Escherichia coli tetracycline efflux determinants in relation to tetracycline residues in chicken

ObjectiveTo screen for Escherichia coli (E. coli) resistant to tetracycline, followed by identification of tet efflux genes by polymerase chain reaction (PCR). In addition, detection of tetracycline residues in chicken livers and kidneys were conducted using high performance liquid chromatography-tandem quadrupole mass spectrometry (HPLC-MS-MS).MethodsStrains of E. coli were isolated from samples of chicken colon and screened for tetracycline resistance. Tetracycline genes conferring resistance (Tc^r) were detected by polymerase chain reaction (PCR). Most of the isolates were resistant to tetracycline (97.9%).ResultsPCR analysis indicated that Tc^r E. coli R-plasmids contained tet(A), tet(B) and a combination of both efflux genes. None of the isolates contained other efflux tet genes tet (C, D, E and Y). High performance liquid chromatography-tandem quadrupole mass spectrometry (HPLC-MS-MS), a sensitive technique, was used to detect residues of chlortetracycline (CTC), oxytetracycline (OTC), doxycycline (DC) in chicken livers and kidneys. The samples containing tetracycline residues were at 0.13-0.65 pg/μL levels.ConclusionsTetracycline and other antibiotics are commonly used in the poultry and meat production industry for prevention of microbial infections. Multiple antibiotic resistant bacteria in Oman have increased to alarming levels, threatening public health, domestic and may have adverse effect on environment.     

Selective attention model with spiking elements

A new biologically plausible model of visual selective attention is developed based on synaptically coupled Hodgkin–Huxley neurons. The model is designed according to a two-layer architecture of excitatory and inhibitory connections which comprises two central neurons and a population of peripheral neurons. Two types of inhibition from the central neurons are present: fixed inhibition which is responsible for the formation of the attention focus, and short-term plastic inhibition which is responsible for the shift of attention. The regimes of synchronous dynamics associated with the development of the attentional focus are studied. In particular, the regime of partial synchronization between spiking activity of the central and peripheral neurons is interpreted as object selection to the focus of attention. It is shown that peripheral neurons with higher firing rates are selected preferentially by the attention system. The model correctly reproduces some observations concerning the mechanisms of attentional control, such as the coherence of spikes in the population of neurons included in the focus of attention, and the inhibition of neurons outside the focus of attention. Sequential selection of stimuli simultaneously present in the visual scene is demonstrated by the model in the frequency domain in both a formal example and a real image.     

A neural model of selective attention and object segmentation in the visual scene: An approach based on partial synchronization and star-like architecture of connections

A brain-inspired computational system is presented that allows sequential selection and processing of objects from a visual scene. The system is comprised of three modules. The selective attention module is designed as a network of spiking neurons of the Hodgkin–Huxley type with star-like connections between the central unit and peripheral elements. The attention focus is represented by those peripheral neurons that generate spikes synchronously with the central neuron while the activity of other peripheral neurons is suppressed. Such dynamics corresponds to the partial synchronization mode. It is shown that peripheral neurons with higher firing rates are preferentially drawn into partial synchronization. We show that local excitatory connections facilitate synchronization, while local inhibitory connections help distinguishing between two groups of peripheral neurons with similar intrinsic frequencies. The module automatically scans a visual scene and sequentially selects regions of interest for detailed processing and object segmentation. The contour extraction module implements standard image processing algorithms for contour extraction. The module computes raw contours of objects accompanied by noise and some spurious inclusions. At the next stage, the object segmentation module designed as a network of phase oscillators is used for precise determination of object boundaries and noise suppression. This module has a star-like architecture of connections. The segmented object is represented by a group of peripheral oscillators working in the regime of partial synchronization with the central oscillator. The functioning of each module is illustrated by an example of processing of the visual scene taken from a visual stream of a robot camera.     

Affinity of hemoglobin for oxygen and prooxidant-antioxidant equilibrium after administration of lipopolysaccharide during correction of the L-arginine—NO pathway

Effects of correction of the L-arginine—NO pathway on the fever reaction, oxygen transport function of the blood, and prooxidant-antioxidant equilibrium in rats injected intramuscularly with lipopolysaccharide were studied. pH, Pco₂, Po₂, and the index of hemoglobin oxygen affinity (p50) were measured in mixed venous blood. Levels of Schiff bases, α-tocopherol, and catalase activity were determined in erythrocytes and in the liver, kidneys, and heart. NO synthase inhibitor attenuated the fever reaction and decreased p50 to 28.89±0.83 mm Hg (in rats administered with lipopolysaccharide, p50 was 34.21±1.63 mm Hg). The increase in the content of Schiff bases and the exhaustion of the antioxidant system in erythrocytes and tissues were less pronounced in rats injected with the NO synthase inhibitor than in animals receiving lipopolysaccharide only. Various parameters of the prooxidant-antioxidant equilibrium correlated with p50. Thus, hemoglobin oxygen affinity and NO are important factors involved in the maintenance of the prooxidant-antioxidant equilibrium in the body. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 127, No. 6, pp. 616–619, June, 1999     

MSCT与微CT在体成像中的对照研究

目的：通过与组织学的对照研究，探讨MSCT和一种新型的μCT系统对评价恶性脑肿瘤体积的诊断准确性。方法：14只小鼠通过立体定向术植入GFP标记的98F一胶质瘤细胞。植入术后第10天所有小鼠行双倍剂量对比增强μCT和MSCT检查。将2种检查方法测量的肿瘤体积与组织病理学结果进行对照分析。     

Pharmacokinetics of amixin after repeated peroral administration to mice

Pharmacokinetics of amixin was studied after repeated administration (5 days) to animals. Perorally administered amixin is characterized by high bioavailability and is present in the circulation in high concentrations for a long time. The main pharmacokinetic parameters were estimated by the method of linear regression because of slow elimination of amixin from organs and tissues. Our results indicate that repeated treatment with amixin holds much promise for the prevention and therapy of chronic diseases (particularly hepatitides). __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 140, No. 12, pp. 661–663, December, 2005     

Spatiotemporal visualization of deep brain stimulation-induced effects in the subthalamic nucleus

Deep brain stimulation (DBS) is a successful surgical therapy used to treat the disabling symptoms of movement disorders such as Parkinson's disease. It involves the chronic stimulation of disorder-specific nuclei. However, the mechanisms that lead to clinical improvements remain unclear. Consequently, this slows the optimization of present-day DBS therapy and hinders its future development and application. We used a computational model to calculate the distribution of electric potential induced by DBS and study the effect of stimulation on the spiking activity of a subthalamic nucleus (STN) projection neuron. We previously showed that such a model can reveal detailed spatial effects of stimulation in the vicinity of the electrode. However, this multi-compartmental STN neuron model can fire in either a burst or tonic mode and, in this study, we hypothesized that the firing mode of the cell will have a major impact on the DBS-induced effects. Our simulations showed that the bursting model exhibits behaviour observed in studies of high-frequency stimulation of STN neurons, such as the presence of a silent period at stimulation offset and frequency-dependent stimulation effects. We validated the model by simulating the clinical parameter settings used for a Parkinsonian patient and showed, in a patient-specific anatomical model, that the region of affected tissue is consistent with clinical observations of the optimal DBS site. Our results demonstrated a method of quantitatively assessing neuronal changes induced by DBS, to maximize therapeutic benefit and minimize unwanted side effects.     

State of the oxygen transport function of blood in rabbits with hyperthermia

Departments of Normal Physiology and Biophycs, Grodno Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR, K. V. Sudakov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 107, No. 6, pp. 652–655, June, 1989.