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M J Waters

Publications and source records attributed to M J Waters.

At least 145 records · Page 8Linked to original sources
PubMed1986

Effect of epidermal growth factor on the membrane potential of cultured porcine thyroid cells.

Cultured porcine thyroid cells maintained in media containing TSH exhibited a membrane potential of -50 mV, and hyperpolarized by about 10 mV within 1 h of the addition of epidermal growth factor (EGF; 10 ng/ml). Follicle cells had depolarized to -45 mV after 4 h of exposure to EGF. Cells maintained in dibutyryl cyclic AMP (dbcAMP) did not alter their membrane potential when exposed to EGF for up to 4 h. Cultures washed to remove the TSH or dbcAMP hyperpolarized to -75 mV within 30 min, and a reversible depolarization to -60 mV was observed on addition of EGF. It was concluded that EGF acts as a physiological antagonist of TSH and also exerts a separate depolarizing influence on cultured thyroid cells.

Animals↗
PubMed1986

Dysgonic fermenter-2 septicemia.

A 62 yr-old man with a recent history of dog bite and a past history of splenectomy developed septicemia and signs suggestive of a generalized Schwartzman reaction, including fever, hypotension, symmetrical peripheral gangrene and laboratory evidence of consumptive coagulopathy. The causative organism was a Dysgonic Fermenter-2 (DF-2), a designation given to an unnamed group of Gram-negative rod shaped bacteria. This organism has not previously been reported in Australia. A review of documented cases of serious infection suggests that splenectomy and dog bite are predisposing factors to disease caused by this organism.

Animals↗
PubMed1986

Evidence for differential binding of growth hormones to membrane and cytosolic GH binding proteins of rabbit liver.

The existence of three GH binding proteins in rabbit liver membranes has been adduced from binding studies with a panel of monoclonal antibodies. Immunologically cross-reactive analogues of 'type 2' binding proteins were shown to exist in rabbit liver cytosol and in affinity purified receptor from liver microsomes. We now report differences in the binding of human and ovine GH with respect to two antigenic determinants on the 'type 1' GH binding protein. The discovery of these differences has enabled the detection of cross-reactive analogues of both binding protein types '1' and '2' in liver cytosol and in affinity purified preparations from liver membranes. These findings show a close structural relationship between the pool of cytosolic GH binding proteins and those present in the membranes; and differential ligand binding to, as well as absolute ligand selection by GH binding proteins, which could reflect the ability of GH to trigger a range of biological responses either through different receptors or differential interaction with particular receptor subtypes.

Animals↗
PubMed1985

Evidence from the use of monoclonal antibody probes for structural heterogeneity of the growth hormone receptor.

We describe the use of four monoclonal antibodies (MAbs) to the rabbit liver growth hormone (GH) receptor and one raised against purified rat liver GH receptor to characterize liver receptor subtypes which differ in their hormone-binding regions. The anti-(rat liver GH receptor) MAb both inhibited and precipitated rat and rabbit GH receptors, but only one-half of 125I-oGH (ovine GH) binding to liver microsomes could be inhibited by excess antibody. Conversely, only one-half of 125I-anti-(rat GH receptor) MAb binding was inhibited by excess oGH and Scatchard plots for this MAb exhibited two components. Although only 50% of 125I-oGH binding to membranes was inhibited by this MAb, all solubilized receptor could be immunoprecipitated. We postulate two epitopes for the anti-(rat GH receptor) MAb, one located at the hormone-binding site (inhibitory site) and one elsewhere (immunoprecipitating site). A second, rabbit-specific antibody (MAb 7) inhibited 85% of hormone binding but only 30% of 125I-anti-(rat GH receptor) MAb binding to rabbit liver microsomes. A combination of this MAb with the anti-(rat GH receptor) MAb totally inhibited 125I-oGH binding. MAb 7 alone totally inhibited 125I-rat GH binding to rabbit liver microsomes, as it did with 125I-oGH binding to purified receptor. On the basis of these results and others we postulate three types of GH receptor in rabbit liver membranes and ascribe approximate extents of 125I-oGH binding to each. A cytosolic 'GH receptor' which is not poly(ethylene glycol)-precipitable is shown to share five epitopes with 'type 2' microsomal receptors. Purified plasma membrane and endoplasmic reticulum fractions derived from a rabbit liver microsomal preparation have identical antigenic characteristics with respect to the GH-binding region, indicating that the heterogeneity we describe is not related to receptor processing. Of the three types of GH receptor in the plasma membrane of the rabbit (and possibly rat) we postulate that one (type 1) corresponds to the GH receptor involved in stimulating growth and possesses all of the epitopes studied here. A second (type 2) appears to be identical with the cytosolic 'GH receptor' and lacks the epitope for the anti-(rat GH receptor) MAb in the hormone binding site region. A third (type 3) does not possess the epitope for the inhibitory anti-(rabbit GH receptor) MAb, appears not to bind rat GH and is lost during purification. The availability of type-specific MAbs will facilitate assignment of specific functions to liver receptor subtypes which mediate the multiple functions of GH.

Animals↗
PubMed1985

A mechanism for the in vitro stimulation of adrenal cortisol biosynthesis by epidermal growth factor.

EGF stimulates adrenal steroidogenesis in ewes and in ovine adrenal slices. In vitro, The stimulation is blocked by the cholesterol synthesis inhibitors compactin and AY 9944. EGF stimulates the incorporation of [14C]acetate into cholesterol. EGF increases the activity of the rate limiting enzyme in cholesterol biosynthesis, HMG CoA reductase. EGF has no effect on the levels of any intermediates involved in the conversion of pregnenolone to cortisol, although ACTH produced changes consistent with 17 alpha-hydroxylase activation. We propose that EGF increases adrenal cortisol synthesis in vitro by a stimulation of cholesterol precursor biosynthesis mediated through activation of HMG CoA reductase.

Adrenal Cortex↗
PubMed1985

Insulin-like growth factor receptor in fetal lamb liver: characterization and developmental changes.

Multiplication-stimulating activity (MSA), an insulin-like growth factor (IGF) (rat IGF II), binds to extracts of many tissues from fetal lambs. We now report the presence of high concentrations of a glycoprotein receptor with a high affinity for MSA-II in microsomes prepared from fetal lamb liver. The binding of radiolabeled MSA-II is inhibited by IGF but not by insulin, human, and ovine GH, ovine PRL, ovine placental lactogen, and mouse epidermal growth factor. The relative potencies of human IGF II, human IGF I, and MSA-II in competing with [125I]MSA-II for binding to this receptor are 100:17:3.5 by weight. Binding is pH, time, and temperature dependent. Gel permeation chromatography of the Triton X-100 soluble receptor indicates a hydrodynamic radius of 6.8 nm. Specific binding increases from mid- to late gestation and is associated with changes in both the affinity and concentration of receptors. Receptor concentration increases from 7.95 +/- 3.94 pmol/mg (mean +/- SE) at 78 days gestation to 15.8 +/- 4.3 pmol/mg at 134-140 days (P less than 0.05), whereas receptor affinity decreases from 1.14 +/- 0.34 X 10(9) liter/mol to 0.63 +/- 0.14 X 10(9) liter/mol over this period (P less than 0.05). The presence of very high concentrations of an IGF receptor in fetal lamb liver suggest that this organ may be a major target for IGF action in fetal life. The increase with advancing gestational age of the concentration of IGF receptors which have preferential specificity for IGF II may function to increase the responsiveness of the fetal lamb liver to IGF II stimulation and so compensate for the decline in plasma concentrations of this growth factor which occur near birth.

Animals↗
PubMed1985

An examination of the proposed roles of placental lactogen in the ewe by means of antibody neutralization.

The physiological role of placental lactogen (PL; chorionic somatomammotrophin) in the ewe has been investigated by infusion of ewes (n = 3) on day 131 of pregnancy with sufficient ovine PL (oPL) antibody to neutralize circulating oPL for at least 12 h. Effectiveness of the antibody neutralization was defined both in vitro and in vivo according to rigorous criteria. Control ewes (n = 3) were infused simultaneously with an equivalent amount of pooled goat gamma globulin. Since both sets of ewes had previously been catheterized with jugular, utero-ovarian and femoral vein catheters and a femoral arterial catheter, it was possible to measure whole body glucose kinetics as well as muscle and uterine glucose, free fatty acid (FFA) and 3-hydroxybutyrate extraction. In addition, plasma levels of insulin, GH, prolactin, insulin-like growth factor-I (IGF-I), IGF-II, progesterone and cholesterol were determined in femoral arterial samples. Neutralization of maternal oPL did not significantly affect whole body glucose metabolism, uterine and muscle glucose extraction, or 3-hydroxybutyrate extraction by muscle. A trend towards lower plasma FFA levels was observed after prolonged infusion, but was not statistically significant. However, plasma insulin levels rose significantly during antibody infusion after an early fall. These observations are rationalized in terms of the known requirements of ruminant metabolism during pregnancy, and contrasted with the accepted model for the role of human PL in the metabolic adjustments of pregnancy. No change in plasma IGF-I, IGF-II or GH was observed, providing no support for the concept that oPL is responsible for maternal somatomedin generation during pregnancy. Similarly, plasma prolactin did not differ between antibody-treated and control groups. Finally, antibody neutralization had no influence on either plasma progesterone or cholesterol, mitigating against a role for oPL in progesterone production during late pregnancy in the ewe.

Animals↗
PubMed1985

Effect of epidermal growth factor on reproductive function of ewes.

Adult Merino ewes were infused via the jugular vein with either saline (n = 5) or epidermal growth factor (EGF) (4.2 micrograms/kg per h, n = 6) for 24 h in either the luteal phase or the follicular phase of the oestrous cycle and reproductive function was examined. Infusion of EGF during the luteal phase caused no detectable change in plasma progesterone or prolactin concentrations over a 7-day period compared with the controls. Infusion of EGF during the follicular phase suppressed the oestrous rise in plasma oestradiol. Luteinizing hormone pulse amplitude was increased and pulse frequency was decreased by the end of the infusion. All control ewes had a pro-oestrous LH surge and mated, but the LH surge and oestrus were prevented by EGF infusion. Nevertheless, plasma progesterone levels rose subsequently in the EGF-infused ewes in parallel with the control ewes, suggesting that the preovulatory follicle had luteinized. Both LH and FSH rose over the 7 days after EGF infusion to levels similar to those in ovariectomized ewes. Thus EGF appears to inhibit follicular oestradiol production, although it does not affect luteal progesterone production or follicular luteinization. We suggest that the alteration in gonadotrophin secretion patterns results from a disturbance of feedback mechanisms between the ovary and the hypothalamopituitary axis, although a direct effect in the brain or the pituitary gland cannot yet be excluded.

Animals↗
PubMed1985

Branhamella catarrhalis, a respiratory tract pathogen.

Branhamella catarrhalis, formerly regarded as an oropharyngeal commensal, has more recently been implicated as an opportunistic pathogen in the respiratory tract. This report describes the isolation of B. catarrhalis from two consecutive samples of empyema fluid and also from sputum in thirteen cases of lower respiratory tract disease, where the isolate was considered to be etiologically significant. The antibiotic therapy required to treat such infections is discussed.

Adult↗
PubMed1984

Immunological and physicochemical evidence for tissue specific prolactin receptors in the rabbit.

Late pregnant and midlactating rabbit tissues (adrenal gland, kidney cortex, liver, mammary gland, and ovary) were examined for evidence of tissue specific differences in PRL receptors by several criteria. These included analysis of association constants, gel filtration, analytical isoelectric focusing, and reactivity with specific anti-PRL receptor antibodies in both the direct competition and immunoprecipitation assays, using membrane bound and Triton X-100 solubilized receptors. Association constants of membrane bound PRL receptors were not significantly different (adrenal, 1.50 +/- 0.26 X 10(10) M-1; kidney cortex, 0.90 +/- 0.22 X 10(10) M-1; liver, 1.31 +/- 0.50 X 10(10) M-1; mammary, 0.95 +/- 0.36 X 10(10) M-1) except the ovarian receptor, which had a significantly higher affinity (2.05 +/- 0.04 X 10(10) M-1) than other tissue receptors. This difference did not result from a difference in tracer degradation. Higher affinity for the ovarian receptor may be a consequence of phospholipid modulation of receptor affinity, since Triton X-100 solubilization abolished this difference in affinity (ovary, 3.63 +/- 0.15 X 10(10) M-1; adrenal, 3.48 +/- 0.44 X 10(10) M-1; mammary, 3.61 +/- 0.41 X 10(10) M-1). However, both the solubilized kidney cortex receptor (2.68 +/- 0.52 X 10(10) M-1) and the solubilized liver receptor (2.40 +/- 0.38 X 10(10) M-1) were significantly different from PRL receptors in the other tissues, implying a possible structural distinction. In addition, clear differences in isoelectric point and immunoreactivity were evident between the kidney cortex receptor and PRL receptors in other tissues. Immunologic evidence of differences between mammary gland, adrenal, ovary, and liver PRL receptors was also obtained, although the degree of difference in the liver receptor was obscured by binding of 125I-ovine PRL to the GH receptor. No differences were seen in elution position of solubilized receptors by gel filtration on Sepharose CL6B. These differences support the notion of structurally distinct PRL isoreceptors in different tissues, although it is also possible that they result from differing proportions of two receptor forms (e.g. plasma membrane and golgi complex forms). It is suggested that the kidney cortex receptor is derived from a more primitive form of the PRL receptor concerned with the regulation of electrolyte balance, whereas PRL receptors in other tissues arose at later times to subserve other specialized functions.

Adrenal Glands↗
PubMed1984

Monoclonal antibodies to the rabbit liver growth hormone receptor: production and characterization.

Monoclonal antibodies to the GH receptor (GHR) have been produced by the application of hybridoma technology to splenic lymphocytes from BALB/C mice immunized with a human (hGH) affinity purified preparation of rabbit liver GHR. Primary screening of 384 wells yielded 4 antibodies able to immunoprecipitate [125I]iodo-hGH complexes with purified GHR and one able to inhibit binding of [125I]iodoovine GH ([125I]iodo-oGH) to rabbit liver microsomes. These cells were cloned and grown as ascitic tumors with loss of 1 of the 4 precipitators. Ascitic fluids contained monoclonal antibodies of high titer (inhibitor and 2 precipitators, 1:2.0 X 10(5); one precipitator, 1:2.0 X 10(4)) and high affinity (precipitators, 2.5-6.0 X 10(9) M-1; inhibitor, high affinity component, 6.4 X 10(10) M-1), which were isotyped as IgG1K and IgG2aK (1 precipitator). These antibodies did not cross-react with rabbit insulin or PRL receptors in the appropriate receptor assays and did not possess antihormone activity. Binding of [125I]iodo-MAb7, the inhibitory antibody, was totally blocked by the addition of excess unlabeled oGH or hGH, although these hormones had no effect on binding of the 125I-labeled precipitators. Scatchard analysis of [125I]iodo-oGH binding in the presence of MAb7 showed decreased binding by loss of sites rather than affinity. Antibody dilution curves and Scatchard plots for MAb7 binding provided evidence for two types of GHR in the rabbit liver, in accord with previously published data based on hormone binding studies. All precipitating antibodies gave an enhancement of [125I] iodo-oGH binding with purified receptor (up to 360% of polyethylene glycol-precipitated control), but only minimal enhancement with solubilized microsomal membranes. This enhancement was shown to be due to an increase in receptor number rather than affinity. After examining a number of hypotheses, we concluded that the enhancement was an artifact resulting from a nonpolyethylene glycol-precipitable species of GHR which could be totally precipitated by the monoclonal antibodies. We have produced and characterized four monoclonal antibodies to the GHR which will be of value in characterizing the structure and function of this receptor.

Animals↗
PubMed1983

Stimulation of adrenal cortisol biosynthesis by epidermal growth factor.

The effect of epidermal growth factor (EGF) on adrenal cortisol biosynthesis in ewes was determined both in vivo and in vitro. There was a progressive rise in plasma cortisol levels after infusion of 2.9 micrograms/kg/h EGF into 5 ewes over 24 h. Mean plasma cortisol rose to a sustained plateau of 700% of the saline control value and fell towards saline control values before the end of the infusion. In vitro, adrenal slices taken from ewes synthesized and released significantly greater amounts of cortisol in response to the addition of EGF or ACTH1-24. EGF and ACTH1-24 gave a maximal stimulation of cortisol biosynthesis between 10 and 100 ng/ml and above 100 ng/ml, respectively. Biologically inactive reduced S-carboxyamidomethyl EGF as well as a number of polypeptide hormones and growth factors were without effect at these dose levels. Stimulation by EGF of cortisol synthesis and secretion was dependent on protein synthesis as it was for ACTH. However, EGF did not synergise with ACTH in promoting cortisol production. These results suggest that EGF may be a regulatory factor affecting adrenal cortisol synthesis and secretion.

Adrenal Cortex↗
PubMed1981

Epidermal growth factor: a critical factor in fetal maturation?

Epidermal growth factor (EGF) infused over 3-14 days into fetal sheep of 110-125 days gestation resulted in a number of morphological and endocrine changes. Striking hypertrophy of the skin, wool follicles and their accessory structures was seen, together with a reduction in the ratio of secondary to primary follicles and degenerative changes in wool fibres associated with shedding of fibres. Adrenal, thyroid, liver and kidney weights were increased while thymus weight was decreased. The increase in adrenal size resulted from cortical hypertrophy and was associated with increased cortisol secretion. Thyroid hypertrophy was accompanied by an increase in colloid stores, decreased plasma thyroxine and reverse triiodothyronine (T3) concentrations, unchanged plasma T3 and thyroid-binding globulin and raised thyrotropin (TSH) levels. Thyrotropin receptor affinity and content per gram of tissue were unchanged. Fetal and maternal plasma prolactin and growth hormone levels, and fetal plasma placental lactogen levels, were unchanged, although there was a significant rise in maternal plasma placental lactogen concentrations with high doses of EGF. Other maturational parameters such as switching from fetal to adult haemoglobin and liver glycogen content were unaffected.

Animals↗
PubMed1981

Fetal and material ovine placental lactogen during hyperglycaemia, hypoglycaemia and fasting.

Hyperglycaemia was produced in chronically catheterized fetal lambs and pregnant-ewes by the infusion of glucose into the fetus. Plasma concentration of placenta lactogen did not change significantly in either fetal or maternal circulation. Fetal and maternal hypoglycaemia was induced by administration of insulin to the fetus and ewe separately. Plasma concentrations of placental lactogen in the fetus did not change significantly but maternal plasma concentrations fell slightly after hypoglycaemia in either fetus or ewe. Plasma concentrations of placental lactogen rose in both the ewe and fetus during prolonged fasting of the ewe. These results neither confirm nor refute a role for placental lactogen in intermediary metabolism of the pregnant ewe and fetus but glucose concentration alone is unlikely to be a significant factor in the control of secretion of this hormone.

Animals↗