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Biomedical subjects

C Lehmann

Publications and source records attributed to C Lehmann.

At least 91 records · Page 5Linked to original sources
PubMed1989

[The hemodynamics of the intestinal arteries of the dog with special reference to the flow rate].

Intestinal haemodynamics was examined invasively in 30 mongrel dogs. Beside registration of blood pressure values of the blood flow were evaluated especially. Measured flow values in the three main intestinal vessels - Truncus coeliacus, A. mesenterica superior and A. mesenterica inferior - were compared to aortal flow. Thereby the sum of intestinal arteries values was equal to intrarenal aortal flow. Two thirds of aortal flow may be expected in the portal vein. These relations make in possible to get informations about physiological intestinal circulation from single values without measurement of all intestinal vessels.

Animals↗
PubMed1988

Phosphorylation, anti-HIV activity and cytotoxicity of 3'-fluorothymidine.

3'-fluorothymidine (FddThd) is well phosphorylated to the 5'-triphosphate in various relevant cell-lines. This results in fairly stable levels of this compound without accumulation of the 5'-monophosphate to the extent described for 3'-azidothymidine (AzT). The di- and triphosphate of FddThd seems unable to influence the ribonucleotide reductase in permeable cells. FddThd protects 50% of the MT-4 cells against the cytopathic effect of HIV at 3 nM, but reduces the number of uninfected viable cells to 50% at 1.1 microM. All other tested human cell-lines displayed a far less antiproliferative sensitivity to FddThd, comparable with that of AzT.

Animals↗
PubMed1988

Test-ordering by multiple physicians increases unnecessary laboratory examinations.

In modern teaching hospitals, patients typically receive direct care from a succession of different physicians, each of whom may order diagnostic tests on the same patient. We examined the association of test-ordering by multiple physicians with unnecessary duplication of 20-test chemistry profiles in 198 consecutively admitted patients. In a multivariate regression model, the number of duplicate chemistry profiles ordered for a patient was significantly correlated with the number of physicians ordering profiles after controlling for the overall intensity of profile testing. In a case-control analysis comparing duplicate with nonduplicate profiles, redundant tests were significantly more likely to have been ordered by a new physician who had not ordered a patient's previous profile than by the same physician who had ordered the previous chemistry panel. We conclude that test ordering by multiple physicians, the prevalent pattern in almost all teaching hospitals, predisposes to unnecessary laboratory examinations.

Clinical Laboratory Techniques↗
PubMed1988

[Warming resuspended erythrocyte concentrates with a new microwave device. In vitro results and clinical experiences in comparison with continuous flow warming].

Rapid warming of stored red cell concentrates demands a technique that provides careful treatment of the erythrocytes, reliability, simple handling, and prompt processing. The Fenwal BW-5, a dry-heat blood warmer, is a well-established blood heating device. However, its use is time-consuming and rather complicated. The newly developed Infusotherm 407 is a microwave blood warmer providing short prewarming time and easy handling, but its safe applicability for resuspended red cells had not previously been proven. MATERIALS AND METHODS. Using the disposable plastic Ery-Set Schiwa (100 ml NaCl 0.9%), 211 red cell concentrates were diluted; 115 were warmed by the Infusotherm 407 and 96 by the Fenwal BW-5. The age of the blood units ranged between 1 and 30 days and the volume between 300 and 350 ml after resuspension. The Infusotherm 407 produces pulsed high-frequency waves that are absorbed by the blood unit and transformed into heat. The swivelling mechanism of the rotating holder allows continuous mixing and uniform warming of the red-cell suspension. The blood temperature is registered on the bag's surface by a thermometer integrated in the rotating holder. At 32 degrees C, the warming process is stopped automatically. Within the Fenwal BW-5 a special plastic bag has to be fixed between two electrically heated thermostat-controlled plates. The bag contains the blood that is passing through in several coils. A constant working temperature is maintained by an electronic monitor system up to a blood flow of 150 ml/min. Several laboratory parameters, i.e. extracellular hemoglobin, potassium, lactate dehydrogenase, as well as mean erythrocyte volume (MCV) and osmotic fragility of the red cells were determined from samples prior to and after blood warming. Thus, apparent hemolysis, morphological changes, or discrete damage to the erythrocytes could be detected. RESULTS. We observed a slight elevation in hemolysis parameters after warming with both devices. The alterations were within the range for stored packed red cells given by the European Public Health Committee. MCV and osmotic fragility remained unchanged. We did not find any comparable data concerning diluted packed red cells for either of the devices. Our own results did not show any significant difference between the two methods of heating. DISCUSSION. From the literature, it is known that the erythrocytes of full-sized blood units with normal hematocrit are not damaged by microwave warming. In contrast, small blood units and undiluted packed red cells revealed considerable hemolysis and distinct changes in MCV and osmotic fragility.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood Transfusion↗
PubMed1987

Inhibition of HIV-associated reverse transcriptase by sugar-modified derivatives of thymidine 5'-triphosphate in comparison to cellular DNA polymerases alpha and beta.

The sugar-modified dTTP analogues 2',3'-didehydro-2',3'-dideoxy-thymidine 5'-triphosphate (ddeTTP), 2',3'-dideoxythymidine 5'-triphosphate (ddTTP), 3'-fluorothymidine 5'-triphosphate (FdTTP), and 3'-azidothymidine 5'-triphosphate (N3dTTP) are demonstrated to be very effective and selective inhibitors of the HIV-associated reverse transcriptase (HIV-RT). This conclusion is based on a comparison of the ID50 values of the compounds for the HIV-RT (ranging from 0.03 microM for ddeTTP to 0.1 microM for ddTTP) and the cellular DNA polymerase alpha (greater than 200 microM). DNA polymerase beta is partially affected by N3dTTP (ID50 = 31 microM) and by the other analogues (ID50 = 1-2.2 microM). FdTTP has proved as effective as N3dTTP (ID50 = 0.05 microM) in suppressing the HIV-RT activity. Kinetic analysis revealed for both dTTP analogues a competitive type of inhibition and the same K1 values (about 0.05 microM).

Cell Line↗
PubMed1986

Dynamics of superhelical DNA studied by photon correlation spectroscopy.

We have conducted photon correlation spectroscopy (PCS) studies on the plasmid pUC8 (2717 bp) in order to elucidate the internal dynamics of this superhelical DNA. We confirm that the first-order autocorrelation function of the scattered light from pUC8 solutions can be separated into two distinct exponential decay components, as first shown by Lewis et al. (R. Lewis, J.H. Huang and P. Pecora, Macromolecules 18 (1985) 944). A thorough analysis of the dependence on scattering vector K of the rates and amplitudes of the two components enables us to assign the slowly relaxing part to the center-of-mass diffusion of the DNA, while the faster component corresponds to rotational, bending and twisting motions of the superhelix. For larger K values the internal motions can be formally expressed in terms of an 'internal diffusion coefficient' Di, whose value of 2.0-2.5 X 10(-11) m2 s-1 is approximately equal to the translational diffusion coefficient predicted for a stiff DNA piece of the persistence length, 65 nm. Comparison of our measured Di values to those predicted from a recent theory of circular worm-like coils (K. Soda, Macromolecules 17 (1984) 2365) shows that the internal motions are faster than the theoretical values. One of the reasons for this discrepancy could be that the theory does not take into account torsional motions, which contribute significantly to the internal dynamics (J.C. Thomas, S.A. Allison, C.J. Appelof and J.M. Schurr, Biophys. Chem. 12 (1980) 177). At low K values, the fast relaxation of superhelical pUC8 is no longer proportional to K2, but reaches a constant value as K approaches zero. This behavior, not seen for the linearized DNA, can be interpreted in terms of rotational diffusion of a flexible rod-like molecule (T. Maeda and S. Fujime, Macromolecules 17 (1984) 2381) and supports an interwound rod-like structure for pUC8 DNA with an average end-to-end distance of 220 nm.

DNA Restriction Enzymes↗
PubMed1985

Pharmacokinetics of tiaprofenic acid in healthy and arthritic subjects.

Disposition kinetics of nonsteroidal, anti-inflammatory tiaprofenic acid (1) and its metabolites were studied in healthy subjects and arthritic patients under treatment with 200 mg of the drug three times daily. The concentration of the drug and its metabolites were measured using a sensitive and specific HPLC method. The pharmacokinetics of tiaprofenic acid in arthritic patients seems to be similar to those in healthy subjects. The drug is rapidly absorbed, extensively bound to plasma proteins and, upon repeated administration, is accumulated in the body only to a limited extent. While only unchanged drug was found in plasma, a negligible amount of the unchanged drug was recovered from urine. The major pathway of drug elimination seems to be through conjugation. The reduced and oxidized metabolites of 1, 2 and 3, respectively also are found in urine as conjugates. The conjugates are, however, relatively unstable and are readily hydrolyzed to their parent compounds upon storage or addition of alkali. As elimination of the drug is dependent upon urinary excretion of the conjugates, it may be influenced by reduced renal function or the presence of other drugs.

Adult↗
PubMed1985

3'-Deoxy-3'-fluorothymidinetriphosphate: inhibitor and terminator of DNA synthesis catalysed by DNA polymerase beta, terminal deoxynucleotidyl transferase and DNA polymerase I.

3'-deoxy-3'-fluorothymidine-5'-triphosphate (dFTTP) was examined with respect to its capacity to inhibit and to terminate DNA-synthesis catalysed by DNA polymerases alpha and beta, terminal deoxynucleotidyl transferase (TdT) and E. coli DNA polymerase I (Klenow fragment). In analogy with 2', 3'-dideoxythymidine-5'-triphosphate (ddTTP) it was found that DNA polymerase beta was much more sensitive to dFTTP inhibition than DNA polymerase alpha. Moreover, the activity of TdT is strongly inhibited by both dFTTP and ddTTP, whereas the two compounds displayed a lower inhibitory potency on DNA polymerase I. Except for DNA polymerase alpha, the other investigated DNA polymerases are able to incorporate dFTTP into poly (dA).oligo (dT) and oligo (dG), respectively. The specific chain-terminating activity of dFTTP has proved for DNA sequencing to be at least equivalent to ddTTP.

Animals↗
PubMed1984

High-performance liquid chromatographic analysis of tiaprofenic acid and its metabolites in plasma and urine by direct injection.

A rapid, convenient, sensitive and selective reversed-phase high-performance liquid chromatographic method was developed to measure tiaprofenic acid, its reduced and oxidized metabolites and their conjugates in biological fluids. The method involved direct injections of plasma and urine samples into the chromatograph before and after alkaline hydrolysis of the conjugates. Concentrations as low as 0.5 micrograms/ml of the drug in plasma and urine were quantifiable. The method was suitable for analysis of tiaprofenic acid and its metabolites in biological fluids after administration of therapeutic doses. Several other non-steroidal anti-inflammatory drugs which were applied to the system did not interfere with the assay.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1983

Sulfonyliminoimidazolidines. A new class of oral hypoglycemic agents. 1. 1-[[p-[2-(acylamino)ethyl]phenyl]sulfonyl]-2-iminoimidazolidines.

A series of 1-[[p-[2-(acylamino)ethyl]phenyl]sulfonyl]-2-iminoimidazolidines has been synthesized. Compounds from this new class of oral hypoglycemic agents lower blood glucose in normal and in streptozotocin-diabetic rats. Potent analogues were obtained by modification of the acyl residue. 1-[[p-[2-(Crotonylamino)ethyl]phenyl]-sulfonyl]-3-cyclohexyl-2-iminoimidazolidine (44) turned out to be the most potent compound in the normal rat (20 times tolbutamide), and 1-[[p-[2-(5-methylisoxazole-3-carboxamido)ethyl]phenyl]sulfonyl]-3-cyclohexyl-2-imino-imidazolidine (30) displayed the highest potency in the diabetic rat (similar to phenformin).

Animals↗
PubMed1983

[Therapy of conventionally uncontrollable hyperhydration with hemofiltration].

The authors report on three extracorporal methods for treating pulmonary hyperhydration which cannot be managed by drugs or respiratory measures. Of these three extracorporal treatment methods, mechanical haemofiltration (MHF) and pump-driven haemofiltration or ultrafiltration (PHF and PUF, respectively) require complicated equipment which can be operated only by personnel well-trained in extracorporal treatment methods. On the other hand, the third method can be handled even in intensive-care wards not equipped with dialysis facilities and which are not able to operate on a mechanical basis: This method is represented by the technique of continuous arteriovenous haemofiltration (CAVH), utilising relatively low doses of heparin so that the method can also be employed on freshly operated patients and accident victims. Although all treatment facilities are available in the authors' hospital, the CAVH method is employed in specific cases, since it places least stress on circulation provided accurate balance of fluid turnover thus achieved is secured.

Blood↗
PubMed1983

[Disturbance of micturition, a harmless side effect of subdural regional anesthesia?].

The authors report on a disturbance of micturition following spinal anaesthesia which due to improper treatment took two months to resolve. The neurological status showed failures which were due both to the anaesthesia (irritation of root in the S 4 and S 5 regions by the spinal needle and action of the local anaesthetic agent) and to the surgery of a relapsing inguinal hernia (irritation existed, we could not exclude the possibility that the primary disturbance of bladder emptying was due to the anaesthesia and not to the surgical procedure of a possible mental component. In any case, the long-term atony resulting from the basically harmless handicap - even requiring placement of a suprapubic bladder fistula - could have been avoided if the postsurgical treatment had been conducted properly and in accordance with good medical practice.

Anesthesia, Conduction↗
PubMed1982

Influence of selective vs. panel chemistry tests on cost and diagnostic time.

In the present economy, much concern has been focused on the cost and medical efficacy of laboratory tests being performed. This study examined the difference in laboratory costs associated with physician's use of selective vs. panel chemistries and the frequency of inefficient use of laboratory tests. A determination of the difference in the average number of laboratory visits needed to reach diagnosis associated with the use of these two test methods was made. The study was conducted at a 270-bed community hospital in suburban New York, where the physicians are free to choose selective and/or panel chemistries. Random selection of 200 outpatient records revealed that three types of ordering patterns existed: panels, selective, and a combination of the two. Of the three, panel testing resulted in substantially lower costs and fewer return visits to the laboratory than either selective or mixed (combination of selective and panel) testing.

Ambulatory Care↗
PubMed1979

Chicken ribosomal DNA: gene frequency and purification by R-loop hybridization.

The genes for ribosomal RNA of chicken are present in about 200--240 copies per haploid genome. The ribosomal genes were separated from the bulk of DNA by different methods. In CsCl-actinomycin D gradients the GC-rich ribosomal DNA is shifted to the lower density side of the bulk of DNA. After hybridization with iodinated ribosomal RNA under conditions where R-loops are formed ribosomal DNA has an increased density. The R-loops can be separated from the bulk of DNA in Cs2-SO4 gradients.

Animals↗
PubMed1978

[Haemodialysis in acute renal failure; technique and surveillance (author's transl)].

Access to the blood stream for haemodialysis is generally via an arterio-venous shunt. Experience has shown that the introduction of two Shaldon catheters (with a modified Seldinger technique) into the upper caval system does not require special surgical knowledge and shortens and simplifies the preparations for haemodialysis in acute renal failure. As the catheters can easily be changed over guide wires, correction of obstructions and bacteriological examinations of the catheter tips do not present a problem. There were no complications. With this simplified access the acute stage of renal failure can be bridged for up to 6--8 weeks. The diameter of the catheters ensures an adequate flow of 150--200 ml/min. In vitro tests with a modified catheter (not yet available commercially) established 1. that the flow rate could be increased by 45 percent without altering the pressure of the return flow, and 2. that its use did not increase the rate of haemolysis. Incorrect placing of the catheters--the venous limb should be higher, i.e. nearer the heart, than the "arterial" catheter--may raise the re-circulating fraction by 6--18 percent. Since heparinization is necessary for haemodialysis but carries the grave risk of haemorrhages, espeically in the patients of an intensive care unit, it is essential to provide the means for estimating partial thromboplastin time at the bed side. This allows the heparin doses to be sufficiently reduced to obviate haemorrhage during and after haemodialysis.

Acute Kidney Injury↗