Monoclonal antibodies against ovalbumin

Fusion of cells of the NS-1 mouse myeloma line with spleen cells from $\text{BALB}\text{c}$ mice immunized against ovalbumin produced hybrid cells which continuously secrete antibodies specific for ovalbumin. One of these cells was used to establish a cloned line. Studies of its antibody obtained either from ascites fluid or from medium from hybridoma cultures showed high titer and specificity against ovalbumin using the double antibody technique with rabbit anti-mouse immunobeads; the antibody proved to be of the IgG₁ (kappa) subclass and type.     

Is supernumerary chromatin involved in gametophytic apomixis of polyploid plants?

Gametophytic apomixis, or unreduced embryo sac development that results in asexual reproduction through seeds, occurs in several families of angiosperms and must be polyphyletic in origin. The molecular mechanisms underlying gametophytic apomixis have not been discovered and are the subject of intense investigation. A common feature of almost all apomicts is their polyploid nature. From genetic mapping studies in both monocots and dicots, there is low genetic recombination associated with a single (rarely two), dominant locus for either aposporous or diplosporous embryo sac formation. In Pennisetum squamulatum and Cenchrus ciliaris, some DNA sequences mapping to the apospory locus are unique to apomictic genotypes and apparently hemizygous. This sequence divergence at the apomixis locus could be a consequence of genome rearrangements and isolation from genetic recombination, both of which may have contributed to the definition of a chromosomal region as supernumerary. The possible involvement of supernumerary chromatin, formed as a result of interspecific hybridization, in the origin of apomixis, is explored here. Received: 26 October 2000 / Revision accepted: 5 April 2001     

The measurement of gamma-glutamyl hydrolase (conjugase) activity in rat brain

An assay using the artificial substrate, 2,4-diamino-10-methyl-pteroylglutamyl-gamma-glutamate (MTX-G₁), was developed to measure gamma-glutamyl hydrolase (conjugase), which hydrolyzes folylpolyglutamates. This assay allows us to: 1) measure conjugase for the first time in rat brain and 2) measure conjugase in a reliable, sensitive and inexpensive manner. The MTX-binding assay results were compared to samples analyzed by HPLC and found to vary by only 13%. The artificial substrate, MTX-G₁, had a lower rate of hydrolysis than pteroylglutamyl-gamma-glutamate (Pte-G₂), 70.7±0.64 and 92.6±0.22 nmoles/hr/mg protein respectively. Conjugase was semi-purified 24 fold in H₂O and found to have a pH optimum of 5.0.     

Molecular Analysis of In Vitro Shoot Organogenesis

Shoot organogenesis is one of the in vitro plant regeneration pathways. It has been widely employed in plant biotechnology for in vitro micropropagation and genetic transformation, as well as in study of plant development. Morphological and physiological aspects of in vitro shoot organogenesis have already been extensively studied in plant tissue culture for more than 50 years. Within the last ten years, given the research progress in plant genetics and molecular biology, our understanding of in vivo plant shoot meristem development, plant cell cycle, and cytokinin signal transduction has advanced significantly. These research advances have provided useful molecular tools and resources for the recent studies on the genetic and molecular aspects of in vitro shoot organogenesis. A few key molecular markers, genes, and probable pathways have been identified from these studies that are shown to be critically involved in in vitro shoot organogenesis. Furthermore, these studies have also indicated that in vitro shoot organogenesis, just as in in vivo shoot development, is a complex, well-coordinated developmental process, and induction of a single molecular event may not be sufficient to induce the occurrence of the entire process. Further study is needed to identify the early molecular event(s) that triggers dedifferentiation of somatic cells and serves as the developmental switch for de novo shoot development.     

Characterization of mucin glycoprotein-specific translation products from swine and human trachea,pancreas and colon

Summary RNA was isolated from cultured swine trachea epithelial cells and mucus-secreting tumor cell lines from human pancreas, lung and colon by extraction with guanidine isothiocyanate. Poly(A)⁺mRNA rich fractions were purified by repeated chromatography on oligo (dT)-cellulose columns and they were translated in a cell-free rabbit reticulocyte system. Translation products labelled with ³⁵S-methionine were isolated by immunoprecipitation with specific antibodies to the polypeptide chains of mucin glycoproteins and they were analyzed by SDS-PAGE and fluorography. A single principal polypeptide band of 67 kDa was found in all cases when the immunoprecipitates were washed with buffer containing bovine serum albumin and unlabeled deglycosylated mucin glycoprotein. The intensity of the 67 kDa band decreased when unlabeled deglycosylated mucin glycoprotein was added to the translation mixture before immunoprecipitation. Affinity purified monospecific antibodies elicited against chemically deglycosylated polypeptide chains of purified mucin glycoproteins from human and swine trachea and Cowper's gland were all equally effective in immunoprecipitating the 67 kDa translation product. Monospecific antibodies directed against the glycosylated and unglycosylated regions of the polypeptide chain yielded single bands with a molecular size of 67 kDa in each case. Peptide profiles obtained by digestion of the 67 kDa translation product with S. aureus V-8 protease were identical to those obtained with deglycosylated human and swine trachea mucin glycoproteins.These stydies clearly demonstrate that the translation product of swine trachea and human lung, colon and pancreatic mucin glycoprotein gene is a single polypeptide chain of 67 kDa. The relative size and properties of the translation products synthesized with poly (A)⁺RNA isolated from mucus-secreting cells derived from three different tissues are similar to those of mucin glycoproteins purified directly from mucus secretions of human and swine trachea epithelium.Abbreviations TFMS Trifluoromethanesulfonic acid - SDS Sodium Dodecyl Sulfate - PAGE Polyacrylamide Gel Electrophoresis - GalNAc N-Acetylgalactosamine - HTMG Human Trachea Mucin Glycoprotein - deHTMG deglycosylated Human Trachea Mucin Glycoprotein - STMG Swine Trachea Mucin Glycoprotein - deSTMG deglycosylated Swine Trachea Mucin Glycoprotein - CCMG Cowper's Gland Mucin Glycoprotein - deCGMG deglycosylated Cowper's Gland Mucin Glycoprotein - HPMG Pancreatic Mucin Glycoprotein from BxPC-3 cells - HCMG Colon Mucin Glycoprotein from SW 403 cells - HLMG Human Lung Mucin Glycoprotein from A-549 cells - STMG⁺deSTMG^– antibodies which bind to immobilized STMG but do not bind to immobilized deSTMG - deSTMG⁺STMG^– antibodies which bind to immobilized deSTMG but do not bind to immobilized STMG - STMG⁺deSTMG⁺ antibodies which bind to both STMG and deSTMG - HTMG⁺deHTMG^– antibodies which bind to immobilized HTMG but do not bind to immobilized deHTMG - deHTMG⁺HTMG^– antibodies which bind to immobilized deHTMG but do not bind to immobilized HTMG - HTMG⁺deHTMG⁺ Antibodies which bind to both HTMG and deHTMG