ISSN:0263-6484    

DOI:10.1002/cbf.290120303

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

ISSN:0263-6484    

DOI:10.1002/cbf.290120304

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

ISSN:0263-6484    

DOI:10.1002/cbf.290120305

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractGlycogen accumulation in pancreatic islet cells in situations of sustained hyperglycaemia may participate in the phenomenon of so‐called B‐cell glucotoxicity. Unexpectedly, however, previously little if any glycogen was found in islet cells of non‐insulin‐dependent diabetic Goto‐Kakizaki rats (GK rats). Therefore, the activities of glycogen synthase, glycogen phosphorylase and α‐amylase were measured in islets of control and GK rats. No significant difference in enzymatic activity was observed between the control and diabetic animals. In the liver, the activity of glycogen synthase appeared even somewhat higher in GK rats than in control animals. It is concluded that the diabetic syndrome in the GK rats does not involve any major anomaly of glycogen synthase and glycogen phosphorylase activity in the liver of these animals, as well as α‐amylase, in pa

ISSN:0263-6484    

DOI:10.1002/cbf.290120306

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractTaxol is an anti‐mitotic agent now being used in the treatment of some cancers, although the manner of its interaction with the microtubular components of the cytoskeleton is still not fully characterized. Here we report the effects of taxol upon a huge, naturally occurring and experimentally amenable aggregate of parallel microtubules from the ovaries of hemipteran insects. Within seconds of exposure to taxol, the microtubule aggregate began to twist upon itself. After a few minutes this movement was complete, the drug having brought about a gross rearrangement of the microtubules, involving coiling on a massive scale. The final form assumed by the microtubule array was influenced by pH and by the presence of microtubule‐associated proteins, salt, cations, and both hydrolysable and non‐hydrolysable nucleotides. The possible mechanisms leading to this rapid structural change are consi

ISSN:0263-6484    

DOI:10.1002/cbf.290120307

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe possibility that inositol lipid metabolism is related to nuclear events accompanying steroid hormone action has been investigated by comparing lipid phosphorylation and breakdown in normal rat liver nuclei and in hypo‐ and hypercortisolemic conditions. Lipid phosphorylationin vitroshowed the presence of diacylglycerol (DAG)‐, phosphatidylinositol (PI)‐ and phosphatidylinositol‐4‐phosphate (PIP)‐kinase activity, with differences between total tissue homogenates and isolated nuclei, relevant to the treatmentin vivo. Administration of hydrocortisone (HC) produced a marked decrease in the phosphorylated nuclear products without influencing the homogenate kinase activity. Under conditions which were optimal for the kinase activities, nuclear PIP‐kinase was strongly increased in presence of a high blood level of HC whereas PI‐kinase activity was reduced. From these observations it appears that the observed differences were due to specific modulation of kinase activities rather than to changes in the availability of substrates.The phosphoinositide‐specific phospholipase C (PLC) activity was also investigated. In the presence of a high HC blood level, the phosphodiesteratic cleavage of PIP strongly increased, while that of phosphatidylinositol bisphosphate (PIP2) was similar in normal and hypercortisolemic conditions. Nuclear phosphoinositide hydrolysis was affected by PLC, β and γ isoforms, which were equally represented in all the conditions investigated, indicating that the observed changes of activity were due to a modulation rather than to a change in the amount of enzyme.These results suggest that inositol lipid metabolism plays a role in the nuclear modifications accompanying steroid hormone induction of trans

ISSN:0263-6484    

DOI:10.1002/cbf.290120308

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe kinetic parameters of the inhibition of pigeon brain acetylchlolinesterase (AChE) by procaine hydrochloride were investigated. Procaine (0·083–1·67 mM) reversibly inhibited AChE activity (15–83 percent) in a concentration dependent manner, the IC50being about 0·38 mM. The Michaelis‐Menten constant (Km) for the hydrolysis of acetylthiocholine iodide was found to be 1·53 × 10−4M and theVmaxwas 1·06 μmol min−1mg−1protein. Dixon as well as Lineweaver‐Burk plots and their secondary replots indicated that the nature of the inhibition is of the linear mixed type which is considered to be a mixture of partial competitive and pure non‐competitive. The values ofKi(slope)andKi(intercepts) were estimated as 0·14 mM and 0·22 mM respectively by the primary Dixon and by the secondary replots of the Lineweaver‐Burk plot. TheKi′/Kiratio shows that procaine has a greater affinity of binding for the periphe

ISSN:0263-6484    

DOI:10.1002/cbf.290120309

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractHexokinase inactivating antibodies were loaded into human erythrocytes using an encapsulation procedure based on hypotonic haemolysis, isotonic resealing and reannealing. Red blood cells loaded with anti‐hexokinase IgG showed 20 percent residual hexokinase activity and reduced glycolytic activity.9Incubation of these cells in the presence of an oxidizing agent such as terbutyl hydroperoxide (TBH) and then in autologous plasma, promoted opsonization by autologous IgG and complement deposition, but not haemolysis. Furthermore, the antihexokinase IgG loaded cells treated with TBH were actively recognized and phagocytosed by macrophages. Thus, metabolic impairment of human erthrocytes promotes autologous IgG binding, C3 deposition and phagocytosis, a mechanism already reported for the removal of senescent erythrocyte

ISSN:0263-6484    

DOI:10.1002/cbf.290120310

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractA Ca2+‐dependent protein kinase ofTetrahymena thermophilahas been partially purified and characterized. The molecular mass of the enzyme is less than that of similar enzymes (for example protein kinase C), being about 55 kDa. After purification and in the presence of Ca2+the enzyme activity increased. The promoter of protein kinase C (PKC) activity, phorbol myristate acetate (PMA), increased the activity while the protein kinase inhibitor H‐7 decreased the activity of the enzyme. The experiments demonstrate the presence, activity and similarity to vertebrate enzymes of a protein kinase at a low level of phylog

ISSN:0263-6484    

DOI:10.1002/cbf.290120311

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

ISSN:0263-6484    

DOI:10.1002/cbf.290120313

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY