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D B Parkinson

Publications and source records attributed to D B Parkinson.

6 recordsLinked to original sources
PubMed2001

Transforming growth factor beta (TGFbeta) mediates Schwann cell death in vitro and in vivo: examination of c-Jun activation, interactions with survival signals, and the relationship of TGFbeta-mediated death to Schwann cell differentiation.

In some situations, cell death in the nervous system is controlled by an interplay between survival factors and negative survival signals that actively induce apoptosis. The present work indicates that the survival of Schwann cells is regulated by such a dual mechanism involving the negative survival signal transforming growth factor beta (TGFbeta), a family of growth factors that is present in the Schwann cells themselves. We analyze the interactions between this putative autocrine death signal and previously defined paracrine and autocrine survival signals and show that expression of a dominant negative c-Jun inhibits TGFbeta-induced apoptosis. This and other findings pinpoint activation of c-Jun as a key downstream event in TGFbeta-induced Schwann cell death. The ability of TGFbeta to kill Schwann cells, like normal Schwann cell death in vivo, is under a strong developmental regulation, and we show that the decreasing ability of TGFbeta to kill older cells is attributable to a decreasing ability of TGFbeta to phosphorylate c-Jun in more differentiated cells.

Animals↗
PubMed1993

Parathyroid hormone gene analysis in autosomal hypoparathyroidism using an intragenic tetranucleotide (AAAT)n polymorphism.

We have identified a polymorphic tetranucleotide consisting of (AAAT)n within the first intron of the parathyroid hormone (PTH) gene, and have used this to investigate the segregation of the PTH gene and idiopathic hypoparathyroidism in 7 affected and 21 unaffected members from three families. An association between the PTH locus and autosomal dominant idiopathic hypoparathyroidism in one family was excluded by observing recombination between the two loci. In the remaining two families with autosomal recessive idiopathic hypoparathyroidism, the PTH locus was not similarly excluded. We had previously demonstrated a donor splice site mutation of the PTH gene in one of these families, and PTH gene abnormalities were therefore sought in the second of these families. DNA sequence analysis of the three exons, together with 4 exon-intron boundaries and the promoter region of the PTH gene revealed no abnormalities, thereby indicating molecular pathology at another locus. Thus, our analysis of idiopathic hypoparathyroidism reveals genetic heterogeneity for this disorder. In addition, our identification of a microsatellite polymorphism of the PTH gene should help further segregation studies of this locus in families with parathyroid disorders.

Base Sequence↗
PubMed1992

A donor splice site mutation in the parathyroid hormone gene is associated with autosomal recessive hypoparathyroidism.

Investigation of one kindred with autosomal recessive isolated hypoparathyroidism, which had resulted from a consanguineous marriage, has identified a g to c substitution in the first nucleotide of intron 2 of the parathyroid hormone (PTH) gene. This donor splice mutation could be detected by restriction enzyme cleavage with Ddel, and this revealed that the patients were homozygous for the mutant alleles, the unaffected relatives were heterozygous, and unrelated normals were homozygous for the wild type alleles. Defects in messenger RNA splicing were investigated by the detection of illegitimate transcription of the PTH gene in lymphoblastoid cells. The mutation resulted in exon skipping with a loss of exon 2, which encodes the initiation codon and the signal peptide, thereby causing parathyroid hormone deficiency.

Base Sequence↗
PubMed1988

Synthetic cataract teaching system for phacoemulsification.

This paper describes a surgical training system for teaching and practicing the necessary skills to perform phacoemulsification, endocapsular phacoemulsification, and small incision intraocular lens insertion techniques. The surgical system includes head, bilateral globes, removable corneas, and replaceable synthetic cataracts of varying density. This synthetic system simulates ocular surgery more closely than previously used animal eyes and allows the surgeon to practice new techniques in laboratory courses and in the operating facility.

Cataract Extraction↗