Cornelis Van Dop

Accelerated growth rates in children treated with growth hormone after renal transplantation.

To determine the usefulness of growth hormone treatment among children with renal allografts, we treated nine children with functioning renal transplants who were less than 16 years of age and had poor growth. The nine children, who were aged 12.6 +/- 4.0 years, had (1) heights greater than 2.5 SD less than the mean for age, (2) growth rates less than or equal to 5 cm/yr, and (3) additional growth potential, as assessed by bone age (8.9 +/- 2.8 year). Insulin-like growth factor I, thyrotropin, and thyroid hormone levels were normal for age in all children. Growth hormone treatment increased growth rates from 1.9 +/- 1.1 cm/yr to 7.2 +/- 1.8 cm/yr without accelerating skeletal maturation and without advancing pubertal status. During growth hormone treatment, serum creatinine concentration rose from 140 +/- 50 to 190 +/- 80 mumol/L (1.6 +/- 0.6 to 2.1 +/- 0.9 mg/dl) (p less than 0.05), and creatinine clearances decreased from 0.79 +/- 0.37 to 0.58 +/- 0.30 ml/sec per 1.73 m2 (47 +/- 22 to 35 +/- 18 ml/min per 1.73 m2) (p less than 0.05) but then remained stable. Growth rates of two patients returned to pretreatment rates when growth hormone treatment was discontinued after 5 and 7 months because of increased serum creatinine values. Growth hormone treatment may be useful as adjunctive therapy for increasing growth rates in selected children with renal allografts who have poor growth; however, serum creatinine concentrations should be closely monitored during such treatment.

Spermatozoa contain a guanine nucleotide-binding protein ADP-ribosylated by pertussis toxin

Spermatozoa from invertebrates (sea urchin, starfish) and vertebrates (trout, guinea pig, bull, pig, human) contain a membrane-bound protein that is ADP-ribosylated by pertussis toxin but not by cholera toxin. The Mr of this protein is 39,000 in invertebrate sperm and 41,000 in mammalian sperm, but 40,000 in trout spermatozoa. The pertussis toxin substrate from sea urchin sperm copurified with [gamma-35S]GTP binding activity. Chymotryptic maps of this ADP-ribosylated protein from sea urchin sperm were the same as those of alpha-subunit of Go from rat brain. Antiserum to the beta-subunit of bovine retinal transducin bound to a sperm protein with Mr approximately 35,000. These studies are the first describing a guanine nucleotide-binding coupling protein in sperm.

Prevalence of polymorphic 21-hydroxylase gene (CA21HB) mutations in salt-losing congenital adrenal hyperplasia

Using genomic restriction analysis of 14 unrelated patients with salt-losing congenital adrenal hyperplasia, we identified three different CA21HB mutation patterns: no detectable restriction fragment abnormalities (16/28 haplotypes), deletion of the active CA21HB gene (9/28), and apparent conversion of the active CA21HB gene to the pseudogene CA21HA (3/28). CA21HB gene deletion was associated with HLA-Bw47 in 6 haplotypes and with absent C4B expression in 7. A variety of HLA and C4 types was associated with the other mutations. Apparent conversion of CA21HB to CA21HA was identified by the disparity between the intensity ratios for the major TaqI and BglII hybridization fragments.

Partial cDNA sequence of the gamma subunit of transducin.

A 151 bp cDNA segment that encodes the amino-terminal portion of the gamma subunit of bovine transducin was isolated from a retinal cDNA library constructed in the expression vector lambda gt11. The base sequence of this cDNA confirms the sequence of the first 39 amino-terminal amino acids reported for the native protein (McConnell et al. (1984) Fed. Proc. 43, 1585). Northern blot analysis indicates that the complete mRNA is approximately 650 bases long and that its expression is limited to the retina.

NAD+-mediated stimulation of adenylate cyclase in cardiac membranes

NAD+ significantly enhances adenylate cyclase activity in crude cardiac membrane preparations. This increase is dose-dependent, does not occur in the presence of nicotinamide, ADP-ribose or NADP+, and can be effected by a 30 min pre-incubation period with NAD+. Time course studies are consistent with an enzymatically mediated modification that used NAD+ as substrate. Furthermore, inhibition of NAD+-mediated activation by arginine suggests that this modulation of cardiac adenylate cyclase is analogous to that catalyzed by endogenous ADP-ribosyl transferases.

Glucose tolerance in children with renal allografts and effect of growth hormone treatment.

We performed oral glucose tolerance tests (oGTTs) on 15 children who had functioning renal allografts received greater than or equal to 18 months previously, had adequate renal function, and had heights greater than 2.5 SD below the mean height for age. Three of the children had impaired glucose tolerance; their mean glucose levels during the last 2 hours of the oGTT were higher (p less than 0.05) than published control values. Integrated glucose concentrations correlated inversely with the prednisone dose on the first day of an alternate-day dosage schedule (R2 = 0.383) and directly with adiposity (partial R2 = 0.322). The integrated insulin concentration correlated directly with the prednisone dose on day 1 of an alternate-day regimen (R2 = 0.355) and with age (partial R2 = 0.163). In 10 children with renal transplants who had been treated with growth hormone for greater than or equal to 6 months, the mean fasting glucose concentration, integrated glucose concentration, and integrated insulin concentration during the oGTTs obtained after 6 months or 12 months of growth hormone treatment were not significantly different (p greater than 0.05) from values measured before the treatment. We conclude that increased integrated concentrations of both glucose and insulin during oGTTs in children with renal allografts correlate with the dose of prednisone administered on the first day of an alternate-day schedule, with age, and with adiposity index. Growth hormone treatment of children with renal allografts who are growing poorly does not significantly affect glucose metabolism as assessed by oGTT.

Prevalence of three mutations in the Gsα gene among 24 families with pseudohypoparathyroidism type Ia

Pseudohypoparathyroidism type Ia (PHP-Ia), an inherited multi-hormone resistance syndrome, is associated with deficient cellular activity of the alpha-subunit of the guanine nucleotide-binding protein (Gs alpha) that stimulates adenylyl cyclase. We determined prevalence of three recently described mutations in exons 1 and 10 of the Gs alpha gene among 24 unrelated patients with PHP-Ia. Restriction analysis was used to detect two mutations that produce unique RFLPs, and allele-specific oligonucleotide hybridization was used to detect the other mutation. As none of these mutations were not found, genomic DNA was analyzed with denaturing gradient gel electrophoresis to screen for other mutations in exon 10. Mutations of the initiation codon and exon 10 in the Gs alpha gene thus rarely (< or = 4% each) cause PHP-Ia and the Gs alpha gene mutations causing PHP-Ia are heterogeneous and unique to each pedigree.

Enhanced growth with growth hormone therapy after renal transplantation

Some children with successful renal transplantation do not grow normally following reduction of immunosuppressive glucocorticoid therapy to an alternate-day regimen [1, 2]. We evaluated a boy aged 10 years 6 months for growth failure. He had presented at age 2 years 6 months with nephrotic syndrome and focal segmental glomerular sclerosis, for which he had received glucocorticoid and cyclophosphamide therapy. Due to progressive renal failure, he began continuous ambulatory peritoneal dialysis at 8 years of age, and underwent cadaveric kidney transplantation at age 8 years 6 months. After renal transplantation, his serum creatinine subsequently remained below 1.0 mg/dl without proteinuria and he received cyclosporine (decreased progressively from 10mg/kg per day to 3 mg/kg per day), azathioprine (2.5 mg/kg per day) and prednisone (progressively decreased from 50 mg /m 2 per day to 9 mg /m 2 per day) therapy. His growth rate remained below 2 cm/year (Fig. 1). Despite further reduction of prednisone therapy (9 mg/m 2 on alternate days), his growth rate remained below 2 cm/year (Fig. 1). Between the ages of 10 years and 10 years 6 months fasting serum growth hormone (GH) after exercise was 6.4 ng/ml and peak serum GH after arginine-l-DOPA was 12.6 ng/ml insulin like growth factor I (IGF-I) was 2.2 U/ml, thyroid-stimulating hormone (TSH) was 0.7 gU/ ml, and thyroxine (T4) was 10.2 .ug/dl. Bone age at 11 years 3 months was delayed with dysharmonic maturation (hand t0 years, wrist 7 years).

PSEUDOHYPOPARATHYROIDISM FROM MATERNAL BUT NOT PATERNAL TRANSMISSION OF A Gα s FRAMESHIFT MUTATION. • 552

The G-protein subunit Gαs couples many hormone receptors, including those for parathyroid hormone (PTH) and thyrotropin (TSH), to the stimulation of adenylyl cyclase within cells. We and others have demonstrated the consistent association of mutations leading to decreased function of Gαs with Albright hereditary osteodystrophy (AHO), characterized by rounded facies, short stature, and brachymetacarpia. Less consistent has been the relationship of these Gαs mutations with the PTH and TSH resistance seen in pseudohypoparathyroidism type Ia (PHP-Ia). In clinical studies of pedigrees affected by AHO, there is a strong association of maternal transmission of the AHO phenotype with the full expression of PHP-Ia in the offspring of these mothers. We studied in more detail a pedigree affected by AHO and PHP-Ia for which we previously reported finding a 4-bp deletion in one allele of the gene for Gαs. Specific exons of the Gαs gene were amplified by PCR with GC-tailed oligonucleotides, using as a template DNA from leukocytes of family members spanning three generations. Denaturing gradient gel electrophoresis of PCR-amplified exon 7 fragments showed that the patriarch of this pedigree, who was affected by mild short stature but no clinical hormonal abnormalities, carried the same heterozygous pattern previously shown by dideoxynucleotide sequencing to represent a deletion of 4 nucleotides in exon 7 resulting in a reading frame shift. Of his three offspring (1 male, 2 female) who inherited the same mutation, erythrocyte Gαs activity as measured by an S49cyc- complementation assay ranged from 58% ± 7.1 to 85% ± 8.5 that of normal control subjects, with all affected by AHO but without any hormonal abnormalities of PHP-Ia. Offspring of the two women with AHO had Gαs activity from 52% ± 12 to 55% that of controls, and all had AHO + hormonal abnormalities (PTH & TSH elevation, hypocalcemia, hyperphosphatemia) consistent with PHP-Ia. In conclusion, this family showed autosomal dominant co-inheritance of AHO and a Gαs frameshift mutation, with expression of hormone resistance (PHP-Ia) associated with maternal but not paternal transmission.

L-TYPE CALCIUM CHANNEL β SUBUNIT mRNA LEVELS ARE DEVELOPMENTALLY REGULATED IN RABBIT HEART. • 143

L-TYPE CALCIUM CHANNEL β SUBUNIT mRNA LEVELS ARE DEVELOPMENTALLY REGULATED IN RABBIT HEART. • 143