Neurotrophic factors play a key role in development, differentiation, synaptogenesis, and survival of neurons in the brain as well as in the process of their adaptation to external influences. The ...serotonergic (5-HT) system is another major factor in the development and neuroplasticity of the brain. In the present review, the results of our own research as well as data provided in the corresponding literature on the interaction of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) with the 5-HT-system of the brain are considered. Attention is given to comparison of BDNF and GDNF, the latter belonging to a different family of neurotrophic factors and being mainly considered as a dopaminergic system controller. Data cited in this review show that: (i) BDNF and GDNF interact with the 5-HT-system of the brain through feedback mechanisms engaged in autoregulation of the complex involving 5-HT-system and neurotrophic factors; (ii) GDNF, as well as BDNF, stimulates the growth of 5-HT neurons and affects the expression of key genes of the brain 5-HT-system–those coding tryptophan hydroxylase-2 and 5-HT
1A
and 5-HT
2A
receptors. In turn, 5-HT affects the expression of genes that control BDNF and GDNF in brain structures; (iii) the difference between BDNF and GDNF is manifested in different levels and relative distribution of expression of these factors in brain structures (BDNF expression is highest in hippocampus and cortex, GDNF expression in the striatum), in varying reaction of 5-HT2A receptors on BDNF and GDNF administration, and in different effects on certain types of behavior.
•The central Arctic Ocean is not isolated, but tightly connected to the northern Pacific and Atlantic Oceans.•Advection into the Arctic Ocean forms lengthy contiguous domains that connect subarctic ...with the arctic biota.•The Arctic Ocean ecosystems are net biomass beneficiaries through advection.•Advective transport can be thought of as trails of life and death in the Arctic Ocean.•As compared to the Pacific gateway the advective supply of zooplankton biomass through the Atlantic gateways is 2–3 times higher.•The Arctic Ocean will more and more rely on an increasing local primary production while the advection of zooplankton will cease.
The central Arctic Ocean is not isolated, but tightly connected to the northern Pacific and Atlantic Oceans. Advection of nutrient-, detritus- and plankton-rich waters into the Arctic Ocean forms lengthy contiguous domains that connect subarctic with the arctic biota, supporting both primary production and higher trophic level consumers. In turn, the Arctic influences the physical, chemical and biological oceanography of adjacent subarctic waters through southward fluxes. However, exports of biomass out of the Arctic Ocean into both the Pacific and Atlantic Oceans are thought to be far smaller than the northward influx. Thus, Arctic Ocean ecosystems are net biomass beneficiaries through advection. The biotic impact of Atlantic- and Pacific-origin taxa in arctic waters depends on the total supply of allochthonously-produced biomass, their ability to survive as adults and their (unsuccessful) reproduction in the new environment. Thus, advective transport can be thought of as trails of life and death in the Arctic Ocean. Through direct and indirect (mammal stomachs, models) observations this overview presents information about the advection and fate of zooplankton in the Arctic Ocean, now and in the future. The main zooplankton organisms subjected to advection into and inside the Arctic Ocean are (a) oceanic expatriates of boreal Atlantic and Pacific origin, (b) oceanic Arctic residents and (c) neritic Arctic expatriates. As compared to the Pacific gateway the advective supply of zooplankton biomass through the Atlantic gateways is 2–3 times higher. Advection characterises how the main planktonic organisms interact along the contiguous domains and shows how the subarctic production regimes fuel life in the Arctic Ocean. The main differences in the advective regimes through the Pacific and Atlantic gateways are presented. The Arctic Ocean is, at least in some regions, a net heterotrophic ocean that – during the foreseeable global warming trend – will more and more rely on an increasing local primary production while the advection of zooplankton, as revealed by models, will cease.
We have studied the electron-phonon interaction (EPI) in multiferroic PrFe3(BO3)4 applying reflection methods in far-infrared (terahertz) spectral range and theoretical simulations. A specific ...feature of PrFe3(BO3)4 is that the 4f-electron excitation of the Pr3+ ion falls into a range between the longitudinal (LO) and transverse (TO) phonon mode frequencies. Simultaneously, inversion of the electronic oscillator occurs: its LO frequency becomes smaller than the TO frequency. With lowering temperature, a coupled electron-phonon mode emerges, and a new effect is observed: the reststrahlen band corresponding to a nondegenerate phonon mode splits. Yet another effect caused by the EPI is the appearance of a gap in the spectrum of electronic excitations of a stoichiometric rare-earth easy-axis antiferromagnet placed into an arbitrarily weak external magnetic field directed along the easy magnetization axis.
We report on a new effect caused by the electron-phonon coupling in a stoichiometric rare-earth antiferromagnetic crystal subjected to an external magnetic field, namely, the appearance of a nonzero ...gap in the spectrum of electronic excitations in an arbitrarily small field. The effect was registered in the low-temperature far-infrared (terahertz) reflection spectra of an easy-axis antiferromagnet PrFe_{3}(BO_{3})_{4} in magnetic fields B_{ext}∥c. Both paramagnetic and magnetically ordered phases (including a spin-flop one) were studied in magnetic fields up to 30 T, and two bifurcation points were observed. We show that the field behavior of the coupled modes can be successfully explained and modeled on the basis of the equation derived in the framework of the theory of coupled electron-phonon modes, with the same field-independent electron-phonon interaction constant |W|=14.8 cm^{-1}.
Highlights • Actual spaceflight considerably decreased BCL-XL gene expression in the hypothalamus. • Long-term spaceflight significantly increased BCL-XL gene expression in the hippocampus. • Actual ...spaceflight considerably reduced BCL-XL gene expression in the striatum. • Shuttle cabin housing also considerably reduced BCL-XL gene expression in the striatum. • Long-term spaceflight failed to affect BAX, BDNF, TrkB and p75 gene expression.
•Hindlimb unloading increased the expression of dopanimergic genes in striatum.•Hippocampus Bcl-xl expression was similar for hindlimb unloading and spaceflight.•Hindlimb unloading did not alter the ...expression of MAOA and 5-HT2A receptor genes.
The study of spaceflight effects on the brain is technically complex concern; complicated by the problem of applying an adequate ground model. The most-widely used experimental model to study the effect of microgravity is the tail-suspension hindlimb unloading model; however, its compliance with the effect of actual spaceflight on the brain is still unclear. We evaluated the effect of one month hindlimb unloading on the expression of genes related to the brain neuroplasticity—brain neutotrophic factors (Gdnf, Cdnf), apoptotic factors (Bcl-xl, Bax), serotonin- and dopaminergic systems (5-HT2A, Maoa, Maob, Th, D1r, Comt), and compared the results with the data obtained on mice that spent one month in spaceflight on Russian biosatellite Bion-M1. No effect of hindlimb unloading was observed on the expression of most genes, which were considered as risk neurogenes for long–term actual spaceflight. The opposite effect of hindlimb unloading and spaceflight was found on the level of mRNA of D1 dopamine receptor and catechol-O-methyltransferase in the striatum. At the same time, the expression of Maob in the midbrain decreased, and the expression of Bcl-xl genes increased in the hippocampus, which corresponds to the effect of spaceflight. However, the hindlimb unloading model failed to reproduce the majority of effects of long-term spaceflight on serotonin-, dopaminergic systems and some apoptotic factors.
The high-resolution optical absorption spectra of NdFe
3
(BO
3
)
4
single crystals have been recorded at temperatures from 4 to 40 K in the IR range of
f
–
f
transitions in a Nd
3+
ion. Light ...linearly polarized at different angles to the
C
2
axes in the basal plane has been passed along the trigonal
C
3
axis. Below the temperature of magnetic moment ordering into a collinear antiferromagnetic structure (
T
N
≈ 30 K), dichroism, that is, the absorption versus polarization dependence, arises. The temperature and angular dependences of dichroism indicate that the magnetic moments of iron are directed along the
C
2
axes up to about 17 K, the number of domains with variously directed
C
2
axes being different. The mechanism of linear dichroism has been discussed. Below 17 K, a smooth transition to the helicoidal magnetic phase has been observed, with the collinear phase coexisting with the helicoidal one. Data presented in this article contradict the earlier concept of magnetic moments fluctuating in the low-temperature phase near the
C
2
axis within the ±10° interval.
Magnetic control of the crystal chirality was announced by Saito et al. Phys. Rev. Lett. 101, (2008) on the ground of experiments in CuB2O4. This claim has raised a sharp dispute in the literature ...because seemed to contradict the fundamental symmetry principles. We settle this dispute on the basis of a high-resolution optical spectroscopy study of excitonic transitions in CuB2O4. We find that a large sublattice-sensitive antiferromagnetic linear dichroism (LD) emerges at the Neel temperature TN=21 K and show how it could simulate a "magnetic-field control of the crystal chirality." We prove that the discovered LD is related microscopically to the magnetic Davydov splitting. This LD is highly sensitive to subtle changes in the spin subsystems, which allowed us to observe a splitting of the phase transition into an incommensurate magnetic phase into two transitions (T1*=8.5 and T2*=7.9 K) and to suggest elliptical spiral structures below T1*, instead of a simple circular helix proposed earlier.
High-resolution far-infrared reflection and polarized ellipsometry, as well as Raman scattering temperature-dependent measurements are used to study spin-phonon and electron-phonon interactions in ...rare-earth (RE) iron borates with the R32 structure of a natural mineral huntite, namely, in RFe3(BO3)4 with R=Pr, Nd, and Sm. Pronounced peculiarities in the ω(T) dependences at the Néel temperature TN≈32K are observed for all the compounds studied and the origin of these peculiarities is discussed. A coupling between lattice phonons and crystal-field excitations of a RE ion manifests itself by a renormalization of frequencies and intensities of coupled modes. Modeling of the spectra has revealed the value of about 15cm−1 for the electron–phonon coupling constant in PrFe3(BO3)4.
•Rare-earth iron borates exhibit peculiarities in the phonon frequencies at TN.•We propose mechanisms of the spin-phonon coupling in RFe3(BO3)4.•A coupling of phonons and crystal-field excitations manifests itself in the spectra.•The electron-phonon coupling constant for PrFe3(BO3)4 amounts to 14.6cm−1.
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