Cytoplasmic filaments and cellular wound healing in amoeba proteus

The flexibility and self-healing properties of animal cell surface membranes are well known. These properties have been best exploited in various micrurgical studies on living cells (2, 3), especially in amoebae (7, 20). During nuclear transplantation in amoebae, the hole in the membrane through which a nucleus passes can have a diameter of 20-30 μm, and yet such holes are quickly sealed, although some cytoplasm usually escapes during the transfer. While enucleating amoebae in previous studies, we found that if a very small portion of a nucleus was pushed through the membrane and exposed to the external medium, the amoeba expelled such a nucleus on its own accord. When this happened, a new membrane appeared to form around the embedded portion of the nucleus and no visible loss of cytoplasm occurred during nuclear extrusion. In the present study, we examined amoebae that were at different stages of expelling partially exposed nuclei, to follow the sequence of events during the apparent new membrane formation. Unexpectedly, we found that a new membrane is not formed around the nucleus from inside but a hole is sealed primarily by a constriction of the existing membrane, and that cytoplasmic filaments are responsible for the prevention of the loss of cytoplasm.     

Alleviation of Stress-Induced Damage to Rat Brain Cells by Transcranial Electromagnetic Stimulation

Biophysics - The effect of transcranial electromagnetic stimulation on immobilization stress-induced damage to rat brain cells was studied. Electromagnetic stimulation was performed by microwave...     

Nonstationary Heart Rate Variability in Respiratory Tests

A new method was proposed for processing a nonstationary heart rate by using frequency-modulated signals rather than amplitude-modulated signals equally spaced over several points of time as in the conventional method. A frequency-modulated signal is a set of identical Gaussian peaks that coincide with the true time points of heart beats. A continuous wavelet transform was used to quantitatively describe the heart rhythm signal. A test with controlled breathing was performed as an example and included three consecutive stages: rest, rhythmic breathing at a specified frequency, and exhalation. Tachograms recorded during the breath test was found to be a nonstationary signal with the alternation of peaks of different spectral ranges. A system of quantitative parameters was developed to describe the dynamics of changes in the spectral properties of the tachogram in transitional areas. A static clustering by the effect of the respiratory test and a dynamic clustering in order to identify the time points when the autonomic nervous system is stressed were performed for all subjects. The article discusses the prospects of using the method as a means to analyze the transient effects in various functional tests and as biofeedback that would help to change the heart rhythm.     

Compensatory substitutions and the evolution of the mitochondrial 12S rRNA gene in mammals

12S ribosomal RNA (rRNA) gene sequences from a suite of mammalian taxa (13 placentals, 4 marsupials, 1 monotreme), for which phylogenetic relationships are well established based on independent criteria, were employed to study the evolution of this gene. Phylogenetic analysis of 12S sequences produces a phylogeny that agrees with expectations. Base composition provides evidence for directional symmetrical substitution pressure in loops; in stems, base composition is much more even. Rates of nucleotide substitution are lower in stems than loops. Patterns of nucleotide substitution show an overall preference for transitions over transversions, with this difference more profound in stems than loops. Among different transversion pathways, there is a wide range of transformation frequencies. An analysis of compensatory substitutions shows that there is strong evidence for their occurrence and that a weighting factor of 0.61 should be applied in phylogenetic analyses to account for the dependence of mutations at stem positions relative to positions where changes are independent. Among stem variables (i.e., stem length, interaction distance, substitution rates, G+C content, and the percentage of bases that are paired), several significant correlations were discovered, but stem length and interaction distance are uncorrelated with other variables.      

Phenotypic variability and therapeutic implications of Candida species in patients with oral lichen planus

We investigated the prevalence and phenotypic variation of Candida species in oral lichen planus (OLP) and the therapeutic implications of our findings. Eighty patients with clinically and histopathologically confirmed cases of OLP (64 non-erosive, 16 erosive) and a control group of 80 healthy individuals with no predisposing factors for oral candidiasis were examined for evidence of Candida infection. Oral swabs and smears were obtained for cytology and culture. Identification, speciation and antifungal susceptibility tests of Candida isolates were performed using an automated microbial identification system. Fifty percent of erosive OLP cases, 28% of non-erosive cases and none of the controls showed evidence of Candida. Candida albicans was found predominantly in non-erosive OLP, while other Candida species were predominate in erosive OLP. Non-Candida albicans isolates (C. glabrata, C. krusei) were resistant to the commonly used antifungals, clotrimazole and fluconazole. Candida infection is common in cases of OLP. We recommend antifungal sensitivity testing prior to antifungal therapy for the erosive form of OLP.     

Diversity of life strategies of pikepech <Emphasis Type="Italic">Sander lucioperca</Emphasis> (L.) in the Lower Volga (by the data of microelement composition of otolithes)

Strontium (Sr) and calcium (Ca) contents and Sr/Ca ratios in otoliths of pikeperch Sander lucioperca have been studied by X-ray fluorescent microanalysis. A sample of 95 specimens from the Lower Volga region are studied. The fish were obtained in a section of the Akhtuba River at a distance of 250–279 km upstream from the Caspian Sea. Some specimens in the sample have low strontium content throughout the otolith. The other fish have increased both Sr content and Sr/Ca ratios in core zones of otolith or near its outer edge: the Sr/Ca ratio is over 6.00 × 10^–3, with a maximum at 10.02 × 10^–3. The fish with a low Sr/Ca ratio live in freshwater and demonstrate a resident life history strategy. Pikeperch that have increased ratios of Sr/Ca in outer zones of otolith demonstrate a migratory life history strategy. These fish leave the freshwater of the Volga and feed in brackish water of the Northern Caspian Sea. Some migratory fish migrate to the sea as underyearlings, stay in a brackish water for 1 year or less, and then return back to fresh water for the rest of its life. The other group migrates back and forth from freshwater to the sea several times during their life. Finally, some fish leave freshwater for 1–2 years, spending this time in the Northern Caspian Sea. The conclusion is that the pikeperch stock in the Lower Volga has a complicated composition and consists of freshwater (residents and rheodromic ones) and migratory (anadromous and semianadromous) fish.     

Microelectrode recording of responses in visually observed neurons of the cat motor cortex

With a contact optical system it is possible to carry out intravital studies of neurons and other structures, stained with vital dyes in reflected light in a specially prepared specimen of the cat cerebral cortex. The high-quality characteristics of the optical system used have made combined morphological and intracellular electrophysiological investigations of these neurons possible. The nature of intravital morphological changes in cortical neurons was established in response to their puncture by microelectrodes with tips with different external diameters and configurations; certain morpho-functional correlations were found in the response of pyramidal neurons to disturbance of their temperature regime.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 8, No. 2, pp. 122–125, March–April, 1976.