Action potential initiation site depends on neuronal excitation

The initiation site in neurons is where the excitatory and inhibitory inputs sum to generate action potentials. It is generally considered to be at a fixed location, typically at the axon hillock or initial segment, although action potentials, or impulses, could in theory arise at a site that shifts dynamically. The data reported here show that the initiation site can shift in a graded manner, by as much as 175 microm, depending on the level of neuronal excitation. Laser axotomy reveals that the Anterior Pagoda (AP) neuron of the leech is excitable within the synaptic neuropil before its axon bifurcates. Using an electrophysiological technique to measure relative delays in impulses arriving at different sites, we have found that depolarization, either by applied current or by synaptic input, can shift the site of impulse initiation in the cell proximally toward the soma and neurites receiving synaptic input. Impulse initiation in this region should enhance the efficacy of inputs synapsing there. Conversely, hyperpolarization can shift the initiation site distally. A shifting initiation site, therefore, may be a mechanism by which synaptic inputs can rapidly enhance or suppress the active response of the AP neuron to other synaptic inputs

A rational approach to improving titer in Escherichia coli‐based cell‐free protein synthesis reactions

Cell‐free protein synthesis (CFPS) is an established method for rapid recombinant protein production. Advantages like short synthesis times and an open reaction environment make CFPS a desirable platform for new and difficult‐to‐express products. Most recently, interest has grown in using the technology to make larger amounts of material. This has been driven through a variety of reasons from making site specific antibody drug conjugates, to emergency response, to the safe manufacture of toxic biological products. We therefore need robust methods to determine the appropriate reaction conditions for product expression in CFPS. Here we propose a process development strategy for Escherichia coli lysate‐based CFPS reactions that can be completed in as little as 48 hr. We observed the most dramatic increases in titer were due to the E. coli strain for the cell extract. Therefore, we recommend identifying a high‐producing cell extract for the product of interest as a first step. Next, we manipulated the plasmid concentration, amount of extract, temperature, concentrated reaction mix pH levels, and length of reaction. The influence of these process parameters on titer was evaluated through multivariate data analysis. The process parameters with the highest impact on titer were subsequently included in a design of experiments to determine the conditions that increased titer the most in the design space. This proposed process development strategy resulted in superfolder green fluorescent protein titers of 0.686 g/L, a 38% improvement on the standard operating conditions, and hepatitis B core antigen titers of 0.386 g/L, a 190% improvement

Pulmonary embolism in obesity‐hypoventilation syndrome

Ekici, Aydanur/0000-0003-1522-6443WOS:000559013600001PubMed: 32745286Introduction Obesity-hypoventilation syndrome occurs with alveolar hypoventilation during sleeping and daytime. Obesity may be a risk factor for venous thromboembolism. However, the venous thromboembolism in the obesity-hypoventilation syndrome is not well characterized. Objective This case series aimed to investigate the presence and clinical features of venous thromboembolism in patients with the obesity-hypoventilation syndrome. Methods Data of eight case reports were collected. Ages ranged from 36 to 73 years. Results All patients had mosaic perfusion and enlarged main pulmonary artery, two had signs of infarction and mostly segmental and subsegmental filling defects. On the basis of this information some conclusions can be drawn carefully. Conclusion Present cases indicate that pulmonary embolism are also very common in patients with obesity-hypoventilation syndrome, anticoagulant therapy is at least as important as the treatment of the current disease. Clinicians will frequently be faced with patients with obesity-hypoventilation syndrome suspected of PE