Ringer's Solution pH Research Articles

Deciphering the induction of Listeria monocytogenes into sublethal injury using fluorescence microscopy and RT-qPCR

The adaptive response of bacterial cells to changing environmental conditions depends on the behavior of single cells within the population. Exposure of Listeria monocytogenes to sublethal acidic conditions in foods or in the gastrointestinal track of the host may induce injuries relevant to difficult physiological states within the dormancy continuum. In this study, exposure to acidic conditions (acetic-AA and hydrochloric acid-HCl adjusted to pH 3.0, 2.7, 2.5 at 20 °C for 5 h) was used to evaluate injury of L. monocytogenes, Scott A strain. To differentiate the resistant sub-population from the total, Tryptic Soy Agar with 0.6 % Yeast Extract (TSAYE) supplemented or not with 5 % NaCl were comparatively used. Sublethally injured cells were detected by comparing plate counts with fluorescence microscopy, using combinations of CFDA (viability) and Propidium-Iodide (death). Effect of acid stress on the relative transcription of clpP, mazE, mazF, relA, gadC, gadD, gadB, sigB, inlA and prfA upon transition of total population into different physiological stages was evaluated through RT-qPCR. AA treated cells showed measurable logarithmic reduction at pH 2.7 and 2.5, while there was a significant percentage of CFDA−/PI+ cells. Evaluation of the potentially culturable population on TSAYE, from the percentage of CFDA/PI-stained cells, revealed that unstained cells represented a non-culturable sub-population. Exposure to Ringer's solution pH 2.7, adjusted with AA, resulted in higher percentages of non-esterase active with membrane integrity cells (CFDA−/PI−) compared to the percentages of the enumerated culturable cells on TSAYE after 4 and 5 h. Under the same conditions, after 1 h of exposure macroscopic observation revealed size colony variations (SCVs) of the total population (CFU on TSAYE). L. monocytogenes retained its culturability after hydrochloric acid exposure, while cells remained metabolically active (CFDA+). However, a stochastic change in cell's shape, was detected after exposure to pH 3.0 and 2.5, adjusted with HCl, for 2 h at 20 °C. A pattern of gene up-regulation was observed during treatment with AA pH 2.7 and HCl pH 3.0 at the 3rd h of exposure. Deciphering L. monocytogenes sublethal injury sheds light into the physiological and molecular characteristics of this state and provides the food science community with quantitative data to improve risk assessment.

Pharmacological Correction of the Results of Irradiation of the Parents for the Assimilation of Carbohydrates in the Small Intestine of Two Generations of their Offspring by the Help of Milk Thistle Fruits

Objective: The study of the assimilation of glucose and maltose in the small intestine of two generations of posterity of irradiated male rats received with a food the milled milk thistle fruits after irradiation. Methods: Exposition of male rats performed once by the help of telegamma-setting “AGAT-R1”, dose was 120 rad/min, field 20×20, distance from the source of irradiation to the field=75 cm, dose-0.5 Gy, exposure - 32 sec. Accumulating mucosa preparations (APS) produced by the method of Ugolev et al. APS incubated for 1 hour at t=37oC in the oxygenated medium. As the incubation medium were used solutions 10 mmol/l of glucose and 5 mmol/l of maltose that were made on the Ringer solution pH 7.4. In all incubation medium the bile was added. The concentration of free glucose and M-glucose formed due to the hydrolysis of maltose was determined using method described in ref. Colorimetrically on photoelectrocolorimeter–CFC- 2MP, λ=625 nm. The statistical processing of the obtained data was conducted using “Primer Biostatistics” software. Results: The 2nd generation of the offspring from the males, which received milk thistle in the food immediately after irradiation, showed the high activity of the transport system for the free glucose and system providing transport of M-glucose produced by the hydrolysis of maltose both. This activity is higher than in the corresponding groups of the 1st generation (p<0,0001) and higher than corresponding data in all experimental groups of 2nd generation (except only group of the posterity of the male rats got milk thistle fruits before irradiation). Conclusion: The use by predecessors of milk thistle after irradiation leads to the radio corrective effect on the systems of transport of glucose and maltose both exactly in second generation of their posterity.

Sarcolemmal slow conductance increase of frog sartorius fibers during hyperpolarization.

The properties of the hyperpolarization-activated sarcolemmal slow conductance increase in frog sartorius muscle fibers have been investigated using ethylenediaminetetraacetic acid disodium salt (EDTA) and propionate Ringer solution. More than 1 sec was required for maximum activation of the sarcolemmal slwo conductance increase. It is suggested that, although the sarcolemmal slow conductance increase was affected by deterioration, the conductance increase is not a direct product of deterioration but it represents a property of the sarcolemma which is encountered in physiological range. The sarcolemmal conductance increase was rather insensitive to the change in pH of Ringer solution. It is inferred that the absence of bellying in newly penetrated intact fibers at neutral and alkaline pHs is caused mainly by the shunting effect of large parallel conductance. Apparent augmentation with EDTA of the sarcolemmal conductance increase infers that Ca ions affect the conductance increase. The conductance increase occurred also in the EDTA-containing Cl-deficient solution. The sarcolemmal slow conductance increase has been compared with the change in Cl conductance reported by Hutter and Warner, and Warner.

Electron Micrography of the Eastern Strain Equine Encephalomyelitis Virus

In recent reports from this laboratory, there have been described the results of preliminary studies with the electron microscope on two small animal viruses, namely, the agent of rabbit papillomatosis and that of the Western strain equine encephalomyelitis. The present paper is concerned with the findings in a similar examination of the Eastern strain equine encephalomyelitis virus. “The virus was propagated in chick embryos and purified by ultracentrifugation as previously described.” The final product was dissolved in Ringer solution pH 8.5. Examinations have been made of the virus obtained from 5 different batches of diseased embryos at various intervals after purification. The dried films for electron micrography were prepared as previously described., A micrograph of the Eastern strain equine encephalomyelitis virus is shown in Fig. 1. For preparation of the film a solution containing 2.2 mg virus per cc in Ringer fluid was diluted fourfold with distilled water. As shown, the predominant images are circular in shape and appear as individuals or small irregular agglomerates dispersed at random over the field. There is present also a small amount of ill-defined amorphous extraneous material. The circular images are, like those of the papilloma and Western strain viruses, uniform in size, shape and appearance.appearance. The central dark area of the images indicates, through greater scattering of electrons, a relatively high density of the corresponding region of the virus particle. Extending peripherally from the central area, the enveloping substance appears to be progressively less dense and finally fades indefinitely into the film background. This appearance of the generality of the images gives the impression to be expected of a spherical particle made up of a loose structure of regularly arranged diffraction centers, the density in the thickest dimension diminishing toward the outer limits.

Effect of Drugs Upon Tonus Waves in Excised Auricle and Coronary Vessels of Terrapin.

Excised terrapin auricles show continuous tonus waves 20 to 42 hours after excision, when kept in oxygenated Ringer's solution pH 7.8 to 8.0, at room temperature 20.5 to 27° C. Immediately after excision, decreasing the pH from 7.4 to 7.0 causes a disappearance of the tonus waves.1 These waves reappear when the auricles are replaced in a solution of pH 7.4. Eighteen to 42 hours after excision these same auricles fail to respond by disappearance of tonus waves until a pH of about 6.2 to 6.0 is reached. In one case the tonus waves disappeared only after the pH was reduced to 5.8 and showed optimum tonus waves at pH 6.8. Phosphate buffered solutions tend to stimulate tonus waves. In some auricles, in which carbonate-HCl buffered Ringer's solution pH 6.6 caused the tonus waves to disappear, phosphate buffered Ringer's solution 6.2 caused an increase in tonus waves, and when this solution was replaced by Ringer's pH 7.4 temporary disappearance of the tonus waves occurred.Small doses of adrenalin (alkaloid) 1:1...