The plerocercoid stage of the tapeworm Spirometra mansonoides produces a functional analog of human growth hormone (hGH). Among the similarities between plerocercoid growth factor (PGF) and hGH is competition for the same receptors on rabbit liver membranes. To take advantage of this characteristic in a purification scheme for PGF, rabbit liver microsomes were solubilized in Triton X-100 and the hGH receptors were purified over an hGH affinity column. The purified receptors from six rabbit livers were coupled to Affi-Gel-10 to create a receptor affinity column which was used to purify PGF. Chromatography of crude PGF over the receptor column resulted in a 1044 fold increase in specific activity. SDS-PAGE in the presence of 2-mercaptoethanol showed that the affinity-purified PGF contained three protein bands with apparent Mrs of 27.5 K, 22 K, and 16.7 K. Injections of the partially-purified PGF into hypophysectomized rats produced a dose-dependent growth response and 400 ng eq of PGF each day for 10 days stimulated a growth response not significantly different from that produced by 250 micrograms of bovine GH each day. Receptor affinity chromatography was an effective method to purify small amounts of PGF in a single step with negligible loss of biological activity.
Infection with Spirometra mansonoides at 22 days of age was associated with delayed sexual maturation in the male rat. Balanopreputial separation occurred at 46.7 ± 0.8 days in controls and at 50.6 ± 0.9 days in worm-treated rats (p < 0.02). This was accompanied by a delay in the normal prepubertal testicular and seminal vesicle weight increases. LH remained normal but serum FSH was depressed as early as 25 days of age. The castration response in worm-treated rats was comparable to that of controls, when the FSH levels were normalized as percentages of resting level. The LH response to castration was diminished. The acute FSH and LH response to GnRH was normal and pituitary stores of gonadotrophin, as estimated by radioimmunoassayable concentrations of FSH and LH, were normal. It can be concluded that puberty onset in males is not linked to body weight gain per se, and that the absence of endogenous GH secretion affects both sexual maturation and gonadotrophin secretion in the prepubertal period.
Syrian golden hamsters can 'recover' from single diabetogenic doses of alloxan and return to normoglycemia. Induction of chronic diabetes was accomplished by multiple injections of streptozotocin.
Plerocercoid larvae of the tapeworm Spirometra mansonoides produce a factor with activities similar to those of growth hormone (GH). Highly selective receptors for GH have been described on cultured human lymphocytes (IM-9 cells) and these cells have been used as a model of binding essentially restricted to human GH (hGH). We compared the displacement of [125I]hGH by hGH and partially purified plerocercoid growth factor (PGF) in assays using rabbit hepatic membranes and IM-9 cells. PGF displaced [125I]hGH from both rabbit hepatic membranes and IM-9 cells in a dose-dependent manner (r greater than 0.98). These results show that PGF specifically binds to hGH receptors on human IM-9 cells and suggest the possibility that PGF will have somatotropic activity in humans.
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