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Biomedical subjects

M A Alonso

Publications and source records attributed to M A Alonso.

83 records · Page 5Linked to original sources
PubMed1982

Molecular basis of the permeabilization of mammalian cells by ionophores.

Mammalian cells become permeable to low-molecular-weight compounds and proteins when they are treated with nigericin. Concentrations of this ionophore that have no effect on protein synthesis induce the entry of the translation inhibitors hygromycin B (Mr 550) and kappa-sarcin (Mr 16800). Treatment of HeLa cells with low concentrations of nigericin stimulate the (Na+/K+)ATPase and, as a consequence, increase the plasma membrane potential. A correlation is observed between the increase in membrane potential and the entry of antibiotics and protein toxins into cells. These results suggest a relationship between the two phenomena and help an understanding of the molecular mechanism for the passage of charged molecules and proteins into mammalian cells. This permeabilization is specific for certain ionophores, such as nigericin and monensin, and does not occur on treatment with amphotericin B, valinomycin or A23187. These compounds depolarize the plasma membrane and drastically block protein synthesis in HeLa cells under these conditions.

Anti-Bacterial Agents↗
PubMed1981

Reversion by hypotonic medium of the shutoff of protein synthesis induced by encephalomyocarditis virus.

Infection of human HeLa cells by picornaviruses produces a drastic inhibition of host protein synthesis. Treatment of encephalomyocarditis virus-infected HeLa cells with hypotonic medium reversed this inhibition; no viral protein synthesis was detected. The blockade of viral translation by hypotonic conditions was observed for a wide range of multiplicities of infection. However, only with low virus-to-cell ratios did cellular protein synthesis resume. The ratio of cellular to viral mRNA translation was strongly influenced by the concentration of monovalent ions present in the culture medium: a high concentration of NaCl or KCl favored the translation of viral mRNA and strongly inhibited cellular protein synthesis, whereas the opposite was true when NaCl was omitted from the culture medium. Once viral protein synthesis had been blocked by hypotonic medium treatment, it resumed when the infected cells were placed in a normal or hypertonic medium, indicating that the viral components synthesized in the infected cells were not destroyed by this treatment. These observations reinforced the idea that ions play a role in discriminating between viral and cellular mRNA translation in virus-infected animal cells.

Culture Media↗
PubMed1979

Compounds affecting membranes that inhibit protein synthesis in yeast.

The regulation of translation has been investigated in yeast cells by means of ionophores and other compounds affecting the ionic concentration inside the cell. Treatment of a variety of cells with these compounds produces a drastic inhibition in the protein-synthesizing activity of the cell. Protein synthesis in yeast is strongly inhibited by amphotericin B and nystatin. Mammalian cells are blocked in their translation capacity by gramicidin D, nigericin, monensin, nystatin, A23187, and bromolasalocid. The effects of these compounds on protein synthesis in Escherichia coli and Staphylococcus aureus were also investigated. Amphotericin B is a powerful inhibitor of both protein and ribonucleic acid syntheses in yeast cells at concentrations that do not affect the transport of the labeled amino acid or nucleoside precursor. The analysis of the polysomal profiles in yeast spheroplasts could indicate that initiation is the target of amphotericin B action on translation. Studies on the reversion of the protein synthesis blockade by amphotericin B by increasing the potassium concentration in the medium suggest that changes in the potassium concentration in cellular cytoplasm might be responsible, at least in part, for the inhibition of protein synthesis.

Amphotericin B↗
PubMedDate not supplied

Current practice in renal anaemia management: two multinational surveys.

The European Best Practice Guidelines recommend that 85% of patients with standard causes of chronic renal failure should achieve a target haemoglobin concentration of > or = 11 g/dL. However, patient outcomes need to be improved as many patients respond suboptimally to treatment and fail to reach these targets. Two multinational surveys of nursing practice in the management of renal anaemia in northern (with comparative data from Australia) and southern Europe were conducted. The aim was to assess variations in the role and amount of responsibility delegated to nurses in renal units throughout Europe and Australia. Patient care could be optimised by developing formal training and educational programmes for nephrology nurses and this has already occurred in many units in the UK.

Anemia↗