An epidemiology-based model to estimate the rate of inappropriateness of tumor marker requests.

BACKGROUND: Appropriateness of tumor markers (TMs) has been retrospectively studied in limited patients' series, matching the requests to clinical records. Methods to monitor appropriateness suitable for use on a large scale are required. This study aims to establish and validate an innovative model to estimate appropriateness based on the comparison between the number of TMs requested and the expected requests inferred from epidemiological data. METHODS: The number of CA15.3, CA19.9 and CA125 requests theoretically expected according to the epidemiology of malignancies in a known geographic area (2 Italian regions) was compared with the number of TMs actually requested - the surveyed requests projected on a regional scale - during a given time span (1 year). The expected number of requests was calculated comparing TMs recommended by guidelines in different clinical scenarios with the prevalence or incidence figures of the examined diseases (carcinomas of breast, pancreas and biliary tract, ovary and endometrium). RESULTS: Suitability of the model was demonstrated with the analysis of 1,891,070 TM requests surveyed in 66 laboratories from Veneto and Tuscany regions. The percentage difference over the total of expected TMs (delta%) ranged from -6.9% for CA15.3 to +1022.6% for CA19.9 in Veneto and from +35.7% for CA15.3 to +1842.6% for CA19.9 in Tuscany. CONCLUSIONS: The presented model was effective in demonstrating higher than expected TM request rates, possibly associated with inappropriate use. Moreover, it can be applied on a large scale survey setting since it circumvents the unavailability of clinical information on test orders.

Oligodendrocytes are a novel source of amyloid peptide generation.

Alzheimer's disease is characterised by regional neuronal degeneration, synaptic loss, and the progressive deposition of the 4 kDa ß-amyloid peptide (Aß) in senile plaques and accumulation of tau protein as neurofibrillary tangles. Aß derives from the larger precursor molecule, amyloid precursor protein (APP) by proteolytic processing via ß- and γ-secretases. While APP expression is well documented in neurons and astrocytes, the case for oligodendrocytes is less clear. The latter cell type is reported to express different isoforms of APP, and we have confirmed this observation by immunocytochemistry in cultures of differentiated rat cortical oligodendrocytes. Moreover, by means of a sensitive electrochemiluminescent immunoassay employing Aß C-terminal specific antibodies, mature oligodendrocytes are shown to secrete the 40 and 42 amino acid Aß species (Aß40 and Aß42). Secretion of Aß peptides was reduced by incubating oligodendrocytes with α- and ß-secretase inhibitors, or a γ-secretase inhibitor. Disturbances of APP processing and/ or synthesis in oligodendrocytes may account for some myelin disorders observed in Alzheimer's disease and other senile dementias.

Identification of neuroprotective properties of anti-MAG antibody: a novel approach for the treatment of stroke?

The inhibitory activity of myelin-associated glycoprotein (MAG) on neurons is thought to contribute to the lack of regenerative capacity of the CNS after injury. The interaction of MAG and its neuronal receptors mediates bidirectional signaling between neurons and oligodendrocytes. The novel finding that an anti-MAG monoclonal antibody not only possesses the ability to neutralise the inhibitory effect of MAG on neurons but also directly protects oligodendrocytes from glutamate-mediated oxidative stress-induced cell death is reported here. Furthermore, administration of anti-MAG antibody (centrally and systemically) starting 1 hour after middle cerebral artery occlusion in the rat significantly reduced lesion volume at 7 days. This neuroprotection was associated with a robust improvement in motor function compared with animals receiving control IgG1. Together, these data highlight the potential for the use of anti-MAG antibodies as therapeutic agents for the treatment of stroke.

Dopamine D2 and D3 receptor agonists limit oligodendrocyte injury caused by glutamate oxidative stress and oxygen/glucose deprivation.

Dopamine receptor activation is thought to contribute adversely to several neuropathological disorders, including Parkinson's disease and schizophrenia. In addition, dopamine may have a neuroprotective role: dopamine receptor agonists are reported to protect nerve cells by virtue of their antioxidant properties as well as by receptor-mediated mechanisms. White matter injury can also be a significant factor in neurological disorders. Using real-time RT-PCR, we show that differentiated rat cortical oligodendrocytes express dopamine D2 receptor and D3 receptor mRNA. Oligodendrocytes were vulnerable to oxidative glutamate toxicity and to oxygen/glucose deprivation injury. Agonists for dopamine D2 and D3 receptors provided significant protection of oligodendrocytes against these two forms of injury, and the protective effect was diminished by D2 and D3 antagonists. Levels of oligodendrocyte D2 receptor and D3 receptor protein, as measured by Western blotting, appeared to increase following combined oxygen and glucose deprivation. Our results suggest that dopamine D2 and D3 receptor activation may play an important role in oligodendrocyte protection against oxidative glutamate toxicity and oxygen-glucose deprivation injury.

Excitatory amino acid induced oligodendrocyte cell death in vitro: receptor-dependent and -independent mechanisms.

Oligodendroglia play an important role in axonal conduction in the CNS and are sensitive to oxidative toxicity induced by glutamate in the absence of ionotropic glutamate receptors. In this study, oligodendrocyte signalling cascades were examined, in response to glutamate-induced oxidative injury and to excitotoxicity. Rat cortical oligodendrocytes, differentiated in culture, were highly vulnerable to glutamate-induced cell death. Competitive inhibition of cystine uptake and increased oxidative stress appeared responsible for this death, and caused an accumulation of intracellular peroxides as well as chromatin fragmentation and condensation. Glutamate receptor subtype agonists (quisqualate, ibotenate) known to inhibit cystine uptake were cytotoxic, but not NMDA itself; moreover, glutamate receptor antagonists were not protective. Oligodendrocytes were also vulnerable to overactivation of glutamate receptors, as kainic acid and AMPA proved to be toxic. AMPA toxicity required the presence of cyclothiazide, suggesting rapid desensitization of AMPA receptors. Glutamate-induced oxidative stress and kainate/AMPA receptor stimulation activated the mitogen-activated protein kinase (MAP kinase) pathway, as well as the transcription factor ELK. However, MAP kinase kinase inhibitors only protected against injury from glutamate-induced oxidative stress. Oligodendrocytes were sensitive to oxygen-glucose deprivation injury as well, in a MAP kinase dependent fashion. Glutamate toxicity may conceivably be operative in neuropathological conditions that disrupt neuronal/oligodendrocyte interactions in axons, e.g. multiple sclerosis and ischaemia-reperfusion injury.