A search for tyrosine kinase receptors expressed in the rat embryonic pancreas.

It is known that during embryonic life, interactions between the pancreatic epithelium and its surrounding mesenchyme are important for proper development of the pancreas. These interactions are thought to be mediated by soluble factors, which could be, as in other tissues, the ligands of tyrosine kinase receptors. In this study, we screened for tyrosine kinase receptors expressed in pancreata of 13-day-old embryonic rats. Using a polymerase chain reaction-based approach that exploits sequence similarities within the catalytic kinase domains of these receptors, we identified 30 different tyrosine kinase receptors. The same approach was then used on cDNA prepared from fractions enriched in epithelium or in mesenchyme. Receptors for factors such as platelet derived growth factors were found to be expressed both in the epithelial and the mesenchymal fractions. Receptors for stem cell factor, for epidermal growth factor family members were mainly found in the epithelial fraction. The profile of expression of receptor tyrosine kinases in the embryonic pancreas was finally compared to the one found in other tissues and cell types, such as kidney, brain or INS-1 cells. Platelet derived growth factor receptors and ErbB2 were found to be enriched in the embryonic pancreas when compared with other tissues. It will now be possible to test the effects of the ligands of the different receptors we have cloned, on the differentiation and growth of the pancreas.

Negative correlation between plasma GHRH values and growth velocity in short prepubertal children.

Numerous data suggest that impaired growth hormone secretion in short children is usually related to abnormal regulation of the hormone at the hypothalamic level. In order to improve our understanding of neurohypothalamic dysfunction in short children, we measured basal and peak (after L-dopa stimulation) plasma growth hormone-releasing hormone levels in 43 prepubertal children. Among them, in 23 children suspected of having hypothalamic growth hormone dysregulation, growth hormone-releasing hormone values were significantly higher than those observed in normal short stature children (n = 20), no longer correlated with peak growth hormone following L-dopa, and negatively correlated with growth velocity. This suggests that a predominant inhibitor of growth hormone secretion, such as an increase in somatostatin tone, might be prevalent in a large number of children with partial growth hormone deficiency and suspected hypothalamic growth hormone dysregulation.

Vitamin A deficiency and nocturnal growth hormone secretion in short children.

In the growth hormone (GH) neurosecretory dysfunction syndrome affecting slowly growing children with delayed bone age, low nocturnal GH secretion is accompanied by normal responses to pharmacological stimuli. We compared plasma vitamin A with physiological nocturnal and stimulated GH secretion in 68 short prepubertal children. Fasting plasma vitamin A correlated with nocturnal GH secretion but not with stimulated GH secretion. Total dietary vitamin A intake was significantly lower in short children with abnormal nocturnal GH secretion than in normal children and in endocrinologically-normal short children. 9 of 12 children with low nocturnal GH secretion and normal stimulated GH peaks who were supplemented with vitamin A 3000 micrograms for 3 months had increased nocturnal GH secretion.

[Critical study of diabetic ketoacidosis in children. Initial description and course during the first 24 hours of treatment]. / Etude critique de l'acidocétose diabétique de l'enfant. Description initiale et évolution au cours des 24 premières heures de traitement.

A critical analysis of the evolution during the first 24 hours was undertaken in 41 children and adolescents (age: 10.1 +/- 4.6 years) treated for diabetic ketoacidosis. Three of 4 children presented with ketoacidosis revealing diabetes. One of 4 was less than 6 years of age. Severe ketoacidosis (pH less than 7.15) concerned one third of children and were more frequent in the group of adolescents with already known diabetes. In these patients, ketoacidotic decompensation was attributed to psychosocial factors in most cases. Evolution was favorable in all cases, without complication. Blood glucose levels decreased from 28.7 mmol/l on arrival to 16.2 mmol/l after 2 hours of treatment and became stable at 10 mmol/l from the 12th to the 24th hours. The corrected blood sodium levels were stable, showing the adequacy of infusion solute osmolarities. Blood potassium was maintained at a normal level owing to early potassium supplementation. Ketoacidosis was corrected after about 12 hours, without bicarbonate administration when pH was greater than 7.15. Average perfused volumes were 3 l/m2/24 hours. Insulin doses were 2 UI/kg/24 hours and were inversely correlated with the admission pH (r = -0.6; p = 0.0001). This study shows the efficacy of a treatment taking into account the pathophysiology of diabetic ketoacidosis and the knowledge of the complication risk factors, by foreseeing the adjustments to be done with respect to individual and/or at risk situations. These precise descriptive data, collected on a large group of patients, establish a reference basis to follow evolution in the course of the treatment of diabetic ketoacidosis in children.

Hypothalamopituitary deficiency and precocious puberty following hyperhydration in diabetic ketoacidosis.

We report on a 5-year-old child who survived an intracerebral crisis, following ketoacidosis-revealing diabetes (DKA), with visual impairment due to a vascular occipital lesion. Two and 4 months after the initial episode, a unique hypothalamopituitary disorder consisting in GH, ACTH, TSH deficiencies and central precocious puberty, was detected. Cranial magnetic resonance images showed no visible lesion in the hypothalamopituitary region. The most likely hypothesis is the ischemia of hypothalamopituitary and occipital regions following possible cerebral edema after hyperhydration. She survived with low visual acuteness and received a combined replacement therapy for the neuroendocrinological deficiencies. This case emphasizes that the rehydration at the initial period of DKA is critical, especially when risk factors for cerebral edema are present (young age, marked hyponatremia). The neuroendocrinological consequences of acute cerebral edema are rare, but physicians must be attentive in survivors of these accidents.

A prospective study of the development of growth hormone deficiency in children given cranial irradiation, and its relation to statural growth.

Although GH deficiency (GHD) is the most frequent hormonal abnormality that occurs after cranial radiation, the natural course of this complication and its relationship to growth in children are not known. Therefore, we undertook a 2-yr prospective study of 16 children, aged 1.7-15 yr at the time of treatment, who received cranial [31-42 Gy (1 Gy = 100 rads)] and spinal radiation for medulloblastoma or ependymoma (group I). Their growth was compared to that of 11 children given similar doses of cranial radiation only (group II). The mean plasma GH response to arginine-insulin test (AITT) was 9.1 +/- 1.5 (+/- SE) micrograms/L in group I and 8.5 +/- 1.8 micrograms/L in group II (P = NS). After 2 yr, 16 of the 27 children had a peak plasma GH value below 8 micrograms/L after AITT, and 10 children had a peak response less than 5 micrograms/L. In addition, in group I, AITT and sleep-related GH secretion were compared; at the 2 yr follow-up only 3 of 13 children had discrepant results. At the 2 yr follow-up children treated by cranial and spinal radiation had a mean height of -1.46 +/- 0.40 SD below the normal mean. In contrast, the children given only cranial radiation had a mean height of -0.15 +/- 0.18 SD; P less than 0.02. Therefore, most of the growth retardation appeared to be due to lack of spinal growth. GHD is thus an early complication of cranial radiation in these children, and no significant growth retardation can be attributed to GHD during the first 2 yr. These data contribute to the organization of follow-up in irradiated children in order to decide when human GH treatment is necessary.

Hypercalcemia in infants with congenital hypothyroidism and its relation to vitamin D and thyroid hormones.

The circulating concentrations of calcium, phosphorus, and vitamin D metabolites were measured in 25 infants (fifteen to 30 days of age) with congenital hypothyroidism before treatment or during the first 6 months of thyroxine therapy. Five of the children before treatment and four during the early 3 months of treatment had mild hypercalcemia (10.8 to 12.4 mg/dl). Hypercalcemia before treatment did not appear to be related to the vitamin D status of the infant nor to an alteration in vitamin D metabolism, but to the presence of a residual thyroid secretion. In contrast, hypercalcemia during thyroxine therapy was related to vitamin D supplementation, even though the serum calcium concentration could not be correlated with the circulating concentration of any of the vitamin D metabolites assayed and obvious changes in vitamin D metabolism could not be demonstrated.

Hypothalamo-pituitary regulation of thyrotrophin secretion in chronically catheterized Brattleboro rats.

Plasma TSH rhythms were measured in Brattleboro (DI) and control Long-Evans (LE) rats with an intracardiac catheter allowing repeated sampling in conscious unstressed animals. The TSH response to thyrotrophin-releasing hormone (TRH; 500 ng/100 g body weight) was also determined. Finally, hypothalamic and pancreatic TRH concentrations and TRH-degrading activity (TRH-DA) were measured by specific radioimmunoassay. Long-Evans rats had a 24-h rhythm with a major modulatory 8-h component. In DI rats, only the 24-h rhythm was detected. The mean 24-h rhythm-adjusted mean TSH level was higher in DI than in LE rats (1.38 +/- 0.05 and 1.14 +/- 0.06 micrograms/l respectively, P less than 0.01). The peak TSH response to TRH was significantly increased in DI rats while the pituitary concentration of TSH was also higher (0.93 +/- 0.09 vs 0.39 +/- 0.06 micrograms/mg wet weight in LE, P less than 0.001). Hypothalamic TRH and TRH-DA were similar in both strains. The response to propylthiouracil-induced hypothyroidism was identical in both strains. We conclude that DI rats have a normal pituitary sensitivity to tri-iodothyronine but a central dysfunction in the pituitary environment leading to some alterations of TSH secretion.

Hypothyroidism increases pancreatic thyrotropin-releasing hormone concentrations in adult rats.

The effect of hypothyroidism on pancreatic TRH (P-TRH) and P-TRH-degrading activity (P-TRH-DA) was studied in adult rats. Hypothyroidism was induced in three groups during 4, 6, or 9 weeks by propylthiouracil (PTU) in drinking water and a low iodine diet (LID). Another group received PTU-LID for 6 weeks, followed by 5 weeks on a normal diet to restore euthyroidism. A possible toxic effect of PTU per se was eliminated by treating one control group with PTU and T3. P-TRH and TRH-DA were measured by specific RIA. In the hypothyroid groups, P-TRH concentrations (mean +/- SEM) were increased 10-fold (6.95 +/- 2.09; 5.51 +/- 1.3; 9.79 +/- 3.3 pg/(mg X 100 g BW), respectively, with a control value of 0.55 +/- 0.39, P less than 0.01). This increase was reversible, as shown by the group on PTU-LID followed by a normal diet (0.58 +/- 0.39, NS). P-TRH-DA present in the control group was decreased after 4 weeks of PTU-LID treatment and totally abolished after 6 and 9 weeks of PTU-LID treatment. In conclusion, these results suggest that thyroid status modulates P-TRH concentrations. This effect may be due to the disappearance of the TRH-DA in response to hypothyroidism. P-TRH stores may be regulated by the enzyme(s) involved in P-TRH-DA.

Postnatal developmental pattern of thyrotrophin releasing hormone-degrading activity in rat plasma, hypothalamus and liver: role of tri-iodothyronine.

Thyrotrophin releasing hormone-degrading activity (TRH-DA) is present in plasma, hypothalamus, pituitary gland, liver and kidney of adults of several species. Each of these tissues contains more than one TRH-degrading enzyme but only one, pyroglutamate aminopeptidase, isolated from the blood, is a TRH-specific enzyme. The aim of this study was to describe the developmental pattern of TRH-DA in the plasma, hypothalamus and liver and the role of tri-iodothyronine (T3) in the development of TRH-DA in the rat. Based on the hypothesis that thyroid hormones stimulate plasma TRH-DA in adult rats, degradation of TRH was studied in hypo- or hyperthyroid rats induced by 6-n-propyl-2-thiouracil or T3 respectively. Tritiated TRH was incubated with plasma and homogenates of hypothalamus or liver. After separation of degradation products by thin-layer chromatography, the amount of degraded [3H]TRH (pmol/50 microliters plasma or homogenate) was taken as a comparative index of TRH-DA. Plasma TRH-DA was not detectable before day 9 while hypothalamic and hepatic TRH-DA was already active at birth. Furthermore, the maturation pattern of total TRH-DA was different in plasma compared with other tissues and T3 appeared to play a significant role in its development. The absence of plasma TRH-DA in the neonatal period, its special thyroid-dependent developmental pattern and the presence of a specific TRH-degrading enzyme in adult blood suggest a physiological regulatory role for this activity.

Immunocytological evidence for oxytocin neurons in the human fetal hypothalamus.

The use of antibodies against oxytocin or neurophysin enabled the detection by immunocytochemistry of oxytocin-neurophysin neurons in the hypothalamus in the human fetus. The perikarya of these neurons are located in the paraventricular and supraoptic nuclei. Immunoreactive neurons occure in the median eminence. The neurophysin immunoreactive neurons were more numerous than the oxytocin immunoreactive neurons. The specificity of the immunocytological reaction was controlled. The first oxytocin-neurophysin neurons are seen as early as the 14th week of gestation.

Establishment of a clone of mouse hypothalamic neurosecretory cells synthesizing neurophysin and vasopressin.

Hypothalamic cells taken from 14-day-old mouse embryos were cultured for 6 days and transformed with simian virus 40. After cloning, a homogeneous cell population was obtained. Its morphological, Ultrastructural, biochemical, and immunochemical properties were studied. These cells possess ultrastructural features of primitive neurosecretory cells. They synthesize (35)S-labeled protein components that have the molecular weight and isoelectric focusing behavior of, and display the same immunoreactivity as, neurophysin. In addition, a (35)S-labeled peptidic fraction with a molecular weight close to 1000 is synthesized and is radioimmunologically indistinguishable from vasopressin. Immunochemical staining shows that both neurophysin and vasopressin are localized in the cytoplasm. These observations strongly suggest that a clone of mouse hypothalamic neurosecretory cells has been obtained with the synthesizing capacities of secretory neurons of the magnocellular hypothalamic nuclei.