Triptorelin stimulated luteinizing hormone concentrations for diagnosing central precocious puberty: study of diagnostic accuracy

PURPOSE

Gonadotropin-releasing hormone (GnRH) stimulation test is the gold standard for diagnosing central precocious puberty (CPP). However, intravenous GnRH is not always readily available. The aim of the present study was to evaluate the diagnostic accuracy of triptorelin-stimulated luteinizing hormone (LH) concentrations in the diagnosis of CPP among girls presenting with premature thelarche compared to the gold standard GnRH test.

METHODS

A prospective, case-control (CPP vs isolated premature thelarche), clinical study evaluating the diagnostic accuracy of triptorelin-stimulated LH concentrations in 60 girls with premature thelarche was performed. All girls underwent stimulation with subcutaneous triptorelin injection and intravenous GnRH in a randomized order. During the stimulation test with triptorelin, LH and FSH were measured at time 0, 30, 60, 90, 120, and 180 min after the injection. Estradiol was sampled 24 h after the injection. During the GnRH test, LH and FSH were measured at time 0, 30, 45, and 60 min. Girls with peak GnRH-stimulated LH concentrations ≥5.0 IU/L were classified as having CPP. Area under the curve (AUC) for triptorelin-stimulated LH concentrations was assessed using the receiver operating characteristic (ROC) analysis.

RESULTS

Triptorelin-stimulated LH concentrations were significantly higher in girls who had CPP according to the GnRH test (53.3%). LH peaked at 180 min after the triptorelin injection. The highest diagnostic accuracy for CPP (AUC = 0.973, sensitivity 96.9%, specificity 89.3%) at 180 min was at a LH concentration ≥3.4 IU/L. The 24 h estradiol concentration did not improve the predictive model.

CONCLUSIONS

Measuring LH concentrations 180 min after triptorelin injection with a cut-off value of ≥3.4 IU/L demonstrated a high diagnostic accuracy compared to the GnRH test. Thus, stimulation with triptorelin can be used as a reliable alternative for diagnosing CPP in girls with premature thelarche.

Mapping the journey of transition: a single-center study of 170 childhood-onset GH deficiency patients

OBJECTIVE

To analyze metabolic parameters, body composition (BC), and bone mineral density (BMD) in childhood-onset GH deficiency (COGHD) patients during the transition period (TP).

DESIGN

Single- center, retrospective study was performed on 170 consecutive COGHD patients (age 19.2 ± 2.0 years, range 16-25) transferred after growth completion from two pediatric clinics to the adult endocrine unit. Two separate analyses were performed: (i) cross-sectional analysis of hormonal status, metabolic parameters, BC, and BMD at first evaluation after transfer from pediatrics to the adult department; (ii) longitudinal analysis of BC and BMD dynamics after 3 years of GH replacement therapy (rhGH) in TP.

RESULTS

COGHD was of a congenital cause (CONG) in 50.6% subjects, tumor-related (TUMC) in 23.5%, and idiopathic (IDOP) in 25.9%. TUMC patients had increased insulin and lipids levels (P < 0.01) and lower Z score at L-spine (P < 0.05) compared to CONG and IDOP groups. Patients treated with rhGH in childhood demonstrated lower fat mass and increased BMD compared to the rhGH-untreated group (P < 0.01). Three years of rhGH after growth completion resulted in a significant increase in lean body mass (12.1%) and BMD at L-spine (6.9%), parallel with a decrease in FM (5.2%).

CONCLUSION

The effect of rhGH in childhood is invaluable for metabolic status, BC, and BMD in transition to adulthood. Tumor-related COGHD subjects are at higher risk for metabolic abnormalities, alteration of body composition, and decreased BMD, compared to those with COGHD of other causes. Continuation of rhGH in transition is important for improving BC and BMD in patients with persistent COGHD.

Continuous Glucose Monitoring as a Valuable Tool in the Early Detection of Diabetes Related to Cystic Fibrosis

Aims: We evaluated the impact of cystic fibrosis-related diabetes (CFRD) on lung disease and nutritional status. Study Design: The retrospective cohort study evaluated the subjects' medical records from 2004 to 2019. All participants older than 10 years diagnosed by a 30-minutely sampled OGTT formed OGTT-CFRD subgroup. The participants diagnosed with continuous glucose monitoring (CGM) (at least two peaks above 11.1 mmol/l and more than 10% of recorded time above 7.8 mmol/l) formed a CFRD-CGM subgroup. The participants without CFRD formed a non-CFRD group. The longitudinal follow-up was made 2 years before and 3 years after insulin therapy initiation. Results: Of 144 participants included, aged 10-55 years (44% males), 28 (19.4%) had CFRD. The HbA1c was significantly lower in the CGM-CFRD in comparison to the OGTT-CFRD subgroup (5.9 ± 0.62 and 7.3 ± 1.7% respectfully; p = 0.04). Subjects with CFRD were malnourished in comparison to non-CFRD, with significant improvements with insulin replacement therapy in regard to BMI Z-score (-1.4 ± 1.3 vs. -0.5 ± 1.2%, p = 0.04) and pulmonary exacerbation score (p = 0.02). In OGTT-CFRD subgroup there is an increase in FEV1 (62.7 ± 26.3 to 65.1 ± 21.7%, p = 0.7) and decrease in FVC (from 76.4 ± 24.2 to 71.2 ± 20%, p = 0.003) from diagnosis to second year of follow-up. In CGM-CFRD subgroup there was a decrease in FEV1 (from 58.2 ± 28.2 to 52.8 ± 25.9%, p = 0.2) and FVC-values (from 72.4 ± 26.5 to 67.4 ± 29.1%, p = 0.08).Chronic Pseudomonas aeruginosa infection was more prevalent in the CFRD group (p = 0.003). Conclusion: Continuous glucose monitoring is a useful tool for insight of glucose impairment and diagnosis of CFRD. Early recognition of CFRD and therapeutic intervention has favorable effects on clinical course of the disease.

Thirty years of the newborn screening program in Central Serbia: the missed cases of congenital hypothyroidism

Milenkovic T, Vukovic R, Radojicic B, Mitrovic K, Todorovic S, Zatezalo L. Thirty years of the newborn screening program in Central Serbia: the missed cases of congenital hypothyroidism. Turk J Pediatr 2019; 61: 319- 324. Newborn Screening (NS) program for congenital hypothyroidism (CH) has completely changed the natural history of this devastating disorder for the vast majority of children with CH. However, cases of missed CH do happen, and it is important to keep this possibility in mind during every day clinical practice. The objective of this study was to analyze the recognized cases of undiagnosed CH by the NS program in Central Serbia in order to evaluate the reasons for such omissions. Data regarding the recognized missed cases of CH between the years of 1983 and 2013 were collected and analyzed. During 30 years of the NS program for CH on the territory of Central Serbia, 1,547,122 newborns were screened, and during this period, 14 children with CH were missed by the NS. Five missed cases were children with athyreosis (35.8%), 8 had ectopic thyroid gland (57.1%) and one child had dyshormonogenesis (7.1%). The median age at diagnosis of CH in these missed cases was 1.12 years (range 0.08-13.5 years). In the group of children with missed diagnosis of CH, 71.4% were missed due to errors during sample collection, and 28.6% of patients were missed due to false negative screening results. Continuous education of neonatologists as well as nurses in neonatal units of maternity hospital are necessary to avoid errors in sample collection. It is of high importance to notice in a discharge list if a child is referred to the hospital before the sample is taken in a maternity hospital. On the other hand, the maternity hospital has to inform the screening laboratory about any child who was referred to another hospital if the blood samples for screening are not taken. Parents should be better informed that each child has to be included in the NS which is obligatory in Serbia. In addition, awareness amongst pediatricians in primary care should be raised regarding the possibility of missed cases of CH.

Factors associated with oxidative stress status in pediatric patients with type 1 diabetes mellitus

Background Oxidative stress is implicated in both, the onset and the progression of type 1 diabetes mellitus (T1DM). There is accumulated evidence of increased biomarkers of oxidative stress in newly diagnosed, T1DM patients without complications, and in those with advanced disease. In this cross-sectional study, we investigated factors affecting oxidative stress status in pediatric patients with T1DM. Methods Advanced oxidation protein products (AOPP), prooxidant-antioxidant balance (PAB), total sulfhydryl (SH) groups, and superoxide dismutase (SOD) activity were determined in 170 children and adolescents with T1DM. Principal component analysis was used to investigate clustering of clinical and laboratory variables associated with elevated oxidative stress and reduced antioxidative defense biomarkers. Results Factor analysis extracted five factors, interpreted as (1) "weight status factor" including age, BMI, waist and hip circumferences; (2) "proatherogenic factor" that included LDL-cholesterol, non-HDL-cholesterol, and triglycerides; (3) "metabolic control factor" including glucose and HbA1c; (4) "renal marker factor" with positive loading of urinary albumin excretion rate and negative loading of GFR; and (5) "antiatherogenic factor" that included HDL-cholesterol. High AOPP levels were independently predicted by "proatherogenic" (OR: 2.32; 95% CI: 1.44-3.71; p < 0.001), "metabolic control" (OR: 2.24; 95% CI: 1.35-3.73; p < 0.01), and "renal marker" (OR: 1.65; 95% CI: 1.03-2.65; p < 0.05) factors. "Renal marker factor" was a significant predictor of PAB (OR: 0.52; 95% CI: 0.34-0.81; p < 0.01). Regarding antioxidative defense markers, reduced SH groups were predicted by "proatherogenic factor" (OR: 0.56; 95% CI: 0.34-0.94; p < 0.05), while "weight status factor" predicted lower SOD activity (OR: 1.66; 95% CI: 1.03-2.67; p < 0.05). Conclusions Cardiometabolic risk factors and renal function are associated with oxidative stress in pediatric T1DM patients.

MON-LB56 Metabolic Profile in 107 Patients With Childhood Onset Growth Hormone Deficiency (CO-GHD) at the Time of Transition From Pediatric to Adulthood Endocrine Care

Vulnerability of the transitional period from childhood to adulthood is particularly challenging in treatment of adolescents with CO-GHD. Altered metabolic profile is well described in GHD, but relevant large monocentric studies in transition patients and young adults with CO-GHD are lacking.Patients and Methods: In a monocentric, observational, retrospective cross-sectional study conducted from 2005-2019, 107 CO-GHD patients were analyzed (17-26 years old, 80 males) at the time of transfer from pediatric to adult endocrine care. Median age at transfer was 19.6 ± 2.2 years. Subjects with congenital and idiopathic GHD (CON) were compared with age-, sex- and BMI-matched patients with hypothalamic/pituitary tumor history (TUM). Glycaemia and insulin during OGTT (peak and AUC), HbA1c, serum total cholesterol, HDL, LDL and triglycerides were analyzed in all patients.Results: Congenital and idiopathic causes of CO-GHD were more frequent than hypothalamic/pituitary tumoral causes (74.8% vs. 25.2%). All patients received GH replacement during childhood for average duration of 5.4 ± 1.4yrs. GH replacement was discontinued prior to transfer for 2.7 ± 0.9yrs. Glycaemia peak, glycaemia AUC and insulin peak in OGTT were not significantly different in TUM vs. CON (p&gt;0.05). However, insulin AUC in OGTT was significantly higher in TUM compared to CON (134.38 ± 23.2 vs 114.62 ± 12.4; p&lt;0.05). HbA1c was similar between the two groups (5.2 ± 0.4% TUM vs 5.0 ± 0.3% CON; p&gt;0.05). Total cholesterol (5.2 ±1.1 vs 4.5 ± 0.8 mmol/l; p&gt;0.05), LDL (3.1 ± 0.9 vs 2.7 ± 0.8 mmol/l; p&gt;0.05) and triglycerides (2.1 ± 1.1 vs 1.1 ± 0,7 mmol/l; p&lt;0.05) were increased in TUM compared to CON, while HDL was decreased in TUM group (1.0±0.1 vs 1.4±0,3 mmol/l; p&lt;0.05).Conclusion: Patients with CO-GHD caused by hypothalamic/pituitary tumors are burdened with a worse metabolic profile at the time of childhood to adulthood transition compared to matched transition patients with congenital CO-GHD.

Association of diabetic ketoacidosis and HbA1c at onset with year-three HbA1c in children and adolescents with type 1 diabetes: Data from the International SWEET Registry

OBJECTIVE

To establish whether diabetic ketoacidosis (DKA) or HbA1c at onset is associated with year-three HbA1c in children with type 1 diabetes (T1D).

METHODS

Children with T1D from the SWEET registry, diagnosed <18 years, with documented clinical presentation, HbA1c at onset and follow-up were included. Participants were categorized according to T1D onset: (a) DKA (DKA with coma, DKA without coma, no DKA); (b) HbA1c at onset (low [<10%], medium [10 to <12%], high [≥12%]). To adjust for demographics, linear regression was applied with interaction terms for DKA and HbA1c at onset groups (adjusted means with 95% CI). Association between year-three HbA1c and both HbA1c and presentation at onset was analyzed (Vuong test).

RESULTS

Among 1420 children (54% males; median age at onset 9.1 years [Q1;Q3: 5.8;12.2]), 6% of children experienced DKA with coma, 37% DKA without coma, and 57% no DKA. Year-three HbA1c was lower in the low compared to high HbA1c at onset group, both in the DKA without coma (7.1% [6.8;7.4] vs 7.6% [7.5;7.8], P = .03) and in the no DKA group (7.4% [7.2;7.5] vs 7.8% [7.6;7.9], P = .01), without differences between low and medium HbA1c at onset groups. Year-three HbA1c did not differ among HbA1c at onset groups in the DKA with coma group. HbA1c at onset as an explanatory variable was more closely associated with year-three HbA1c compared to presentation at onset groups (P = .02).

CONCLUSIONS

Year-three HbA1c is more closely related to HbA1c than to DKA at onset; earlier hyperglycemia detection might be crucial to improving year-three HbA1c.

Evidence for the synthesis of an unusual high spin (S = 7/2) [Cu–3Fe–4S] cluster in the radical-SAM enzyme RSAD2 (viperin)

We demonstrate the synthesis of an unusual high spin [Cu–3Fe–4S] cluster in the radical S-adenosylmethionine enzyme RSAD2 (also known as viperin).

Pediatric siMS score: A new, simple and accurate continuous metabolic syndrome score for everyday use in pediatrics

BACKGROUND

The dichotomous nature of the current definition of metabolic syndrome (MS) in youth results in loss of information. On the other hand, the calculation of continuous MS scores using standardized residuals in linear regression (Z scores) or factor scores of principal component analysis (PCA) is highly impractical for clinical use. Recently, a novel, easily calculated continuous MS score called siMS score was developed based on the IDF MS criteria for the adult population.

OBJECTIVE

To develop a Pediatric siMS score (PsiMS), a modified continuous MS score for use in the obese youth, based on the original siMS score, while keeping the score as simple as possible and retaining high correlation with more complex scores.

SUBJECTS AND METHODS

The database consisted of clinical data on 153 obese (BMI ≥95th percentile) children and adolescents. Continuous MS scores were calculated using Z scores and PCA, as well as the original siMS score. Four variants of PsiMS score were developed in accordance with IDF criteria for MS in youth and correlation of these scores with PCA and Z score derived MS continuous scores was assessed.

RESULTS

PsiMS score calculated using formula: (2xWaist/Height) + (Glucose(mmol/l)/5.6) + (triglycerides(mmol/l)/1.7) + (Systolic BP/130)-(HDL(mmol/l)/1.02) showed the highest correlation with most of the complex continuous scores (0.792-0.901). The original siMS score also showed high correlation with continuous MS scores.

CONCLUSION

PsiMS score represents a practical and accurate score for the evaluation of MS in the obese youth. The original siMS score should be used when evaluating large cohorts consisting of both adults and children.

Postprandial hyperinsulinemic hypoglycemia in a child as a late complication of esophageal reconstruction

BACKGROUND

Postprandial hyperinsulinemic hypoglycemia (PHH) is an increasingly recognized complication of gastric bypass surgery in obese adults, distinct from the "dumping syndrome".

CASE PRESENTATION

Upon birth, primary repair of esophageal atresia was performed, and at the age of 14 months definite esophageal reconstruction was performed. At the age of 3 years, recurrent brief episodes of symptomatic hypoglycemia started. At the age of 5.7 years the girl was admitted to our clinic and investigations indicated hyperinsulinemic hypoglycemia. Oral glucose tolerance test (OGTT) and continuous glucose monitoring results revealed frequent postprandial hypoglycemic events, which were always preceded by early postprandial hyperglycemia. It was concluded that the patient had PHH caused by a delayed and hyperinsulinemic response to carbohydrate intake as a result of esophagogastric surgery. Treatment with acarbose was titrated using flash glucose monitoring, which resulted in satisfactory glucose regulation.

CONCLUSIONS

This is the first described case of a child with PHH following esophageal reconstruction.

Early Presentation of Hyperinsulinism/Hyperammonemia Syndrome in Three Serbian Patients

Hyperinsulinism/hyperammonemia (HI/HA) syndrome is considered as the second most common type of hereditary HI. Correlation of genotype and phenotype in HI/HA syndrome has been described in several studies. We present three Serbian patients with HI/HA syndrome with emphasis on a possible correlation between genotype and clinical manifestations. Patient 1 was heterozygous for a de novo mutation p.S445L in the GLUD1 gene, while patients 2 and 3 (son and mother) both carry the p.R221C mutation. Early onset of hypoglycaemia with generalized seizures was recorded in infancy in all three patients. The two male patients had mild developmental delay, while the female patient presented with epilepsy. Analysis of Serbian patients with HI/HA syndrome confirms the association of p.S445L and p.R221C mutations with hypoglycaemic seizures noted within the first three months of life and with subsequent risk for cognitive impairment and/or epilepsy.

Changes in the incidence and etiology of congenital hypothyroidism detected during 30 years of a screening program in central Serbia

Congenital hypothyroidism (CH) is the most frequent congenital endocrine disorder. The purpose of the present study was to determine the incidence of CH in Central Serbia from 1983 to 2013. Newborn screening for CH was based on measuring neonatal thyroid-stimulating hormone (TSH) using a 30 mU/l cutoff (CO) until 12/1987 (P1), 15 mU/l until 12/1997 (P2), 10 mU/l until 12/2006 (P3), and 9 mU/l thereafter (P4). During the study period, there were 1,547,122 live births screened for CH. Primary CH was detected in 434 newborns, with incidence of 1:3728. With gradual lowering of the CO, the incidences of CH increased from 1:5943 in P1 to 1:1872 in P4 (p < 0.001). Incidence of CH with ectopic and enlarged gland doubled (p < 0.001), while prevalence of athyreosis remained relatively constant. The most prominent finding was the increase in the transient CH from none in P1 to 35 % of all CH patients in P4.

CONCLUSION

The overall incidence of CH in Central Serbia during study period nearly tripled, with a significant increase in almost all etiological categories, and was associated with lowering TSH cutoffs as well as other yet unidentified factors. Further studies are needed to identify other factors associated with increasing incidence of CH.

WHAT IS KNOWN

Congenital hypothyroidism (CH) is the main cause of preventable mental retardation. Recent reports have indicated a progressive increase in the incidence of primary CH throughout the world, partially explained by lowering of the TSH cutoff values.

WHAT IS NEW

During the study period associated with lowering of the TSH cutoffs, the overall incidence of CH in Serbia tripled, including transient CH, ectopy, and dyshormonogenesis, while prevalence of athyreosis remained stable during 30 years. Significant increase in the incidence of both permanent and transient CH was observed, associated with lowering of TSH cutoffs as well as other yet unidentified factors.

Preserved insulin sensitivity predicts metabolically healthy obese phenotype in children and adolescents

Available data on metabolically healthy obese (MHO) phenotype in children suggest that gender, puberty, waist circumference, insulin sensitivity, and other laboratory predictors have a role in distinguishing these children from metabolically unhealthy obese (MUO) youth. The goal of this study was to identify predictors of MHO phenotype and to analyze glucose and insulin metabolism during oral glucose tolerance test (OGTT) in MHO children. OGTT was performed in 244 obese children and adolescents aged 4.6-18.9 years. Subjects were classified as MHO in case of no fulfilled criterion of metabolic syndrome except anthropometry or as MUO (≥2 fulfilled criteria). Among the subjects, 21.7 % had MHO phenotype, and they were more likely to be female, younger, and in earlier stages of pubertal development, with lower degree of abdominal obesity. Insulin resistance was the only independent laboratory predictor of MUO phenotype (OR 1.59, CI 1.13-2.25), with 82 % sensitivity and 60 % specificity for diagnosing MUO using HOMA-IR cutoff point of ≥2.85. Although no significant differences were observed in glucose regulation, MUO children had higher insulin demand throughout OGTT, with 1.53 times higher total insulin secretion.

CONCLUSION

Further research is needed to investigate the possibility of targeted treatment of insulin resistance to minimize pubertal cross-over to MUO in obese children.

WHAT IS KNOWN

• Substantial proportion of the obese youth (21-68 %) displays a metabolically healthy (MHO) phenotype. • Gender, puberty, waist circumference, insulin sensitivity, and lower levels of uric acid and transaminases have a possible role in distinguishing MHO from metabolically unhealthy obese (MUO) children.

WHAT IS NEW

• Insulin resistance was found to be the only significant laboratory predictor of MUO when adjusted for gender, puberty, and the degree of abdominal obesity. • Besides basal insulin resistance, MUO children were found to have a significantly higher insulin secretion throughout OGTT in order to maintain glucose homeostasis.

Molecular genetic study of congenital adrenal hyperplasia in Serbia: novel p.Leu129Pro and p.Ser165Pro CYP21A2 gene mutations

PURPOSE

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disease characterized by impaired adrenal steroidogenesis and most often caused by CYP21A2 gene mutations. For the first time, we reported complete spectrum and frequency of CYP21A2 gene mutations in 61 unrelated patients with classical and non-classical CAH from Serbia.

METHODS

Direct DNA sequencing of whole CYP21A2 gene and polymerase chain reaction with sequence-specific primers for detection of CYP21A1P/CYP21A2 chimeras were combined.

RESULTS

We identified 18 different pathogenic alleles-two of them novel. Mutation detection rate was highest in patients with salt-wasting form of CAH (94.7%). The most prevalent mutation was intron 2 splice site mutation, c.290-13A/C>G (18.5%). Other mutation frequencies were: CYP21A1P/CYP21A2 chimeras (13%), p.P30L (13%), p.R356W (11.1%), p.G110fs (7.4%), p.Q318X (4.6%), p.V281L (4.6%), p.I172N (2.8%), p.L307fs (2.8%), p.P453S (1.9%), etc. Mainly, frequencies were similar to those in Slavic populations and bordering countries. However, we found 6.5% of alleles with multiple mutations, frequently including p.P453S. Effects of novel mutations, c.386T>C (p.Leu129Pro) and c.493T>C (p.Ser165Pro), were characterized in silico as deleterious. The effect of well-known mutations on Serbian patients' phenotype was as expected.

CONCLUSIONS

The first comprehensive molecular genetic study of Serbian CAH patients revealed two novel CYP21A2 mutations. This study will enable genetic counseling in our population and contribute to better understanding of molecular landscape of CAH in Europe.

Metabolic syndrome in obese children and adolescents in Serbia: prevalence and risk factors

OBJECTIVE

To assess the prevalence of metabolic syndrome (MS) in obese children and adolescents in Serbia.

SUBJECTS AND METHODS

The study group consisted of 254 subjects (148 female and 106 male), aged 4.6-18.9 years with diet-induced obesity (body mass index ≥95th percentile). Presence of MS using the International Diabetes Federation definition was assessed in all subjects, as well as oral glucose tolerance test and insulin resistance indices.

RESULTS

Overall prevalence of MS in all subjects aged ≥10 years was 31.2%, namely, 28.7% in children aged 10 to <16 years and 40.5% in adolescents ≥16 years. When adjusted for age, gender and pubertal development, higher degree of obesity was a strong predictor of MS. Multivariate analysis showed that taller subjects and those with higher degree of insulin resistance were at significantly higher risk of MS, independent of the degree of obesity.

CONCLUSIONS

High prevalence of MS emphasizes the need for prevention and treatment of childhood obesity.

The catalytic mechanism of A-type dye-decolourising peroxidase BsDyP: neither aspartate nor arginine is individually essential for peroxidase activity

BsDyP from Bacillus subtilis belongs to the new dye-decolourising peroxidase (DyP) family. Here, we use transient kinetics to provide details on the catalytic cycle of BsDyP.

Coupling native page/activity-staining with SDS-PAGE/immunodetection for the analysis of glutamine synthetase isoforms in spinach

Glutamine synthetase (GS) is a key nitrogen-assimilating enzyme in plants and a target for the broad-spectrum herbicide glufosinate. Understanding its kinetic and structural properties is of major agricultural importance. Spinach (Spinacia oleracea) is classified as a plant expressing only chloroplastic GS activity. We have analyzed soluble proteins in the spinach by coupling native polyacrylamide gel electrophoresis (PAGE)-activity detection, based on phosphate precipitation, with SDS-PAGE/immunoblotting. One cytosolic (GS1) isoform from the roots and two chloroplastic (GS2) isoforms expressed in leaves were resolved by native PAGE. The identity of the obtained bands was established by the application of GS-specific inhibitors, L-methionine sulfoximine and glufosinate. Examination by sodium dodecyl sulfate (SDS)-PAGE/ Western analysis with anti-GS antibodies, confirmed the identity of the active bands and revealed that both chloroplastic isoforms are composed of 44 kDa subunits, while the cytosolic isoform consists of 40 kDa subunits. The presence of more GS2 isozymes than encoded in the spinach genome is discussed in terms of posttranslational modifications.

Impaired receptor clustering in congenital myasthenic syndrome with novel RAPSN mutations

OBJECTIVE

Congenital myasthenic syndromes (CMS) with underlying RAPSN mutations turned out to be of high clinical relevance due to their worldwide frequency. To date, all reported patients with CMS with sequence variations in the translated region of RAPSN carry the mutation N88K on at least one allele. The authors report two patients lacking the common N88K allele but harboring differing novel mutations of the RAPSN gene on both alleles: one patient is homozygous for a missense mutation (R164C); the second patient is compound heterozygous for a splice (IVS1-15C>A) and another missense mutation (L283P).

METHODS

The authors analyzed the RAPSN gene for sequence variations and carried out in vitro studies in order to delineate the potential pathogenicity of the three novel RAPSN mutations.

RESULTS

For the putative splice mutation (IVS1-15C>A), the authors constructed wild-type and mutated RAPSN minigenes for transfection and subsequent RNA analysis. The mutation generates a novel acceptor splice site leading to retention of 13 nucleotides of intron 1 in the mature mRNA and subsequently to a frameshift transcript. Cotransfection of wild-type AChR subunits with RAPSN-constructs carrying R164C and L283P indicate that both mutations diminish coclustering of AChR with rapsyn.

CONCLUSIONS

Screening for the common mutation RAPSN N88K facilitates targeted genetic analysis in congenital myasthenic syndromes. However, absence of a N88K allele does not exclude underlying RAPSN mutations as cause of the congenital myasthenic syndromes. Sequencing of the entire gene may be considered in patients with joint contractures and respiratory problems even in the absence of the mutation N88K.

Survival and mortality of myotonic dystrophy type 1 (Steinert's disease) in the population of Belgrade

The purpose of this investigation was to determine survival and mortality in patients with myotonic dystrophy type 1 (DM1) in the Belgrade population within the period from 1983 to 2002. Data of a number of diagnosed DM1 patients with their demographic, clinical and genetic characteristics were gathered from hospital records in all neurologic institutions in Belgrade for the period 1983-2002. Death certificates were reviewed to determine the cause of death. Survival analysis by life table method and Cox proportional hazard model was performed. Within the observed period, in the population of Belgrade, 15 fatal outcomes among 101 patients with DM1 were registered. Average DM1 mortality rate was 0.5/1,000,000 (95% CI 0.3-0.8), and standardized mortality ratio (SMR) was 5.3. A significant inverse correlation was found between age at onset of DM1 and CTG repeats (P=0.023). The cumulative probability of 15-year survival for DM1 patients in Belgrade was 49+/-5% (48+/-2% for males and 50+/-7% for females). Younger age at onset was a significant unfavorable prognostic factor (hazard ratio=4.2; P=0.012).

Interaction of bacteriophage lambda protein phosphatase with Mn(II): evidence for the formation of a [Mn(II)]2 cluster

The interaction of bacteriophage lambda protein phosphatase with Mn2+ was studied using biochemical techniques and electron paramagnetic resonance spectrometry. Reconstitution of bacteriophage lambda protein phosphatase in the presence of excess MnCl2 followed by rapid desalting over a gel filtration column resulted in the retention of approximately 1 equiv of Mn2+ ion bound to the protein. This was determined by metal analyses and low-temperature EPR spectrometry, the latter of which provided evidence of a mononuclear high-spin Mn2+ ion in a ligand environment of oxygen and nitrogen atoms. The Mn2+-reconstituted enzyme exhibited negligible phosphatase activity in the absence of added MnCl2. The EPR spectrum of the mononuclear species disappeared upon the addition of a second equivalent of Mn2+ and was replaced by a spectrum attributed to an exchange-coupled (Mn2+)2 cluster. EPR spectra of the dinuclear (Mn2+)2 cluster were characterized by the presence of multiline features with a hyperfine splitting of 39 G. Temperature-dependent studies indicated that these features arose from an excited state. Titrations of the apoprotein with MnCl2 provided evidence of one Mn2+ binding site with a micromolar affinity and at least one additional Mn2+ site with a 100-fold lower affinity. The dependence of the phosphatase activity on Mn2+ concentration indicates that full enzyme activity probably requires occupation of both Mn2+ sites. These results are discussed in the context of divalent metal ion activation of this enzyme and possible roles for Mn2+ activation of other serine/threonine protein phosphatases.

Evidence for differential binding of isoniazid by Mycobacterium tuberculosis KatG and the isoniazid-resistant mutant KatG(S315T)

Isoniazid is a mainstay of antibiotic therapy for the treatment of tuberculosis, but its molecular mechanism of action is unclear. Previous investigators have hypothesized that isoniazid is a prodrug that requires in vivo activation by KatG, the catalase-peroxidase of Mycobacterium tuberculosis, and that resistance to isoniazid strongly correlates with deletions or point mutations in KatG. One such mutation, KatG(S315T), is found in approximately 50% of clinical isolates exhibiting isoniazid resistance. In this work, 1H nuclear magnetic resonance T1 relaxation measurements indicate that KatG and KatG(S315T) each bind isoniazid at a position approximately 12 A from the active site heme iron. Electron paramagnetic resonance spectroscopy revealed heterogeneous populations of high-spin ferric heme in both wild-type KatG and KatG(S315T) with the ratios of each species differing between the two enzymes. Small changes in the proportions of these high-spin species upon addition of isoniazid support the finding that isoniazid binds near the heme periphery of both enzymes. Titration of wild-type KatG with isoniazid resulted in the appearance of a "type I" substrate-induced difference spectrum analogous to those seen upon substrate binding to the cytochromes P450. The difference spectrum may result from an isoniazid-induced change in a portion of the KatG heme iron from 6- to 5-coordinate. Titration of KatG(S315T) with isoniazid failed to produce a measurable difference spectrum indicating an altered active site configuration. These results suggest that KatG(S315T) confers resistance to isoniazid through subtle changes in the isoniazid binding site.

Association of progressive myoclonic epilepsy and spinal muscular atrophy

It is well known that certain hereditary diseases of the nervous system sometimes occur concurrently within particular families. This report presents a Yugoslav family of Hungarian origin in whom 2 brothers had progressive myoclonic epilepsy and proximal weakness and atrophy of muscles. Electromyography and muscle biopsy confirmed neurogenic atrophy. Electroencephalography disclosed paroxysmal spike-and-wave and polyspike-and-wave complexes with photic-induced myoclonic jerking. The combination of these clinical features is extremely rare and probably constitutes a clinical syndrome that has not been reported previously.

Serotonin preferentially hyperpolarizes capsaicin-sensitive C type sensory neurons by activating 5-HT1A receptors

The effects of serotonin (5-HT) were investigated by intracellular recording from 179 dorsal root ganglion (DRG) cells classified by conduction velocity. Bath applied 5-HT depolarized 82% and hyperpolarized 4% of the A-type cells. In C-type cells, 5-HT depolarized only 41%, but hyperpolarized 39% of the cells. The depolarizing responses were of two types; an increase or decrease in R(in), mediated by 5-HT2or3 receptors, respectively. These receptors were observed in both A- and C-type cells. Hyperpolarizing responses were largely confined to A(delta)- and C-type cells. Carboxamidotryptamine and 8-OH-dipropylamino-tetralin were full agonists in eliciting hyperpolarization, and metitepin, spiperone and spiroxitrine behaved as competitive antagonists. This indicated that hyperpolarization was mediated by a 5-HT1A receptor. A 5-HT1A&3 receptor were found co-localized on some C-type cells. A strong depolarizing response to capsaicin was observed in the subgroup of C-type neurons that were also hyperpolarized by 5-HT. Thus a co-localization of capsaicin and 5-HT1A receptors was also observed.

Prolactin secretion in myotonic dystrophy

In order to evaluate prolactin secretion in females with myotonic dystrophy (MD) prolactin responses to TRH, metoclopramide and bromocriptine were studied in 13 women with myotonic dystrophy (10 normoprolactinaemic and 3 hyperprolactinaemic) and 8 healthy women. Following TRH administration mean maximal net increase was significantly higher in a group of normoprolactinaemic patients with MD in comparison to controls (p less than 0.05). In three patients with increased basal prolactin levels an exaggerated prolactin response to TRH has been observed. Normal prolactin response in a group of normoprolactinaemic as well as in hyperprolactinaemic patients have been observed following metoclopramide bolus injection. Following bromocriptine administration, maximal net decrease in prolactin levels has been found to be greater in normoprolactinaemic patients compared to healthy subjects, although the difference was statistically insignificant. The suppressive action of bromocriptine was more pronounced in patients with hyperprolactinaemia. Those results showed that there is some derangement in prolactin secretion in myotonic dystrophy leading to increased prolactin levels in some patients. Although the mechanism of this derangement has not been clarified yet it seems that it is not mediated via dopaminergic receptors.