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Biomedical subjects

W Renn

Publications and source records attributed to W Renn.

At least 55 records · Page 3Linked to original sources
PubMed1993

Flashlamp exited pulsed dye laser and electrohydraulic lithotripsy: in vitro study on tissue effects.

Intracorporal lithotripsy has gathered momentum in the management of gallstone disease due to the increasing sophistication of technical equipment for the percutaneous, as well as the retrograde-endoscopic route. Laser-induced shock wave lithotripsy (LISL) and electrohydraulic lithotripsy (EHL) have proved feasible by allowing reliable fragmentation of biliary calculi. Evaluation of therapeutic risks, e.g., effects of accidental irradiation of the gallbladder wall, has been performed in small sample sizes only. We investigated the effects of LISL and EHL on multiple sets of human and porcine gallbladders under in vitro conditions. Gallbladders were freshly harvested, mounted, and immersed in different mediums (normal saline, blood, bile). They were swiftly exposed to LISL (Pulsolith¿) and EHL (Lithotron EL 23¿) under differing experimental conditions (energy setting, pulse mode, exposition time, medium, probe pressure) and subjected to standard procedures for morphometric evaluation (Bioquant¿). Tissue effects were described by the depth (d) and width (w) of the cratered lesions, as well as the extension of the damage in the surrounding tissue(s). Serial cuts of the exposed areas yielded 894 section for morphometric analysis. Multivariate analysis of variance (MANOVA) revealed a significant effect of laser energy (p[d] less than 0.002, p[w] < 0.05, p[s] < 0.05), medium (p[d] less than 0.03, p[w] < 0.001, p[s] < 0.04, and exposition time (p[d] less than 0.001, p[s] < 0.001) on the degree of tissue lesion.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1992

Cognitive and psychomotor function during severe insulin-induced hypoglycaemia in insulin-dependent diabetic patients.

Cognitive and psychomotor function, hormonal counterregulation and symptom awareness during severe insulin-induced hypoglycaemia were evaluated in 10 insulin-dependent diabetic patients. The glucose-clamp technique (Biostator) was applied to achieve a stable hypoglycaemic (39 +/- 2 mg/dl) plateau. A battery of 7 neuropsychological tests and a standardized questionnaire assessing hypoglycaemia symptoms were administered during euglycaemia and hypoglycaemia. There was a significant increase in counterregulatory hormone response (cortisol, growth hormone, p less than 0.05). Every patient experienced symptoms during severe hypoglycaemia. Four patients, however, were not aware of this threatening metabolic state. There was a significant performance decrement in all but two neuropsychological tests (Aiming Center I, Aiming Center II, Line Tracing Errors, Reaction Time, p less than 0.01; Digit Symbol, p less than 0.05). Performance of simple motor tasks as well as cognitive tasks requiring complex discrimination deteriorated similarly. Furthermore, the patients' general well-being (subjective condition) worsened considerably. In conclusion, a significant impairment of neuropsychological functions emerged during severe hypoglycaemia in insulin-dependent diabetes mellitus, even in the face of adequate hormonal counterregulation, and did not always coincide with an appropriate patient awareness of the actual metabolic state.

Adult↗
PubMed1992

Catecholamine response during human and pork insulin-induced hypoglycemia in IDDM patients.

OBJECTIVE: To evaluate the catecholamine response during human and pork insulin-induced hypoglycemia. RESEARCH DESIGN AND METHODS: Ten insulin-dependent diabetes mellitus (IDDM) patients without any signs of autonomic neuropathy received either human or pork insulin in a randomized crossover fashion on 2 nonconsecutive days. The glucose clamp technique was applied to achieve stable glycemic plateaus of 5.6, 3.3, 2.2, and 1.7 mM. RESULTS: The effect of both types of insulin on glucose metabolism and circulating catecholamines was almost identical. There was a sharp rise of both epinephrine (P less than 0.05) and norepinephrine (P less than 0.02) during hypoglycemia, which did not depend on the type of insulin applicated. Symptom awareness increased significantly during the decrease of blood glucose concentration. Only during developing hypoglycemia (3.3-mM plateau), was this effect more pronounced (cumulative symptom score 2 vs. 26, P less than 0.05) with pork insulin. CONCLUSIONS: AN attenuated catecholamine secretion seems not to be the putative mechanism of a reduced awareness of human insulin-induced hypoglycemia.

Adult↗
PubMed1992

Simple computer-assisted diagnosis of acute myocardial infarction in patients with acute thoracic pain.

In order to minimize the initial diagnostic uncertainty in patients suspected of having acute myocardial infarction, we prospectively extracted predictive variables from previous history, ECG, and clinical chemical parameters of 87 patients, who were admitted for acute thoracic pain. The variables thus extracted were: Thoracic pain in previous history, duration of pain, white blood cell count, blood glucose, creatine-kinase, and S-T elevation in the ECG. These parameters were used for formulating a mathematical model based upon univariate and multivariate statistical methods. The sensitivity of the model in the study population was 95% and the specificity 77%. Correct classification was achieved in 89% of cases. In a second phase, the prognostic index was prospectively evaluated in a second set of 122 consecutive patients. In this test population, the sensitivity was 89% and the specificity 86%. 87% of patients were classified correctly.

Adult↗
PubMed1992

Increase in glucose consumption by acetylcysteine during hyperglycemic clamp. A study with healthy volunteers.

Thiols have been shown to be related to insulin secretion and to uptake of glucose into tissues. In the present study the effects of i.v. administration of acetylcysteine (N-acetylcysteine, NAC, CAS 616-91-1) on glucose consumption and plasma free thiols were studied in young healthy volunteers during hyperglycemic clamp. NAC (0.5-2.0 mg/kg) significantly increased glucose consumption. This effect was not obvious at higher doses of NAC. Plasma free NAC depended on the dose of NAC injected. The t1/2 of NAC was 11 min. NAC produced significant increases of plasma cysteine concentrations, and a slight but insignificantly increase of plasma glutathione. These data suggest that a moderate increase in plasma thiols augments glucose consumption during hyperglycemic clamp.

Acetylcysteine↗
PubMed1991

Selected ion monitoring gas chromatography/mass spectrometry using uniformly labelled (13C)glucose for determination of glucose turnover in man.

An optimized method is described for the mass fragmentographic determination of uniformly labelled (13C)glucose in human plasma using a butylboronic acid acetate derivative, and capillary gas chromatography. The advantages of the method are the ease and speed of the derivatization procedure, the small sample size, high precision (interassay coefficient of variation 5.7%), and applicability of a relatively low-cost mass spectrometer. This method allows glucose tracer experiments to be performed in man using the bolus injection technique, necessitating analysis of many samples. The results on glucose turnover obtained in a clinical experiment were in full agreement with previously published data.

Adult↗
PubMed1991

Different awareness of hypoglycaemia induced by human or purified pork insulin in type I diabetic patients.

Recently, there have been reports on a diminished awareness of hypoglycaemia after a switch from purified pork insulin (PPI) to human insulin (HI) in insulin-dependent diabetes mellitus (IDDM). To clarify this phenomenon we investigated nine IDDM patients without signs of autonomic neuropathy. After an overnight euglycaemic clamp, blood glucose was lowered to hypoglycaemic levels by means of an artificial pancreas (Biostator) on 2 days. Insulin was used in a double-blind, randomized, cross-over fashion, either PPI or HI. The symptomatology and the hormonal counterregulation of developing hypoglycaemia was recorded. Venous concentrations of free insulin, cortisol, glucagon, growth hormone and the prevailing blood glucose were similar under both insulins. Eight out of nine IDDM patients felt more symptoms and at a higher blood glucose concentration under PPI than under HI. The first symptom of developing hypoglycaemia appeared at a mean blood glucose concentration of 61.1 +/- 5.4 mg.dl-1 under PPI and 44.4 +/- 5.3 mg.dl-1 under HI respectively (P less than 0.05). We conclude that HI may cause symptoms of hypoglycaemia to appear later and with a lesser number in comparison to PPI.

Adult↗
PubMed1991

Platelet endoperoxide/thromboxane A2 (PGH2/TXA2) receptors in patients with myeloproliferative disorders.

In patients with myeloproliferative disorders (MPD) an altered sensitivity of platelets to antiaggregatory prostaglandins and to the endoperoxide analogue U 46619 has been found. In this study we examined U 46619-induced platelet aggregation and binding of the endoperoxide/thromboxane A2 (TXA2) receptor antagonist SQ 29548 in 11 patients with MPD and 11 healthy controls. Although platelet responsiveness to U 46619 was significantly enhanced (p less than 0.05) in MPD, binding affinity and binding capacity of the corresponding endoperoxide/TXA2 receptor were not altered (Bmax 0.67 +/- 0.20 vs. 0.58 +/- 0.14 pmol/10(9) platelets, Kd 0.41 +/- 0.11 vs. 0.55 +/- 0.09 nM). These data exclude the possibility that changes in the presentation of endoperoxide/TXA2 receptors are responsible for the enhanced platelet sensitivity to endoperoxides found in MPD.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1990

Symptoms of hypoglycemia--a comparison between porcine and human insulin.

For more than 2 years now it has been controversially debated whether awareness of hypoglycemia is reduced when type I diabetic patients are switched from porcine to human insulin. In order to address this question, we studied nine C-peptide negative diabetics (age 27.6 years, Broca index 106%, duration of diabetes 5.7 years, HbA1, 8.8%) in comparison with eight healthy volunteers (age 22.4 years, Broca index 104%). Following euglycemic monitoring overnight, a controlled hypoglycemia was induced by altering the algorithms of the Biostator. This was done in a double-blind, cross-over fashion using porcine or human insulin on 2 nonconsecutive days. There were no differences between the results obtained with respect to the time course of the study, blood glucose, amount of insulin infused, and concentration of venous free insulin achieved. Of the nine diabetics, eight were aware of hypoglycemia at a higher blood glucose level under porcine insulin. The first symptom of hypoglycemia was perceived at a mean blood glucose level of 61.1 +/- 5.4 mg/dl under porcine insulin and of 44.4 +/- 5.3 mg/dl under human insulin (P less than or equal to 0.05). Thirty symptoms were noted under porcine insulin exclusively or preferentially as opposed to only eight which were observed exclusively or preferentially under human insulin. The healthy volunteers evidenced fewer symptoms at lower blood glucose concentrations than the diabetics. The clear difference between human and porcine insulin could not unequivocally be reproduced in this group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Plasma vitamin E and beta-carotene concentrations during radiochemotherapy preceding bone marrow transplantation.

Blood from 19 patients was examined for the essential antioxidants alpha-tocopherol and beta-carotene before, during, and after bone marrow transplantation (BMT). Marrow ablation and immunosuppression for BMT conditioning was achieved by treatment with high-dose chemotherapy, mostly combined with total body irradiation. All patients required total parenteral nutrition beginning 1 wk before BMT. After conditioning therapy the concentration of absolute and lipid-standardized alpha-tocopherol and beta-carotene in plasma decreased significantly, presumably as a result of an enhanced breakdown of these antioxidants. The loss of these lipid-soluble antioxidants has to be considered as a possible cause for early posttransplant organ toxicity.

Adolescent↗
PubMed1988

[Significance of ultrasonics in the placement of a central venous catheter].

An ultrasound investigation was undertaken of the neck region of 42 patients with normal neck anatomy in order to determine whether the results of ultrasound-gained topographical data provided pointers to the choice of entry site to the internal jugular vein (IJV). In addition, the IJV was punctured under ultrasound control in 23 patients in an intensive care unit in whom there was a problem of increased bleeding tendency, anatomical difficulty or previously failed "blind" puncture. In all of them a central venous catheter was placed without complication by the Seldinger technique via the primary chosen point for puncture. An approach through the sternocleidomastoid muscle, between the cricoid level and the "central" place of puncture between the two bellies of the sternocleidomastoid muscle proved to be the most satisfactory compromise between easy application of the ultrasound head, large vein diameter and reduction of any risk of mistakenly puncturing artery or pleura. This approach has to be varied according to the ultrasound findings. It is concluded from this experience that ultrasound is suitable for the placement of central venous catheters. But since the equipment is bulky it cannot be used in an emergency.

Adult↗
PubMed1988

Desensitization of platelets to iloprost. Loss of specific binding sites and heterologous desensitization of adenylate cyclase.

The binding characteristics of [3H]prostacyclin and [3H]iloprost ([3H]5-[(E)-(1S,5S,6R,7R)-7-hydroxy-6-[(E)-(3S,4RS) -3-hydroxy-4-methyl-1-octen-6-inyl]-bicyclo[3.3.0]octan-3-yl idene] -pentanoic acid) and platelet adenylate cyclase activities were investigated in platelet-rich plasma preincubated with iloprost. The exposure of platelets to 0.1 microM iloprost (12 h, 20 degrees C) caused a significant loss of iloprost binding sites (P less than 0.01) without causing changes in binding affinity. This loss of specific [3H]iloprost binding was time- and dose-dependent. The reduction of iloprost receptor density was accompanied by an impaired responsiveness of platelet adenylate cyclase to iloprost, prostaglandin D2 and forskolin. In contrast, basal adenylate cyclase activity was not affected by iloprost pretreatment. The diminished response of the enzyme to GTP and NaF pointed to an involvement of the stimulatory guanyl nucleotide-binding protein (Gs) in iloprost-induced heterologous desensitization. Consequently, [32P]NAD+ and cholera toxin were used for the direct labelling of Gs. Platelet membranes desensitized to iloprost incorporated less label into the 45 kD subunit of Gs. These data suggest that the site of action of iloprost for heterologous desensitization of human platelet adenylate cyclase is located on Gs.

Adenosine Diphosphate↗
PubMed1988

[Evaluating 2 simple procedures for ultrasound assessment of gastric emptying].

For evaluation of 2 simple methods gastric emptying was studied simultaneously by ultrasound and scintigraphy. In 12 patients (25-76 years-old) gastric emptying was quantified by scintigraphy after ingestion of 300 ml Tc-99m-labelled orange juice; simultaneously, the region of the gastric antrum was measured in 5-minute intervals in the aortic longitudinal section. In the following day gastric emptying was studied after ingestion of the identical volume of orange juice by planimetry of the maximal gastric area in an anatomical long-axis section in dextro-decline position. By linear regression analysis a significant correlation coefficient (r = 0.83, p less than 0.001) was obtained between the results of the sonographic antrum method and scintigraphy and between scintigraphy and the sonographic dextro-decline method (r = 0.83, p less than 0.001). These results imply that gastric emptying of fluids can be quantified by both simple sonographic methods. The sonographic dextro-decline method is less influenced by air and hence easier to perform.

Adult↗