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Biomedical subjects

H Mann

Publications and source records attributed to H Mann.

At least 109 records · Page 6Linked to original sources
PubMed1983

Computed tomography of lambdoid calvarial defect in neurofibromatosis. A case report.

A patient with neurofibromatosis is reported in whom cranial computed tomography (CT) revealed a calvarial defect with an associated soft-tissue mass in the region of the left lambdoid suture. This defect has been the subject of several previous reports, having been demonstrated by means of conventional skull radiography. It should be included in the differential diagnosis when a lytic calvarial lesion is found on CT.

Adult↗
PubMed1983

Electrodialysis and reverse osmosis as a regeneration system for hemofiltrate.

The separation of urea from the hemofiltrate (or from spent dialysis fluid) must be considered the critical step in all regeneration systems. A promising solution for this problem is the combination of electrodialysis and reverse osmosis. A mathematical stimulation of the process and in vitro experiments have been carried out in order to determine operating conditions and design specifications. The experiments confirmed the predicted performance of the regeneration system with respect to the separation of urea and the recovery of electrolytes. As expected, some ionic toxins, such as uric acid, and some middle molecules are recovered also. These substances, however, can be easily removed by a small adsorption cartridge.

Adsorption↗
PubMed1982

Continuous enrichment of albumin in relation to globulins in plasma.

This in vitro study deals with the problem of continuous separation of albumin from globulins in patient's plasma and reinfusion of the useful components of the plasma to the patient as the substitution fluid during a plasma exchange (PE) treatment. A cascade filtration system is developed to generate continuously two plasma fractions, one rich in globulins and the other rich in albumins, using two filters (H1P100 filter with a molecular weight cutoff 100,000 and Diafilter 20 with a molecular weight cutoff 30,000). For example, the system is able to increase the albumin/globulin ratio of plasma from 0.42 to 1.98, and the albumin concentration in the secondary plasma fraction is about seven times higher than that in the primary plasma fraction. This system is expected to be clinically useful in eliminating the side effects inherent in the usage of any other substitution fluid during a PE treatment.

Blood↗
PubMed1981

Large-scale isolation of middle and higher molecular weight uremic toxins.

Reverse osmosis (40 bar) using membranes with a nominal cut-off of 500 Dalton is a useful method for the desalting and concentration of hemofiltrates (20-30 L) or even dialysates (120-240 L) from patients with end-stage renal failure. The removal of electrolytes and lower molecular weight solutes from the middle and higher molecular weight fractions can be carried out in one step. The freeze-dried residues show characteristic differences in their molecular weight distributions which are dependent upon their origin (Cuprophane dialysates or RP-6-hemofiltrates). Subfractionation is performed using Sephadex G-15 macrocolumns (2 m x 5 cm), the LKB-Ultrogel AcA 54 and Sephacryl S-200 as well as ion exchange chromatography. The fractions are characterized by their ability to suppress the incorporation of 3H-thymidine into rat bone-marrow as well as HeLa cell cultures. The greatest inhibitory activity originates from those fractions which are not dialysable using Visking tubes in vitro. The results indicate that the middle and higher molecular weight spectra do in fact overlap, suggesting that also higher molecular weight substances are involved in uremic intoxication.

Animals↗
PubMed1980

[Automatic recognition of age - specific development of the EEG in infancy and early childhood - a five year follow-up study (author's transl)].

This study was initiated with a view to early detection of dysfunctions of the central nervous system (CNS) and to observe the physiological development of the CNS by means of EEG obtained in the age-groups: new-born, half, 1, 2, 3, 4 and 5 years. This was supported by standardized clinical examinations for neurological and somatic findings and by standardized tests of psychomotoric and intellectual development. In this investigation the data as used for automatic processing consisted of 110 EEGs in the age-groups: half, 1, 2, 3 and 4 years. Bipolar EEGs were recorded using "ten-twenty" method with the following leads: F4--C4, P4--O2, F3--C3 and P3--O1. For feature extraction three methods of data reduction were applied, i.e. interval-amplitude, spectral analysis and the autoregressive model. From the features thus obtained, age-specific frequency parameters were selected by statistical methods; further evaluation was performed by cluster and discriminant analysis. The former showed an unequivocal case grouping for each age-group. Using unmatched samples of only clinically healthy children from the three age-groups 1/2, 1 and 2 years, linear discriminant analysis were applied to the parameters of the three methods of data reduction. This procedure yields in mean recognition rates of 95%, 98% resp. 98% in hold-one-out classification. Similar results are obtained with samples from four or five age groups (1/2 to 4 years). The results of this type of automatic EEG analysis show that discriminant analysis can be used to allocate EEGs to specific age-groups; hence, it may readily be ascertained whether differences between chronological age and development age as evidenced by the EEG exist.

Age Factors↗
PubMed1978

Preparative isolation of middle molecular weight fractions from the hemofiltrate of patients with chronic uremia.

Fractions in the molecular weight range of the so-called middle molecules (500--3000 daltons) were isolated on a preparative scale from hemofiltrate of patients. Hemofiltration was performed with an RP-6 dialyzer using a predilution technique. The hemofiltrate was concentrated and desalinated by reverse osmosis with membranes with a normal cut-off of 500 daltons. The retentate was freeze-dried, redissolved in volatile buffer and fractionated on Sephadex G-15 macrocolumns. The middle molecule molecular weight range in the elution profiles (detected at 206 and 280 nm simultaneously) was marked with peptides. Isolated fractions in the middle molecule molecular weight range showed strong inhibitory activity upon 3H-thymidine incorporation into rat bone-marrow cells in vitro. The described combination of hemofiltration, reverse osmosis and gel chromatography is suggested as a useful approach to the isolation of these ninhydrin-positive substances which, according to their proved heterogeneity, are to be subfractionated by further procedures.

Chromatography, Gel↗
PubMed1978

Theoretical aspects of various ultrafiltration methods in artificial kidney therapy.

A mathematical model including urea, creatinine and other osmotically important solutes (such as sodium, potassium and chloride) is applied to calculate volume shifts, caused by ultrafiltration, between the fluid compartments of the body. The volume shifts between the intracellular (ICV) and the extracellular (ECV) compartments are mainly caused by alteration of extracellular sodium concentration. Various methods of achieving ultrafiltration, including conventional dialysis, initial ultrafiltration using Cuprophan (without dialysis) or hemofiltration, produce different responses. In choosing a method, one must consider that both a rapid decrease of ECV and a fast shift of water from ICV to ECV should be avoided. In pure hemofiltration, ultrafiltrate is isotonic and water is removed from ECV only. Hemofiltration with dilution produces a very slow shift of water between ICV and ECV dependent on sodium concentration of plasma and diluting fluid. In initial ultrafiltration through Cuprophan, water is shifted from ICV to ECV. With ultrafiltration throughout the entire dialysis, there are pronounced shifts between ICV and ECV dependent on the difference of the sodium concentration between plasma and dialysate.

Biological Transport, Active↗
PubMed1977

Influences of the site of diluting fluid substitution on hemodiafiltration processing.

In hemodiafiltration, the diluting fluid can be substituted before or after the ultrafilter. The advantages and disadvantages of each method are discussed below. To avoid hemoconcentration when passing through the ultrafilter, we prefer substitution of the diluting fluid to blood before the ultrafilter and accept the greater composition of diluting fluid.

Hematocrit↗
PubMed1977

Amino acid loss during hemofiltration.

Loss of free amino acids during hemodiafiltration therapy was investigated in 5 dogs. Hemodiafiltration was performed with a cellulose-acetate membrane with a limit of molecular separation at MW 19,000. The concentration of amino acids was investigated in ultrafiltrate and in blood at the beginning and at the end of diafiltration. Loss of amino acids in the ultrafiltrate was seven times as much as free amino acid content of plasma, whereas amino acid concentration in plasma decreased only slightly (20%). Applying these results to hemodiafiltration in man, it is concluded that loss of amino acids in hemodiafiltration is not greater than in conventional hemodialysis therapy.

Amino Acids↗
PubMed1976

[Changes of left ventricular transverse diameter and of contractility after haemodialysis (author's transl)].

In 26 patients (8 women, 18 men; mean age 47 +/- 3 years) who participated in a regular dialysis programme twice weekly the left ventricular diameter, the mean velocity of fibre shortening, the ventricular wall thickness, and the muscle mass were determined echocardiographically. Left ventricular muscle mass (187 +/- 13 g), left ventricular posterobasal wall thickness (14,7 +/- 0,6 mm) and septal thickness (16,4 +/- 0,8 mm) were pathologically increased due to chronic pressure and volume overloading. After an average dialysis time of 12 hours the body weight was reduced by 2,6 +/- 0,4 kg (+ 1,0 to -7,8 kg). The left ventricular transverse diameter changed from 55,3 to 50,2 mm (P less than 0,001) which correlated with a decrease of the enddiastolic volume from 160 +/- 11 to 125 +/- 10 ml (P less than 0,01(. Despite increased cardiac frequency and unchanged diastolic and systolic pressure no significant increase of the mean velocity of fibre shortening (0,93 +/- 0,06 vector 1,13 +/- 0,09 circ/s) occurred. The results show that loss of fluid during haemodialysis led to a significant decrease of the enddiastolic transverse diameter and the enddiastolic left ventricular volume. However, dialysis does not lead to an increase of the mean velocity of fibre shortening as a parameter of improved contractility.

Adult↗
PubMed1976

Biological balance of sodium and potassium: a control system with oscillating correcting variable.

The rhythm of renal sodium and potassium excretion was measured in 4-h-intervals in 12 subjects. Each person exhibited clear circadian variations of each variable with a maximum between 8 a.m. and 4 p.m. In each subject and for both circadian rhythms the oscillation mean was correlated to the range of oscillation (amplitude). Increase in sodium or potassium excretion during 1 day resulted in an increase of oscillation range. The oscillation means of sodium and potassium periodicity did not correlate. The properties of biological control systems with oscillating correcting variables are comparable to those of technical control systems. The significance of circadian rhythm for the control of electrolyte balance is indicated.

Circadian Rhythm↗