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Biomedical subjects

M Garrison

Publications and source records attributed to M Garrison.

10 recordsLinked to original sources
PubMed1991

Flow support catheter for prolonged maintenance of coronary blood flow.

A newly designed flow support catheter with a supporting wire mesh cage which can be expanded into a tubular configuration and then readily reduced was evaluated in mongrel dogs. Regional myocardial blood flow (RMBF) was measured using the radioactive microsphere technique in the area of both balloon-denuded instrumented and control non-instrumented coronary arteries following placement of either a fixed-wire or a higher profile rapid exchange flow support catheter. At 5, 20, and 180 min following delivery and expansion of either device, RMBF was not significantly different in left ventricular subepicardium and subendocardium perfused by the instrumented vs. the control coronary arteries. Angiography demonstrated widely patent instrumented arteries in 15/18 dogs; in no dog was side branch occlusion observed. Significant cage thrombus deposition was seen angiographically in 3 animals causing temporary total coronary occlusion in 1. Following reduction and removal of the flow support catheter, vessel patency was present in all dogs. The flow support catheter is an effective endovascular stenting device capable of providing structural arterial support, while simultaneously maintaining distal coronary blood flow. It is envisioned that the primary application of this catheter will be to enable primary salvage of vessels acutely injured during coronary angioplasty, by "tacking up" intimal flaps for an extended period. It may also provide a bridge to emergency surgical revascularization.

Angioplasty, Balloon, Coronary↗
PubMed1990

Upper airway distensibility and collapsibility in patients with obstructive sleep apnea.

The present study was performed to evaluate the distensibility and collapsibility characteristics of regional segments of the UA in patients with OSA and in normal subjects in response to changes in airway pressure. Seventeen male patients with moderately severe OSA and 13 normal subjects underwent CT of the UA in the supine position while awake. Axial views were obtained from the level of the hard palate to the hypopharynx under conditions of -5, 0, and +10 cm H2O of CAP. The results indicated that the Amin occurred within 20 mm of the hard palate in the retropalatal region of the UA in 16 (94 percent) of the 17 patients and in 12 (92 percent) of the 13 normal subjects. Continuous negative airway pressure of -5 cm H2O failed to significantly decrease either Amin or Amean in either the patients or normal subjects, suggesting good UA load compensation during wakefulness. Continuous positive airway pressure of 10 cm H2O significantly increased Amin and Amean to a similar extent in both groups. The Amin was significantly smaller by 40 percent, 33 percent, and 37 percent in the patients with OSA, compared to the normal subjects, at -5, 0, and +10 cm H2O of CAP, respectively. In contrast, Amean did not differ between the groups. The CT scan criterion of Amin less than or greater than 1.0 cm2 during tidal ventilation of atmospheric pressure correctly categorized patients with OSA and normal subjects with an accuracy of 70 percent. While the behavior of the UA in response to nasal CPAP and CNAP failed to increase the accuracy of CT scan criteria to a level sufficient for clinical use in the diagnosis of OSA, the results clearly indicate that structural changes in the UA contribute to the development of OSA.

Airway Resistance↗
PubMed1989

Evaluation of a two-compartment Bayesian forecasting program for predicting vancomycin concentrations.

The application of a two-compartment Bayesian forecasting program for vancomycin was tested retrospectively in 45 adult patients with stable renal function. Serial blood samples from 25 of these patients were used to determine population-based parameter estimates. The predictive performance of the Bayesian program was assessed by using both non-steady-state and steady-state vancomycin concentrations as feedback information. Overall, the program tended to underpredict peak and trough steady-state vancomycin serum concentrations. A larger mean prediction error (ME) was seen when non-steady-state feedback serum concentrations were used compared with using population-based parameter estimates (no feedback). In contrast, a marked improvement in ME (peaks: -1.03 versus -2.61; troughs: -1.60 versus -2.07) was seen when steady-state feedback serum concentrations were used compared with no feedback data. Precision improved when either feedback serum concentrations were used to predict steady-state peak and trough vancomycin concentrations. The results from this clinical evaluation demonstrate that the initial pharmacokinetic parameter estimates for a two-compartment Bayesian model provided accurate prediction of steady-state vancomycin concentrations. Prediction bias and precision were improved when steady-state vancomycin concentrations were used to determine individualized pharmacokinetic parameters.

Adult↗
PubMed1989

Individualizing vancomycin dosage regimens: one- versus two-compartment Bayesian models.

The absolute and relative predictive performances of one- and two-compartment Bayesian forecasting models were evaluated and compared. Initial population parameters were derived from 25 adult patients with stable renal function and who were being treated for presumed or documented gram-positive infections. The performance of each model was compared using these population parameters with and without steady-state or non-steady-state feedback concentrations to predict future peak and trough concentrations in an additional 20 patients. Both models tended to underpredict vancomycin peak and trough concentrations obtained at steady state. The use of a two-compartment model resulted in statistically less bias and more precise predictions of vancomycin peak concentrations when either population parameters or non-steady-state concentrations were used for future predictions. No difference in model performance was observed when steady-state concentrations were used to predict future steady-state concentrations. The results of this evaluation demonstrate that the two-compartment Bayesian model is less biased and more precise in determining future vancomycin serum concentrations given only population parameters or non-steady-state feedback information. No difference in model performance could be discerned when steady-state concentrations were used as feedback information.

Adolescent↗
PubMed1989

Comparison of two office tests for determining blood theophylline levels.

The blood theophylline level determination is an important therapeutic tool, but reference laboratories can take from 1 to 3 days before giving results. Several quicker in-office methods for testing blood theophylline levels are currently available. Two methods were compared for reliability and accuracy. Both proved to be accurate, but the Acculevel method was more reliable than the Seralyzer method. The Acculevel appears to be a preferable method for in-office testing of serum theophylline levels.

Humans↗
PubMed1987

Synthesis and secretion of lipoprotein lipase in 3T3-L1 adipocytes. Demonstration of inactive forms of lipase in cells.

3T3-L1 adipocytes in culture incorporated [35S]methionine into a protein which could be immunoprecipitated with chicken antiserum to bovine lipoprotein lipase. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed this protein had an Mr of 55,000, similar to that of bovine lipoprotein lipase, and accounted for 0.1-0.5% of total protein synthesis in the adipocytes. Lipoprotein lipase protein was present in small amounts in confluent 3T3-L1 fibroblasts, and the amount increased many-fold as the cells differentiated into adipocytes. This increase was accompanied by parallel increases in cellular lipase activity and secretion. When cells were grown with [35S]methionine, the amount of label incorporated into lipoprotein lipase increased for 2 h and then leveled off. Pulse-chase experiments showed that half-life of newly synthesized lipase was about 1 h. Turnover of lipoprotein lipase in control cells involved both release to the medium and intracellular degradation. When N-linked glycosylation was blocked by tunicamycin, the cells synthesized a form of lipase that had a smaller Mr (48,000), was catalytically inactive, and was not released to the medium. Radioimmunoassay demonstrated that 3T3-L1 adipocytes contained an unexpectedly large amount of lipoprotein lipase protein. 55% of the enzyme protein in acetone/ether powder of the cells was insoluble in 50 mM NH3/NH4Cl at pH 8.1, a solution commonly used to extract lipoprotein lipase; 27% of the lipase protein was soluble but did not bind to heparin-Sepharose and had very low lipase activity; and the remaining 13% was soluble, bound to heparin-Sepharose, and had high lipolytic activity. About one-half of the lipase released spontaneously to the medium was inactive, and lipase inactivation proceeded in the medium with little loss of enzyme protein. Lipoprotein lipase released heparin, in contrast, was fully active and more stable. When protein synthesis was blocked by cycloheximide, the level of lipoprotein lipase activity in adipocytes decreased more rapidly than the amount of lipase protein in the cells. Most of the inactive lipoprotein lipase in adipocytes probably results from dissociation of active dimeric lipase, but some could be a precursor of active enzyme.

Adipose Tissue↗