Membrane glycoproteins and cellular ageing

Aged cells have significantly fewer food vacuoles and ingest fewer bacteria than young cells. Loss of food vacuoles was explained by a decreasing difference in the food vacuole formation and excretion rates; the formation rate declined more rapidly than the excretion rate, approaching equivalence at 160 fissions, when the proportion of cells with no food vacuoles, in the presence of excess food, abruptly increased. A model for cellular aging is presented in which control of organelle numbers and cyclical interactions between the nucleus and cytoplasm may be of critical importance.

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“…The latter is consistent with the idea that cell membrane alterations may occur in aging cells (45).…”

Section: Smith-sonneborn and Rodermel Organelles And Agingsupporting

confidence: 79%

Loss of endocytic capacity in aging Paramecium. The importance of cytoplasmic organelles.

Smith-Sonneborn¹,

Rodermel²

1976

The Journal of Cell Biology

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“…Based mostly on biochemical and genetic studies with myoinositol-deficient systems, a model is proposed here suggesting a coupled operation of the gluconeogenic enzyme, fructose 1,6_bisphosphatase and myo-inositol synthase, as the probable regulatory event for cell survival under conditions of myo-inositol deficiency. Deficiency of this compound induces remarkable changes in the metabolic makeup of the cell, manifested in the abnormal accumulation of lipids [20], alterations of sugar transport [21], and changes in the membrane structure and properties [22,23]. Acute starvation for myo-inositol has been reported to lead to loss of cell viability, a phenomenon known commonly as 'inositol-less death' [22-241.…”

Section: Introduction Myo-inositol (Hexahydroxycyclohexane)mentioning

confidence: 99%

Untitled

1981

FEBS Letters

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Serum‐mediated regulation of amino acid transport in cultured chick embryo fibroblasts

Tramacere

Borghetti

Guidotti

1977

Journal Cellular Physiology

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When chicken serum was added to serum-deprived quiescent cultures of chick embryo fibroblasts the activity of amino acid transport by means of the A system, as measured by a-aminoisobutyric acid and L-proline uptake after discrimination of the contribution of interacting systems, increased with time of exposure to serum between 30 and 120 minutes (remaining constantly high thereafter). Under the same conditions, DNA synthesis, as measured by thymidine incorporation, increased abruptly six to eight hours after the addition of serum. Serum-mediated increases of transport activity by the A system have also been detected with glycine, L-alanine and L-serine. Transport activities of systems ASC, L and Ly+ did not change appreciably (or decreased slightly) after the addition of serum. The stimulation of amino acid transport was apparently proportional to the length of exposure to serum; its rate declined progressively with time after withdrawal of serum from the culture medium. Kinetic analysis indicated that stimulation of the activity of transport system A by serum occurred through a mechanism affecting V, , , rather than K,; stimulation was prevented by inhibitors of protein synthesis. Our results indicate that the A transport system is the only system which is regulated by serum in cultured avian fibroblasts.Remarkably, the A transport system appears to be the target on which widely different factors and conditions converge to regulate amino acid transport in eukaryotic cells. Each system acts on a discrete group of amino acids with rather extensive overlap of substrate reactivity (Christensen, '69, '73). Therefore, the characterization of a specific regulatory effect on the transport process re-J. CELL. PHYSIOL., 93: 425-434.quires the formal identification of the system(s) involved (Christensen, '76).The purpose of the present study was to characterize the serum-dependent control mechanism of amino acid transport in cultured avian fibroblasts. The results to be presented indicate that changes in transport activity for amino acids occur earlier than the onset of DNA synthesis in cells committed by serum to enter into the S phase of the cell cycle. These changes consist of increases in activity of only one discrete transport system for amino acids; the A system. They require continuous exposure to serum, are likely to reflect an acceleration of the maximal transport velocity and are abolished by inhibitors of protein synthesis.

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Membrane glycoproteins and cellular ageing

Cited by 11 publications

References 10 publications

Loss of endocytic capacity in aging Paramecium. The importance of cytoplasmic organelles.

Loss of endocytic capacity in aging Paramecium. The importance of cytoplasmic organelles.

Untitled

Serum‐mediated regulation of amino acid transport in cultured chick embryo fibroblasts

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