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Results for “HYDROGEN ION CONCENTRATION”

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At least 73 records · Page 4Linked to original sources
PubMed1985

Optimization of hydrogen-ion concentration during aspiration of oocytes and culture and transfer of embryos.

Rapid and marked shifts in pH can have deleterious effects on oocytes and embryos. Such shifts are most likely to occur during laparoscopy and examination of gametes and embryos. We studied the rate of pH change of follicular fluid and bicarbonate- and phosphate-based media during exposure to 100% CO2 with a constant surface area to volume ratio. All solutions tested developed a pH below the physiological range of 7.30-7.50 within 2 min of exposure to 100% CO2. We also examined the rate of increase in pH due to CO2 loss from media in room air within standard organ culture dishes and tubes. After exposure to ambient conditions for 2 min, the pH of modified Ham's F-10 medium in organ culture dishes rose above the physiological range. We have used a needle laparoscope to confirm intraperitoneal placement prior to the insufflation of a 5% CO2 gas mixture for laparoscopic oocyte retrieval. We have carried out all examinations of oocytes and embryos within a pediatric isolette equipped with an automatic CO2 controller to maintain a 5% CO2 environment. We have transferred embryos in 15% fetal cord serum to avoid the alkaline pH associated with a high concentration of equilibrated heat-inactivated preovulatory serum. These simple techniques can optimize the hydrogen-ion concentration of media during the entire process of in vitro fertilization and embryo transfer.

Carbon Dioxide↗
PubMed2001

Disturbances in cellular features and elemental homeostasis in the integument of a freshwater fish Channa punctatus (Bloch) in relation to hydrogen ion concentration of polluted water.

Scanning electron microscopy revealed that the cellular and morphological defects in the integument of Channa punctatus, associated with heavy metal and other environmental pollution was related to a significant extent to the hydrogen ion concentration of the water. At low pH, the epidermis showed severe lesions, and the scale lost its attachment with the skin, due to lepidontal alterations of the circuli. Atomic absorption spectroscopic analysis of the tissue indicated disturbances in the homeostasis of several elements, which probably played a major role in causing the cellular and morphological defects. Experimental monitoring of the pH of the polluted water to near-neutral, reduced significantly the extent of cellular and morphological defects and disturbances in elemental homeostasis.

Acids↗
PubMedDate not supplied

Calcium and hydrogen ion concentrations in the parasitophorous vacuoles of epithelial cells infected with the microsporidian Encephalitozoon hellem.

Microsporidia of the genus Encephalitozoon undergo merogony and sporogony in a parasitophorous vacuole within the host cell. Cultured green monkey kidney cells infected with Encephalitozoon hellem were loaded with the fluorescent dyes fura-2 or BCECF in order to measure intracellular concentrations of calcium and hydrogen ions respectively. Both the parasitophorous vacuole calcium concentration and pH values resembled those of the host cell cytoplasm in infected cells. Calcein entered the parasitophorous vacuole but not other host cell vacuoles or parasite stages within the parasitophorous vacuole. The lack of a pH or calcium concentration gradient across the parasitophorous vacuole membrane and the permeability of this membrane to a large anion such as calcein suggest that the vacuole membrane surrounding E. hellem resembles that surrounding some other intracellular parasites such as Toxoplasma gondii. A potential role is discussed for the parasitophorous vacuole calcium concentration in germination in situ.

Animals↗
PubMed1972

The influence of hydrogen ion concentration on calcium binding and release by skeletal muscle sarcoplasmic reticulum.

Calcium release and binding produced by alterations in pH were investigated in isolated sarcoplasmic reticulum (SR) from skeletal muscle. When the pH was abruptly increased from 6.46 to 7.82, after calcium loading for 30 sec, 80-90 nanomoles (nmole) of calcium/mg protein were released. When the pH was abruptly decreased from 7.56 to 6.46, after calcium loading for 30 sec, 25-30 nmole of calcium/mg protein were rebound. The calcium release process was shown to be a function of pH change: 57 nmole of calcium were released per 1 pH unit change per mg protein. The amount of adenosine triphosphate (ATP) bound to the SR was not altered by the pH changes. The release phenomenon was not due to alteration of ATP concentration by the increased pH. Native actomyosin was combined with SR in order to study the effectiveness of calcium release from the SR by pH change in inducing super-precipitation of actomyosin. It was found that SR, in an amount high enough to inhibit superprecipitation at pH 6.5, did not prevent the process when the pH was suddenly increased to 7.3, indicating that the affinity of SR for calcium depends specifically on pH. These data suggest the possible participation of hydrogen ion concentration in excitation-contraction coupling.

Actomyosin↗
PubMed2000

Thermodynamic considerations of arteriovenous gradients of hydrogen ion concentration and carbon dioxide tension.

It is shown that, in a multicompartmental homeostatic system, the extent of interaction between any two compartments can be assessed by determination of the difference in free energy change of one particular reaction, or a series of coupled reactions, operative in both of the compartments under consideration. Hydrogen ion concentration and carbon dioxide tension have been used to determine free energy change difference relationships between the venous and arterial compartments (-deltadeltaG(a-v)) of the circulatory system. Data from the literature (from two studies of congestive heart failure and one study of experimentally induced cardiac arrest) are used to calculate -deltadeltaG(a-v). It was found that in control subjects -deltadeltaG(a-v) is close to zero, whereas in congestive heart failure or cardiac arrest, the value rises to 150 cal mol(-1) or more, whereas in blood, the approach towards equilibrium between hydrogen and bicarbonate ions and dissolved carbon dioxide (aqueous CO2) is known to be only moderately rapid. It is concluded that, in the system under study, and with respect to the reaction H+ + HCO3- = CO2 + H2O, a high value for the free energy change difference between the two compartments (high -deltadeltaG(a-v)) must be due to an insufficient blood circulation rate. Accordingly, -deltadeltaG(a-v) is probably a quantitative measure of cardiac insufficiency.

Blood Circulation↗