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Biomedical subjects

R C Lee

Publications and source records attributed to R C Lee.

At least 55 records · Page 3Linked to original sources
PubMed1999

An independent, inverse association of high-density-lipoprotein-cholesterol concentration with nonadipose body mass.

BACKGROUND: Increasing body mass index (BMI) is associated with progressively lower serum HDL-cholesterol concentrations, although the underlying body-composition compartment accounting for this unfavorable lipid change remains uncertain. OBJECTIVE: Because growing evidence favors a role of lean tissue in HDL homeostasis, the hypothesis was tested that non-adipose tissue components of body mass explain the inverse association of HDL cholesterol and BMI. DESIGN: Fasting serum lipid concentrations and body composition [total, subcutaneous, and visceral adipose tissue; adipose tissue-free mass (ATFM); and skeletal muscle by whole-body magnetic resonance imaging and body cell mass by 40K counting) were evaluated in healthy adults. Body-composition compartments were expressed as height2-normalized indexes. RESULTS: An inverse correlation was observed between serum HDL cholesterol and BMI in women (n = 68; R2 = 0.08, P = 0.023) and men (n = 61; R2 = 0.07, P = 0.046). Significant inverse correlations (P = 0.005-0.02) were also observed between HDL cholesterol and nonadipose components (ie, ATFM, skeletal muscle, and body cell mass) but not between HDL cholesterol and any adipose tissue component. The association between HDL cholesterol and ATFM remained significant after serum triacylglycerol was controlled for. When BMI was entered into the HDL cholesterol-ATFM regression model, BMI was not a significant independent variable. The strongest correlate of serum triacylglycerol was visceral adipose tissue (P = 0.002 for both women and men). CONCLUSIONS: Lean tissues and body cell mass appear to account in part for the long-observed inverse association of HDL cholesterol and BMI. These observations suggest a link between nonadipose tissue compartments and the greater cardiovascular risk associated with high BMI.

Adipose Tissue↗
PubMed1998

The future of biothermal engineering.

This is a report on a three-day workshop held at the Allerton House of the University of Illinois. The first day consisted of invited tutorials on topics related to biothermal engineering: biological structures, analysis of microvascular heat transfer, temperature measurement, cryobiology and cryosurgery, burns, and industrial and consumer applications. The rest of the workshop consisted of discussions in small groups and in plenary sessions dealing with relevant topics. Although the discussions endeavored to be as comprehensive as possible, the specific topics were selected by the participants based on their expertise and interests. The main areas examined were: Instrumentation, Priority applications, Mathematical modeling, Thermal injury. The reliable measurement of the temperature distribution inside the living tissue is still the premier problem of instrumentation although the measurement of other parameters, such as properties, blood perfusion or heat flux, is also of great importance. The most important applications are medical, industrial, consumer, agricultural, space, and military. The degree of sophistication needed in the analysis of specific problems varies a great deal from relatively simple heat conduction models to complicated ones including blood perfusion, anisotropy, and the influence of large blood vessels. For many applications new experimental data are still needed. There have been significant advances in the modeling of living tissue with increasing understanding of its thermal behavior. The consensus was, however, that the models will always have to be tissue or organ specific and some new models are still to be developed.

Animals↗
PubMed1998

Non-linear microscale alterations in membrane transport by electropermeabilization.

The purpose of this study was to quantify the changes in cell membrane conductance in response to electropermeabilization, which may elucidate the mechanisms of tissue injury resulting from high-voltage electrical shock. A high-speed, space-clamp and voltage-clamp experimental configuration was used. The pulse parameters of an imposed transmembrane potential that are instrumental in membrane properties alteration were precisely controlled. The dynamics of the non-linear electroporation response was characterized.

Animals↗
PubMed1998

Poloxamer 188 enhances functional recovery of lethally heat-shocked fibroblasts.

Damage to the cell membrane has been implicated as the primary event in the pathogenesis of heat shock, generally resulting in loss of cellular homeostasis and cell death. Thus a promising mode of therapy would involve the restoration of cell membrane integrity. Surfactant molecules, specifically triblock polymers such as Poloxamer 188 (P-188), possess the ability to self-aggregate into membrane-like structures in aqueous solutions and have been shown to restore membrane integrity. The objective of this study was to develop functional and morphological assays to determine whether treatment with P-188 after heat shock enhances the recovery of thermally damaged cells. Human foreskin fibroblasts were placed in sterile vials and heated by immersion in a calibrated water bath for various lengths of time at predefined temperatures. Cell recovery after heat shock was assessed using a functional assay based on the ability of the cells to contract fibroblast populated collagen lattices (FPCLs). Subsequent to heating, collagen lattices were prepared with control (no heat, no P-188) and heat shocked cells (with and without P-188). Our results indicate that treatment with low concentrations of P-188 after heat shock was effective in ameliorating both the morphological integrity and the contractile function of thermally damaged cells. Further, we observed that P-188 was most effective in improving the contractile ability of cells heat shocked at 45 degrees C; however, it had no influence on the contractility of cells exposed to higher temperatures. Our results suggest that there exists a threshold of thermal stress (45 degrees C for 20-60 min) beyond which treatment with low concentrations of P-188 (0.5 mg/ml) is ineffective in minimizing cell damage. Moreover, the results of our morphological assays indicate that cells treated with P-188 after heat shock maintain their cytoskeletal organization, whereas untreated cells exhibit filamentous actin depolymerization.

Actin Cytoskeleton↗
PubMed1998

Uncertainty analysis methods for comparing predictive models and biomarkers: A case study of dietary methyl mercury exposure.

Biologically based markers (biomarkers) are currently used to provide information on exposure, health effects, and individual susceptibility to chemical and radiological wastes. However, the development and validation of biomarkers are expensive and time consuming. To determine whether biomarker development and use offer potential improvements to risk models based on predictive relationships or assumed values, we explore the use of uncertainty analysis applied to exposure models for dietary methyl mercury intake. We compare exposure estimates based on self-reported fish intake and measured fish mercury concentrations with biomarker-based exposure estimates (i.e., hair or blood mercury concentrations) using a published data set covering 1 month of exposure. Such a comparison of exposure model predictions allowed estimation of bias and random error associated with each exposure model. From these analyses, both bias and random error were found to be important components of uncertainty regarding biomarker-based exposure estimates, while the diary-based exposure estimate was susceptible to bias. Application of the proposed methods to a simple case study demonstrates their utility in estimating the contribution of population variability and measurement error in specific applications of biomarkers to environmental exposure and risk assessment. Such analyses can guide risk analysts and managers in the appropriate validation, use, and interpretation of exposure biomarker information.

Animals↗
PubMed1998

Surfactant administration reduces testicular ischemia-reperfusion injury.

PURPOSE: The mechanism of testicular ischemia-reperfusion injury has not been well delineated. We determined the efficacy of a biocompatible surfactant (tetronic 1107) to reduce tissue injury and evaluated cell membrane integrity as reflected by calcium ion permeability in an in vivo animal model of testicular ischemia-reperfusion. MATERIALS AND METHODS: Three groups of male Sprague-Dawley rats (6 per group) were studied. Group 1 was the nonoperative control, and groups 2 and 3 underwent 4 hours of unilateral testicular ischemia followed by 4 hours of reperfusion. Ten minutes after reperfusion 0.4 ml. saline was administered intravenously to group 2 and 180 mg./kg. surfactant tetronic 1107 to group 3. 99mTechnetium pyrophosphate was used to monitor calcium ion uptake by the ipsilateral and contralateral testicles. Both testicles were also examined histologically. RESULTS: The surfactant treated animals had markedly diminished hemorrhagic discoloration and vascular congestion compared to saline treated animals. These results were confirmed microscopically with improved nuclear chromicity and disarray of germ cell layers of the seminiferous tubules. The surfactant treated group also had a statistically significant (p <0.05) reduction in radiotracer uptake compared to the saline treated animals, confirming a reduction in calcium ion permeability. CONCLUSIONS: The results of this study suggest that tetronic 1107 is effective in reducing tissue damage in a testicular ischemia-reperfusion animal model.

Animals↗
PubMed1998

Steroid cell tumors of the ovary: clinical, ultrasonic, and MRI diagnosis--a case report.

Steroid cell tumors of the ovary are rare sex-cord neoplasms which account for less than 0.1% of all ovarian tumors. They have been divided into two subtypes according to their cell of origin as follows: stromal luteoma, and Leydig cell tumors, and a third subtype with lineage unknown is a steroid cell tumor, not otherwise specified (NOS). The clinical presentation may take many forms, including pain, abdominal distention and bloating, but perhaps the most interesting and noticeable presentations are those related to the hormonal activity and virilizing properties of the tumor. No radiological features of the steroid cell tumor, NOS have been presented in the literature. This report presents the MRI and ultrasonographic findings of a patient having steroid cell tumor, NOS, of the right ovary with metastasis to the uterus.

Female↗
PubMed1998

Neuropsychological symptom presentation after electrical injury.

OBJECTIVE: This study explored the relationship of neuropsychological complaints to accident- and injury-related characteristics, affective state, and work status in a group of electrical injury (EI) patients. METHODS: Sixty-three EI patients and 22 electricians with no history of electrical shock completed the Neuropsychological Symptom Checklist and the Beck Depression Inventory as part of an extensive neuropsychological evaluation. RESULTS: The EI group endorsed significantly more physical, cognitive, and emotional symptoms than did the controls. Symptom complaints were not related to injury parameters or litigation status. Only the time interval between injury and assessment accounted for differences in symptom presentation, with patients in the postacute stages of recovery showing the most cognitive and emotional complaints. CONCLUSION: The neuropsychological syndrome of electrical injury survival includes physical, cognitive, and emotional complaints. Considering that most electrically injured patients are treated within the acute medical setting, greater attention needs to be directed early in the course of treatment toward addressing neuropsychologic and psychiatric issues.

Accidents, Occupational↗
PubMed1998

Three-dimensional wound surface area calculations with a CAD surface element model.

A quadrature scheme is presented for the calculation of three-dimensional (3-D) wound surface area from a 3-D CAD surface element model (SEM) and a two-dimensional (2-D) wound image. The algorithm employs discrete summation over the 2-D wound region with local curvature obtained from the SEM. An approximation is derived for the error due to elemental discretization, and is found to be negligible for the resolution considered here. The alternative method of direct summation over surface element space is shown to result in significant fringe error along the wound boundary.

Adult↗
PubMed1998

Spiral computed tomographic angiography--a new technique for evaluation of vascular access in hemodialysis patients.

Spiral computed tomographic angiography (CTA), a new noninvasive imaging technique, was used to study 10 arteriovenous fistulas (AVF) in 9 hemodialysis patients. Digital subtraction angiography (DSA) was also performed as a gold standard for comparison. AVF stenosis was graded by a four-point scale: grade 0, well patency of supplying artery, anastomosis and drainage vein; grade 1, < 50% stenosis; grade 2, 50-70% stenosis; grade 3, 70-99% stenosis, and grade 4, total occlusion. We found CTA correlated closely to DSA in detecting both stenosis and dilatation of AVF and it spared all the shortcomings of DSA. CTA has the potential to be alternative for imaging of dialysis fistulas. Further studies will be performed to specify the role of CTA images in the assessment of the hemodialysis vascular access.

Adult↗
PubMed1998

Normal and variant anatomy of hepatic arteries: angiographic experience.

BACKGROUND: Anatomic variation of hepatic arteries is reported to occur in 25-50% of the general population. Knowledge of the existing variations is important in planning and conducting surgical or radiologic procedures in the upper abdomen, such as liver transplantation and transarterial chemo-embolization (TACE). METHODS: Based on data from 321 patients undergoing upper abdominal arteriography, hepatic artery anatomy was analyzed and classified into three groups (single, double and multiple hepatic arteries at hepatic hilum) according to Suzuki's classification. Each group was subdivided into three types (celiac, mesenteric and mixed types) according to the origin of the hepatic arteries. The variations within each type were recorded. RESULTS: Two hundred and sixty one patients (68.%) had single hepatic arteries. One hundred and five patients (27.6%) had double hepatic arteries and only fifteen patients had multiple hepatic arteries. All of these variants, including twenty subtypes, were identified. CONCLUSIONS: This study, based on Suzuki's classification, provides basic data for the anatomic variations of hepatic arteries for the Chinese population in Taiwan.

Female↗
PubMed1998

High resistance index of Doppler ultrasound in tuberculous peritonitis presenting as abdominal carcinomatosis: report of two cases.

The radiologic features of tuberculous peritonitis (TB peritonitis) are seldom reported, and the use of color Doppler ultrasound in the diagnosis of TB peritonitis is even less common. Herein, we present two patients (a 29-year-old woman and a 56-year-old woman) who were evaluated for months of progressive enlargement of the abdomen, poor appetite and weight loss. In both patients, clinical and laboratory examinations suggested carcinoma, except a very high vascular resistance (resistance index 1.0 and 0.89, respectively) of the tumor feeding vessels detected by color Doppler ultrasound. TB peritonitis was finally diagnosed by exploratory laparotomy. Both patients were treated using a four-drug regimen of isoniazid, rifampicin, ethambutol hydrochloride and pyrazinamide for nine months and were clinically cured. In conclusion, if color Doppler ultrasound reveals normal ovaries, ascites containing thin, delicate incomplete or complete septa, and only a few high-resistance tumor feeding vessels in the abdominal cavity (resistance index > or = 0.80), TB peritonitis should be considered.

Abdominal Neoplasms↗
PubMed1998

The problem scar.

Through deeper understanding of the physiology of wound healing and physico-chemical principles of scarring, biomedical science facilitates the development of new strategies in treatment and prevention of problem scars. It is important for practicing physicians and surgeons to be better aware of the full range of available techniques to control scar formation, and for any medical intervention to be planned in such a way that potential problems are apprehended and minimized or avoided. This article describes the clinical applications of recent research in scar control in order to provide such guidance.

Cicatrix↗
PubMed1998

Preoperative diagnosis of primary fallopian tube carcinoma by magnetic resonance imaging: a case report.

Because of the rarity and insidious onset of primary adenocarcinoma of the fallopian tube, early diagnosis is very difficult. Primary fallopian tube carcinoma is also rarely diagnosed preoperatively. This report reviews the value of magnetic resonance imaging (MRI) in aiding the detection of early-stage primary fallopian tube carcinoma in a 48-year-old female. The diagnosis was based on clinical suspicion, elevated CA-125 and MRI. MRI demonstrated the tumor as an area of solid masses with marked enhancement after gadolinium-diethylenetetraaminepentaacetic acid (Gd-DTPA) administration. Primary fallopian tube carcinoma was confirmed by pathologic examination. We hope that, with improvements in imaging, early diagnosis of such a malignant disease could become routinely possible in the future.

Fallopian Tube Neoplasms↗
PubMed1997

The cold shock domain protein LIN-28 controls developmental timing in C. elegans and is regulated by the lin-4 RNA.

Mutations in the heterochronic gene lin-28 of C. elegans cause precocious development where diverse events specific to the second larval stage are skipped. lin-28 encodes a cytoplasmic protein with a cold shock domain and retroviral-type (CCHC) zinc finger motifs, consistent with a role for LIN-28 in posttranscriptional regulation. The 3'UTR of lin-28 contains a conserved element that is complementary to the 22 nt regulatory RNA product of lin-4 and that resembles seven such elements in the 3'UTR of the heterochronic gene lin-14. Both lin-4 activity and the lin-4-complementary element (LCE) are necessary for stage-specific regulation of lin-28. Deleting the LCE produces a dominant gain-of-function allele that causes a retarded phenotype, indicating that lin-28 activity is a switch that controls choices of stage-specific fates.

Animals↗
PubMed1997

Injury by electrical forces: pathophysiology, manifestations, and therapy.

The pathogenesis and pathophysiologic features of electrical injury are more complex than once thought. The relative contributions of thermal and pure electrical damage depend on the duration of electric current passage, the orientation of the cells in the current path, their location, and other factors. If the contact time is brief, nonthermal mechanisms of cell damage will be most important and the damage is relatively restricted to the cell membrane. When contact time is much longer, however, heat damage predominates and the whole cell is affected directly. These parameters also determine the anatomic tissue distribution of injury. Damage by Joule heating is not known to be dependent on cell size, whereas larger cells are more vulnerable to membrane breakdown by electroporation. Cells do survive transient plasma membrane rupture under appropriate circumstances or if therapy is instituted quickly. If membrane permeabilization is the primary cellular pathologic condition, then injured tissue may be salvageable and the challenge for the future is to identify a technique to reseal the damaged membranes promptly. Present standards of care for electrical injury require a fully staffed and well-equipped intensive care unit, available operating suites, and the availability of the full range of medical specialists. Major teaching hospitals with burn centers may be the ideal setting for the treatment of an electrical trauma victim. After the initial resuscitation, efforts are directed primarily towards preventing additional tissue loss mediated through the compartment syndrome, compressive neuropathies, or the presence of necrotic tissue. Renal and cardiac failure caused by the release of intracellular muscle contents into the circulation must be prevented. Attention can then be directed towards maximizing tissue salvage and preventing late skeletal and neuromuscular complications. Reconstructive procedures that transfer healthy tissue from a distance are necessary to optimize the functional value of the remaining tissue. Finally, unless the patient is rehabilitated psychologically, the real benefit from other sophisticated care will not be fully realized. These goals are important throughout the acute care of the patient. In the future, new guidelines for treating electrical trauma will be based on a clearer understanding of the relevant pathophysiologic features. These strategies will rely on improved diagnostic imaging and on reversing the fundamental problem of cell membrane damage. Moreover, complex biochemical and organ system pathophysiologic interactions will require careful management. If successful, research efforts presently underway should improve the prognosis of victims after electrical trauma.

Burns, Electric↗