Ethylene production in habituated and auxin-requiring tobacco callus cultures. Does ethylene play a role in the habituation?

Ethylene production of habituated and auxin-requiring tobacco ( Nicotiana tabacum L. cv. Xanthi) callus cultures were compared. More ethylene was produced by auxinrequiring i.e. auxin-heterotrophic cultures than by habituated ones. Treatment with 2,4-dichlorophenoxyacetic acid increased the ethylene evolution of habituated cultures over the range 10⁻⁷ to 10⁻⁴ M , which suggests that the higher ethylene production of auxin-dependent callus is caused by the 2,4-D in the medium. The IAA levels depended on the age of both types of callus cultures.     

Shemin pathway and peroxidase deficiency in a fully habituated and fully heterotrophic non-organogenic sugarbeet callus: an adaptative strategy or the consequence of modified hormonal balances and sensitivities in these cancerous cells? A review and reassessment

There are many arguments for considering a specific fully habituated (auxin and cytokinin-independent) and fully heterotrophic non-organogenic (HNO) sugarbeet callus cell line as terminating a neoplastic progression, and thus to be made of cancerous cells. The similarities with animal tumour and cancer cells are recalled. All types of habituated tissues examined in the literature share at least three common biochemical characteristics: low apparent peroxidase activity, high content of polyamines (PAs) and low production of ethylene. However, results concerning their auxin and cytokinin levels are not consistent. Peroxidase synthesis in the achlorophyllous HNO callus appears to arise from aminolevulinic acid (ALA) synthesis through the Shemin pathway, commonly used by animals and fungi. This pathway is limited by disturbed nitrogen metabolism that diverts glutamate (directly used for ALA synthesis in green higher plants) from the Kreb's cycle into PA synthesis. There is no argument to suggest that the low ethylene production is caused by a competition with PAs for their common precursor, S-adenosylmethionine. The results we report here indicate modified anabolic and catabolic pathways of auxins and cytokinins but also the possibilities of unusual compounds playing similar roles (dehydrodiconiferyl alcohol glucosides, for instance). A higher turnover of PAs is shown in the HNO callus, which could suggest a role for H2O2 and gamma-aminobutyric acid, products or intermediates in the PA catabolic pathway, as secondary messengers. The habituated cells retain some sensitivity towards exogenous auxins and cytokinins. Their increased sensitivity to PAs and ethylene suggests modified hormonal balances for the control of these actively dividing cells.     

Is passive observation of habituated animals truly passive?

The term “habituated” is sometimes used to imply that animals no longer respond to the presence of a human observer. There is an accumulating body of evidence, however, suggesting that habituated animals that no longer perceive humans as a direct threat nevertheless continue to respond to their presence in other ways. Data were collected from a troop of free-ranging vervet monkeys in the Klein Karoo of South Africa for months 5–12 of their habituation period to determine how self-directed behaviour (SDB) was affected by human presence across time. SDB decreased across the 8 month period, indicating that habituation was ongoing. The human observer’s location in relation to the focal animal had a significant effect on SDB. Furthermore, when the habituation period was divided into an early and a late phase this pattern did not arise until the later habituation period (9–12 months). This evidence suggests that animals continue to respond to human presence as they become habituated, although the observed responses change.     

Protozoa inhibition by different salts: Osmotic stress or ionic stress?

Cell density and morphology changes were tested to examine the effects of salts including NaHCO₃, NaCl, KHCO₃, and KCl at 160 mM on protozoa. It was demonstrated that ionic stress rather than osmotic stress led to protozoa cell death and NaHCO₃ was shown to be the most effective inhibitor. Deformation of cells and cell shrinkage were observed when protozoan cells were exposed to polyethylene glycol (PEG) or any of the salts. However, while PEG treated cells could fully recover in both number and size, only a small portion of the salt‐treated cells survive and cell size was 36–58% smaller than the regular. The disappearance of salt‐treated protozoa cells was hypothetically attributed to disruption of the cytoplasmic membrane of these cells. It is further hypothesized that the PEG‐treated protozoan cells carried out regulatory volume increase (RVI) after the osmotic shock but the RVI of salt‐treated protozoa was hurdled to varied extents. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1418–1424, 2017     

Disability; is it permanent?

Too often cases of industrial injuries are submitted for permanent disability rating before maximum recovery is attained and the condition is permanent and stationary. This is frequently a situation that is detrimental to the injured working man, since his physical disability might be further reduced by additional treatment, and his future earning power and economic status thus be improved. Also it may be detrimental to the insurance carrier and/or employer, since in some instances it results in increased permanent disability award payments for portions of the condition which are not truly permanent. Inadequate medical reports also are a frequent cause of unfair awards. The necessary factors used to arrive at proper conclusions, the errors that have been observed and the importance of this problem are discussed.     

Carina? and Esteem?: A Systematic Review of Fully Implantable Hearing Devices

Objective

To review the outcomes of the fully implantable middle ear devices Carina and Esteem regarding the treatment of hearing loss.

Data Sources

PubMed, Embase, Scielo, and Cochrane Library databases were searched.

Study Selection

Abstracts of 77 citations were screened, and 43 articles were selected for full review. From those, 22 studies and two literature reviews in English directly demonstrating the results of Carina and Esteem were included.

Data Extraction

There were a total of 244 patients ranging from 18 to 88 years. One hundred and 10 patients were implanted with Carina and with 134 Esteem. There were registered 92 males and 67 females. Five studies provided no information about patients’ age or gender. From the data available, the follow-up ranged from 2 to 29.4 months.

Data Synthesis

The comparison of the results about word recognition is difficult as there was no standardization of measurement. The results were obtained from various sound intensities and different frequencies. The outcomes comparing to conventional HAs were conflicting. Nevertheless, all results comparing to unaided condition showed improvement and showed a subjective improvement of quality of life.

Conclusion

There are still some problems to be solved, mainly related to device functioning and price. Due to the relatively few publications available and small sample sizes, we must be careful in extrapolating these results to a broader population. Additionally, none of all these studies represented level high levels of evidence (i.e. randomized controlled trials).     

Hereditary tyrosinemia: an endoplasmic reticulum stress disorder?

Hereditary tyrosinemia type 1 (HT1) is the most severe metabolic disease associated with tyrosine catabolism. An accumulation of toxic metabolites seems responsible for the pathology of HT1. The metabolite fumarylacetoacetate, accumulating due to a deficiency in fumarylacetoacetate hydrolase, displays apoptogenic, mutagenic, aneugenic and mitogenic activities. These effects may underlie the tumorigenic phenomenon observed in HT1. Fumarylacetoacetate in addition to causing disturbances in Ca2+ homeostasis, may induce endoplasmic reticulum stress.     

Protein SUMOylation and phase separation: partners in stress?

Protein SUMOylation is one of the most prevalent post-translational modifications (PTMs) and important for maintaining cellular homeostasis in response to various cellular stresses. Emerging evidence reveals the role of liquid–liquid phase separation (LLPS)/biomolecular condensates in cellular SUMOylation, potentially solving a puzzle regarding the cellular mechanism of SUMOylation regulation.     

Chlorinative stress: An under appreciated mediator of neurodegeneration?

Oxidative stress has been implicated as playing a role in neurodegenerative disorders, such as ischemic stroke, Alzheimer's, Huntington's, and Parkinson's disease. Persuasive evidences have shown that microglial-mediated oxidative stress contributes significantly to cell loss and accompanying cognitive decline characteristic of the diseases. Based on the facts that (i) levels of catalytically active myeloperoxidase are elevated in diseased brains and (ii) myeloperoxidase polymorphism is associated with the risk of developing neurodegenerative disorders, HOCl as a major oxidant produced by activated phagocytes in the presence of myeloperoxidase is therefore suggested to be involved in neurodegeneration. Its association with neurodegeneration is further showed by elevated level of 3-chlorotyrosine (bio-marker of HOCl in vivo) in affected brain regions as well as HOCl scavenging ability of neuroprotectants, desferrioxamine and uric acid. In this review, we will summary the current understanding concerning the association of HOCl and neuronal cell death where production of HOCl will lead to further formation of reactive nitrogen and oxygen species. In addition, HOCl also causes tissue destruction and cellular damage leading cell death.     

Disturbance and stress: different meanings in ecological dynamics?

There is an increasing frequency of papers addressing disturbance and stress in ecology without clear delimitation of their meaning. Some authors use the terms disturbance and stress exclusively as impacts, while others use them for the entire process, including both causes and effects. In some studies, the disturbance is considered as a result of a temporary impact, which is positive for the ecosystem, while stress is a negative, debilitating impact. By developing and testing simple theoretical models, the authors propose to differentiate disturbance and stress by frequency. If the frequency of the event enables the variable to reach a dynamic equilibrium which might be exhibited without this event, then the event (plus its responses) is a disturbance for the system. If frequency prevents the variable’s return to similar pre-event dynamics and drives or shifts it to a new trajectory, then we are facing stress. The authors propose that changes triggered by the given stimuli can be evaluated on an absolute scale, therefore, direction of change of the variable must not be used to choose one term or the other, i.e. to choose between stress and disturbance.     

Toxin-antitoxin pairs in bacteria: killers or stress regulators?

Plasmid toxin-antitoxin systems, which kill daughter cells that fail to inherit the plasmid genome, have chromosomal homologs in eubacteria and archaea. In this issue of Cell, Pederson et al. show that the E. coli RelE toxin cleaves mRNA in the ribosomal A site, potentially allowing it to function as a stress regulator during amino acid starvation.