An Experimental and Theoretical Study of the Reactions OIO + NO and OIO + OH

The kinetics of the reaction OIO+NO were studied by pulsed laser photolysis/time-resolved cavity ring-down spectroscopy, yielding k(235-320 K)=7.6(+4.0)(-3.1) x 10(-13) exp[(607+/-128)/T] cm3 molecule-1 s-1. Quantum calculations on the OIO+NO potential-energy surface show that the reactants form a weakly bound OIONO intermediate, which then dissociates to the products IO+NO2. Rice-Ramsberger-Kassel-Markus (RRKM) calculations on this surface are in good accord with the experimental result. The most stable potential product, IONO2, cannot form because of the significant rearrangement of OIONO that would be required. The reaction OIO+OH was then investigated by quantum calculations of the relevant stationary points on its potential-energy surface. The very stable HOIO2 molecule can form by direct recombination, but the bimolecular reaction channels to HO2+IO and HOI+O2 are closed because of significant energy barriers. RRKM calculations of the HOIO2 recombination rate coefficient yield krec,0=1.5x10(-27) (T/300 K)(-3.93) cm6 molecule-2 s-1, krec,infinity=5.5x10(-10) exp(46/T) cm3 molecule-1 s-1, and Fc=0.30. The rate coefficients of both reactions are fast enough around 290 K and 1 atm pressure for these reactions to play a potentially important role in the gas phase and aerosol chemistry in the marine boundary layer of the atmosphere.

Pharmacodynamics and pharmacokinetics of eptifibatide in patients with acute coronary syndromes: prospective analysis from PURSUIT

BACKGROUND

Platelet deposition and aggregation are central to the pathogenesis of ischemic complications of acute coronary syndromes (ACS). Pharmacodynamic effects of the platelet glycoprotein IIb/IIIa antagonist eptifibatide have been delineated in healthy subjects but not in patients with ACS. We assessed effects of eptifibatide on ex vivo platelet aggregation in patients enrolled in the Platelet glycoprotein IIb/IIIa in Unstable angina: Receptor Suppression Using Integrilin (eptifibatide) Therapy (PURSUIT) trial of ACS.

METHODS AND RESULTS

Patients were randomly assigned to an intravenous bolus (180 microgram/kg) and 72-hour infusion of eptifibatide (2.0 microgram/kg per minute, n=48) or placebo (n=50). We assessed correlations of plasma eptifibatide levels with receptor occupancy and inhibition of ex vivo platelet aggregation at 5 minutes and 1, 4, 24, 48, and 72 hours during treatment and 4 and 8 hours after termination of infusion. Blood was collected in buffered citrate and D-phenylalanyl-L-prolyl-L-arginine chloromethylketone anticoagulants. Although eptifibatide produced profound, prolonged inhibition of platelet aggregation during therapy, aggregation appeared to recover partially by 4 hours after the bolus. The aggregation response was greater with thrombin receptor agonist peptide versus ADP stimulation; inhibition of platelet aggregation was greater in blood samples anticoagulated with citrate versus D-phenylalanyl-L-prolyl-L-arginine chloromethylketone (PPACK). Plasma eptifibatide levels correlated significantly with receptor occupancy but not with inhibition of platelet aggregation.

CONCLUSIONS

A bolus and infusion of eptifibatide inhibits platelet aggregation profoundly in patients with ACS and is followed by brief, partial recovery. These results enhance our understanding of the relation between pharmacodynamic and clinical effects of eptifibatide in such patients and may have important implications for its use in percutaneous interventions.

NO rotational orientation following 308 nm photodissociation of NO2

The rotational angular momentum orientation and alignment of the NO fragments generated via linearly polarized 308 nm photodissociation of NO2 has been determined using laser induced fluorescence. By observing the dependence of the photofragment NO Doppler-resolved transition line shapes on experimental geometry, it has proved possible to determine multipole moments of the photofragment angular momentum distribution up to, and including, rank 3. The implications of the results for the mechanism of the dissociation are considered.

Design and methodology of the ESPRIT trial: evaluating a novel dosing regimen of eptifibatide in percutaneous coronary intervention

BACKGROUND

Clinical trials of the glycoprotein (GP) IIb/IIIa inhibitors have shown that these potent antiplatelet agents are effective in reducing the ischemic complications of percutaneous coronary interventions. However, even though stents are now implanted in >75% of percutaneous interventional procedures, only one study, a trial of the monoclonal antibody abciximab, has formally evaluated adjunctive GP IIb/IIIa inhibition in this setting.

METHODS AND RESULTS

Eptifibatide, a nonimmunogenic and rapidly reversible inhibitor of the platelet receptor integrin IIb/IIIa, has also undergone evaluation as an adjunct to coronary intervention. In clinical trials performed heretofore, however, it has appeared to have less relative clinical efficacy than the monoclonal antibody abciximab. Since the early seminal trials, it has been recognized that the doses of eptifibatide previously used achieved only 30% to 50% of maximal platelet GP IIb/IIIa integrin inhibition. This is considerably less than the 80% level of receptor inhibition that has been proposed to prevent coronary thrombus formation in animal models and that has been achieved in clinical trials with abciximab.

CONCLUSIONS

The Enhanced Suppression of the Platelet IIb/IIIa Receptor with Integrilin Therapy (ESPRIT) trial was designed to test the safety and efficacy of a high-dose, "180/2.0/180" double-bolus regimen of eptifibatide (a 180-microg/kg bolus followed 10 minutes later by a second 180-microg/kg bolus of eptifibatide combined with a 2.0-microg/kg per minute infusion) as an adjunct to nonacute percutaneous coronary intervention with stent implantation. In this report, we review the rationale, design, and methods of this clinical investigation.

Dose-finding, safety, and tolerability study of an oral platelet glycoprotein IIb/IIIa inhibitor, lotrafiban, in patients with coronary or cerebral atherosclerotic disease

BACKGROUND

Antiplatelet therapy is the mainstay of the treatment and secondary prevention of cardiovascular and cerebrovascular ischemic events. We assessed the safety, tolerability, and pharmacodynamics of lotrafiban, an oral platelet glycoprotein IIb/IIIa inhibitor, as a secondary prevention strategy in patients with cerebrovascular or cardiovascular disease.

METHODS AND RESULTS

Overall, 451 patients with a recent cardiovascular or cerebrovascular acute ischemic event were randomized in a double-blind fashion to 1 of 5 dosing regimens for 12 weeks: placebo or 5, 20, 50, or 100 mg lotrafiban, both twice daily with 300 to 325 mg/d aspirin. The primary end point was the incidence and tolerability of major and minor bleeding during treatment. Secondary end points included inhibition of platelet aggregation and clinical events. The placebo and lotrafiban 5-mg groups had similarly low rates of minor and major bleeding, but the 100-mg arm was terminated early because of excess major bleeding. Protocol-defined thrombocytopenia (<100 000 platelets/microL) occurred in 5 lotrafiban-treated patients (1.4%, 95% CI 0.2% to 2.7%) and 1 placebo patient (1.1%, 95% CI 0% to 3.1%). Three lotrafiban-treated patients had a nadir platelet count <20 000/microL (0.9%, 95% CI 0% to 1.8%). Lotrafiban produced dose-dependent inhibition of platelet aggregation; 5 mg lotrafiban did not differ significantly from placebo, whereas 100 mg inhibited aggregation by nearly 100%.

CONCLUSIONS

-Lotrafiban provides dose-dependent platelet inhibition when administered to a range of patients with atherosclerosis. The level of platelet inhibition appears to correlate with bleeding risk and drug tolerability.

Carcinoembryonic antigen in breast nipple aspirate fluid

New diagnostic tools are needed to complement mammography and physical examinations for early detection of breast cancer, particularly among younger women. We evaluated the tumor biomarker, carcinoembryonic antigen (CEA), in 215 nipple aspirate fluid (NAF) samples collected from one or both breasts of 147 women, ages 27-87 years. Most subjects were recruited at the time of mammography examination. The 215 nipple fluid CEAs range from undetectable levels to 8400 ng/ml (median, 1100 ng/ml). Normal serum CEA levels are less than 6 ng/ml. There are no significant differences between the CEAs in fluid from normal breasts (112 samples) and breasts with various histories of tumors (total, 103 samples). Analyses for determinants of CEAs in fluids from normal breasts show higher levels among current smokers (P = 0.03) and marginal elevations among nulliparous women (P = 0.07). CEAs in these samples are not correlated with age, menopausal status, current hormone use, prior breastfeeding, or family history of breast cancer. Follow-up studies of these women and comparisons of CEAs in fluids from normal and cancer-containing breasts will help clarify whether this biomarker is useful for risk assessment or early cancer detection.

Selective inhibitors of monoamine oxidase. 4. SAR of tricyclic N-methylcarboxamides and congeners binding at the tricyclics' hydrophilic binding site

Linear [6.6.6] tricyclic moieties whose center ring is made of two atoms of differing size (here primarily thioxanth-9-ones and phenoxathiins) monosubstituted meta to the sulfur by C(O)NHMe include potent and selective inhibitors of monoamine oxidase A. Similarities with effects on SAR of acylamide and of diazapentacyclic substitution on such rings, including positional variables, the requirement for monomethylation (primary and dialkylated amides are inactive and higher monoalkylated amides show little or no potency), and that sulfur is optimally in sulfone form, suggest that binding to the enzyme occurs similarly in each series. No significantly greater rise in blood pressure was found in rats given sufficient 8 to inhibit most brain and liver MAO A and then followed by oral tyramine than was found on administration of tyramine to controls. This is in contrast to a large blood pressure rise in rats pretreated with phenelzine followed by tyramine, and in accord with the belief that an inhibitor selective for MAO A which is reversibly bound to the enzyme and therefore displaced by any ingested tyramine will not lead to the "cheese effect" (hypertension during treatment with MAO inhibitors usually caused by ingestion of foods containing tyramine).

Comparison of primary charge separation in the photosystem II reaction center complex isolated from wild-type and D1-130 mutants of the cyanobacterium Synechocystis PCC 6803

We compare primary charge separation in a photosystem II reaction center preparation isolated from a wild-type (WT) control strain of the cyanobacterium Synechocystis sp. PCC 6803 and from two site-directed mutants of Synechocystis in which residue 130 of the D1 polypeptide has been changed from a glutamine to either a glutamate (mutant D1-Gln130Glu), as in higher plant sequences, or a leucine residue (mutant D1-Gln130Leu). The D1-130 residue is thought to be close to the pheophytin electron acceptor. We show that, when P680 is photoselectively excited, the primary radical pair state P680+Ph- is formed with a time constant of 20-30 ps in the WT and both mutants; this time constant is very similar to that observed in Pisum sativum (a higher plant). We also show that a change in the residue at position D1-130 causes a shift in the peak of the pheophytin Qx-band. Nanosecond and picosecond transient absorption measurements indicate that the quantum yield of radical pair formation (phi RP), associated with the 20-30-ps component, is affected by the identify of the D1-130 residue. We find that, for the isolated photosystem II reaction center particle, phi RP higher plant > phi RP D1-Gln130Glu mutant > phi RP WT > phi RP D1-Gln130Leu mutant. Furthermore, the spectroscopic and quantum yield differences we observe between the WT Synechocystis and higher plant photosystem II, seem to be reversed by mutating the D1-130 ligand so that it is the same as in higher plants. This result is consistent with the previously observed natural regulation of quantum yield in Synechococcus PS II by particular changes in the D1 polypeptide amino acid sequence (Clark, A.K., Hurry, V. M., Gustafsson, P. and Oquist, G. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 11985-11989).

The role of health care ADR (alternative dispute resolution) in reducing legal fees

An increasingly complex health care system undergoing rapid changes is an ideal set-up for frequent conflicts among the numerous participants. While conflict is inevitable, the manner in which it is handled can markedly affect the outcome of the dispute and the future relationship of the parties, as well as the emotional and financial cost of the dispute. This article presents an overview of the principles and processes of alternative dispute resolution (ADR), and describes how these processes are currently being used to resolve health care disputes.

Reducing legal fees in medical group practices. The role of health care alternative dispute resolution

Conflict is a growth industry, particularly in an increasingly complex health care system. Litigation is the most common, and most costly, method of settling health care disputes. Highly adversarial, the process of litigation often generates as much, if not more, hostility than the original dispute. In addition, satisfaction with the outcome is very low. The challenge that has arisen is to manage the conflicts so that the underlying needs and interests of all the parties can best be met. Often the techniques and processes of alternative dispute resolution (ADR) can be successfully used in resolving these sorts of conflicts quickly, cheaply and with greater satisfaction for all parties. Various applications of ADR are currently being used or tested in a variety of health care disputes in the United States and Canada. Tremendous success has been achieved in mediating medical malpractice claims, medical staff disputes, economic credentialing conflicts, insurer relations issues and denial of coverage disputes. Professional relations and departmental staff disputes, partnership and employee conflicts, and organizational disputes within clinics, HMOs and large group practices have all been found particularly amenable to ADR. These are all situations in which everyone benefits from quick, non-hostile resolutions and on-going relationships can continue.

Photochemistry and spectroscopy of a five-chlorophyll reaction center of photosystem II isolated by using a Cu affinity column

A reaction center of photosystem II was isolated from Pisum sativum by using immobilized metal affinity chromatography. This reaction center is photochemically active and has a room temperature Qgamma chlorophyll (Chl) absorption band peaking at 677.5 nm. From HPLC analysis, the pigment stoichiometry was suggested to be 5 Chls per 1 beta-carotene per 2 pheophytins. Low-temperature absorption measurements at 77 K were consistent with the removal of one of the Chls associated with the usual form of the reaction center isolated by using ion-exchange chromatography. Transient absorption spectroscopy on the picosecond time scale indicated that the Chl removed belongs to a pool of Chl absorbing at approximately 670 nm (C670II) that transfers energy relatively slowly to the primary donor P680 in support of our recently proposed model. The results also support the previous conclusion that radical pair formation is largely associated with a 21-ps time constant when P680 is directly excited and that the identity of C670II is likely to be peripherally bound Chls possibly ligated to conserved His residues at positions 118 on the D1 and D2 proteins.

Does slow energy transfer limit the observed time constant for radical pair formation in photosystem II reaction centers?

We have used spectrally photoselective femtosecond transient absorption spectroscopy on photosystem II reaction centers to show that there are at least two pools of chlorin molecules/states which can transfer excitation energy to P680, the primary electron donor in photosystem II. It has previously been shown that one chlorin pool equilibrates with P680 in 100 fs [Durrant et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 11632-11636], and we report here the observation of energy transfer from a second more weakly coupled chlorin pool. The effect of the weakly coupled pool is to increase the apparent time constant for radical pair formation from 21 ps when P680 is selectively excited to 27 ps when the accessory chlorins are excited. We conclude that it is possible to observe both radical pair formation somewhat slowed by an energy transfer step and radical pair formation not limited by this slow energy transfer, depending upon which chromophores are initially excited. These observations provide evidence that when using photoselective excitation of P680, the observed 21 ps time constant for radical pair formation is not limited by a slow energy transfer step.

Rate of oxidation of P680 in isolated photosystem 2 reaction centers monitored by loss of chlorophyll stimulated emission

We have continued our studies of the primary photochemistry of isolated photosystem 2 reaction centers using femtosecond transient absorption spectroscopy. Experiments were performed over a wide range of excitation and probe wavelengths, using several data collection time scales. This has enabled us to resolve five different lifetimes ranging between 100 fs and 200 ps plus a nanosecond component. We demonstrate here and elsewhere [e.g., Durrant, J.R., Hastings, G., Joseph, D. M., Barber, J., Porter, G., & Klug, D. R. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 11632-11636] that the kinetic spectra associated with all but two of these lifetimes are clearly distinguishable. We have previously reported that a 21-ps lifetime is associated with pheophytin reduction [Hastings, G., Durrant, J. R., Hong, Q., Barber, J., Porter, G., & Klug, D. R. (1992) Biochemistry 31, 7638-7647]. In this paper, we show that it is possible to spectrally and temporally resolve stimulated emission from PS2 reaction centers with great accuracy and that this stimulated emission is largely unaffected by those kinetic components which are faster than 21 ps. The observation of a distinct stimulated emission band allows us to distinguish charge-separated states from chlorin singlet states. In this way, we are able to show that the proportion of charge-separated states prior to the 21-ps component is between 0% and 25%. We also show that the shape of the spectrum which we obtain for the state P680+Ph- is essentially invariant between 100 ps and 9 ns, and is the same as that previously reported for P680+Ph- by other researchers.(ABSTRACT TRUNCATED AT 250 WORDS)

Subpicosecond equilibration of excitation energy in isolated photosystem II reaction centers

Photosystem II reaction centers have been studied by femtosecond transient absorption spectroscopy. We demonstrate that it is possible to achieve good photoselectivity between the primary electron donor P680 and the majority of the accessory chlorins. Energy transfer can be observed in both directions between P680 and these accessory chlorins depending on which is initially excited. After excitation of either P680 or the other chlorins, the excitation energy is observed to equilibrate between the majority of these pigments at a rate of 100 +/- 50 fs-1. This energy-transfer equilibration takes place before any electron-transfer reactions and must therefore be taken into account in studies of primary electron-transfer reactions in photosystem II. We also show further evidence that the initially excited P680 excited singlet state is delocalized over at least two chlorins and that this delocalization lasts for at least 200 fs.

An application of life table method in the study of length of stay

Life table method was presented as a method of choice to analyse data arising out of longitudinal studies. The method was employed to study length of stay (LOS) of psychiatric in-patients. The result obtained was compared with LOS calculated by traditional methods. The LOS was 58-60 days computed by traditional methods for the year 1985 for our centre. This was shown by the life table method as the expected LOS at the time of admission. The life table method demonstrated that the rate of discharge increased as the length of stay increased upto 30 days and decreased afterwards. On the other hand, the expected further LOS increased as the length of stay increased upto 3 years. The implications of the findings were discussed.

High tibial osteotomy for varus gonarthrosis. A long-term follow-up study

We evaluated the results in eighty-three patients (ninety-five knees) who had had a high tibial osteotomy for either unicompartmental osteoarthritis or osteonecrosis. The operations were performed between 1965 and 1976. The mean length of follow-up was 8.9 years (range, five to fifteen years). The early results were promising: at two years 97 per cent and at five years 85 per cent of the knees had either an excellent or a good result. At subsequent follow-up, however, only sixty knees (63 per cent) had an excellent or good result, and in the remainder recurrent pain had developed. Twenty-two knees (23 per cent) had been revised to a total knee arthroplasty because of pain. The alignment obtained by the osteotomy was not as important in determining the long-term result as we had previously believed. Although recurrent varus deformity was observed in more than one-quarter of the knees, it was not necessarily associated with an unsatisfactory result. The passage of time was the most important factor in determining the result, as only fifteen (37 per cent) of the knees that had been followed for more than nine years were pain-free. We now believe that total knee arthroplasty is a more suitable operation for patients who are more than sixty years old and that high tibial osteotomy should be reserved for patients who have a strenuous occupation or who wish to continue to participate in sports activities.

Bone-block iliotibial-band transfer for anterior cruciate insufficiency

The anterior distal part of the iliotibial trace with attached bone block from Gerdy's tubercle was used as an intra-articular graft fixed by a screw to the tibia to control anterior instability (otherwise known as anterior, anteromedial, or anterolateral laxity) in twenty-four knees which were followed for two to four years. Concomitant single-plane 2+ to 4+ medial instability was present in eleven knees and was treated in five of them by simple immobilization, by imbrication of the medial collateral ligament, or by the Vigliani procedure. At follow-up, stability was improved and the result was rated good or excellent in twenty-one (88 per cent) of the twenty-four knees. The operation is applicable to the majority of chronic laxities of the knee and, because no immobilization is necessary, the postoperative care is much simplified and the rehabilitation time is much shorter. The procedure is contraindicated where there is posterior or single-plane lateral laxity.