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Biomedical subjects

C Hahn

Publications and source records attributed to C Hahn.

At least 73 records · Page 4Linked to original sources
PubMed1995

Serum concentration of 7 alpha-hydroxycholesterol as an indicator of bile acid synthesis in humans.

The serum concentration of 7 alpha-hydroxycholesterol as an indicator of total bile acid synthesis was investigated under different experimental conditions in humans. 7 alpha-Hydroxycholesterol was measured by gas-liquid chromatography-mass spectrometry, using [2H7]7 alpha-hydroxycholesterol and/or 5 alpha-cholestane-3 beta, 6 beta-diol as internal standards, and bile acid synthesis was estimated by the fecal balance method. Intraindividual variation was small when the concentration of 7 alpha-hydroxycholesterol was determined twice in the same subject 2 days to 11 months apart (7.3 +/- 6.5%, n = 52). In patients with advanced cirrhosis of the liver (n = 22) 7 alpha-hydroxycholesterol was 3.4-fold lower (22 ng/ml +/- 8) compared to matched controls (75 ng/ml +/- 19). Administration of cholestyramine (4 g b.i.d.) for 14 days increased 7 alpha-hydroxycholesterol concentration in five healthy volunteers from 40 +/- 11 ng/ml to 181 +/- 95 ng/ml (P = 0.02) and fecal excretion of acidic sterols from 254 +/- 60 mg/d to 1336 +/- 344 mg/d (P < 0.01). Although a significant correlation was found between 7 alpha-hydroxycholesterol in serum and bile acid synthesis in patients with hypercholesterolemia (r = 0.847, P < 0.001, n = 17), it was impossible to accurately determine bile acid synthesis from the serum levels of 7 alpha-hydroxycholesterol. Thus, determination of 7 alpha-hydroxycholesterol concentrations in serum can be used to assess changes in bile acid synthesis rates over short and long term periods under various experimental conditions, but not to calculate bile acid synthesis correctly.

Bile Acids and Salts↗
PubMed1994

The hospital cost (fiscal year 1991/1992) of a simple perioperative allogeneic red blood cell transfusion during elective surgery at Duke University.

We sought to determine the actual cost to Duke University Medical Center of a perioperative red blood cell transfusion. A recent audit at Duke University Medical Center determined the base average direct and indirect hospital costs for providing a unit of red blood cells. The Transfusion Service's base cost for providing an allogeneic unit of red blood cells was $113.58. To obtain the actual hospital cost of transfusing a unit of red blood cells in the perioperative period, associated costs were calculated and added to the Transfusion Service's base cost. These associated costs included compatibility tests on multiple units per each unit transfused in the perioperative period, performing ABO and Rh typing and antibody screening on samples from patients who were not subsequently transfused, compatibility tests on units not issued, handling costs of units issued but not used, physically administering the blood, and the cost of the recipient contracting an infectious disease or developing a transfusion reaction. These associated costs increased the cost of transfusing an allogeneic unit of red blood cells in the perioperative period to $151.20. Perhaps the techniques described in the study can be used to quantify cost/benefit ratios associated with future changes in transfusion practice.

Blood Banks↗
PubMed1994

Warm and cold blood cardioplegia. Comparison of myocardial function and metabolism using 31p magnetic resonance spectroscopy.

BACKGROUND: Standard myocardial protection during cardiac surgery uses hypothermic arrest, but warm heart surgery, recently introduced, is now used in many centers. We hypothesized that warm continuous blood cardioplegia (WCBC) would provide better myocardial preservation than cold continuous blood cardioplegia (CCBC). METHODS AND RESULTS: In isolated cross-perfused canine hearts, left ventricular (LV) function and myocardial O2 consumption (MVO2) were measured at constant LV volume, coronary perfusion pressure, and heart rate before and after 75 minutes of arrest at 37 degrees C or 10 degrees C. Metabolism was evaluated by 31P nuclear magnetic resonance spectroscopy. LV resting tone increased transiently after arrest by CCBC but not WCBC (38 +/- 3.9 versus 2.9 +/- 0.5 mm Hg, P < .0005). Myocardial ATP changed over time differently in the groups (P < .001), declining at the outset of CCBC and returning to control levels during the recovery period after CCBC or WCBC. Intracellular pH rose from 7.17 +/- 0.03 to 7.85 +/- 0.05 during CCBC (P < .0005 versus WCBC). MVO2 declined dramatically during arrest at either temperature but to a lower value during CCBC (P < .0005). LV pressure recovered to 86.1 +/- 5.1% of its prearrest value after CCBC and to 97.2 +/- 7.8% following WCBC (P = NS). After CCBC but not WCBC, there were small but significant increases in LV end-diastolic pressure (by 1.3 mm Hg, P < .05) and in the LV relaxation constant, tau (from 37.3 +/- 1.5 to 42.3 +/- 2.4 milliseconds, P < .05). CONCLUSIONS: The increase in intracellular pH during CCBC is largely accounted for by physicochemical factors. Group differences in ATP over time may be related to rapid cooling contracture during CCBC. The data suggest that CCBC mildly impairs LV function but that WCBC preserves function and metabolism at or near prearrest levels.

Adenosine Triphosphate↗
PubMed1993

Allergic contact reaction to dexpanthenol: lymphocyte transformation test and evidence for microsomal-dependent metabolism of the allergen.

In a patient with contact dermatitis, dexpanthenol was found to be the causative allergen. There was a positive reaction to dexpanthenol on patch testing. Controls did not show any positive reactions to dexpanthenol on patch testing. Additionally, an LTT was performed. After preincubation with dexpanthenol-modified microsomes, we observed an increase in lymphocyte proliferation to dexpanthenol, in comparison to dexpanthenol without microsomes, suggesting that microsomal metabolism plays a rôle in the pathogenesis of dexpanthenol sensitization, because microsomes are known to possess drug metabolizing enzymes such as cytochrome P450.

Cell Division↗
PubMed1990

[Contrast-enhanced CT of the mediastinum in lymph node diagnosis].

In mediastinal lymphoadenopathy diagnostic problems arise if lymphomas are of the same density as cardial or vascular structures. For this reason, CT based on contrast enhancement must definitely ensure a significantly greater enhancement of vascular structures than of non-vascular ones during the entire scan period. We studied 4 groups of 20 patients each employing standardised CT examinations employing 100 ml. contrast medium in different concentrations (200 and 300 mg. iodine/ml., respectively) and an injection flow rate of 0.7 and 2.0 ml/s. The results show that higher iodine concentrations produce a significantly greater enhancement in the aorta than a lower iodine concentration independent of the flow rate. Although a lower flow rate slightly delayed the enhancement increase, this was nevertheless higher than 60 HU within a period of 4 minutes. Hence, we recommend to perform contrast enhanced CT of the mediastinum using lower flow rates (0.5-1.0 ml/s.) and a higher contrast medium concentration (300 mg. iodine/ml.).

Adult↗
PubMed1989

SWAT team approach to ventricular assistance.

In 1986, the Cardiovascular Research Institute in Sion, Switzerland, created a flying bridge-to-cardiac transplantation team. This team, consisting of two physicians, a physicist, a biomedical engineer, and two intensive care nurses, has participated in 23 bridges to cardiac transplantation in 11 cardiovascular surgery centers in Europe. The cardiac function of all patients was 100% supported by paracorporeal pneumatic biventricular Pierce-Donachy devices. Twenty of the 23 patients have had transplantation, and 11 are alive and well. The bridge-to-cardiac transplantation team, which travels with a transportable driver and the ventricle sets, supervises the bridged patients 24 hours a day until cardiac transplantation is performed.

Adolescent↗
PubMed1989

[Investigations on methods of quantitative polarization optical estimation of neutral carbohydrates in extracellular matrix].

By means of the fluorescence PAS-reaction using a Schiff-type reagent substituted with acriflavine, the neutral carbohydrates were demonstrable selectively in the human trophoblast basement membrane. The reaction product is characterized by a typical birefringence that can be measured in the polarized light. The results obtained from ascertainment of the dispersion of the birefringence before and after the histochemical reaction, as well, gave further evidence for specificity and a definite improvement of the measurement of path differences.

Acriflavine↗
PubMed1987

Partial nucleotide sequence of St. Louis encephalitis virus RNA: structural proteins, NS1, ns2a, and ns2b.

cDNA clones of the St. Louis encephalitis (SLE) virus genome have been obtained and the nucleotide sequence of 4.7 kb corresponding to the 5' terminal half of the genome determined. The genome contains a 5' noncoding region of 98 nucleotides followed by a single continuous open reading frame that encodes three structural proteins in the order capsid (C), membrane precursor (prM)-membrane (M), and envelope (E). Immediately following the C-terminus of E are located nonstructural proteins NS1 through NS3. The SLE amino acid sequence homology with yellow fever (YF), Murray Valley encephalitis (MVE), West Nile (WN), and dengue-2 (DEN) viruses over the sequenced region is 39, 66, 64, and 43%, respectively. The start of each SLE protein has been assigned on the basis of N-terminal sequence data and potential proteolytic cleavage sites homologous with YF and MVE viruses. Flaviviruses have conserved glycosylation sites in prM and NS1 proteins, although only one of the two glycosylation sites in the SLE E protein is conserved in MVE and DEN viruses. An evolutionary tree showing relationships of SLE, MVE, WN, YF, and DEN-2 flaviviruses is proposed on the basis of the amino acid sequences of the C proteins.

Base Sequence↗
PubMed1986

Glucose-insulin interactions during cardiopulmonary bypass. Hypothermia versus normothermia.

Since hypothermia is commonly used to lower local and general metabolism during cardiopulmonary bypass, we attempted to identify its specific effects on glucose-insulin interactions. A group of nondiabetic patients undergoing hypothermic (28 degrees C) cardiopulmonary bypass with ischemic (cold) cardiac arrest was compared to a similar group operated on under normothermic conditions with potassium cardioplegia. In the absence of exogenous dextrose administration, hypothermia blocked insulin secretion for the duration of the operation. It also inhibited insulin secretion in response to an exogenous dextrose load (e.g., the priming fluid of the cardiopulmonary bypass circuit) or a glucagon injection, but this inhibition was lifted by rewarming. Blood glucose levels, which during normothermia were mildly elevated even in the absence of dextrose administration, remained normal during the hypothermic phase of cardiopulmonary bypass. By the end of the rewarming period, however, blood glucose levels had reached the same level as observed under normothermic bypass, a fact suggesting that the cold inhibition of hepatic glucose production had been only temporary. Cold inhibition of hepatic glucose production also explains why glucose clearance after a sudden dextrose load was initially faster at low body temperature than at normal temperature. Glucose-clamp studies indicated that insulin resistance was initiated by anesthesia and surgical trauma, and further accentuated by cardiopulmonary bypass, in association with elevated levels of hormones indicative of surgical stress. Regardless of body temperature changes, the assimilation of glucose by nondiabetic subjects during and immediately after bypass called for the infusion of large doses of insulin. A comparison with diabetic subjects showed that insulin-dependent patients (type I diabetes) required no more insulin during cardiopulmonary bypass than normal subjects, whereas patients with type II diabetes exhibited a marked insulin resistance during the operation and in the immediate postoperative period.

Adult↗
PubMed1985

Interaction of the staphylococcin-like peptide Pep 5 with cell walls and isolated cell wall components of Gram-positive bacteria.

Unlike bacteriocins of Gram-negative bacteria, the strongly basic staphylococcin-like peptide Pep 5 lacked specific receptor mediated binding to sensitive Gram-positive bacteria. Studies with whole cells, purified cell walls, teichoic acids, and lipoteichoic acids strongly suggested that it binds reversibly via electrostatic interaction to negatively charged groups. Thus, Pep 5 binding could be reversed by sufficiently high concentrations of monovalent (K+, 150-250 mM) and divalent (Ca2+, 15-30 mM) cations (Fig. 1, 2) and by low pH (pH 2), where Pep 5 binding groups are protonated. Cells of Staphylococcus cohnii 22 with a reduced teichoic acid content showed a reduced Pep 5 binding capacity (Fig. 3). The results indicate that teichoic, teichuronic, and lipoteichoic acids are the unspecific cell wall binding sites for Pep 5.

Adsorption↗