Michael Cardamone

Inherited myopathies and muscular dystrophies.

The inherited myopathies and muscular dystrophies are a diverse group of muscle diseases presenting with common complaints and physical signs: weakness, motor delay, and respiratory and bulbar dysfunction. The myopathies are caused by genetic defects in the contractile apparatus of muscle, and defined by distinctive histochemical or ultrastructural changes on muscle biopsy. The muscular dystrophies, in contrast, are diseases of muscle membrane or supporting proteins, which are generally characterized by pathological evidence of ongoing muscle degeneration and regeneration. Diagnosis of these disorders is contingent on a targeted history and examination, biochemical and neurophysiological assessment, muscle biopsy, and genetic testing. Treatment is focused on symptomatic management and rehabilitation, and monitoring for disease complications.

A genetic diagnostic approach to infantile epileptic encephalopathies

Epileptic encephalopathies are characterized by frequent severe seizures, and/or prominent interictal epileptiform discharges on the electroencephalogram, developmental delay or deterioration, and usually a poor prognosis. The epileptiform abnormalities themselves are believed to contribute to the progressive disturbance in cerebral function. Determining the underlying aetiology responsible for infantile epileptic encephalopathy is a clinical challenge worth undertaking to facilitate advice on the recurrence risk and to allow for the option of prenatal testing, as often this category of epilepsy is associated with devastating hardship for families. This review takes advantage of recently published studies that have identified new genes associated with epilepsy and focuses on known monogenic causes where detection is useful for the process of genetic counselling. Based on the review, we present a diagnostic work-up in order to triage specific genetic testing for infants presenting with an epileptic encephalopathy.

Congenital and childhood myotonic dystrophy: Current aspects of disease and future directions

Myotonic dystrophy type 1 (DM1) is multisystem disease arising from mutant CTG expansion in the non-translating region of the dystrophia myotonica protein kinase gene. While DM1 is the most common adult muscular dystrophy, with a worldwide prevalence of one in eight thousand, age of onset varies from before birth to adulthood. There is a broad spectrum of clinical severity, ranging from mild to severe, which correlates with number of DNA repeats. Importantly, the early clinical manifestations and management in congenital and childhood DM1 differ from classic adult DM1. In neonates and children, DM1 predominantly affects muscle strength, cognition, respiratory, central nervous and gastrointestinal systems. Sleep disorders are often under recognised yet a significant morbidity. No effective disease modifying treatment is currently available and neonates and children with DM1 may experience severe physical and intellectual disability, which may be life limiting in the most severe forms. Management is currently supportive, incorporating regular surveillance and treatment of manifestations. Novel therapies, which target the gene and the pathogenic mechanism of abnormal splicing are emerging. Genetic counselling is critical in this autosomal dominant genetic disease with variable penetrance and potential maternal anticipation, as is assisting with family planning and undertaking cascade testing to instigate health surveillance in affected family members. This review incorporates discussion of the clinical manifestations and management of congenital and childhood DM1, with a particular focus on hypersomnolence and sleep disorders. In addition, the molecular genetics, mechanisms of disease pathogenesis and development of novel treatment strategies in DM1 will be summarised.

Ten-year single-center experience of the ketogenic diet: factors influencing efficacy, tolerability, and compliance

OBJECTIVES To evaluate the efficacy, tolerability, and compliance of 3 ketogenic diets, the classical ketogenic diet, medium-chain triglyceride (MCT), and modified Atkins diet. STUDY DESIGN A single-center, retrospective study of 48 children with intractable epilepsy receiving ketogenic diets from 2003 to 2012. Patient demographics, epilepsy history, nutritional management, and side effects were collated. Compliance and tolerability were assessed by recording reasons for diet modification and cessation. The value of potassium citrate supplementation for preventing nephrolithiasis was reviewed. RESULTS Median age at ketogenic diet initiation was 3.8 years (IQR: 2.3-7 years). The majority had intractable epilepsy, and 33 of the 48 children (69%) had epileptic encephalopathies. Three (6%) patients became seizure free, 35 (73%) reported <50%-90% reduction, and 10 (21%) had 0%-50% reduction during a 2-year period. Diet duration or ketogenic diet type did not predict reduction in seizures (P = .381; P = .272). Constipation (n = 31, 65%) was very common. Food refusal (n = 3, 6%) and poor parental compliance (n = 5, 10%) were common reasons cited for cessation. There were lower rates of side effects for modified Atkins diet. Diet cessation was greatest for MCT; however, 3 patients on MCT ceased therapy because adequate seizure control was achieved. Nephrolithiasis was reported in 1 patient before potassium citrate was used and 2 patients noncompliant with potassium citrate supplementation developed hypercalciuria. CONCLUSION The 3 ketogenic diets were comparably effective in seizure control and generally well-tolerated. Potassium citrate supplementation is an effective prophylactic supplement for the prevention of nephrolithiasis.

Asparagine Synthetase Deficiency causes reduced proliferation of cells under conditions of limited asparagine

Asparagine Synthetase Deficiency is a recently described cause of profound intellectual disability, marked progressive cerebral atrophy and variable seizure disorder. To date there has been limited functional data explaining the underlying pathophysiology. We report a new case with compound heterozygous mutations in the ASNS gene (NM_183356.3:c. [866G>C]; [1010C>T]). Both variants alter evolutionarily conserved amino acids and were predicted to be pathogenic based on in silico protein modelling that suggests disruption of the critical ATP binding site of the ASNS enzyme. In patient fibroblasts, ASNS expression as well as protein and mRNA stability are not affected by these variants. However, there is markedly reduced proliferation of patient fibroblasts when cultured in asparagine-limited growth medium, compared to parental and wild type fibroblasts. Restricting asparagine replicates the physiology within the blood-brain-barrier, with limited transfer of dietary derived asparagine, resulting in reliance of neuronal cells on intracellular asparagine synthesis by the ASNS enzyme. These functional studies offer insight into the underlying pathophysiology of the dramatic progressive cerebral atrophy associated with Asparagine Synthetase Deficiency.

A spectroscopic and equilibrium binding analysis of cationic detergent-protein interactions using soluble and insoluble recombinant porcine growth hormone.

Overexpression of cloned eukaryote genes in bacteria often leads to the formation of insoluble refractile bodies which require solubilization by harsh denaturants or detergents. We describe the conformational changes associated with the binding of a surfactant, cetyltrimethylammonium chloride (CTAC) to recombinant porcine growth hormone (PGH). The stoichiometry of binding by CTAC to the soluble and insoluble forms of recombinant PGH was also assessed. Optimum CTAC binding and protein solubilisation were obtained at 50 degrees C and at extreme pH. Increased ionic strength and changes in pH towards the isoelectric point of PGH (pH 6) decreased both the binding of CTAC and the efficiency of solubilising PGH from inclusion bodies. The positive charge on the quaternary ammonium head group of CTAC was found to be critical in the binding of CTAC to PGH and for the subsequent solubilisation of inclusion bodies. The binding of CTAC to the soluble form of PGH caused appreciable changes to the tertiary structure of the protein but did not significantly alter secondary structure, or cause complete unfolding. These observations help to explain earlier results which demonstrate that urea, guanidine hydrochloride and CTAC solubilized recombinant PGH molecules behave differently during in vitro refolding (Puri, N.K., Crivelli, E.C., Cardamone, M., Fiddes, R., Bertolini, J., Ninham, B. and Brandon, M.R. (1992) Biochem. J. 285, 871-879.).

In vitro testing of a pulsatile delivery system and its in vivo application for immunisation against tetanus toxoid

Abstract Problems such as patient compliance and overdosing call for the development of pulsatile drug delivery devices. The in vitro and in vivo testing of a pulsatile delivery device for tetanus toxoid are described. In vitro release studies indicate that the delivery of the entrained active is dependent upon the driving mechanism, a fluid-activated swelling agent. The delivery profile is influenced by the physicochemical properties of the biomaterials used to construct the implant, such as polyethylene porosity, excipients and the design properties of the device. Solid formulations of tetanus toxoid antigen were intermittently released into the subcutaneous tissues in sheep using the delivery device. The in vivo release of the lyophilised and compressed powder of tetanus toxoid containing excipient materials (including lactose, cellulose and magnesium stearate) was monitored indirectly by measuring levels of antibodies against tetanus toxoid in sera of mice and sheep. The antibody titres generated by our devices were no different to the titres generated by subcutaneous injection of an alum-adjuvanted liquid formulation of tetanus toxoid. The pulsatile delivery devices described should facilitate the delivery of most vaccine antigens and pharmaceuticals.

Arterial ischemic stroke in children with cardiac disease

Objective: To describe the spectrum of cardiac disorders, timing in relation to interventional procedures, and outcome in children with cardiac disease and arterial ischemic stroke (AIS). Methods: Children younger than 18 years with cardiac disease and radiologically confirmed AIS admitted to the Royal Childrens Hospital Melbourne between 1993 and 2010 were retrospectively identified using ICD-9 and ICD-10 searches. Results: Seventy-six children with cardiac disease and radiologically confirmed AIS were identified with the median age at diagnosis of 5 months (interquartile range 0–58). Cardiac lesions included cyanotic congenital heart disease (CHD) in 42 (55%), acyanotic heart disease in 24 (29%), cardiomyopathies/myocarditis in 6 (8%), infective endocarditis in 3 (4%), and primary arrhythmias in 3 (4%). Stroke occurred following cardiac procedures in 52 patients (68%): 41 post cardiac surgery (4.6 strokes per 1,000 surgical procedures) and 11 post cardiac catheterization (1.7 strokes per 1,000 catheterizations). The median time from procedure to diagnosis of stroke was 3 days (interquartile range 2–7), with 68% (95% confidence interval 58%–79%) of strokes estimated to occur within the periprocedural period. Prevalence of periprocedural stroke varied by diagnostic category, but was most common in patients with cyanotic CHD undergoing palliative surgery (22/2,256, 1%) (p < 0.005). There were 3 AIS-related deaths, and 54 survivors (84%) had persisting neurologic deficits. Conclusions: Infants with cyanotic CHD were most frequently affected by AIS during the periprocedural period. Prospective cohort studies are required to determine effective primary and secondary prevention strategies.

A relationship between the starting secondary structure of recombinant porcine growth hormone solubilised from inclusion bodies and the yield of native (monomeric) protein after in vitro refolding

Recombinant porcine growth hormone (rPGH) was solubilised from inclusion bodies (IBs) using either 6 M guanidinium hydrochloride (GnHCl), 7.5 M urca or by a novel method using a cationic surfactant, cetyltrimethylammonium chloride (CTAC). Circular dichroism (CD) analysis of the secondary (2°) structure of the urea‐ and GnHCl‐solubilised rPGH showed the absence of α‐helical content with the majority of the molecule existing in a ‘random coil’ structure. In contrast, the CTAC‐solubilised rPGH displayed significant starting 2° structure (10–15% α helix; 30–40% β structure). The three rPGH preparations were refolded in vitro against weak urea, GnHCl or aqueous buffers, resulting in an average refolding efficiency of 50% native (monomeric) rPGH for CTAC solubilised IBs and only 20% for urea or GnHCl solubilised IBs. We conclude that the method of solubilisation of IBs and the resultant difference in the starting 2° structure of rPGH, particularly α‐helical content, is a major in vitro factor that apparently predetermines the aggregation/refolding behaviour rPGH irrespective of refolding environment.

Severe iron‐deficiency anaemia in adolescents: Consider Helicobacter pylori infection

Aim:  This article describes the association of severe iron‐deficiency anaemia with Helicobacter pylori gastritis.