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Biomedical subjects

Z Hochberg

Publications and source records attributed to Z Hochberg.

At least 91 records · Page 5Linked to original sources
PubMed1991

A mutation in CYP11B1 (Arg-448----His) associated with steroid 11 beta-hydroxylase deficiency in Jews of Moroccan origin.

Steroid 11 beta-hydroxylase (P450c11) deficiency (failure to convert 11-deoxycortisol to cortisol) causes less than 10% of cases of congenital adrenal hyperplasia in most populations, but it is relatively frequent in Jews of Moroccan origin. P450c11 is encoded by the CYP11B1 gene which is located on chromosome 8q22 along with a homologous gene of unknown function, CYP11B2. To identify mutations in CYP11B1 associated with 11 beta-hydroxylase deficiency in Moroccan Jews, oligonucleotides were used that selectively amplified portions of CYP11B1 in polymerase chain reactions without amplifying CYP11B2. Sequence analysis of amplified fragments from one patient revealed a single base substitution in exon 8, codon 448 from CGC (arginine) to CAC (histidine). This residue is within the "heme binding" peptide that contains a cysteine that is a ligand to the heme group. The equivalent of Arg-448 is found in every known eukaryotic P450, and therefore it seems likely that a mutation of this residue would adversely affect enzymatic activity. 11 of 12 affected alleles from six Moroccan Jewish families carried the mutation in codon 448. This mutation is not normally present in CYP11B2 and thus appears to have arisen in CYP11B1 as a true point mutation rather than a gene conversion.

Adrenal Hyperplasia, Congenital↗
PubMed1991

Twenty-four-hour profile of plasma growth hormone-binding protein.

In experimental animals each burst of GH pulse is followed by a wave of receptor turnover and an increase in serum GH-binding protein (GH-BP), which occurs 60 min after the GH peak. The present report describes the 24-h profile of plasma GH-BP and its correlation to GH pulsatility in normal individuals. Four normally growing children in early puberty were the subjects of this study. Blood was withdrawn continuously for 24 h in 30-min fractions. Pulse analysis of both GH and GH-BP was performed by the Pulsar program. The vast majority of the GH pulses were accompanied by GH-BP pulses within 30 min. Correlation of plasma GH levels to GH-BP levels on the residual series above the smoothed baseline of all 172 individual samples was r = 0.447 (P less than 0.001). Thus, plasma GH-BP levels fluctuate rapidly in relation to the pulsatility of plasma GH levels. This may influence the GH disappearance rate and brings into question some of the deconvolution calculations of GH secretory impulses.

Carrier Proteins↗
PubMed1991

Decreased serum growth hormone-binding protein in patients with liver cirrhosis.

The recently characterized GH-binding protein (GH-BP) has an amino acid sequence identical to the extracellular domain of the GH receptor. Serum GH-BP reflects the amount of GH receptors, and the liver seems to be their main source. To evaluate the effect of liver disease on GH-BP, 52 patients with liver cirrhosis were studied. Serum GH-BP was measured by a binding assay with dextran-coated charcoal separation. Levels of GH-BP were correlated against the clinical state, assessed by Pugh's score. The GH-BP of 31 Pugh's class A patients was 9.7 +/- 0.5%/50 microL serum, and that of 21 Pugh's class B and C patients was 7.2 +/- 0.5%/50 microL serum compared to 11.3 +/- 0.5%/50 microL serum in age-matched controls. GH-BP correlated negatively with Pugh's score and serum bilirubin, and positively with serum albumin. It did not correlate with serum liver enzymes or serum insulin-like growth factor-I. Scatchard analysis of GH binding to the GH-BP revealed similar binding affinities in Pugh's A, B, and C patients and controls. The binding capacity in cirrhosis was significantly lower than that in controls. We conclude that serum GH-BP is controlled mainly by the liver and can provide an additional measure of disease severity in liver cirrhosis.

Adult↗
PubMed1991

The effect of human growth hormone therapy on GH binding protein in GH-deficient children.

Previous studies have described the close similarity of the GH binding protein to the liver membrane GH receptor. Since GH regulates its own liver receptors, we examined the effects of short- and long-term hGH therapy on GH binding protein in children with GH deficiency. Six GH-deficient children received their first hGH dose ever, and the pharmacodynamics of serum GH was followed for 12 h, along with measurements of GH binding protein activity. Over the first 6 h, serum GH and GH binding protein activity exhibited a parallel increase, followed by gradual decrease. At 8 h, some of the patients exhibited an apparent second peak in GH binding protein, despite the continuous decrease in serum hGH. During the period of hGH treatment, serum GH binding protein increased progressively over a period of 6 months. In a second uncontrolled group of 7 GH-deficient patients who had been treated with hGH for 30-36 months, GH binding protein activity was also significantly higher than pretreatment values. We suggest that the short-term pharmacodynamic changes probably represent the endogenous turnover of the GH receptor, whereas the elevated GH binding protein activity on hGH treatment may reflect up-regulation of the GH receptor.

Body Height↗
PubMed1991

Seasonal variation in growth during growth hormone therapy.

Seasonal variation in growth of normal children has been well described, although the mechanism by which it occurs has not been elucidated. The growth of 52 growth hormone-deficient children treated with synthetic human growth hormone was analyzed. A similar seasonal variation was observed, with mean (+/- SEM) peak growth occurring in the summer (8.2 +/- 0.3 cm/y) and winter (7.7 +/- 0.2 cm/y), and trough growth occurring in the autumn (6.9 +/- 0.3 cm/y). Forty-seven percent of subjects grew minimally during the autumn, and only two children showed peak growth in that season. Individual variations between maximal and minimal growth seasons amounted to 3.5 +/- 0.3 cm/y. The seasonal pattern was statistically significant for the group as a whole, for the prepubertal subgroup, and for the boys. The variation persisted when the first year of treatment was excluded to avoid bias of the initial growth spurt. The season of onset of therapy did not affect total growth during the first year. The demonstration of a seasonal pattern in growth of these children suggests that the seasonal variation may be mediated by peripheral rather than central factors. Paired clonidine-provoked growth hormone levels and an integrated concentration of 24-hour growth hormone levels and serum levels of insulinlike growth hormone I measured in a control group of normally growing children were also analyzed and showed no seasonal variation. This further suggests that peripheral rather than central factors are responsible for the seasonal variation in children's growth.

Adolescent↗
PubMed1990

The molecular basis of hereditary 1,25-dihydroxyvitamin D3 resistant rickets in seven related families.

Hereditary 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] resistant rickets (HVDRR) is an autosomal recessive disease caused by target organ resistance to the action of 1,25(OH)2D3, the active form of the hormone. The defect in target cells is heterogenous and commonly appears to be a mutation in the gene encoding the vitamin D receptor (VDR). We have studied cultured skin fibroblasts and Epstein-Barr virus transformed lymphoblasts of seven family branches of an extended kindred having eight children affected with HVDRR. We have previously shown that cells from three affected children in this group contain an "ochre" nonsense mutation coding for a premature stop codon in exon 7 within the steroid-binding domain of the VDR gene. In the current studies, we found that cells from affected children failed to bind [3H]1,25(OH)2D3 and had undetectable levels of VDR as determined by immunoblots using an anti-VDR monoclonal antibody. Measurement of VDR mRNA by hybridization to a human VDR cDNA probe showed undetectable or decreased abundance of steady-state VDR mRNA. Parents, expected to be obligate heterozygotes, showed approximately half the normal levels of [3H]1,25(OH)2D3 binding, VDR protein, and mRNA. The mutation at nucleotide 970 (counting from the mRNA CAP site) results in the conversion of GTAC to GTAA, which eliminates an Rsa I restriction enzyme site and facilitates identification of the mutation. We found that polymerase chain reaction (PCR) amplification of exons 7 and 8 from family members and subsequent Rsa I digestion allows detection of the specific genotype of the individuals. When Rsa I digests of PCR-amplified DNA are subjected to polyacrylamide gel electrophoresis, children with HVDRR exhibit a homozygous banding pattern with loss of an Rsa I site. Parents exhibit a heterozygotic DNA pattern with detection of both normal and mutant alleles. In summary, our data show that the genetic abnormality is a point mutation within the steroid-binding domain of the VDR in all seven related families with HVDRR. Analysis of restriction fragment length polymorphism at the 970 locus of PCR-amplified DNA fragments can be used to diagnose this mutation in both affected children and parents carrying the disease.

Blotting, Northern↗
PubMed1990

Water, electrolyte, and endocrine homeostasis in infants with bronchiolitis.

Twenty-two of 23 consecutive infants with bronchiolitis, 5.5 +/- 3.5 mo of age, showed a 1.9 +/- 1.4% increase in body weight, increased urinary osmolality of 737 +/- 193 mmol/L with low plasma osmolality of 275 +/- 4 mmol/L, and markedly elevated plasma antidiuretic hormone (ADH) levels of 114 +/- 225 pg/mL. Increased ADH, which usually suppresses plasma renin activity, was associated with increased plasma renin activity of 11-55 ng angiotensin 1/mL/h (normal for age less than 10 ng angiotensin 1/mL/h). Hyperaldosteronism was evident from the low fractional excretion of sodium of 0.27 +/- 0.2% and high fractional excretion of potassium of 21 +/- 15%. Serum sodium concentrations were normal. All of the pathologic findings returned to normal when the bronchiolitis subsided. A control group of 10 infants with nonrespiratory febrile illness did not show any of the above abnormalities. Thus, bronchiolitis of infancy is characterized by both increased ADH secretion and hyperreninemia with secondary hyperaldosteronism, which induce water retention but counterbalance each other with respect to serum sodium. Increased ADH secretion as well as increased plasma renin activity are not "inappropriate," but rather suggest a response to the perception of hypovolemia by intrathoracic receptors. We therefore conclude that the clinical management of bronchiolitis requires close monitoring of body wt and plasma osmolality-urinary osmolality relationship; serum sodium levels may be misleading.

Blood Volume↗
PubMed1990

Alterations of human growth hormone binding by rat liver membranes during hypo- and hyperthyroidism.

Hypothyroid rats treated with human GH (hGH) were partially refractory to the latter's effects. The present study was undertaken to investigate the role of hypo- and hyperthyroidism on the GH receptor. Seven-week-old rats were rendered either hypothyroid, by methimazole, or hyperthyroid, by a daily overdose of T4, during weeks 7-14 of life. Livers were homogenized and overlaid on sucrose discontinuous density gradient. Removal of endogenous ligand from the receptor was performed by exposing the membranes to MgCl2. hGH was used with excess ovine PRL to characterize somatogenic specific binding. Lactogenic specific binding was calculated by subtracting somatogenic specific binding from the total specific binding. Creatine kinase was also measured in homogenized livers. Liver membranes of the hypothyroid rats showed a significant decline in somatogenic and lactogenic binding of hGH. This was true for both the free unoccupied binding sites and total binding after dissociation of the endogenous ligand. Replacement of T4 for 2 weeks restored hGH binding to control values. Hyperthyroid rats had high somatogenic and lactogenic hGH binding. Creatine kinase activity decreased significantly in liver homogenates of hypothyroid rats, was restored by T4 replacement, and increased significantly in hyperthyroid rats. Thus, lactogenic and somatogenic receptors are directly related to the thyroid status in vivo.

Animals↗
PubMed1990

The interrelationship of growth hormone (GH), liver membrane GH receptor, serum GH-binding protein activity, and insulin-like growth factor I in the male rat.

Indirect evidence suggests that the serum GH-binding protein (GH-BP) is related and possibly derived from the GH-receptor. GH, through its specific receptor, is the major regulator of insulin-like growth factor I (IGF-I) synthesis. The present study was undertaken to correlate serum GH-BP activity with liver plasma membrane GH receptors and their effects on serum IGF-I concentration during spontaneous pulsation of rat (r)GH in the normal male rat and after continuous delivery of human (h)GH to hypophysectomized male rats. In the first set of experiments, 45-day-old male rats were decapitated at 15 min intervals for 4 h. Serum GH-BP levels fluctuated with a 60 min lag behind the rGH levels. IGF-I pulsated over a 3-fold concentration range. IGF-I peak levels coincided with one of the rGH peaks, but its periodicity was longer than 3 h. Taken together with our previous studies on the turnover of the GH receptors, we suggest that each GH surge results in individual pulse-related turnover wave of receptor internalization and recycling. This is accompanied by a parallel increase in serum GH-BP activity. The GH and the receptor wave are responsible for an individual secretion pulse of IGF-I. In the second set of experiments male rats were hypophysectomized at 35 days of age. Four days later osmotic minipumps were implanted for continuous delivery of hGH. After 6 days of hGH treatment the rats were killed, blood was collected for hGH, GH-BP, and IGF-I determination, and the livers were removed. Plasma membranes were prepared, and lactogenic and somatogenic binding of [125I]hGH was evaluated. Removal of endogenous ligand was performed by exposing the membranes to 3 M MgCl2. Continuous administration of hGH induced a dose-dependent increase in liver membrane lactogenic and somatogenic binding. Parallel to that increase, serum GH-BP also increased in a dose-dependent manner, and the correlation between serum GH-BP and the liver membrane receptor was significant. Furthermore, hGH induced a dose-dependent increase in IGF-I concentration. There was a close correlation between IGF-I concentration and liver somatogenic receptors. It is concluded that up-regulation of the liver membrane GH receptors is accompanied by increased GH-BP and IGF-I. In both the pulsation experiment and the continuous infusion experiment, GH-BP closely correlated with the liver membrane GH receptor.

Animals↗
PubMed1990

A new and convenient assay of growth hormone-binding protein activity in human serum.

The recent discovery of a GH-binding protein (GH-BP) in human serum has important implications for the distribution, metabolism, and physiological activity of human GH (hGH). In this report we describe an accurate, simple, and rapid assay for measuring GH-BP in human serum, based on the dextran-coated charcoal technique for separating bound from free hGH. The present method reduces the degree of dissociation of the GH-BP complex during the separation procedure, thus increasing accuracy, allows routine use of small working volumes of sera, and can be practically used for running large scale assays. Binding of [125I]hGH to human serum GH-BP, identified and characterized by this procedure, was time, temperature, and dose dependent; the binding was highly specific for hGH and with a high affinity (Ka, 1.08 +/- 0.19 x 10(9) L/mol). Preliminary results, expressed as percent specifically bound [125I]hGH corrected for endogenous hGH, indicate that the mean GH-BP activity in 50 microL sera from normal adult men and women was 11.32 +/- 0.45%. Significantly lower values were obtained in sera of infants, 3 days after birth (1.65 +/- 0.15%), and in short-statured children with normal GH secretion (7.38 +/- 0.22%). In patients with liver cirrhosis GH-BP levels decreased to 5.93 +/- 1.14%. The availability of a simple and convenient procedure for large scale determination of GH-BP coupled with the suggestion that this protein can reflect the GH receptor provides us with an indirect means for assessing changes in GH receptor activity in various physiological and pathological conditions.

Adult↗
PubMed1990

Prenatal diagnosis of vitamin D-dependent rickets, type II: response to 1,25-dihydroxyvitamin D in amniotic fluid cells and fetal tissues.

Vitamin D-dependent rickets type II (VDDR-II; hereditary resistance to 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]), an autosomal recessive genetic disease that results from a failure to respond to 1,25-(OH)2D3, is characterized by severe rickets, hypocalcemia, growth retardation, and high prevalence of alopecia. We used amniotic fluid cells in the 17th week of gestation to detect VDDR-II in fetuses at risk for the defect. First, we demonstrated in cells obtained from 15 control pregnancies the presence of a specific high affinity 1,25-(OH)2D3 receptor (Kd = 0.3 x 10(-11) mol/L; maximal number of binding sites, 6.1 fmol/mg protein) and 1,25-(OH)2D3-induced 25-hydroxyvitamin D3-24-hydroxylase activity (up to 30-fold increase). Amniotic fluid cells from a woman who had already given birth to a child with VDDR-II contained receptors that bound [3H]1,25-(OH)2D3 normally and responded to 1,25-(OH)2D3 stimulation with a 10-fold increase in 24-hydroxylase activity. The fetus was, therefore, judged unaffected, and a normal baby girl was born. At the age of 16 months she did not demonstrate clinical or biochemical features of VDDR-II. Amniotic fluid cells from another mother of a child with VDDR-II were unable to bind [3H]1,25-(OH)2D3, and the hormone failed to stimulate 24-hydroxylase activity. VDDR-II in this fetus was confirmed after termination of pregnancy by the total inability of 1,25-(OH)2D3 to stimulate 24-hydroxylase activity in tissue explants and cell cultures prepared from the fetus's kidney and skin. In contrast, tissues from dead control fetuses responded to stimulation by 1,25-(OH)2D3 with a 3- to 10-fold increase in 24-hydroxylase activity. Fetal kidney and skin explants and cell cultures also synthesized a [3H]1,25-(OH)2D3-like metabolite from [3H]25-OHD3 as early as the 17th week of gestation. 1,25-(OH)2D3 (10 nM) decreased the in vitro synthesis of the [3H]1,25-(OH)2D3-like metabolite in tissues from dead control fetuses, but not from the affected fetus. Thus, human fetuses at midgestation already have the regulatory mechanisms responsive to 1,25-(OH)2D3 present postnatally. The prenatal diagnosis of VDDR-II is now possible and is indicated in a high risk family.

Adult↗
PubMed1989

An ochre mutation in the vitamin D receptor gene causes hereditary 1,25-dihydroxyvitamin D3-resistant rickets in three families.

Hereditary 1,25-dihydroxyvitamin D3-resistant rickets is a rare autosomal-recessive disease resulting from target-organ resistance to the action of the active hormonal form of vitamin D. Four affected children from three related families with the classical syndrome of hereditary 1,25-dihydroxyvitamin D3-resistant rickets and the absence of detectable binding to the vitamin D receptor (VDR) in cultured fibroblasts or lymphoblasts were examined for genetic abnormalities in the VDR gene. Genomic DNA from Epstein-Barr virus-transformed lymphoblasts of eight family members was isolated and amplified by polymerase chain reaction techniques. Amplified fragments containing the eight structural exons encoding the VDR protein were sequenced. The DNA from all affected children exhibited a single C----A base substitution within exon 7 at nucleotide 970 that resulted in the conversion of the normal codon for tyrosine (TAC) into a premature termination codon (TAA) at amino acid 292. This mutation causes a truncation of the VDR protein thereby deleting a large portion of the steroid hormone binding domain (amino acids 292-424). Although the affected children were all homozygotic for the mutation, the four parents tested all exhibited both wild-type and mutant alleles, indicating a heterozygous state. The functional consequences of this mutation were confirmed after expression of the recreated mutant VDR cDNA in mammalian cells. Recreated mutant receptor exhibited no specific 1,25-[3H]dihydroxyvitamin D3 binding and failed to activate a cotransfected VDR promoter-reporter gene construct. Thus these findings identify an ochre mutation in a human steroid hormone receptor in patients with hereditary 1,25-dihydroxyvitamin D3-resistant rickets.

Amino Acid Sequence↗
PubMed1989

Effects of human growth hormone upon term placental hormone secretion in vitro.

The role of human growth hormone (hGH) on placental hormone secretion at term was investigated in two in vitro models: placental explants and cultured trophoblastic cells. Physiological concentrations of hGH caused a significant dose-dependent increase in placental lactogen and progesterone secretion. In the explant model it stimulated estradiol secretion. In order to determine whether this stimulatory effect on estradiol is exerted via aromatase, an isolated cell culture was utilized where androstenedione was supplied as substrate. In this model, hGH exerted a mild inhibitory effect. In conclusion, hGH at levels present in the fetal circulation exerts a significant stimulatory effect upon placental function as reflected by both peptide and steroid hormone production and secretion. The effect of estradiol secretion is the end result of an inhibitory effect on androgen aromatization and a stimulatory effect on earlier steps.

Androstenediols↗
PubMed1989

Defective leukocyte fungicidal activity in end-organ resistance to 1,25-dihydroxyvitamin D.

Recent studies have shown 1,25(OH)2D3 receptor-mediated modulation of leukocyte proliferation, differentiation, and function. We examined the phagocytosis and killing of microorganisms by neutrophils and monocytes from five patients of three families with hereditary resistance to 1,25(OH)2D3. Phagocytosis of microorganisms by patients' neutrophils and monocytes was normal. However, defective neutrophil killing activity toward Candida albicans (30-40% of controls) was found in all patients. The killing of Staphylococcus aureus was normal. The neutrophil chemiluminescence, nitroblue tetrazolium (NBT) dye reduction, and the generation of superoxide ions and hydrogen peroxide by neutrophils and monocytes after induction by either soluble stimuli or zymozan particles, did not differ from those in controls. The neutrophil myeloperoxidase activity was also normal. Monocytes obtained from two patients of different families before long-term calcium infusion therapy and after they became normocalcemic, demonstrated a similar impaired fungicidal activity toward Saccharomyces cerevisiae, indicating that hypocalcemia itself was not the cause of the killing defect. However, the addition of the Ca+2 ionophore A23187 (1 microM) to the test medium restored the monocyte fungicidal activity to normal. As patients' neutrophil cytosolic free calcium concentration was similar to that in controls, it is suggested that 1,25-(OH)2D3 exerts its effect on leukocyte function by a putative receptor-mediated regulation of subcellular calcium localization which may be important for fungicidal activity.

Calcitriol↗