Biomedical subjects

T L Saunders

Publications and source records attributed to T L Saunders.

25 records · Page 2Linked to original sources

PubMed1990

The Pit-1 transcription factor gene is a candidate for the murine Snell dwarf mutation.

Two nonallelic mouse mutations with severe dwarf phenotypes are characterized by a lack of growth hormone, prolactin, and thyroid stimulating hormone. The cells that normally synthesize these pituitary hormones express a common transcription factor called GHF-1 or Pit-1. Using an intersubspecific backcross, we have demonstrated tight linkage of the Pit-1 and Snell dwarf (dw) genes on mouse chromosome 16. No recombination was observed between Pit-1 and dw in 110 individuals examined. Southern blot analysis of genomic DNA reveals that the Pit-1 gene is rearranged in C3H/HeJ-dwJ/dw mice but not in coisogenic +/+ animals, providing molecular evidence that a lesion in the Pit-1 gene results in the Snell dwarf phenotype. Demonstration of low levels of Pit-1 expression in Ames dwarf (df) mice implies that both Pit-1 and df expression may be required for pituitary differentiation.

Animals↗

PubMed1990

Transgenic mouse model of the mild dominant form of osteogenesis imperfecta.

Osteogenesis imperfecta type I is a mild, dominantly inherited, connective tissue disorder characterized by bone fragility. Mutations in type I collagen account for all known cases. In Mov-13 mice, integration of a murine retrovirus within the first intron of the alpha 1(I) collagen gene results in a null allele blocked at the level of transcription. This study demonstrates that mutant mice heterozygous for the null allele are a model of osteogenesis imperfecta type I. A defect in type I collagen production is associated with dominant-acting morphological and functional defects in mineralized and nonmineralized connective tissue and with progressive hearing loss. The model provides an opportunity to investigate the effect of a reduced amount of type I collagen on the structure and integrity of extracellular matrix. It also may represent a system in which therapeutic strategies to strengthen connective tissue can be developed.

Animals↗

PubMed1987

cDNA cloning and sequencing reveals that the electrophoretically constant DR beta 2 molecules, as well as the variable DR beta 1 molecules, from HLA-DR2 subtypes have different amino acid sequences including a hypervariable region for a functionally important epitope.

Two-dimensional gel electrophoresis (2D-PAGE) of DR molecules from three different Dw subtypes (Dw2, Dw12, and FJO) of the HLA-DR2 haplotype reveals that at least two DR beta genes are expressed. Protein mixing experiments demonstrate that one of the two expressed DR beta molecules is electrophoretically variable (referred to as DR beta 1), and the other (DR beta 2) migrates constantly among DR2 subtypes. We have constructed cDNA libraries from Dw12 and FJO homozygous typing cells (HTC DHO for Dw12 and HTC FJO for FJO) and isolated DR beta cDNA clones. Four of these clones (FJO-13, DHO-8, FJO-6, and DHO-7) were sequenced, and the deduced amino acid sequences were compared with each other and with two published amino acid sequences for the DR beta molecules derived from a DR2-Dw2HTC. Prediction of the migration patterns on 2D-PAGE from the amino acid sequences of these and other DR beta molecules allows the tentative designation of the two full-length cDNA (DHO-8 and FJO-13) as coding for DR beta 2 molecules and the other two cDNA (DHO-7 and FJO-6) for DR beta 1 molecules. Amino acid sequence comparisons also show that the constantly migrating DR beta 2 molecules, as well as the electrophoretically variable DR beta 1 molecules, from Dw2, Dw12, and FJO have different primary amino acid sequences, including a clustered difference in the third hypervariable region of the polymorphic first domain.

Amino Acid Sequence↗

PubMed1987

Comparison of DR beta 1 alleles from diabetic and normal individuals.

Insulin-dependent diabetes (IDD) is positively associated with HLA-D proteins. A critical question is whether or not sequence differences within the HLA-D coding region are the same or different in diabetics and normal individuals of the same haplotype. We have isolated both DR beta 1 alleles from a Dw4/LD MN2 cDNA library and compared them to DR beta 1 genes isolated from normal individuals of the same Dw phenotype. We found no nucleotide differences in the coding region between the normal and diabetic alleles of DR beta 1 suggesting to us that DNA differences other than the DR beta 1 coding region may account for the observed association of HLA-D and diabetes.

Alleles↗

PubMed1985

The effect of purification on the immunogenicity of tumor-specific transplantation antigens.

Immunization with the tumor-specific transplantation antigens (TSTA) of experimental, chemically induced sarcomas engenders specific host resistance to challenge with viable, homotypic neoplastic cells. The strength of tumor resistance depends upon the physical state of the TSTA used for immunization. Treatment with 10(5)-10(6) irradiated tumor cells, a 2-log dose range, induces complete rejection of neoplastic challenges, while immunization within a 1-log dose range with crude 3 M KCl or with 2.5% butanol extracts containing TSTA evokes a weak state of resistance characterized by decreased outgrowth of tumor challenges, but not neoplastic regression. The reduced immunogenicity may be due to either contamination with substances that antagonize host resistance, for example by induction of suppressor cells, or an intrinsic limitation by virtue of the molecular properties of extracted compared with cell-surface TSTA. MCA-F and MCA-D, two noncross-reactive fibrosarcomas induced in C3H/HeJ mice with 3-methylcholanthrene, were employed to compare the relative immunogenic activity of intact tumor cells, 2.5% butanol extracts, and materials sequentially purified by preparative isoelectric focusing (pIEF), preparative isotachophoresis (pITP), and high performance gel permeation chromatography (HPGPC). Immunoprotective TSTA activity purified 50,000-fold by this protocol extended the effective dose range by four to five logs: 15 pg to 1.5 micrograms MCA-F or 1 pg to 10 ng MCA-D antigen-induced specific host resistance. However, despite the appreciable purification of TSTA, immunization with extracted materials only delayed neoplastic outgrowth. They induced neither immediate rejection nor only temporary progression of transplanted tumor cells. Thus, purified TSTA preparations by themselves lack the immunogenic properties of intact cells that result in maximal induction of tumor resistance.

Animals↗

PubMed1983

Purification of immunoprotective tumor antigens by preparative isotachophoresis.

Tumor-specific transplantation antigens (TSTA) were purified from 3 M KCl and butanol extracts of C3H/HeJ 3-methylcholanthrene-induced fibrosarcomas by preparative isotachophoresis (pITP). Fractions from pITP which reacted with antisera to TSTA preparations in an enzyme-linked immunospecific assay were tested in vivo for induction of resistance to the growth of transplanted tumor cells. Isotachophoresis of crude 3 M KCl extracts yielded TSTA that was immunogenic at doses between 17 and 124 micrograms. Isotachophoresis of TSTA partially purified from crude 3 M KCl or butanol extracts by preparative isoelectric focusing (pIEF) of 3 M KCl and butanol extracts yielded TSTA that was immunogenic over a two-fold log dose range. As little as 10 ng purified TSTA reduced tumor growth by 50%. Tumor growth reduction was specific, and immunized animals survived longer than non-immunized controls. A purification of 10,000-fold over crude 3 M KCl extracts and 2,500-fold over crude butanol extracts was obtained. These results suggest that TSTA from murine tumor cells is preparatively purified by following extraction with pIEF and then pITP.

Amino Acids↗

PubMedDate not supplied

Polymorphism of human Ia antigens generated by reciprocal intergenic exchange between two DR beta loci.

Class II molecules encoded by the human major histocompatibility complex (MHC) are involved in regulating T-cell response to antigens. The mechanisms for generating polymorphism in products of the MHC have been studied extensively for both the murine H-2 and the human HLA complex. Such studies indicate that point mutations plus selection have a major role in the generation of polymorphisms of class I and class II MHC genes. However, a non-reciprocal gene conversion mechanism has been proposed to explain several examples of clustered sequence variation in MHC genes. In all these examples, the proposed gene conversion event is unidirectional; that is, one of the two interacting genes acts as sequence donor and the other as sequence recipient. No examples of potential reciprocal genetic exchange (as occurs in the fungal system), in which the two interacting genes act as both donor and recipient of gene fragments, have been found in the MHC system or in other multigene families of higher organisms. We sequenced two different HLA-DR beta complementary DNAs from each of two different cells all expressing the same serologically defined determinant (DR2) but different T-cell-recognized (Dw) specificities (Dw12 and MN2). Sequence comparisons of these four cDNA clones (and two DR beta amino-acid sequences from the DR2-Dw2 subtype) suggest that new coding sequences for DR beta molecules in the DR2 haplotypes are potentially generated by reciprocal intergenic exchange.

Amino Acid Sequence↗