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Biomedical subjects

H Rabe

Publications and source records attributed to H Rabe.

At least 55 records · Page 3Linked to original sources
PubMed1988

[Doppler flow velocities in cerebral arteries in relation to intravenous phenobarbital in premature infants weighing between 500 and 1,500 g].

In very premature ventilated infants (GA 25-30 weeks, BW 575-1420 g) values for heart frequency, mean arterial blood pressure and pCO2 were obtained, and also Doppler-sonographic measurements of the right internal carotid artery were performed to assess cerebral haemodynamics, before and 5-10 min after the intravenous injection of 20 mg/kg phenobarbitone (study I/n = 10) or 5 mg/kg phenobarbitone (study II/n = 10). There were no significant changes in any of these parameters. Therefore phenobarbitone does not have seem to have any significant effect on cerebral haemodynamics up to a dosage of 20 mg/kg, so that there is no apparent effect on the risk of cerebral haemorrhage. On the other hand this study confirms that phenobarbitone can be used in very low birth weight preterm infants with this dosage without causing any substantial haemodynamic risk.

Birth Weight↗
PubMed1987

Chemical modification of cytochrome P-450 LM4. Identification of functionally linked tyrosine residues.

Cytochrome P-450 LM4 (RH, reduced flavoprotein:oxygen oxidoreductase (RH-hydroxylating), EC 1.14.14.1) from rabbit liver microsomes was chemically modified with tetranitromethane. Nitration of two tyrosine residues inhibits the p-nitrophenetole O-deethylase activity of the enzyme by about 80%. Sequencing the 3-nitrotyrosine-containing peptides after HPLC tryptic peptide mapping reveals that mainly Tyr-243 and Tyr-271 are nitrated, whereas Tyr-71, Tyr-188 and Tyr-365 are modified to a lower extent. Nitration of tyrosine residues affects the complex formation with p-nitrophenetole, alpha-naphthoflavone and metyrapone as indicated by an increased affinity towards p-nitrophenetole and by a decreased affinity for the latter compounds. Furthermore, nitration interferes with the electron transfer from NADPH-cytochrome P-450-reductase to cytochrome P-450 LM4 resulting in a slowed down reduction reaction. The results suggest that Tyr-243 and Tyr-271 of cytochrome P-450 LM4 are functionally involved in the interaction with NADPH-cytochrome P-450 reductase.

Amino Acid Sequence↗
PubMed1987

[Initial experiences with the determination of neopterin in the urine of females with genital and breast tumors].

The quantitative analysis of urinary neopterin was carried out ahead of the operation by means of high performance liquid chromatography (HPLC). The sample included 98 women with genital or breast neoplasias. Significant differences have been found between the patients with benign or preinvasive neoplasias as well as women with malignancies (p less than 0.001) as compared to a control group of healthy females. The neopterin levels of the malignant tumors were definitely higher than those of the benign tumors (p less than 0.01). As far as genital tract cancer ist concerned, the neopterin levels found were in 51.5 per cent of the cases above the estimated limit with a specificity of 95.1 per cent in healthy patients and 79.5 per cent within the group of nonmalignant gynecologic lesions. The neopterin levels established in patients with genital tract malignancies appear to be related with the stage of the development of the disease (i.e. levels and positive rate are significantly higher in stages III and IV as compared to stages I and II; p less than 0.01). Tests of women with breast cancer showed the smallest number of raised neopterin levels. The average level of the last mentioned cases didn't differ greatly from the levels of the benign breast tumors. Tests of the patients with cancer after treatment showed in 68.8 per cent of all cases neopterin levels corresponding to the clinical findings. However, cases of smaller recurrent tumors may be accompanied by normal neopterin levels as well.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopterins↗
PubMed1986

Phosphatidylglycerol of rat lung. Intracellular sites of formation de novo and acyl species pattern in mitochondria, microsomes and surfactant.

The subcellular site of phosphatidylglycerol (PG) formation for lung surfactant has not been convincingly clarified. To approach this problem we analysed the acyl species pattern of lung PG in mitochondria, microsomes and surfactant by h.p.l.c. separation of its 1,2-diacyl-3-naphthylurethane derivatives. Both mitochondrial and microsomal PG proved identical with surfactant PG, containing the major species 1-palmitoyl-2-oleoyl-PG and 1,2-dipalmitoyl-PG. The fatty acid composition of mitochondrial PG differs markedly from that of diphosphatidylglycerol. This may be taken as an indication that mitochondrial PG is synthesized on purpose to form surfactant, rather than being only the precursor of diphosphatidylglycerol. In vitro, sn-[U-14C]glycerol 3-phosphate incorporation into PG of mitochondria or microsomes occurs in the presence of CTP, ATP and CoA but independently of the supply of exogenous lipoidic precursors. Although the rate in vitro of autonomous PG synthesis, and the endogenous PG content, are higher in mitochondria than in microsomes, it is assumed that both subcellular fractions are involved in PG formation for surfactant.

Animals↗
PubMed1986

[Noninvasive study of intracerebral circulation in premature and newborn infants with pulsed Doppler sonography. Principles, measuring technics, reference values].

This paper describes our method to evaluate neonatal cerebral circulation in a semiquantitative way by transfontanellar pulsed Doppler ultrasonography. We defined three arterial (internal carotid, basilar, and anterior cerebral artery) and three venous (internal cerebral and internal jugular vein; sinus rectus) sites for measurement of peak systolic, end diastolic, and mean velocity. Reference values, intraindividual and interindividual variation are calculated for infants between 750 and 4000 g body weight. Among all possible measurements follow up of mean velocity of the internal carotid artery in an individual infant is most reliable.

Birth Weight↗
PubMed1985

The molecular species of phosphatidic acid, diacylglycerol and phosphatidylcholine synthesized from sn-glycerol 3-phosphate in rat lung microsomes.

The species pattern of phosphatidic acid, diacylglycerol and phosphatidylcholine synthesized from [14C]glycerol 3-phosphate was measured using a newly developed HPLC technique yielding 13 molecular species. A direct comparison of these species patterns presupposes determination of the lipolytic activity of lung microsomes. The lipolytic activity was quantitatively determined by measuring the changes of the endogenous concentration of diacylglycerol, triacylglycerol and free fatty acids. The species pattern of endogenous diacylglycerol measured in the time-course of lipolysis did not show any changes up to an incubation period of 20 min, suggesting that the lipolytic activity showed only a very low selectivity for individual substrate species. Diisopropylfluorophosphate (5 mumol/mg microsomal protein) strongly decreased the lipolytic activities as well as the microsomal phosphatidate phosphohydrolase activity, as measured by means of exogenous phosphatidic acid, and also the generation of phosphatidic acid from [14C]glycerol 3-phosphate. In lung microsomes, labeled phosphatidic acid and diacylglycerols were synthesized from the endogenous free fatty acids and sn-[14C]glycerol 3-phosphate, which had previously been added. By addition of CDPcholine to the prelabeled microsomes the synthesis of phosphatidylcholine was measured. After hydrolysis of phosphatidic acid and phosphatidylcholine with cytoplasmatic phosphatidate phosphohydrolase or phospholipase C, respectively, the de novo synthesized species patterns of these two lipids and of the diacylglycerol were determined. Comparison of the species pattern of de novo synthesized phosphatidic acid with that of diacylglycerol largely showed the same distribution of radioactivity among the individual species, except that the relative proportion of label was higher in the 16:0/16:0 and 16:0/18:0 species of phosphatidic acid and lower in the 16:0/20:4 and 18:0/20:4 species than in the corresponding species of diacylglycerol. The species pattern of de novo-synthesized diacylglycerol showed no differences from that of the phosphatidylcholine synthesized from it. From this result we concluded that the cholinephosphotransferase of lung microsomes is nonselective for individual species of the diacylglycerol substrate. The 16:0/18:1 and 16:0/18:2 species of phosphatidic acid, diacylglycerol and phosphatidylcholine showed a higher synthesis rate than their 18:0 counterparts, whereas the 16:0 or 18:0 analogues of species containing 20:4 and 22:6 fatty acids showed nearly the same synthesis rates.(ABSTRACT TRUNCATED AT 400 WORDS)

1-Acylglycerol-3-Phosphate O-Acyltransferase↗
PubMed1985

Metallographic texture analysis of dental materials by polarizing microscopy in the incidental light.

Incidental polarized light microscopy can be used for the optical analysis of crystal phases with similar anisotropic behavior or preferred textures in polished sections. In this method, the vibration mode of the reflected light is determined by remarkable interference colors in the microscope using a compensator plate. The application of this method for the analysis of dental materials is demonstrated with amalgams and gold-reduced alloys. As a prerequisite, a modified procedure for preparing suitable polished sections of inhomogenous materials is described. Employing this optical and a crystallographic computing method, more detailed information about the way of element replacement in the course of the chemical reaction can be obtained. The results of these investigations also warrant the assumption that coherent crystal intergrowth which prefers low indicated and closely packed lattice directions, gives rise to a good adhesive strength of the bonding in the alloy.

Crystallography↗
PubMed1984

Diacylglycerol species in microsomes and mitochondria of normal and dystrophic human muscle.

The concentration of 1.2-diacylglycerol in mitochondria and microsomes of normal human muscle was estimated to be 1.7 +/- 0.6 and 9.2 +/- 1.9 nmol X mg protein-1, respectively. The molecular species profile of 1.2-diacylglycerol was obtained using high pressure liquid chromatography which yielded 14 fractions. Corresponding studies were carried out for normal and dystrophic muscle. No significant difference could be seen between the 1.2-diacylglycerol patterns in normal muscle mitochondria and in microsomes. There was a radical shift in the 1.2-diacylglycerol pattern in both dystrophic organelles, mainly with a decrease in 16:0/16:0 species. In dystrophic mitochondria the total level of 1.2-diacylglycerol was higher.

Diglycerides↗
PubMed1984

Chemical modification of cytochrome P-450 LM2. Characterization of tyrosine as axial heme iron ligand trans to thiolate.

Phenobarbital-inducible isozyme cytochrome P-450 LM2 (RH, reduced-flavoprotein:oxygen oxidoreductase (RH-hydroxylating), EC 1.14.14.1) from rabbit liver microsomes has been modified with N-acetylimidazole and tetranitromethane. Up to four tyrosine residues of cytochrome P-450 LM2 are accessible to O-acetylation and to nitration. N-Demethylase activity, spectral dissociation constants and substrate binding kinetics of differently acetylated enzyme indicate the existence of two groups of accessible tyrosines also differing in their reactivity towards N-acetylimidazole. The fast-reacting tyrosine residue representing the first group is involved in the binding of the type II substrate aniline and appears to be located near the heme as shown by the protecting effect of the inhibitor metyrapone against modification, but obviously is not necessary for N-demethylation. Acetylation of one further tyrosine residue, however, caused an almost complete inhibition of the enzyme, indicating its involvement in the catalytic mechanism at the active center. Nitration of two tyrosine residues inactivates to about 20%. Obviously the third and fourth tyrosine residue are without functional importance. The experiments evidencing two functionally linked tyrosines are in line with HPLC analyses of tryptic peptides of cytochrome P-450 LM2 nitrated in the presence of metyrapone which gave evidence for the location of two distinct tyrosine residues in the active center. Nitration of tyrosine residues results in the partial formation of a hyperporphyrin spectrum of cytochrome P-450 LM2. Its appearance is prevented in the presence of metyrapone and can be reversed by reduction of the nitrotyrosinate .

Acetylation↗
PubMed1984

Identification of lysine (384) in cytochrome P-450 LM2 as functionally linked residue.

Fluorescein isothiocyanate was selectively bound to the epsilon-amino group of a lysine residue of cytochrome P-450 LM2 at rho H 8.15. The decrease in the N-demethylase activity after modification evidences the functional importance of the modified group. After tryptic digestion the FITC-labeled peptide was isolated by means of HPLC and its amino acid composition determined. It was shown that the FITC-peptide can be attributed to the sequence Gly (379)- Arg (400) and that the label is selectively bound to Lys (384).

Amino Acid Sequence↗
PubMed1984

Chemical modification of tyrosine residues at the active centre of cytochrome P-450 CAM.

Soluble cytochrome P-450 CAM from Pseudomonas putida (EC 1.14.14.1) was chemically modified with tetranitromethane. At least five out of totally nine tyrosine residues are accessible to nitration as shown by tryptic peptide mapping using HPLC. Modification in the presence of the inhibitor metyrapone and subsequent peptide mapping indicate the location of one tyrosine residue at the active centre of cytochrome P-450 CAM.

Aryl Hydrocarbon Hydroxylases↗