Disruption of microtubules inhibits cytoplasmic ribonucleoprotein stress granule formation

Stress granules are RNP-containing particles arising in the cytoplasm in response to environmental stress. They are dynamic structures assembling and disassembling in the cytoplasm very rapidly. We have studied whether the cytoskeleton is involved in the formation of stress granules. Stress granules were induced in CV-1 cells by sodium arsenate treatment and visualized by immunofluorescent staining with antibodies either to the p170 subunit of eIF3 or to poly(A)-binding protein. Treatment with sodium arsenate for 30-120 min led to assembling of stress granules in a majority of CV-1 cells. Disruption of MT array with nocodazole treatment abolished arsenate-induced formation of stress granules. A similar effect was induced by the microtubule-depolymerizing drug vinblastine, though the influence of the microtubule-stabilizing drug paclitaxel was opposite. Nocodazole treatment did not prevent arsenate-induced phosphorylation of the eIF-2alpha factor, essential for stress granule formation, suggesting that the presence of intact MT array is required for granule assembly. Unexpectedly, treatment of cells with the actin filament-disrupting drug latrunculin B slightly enhanced stress granule formation. We propose that stress granule formation is microtubule-dependent process and likely is facilitated by the motor protein-driven movement of individual stress granule components (e.g., mRNP) along microtubules.     

RAPD analysis of the flax (Linum usitatissimum L.) varieties and hybrids of various productivity

Genetic polymorphism in varieties and hybrids of cultivated flax (Linum usitatissimum L.) has been investigated by RAPD-PCR. Analysis with 15 primers has revealed varietal specificity and hybrid inheritance of RAPD alleles. This allows genetic certification of the original varieties and their hybrids for breeding purposes. Polymorphic amplification products were obtained in RAPD analysis of DNA from two cultivated flax varieties with the use of 10-11 nucleotide primers.     

Changes in the fluorescence of chlorophyll alpha and beta-carotene under the action of hydrogen peroxide

Changes in the fluorescence of beta-carotene and chlorophyll a and their mixtures in different molar ratios under the action of hydrogen peroxide have been registered in two cases: (1) in Langmuir films and (2) in a complex with bovine serum albumin in water solution. Changes in the fluorescence of Langmuir-Shaefer films of Zn ethioporphyrine II under the action of hydrogen peroxide in different molar ratios have also been shown. No shifts of pigment band maxima have been registered.     

Antibacterial effect of peptide conjugates with a quaternized chitosan derivative and its estimation by the method of atomic force microscopy

We obtained a number of conjugates based on a quaternized chitosan derivative and antimicrobial peptides (melittin and warnerin) crosslinked by microbial transglutaminase. We determined the optimal conditions for the synthesis (30 minutes, with a mole ratio of peptides and chitosan derivative of 1.4: 100) and studied the antibacterial properties of obtained conjugates. The antibacterial effect of the conjugates was found to be greater than that of their components. The antibacterial activity of the conjugates was determined by the double-dilution method and by atomic force microscopy.     

Metabolic activity of pigeon thalamic and telencephalic auditory centers

Distribution of activity of mitochondrial oxidative enzyme cytochrome oxidase (CO) was studied in the thalamic (Ov) and telencephalic (field L) auditory centers of the pigeon Columbia livia. Different levels of CO activity are found in the core and belt of the centers: the high CO activity in the core of Ov (nCe) and telencephalic field L2 and the much lower or absent in the peripheral regions (Ovl, Ovm, SPO and L1 and L3). Comparison of our data with those of various avian and reptile species confirms the concept of the common plan of rostral auditory centers in sauropsid amniotes by the principle of the center-periphery (core-belt), which is characteristic of the corresponding mammalian centers. The separation of the central and peripheral parts of these centers is better pronounced in birds than in reptiles.     

Calcium-binding proteins and metabolic activity in thalamotelencephalic parts of the turtle visual system

Distribution of three calcium-binding proteins (CaBPr) calbindin (CB), calretinin (CR) and parvalbumin (PV) in parallel with metabolic activity (cytochrome oxidase, CO) was studied in telencephalic projection zones of the tecto- and thalamofugal visual pathways in experiments on the Horsfield's terrapin Testudo horsfieldi and the pond turtle Emys orbicularis. It was shown that the nucleus rotundus (Rot) and dorsal lateral geniculate nucleus (GLd) terminal fields in both zones (dorsolateral region of the anterior ventricular ridge, Advrdl and dorsolateral cortex, Cxdl, respectively) were CB-immunoreactive (-ir) in the both studied turtle species. The highest density of CB-ir terminals and the focus of rotundal projections in the Advrdl core coincided precisely. The GLd terminal field in Cxdl also was CR-ir. The PV contribution to innervation of both projectional zones was much lower, especially to innervation of Cxdl from GLd. In spite of similar CB-ir innervation, the projectional field of the tectofugal pathway of Advrdl had the much higher CO activity than of that of the thalamofugal pathway in Cxdl. The neurons immunoreactive to all three CaBPr types were distributed in Cxdl in different ratios in each of layers. In the visual Advrdl area the overwhelming majority were PV-ir neurons, whereas CB-ir neurons were absent. The conclusion is made that in spite of the CB- or CB/CR-immunoreactivity predominates over the PV-immunoreactivity in both thalamotelencephalic pathways of the visual system, the tectofugal (rotundo-Advrdl) pathway having the higher metabolic activity.     

Translation initiation factor eIF3 is able to bind with microtubules in mammalian cells

Association of the translation apparatus with the cytoskeleton is essential for its transportation within the cell and probably also for translation regulation. Very little is known about the involvement of particular proteins of this association. A polypeptide homologous with the heavy chain of translation initiation factor eIF3 p170 was found earlier in a microtubule preparation from adrenal cells. Antibody A167 directed against the recombinant fragment of p170 has been generated to study eIF3 interaction with microtubules in mammalian cells. This antibody was shown to recognize a single 170 kDa polypeptide in eIF3 preparations as well as in homogenates of various cell types. A167 allowed detection of the 170 kDa polypeptide in microtubule preparation from bovine brain and confirmation of its presence in microtubule preparations from adrenal cells. As shown by immunofluorescence microscopy using A167, the 170 kDa polypeptide is mainly located in the endoplasm within numerous small and some large granules. Cell treatment with cycloheximide resulted in growth and clustering of the large granules, and partial antigen redistribution along cellular microtubules. These new experimental data indicate that mammalian translation factor eIF3 may bind with microtubules.     

Distribution of calcium-binding proteins parvalbumin and calbindin in the thalamic auditory center in pigeons

Distribution of calcium-binding proteins (CaBPr) parvalbumin (PV) and calbindin (CB) in the thalamic auditory center (nucleus ovoidalis, Ov) was studied in the pigeon (Columba livia). Two parts of Ov were distinguished on the basis of their cytoarchitectonics and distribution of PV and CB immunoreactivity. The central lemniscal region (core, nCe) contains both dense PV-ir neuropil and PV-ir neurons overlapped with scant CB-ir neuropil and weaker stained CB-ir neurons. The peripheral extralemniscal region (belt), consisting of peri/paraovoidal nuclei (Ovl, Ovm, SPO), contains only CB-ir neuropil and strongly stained CB-ir neurons morphologically differing from CB-ir neurons in the nCe. A comparative analysis of our data on the distribution of PV and CB immunoreactivity in the thalamic auditory relay center in pigeons and related literature data obtained on other avian, reptilian and mammalian species indicates high evolutionary conservatism of its extralemniscal region across all sauropside amniotеs and mammals in contrast to plasticity of its central lemniscal region due to adaptive, ecologically dependent transformations during the evolution.