Analysis of a model for antagonistic muscles

In the present work a linear model for a pair of antogonistic muscles is analysed. Each constituent muscle in this model is identical to ones considered previously (Stein and Ouztöreli, 1976). Analytical properties of the antagonistic muscles and dynamics of the system are described and some numerical results are discussed. The natural modes of the system are determined by a fourth order polynomial, which most commonly has one pair of conjugate complex roots and two negative real roots. The filtering of neural inputs through the active state properties of the muscle increases the order of the system to fifth order for these inputs.This work was partly supported by the National Scientific and Engineering Research Council of Canada Grant NRC-A4345 and by the Medical Research Council of Canada Grant MRC-MT-3307 through the University of Alberta     

Response analysis of vertebrate retina

In a recent work (Ouztöreli, 1980) a mathematical model for studying the neural activities in a vertebrate retina has been investigated, where the basic network contains five interconnected neurons: a receptor cell, a bipolar cell, a horizontal cell, an amacrine cell, and a retinal ganglion cell. More recently, in (Ouztöreli and O'Mara, 1980) the basic network has been extended to a larger network containing twelve neurons. In both of these works, the performances of the basic and extended models were discussed under different structural and processing conditions with constant inputs by using the results of one of our earlier work (Ouztöreli, 1979). In the present paper we investigate by simulations the responses of the basic retinal network to piecewise constant and periodic inputs. The step and frequency responses of the extended retinal network will be discussed in a forthcoming paper.This work was partially supported by the Natural Sciences and Engineering Research Council of Canada under Grant A-4345 through the University of alberta     

The Concanavalin A agglutinating system of cell membranes.

The hopes raised by the finding of differential Concanavalin A (Con A) agglutinability of normal and transformed cells in efforts to quantify differences between these cell lines seem not to have been justified. In this paper, the development of information on the mechanism of action of Con A on the cell surface, as well as the theories put forward at each stage of this development are surveyed. In this respect, investigations on Con A constitute a case history in biological research. The involvement of glycoproteins and galactosyltransferases in cell-cell interactions and their relations to Con A are also reviewed.     

Tenascin-R: role in the central nervous system

Tenascin-R (TN-R), a member of the tenascin family of extracellular matrix glycoproteins, is exclusive to the nervous system. It affects cell migration, adhesion and differentiation, although no remarkable clinical consequences have been shown in knock-out animal models. TN-R's expression pattern suggests a possible primary or secondary role in certain neurological problems including malformations, tumors and neurodegenerative disorders. This review summarizes the structure and molecular interactions of this molecule and discusses its function and possible roles in the central nervous system.     

How Honeybees Defy Gravity with Royal Jelly to Raise Queens

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Genetic alterations in gastric precancerous lesions

To investigate the occurrence of 17p (p53) loss of heterozygosity (LOH) and increased 4N or aneuploidy in gastric precancerous lesions (GPL), and their association with Helicobacter pylori (H pylori) infection. A total of 78 gastric mucosal biopsy specimens, including 10 normal mucosa and 68 gastric precancerous lesions [chronic atrophic gastritis (CAG, n = 20), intestinal metaplasia (IM, n = 12), low grade dysplasia (LGD, n = 15), and high grade dysplasia (HGD, n = 21)] were studied using PCR and flow cytometry. A modified Giemsa staining technique was used to detect H pylori. The study was performed in Erzurum Numune Hospital between 2007 and 2009. 17p (p53) LOH was observed in (1/20) 5% of CAG, in (2/12) 16% of IM, in (3/15) 20% of LGD and in (11/21) 53% of HGD. There was correlation between prevalence of 17p (p53) LOH and histological type of GPL (P = 0.004). Similarly, increased 4N or aneuploidy was detected in (1/20) 5% of CAG, in (1/12) 8% of IM, in (2/15) 13% of LGD and in (9/21) 43% of HGD. The correlation was found between aneuploidy and histological type of GPL (P = 0.009). However, there was no correlation between presence of H pylori infection in histological type of GPL (P = 0.921). On the other hand, a significant association was found between increased 4N or aneuploidy and 17p (p53) LOH in all of GPL (P = 0.0001). However, there was no statistically significant association between H pylori infection and 17p (p53) LOH or increased 4N/aneuplody in GPL. 17p (p53) LOH and increased 4N or aneuploidy are closely related to the early stages of gastric carcinogenesis.     

Influence of 50 Hz frequency sinusoidal magnetic field on the blood-brain barrier permeability of diabetic rats

The combined effects of diabetes and a 50 Hz, 5 mT RMS flux density sinusoidal magnetic field for 8 h a day, for 21 consecutive days on the permeation of Evans-blue dye through the blood-brain barrier were studied in male Wistar albino rats. Our results suggest that magnetic field has no effect on the blood-brain barrier permeability in normoglycemic animals, but that diabetic rats are vulnerable to magnetic fields.     

Radionuclides content in grape molasses soil samples from Central Black Sea region of Turkey

The activity concentrations of radionuclides in grape molasses soil samples collected from Zile (Tokat) plain in the Central Black Sea region of Turkey were measured by using gamma spectrometer with a NaI(Tl) detector. Also, the concentrations of ²²²Rn in soil samples and air were estimated essentially taking the activity concentrations of ²²⁶Ra measured in soil samples. Grape molasses soil samples with calcium carbonate content are used for sedimentation for making molasses in this region. The average activity concentrations of ²³²Th, ²²⁶Ra, ⁴⁰K, and ¹³⁷Cs were found as 62 ± 2, 68 ± 3, 479 ± 35, and 8.0 ± 0.3 Bq kg^?1, respectively. The average concentrations of ²²²Rn in soil samples and air were estimated to be 50 kBq m^?3 and 144 Bq m^?3. From the activity concentrations, absorbed gamma dose rate in outdoor air (D), annual effective dose from external exposure (E_E), annual effective dose from inhalation of radon (E_I), and excess lifetime cancer risk (ELCR) were estimated in order to assess radiological risks. The average values of D, E_E, E_I, and ELCR were found to be 90 nGy h^?1, 110 μSv y^?1, 1360 μSv y^?1, and 4 × 10^?4, respectively.     

Dynamics of brain rhythmic and evoked potentials

In this study, the simultaneously recorded and selectively averaged evoked potentials in some of the structures of the auditory pathway (acoustical cortex, medial geniculate nucleus, inferior colliculus), in the reticular formation and the hippocampus of the awake cat as well as the simultaneous amplitude frequency characteristics of these structures are given. The power spectral density functions computed from the simultaneously recorded spontaneous activity of these structures are also presented. Using these results, the following analyses are accomplished: (1) determination of the dynamics of potentials simultaneously obtained from various brain structures, in order to evaluate the common features of their system characteristics; (2) determination of the relationship (or interactions) between rhythmic activity and evoked potentials of the brain, and (3) elaboration of a working hypothesis for the dynamics of potentials of the brain. Some suggestions and comments are also made for investigators working toward theories or dynamic models of signal transmission in the brain.