Biomedical subjects

R De Armas

Publications and source records attributed to R De Armas.

3 recordsLinked to original sources

PubMed2006

Platelet-activating factor and human meningiomas.

Meningiomas are common primary intracranial tumours. Platelet-activating factor (PAF) is an inflammatory and angiogenic lipid mediator involved in several types of cancer. The presence of PAF receptor (PAF-R) transcripts, the levels of PAF, the phospholipase A2 activity (PLA2, the enzymatic activity implicated in PAF formation) and the PAF acetylhydrolase activity (AHA, the PAF degrading enzyme) were investigated in 49 human meningiomas. PAF-R transcripts, PAF, PLA2 and AHA were detected in meningiomas. However, their levels did not correlate with biological parameters such as the tumour grade, the presence of associated oedema, necrosis, mitotic index as well as intensity of the neovascularization and chronic inflammatory response. In conclusion, PAF is present in meningiomas where it might act on tumour growth by altering the local angiogenic and/or cytokine networks as previously suggested for human breast and colorectal cancer.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed2004

Demyelinating peripheral neuropathy associated with hemophagocytic lymphohistiocytosis. An immuno-electron microscopic study.

We report the case of an 11-year-old male who developed subacute diffuse polyradiculoneuropathy, associated with digestive symptoms and Epstein-Barr virus infection. Parental consanguinity was present. The laboratory findings including bone marrow smear were consistent with hemophagocytic lymphohistiocytosis (HLH). Electrophysiological study of peripheral nerves revealed an intense and diffuse demyelinating process. The histological nerve lesions were severe and purely demyelinating. Most axons were intact. There was a diffuse infiltration of the nerve parenchyma by mononuclear cells. Immuno-electron microscopic study evidenced entry of macrophages into Schwann cell cytoplasm with dissociation of myelin sheaths. This boy died several months after the onset of the neuropathic symptoms. HLH is a rare genetic or acquired disorder in childhood characterized by abnormal immune activation, which induces an uncontrolled inflammatory response with sustained hyperactivation of T lymphocytes and macrophages. Only very rare cases of peripheral nerve involvement have been described in HLH. This is the first case showing that peripheral nerves, as other viscera, may be destroyed by the macrophagic infiltration, which characterizes HLH.

Child↗

PubMed1998

Effects of 2,3-butanedione monoxime on excitation-contraction coupling in frog twitch fibres.

10 and 30 mM 2,3-butanedione monoxime (BDM) applied extracellularly to voltage-clamped frog skeletal muscle twitch fibres suppressed both Ca2+ release flux and intramembranous charge movement. Both effects could be clearly separated. The early peak of the Ca2+ release flux was suppressed at every test voltage. The steady level attained at the end of a 100 ms clamp depolarization was relatively spared for lower depolarizing pulses, but was as suppressed as the peak at voltages above -20 mV. The intramembranous charge movement was affected mainly in the I gamma component. The drug had a distinct effect on the kinetics of the intramembranous charge movement current around the threshold for Ca2+ release. The three kinetic components of I gamma were simultaneously affected. For more positive depolarizations where the kinetic effect was not evident, the oxime had no significant effect on the charge moved. Under conditions in which I gamma was absent (i.e. stretched fibres, intracellular solutions containing 6 to 10 mM BAPTA), treatment with 10 mM BDM had a small, not significant suppressive effect on the maximum charge moved (Qmax), while it affected Ca2+ release significantly. When 10 mM BDM was applied in the presence of 0.2 mM tetracaine, the local anaesthetic-resistant Ca2+ release flux was not further suppressed by the oxime.

Anesthetics, Local↗