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Biomedical subjects

G Ray

Publications and source records attributed to G Ray.

At least 19 recordsLinked to original sources
PubMed1995

Inversion of (R)- to (S)-ketoprofen in eight animal species.

The (R)-enantiomer of the NSAID ketoprofen was administered orally at 20 mg/kg to a series of 8 animal species. In all species, a highly significant degree of inversion occurred after 1 h which varied from 27% (gerbil) to 73% (dog) and persisted or increased in plasma samples obtained 3 h after drug administration. Although the (R)-enantiomer was inactive as an inhibitor of cyclooxygenase, the analgesic effects of that isomer was almost the same as the (S)-isomer in animal analgesic assays, following oral administration of the drugs to mice and rats. Taken together, the present results suggest that (R)-ketoprofen administered alone functioned primarily as a prodrug for (S)-ketoprofen under the experimental conditions of this study.

Administration, Oral↗
PubMed1992

Consolidation hemibody radiotherapy following induction combination chemotherapy in high-tumor-burden multiple myeloma.

PURPOSE: Curative therapy for multiple myeloma continues to be an elusive goal. This report discusses the Northern California Oncology Group (NCOG) phase I and II trial in high-tumor-burden disease that used a strategy that consisted of induction chemotherapy (vincristine, melphalan, cyclophosphamide, and prednisone [VMCP]) for eight cycles followed by sequential hemibody radiation therapy (RT) and subsequent chemotherapy for an additional eight cycles. PATIENTS AND METHODS: Seventy-two previously untreated stage III myeloma patients were entered onto the study. Sixty-nine received induction chemotherapy, 40 received induction chemotherapy and hemibody RT, and 23 received induction chemotherapy, hemibody RT, and consolidative chemotherapy. RESULTS: Twenty-two complete responses (CRs) were obtained by induction chemotherapy, with four additional CRs after RT and consolidative chemotherapy. Nineteen patients developed grade 4 hematologic toxicity primarily after upper hemibody RT. Eight of these developed long-standing neutropenia or thrombocytopenia. Median survival of the group was 134 weeks, which was not significantly different from other approaches. CONCLUSIONS: Hemibody RT can be combined with chemotherapy as induction therapy and can be safely administered in a community setting. However, as administered here no survival advantage was demonstrated.

Adult↗
PubMed1989

Stiffness and strain energy criteria to evaluate the threshold of injury to an intervertebral joint.

This study is focused to evaluate the threshold of injury to an intervertebral joint based on its mechanical response. The load-deflection behavior of the intervertebral joint indicated non-linear and sigmoidal characteristics with continuously changing stiffness (a measure of the ability to withstand external force). The load corresponding to the point of zero stiffness was identified, according to the classical theories of mechanics, as the maximum load carrying capacity. Further, the initiation of trauma was defined to occur at the point on the load-deflection curve at which the stiffness begins to decrease for the first time. The load, stiffness and energy absorbing capabilities of normal and degenerated intervertebral joints at the initiation of trauma was determined. Axial compressive load experiments were conducted on nine intervertebral joints of fresh human male cadavers and the resulting load-deflection responses were transformed into stiffness-deflection responses using the derivative principle. Energy characteristics were also derived. Load, stiffness and energy at the initiation of trauma were found to be 9.0 kN, 2850 N mm-1, and 10.2 J for normal and 4.4 kN, 1642 N mm-1, and 5.8 J for degenerated segments, respectively. The load and energy values at failure were 11.0 kN, and 18.0 J for normal and 5.3 kN and 5.7 J for degenerated intervertebral joints, respectively.

Biomechanical Phenomena↗
PubMed1988

Microtrauma in the lumbar spine: a cause of low back pain.

Excessive mechanical stress on the intervertebral disc may be one of the causes of low back pain. Most studies testing this thesis, however, have been based on quantification of the mechanical response of functional units at failure. Typically, radiography is used to demonstrate trauma to the vertebral body at the failure load. The description of failure and radiographic demonstration of damage are meaningful in specifying the tolerance limits of the structure. It is important, however, to understand the sequence underlying the initiation of injury, which may occur at subfailure physiological loads. In this study, we identified the initiation of injury to the lumbar spine by subjecting functional units to axial compressive loads using the mechanical response as a basis. Because conventional radiography failed to detect trauma at this level, advanced sectioning techniques were used. The initiation of injury (microtrauma) is defined as the point on the load-deflection curve where the structure exhibits a decreasing level of resistance for the first time before reaching its ultimate load-carrying capacity. The load deflection curve on this basis was classified into the ambient or preload phase, physiological loading phase, traumatic phase, and post-traumatic phase. Structures loaded to the end of the physiological loading phase did not exhibit any yielding or microtrauma. Injury in the form of microfractures of the endplate not detected on radiography, however, was observed under cryomicrotomy for structures loaded into the traumatic loading phase.

Adult↗
PubMed1987

Mathematical and finite element analysis of spine injuries.

A critical review of the anatomical, physiological, epidemiological, and biomechanical aspects of spine injuries are presented. These are discussed in light of the mechanical load that produces the trauma. Emphasis is given to the mathematical and finite element modeling aspects of spinal injury that focuses on the tolerance criteria. In the area of spinal mechanics, static and dynamic models are reviewed. Included are the continuum and discrete parameter models of the intact spine and finite element models of its components. A section on the role of constituent law in the assessment of trauma to the spine is given. Finally, a discussion follows on the future research in this domain.

Humans↗
PubMed1985

A mother's tale.

Explore the source record for details and available documents.

Attitude of Health Personnel↗
PubMed1985

Assessment of single vessel coronary artery disease: results of exercise electrocardiography, thallium-201 myocardial perfusion imaging and radionuclide angiography.

The sensitivity of the commonly used stress tests for the diagnosis of coronary artery disease was analyzed in 46 patients with significant occlusion (greater than or equal to 70% luminal diameter obstruction) of only one major coronary artery and no prior myocardial infarction. In all patients, thallium-201 perfusion imaging (both planar and seven-pinhole tomographic) and 12 lead electrocardiography were performed during the same graded treadmill exercise test and radionuclide angiography was performed during upright bicycle exercise. Exercise rate-pressure (double) product was 22,307 +/- 6,750 on the treadmill compared with 22,995 +/- 5,622 on the bicycle (p = NS). Exercise electrocardiograms were unequivocally abnormal in 24 patients (52%). Qualitative planar thallium images were abnormal in 42 patients (91%). Quantitative analysis of the tomographic thallium images were abnormal in 41 patients (89%). An exercise ejection fraction of less than 0.56 or a new wall motion abnormality was seen in 30 patients (65%). Results were similar for the right (n = 11) and left anterior descending (n = 28) coronary arteries while all tests but the planar thallium imaging showed a lower sensitivity for isolated circumflex artery disease (n = 7). The specificity of the tests was 72, 83, 89 and 72% for electrocardiography, planar thallium imaging, tomographic thallium imaging and radionuclide angiography, respectively. The results suggest that exercise thallium-201 perfusion imaging is the most sensitive noninvasive stress test for the diagnosis of single vessel coronary artery disease.

Adult↗
PubMed1985

Myocardial perfusion after aortocoronary bypass surgery: measurements at rest and after administration of isoproterenol.

This study examined quantitative regional myocardial perfusion (RMP) measured by the washout of 133Xe at rest and after an isoproterenol challenge in 50 patients (group I) studied 8 to 14 days after they underwent saphenous vein bypass grafting to the left coronary artery, and compared this with RMP measured in the native left coronary artery in 14 patients (group II) with significant coronary artery disease and in 12 normal subjects (group III). The double product of the heart rate and aortic systolic pressure was used as an indicator of demand. The statistical significance of group comparisons was analyzed with Dunn's multiple comparisons among means test. Analysis of the data showed no significant difference among the groups with respect to aortic systolic pressure. In subjects at rest, heart rate was lower in groups II and III than in group I, and double product was lower in group II than in group I. After isoproterenol, both heart rate and double product were lower in group II compared with groups I and III, but there was no significant difference between groups I and III with respect to heart rate or double product. Mean resting RMP in group II was lower than in group I; however, results of other group comparisons were insignificant for resting parameters. After isoproterenol, mean flow (ml/100 g/min) in group I was similar to flow in group III (130 +/- 24 vs 139 +/- 26). In contrast, the average flow response after isoproterenol was significantly less in group II when compared with that in group I (105 +/- 20 vs 130 +/- 24) and with that in group III (105 +/- 20 vs 139 +/- 26). Because of differences in levels of demand with isoproterenol, the change in flow was normalized to the percent increase in double product. These data showed results similar to those above, i.e., normalized RMP in patients with coronary artery disease was significantly lower than that in normal subjects (82 +/- 41 vs 119 +/- 57) and in revascularized patients (82 +/- 41 vs 105 +/- 54). However, there was no significant difference between normal subjects and patients who had undergone surgery. To further evaluate the relationship of flow response to demand parameters, we plotted RMP/double product vs resistance. The data revealed a significant correlation between these variables in all groups both in subjects at rest and after isoproterenol.(ABSTRACT TRUNCATED AT 400 WORDS)

Coronary Artery Bypass↗
PubMed1984

Comparison of the analysis of delta 9-tetrahydrocannabinol capsules by high-performance liquid chromatography and capillary gas chromatography.

The modification of a high-performance liquid chromatography (HPLC) system and the development of a capillary gas-chromatographic (GC) system for the analysis of delta 9-tetrahydrocannabinol, encapsulated in soft gelatin capsules, are described. A photodiode array detector was used to evaluate peak homogeneity after each HPLC system modification. Sesame oil was separated from the extract by Sep-Pak filtration prior to GC analysis. Quantitation by both systems had r values greater than 0.999 and R.S.D. values less than 1.0%. Simultaneous capsule assays by both methods agreed within 1%.

Capsules↗