Identification and quantification of mRNA for nerve growth factor in histological preparations

Comparative study of renin-containing cells. Histological approaches

The juxtaglomerular apparatus is known to be the functional unit of renin control. In the present review, the author will describe the comparative characteristics of renin-containing (RC) cells as well as extrarenal distribution, paying special attention to developmental and topographical approaches. The characteristic locality of RC cells suggests that the secretion of renin is performed at a site beside the adventitia or via the glomerular capillaries. Ontogenetical and phylogenetical investigations of RC cells have provided interesting findings on their morphogenesis. Analysis of the endocrine kidney after unilateral obstruction of the ureter provides some findings about the origin of RC cells and the processing of renin granules. Observation of developing adrenal renin suggests that there is important involvement of angiotensin II produced by renin synthesis in the morphogenesis of the adrenal gland in the fetal stage. Coagulating gland (CG) renin is characterized by testosterone-regulated and exocrine mechanisms. Recently, all or some of the components of the renin-angiotensin system (RAS) have been reported to be synthesized and secreted outside of classical organs or tissues. In the future, the real function of local RAS will be clarified by using gene targeting in mice.

The granular convoluted tubule (GCT) cell of rodent submandibular glands

The granular convoluted tubule (GCT) is a segment of the duct system of all rodents, situated between the striated and intercalated ducts. It has the peculiar property of synthesizing a large variety of biologically active polypeptides whose role in saliva remains unknown. The literature on the fine structure of GCT cells is critically reviewed. Some recent developments on endocrine regulation of the structure and contents of rodent GCT cells are summarized, with emphasis on EGF, NGF, renin, and kallikrein proteases. A survey of the distribution of GCT cells in several vertebrate families is presented.

The role of nerve growth factor in collateral reinnervation by cutaneous C-fibres in the rat

We have investigated whether chronic nerve growth factor (NGF) depletion affects the development of transmedian collateral reinnervation by C-fibres. Using a dye-labelled plasma extravasation technique in rats, the extent of transmedian innervation of the skin by C-fibres in the inferior alveolar nerve (IAN) was determined 8-10 weeks after sectioning and preventing regeneration of the contralateral IAN. Another group of animals were immunised against NGF prior to the nerve section and a third group acted as unoperated controls. A small but significant transmedian collateral reinnervation by C-fibres developed after contralateral denervation alone, but was not found in the animals also immunised against NGF. These results suggest that NGF is essential for the development of collateral reinnervation from cutaneous C-fibres.

A role for nerve growth factor in collateral reinnervation from sensory nerves in the guinea pig

We have investigated whether chronic nerve growth factor (NGF) depletion affects the development of a transmedian collateral reinnervation. The extent of transmedian innervation of the skin supplied by the left inferior alveolar nerve (IAN) was determined either immediately, 2 days or 7-9 weeks after sectioning and preventing regeneration of the contralateral IAN and in another group of animals left to recover for 7-9 weeks but also autoimmunised against NGF. Transmedian innervation was measured by recording the area from which a jaw-opening reflex could be evoked and by recording activity in the left IAN during mechanical and electrical stimulation of the skin. Nerve recording during electrical stimulation revealed extensive transmedian collateral reinnervation 7-9 weeks after denervation but this was prevented by NGF autoimmunisation. No change in transmedian innervation could be detected in any of the groups by nerve recording during mechanical stimulation and reflex responses revealed changes in the anaesthetic area which could not be attributed to collateral reinnervation. These results suggest that NGF plays an important role in collateral reinnervation from high-threshold sensory nerves.

Detection of nerve growth factor and its mRNA by separate and combined immunohistochemistry and in situ hybridization in mouse salivary glands

Intense labelling of secretory cells in the male mouse submandibular gland was observed after in situ hybridization using mouse nerve growth factor (NGF) cDNA probes. Under the same conditions, sparse less intensely labelled cells were also found in the sublingual gland. Hybridization to a chicken NGF cDNA probe gave weak labelling on the glands in accordance with a weak cross-hybridization between mouse NGF mRNA and chicken NGF cDNA probes, whereas no labelling was seen using pUC9 DNA as a hybridization probe. A combination of in situ hybridization and immunohistochemistry was also carried out on the same sections of submandibular gland. A good correlation was seen between actively synthesizing and intensely immunoreactive cells in the gland. The technique described here allows the detection of individual cells synthesizing relatively low levels of NGF. The combination of in situ hybridization and immunocytochemistry on the same section should be particularly useful in cases where NGF is transported away from its site of synthesis.

Co-localization of the nerve growth factor precursor protein and mRNA in the mouse submandibular gland

Indirect immunofluorescence on frozen sections of the mouse submandibular gland (MSG) and affinity-purified sera directed against synthetic peptides that reproduce sequences of the nerve growth factor (NGF) precursor protein permitted its localization in the basal parts of the cells forming the secretory tubules. In situ hybridization experiments employing 35S-labeled NGF cDNA probe localized the NGF mRNA in the same region. Conversion of proNGF to mature NGF results in an altered localization of the cleaved peptide throughout the cytoplasm of the tubular cells with a preferential concentration at their apical pole.

Immunohistochemical evidence for the distribution of nerve growth factor in the embryonic mouse

The distribution of nerve growth factor-like immunoreactivity has been examined in the embryonic mouse with special reference to the CNS. The intensity of the immunoreactive stain was found to be greatest on embryonic days 15 and 16. The antigen is widespread and present in high concentrations in both the PNS and CNS. Most intense staining was detected in cranial nerve tracts, hippocampus, developing white matter of the spinal cord and tegmentum. Lower intensities were found within diencephalic regions, spinal cord grey matter, medullary fibre tracts and cerebellum. These results support the increasing evidence suggesting that the trophic molecule nerve growth factor has an important role to play in the development of central as well as peripheral neurons.

Transport of endogenous nerve growth factor in the proximal stump of sectioned nerves

Immunohistochemistry has been used to demonstrate the presence of nerve growth factor (NGF)-like immunoreactivity in normal and sectioned mouse sciatic nerves. In normal nerves, immunoreactive material was not visible unless a silk ligature had previously been applied to constrict the nerves, and only then in the segment of nerve immediately distal to the ligation. Immunoreactivity was visible as early as 2 h after application of the ligature. When nerves were sectioned prior to ligation to prevent the transport of material from nerve terminals within innervated tissues, the NGF-like immunoreactivity continued to accumulate. This accumulation also occurred when a portion of the proximal stump from sectioned nerves was removed from the animal and placed in culture. Quantitative estimate of NGF concentrations with a sensitive immunoassay showed that the amount of NGF present within a segment of the proximal stump of sectioned nerves more than doubled in a 24 h period. The findings indicate that NGF is produced by cells within sectioned nerves, and further suggest that in the normal intact nerve at least a proportion of the NGF being transported derives from these cells.

Nerve growth factor immunohistochemistry and biological activity in the rat iris

Nerve growth factor (NGF) production in the cultured rat iris was examined using immunohistochemistry and bioassay of irides and conditioned media. NGF immunoreactivity increased steadily with days in culture so that the intensity of staining was maximal after 6 days of culture. The localization was shown to be sensitive to the presence of cross-linking fixatives such as formaldehyde and glutaraldehyde and this effect was only partially alleviated by the use of very high concentrations of antibodies. NGF immunoreactivity was localized in Schwann cells and possibly nerve axons, but with no antigen detectable in smooth muscle fibres. Media conditioned over irides initially supported a high percentage of dissociated sympathetic neurons, but the number supported decreased with time in culture until day 4. Moreover, the use of antibodies to NGF allowed the detection of at least two types of neuronotropic activity, NGF accounting for at least 94% of the total trophic activity present after 4 days of culture. These findings provide support for the proposal that Schwann cells produce NGF and question the accepted hypothesis that the molecule is produced by smooth muscle fibres as a peripheral maintenance factor for sympathetic and sensory nerves. The results also suggest that two survival factors may be involved in the regulation of sympathetic function.