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Biomedical subjects

U Fischer

Publications and source records attributed to U Fischer.

At least 271 records · Page 15Linked to original sources
PubMed1988

The GOD-H2O2-electrode as an approach to implantable glucose sensors.

The long-term function of glucose sensors under in-vivo conditions is the first prerequisite in the development of glucose-controlled insulin infusion systems. Amperometric enzyme glucose sensors measuring H2O2 from the enzymatic glucose oxidation are defeated to certain poisoning effects of the electrochemical system and to alterations of the diffusional properties, both resulting in unpredictable changes of the sensor signal. To interpret the signal of subcutaneously implanted sensors after reaching a certain balance of the altering processes, the wick-technique has been established as an independent reference method applicable in the interstitial fluid. Based on the comparison of the wick-glucose concentration and the circulating plasma glucose concentration the in vivo-calibration of the sensor current according to plasma glucose concentration is proven.

Animals↗
PubMed1987

The effect of prehepatic insulin administration on alanine flux rates in diabetic dogs.

The in vivo flux rates of glucose (6-3H-glucose) and of alanine (U-14C-alanine) were measured in insulin-dependent chronically diabetic dogs which were infused with insulin employing a bedside-type artificial B cell and either the peripheral or the portal venous route. In comparison with non-diabetic control animals the diabetic dogs had near-normal patterns of glucose metabolism and pancreatic glucagon regardless of the route of insulin administration. They also showed reduced basal portal but moderately elevated peripheral insulin levels on peripheral and near-normal peripheral values on portal insulin infusion. Both concentration and production rates of alanine were reduced on peripheral (0.142 +/- 0.016 mmol/l, 4.73 +/- 0.49 mumol.kg-1.min-1, p less than 0.05) but normal on portal insulin (0.206 +/- 0.030 mmol/l, 6.33 +/- 0.63 mumol.kg-1.min-1). The alanine clearance was slightly elevated or normal in the diabetic dogs, and the glucose production from alanine showed a strongly delayed response to an exogenous glucose load on either route of insulin administration. It is concluded that the peripheral hyperinsulinism during posthepatic insulin administration stimulates glucose utilisation to a normal extent, but inhibits the provision of amino groups in resting muscle. Alanine synthesis is thereby reduced, and the carbon moieties are shunted from glucose into circulating lactate. Long-term studies are needed to elucidate the role of the liver under these conditions.

Alanine↗
PubMed1987

Assessment of subcutaneous glucose concentration: validation of the wick technique as a reference for implanted electrochemical sensors in normal and diabetic dogs.

Employing saline-impregnated cotton threads, an implanted-wick technique was adopted in dogs to obtain specimen from the subcutaneous interstitial compartment in order to estimate its glucose concentration. By measuring the protein, potassium and haemoglobin contents, the centrifuged wick fluid was shown to contain the interstitial concentration of solutes after an equilibration time of approximately 15 min. In normal and in diabetic animals the steady state subcutaneous glucose concentration was almost identical to the circulating glucose level when ranged between 2 and 25 mmol/l. Slow alterations in the circulating glucose profile such as those which appear during an oral glucose tolerance test are closely mirrored by the respective levels in the wick fluid. Fast alterations, however, show deviations. The wick-based glucose levels are well paralleled by the current of Clark type glucose oxidase sensors implanted at the same site. Since, on the basis of in vitro calibrations the sensor outputs have only indicated apparent tissue glucose concentrations of between 70 and 90% of glycaemia, another reference is needed for calibration. Under steady state conditions, the wick method, and on this basis in routine measurements the blood glucose concentration, may be recommended as a reference of implanted sensors which can otherwise not be calibrated in situ.

Animals↗
PubMed1987

[Staging in Hodgkin's lymphoma. Exploratory laparotomy with splenectomy].

In the present paper, 66 Studies on exploratory laparotomy with splenectomy in Hodgkin's lymphoma from Western Europe and the USA are presented in tables. This statistical compilation on 7183 laparotomies shows that the spleen was involved in 39.9% (2685 out of 6900 cases investigated), the liver in only 7.7% (446 out of 5789) and the abdominal lymph nodes were involved in 30.3% (1389 out of 4578) of the cases. Altogether, laparotomy with splenectomy led to a change in staging in 33% of the patients (1892 out of 5745). In the period from 1970 to 1986, 123 patients with Hodgkin's lymphoma were laparotomized (and also splenectomied apart from one exception) at the Surgical Division, University of Göttingen. The patients comprised 52 cases in the context of primary staging and 71 cases in the context of secondary staging. In 43 cases (35.2%) the spleen was affected, in seven cases (5.7%) the liver was affected, and there was combination with spleen involvement in each case. Infiltration of abdominal lymph nodes was shown in 38.2% (26/68). Exploratory laparotomy led to a change in stage in 46 cases (37.1%) comprising 28 improvements and 18 deteriorations. Before laparotomy, 15 patients were in stage I, 29 in stage II, 44 in stage III and 21 in stage IV. After pathological staging, 14 were in stage I, 40 were in stage II, 47 were in stage II and 19 were in stage IV. Out of the 14 patients who could not be assigned to any stage before the operation, 11 could be definitively staged afterwards. In addition, lymphography was performed in 103 patients, liver and spleen scintigraphy in 51 patients, sonography in 30 patients and computer tomography in 22 patients. In the re-examination of the lymph node situation in the retroperitoneal space, lymphography attained a specificity of 48% and a sensitivity of 71.4% with a positive prediction precision of 35.7% and a negative prediction precision of 88.8%.

Hodgkin Disease↗
PubMed1987

Genetic heterogeneity in different BB rat subpopulations.

Two different BB-rat subpopulations were followed over 7 inbred generations under identical environmental conditions: BB/OK as derived in 1983 from the original stock in Ottawa, BB/PhiK as derived in 1983 from a stock at the University of Pennsylvania, Philadelphia. They showed significant differences in incidence, age at onset, untreated survival time of diabetes, leucopenia and body weight gain. By crossing experiments these phenotypical differences could be attributed to a genetic diversity between the 2 subpopulations. It is concluded that this genetic diversity is based on the heterogeneity of the parental BB Wistar rat stock and that the genetic differentiation between subpopulations of a different history is favoured by the "bottle neck effect", selection, mutation and genetic drift. The study of defined subpopulations and of their genetic interaction will provide deeper insight into the mechanisms of inheritance of diabetes in different species.

Animals↗
PubMed1987

[Lymphography in Hodgkin's lymphoma. Diagnostic value based on the current status of experience and knowledge].

Lymphography was carried out at least once in 355 patients with Hodgkin's lymphoma (HL). In 229 patients, there was a histological subclassification: 26 LP, 63 NS, 122 NC and 18 LD cases. The lymphographic manifestations could be subdivided empirically into two superordinate groups: 1. lymph nodes closely linked together in chains (LC) with dense structures as well as LC destructions, LC debris and 2. LC of varying size with pathological internal structure. Apart from in the NS type, a correlation between the lymphological appearance and the histological subtype could not be discerned in any other histological subgroup. After lymphography, 61.6% of stages I and II were assigned to stage III. The staging of the lymphography was: stage I 24.5%, stage II 47.3%, stage III 10% and stage IV 9%, and after lymphography: stage I 9.9%, stage II 17.7%, stage III 63.1% and stage IV 9.3%. From a qualitative point of view, lymphography is superior to all other methods in the diagnosis of malignant lymphomas and should hence be carried out obligatorily in suspicion of a malignant lymphoma.

Adolescent↗
PubMed1987

[Lymphography in malignant testicular tumors].

Experience and results are reported on the basis of more than 380 lymphographic investigations in patients with a malignant testicular tumor. In 61% of these patients, there was suspicion of a metastatic infiltration of the retroperitoneal lymph nodes. In 75 patients, histological checking of the lymphographic finding was possible on the basis of a retroperitoneal lymphadenectomy. Lymphography was shown to have a precision of 81%. Lymphography is obligatory as a complement to other techniques of investigation such as sonography and computer tomography in patients with malignant testicular tumor, since the greatest diagnostic information can be expected from combined application of all three methods.

Humans↗
PubMed1986

[Status and perspectives of automated insulin therapy].

The aim of the optimization of insulin supply in insulin-dependent diabetes mellitus is by means of restoration of blood glucose regulation resembling the physiological control to contribute to the secondary prevention of the late diabetes-specific complications. An individually different permanent supply of a basic insulin dose, the adapted application of additional doses during the meals and the avoidance of an induced hyperinsulinism are to be achieved. Several apparative or biomaterial-depending techniques of an optimized insulin supply are still at the stage of technological research and of animal experiments: bioartificial (hybrid) pancreas and implantable therapeutic systems. Artificial beta-cells (feedback controlled insulin infusion systems) are hitherto commercially available only as bedside apparatuses and for this reason above all suitable for purposes of research; portable and in a few cases implantable insulin pumps (not automatically glucose-dependent controlled) are at present subject of long-term, controlled clinical-ambulatory studies on the borderline to highly specialized therapy. From experience in the use of these methods results the strategy of an "intensified conventional" insulin therapy which may be recommended for wide-spread application.

Blood Glucose↗
PubMed1986

[Continuous monitoring of subcutaneous glucose concentration using implanted enzyme electrodes].

The subcutaneous glucose concentration was continuously monitored in the neck of healthy unanaesthetized dogs employing a miniaturized glucose oxidase/H2O2 sensor. Under steady state conditions it amounted to approximately 50% of the circulating level. Induced alterations (oral or intravenous glucose loads) were mirrored with a delay, which was mainly determined by the sensor characteristics. Minor alterations in circulating glucose concentration (e.g. from 4.5 up to 7.5 mmol/l within 60 min) as induced by the oral load do not alter the concentration ratio between interstitial glucose and glycoemia.

Animals↗
PubMed1985

Alterations in alanine metabolism in diabetic dogs during short-term treatment with an artificial B cell.

The flux rates of plasma glucose and alanine were studied isotopically (6-3H-glucose and U-14C-alanine simultaneously) in resting chronically diabetic dogs during short-term treatment with an artificial B cell where the insulin was infused into a peripheral vein. Despite perfect blood glucose control and normal glucose flux rates, the concentration and rates of appearance and disappearance of alanine were significantly elevated in the diabetic animals before, during and after an exogenous glucose load. The incorporation of the carbon moiety of alanine into circulating glucose was also increased, but diminished to a near-normal extent when exogenous glucose was given. The plasma clearance rates for alanine in the diabetic dogs were normal throughout the study. It is concluded that normal blood glucose control in diabetes does not necessarily mean normalization of the entire metabolic network. On the basis of peripheral hyperinsulinaemia alanine formation from glucose and branched chain amino acids is elevated in muscle. This may explain increased flux of alanine despite normal blood glucose control.

Alanine↗