Influence of dissolved oxygen concentration on the biosynthesis of cephalosporin C.

Cephalosporin C was produced by a highly productive strain of Cephalosporium acremonium under industrial production conditions by fed-batch cultivation in a 40-l stirred-tank reactor using a complex medium containing 50 g l-1 peanut flour. The influence of dissolved oxygen concentration (pO2, DOC), which was maintained at different constant levels between 5 and 40% of its saturation value, during the production phase by means of a parameter-adaptive pO2-controller, on the cephalosporin C biosynthesis, was investigated. The concentrations of cephalosporin C (CPC) and its precursors penicillin N (PEN N), deacetoxycephalosporin C (DAOC), and deacetylcephalosporin C (DAC) were monitored by on-line HPLC. The concentrations of amino acids, valine (VAL), cysteine (CYS), alpha-amino-adipic acid (alpha-AAA), the dipeptide alpha-amino-adipyl-cysteine (AC), and the tripeptide alpha-amino-adipyl-cysteinyl-valine (ACV) were determined by off-line HPLC. By reducing the pO2 in the production phase from 40 to 5% of its saturation value, the CPC concentration diminished from 7.2 to 1.1 g l-1 and the PEN N concentration increased from 2.57 to 7.65 g l-1. The DAC concentration also dropped from 3.13 to 0.42 g l-1; however, the DAOC concentration was less influenced. The concentrations of AC and ACV were also less affected. The small DOC did not lead to an accumulation of the intermediate AC and ACV during the production phase. With increasing DOC in the range of 5-20%, the maximal specific production rate, the cell mass concentration-based and the substrate-based yield coefficients for CPC increased almost linearly, and fell back for PEN N.(ABSTRACT TRUNCATED AT 250 WORDS)     

Purification of Trypanosoma cruzi surface proteins involved in adhesion to host cells

We have identified four surface 83 kDa proteins of pI values 6.3, 6.4, 6.5 and 6.6 in T. cruzi trypomastigotes which specifically bind to rat heart myoblasts. These proteins were purified by isoelectric focusing and anion-exchange chromatography in an FPLC system. These 83 kDa proteins inhibit the attachment of trypomastigotes to myoblasts in a concentration-dependent manner, indicating that these trypomastigote proteins mediate the attachment of trypomastigotes to heart myoblasts.     

Stabilization of Z-DNA by demethylation of thymine bases: 1.3-A single-crystal structure of d(m5CGUAm5CG)

Methylation of cytosine bases at the C5 position has been known to stabilize Z-DNA. We had previously predicted from calculations of solvent-accessible surfaces that the methyl group at the same position of thymine has a destabilizing effect on Z-DNA. In the current studies, the sequence d(m5CGUAm5CG) has been crystallized and its structure solved as Z-DNA to 1.3-A resolution. A well-defined octahedral hexaaquomagnesium complex was observed to bridge the O4 oxygens of the adjacent uridine bases at the major groove surface, and four well-structured water molecules were found in the minor groove crevice at the d(UA) dinucleotide. These solvent interactions were not observed in the previously published Z-DNA structure of the analogous d(m5CGTAm5CG) sequence. A comparison of the thymine and uridine structures supports our prediction that demethylation of thymine bases helps to stabilize Z-DNA. A comparison of this d(UA)-containing Z-DNA structure with the analogous d(TA) structure shows that access of the O4 position is hindered by the C5 methyl of thymine due to steric and hydrophobic inhibition. In the absence of the methyl group, a magnesium-water complex binds to and slightly affects the structure of the Z-DNA major groove surface. This perturbation of the solvent structure at the major groove surface is translated into a much larger 1.41-A widening of the minor groove crevice, thereby allowing the specific binding of two water molecules at well-defined sites of each internal d(UA) base pair. Possible mechanisms by which modifications at the major groove surface of Z-DNA can affect the solvent properties of the minor groove crevice are discussed.     

Single-cell transcriptomic atlas of primate cardiopulmonary aging

Aging is a major risk factor for many diseases,especially in highly prevalent cardiopulmonary comorbidities and infectious diseases including Coronavirus Diseas...     

A Human Active Lower Limb Model for Chinese Pedestrian Safety Evaluation

A subsystem impactor test for pedestrian lower limb injury evaluation has been brought in China New Car Assessment Protocol(CNCAP).Concerning large anthropometr...     

SARS-CoV-2 envelope protein causes acute respiratory distress syndrome (ARDS)-like pathological damages and constitutes an antiviral target

Cytokine storm and multi-organ failure are the main causes of SARS-CoV-2-related death. However, the origin of excessive damages caused by SARS-CoV-2 remains largely unknown. Here we show that the SARS-CoV-2 envelope (2-E) protein alone is able to cause acute respiratory distress syndrome (ARDS)-like damages in vitro and in vivo. 2-E proteins were found to form a type of pH-sensitive cation channels in bilayer lipid membranes. As observed in SARS-CoV-2-infected cells, heterologous expression of 2-E channels induced rapid cell death in various susceptible cell types and robust secretion of cytokines and chemokines in macrophages. Intravenous administration of purified 2-E protein into mice caused ARDS-like pathological damages in lung and spleen. A dominant negative mutation lowering 2-E channel activity attenuated cell death and SARS-CoV-2 production. Newly identified channel inhibitors exhibited potent anti-SARS-CoV-2 activity and excellent cell protective activity in vitro and these activities were positively correlated with inhibition of 2-E channel. Importantly, prophylactic and therapeutic administration of the channel inhibitor effectively reduced both the viral load and secretion of inflammation cytokines in lungs of SARS-CoV-2-infected transgenic mice expressing human angiotensin-converting enzyme 2 (hACE-2). Our study supports that 2-E is a promising drug target against SARS-CoV-2.Subject terms: Cell death, Molecular biology     

Environmental filtering rather than dispersal limitation dominated plant community assembly in the Zoige Plateau

Identifying the mechanisms that underlie the assembly of plant communities is critical to the conservation of terrestrial biodiversity. However, it is seldom measured or quantified how much deterministic versus stochastic processes contribute to community assembly in alpine meadows. Here, we measured the decay in community similarity with spatial and environmental distance in the Zoige Plateau. Furthermore, we used redundancy analysis (RDA) to divide the variations in the relative abundance of plant families into four components to assess the effects of environmental and spatial. Species assemblage similarity liner declined with geographical distance (p < .001, R ² = .6388), and it decreased significantly with increasing distance of total phosphorus (TP), alkali‐hydrolyzable nitrogen (AN), available potassium (AK), nitrate nitrogen (NO₃ ⁺–N), and ammonia nitrogen (NH₄ ⁺–N). Environmental and spatial variables jointly explained a large proportion (55.2%) of the variation in the relative abundance of plant families. Environmental variables accounted for 13.1% of the total variation, whereas spatial variables accounted for 11.4%, perhaps due to the pronounced abiotic gradients in the alpine areas. Our study highlights the mechanism of plant community assembly in the alpine ecosystem, where environmental filtering plays a more important role than dispersal limitation. In addition, a reasonably controlled abundance of Compositae (the family with the highest niche breadth and large niche overlap value with Gramineae and Cyperaceae) was expected to maintain sustainable development in pastoral production. These results suggest that management measures should be developed with the goal of improving or maintaining suitable local environmental conditions.     

Distinct basolateral amygdala excitatory inputs mediate the somatosensory and aversive-affective components of pain

Pain is a multidimensional perception that includes unpleasant somatosensory and affective experiences; however, the underlying neural circuits that mediate different components of pain remain elusive. Although hyperactivity of basolateral amygdala glutamatergic (BLA^Glu) neurons is required for the somatosensory and emotional processing of pain, the precise excitatory inputs to BLA^Glu neurons and their roles in mediating different aspects of pain are unclear. Here, we identified two discrete glutamatergic neuronal circuits in male mice: a projection from the insular cortex glutamatergic (IC^Glu) to BLA^Glu neurons, which modulates both the somatosensory and affective components of pain, and a projection from the mediodorsal thalamic nucleus (MD^Glu) to BLA^Glu neurons, which modulates only the aversive-affective component of pain. Using whole-cell recording and fiber photometry, we found that neurons within the IC→BLA and MD→BLA pathways were activated in mice upon inflammatory pain induced by injection of complete Freund’s adjuvant (CFA) into their paws. Optical inhibition of the IC^Glu→BLA pathway increased the nociceptive threshold and induced behavioral place preference in CFA mice. In contrast, optical inhibition of the MD^Glu→BLA pathway did not affect the nociceptive threshold but still induced place preference in CFA mice. In normal mice, optical activation of the IC^Glu→BLA pathway decreased the nociceptive threshold and induced place aversion, while optical activation of the MD^Glu→BLA pathway only evoked aversion. Taken together, our results demonstrate that discrete IC^Glu→BLA and MD^Glu→BLA pathways are involved in modulating different components of pain, provide insights into its circuit basis, and better our understanding of pain perception.     

Friend or Foe? Implication of the autophagy-lysosome pathway in SARS-CoV-2 infection and COVID-19

There is increasing amount of evidence indicating the close interplays between the replication cycle of SARS-CoV-2 and the autophagy-lysosome pathway in the host cells. While autophagy machinery is known to either assist or inhibit the viral replication process, the reciprocal effects of the SARS-CoV-2 on the autophagy-lysosome pathway have also been increasingly appreciated. More importantly, despite the disappointing results from the clinical trials of chloroquine and hydroxychloroquine in treatment of COVID-19, there is still ongoing effort in discovering new therapeutics targeting the autophagy-lysosome pathway. In this review, we provide an update-to-date summary of the interplays between the autophagy-lysosome pathway in the host cells and the pathogen SARS-CoV-2 at the molecular level, to highlight the prognostic value of autophagy markers in COVID-19 patients and to discuss the potential of developing novel therapeutic strategies for COVID-19 by targeting the autophagy-lysosome pathway. Thus, understanding the nature of such interactions between SARS-CoV-2 and the autophagy-lysosome pathway in the host cells is expected to provide novel strategies in battling against this global pandemic.