percentage of bycatch captured in survey samples in 1996

Correlating network structure with functional properties of capillary alginate gels for muscle fiber formation

Capillary alginate gels have the potential to be used as scaffold for the growth of muscle cells for cultured meat owing to the formation of aligned skeletal muscle cells along the length of self-assembled micro-capillaries within the calcium alginate gel. The functional properties (mechanical and permeability) of the gels were determined and correlated to the nano-lengthscale of the gel network using small-angle X-ray scattering. Calcium ions were let to diffuse into the alginate solution in order to obtain spontaneously formed capillaries. We show that the resulting calcium alginate network is isotropic in the plane perpendicular to the inflow of cross linking ions while anisotropic in the parallel plane. The structural anisotropicity is reflected in the mechanical properties (measured via uniaxial stress relaxation) of the gel, where a larger force is required to compress the gel in the isotropic plane than in the anisotropic plane. The findings suggest that the network is layered, or composed of “sheets” with denser regions of alginate, sheets that are weakly attached to each other, similar to the structure of bacterial cellulose. Such structure would further explain the increased permeability of labeled dextran (as determined using fluorescence recovery after photo-bleaching) that we observed in the alginate gels used in this study, as compared to internally set calcium alginate gel

Correlating network structure with functional properties of capillary alginate gels for muscle fiber formation

Capillary alginate gels have the potential to be used as scaffold for the growth of muscle cells for cultured meat owing to the formation of aligned skeletal muscle cells along the length of self-assembled micro-capillaries within the calcium alginate gel. The functional properties (mechanical and permeability) of the gels were determined and correlated to the nano-lengthscale of the gel network using small-angle X-ray scattering. Calcium ions were let to diffuse into the alginate solution in order to obtain spontaneously formed capillaries. We show that the resulting calcium alginate network is isotropic in the plane perpendicular to the inflow of cross linking ions while anisotropic in the parallel plane. The structural anisotropicity is reflected in the mechanical properties (measured via uniaxial stress relaxation) of the gel, where a larger force is required to compress the gel in the isotropic plane than in the anisotropic plane. The findings suggest that the network is layered, or composed of “sheets” with denser regions of alginate, sheets that are weakly attached to each other, similar to the structure of bacterial cellulose. Such structure would further explain the increased permeability of labeled dextran (as determined using fluorescence recovery after photo-bleaching) that we observed in the alginate gels used in this study, as compared to internally set calcium alginate gel

Cardiovascular and sympathetic neural responses to handgrip and cold pressor stimuli in humans before, during and after spaceflight

Astronauts returning to Earth have reduced orthostatic tolerance and exercise capacity. Alterations in autonomic nervous system and neuromuscular function after spaceflight might contribute to this problem. In this study, we tested the hypothesis that exposure to microgravity impairs autonomic neural control of sympathetic outflow in response to peripheral afferent stimulation produced by handgrip and a cold pressor test in humans. We studied five astronauts ≈72 and 23 days before, and on landing day after the 16 day Neurolab (STS-90) space shuttle mission, and four of the astronauts during flight (day 12 or 13). Heart rate, arterial pressure and peroneal muscle sympathetic nerve activity (MSNA) were recorded before and during static handgrip sustained to fatigue at 40 % of maximum voluntary contraction, followed by 2 min of circulatory arrest pre-, in- and post-flight. The cold pressor test was applied only before (five astronauts) and during flight (day 12 or 13, four astronauts). Mean (± s.e.m.) baseline heart rates and arterial pressures were similar among pre-, in- and post-flight measurements. At the same relative fatiguing force, the peak systolic pressure and mean arterial pressure during static handgrip were not different before, during and after spaceflight. The peak diastolic pressure tended to be higher post- than pre-flight (112 ± 6 vs. 99 ± 5 mmHg, P = 0.088). Contraction-induced rises in heart rate were similar pre-, in- and post-flight. MSNA was higher post-flight in all subjects before static handgrip (26 ± 4 post- vs. 15 ± 4 bursts min−1 pre-flight, P = 0.017). Contraction-evoked peak MSNA responses were not different before, during, and after spaceflight (41 ± 4, 38 ± 5 and 46 ± 6 bursts min−1, all P > 0.05). MSNA during post-handgrip circulatory arrest was higher post- than pre- or in-flight (41 ± 1 vs. 33 ± 3 and 30 ± 5 bursts min−1, P = 0.038 and 0.036). Similarly, responses of MSNA and blood pressure to the cold pressor test were well maintained in-flight. We conclude that modulation of muscle sympathetic neural outflow by muscle metaboreceptors and skin nociceptors is preserved during short duration spaceflight