Delayed changes of chromogranin A immunoreactivity (CgA ir) in human striate cortex during postnatal development

Postnatal development of the human primary motor cortex: a quantitative cytoarchitectonic analysis

The postnatal development of the human primary motor cortex (area 4) was analyzed in 54 individuals ranging in age from birth to 90 years. Three parameters defining major cytoarchitectonic features (areal fraction, numerical density and mean area of cells) were measured in vertical columns extending from the pial surface to the border between cortex and underlying white matter. The data were compiled in profile curves that reveal or more detailed laminar pattern than the classical cytoarchitectonic descriptions. The most pronounced decreases in numerical density and areal fraction of Nissl-stained cells profiles during early postnatal ontogeny are observed in layer II. A clearly delineable layer IV, which is still recognizable in the newborn, disappears gradually during the first postnatal months. Although the width of the cortex as a whole increases during this period, layer V, the main source of pyramidal tract fibers, is the only lamina that also increases in relative thickness. The other layers remain stable or become relatively thinner. These results reveal specific laminar growth processes in area 4, which take place in parallel with the functional maturation of the cortical motor system.

Ontogenic development and distribution of mRNAs of chromogranin A and B, secretogranin II, p65 and synaptin/synaptophysin in rat brain

We have studied by in situ hybridization the mRNA levels of several constituents of transmitter storing vesicles during ontogenic development of rat brain. The following vesicle components were investigated: chromogranin A and B and secretogranin II, representing secretory peptides of large dense core vesicles, and the membrane proteins p65 and synaptin/synaptophysin which are found in both large and small synaptic vesicles but are concentrated in the latter ones. Several ontogenic patterns were observed: concomitant increases of most or all mRNAs in certain brain regions, e.g. in the thalamic nuclei at gestational day 18 or in the cortex at postnatal day 6. For some areas selective increases for the various chromogranin mRNAs occurred, thus throughout development the substantia nigra compacta contained only the chromogranin B mRNA, whereas the lateral and medial geniculate nuclei and the medial tuberal nucleus expressed only secretogranin II mRNA. In the paraventricular hypothalamic nucleus, secretogranin II mRNA declined at P1 and then increased again. In the intermediate cortex there was a rather selective appearance of a high level of chromogranin A mRNA already at gestational day 16. In general the mRNAs for the membrane components become detectable by in situ hybridization together with the chromogranin mRNA, however, in the claustrum a high level of the p65 mRNA is present already at gestational day 16 whereas the chromogranin mRNA only appears at day 20. In some nuclei there was also a differential expression of the membrane components with e.g. the synaptophysin mRNA being present without any concomitant appearance of p65. These results establish that the ontogenic development of the investigated components in many brain areas simply indicate the starting point of biosynthesis of both types of vesicles finally leading to functional synapses. In those cases where a selective dissociation in the biosynthesis of these components occurs, a functional relevance of one component for a certain stage of development might be postulated. Since these data define the time of onset of vesicle biosynthesis in the various brain regions, future studies on single components of these vesicles can be interpreted in the context of the present findings.

Chromogranin A, a soluble synaptic vesicle protein, is found in cortical neurons other than previously defined peptidergic neurons in the human neocortex

Neuropeptides in the cerebral cortex have previously been identified in non-pyramidal neurons only. By comparing the location of chromogranin A (CgA), a soluble protein of large dense-core synaptic vesicles, with that of SMI-32, neuropeptide Y (NPY), parvalbumin (PV) and calbindin (CaBP) using double label immunohistochemistry, we demonstrate that CgA is present in pyramidal neurons as well as in several subtypes of non-pyramidal neurons.

Quantitative dot-blot assay for proteins using enhanced chemiluminescence

A sensitive non-radioactive method for detection of specific proteins on Western blots is commercially available. The protein is immobilized on nitrocellulose membrane and immunolabelled with HRP-conjugated secondary antibody. HRP catalyzes the oxidation of luminol, a cyclic diacylhydrazide, resulting in the emission of light which is recorded on film. Using dot blot, we have shown that the signal generated by this system is proportional to the amount of protein loaded onto the membrane. Standard curves were linear (r2 greater than 0.95) over a 10-50-fold range. Linearity was also achieved with tissue extracts probed for a specific antigen. The sensitivity of the method is such that less than 10 fmol protein can be measured. The sensitivity and range are comparable to a previously reported dot-blotting assay based on the use of 125I-protein A, but the method does not require the handling of radioactive compounds. This method was used to estimate the level of chromogranin A in a mixture of proteins extracted from human brain.