Cell death and survival alterations in Malpighian tubules of Triatoma infestans following heat shock.

In this study, we examined cell survival and cell death in response to heat shock in an insect organ composed of highly polyploid cells no longer capable of cell division. For this, the frequency of nuclear phenotypes in Feulgen-stained Malpighian tubules of the blood-sucking insect, Triatoma infestans, was analyzed at various times after a short heat shock with or without subsequent moderate fasting. Cell death DNA fragmentation was studied immunocytochemically. Normal phenotypes and phenotypes indicative of cell survival (heterochromatin decondensation, nuclear fusion) and death (apoptosis, necrosis) were observed, especially in heat-shocked specimens. While the number of total and normal nuclei decreased following heat shock, the frequency of apoptosis increased during a short period (7 days) after heat shock. During a 30-day period following heat shock, the frequency of necrosis in fasted but not in fully nourished nymphs increased simultaneously with a decrease in the frequency of apoptosis. This finding suggests that the stress promoted by heat shock, but not that associated with heat shock plus fasting, can be dealt with by the apoptosis program. When considering the forms of cell survival, heterochromatin decondensation was more relevant in fully nourished nymphs, whereas nuclear and cell fusions were more important in fasted specimens. The forms of cell survival and cell death reported here may have protected the organ from damage by the stressing agents. In cells with no induction or accumulation of heat-shock proteins, cell death and the forms of cell survival observed here were the probable consequence.

Insulin modulates STAT3 protein activation and gene transcription in hepatic cells.

Treatment of rat hepatoma cells with insulin attenuated the interleukin 6 (IL-6) stimulation of acute phase plasma protein genes. To identify the potential mechanism of this action, the influence of insulin on IL-6 signal transduction was determined. An insulin dose-dependent reduction in signal transducer and activator of transcription 3 (STAT3) gene transcription, mRNA accumulation, protein concentration, and IL-6-inducible DNA binding activity was detected. A reduction in the IL-6-activated sis-inducible element binding of STAT3 was observed within 4 h of insulin treatment, whereas a maximal 3-4-fold lower STAT protein concentration was measured after 8-24 h of insulin treatment. Insulin mediated a similar magnitude reduction in the amount of mRNA encoding the IL-6 receptor alpha subunit and IL-6 binding activity. These effects of insulin appear to contribute to the strongly suppressed transcriptional induction of the IL-6-responsive acute phase plasma protein genes.

Outcome of lower L-thyroxine dose for treatment of congenital hypothyroidism.

The appropriateness of the recommended L-thyroxine dose (10-15 micrograms/kg/day) for the treatment of congenital hypothyroidism has been questioned because of the risk of iatrogenic hyperthyroidism. We report the outcome of 23 newborns with congenital primary hypothyroidism treated with 25 micrograms L-thyroxine per day (5.3-9.2 micrograms/kg/day) and followed for an average of 59 months. Serum thyroxine (T4) values increased (X = 11.4 +/- 2.7 micrograms/dL) within 4 weeks posttherapy; eight infants had T4 levels > or = 13 micrograms/dL on only half the currently recommended dose. Thyroid-stimulating hormone (TSH) values remained elevated in 18 of 21 patients for 2-21 months despite a high-normal T4. Psychometric tests were performed in 19 of the 23 patients. The mean Full Scale IQ for the congenital hypothyroid group (n = 16) was 101.4 +/- 13.2 with comparable Verbal and Performance IQ scores. Patients with a bone age (BA) of < or = 32 weeks or T4 < 2 micrograms/dL at initial evaluation had significantly Lower Verbal IQ scores. A standardized parent-report assessment of behavioral and emotional functioning revealed subgroup scale scores that were indistinguishable from nonclinical norms. We conclude that (1) average range IQ scores and positive behavioral adaptation are observed in congenitally hypothyroid children treated with L-thyroxine doses lower than currently recommended; (2) the L-thyroxine dose should be individualized to prevent iatrogenic hyperthyroidism; (3) TSH normalization should not be a primary objective of treatment, and (4) a prospective study comparing the advantages and risks of different doses of L-thyroxine is needed.

STAT3 and STAT5B are targets of two different signal pathways activated by hematopoietin receptors and control transcription via separate cytokine response elements.

Transient transfection of expression vectors for various members of the hematopoietin receptor family and STAT proteins into COS-1 cells indicated that each receptor was capable of stimulating the DNA binding activity of STAT1, STAT3, and STAT5B. However, gp130 preferentially activated STAT1 and STAT3. Activation of STAT5B differed from that of the other two in that the box 3 sequence motif in the cytoplasmic domain of gp130 was not required. Moreover, STAT5B and STAT3 enhanced gene transcription via separate regulatory elements. This study has identified two potential signal transduction pathways by which hematopoietin receptors, including the interleukin-6 receptor, control transcription of acute phase plasma protein genes in hepatic cells.

Receptors for interleukin-3 (IL-3) and growth hormone mediate an IL-6-type transcriptional induction in the presence of JAK2 or STAT3.

To determine the specificity of signal transducer and activator of transcription (STAT) protein activation by box 3 motif-deficient hematopoietin receptors, expression vectors encoding the receptors for growth hormone, interleukin-3 (IL-3), and IL-4 were transiently transfected into COS-1 cells, together with expression vectors for Janus kinases (JAKs) and STAT proteins. Each receptor mediated a dose-dependent activation of STAT1 and STAT3, and for IL-3R and GHR this process was enhanced by JAK2. The data suggest that a box 3 motif in the cytoplasmic domain of the signal-transducing receptor to the JAK/STAT pathway. Transfection of the receptors, in combination with STAT3, into HepG2 cells reconstituted a cytokine-dependent stimulation of gene transcription through IL-6 response elements, providing evidence for a functional role of STAT3 in controlling gene expression.

Microalbuminuria in an adolescent cohort with insulin-dependent diabetes mellitus.

To document the incidence of microalbuminuria in children and adolescents with longstanding insulin-dependent diabetes mellitus (IDDM) and to compare the clinical characteristics and determinant risk factors of those with and without microalbuminuria, 135 adolescent patients with IDDM for 5 years or longer were evaluated. The study population was divided on the basis of microalbumin excretion into normal (< 20 micrograms/min), incipient (20-200 micrograms/min), and overt (> 200 micrograms/min) nephropathy groups. There were 106 patients in the normal group, 24 patients in the incipient group, and five in the overt nephropathy group. Glycosylated hemoglobin, cholesterol concentration, and glomerular filtration rate (GFR) were analyzed. The incidence of incipient and overt nephropathy was 17.8% and 3.7%, respectively. Mean cholesterol concentration in the incipient and overt nephropathy groups (208 +/- 39 mg/dL [5.4 +/- 1.0 mmol/L]) and 227 +/- 49 mg/dL [5.9 +/- 1.3 mmol/L], respectively) was significantly higher than the normal group (186 +/- 37 mg/dL [4.8 +/- 0.9 mmol/L] P < 0.05). Similarly, systolic and diastolic blood pressures were significantly higher in the incipient and overt nephropathy groups compared to the normal group. This study confirms the high incidence of incipient and overt nephropathy in adolescents with IDDM early in the course of the disease.

Short stature: a psychosocial burden requiring growth hormone therapy?

BACKGROUND: Changes in the diagnosis of endocrine-based growth disorders and the advent of biosynthetic growth hormone have altered the long-standing policy of treating only those individuals with "classic" growth hormone deficiency. One justification for treating short children is to improve their psychosocial adaptation. The present investigation assessed the positive and negative behavioral adaptation, self-perceptions of domain-specific competencies, and global self-worth of a large, diagnostically heterogeneous sample of children and adolescents referred to pediatric endocrinologists for a growth evaluation. METHODS: All patients seen in a pediatric endocrine clinic (180 boys and 78 girls; 4 to 18 years) with a height at the fifth percentile or lower were included. Parents of all participating children completed the Child Behavior Checklist. Patients 8 years and older completed the Self-Perception Profile and those 11 years and older, in addition, completed the Youth Self Report. Short-stature (SS) subjects were compared with normative and psychiatric samples. RESULTS: The SS boys were described by parents as being significantly less socially competent and showing more behavioral and emotional problems than a normative sample selected for mental health. However, they were significantly more socially competent and showed fewer psychopathologic symptoms than a psychiatric referred sample of comparable age. The SS boys described themselves as less socially active but did not report more behavior disturbance than the normative sample. The SS boys' self-perceptions of domain-specific competencies and global self-worth were comparable to a normative comparison group with the exception that older subjects (13 years or older) described their athletic abilities more positively and their work competence more negatively. The SS girls were, with few exceptions, indistinguishable from the normal comparison groups on both parent- and self-report measures of social competency and behavior disturbance. Younger SS girls (ages 8 to 12 years) described their athletic competence and behavioral conduct more positively than the comparison group on the self-esteem questionnaire. Patient height deficit was unrelated to scores on the three questionnaires. Finally, no statistically significant differences in psychosocial functioning were detected between children with "normal-variant" SS and those with pathologic growth disorders. SS and those with pathologic growth disorders. CONCLUSIONS: Short-stature girls show more adaptive psychosocial functioning than SS boys. In either sex, SS does not appear to be associated with clinically significant psychosocial morbidity. Severity of the height deficit does not correlate with the level of behavioral adaptation. These observations challenge the justification of providing growth hormone therapy for all short children to improve their psychosocial functioning.

Insulin cooperates with IL-1 in regulating expression of alpha 1-acid glycoprotein gene in rat hepatoma cells.

Insulin treatment of the rat hepatoma H-35 cells results in a reduced stimulation of acute phase plasma protein gene expression by IL-1- and IL-6-type cytokines. The cell response to insulin appears to involve both stimulatory and inhibitory regulatory mechanisms because a clonal variant line of the H-35 cells has been identified in which insulin increases specifically the IL-1 stimulation of alpha 1-acid glycoprotein (AGP) gene, while still reducing the expression of the other acute phase protein genes. The magnitude of insulin and cytokine effect is dependent upon the proliferation state of the cell culture. One of the genetic targets of the insulin stimulation has been located to the cytokine-response element of the AGP gene and involves a cooperativity with the 5' adjacent IL-1-responsive element. The molecular mechanism of insulin inhibition, however, remains to be identified.

Divergent transforming growth factor-beta effects on IL-6 regulation of acute phase plasma proteins in rat hepatoma cells.

The rat hepatoma cell line, H-35, responds to IL-1- and IL-6-type cytokines by an increased transcription of specific acute phase plasma protein (APP) genes. Transforming growth factor-beta (TGF-beta), although ineffective on its own in regulating APP genes, modulates the action of the IL-type cytokines. In growing cultures, the IL-6 and IL-11 stimulation of thiostatin and hemopexin is enhanced by TGF-beta, whereas the stimulation of other APP is reduced. The effects of leukemia inhibitory factor, ciliary neurotrophic factor, IL-1, and TNF-alpha are generally attenuated by TGF-beta. Enhancement by TGF-beta of the IL-6-induced response can be explained in part by the fact that TGF-beta, in combination with dexamethasone, stimulates severalfold the expression of the 80-kDa ligand-binding subunit of IL-6R. Serum deprivation of H-35 cells for 3 days leads to an enhanced basal and cytokine-stimulated level of APP gene expression concomitant with a loss of the divergent regulatory effect of TGF-beta. In growth-arrested H-35 cells, TGF-beta still enhances the IL-6R expression but it attenuates all IL-6 effects on APP genes. These data suggest that TGF-beta influences the signal transduction of the IL-type cytokines by separate mechanisms and that the manifestation of the TGF-beta action is modulated by the growth state of the cell culture.

Effect of dietary protein intake on renal growth: possible role of insulin-like growth factor-I.

Insulin-like growth factor-I (IGF-I) has been implicated as a possible mediator of renal hypertrophy after uninephrectomy and diabetes mellitus. Because renal hypertrophy is also a consequence of high protein intake, we studied the effect of varying concentrations of dietary protein on circulating levels and renal tissue content of IGF-I. Male Sprague-Dawley rats were fed isocaloric diets containing high (50%, HP), normal (20%, NP) or low (6%, LP) dietary protein for up to 14 days before they were killed. As expected, renal size (dry kidney weight) was greater in HP-fed rats and smaller in LP-fed rats when compared with NP-fed animals (HP, 1415 +/- 26 mg [p < 0.01 vs NP]; NP, 1148 +/- 27 mg; LP, 838 +/- 16 mg [p < 0.01 vs NP]), and most of the relative changes in kidney size occurred during the first week of ingestion of the experimental diet. Renal hypertrophy in the HP-fed animals was accompanied at day 3 by a significant rise in kidney tissue IGF-I that remained elevated at day 7 but had fallen to baseline values by day 14. The rise in renal IGF-I content in the HP-fed rat was accompanied by increases in circulating IGF-I on day 3 only. Both circulating and renal tissue IGF-I levels were suppressed in the LP-fed animals at 3, 7, and 14 days. These data confirm that varying dietary protein intake has profound effects on both circulating and renal IGF-I levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-6 signal communication to the alpha 1-acid glycoprotein gene, but not junB gene, is impaired in HTC cells.

In the rat hepatoma (HTC) cell line, transcription of the alpha 1-acid glycoprotein (AGP) gene is prominently stimulated by dexamethasone. Although interleukin (IL)-1 and IL-6 synergistically enhance expression of the AGP gene in liver, they have no detectable effect on this gene in HTC cells. Nevertheless, HTC cells have mRNA encoding the IL-6 receptor subunits and respond to IL-6 by increasing expression of the junB gene. The mRNA for the 80-kDa IL-6 receptors is increased severalfold following dexamethasone treatment. Even with elevated IL-6 receptor expression, no IL-6 regulation of the AGP gene is observed. The lack of response to IL-6 is also found with the transfected AGP gene sequence, suggesting the absence of specific trans-acting factors. Since IL-6 promotes only a minimal stimulation of the CCAAT/enhancer-binding protein beta, HTC cells lack the indirect IL-6 signaling pathway to acute phase plasma protein genes that has been found to be crucial in other hepatoma cell lines. Considering that a similar IL-6 regulation of the junB gene is manifested in HTC cells and normal liver, a separate IL-6 signal-transducing pathway controlling the AGP gene is assumed to be missing in HTC cells.

Role of CAAT-enhancer binding protein isoforms in the cytokine regulation of acute-phase plasma protein genes.

Rat hepatic cells respond to interleukin (IL) -1, IL-6, and dexamethasone treatment by increasing the transcription rate of acute-phase plasma protein genes. The same conditions lead to changes in the expression of CAAT-enhancer binding protein (C/EBP) isoforms which are specific to the hepatic cell line. To identify the relationship between C/EBP isoforms and acute-phase protein gene activation, the hormone-specific expression of C/EBP alpha, beta, and delta was determined in H-35 and HTC cells and was compared to acute-phase liver. C/EBP beta was found to be the principal isoform in hepatoma cells and to be strongly stimulated by cytokines and dexamethasone in H-35 cells. Transactivating functions were observed for all three C/EBP isoforms by cotransfection of CAT gene reporter constructs containing cytokine and glucocorticoid response elements of acute-phase protein genes and expression plasmids for mouse C/EBP alpha, beta, and delta into rat and human hepatoma cells. The degree of C/EBP-mediated transactivation was, however, extremely variable among the different regulatory elements. Transcription run-on reactions with nuclei from transiently transfected H-35 cells indicated that cotransfected C/EBP beta increases basal expression of reporter gene constructs as well as the dexamethasone-mediated stimulation of constructs containing the glucocorticoid response elements of the rat alpha 1-acid glycoprotein gene, but did not accelerate or enhance hormone-dependent transcription activation of reporter gene plasmids containing the IL-6 regulatory element of the beta-fibrinogen gene. Activation of the reporter gene constructs appeared to be temporally and quantitatively correlated with the amount of nuclear C/EBP as determined by two-dimensional Western and Southwestern blot analyses.

Insulin is a prominent modulator of the cytokine-stimulated expression of acute-phase plasma protein genes.

Several endocrine hormones which influence liver metabolism are known to increase in activity during the acute phase of injury or inflammation. We determined whether these hormones have the potential to influence acute-phase protein production in human and rat hepatoma cells. Catecholamines, glucagon, growth hormone, triiodothyronine, and cyclic nucleotides individually or in combination did not modulate the basal or the interleukin-1 (IL-1)-, IL-6-, and dexamethasone-stimulated levels of acute-phase plasma proteins. Insulin, however, was found to be a rapid, nonspecific, and dose-dependent inhibitor of the cytokine and glucocorticoid stimulation of acute-phase protein gene expression and to exert its effect at the transcriptional level. The insulin inhibition applied to all cytokines tested but to various degrees, depending upon the particular acute-phase gene. Insulin resulted in an early and prominent increase in the transcription of genes encoding the AP-1 components of JunA, JunB, and c-Fos, as has been observed for other growth factors. However, the effect of insulin on C/EBP beta was unexpected and paradoxical: while insulin completely inhibited the transcriptional activation of the C/EBP beta gene in cytokine- and dexamethasone-treated cells, the level of cytoplasmic C/EBP beta RNA was elevated. Quantitation of C/EBP beta mRNA by Northern (RNA) blot analysis and of C/EBP beta DNA binding activity by Southwestern (DNA-protein) blot analysis showed that insulin, when combined with cytokines and dexamethasone, stimulated both the mRNA and DNA binding activity by a factor of 1.6 compared with that of cells treated with cytokines and dexamethasone alone. Transient transfection of H-35 and HepG2 cells with a chloramphenicol acetyltransferase (CAT) gene expression vector containing the C/EBP beta response element also resulted in a 1.5-fold increase of C/EBP beta-mediated transcription in insulin-treated cells. Transfection of CAT gene constructs containing increasing lengths of heptaglobin gene 5' flanking sequences indicated that insulin inhibition of IL-6 stimulation required the presence of the region from -4100 to -1030. These results suggest that insulin has the potential to control the transcription of acute-phase genes by at least two separate mechanisms.

The action of interleukin 6 and leukaemia inhibitory factor on liver cells.

The hepatic action of cytokines has generally been analysed in terms of the acute-phase response of the liver. The qualitative and quantitative changes in the expression of plasma proteins serve as defining criteria for cytokine function. Interleukin 6 (IL-6) and leukaemia inhibitory factor (LIF) are representatives of a group of cytokines which display strikingly similar effects in both human and rodent liver cells. Hallmarks of the action of these cytokines are the stimulation of type 2 acute-phase plasma proteins and enhancement of the effect of interleukin 1 (IL-1) or tumour necrosis factor alpha (TNF-alpha) on type 1 acute-phase plasma proteins. The transcriptional activation of the various acute-phase plasma protein genes involves common cis-acting regulatory elements whose sequences and location relative to the transcription start site vary from gene to gene. The activity of the IL-6- and LIF-responsive genes depends in part on transcription factors including several members of the C/EBP family, JunB and the glucocorticoid receptor. The expression of these transcription factors is in turn under cytokine-specific control. In a few cases, expression is temporally correlated with the activation of 'late' acute-phase protein genes. The finding that structurally distinct cytokines interact with separate receptors but elicit an almost identical liver cell response demands a reassessment of the contribution of each factor to the in vivo acute-phase response.

Sex steroids do not influence somatic growth in childhood.

The influence of sex steroids on somatic growth during childhood was evaluated by reviewing linear growth characteristics of 18 agonadal patients with normal sex chromosomes. None of the heights throughout childhood and before the onset of sex steroid therapy were below 2 SDs of the mean. Based on the normal z scores of these patients, we concluded that somatic growth throughout the childhood and prepubertal years is not sex-steroid dependent.