Rat brain slices oxidize glucose at high rates: a (13)C NMR study

Since glucose is the main cerebral substrate, we have characterized the metabolism of various ¹³C glucose isotopomers in rat brain slices. For this, we have used our cellular metabolomic approach that combines enzymatic and carbon 13 NMR techniques with mathematical models of metabolic pathways. We identified the fate and the pathways of the conversion of glucose carbons into various products (pyruvate, lactate, alanine, aspartate, glutamate, GABA, glutamine and CO₂) and determined absolute fluxes through pathways of glucose metabolism. After 60 min of incubation, lactate and CO₂ were the main end-products of the metabolism of glucose which was avidly metabolized by the slices. Lactate was also used at high rates by the slices and mainly converted into CO₂. High values of flux through pyruvate carboxylase, which were similar with glucose and lactate as substrate, were observed. The addition of glutamine, but not of acetate, stimulated pyruvate carboxylation, the conversion of glutamate into succinate and fluxes through succinate dehydrogenase, malic enzyme, glutamine synthetase and aspartate aminotransferase. It is concluded that, unlike brain cells in culture, and consistent with high fluxes through PDH and enzymes of the tricarboxylic acid cycle, rat brain slices oxidized both glucose and lactate at high rates.     

Mapping Potential Amplification and Transmission Hotspots for MERS-CoV,Kenya

Dromedary camels have been implicated consistently as the source of Middle East respiratory syndrome coronavirus (MERS-CoV) human infections and attention to prevent and control it has focused on camels. To understanding the epidemiological role of camels in the transmission of MERS-CoV, we utilized an iterative empirical process in Geographic Information System (GIS) to identify and qualify potential hotspots for maintenance and circulation of MERS-CoV, and produced risk-based surveillance sites in Kenya. Data on camel population and distribution were used to develop camel density map, while camel farming system was defined using multi-factorial criteria including the agro-ecological zones (AEZs), production and marketing practices. Primary and secondary MERS-CoV seroprevalence data from specific sites were analyzed, and location-based prevalence matching with camel densities was conducted. High-risk convergence points (migration zones, trade routes, camel markets, slaughter slabs) were profiled and frequent cross-border camel movement mapped. Results showed that high camel-dense areas and interaction (markets and migration zones) were potential hotspot for transmission and spread. Cross-border contacts occurred with in-migrated herds at hotspot locations. AEZ differential did not influence risk distribution and plausible risk factors for spatial MERS-CoV hotspots were camel densities, previous cases of MERS-CoV, high seroprevalence and points of camel convergences. Although Kenyan camels are predisposed to MERS-CoV, no shedding is documented to date. These potential hotspots, determined using anthropogenic, system and trade characterizations should guide selection of sampling/surveillance sites, high-risk locations, critical areas for interventions and policy development in Kenya, as well as instigate further virological examination of camels.     

Protein secretion in Lactococcus lactis : an efficient way to increase the overall heterologous protein production

Lactococcus lactis, the model lactic acid bacterium (LAB), is a food grade and well-characterized Gram positive bacterium. It is a good candidate for heterologous protein delivery in foodstuff or in the digestive tract. L. lactis can also be used as a protein producer in fermentor. Many heterologous proteins have already been produced in L. lactis but only few reports allow comparing production yields for a given protein either produced intracellularly or secreted in the medium. Here, we review several works evaluating the influence of the localization on the production yields of several heterologous proteins produced in L. lactis. The questions of size limits, conformation, and proteolysis are addressed and discussed with regard to protein yields. These data show that i) secretion is preferable to cytoplasmic production; ii) secretion enhancement (by signal peptide and propeptide optimization) results in increased production yield; iii) protein conformation rather than protein size can impair secretion and thus alter production yields; and iv) fusion of a stable protein can stabilize labile proteins. The role of intracellular proteolysis on heterologous cytoplasmic proteins and precursors is discussed. The new challenges now are the development of food grade systems and the identification and optimization of host factors affecting heterologous protein production not only in L. lactis, but also in other LAB species.     

Efficient one-step production of astaxanthin by the microalga Haematococcus pluvialis in continuous culture

The performance of Haematococcus pluvialis in continuous photoautotrophic culture has been analyzed, especially from the viewpoint of astaxanthin production. To this end, chemostat cultures of Haematococcus pluvialis were carried out at constant light irradiance, 1,220 microE/m2.s, and dilution rate, 0.9/d, but varying the nitrate concentration in the feed medium reaching the reactor, from 1.7 to 20.7 mM. Both growth and biomass composition were affected by the nitrate supply. With saturating nitrate, the biomass productivity was high, 1.2 g/L.d, but astaxanthin accumulation did not take place, the C/N ratio of the biomass being 5.7. Under moderate nitrate limitation, biomass productivity was decreased, as also did biomass concentration at steady state, whereas accumulation of astaxanthin developed and the C/N ratio of the biomass increased markedly. Astaxanthin accumulation took place in cells growing and dividing actively, and its extent was enhanced in response to the limitation in nitrate availability, with a recorded maximum for astaxanthin cellular level of 0.8% of dry biomass and of 5.6 mg/L.d for astaxanthin productivity. The viability of a significant continued generation of astaxanthin-rich H. pluvialis cells becomes thus demonstrated, as also does the continuous culture option as an alternative to current procedures for the production of astaxanthin using this microalga. The intensive variable controlling the behavior of the system has been identified as the specific nitrate input, and a mathematical model developed that links growth rate with both irradiance and specific nitrate input. Moreover, a second model for astaxanthin accumulation, also as a function of irradiance and specific nitrate input, was derived. The latter model takes into account that accumulation of astaxanthin is only partially linked to growth, being besides inhibited by excess nitrate. Simulations performed fit experimental data and emphasize the contention that astaxanthin can be efficiently produced under continuous mode by adjustment of the specific nitrate input, predicting even higher values for astaxanthin productivity. The developed models represent a powerful tool for management of such an astaxanthin-generating continuous process, and could allow the development of improved systems for the production of astaxanthin-rich Haematococcus cells.     

Autoradiographic localization of [3H]-GABA accumulation in the sixth abdominal ganglion of the cockroach, Periplaneta americana L.

Localization of [³H]-GABA accumulation in the sixth abdominal ganglion of the cockroach was achieved using autoradiography.Light and electron microscope autoradiographic results provide direct evidence for glial accumulation of [³H]-GABA via a Na⁺-dependent carrier system. The functional role of the glial uptake of GABA is discussed.     

School racial segregation and long-term cardiovascular health among Black adults in the US: A quasi-experimental study

BackgroundCardiovascular disease (CVD) disproportionately affects Black adults in the United States. This is increasingly acknowledged to be due to inequitable distribution of health-promoting resources. One potential contributor is inequities in educational opportunities, although it is unclear what aspects of education are most salient. School racial segregation may affect cardiovascular health by increasing stress, constraining socioeconomic opportunities, and altering health behaviors. We investigated the association between school segregation and Black adults’ CVD risk.Methods and findingsWe leveraged a natural experiment created by quasi-random (i.e., arbitrary) timing of local court decisions since 1991 that released school districts from court-ordered desegregation. We used the Panel Study of Income Dynamics (PSID) (1991 to 2017), linked with district-level school segregation measures and desegregation court order status. The sample included 1,053 Black participants who ever resided in school districts that were under a court desegregation order in 1991. The exposure was mean school segregation during observed schooling years. Outcomes included several adult CVD risk factors and outcomes. We fitted standard ordinary least squares (OLS) multivariable linear regression models, then conducted instrumental variables (IV) analysis, using the proportion of schooling years spent in districts that had been released from court-ordered desegregation as an instrument. We adjusted for individual- and district-level preexposure confounders, birth year, and state fixed effects. In standard linear models, school segregation was associated with a lower probability of good self-rated health (−0.05 percentage points per SD of the segregation index; 95% CI: −0.08, −0.03; p < 0.001) and a higher probability of binge drinking (0.04 percentage points; 95% CI: 0.002, 0.07; p = 0.04) and heart disease (0.01 percentage points; 95% CI: 0.002, 0.15; p = 0.007). IV analyses also found that school segregation was associated with a lower probability of good self-rated health (−0.09 percentage points; 95% CI: −0.17, −0.02, p = 0.02) and a higher probability of binge drinking (0.17 percentage points; 95% CI: 0.04, 0.30, p = 0.008). For IV estimates, only binge drinking was robust to adjustments for multiple hypothesis testing. Limitations included self-reported outcomes and potential residual confounding and exposure misclassification.ConclusionsSchool segregation exposure in childhood may have longstanding impacts on Black adults’ cardiovascular health. Future research should replicate these analyses in larger samples and explore potential mechanisms. Given the recent rise in school segregation, this study has implications for policies and programs to address racial inequities in CVD.

Min Hee Kim and colleagues investigate the association between exposure to school racial segregation in childhood and long-term cardiovascular health among Black adults in the United States.     

Production and purification of an untagged recombinant pneumococcal surface protein A (PspA4Pro) with high-purity and low endotoxin content

Applied Microbiology and Biotechnology - Streptococcus pneumoniae is the main cause of pneumonia, meningitis, and other conditions that kill thousands of children every year worldwide. The...