Effects of the potential allelochemical α-asarone on growth,physiology and ultrastructure of two unicellular green algae

The effects of the natural phenylpropanoid -asarone on growth pattern, photosynthesis, respiration and cell structure of two microalgae have been investigated. In cultures ofAnkistrodesmus braunii -asarone decreases in the medium and induces a lag in growth. Both phenomena were dependent on the number of cells inoculated. By contrast, in cultures ofSelenastrum capricornutum a constant decrease of the growth rate at all inocula was observed and only a slight decrease of -asarone in the medium occurred. In both algae -asarone caused an initial inhibition of photosynthesis, followed by a resumption of control values. The respiratory rate ofA. braunii was not significantly affected by -asarone, whereas inS. capricornutum respiration lowered to 60% of the control in the first 48 h and subsequently rose to values exceeding the controls by 20%. Ultrastructural observations carried out 24 and 72 h after the addition of -asarone showed modifications of cell wall inA. braunii, an increase in the number of mithocondrial profiles per cell section inS. capricornutum, and an accumulation of electron-dense deposits in the vacuoles of both algae.Author for correspondence     

The effect of sevoflurane on developing A/J strain mouse embryos using a whole-embryo culture system—the incidence of cleft lip in culture embryos

A/J strain mice have a high spontaneous incidence of cleft lip (ICL) and/or palate. The primary palate-related effects of sevoflurane on developing A/J strain mouse embryos (embryos) were studied using a whole-embryo culture (WEC) system. This system could separate the direct effects of sevoflurane from those that are maternally mediated. A total of 205 10.5-d embryos were cultured for 24 h in either a control group (control gas: 95% O₂ and 5% CO₂) or sevoflurane-administered groups (1/4, 1/2, and 1 minimum alveolar concentration (MAC) with control gas) for 8 h. After 16 h, 11.5-d culture embryos were examined in terms of crown-rump length, number of somites, and protein content. Crown-rump length in the 1 MAC was significantly shorter than in the control group (p?<?0.05). Protein content in the 1/2 MAC (p?<?0.05) and 1 MAC (p?<?0.001) was significantly lower than in the control group. The ICL showed no significant differences between each group. (The ICL rose with an increase in the sevoflurane concentration, but this was not significant). The positive findings in this study indicate that a WEC system is useful for studying the mechanisms of ICL (teratogenicity) associated with sevoflurane.     

Managing to harvest? Perspectives on the potential of aquaculture

Aquaculture has been one of the most rapid and technically innovative of food production sectors globally, with significant investment, scientific and technical development and production growth in many parts of the world over the past two decades. While this has had a significant effect on the global supply of aquatic food products and had an important impact in rural and urban food supply and employment in many developing economies, growth and increasing internationalization has not been without concern for natural resource use, environmental impact and social disruption. The expectations for production and diversification are now significant and while the scientific and technical means are already available to meet much of the intended targets, practical constraints of investment, profitability, resource access and system efficiency are likely to become far more important constraints for the future. This review offers a contemporary perspective on the ways in which the sector might develop, its interactions with constraints and the strategies that may be required to ensure that future development is both positive and sustainable.     

Jensen’s inequality as a tool for explaining the effect of oscillations on the average cytosolic calcium concentration

It has often been asked which physiological advantages calcium (Ca²⁺) oscillations in non-excitable cells may have as compared to an adjustable stationary Ca²⁺ signal. One of the proposed answers is that an oscillatory regime allows a lowering of the average Ca²⁺ concentration, which is likely to be advantageous because Ca²⁺ is harmful to the cell in high concentrations. To check this hypothesis, we apply Jensen’s inequality to study the relation between the average Ca²⁺ concentration during oscillations and the Ca²⁺ concentration at the (unstable) steady state. Jensen’s inequality states that for a (strictly) convex function, the function value of the average of a set of argument values is lower than the average of the function values of the arguments from that set. We show that the kinetics of the Ca²⁺ efflux out of the cell is crucial in this context. By analytical calculations we derive that, if the Ca²⁺ efflux is a convex function of the cytosolic Ca²⁺ concentration, then oscillations lower the average Ca²⁺ concentration in comparison to the unstable steady state. If it is a concave function, the average Ca²⁺ concentration is increased, while it remains the same if that function is linear. We also analyse the case where the efflux obeys a Hill kinetics, which involves both a convex and a concave part. The results are illustrated by numerical simulations and simple example models. The theoretical predictions are tested with three experimental data sets from the literature. In two of them, the average appears to be higher than the steady-state value, while the third points to approximate equality. Thus oscillations may be used in real cells to tune the average Ca²⁺ concentration in both directions.     

The effect of culture and membrane potential on Goα expression in neonatal rat cardiac myocytes

The effects of culture and membrane potential on G_o39 expression were examined in neonatal rat cardiac myocytes. During six days of culture, the amount of G_o39 in myocytes increased six-fold. The increase in G_o39 appeared to be programmed, since G_o39 of rat hearts also increased in vivo within three days after birth before declining by six days after birth. Furthermore, the age of the rat from which cardiac myocytes were isolated determined the amount of G_o39 that accumulated in cultured cells with myocytes from two day-old rats producing more G_o39 than myocytes from six day-old rats. In addition, agents which alter membrane potential (KCl and bupivacaine) inhibited the accumulation of G_o39 in cultured myocytes. In an attempt to identify the signaling pathway in which cardiac G_o39 is involved, muscarinic receptor-stimulated inositol phosphate production was examined, but was found to be comparable in myocytes that had six-fold differences in G_o39 content. Thus G_o39 does not appear to couple muscarinic receptors to phospholipase C in rat cardiac myocytes.     

Transplanting the leafy liverwort Herbertus hutchinsiae: a suitable conservation tool to maintain oceanic-montane liverwort-rich heath?

Background: Translocating plants for conservation purposes can be a useful tool to enhance existing populations, restore lost populations or create new ones, but has rarely been done for bryophytes, especially liverworts.

Aims: Here, the leafy liverwort Herbertus hutchinsiae, a representative species of oceanic-montane liverwort-rich heath, was translocated to unoccupied habitat within its current range, to establish whether its restricted distribution is due to habitat or dispersal limitation.

Methods: Feasibility of establishing new populations outside the current distribution range was assessed, to test the suitability of the species for assisted colonisation. Furthermore, transplants were grown at degraded sites where the species had declined to assess potential for restoration.

Results: Although maximal growth rates occurred within-range, transplants grew at all sites, indicating that the species could be dispersal limited; a conclusion supported by distribution modelling.

Conclusions: Assisted colonisation is thus an option for this species to overcome dispersal limitation and to track future climate space. Reinforcement of populations at degraded sites is only recommended if the pressure causing the degradation has been removed. These findings provide an evidence base for practical conservation management.     

Electrophysiological approach of the antiepileptic effect of dexamethasome on hippocampal slice culture usihg a multirecording system: The physiocard®

The in vitro antiepileptic activity of the synthetic glucocorticoid dexamethasone (DEX) was tested in rat hippocampal organotypic cultures on the field potential epileptiform activity induced by picrotoxin (PTX). Spontaneous as well as evoked electrophysiological activities have been studied through the extracellular multirecording Physiocard® system. PTX typically elicited seizure-like discharges (epileptiform bursts) in the hippocampus neurons. Those epileptiform bursts can be divided in two groups, one rhythmic which lasted 43 ± 24s (mean ± sd) at a frequency of 4.6 ± 1.9Hz and the other arhythmic composed of population spikes, which occurred during 14.3 ± 6.9min. In the presence of DEX at different concentrations, results obtained were: 1) DEX 1μM decreased the occurrence of the two different groups of spontaneous epileptiform bursts, most of the time to zero. 2) DEX 50μM prevented totally the occurrence of epileptiform bursts. 3) DEX 50μM contrarily to DEX 1μM avoided the decrease of evoked field potentials' amplitude induced by PTX 3μM on all simultaneous recorded points. Those results suggest that synthetic glucocorticoid DEX presents an acute antiepileptic effect in a dose dependent manner on the hippocampus tissue.     

Comment on “Feasibility of Raman spectroscopy as a potential in vivo tool to screen for pre-diabetes and diabetes”

This paper comments recent findings about Raman spectroscopy application for in vivo noninvasive diabetes detection, published in the Journal of Biophotonics by E. Guevara et al. (J. Biophotonics 2022 , 15, e202200055). The proposed results may be not entirely correct due to possible overestimation of classification models and absence of additional information regarding age of tested volunteers.     

The effect of 17β-estradiol treatment on the mass and the turnover of bone in ovariectomized rats taking a mild dose of thyroxin

We performed the dosing experiment to establish whether estrogen administration has any beneficial effects on the mass and the turnover of bone in ovariectomized rats taking a mild dose of thyroxin. Thirty-five Wistar rats, 28 weeks of age, received ovariectomies (OVX) or sham operations and were divided into five groups. Group I was the sham group, Groups 2–5 were ovariectomized. Group 2 was the OVX-control, Group 3 treated with thyroxin 30 μg/kg/day (T4), Group 4, 17β-estradiol 0.3 mg/kg/week (E2), and Group 5, the combination of T4 and E2. The duration of the experiment was 12 weeks. At the end of the experiment, serum chemistries were measured. Bone minerals in the femur were determined with single photon absorptiometry and bone turnover was assessed histomorphometrically. Alkaline-phosphatase increased in Group 3 (OVX-T4), but it reduced in Groups 4 (OVX-E2) and 5 (OVX-T4 + E2). Bone minerals decreased in Groups 2 (OVX) and 3. In Group 4, it was preserved at the same level as in Group 1. Group 5 showed a significant increase of bone mass compared with Group 1. Eroded surface and osteoid surface increased in Groups 2 and 3 and they were reduced in Groups 4 and 5. Bone volume and mineral apposition rate were at a maximum in Group 5. This study demonstrated that 17β-estradiol was capable of preventing the bone mass decrease by regulating the turnover in ovariectomized rats taking a mild dose of thyroxin. Osteoblast function appeared to be stimulated in combination with 17β-estradiol and thyroxin.     

Investigating the effect of a single glycine to alanine substitution on interactions of antimicrobial peptide latarcin 2a with a lipid membrane

Latarcins are linear, α-helical antimicrobial peptides purified from the venom of the Central Asian spider Lachesana tarabaevi, with lytic activity against Gram-positive and Gram-negative bacteria, erythrocytes, and yeast at micromolar concentrations. In this work, we investigated the role of the hinge in latarcin 2a (ltc2a, GLFGKLIKKFGRKAISYAVKKARGKH-COOH), which adopts a helix–hinge–helix conformation in membrane-mimicking environments, on peptide–membrane interactions and its potential effect on the selective toxicity of the peptide. A modified latarcin 2a, ltc2aG11A, obtained by replacing the glycine at position 11 with alanine (ltc2aG11A, GLFGKLIKKFARKAISYAVKKARGKH-COOH), adopts a more rigid structure due to the reduced conformational flexibility. Langmuir monolayer measurements combined with atomic force microscopy and X-ray photoemission electron microscopy (X-PEEM) indicate that both peptides bind and insert preferentially into anionic compared with zwitterionic phospholipid monolayers. Modified ltc2aG11A was found to be more disruptive of supported phospholipid bilayer modeling mammalian cell membrane. However, no considerable difference in lytic activity of the two peptides toward bacterial membrane was found. Overall the data indicate that decrease in the flexibility of ltc2a induced by the modification in the hinge region is likely to increase the peptide’s nonspecific interactions with zwitterionic cell membranes and potentially increase its toxicity against eukaryotic cells.     

OntoDas – a tool for facilitating the construction of complex queries to the Gene Ontology

Background  

Ontologies such as the Gene Ontology can enable the construction of complex queries over biological information in a conceptual way, however existing systems to do this are too technical. Within the biological domain there is an increasing need for software that facilitates the flexible retrieval of information. OntoDas aims to fulfil this need by allowing the definition of queries by selecting valid ontology terms.     

Is the effect of wounding on leaf senescence due to ethylene?

Wounding delays the loss of chlorophyll (Chl) that normally occurs when oat (Avena sativa L.) leaf segments are held in the dark. There was a continued increase in ethylene production during the senescence of the control segments; in contrast, ethylene production by the wounded segments, although it increased by a factor of 2–3 times, reached its peak in 48 h and then dropped sharply to below the basal level. Added 1-aminocyclopropane-1-carboxylic acid (ACC) caused a very large increase in ethylene production in both control and wounded segments, but it increased the rate of Chl loss, though only marginally. Aminoethoxyvinylglycine (AVG) inhibited ethylene production by both control and wounded segments and this did decrease the Chl loss, but only in the control segments. In the wounded segments, AVG antagonized the Chl-retaining action of the wound. Since wounding delayed the loss of Chl and yet caused a moderate increase in ethylene production, we conclude that the ethylene production by senescing oat leaves is not the main controlling influence in the wounding effect. The data also throw doubt on the causal participation of ethylene in normal Chl loss by these leaves in darkness.     

Captive breeding—a useful tool in the preservation of biodiversity?

Within the next decades species extinction may eliminate between 20 and 50% of the Earth's species. Captive breeding has often been claimed to be a useful tool in preservation of biodiversity. The role of zoos in conservation work and the value of captive breeding are discussed; the latter exemplified by the Peregrine Falcon (Falco peregrinus) Programme and the Arabian oryx (Oryx leucoryx) Programme. Captive breeding programmes are very resource demanding and can only be afforded for a very small number of species, which limits their value significantly. Zoos deal mainly with vertebrates, but these comprise less than 3% of the described species, and although the 878 zoos considered hold more than 20 000 specimens of 140 threatened mammal species, they probably only contribute to the conservation of 20 full species. The situation for birds, reptiles and amphibians is even worse. Zoos face serious problems with minimum viable population sizes and hybridization. However, zoos can make a major contribution to preservation of biodiversity through educating and informing the public. Today, where the crisis of extinction of species has reached such daunting dimensions, captive breeding and otherex situ conservation tools should be the last resort for preserving biodiversity, and captive breeding must not become an excuse to avoid dealing with preservation of habitats.     

Modeling the effect of oxygen mass transfer on β-lactam antibiotic production by immobilizedCephalosporium acremonium

Summary The oxygen effect on the production of -lactam antibiotics was investigated whenCephalosporium acremonium was immobilized in calcium alginate. Theoretical effectiveness factors were calculated and compared with experimental ones. The approximate expressions of effectiveness factors reported in the literature were compared with the numerically obtained solutions to provide the best approximated expression for immobilizedC. acremonium cells. Yamane's approximate expression of effectiveness factor was best fit with the solutions numerically obtained in this investigation.     

Is the Phytophthora citrophthora culture filtrate a reliable tool for the in vitro selection of resistant Citrus variants?

Summary Nucellar calli from four Citrus cultivars with known resistance to the Phytophthora citrophthora pathogen were chosen as experimental material to test the pathogen's response to culture filtrate (CF). Sensitivity of the four calli to CF of the fungus was in reverse order to what is known on the susceptibility of the cultivars in vivo. Sensitivity of protoplasts derived from the same four calli to 2,4-dichlorophenoxyacetic acid (2,4-D) was in the same order as that of calli to CF. Protoplasts derived from calli selected for tolerance to CF showed a higher plating efficiency with increasing concentration of CF in the medium. TLC and GLC determinations showed the presence of indole acetic acid in the culture filtrate. Results indicate that CF of P. citrophthora cannot be used as a selection tool in vitro.Contribution No. 1655-E, 1986 series, from the Agricultural Research Organization, Bet-Dagan, Israel     

Influence of the radial profile of the electric potential on the confinement of a high-β two-component plasma in a gas-dynamic trap

One of the most important problems to be studied in the gas-dynamic trap (GDT) facility is the investigation of MHD stability and cross-field transport in a plasma with a relatively high value of β = πp/B ². Recent experiments demonstrated that the radial electric field produced in the plasma by using radial limiters and coaxial end plasma collectors improves plasma stability in axisymmetric magnetic mirror systems without applying special MHD stabilizers. The experimental data presented in this work show that stable plasma confinement can be achieved by producing a radial potential drop across a narrow region near the plasma boundary. Creating radial electric fields of strength 15–40 V/cm causes a shear plasma flow, thereby substantially increasing the plasma confinement time. When all the radial electrodes were grounded, the confinement was unstable and the plasma confinement time was much shorter than the characteristic time of plasma outflow through the magnetic mirrors. Measurements of cross-field plasma fluxes with the use of a specially designed combined probe show that, in confinement modes with differential plasma rotation, transverse particle losses are negligibly small as compared to longitudinal ones and thus can be ignored. It is also shown that, when the GDT plasma is in electric contact with the radial limiters and end collectors, the growth rate of interchange instability decreases considerably; such a contact, however, does not ensure complete MHD stability when the electrodes are at the same potential.     

The effect of G2-treatments with 2′-deoxyadenosine on the frequency of chromatid aberrations in human lymphocytes depends on the type of culture

The effect of G₂-treatments with 2-deoxyadenosine (dAdo) on the frequency of chromatid aberrations in X-irradiated and unirradiated human lymphocytes depends on the method of culture. In whole-blood cultures dAdo alone produced very few if any aberrations, but in the presence of inhibitors of adenosine deaminase (ADA), such as EHNA or coformycin, a high frequency of chromatid gaps, chromatid breaks, and isochromatid breaks were produced. In cultures of purified lymphocytes, dAdo produced aberrations even in the absence of an ADA inhibitor. Apparently the lymphocytes are protected against the chromosome-damaging effect of dAdo by the ADA activity of the erythrocytes. — When given as a post-treatment, dAdo also enhances the frequency of chromatid aberrations induced by X-rays in G₂. In whole-blood cultures this effect is obtained even in the absence of an ADA inhibitor, although the concentration required to produce enhancement is about twenty times higher than in the presence of the inhibitor.     

Identification of sterols and alcohols produced by green algae of the generaChlorella andScenedesmus by means of gas chromatography—mass spectrometry

Sterols and alcohols isolated from a collection of industrially important fresh-water green algaeChlorella kessleri, Scenedesmus acuminatus, S. acutus andS. acutus var.Tomasclli cultivated heterotrophically or autotrophically under pilot plant conditions, were identified and quantified by gas chromatography — mass spectrometry. Previsously demonstrated sterols with double bonds in position 5 and 7 were detected. In addition, cholesta-5,7,22-trien-3 β-oI that had not yet been described in green algae was found inS. acutus. Alcohols were found only inC. kessleri cultivated under heterotrophic conditions. Some saturated and unsaturated alcohols were detected for the first time in green algae.