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At least 847 records · Page 47Linked to original sources
PubMed2006

Ultrasound elastomicroscopy using water jet and osmosis loading: potentials for assessment for articular cartilage.

Research in elasticity imaging typically relies on 1-10 MHz ultrasound. Elasticity imaging at these frequencies can provide strain maps with a resolution in the order of millimeters, but this is not sufficient for applications to skin, articular cartilage, or other fine structures. In this paper, we introduced two methods of ultrasound elastomicroscopy using water jet and osmosis loading for imaging the elasticity of biological soft tissues with high resolutions. In the first system, the specimens were compressed using water jet compression. A water jet was used to couple a focused 20 MHz ultrasound beam into the specimen and meanwhile served as a "soft" indenter. Because there was no additional attenuation when propagating from the ultrasound transducer to the specimen, the ultrasound signal with high signal-to-noise ratio could be collected from the specimens simultaneously with compressing process. The compression was achieved by adjusting the water flow. The pressure measured inside the water pipe and that on the specimen surface was calibrated. This system was easily to apply C-scan over sample surfaces. Experiments on the phantoms showed that this water jet indentation method was reliable to map the tissue stiffness distribution. Results of 1D and 2D scanning on phantoms with different stiffness are reported. In the second system, we used osmotic pressure caused by the ion concentration change in the bathing solutions for the articular cartilage to deform them. When bovine articular cartilage specimens were immerged in solutions with different salt concentration, a 50 MHz focused ultrasound beam was used to monitor the dynamic swelling or shrinkage process. Results showed that the system could reliably map the strain distribution induced by the osmotic loading. We extract intrinsic layered material parameters of the articular cartilage using a triphasic model. In addition to biological tissues, these systems have potential applications for the assessment of bioengineered tissues, biomaterials with fine structures, or some engineering materials. Further studies are necessary to fully realize the potentials of these two new methods.

Algorithms↗
PubMed2004

A critical perspective of the use of (13)C-isotopomer analysis by GCMS and NMR as applied to cardiac metabolism.

The aim of this article is to provide a guide for metabolic physiologists and bioengineers to the combined use of gas chromatography-mass spectrometry (GCMS) and nuclear magnetic resonance (NMR) in stable isotope investigations in any biological systems. Building on our past experience with these two techniques, as applied separately to the investigation of citric acid metabolism in the ex vivo perfused rat heart we initiated a collaborative study for their critical evaluation. This article, which expands on our previous work (Mol. Cel. Biol., 2003), directly compares GCMS- and NMR-determined 13C-isotopomer and flux data obtained from ex vivo rat heart perfusion studies with 13C-substrates. Overall we have found excellent agreement between the 13C-enrichments of GCMS- and NMR-determined citric acid cycle metabolites (citrate, 2-ketoglutarate, succinate and malate) and glutamate; however the unlabeled component (M) was consistently underestimated by NMR. Despite this discrepancy there was reasonably good agreement in the relative fluxes of 13C-substrates through the citric acid cycle determined by the two techniques. Nevertheless, further investigations appear necessary before maximal advantage can be taken of the complementary 13C-isotopomer and flux data of GCMS and NMR for probing the dynamics of cellular metabolism.

Animals↗
PubMed2005

Localized gene expression following administration of adeno-associated viral vectors via pancreatic ducts.

Gene transfer into pancreatic cells in vivo could be of immense therapeutic benefit in cases of type 1 diabetes (T1D) through the production of molecules capable of interrupting the progression of autoimmunity or promoting regeneration of insulin-secreting beta cells. We adapted a clinically relevant surgical technique (endoscopic retrograde cholangiopancreatography) to deliver rAAV encoding human alpha1-antitrypsin (approved gene symbol SERPINA1) to the pancreas of 3-week-old Fisher 344 rats and C57BL/6 mice. We compared natural as well as bioengineered serotypes of rAAV (rAAV1, rAAV2/Apo, rAAV8) as well as different promoters (chicken beta-actin, human insulin) for their expression in vivo. Rats injected with rAAV1 showed the highest hAAT expression (week 2, rAAV1/CB-AT, 579 +/- 457 ng/ml). In mice, rAAV8 vector delivered the highest serum concentration of hAAT (week 2, rAAV8/CB-AT, 19 +/- 6 microg/ml). The chicken beta-actin promoter provided the highest expression in both rodent experiments. Immunohistochemical staining indicated transduction primarily of pancreatic acinar cells with either the rAAV1/CB-AT vector in the rat or the rAAV8/CB-AT vector in the mouse. This study demonstrates that rAAV vectors can be designed to deliver therapeutic genes efficiently to the pancreas and achieve high levels of gene expression and may be useful in treating pancreatic disorders, including T1D.

Animals↗
PubMed2005

Biomimetic delivery of keratinocyte growth factor upon cellular demand for accelerated wound healing in vitro and in vivo.

Exogenous keratinocyte growth factor (KGF) significantly enhances wound healing, but its use is hampered by a short biological half-life and lack of tissue selectivity. We used a biomimetic approach to achieve cell-controlled delivery of KGF by covalently attaching a fluorescent matrix-binding peptide that contained two domains: one recognized by factor XIII and the other by plasmin. Modified KGF was incorporated into the fibrin matrix at high concentration in a factor XIII-dependent manner. Cell-mediated activation of plasminogen to plasmin degraded the fibrin matrix and cleaved the peptides, releasing active KGF to the local microenvironment and enhancing epithelial cell proliferation and migration. To demonstrate in vivo effectiveness, we used a hybrid model of wound healing that involved transplanting human bioengineered skin onto athymic mice. At 6 weeks after grafting, the transplanted tissues underwent full thickness wounding and treatment with fibrin gels containing bound KGF. In contrast to topical KGF, fibrin-bound KGF persisted in the wounds for several days and was released gradually, resulting in significantly enhanced wound closure. A fibrinolytic inhibitor prevented this healing, indicating the requirement for cell-mediated fibrin degradation to release KGF. In conclusion, this biomimetic approach of localized, cell-controlled delivery of growth factors may accelerate healing of large full-thickness wounds and chronic wounds that are notoriously difficult to heal.

Animals↗
PubMed1988

Radioimmunoguided surgery using monoclonal antibody.

The potential proficiency of radioimmunoguided surgery in the intraoperative detection of tumors was assessed using labeled monoclonal antibody B72.3 in 66 patients with tissue-proved tumor. Monoclonal antibody B72.3 was injected 5 to 42 days preoperatively, and the hand-held gamma-detecting probe was used intraoperatively to detect the presence of tumor. Intraoperative probe counts of less than 20 every 2 seconds, or tumor-to-adjacent normal tissue ratios less than 2:1 were considered negative (system failure). Positive probe counts were detected in 5 of 6 patients with primary colon cancer (83 percent), in 31 of 39 patients with recurrent colon cancer (79 percent), in 4 of 5 patients with gastric cancer (80 percent), in 3 of 8 patients with breast cancer (37.5 percent), and in 4 of 8 patients with ovarian cancer (50 percent) undergoing second-look procedures. Additional patients in each group were scored as borderline positive. Overall, radioimmunoguided surgery using B72.3 identified tumors in 47 patients (71.2 percent), bordered on positive in 6 patients (9.1 percent), and failed to identify tumor in 13 patients (19.7 percent). Improved selection of patients for antigen-positive tumors, the use of higher affinity second-generation antibodies, alternate routes of antibody administration, alternate radionuclides, and more sophisticatedly bioengineered antibodies and antibody combinations should all lead to improvements in radioimmunoguided surgery.

Antibodies, Monoclonal↗
PubMed2002

[When and why to use penile prostheses: seven years of experience].

During the last years important changes in the management of the patients with erectile dysfunction have been verified. Psychologist, neuro-physiologist and bioengineers have given a valuable help in this field. Implant surgery represents, to our notice, the curative more acceptable choice for patient and the partner, since the results are excellent and the materials used extremely manageable. In each case the degree of satisfaction of the patient remains the only legitimate indicator currently for establish the effectiveness of the therapy.

Adult↗
PubMed1997

Energy cost of walking: comparison of "intelligent prosthesis" with conventional mechanism.

OBJECTIVE: To determine physiological energy cost with Blatchford's "Intelligent Prosthesis" (IP) compared to energy cost with a conventional pneumatic swing phase control (PSPC) mechanism. DESIGN: Before-After trial: subjects fitted with IP walked on programmable treadmill at speeds: 6 min slow, 6 min fast, 8 min while speed changed, between slow, normal, and fast, every minute, and 6 min normal. Breath-by-breath analysis of subject's expired air determined average Vo2 (L/min) within each period. Procedure repeated after 1-week interval using PSPC prosthesis. Testing sessions supervised by experienced prosthetist. SETTING: Rehabilitation centre. SUBJECTS: Volunteer sample. Three men, unilateral transfemoral traumatic amputee patients, ages 39 to 59 years. Normally used ischial containment socket, Blatchford Endolite Stabilised Stance Flex knee with PSPC and Multiflex foot and ankle. INTERVENTIONS: Fitting, programming, and alignment of IP (own socket) by Bioengineering Unit's resident prosthetist, IP's microprocessor programmed to facilitate five walking speeds. MAIN OUTCOME MEASURE: Physiological energy cost (Vo2), of using IP compared to using PSPC mechanism. RESULTS: Two subjects displayed reduced Vo2 of between 5.6% and 9.0% using IP compared to PSPC prosthesis at a pace either faster or slower than their normal pace. Third subject showed no significant change in oxygen consumption despite IP unit being heavier. All subjects displayed reduced Vo2 (averaging 4.1%) using IP for period of variable speed walking. CONCLUSIONS: Although differences were small, they tend to indicate that use of the heavier IP unit lowered the energy cost of walking at speeds other than the amputee's normal pace.

Amputees↗
PubMed2003

Large-scale purification of an antibody directed against hepatitis B surface antigen from transgenic tobacco plants.

The application of bioengineering to plants for production of biological products for human and animal use has expanded in recent years. The reasons for this expansion are several and include advances in the technology for novel production systems and the need for very large quantities of therapeutic proteins. The process of growing pharmaceutical proteins in plants, extracting, and purifying is a hard task considering the lack of available information concerning these topics. In this work, a recombinant murine monoclonal antibody specific for the hepatitis B surface antigen, expressed in stably transformed transgenic Nicotiana tabacum plants, was purified by means of a recombinant protein A Streamline chromatography as the main purification step. The antibody expression level varied with the age of the plants and the number of harvests from 40 to 15microg/ml and the maximum process yield was about 25mg of plantibody/kg of biomass. Protein A Streamline chromatography was successfully used in the purification process yielding a recovery of about 60% and a plantibody SDS-PAGE purity of over 90% but unexpectedly, previous clarification steps could not be totally avoided. The amino acid sequence recognized by this affinity purified plantibody was similar to its murine counterpart verifying the potentiality of plants to replace animals or bioreactors for large-scale production of this monoclonal antibody.

Amino Acid Sequence↗
PubMed2003

Regression of juvenile idiopathic scoliosis.

For a young scoliotic boy the customary "wait and watch" management program for rapidly progressive juvenile idiopathic scoliosis was considered unsatisfactory in view of the poor prognosis. The management program devised was based on the congenital postural induction concept of scoliosis with progression accruing from mechanically induced bioengineering fatigue, cumulative molecular scissions, laxity of ligaments, and secondary bone deformation. A coexisting pelvic tilt with restricted movement of the hip and shoulder joints was overlooked initially. Possibly induced simultaneously with the scoliosis, it is considered a contributory factor in scoliosis progression and requires early diagnosis and correction. The rapid improvement in this child's spinal status achieved by physiological traction and specifically designed exercises was such that as a preventive measure the technique warrants further clinical assessment on young scoliotics.

Child, Preschool↗
PubMed2003

Treatment of uterine fibroid tumors in an in situ rat model using high-intensity focused ultrasound.

OBJECTIVE: To determine the efficacy and safety of high-intensity focused ultrasound (HIFU) for the treatment of uterine fibroid tumors in an in situ animal model. DESIGN: High-intensity focused ultrasound was applied intraoperatively to uterine fibroid tumors in rats. SETTING: Department of Bioengineering, and Applied Physics Laboratory, University of Washington, Seattle, Washington. ANIMAL(S): Thirty-five tumors in 27 Eker rats that had spontaneous in situ uterine fibroids were randomly assigned into two groups receiving HIFU (n = 29) or sham (n = 6) treatments. INTERVENTION(S): Animals were anesthetized, and tumors were exposed surgically. The HIFU was applied at 3.5 MHz in 10-second bursts to produce coagulative necrosis lesions (3 mm by 10 mm), spaced 5 mm apart. Sham treatments consisted of exposing the tumors, and handling them similarly to those in the HIFU treatment group, but HIFU was not applied. MAIN OUTCOME MEASURE(S): Tumor volume was measured every week transabdominally using B-mode ultrasound imaging. Gross examination and histological analysis were performed after euthanasia. RESULT(S): More than half of the tumors in the HIFU treatment group showed significant tumor volume reduction. The average tumor volume in the sham treatment group increased 40-fold. Gross and histological analysis showed coagulative necrosis of tumor cells in the HIFU treatment group. CONCLUSION(S): The HIFU may provide an effective and safe method of treating uterine fibroid tumors.

Animals↗
PubMed2003

Vascular mechanics in the clinic.

The bioengineer has more to contribute to medicine than he/she ever has in the past. The successful contribution must be based on such experiences as described by Donald McDonald in his collaboration with John Womersley. Clinician and engineer must come to know the other's problems, their weaknesses and their strengths. They must be prepared to compromise, but to know where compromise is warranted, and where it is not. The clinician must be prepared to change if he/she is to gain help from the engineer. Blind acceptance of old concepts (of "hypertension", and of cuff sphygmomanometric accuracy, etc.) needs enlightenment, while acceptance of physiological reality such as wave reflection needs emerge. The clinician's vocabulary will need to change. This chapter opens with a discussion of a time where knowledge of engineering, physics, physiology and medicine was meagre. These disciplines were small, but they did interconnect through the work of renaissance (and later) scientists. With increase in knowledge, the disciplines enlarged, and grew apart from each other. The challenge of today is to bring these closer together so that there may be some connection, some overlap, and so that the crevices between the disciplines are not so deep, and not such a deterrent to those who wish to engage in interdisciplinary activity.

Animals↗
PubMed1999

Interstitial cellular and matrix restoration of cardiac valves after cryopreservation.

OBJECTIVES: We previously characterized the porcine aortic leaflet interstitial cell phenotype as having both synthetic and contractile characteristics; that is, it is a myofibroblast. In this study we hypothesized (1) that the cryopreservation of aortic valves causes a significant reduction in cell density, (2) that it simultaneously causes alterations in representative components of extracellular matrix, and (3) that both of these processes are reversible. METHODS: Seventy-two leaflets from 24 porcine aortic valves were studied. Whole valves were subjected to variable lengths of preharvest ischemia (group 1), ischemia followed by processing analogous to clinical methods (group 2), and ischemia followed processing with an organ culture type of resuscitation (group 3). Vital dye exclusion by cells enzymatically dispersed from leaflets was used to quantify viability. Electron and light microscopy, immunohistochemical assay, and a silicone rubber substratum contractility assay were used both in dispersed cell preparations and in leaflet cross sections to examine structural, ultrastructural, and functional changes across the 3 groups through a range of preharvest ischemic times. RESULTS: Results indicated that harvest ischemic periods between 2 and 24 hours after donor death were not responsible for cell number reductions. During this interval overt dissolution of chondroitin sulfate simultaneous with a relative sparing of fibronectin was evidenced by immunohistochemical staining. Although not reduced in number, ischemic interstitial cells did show significant ultrastructural evidence of injury and suppressed monoclonal binding to vimentin and alpha-smooth muscle actin. After cryopreservation, viable cell numbers were always markedly reduced at all ischemic intervals and damage to both soluble extracellular matrix components and cell ultrastructure was increased. At all time and processing points, however, some retention of matrix secretory and cellular contractile capabilities was observed among the surviving cells. After the extended periods of preharvest ischemia (2-24 hours) followed by processing, a restitution of functioning cells was accomplished by means of whole-leaflet incubation in 15% fetal bovine serum. CONCLUSIONS: After application of the described methods, new cells within restored intact leaflets as well as in single-cell preparations demonstrated normal ultrastructure and contractile and synthetic functions (normal phenotypic expression). If functioning leaflet interstitial cells can contribute to homograft durability, bioengineering methods for pretransplantation cell repopulation could be refined with these techniques and applied to clinical valve transplantation.

Actins↗
PubMed2003

Vasoconstrictive effect of topical applied corticosteroids measured by laser doppler imaging and reflectance spectroscopy.

Topical application of corticosteroids induces blanching of the skin, based on changes of the underlying microcirculation of the skin. Usually the intensity of blanching after topical application of corticosteroids is measured subjectively by a trained observer using a visual score. In order to obtain an objective determination of the blanching effect and to assess the underlying effect of the skin perfusion, it is necessary to use noninvasive bioengineering techniques. The aim of this study was to compare changes in the vascular plexus during 72 h after topical application of corticosteroids of different potencies with control sites by two noninvasive techniques: laser Doppler imaging (LDI) and diffuse reflectance spectroscopy (DRS). We used the most potent vasoconstrictor, Clobetasol-di-propionate. After 8 h (1.49 Rm (mean reflectance) +/- 0.6 SEM) and after 30 h (0.52 Rm +/- 0.36) DRS showed significant changes in blood flow (during blanching and reactive hyperemia). LDI showed a slight change after 8 h (-0.04 aU (arbitrary units) +/- 0.02 blanching) and a second, significant reaction after 30 h (LDI: 0.18 aU +/- 0.04 reactive hyperemia). In LDI after 30 h higher values were found in men than in women (clobetasol-17-propionate under occlusion Deltat(30)-t(0) men: 0.47 aU +/- 0.18; n = 7; Deltat(30)-t(0) women: 0.14 aU +/- 0.02; n = 10; P = 0.025). This leads to the conclusion that DRS is of more value for the detection of blanching than LDI, which has its sensitivity in the hyperperfused skin. Measurement with both devices showed clear differences in men and women, which means that sex differences should be taken into account.

Administration, Topical↗
PubMed2001

Soybean sterol composition and utilization by Phytophthora sojae.

The sterol fraction of Glycine max (soybean) was found to contain a mixture of 13 major sterols which differed dramatically in composition between seeds and shoots. Typical C4-desmethyl Delta(5)-sterols, including sitosterol, predominate the sterol mixture of shoots, whereas C4-methyl sterol intermediates, cycloartenol and 24(28)-methylene cycloartanol, accumulate in seeds. The significance of modified sterol profile of shoot compared to seed was relevant to the physiology of Phytophthora sojae, a phytopathogen of soybean shown to be auxotrophic for sterol. Sterols native to the host plant containing a C4-methyl group, such as cycloartenol, were not utilized by the fungus. Alternatively, all Delta(5)-sterols added to the culture media of P. sojae supported normal growth and promoted viable oospore production. The results demonstrate the importance of sterols in plant-fungal interactions and offer the possibility of bioengineering the phytosterol pathway for resistance to phytopathogens which scavenge specific sterols of the host plant to complete the life cycle.

Molecular Structure↗
PubMed1997

Chronic wounds.

Skin ulcers are the most common chronic wounds. Current management principles and theories of causation of the most common ulcers--pressure, diabetic, and venous--are described. Issues related to occlusive dressings, compression dressings, topical antimicrobials, debridement, growth factors, grafting, and bioengineered tissue therapy are discussed. Special emphasis is placed on regulatory concerns.

Administration, Topical↗
PubMed1976

The core pathobiology and integrated medical science of adult acute respiratory insufficiency.

The straightforward core pathobiologic facts needed for the clinician's basic understanding of the clinical course and pathophysiology of progressive acute respiratory insufficiency (ARI) seen in surgical practice are summarized in the opening paragraphs. The remainder of the article provides the detailed evidence for elucidating the morphogenesis, i.e., the sequence of pathologic events, which determines the natural and the therapeutically altered clinicopathophysiologic courses of ARI. The attempt is to integrate observations concerning altered structure, cell biology, pathophysiology, physiologic function test data, bioengineering principles, clinical course, therapeutic management, and historical aspects of the disease process, into a detailed multidisciplinary but comprehensive explanation of this very complex, difficult disease process.

Airway Resistance↗
PubMed1999

Clinical experience with soluble TNF p75 receptor in rheumatoid arthritis.

OBJECTIVES: Managing rheumatoid arthritis (RA) can be difficult: the disease may follow an unpredictable course, and therapies are often ineffective or toxic. Etanercept, a bioengineered fusion protein derived from the human soluble tumor necrosis factor p75 receptor, recently has been approved for use in patients with refractory RA. METHODS: Published data on clinical experience with etanercept in conjunction with case illustrations are presented. RESULTS: Reports from clinical trials of patients with refractory RA indicate that etanercept significantly improves measures of disease activity, including swollen and tender joint counts, morning stiffness, pain, and erythrocyte sedimentation rate, compared with placebo. In the phase 3 trial, swollen joint counts improved by 47% in patients receiving etanercept 25 mg compared with a 7% worsening in patients receiving placebo. The drug is well tolerated; injection site reaction, the most frequent adverse event, was minor and manageable. In long-term studies, etanercept remains well tolerated and effective. Our clinical experience indicates that patients with refractory RA experience dramatic symptomatic relief, along with reduced fatigue and improved quality of life. One of 18 patients discontinued treatment; the rest have remained on therapy for up to 18 months. CONCLUSIONS: Etanercept diminishes disease activity in patients with refractory RA. Its favorable safety profile provides symptom control without major toxicity. Etanercept is an important addition to RA therapeutic agents.

Adult↗
PubMed1996

Phytase.

Of all the sources of phytase that have been studied (plant, animal, and microorganisms), the highest yields are produced by a wild-type strain A. niger NRRL 3135 (12.7 mg P/hr/ml = 6.8 microns P/ml/min = 113.9 nKat/ml) in a mineral salt medium in which total phosphate (4 mg %) is limiting for growth and cornstarch and glucose are the carbon sources. Synthesis of the enzyme is repressed by phosphate in the wild-type strain. Aspergillus niger NRRL 3135 produces two phytases one with pH optima at 2.5 and 5.5 (phyA) and one with an optimum at pH 2.0 (phyB). It also produces a pH 6.0 optimum phosphatase that has no phytase activity. These three glycoproteins have been purified to homogeneity, characterized, sequenced, and cloned. The sequences have been compared to each other, other phytases, and to known phosphatases. Their homology has been determined. The active sites of phytases show remarkable homology to the active site residues of the members of a particular class of acid phosphatase (histidine phosphatase). The most conserved sequence is RHGXRXP. Phytase has been covalently immobilized on Fractogel TSK HW-75 F and glutaraldehyde-activated silicate. It has been immobilized on agarose. Losses of activity have been noted on immobilization but these may be minimized by future research. It should be possible to commercially produce and recover penta-, tetra-, tri-, di-, and monoinositol phosphates using immobilized phytase if markets develop for those products. Phytase (phyA) from A. niger NRRL 3135 has been cloned into an A. niger glucoamylase producing strain CBS 513.88 using a construct that has a glucoamylae promoter and an A. niger NRRL 3135 leader sequence, and that is devoid of phosphate repression. The yield of the secreted enzyme was increased 52-fold above that of wild-type A. niger NRRL 3135. The bioengineered organism produces 270 microns P/ml/min (4500 nKat/ml) which is approximately 7.9 g/liter in the medium. The yield of the secreted enzyme was increased 1440-fold above that of wild type CBS 513.88. Commercial preparations of the cloned enzyme are available. Phytase (phyA) has been cloned into tobacco and canola. The enzyme is localized in the seed and expressed at high levels. Feeding of the seed to animals has made the phytin-P in the commercial diets available to the animals. The efficacy of feeding phytase to monogastric animals (poultry and swine) has been established. The amount of enzyme that is necessary to be added to commercial diets has been titred for broilers, layers, turkeys, ducks, and swine. The units of enzyme required are related to the phytin-P content in the diet. The use of the enzyme as a feed additive has been cleared in 22 countries. If phytase were used in the diets of all of the monogastric animals reared in the U.S., it would release phosphorus that has a value of $1.68 x 10(8) per year. The FDA has approved the enzyme preparation as GRAS. The effect of feeding phytase to animals enables assimilation of the P found in feed ingredients and diminishes the amount of phosphate in the manure and subsequently entering the environment. The effect of feeding phytase to animals on pollution has been quantitatively determined. If phytase were used in the diets of all of the monogastric animals reared in the United States, it would preclude 8.23 x 10(7) kg P from entering the environment.

6-Phytase↗