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Biomedical subjects

S L Xie

Publications and source records attributed to S L Xie.

9 recordsLinked to original sources
PubMed1998

Plasma tumor necrosis factor-alpha, its soluble receptors and interleukin-1beta levels in critically burned patients.

Levels of plasma TNF-alpha, interleukin-1beta(IL-1beta ), soluble TNF-receptor I (sTNF-R I) and soluble TNF-receptor II (sTNF-R II) were determined in 16 critically burned patients. Seven of the 16 patients showed hypovolemic shock (shock group), 9 with sepsis (sepsis group), 8 with multiple organ dysfunction syndrome (MODS group) and 6 of them died (non-survival group). Plasma TNF-alpha, sTNF-R I and R II were significantly higher in the shock group, the MODS group and the non-survival group than each of the control groups. TNF-alpha and sTNF-Rs increased gradually in the MODS group and the non-survival group from 1 to 5 days postburn. TNF-alpha, sTNF-R I and R II correlated positively with Goris' multiple organ failure score. Molecular sTNF-Rs/TNF-alpha ratios were lower in the sepsis group than in the non-sepsis group. These results suggest that circulating TNF and soluble TNF receptors system play an important role in the development of burn shock and MODS; high molecular ratios of endogenous sTNF-Rs might not reduce the morbidity of MODS and the mortality in critically burned patients.

Adolescent↗
PubMed1995

A model of human microvascular exchange.

A compartmental model consisting of the circulation, a general interstitium, and the lymphatics, is formulated to describe the transport and distribution of fluid and plasma proteins (albumin) in the human microvascular exchange system. Transcapillary mass exchange is assumed to occur via a coupled Starling mechanism. Unknown or poorly quantified model parameters are estimated by statistical fitting of simulation predictions to five different sets of experimental data. The data consist of steady-state and transient plasma and interstitial volumes and colloid osmotic pressures measured under laboratory or clinical conditions for normal humans and for patients with nephrotic syndrome or mild heart disease. In all cases, it is assumed that the system response to perturbations imposed either artificially or through illness is due to changes in the Starling driving forces. The three best-fit parameters were found to be normal capillary hydrostatic pressure, Pc,o = 11.0 mm Hg; albumin reflection coefficient, sigma = 0.99; and lymph flow sensitivity, LS = 43.1 ml/mm Hg.hr. Three other parameters, which were unknown but related to the estimated parameters through steady-state mass balance equations, were determined to be fluid filtration coefficient, KF = 121.1 ml/mm Hg.hr; albumin permeability-surface area product, PS = 73.0 ml/hr; and normal lymph flow, JL,o = 75.7 ml/hr. The fully described model was validated by comparisons between (1) simulation predictions and data used in parameter estimation, (2) estimated transport parameters and available literature values, and (3) model predictions and an additional set of experimental data.

Cardiac Output, Low↗
PubMed1994

[Occult breast cancer: 9 cases report and review].

From 1977 to 1994, 9 breast cancer were treated. All patients presented axillary node enlargement as first sign. Six patients were treated by radical or modified radical mastectomy and 3 by axillary node excision. All patients received postoperative adjuvant radiotherapy and chemotherapy. Among the 6 patients treated by radical or modified radical mastectomy, 4 survived over 10 years after surgery, 1 died of heart disease at 8 years, and 1 on chemotherapy is for 4 months. The three patients treated by axillary node excision, all died of the disease at 8-32 months. It is considered that radical or modified radical mastectomy with adjuvant radiotherapy and chemotherapy is a suitable treatment selection for occult breast cancer.

Adult↗
PubMed1993

A model of human microvascular exchange: parameter estimation based on normals and nephrotics.

A mathematical model is formulated and used to describe the distribution and transport of fluid and albumin in the human circulation, interstitium and lymphatics. Two transcapillary mass exchange mechanisms are investigated: a homoporous 'coupled Starling model', in which transcapillary albumin diffusion and convection occur within the same pathway, and a heteroporous 'plasma leak model', in which variations in structure and pressure are permitted along the length of the capillary. Parameters used in the transport models are determined based on statistical fitting of simulation predictions to experimental data from normal humans and nephrotic patients. The data consists of interstitial fluid volumes and interstitial colloid osmotic pressures as functions of plasma colloid osmotic pressure. Model validation is carried out based on comparison of (i) simulation predictions with experimental data used in parameter estimation, (ii) estimated transport parameters with experimentally determined values, and (iii) simulation predictions with a set of dynamic data from an albumin infusion study. While both models with their best-fit parameter estimates provide a good representation of experimental data, the drawbacks of the plasma leak model are three-fold: it requires more estimated parameters than the coupled Starling model, little experimental information exists with which to compare these parameters and, with the best fit values obtained, the plasma leak mechanism becomes insignificant. The model that employs a Starling-type exchange mechanism will therefore be favoured in future applications.

Arteries↗
PubMed1991

Rechargeable glucose electrodes for long-term implantation.

A unique enzyme electrode was designed using glucose oxidase immobilized on fine graphite powder. The graphite-enzyme is in a fluid state which enables recharging of the system when the enzyme activity decreases, therefore allowing the system to have a long lifetime in a diabetic patient. The sensor was tested using glucose concentration in the range of 20-300 mg d-1. The electrode construction includes a hydrophobic membrane and a platinum electrode for detection of hydrogen peroxide. The signal output is large with minimal noise when tested in buffer. The sensor has been performing at ambient temperature for 4 months when stored overnight at 4 degrees C.

Biosensing Techniques↗
PubMedDate not supplied

Performances of potentially implantable rechargeable glucose sensors in vitro at body temperature.

The authors developed a glucose sensor that operates in vitro at 37 degrees C for at least three months without recharging. The use of fine carbon particles upon which to immobilize the glucose oxidase makes it possible to recharge the sensor when enzymatic activity diminishes. This may enable the sensor to perform for at least a year when implanted, and thus reduce the frequency of surgical replacement. Recharging is accomplished by inserting a hypodermic needle into the septum of an implanted reservoir. Three types of carbon were investigated: graphite powder, carbon lamp black, and low-temperature isotropic carbon powder (ULTI). Two cross-linking procedures were tested. The sensor that remained operational for the longest time used the ULTI and the cross-linking procedure that mixed the enzyme, immobilized on carbon powder, with albumin and glutaraldehyde. This sensor operated continuously at 37 degrees C for at least three months. Further, it was put through four recharge cycles with ten days of successful operation after each without change. The sensor is very stable and the results obtained with it are reproducible.

Biosensing Techniques↗