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Biomedical subjects

H Rabe

Publications and source records attributed to H Rabe.

At least 37 records · Page 2Linked to original sources
PubMed1991

Cerebral hemodynamics in perinatal pharmacology.

The influence on cerebral hemodynamics of drugs given to infants less than 32 gestational weeks, at high risk for intracerebral hemorrhage, can be easily assessed by pulsed Doppler technique. We report on our studies in these infants who were treated with the following drugs: diazepam (0.5 mg/kg BW i.v.), pethidine (1 mg/kg BW i.v.), pancuronium bromide (0.1 mg/kg BW i.v.), phenobarbitone (loading dose = 20 mg/kg BW, maintenance dose 5 mg/kg BW i.v.), theophylline (loading dose = 6 mg/kg BW, maintenance dose = 1.5 mg/kg BW i.v.) and bovine surfactant SF-RI 1 (50 mg/kg BW intratracheally). All studied drugs proved to be safe at the administered dosage with regard to their influence on cerebral hemodynamics in very immature infants.

Cerebrovascular Circulation↗
PubMed1991

[Analysis of hyaluronic acid in punctates in biochemical functional tests of joints].

The punctates of the biochemical joint function test contain hydroxyethyl starch which disturbs the assay of uronic acid and glucosamine for the estimation of hyaluronate. Therefore hyaluronate (0.03-0.75 g/l) was estimated by precipitation with Alcian blue on cellulose acetate membranes and measuring of the absorbance at 678 nm after dissolution in aqueous SDS (75 g/l). The gel-filtration HPLC separates the high-molecular-mass hyaluronate from low-molecular-mass impurities of biological samples. By comparing with a standard curve (0.5-2.5 g/l hyaluronate) the concentration can be determined. The results obtained by the two methods were significantly correlated (p less than 0.05). The Alcian blue technique is useful for rapid screening, the HPLC technique to confirm these values.

Cellulose↗
PubMed1990

Acoustic power measurements of Doppler ultrasound devices used for perinatal and infant examinations.

Acoustic power output levels were measured in four different pulsed Doppler systems (transcranial, Duplex mode, colour mode, miniature for continuous monitoring) currently used for examination of fetal and infant blood flow velocities. The frequencies of the transducers ranged from 2 to 8 MHz. The devices were studied at three to five different intensity settings. The measurements were performed using the radiation force balance of the Fraunhofer-Institut, which was especially adapted for this study. Each of the four devices was tested while running in its commonly used mode, and comparison showed that their acoustic power values varied widely: 96.8 mW (2 MHz, EME TC2-64B), 8.7 mW (5 MHz, ATL Mk 500), 61.9 mW (3.5 MHz, Acuson 128) and 13.5 mW (5 MHz, HP 77020). All transducers had total power output levels below the limits recommended by the American Institute for Ultrasound in Medicine and Biology in the conclusions on a thermal bioeffects mechanism, which were approved in October 1987.

Acoustics↗
PubMed1990

Dependency of Doppler parameters in the anterior cerebral artery on behavioural states in preterm and term neonates.

To investigate changes of intracerebral blood flow velocity correlated to different behavioural states, pulsed Doppler measurements were performed on anterior cerebral artery in 12 preterm and term neonates under polygraphic recordings and in view of the infants' behavioural state. Under very strict definition of the behavioural states there were significant differences in the parameters Vm (+25%), Vd (+75%), and Vs (+11%) in active compared to quiet sleep state. MABP was not significantly different in all examined behavioural states. From our results we conclude that in further Doppler studies the infants' behavioural state at the time of measurement should be assessed carefully.

Blood Circulation↗
PubMed1990

[Circulatory monitoring in very low birth weight infants using Doppler sonography].

Doppler-ultrasonography measures blood flow velocity, which is proportional to blood flow if the vessel's diameters remain constant. Perfusion of brain, kidneys and gut can thus be estimated by transcutaneous ultrasonography at specific locations on the internal-carotid artery, renal artery and upper mesenteric artery. Cardiac output can be derived from measurements taken on the ascending aorta. The procedures of measurement are easy to learn, but interpretation is more critical. Doppler-ultrasonography has been applied in persistent ductus arteriosus, asphyxia, hyperventilation, brain death, impact of drugs on brain circulation, seizures, hydrocephalus, and shock. Future aims are the development of miniaturized doppler-sensors with low energy output for continuous monitoring, and the definition of guidelines for clinical applications.

Blood Flow Velocity↗
PubMed1989

Species pattern of phosphatidic acid, diacylglycerol, CDP-diacylglycerol and phosphatidylglycerol synthesized de novo in rat liver mitochondria.

Rat liver mitochondria were incubated with [3H]glycerol 3-phosphate, ATP, CTP and coenzyme A allowing acylatin of glycerophosphate with endogenous fatty acids and the further conversion of labelled phosphatidic acid (PA) to diacylglycerol (DG), CDP-diacylglycerol (CDP-DG) and phosphatidylglycerol (PG). In these glycerolipids, the distribution of label among the individual molecular species was found to be similar, with 16:0-18:1, 16:0-18:2 and 18:0-18:2/16:0-16:0 being the main species. It was concluded that mitochondrial enzymes involved in the de novo synthesis of these glycerolipids exhibited no acyl selectivity for their substrates. The pattern of molecular species of mitochondrial PA, DG and CDP-DG closely approached that of the same glycerolipids synthesized de novo in isolated rat liver microsomes.

Animals↗
PubMed1989

The de novo synthesis of molecular species of phosphatidylinositol from endogenously labeled CDP diacylglycerol in alveolar macrophage microsomes.

The de novo synthesis of molecular species of phosphatidylinositol (PI) from endogenously labeled CDP diacylglycerol (CDP-DG) and phosphatidic acid (PA), with [14C]-glycerol 3-phosphate, in microsomes of macrophages was studied using a recently developed HPLC technique. Endogenously labeled PA, CDP-DG, and PI were sequentially formed from labeled glycerol 3-phosphate through the addition of CoA, CTP, and then inositol into microsomes. The rate of formation of CDP-DG from endogenously labeled PA was low as compared with those of PA and PI. The low rate of CDP-DG synthesis suggests that it may be the rate-limiting step in the de novo synthesis of PI. Analysis of newly synthesized molecular species of PI by HPLC revealed that large proportions of radioactivity were associated with the 16:0-18:1, 16:0-18:2, 18:1-18:2, and 18:2-18:2 species, and a small amount, 2-3%, of radioactivity was associated with the 18:0-20:4 species. The profiles of newly synthesized PA and CDP-DG species were quite similar to those of PI species. This suggests that the enzymes involved in the formation of PI species from glycerol 3-phosphate show little specificity toward different molecular species of substrates. The results of the present study also suggest that free fatty acid composition in microsomes greatly affect the composition of the molecular species of PI synthesized through the de novo pathway, since the proportion of fatty acids utilized for the de novo synthesis of PI species was similar to that of free fatty acids in the microsomal membrane.

Adenosine Triphosphate↗
PubMed1989

Acute and protracted effects of intratracheal surfactant application on internal carotid blood flow velocity, blood pressure and carbondioxide tension in very low birth weight infants.

As a part of a multicentre clinical trial of prophylactic treatment with bovine surfactant (SF-RI 1) given to immature infants below 31 gestational weeks, short term and protracted effects on cerebral haemodynamics were assessed by Dopplersonographic measurements of the right internal carotid artery. Measurements were performed every 10 min for 1 h after intratracheal application of the surfactant in ten treated infants. The results of additional measurements every 12 h up to the age of 100 h were compared with a control group. In single cases there were changes of time averaged mean maximum velocity (Vmax) of as much as 100% immediately after intratracheal surfactant application, although the mean short term and protracted variability of Vmax was the same as the protracted variability in the control group. Variability of mean arterial blood pressure and transcutaneous carbondioxide tension (tcpCO2) was even less. With proper adjustment of ventilatory settings intratracheal treatment with surfactant does not affect variability or absolute values of internal carotid Vmax, mean arterial blood pressure and transcutaneous pCO2 in low birth weight infants within 100 h after application.

Blood Flow Velocity↗
PubMed1989

[Materials properties of zinc phosphate cements after delayed setting on refrigerated slabs].

Two of the zinc phosphate cements commonly used in orthodontics were mixed, with special attention being paid to the longest possible working time, and examined by scientific methods. The results showed that mixing should generally be carried out on frozen slabs (-18 degrees C to -24 degrees C) and for not longer than 5 min. If a maximum compressive strength is required, mixing should be done at refrigerator temperature (+4 degrees C to +8 degrees C) for no more than 1.5 min by accepting a shorter working time. Neither cement shows any notable physicochemical differences, as regards the material.

Chemical Phenomena↗
PubMed1989

Influence of anesthetic induction with halothane and isoflurane on internal carotid blood flow velocity in early infancy.

In contrast to adult humans and animals, so far there are no studies in infancy on the effects of halothane and isoflurane on cerebral hemodynamics. We used transfontanellar Doppler ultrasonography to close this gap. In the study we looked at changes of Vmax as a measure of changes in cerebral blood flow. In 10 infants (4.7 +/- 1.0 kg BW) Vmax decreased 5 min after anesthetic induction with halothane 1.5% at 33%, and in a comparable group of 10 infants (5.3 +/- 1.2 kg BW) 5 min after anesthetic induction with an equipotential dose of isoflurane 2.5% at 28%. In 4 infants there was even a retrograde diastolic flow under anesthetic induction. This decrease was so far never seen in adults, in whom halothane increases cerebral blood flow and isoflurane has only little effect.

Aging↗
PubMed1989

[Neopterin--a prognostic marker in HIV infection].

28 HIV-infected persons (19 stadium II, 5 stadium III, 4 stadium IV) were investigated for CD4+ lymphocytes, HIV p24 core antigen and urinary neopterin. Monitoring the course of infection repeated estimations were done. Urinary neopterin was found elevated in 26 out of 28 infected people (p less than 0.001). There is an increase in urinary neopterin levels associated with clinical progression in the course of HIV-infection. An inverse correlation to CD4+ lymphocyte count exists. High levels of neopterin early indicate a clinical progression to disease, as well as a decrease of CD4+ lymphocytes below 0.4 or 0.2 Gpt/l, respectively, and a reappearance of HIV p24 core antigen. The course of 5 cases is presented. In HIV-infection urinary neopterin is a suitable marker of activity and progression.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Cerebral blood flow velocity assessed by Doppler technique after intravenous application of diazepam in very low birth weight infants.

Studies on the side effects of diazepam on the particularly vulnerable brain of preterm infants have not been done so far. We studied changes of blood flow velocity in the anterior, basilar and internal carotid artery by Doppler technique in 11 preterm infants less than 1,500 g who were given 0.5 mg/kg i.v. diazepam. The flow velocities in the internal carotid and basilar artery did not change significantly and values for carbon dioxide tension, mean arterial blood pressure and HF remained stable. There was a marked increase of flow velocity in the anterior cerebral artery. We conclude that diazepam in this dosage does not cause dangerous haemodynamic changes in the premature brain.

Blood Flow Velocity↗
PubMed1988

Species pattern of phosphatidylinositol from lung surfactant and a comparison of the species pattern of phosphatidylinositol and phosphatidylglycerol synthesized de novo in lung microsomal fractions.

1. Phosphatidylinositol (PI) is a minor component of lung surfactant which may be able to replace the functionally important phosphatidylglycerol (PG) [Beppu, Clements & Goerke (1983) J. Appl. Physiol. 55, 496-502] without disturbing lung function. The dipalmitoyl species is one of the main species for both PI (14.4%) and PG (16.9%). Besides the C16:0--C16:0 species, the C16:0--C18:0, C16:0--C18:1, C16:0--C18:2 and C18:0--C18:1 species showed comparable proportions in the PG and PI fractions. These similarities of the species patterns and the acidic character of both phospholipids could explain why surfactant PG may be replaced by PI. 2. PI and PG were radiolabelled by incubation of microsomal fractions with [14C]glycerol 3-phosphate (Gro3P). For 11 out of 14 molecular species of PI and PG we measured comparable proportions of radioactivity. The radioactivity of these 11 species accounted together for more than 80% of the total. The addition of inositol to the incubation system decreased the incorporation in vitro of Gro3P into PG and CDP-DG (diacylglycerol) of lung microsomes (microsomal fractions), but did not change the distribution of radioactivity among the molecular species of PG. These results supported the idea that both acidic surfactant phospholipids may be synthesized de novo from a common CDP-DG pool in lung microsomes.

Acylation↗
PubMed1988

Comparison of the HPLC-separated species patterns of phosphatidic acid, CDP-diacylglycerol and diacylglycerol synthesized de novo in rat liver microsomes (a new method).

The species pattern of phosphatidic acid was compared with that of CDP-diacylglycerol and diacylglycerol synthesized de novo by glycerol 3-phosphate acylation in a CoA ester-generating system in liver microsomes. The similarity of the species patterns of phosphatidic acid and CDP-diacylglycerol indicated that the CTP-phosphatidyl cytidylyltransferase showed no selectivity for individual species of its phosphatidic acid substrate. Since the species pattern of diacylglycerol deviated from that of phosphatidic acid, a slight acyl selectivity of the phosphatidic acid phosphohydrolase or a slight inhomogeneity of its substrate pool might be assumed. For the determination of the molecular species of CDP-diacylglycerol, a new method was developed. By incubation of CDP-diacylglycerol with oligonucleate 5'-nucleotidohydrolase (phosphodiesterase), phosphatidic acid was produced. The CDP-diacylglycerol-derived phosphatidic acid was methylated with diazomethane and then separated by reverse-phase HPLC in 15 molecular species.

Animals↗
PubMed1988

Molecular species of phosphatidylcholine and phosphatidylglycerol in rat lung surfactant and different pools of pneumocytes type II.

It is not yet completely understood how a cell is able to export specific phospholipids, like dipalmitoylphosphatidylcholine (dipalmitoyl-PC), which is secreted by pneumocytes type II, into pulmonary surfactant. The acyl species composition of [3H]PC which was synthesized in type II cells in the presence of [2-3H]glycerol resembled the species composition of PC localized in intracellular pneumocyte membranes. This species pattern was different from the pattern of PC of lamellar bodies, i.e., intracellularly stored surfactant, by a higher proportion of dipalmitoyl-PC mainly at expense of 1-palmitoyl-2-oleoyl-PC. Lamellar body PC in turn showed the same species distribution as surfactant PC. The data suggest that subcellular compartmentation and/or intracellular transfer of PC destined to storage in lamellar bodies, but not secretion of lamellar bodies, involves an enrichment of dipalmitoyl-PC and a depletion of 1-palmitoyl-2-oleoyl-PC. In contrast, the acyl species pattern of phosphatidylglycerol does not seem to undergo gross changes on the path from synthesis to secretion.

Animals↗
PubMed1988

Molecular species of mitochondrial phosphatidylcholine in rat liver and lung.

The acyl species of mitochondrial phosphatidylcholine from rat liver and lung were analysed by HPLC separation of the 1,2-diacyl-3-naphthylurethane derivatives. Comparison of phosphatidylcholine species patterns in microsomal, mitochondrial and submitochondrial fractions revealed only minor differences, whereas mitochondria from liver and lung differed markedly in the molecular composition of their respective phosphatidylcholine species.

Animals↗
PubMed1988

Comparative studies on the accessibility and functional importance of tyrosine residues in cytochrome P-450 isozymes.

Cytochromes P-450 LM2 and P-450 LM4 from rabbit liver microsomes were chemically modified with tetranitromethane. Nitration of two tyrosine residues of both isozymes inhibits the benzphetamine N-demethylase activity of P-450 LM2 as well as the p-nitrophenetole O-deethylase activity of P-450 LM4 by about 80%. For identification of the modified tyrosine residues the inactivated enzymes were digested with trypsin, and the labeled peptides were separated by HPLC. Sequencing of the 3-nitrotyrosine-containing peptides from cytochrome P-450 LM2 showed that the tyrosine residues at positions 235 and 380 were nearly fully nitrated, while Tyr-348, Tyr-484 and Tyr-111 were only partially labeled (about 40-50%). In the presence of the heme-binding inhibitor metyrapone, Tyr-380 is partially protected against modification, and the extent of inactivation is diminished as well. These results suggest that Tyr-380 of cytochrome P-450 LM2 presents a catalytically essential amino acid residue at its active center. Sequence analyses of the 3-nitrotyrosine-containing peptides from cytochrome P-450 LM4 revealed that mainly Tyr-243 and Tyr-271 were labeled, whereas Tyr-71, Tyr-188 and Tyr-365 are modified to a lower extent (about 30-45%). Tyr-243 and Tyr-271 of cytochrome P-450 LM4 are suggested to be functionally involved in the interaction with NADPH-cytochrome P-450-reductase.

Amino Acid Sequence↗