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Biomedical subjects

M Wilhelm

Publications and source records attributed to M Wilhelm.

At least 199 records · Page 11Linked to original sources
PubMed1989

Scalp hair as an indicator of aluminium exposure: comparison to bone and plasma.

1. Aluminium concentrations were measured in hair, plasma and bone samples from different groups of chronic renal insufficient patients and from a control group (75 healthy volunteers plus 21 deceased subjects). A cross-sectional study with 40 haemodialysis patients and two longitudinal studies were undertaken, the first comprising of 12 home haemodialysis patients and the second 16 patients undergoing continuous ambulatory peritoneal dialysis (CAPD). 2. Before introduction of water treatment by reverse osmosis, the hair aluminium levels of home haemodialysis patients were elevated compared to controls. Aluminium in the hair of all other groups were within the normal range. Hair aluminium levels were not related to the daily aluminium intake, nor to the cumulative aluminium intake, nor to bone and plasma aluminium concentrations. 3. Plasma aluminium concentrations in all patients were higher than in the controls. Dialysis without reverse osmosis water treatment increased aluminium plasma levels. After installation of reverse osmosis units there was a decrease in the aluminium concentrations in plasma. In CAPD patients insignificant increases in the aluminium levels in plasma were observed. When low contaminated dialysis fluid was available the plasma aluminium concentrations returned to the initial level. 4. Aluminium concentrations in bone were increased in renal insufficient patients compared with controls. Aluminium bone content increased with increasing cumulative aluminium intake by phosphate binding therapy. 5. Hair analysis is of very limited value for the diagnosis of aluminium exposure. Bone analysis is suitable for the assessment of the individual body burden.

Adult↗
PubMed1989

Hair lead levels in young children from the F.R.G.

Hair lead (PbH) levels were measured in 474 children, aged 3-7 years, living in an industrialized (Duisburg) and in a rural area (Westphalia) of the F.R.G. by atomic absorption spectrometry. PbH values were log-normally distributed. All mean concentrations are therefore given as geometric means. The overall mean PbH content was 2.7 mg/kg. In the summer PbH levels were higher than in the winter (3.8 vs. 1.4 mg/kg) and the values from the urban children were higher compared with those from rural children (3.7 vs. 1.9 mg/kg). Boys had more Pb in their hair than girls (3.9 vs. 2.0 mg/kg) and PbH levels decreased between the 4th and 7th year. In the industrialized area the PbH content of children whose fathers were factory workers, was higher than that of children whose fathers had other occupations (4.2 vs. 3.0 mg/kg). Non-German children had more Pb in their hair than German children (5.2 vs. 3.6 mg/kg). Pb content in the soil from the Duisburg area was related to PbH concentrations (R = 0.34). Since our observations are in line with the results of similar studies which used blood samples to monitor Pb exposure in children, we conclude that by using standardized conditions hair analysis is a valuable screening method.

Child↗
PubMed1989

Calcium alginate, an aluminum-free phosphate binder, in patients on CAPD.

Since dialysis solutions in CAPD are now nearly aluminum free, the only source for elevated aluminum levels are aluminum-containing phosphate binders. Elimination with CAPD is insufficient to prevent aluminum accumulation. Therefore, we investigated a phosphate binder consisting of calcium alginate, a natural polyuronic acid, containing 100 mg calcium/g substance in 14 patients on CAPD over a period of one year. The patients had previously been treated with aluminum-containing phosphate binders for a period of 24.3 +/- 21.3 months. During a period of 3 weeks before changing to the new phosphate binder the mean (+/- SD) serum phosphorus concentration was 1.8 +/- 0.4 mmol/l, while at the end of one year of treatment with calcium alginate the concentration was 1.6 +/- 0.4 mmol/l. In order to lower serum phosphorus to this level, it was necessary to increase the mean (+/- SD) amount of calcium alginate from 6.9 +/- 1.3 g per day at the beginning of the study to 8.3 +/- 2.1 g per day at the end. The mean (+/- SD) serum calcium concentration did not change throughout the study period. Serum levels of alkaline phosphatase, 1.25 (OH)2 vitamin D3, and intact parathyroid hormone did not change as well. The mean (+/- SD) serum aluminum level declined from 36.0 +/- 20 to 14.0 +/- 11.3 micrograms/l after 6 months (p less than 0.001). In conclusion, calcium alginate is a good alternative to aluminum-containing phosphate binders and to phosphate binders on a calcium base as it does not lead to hypercalcemia. It prevents aluminum intoxication and has no serious side effects.

Alginates↗
PubMed1988

Variables influencing cadmium concentrations in hair of pre-school children living in different areas of the Federal Republic of Germany.

The influence of several factors on cadmium (Cd) concentrations in the hair of 474 pre-school children was examined. The study was performed in an industrial (Duisburg) and rural area (Westfalen) of the (FRG). Season, sex, hair color, and place of residence were found to be the main factors influencing Cd levels in hair. Concentrations of Cd in samples obtained during summer were on the average nearly twice as high as those sampled during winter (geometric means: 116.1 vs. 63.7 ng/g). Boys had more Cd in their hair than girls (111.5 vs. 74.0 ng/g). Cd levels in hair decreased from red to blond, to brown, and black hair. Children living in Duisburg had more Cd in their hair than those from rural areas (103.9 vs. 77.0 ng/g). Cd content in hair was inversely related to age.

Cadmium↗
PubMed1988

Hair zinc of young children from rural and urban areas in North Rhine-Westphalia, Federal Republic of Germany.

Hair zinc levels were estimated by atomic absorption spectrophotometry in 474 children, aged 3-7 years, from 11 kindergartens in a highly industrialized and polluted area (Duisburg) and 8 kindergartens in a rural area of North Rhine-Westphalia. The mean hair zinc level amounted to 118 micrograms/g, increasing between the 4th and 7th year of life. At all ages the values from the urban toddlers were lower than from rural toddlers, and in both regions they were higher in winter than in summer. Children with frequent upper respiratory tract infections (greater than 6 infections/year) showed significantly lower zinc hair values, independent of their age. Low hair zinc values (below 70 micrograms/g) were frequently found, raising the question as to whether this is a normal, age-related phenomenon, or whether it indicates a suboptimal zinc status of young children from North Rhine-Westphalia.

Child↗
PubMed1988

Elimination of absorbed aluminum in patients undergoing continuous ambulatory peritoneal dialysis.

Intestinal absorption of aluminum (Al) from the phosphate binder aluminum-hydroxide-chloride (PhosphonormR) and successive renal and peritoneal Al elimination were studied in 11 patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Al was measured by atomic absorption spectrometry in serum, urine, and dialysis fluid. Al levels in serum of all patients increased in average from 28.6 micrograms/l immediately before to a peak level of 41.6 microgramsWl 4 h after intake of 342 mg Al. After 24 h serum Al (34.0 micrograms/l) was still increased. Elimination across the peritoneum increased from 5.6 micrograms Al during the first 4 h to peak levels of 12.9 micrograms between hour 8 and 12 and decreased to 8.1 micrograms during the last 12 h. The Al clearance of the peritoneum was 0.43 ml/min. In the 6 patients with residual diuresis the renal Al excretion was higher than the peritoneal removal (48.1 micrograms/24 h vs. 24.8 micrograms/24 h). The renal Al clearance amounted to 1.6 ml/min. Assuming a gastrointestinal absorption quotient of 0.1% it is concluded that Al removal by CAPD in patients receiving 342 mg Al/day is not sufficient to prevent Al accumulation. In patients with remaining diuresis, the renal Al elimination exceeds the Al removal by the peritoneum.

Administration, Oral↗
PubMed1987

Effects of cadmium in rat hepatocytes: interaction with aluminum.

The influence of aluminium (Al) chloride on toxic responses to cadmium (Cd) chloride of hepatocytes isolated from fed rats were investigated. Hepatocytes exposed to 50-200 microM Al took up the Al-ion more efficiently when the cells were simultaneously incubated with 50 microM Cd for 60 min. Aluminium (50-200 microM) could not prevent the release of about 50% of lactate dehydrogenase (LDH) from cells due to 50 microM Cd. Aluminium itself increased LDH leakage only to a moderate extent, indicating the low toxicity of Al to hepatocytes. Cadmium diminished the total hepatocellular thiols (protein + non-protein) and, even more pronounced, the acid soluble thiols after 60 min of incubation. However, this response to Cd was inhibited by simultaneous exposure to 50-200 microM Al in an Al concentration-dependent manner. Concomitantly, the Cd-dependent lipid peroxidation (LPO; measured as thiobarbituric acid reactants) at 60 min was decreased by Al, which itself did not enhance basal LPO in hepatocytes. These data show that Al partly protects hepatocytes from Cd-induced depletion of acid soluble thiols (i.e. reduced glutathione) and from stimulation of LPO. However, Al did not prevent the Cd-induced damage of the cell membrane.

Aluminum↗
PubMed1987

Uptake and distribution of aluminium in rat hepatocytes and its effect on enzyme leakage and lactate formation.

Aluminium (Al) chloride (10-200 microM) increased the Al content in hepatocytes isolated from fed male rats in a time- and concentration-dependent manner. After 60 min of incubation with 100 microM Al about 45% of cellular Al was found each in the mitochondrial and the postmitochondrial fraction of hepatocytes, whereas about 5% of Al sedimented with nuclei and cell debris. Concomitantly, the leakage of lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) increased in the presence of Al time- and concentration-dependently, but only to a moderate extent. Aluminium (10-200 microM) also accelerated the formation of lactate by hepatocytes. No significant differences were found in Al uptake and distribution and its effect on LDH leakage and lactate formation when the metal ion was given as AlCl3, Al(NO3)3 or Al(lactate)3. Al concentrations (AlCl3) exceeding 250 microM severely disturbed the determination of LDH, AST and lactate in a cell free system. The data suggest only a moderate toxicity of Al compounds to isolated hepatocytes, when given in amounts approximating (patho)physiological conditions.

Alanine Transaminase↗
PubMed1987

Effects of ionizing radiation on artificial (planar) lipid membranes. I. Radiation inactivation of the ion channel gramicidin A.

The ion channel formed by the pentadecapeptide gramicidin A in planar lipid membranes is extremely sensitive to ionizing radiation. The membrane conductance may drop by several orders of magnitude under appropriate experimental conditions (low pH and presence of oxygen). The radiation sensitivity is strongly reduced for gramicidin M-. This analogue has the four tryptophan residues replaced by phenylalanines. Experiments performed in the presence of various radical scavengers suggest that the inactivation of the channel is due to a combined action of OH and of HO2 radicals at the tryptophan residues. The shape of the inactivation curves following continuous radiolysis or pulse radiolysis were found to be in fair agreement with a simple model which assumes that the damage of a single tryptophan residue is sufficient for channel inactivation. The conductance of inactivated channels could not be resolved within the experimental accuracy. This is contrary to photolysis of gramicidin channels found by Busath and Waldbilling (1983), where a broad distribution of low conductance states was observed. The inactivation by radiolysis seems to represent an 'all-or-none-process' of the channel conductance.

Dose-Response Relationship, Radiation↗
PubMed1987

Effect of ionizing radiation on artificial (planar) lipid membranes. II. The ion carriers valinomycin and nonactin as probes for radiation induced structural changes of the membrane.

Planar lipid membranes in the presence of the ion carriers valinomycin or nonactin were irradiated with 14 MeV electrons from a linear accelerator. A large increase of the membrane conductance by up to more than two orders of magnitude was found. The effect is virtually abolished either at high pH, or in the absence of oxygen, or in the presence of the radical scavenger ethanol. A further prerequisite for the effect is the presence of unsaturated fatty acid residues. A kinetic analysis of the carrier transport model based on current-voltage curves and on voltage-jump relaxation experiments was performed as a function of radiation dose. Only the translocation rate constant, kMS, of the charged carrier-ion complex was found to be influenced by irradiation. The effect is interpreted as an increase of the polarity (dielectric constant) of the membrane interior induced by the presence of polar products of lipid peroxidation. A combined action of OH- and HO2-radicals seems to be responsible for the phenomena. At large radiation doses (greater than or equal to 10(3) Gy) a reduction of the membrane conductance was observed. This is interpreted as an increased microviscosity, possibly caused by cross-linking of fatty acid residues. Ion carriers represent sensitive probes of radiation induced membrane damage.

Anti-Bacterial Agents↗
PubMed1987

Aluminum load in chronic intermittent plasma exchange.

Aluminum (Al) loading due to administration of human albumin (HA) solutions was studied in 2 patients with stable renal function who underwent plasma exchange once (patient A) and twice (patient B) per week for treatment of hyperviscosity syndrome. Al was determined by Zeeman-AAS in plasma before, during and after treatment, also in bone of one patient and in various preparations of HA from different manufacturers. In addition, the net Al uptake (difference between total Al influx and efflux) and the 24th urinary excretion between 2 exchanges were determined. The electrolyte solution used for dilution had no detectable Al, while HA contained between 15 and 1900 micrograms Al/l. Increase of Al in plasma after treatment was clearly related to Al content of the HA used. When the patients received substitution solutions based on inadvertently highly Al contaminated 20% HA (1419 micrograms/l), the average net uptake was 2265 in patient A and 2049 micrograms in patient B and plasma Al rose from 8.4 respectively 18.0 before to 69.2 and 86.5 micrograms/l after treatment. By using medium Al contaminated HA (574 micrograms/l), the net uptake was 742 (pat. A) and 819 micrograms (pat.B), and there was an elevation of plasma Al from 5.1 respectively 18.2 to 34.2 and 39.8 micrograms/l. Following a net uptake of 870 micrograms patient A excreted 668 micrograms Al until the next treatment (23% positive balance). Treating patient A with a low Al HA (47 micrograms/l), there was a slight increase of plasma Al from 10.8 to 16.2 micrograms/l, the net Al uptake was negligible (less than 10 micrograms), and the weekly Al balance was negative. After 10 months of plasma exchange therapy (patient A) there was no increase of Al in bone (6.4 micrograms/g). We conclude, that the use of HA with a low Al contamination is recommended for all patients receiving this therapy during chronic intermittent plasma exchange or for other indications, especially in cases with impaired renal function.

Adult↗
PubMed1986

[Mechanical sutures in digestive surgery. A critical study].

An objective review of the experimental and clinical literature comparing stapled- and hand-sutured anastomoses in gastrointestinal surgery is presented. Experimental studies support the hypothesis that stapled-sutured lines heal by primary intention, thus avoiding the inflammatory time lag, and resulting in a stronger wound during the first post-operative week. In contrast, manual sutures always produce an early inflammatory reaction with a transitory rise in collagenase activity in the submucosa, which explains the particular fragility of the anastomosis during that phase. Nevertheless, it was difficult to find a concordance between this histological quality of the stapled suture line and clinical results. In oesophageal surgery, a slightly higher rate of stenosis and a lower rate of anastomotic leakage were observed. In gastric and colorectal surgery, the superiority of the stapled suture was not proved. However, in colorectal randomized studies, the presence of "withdrawn" group for which the stapler was the only technically possible alternative, provides undeniable proof that this technique is an indispensable adjunct in modern digestive surgery. Conversely, its value seems negligible in surgery of the small bowel or of the intraperitoneal colon where manual suturing remains the technique of choice.

Acute-Phase Reaction↗
PubMed1986

Direct monoclonal antibody rosetting. An effective method for weak antigen detection and large scale separation of human mononuclear cells.

A direct monoclonal antibody rosetting technique is described which serves as a simple, reliable, and very sensitive method for the detection of surface antigens on human leukocytes. In this technique the discriminative monoclonal anti-leukocyte antibodies are directly coupled to ox erythrocytes (oxE) by use of CrCl3. The procedure can be applied to the effective separation of mononuclear cell subsets. By choosing a gradient of appropriate density labeled cells are either isolated in high purity or quantitatively eliminated. This technique proved to be particularly suitable for the large scale purification of autologous or allogeneic bone marrow transplants where either leukemic cells or T cells have to be completely eliminated without damaging sensitive stem cells.

Animals↗
PubMed1985

Nucleotide sequence of the Bacillus subtilis xylose isomerase gene: extensive homology between the Bacillus and Escherichia coli enzyme.

The xylose isomerase gene from Bacillus subtilis was cloned from a genomic BamH1 library by complementation of an isomerase defective Escherichia coli strain as previously described. The ATG initiation codon is preceded by a Shine-Dalgarno sequence and two hexamers being characteristic for the promoter region of Bacillus genes. The structural gene consists of 1320 base pairs, thus coding for a polypeptide chain of 440 amino acids with a molecular weight of 49 680. The polypeptide primary structure shows over 50% homology to that of the E. coli xylose isomerase.

Aldose-Ketose Isomerases↗