Nuclear pores in the apoptotic cell

Summary During apoptosis, nuclear pores undergo strong modifications, which are described here in five different apoptotic models. Conventional electron microscopy, supported by freeze-fracture analysis, showed a constant migration of nuclear pores towards the diffuse chromatin areas. In contrast, dense chromatin areas appear pore-free and are frequently surrounded by strongly dilated cisternae. A possible functional significance of this pore behaviour during apoptosis is discussed.     

Mapping of the contraction-induced phosphoproteome identifies TRIM28 as a significant regulator of skeletal muscle size and function

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Protein methylation as a marker of aspartate damage in glucose-6-phosphate dehydrogenase-deficient erythrocytes: role of oxidative stress.

The 'Mediterranean' variant of glucose-6-phosphate dehydrogenase (G6PD) deficiency is due to the C563CT point mutation, leading to replacement of Ser with Phe at position 188, resulting in acute haemolysis triggered by oxidants. Previous work has shown increased formation of altered aspartate residues in membrane proteins during cell ageing and in response to oxidative stress in normal erythrocytes. These abnormal residues are specifically recognized by the repair enzyme L-isoaspartate (d-aspartate) protein O-methyltransferase (PCMT; EC 2.1.1.77). The aim of this work was to study the possible involvement of protein aspartate damage in the mechanism linking the G6PD defect and erythrocyte injury, through oxidative stress. Patients affected by G6PD deficiency (Mediterranean variant) were selected. In situ methylation assays were performed by incubating intact erythrocytes in the presence of methyl-labelled methionine. Altered aspartate residues were detected in membrane proteins by methyl ester quantification. We present here evidence that, in G6PD-deficient erythrocytes, damaged residues are significantly increased in membrane proteins, in parallel with the decay of pyruvate kinase activity, used as a cell age marker. Erythrocytes from patients were subjected to oxidative stress in vitro, by treatment with t-butylhydroperoxide, monitored by a rise in concentration of both methaemoglobin and thiobarbituric acid-reactive substances. L-Isoaspartate residues increased dramatically in G6PD-deficient erythrocytes in response to such treatment, compared with baseline conditions. The increased susceptibility of G6PD-deficient erythrocytes to membrane protein aspartate damage in response to oxidative stress suggests the involvement of protein deamidation/isomerization in the mechanisms of cell injury and haemolysis.     

Sex-related genes expression in juveniles of red abalone,Haliotis rufescens (Swanson, 1822)

The red abalone, Haliotis rufescens (Swanson 1822), is an important species for commercial aquaculture in Mexico, with annual production levels around 68 t. Not surprisingly, there is great interest in increasing production and its cultivation success. In order to have a better understanding of the genes involved in the sexual differentiation, this study analyzed the early differential expression of eight sex-related genes (VCP 2.2, VERL, VTGI, DMRT1, FP, LYS, SARIP, TEKT A1) by RT-qPCR in abalones from 5 to 45 mm of shell length. Sex identification was evaluated using VERL and LYS genes expression levels. These genes differentiated females and males from 16 mm of shell length and above. All eight sex-specific genes showed expression in all organisms. However, their level was higher in the sex group to which they correspond. In contrast, differential expression levels occurred in individuals with a shell length of 26–35 mm and 36–45 mm. These results suggest that sex gene expression is not entirely sex specific, and sexual differentiation in red abalone occurs between 16 and 25 mm of shell length. More studies are needed to determine the function of these genes in the sex that they are not associated with.     

Population decline in tree swallows ( Tachycineta bicolor ) linked to climate change and inclement weather on the breeding ground

Population decline and the threat of extinction are realities currently facing many species. Yet, in most cases, the detailed demographic data necessary to identify causes of population decline are unavailable. Using 43 years (1975−2017) of data from a box-nesting population of tree swallows (Tachycineta bicolor), we identified reduced survival of offspring as a probable demographic cause of population decline. Poor fledging success was associated with increased predation and poor weather conditions during early nestling development. Low juvenile survival and subsequent recruitment was linked to poor weather conditions during the post-fledging period and may also be linked to conditions on the wintering grounds. Regional weather conditions during critical stages of breeding (early nestling and post-fledging) have become progressively worse over the 43-year study period. None of the other factors linked to offspring survival have similarly deteriorated. Overall, our results suggest tree swallows should be added to the growing list of species challenged by climate change, and that other species of aerial insect specialists may face similar impacts of climate change.     

Comparing temporal dynamics of compositional reorganization in long-term studies of birds and fish

The composition of ecological assemblages has changed rapidly over the past century. Compositional reorganization rates are high relative to rates of alpha diversity change, creating an urgent need to understand how this compositional reorganization is progressing. We developed a quantitative framework for comparing temporal trajectories of compositional reorganization and applied it to two long-term bird and marine fish datasets. We then evaluated how the number and magnitude of short-term changes relate to overall rates of change. We found varied trajectories of turnover across birds and fish, with linear directional change predominating in birds and non-directional change more common in fish. The number of changes away from the baseline was a more consistent correlate of the overall rate of change than the magnitude of such changes, but large unreversed changes were found in both fish and birds, as were time series with accelerating compositional change. Compositional reorganization is progressing through a complex mix of temporal trajectories, including both threshold-like behaviour and the accumulation of repeated, linear change.     

Extreme heatwave drives topography-dependent patterns of mortality in a bed-forming intertidal barnacle,with implications for associated community structure

Heatwave frequency and intensity will increase as climate change progresses. Intertidal sessile invertebrates, which often form thermally benign microhabitats for associated species, are vulnerable to thermal stress because they have minimal ability to behaviourally thermoregulate. Understanding what factors influence the mortality of biogenic species and how heatwaves might impact their ability to provide habitat is critical. Here, we characterize the community associated with the thatched barnacle, Semibalanus cariosus (Pallass, 1788), in British Columbia (BC), Canada. Then, we investigate what site-level and plot-level environmental factors explained variations in barnacle mortality resulting from an unprecedented regional heatwave in BC, Canada. Furthermore, we used a manipulative shading experiment deployed prior to the heatwave to examine the effect of thermal stress on barnacle survival and recruitment and the barnacle-associated community. We identified 50 taxa inhabiting S. cariosus beds, with variations in community composition between sites. Site-scale variables and algal canopy cover did not predict S. cariosus mortality, but patch-scale variation in substratum orientation did, with more direct solar irradiance corresponding with higher barnacle mortality. The shading experiment demonstrated that S. cariosus survival, barnacle recruitment, and invertebrate community diversity were higher under shades where substratum temperatures were lower. Associated community composition also differed between shaded and non-shaded plots, suggesting S. cariosus was not able to fully buffer acute thermal stress for its associated community. While habitat provisioning by intertidal foundation species is an important source of biodiversity, these species alone may not be enough to prevent substantial community shifts following extreme heatwaves. As heatwaves become more frequent and severe, they may further reduce diversity via the loss of biogenic habitat, and spatial variation in these impacts may be substantial.     

Increased incorporation of aspartate and decreased incorporation of orotate in fibroblasts from Lesch-Nyhan patients as revealed by autoradiography

While it has been known for many years that tissues from Lesch-Nyhan patients are deficient in hypoxanthine-guanine phosphoribosyl transferase, it has been demonstrated more recently that erythrocyte lysates show an increase in the levels of enzymes which participate in “de novo” synthesis of pyrimidines. Also, we were able to demonstrate, using autoradiography, an increased rate of incorporation of aspartate into the nucleus of intact cultured fibroblasts from a Lesch-Nyhan patient. We have now confirmed this finding. In this paper we show increased incorporation of aspartate into the nucleus of cells from three other patients. Interestingly, the incorporation of orotate is decreased in the fibroblasts from the four patients studied. The incorporation of leucine is the same in Lesch-Nyhan fibroblasts as in normal fibroblasts. The significance of these findings is briefly discussed.