Selective quantitative analysis of the intensity of immunohistochemical reactions

Singing modulates parvalbumin interneurons throughout songbird forebrain vocal control circuitry

Across species, the performance of vocal signals can be modulated by the social environment. Zebra finches, for example, adjust their song performance when singing to females ('female-directed' or FD song) compared to when singing in isolation ('undirected' or UD song). These changes are salient, as females prefer the FD song over the UD song. Despite the importance of these performance changes, the neural mechanisms underlying this social modulation remain poorly understood. Previous work in finches has established that expression of the immediate early gene EGR1 is increased during singing and modulated by social context within the vocal control circuitry. Here, we examined whether particular neural subpopulations within those vocal control regions exhibit similar modulations of EGR1 expression. We compared EGR1 expression in neurons expressing parvalbumin (PV), a calcium buffer that modulates network plasticity and homeostasis, among males that performed FD song, males that produced UD song, or males that did not sing. We found that, overall, singing but not social context significantly affected EGR1 expression in PV neurons throughout the vocal control nuclei. We observed differences in EGR1 expression between two classes of PV interneurons in the basal ganglia nucleus Area X. Additionally, we found that singing altered the amount of PV expression in neurons in HVC and Area X and that distinct PV interneuron types in Area X exhibited different patterns of modulation by singing. These data indicate that throughout the vocal control circuitry the singing-related regulation of EGR1 expression in PV neurons may be less influenced by social context than in other neuron types and raise the possibility of cell-type specific differences in plasticity and calcium buffering.

[(18)F]flutemetamol amyloid positron emission tomography in preclinical and symptomatic Alzheimer's disease: specific detection of advanced phases of amyloid-β pathology

BACKGROUND

Amyloid positron emission tomography (PET) has become an important tool to identify amyloid-β (Aβ) pathology in Alzheimer's disease (AD) patients. Here, we determined the diagnostic value of the amyloid PET tracer [(18)F]flutemetamol in relation to Aβ pathology at autopsy.

METHODS

[(18)F]flutemetamol PET was carried out in a cohort of 68 patients included in a [(18)F]flutemetamol amyloid PET imaging end-of-life study (GE067-007). At autopsy, AD pathology was determined and Aβ plaque pathology was classified into phases of its regional distribution (0-5).

RESULTS

[(18)F]flutemetamol PET was universally positive in cases with advanced stage postmortem Aβ pathology (Aβ phases 4 and 5). Negative amyloid PET was universally observed in nondemented or non-AD dementia cases with initial Aβ phases 1 and 2, whereas 33.3% of the phase 3 cases were positive.

CONCLUSIONS

[(18)F]flutemetamol amyloid PET detects primarily advanced stages of Aβ pathology in preclinical and symptomatic AD cases.

Computer-assisted quantitative analysis of immunofluorescence staining of the extracellular matrix in rat dorsal and ventral spinal roots

The endoneurial extracellular matrix (ECM) is produced by Schwann cells and fibroblasts under the control of axons. Dorsal and ventral spinal roots contain different types of axons, but information is not available on differences in the composition of their ECM. A comparison was made of the intensity of immunofluorescence staining of chondroitin sulfate proteoglycan, fibronectin, tenascin and thrombospondin in the endoneurial ECM of rat dorsal and ventral spinal roots. Sections of dorsal and ventral roots were incubated simultaneously for indirect immunofluorescence detection of the epitopes studied. Brightness of immunofluorescence staining was assessed by computer-assisted image analysis using interactive segmentation of digitized images to select areas to be analyzed. Our results revealed quantitative differences in the composition of endoneurial ECM of spinal dorsal and ventral roots, probably due to the presence of different types of axons. The ECM composition of the endoneurium in dorsal and ventral roots may be related with the creation of extrinsic conditions that support differential regeneration of afferent and motor axons after injury.

Changes in myocardial cytoskeletal intermediate filaments and myocyte contractile dysfunction in dilated cardiomyopathy: an in vivo study in humans

AIM

To investigate in vivo the intermediate cytoskeletal filaments desmin and vimentin in myocardial tissues from patients with dilated cardiomyopathy, and to determine whether alterations in these proteins are associated with impaired contractility.

METHODS

Endomyocardial biopsies were performed in 12 patients with dilated cardiomyopathy and in 12 controls (six women with breast cancer before anthracycline chemotherapy and six male donors for heart transplantation). Biopsy specimens were analysed by light microscopy and immunochemistry (desmin, vimentin). Myocyte contractile protein function was evaluated by the actin-myosin in vitro motility assay. Left ventricular ejection fraction was assessed by echocardiography and radionuclide ventriculography.

RESULTS

Patients with dilated cardiomyopathy had a greater cardiomyocyte diameter than controls (p < 0.01). The increase in cell size was associated with a reduction in contractile function, as assessed by actin-myosin motility (r = -0.643; p < 0.01). Quantitative immunochemistry showed increased desmin and vimentin contents (p < 0.01), and the desmin distribution was disturbed in cardiomyopathy. There was a linear relation between desmin distribution and actin-myosin sliding in vitro (r = 0.853; p < 0.01) and an inverse correlation between desmin content and ejection fraction (r = -0.773; p < 0.02). Negative correlations were also found between myocardial vimentin content and the actin-myosin sliding rate (r = -0.74; p < 0.02) and left ventricular ejection fraction (r = -0.68; p < 0.01).

CONCLUSIONS

Compared with normal individuals, the myocardial tissue of patients with dilated cardiomyopathy shows alterations of cytoskeletal intermediate filament distribution and content associated with reduced myocyte contraction.

Increased activity in the form of endurance training increases calcitonin gene-related peptide content in lumbar motoneuron cell bodies and in sciatic nerve in the rat

The relative content of calcitonin gene-related peptide in lumbar motoneuron cell bodies (semiquantitative immunohistochemistry) and sciatic nerve was examined in rats who had previously undergone a 16-week period of endurance training on a motor-driven treadmill. Soleus motoneurons were identified in the spinal cord by their fluorescence following injection of FluoroGold into the muscle one week before killing. In sedentary rats, calcitonin gene-related peptide was detectable in 76-90% of motoneurons, with no difference in the proportions of negative cells, or in the mean staining intensity of positive cells, between soleus and neighbouring (presumptive fast hindlimb muscle) unlabelled moto-neurons. In endurance-trained rats, the estimated content of calcitonin gene-related peptide was significantly increased (90%) in cell bodies of soleus and neighbouring motoneurons, with no training-induced alterations in the proportions of calcitonin gene-related peptide-positive cells in either sample. The content of the neuropeptide was also significantly higher (37%) in sciatic nerve of endurance-trained rats. Relative accumulation of calcitonin gene-related peptide proximal to a sciatic nerve ligature applied 4 h before, however, was unchanged. The increases in calcitonin gene-related peptide in motoneuron cell bodies and sciatic nerve axons following endurance training may indicate an up-regulation of the synthesis, transport and terminal release of this neuropeptide, which could play a significant role in other morphological and functional adaptations which are known to occur at the neuromuscular junction following this chronic change in activity level.

A semiquantitative image-analytical method for the recording of dose-response curves in immunocytochemical preparations

Knowledge about intracellular signal transduction cascades is largely based on investigations of cultured cells whose responses to different stimuli are typically quantified via RIA, ELISA, or immunoblots. These techniques, which require relatively large amounts of biological material, are performed with homogenized cells and therefore do not allow localization of the molecules under investigation. We describe a protocol for recording dose-response curves directly from immunocytochemical preparations using rat pinealocytes as a model system. The cells were exposed to beta-adrenergic stimuli inducing the phosphorylation of the transcription factor CREB (mediated by PKA), an increase in ICER protein levels, and synthesis and release of melatonin. Melatonin concentrations were determined by ELISA. cPKA, phosphorylated CREB, and ICER were demonstrated by immunocytochemistry and immunoblots. Dose-response curves were recorded by measuring the integrated density of the immunoreactive sites with an image analysis program. Dose-response curves from immunoblots and immunocytochemical preparations showed almost identical dynamics, validating the immunocytochemical approach, which minimizes the amount of biological material needed for such studies, allows combined quantification and localization of biomolecules, and may even be more sensitive than immunoblotting.

Non-invasive image acquisition and advanced processing in optical bioimaging

Light is a most versatile tool for investigating biological systems and phenomena; the range, non-destructiveness, spatial discrimination and speed of optical imaging are all important for investigating structure and function at the cellular, tissue or even whole organism level. In live biological imaging, where the technological requirements are heightened, other features of light, such as coherence and wavelength, are used to generate the additional contrast and resolution needed. We report here recent improvements in our ability to image biological specimens optically, focusing on (a) spectral resolution and the related image processing issues, and (b) tomographic three-dimensional fluorescence imaging in vivo.

Quantitative measurement of protein kinase C immunoreactivity in rod bipolar cells of the goldfish retina

The intensity of the immunohistochemical reaction (IIR) against the alpha species of protein kinase C (PKC) was quantified in the rod bipolar cells (RBC) of the goldfish retina using of image analysis. Retinae incubated in control Ringer solution showed similar IIR in both the soma and the axon terminal (IIR-ratio approximately 1). Activation of PKC induces the 'transport' of the enzyme to the synaptic terminal of RBC and an increase in the IIR-ratio. In the present report, the effect of retinal neurotransmitters on the IIR-ratio and the time course of PKC transport was studied.