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D F Cameron

Publications and source records attributed to D F Cameron.

At least 19 recordsLinked to original sources
PubMed2002

A unique cytoplasmic marker for extratesticular Sertoli cells.

In the absence of a definitive cell marker for testis-derived Sertoli cells, their identification in cell culture or in Sertoli cell-facilitated cell transplantation protocols is difficult and limits the creditable evaluation of experimental results. However, the production by prepubertal Sertoli cells of Mullerian inhibiting substance (MIS) presents the possibility of specifically identifying extratesticular Sertoli cells as well as Sertoli cells in situ, by the immunodection of this unique glycoprotein. This study was designed to determine if isolated rat Sertoli cells could be identified by routine immunocytochemistry utilizing an antibody raised against MIS. Sertoli cells immunostained for MIS included Sertoli cells in situ and freshly isolated, cultured and cocultured Sertoli cells, and Sertoli cells structurally integrated with NT2 cells in simulated microgravity. Detection of MIS was also determined by Western blot analysis.

Animals↗
PubMed2001

Sites of lanthanum occlusion in the testis of the crayfish Procambarus paeninsulanus (Crustacea: Cambaridae).

The presence of stage-dependent occlusive junctions between adjacent Sertoli cells in the seminiferous epithelium of the crayfish testis was demonstrated by a lanthanum tracer study. The germinal epithelium did not appear to be compartmentalized, as evidenced by access of lanthanum to spermatogonia, spermatocytes, and spermatids. During late spermiogenesis, when encapsulated stage VI spermatids were concentrated in the center of an acinus, lanthanum was excluded apically, coincident with lumen formation. This is the first study examining occluding junctions using a barrier penetration method in the testis of a crustacean.

Animals↗
PubMed2001

Formation of Sertoli cell-enriched tissue constructs utilizing simulated microgravity technology.

Cell transplantation therapy for diabetes and Parkinson's disease offers hope for long-term alleviation of symptoms. However, successful protocols remain elusive due to obstacles, including rejection and lack of tropic support for the graft. To enhance engraftment, testis-derived postmitotic Sertoli cells have been cotransplanted with islets in the diabetic rat (Db) and neurons in the Parkinsonian rat (PD). Sertoli cell tropic, regulatory, and nutritive factors that nourish and stimulate germ cells also support isolated neurons and islets in vitro. Likewise, immunosuppressive properties of Sertoli cells, extant in the testis, are expressed by extratesticular Sertoli cells evidenced by allo- and xenograft immunoprotection of grafts in both the CNS (in the PD model) and the periphery (in the Db model). On this basis, we have created Sertoli islet cell aggregates (SICA) and Sertoli neuron aggregated cells (SNAC) using simulated microgravity culture technology developed by NASA. Isolated rat and pig Sertoli cells were cocultured with neonatal pig islets (SICA) and with immortalized N-Terra-2 (NT2) neurons (SNAC) in the HARV biochamber. Formed aggregates were assayed for desirable functional and structural characteristics. Cell viability in SICA and SNAC exceeded 90% and FasL immunopositive Sertoli cells were present in both. Sertoli cells did not interfere with insulin secretion by SICA and promoted differentiation of NT2 cells to the dopaminergic hNT cell type in SNAC. Addition of Matrigel resulted in structural reorganization of the aggregates and enhanced insulin secretion. We conclude that SICA, SNAC, and Matrigel-induced islet- and neuron-filled "Sertoli cell biochambers" are suitable for long-term transplantation treatment of Db and PD.

Animals↗
PubMed2001

Formation of insulin-secreting, Sertoli-enriched tissue constructs by microgravity coculture of isolated pig islets and rat Sertoli cells.

Pancreatic islets, isolated from neonatal pigs, and Sertoli cells, isolated from prepubertal rats, were cocultured in simulated microgravity utilizing the NASA-developed highly accelerating, rotating vessel (HARV) biochamber. Following 5 d of incubation, three-dimensional Sertoli-islet cell aggregates (SICA) retained the ability to secrete insulin when exposed to elevated glucose. SICA contained FasL-positive Sertoli cells and insulin-positive beta-cells randomly organized within the spherical construct. The addition of 1% Matrigel induced the reorganization of aggregates (SICAs formed in the presence of Matrigel [SICAmgs]) showing the peripherialization and epithelialization of Sertoli cells and the centralization of islets in association with lumen-like spaces. The Sertoli cells, but not Matrigel, aided in preserving the structural integrity of HARV-incubated islets. Neither Matrigel nor Sertoli cells appeared to interfere with the ability of SICA or SICA mg to secrete insulin and express FasL.

Animals↗
PubMed2001

Identification of causal relationships among traits related to drought resistance in Stylosanthes scabra using QTL analysis.

Previous studies have shown that a negative relationship exists between transpiration efficiency (TE) and carbon isotope discrimination (Delta) and between TE and specific leaf area (SLA) in Stylosanthes scabra. A glasshouse experiment was conducted to confirm these relationships in an F(2) population and to study the causal nature of these relationships through quantitative trait loci (QTL) analysis. One hundred and twenty F(2) genotypes from a cross between two genotypes within S. scabra were used. Three replications for each genotype were maintained through vegetative propagation. Water stress was imposed by maintaining plants at 40% of field capacity for about 45 d. To facilitate QTL analysis, a genetic linkage map consisting of 151 RAPD markers was developed. Results from this study show that Delta was significantly and negatively correlated with TE and biomass production. Similarly, SLA showed significant negative correlation with TE and biomass production. Most of the QTL for TE and Delta were present on linkage groups 5 and 11. Similarly, QTL for SLA, transpiration and biomass productivity traits were clustered on linkage groups 13 and 24. One unlinked marker was also associated with these traits. There were several markers coincident between different traits. At all the coincident QTL, the direction of QTL effects was consistent with phenotypic data. At the coincident markers between TE and Delta, high alleles of TE were associated with low alleles of Delta. Similarly, low alleles of SLA were associated with high alleles of biomass productivity traits and transpiration. At the coincident markers between trans-4-hydroxy-N:-methyl proline (MHP) and relative water content (RWC), low alleles of MHP were associated with high alleles of RWC. This study suggests the causal nature of the relationship between TE and Delta. Phenotypic data and QTL data show that SLA was more closely associated with biomass production than with TE. This study also shows that a cause-effect relationship may exist between SLA and biomass production.

Alleles↗
PubMed2000

Endurance training increases the expression of mitochondrial and nuclear encoded cytochrome c oxidase subunits and heat shock proteins in rat skeletal muscle.

Cytochrome c oxidase (CCO) is an enzyme complex found on the inner mitochondrial membrane and serves as the final electron acceptor in mitochondrial electron transport. Heat shock proteins (HSPs) are involved in the import of nuclear encoded protein subunits into the mitochondria and induce conformational changes to form active enzyme complexes. As both the nuclear and mitochondrial encoded subunits of CCO have been shown to increase in activity and expression in muscle subsequent to artificial loading, and as exercise has been shown to induce HSPs, we sought to determine whether 16-20 weeks of treadmill exercise would result in enhanced CCO subunit expression, and to determine if there was a relationship between this expression and HSP content in medial gastrocnemius muscle of Fischer 344 rats. Our results indicated that endurance training resulted in a 53%, 87% and 80% increase (P<0.05) in the levels of HSP 60, CCO subunit II and CCO subunit VI, respectively. Enzymatic activity of CCO was 84% greater (P<0.05) after endurance training. Mann Whitney U analyses showed that CCO subunit II and VI increased to the same extent as HSP 60 after endurance training. It appears that 16-20 weeks of endurance training leads to uniform increases in CCO subunits and parts of the transport and assembly mechanisms required for CCO enzyme assembly. The similarity among the increases in CCO subunits II and VI protein levels and the increase in CCO enzyme activity suggest that this increase in activity is due to an increase in the amount of CCO enzyme.

Animals↗
PubMed1999

Sertoli cells enhance the survival of co-transplanted dopamine neurons.

One of the major issues in neural transplantation is the low survival rate (<5%) of transplanted dopamine (DA) neurons [3]. Recently it has been shown that it is possible to enhance the survival of these neurons, which in turn may decrease the amount of tissue that is required for each transplantation patient. The present paper demonstrates a novel approach for enhancing neuronal survival by co-transplantation of neuronal tissue with Testis-derived Sertoli cells (SC). This strategy could improve neuronal survival through the provision of trophic support.

Animals↗
PubMed1999

Sertoli cells decrease microglial response and increase engraftment of human hNT neurons in the hemiparkinsonian rat striatum.

Sertoli cells (SCs) provide immune protection and nutritive support to the developing germ cells in the testis. Sertoli cells have also been shown to provide immune protection to islets transplanted outside the testes. In this study, the ability of these cells to diminish the infiltration/activation of microglia into a neural graft implanted in the lesioned striatum of a hemiparkinsonian rat was investigated. Human neuron-like cells (hNT neurons) were implanted either alone or in combination with rat SCs. Three months later, the animals were sacrificed and immunohistochemistry was performed to determine the survival of the xenografted neurons as well as microglial infiltration/activation. Cotransplantation of the SCs with the hNT neurons increased graft survival and was associated with an increase in graft size. Furthermore, there were fewer microglia present in the grafted tissue of the cotransplantation groups. These results show that SCs retain their immunosuppressive ability even within the brain. As immune responses to grafted neural tissue within the central nervous system become better understood, this ability of the SCs to provide localized immunosuppression to the transplanted tissue may become more important. This is particularly true as the search for alternative sources of neural tissue to treat neurodegenerative diseases expands to encompass other species.

Animals↗
PubMed1998

Preparation of cell suspensions for co-transplantation: methodological considerations.

The purpose of the current study was to determine the optimal strategy for preparing cell suspensions for co-transplantation. In the first experiment, the number of Sertoli cell (SC) aggregates and the number of tyrosine hydroxylase positive neurons were compared over time when cell suspensions of Sertoli or ventral mesencephalic cells were kept as a co-suspension mixed at 0 h. Cells from each suspension were dispensed onto glass slides in a manner similar to transplantation. When dispensed in this manner, the number of SC aggregates and TH-positive neurons decreased over 4 h. In experiment 2, the cell suspensions were mixed just prior to injection at each of four timepoints, the number of aggregates and TH neurons was consistent over time. Clearly this latter strategy resulted consistent recovery of both cell types for transplants up to 3 h after suspension preparation.

Animals↗
PubMed1998

Sertoli cell transplants: their use in the treatment of neurodegenerative disease.

The efficacy of treating neurodegenerative diseases with the transplantation of fetal tissue has been demonstrated in animal models of Parkinson's disease, Huntington's disease and stroke. In the clinical setting, neural transplantation as a treatment for patients with Parkinson's disease has shown promising results. However, for this treatment method to be effective neuronal survival needs to be improved through either trophic support or localized immunoprotection. Co-transplanting Sertoli cells, which express many nutritive, regulatory, trophic and immunosuppressive factors, with fetal neural cells could provide both of these requirements. Such a strategy could enhance the recovery benefits associated with transplantation and decrease the need for, and the risks associated with, long-term systemic immunosuppression.

Animals↗
PubMed1997

Survival of rat and porcine Sertoli cell transplants in the rat striatum without cyclosporine-A immunosuppression.

The use of cyclosporine-A (CsA) immunosuppression for neural transplantation has become the treatment of choice for ameliorating host-graft rejection responses in human and animal transplant studies. However, the cytotoxic effects of CsA have warranted a search for alternative methods of protecting neural transplants. Sertoli cells produce an immunosuppressant factor, Fas ligand (Fas-L), that may provide the testis with its immunoprivileged status. Therefore, it has recently been suggested that these cells may be useful in producing localized immunosuppression for transplants. If Sertoli cells do produce localized immunosuppression, then it should be possible to successfully transplant Sertoli cells without additional immunosuppression following transplant surgery. The present study was undertaken to determine whether rat or porcine Sertoli cells transplanted into rat brain would survive for an extended period of time without CsA immunosuppression. Isolated rat or porcine Sertoli cells prelabeled with DiI were transplanted into normal rat brain. We report that both rat Sertoli cell allografts and porcine Sertoli cell xenografts survived for at least 2 months posttransplantation into the rat brain without CsA immunosuppression, indicating that these grafts were capable of producing sufficient localized immunosuppression to survive at the site of transplant without additional systemic immunosuppression.

Animals↗
PubMed1997

Intracerebral transplantation of testis-derived sertoli cells promotes functional recovery in female rats with 6-hydroxydopamine-induced hemiparkinsonism.

Recently, we demonstrated amelioration of behavioral deficits associated with 6-hydroxydopamine-induced hemiparkinsonism by transplanting rat testis-derived Sertoli cells into adult male rat brains. In the present study, we used adult female hemiparkinsonian rats to investigate whether the beneficial effects of transplantation of Sertoli cells may be differentially affected by gender of the animal transplant recipient. At 1 month posttransplantation, animals transplanted with Sertoli cells showed functional recovery as revealed by significant reductions in apomorphine-induced rotational behavior and asymmetrical elevated body swing behavior. Control animals that received medium alone did not display any visible behavioral recovery. These results suggest that transplantation of Sertoli cells is not male hormone-dependent and further support the use of these cells as a graft source for Parkinson's disease and other neurological disorders.

Animals↗
PubMed1997

Testis-derived Sertoli cells have a trophic effect on dopamine neurons and alleviate hemiparkinsonism in rats.

Neural tissue transplantation has become an alternative treatment for Parkinson's disease (PD) and other neurodegenerative disorders. The clinical use of neural grafts as a source of dopamine for Parkinson's disease patients, although beneficial, is associated with logistical and ethical issues. Thus, alternative graft sources have been explored including polymer-encapsulated cells and nonneural cells (that is, adrenal chromaffin cells) or genetically modified cells that secrete dopamine and/or trophic factors. Although progress has been made, no current alternative graft source has ideal characteristics for transplantation. Emerging evidence suggests the importance of trophic factors in enhancing survival and regeneration of intrinsic dopaminergic neurons. It would be desirable to transplant cells that are readily available, immunologically accepted by the central nervous system and capable of producing dopamine and/or trophic factors. Sertoli cells have been shown to secrete CD-95 ligand and regulatory proteins, as well as trophic, tropic, and immunosuppressive factors that provide the testis, in part, with its "immunoprivileged" status. The present study demonstrated that transplantation of rat testis-derived Sertoli cells into adult rat brains ameliorated behavioral deficits in rats with 6-hydroxydopamine-induced hemiparkinsonism. This was associated with enhanced tyrosine hydroxylase (TH) immunoreactivity in the striatum in the area around the transplanted Sertoli cells. Furthermore, in vitro experiments demonstrated enhanced dopaminergic neuronal survival and outgrowth when embryonic neurons were cultured with medium in which rat Sertoli cells had been grown. Transplantation of Sertoli cells may provide a useful alternative treatment for PD and other neurodegenerative disorders.

Animals↗
PubMed1996

Testis-derived Sertoli cells survive and provide localized immunoprotection for xenografts in rat brain.

Transplantation of neural tissue into the mammalian central nervous system has become an alternative treatment for neurodegenerative disorders such as Parkinson's disease. Logistical and ethical problems in the clinical use of human fetal neural grafts as a source of dopamine for Parkinson's disease patients has hastened a search for successful ways to use animal dopaminergic cells for human transplantation. The present study demonstrates that transplanted testis-derived Sertoli cells into adult rat brains survive. Furthermore, when cotransplanted with bovine adrenal chromaffin cells (xenograft), Sertoli cells produce localized immunoprotection, suppress microglial response and allow the bovine cells to survive in the rat brain without continuous systemic immunosuppressive drugs. These novel features support Sertoli cells as a viable graft source for facilitating the use of xenotransplantation for Parkinson's disease and suggest their use as facilitators, (i.e., localized immunosuppression) for cell transplantation in general.

Animals↗
PubMed1996

CNS immunological modulation of neural graft rejection and survival.

Neural transplantation therapy as a possible alternative treatment for neurological movement disorders, such as in Parkinson's disease (PD), has accentuated research interest on the immune status of the central nervous system (CNS). Most animal studies concerned with neural transplantation for the treatment of PD have utilized dopamine (DA) neurons from tissues of the embryonic ventral mesencephalon. Rat embryonic DA neurons, grafted either as solid blocks or dissociated into a cell suspension and stereotaxically injected intraparenchymally into a rat lesion model of PD, have been shown to survive and form connections with the host brain, and ameliorate the behavioral deficits of PD. Similarly, studies on nonhuman primate models of PD provide considerable support for neural transplantation of DA neurons as an experimental clinical procedure for the treatment of PD. To this end, experimental clinical trials have been centered upon transplantation of the embryonic ventral mesencephalic cells for PD patients. Although not conclusive, the findings from clinical studies have provided some evidence that most patients with marked increases in fluorodopa uptake (indicating graft survival) have been immunosuppressed. Furthermore, immune reactions have been observed in rats xenografted with human embryonic tissue. Of note, embryonic ventral mesencephalic tissues compared to adult tissues produce better morphological and long-lasting behavioral amelioration of the neurobehavioral deficits of PD, thus advocating the use of grafts from young donors (embryo) to circumvent the CNS immune rejection. The possible graft rejection due to CNS immune reactions, coupled with the social and ethical problems surrounding the use of embryonic neural tissue, and the logistical problems concerning tissue availability have prompted the development of alternative sources of DA-secreting cells. To circumvent these obstacles, several methods have been suggested including the use of immunosuppressants such as Cyclosporine-A, transplantation of autografts, polymer-encapsulated DA-secreting cells, co-culturing and co-transplantation of DA-secreting cells with microcarrier beads, with Sertoli cells, or with fragments of a monoclonal antibody that can mask the MHC class I antigens, and genetically modifying cells that can withstand CNS immune reactions. Some of these techniques allow transplantation of allograft (same species transplantation), or even xenograft (cross species transplantation) without immunosuppression of the recipient. We discuss recent CNS immunosuppression techniques that pose some promise for enhanced survival of neural grafts. When possible, advantages and disadvantages of each method are presented. Hopefully, such critical analysis of different immunosuppression techniques will produce innovated ideas that will lead to a better understanding of CNS immune response and its modulatory function on graft rejection and survival.

Adrenal Medulla↗
PubMed1994

Opioid inhibition of adrenergic and dopaminergic but not serotonergic stimulation of luteinizing hormone releasing hormone release from immortalized hypothalamic neurons.

Opioids are known to have an inhibitory effect on the secretion of luteinizing hormone releasing hormone (LHRH) when administered to whole animals in vivo or when applied to hypothalamic fragments in vitro. Whether opioids have this effect by acting directly on the LHRH secreting neurons or require the mediation of an interneuron is controversial. To examine this question, a clonal cell line derived from a hypothalamic neuron (GT1-7) was perfused and fractions collected every 6 min. Morphine treatment had no effect on basal secretion of LHRH, nor on the spontaneous, pulsatile release of LHRH. Isoproterenol, dopamine, and serotonin all produced significant increments in LHRH secretion. Pretreatment of GT1-7 cells for 2 h with morphine, suppressed the LHRH response to isoproterenol and dopamine but had no apparent effect on serotonin-induced LHRH release. These data indicate that morphine has a direct effect on GT1-7 cells that alters their responsiveness to some, but not all, LHRH secretagogues. These results suggest that, in vivo, the inhibitory effects that opioids have on LHRH release may not require an interneuron.

Adrenergic Agents↗