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Biomedical subjects

G E Miller

Publications and source records attributed to G E Miller.

At least 55 records · Page 3Linked to original sources
PubMed1986

Performance of the Smeloff aortic valve beyond ten years.

The Smeloff aortic valve has remained unchanged in design and material since 1966. To assess the long-term performance of this prosthesis, we reviewed 394 consecutive patients undergoing elective aortic valve replacement. Concomitant coronary artery bypass grafting was performed in 26.4% of these patients. Follow-up was complete in 96%; maximum follow-up was 13.1 years (mean 4.3 years). The operative mortality was 7.4%. Actuarial survival rate, including operative mortality, was 66.3% +/- 2.8% at 5 years and 48.7% +/- 4.5% at 10 years. Thromboembolism for the entire group occurred at a rate of 3.8% per patient-year. Patients who underwent anticoagulation continuously had a rate of embolision of 1.8% per patient-year. All patients had a 5 year embolus-free rate of 91% +/- 2% and a 10 year embolus-free rate of 85% +/- 3%. Patients receiving anticoagulants had a 5 year embolus-free rate of 92% +/- 2% and a 10 year embolus-free rate of 89% +/- 3%. There was no mechanical failure or prosthetic thrombosis in 1,690 patient-years of follow-up. The Smeloff aortic valve has excellent long-term durability and thromboembolism is low in patients receiving anticoagulants.

Actuarial Analysis↗
PubMed1985

Prosthetic valve replacement using annular preservation technique.

Preservation of as much annulus as possible is an extremely important aspect of prosthetic valve replacement. A method is described that allows intact removal of a prosthetic valve without damage to the annulus. This simple technique has been used regularly for three years, and there have been no complications.

Heart Valve Prosthesis↗
PubMed1985

The mechanics of terminal lymph flow.

The effects of external pressure on the terminal lymphatic clearance rate are studied. Sulfur colloid tagged with 99mTc is injected into the subcutaneous tissue in the hind thigh of canines. The activity of the tracer is measured over the injection site for 90 min to determine the lymphatic clearance rate of the sulfur colloid. Several experiments are performed at different external pressures applied to the surface of the canine thigh. A two-compartment model is defined to determine both the terminal lymphatic flow rate per unit volume of tissue and the diffusion constant (sulfur colloid/interstitial fluid) from the raw data. Experimental results indicate that increases in the external pressure applied to the skin cause terminal lymphatic clearance rates to increase until the pressure reaches 60 mm Hg. At this level, some test results showed reduced levels of clearance. At 75 mm Hg, the lymphatic clearance of sulfur colloid from the subcutaneous tissue was stopped suggesting occlusion of the vessels resulting from vessel collapse.

Animals↗
PubMed1983

Mechanisms of diethyldithiocarbamate-induced loss of cytochrome P-450 from rat liver.

A single, intraperitoneal injection of diethyldithiocarbamate (DDTC) to adult, male Sprague-Dawley rats decreased hepatic cytochrome P-450 (P-450) concentrations. This effect was dose-dependent over a range of 250 to 750 mg/kg and most prominent 24-36 hr after dosing. Depletion of hepatic glutathione (GSH) by diethylmaleate (DEM) administration significantly decreased P-450 8 hr after concurrent treatment with DDTC at a dose which given alone had little effect on P-450 concentrations. When hepatic microsomes were incubated with DDTC in the presence of NADPH, P-450 was converted to cytochrome P-420 (P-420). Similar incubations employing [35S]DDTC demonstrated strict NADPH-dependent binding of labeled sulfur to microsomal membranes, suggesting that diminished P-450 concentrations are related to the metabolic activation of DDTC. Addition of reduced GSH to incubation mixtures blocked the binding of 35S to microsomal membranes, as well as conversion of P-450 to P-420. DDTC inhibited NADPH-ADP3+ mediated peroxidation of microsomal lipids in vitro, suggesting that the effect of DDTC on P-450 does not result from stimulation of lipid peroxidation, but may be influenced by the levels of hepatic GSH. DDTC treatment 1 hr after P-450 was pulse labeled by an intravenous injection of [3H]delta-aminolevulinic acid resulted in a 2-fold increase in the rate of loss of radioactivity associated with membrane-bound P-450 heme during the next 20 hr. Within this time interval, hepatic heme oxygenase (HO) activity increased and at 8 hr after dosing was 7-fold greater than control values in the livers, but was unchanged in the kidneys and spleens of DDTC-treated animals. An elevation of hepatic delta-aminolevulinic acid synthetase (delta-ALAS) activity occurred at 8 and 24 hr after DDTC treatment. Since this enzyme is rate limiting in the biosynthesis of heme, its increased activity may represent a compensatory response to offset the DDTC-mediated loss of P-450 heme.

5-Aminolevulinate Synthetase↗
PubMed1981

Lymphatic clearance during compressive loading.

Lymphatic clearance of radioactive sulfur colloid is measured as a function of externally applied pressure on the hind limb of mongrel dogs. A dead weight device is placed over the site of subcutaneous injection. A solid state Si (Li) is placed into a slot at the bottom of the device to continuously record activity of the tracer. An exponential decrease in activity is modeled as a dual decay resulting from both tracer half life decay and lymphatic clearance of the tagged sulfur colloid. External pressure is seen to enhance lymph clearance until a critical closing pressure is reached, whereupon the vessel collapses and lymph flow is drastically reduced. A closing pressure of 60 mmHg is observed for several experiments. Lymph flow per tissue volume is seen to rise from a mean of 0.324 ml/hr/ml for uncompressed tissue to 0.96 ml/hr/ml for fully enhanced flow in other experiments at 60 mmHg. Results at a pressure of 75 mmHg show almost no lymph clearance suggesting complete vessel closure.

Animals↗
PubMed1980

Lymphatic clearance of radioactive sulfur colloid.

Lymphatic clearance of radioactive sulfur colloid is measured in the hind limb of five mongrel dogs. A solid state Si(Li) detector is placed onto the skin to continuously record activity over the site of subcutaneous injection. Decrease in activity follows an exponential decay which is modeled as a dual decay occurring from both the radioactive decay of the tracer and the lymph clearance of the tagged sulfur colloid. The calculated decay constants for lymph clearance flow per tissue volume result in a mean value of 0.233 +/- 0.077 ml/hr/ml which is consistent with results of other investigators. Adjacent lymph nodes are monitored with a scintillation detector to show that the colloid is absorbed by the lymph vessels. The carotid artery and liver are similarly monitored to show that there is little or no capillary absorption of the tagged colloid.

Animals↗
PubMed1978

Long-term survival after single aortic or mitral valve replacement with the present model of Smeloff-Cutter valves.

Two hundred fourteen survivors of single aortic (AVR) or mitral valve replacement (MVR) were evaluated. The present model of the Smeloff-Cutter prosthesis was used in these patients, and the series was started in September, 1966, following the last structural change in the valve. Clinical follow-up ended in September, 1976. Bleeding, thromboembolism, and peristent left ventricular dysfunction were the major complications. Thromboembolism occurred at a rate of 0.13 percent per month of patient follow-up. Late deaths occurred in 19.2 percent of patients, half of these within the first year. Acturarial data indicated a 5 year survival rate of approximately 75 percent after both mitral and aortic replacements. Bleeding and thromboembolism were more frequent causes of death after mitral replacement. Myocardial function was of greatest importance in long-term survival after replacement of either valve. Variations in warfarin dosage significantly affected both bleeding and thromboembolic complications.

Anticoagulants↗
PubMed1977

Relationship between dialyzer reuse and the presence of anti-N-like antibodies in chronic hemodialysis patients.

One hundred eleven chronic hemodialysis patients from five dialysis units were tested for the presence of antibodies reactive with red blood cell N substance; 77 patients were available for follow-up study after 18 to 24 months. Initially, 18 patients (16%) had serum anti-N-like antibodies. Thirteen of these patients were in a home dialysis program and were reusing hollow fiber dialyzers. The other five had practiced hollow fiber dialyzer reuse in the past. None of 37 patients using coil dialyzers had anti-N-like antibody. On follow-up testing, anti-N-like antibody persisted in all patients restudied except for one who had a successful renal transplant. Anti-N-like antibodies developed in four additional patients: three were reusing hollow fiber dialyzers at the time, but one had not reused dialyzers for 24 months. Statistical analyses indicated that dialyzer reuse, hollow fiber dialyzers, and home dialysis were significantly related to the presence of anti-N-like antibodies. We interpret the clinical and statistical data to indicate that dialyzer reuse is the major clinical factor in the development of anti-N-like antibody. The likely mechanism involves the prolonged exposure of red cells trapped in the dialyzer to formaldehyde used in preparing dialyzers for reuse. No adverse clinical effects of anti-N-like antibodies were evident in our patients, but hemolysis and acute transplant failure have been reported by others.

Antibodies, Anti-Idiotypic↗
PubMed1977

A study of oxidation of dental amalgams with age.

A quantitative test for corrosion due to oxidation has been accomplished. The oxygen concentration of dental amalgams was measured by fast neutron activation which provides a means of detecting oxygen in as small a quantity as 10 to 20 micrograms. An increase in oxygen content with age of spherical blend amalgam implants was observed, comfirming the importance of oxidation processes in in vivo corrosion.

Adolescent↗