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Biomedical subjects

M E Geffner

Publications and source records attributed to M E Geffner.

At least 37 records · Page 2Linked to original sources
PubMed1995

Insulin-like growth factor I resistance in immortalized T cell lines from African Efe Pygmies.

Previous investigations suggested that resistance to GH was the cause of short stature of African Pygmies. Because many of the actions of GH are mediated by insulin-like growth factor I (IGF-I), we sought to determine whether Pygmy tissue was responsive to IGF-I. An initial effort to obtain HTLV-II-transformed T lymphoblast cell lines resulted in a single cell line that showed complete resistance to both IGF-I and GH in a clonal proliferation assay as well as decreased IGF-I binding. In the current study, we examined T cell lines from seven Efe Pygmy subjects, three neighboring Lese farmers, and six American controls and quantified clonal responses to IGF-I, GH, and insulin. The T cell lines from the Efe Pygmies were all completely resistant to the growth-promoting actions of IGF-I concentrations less than 250 micrograms/L and GH concentrations less than 500 micrograms/L. The Lese population, with whom there is admixture with the Efe population, showed heights and clonal responses to IGF-I and GH intermediate between those of Pygmies and American controls. The Pygmy T cell lines showed reduced clonal proliferation in response to high insulin concentrations known to act through the IGF-I receptor. These findings indicate that genetic IGF-I resistance is present in the T cell lines of Efe Pygmies and suggest that unresponsiveness to IGF-I may be responsible for their short stature.

Adult↗
PubMed1994

Continuous insulin infusions in neonates: pharmacologic availability of insulin in intravenous solutions.

Continuous insulin infusion is sometimes used in very low birth weight infants with glucose intolerance. We studied the availability of insulin to the neonate by means of a laboratory-simulated clinical infusion under both flushed and non-flushed conditions. Although loss of insulin was noted with both solutions (0.5 U/ml), under the nonflushed condition only 55.9% of the prescribed dose for the first 2 hours was delivered before the delivery rate of the flushed system, 71.4%, was approached. These findings have implications for neonatal insulin administration.

Adsorption↗
PubMed1994

Divergent dimerization properties of mutant beta 1 thyroid hormone receptors are associated with different dominant negative activities.

Syndromes of resistance to thyroid hormones are caused by mutations in the T3-binding domain of the c-erbA beta thyroid hormone receptor gene. The S receptor (deletion of THR332) is a potent dominant negative protein cloned from a kindred with generalized resistance to thyroid hormones. The G-H receptor (ARG311HIS) has compromised dominant negative function and was found in both normal individuals and in a patient with severe pituitary resistance to thyroid hormones. We have investigated the mechanism responsible for the difference in receptor phenotypes by analyzing the binding of S and G-H receptors to thyroid hormone response elements with electrophoretic mobility shift analysis. Wild-type human c-erbA beta 1 (WT), S, and G-H receptors were synthesized in reticulocyte lysate, reacted with a thyroid hormone response element consisting of a direct repeat with 4 base pairs (DR+4; AGGTCA CAGG AGGTCA), and the products analyzed by gel shift. G-H receptor homodimerization was greatly impaired; G-H formed predominantly monomeric complex compared with monomeric and homodimeric WT complexes. The G-H receptor was able to form heterodimeric complexes with cellular thyroid hormone receptor auxiliary protein (TRAP) factors including the human retinoid X receptor-alpha. When TRAP was limiting, the levels of G-H heterodimeric complex were 2- to 3-fold reduced compared with WT receptor. In contrast to the WT and G-H receptors, the S receptor formed almost exclusively homodimeric complex with DR+4; the approximate ratio of S:WT:G-H homodimeric complexes at equivalent concentrations of receptors was 60:20:1. A measurable increase (1.2- to 2.6-fold) in heterodimeric complex formation was observed with the S receptor relative to WT when TRAP was at limiting concentration. As reported previously by others, thyroid hormone significantly reduced the WT homodimeric complex with DR+4. There was no effect on the S homodimeric complex. Finally, the WT, S, and G-H receptors formed different complexes with the element consisting of an inverted repeat with 5 base pairs (IR+5; AGGTCA ACAGT TGACCT) and the IR element (AGGTCA TGACCT), which were differently regulated by thyroid hormone. The S receptor bound as a homodimer with IR+5, whereas the WT receptor bound as a homodimer only with thyroid hormone. No homodimeric complex formed with IR+5 and the G-H receptor. Qualitatively similar results were observed with the IR element. We conclude that the ARG311HIS mutation severely perturbs the homodimerization and, to a much less degree, heterodimerization functions of the c-erbA beta 1 receptor. Furthermore, the THR332 deletion mutation augments homodimerization of the c-erbA beta 1 receptor. These results indicate that different mutations in the c-erbA beta 1 thyroid hormone receptor have divergently affected dimerization activities which seem to influence the level of dominant negative activity in man.

Amino Acid Sequence↗
PubMed1994

Growth hormone induces resistance to the mitogenic action of insulin through local IGF-I. Studies in normal and Pygmy T-cell lines.

Growth hormone (GH) and insulin have both mitogenic and metabolic actions. The growth-promoting effects of GH in vivo are thought to be mediated by insulin-like growth factor-I (IGF-I), whereas the metabolic effects of GH are thought to be either direct or mediated by factors other than IGF-I. In previous studies using HTLV-II-transformed T-lymphoblast cell lines established from normal individuals, we have shown that GH preincubation induces resistance to the growth-promoting (mitogenic) action of insulin. In this study, using T-cell lines from 3 American control subjects, 1 African control subject, and 1 African Pygmy (the latter previously shown to be resistant to the growth-promoting actions of both IGF-I and GH), we examined the role of local IGF-I in the mediation of GH-induced resistance to the mitogenic action of insulin. In these studies, we quantified the stimulation of T-cell colony formation in response to insulin in the presence and absence of either GH or IGF-I.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Insulin-like growth factor-I unresponsiveness in an Efe Pygmy.

The cause of short stature in African Pygmies is unknown, but some evidence suggests that they are GH resistant. Since IGF-I mediates many actions of GH, we sought to determine if Pygmy tissue is responsive to IGF-I. We established HTLV-II-transformed cell lines from 1 Efe Pygmy, 1 African control, and 3 American controls, and quantified in vitro colony formation in response to IGF-I, GH, and insulin, and assessed IGF-I receptor binding. The Pygmy T-cell line showed no clonal responsiveness following stimulation with physiologic concentrations of IGF-I or any concentration of GH, but responded normally to insulin. IGF-I binding studies showed no binding to the Pygmy T-cell line with normal binding to control cells. The primary abnormality in this Pygmy T-cell line is IGF-I resistance at the receptor level with secondary GH resistance.

Adult↗
PubMed1993

The influence of luteinizing hormone and insulin on sex steroids and sex hormone-binding globulin in the polycystic ovarian syndrome.

OBJECTIVE: To examine the relationship between hyperinsulinemia, sex hormone-binding globulin (SHBG), and body mass index (BMI) on LH-induced hyperandrogenemia in patients with polycystic ovarian syndrome (PCOS). DESIGN: Insulin responses during an oral glucose tolerance test (OGTT) were assessed in 25 consecutive women with PCOS and 20 control women matched for BMI. Insulin responses and sensitivity (SI) were also determined using a frequently sampled intravenous glucose tolerance test (IVGTT). SETTING: The clinical research center at a university medical center. MAIN OUTCOME MEASURES: Serum LH, SI, and basal, peak, and area under the curve (AUC-insulin responses) were determined and correlated with SHBG, androstenedione (A), T, and free T concentrations. RESULTS: Compared with controls, the AUC-insulin response during OGTT was greater in PCOS, with an average increase of 44%. During IVGTT, AUC-insulin response was also significantly higher in PCOS versus controls, with an average increase of 53%. In addition, SI was reduced in PCOS versus controls with an average decrease of 53%. The average differences in oral- and intravenous-glucose-induced hyperinsulinemia and in insulin sensitivity between PCOS and controls were relatively constant across the entire physiological range of BMI. In PCOS, baseline LH showed strong positive correlations with baseline A and T. However, there were no significant correlations between either basal, peak, or AUC-insulin response during OGTT and IVGTT with basal T or A concentrations or between insulin and androgen levels measured at 30-minute intervals throughout the OGTT. However, basal, peak, and AUC-insulin responses during OGTT were strongly correlated with fasting SHBG binding capacity. CONCLUSIONS: These data are consistent with the hypothesis that hyperinsulinemia in PCOS influences the biologically active component of T by lowering SHBG concentrations while having little apparent impact on LH-induced secretion of androgens in vivo.

Administration, Oral↗
PubMed1993

An arginine to histidine mutation in codon 311 of the C-erbA beta gene results in a mutant thyroid hormone receptor that does not mediate a dominant negative phenotype.

We have examined the c-erbA beta thyroid hormone receptor gene in a kindred, G.H., with a member, patient G.H., who had a severe form of selective pituitary resistance to thyroid hormones (PRTH). This patient manifested inappropriately normal thyrotropin-stimulating hormone, markedly elevated serum free thyroxine (T4) and total triiodothyronine (T3), and clinical hyperthyroidism. The complete c-erbA beta 1 coding sequence was examined by a combination of genomic and cDNA cloning for patient G.H. and her unaffected father. A single mutation, a guanine to adenine transition at nucleotide 1,232, was found in one allele of both these members, altering codon 311 from arginine to histidine. In addition, a half-sister of patient G.H. also harbored this mutant allele and, like the father, was clinically normal. The G.H. receptor, synthesized with reticulocyte lysate, had significantly defective T3-binding activity with a Ka of approximately 5 x 10(8) M-1. RNA phenotyping using leukocytes and fibroblasts demonstrated an equal level of expression of wild-type and mutant alleles in patient G.H. and her unaffected father. Finally, the G.H. receptor had no detectable dominant negative activity in a transfection assay. Thus, in contrast to the many other beta-receptor mutants responsible for the generalized form of thyroid hormone resistance, the G.H. receptor appeared unable to antagonize normal receptor function. These results suggest that the arginine at codon 311 in c-erbA beta is crucial for the structural integrity required for dominant negative function. The ARG-311-HIS mutation may contribute to PRTH in patient G.H. by inactivating a beta-receptor allele, but it cannot be the sole cause of the disease.

Adolescent↗
PubMed1993

In vitro insulin-like growth factor-I, growth hormone, and insulin resistance occurs in symptomatic human immunodeficiency virus-1-infected children.

Poor growth is a common feature of symptomatic children (Centers for Disease Control stage P2) infected with human immunodeficiency virus-1 (HIV-1). However, several previous studies have failed to show any relationship between serum hormone levels and poor growth. To assess the roles of hormone deficiency and hormone resistance in the development of poor growth in HIV-1-infected children, we studied six asymptomatic Centers for Disease Control stage P1 [height SD score = 0.01 +/- 1.0 (mean +/- SD)], 10 P2 (height SD score = -2.0 +/- 1.0), and six short, normal children (height SD score = -2.4 +/- 1.2). Mean weight:height SD scores were similar in all three groups, suggesting that gross nutritional status did not differ between groups. There were no significant differences between groups with respect to mean plasma levels of IGF-I, thyroid hormones, TSH, and cortisol. As an index of hormone sensitivity, we quantified in vitro colony formation of erythroid progenitor cells, isolated from peripheral blood of study subjects, in response to IGF-I, growth hormone (GH), and insulin. P2 subjects had a quantitative mean reduction in erythroid progenitor cells colony formation in response to IGF-I of 32% compared with P1 subjects (p = 0.001 by analysis of variance) and 21% compared with controls (p = 0.006); in response to GH of 21% compared with controls (p = 0.015); and in response to insulin of 35% compared with P1 subjects (p = 0.038) and 34% compared with controls (p = 0.004).(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1993

Growth hormone induces insulin resistance in Laron dwarf cells via lactogenic receptors.

GH is the hormone primarily responsible for regulating body size within the genetic program. While GH has pleiotropic actions on cellular growth and metabolism, most of its effects are believed to be mediated by a single GH receptor. This receptor is not functional in tissues from patients with Laron dwarfism. We used human T-cell leukemia virus-immortalized T-lymphoblast cell lines from Laron dwarfs and normal individuals to examine the mechanism of GH-induced insulin resistance at the cellular level. GH (5-500 micrograms/L) caused a profound decrease in the sensitivity of normal T-lymphoblasts in response to all insulin concentrations (P < 0.0001 vs. insulin alone); pretreatment with GH and GH receptor antibody significantly improved sensitivity to all concentrations of insulin (P = NS vs. insulin alone). Preincubation with GH and PRL receptor antibody was associated with partial improvement in insulin sensitivity (P = 0.004 vs. insulin alone). Thus, in normal T-cell lines, the major pathway of GH-induced insulin resistance appears to be directed by the GH receptor, with a smaller effect mediated through the PRL receptor. While T-cell lines from Laron dwarfs do not respond to GH in clonal proliferation assays, GH (50 and 100 micrograms/L) caused profound insulin resistance in these cells (P = 0.008 and P < 0.0001, respectively, vs. insulin alone). GH receptor antibody did not abrogate this effect at any insulin concentration (P = NS vs. insulin alone), but there was partial restoration of insulin sensitivity when GH and PRL receptor antibody were coincubated (P = 0.0069 vs. insulin alone). Thus, in Laron T-cell lines, PRL and perhaps other lactogenic receptors appear to mediate GH-induced insulin resistance. The kinetics of GH-induced insulin resistance in Laron T-cells were also distinct from the pattern seen in normal T-cells, and unlike in normal cells, GH had no effect on insulin-like growth factor-I-induced clonal expansion of Laron T-cell lines (P = NS vs. insulin-like growth factor-I alone). These results provide evidence for an alternative pathway of GH action revealed in cells lacking classical growth responses to GH.

Adolescent↗
PubMed1993

Dominant and nondominant negative C-erbA beta 1 receptors associated with thyroid hormone resistance syndromes augment 12-O-tetradecanoyl-phorbol-13-acetate induction of the collagenase promoter and exhibit defective 3,5,3'-triiodothyronine-mediated repression.

C-erbA receptors and v-erbA have been shown to functionally interact with 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-inducible gene expression. These proteins enhance trans-activation by c-jun, and the c-erbA receptors in the presence of thyroid hormone repress TPA and c-jun induction of transcription. Also, v-erbA can abrogate T3-mediated repression. We have examined how dominant negative (S and CL) and nondominant negative (G-H) receptors cloned from various patients with thyroid hormone resistance syndromes affect expression of the collagenase promoter induced with TPA. The CL receptor (ARG315HIS mutation) has a 2-fold reduction in T3-binding affinity compared with human c-erbA beta 1 wild-type (WT) receptor, whereas the G-H receptor (ARG311HIS) and S receptor (deletion, THR codon 332) have T3-binding affinities reduced by 100-fold and greater than 100-fold, respectively. These mutant receptors were cotransfected with a collagenase promoter (-1200 to +63 base pairs) chloramphenicol acetyltransferase reporter gene (Col-CAT) into COS-7 cells. Levels of CAT reporter gene expression after transient transfection were determined in the presence or absence of 3-10 nM T3 and the presence or absence of 100 nM TPA. Unoccupied CL receptor and G-H and S receptors stimulated TPA-induced Col-CAT expression 1.5- to 9-fold. The CL receptor with thyroid hormone totally repressed TPA induction of the collagenase receptor. In the presence of thyroid hormone, the enhancing effects by S and G-H receptors on TPA-induced Col-CAT expression were unaffected and minimally diminished, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1992

Insulin and IGF-I stimulate normal and virally transformed T-lymphocyte cell growth in vitro.

We used normal and HTLV-II-transformed T-lymphocytes as target cells to study clonal proliferative responses to physiologic and supraphysiologic concentrations of insulin and IGF-I. Responses of both growth factors were measured in the presence and absence of alpha IR-3, and IGF-I receptor-blocking antibody. A biphasic response to insulin was noted in all cell lines with the first peak [78 +/- 6.6% (mean +/- SE) above control] occurring at 1.4 or 1.6 nmol/liter and a second peak (84 +/- 4.9% above control) occurring at 18.0 nmol/liter. Following preincubation with alpha IR-3, the overall clonal profile in response to insulin was significantly reduced [F(7,56) = (10.4, p < .0001] as a result of blunting at high physiologic and supraphysiologic insulin concentrations, i.e., > or = 1.6 nmol/liter. As expected, the overall clonal profile in response to IGF-I was blocked by alpha IR-3 [F(4,32) = 11.6, p < .0001]. These data show that insulin at both physiologic and supraphysiologic concentrations, as well as IGF-I, stimulate virally transformed T-lymphoblast growth. The significant inhibition of growth responses to high concentrations of insulin and to IGF-I by alpha IR-3 suggests mediation of these effects through the IGF-I receptor. Similar studies were performed using freshly isolated, phytohemagglutinin (PHA)-stimulated T-lymphocytes. The overall response to insulin was significantly reduced compared to the profile of transformed T-lymphoblasts [F(7,70) = 4.9, p = .0002] as a result of blunting at physiologic insulin concentrations < 1.8 nmol/liter. In response to IGF-I, the clonal profile of PHA-stimulated T-lymphocytes was slightly reduced compared to that of virally transformed T-lymphoblasts [F(4,40) = 3.4, p = .0174]. Thus, both insulin and IGF-I receptor-effector mechanisms are involved in the growth of virally transformed T-lymphoblasts, whereas the IGF-I receptor-effector mechanism appears to play a more significant role in the growth of normal, mitogen-activated T-lymphocytes.

Cell Division↗
PubMed1992

Bromocriptine and Triac therapy for hyperthyroidism due to pituitary resistance to thyroid hormone.

Although a number of patients with generalized resistance to thyroid hormone have been treated with bromocriptine (Brc), only one previously reported patient with nontumoral TSH-mediated hyperthyroidism, presumably due to pituitary resistance to thyroid hormone (PRTH), has been successfully treated with bromocriptine (Brc). In addition, several studies suggested that the T3 analog 3,5,3'-triiodothyroacetic acid (Triac) may control hyperthyroidism in patients with PRTH. In the current study a patient with PRTH diagnosed at age 15 yr underwent separate therapeutic trials with Brc and Triac, during which time physical parameters, thyroid function tests, systolic time intervals (STI), and oxygen consumption (VO2) were measured. On Brc therapy (12.5 mg/day), heart rate decreased (108 to 72/min), TSH decreased (5.7 to 1.2 mU/L), T3 decreased (9.9 to 1.7 nmol/L), free T4 decreased (205 to 21 pmol/L), STI lengthened (left ventricular ejection time, 0.389 to 0.405 s), and VO2 did not change (164 to 162 mL/min). We found no significant clinical improvement with a maximal dose of Triac (2.1 mg/day), only minimal reduction in goiter size; mild decreases in T3 (9.9 to 6.7 nmol/L), free T4 (205 to 113 pmol/L), and TSH (5.7 to 5.4 mU/L); no change in STI (left ventricular ejection time, 0.389 to 0.401 sec); and an increase in O2 consumption (VO2, 164 to 209 mL/min). Thus, the results favor Brc as effective therapy for this patient with PRTH.

Adolescent↗
PubMed1992

Permanent diabetes without serological evidence of autoimmunity after transient neonatal diabetes.

OBJECTIVE: To describe a probable association between TNDM and subsequent permanent IDDM. RESEARCH DESIGN AND METHODS: A longitudinal follow-up of a single case from birth to 12 yr of age was conducted analyzing sequential OGTTs, ICAs, AIAs, anti-GAD antibodies, and other organ-specific and nonspecific antibodies. RESULTS: A small-for-gestational-age infant developed hyperglycemia at 20 h of age and required insulin therapy for the 1st 14 wk of life (TNDM). Transient hyperglycemia and ketonuria were noted again at age 2 yr 10 mo during an intercurrent illness, but OGTT was normal; and ICA, AIA, anti-GAD65 and anti-GAD67 antibodies, antithyroid microsomal, anti-gastric parietal cell, antiadrenal, antisteroidal, and antinuclear antibodies were negative 3 wk later. At age 9 yr, hyperglycemia returned and persisted in the setting of hypoinsulinemia; ICA, AIA, anti-GAD65 and anti-GAD67 antibodies, and other organ-specific and nonspecific antibodies were again negative. Insulin therapy was initiated and has been maintained over 3 yr of follow-up. CONCLUSIONS: Our case is the fifth reported with permanent diabetes occurring after resolution of TNDM. The etiology of permanent diabetes in this setting is unknown but, unlike classical IDDM, appears unrelated to autoimmunity in our patient. The true frequency of this association remains unknown.

Autoantibodies↗
PubMed1992

Insulin and insulin-like growth factor-I responsiveness in polycystic ovarian syndrome.

OBJECTIVE: To assess insulin and insulin-like growth factor I (IGF-I) action in women with polycystic ovarian syndrome (PCOS). DESIGN: Hyperinsulinemia was determined by measuring the insulin responses during a 2-hour oral glucose tolerance test (OGTT). Quantification of in vivo insulin action was determined by a frequently sampled intravenous (IV) OGTT with minimal modeling analysis. In vitro sensitivity to insulin at physiological and supraphysiological concentrations and to IGF-I was assessed by examining colony formation of two hematopoietic cell populations, burst-forming units of the erythroid line (BFU-E) and human leukemia virus immortalized T-cell lines. (The proliferative responses of BFU-E, a primary tissue explant, are presumably conditioned by factors in the immediate blood-borne environment, whereas proliferative responses of T-cell lines are presumed to reflect intrinsic target-cell hormone sensitivity.) SETTING: Tertiary care research institution. PATIENTS: Eight patients (4 obese and 4 nonobese) with PCOS and three healthy women for reference controls. RESULTS: Nonobese (P less than 0.04) and obese patients with PCOS (P less than 0.01) both demonstrated significant hyperinsulinemia after OGTT. In vivo insulin resistance was observed in both nonobese (P less than 0.03) and obese PCOS subjects (P less than 0.01) using frequently sampled IV OGTT. Both nonobese (P less than 0.03) and obese patients with PCOS (P less than 0.01) had blunted in vitro clonal responses of BFU-E, with normal T-cell line clonal responsiveness to physiological levels of insulin and normal BFU-E and T-cell line clonal responses to IGF-I. CONCLUSIONS: These findings demonstrate the following in both nonobese and obese patients with PCOS: (1) there is in vivo hyperinsulinemia and resistance to insulin action on glucose disposal; (2) with BFU-E, there is in vitro resistance to the mitogenic action of insulin but normal responsiveness to IGF-I; and (3) there is normal in vitro mitogenic responsiveness of T-cell lines to both insulin and IGF-I. The intrinsically normal mitogenic responsiveness to insulin and, especially to IGF-I, whether or not under the influence of the bloodborne milieu, provides a mechanism whereby hyperinsulinemia could directly contribute to the ovarian abnormalities that characterize PCOS.

Adult↗
PubMed1991

Pediatric germ cell and human chorionic gonadotropin-producing tumors. Clinical and laboratory features.

Germ cell tumors may cause various aberrations in pubertal development. In prepubertal boys, these tumors may secrete human chorionic gonadotropin, resulting in precocious puberty. Human chorionic gonadotropin and alpha-fetoprotein are both useful as germ cell tumor markers in the diagnosis and detection of recurrence. Pregnancy-specific beta 1-glycoprotein, another oncoplacental antigen, has been used as a tumor marker for trophoblastic neoplasms, but not previously for human chorionic gonadotropin-producing tumors associated with precocious puberty. Patients with germ cell tumors may also have abnormal karyotypes. Herein, we describe six male pediatric patients with germ cell tumors and pubertal derangements seen during an 8-year period. We confirm the high incidence of associated sexual precocity, the usefulness of alpha-fetoprotein, human chorionic gonadotropin, and pregnancy-specific beta 1-glycoprotein as tumor markers in the diagnosis and follow-up of these patients, and the occurrence of sex chromosomal abnormalities.

Adolescent↗