Biomedical subjects

C M Foster

Publications and source records attributed to C M Foster.

At least 19 recordsLinked to original sources

PubMed2000

Changes in serum inhibin, activin and follistatin concentrations during puberty in girls.

Serum concentrations of inhibin A, inhibin B, activin A and follistatin were determined using two-site enzyme-linked immunosorbent assays (ELISA) during pubertal ovarian development in 28 girls and five follicular phase women. Blood obtained every 15 to 20 min overnight was pooled for peptide determination. Serum inhibin A concentrations increased in mid puberty, exhibiting positive correlations with bone age (r = 0.527, P = 0.0016) and oestradiol concentrations (r = 0.581, P = 0.0005). Inhibin B concentrations peaked in mid puberty and declined thereafter, but remained greater than concentrations seen in prepubertal girls, and correlating positively with oestradiol (r = 0.362, P = 0.046) and follicle stimulating hormone (FSH) concentrations (r = 0.369, P = 0.038). Total activin A concentrations did not vary significantly across pubertal stages. Total follistatin concentrations, determined by radioimmunoassay, decreased with advancing puberty, exhibiting negative correlations with bone age (r = -0.634, P = 0.0001) and oestradiol concentration (r = -0.687, P = 0.0001). Follistatin concentrations determined by an ELISA specific for follistatin 288 were greatest in mid-pubertal girls, but concentrations in late puberty were less than those in early puberty. The free follistatin assay indicated that all circulating follistatin was activin-bound. These results suggest that significant changes in serum concentrations of FSH-regulatory peptides accompany the onset of puberty.

Activins↗

PubMed2000

Accumulation of ENOD2-like transcripts in non-nodulating woody papilionoid legumes.

Japanese pagodatree (Styphnolobium japonicum [L.] Schott) and American yellowwood (Cladrastis kentukea Dum.-Cours.) Rudd are the first woody, non-nodulating papilionoid legumes shown to possess putative early nodulin 2 (ENOD2) genes. ENOD2 cDNAs from Japanese pagodatree (807 bp) and American yellowwood (735 bp) have 75% to 79% sequence identity to ENOD2 sequences and encode deduced proteins that possess conserved ENOD2 pentapeptides (PPHEK and PPEYQ). Lower percentages of glucose and higher percentages of histidine and valine suggest that SjENOD2 and CkENOD2 are different from other ENOD2s. Hybridization analyses indicate the clones represent ENOD2 gene families of two to four genes in Japanese pagodatree and American yellowwood genomes, and ENOD2-like transcripts were detected in stems and flowers, as well as roots. Only roots of control species that nodulate, Maackia amurensis Rupr. & Maxim. and alfalfa (Medicago sativa), produced pseudonodules after treatment with zeatin or 2,3,5-triiodobenzoic acid, an auxin transport inhibitor. Accumulation of MaENOD2 transcripts was enhanced during the first 10 d of treatment, but 2,3,5-triiodobenzoic acid and zeatin enhanced transcript accumulation after 30 d in roots of Japanese pagodatree and American yellowwood. Characteristics that distinguish ENOD2 gene families in basal, non-nodulating woody legumes from other ENOD2 genes may provide new information about the function of these genes during symbiotic and non-symbiotic organ development.

Amino Acid Sequence↗

PubMed1998

Utilization of microhomologous recombination in yeast to generate targeting constructs for mammalian genes.

We have developed a new procedure utilizing microhomologous recombination in yeast to generate targeting constructs for producing targeted mutations in mice. This procedure is rapid and efficient, and should be directly applicable to all mammalian genes. Moreover, only minimal information about the locus being targeted is required. The feasibility of this approach was demonstrated by producing another allele of the mouse Tg737 polycystic kidney gene.

Alleles↗

PubMed1998

In pubertal girls, naloxone fails to reverse the suppression of luteinizing hormone secretion by estradiol.

Estradiol (E2) negative feedback on LH secretion was examined in 10 pubertal girls, testing the hypothesis that E2 suppresses LH pulse frequency and amplitude through opioid pathways. At 1000 h, a 32-h saline infusion was given, followed 1 week later by an E2 infusion at 13.8 nmol/m2 x h. During both infusions, four iv boluses of saline were given hourly beginning at 1200 h, and four naloxone iv boluses (0.1 mg/kg each) were given hourly beginning at 1200 h on the following day. Blood was obtained every 15 min for LH determination and every 60 min for E2 determination from 1200 h to the end of the infusion. E2 infusion increased the mean serum E2 concentration from 44+/-17 to 112+/-26 pmol/L (P < 0.01). The mean LH concentration between 2200-1200 h decreased from 3.19+/-0.89 to 1.99+/-0.65 IU/L (P = 0.014), and LH pulse amplitude decreased from 3.4+/-0.6 to 2.6+/-0.5 IU/L (P = 0.0076). Although there were 1.2 fewer pulses during E2 infusion compared to saline infusion, differences did not reach significance (P = 0.1; 95% confidence interval for the difference, -3.5, 1.1). Pituitary responsiveness to GnRH, assessed at the end of the infusion by administering 250 ng/kg GnRH iv, did not change during E2 infusion. The effect of naloxone blockade of opioid activity on LH secretion was determined by assessing the area under the curve (AUC) from 1200-1600 h. During saline infusion, the LH AUC was 1122+/-375 IU/L during saline boluses and 1575+/-403 IU/L during naloxone boluses (P = 0.39). When E2 was infused, the LH AUCs during saline and naloxone boluses were 865+/-249 and 866+/-250 IU/L, respectively. Thus, in pubertal girls: 1) E2 decreases the LH concentration and LH pulse amplitude; 2) the main site of negative feedback effect of E2 appears to be at the level of the hypothalamus; 3) an increase in LH secretion after naloxone administration could not be demonstrated in these girls and may depend on the maturity of the hypothalamic-pituitary-gonadal axis; and 4) opioid receptor blockade does not reverse the E2 inhibition of LH secretion even in the most mature girls. Thus, E2 suppression of LH secretion in pubertal girls appears to be mediated by a decrease in hypothalamic GnRH secretion that is independent of opioid pathways.

Adolescent↗

PubMed1997

Post-translational processing in the Golgi plays a critical role in the trafficking of the luteinizing hormone/human chorionic gonadotropin receptor to the cell surface.

Point mutations in the luteinizing hormone/human chorionic gonadotropin (LH/hCG) receptor have been shown to cause constitutive activation which results in precocious puberty in affected males. We introduced one of these mutations, Asp-556 --> Gly, into the rat LH/hCG receptor and demonstrated that the mutant receptor constitutively activated adenylate cyclase in transfected 293 T cells. The cell surface expression of the mutant receptor was lower than that of the wild type receptor. Pulse-chase studies showed that the 73-kDa precursor of both the mutant and wild type receptors was synthesized at comparable efficiencies. However, post-translational processing of the mutant receptor to the mature 92-kDa form, which has N-linked complex type oligosaccharide chains, was impaired. Sensitivity of the mutant receptor to peptide-N-glycanase F and endoglycosidase H, and insensitivity to sialidase indicated that the 73-kDa species represents the high mannose form that has not yet been trafficked through the medial and trans Golgi. Additionally, although the wild type receptor was palmitoylated, the mutant receptor was not. Although the high mannose 73-kDa species is capable of binding LH/hCG, our results show that post-translational processing in the Golgi is required for the mature 92-kDa receptor to reach the cell surface.

Amidohydrolases↗

PubMed1997

Risky behavior and risk in adolescents with IDDM.

PURPOSE: To determine: (1) the frequency of risky behaviors (alcohol and other drug use, smoking cigarettes, smokeless tobacco use, and unprotected intercourse); (2) the perception of general risks and diabetes-related risks from risky behaviors; (3) if perception of risk is related to engaging in risky behaviors; and (4) if perception of general risks and diabetes-related risks are influenced by age, gender, or race in adolescents with insulin dependent diabetes mellitus (IDDM). Decreasing risky behaviors in youth with IDDM is important because of their increased vulnerability to specific disease related physiologic and pathologic changes. METHODS: A descriptive, cross-sectional design was used. Data on risky behavior and perception of risk were obtained by self-report during a regularly scheduled clinic visit. One hundred and fifty-five adolescents between ages of 10-20 years participated. Correlational and student's t-test analyses were used to test relationships and group differences (age, race, gender). RESULTS: Thirty-nine percent of the sample reported alcohol use, 34% reported smoking cigarettes, 8% reported smokeless tobacco use, 10% reported drug use, and 29% reported unprotected intercourse. Perception of risk to peers from these behaviors was significantly higher (t = 8.1, df 153; p < .001) than risk to self. Females reported significantly lower (t = 3.08, df 52; p < .002) risk to self than males. There was no difference in perception of risk between youth who reported participating in risky behaviors (N = 38%) and those who did not (62%). Not surprisingly, the frequency of risky behavior increased with age (F = 15.46; p < .001). CONCLUSIONS: Compared to community samples of middle school children, our sample had lower rates for most risky behaviors. As with community samples, the physical risks were known and perceived to be higher for peers than self. Perception of risk was not related to self-reports of risky behaviors. The lower rate of risky behaviors might reflect the success of educational efforts directed toward diabetes management or may be due to later initiation of behaviors, especially if personal social development is delayed. Additional research is indicated in order to understand the timing and trajectory of risky behavior and whether or not perception of risk deters youth with IDDM from engaging in risky behavior.

Adolescent↗

PubMed1997

Acute effects of estradiol infusion and naloxone on luteinizing hormone secretion in pubertal boys.

We have shown previously in pubertal boys that testosterone (T) suppresses the nocturnal augmentation of luteinizing hormone (LH) secretion principally by decreasing LH pulse frequency. As T can be aromatised to estradiol (E2), and E2 effects on LH secretory dynamics may be separate from those of T, we examined the effects of acute E2 infusion on LH secretion in pubertal boys. Opioid receptor blockade has been reported to increase LH secretion after estradiol suppression in adult men, so we also examined whether naloxone might augment LH secretion during E2 treatment in pubertal boys. Starting at 1000 h, eight pubertal boys were given a 33 h saline infusion, followed 1 week later by an E2 infusion at 4.6 nmol/m2/h. During both infusions, four iv boluses of saline were given hourly beginning at 1200 h on the first day, and four naloxone iv boluses, 0.1 mg/kg each, were given hourly beginning at 1200 h on the second day. Blood was obtained every 15 min for LH, and every 60 min for T and E2, from 1200 h until the end of the infusion. Pituitary responsiveness to gonadotropin-releasing hormone (GnRH) was assessed after both infusions by iv administration of 250 ng/kg synthetic GnRH. Estradiol infusion increased the mean plasma E2 concentration from 23 +/- 4 to 46 +/- 6 pmol/L (P < 0.01) and suppressed mean plasma T from 4.9 +/- 1.4 to 3.0 +/- 3.5 nmol/L (saline vs. E2 infusion, P < 0.05). The overall mean LH was suppressed by E2 infusion from 3.7 +/- 0.5 to 2.2 +/- 0.4 IU/L (saline vs. E2 infusion, P < 0.01). LH pulse frequency was suppressed by 50%, whereas mean LH pulse amplitude was not different between saline and E2 infusions. Administration of naloxone did not alter the mean LH, LH pulse frequency, or amplitude during either saline or E2 infusions. Pituitary responsiveness to exogenous GnRH was similar during both infusions. These studies indicate that E2 produces its negative feedback in pubertal boys principally by suppression of LH pulse frequency, and naloxone does not reverse these suppressive effects. Thus E2 suppression of LH secretion is mediated by a decrease of hypothalamic GnRH secretion that is independent of endogenous opioid pathways.

Adolescent↗

PubMed1997

Changes in serum immunoreactive and bioactive growth hormone concentrations in boys with advancing puberty and in response to a 20-hour estradiol infusion.

Acceleration of linear growth during puberty is associated with increased GH secretion, although the relationship between growth and GH is complex. As GH exists as a family of isoforms, some of which may not be identified by immunoassay, there may be alterations in isoform secretion during pubertal maturation that result in increased growth. The changes in serum immunoreactive and bioactive GH concentrations across pubertal maturation were determined in 30 boys, aged 6.5-19.3 yr, with idiopathic short stature or constitutional delay of adolescence. Data were grouped as follows: 1) 6 prepubertal boys with bone age 7 yr or less; 2) 5 prepubertal boys with bone age of more than 7 yr, 3) 10 boys in early puberty; 4) 9 boys with mid- to late puberty. Blood was obtained every 20 min from 2000-0800 h. An equal aliquot of each serum sample was pooled for determination of GH by bio- and immunoassays. The mean serum immunoreactive GH concentration increased from 2.1 +/- 0.3, 1.8 +/- 0.3, and 2.9 +/- 0.5 micrograms/L in groups 1, 2, and 3, respectively, to a peak of 4.6 +/- 0.7 micrograms/L in group 4 (P < 0.05 vs. groups 1-3). The mean serum GH bioactivity was 48 +/- 13 micrograms/L in group 1 and declined to 39 +/- 8 and 31 +/- 3 micrograms/L in groups 2 and 3, increasing to a maximum of 64 +/- 15 micrograms/L in group 4 (P < 0.05 vs. group 3). The ratio of bioactive to immunoreactive GH suggests that the biopotencies of secreted isoforms do not increase during pubertal maturation. The role of E2 in increasing GH secretion was characterized in 8 additional early pubertal boys. Each boy received a saline infusion from 1000-0800 h, followed 1 week later by an infusion of E2 at 4.6 nmol/m2.h. Blood was obtained every 15 min from 2200-0800 h for GH and LH and every 60 min for E2 and testosterone. An equal aliquot of each overnight serum sample was pooled for insulin-like growth factor I (IGF-I) and GH by immuno- and bioassays. The mean serum LH concentration decreased from 5.0 +/- 0.9 to 2.3 +/- 0.6 IU/L (P < 0.01), and the E2 concentration increased from 22 +/- 4 to 81 +/- 26 pmol/L (P < 0.01) during saline and E2 infusions, respectively. Mean serum GH concentrations as measured by immunoassay were similar during both infusions (6.6 +/- 1.4 vs. 9.7 +/- 2.1 micrograms/L; saline vs. E2 infusion, respectively). In contrast, the mean serum GH concentration, as measured by bioassay, decreased from 48 +/- 10 micrograms/L during saline infusion to 16 +/- 3 micrograms/L during E2 infusion (P < 0.05). The mean serum IGF-I concentration also decreased significantly from 116 +/- 17 to 93 +/- 15 micrograms/L (saline vs. E2 infusion, respectively; P < 0.05). Thus, although mean overnight serum GH concentrations increase in late puberty, whether measured by immuno- or bioassay, an acute increase in E2 produces an acute decline in serum GH bioactivity and a lesser decline in the serum IGF-I concentration. These unexpected changes indicate that E2 may affect pubertal growth and GH secretion in a complex or biphasic manner depending on the context in which it is administered.

Adolescent↗

PubMed1996

Comparison of the neuroendocrine control of pubertal maturation in girls and boys with spontaneous puberty and in hypogonadal girls.

Puberty in boys is characterized by a nocturnal increase in mean LH concentration and LH pulse frequency. To determine whether similar mechanisms exist in girls, nocturnal serum LH concentrations were determined in 16 girls with constitutional delay of adolescence or idiopathic short stature who had or have subsequently been shown to have spontaneous puberty. Mean LH and LH pulse frequency and amplitude were analyzed in 3-h blocks and compared to those in 20 pubertal boys. Girls had an increase in mean LH concentration from 3.6 +/- 0.7 IU/L at 2000-2250 h to 4.8 +/- 0.9 IU/L at 0200-0450 h. LH pulse frequency increased from 0.27 +/- 0.11 pulses/girl.h at 2000-2250 h to 0.54 +/- 0.10 pulses/girl.h at 0200-0450 h. The increase in LH pulse amplitude, from 2.0 +/- 0.8 IU/L at 2000-2250 h to 4.1 +/- 1.1 IU/L at 2300-0150 h, did not achieve statistical significance because many girls had no pulses from 2000-2250 h. With advancing age, the day/night differences in LH concentration and LH pulse frequency disappeared in girls, but were preserved in boys of same pubertal stage. The effect of lack of estrogen on LH pulse characteristics was inferred by analyzing the LH profiles of 15 girls with gonadal dysgenesis who were age-matched to girls with spontaneous puberty. The girls with gonadal dysgenesis had an increase in mean LH concentration after 0200 h, but LH pulse frequency was rapid in all time blocks; the nocturnal increase in LH concentration was secondary to a significant increase in LH pulse amplitude. Older girls with gonadal dysgenesis had a loss of nighttime augmentation of LH secretion similar to that seen in girls with spontaneous puberty. These data suggest that the apparent slower LH pulse frequency encountered in girls with spontaneous puberty during waking hours may be related to estrogen suppression of LH pulse amplitude, which masks the true daytime LH pulse frequency. With or without pubertal estrogen exposure, developmental progression of LH secretion occurs more rapidly in girls than in boys. Thus, intrinsic sex differences exist in the timing and tempo of endocrine control of pubertal maturation between boys and girls.

Adolescent↗

PubMed1995

Comparison of growth hormone and insulin-like growth factor-I regulation of estradiol and progesterone production in human luteinized granulosa cells.

Growth hormone (GH) appears to affect the timing of puberty in children. The effects of GH on puberty may be related to direct GH action on ovarian function or may be mediated by IGF-I. To determine the likelihood that GH has direct effects on ovarian function, we compared the ability of GH and IGF-I to increase luteinized granulosa cell steroidogenesis in the absence and presence of gonadotropins. Cells were obtained from women undergoing in vitro fertilization for tubal disorders or male factor infertility and were placed in static culture. GH alone failed to alter progesterone or estradiol accumulation in the medium of cultured luteinized granulosa cells. IGF-I produced no increase in progesterone accumulation but increased estradiol accumulation 5.6-fold compared with cells treated with vehicle. The combination of GH and FSH produced an 0.83-fold increase in estradiol accumulation, whereas the combination of IGF-I and FSH resulted in a 2.9-fold increase in estradiol accumulation above FSH alone. Thus the direct effects of GH on granulosa cell steroid synthesis are modest compared with those of IGF-I. If GH has an effect on ovarian development at puberty, it is likely to be mediated by a GH-induced increase in circulating IGF-I.

Cells, Cultured↗

PubMed1994

Vaccination with the immediate-early protein ICP47 of herpes simplex virus-type 1 (HSV-1) induces virus-specific lymphoproliferation, but fails to protect against lethal challenge.

Assessing the immunobiological function of the individual proteins of herpes simplex virus-type 1 (HSV-1) continues to be important in elucidating virus-host interactions and for the rational design of subunit vaccines. In this report, the non-structural, immediate-early protein ICP47 of HSV-1 was examined for its ability to induce virus-specific immune responses. The ICP47 protein, when expressed from a recombinant vaccinia virus or when produced by cell-free, in vitro translation, induced a vigorous HSV-1-specific lymphoproliferative response. However, other common parameters of immunity such as neutralizing antibody, delayed-type hypersensitivity, and class I major histocompatibility complex (MHC)-restricted cytotoxic T lymphocytes (CTL) were not induced by ICP47. Moreover, mice immunized with vaccinia-expressed ICP47 were unable to survive lethal challenge with virulent HSV, indicating that in spite of its ability to induce significant HSV-1-specific lymphoproliferation, ICP47 appears unable to afford protective immunity in vivo. Possible reasons for this failure and the implications of these results in terms of vaccine design are discussed.

Animals↗

PubMed1994

Growth hormone bioactivity in girls with Turner's syndrome: correlation with insulin-like growth factor I.

We have recently developed a new bioassay for growth hormone (GH) in serum, which is based on the ability of GH to suppress glucose use in cultured murine adipocytes. We tested the hypothesis that bioactive GH (B-GH) concentrations would correlate better with the GH-dependent peptides, IGF-I, and IGF-binding protein-3 (IGFBP-3) than would GH determined by conventional RIA (RIA-GH). Twenty-five girls with Turner's syndrome were studied. The subjects had ages ranging from 4.8 to 15.9 y and height SD from the mean (SD score) ranging from -0.77 to -5.67. Blood samples were obtained every 15 or 20 min for 12 h overnight. For each girl, an equal aliquot of each overnight sample was pooled for determination of B-GH, RIA-GH, IGF-I, IGFBP-3, LH, FSH, and estradiol. Measurable estradiol concentrations were present in six girls and were sufficient to suppress gonadotropin concentrations in two girls, but they did not alter B-GH, RIA-GH, IGF-I, and IGFBP-3 concentrations compared with the age-matched girls without measurable estradiol concentrations. Hence, data for all girls were combined for subsequent regression analyses. RIA-GH did not correlate significantly with B-GH, IGF-I, or IGFBP-3. B-GH exhibited a significant correlation with IGF-I (r = 0.407, p < 0.05), and the correlation with IGFBP-3 was better than that for RIA-GH (r = 0.355 versus 0.064, B-GH and RIA-GH, respectively). None of the B-GH, RIA-GH, IGF-I, or IGFBP-3 concentrations had a significant correlation with height SD score or height velocity SD score.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1994

Nocturnal naloxone fails to reverse the suppressive effects of testosterone infusion on luteinizing hormone secretion in pubertal boys.

LH secretion is maximal during the night in pubertal boys, and testosterone (T) administration blunts this nocturnal rise of LH. We have previously shown that in pubertal boys, the acute negative feedback effects of T infusion on LH secretion during the daytime cannot be reversed by opioid receptor blockade. To determine whether the nocturnal secretion of LH in early puberty is regulated by endogenous opioid pathways, we determined whether naloxone during the night affected LH secretion or T-mediated suppression of LH secretion. Seven pubertal boys (bone age, 11-13.5 yr) were given a control infusion of saline, followed 1 week later by an infusion of T at 960 nmol/m2.h for 41 h starting at 2000 h. During both saline and T infusions, six iv boluses of saline were given hourly beginning at 2400 h on the first day, and six iv boluses of naloxone (0.1 mg/kg each) were given hourly beginning at 2400 h on the second day. Starting at 2200 h, blood was obtained every 15 min for LH and every 30 min for T determinations for 14 h each night. Pituitary responsiveness was assessed at the end of each study night by i.v. bolus administration of 250 ng/kg synthetic GnRH. T infusion increased the mean T concentration 6-fold (P < 0.0001) and suppressed the mean plasma LH concentrations from 5.6 +/- 0.6 to 3.8 +/- 0.6 IU/L (P < 0.01). The nocturnal augmentation of LH secretion was suppressed by the infusion of T, and this suppression was not reversed by naloxone. The mean nighttime plasma LH (2400-0600 h) was 8.1 +/- 1.1 IU/L during the control saline infusion and 5.1 +/- 0.6 IU/L during the T infusion (P < 0.01). The mean LH level was 4.0 +/- 0.7 IU/L during the administration of naloxone boluses concomitantly with the T infusion, not significantly different from that during the T infusion. Likewise, LH pulse frequency during the same time period was decreased by T infusion from 0.6 +/- 0.1 to 0.36 +/- 0.04 pulses/boy.h (P < 0.05), and it was unaltered by coadministration of naloxone (0.38 +/- 0.12 pulses/boy.h). Naloxone administration during the saline infusion did not increase either the mean plasma LH concentration (7.5 +/- 0.7 IU/L; P = NS vs. saline control) or the LH pulse frequency (0.69 +/- 0.1 pulses/boy.h; P = NS vs. saline control). Pituitary responsiveness to GnRH was similar on each of the 4 nights during either saline or T infusions.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed1993

Bioactivity of human growth hormone in serum: validation of an in vitro bioassay.

GH, in clinical practice, is determined by RIA, but RIA estimates may not accurately reflect serum GH bioactivity. The available measures of GH bioactivity lack either sensitivity, specificity, or a physiologically relevant end point. The objective of this research was to develop a physiologically relevant GH bioassay which would not only measure the bioactivity of purified GH preparations, but would also have sufficient sensitivity to measure GH bioactivity in human serum. The method consisted of incubating murine 3T3-F442A adipocytes in serum-free medium containing BSA, 14C-glucose, and increasing concentrations of GH or test materials for 24 h, followed by measurement of conversion of glucose to lipid. Interference by nonspecific serum factors was reduced by the addition of 10 micrograms/liter insulin, 25 nM dexamethasone, and 37 nM estradiol to the medium. In the presence of 10 micrograms/liter insulin, 50 micrograms/liter insulin-like growth factor-1 did not alter the ability of GH to suppress lipid accumulation. Epinephrine and glucagon could suppress lipid accumulation but only at concentrations greatly in excess of the physiological range in serum. Twenty two thousand dalton hGH produced dose-dependent suppression of lipid accumulation which was linear between 0.625 and 10 micrograms/liter (r = 0.926; P = 0.0001) with a half-maximal response of 3.0 +/- 0.2 micrograms/liter (n = six experiments). The intra- and interassay coefficients of variation were 7% and 19%, respectively. The assay was specific for GH since addition of human PRL produced suppression of lipid accumulation only at concentrations where contamination of the preparation by GH became a significant factor. ACTH also suppressed lipid accumulation but only at doses of 1000 micrograms/liter or greater. Human placental lactogen and hLH, hFSH, and hTSH did not cross-react with GH in this assay. Addition of human serum did not alter the slope of ED50 of the GH dose-response curve. Pools of serum from prepubertal and pubertal boys and girls, subjects treated with arginine or insulin, a diabetic girl, and a boy with gigantism who had a serum GH content of 80 micrograms/liter by RIA and 40 micrograms/liter by bioassay, produced dose response curves parallel to that of the GH standard curve. Serum from patients with hypopituitarism did not produce significant suppression of lipid accumulation in any assay. Recovery of 5 micrograms/liter GH added to human serum was 94%. Twenty thousand dalton GH also suppressed lipid accumulation in this assay, but was 2-fold less potent than 22,000 dalton GH.(ABSTRACT TRUNCATED AT 400 WORDS)

Adipose Tissue↗

PubMed1993

Luteinizing hormone pulse characteristics in early pubertal boys are the same whether measured by radioimmuno- or immunofluorometric assay.

We tested the hypothesis that the improved sensitivity of immunofluorometric (IFMA) assays will lead to an increase in the number of detectable LH pulses compared to RIA in early pubertal boys, in whom LH secretion is low. To test this hypothesis we determined plasma LH concentrations in six pubertal boys (bone age, 12-16 yr) by IFMA and compared the results to RIA data reported previously. Each boy was given an infusion of saline, followed 1 week later by an infusion of testosterone (T; 960 nmol/h) for 33 h starting at 1000 h. Starting at 1200 h, blood was obtained every 15 min for LH determinations (RIA and IFMA) and every 30 min for T measurements. At the end of both studies, responses to GnRH (250 ng/kg) were assessed. The assay sensitivities for LH by RIA and IFMA (Delfia hLH Spec Pharmacia Diagnostics ENI, Columbia, MA) were 1.0 and 0.05 IU/L, respectively. LH pulses were identified by three independent pulse detection programs: Detect, Cluster, and Kushler-Brown. The correlation for LH values as measured by RIA and IFMA was highly significant (r = 0.81). There was a poor correlation between LH values determined by IFMA and RIA when LH values within 4 times the SD of each assay sensitivity were compared (r = 0.08; P = NS). T infusion suppressed LH pulse frequency by 40% and 66%, as determined by RIA and IFMA, respectively (P = NS). Using the Detect program, during the complete study in all 6 boys, 117 pulses of LH were identified by RIA and 93 by IFMA (79% ratio of detection IFMA/RIA). During saline infusion there were 73 vs. 69 LH pulses (94%), while during T infusion there were 24 vs. 44 LH pulses (55%), as detected by IFMA vs. RIA, respectively. Administration of naloxone did not accelerate LH pulse frequency during T infusion, as determined by either method. Changes in pituitary responses to exogenous GnRH also showed similar trends of augmentation by T infusion by both methods. We conclude that the use of IFMA does not lead to the anticipated increase in the detectability of LH pulsatility. Actually, fewer LH pulses were identified by IFMA in this group of boys. We speculate that this is due to the increased specificity of the IFMA assay. More significant was the finding that the physiological interpretation of the effects of T and naloxone on LH pulse frequency and responses to GnRH did not change whether LH was measured by RIA or IFMA.

Adolescent↗

PubMed1992

Evaluation of gonadotropin responses to synthetic gonadotropin-releasing hormone in girls with idiopathic hypopituitarism.

We hypothesized that prepubertal girls with gonadotropin deficiency would produce less follicle-stimulating hormone (FSH) in response to synthetic gonadotropin-releasing hormone (GnRH) than would gonadotropin-sufficient children. To test this hypothesis, we performed 103 GnRH tests serially in 21 children who had idiopathic hypopituitarism with growth hormone deficiency. We tried to predict whether puberty would occur in the 17 girls with bone ages of 8 years or less. Of these 17 girls, 4 failed to have spontaneous secondary sexual characteristics by age 16 1/2 years, and 12 had spontaneous complete pubertal development. One girl had incomplete pubertal maturation with partial gonadotropin deficiency; her results were combined with those of the girls who had no spontaneous pubertal development. With increasing bone age, the girls with complete pubertal development had a decrease in the increment of FSH released in response to GnRH, although basal gonadotropin concentrations did not change. For GnRH tests performed at bone ages of 8 years or less, basal luteinizing hormone (LH) values did not differ between girls with complete puberty and those with absent or incomplete puberty. However, basal FSH and the incremental response of LH and FSH to GnRH were greater in those with complete puberty. Only two girls with prepubertal bone ages at the time of testing, who subsequently had complete puberty, had incremental FSH responses to GnRH that were less than 5 IU/L. Individual incremental LH responses to GnRH did not discriminate well between groups. None of the girls with adrenocorticotropic hormone deficiency, either originally or subsequently, had spontaneous puberty, but 4 of 12 girls with thyrotropin deficiency, either originally or subsequently, had complete puberty. We conclude that a significant increase in GnRH-stimulated FSH suggests that spontaneous pubertal development will occur in girls with idiopathic hypopituitarism. However, a low FSH response to GnRH may not be diagnostic of gonadotropin deficiency.

Child↗

PubMed1992

Acute effects of testosterone infusion and naloxone on luteinizing hormone secretion in normal men.

To evaluate the role of endogenous opioid pathways in the acute suppression of LH secretion by testosterone (T) infusion in men, we studied eight normal healthy volunteers who received a saline infusion, followed 1 week later by a T infusion (960 nmol/h) starting at 1000 h and lasting for 33 h. After 2 h of infusion (both saline and T), four iv boluses of saline were given hourly, and after 26 h of infusion, four hourly iv boluses of naloxone were given. Blood was obtained every 15 min for LH and every 30 min for T. T infusion increased the mean plasma T concentration 2.1-fold (18.7 +/- 2.1 to 39.5 +/- 3.5 nmol/L, saline vs. T infusion, P < 0.01). The mean plasma LH concentration was 7.9 +/- 0.5 IU/L during the saline control study and was decreased to 6.9 +/- 0.6 IU/L by the infusion of T (P < 0.05). LH pulse frequency was similar during both saline and T infusions (0.48 +/- 0.02 vs. 0.43 +/- 0.04 pulses/man.h, saline vs. T infusion). The mean LH pulse amplitude decreased from 4.3 +/- 0.4 IU/L during saline infusion to 3.3 +/- 0.2 IU/L during T infusion (P < 0.05). The administration of naloxone increased the mean plasma LH concentration significantly during saline infusion (7.6 +/- 0.4 to 10.0 +/- 0.9 IU/L, saline vs. naloxone boluses, P < 0.01), but not during T infusion (6.9 +/- 0.6 vs. 7.3 +/- 0.6 IU/L). LH pulse frequency increased significantly after the administration of naloxone during both saline and T infusions (0.54 +/- 0.04 to 0.71 +/- 0.08 pulses/man.h, saline vs. naloxone boluses during saline infusion, and 0.46 +/- 0.08 to 0.60 +/- 0.07 pulses/man.h during T infusion; P < 0.05). LH pulse amplitude was suppressed by T infusion, but administration of naloxone did not reverse this suppression. The mean amplitude of the LH response to exogenous GnRH (250 ng/kg) was decreased by T infusion from 48 +/- 13.5 to 31.2 +/- 8.5 IU/L (P < 0.01). Therefore, in men, the administration of naloxone increases LH pulse frequency during both saline and T infusions, but the acute suppression of LH pulse amplitude seen with T infusion was not reversed by naloxone. This pattern contrasts sharply with the effects of T infusion in pubertal boys, as elucidated by our earlier studies. The negative feedback effects of T on LH secretion are primarily hypothalamic in early pubertal boys and change to pituitary suppression in men.

Adult↗

PubMed1991

MHC II-restricted, CD4+ cytotoxic T lymphocytes specific for herpes simplex virus-1: implications for the development of herpetic stromal keratitis in mice.

Herpetic stromal keratitis (HSK) appears to represent an immunopathological reaction in which CD4+ T cells play a prominent role. However, the exact immunopathological mechanism(s) utilized by CD4+ T cells during HSK remains to be elucidated. In this study, the presence of cytotoxic CD4+ T lymphocytes in the cervical and retropharyngeal lymph nodes of Balb/c mice experiencing HSK was investigated. After in vitro depletion of CD4+ or CD8+ T cells with specific monoclonal antibodies and complement treatment, the cytotoxic functions of the remaining T cell populations were assayed by using target cells expressing either MHC Class I or both Class I and Class II. Our results showed the presence of a distinct cytotoxic T lymphocyte (CTL) population which was CD4+ and demonstrated lytic activity in a Class II-restricted fashion. Furthermore, these cells were able to develop into efficient effector CTL in the absence of CD8+ T lymphocytes as assessed by in vivo depletion experiments. Immunohistochemical methods were also utilized to show the presence of both CD4+ lymphocytes and I-A+ cells in the corneal tissues during HSK. These findings support the notion that direct lysis of infected Class II-bearing corneal cells by CD4+ CTL might be one of the mechanisms leading to stromal immunopathology in herpetic infections.

Animals↗