Term Neonate Born With Right Upper Extremity Skin Necrosis at Birth: A Case Report

Congenital skin and soft tissue necrosis is a rare condition associated with significant morbidity and mortality in neonates. The authors treated a neonate born with significant skin necrosis of the right forearm. The case report is followed by a literature review and discussion of previously published reports of neonatal skin necrosis. A term female neonate was admitted to our hospital at 24 h of age for skin necrosis of the right forearm with sloughing and edema below the right elbow and contractures of her fingers. Topical treatment with cleansing and antibiotic application was initiated. The LUNA florescent microangiography showed superficial perfusion defects in the arm and dorsum of the hand along with overt ischemia over the dorsal aspect of the forearm. She was treated with intravenous antibiotics following a sepsis evaluation. Subsequently, she developed hypotension treated with fluid boluses, dopamine, and stress dose steroids. Concerns of wound infection and sepsis led to debridement of the necrotic area within the first 24 h post-admission. Wet-to-dry dressing changes using Vashe wound solution were begun postoperatively.; followed by placement of Integra on postoperative day-of-life (DOL) 7; dressing takedown on DOL 12; and autografting of the right hand and forearm with disarticulation of the 4th distal interphalangeal joints and right 5th distal interphalangeal transection on DOL 24. Postoperative dressing care was continued during the remainder of the hospital stay, she remained stable without any further complications and was discharged home on DOL 34 with outpatient clinic follow-up.

Pediatric Shock Review

Shock occurs when there is energy failure due to inadequate oxygen/glucose delivery to meet metabolic demands. Shock is a leading cause of death and disability in children worldwide. Types of shock include hypovolemic, cardiogenic, distributive, and obstructive. This review provides an overview of the epidemiology, pathophysiology, and clinical signs and symptoms of each of these types of shock, followed by a discussion of advancements in diagnostic tests and tools and management/treatment principles for different categories of shock.

The Changing Landscape of Global Child Health Education in the United States and the Effects of the COVID-19 Pandemic and Civil Unrest

The events of recent years have affected the landscape of global child health education (GCHE) in the United States. War, racism, forced displacement, and the coronavirus disease 2019 (COVID-19) pandemic had global repercussions that reached US GCHE. The aim of this article is to examine the effect of these events on the landscape of GCHE in the US. Key areas of GCHE have been reframed, reshaped, and accelerated by these events. Travel restrictions accelerated virtual learning opportunities. Core curriculum needed to be reconsidered to address antiracism, equity, and decolonization. Expansion of GCHE activities, including local-global electives, was needed to meet increased resident demand and help address local community needs. Inequities in international partnerships were further highlighted, requiring new approaches. Global research education and practices were also affected with a rapid expansion in virtual opportunities and further development of education in equitable research practices. [Pediatr Ann. 2023;52(9):e324-e329.].

Comparative Efficacy of Humidifiers for Noninvasive Infant Respiratory Support

Background: Delivery of cold, dry air to infants while supporting their breathing can irritate and damage their sensitive nares. In high resource settings, electric heated humidifiers are used to mitigate this problem. In many resource-constrained settings, passive non-electric bubbling humidifiers are instead used. We here compare the efficacy of conventional electric heated humidification, custom-built low cost heated humidification, passive non-electric bubbling humidification and a control (no humidification). Methods: In a hospital patient room (Temperature 22C, humidity 50%), the temperature and humidity delivered to a simulated patient lung via a BC161-10 Fisher Paykel bubble CPAP system were measured with conventional electric heated humidification, low cost custom-built heated humidification, passive bubbling humidification and no humidification. (Delivered CPAP: 5 cm H2O; flow rate varied from 4 to 8 LPM in 2 LPM increments.) Results: As flow rate was varied from 4 - 8 LPM, delivered relative humidity (standard deviation) with each humidifier was as follows: control 10% (3.6%), passive bubbler 44% (3.7%), custom-built humidifier 67% (1.7%), electric heated humidifier 91% (0.86%). Delivered temperature with the electric heated humidifier was 38C (0.21C) vs. 33C for all other setups. Conclusions: Conventional electric heating humidification is more effective than passive bubbling humidification, and the custom-built low cost humidifier provides an intermediate degree of humidification. Through further improvement of this concept with a heated inspiratory circuit and sensor based control of the heating element, an effective yet low cost solution heating humidification could be developed.

Innovations and adaptations in neonatal and pediatric respiratory care for resource constrained settings

Respiratory disease is a leading cause of death in children under 5 years of age worldwide, and most of these deaths occur in low- to middle-income countries (LMICs) where advanced respiratory care technology is often limited. Much of the equipment required to provide advanced respiratory care is unavailable in these areas due to high costs, the need for specialty trained personnel, and myriad other resource constraints that limit uptake and sustainable use of these devices, including reliable access to electricity, sensitive equipment needing frequent maintenance, single-patient-use supplies, and lack of access to sterilization equipment. Compounding the problem, pediatrics is uniquely challenging in that one size does not fit all, or even most patients. Despite these substantial barriers, numerous innovations in respiratory care technology have been made in recent years that have brought increasing access to high quality respiratory care in some of the most remote areas of the world. In this article, we intend to review the global burden of respiratory diseases for children, highlight the prototypical innovations that have been made in bringing respiratory care to LMICs, spotlight some of the technologies being actively developed to improve respiratory care in resource-constrained settings, and conclude with a discussion highlighting areas where further innovation is still needed.

Pediatric Critical Care in Resource Limited Settings-Lessening the Gap Through Ongoing Collaboration, Advancement in Research and Technological Innovations

Pediatric critical care has continued to advance since our last article, "Pediatric Critical Care in Resource-Limited Settings-Overview and Lessons Learned" was written just 3 years ago. In that article, we reviewed the history, current state, and gaps in level of care between low- and middle-income countries (LMICs) and high-income countries (HICs). In this article, we have highlighted recent advancements in pediatric critical care in LMICs in the areas of research, training and education, and technology. We acknowledge how the COVID-19 pandemic has contributed to increasing the speed of some developments. We discuss the advancements, some lessons learned, as well as the ongoing gaps that need to be addressed in the coming decade. Continued understanding of the importance of equitable sustainable partnerships in the bidirectional exchange of knowledge and collaboration in all advancement efforts (research, technology, etc.) remains essential to guide all of us to new frontiers in pediatric critical care.

A Low-Resource Oxygen Blender Prototype for Use in Modified Bubble CPAP Circuits

Continuous positive airway pressure (CPAP) is a method of respiratory support used around the world to treat children with lower respiratory tract infections (LRTI) (WHO, 2016, Oxygen Therapy for Children, World Health Organization, Geneva, Switzerland, Report). Bubble continuous positive airway pressure (bCPAP) is an effective form of CPAP that is currently used in both high- and low-resource countries. Low-cost, modified bCPAP devices have been designed as an ideal form of CPAP in low-resource areas (Bjorklund, A. R., Mpora, B. O., Steiner, M. E., Fischer, G., Davey, C. S., and Slusher, T. M., 2018, “Use of a Modified Bubble Continuous Positive Airway Pressure (bCPAP) Device for Children in Respiratory Distress in Low- and Middle-Income Countries: A Safety Study,” Paediatr. Int. Child Health, 39(3), pp. 1–8). However, patients in low-resource settings undergoing bCPAP treatment are often given pure oxygen, which has been linked to retinopathy of prematurity, cardiovascular complications, and patient mortality (Rodgers, J. L., Iyer, D., Rodgers, L. E., Vanthenapalli, S., and Panguluri, S. K., 2019, “Impact of Hyperoxia on Cardiac Pathophysiology,” J. Cell. Physiol., 234(8), pp. 1–9; Ramgopal, S., Dezfulian, C., Hickey, R. W., Au, A. K., Venkataraman, S., Clark, R. S. B., and Horvat, C. M., 2019, “Association of Severe Hyperoxemia Events and Mortality Among Patients Admitted to a Pediatric Intensive Care Unit,” JAMA Network Open, 2(8), p. e199812). This problem is typically avoided by using commercial oxygen blenders, which can titrate down the concentration of oxygen delivered to the minimum needed; however, these blenders can cost nearly 1000 USD and are almost always unavailable in low-resource settings. The lack of available low-cost oxygen blenders compatible with modified bCPAP circuits creates a barrier for low-resource hospitals to be able to provide blended oxygen to patients. There is a need for a low-cost oxygen blender for use in low-resource settings. We propose a passive oxygen blender that operates via entrainment of atmospheric air. The device can easily be assembled in low-resource areas using a 22 gauge hypodermic needle, two 3 cc syringes, tape or super glue, and the materials required for bCPAP—for approximately 1.40 USD per device. The blender has not been clinically tested yet, but can achieve oxygen concentrations as low as 60% with bCPAP levels of 5 cm H2O (490 Pa) when used in a standard bCPAP circuit without a patient.

The Assessment, Evaluation, and Management of the Critically Ill Child in Resource-Limited International Settings

Providing evidence-based care to the critically ill child including assessment, evaluation, and management in resource-limited settings provides unique challenges and limitless opportunities to significantly impact morbidity and mortality in these settings. Difficulties encountered include: determining which disease processes will benefit most from critical care in resource-limited settings, lack of triage tools and adjuncts to help with assessment, finite laboratory and radiological tests, limited understanding of key findings in critically ill/injured pediatric patients, (especially by those without pediatric focused training), and finally, lack of supplies, medicines, equipment, and training of health care providers to appropriately treat critically ill children in these resource-limited settings. In this review, the most common problems encountered and possible solutions to overcome these obstacles are discussed.

Considerations in Caring for Adult Patients in the Pediatric Intensive Care Unit

Pediatric providers are caring for a growing number of adults in pediatric in-patient settings due to the increasing survival of patients with historically pediatric disease. Beyond understanding the unique medical management of these patients, adult-specific ethical and legal issues must be considered. The aim of this article is to discuss four major issues unique to caring for adult patients: advance directives, confidentiality, decision-making capacity, and palliative care. To our knowledge, no literature exists focusing on the consideration of these specific concepts for the pediatric provider. An understanding of these issues in caring for adult patients in pediatric settings will enable pediatric practitioners to better consider patient autonomy, protect patient privacy, and ensure appropriate decision-making in critically ill patients.

Daily eating events among co-living and single-living, diseased older men

OBJECTIVES

To analyse, describe and compare the frequency and energy intake of eating events, including specific food items, among diseased older men living in ordinary housing.

DESIGN

Descriptive and explorative.

SETTING

Interviews were performed in the participants' home.

PARTICIPANTS

Thirty-five co-living and 26 single-living men, 64-88 years of age. Participants had one of three chronic diseases associated with difficulties in buying and preparing food and with difficulties related to the meal situation: Parkinson's disease, rheumatoid arthritis or stroke.

MEASUREMENTS

A repeated 24-h recall was used to assess food intake and meal patterns.

RESULTS

Eating events were distributed over a 24-h period. Co-living men had a higher (p=0.001) number of eating events/day; both hot and cold eating events were consumed more frequently. There was no difference between groups concerning energy intake. Co-living men more often had hot eating events cooked from raw ingredients (p=0.001) and a greater mix of vegetables/roots (p=0.003) included in such eating events.

CONCLUSION

Single-living men may constitute a vulnerable group from a nutritional perspective, while co-living men, besides the pleasure of eating with another person, seem to get support with food and eating events from their partners. Hence, the group of single-living men, particularly those with a disability, should receive particular attention with regard to possible food-related difficulties.

Risk factors for fatal infectious complications developing late after allogeneic stem cell transplantation

Infectious complications remain a major problem contributing to significant mortality after hematopoietic allogeneic stem cell transplantation (HSCT). Few studies have previously analyzed mortality due to late infections. Forty-four patients dying from an infectious complication were identified from a cohort of 688 consecutive patients surviving more than 6 months without relapse. A control group of 162 patients was selected using the year of HSCT as the matching criterion. Out of 44 patients, 30 (68%) died from pneumonia, 7/44 (16%) from sepsis, 5/44 (11%) from central nervous system infection and 2/44 (4.5%) from disseminated varicella. The cumulative incidences of different types of infection were 1.6% for viral, 1.5% for bacterial and 1.3% for fungal infections and 0.15% for Pneumocystis jirovecii pneumonia. The majority (66%) of the lethal infections occurred within 18 months after HSCT. Acute GVHD (relative risk (RR): 7.19, P<0.0001), chronic GVHD (RR: 6.49, P<0.001), CMV infection (RR: 4.69, P=0.001), mismatched or unrelated donor (RR: 3.86, P=0.004) and TBI (RR: 2.65, P=0.047) were independent risk factors of dying from a late infection. In conclusion, infections occurring later than 6 months after HSCT are important contributors to late non-relapse mortality after HSCT. CMV infection or acute GVHD markedly increase the risk.

Long-term rAAV-mediated gene transfer of GDNF in the rat Parkinson's model: intrastriatal but not intranigral transduction promotes functional regeneration in the lesioned nigrostriatal system

Previous studies have used recombinant adeno-associated viral (rAAV) vectors to deliver glial cell line-derived neurotrophic factor (GDNF) in the substantia nigra to protect the nigral dopamine (DA) neurons from 6-hydroxydopamine-induced damage. However, no regeneration or functional recovery was observed in these experiments. Here, we have used an rAAV-GDNF vector to express GDNF long-term (6 months) in either the nigral DA neurons themselves, in the striatal target cells, or in both of these structures. The results demonstrate that both nigral and striatal transduction provide significant protection of nigral DA neurons against the toxin-induced degeneration. However, only the rats receiving rAAV-GDNF in the striatum displayed behavioral recovery, accompanied by significant reinnervation of the lesioned striatum, which developed gradually over the first 4-5 months after the lesion. GDNF transgene expression was maintained at high levels throughout this period. These results provide evidence that rAAV is a highly efficient vector system for long-term expression of therapeutic proteins in the nigrostriatal system.

Neurturin exerts potent actions on survival and function of midbrain dopaminergic neurons

Glial cell line-derived neurotrophic factor (GDNF) exhibits potent effects on survival and function of midbrain dopaminergic (DA) neurons in a variety of models. Although other growth factors expressed in the vicinity of developing DA neurons have been reported to support survival of DA neurons in vitro, to date none of these factors duplicate the potent and selective actions of GDNF in vivo. We report here that neurturin (NTN), a homolog of GDNF, is expressed in the nigrostriatal system, and that NTN exerts potent effects on survival and function of midbrain DA neurons. Our findings indicate that NTN mRNA is sequentially expressed in the ventral midbrain and striatum during development and that NTN exhibits survival-promoting actions on both developing and mature DA neurons. In vitro, NTN supports survival of embryonic DA neurons, and in vivo, direct injection of NTN into the substantia nigra protects mature DA neurons from cell death induced by 6-OHDA. Furthermore, administration of NTN into the striatum of intact adult animals induces behavioral and biochemical changes associated with functional upregulation of nigral DA neurons. The similarity in potency and efficacy of NTN and GDNF on DA neurons in several paradigms stands in contrast to the differential distribution of the receptor components GDNF Family Receptor alpha1 (GFRalpha1) and GFRalpha2 within the ventral mesencephalon. These results suggest that NTN is an endogenous trophic factor for midbrain DA neurons and point to the possibility that GDNF and NTN may exert redundant trophic influences on nigral DA neurons acting via a receptor complex that includes GFRalpha1.

Selective immunolesioning of the basal forebrain cholinergic system disrupts short-term memory in rats

Selective depletion of nerve growth factor receptor-bearing neurons in the basal forebrain cholinergic system nuclei by the immunotoxin 192 IgG-saporin offers a new and highly useful tool for the study of the role of the forebrain cholinergic system in cognitive functions. In the present study, we have tested the effects of 192 IpG-saporin in an operant delayed matching-to-position task which has previously been used to discriminate between delay-dependent learning impairments and delay-independent disturbances of non-mnemonic processes. Rats were first trained to criterion performance and then received intraventricular injections of 5 microg of 192 IgG-saporin 4 weeks prior to a second testing session. Rats with 192 IgG-saporin lesions displayed a significant delay-dependent decline in performance compared to normal controls, indicating a deficit in short-term memory. Administration of the muscarinic blocker scopolamine (0.5 mg/kg, i.p.) produced more pronounced impairment in the performance of the normal control rats across all delays, and induced further impairment also in animals with 192 IgG-saporin lesions. These effects were not observed following control injections of methyl scopolamine, suggesting that the impairment induced by scopolamine was due to the blockade of central muscarinic receptors. No improvement in performance was observed in either group following systemic treatment with the muscarinic cholinergic agonist arecoline (1.00 mg/kg). Biochemical and morphological analyses confirmed the selective and severe (>90-95%) depletion of cholinergic neurons throughout the septal-diagonal band area and the nucleus basalis region by the intraventricular 192 IgG-saporin treatment. Although the immunotoxin was observed to produce additional damage to the cerebellar Purkinje cells, no gross motor abnormalities were observed that could contribute to the effects on accuracy in the task used here. In conclusion, the results show that selective combined lesions of the basal forebrain cholinergic neurons in the septal-diagonal band area and nucleus basalis produce long-lasting impairments in short-term memory, thus providing further support for a role of this system in cognitive functions.

Dopaminergic neuronal degeneration and motor impairments following axon terminal lesion by instrastriatal 6-hydroxydopamine in the rat

6-Hydroxydopamine-induced nerve terminal lesion of the nigrostriatal system may provide a partial lesion model of Parkinson's disease useful for the assessment of neuroprotective treatments and behavioral recovery after therapeutic intervention. The aim of the present study was to assess the retrograde degenerative changes in the dopaminergic neurons of the substantia nigra and the associated behavioral and neurochemical consequences of intrastriatal injections of 6-hydroxydopamine in young adult rats. Four groups of rats were stereotaxically injected in the right striatum with graded doses of 6-hydroxydopamine ranging from 0 to 20 mu g. Structural and functional deficits were quantified by tyrosine hydroxylase-immunoreactive nigral cell numbers, striatal dopamine content, skilled paw use, and drug-induced rotation. The results show that striatal 6-hydroxydopamine lesions produce dose-dependent decreases in striatal dopamine levels and tyrosine hydroxylase-immunoreactive cell numbers in the ipsilateral substantia nigra, accompanied by a significant long-lasting atrophy of the remaining dopaminergic neurons. Paw reaching test scores on the side contralateral to the lesion were non-linearly correlated with dopaminergic neuronal cell loss and exhibited a clear symptomatic threshold such that impaired paw use appeared only after >50% loss of nigral dopamine neurons or a reduction of 60-80% of striatal dopamine levels. The behavioral, cellular, and neurochemical effects of the nerve terminal lesion thus bear some resemblance to the early stages of Parkinson's disease, where the severity of motor impairment is correlated with the loss of dopamine in the striatum and dopaminergic neuronal loss in the substantia nigra. Rats with intrastriatal 6-hydroxydopamine lesions thus provide a model of progressive dopamine neuron degeneration useful not only for the exploration of neuroprotective therapeutic intervention but also for the study of mechanisms of functional and structural recovery after subtotal damage of the nigrostriatal dopamine system.

Age-related impairments in spatial memory are independent of those in sensorimotor skills

Seventy-five aged rats were tested for a variety of motor and cognitive tests which generated 20 separate measures of performance. Considerable variability was observed on many measures in the aged population. Multivariate analyses were performed on the data to determine 1) the extent of intercorrelations between the measures for the aged rats, and 2) whether clusters of related and/or unrelated behavioral measures could be determined. Aged rats that were impaired on measures of cognitive performance are not necessarily impaired in their motor performance and vice versa. These results demonstrate that different age-related variables affect cognitive and motor systems, and suggest that age-related declines in different functional anatomical systems, such as the limbic system and the basal ganglia may progress independently.

NGF receptor reexpression and NGF-mediated cholinergic neuronal hypertrophy in the damaged adult neostriatum

Adult cholinergic interneurons of the neostriatum are not immunoreactive for monoclonal antibody to NGF receptor, whereas the developing neostriatum is immunoreactive for this same antibody. Chronic NGF infusion into the adult neostriatum resulted in reexpression of the NGF receptor such that many cholinergic interneurons became immunoreactive for NGF receptor. NGF infusion dramatically increased the size and choline acetyltransferase immunoreactivity of these same cholinergic neurons. Additionally, in situ hybridization demonstrated an increase in the number of cells expressing NGF receptor mRNA in the NGF-infused striatum. These findings indicate that central cholinergic neurons which lose their NGF receptors during postnatal development will resume their NGF responsiveness when the tissue is damaged. Such a damage-induced mechanism may act to enhance the action of trophic factors, including NGF, released at the site of injury and enhance the responsiveness of damaged CNS neurons to exogenously administered trophic factors.

Intracerebral neuronal grafting in experimental animal models of age-related motor dysfunction

The combined morphological, biochemical, electrophysiological, and behavioral data summarized above show that implanted embryonic nerve cells in some cases can substitute quite well for a lost intrinsic neuronal system in mammals. The intracerebral implants probably exert their effects in several ways. The functional effects seen with grafts placed into one of the cerebral ventricles (such as those described in the studies of Perlow et al., Freed et al., and Gash et al.) are thus probably explained on the basis of a diffuse release of an active amine or peptide into the host CSF and adjacent brain tissue. In other instances, as in animals with DA-rich grafts reinnervating the neostriatum, we believe that the available data provide quite substantial evidence that the behavioral recovery is caused by the ability of the grafted neurons to reinnervate relevant parts of the host brain. This is illustrated by the studies mentioned above that show that the degree of functional recovery in 6-OHDA-lesioned rats with nigral transplants is directly correlated with the extent of striatal DA reinnervation and that the "profile" of functional recovery is dependent on that area of the striatal complex that is reinnervated by the graft. This point is particularly well illustrated in a further study in which rats with electrodes implanted into the center of intracortical nigral grafts were allowed to "self-stimulate" via the graft. The results show that the graft can indeed sustain self-stimulation behavior and that the rate of lever-pressing is related to the proximity between the electrode tip and the DA-containing neurons in the graft. This strongly supports the notion that the implanted DA neurons can transmit behaviorally meaningful and temporally organized information to the host brain via their efferent connections. To what extent the intracerebral implants can be functionally integrated with the host brain is still poorly known, though, and it therefore remains an interesting question for further investigation. The chances for extensive integration may be greatest for neuronal suspension grafts implanted as deposits directly into the depth of the brain, but even solid grafts inserted as whole pieces into the brain have, in several cases, been seen to become reinnervated from the host brain in adult and developing recipients. Nevertheless, a recent HRP study failed to detect any host afferents to intracortical solid nigral grafts, despite the fact that these grafts had themselves formed extensive DA connections in the host striatum and had produced behavioral recovery.(ABSTRACT TRUNCATED AT 400 WORDS)

Continuous infusion of nerve growth factor prevents basal forebrain neuronal death after fimbria fornix transection

Neurons in the rat medial septum (MS) and vertical limb of the diagonal band of Broca (VDB) undergo a rapid and severe cell death after transection of their dorsal projection to the hippocampus by aspiration of the ipsilateral fimbria fornix and supracallosal striae. By 2 weeks posttransection, the extent of neuronal loss was 50% of the total neurons and 70% of the cholinergic neurons in the MS and 30% of the total neurons and 40% of the cholinergic neurons in the VDB. We hypothesized that (i) the death was due to the loss of a hippocampus-derived neuronotrophic factor, and (ii) exogenous nerve growth factor (NGF) might provide trophic support to the MS/VDB cholinergic neurons, in light of recent reports that the septal diagonal band cholinergic neurons are responsive to NGF and that NGF is present and produced in the hippocampus. In the present study, we attempted to prevent the transection-induced neuronal death by continuous infusion of exogenous 7S NGF (1 microgram/wk) through an intraventricular cannula device. We report here that NGF treatment significantly reduces both the total neuronal and cholinergic neuronal death found 2 weeks after fimbria fornix transection; there was a sparing of 50% of the neurons in the MS and essentially 100% of those in the VDB that otherwise would have died. We conclude that NGF also has a protective effect on noncholinergic neurons since calculations indicate that 80% of the NGF-affected neurons are noncholinergic.

Retrograde cell changes in medial septum and diagonal band following fimbria-fornix transection: quantitative temporal analysis

Complete unilateral fimbria-fornix transections, including the overlying cingulate cortex, were administered to female rats. At time points from 1 day to 6 weeks, the septal-diagonal band region was examined using acetylcholinesterase histochemistry, Cresyl Violet cell staining, and choline acetyltransferase biochemistry. As early as 1 day following the transection a decrease in acetylcholinesterase positive cell body staining was observed in the medial septum; however, no loss of Nissl-stained neurons was measured in Cresyl Violet stained sections until 1 week after the lesion. Maximal loss of acetylcholinesterase-positive cells, as visualized after irreversible acetylcholinesterase inhibition, was measured at 1 week, and no further change was observed at time points up to 6 weeks after operation. The loss of acetyltransferase-positive cells was greatest in the medial septal area (-65%) and the vertical limb of the diagonal band (-55%). Little cell loss was measured in the horizontal limb of the diagonal band. This is consistent with the known projections of these cell bodies. Remaining acetylcholinesterase-positive cell bodies in the medial septum had shrunk by about 20% (measured as the diameter along the major axis). A marked neuronal cell loss (about 50%) was demonstrable in the medial septum and vertical limb of the diagonal band in the Cresyl Violet-stained sections, too. A pile-up of acetylcholinesterase-stained material was observed in the dorsal-lateral quadrant of the septal area just proximal to the lesion at 1 day following transection. This pile-up occurred in the medial septum and diagonal band area up to 1 week following the transection, and had nearly disappeared by 2 weeks post-transection. Choline acetyltransferase biochemical activity, measured in samples of whole septum, decreased significantly at 1 day but subsequently returned to control levels. By 2 weeks following transection, an increase in acetylcholinesterase-positive stained fibers was observed in the dorsal-lateral quadrant of the septum, ipsilateral to the lesion relative to the contralateral septum. This response, which was interpreted as sprouting from the lesioned axons proximal to the transection, probably accounted for the rise in choline acetyltransferase biochemical activity in the whole septum following the reduction on the first day.

Transplanted septal neurons make viable cholinergic synapses with a host hippocampus

Cell suspensions from the fetal septal region were injected stereotaxically into the hippocampus of fornix-fimbria-transected adult rats. The host rats were sacrificed up to 3 months after the operation and the hippocampus sliced into 350 microns transverse slices. Intracellular recording was made from CA1 neurons adjacent to the graft. Electrical stimulation of the graft produced a voltage-dependent depolarization in some recorded neurons. This was associated with an increase in spontaneous and anodal break action potential discharges. In addition, a slow after-hyperpolarization (AHP) which typically follows a burst discharge was blocked during the depolarization indicating that the stimulation may block a Ca2+-dependent K+ current. The effects of the stimulation were antagonized by atropine. A response to the stimulation was seen 2 weeks but not 1 week after grafting. Over time, cells that were located away from the graft became activated by the stimulation. This was correlated with the extent of proliferation of acetylcholinesterase-containing fibers around the graft. These results suggest that grafted septal neurons make viable cholinergic connections with a host hippocampus.

Reformation in adult rats of functional septo-hippocampal connections by septal neurons regenerating across an embryonic hippocampal tissue bridge

Implants of embryonic hippocampus, placed into a cavity transecting the septo-hippocampal pathway in adult rats, have previously been shown to promote the regeneration of the lesional septo-hippocampal axons across the cavity. The present study provides electrophysiological evidence that these regenerating acetylcholinesterase-containing axons are able to re-establish atropine-sensitive excitatory synaptic connections in the grafted hippocampus as well as in the dorsal part of the initially denervated host hippocampus, thus demonstrating that intracerebral tissue implants can promote true, functional regeneration across a major tissue defect in the adult mammalian CNS.

Intracephalic implants: a technique for studying neuronal interactions

Implants of embryonic neural tissue from all regions of the neuraxis survive grafting to the brains of adult rats. After implantation, neurogenesis and differentiation continue, and connections are formed with the mature host brain. Thus, the intracephalic implants provide excellent model systems for studying cellular interactions that regulate synaptogenesis and determine the cytoarchitectonic organization of developing neural tissues.