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Biomedical subjects

J Greve

Publications and source records attributed to J Greve.

At least 109 records · Page 6Linked to original sources
PubMed1989

Skin blood flow changes during apneic spells in preterm infants.

Changes in skin blood flow during apneic spells were determined in 18 preterm infants using a diode laser Doppler flow meter without light conducting fibres. Heart rate, nasal air flow, impedance pneumography, skin and incubator temperature and laser Doppler skin blood flow were recorded simultaneously in each infant. During 212 apneic spells with a duration of 11.6 +/- 7.5 s (mean +/- S.D.) (range 6.0-48.0 s), the laser Doppler skin blood flow was measured. In all children except one, the majority of the apneic spells was associated with a decrease in skin blood flow. During 155 apneic spells (73%) skin blood flow decreased significantly P less than 0.025), the maximum decrease being 16.7 +/- 14.8%, 28.5 +/- 23.9% and 18.9 +/- 16.1% (mean +/- S.D.) for central, obstructive and mixed apneic spells, respectively. The decrease in skin blood flow started immediately after the beginning of apneic spells in 71%, the rest started with a mean delay of 3.4 s (range 0.1-7.0 s). No relation was found between the decrease in skin blood flow and the duration of the apneic spells. Thirty-four percent of the apneic spells were accompanied by bradycardia. In apneic spells accompanied by bradycardia the decrease in skin blood flow was not related to the fall in heart rate.

Blood Flow Velocity↗
PubMed1989

Postocclusive reactive hyperaemia of cutaneous blood flow in premature newborn infants.

Reactive hyperaemia, which occurs after a period of arterial occlusion is the result of an autoregulatory mechanism, involving local factors and autonomic nerve system control. To determine this autoregulatory mechanism in cutaneous blood flow in premature newborns measured the cutaneous reactive hyperaemia response after a 1 min occlusion, using a diode laser Doppler flowmeter applied to the skin. Twenty-four infants with a gestational age ranging from 25 to 37 weeks and a postnatal age of 0.3 to 72 days were studied. The reactive hyperaemia response is described by the parameters maximal cutaneous blood flow (Vmax), the time to reach maximal flow (tmax), the time taken for blood flow to return to baseline following Vmax (t(end)) and the % increase in cutaneous blood flow above preocclusional level (overshoot). A cutaneous reactive hyperaemia response could be elicited in all infants. Following occlusion the Vmax was 2,640 +/- 1,050 mV (mean +/- SD), the tmax was 7.6 +/- 3.9 sec (mean +/- SD), the t(end) was 35.6 +/- 14.6 sec (mean +/- SD) and the overshoot was 74.6 +/- 34% (mean +/- SD). A negative correlation was found between hematocrit and tmax (r = -0.62, p less than 0.01). No influence of postconceptional age, postnatal age, skin and rectal temperature, incubator temperature, weight, and transcutaneous oxygen tension on the reactive hyperaemia parameters could be found. We conclude that reactive hyperaemia of cutaneous blood flow can be elicited in premature newborn infants irrespective of postconceptional age, and that the hematocrit is inversely related to the time to reach maximal flow after occlusion.

Age Factors↗
PubMed1988

Four-parameter white blood cell differential counting based on light scattering measurements.

Measurement of the depolarized orthogonal light scattering in flow cytometry enables one to discriminate human eosinophilic granulocytes from neutrophilic granulocytes. We use this method to perform a four-parameter differential white blood cell analysis. A simple flow cytometer was built equipped with a 5-mW helium neon laser that measures simultaneously four light scattering parameters. Lymphocytes, monocytes, and granulocytes were identified by simultaneously measuring the light scattering intensity at angles between 1.0 degrees and 2.6 degrees and angles between 3.0 degrees and 11.0 degrees. Eosinophilic granulocytes were distinguished from neutrophilic granulocytes by simultaneous measurement of the orthogonal and depolarized orthogonal light scattering. Comparison of a white blood cell differentiation of 45 donors obtained by the Technicon H-6000 and our instrument revealed good correlations. The correlation coefficients (r2) found were: 0.99 for lymphocytes, 0.76 for monocytes, 0.99 for neutrophilic granulocytes, and 0.98 for eosinophilic granulocytes. The results demonstrate that reliable white blood cell differentiation of the four most clinically relevant leukocytes can be obtained by measurement of light scattering properties of unstained leukocytes.

Basophils↗
PubMed1988

Application of orthogonal light scattering for routine screening of lymphocyte samples.

Orthogonal and forward light-scattering properties of lymphocytes were measured from patients with different lymphocytic diseases in order to determine the potential value of light scattering as a screening device. Monitoring of orthogonal light scattering of lymphocytes of a B-cell chronic lymphocytic leukemia patient during splenic irradiation (SI) revealed the selective decrease of malignant cells and the fact that the major part of the residual lymphocytes were cytotoxic lymphocytes. By combining forward and orthogonal light scattering it was shown that lymphocytes from a patient with T gamma lymphocytosis were abnormal. Orthogonal light scattering also showed an increase in cytotoxic lymphocytes in a patient with mononucleosis infectiosa and in a splenectomized patient. Orthogonal light scattering of lymphocyte subpopulations showed that the leu8+ population of a patient with mononucleosis infectiosa was bidisperse. For elderly donors the occurrence of CD3+, CD4+, CD8+, and HNK-1+ lymphocytes with a large orthogonal light scattering varied considerably. The CD8+ lymphocytes of these donors consisted mainly of cytotoxic lymphocytes. These results show that determination of light-scattering properties of lymphocytes may yield important diagnostic information and can indicate when further investigation of the lymphocytes by means of immunofluorescence is necessary.

Adolescent↗
PubMed1988

Flow cytometric characterization of chronic lymphocyte leukaemias using orthogonal light scattering and quantitative immunofluorescence.

Light scattering properties and antigen distribution of lymphocytes labeled with the monoclonal antibodies CD 5 and CD 20 were determined for 19 patients with a chronic B-cell derived leukaemia. The density of the antigen detected by the monoclonal antibody CD 5 appeared to be considerably lower on malignant B-lymphocytes of the patients as compared with T lymphocytes. A large variation was observed in the amount of receptors for the monoclonal antibodies CD 5 and CD 20 on the malignant cells of the different patients. B-cell chronic lymphocytic leukaemia (B-CLL) patients were clearly distinguishable from leukaemic follicular non Hodgkin lymphoma patients (LF-NHL, formerly lymphosarcoma cell leukaemia) and from a patient with a prolymphocytoid transformation (PLT) of the B-CLL according to the amount of the antigens for CD 5 and CD 20. Within the B-CLL patient population, no relation of progression of the disease with distribution of these antigens could be observed. In one patient the extraordinary phenotype CD 20+, CD 11+, leu 8+, CD 5- of the malignant lymphocytes was observed. An experimentally simple method to differentiate between the various chronic lymphocytic leukaemias (CLL) appeared to be the determination of orthogonal light scattering properties of lymphocytes. In healthy donors one can always distinguish two populations of lymphocytes in the orthogonal light scatter histograms. Lymphocytes of B-CLL patients show one uniform population with a relatively small orthogonal light scattering signal, lymphocytes of our patients with PLT of B-CLL or with LF-NHL show one uniform population with a relatively large orthogonal light scattering signal.

Antibodies, Monoclonal↗
PubMed1988

Abnormal distribution of CD8 subpopulation in B-chronic lymphocytic leukemia identified by flow cytometry.

We studied the occurrence of T-cell subpopulations for patients with B-cell chronic lymphocytic leukemia. The CD8+ population was divided into CD8+ suppressor (CD8a+) and CD8+ cytotoxic (CD8b+) lymphocytes using difference in orthogonal light scattering. Average CD4+/CD8+ ratios determined for all patients were decreased. For individual patients this sometimes was not true. In contrast CD4+/CD8a+ ratios were markedly increased in all individual patients. The CD8+ lymphocytes appeared to consist mainly of CD8b+ lymphocytes. Moreover the CD8b+/CD8+ ratio correlated with clinical stage: untreated patients (stage 0 of Rai) have smaller CD8b+/CD8+ ratios than patients with advanced stages of Rai.

Adult↗
PubMed1988

Resonance Raman spectroscopy of complexes of the helix destabilizing proteins GP32 and GP5 with poly(rA) and poly(dA).

The bacteriophage T4 helix destabilizing protein (hdp) gp32 and its complexes with poly(rA) and poly(dA) were studied with ultra-violet resonant Raman spectroscopy. The UV-resonant Raman (UV-RR) spectrum of the complex of gp5, the coat protein of bacteriophage M13, with poly(dA) was also measured and is compared with the spectrum of the gp 32/poly(dA) complex. The excitation wavelength was 245.1 nm. This is on the far UV-side of the first absorption bands of adenine and near a "window" in the protein absorption spectrum. The overlap of fluorescence due to chromophores present in the protein and resonance Raman scattering was prevented by this choice of wavelength. The spectra of the protein/polynucleotide complexes are compared with the native nucleotide spectra measured at varying temperatures. The hyperchromicity which is expected when a nucleotide changes from a stacked to an unstacked conformation was not observed for poly(rA), neither upon temperature increase nor on protein binding. In both cases poly(dA) revealed a clear hyperchromicity. This different behavior of poly(rA) and poly(dA) is probably a consequence of their different conformations. The contributions of the proteins to the spectra is weak except for two bands, at 1550 and 1610 cm-1 due to tryptophan (in case of gp32) and one band near 1610 cm-1 due to tyrosine and phenylalanine.

Chemical Phenomena↗
PubMed1988

The effects of splenic irradiation on lymphocyte subpopulations in chronic B-lymphocytic leukemia.

We describe the effect of splenic irradiation (SI) (0.5-1 Gy weekly) on lymphocyte subpopulations for 7 patients with progressive B chronic B-lymphocytic leukemia (B-CLL). Using specific cellular characteristics we could distinguish normal from abnormal cells. The irradiation resulted in a decrease of lymph node size, reduction in spleen volume and decrease in peripheral blood lymphocytes. The one exception was a patient with a prolymphocytoid transformation of B-CLL. For 3 patients SI had to be interrupted or stopped because of severe cytopenia. Quantitation of malignant B cells and normal T lymphocytes revealed that the total irradiation dose which resulted in a specific decrease of malignant lymphocytes varied from patient to patient. Normal T-cell subpopulations, which were increased before SI, decreased to normal or abnormally low values during SI. In previously untreated patients, natural killer (NK) cell numbers decreased more rapidly than T-cell subpopulations. For 2 patients refractory to chemotherapy an increase of NK cells was observed upon SI.

Antigens, Differentiation↗
PubMed1988

Forehead skin blood flow in normal neonates during active and quiet sleep, measured with a diode laser Doppler instrument.

Changes in forehead skin blood flow during active and quiet sleep were determined in 16 healthy neonates using a recently developed semi-conductor laser Doppler flow meter with-out light conducting fibres. Measurements were carried out at a postnatal age varying from 5 hours to 7 days. The two sleep states could be distinguished in 17 recordings. The mean skin blood flow values during active sleep were significantly higher (p less than 0.01) than those during quiet sleep, the mean increase being 28.1%. The variability of the flow signal, expressed as the coefficient of variation, changed significantly from 23.1% during active sleep to 18.2% during quiet sleep.

Forehead↗
PubMed1988

Effect of single and repeated intravenous doses of omeprazole on pentagastrin stimulated gastric acid secretion and pharmacokinetics in man.

Single intravenous doses of 10, 20, 40, and 80 mg and repeated once daily intravenous doses of 10 and 20 mg omeprazole induced a powerful and long lasting inhibition of pentagastrin stimulated gastric acid secretion (PAO) in healthy male volunteers. Single intravenous doses of 10, 20, 40, and 80 mg omeprazole inhibited PAO by 30% (p less than 0.01), 45% (p less than 0.01), 61% (p less than 0.01), and 80% (p less than 0.01), respectively when measured 1.5 h after dose, and by 20% (NS), 27% (NS), 36% (p less than 0.01) and 59% (p less than 0.01), respectively when measured 24 h after dose. Six days after repeated once daily intravenous doses of 10 and 20 mg omeprazole, PAO was inhibited by 63% (p less than 0.01) and 82% (p less than 0.01), respectively when measured 1.5 h after dose, and by 32% (p less than 0.01) and 43% (p less than 0.01), respectively when measured 24 h after dose. The inhibition of PAO by 10 mg administered intravenously as a single bolus injection was comparable with the inhibition by 20 mg as a single oral dose. Repeated once daily administration of 10 mg intravenously and 20 mg orally also resulted in comparable reductions in PAO. The reduction in PAO after repeated once daily oral administration of 20 mg was comparable with the effect of a single intravenous dose of 40 mg. Terminal half lives were short, but significantly (p less than 0.05) prolonged after a single intravenous injection of 80 mg. Repeated once daily intravenous administration of 10 and 20 mg did not result in prolongation of terminal half lives. It is concluded that intravenous administration of omeprazole causes a potent and long acting inhibition of pentagastrin stimulated gastric acid secretion in man. Its potency is augmented after repeated once daily administration.

Adult↗
PubMed1987

A Raman scattering study of the helix-destabilizing gene-5 protein with adenine-containing nucleotides.

Raman spectra of gp5 and complexes of gp5 with poly(rA) and poly(dA) have been determined and analysed. From a fit of the amide I-band with model spectra it follows that the secondary structure of gp5 contains 52% beta-sheet, 28% undefined conformation and 19% alpha-helix. The band at 1032 cm-1 due to phenylalanine has an anomalous intensity both in the spectra of the complexes and the free protein. This possibly indicates a stacked structure present in the protein. Binding of gp5 to poly(rA) and poly(dA) influences the intensity of bands near 1338 and 1480 cm-1 which are considered to be marker-bands for the phosphate-sugar-base conformer. A change in conformation of the nucleotides is also reflected by vibrations originating in the phosphate- and sugar-residues of the backbone. In the spectrum of complexed poly(rA) the intensity of the conformation sensitive band at 813 cm-1, which is due to the phosphodiester group, is zero. It seems that gp5 forces poly(rA) and poly(dA) to a similar conformation. A marker band for stacking interaction in poly(rA) indicates that stacking interactions in the complex have increased.

Coliphages↗
PubMed1987

Multiple wavelength illumination in flow cytometry using a single arc lamp and a dispersing element.

The principle of a multiple wavelength illumination method for flow cytometers, based upon a combination of a helium-neon laser and an arc lamp as illumination sources is described. By using a prism, the light from the arc lamp is dispersed and the different colors are imaged at different places on the sample stream. The small angle light scattering from the helium-neon laser light is measured as a relevant parameter and serves as a trigger signal for subsequent measurements of fluorescence or scattering of light from the arc lamp. Two experimental systems are described utilizing this principle: a system where the emission is detected orthogonally with respect to the direction of the illumination beams, and an epi-illumination system. With the orthogonal set-up multiple wave-length right angle scattering measurements are possible. This is illustrated by showing that the orthogonal scattering from erythrocytes is strongly dependent on the illumination wavelength. It is further shown that the apparatus is suitable for the measurement of intracellular pH using the pH dependence of the excitation spectrum of fluorescein. The epi-illumination system allows excitation of two (or more) fluorescent dyes with different excitation spectra. In this case the emission spectra of the fluorescent dyes may overlap substantially. This is shown by simultaneous measurement of DNA and protein of Chinese hamster lung cells using mitramycin and tetramethyl rhodamin isothiocyanate (TRITC).

DNA↗
PubMed1987

Light-scattering polarization measurements as a new parameter in flow cytometry.

Polarization measurement of orthogonal light scattering is introduced as a new optical parameter in flow cytometry. In the experimental setup, the electrical field of the incident laser beam is polarized in the direction of the sample flow. The intensity of the orthogonal light scattering polarized along the direction of the incoming laser beam is called depolarized orthogonal light scattering. Theoretical analysis shows that for small values of the detection aperture, the measured depolarization is caused by anisotropic cell structures and multiple scattering processes inside the cell. Measurements of the orthogonal depolarized light scattering in combination with the normal orthogonal light scattering of human leucocytes revealed two populations of granulocytes. By means of cell sorting it was shown that the granulocytes with a relatively high depolarization are eosinophilic granulocytes. Similar experiments with human lymphocytes revealed a minor subpopulation of yet-unidentified lymphocytes with a relative large orthogonal light-scattering depolarization. The results were obtained with an argon ion laser tuned at different wavelengths as well as with a 630-nm helium neon laser. These results show that measurement of depolarized orthogonal light scattering is a useful new parameter for flow-cytometric cell differentiation.

Blood Cells↗
PubMed1986

Discrimination of human cytotoxic lymphocytes from regulatory and B-lymphocytes by orthogonal light scattering.

Light scattering properties of human lymphocyte subpopulations selected by immunofluorescence were studied with a flow cytometer. Regulatory and B-lymphocytes showed a low orthogonal light scatter signal, whereas cytotoxic lymphocytes identified with leu-7, leu-11 and leu-15 revealed a large orthogonal light scatter signal. Two populations in light scatter histograms could be observed with monoclonal antibodies directed against determinants present on both regulatory and cytotoxic lymphocytes. By analysis of the lymphocytes of 16 individuals we found a linear relation between the number of cells with a large orthogonal light scattering and the number of cytotoxic lymphocytes identified with leu-7, leu-11 and leu-15. These observations demonstrate physical differences between cytotoxic lymphocytes and regulatory and B lymphocytes. Moreover, the results suggest a method to estimate the amount of cytotoxic lymphocytes without using monoclonal antibodies.

B-Lymphocytes↗
PubMed1986

Physical discrimination between human T-lymphocyte subpopulations by means of light scattering, revealing two populations of T8-positive cells.

Light-scattering properties of human T-lymphocyte subpopulations selected by immunofluorescence were studied. Based on differences in orthogonal light scattering, two subpopulations of T8-positive cells can be distinguished. The first population (T8a) has the same orthogonal light-scattering properties as T4-positive cells, whereas the orthogonal light scattering of the second population (T8b) was about 70% larger. Orthogonal light scattering of Leu7-positive lymphocytes resembles that of the T8b population. We have studied the occurrence of the subpopulation in healthy individuals and we discuss their possible functional identification. Light-scattering properties of lymphocyte subpopulations in two patients with B-cell chronic lymphatic leukemia suggest that this observation is of clinical interest.

Antibodies, Monoclonal↗
PubMed1986

Micro-Raman line broadening in synthetic carbonated hydroxyapatite.

Using a Raman microspectrometer, we have recorded Raman spectra of synthetically produced hydroxyapatite samples with varying carbonate contents. The apatites were produced from aqueous solutions at about 40 degrees C. From line-broadening values of the symmetric phosphate stretch, it was concluded that the carbonate substitution in these lattices has a maximum of 4.5 wt %. Both phosphate and hydroxyl ions seem to be involved in the carbonate substitution process.

Carbonates↗