Uptake of calcium in wheat and cucumber roots

Uptake of Ca²⁺(⁴⁵Ca) was investigated in plants of wheat ( Triticum aestivum L. var. Svenno) and cucumber ( Cucumis sativus L. var. Cilla) cultivated in a nutrient solution with various Ca²⁺ concentrations. The adsorption of Ca²⁺ was higher in cucumber roots than in wheat roots especially at lower Ca²⁺ levels in the external medium. The intracellular fraction of Ca²⁺ was less than 20% of the total Ca²⁺ in wheat roots and less than 10% of the total Ca²⁺ in cucumber roots. The uptake of Ca²⁺ in cucumber was about 40 times higher than in wheat. Transport of Ca²⁺ in the roots towards the endodermis is suggested to take place mainly in the apoplastic pathway regulated by the availability of negatively charged binding sites along the cell wall continuum. Further transport of Ca²⁺ towards the stele may involve diffusion of Ca²⁺ into the symplasm in the vicinity of the endodermis. An active extrusion of Ca²⁺ towards the stele or towards the external medium is suggested to play a role in the regulation of Ca²⁺ uptake.     

Immunological studies in ulcerative colitis: extract, fractionation, and immunological characterization of germ-free rat colon antigen

Intestinal mucins from germ-free rats contained antigens reactive with sera from patients with ulcerative colitis, in addition to human blood group A- and H-like antigens. A crude antigen extract was obtained by phenol-water extraction at 65 °C. Two intestinal glycoproteins were purified from the extract by fractionated ethanol precipitation, ion-exchange chromatography, and gel filtration. The two glycoproteins (2aI and 4aIIb) were homogeneous in regard to electrical charge and molecular size. Both were glycoproteins of the blood group substance type. Component 2aI was very rich in N-acetylgalactosamine and threonine and low in N-acetylglucosamine and sialic acid(s). It had strong blood group A-like activity, weak blood group H activity, and no colon antigen activity as defined by patients' sera. Component 4aIIb was rich in sialic acid(s). About 40% of the sera from patients with ulcerative colitis reacted with this component. No blood group A- or H-like activity could be demonstrated. Colon antigen activity was sensitive to periodate oxidation, but resistant to boiling at neutral pH. It was very sensitive to acid hydrolysis. In fact, colon antigen activity was significantly reduced when subjected to weak acid hydrolysis under conditions which only appeared to release sialic acids.     

A chondroitin sulphate proteoglycan from human cultured glial cells aggregates with hyaluronic acid

Media harvested from cultures of glial cells grown in the presence of ³⁵S-sulphate were shown to contain ³⁵S-labelled proteoglycans. One of the components was a chondroitin sulphate proteoglycan that had an apparent monomer size similar to that of cartilage-derived chondroitin sulphate proteoglycan. The glial proteoglycan formed aggregates in the presence of hyaluronic acid; aggregation was abolished in the presence of deca- to tetradecasaccharides derived from hyaluronic acid or by previous reduction and alkylation of the proteoglycan. It is concluded that the ability to produce large chondroitin sulphate proteoglycan molecules capable of binding to hyaluronic acid is not confined to cartilage cells.     

Formation of DNA-binding products from isolated benzo[a]pyrene metabolites in rat liver nuclei

Liver nuclei from 3-methylcholanthrene-treated rats in the presence of NADPH metabolized 3- and 9-hydroxybenzo[a]pyrene and 7,8-dihydro-7,8-dihydroxybenzo[a]pyrene to products that bound to DNA. Maximal binding was obtained with the dihydrodiol which was approximately 3-fold that with 9-hydroxybenzo[a]pyrene, and 60-fold that with 3-hydroxybenzo[a]pyrene, as substrates. Both 4,5-dihydro-4,5-dihydroxybenzo[a]pyrene and 9,10-dihydro-9,10-dihydroxybenzo[a]pyrene were also extensively metabolized by the nuclear fraction but did not give rise to DNA-binding products.

The available evidence suggests that the DNA binding species derived from 9-hydroxy-benzo[a]pyrene is 9-hydroxy-benzo[a]pyrene-4,5-oxide and from 7,8-dihydro-7,8-dihydroxybenzo[a]pyrene, as previously observed in different systems, 7,8-dihydro-7,8-dihydroxy-benzo[a]pyrene-9,10-oxide.     

Ultrastructure of the enlarged cecum in germfree rats

Summary The cecum of germfree rats, as studied by light microscopy and scanning and transmission electron microscopy, differs in many respects from the cecum of conventional rats. Epithelial cells in germfree rats are taller and have larger nuclei and longer microvilli than similar cells in conventional rats. The cecal mucosa of germfree rats shows a larger variability in the arrangement of the crypts of Lieberkühn than does the mucosa of conventional rats. Some crypts are funnel-shaped and connected close to the mucosal surface with adjacent similar crypts to form long valleys. Less wide crypts open on elevated regions of the mucosal surface. The lamina propria of germfree animals is devoid of plasma cells but rich in mast cells. Germfree animals show hypertrophy of the tunica muscularis externa.In conventional rats the cecal lumen contains a large variety of morphologically different bacteria. However, the lumen of the crypts of Lieberkühn contains only one type of elongated bacteria, which are present in large amounts. This finding suggests that symbiotic relations may be of particular importance in the crypts of Lieberkühn in the cecum.Supported by research grants from the Swedish Medical Research Council (206), Knut och Alice Wallenbergs Stiftelse and Stiftelsen Therese och Johan Anderssons Minne.     

Studies on the differentiation capacity of neural epithelium cells in chick embryos

Cell and Tissue Research -     

Insular patterns of calicioid lichens in a boreal old-growth forest-wetland mosaic

Fragmentation of the forested landscape poses a threat to many aspects of biodiversity associated with old-growth forests Studies of the effects of forest fragmentation are often complicated by the variation in composition and age of patches and the matrix This study used a system of isolated stands where patch age and composition were similar and the matrix variability negligible The patches were composed of old-growth Picea abies stands of varying size and shape in a wetland matrix The study organisms were epiphytic crustose calicioid lichens (also known as Caliciales), many of which are very substrate-specific and restricted to old-growth stands The aim of the study was to measure the effect of patch size, patch isolation, habitat and substrate quality on the species riochness and composition of epiphytic calicioids Twenty-four patches ranging from 0 4 to 15 9 ha in size were studied All species of calicioid lichens were registered in 0 1 ha plots in each patch Isolation was measured as the percentage of available habitat within 400 m of a patch Twenty-two species were found with an average of 9 48 ± 0 26 (SE) species per patch and 292 ± 0 18 (SE) species per tree Species richness at patch level correlated with stand structure, primarily tree density, while number of species per tree (reflecting population size) was strongly correlated with island size and several stand variables There was no effect of isolation on species richness Species composition was influenced by both substrate variables and patch size The species composition on the islands showed a significant nestedness, i e species composition on species-poor islands constituted a non-random subset of the species composition on species-rich islands We propose that the explanation for the strong relationship between species richness at tree level and stand size is an edge effect which implies that unaffected interior areas only occur on large islands The different microclimate of the patch edge enables only the hardiest species to establish large populations there whilst shade and moisture demanding species are restricted to the interiors of larger islands     

RESOURCE ALLOCATION AND MATING SYSTEMS IN BUTTERFLIES

A cross-taxonomic comparison of resources allocated to reproductive reserves at adult eclosion reveals that females belonging to polyandrous species receive more ejaculate material and allocate proportionally less of their total reserves to potential reproduction compared to females belonging to monandrous species. These results suggest that adult females of polyandrous species have a higher expected nutrient income and are consistent with the idea that females can benefit from male nutrient donations transferred during mating. Males show the opposite pattern: males of polyandrous species allocate proportionally more to reproduction. This is expected since males in polyandrous species have both proportionally heavier ejaculates and have a higher ejaculative production capacity than do males in monandrous species. Interestingly, adults of the genus Heliconius which can obtain nutrients crucial to reproduction by pollen feeding do not seem to follow these patterns as strong as only nectar-feeding butterflies. Instead, the association between degree of polyandry and resources allocated to reproduction is relaxed.