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In adult mammals, brain catecholamines participate in the central control of gonadotrophin release (for review, see Coppola, 1971). The rôle of brain amines in the process of puberty is less well understood. In the female rat, the first external sign of puberty, vaginal opening (VO), is closely associated with first ovulation and onset of vaginal cyclicity. This indicates that the cyclic release mechanism must become functional at or before that time. The drug 6-hydroxydopamine (6-OHDA) selectively impairs or destroys central catecholaminergic neurones after its injection into a brain ventricle (Malmfors & Thoenen, 1971), interferes with ovulation (Ruf, 1971), and prevents the compensatory release of gonadotrophins initiated by hemigonadectomy (Zolovick, 1972). In this study, we investigated the effect of 6-OHDA on VO in the pubescent rat to see whether the maturation of adrenergic inputs to hypothalamic peptidergic neurones may be a component of the pubertal process.
About 250 female Sprague-Dawley rats,
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ABSTRACT
Thyroid peroxidase (TPO) is a glycoprotein enzyme which catalyses the iodination of thyroglobulin and the coupling of iodinated tyrosines. Human TPO (hTPO) is the microsomal antigen recognized by the autoantibodies in the serum of patients with autoimmune thyroid disease.
An active detergent-solubilized immunoaffinitypurified hTPO was deglycosylated, either by peptide N-glycosidase F (PNGase F) or by endo-β-N-acetylglucosaminidase H (endo H), and the enzymatic activity and immunoreactivity of the native and degylcosylated forms were compared. Electrophoretic controls and affinoblotting with concanavalin A showed that deglycosylation was not total and that it was more pronounced with endo H than with PNGase F. The enzymatic activity of hTPO was inhibited by endo H deglycosylation, but not by PNGase F deglycosylation; this inhibition was not due to aggregation and/or insolubilization of the molecule subsequent to deglycosylation. Immunoreactivity was monitored by enzyme-linked immunosorbant assay (ELISA) with 13 mouse monoclonal antibodies, rabbit polyclonal antibodies and antibodies from serum of patients with Hashimoto's thyroiditis. In contrast with enzymatic activity, immunoreactivity was not modified or was slightly enhanced (with four monoclonal antibodies) by deglycosylation.
The results indicate that strong, if not total, deglycosylation induces a modification of the tertiary structure of hTPO, which affects the enzymatic site but does not modify markedly the epitopes implicated in the recognition of the molecule by the antibodies tested.
Journal of Endocrinology (1992) 132, 317-323