Cell surface component(s) involved in rat hepatocyte intercellular adhesion

Aggregation of rat hepatocytes was effectively inhibited by monovalent antibodies (Fab fragments) directed against hepatocyte plasma membranes, but monovalent antibodies against some distinct, known hepatocyte surface antigens had no effect. Surface antigens, which neutralized the Fab inhibiting effect on cell aggregation, could be solubilized from plasma membranes by limited proteolytic digestion. Thus, hepatocyte intercellular adhesion seems to involve specific cell surface components, which may be proteins or protein derivatives.     

Correction of chlorophyll-defective male-sterile winter oilseed rape (Brassica napus) through organelle exchange: Characterization of the chlorophyll deficiency

Jarl, C. I., Ljungberg, U. K. and Bornman, C. H. 1988. Correction of chlorophyll-defective male-sterile winter oilseed rape ( Brassica napus ) through organelle exchange: Characterization of the chlorophyll deficiency. - Physiol. Plant. 72: 505–510.
As is known, the introduction of male-sterile Raphanus sativus L. cytoplasm into Brassica napus L. results in male-sterile oilseed rape plants, which display a temperature-related chlorophyll defect. The influences of temperature and irradiance on this defect were investigated. Compared to a line of normal (green phenotype) male-fertile oilseed rape, the male-sterile line had reduced chlorophyll content, fewer chloroplasts per cell, an altered ultrastructure of the chloroplasts and reduced activities of both photosystems, although the relative amounts of the photosystems and the chlorophyll a/b ratio were similar. The lower activity of the photosystems is explained by a decreased functional antennae size and a reduced efficiency in the interactions between the nuclear-encoded light-harvesting proteins and the reaction centres coded for by the plastome. Some thylakoid polypeptides differed in proportion between the male-fertile line with green phenotype and the male-sterile line with chlorotic phenotype. Characters, in which the two lines exhibited differences, are ascribed to difficulties in molecular communication between the oilseed rape nucleus and the radish cytoplasm, which are combined in the deficient male-sterile line.     

Mass transfer in blood oxygenators using blood analogue fluids

Mass transfer correlations for hollow fiber blood oxygenators have been determined experimentally using Newtonian and non-Newtonian blood analogue fluids. The Newtonian fluids consisted of deionized water and glycerol/water mixtures. The non-Newtonian fluids were prepared by adding small amounts of xanthan gum to the Newtonian blood analogue fluids. The rheological behavior of the non-Newtonian blood analogue fluids was modeled using the power law. The diffusion of oxygen into and out of the Newtonian and non-Newtonian blood analogue fluids has been studied. The liquid stream flowed outside and across bundles of woven hollow fibers, while the gas stream flowed inside the fibers.     

Soil acidity and distribution of species on tussocks and interspaces in schoenus vegetation of South and Southeast Sweden

Summary In five South Swedish provinces the vertical distribution of species in Schoenus phytocoenoses, especially bryophytes, were studied by belt transects and analysed by RA. Results indicate that the sequence of bryophyte dominants: Scorpidium scorpioides-Drepanocladus revolvens-Campylium stellatum-Tomenthypnum nitens-Sphagnum fuscum reported by Du Rietz (1949) is distinctly developed in Uppland. A shorter sequence: Scorpidium scorpioides-Drepanocladus revolvens/Campylium stellatum-Ctenidium molluscum, is developed on Öland. In Skåne and Östergötland it is not possible to demonstrate any bryophyte sequence common to all transects and probable reasons for this are discussed. The distribution of the vascular plants confirmed the results of earlier investigations. Several types of relationships between pH and height above interspaces are found and it is assumed that these relationships are due to water fluctuations.I wish to express my gratitude to Nils Malmer, Head of the Department, for valuable advice, to Germund Tyler for help in the field work, to Robert Dewsnap for revision of the English text, and to Mimmi Varga and Brita Billstein for technical assistance.Nomenclature as in Tyler (1980a).The study is the shortened and revised third part of a doctor's thesis.     

Food selectivity versus prey availability: a study using the marine fish Pomatoschistus microps

Summary The food selection of the common goby, Pomatoschistus microps Krøyer, was studied in the field and in laboratory experiments on the Swedish west coast. The three most important prey organisms for P. microps in the study area were Corophium volutator, chironomid larvae and Nereis spp. Corophium was consumed more than any other prey, even when it was not the most abundant prey species in the bottom. One reason may be the higher activity of Corophium above the sediment surface, which may increase its visibility and consequently its vulnerability to visual predators. When P. microps was offered Corophium and chironomid larvae with similar exposure in laboratory experiments, it showed no preference for either of the prey items. It always took the closest mobile prey, regardless of species and size.     

Crystal structure,conformational analysis,and molecular dynamics of tetra-O-methyl-(+) -catechin

The structure of tetra-O-methyl- (+) -catechin has been determined in the crystalline state. Two independent molecules, denoted structure A and structure B, exist in the unit cell. Crystals are triclinic, space group P1, a = 4.8125(2) Å, b = 12.9148(8) Å, c = 13.8862(11) Å, α = 86.962(6) °, β = 89.120(5)°, γ = 88.044(5)°, Z = 2, D_c = 1.336 g cm^?3, R = 0.033 for 6830 observations. The heterocyclic rings of the crystal structures are compared to previous results for 8-bromotetra-O-methyl-(+)-catechin, penta-O-acetyl-(+)-catechin, and (?) -epicatechin. One of the two molecules has a heterocyclic ring conformation similar to that observed previously for (?)-epicatechin, and the other has a heterocyclic ring conformation similar to one predicted earlier in a theoretical analysis of dimers of (+)-catechin and (?) -epicatechin. Both structure A and structure B in the crystal have heterocyclic ring conformations that place the dimethoxyphenyl substituent at C(2) in the equatorial position. However, this heterocyclic ring conformation does not explain the proton nmr coupling constant measured in solution. Molecular dynamics simulations show an equatorial ? axial interconversion of the heterocyclic ring, which can explain the nmr results. © 1993 John Wiley & Sons, Inc.     

Evidence for a selective migration of fetus-specific CD4+CD25bright regulatory T cells from the peripheral blood to the decidua in human pregnancy

During pregnancy, the maternal immune system has to tolerate the persistence of fetal alloantigens. Many mechanisms contribute to the prevention of a destructive immune response mediated by maternal alloreactive lymphocytes directed against the allogeneic fetus. Murine studies suggest that CD4(+)CD25(+) T cells provide mechanisms of specific immune tolerance to fetal alloantigens during pregnancy. Previous studies by our group demonstrate that a significantly higher percentage of activated T cells and CD4(+)CD25(bright) T cells are present in decidual tissue in comparison with maternal peripheral blood in human pregnancy. In this study, we examined the phenotypic and functional properties of CD4(+)CD25(bright) T cells derived from maternal peripheral blood and decidual tissue. Depletion of CD4(+)CD25(bright) T cells from maternal peripheral blood demonstrates regulation to third party umbilical cord blood cells comparable to nonpregnant controls, whereas the suppressive capacity to umbilical cord blood cells of her own child is absent. Furthermore, maternal peripheral blood shows a reduced percentage of CD4(+)CD25(bright)FOXP3(+) and CD4(+)CD25(bright)HLA-DR(+) cells compared with peripheral blood of nonpregnant controls. In contrast, decidual lymphocyte isolates contain high percentages of CD4(+)CD25(bright) T cells with a regulatory phenotype that is able to down-regulate fetus-specific and fetus-nonspecific immune responses. These data suggest a preferential recruitment of fetus-specific regulatory T cells from maternal peripheral blood to the fetal-maternal interface, where they may contribute to the local regulation of fetus-specific responses.     

Influence of predation risk on individual competitive ability and growth in Eurasian perch, Perca fluviatilis

We studied the potential influence of predation risk on the competitive ability and habitat use of foraging perch and the effect of these interactions on growth. Groups of four similar-sized young-of-the-year perch were in visual contact with a piscivorous perch during feeding. The fry had the choice of vegetation and open habitat, with food presented in the open habitat. Competitive ability, defined as proportion of prey attacks, varied between perch individuals and was unaffected by predation risk. The variation in proportion of prey attacks was affected by relative size within each replicate group, despite small size differences (±1 mm), with the largest individual being a better competitor than the smallest ones. The degree of boldness, measured as the proportion of time spent in the open habitat, was significantly related to both competitive ability and prey attack order. Observations of aggressive behaviour indicated a possible occurrence of interference competition, which may contribute to the appearance of different competitive abilities between individuals within a group of perch. A significant correlation was found between competitive ability and growth. Growth variation within groups was not affected by predation risk.     

Predicting the distribution of <Emphasis Type="Italic">Encephalartos latifrons</Emphasis>, a critically endangered cycad in South Africa

This study evaluates how a modelling approach to determine areas of suitable habitat for the Critically Endangered Albany cycad Encephalartos latifrons can assist in systematic conservation planning for this and other rare and threatened cycads. A map distinguishing suitable from unsuitable habitat for E. latifrons was produced and important environmental predictors (climate, geology, topography and vegetation) influencing the suitable habitat were estimated. The maximum entropy (MaxEnt) modelling technique was chosen for this study as it has consistently performed well compared with alternative modelling methods and is also an appropriate model choice when the sample size is small and locality records are relatively few. Predicted habitat suitability showed that some locations chosen for translocation and restoration of E. latifrons specimens are not suitable. This revealed that modelling suitable habitat can guide relocation and regeneration of E. latifrons and perhaps other threatened cycads with restricted distributions and few locality records. The species distribution model constructed for E. latifrons is the first reported habitat model for a Critically Endangered cycad in South Africa. The results may be incorporated into conservation planning and structured decision-making about translocations and restoration programmes involving vulnerable cycads, which are among the most threatened organisms globally.