Abnormal cortical excitation in response to photic stimulation (photosensitivity) has historically been associated with generalized epilepsies, in patients outside of infancy. At our tertiary centre, ...we encountered a patient with infantile spasms secondary to a mutation in ALG13 (c320A>G) who had photic stimulation‐induced epileptic spasms over a broad range of frequencies on multiple EEGs, which were worse without treatment and decreased as treatment was escalated. This is the first reported case of epileptic spasms triggered by photic stimulation and it is unclear whether the phenomenon is unique to this patient, to those with this mutation or whether it is present in a broader group of patients with infantile spasms.
While adult zebrafish, Danio rerio, possess ammonia and urea transporters (Rh and UT proteins, respectively) in a number of tissues, they are most heavily concentrated within the gills. UT has a ...diffuse expression pattern within Na+-K+-ATPase (NKA)-type mitochondrion-rich cells and Rh proteins form a network similar to the arrangement seen in pufferfish gills (Nakada et al., 2007b). Rhag expression appeared to be limited to the pillar cells lining the blood spaces of the lamellae while Rhbg was localized to the outer layer of both the lamellae and the filament, upon the pavement cells. Exposure to high external ammonia (HEA) or phloretin increased tissue levels of ammonia and urea, respectively, in adult and juvenile zebrafish; however, the responses to these stressors were age dependent. HEA increased mRNA levels for a number of Rh proteins in embryos and larvae but did not elicit similar effects in adult gills, which appear to compensate for the unfavourable ammonia excretory gradient by increasing expression of V-type H+-ATPase. Phloretin exposure increased UT mRNA levels in embryos and larvae but was without effect in adult gill tissue. Surprisingly, in both adults and juveniles, HEA increased the mRNA expression of UT and phloretin increased the mRNA expression of Rh proteins. These results imply that, in zebrafish, there may be a tighter link between ammonia and urea excretion than is thought to occur in most teleosts.
•Epilepsy in response to bathing can have varied triggers and semiologies•MDB5-associated neurological disorder, MAND, can result in reflex epilepsy•The genotypes associated with bathing epilepsy ...should expand to include 2q22.3q23.2•A modified EEG montage can safely capture an ictal reflex bathing seizure•Untreated bathing related reflex epilepsy with autonomic involvement has the potential for significant injury.
► Behavioural memory at 3h (ITM) and 24h (LTM) are identical. ► Neuronal memory at 3h (ITM) and 24h (LTM) are significantly different. ► Excitability of specific interneuron decreases following ...training. ► A memory trace remains in the neuron after behavioural memory disappears.
Both intermediate-term memory (ITM) and long-term memory (LTM) require novel protein synthesis; however, LTM also requires gene transcription. This suggests that the behavioural output of the two processes may be produced differently at the neuronal level. The fresh-water snail, Lymnaea stagnalis, can be operantly conditioned to decrease its rate of aerial respiration and, depending on the training procedure, the memory can last 3h (ITM) or >24h (LTM). RPeD1, one of the 3 interneurons that form the respiratory central pattern generator (CPG) that drives aerial respiration, is necessary for memory formation. By comparing RPeD1’s electrophysiological properties in naïve, ‘ITM-trained’, ‘LTM-trained’ and yoked control snails we discovered that while the behavioural phenotype of memory at 3 and 24h is identical, the situation at the neuronal level is different. When examined 3h after either the ‘ITM’ or ‘LTM’ training procedure RPeD1 activity is significantly depressed. That is, the firing rate, input resistance, excitability and the number of action potential bursts are all significantly decreased. In snails receiving the ITM-training, these changes return to normal 24h post-training. However, in snails receiving the ‘LTM-training’, measured RPeD1 properties (firing rate, excitability, membrane resistance, and the number of action potential bursts fired) are significantly different at 24h than they were at 3h. Additionally, 24h following LTM training RPeD1 appears to be functionally “uncoupled” from its control of the pneumostome as the link between RPeD1 excitation and pneumostome opening is weakened. These data suggest that the behavioural changes occurring during LTM are due to more widespread neuronal reorganization than similar behavioural changes occurring during ITM. Thus ITM and LTM are not just distinct in a chronological and transcriptional manner but are also distinct at the level of neuronal properties.
► Low environmental calcium blocks long-term memory formation but not memory recall. ► The effect of environmental calcium concentration on memory formation is acute. ► Neurophysiological correlates ...with behavioral change occur in the neuron RPeD1. ► Low calcium environments may prevent L. stagnalis responding to novel stressors.
The freshwater snail Lymnaea stagnalis (L.) is considered a calciphile and exhibits reduced growth and survival in environments containing less than 20mg/l environmental calcium. Although it has no apparent effect on survival at 20mg/l, reducing environmental calcium increases metabolic demand, and as such we consider that this level of calcium acts as a stressor on the snail. We exposed snails to acute periods of low environmental calcium and tested their ability to form intermediate-term memory (ITM) and long-term memory (LTM) following one trial operant conditioning (1TT) to reduce aerial respiratory activity in hypoxic conditions. We also assessed whether there were changes in the electrophysiological properties of a single neuron, right pedal dorsal 1 (RPeD1), which has been demonstrated to be necessary for LTM formation. Following training in high (80mg/l) environmental calcium, L. stagnalis formed ITM and LTM lasting 24h and demonstrated a significant reduction in all activity measured from RPeD1; however when snails were exposed to low (20mg/l) environmental calcium they were able to form ITM but not LTM. Although no behavioral LTM was formed, a partial reduction in RPeD1 activtiy measured 24h after training was observed, indicating a residual effect of training. The strong effect that environmental calcium concentration had on physiology and behavior in response to training to reduce aerial respiration in L. stagnalis suggests that it is an element of gastropod husbandry that needs to be carefully considered when studying other traits. This study also indicates that L. stagnalis found naturally in low calcium environments may be less able to adapt to novel stressors than populations found in harder waters.
► Strain differences in memory forming ability. ► A neuron, RPeD1 known to be necessary for memory was studied. ► RPeD1 in the superior memory forming strain is ‘primed’ for memory formation. ► With ...training RPeD1 becomes less excitable. ► The less excitable state of RPeD1 is a neuronal correlate of behavioural memory.
The ability to learn and form long-term memory (LTM) can enhance an animal’s fitness, for example, by allowing them to remember predators, food sources or conspecific interactions. Here we use the pond snail, Lymnaea stagnalis, to assess whether variability between natural populations (i.e. strains) in memory forming capabilities correlates with electrophysiological properties at the level of a single neuron, RPeD1. RPeD1 is a necessary site of LTM formation of aerial respiratory behaviour following operant conditioning. We used strains from two small, separate permanent ponds (TC1 and TC2). A comparison of the two populations showed that the TC1 strain had enhanced memory forming capabilities. Further, the behavioural phenotype of enhanced memory strain was explained, in part, by differences in the electrophysiology of RPeD1. Compared to RPeD1 from the naive TC2 strain, RPeD1 from the TC1 strain has both a decreased resistance and decreased excitability. Moreover, 24h after a single 0.5h training session, those membrane properties, as well as the firing and bursting rate, decrease further in the TC1 strain but not in the TC2 strain. The initial differences in RPeD1 properties in the TC1 strain coupled with their ability to further change these properties with a single training session suggests that RPeD1 neurons from the TC1 strain are “primed” to rapidly form memory.
The nature of ammonia and urea excretion was examined in the Pacific hagfish (
Eptatretus stoutii), which, under resting conditions, excreted similar quantities of nitrogen as either ammonia or urea. ...In the presence of high external ammonia (HEA) concentrations, ammonia was taken up at high rates and then excreted at similarly high rates upon return to normal water. However, although elevated by HEA, plasma ammonia levels were maintained at approximately 1–4
μmol
N
g
−
1
, reflecting time-dependent decreases in the rates of ammonia uptake, the possible conversion of ammonia to urea, and the potential active excretion of ammonia against a gradient. Internal injections of NH
4Cl caused marked increases in the rate of ammonia excretion and a delayed increase in urea excretion that may have resulted from increasing urea levels in the plasma. Conversely, when the rate of urea excretion was reduced in the presence of 0.1
mM phloretin, ammonia excretion was significantly elevated. Rates of urea excretion were initially increased by approximately 1000-fold following internal urea injections while the presence of high external urea levels (5–100
mM final concentration) resulted in associated linear increases in plasma urea levels. Using hagfish skin mounted in Ussing chambers, the rate of diffusion of ammonia across the skin exceeded that of urea by approximately four times when equivalent gradients were imposed. Based on western blotting and immunocytochemistry, hagfish gill appears to possess Rh proteins (Rhag, Rhbg and Rhcg1) and urea transporter proteins. Despite the tolerance of hagfish to high levels of ammonia and urea, it is suggested that the presence of ammonia and urea transporter proteins may be required during the period of time hagfish spend in burrows or while feeding, when conditions of high ammonia and/or urea might be encountered.
•We present the fourth documented potential case suggestive of “true” neuromyelitis optica spectrum disorder (NMOSD) meeting the current criteria associated with dengue infection.•Most reported cases ...of acute dengue infection presenting with a core clinical phenotype listed in the 2015 NMOSD diagnostic criteria were not tested for AQP4-IgG antibody.•Cases with acute DENV-infection with a neurological manifestation presented with a spinal cord phenotype, the majority with a LETM.•AQP4-IgG status might be helpful in a suggestive neurological presentation associated with dengue infection and subsequent decisions regarding long term immunotherapy.
: Neuromyelitis Optica Spectrum Disorder can be associated with parainfectious and post-infectious triggers. Dengue virus infection is one of the most common arbovirus infections in the world, and may present with neurological manifestations.
: We present a case of DENV-associated with LETM and positive aquaporin-4 IgG, and a systematic review of published cases.
: Medline (Ovid) and PubMed were search through June 2021, for case reports, series and observational studies that described patients with DENV-associated LETM and/or NMOSD.
: An adolescent girl who had recently immigrated from a Dengue-endemic region presented with a LETM with high positive AQP4-IgG titer and seropositive DENV IgM/IgG antibodies. She responded well to steroids and subsequently started maintenance rituximab for her NMOSD diagnosis. Literature review: 22 publications describing 27 patients met inclusion criteria. In addition to this case, three published cases met current criteria for NMOSD with serological evidence of acute DENV infection.
: It is unknown whether there is a pathophysiological association between DENV infection and NMOSD. Regardless, if an immune-mediated event is suspected, particularly NMOSD, appropriate immunotherapy should be considered early. Decision regarding long term immunotherapy may depend on index of suspicion of true NMOSD, and this is where AQP4-IgG status and follow-up is helpful.
Do zebrafish Rh proteins act as dual ammonia-CO2 channels? Perry, Steve F.; Braun, Marvin H.; Noland, Marie ...
Journal of experimental zoology. Part A, Ecological genetics and physiology,
11/2010, Letnik:
313A, Številka:
9
Journal Article
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