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Biomedical subjects

I Rogers

Publications and source records attributed to I Rogers.

30 records · Page 2Linked to original sources
PubMed1998

Effect of maternal age and conditions of fertilization on programmed cell death during murine preimplantation embryo development.

One of the major morphological anomalies observed in many human pre-embryos is extensive cellular fragmentation. Previously we confirmed that embryo fragmentation seemed to be associated with the activation of programmed cell death (PCD). The purpose of our experiments was to establish a rate for murine embryo fragmentation in vivo after hormonal stimulation in young versus older females and to compare it with the rate of embryo fragmentation during in-vitro fertilization (IVF). While murine maternal age beyond 40 weeks increased the rate of embryo fragmentation following in-vivo fertilization (P = 0.001), oocytes from females of all ages had a uniformly high rate of fragmentation when fertilized in vitro (33%). None of the fragmented murine embryos proceeded further in development. In the mouse, fragmentation occurs exclusively during the first cell cycle. Furthermore, IVF significantly reduced the rate of blastocyst formation (P = 0.0001) and decreased the mean cell number at the blastocyst stage in comparison with embryos produced in vivo (P < 0.0001). The cell death index was significantly affected by both maternal age (P = 0.005) and IVF (P = 0.0001). Identification of specific factors which trigger PCD, especially those associated with IVF, may enable us to lower the rates of fragmentation in preimplantation embryos and thereby increase pregnancy rates after human IVF.

Animals↗
PubMed1997

Paternal transmission of the mouse Thp mutation is lethal in some genetic backgrounds.

Thp is a large deletion on chromosome 17 which includes the maternal lethal gene Tme. Documentation of inheritance patterns suggests that Tme is an imprinted gene which is required for viability; maternal deletion is lethal while paternal deletion is viable. However, paternal transmission of Thp is rarely the expected 50%. We show here that paternally inherited Thp is lethal in some strains, providing evidence of an incompletely penetrant, dosage sensitive lethal allele of a locus that probably maps to the hairpin tail region of chr. 17. Interpretation of the various phenotypes associated with loss of the putative Tme gene, Igf2r, may need to be revised in view of these observations.

Abnormalities, Multiple↗
PubMed1996

Epigenetic alterations brought about by lithium treatment disrupt mouse embryo development.

The commonly accepted mechanism by which LiCl dorsalizes amphibian embryos is a respecification of ventral blastomeres, presumably through realignment of dorsal positional information in the embryo. An alternative mechanism, however, is an epigenetic change in the competence of cells to respond to cues they may be normally exposed to without effect. In order to test this hypothesis, we treated mouse preimplantation embryos, which do not possess any axial positional information, with LiCl, and observed axial abnormalities which must have been elaborated several days after treatment. We interpret this as support for the hypothesis that cellular competence rather than positional information is altered by LiCl, and suggest that this competence may be altered through the action of lithium sensitive enzymes that interact with chromatin.

Animals↗
PubMed1993

Site of action of imprinted genes revealed by phenotypic analysis of parthenogenetic embryos.

The phenotypes of early post-implantation parthenogenetic embryos were examined. The spectrum of phenotypes suggested that three stages are adversely affected by imprinting--implantation, pregastrulation, and postgastrulation. Survival of parthenogenetic embryos past these developmental blocks can be improved but not completely overcome by experimental asynchrony. These results suggest that imprinting may be "leaky" at early stages.

Animals↗
PubMed1988

Several epitopes of p85 glycoprotein (CDw44) are dependent on intact disulphide bonds. Isolation of cDNA clones requires a polyclonal antibody raised against the reduced protein.

Monoclonal antibodies 50B4 and 50E6 recognize two distinct epitopes of human p85 glycoprotein (CDw44). Both epitopes are destroyed by reduction of the purified glycoprotein as demonstrated by inhibition of cellular radioimmunoassay and Western blot analysis. Endoglycosidase F treated p85 glycoprotein, with an apparent molecular weight of 73,000, is still reactive with both monoclonal antibodies. Thus both epitopes are conformational determinants of the polypeptide chain. A rabbit antibody produced against purified native p85 glycoprotein also reacted only with the non-reduced form of p85. Repeated immunizations with SDS-dissociated and reduced p85 yielded a polyclonal antibody reactive by Western blot analysis with reduced and non-reduced forms of p85 glycoprotein. When a HOON leukemia cell line cDNA expression library was screened with this polyclonal antibody, two cDNA clones were isolated which reacted specifically with the antiserum and not with the control non-immune serum. Preliminary characterization of these clones indicates that they are p85-related.

Antibodies↗
PubMed1987

Further characterization of erythrocyte p80 and the membrane protein defect of In(Lu) Lu(a-b-) erythrocytes.

We have previously shown that the In(Lu) gene down-regulates expression of an erythrocyte protein antigen identified by murine monoclonal antibody (MoAb) A3D8. In the present study we have examined In(Lu) Lu(a-b-) erythrocytes for expression of additional epitopes on the erythrocyte 80 kilodalton protein (p80) bearing the A3D8 antigen. Using a total of seven additional MoAbs that recognize three epitopes on erythrocyte p80, we have shown that In(Lu) Lu(a-b-) erythrocytes exhibit down-regulation of expression of all three epitopes. In(Lu) erythrocytes also showed a reduction in their reactivity to rabbit antibodies produced against purified p80 from either erythrocytes or lymphocytes. Furthermore the reactivity of the MoAbs was not altered by treatment of the cells with neuraminidase but was substantially reduced by treatment of cells with trypsin or chymotrypsin. The polyclonal anti-p80 sera were shown to react with a fragment of 50,000 daltons, still associated with erythrocyte ghosts, following treatment of the cells with trypsin or chymotrypsin. Treatment of erythrocytes with the thiol-reactive reagent AET decreased their reactivity with the MoAbs but had a variable effect on their reactivity with polyclonal antibodies. Erythrocyte p80 is a glycoprotein with N-linked oligosaccharides, as demonstrated by its binding to concanavalin A (Con A) and Len culinaris lectins. Following Endoglycosidase F treatment, erythrocyte p80 underwent a reduction in apparent mol wt of 11,000. The presence of a reduced amount of an intact p80 glycoprotein, seen by a decrease in reactivity with MoAbs directed at three distinct epitopes and with two different polyclonal antibodies, suggests that the In(Lu) gene interferes with expression by erythrocytes of the entire p80 glycoprotein.

Antibodies, Monoclonal↗
PubMed1986

The primary structure of rat parathymosin.

Parathymosin has been isolated from rat thymus and from rat liver. Its primary structure is reported as follows: (Sequence; see text). The blocking group at the NH2 terminus was identified by mass spectrometry as acetyl. Regions homologous to amino acid sequences in prothymosin alpha were found to be located between residues 14-20, 23-25, 33-39, 41-43, and 83-87 of parathymosin.

Amino Acid Sequence↗