Publications

BACKGROUND

Dorsal root ganglia (DRG)-neurons are commonly characterized immunocytochemically. Cells are mostly grouped by the experimenter's eye as "marker-positive" and "marker-negative" according to their immunofluorescence intensity. Classification criteria remain largely undefined. Overcoming this shortfall, we established a quantitative automated microscopy (QuAM) for a defined and multiparametric analysis of adherent heterogeneous primary neurons on a single cell base.The growth factors NGF, GDNF and EGF activate the MAP-kinase Erk1/2 via receptor tyrosine kinase signalling. NGF and GDNF are established factors in regeneration and sensitization of nociceptive neurons. If also the tissue regenerating growth factor, EGF, influences nociceptors is so far unknown. We asked, if EGF can act on nociceptors, and if QuAM can elucidate differences between NGF, GDNF and EGF induced Erk1/2 activation kinetics. Finally, we evaluated, if the investigation of one signalling component allows prediction of the behavioral response to a reagent not tested on nociceptors such as EGF.

RESULTS

We established a software-based neuron identification, described quantitatively DRG-neuron heterogeneity and correlated measured sample sizes and corresponding assay sensitivity. Analysing more than 70,000 individual neurons we defined neuronal subgroups based on differential Erk1/2 activation status in sensory neurons. Baseline activity levels varied strongly already in untreated neurons. NGF and GDNF subgroup responsiveness correlated with their subgroup specificity on IB4(+)- and IB4(-)-neurons, respectively. We confirmed expression of EGF-receptors in all sensory neurons. EGF treatment induced STAT3 translocation into the nucleus. Nevertheless, we could not detect any EGF induced Erk1/2 phosphorylation. Accordingly, intradermal injection of EGF resulted in a fundamentally different outcome than NGF/GDNF. EGF did not induce mechanical hyperalgesia, but blocked PGE2-induced sensitization.

CONCLUSIONS

QuAM is a suitable if not necessary tool to analyze activation of endogenous signalling in heterogeneous cultures. NGF, GDNF and EGF stimulation of DRG-neurons shows differential Erk1/2 activation responses and a corresponding differential behavioral phenotype. Thus, in addition to expression-markers also signalling-activity can be taken for functional subgroup differentiation and as predictor of behavioral outcome. The anti-nociceptive function of EGF is an intriguing result in the context of tissue damage but also for understanding pain resulting from EGF-receptor block during cancer therapy.

OBJECTIVE

The heptavalent pneumococcal conjugate vaccine contributed to a substantial decrease in the number of ambulatory visits attributable to acute otitis media (AOM) and amoxicillin use for AOM increased after publication of American Academy of Pediatrics guidelines regarding AOM. Our objective was to determine whether similar trends occurred for children with acute sinusitis.

METHODS

We analyzed data from the National Ambulatory Medical Care Survey and National Hospital Ambulatory Medical Care Survey (1998-2007), which are nationally representative surveys of office and emergency department visits. For children younger than 18 years with diagnosed acute sinusitis (N = 538), we examined time trends in visit rates and antibiotic prescribing. Multivariate logistic regression analyses were used to identify factors associated with narrow-spectrum antibiotic prescribing.

RESULTS

Between 1998 and 2007, the annual visit rate for acute sinusitis remained stable, ranging from 11 to 14 visits per 1000 children (P = .67). No change occurred in the proportion of visits with receipt of an antibiotic (82%; P = .71); however, the proportion with receipt of amoxicillin increased from 19% to 58% during the study period (P < .01). Prescriptions for broader-spectrum agents, especially macrolides (18% overall), remained common.

CONCLUSIONS

Unlike the visit rate for AOM, the visit rate for acute sinusitis among children did not decrease after introduction of the pneumococcal conjugate vaccine. Although prescriptions for amoxicillin increased in accordance with the guidelines, reducing unnecessary prescriptions for macrolides remains an important target for campaigns promoting judicious antibiotic use.