The aim of study was to review the status of arterial pH, pO2 and pCO2 under general anesthesias in dependence on the light-dark (LD) cycle in spontaneously breathing rats. The experiments were performed using three- to four-month-old pentobarbital(P)-, ketamine/xylazine(K/X)- and zoletil(Z)-anesthetized female Wistar rats after a four-week adaptation to an LD cycle (12 h light:12 h dark). The animals were divided into three experimental groups according to the anesthetic agent used: P (light n=11; dark n=8); K/X (light n=13; dark n=11); and Z (light n=18; dark n=26). pH and blood gases from arterial blood were analyzed. In P anesthesia, LD differences in pH, pO2, and pCO2 were eliminated. In K/X anesthesia, parameters showed significant LD differences. In Z anesthesia, LD differences were detected for pH and pO2 only. Acidosis, hypoxia, and hypercapnia have been reported for all types of anesthesia during the light period. In the dark period, except for P anesthesia, the environment was more stable and values fluctuated within normal ranges. From a chronobiological perspective, P anesthesia was not the most appropriate type of anesthesia in these rat experiments. It eliminated LD differences, and also produced a more acidic environment and more pronounced hypercapnia than K/X and Z anesthesias., P. Svorc, D. Petrášová, P. Svorc Jr., and Obsahuje bibliografii
The characterization of ultra-soft soil behavior is one of the most difficult challenges since the water content in such soils is very high. Hence, nondestructive or special measurement is required. Therefore, the behavior of untreated and treated ultra-soft soil was characterized using both miniature penetrometer and electrical methods. The ultra-soft soil was prepared with 2% to 10% bentonite. The soil with 10% bentonite was treated with 2% to 10% lime and with 1% to 10% polymer separately. The pH, CIGMAT miniature penetrometer, and electrical resistivity combined with the measured shear strength from the modified vane shear device were used to characterize the ultra-soft soils. The CIGMAT miniature penetrometer penetration varied linearly with the shear strength of the untreated and treated soft soils with 10% bentonite. Relative electrical resistivity decreased by 246% when the bentonite content was increased from 2% to 10% in the ultra-soft soil. The addition of 10% of the lime to the ultra-soft soil with 10% of bentonite content decreased the relative electrical resistivity by 171%. The addition of 10% of the polymer to the ultra-soft soil with 10% of bentonite content reduced the relative electrical resistivity by 545%. Power law, linear and hyperbolic models were used to predict the shear strength- electrical resistivity relationship for the untreated, lime-treated and polymer-treated ultra-soft soils respectively. The CIGMAT miniature penetrometer was modeled using 3-D axisymmetric finite element method, which predicted the penetration of CIGMAT penetrometer that agreed well with the experimental results of the ultra-soft soils.
31P MR spectroscopy was used to measure the signal intensity ratios of high-energy metabolites for the calculation of free cytosolic magnesium concentration [fMg2+] and pH in the calf muscles of patients with primary juvenile hypertension and of healthy controls. Surface coil and spectroscopic imaging techniques were used. In patients with hypertension, the concentrations of [fMg2+] was 788±33 mmol/l and intracellular pH was 7.05±0.02; these values were not significantly different from the results obtained in healthy controls ([fMg2+], 776±21 mmol/l and pH, 7.06±0.01). Biochemical assays of magnesium in the serum (S-Mg) and in urine (DU-Mg) confirmed this finding. Significant differences in the relative signal intensities of high-energy phosphates between patients with primary juvenile hypertension and healthy controls were observed: a) signal intensity ratios of PCr/Pi, PCr/PbATP, PDE/PbATP were increased, and b) Pi/PDe, Pi/PATP were decreased. The results were the same irrespective of whether the surface coil method or 31P spectroscopic imaging were employed., M. Hájek, D. Palyzová, M. Kořínek, D. Kurková., and Obsahuje bibliografii
Optical fiber sensors can bring many advantages to biological, medical or environmental applications. They offer small size, immunity to electro-magnetic field and limited unwanted interaction with measured sample. One of the key parameters monitored in biological systems is the acidity of environment expressed as pH. The article deals with development of an optical pH-sensor with tapered fiber probes. The principle of the sensor is based on measurement of fluorescence emission of hydroxypyrene-1,3,6-pyrene trisulfonic acid trisodium salt (HPTS, pyranine) at two different excitation wavelengths (405 nm and 450 nm). The sensor was sensitive to pH in range from 5.5 to 7.5 with resolution of ± 0.15 pH unit and the tapered fiber probes allowed in-vivo measurement in microscopic biological samples. and Optické vláknové senzory mohou přinést řadu výhod při využití v oblastech biologie, medicíny či v ochraně životního prostředí. Vyznačují se malými rozměry a odolností vůči elektromagnetickému poli, přičemž nežádoucí ovlivnění měřených vzorků je u nich též velmi omezeno. Jedním z důležitých parametrů sledovaných u biologických systémů je kyselost prostředí, vyjádřená jako pH. Článek popisuje vývoj optického pH -senzoru využívajícího zúžené vláknové sondy. Princip měření je založen na sledování emise fluorescence sodné soli kyseliny hydroxypyren-1,3,6-pyrentrisulfonové (pyranin) při excitaci dvěma odlišnými vlnovými délkami (405 nm a 450 nm). Senzor vykazoval citlivost na pH v rozsahu od 5,5 do 7,5, přičemž dosažené rozlišení činilo ±0,15 pH jednotky. Použití zúžených vláknových sond pak umožnilo in-vivo měření v mikroskopických biologických vzorcích.
The effects of decreasing extracellular pH from 7.4 to 6.0 or 5.8 on whole cell membrane currents induced by GABA (10-100 //M) were studied in dorsal root ganglion (DRG) neurons of the frog in short-term culture using the whole cell patch-clamp technique. In 45 of 50 cells the GABA currents were the same at both normal and reduced pH. In the remaining 5 cells, acidification increased the response. The reversal potential for the current, about +5 mV, was the same at reduced and normal pH. These results contrast with the effect of the same pH reduction which markedly reduces the current resulting from glutamate activation of receptors on central neurons (Traynelis and Cull-Candy 1990, Vyklicky Jr. et ai 1990, Tang et al. 1990). These findings suggest that acidification under pathophysiological conditions plays a protective role in preventing excessive excitation not only by decreasing glutamate responses but also by leaving the inhibitory GABAa responses intact.
Pathogenic and nonpathogenic strains of Cryptobia salmositica Katz, 1951 and C. bullocki Strout, 1965 produced hydrogen peroxide, pyruvate and lactate under in vitro conditions in Minimum Essential Medium (MEM). As parasite number increased, the phenol red in the medium changed from red to yellow. This change was not associated with a decrease in pH, or an increase in pyruvate or lactate, but was correlated with an increased secretion of hydrogen peroxide. Parasites incubated at 10°C in medium at pH 6.0, 6.5, 7.0 and 7.3 were active for about 1 week with decreasing activity in the absence of serum. Parasites in saline (pH 6.0, 6.5, 7.0 and 7.3) were nonmotile within 24 h and were dead in about 1 week. This suggests that these Cryptobia spp. are sensitive to changes in pH and require medium which is buffered, either with serum or Hepes.
The article presents a method of pH measurement of aqueous humour during cataract surgery. The method uses a fiber optic sensor with immobilized fluorescent dye. A functional sample of fiber optic pH meter was used for measurements, developed in cooperation of the Institute of Photonics and Electronics, Academy of Sciences of the Czech Republic, v.v.i., Safibra, s.r.o. and SQS Vláknová optika a.s. The accuracy of determined pH values was 0.04 pH unit or better. and V článku je prezentována metodika měření nitrooční tekutiny během operace katarakty (šedého zákalu), která je založena na použití vláknově optického senzoru s imobilizovaným fluorescenčním barvivem. K měření byl použit funkční vzorek vláknově optického pH metru vyvinutý ve spolupráci Ústavu fotoniky a elektroniky, Akademie věd ČR, v.v.i., Safibra, s.r.o. a SQS Vláknová optika a.s. Hodnoty pH byly stanoveny s přesností 0,04 nebo lepší.
Our experiments on metabolic processes in the rumen were performed on sixteen 5-month-old lambs divided into 4 groups (defaunated - D, totally refaunated - T, partially refaunated - P and intact - 1). The absence or presence of protozoa in the rumen did not significantly affect the pH values. The greatest differences in NH3 concentration in the rumen before feeding were found between the T and D group (P<0.05). The animals of the T and I groups had higher NH3 concentrations than the D and P groups 1-5 hours after feeding (P<0.05 to PcO.OOl). Blood urea concentrations before and after feeding were significantly higher in the group I compared to the other groups (P<0.05 to PcO.OOl). Significant differences in the total nitrogen in rumen fluid were only found between groups D and I. The values of protozoan nitrogen in the rumen and their mutual relationship among the groups could be expressed by the following ratios: I>T>P>D. Proportions of the values of bacterial nitrogen followed in this order: D>P>T>I. The animals in group D had a significantly higher level of residual nitrogen than those in the other groups (P<0.05).
Incubation of maize NADP-malic enzyme with tetranitromethane (TNM) resulted in a total loss of enzyme activity. The loss of enzyme activity was not observed at pH 6.3 but at pH 8.0. NADP-malic enzyme was inactivated to almost 90 % by incubation with an 80-fold molar excess of TNM for 5 min at 30 °C. The substrate malate or Mg2+ alone gave no protection, while NADP provided considerable protection. NADP in the presence of malate and Mg2+ totally protected the enzyme activity, suggesting that tyrosine residue may be located at or near the active site of maize NADP-malic enzyme. The spectral analysis of the modified enzyme indicated that modification of at least one tyrosine residue per subunit resulted in complete loss of the enzyme activity. The fluorescence study of unmodified and modified enzymes postulated that essential tyrosine residue at maize NADP-malic enzyme is possibly involved in malate binding. and S. R. Rao, B. G. Kamath, A. S. Bhagwat.