Glycogen phosphorylase (E.C.2.4.1.1) was the first enzyme shown to be regulated by allosteric effectors and by protein phosphorylation. Transcriptional control of bacterial phosphorylases further extends the range of regulatory mechanisms by which phosphorylases contribute to the control of carbohydrate metabolism. Despite their regulatory differences, all known phosphorylases share catalytic and structural properties and a strongly conserved pyridoxal-5'-phosphate binding site; this makes phosphorylases highly attractive for investigations into the evolution of regulatory mechanisms. The primary and tertiary structure of rabbit muscle phosphorylase has been determined completely. Recently, comparable amino acid sequences from plants and bacteria have been resolved. Here we report the sequence of 687 amino acids of Escherichia coli maltodextrin phosphorylase, deduced from a cloned malP gene sequence. Alignment of animal and bacterial phosphorylase sequences shows strong homology (48%) throughout 91% of the polypeptide chain enclosing the extrinsic catalytic region. Within this region, structural homology identifies a presumed phosphate-binding site from which the allosteric 5' AMP binding site of rabbit muscle phosphorylase might have developed. From the decreased alignment at the N-terminus and the presence of additional residues compared with bacterial phosphorylases, we conclude that the regulatory sequences that also carry the phosphorylation site in the muscle enzyme were joined to a presumed ancestral precursor gene by gene fusion after separation of the eukaryotic and prokaryotic lines of descent.

Adenosine Monophosphate↗

PubMedDate not supplied

[Spinal cord tumors in childhood--experience with 31 patients].

Spinal tumors are rare diseases of childhood. The initial symptoms are often very uncharacteristic and the diagnosis is delayed for a long time. From 1970-1983 31 children with intraspinal tumors were seen. The location of these tumors was 7 times intramedullar, 13 times extramedullar-intradural and 11 times extradural. History, findings and treatment of these patients are reported and compared with the available literature. Despite the well known diagnostic problems, early diagnosis and treatment are of the greatest importance for the prognosis.

Adolescent↗

PubMedDate not supplied

Medulloblastoma: experience of a single institution.

BACKGROUND: The treatment of medulloblastoma has changed considerably during the last decades. Treatment differences between centers may affect a multicenter analysis. We analyzed data from patients of a single institution gathered over a long period of time. PATIENTS: Between 1968 and 1995, 60 patients with medulloblastoma were treated at the University of Munster. Thirty-six were male, 24-female. The ages ranged between 11 months and 32 years. METHODS: Data were retrospectively analyzed from files. Survival was estimated using the Kaplan Meier method and compared using the logranktest and multivariance analysis. RESULTS: The 5-year survival rate was 37%. This included an early mortality of 20% within the first two months, prior to 1980. Significant single, positive, prognostic factors included: no solid metastases (p = 0.001), age > 10 years (p < 0.002); total resection (p < 0.025); posterior fossa radiation with more than 50 Gy (p = 0.04); and intense chemotherapy (p = 0.02). Male patients did slightly worse (not significant). The three-year event-free survival rate of 16 patients treated after 1991 was 70%. CONCLUSION: The prognosis of medulloblastoma has clearly improved with the reduction of the perioperative mortality, standardized radiotherapy, and the introduction of intense chemotherapy.

Adolescent↗

PubMedDate not supplied

Increase of Bmax-values of beta-adrenoceptor sites after chronic treatment with reserpine?

After treatment of rats with 5 x 0.5 mg/kg/d reserpine in membrane preparations from the parotid gland no increase in the total number of beta-adrenoceptors (Bmax) was observed using the antagonist ligand (-)3H-dihydroalprenolol. There occurred, however, a pronounced increase of the high affinity agonist binding component. Thus, it appears that not the absolute number of beta-adrenoceptor sites but the relative amount of high affinity sites is most sensitive against the sensitization process. The results are in contrast to those of other authors. We suspect that increases of Bmax-values after reserpine can be simulated by the loss of noradrenaline whereas in control membranes noradrenaline is still bound to the adrenoceptors thus preventing the radioactive ligand from access to these sites. We highly recommend to use preincubation methods prior to ligand binding studies in order to remove endogenous ligands still bound to the high affinity site of the beta-adrenoceptor.

Animals↗