Members of the proline-rich protein (PRP) family of mouse parotid glands were analysed before and after stimulation with the beta-agonist isoprenaline by using a monoclonal antibody raised against the induced PRP A3(0) (GP-27). Antibody NAL1 reacted strongly with isoprenaline-induced B-type PRP precursors and their salivary counterparts, but not against the A-type PRPs A1(0) (Gp-66) and A2(0) (GP-45) or human salivary proteins, and it is likely that NAL1 recognizes a proline-rich repeat variant unique to this group of rodent PRPs. PRP-related antigens were observed in the parotid glands (N1(0) and N2(0] and saliva of normal mice. The antigens were located immunocytochemically in secretory granules of parotid acinar cells of both normal and isoprenaline-stimulated mice. The total amount of PRP antigens increased 16-fold from 2.5 to 40% of parotid protein after 10 days of isoprenaline treatment, as estimated by enzyme-linked immunosorbent assay. Immunoblotting showed that new PRP species appeared during the period of increase. After treatment with isoprenaline, B-type PRPs appeared first, followed by A3(0) and another member of the family. These results show that the mouse PRP family is larger than previously thought and can be divided immunologically into sub-groups. That a subset of PRPs are produced in the normal mouse indicates that there is differential beta-adrenergic regulation within the family, and also has implications for the role of PRPs in the normal maintenance of healthy dentition and other processes.

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Spinal cord regeneration following treatment with a novel membrane-spanning peptide (MSP) expressing the isoleucine-lysine-valine-alanine-valine (IKVAV) epitope was assessed in Balb-c mice. After hemilaminectomy and compression injury, mice were treated with IKVAV, IKVAV-MSP, peptide or vehicle control. Functional improvement was assessed using modified Basso, Beattie, and Bresnahan Scale (mBBB) and spinal cord segments were studied histologically 28 days after injury. IKVAV-MSP group scores increased significantly compared with control groups after 4 weeks of observation (p < 0.05). The number of protoplasmic astrocytes, neurons and muscle bundle size in the IKVAV-MSP mice were significantly increased (p < 0.001; p < 0.05 and p < 0.007; respectively). This study demonstrates that it is possible to promote functional recovery after SCI using bioactive IKVAV presenting cell membrane-spanning peptides.

Rabbit polyclonal antibodies against isoproterenol-induced mouse proline-rich proteins (PRPs) were used to localize PRPs in the parotid salivary glands of normal adult BALB/c mice. The antibodies recognized both acidic-type and basic-type PRPs. Immunoblotting experiments revealed that the glands contained an acidic-type and a basic-type PRP. Parotid gland tissue was fixed with Karnosky's fixative and embedded in Lowicryl resin at low temperature. PRPs were localized at the electron microscope level using an indirect post-embedding staining technique with protein A-gold. The secretion granules of the acinar cells were strongly labelled. Pre-absorption of the antibody with purified acidic-type and basic-type PRPs indicated that the basic-type PRP is mainly located at the periphery of the granules but that the acidic-type PRP is more evenly distributed within the granules. Pre-absorption of the antibody with alpha-amylase did not affect the staining pattern, suggesting minimal cross-reactivity. PRPs were also detected within the rough endoplasmic reticulum and the Golgi apparatus of acinar cells, within the granules of the proacinar cells and in the lumena of the ducts, but not within the intercalated or striated duct cell granules.

A cell membrane spanning peptide was used to increase the concentration of the IKVAV motif within damaged mouse spinal cord tissue. This peptide was injected directly to the lesion 24 hours after spinal cord compression injury. Because the membrane-spanning portion of the peptide adheres to tissue upon injection with a long half-life we hypothesized that the bioactive IKVAV sequence will provide a sustained regenerative signal at the sight of injury. Five different groups of mice were used and cellular morphology observations were undertaken using light and electron microscopy. Three surgical control groups: IKVAV, peptide and mannitol; one surgical treatment group: IKVAV-peptide; and one non-surgical control group: normal, were used in this experiment. In this study, treatment with IKVAV-peptide after SCI resulted in an increased number of protoplasmic astrocytes, large active motor neurons, and regeneration of muscle bundles followed by behavioral improvement. In this paper, we describe the cellular differences between all groups.