Biomedical subjects

L Cesaro

Publications and source records attributed to L Cesaro.

22 records · Page 2Linked to original sources

PubMed1975

Electrical properties of amphibian urinary bladder epithelia. I. Inverse relationship between potential difference and resistance in tightly mounted preparations.

In an attempt to find a high-resistance epithelium suitable for microelectrode work, we have studied the electrical properties of Necturus and Amphiuma urinary bladders in comparison to toad bladder. Improved mounting techniques were developed, which yield better reproducible degrees of distension and prevent electrical leaks around the edge of the preparation in the Ussing chamber. Transepithelial potential difference and resistance was measured with NaCl Ringer's on either surface of the epithelium, as well as under conditions of ion substitutions and in the presence of amiloride. Compared to data from conventionally mounted toad bladders reported in the literature, our experiments yielded higher potential differences and resistances in all three species. In Necturus values of up to 175 mV and 75 komega cm2 were recorded. Furthermore an inverse relationship was observed between potential difference and resistance, which was not noticed previously with the conventional mounting technique. The relationship is discussed quantitatively in terms of the two-membrane model of active Na+ transport, for which it provides further supportive evidence.

Amiloride↗

PubMedDate not supplied

An exploration of the effects of constraints on the phosphorylation of synthetic protein tyrosine kinase peptide substrates.

We synthesized by classical solution methods three conformational constrained analogues of EDNEYTA, a heptapeptide sequence that represents the common major autophosphorylation site of the protein tyrosine kinases (PTKs) of the Src family. The correlation between the different structural properties induced by the modifications of the native sequence and the propensity of the peptides to act as PTK substrates was examined. The kinetic data obtained indicate that the introduction of the tyrosine-analogue constraints Tic(OH) and MeTyr, which block the ring flexibility, completely prevents the phosphorylation catalysed by the kinases Lyn and Fgr. On the other hand PTKIIB/p38syk can phosphorylate the two derivatives albeit with an efficiency lower than that found with the native sequence. A third derivative contained side chain to side chain cyclization. This analogue, in which the freedom of the phenolic moiety is not altered, can be phosphorylated by all the PTKs tested with kinetic constants comparable to the parent peptide.

Circular Dichroism↗

PubMedDate not supplied

CK2: a protein kinase in need of control.

Protein kinase CK2 is a heterotetrameric alpha2beta2 Ser/Thr protein kinase with some features unusual among the eukaryotic protein kinases: (1) CK2 recognizes phosphoacceptor sites specified by several acidic determinants; (2) CK2 can use both ATP and GTP as phosphoryl donors; and (3) the regulatory properties of CK2 are poorly understood; it is insensitive to any known second messenger and displays high basal activity. To gain insight into CK2 regulation and to understand its unusual properties, site-directed mutagenesis experiments on both subunits and X-ray crystallographic studies of the catalytic alpha-subunit were performed. The noncatalytic beta-subunit has at least three functions: (1) it protects the alpha-subunit against denaturing agents or conditions; (2) it alters the substrate specificity of the alpha-subunit; and (3) it modulates the activity of the enzyme, i.e., depending on the substrate, it increases or decreases the activity of the alpha-subunit. Mutagenesis experiments revealed that an acidic stretch between amino acids 55 and 64 has a down-regulatory and autoinhibitory function. Mutational analysis of the alpha-subunit has revealed a network of unique basic residues that are responsible for the recognition of phosphoacceptor substrates and for down-regulation by the beta-subunit and by polyanionic inhibitors. The resolution of the crystal structure of Zea mays CK2 alpha-subunit has disclosed the structural features that are responsible for high basal activity and for unusual response to nucleotide analogs. The increasing knowledge of CK2 structure-function relationships will allow the design of highly selective inhibitors of this pleiotropic kinase with oncogenic potential.

Amino Acid Sequence↗

PubMedDate not supplied

[Tolosa-Hunt syndrome. TC findings in a case].

The Tolosa Hunt Syndrome is a rare neurological disease. It can be the consequence of a number of processes localized in the cavernous sinus or near to it. The diagnosis has been until now a diagnosis of exclusion, even if the phlebography can give more informations. Recently the possibility of demonstrating the process has been obtained by the high resolution CT scan that can show peculiar findings as in the case that we are describing.

Cavernous Sinus↗