The use of RAPD markers for the detection of gene introgression in potato

Randomly Amplified Polymorphic DNAs were employed to demonstrate that potato dihaploids generated after interspecific pollination of a tetraploid Solanum tuberosum cultivar (Pentland Crown) by Solanum phureja dihaploid inducer clones could not be of parthenogenetic origin. Of six different 10-mer oligonucleotides, four generated products from total potato dihaploid genomic DNAs which were not derived from the S. tuberosum parent. Gel electrophoresis and Southern analysis indicated that these amplified bands originated from S. phureja. The results are discussed in the context of recent cytological and molecular evidence which demonstrates that potato dihaploids are aneusomatic (Clulow et al. 1991) and emphasises this approach as a general methodology for the detection of alien gene introgression in both natural and cultivated plant populations.     

Glycosylation at specific sites of erythropoietin is essential for biosynthesis, secretion, and biological function

The glycoprotein hormone erythropoietin (Ep), the primary regulator of erythropoiesis, is synthesized by the kidney and secreted as the mature protein with three N-linked and one O-linked oligosaccharide chains. To investigate the role(s) of each carbohydrate moiety in the biosynthesis and function of Ep, we have used oligonucleotide-directed mutagenesis of a cDNA for human Ep to alter the amino acids at each of the carbohydrate attachment sites. Each mutated cDNA construct was expressed in stably transfected sublines of a kidney cell line, baby hamster kidney. We show, by preventing attachment of N-linked carbohydrate at asparagines 38 or 83, or preventing O-linked glycosylation at serine 126, that glycosylation of each of these specific sites is critical for proper biosynthesis and secretion of Ep. Fractionation of cellular extracts demonstrated that the mutant proteins lacking glycosylation at each of these three sites, (38, 83, and 126) were associated mainly with membrane components or were degraded rapidly. Less than 10% of these three mutant proteins were processed properly and secreted from the cells. The Ep protein lacking N-linked glycosylation at asparagine 24 is synthesized and secreted as efficiently as native Ep. The carbohydrates at positions 24 and 38 may be involved in the biological activity of Ep, since the absence of either of the oligosaccharide side chains at these positions reduced the hormone's biological activity.     

The effect of sulfide and an increased food supply on the meiofauna and macrofauna at the East Flower Garden brine seep

A sulfurous brine seep at the East Flower Garden Bank, northwest Gulf of Mexico, produces conditions conducive to the growth of a luxuriant prokaryotic biota. Hydrodynamic cropping continually harvests this biota and distributes it to sandy-bottom and hard-bank benthic communities downstream of the seep. Consequently, both macro- and meiofaunal abundances are dramatically increased above the regional norm in parts of the seep system. When sulfide is present, the lower Bilaterian groups belonging to the meiofauna dominate the community; without sulfide, macrofaunal groups, particularly crustaceans, dominate the community. Outside the influence of the seep, meiofaunal copepods predominate. Changes in taxonomic composition and abundance indicate that the sandy-bottom benthos at 70–80 m depth at the East Flower Garden bank is foodlimited and that, under these conditions, meiofauna, particularly the higher Bilaterian groups, dominate the community numerically. Perhaps, under food-limiting conditions, meiofauna compete favorably with macrofauna for food.     

Non-cross-reactive monoclonal antibodies to human chorionic gonadotropin generated after immunization with a synthetic peptide

Noncross-reactive monoclonal antibodies specific for human chorionic gonadotropin (hCG) were obtained after pre-selection for submolecular specificity with a synthetic peptide immunogen. Mice were immunized with a synthetic peptide representing a segment unique to the beta-subunit of hCG (amino acid residues 109-145), conjugated to diphtheria toxoid. We then derived nine different hybridomas that secreted monoclonal antibodies reactive with both native hCG and isolated C-terminal peptide, after somatic cell hybridization of immune spleen cells with a nonsecretory myeloma cell line. None of the nine monoclonal antibodies, termed beta-hCG-CTPa1----a9, reacted with hLH, hFSH, or hTSH, although these pituitary hormones display extensive amino acid sequence homology with hCG. The noncross-reactive anti-beta-hCG monoclonal antibodies show apparent association constants on the order of 10(9) to 10(10) M-1. A sandwich-type enzyme-linked immunosorbent assay was set up with cut-off values of around 5 mIU/ml. These antibodies might have important implications for: a) improving the diagnosis and clinical management of pregnancy; b) monitoring the course of development of carcinomas which secrete the hormone, through in vitro assays or in vivo radioimmunodetection; c) evaluating the antibodies' therapeutic potential against such carcinomas; d) studying the biologic functions of the C-terminal segment of beta-hCG; and e) addressing the anti-fertility effect of antibodies raised against that segment.     

The effect of visual deprivation upon the basal dendrites of Meynert cells in the striate cortex of the monkey

The basal dendrites of Meynert cells in the striate cortex have been studied with the Golgi method in the brains of monkeys that had been reared for varying periods with the eyelids closed over one eye. The lengths and arrangement of the dendrites were compared with those in normal brains. In the visually deprived brain almost half of the cells had basal dendrites that were apparently normal with the dendritic fields in the form of an ellipse and the long axes parallel to the direction of the ocular dominance bands. The other cells had dendritic fields that have rarely been seen in normal material and two distinct types could be recognized. The 'lop-sided' cell had an ellipsoidal dendritic field with the major axis parallel to the ocular dominance bands, but the extents of the dendrites along the minor axis were very asymmetric; the ratio of the means of the long and short arms of the minor axis of the 'lop-sided' cell is 2.3:1 compared with 1.1:1 in normal brains. The 'perpendicular' type of cell also had an ellipsoidal dendritic field but the relation of the major and minor axes to the direction of the ocular dominance bands was the reverse of the normal cell, with the long axis of the ellipse being aligned perpendicular to the bands. 'Lop-sided' cells formed approximately 18% of the total of Meynert cells studied and the 'perpendicular' 32%. The proportion of the cells with abnormal basal dendritic fields, and particularly the 'perpendicular', increased with longer durations of eyelid closure. It is suggested that the alterations in the dendritic fields of the 'lop-sided' and 'perpendicular' cells may be correlated with the changes in width of the ocular dominance bands that are known to occur after monocular eyelid suture.     

Chemical modification of arginine residues of lung galaptin and fibronectin. Effects on fibroblast binding.

Lung galaptin bound to lung fibroblasts with a Kd of 190 nM, and this binding could be inhibited by 20 mM-lactose. Selective modifications of the arginine residues of galaptin with cyclohexane-1,2-dione did not change its lectin activity or its binding to fibroblasts. By contrast, modification of the arginine residues of plasma fibronectin resulted in a marked diminution of protein-fibroblast binding. Selective modification of arginine residues may provide a useful probe for -Arg-Gly-Asp-Xaa cell-binding sequences of proteins.     

Oxidation and chemical modification of lung beta-galactoside-specific lectin.

Galaptins are small, soluble, lectins with a specificity for beta-galactose residues. Many galaptins are inactivated by atmospheric oxygen and are protected by disulphide-reducing reagents. We find that each subunit of rat lung galaptin contains one residue of tryptophan and six of cysteine. Oxygen inactivates rat lung galaptin by oxidation of the cysteine residues. During oxidation, the normal dimeric structure is maintained and all disulphide bonds are formed within individual subunits. Exogenous thiols protect against inactivation, but oxidized thiols accelerate inactivation. Human lung fibroblast galaptin is almost completely inactivated within 1 h in tissue culture medium at 37 degrees C. Alkylation of native rat lung galaptin with iodoacetate or ethyleneimine causes substantial loss of activity. The dimeric galaptin structure is maintained. In contrast, alkylation with iodoacetamide yields carboxamidomethyl-galaptin, which is fully active and stable to atmospheric oxygen in the absence of disulphide-reducing reagents. This derivative is very useful for studies of galaptin properties and function.     

The deposition of bacterial cells from laminar flows onto solid surfaces

In a previous article, the authors proposed a simple model for the rate of removal of bacterial cells from solid surfaces by fluid shear. This Model has been extended to include the deposition of cells from a flowing suspension. The theory is compared to experimentally obtained data for the deposition of Bacillus cereus cells onto the surface of glass capillaries. The effect of a hydrophobic surface, siliconized glass, and the addition of an antifoam agent to the suspension is also investigated.     

Gammaphotography

The Anger scintillation camera greatly broadens the range of studies performed by radioisotope imaging devices. Its ability to view in any direction, to make an image simultaneously of an entire field of view, and to obtain images rapidly, all serve to make scintiphotography analogous to fluoroscopy. Illustrations of its uses in static and dynamic gammaphotography and in numerical data processing are described.