Browsing by Author "von Holt, C"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Open Access
    Histone modification during the induction of tyrosine transaminase
    (1972) Graaff, G De V; von Holt, C
    "The induction phenomenon is a useful model for the study of mechanisms which regulate the synthesis of specific enzymes in mammalian tissue, as well as for the role of hormones in this process". The in vivo administration of hormone initiates a chain of reactions which culminate in the increase of protein synthesis. Many hepatic enzymes are thus affected resulting in an increase of their activity. Studies of the giant chromosomes in the salivary glands of Chironomus tentans provided the first indications that the earliest intracellular effects of hormone administration are at the genetic level. Injection of the insect moulting hormone, ecdysone, into last instar larvae of Chironomus tentans results in puff formation at specific loci of the chromosomes shortly after hormone administration. Since puffs are local and reversible alterations of the chromosome, formed at sites which are active in the synthesis of informational RNA, their formation shows a change in activity of particular gene loci in response to ecdysone.
  • Thumbnail Image
    Item
    Open Access
    Rat liver nuclear envelope insulin binding and its effects on endogenous protein kinases
    (1992) Sabbatini, G P; Sabbatini, G P; von Holt, C; Von Holt, Claus
    The postulated model for the insulin - stimulated induction of mRNA efflux (Purrello et al., 1983) is based on the demonstrated binding of insulin to intracellular membrane structures (see chapter 2, section 2.2.1), and the in vitro effect of insulin on nuclear envelope phosphorylation, NTPase activity, and mRNA efflux (see chapter 5, section 5.1). These independent observations have led to the development of a model for the direct induction by insulin, at the level of the nucleus, of mRNA efflux (figure 1.1). However, the specific intracellular insulin binding has been inf erred from kinetic or morphological studies which have not identified a discrete membrane - bound polypeptide(s) as an insulin docking molecule in situ (Goldfine, 1981). Also, the stimulation of NTPase activity has only been established by monitoring the level of general ATP hydrolysis of nuclear envelope fractions in the presence and absence of insulin (Purrello et al., 1983). The scope of this thesis has been to further the understanding of this mechanism by attempting to a) unequivocally identify a specific nuclear envelope - associated insulin docking polypeptide in situ and b) to demonstrate that insulin directly affects the ATP - binding of nuclear envelope ATP - binding proteins. The latter would demonstrate a primary effect of insulin i.e. the modulation of the ATP - binding capacity of identified NTPases / protein kinases (or their release from some inactive storage form), and not a general phenomenon such as elevated ATP.