Parents' early healthcare transition experiences with preterm and acutely ill infants: a scoping review.

BACKGROUND: Parents undergo multiple transitions following the birth of an ill infant: their infant's illness-health trajectory, neonatal intensive care unit hospitalization and transfers from one healthcare setting to another, while also transitioning to parenthood. The objective of this review was to map and synthesize evidence on the experiences and needs of parents of preterm or ill infants as they transition within and between healthcare settings following birth. METHODS: The scoping review followed Arskey and O'Malley's () framework, enhanced by Levac et al. (). Relevant studies were identified through a comprehensive search strategy of scientific and grey literature databases, online networks, Web of Science and citation lists of relevant articles. Inclusion criteria encompassed a focus on infants undergoing a healthcare transition, and the experiences and needs of parents during transition. Studies were appraised for design quality, and data relevant to parent experiences were extracted and underwent thematic analysis. RESULTS: A total of 7773 records were retrieved, 90 full texts reviewed and 11 articles synthesized that represented a total sample of 435 parents of preterm or ill infants. Parents reported on their experiences in response to their infant's transition within and between hospitals and across levels of neonatal intensive care unit, intermediate and community hospital care. Ten studies used qualitative research methods, while one employed quantitative survey methods. Four key themes were identified: that of parent distress throughout transition, parenting at a distance, sources of stress and sources of support. Parents' stress resulted from not being informed or involved in the transition decision, inadequate communication and perceived differences in cultures of care across healthcare settings. CONCLUSIONS: Opportunities to improve parents' early transition experiences include enhanced engagement, communication, information-sharing and shared decision-making between health care providers and parents. Future areas of research should focus on early transition interventions to advance parent capacity, confidence and closeness as the primary nurturer.

A qualitative exploration of the experiences of children with spina bifida and their parents around incontinence and social participation.

BACKGROUND: Urinary incontinence is frequently experienced by children with spina bifida, putting them at increased risk for low self-esteem and impacting upon participation in home, school and leisure activities. However, little is known about children's experiences of these continence issues. OBJECTIVE: This study explored the experiences of children and young people with spina bifida around continence issues, social participation and peer relationships, in order to identify potential areas of support healthcare professionals can provide. METHODS: Children and youth aged 6-18 years with diagnoses of spina bifida and neurogenic bladder and their parents were invited to participate in semi-structured interviews. Descriptive thematic analysis was employed. RESULTS: Eleven children (with a range of mobility levels, types of spina bifida and degrees of bladder control) and their parents participated in the study. Three broad themes were identified, which encompassed the following: (1) normal versus different; (2) independence, ownership and the road to continence; and (3) peer relationships and acceptance. DISCUSSION: The experiences discussed by the children and parents in this study ranged from minimal impact of incontinence on their day-to-day living to significant social isolation and rejection. The stigma of incontinence was apparent in all interviews. Children and youth who were able to control their bladder with minimal accidents had greater independence and more opportunities for social participation. Healthcare professionals need to take into account that parents and their children may differ in attitudes and desires about the management of incontinence.

Decision-making for extremely preterm infants with severe hemorrhages on head ultrasound: Science, values, and communication skills.

Severe intracranial hemorrhages are not rare in extremely preterm infants. They occur early, generally when babies require life-sustaining interventions. This may lead to ethical discussions and decision-making about levels of care. Prognosis is variable and depends on the extent, location, and laterality of the lesions, and, importantly also on the subsequent occurrence of other clinical complications or progressive ventricular dilatation. Decision-making should depend on prognosis and parental values. This article will review prognosis and the uncertainty of outcomes for different lesions and provide an outline of ways to conduct an ethically appropriate discussion on the decision of whether to continue life sustaining therapy. It is possible to communicate in a compassionate and honest way with parents and engage in decision-making, focussing on personalized information and decisions, and on function, as opposed to diagnosis.

The Phenotypic Spectrum of New-onset IBD in Canadian Children of South Asian Ethnicity: A Prospective Multi-Centre Comparative Study.

BACKGROUND: Canadian-born children of South Asian [SA] ethnicity develop inflammatory bowel disease [IBD] at similar rates to those among Caucasian children. We evaluated the variation in phenotypic spectrum of IBD in SA and Caucasian children in a national paediatric inception cohort of new-onset IBD. METHODS: Patients aged <17 years, enrolled in a Canadian nationwide inception cohort study, were included. Baseline demographic and IBD phenotypic features were compared between SA and Caucasian children. Longitudinal outcomes through 18 months of follow-up were compared matched by propensity scores. RESULTS: Of 1156 children enrolled over 2014 to 2019, 623 were Caucasian [98% and 88% parents Canadian born] and 114 SA [79% Canadian born, 87% parents SA born]. Fewer SAs have a first-degree relative with IBD, 6% vs 19% in Caucasians, p = 0.002. SAs present at a younger age, median age 11.4 years (interquartile range [IQR] 9.2-14.3) vs 13 years [IQR 10.9-15 years], p = 0.03 and more commonly with a UC/IBD-U [ulcerative colitis/IBD-unclassified] subtype [ratio of UC/IBD-U to CD 1.2:1 vs 1:1.8 for Caucasians, p <0.001]. Additionally, a greater proportion of SA CD patients present with colonic-only disease [colonic-only CD/UC/IBD-U in SAs 67% vs 57% for Caucasians, p = 0.001], and among those with CD, colonic CD in SAs 31% vs 23% in Caucasians, p = 0.20]. Perianal fistulising disease was also numerically more common in SAs (14 [27%] vs 64 [18%], p = 0.06]. Adjusting for differences in phenotypic presentation, anti-tumour necrosis factor [TNF] exposure, and time to initiation was similar, and two-thirds of children, whether anti-TNF exposed or naïve, were in corticosteroid-free clinical remission at 18 months irrespective of ethnicity. CONCLUSIONS: The phenotypic spectrum of new-onset IBD in SA children differs from that of Caucasian children, but treatment and clinical course are similar within phenotypic subgroups.

Irradiated sporozoite vaccine induces HLA-B8-restricted cytotoxic T lymphocyte responses against two overlapping epitopes of the Plasmodium falciparum sporozoite surface protein 2.

Vaccines designed to protect against malaria by inducing CD8+ cytotoxic T lymphocytes (CTL) in individuals of diverse HLA backgrounds must contain multiple conserved epitopes from various preerythrocytic-stage antigens. Plasmodium falciparum sporozoite surface protein 2 (PfSSP2) is considered an important antigen for inclusion in such vaccines, because CD8+ CTL against the P. yoelii SSP2 protect mice against malaria by eliminating infected hepatocytes. To develop PfSSP2 as a component of malaria vaccines, we investigated the presence of anti-PfSSP2 CTL in two HLA-B8+ volunteers immunized with irradiated P. falciparum sporozoites and characterized their CTL responses using PfSSP2-derived 15-amino acid peptides bearing the HLA-B8-binding motif. Peripheral blood mononuclear cells from both volunteers stimulated with recombinant vaccinia expressing PfSSP2 displayed antigen-specific, genetically restricted, CD8+ T cell-dependent CTL activity against autologous target cells expressing PfSSP2. Of the five HLA-B8 motif-bearing 15-mers identified in the PfSSP2 sequence, two peptides sharing a 10-amino acid overlap sensitized HLA-B8-matched target cells from both volunteers for lysis by peptide-stimulated effectors. The CTL activity was HLA-B8 restricted and dependent on CD8+ T cells. Analysis of the three shorter peptides representing HLA-B8 motif-bearing sequences within the two positive peptides for their ability to bind to HLA-B8 in vitro, and to sensitize target cells for lysis by effectors stimulated with the 15-mers, identified two overlapping HLA-B8-restricted CTL epitopes. Available data indicate that the sequence of one CTL epitope is conserved and the other is variant among P. falciparum isolates. Circulating activated CTL against the conserved epitope could be directly identified in one of the two volunteers. The identification of two HLA-B8-restricted CTL epitopes on PfSSP2 provides data critical to developing an epitope-based anti-liver stage malaria vaccine.

Phenotypic Variation in Paediatric Inflammatory Bowel Disease by Age: A Multicentre Prospective Inception Cohort Study of the Canadian Children IBD Network.

BACKGROUND AND AIMS: Incidence of paediatric inflammatory bowel disease [IBD] in Canada is among the highest worldwide, and age of onset may be decreasing. In a multicentre nationwide inception cohort study, we examined variation in phenotype of IBD throughout the paediatric age spectrum. METHODS: Children aged ≥2 years [y] and <17y [A1 age at diagnosis], with new onset IBD, were systematically evaluated at sites of the Canadian Children IBD Network. Prospectively recorded phenotypic data were compared between age groups. RESULTS: Among 1092 children (70% Caucasian; 64% Crohn's disease [CD], 36% ulcerative colitis/inflammatory bowel disease unclassified [UC/IBD-U]; median age 13 y, interquartile range [IQR] 11-15 y), 210 [19%] were diagnosed before the age of age 10 y [Paris A1a] and 43 [4%] before age 6 y (very-early-onset [VEO-IBD]). CD was less common in younger children [42%, 56%, 66%, respectively, of VEO-IBD, A1a; A1b]. Colon-only IBD [UC/IBDU or CD-colon] was present in 81% of VEO-IBD and 65% of A1a; ileal disease increased progressively, reaching plateau at age 10 y. CD location was ileocolonic [L3] in 53% overall. Ileitis [L1] increased with age [6% of VEO-IBD; 13% of A1a; 21% of A1b], as did stricturing/penetrating CD [4% of A1a; 11% of A1b]. At all ages UC was extensive [E3/E4] in >85%, and disease activity moderate to severe according to Physician's Global Assessment [PGA] and weighted Paediatric Crohn's Disease Activity Index/Paediatric Ulcerative Colitis Activity Index [wPCDAI/PUCAI] in >70%. Heights were modestly reduced in CD [mean height z score -0.30 ± 1.23], but normal in UC/IBD-U. CONCLUSIONS: Paris classification of age at diagnosis is supported by age-related increases in ileal disease until age 10 years. Other phenotypic features, including severity, are similar across all ages. Linear growth is less impaired in CD than in historical cohorts, reflecting earlier diagnosis.

Guideline No. 410: prevention, screening, diagnosis, and pregnancy Management for fetal neural tube defects

This revised guideline is intended to provide an update on the genetic aspects, prevention, screening, diagnosis, and management of fetal neural tube defects. Target population: Women who are pregnant or may become pregnant. Neural tube defect screening should be offered to all pregnant women. For prevention: a folate-rich diet, and folic acid and vitamin B12 supplementation, with dosage depending on risk level. For screening: second-trimester anatomical sonography; first-trimester sonographic screening; maternal serum alpha fetoprotein; prenatal magnetic resonance imaging. For genetic testing: diagnostic amniocentesis with chromosomal microarray and amniotic fluid alpha fetoprotein and acetylcholinesterase; fetal exome sequencing. For pregnancy management: prenatal surgical repair; postnatal surgical repair; pregnancy termination with autopsy. For subsequent pregnancies: prevention and screening options and counselling. The research on and implementation of fetal surgery for prenatally diagnosed myelomeningocele has added a significant treatment option to the previous options (postnatal repair or pregnancy termination), but this new option carries an increased risk of maternal morbidity. Significant improvements in health and quality of life, both for the mother and the infant, have been shown to result from the prevention, screening, diagnosis, and treatment of fetal neural tube defects. The benefits for patient autonomy and decision-making are provided in the guideline. Harms include an unexpected fetal diagnosis and the subsequent management decisions. Harm can also result if the patient declines routine sonographic scans or if counselling and access to care for neural tube defects are delayed. Cost analysis (personal, family, health care) is not within the scope of this clinical practice guideline. A directed and focused literature review was conducted using the search terms spina bifida, neural tube defect, myelomeningocele, prenatal diagnosis, fetal surgery, neural tube defect prevention, neural tube defect screening, neural tube defect diagnosis, and neural tube defect management in order to update and revise this guideline. A peer review process was used for content validation and clarity, with appropriate ethical considerations. The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See online Appendix A (Tables A1 for definitions and A2 for interpretations of strong and weak recommendations). Maternity care professionals who provide any part of pre-conception, antenatal, delivery, and neonatal care. This guideline is also appropriate for patient education.

Targeting of peptidergic vesicles in cotransmitting terminals.

In the present study, we examined the targeting of neuropeptide-containing vesicles in terminals of neurons that release both neuropeptides and classical transmitters. Single neurons were electrically stimulated with patterns of activity that were recorded in freely behaving animals. The amount of peptide release was measured biochemically using a radioimmunoassay, and the targeting of peptidergic vesicles was quantified using immunoelectronmicroscopy. Repeated electrical stimulation of single neurons produced a very large increase in peptide release. Peptide release is paralleled by a twofold increase in the number of peptidergic vesicles docked at the portion of the terminal membrane that is away from the target muscle. This is in stark contrast to cholinergic vesicles, which aggregate at, and are released from the conventional release sites in close apposition to the muscle. This differential targeting of cholinergic and peptidergic vesicles may play a significant role in the distinct release requirements and spatial and temporal characteristics of the actions of conventional and peptidergic transmitters.

Synthesis and immunological characterization of 104-mer and 102-mer peptides corresponding to the N- and C-terminal regions of the Plasmodium falciparum CS protein.

We investigated the immunogenicity and the conformational properties of the non-repetitive sequences of the Plasmodium falciparum circumsporozoite (CS) protein. Two polypeptides of 104 and 102 amino acids long, covering, respectively, the N- and C-terminal regions of the CS protein, were synthesized using solid phase Fmoc chemistry. The crude polypeptides were purified by a combination of size exclusion chromatography and RP-HPLC. Sera of mice immunized with the free polypeptides emulsified in incomplete Freund's adjuvant strongly reacted with the synthetic polypeptides as well as with native CS protein as judged by ELISA and IFAT assays. Most importantly, these antisera inhibited the sporozoite invasion of hepatoma cells. In addition, sera derived from donors living in a malaria endemic area recognized the CS 104- and 102-mers. Conformational studies of the CS polypeptides were also performed by circular dichroism spectroscopy showing the presence of a weakly ordered structure that can be increased by addition of trifluoroethanol. The obtained results indicate that the synthetic CS polypeptides and the natural CS protein share some common antigenic determinants and probably have similar conformation. The approach used in this study might be useful for the development of a synthetic malaria vaccine.

Systematic review with meta-analysis: magnetic resonance enterography signs for the detection of inflammation and intestinal damage in Crohn's disease.

BACKGROUND: In the treatment of Crohn's disease (CD), mucosal healing has become a major goal, with the hope of avoiding intestinal damage from chronic inflammation. Magnetic resonance enterography (MRE) has emerged as a non-invasive means of monitoring inflammation and damage. AIMS: As part of the development of MRE-based multi-item measures of inflammation and damage for paediatric studies, we carried out a systematic review and meta-analysis to identify MRE variables used to describe these two distinct concepts. METHODS: 2501 studies of MRI and CD were identified. Studies written in any language reporting individual MRE signs for patients diagnosed with CD were included. Two-hundred-and-forty-four studies were fully reviewed and 62 were included (inflammation, n = 51; damage, n = 24). Sensitivity, specificity and associated confidence intervals were calculated, and hierarchical summary ROC curves were constructed for each MRE sign. RESULTS: A total of 22 MRE signs were used to reflect inflammation, and 9 to reflect damage. Diagnostic accuracy of MRE signs of inflammation and damage was heterogeneous; however, wall enhancement, mucosal lesions and wall T2 hyperintensity were the most consistently useful for inflammation (most sensitivities >80% and specificities >90%), and detection of abscess and fistula were most consistently useful for damage (most sensitivities >90%, specificities >95%). CONCLUSIONS: Identifying the best MRE variables to reflect inflammation and damage will maximise the utility of this rapidly emerging technique and is the first stage of constructing MRE-based indices for evaluating inflammation and intestinal damage.

Functional roles of peptide cotransmitters at neuromuscular synapses in Aplysia.

Neuromuscular synapses in Aplysia have been used as model systems to study peptidergic cotransmission. Here we describe neuromuscular preparations in which it has been possible to investigate the physiological consequences of peptide transmitter release in detail. In the first preparation, the release of peptide cotransmitters from identified motor neuron B15 has been shown to be sensitive to the pattern of stimulation. High frequencies and long burst durations evoke peptide release that modulates muscle contractions in a manner similar to that produced by exogenous cotransmitter. By contrast, the release of the same peptide transmitters from motor neuron B1 show little dependence on pattern. We conclude that there are no stimulation patterns that are prerequisites for peptide release. Peptide cotransmitter release from motor neuron B47 has also been studied. B47, depending on the stimulation pattern, uses either ACh, which acts as a conventional inhibitory transmitter, or ACh plus neuropeptides, which act as excitatory modulatory cotransmitters. Thus, neuropeptide cotransmitters have the capability to greatly increase synaptic plasticity at neuromuscular synapses.

Na/Ca exchanger and PMCA localization in neurons and astrocytes: functional implications.

Immunocytochemistry reveals that the Na/Ca exchanger (NCX) in neuronal somata and astrocytes is confined to plasma membrane (PM) microdomains that overlie sub-PM (junctional) endoplasmic reticulum (jER). By contrast, the PM Ca(2+) pump (PMCA) is more uniformly distributed in the PM. At presynaptic nerve terminals, the NCX distribution is consistent with that observed in the neuronal somata, but the PMCA is clustered at the active zones. Thus, the PMCA, with high affinity for Ca(2+) (K(d) congruent with 100 nM), may keep active zone Ca(2+) very low and thereby "reprime" the vesicular release mechanism following activity. NCX, with lower affinity for Ca(2+) (K(d) congruent with 1,000 nM), on the other hand, may extrude Ca(2+) that has diffused away from the active zones and been temporarily sequestered in the endoplasmic reticulum. The PL microdomains that contain the NCX also contain Na(+) pump high ouabain affinity alpha2 (astrocytes) or alpha 3 (neurons) subunit isoforms (IC(50) congruent with 5-50 nM ouabain). In contrast, the alpha1 isoform (low ouabain affinity in rodents; IC(50) >10,000 nM), like the PMCA, is more uniformly distributed in these cells. The sub-PM endoplasmic reticulum in neurons (and probably glia and other cell types as well) and the adjacent PM form junctions that resemble cardiac muscle dyads. We suggest that the PM microdomains containing NCX and alpha 2/alpha 3 Na(+) pumps, the underlying jER, and the intervening tiny volume of cytosol (<10(-18) l) form functional units (PLasmERosomes); diffusion of Na(+) and Ca(2+) between these cytosolic compartments and "bulk" cytosol may be markedly restricted. The activity of the Na(+) pumps with alpha 2/alpha 3 subunits may thus regulate NCX activity and jER Ca(2+) content. This view is supported by studies in mice with genetically reduced (by congruent with 50%) alpha 2 Na(+) pumps: evoked Ca(2+) transients were augmented in these cells despite normal cytosolic Na(+) and resting Ca(2+) concentrations ([Na(+)](CYT) and [Ca(2+)](CYT)). We conclude that alpha 2/alpha 3 Na(+) pumps control PLasmERosome (local) [Na(+)](CYT). This, in turn, via NCX, modulates local [Ca(2+)](CYT), jER Ca(2+) storage, Ca(2+) signaling, and cell responses.

Safety, immunogenicity, and efficacy of a malaria sporozoite vaccine administered with monophosphoryl lipid A, cell wall skeleton of mycobacteria, and squalane as adjuvant.

A Plasmodium falciparum circumsporozoite protein (PfCSP) recombinant fusion protein, R32NS1(81), formulated with monophosphoryl lipid A, cell wall skeleton of mycobacteria, and squalane (Detox) was administered to 12 volunteers. One volunteer had malaise and self-limited painful induration at the injection site after the second dose and declined further immunization. The other 11 volunteers tolerated the three doses of 1,230 micrograms of vaccine, but most complained of sore arms; in five cases the pain or malaise was severe enough to interfere with work or sleep. Two weeks after the third dose of vaccine, four of the 11 immunized volunteers had > or = 14 micrograms/ml of antibodies to the repeat region of the PfCSP in their serum. Two of these four volunteers did not develop P. falciparum parasitemia when challenged by the bite of five mosquitoes carrying P. falciparum sporozoites. The seven volunteers with lower levels of antibodies and 11 of 11 controls developed parasitemia. These data are consistent with other studies, and indicate that vaccine-induced antibodies against the repeat region of PfCSP can prevent effective sporozoite infection of hepatocytes in humans. The challenge is to improve the immunogenicity of PfCSP-based vaccines, and to develop methods for including PfCSP peptides as components of multitarget malaria vaccines.

Computed tomography and ultrasound in diagnosis of pelvic lipomatosis.

Computed tomography (CT) and ultrasound are emerging as useful diagnostic adjuvants in the confirmation of pelvic lipomatosis. A case of pelvic lipomatosis studied by CT and sonography is presented. These two techniques offer greater precision in the demonstration of fatty tissue density within the true pelvis. The findings appear characteristic and unique. CT and ultrasound confirmation of pelvic lipomatosis provide added confidence in an accurate clinical diagnosis and may obviate the need for diagnostic surgical exploration.

Time to act on staffing cutbacks.

As a full-time auxiliary for over 20 years with the same health authority, I work with an efficient, hard-working and dedicated team of qualified nurses whose main aim is our clients' well-being.

Expression of diverse neuropeptide cotransmitters by identified motor neurons in Aplysia.

Neuropeptide synthesis was determined for individual identified ventral-cluster neurons in the buccal ganglia of Aplysia. Each of these cells was shown to be a motor neuron that innervates buccal muscles that generate biting and swallowing movements during feeding. Individual neurons were identified by a battery of physiological criteria and stained with intracellular injection of a vital dye, and the ganglia were incubated in 35S-methionine. Peptide synthesis was determined by measuring labeled peptides in extracts from individually dissected neuronal cell bodies analyzed by HPLC. Previously characterized peptides found to be synthesized included buccalin, FMRFamide, myomodulin, and the 2 small cardioactive peptides (SCPs). Each of these neuropeptides has been shown to modulate buccal muscle responses to motor neuron stimulation. Two other peptides were found to be synthesized in individual motor neurons. One peptide, which was consistently observed in neurons that also synthesized myomodulin, is likely to be the recently sequenced myomodulin B. The other peptide was observed in a subset of the neurons that synthesize FMRFamide. While identified motor neurons consistently synthesized the same peptide(s), neurons that innervate the same muscle often express different peptides. Neurons that synthesized the SCPs also contained SCP-like activity, as determined by snail heart bioassay. Our results indicate that every identified motor neuron synthesizes a subset of these methionine-containing peptides, and that several neurons consistently synthesize peptides that are likely to be processed from multiple precursors.

Activity of multiple identified motor neurons recorded intracellularly during evoked feedinglike motor programs in Aplysia.

1. The firing patterns of 22 motor neurons were determined by simultaneously recording intracellularly from up to 7 neurons during evoked feedinglike buccal motor programs (BMPs). Intracellular stimulation of cerebral-buccal interneuron 2 (CBI-2) or tactile stimulation of the odontophore were used to elicit BMPs in a reduced preparation. 2. Evoked BMPs were identified as either ingestive-like (iBMP) or egestive-like (eBMP) on the basis of their similarity to those previously recorded in select neurons in freely behaving animals. Neurons were divided into the p-group, r-group, or c-group, on the basis of the phase relationships of rhythmic membrane depolarizations and hyperpolarizations during evoked BMPs. Depolarization of the p-, r-, and c-group neurons was associated with radular protraction, retraction, and closure, respectively. With one exception, the motor neurons segregated into the same groups during iBMPs and eBMPs. The exception, B7, was categorized as a c-group neuron during iBMPs, but as an r-group neuron during eBMPs. 3. Every motor neuron exhibited cyclic membrane depolarizations and hyperpolarizations, and over one-half of the neurons fired bursts of action potentials, during both iBMPs and eBMPs. The neurons fired in patterns that would be likely to release both their conventional and peptide transmitters. 4. A marked hyperpolarizing step in the p-group neurons coincident with a depolarization in the r-group neurons was observed during both iBMPs and eBMPs, suggesting a degree of shared premotor circuitry for the two BMPs. 5. A shift in the timing of activity in c-group neurons relative to that in p- and r-group neurons during iBMPs and eBMPs was observed and correlates well with the shift in phase of radular closure relative to protraction and retraction, which is useful in distinguishing ingestion from egestion in the behaving animal. 6. The firing patterns recorded in neurons that innervate overlapping populations of muscle fibers suggested that there would be complex interactions of multiple transmitters. This is particularly intriguing in the case of I3a muscle fibers, which are innervated by two excitatory and one inhibitory neuron. The firing patterns recorded in these neurons suggest that the inhibitory motor neuron may serve to not only block inappropriate contractions, but also to specifically shape evoked contractions during feeding.

Cholinergic neuromuscular synapses in Aplysia have low endogenous acetylcholinesterase activity and a high-affinity uptake system for acetylcholine.

In the present study, we have demonstrated that ACh is the predominant fast excitatory transmitter used by identified motor neurons innervating feeding muscles in Aplysia. A detailed study of ACh metabolism was then carried out in a well-characterized neuromuscular preparation, intrinsic muscle 5 (15). This neuromuscular system has a high-affinity uptake system for choline. The rate of uptake of choline was increased by motor neuron stimulation, and this increased uptake appears to be selectively targeted to motor neuron terminals. These properties appear similar to those observed in vertebrate neuromuscular preparations. However, we have made two observations that are surprising in light of our knowledge concerning the vertebrate neuromuscular junction where released ACh is rapidly hydrolyzed by acetylcholinesterase (AChE) to choline, which is then taken up by a high-affinity uptake system. This Aplysia neuromuscular system has limited endogenous AChE activity and contains a separate high-affinity uptake system for ACh itself that actually has a higher velocity than that for choline uptake. It is possible that the uptake system for ACh is involved in terminating the action of released transmitter in a manner similar to that previously described for noncholinergic transmitters. Using this preparation, we have demonstrated release of labeled ACh in response to intracellular stimulation of identified motor neurons. The release per spike appears to be highly plastic,increasing markedly with stimulation frequency. This preparation is amendable to study the regulation of release of peptide and conventional transmitters from the terminals of individual neurons.