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Biomedical subjects

D Gershon

Publications and source records attributed to D Gershon.

At least 37 records · Page 2Linked to original sources
PubMed1999

The function of hypoxia-inducible factor 1 (HIF-1) is impaired in senescent mice.

Senescent organisms respond poorly to hypoxic stress. The transcription factor hypoxia-inducible factor 1 (HIF-1) plays a critical role in the coordinated genetic program that is induced in all tissues to adapt to hypoxic stress by binding to a specific DNA hypoxia-responsive recognition element (HRE). This study was designed to address whether aging is associated with an alteration in HIF-1 production and function. Young and old mice were exposed to hypoxia for various lengths of time. We found a severe impairment in the capacity of the old animals to form a HIF-1-HRE complex. This attenuation in the capacity to form HIF-1-HRE complexes in senescent tissues may explain the decreased ability of such tissues to respond to hypoxic stress.

Aging↗
PubMed1999

The mitochondrial theory of aging: is the culprit a faulty disposal system rather than indigenous mitochondrial alterations?

Mitochondrial damage and the proportion of effete mitochondria in cells increase with age. According to the mitochondrial theory of aging, this phenomenon is mostly due to oxidative damage and is a major (and, some argue, the main) determinant of aging. It will be argued briefly that this phenomenon plays a role that is not exclusively crucial in aging. It will also be contended, essentially on theoretical grounds (for lack of sufficient current information), that there is low probability that the accumulation of reduced degradation of affected mitochondria is due to diminished production of hydroxyl radicals, as suggested by Aubrey and de Grey (1997) and expanded by Kowald (in this issue). What seems more likely is that the phagolysosomal disposal system of effete mitochondria is considerably altered in cells of aging organisms. Also, in view of the significant role of damaged mitochondria in the initial steps in apoptosis and the lack of evidence of massive apoptosis of cells in senescent individuals, the damage that exists may be milder than anticipated by the mitochondrial theory of aging. A brief fundamental summary on the biology of mitochondria is included for the sake of better understanding the arguments presented in this article. Also, suggestions are made for experimental testing of the hypotheses presented by Aubrey and de Grey (1997) and Kowald (1999).

Aging↗
PubMed1996

Expression of the transporter for antigen processing-1 (Tap-1) Gene in subpopulations of human trophoblast cells.

Heterodimers of transporter for antigen processing proteins, Tap-1 and Tap-2, are essential components of the pathway that leads to expression of conventional HLA-A, -B class I transplantation antigens on cell surfaces. In this study, expression of the Tap-1 gene in trophoblast cells, some of which display novel and unconventional HLA class I molecules that include HLA-G and an HLA-C-like antigen, was investigated by using in situ hybridization to identify Tap-1 mRNA and immunohistochemistry to detect Tap-1 protein. The experiments were done on semiserial sections of paraformaldehyde-fixed tissues. In first trimester placentas, expression of the Tap-1 gene correlated with expression of HLA class I antigens in trophoblast cells. HLA-G/C positive extravillous cytotrophoblast cells exhibited high intensity in situ hybridization signals for Tap-1 mRNA and strong staining with anti-Tap-1 whereas Tap-1 gene products were rarely detected in HLA class I antigen negative syncytiotrophoblast and villous cytotrophoblast cells. Relationships were less definitive in term tissues. Although Tap-1 protein was detectable in extravillous cytotrophoblast cells (chorionic cytotrophoblast cells) as expected, HLA class I negative syncytiotrophoblast contained low intensity hybridization and immunostaining signals. Collectively, the data suggest that (1) as with conventional HLA class I antigens in other types of cells, the pathway leading to expression of novel HLA class I antigens in trophoblast cells includes transport of peptides by Tap-1, and that (2) deficiencies in Tap-1 might account in (whole or in) part for the failure of some trophoblast cells to express HLA class I antigens.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Influence of 17 beta-estradiol and progesterone on rat ocular lens.

The effect of 17 beta-estradiol and progesterone on ocular lens in rats and untreated controls was studied. In the treated lenses, the activity of hexokinase and glucose-6-phosphate dehydrogenase remained unchanged. The activity of aldolase was increased in 18- and 20-month-old lenses as compared to controls. Aldose reductase activity was decreased at the age of 20 months (p < 0.001). Structural lens proteins studies by SDS polyacrylamide gel electrophoresis and immunodecoration with specific antibodies for crystallines alpha A + alpha B and beta + gamma suggest some protective effect in treated animals.

Aldehyde Reductase↗
PubMed1995

Cellular distribution of proteasome subunit Lmp7 mRNA and protein in human placentas.

Human leucocyte antigen (HLA) class I antigen expression is closely controlled in placental trophoblast cells, which interface directly with genetically disparate maternal blood and tissues during pregnancy. In this study, the possibility that LMP7, a proteasome component that may be required for processing of class I-associated peptides, might be lacking or refractory to cytokine induction in trophoblast cells that fail to display HLA class I antigens was investigated. Analysis of Lmp7 mRNA and protein in paraformaldehyde-fixed placentas by in situ hybridization and immunohistochemistry revealed that both HLA class I-positive and HLA class I-negative trophoblast cells contain Lmp7 gene products. Consistent with these results, northern blot hybridization studies showed that HLA class I-positive (JEG-3) and HLA null (Jar) trophoblast-derived cell lines contain Lmp7 mRNA. After 48 hr of exposure to HLA class I-modulating cytokines, Lmp7 mRNA levels in JEG-3 cells were markedly increased by two interferons (IFN-beta, IFN-gamma) and tumour necrosis factor (TNF) whereas at the same time point, Jar cell Lmp7 mRNA was modestly enhanced by IFN-gamma. Collectively, the findings indicate that expression of HLA class I antigens in trophoblast cells is unlikely to be restricted by lack of Lmp7 gene products and suggest that endogenous placental cytokines may have different influences on Lmp7 mRNA levels in phenotypically distinct trophoblast subpopulations.

Blotting, Northern↗