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Biomedical subjects

P Barth

Publications and source records attributed to P Barth.

At least 19 recordsLinked to original sources
PubMed1992

Purification and electrospray mass spectrometry of aldose reductase from pig lens.

Aldose reductase (alditol: NADP+ 1-oxidoreductase, EC 1.1.1.21) has been purified from pig lens to homogeneity by a rapid and efficient three-step procedure involving poly(ethylene glycol) fractionation, ion-exchange chromatography and chromatofocusing. The homogeneity of the purified enzyme was examined by polyacrylamide gel electrophoresis under native and denaturing conditions, by isoelectric focusing and by high-performance liquid chromatography on a size-exclusion column. The highly purified enzyme is a monomeric protein with a molecular mass of 35,775 +/- 3 Da as determined by electrospray mass spectrometry (ESMS). This purification procedure is particularly suited for the preparation of triclinic single crystals of pig lens aldose reductase, which are currently used in X-ray studies of this enzyme.

Aldehyde Reductase↗
PubMed1992

Novel NADPH-binding domain revealed by the crystal structure of aldose reductase.

Aldose reductase is the first enzyme in the polyol pathway and catalyses the NADPH-dependent reduction of D-glucose to D-sorbitol. Under normal physiological conditions aldose reductase participates in osmoregulation, but under hyperglycaemic conditions it contributes to the onset and development of severe complications in diabetes. Here we present the crystal structure of pig lens aldose reductase refined to an R-factor of 0.232 at 2.5-A resolution. It exhibits a single domain folded in an eight-stranded parallel alpha/beta barrel, similar to that in triose phosphate isomerase and a score of other enzymes. Hence, aldose reductase does not possess the expected canonical dinucleotide-binding domain. Crystallographic analysis of the binding of 2'-monophospho-adenosine-5'-diphosphoribose, which competitively inhibits NADPH binding reveals that it binds into a cleft located at the C-terminal end of the strands of the alpha/beta barrel. This represents a new type of binding for nicotinamide adenine dinucleotide coenzymes.

Aldehyde Reductase↗
PubMed1992

Structural and functional impairment of surfactant protein A after exposure to nitrogen dioxide in rats.

The major surfactant protein A (SP-A) determines the dynamics of surfactant metabolism and function. We now for the first time studied the in vivo exposure of the SP-A to nitrogen dioxide (NO2) and compared it to in vitro exposure effects. Several properties that are believed to possess physiological functions were investigated. Exposure of rat SP-A to NO2 showed 1) a higher alveolar pool size after in vivo exposure, 2) a slightly decreased mannose binding capacity for the in vivo exposed form but a highly decreased binding after in vitro exposure, 3) an affected protein-lipid aggregation that was impaired most by the in vitro exposed protein, 4) a low inhibition for the secretion of phosphatidylcholine in isolated type II pneumocytes, and 5) no difference in apparent molecular weight and immunological reactivity of the differently exposed SP-A. The NO2-induced alterations of the SP-A may contribute to the pulmonary toxicity of this oxidant. It is clear from this study that the extend of the effects from in vivo and in vitro exposure are different. Therefore both forms of exposure are necessary to assess the biological significance of NO2 exposure.

Animals↗
PubMed1991

[Study of early myocardial infarction by nuclear magnetic resonance imaging with gadolinium Dota injection].

Ten patients with acute myocardial infarction were studied by magnetic resonance imaging (MRI) with injection of a paramagnetic contrast agent: Gadolinium-DOTA (Gd-DOTA). The time interval between the onset of symptoms and MRI was 8 to 12 days. The site of infarction was determined in all cases by Thallium 201 scintigraphy (hypofixation) and selective ventriculography (segmental wall anomalies): anterior (6 cases), inferior (4 cases). MRI was performed with a 0.5 Tesla CGR Magniscan by the multiple spin technique. A series of tomographic sections was recorded immediately after intravenous injection of 0.4 mmol/Kg of Gd-DOTA. Recent myocardial infarction with parenchymal oedema gives an enhanced transmural signal: only 3 patients had a sufficiently contrasted image on the 1st spin echo. After Gd-DOTA, 7 patients had significantly increased contrast on this echo and in all excellent contrast between infarcted and healthy myocardium was obtained in 9 of the 10 patients. There was excellent correlation concerning the site of infarction between Thallium scintigraphy and left ventriculography. The intensity of signal and T2 relaxation time of different myocardial segments was studied by the regions of interest technique: the ratio of signal intensity of infarcted/healthy myocardium was 1.3 before and 1.7 after Gd-DOTA on first spin echo images. The mean T2 was 54.1 +/- 9 ms in healthy and 82 +/- 28 ms in infarcted myocardium. After Gd-DOTA, both values decreased and tended to equalize.(ABSTRACT TRUNCATED AT 250 WORDS)

Diastole↗
PubMed1991

[Techniques for ultrasound imaging of meniscus lesions. Experimental principles].

The fact that a lesion of the knee meniscus presents in ultrasound as a hard, glaring reflection of sound waves is considered to be well established today. Nevertheless, different examiners report variable results. When looking for the reasons for these variations, we tried to determine whether different examination techniques are the cause or the technical equipment used. Thus we ran tests with isolated menisci containing artificial lesions in a waterbath. We found that sound waves falling on the object at an angle of 45 degrees in reference to the meniscal axis provide optimal imaging of the lesion. In contrast, the reflection of sound waves is very weak when the angle of incidence is about 10 degrees. As a result of these tests, a dynamic examination with tilting movements of the scanner in the vertical axis is recommended. The method of visualizing the menisci perpendicular to the axis of the leg was found to be much more difficult without yielding additional information. We thus suggest that this method of examination should not be used.

Humans↗
PubMed1990

Influence of low osmolality contrast media on electrophysiology and hemodynamics in coronary angiography: differences between an ionic (ioxaglate) and a nonionic (iohexol) agent.

It has recently been suggested that the addition of sodium to low osmolality contrast media may reduce the incidence of ventricular fibrillation and conduction disturbances during coronary angiography. In a randomized, double blind study of 30 patients undergoing coronary angiography we therefore examined the electrophysiological and hemodynamic effects of the two low osmolality contrast media-ioxaglate (with sodium) and iohexol (without sodium). Standard ECG, aortic blood pressure, and His bundle electrocardiogram were recorded. The contrast media were well tolerated and no serious arrhythmias were observed. Both induced a transient decrement in systolic blood pressure and reduction in heart rate 10 s following contrast injection (all P less than 0.01). Ioxaglate prolonged the QT interval at 10 s (P less than 0.01) and also when analysed for the whole observation period (120 s) (P less than 0.05), whereas iohexol did not cause any significant changes in the QT-interval. The AH-interval was prolonged by ioxaglate at 10 s (P less than 0.01), but not altered by iohexol. Thus, other factors than osmolality and sodium content might contribute to QT prolongation, since only the contrast agents with sodium (ioxaglate) induced QT prolongation in this study.

Adult↗
PubMed1989

Comparison of sodium-meglumine ioxaglate and iopromide in coronary angiography.

A clinical study was carried out in 20 patients in coronary angiography to compare two low-osmolar contrast media, sodium-meglumine ioxaglate and iopromide. Ten patients presented a stage III coronary disease and the other ten had a stage IV coronary disease. In the latter group, 70% of the patients received sodium-meglumine ioxaglate and 30% were given iopromide. None of the patients given iopromide had a previous history of allergic-like reactions to contrast media as opposed to the sodium-meglumine ioxaglate group where two patients had a previous hypersensitivity reaction to contrast agents. In spite of these adverse conditions in the sodium-meglumine ioxaglate group, no significant difference was found between both preparations as to overall tolerability. The following side effects were observed: slight nausea and wheezing in a patient given sodium-meglumine ioxaglate; medium intense nausea, vomiting and headache in a patient administered iopromide; one case of angina pectoris occurring 8 minutes post-injection of iopromide. Similarly, no significant difference in overall cardiac tolerability could be found between the two contrast media, although sodium-meglumine ioxaglate would tend to be better tolerated in terms of heart rate and contractility. Radiographic efficacy was considered to be equivalent for both contrast agents though the test solutions had different iodine concentrations. In summary, the two low osmolar contrast media proved well tolerated and showed satisfactory diagnostic efficacy in this population at high cardiovascular risk.

Angiography↗
PubMed1989

Comparison of Telebrix Gastro and Gastrografin in abdominal computed tomography.

Palatability as well as the side effects and computed tomographic image quality associated with the oral use of Telebrix Gastro (ioxithalamate) and Gastrografin (amidotrizoate) in bowel opacification were compared in a double-blind study involving 100 patients in a 24-hour protocol. There was a tendency (p = 0.07) for Telebrix Gastro to show greater palatability. The difference between the 2 groups in terms of patient discomfort was too small to reach statistical significance (p less than 0.09). There was no statistical difference between the agents with respect to image quality. In 87% of cases in both groups bowel filling was adequate.

Contrast Media↗
PubMed1987

Crystallization and preliminary X-ray study of pig lens aldose reductase.

Crystals of pig lens aldose reductase have been grown from polyethylene glycol solutions at pH 6.2 and analysed by X-ray diffraction. Two crystal forms were obtained. The first belongs to space group P1 with unit cell dimensions a = 81.3 A, b = 85.9 A, c = 56.6 A, alpha = 102.3 degrees, beta = 103.3 degrees, gamma = 79.0 degrees, with four molecules in the unit cell related by a 222 non-crystallographic symmetry. The second crystal form is hexagonal. The space group is P6(2)22 with a = b = 101 A, c = 257 A and two molecules in the asymmetric unit. Both forms are suitable for X-ray structure analysis to better than 3 A resolution.

Aldehyde Reductase↗
PubMed1984

[Clinical use in adults of 2 new muscle relaxants: atracurium and vecuronium].

115 general and urologic surgery adult patients, ASA class I-II, were divided in four groups according to initial bolus and relaxant used: group A atracurium 0.6 mg X kg-1, group B 0.5 mg X kg-1, group C vecuronium 0.1 mg X kg-1 and group D pancuronium 0.1 mg X kg-1. When the single twitch recovered to 25% of control height (T25), subgroups were individualized depending on whether repeat doses of 1/3 of initial bolus were given or not, and whether reversal was spontaneous or obtained by a standard dose of neostigmine 2.5 mg and atropine 1.25 mg. By ulnar nerve stimulation at the wrist, the force of thumb adduction was recorded on a polygraph; single twitch (tw), train of four (tof) and ratio tof 4/1 (Rtof) were measured. Anaesthesia was induced with thiopentone and fentanyl without premedication and maintained with fentanyl and N2O in oxygen; the trachea was intubated once the block was at its maximum. The onset time of maximal block was 5 min for groups A, B and C, and 7.9 min for group D. T25 was 39.9 +/- 8.5 min for group A, 34.4 +/- 9.7 min for group B, 28.9 +/- 9.9 min for group C and 70.7 +/- 25.9 min for group D. A Rtof equal to 75% was achieved in less than 65 min with atracurium and vecuronium, but much later with pancuronium. Reversal at T25 was efficient, but not really required, for atracurium and vecuronium, but necessary and useful for pancuronium.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1978

Classification of leukemic cells by Ia alloantigens and complement receptors. Surface probes for cell differentiation.

Of particular interest in the study of cell membrane markers of leukemic cells were cytotoxic and immunofluorescent results obtained in comparing Ia alloantigen and complement receptor (CR) expression on normal leukocytic and leukemic cell types. Using discontinuous Ficoll gradients, Ia alloantigens were found on varying numbers of leukemic myelo- and lymphoblasts, and on the early stages of normal melocytes. Ia alloantigens, however, were not detectable on mature polymorphonuclear cells. This establishes human Ia alloantigens as cell surface differentiation markers. The appearance of complement receptors was observed later than that of Ia alloantigens. CR1 (EAC1-4b) showed up later in the differentiation than CR2 (EAC1-3d). Thus, an immunological discrimination between AML blasts and CML blast crisis blasts appears to be possible: AML blasts are mostly Ia-positive but CR-negative, whilst CML blast crisis cells are only 20-30% Ia-positive and carry complement receptors in at least equal amounts. The AML blast cell would appear as the less-differentiated cell type when compared to the CML blast crisis cells. The picture, however, remains complex since in CML blast crisis at least three different types of blast cells can be identified: an Ia-positive and an Ia-negative myeloid blast as well as an Ia-positive lymphoid blast. The quantitative composition of these three elements within the myeloid differentiation profile can vary somewhat from patient to patient. Furthermore, these studies revealed a disturbed differentiation of leukemic cell types.

B-Lymphocytes↗