The Force-Frequency Dependence in the Heart Papillary Muscle of Ground Squirrel as a Reflection of Changes in the Functional State of Animals during the Annual Cycle

Biophysics - Abstract—A study was conducted to explore the characteristics of the dependence of the contraction force (isometric mode at 30°C) on the frequency of stimulation...     

Pilot study of the Urals population by tooth electron paramagnetic resonance dosimetry

During 1949–1956, about 76 × 10⁶ m³ of radioactive liquid waste containing a total activity of 10¹⁷ Bq was discharged into the Techa River by the first Russian industrial nuclear facility Mayak. As a consequence, the population living in the river valley received considerable internal and external radiation doses. The results of a first application of electron paramagnetic resonance (EPR) of tooth enamel for a retrospective individual dose evaluation of the residents of the Techa riverside are presented. Three main contributions to the dose absorbed in tooth enamel have been considered: external exposure mainly from the Techa River sediments, internal exposure mainly due to ⁹⁰Sr; and background radiation including all other sources of exposure except the Techa River. The teeth of 86 inhabitants of the town Kamensk-Uralskii were analysed to determine the age-dependent contribution of the background radiation to the enamel dose. For 22 residents of the middle and lower Techa riverside, measurements of the ⁹⁰Sr whole-body content and EPR measurements of the absorbed dose in enamel were used to establish a correlation between these two quantities. Finally, absorbed doses in the enamel of five residents of the upper Techa riverside were determined by the EPR method. Contributions of the background radiation and the internal ⁹⁰Sr contamination were subtracted to determine the external exposure of the residents.     

Inactivation of viruses in bubbling processes utilized for personal bioaerosol monitoring

A new personal bioaerosol sampler has recently been developed and evaluated for sampling of viable airborne bacteria and fungi under controlled laboratory conditions and in the field. The operational principle of the device is based on the passage of air through porous medium immersed in liquid. This process leads to the formation of bubbles within the filter as the carrier gas passes through and thus provides effective mechanisms for aerosol removal. As demonstrated in previous studies, the culturability of sampled bacterium and fungi remained high for the entire 8-h sampling period. The present study is the first step of the evaluation of the new sampler for monitoring of viable airborne viruses. It focuses on the investigation of the inactivation rate of viruses in the bubbling process during 4 h of continuous operation. Four microbes were used in this study, influenza, measles, mumps, and vaccinia viruses. It was found that the use of distilled water as the collection fluid was associated with a relatively high decay rate. A significant improvement was achieved by utilizing virus maintenance fluid prepared by using Hank's solution with appropriate additives. The survival rates of the influenza, measles, and mumps viruses were increased by 1.4 log, 0.83 log, and 0.82 log, respectively, after the first hour of operation compared to bubbling through the sterile water. The same trend was observed throughout the entire 4-h experiment. There was no significant difference observed only for the robust vaccinia virus.     

Effects of Nickel Chloride on Myocardial Contractile Properties in Active Ground Squirrels with Different Responses to Hypothermia

Biophysics - The effects of 1.5 mM nickel chloride on the contraction force, the force–frequency relation, and post-rest potentiation in the myocardium were studied in active Urocitellus...     

Role of Photorespiration and Cyclic Electron Transport in C<Subscript>4</Subscript> Photosynthesis Evolution in the C<Subscript>3</Subscript>–C<Subscript>4</Subscript> Intermediate Species <Emphasis Type="Italic">Sedobassia sedoides</Emphasis>

Plants from two Sedobassia sedoides (Pall.) Aschers populations (Makan and Valitovo) (Chenopodiaceae) with C₂ photosynthesis (precursor of C₄ photosynthesis in phylogenesis) and photorespiratory CO₂-concentrating mechanism were studied. Genetic polymorphism and isotope discrimination (δ¹³С) levels of the plants were determined under natural conditions, and their morpho-physiological parameters such as fresh and dry biomass of the above ground parts of plants, functioning of photosystem I (PSI) and photosystem II (PSII), intensity of net photosynthesis (A), transpiration (E), photorespiration and water use efficiency (WUE) of plants were calculated under control and salinine conditions (0 and 200 mM NaCl). Results of the population-genetic analysis showed that the Makan population is polymorphic (plastic) and the Valitovo population is monomorphic (narrowly specialized). There were no significant differences between the populations based on δ¹³С values or growth parameters, PSII, A, E and WUE under control conditions. Under saline conditions, dry biomass accumulation decreased in the Makan population by 15% and by more than 2- fold in the Valitovo population. Population differences were revealed in terms of photorespiration intensity and P700 oxidation kinetics under control and saline conditions. Under control conditions, Makan plants were characterized by a higher photorespiration intensity, which decreased by 2-fold under saline conditions to the photorespiration level of Valitovo plants. Cyclic electron transport activity was minimal in the control Makan plants, and it increased by almost 2-fold under saline conditions to the level of that in Valitovo plants under control and saline conditions. Under control conditions, photosynthesis in Makan plants can be specified as the proto-Kranz type (transitional type from C₃ to C₂) and that in Valitovo plants can be specified as the C₂ type (C₄ photosynthesis with photorespiratory CO₂-concentrating mechanism), based on their photorespiration level and cyclic electron transport activity. Under saline conditions, Makan plants exhibited features of C₂ photosynthesis. Intraspecific functional differences of photosynthesis were revealed in different populations of intermediate C₃–C₄ plant species S. sedoides which reflect the initial stages of formation of a photorespiratory CO₂-concentrating mechanism during C₄ photosynthesis evolution, accompanied by decrease in salt tolerance.     

Sulfur,carbon, and nitrogen stable isotope ratios in soft tissues and trophic relationships of fish from the near-shore waters of the peter the great bay in the Sea of Japan

Stable isotope ratios of sulfur (³⁴S/³²S), carbon (¹³C/¹²C), and nitrogen (¹⁵N/¹⁴N) were analyzed in the soft tissues of 12 common species of fish from the near-shore waters of the Peter the Great Bay in the Sea of Japan. The average δ¹³C values of individual species varied from −20.7‰ for planktivorous fish to −16.8‰ for benthivorous fish, reflecting the growing relative contribution of benthic primary producers to fish nutrition. The majority of the various species representatives studied can be assigned to one trophic level, as indicated by their narrow range of δ¹⁵N values (9.9 to 12.6‰). Large interspecific variations were found in the sulfur stable isotope ratios of fish (the mean δ³⁴S values ranged from 11.2 to 19.5‰). This is the result of the different contributions to fish nutrition of infaunal invertebrates that are depleted in ³⁴S due to the microbial food chain of the bottom sediments.     

Inactivation of Viruses in Bubbling Processes Utilized for Personal Bioaerosol Monitoring

A new personal bioaerosol sampler has recently been developed and evaluated for sampling of viable airborne bacteria and fungi under controlled laboratory conditions and in the field. The operational principle of the device is based on the passage of air through porous medium immersed in liquid. This process leads to the formation of bubbles within the filter as the carrier gas passes through and thus provides effective mechanisms for aerosol removal. As demonstrated in previous studies, the culturability of sampled bacterium and fungi remained high for the entire 8-h sampling period. The present study is the first step of the evaluation of the new sampler for monitoring of viable airborne viruses. It focuses on the investigation of the inactivation rate of viruses in the bubbling process during 4 h of continuous operation. Four microbes were used in this study, influenza, measles, mumps, and vaccinia viruses. It was found that the use of distilled water as the collection fluid was associated with a relatively high decay rate. A significant improvement was achieved by utilizing virus maintenance fluid prepared by using Hank's solution with appropriate additives. The survival rates of the influenza, measles, and mumps viruses were increased by 1.4 log, 0.83 log, and 0.82 log, respectively, after the first hour of operation compared to bubbling through the sterile water. The same trend was observed throughout the entire 4-h experiment. There was no significant difference observed only for the robust vaccinia virus.     

Changes of activity of the protein-synthesizing system of brain neurons of the ground squirrel Citellus undulatus during hibernation and hypothermia

Using fluorescent and electron microscopy a comparative analysis was performed of components of the protein-synthesizing system of hippocampal neurons both in ground squirrels in various phases of the torpor-activity cycle and in rats cooled under the hypoxia-hypercapnia conditions. Results of the study have shown that in hippocampal neurons of the ground squirrels entering the natural torpor state and of rats under conditions of artificial hypothermia to 17°C, similar mechanisms might be possible to function, one of their obligatory components being a generalized decrease of activity of the protein-synthesizing system with its subsequent restoration at the exit from hypothermia. Cessation of hypoxia-hypercapnia even under conditions of a further temperature decrease restored the rat neuronal protein-synthesizing activity, which seems to indicate the presence of a potential possibility of adaptation of brain neurons in vivo to low temperatures, at which the integral organism of non-hibernating homoeothermic animals does not survive.     

Three-dimensional microarchitecture of the plates (primary, secondary, and carinar process) in the developing tooth of Lytechinus variegatus revealed by synchrotron X-ray absorption microtomography (microCT)

This paper reports the first noninvasive, volumetric study of entire cross-sections of a sea urchin tooth in which the individual calcite structural elements could be resolved. Two cross-sectionally intact fragments of a Lytechinus variegatus tooth were studied with synchrotron microCT (microcomputed tomography) with 1.66 microm voxels (volume elements). These fragments were from the plumula, that is the tooth zone with rapidly increasing levels of mineral; one fragment was from a position aboral of where the keel developed and the second was from the zone where the keel was developing. The primary plates, secondary plates, carinar process plates, prisms, and elements of the lamellar-needle complex were resolved. Comparison of the microCT data with optical micrographs of stained thin sections confirmed the identifications and measured dimensions of the characteristic microarchitectural features. The interplay of reinforcing structures (plates and prisms) was more clearly revealed in the volumetric numerical data sets than in single or sequential slices. While it is well known that the primary plates and prisms in camarodont teeth are situated to improve resistance to bending (which can be termed primary bending), the data presented provide a new understanding of the mechanical role of the carinar process plates, that is, a geometry consistent with that required in the keel to resist lateral or transverse bending of the tooth about a second axis. The increase in robustness of teeth incorporating lateral keel reinforcement suggests that the relative development of carinar processes (toward a geometry similar to that of L. variegatus) is a character which can be used to infer which sea urchins among the stirodonts are most primitive and among the camarodonts which are more primitive.     

MicroCT quantification of in vitro bone resorption of neonatal murine calvaria exposed to IL-1 or PTH

This study investigated how effectively a laboratory microCT (X-ray micro-computed tomography) system can quantify bone resorption in an in vitro calvarial model and how well this measure correlates with a conventional assay for calcium release (fluorometric titration). In vitro bone resorption in neonatal murine calvaria was quantified for 0.3 or 1.0 nM interleukin-1 (IL-1) or for 1.0 or 10.0 nM parathyroid hormone (PTH) treatment. Compared to control calvaria, a significantly greater fraction F of the calvarial "shell" (computed from the volumetric microCT data) was resorbed in treated calvaria of 5- to 7-day-old pups from the same litter. Excellent correlation (R2 = 0.8234) was observed between F and calcium release, and, unlike the calcium assay, the 3-D maps revealed where bone was resorbed. Mineral was preferentially lost near the sutures, and areas away from the suture were left relatively intact. MicroCT of calvaria before and after 96 h culture demonstrated that this X-irradiation neither increased control resorption nor prevented responses in the treated calvaria. Observations on calvaria from intact mice aged 1, 3, 5, 8, and 11 days showed uniformly distributed mineral (not a pronounced patchwork of "high" and "low" mineral regions) and increasing levels of mineral with age; this suggested that the spatial patterns of resorption were not related to inhomogeneities in the starting mineral distribution.