An ultimate, compact, seal-less centrifugal ventricular assist device: Baylor C-Gyro pump

We have developed a compact, seal-less, all-purpose centrifugal pump, the Baylor C-Gyro pump, which is intended as a long-term ventricular assist device (VAD) as well as a cardiopulmonary bypass pump. In attaining this goal, we began with eliminating the shaft seals by adopting a pivot bearing system at the impeller shaft. In addition, a ring magnet encased in the bottom of the impeller was coupled magnetically to a driver magnet placed outside the pump housing (C1 Prototype). This first model yielded satisfactory performance in vitro with a flow rate of 8 L/min against 250 mm Hg at 2,400 rpm, and an index of hemolysis (IH) of 0.0083 g/100 L using bovine blood. In the second model, the C1 Eccentric Inlet Port Model, the inlet bearing support bar in the prototype were eliminated without reducing the prototype's performance. These designs for antithrombogenicity are being tested by the first in vivo experiment, which has lasted for more than 2 weeks.

The need for standardizing the index of hemolysis

Hemolysis is one of the most important performance parameters of blood pumps. However, comparative in vitro evaluation of the reported hemolysis effect is difficult owing to the lack of uniformity in the test methods used. Currently, three types of formulas are generally accepted and widely used for the index of hemolysis: the traditionally used index of hemolysis (defined as grams of plasma free hemoglobin released per 100 L of blood pumped); the normalized index of hemolysis (normalized by hematocrit); and the modified index of hemolysis (taking into account not only hematocrit but also hemoglobin). In addition, the tested blood conditions are often not indicated in the reports. To address this confusing situation, all three indices of hemolysis were routinely derived in our laboratory. To avoid further confusion, the tested blood conditions and test loop were defined in each study in our laboratory. If we limit the acceptable range of hemoglobin in human blood, the normalized index of hemolysis is sufficient. Furthermore, using milligrams as the unit of expression would be easier and reasonable for comparing the less hemolytic blood pumps, such as the centrifugal pumps that are currently available clinically. We would like to propose this value of a normalized index of hemolysis in milligrams as the most useful formula for the index of hemolysis in the assessment of various types of rotary blood pumps.

Totally implantable total artificial heart and ventricular assist device with multipurpose miniature electromechanical energy system

A multipurpose miniature electromechanical energy system has been developed to yield a compact, efficient, durable, and biocompatible total artificial heart (TAH) and ventricular assist device (VAD). Associated controller-driver electronics were recently miniaturized and converted into hybrid circuits. The hybrid controller consists of a microprocessor and controller, motor driver, Hall sensor, and commutation circuit hybrids. The sizing study demonstrated that all these components can be incorporated in the pumping unit of the TAH and VAD, particularly in the centerpiece of the TAH and the motor housing of the VAD. Both TAH and VAD pumping units will start when their power line is connected to either the internal power pack or the external battery unit. As a redundant driving and diagnostic port, an emergency port was newly added and will be placed in subcutaneous location. In case of system failure, the skin will be cut down, and an external motor drive or a pneumatic driver will be connected to this port to run the TAH. This will minimize the circulatory arrest time. Overall efficiency of the TAH without the transcutaneous energy transmission system was 14-18% to deliver pump outputs of 4-9 L/min against the right and left afterload pressures of 25 and 100 mm Hg. The internal power requirement ranged from 6 to 13 W. The rechargeable batteries such as NiCd or NiMH with 1 AH capacity can run the TAH for 30-45 min. The external power requirement, when TETS efficiency of 75% was assumed, ranged from 8 to 18 W. The accelerated endurance test in the 42 degrees C saline bath demonstrated stable performance over 4 months. Long-term endurance and chronic animal studies will continue toward a system with 5 years durability by the year 2000.

In vitro and in vivo validation tests for total artificial heart

Properly planned in vitro and in vivo studies are mandatory to validate blood pump performance. However, standard procedures for in vitro and in vivo tests of total artificial heart (TAH) performance still do not exist. At Baylor College of Medicine, standard tests procedures for performance validation of the totally implantable TAH have been established. In this paper, these in vitro tests protocols (performance mapping tests, accelerated endurance test, hemolysis test, flow visualization tests, etc.) are described as well as in vivo test procedures (TAH implantation procedure, including surgical technique, postoperative management and tests, etc.). In addition, pathological protocols are presented. In our experience, these procedures are very simple, easy to perform, and inexpensive. These protocols are proposed as standard in vitro and in vivo tests for a TAH.

Successful thermal management of a totally implantable ventricular assist system

Thermal management of the implantable ventricular assist system (VAS) is important not only from the pathophysiological point of view but also from the standpoint of system endurance. The heat distribution within the Baylor VAS was measured using different motor housing materials and environmental conditions. The temperature of the circulating water in the mock loop was set at 37 degrees and 42 degrees C. A polycarbonate motor housing was not a suitable material because of the high temperature development in the actuation system. An anodized aluminum housing demonstrated excellent heat conductivity. The surface temperature of this motor housing was 41.6 degrees C when immersed in circulating water at 42 degrees C. Heat conduction from the motor to the circulating blood revealed an effective thermal path. In the worst case, the heat flux of the motor to the circulating blood revealed an effective thermal path. In the worst case, the heat flux of the motor housing was calculated to be less than 0.062 W/cm2--an acceptable level for the surrounding tissues.

Flow visualization in the Baylor total artificial heart

To analyze the flow patterns of the left and right blood chambers of the total artificial heart (TAH), flow visualization studies were performed. Two setup levels were used for the flow visualization studies. For estimating the global flow patterns, the pumps were illuminated using incandescent light, and the patterns were recorded by either videotape or photography. To evaluate sectional flow patterns, a laser light was applied, and the pump could be scanned segmentally. The flow patterns were recorded by a high-speed camera. A signal was also used that synchronized the timing of the camera shutter to the pusher-plate movement signal. In the left pump chamber, major stagnations were observed in the middle area of the inflow site. To solve this problem, a modification was made that changed the inflow direction appropriately. After evaluation of the inflow port direction, a proper flow pattern was obtained, which was validated by a global flow visualization study. Furthermore, both pump chambers indicated excellent flow patterns as obtained by a segmental flow visualization study method utilizing a laser light. The Baylor TAH demonstrated excellent flow patterns in flow visualization studies, with antithrombogenicity expected. These flow visualization studies are very useful not only for validations of global flow patterns but also for validations of local areas of stagnation in various blood pumps.

Cardiopulmonary bypass with Nikkiso and BioMedicus centrifugal pumps

In our department, a new compact and atraumatic centrifugal pump, Nikkiso, was developed as a second-generation cardiopulmonary bypass pump. To assess and confirm the function and controllability of this pump, comparative studies of cardiopulmonary bypass with Nikkiso and BioMedicus centrifugal pumps were performed using calves. Both pumps provided pump flows of 60-70 ml/kg/min without incidence. The hemodynamics of both groups were stable and within the normal range, and no leakage or thrombus formations were observed in either pump. All hematology and biochemistry data showed no significant differences between the two groups. Plasma free hemoglobin values of the Nikkiso pump tended to be lower than those of the BioMedicus pump. The Nikkiso pump was easy to handle because of its smaller size, and air removal was easily performed because of its low priming volume. The Nikkiso pump demonstrated easy manipulation and good controllability. This compact, atraumatic centrifugal pump meets the requirements for a second-generation cardiopulmonary bypass pump.

[Endopyelotomy for ureteropelvic junction obstruction: results and complications]

We treated eleven cases of primary ureteropelvic junction obstruction with percutaneous endopyeltomy. Endopyelotomy was successful in nine of the eleven cases. Complications during and after endopyelotomy occurred in three cases, two of which had pyelonephritis and the other severe postoperative hemorrhage requiring blood transfusion due to incision of a posterior crossing vessel. In this last case, the kidney was supplied by three arteries. The lower segmental artery passed behind the ureter. We emphasized that angiography should be performed to rule out the presence of a posterior crossing vessel before endopyelotomy, when it is doubtful if an extrinsic cause of ureteropelvic junction obstruction is present.

Efficient laser-diode-pumped neodymium-doped calcium-niobium-gallium-garnet laser

Efficient lasing of Nd:Ca (Nb, Ga)(2-x) Ga(3)-garnet (CNGG) disordered crystal pumped by a laser diode was demonstrated. In the end-pumped cw lasing experiment with a single-stripe diode, a slope efficiency of 24.2% and a maximum optical conversion efficiency of 19.3% were obtained. It was shown that the dependence of cw output power on the pump wavelength is insensitive compared with Nd:YAG because of the broad pump absorption bandwidth of Nd:CNGG. From the diode-bar-pumped experiment, it was confirmed that Nd:CNGG is a promising material for diode-bar pumping to obtain high average power with good beam quality, because of its advantages of a broader pump absorption band compared with that of Nd:YAG and the higher thermal conductivity compared with Nd-doped glasses.

[Studies of combined treatment of radiofrequency hyperthermia with anticancer agents or irradiation for invasive bladder cancer]

Using an in vitro colony forming assay system, the cytotoxic effects of anticancer agents alone, adriamycin (ADM) and bleomycin (BLM), and the combined effects of hyperthermia and anticancer agents on cultivated KK-47 cells were investigated. When the hyperthermia was combined with various concentrations of ADM ranging from 0.005 to 0.1 microgram/ml and BLM from 0.01 to 1.0 microgram/ml, enhanced cell killing effects were obtained at the concentration of less than 0.02 microgram/ml of ADM and with an increase of BLM concentration. In DNA specimens obtained from the livers of chick embryos inoculated with human tumor cultivated cells, the polymerase chain reaction technique was used to amplify a DNA fragment specific to the beta-globin gene. By detecting these amplified DNA fragments, the feasibility of efficiently detecting metastatic cells present in chick embryo was demonstrated in vivo. Hyperthermic therapy showed inhibitory effects on the growth of metastasized cultivated cells in a thermal dose-dependent manner. Combination therapy of ADM, mitomycin and carboplatin and hyperthermia had an enhanced inhibitory activity on the growth of metastasized cultivated human tumor cells derived from bladder cancer. Hyperthermia using radiofrequency-capacitive heating in combination with irradiation or anticancer agents, was performed in a total of 56 patients with T2 to T4 invasive urinary bladder cancer. A tumor regression rate of 50 percent or more was obtained in 21 of these 56 patients. We have to follow up the patients for longer periods more precisely to evaluate the role of these treatments.

Azidobutyryl clentiazem, a new photoactivatable diltiazem analog, labels benzothiazepine binding sites in the alpha 1 subunit of the skeletal muscle calcium channel

[3H]Azidobutyryl clentiazem, a new photoactivable diltiazem derivative, has a higher binding affinity than azidobutyryl diltiazem. It can be covalently incorporated into the alpha 1 subunit of the skeletal muscle calcium channel by UV irradiation, which allows the benzothiazepine binding site to be determined. The photolabeled alpha 1 subunit and its proteolytic fragments were analyzed with a panel of sequence-directed antibodies. The results suggest that the linker region between segment S5 and S6 of domain IV is involved in benzothiazepine binding. This site is different from the dihydropyridine and verapamil binding sites.

[A case of complete remission of metastatic skin carcinoma (erythema type) from advanced gastric cancer by CDDP administration]

A 75-year-old female with skin metastasis from advanced gastric cancer (portion A, tub2, ss beta, n2, P0H0, Borrmann 3-type) was successfully treated with CDDP at a dosage of 25 mg/body every week or two. She had undergone R2 curative subtotal gastrectomy in October 1986, and had orally taken tegafur 300 mg/day as postoperative adjuvant chemotherapy. Three years after the operation, she had skin erythema at chest and neck. A pathological examination revealed that the skin erythema was a metastasis of gastric cancer. After administration of 5-FU and MMC, the skin lesion diminished in size, but in November of 1990, it expanded again. Administration of 5-FU, MMC and epirubicin was not effective. The skin lesion expanded extensively and changed to nodular type. CDDP was intermittently administered from August 1991 to December 1991, 25 mg/body div. every week or two; the total volume of CDDP reached 225 mg. The metastatic skin carcinoma disappeared and a complete response was obtained. CEA, which had been high (190 ng/ml), regained the normal level. Thrombocytopenia and liver dysfunction developed as side effects, but reduced after cessation of CDDP administration. The patient has been well for 3 years and 6 months since the onset of the skin metastasis.

[An epidemiological study on chronicity and incidence of hepatocellular carcinoma in the sequence of epidemic hepatitis]

From November 1951 to 1954, 416 patients in Kumayama Town, Okayama Prefecture, suffered from epidemic hepatitis, so-called "Kumayama Hepatitis". The mortality rate was 13.98% in the first one year, and the rate of progress to chronic hepatitis after 10 years was 24.6%. In the present study surveyed in 1991, 720 residents in this area had 13.6% positive anti-HCV (C100-3), significantly higher than in control areas. The rate of positive anti-HBs and abnormal liver functions in the subjects with positive anti-HCV was 42.9% and 40.8%, respectively. In 29 patients with clinically typical "Kumayama Hepatitis", the positivity rate of anti-HA IgG, anti-HBs, and anti-HCV, and the prevalence of abnormal liver function was 82.8%, 41.4%, 34.5%, and 10.3%, respectively. In conclusion, it is suggested that the hepatitis epidemic in Kumayama Town was caused by HAV and superinfected by HCV and/or HBV, then its clinical manifestations became complicated.

Identification of 1,4-dihydropyridine binding domains within the primary structure of the alpha 1 subunit of the skeletal muscle L-type calcium channel

Calcium channel blockers are drugs that bind to the alpha 1 subunit of L-type calcium channels and selectively inhibit ion movements through these channels. Determination of the mechanism of channel blockade requires localization of drug-binding sites within the primary structure of the receptor. In this study the 1,4-dihydropyridine-binding site of the membrane bound receptor has been identified. The covalently labeled receptor was purified and digested with trypsin. The labeled peptide fragments were immunoprecipitated with sequence-directed antibodies. The data indicate the existence of at least three distinct dihydropyridine-binding domains within the primary structure of the alpha 1 subunit.

Flow cytometric DNA analysis demonstrates contralateral testicular deterioration in experimental unilateral testicular torsion of prepubertal rats

It has been postulated that unilateral testicular torsion causes damage to the contralateral testis and reduces fertility. However, in animal studies such an effect has not been fully proven by histopathologic examination or other conventional assays of spermatogenesis. We investigated the effect of unilateral testicular torsion on contralateral spermatogenesis in prepubertal rats using quantitative flow cytometric DNA analysis. Male rats were divided into three groups which underwent sham-operation, simple hemiorchiectomy or unilateral testicular torsion. Five weeks after these operations, fertility and spermatogenesis by flow cytometry were evaluated. No significant differences were observed in body weight, contralateral testicular weight or serum testosterone concentration among the three experimental groups. In the torsion group, mean seminiferous tubular diameter, number of foetuses, fertility rate and percentage of haploid cells were all significantly decreased compared to the other two groups. These results suggest that unilateral testicular torsion causes damage to the contralateral testis and consequently can reduce the future fertility of prepubertal rats.

A fluid dynamic analysis of a rotary blood pump for design improvement

The proper design of a left ventricular assist device (LVAD) requires an understanding of the pump's fluid dynamic and biocompatible properties. A hydraulically efficient system minimizes the power required for pumping. Biocompatibility refers to the ability to pump blood with minimal hemolysis and thrombus formation. Typically, shear stresses below a threshold level will not damage blood significantly. A fluid dynamic analysis of a prototype centrifugal pump designed for use as an LVAD was performed to establish flow characteristics. A flow visualization technique using Amberlite particles suspended in a glycerin/water blood analogue was used. The system was illuminated with a 1 mm planar beam strobed helium-neon laser, and the results were recorded photographically. An analysis of photographs revealed laminar and turbulent flows with vortices within an illuminated plane in both the inlet and outlet port areas. From these data, velocity and shear stress profiles were generated that showed possible areas of improvement. It was concluded that the outlet port design could be improved by changing its angle and the continuity of its expansion. The inlet port could also be improved by smoothing the transition area between the inlet tube and the pump body to allow for gradual acceleration of the entering fluid.

[Analysis of proliferating cell nuclear antigen and nucleolar organizer region in testicular tumors]

Immunohistochemical staining using the monoclonal antibody of proliferating cell nuclear antigen (PCNA) and argyrophilic nucleolar organizer region associated protein (AgNOR) staining were performed on 28 paraffin-embedded testicular tumors, and their correlation was assessed according to histological type, clinical staging and tumor markers. PCNA positive rates and AgNOR numbers in nuclei were 57.9%, 4.38 in seminomas, 63.4%, 5.79 in embryonal carcinomas, 37.7%, 2.63 in teratomas, 61.3%, 4.43 in yolk sac tumors, 79.5%, 7.12 in choriocarcinomas, and 20.9%, 3.03 in cells of the normal seminiferous tubule, respectively. In pure seminomas, the PCNA positive rates and AgNOR numbers of the stage II to III group (72.6%, 4.75) were higher than those of the stage I group (47.8%, 3.67), but there was no significant difference between the two groups. There was a significant correlation between PCNA positive rate and AgNOR number in all specimens (r = 0.76, p < 0.002). These findings indicate that PCNA and AgNOR are suitable indicators for proliferative activity of testicular tumors.

Baylor Gyro Pump: a completely seal-less centrifugal pump aiming for long-term circulatory support

A seal-less centrifugal pump aiming for long-term circulatory support has been developed. In this model, shaft seals that cause thrombus formation and blood leakage were eliminated. A brushless direct current motor was incorporated as a driving unit, and pivot bearings were used to support the impeller. With reference to its motor-driven system, this pump was named the M-Gyro Pump. The first model (M1) yielded an index of hemolysis of 0.005 g/100 L using bovine blood and demonstrated satisfactory performance as a right heart assist for 2 days (4 L/min, 60 mm Hg, 1,800 rpm). The second model (M2) has been developed for left heart assist by employing a stronger motor. The pump capacity was improved to 6 L/min against 240 mm Hg at 1,800 rpm, but significant heat generation was observed. By optimization of motor efficiency, the M2 model can be improved to meet the requirements of a pump for left heart assist.

A comparison of current expressions of nasal patency

Rhinomanometry is well established as a useful clinical method for objective assessment of nasal patency, although several expressions of nasal patency have been reported and universal standardization has not been achieved. In this communication, nasal resistances were calculated from the equation R = delta P/V (R; resistance; delta P; transnasal differential pressure; V; nasal airflow) at delta P 100 Pa and at peak flow. Time-averaged nasal resistances and integrated nasal patencies were measured in 350 adult patients by Rhinorheograph MPR-1100 and processed by a NI-101 computer program. The values from the equation R = delta P/V at delta P 100 Pa were slightly lower than those from the same equation at peak flow or those from the time-averaging method. Correlations between the values of nasal resistance at peak flow and the time averaging method were very close to the line of identity. No significant correlations were demonstrated between integrated nasal patency and the values from the other three expressions. The differences of the results from these expression are discussed.

Direct and indirect effects of human interferon alpha on renal cell carcinoma: a new in vitro assay system for evaluating cytokine-mediated antitumor effects

A highly purified natural alpha-interferon (nIFN alpha) was tested in vitro for direct and indirect antiproliferative activity against renal cell carcinoma (RCC), using a modified human tumor clonogenic assay and clinically achievable concentrations. In preclinical experiments, the indirect (cytokine-mediated) antiproliferative activity of nIFN alpha was investigated using ACHN cells (established human RCC cell line). Continuous exposure to nIFN alpha at concentrations of more than 5 IU/ml in the presence of feeder cells (a mixture of 5 x 10(4) monocytes/dish and 5 x 10(5) lymphocytes/dish, obtained from healthy donors) significantly inhibited colony formation of ACHN cells in comparison with growth inhibition in the absence of feeder cells (P < 0.05). Various cytokines were measured in the supernatants lying over the medium on the feeder-layer agarose containing the same conditioned feeder cells. With IFN alpha at 500 IU/ml, tumor necrosis factor alpha (TNF alpha) and IFN gamma were detected at markedly high levels for 2-24 h. Neutralizing anti-TNF alpha monoclonal antibody significantly reduced the indirect antiproliferative activity. Using our modified human tumor clonogenic assay technique, sufficient numbers of colonies for drug testing were observed in 19 of 31 surgical specimens (61.3%). In these clinical materials, nIFN alpha at a clinically achievable concentration (50 IU/ml) significantly inhibited colony growth in the presence of feeder cells consisting of 5 x 10(4) monocytes/dish and 5 x 10(5) lymphocytes/dish, obtained from the patient whose tumor was examined (P < 0.05). In colony-forming cases, a significant correlation between the percentage colony survival and TNF alpha concentration in the supernatant was observed (r = -0.95, P < 0.01). These results suggest that this assay system may be an appropriate technique for evaluating the antiproliferative activities of nIFN alpha involving cytokine-mediated action, and that TNF alpha may play an important role in this cytokine-mediated activity.

The Baylor-ABI electromechanical total artificial heart. Accelerated endurance testing

To test the durability of each part or assembled component of the Baylor-ABI total artificial heart (TAH), the authors performed an endurance test under severe conditions. The TAH was immersed in a saline bath at 42 degrees C, which is 4-5 degrees C higher than normal body temperature. This is an accelerated endurance test because of the elevated temperatures. In this accelerated endurance test loop, the 42 degrees C heated saline was circulated not only in the pump but also outside the pump. During pumping, temperatures of the motor and outside surface of the centerpiece were continuously measured. This testing showed that during almost 4 months of pumping no electromechanical troubles were observed. Both inside (motor) and outside temperatures were stable and the differences in both temperatures were only 3-4 degrees C, demonstrating that heat generation is not a problem. The voltage and current required in this system remained constant, indicating stable and reliable performance. Based on these results, this pump is expected to run continuously over a long duration in a normal physiologic environment. This accelerated endurance test system is very suitable for estimating the influence of heat generation by the actuator of blood pumps. It is also quite useful in validating the durability of various cardiac prosthesis.

Development of the Baylor-Nikkiso centrifugal pump with a purging system for circulatory support

The Baylor-Nikkiso centrifugal pump is a magnetically coupled system with a V-ring seal separating the pump and the actuator chamber. To prevent thrombus formation behind the impeller and to extend the life of the pump to 2 weeks of continuous operation, we incorporated a purging chamber behind the V-ring seal. An external pump connected to this purging chamber infused fluid at a constant rate to wash the shaft-seal area. To evaluate the effectiveness of the purging system, we have carried out biventricular bypass experiments using calves. The purging system was successful in reducing the level of thrombus formation after 2 weeks of operation. The results of these studies confirmed that the Baylor-Nikkiso centrifugal pump with this purging system is suitable for at least 2 weeks of continuous operation as a circulatory support system.

Inhibition of metalloproteinase activity of rheumatoid arthritis synovial cells by a new inhibitor [BE16627B; L-N-(N-hydroxy-2-isobutylsuccinamoyl)-seryl-L-valine]

The effect of a new metalloproteinase (MP) inhibitor [BE16627B; L-N-(N-hydroxy-2-isobutylsuccinamoyl)-seryl-L-valine, MW: 375.2] isolated from Streptomyces sp. was evaluated by using primary cultures of synovial cells from rheumatoid arthritis patients. BE16627B selectively inhibited MPs such as human stromelysin and 92 kD gelatinase. After the cells were cultured with BE16627B for 5 days, BE16627B inhibited MP activity in the primary culture supernatants from synovial cells in a dose-dependent fashion without showing apparent cytotoxicity or affecting the production and secretion of MPs. Its IC50 for active collagenolysis before activation by trypsin was 25 microM.