Biochemical lesions of respiratory enzymes and configurational changes of mitochondria in vivo

Summary Correlative biochemical and electron microscopic alterations were observed in chick embryo myoblasts in vitro after treatment with fluoroacetate. Fluoroacetate poisoning caused an increase of citrate and a decrease of ATP in the cultures. Cell respiration was only slightly impaired by fluoroacetate in the first 10 min but was inhibited to 30% one hour after exposure to the poison. Fluoroacetate did not affect oxidative phosphorylation. The evidence suggests that fluoroacetate was transformed in myoblasts into fluorocitrate which inhibited the mitochondrial-bound aconitate hydratase as in adult tissues. Ultrastructural changes in the majority of the fluoroacetate-treated cells were observed. Very few myoblasts appeared unaffected by the poison. Mitochondria were specifically altered. The early changes occurred in the mitochondrial matrix where the inhibited enzyme is known to be located and were followed by modifications in the configuration and structure of cristae. Exogenous fluorocitrate caused ultrastructural changes in the mitochondria similar to that provoked by fluoroacetate. The localization of the early change in the mitochondrial matrix and the evaluation of the structural modifications suggest a correlation between the biochemical lesion, i.e. the inhibition of aconitate hydratase, and the change revealed in the mitochondrial structure containing the inhibited enzyme.This work was supported by grants of the Consiglio Nazionale delle Ricerche to both InstitutesThe present study is dedicated to Prof. Otto Bucher on occasion of his 65th birthday     

Estimating colonization potential of migrant tree species

Plant populations migrating in response to climate change will have to colonize established communities. Even if a population disperses to a new region with a favorable climate, interactions with other species may prevent its establishment and further spread. The potential of these species to grow along with residents will be a critical factor controlling their response to climate change. To determine the capacity of migrating species to colonize established communities we conducted extensive long-term transplant experiments where potential tree migrant species, i.e. species within 'migration range,' were planted side by side with resident ones. Potential immigrants were selected to be representative species of their native communities. For both groups, residents and potential migrants (17 species), we compared their growth response along gradients in soil moisture and light availability. Rather than manipulate climate directly, we exploited natural microclimatic gradients and the fluctuations in climate that occurred during the 5-year experiment. Experimental results were used to estimate growth in the context of novel climate and relevant establishment factors. Results suggest that potential immigrant species had similar growth rates in the new environment than those from resident species ensuring their ability to establish in the area. However, contrary to our expectations, the soil moisture requirements for the immigrant group were similar to those of the resident species. These results could have major implications for vegetation changes under the predicted drier climate for the region. If it is the case that neither resident species nor potential migrants are able to maintain stable populations, the region may experience a decline in local biodiversity.     

Macroinvertebrate communities of mediterranean ponds (North Iberian Plateau): importance of natural and human-induced variability

1. The effects of natural and human‐induced variability on the composition of macroinvertebrate communities of 28 ponds located in the North Iberian Plateau (Spain) were studied to determine the best predictors of community structure. 2. Constrained ordination was used to identify the main factors explaining the among‐pond variance in abundance (as catch per unit effort) of total macroinvertebrate and Chironomidae assemblages and trophic structure (functional feeding groups). 3. Variance partitioning showed that human disturbance (represented by a pond condition index, total phosphorus concentration and pesticides) was the best predictor of macroinvertebrate community structure, whereas factors, such as habitat and biotic variables were of secondary importance. Factors controlling the chironomid community were broadly similar to those acting on the whole community of macroinvertebrates. In contrast, trophic structure was mainly determined by habitat and biotic variables. 4. Our results show that macroinvertebrates may be used as effective indicators of the ecological status of Mediterranean ponds. The Chironomidae deserve special attention because they were the dominant group in the study ponds and the strongest explanatory variable for their distribution was degradation.     

A new species of Agrostis (Gramineae) in the A. alpina complex

A new species of Agrostis L. (A. barceloi ) is described from the northern mountains of Mallorca (Balearic Islands). The new taxon belongs to sect. Agtush and is mainly related to A. alpina Scop. and A. schleicheri Jord. & Verl. on morphological grounds. However, A. barceloi differs from A. alpina by its narrowly-lanceolate inflorescence, with panicle branches erect during and after anthesis, non-scabrid leaves, and by smaller lemmas and others. The new species is distinguished from A. schleicheri by the smaller spikelets, lemma, palea, and anthers. In addition, A. barceloi is tetraploid (2n = 28), and differs cytologically from the diploid A. alpina (2n= 14) and the hexaploid A. schleicheri (2n = 56).     

Some trends in the somatic development of children and adolescents under iodine-deficiency: materials from the Saratov region

2,106 girls and 2,169 boys from 7 to 17 were investigated in 2002-2004 in three urban settlements of the Saratov region (Povolzhje area): the town of Khvalynsk, population 15,000, with a low level of industrialization; the city of Balakovo, population 220,000, highly industrialized and with a nuclear power station; and the city of Saratov, population around 1,000,000 a regional capital, and also highly industrialized. The whole area, particularly the location of Khvalynsk, is also characterized by iodine deficiency (iodine concentration is 0.78 mkg/kg v. normal values of 5-7 mkg/kg).The program included about 30 anthropometric measurements, evaluation of developmental stages of secondary sexual characteristics, and information on menarcheal age by the status quo method. Information on parental occupation and education, as well as number of children per family was collected by questionnaire. For the analysis all the data were standardized, and further comparisons were made irrespective of age groups. The significance of differences was assessed by one-way ANOVA. For height, weight and chest circumference there are significant differences among the three populations (p < 0.001), with Khvalynsk children being the smallest in body height and weight. However, in chest circumference they are close to or even bigger (girls) than Balakovo children. The children from Khvalynsk are characterized by the lowest values for subcutaneous fat layer, both on the trunk and extremities. For the age of menarche, Khvalynsk girls have the highest values: 13 years 5 months (13.42). In Balakovo and Saratov, the corresponding figures are identical: 13 years 2 months (13.17). Secular changes in Khvalynsk and Saratov children are discussed as compared to the literature.     

Interaction between wind-induced seiches and convective cooling governs algal distribution in a canyon-shaped reservoir

1. Wind is considered the dominant factor controlling phytoplankton distribution in lentic environments. In canyon‐shaped reservoirs, wind tends to blow along the main axis generating internal seiches and advective water movements that jointly with biological features of algae can produce a heterogeneous phytoplankton distribution. Turbulence generated by wind stress and convection will also affect the vertical distribution of algae, depending on their sinking properties. 2. We investigated the vertical and horizontal distribution of phytoplankton during the stratification period in Sau Reservoir (NE Spain). Sites along the main reservoir axis were sampled every 4 h for 3 days, and profiles of chlorophyll‐a and temperature were made using a fluorescent FluoroProbe, which can discriminate among the main algal groups. Convective and wind shear velocity scales, and energy dissipation were calculated from meteorological data, and simulation experiments were performed to describe non‐measured processes, like vertical advection and sinking velocity of phytoplankton. 3. Wind direction changed from day to night, producing a diel thermocline oscillation and an internal seiche. Energy dissipation was moderate during the night, and mainly attributed to convective cooling. During the day the energy dissipation was entirely attributed to wind shear, but values indicated low turbulence intensity. 4. The epilimnetic algal community was mainly composed of diatoms and chlorophytes. Chlorophytes showed a homogeneous distribution on the horizontal and vertical planes. Diatom horizontal pattern was also homogeneous, because the horizontal advective velocities generated by wind forcing were not high enough to develop phytoplankton gradients along the reservoir. 5. Diatom vertical distribution was heterogeneous in space and time. Different processes dominated in different regions of the reservoir, due to the interaction between seiching and the daily cycle of convective‐mediated turbulence. As the meteorological forcing followed a clear daily pattern, we found very different diatom sedimentation dynamics between day and night. Remarkably, these dynamics were asynchronous in the extremes of the seiche, implying that under the same meteorological forcing a diatom population can show contrasting sedimentation dynamics at small spatial scales (approximately 10³ m). This finding should be taken into account when interpreting paleolimnological records from different locations in a lake. 6. Vertical distribution of non‐motile algae is a complex process including turbulence, vertical and horizontal advection, variations in the depth of the mixing layer and the intrinsic sinking properties of the organisms. Thus, simplistic interpretations considering only one of these factors should be regarded with caution. The results of this work also suggest that diatoms can persist in stratified water because of a synergistic effect between seiching and convective turbulence.