Biomedical subjects
Publications and source records attributed to E Hofmann.
The isozyme distribution of glycogen phosphorylase (EC 2.4.1.1) was studied in adult rat liver and isolated non-parenchymal liver cells by means of immuno-titration. In adult rat liver, the L-type of glycogen phosphorylase was found to dominate, whereas the heterogeneous non-parenchymal liver cell population apparently contains all three glycogen phosphorylase isozymes.
The placental glycogen content per g wet weight decreases after the 16th day of gestation but remains nearly constant till the 21st day of gestation when expressed per placenta as whole organ. Injection of insulin to rat fetuses at the 21st day of gestation gives rise to hypoglycemia and an increase of the glycogen content in liver and in placenta. Intrauterine glucagon application makes fetuses hyperglycemic in consequence of a mobilization of the placental glycogen stores. Hepatic glucose production appears in later stages because of the low activity of glucose 6-phosphatase as demonstrated by the effect of glucagon on the hepatic glucose 6-phosphate concentration.
Computed tomography findings were studied after successful lumbar disk surgery. All patients were asymptomatic after the operation thus presenting morphological changes that probably correspond to regular postoperative conditions. Small seromas in the area of surgery are well-known "normal" findings and have no pathological significance. Dorsal bulging at the level of the intervertebral disc operated upon has not yet been studied systematically. This protrusion that can even exceed the preoperative amount of bulging is due to swelling and folding of the posterior longitudinal ligament. In our patients it disappeared spontaneously within a few months and it should not be confused with real recurrent or residual disc herniation.
Binding and uptake of asialothyroglobulin by freshly isolated rat hepatocytes were studied in dependence on temperature as well as on the concentrations of the ligand and of calcium ions. The endocytosis of native thyroglobulin occurred as a nonspecific process. The number of galactose-specific receptors on the hepatocyte surface was estimated to be 47,400 per cell. The cells exhibited only a single class of binding sites with an association constant for asialothyroglobulin of Kass = 0.18.10(8)M-1. The internalization of surface-bound asialothyroglobulin appeared to be a first-order process. The rate constant of internalization ki, was estimated to be 0.6.10(-3) s-1. The obtained data provide an explanation of the extreme half-life of asialothyroglobulin in the circulation.
In fetal rat liver the concentration of fructose 2,6-bisphosphate is decreased by administration of glucagon. The glucagon effect, i.e., the phosphorylation state of phosphofructokinase 2, dominates over the substrate supply. Insulin was found to increase fructose 2,6-bisphosphate only when exogenous glucose is supplied simultaneously. The total activity of phosphofructokinase 2 exhibits remarkable developmental changes. It is high at term, moderate in the fetal as well as in the mature organ, and low during suckling. The level of the enzyme during development is controlled by pancreatic and adrenal hormones.
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Adrenalectomy of suckling rats is complicated by a high mortality rate, caused by the loss of blood (early mortality) and by the disturbed sodium-potassium balance (late mortality). Treatment of the abdominal cavity with a thrombin solution and a daily administration of deoxycorticosterone glucoside (DOC) decrease the total mortality remarkably. DOC treatment has no influence on renal beta-glucosidase and beta-galactosidase as well as on hepatic tyrosine aminotransferase activity, whereas hepatic serine dehydratase activity exhibits a time- and dosage-dependent response to this hormone. The DOC effect is very likely a consequence of the glucocorticoid-like action of the synthetic hormone, which competes with the endogenous glucocorticoids for the hepatic receptor molecules.
Yeast phosphofructokinase is known to be effectively activated by fructose-2,6-bisphosphate and AMP. In the absence of the two effectors, fructose-1,6-bisphosphate activates or inhibits the enzyme according to the concentrations of the substrates and of inorganic phosphate. At cellular concentrations of the substrates, however, the effects of fructose-1,6-bisphosphate are negligible. Whereas the activation of the enzyme by AMP is not affected by fructose-1,6-bisphosphate, the latter was found to diminish strongly the activity of the fructose-2,6-bisphosphate-activated enzyme. Inorganic phosphate amplifies the activating effect of fructose-2,6-bisphosphate and augments also the deactivation of the fructose-2,6-bisphosphate-activated enzyme. The deactivating action of fructose-1,6-bisphosphate with respect to fructose-2,6-bisphosphate dominates at low concentrations of fructose-6-phosphate and high levels of ATP and might be of regulatory significance.
Binding of fructose-1,6-bisphosphate to yeast phosphofructokinase (EC 2.7.1.11) was measured in a concentration range of 5 to 200 microM of fructose-1,6-bisphosphate with the ultrafiltration technique. At saturation two molecules of fructose-1,6-bisphosphate are bound per subunit of the octameric enzyme. Two distinct types of binding sites have been observed. The high affinity sites (KH = 32.7 +/- 5 microM) exhibit a hyperbolic response in respect to the binding of fructose-1,6-bisphosphate, the low affinity sites (KL = 57.2 +/- 6 microM) show significant positive cooperativity.
The activities of beta-glucosidase as well as of alpha- and beta-galactosidase increase in the renal cortex of the rat during the early postnatal development. However, while the two galactosidases reach adult values around the end of the second week of life, beta-glucosidase activity exhibits a second steep increase after the third post-uterine week. This rise in activity correlates with the functional maturation of kidney and is confined nearly exclusively to the cytosolic isozyme. The effects of taurocholate, Triton X-100, and dexamethasone on beta-glucosidase isozymes were studied. The results suggest that taurocholate should be included in the assay medium for the measurement of the beta-glucocerebrosidase activity in the diagnosis of Gaucher's disease. For the determination of the total beta-glucosidase activity in samples containing mainly the lysosomal isozyme (perinatal kidney, isolated lysosomes) the use of Triton X-100 is recommended.
The inhibition of pig liver fructose 1,6-bisphosphatase by fructose 2,6-bisphosphate has been investigated over a wide range of substrate concentration by measuring the release of labelled inorganic phosphate from [1-32P]fructose 1,6-bisphosphate. The activity of the enzyme can be inhibited completely by fructose 2,6-bisphosphate. The inhibiting effect is most pronounced at low substrate concentrations. The results have been analyzed in terms of a mathematical model assuming a competitive interaction of fructose 1,6-bisphosphate and fructose 2,6-bisphosphate at the catalytic site as well as a synergistic cooperation of the two hexose bisphosphates at an inhibiting allosteric site of the enzyme.
Glucose-6-phosphate dehydrogenase (EC 1.1.1.49) prepared from baker's yeast binds to immobilized Cibacron Blue F3G-A and Procion Red HE-3B. In this paper the two dyes are compared with respect to their use in the purification of this enzyme. Cibacron Blue chromatography was found useful at an early stage of purification for the removal of contaminating hexokinase, phosphoglucose isomerase and phosphoglucomutase. With Procion Red HE-3B Sepharose the NADP dependent enzymes phosphogluconate dehydrogenase and glutathione reductase are separable from glucose-6-phosphate dehydrogenase. Unlike Cibacron Blue gel chromatography, the enzyme can be specifically eluted from Procion Red HE-3B Sepharose by a NADP gradient. Other monochlorotriazine dyes like Xirone Brillant Red BHD, 4BHD, 6BHD and GHD and the dichlorotriazine dye Procion Brown MX-5BR immobilized to Sepharose have only little binding affinity to glucose-6-phosphate dehydrogenase. The binding behaviour of different immobilized triazine dyes for pre-purified and purified glucose-6-phosphate dehydrogenase is compared. In addition, the influence of the free dyes on the activity of glucose-6-phosphate dehydrogenase is studied. It is demonstrated that the results of kinetic and binding studies with the purified enzyme are not uncritically applicable for the selection of a dye as ligand for affinity chromatography during enzyme preparation.
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A 59-year-old man developed a nephrotic syndrome and mild renal failure after treatment with phenylbutazone. Light microscope examination of a renal biopsy specimen showed minimal glomerular alterations, and electron microscopy showed diffuse fusion of epithelial cell foot processes without immune deposits. The interstitium revealed focal lymphocyte infiltrates identified as activated T-cells by immune histologic differentiation. The unusual combination of nephrotic syndrome with acute interstitial nephritis is a rare adverse reaction of nonsteroidal antiinflammatory drugs (NSAID). A disordered cell-mediated immunity could lead to interstitial infiltration of T-lymphocytes which, releasing lymphokines and a vascular permeability factor, cause the glomerular proteinuria. In addition, NSAID inhibition of prostaglandin synthesis may enhance production of these lymphocyte-derived substances. Since the nephrotic syndrome persisted 5 months after withdrawal of phenylbutazone, steroid therapy was initiated and 2 months later the renal insufficiency and proteinuria were resolved.
Fructose 1,6-bisphosphate decreases the activation of yeast 6-phosphofructokinase (ATP:fructose 6-phosphate 1-phosphotransferase, EC 2.7.1.11) by fructose 2,6-bisphosphate, especially at cellular substrate concentrations. AMP activation of the enzyme is not influenced by fructose 1,6-bisphosphate. Inorganic phosphate increases the activation by fructose 2,6-bisphosphate and augments the deactivation of the fructose 2,6-bisphosphate activated enzyme by fructose 1,6-bisphosphate. Because various states of yeast glucose metabolism differ in the levels of the two fructose bisphosphates, the observed interactions might be of regulatory significance.
The cooperation of phosphofructokinase-2 and fructose-2,6-bisphosphatase is investigated. Experimentally derived rate laws of the kinase and bisphosphatase activities introduced into the respective differential equations permitted to describe the time evolution of fructose-2,6-bisphosphate to quasi-stationary levels. The two enzyme activities were found to exert strong temperature dependence. The quasi-stationary levels of fructose-2,6-bisphosphate, however, are independent on temperature.
In a reconstituted enzyme system multiple stationary states and oscillatory motions of the substrate cycle catalyzed by phosphofructokinase and fructose 1,6-bisphosphatase are significantly influenced by fructose 2,6-bisphosphate. Depending on the initial conditions, fructose 2,6-bisphosphate was found either to generate or to extinguish oscillatory motions between glycolytic and gluconeogenic states. In general, stable glycolytic modes are favored because of the efficient activation of phosphofructokinase by this effector. The complex effect of fructose 2,6-bisphosphate on the rate of substrate cycling correlates with its synergistic cooperation with AMP in the activation of phosphofructokinase and inhibition of fructose 1,6-bisphosphatase.