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PubMed2005

Principles of biological adaptation of organisms in artificial ecosystems to changes of environmental factors.

Studying material transformations and biotic cycling in artificial ecosystems (AES), we need to know the principles of biological adaptation of active organisms to change in the environment. Microorganisms in AES for water purification are the most active transforming organisms and consumers of the organic substances contained in wastes. Utilization of organic substances is directly connected with the energy fluxes used by AES. According to energy criteria, the energy fluxes used by a biological system tend to reach maximum values under stable conditions. Unutilized substrate concentration decreases as a result of biological adaptations. After a dramatic change in environmental factors, for example, after a sharp increase in the flow rate of organic substances, the biological system is not able to react quickly. The concentration of unutilized substrate increases and the energy flux used by the biological system decreases. The structure of the microbial community also changes, with a decrease in biological diversity. The efficiency of energy use by simple terrestrial ecosystems depends on the energetic intensity and interactions between plants and rhizospheric microorganisms.

Biodegradation, Environmental↗
PubMedDate not supplied

Development of a novel artificial matrix with cell adhesion peptides for cell culture and artificial and hybrid organs.

The authors present a novel artificial matrix with high cell adhesion and growth rate that was produced by chemical fixation of an RGD-containing peptide (Arg-Gly-Asp) on a polyvinyl alcohol (PVA) surface. The logical sequence behind the molecular design of an artificial matrix that mimics natural adhesive proteins, such as fibronectin, is based on the fact that an RGD tripeptidyl amino sequence is the minimal common adhesion site of adhesive proteins. Activation of surface hydroxyl groups by carbonyl diimidazole successfully incorporated GRGDSP (Gly-Arg-Gly-Asp-Ser-Pro) onto PVA films. The resultant film surface was found to be bioactive, molecularly recognizing the adhesive receptor of bovine endothelial cells. Thus, the artificial matrix mimics active adhesion sites and serves as a novel artificial matrix that may be useful for cell culture, tissue-compatible implants, and hybrid artificial organs.

Animals↗
PubMed2004

The power-law mathematical model for blood damage prediction: analytical developments and physical inconsistencies.

Blood trauma caused by medical devices is a major concern. Complications following the implantation/application of devices such as prosthetic heart valves, cannulae, blood pumps, tubing, and throttles lead to sublethal and lethal damage to platelets and erythrocytes. This damage is provided by the alterations in fluid dynamics, providing a mechanical load on the blood corpuscle's membrane by means of the shear stress. An appropriate quantification of the shear-induced hemolysis of artificial organs is thought to be useful in the design and development of such devices in order to minimize device-induced blood trauma. To date, a power-law mathematical relationship using the time of exposure of a blood corpuscle to a certain mechanical load and the shear stress itself (derived under the peculiar condition of uniform shear stress) has served as a basic model for the estimation of the damage to blood, investigated by means of numerical and/or experimental fluid dynamical techniques. The aim of the present article is to highlight the effect of a time-varying mechanical loading acting on blood cells based on the usual power-law model; furthermore, the effect of the loading history of a blood particle is discussed, showing how the past history of the shear acting on a blood corpuscle is not taken into account, as researchers have done until now. The need for a reassessment of the power-law model for potential blood trauma assessment is discussed by using a mathematical formulation based on the hypotheses of the existence of damage accumulation for blood with respect to time and with respect to shear stress, to be applied in complex flow fields such as the ones established in the presence of artificial organs.

Algorithms↗
PubMedDate not supplied

A new fiber optic probe for cellular visualization.

Thrombus formation within artificial organs has been shown, at least in part, to be caused by retarded or stagnant blood flow. The goal of this work was to develop a magnifying fiber optic probe capable of visualizing particle flow and cellular deposition in a physiologically relevant cellular suspension (blood). The probe has minimal cross sectional area to allow for access to confined areas and to minimize flow disturbance. The probe consists of a germanium oxide fiber optic bundle and a gradient index imaging lens. Fluorescent microspheres of 48 microns, 7 microns, and 3 microns in diameter were imaged after deposition on to a cover slip. The flow (1.44 mm/sec) of 3 microns microspheres suspended in buffer alone and with red cell hematocrits of 10%, 25% and 45% were also visualized. To investigate the potential for this probe to detect ongoing thrombosis, fluorescently labeled human platelets were observed depositing on surfaces from a stagnant platelet rich buffer. These initial data suggest that this probe may offer a technique for the visualization of blood cell adhesion on the interior of artificial organs and the local quantification of flow in such devices.

Artificial Organs↗
PubMed2003

Honoring living legends.

From August 17 to 19, 2001, the University of Ottawa Heart Institute hosted the 6th Symposium of the World Artificial-Organ, Immunology and Transplantation Society (WAITS 2001). During WAITS 2001 a very special session entitled "Living Legends-Lessons Learned and Future Visions" was held. This session brought together giants in the field who had pioneered organ transplantation, cardiovascular surgery, pacemakers, and artificial hearts, among many other major contributions. The purpose of the session was to both honor and learn from those who have contributed greatly to the major scientific and technological advances in our field during the twentieth century.

Animals↗
PubMedDate not supplied

Long-term preservation of a beating heart in an artificial environment.

The natural heart could be preserved in the beating state, with appropriate afterload, for more than 24 hrs if supported by blood compatible artificial organs and biomedical engineering techniques. An artificial environment was developed using this philosophy. The system was constructed from four subsystems: circulatory, respiratory, metabolic, and environmental. In the circulatory subsystem, diastolic pressure was held at 70 to 100 mmHg by computer aided peripheral resistance, and a left ventricular assist device (LVAD) could be added when cardiac function was weakened. The respiratory subsystem was composed of an artificial lung and computer aided gas mixer for O2, CO2, and air, which kept blood PO2 and PCO2 within physiologic levels. In the metabolic subsystem, glucose and insulin were injected by infusion pump so as to maintain blood sugar within 100 to 200 mg/dl, whereas the environmental system preserved the isolated heart at 37 degrees C in a sterile water bath. Goats' hearts were connected to this system, and continued to beat for a maximum of 24 hours.

Animals↗
PubMed1984

Lung and heart-lung transplantation.

This report is a brief summary on current events related to lung and heart-lung transplantation. Eleven patients have undergone transplantation of the heart and both lungs at Stanford University. The ages ranged from 22-45, the average age being about 36 years, and included were four females and seven males. The diagnosis was primary pulmonary hypertension in three and Eisenmenger syndrome--congenital heart disease with pulmonary hypertension--in eight. Eight patients are living and well, two to more than 24 months after transplantation of the heart and both lungs. All these patients were discharged and are fully rehabilitated, which is an important consideration. There have been three operative deaths, one was secondary to two previous operations that made our operation much too long, another was secondary to the use of intravenous cyclosporine, and the third was related to the poor maintenance of the donor lung. Three of the eleven patients were catheterized following the transplant from six months to a year after transplantation, and the pulmonary artery pressure and pulmonary vascular resistance were absolutely normal in all three of these individuals. Of course the plan is to go ahead with further catheter studies at yearly intervals in all of the patients. The last patient underwent transplantation in January, 1983. I think no matter how effective or how ingenious the medical staff is with artificial organs, it will be a long time before these early results of transplantation of the heart and both lungs can be matched by any types of artificial organ implants.

Adult↗
PubMed2005

Application of blood purification to non-renal organ failure.

The application of artificial organs to the task of blood purification in the setting of non-renal organ failure simultaneously presents important challenges and opportunities. Failures of cardiovascular, hepatic, coagulation and immune systems are all characterized by dysregulation leading to multi-organ failure. When sustained, these conditions result in multiple organ system dysfunction and death and are far too common in modern intensive care units (ICUs). While the pathogenesis of each of these organ failures is complex and variable, brought about by a variety of underlying conditions, the potential to improve patient outcomes by simultaneously targeting multiple pathways can perhaps best be realized by blood purification. Unlike drug strategies, which are usually limited to one component of these complex networks, blood purification is, by its very nature, broad spectrum and self regulating. For example, as the concentration of mediators or toxins increases, so does removal. Furthermore, given the many failed trials of specific therapy, the recent focus of immunomodulatory therapy in sepsis has shifted to non-specific methods of influencing the entire inflammatory response without suppressing it. In this issue of the journal, members of the Acute Dialysis Quality Initiative (ADQI) present systematic reviews on the application of hemofiltration, ultrafiltration, plasma therapies and liver-assist therapy for the treatment of non-renal organ failure. The focus of these reviews is on clinical evidence as well as recommendations for future research.

Animals↗
PubMed1997

Usability for genetic evaluations of records from herds participating in progeny test programs of artificial insemination organizations.

Thirteen AI organizations provided identification of herds that participated in their progeny test programs in 1989 and 1990; 15% of those herds participated in programs of more than one AI organization, but only 2.6% participated in programs of more than two AI organizations. Of the 19,589 participating herds, 82 and 76% were enrolled in DHI test plans that were considered to be usable for genetic evaluations during 1991 and 1992. For herds that had participated in AI progeny test programs, mean percentages of usable records were 77% in 1991 and 78% in 1992; the mean percentages of usable records for nonparticipating herds were 62% in 1991 and 60% in 1992. Participating herds had larger mean herd sizes, higher means and standard deviations of milk yields, younger cows, and a lower percentage of registered cows than did nonparticipating herds. Analysis of variance was used to explain the variation in the percentage of records that were usable for genetic evaluations. Herds that participated in AI progeny test programs or that had smaller herd sizes, higher mean milk yields, younger cows, or larger percentages of registered cows had higher percentages of records that were usable for genetic evaluations. Improved usability of records for genetic evaluations would increase the efficiency of AI progeny testing, and consideration of herd characteristics associated with higher percentages of usable records should aid AI organizations in evaluating prospective herds for progeny test programs.

Animals↗
PubMed2005

A novel formulation for blood trauma prediction by a modified power-law mathematical model.

With the increasing use of artificial organs, blood damage has been raising ever more clinical concern. Blood trauma is in fact a major complication resulting from the implantation of medical devices and the use of life support apparatuses. Red blood cells damage predictive models furnish critical information on both the design and the evaluation of artificial organs, because their correct usage and implementation are thought to provide clear and rational guidance for the improvement of safety and efficacy. The currently adopted power-law shear-induced haemolysis prediction model lacks sensitivity with respect to the cumulative effect of previously applied stress magnitudes. An alternative model is proposed where a mechanical quantity was defined, able to describe the blood damage sustained by red cells under unsteady stress conditions, taking into account the load history. The proposed formulation predicted the same trend as the available experimental data. The obtained results have to be considered a preliminary validation of the basic hypothesis of this modified red blood cell damage prediction model. To date, the necessity to design further experiments to validate the proposed damage function clashes with the limitations inherent to current systems to get the time-varying shear stress completely under control.

Algorithms↗
PubMedDate not supplied

Inflammatory response to implants.

The implantation of artificial organs, medical devices, or biomaterials results in injury and initiation of the inflammatory response. This inflammatory response to implants has as its components acute inflammation, chronic inflammation, foreign body reaction with granulation tissue, and macrophage and foreign body giant cell interactions. The form and topography of the surface of the artificial organ, medical device, prosthesis, or biomaterial can determine the composition of the foreign body reaction. The normal foreign body reaction consists of macrophages and foreign body giant cells at the surface of the implant with subjacent fibroblastic proliferation and collagen deposition, and capillary formation. Macrophages play a pivotal role in the response of tissue to implants. An hypothesis on the role of complement activation and complement-mediated cellular adhesion to implant surfaces has been presented. Macrophage adhesion and subsequent activation leading to cell-mediator and cell-cell communication is described.

Acute Disease↗
PubMedDate not supplied

New trends in blood purification.

Considering the different methods of blood purification, designed and developed during the last ten years, some common trends can be pointed out (Table 4). The uniformity of treatment during the first 30 years has been substituted by a variety of new methods, allowing a specific attribution to different underlying diseases. Whereas haemodialysis, haemofiltration and intermittent peritoneal dialysis exhibit a relatively broad spectrum of indications, CAPD, haemoperfusion and plasmapheresis are restricted to a reduced number of underlying diseases. Certain diseases, until a few years ago regarded as a contra-indication for blood purification treatment, are today considered to be specific indications for newly developed methods of treatment, for example diabetic nephropathy for CAPD and vascular instability for haemofiltration or its modifications. Apart from this individualization an important trend of modern artificial kidney design has been the attempt to miniaturize the devices in order to facilitate their application and to encourage self-treatment. This trend could result in a concentration of the patients on self-care and a substantial reduction of treatment costs. Moreover, a miniaturized artificial organ could reduce many immunological problems, which today result from transplantation of natural kidney. Imitation of the natural kidney has been an important goal of many investigators during the last years. Promising approaches have been attempted by the development of haemofiltration, imitating the process of glomerular filtration, or continuous ambulatory peritoneal dialysis, copying the continuously excreting natural kidney. In his assay 'De Urina', Homer Smith says, 'This liquid, which commonly inspires men only with contempt and disgust, which is generally ranked amongst vile and repulsive matters has become, in the hands of the chemists, a source of important discoveries'. Today the inspiration of the chemists has been replaced by the unceasing endeavours of technicians to create an artificial organ which produces a urine of similar qualities.

Blood↗
PubMed1989

Adhesion of polymorphonuclear leukocytes to protein-coated and platelet adherent surfaces.

Since protein adsorption and platelet adhesion are likely to precede significant contact of leukocytes with the surfaces of artificial organs, we have chosen to study polymorphonuclear leukocyte (PMN) adhesion in a sequential manner. The work presented here deals with the effects of flow and surface type on PMN adhesion to fibrinogen- and albumin-coated glass. We compared direct adhesion to adsorbed protein with adhesion to adsorbed protein having adherent platelets. These experiments were designed to see if PMN's might preferentially adhere to albumin or fibrinogen and whether a particular morphological form of adherent platelet could promote PMN adhesion. The adhesion of PMN's to spread platelets on albumin or fibrinogen occurs to a greater extent than in the absence of platelets. Adhesion of PMN's to spread platelets may be an important mechanism for their depletion from the circulation during artificial organ use.

Adult↗
PubMed2000

Lipid oxidation deletes the nanodomain organization of artificial membranes.

Nanoscopic domains with different crystal structures have been induced in closed artificial membranes and have been directly imaged by atomic force microscopy at a spatial resolution better than 0.3 nm. These observations provide experimental evidence to the hydrophobic mismatching theory of lateral phase separation phenomena. Under oxidant conditions, the lipid-lipid assembly reorganizes into a new steady-state structure with disappearance of specific nanodomains. This finding may contribute to understanding the mechanism of peroxidative damage to membrane properties. In fact, alterations of specific modes of molecular conformation and packing may lead to perturbation of specific properties.

Lipids↗
PubMed2000

The bicentennial of the Voltaic battery (1800-2000): the artificial electric organ.

Alessandro Volta invented the electric battery at the end of 1799 and communicated his invention to the Royal Society of London in 1800. The studies that led him to develop this revolutionary device began in 1792, after Volta read the work of Luigi Galvani on the existence of an intrinsic electricity in living organisms. During these studies, Volta obtained a series of results of great physiological relevance, which led him to anticipate some important ideas that marked the inception of modern neuroscience. These results have been obscured by a cultural tradition that has seen Volta exclusively as a physicist, lacking interest for biological problems and opposed in an irreversible way to the physiologist, Luigi Galvani.

Animals↗