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Biomedical subjects

J P Roth

Publications and source records attributed to J P Roth.

14 recordsLinked to original sources
PubMed2001

Application of the Marcus cross relation to hydrogen atom transfer reactions.

The transfer of a hydrogen atom-a proton and an electron-is a fundamental process in chemistry and biology. A variety of hydrogen atom transfer reactions, involving iron complexes, phenols, hydroxylamines, tBuOOH, toluene, and related radicals, are shown to follow the Marcus cross relation. Thus, the Marcus theory formalism based on ground-state energetics and self-exchange rates, originally developed for electron transfer processes, is also valuable for hydrogen atom transfer. Compounds that undergo slow proton transfer (C-H bonds) or slow electron transfer (cobalt complexes) also undergo slow hydrogen atom transfer. Limitations of this approach are also discussed.

Chemical Phenomena↗
PubMed1998

Colonoscope flexural rigidity measurement.

A testing device is developed that determines the stiffness, or flexural rigidity, of an endoscope at specific locations down its length by subjecting it to a compressive axial force, a situation similar to the actual forces applied to the endoscope during a clinical procedure. The endoscope is made to deform in a similar fashion to a slender buckled column and the force causing this deformation is related to the flexural rigidity using column buckling theory. A direct relationship between the critical load needed to cause buckling and the square of column length L is demonstrated experimentally and is expected theoretically, giving confidence in the application of column buckling theory to endoscope testing. Additional confidence in the validity of the column buckling test results is obtained by their similarity to data obtained by subjecting the endoscope to a transverse load, determining deflection, and modelling the endoscope as a bent elastic beam. Several makes and models of endoscopes were tested, with flexural rigidity values typically ranging between 160 to 240 Ncm2. The effect of a metal stiffener inserted in an endoscope's accessory channel is quantified, as is the change in flexural rigidity down the insertion shaft of a graded-stiffness endoscope. Significant differences in flexural rigidity were obtained between identical endoscopes, each sharing similar usage histories, indicating the need for flexural rigidity measurements for each individual endoscope of a particular model line, though a more extensive study is required to reliably determine scope-to-scope stiffness variations for a particular model line.

Colonoscopes↗
PubMed1986

Acute peripheral arterial and graft occlusion: treatment with selective infusion of urokinase and lysyl plasminogen.

Thirty-five patients hospitalized for recent angiographically documented arterial occlusion in the legs (27 femoropopliteal arteries and eight grafts) benefited from local fibrinolytic therapy delivered at the site of the occlusion with a 4- or 5-F catheter. This therapy combined a continuous urokinase (UK) infusion of 1,000 U/kg/hour and a lysyl plasminogen (LYS-PLG) infusion of 15 microkatals every 30 minutes. Angiographically confirmed lysis was obtained in 85% of the cases. Only 3% of the patients had major and 6% had minor groin hematomas. Only two patients had concentrations of fibrinogen as low as 100 mg/dl. Intravascular infusion of UK-LYS-PLG is as effective as streptokinase. Its excellent tolerance makes it a good alternative in the treatment of acute ischemia in the lower limbs.

Adult↗
PubMed1985

[Results of in situ arterial thrombolysis by the combination of urokinase and lysyl plasminogen in acute arterial occlusive diseases of the lower limbs].

35 patients with acute arterial occlusions [27] and graft thromboses [8], responsible for severe and recent ischemia, were treated by fibrinolytic therapy (Urokinase: 1 000 units/kg/hour, and Lys Plasminogen). These drugs were delivered at the site of occlusions using a 5 French catheter. Angiographically, initial success was obtained in 30 patients (85%) and a significant clinical benefit persisted 5 months later, in 20 patients (57%). 4 distal embolisms during the treatment were noted, and one woman died a few hours after the withdrawal of an axillary catheter of a cerebellar infarction. Only two minor (6%) and one severe (3%) groin hematoma were encountered. No patient had at any moment a fibrinogen concentration lower than 1 g/l. Thus, the thrombolytic treatment used in the study appears as effective as locally administered Streptokinase but better tolerated.

Acute Disease↗
PubMed1983

[Current indications for intravenous numerical angiography in the study of the ilio-femoral axis].

A study of the arterial axis from the aortic bifurcation to the femoral bifurcation was conducted by intravenous digital angiography in 40 patients. In 92.5% of these, opacification and visualization of the arteries were good or excellent. In 12 out of 15 patients the images were judged to be of the same quality as those obtained by conventional arteriography. A limitation of the method is the size of the intensifying screen (23 cm), which only allows exploration of one segment at each injection. This, however, is a minor drawback when this technique is used for control examination after percutaneous angioplasty or to investigate an accident of catheterization.

Adolescent↗