Almost 10 years ago, a study was published which examined the amino acid pairs represented by particular triplet codons and their complementary sequences (anti-sense codons) (Biro, 1981). These complementary amino acid pairs displayed 'hydropathic anti-complementarity' in that hydrophobic residues almost always were partnered with hydrophilic amino acids, whereas amphiphilic residues tended to be paired with other amphiphilic amino acids (Blalock & Smith, 1984). These reports remained no more than interesting observations on the nature of the genetic code until the remarkable finding that the peptides adrenocorticotrophin(1–24) (ACTH(1–24)) and γ-endorphin (a 17-mer) bound specifically and with a relatively high degree of affinity (∼10⁻⁶ mol/l) to their respective complementary peptides (CP)—molecules synthezised using a template RNA complementary to the original mRNA for the peptides, translation being in a 5′→3′ direction and in the same reading frame (Bost, Smith & Blalock, 1985a). In the intervening years, evidence for the binding

The past few years have seen a dramatic increase in knowledge in relation to the molecular structures of both growth hormone(s) (GH) and their polypeptide receptors (GHR). In addition to older data providing the sequences of numerous mammalian and nonmammalian GHs, cDNAs for mouse (Smith et al. 1989), rat (Mathews et al. 1989), rabbit, human (Leung et al. 1987), ovine (Adams et al. 1990), bovine (Hauser et al. 1990) and porcine (Cioffi et al. 1990) GHRs have recently been cloned and sequenced. Further to this, a high resolution X-ray crystal structure for porcine GH has been published (AbdelMeguid et al. 1987), and very recently the cocrystallization of human (h) GH with the extracellular domain of the GHR has been achieved (De Vos et al. 1992). These studies have revealed GHs to be 4α helix bundle proteins with one molecule of GH binding in an asymmetric fashion to two molecules of

SUMMARY

1. Para-amino-salicylic acid (PAS sodium salt) given to rats under the experimental conditions described produces a fall of radio-iodine uptake to 10% of the control value at the end of 16 days. After 30 days this low level is unchanged.

2. Oxygen consumption falls gradually to 12% below the control value at the end of 30 days' treatment with PAS.

3. Thyroxine with PAS abolishes the fall in oxygen consumption and raises the radio-iodine uptake slightly above that given with PAS alone.

4. Methyl thiouracil with PAS does not depress the oxygen consumption level below that obtained with PAS alone. The radio-iodine uptake is raised slightly above that found with PAS.

5. After 15 weeks' administration of PAS radio-iodine uptake is more than double that of the control value.

6. The rise in radio-iodine uptake when thyroxine and methyl thiouracil are given with PAS and when PAS treatment is prolonged, is accompanied by structural changes in the thyroid gland indicative of an increased output of thyrotrophic hormone.

7. After 29 weeks' treatment with PAS signs of exhaustion of the thyroid gland appear. Complete degeneration of the follicular epithelium was observed in some animals at this time.

8. The structural changes in the gland are reversible even after 25 weeks' treatment with PAS at a dose level of 1 mg/g body weight/day.

Abstract

Lactation was suppressed in rats using a combined treatment of bromocriptine (to reduce prolactin concentrations) and a specific antiserum to rat GH administered twice daily for 2 days. When milk production had ceased, as determined by litter weight loss and the absence of milk in the stomachs of pups, attempts were made to reinitiate lactation using prolactin, GH, insulin-like growth factor-I (IGF-I) precomplexed to recombinant human IGF-binding protein-3 (hIGFBP-3) or IGF-I plus IGF-II precomplexed to hIGFBP-3. Despite the fact that all treatments except prolactin led to increases in serum IGFs and IGFBP-3, only prolactin and GH provoked the reinitiation of milk production as determined by increased litter weight gain, milk in the stomach of pups and a significant increase in the weight of the mammary glands.

Since the mammary gland has been shown to produce IGFBPs which may inhibit IGF action we also tested three IGF-I analogues, R₃-IGF-I, Long-IGF-I and Long-R₃-IGF-I. R₃-IGF-I has a single amino acid substitution (Glu to Arg) at position 3 whereas Long-IGF-I has a 13 amino acid N-terminal extension. These modifications dramatically reduce the ability of these analogues to bind to IGFBPs although they remain active at the IGF-I receptor. Such IGF analogues would therefore be expected to be active irrespective of the production of inhibitory IGFBPs. However, none was effective in reinitiating lactation, even at doses which have been shown to be biologically effective in terms of nitrogen retention.

We therefore conclude that, despite the fact that GH induces increases in serum IGF-I, IGF-II and IGFBP-3 when administered to lactating rats, the combination of all of these factors fails to reinitiate lactation. The biological significance of these changes and the mechanism by which GH stimulates milk secretion, when there appear to be no GH receptors on mammary epithelial cells, remain unclear, although the fact that both GH and prolactin were able to prevent reductions in DNA content of the gland suggest that regulation of apoptosis may be involved.

Journal of Endocrinology (1994) 140, 211–216

Fibrosis is associated with epithelial repair. It involves the activation of fibroblasts, increased production of extracellular matrix proteins and transdifferentiation to contractile, myofibroblasts that aid in wound contraction. This provisional matrix plugs the injured epithelium and provides a scaffold for epithelial cell migration, involving an epithelial–mesenchymal transition (EMT). When epithelial injury involves blood loss, this leads to platelet activation, the production of several growth factors and an acute inflammatory response. Under normal circumstances, the epithelial barrier is repaired and the inflammatory response resolves. However, in fibrotic disease, the fibroblast response continues, resulting in unresolved wound healing. The fibrotic diseases range from scleroderma, where the problem may be restricted to the skin and where it is not life-threatening, through to systemic forms that can manifest as, for example, idiopathic pulmonary fibrosis, in which death is inevitable within 3–5 years. Anti-inflammatory treatments have failed to ameliorate the disease condition and focus has instead turned to transforming growth factor-β1 (TGFB1), since it induces many of the processes involved, including fibroblast activation and EMT. Most recently, however, a new player in this process has been described, IGF-binding protein-5 (IGFBP5). IGFBP5 has also been shown to induce similar effects to TGFB1, but, in addition, it is strongly implicated in the process of senescence which is now believed to be a significant factor in these diseases. We examine the evidence for this role of IGFBP5 and identify some of the therapeutic targets which might be used to ameliorate these diseases of unknown cause.

ABSTRACT

The role of GH was examined using an antiserum to rat GH (anti-rGH). When administered to lactating rats on day 2 of lactation it was without effect, whereas bromocriptine markedly suppressed milk production, with no additional effect of combined treatment. On day 6 of lactation, treatment with anti-rGH was also without effect, whilst bromocriptine again suppressed milk production. Combined treatment, however, suppressed milk synthesis completely, suggesting that GH was capable of maintaining about 50% of normal milk yield in the absence of prolactin at day 6 of lactation. By day 14 of lactation, anti-rGH treatment alone was capable of decreasing milk yield by about 20%, and again milk secretion only stopped completely when GH and prolactin were suppressed. These data suggest that the role of GH in supporting lactation increases as lactation progresses.

The effects of GH in stimulating growth and in increasing milk yield in ruminants have been proposed to be mediated via insulin-like growth factor-I (IGF-I). In rats treated with anti-rGH, both IGF-I and IGF-II were decreased in serum. The concentration of the major IGF-binding protein (IGFBP-3) was not, however, affected by inhibition of GH or prolactin individually, but was decreased in animals treated with bromocriptine and anti-rGH. In animals given both bromocriptine and anti-rGH, concurrent treatment with recombinant bovine GH maintained milk yield at 50% of control values and normalized serum IGF-I, IGF-II and IGFBP-3 concentrations. By contrast, concurrent treatment with IGF-I or IGF-II, despite normalizing their respective concentrations in serum, failed to affect milk yield.

These results suggest that neither IGF-I nor IGF-II is capable of mediating the effects of GH alone. It is, however, possible that they play a part in a coordinated series of responses to GH involving IGF-I, IGF-II and IGFBP-3.

Journal of Endocrinology (1992) 134, 377–383

The ability of site-specific antipeptide antisera to enhance the biological activity of ovine FSH (oFSH) in vivo was investigated using hypopituitary Snell dwarf mice. These animals were shown to respond to increasing doses of oFSH (3·3–90 μg/day), administered in two daily injections over a 5-day treatment period, in a highly significant dose-dependent fashion. The responses measured were increases in uterine weight, ovarian weight and the index of keratinisation in vaginal smears. The dose-dependent response to oFSH confirmed the suitability of this animal model for these investigations and suggested the suboptimal dose of oFSH (20 μg/day) for use in enhancement studies.

Five peptides derived from the β subunit of bovine FSH (bFSH) (A, residues 33–47; B, 40–51; C, 69–80; D, 83–94; E, 27–39) were used to generate polyclonal antipeptide antisera. Of these peptides, only A and B produced an antiserum (raised in sheep) capable of recognising ¹²⁵I-bFSH in a liquid phase RIA. Antisera prepared against peptide A or peptide B were found to significantly enhance the biological activity of 20 μg oFSH/day over a 5-day treatment period. The response to antipeptide antisera alone did not differ significantly from that observed in PBS-injected control animals, neither did the response to FSH alone differ from that observed in animals treated with FSH plus preimmune serum. Thus the enhanced responses are dependent upon the presence of FSH plus antipeptide antiserum. Peptides A and B are located in a region thought to be involved in receptor recognition, this may have implications for the mechanism underlying this phenomenon and/or the structure/function relationships of FSH.

That FSH-enhancing antisera can be generated by immunisation of animals with peptides A and B suggests that it may be possible to develop these peptides as vaccines capable of increasing reproductive performance, such as ovulation rate. The high degree of sequence homology between ovine, bovine and porcine (and to a lesser extent human and equine) FSH in the region covered by peptides A and B suggests that these peptides could also be used to promote and regulate ovarian function in all of these species.

Journal of Endocrinology (1997) 152, 355–363

A reciprocal relationship between the endocrine and immune system has been demonstrated under pathophysiological conditions. However, few studies have assessed the relationship between thyroid hormones and immune function in apparently healthy individuals. Therefore, to clarify our understanding of normal physiological endocrine–immune interactions this study aimed to examine the interrelationships between thyroid hormones and immunity in healthy individuals. Total triiodothyronine (T₃), total thyroxine (T₄) and markers of immune status were assessed in 93 free-living and apparently healthy individuals aged 55–70 years. T₃ and T₄ concentrations were determined by commercially available kits. Immune status was assessed using flow cytometry and biochemical markers. Statistical analysis was performed by partial correlation, controlling for age. Thyroid hormone concentration was positively associated with markers of inflammation (P≤0.05), natural killer-like T cells (P≤0.001), expression of interleukin-6 (IL6) by activated monocytes (P≤0.05); percentage expression of memory T-lymphocytes (P≤0.01), memory T-helper lymphocytes (P≤0.05) and memory T-cytotoxic lymphocytes (P≤0.05), and higher IL2 receptor density on CD3+T-lymphocytes (P≤0.05). Thyroid hormone concentration was inversely associated with early lymphocyte apoptosis (P≤0.05) and the ratio of naïve- to memory T-cytotoxic lymphocytes (P≤0.05). The current study provides preliminary evidence of a role for T₃ and T₄, within normal physiological ranges, in the maintenance of lymphocyte subpopulations, and in mediating the inflammatory response. In conclusion, these findings highlight the potential implications of altered thyroid function in older individuals and the importance of future research examining thyroid–immune interactions.