Quantification of adipose tissue by MRI: relationship with anthropometric variables.

This study had two objectives: 1) to establish magnetic resonance imaging (MRI) as a tool for measuring total and regional adipose tissue (AT) distribution in humans and 2) to assess the relationship between selected anthropometric variables and MRI-measured AT. Twenty-seven healthy men varying in age [40.8 +/- 14.5 (SD) yr], body mass index (28.5 +/- 4.8), and waist-to-hip ratio (WHR, 0.96 +/- 0.07) participated in the study. Total AT volume was determined using a linear interpolation of AT areas obtained on consecutive slices (n = 41) taken from head to toe (10-mm thickness, 50-mm centers). The mean change for repeated measures of total AT volume was 2.9% (range 0.9-4.3%). Large interindividual differences were observed for total AT volume (6.9-59.3 liters), subcutaneous AT (6.3-49.8 liters), and visceral AT (0.5-8.5 liters). Visceral AT represented 18.3% of the total AT. The single best predictor of total adiposity was waist circumference (R2 = 0.92). For visceral AT volume, WHR was the strongest anthropometric correlate (r = 0.85, P less than 0.01). When controlled for age and adiposity, however, WHR explained only 12% of the variation in absolute visceral AT and less than 1% of the variation in visceral-to-subcutaneous ratio. Age was a better predictor of visceral-to-subcutaneous ratio than level of adiposity or WHR. The results of this study demonstrate that MRI offers a reliable measure of regional and total AT distribution in humans and, thus, is of value as a research tool.     

Effects of cell heterogeneity on production of polypeptide growth factors and mesoderm-inducing activity by Xenopus laevis XTC cells

The Xenopus laevis XTC cell line has been analyzed for the production of polypeptide growth factors and mesoderm-inducing activity. By the use of specific biological assays, it is shown that XTC cells produce a growth factor functionally related to the platelet-derived growth factor (PDGF) and two transforming growth factor (TGF)β-like activities. Mesoderm-inducing activity, as measured on X. laevis ectodermal explants from stage 10 embryos, was found to coelute on a Bio-Gel P-100 column with one of the TGFβ-like activities at an apparent molecular weight of 6–10 kDa. Analysis of the DNA content from XTC cells by flow cytometry demonstrated that the cell line is heterogeneous and consists of both tetraploid and diploid cells. Cloning of the XTC cells and selecting single-cell colonies on the basis of their ability to grow in soft agar resulted in the isolation of several homogeneous, morphologically different clonal derivatives. Analysis of conditioned medium from these clonal derivatives showed that only one of them, the only diploid line among six investigated, produced a strong heat- and acid-stable mesoderm-inducing activity that induced notochord and muscle formation in stage 10 X. laevis ectodermal expiants. The relation between this activity and a recently described TGFβ-like mesoderm-inducing factor obtained from XTC-conditioned medium will be discussed. In conclusion, a clonal cell line derived from X. laevis XTC cells which provides a good source for further characterization of mesoderm-inducing factors has been established.     

Receptor-active glycolipids of epithelial cells of the small intestine of young and adult pigs in relation to susceptibility to infection with Escherichia coli K99

Glycolipids from mucosa scrapings of small intestine of neonatal and adult pigs were tested by the thin-layer chromatogram overlay assay for the binding of Escherichia coli K99. There was practically no binding to acid or non-acid glycolipids of adult pig, known to be resistant to infection with this bacterium. However, piglets, which are susceptible to infection, showed a clear binding to a doublet band in the acid glycolipid fraction. The receptor-active glycolipid was isolated and shown by mass spectrometry, NMR spectroscopy and degradation methods to be NeuGc alpha-3Gal beta 4Glc beta Cer (NeuGc-GM3), the two bands being due to heterogeneity of the ceramide. When tested against various reference glycolipids, NeuAc-GM3 was shown to be inactive. This ganglioside was dominating in adult pig. The apparent developmental disappearance of N-glycolyl groups in glycolipids of intestinal mucosa may have a correspondence in protein-linked sequences as well as thus explain the resistance of adult pigs to infection with E. coli K99.     

Members of the alpha-amylase inhibitors family from wheat endosperm are major allergens associated with baker's asthma

We have identified the major antigens or IgE binding components from wheat flour. Thirty-five sera from patients with baker's asthma were used to analyze the reaction with wheat salt-soluble proteins. We found a 15 kDa SDS-PAGE band which reacted with all sera tested. Purified members of the alpha-amylase inhibitor family, which are the main components of the 15 kDa band, were recognized by specific IgE when tested with a pool of reactive sera. Immunodetection after two-dimensional electrophoretic fractionation of crude inhibitor preparations from wheat endosperms also detected several inhibitor subunits as major low-molecular-weight allergens.     

Genetic Analysis of the Shaker Gene Complex of Drosophila Melanogaster

The Shaker complex (ShC) spans over 350 kb in the 16F region of the X chromosome. It can be dissected by means of aneuploids into three main sections: the maternal effect (ME), the viable (V) and the haplolethal (HL) regions. The mutational analysis of ShC shows a high density of antimorphic mutations among 12 lethal complementation groups in addition to 14 viable alleles. The complex is the structural locus of a family of potassium channels as well as a number of functions relevant to the biology of the nervous system. The constituents of ShC seem to be linked by functional relationships in view of the similarity of the phenotypes, antimorphic nature of their mutations and the behavior in transheterozygotes. We discuss the relationship between the genetic organization of ShC and the functional coupling of potassium currents with the other functions encoded in the complex.     

Expression patterns of mRNAs for α-fetoprotein and albumin in the developing rat: the ontogenesis of hepatocyte heterogeneity

Summary In developing and normal adult rat liver the expression patterns of the mRNAs for -fetoprotein (AFP) and albumin (ALB) were analysed byin situ hybridization using specific³⁵S-labelled complementary DNA probes. In the developing liver AFP and ALB mRNA are found from embryonic day (ED) 11 and 12, respectively, onward. At ED 20 the first signs of a zonal distribution of these mRNAs across the liver lobule can be observed, AFP mRNA concentration being higher in the pericentral area and ALB mRNA concentration higher in the periportal area. This distribution pattern of reciprocal, overlapping gradients of mRNA can be clearly recognized in the neonatal period. In the adult liver AFP mRNA can no longer be detected and similar to the neonatal situation, ALB mRNA is expressed across the entire porto-central distance decreasing in concentration going from the portal to the central area.Transient extra-hepatic expression of AFP mRNA is found in the embryonic heart and in the epithelial lining of intestine and lung furthermore, AFP and ALB mRNA are found to be transiently expressed in the developing renal tubules. Similar expression patterns have been observed for other liver-characteristic mRNAs (Moormanet al., 1990), suggesting that common regulatory factors are operative during development.     

Phytoplankton primary production and nutrients in the Oosterschelde (The Netherlands) during the pre-barrier period 1980–1984

Phytoplankton primary production, nutrient concentrations and turbidity were monitored at three stations in the Oosterschelde during 1980–1984 as part of an ecosystem study.From comparisons of dissolved nutrient ratios with the nutrient requirements of phytoplankton, and of ambient nutrient concentrations with half-saturation constants for nutrient uptake by natural phytoplankton populations it was concluded that silicate was a limiting nutrient for diatoms after the spring bloom until the end of the summer. Dissolved inorganic nitrogen and phosphate were not considered to be limiting to phytoplankton growth.In general, the phytoplankton growing season started during the first fortnight of April and ended at the end of September. Column production in the whole Oosterschelde varied between 201 and 540 g C m^–2 yr^–1 and was, on average, 25% higher in the western part than in the eastern part. Basin production in the Oosterschelde varied between 120 and 466 g C m^–2 yr^–1 and was, on average, 55% higher in the western part than in the eastern part; this difference could be explained by differences in the ratio of euphotic depth to mean depth of the compartments.Estimated carbon-specific growth rates in the eastern part varied between < 0.1 and 3 d^–1 and in the western part between < 0.1 and 1 d^–1. This difference could be explained by the great differences in depth of the compartments. Carbon-specific growth rates are discussed in relation to phytoplankton loss rates. It is suggested that in the eastern part sedimentation must be an important sink for phytoplankton.Communication no. 473 of the Delta Institute for Hydrobiological Research, Yerseke, The Netherlands.     

Zebra mussels (Dreissena polymorpha): a new perspective for water quality management

In the evaluation of the role of lake restoration programmesin situ measurements of the filtration rate of the freshwater musselDreissena polymorpha have been performed in Lake Wolderwijd, The Netherlands. The filtration rate mainly depends on the suspended matter content of the water, and shows an inverse exponential relationship with this factor. The filtration activity is temperature indifferent between approx. 5 and 20 °C. At low temperatures the filtration rate drops abruptly, at high temperatures gradual inhibition occurs. The filtration rate shows a sigmoidal relation with the length of the mussel. The largestD. polymorpha have a diminished filtration rate compared to animals of smaller size. This might be a degenerative feature of the oldest mussels. In Lake Wolderwijd a population density of 675 per m² is required to compensate phytoplankton growth by grazing. Manipulation of the size of the population can be executed by adding suitable substrates for the mussel.