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Biomedical subjects

P Kotanko

Publications and source records attributed to P Kotanko.

At least 37 records · Page 2Linked to original sources
PubMed1997

Open-flow microperfusion of subcutaneous adipose tissue for on-line continuous ex vivo measurement of glucose concentration.

OBJECTIVE: To evaluate a novel technique for on-line continuous glucose measurement in subcutaneous adipose tissue, and to investigate its accuracy for detection of hypoglycemia. RESEARCH DESIGN AND METHODS: The method combined an open-flow microperfusion of subcutaneous adipose tissue using a double lumen catheter and an extracorporeal sensor cell. An isotonic ion-free solution was perfused through the inner lumen of the catheter, equilibrated with the subcutaneous tissue fluid, and sampled through the outer lumen. The recovery was continuously monitored as the ratio between the measured sampled fluid conductivity and the subcutaneous tissue fluid conductivity (assumed to have a constant value of 1.28 S/m at 25 degrees C). Glucose concentration was calculated on-line from the measured glucose in the sampled fluid and the measured recovery in healthy volunteers during hyperglycemic glucose loads (n = 8), hypoglycemic hyperinsulinemic clamp (n = 6), and a 24-h monitoring period (n = 7). RESULTS: Subcutaneous glucose concentrations in the fasting state were 94% of the plasma glucose concentrations in arterialized venous samples. According to the error grid analysis, 96.9% of the on-line measured subcutaneous glucose concentrations during hyperglycemia and 96.3% during hypoglycemia were in accurate or acceptable zones. The mean differences between the measured subcutaneous glucose and the actual plasma glucose concentration were -0.06-3.3 mmol/l (hyperglycemia), and -0.6-1.1 mmol/l (hypoglycemia). CONCLUSIONS: By combining open-flow microperfusion, glucose sensor, and conductivity measurement, glucose concentration in the subcutaneous adipose tissue can be monitored on-line, extracorporeally, and continuously without any in vivo calibration, and gives accurate measurements during hyper- and hypoglycemia.

Adipose Tissue↗
PubMed1997

Evidence of accelerated gastric emptying in longstanding diabetic patients after ingestion of a semisolid meal.

UNLABELLED: This study investigated the prevalence of accelerated gastric emptying in 40 consecutive nonselected patients with longstanding insulin-dependent diabetes mellitus (range 11-54 yr; mean 27 yr). METHODS: The gastric emptying of a semisolid meal labeled with 99mTc was continuously recorded with a dual-head gamma camera for 90 min in patients who were supine. RESULTS: Eleven patients demonstrated delayed gastric emptying, but three male diabetics showed accelerated gastric emptying with retention values that were different from controls already after 10 min of recording (89% +/- 3% versus 96% +/- 4%; p < 0.02). During the 90-min segment, accelerated gastric emptying reduced initial gastric contents to 11% +/- 8% (p < 0.001) as compared to 50% +/- 10% in control subjects and 78% +/- 6% (p < 0.001) in patients with delayed gastric emptyings. Accelerated gastric emptying was characterized by an almost equal initial meal distribution in proximal and distal compartments of stomach, both emptying approximately 90% of their contents within 90 min. Normal and delayed gastric emptying was characterized by a 60%-40% initial ratio of meal distribution between gastric compartments. During normal emptying, both compartments reduced contents with approximately 50%, but delayed gastric emptying was caused by only a 15% reduction of proximal contents accompanied by a 34% reduction in distal contents. CONCLUSION: Recording in the supine position to abolish gravitational influences demonstrated accelerated gastric emptying of a firm semisolid meal with a prevalence of 8%. However, delayed gastric emptying was shown as the predominant gastric manifestation of longstanding insulin-dependent diabetes mellitus with a prevalence of 28%.

Case-Control Studies↗
PubMed1996

Thin-film microbiosensors for glucose-lactate monitoring.

A miniaturized device for simultaneous measurement of glucose and lactate levels was produced by means of photopatterning of enzyme-containing photosensitive membrane precursors. This device shows no cross-talk and a lifetime for both the glucose and the lactate sensors of more than 2 weeks when continuously operated in undiluted bovine serum. Linear response ranges of up to 40 mM for glucose and 25 mM for L-lactate, in combination with 95% response times of < 30 s, were realized. The devices are mass produced by means of thin-film technology on flexible carriers to give catheter-type multisensing devices for in vivo applications. Ex vivo experiments, performed with human volunteers, where the device was continuously operated in an extracorporeal, undiluted, heparinized blood stream for 6 h, gave a correlation of r > 0.98 with respect to laboratory techniques. Subcutaneous measurements of glucose levels in pigs were close to the corresponding blood levels obtained without in vivo calibration.

Adult↗
PubMed1996

Reduced renal allograft survival is related to low urinary N-acetyl-beta-D-glucosaminidase excretion during the first posttransplant month.

The excretion of urinary N-acetyl-beta-D-glucosaminidase (NAG) was measured daily between day 7 and day 28 in 33 renal allograft recipients enjoying an entirely uncomplicated first postoperative month. Graft status was evaluated after 4 and 6 years and related to NAG excretion. After 4 years, 6 patients had experienced graft loss due to chronic rejection. Posttransplant urinary NAG excretion in the group of patients with failing grafts was significantly lower (9.4 +/- 6.3 vs. 17.2 +/- 8.5 U/g urinary creatinine, P = 0.036). Univariant analysis of recipient and donor characteristics revealed urinary NAG excretion to be the only parameter significantly differing between the groups. After 6 years, a total of 8 patients had lost their grafts. The posttransplant urinary NAG excretion in this group was 10.8 +/- 6.2 U/g; in the 25 patients with functioning grafts NAG excretion was 17.4 +/- 8.8 U/g (P = 0.064). A very low urinary NAG excretion ( < 7 U/g) was seen in 5 patients and associated with poor graft survival after 4 and 6 years (odds ratios 12.5 (1.9-82.1) and 6.9 (1.1-44.8), respectively. Kaplan-Meier analysis showed a reduced graft survival in this subgroup (P = 0.031). Receiver operating characteristics (ROC) analysis demonstrated an association between low NAG excretion and graft survival rates both at 4 and 6 years (area under the ROC curve 0.799 +/- 0.115, P, 0.05, and 0.747 +/- 0.104, P < 0.05, respectively). Cox proportional hazards analysis identified a low urinary NAG excretion as an independent prognostic risk factor. Urinary NAG excretion was expressed as unit per gram of urinary creatinine; as the amount of NAG excreted depends on the graft mass, and the amount of urinary creatinine depends on the recipient body mass, a low NAG excretion (in terms of U/g urinary creatinine) could be a surrogate marker of an unfavorable low graft to body weight ratio, which, in turn, might be associated with a reduced graft survival.

Acetylglucosaminidase↗
PubMed1996

Portable device for continuous fractionated blood sampling and continuous ex vivo blood glucose monitoring.

The objective of the study was to develop and evaluate a portable device for continuous fractionated blood sampling and continuous ex vivo monitoring of blood glucose. The inner lumen of a double lumen catheter (18 gauge x 45 mm) was placed in a peripheral vein and perfused with heparin solution (1.4 U min-1). The outer lumen was used to collect heparinized blood into 48 vacuum tubes at programmable sample volumes and time intervals (0.2-2 ml in 2.5-30 min). A sensor flow chamber with an internal volume of 1 mm3 incorporating a miniaturized thin-film amperometric glucose sensor was placed in the sampling line for continuous ex vivo blood glucose monitoring. Blood glucose and plasma insulin were measured during a frequently sampled intravenous glucose tolerance test (250 mg kg-1) and a subsequent oral glucose tolerance test (150 g) over 6 h in eight healthy volunteers (BMI 24.5 +/- 3.2 kg m-2). Additionally, in four experiments blood glucose was measured on-line using the glucose sensors. The overall correlation coefficients for whole blood glucose and plasma insulin between the manually drawn samples and the vacuum tubes were 0.73 and 0.87, respectively (p < 0.001). The miniaturized glucose sensor exhibited a linear measuring range of 25 mmol-1 glucose concentration and 95% response times of less than 30 s. Sensor readings and laboratory analyser results for the blood glucose measurement correlated between 0.93 and 0.98 (p < 0.001). In summary, continuous fractionated blood sampling and ex vivo blood glucose monitoring in ambulatory subjects is possible with a portable device.

Adult↗
PubMed1995

Numerical approximation of mathematical model for absorption of subcutaneously injected insulin.

A pharmacokinetic model is modified to enable quantitation of subcutaneous insulin absorption following insulin injections of soluble insulin and monomeric insulin analogues. The model for soluble insulin includes diffusion, equilibration between hexameric and dimeric insulin and absorption of dimeric insulin molecules. Numerical approximation is carried out by modelling the whole system as a capacitor-resistor network with lumped elements and discrete sources and sinks. By means of the analytical solution for monomeric-insulin absorption, it can be shown that the approximation scheme yields sufficiently accurate results. The modified model for soluble insulin demonstrates dose- and concentration-dependent insulin absorption within the range of therapeutic concentrations and volumes. Additionally, parameters are estimated from published glucose-clamp data. The results of the data fitting indicate that the model presented is adequate for pharmacological studies. The model is suitable for individual parameter estimation from the time course of plasma insulin or from the disappearance curves of radiolabelled injected insulin.

Humans↗
PubMed1994

Salt and asthma.

Explore the source record for details and available documents.

Asthma↗
PubMed1993

Pharmacokinetic model for the absorption of subcutaneously injected soluble insulin and monomeric insulin analogues.

A subcutaneous insulin absorption model is presented for parameter estimation from the time course of plasma insulin. Modifications of a published model were made for the absorption of soluble insulin and monomeric insulin analogues in the range of therapeutic concentrations and volumes. The modified diffusion-dissociation model with distributed parameters was approximated by a multiple-compartment model. Subcutaneous absorption of soluble insulin and monomeric insulin analogues with various volumes, concentrations, and injection depths was simulated. The model for soluble insulin exhibits volume, concentration, and injection depth dependent absorption, as experimentally observed. It was found that binding of soluble insulin in the subcutaneous tissue is negligible for U-40 and U-100 strengths. The absorption of identical doses (10 U) of soluble U-40 insulin was markedly faster (T-50% = 159.4 min) than the absorption of U-100 (T-50% = 196.2 min). According to the simulation results, the absorption rate of monomeric analogues is not dependent on concentration. No significant chances of the absorption rate could also be observed by varying volume and injection depth of the monomeric analogues.

Computer Simulation↗
PubMed1992

Beta 2-adrenoceptor density in fibroblast culture correlates with human NaCl sensitivity.

To study salt sensitivity in humans and its relation to expression of adrenoceptors, 20 male normotensive Caucasians were investigated on a diet of 180 mmol NaCl/day followed by 60 mmol NaCl/day over 2 wk and again by 180 mmol NaCl/day over 2 wk, and blood pressure changes were assessed by long-term oscillatory blood pressure monitoring under basal conditions. Individual cell cultures of skin fibroblasts from skin biopsies were also established, and alpha 2- and beta 2-adrenoceptors were measured. Seven subjects were salt sensitive, and the remainder were salt resistant. Cultured skin fibroblasts in salt-sensitive subjects express less than half the number of beta 2-adrenoceptors compared with salt-resistant subjects (65 +/- 12.7 vs. 173 +/- 14.8 fmol/mg, P less than 0.001), and there is a correlation between the absolute rise of blood pressure on a high-salt diet and the density of beta 2-adrenoceptors (r = -0.67, P less than 0.01). It remains to be established whether a reduced in vitro density of beta 2-adrenoceptors in cultured cells is causally related to salt sensitivity in normotensive humans.

Binding Sites↗
PubMed1991

[Further advances in the salt sensitivity hypothesis in man].

The hypothesis, proposed by us since 1981, that genetically determined salt sensitivity exists in the normotensive population has been confirmed by other groups. We propose that in salt sensitive subjects an augmented upregulation of alpha-2 combined with simultaneous downregulation of beta-2 adrenoceptors by a high salt diet (resulting in an increase in the "operative" adrenoceptor ratio) is responsible for the rise of blood pressure. In salt resistant subjects the "operative alpha-2/beta-2 adrenoceptor ratio" does not increase on a high salt intake. The adrenoceptor changes in salt sensitive subjects probably lead to an increased central sympathetic outflow (through receptor changes in certain brain areas) and to simultaneous enhanced end-organ response in resistance vessels and in the kidney, causing enhanced vasoconstriction and enhanced sodium reabsorption. Long term follow up of salt sensitive normotensives will show, whether they develop "essential hypertension" in the future.

Absorption↗
PubMed1990

Urinary excretion of N-acetyl-beta-D-glucosaminidase in patients after cyclosporin-treated corneal grafting.

Allograft rejection occurs in up to 70% of high-risk keratoplasty patients. For this reason short-term Cyclosporin treatment was administered for three months to prevent graft loss. Of 23 renal healthy patients, 19 enjoyed long-term graft acceptance. We evaluated in these patients N-acetyl-beta-D-glucosaminidase (NAG) excretion as a marker of renal tubular damage. All patients, except one, showed urinary NAG excretion to be within the normal range. From this we conclude that no renal tubular damage occurs after short-term Cyclosporin treatment.

Acetylglucosaminidase↗