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Biomedical subjects

R Janzen

Publications and source records attributed to R Janzen.

At least 19 recordsLinked to original sources
PubMed1998

[The effect of endothelin on granulocyte-endothelium interaction].

PURPOSE: The interaction of activated granulocytes and endothelial cells influences not only capillary permeability but also increases pulmonary vascular resistance. The aim of this study was to evaluate the role of endothelin-1 (ET-1) during the granulocyte-mediated increase in pulmonary pressure. METHODS: The experiments were performed on isolated and ventilated rabbit lungs perfused with a blood-free buffer solution. Isolated, washed human granulocytes were injected into the pulmonary artery and stimulated by 10(-6) M N-formyl-L-leucin-methionyl-L-phenylalanine (FMLP). Pulmonary arterial pressure (PAP) was continuously registered, and perfusate samples were taken to determine ET-1 and eicosanoid levels. To analyse the role of ET-1, six lung preparations were pretreated with the ETA receptor antagonist BQ123 (10(-6) M) prior to FMLP injection. To analyse the role of thromboxane A2, six additional lung preparations were pretreated with the cyclooxygenase inhibitor diclofenac (10 micrograms/ml). Additionally, granulocytes were stimulated in vitro with FMLP for 15 min, and ET-1 concentration was measured in the supernatant. RESULTS: Immediately after FMLP injection, PAP increased to 18.5 +/- 1.6 mmHg, descending to values 4.8 +/- 0.8 mmHg above the baseline after 15 min. At this time, ET-1 could be detected in the perfusate. The concentrations of the cyclooxygenase products thromboxane A2 and prostacyclin remained nearly unchanged during the observation period. Pretreatment with the ETA receptor antagonist BQ123 significantly reduced the pressure response after FMLP injection (p < 0.01 at 5 and 10 min; p < 0.05 at 15 and 30 min). Pretreatment with the cycloocygenase inhibitor diclofenac failed to inhibit the pressure reaction evoked by activated granulocytes. In contrast to this, ET-1 was not detected after in vitro stimulation of granulocytes. CONCLUSION: ET-1 is involved as a mediator of pulmonary vasoconstriction due to granulocyte activation. Since in vitro FMLP-stimulation of human granulocytes did not induce ET-1 production, it seems likely that isolated activated granulocytes would not produce ET-1, but provoke the endothelial cells to release ET-1 in the pulmonary circulation.

Animals↗
PubMed1998

Endothelin-1 and thromboxane A2 increase pulmonary vascular resistance in granulocyte-mediated lung injury.

OBJECTIVE: To examine the pathophysiologic role of vasoactive eicosanoids and endothelin-1 in granulocyte-mediated effects in the pulmonary vasculature. DESIGN: Prospective experimental study in rabbits. SETTING: Experimental laboratory in a university teaching hospital. SUBJECTS: Thirty adult rabbits. INTERVENTIONS: The experiments were performed on 30 isolated and ventilated rabbit lungs that were perfused with a cell- and plasma-free buffer solution. MEASUREMENTS AND MAIN RESULTS: The pulmonary arterial pressure and the lung weight gain were continuously registered. Intermittently perfused samples were taken to determine endothelin-1 and thromboxane A2 concentrations. Six experiments without intervention served as the sham group. The granulocytes in the pulmonary circulation were stimulated with N-formyl-L-leucin-methionyl-L-phenylalanine (FMLP; 10(-6) M; control, n = 6). To investigate whether activated granulocytes influence the pulmonary vasculature via endothelin-1, the endothelin-A receptor antagonist LU135252 (10(-6) M) was added to the perfusate before FMLP injection (n = 6). The potential involvement of thromboxane A2 in granulocyte-endothelial interaction was investigated by pretreatment with the cyclooxygenase inhibitor diclofenac (10 microg/mL; n = 6). Activation of granulocytes resulted in an acute increase in pulmonary arterial pressure (>9 mm Hg), which was followed by a second delayed pressure increase after 60 mins (>14 mm Hg) and was paralleled by a massive generation of thromboxane A2 (>250 pg/ mL). Fifteen minutes after FMLP-injection, endothelin-1 was detectable in the perfusate. Pretreatment with the selective endothelin-A antagonist LU135252 significantly (p< .01) reduced the initial pressure response after FMLP stimulation, while diclofenac significantly reduced (p < .05) the delayed pressure increase. Using diclofenac (10 microg/mL) in conjunction with LU135252 (10(-6) M; n = 6) before FMLP injection significantly reduced the early and the delayed pressure increase. CONCLUSIONS: Activated granulocytes seem to enhance pulmonary vascular resistance via endothelin-1 and thromboxane A2. The endothelin-1 effects are probably mediated via endothelin-A receptors since the endothelin-A receptor antagonist LU135252 was able to suppress the early pressure reaction after FMLP injection, whereas the cyclooxygenase inhibitor diclofenac was able to reduce the second pressure increase.

6-Ketoprostaglandin F1 alpha↗
PubMed1993

On the guidance of regenerating axons from a half-retina in the adult goldfish.

We have examined the guidance of regenerating optic axons from half-retinal fragments in the goldfish. Axons regenerating from a dorsal, ventral, or nasal half-retina showed no bias to grow through the retinotopically appropriate parts of the optic tract. By contrast, axons from a temporal half-retina did show a bias, albeit a small one, to grow through the correct part of the tract. In addition, we found evidence that axons from the temporal quadrant of dorsal or ventral half-retinas showed a similar bias. In the optic tectum, axons regenerating from a dorsal, ventral, or temporal half-retina showed strong biases to invade the retinotopically appropriate portion of the synaptic field. Of these three, temporal axons showed the sharpest restriction in their field of innervation. Nasal fibers were unique in that they invaded the entire tectum with little evidence of a preference for their appropriate field. Our results indicate that there is minimal guidance offered to regenerating optic axons in the optic tract. However, once dorsal, ventral, or temporal axons reach the tectum they appear to encounter strong organizing forces which constrain them to preferentially invade their retinotopically appropriate areas. Nasal axons appear to be exempt from these forces. In both the optic tract and tectum, axons from a temporal half-retina are the most effectively guided and constrained.

Animals↗
PubMed1990

[Mixed venous versus central venous oxygen saturation in intensive medicine].

Mixed venous oxygen saturation (SvO2) has been established as a useful guide in observing whole body oxygenation. Since SvO2 provides limited information about adequate tissue oxygenation for a specific organ, the usefulness of central venous saturation (ScvO2) as a guide was analysed, which is a less invasive parameter. In 19 ICU patients 44 pairs of blood samples were drawn from a separate central venous catheter and from the tip of an SG-catheter. The correlation of oxygen partial pressures was 0.687 and the correlation of the saturation reached 0.779. The calculation of venous admixture showed a correlation of 0.901. It is concluded that ScvO2 yields adequate information on the oxygen saturation of venous return.

Catheterization, Central Venous↗
PubMed1987

Evaluation of advanced silica packings for the separation of biopolymers by high-performance liquid chromatography. III. Retention and selectivity of proteins and peptides in gradient elution on non-porous monodisperse 1.5-microns reversed-phase silicas.

Following previous studies of the use of non-porous monodisperse 1.5-microns n-octyl- and n-octadecyl-bonded silicas in gradient elution of proteins, this work was aimed at elucidating further the properties of this novel column material for peptide and protein separations in comparison with wide-pore silicas. First, it is demonstrated that with short columns (e.g., 35 X 8 mm I.D.) packed with these non-porous reversed-phase materials, mixtures of small peptides and mixtures of proteins can be very efficiently resolved. When the chain length of the bonded ligand was varied, the retention of a test set of proteins in gradient elution followed the ligand sequence C18 greater than C8 approximately C4 approximately phenyl greater than C2 under constant elution conditions, and the selectivity remained unchanged. Comparison of the S values of these proteins, as determined from evaluation of the log k' vs. phi dependences with non-porous silicas and with a LiChrospher Si 1000 C8 with identical accessible ligand surface areas per unit column volume, indicated lower values for the non-porous materials (k' = capacity factor; phi = molar fraction of organic solvent; S = slope of the plot of log k' vs. phi). The origin of this behaviour is discussed.

Caseins↗
PubMed1987

Evaluation of advanced silica packings for the separation of biopolymers by high-performance liquid chromatography. IV. Mobile phase and surface-mediated effects on recovery of native proteins in gradient elution on non-porous, monodisperse 1.5-microns reversed-phase silicas.

The reversed-phase chromatography of proteins by gradient elution with acidic, low-ionic-strength aqueous-organic eluents is often associated with losses of the biological activity of the protein. In this study, the enzymatic activities of catalase, horseradish peroxidase and pepsin were examined under static and dynamic column conditions on non-porous, monodisperse 1.5-microns reversed-phase silicas with various n-alkyl ligands. Catalase readily lost its enzymatic activity under the influence of the acidic aqueous-organic eluents in the absence of the reversed-phase packing, whereas peroxidase was partially deactivated as a result of combined mobile phase and stationary phase effects but regained its activity on storage after elution. The enzymatic activity of pepsin was found to be very dependent on the column residence time and on the type of bonded n-alkyl ligand employed.

Catalase↗
PubMed1987

Evaluation of advanced silica packings for the separation of biopolymers by high-performance liquid chromatography. V. Performance of non-porous monodisperse 1.5-microns bonded silicas in the separation of proteins by hydrophobic-interaction chromatography.

Non-porous monodisperse 1.5-microns silicas were allowed to react with (A) and (B) N-acetylaminopropyltriethoxysilane to generate bonded phases useful in high-performance hydrophobic-interaction chromatography (HIC). Differences in the selectivity were observed between the amide and the ether phase. Peak capacities between 10 and 30 were achieved for several proteins with the amide and ether phase packed into columns of 36 X 8 mm I.D. and elution of the proteins under chromatographic conditions in which the gradient volume, VG, was held constant by varying the gradient time between 20 and 2.5 min and the flow-rate between 0.5 and 4.0 ml/min. The S values derived from the dependences of log k' on the volume fraction of the low ionic strength buffer, phi b, were of the same magnitude as reported for porous HIC silicas and showed a dependence on the molecular weight of the protein. Using these HIC stationary phases based on non-porous 1.5-microns supports, fast separations (less than 5 min) could be carried out with high biological recoveries.

Ammonium Sulfate↗
PubMed1987

The acute phase response to inflammation: the role of monokines in changes in liver glycoproteins and enzymes of glycoprotein metabolism.

The role of monocyte derived factors in the acute phase response to inflammation is discussed. The kinetics of response of alpha 1-acid glycoprotein, sialyltransferase and albumin to a rat monokine preparation is described. There was an increase in synthesis of alpha 1-acid glycoprotein and sialyltransferase and a decrease in albumin synthesis following administration. However, the kinetics of response of sialyltransferase to the monokine was much slower than was found for the other two proteins. The possibility that sialyltransferase responds to a different monokine compared to the other acute phase proteins is discussed.

Acute-Phase Reaction↗
PubMed1987

Studies on the effect of inflammation on the acute phase response using rat liver slices.

Liver slices from control and inflamed rats were incubated in McCoy's medium and incorporation of [3H]leucine into liver and medium proteins and into albumin and alpha 1-acid glycoprotein was monitored over 48 hr. The release of the new acute phase reactant, sialyltransferase was also monitored in this system. Earlier observations in which liver slices were incubated for 6 hr showed that increased leucine incorporation into liver and medium proteins and alpha 1-acid glycoprotein, coupled with decreased incorporation into albumin, correlated with the acute phase response of these proteins. Increased incorporation of leucine into these proteins was found following 48 hr incubation in McCoy's medium showing that slices were able to express the changes characteristic of the acute phase response over this longer time period of incubation. Sialyltransferase was released into medium in a linear fashion up to 15 hr and continued to increase for 30 hr in this system; there was a substantial increase in release of enzyme activity from slices from inflamed rats when compared to controls. Monokine-conditioned medium prepared from peritoneal exudate cells isolated from rats at various times after lipopolysaccharide administration was used to induce the acute phase response by intraperitoneal injection. Slices were prepared from these rats and sialyltransferase release from slices was monitored. Monokines prepared from peritoneal exudate cells isolated from rats at about 30 hr were most effective in stimulating sialyltransferase release from liver slices.

Acute-Phase Reaction↗
PubMed1986

Packings and stationary phases in preparative column liquid chromatography.

Although the theoretical treatment of chromatographic processes on a preparative scale provides guidelines to the extent to which packing and stationary phase properties affect the target quantities such as sample input, throughput and resolution times sample input, a series of additional criteria were established to judge the quality of a packing in preparative column liquid chromatography. These include bed stability and flow resistance, chemical resistance and purity, solute accessibility, mass and biological recovery, fouling, regeneration and cost. Applying these criteria, the relative importance of physical and chemical structure parameters of packings and stationary phases was assessed. Commercial packings with mean particle diameters dp greater than 20 micron were listed for adsorption, size exclusion, ion-exchange and affinity chromatography. An analysis of the characteristic features of phase systems showed that adsorption media offer a high selectivity combined with adequate loadability, whereas ion exchangers and affinity media were best suited for biospecific solutes, particularly biopolymers, which can be attributed to their high selectivity and loadability.

Chemical Phenomena↗
PubMed1982

The patterns of protein synthesis during foetal and neonatal organ development in the mouse are remarkably similar.

The extent to which differential gene expressions can be correlated with organ development was examined at the level of protein synthesis during pre- and postnatal development in the mouse. High resolution, equilibrium, two-dimensional polyacrylamide gel electrophoresis detected, for each of five to ten successive stages for each of seven organ systems, between 850 and 1000 separate newly synthesized proteins. The possibility that the 1000 detectable proteins synthesized at any one time during organ development represent a sampling bias was contra-indicated (a) because a different and larger population of [14C]amino acid-incorporating protein syntheses gave similar results and (b) because nonequilibrium isoelectric focusing, electrophoresis, isoelectric points between pH 5.5 and 8.7 confirmed the results from yet a different population of protein syntheses. Within limits of the sampling of protein syntheses, the entire period of organ development examined proceeds with altered expression of small proportion of the total proteins being synthesized. While all protein changes were stage specific, approximately three organ-specific protein syntheses were detected per organ system. One family of five protein syntheses seen in 16-day foetuses had homologous primary structures and presumably are keratins derived from a single genomic expression. These selected stage-specific protein syntheses examined by electrophoresis of partial proteolytic digests disclosed a programme for post-translational changes in protein syntheses. The current observations indicate that the examined pre- and postnatal organ development of the seven organs occurs in the presence of greater than 99% similarity among proteins synthesized in the same and different organ systems. Functional differentiation during organogenesis, therefore, occurs in the presence of less than 1% change in qualitative or quantitative switch in protein syntheses. Evidence is presented to indicate that even this remarkably small number of changes in protein syntheses during functional organ differentiation may be derived from an even smaller subset of gene expressions. Collectively, the data suggest that explanatory mechanisms for molecular organogenesis must encompass both selective gene expressions along with post-translational programmed events.

Amino Acids↗
PubMed1979

[Neurological cardinal symptoms of internal diseases (author's transl)].

The old rule:"Frequent is frequent, Seldom is seldom" is only true of etiological entities. With symptoms and syndromes which are hastily diagnosed as "typical" or "atypical" just because they are frequent, serious misdiagnoses may occur and critical details both in the history and in the physical examination may be overlooked. The terminal reaction of the body, i. e. the phenomenological entities are a principium cognoscendi for the doctor as for the patient they are principium agendi which send him to the doctor. The task of the neurologist is to set out the neurological cardinal and warning symptoms as signposts for a satisfactory internist investigation and to a jointly controlled therapy.

Brain Diseases↗