Mechanisms of chromosome banding

Photo-oxidation of mitotic human chromosomes has been used in conjunction with anti-cytosine and anti-adenosine antibodies to produce R-banding. To elucidate the mechanism of this banding procedure we have examined the effect of photo-oxidation alone on chromosomes and nuclei. With short exposures to light in the presence of dilute methylene blue, C-band areas on chromosomes 1, 9, 16 and the terminal segment of the Y stain poorly. We call this phenomena reverse C-banding. After 18 h of exposure to light the chromosomes are swollen and show very little staining with quinacrine or Giemsa. Quantitative autoradiography shows that their DNA is almost completely extracted. Cytophotometric measurements also confirm that nuclear DNA is progressively extracted according to the length of exposure to light. When chromosomes are exposed to dilute methylene blue alone, without light, G-banded chromosomes result. We suggest the following explanation for these observations. In dilute methylene blue, C-band regions take up the greatest amount of dye and after short periods of photo-oxidation the DNA of these regions is preferentially destroyed resulting in reverse C-banding. Autoradiography in photo-oxidized chromosomes suggested that this preferential destruction of C-segments occurred in our experiments. With more prolonged exposure the DNA of the G-bands regions is preferentially destroyed and staining the remaining DNA with sensitive fluorescent labeled anti-C antibodies results in R-banding.     

On the fine structure of the electrocyte of Electrophorus electricus L.

Summary The general ultrastructure of the electrocyte, the basic unit of the electric organs of Electrophorus electricus, is analyzed. Presented herein are detailed observations of the syncytial surface, its fibrillar coat, invaginations of the plasma membrane and synaptic terminals. Using Thiéry's method glycogen granules were identified in the syncytial cytoplasm and inside the synaptic terminals, their size and structure being compatible with the muscular origin of the electric organs, to which the filamentous meshwork found in the cytoplasm may be related. Among the perinuclear-organelles, are dense bodies with crystalline patterns. The mitochondrial matrix contains dense granules, their size and structure varying according to the organ to which they belong and to the fixation method used.This work has been supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Conselho de Ensino para Graduados da UFRJ and Banco Nacional de Desenvolvimento Econômico, FUNTEC-241     

The ecology of chronic wasting disease in wildlife

Prions are misfolded infectious proteins responsible for a group of fatal neurodegenerative diseases termed transmissible spongiform encephalopathy or prion diseases. Chronic Wasting Disease (CWD) is the prion disease with the highest spillover potential, affecting at least seven Cervidae (deer) species. The zoonotic potential of CWD is inconclusive and cannot be ruled out. A risk of infection for other domestic and wildlife species is also plausible. Here, we review the current status of the knowledge with respect to CWD ecology in wildlife. Our current understanding of the geographic distribution of CWD lacks spatial and temporal detail, does not consider the biogeography of infectious diseases, and is largely biased by sampling based on hunters' cooperation and funding available for each region. Limitations of the methods used for data collection suggest that the extent and prevalence of CWD in wildlife is underestimated. If the zoonotic potential of CWD is confirmed in the short term, as suggested by recent results obtained in experimental animal models, there will be limited accurate epidemiological data to inform public health. Research gaps in CWD prion ecology include the need to identify specific biological characteristics of potential CWD reservoir species that better explain susceptibility to spillover, landscape and climate configurations that are suitable for CWD transmission, and the magnitude of sampling bias in our current understanding of CWD distribution and risk. Addressing these research gaps will help anticipate novel areas and species where CWD spillover is expected, which will inform control strategies. From an ecological perspective, control strategies could include assessing restoration of natural predators of CWD reservoirs, ultrasensitive CWD detection in biotic and abiotic reservoirs, and deer density and landscape modification to reduce CWD spread and prevalence.     

Revisiting the coupling of fatty acid to phospholipid synthesis in bacteria with FapR regulation

A key aspect in membrane biogenesis is the coordination of fatty acid to phospholipid synthesis rates. In most bacteria, PlsX is the first enzyme of the phosphatidic acid synthesis pathway, the common precursor of all phospholipids. Previously, we proposed that PlsX is a key regulatory point that synchronizes the fatty acid synthase II with phospholipid synthesis in Bacillus subtilis. However, understanding the basis of such coordination mechanism remained a challenge in Gram-positive bacteria. Here, we show that the inhibition of fatty acid and phospholipid synthesis caused by PlsX depletion leads to the accumulation of long-chain acyl-ACPs, the end products of the fatty acid synthase II. Hydrolysis of the acyl-ACP pool by heterologous expression of a cytosolic thioesterase relieves the inhibition of fatty acid synthesis, indicating that acyl-ACPs are feedback inhibitors of this metabolic route. Unexpectedly, inactivation of PlsX triggers a large increase of malonyl-CoA leading to induction of the fap regulon. This finding discards the hypothesis, proposed for B. subtilis and extended to other Gram-positive bacteria, that acyl-ACPs are feedback inhibitors of the acetyl-CoA carboxylase. Finally, we propose that the continuous production of malonyl-CoA during phospholipid synthesis inhibition provides an additional mechanism for fine-tuning the coupling between phospholipid and fatty acid production in bacteria with FapR regulation.     

Length–weight relationships of five selected demersal fishes from the Cabo Verde Islands (eastern-central Atlantic)

The length–weight relationships (LWR) were estimated for five selected demersal marine fishes from the relatively undisturbed shelves and slopes of the Cabo Verde Islands. Most of them were of ecological and/or commercial interest. Occasional sampling was carried out during different fisheries research projects. LWRs were taken for the following bycatch species for which no such estimates exists in the science literature: Myroconger compressus, Synaphobranchus affinis, Physiculus cyanostrophus, Physiculus caboverdensis and Canthidermis maculata. Total length and fork length (to the nearest 0.1 cm) and total weight (to the nearest 0.1 g) were determined. The resulting length–weight equations are characterized by a high accompanying coefficient of correlation. The present data help improving the knowledge base needed for further fish biology studies and fisheries management.     

Enhancement of salt tolerance in corn using Azospirillum brasilense: an approach on antioxidant systems

Journal of Plant Research - Salinity has become one of the major factors limiting agricultural production. In this regard, different cost-effective management strategies such as the use of plant...