Cardiac lipoprotein lipase: effects of lipopolysaccharide and tumor necrosis factor

Summary Lipopolysaccharide (LPS), the active principle of certain endotoxins, protein-free perfused in rat hearts leads in 3 h to a considerable loss of lipoprotein lipase (LPL) activity. In the presence of albumin LPS has virtually no effect. Tumor necrosis factor (TNF) added instead of LPS had no effects on LPL activity during 3 hin vitro perfusion. LPS injected into rats intravenously leads within 3 h to severe toxic phenomena amongst which increased capillary permeability. This was visualized as increased rate of interstitial fluid formation in Langendorff hearts mounted 3 h after rats had been treated with LPS. LPL activity did not decline in 3 h lasting endotoxemia. Six hours after LPS injection, however, cardiac LPL activity was considerably lowered, although immunoblotting and immunohistochemistry still showed LPL protein to be present. These date indicate the presence of a considerable pool of inactive LPL protein in addition to active LPL, that can be released in the presence of heparin. The LPL activity is lowered by LPS injection after a lag phase of at least 3 h, while capillary endothelial cells are influenced more rapidly. The relatively late expression of TNF toxicity in cardiomyocytes of the intact heart is discussed.     

Theories of the biogenesis of flavonoid compounds (Part II)

The Botanical Review -     

Fibroblast dedifferentiation as a determinant of successful regeneration

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Molecular mechanisms involved in the production of cromosomal aberrations II. Utilization of neurospora endonuclease for the study of aberration production by X-rays in G1 and G2 stages of the cell cycle

Chinese hamster ovary cells (CHO) were X-irradiated in G₁ and G₂ stages of the cell cycle and subsequently Neurospora endonuclease (NE) (E.C.3.1.4), an enzyme which is specific in cleaving single-stranded DNA, was introduced into the cells, after making the cells permeable by treatment with inactivated Sendai virus. With this treatment all classes of X-ray-induced chromatid aberrations increased in G₂ cells, whereas in G₁ cells an increase in cromosome type of aberrations was found, associated with a profound induction of chromatid type of aberrations as well. Duration of the availability of single-strand gaps for the action of NE has been studied in G₂ cells following X-irradiation and the influence of different parts of the G₂ stage on the type and frequencies of chromatid aberrations was discerned. While the increase in chromosome type of aberrations by NE in X-irradiated G₁ cells has been interpreted as due to the conversion of DNA single-strand breaks or gaps to double-strand breaks by NE, the induction of chromatid aberrations in G₁ has been assumed to be due to conversion of some of the damaged bases strand breaks by NE. Biochemical evidence is presented for the conversion by NE of DNA single-strand breaks induced by X-rays into double-strand breaks using neutral sucrose gradient centrifugation.     

Endothelial nitric oxide synthase and its negative regulator caveolin-1 localize to distinct perinuclear organelles.

Caveolin-1 is a member of a subset of intracellular proteins that regulate endothelial nitric oxide synthase (eNOS) activity. In caveolae, caveolin-1 inhibits eNOS activity via a direct interaction with the enzyme. Previous work has indicated that both eNOS and caveolin-1 are also localized at the perinuclear Golgi complex. Whether caveolin-1 is involved in eNOS regulation in this cell compartment is unknown. Here we studied the localization of eNOS and caveolin-1 in the perinuclear region of primary bovine aortic endothelial cells. By immunofluorescence microscopy we show that both eNOS and caveolin-1 co-localize with Golgi markers. On treatment of the cells with the microtubule-depolymerizing drug nocodazole, the Golgi complex is scattered and caveolin-1 is found in vesicles at the periphery of the cell, while eNOS is localized at large structures near the nucleus. The nocodazole-induced redistribution of eNOS is similar to that of cis-, medial-, and trans-Golgi markers, while the caveolin-1 redistribution resembles that of sec22, a marker for the intermediate compartment. The localization of eNOS and caveolin-1 at distinct perinuclear compartments that behave differently in the presence of nocodazole indicates that eNOS activity is not regulated by caveolin-1 in the Golgi complex.