High-level expression of EphA2 receptor tyrosine kinase in prostatic intraepithelial neoplasia

EphA2 is a transmembrane receptor tyrosine kinase that is overexpressed in many carcinomas. Specific targeting of EphA2 with monoclonal antibodies is sufficient to inhibit the growth, migration and invasiveness of aggressive cancers in animal models. Using immunohistochemical analyses, we measured the expression of EphA2 in prostatic adenocarcinoma, high-grade prostatic intraepithelial neoplasia, and adjacent benign prostate tissue from ninety-three radical prostatectomy specimens. These results were related to multiple clinical and pathologicalcharacteristics. The fraction of cells staining positively with EphA2 in benign prostatic epithelium (mean, 12%) was significantly lower than that in high-grade prostatic intraepithelial neoplasia (mean, 67%, P < 0.001) and prostatic adenocarcinoma (mean, 85%, P < 0.001). Moreover, the intensity of EphA2 immunoreactivity in prostatic adenocarcinoma was significantly higher than in benign prostatic tissue (P < 0.001) or high-grade prostatic intraepithelial neoplasia (P < 0.001). Benign prostatic epithelium showed weak or no immunoreactivity for EphA2 in all cases examined. Whereas EphA2 immunoreactivity related to neoplastic transformation, it did not correlate with other clinical and pathological parameters examined. Our data suggest that EphA2 levels increase as prostatic epithelial cells progress toward a more aggressive phenotype. Progressively higher levels of EphA2 in high-grade prostatic intraepithelial neoplasia and prostatic carcinoma are consistent with recent evidence that EphA2 functions as a powerful oncogene. Moreover, the presence of high levels of EphA2 in these cells suggests opportunities for prostate cancer prevention and treatment.     

Methodologic problems in establishing normal values for IgG subclass concentrations in a pediatric population; comparison of radial immunodiffusion and ELISA methods

The aim of this study was to establish an enzyme-linked immunosorbent assay (ELISA) to measure IgG subclasses by means of monoclonal antibodies. The distribution of IgG subclass protein concentrations in sera from 227 healthy Danish children and 90 adults was measured. Furthermore, this newly established ELISA was compared with different assay systems for determination of IgG subclasses: two radial immunodiffusion methods (RID), one using polyclonal and one using monoclonal antibodies, as well as a commercially available ELISA kit. There was good agreement of results obtained by the different methods of measuring IgG3 and IgG4 concentrations. There was good correlation between results obtained by both RID methods. Despite good correlation between the assays, the ELISA kit showed higher levels of IgG1 in all investigated sera, and the ELISA kit showed no correlation with the other methods, when IgG2 was measured. Analysis of the normal ranges measured by ELISA developed in our laboratory and by RID with polyclonal antibodies showed that the levels obtained by RID were higher than those obtained by our ELISA in sera with low levels of both IgG1 and IgG2, and lower in sera with high concentrations of these two immunoglobulins. Our results emphasize the importance of establishing age-related normal limits for any novel assay measuring IgG subclass concentrations.     

The control of retinogeniculate transmission in the mammalian lateral geniculate nucleus

Summary In the mammalian visual system, the lateral geniculate nucleus is commonly thought to act merely as a relay for the transmission of visual information from the retina to the visual cortex, a relay without significant elaboration in receptive field properties or signal strength. However, many morphological and electrophysiological observations are at odds with this view. Only 10–20% of the synapses found on geniculate relay neurons are retinal in origin. Roughly half of all synapses derive from cells in layer VI of visual cortex; roughly one third are inhibitory and GABAergic, derived either from interneurons or from cells of the nearby perigeniculate nucleus. Most of the remaining synapses probably derive from cholinergic, noradrenergic, and serotonergic sites within the brainstem reticular formation. Moreover, recent biophysical studies have revealed several ionic currents present in virtually all thalamic neurons. One is a Ca²⁺-dependent K⁺ current underlying the afterhyperpolarization (or the I_AHP), which may last up to 100–200 ms following an action potential. Activation of the I_AHP leads to spike frequency adaptation in response to a sustained, suprathreshold input. Intracellular recordings from other neuronal preparations have shown that the I_AHP can be blocked by noradrenalin or acetylcholine, leading to an increased cellular excitability. Another ionic current results from a voltage- and time-dependent Ca²⁺ conductance that produces a low threshold spike. Activation of this conductance transforms a geniculate neuron from a state of faithful relay of information to one of bursting behavior that bears little relationship to the activity of its retinal afférents. We propose that state-dependent gating of geniculate relay cells, which may represent part of the neuronal substrate involved in certain forms of selective visual attention, can be effected through at least three different mechanisms: (1) conventional GABAergic inhibition, which is largely controlled via brainstem and cortical afferents through interneurons and perigeniculate cells; (2) the I_AHP, which is controlled via noradrenergic and cholinergic afferents from the brainstem reticular formation; and (3) the low threshold spike, which may be controlled by GABAergic inputs, cholinergic inputs, and/or the corticogeniculate input, although other possibilities also exist. Furthermore, it seems likely that gating functions involving the corticogeniculate pathway are suited to attentional processes within the visual domain (e.g., saccadic suppression), whereas brain-stem inputs seem more likely to have more global effects that switch attention between sensory systems. In any case, it is now abundantly clear that geniculate circuitry and the intrinsic electrophysiological properties of geniculate neurons are no longer compatible with the notion that the lateral geniculate nucleus serves as a simple relay.     

An autoradiographic study of chondrocyte transformation into chondroclasts and osteocytes during bone formation In vitro

Excised mouse pubic bone rudiments were exposed to H³-thymidine. Rudiments preserved immediately after exposure consisted of mesenchyme with a large number of cells showing intense radioactivity. Rudiments incubated on a filter membrane after exposure went through the developmental stages of complete chondrification of the pubic rami followed by periosteal and then endochondral bone formation. Only chondrocytes showed radioactivity in rami consisting of cartilage and periosteal bone that were preserved prior to endochondral ossification. Cell types showing radioactivity in rami preserved during endochondral ossification were chondrocytes, chondroclasts, and osteoblasts and osteocytes of endochondral bone. The results of the study demonstrated that hypertrophic chondrocytes of the calcified cartilage of a developing mammalian long bone not only survive dissolution of their matrix, but transform into chondroclasts and osteoprogenitor cells that give rise to osteoblasts and osteocytes which form endochondral bone in the absence of blood vessels.     

The Acoustic Startle Response in Inbred Roman High- and Low-Avoidance Rats

To investigate the emotional reactions of two rat strains selectively bred for good and poor two-way avoidance acquisition (RHA/Verh and RLA/Verh), male animals of both strains were tested in an acoustic startle response test. They received 40 acoustic stimuli followed by 10 electric foot shocks and another 30 acoustic stimuli. RLA/Verh rats showed a significantly higher startle response compared to RHA/Verh animals, indicating a stronger emotional reaction to acoustic stimuli. In addition, the former showed a stronger response to foot shocks. Combined with earlier findings, we conclude that selection for two-way avoidance learning does not result in cognitive defects in the RLA/Verh strain but, rather, in stronger emotional reactions to fearful stimuli.