Levels of the beta-subunit of nerve growth factor (beta-NGF) were measured in the central nervous and peripheral tissues of mice using a highly sensitive, sandwich-type enzyme immunoassay system. Antiserum was raised in rabbits against the 7S form of NGF, which was purified from mouse submandibular glands. beta-NGF-specific antibody isolated on a column of Sepharose CL-4B coupled with purified beta-NGF reacted only with beta-NGF. The assay for beta-NGF was performed by incubation of F(ab')2 fragments of the antibody immobilized on a polystyrene ball with tissue extract and then with the same antibody Fab' fragments labeled with beta-D-galactosidase, followed by measurement of galactosidase activity. Our assay system was found to be highly sensitive (minimal detection limit, 0.3 pg/0.3 ml of assay mixture). Furthermore, the presence of gelatin hydrolysates and protease inhibitors during preparation of tissue extracts enabled us to determine the precise levels of beta-NGF in almost all organs of mice. The amount of beta-NGF in submandibular glands was extremely high, and its level increased rapidly until mice were 2 months of age; then, the level continued to increase slowly until mice were 1 year old (3-5 mg/g of tissue). In serum, some of the 2-month-old males, but none of the females, exhibited a fairly high level of beta-NGF (greater than 100 pg/ml).(ABSTRACT TRUNCATED AT 250 WORDS)
Abstract Structural changes in proteoglycans (PGs) were examined during the neuritogenesis of PC12 cells induced by nerve growth factor (NGF). (1) A heparan sulfate (HS) PG and a chondroitin sulfate (CS) PG were synthesized by PC 12 cells, irrespective of the presence of NGF or the duration of culture. PGs released from PC12 cells into the culture medium were mostly CSPGs. (2) In the absence of NGF, the apparent molecular mass of HSPG prepared from PC 12 cells after 3 days of culture was in the range of 90–190 kDa for the intact form ( K av = 0.38 on Sepharose CL‐6B), 12 kDa for HS, and 61 kDa for the core protein. In the presence of NGF, these values were 90–190 kDa, 10 kDa, and 51 kDa and 61 kDa, respectively. The intact forms of cell‐associated CSPG had apparent molecular mass ranges of 120–150 kDa and 120–190 kDa ( K av = 0.38 and 0.34), with CSs of 15 kDa and 20 kDa in the presence and absence of NGF, respectively. The apparent molecular mass of the core protein of cell‐associated CSPG was 92 kDa, irrespective of the presence of NGF. The molecular sizes of cell‐associated PGs and their glycosaminoglycans remained unchanged during culture. (3) CSPGs released by PC12 cells into the culture medium were separated into two peaks (I and II) by column chromatography on DEAE‐cellulose. The peak II fraction prepared from the medium with NGF after 3 days of culture consisted of CSPG with K av = 0.22 on Sephacryl S‐300 [40–84 kDa by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE)]. The CS and core protein of this CSPG had apparent molecular masses of 26 kDa and 15–17 kDa, respectively. The peak I fraction was separated further into three fractions of different molecular sizes on Sephadex G‐200 (I‐1,I‐2,I‐3). In the presence of NGF, peak I‐1 prepared after 3 days of culture consisted of mostly CSPG (130–170 kDa by SDS‐PAGE; K av = 0.13 on Sephacryl S‐300) with CS of 32 kDa and a core protein of 105 kDa. Peaks 1–2 and 1–3 contained, respectively, CSPGs of 38–74 kDa and 31–56 kDa for their intact forms, with CSs of 25 kDa and 15 kDa. The apparent molecular masses of the core proteins of their CSPGs were 15–17 kDa. These CSPGs had similar molecular sizes, irrespective of the presence of NGF or the duration of culture. (4) These results indicate that structural changes in PGs during the neuritogenesis in PC12 cells induced by NGF occurred mostly in cell‐associated PGs and preceded elongation of neurites.
Abstract The addition of chondroitin sulphate proteoglycans (CSPGs), purified from the rat brain, to the culture medium of PC12D cells inhibited their proliferation and neurite outgrowth. Therefore, we investigated the effects of several extracellular components on the inhibitory actions of CSPGs on PC12D cells, as well as their immunocytochemical distribution in the rat embryo to determine whether the findings in vitro could be reproduced in vivo. Coating of the substratum with polylysine was necessary for the appearance of the inhibitory effects of brain CSPGs on PC12D cells. The additional pretreatment of polylysine‐coated dishes with laminin or fibronectin promoted the outgrowth of neurites from PC12D cells. Laminin and fibronectin, but not collagen (types I and IV) and CELL‐TAK (cell adhesion molecules), prevented the inhibitory effects of brain CSPGs in a concentration‐dependent manner. Doses producing 50% reduction by laminin (or fibronectin) of the CSPG effects were 1.5 (or 25) μg/ml for neurite outgrowth and 2.2 (or 28) μg/ml for proliferation. The ratio of dish‐attached CSPGs to laminin necessary for 50% reduction was about ∼50:l (wt/wt). Laminin from any source had the same effect. Brain CSPGs also obviously impeded the growth of fibres from dorsal root ganglion explants and primary cultured dorsal root ganglion neurons. Neurocan (a major CSPG in the brain)‐like immunoreactivity was detected in the boundary caps and roof plate in the rat embryo at 13.5 days of gestation, when DRG neurons were extending their axons to the neural tube. The distributions of laminin and tenascin appeared, respectively, to be slightly and considerably different from that of neurocan. These results suggest that brain CSPGs can generate barriers to the growth of axons from the dorsal root ganglion and that the ratio of CSPGs to laminin may be important in regulating such growth.
Accumulating evidence suggests the possible association between the concentrations of serum brain-derived neurotrophic factor (BDNF) and psychiatric disease with impaired brain development. Yet the reasons remain unclear. We therefore investigated the characteristics of serum BDNF as well as its age-related changes in healthy controls in comparison to autism cases. BDNF was gradually released from platelets at 4 degrees C, reached a maximal concentration after around 24 h, and remained stable until 42 h. At room temperature, BDNF was found to be immediately degraded. Circadian changes, but not seasonal changes, were found in serum levels of BDNF existing as the mature form with a molecular mass of 14 kDa. In healthy controls, the serum BDNF concentration increased over the first several years, then slightly decreased after reaching the adult level. There were no sex differences between males and females. In the autism cases, mean levels were significantly lower in children 0-9 years old compared to teenagers or adults, or to age-matched healthy controls, indicating a delayed BDNF increase with development. In a separate study of adult rats, a circadian change in serum BDNF was found to be similar to that in the cortex, indicating a possible association with cortical functions.
