Controlling the near‐infrared transparency of costal cartilage by impregnation with clearing agents and magnetite nanoparticles

Penetration depth of near‐infrared laser radiation to costal cartilage is controlled by the tissue absorption and scattering, and it is the critical parameter to provide the relaxation of mechanical stress throughout the whole thickness of cartilage implant. To enhance the penetration for the laser radiation on 1.56 μm, the optical clearing solutions of glycerol and fructose of various concentrations are tested. The effective and reversible tissue clearance was achieved. However, the increasing absorption of radiation should be concerned: 5°C‐8°C increase of tissue temperature was detected. Laser parameters used for stress relaxation in cartilage should be optimized when applying optical clearing agents. To concentrate the absorption in the superficial tissue layers, magnetite nanoparticle (NP) dispersions with the mean size 95 ± 5 nm and concentration 3.9 ± 1.1 × 10¹¹ particles/mL are applied. The significant increase in the tissue heating rate was observed along with the decrease in its transparency. Using NPs the respective laser power can be decreased, allowing us to obtain the working temperature locally with reduced thermal effect on the surrounding tissue.      

Heat shock increases thermotolerance of photosynthetic electron transport and the content of chloroplast membranes and lipids in wheat leaves

Preliminary heating of 15-16-day-old wheat (Triticum aestivum L.) plants for 3 h at 37–38°C (heat shock, HS) increased the tolerance of photosynthetic electron transport (determined as the reduction of 2,6-dichlorophenol indophenol by isolated chloroplasts) toward heating of leaves at 42–48°C in high light (100 klx). At the same time, HS did not affect the activity of the xanthophyll cycle reactions in the 30–48°C temperature range. HS exposure induced an increase in the thylakoid length, the number of grana, and the average number of thylakoids per granum. The volume of the thylakoid system increased 1.4-fold. Such indices as the total content of chlorophylls (a + b), the chlorophyll a/b ratio, as well as the contents of individual carotenoids, chloroplast membrane proteins, and the soluble leaf proteins remained unchanged. The de novo photosynthetic membrane formation was accompanied by the 1.5-fold increase in major chloroplast lipids. It was concluded that, in mature wheat chloroplasts, HS induced the formation of thylakoids characterized by a changed molecular structure and by increased lipid/protein and lipid/chlorophyll ratios.     

Impact of Local Damage on Transpiration of Pea Leaves at Various Air Humidity

Russian Journal of Plant Physiology - Local damages induce a wide spectrum of functional responses in intact parts of the plant, including changes in transpiration and CO2 assimilation, which may...     

Cytochrome P4501A1, glutathione S-transferase M1 and T1 gene polymorphisms in chronic myeloid leukemia

Polymorphic variants of cytochrome P4501A1 (CYP1A1), glutathione-S-transferase M1 (GSTM1) and T1 (GSTT1) distribution was studied in patients with chronic myeloid leukemia (CML) and healthy individuals. It was shown that homozygotes for the GSTT1 gene deletion occur significantly more frequently in the CML patient group compared to the control group (13.17% versus 24.10% in CML patients, Chi2 = 4.40, p < 0.05; OR = 2.09; 95% CI = 1.10-3.99). In contrast, no significant difference was observed between the healthy individuals and CML patients in the frequency of polymorphic variants of GSTM1 and CYP1A1 genes (p > 0.05).     

Heat-Induced Increase in the Tolerance of the Wheat Photosynthetic Apparatus to Combined Action of High Temperature and Visible Light: CO2 Fixation,Photosynthetic Pigments,and Chloroplast Ultrastructure

Heating of the leaves of 15-day-old wheat (Triticum aestivum L.) plants at 42°C in the light (370 W/m² PAR) suppressed their ability to fix CO₂ twice stronger than heating in darkness. Heat hardening (3 h at 38–39°C) improved the tolerance of photosynthesis to combined action of high light and temperature but did not affect the tolerance to photoinhibition at 30°C. Hardening did not induce changes in the levels of photosynthetic pigments and their ratios. De-epoxidation of violaxanthin turned out to be more tolerant to photoinhibition at 42°C than CO₂ fixation. Protective effect of hardening was not related to the accumulation of zeaxanthin and activation of the xanthophyll cycle. Hardening protected the most sensitive population of chloroplasts against heat-induced photodamage and simultaneously increased the number and length of thylakoids. An increase in the volume of the thylakoid system was also induced by heating at 42°C and exposure to high light at 30°C. The formation of additional thylakoids and grana of shade type was not associated with improved tolerance of photosynthesis to heat and light stresses.     

Influence of variation potential on resistance of the photosynthetic machinery to heating in pea

Electrical signals [action potentials (APs) and variation potentials (VPs)] induced by local stimuli are a mechanism that underlies rapid plant response to environmental factors. Such signals induce a number of functional responses, including changes in photosynthesis. Ultimately, these responses are considered to increase plant resistance to stress factors, but this question has been poorly investigated. We studied the influence of VP on photosynthesis and resistance of the photosynthetic machinery to heating in leaves of pea (Pisum sativum). Localized burning induced a VP that decreased photosynthesis parameters [CO₂ assimilation rate and quantum yields of photosystem I (PSI) and photosystem II (PSII)]. The photosynthetic response was initiated by a decrease in photosynthesis dark‐stage activity, which in turn increased resistance of PSI to heating. Three results supported this hypothesized mechanism: (1) the magnitude of VP‐induced decrease in CO₂ assimilation and enhanced PSI resistance to heating were highly correlated; (2) the VP influence on PSI resistance to heating was suppressed under a low external CO₂ concentration and (3) decreasing external CO₂ concentration imitated the VP‐induced photosynthetic response and increased PSI resistance to heating.     

Influence of a variation potential on photosynthesis in pumpkin seedlings (Cucurbita pepo L.)

The influence of a variation potential on photosynthesis in pumpkin seedlings (Cucurbita pepo L.) was investigated in our work. It was shown that the variation potential induced by cotyledon burning propagates into a leaf. It decreases CO₂ assimilation and transpiration as well as increases nonphotochemical quenching. Investigation of isolated chloroplasts showed that lowering of the pH in incubation medium from 6.9–7.2 to 6.5 increases nonphotochemical quenching. It was proposed that lowering of the cytoplasmic pH induced by the variation potential takes place in the photosynthetic response development.     

Seasonal structural and functional changes in the photosynthetic apparatus of evergreen conifers

We conducted a detail study of the photosynthetic apparatus in assimilating organs of three introduced evergreen conifer species: Taxus cuspidate S. et Z. ex E. (Far-Eastern yew), Thuja occidentalis L. (arbovitae “green”), and Th. occidentalis f. “Reingold” (arbovitae “yellow”) at various times in their life cycle. We studied the potential photosynthesis rate; composition and ratios of pigments, including primary carotenoids; the violaxanthin cycle (VC) activity, the synthesis of a secondary carotenoid, rhodoxanthin; and chloroplast ultrastructure. In winter and spring, β-carotene and lutein (primary carotenoids) contents were relatively constant in yew and arbovitae “yellow”. In December, the VC in yew was balanced and in arbovitae “yellow” unbalanced. In arbovitae “yellow”, the zeaxanthin pool was heterogeneous, and only part of it took part in the VC. It can be assumed that the other part of the pool can be oxidized to form a secondary carotenoid, rhodoxanthin. This secondary carotenoid was also accumulated in arbovitae “green”; its synthesis took place during the season, when the photosynthesis rate of plants was the lowest, and a significant chloroplast reorganization occurred (the number of thylakoids in grana decreased and plastoglobules appeared). We suppose that rhodoxanthin forms a filter for the light under the conditions of high insolation in winter. Thus, the evergreen conifer plants studied, which are adapted to growing at high latitudes where temperature is low and insolation is high in winter and spring, have a system for protecting the photosynthetic apparatus against photodestruction. In the basis of this system, the primary and secondary carotenoids lie, whose content changes during the year.