Spatial scale and meiobenthic copepod recolonisation: testing the effect of disturbance size in a seagrass habitat

A central problem in relating disturbance to community structure lies in determining how community structure is affected by the size of disturbance events. In soft-bottom habitats, recovery rate and patterns of macrobenthic community are usually affected by the spatial scale of disturbance. Thus far, no studies have explicitly addressed these issues for meiobenthic copepods. To test the effects of the size of hypoxia/anoxia disturbance on the recovery of meiobenthic copepod communities in a vegetated (Ruppia cirrhosa) sediment, a field experiment was set up in Valle Smarlacca, a brackish lagoon on the northern Adriatic coast of Italy. Plots of three different sizes—small (40×40 cm), medium (80×80 cm) and large (160×160 cm)—were exposed to experimentally induced hypoxia/anoxia for 5 days. Control plots of 40×40 cm were added, for comparison with ambient abundance. Recolonisation and community recovery were then observed for 12 days, with samplings on days 0, 1, 3, 5, 7, 9 and 12. Sampling was designed to focus on the distance from source pools of colonists. The induced anoxia had a severe impact on the copepods, but the impact of the disturbance was independent of plot size. Copepod abundance increased linearly over time, and no differences in recolonisation rate among the differently sized plots were observed. Recolonisation comprised two phases: until day 3, abundances were low and very similar in all plot sizes; from day 5 onwards, abundances of the dominant species (which were the same in control and disturbed plots) increased, and a more diversified pattern among disturbance sizes was observed. Multivariate analyses showed a gradual response of community structure to disturbance size: copepod assemblages in small plots attained the same structure of the control plots at day 5, while for larger-sized plots this occurred later and was observed on the following sampling date. However, clear differences among the three disturbance sizes were never detected. Variability in community structure seemed to respond more to the overall impact of disturbance than to the size of the disturbed area. In the seagrass meadows of the Valle Smarlacca, several factors seem to influence the structural organisation of meiobenthic copepod communities during recolonisation processes. Among others, the recovery of the vegetated habitat to suitable conditions seems to play a much more relevant role than the size of the disturbed patches.     

Circulating hematopoietic progenitor cells in runners.

Because endurance exercise causes release of mediators and growth factors active on the bone marrow, we asked whether it might affect circulating hematopoietic progenitor cells (HPCs) in amateur runners [n = 16, age: 41.8 +/- 13.5 (SD) yr, training: 93.8 +/- 31.8 km/wk] compared with sedentary controls (n = 9, age: 39.4 +/- 10.2 yr). HPCs, plasma cortisol, interleukin (IL)-6, granulocyte colony-stimulating factor (G-CSF), and the growth factor fms-like tyrosine kinase-3 (flt3)-ligand were measured at rest and after a marathon (M; n = 8) or half-marathon (HM; n = 8). Circulating HPC counts (i.e., CD34(+) cells and their subpopulations) were three- to fourfold higher in runners than in controls at baseline. They were unaffected by HM or M acutely but decreased the morning postrace. Baseline cortisol, flt3-ligand, IL-6, and G-CSF levels were similar in runners and controls. IL-6 and G-CSF increased to higher levels after M compared with HM, whereas cortisol and flt3-ligand increased similarly postrace. Our data suggest that increased HPCs reflect an adaptation response to recurrent, exercise-associated release of neutrophils and stress and inflammatory mediators, indicating modulation of bone marrow activity by habitual running.     

Microsporogenesis of the feathers (fertile branches derived from annual buds) in Vitis vinifera,cv Picolit giallo

Abstract

Using light and electron microscopy, we have studied the microsporogenesis and tapetal development of the feathers in two different low producing clones of Picolit giallo (sp. Vitis vinifera). In these clones while the productivity of the main branches (fertile branches originated from buds, formed in the previous year, that remained silent during the winter) is very low, that of the feathers (fertile branches derived from annual buds) is always normal.

The microsporogenesis and tapetal development proceed normally in almost all the examined anthers; it is remarkable that at the tetrad stage the tapetal cells appear well structured without any degeneration symptom, unlike what observed for the main branches. Moreover in most of the mature anthers the pollen grains are numerous, pleinty of organelles and show sometimes thickenings in the callose layer under their wall. The tapetal cells of these anthers have disappeared. Only in few anthers we observed the presence of collapsed pollen grains and tapetal cells with anomalous development, that are still present when the pollen grains are mature. This rare situation for the feathers is on the contrary frequent for the main branches.     

Purification of proteinase-like and Na+/K(+)-ATPase stimulating substance from plasma of insulin-dependent diabetics and its identification as alpha 1-antitrypsin.

The purpose of this study was to purify and identify the proteinase-like substance previously recognized as responsible for the Na+/K(+)-ATPase stimulating property of plasma from insulin-dependent diabetic subjects. Anion-exchange chromatography followed by two-step heparin affinity chromatography resulted in a fraction highly enriched in both potent Na+/K(+)-ATPase stimulating activity and potent proteolytic activity. Approx. 400 micrograms of purified protein was isolated from 62 mg of starting plasma proteins. When analyzed on sodium dodecyl sulfate gels the active fraction consisted mainly of one polypeptide band with an apparent molecular mass of 66 kDa under either reducing or nonreducing conditions. The proteinase-like properties of the purified fraction were further revealed by its ability to clot plasma, split fibrinogen with production of fibrinopeptide A and induce shape change in human platelets and irreversible platelet aggregation in the presence of the stable analogue of endoperoxides U46619. Its additional capacity to affect platelet phosphoinositol metabolism was shown by the stimulation of protein kinase C-dependent phosphorylation of 47 kDa platelet membrane protein. In designing an identification protocol for the purified fraction, it was postulated that plasma proteinases are probably bound to their inhibitors, to form a stable covalently linked complex. The possibility that a proteinase-proteinase inhibitor complex was purified instead of single proteinase(s) was investigated. Neither trypsin nor neutrophil elastase were present in the active fraction whereas, among the possible plasma proteinase inhibitors tested, immunoreactivity was observed only in the presence of alpha 1-antitrypsin (alpha 1 AT) antiserum. Double immunodiffusion showed that control human alpha 1 AT and the plasma-purified fraction shared common antigens. Furthermore, both isoelectric focusing and amino acid composition analysis showed that the two substances were similar. The results obtained indicate that alpha 1 AT is apparently the only active component of the purified fraction from the plasma of insulin-dependent diabetics, thus suggesting that an altered form of the inhibitor is responsible for the broad range of proteinase-like effects elicited by the plasma-purified fraction.     

Chronic administration of EGb 761 modulates synaptic and mitochondrial plasticity in adult vitamin E-deficient rats.

A computer-assisted morphometric study has been carried out on synaptic junctions and synaptic mitochondria in the dentate gyrus supragranular layer of vitamin E-deficient rats undergone chronic administration of the extract EGb 761 from Ginkgo biloba leaves (100 mg/kg body weight, daily, from 4 to 7 months of age). Control animals were fed with the vitamin E-deficient diet from 1 to 7 months of age. Numeric density (Nv), surface density (Sv) and average size of the synaptic junctions (S), mitochondrial numeric density (Nvm), volume density (Vv) and average volume (V) were the measured parameters. In EGb 761-treated animals, Nv was significantly increased and S significantly decreased, while Sv was unchanged. EGb 761 administration resulted in an increased percentage of synapses of smaller size. In EGb 761-treated rats, Nvm significantly increased and V significantly decreased, while no significant difference of Vv was found. The population of synaptic mitochondria in EGb 761 -treated animals was composed of a higher number of smaller organelles. The measured parameters report on the structural dynamics of synapses and mitochondria, thus our findings support that EGb 761 administration is able to improve the physiological adaptive capacities of the investigated structures by a positive modulation of their morphofunctional features.