Macromolecular Synthesis and Degradation in Arthrobacter During Periods of Nutrient Deprivation

Cells of Arthrobacter atrocyaneus and A. crystallopoietes, harvested during their exponential phase, were starved in 0.03 M phosphate buffer (pH 7.0) for 28 days. During this time, the cells maintained 90 to 100% viability. Experimental results were similar for both organisms. Total cellular deoxyribonucleic acid was maintained. Measurable degradation rates for deoxyribonucleic acid as determined by radioisotope techniques were not observed, and only during the initial hours of starvation could a synthetic rate be determined. Total ribonucleic acid levels remained stable for the first 24 h of starvation, after which slow, continuous loss of orcinol-reactive material occurred. Synthetic and degradative rates of ribonucleic acid, as determined by radioisotope techniques, dropped quickly at the onset of starvation. Constant basal rates were attained after 24 h. In A. atrocyaneus, total cell protein was degraded continuously from the onset of starvation. In A. crystallopoietes, total cell protein remained stable for the first 24 h, after which slow continuous loss occurred. After 28 days, the total protein per cell was similar for both organisms. In the first week, amino acid pools stabilized at about 50% of the values characteristic of growth. Rates of degradation of protein decreased rapidly for the first 24 h for both organisms, but leveled to a constant basal rate thereafter. Rates of new protein synthesis dropped during the first 24 h and by 48 h achieved a constant basal rate.     

Stimulation of growth and phospholipase A2 by the peptides mastoparan and melittin and by the auxin 2,4-dichlorophenoxyacetic acid

The peptide mastoparan from wasp venom and the peptide melittin from bee venom stimulated growth in etiolated zucchini (Cucurbita pepo L.) hypocotyls. Both peptides were only effective in hypocotyls with abraded cuticles. At concentrations of 2 g ml^–1 peptide growth was stimulated 72% by mastoparan and 50% by melittin after 2 h as compared to the controls. Mastoparan (5 g ml^–1), melittin (10 g l^–1) and 2,4-dichlorophenoxyacetic acid (5×10^–4 M) stimulated accumulation of ¹⁴C-choline-labeled lysophosphatidylcholine in less than 10 min in cultured soybean cells (Glycine max L.), all to about the same extent. The effects of these peptides are among the first to be reported on plant cells and may be related to important events coupled to growth stimulation.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid     

The ribosome binding sites recognized by E. coli ribosomes have regions with signal character in both the leader and protein coding segments.

Oligonucleotide analysis, by a novel computerized procedure, was first applied to determine the sequence of an ideal E. coli promoter (Scherer et al., Nucl. Acids Res. 1978, 5:3759-3773) and has now been used to obtain the sequence of nucleotides that should be present in a messenger RNA for optimum binding to the E. coli ribosome. This sequence is: UU.UUAAAAAUUAAGGAGGUAUAUUAUGAAAAAAAUUAAAAAACUCAA AA U A AUA A CUC G. Comparison of this sequence with each of the 68 ribosome binding site sequences used to generate it shows a preference rather than an absolute requirement for a specific base in any given position. The preference for certain bases persists along the whole length of the RNA within the ribosome binding domain even though nearly half of that length includes translated codons. Thus messages without leader sequences (like lambda CI mRNA) can still have some affinity for the ribosome. Part of the model sequence is complementary to the 3'end of 16S rRNA.     

Regulatory effect of hydrogen on nitrogenase activity of the blue-green alga (cyanobacterium) Nostoc muscorum.

Preincubation of the blue-green alga (cyanobacterium) Nostoc muscorum under an atmosphere of argon plus acetylene in the light led to a greater than fourfold increase of light-induced hydrogen evolution and to a 50% increase of acetylene reduction, as compared to cells that had not been preconditioned. The basic and the increased hydrogen evolution were both due to nitrogenase activity. Furthermore, after preincubation the hydrogen uptake, usually observed with unconditional cells, was abolished. Nostoc preincubated under acetylene evolved hydrogen in the light even in the presence of nitrogen for at least 2 h, with a 15-fold increase as compared to the unconditioned cells. These acetylene effects could be completely abolished by the presence of hydrogen during acetylene preincubation. These findings indicate that the hydrogen concentration in N. muscorum cells plays a role in regulation of nitrogenase activity.     

In vitro stimulation by 2,4-dichlorophenoxyacetic acid of an ATPase and inhibition of phosphatidate phosphatase of plant membranes.

The auxin herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was shown to modulate the activities of several phosphatases with membranes isolated from soybean hypocotyls under conditions where degradative changes in the membranes were minimized. The medium for isolation of membranes consisted of 0.1 M Tris/HCl or Tris/acetate, pH 6.5, 0.5 M sucrose, 4% choline ($\text{w}\text{w}$) and 4% ethanolamine ($\text{v}\text{v}$) to inhibit phospholipase D, 20 mM EGTA [ethyleneglycol-bis- (β aminoethyl ether) N,N-tetracetic acid] and 1 mM nupercaine, to inhibit phospholipase A. In contrast, the inactive auxin analog 2,3-D, did not influence ATPase activity. Endogenous release of inorganic phosphate from an unidentified source was also stimulated 30% by 2,4-D. Phosphatidate phosphatase was inhibited by 2,4-D, whereas hydrolysis of glucose-6-phosphate was not influenced by 2,4-D under the same conditions. These observations may be of relevance to the proton pump hypothesis of growth regulation.     

Participation of L-ascorbate:ferricytochrome b5 oxidoreductase in ascorbate-dependent fatty acid desaturation of rat liver microsomes.

The microsomal enzyme ascorbate-cytochrome b5 reductase participates in the ascorbate-dependent fatty acid desaturation. Three pieces of evidence are given for this statement: 1) Comparison of the rate of ascorbate-dependent oleate formation with the rate of reduction of cytochrome b5 in microsomes and in the isolated detergent form shows that only the enzymatic reduction of cytochrome b5 is fast enough to support oleate formation; 2) added enriched ascorbate-cytochrome b5 reductase increases the rate of return of stearoyl-CoA oxidised cytochrome b5 back to the reduced state; 3) addition of enriched ascorbate-cytochrome b5 reductase increases the rate of ascorbate-dependent oleate formation in rat liver microsomes.     

Radioimmunological and biological measurement of prostaglandins in rabbit urine : Decrease of PGE2 excretion at high NaCl intake

The estimation of prostaglandin (PG) E₂ and of PGF_2α by radioimmunoassay is described in detail. PGE₂ was measured after conversion to either PGB₂ or PGF_2α and the results compared to bioassay. The methods were used to follow the excretion of PGE₂ and PGF_2α after salt loading in rabbits. A marked reduction of PGE₂ levels was observed at high NaCl intake, while PGF_2α excretion remained unchanged.     

The Role of Adipocytes and Adipocyte‐Like Cells in the Severity of COVID‐19 Infections

Coronavirus disease‐2019 (COVID‐19), caused by the highly pathogenic severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), demonstrates high morbidity and mortality caused by development of a severe acute respiratory syndrome connected with extensive pulmonary fibrosis. In this Perspective, we argue that adipocytes and adipocyte‐like cells, such as pulmonary lipofibroblasts, may play an important role in the pathogenic response to SARS‐CoV‐2. Expression of angiotensin‐converting enzyme 2 (the functional receptor for SARS‐CoV) is upregulated in adipocytes of patients with obesity and diabetes, which turns adipose tissue into a potential target and viral reservoir. This may explain why obesity and diabetes are potential comorbidities for COVID‐19 infections. Similar to the recently established adipocyte‐myofibroblast transition, pulmonary lipofibroblasts located in the alveolar interstitium and closely related to classical adipocytes demonstrate the ability to transdifferentiate into myofibroblasts that play an integral part of pulmonary fibrosis. This may significantly increase the severity of the local response to SARS‐CoV‐2 in the lung. To reduce the severity and mortality associated with COVID‐19, we propose to probe for the clinical response to thiazolidinediones, peroxisome proliferator activated receptor γ agonists that are well‐known antidiabetic drugs. Thiazolidinediones are able to stabilize lipofibroblasts in their “inactive” state, preventing the transition to myofibroblasts and thereby reducing the development of pulmonary fibrosis and stimulating its resolution.     

Evaluating the effectiveness of retention forestry to enhance biodiversity in production forests of Central Europe using an interdisciplinary,multi‐scale approach

Retention forestry, which retains a portion of the original stand at the time of harvesting to maintain continuity of structural and compositional diversity, has been originally developed to mitigate the impacts of clear‐cutting. Retention of habitat trees and deadwood has since become common practice also in continuous‐cover forests of Central Europe. While the use of retention in these forests is plausible, the evidence base for its application is lacking, trade‐offs have not been quantified, it is not clear what support it receives from forest owners and other stakeholders and how it is best integrated into forest management practices. The Research Training Group ConFoBi (Conservation of Forest Biodiversity in Multiple‐use Landscapes of Central Europe) focusses on the effectiveness of retention forestry, combining ecological studies on forest biodiversity with social and economic studies of biodiversity conservation across multiple spatial scales. The aim of ConFoBi is to assess whether and how structural retention measures are appropriate for the conservation of forest biodiversity in uneven‐aged and selectively harvested continuous‐cover forests of temperate Europe. The study design is based on a pool of 135 plots (1 ha) distributed along gradients of forest connectivity and structure. The main objectives are (a) to investigate the effects of structural elements and landscape context on multiple taxa, including different trophic and functional groups, to evaluate the effectiveness of retention practices for biodiversity conservation; (b) to analyze how forest biodiversity conservation is perceived and practiced, and what costs and benefits it creates; and (c) to identify how biodiversity conservation can be effectively integrated in multi‐functional forest management. ConFoBi will quantify retention levels required across the landscape, as well as the socio‐economic prerequisites for their implementation by forest owners and managers. ConFoBi's research results will provide an evidence base for integrating biodiversity conservation into forest management in temperate forests.