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Biomedical subjects

W Schubert

Publications and source records attributed to W Schubert.

170 records · Page 10Linked to original sources
PubMedDate not supplied

Flavonoids in grapefruit juice inhibit the in vitro hepatic metabolism of 17 beta-estradiol.

Naringenin, quercetin and kaempferol, which may be found in glycoside form in natural compounds such as grapefruit, are potent inhibitors of cytochrome P-450 metabolism. The influence of these flavonoids on the metabolism of 17 beta-estradiol was investigated in a microsome preparation from human liver. The flavonoids were added in concentrations of 10, 50, 100, 250 and 500 mumol/l to the microsome preparation. The metabolism of 17 beta-estradiol was concentration dependently inhibited by all the flavonoids tested. Addition of the flavonoids to the microsome preparation did not influence estrone formation, while a potent inhibition of estriol formation was observed. At the highest concentrations tested of the respective flavonoid, there was approximately 75-85% inhibition of estriol formation. However, naringenin was a less potent inhibitor of 17 beta-estradiol metabolism as compared to quercetin and kaempferol. The most likely mechanism of action of the flavonoids on 17 beta-estradiol metabolism is inhibition of the cytochrome P-450 IIIA4 enzyme, which catalyzes the reversible hydroxylation of 17 beta-estradiol into estrone and further into estriol. These hydroxylation processes represent the predominant steps of the hepatic metabolic conversion of endogenous as well as exogenous 17 beta-estradiol. This interaction would be expected to inhibit the first-pass metabolism of 17 beta-estradiol, and this has recently been demonstrated after oral administration of 17 beta-estradiol to women.

Adult↗
PubMedDate not supplied

Ultraviolet mutagenesis of radiation-sensitive (rad) mutants of the nematode Caenorhabditis elegans.

A mutational tester strain (JP10) of the nematode C. elegans was used to capture recessive lethal mutations in a balanced 300 essential gene autosomal region. The probability of converting a radiation interaction into a lethal mutation was measured in young gravid adults after exposure to fluences of 254-nm ultraviolet radiation (UV) ranging from 0 to 300 Jm-2. Mutation frequencies as high as 5% were observed. In addition, three different radiation-hypersensitive mutations, rad-1, rad-3 and rad-7 were incorporated into the JP10 background genotype, which allowed us to measure mutation frequencies in radiation-sensitive animals. The strain homozygous for rad-3 was hypermutable to UV while strains homozygous for rad-1 and rad-7 were hypomutable. Data showing the effects of UV on larval development and fertility for the rad mutants is also shown and compared for wild-type and JP10 backgrounds.

Animals↗
PubMedDate not supplied

Molecular genetic evidence for early evolutionary origin of budding peptidoglycan-less eubacteria.

Recent studies on the cell wall composition of budding, non-prosthecate bacteria have shown that representatives of the genera Planctomyces and Pasteuria (sensu Staley, 1973) lack the peptidoglycan moiety, which is the characteristic feature of eubacterial cell walls, but possess an as yet unidentified protein sheet instead; in this respect Planctomyces and Pasteuria strains resemble certain archaebacteria more than eubacteria. To determine their phylogenetic positions, the 16S ribosomal RNAs of three budding, peptidoglycan-less strains with and without stalks were subjected to partial sequence analyses. As we report here, the comparison of data with those obtained from about 320 eubacterial and 40 archaebacterial strains revealed that the strains investigated are not members of the archaebacterial kingdom but represent an ancient line of descent of the eubacterial kingdom. Furthermore the diphtheria toxin reaction of Planctomyces and Pasteuria shows that they behave like eubacteria.

Bacteria↗
PubMedDate not supplied

Halo immobilization in the treatment of burns to the head, face, and neck.

The care of burns to the head, face, and neck remains a challenge to the clinician. From 1978 to 1986, halo traction was used as an immobilizing device and as a protective frame for 31 patients with burns to the head (n = 8), face (n = 24), and neck (n = 28). The patients ranged in age from 8 months to 80 years (mean = 16 years) and had second- and third-degree burns covering a total body surface area of 8% to 75% (mean = 28%). The halo was used for an average of eight days (range one to 19 days) and served to immobilize and protect areas of fresh skin grafts, as well as to elevate and protect scalp donor sites (n = 10). Traction was initially used in patients who were confused and uncooperative, and in patients whose burns involved the neck to provide extension for prophylaxis against contractures. Treatment side effects included intermittent headache and backache, the latter occurring especially in the patients subjected to hyperextension. Eight patients (26%) complained of discomfort, which was reduced with adequate analgesia, sedation, and emotional support. The halo had to be removed from one patient after one day because of a loose pin, and in another patient after eight days because of the development of cellulitis at a pin site. Halo immobilization was used successfully to minimize graft loss in 30 of 31 patients.

Adolescent↗
PubMedDate not supplied

Burns from hot oil and grease: a public health hazard.

We examined the incidence, etiology, and morbidity of burns due to hot oil and grease. Over a 10-year period from 1976 to 1985, of 1818 patients hospitalized for burns, 85 (4.7%) injuries were due to hot grease or oil. The mean age was 20 years; 34% of patients were less than 8 years old. The mean total body surface areas of second- and third-degree burns was 11.5% (range 0.5% to 40%), and the average length of hospital stay was 19.6 days. Fifty-eight percent of patients required split-thickness skin grafting (n = 49), three required intubation, and one required tracheostomy. Seventy-eight percent of oil burns occurred in the home. The most common circumstances consisted of children who grabbed the handle or electric cord of a frying pan and pulled the hot oil down onto themselves. (Nineteen of the 29 children were less than 8 years old (66%).) Burns due to cooking oil and grease are associated with considerable morbidity. The high boiling point, high viscosity, and potential combustibility of oil increase the potential soft-tissue damage when compared with typical scald injuries from hot water. The dangers of children pulling on the appliance, the dangers of transporting hot oil, the importance of supervision while children are cooking, and the importance of knowledge of the management of grease fires is stressed. Public education is needed to underline the potential seriousness of these burns.

Accidents, Home↗