Design of ionophores for ion-selective microsensors

Requirements for a reliable use of liquid membrane microelectrodes are discussed in terms of stability, response time, and lifetime on the basis of membrane technological considerations. The selectivity of H+, Li+, Na+, K+, Mg2+, Ca2+, and Cl- microelectrodes is critically evaluated using the Nikolskii-Eisenman formalism. Recent progress in the design of new ionophores is presented. A novel neutral carrier-based Ca2+-selective microelectrode with a detection limit of about 5 X 10(-10) M Ca2+ at a background of 125 mM K+ has been realized. An neutral carrier-based microelectrode for H+ with extended pH range of the sample solution is now available. Promising developments in the field of Li+-, Mg2+-, and Cl--selective ionophores are discussed.

Cell contamination due to the use of carrier-based microelectrodes

When using microelectrodes for intracellular ion activity studies, some uncertainties such as interference from cytosolic components at the microelectrode, cell damage, and cell contamination may arise. A model, which treats kinetic processes of the loss of carriers from the membrane phase of microelectrodes into the cytosol and cell membrane, is used for an estimation of the extent and time course of contamination by impaled ion-selective microelectrodes. An isolated model cell consisting of a plasma membrane surrounding a cytosolic milieu is assumed. The results of its considerations represent a worst case situation, in which significant contamination of the cell membrane of such a small isolated single cell might occur during time periods of electrophysiological experiments. In more complex situations, such as in intact tissues, the equilibrium membrane concentrations may be substantially less.

Valinomycin-based K+ selective microelectrodes with low electrical membrane resistance

A valinomycin-based membrane phase for microelectrodes with relatively low electrical membrane resistances is described. Microelectrodes with tip diameters of about 1 micron exhibit resistances of about 10(10) omega. Extremely high K+ selectivities are obtained, e.g. a rejection of Na+ by a factor of 5000 and of acetylcholine by a factor of 3400. At a constant background of 140 and 500 mM Na+, the detection limit of the K+ sensor is at 1.6 X 10(-5) and at 2.5 X 10(-5) M K+, respectively.

The sexual scripting of oral genital contacts

There is evidence from a number of sources that contemporary cultural scenarios for sexual conduct are often very approving of oral genital sex. Two surveys of sexual conduct are analyzed to examine the changes in interpersonal sexual scripts for oral genital sex for cohorts of white and college-educated young people who entered young adulthood between 1928 and 1943 and 1963 to 1967. Males in the earlier cohort had an excess of fellatio during the premarital period from erotic contacts with prostitutes and transient partners. In contacts with potential marital partners and in marriage men and women had equivalent rates of oral sex indicating a greater sexual reciprocity in these affectional relationships. In the latter cohort male and female rates of oral sex before marriage are substantially greater than for the earlier period but are equivalent for the two genders. In both periods oral sex is most common among the coitally experienced and is initiated by males. Evidence is found for an increased amount of sexual activity unlinked to marriage, what might be labeled pre-premarital sex. Male participation in oral sex seems responsive to opportunity, lowered moral inhibition, and emotional commitment while females' participation seems more linked to features of the ongoing relationship. In a review of studies in the 1970s and 1980s a further major increase in the incidence of oral sex in the period before marriage can be found. From these data it appears that oral sex has become, over the last 50 years, part of the sexual scripts of many young people and is a common, though not necessarily a frequent, component of sexual relations in contemporary marriage.

Variables influencing the timing of marrow transplantation in patients with chronic myelogenous leukemia

The prognosis for patients with chronic myelogenous leukemia (CML) has improved only for patients who can receive marrow transplantation from a histocompatible sibling. The timing of the marrow transplant is made difficult by the high peritransplant mortality of 20% to 35% and a group of patients with a prolonged chronic phase of CML, which can be identified on the basis of prognostic indexes (age, percent blood myeloblasts, spleen size, and platelet count). We have developed a mathematic model and computer program that consider age, prognostic index, and projected survival rate by transplantation to balance the risk of peritransplant mortality against the risk of delaying the transplantation of patients with Philadelphia chromosome-positive CML. The computation assesses the risk of delaying transplantation; it does not offer the option of avoiding transplantation, since long-term survival ultimately requires transplantation. Three prognostic groups were considered as described by Sokal and co-workers (Blood 63:789, 1984) (I, best; II, intermediate; III, worst prognosis). The computation used the projected survival rates of transplantation from the Seattle experience and from the International Bone Marrow Transplant Registry. As an example of the model's utility, we have determined the ratio of the calculated life expectancy to the normal life expectancy for hypothetical patients up to 50 years of age in each of the three prognostic categories. A value of 20% is used for patients who successfully receive transplants after the onset of the accelerated phase. The analysis allows assessment of the risk of delaying transplantation for a finite time in patients with CML. The importance of the method rests in its consideration of multiple variables, including the peritransplant mortality, transplant projected survival before and upon entering the accelerated phase, age, prognostic group, and other risk factors. The program permits a change in these parameters as new information or advances in treatment occur. This analysis does not replace the diagnostic deliberations of the clinician. Rather, it provides a numeric framework for prognosis based on the currently available data. The physician in conjunction with the patient, not the algorithm, makes the decisions of whether and when to transplant.

Ion-selective membrane electrodes for clinical use

We review ion-selective solvent polymeric membrane electrodes for clinical use. The particular requirements that the clinical application set on the membrane are discussed in terms of selectivity, stability, lifetime, and response time. The performance of currently available electrodes is reviewed, with consideration of actual problems that arise in clinical practice.

Ion-selective membrane electrodes for clinical use

We review ion-selective solvent polymeric membrane electrodes for clinical use. The particular requirements that the clinical application set on the membrane are discussed in terms of selectivity, stability, lifetime, and response time. The performance of currently available electrodes is reviewed, with consideration of actual problems that arise in clinical practice.

Sexual scripts: permanence and change

A general introduction to scripting theory is offered, attempting to provide links between macrolevel considerations of sociocultural development and general theories of individual development. The scripting of behavior is examined on three distinct levels: cultural scenarios (instruction in collective meanings), interpersonal scripts (the application of specific cultural scenarios by a specific individual in a specific social context), and intrapsychic scripts (the management of desires as experienced by the individual). These concepts of the scripting of behavior are then applied to sexual behavior. Interpersonal scripts are seen as the ordering of representations of self and other that facilitate the occurrence of a sexual act; intrapsychic scripts represent the ordering of images and desires that elicit and sustain sexual arousal. Issues of stability and change in sexual scripts are then examined in terms of the changing circumstances and requirements associated with movement through the life cycle.

Cell counts in cerebral cortex of an autistic patient

Numbers of neurons and glia were counted in the cerebral cortex of one well-documented case of autism and two age- and sex-matched controls. Areas in which cell counts were made were primary auditory cortex, Broca's speech area, and auditory association cortex. No consistent differences in cell density were found between the brains of the autistic patient and the control patients.

Multicomponent analysis of amino acid transport in human lymphocytes. Diminished L-system transport in chronic leukemic B lymphocytes

We have examined the amino acid transport in B cell chronic lymphocytic leukemia and compared it with the amino acid transport in isolated B lymphocytes from human blood and tonsils. L-system transport was measured with 2-amino-2-carboxy-bicyclo (2,2,1)-heptane, which is a synthetic amino acid whose transport is limited to the L-system. Amino acid uptake was subjected to a multicomponent analysis that partitioned the total uptake into the saturable carrier-mediated transport system and the uptake by diffusion. The maximal velocity of L-system transport in chronic lymphocytic leukemia cells, 81 mumol/1 cell water per min, was less than 10% that of blood B lymphocytes, which was 1,029 mumol/1 cell water per min. The uptake of 2-amino-2-carboxy-bicyclo (2,2,1)-heptane by tonsillar B cells, by a B lymphocyte cell line, and by blood T-lymphocytes was also 10-fold greater than that observed in chronic lymphocytic leukemic cells. Similarly, the L-system uptake of leucine and phenylalanine, which are naturally occurring amino acids usually transported primarily by the L-system, was reduced in chronic lymphocytic leukemic B cells to 15 and 10% of normal B cells, respectively. Total leucine uptake by chronic lymphocytic leukemic cells, however, was sustained at 30% of that expected because of transport via an alternative transport system. The A- or ASC-systems, the other major amino acid transport pathways, were not defective in chronic lymphocytic leukemic cells. These data indicate that there is a specific, profound decrease in L-system carrier-mediated amino acid transport in chronic lymphocytic leukemic B cells, as judged by the system-specific synthetic amino acid, 2-amino-2-carboxy-bicyclo (2,2,1)-heptane. This defect was confirmed by studies with two naturally occurring L-system amino acids, leucine and phenylalanine. This specific abnormality of membrane transport by chronic lymphocytic leukemic B lymphocytes is not shared by other B lymphocyte types, and thus appears to be related to the neoplastic nature of the leukemic B cells rather than to their immunologic subtype.

Neutral carrier electrode for continuous measurement of blood Ca2+ in the extracorporeal circulation

A neutral-carrier-based Ca2+-selective electrode exposed to whole blood exhibited an EMF-stability better than 0.13 mV (approximately 1% change of the initial activity) during 3.7 to 6.6 h. It has been used successfully to monitor ionic Ca2+ in the extracorporeal circulation during administration of calcitonin to dogs. Data simulation shows that the apparent concentration of ionic Ca2+ is affected by the concentration of Na+. A variation in [Na+] by +/- 5 mmol/L from a value of 143 mmol/L used for the calibration leads to uncertainties of +/- 0.8% in the Ca2+ concentration and +/- 0.2% in the Ca2+ activity if 3 mol/L KCl is used as the reference electrode solution. When an isotonic solution was used as reference electrolyte, errors of +/- 0.8% and +/- 1.7%, respectively, were observed.

Neutral carrier electrode for continuous measurement of blood Ca2+ in the extracorporeal circulation

A neutral-carrier-based Ca2+-selective electrode exposed to whole blood exhibited an EMF-stability better than 0.13 mV (approximately 1% change of the initial activity) during 3.7 to 6.6 h. It has been used successfully to monitor ionic Ca2+ in the extracorporeal circulation during administration of calcitonin to dogs. Data simulation shows that the apparent concentration of ionic Ca2+ is affected by the concentration of Na+. A variation in [Na+] by +/- 5 mmol/L from a value of 143 mmol/L used for the calibration leads to uncertainties of +/- 0.8% in the Ca2+ concentration and +/- 0.2% in the Ca2+ activity if 3 mol/L KCl is used as the reference electrode solution. When an isotonic solution was used as reference electrolyte, errors of +/- 0.8% and +/- 1.7%, respectively, were observed.