Current status of acute necrotizing ulcerative gingivitis.
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Dentistry↗
Biomedical subjects
L Gordon
Publications and source records attributed to L Gordon.
The game plan to success: a management program.
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Laboratories, Dental↗
Soluble tumor necrosis factor receptors are increased in hemodialysis patients.
Tumor necrosis factor-alpha (TNF alpha) interacts with cells through specific membrane receptors. Exposure to agonists, such as C5a, causes cells to shed these receptors, forming soluble TNF alpha binding proteins (sTNFR). Because cellulose membranes activate complement, we tested the hypothesis that dialysis with these membranes contributes to the increased levels of sTNFR observed in hemodialysis patients. sTNFR levels were measured pre- and post-dialysis in patients treated with dialyzers containing new cellulose membranes. Plasma sTNFR concentrations were markedly increased pre-dialysis, compared with normal (38.3 +/- 13.5 ng/ml versus 2.1 +/- 0.7 ng/ml), and increased further during dialysis, even after post-dialysis concentrations were corrected for hemoconcentration. We examined the impact of the increased sTNFR levels on the ability of TNF alpha to prime neutrophil superoxide production in cross-incubation experiments. When normal neutrophils were incubated with TNF alpha in the presence of hemodialysis patient plasma, the resulting increase in fMLP stimulated superoxide production was significantly less than when normal plasma was used. Incubation of hemodialysis patient neutrophils in normal plasma only partly restored their ability to be primed by TNF alpha, suggesting an intrinsic functional defect in these cells, in addition to the effects of sTNFR. Our results suggest that dialysis with cellulose membranes contributes to the increased levels of sTNFR observed in dialysis patients, and that these concentrations are sufficient to impair the normal actions of TNF alpha.
Adult↗
An implantable centrifugal blood pump for long term circulatory support.
A compact centrifugal blood pump was developed as an implantable left ventricular assist system. The impeller diameter is 40 mm and the pump dimensions are 55 x 64 mm. This first prototype was fabricated from titanium alloy, resulting in a pump weight of 400 g including a brushless DC motor. Weight of the second prototype pump was reduced to 280 g. The entire blood contacting surface is coated with diamond like carbon to improve blood compatibility. Flow rates of over 7 L/min against 100 mmHg pressure at 2,500 rpm with 9 W total power consumption have been measured. A newly designed mechanical seal with a recirculating purge system ("Cool-Seal") is used as a shaft seal. In this seal system, seal temperature is kept under 40 degrees C to prevent heat denaturation of blood proteins. Purge fluid also cools the pump motor coil and journal bearing. The purge fluid is continuously purified and sterilized by an ultrafiltration filter incorporated into the paracorporeal drive console. In vitro experiments with bovine blood demonstrated an acceptably low hemolysis rate (normalized index of hemolysis = 0.005 +/- 0.002 g/100 L). In vivo experiments are currently ongoing using calves. Via left thoracotomy, left ventricular apex-descending aorta bypass was performed utilizing a PTFE (Polytetrafluoroethylene) vascular graft, with the pump placed in the left thoracic cavity. In two in vivo experiments, pump flow rate was maintained at 5-8 L/min, and pump power consumption remained stable at 9-10 W. All plasma free hemoglobin levels were measured at < 15 mg/dl. The seal system has demonstrated good seal capability with negligible purge fluid consumption (< 0.5 ml/ day). Both animals remain under observation after 162 and 91 days of continuous pump function.
Animals↗
Long-term animal experiments with an intraventricular axial flow blood pump.
A miniature intraventricular axial flow blood pump (IVAP) is undergoing in vivo evaluation in calves. The IVAP system consists of a miniature (phi 13.9 mm) axial flow pump that resides within the left ventricular (LV) chamber and a brushless DC motor. The pump is fabricated from titanium alloy, and the pump weight is 170 g. It produces a flow rate of over 5 L/min against 100 mmHg pressure at 9,000 rpm with an 8 W total power consumption. The maximum total efficiency exceeds 17%. A purged lip seal system is used in prototype no. 8, and a newly developed "Cool-Seal" (a low temperature mechanical seal) is used in prototype no. 9. In the Cool-Seal system, a large amount of purge flow is introduced behind the seal faces to augment convective heat transfer, keeping the seal face temperature at a low level for prevention of heat denaturation of blood proteins. The Cool-Seal system consumes < 10 cc purge fluid per day and has greatly extended seal life. The pumps were implanted in three calves (26, 30, and 168 days of support). The pump was inserted through a left thoracotomy at the fifth intercostal space. Two pursestring sutures were placed on the LV apex, and the apex was cored with a myocardial punch. The pump was inserted into the LV with the outlet cannula smoothly passing through the aortic valve without any difficulty. Only 5 min elapsed between the time of chest opening and initiation of pumping. Pump function remained stable throughout in all experiments. No cardiac arrhythmias were detected, even at treadmill exercise tests. The plasma free hemoglobin level remained in the acceptable range. Post mortem examination did not reveal any interference between the pump and the mitral apparatus. No major thromboembolism was detected in the vital organs in Cases 1 or 2, but a few small renal infarcts were detected in Case 3.
Animals↗