Study of the amniotic fluid from smokers and non-smokers in the Ames test

Amniotic fluid from smokers and non-smokers was tested by the Salmonella/mammalian microsome test. Concentrated amniotic fluid from heavy smokers at term showed an increase in the number of revertants with increasing exposure to tar. However, some of the non-smokers had a higher number of revertants than the smokers. No significant differences were found between second-trimester samples from smokers and non-smokers, but the limited volumes available at this stage of pregnancy may be a source of error.     

Haemagglutinating and Hydrophobic Properties of Corynebacterium (Eubacterium) Suis

Corynebacterium (Eubacterium) suis strains from boars and sows haemagglutinated erythrocytes of different animal species (calf, guinea pig, poultry, pig, and human). The haemaigglutination was man nose resistant (MR) and was neither inhibited by L-fucose nor D-galactose. The hydrophobicity measured by salt aggregation test (0.1–0.9 mol/1 (NH4)2SO4) and the hydrophobic interaction chromatography test (90 % retention in octyl sepharose) together with the haemagglutinating activity, indicated the presence of fimbriae on the bacteria. The haemagglutinating and hydrophobic properties were heat-sensitive (60°C for 10 min) suggestive of the presence of a protein structure. Two types of fimbria-tion were demonstrated by electron microscopy. Fetuin and glyco^ protein inhibited the haemagglutination, whereas porcine mucin was without any effect. These results indicate that branched glycoproteins might be important receptors for these fimbriae. The pathogenic aspects of C. suis are discussed, based on recent acquired knowledge of the effect of other pyelonephritogenic bacteria.     

Enigmatic Cyst-Forming Sporozoon in the Spinal Cord of a Dog

A female racing greyhound dog was presented to the clinic at the age of 3 months with a 2 months’ history of irregular hindleg movements and thin hindleg muscles. On examination 1 month later, a squatting standing posture, a week proprio-ceptive positioning reaction, and severe atrophy and pain of the lumbar and thigh muscles, were evident. The dog was sacrificed and necropsied. The adrenals, hindleg muscles, kidneys, myo-cardium, peripheral nerves, spinal cord, thyroid, and tonsils were fixed in 10 % neutral buffered formalin and processed for histo-pathology.     

Protein G: a powerful tool for binding and detection of monoclonal and polyclonal antibodies

Protein G is an immunoglobulin (IgG)-binding bacterial cell wall protein recently isolated from group G streptococci. We have investigated the avidity of protein G for various monoclonal and polyclonal Ig of the IgG class, and compared it with the binding properties of protein A, the staphylococcal Fc-binding protein. Radiolabeled Ig were mixed with Sepharose-coupled protein G or protein A, and the amounts of radioactivity bound to the matrix-coupled bacterial proteins were determined. The avidity was found to be greater for protein G than for protein A for all examined Ig. Protein G bound all tested monoclonal IgG from mouse IgG1, IgG2a, and IgG3, and rat IgG2a, IgG2b, and IgG2c. In addition, polyclonal IgG from man, cow, rabbit, goat, rat, and mouse bound to protein G, whereas chicken IgG did not. The binding property of protein G was additionally exploited in the Western blot assay, in which iodine-labeled protein G was used successfully for the detection of a rat monoclonal antibody against ovalbumin, and for the detection of rabbit and goat polyclonal whole antisera against human urinary proteins. In these experimental situations, protein G was found to be a powerful reagent for the detection of IgG, and consequently the antigen against which these antibodies are directed.     

A comparison between dopamine-stimulated adenylate cyclase and 3H-SCH 23390 binding in rat striatum

Methods for measuring 3H-SCH 23390 binding and dopamine (DA) stimulated adenylate cyclase (AC) were established in identical tissue preparations and under similar experimental conditions. Pharmacological characterization revealed that both assays involved interaction with the D1 receptor or closely associated sites. In order to investigate whether the binding sites for 3H-SCH 23390 and DA in fact are identical, the antagonistic effects of a variety of pharmacologically active compounds were examined. Surprisingly, the Ki-values obtained from Schild-plot analysis of the antagonism of DA-stimulated AC, were 80-240 times higher than the Ki-values obtained from competition curves of 3H-SCH 23390 binding. Since both assays were performed under identical conditions, the differences in Ki-values indicate the possibility of different binding sites for DA and 3H-SCH 23390 or, that DA and 3H-SCH 23390 label different states of the same receptor.     

Nesting holes and food supply in relation to forest bird densities on islands and mainland

Summary Bird densities were estimated on 41 small islands and two mainland plots at a South Swedish lake both in 1976 and 1983. In the latter year, three additional plots were also censused. The ratio between combined densities of hole-nesting birds on the mainland and on islands was 3:1 both in plots without and with nest boxes. In plots with boxes combined densities of hole-nesting birds doubled compared with control plots. This increase was caused by a tenfold increase of pied flycatcher Ficedula hypoleuca. Territories of this species were on average established about a week later on the islands compared with the mainland. Furthermore, 50% of the males on the islands did not attract a female. Densities of great tit Parus major, marsh tit Parus palustris and nuthatch Sitta europaea were unaffected by increased nesthole availability. For P. major this result contrasts with those in other studies.The density of chaffinch Fringilla coelebs in habitats with similar height and vertical structure was two times higher on the islands compared to the mainland. On the islands the density was the same on islands with only one pair and on those with two or more pairs. In spring, there were no significant differences between islands and the mainland in the proportion of leaves with insect feeding traces. The proportion of Salix leaves with feeding traces increased with island size, but this was not so for Alnus and Betula leaves. In late summer, the proportion of leaves with feeding traces were halved inside a plot with nest boxes and hence increased bird densities compared to a nearby control plot. This result was the same along the lake shore and about 150 m away from the shore.The discussion centers on the effect of man on the food-and nest site-availability of hole-nesting birds, food limitation of insectivorous birds and density compensation on islands.     

Mechanism for Cd2+ inhibition of (K++ Mg2+)ATPase activity and K+ (86Rb+) uptake join roots of sugar beet (Beta vulgaris)

Steady state kinetics were used to examine the influence of Cd²⁺ both on K⁺ stimulation of a membrane-bound ATPase from sugar beet roots (Beta vulgaris L. cv. Monohill) and on K⁺(⁸⁶Rb⁺) uptake in intact or excised beet roots. The in vitro effect of Cd²⁺ was studied both on a 12000–25000 g root fraction of the (Na⁺+K⁺+Mg²⁺)ATPase and on the ATPase when further purified by an aqueous polymer two-phase system. The observed data can be summarized as follows: 1) Cd²⁺ at high concentrations (>100 μM) inhibits the MgATPase activity in a competitive way, probably by forming a complex with ATP. 2) Cd²⁺ at concentrations <100 μM inhibits the specific K⁺ activation at both high and low affinity sites for K⁺. The inhibition pattern appears to be the same in the two ATPase preparations of different purity. In the presence of the substrate MgATP, and at K⁺ <5 mM, the inhibition by Cd²⁺ with respect to K⁺ is uncompetitive. In the presence of MgATP and K⁺ >10 μM, the inhibition by Cd²⁺ is competitive. 3) At the low concentrations of K⁺, Cd²⁺ also inhibits the 2,4-dinitrophenol(DNP)-sensitive (metabolic) K⁺(⁸⁶Rb⁺) uptake uncompetitively both in excised roots and in roots of intact plants. 4) The DNP-insensitive (non metabolic) K⁺(⁸⁶Rb⁺) uptake is little influenced by Cd²⁺. As Cd²⁺ inhibits the metabolic uptake of K⁺(⁸⁶Rb⁺) and the K⁺ activation of the ATPase in the same way at low concentrations of K⁺, the same binding site is probably involved. Therefore, under field conditions, when the concentration of K⁺ is low, the presence of Cd²⁺ could be disadvantageous.     

Amino acid sequence homologies between rabbit, rat, and human serum retinol-binding proteins

The main transporting protein for vitamin A in rabbit serum, the retinol-binding protein (RBP), was isolated and its amino acid sequence determined. Rabbit RBP was found to be highly homologous to human RBP, whose amino acid sequence was elucidated earlier, and to rat RBP. The rat RBP sequence was obtained by combining information deduced from the nucleotide sequences of two overlapping cDNA clones with the NH2-terminal sequence of the isolated protein determined by automated Edman degradation. The identity between the three proteins is approximately 90%. The high degree of homology between RBP molecules from different species is probably explained by the fact that RBP participates in at least three types of molecular interactions: in the binding of prealbumin, in the interaction with retinol, and in the recognition of a specific cell surface receptor. All these interactions should lead to a conservation of RBP structure. The amino acid differences between rabbit, rat, and human RBP are discussed in light of the recent elucidation of the three-dimensional structure of human RBP. Hybridization of a probe isolated from a rat RBP cDNA clone to restriction enzyme-digested genomic DNA from rat and mouse suggests that RBP is encoded by a single gene.     

A high-affinity folate binding protein in normal human leukocytes: Ligand binding characteristics,ionic charge and molecular size

High-affinity binding of [³H]folate to supernatant from homogenized human leukocytes containing large amounts of binding protein displayed apparent positive cooperativity. The DEAE-Sepharose^® CL-6B chromatographic profile of the supernatant at pH 6.3 contained a major peak of folate binding (M_r approx. 25 000) in the front effluent and a smaller more acidic peak (M_r approx. 25 000) that emerged after a rise in NaCl from 30 mmol/l to 1 mol/l. Triton X-100 solubilized ceil sediment from the leukocyte homogenate contained some high-affinity folate binding activity (M_r approx 25 000), typically 5–10% of the total binding activity.