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At least 55 records · Page 3Linked to original sources
PubMed1978

[Effect of chemical modification of the surface of erythrocytes on their stability to the hemolytic action of sodium alkyl sulfates].

The hemolytic action of a homologous series of sodium alkyl sulfates (C8 to C15) on dog and human erythrocytes was measured. The influence of trypsin, pronase and neuraminidase treatments on the lytic resistance of human red cells was studied. A new approach evaluating the hemolytic activity of ionic surfactants is expressed as a ratio of a concentration providing 50% lysis to its CMC-value. The results obtained are examined for their bearing on the use of surfactants as a means to study the structure organization of biological membranes.

Animals↗
PubMed1976

The features of sperm maturation in the epididymis of a marsupial, the brushtailed possum Trichosurus vulpecula.

Possum spermatozoa undergo a distinctive process of maturation in the epididymis, as shown by change in the properties of the sperm surface, by modification of their morphology and by their increasing capacity for progressive motility. Modification of the sperm surface over the head and tail is demonstrated by the different affinities of sperm from successive regions of the epididymis for FITC-conjugated wheat germ agglutinin and concanavalin A, and for cationic ferric oxide colloidal particles. Changes in sperm head morphology are caused by (1) a dramatic reshaping and consolidation of the acrosome in which excess plasma membrane overlying it is sloughed as a cluster of vesicles, (2) a reorientation of the nucleus almost parallel to the axis of the tail and (3) distal movement of the droplet from its initial envelopment of the nucleus to an eccentric position on the anterior segment of the midpiece. Spermatozoa released from the testis and caput epididymidis are essentially immotile or exhibit only lazy uncoordinated movements, whereas many from the corpus and most from the more distal regions of the epididymis display an energetic, progressive motility imparted by a rapid and stiff tail beat of narrow arc. This maturation of the capacity for motility is accompanied by an enhanced stability of the dense fibers and sheath, which became more resistant to the disruptive action of SDS and DTT, and by changes in the ultrastructure of the sperm tail. These include modification of the matrix of the mitochondria and also an unusual differentation of the midpiece into two distinct segments. The anterior segment is defined by profuse peri-mitochondrial stacks of membranes which developed as spermatozoa pass through the epididymis. These membranes, although prominent in mature spermatozoa fixed in situ, appear sparse and disorganised in spermatozoa fixed after 15 to 30 minutes of active motility in physiological medium, suggesting their possible utilisation in motile spermatozoa. The posterior segment is characterised by a thick peri-mitochondrial cytoplasmic sleeve, by spirally arranged parallel fibrous bands immediately beneath the plasma membrane and, subsequently, as spermatozoa pass into the lower corpus epididymidis, by rows of flask-shaped surface invaginations which develop between the spiral bands. Despite broad similarities in the features of sperm maturation in this marsupial and in eutherian mammals, there are distinct differencesin the structural organisation of their spermatozoa, particularly in the pserm head. Until more is known of the details of fertilisation in marsupials the significance of these differences will remain unclear.

Agglutinins↗
PubMed1978

Elimination of Escherichia coli K88 adhesion determinant by antibody in porcine gut and mammary secretions following oral immunization.

1) Although virulence of enteropathogenic E. coli in the pig is essentially associated with the K88 adhesion determinant, protection of the neonate and weanling is not necessarily dependent upon antibodies to this surface antigen. 2) Modification of the surface antigenic characteristics of enteropathogens occurs in the presence of antibody, suggesting an immune mechanism of induced loss of the genetic elements responsible for the synthesis of K88. 3) Antibodies directed against the K88 antigen do not seem to participate in the elimination of the K88 antigen. These observations provide a new concept that antibody mediated mechanisms of host defense include elimination of virulence determinants, a feature vital to maintaining the balance of the host pathogen relationship favorable to the host.

Administration, Oral↗
PubMed1976

Aortic endothelial and sub-endothelial lesions in early stages of experimental atherogenesis and in scurvy.

The endothelial and sub-endothelial lesions during early stages of experimental atherogenesis and scurvy have been studied by means of scanning EM and transmission EM, making use also of the Con-A reaction. The surface coat modifications were accompanied by formation of vacuoles in the endothelial cells and by sub-endothelial 'oedema', not only in rabbits fed a hypercholesterolic diet but also in scorbutic guinea pigs. The endothelial lesions were sometimes found even before clear modifications of the Con-A surface reactive layer were apparent.

Animals↗
PubMed1977

Modification of Drosophila cell surfaces by concanavalin A.

The effect of Con A on the surface morphology of cultured cells of Drosophila melanogaster growing on coverglasses was examined by scanning electron microscopy. With low lectin concentrations (5--10 microgram/ml) surface filaments disappeared and the cells flattened and spread against the glass surface. Cytoplasmic fusion bridges were observed in areas where cells made contact. Concentrations of Con A ranging between 50--500 microgram/ml caused cell shrinkage and surface distortions without cell flattening and filament loss. These morphologic effects were not apparent if Con A binding sites were blocked by preincubation with alpha-methyl-D-mannopyranoside before application to the cell cultures. However, once the Con A-mediated changes were in effect, the cells failed to show recovery when they were returned to growth medium and a majority of the cells on the coverglasses degenerated. Presumably the cells whose morphology appears unaffected by Con A treatment are the survivors that repopulate cultures returned to growth medium.

Animals↗
PubMed1976

Modifications of mammalian cell surfaces induced by sugars: scanning electron microscopy.

Substitution of galactose, xylose, or mannose for glucose in the growth medium of L cells or the addition of equal concentrations of the alternate sugars to glucose-containing medium results in marked morphologic changes. The changes are revealed by conventional staining for light microscopy and by scanning electron microscopy. L cells grow indefinitely on combinations of equal concentrations of glucose and galactose, xylose, or mannose. There appear to be no significant differences in growth rate on glucose compared to the combinations of sugars cited. Cells subcultured from glucose to the combinations while undergoing rapid multiplication show marked morphologic changes by light and scanning electron microscopy within 36 hr. Of particular note are the loss of microvilli; flattening of the cells; assumption of polygonal shape; prominence of nuclei and nucleoli; and changes in the structure and distribution of filopodia. Virtually all cells in the population exhibit the changes noted.

Cell Division↗
PubMed1977

Aortic surface coat scanning electron-microscopic modifications after short-term hypercholesterolic diet, visualized in rabbits by con A-haemocyanin reaction.

Modifications of the aortic endothelial surface coat have been visualized at SEM with the use of the Con A-haemocyanin method. After fifteen days of an atherogenic diet, a strong increase of the reactive coat was evident in areas near the orifice of the collateral branches. In other areas, the reaction appeared to be intensely diminished.

Animals↗
PubMedDate not supplied

Increased binding of concanavalin A at the cell surface following exposure to thyroliberin.

Thyroliberin (THR) binds specifically to SD1 rat prolactin cells and increases prolactin release. THR-induced modifications of surface membrane of intact SD1 cells were looked for, using concanavalin A (Con A) as a probe. At the electron microscope level the binding was restricted to the cell surface. Preexposure of the cells to TRH (27 nM) for 30 min at 37 degrees C increased the binding of Con A by 28--120%. Such an increase was not observed with low doses of TRH (13.5 and 2.7 nm) nor after only a 10-min exposure to 27 nM TRH. This effect is specific for TRH; it was not observed with other peptiDES. Simultaneous exposure to Con A and [3H] TRH did not alter [3H]TRH binding, but preexposure to Con A reduced the [3H]TRH binding by 10%, which may be due to steric hindrance. It is concluded that TRH induces an increased exposure of surface membrane glycoproteins in intact SD1 cells.

Cell Line↗
PubMed1979

Detection of memory cells by chemical modification of the lymphocyte cell surface.

Stringent alloantigen requirements, necessary for the differentiation of human memory cells into specific secondary cytolytic T cells (2 degrees CTL), can be bypassed by chemical modification of memory cells with the mitogenic oxidising agent, galactose oxidase. Treatment of memory cells generated in a long-term primary mixed lymphocyte culture with neuraminidase and galactose oxidase (NAGO) results in the differentiation of memory cells into 2 degrees CTL. In contrast, treatment of unprimed cells with NAGO does not result in CTL production despite the proliferation resulting from such treatment.

Cell Membrane↗
PubMed1977

Studies on the surface structure of the intracytoplasmic membrane in the photosynthetic purple bacterium Chromatium vinosum by means of chemical modification.

By means of a chemical modification technique, the surface structure of the intracytoplasmic membrane (chromatophores) of the photosynthetic bacterium Chromatium vinosum was investigated. Trinitrobenzenesulfonate was employed to modify the primary amino groups of phosphatidylethanolamine and proteins. The experimental results indicate that upon the chemical modification of intact cells, the amino groups on the inner surface of the chromatophores are trinitrophenylated, while upon the modification of isolated chromatophores, the amino groups of the outer surface are trinitrophenylated. Phosphatidylethanolamine is essentially equally distributed on the inner and outer surfaces of the chromatophores, while most proteins exist at the outer surface. In particular, a protein fraction, which is soluble in a mixture of chloroform/methanol, is located at the outer surface exposing a part of the amino groups in the aqueous phase.

Bacterial Chromatophores↗
PubMed2024

Adeno-Associated Virus Engineering and Load Strategy for Tropism Modification, Immune Evasion and Enhanced Transgene Expression.

Gene therapy aims to add, replace or turn off genes to help treat disease. To date, the US Food and Drug Administration (FDA) has approved 14 gene therapy products. With the increasing interest in gene therapy, feasible gene delivery vectors are necessary for inserting new genes into cells. There are different kinds of gene delivery vectors including viral vectors like lentivirus, adenovirus, retrovirus, adeno-associated virus et al, and non-viral vectors like naked DNA, lipid vectors, polymer nanoparticles, exosomes et al, with viruses being the most commonly used. Among them, the most concerned vector is adeno-associated virus (AAV) because of its safety, natural ability to efficiently deliver gene into cells and sustained transgene expression in multiple tissues. In addition, the AAV genome can be engineered to generate recombinant AAV (rAAV) containing transgene sequences of interest and has been proven to be a safe gene vector. Recently, rAAV vectors have been approved for the treatment of various rare diseases. Despite these approvals, some major limitations of rAAV remain, namely nonspecific tissue targeting and host immune response. Additional problems include neutralizing antibodies that block transgene delivery, a finite transgene packaging capacity, high viral titer used for per dose and high cost. To deal with these challenges, several techniques have been developed. Based on differences in engineering methods, this review proposes three strategies: gene engineering-based capsid modification (capsid modification), capsid surface tethering through chemical conjugation (surface tethering), and other formulations loaded with AAV (virus load). In addition, the major advantages and limitations encountered in rAAV engineering strategies are summarized.

Dependovirus↗