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Biomedical subjects

Y Nosé

Publications and source records attributed to Y Nosé.

At least 19 recordsLinked to original sources
PubMed1992

Selective removal of cholesterol by plasmapheresis and the progression of atherosclerosis.

There is a strong correlation of plasma cholesterol levels with the risk of coronary heart diseases as shown by epidemiologic studies. This study was undertaken to evaluate the effect of plasma cholesterol lowering on the progression of atherosclerosis in the homozygous Watanabe heritable hyperlipidemic (WHHL) rabbit. The effect of cholesterol lowering, which was accomplished by thermofiltration (on-line plasma separation with plasma filtration at 39 degrees C) was evaluated by comparison between treated and untreated control groups. Thermofiltration reduced significantly the mean plasma level of total cholesterol (284 vs. 655 mg/dl, P = 0.0005) and the percent aortic area occupied by atherosclerotic plaque (15.0 vs. 44.2%, P = 0.0003). The total lipid and cholesterol contents in the aortas in the treated group were also significantly lower than those in the control group. Microscopically, thickness measurements of the lesions showed that the mean thickness of the fibrous cap and the ratio of the thickness of the intima to that of the media were smaller for the treated group than the control group. This study demonstrated the slowing or stopping of the progression of atherosclerosis by lowering the plasma total cholesterol level in WHHL rabbits.

Animals↗
PubMed1992

A compact centrifugal pump for cardiopulmonary bypass.

A majority of the cardiopulmonary bypass (CPB) systems still utilize bulky roller pumps. A direct-drive small centrifugal pump intended for second-generation CPB pump has been developed. The pump has a 50 mm diameter impeller and provides a 6 L/min flow at 3,000 rpm against 300 mm Hg. A flexible drive shaft allows us to separate the pump head from the console resulting in easier manipulation. An in vitro study showed that the pump generated less hemolysis (index of hemolysis = 0.0011, comparable to the value for Bio-medicus BP-80). To improve blood flow around the shaft-seal region and to reduce thrombus formation around the shaft, six holes were drilled through the impeller. In biventricular bypass experiments using calves, our pump demonstrated excellent antithrombogenicity and durability for 48 h. And the compact and atraumatic centrifugal pump system showed excellent performance and easy manipulation under actual CPB conditions in animal.

Animals↗
PubMed1992

Versatile one-piece total artificial heart for bridge to transplantation or permanent heart replacement.

A versatile, one-piece total artificial heart (TAH) system that can be driven by either an electromechanical acutator (EM-TAH) or a pneumatic source (P-TAH) has been developed. The common units for both TAHs are the conically shaped left and right pusher-plate-type pumps (63 ml SV) that sandwich a thin centerpiece (18 mm) having a respective actuator. The EM actuator, mounted in the middle of the centerpiece, consists of a direct-current brushless motor and a roller screw while the pneumatic actuator consists of a low-pressure air source. The outer diameter of the pumping unit is 97 mm with its central thickness being 82 mm; overall volume is 510 cc. The TAH is operated in the left master alternative ejection mode with the left pump fill signal. High-flex-life Hexsyn rubber is used as the diaphragm, and the blood-contacting surface is coated with dry gelatin. The TAH can provide 3-8 L/min flow with a preload of 1-10 mm Hg against 100 mm Hg afterload. Anatomical fit of the pumping unit has been demonstrated in the pericardial space of 26 heart transplant recipients with average body weight of 78 kg. To date, 2 P-TAH and 4 EM-TAH (1 week) implantations were performed in 80-100 kg calves demonstrating excellent anatomical fit, controllability, and biocompatibility. This versatile TAH is suitable for a bridge to transplantation or permanent heart replacement.

Animals↗
PubMed1992

Is a totally implantable artificial heart realistic?

The incidence of local infection that occurred after the implantation of the intrathoracic Jarvik 7 total artificial heart (J-7 TAH) in patients was a major problem of this cardiac prosthesis. Infection rates increased when the J-7 TAH was implanted for longer periods of time, which was contrary to the results that were obtained by the implantation of the left ventricular assist devices (LVAD) either in the abdominal cavity or in the abdominal wall. Currently, the general belief is that the implantation of a cardiac prosthesis inside of the chest cavity is not safe, due to higher rates of infection. Thus, Part I of this paper deals with the question: "Is a total artificial heart physiologically acceptable?" We believe structural differences of the J-7 TAHs and other LVADs are an important part of the problem. The J-7 TAH is a volumetrically dynamic pump, and the other LVADs are a volumetrically fixed stationary pump. Based upon experiences of this investigator, intrathoracic implantation of a smooth surface pulsating device (or a volumetrically dynamic pump) generated persistent local inflammatory reactive tissues directly adjacent to the device. These tissue capsules were nonadherent to the device, and therefore may produce an ideal environment for allowing bacteria to grow. The findings were opposite to those for a non-pulsating surface pump inside the chest cavity. Part II of this paper discusses the question: "Is a totally implantable artificial heart technically achievable?" Many technical problems for the totally implantable TAH were already resolved during the development program of the totally implantable LVAD. However, there are three TAH specific problems that remain to be solved before achieving a clinically useful totally implantable TAH system. They are (a) anatomical compatibilities of the TAH system; (b) reliable control of the TAH system, (c) reliable and effective long-term operation of the TAH system. We have resolved the anatomical problem by the integral design of the pump-actuator system. Overall size of the hard shell Baylor TAH system is 510 cm3 with a diameter of 97 mm and a width of 82 mm. Its stoke volume was reduced to 63 cm3. The stable and reliable control of TAH performances was established by the three sets of Hall effect sensors with left master alternate mode of pumping. No physiological parameter was used as a feedback signal. Reliable long-term operation of the TAH system was established by the electromechanical actuation system. A simple drive mechanism with commercially available components and subsystems was used.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Immunomodulating effects of serum-material interactions.

The objective of this study is to evaluate an in vitro model to assess the effects of serum-material interactions on complement activation, macromolecular adsorption, and lymphocyte response. Minifilters of clinically available materials (PVA, EVAL-4A, and EVAL-D) used in extracorporeal therapies were evaluated. The test circuit consisted of a pump, sterile tubing, collection vessels, and the minifilter. A sham circuit similar to the test circuit was constructed, but without the filter. Serum flow rates and volumes processed were scaled down to those of clinical use. Post PVA serum showed the highest degree of complement activation, macromolecular solute adsorption, and lymphocyte suppressive response when incubated with Con-A, PHA, PWM, and Candida. Post EVAL-4A sera enhanced the response of lymphocytes to Con-A and PHA, while Post EVAL-D sera showed a slight suppression to these mitogens. Blood-material interactions have been shown to cause blood cellular changes. The in vitro model employed is simple to apply and does not require an animal or patient. The membrane modules used are a mini-type of clinically available extracorporeal filters, and there is a greater direct relevancy to clinical applications than there would be using specially formulated materials. This system would provide useful preclinical information in evaluating the effect of serum-material interactions.

Blood Physiological Phenomena↗
PubMed1991

Artificial liver. State of the art.

If an effective hepatic assist system existed, it could serve as a bridge to transplantation. Most of the patients waiting for liver transplantation have chronic liver insufficiency but are not in hepatic coma. Various hepatic assist systems have been used to salvage patients with acute liver insufficiency. Most attempts have been disappointing. The methods used have included plasma exchange, plasma adsorption, double filtration, cryofiltration, thermofiltration, the combination of plasma exchange and amino acid hemodialysis, and others. For patients with chronic liver disease with moderate liver function impairment and limited to one or only a few areas of metabolic abnormality, a hepatic assist might allow the life of the patient to be maintained temporarily. The application of hepatic assist methods for chronic liver disease patients treated at the Cleveland Clinic has been encouraging. One of the patients who suffered from sclerosing cholangitis has maintained a near-normal life for almost five years by 170 plasma treatments. This is in spite of the fact that, at the onset of treatment, the patient was nearly comatose. Unfortunately, this patient did not wish to receive a liver transplantation. Based upon this experience, the concept of a bridge to transplantation approach to hepatic assist devices appears feasible. In addition, it is speculated that hepatic assistance during the early recovery stage of liver transplantation and during mild episodes of rejection may be useful.

Animals↗
PubMed1991

Characterization of rehydrated gelatin gels.

Five percent glutaraldehyde cross-linked gels have shown excellent blood compatibility as coatings for cardiac prostheses. A method was developed for producing thin dehydrated coatings using a proprietary dehydration procedure and ethylene oxide (EO) sterilization. The swollen surfaces of rehydrates versus wet (original) gels were compared. Within 30 min of saline rehydration, dry 30-50-microns films on textured surfaces became smooth, uniform, and comparable to original gelatin gels. Mechanical test results after rehydration showed values for strain remain unchanged (39.3 + 10.0 to 40.0 + 7.8%), but stress increased (2.79 + 1.21 to 4.22 + 1.60 dyne/cm2; p less than 0.01). The contact angle data reported gamma C values of 26.1 and 30.4 dyne/cm for original and rehydrated gels. Using a coulometric titrimeter, the measured water content of original gels was reduced from 85 to 3.4% after drying. Dried and saline rehydrated gels had a 73.2% moisture content. Gels shrank 8.8% of their original length after rehydration; however, the thickness of all pump coatings remained stable. Two-hour incubations with bovine platelet rich plasma showed no differences in platelet reactivity or morphology when compared to original gels. Light microscopy and scanning electron microscopy (SEM) showed no evidence of gel cracking or surface defects after pump endurance testing for 3 and 5 weeks. The process of dehydration eliminates the wet storage and sterility problems of such hydrogels and provides a stable film coating for a variety of blood-contacting substrates.

Biocompatible Materials↗
PubMed1991

Dynamic rehabilitation of the paralyzed face: III: Balanced coupling of oral and ocular musculature from the intact side in the canine.

We have recently demonstrated the feasibility of artificial agonist/antagonist coupling between intact facial and reinnervated strap muscles in the rabbit. The present study broadens this principle to involve bi-level cross-facial innervation. After severing the facial innervation unilaterally in four dogs, a nerve pedicle from a cervical motor nerve was implanted into the orbicularis oris and from the deep temporal nerve into the orbicularis oculi. After neurotization (5.6 months), the pedicles were electrically stimulated to verify muscular response. Graded contraction on the intact side was induced by stimulating the ipsilateral facial nerve with currents of various pulse widths. The resulting compression of a strain gauge on the intact face triggered a two-channel, opto-isolated, pulse width-modulated stimulator to produce agonistic graded contraction at one level of the reinnervated side (e.g., oral) and reciprocal relaxation in its reinnervated counterpart (e.g., ocular). The sophistication of the present model--as compared to the original pilot study--brings us one step closer to dynamic human facial rehabilitation.

Animals↗
PubMed1991

Effects of single-dose infusion of pyridoxalated-hemoglobin-polyoxyethylene conjugate solution on canine renal function.

Pyridoxalated-hemoglobin-polyoxyethylene conjugate (PHP) is an acellular oxygen-carrying red blood cell substitute made from outdated human red blood cells. This study assessed the effect of PHP on renal function when PHP was infused with a clinically relevant dosage. A single dose of PHP that contains 8% wt/vol each of hemoglobin and maltose or an 8% maltose control solution was infused into the intact circulation of eight dogs (five dogs for PHP and three for the control; 20 ml/kg each, at the rate of 2.5 ml/h/kg for 8 h) in the awake state. Serial measurements of glomerular filtration rate (GFR) and renal plasma flow (RPF) were carried out before and after infusion for up to 2 weeks, along with determinations of urine volume flow rate, fractional excretion of sodium (FES), and free water clearance (CH2O). The results showed an elevation of plasma colloid osmotic pressure by an average of 4.4 mm Hg immediately postinfusion with PHP solution. An average 23% decrease in GFR, without notable changes in RPF immediately postinfusion, was observed in the PHP group; the value returned to the preinfusion level by 1 week postinfusion. Increases in parameters such as urine output, FES, and CH2O, which were more pronounced in the PHP group, were observed for 24 h after the infusion in both groups. Light microscopic examination of kidney specimens taken at 2 weeks postinfusion revealed a slight degree of vacuole formation in approximately 80% of the proximal tubules in the PHP group. The tubules were devoid of typical pathologic features of acute renal failure, and the vacuoles did not cause any observable changes in the assessed tubular functions.

Animals↗
PubMed1991

Rapid improvement in a patient with leukocytoclastic vasculitis with secondary mixed cryoglobulinemia treated with cryofiltration.

A patient with leukocytoclastic vasculitis (LCV) with secondary mixed cryoglobulinemia was treated by cryofiltration in an effort to stop the progression of the disease despite the use of high dose prednisone. Three cryofiltration procedures within one week were performed on this patient. Clinical assessments made through the course of this therapy and the followup period showed excellent response. Peripheral blood mononuclear cell transformation functions (MNC-TF) were evaluated at the pre-1st and post-2nd cryofiltration treatment. MNC-TF pretreatment were significantly suppressed. Post-2nd cryofiltration, MNC-TF were improved. Our study demonstrates that cryofiltration is a safe and effective treatment of a patient with LCV with secondary mixed cryoglobulinemia, without requiring plasma replacement products.

Adolescent↗
PubMed1990

Electrical control of gastric emptying in denervated and reinnervated canine stomach: a pilot study.

Gastric emptying of solids is abnormally slow after vagotomy. To determine whether it was possible to accelerate emptying by electrical stimulation either of the gastric wall directly or of a "foreign" nerve brought in to reinnervate the stomach, eight dogs underwent truncal vagotomy (TV); five of the dogs received intercostal nerve muscle pedicle (NMP) implants. Gastric atony was demonstrated postoperatively in all animals up to 4 months later by means of radiological contrast studies. After allowing time for neurotization to occur (mean 78 days), the cervical vagi were stimulated to confirm that TV was complete. Gastric peristalsis, intraluminal pressures, and emptying were assessed during stimulation of the NMPs and of the gastric wall, followed by sacrifice for histologic study. Neither reinnervation alone nor stimulation of the NMPs improved emptying. Although viable somatic nerve was found in the gastric wall, nerve sprouting was not. By contrast, stimulation of the gastric wall with trains of pulses (20 Hz, 2-10 ms, 2-5 mA) evoked peristalsis in all animals. We conclude that somatic nerve tissue cannot produce functional reinnervation of a visceral organ; however, direct muscular stimulation can accelerate gastric emptying after TV.

Abdominal Muscles↗