Clinicians hold the key to profitable managed care contracting.

A managed care contract's effect on the financial health of an organization is related in part to utilization and quality management issues. Physicians and other clinicians who are involved in case management can illuminate how these issues, in relation to the contract terms, can affect the organization's bottom line. Clinicians should be part of a contract-negotiating team that also includes financial professionals and contract negotiators, in addition to legal counsel.

Temperature dependence of Ca2+ wave properties in cardiomyocytes: implications for the mechanism of autocatalytic Ca2+ release in wave propagation.

Digital imaging microscopy of fluo-3 fluorescence was used to study the velocity and shape of intracellular Ca2+ waves in isolated rat cardiomyocytes as a function of temperature. Decreasing the temperature from 37 to 17 degrees C reduced the longitudinal wave velocity by a factor of 1.8 and remarkably slowed the decay of [Ca2+]i in the trailing flank of a wave. Using image analysis, rise times, and half-maximum decay times of local Ca2+ transients, which characterize the processes of local Ca2+ release and removal, were determined as a function of temperature. Apparent activation energies for wave front propagation, local Ca2+ release, and local Ca2+ removal were derived from Arrhenius plots and amounted to -23, -28, and -46 kJ/mol, respectively. The high activation energy of Ca2+ removal, which arises from the activity of the sarcoplasmic reticulum (SR) Ca2+ ATPase, relative to those of longitudinal wave propagation and local Ca2+ release excludes the hypothetical mechanism of regenerative "spontaneous Ca2+ release," in which Ca2+ that has been taken up from the approaching wavefront triggers Ca2+ release at a luminal site of the SR. It is consistent, however, with the hypothesis that Ca2+ wave propagation is based on Ca(2+)-induced Ca2+ release where Ca2+ triggers release on the cytosolic face of the SR.

Anisotropic propagation of Ca2+ waves in isolated cardiomyocytes.

Digital imaging microscopy of fluor-3 fluorescence was used to study the propagation of intracellular Ca2+ waves in isolated adult rat cardiomyocytes from 17 to 37 degrees C. Ca2+ waves spread in both transverse and longitudinal direction of a myocyte. Transverse propagation was pronounced in waves starting from a focus at the edge of a myocyte and in waves following an irregular, curved path (spiral waves). For the former type of waves, propagation velocities were determined. Both transverse and longitudinal wave components propagated at constant velocity ranging from 30 to 125 micron/s. Myocytes were anisotropic with respect to wave propagation: waves propagated faster in the longitudinal than in the transverse direction. The ratio between longitudinal and transverse velocity increased from 1.30 at 17 degrees C to 1.55 at 37 degrees C. Apparent activation energies for transverse and longitudinal wave propagation were estimated to be -20 kJ/mol, suggesting that these processes are limited by diffusion of Ca2+. Direction-dependent propagation velocities are interpreted to result from the highly ordered structure of the myocytes, especially from the anisotropic arrangement of diffusion obstacles such as myofilaments and mitochondria.

[Regulation of the catalytic activity of the monooxygenase enzyme system depending of the substrate structure and phospholipid composition of the model membrane]. / Reguliatsiia kataliticheskoi aktivnosti monooksigenaznoi fermentoi sistemy v zavisimosti ot struktury substrata i fosfolipidnogo sostava model'noi membrany.

A comparative study of pentoxy- and benzyloxyresorufin dealkylation by a monooxygenase enzyme system in dilauroylphosphatidylcholine micelles and in proteoliposomes was carried out. In proteoliposomes whose lipid matrix is formed by double phospholipid mixtures, a cooperative regulation of the oxidation reaction was found. It was shown that the cooperativity of this process depends on the substrate type as well as on the phospholipid composition of the vesicles and decreases during peroxide oxidation of lipids. The results obtained are discussed in terms of protein-protein and protein-phospholipid interactions in the oligomer ensembles consisting of several cytochrome P-450 LM2 molecules.

31P-NMR spectroscopy of phosphate compartmentation during ischaemia in hearts protected by cardioplegic treatment.

Four tissue compartments, differing in proton and inorganic phosphate concentration, were resolved by 31P-NMR spectroscopy in samples from dog hearts after cardioplegic treatment with HTK solution. Inversion of the physiological cytoplasmic-mitochondrial pH gradient was observed. The considerable ensuing acidosis of the matrix is discussed with regard to a possible delocalization of ferrous ions.

A perfusion chamber for high-resolution light microscopy of cultured cells.

A perfusion chamber suitable for general microscopic work on upright and inverted microscopes with cultured cells is described. The device features a minimal internal volume and large field of view within small outer dimensions. In particular the chamber body is very flat to accommodate large-aperture condenser and objective lenses. It is constructed of innocuous, sterilizable materials, incorporates permanent seals for the windows, is robust and simple to use.

Heterogeneity of biotransformation of fluoranthene in perifused liver cells.

Pathways of biotransformation of the carcinogenic polycyclic hydrocarbon fluoranthene in individual isolated perifused liver cells were delineated using noninvasive microfluorescence spectroscopic techniques. An example of heterogeneity of coupling between phase I and phase II enzymes detected in a population of beta-naphthoflavone-induced rat liver cells demonstrates the usefulness of the experimental model of perifused liver cells.

Effects of nitrogen mustard on potassium transport systems and membrane structure of Ehrlich ascites tumor cells.

By Ehrlich ascites tumor cells 86Rb+ has been shown to be a suitable tracer for K+-transport. Sixty percent of the total 86Rb-uptake into these cells is ouabain-inhibitable, 30% is sensitive to furosemide and 10% enters the cells by ouabain and furosemide-insensitive systems. N-Mustard inhibits both the ouabain-sensitive and the furosemide-inhibitable systems. The uptake which is resistant to both inhibitors is not affected by the alkylating drug. At N-mustard concentrations below 10 microM, the reduction of the Rb-uptake is predominantly due to the inhibition of the furosemide-sensitive transport. Higher concentrations are required before a significant inhibition of the ouabain-sensitive transport can be observed. The dose response curve of the furosemide-sensitive transport--not, however, of the ouabain inhibitable pump--corresponds to the dose response curve for the antiproliferative activity of N-mustard. The recovery of the furosemide-sensitive transport after a single exposure to N-mustard is relatively slow and--in contrast to the repair of DNA cross-links--is characterized by an initial 4-hr lag period. Furosemide alone does not interfere with cell multiplication. The inhibition of the transport system alone does, therefore, not explain the antitumor activity of N-mustard. The effect is discussed as a marker for membrane lesions after exposure to alkylating agents. In order to investigate the influence of N-mustard on membrane structure, membranes were labelled with diiodofluoresceiniodoacetamide. Anisotropy curves obtained from time-dependent depolarization of delayed fluorescence indicated a mustard induced immobilization of membrane constituents. Lateral diffusion of lipophilic probes was determined by following the quenching of fluorescence of pyrene by cetylpyridinium. The latter studies yielded no evidence for a change in membrane lipid fluidity. The data are interpreted as the results of cross-links of membrane proteins by the bifunctional alkylating agent.

Anoxia influences the lateral diffusion of a lipid probe in the plasma membrane of isolated cardiac myocytes.

Using the technique of fluorescence photobleaching recovery we have measured the characteristics of lateral diffusion of oleylaminofluorescein (OAF) in the plasma membrane of isolated rat cardiac myocytes under normoxic and anoxic conditions. The normoxic pattern is one of slow diffusion and low recovery (D = 1.8 +/- 0.3 X 10(-10)cm2/s, r = 0.44 +/- 0.059), while under anoxic conditions faster diffusion and higher recovery (D = 2.5 +/- 0.4 X 10(-9)cm2/s, r = 0.58 +/- 0.063) are observed, the change proceeding via an intermediate stage with a yet faster diffusing species (D greater than 2.5 X 10(-9)cm2/s). The process is reversible. We hypothesize that under normoxic conditions the lateral diffusion of OAF is hindered by the division of the cell membrane into a patchwork of more or less isolated domains by lateral and longitudinal barriers of spectrin (7, 13) which are rearranged under anoxic conditions to another pattern which permits the label greater, but still not unrestricted, freedom of movement.

Cytochrome P-450 rotamers control mixed-function oxygenation in reconstituted membranes. Rotational diffusion studied by delayed fluorescence depolarization.

1. Rotational diffusion of purified rabbit-liver microsomal cytochrome P-450 LM2 in reconstituted lipid-vesicle membranes was investigated by measurement of time-dependent polarized emission of delayed fluorescence. 2. Cytochrome P-450 labelled with diiodofluorescein iodoacetamide exhibited strict uniaxial rotation about the normal to the membrane. 3. Benzphetamine retards rotation, while reduction of the cytochrome P-450 substrate-complex accelerates rotation. 4. A model is proposed in which cytochrome P-450 forms disc-shaped rotamers immersed in the bilayer membrane to a depth which is varied by substrate-induced and redox state-dependent conformational changes. The model describes a regulating mechanism of the electron transfer-controlling mixed-function oxygenation.

Nucleotide metabolism by microsomal UDP-glucuronyltransferase and nucleoside diphosphatase as determine by 31P nuclear-magnetic-resonance spectroscopy.

31P n.m.r. spectroscopy was used to study the nucleotide kinetics of UDP-glucuronyltransferase and associated reactions in the liver microsomal fraction. The effects of Mg2+ and EDTA on these reactions were investigated qualitatively. It was found that the rabbit microsomal fraction has no nucleoside pyrophosphatase activity, that UDP was immediately hydrolysed and that it was released from the microsomal surface. Reverse glucuronyltransferase could be demonstrated. The results are discussed with reference to functional coupling of UDP-glucuronyltransferase to other enzymes and the effects of Mg2+ and EDTA on the system.