Showing papers in "Doklady Biological Sciences in 2002"

Methane generation in permafrost sediments.

Abstract: Discovery of viable microorganisms in permafrost [1–4] raised the problem of their metabolic status It is uncertain whether or not the microorganisms stored in permafrost sediments remain metabolically active The use of radioactively labeled compounds is one of a few methods of detection of metabolic processes in permafrost sediments It was shown [5] that microbial lipids could be synthesized in permafrost sediments

Discovery of Viable Methanotrophic Bacteria in Permafrost Sediments of Northeast Siberia

Abstract: Permafrost regions occupy some two thirds of Rus-sia. It was found that fine-dispersion permafrost rocksare specific natural depositories of viable aerobic andanaerobic microbial communities [1, 2]. It should benoted that, the total count of microorganisms in perma-frost sediments is only one order of magnitude less thanin tundra soils. Moreover, there is evidence thatbecause of the presence of unfrozen water stronglybound to soil particles, the metabolic activity of cold-adapted microorganisms is maintained at a sufficientlyhigh level. For example, it was shown that metabolicactivity of some microorganisms is observed at subzerotemperatures as low as –17°e [3, 4]. The presence ofcarbon-containing gases, CH

A New Early Cretaceous Mammal from Western Siberia

Abstract: The first Mesozoic mammal in Siberia (and in Rus-sia) was discovered by E.N. Maschenko in 1995 in theEarly Cretaceous Shestakovo locality (ChebulinskiiDistrict, Kemerovo Region) [1]. Representatives of atleast six mammalian species belonging to Gobicon-odontidae, Docodonta, and Peramura have been discov-ered in Shestakovo [2]. The majority of specimensbelong to Gobiconodon , a “triconodont” genus, whichwas widespread in the Early Cretaceous of the northernHemisphere.Here, we describe a new member of the family Per-amuridae established as a special group, Peramura(sublegion Zatheria, legion Cladotheria, infraclassHolotheria, subclass Theriiformes) [3]. Peramura ismost closely related to tribosphenic mammals [3, 4]and, therefore, important for the understanding of theirorigin and early evolution. This paraphyletic taxoncomprises forms with dental structures that fill themorphological gap between the Symmetrodonta andTribosphenida. To date, it has only been known fromthe Jurassic and Lower Cretaceous of Europe andAfrica [3, 4].The nomenclature of dental structures is given afterSigogneau-Russell [3], the designations of wear facetsare given after Crompton [5]. Measurements, mm,( L ) length and ( W ) width.Family Peramuridae Kretzoi, 1946.Genus Kiyatherium Maschenko, Lopatin, etVoronkevich, gen. nov. Etymology. From the Kiya River. Type species. Kiyatherium cardiodens Maschenko, Lopatin, et Voronkevich, sp. nov. Diagnosis. Dental formula of postcanines P1–P5M1–M3. Occlusal surface of P4–M2 V-shaped, ectof-lexus of M1–M2 sharp and deep. P5 molariform, withlarge and high stylocone and well-developed lingualcingulum. M1–M3 double-rooted. Preparacrista ofM1–M2 positioned obliquely to axis of tooth row.Metacone absent. Lingual cingulum of M1–M2 welldeveloped. Buccal part of molars relatively slightlyexpanded. Parastylar lobe of M3 considerably reduced.Prominent diastema present between canine and P1. Species composition. Type species. Comparison. Differs from Peramus Owen, 1871, Palaeoxonodon Freeman, 1979, Abelodon Brunet et al. ,1991, Magnimus Sigogneau-Russell, 1999, and Afriquiamus Sigogneau-Russell, 1999, in the well-developed lingual cingulum of M1–M2 and in theabsence of true metacone. From all these genera, exceptfor Afriquiamus , it differs by the oblique rather thantransverse preparacrista of M1 and M2. In addition, itdiffers from Magnimus in the double-rooted M1 andM2 and from Peramus in the presence of a prominentdiastema between C and P1, the shape of P4 and P5, thestructure of P5, and in a less expanded buccal part ofM1 and M2 and more reduced M3. Kiyatherium cardiodens Maschenko, Lopatin, etVoronkevich, sp. nov. Etymology. Latin cardium (heart) and dens (tooth). Holotype. Paleontological Museum of the TomskState University (PM TGU), no. 16/2-50 (Figs. 1a, 1b);fragmentary left maxilla with the canine, P1–P5, andM1–M3; Kemerovo Region, Shestakovo 3 locality;Lower Cretaceous, Ilek Formation. Description. Nine teeth are preserved in the upperjaw, the anteriormost of which is located in the proxim-ity of the incisor foramen and identified as a canine.The fifth postcanine is characterized by an incompleteeruption, and the two successive teeth are considerablyworn and expanded buccolingually. Therefore, the fiveanterior postcanines are interpreted as premolars P1–P5;and the three posterior teeth, as molars M1–M3. Theanterior part of the maxilla deviates ventrally at thelevel of P1, similarly to that of Peramus tenuirostris Owen [4]. The large infraorbital foramen is located aboveP3. The incisor foramen is oval and relatively large.The canine is small, single-rooted, chisel-shaped,with a simple conical crown, and strongly curved dis-tally (perhaps, as a result of deformation). P1–M3 aredouble-rooted. The P1–P3 crowns are elongated mesio-distally. P3 shows a massive main cusp (paracone),which is worn apically and distally, and an accessorydistal cuspule. A large wear facet ascends along the dis-tolingual side of the crown. P4 is bicuspid; the main

Feeding of the symbiotic polychaete Gastrolepidia clavigera (Polynoidae) and its interactions with its hosts.

Abstract: Parasitism is less widespread in polychaetes than commensalism is. The latest review [1] describes 375 species of symbiotic polychaetes, with 294 of them being considered commensal and only 81, parasitic. This situation is even more distinct in the family Polynoidae (scale-worms), which includes more than 50 of symbiotic polychaetes. Only one out of 160 species of symbiotic scale-worms (Thormora johnstoni) is considered parasitic [2]. Thus, parasitism is generally considered to be an exceptionally rare phenomenon in scale-worms. On the one hand, this situation reflects evolutionary trends in the class Polychaeta and the family Polynoidae; on the other hand, it is explained by the fact that the biology of symbionts has not been studied sufficiently (see [1] for definitions of the terms). Most symbiotic polychaete species has been assigned to commensals without special studies, only due to the absence of manifest "parasitic" features in their organi-zation. There are various approaches to studying the interactions between symbionts. In theory, it is necessary to analyze the effects of symbionts on the mortality and metabolism of their hosts to determine the type of their interactions. However, for many associations, this approach is too difficult because it requires much time and special equipment. Therefore, such studies are seldom performed on symbiotic associations of marine animals (see, e.g., [3]); there are no published studies of this type on any association containing polychaetes. At the same time, the type of the symbiont-host interactions may sometimes be determined by indirect methods, such as morphological and functional analysis of the foodprocuring system and the digestive tract [4], direct observation of the feeding [5], and analysis of the intestinal contents [6]. The object of this study was the polychaete Gastrolepidia clavigera Schmarda from family Polynoidae. This polychaete is widely spread in the Indian-West Pacific region and is a symbiont of holothurians of families ___________________

Baikal invaders have become dominant in the upper Yenisei benthofauna.

Abstract: Natural and anthropogenic invasions are often observed in aquatic ecosystems. Various organisms, including endemic Baikal amphipods, were found to play the role of invaders [1]. The Angara River connects Lake Baikal with the Yenisei River. Although Baikal amphipods, including Gmelinoides fasciatus Stebb., have long since been found in the Yenisei River, the area of distribution of these invertebrates was reported to stretch over the river only downstream of its confluence with the Angara River [2]. According to V.N. Greze, typical litoreophilous organisms (larvae of caddis-flies, May-flies, and buffalo gnats) used to be absolutely dominant components of zoobenthos in the Yenisei River upstream of its confluence with the Angara River [2].

The mitochondrial antioxidants thioredoxin-2 and Mn-superoxide dismutase are involved in the mechanisms of brain hypoxic tolerance.

Abstract: The mitochondrial antioxidants thioredoxin-2 and Mn-superoxide dismutase are involved in the mechanisms of brain hypoxic tolerance

The jaw apparatus of the heteromorphic ammonite Australiceras whitehouse, 1926 (Mollusca: Cephalopoda) from the Aptian of the Volga region.

Abstract: Buccal apparatuses (lower and upper jaws together with radula) of ammonoid are rarely found and are known only in a few ammonoid genera [1, 2] since their taxonomic assignment is only possible in those cases when they are preserved within the shell. Their preservation within a body chamber only occurs in those rare instances when the soft body of the mollusk is decomposed in situ. The necessary taphonomic conditions include an oxygen deficient environment with rapidly accumulating soft sediments, few or no scavengers, low rates of separation of soft tissues from the shell, and rapid sinking of dead organisms into the sediment. Appropriate conditions existed in the Early Aptian in the Russian Sea [3, 4], the region where the uniquely preserved buccal apparatuses of Aconeceras , which are strikingly similar in the structure of the radula to the buccal apparatuses of recent bathypelagic octopuses, have been found [5, 6]. Here, we describe two newly found jaw apparatuses of the heteromorphic ammonite Australiceras , a genus characterized by a wide geographic distribution (Central Russia, Caucasia, Germany, France, England, Pakistan, Australia, Columbia, and California) and a narrow stratigraphic range (Aptian). This is one of the first finds of paired lower and upper jaws in heteromorphic ammonoids, the paleobiology of which, including locomotion and feeding habits, is poorly understood. Australiceras secreted large shells (as large as 400 mm or more in diameter) with crioceratid coiling and an arcuate hook-shaped terminal body chamber. Materials and methods. The morphology, microstructure, and elemental chemical composition of two specimens collected by I.A. Shumilkin and G.N. Uspenskii (Ul’yanovsk) in the vicinity of Ul’yanovsk and donated to one of the authors I. A. M. have been studied using a scanning electron microscope and an electron-probe microanalyzer. According to [7], these specimens are from the Deshayesites deshayesi–Proaustraliceras tuberculatum Zone. Both specimens are housed at the Paleontological Institute (PIN) of the Russian Academy of Sciences. The first specimen (PIN, no. 3871/109) consists of the lower (partially destroyed) and upper jaws, arranged one inside the other in the large fragment of the coarsely ribbed body chamber with a diameter of 75–80 mm. The length, height, and width of the apparatus are 55– 60, 35–40, and 48–52 mm, respectively. The second specimen (PIN, no. 3871/110) consists of the left halves of the lower and upper jaws, which lie in the body chamber near the last septum; the height and width of the body chamber are 80 and 72 mm, respectively. The right half of the apparatus and the fragment of the enclosing shell were lost during preparation. Morphology. The jaw apparatus (Fig. 1) is large and black in color; in adult individuals, its width and height are approximately half as large as those of the body chamber. The apparatus (Fig. 1a) consists of the massive lower jaw and “lighter” upper jaw; the former covers the entire length and two-thirds of the height of the latter. The lower and upper jaws have the same architecture (Figs. 1c, 1d), each being formed by a pair of wing-shaped structures connected with each other (hereinafter referred to as wings), which are ornamented by growth rings and delicate longitudinal ribs. Nevertheless, they differ in general configuration, curvature, sizes, and the length of the joint between the wings. The surface area and capacity of the lower jaw is large. The joint between its wings is as long as the jaw apparatus and runs along the entire straight ventral edge (Figs. 1a, 1d) to form the continuous bottom of the jaw apparatus. The height of the lower jaw is maximum in its posterior part. At the boundary between the ventral and lateral sides, the wings form a sharp flexure. The anterior edge forms a gently sloping U-shaped depression; the angle between the ventral side and the anterior edge of the wing is about 45 ° –50 ° . The posterior edge is straight and perpendicular to the ventral side, with rounded upper angles. The upper jaw (Figs. 1b, 1c), which is narrower than the lower one, has an opening at GENERAL BIOLOGY

The role of glacial epochs in the formation of chromosomal polymorphism in the common shrew Sorex araneus L. (Insectivora, Mammalia).

Abstract: To date, 67 chromosomal races of the common shrew have been found throughout the Palearctic range of the species. Chromosomal forms have also been found in many other European mammalian species. The effects of glacial epochs [1], seismic activity in highland regions, and viral pandemics [2] were regarded as factors of their formation. In this study, we demonstrated that chromosomal races of the common shrew were formed in isolated populations of glacial origin.

Microarray technology in studying the effect of melatonin on gene expression in the mouse heart.

Abstract: In recent years, numerous and sometimes contradictory data on the key role of the epiphysis (pineal gland) in aging and the antioxidant processes have attracted much attention [1, 2]. In various animal species, the night production of the epiphyseal indole hormone melatonin decreases with age, and the circadian rhythm of melatonin release into circulation is disturbed [2, 3]. After epiphysectomia, the animal’s life span decreases, whereas administration of melatonin to animals of various species (mice, rats, Drosophila, and flatworms) increases their life span [2, 4]. We recently showed that long-term melatonin administration to female CBA mice resulted in a retarded dynamics of the biologicalage markers and increased the life span [5]. However, little is known about the molecular mechanisms underlying the melatonin effect on gene expression, though the hormone was found to be mainly accumulated in the cell nuclei and incorporated into chromatin in most tissues and organs [6]. We studied the effect of melatonin on the expression of genes in the heart of CBA mice after the hormone was administered at a geroprotective dose.

Endocytosis of exopolysaccharides of the potato ring rot causal agent by host-plant cells.

Abstract: Endocytosis as the mode of the extracellular macromolecule transport by the invagination of the plasma membrane and vesicle formation is a multifunctional process. It is studied in animal cells in detail [1]. Endocytosis in plant cells was also reliably demonstrated [2]. Similarities in the mechanisms and role of this process in plant and animal cells becomes progressively evident [3, 4]. Some data concerning the role of endocytosis in plant immunity are also known. The uptake of elicitors of plant defense responses (oligogalacturonic acid from the pectin of citrus plants or glycoproteins of fungal pathogens) by plant cells was shown [5]. The authors believe that this process was a receptor-mediated endocytosis. In addition, some date indicate that exometabolites of the phytopathogenic fungus were internalized by the plant cell via clathrin-coated vesicles during haustoria penetration into plant tissues [6]. In both studies, the interactions between the pathogen and host-plant were incompatible. The authors interpret the internalization of exogenous compounds as either the involvement of these compounds in the chain of the defense-signal transduction or as the removal of the external stimulus (ligand–receptor complex) from the plasma membrane after signal sending [5–7].

Viability of higher plant seeds of late pleistocene age from permafrost deposits as determined by in vitro culturing.

Abstract: Studies of loess–ice deposits in coastal lowland regions of northern Yakutia revealed that bulk permafrost rocks, chronologically attributed to the late Pleistocene epoch, contained many buried burrows of rodents. These fossil burrows were found to contain large paleological ecology material, including fruitage and seeds of plants. In some burrows, the number of items of this material reached 600000–800000. Most frequently, these were burrows of a species of ground squirrel of the subgenus Urocitellus [5].

Tissue morphogenesis under the conditions of implantation of polyhydroxybutyrate, a biodegradable polymer.

Abstract: Polyhydroxybutyrate (PHB), a polymer of hydroxybutyric acid, is a biocompatible polyester of natural origin. Medical applications of this polymer as a material for tissue engineering, various surgical elements, and dosed supply of pharmacological substances are extensively studied worldwide [1–3]. In addition to reliable fixation of surgical suture, implanted biodegradable sutural material should also undergo gradual degradation. The rate of biodegradation of the suture should be adequate to the kinetics of tissue recovery. The products of degradation of a biodegradable sutural material should be absolutely harmless for human organism, easily eliminated from the zone of implantation, and cause no negative reactions in the surrounding tissues or the human body as a whole [4]. The goal of this work was to analyze the postoperative reaction of biological tissues in vivo induced by implanted PHB surgical sutural threads. The sutural threads used in our experiments were made of PHB synthesized by the bacteria Ralstonia eutropha B5786. The technology of manufacture of the PHB surgical sutural threads was developed at the Institute of Biophysics, Siberian Division, Russian Academy of Sciences. Conventional surgical materials (silk and catgut) were used as control. Multifiber sutural threads were manufactured using the gel-technology described in [5]. Polyhydroxybutyrate was synthesized at the Institute of Biophysics, Siberian Division, Russian Academy of Sciences, as described in [6]. The experimental procedure was descried in [7]. Sexually mature Wistar female rats with an initial body weight of 180–200 g were used. When the animals had been anesthetized by ether inhalation, a 2-cm-long longitudinal incision was made under aseptic conditions through the skin and muscles of the right femur. The muscle incisions in experimental animals were sutured with three PHB threads (the total suture length was 3.0–3.5 cm). The muscle incisions in two control groups were sutured with silk and catgut. Skin incisions were sutured with silk. Animals were euthanized by overdose of ether inhalation 1, 2, 4, 8, 16, or 24 weeks after the surgery, and fragments of tissues surrounding the implants were assayed.

Salicylic acid induces dissipation of the proton gradient on the plant cell plasma membrane.

Abstract: Recently, the role of salicylic acid in plant cell responses to various effects has been intensely studied by many researchers. It was shown that pathogens induce production of large amounts of salicylic acid in plant cells (its concentration may increase by one or two orders of magnitude) [1, 2]. Note that salicylic acid may be released into the apoplast and circulate in the plant [3]. The cause of the production and release of large amounts of salicylic acid from cells remains unknown. Published data describe the phenomenon of salicylic acid-induced activation of gene expression and synthesis of defence proteins [2] (including the synthesis of alternative oxidase [4]). However, one of the simplest mechanisms of the salicylic acid effect on cells (pathogen cells, in particular) is apparently based on its protonophore properties and ability to dissipate the proton gradient across the membrane. The protonophore properties of salicylic acid are described in [5], where it is regarded as a typical agent uncoupling oxidation and phosphorylation. The uncoupling effect of salicylic acid is also described in [4]. In view of this, we attempted to study the effect of salicylic acid on the respiration and growth of wheat seedling root cells, their membrane potential, ä + release from them, pH of the incubation medium, and the effect of salicylic acid on the mitotic index of pea root cells.

Polyaxial cleavage in sponges (Porifera): a new pattern of metazoan cleavage.

Abstract: Cleavage is an important stage of animal embryo-genesis marked by the emergence of multicellularity ofan organism and by ooplasmic segregation of morpho-genetic determinants. In addition, cleavage is a highlycoordinated process of diagnostic significance. Cleav-age patterns are often used to investigate the phyloge-netic relationships in various animal groups [1].Analysis of early development of sponges( Porifera ), including cleavage, is of particular interestbecause of their key position at the base of the phyloge-netic tree for Metazoa. However, studies speciallyaddressing the stage of egg cleavage in sponges werevery few until the past two decades [2–5]. It is now wellknown that, in all sponge species, the whole egg dividescompletely (holoblastic cleavage). The process is usu-ally uniform, but the cleavage patterns may signifi-cantly vary from species to species. In most species,cleavage division planes are randomly oriented (chaoticcleav age). A unique type of cleavage called tablepalyntomy occurs in some species of the subclassCalcaronea [4]. In the glass sponge Oopsacas minuta (Hexactinellida), cleavage is pseudospiral [5]. In manyoviparous species of the class Demospongiae, cleavagefollows a nearly radial pattern [6].Of particular interest is analysis of cleavage insponges of the order Halisarcida, which are the mostprimitive of Demospongiae [7, 8]. The goal of thisstudy was to reexamine the cleavage period of Hal-isarca dujardini development using light and electron(scanning and transmission) microscopy. Sponges ofthis species are dioecious and viviparous. Theirembryos develop within temporary follicles. Each fol-licle consists of pinacocyte-like follicular cells and anouter collagen layer. Before maturation division, theoocyte is oval, with a round nucleus at the center. Yolkgranules are uniformly distributed throughout theoocyte.The first cleavage division in H. dujardini is uniformand proceeds in the meridional plane. The cleavage fur-rows are of the bipolar type. The subsequent cleavageproceeds asynchronously. During the second cleavagedivision, the orientation of mitotic spindles relative toeach other varies from parallel to perpendicular(Fig. 1a). Thereafter, cleavage goes on asynchronously.From the third cleavage division onward, mitotic spin-dles are always formed parallel to the surface; there-fore, the cleavage furrows run perpendicular to the sur-face (Fig. 1b). The eight-cell embryo is round orslightly oval in the cross-section and never appears as alamina-like structure described earlier [7].Cleavage leads to the formation of an apolar coelo-blastula with a small cavity inside. The cavity isbounded with long wedge-shaped cells (Fig. 1c). At thestage of approximately 100 cells, blastomeres exhibit adistinct apicobasal polarity.In our previous studies [2, 8], some primitive traitswere described in H. dujardini cleavage. These were,first of all, the absence of any determinate spatial rela-tionships among blastomeres within the embryo. Con-ceivably, the origin of these primitive traits should besought in the absence of mature egg patterning (prepat-terning) [9], which is usually regarded to be a commonprimitive trait of egg organization in sponges [10].Throughout the H. dujardini egg, its structure remainsuniform. Holoblastic uniform asynchronous cleavage istypical of all the Halisarcida species studied, such as H. dujardini, H. metschnicovi , and H. nahantensis [2, 7, 8, 11]. A distinctive feature of the cleavage stageof H. dujardini development is the long retention of theblastula-like appearance by the embryo (from the eight-cell to the prelarval stage), which is due to the early for-mation of cleavage division planes of similar type run-ning parallel to the embryo surface [2, 8]. The samecleavage pattern was described for H. nahantensis [11].This cleavage pattern is unique among the viviparousDemospongiae but quite usual in Calcinea (class Cal-carea), which form a monolayer flagellated blastula [12].At present, eight major patterns of holoblastic cleav-age are distinguished in animals [1]. Chaotic cleavageproduces no patterning in blastomere distribution. Pas-sage of all cleavage furrows along the animal–vegetal

Role of cyclic nucleotides in mediating the nitric oxide (II) effects on transmitter release and the electrogenesis of motor nerve endings.

Abstract: Nitric oxide (II) is a potent neuromodulator in the central and peripheral nervous systems. It has both excitatory and inhibitory effects on the synaptic transmission [3]. For example, NO was shown to enhance posttetanic potentiation in hippocampal and cerebellar neurons, as well as transmitter release from the neurons of the forebrain and striatum [8]. NO increased the amplitude of muscle contraction evoked by nerve stimulation of rat diaphragm preparation acting at the presynaptic level [7]. At the same time, donors of exogenous NO can attenuate the transmitter release from synaptosomes and cortical neurons [6] and inhibit its secretion in the frog neuromuscular junction [2, 5, 12, 15]. The NO effects are thought to be mediated by activation of soluble guanylyl cyclase [3]. Nevertheless, the multiplicity of the NO effects in different synapses suggests alternative targets of NO. It was shown, e.g., that NO attenuates the adenylyl cyclase activity [4], modifies the regulatory proteins of ryanodine receptors, inhibits IP 3 -receptors [11], etc., which lead to changes in the intracellular Ca 2+ concentration. In this work, we studied the role of second messengers (cAMP and cGMP) in the NO effects on the frog motor nerve endings (MNEs). Experiments were performed on neuromuscular junctions of the frog ( Rana ridibunda ) cutaneus pectoris muscles in autumn and winter under the conditions of permanent perfusion at 20 ° C using normal frog Ringer’s solution of the following composition (in mM): NaCl, 118.0; KCl, 2.5; CaCl 2 , 0.4–0.3; MgCl 2 , 2.4–4.0; NaHCO 3 , 2.4 (pH 7.4–7.6). The solution contained a reduced concentration of calcium ions to prevent the muscle contraction. The extracellular recording of synaptic signals was made with glass microelectrodes filled with a NaCl solution (2.0 M) (inner tip diameter, 1 to 3 μ m; resistance, 2 to 5 M Ω ). With the use of an interference–polarization microscope, 400 × , the microelectrodes were placed on the MNE proximal parts (5 to 30 μ m away from the last myelinated axonal segment) under visual control. The motor nerve was stimulated with 0.3 to 0.4-ms rectangular electric stimuli characterized by an overthreshold amplitude and a frequency of 0.5 to 1 stimuli per second. The ionic currents forming the MNE action potential followed by the endplate current (EPC) resulted in a three-phase MNE response to each stimulus (+ – +) [1]. The first positive phase is known to be a passive (capacitive) current generated by the inflow action potential; the second negative phase was a result of the sodium influx into the MNE, and the third positive phase was the potassium outflow current through potential-dependent and calcium-activated potassium channels. Since the experiments were performed at a low extracellular concentration of Ca 2+ , the calcium-activated potassium current in MNEs may be neglected; hence, the potential-dependent potassium current mainly accounted for the third phase of the MNE response. Analysis, averaging and accumulation of the signals recorded were performed using a Pentium II PC and a specially developed Ritm software. At each phase of the MNE response, its amplitude and duration relative to the baseline, as well as the EPC amplitude, were determined. The following chemicals were used in the experiments: sodium nitroprusside, an exogenous nitric oxide donor; L -arginine, a substrate for NO synthase, which increases endogenous NO concentration; the membrane-penetrating, nonhydrolyzable cAMP and cGMP analogs 8Br-cAMP and 8Br-cGMP, respectively; and 1,4-dihydro-5-[2propoxiphenyl]-7H-1,2,3-trizolo[4,5-d]pyrimidine (Zaprinast) (Sigma, United States), an inhibitor of cGMP-specific phosphodiesterase V. The EPC quantum content ( m ) was estimated by counting the number of zero reactions: m = ln N / N 0 , where N is the number of stimuli and N 0 is the number of stimuli that failed to induce EPC. Student’s parametric t test was used for statistical treatment of the results obtained. Effects of endogenous and exogenous NO on the transmitter release and the MNE ionic currents. Addition of sodium nitroprusside (Fig. 1a) or L -arginine (Fig. 1b) at concentrations of 100 μ mol/l into Ringer’s solution led to a pronounced decrease in the PHYSIOLOGY

Photosynthesis, respiration, and transpiration in maize seedlings under hypoxia induced by complete flooding.

Abstract: The majority of terrestrial plants cease to grow and even perish after prolonged shoot flooding. Complete flooding exerts an adverse effect on plants, especially on leaf metabolism evolutionary adapted to the life in the air. Flooding results in a persistently increased hypoxia and an increase in the water content in plant tissues. The oxygen deficiency becomes more serious in the direction from the leaf to root zone [1]. Reparation is possible only after a short-term flooding.

New definitions of the concepts and terms ecosystem and biogeocenosis.

Abstract: The terms ecosystem and biogeocenosis were coined by Tansley in 1935 [1] and by Sukachev in the 1940s [2], respectively. These terms are widely used in biological research [3–10], and there are several definitions of the term ecosystem [4–8]. However, a large body of new biological information has been accumulated since the time of introduction of these terms. Therefore, a revision of the currently accepted concepts of natural objects and interpretation of basic ecological terms (e.g., ecosystem and biogeocenosis) may be proposed. It seems reasonable to continue the search for new variants of definitions of these terms.

Effect of pulsed laser radiation on regeneration of injured muscles with different regeneration capacities and the state of the thymus.

Abstract: There is now ample experimental evidence that lowintensity laser radiation (LILR) stimulates regeneration of injured biological tissues and facilitates recovery of pathological lesions in the body [1]. On the other hand, it is widely believed that the efficiency of any external effector, including laser radiation, is determined not only by the absolute magnitude of the effector, but also by the initial state of the biological system exposed [2]. It has also been reported that exposure to therapeutic doses of LILR may cause a decrease in the functional activity of the immune system [3–5]. According to our earlier findings [6, 7], radiation of He–Ne and infrared (IR) lasers stimulates regeneration of injured rat skeletal muscles exposed to ionizing radiation at a dose of 20 Gy. The He–Ne and IR laser radiation was also shown to facilitate healing of skin wounds [6, 7]. The positive dynamics of recovery processes is accompanied by a significant increase in the functional load on the thymus and a long-term decrease in the thymus activity [8]. In these experiments, laboratory animals were treated with a total dose of laser radiation of 7.2 or 24 J/cm 2 .

Relative effects of soil and surface air on mammal burrow temperature: a study of the bobac burrow as an example.

Abstract: During the warm season, burrow temperature is under control of two media: the soil in which a mammal has dug its burrow and the surface air over the burrow opening. Heat is exchanged between the burrow and the soil mainly via conduction and between the burrow and the surface air via convection. These two interacting processes determine the thermal conditions within a burrow. Earlier [1], we assumed that air convection is slow within a burrow and described the thermal state of the air in the burrow as quasi-stationary. However, at that time, we had no direct data on the depth profile of temperature to justify this assumption. Instead, we used the data obtained by solving a mathematical model [2]. In this study, we monitored not only temperatures in the burrow and in the near-ground layer of air, but also in the soil. Our goal was to assess how the burrow temperature is related to the temperatures in the two media (soil and surface air), and thereby to compare the relative contributions of the two heat transfer processes (conduction and convection).

An optimization model of the photosynthetic leaf: the model of optimal photosynthetic CO2 fixation within leaves of mesophytic C3 plants.

Abstract: The main function of the photosynthetic leaf is to convert light energy into chemical energy and to assimilate CO 2 . Coordination of these functions as related to the heterogeneous leaf structure and the distribution of metabolism within the leaf has been investigated in many studies [1‐5, etc.]. Presumably, after hundreds of millions of years of selection, the typical mesophytic leaf structure and the distribution of metabolic activity within it are relatively optimal. The stimuli that result in the formation of specific structural or functional features of the leaf may emerge through generalization of the experimental data using the unified theory of ecological utility. To describe the functioning of biological systems on the basis of the rule of maximal ecological utility (MEU) [6], the function of partial ecological utility is entered for each defined parameter of the system. It is possible to use any limited monomial function [7]. At optimal functioning of a system, the general utility as a product of partial utilities (in the case of their independence from each other) should be maximized. Some authors suppose that photosynthesis follows the light absorption gradient [8]. However, light absorption decreases from the top, illuminated surface to the bottom of the leaf [5], while the maximal CO 2 fixation occurs in the middle of palisade mesophyll [9]. The results imply that a significant amount of absorbed light energy may not be utilized directly for CO 2 fixation at the top of the leaf. It is possible that low photosynthesis in the upper layer of the palisade is due to excess illumination, which induces the formation of oxygen radicals (O 2 uptake under saturated light might reach 50% of its maximal evolution [10]). If the presumption is correct, the optimization of CO 2 fixation within the leaf should take place when the total utility of the two functions, (1) light absorption for photosynthesis and (2) protection from light intensities that can cause photodestruction, is maximized. The goal of the present work was to use the MEU rule to describe an optimal model of photosynthesis in a bifacial, mesophytic leaf of a C 3 plant. Let us consider this on a simplified model, where the leaf is a flat plate, and its surface is illuminated by light ( I 0 ; ν in the PAR range). The light is absorbed by chlorophyll ( a / b = 3/1 [9]) in a layer of phototrophic cells in the depth of the plate; the plate itself has the same absorption spectrum. In such a leaf, the function r ( z ) (partial utility of protection from photodestruction) and the function s ( z ) (partial utility of light absorption for photosynthesis) depend on the depth of the photosynthetic layer within the relative thickness ( h ) of the leaf (the variable h is incorporated by variable z , where

The synthesis and degradation of juvenile hormone in Drosophila are under common control.

Abstract: It is known that, in insect adults ( Drosophila , in particular), juvenile hormone controls many processes: together with ecdysteroids, it initiates the synthesis of yolk proteins in the corpora allata and ovarian follicular cells immediately after the adult eclosion; maintains it on a specific level after fertilization; enables absorption of the yolk proteins by the oocytes; and determines sexual behavior, the synthesis of pheromones, and histolysis of the larval corpora allata [1–4]. To coordinate these processes, the juvenile hormone titer in the hemolymph should be strictly controlled. It was shown that specific neuropeptides that exhibit the allatotropic and allatostatic effects are involved in the regulation of the juvenile hormone synthesis and that the production of allatostatin is, in turn, regulated by the juvenile hormone level [5, 6]. In addition, it was demonstrated that the juvenile hormone degradation is also regulated during larva and adult development [7, 8]. Earlier, when comparing our data on the changes in the juvenile hormone degradation in the course of maturation of D. melanogaster females [9] with the data on the time course of the juvenile hormone synthesis in females of this species [6], we discovered that the synthesis and degradation of this hormone are in antiphase and assumed that these processes in D. melanogaster are under the same control [10]. We also found that the biogenic amines dopamine and octopamine may serve as controlling elements. Dopamine apparently stimulates the synthesis and inhibits the degradation of the juvenile hormone in immature females (which require a high level of this hormone to initiate vitellogenesis) and, conversely, inhibits the synthesis and stimulates the degradation of the juvenile hormone in the intensely reproducing females [11], which do not need a high level of juvenile hormone to maintain vitellogenesis [3]). In this study, we demonstrated that an experimentally induced change in the juvenile hormone titer in D. virilis females leads to a change in the rate of the juvenile hormone degradation and that the mutation that causes a decrease in the juvenile hormone degradation in young females is apparently accompanied by an increase in the juvenile hormone synthesis.

Neural critical bands and inhibition in the auditory midbrain of the house mouse (Mus domesticus).

Abstract: Critical bands is a well-known psychophysical phenomenon to describe the mechanisms of sound frequency analysis [1–3]. Studies on the neurophysiological basis of perceptual critical bands (CBs) showed that the main properties of CBs are coded by the neural activity of the auditory midbrain [4–7]. Analysis of the shape of the receptive fields of inferior colliculus neurons in relation to neural critical bandwidths raised the hypothesis that inhibition is a main neurophysiological mechanism of critical bandwidth regulation [5, 8].

Biodiversity Protection and Quality of Water: The Role of Feedbacks in Ecosystems

Abstract: V.I. Vernadsky pointed out that “the living matter in the biosphere plays a fundamental and active role, and in exercising its power it is in no way comparable with anything else, with any other geological factor.” [1]. Finding concrete evidence that support this statement still remains an important aspect in the study of ecosystems, including aquatic systems. To reach a sustainable use of water resources, we have to maintain a proper self-purifying potential of water bodies, which sustains the water quality that is necessary for the consumption of water as a useful resource [2]. To maintain the selfpurification potential under the conditions of anthropogenic stress, analysis of the factors that are the main prerequisites for the maintenance of water quality in water bodies is necessary; the analysis must include

Effects of orthovanadate and genistein on the plasma membrane Cl(-)-ATPase sensitive to GABA-ergic ligands in the bream (Abramis brama L.) brain.

Abstract: In plasma membranes of the fish brain, we found a Cl – stimulated Mg 2+ ATPase whose “basal” Mg 2+ ATPase activity was stimulated by Cl – -ions (Cl − ATPase) [1]. The properties of this enzyme differed significantly from those of the Cl – ATPase (Cl − pump) in the mammalian (rat) brain [2]. In particular, the two enzymes differed in the pH optimum, ä å of the ATP hydrolysis, and sensitivity to inhibitors [3]. In addition, Cl – stimulated Mg 2+ ATPase of the fish brain was regulated by γ aminobutiric acid (GABA), the mediator that, via GABA receptors, controls the Cl − transport through the postsynaptic membrane [4, 5]. Thus, at pH 8.5 of the incubation medium, this mediator activated the basal Mg 2+ ATPase activity and inhibited the Cl – ATPase activity [4]. Conversely, at a physiological (pH 7.4) of the incubation medium, when the Cl – ATPase activity was not detectable, whereas the basal Mg 2+ ATPase activity was increased, GABA inhibited the latter and induced the Cl – ATPase activity [6]. The GABA effect on the enzyme was eliminated after addition of picrotoxin, which blocked GABA receptors [4, 6]. These data suggest that the mediator of the suppressing receptors affects the Cl – stimulated Mg 2+ -ATPase of the fish brain in a receptor-dependent manner.

The GABAergic midbrain system is involved in the control of sleep and temperature homeostasis in pigeons.

Abstract: formation of the caudal midbrain region. The pigeon and mammalian (cat) midbrain GABAergic systems are assumed to differ in structural and functional organization. This study was performed with five adult pigeons ( Columba livia ) weighing 350‐390 g under the conditions of free behavior. The birds were anesthetized with Nembutal (25 mg/kg body weight) seven to ten days before the experiments. During the experiment, each animal was placed into a climatic chamber at 21 ‐ 1i C with a 12-h photoperiod. The operation technique and computer recording (the SASR 8800 system; United States) of electroencephalograms, electrooculograms, electromyograms, electrocardiograms, brain temperature (hypothalamus), and skin temperature of the unfeathered part of the foot were previously described [3, 4, 7]. The data were analyzed at a 1-s epoch. Saline (0.5 μ l, control), muscimol (0.3‐0.5 μ g/0.3‐0.5 μ l, Serva), and a GABA A receptor antagonist bicuculline (0.5‐1.0 μ g/ 0.5 μ l, Sigma) were bilaterally administered through guide cannulae 10 to 15 min prior to switching off the light. Figure 1 shows the places of microinjections (atlas: [8]). The microinjections ( n = 48) were made into the following midbrain caudal regions: I, the ventrolateral region of the substantia grisea centralis (coordinates A2.25‐A2.75; L1.7‐1.9; H9.5; II, ventral to the substantia grisea centralis, including the locus coeruleus (A2.25‐2.75; L1.7‐1.9; H10.0‐10.5); III, the dorsolateral region of the substantia grisea centralis (A2.25‐2.75; L1.7‐1.9; H8.5‐9.0); IV, the reticular formation and ventral to region II, at the border of the nucleus reticularis pontis oralis (A2.25‐2.75; L1.7‐ 1.9; H11.0). I. After a 18 ‐ 2-min latent period, muscimol caused an increase (compared to the control) in the total SWS time and duration of the SWS episodes during four hours (Fig. 2). After administration of bicuculline at a dose of 1 μ g, the total PS time decreased for two to three hours. A muscimol-induced decrease in brain temperature was caused by a more significant (2.2-fold) temperature decrease in the SWS episodes and a lesser temperature increase in the wakefulness and PS episodes (4- and 1.4-fold, respectively). The muscimol hypothermic effect was, probably, caused by a reduced heat produc

The phenomenon of endoparasitism at early stages of fish development.

Abstract: Since 1993, early fish development in Nha Trang Bay of the South China Sea has been studied at the Primorskii Department of the Russian–Vietnamese Research Tropical Center. The embryological material examined was mostly live eggs from the samples of ichthyoplankton. Our long-term study showed that the density of eggs and larvae infected with the endoparasites tended towards an increase. In 1993, only some embryos in the live ichthyoplankton contained these parasitic organisms in their yolk sacs; the amount of the infected eggs ranged from 0 to 2–3%. The proportion of the infected fish eggs and larvae increased every year to become a large-scale process. In March and April 2001, a control sampling was made at seven stations in Nha Trang Bay to determine the degree of fish infection with the parasite. The results obtained showed that from 25 to 80% (on average, 55%) of eggs and prelarvae were already infected.