PubMed Health⌕ Search

Biomedical subjects

J R Rodgers

Publications and source records attributed to J R Rodgers.

At least 37 records · Page 2Linked to original sources
PubMed1990

The role of physical forces on cytotoxic T cell-target cell conjugate stability.

Theoretical considerations suggest that external forces play a significant role in cell-cell conjugate formation and may lead to the misinterpretation of adhesion data. To test this, the stability of conjugates formed between CTL and fibroblast target cells (TC) was examined in the controlled shear environment of a parallel plate flow chamber. Murine fibroblast targets expressing class I maternally transmitted Ag Mtaa or Mtab were grown on a glass slide that formed one wall of the flow chamber and were used in conjunction with anti-Mtaa and anti-Mtab specific mouse CTL clones to establish a panel of Ag-reciprocal targets and lymphocytes. Although cytolysis assays indicated that lymphocytes recognized and destroyed appropriate but not inappropriate targets, the stability of some CTL/TC conjugates was Ag independent. In all cases, the conjugate stability was shear dependent over a 100-fold range (0.04 to 4.0 dynes/cm2). For some clones, the ratio of the stabilities of Ag-specific CTL/TC conjugates to nonspecific conjugates was significantly enhanced with increasing shear. This implies that the role of Ag specificity in CTL/TC adhesion may be misinterpreted if the shear environment of CTL/TC conjugates is unknown or uncontrolled. Kinetic analysis revealed that conjugate stability was dependent on the exposure time to external forces and that there existed two populations of conjugates; weak associations that disengaged within the first 30 s of flow, and strong associations that remained attached even after a 5-min exposure to a steady shear stress. The stability of Ag-specific CTL/TC conjugates at 0.04 dynes/cm2 was enhanced by 50% as the temperature was increased from 25 to 37 degrees C, whereas the stability of nonspecific CTL/TC associations was not affected. This result indicates that significant Ag-specific strengthening may occur at physiologic temperatures. This work suggests the importance of attention to role of fluid mechanical shear stress in standard adhesion assays.

Animals↗
PubMed1990

Specialized functions of MHC class I molecules. I. An N-formyl peptide receptor is required for construction of the class I antigen Mta.

Maternally transmitted factor (Mtf) is a mitochondrial gene that controls the antigenic polymorphism of the MHC class I maternally transmitted antigen (Mta). Synthetic peptides from the NH2 terminus of the mitochondrially encoded NADH dehydrogenase subunit 1 (ND1) mimic Mtf peptide activity in an allele-specific manner. We show that the minimal ND1-alpha peptide length recognized by Mtaa-specific polyclonal CTLs was between 8 and 12 amino acids, while some Mtaa-specific CTL clones recognized a six amino acid peptide. The N-formyl group at the NH2 terminus of ND1 was essential for Mta activity. Competition experiments using N-substituted ND1-alpha peptides showed that an N-formyl peptide receptor on the target cell, which differs from the chemotactic peptide receptor, was required for Mta expression. The specificity of this receptor can account for the distinct immune restriction of Mta in which Mtf peptides are uniquely restricted by Hmt. It is possible that the Hmt gene product is the N-formyl peptide receptor itself and that it represents a class I antigen presentation molecule specialized for binding, transport, and immune presentation of N-formyl-peptide antigens of mitochondrial and prokaryotic origin.

Animals↗
PubMed1990

Retrovirus-mediated insertional mutagenesis: phagemid rescue of flanking DNA by selecting plasmid ori.

A method for screening recombinant lambda libraries was devised to select phage containing genomic regions containing provirus insertions of retroviruses that carry the kanamycin and G418 resistance factor neo and the origin of replication derived from pBR322 (oripBR). Such recombinants are phagemids, able to replicate as bacteriophages or as plasmids under lambda repressor control. lambda repressor was cloned into a plasmid derived from pSC101 that is compatible with pBR322-derived phagemids. A strain carrying this plasmid may be used to select phagemids derived from a single proviral insertion with 100% efficiency from complex recombinant libraries. Homologous recombination between proviral long terminal repeats was observed at a rate of 10(-4)/plaque-forming unit in recABC+ strains. Despite this frequency, intact phagemids are easily recovered as phage after temperature shift to 42 degrees C. Since oripBR itself is a selectable marker in this system, the method could be applied to recover any sequence carrying the ori sequence from pBR322.

Bacteriophage lambda↗
PubMed1989

An unexpectedly labile mitochondrially encoded protein is required for Mta expression.

Maternally transmitted antigen (Mta) is a mouse major histocompatibility antigen recognized by cytotoxic T lymphocytes. A role for mitochondria in expression of this class I-like cell surface antigen has been previously established. We now show that a labile product of mitochondrial protein synthesis is required for Mta expression. Reexpression of Mta determinants after enzymatic removal occurred within 24 h, and the regeneration process was sensitive to chloramphenicol (CAP), a selective inhibitor of mitochondrial protein synthesis. Additionally, target cells treated with CAP for as little as 18 h showed diminished expression of Mta. The estimated half-life for Mtf products ranged from 6 to 15 h, less than the half-lives of known mitochondrial translation products. This suggests that the Mtf product is not generated by the normal turnover of stable mitochondrial respiratory proteins. Instead, these results indicate the existence of either labile unknown mitochondrially encoded peptides or a rapid turnover pathway for known mitochondrial products.

Animals↗
PubMed1988

Regulation of Qa-1 expression and determinant modification by an H-2D-linked gene, Qdm.

We examined the regulation of cell surface expression of the Qa-1 alloantigens using a panel of monoclonal anti-Qa-1 cytotoxic T-lymphocyte (mCTL) lines. In contrast to previous reports of tissue-specific expression, we found that Qa-1 was widely expressed, resembling the prototypical class I H-2K/D molecules. We further found that an H-2D-linked gene, which we termed Qdm for Qa-1 determinant modifier, controlled expression of certain CTL-defined Qa-1 antigenic determinants. H-2Dk homozygous haplotypes expressed a recessive allele of the modifier, Qdmk, whereas all other H-2 haplotypes tested expressed a dominant allele, Qdm+. The Qdm+ allele regulated in trans Qa-1 epitope expression from a Qdmk chromosome, modifying expression of particular CTL-defined Qa-1 antigenic determinants rather than affecting levels of cell surface expression. Mechanisms of Qdm function may include either a novel protein modification system or an unprecedented case of antigen recognition restricted by a nonclassical major histocompatibility complex molecule.

Animals↗
PubMed1987

Maternally transmitted antigens are codominantly expressed by mouse cells containing two kinds of mitochondrial DNA.

Mtf, a cytoplasmic, probably mitochondrial factor, controls Mta polymorphism. We tested for dominance between two forms of Mtf to determine whether Mta is controlled by positive or negative genetic mechanisms. We fused Mtf-disparate cells containing distinct mtDNA markers and selected for hybrids containing both. Such mtDNA heteroplasmons codominantly and stably express alternative Mta antigens. Stable codominance excludes negative genetic mechanisms as well as a model of induced nuclear compensation, and implies Mtf controls Mta expression through a positive genetic mechanism.

Animals↗
PubMed1987

Unglycosylated Mtaa expresses an Mtab-like determinant.

Antigenic polymorphism of the class I-like maternally transmitted antigen (Mta) is controlled by a maternally transmitted factor (Mtf) thought to reside in mitochondria. However, the mechanisms by which Mtf generates antigenic polymorphism are not known. To address this issue, we investigated a possible role of posttranslational oligosaccharide addition in the formation of Mta determinants. We examined the expression of Mta on cytotoxic T lymphocyte (CTL) target cells cultured in tunicamycin (TM), a known inhibitor of asparagine(N)-linked glycosylation. Of 18 Mtab-specific CTL lines, 8 lysed TM-treated Mtaa targets. Furthermore, a subclone of one of these eight lines, 17D5.G2, lysed TM-treated targets from all Mtaa strains tested, regardless of H-2K/D haplotype. On the other hand, this CTL clone did not lyse TM-treated target cells from the Mta null, but H-2 expressing strain B10.CAS2. Therefore expression of this Mtab-like determinant is concordant with the expression of Mtaa and seems unlikely to represent a cross-reactive H-2K/D epitope. Our data suggest that an Mtab-like determinant is expressed on unglycosylated Mtaa molecules. Thus, N-linked oligosaccharides probably prevent the expression of an Mtab-like determinant on the Mtaa molecule. We discuss how Mtf may contribute to Mta polymorphism through glycosylation.

Animals↗
PubMed1981

Construction and preliminary characterization of the rat casein and alpha-lactalbumin cDNA clones.

We have constructed a double-stranded cDNA library using total poly(A)-containing RNA extracted from 8-day lactating rat mammary gland and have utilized this library to isolate clones for each of the four major milk proteins. These four cDNA clones, representing the three major rat caseins and alpha-lactalbumin, were initially identified by colony hybridization with labeled cDNA probes synthesized from individual mRNA fractions purified by preparative gel electrophoresis. Additional characterization was accomplished by hybridizing individual clones labeled with 32P by nick translation to a Northern gel blot of an enriched fraction of the four major milk protein mRNAs. The individual mRNAs were clearly resolved by electrophoresis on fully denaturing methylmercury hydroxide agarose gels. The identity of each milk protein clone was further established by the location of unique restriction enzyme sites within each clone. Final identification of each clone was performed by hybrid-arrested cell-free translation. The sizes of the milk protein cDNA clones ranged frm 70% for the alpha-lactalbumin gene to essentially full length for the gamma-casein gene, in comparison to their respective mRNAs. This represents the first isolation of a family of peptide hormone-responsive genes.

Animals↗
PubMed1977

The Protein Data Bank. A computer-based archival file for macromolecular structures.

The Protein Data Bank is a computer-based archival file for macromolecular structures. The Bank stores in a uniform format atomic co-ordinates and partial bond connectivities, as derived from crystallographic studies. Text included in each data entry gives pertinent information for the structure at hand (e.g. species from which the molecule has been obtained, resolution of diffraction data, literature citations and specifications of secondary structure). In addition to atomic co-ordinates and connectivities, the Protein Data Bank stores structure factors and phases, although these latter data are not placed in any uniform format. Input of data to the Bank and general maintenance functions are carried out at Brookhaven National Laboratory. All data stored in the Bank are available on magnetic tape for public distribution, from Brookhaven (to laboratories in the Americas), Tokyo (Japan), and Cambridge (Europe and worldwide). A master file is maintained at Brookhaven and duplicate copies are stored in Cambridge and Tokyo. In the future, it is hoped to expand the scope of the Protein Data Bank to make available co-ordinates for standard structural types (e.g. alpha-helix, RNA double-stranded helix) and representative computer programs of utility in the study and interpretation of macromolecular structures.

Computers↗
PubMed1977

The enkephalins and opiates: structure-activity relations.

The X-ray structures of 9 "opiate" drugs which exhibit a range of pharmacological activity have been examined in detail leading to the theory that one of the reasons why the enkephalins and related peptides possess morphine-like activity is because they have a tyrosine, and hence a "tyramine", residue at the amino terminal position. This residue or a conformationally similar moiety, can be shown to be present in many opiates and analogues.

Amino Acid Sequence↗