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F Horn

Publications and source records attributed to F Horn.

At least 91 records · Page 5Linked to original sources
PubMed1987

Decreased protein kinase C activity in psoriatic versus normal epidermis.

To study the possible involvement of protein kinase C in psoriasis, we determined the activity of this enzyme in involved and uninvolved epidermis from psoriasis patients as well as in normal epidermis from controls. Protein kinase C activity was measured in the 100,000 g supernatants and in the detergent-solubilized particulate fractions of tissue homogenates after partial purification by DEAE-cellulose chromatography. The total enzyme activities per gram protein for normal, involved, and uninvolved epidermis were 127 +/- 11.9 mU/g, 64.7 +/- 8.6 mU/g, and 88.5 +/- 14.4 mU/g, respectively. The respective values for total enzyme activity per mg DNA were 7.04 +/- 0.48 mU/mg, 4.28 +/- 0.54 mU/mg, and 5.02 +/- 0.66 mU/mg. By both data bases, protein kinase C activity was statistically lower in the psoriatic skin biopsies than in those from control persons, whereas no significant difference was found between involved and uninvolved epidermis from psoriasis patients. We hypothesize that alterations in protein kinase C-mediated processes due to decreased protein kinase C activity may play a significant role in the pathophysiology of psoriasis.

Chromatography, DEAE-Cellulose↗
PubMed1986

Purified pyruvate kinases type M2 from unfertilized hen's egg are substrates of protein kinase C.

To characterize pyruvate kinase isoenzymes from cells with the capability to proliferate, this enzyme was purified from yolk and vitelline membrane of unfertilized hen's egg. Pyruvate kinase type M2 from vitelline membrane was obtained in a homogeneous form after a 1150-fold purification to a specific enzymatic activity of 450 mumol X min-1 X mg-1. It was saturated half-maximally with phosphoenolpyruvate at KPPrv0.5 = 0.36 mM phosphoenolpyruvate and was activity by fructose 1,6-bisphosphate and L-serine at suboptimal substrate concentrations. After 11 000-fold purification to a specific enzymatic activity of 60 mumol X min-1 X mg-1, the pyruvate kinase isoenzymes type M2 (KPPrv0.5 = 0.32 mM) and M1 (KPPrv0.5 = 0.04 mM) were obtained from the yolk substance. Kinetic differences were noted between the pyruvate kinase type-M2 isoenzymes from vitelline membrane and yolk. A comparison of the amino acid composition of the purified pyruvate kinase isoenzymes from hen's egg revealed that all isoenzymes were related to pyruvate kinase type M1 from chicken breast muscle. The M2-type isoenzyme from vitelline membrane was related to the M2-type isoenzyme from chicken tumors, but was not related to the M2-type pyruvate kinase from chicken lung or liver. Protein kinase C from chicken oviduct phosphorylated in vitro both pyruvate kinase M2 isoenzymes from the unfertilized hen's egg preferably at serine and less at threonine residues. Pyruvate kinase type M1 from egg yolk was a weak substrate of protein kinase C. An activation of pyruvate kinase type M2 from vitelline membrane was observed at suboptimal concentrations of phosphoenolpyruvate under the conditions of phosphorylation, in the presence of phosphatidylserine.

Amino Acids↗
PubMed1985

Protein kinase C interferes with Ni-mediated inhibition of human platelet adenylate cyclase.

Addition of phorbol ester-activated, partially purified protein kinase C to membranes of human platelets had no effect on forskolin stimulation of the adenylate cyclase and increased stimulation by prostaglandin E1 only at high GTP concentrations by preventing inhibition by GTP. Hormonal inhibition of the platelet adenylate cyclase by epinephrine was eliminated or largely impaired. At low GTP concentrations, epinephrine even caused a small increase in cyclase activity. The data suggest that activated protein kinase C interferes with GTP- and hormone-induced adenylate cyclase inhibition probably by phosphorylating the inhibitory guanine nucleotide-binding regulatory component Ni.

Adenylyl Cyclase Inhibitors↗
PubMed1985

Partial purification and characterization of the calcium-dependent and phospholipid-dependent protein kinase C from chick oviduct.

The calcium-dependent and phospholipid-dependent protein kinase C is partially purified (2000-fold) from chick oviduct cytosol by chromatography on DEAE-cellulose, Sephadex G150 and (after affinity binding of the enzyme to phosphatidylserine-diolein liposomes) on Bio-Gel A-0.5m. The enzyme is activated by phosphatidylserine and calcium ions. Diolein increases the affinity of the enzyme for both cofactors and can be replaced by the tumour-promoting phorbol ester 12-O-tetradecanoyl-phorbol 13-acetate. Phosphatidylserine can be replaced by unsaturated long-chain fatty acids. Quercetin and phloretin inhibit the kinase reversibly competing with ATP. Several oviduct proteins are found to be phosphorylated by the partially purified enzyme. One of the substrates, a 78-kDa protein, appears to be ovotransferrin.

Animals↗
PubMed1985

Cyclosporin A inhibits biological effects of tumor promoting phorbol esters.

The antilymphocytic and antiphlogistic agent cyclosporin A (CsA) inhibits in vivo various effects induced by the tumor promoting phorbol ester 12-0-tetradecanoylphorbol-13-acetate (TPA). These include the edema of the mouse ear, the alkaline phosphatase (AP) activity and the ornithine decarboxylase (ODC) activity in mouse epidermis as well as the generation of a specific arachidonic acid (AA) metabolite in mouse epidermis. AA metabolism in an epidermal cell-free system of mouse epidermis was not suppressed by CsA. According to thin layer chromatography the TPA-induced and as yet unidentified AA metabolite exhibits a polarity between that of 5-HETE and 12-/15-HETE. Studies with inhibitors indicate it to be a lipoxygenase product.

Animals↗
PubMed1984

Calcium and phospholipid-dependent protein kinase activity in mouse epidermis cytosol. Stimulation by complete and incomplete tumor promoters and inhibition by various compounds.

Calcium- and phospholipid-dependent protein kinase (Ca, PL-PK) activity is detectable in mouse epidermis cytosol. It can be stimulated in vitro by complete and incomplete tumor promoters (12-0-tetradecanoylphorbol-13-acetate (TPA) and 12-0-retinoylphorbol-13-acetate (RPA], respectively. Effective inhibition of the enzyme activity is achieved with quercetin and phloretin, whereas the lipoxygenase and cyclooxygenase inhibitors nordihydroguaiaretic acid (NDGA) and esculetin show just weak or no inhibition. Quercetin inhibits the lipoxygenase and cyclooxygenase equally well as the Ca, PL-PK, whereas the strong Ca, PL-PK inhibitor phloretin is absolutely ineffective in inhibiting the lipoxygenase/cyclooxygenase. The application of these inhibitors in differentiating tumor promoter induced effects in vivo is proposed.

Animals↗
PubMed1983

Inhibition of the calcium- and phospholipid-dependent protein kinase activity from mouse brain cytosol by quercetin.

The flavonoid quercetin is a potent inhibitor of calcium- and phospholipid-dependent protein kinase (Ca, PL-PK) activity from mouse brain. Half-maximal inhibition of the kinase occurs at about 10 microM. If the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) is used instead of calcium as a stimulating factor of the kinase enzyme activity is still inhibited by quercetin. The kinase inhibitor, however, does not interfere with the binding of TPA to its receptor.

Adenosine Triphosphate↗
PubMed1983

[Diagnosis, etiology and clinical course of acute and chronic pericarditis].

Between 1976 and 1982 18 patients with acute and 13 with chronic pericarditis (excluding constrictive pericarditis) were seen at the Medical Outpatient Clinic, University Hospital, Zürich. The prominent symptom in acute pericarditis was chest pain (15/18 patients versus 0/13 in chronic pericarditis, p less than 0.001) and in chronic pericarditis dyspnea (7/13 patients versus 1/18 in acute pericarditis, p less than 0.005). Pericardial friction rub and ST elevation were significantly more frequent in acute than in chronic pericarditis. In contrast, elevation of venous pressure occurred more often in the chronic than in the acute form. During the follow-up of 3.2 years the NYHA class decreased from 2.5 to 1.2 (p less than 0.001) in the group with acute pericarditis although 7 recurrences occurred in 3 patients within the first two years. The follow-up in the patients with chronic pericarditis was 4.4 years and the NYHA class decreased from 2.4 to 1.4 (p less than 0.05). There were, however, two deaths in the group with chronic pericarditis and pericardiocentesis and/or pericardiectomy had to be performed in 8/13 patients.

Adult↗
PubMed1983

Soluble phorbol ester binding sites and phospholipid- and calcium-dependent protein kinase activity in cytosol of chick oviduct.

A large amount of specific high affinity binding sites for tumor promoting phorbol esters as well as of a Ca2+- and phospholipid-dependent protein kinase is present in cytosol of chick oviduct. 12-O-Tetradecanoyl-phorbol-13-acetate (TPA) is able to replace either Ca2+ or the phospholipid phosphatidylserine as activators of the kinase to some extent. The maximum activity of the enzyme in the presence of Ca2+ and phosphatidylserine, however, cannot be increased further by TPA. Various second stage tumor promoters also exhibit the capacity to stimulate the protein kinase, whereas the non-promoting phorbol ester 4-O-methyl-TPA, as well as the non-promoting, but with respect to other responses TPA-like, calcium ionophore A23187, do not affect the kinase.

Animals↗
PubMed1983

Regulatory properties of the pyruvate dehydrogenase complex from Escherichia coli. Studies on the thiamin diphosphate-dependent lag phase.

The pyruvate dehydrogenase complex from Escherichia coli shows an appreciable lag phase (tau) of some minutes when its overall reaction rate was tested with very limiting amounts of thiamin diphosphate. tau depends on the concentration of thiamin diphosphate in a nonlinear fashion. Sodium diphosphate, a competitive inhibitor with respect to thiamin diphosphate (Ki = 5.2 . 10(-4) M) prolongs the lag, while the strongly binding transition state analog thiamin thiazolone diphosphate has no effect. tau is independent of the enzyme concentration, thus no dissociation-association step is involved. Incubation of the pyruvate dehydrogenase complex with thiamin diphosphate, Mg2+, and pyruvate leads to a shortening of the lag phase, as well as to a decrease of the intrinsic tryptophan fluorescence in a time-dependent process, which evinces the same characteristics as tau. Dependence of pyruvate, as well as of the substrate analog methylacetylphosphonate, can be established by measurements of fluorescence quenching, thus ruling out an essential role of hydroxyethyl thiamin diphosphate in the process reflected by the lag phase. The results demonstrate that the lag phase is induced after the binding of both thiamin diphosphate . Mg2+ and pyruvate to the catalytic site to form a ternary enzyme complex, which undergoes subsequently a slow conformational change to an active enzyme form. This change is confined to single subunits, and no interactions between neighboring monomers could be observed. A model is proposed to describe the mechanism represented by the lag phase.

Diphosphates↗
PubMed1981

[An unusual case of repeated self mutilation (author's transl)].

An unusual case is presented of repeated, life-threatening self mutilation, elicited by the topical application of sodium hydroxide, which necessitated several operations, including amputation of the left lower leg. Histological examination revealed colliquation necrosis and a striking eosinophilia. The latter feature, which was not reproducible in an animal experiment, may be related to a defect of leucocyte locomotion in the present case.

Adolescent↗
PubMed1980

Eccrine porocarcinoma.

Eccrine porocarcinoma is an extremely rare malignant skin tumor arising from the eccrine sweat duct unit (acrosyringium). It presents histologically with nests of clear tumor cells in the epidermis and superficial dermis. In addition such clear tumor cells lie isolated high up in the epidermis, closely resembling Paget cells. The various tumors, which may originate from the acrosyringium and the histologic differential diagnosis of eccrine porocarcinoma are discussed.

Adenoma, Sweat Gland↗