Follow-up of adolescents with diabetes after transition from paediatric to adult care: results of a 10-year prospective study

OBJECTIVE

Our main objective in this study was to identify the type of clinical care received by young type 1 diabetic patients who have made the transition from paediatric to adult care, and to assess the metabolic status of long-term treatment after the transition.

METHODS

A standardized questionnaire was used prospectively to follow 99 patients with type 1 diabetes mellitus after their transition to adult care. This survey was done once a year, from 1998 to 2008.

RESULTS

Directly after transition from paediatric care 38.4% of patients were found at specialised outpatient units; whereas 41.1% received care at a diabetes centre and 20.5% were monitored by general practitioners or specialists in internal medicine. Five-year results showed that 25.0% had continued to visit an outpatient unit; 41.7% were still visiting a diabetes centre; and 33.3% had remained in the care of general practitioners or internal specialists. We observed a trend showing slight improvements in the HbA1c values over time, however no major changes in metabolic control were observed after transition.

CONCLUSIONS

Transition marks a critical phase for young, diabetic patients as they may frequently switch from one physician or centre to another. The individual optimization of therapy, established during paediatric care, provides the decisive groundwork for disease control in young adults.

Nonadherence consensus conference summary report

This report is a summary of a 'Consensus Conference' on nonadherence (NA) to immunosuppressants. Its aims were: (1) to discuss the state-of-the-art on the definition, prevalence and measurement of NA, its risk factors and impact on clinical and economical outcomes and interventions and (2) to provide recommendations for future studies. A two-day meeting was held in Florida in January 2008, inviting 66 medical and allied health adherence transplant and nontransplant experts. A scientific committee prepared the meeting. Consensus was reached using plenary and interactive presentations and discussions in small break-out groups. Plenary presenters prepared a summary beforehand. Break-out group leaders initiated discussion between the group members prior to the meeting using conference calls and e-mail and provided a summary afterward. Conclusions were that NA: (a) is more prevalent than we assume; (b) is hard to measure accurately; (c) tends to confer worse outcomes; (d) happens for a number of reasons, and system-related factors including the patient's culture, the healthcare provider and the setting and (e) it is not currently known how to improve adherence. This consensus report provided some roadmaps for future studies on this complicated, multifaceted problem.

Continuous rise in incidence of childhood Type 1 diabetes in Germany

AIMS

To assess the incidence and the trend in incidence of Type 1 diabetes (T1DM) in children and adolescents < 15 years of age in Baden-Württemberg (BW), Germany.

METHODS

BW is Germany's third largest federal state. All 31 paediatric departments in BW and one diabetes centre participated in the study. Case registration was done according to the EURODIAB criteria. The degree of ascertainment was 97.2%.

RESULTS

From 1987 to 2003, the age- and sex-standardized incidence rate was 14.1/100,000 per year [95% confidence interval (CI) 13.7, 14.6, n = 4017]. The estimated annual increase in incidence was 3.8% (95% CI 1.1, 6.6). Compared with the first years of our registry, the current mean number of new cases of T1DM has doubled (1987-1989, n = 153; 2000-2003, n = 302). Generally, the highest rise in incidence occurred in the youngest age group of 0-4-year-old patients (5.8%; 95% CI 2.5, 9.3), followed by the age groups 5-9 (3.4%; 95% CI 0.8, 6.0) and 10-14 (2.7%; 95% CI 0.3, 5.1).

CONCLUSIONS

In Germany, the number of children and adolescents with new-onset T1DM has been rising at a faster pace than expected. A distinct shift to younger age at onset has been observed in Germany.

Homeostatic plasticity studied using in vivo hippocampal activity-blockade: synaptic scaling, intrinsic plasticity and age-dependence

Homeostatic plasticity is thought to be important in preventing neuronal circuits from becoming hyper- or hypoactive. However, there is little information concerning homeostatic mechanisms following in vivo manipulations of activity levels. We investigated synaptic scaling and intrinsic plasticity in CA1 pyramidal cells following 2 days of activity-blockade in vivo in adult (postnatal day 30; P30) and juvenile (P15) rats. Chronic activity-blockade in vivo was achieved using the sustained release of the sodium channel blocker tetrodotoxin (TTX) from the plastic polymer Elvax 40W implanted directly above the hippocampus, followed by electrophysiological assessment in slices in vitro. Three sets of results were in general agreement with previous studies on homeostatic responses to in vitro manipulations of activity. First, Schaffer collateral stimulation-evoked field responses were enhanced after 2 days of in vivo TTX application. Second, miniature excitatory postsynaptic current (mEPSC) amplitudes were potentiated. However, the increase in mEPSC amplitudes occurred only in juveniles, and not in adults, indicating age-dependent effects. Third, intrinsic neuronal excitability increased. In contrast, three sets of results sharply differed from previous reports on homeostatic responses to in vitro manipulations of activity. First, miniature inhibitory postsynaptic current (mIPSC) amplitudes were invariably enhanced. Second, multiplicative scaling of mEPSC and mIPSC amplitudes was absent. Third, the frequencies of adult and juvenile mEPSCs and adult mIPSCs were increased, indicating presynaptic alterations. These results provide new insights into in vivo homeostatic plasticity mechanisms with relevance to memory storage, activity-dependent development and neurological diseases.

Cell type-specific gating of perisomatic inhibition by cholecystokinin

Parvalbumin- and cholecystokinin (CCK)-expressing basket cells provide two parallel, functionally distinct sources of perisomatic inhibition to postsynaptic cells. We show that exogenously applied CCK enhances the output from rat parvalbumin-expressing basket cells, while concurrently suppressing GABA release from CCK-expressing neurons through retrograde endocannabinoid action. These results indicate that CCK may act as a molecular switch that determines the source of perisomatic inhibition for hippocampal principal cells.

Opposing Modifications in Intrinsic Currents and Synaptic Inputs in Post-Traumatic Mossy Cells: Evidence for Single-Cell Homeostasis in a Hyperexcitable Network

Recent experimental and modeling results demonstrated that surviving mossy cells in the dentate gyrus play key roles in the generation of network hyperexcitability. Here we examined if mossy cells exhibit long-term plasticity in the posttraumatic, hyperexcitable dentate gyrus. Mossy cells 1 wk after fluid percussion head injury did not show alterations in their current-firing frequency ( I-F) and current-membrane voltage ( I-V) relationships. In spite of the unchanged I-F and I-V curves, mossy cells showed extensive modifications in Na+, K+ and h-currents, indicating the coordinated nature of these opposing modifications. Computational experiments in a realistic large-scale model of the dentate gyrus demonstrated that individually, these perturbations could significantly affect network activity. Synaptic inputs also displayed systematic, opposing modifications. Miniature excitatory postsynaptic current (EPSC) amplitudes were decreased, whereas miniature inhibitory postsynaptic current (IPSC) amplitudes were increased as expected from a homeostatic response to network hyperexcitability. In addition, opposing alterations in miniature and spontaneous synaptic event frequencies and amplitudes were observed for both EPSCs and IPSCs. Despite extensive changes in synaptic inputs, cannabinoid-mediated depolarization-induced suppression of inhibition was not altered in posttraumatic mossy cells. These data demonstrate that many intrinsic and synaptic properties of mossy cells undergo highly specific, long-term alterations after traumatic brain injury. The systematic nature of such extensive and opposing alterations suggests that single-cell properties are significantly influenced by homeostatic mechanisms in hyperexcitable circuits.

Prevention of plasticity of endocannabinoid signaling inhibits persistent limbic hyperexcitability caused by developmental seizures

Depolarization-induced suppression of inhibition (DSI) is an endocannabinoid-mediated short-term plasticity mechanism that couples postsynaptic Ca2+ rises to decreased presynaptic GABA release. Whether the gain of this retrograde synaptic mechanism is subject to long-term modulation by glutamatergic excitatory inputs is not known. Here, we demonstrate that activity-dependent long-term DSI potentiation takes place in hippocampal slices after tetanic stimulation of Schaffer collateral synapses. This activity-dependent, long-term plasticity of endocannabinoid signaling was specific to GABAergic synapses, as it occurred without increases in the depolarization-induced suppression of excitation. Induction of tetanus-induced DSI potentiation in vitro required a complex pathway involving AMPA/kainate and metabotropic glutamate receptor as well as CB1 receptor activation. Because DSI potentiation has been suggested to play a role in persistent limbic hyperexcitability after prolonged seizures in the developing brain, we used these mechanistic insights into activity-dependent DSI potentiation to test whether interference with the induction of DSI potentiation prevents seizure-induced long-term hyperexcitability. The results showed that the in vitro, tetanus-induced DSI potentiation was occluded by previous in vivo fever-induced (febrile) seizures, indicating a common pathway. Accordingly, application of CB1 receptor antagonists during febrile seizures in vivo blocked the seizure-induced persistent DSI potentiation, abolished the seizure-induced upregulation of CB1 receptors, and prevented the emergence of long-term limbic hyperexcitability. These results reveal a new form of activity-dependent, long-term plasticity of endocannabinoid signaling at perisomatic GABAergic synapses, and demonstrate that blocking the induction of this plasticity abolishes the long-term effects of prolonged febrile seizures in the developing brain.

Postsynaptic origin of CB1-dependent tonic inhibition of GABA release at cholecystokinin-positive basket cell to pyramidal cell synapses in the CA1 region of the rat hippocampus

Cholecystokinin-positive (CCK+) basket cells are a major source of perisomatic GABAergic inputs to CA1 pyramidal cells. These interneurons express high levels of presynaptic cannabinoid type 1 (CB1) receptors that mediate short-term depression of GABA release following depolarization of postsynaptic cells. However, it is not known whether GABA release from CA1 CCK+ basket cells is under tonic endocannabinoid inhibition. In paired patch-clamp recordings, action potentials in presynaptic CCK+ basket cells evoked large IPSCs with fast kinetics in pyramidal cells. The proportion of action potentials that failed to evoke GABA release varied markedly between pairs, from highly reliable to virtually silent connections. Application of the CB1 receptor antagonist AM251 (10 microm) decreased the proportion of failures, revealing a persistent suppression of synaptic transmission by CB1 receptors. However, AM251 had no significant effect on the failure rate when the calcium chelator BAPTA (10 mm) was introduced into the postsynaptic cell, indicating that the tonic inhibition of GABA release by CB1 receptors is homosynaptically controlled by the postsynaptic cell, and that it is not due to constitutive CB1 receptor activity. Application of muscarinic or metabotropic glutamate receptor agonists inhibited synaptic transmission exclusively through the release of endocannabinoids from postsynaptic cells in a manner that could not be blocked by postsynaptic BAPTA, and had no direct effect on transmission. In contrast, GABA(B) receptor activation directly blocked GABA release, but there was no evidence for tonic inhibition of GABA release by GABA(B) receptors. Neither serotonergic nor mu-opioid agonists had significant influence on GABA release from CCK+ axon terminals. These results reveal that GABA release from CA1 CCK+ basket cells is under homosynaptic tonic inhibition by endocannabinoids, and it is subject to both direct and indirect modulation by various G-protein-dependent neuromodulators.

C-terminal HERG (LQT2) mutations disrupt IKr channel regulation through 14-3-3ϵ

Beta-adrenergic receptor-mediated cAMP or protein kinase A (PKA)-dependent modulation of cardiac potassium currents controls ventricular action potential duration (APD) at faster heart rates. HERG (KCNH2) gene mutations are associated with congenital long-QT syndrome (LQT2) and affect IKr activity, a key determinant in ventricular repolarization. Physical activity or emotional stress often triggers lethal arrhythmias in LQT2 patients. Beta-adrenergic stimulation of HERG channel activity is amplified and prolonged in vitro by the adaptor protein 14-3-3epsilon. In LQT2 families, we identified three novel heterozygous HERG mutations (G965X, R1014PfsX39, V1038AfsX21) in the C-terminus that led to protein truncation and loss of a PKA phosphorylation site required for binding of 14-3-3epsilon. When expressed in CHO cells, the mutants produced functional HERG channels with normal kinetic properties. We now provide evidence that HERG channel regulation by 14-3-3epsilon is of physiological significance in humans. Upon co-expression with 14-3-3epsilon, mutant channels still bound 14-3-3epsilon but did not respond with a hyperpolarizing shift in voltage dependence as seen in wild-type channels. Co-expression experiments of wild-type and mutant channels revealed dominant-negative behavior of all three HERG mutations. Simulations of the effects of sympathetic stimulation of HERG channel activity on the whole-cell action potential suggested a role in rate-dependent control of APD and an impaired ability of mutant cardiac myocytes to respond to a triggered event or an ectopic beat. In summary, the attenuated functional effects of 14-3-3epsilon on C-terminally truncated HERG channels demonstrate the physiological importance of coupling beta-adrenergic stimulation and HERG channel activity.

Novel Mitochondrial DNA Length Variants and Genetic Instability in a Family with Diabetes and Deafness

We have identified two locations with novel multiplasmic length variants in the mitochondrial DNA of a family with diabetes and deafness. At nt568 in the D-loop, the 6-bp polycytidine tract was found to be variable in length up to a total of 12 residues. A second region with length variants was found at nt8281 in the intergenic COII-tRNA(Lys) region, which consists of two copies of the 9-bp repeat CCCCCTCTA. Only the second repeat occurs in a heteroplasmic C(9-14)A form with both T residues largely deleted. In addition, the mtDNA contained a number of new homoplasmic point mutations. Both length variants are stably inherited in a maternal way with no major changes in their length distribution. In contrast, during culture of fibroblasts from the proband the average length of the polycytidine tracts is increased at both locations indicating a fibroblast-specific genetic instability. Cybrid cells containing mtDNA from the proband proliferate less efficient than cybrids with wild-type mtDNA in co-culture experiments, suggesting functional consequences of the mtDNA length variants or the additional homoplasmic point mutations. Since oxygen consumption was not severely affected, these mutation seem less detrimental for mitochondrial function than the A3243G diabetogenic mutation and most other pathogenic mtDNA mutations. The contribution of mtDNA length variants to the phenotype of members of this family is discussed.

Presynaptic, activity-dependent modulation of cannabinoid type 1 receptor-mediated inhibition of GABA release

Endocannabinoid signaling couples activity-dependent rises in postsynaptic Ca2+ levels to decreased presynaptic GABA release. Here, we present evidence from paired recording experiments that cannabinoid-mediated inhibition of GABA release depends on the firing rates of the presynaptic interneurons. Low-frequency action potentials in post hoc identified cholecystokinin-positive CA1 basket cells elicited IPSCs in the postsynaptic pyramidal cells that, as expected, were fully abolished by the exogenous application of the cannabinoid receptor agonist WIN55,212-2 [R-(+)-(2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrol[1,2,3-de]-1,4-benzoxazin-6-yl)(1-naphthalenyl) methanone monomethanesulfonate] at 5 microM. However, the presynaptic basket cells recovered from the cannabinoid agonist-induced inhibition of GABA release when the presynaptic firing rate was increased to > or =20 Hz. Pharmacological experiments showed that the recovered transmission was exclusively dependent on presynaptic N-type Ca2+ channels. Furthermore, the increased presynaptic firing could also overcome even complete depolarization-induced suppression of inhibition, indicating that the magnitude of DSI markedly depends on the activity levels of basket cells. These results reveal a new locus of activity-dependent modulation for endocannabinoid signaling and suggest that endocannabinoid-mediated inhibition of GABA release may differ in distinct behavioral states.

Coeliac disease in children with Type 1 diabetes mellitus: the effect of the gluten-free diet

PATIENTS AND METHODS

We assessed the frequency of coeliac disease in 281 children with Type 1 diabetes and the effect of gluten-free diet (GFD) in newly diagnosed cases. Serological screening was performed using anti-gliadin and anti-endomysium antibodies. Data were obtained about clinical symptoms, height and weight-for-height.

RESULTS

A small intestinal biopsy was recommended to 18 patients (6.4%) with positive serological results and 12 children agreed. Nine of them had coeliac disease. Three out of nine coeliac children complained about gastrointestinal symptoms. On a GFD, the symptoms disappeared in two patients. Iron-deficiency anaemia was present in four subjects and disappeared in the three patients who accepted the GFD. In three patients (33%), coeliac disease was asymptomatic. Height and weight-for-height were in the normal range for all patients. For well-complying patients, there was a significant increase in height standard deviation at diagnosis and on follow-up (-0.28 vs. +0.35) (P = 0.03). Changes in weight-for-height were not significant (-4.0% vs. +1.4%) (P = 0.28). There was a trend to an improvement in HbA(1c) (8.0 vs. 7.3%) (P = 0.05).

CONCLUSIONS

Serological screening is effective. There is a therapeutic benefit for some screening-detected patients, but confirmatory studies are needed.

Pacemaker channel dysfunction in a patient with sinus node disease

The cardiac pacemaker current I(f) is a major determinant of diastolic depolarization in sinus nodal cells and has a key role in heartbeat generation. Therefore, we hypothesized that some forms of "idiopathic" sinus node dysfunction (SND) are related to inherited dysfunctions of cardiac pacemaker ion channels. In a candidate gene approach, a heterozygous 1-bp deletion (1631delC) in exon 5 of the human HCN4 gene was detected in a patient with idiopathic SND. The mutant HCN4 protein (HCN4-573X) had a truncated C-terminus and lacked the cyclic nucleotide-binding domain. COS-7 cells transiently transfected with HCN4-573X cDNA indicated normal intracellular trafficking and membrane integration of HCN4-573X subunits. Patch-clamp experiments showed that HCN4-573X channels mediated I(f)-like currents that were insensitive to increased cellular cAMP levels. Coexpression experiments showed a dominant-negative effect of HCN4-573X subunits on wild-type subunits. These data indicate that the cardiac I(f) channels are functionally expressed but with altered biophysical properties. Taken together, the clinical, genetic, and in vitro data provide a likely explanation for the patient's sinus bradycardia and the chronotropic incompetence.

Activation of GABA(A) receptors by guanidinoacetate: a novel pathophysiological mechanism

Guanidinoacetate methyltransferase (GAMT) deficiency is an autosomal recessively inherited disorder of creatine biosynthesis. The disease occurs in early life with developmental delay or arrest and several neurological symptoms, e.g., seizures and dyskinesia. Both the deficiency of high-energy phosphates in neurons and the neurotoxic action of the accumulated metabolite guanidinoacetate (GAA) are candidate mechanisms for the pathophysiology of this disease. To examine a potential role of GAA accumulation, we analyzed the electrophysiological responses of neurons induced by GAA application in primary culture and acute murine brain slices. GAA evoked picrotoxin- and bicuculline-sensitive GABA(A) receptor-mediated chloride currents with an EC(50) of 167 microM in cortical neurons. Pathophysiologically relevant GAA concentrations hyperpolarized globus pallidus neurons and reduced their spontaneous spike frequency with an EC(50) of 15.1 microM. Furthermore, GAA acted as a partial agonist at heterologously expressed GABA(A) but not GABA(B) receptors. The interaction of GAA with neuronal GABA(A) receptors represents a candidate mechanism explaining neurological dysfunction in GAMT deficiency.

I(h) channels contribute to the different functional properties of identified dopaminergic subpopulations in the midbrain

Dopaminergic (DA) midbrain neurons in the substantia nigra (SN) and ventral tegmental area (VTA) are involved in various brain functions such as voluntary movement and reward and are targets in disorders such as Parkinson's disease and schizophrenia. To study the functional properties of identified DA neurons in mouse midbrain slices, we combined patch-clamp recordings with either neurobiotin cell-filling and triple labeling confocal immunohistochemistry, or single-cell RT-PCR. We discriminated four DA subpopulations based on anatomical and neurochemical differences: two calbindin D28-k (CB)-expressing DA populations in the substantia nigra (SN/CB+) or ventral tegmental area (VTA/CB+), and respectively, two calbindin D28-k negative DA populations (SN/CB-, VTA/CB-). VTA/CB+ DA neurons displayed significantly faster pacemaker frequencies with smaller afterhyperpolarizations compared with other DA neurons. In contrast, all four DA populations possessed significant differences in I(h) channel densities and I(h) channel-mediated functional properties like sag amplitudes and rebound delays in the following order: SN/CB- --> VTA/CB- --> SN/CB+ --> VTA/CB+. Single-cell RT-multiplex PCR experiments demonstrated that differential calbindin but not calretinin expression is associated with differential I(h) channel densities. Only in SN/CB- DA neurons, however, I(h) channels were actively involved in pacemaker frequency control. In conclusion, diversity within the DA system is not restricted to distinct axonal projections and differences in synaptic connectivity, but also involves differences in postsynaptic conductances between neurochemically and topographically distinct DA neurons.

Impact of total body water errors on Kt/V estimates in children on peritoneal dialysis

Determining Kt/V in peritoneal dialysis (PD) requires estimation of total body water (TBW). The Dialysis Outcomes Quality Initiative (DOQI) guidelines recommend use of the Mellits and Cheek (MC) formulas for the estimation of TBW in children. However, the MC formulas were developed from healthy children and may not apply to children on PD. Re-evaluating the MC data with additional, recent data from healthy infants has led to the development of new formulas. In addition, and as part of a prospective study of children initiating PD, the Pediatric Peritoneal Dialysis Study Consortium (PPDSC) has directly measured TBW using H2[18O]. To assess the impact of various TBW estimates, KPDt/V values prospectively collected in 24 children were calculated using H2[18O]-measured TBW (O18), MC-derived TBW (MCD), and new-formula TBW (NEW). The mean weekly KPDt/V by O18 was 2.2; by MCD, it was 2.0; and by NEW, it was 2.0. The results derived using the O18 method varied from both the MCD and the NEW results (p < 0.001). The mean deviation from the measured KPDt/V using O18 was 9.5% (maximum: 16%) using the MCD estimate and 7.8% (maximum: 18%) using the NEW formulas. Determinations of KPDt/V are significantly affected by the method of estimating TBW. The PPDSC formulas for children on PD based on the use of H2[18O] offer the most accurate means of calculating TBW and should replace formulas derived from healthy children. The use of Kt/V itself as a marker of adequacy in children will be validated only in prospective studies.

Varying clinical presentations at onset of type 1 diabetes mellitus in children--epidemiological evidence for different subtypes of the disease?

OBJECTIVE

On the basis of 2121 case observations between 1987 and 1997, we describe the clinical and laboratory characteristics of diabetes mellitus type 1 at its onset. Our objective is to analyze whether clinical presentation follows a uniform pattern or whether there is evidence for different subtypes.

RESEARCH DESIGN AND METHODS

Thirty-one pediatric hospitals and one diabetes center in Baden-Wuerttemberg (BW), Germany, participated in this study. The hospital records of 2121 children below 15 yr of age were examined retrospectively. Statistical analysis was done after logarithmic transformation into a normal distribution.

RESULTS

The average duration of symptoms was found to be 15.2 d (95% CI (Confidence Intervals) = 14.3-16.1) ranging between 2.0 and 180 d (95% central range). The most frequent symptoms were polyuria and polydipsia; 7.2% presented with altered level of consciousness. The mean blood glucose value was 407.9 mg/dL (95% CI = 400.0-416.0), corresponding to 23.3 mmol/L (95% CI = 22.8-23.8). The median pH value was 7.35 (95% CI = 7.34-7.36), and the median base excess was -5 mmol/L (95% CI =-5 to -4). The younger patients had a shorter duration of symptoms and suffered most frequently from ketoacidosis.

CONCLUSIONS

Although the symptoms of diabetes at its onset follow a uniform pattern, the clinical presentation and duration of symptoms indicate that there may be various forms of type 1 diabetes.

Diabetes incidence in children of different nationalities: an epidemiological approach to the pathogenesis of diabetes

AIMS/HYPOTHESIS

Incidence studies of children with Type I (insulin-dependent) diabetes mellitus and different ethnic backgrounds are known to provide important insights into the pathogenesis of the disease. For this reason, we compared the incidence rate in Baden-Württemberg, Germany, of children who were not of German descent with that of German children as well as with the reported incidence rates pertaining to the countries of origin of the children who were not of German descent.

METHODS

Our study was based on the Baden-Württemberg incidence register, part of the EURODIAB TIGER network, which includes 2,121 children aged 0-14 years, diagnosed as having Type I diabetes between 1987 and 1997. The study covered a population at risk of 1.8 million children, which represents 13.3% of the total number of children in Germany.

RESULTS

The total incidence rate was found to be 12.5 per 100,000 per year (95 %-CI 12.0-13.0); for German children alone it was calculated as 13.5 (95%-CI 12.9-14.1) and for children who were not of German descent it was significantly lower at 6.9 per 100,000 per year (95%-CI 5.8-8.0). The percentage of children who were not of German descent with Type I diabetes (8.3 %) is smaller than that among the general population (15.2%). Children from former Yugoslavia, Italy and Greece had incidence rates closer to their countries of origin than to the incidence rate of German children.

CONCLUSION/INTERPRETATION

Our findings indicate that genetic factors play a predominant role in the pathogenesis of Type I diabetes. However, the influence of certain aspects of life-style, which remain constant even after immigration, cannot be excluded.

Fathers of children with diabetes mellitus and their role in coping strategies in the family

Family structure and social disadvantage are thought to have adverse effects on the outcome of diabetes mellitus (DM). While there are data on family functioning and maternal coping in relation to some measures of metabolic control, little is known about the role of fathers in respect to coping and outcome of DM. We are presently conducting prospective studies to assess the role of fathers in families with children with DM. In addition, family functioning and psychosocial factors are being investigated in relation to putative effects on metabolic control. Structured questionnaire studies are being performed in 182 children and adolescents with type 1 DM. Similar questions are also put to the families. Mean age of the patients is 12.9 years, range 1.8-18 years, with an equal distribution between the sexes. Metabolic control as assessed by the mean of the last four HbA1c values (HPLC method; intra-assay coefficient of variation [CV] 2.1-3.3%, interassay CV 2.6-4.3%) is 7.4%; range 5.0-14.8%. The patients attend outpatient clinics at an average interval of six weeks. Structured educational in-patient programs are attended by less than one-third of the patients. There is a large prevalence of unemployment in the families. In the majority of cases mothers accompany their children to the clinic while fathers are absent. It is the mothers who adjust daily insulin doses, take care of food preparation and ensure the children's self-assessment. In conclusion, our preliminary data suggest that the role of fathers in diabetes management is rather passive and emotionally labile. Special educational programs targeted towards the fathers of children with DM and towards improving parental interactive strategies are urgently needed to better use parental resources of coping and support.

Seasonality of birth in children (0-14 years) with diabetes mellitus type 1 in Baden-Wuerttemberg, Germany

The aim of the study was to find out whether children with diabetes type 1 in Baden-Wuerttemberg present a pattern of seasonality in their month of birth. A cohort of 1,184 children and adolescents (0-14 years) diagnosed as having diabetes between January 1st, 1987 and June 30th, 1997 were included in the study. Monthly and seasonal patterns of birth of patients with diabetes were compared with the pattern of normal live births (n = 2,724,746) during the years 1972-1997 and the seasonality of onset of disease. Statistical analysis was made using Student's t-test to compare the means between four yearly seasons and single cosinor analysis for a period of 12 months. The children and adolescents with diabetes had a significantly different seasonality in month of birth pattern from that registered in the general population, demonstrating fewer births during the months April-June and July-September. This seasonality pattern also differs from those registered in Israel, Sardinia and Slovenia, in which the population with diabetes type 1 had most births during these months.

Single-cell mRNA expression of HCN1 correlates with a fast gating phenotype of hyperpolarization-activated cyclic nucleotide-gated ion channels (Ih) in central neurons

Hyperpolarization-activated currents (Ih) are key players in shaping rhythmic neuronal activity. Although candidate genes for Ih channels have been cloned (HCN1-HCN4), the subunit composition of different native Ih channels is unknown. We used a combined patch-clamp and qualitative single-cell reverse transcription multiplex polymerase chain reaction (RT-mPCR) approach to analyse HCN1-4 coexpression profiles in four neuronal populations in mouse CNS. Coexpression of HCN2, HCN3 and HCN4 mRNA was detected in single neurons of all four neuronal cell types analysed. In contrast, HCN1 mRNA was detected in neocortical and hippocampal pyramidal neurons but not in dopaminergic midbrain and thalamocortical neurons. HCN1 expression was correlated with significantly faster activation kinetics on the level of individual neurons. Semiquantitative single-cell RT-mPCR analysis demonstrated that HCN1 mRNA expression is at least eightfold higher in cortical neurons than subcortical neurons. We show that single neurons possess complex coexpression patterns of Ih candidate genes. Alternative expression of HCN1 is likely to be an important molecular determinant to generate the different neuronal Ih channel species adapted to tune either subcortical or cortical network activity.

The weaver mouse gain-of-function phenotype of dopaminergic midbrain neurons is determined by coactivation of wvGirk2 and K-ATP channels

The phenotype of substantia nigra (SN) neurons in homozygous weaver (wv/wv) mice was studied by combining patch-clamp and single-cell RT-multiplex PCR techniques in midbrain slices of 14-d-old mice. In contrast to GABAergic SN neurons, which were unaffected in homozygous weaver mice (wv/wv), dopaminergic SN neurons possessed a dramatically altered phenotype with a depolarized membrane potential and complete loss of spontaneous pacemaker activity. The gain-of-function phenotype was mediated by a large, nonselective membrane conductance exclusively present in (wv/wv) dopaminergic SN neurons. This constitutively activated conductance displayed a sensitivity to external QX-314 (IC(50) = 10.6 microM) very similar to that of heterologously expressed wvGirk2 channels and was not further activated by G-protein stimulation. Single-cell Girk1-4 expression profiling suggested that homomeric Girk2 channels were present in most dopaminergic SN neurons, whereas Girk2 was always coexpressed with other Girk family members in GABAergic SN neurons. Surprisingly, acute QX-314 inhibition of wvGirk2 channels did not induce wild-type-like pacemaker activity but instead caused membrane hyperpolarization. Additional application of a blocker of ATP-sensitive potassium channels (100 microM tolbutamide) induced wild-type-like pacemaker activity. We conclude that the gain-of-function weaver phenotype of dopaminergic substantia nigra neurons is mediated by coactivation of wvGirk2 and SUR1/Kir6. 2-mediated ATP-sensitive K(+) channels. We also show that in contrast to wild-type neurons, all (wv/wv) dopaminergic SN neurons expressed calbindin, a calcium-binding protein that marks dopaminergic SN neurons resistant to neurodegeneration. The identification of two ion channels that in concert determine the weaver phenotype of surviving calbindin-positive dopaminergic SN neurons will help to understand the molecular mechanisms of selective neurodegeneration of dopaminergic SN neurons in the weaver mouse and might be important in Parkinson's disease.

Temporal, seasonal, and geographical incidence patterns of type I diabetes mellitus in children under 5 years of age in Germany

AIMS/HYPOTHESIS

To estimate the national incidence of Type I (insulin-dependent) diabetes mellitus in children under 5 years of age in Germany and to analyse temporal, seasonal, and geographical patterns of the diabetes incidence.

METHODS

During 1993-1995 newly diagnosed subjects were prospectively registered by the hospital-based 'German Paediatric Surveillance Unit' with monthly inquiries in all paediatric departments in Germany. Level of ascertainment was estimated by capture-recapture-analysis using two independent regional data sources.

RESULTS

During 1993-1995 the national incidence was 8.10 (95 %-CI: 7.61, 8.61) per 100 000 person-years, ranging in-between lower rates in west European countries and higher rates in northern Europe. Degree of ascertainment was about 85 %. Male to female ratio was 1.11 (95 %-CI: 0.98, 1.25). Compared with results of previous regional studies in the east and the south-west of Germany a 3- and 1.3-fold incidence increase was observed, respectively. Multivariate Poisson regression analysis showed season, geographical region, and interactions of age at onset with sex and calendar year to be independent significant predictors of the incidence. Incidence variation by age was different between boys and girls. A significant incidence increase by calendar year was found in 3- and 4-year-old children only. In summer and fall the incidence was higher than in winter and springtime, in the northern parts of the country higher than in the southern parts.

CONCLUSION/INTERPRETATION

This study reports first national incidence data of Type I diabetes in children under the age of 5 years in Germany. Observed marked temporal, seasonal, and geographical incidence variations strongly support the causal role of environmental factors in disease aetiology.

A temporal deficit in juvenile diabetics

BACKGROUND

In this study we examined the temporal domain of visual function in diabetics without retinopathy by examining wavelength discrimination ability at two exposure durations. The results were compared to those found by heterochromatic brightness matching and anomaloscope matches.

METHODS

Wavelength discrimination was performed between 440 and 540 nm at exposure times of 1 s and 0.04 s in eight juvenile diabetic patients without retinopathy. The monochromatic stimuli were presented in Maxwellian view and were set to be equally bright prior to the experiment using heterochromatic brightness matching. In addition, Rayleigh and Moreland anomaloscope matches were performed. The results of the diabetic group were compared to those of an age-matched control group of eight subjects with normal colour vision.

RESULTS

Wavelength discrimination showed no difference between the groups for an exposure time of 1 s. With an exposure duration of 0.04 s, however, the diabetics show raised thresholds for the shortest wavelengths tested. In addition, brightness matches were increased at the short wavelengths, and anomaloscope matches showed a decrease in the match range for the Moreland (blue-yellow) equation.

CONCLUSION

The results indicate post-receptoral alterations in diabetic patients with no visible changes in their retinae.

Glutaric aciduria type I: pathomechanisms of neurodegeneration

In organotypic corticostriatal and hippocampal slice cultures from rat brain, 3-hydroxyglutaric acid but not glutaric and glutaconic acids induced neurodegeneration by activation of NMDA receptors. Electrophysiological investigations (Xenopus laevis oocytes expressing glutamate receptors; rat mixed cortex culture) revealed no direct interaction of 3-hydroxyglutaric acid with glutamate receptors. We speculate that 3-hydroxyglutaric acid induces a mild energy deprivation that interferes with the voltage-dependent Mg(2+)-block of NMDA receptors.

Development of brightness matching and colour vision deficits in juvenile diabetics

We studied hue discrimination and brightness matching throughout the spectrum in ten juvenile patients suffering from diabetes mellitus (Type I) with no (eight patients) or mild (two patients) retinopathy. In addition, the FM 100-Hue test was performed. The data were collected once every year over 5 years. Over the 5 years, the diabetics show a continual change in the shape of their brightness matching function. Wavelength discrimination ability remains quite stable with time at the long end of the spectrum but is variable at short wavelengths. FM-100 error scores remain similar over the period tested, at a level slightly higher than that of a control group. Additional experiments show that the sensitivity of the S-cone in the diabetic group is similar to that of controls. The results can be explained by an early relative reduction in the sensitivity of post-receptoral processes in juvenile diabetics.

Preretinopic changes in the colour vision of juvenile diabetics

AIMS

To examine the colour vision of juvenile patients suffering from diabetes mellitus without retinopathy in relation to metabolic and ophthalmic state.

METHODS

Metameric matches, both Rayleigh (red/green) and Moreland (blue/green) were used to test the colour vision yearly of 10 juvenile patients. The patients were monitored over 4 years, and during the final year, their blood glucose level was determined directly after testing colour vision. An ophthalmic examination was performed on the day of colour vision testing and blood and urine were analysed regularly throughout the 4 years. Their results are compared with an aged matched control group of 20 subjects, seven of whom were retested after 9-16 months.

RESULTS

After 4 years, the colour vision results show an enlarged matching range for the Moreland match, as well as a smaller increase in the matching range for the Rayleigh match. No significant correlation was found between blood glucose at the time of testing and any of the variables measured.

CONCLUSION

The pattern of colour vision deficits in metameric matching shown by juvenile diabetics is consistent with postreceptoral alterations of the inner retina, at this preretinopic stage of disease. Duration of diabetes is correlated with both colour vision changes and morphological alteration of the retina.