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PubMed1995

[Activation of complement during hemodialysis].

In hemodialysis using 3 types of dialysis membrane materials [regenerated cellulose (RC), cellulose triacetate (CTA), and polysulfone (PS)], activation of the complement, reduction of white blood cells, and variation of vitronectin (VN) were observed. RC membrane caused a significant reduction of white blood cells and elevations of Bb and soluble membrane attack complex (S-MAC), indicating a strong activation of the alternative complement pathway. Especially, the increase of S-MAC persisted for a long time during hemodialysis. Because reduction of VN was transient, it was assumed that the S-MAC escaping removal by VN receptors might have persisted in the circulation. These findings suggested that S-MAC would become useful as an index for evaluating biocompatibility of various artificial organs including dialysis membranes.

Aged↗

PubMed2001

Impact of metal pools and soil properties on metal accumulation in Folsomia candida (Collembola).

Soil-dwelling organisms are exposed to metals in different ways. Evidence exists for predominant pore water uptake of metals by soft-bodied oligochaete species. In the present research, uptake kinetics of metals and the metalloid As by the semi-soft-bodied springtail Folsomia candida were studied, for which uptake via the pore water is less obvious. Springtails were exposed in 16 field soils and in metal-spiked artificial Organization for Economic Cooperation and Development (Paris, France) soil (OECD soil). Subsequently, accumulation parameters were statistically related to soil metal pools and soil properties. In Cd-spiked OECD soil, internal Cd levels were linearly related to external Cd concentrations, whereas the springtails maintained fixed internal levels of Cu and Zn regardless of spiked concentrations. In the field soils, all body concentrations of the elements As, Cr, and Ni were below detection limit. The essential metals Cu and Zn were presumably regulated, and no influence of soil characteristics could be demonstrated. For Cd and Pb, accumulation patterns were correlated mainly to solid-phase soil characteristics. The presence of these explanatory variables in the multiple correlations suggests that an uptake mechanism that is solely determined by pore water concentrations should not be taken as a universally applicable principle in risk assessments of metals for soil invertebrates. Cadmium in OECD soils was more available for uptake than in the field soils. The difference remained when extractability was taken into account. The results suggest that experiments in OECD soil cannot be used directly in risk assessment for nonessential metals (at least for F. candida), although a reduction of uncertainties in metal risk assessment can be reached by consistent use of body residues rather than external concentrations.

Animals↗

PubMedDate not supplied

Development of a hybrid artificial pancreas with a dense polyurethane membrane.

We have synthesized a series of strong, elastomeric polyurethaneureas and have used them to fabricate non-porous film and hollow fiber membranes. The solvent cast membranes are non cytotoxic, angiogenic, and permeable to gases, nutrients, secretagogues, and cell products via purely concentration driven transport. Permeability to water, glucose, and protein increases monotonically with membrane water absorption above a threshold value. Water absorption increases with soft segment hydrophilicity, soft segment molecular weight, and soft segment volume fraction of the (dry) segmented polyurethanes. Cell lines (RAJI and MOPC-31C) and primary cells (porcine islets) contained within our membranes have been maintained in culture for up to 6 months with nutrients supplied only by the external media. Cells within membrane devices were protected from immune rejection when implanted into murine hosts. Simple, compact devices containing porcine islets restored normoglycemia and near normal response to glucose tolerance tests in diabetic mice for at least 2 months. Explants had a high degree of vascularization adjacent to the membrane, with little or no fibrous tissue. These properties, and the material's ability to support cell function and protect xenogeneic cells from immunologic rejection, suggest that it would be useful in the construction of hybrid artificial organs and in in vitro cell culture.

Animals↗

PubMed1998

Brain nicotinic receptors: structure and regulation, role in learning and reinforcement.

The introduction, in the late sixties, of the concepts and methods of molecular biology to the study of the nervous system had a profound impact on the field, primarily through the identification of its basic molecular components. These structures include, for example, the elementary units of the synapse: neurotransmitters, neuropeptides and their receptors, but also ionic channels, intracellular second messengers and the relevant enzymes, cell surface adhesion molecules, or growth and trophic factors [21,78,81, 52,79]. Attempts to establish appropriate causal relationships between these molecular components, the actual organisation of neural networks, and a defined behavior, nevertheless, still must overcome many difficulties. A first problem is the recognition of the minimum levels of organisation, from the molecular, cellular, or multicellular (circuit) to the higher cognitive levels, that determine the given physiological and/or behavioral performance under investigation. A common difficulty (and potential source of errors of interpretation) is to relate a cognitive function to a network organization which does not possess the required structural complexity and vice-versa. Another problem is to distinguish, among the components of the system, those which are actually necessary and those which, taken together, suffice for a given behavior to take place. Identification of such a minimal set of building blocks may receive decisive insights from the elaboration of neurally plausible formal models that bring together, within a single and coherent 'artificial organism', the neuronal network, the circulating activity, and the behavior they determine (see [42,43,45,72,30]). In this communication, we shall attempt, still in a preliminary fashion, to bring together: (1) our recent knowledge on the molecular biology of brain nicotinic receptors (nAChRs) and their allosteric properties and (2) integrated behaviors, such as cognitive learning, investigated for instance with delayed-response or passive avoidance tasks that are likely to involve nAChRs in particular at the level of reinforcement (or reward) mechanisms (see [18,29,135]).

Allosteric Regulation↗

PubMed1992

A problem with modern dental materials.

It may come as a surprise to learn that there is more than one discipline in medicine dealing with artificial organs. The obvious one is bio-engineering, which is largely concerned with fashioning existing biologically acceptable materials into useful spare parts such as hip or knee joints. The materials themselves hardly change, and the difference between rival prostheses lies more in design than novel chemistry. This is the world of titanium or cobalt-chromium joint designs, bone screws and plates, orthotic limbs, supports and wheelchairs, and futuristic ideas such as miniature video cameras for artificial eyes.

Biocompatible Materials↗

PubMed2002

The effect of ageing on the toxicity of zinc for the potworm Enchytraeus albidus.

Different extractable zinc fractions and the ecotoxicity of zinc in Enchytraeus albidus were assessed using freshly spiked artificial soils and spiked soils which had been aged for 8 weeks. Standard artificial Organization for Economic Cooperation and Development (OECD)-soils were aged in four different ways: (1) storing at 20 degrees C; (2) percolation followed by storing at 20 degrees C; (3) alternately heating at 60 degrees C and storing at 20 degrees C; and (4) alternately freezing at -20 degrees C and storing at 20 degrees C. Ageing had no clear influence on the pore water concentration, the water soluble and the calcium chloride extractable fraction of zinc in the artificial soils. Similarly, the 21d LC50 and the 42d EC50(reproduction) for E. albidus were not influenced by the different treatments. This absence of zinc fixation in the artificial soil during ageing was probably due to the use of kaolinite clay in OECD-soil.

Animals↗

PubMedDate not supplied

Myoelectric control of a computer animated hand: a new concept based on the combined use of a tree-structured artificial neural network and a data glove.

This paper proposes a new learning set-up in the field of control systems for multifunctional hand prostheses. Two male subjects with a traumatic one-hand amputation performed simultaneous symmetric movements with the healthy and the phantom hand. A data glove on the healthy hand was used as a reference to train the system to perform natural movements. Instead of a physical prosthesis with limited degrees of freedom, a virtual (computer-animated) hand was used as the target tool. Both subjects successfully performed seven different motoric actions with the fingers and wrist. To reduce the training time for the system, a tree-structured, self-organizing, artificial neural network was designed. The training time never exceeded 30 seconds for any of the configurations used, which is three to four times faster than most currently used artificial neural network (ANN) architectures.

Amputees↗

PubMedDate not supplied

[At the beginning of the third millennium: what kind of surgery, what kind of surgeon?].

Technological progress and the evolution of biological knowledge lead us to expect major developments in the fields of organ replacement, minimally invasive surgery and tumour therapy in the coming decades. It is widely believed that xenotransplantation may offer a possible solution to the problem of the current chronic shortage of donors, though their use at present encounters formidable immunological obstacles, particularly as regards discordant transplants. Genetic engineering and the realisation of transgenic donors as well as new strategies aimed at modifying the immune status of the donor may well be the key to new developments in this sector. Selective culturing of tissues and the production of totally implantable artificial organs are additional lines of research which may provide useful means of meeting the increasing demand for organs. The enormous advances made in the field of high-tech solutions applied to the biomedical disciplines are destined to open up new frontiers in diagnostics, operating technique and the permanent training of surgeons. In particular, we are about to witness an extension of the use of computer technology and robotics, embracing the simulation and reproduction of virtual reality, telemedicine (teleconsulting and telesurgery) and the creation of experimental models. Minimally invasive surgery will unquestionably benefit from this progress with the possibility of extending its range of indications to procedures in which human limitations are more evident owing to difficulties of access and the size of the target, at the same time guaranteeing high-precision manoeuvres. In the oncological field, high expectations accompany the advances in our knowledge of molecular biology with the genetic mapping of tumours which may pave the way for screening programs and gene therapy. Alongside the scientific and technological development of the surgery of the future, we can expect to see the increasing emergence of: a) economic problems related to the progressive increase in healthcare costs, amongst other things as a result of the powerful impact of high-tech solutions; b) social problems in terms of the inevitable conflict between cost-containment policies and the right to healthcare; c) moral and bioethical problems relating to the possible establishment of genetic registries and to the different patient-care provider relationship which is likely to come about as the result of the interference of machines or robots. The surgeon's persona may undergo profound changes, not merely from the technical and professional training standpoint, but also with regard to his or her effective role, which may no longer be that of a central, dominant figure, but may be scaled down in a context of multidisciplinary co-operation.

Ethics, Medical↗

PubMed1997

[Development of extracorporeal membrane oxygenation for neonates with severe respiratory failure].

Extracorporeal membrane oxygenation (ECMO) is one of the most highly developed artificial organ treatment of the last decade. Especially for severe neonatal respiratory failure, ECMO has become standard treatment in Japan following the same pattern as in the USA. In the USA, more than 12,000 infants have been registered for ECMO treatment by the Extracorporeal Life Support Organization (ELSO), and their total survival rate is above 80%. Recently, to avoid ligating the carotid artery, most neonates who required ECMO have been supported by a veno-venous (V-V) bypass using a double-lumen catheter via the right internal jugular vein into the right atrium. To prevent bleeding complications, the introduction of Nafamostat Mesilate and the development of a heparin-coated system would be advantageous. Progresses in these instruments and perfusing techniques might enlarge the indications of ECMO. We performed an experiment on fetus ECMO as artificial placenta. The fetuses were incubated for 10-237 hours by A-V ECMO using a centrifugal pump successfully and maturation of the lung was revealed. In the future the fetus ECMO could be introduced clinically as a back-up system for fetal surgeries and incubation for extra-premature infants.

Cystic Adenomatoid Malformation of Lung, Congenita↗

PubMed2004

Differential distribution of elastic tissue in human natural skin and tissue-engineered skin.

Tissue-engineered skins (TES), manufactured by epidermal and dermal equivalents, are now being used in biological, pharmacotoxicological and clinical applications. It is thus interesting to know to what extent artificial organs are similar to natural counterparts. Elastic fibres are important constituents of the extracellular matrix of natural skin (NS). The aim of our study was to investigate the possible occurrence and distribution of elastic tissue in a model of human TES using different histochemical techniques, including classical Orcein and Fuchsin-Resorcin methods and immunohistochemistry, at both light and electron microscopical levels. Immunoperoxidase and high resolution immunogold methods were used. In NS, classical staining techniques and elastin-immunohistochemistry revealed a well-organized network of elastic fibres. High resolution immunocytochemistry revealed an intense labelling in the amorphous component of elastic fibres. Fibres of different diameters were immunostained. In TES, no stained elastic fibres were observed using classical staining techniques, and the interpretation of immunoperoxidase observations was not clear-cut. In contrast, immunogold staining at the electron microscopical level provided specific labelling of elastin-like immunoreactive material in the dermal equivalent. However, ultrastructural immunocytochemistry revealed that elastic tissue organization in TES was poor compared to that in NS. This study demonstrates that elastic fibres are a component of the extracellular matrix in this model of TES and suggests that fibroblasts of the dermal equivalent are engaged in matrix secretion. Nevertheless, the level of extracellular matrix organization in TES is low compared to NS. Moreover, this study also suggests that different models of bilayered TES may differ with respect to extracellular matrix organization. These aspects should be considered when TES is used in biological and pharmacotoxicological studies. A better understanding of the factors influencing extracellular matrix formation in TES is necessary to achieve further development of skin generation in vitro.

Cells, Cultured↗

PubMedDate not supplied

Cardiovascular applications of biomaterials and implants--an overview.

This paper was originally commissioned by the UK Department of Health as a contribution to the work of its Biomaterials and Implants Research Advisory Group. This group was set up under the Chairmanship of Professor Sir Colin Berry with the following terms of reference: (i) to identify recent advances in the field of biomaterials; (ii) to consider the future contribution of biomaterials in improving human health; (iii) to advise the Standing Group on Health Technology in areas where developments and assessment are needed; and (iv) to report to the Director of Research and Development (Professor Sir Michael Peckham) by October 1995. The cardiovascular field was one of several areas in biomaterials/implants considered by the Advisory Group. Amongst other areas considered were orthopaedics, dentistry, urology, wound repair and ophthalmology. Additionally, consideration was also given to such topics as chemical and biochemical sensors, drug release, hydrogels, membranes and artificial organs. The final report of the Advisory Group will be published at the end of this year. However, the Department has agreed that individual working papers such as the present one can be published independently in appropriate scientific journals.

Adolescent↗

PubMed2001

Uremic toxicity: present state of the art.

The uremic syndrome is a complex mixture of organ dysfunctions, which is attributed to the retention of a myriad of compounds that under normal condition are excreted by the healthy kidneys (uremic toxins). In the area of identification and characterization of uremic toxins and in the knowledge of their pathophysiologic importance, major steps forward have been made during recent years. The present article is a review of several of these steps, especially in the area of information about the compounds that could play a role in the development of cardiovascular complications. It is written by those members of the Uremic Toxins Group, which has been created by the European Society for Artificial Organs (ESAO). Each of the 16 authors has written a state of the art in his/her major area of interest.

Cardiovascular Diseases↗

PubMedDate not supplied

Characteristics of hepatocytes derived from early ES cells and treatment of surgically induced liver failure rats by transplantation.

BACKGROUND: Although liver transplantation has become a standard therapy for diseases such as fulminant hepatitis and cirrhosis, the lack of donor organs remains a major problem. One solution is the development of transplantable hepatocytes. The metabolic characteristics as well as function and adaptation of hepatocytes (R-EES-hep cell) derived from rat early embryonic stem cells were examined after transplantation into rats with surgically induced liver failure. METHODS: Rat hepatocyte cell lines were established from early embryonic stem cells cultured in the presence of embryotrophic factors by colony cloning methods. The cell lines were established from two cell embryos taken from spontaneous dwarf rats using the novel method of Ishiwata et al. Morphologic differentiation as well as albumin and bilirubin production were observed by immunostaining. R-EES-hep cells were transplanted into the spleens of 90% hepatectomized, surgically induced liver failure rats to analyze survival rates. RESULTS: When cultured in type I collagen gel the cells formed cordlike structures resembling the liver. Both albumin and bilirubin production were observed when transplanted; the spleen was converted into a liver-like structure with prolonged survival of the 90% hepatectomized rats for up to 3 months up to the time of killing. CONCLUSIONS: R-EES-hep cells showed many of the distinctive metabolic characteristics of the liver. These cells may be efficient for further research and application for hepatic cell transplantation to treat liver insufficiency patients and as biologic artificial organs.

Animals↗

PubMed1993

Endothelium: the next frontier in biocompatibility.

Vascular endothelium plays a central role in two specific functional systems. It controls vascular tone, hemostasis, and substance transport. The endothelium is the "docking station" for trapping, deactivation, and regeneration of activated blood compounds and provides the principal clearance mechanism for biologically active mediators released by different cell types. The second function is a regenerational one. During the period between insults (or between dialysis sessions), the endothelium has to restore the "first line of defense," that is, to regenerate the injured athrombogenic surface of the vessel wall and its antioxidative potential, defoliate damaged endothelial cells, and interpolated new ones. These two important endothelial activities are required over and above its basic functions. Future research in artificial organs must take into account that continuous or intermittent blood-membrane contact creates an altered endothelial response. These altered responses may result in adaptional reactions that may differ substantially in the acutely ill patient on continuous venovenous hemofiltration (CVVH) or in a stable patient on maintenance hemodialysis. By a reduction in such factors as immediate or delayed cell-cell interactions (direct or indirect), it may be possible to influence the long-term outcome of chronic hemodialysis patients. Other research should strive to enhance those factors of endothelial function that are essential in the defensive and restorative properties of endothelial tissue. This is especially important in such continuous therapies as CVVH, long-term membrane oxygenation, and artificial heart and blood vessels. Currently, there are more unanswered questions than possible answers concerning endothelial functions in long-term hemodialysis patients, but it is clear that excluding endothelial cell behavior from investigation of extracorporeal therapy in the future would be a substantial omission.

Animals↗

PubMed2006

Quantifying the effect of soil moisture on the aerobic microbial mineralization of selected pesticides in different soils.

A standardized quantitative approach was developed to reliably elucidate the effect of increasing soil moisture on pesticide mineralization. The mineralization of three aerobically degradable and chemically different 14C-labeled pesticides (isoproturon, benazolin-ethyl, and glyphosate) was studied under controlled conditions in the laboratory at an identical soil density of 1.3 g cm(-3). The agricultural soils used are characterized by (i) large variations in soil texture (sand content 4-88%) and organic matter content (0.97-2.70% org. C), (ii) fairly diverse soil-water retention curves, and (iii) differing pH values. We quantified the effect of soil moisture on mineralization of pesticides and found that (i) at soil water potential < or = -20 MPa minimal pesticide mineralization occurred; (ii) a linear correlation (P < 0.0001) exists between increasing soil moisture (within a soil water potential range of -20 and -0.015 MPa), and increased relative pesticide mineralization; (iii) optimum pesticide mineralization was obtained at a soil water potential of -0.015 MPa, and (iv) when soil moisture approximated water holding capacity, pesticide mineralization was considerably reduced. As both selected pesticides and soils varied to a large degree, we propose that the correlation observed in this study may be also valid in the case of aerobic degradation of other native and artificial organic compounds in soils.

Aerobiosis↗

PubMed2002

Holmium: YAG laser-induced liquid jet knife: possible novel method for dissection.

BACKGROUND AND OBJECTIVES: Making surgical incisions in vessel-rich organs without causing bleeding is difficult. Thus, it is necessary to develop new devices for this purpose, especially for surgery involving small vessels as in neurosurgery, where damage against even small cerebral vessels result in severe neurological deficits. STUDY DESIGN/MATERIALS AND METHODS: A laser-induced liquid jet was generated by irradiating pulsed Holmium Yttrium-Aluminum-Garnet (Ho: YAG) laser (beams of 350 microseconds pulse width) within a copper tube (internal diameter, 1 mm) with pure water (150 ml /hour). Ho: YAG laser beams were irradiated through an optical fiber (core diameter, 0.4 mm). The influence of the input of laser energy, structure of the nozzle, and the stand-off distance between the optical fiber tip and nozzle exit on the jet velocity was measured by a high-speed video camera to evaluate controllability of jet. The effect on artificial organs made of 10 and 30%(w/v) gelatin, each of which represent features of soft tissue and blood vessels. RESULTS: Jet velocity increased in proportion to gain in laser energy input, and maximum penetration depth into 10%(w/v) gelatin was 35 mm by single exposure at 350 mJ/pulse without impairing a vessel model. Shapes of nozzle also modified jet velocity with optimal nozzle/tube area ratio of 0.25. CONCLUSIONS: The laser-induced liquid jet has excellent potential as a new tool for removing soft tissue without damaging vital structures.

Dissection↗

PubMed2005

[Recurrent Candida sepsis with prolonged respiratory failure and severe liver dysfunction].

Systemic mycoses, especially pulmonary diseases and septicemia are observed increasingly at intensive care units. Essential risk factors for development of candidosis are the expanded use of antibiotics and immunocompromised patients, caused either as a result of a severe underlying disease or iatrogenically induced after organ transplantation. Candida albicans is the most frequent pathogen in microbiological findings. Blood cultures are only positive in massive fungemia. We report a 50-year-old patient with recurrent Candida-septicemia: rupture of the distal esophagus after dilatation because of cardiac achalasia with mediastinal emphysema and mediastinitis. Severe acute respiratory distress syndrome after aspiration with septic shock and acute renal failure at the beginning. Long-term mechanical ventilation, continuous renal replacement therapy and multifarious antibiotic therapy. Early microbiological samples of several positive blood cultures and bronchoalveolar lavages revealed the presence of Candida albicans. In the further clinical course, detection of Pseudomonas species in bronchoalveolar lavages and Staphylococci as well as Enterococci in a number of positive blood cultures. Later on development of a severe liver dysfunction with test results that showed an intrahepatic cholestasis. Because of coagulation failure commencement of artificial liver support with the MARS-system (molecule adsorbent recirculating system). Decrease of high bilirubin levels was accompanied by improvement of clinical condition of the patient. In the following course, repeated severe systemic infections with phases of septicemia or rather septic shock and detection of Candida in several positive blood cultures and bronchoalveolar lavages. In each case increasing bilirubin levels with signs of intrahepatic cholestasis and each time improvement with antimycotic therapy (voriconazol, caspofungin and fluconazol). The patient showed more and more signs of immunodeficiency in the sequel. The clinical appearance of candidosis is manifold. Systemic Candida infections are frequent in patients with immunodeficiency. A recurrent Candida septicemia with prolonged respiratory failure and severe liver dysfunction in form of cholestatic hepatosis, that improved several times with antimycotic therapy in combination with evidence based intensive care measures and artificial organ support is a comparatively rare event.

Candida↗

PubMed1998

Fatty acid transport and utilization for the developing brain.

To determine the transport and utilization of dietary saturated, monounsaturated, and n-6 and n-3 polyunsaturated fatty acids for the developing brain and other organs, artificially reared rat pups were fed a rat milk substitute containing the perdeuterated (each 97 atom% deuterium) fatty acids, i.e., palmitic, stearic, oleic, linoleic, and linolenic, from day 7 after birth to day 14 as previously described. Fatty acids in lipid extracts of the liver, lung, kidney, and brain were analyzed by gas chromatography-mass spectrometry to determine their content of each of the deuterated fatty acids. The uptake and metabolism of perdeuterated fatty acid lead to the appearance of three distinct groups of isotopomers: the intact perdeuterated, the newly synthesized (with recycled deuterium), and the natural unlabeled fatty acid. The quantification of these isotopomers permits the estimation of uptake and de novo synthesis of these fatty acids. Intact perdeuterated palmitic, stearic, and oleic acids from the diet were found in liver, lung, and kidney, but not in brain. By contrast, perdeuterated linoleic acid was found in all these organs. Isotopomers of fatty acid from de novo synthesis were observed in palmitic, oleic, and stearic acids in all tissues. The highest enrichment of isotopomers with recycled deuterium was found in the brain. The data indicate that, during the brain growth spurt and the prelude to myelination, the major saturated and monounsaturated fatty acids in brain lipids are exclusively produced locally by de novo biosynthesis. Consequently, the n-6 and n-3 polyunsaturated fatty acids must be transported and delivered to the brain by highly specific mechanisms.

Animals↗