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At least 649 records · Page 36Linked to original sources

PubMed2004

[Biomaterials].

Biomaterials are essential components in the development of artificial organs. Synthetic polymers are widely used for a number of biomedical applications: a) as medical supplies, b) devices to support or replace malfunctioning body parts or c) systems with a local therapeutic function. The design of biomaterials has developped over the past three decades from devices with a mechanical function, over systems with a dedicated function (degradable, drug releasing, surface modified) to devices which are tailor made to interact in a smart way with the biological environment. At present polymers are attractive materials to construct scaffolds for tissue regeneration and regenerative medicine. The material design is adapted to the requirements for cell ingrowth, cell migration, angiogenesis etc. This is mainly controlled by the surface topography and chemistry that play a key role in the interfacial material-cell communication. This remarkable development is the direct result of a multi-disciplinary approach, combining material science with engineering, cell biology, molecular biology, medicine and regulatory guidelines.

Animals↗

PubMed2006

Biofluid mechanics--an interdisciplinary research area of the future.

Biofluid mechanics is a complex field that focuses on blood flow and the circulation. Clinical applications include bypass and anastomosis surgery, and the development of artificial heart valves and vessels, stents, vein and dialysis shunts. Biofluid mechanics is also involved in diagnostic and therapeutic measures, including CT and MRI, and ultrasound. The study of biofluid mechanics involves measuring blood flow, pressure, pulse wave, velocity distribution, the elasticity of the vessel wall, the flow behavior of blood to minimize complications in vessel,- neuro-, and heart surgery. Biofluid mechanics influence the lungs and circulatory system, the blood flow and micro-circulation; lymph flow, and artificial organs. Flow studies in arterial models can be done without invasive techniques on patients or animals. The results of fluid mechanic studies have shown that in the addition to basic biology, an understanding of the forces and movement on the cells is essential. Because biofluid mechanics allows for the detection of the smallest flow changes, it has an enormous potential for future cell research. Some of these will be discussed.

Biomechanical Phenomena↗

PubMedDate not supplied

Control of cellular orientation in two-dimensional tissue formation. Surface topologic effect of collagen fibers on endothelialization.

The authors studied the effect of polymorphous states of collagen on in vitro cellular orientation of bovine aortic endothelial cells (ECs). Little orientation of adherent ECs was observed on a nonoriented collagen coated surface, irrespective of culture period. Only ECs that adhered to fiber bundles 10 microns in diameter exhibited cellular elongation or alignment. The collagen membrane with highly oriented fine fibers provided no cellular alignment for ECs in sparse culture. Resultant confluent monolayers, however, were characterized by cellular orientation, suggesting that surface microtopology of collagen induces cellular orientation on incubation. Control of cellular orientation would be an elementary requirement for cell seeding technology leading to hybrid artificial organs.

Animals↗

PubMed1991

[The role of electrocardiographic examination in the complex evaluation of potential heart donors].

From October, 1986 to February, 1990 eighty-five potential donors with death of the brain were examined at the Scientific Research Institute of Transplantology and Artificial Organs, USSR Ministry of Public Health. Thirty of them were used as heart donors in orthotopic transplantation of the heart; 24 (80%) were males and 6 (20%) females. The cause of death of the brain was craniocerebral trauma in 13, brain tumor in 9, hemorrhage into the brain tissue in 7 cases, and gunshot injury to the skull with damage to the brain in one case. In appraisal of the donors; in 8 (26.7%) cases the ECG did not differ from the initial one, in another 8 cases (26.7%) the ECG demonstrated electrolyte disorders in the form of hypokalemia , still in another 8 cases right bundle-branch block was encountered, in 2 (6.65%) the ECG showed transient form of cardiac fibrillation, in still another 2 cases I-II degree atrioventricular block was found, in one (3.3%) right and left bundle-branch block was demonstrated, and in one case the ECG showed diminished nutrition in the region of the posterior left-ventricular wall. All donors had disorders of homeostasis characteristic of patients with death of the brain, while the condition of hemodynamics conformed to these disorders. It is concluded on the basis of the obtained data that electrocardiographic monitoring is expedient and that it plays a role in complex appraisal of a potential heart donor.

Adolescent↗

PubMed1990

Protein adsorption and cellular adhesion and activation on biomedical polymers.

The design and development of new biomedical polymers for clinical application in devices, prostheses, and artificial organs requires a basic and fundamental understanding of biological interactions with biomedical polymers. Efforts in our laboratory have been directed towards appreciating the humoral and cellular interactions which govern protein adsorption and cellular adhesion and activation on biomedical polymers. Information and data are presented on protein adsorption from whole human blood, complement activation and receptors, and monocyte/macrophage adhesion and activation with growth factor release. Supported by experimental evidence, concepts regarding protein/polymer, cell/polymer, cell/protein/polymer, and cell/cell interactions as they are related to in vivo events are presented.

Adsorption↗

PubMed1990

Adsorption of Hageman factor (factor XII) and other human plasma proteins to biomedical polymers.

Protein adsorption to surfaces occurs whenever blood comes into contact with biomaterials, prosthetic devices, and artificial organs. The plasma protein Hageman factor (factor XII) present at the interface between blood and foreign surfaces can be qualitatively and quantitatively detected after in vitro perfusion of anticoagulated human blood through important biomedical polymers. We have determined protein adsorption by a modified radioimmunoassay and by scanning electron microscopy using immunogold labeling techniques. The materials used included vascular graft materials (Dacron and expanded polytetrafluoroethylene) and the National Heart, Lung, and Blood Institute-Devices and Technology Branch reference materials polydimethylsiloxane, polyethylene, and silicone rubber. Factor VIII-von Willebrand factor, another trace plasma protein, and other plasma proteins such as fibrinogen, immunoglobulin G, albumin, fibronectin, and hemoglobin were also detected at the blood-contacting surface. At physiologic flow rates, the adsorption of these proteins from the circulating blood to the surface of these materials appears to be a function of time, with certain materials, as well as of the physical and chemical characteristics of the material surface. Hageman factor adsorption to surfaces, quantified under static conditions, occurs at nanogram concentrations. These data suggest that trace proteins, such as those important in the activation of the coagulation cascade, can significantly affect the blood compatibility or thrombogenicity of an implanted device.

Adsorption↗

PubMedDate not supplied

Endothelialization of vascular prostheses by transplantation of venous tissue fragments.

A method to accelerate the endothelialization of vascular prostheses by seeding venous tissue fragments was developed. A piece of peripheral vein was obtained, chopped into small fragments, and stirred into 20 ml of saline, making a tissue suspension. This suspension was sieved through the wall of a highly porous vascular prosthesis (water porosity: 3,600-4,000). The prostheses, (7 mm ID and 5.7 cm in length) seeded with tissue fragments, were implanted into the thoracic descending aortae of 20 dogs, and were removed from 1 to 371 days after implantation. Ten prostheses, preclotted with fresh blood, were used as controls. In the seeded grafts, an infinite number of endothelial cells migrated and proliferated from the fragments. These had produced numerous capillaries by 5 days after implantation that had reached and opened onto the luminal surface of the prosthesis. From these openings, numerous endothelial cells spread out and formed colonies. With the increase in the size of the colonies, the inner surface was completely endothelialized within 5 weeks. This quick neointimal formation by seeding venous tissue fragments might be applicable to several artificial organs.

Animals↗

PubMed1989

[Evolutionary biological aspects of the physiology of extracorporeal CO2 removal].

Extracorporeal CO2 elimination (ECCO2-R) is a new approach to the treatment of severe respiratory failure. Gas exchange is separated into oxygen uptake by apneic oxygenation through the natural lungs while CO2 is removed extracorporeally with an artificial organ. The physiological conditions of both processes can thus be optimized. In the course of evolution, a similar bimodal gas exchange has developed during the respiratory transition from aquatic gas exchange to pulmonary gas exchange: In air-breathing fish or amphibia oxygenation is accomplished predominantly via the lungs while CO2 is eliminated via gill or skin. Today's air-breathing vertebrates maintain a considerable respiratory acidosis which has to be compensated for by an appropriate bicarbonate level. This is dependent upon gill reduction and skin armor to prevent evaporation leading to a rise in pCO2 from 3-4 to 40 mmHg and a tenfold increase of serum bicarbonate levels. We believe that the developmental history of respiration justifies the use of a bimodal gas exchange system. It is clinically applied as extracorporeal CO2 removal with membrane lungs (ECCO2-R) or, still under investigation, in a hemodialysis-related procedure (extracorporeal bicarbonate/CO2 removal: ECBicCO2).

Animals↗

PubMedDate not supplied

[Results of transplantation of pancreatic islet cell cultures to patients with diabetes mellitus].

Altogether 110 intramuscular pancreatic islet cell (PIC) culture transplantations were performed in diabetes mellitus patients from April 1981 to May 1984 at the Research Institute of Transplantology and Artificial Organs, USSR Ministry of Health: 65 allotransplantations of human fetal PIC and 45 xenotransplantations fo swine fetal PIC. Immunosuppressive therapy was not employed. The paper is concerned with an analysis of a therapeutic effect of the IC cell cull culture transplantation on 30 patients who were followed-up for not less than 1 year after operation. A pronounced and long-term antidiabetic effect was observed in wost of the recepients subjected to the intramuscular human fetal PIC culture transplantation: demand in exogenous insulin decreased, a durable stabilization of a course of disease in patients with labile diabetes mellitus was observed, and in patients with such diabetic complications as polyneuropathy, retinopathy and glomerulosclerosis certain regress of these complications was observed. As to the results of the intramuscular swine fetal PIC culture xenotransplantation the authors note that xenogenic transplantation as compared with IC culture allotransplantation possesses a less noticeable offect on diabetes mellitus complications.

Abdominal Muscles↗

PubMed1985

Platelet and coagulation parameters following millisecond exposure to laminar shear stress.

Blood flowing through artificial organs or arterial stenoses is subjected to high shear for short times. To clarify the effects of short acting high shear forces upon platelets, heparinized PRP was exposed to viscometric flow (57-255 N/m2; 7-700 ms). Before and after shear exposure beta-TG release, LDH liberation, platelet count, and ADP-induced aggregation were assayed. Stypven time-monitored platelet procoagulant activity, determined after heparin neutralization by protamine, proved to be the most sensitive indicator for shear-induced platelet alteration. A shear stress of 170 N/m2, acting for as short a time as 7 ms made available procoagulant phospholipids, whereas beta-TG and LDH liberation required 255 N/m2 for 7 ms, and ADP refractoriness was found only after 113 ms exposure to 255 N/m2. Under these conditions the percent release of beta-TG does not exceed the liberation of LDH, suggesting that the evidence for "shear induced platelet activation" from experiments with exposure times of minutes, is most likely a conventional biochemical rather than biophysical effect.

Adenosine Diphosphate↗

PubMed1986

Enzyme-based hemoperfusion and blood treatment.

Enzyme-based artificial organs are being developed as metabolic assist devices. These are required when normal metabolism is impaired, or when the body is overloaded by undesired metabolites or toxins. The implementations of this approach for treating a genetic disease, and for metabolic support in liver failure are envisaged. The kinetic aspects and mass transfer characteristics of bioreactors for these systems are considered in detail.

Blood↗

PubMed1988

Differences in the release of cholesterol from taurocholate versus taurochenodeoxycholate micellar solutions.

The maximal micellar solubility, distribution and apparent monomer activity of cholesterol in taurine-conjugated cholate and chenodeoxycholate micellar solutions were studied to clarify the different modulating effect of these bile salt species on cholesterol uptake in an intestinal lumen. The maximal micellar solubility was significantly greater in taurochenodeoxycholate. The intermicellar cholesterol monomer concentration was not significantly different between the two kinds of micellar solution. However, the apparent cholesterol monomer activity determined using an artificial organic phase (polyethylene disc) was significantly higher in taurocholate than that in taurochenodeoxycholate. A linear relationship between the intermicellar cholesterol concentration and the apparent cholesterol monomer activity was found, with the slope depending upon the bile salt species. It is concluded that the difference in partitioning of cholesterol from taurocholate and taurochenodeoxycholate micelles into a fixed organic phase may contribute in part to the different regulating effects of these bile salts on the uptake of cholesterol in the intraluminal phase.

Chenodeoxycholic Acid↗

PubMedDate not supplied

[The effect of silicone resin for medical use on the balance of calcium fractions in human blood serum].

Influence of polymeric material upon the character of formation of ion calcium complexes in the blood serum of man was demonstrated and described by following parameters: quantity of binding sites, equilibrium constant for association and Hill's coefficient. These indexes were proposed to be used as evaluation criterion of calcinosis predisposition in articles used for artificial organs.

Adult↗

PubMed1986

Contributions of aerospace medicine to clinical medicine.

The contributions of aerospace medicine to clinical medicine far exceed the aggregate of the clinical applications of individual technologies which originated in aerospace medicine, important though these be. Contributions of aerospace medicine to clinical medicine will be discussed in seven categories: The raising of issues, questions, and need for systems for protection or support for man before such issues and needs were recognized by clinicians to be important or feasible; Contributing to the manpower pool of able clinical investigators through recruitment and special training in research; Providing fundamental insights into specific biologic processes of clinical significance; The recruitment of disciplines not previously involved extensively in addressing biologic problems and the creation or strengthening of hybrid disciplines such as bionics and bioengineering; Pioneering emphasis on safety, prevention and environmental health now being incorporated into clinical medicine; The development of specific research technologies which have been used to address an array of clinical problems; Specific technologies of clinical significance to which aerospace medicine has contributed, including systems for air transport of patients, many components of modern systems for patient monitoring, components of circulatory and ventillatory support systems, hypoxia warning systems, prevention of toxic exposure and treatment of toxic injury, prevention and treatment of burns, restraint systems, artificial organs, the application of models to clinical practice, and the ordering and automating of information processing.

Aerospace Medicine↗

PubMedDate not supplied

Haemoperfusion in the management of end-stage renal disease.

Haemoperfusion, mainly in the form of activated charcoal haemoperfusion, has been investigated for the treatment of end-stage renal disease. Short-term studies have demonstrated that charcoal haemoperfusion devices in combination with haemodialysis are safe, produce reversal of certain symptoms of uraemia, but do little to define the role of haemoperfusion in the management of end-stage renal disease. Long-term studies, however, have demonstrated that reduction in dialysis time may be achievable with the addition of charcoal haemoperfusion to dialysis or ultrafiltration in the routine management of the dialysis patient. However, since charcoal as an adsorbent fails to remove important uraemic toxins such as water, urea, electrolytes, phosphate and sulphate, haemoperfusion does require the addition of dialysis or ultrafiltration for the removal of such toxins. In future, haemoperfusion will probably consist of sorbents added to an ultrafiltration or dialysis device to form a hybrid artificial organ that will combine sorbents suitable for removal of urea, phosphate, etc., and will be a useful treatment in the routine management of end-stage renal disease.

Charcoal↗

PubMed1995

[Peritoneal dialysis of substitution: how to evaluate the quality of purification, the criteria of dialysis efficacy].

Peritoneal dialysis adequacy in the narrowest sense of the world can be evaluated by several indexes. Residual kidney function and caloric protein intake strongly affect the protein metabolism (creatinine, urea) they reflect. The correlation between dialysis adequacy indexes and clinical issue (survival, mortality and morbidity) is rather poor. Each index sets the inferior security limit, but in no way a target to be aimed at. Furthermore, the artificial organ should maintain a normal fluid and electrolyte balance and blood pressure, as performed by the natural kidney. The posology indexes do not materialize this important function. No single indicator can replace clinical evaluation and good sense.

Dietary Proteins↗

PubMed1994

[Training of surgeons for laboratory research].

A degree in surgical research has been set up in 1986 in France. It includes a one-year full time work in a research laboratory, and seminars (one to three days long, each). General surgical research objectives are gathered in a first seminar. Then, candidates select one among four optional subjects: biomaterials-artificial organs, transplantation, oncology, and neurosciences. Two prerequisites are necessary in order to register. The first is to write a research project according to standardized rules, and the second is to attend two seminars, one dealing with scientific communication and the other with methodology in clinical research. A nation-wide valid Academic degree is delivered to candidates who pass an oral presentation of their research report and who attended all seminars according to the optional subject that they selected. From 1986 to 1993, 434 students attended the formation. They came from different regions of France, proving the nation-wide characteristic of the degree, and some from foreign countries. Seminars were held in different French University towns. An increasing number of students become Ph.D.

Education, Medical, Graduate↗

PubMed1994

Biocompatibility of cardiopulmonary bypass: influence on blood compatibility of device type, mode of blood flow and duration of application.

The biocompatibility of artificial organs is recognised as an area presenting difficulties in terms of the complexity of the situation. The nature of the blood response involving interactions of systems, pattern and extent of change, patient status and the influence of the whole device contribute to the complexity. Recognising these, the profile of the blood response to cardiopulmonary bypass (CPB), with respect to type of device, mode of blood flow, duration of the procedure and patient status, has been evaluated by monitoring contact phase activation [Factor XII-like activity (FXIIA)], fibrinolytic activity [Fibrin degradation products (X-FDP's)], complement activation (C3a, C5a), leucocyte activation [Granulocyte elastase (GE)] and platelet and white cell imaging. FXIIA, X-FDP's, and GE rose gradually during CPB, with levels remaining elevated post-operatively for up to 48 h. In contrast, C3a levels rose sharply with no significant elevation in the post-operative period, while C5a did not show significant changes during bypass. The use of pulsatile perfusion resulted in lesser activation of the parameters, although these were significantly less only for GE. The alterations in FXIIA, X-FDP's, C3a and GE correlated positively with the duration of CPB, with this effect pronounced in the post-operative period for FXIIA, X-FDP's and GE. However, these changes had no apparent influence on clinical outcome and the majority of patients had uncomplicated post-operative recoveries. With respect to the use of bubble/membrane oxygenators, platelet and white cell deposition and the patterns of change for FXIIA and C3a were similar in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Biocompatible Materials↗