Do Activities Performed within the Intra-Contrast Rest Interval Affect Neuromuscular Performance during Complex-Contrast Training Protocols?

The aim of this study was to analyze the acute effects of including different exercises within the intra-contrast rest interval (ICRI) of a complex-contrast training (CCT) session. Seventeen recreationally active males completed three different CCT protocols. Programs consisted of a contrast pair combining a moderate-intensity conditioning activity (i.e., a back squat) with a lower-body high-velocity exercise (i.e., a vertical jump) and only differed in the activities performed during the ICRI: 1) passive recovery (CCTPASS); 2) a mobility exercise (CCTMOB); and 3) an upper-body high-intensity strength exercise (i.e., a bench press) (CCTSTR). Countermovement jump and bench press throw metrics were evaluated at baseline and after each set during the workout. The rate of perceived exertion was recorded post-session. Non-significant differences in performance were found between CCTPASS, CCTMOB and CCTSTR throughout the session. Significant declines (p < 0.05) were observed for CMJ peak power in the last 2-3 repetitions of each set, irrespective of the protocol. CCTSTR was perceived as more intense than CCTPASS and CCTMOB (p < 0.05). From a neuromuscular performance perspective, including activities during the ICRI (mobility drills or high-intensity strength exercises) may be a suitable strategy to optimize CCT prescription since the acute responses were similar to those found with passive rest periods. Finally, prescribing a lower number of repetitions per set is recommended to attenuate mechanical performance impairment during CCT protocols, irrespective of the activities completed within the ICRI.

Exploring countermovement jump variables across competitive levels and playing positions in futsal

Introduction

The aims of this study were to compare several countermovement jump (CMJ) kinetic variables between professional (PRO) and semi-professional (SEMI-PRO) futsal players and examine the differences amongst playing positions.

Methods

CMJ performance from 56 male futsal players (25.2 ± 4.8 years; weight: 74.4 ± 6.4 kg) was analysed. Players were separated into PRO (n = 29; 27.0 ± 4.4 years; 75.4 ± 6.0 kg) and SEMI-PRO (n = 27; 22.7 ± 4.3 years; 73.1 ± 6.8 kg), and according to playing position: defenders (n = 16; 25.4 ± 3.7 years; 75.2 ± 6.0 kg), wingers (n = 26; 23.5 ± 4.5 years; 72.0 ± 6.9 kg), and pivots (n = 14; 28.0 ± 5.6 years; 77.8 ± 4.3 kg). Linear mixed models and effect sizes were used for the analyses based on the mean of two jumps for each variable.

Results

PRO players presented a deeper center of mass (COM) displacement (p = 0.002, ES = 0.83), greater eccentric (Ecc) absolute (p = 0.019, ES = 0.61) and relative peak power (p = 0.046, ES = 0.52), and achieved greater Ecc peak velocities (p = 0.004, ES = 0.76) when compared to SEMI-PRO. Non-significant and trivial-to-small differences were observed in all the other CMJ variables according to the competitive level and playing position.

Discussion

Ecc capabilities (i.e., deeper COM displacement, greater Ecc absolute and relative peak power, and peak velocity) during vertical jump seem to differentiate PRO and SEMI-PRO players. However, CMJ variables do not discriminate amongst playing positions in futsal players.

Myotendinous Thermoregulation in National Level Sprinters after a Unilateral Fatigue Acute Bout-A Descriptive Study

In the last decade there has been a growing interest in infrared thermography in the field of sports medicine in order to elucidate the mechanisms of thermoregulation. The aim of this study was to describe bilateral variations in skin temperature of the anterior thigh and patellar tendon in healthy athletes and to provide a model of baseline tendon and muscle thermoregulation in healthy sprinters following a unilateral isokinetic fatigue protocol. Fifteen healthy national-level sprinters (eleven men and four women), with at least 3 years of athletic training experience of 10-12 h/week and competing in national-level competitions, underwent unilateral isokinetic force testing and electrostimulation in which their body temperature was measured before, during, and after the protocol using an infrared thermographic camera. ANOVA detected a significant difference in the time × side interaction for patellar temperature changes (p ≤ 0.001) and a significant difference in the time/side interaction for quadriceps temperature changes (p ≤ 0.001). The thermal challenge produces homogeneous changes evident in quadriceps areas, but not homogeneous in tendon areas. These data show that metabolic and blood flow changes may depend on the physical and mechanical properties of each tissue. Future research could be conducted to evaluate the predictive value of neuromuscular fatigue in the patellar tendon and quadriceps after exercise in order to optimize post-exercise recovery strategies.

Does External Load Reflect Acute Neuromuscular Fatigue and Rating of Perceived Exertion in Elite Young Soccer Players?

ABSTRACT

Martínez-Serrano, A, Freitas, TT, Franquesa, X, Enrich, E, Mallol, M, and Alcaraz, PE. Does external load reflect acute neuromuscular fatigue and rating of perceived exertion in elite young soccer players? J Strength Cond Res 37(3): e1-e7, 2023-This study aimed to analyze the acute and residual effects of increased high-speed running (HSR) demands during an in-season training microcycle in young elite soccer players on localized neuromuscular fatigue (NMF) of the knee extensors (KE), posterior chain muscles, and rating of perceived exertion (RPE). Thirty-four elite young soccer players (age = 17.1 ± 0.8 years) were assessed in 2 consecutive days at different time points (baseline, POST-activation gym-based session, POST-small-sided game [SSG], POST-training 1 [TR1], POST-6H, POST-24H, POST-preventive gym-based session, and POST-training 2 [TR2]). Neuromuscular fatigue of the KE and posterior chain muscles was measured with a maximum voluntary isometric contraction (MVIC). External (total distance, number of accelerations or decelerations, and HSR distance) and internal (RPE) load was assessed during the SSG, TR1, and TR2 sessions. Players were divided through a median split, into "HIGH" or "LOW" group according to the training demands. The alpha level was set at p ≤ 0.05. A 2-way mixed effects model ANOVA showed a significant decreased in 90:20 MVIC after TR1 in the "HIGH" HSR group ( p = 0.037; effect size [ES] = 0.45). No significant differences in RPE were found after TR1 ( p = 0.637; ES = 0.58) and TR2 ( p = 0.109; ES = 0.62) when comparing the "HIGH" HSR group with the "LOW" HSR group. Assessing player's force production capabilities can be an effective strategy to detect NMF when HSR demands are acutely increased. Special caution should be taken when prescribing the training load of the training session based solely on RPE, as NMF might be present.

Electromyography, Stiffness and Kinematics of Resisted Sprint Training in the Specialized SKILLRUN® Treadmill Using Different Load Conditions in Rugby Players

This study’s aim was to analyze muscle activation and kinematics of sled-pushing and resisted-parachute sprinting with three load conditions on an instrumentalized SKILLRUN^® treadmill. Nine male amateur rugby union players (21.3 ± 4.3 years, 75.8 ± 10.2 kg, 176.6 ± 8.8 cm) performed a sled-push session consisting of three 15-m repetitions at 20%, 55% and 90% body mas and another resisted-parachute session using three different parachute sizes (XS, XL and 3XL). Sprinting kinematics and muscle activity of three lower-limb muscles (biceps femoris (BF), vastus lateralis (VL) and gastrocnemius medialis (GM)) were measured. A repeated-measures analysis of variance (RM-ANOVA) showed that higher loads during the sled-push increased (VL) (p ≤ 0.001) and (GM) (p ≤ 0.001) but not (BF) (p = 0.278) activity. Furthermore, it caused significant changes in sprinting kinematics, stiffness and joint angles. Resisted-parachute sprinting did not change kinematics or muscle activation, despite producing a significant overload (i.e., speed loss). In conclusion, increased sled-push loading caused disruptions in sprinting technique and altered lower-limb muscle activation patterns as opposed to the resisted-parachute. These findings might help practitioners determine the more adequate resisted sprint exercise and load according to the training objective (e.g., power production or speed performance).

Impedance-based Real-time Monitoring of Neural Stem Cell Differentiation

We present here the first impedance-based characterization of the differentiation process of two human mesencephalic fetal neural stem lines. The two dopaminergic neural stem cell lines used in this study, Lund human mesencephalic (LUHMES) and human ventral mesencephalic (hVM1 Bcl-X_L), have been developed for the study of Parkinsonian pathogenesis and its treatment using cell replacement therapy. We show that if only relying on impedance magnitude analysis, which is by far the most usual approach in, e.g., cytotoxicity evaluation and drug screening applications, one may not be able to distinguish whether the neural stem cells in a population are proliferating or differentiating. However, the presented results highlight that equivalent circuit analysis can provide detailed information on cellular behavior, e.g. simultaneous changes in cell morphology, cell-cell contacts, and cell adhesion during formation of neural projections, which are the fundamental behavioral differences between proliferating and differentiating neural stem cells. Moreover, our work also demonstrates the sensitivity of impedance-based monitoring with capability to provide information on changes in cellular behavior in relation to proliferation and differentiation. For both of the studied cell lines, in already two days (one day after induction of differentiation) equivalent circuit analysis was able to show distinction between proliferation and differentiation conditions, which is significantly earlier than by microscopic imaging. This study demonstrates the potential of impedance-based monitoring as a technique of choice in the study of stem cell behavior, laying the foundation for screening assays to characterize stem cell lines and testing the efficacy epigenetic control.

Effects of cytomegalovirus infection in human neural precursor cells depend on their differentiation state

Cytomegalovirus (CMV) is the most common cause of congenital infection in developed countries and a major cause of neurological disability in children. Although CMV can affect multiple organs, the most important sequelae of intrauterine infection are related to lesions of the central nervous system. However, little is known about the pathogenesis and the cellular events responsible for neuronal damage in infants with congenital infection. Some studies have demonstrated that neural precursor cells (NPCs) show the greatest susceptibility to CMV infection in the developing brain. We sought to establish an in vitro model of CMV infection of the developing brain in order to analyze the cellular events associated with invasion by this virus. To this end, we employed two cell lines as a permanent source of NPC, avoiding the continuous use of human fetal tissue, the human SK-N-MC neuroblastoma cell line, and an immortalized cell line of human fetal neural origin, hNS-1. We also investigated the effect of the differentiation stage in relation to the susceptibility of these cell lines by comparing the neuroblastoma cell line with the multipotent cell line hNS-1. We found that the effects of the virus were more severe in the neuroblastoma cell line. Additionally, we induced hNS-1 to differentiate and evaluated the effect of CMV in these differentiated cells. Like SK-N-MC cells, hNS-1-differentiated cells were also susceptible to infection. Viability of differentiated hNS-1 cells decreased after CMV infection in contrast to undifferentiated cells. In addition, differentiated hNS-1 cells showed an extensive cytopathic effect whereas the effect was scarce in undifferentiated cells. We describe some of the effects of CMV in neural stem cells, and our observations suggest that the degree of differentiation is important in the acquisition of susceptibility.

A compact multifunctional microfluidic platform for exploring cellular dynamics in real-time using electrochemical detection

Dopamine detection from PC12 cell populations and monitoring of yeast redox metabolism demonstrate the multifunctionality of the compact microfluidic cell culture and electrochemical analysis platform with in-built fluid handling and detection unit.

Bcl-XL modulates the differentiation of immortalized human neural stem cells

Understanding basic processes of human neural stem cell (hNSC) biology and differentiation is crucial for the development of cell replacement therapies. Bcl-X(L) has been reported to enhance dopaminergic neuron generation from hNSCs and mouse embryonic stem cells. In this work, we wanted to study, at the cellular level, the effects that Bcl-X(L) may exert on cell death during differentiation of hNSCs, and also on cell fate decisions and differentiation. To this end, we have used both v-myc immortalized (hNS1 cell line) and non-immortalized neurosphere cultures of hNSCs. In culture, using different experimental settings, we have consistently found that Bcl-X(L) enhances neuron generation while precluding glia generation. These effects do not arise from a glia-to-neuron shift (changes in fate decisions taken by precursors) or by only cell death counteraction, but, rather, data point to Bcl-X(L) increasing proliferation of neuronal progenitors, and inhibiting the differentiation of glial precursors. In vivo, after transplantation into the aged rat striatum, Bcl-X(L) overexpressing hNS1 cells generated more neurons and less glia than the control ones, confirming the results obtained in vitro. These results indicate an action of Bcl-X(L) modulating hNSCs differentiation, and may be thus important for the future development of cell therapy strategies for the diseased mammalian brain.

Neuroprotective and behavioral efficacy of nerve growth factor-transfected hippocampal progenitor cell transplants after experimental traumatic brain injury

OBJECT

Immortalized neural progenitor cells derived from embryonic rat hippocampus (HiB5), were transduced ex vivo with the gene for mouse nerve growth factor (NGF) to secrete NGF (NGF-HiB5) at 2 ng/hr/10(5) cells in culture.

METHODS

Fifty-nine male Wistar rats weighing 300 to 370 g each were anesthetized with 60 mg/kg sodium pentobarbital and subjected to lateral fluid-percussion brain injury of moderate severity (2.3-2.4 atm, 34 rats) or sham injury (25 rats). At 24 hours postinjury, 2 microl (150,000 cells/microl) of [3H]thymidine-labeled NGF-HiB5 cells were transplanted stereotactically into three individual sites in the cerebral cortex adjacent to the injury site (14 rats). Separate groups of brain-injured rats received nontransfected (naive [n])-HiB5 cells (12 animals) or cell suspension vehicle (eight animals). One week postinjury, animals underwent neurological evaluation for motor function and cognition (Morris water maze) and were killed for histological, autoradiographic, and immunocytochemical analysis. Viable HiB5 cell grafts were identified in all animals, together with reactive microglia and macrophages located throughout the periinjured parenchyma and grafts (OX-42 immunohistochemistry). Brain-injured animals transplanted with either NGF-HiB5 or n-HiB5 cells displayed significantly improved neuromotor function (p < 0.05) and spatial learning behavior (p < 0.005) compared with brain-injured animals receiving microinjections of vehicle alone. A significant reduction in hippocampal CA3 cell death was observed in brain-injured animals receiving transplants of NGF-HiB5 cells compared with those receiving n-HiB5 cells or vehicle (p < 0.025).

CONCLUSIONS

This study demonstrates that immortalized neural stem cells that have been retrovirally transduced to produce NGF can markedly improve cognitive and neuromotor function and rescue hippocampal CA3 neurons when transplanted into the injured brain during the acute posttraumatic period.

Human neural stem cells in vitro. A focus on their isolation and perpetuation

Because of their ability to generate all the cell types in the nervous system, neural stem cells are promising candidates for the development of cellular and genetic therapies for nervous system disorders and, in particular, neurodegenerative diseases. In recent years, researchers have discovered ways of expanding and perpetuating these cells in culture, as well as different sources for these tissue-specific stem cells, ranging from embryonic to adult tissue, and also from human pluripotent stem cells. Current efforts are oriented to the understanding of the molecular mechanisms controlling their fate decisions, their genetic engineering, and how to harness their potential to make them useful from a therapeutic point of view.

Genetically perpetuated human neural stem cells engraft and differentiate into the adult mammalian brain

Human neural stem cells (HNSCs) may serve as a cellular vehicle for molecular therapies as well as for cell replacement in the human CNS. The survival, integration, and differentiation of HNSC.100, a multipotent cell line of HNSCs (A. Villa et al. (2000), Exp. Neurol. 161, 67-84), conditionally perpetuated by genetic and epigenetic means, was investigated after transplantation to the striatum and substantia nigra of the adult, intact rat brain. These are two key regions in the mammalian brain involved in the control of voluntary movement and motor coordination, among other functions. Soon after transplantation (1 week), the cells had already integrated in a nondisruptive manner into the surrounding tissue and migrated out of the implantation site to different distances depending on graft location (in the range of 0.5-2.5 mm). Cell migration was markedly more extensive in the striatum, where the cells colonized the whole extent of the caudate-putamen, than in the substantia nigra region. The engrafted cells completely downregulated the stem cell marker nestin and, due to their multipotential nature, differentiated and expressed mature neural markers. As expected from cells grafted into nonneurogenic regions of the intact brain, the majority of differentiated cells expressed GFAP (astroglia), but expression of other markers, like GalC (oligodendroglia) and MAP2, beta-tubulin III, NeuN, and NSE (for mature neurons) could also be detected. These results demonstrate that genetically perpetuated HNSCs, once transplanted, find residence in the host brain, where they differentiate, generating mature neural cells in the host, chimeric, adult mammalian brain. HNSCs cell lines may be a highly useful model for the development of humanized systems for cell replacement and/or gene transfer to the CNS, which will likely be strong candidates for future therapeutic application in human neurodegenerative conditions.

Establishment and properties of a growth factor-dependent, perpetual neural stem cell line from the human CNS

The ready availability of unlimited quantities of neural stem cells derived from the human brain holds great interest for basic and applied neuroscience, including therapeutic cell replacement and gene transfer following transplantation. We report here the combination of epigenetic and genetic procedures for perpetuating human neural stem cell lines. Thus we tested various culture conditions and genes for those that optimally allow for the continuous, rapid expansion and passaging of human neural stem cells. Among them, v-myc (the p110 gag-myc fusion protein derived from the avian retroviral genome) seems to be the most effective gene; we have also identified a strict requirement for the presence of mitogens (FGF-2 and EGF) in the growth medium, in effect constituting a conditional perpetuality or immortalization. A monoclonal, nestin-positive, human neural stem cell line (HNSC.100) perpetuated in this way divides every 40 h and stops dividing upon mitogen removal, undergoing spontaneous morphological differentiation and upregulating markers of the three fundamental lineages in the CNS (neurons, astrocytes, and oligodendrocytes). HNSC.100 cells therefore retain basic features of epigenetically expanded human neural stem cells. Clonal analysis confirmed the stability, multipotency, and self-renewability of the cell line. Finally, HNSC.100 can be transfected and transduced using a variety of procedures and genes encoding proteins for marking purposes and of therapeutic interest (e.g., human tyrosine hydroxylase I).

BDNF gene transfer to the mammalian brain using CNS-derived neural precursors

Neural stem cell lines represent a homogeneous source of cells for genetic, developmental, and gene transfer and repair studies in the nervous system. Since both gene transfer of neurotrophic factors and cell replacement strategies are of immediate interest for therapeutical purposes, we have generated BDNF-secreting neural stem cell lines and investigated to what extent different endogenous levels of BDNF expression affect in vitro survival, proliferation and differentiation of these cells. Also, we have investigated the in vivo effects of such BDNF gene transfer procedure in the rat neostriatum. Hippocampus- and cerebellum-derived cell lines reacted differently to manipulations aimed at varying their levels of BDNF production. Over-expression of BDNF enhanced survival of both cell types, in a serum-deprivation assay. Conversely, and ruling out unspecific effects, expression of an antisense version of BDNF resulted in compromised survival of cerebellum-derived cells, and in a lethal phenotype in hippocampal progenitors. These data indicate that endogenous BDNF level strongly influences the in vitro survival of these cells. These effects are more pronounced for hippocampus- than for cerebellum-derived progenitors. Hippocampus-derived BDNF overproducers showed no major change in their capacity to differentiate towards a neuronal phenotype in vitro. In contrast, cerebellar progenitors overproducing BDNF did not differentiate into neurons, whereas cells expressing the antisense BDNF construct generated cells with morphological features of neurons and expressing immunological neuronal markers. Taken together, these results provide evidence that BDNF controls both the in vitro survival and differentiation of neural stem cells. After in vivo transplantation of BDNF-overproducing cells to the rat neostriatum, these survived better than the control ones, and induced the expected neurotrophic effects on cholinergic neurons. However, long-term (3 months) administration of BDNF resulted in detrimental effects, at this location. These findings may be of importance for the understanding of brain development, for the design of therapeutic neuro-regenerative strategies, and for cell replacement and gene therapy studies.

Surgical treatment for bunions in adolescents

The results of three different surgical procedures for the correction of bunions on 25 adolescent feet (distal soft-tissue procedure, proximal closing-wedge osteotomy of the first metatarsal with distal soft-tissue procedure, and proximal phalangeal osteotomy) are reviewed. The results with an average follow-up of 3.5 years were excellent or good in 21 cases, and fair or poor in 4. The average correction of the metatarsophalangeal angle, the intermetatarsal angle, and the hallux valgus interphalangeus angle was, respectively, 9.88, 3.11, and 0.0 degrees for the first procedure, 21.0, 6.87, and 0.0 degrees for the second, and 11.0 0.9, and 22.5 degrees for the third. We conclude that distal soft-tissue reconstruction allows only mild to moderate correction of the metatarsophalangeal and intermetatarsal angles, and the association of a proximal osteotomy of the first metatarsal produces an statistically significant better correction (p < 0.05). Hallux valgus interphalangeus deformities are corrected only by proximal phalanx osteotomies. The selection of a particular procedure should therefore be based on an appropriate preoperative planification.

Amelioration of ischaemia-induced neuronal death in the rat striatum by NGF-secreting neural stem cells

The objective of the present study was to explore whether grafted immortalized neural stem cells, genetically modified to secrete nerve growth factor (NGF), can ameliorate neuronal death in the adult rat striatum following transient middle cerebral artery occlusion (MCAO). One week after cell implantation in the striatum, animals were subjected to 30 min of MCAO. Striatal damage was evaluated at the cellular level after 48 h of recirculation using immunocytochemical and stereological techniques. The ischaemic insult caused an extensive degeneration of projection neurons, immunoreactive for dopamine- and adenosine 3': 5'-monophosphate-regulated phosphoprotein with a molecular weight of 32 kilodaltons (DARPP-32). 3H-Thymidine autoradiography demonstrated surviving grafted cells in the lesioned striatum in all transplanted rats. The loss of striatal projection neurons was significantly reduced (by an average of 45%) in animals with NGF-secreting grafts, whereas control cells, not producing NGF, had no effect. The neuroprotective action of NGF-secreting grafts was also observed when the total number of striatal neurons immunopositive for the neuronal marker NeuN was quantified, as well as in cresyl violet-stained sections. The present findings indicate that administration of NGF by ex vivo gene transfer and grafting of neural stem cells can ameliorate death of striatal projection neurons caused by transient focal ischaemia.

Ex vivo nerve growth factor gene transfer to the basal forebrain in presymptomatic middle-aged rats prevents the development of cholinergic neuron atrophy and cognitive impairment during aging

Nerve growth factor (NGF) is able to restore spatial learning and reverse forebrain cholinergic neuron atrophy when administered intracerebrally to behaviorally impaired aged rats. In the present study, behaviorally unimpaired, middle-aged rats (14-16 months old) received transplants of ex vivo transduced, clonal NGF-secreting immortalized neural progenitor cells, bilaterally in the nucleus basalis and septum. During the subsequent 9 months the aged control animals developed the expected impairment in spatial learning in the water maze task, whereas the animals with NGF-secreting grafts maintained a performance level not different from the 12-month-old control rats. The marked age-induced atrophy (-25%) of the cholinergic neurons in medial septum and nucleus basalis, seen in the aged control rats, was not present in the NGF-treated aged animals. 3H-labeled thymidine autoradiography showed that the transduced cells survived well and had become integrated into the host tissue surrounding the injection sites, and reverse transcription-PCR analysis revealed expression of the NGF transgene, at both 4 and 9 months postgrafting, in the grafted tissue. The results show that long-term supply of NGF from ex vivo transduced immortalized neural progenitor cells locally within the nucleus basalis and septum can prevent the subsequent development of age-dependent neuronal atrophy and behavioral impairments when the animals reach advanced age.

In utero gene transfer reveals survival effects of nerve growth factor on rat brain cholinergic neurones during development

Nerve growth factor (NGF) is a maintenance factor for cholinergic neurones in the brain, but its properties as a developmental survival factor are largely unknown. The low accessibility of the developing mammalian brain to experimental manipulation makes it difficult to increase NGF levels during the early phases of brain development. In the present study we have used an in utero, ex-vivo gene transfer approach to explore NGF actions during development of the cholinergic system in the rat brain. Significantly increased numbers of cholinergic neurones were found only in the mesopontine complex in animals receiving NGF-secreting transplants, whereas the cholinergic neurones in the basal forebrain and striatum were not clearly affected. The present results suggest that overexpression of NGF during development may promote the survival of distinct populations of central cholinergic neurones into adulthood.

Immortalized neural progenitor cells for CNS gene transfer and repair

Immortalized multipotent neural stem and progenitor cells have emerged as a highly convenient source of tissue for genetic manipulation and ex vivo gene transfer to the CNS. Recent studies show that these cells, which can be maintained and genetically transduced as cell lines in culture, can survive, integrate and differentiate into both neurons and glia after transplantation to the intact or damaged brain. Progenitors engineered to secrete trophic factors, or to produce neurotransmitter-related or metabolic enzymes can be made to repopulate diseased or injured brain areas, thus providing a new potential therapeutic tool for the blockade of neurodegenerative processes and reversal of behavioural deficits in animal models of neurodegenerative diseases. With further technical improvements, the use of immortalized neural progenitors may bring us closer to the challenging goal of targeted and effective CNS repair.

Survival, integration, and differentiation of neural stem cell lines after transplantation to the adult rat striatum

The in vivo properties of four different neural stem cell lines, generated from embryonic striatum or hippocampus by immortalization with the temperature-sensitive (s) A58/U19 allele of the SV40 Large T-antigen, have been studied with respect to their ability to survive, differentiate, and integrate after transplantation to the adult rat striatum. The cells were labeled with [3H]thymidine prior to grafting, and combined autoradiography and immunohistochemistry was used to characterize their phenotypic differentiation within the adult brain environment. The results show that all four types of cells survived well, up to at least 1.5-6 months postgrafting, without any signs of tissue perturbation or tumor formation. The cells underwent, on average, 2-3 cell divisions during the first 5 days after implantation and exhibited extensive migration over a distance of 1-1.5 mm from the injection site to become morphologically integrated with the surrounding host striatum. The cell number and tissue distribution attained by 2 weeks remained stable for up to 6 months postgrafting with the exception of one cell line, which showed a 40% loss of cells between 2 and 6 weeks. Twice the number of [3H]thymidine-labeled cells were recovered when the cells were grafted into a 1-week-old excitotoxic striatal lesion, probably due to an increased proliferation of the cells in response to the neuron-depleting depleting lesion. The immortalized cells behaved as multipotent neural progenitors. The vast majority of the cells developed a glial-like morphology, 6-14% being clearly GFAP-positive; however, a small but consistent proportion of them (1-3%) expressed MAP-2 and exhibited neuron-like morphology. In mature transplants about 75-80% of the grafted cells were located in the striatal grey matter, and 10-15% in white matter, some of which are proposed to have differentiated into oligodendrocytes. Remaining 5-10% occurred around small blood vessels (resembling pericytes) and in the subventricular zone underneath the ependyma of the lateral ventricle. It is concluded that the ts cell lines are highly suitable for intracerebral transplantation and that they allow the creation of a regionally confined cellular chimeras where the graft-derived glial cells become stably integrated with the resident glial cell matrix.

Modulation of presynaptic calcium homeostasis by nitric oxide

In the present work, we have adapted established microfluorimetric techniques based on the calcium indicator Fura-2, for the study of synaptosomal calcium homeostasis regulation in an immobilized synaptosomal preparation from the rat hippocampus. With this tool, we have addressed the actions of two proposed interneuronal messengers, nitric oxide (NO) and arachidonic acid (AA). NO donors (sodium nitroprusside, SNP and hydroxylamine, HX) and AA induced an increase in depolarization-induced calcium transients (both in magnitude and duration). However, resting calcium levels were not modified by NO, whereas AA application resulted in an steady increase in Ca. The effects of SNP were blocked when EGTA was present between depolarizations, suggesting that a minimum level of internal calcium load is required for NO effects. The effects of NO on Cai transients are persistent up to 90 min after drug application, and could be involved in some of the forms of synaptic plasticity where NO plays a role.

Protection of the neostriatum against excitotoxic damage by neurotrophin-producing, genetically modified neural stem cells

Huntington's disease is a progressive neurodegenerative disease that affects the striatum, above all, the GABAergic striatal projection neurons. In the present study, we have explored the use of genetically modified neural stem cell lines producing nerve growth factor (NGF) or brain-derived neurotrophic factor (BDNF) as a means to protect the striatal neurons against excitotoxic damage after transplantation to the striatum, 1 week before the injection of quinolinic acid into the same area. One month after the lesion, striatal degeneration, lesion size, and loss of DARPP-32-positive projection neurons were only slightly affected by the BDNF-secreting cells, but substantially prevented when NGF-producing stem cells were used as a source of exogenous trophic factor; innervation of the target fields (pars reticulata of the substantia nigra and the globus pallidus) was preserved as well. Cholinergic striatal interneurons (choline acetyltransferase- immunoreactive) were affected by the lesion and completely rescued by the NGF-transduced cells. The astroglial and microglial reactions to the excitotoxic lesion were substantially reduced in the striata, which had received transplants of NGF-producing cells. The generalized protective effects of the NGF-producing cell grafts in this model are discussed in the context of an indirect action preventing the development of toxicity mediated by cellular elements in the host striatum in response to the excitotoxin. We conclude that continuous supply of trophic factors by means of genetically modified neural stem cells represents a highly effective procedure to counteract neuronal degeneration in the excitotoxically lesioned striatum.

Cytosolic and mitochondrial calcium in synaptosomes during aging

Synaptosomal [Ca2+]i levels increase during aging, particularly in the old rat hippocampus, both under basal conditions and after high K depolarization. This is probably the result of age-dependent modifications in calcium buffering and extrusion systems rather than due to increased calcium influx, since calcium uptake through synaptosomal voltage gated calcium channels decreases in old animals. The calcium binding capacity of the cytosolic compartment (i.e, that excluded from mitochondria and endoplasmic reticulum) of synaptosomes was markedly reduced in old rats. Calcium compartmentation in synaptosomal mitochondria, is also reduced during aging, and this is associated with a decrease in activity of the mitochondrial calcium uniporter. Taken together, these modifications point towards a clear deterioration of the cell calcium homeostatic mechanisms towards increased [Ca2+]i in old age, specially under conditions of high calcium loads, a situation that may exacerbate neuronal vulnerability to excitotoxicity.

Long-term functional recovery from age-induced spatial memory impairments by nerve growth factor gene transfer to the rat basal forebrain

Nerve growth factor (NGF) stimulates functional recovery from cognitive impairments associated with aging, either when administered as a purified protein or by means of gene transfer to the basal forebrain. Because gene transfer procedures need to be tested in long-term experimental paradigms to assess their in vivo efficiency, we have used ex vivo experimental gene therapy to provide local delivery of NGF to the aged rat brain over a period of 2.5 months by transplanting immortalized central nervous system-derived neural stem cells genetically engineered to secrete NGF. By grafting them at two independent locations in the basal forebrain, medial septum and nucleus basalis magnocellularis, we show that functional recovery as assessed in the Morris water maze can be achieved by neurotrophic stimulation of any of these cholinergic cell groups. Moreover, the cholinergic neurons in the grafted regions showed a hypertrophic response resulting in a reversal of the age-associated atrophy seen in the learning-impaired aged control rats. Long-term expression of the transgene lead to an increased NGF tissue content (as determined by NGF-ELISA) in the transplanted regions up to at least 10 weeks after grafting. We conclude that the gene transfer procedure used here is efficient to provide the brain with a long-lasting local supply of exogenous NGF, induces long-term functional recovery of cognitive functions, and that independent trophic stimulation of the medial septum or nucleus basalis magnocellularis has similar consequences at the behavioral level.

CNS-derived neural progenitor cells for gene transfer of nerve growth factor to the adult rat brain: complete rescue of axotomized cholinergic neurons after transplantation into the septum

A CNS-derived conditionally immortalized temperature-sensitive neural progenitor (CINP) cell line was used to generate NGF-secreting cells suitable for intracerebral transplantation. The cells were transduced by repeated retroviral infection, using a vector containing the mouse NGF cDNA under the control of the LTR promoter. Subcloning at the permissive temperature (33 degrees C) identified a highly NGF-secreting clone (NGF-CINP), which contained multiple copies of the transgene and released NGF at a rate of 2 ng/hr/10(5) cells in vitro, both at 33 and 37 degrees C, which was approximately 1 order of magnitude higher than what was possible to achieve in the heterogeneously infected cell cultures. After transplantation to the brain, the NGF-CINPs differentiated into cells with a predominant glia-like morphology and migrated for a distance of 1-1.5 mm from the implantation site into the surrounding host tissue, without any signs of overgrowth and tumor formation. Grafts of NGF-CINP cells implanted into the septum of adult rats with complete fimbria-fornix lesion blocked over 90% of the cholinergic cell loss in the medial septum and grafts placed in the intact striatum induced accumulation of low-affinity NGF receptor positive fibers around the implantation site. Expression of the NGF transgene in vivo was demonstrated by RT-PCR at 2 weeks after grafting. It is concluded that the immortalized neural progenitors have a number of advantageous properties that make them highly useful experimental tools for gene transfer to the adult CNS.

Reversal of age-dependent cognitive impairments and cholinergic neuron atrophy by NGF-secreting neural progenitors grafted to the basal forebrain

A highly NGF-secreting cell line was generated by retroviral transduction of a conditionally immortalized CNS-derived neural progenitor cell line. After transplantation to the nucleus basalis magnocellularis (NBM), the cells continue to express the NGF transgene for at least 10 weeks, producing sufficient NGF to reverse cholinergic neuron atrophy in aged rats and induce cellular hypertrophy in young rats. In cognitively impaired aged rats, transplants of the NGF-secreting cells placed either in the NBM and septum or in only the NBM induced a near-complete reversal of the spatial learning impairment. This was accompanied by a normalization of the size of the cholinergic neurons in the grafted areas. The results demonstrate that locally increased supply of NGF to the basal forebrain cholinergic nuclei has a significant impact on cognitive function and support the usefulness of neural progenitor cells for a long-term localized delivery of neurotrophins to the CNS.

The role of pyruvate in neuronal calcium homeostasis. Effects on intracellular calcium pools

It has long been known that pyruvate is essential for survival of prenatal neurons in culture. To understand the role of exogenous pyruvate in neuronal calcium homeostasis, we have investigated the effects of pyruvate (plus malate) addition to dissociated adult rat hippocampal and cerebral cortex cells and cultured CNS neurons having an unrestricted glucose supply. We found that pyruvate (plus malate) increased the respiration rate while ATP levels were unchanged. At the same time, cytosolic free calcium concentrations, [Ca2+]i, decreased while total 45Ca2+ and 40Ca2+ accumulation increased. The extra Ca2+ accumulated by the cells is attributable to an increase in the size of the intracellular calcium pools. Two such pools were identified on the basis of their sensitivity to specific drugs. The first pool was mobilized by thapsigargin plus tert-butyl hydroquinone and caffeine while the second pool was discharged by the mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxphenylhydrazone (FCCP) (plus oligomycin). The two pools represented about 15-20% and 15-30%, respectively, of the rapidly exchangeable 45Ca2+ pools in cerebral cortex cells. In cultured hippocampal neurons, the collapse of the mitochondrial membrane potential (as induced by uncouplers (FCCP) or respiratory chain inhibitors (antimycin) caused a large increase in [Ca2+]i which varied in size and shape among cells and was reduced by external Ca2+ chelation. The latter condition also resulted in a partial discharge of FCCP-releasable 45Ca2+. The effects of FCCP did not result simply from ATP depletion since incubation in glucose-free medium and sequential additions of 2 mM deoxyglucose and 10 microM oligomycin, conditions that led to a dramatic reduction in cellular ATP levels, did not abolish the FCCP-induced [Ca2+]i rise. Taken together, the results indicate that mitochondria harbor a significant proportion of cellular Ca2+. The sensitivity of the mitochondrial pool size to pyruvate (plus malate) questions previous hypotheses concerning a kinetic limitation for Ca2+ accumulation in mitochondria in resting neurons.

The activity of synaptosomal calcium channels is inversely correlated with working memory performance in memory impaired, aged rats

Aged, memory-impaired rats do not learn an 8-arm radial maze task but differ in their performance along testing. The aim of this study was to determine whether any of the systems that govern calcium homeostasis in synaptosomes may be related to that difference in performance. A negative correlation between initial (5 s) K(+)-stimulated 45Ca2+ uptake and the behavioral scores from the last testing sessions was obtained K(+)-stimulated 45Ca2+ uptake showed also a negative correlation with an improvement score that evaluates the progress made by the rat along testing. The results support the notion that calcium inflow through synaptosomal voltage gated calcium channels in old rats is inversely correlated with their behavior. This may explain the beneficial effects of organic calcium channel blockers on behavioral performance in aged animals.

Age-related changes in calcium homeostatic mechanisms in synaptosomes in relation with working memory deficiency

Aging is associated with alterations in different systems that govern neuronal calcium homeostasis. This study was designed to determine whether any of these alterations may contribute to the decline in spatial working memory that is observed in old rats. Several parameters [initial (5 s) and steady state (15 min) 45Ca2+ uptake, FCCP-releaseable 45Ca2+, [Ca2+]i levels, depolarization-induced phosphoprotein (P97, PP65, P42) dephosphorylation and acetylcholine levels and release) involved in calcium homeostasis/signaling were determined in whole brain synaptosomes derived from adult (9-month-old) and old (24-month-old) rats that were evaluated for spatial memory performance in the eight-arm radial maze. The neurochemical analysis indicated that both the 9- and 24-month-old rats were impaired with respect to 3-month-old animals. When learners (animals reaching criterion; RC) were compared to memory impaired rats (MI), it was found that the FCCP-releaseable 45Ca2+ of synaptosomes, that reflects mitochondrial calcium, was lower in the MI than the RC rats and was correlated with the behavioral performance of the rats in their first testing sessions. The results suggest that the loss of calcium uptake capacity in synaptic mitochondria during aging may be associated with impaired working memory in old animals.

Regulation of cytosolic free calcium concentration by intrasynaptic mitochondria

By the use of digitonin permeabilized presynaptic nerve terminals (synaptosomes), we have found that intrasynaptic mitochondria, when studied "in situ," i.e., surrounded by their cytosolic environment, are able to buffer calcium in a range of calcium concentrations close to those usually present in the cytosol of resting synaptosomes. Adenine nucleotides and polyamines, which are usually lost during isolation of mitochondria, greatly improve the calcium-sequestering activity of mitochondria in permeabilized synaptosomes. The hypothesis that the mitochondria contributes to calcium homeostasis at low resting cytosolic free calcium concentration ([Ca2+]i) in synaptosomes has been tested; it has been found that in fact this is the case. Intrasynaptic mitochondria actively accumulates calcium at [Ca2+]i around 10(-7) M, and this activity is necessary for the regulation of [Ca2+]i. When compared with other membrane-limited calcium pools, it was found that depending on external concentration the calcium pool mobilized from mitochondria is similar or even greater than the IP3- or caffeine-sensitive calcium pools. In summary, the results presented argue in favor of a more prominent role of mitochondria in regulating [Ca2+]i in presynaptic nerve terminals, a role that should be reconsidered for other cellular types in light of the present evidence.

NMDA-induced increase in [Ca2+]i and45Ca2+ uptake in acutely dissociated brain cells derived from adult rats

A preparation of acutely dissociated brain cells derived from adult (3-month-old) rat has been developed under conditions preserving the metabolic integrity of the cells and the function of N-methyl-D-aspartate (NMDA) receptors. The effects of glutamate and NMDA on [Ca2+]i measured with fluo3 and 45Ca2+ uptake have been studied on preparations derived from hippocampus and cerebral cortex. Glutamate (100 microM) and N-methyl-DL-aspartate (200 microM) increased [Ca2+]i by 26-12 nM and 23-9 nM after 90 s in cerebral cortex and hippocampus, and stimulated 45Ca2+ uptake about 16-10% in the same regions. The increases in [Ca2+]i and 45Ca2+ uptake were inhibited by 40% in the presence of 1 mM MgCl2 and by 90-50% in the presence of MK-801. The results indicate (a) that a large fraction of the [Ca2+]i response to glutamate in freshly dissociated brain cells from the adult rat involves NMDA receptors, (b) when compared with results in newborn rats, there is a substantial blunting of the [Ca2+]i increase in adult age.

Conditions restricting depolarization-dependent calcium influx in synaptosomes reveal a graded response of P96 dephosphorylation and a transient dephosphorylation of P65

Temporal changes in the phosphorylation level of synaptosomal phosphoproteins following depolarization of synaptosomes were investigated under conditions restricting calcium influx. High-K+ depolarization in media of low [Na+]o (32 mM during preincubation and depolarization) at pH 6.5 resulted in a pronounced fall in the cytosolic free calcium concentration transient, and in a reduction in the initial K(+)-stimulated 45Ca2+ uptake and endogenous acetylcholine release relative to the values obtained with control synaptosomes (preincubated and depolarized in Na(+)-based media). This reduction was paralleled by a decrease in the rate of dephosphorylation of the synaptosomal protein P96. A slower dephosphorylation of P96 also was observed on exposure to 20 microM veratridine at 0.5 mM external calcium. Our results indicate that, similar to synapsin I phosphorylation, P96 dephosphorylation shows a graded response to the amount of calcium entering the presynaptic terminal. Depolarization of synaptosomes under conditions restricting the influx of calcium revealed a transient dephosphorylation (reversed within 10 s) of the phosphoprotein P65. The possible significance of this finding to the process of neurotransmitter release is discussed.

Effect of Quin-2 on 45Ca2+ uptake mediated by Na+i/Ca2+o exchange and 45Ca2+ efflux in rat brain synaptosomes: a requirement for [Ca2+]i

The Na+/Ca2+ exchanger of squid axons, barnacle muscle and sarcolemma requires micromolar intracellular calcium for activation in the Na+i/Ca2+o exchange mode ('reverse' Na+/Ca2+ exchange). The requirement for [Ca2+]i has been demonstrated with the use of intracellular calcium buffers, such as Quin-2, to inhibit Na+i/Ca2+o exchange. However, the inhibition of Na+i/Ca2+o exchange in mammalian nerve terminals loaded with Quin-2 has not been observed [7], suggesting a lower sensitivity to low [Ca2+]i for this system. In contrast, the results reported herein indicate that 45Ca2+ uptake in synaptosomes through Na+i/Ca2+o exchange is inhibited by Quin-2 much in the same way as it is in the squid, provided that synaptosomes are preincubated in low Ca2+ medium to avoid saturation of Quin-2. Under these conditions, 45Ca2+ efflux via Ca2+i/Ca2+o exchange is also inhibited. Our results indicate that the Na+i/Ca2+o and Ca2+i/Ca2+o modes of the Na+/Ca2+ exchanger from rat brain synaptosomes require intracellular calcium for activation. However, because no clear relationship between the observed [Ca2+]i values and the inhibition of Na+i/Ca2+o exchange has been found, it is suggested that localised submembrane calcium concentrations not detected by the [Ca2+]i probe might regulate the exchanger.

Caffeine-sensitive calcium stores in presynaptic nerve endings: a physiological role?

Ca2+-sensitive minielectrodes and the fluorescent cytosolic calcium probes, quin2 and fura2, were used to study some aspects of calcium homeostasis in intact and permeabilized synaptosomes from whole rat brain. Experiments in permeabilized synaptosomes revealed the existence of a vesicular, non-mitochondrial, ATP-dependent calcium uptake system with a vanadate sensitivity similar to that of brain microsomes, or endoplasmic reticulum-type calcium sequestering organelles. By using the fluorescent probes it was possible to show that caffeine mobilizes calcium from these internal stores in intact synaptosomes. Our results indicate a role of the caffeine sensitive calcium stores in the buffering of calcium loads elicited by plasma membrane depolarization.

Reduction of K+-stimulated 45Ca2+ influx in synaptosomes with age involves inactivating and noninactivating calcium channels and is correlated with temporal modifications in protein dephosphorylation

The voltage-dependent calcium uptake in rat brain synaptosomes was measured under conditions in which [Ca2+]o/[Na+]i exchange was minimized to characterize the voltage-sensitive calcium channels from rats of different ages. In solutions of CaCl2 concentrations of less than 500 microM, the initial (5-s) calcium uptake declined by approximately 20-50% in 12- and 24-month-old rats relative to 3-month-old adults. Depolarization of synaptosomes from 3-month-old rats in a calcium-free medium or in the presence of 0.5 mM CaCl2 led to an exponential decline of the calcium uptake rate after 20 s (voltage- or voltage-and-calcium-dependent inactivation) to approximately 66 and 34% of the initial value with a t1/2 of 1.6 or 0.7 s, respectively. The presence of 1 microM nifedipine resulted in a 15-25% reduction of 45Ca2+ uptake rates, which appeared to affect noninactivating calcium channels, but addition of the calcium channel agonist Bay K 8644 was without effect. In 24-month-old rats, inactivation of 45Ca2+ uptake in calcium-free media was nondetectable, and in the presence of 0.5 mM CaCl2, the rate and extent of inactivation were also much lower than in 3-month-old animals (the t1/2 was 0.9 s, and the calcium uptake rate at 20 s was 55% of its initial value). Moreover, the presence of 1 microM nifedipine was without effect on initial calcium uptake or inactivation in synaptosomes from 24-month-old rats. These results indicate that the decrease in calcium channel-mediated 45Ca2+ uptake involves an inhibition or block of both dihydropyridine-resistant and -sensitive calcium channels.(ABSTRACT TRUNCATED AT 250 WORDS)