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Biomedical subjects

W Burmeister

Publications and source records attributed to W Burmeister.

At least 19 recordsLinked to original sources
PubMed1997

Calibration and application of an X-ray image intensifier/ charge-coupled device detector for monochromatic macromolecular crystallography.

Charge-coupled device (CCD)-based X-ray detectors allow data to be collected much more quickly (approximately 10 times) than with current on-line imaging-plate systems. At the ESRF, X-ray image intensifier/CCD detector systems have been developed. These have great potential as fast read-out detectors for macromolecular and other forms of crystallography. They are relatively large sensitive X-ray detectors but have two inherent weaknesses: convex detection surfaces leading to spatial distortion and non-uniformity of intensity response, and susceptibility to small changes in magnetic fields. A large improvement has been made to the accuracy obtained by non-uniformity of response calibration and correction, using fluorescence from doped lithium borate glasses. Monochromatic macromolecular crystallography demonstration experiments with external user groups have shown that high-quality results may be obtained under real experimental conditions.

Journal Article↗
PubMed1996

All-trans retinoic acid reduces membrane fluidity of human dermal fibroblasts. Assessment by fluorescence redistribution after photobleaching.

All-trans retinoic acid (RA) preserves human dermal fibroblast viability and stimulates proliferation in vitro. These effects are mediated, at least in part, by reducing the extracellular Ca2+ requirement. The same concentrations of RA that reduce the extracellular Ca2+ requirement also interrupt movement of Ca 2+ across the fibroblast plasma membrane. Based on these observations, we have examined the effects of RA on membrane properties that could influence Ca2+ movement. Fibroblasts were labeled with 1-acyl-2-(N-4- nitrobenzo-2-oxa-1,3 diazole)-amino-caproyl phosphatidyl-choline (a fluorescent phospholipid analogue) and examined for fluorescence redistribution after photobleaching (FRAP) with a pulse of intense light as a measure of membrane fluidity. Using this approach, we observed that membrane fluidity was higher when the cells were incubated in medium containing a low (sub-optimal) level of extracellular Ca2+ (0.15 mmol/L) than in a medium containing an optimal concentration (1.4 mmol/L). Treatment of the cells with 3 micromol/L RA reduced membrane fluidity of the cells under both high- and low-Ca2+ conditions. These findings demonstrate that RA has a direct effect on the plasma membrane of human dermal fibroblasts. This provides a possible mechanism for the previously identified inhibition of Ca2+ movement across the membrane of the same cells and for the previously identified protective effects against lysis under low-Ca2+ conditions.

Calcium↗
PubMed1995

Human skin in organ culture. Elaboration of proteolytic enzymes in the presence and absence of exogenous growth factors.

Proteinase levels were assessed in organ culture fluids from human neonatal foreskin maintained under growth factor-free conditions and in the presence of a combination of growth factors (ie, epidermal growth factor, insulin, hydrocortisone, pituitary extract, and all-trans-retinoic acid). Analysis of culture fluids by gelatin zymography revealed the presence of 92-kd and 72-kd gelatinases. There was a greater amount of 92-kd gelatinase activity in the presence of growth factors whereas the levels of 72-kd gelatinase were similar in growth factor-free and growth factor-containing media. Experiments with keratinocytes and fibroblasts in monolayer culture and with isolated dermal tissue in organ culture indicated that the epithelial component was responsible for most of the 92-kd gelatinase activity whereas fibroblasts were primarily responsible for the 72-kd gelatinase activity. Activation with aminophenyl mercuric acetate, requirement for divalent cations, inhibition with EDTA, and insensitivity to inhibition with phenylmethyl sulfonyl fluoride indicated that both gelatinases were metalloproteinases. In additional studies, culture fluids were examined for the presence of plasminogen activator activity. This was detected in culture fluids from tissues maintained under both conditions but was increased in the growth factor-containing medium. The increased amount seen in the growth factor-containing medium appeared to be due almost entirely to a single factor, ie, all-trans-retinoic acid. In monolayer culture, both keratinocytes and fibroblasts produced plasminogen activator; the level was higher in keratinocyte culture fluids than in culture fluids from fibroblasts.

Cells, Cultured↗
PubMed1992

Whole-body cesium 137 activity up to 4 years after the Chernobyl reactor accident in premature newborns, newborns, infants, and children.

Cesium 137 activity was measured after the Chernobyl incident in a whole-body radiation counter (4-pi-scintillation counter) in 85 premature and mature newborns (group 1), 174 infants and young children up to 2 11/12 years (group 2), and 48 children between 3 and 8 years (group 3) from Bonn (Germany) and surroundings. In 1987 the mean level of radioactivity in group 2, at 3.7 Bq/kg body weight corresponding to a mean radiation exposure of 11 muSv/y, was lower than that of group 1 (5.8 Bq/kg, 17 muSv/y) and 3 (9.4 Bq/kg, 28 muSv/y). Up to 1990 the values of all groups revealed a continuous decrease. The latest measurements showed mean values of 0.5 Bq/kg (1.5 muSv/y) in group 1, 0.6 Bq/kg (1.8 muSv/y) in group 2, and 0.8 Bq/kg (2.4 muSv/y) in group 3. A comparison with present cesium 137 values and determinations of the end of the 1950s and beginning of 1960s, both in adults, showed good agreement. The effective dose-equivalent rates amounted to less than 1% of that from natural radiation exposure. These levels should present no teratogenic risks to the population studied and, while there are theoretical mutagenic risks, the dose is so low that no increase in measurable mutagenic effects should be observed.

Accidents↗
PubMed1989

25 Hydroxyvitamin D and vitamin E absorption in healthy children and children with chronic intrahepatic cholestasis.

Patients with chronic cholestasis have reduced 25-hydroxyvitamin D (25OHD) and vitamin E levels. We determined serum concentrations of 25OHD, 1,25-dihydroxyvitamin D [1,25(OH)2D] and vitamin E before and after oral administration of 10 micrograms/kg body weight 25-hydroxyvitamin D3 (25OHD3) and 100 IU/kg body weight vitamin E, respectively, in 4 patients with intrahepatic cholestasis and 6 healthy children. Vitamin E increased in all controls but in only one of the four patients. In contrast, oral 25OHD3 induced a normal rise in circulating 25OHD and 1,25(OH)2D. The low serum levels of 25OHD in the patients before the oral bolus may have been due to inadequate parenteral vitamin D administration and/or to the simultaneous phenobarbital treatment. The latter possibility is supported by the increase of serum 25OHD into the normal range after withdrawal of phenobarbital in one of the four patients. We conclude that vitamin E has to be supplemented parenterally or in water-soluble oral form. Further studies are necessary to clarify whether high-dose long-term oral 25OHD3 supplementation is sufficient to prevent vitamin D deficiency in patients with chronic cholestasis.

Adolescent↗
PubMed1988

[One year after Chernobyl. Cesium-137 levels in premature, newborn and nursing infants and in younger and older children of Bonn and environs].

From May to August 1987, 137Cs activity was measured in a total-body counter (4 pi counter) in 33 premature and mature newborns (group I), 40 infants and young children up to 2 4/12 years of age (group II), and 15 children between 3 and 6 8/12 years (group III), all from Bonn or its environs. The mean of measurements in group II, at 3.7 Bq/kg body-weight, was lower than that of group I (5.8 Bq) and III (9.4 Bq). Mean radiation exposure, calculated from these data, was 1.7 mrem/a for group I, 1.1 mrem/a for group II, and 2.8 mrem/a for group III. A comparison with present Cs values in adults and measurements made at the end of the 1950's and beginning of 60's showed good agreement. There were no significant differences, as regards Cs activity, between newborns or infants who had been formula-fed or breast-fed. The measured radiation exposure of the three groups is about 1% of natural radiation exposure. Thus, present-day results indicate that there will be no damage to health outside the natural scatter.

Accidents↗
PubMed1988

Serum vitamin D metabolites do not change in response to intravenous injection of thyrotropin releasing hormone (TRH) and growth hormone releasing factor (GHRF 1-44) in children.

Several reports claim that thyroid hormones and growth hormone participate in the regulation of vitamin D synthesis. We investigated whether there was a direct effect of their releasing hormones on vitamin D metabolism. TRH (7 micrograms/kg) was injected iv in 8 children with euthyroid diffuse goiter and GHRF (1 microgram/kg) in 10 short normal children. TRH injection induced significant TSH elevations but no changes in serum vitamin D metabolites, calcium and phosphorus. GHRF administration resulted in marked growth hormone elevations without alterations in the serum vitamin D metabolites, calcium and phosphorus. These results indicate no direct effect of TRH or GHRF itself on vitamin D metabolism, as well as a lack of very short term effect of growth hormone and TSH.

Calcifediol↗
PubMed1987

[Functional results following complicated injuries of the extremities--how can they be improved?].

This study evaluates the critical points in the management of 48 patients with injured arteries of the lower limb between 1980 and 1986. 77% of the traumas were resultant from blunt vehicular traffic mishaps. 13 patients were treated within 6 h, 8 patients later than 6 h, 21 patients later than 24 h post injury. Delays in diagnosis occurred due to lack of or no indication for vascular trauma. Careful physical examination and aggressive use of angiography is essential in improving limb salvage rates, while doppler investigation may lead to improper diagnosis. Overall limb salvage was 69%, however, no reconstruction was possible in 6 cases (13%). 38 of the 42 arterial reconstructions required interposition of venous bypass grafts, four end to end anastomoses. Eleven patients had associated venous injuries, which in nine cases were repaired. Venous ligation in three cases was attributed with increased complication. In three cases ischemia time was shortened by the use of temporary javid shunts for rapid restoration of arterial flow. 50% of the patients were found to require fasciotomy, either pre- or postvascular repair. Early fasciotomy, however was found to be most beneficial. Fractures were treated in 15 cases with the external fixator, in 21 cases with internal fixation. Delayed revascularization after 24 h combined with aggressive debriding of muscle necrosis and the employment of vascularized muscular and skin flaps resulted in a decline in amputation rates and improved functional results.

Adult↗
PubMed1985

[Vitamin D sterol in human milk, cow's milk and baby food].

A review is given of the results of vitamin D determinations in human and cow's milk using physico-chemical methods. Thereby only parent vitamin D is determined. Further, the results obtained with protein-binding assays are discussed in detail. With the aid of these newer methods the concentrations of hydroxylated vitamin D derivatives can also be measured. A comparison of the concentration of these vitamin D metabolites in human milk and infant formulas based upon cow's milk suggests that the higher anti-rachitic activity of human milk is connected with its higher concentration of 25-hydroxy-vitamin D.

Animals↗
PubMed1985

Lithotripsy of urinary concrement in the sigmoid after ureterosigmoidostomy.

A urinary concrement which appeared in the sigmoid of a 63-year-old man after ureterosigmoidostomy was extracted by endoscopy. The stone was situated proximal to a radiogenic stenosis. Because of the disproportion between the stone and the sigmoidal stenosis, mechanical lithotripsy had to be done before the concrement could be completely extracted.

Colon, Sigmoid↗
PubMed1984

[Relation of age at menarche and fertility period to body composition as related to surface area. A hypothesis].

From the potassium-40 values, the body weight, and the height of 4112 girls and women aged 8 to 65 years, we derive an association between menstruation and body cell mass/surface area quotient. In girls reaching a body weight of 47.8 kg, i.e. the body weight during the menarche according to Frisch and Revelle, the body cell mass/surface area quotient is 16.8 kg/m2 and remains such during the time of regular menstruations.

Adolescent↗
PubMed1984

[Does calcifediol replace vitamin D as a preventive and therapeutic agent?].

Cholecalciferol (CC) given orally is not utilized as efficiently as the CC produced by cutaneous UV light. The infant receives only minute amounts of CC by breast feeding, abolishing therefore the role of a vitamin for CC. The most important D-metabolite of human milk, the calcifediol (CF), however, has transient vitamin character. CF is both resorbed more efficiently by the intestine and it effects mineral metabolism faster via kidney than CC, which needs hydroxylation in the liver first. Thus CF shows advantages in prophylaxis and therapy. However, different (lower) dosages and the danger of hypercalcemia should be kept in mind using CF.

Breast Feeding↗
PubMed1984

Vitamin D, 25-hydroxy-vitamin D and 1,25-dihydroxy-vitamin D in cow's milk, infant formulas and breast milk during different stages of lactation.

Vitamin D and its metabolites were determined in cow's milk, infant formulas, and colostrum, transitional and mature breast milk by specific protein-binding assays following HPLC (high-pressure liquid chromatography). Cow's milk contains (mean +/- SEM) 50.4 +/- 4.1 pg/ml vitamin D (n = 10), 499 +/- 47 pg/ml 25-OH D (n = 10) and 9.7 +/- 1.0 pg/ml 1,25 (OH)2D (n = 3). 86.6% of the added vitamin D3 was recovered from infant formulas. The mean content (mean +/- SEM) of 25-OH D and 1,25(OH)2D of infant formulas are 299 +/- 35 pg/ml and 5.4 +/- 0.9 pg/ml (n = 9), respectively. Vitamin D concentration of colostrum and mature breast milk is 122 +/- 3.4 pg/ml (n = 7, mean +/- SEM) and 38 +/- 3.3 pg/ml (n = 9) respectively; the 25-OH D content increases from 294 +/- 50.6 pg/ml (n = 10) to 845 +/- 190 pg/ml (n = 14) during lactation. The increase of 1,25-(OH)2D from early to mature breast milk (3.2 +/- 0.6 pg/ml, n = 8 versus 5.3 +/- 0.7 pg/ml, n = 20) is still statistically significant.

Animals↗