Codon specificity of starvation induced misreading

Summary Mistranslated derivatives of the coat protein of the bacteriophage MS2 were isolated from infected cells starved for asparagine. This protein contains a high level of lysine for asparagine substitutions. By peptide analysis and amino acid sequencing we show that there is a six-fold greater frequency of errors at AAU codons than at AAC codons. This ratio is the same as that found in unstarved cells where the overall error frequency is 100-fold less. We also demonstrate that, at least for AAC codons, context affects error frequency.     

Met-enkephalin levels during PTCA-induced myocardial ischemia.

Met-enkephalin (Met-enk) has been demonstrated to modulate myocardial-ischemia mechanisms via the opioid receptors, but no studies are now available on Met-enk levels in the coronary circulation.In this experience Met-enk levels were evaluated in aortic root and in coronary sinus at baseline (T0), during PTCA induced transient ischemia (T1) and during reperfusion (T2). No significant differences were found at any time. Thus, it appears that there is no Met-enk extraction from the coronary circulation during provoked myocardial ischemia and no Met-enk release from the ischemic heart.     

Regulation of chondrocyte gene expression by osteogenic protein-1

Introduction  

The objective of this study was to investigate which genes are regulated by osteogenic protein-1 (OP-1) in human articular chondrocytes using Affimetrix gene array, in order to understand the role of OP-1 in cartilage homeostasis.     

Differential modulation of human melanoma cell metalloproteinase expression by alpha2beta1 integrin and CD44 triple-helical ligands derived from type IV collagen

Tumor cell binding to components of the basement membrane is well known to trigger intracellular signaling pathways. Signaling ultimately results in the modulation of gene expression, facilitating metastasis. Type IV collagen is the major structural component of the basement membrane and is known to be a polyvalent ligand, possessing sequences bound by the alpha1beta1, alpha2beta1, and alpha3beta1 integrins, as well as cell surface proteoglycan receptors, such as CD44/chondroitin sulfate proteoglycan (CSPG). The role of alpha2beta1 integrin and CD44/CSPG receptor binding on human melanoma cell activation has been evaluated herein using triple-helical peptide ligands incorporating the alpha1(IV)382-393 and alpha1(IV)1263-1277 sequences, respectively. Gene expression and protein production of matrix metalloproteinases-1 (MMP-1), -2, -3, -13, and -14 were modulated with the alpha2beta1-specific sequence, whereas the CD44-specific sequence yielded significant stimulation of MMP-8 and lower levels of modulation of MMP-1, -2, -13, and -14. Analysis of enzyme activity confirmed different melanoma cell proteolytic potentials based on engagement of either the alpha2beta1 integrin or CD44/CSPG. These results are indicative of specific activation events that tumor cells undergo upon binding to select regions of basement membrane collagen. Based on the present study, triple-helical peptide ligands provide a general approach for monitoring the regulation of proteolysis in cellular systems.     

Characterization of Aspergillus nidulans mutants deficient in cell wall chitin or glucan.

By screening for the osmotically remediable phenotype, mutations in two genes (orlA and orlB) affecting the cell wall chitin content of Aspergillus nidulans were identified. Strains carrying temperature-sensitive alleles of these genes produce conidia which swell excessively and lyse when germinated at restrictive temperatures. Growth under these conditions is remedied by osmotic stabilizers and by N-acetylglucosamine (GlcNAc). Remediation by GlcNAc suggests that the mutations affect early steps in the synthesis of chitin. Temperature and medium shift experiments indicate that the phenotype is the result of decreased synthesis rather than increased chitin degradation and that osmotic stabilizers act to stabilize a defective wall rather than to stabilize the gene product. Two genes, orlC and orlD, which affect cell wall beta-1,3-glucan content were also identified. Walls from strains carrying mutations in these genes exhibit normal amounts of alpha-1,3-glucan and chitin but reduced amounts of beta-1,3-glucan. As for the chitin-deficient mutants, orlC and orlD mutants spontaneously lyse on conventional media but are remedied by osmotic stabilizers. These results indicate that both chitin and beta-1,3-glucan are likely to contribute to the structural rigidity of the cell wall.     

Changes in the rate of chitin-plus-chitosan synthesis accompany morphogenesis of Mucor racemosus.

The in vivo differential rates of chitin-plus-chitosan biosynthesis in Mucor racemosus were determined under a variety of conditions, leading to yeast cell or mycelial morphology. Chitin-chitosan was determined as hot NaOH-insoluble radioactivity derived from N-acetyl-D-[1-3H]glucosamine in the medium. Control experiments demonstrated that the labeled material possessed the properties of chitin-plus-chitosan. Our results indicate that Mucor yeasts have a relatively low differential rate of chitin-plus-chitosan synthesis and that mycelial cells have a threefold-elevated differential rate. Treatment of aerobic cells with exogenous N6, O2-dibutyryl cyclic adenosine 3',5'-monophosphate, an agent which induces yeast cell morphology, also results in a lowered rate of chitin-plus-chitosan synthesis. Control experiments eliminated the possibility that the observed rate changes were due to changes in endogenous pool size, uptake of exogenous N-acetyl-p-[1-3H]glucosamine, or alterations in growth rate. Therefore, the changes are seemingly linked to morphogenesis. These results strengthen the idea that cyclic adenosine 3',5'-monophosphate plays an important role in dimorphism in Mucor. In addition, pulse-chase experiments suggest that considerable modification of newly synthesized chitin plus chitosan in both yeast cells and mycelia occurs in vivo.     

Cystic echinococcosis in humans: our clinic experience

Echinococcosis in humans is a zoonotic infection caused by larval stages of cestode species of the Echinococcus genus. In cystic echinococcosis (CE), caused by Echinococcus granulosus, the liver is the first and the more frequent involved organ, followed by the lung. Heart, spleen, kidney and brain are usually less involved. The finding of a cyst in course of echinococcosis is usually fortuitous, during ultrasound examination, X-ray or CT. The Authors report 4 cases of human CE admitted to the Department of Infectious Diseases University of Naples "Federico II". Each case is peculiar both for the organ involved by the cysts and for the symptomatolgy. The abdominal pain, in case 1 caused by gallstones, allowed, by the ultrasound examination, to find several hydatid cysts in the liver, never symptomatic until then. The woman, in case 2, was operated for cysts in the lung, without receiving pharmacological prophylaxis. The same occurred in case 4, in which the lack of prophylaxis caused very serious relapses. In case 3, the young woman underwent an ultrasound examination because of an abdominal pain. A unique large cyst extended only in the spleen. The specific serology for immunoglobulin anti-E. granulosus resulted positive 1:61 (n.v. < 50). The Albendazole therapy caused the disappareance of pain, quickly. Later, the patient was splenectomized. It's not clear why only the spleen was involved and why the anti-E. granulosus serum levels of were increased only a little. The man, in case 4, was admitted with chest pain and electrocardiographic findings of myocardial anterior ischemia. He underwent surgical treatment of three hepatic cysts by E. granulosus, during the previous year. Two-dimensional echocardiography, transesophageal echocardiography, and cardiac magnetic resonance revealed a round cystic mass, 6 x 6 mm, located in the middle interventricular septum. The cardiac isoenzymes were in the normal ranges, but the anti-E. granulosus immunoglobulins were positive 1:5120 (n.v. < 64). The patient was treated with Albendazole. This caused the almost simultaneous disappearance of the circular cystic and clinical and electrocardiographic findings of myocardial ischemia. A cardiac hydatid cyst is an uncommon lesion, occurring in about 0.4-2% of patients with echinococcosis. In conclusion, Cystic echinococcosis is a problem in Mediterranean regions because of the high population of stray dogs, favourable conditions created by man and, above all, the illegal slaughtering.