The Comparative Effects of Mesenchymal Stem Cell Transplantation Therapy for Spinal Cord Injury in Humans and Animal Models: A Systematic Review and Meta-Analysis

Animal models have been used in preclinical research to examine potential new treatments for spinal cord injury (SCI), including mesenchymal stem cell (MSC) transplantation. MSC transplants have been studied in early human trials. Whether the animal models represent the human studies is unclear. This systematic review and meta-analysis has examined the effects of MSC transplants in human and animal studies. Following searches of PubMed, Clinical Trials and the Cochrane Library, published papers were screened, and data were extracted and analysed. MSC transplantation was associated with significantly improved motor and sensory function in humans, and significantly increased locomotor function in animals. However, there are discrepancies between the studies of human participants and animal models, including timing of MSC transplant post-injury and source of MSCs. Additionally, difficulty in the comparison of functional outcome measures across species limits the predictive nature of the animal research. These findings have been summarised, and recommendations for further research are discussed to better enable the translation of animal models to MSC-based human clinical therapy.

Nicotinamide restricts neural precursor proliferation to enhance catecholaminergic neuronal subtype differentiation from mouse embryonic stem cells

Emerging evidence indicates that a strong relationship exists between brain regenerative therapies and nutrition. Early life nutrition plays an important role during embryonic brain development, and there are clear consequences to an imbalance in nutritional factors on both the production and survival of mature neuronal populations and the infant’s risk of diseases in later life. Our research and that of others suggest that vitamins play a fundamental role in the formation of neurons and their survival. There is a growing body of evidence that nicotinamide, the water-soluble amide form of vitamin B₃, is implicated in the conversion of pluripotent stem cells to clinically relevant cells for regenerative therapies. This study investigated the ability of nicotinamide to promote the development of mature catecholaminergic neuronal populations (associated with Parkinson’s disease) from mouse embryonic stem cells, as well as investigating the underlying mechanisms of nicotinamide’s action. Nicotinamide selectively enhanced the production of tyrosine hydroxylase-expressing neurons and serotonergic neurons from mouse embryonic stem cell cultures (Sox1GFP knock-in 46C cell line). A 5-Ethynyl-2´-deoxyuridine (EdU) assay ascertained that nicotinamide, when added in the initial phase, reduced cell proliferation. Nicotinamide drove tyrosine hydroxylase-expressing neuron differentiation as effectively as an established cocktail of signalling factors, reducing the proliferation of neural progenitors and accelerating neuronal maturation, neurite outgrowth and neurotransmitter expression. These novel findings show that nicotinamide enhanced and enriched catecholaminergic differentiation and inhibited cell proliferation by directing cell cycle arrest in mouse embryonic stem cell cultures, thus driving a critical neural proliferation-to-differentiation switch from neural progenitors to neurons. Further research into the role of vitamin metabolites in embryogenesis will significantly advance cell-based regenerative medicine, and help realize their role as crucial developmental signalling molecules in brain development.

Retroviral insertional mutagenesis implicates E3 ubiquitin ligase RNF168 in the control of cell proliferation and survival

The E3 ubiquitin ligase RNF168 is a ring finger protein that has previously been identified to play an important regulatory role in the repair of double-strand DNA breaks.  In the present study, an unbiased forward genetics functional screen in mouse granulocyte/ macrophage progenitor cell line FDCP1 has identified E3 ubiquitin ligase RNF168 as a key regulator of cell survival and proliferation. Our data indicate that RNF168 is an important component of the mechanisms controlling cell fate, not only in human and mouse haematopoietic growth factor-dependent cells, but also in the human breast epithelial cell line MCF-7. These observations therefore suggest that RNF168 provides a connection to key pathways controlling cell fate, potentially through interaction with PML nuclear bodies and/or epigenetic control of gene expression. Our study is the first to demonstrate a critical role for RNF168 in the in the mechanisms regulating cell proliferation and survival, in addition to its well-established role in DNA repair.

Nicotinamide alone accelerates the conversion of mouse embryonic stem cells into mature neuronal populations

Introduction

Vitamin B₃ has been shown to play an important role during embryogenesis. Specifically, there is growing evidence that nicotinamide, the biologically active form of vitamin B₃, plays a critical role as a morphogen in the differentiation of stem cells to mature cell phenotypes, including those of the central nervous system (CNS). Detailed knowledge of the action of small molecules during neuronal differentiation is not only critical for uncovering mechanisms underlying lineage-specification, but also to establish more effective differentiation protocols to obtain clinically relevant cells for regenerative therapies for neurodegenerative conditions such as Huntington’s disease (HD). Thus, this study aimed to investigate the potential of nicotinamide to promote the conversion of stem cells to mature CNS neurons.

Methods

Nicotinamide was applied to differentiating mouse embryonic stem cells (mESC; Sox1GFP knock-in 46C cell line) during their conversion towards a neural fate. Cells were assessed for changes in their proliferation, differentiation and maturation; using immunocytochemistry and morphometric analysis methods.

Results

Results presented indicate that 10 mM nicotinamide, when added at the initial stages of differentiation, promoted accelerated progression of ESCs to a neural lineage in adherent monolayer cultures. By 14 days in vitro (DIV), early exposure to nicotinamide was shown to increase the numbers of differentiated βIII-tubulin-positive neurons. Nicotinamide decreased the proportion of pluripotent stem cells, concomitantly increasing numbers of neural progenitors at 4 DIV. These progenitors then underwent rapid conversion to neurons, observed by a reduction in Sox 1 expression and decreased numbers of neural progenitors in the cultures at 14 DIV. Furthermore, GABAergic neurons generated in the presence of nicotinamide showed increased maturity and complexity of neurites at 14 DIV. Therefore, addition of nicotinamide alone caused an accelerated passage of pluripotent cells through lineage specification and further to non-dividing mature neurons.

Conclusions

Our results show that, within an optimal dose range, nicotinamide is able to singly and selectively direct the conversion of embryonic stem cells to mature neurons, and therefore may be a critical factor for normal brain development, thus supporting previous evidence of the fundamental role of vitamins and their metabolites during early CNS development. In addition, nicotinamide may offer a simple effective supplement to enhance the conversion of stem cells to clinically relevant neurons.

Magnetic Nanoparticle-Mediated Gene Delivery to Two- and Three-Dimensional Neural Stem Cell Cultures: Magnet-Assisted Transfection and Multifection Approaches to Enhance Outcomes

Neural stem cells (NSCs) have high translational potential in transplantation therapies for neural repair. Enhancement of their therapeutic capacity by genetic engineering is an important goal for regenerative neurology. Magnetic nanoparticles (MNPs) are major non-viral vectors for safe bioengineering of NSCs, offering critical translational benefits over viral vectors, including safety, scalability, and ease of use. This unit describes protocols for the production of suspension (neurosphere) and adherent (monolayer) murine NSC cultures. Genetic engineering of NSCs with MNPs and the application of 'magnetofection' (magnetic fields) or 'multifection' (repeat transfection) approaches to enhance gene delivery are described. Magnetofection of monolayer cultures achieves optimal transfection, but neurospheres offer key advantages for neural graft survival post-transplantation. A protocol is presented which allows the advantageous features of each approach to be combined into a single procedure for transplantation. The adaptation of these protocols for other MNP preparations is considered, with emphasis on the evaluation of procedural safety. © 2017 by John Wiley & Sons, Inc.

The hormone response element mimic sequence of GAS5 lncRNA is sufficient to induce apoptosis in breast cancer cells

Growth arrest-specific 5 (GAS5) lncRNA promotes apoptosis, and its expression is down-regulated in breast cancer. GAS5 lncRNA is a decoy of glucocorticoid/related receptors; a stem-loop sequence constitutes the GAS5 hormone response element mimic (HREM), which is essential for the regulation of breast cancer cell apoptosis. This preclinical study aimed to determine if the GAS5 HREM sequence alone promotes the apoptosis of breast cancer cells. Nucleofection of hormone-sensitive and –insensitive breast cancer cell lines with a GAS5 HREM DNA oligonucleotide increased both basal and ultraviolet-C-induced apoptosis, and decreased culture viability and clonogenic growth, similar to GAS5 lncRNA. The HREM oligonucleotide demonstrated similar sequence specificity to the native HREM for its functional activity and had no effect on endogenous GAS5 lncRNA levels. Certain chemically modified HREM oligonucleotides, notably DNA and RNA phosphorothioates, retained pro-apoptotic. activity. Crucially the HREM oligonucleotide could overcome apoptosis resistance secondary to deficient endogenous GAS5 lncRNA levels. Thus, the GAS5 lncRNA HREM sequence alone is sufficient to induce apoptosis in breast cancer cells, including triple-negative breast cancer cells. These findings further suggest that emerging knowledge of structure/function relationships in the field of lncRNA biology can be exploited for the development of entirely novel, oligonucleotide mimic-based, cancer therapies.

Endocytotic potential governs magnetic particle loading in dividing neural cells: studying modes of particle inheritance

AIM

To achieve high and sustained magnetic particle loading in a proliferative and endocytotically active neural transplant population (astrocytes) through tailored magnetite content in polymeric iron oxide particles.

MATERIALS & METHODS

MPs of varying magnetite content were applied to primary-derived rat cortical astrocytes ± static/oscillating magnetic fields to assess labeling efficiency and safety.

RESULTS

Higher magnetite content particles display high but safe accumulation in astrocytes, with longer-term label retention versus lower/no magnetite content particles. Magnetic fields enhanced loading extent. Dynamic live cell imaging of dividing labeled astrocytes demonstrated that particle distribution into daughter cells is predominantly 'asymmetric'.

CONCLUSION

These findings could inform protocols to achieve efficient MP loading into neural transplant cells, with significant implications for post-transplantation tracking/localization.

Molecular and Cellular Mechanisms of Action of Tumour Suppressor GAS5 LncRNA

It is increasingly recognised that lncRNAs play essential regulatory roles in fundamental biological processes and, consequently, that their dysregulation may contribute to major human diseases, including cancer. Better understanding of lncRNA biology may therefore offer new insights into pathogenetic mechanisms and thereby offer novel opportunities for diagnosis and therapy. Of particular interest in this regard is GAS5 lncRNA, which is down-regulated in multiple cancers, with expression levels related to both clinico-pathological characteristics and patient prognosis. Functional studies have further shown that GAS5 lncRNA both inhibits the proliferation and promotes the apoptosis of multiple cell types, and that together these cellular mechanisms of action are likely to form the basis of its tumour suppressor action. At the same time, advances have been made in our understanding of the molecular mechanisms of GAS5 lncRNA action in recent years, including riborepression of certain steroid hormone receptors and sequestration of miR-21, impacting key regulatory pathways of cell survival. Overall this accumulating knowledge has the potential to improve both the diagnosis and treatment of cancer, and ultimately patient outcome.

Reciprocal regulation of GAS5 lncRNA levels and mTOR inhibitor action in prostate cancer cells

BACKGROUND

New therapies are required for castrate-resistant prostate cancer (CRPC), and growth-arrest specific 5 (GAS5) lncRNA, which riborepresses androgen receptor action, may offer novel opportunities in this regard. This lncRNA promotes the apoptosis of prostate cancer cells and its levels decline as prostate cancer cells acquire castrate-resistance, so that enhancing GAS5 expression may improve the effectiveness of chemotherapies. Since GAS5 is a member of the 5' terminal oligopyrimidine gene family, we have examined mTOR inhibition as a strategy to increase GAS5 expression. Furthermore, we have determined if GAS5 itself mediates the action of mTOR inhibitors, as demonstrated for other chemotherapeutic agents in prostate cancer cells.

METHODS

The effects of mTOR inhibitors on GAS5 lncRNA levels and cell growth were determined in a range of prostate cancer cell lines. Transfection of cells with GAS5 siRNAs and plasmid constructs was performed to determine the involvement of GAS5 lncRNA in mTOR inhibitor action.

RESULTS

First generation mTORC1, combined mTORC1/mTORC2 and dual PI3K/mTOR inhibitors all increased cellular GAS5 levels and inhibited culture growth in androgen-dependent (LNCaP) and androgen-sensitive (22Rv1) cell lines, but not in androgen-independent (PC-3 and DU 145) cell lines. The latter exhibited low endogenous GAS5 expression, and GAS5 silencing in LNCaP and 22Rv1 cells decreased the sensitivity to mTOR inhibitors, whereas transfection of GAS5 lncRNA sensitized PC-3 and DU 145 cells to these agents.

CONCLUSION

mTOR inhibition enhances GAS5 transcript levels in certain prostate cancer cell lines. This selectivity is likely to be related to endogenous GAS5 expression levels, since GAS5 lncRNA is itself required for mTOR inhibitor action in prostate cancer cells.

Influence of Amplitude of Oscillating Magnetic Fields on Magnetic Nanoparticle-Mediated Gene Transfer to Astrocytes

Functionalized magnetic nanoparticles (MNPs) are emerging as a major nanoplatform for regenerative neurology, particularly as transfection agents for gene delivery. Magnetic assistive technology, particularly the recent innovation of applied oscillating magnetic fields, can significantly enhance MNP-mediated gene transfer to neural cells. While transfection efficiency varies with oscillation frequency in various neural cell types, the influence of oscillation amplitude has not yet been investigated. We have addressed this issue using cortical astrocytes that were transfected using MNPs functionalized with plasmid encoding a reporter protein. Cells were exposed to a range of oscillation amplitudes (100–1000 μm), using a fixed oscillation frequency of 1 Hz. No significant differences were found in the proportions of transfected cells at the amplitudes tested, but GFP-related optical density measurements (indicative of reporter protein expression) were significantly enhanced at 200 μm. Safety data show no amplitude-dependent toxicity. Our data suggest that the amplitude of oscillating magnetic fields influences MNP-mediated transfection, and a tailored combination of amplitude and frequency may further enhance transgene expression. Systematic testing of these parameters in different neural subtypes will enable the development of a database of neuro-magnetofection protocols — an area of nanotechnology research where little information currently exists.

Conserved sequence-specific lincRNA-steroid receptor interactions drive transcriptional repression and direct cell fate

The majority of the eukaryotic genome is transcribed, generating a significant number of long intergenic noncoding RNAs (lincRNAs). Although lincRNAs represent the most poorly understood product of transcription, recent work has shown lincRNAs fulfill important cellular functions. In addition to low sequence conservation, poor understanding of structural mechanisms driving lincRNA biology hinders systematic prediction of their function. Here we report the molecular requirements for the recognition of steroid receptors (SRs) by the lincRNA growth arrest-specific 5 (Gas5), which regulates steroid-mediated transcriptional regulation, growth arrest and apoptosis. We identify the functional Gas5-SR interface and generate point mutations that ablate the SR-Gas5 lincRNA interaction, altering Gas5-driven apoptosis in cancer cell lines. Further, we find that the Gas5 SR-recognition sequence is conserved among haplorhines, with its evolutionary origin as a splice acceptor site. This study demonstrates that lincRNAs can recognize protein targets in a conserved, sequence-specific manner in order to affect critical cell functions.

Regulation of apoptosis by long non-coding RNA GAS5 in breast cancer cells: implications for chemotherapy

The putative tumour suppressor and apoptosis-promoting gene, growth arrest-specific 5 (GAS5), encodes long ncRNA (lncRNA) and snoRNAs. Its expression is down-regulated in breast cancer, which adversely impacts patient prognosis. In this preclinical study, the consequences of decreased GAS5 expression for breast cancer cell survival following treatment with chemotherapeutic agents are addressed. In addition, functional responses of triple-negative breast cancer cells to GAS5 lncRNA are examined, and mTOR inhibition as a strategy to enhance cellular GAS5 levels is investigated. Breast cancer cell lines were transfected with either siRNA to GAS5 or with a plasmid encoding GAS5 lncRNA and the effects on breast cancer cell survival were determined. Cellular responses to mTOR inhibitors were evaluated by assaying culture growth and GAS5 transcript levels. GAS5 silencing attenuated cell responses to apoptotic stimuli, including classical chemotherapeutic agents; the extent of cell death was directly proportional to cellular GAS5 levels. Imatinib action in contrast, was independent of GAS5. GAS5 lncRNA promoted the apoptosis of triple-negative and oestrogen receptor-positive cells but only dual PI3K/mTOR inhibition was able to enhance GAS5 levels in all cell types. Reduced GAS5 expression attenuates apoptosis induction by classical chemotherapeutic agents in breast cancer cells, providing an explanation for the relationship between GAS5 expression and breast cancer patient prognosis. Clinically, this relationship may be circumvented by the use of GAS5-independent drugs such as imatinib, or by restoration of GAS5 expression. The latter may be achieved by the use of a dual PI3K/mTOR inhibitor, to improve apoptotic responses to conventional chemotherapies.

Identifying the cellular targets of drug action in the central nervous system following corticosteroid therapy

Corticosteroid (CS) therapy is used widely in the treatment of a range of pathologies, but can delay production of myelin, the insulating sheath around central nervous system nerve fibers. The cellular targets of CS action are not fully understood, that is, "direct" action on cells involved in myelin genesis [oligodendrocytes and their progenitors the oligodendrocyte precursor cells (OPCs)] versus "indirect" action on other neural cells. We evaluated the effects of the widely used CS dexamethasone (DEX) on purified OPCs and oligodendrocytes, employing complementary histological and transcriptional analyses. Histological assessments showed no DEX effects on OPC proliferation or oligodendrocyte genesis/maturation (key processes underpinning myelin genesis). Immunostaining and RT-PCR analyses show that both cell types express glucocorticoid receptor (GR; the target for DEX action), ruling out receptor expression as a causal factor in the lack of DEX-responsiveness. GRs function as ligand-activated transcription factors, so we simultaneously analyzed DEX-induced transcriptional responses using microarray analyses; these substantiated the histological findings, with limited gene expression changes in DEX-treated OPCs and oligodendrocytes. With identical treatment, microglial cells showed profound and global changes post-DEX addition; an unexpected finding was the identification of the transcription factor Olig1, a master regulator of myelination, as a DEX responsive gene in microglia. Our data indicate that CS-induced myelination delays are unlikely to be due to direct drug action on OPCs or oligodendrocytes, and may occur secondary to alterations in other neural cells, such as the immune component. To the best of our knowledge, this is the first comparative molecular and cellular analysis of CS effects in glial cells, to investigate the targets of this major class of anti-inflammatory drugs as a basis for myelination deficits.

Magnetic nanoparticle mediated transfection of neural stem cell suspension cultures is enhanced by applied oscillating magnetic fields

Safe genetic modification of neural stem cell (NSC) transplant populations is a key goal for regenerative neurology. We describe a technically simple and safe method to increase transfection in NSCs propagated in the neurosphere (suspension culture) model, using magnetic nanoparticles deployed with applied oscillating magnetic fields ('magnetofection technology'). We show that transfection efficiency was enhanced over two-fold by oscillating magnetic fields (frequency=4 Hz). The protocols had no effect on cell viability, cell number, stem cell marker expression and differentiation profiles of 'magnetofected' cultures, highlighting the safety of the technique. As far as we are aware, this is the first successful application of magnetofection technology to suspension cultures of neural cells. The procedures described offer a means to augment the therapeutic potential of NSCs propagated as neurospheres - a culture model of high clinical translational relevance - by safe genetic manipulation, with further potential for incorporation into 'magneto-multifection' (repeat transfection) protocols.

FROM THE CLINICAL EDITOR

This team of investigators describe a simple and safe method to increase transfection in neural stem cells using magnetic nanoparticles deployed with oscillating magnetic fields, demonstrating a greater than two-fold transfection efficiency increase by applying low frequency magnetic oscillation.

Differences in magnetic particle uptake by CNS neuroglial subclasses: implications for neural tissue engineering

Aim: To analyze magnetic particle uptake and intracellular processing by the four main non-neuronal subclasses of the CNS: oligodendrocyte precursor cells; oligodendrocytes; astrocytes; and microglia. Materials & methods: Magnetic particle uptake and processing were studied in rat oligodendrocyte precursor cells and oligodendrocytes using fluorescence and transmission electron microscopy, and the results collated with previous data from rat microglia and astrocyte studies. All cells were derived from primary mixed glial cultures. Results: Significant intercellular differences were observed between glial subtypes: microglia demonstrate the most rapid/extensive particle uptake, followed by astrocytes, with oligodendrocyte precursor cells and oligodendrocytes showing significantly lower uptake. Ultrastructural analyses suggest that magnetic particles are extensively degraded in microglia, but relatively stable in other cells. Conclusion: Intercellular differences in particle uptake and handling exist between the major neuroglial subtypes. This has important implications for the utility of the magnetic particle platform for neurobiological applications including genetic modification, transplant cell labeling and biomolecule delivery to mixed CNS cell populations.

Original submitted 23 March 2012; Revised submitted 24 July 2012; Published online 22 November 2012

Long non-coding RNA GAS5 regulates apoptosis in prostate cancer cell lines

While the role of small non-coding RNAs, such as miRNAs, in apoptosis control is well established, long non-coding RNAs (lncRNAs) have received less attention. Growth Arrest-Specific 5 (GAS5) encodes multiple snoRNAs within its introns, while exonic sequences produce lncRNA which can act as a riborepressor of the glucocorticoid and related receptors. GAS5 negatively regulates the survival of lymphoid and breast cells, and is aberrantly expressed in several cancers. Although cellular GAS5 levels decline as prostate cancer cells acquire castration-resistance, the influence of GAS5 on prostate cell survival has not been determined. To address this question, prostate cell lines were transfected with GAS5-encoding plasmids or GAS5 siRNAs, and cell survival was assessed. Basal apoptosis increased, and cell survival decreased, after transfection of 22Rv1 cells with plasmids encoding GAS5 transcripts, including mature GAS5 lncRNA. Similar effects were observed in PC-3 cells. In stable clones of 22Rv1, cell death correlated strongly with cellular GAS5 levels. Induction of 22Rv1 cell death by UV-C irradiation and chemotherapeutic drugs was augmented in cells transiently transfected with GAS5 constructs, and attenuated following down-regulation of GAS5 expression. Again, in these experiments, cell death was strongly correlated with cellular GAS5 levels. Thus, GAS5 promotes the apoptosis of prostate cells, and exonic sequence, i.e. GAS5 lncRNA, is sufficient to mediate this activity. Abnormally low levels of GAS5 expression may therefore reduce the effectiveness of chemotherapeutic agents. Although several lncRNAs have recently been shown to control cell survival, this is the first report of a death-promoting lncRNA in prostate cells.

Fe3O4-PEI-RITC magnetic nanoparticles with imaging and gene transfer capability: development of a tool for neural cell transplantation therapies

PURPOSE

To develop Fe(3)O(4)-PEI-RITC magnetic nanoparticles with multimodal MRI-fluorescence imaging and transfection capability, for use in neural cell replacement therapies.

METHODS

The Fe(3)O(4)-PEI-RITC MNPs were synthesised through a multi-step chemical grafting procedure: (i) Silanisation of MNPs with 3-iodopropyltrimethoxysilane; (ii) PEI coupling with iodopropyl groups on the MNP surface; and (iii) RITC binding onto the PEI coating. The cell labelling and transfection capabilities of these particles were evaluated in astrocytes derived from primary cultures.

RESULTS

Fe(3)O(4)-PEI-RITC MNPs did not exert acute toxic effects in astrocytes (at ≤ 6 days). Cells showed rapid and extensive particle uptake with up to 100% cellular labelling observed by 24 h. MRI and microscopy studies demonstrate that the particles have potential for use in bimodal MR-fluorescence imaging. Additionally, the particles were capable of delivering plasmids encoding reporter protein (approximately 4 kb) to astrocytes, albeit with low efficiencies.

CONCLUSIONS

Multifunctional Fe(3)O(4)-PEI-RITC MNPs were successfully prepared using a multi-step synthetic pathway, with the PEI and RITC chemically bound onto the MNP surface. Their combined MR-fluorescence imaging capabilities with additional potential for transfection applications can provide a powerful tool, after further development, for non-invasive cell tracking and gene transfer to neural transplant populations.

Magnetic nanoparticle-mediated gene transfer to oligodendrocyte precursor cell transplant populations is enhanced by magnetofection strategies

This study has tested the feasibility of using physical delivery methods, employing static and oscillating field "magnetofection" techniques, to enhance magnetic nanoparticle-mediated gene transfer to rat oligodendrocyte precursor cells derived for transplantation therapies. These cells are a major transplant population to mediate repair of damage as occurs in spinal cord injury and neurological diseases such as multiple sclerosis. We show for the first time that magnetic nanoparticles mediate effective transfer of reporter and therapeutic genes to oligodendrocyte precursors; transfection efficacy was significantly enhanced by applied static or oscillating magnetic fields, the latter using an oscillating array employing high-gradient NdFeB magnets. The effects of oscillating fields were frequency-dependent, with 4 Hz yielding optimal results. Transfection efficacies obtained using magnetofection methods were highly competitive with or better than current widely used nonviral transfection methods (e.g., electroporation and lipofection) with the additional critical advantage of high cell viability. No adverse effects were found on the cells' ability to divide or give rise to their daughter cells, the oligodendrocytes-key properties that underpin their regeneration-promoting effects. The transplantation potential of transfected cells was tested in three-dimensional tissue engineering models utilizing brain slices as the host tissue; modified transplanted cells were found to migrate, divide, give rise to daughter cells, and integrate within host tissue, further evidencing the safety of the protocols used. Our findings strongly support the concept that magnetic nanoparticle vectors in conjunction with state-of-the-art magnetofection strategies provide a technically simple and effective alternative to current methods for gene transfer to oligodendrocyte precursor cells.

Candidate tumour suppressor Fau regulates apoptosis in human cells: an essential role for Bcl-G

FAU, which encodes a ubiquitin-like protein (termed FUBI) with ribosomal protein S30 as a carboxy-terminal extension, has recently been identified as a pro-apoptotic regulatory gene. This activity may be mediated by Bcl-G (a pro-apoptotic member of the Bcl-2 family) which can be covalently modified by FUBI. FAU gene expression has been shown to be down-regulated in human breast, prostate and ovarian tumours, and this down-regulation is strongly associated with poor prognosis in breast cancer. We demonstrate here that ectopic FAU expression increases basal apoptosis in human T-cell lines and 293T/17 cells, whereas it has only a transient stimulatory effect on ultraviolet-C (UVC)-induced apoptosis. Conversely, siRNA-mediated silencing of FAU gene expression has no effect on basal apoptosis, but attenuates UV-induced apoptosis. Importantly, prior knockdown of Bcl-G expression ablates the stimulation of basal apoptosis by FAU, consistent with an essential downstream role for Bcl-G, itself a candidate tumour suppressor, in mediating the apoptosis regulatory role of FAU. In 293T/17 cells, Bcl-G knockdown also attenuates UV-induced apoptosis, so that Bcl-G may constitute a common factor in the pathways by which both FAU and UV-irradiation induce apoptosis. UV irradiation increases Bcl-G mRNA levels, providing an explanation for the transient nature of the effect of ectopic FAU expression on UV-induced apoptosis. Since failure of apoptosis is fundamental to the development of many cancers, the pro-apoptotic activity of the Fau/Bcl-G pathway offers an attractive explanation for the putative tumour suppressor role of FAU.

The transfection of multipotent neural precursor/stem cell transplant populations with magnetic nanoparticles

Multipotent neural precursor/stem cells (NPCs) are a major transplant population with key properties to promote repair in several neuropathological conditions. Magnetic nanoparticle (MNP)-based vector systems, in turn, offer a combination of key benefits for cell therapies including (i) safety (ii) delivery of therapeutic biomolecules (DNA/siRNA) enhanceable by 'magnetofection' approaches (iii) magnetic cell targeting of MNP-labelled cells to injury sites and (iv) non-invasive imaging of MNP-labelled transplant populations for cell tracking. However, the applications of the versatile MNP platform for NPC transplantation therapies have received limited attention so far. We have evaluated the potential of MNP vectors for gene transfer to NPCs using a neurosphere culture model system; we also assessed repeat transfection ("multifection") and repeat transfection plus applied magnetic field ("magneto-multifection") strategies [to enhance transfection efficiency]. We show for the first time that MNPs can safely mediate single/combinatorial gene delivery to NPCs. Multifection approaches significantly enhanced transfection with negligible toxicity; no adverse effects were observed on stem cell proliferation/differentiation. "Multifected" NPCs survived and differentiated in 3D neural tissue arrays post-transplantation. Our findings demonstrate that MNPs offer a simple and robust alternative to the viral vector systems currently used widely to transfect neural stem cells in neurobiology/neural transplantation research.

Apoptosis regulators Fau and Bcl-G are down-regulated in prostate cancer

BACKGROUND

The molecular control of cell death through apoptosis is compromised in prostate cancer cells, resulting in inappropriate cell survival and resistance to cytotoxic therapy. Reduced expression of the functionally connected apoptosis-regulators and candidate tumor suppressors Fau and Bcl-G has recently been implicated in oncogenesis in other tissues. The present study examines the hypothesis that reduced expression of these genes may be involved in prostate cancer.

METHODS

Fau and Bcl-G mRNA levels were determined by real time RT-PCR in two independent prostate tissue collections. In experiments in vitro, Fau and Bcl-G levels in prostate cancer cell lines were reduced using RNA interference and the effects on sensitivity to UVC irradiation were determined.

RESULTS

Fau and Bcl-G mRNA levels were both lower in prostate cancer tissue than in normal prostate and Benign Prostate Hyperplasia. Active down-regulation of Fau and Bcl-G expression in vitro resulted in decreased sensitivity to UVC-induced cytotoxicity. Simultaneous down-regulation of Fau and Bcl-G produced a decrease in sensitivity which was similar to either gene alone.

CONCLUSIONS

Fau and Bcl-G mRNA levels are both decreased in prostate cancer. In prostate cancer cell lines in vitro such down-regulation results in reduced sensitivity to UVC-induced cytotoxicity, consistent with the putative roles of these genes as candidate prostate tumor suppressors. The absence of an additive effect when Fau and Bcl-G were down-regulated simultaneously is consistent with the two genes acting in the same apoptosis pathway, for example, with the pro-apoptotic effects of Fau being mediated through modulation of Bcl-G.

Dysregulated expression of Fau and MELK is associated with poor prognosis in breast cancer

Introduction

Programmed cell death through apoptosis plays an essential role in the hormone-regulated physiological turnover of mammary tissue. Failure of this active gene-dependent process is central both to the development of breast cancer and to the appearance of the therapy-resistant cancer cells that produce clinical relapse. Functional expression cloning in two independent laboratories has identified Finkel–Biskis–Reilly murine sarcoma virus-associated ubiquitously expressed gene (Fau) as a novel apoptosis regulator and candidate tumour suppressor. Fau modifies apoptosis-controller Bcl-G, which is also a key target for candidate oncoprotein maternal embryonic leucine zipper kinase (MELK).

Methods

We have used RNA interference to downregulate Fau and Bcl-G expression, both simultaneously and independently, in breast cancer cells in vitro to determine the importance of their roles in apoptosis. Expression of Fau, Bcl-G and MELK was measured by quantitative RT-PCR in breast cancer tissue and in matched breast epithelial tissue from the same patients. Expression data of these genes obtained using microarrays from a separate group of patients were related to patient survival in Kaplan–Meier analyses.

Results

siRNA-mediated downregulation of either Fau or Bcl-G expression inhibited apoptosis, and the inhibition produced by combining the two siRNAs was consistent with control of Bcl-G by Fau. Fau expression is significantly reduced in breast cancer tissue and this reduction is associated with poor patient survival, as predicted for a candidate breast cancer tumour suppressor. In addition, MELK expression is increased in breast cancer tissue and this increase is also associated with poor patient survival, as predicted for a candidate oncogene. Bcl-G expression is reduced in breast cancer tissue but decreased Bcl-G expression showed no correlation with survival, indicating that the most important factors controlling Bcl-G activity are post-translational modification (by Fau and MELK) rather than the rate of transcription of Bcl-G itself.

Conclusions

The combination of in vitro functional studies with the analysis of gene expression in clinical breast cancer samples indicates that three functionally interconnected genes, Fau, Bcl-G and MELK, are crucially important in breast cancer and identifies them as attractive targets for improvements in breast cancer risk prediction, prognosis and therapy.

Maternal hypothyroidism in the rat influences placental and liver glycogen stores: fetal growth retardation near term is unrelated to maternal and placental glucose metabolic compromise

Maternal hypothyroidism impairs fetal growth in the rat, but the mechanisms by which this occurs are unknown. Since the fetus derives its glucose supply from the mother, and maternal thyroidectomy may disturb maternal and placental glucose metabolism, we postulated that maternal and/or placental glucose metabolic compromise may contribute to fetal growth retardation in hypothyroid dams. Feto-placental growth, tissue glycogen stores and glucose levels in sera and amniotic fluid were determined in rat dams partially thyroidectomized (TX) before pregnancy and in euthyroid controls. Fetal body weight at 16, 19 and 21 days gestation (d.g.) was related to pre-mating maternal serum total thyroxine (TT(4)) levels; permanent fetal growth retardation occurred in severely (TX(s); pre-mating maternal serum TT(4)<or=16.19 nM) - but not in moderately (TX(m)) - hypothyroid dams. In TX(s) dams, glycogen concentration was elevated in maternal liver and in the fetal side of the placenta at 16 and 19 d.g., and in the maternal side of the placenta at 19 and 21 d.g., despite maternal euglycemia. In contrast, fetal liver glycogen concentration was deficient in TX(m) dams at 19 d.g. and in TX(s) dams at 19 and 21 d.g., and fetal hypoglycemia occurred in TX(s) dams at 21 d.g. Multiple regression analyses indicate that these fetal deficits are strongly associated with the retardation in fetal growth, while the elevated maternal liver and placental glycogen concentrations have no impact on fetal growth near term. The mechanisms by which severe maternal hypothyroidism permanently retards rat fetal growth remain to be determined.

Influence of maternal hyperthyroidism in the rat on the expression of neuronal and astrocytic cytoskeletal proteins in fetal brain

Maternal hypothyroidism during pregnancy impairs brain function in human and rat offspring, but little is known regarding the influence of maternal hyperthyroidism on neurodevelopment. We have previously shown that the expression of neuronal and glial differentiation markers in fetal brain is compromised in hypothyroid rat dam pregnancies and have now therefore extended this investigation to hyperthyroid rat dams. Study groups comprised partially thyroidectomised dams, implanted with osmotic pumps infusing either vehicle (TX dams) or a supraphysiological dose of thyroxine (T4) (HYPER dams), and euthyroid dams infused with vehicle (N dams). Cytoskeletal protein abundance was determined in fetal brain at 21 days of gestation by immunoblot analysis. Relative to N dams, circulating total T4 levels were reduced to around one-third in TX dams but were doubled in HYPER dams. Fetal brain weight was increased in HYPER dams, whereas litter size and fetal body weight were reduced in TX dams. Glial fibrillary acidic protein expression was similar in HYPER and TX dams, being reduced in both cases relative to N dams. alpha-Internexin (INX) abundance was reduced in HYPER dams and increased in TX dams, whereas neurofilament 68 (NF68) exhibited increased abundance in HYPER dams. Furthermore, INX was inversely related to - and NF68 directly related to - maternal serum total T4 levels, independently of fetal brain weight. In conclusion, maternal hyperthyroidism compromises the expression of neuronal cytoskeletal proteins in late fetal brain, suggestive of a pattern of accelerated neuronal differentiation.

Thyroid hormone receptor expression in rat placenta

The expression of c- erbAalpha and -beta encoded thyroid hormone receptors (TR) was investigated in rat placenta between 16 and 21 days of gestation (dg), and in fetal liver and brain at 16 dg, using semi-quantitative RT-PCR and nuclear 3,5,3'-triiodothyronine (T(3)) binding. TRalpha1, TRbeta1, c- erbAalpha 2 and c- erbAalpha 3 mRNA abundance was unchanged in placenta between 16 and 21 dg, as was the dissociation constant (K(d)) of T(3) binding. The maximal T(3) binding capacity (B(max)) in placenta doubled over this period, suggesting placental TR binding activity is post-transcriptionally regulated. Transcript abundance in tissues at 16 dg can be summarized: TRalpha1, placenta=fetal liver<fetal brain; TRbeta1, placenta=fetal liver>fetal brain; c- erbAalpha 2 and alpha3, placenta=fetal liver<fetal brain; TRbeta2; none detected. T(3)binding in fetal liver and brain exhibited equivalent K(d) and B(max), the K(d) being less than 50 per cent of that in placenta, though B(max) was unchanged. The higher K(d)in placenta may reflect tissue-specific patterns of TR modification. In conclusion, rat placenta expresses significant levels of c- erbAalpha and -beta transcripts and protein, providing a possible mechanism of action for T(3) of maternal and fetal origin in this tissue.

Maternal thyroid status regulates the expression of neuronal and astrocytic cytoskeletal proteins in the fetal brain

Maternal thyroid hormone (TH) crosses the placenta and is postulated to regulate fetal brain development. However, TH-dependent stages of fetal brain development remain to be characterised. We have therefore compared the levels of several neuronal and glial cytoskeletal proteins in fetal brains from normal (N) and partially thyroidectomised (TX) rat dams by immunoblotting. Pregnancies were studied both before and after the onset of fetal TH secretion, which occurs at 17.5 days gestation (dg) in the rat. Maternal hypothyroidism disrupted fetal growth, so that fetal body and brain weights were reduced near term. Vimentin expression was unaffected, however, indicating normal acquisition of neuronal and glial precursor cells. Fetal brain levels of glial fibrillary acidic protein (GFAP) were reduced at 21 dg, suggesting delayed astrocytic differentiation, although regression analysis demonstrated appropriate GFAP levels for brain weight. Levels of alpha-internexin, the earliest neurofilament protein expressed in fetal brain were reduced at 16 dg in TX dams, but increased at 21 dg. The ontogeny of neurofilament-L was also perturbed in these pregnancies, with deficient levels apparent at both 16 and 21 dg. These effects on neuronal cytoskeletal proteins were unrelated to fetal brain growth retardation. These findings confirm that maternal hypothyroidism disrupts early fetal brain development. Early disturbances in neuronal differentiation are not corrected by the onset of fetal TH secretion. Such disturbances may contribute to the neurological damage observed in children born to hypothyroxinaemic mothers.

Maternal hypothyroxinemia influences glucose transporter expression in fetal brain and placenta

The influence of maternal hypothyroxinemia on the expression of the glucose transporters, GLUT1 and GLUT3, in rat fetal brain and placenta was investigated. Fetal growth was retarded in hypothyroxinemic pregnancies, but only before the onset of fetal thyroid hormone synthesis. Placental weights were normal, but placental total protein concentration was reduced at 19 days gestation (dg). Immunoblotting revealed a decreased abundance of GLUT1 in placental microsomes at 16 dg, whereas GLUT3 was increased. Fetal serum glucose levels were reduced at 16 dg. In fetal brain, the concentration of microsomal protein was deficient at 16 dg and the abundance of parenchymal forms of GLUT1 was further depressed, whereas GLUT3 was unaffected. Northern hybridization analysis demonstrated normal GLUT1 mRNA levels in placenta and fetal brain. In conclusion, maternal hypothyroxinemia results in fetal growth retardation and impaired brain development before the onset of fetal thyroid function. Glucose uptake in fetal brain parenchyma may be compromised directly, due to deficient GLUT1 expression in this tissue, and indirectly, as a result of reduced placental GLUT1 expression. Though corrected by the onset of fetal thyroid hormone synthesis, these deficits are present during the critical period of neuroblast proliferation and may contribute to long term changes in brain development and function seen in this model and in the progeny of hypothyroxinemic women.

SHORT COMMUNICATION maternal thyroid dysfunction and c- fos and c- jun expression in rat placenta

Maternal thyroid dysfunction is associated with perturbed fetal brain development and neurological deficits in adulthood in rat and human. To investigate whether these effects occur secondary to placental dysfunction, c- fos and c- jun expression in placenta from normal (euthyroid) and moderately hypothyroid rat dams were investigated by Northern hybridization analysis. In normal placenta, c- fos expression increased by 74 per cent between 16 and 21 days of gestation (dg) whereas c- jun expression declined by 46 per cent. Moderate maternal hypothyroidism depressed placental c- fos expression by 32 per cent at 19 dg, but elevated c- fos and c- jun expression by 139 and 86 per cent, respectively, at 21 dg. Maternal hypothyroidism may therefore induce c- fos/c- jun -related placental dysfunction, but only relatively late in gestation when fetal thyroid function is already established.

Maternal hypothyroxinemia disrupts neurotransmitter metabolic enzymes in developing brain

Maternal thyroid status influences early brain development and, consequently, cognitive and motor function in humans and rats. The biochemical targets of maternal thyroid hormone (TH) action in fetal brain remain poorly defined. A partially thyroidectomized rat dam model was therefore used to investigate the influence of maternal hypothyroxinemia on the specific activities of cholinergic and monoaminergic neurotransmitter metabolic enzymes in the developing brain. Maternal hypothyroxinemia was associated with reduced monoamine oxidase (MAO) activity in fetal whole brain at 16 and 19 days gestation (dg). A similar trend was observed for choline acetyltransferase (ChAT) activity. In contrast, DOPA decarboxylase (DDC) activity was markedly elevated at 21 dg. Further study of these enzymes at 14 dg showed no differences between normal and experimental progeny - suggesting they become TH sensitive after this age. Tyrosine hydroxylase (TyrH) and acetylcholinesterase (AChE) activities were unaffected prenatally. During postnatal development, the activities of TyrH, MAO, DDC and, to a lesser extent, AChE were increased in a brain region- and age-specific manner in experimental progeny. The prenatal disturbances noted in this study may have wide-ranging consequences since they occur when neurotransmitters have putative neurotropic roles in brain development. Furthermore, the chronic disturbances in enzyme activity observed during postnatal life may affect neurotransmission, thereby contributing to the behavioural dysfunction seen in adult progeny of hypothyroxinemic dams.

Transport of thyroid hormones to target tissues

Endemic iodine deficiency is associated with maternal hypothyroxinemia and a relatively high incidence of neurological disorders in the offspring. The previous assumption that the placenta is impermeable to maternal thyroid hormone, has resulted in the erroneous suggestion that iodine per se has an essential role in brain development. Furthermore, the observed factorial rise in thyroxine-binding globulin (TBG) in pregnancy has often been misinterpreted as preventing thyroid hormone loss to either the fetal compartment or excretory systems. However, physiochemical analysis of the role of specific binding proteins in hormone delivery, combined with epidemiological evidence and evolutionary considerations has led us to postulate that a) maternal thyroxine (T4) is transported to the fetus, and is of crucial importance in early fetal development, and b) TBG forms part of a control system specifically designed to maintain at an optimal level the T4 environment to which the developing fetus is exposed. Placental transfer of maternal T4 in a variety of mammalian species (including humans) is now well established. Further experimental studies in rats have shown that perturbation of the intrauterine thyroid hormone environment during critical phases of brain development results in a spectrum of biochemical dysgenesis. For example, in fetal brains deriving from hypothyroxinemic (Tx) rat dams, severe disruption of phosphate metabolism is observed and the ontogenesis of two enzyme activities associated with growth control, protein kinase C and ornithine decarboxylase, are compromised. Development of brain function is also impaired, as evidenced by the dysgenesis of certain neurotransmitter metabolic activities (choline acetyltransferase and DOPA decarboxylase).(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of the maternal thyroid hormone environment during pregnancy on the ontogenesis of brain and placental ornithine decarboxylase activity in the rat

The influence of maternal hypothyroxinaemia on early brain and placental development was examined in a partially thyroidectomized (parathyroid-spared; TX) rat dam model. Ornithine decarboxylase (ODC) specific activity, along with more general indices of cell growth, were determined in prenatal whole brain (at 15, 19 and 22 days of gestation), postnatal brain regions (at 5, 10 and 14 days) and placenta. Maternal hypothyroxinaemia resulted in reductions in fetal body weight, brain weight, brain DNA content and brain total protein content at 15 days of gestation; the latter effect persisting until 19 days of gestation. Further changes in brain cell growth were observed near term, when an increase in the DNA concentration was accompanied by a decrease in the total protein:DNA ratio. Growth of the postnatal brain regions appeared normal, with the exception of an isolated increase in the protein content of the cerebellum at postnatal day 5. Determination of the specific activity of brain ODC revealed a complex pattern of change in the progeny of TX dams, superimposed upon the normal ontogenetic decline. In the fetal brain, activity was initially deficient at 15 days of gestation but was increased at 22 days of gestation relative to controls. The compromise extended into the postnatal period; ODC specific activity being transiently reduced in the brainstem, the subcortex and the cerebral cortex. Placental development was less consistently affected; wet weight, gross indices of cell growth (DNA content, DNA concentration, total protein:DNA ratio) and ODC specific activity were all normal in the TX dam. However, cytosolic and total protein concentrations were reduced at 15 and 19 days of gestation respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypothyroidism in the adult rat causes brain region-specific biochemical dysfunction

The influence of hypothyroidism in the adult rat on brain biochemistry was investigated. Hypothyroidism was induced in 6-month-old male rats by partial thyroidectomy coupled with the administration of 6-n-propyl-2-thiouracil (0.005%, w/v) in the drinking water. Age-matched euthyroid males served as the controls. Hypothyroidism resulted in brain region-specific changes in certain catabolic enzyme activities. Acid phosphatase activity was reduced in the cerebellum (by 34%) and the medulla (by 38%), whereas alkaline phosphatase activity was decreased in the midbrain (by 37%) and the subcortex (by 49%). A differential response was also observed in the case of aryl sulphatase activity: aryl sulphatase A (myelin-degradative activity) was diminished in the cerebellum (by 56%), whereas aryl sulphatase B remained unchanged in all regions. Acetylcholine esterase activity was reduced in the cerebellum (by 45%), the medulla (by 34%) and the subcortex (by 45%), whereas monoamine oxidase activity was affected in only one region, the cerebellum, where it was increased by (61%). The compromise of myelin and neurotransmitter degradative enzyme activities may place severe restrictions on normal brain function. The vulnerability of the adult rat cerebellum to the effects of thyroidectomy is commensurate with the known clinical signs of cerebellar dysfunction in adult hypothyroid man. These findings raise the possibility of an important role for the thyroid hormones in the mature brain.

Distance education: turf and technology

Distance learning fits with the mission and strategic plan of the University of Texas at Arlington. We believe these educational opportunities in nursing are highly desirable. The Board of Nurse Examiners for the State of Texas has approved this project and the Texas Higher Education Coordinating Board has approved it as a pilot project. The school will continue evaluation and creative problem-solving in the use of distance education.

Effects of caffeinated coffee on intraocular pressure

This study examined the effects of caffeinated coffee on the intraocular pressure of nonglaucomatous subjects. Subjects were randomly assigned to receive each of three treatments: caffeinated coffee, hot water, and no fluid. All subjects were given the three treatment conditions over 3 days. The study revealed that intraocular pressure after ingesting caffeinated coffee was significantly higher than after receiving the other two treatment conditions. It was further found that increased intraocular pressure was maintained at significant levels over a 3-hour period. No significant changes were found in the pulse rate, and findings on blood pressure were inconclusive.

Education of nurses for rural practice

There is an excitement about the potential for nursing to make a difference in meeting rural health needs in the 1990s. Work places are attempting to respond to salary compressions and offering more autonomy for nursing over its own practice. There is better communication among hospital administrators, physicians, and nurses. Schools of nursing are more responsive to the needs of nontraditional students, and the federal and state governments are working together to find solutions. Innovation and creativity are key ingredients in our approach to ensuring rural nurse providers for the future.

Effect of maternal hypothyroxinaemia in the rat on brain biochemistry in adult progeny

The effects of maternal hypothyroxinaemia during pregnancy on subsequent brain biochemistry in progeny was studied. Normal and partially thyroidectomized rat dams were mated and progeny allowed to grow to adulthood. Brain regions (cerebellum, medulla, midbrain, cerebral cortex and paleocortex) were dissected out and the activities of various cell marker enzymes were determined, along with cholesterol contents. Maternal hypothyroxinaemia was without effect on body weight, brain weight or thyroid status of adult progeny. Oligodendroglial marker enzyme activities were altered in progeny from thyroidectomized dams. 2',3'-Cyclic nucleotide 3'-phosphohydrolase was decreased in the medulla (by 37%) and midbrain (by 32%). 5'-Nucleotidase was also diminished in the same brain regions, by 33% in the medulla and by 35% in the midbrain. In contrast, oleate esterase was increased (by 39%) in the paleocortex. Although these enzymes are putatively involved in myelin metabolism, no changes were observed in the concentration of a major myelin lipid (cholesterol). The activity of beta-D-glucuronidase (a general neuronal marker) was decreased (by 30%) in the paleocortex, whereas N-acetyl-beta-D-galactosaminidase (a general glial marker) was unchanged in all brain regions. In summary, maternal hypothyroxinaemia has irreversible effects on brain biochemistry in adult progeny. The damage is parameter-selective and brain region-specific, analogous to the pattern of neurological damage seen in offspring born to hypothyroxinaemic women in iodine-deficient endemias.

The impaired nursing student

Nursing students are at risk for abusing chemical substances during the nursing education experience. To assist faculty and administrators address this issue, characteristics of the chemically dependent nursing student are described. The authors also discuss teaching strategies and preventive approaches that might impact on the student's current or potential substance abuse.

The effect of 3,5,3'-triiodothyronine on leucine uptake and incorporation into protein in cultured neurons and subcellular fractions of rat central nervous system

Previous studies have shown that nuclear thyroid hormone receptors in rat brain are preferentially localized within neurons. These cells also synthesize protein at a high rate, and the aim of the present study was to investigate any relationship between these two characteristics. In this paper we have shown that T3 stimulates leucine uptake and incorporation into protein in primary cell cultures of neurons. Stimulation was apparent with concentrations of hormone as low as 1.25 nM and increased in a dose-dependent manner up to 10 nM T3. However, the rapidity of the effect (evident at 25 min, and significant at 40 min) suggests that protein synthesis is stimulated at the level of translation, rather than transcription. More detailed study with 5 nM T3, revealed that incorporation into both soluble (cytoplasmic) and insoluble (membrane-associated) protein fractions was stimulated to similar degrees, and therefore the effect on protein synthesis was general. Furthermore, T3-mediated stimulation of leucine uptake into neurons was completely abolished in the presence of the protein synthesis inhibitors, actinomycin D and cycloheximide, and therefore the effect on leucine uptake was attributed to an increased requirement for the amino acid in protein synthesis (pleiotrophic effect). Parallel studies conducted with synaptosomes and mitochondria isolated from the central nervous system of adult euthyroid animals revealed that 5 nM T3 was without effect on leucine uptake and incorporation into protein. Possible reasons for this lack of effect are discussed.