Biomedical subjects
Publications and source records attributed to J A Scott.
Plasma membrane potential is an important physiologic parameter dependent both upon cellular metabolism and upon the integrity of the cell membrane. Oxygen radicals have been shown to produce significant and early changes in the membrane potential. This data is reviewed along with the physico-chemical origins of the membrane potential and methods of its measurement.
We quantitated the presence of intracellular oxidizing species in response to oxidative stimuli using fluorescent cell analytic techniques. The studies were performed with a laser-activated flow cytometry system using 2',7'-dichlorofluorescin diacetate (DCFDA) as a probe for intracellular oxidation events. Oxygen radical formation was initiated by the addition of FeCl2 or xanthine oxidase to the culture media. Xanthine oxidase and FeCl2 both increased intracellular DCFDA oxidation over control (p less than .001). Increases in intracellular DCFDA oxidation in response to xanthine oxidase exposure were inhibited by extracellular superoxide dismutase, catalase and dimethyl sulfoxide (p less than 0.001), implicating the superoxide anion, hydrogen peroxide, and the hydroxyl radical in producing the changes in intracellular dichlorofluorescein fluorescence. Increases in intracellular DCFDA oxidation in response to xanthine oxidase correlated with loss of cellular viability, as established by decreased plating efficiency. We conclude that relative intracellular oxidation can be quantitated within the cultured renal cell and that some extracellularly generated radicals may be capable of traversing the intact cell membrane to oxidize DCFDA in the cell interior.
A mathematical model of the human eye based on the bioheat transfer equation is developed. The intraocular temperature distribution is calculated using the Galerkin finite element method. A difficulty associated with the development of an accurate model of the human eye is the lack of reliable biological data available on the constants and parameters that are used in the model. These parameters include the thermal conductivities of the ocular tissues, the heat loss from the anterior corneal surface to the surroundings by convection and evaporation, and the convective heat loss from the sclera to the body core. The different values for the parameters reported in the ophthalmic literature are employed in the model, and the sensitivity of the temperature distribution to uncertainties in the parameters is investigated. A set of control parameter values is suggested for the normal human eye. The effect of the ambient temperature and the body-core temperature on the temperature distribution in the human eye is considered.
Long-term industrial exposure to low levels of infrared radiation has for many years been associated with the development of cataracts; the injury mechanism is widely held to be thermal. A finite element model of the human eye is employed to calculate the temperature rises experienced by the intraocular media when exposed to infrared radiation. The model is used to calculate transient and steady-state temperature distributions for various exposure times and a range of incident irradiances. The effect of the eye's natural cooling mechanisms on the heating is investigated. Specific absorption rates in the infrared irradiated eye are presented. For a radiation source of 1500 degrees C, absorption of radiant energy by the iris and the lens combined with conduction of heat from the anterior regions is found to be responsible for increases in the lens temperature of 1-2 degrees C, but under extreme exposure conditions the temperature rises are found to be substantially higher.
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The present study analyzed the changes in Na+-dependent sugar transport and transepithelial electrical resistance as LLC-PK1 cells reorganize into epithelial membranes. Sugar influx increased to reach a maximum 9 h after plating. The increase in the transepithelial electrical resistance, however, showed a significant delay, reaching steady state 15 h after plating. No changes in the electrochemical Na+ gradient were observed during the reorganization of the epithelial membranes. Kinetic analysis and [3H]phlorizin-binding studies showed that the increase in sugar influx resulted from an increase in the number of carriers. Unidirectional sugar influx measurements indicated that the sugar transporters were primarily located at the apical surface of the epithelial cells. These observations are consistent with the hypothesis that the sorting of native proteins occurs intracellularly before their insertion in the apical membrane, or as an alternative that they are randomly inserted, but then immediately sorted such as any carrier could be detected in the basolateral side during the reorganization process. In addition, the results suggest that the functional development of the apical membrane may occur before the complete sealing of the intercellular space during the development of the occluding junctions. Furthermore, development of the sugar transport system and occluding junctions was inhibited by cycloheximide and puromycin but not by actinomycin D, suggesting that the expression of epithelial cell polarization is probably a posttranslational event in the protein synthesis.
The Waveney Goal Post Appliance was designed to stabilize the second supportive phase of Clark's Twin Block therapy (1982). It is to be worn full time and is simple to construct, and well tolerated. It can be used to stabilize the dentition following most forms of functional treatment.
Current therapy for dural sinus thrombosis consists of supportive measures, anticoagulation therapy, and in some cases intravenous infusion of a fibrinolytic agent. A patient with extensive dural sinus thrombosis was successfully treated with local urokinase infusion. The technique and rationale for this aggressive therapy are discussed.
A system for extending continuing education in genetics to nurses and other practicing health professionals was developed in an eight-state area. Coordinators from state agencies received special training at the University of Colorado to administer the course in local communities. A combination of classroom instruction, independent study, computer-assisted instruction, and case-study methods for course delivery was included. More than 300 health professionals have completed the course, and 14 coordinators from seven states have been prepared to administer future courses. The model has demonstrated high potential for replication in other regions.
The first training program for genetic counselors began in 1969. Since then a number of other programs have been developed and more than 650 individuals have graduated from these programs. This article reviews the development and current status of training opportunities for genetic counselors. Twelve programs that currently grant a master's-level degree in genetic counseling are reviewed. Other areas, such as certification and licensure, that reflect genetic counseling training or such issues of professional growth as continuing education and career advances are addressed.
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Cell membrane potential was measured with a flow cytometer by quantitating the intracellular accumulation of a fluorescent cationic carbocyanine dye. We used this system to demonstrate depolarization upon the addition of hydrogen peroxide (10-1,000 microM) and ferrous chloride (25-100 microM) to cultures of either neonatal rat myocardial or LLC-PK1 renal epithelial cells. Ferrous chloride-induced depolarization was prevented by superoxide dismutase, catalase and dimethyl sulfoxide, suggesting roles for the superoxide anion, hydrogen peroxide and the hydroxyl radical in effecting this depolarization, possibly through a Fenton-type reaction mechanism. Supplementation of either cell type with 2 microM tocopherol acid succinate during growth in tissue culture, prior to exposure to the oxidizing agent, decreased the magnitude of the depolarization in both cell types. The results are consistent with a role for tocopherols in scavenging free radical species responsible for the depolarization of the cell membrane.
We employed a carbocyanine dye (1,1',3,3,3',3'-hexamethylindocarbocyanine iodide) to measure the plasma membrane potential of LLC-PK1 renal epithelial cells exposed to either xanthine oxidase-generated oxygen radicals or to hydrogen peroxide. Measurements were performed using a fluorescent-activated cell sorter to record fluorescence on a cell by cell basis. Initial exposure of cells to low concentrations of either H2O2 or xanthine oxidase resulted in a transient increase in membrane potential relative to control cells (P less than 0.001), followed by an exponential decline in potential (P less than 0.001). The addition of extracellular catalase diminished the H2O2-related decline in potential, consistent with a role for hydrogen peroxide in producing this effect. Pretreatment of cells with inhibitors of intracellular catalase and superoxide dismutase prior to exposure to xanthine oxidase caused an even larger decline in potential (P less than 0.001). Cells could be partially protected from the radical-mediated loss of potential by incubating them in a hypertonic (400 mosmolal) environment during radical exposure. Similarly, the loss of membrane potential was increased after incubation of cells in a hypotonic (200 mosmolal) environment during radical exposure. These observations are consistent with a reduction in membrane potential effected by exposure to oxygen radicals (including superoxide anion and hydrogen peroxide). This reduction may be prevented, in part, by radical scavenging enzymes and by reducing the degree of cellular swelling in response to oxygen radical exposure.
Surgery remains the treatment of choice for massive and recurrent hemoptysis. In some instances, however, immediate surgical intervention is contraindicated. In these situations, bronchial artery embolization (BAE) has proved to be a successful definitive treatment for non-surgical candidates and a palliative therapy in patients requiring hemodynamic stabilization prior to surgery. The most serious complication of BAE is spinal cord ischemia. This relates directly to the potential anastomotic connections between the bronchial circulation and the anterior spinal artery. Somatosensory evoked potentials (SSEPs) have been used in the past to monitor spinal cord ischemia during procedures that threaten the vascularity of the spinal cord. The authors report two cases in which SSEPs were employed to monitor spinal cord ischemia during bronchial artery embolization.
The formation of intercellular communication during epithelial reorganization of LLC-PK1 cells was studied with a new, nondisruptive flow cytometric technique. The assembly of these junctions, as demonstrated by cell-to-cell transfer of the fluorescent dye carboxy dimethyl fluorescein, occurs very early during epithelial reorganization. Close cell-to-cell interaction is required for the assembly to occur. Low temperature, treatment with 10(-3) M ouabain, or treatment with the Ca2+ ionophore A23187 inhibits assembly of these junctions. Removal of Ca2+ from the incubation medium, on the other hand, has no effect. Cycloheximide (10(-6) M) is also without effect, suggesting that protein synthesis is not required during the assembly of the junctions and that either the trypsin used to disperse the cells does not affect the junctional components or the cells have a rather extensive reserve pool of junctional precursors. The concomitant delay in the development of intercellular communication and the reorganization of the epithelial membrane, as previously observed with cells in asynchronous growth [Am. J. Physiol. 251 (Renal Fluid Electrolyte Physiol. 20): F978-F987, 1986], is consistent with the theory that junctional intercellular communication coordinates cellular activity during epithelial reorganization.
Na+ influx and efflux from confluent monolayers of an epithelial cell line with multiple differentiated characteristics of the straight segment of the renal proximal tubule were studied in the presence and absence of a pH gradient. The results show that Na+ influx in the absence of a pH gradient is inhibited by amiloride as well as by complete replacement of Cl- by an impermeable anion, such as isethionate. Dissipation of cell membrane potential by increasing the potassium concentration of the extracellular medium in the presence of valinomycin also inhibited Na+ influx, whereas sodium influx induced by an H+ gradient was not affected. Inhibition of Na+ influx by different maneuvers produced hyperpolarization of the plasma cell membrane, as would be expected if the sodium movement involved net displacement of charges. Calcium and other divalent and trivalent cations also inhibited Na+ influx measured in the absence of an H+ gradient. Na+ influx induced by a pH gradient, however, was not affected. Like the Na+-H+-exchange system, the conductive Na+ pathway is localized in the apical membrane of the epithelial cells. From these results, we conclude that at least a fraction of transepithelial Na+ transport in LLC-PK1 monolayers occurs through a simple rheogenic transport system.
Radionuclide imaging is the diagnostic procedure of choice for evaluation of acute disorders of the scrotum, permitting rapid differentiation of torsion of the spermatic cord from inflammatory processes. The method is less successful in diagnosing torsion of the testicular appendages. In the majority of reported cases of torsion of the appendix testis the scan appears normal. In a very limited number of cases increased perfusion to the affected side has been noted. We report a case of metachronous torsion of both the appendices testis. In each instance, there was decreased tracer uptake on the affected side, suggestive of early torsion of the testicle. The sequential involvement of each testis with a nine month interval between respective torsions provides a unique example where each testis serves, sequentially, as a normal control for the torsed contralateral appendage.
Studies of Na+ and H+ transport by confluent monolayers of the epithelial cell line LLC-PK1 were performed to verify the presence of a Na+/H+ exchange system. The presence of an outwardly directed H+ gradient produced a large stimulation of Na+ influx measured under net flux conditions. Amiloride (10(-3) M) completely inhibited Na+ influx stimulated by the H+ gradient and part of the Na+ influx measured in the absence of a pH gradient. Half-maximal inhibition of the Na+ influx stimulated by a pH gradient at 143 mM Na was observed at 5 microM amiloride. The presence of an inwardly oriented proton gradient also stimulated Na+ efflux from Na+-loaded cells. The stimulation was completely inhibited by the presence of 10(-3) M amiloride in the washout medium. These results indicate that this system could operate in the opposite direction depending on the orientation of the Na+ and H+ gradient. Incubation in Na+-free medium or in the presence of 10(-3) M ouabain resulted in a dramatic decrease of H+ release from LLC-PK1 cells. This H+ release was largely, although not completely, inhibited by 10(-4) M amiloride. Neither chloride substitution by the impermeable anion isethionate nor incubation in the presence of the ionophore valinomycin in high K+ medium affected Na+ influx by stimulated by a pH gradient. Inhibition of the Na+ influx by amiloride occurred only from the apical side of the monolayer. These results indicate that the Na+/H+ exchange system in LLC-PK1 monolayers is specifically localized in the apical membrane of the epithelial cells.