Increased UDP-Glucuronyltransferase in putative preneoplastic foci of human liver after long-term use of oral contraceptives

Previous research by the authors had suggested that uridine-diphosphate-glucuronyl-transferase (UDP-GT) is a useful preneoplastic marker in chemical carcinogenesis. Recently the authors report that they found typical clear cell foci in a macroscopically normal liver surrounding focal nodular hyperplasia with a 6 cm diameter in a 27-year old woman who had been using oral contraceptives (OCs) containing ethinyl-estradiol and lynestrenol for 9 years. These foci were further characterized by a reduction of canalicular and cytoplasmic ATPase activity, an increased glycogen content, and a positive immunohistochemical reaction for UDP-GT. OC users develop 2 basic types of benign liver tumors: hepatic adenoma and focal nodular hyperplasia. Hepatic adenoma appears to be caused by OCs, whereas the relationship between OC use and focal nodular hyperplasia is less clear. The tumorigenic action of OCs has been ascribed to a promotor action on liver cells; however, there is no evidence that OCs are initiators of liver tumors. The case reported shows 2 manifestations of toxic lesions promoted by OC use: the development of focal nodular hyperplasia and enzyme-altered foci comparable to those seen in experimental liver carcinogenesis. Further studies are needed to get more information about the preneoplastic potential of these foci in humans. Since enzyme-altered foci could not be identified in the liver tissue of healthy women, these foci may be of prognostic significance in longterm OC users.     

Comparison of the biosynthesis of the methanobacterial pseudomurein and the eubacterial murein

From cell extracts of the archaebacterium Methanobacterium thermoautotrophicum 11 putative precursors of the pseudomurein were isolated and characterized. On the basis of the isolated intermediates, a biosynthetic pathway of the pseudomurein is proposed. Compared to the eubacterial murein the biosynthetic stages follow different pathways as indicated by the occurrence of a nucleotide-activated disaccharide and nucleotide-activated peptides.     

The action spectrum for maximal photosensitivity of germination

 Fruits of Garden Lettuce, imbibed in 0.01 M KNO₃, were depleted of maternal active phytochrome B by saturating deep-red exposure and photosensitized by chilling for 1 week at 4  °C. Twenty saturated fluence-response curves for photoinduced germination were elaborated between 300 and 800 nm, using exposure periods from 6 to 600 s at 22.5  °C; there is linear and closely parallel regression in the logarithmic probability net. The reciprocals of the half-response fluences obtained gave the apparent conversion spectrum of the controlling pigments and this was corrected for the transmittance of the seed-coat. It is a phytochrome spectrum of P _r with photoconversion cross-sections of 1.2·10⁹ and 4.5·10³ m² mol^–1 at 666 and 800 nm, respectively. This means that for half-saturated germination of sensitized seed, fewer than 1 out of 200,000 phytochrome A molecules have to be photoconverted to P _fr, and no photo-reversibility by deep-red was found. Therefore, all spectral colours of nightly moon- or skylight should stimulate the germination of sensitized weed seeds if they are exposed at the soil surface between sequential tillage operations. Received: 28 April 2000 / Accepted in revised form: 28 July 2000     

Spatial distribution of calcium in food, water and soil and its possible influence on rickets disease in Northern Nigeria

Since the 1990s, children of the Gbagyi tribe in Northern Nigeria have been suffering severe rickets with an incidence of up to 40% in the children's generation. The disease seems to be prevalent in an area of approximately 100 km(2) south-east of Kaduna. According to broad medical studies in that area, there is no evidence for a genetic disposition but for a nutritional cause of the disease. A lack of calcium was found in blood and was calculated to originate from diet. We therefore checked parent material, soil, maize cobs (Zea mays) and drinking water for their specific Ca contents from a region with rickets problem (study area A) and compared the results to Ca amounts in similar samples from a region where rickets is unknown among the Gbagyi population (study area B). It thereby became apparent that there are no differences in mineralogical composition of the parent material between the study areas, but that Ca contents in soil, maize cobs and drinking water are 47.6%, 26.6%, respectively, 79.1% lower in study area A compared to study area B. This result suggests that there may indeed be a nutritionally and/or environmentally influence on rickets disease. Nevertheless, further research on this topic is required.