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Biomedical subjects

E Wilkins

Publications and source records attributed to E Wilkins.

At least 19 recordsLinked to original sources
PubMed1998

Immunosensors: electrochemical sensing and other engineering approaches.

This article overviews the engineering approaches and the recent trends in the development of alternative immunoassay systems. A brief description of the main principles and limitations of conventional immunoassay is given. Immunosensing approaches overcoming these limitations are discussed. Alternatives to traditional immunoassay systems are discussed in terms of the enhancement of immunointeraction processes and in terms of the various detection principles. Applications of flow-injection techniques to the development of immunosensing systems are presented. Immunosensors are categorized based on the detection principle employed, as immunoelectrodes (electrochemical immunosensors), piezoelectric immunosensors, or as sensors based on optical detection of the immunointeraction. The discussion focuses on electrochemical immunosensors. In conclusion, the engineering issues involved in immunosensor development are outlined and trends towards practical applications are discussed.

Animals↗
PubMed1997

Flow-through amperometric immunosensor: fast 'sandwich' scheme immunoassay.

A flow-through immunosensor based on a high-surface-area carbon immunoelectrode has been developed. Dispersed carbon material serves as a carrier for immobilized antibodies and at the same time as an electrode material. The 'sandwich' scheme of immunoassay has been used. Iodine formed as a result of the enzymatic oxidation of iodide by a peroxidase label has been detected amperometrically. The immunosensor consists of a disposable sensing element (immunocolumn) containing dispersed carbon material with immobilized antibodies which also acts as a working electrode. A current collector connects the working electrode to the measuring device. The electrochemical detection time of the peroxidase-labeled immuno-complex does not exceed several minutes. The overall time of analysis including flowing of analyte, flowing of antigen, washing and detection stages is as low as 22 min. This technique allows fast determination of rabbit IgG (used as a model analyte) with a low detection limit in the picomolar range and also the determination of human IgM in blood plasma with a low detection limit in the nanomolar range.

Animals↗
PubMed1997

Implantation of a refillable glucose monitoring-telemetry device.

This study describes the components and short-term in vivo evaluation of an integrated implantable system consisting of an amperometric glucose biosensor, a miniature potentiostat, a FM signal transmitter, and a power supply. The device (dimensions: 5.0 x 7.0 x 1.5 cm) was implanted subcutaneously in healthy mongrel dogs. The biosensor performance was evaluated in vitro prior to implantation using standard solutions simulating the physiological environment. A linear response to glucose concentration was observed throughout the physiological and pathophysiological range (with an upper limit of 25 mM glucose, and a sensitivity of 0.5 microA/mM). The results of short-term subcutaneous implantation of the integrated system demonstrated good agreement between the glucose concentration measured by the biosensor and that obtained using standard glucose determination methods. The delay-time between the tissue glucose level (measured by the biosensor) and the blood glucose level (obtained by standard methodology) was 3-7 min. These results demonstrated the feasibility of data transmission by a telemetry system through the skin of a dog and allowed the commencement of chronic in vivo testing. During the chronic implantation the biosensor was refilled in vivo. A rejuvenation of the sensor's response after refilling was observed suggesting the potential of such sensors for long-term implantation.

Animals↗
PubMed1996

Glucose monitoring: state of the art and future possibilities.

This article reviews the development of glucose monitoring techniques and approaches during the last decade. The predominance of the electrochemical measuring principles reported in the literature makes them a focus of this work. Biosensors are still in the main stream of the research interest of most teams due to their high selectivity for glucose determination. Systematization and classification of the glucose monitoring principles and types of glucose sensors is shown. The review gives a brief description of the basic operational principles of the most popular types of glucose biosensors, providing an enhanced bibliography of the original works of the main groups in establishing or significantly contributing to the development of the particular type of glucose biosensor. Different design approaches are overviewed including needle-type sensors, sensors for chronical implantation and the combination of the glucose biosensors with microdialysis sampling technique. The authors approach for replacing of the spent enzyme and thus recharging the sensor in situ while implanted is widely discussed. This approach provides a way to increase the lifespan of the system and ultimately, it could lead to rare transcutaneous interventions for refilling of the implanted sensor.

Biomedical Engineering↗
PubMed1996

Short-term canine implantation of a glucose monitoring-telemetry device.

In this study we report the development and short-term in vivo evaluation of an integrated implantable device consisting of an amperometric glucose biosensor, a miniature potentiostat, a FM signal transmitter, and power supply. The device (dimensions: 5.0 x 7.0 x 1.5 cm) was implanted under the skin of medium-size anaesthetized dog. The experimental set-up included several methods for data collection: analog recording via wired X-T chart recorders; data collection by wearable microprocessor--data logger, and remote data collection via antenna and receiver linked to a computer-based data acquisition system. The device (sensor) performance was evaluated in vitro prior to implantation, using different model solutions simulating the physiological environment. A linear response to glucose concentration was obtained up to 25 mM glucose, with a sensitivity of 0.5 microA/mM. The results of short-term subcutaneous implantation of the integrated device reveal adequate monitoring of an artificially-induced glycaemia. The delay-time was 3-7 minutes. These tests demonstrate the feasibility of data transmission by the telemetry system through the skin of a medium-sized dog and allow the commencement of chronic in vivo experimentation.

Animals↗
PubMed1995

Integrated implantable device for long-term glucose monitoring.

In this study we report the development of an integrated implantable device for glucose monitoring. The dimensions of the device (5.0 x 7.0 x 1.5 cm) allow implantation under the abdominal skin of a large animal for in vivo evaluation of sensor performance. The experimental set-up includes amperometric glucose biosensor, a miniature potentiostat, an FM signal transmitter, a power supply and an antenna and receiver linked to a computer-based data acquisition system. The device performance was evaluated in vitro using a ten-day continuous test and other long-term operation experiments. The biosensor was tested in different model solutions that simulated the physiological environment in which it will be ultimately used. A linear response to glucose concentration was obtained up to 25 mM glucose, with a sensitivity of less than 0.5 microA/mM. The ability of the biosensor to measure glucose levels in serum was also tested, and a good correlation demonstrated between glucose serum levels measured by routine technique and those measured using the biosensor (R2 = 0.993; slope = 0.996). Initial results obtained from the short-term subcutaneous implantation of the sensor demonstrate its potential for the monitoring of glucose concentration in vivo.

Animals↗
PubMed1995

Effect of interference on the performance of glucose enzyme electrodes using Nafion coatings.

The negatively charged perfluorinated ionomer Nafion was used as a coating on hydrogen peroxide detecting platinum electrode as well as on a polycarbonate diffusion membrane in the construction of a glucose amperometric enzyme electrode. The current response of these electrodes to hydrogen peroxide, ascorbic acid, acetaminophen, uric acid and glucose was studied and the coating procedure was optimized. It was confirmed that the Nafion coating prevents interference by anionic substances such as ascorbic acid and uric acid, and decreases acetaminophen interference. In this regard it was shown that coating the glucose diffusion membrane (polycarbonate) was more effective than coating the platinum wire itself, because of the prevention of the homogeneous redox reaction of the interference species with hydrogen peroxide, as well as the additional diffusional resistance to the glucose flux. The glucose levels in serum samples were estimated and the stability of the enzyme electrodes during continuous operation in serum was studied. An enzyme electrode with constant sensitivity of ca. 1 microA/mM and a linear range of up to 15 mM, unaffected by contact with serum, is reported.

Biosensing Techniques↗
PubMed1995

Marked variation in pyrimethamine disposition in AIDS patients treated for cerebral toxoplasmosis.

We have characterized the disposition of pyrimethamine in 20 adults with advanced AIDS. After the first dose, the area under concentration versus time curves (corrected for dose-size) varied 13-fold. This marked variation in drug levels was also noted during accumulation towards steady-state: pyrimethamine levels were consistently below the suggested lower end of the therapeutic range (750 mg/L) in three severely ill patients with perturbed consciousness (two of whom received the drug by nasogastric tube). Possible mechanisms for these observations are discussed. Pyrimethamine levels may be an important determinant of the rate of response to treatment by AIDS patients with toxoplasmosis: therapeutic drug monitoring may have a role.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Use of charged membranes to control interference by body chemicals in a glucose biosensor.

The prerequisite for the continuous in vivo monitoring of glucose concentration is the development of an implantable glucose sensor with long-term stability. A new enzyme electrode concept featuring fluid-state glucose oxidase modified carbon powder along with a cross-linked glucose oxidase enzyme layer has been developed. The glucose sensor incorporating this enzyme electrode has been tested in vitro at 37 degrees C. It has a lifetime of three months after which it can be recharged with fresh enzyme. The next step in the characterization of this sensor is its in vitro behaviour in the presence of interfering substances commonly encountered in human blood. Here we report such a study of the sensor. The glucose diffusion membranes used were polycarbonate membranes. We used standard polycarbonate membranes (membranes treated with polyvinylpyrrolidone or PVP), PVP-free polycarbonate membranes, and standard polycarbonate membranes coated with positively and negatively charged hydrogel layers. The sensors showed a response to glucose concentrations < 300 mg dL-1, both in pure phosphate buffer and in the presence of interferences. The influence of ascorbic acid, bilirubin, creatinine, L-cystine, glycine, uric acid and urea on the amperometric signal of the sensor was investigated. The polycarbonate membrane coated with the negatively charged hydrogel layer provided good protection for the enzyme electrode, especially in the presence of ascorbic acid and uric acid.

Biosensing Techniques↗
PubMed1994

A longitudinal study of per cent agalactosyl IgG in tuberculosis patients receiving chemotherapy, with or without immunotherapy.

An increased percentage of circulating IgG molecules that lack galactose from the oligosaccharides on the CH2 domain correlates with disease severity in tuberculosis, rheumatoid arthritis and Crohn's disease. We have recently observed that a single injection of 10(9) autoclaved Mycobacterium vaccae given to tuberculosis patients 7 days after the initiation of chemotherapy causes accelerated clinical improvement, and clearance of bacilli from the sputum. We now show that this immunotherapy also causes rapid loss of agalactosyl IgG, detectable within 14-21 days, whereas chemotherapy alone causes agalactosyl IgG to rise further for up to 2 months. There is simultaneous inhibition of the antibody response to lipoarabinomannan, and transient enhancement of the tuberculin skin-test response. These findings are compatible with a shift from antibody production towards increased cell-mediated immunity. The ideal treatment for tuberculosis would supplement a truncated course of chemotherapy with an immunotherapeutic preparation able to down-regulate the Koch phenomenon and replace it with an efficiently bactericidal mechanism. We tentatively postulate that a fall in per cent agalactosyl IgG [%Gal(0)] in tuberculosis patients may be a marker of such a change.

Adolescent↗
PubMed1994

Breast reconstruction in older women.

BACKGROUND: More than 50% of breast cancer care in the United States occurs in women over age 65 years. This study investigates age-related differences in breast reconstruction practices after mastectomy for breast cancer. METHODS: Retrospective review of University of Michigan Breast Care Center patients revealed 242 female patients with breast cancer who underwent postmastectomy breast reconstruction from 1980 through 1991. Data were complied concerning patient age, reconstruction interval (immediate or delayed), type of breast reconstruction performed, reconstruction-associated complications, and the number of postreconstruction procedures required to obtain the final result. Statistical comparisons were made with the chi-squared test. RESULTS: There were 224 patients aged less than 60 years (range 27 to 59 years; median, 44 years) and 18 patients aged 60 years or more (oldest, 68 years). Of the 18 older patients, three underwent delayed transverse rectus abdominus muscle (TRAM) reconstruction; one received a delayed latissimus dorsi flap placed over a silicone gel prosthesis, and 14 underwent 18 reconstructions (4 bilateral) with silicone gel implants (6 immediate, 12 delayed). The younger patients underwent 269 breast reconstructions (45 bilateral), including 92 autogenous tissue reconstructions (34 immediate TRAM, 58 delayed TRAM), 60 immediate and 88 delayed insertions of an expander or prosthesis, and 29 latissimus dorsi flaps with implant reconstructions (3 immediate, 26 delayed). Seven complications (32%) occurred in the 22 breast reconstructions performed in older women, including capsular contracture surrounding an implant (six patients) and a ventral hernia in one patient with a TRAM flap. Complications occurred in 134 breast reconstructions (50%) performed in younger women. All were related to the reconstruction. In the older women a mean of 1.7 +/- 0.7 operations was required to achieve a final reconstruction result versus 2.1 +/- 1.1 in the younger women (not significant). More operations were required in younger women undergoing prosthetic reconstruction than in older women, but this difference was not statistically significant (2.4 +/- 1.2 versus 1.9 +/- 0.7; p = 0.07). Autogenous tissue reconstruction was performed less frequently in older women (14% versus 34%; p < 0.05). No age-related difference was noted in the rate of immediate (versus delayed) reconstruction (27% versus 36%, respectively). Complications occurred more frequently in women who underwent prosthetic breast reconstruction, particularly in younger women (32% in older women and 64% in younger women; p < 0.01). The complication rate for immediate breast reconstruction in older women (all prosthetic) was less than in younger women (17% versus 59%; p < 0.05). For delayed prosthetic reconstructions, complications also occurred less frequently in older than younger women (38% versus 67%; p < 0.05). Between 1988 and 1992, 91 older women and 180 younger women underwent mastectomy for breast cancer; only 7% of older women versus 38% of younger women underwent breast reconstruction (p < 0.001). CONCLUSIONS: Breast reconstruction is a safe option for older women requiring mastectomy. The full array of reconstruction options (autogenous tissue or implants, immediate or delayed) should be considered for use in women of all ages.

Adult↗
PubMed1993

Benefits of a multidisciplinary approach to breast care.

The University of Michigan Breast Care Center (BCC) was established in 1985 to provide comprehensive, multidisciplinary diagnosis and treatment of benign and malignant breast disease. This work presents an overview of our experience in the BCC and assesses the clinical, academic, financial, and educational effectiveness of the program. A database was used to generate a list of all patients seen in the BCC between February 1, 1985 and December 31, 1991. Participating departments provided information regarding outpatient, inpatient, clinical and consultative activities, and referral patterns attributable to BCC endeavors. BCC educational and academic activities were reviewed and profiled. Clinical information was culled from the BCC database, hospital records, and the hospital tumor registry. The BCC has resulted in a fivefold increase in breast care related activity at the University of Michigan Medical Center. Over half of the patients treated in the BCC with primary operable breast cancer receive breast-conserving therapy. The BCC performs a unique educational function, providing the primary breast care experience for house staff as well as one third of the third year medical school class. The BCC supports over 20 clinical research protocols, and patient enrollment in clinical trials has increased dramatically since 1985. The BCC also provides support to basic science researchers receiving over 2.5 million dollars in peer reviewed direct cost support. These data suggest that a multidisciplinary approach to patient care as embodied by the BCC can be clinically, financially, and academically superior and productive. This model warrants further investigation not only in the field of breast care, but also in other clinical situations that require multidisciplinary input and therapy.

Breast Diseases↗
PubMed1993

Trés difficile.

Explore the source record for details and available documents.

Anti-Bacterial Agents↗
PubMed1993

The use of omental transposition in the treatment of recurrent sarcoma of the back.

We report 2 patients with paraspinous sarcoma treated with omental transposition tunneled through a defect in the lumbar fascia that resurfaced in the soft tissues of the lower back. Traditional reconstruction with skin flaps was unsatisfactory because of prior irradiation to the area. In 1 patient the omentum obliterated a cavity connecting the dura to the skin to prevent cerebrospinal fluid leak. In the other patient a large soft tissue defect overlying the lower back and dura was covered with omentum and skin grafted. Although both patients lived < 2 years, the durable wound coverage remained intact over the surgical site.

Adult↗