Search PubMed⌕ Search

Biomedical subjects

H Walter

Publications and source records attributed to H Walter.

At least 19 recordsLinked to original sources
PubMed1992

Erythrocyte partitioning in dextran-poly(ethylene glycol) aqueous phase systems. Events in phase and cell separation.

Early events in the partitioning process which involve characteristic kinetics of cell- and phase-specific interactions and phase separation have been described previously. This paper reports on red cell-phase droplet interactions pertaining at the time of usual phase sampling (i.e., the time at which a clear bulk interface is first apparent) and beyond in cell partitioning and countercurrent distribution experiments. In non-charge-sensitive phase systems close to the critical point, cells can be free or attached to phase droplets. Cells that are free are virtually completely in the top phase, whereas different cell populations that show essentially complete binding to droplets can nevertheless have different partition ratios and be separated, thus reflecting the effects of the difference in the cells' avidity for the phase droplets during the early, elapsed events in partitioning. At higher polymer concentrations (i.e., higher interfacial tensions), the cell populations, completely bound to phase droplets, partition completely to the interface, and consequently cannot be separated. When such systems are made charge-sensitive by the generation of a Donnan potential between the phases or made into affinity systems by the incorporation of PEG ligands (e.g., PEG-palmitate), there is a decrease in the avidity of the cells for phase droplets. The resulting increase in the ratio of free to droplet-bound red cells in the top phase at the time of sampling correlates with an increase in the partition ratio, P, observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effect of cell exposure to top or bottom phase prior to cell partitioning in dextran-poly(ethylene glycol) aqueous phase systems: erythrocytes as a model.

Cells exposed to dextran (Dx)-rich bottom phase prior to cell partitioning in Dx-poly(ethylene glycol) (PEG) aqueous two-phase systems have lower partition ratios than cells exposed to PEG-rich top phase. Aspects of this previously observed phenomenon were explored. In the present work charge-sensitive phases made with Dx T500 and PEG 8000 were used exclusively. It was found that: (1) even on countercurrent distribution (CCD) red cells (RBC) loaded in bottom phase have a lower apparent partition ratio, G, than the same cells loaded in top phase; (2) when part of the same cell population is loaded into top phase and part into bottom phase of the same load cavities for CCD, with the cells loaded into top or bottom bearing an isotopic tracer (51Cr), the cells loaded into top phase have a higher G value than the cells loaded into bottom phase; (3) the shift in the CCD curves of human or of rat RBC between cells loaded in top or bottom phase using systems having the same polymer concentration (though different salt compositions) shows no striking difference and is, for the number of experiments run, not statistically significant; (4) when the quantity of cells loaded for CCD is reduced from 10(9) to 10(8), the G value of cells loaded in top phase is reduced slightly while that of cells loaded in bottom phase is diminished more appreciably; (5) increasing polymer concentrations yield larger differences in G values between (rat) RBC loaded in top or bottom phase; (6) when cells exposed to top or bottom phase, respectively, are centrifuged and suspended in bottom or top phase, respectively, their CCD patterns are qualitatively similar to cells exposed to these latter respective phases initially; (7) rat RBC populations containing 59Fe-labeled cells of different but distinct age are fractionated on CCD irrespective of whether loaded in top or bottom phase. An exception are populations containing very young mature labeled cells (e.g., 4-d old) which are resolved when loaded in top phase but not in bottom phase. Thus cell populations exist which can be resolved by CCD when loaded in one of the phases but not when loaded in the other. Glutaraldehyde-fixed rat RBC containing 4-d old labeled cells are fractionated by CCD irrespective of whether loaded in top or bottom phase.

Animals↗
PubMed1992

Genetic structure of the population of Sicily.

Genetic heterogeneity within Sicily was investigated on the basis of ACP1, ADA, ESD, GLO1, PGD, PGM1, PGM2, SODA, ABO, and MN gene frequencies, and compared to those of other regions of Italy for which these same loci have been examined. Correspondence analysis revealed no differences within the island, at least at the provincial level, but showed genetic differentiation among Italian regions, distinctly clustering northern, central, and southern populations, respectively. These data indicate a close relationship between Sicily and southern Italy. In addition, the contribution of Middle Eastern populations to the gene pool of Sicily was evident.

ABO Blood-Group System↗
PubMed1992

Individual somatotopy of primary sensorimotor cortex revealed by intermodal matching of MEG, PET, and MRI.

A method for comparing estimated magnetoencephalographic (MEG) dipole localizations with regional cerebral blood flow (rCBF) activation areas is presented. This approach utilizes individual intermodal matching of MEG data, of rCBF measurements with [15O]-butanol and positron emission tomography (PET), and of anatomical information obtained from magnetic resonance (MR) images. The MEG data and the rCBF measurements were recorded in a healthy subject during right-sided simple voluntary movements of the foot, thumb, index finger, and mouth. High resolution 3D-FLASH MR images of the brain consisting of 128 contiguous sagittal slices of 1.17-mm thickness were used. MEG/MR integration was performed by superimposing the 3D head coordinate system constructed during the MEG measurement onto the MR image data using identical anatomical landmarks as references. PET/MR integration was achieved by a phantom-validated iterative front-to-back-projection algorithm resulting in one integrated MEG/PET/MR image. The estimated dipole locations followed the somatotopic organisation of the task-specific rCBF increases as evident from PET, although they did not match point-to-point. Our results demonstrate that intermodal matching of MEG, PET and MR data provides a tool for relating estimated neuromagnetic field locations to task-specific rCBF changes in individual subjects. Our method offers the perspective of refined dipole modelling.

Adult↗
PubMed1992

Investigations on the variability of blood group polymorphisms among sixteen tribal populations from Orissa, Madhya Pradesh and Maharashtra, India.

Sixteen tribal populations from Orissa, Madhya Pradesh and Maharashtra have been typed for the polymorphic blood group systems A1A2B0, MNSs, Rhesus, Kell, Duffy and Diego. The heterogeneity in the distribution of haplotype and allele frequencies, respectively, is partly considerable. It is supposed that this is due to the operation of several microevolutionary factors, such as genetic drift, social and geographic isolation and gene flow. This is discussed in detail.

Alleles↗
PubMed1992

Investigations on the variability of four genetic serum protein markers in Poland.

198 unrelated male and female Poles from Ostrów Wielkopolski (Central Poland) and 228 unrelated male and female Kashubes from Kościerzyna (Northern Poland) have been typed for four polymorphic serum protein systems: HP, TF, GC, and PI. Phenotype and allele frequencies of all these four polymorphic systems are quite different between Poles and Kashubes. Comparisons with some other Central and East European population samples (Slovaks, Hungarians, Matyos, Gypsies) revealed a considerable genetic heterogeneity among them. Genetic distance analysis showed that Hungarians and Matyos as well as Poles and Slovaks are found in two subclusters, which are linked up to one cluster. Gypsies and especially Kashubes exhibit a distinct position from this cluster. This genetic distance pattern can be explained satisfactorily considering the ethnohistory of the population groups under study.

Blood Proteins↗
PubMed1992

Investigations on the variability of four genetic serum protein markers (HP; TF, GC and PI subtypes) in Italy.

14 population samples from various Italian regions with a total of 2.577 unrelated male and female individuals were typed for four polymorphic serum protein polymorphisms: HP, and TF, GC and PI subtypes. The regional distribution of the allele frequencies of these four polymorphisms shows a considerable heterogeneity, which is for the most part statistically significant, thus indicating an obvious genetic variability of the population of the Italian Peninsula.

Alleles↗
PubMed1991

Partitioning of cells in dextran-poly(ethylene glycol) aqueous phase systems. A study of settling time, vessel geometry and sedimentation effects on the efficiency of separation.

The effect of prolonged settling times (up to 2 h), in high- and low-phase columns, on the cell partition ratios measured and on the separability of cell populations was examined. With closely related cell populations, modelled by rat erythrocytes in which subpopulations of red blood cells of distinct age were labeled isotopically, it was found that partitioning proceeds over the entire time period examined as evidenced by the continuous change in relative specific activity of cells in the top phase as the partition ratio falls. In control cell sedimentation experiments in top phase there was almost no change in the quantity of cells present when vertical settling (i.e., high-phase columns) was used and no separation of specific subpopulations was found. In the horizontal settling mode the initially higher cell partition ratio, as compared to vertical settling, decreased to a greater extent with longer time intervals; a given purity of cells only being obtained at a lower partition ratio than in the vertical settling mode. Cell sedimentation in top phase was appreciable with time in the horizontal settling mode but did not result in a separation of cell subpopulations. The effect of relative cell partition ratios and sizes in high- and low-phase columns on the efficiency of separation was examined by use of rat or sheep 51Cr-labeled red cells mixed with an excess of human unlabeled erythrocytes. Rat and sheep red cells are appreciably smaller than human erythrocytes. Rat red cells have higher, and sheep red cells lower partition ratios than human erythrocytes. With vertical settling, over a 2-h period, there is no appreciable contribution to the change in relative specific activities by cell sedimentation. However, the more rapid sedimentation of the larger human red cells has, with time, a measurable effect on the relative specific activities obtained during cell partitioning when run in the horizontal mode: enhancing the rat-human and diminishing the sheep-human cell separations. Partitioning cells in high-phase columns is of advantage with respect to increasing separation efficiency and virtually eliminating the influence of other physical parameters (e.g., cell size). Since the cell partitioning process continues for long periods of time, yielding ever-lower partition ratios with increasing proportions of cells with higher P values, a time may be selected which balances desired relative cell purity and yield.

Animals↗
PubMed1991

Gm and Km allotypes in four Sardinian population samples.

Serum samples of 683 unrelated male and female individuals of four Sardinian population samples (Sassari, Nuoro, Oristano and Cagliari) were typed for G 1 m (1,2,3,17), G 3 m (5,6,10,11,13,14,15,16,21,26), and Km (1). Phenotype, haplotype (Gm), and allele frequencies (Km), respectively, show a remarkable variability between these four population samples. Comparisons with other Italian populations reveal the considerable genetic difference of the Sardinians, which is in particular caused by the presence of the haplotype Gm1,3;5,10,11,13,14,26 in them. This haplotype is quite uncommon in Europeans and may reflect gene flow from Eastern populations (Phoenicians?) who came to this island in ancient-history times.

Alleles↗
PubMed1991

Evaluation of the extent of the early Maillard-reaction in milk products by direct measurement of the Amadori-product lactuloselysine.

A new method for the evaluation of the extent of lysine modification caused by the Maillard reaction is presented, based on the direct determination of the Amadori product lactuloselysine plus unmodified lysine after complete enzymatic hydrolysis by ion-exchange chromatography. Using a simple mathematical relation, the amount of modified lysine in milk products can be estimated without knowledge of the initial lysine value before heating or storage.

Animals↗
PubMed1991

Induction of vascular injury by Pseudomonas aeruginosa cytotoxin in rabbit lungs is associated with the generation of different leukotrienes and hydroxyeicosatetraenoic acids.

Pseudomonas aeruginosa cytotoxin, a transmembrane pore-forming protein, causes an increase in pulmonary microvascular permeability with subsequent lung edema formation, possibly related to the induction of arachidonic acid (AA) lipoxygenase products. To investigate this, isolated rabbit lungs were perfused with cytotoxin-containing buffer (6.5 and 13 micrograms of toxin/ml). A severalfold increase in the capillary filtration coefficient was induced, both preceded and accompanied by a marked time- (15-60 min) and dose-dependent release of cysteinyl leukotrienes (LT), LTB4, and 5-, 12-, and 15-hydroxyeicosatetraenoic acids (HETEs) into the lung perfusate. In the bronchoalveolar lavage fluid, corresponding AA-derived products were detected; the total sum of HETEs surpassed that of cysteinyl LTs in this compartment. The lipoxygenase inhibitors AA861 (10 microM) and nordihydroguaiaretic acid (100 microM) and EGTA (5 mM) suppressed the intravascular and alveolar liberation of all 5-lipoxygenase-derived AA metabolites, paralleled by a marked reduction and retardation of microvascular permeability increase (AA861). It thus seems that Pseudomonas cytotoxin induces generation of LTs and HETEs in rabbit lungs that may contribute to the development of pulmonary microvascular injury evoked by this bacterial agent.

Animals↗
PubMed1991

Investigations on the ethnic variability of the ABO blood group polymorphism in Iran.

112 Iranian population samples with a total of 600954 individuals are analyzed concerning the ethnic variability of ABO allele frequencies. The genetic heterogeneity within and between these population samples is considerable. This heterogeneity is discussed with regard to the ethnohistory of Iran. The most striking ABO allele frequencies are observed in Assyrians, Armenians and Zoroastrians, which differ extremely from that of all the other hitherto studied ethnic groups of Iran. Obviously varying ABO allele frequencies are seen also in Yazdis as well as in Turkomans and Arabs living in Iran. And finally the Iranian Jews reveal clear frequency differences in comparison with all the other Iranian population groups. It can be assumed that the specific ABO allele frequencies found in the above mentioned ethnic groups are connected with their different geographical origin as well as with their marked endogamy.

ABO Blood-Group System↗
PubMed1990

On the relation between surface area and partitioning of particulates in two-polymer aqueous phase systems.

Partitioning in dextran-poly(ethylene glycol) aqueous two-phase systems is an established method for the separation of biomaterials. Size and surface properties are generally regarded as parameters which contribute to the determination of the materials' partition coefficients, K. While molecular weight or surface area can be one of the determinants of the K value of biomaterials in the size range of macromolecules to very small particulates (e.g. some viruses), partitioning liposomes of identical surface properties and different but distinct sizes indicate that surface areas greater than about 0.2 microns 2 do not affect the K value obtained. Analysis of available partitioning data of much larger particulates (i.e. cells) reveals that surface properties per unit area outweight surface area per se in determining the K value in non-charge-sensitive, charge-sensitive and biospecific affinity phase systems.

Animals↗
PubMed1990

Differential effect of pH on the density and volume of rat reticulocytes and erythrocytes. Relevance to their fractionation by centrifugation.

Rats were injected with 59Fe-ferrous citrate and bled thereafter at different times (16 h to 49 d). This gave rise to red cell populations in which cells corresponding in age to the time elapsed between injection and bleeding were labeled. The anticoagulant used was either acid-citrate-dextrose (ACD) with a pH adjusted to 7.3 or ACD (pH 5.1). Final pH of the collected blood was about 7.2-7.4 in the former case and 6.4-6.7 in the latter. Red cells were then centrifuged (5) and approximately 7-10% of the packed cells from the top and 7-10% from the bottom of the cell column collected. When reticulocytes are the predominant labeled red cell population, as in blood obtained for about 24 h after isotope injection, a fractionation of these cells and mature erythrocytes is in evidence only when blood is collected at the higher pH. Thus, at pH 7.2-7.4 ratios of specific radioactivities of cells in top fraction/cells in an unfractionated sample are about 3, whereas at pH 6.4-6.7, the analogous ratios are 1 or less. These differences in specific activity ratios, as a function of pH at collection, virtually disappear after about 4 d following isotope injection. The lower pH is known to increase the volume and decrease the density of mature red blood cells. The marked effect of pH on cellular fractionation could be correlated with the smaller change in rat reticulocyte density and volume in acid medium. At pH 6.4-6.7, the densities of mature erythrocytes and reticulocytes are so close that their physical separation by centrifugation is not feasible.

Animals↗
PubMed1979

Genetic markers and leprosy in South African negroes: Part II. Erythrocyte enzyme polymorphisms.

The phenotype frequencies of the erythrocyte enzyme polymorphisms acid phosphatase (aP), phosphoglucomutase loci 1 and 2 (PGM1 and PGM2), adenylate kinase (AK), adenosine desaminase (ADA), esterase D (EsD) and 6-phosphogluconate dehydrogenase (6-PGD) were determined on a sample of 234-248 South African Negroes with leprosy. These results were compared with data of 841--997 healthy Negro controls of similar geographical and ethnic origin, in order to determine whether or not any association exists between specific phenotypes and the manifestation of leprosy. A part of the data included in the present study were compared with the data of a similar comparative analysis on Mozambican Negroes. With regard to the polymorphisms aP, PGM1 and PGM2, the results derived from South Africa and Mozambique exhibit reverse patterns of deviations from the null hypothesis. From this it does not appear justified to postulate an association between these genetic markers and the occurrence of leprosy. For the enzyme polymorphisms ADA, AK and EsD (data are confined to South African Negroes only) the distribution of phenotypes between patients and controls was very similar. The differences were not statistically significant. However, observations on the 6-PGD polymorphism (data are confined to South African Negroes only) showed an excess of phenotype PGD A among leprosy patients as compared with controls. The difference was statistically highly significant. Further studies based on additional samples are required to substantiate whether or not the statistical outcome reflects a true association between this phenotype and leprosy.

Acid Phosphatase↗