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Background and Purpose: Ketogenic diet (KD) improves seizure control in patients with drug-resistant forms of epilepsy; however, the mechanism of action remains poorly understood. Increased mitochondrial levels of glutathione (GSH) might contribute to a change in seizure susceptibility suggestive of possible anticonvulsant role for GSH. Our goals were to quantify changes of absolute GSH levels in the brain by in vivo MR spectroscopy and correlate that with degree of seizure control in patients on KD. Methods: Five cognitively normal adult patients with drug-resistant epilepsy were initially included and 2 completed the study. Each patient was evaluated by a neurologist and registered dietitian at baseline, 1, 3, and 6 months for seizure status and diet adherence. Each patient received a baseline short TE single-voxel water-suppressed point-resolved spectroscopy (PRESS) 1 H MRS in parieto/occipital grey matter and parietal white matter on a 3 Tesla General Electric magnet prior to starting the ketogenic diet and a follow-up stury at 6 months. Multiple metabolites, including GSH, were quantified using LCModel.Results: After being on ketogenic diet for 6 months, both patients (42-years-old male and 35-years-old female) demonstrated marked increases in absolute GSH level in both gray matter (0.1 to 1.4 and 0.1 to 0.7 IU) and white matter (0.65 to 1.5 and 0.8 to 2 IU), as well as 50% improvements in seizure duration and frequency. Other metabolites including ketone bodies, Acetone (Acn), Beta hydroxybutyrate (βHB), and acetoacetate (AcAC), did not demonstrate consistent changes. Conclusion: Markedly increased levels of GSH (7-fold and 14-fold) were observed in longitudinal prospective study of two adult patients with intractable epilepsy with 50% seizure improvement after initiation of ketogenic diets. This pilot study supports the possible anticonvulsant role of GSH in the brain.

Similar to the pathogenesis of autoimmune disease, SARS-CoV-2 (COVID-19) infection has been shown to be associated with dysregulated and persistent inflammatory reactions and production of some antibodies. We report 3 pediatric patients found to have serum SARS-CoV-2 antibodies who presented with neurologic findings suggestive of postinfectious autoimmune-mediated encephalitis. All 3 cases showed lymphocytic pleocytosis on cerebrospinal fluid studies and marked improvement in neurologic symptoms after high-dose intravenous corticosteroids. The manifestations of SARS-CoV-2 infection in the pediatric population are still an evolving area of study, and these cases suggest autoimmune-mediated encephalitis as yet another SARS-CoV-2 related complication.

Focal segmental glomerulosclerosis (FSGS) is an etiologically heterogeneous disorder. Genetic FSGS may be either limited to the kidney or part of a genetic syndrome with other systemic involvement. At least 21 and 34 genes have been reported for renal-limited and syndromic FSGS, respectively. The TRIM8 gene encodes a tripartite motif protein, which is an E3 ubiquitin-protein ligase that promotes proteasomal degradation of the suppressor of cytokine signaling 1 (SOCS1) and participates in the activation of interferon-gamma signaling. The TRIM8 gene is expressed in various tissues including the kidney and the central nervous system (CNS). An association between a mutation in the TRIM8 gene and childhood-onset FSGS has not been well established. We describe an 8-year-old Hispanic male with infantile onset motor and developmental delay, seizures, and proteinuria secondary to FSGS. Next generation sequencing revealed a heterozygous de novo pathogenic variant in the TRIM8 gene (C1380T>A, p.Tyr460*). Immunohistochemical staining using anti-TRIM8 and anti-SOCS1 antibodies showed no significant TRIM8 expression and strong expression of SOCS1 in the renal biopsy tissue. De novo truncating mutations of TRIM8 have been previously reported in childhood-onset epileptic encephalopathy. A molecular analysis of TRIM8 should be considered in children with FSGS and clinical abnormalities of the central nervous system.

Pathogenic de novo variants in the X-linked gene SLC35A2 encoding the major Golgi-localized UDP-galactose transporter required for proper protein and lipid glycosylation cause a rare type of congenital disorder of glycosylation known as SLC35A2-congenital disorders of glycosylation (CDG; formerly CDG-IIm). To date, 29 unique de novo variants from 32 unrelated individuals have been described in the literature. The majority of affected individuals are primarily characterized by varying degrees of neurological impairments with or without skeletal abnormalities. Surprisingly, most affected individuals do not show abnormalities in serum transferrin N-glycosylation, a common biomarker for most types of CDG. Here we present data characterizing 30 individuals and add 26 new variants, the single largest study involving SLC35A2-CDG. The great majority of these individuals had normal transferrin glycosylation. In addition, expanding the molecular and clinical spectrum of this rare disorder, we developed a robust and reliable biochemical assay to assess SLC35A2-dependent UDP-galactose transport activity in primary fibroblasts. Finally, we show that transport activity is directly correlated to the ratio of wild-type to mutant alleles in fibroblasts from affected individuals.

Pediatric stroke is particularly challenging because of its variable presentation and relative rarity. Diagnosis of pediatric stroke is often delayed while other diagnoses are considered, unfortunately leading to a loss of therapeutic opportunity. Recent research advances in adult stroke such as multimodal imaging and a clinical trial showing benefits in extending the therapeutic window for thrombolytics are likely to have important implications in pediatric stroke. We describe the case of a 13-year-old boy presenting with acute stroke where multimodal magnetic resonance imaging with perfusion and permeability images allowed safe treatment with thrombolysis outside the standard treatment time window.

Few studies have focused on tolerability and adverse events associated with natural adrenocorticotropic hormone injections for treatment of infantile spasms. Using a retrospective chart review of 130 patients, the authors compare major adverse events, weight and blood pressure changes, and unplanned medication changes associated with adrenocorticotropic hormone (ACTH) injections versus other antiepileptic drugs. Children treated with adrenocorticotropic hormone injections experienced significant short-term weight gain and blood pressure elevations, which were readily reversible with weaning off the drug. Twenty-three percent of patients treated with adrenocorticotropic hormone (14 of 60) and 17% of patients treated with other antiepileptic drugs (11 of 65) experienced a major adverse event during treatment. Few patients overall required a change in medication due to intolerable side effects. Despite early changes in weight and blood pressure, short courses of high-dose natural adrenocorticotropic hormone are generally well tolerated with no increased major adverse events when compared to antiepileptic drugs in the treatment of infantile spasms.

Flap endonuclease-1 (FEN-1) is a critical enzyme for DNA replication and repair. Intensive studies have been carried out on its structure-specific nuclease activities and biological functions in yeast cells. However, its specific interactions with DNA substrates as an initial step of catalysis are not defined. An understanding of the ability of FEN-1 to recognize and bind a flap DNA substrate is critical for the elucidation of its molecular mechanism and for the explanation of possible pathological consequences resulting from its failure to bind DNA. Using human FEN-1 in this study, we identified two positively charged amino acid residues, Arg-47 and Arg-70 in human FEN-1, as candidates responsible for substrate binding. Mutation of the Arg-70 significantly reduced flap endonuclease activity and eliminated exonuclease activity. Mutation or protonation of Arg-47 shifted cleavage sites with flap substrate and significantly reduced the exonuclease activity. We revealed that these alterations are due to the defects in DNA-protein interactions. Although the effect of the single Arg-47 mutation on binding activities is not as severe as R70A, its double mutation with Asp-181 had a synergistic effect. Furthermore the possible interaction sites of these positively charged residues with DNA substrates were discussed based on FEN-1 cleavage patterns using different substrates. Finally data were provided to indicate that the observed negative effects of a high concentration of Mg(2+) on enzymatic activity are probably due to the competition between the arginine residues and metal ions with DNA substrate since mutants were found to be less tolerant.

It is thought that the high protein density in the mitochondrial matrix results in severely restricted solute diffusion and metabolite channeling from one enzyme to another without free aqueous-phase diffusion. To test this hypothesis, we measured the diffusion of green fluorescent protein (GFP) expressed in the mitochondrial matrix of fibroblast, liver, skeletal muscle, and epithelial cell lines. Spot photobleaching of GFP with a 100× objective (0.8-μm spot diam) gave half-times for fluorescence recovery of 15–19 ms with >90% of the GFP mobile. As predicted for aqueous-phase diffusion in a confined compartment, fluorescence recovery was slowed or abolished by increased laser spot size or bleach time, and by paraformaldehyde fixation. Quantitative analysis of bleach data using a mathematical model of matrix diffusion gave GFP diffusion coefficients of 2–3 × 10−7 cm2/s, only three to fourfold less than that for GFP diffusion in water. In contrast, little recovery was found for bleaching of GFP in fusion with subunits of the fatty acid β-oxidation multienzyme complex that are normally present in the matrix. Measurement of the rotation of unconjugated GFP by time-resolved anisotropy gave a rotational correlation time of 23.3 ± 1 ns, similar to that of 20 ns for GFP rotation in water. A rapid rotational correlation time of 325 ps was also found for a small fluorescent probe (BCECF, ∼0.5 kD) in the matrix of isolated liver mitochondria. The rapid and unrestricted diffusion of solutes in the mitochondrial matrix suggests that metabolite channeling may not be required to overcome diffusive barriers. We propose that the clustering of matrix enzymes in membrane-associated complexes might serve to establish a relatively uncrowded aqueous space in which solutes can freely diffuse.

We study the reaction efficiency of a surficial process in which a diffusing, tumbling dipole A reacts (eventually and irreversibly) with a stationary target dipole B. In contrast to earlier studies of such irreversible diffusion‐reaction events (A+B→C), we consider the situation where at each and every site of the space accessible to the diffusing coreactant A, there is also embedded a fixed dipole. To quantify the influence on the reaction efficiency of (angle‐averaged, dipole–dipole) potential interactions between the tumbling dipole A and the ensemble of stationary dipoles, we design a lattice‐statistical model to describe this problem and use both analytical methods and numerical techniques rooted in the theory of finite Markov processes to work out its consequences. Specifically, we define the reaction space to be an n×n=N square‐planar lattice with the target dipole occupying the centrosymmetric site in that space and determine the mean number of steps required before the irreversible event, A+B→C, occurs. Our results reveal two qualitatively‐distinct regimes of behavior for this diffusion‐reaction process, a low temperature (or strong coupling) regime dominated by nearest‐neighbor excursions only, and a high‐temperature (or weak‐coupling) regime dominated by non‐nearest neighbor excursions of the tumbling dipole A, with the transition between these two regimes occurring over a relatively narrow range of interparticle couplings. This behavior has the character of an ‘‘order–disorder’’ transition and is interpreted here in terms of an ‘‘order parameter’’ W related to a generalized Onsager length. The behavior uncovered is studied as a function of system size and of the boundary conditions imposed.

The benefits of hemicraniectomy for malignant middle cerebral artery (MCA) stroke may not be apparent in the 3 to 6 months in which final outcomes are assessed in research studies. We present the case of a 15 year-old who underwent hemicraniectomy for malignant MCA stroke and was significantly disabled 3 and 6 months after event. Over the long-term she was able to graduate from university, play tennis, and live an independent life. Although functional independence with only minor disability is relatively rare in adult hemicraniectomy patients, this outcome may be more easily achieved in children during a longer period of follow-up.

Studies have suggested disparate variables affecting long-term outcomes in patients with infantile spasms. Using a retrospective chart review, the authors identified 109 patients who had follow-up data for at least 1 year since the onset of spasms. Patient and treatment variables were recorded, in addition to neurodevelopmental and seizure outcomes. Etiology was strongly associated with motor and cognitive status but not with long-term seizure control. Lag time to initiation of treatment was not predictive of any outcome, nor for need to use a second agent to resolve spasms, even when controlling for etiology. However, patients who responded to the first medication achieved superior seizure and cognitive outcomes. The delayed impact of individual medications could not be analyzed because many patients received multiple agents. While etiology and response to first medication predict better outcomes, the majority of patients with infantile spasms continue to have epilepsy with long-term motor and cognitive disabilities.

Botulinum toxins are potent neurotoxins used in a variety of neurological disorders. Few pediatric reports have been published to date regarding the potential hazards of therapeutic use of botulinum toxins. We describe the case of a 10-year-old boy who developed systemic weakness following treatment of spasticity with botulinum toxin type B. The patient developed iatrogenic botulism with ptosis, facial diplegia, neck flexor and extensor weakness, and profound hypopharyngeal laxity with respiratory compromise from which he eventually recovered. Clinicians should be mindful of the risk for systemic botulism when using local injections of the neurotoxin.

RNA primer removal from Okazaki fragments during lagging-strand replication and the excision of damaged DNA bases requires the action of structure-specific nucleases, such as the mammalian flap endonuclease 1 (FEN-1). This nuclease contains two conserved motifs enriched with acidic amino acid residues that are important for catalytic function. Similar motifs have been identified in nucleases found in viruses, archebacteria, eubacteria, and in eukaryotes ranging from yeast to humans. Unique among these proteins, the putative FEN-1 homologue in Escherichia coli is contained within the N-terminal region of the DNA polymerase I (PolN). To demonstrate that the cellular functions of FEN-1 reside in PolN, we cloned and expressed the amino terminal domain (323 amino acid residues) of PolI in a Saccharomyces cerevisiae strain lacking the FEN-1 homologue RAD27. Overexpression of PolN suppressed, to varying degrees, phenotypes associated with a rad27 null strain. These include temperature sensitivity, Okazaki fragment processing, a mutator phenotype, a G2/M cell cycle arrest, minichromosome loss, and methyl methane sulfonate sensitivity. We purified Rad27 and PolN proteins in order to determine whether differences in their intrinsic nuclease activities or interaction with proliferating cell nuclear antigen (PCNA) could explain the partial suppression of some phenotypes. We found that the in vitro nuclease activities of Rad27 were more potent than those of PolN and the activity of Rad27, but not PolN, was stimulated by PCNA. We conclude that the N-terminal nuclease domain of E. coli polymerase I encodes a functional homologue of FEN-1.