Nephrogenic syndrome of inappropriate antidiuresis (NSIAD): a paradigm for activating mutations causing endocrine dysfunction

Mutations of G protein-coupled receptors are responsible for a wide range of diseases. With respect to water balance and vasopressin signaling, more than 180 different inactivating mutations have been previously described in the V2 vasopressin receptor (V2R), resulting in nephrogenic diabetes insipidus. In contrast, we have recently described the first known patients with V2R activating mutations. Patients with these novel gain-of-function V2R mutations have a disorder which we have termed "nephrogenic syndrome of inappropriate antidiuresis" (NSIAD): a clinical presentation consistent with the syndrome of inappropriate antidiuretic hormone secretion but with undetectable levels of arginine vasopressin (antidiuretic hormone). The mechanisms by which these mutations constitutively activate the V2R are currently being investigated.

Nephrogenic syndrome of inappropriate antidiuresis: a novel disorder in water balance in pediatric patients

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a common cause of hyponatremia. We report findings in 2 unrelated male infants whose clinical presentation and laboratory findings were consistent with SIADH, but who exhibited unmeasurable arginine vasopressin (AVP) levels on repeated occasions. We hypothesized that these infants had a novel gain of function defect in the AVP-signaling pathway. DNA sequencing of each patient's vasopressin V2 receptor (V2R) gene identified mutations (R137C or R137L) in each. R137H mutations have been reported previously to cause nephrogenic diabetes insipidus. To further characterize the effects of these mutations, we re-created each mutation by site-directed mutagenesis in a vasopressin V2R expression vector and cotransfected COS-7 cells with wild-type and mutant vasopressin V2R vectors and a cyclic adenosine monophosphate-responsive luciferase reporter plasmid. The luciferase activity was induced 7.5-fold (R137L mutant; P = 0.0037) and 4-fold (R137C mutant; P = 0.013) more than the wild-type vasopressin V2R, which is the empty vector or the inactivating R137H mutant. This novel gain of function mutation in the vasopressin V2R can cause constitutive activation of the receptor and resultant hyponatremia. These findings represent a previously unrecognized genetic disease, which was designated as nephrogenic syndrome of inappropriate antidiuresis. A number of questions have emerged, including the following: (1) What is the frequency? (2) Are there nonrenal manifestations? (3) Are heterozygotes affected? (4) What is the optimal therapy? and (5) How do these mutations cause constitutive activation of the receptor?

Oral urea for the treatment of chronic syndrome of inappropriate antidiuresis in children

We report the successful use of oral urea in the management of children with chronic syndrome of inappropriate antidiuretic hormone secretion (SIAD). We performed a retrospective review of four children with chronic SIAD. After initial attempts at management with fluid restriction, each was started on a 30% to 50% oral urea solution, and the dose was titrated until normal serum sodium was achieved. Fluid intake was liberalized after serum sodium normalization. All four children normalized their serum sodium. No side effects or toxicities were experienced. Oral urea is a safe, effective treatment for chronic SIAD in children.

Nephrogenic syndrome of inappropriate antidiuresis

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a common cause of hyponatremia. We describe two infants whose clinical and laboratory evaluations were consistent with the presence of SIADH, yet who had undetectable arginine vasopressin (AVP) levels. We hypothesized that they had gain-of-function mutations in the V2 vasopressin receptor (V2R). DNA sequencing of each patient's V2R gene (AVPR2) identified missense mutations in both, with resultant changes in codon 137 from arginine to cysteine or leucine. These novel mutations cause constitutive activation of the receptor and are the likely cause of the patients' SIADH-like clinical picture, which we have termed "nephrogenic syndrome of inappropriate antidiuresis."

Akt phosphorylation is not sufficient for insulin-like growth factor-stimulated myogenin expression but must be accompanied by down-regulation of mitogen-activated protein kinase/extracellular signal-regulated kinase phosphorylation

IGF-I has a unique biphasic effect on skeletal muscle differentiation. Initially, IGF-I inhibits expression of myogenin, a skeletal muscle-specific regulatory factor essential for myogenesis. Subsequently, IGF-I switches to stimulating expression of myogenin. The mechanisms that mediate this switch in IGF action are incompletely understood. Several laboratories have demonstrated that the phosphatidylinositol-3-kinase/Akt signaling pathway is essential for myogenic differentiation and have suggested that this pathway mediates IGF-I stimulation of myogenin mRNA expression, an early critical step in the differentiation process. These studies, however, did not address concurrent Akt and MAPK/ERK1/2 phosphorylation, the latter of which is also known to regulate myogenic differentiation. In the present study in rat L6E9 muscle cells, we have manipulated ERK1/2 phosphorylation with either an upstream inhibitor or activator and examined concurrent levels of Akt and ERK1/2 phosphorylation and of myogenin mRNA expression in response to treatment with IGF-I. We find that even in the presence of phosphorylated Akt, it is only when ERK1/2 phosphorylation is inhibited that IGF-I can stimulate myogenin mRNA expression. Thus, although Akt phosphorylation may be necessary, it is not sufficient for induction of myogenic differentiation by IGF-I and must be accompanied by a decrease in ERK1/2 phosphorylation.

Early stimulation and late inhibition of extracellular signal-regulated kinase 1/2 phosphorylation by IGF-I: a potential mechanism mediating the switch in IGF-I action on skeletal muscle cell differentiation

IGF-I has a unique biphasic effect on skeletal muscle cell differentiation. Initially, IGF-I inhibits differentiation and promotes proliferation of skeletal myoblasts. Subsequently, IGF-I switches to stimulating differentiation of these cells. The mechanisms responsible for this switch in IGF action remain unknown. We have examined the role of extracellular signal-regulated kinase (Erk)1/2 signaling in mediating the early inhibitory and late stimulatory effects of IGF-I on the gene expression of myogenin, a skeletal muscle-specific transcription factor essential for myogenic differentiation. We find that, concurrent with its early inhibitory and late stimulatory effects on myogenin mRNA, IGF-I has a biphasic but opposite effect on phosphorylation of Erk1/2: initially, IGF-I increases and subsequently decreases the phosphorylation of Erk1/2 in comparison to untreated cells. Cotreatment with an inhibitor of Erk1/2 activation prevents the early IGF-I-stimulation of Erk1/2 phosphorylation and partially reverses IGF-I-inhibition of myogenin mRNA. Conversely, preventing the late IGF-I-induced decrease in Erk1/2 phosphorylation blocks IGF-I-stimulation of myogenin mRNA. Our data indicate that the time-dependent, opposing effects of IGF-I on skeletal muscle cell differentiation are mediated, at least in part, by biphasic but opposite effects on activation of the Erk1/2 MAPK signaling pathway.

Growth factor-stimulated phosphorylation of Akt and p70(S6K) is differentially inhibited by LY294002 and Wortmannin

The phosphoinositide 3-kinase (PI3K) inhibitors, LY294002 (LY) and wortmannin (WM), are widely used to examine the role of PI3K in growth factor signaling. These compounds inhibit the kinase action of PI3K, thus preventing the accumulation of PI(3,4,5)P3 and PI(3,4)P2 (PIs) and subsequent phosphorylation and activation of the downstream effectors of PI3K, Akt and p70(S6K). The efficacy of these inhibitors has been demonstrated by measuring cellular levels of PIs or the kinase activity of immunoprecipitated PI3K. However, their effects on activation of Akt and p70(S6K), more widely used markers of PI3K activation, has not been formally tested. We have examined the effects of LY and WM on phosphorylation of Akt and p70(S6K) by insulin-like growth factor-I, insulin, and platelet-derived growth factor in skeletal muscle cells. LY is much less effective in blocking the phosphorylation of Akt than p70(S6K); at concentrations which completely inhibit phosphorylation of p70(S6K), phosphorylation of Akt is only partially inhibited by LY. WM also inhibits IGF-I-stimulated phosphorylation of Akt and p70(S6K) with unequal potency but is equally effective in blocking insulin-stimulated phosphorylation of these peptides. Our data demonstrate that inhibiting PI3K signaling through one of its downstream mediators (p70(S6K)) may not indicate complete blockage of the PI3K pathway which may be signaling through an alternate downstream branch (Akt). These findings indicate that the efficacy of LY and WM in blocking PI3K-activation of Akt and p70(S6K) must be tested within the context of every experiment, and that the results obtained with the use of these inhibitors must be interpreted according to their specific effects on the PI3K/Akt and PI3K/p70(S6K) signaling pathways.

Functional inactivation of the IGF-I receptor delays differentiation of skeletal muscle cells

Skeletal myoblasts are inherently programmed to leave the cell cycle and begin the differentiation process following removal of exogenous growth factors. Serum withdrawal results in a marked induction of IGF production which is essential for skeletal muscle differentiation in vitro. However, the potential role of the tyrosine kinase IGF-I receptor (thought to be the principal mediator of both IGF-I and II signaling in skeletal muscle) in the decision of myoblasts to begin differentiation following serum withdrawal is unknown. To explore the role of the IGF-I receptor in this decision by skeletal myoblasts, we functionally inactivated endogenous IGF-I receptors in mouse C2C12 cells using a dominant negative, kinase-inactive IGF-I receptor in which the ATP-binding site lysine (K) at residue 1003 has been mutated to alanine (A). Cell lines with the greatest degree of mutant IGF-I receptor expression (A/K cells) demonstrated functional inactivation of endogenous IGF-I receptors as determined by their impaired ability to phosphorylate the principal substrate of the IGF-I receptor, IRS-1, in response to treatment with IGF-I. In addition, the proliferative response of myoblasts to IGF-I was completely abolished in A/K cells. Following withdrawal of exogenous growth factors, A/K cells demonstrated a marked delay in the induction of the gene expression of myogenin, a skeletal muscle-specific transcription factor essential for differentiation, and a subsequent delay in the induction of muscle creatine kinase activity. Delayed differentiation in A/K cells was associated with prolonged phosphorylation of the cell cycle regulatory retinoblastoma (Rb) protein; it is the un- (or hypo-) phosphorylated form of Rb which is known to promote differentiation in skeletal myoblasts. Thus, the IGF-I receptor regulates the timing of myoblast differentiation induced by serum withdrawal. The delayed differentiation of skeletal myoblasts with functionally inactive IGF-I receptors may result, at least in part, from delayed induction of myogenin gene expression and prolonged phosphorylation of the Rb protein.

Opposing early inhibitory and late stimulatory effects of insulin-like growth factor-I on myogenin gene transcription

Insulinlike growth factors (IGFs) stimulate skeletal muscle cell differentiation in association with an increase in the mRNA of myogenin, a member of the MyoD family of skeletal muscle-specific transcription factors that plays an essential role in the differentiation process. However, this is a relatively late effect, requiring treatment periods of >24 h. In contrast, IGFs initially inhibit skeletal muscle cell differentiation, associated with a marked reduction in myogenin mRNA. The mechanisms by which IGF-I initially inhibits and subsequently stimulates myogenin expression are unknown. In the first 24 h, we find that IGF-I inhibits myogenin gene transcription by >80% but has no effect on myogenin mRNA stability. Similarly, in the first 24 h, IGF-I markedly inhibits myogenin promoter activity; the sequence -145 to -9 of the myogenin gene is sufficient to confer this inhibitory effect of IGF-I. In contrast, 48 h of treatment with IGF-I results in an increase in myogenin promoter activity that parallels the increase in myogenin steady-state mRNA. This increase in promoter activity is completely prevented in constructs lacking the sequence -1,565 to -375 of the myogenin gene. These data indicate that the early inhibitory and late stimulatory effects of IGF-I on myogenin expression are mediated at the level of transcription, and that these time-dependent, opposing effects of IGF-I on myogenin transcription are mediated by distinct regions of the myogenin gene. To our knowledge, this is the first demonstration of a gene whose promoter activity is initially inhibited and subsequently stimulated by IGF-I.

Peptide mapping and characterisation of glycation patterns of the glima 38 antigen recognised by autoantibodies in Type I diabetic patients

AIMS/HYPOTHESIS

Glima 38 is an N-glycated neuroendocrine membrane protein of M(r) 38,000, which is recognised by autoantibodies in approximately 20% of patients with Type I (insulin-dependent) diabetes mellitus. The aim of this study was to characterise the carbohydrate moiety and generate peptide maps of glima 38.

METHODS

Sera of high immunoreactivity to glima 38 were used to isolate 35-S methionine-labelled protein from betaTC-3 cells and a neuronal cell line GT1.7. Tunicamycin was used to inhibit N-glycation of glima 38 and define the core protein. The carbohydrate moiety was characterised for tunicamycin sensitivity, lectin binding and susceptibility to different endoglycosidases. The protein moiety was subjected to digestion by proteases to define peptide maps.

RESULTS

The autoreactive epitopes in glima 38 recognised by Type I diabetic sera are conformational and independent of the carbohydrate moiety. Inhibition of N-glycation of glima 38 in vivo, shows a protein core of M(r) 22,000 in both pancreatic beta-(betaTC3) and neuronal (GT1.7) cell lines. The carbohydrate moieties in the two cell types are distinct but contain a similar amount of terminal sialic acid residues and at least five oligosaccharide chains Glima 38 binds Triticum vulgare and Ricinus communis I lectins. Endoproteinase treatment of the M(r) 22,000 core protein results in peptides of M(r) 4500 and M(r) 20,000 with Lys-C, and peptides of M(r) 4000 and M(r) 11,000-12,000 with Glu-C/V8 and Asp-N proteases.

CONCLUSION/INTERPRETATION

The biochemical properties of glima 38 define it as a new autoantigen in Type I diabetes and provide a basis for its purification.

Long-term outcome in children and adolescents after transsphenoidal surgery for Cushing's disease

Cushing's disease refers specifically to an ACTH-producing pituitary adenoma that stimulates excess cortisol production. Transsphenoidal surgery is the treatment of choice in children and adolescents, but disparate cure rates have been reported, ranging from 50-98%. The discrepancies in cure rate are due primarily to the technical success of the surgery and the length and method of follow-up. We studied 42 consecutive children and adolescents (age, < or = 18 yr) who underwent transsphenoidal exploration for the primary treatment of Cushing's disease at University of California-San Francisco from 1974-1993. Only 7 patients had persistent disease, defined as evidence of Cushing's disease within 6 months of surgery, yielding an initial remission rate of 83%. We comprehensively evaluated 26 of the 35 patients who experienced an initial remission, including testing of the ACTH-adrenocortical axis. The mean duration of follow-up is 7.2 yr (range, 1.5-13.6 yr). Seven experienced a relapse of Cushing's disease, yielding a net remission rate of 73%. Relapses occurred an average of 4.2 yr postoperatively (range, 0.75-6.2 yr). Five patients experienced relapse within 5 yr of surgery, whereas 2 relapsed more than 5 yr postoperatively. Repeat transsphenoidal surgery was performed in 8 patients with persistent or recurrent disease, and 6 of these remain in remission. Low serum or urinary cortisol measurements within the first post-operative week predicted remission of Cushing's disease, but were not necessarily predictive of long-term cure. Hypercortisolism had significant effects on bone metabolism, as reflected by both diminished bone density in the majority of patients examined and decreased growth rate. Both parameters improved after surgical care, although they did not fully normalize. We conclude that transsphenoidal surgery is a safe and effective treatment for pediatric Cushing's disease, but long-term surveillance is necessary to detect possible recurrences.

Adjunctive growth hormone during ovarian hyperstimulation increases levels of insulin-like growth factor binding proteins in follicular fluid: a randomized, placebo-controlled, cross-over study

GH increases circulating insulin-like growth factor I (IGF-I), which can promote the growth and differentiated function of ovarian granulosa and theca cells. Reported studies of GH as an adjunct to menotropin stimulation in women, largely those with ovarian dysfunction, have not consistently shown a benefit of GH, despite increases in serum and follicular fluid IGF-I. We hypothesized that changes in intrafollicular IGF-binding proteins (IGFBPs), which can antagonize IGF actions on granulosa cells, may underlie the inconsistent effects of GH. In the present study of GH, administered in double-blind, placebo-controlled, cross-over fashion to regularly cycling women undergoing in vitro fertilization, we found that follicular fluid levels of IGFBP-1, -3, and -4 and serum levels of IGFBP-3, as well as follicular fluid and serum IGF-I, were significantly increased in the GH-treated cycles, when compared with the placebo cycle of the same patient. We suggest that the net increase in intrafollicular IGFBPs in GH cycles may mitigate the potential beneficial effect of increased IGF-I.

Differential regulation of insulin-like growth factor-I (IGF-I) receptor gene expression by IGF-I and basic fibroblastic growth factor

Insulin-like growth factor-I receptor (IGF-IR) gene expression is regulated by various stimuli, including hormones, growth factors, and nutritional status. We have investigated the molecular mechanism by which two growth factors, insulin-like growth factor-I (IGF-I) and basic fibroblast growth factor (bFGF) regulate IGF-IR gene expression. bFGF increases the endogenous IGF-IR mRNA levels and IGF-IR promoter activity. This effect is mediated by a region of the IGF-IR promoter located between nucleotides -476 and -188 in the 5'-flanking region. In contrast, IGF-I decreases the IGF-IR mRNA levels. IGF-I down-regulates IGF-IR transcriptional activity as deduced from experiments in which the levels of pre-mRNA and mRNA were measured. IGF-I reduced pre-mRNA and mRNA levels in parallel, while the mRNA stability was found to be unchanged by IGF-I treatment. While these results strongly suggest an effect of IGF-I on IGF-IR transcriptional activity, no specific IGF-I response element was demonstrated in the 5'-untranslated region or 5'-flanking region studied. Thus, bFGF and IGF-I have differential effects on IGF-IR gene transcription, with the IGF-I response region as yet unidentified.

Opposing early and late effects of insulin-like growth factor I on differentiation and the cell cycle regulatory retinoblastoma protein in skeletal myoblasts

The mechanisms by which insulin-like growth factors (IGFs) can be both mitogenic and differentiation-promoting in skeletal myoblasts are unclear because these two processes are believed to be mutually exclusive in this tissue. The phosphorylation state of the ubiquitous nuclear retinoblastoma protein (Rb) plays an important role in determining whether myoblasts proliferate or differentiate: Phosphorylated Rb promotes mitogenesis, whereas un- (or hypo-) phosphorylated Rb promotes cell cycle exit and differentiation. We hypothesized that IGFs might affect the fate of myoblasts by regulating the phosphorylation of Rb. Although long-term IGF treatment is known to stimulate differentiation, we find that IGFs act initially to inhibit differentiation and are exclusively mitogenic. These early effects of IGFs are associated with maintenance of Rb phosphorylation typical of proliferating cells; upregulation of the gene expression of cyclin-dependent kinase 4 and cyclin D1, components of a holoenzyme that plays a principal role in mediating Rb phosphorylation; and marked inhibition of the gene expression of myogenin, a member of the MyoD family of skeletal muscle-specific transcription factors that is essential in muscle differentiation. We also find that IGF-induced inhibition of differentiation occurs through a process that is independent of its mitogenic effects. We demonstrate, thus, that IGFs regulate Rb phosphorylation and cyclin D1 and cyclin-dependent kinase 4 gene expression; together with their biphasic effects on myogenin expression, these results suggest a mechanism by which IGFs are initially mitogenic and subsequently differentiation-promoting in skeletal muscle.

Embryonic expression of tenascin-X suggests a role in limb, muscle, and heart development

Tenascin-X (TN-X) is the newest member of the tenascin family of extracellular matrix proteins and it is highly expressed in muscular tissues during development. To gain insight into the possible functions of TN-X during development, we evaluated its expression in the rat embryo. Using an 800 bp cDNA encoding the fibrinogen-like domain of TN-X, we show that TN-X expression begins in migrating cells of the epicardium in the E12 heart. The epicardium provides progenitors of fibrous and vascular tissue to the developing heart. After the epicardium is complete, TN-X is expressed in the sub-epicardial space in association with developing blood vessels, and later by non-myocytes dispersed through the myocardial wall. A similar pattern of TN-X expression, first in connective tissue surrounding muscle, and then by a subset of cells within muscle, was seen in para-axial, body wall, craniofacial, and appendicular muscle. This pattern suggests a role in connective tissue cell migration and late muscle morphogenesis. TN-X is also highly expressed in the interdigital space at E15 and surrounding developing tendons, suggesting an additional role in cell fate determination. Although the pattern of TN-X expression is distinct from that of tenascin C, they are frequently expressed in close proximity. Indirect genetic evidence in humans suggests an essential function for TN-X, and the pattern of TN-X expression in heart, skeletal muscle, and limb is consistent with this hypothesis.

Skeletal muscle cell-derived insulin-like growth factor (IGF) binding proteins inhibit IGF-I-induced myogenesis in rat L6E9 cells

The insulin-like growth factors (IGFs) stimulate the differentiation of skeletal muscle cells. IGF binding proteins (IGFBPs), which are expressed by skeletal muscle cells, may enhance or inhibit IGF actions. To explore the role of skeletal muscle-derived IGFBPs in IGF-induced myogenesis, we compared the differentiation-inducing effects of IGF-I and des(1-3)IGF-I in rat L6E9 skeletal myoblasts. Des(1-3)IGF-I is a naturally occurring IGF-I analog with markedly reduced affinity for IGFBPs but with an affinity for the IGF-I receptor that is comparable to that for native IGF-I. We find that rat L6E9 cells produce principally IGFBP-4 and BP-6, with a minor component of IGFBP-5. Both IGFBP-4 and BP-6 accumulate during differentiation and increase further in response to IGF-I or des(1-3)IGF-I treatment. We find that an IGF-I analog with reduced affinity for IGFBPs is significantly more potent than native IGF-I in stimulating myogenesis (as assessed by myogenin messenger RNA abundance and muscle creatine kinase activity), indicating that IGFBPs expressed by skeletal muscle cells inhibit differentiation induced by IGF-I. In view of the relative abundance of IGFBP-4, its relatively high affinity for IGF-I and the low affinity of IGFBP-6 for IGF-I, it is likely that the inhibitory effect of rat skeletal muscle-derived IGFBPs on IGF-I-induced myogenesis is mediated principally by IGFBP-4.

An insulin-like growth factor-II (IGF-II) analog with highly selective affinity for IGF-II receptors stimulates differentiation, but not IGF-I receptor down-regulation in muscle cells

The insulin-like growth factors (IGFs) stimulate the growth and differentiation of muscle cells. IGF-II, the principal IGF peptide expressed by differentiating muscle cells, has been implicated in at least two autocrine/paracrine actions in this tissue: stimulation of differentiation and down-regulation of the IGF-I receptor. To determine which IGF receptor subtypes mediate these effects of IGF-II, we treated mouse BC3H-1 muscle cells with native IGF-II or [Leu27]IGF-II, an analog with high affinity for IGF-II receptors (comparable to that seen with native IGF-II) but markedly reduced affinity for IGF-I and insulin receptors. Muscle cell differentiation was assessed by the expression of myogenin mRNA and by the binding of alpha-bungarotoxin to the nicotinic acetylcholine receptor. IGF-I receptor down-regulation was assessed by receptor binding and mRNA abundance. Although less potent than IGF-II, the [Leu27]IGF-II analog stimulated myogenin gene expression and acetylcholine receptor binding in concentrations at which the analog interacted with IGF-II receptors, but not significantly with IGF-I receptors. In IGF-I receptor down-regulation studies, IGF-II pretreatment significantly decreased binding of IGF-I to the IGF-I receptor and decreased IGF-I receptor mRNA, whereas the IGF-II analog had only minimal effects. Thus, in addition to the IGF-I receptor which has been previously found to signal IGF-induced myogenesis, these results implicate a role for the IGF-II receptor in this process. In contrast, IGF-I receptor down-regulation induced by IGF-II is mediated through IGF-I, but not IGF-II, receptors in muscle cells.

Mechanisms of insulin-like growth factor (IGF)-II-induced IGF-I receptor down-regulation in BC3H-1 muscle cells

Muscle is an important target tissue for insulin-like growth factor (IGF) action. We have previously demonstrated that treatment of myoblasts with IGF-II decreased IGF-I receptor biosynthesis and steady-state mRNA levels. In addition, muscle cell differentiation was associated with a marked increase in the expression and secretion of IGF-II followed by similar down-regulation of the IGF-I receptor, suggesting an autocrine role for IGF-II in this process. To explore further the mechanisms by which IGF-II decreases IGF-I receptor expression in BC3H-1 muscle cells, dose-response studies of IGF-I and -II treatment on the amount of IGF-I receptor mRNA were carried out. In addition, to determine whether IGF-II decreases IGF-I receptor expression by stimulating receptor protein degradation, pulse/chase experiments with [35S]methionine/cysteine were carried out. Both IGF-I and -II induced significant down-regulation of IGF-I receptor mRNA. At low concentrations, IGF-I was more potent than IGF-II in inhibiting IGF-I receptor mRNA accumulation, suggesting that IGF-I receptor down-regulation induced by IGF-II is mediated principally through the IGF-I receptor in these cells. In addition, IGF-II decreased IGF-I receptor expression by stimulating receptor protein degradation as demonstrated by pulse/chase analysis of metabolically labelled receptors. Thus, IGF-II induces IGF-I receptor down-regulation in muscle cells through multiple mechanisms, including decreasing IGF-I receptor mRNA and stimulating IGF-I receptor protein degradation.

Successful treatment with hydrochlorothiazide and amiloride in an infant with congenital nephrogenic diabetes insipidus

We report a 9-month-old male Latino infant with congenital nephrogenic diabetes insipidus (NDI) who presented with hypernatremic dehydration aggravated by severe gastroenteritis. Initially, the infant was managed with intravenous fluids followed by standard 20 cal/ounce formula and pharmacological therapy, resulting in normalization of his serum sodium level. While hydrochlorothiazide therapy alone or in combination with prostaglandin inhibitors or amiloride has been successful in children and adolescents, this is the first report of the successful use of hydrochlorothiazide and amiloride in an infant with congenital NDI.

Comparison of various agents in contrast enhancement of color Doppler flow images: an in vitro study

The commercially manufactured contrast agents, Echovist and Albunex, were compared with sonicated conventional agents, indocyanine green, 29% renografin-60, 0.9% normal saline and 25% mannitol in their ability to enhance color Doppler flow signals. In a pneumatically regulated pulsatile flow system, a glycerine, saline (0.9%) and sand (5 microns particle size) solution was imaged using a 2.5 MHz phased-array transducer. Four different flow velocities (0.40, 0.35, 0.30 and 0.25 m/s) as measured by color Doppler guided pulse Doppler were utilized. All color Doppler settings were kept constant throughout the study. Utilizing a power injector, four different volumes (1.0, 1.5, 2.0 and 2.5 mL) of each contrast agent were injected into the flow medium at various transducer angles (20, 30, 40 and 60 degrees) and various distances from the transducer (3.38, 5.5, 6.76 cm). For Echovist and Albunex, several concentrations varying from 2% to 100% were used. Keeping instrument settings constant, color flow areas obtained before and after each contrast injection were planimeterized and the percent increase in the color flow area computed and compared. At full (100%) concentration, 20 degrees transducer angle and a flow velocity of 0.40 m/s, the maximum increase in the color flow area was 568%, 251%, 180%, 110%, 71%, and 38% for Echovist, Albunex, sonicated indocyanine green, renografin, normal saline and mannitol, respectively. However, a significant reduction in the degree of color flow enhancement was observed, with decreases in the concentration of these agents, and increases in the Doppler beam incident angle or distance from the transducer. Increasing the flow velocity of the medium into which contrast was injected did not produce significant changes in the contrast enhancement effect for all agents except Echovist. Increasing the injection volume significantly increased the color flow area for sonicated agents but not for Echovist or Albunex. This preliminary in vitro study shows that the commercially manufactured contrast agents, Echovist and Albunex, are much superior to sonicated conventional contrast agents in the enhancement of color Doppler flow signals. Of the sonicated agents, indocyanine green had the best enhancement capability.

Growth factor receptor regulation in the Minn-1 leprechaun: defects in both insulin receptor and epidermal growth factor receptor gene expression

Leprechaunism is a disorder characterized by intrauterine growth retardation, distinctive dysmorphology, and extreme insulin resistance due to structural abnormalities of the insulin receptor (IR). In addition to the IR, it has been suggested that abnormalities of the other growth factor receptors may occur in this syndrome. Using fibroblasts from the Minn-1 leprechaun, we have now investigated the expression of three different growth factor receptor genes: the IR, the insulin-like growth factor-I receptor (IGF-IR), and the epidermal growth factor receptor (EGFR). In agreement with previous studies, we found decreased insulin binding to fibroblasts from the Minn-1 leprechaun. In these cells, the IR transcription rate was not decreased, and sequence analysis of the IR promoter region of the patient showed no abnormalities. Both single-stranded conformational polymorphism analysis (SSCP) and DNA sequencing confirmed a previously reported nonsense mutation in one of the patient's two IR alleles at exon 14. mRNA levels for the IR were markedly decreased, suggesting that IR mRNA turnover was enhanced. We then studied the expression of the closely related IGF-IR Ligand binding, mRNA content, and transcription rate were all normal. In contrast to the IGF-IR, when the EGFR was studied, ligand binding and mRNA content were markedly decreased. These studies therefore raise the possibility that the phenotypic expression of leprechaunism results from defects in the expression of both the IR and the EGFR.

Induction and peak gene expression of insulin-like growth factor II follow that of myogenin during differentiation of BC3H-1 muscle cells

Acting through hormonal and/or autocrine/paracrine mechanisms, the insulin-like growth factors (IGFs) stimulate the differentiation of muscle cells. Previous studies have suggested that one mechanism by which IGFs stimulate muscle cell differentiation is by increasing the expression of myogenin, a DNA binding protein that regulates the expression of muscle-specific genes. While exogenous IGF peptides increase myogenin mRNA, the role of endogenously produced IGF peptides in myogenin expression has not been established. In addition, the potential role of IGFs in regulating the expression of Id, a protein in myoblasts that can inhibit the action of myogenin-like peptides, is also unknown. In the present study, we have examined the kinetics of accumulation of myogenin and IGF-II mRNAs during differentiation of BC3H-1 mouse muscle cells and have explored the potential role of IGFs in regulating Id expression. During differentiation induced by serum withdrawal, induction of myogenin expression preceded that of IGF-II, the principal IGF peptide expressed by these cells. In addition, Id expression decreased within two hours in serum-free medium and was not affected by IGF treatment. Thus, these studies suggest that endogenously-produced IGF-II may stimulate muscle cell differentiation after both the decrease in Id and the induction of myogenin gene expression have occurred.

A monoclonal antibody to the T-cell receptor increases IGF-I receptor content in normal T-lymphocytes: comparison with phytohemagglutinin

The biological effects of the IGFs are mediated through interaction with specific cell surface receptors. It has been previously reported that mitogenic activation of T-lymphocytes by phytohemagglutinin (PHA) is associated with increased IGF-I receptor content. However, the mechanisms which regulate IGF-I receptor expression during T-lymphocyte activation are unknown. To explore further the regulation of IGF-I receptor expression in T-cells, we investigated IGF-I receptor content and mRNA abundance in T-lymphocytes after stimulation either by PHA or OKT-3, the latter being a monoclonal antibody directed against the CD-3 antigen of the T-cell receptor. IGF-I binding in T-cells demonstrated increased IGF-I receptor content after stimulation by both PHA and OKT-3. Peak binding was induced after 72 h of treatment with PHA and 48 h of treatment with OKT-3. Affinity cross-linking of 125I-IGF-I to T-cell membranes demonstrated a single approximately 130 kDa band which was increased after treatment with PHA or OKT-3. This band was inhibited by the addition of alpha-IR3, a monoclonal antibody to the IGF-I receptor. Both PHA and OKT-3 increased IGF-I receptor mRNA abundance with peak increases at 20 h and 60 h, respectively. Parallel increases in IGF-I receptor and beta-actin mRNA abundance were observed, consistent with previous studies demonstrating increased actin gene expression after T-cell activation. Thus, the increase in IGF-I receptor mRNA abundance markedly preceded the increase in IGF-I receptor content after PHA stimulation, but the increase in IGF-I receptor mRNA abundance followed the increase in IGF-I receptor content after OKT-3.(ABSTRACT TRUNCATED AT 250 WORDS)

Exogenous growth hormone inhibits bovine but not murine pituitary growth hormone secretion in vitro: evidence for a direct feedback of growth hormone on the pituitary

To test the hypothesis that one aspect of growth hormone (GH) regulation involves a direct effect of GH on its own secretion at the level of the pituitary, we evaluated the effects of human GH on basal and GH-releasing factor (GRF)-induced GH secretion in rat and bovine pituitary cell cultures. Both 4 h (acute) and 24 h (chronic) exposure of bovine pituitary cells to exogenous human GH significantly (p less than 0.001) reduced GH secretion. Acute treatment resulted in a decrease in GH secretion from 579 +/- 24 to 500 +/- 17 ng/ml 4 h (mean +/- SEM, n = 24) while chronic treatment resulted in a GH decrease from 595 +/- 21 to 483 +/- 17 ng/ml/4 h. In contrast, human GH treatment of rat somatotropes had no effect on basal GH secretion. GRF-stimulated GH secretion was not affected by either acute or chronic GH exposure in either species. These results demonstrate that there are species-specific differences in the ability of GH to regulate its own secretion and provide evidence for a direct inhibitory effect of GH at the level of the bovine pituitary.

Fibroblast growth factor inhibits insulin-like growth factor-II (IGF-II) gene expression and increases IGF-I receptor abundance in BC3H-1 muscle cells

Muscle is an important target tissue for insulin-like growth factor (IGF) action. We have previously reported that muscle cell differentiation is associated with down-regulation of the IGF-I receptor at the level of gene expression that is concomitant with an increase in the expression and secretion of IGF-II. Furthermore, treatment of myoblasts with IGF-II resulted in a similar decrease in IGF-I receptor mRNA abundance, suggesting an autocrine role of IGF-II in IGF-I receptor regulation. To explore further the role of IGF-II in IGF-I receptor regulation, BC3H-1 mouse muscle cells were exposed to differentiation medium in the presence of basic fibroblast growth factor (FGF), a known inhibitor of myogenic differentiation. FGF treatment of cells resulted in a 50% inhibition of IGF-II gene expression compared to that in control myoblasts and markedly inhibited IGF-II secretion. Concomitantly, FGF resulted in a 60-70% increase in IGF-I binding compared to that in control myoblasts. Scatchard analyses and studies of gene expression demonstrated that the increased IGF-I binding induced by FGF reflected parallel increases in IGF-I receptor content and mRNA abundance. These studies indicate that FGF may up-regulate IGF-I receptor expression in muscle cells through inhibition of IGF-II peptide expression and further support the concept of an autocrine role of IGF-II in IGF-I receptor regulation. In addition, these studies suggest that one mechanism by which FGF inhibits muscle cell differentiation is through inhibition of IGF-II expression.

Progestins induce down-regulation of insulin-like growth factor-I (IGF-I) receptors in human breast cancer cells: potential autocrine role of IGF-II

Insulin-like growth factor-I (IGF-I) receptors are present in breast cancer cells and may play a role in breast cancer cell growth. We have studied the effect of progestins on IGF-I receptors in T47D human breast cancer cells. T47D cells constitutively express high levels of progesterone receptors and are a model for studying the regulation of cellular functions by progestins. Treatment of T47D cells with either progesterone or the synthetic progestin promegestone (R5020) decreased IGF-I receptor content by approximately 50%, as measured by Scatchard analysis and receptor biosynthesis studies. In contrast to progestins, estradiol, dexamethasone, and dihydrotestosterone did not influence IGF-I receptor content. No effect of R5020 was seen after 12 h of incubation, a near-maximal effect was seen after 24 h, and greatest effects were seen after 72 h. R5020 decreased IGF-I receptor mRNA abundance, indicating that progestins acted at the level of gene expression. However, progestins also increased the secretion of IGF-II, a ligand for the IGF-I receptor. In contrast to IGF-II, T47D cells did not express IGF-I. The addition of exogenous IGF-II to T47D cells down-regulated both IGF-I receptor binding and IGF-I receptor mRNA abundance. This study indicates, therefore, that progestins regulate IGF-I receptors in breast cancer cells and suggests that this regulation occurs via an autocrine pathway involving enhanced IGF-II secretion.

Regulation of insulin-like growth factor (IGF) I receptor expression during muscle cell differentiation. Potential autocrine role of IGF-II

Muscle is an important target tissue for insulin-like growth factor (IGF) action. The presence of specific, high affinity IGF receptors, as well as the expression of IGF peptides and binding proteins by muscle suggest that a significant component of IGF action in this tissue is mediated through autocrine and/or paracrine mechanisms. To explore autocrine/paracrine action of IGFs in muscle, we studied the regulation of the IGF-I receptor and the expression of IGF peptides during differentiation of the mouse BC3H-1 muscle cell line. Differentiation from myoblasts to myocytes was associated with a 60% decrease in IGF-I receptor sites determined by Scatchard analysis. Analysis of mRNA abundance and protein labeling studies indicated that the decrease in IGF-I receptor sites was associated with similar reductions in IGF-I receptor gene expression and receptor biosynthesis. IGF-II peptide gene expression was detected in myoblasts and increased 15-fold with differentiation; the increase in IGF-II gene expression preceded the decrease in IGF-I receptor gene expression. In contrast, IGF-I peptide gene expression was low in myoblasts and decreased slightly with differentiation. To explore the potential role of endogenous IGF-II in the differentiation-associated decrease in IGF-I receptor expression, we investigated the effects of IGF-II treatment in myoblasts. The addition of IGF-II to undifferentiated myoblasts resulted in downregulation of the IGF-I receptor which was associated with decreased IGF-I receptor biosynthesis and decreased IGF-I receptor mRNA abundance. These studies suggest, therefore, that IGF-I receptor expression during muscle cell differentiation may be regulated, at least in part, through autocrine production of IGF-II.

A rapid and simple one step method for isolation of poly(A)+ RNA from cells in monolayer

A simple method was developed to isolate low abundance hormone receptor poly(A)+ RNA from cells in tissue culture. Adherent cells in tissue culture plates were directly released with proteinase K and solubilized in SDS. Oligo(dT) cellulose was directly added to the lysate to obtain poly(A)+ RNA. Yields and purity of the poly(A)+ RNA were comparable to other more lengthy methods. IGF-I receptor and insulin receptor mRNA could be detected on Northern blot without any degradation.

Preventing IUCD-related pelvic infection: the efficacy of prophylactic doxycycline at insertion

Most of the small increased risk in pelvic inflammatory disease (PID) associated with the intrauterine contraceptive device (IUCD) appears to be caused by bacterial contamination of the endometrial cavity at the time of insertion. This randomized clinical trial of 1813 women in Nairobi, Kenya, assessed the effectiveness of 200 mg of doxycycline given orally at the time of insertion in reducing the occurrence of PID. The rate of this infection in the doxycycline-treated group was 31% lower than that in the placebo-treated group (1.3 and 1.9%, respectively; RR 0.69; 95% CI 0.32 to 1.5). The rate of an unplanned IUCD-related visit to the clinic was also 31% lower in the doxycycline-treated group (RR 0.69; 95% CI 0.52 to 0.91). Although the significance level (P = 0.17) for the reduction is PID does not meet the conventional standard of 0.05, the results may be suggestive of an effect. Moreover, the reduction in IUCD-related visits (P = 0.004) not only represents an important decrease in morbidity but also substantiates the reduction found for PID. Further studies are needed to corroborate these results. Consideration should be given to the prophylactic use of doxycycline at the time of IUCD insertion as an approach to preventing PID and other IUCD-related morbidity.

Short term continuous intravenous infusion of growth hormone (GH) inhibits GH-releasing hormone-induced GH secretion: a time-dependent effect

We previously reported that GH secretion evoked by GHRH is inhibited after 5 days of treatment with im GH. This impaired pituitary response was associated with a significant increase in the serum concentration of insulin-like growth factor I (IGF-I). To dissociate the possible effects of circulating IGF-I from other effects of GH on the pituitary response to GHRH, we carried out the following study in eight normal men. A bolus injection of GHRH (1 microgram/kg, iv) was administered 2 h after the start of a 4-h continuous iv infusion of GH (180-micrograms bolus dose, then 3 micrograms/min in 150 mmol/L NaCl) or placebo (150 mmol/L NaCl). In addition, a similar injection of GHRH was given 4 h after the start of a 6-h continuous iv GH infusion (180-micrograms bolus dose, then 3 micrograms/min). During the GH infusions, plasma GH levels reached steady state concentrations in the 9-13 micrograms/L range. The mean GHRH-induced GH response was not significantly blunted during the 4-h infusions of GH [724 +/- 163 (+/- SE) vs. 1184 +/- 373 micrograms.min/L during placebo; P = 0.29], but was significantly inhibited during the 6-h GH infusions (226 +/- 105 micrograms.min/L; P = 0.04 vs. control). Serum IGF-I or plasma glucose did not change significantly throughout the GH infusions. During the 6-h GH infusions, plasma FFA increased to levels significantly above basal values during the last 3 h of the 6-h infusion. These results indicate that short term GH infusion inhibits the plasma GH response to GHRH in a time-dependent manner. The inhibition is not due to changes in circulating IGF-I and glucose concentrations. Fluctuations in hypothalamic somatostatin secretion, changes in lipid or other GH-dependent metabolites, paracrine effects of IGF-I, or a direct effect of GH itself may cause the impaired pituitary responsiveness during short term iv GH infusion.

Reproductive mortality in the United States: recent trends and methodologic considerations

Between 1975 and 1982, the annual number of deaths attributable to pregnancy and childbirth, induced abortion, and contraception in the United States declined from 1,083 to 751. The mortality rates for each of these components decreased by 35,89, and 35 per cent, respectively, and the overall reproductive mortality rate dropped by 35 per cent. The death rate due to pregnancy and childbirth is 25 times greater than that due to induced abortion and eight times more than that to contraceptive-associated mortality. In 1982 nearly 30 million women used contraceptives, while slightly fewer than four million women were pregnant to term. The decrease in contraceptive-associated mortality between 1975 and 1982 probably reflects a combination of safer contraceptives, fewer women using contraceptive methods that may not be safest for them, and an increasing number of sterilizations, which remove women from the group at highest risk of contraceptive-related mortality. Maternal mortality appears to be slowing its rate of decline, while induced abortion mortality has been very low since the legalization of abortion.

The effect of pulsatile administration, continuous infusion, and diurnal variation on the growth hormone (GH) response to GH-releasing hormone in normal men

To examine the relative effectiveness of GH-releasing hormone (GHRH) given either as multiple iv pulses or as a continuous iv infusion, we studied the GH response to a nearly equivalent total dose of GHRH-44 administered by both routes in a group of normal men. Further, in view of the pulsatile nature of GH secretion and its augmentation with sleep, we investigated whether a diurnal difference in GH release was present during chronic pulsatile administration of GHRH during day and night. Seven men received six GHRH pulses (1 microgram/kg, iv) at 2-h intervals during both day (0900-2100 h) and night (2100-0900 h), and four underwent nighttime placebo pulsing. Eight men received a daytime continuous GHRH infusion (0.15 microgram/kg X h for 5 h, followed by 0.75 microgram/kg X h for 5 h) and a separate 10-h placebo infusion. The GH response to a bolus dose of GHRH (1 microgram/kg, iv) was determined after both continuous GHRH and placebo infusions. No significant difference was found in the GH area response (mean +/- SEM) during total day and night GHRH pulsing periods (6095 +/- 1192 vs. 6506 +/- 1483 ng/min X ml; P = NS). GH secretion was blunted after the initial daytime GHRH pulse (P = 0.02), and only two of seven men had a GH increase after the second pulse; responsiveness was restored after the fourth pulse. In contrast, all subjects responded to the second nighttime GHRH pulse. During continuous GHRH infusions, GH secretion was unsustained and pulsatile. The incremental GH response to a single GHRH bolus dose was decreased after GHRH infusion compared to that after placebo (4.4 +/- 1.8 vs. 10.3 +/- 3.4 ng/ml; P less than 0.05). No difference was found in the total GH area response to a nearly equivalent dose of GHRH administered as either multiple pulses or continuous infusion followed by a single GHRH bolus dose. The apparent pulsatile nature of GH secretion during continuous GHRH infusion and the lack of a significant difference in the GH response to a nearly equivalent dose of GHRH administered as either multiple pulses or a continuous infusion suggest that GHRH need not be administered in a pulsatile manner to be an effective therapeutic agent for the stimulation of GH secretion in children with hypothalamic GHRH deficiency.

Exogenous growth hormone inhibits growth hormone-releasing factor-induced growth hormone secretion in normal men

Previous studies from this laboratory and by others in rats, monkeys, and humans support the concept that growth hormone (GH) can regulate its own secretion through an autofeedback mechanism. With the availability of human growth hormone-releasing factor (GRF), the possible existence of such a mechanism was reexplored by examining the effect of exogenous GH on the GH response induced by GRF-44-NH2 in six normal men (mean age, 32.4 yr). In all subjects the plasma GH response evoked by GRF-44-NH2 (1 microgram/kg i.v. bolus) was studied before and after 5 d of placebo (1 ml normal saline i.m. every 12 h), and then before and 12 h after 5 d of biosynthetic methionyl human GH (5 U i.m. every 12 h). The GH response to GRF (maximal increment over time 0 value) was significantly inhibited after GH treatment (0-1.3 vs. 2.3-11.2 ng/ml before treatment, P = 0.05), but was not significantly affected by placebo. This impaired pituitary response to GRF persisted for at least 24 h following exogenous GH treatment in two subjects who underwent further study. Serum somatomedin-C concentrations were significantly increased after 5 d of GH treatment (2.66-5.00 vs. 0.92-1.91 U/ml before treatment, P = less than 0.01). The impaired pituitary response to GRF may be mediated indirectly through somatomedin, somatostatin, by a direct effect of GH on the pituitary somatotropes, or by all of these mechanisms. These data suggest that after GH treatment, the blunted GH response to synthetic GRF is not solely a consequence of the inhibition of hypothalamic GRF secretion.

Testicular changes in gonadotropin-independent familial male sexual precocity. Familial testotoxicosis

A recently described form of male sexual precocity characterized by active Leydig cell differentiation and premature onset of spermatogenesis in the absence of pituitary gonadotropin stimulation has been termed familial testotoxicosis. The clinical and endocrine findings in the condition are consistent with an inherited intratesticular defect rather than central or true precocious puberty. In this report, testicular changes in biopsy specimens from a series of affected patients are presented. In all of the cases, Leydig cells demonstrated nuclear and cytoplasmic features characteristic of fully differentiated steroidogenic cells. Reinke crystals were absent. Germ cells at all stages of spermatogenesis were present, but there was evident disorganization of maturation. Spermatids exhibited a variety of structural abnormalities. Sertoli cells were characterized by complex cytoplasmic differentiation, Charcot-Böttcher crystals, and tight junction formation. The morphologic changes indicate premature differentiation of all of the major testicular cell types and are consistent with a distinctive type of intratesticular abnormality.

Pituitary gonadotropin-independent male-limited autosomal dominant sexual precocity in nine generations: familial testotoxicosis

A recently described, distinct form of male sexual precocity is characterized by premature Leydig and germinal cell maturation in the absence of pituitary gonadotropin stimulation. Analysis of a nine-generation kindred with at least 28 affected males supports sex-limited autosomal dominant transmission. Three boys, with precocious sexual development at 1 to 4 years of age, had low basal plasma gonadotropin values without pubertal-type pulsatility and a minimal rise in luteinizing hormone after acute stimulation with luteinizing hormone releasing factor or its potent analog D-Trp6-Pro9-NEt-LRF, distinguishing them from boys with true precocious puberty. Two affected adults had a mature luteinizing hormone response to LRF. Testicular biopsies showed a progression of abnormalities in the seminiferous tubules from childhood to maturity; in one adult this disorder was associated with marked oligospermia and selective elevation of plasma follicle-stimulating hormone. The findings are consistent with an inherited intratesticular defect. Furthermore, the majority of cases of familial male sexual precocity seem to be examples of this disorder rather than central or true precocious puberty.

Effect of growth hormone (GH)-releasing hormone (GRH) on plasma GH in relation to magnitude and duration of GH deficiency in 26 children and adults with isolated GH deficiency or multiple pituitary hormone deficiencies: evidence for hypothalamic GRH deficiency

Synthetic, amidated, 44 amino acid GH-releasing hormone ( GRH -44) was administered iv at a dose of 5 micrograms/kg to 20 patients with severe GH deficiency (GHD), 6 children and adolescents with partial GHD, and 6 non-GH deficient ( NGHD ) children and adolescents. The 17 patients with severe GHD that responded to GRH -44 had lower peak concentrations of plasma GH than the NGHD individuals (5.0 +/- 1.2 (SEM) vs. 27.2 +/- 3.5 ng/ml; P less than 0.0001). The children and adolescents with severe GHD tended to have higher peak GH responses to GRH -44 than the GHD adults (6.9 +/- 1.7 vs. 2.4 +/- 0.3 ng/ml) although the difference was not significant. The peak GH concentration was attained earlier in the GHD children and adolescents than in the GHD adults (28 +/- 4.7 vs. 69.3 +/- 13 min, P less than 0.004). There was a negative correlation between chronological age and peak plasma GH response to GRH in the children and adolescents with severe GHD (r = -0.758, P less than 0.02). Children and adolescents with partial GHD had a higher mean peak concentration of plasma GH (13. 1 +/- 1.8 ng/ml) than the children, adolescents, and adults with severe GHD (P less than 0.04), but one lower than the NGHD children and adolescents (P less than 0.05). In both severe and partial GHD the GH response to GRH was greater than that elicited by standard pharmacological tests. Serum somatomedin-C did not increase after a single pulse of GRH -44 in the 12 GHD patients studied. PRL increased minimally 30 min after 5 micrograms/kg iv GRH -44 in patients with multiple hypothalamic-pituitary hormone deficiencies but not in patients with isolated GHD or in NGHD individuals. The GH responses to GRH suggest that the majority of patients with isolated GHD as well as those with multiple hypothalamic-pituitary hormone deficiencies have deficiency of hypothalamic GRH . Lack of a GH response to a single pulse of GRH does not exclude GRH deficiency as priming of the somatotrope with multiple pulses of GRH may be necessary to rule out a hypothalamic defect in the nonresponders. The results of this study support the potential usefulness of GRH or its analogs in the diagnosis and treatment of selected patients with disorders of GH secretion.

Gonadotropin-independent familial sexual precocity with premature Leydig and germinal cell maturation (familial testotoxicosis): effects of a potent luteinizing hormone-releasing factor agonist and medroxyprogesterone acetate therapy in four cases

Four boys with sexual precocity are described in whom pubertal concentrations of plasma testosterone were associated with premature Leydig and germinal cell maturation without activation of the hypothalamic-pituitary gonadotropin unit. Extensive laboratory evaluation localized the source of testosterone secretion to the testes, and testicular biopsy revealed maturation of Leydig cells and spermatogenic elements. These events appear to be nongonadotropin-dependent in view of the absence of a pubertal pattern of pulsatile LH secretion, persistence of a prepubertal LH response to LRF even after long standing sexual precocity, prepubertal basal levels of LH and undetectable hCG, and the absence of biologically active LH-hCG by bioassay. Indirect immunofluorescence studies failed to demonstrate an immunoglobulin in the patients' sera that bound to Leydig cells or seminiferous tubules of normal adult human testes. The potent LRF analog D-Trp6-Pro9-NEt-LRF did not result in suppression of plasma testosterone or Leydig cell function even after 3 months of daily treatment in two patients which provides additional support of pituitary gonadotropin independence and of the lack of a direct effect of the analog on Leydig cell function. Oral medroxyprogesterone acetate treatment in two patients was associated with a striking decrease in both plasma testosterone concentration and height velocity. In the only patient in whom a complete family history could be obtained (three of four patients were adopted), sexual precocity was noted in the maternal grandfather. As this familial syndrome is characterized by a prepubertal hypothalamic-pituitary gonadotropin unit and apparent gonadotropin-independent maturation of Leydig cells and germinal epithelium, possibly due to an intratesticular inborn error, we propose the term "familial testotoxicosis" to describe this group of sexually precocious boys.

Synthetic human pancreas growth hormone-releasing factor (hpGRF1-44-NH2) stimulates growth hormone secretion in normal men

A synthetic replicate of human pancreas growth hormone-releasing factor, hpGRF1-44-NH2, (hpGRF44), a 44-amino acid amidated peptide, was administered to seven normal men. In addition to placebo, 4 subjects received 3 doses of hpGRF44 (0.5 microgram/kg, 5 micrograms/kg, 10 micrograms/kg), while one subject received 2 doses (5 micrograms/kg, 10 micrograms/kg) and 2 subjects received one dose (0.5 microgram/kg or 5 micrograms/kg), each as a rapid intravenous injection. A significant increase in circulating growth hormone (GH) was observed at each dose (0.5 microgram/kg, p = 0.05; 5 micrograms/kg, p less than 0.005; 10 micrograms/kg, p = 0.01) when compared to placebo, with equivalent maximal responses. At all doses studied a rise in plasma GH occurred within 5 min, with a peak response in most patients at 30-45 min. There were no associated changes in any of the other anterior pituitary hormones or insulin. Other than transient flushing and minimal changes in vital signs, no side effects were noted. The results of these studies support the potential usefulness of hpGRF44 for the assessment of GH secretion and reserve, and of this peptide or an analog as a therapeutic agent to stimulate GH release.

Effect of sodium chloride on longevity in mice

The effects of dietary sodium chloride on the longevity, body weight, and food consumption in a normotensive strain (A/J) of mice was studied. Four groups of 50 mice each were fed diets containing 0.5 (control group), 1.5, 2.5, and 4.5% sodium chloride. The mean life span was 115.2 wk in the control group, and 115.5, 110,5, and 116.1 wk for groups 2, 3, and 4, with no significant differences from the control group. No differences were present in food consumption, but a graded weight loss was present after the 20th wk, which persisted throughout the experiment. No significant effect of salt loading was demonstrable on the extravascular fluid movement in either acute experiments or in the long-term dietary sodium chloride groups.

Effect of age on transvascular fluid movement

Swellings of the mouse tail and ear were produced by subjecting them to subatmospheric pressures of minus 40 to minus 80 mmHg for 15-60 min. Increase in volume was measured volumetrically in the tail and gravimetrically in the ear. Blood volume increases in the tail, as measured with 51Cr erythrocytes, contributed a minor part of the fluid increase. Comparison of mice from 3 to 36 wk in age showed a large decrease of fluid movement with age, with major changes during the growth period. Study of permeability of the ear under decreased pressure,to intravenously administred Evans blue, showed no influence of age on permeability to the protein-bound dye. Measurement of transmission of the applied negative pressure through the skin, and of compliance of the tissues of the ear and tail in mice of different age groups, indicated that these factors were not responsible for the observed changes with age.