Determination of phosphonoformic acid in human plasma and urine by high-performance liquid chromatography with electrochemical detection

Trisodium phosphonoformate (foscarnet) is used in the treatment of cytomegalovirus infections in immunocompromised patients, such as bone marrow and renal transplant recipients, as well as patients with the acquired immune deficiency syndrome. A simple high-performance liquid chromatographic assay is described using an electrochemical detector. The method is accurate, precise and reproducible. Hydrochlorothiazide is used as the internal standard. This assay allows measurement of foscarnet in biological fluids at concentrations as low as 33 microM. This method is being used for the analysis of samples in clinical trials and is important in the evaluation of the pharmacokinetic disposition of the drug.

Neural network model using interpattern association

This paper investigates a neural network model-interpattern association (IPA) model-in which the basic logical operations are used to determine the interpattern association (i.e., association between the reference patterns), and simple logical rules are applied to construct tristate interconnections in the network. Computer simulations for the reconstruction of similar English letters embedded in the random noise by the IPA model have shown improved performance compared with the Hopfield model. A 2-D hybrid optical neural network is used to demonstrate the usefulness of the IPA model. Since there are only three gray levels used in the interconnection weight matrix for the IPA model, the dynamic range imposed on a spatial light modulator is rather relaxed, and the interconnections are much simpler than the Hopfield model.

Ethanol protects the heart against the calcium paradox injury

Rat hearts were depleted of Ca2+ (less than 10(-9) M) for 10 min, followed by 15 min of Ca2+-repletion. The calcium paradox injury occurs during Ca2+-repletion, after a period of calcium depletion. The calcium paradox injury was assessed by percent recovery (hemodynamics, [Ca2+]i, and energy levels) during Ca2+-repletion. A decrease in Na+ concentration during Ca2(+)-depletion did not allow for recovery during Ca2(+)-repletion, however 2.5% and 5% ethanol during Ca2(+)-depletion allowed for an approximate 50% recovery during Ca2(+)-repletion. A combination of ethanol (2.5% or 5%) with a low extracellular Na+ concentration (88 mM) allowed for complete recovery. Ethanol prevented a depletion of diastolic [Ca2+]i during Ca2(+)-depletion, and allowed for a return of normal diastolic [Ca2+]i during Ca2(+)-repletion. Ethanol modulates the activity of the Na+/Ca2+ exchanger and protects against the Ca2(+)-paradox injury.

Two-dimensional programmable optical neural network

A 2-D hybrid optical neural network using a high resolution video monitor as a programmable associative memory is proposed. Experiments and computer simulations of the system have been conducted. The high resolution and large dynamic range of the video monitor enable us to implement a hybrid neural network with more neurons and more accurate operation. The system operates in a high speed asynchronous mode due to the parallel feedback loop. The programmability of the system permits the use of orthogonal projection and multilevel recognition algorithms to increase the robustness and storage capacity of the network.

Phase measurement of a Fourier spectrum by a fringe-scanning phase-conjugate interferometer

We present a novel method for obtaining the phase distribution of an object spectrum by using a fringe-scanning phase-conjugate interferometer. A detailed analysis of the proposed technique is provided, and experimental demonstrations for validating this technique are also given. The major advantages of this method are its potentially high accuracy and its low space-bandwidth-product requirement for the detection system.

High-sensitivity fluorescence detector fluorescein isothiocyanate derivatives of amino acids separated by capillary zone electrophoresis

A fluorescence detector has been developed for capillary zone electrophoresis that produces a ten-fold improvement in precision compared with the previous state-of-the-art in fluorescence detection. This instrument, which is based on a sheath-flow cuvette flow chamber and a 0.05-W argon ion laser beam, combines a high numerical aperture collection optic, N.A = 0.65, with a high quantum yield photomultiplier tube, phi approximately = 0.15 at the wavelength of maximum emission. Detection limits (3 sigma) range from the injection of 1.7 . 10(-21) mol (1.3 . 10(-12) M) of fluorescein isothiocyanate (FITC)-labeled arginine, the best case, to 6 . 10(-21) mol (5.6 . 10(-12) M) of FITC-cysteine, the worse case. Signal linearity extends for at least five orders of magnitude from the detection limit to greater than 10(-16) mol (10(-7) M) injected.

Integrated optical interferometer with a stacked waveguide structure

An integrated optical interferometer consisting of Al(2)O(3) waveguides placed upon an oxidized Si substrate is presented. The two waveguides forming the branches of the interferometer are stacked on top of each other with a SiO(2) buffer layer in between. The interferometer further contains two directional couplers which are realized by bending the upper waveguide toward the lower one. A masked evaporation technique is introduced to fabricate the directional couplers. The operation of the interferometer is confirmed in temperature-sensing experiments while the application of the interferometer to humidity measurement is discussed.

Human antithrombin II (AT3) gene length polymorphism revealed by the polymerase chain reaction

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Grating-encoded multichannel photorefractive incoherent-to-coherent optical conversion

A dynamic multichannel incoherent-to-coherent optical converter based on the photorefractive effect of SBN:Ce is described. A number of grating-encoded input images, illuminated by incoherent light, are projected onto the crystal to yield photoinduced phase gratings. Coherent positive replicas of these images are simultaneously reconstructed by a coherent read beam. A simple theoretical description of this converter and corresponding experimental results are presented.

Effects of perfusion pressure on energy and work of isolated rat hearts

A chemomechanical study of hypertrophied hearts of 6-month-old spontaneously hypertensive rats (SHR) and that of age-matched Wistar-Kyoto (WKY) rats was carried out, analyzing the response of the heart to steady-state changes in coronary perfusion pressure. The ratio of heart (dry)-to-body (wet) weight of WKY rats was 0.37 +/- 0.02 (10(-3] and for SHR was 0.58 +/- 0.03 (10(-3] (p less than 0.01). In the apex-ejecting, isolated, pyruvate-perfused working hearts of WKY rats and SHR, coronary flow was constant when coronary perfusion pressure was set between 140 and 190 cm H2O (range of autoregulation). Coronary flow was perfusion pressure dependent when the coronary perfusion pressure was set below 110 cm H2O for both WKY rats and SHR. Cardiac output, developed pressure, rate of pressure development (dP/dt), and oxygen consumption were constant in the range of autoregulation but decreased in the direction of coronary flow when coronary flow was reduced by a drop in perfusion pressure. Similarly, the phosphorylation potential, phosphocreatine, adenosine triphosphate, and cyclic adenosine monophosphate were constant in the range of autoregulation but decreased directionally with coronary perfusion pressure below 110 cm H2O for both SHR and WKY rats. There was a significantly lower phosphorylation potential in SHR as compared with WKY rats when coronary perfusion pressure was reduced to 80 cm H2O. In the region of autoregulation, coronary flow and oxygen consumption were significantly less in SHR, although developed pressure was significantly greater at both high and low workloads.(ABSTRACT TRUNCATED AT 250 WORDS)

Reversibility of chronic alcohol cardiac depression: 31P magnetic resonance spectroscopy in hamsters

In order to investigate the reversibility of chronic alcohol cardiac depression, hamsters were fed with 50% ethanol for 3 1/2 months, reaching serum alcohol levels of 0.13 +/- 0.11 g/dl (mean +/- SD). Alcohol was then withdrawn for 2 days. Isolated hearts were perfused according to a modified Langendorff method. Energy metabolites were studied using 31P magnetic resonance spectroscopy of isolated perfused hearts standardized by HPLC analysis of freeze-clamped tissue. Total intracellular calcium [Ca2+]i was measured with atomic absorption spectrophotometry, marking the extracellular space in vivo with K(CoEDTA). In alcohol-treated hamster hearts developed pressure was significantly depressed compared to controls. End-diastolic pressure was significantly increased. Coronary flow was not changed, whereas oxygen consumption and high-energy phosphate levels were significantly depressed. Intracellular pH was significantly decreased. [Ca2+]i was significantly increased. Heart weights were significantly lower. After alcohol withdrawal ventricular function, high-energy phosphate levels, and [Ca2+]i were not significantly different from control. The results indicate that chronic alcohol consumption depresses ventricular function and energy levels and also leads to myocardial acidosis. The increase in intracellular calcium likely causes mitochondrial dysfunction. Withdrawal of alcohol is associated with reversibility of functional and energetic cardiac depression.

The human villous cytotrophoblast: interactions with extracellular matrix proteins, endocrine function, and cytoplasmic differentiation in the absence of syncytium formation

Human syncytiotrophoblasts are derived from villous cytotrophoblasts by cell fusion. Coincident with this morphologic transformation, trophoblasts acquire specific endocrine functions, including elaboration of chorionic gonadotropin (hCG). We wondered if syncytia formation was a prerequisite for biochemical differentiation or simply was one part of the differentiation program. By growing purified human cytotrophoblasts under serum-free conditions and manipulating the culture surface, we were able to disassociate morphologic from biochemical differentiation. We have shown previously (Endocrinology 1986, 118:1567) that human cytotrophoblasts grown in the presence of fetal calf serum flatten out, aggregate, and form functional syncytiotrophoblasts in vitro over 24-96 hr. Here we demonstrate that when grown in the absence of serum, the cells do not undergo these morphologic changes, but remain as individual spherical cells. If the culture surface was precoated with fibronectin or a variety of collagens, but not albumin, the cells regained their ability to flatten, aggregate, and form syncytia. Attachment to and syncytia formation on fibronectin was blocked by the addition of the R-G-D-S-containing peptide, Gly-Arg-Gly-Asp-Ser-Pro. Attachment to and syncytia formation on type I collagen was blocked by anti-human fibronectin F(ab')2 fragments, while association with type IV collagen was not affected by this antibody, suggesting that fibronectin mediates trophoblast association with type I collagen, but not type IV. Although syncytia formation did not occur when cytotrophoblasts were cultured under serum-free conditions in the absence of ECM proteins, biochemical differentiation was not affected. These cells secreted hCG at the same rate under serum-free conditions whether they were plated on plastic only--which prevented syncytia formation--or fibronectin, laminin or, type IV collagen--which allowed syncytia formation to occur. Furthermore, cytoplasmic differentiation in the absence of syncytia formation was confirmed by performing transmission electron microscopy on cytotrophoblasts grown under serum-free conditions in the presence of 8-bromo-cAMP. We conclude that syncytia formation is not a prerequisite for biochemical differentiation, but simply part of the trophoblast differentiation program.

Multibeam coupling in photorefractive SBN:Ce

Theoretical and experimental results are presented for simultaneous multibeam coupling in photorefractive SBN:Ce. Within a single crystal, multiple signals are amplified through a coupling process that employs a single pump. The coupling gain of each signal results from coupling both between the pump and the signal and between different signals. The amount of gain that each signal receives is dependent on the intensity of the incident signal; thus a competition for the gain exists among the various signals.

31P and 1H magnetic resonance spectroscopy of acute alcohol cardiac depression in rats

Cardiac depression in the isolated rat heart perfused with 4% ethanol was correlated with intracellular phosphate energetics and tissue water distributions. Energy metabolites were assessed using 31P magnetic resonance spectroscopy (MRS) and correlated to the mitochondrial redox state using epicardial surface fluorometry. Changes in myocardial water compartmentation were measured by using 1H NMR spectroscopy with an extracellular chemical-shift reagent (DyTTHA) and correlated to results of 2D echocardiography (2DE). During alcohol perfusion there was a significant decrease in developed pressure and in coronary flow. No change was seen in ATP, PCr, pHi, Pi, or NADH. After withdrawal of alcohol from the perfusate cardiac function reverted to control values without a depletion of energy levels. During alcohol perfusion 1H MRS showed a marked redistribution of water from the intra- to the extracellular space, corresponding to a 35% left ventricular wall thinning confirmed by 2DE. The results indicate that acute alcohol cardiac depression is related to a dehydration of myocardial cells, but is not associated with intracellular acidosis or energy depletion.

Increased left ventricular diastolic stiffness in the early phase of hereditary cardiomyopathy

Isolated hearts from normal and cardiomyopathic hamsters (160 to 180 days of age) were perfused through the aorta and assessed by echocardiographic and 31P-NMR (nuclear magnetic resonance) techniques. A decreased left ventricular systolic pressure in cardiomyopathic hamsters was associated with diminished cardiac size and left ventricular wall thickness. However, the ratio of inner/outer cross-sectional area and estimated left ventricular volume at any given left ventricular weight was significantly higher, indicating relative left ventricular chamber enlargement in cardiomyopathic hamsters. Left ventricular volumes were increased with an intraventricular balloon. Gradual inflation of the balloon resulted in increments of left ventricular systolic and developed stress that rose to the same values in both groups. At this point, the normalized stress-strain relationship was approximately two times steeper for cardiomyopathic hamsters, while at lower strain values the diastolic stress in cardiomyopathic hamsters was less than in controls, possibly due to cardiac dilatation. Almost the same degree of dilatation was induced in control hearts by the acute addition of 1% alcohol, but it was not followed by increased diastolic stiffness. Examination of hearts by 31P-NMR techniques revealed a decreased phosphocreatine/inorganic phosphate (PCr/Pi) ratio in the cardiomyopathic hamsters that progressed further with balloon inflation and was associated with a relative fall in PCr and adenosine triphosphate (ATP) content. Results suggest increased diastolic stiffness in cardiomyopathic hamsters, which was not seen in acute cardiac depression with alcohol. Diastolic volume overload with increased wall stress is probably the major factor contributing to increased diastolic stiffness early in the cardiomyopathy.

Mechanics and energetics of overstretch: the relationship of altered left ventricular volume to the Frank-Starling mechanism and phosphorylation potential

Isovolumic perfused rat hearts containing an intraventricular balloon were used to assess the effects of incremental balloon volumes on developed pressure, oxygen consumption, coronary flow, phosphorylation potential obtained by P-31 nuclear magnetic resonance, wall thickness obtained by two-dimensional echocardiography, and diastolic wall stress. Three phases in developed pressure were noted: (1) volumes from 0 to 150 microliter resulted in a continuous increase in developed pressure; (2) with volumes from 150 to 250 microliter, developed pressure remained constant whereas developed (systolic) and diastolic wall stress rose sharply; and (3) with volumes from 250 to 400 microliter, developed pressure fell whereas developed (systolic) and diastolic wall stress continued to rise. The ln [(PCr)/(Pi)] was in synchrony with oxygen consumption at 0 and 50 microliter balloon volumes, and then diverged at volumes greater than 100 microliter. Oxygen consumption increased from 0 to 50 microliter, was constant from 50 to 250 microliter balloon volume, and then declined. The ln [(PCr)/(Pi)] fell precipitously at balloon volumes greater than 100 microliter, most likely limited by oxygen consumption. Coronary flow did not change significantly until 250 microliter or more of water was added to the balloon, and then it started to decline. Volumes greater than 100 microliter result in overstretch of myofibers, as observed by the precipitous decline in ln [(PCr)/(Pi)], and the steep increase in diastolic wall stress. With excessive volume loading, the drop in phosphorylation potential, ln [(PCr)/(Pi)], appears to contribute to the decrease in developed pressure.

Reversibility of acute alcohol cardiac depression: 31P NMR in hamsters

Isolated hamster hearts were perfused with 2% ethanol for 30 min and then reequilibrated with control medium. One group of hamsters was pretreated with verapamil. Another group received diltiazem. Myocardial verapamil levels were 9.5 +/- 0.7 mg/g dry wt; diltiazem levels were 22 +/- 7 mg/g dry wt. Energy metabolites were assessed by using 31P NMR standardized with high-pressure liquid chromatography of freeze-clamped tissue. Intracellular calcium was measured by atomic absorption spectrophotometry, marking the extracellular space with K(CoEDTA). After 30 min of perfusion, untreated hamster hearts showed a 74% decrease in developed pressure, a marked increase in end-diastolic pressure, a decrease of ATP from 9.8 to 8.8 mmol, and an increase of Pi from 6.7 to 9.8 mmol, but no change of phosphocreatine (PCr) or intracellular pH (pHi). Verapamil pretreatment partially prevented cardiac depression during alcohol perfusion. Whereas diltiazem had no protective effect. After reequilibration, developed pressure and oxygen consumption significantly exceeded control values. ATP decreased to 8 mmol; pHi, PCr, and Pi showed no significant change. Verapamil-pretreated hearts showed better performance than untreated hearts without change in PCr and Pi, whereas ATP dropped slightly to 8.7 mmol. Thus, functional cardiac depression resulting from acute alcohol exposure is reversible. Increased intracellular calcium levels during alcohol exposure normalized after the removal of alcohol. There was no major change in high-energy phosphates during alcohol exposure or after the removal of alcohol. Verapamil protects the heart from functional depression during alcohol exposure without affecting energy resources.

Chemomechanics of altered perfusion pressure in rat hearts

In an apex-ejecting isolated perfused working rat heart, as well as isovolumic preparations of rat hearts, perfusion pressure was studied independent of afterload. A decrease in perfusion pressure caused an immediate decrease in developed pressure (10s). There was a significant increase in free Pi and the phosphorylation potential after 20-30 min of perfusion at a reduced coronary flow induced by a reduction in perfusion pressure. Developed pressure decreased prior to the phosphorylation potential and inorganic phosphate; however, the phosphorylation set a limit to maximum work performance. At a perfusion pressure of 140 cm H2O and an afterload of 140 cm H2O, work imposed on the heart was maximum; there was no further increase in work.