Neural reprogramming in retinal degeneration

PURPOSE

Early visual defects in degenerative diseases such as retinitis pigmentosa (RP) may arise from phased remodeling of the neural retina. The authors sought to explore the functional expression of ionotropic (iGluR) and group 3, type 6 metabotropic (mGluR6) glutamate receptors in late-stage photoreceptor degeneration.

METHODS

Excitation mapping with organic cations and computational molecular phenotyping were used to determine whether retinal neurons displayed functional glutamate receptor signaling in rodent models of retinal degeneration and a sample of human RP.

RESULTS

After photoreceptor loss in rodent models of RP, bipolar cells lose mGluR6 and iGluR glutamate-activated currents, whereas amacrine and ganglion cells retain iGluR-mediated responsivity. Paradoxically, amacrine and ganglion cells show spontaneous iGluR signals in vivo even though bipolar cells lack glutamate-coupled depolarization mechanisms. Cone survival can rescue iGluR expression by OFF bipolar cells. In a case of human RP with cone sparing, iGluR signaling appeared intact, but the number of bipolar cells expressing functional iGluRs was double that of normal retina.

CONCLUSIONS

RP triggers permanent loss of bipolar cell glutamate receptor expression, though spontaneous iGluR-mediated signaling by amacrine and ganglion cells implies that such truncated bipolar cells still release glutamate in response to some nonglutamatergic depolarization. Focal cone-sparing can preserve iGluR display by nearby bipolar cells, which may facilitate late RP photoreceptor transplantation attempts. An instance of human RP provides evidence that rod bipolar cell dendrite switching likely triggers new gene expression patterns and may impair cone pathway function.

Imaging central nervous system myelin by positron emission tomography in multiple sclerosis using [methyl-¹¹C]-2-(4'-methylaminophenyl)- 6-hydroxybenzothiazole

OBJECTIVE

Imaging of myelin tracts in vivo would greatly improve the monitoring of demyelinating diseases such as multiple sclerosis (MS). To date, no imaging technique specifically targets demyelination and remyelination. Recently, amyloid markers related to Congo red have been shown to bind to central nervous system (CNS) myelin. Here we questioned whether the thioflavine-T derivative 2-(4'-methylaminophenyl)-6-hydroxybenzothiazole (PIB), which also binds to amyloid plaques, could serve as a myelin marker.

METHODS

PIB fixation to myelin was studied by fluorescence in the normal and dysmyelinating mouse brain, as well as in the postmortem brain of MS patients. Positron emission tomography (PET) experiments were conducted using [¹¹C]PIB in baboons and in a proof of concept clinical study in 2 MS patients.

RESULTS

Applied directly on tissue sections or after intraperitoneal injection, PIB stained CNS myelin, and the decrease in the level of fixation paralleled the amount of myelin loss in a dysmyelinating mutant. In normally myelinated areas of postmortem MS brain, demyelinated and remyelinated lesions were clearly distinguishable by the differential intensity of labeling observed with PIB. PET using intravenously injected radiolabeled [¹¹C]PIB imaged CNS myelin in baboons and humans. In MS patients, the dynamic analysis of PET acquisitions allowed quantitative assessment of demyelination.

INTERPRETATION

PIB could be used as an imaging marker to quantify myelin loss and repair in demyelinating diseases.

Dopamine (D2/3) receptor agonist positron emission tomography radiotracer [11C]-(+)-PHNO is a D3 receptor preferring agonist in vivo

[11C]PHNO is a recently introduced agonist to image DA D2-like receptors with Positron Emission Tomography (PET). In cats and humans, [11C]PHNO revealed an atypical distribution compared to radiolabeled D2-like antagonists (such as [11C]raclopride) or other D2-like agonists (such as [11C]NPA), as it displayed unusual high binding in the globus pallidus (GP). The goal of this study was to assess the pharmacological nature of the binding of [11C]PHNO in the GP in nonhuman primates. As previously reported in humans, [11C]PHNO equilibrium specific to nonspecific equilibrium partition coefficients (V3'') in baboons was much higher in GP (3.88 +/- 1.15) than in the dorsal striatum (DST, 2.07 +/- 0.43), whereas the reverse was true for [11C]raclopride (1.48 +/- 0.41 in GP, 2.56 +/- 0.91 in DST) and [11C]NPA (0.87 +/- 0.19 in GP, 1.02 +/- 0.13 in DST). Administration of unlabeled raclopride resulted in similar reductions of [11C] PHNO V3'' and [11C]raclopride V3'' in both the GP and the DST. This observation demonstrated that the [11C]PHNO binding in the GP was specific to D2-like receptors. To evaluate the respective contribution of D3 and D2 receptors to the binding potential (BP) of [11C]PHNO and [11C]raclopride, experiments were carried out with the selective D3 partial agonist 1-(4(2-Napthoylamino)butyl)-4-(2-methoxyphenyl)-1A-piperazine HCL (BP897). BP897 reduced [11C]raclopride V3'' by 29% +/- 9%, 19% +/- 8%, and 10% +/- 7% in GP, VST, and DST, respectively, a result consistent with expectation from postmortem studies (D3/D2 ratio in GP > VST > DST). BP897 reduced [11C]PHNO V3'' by 57% +/- 11%, 30% +/- 11%, and 13% +/- 8% in GP, VST, and DST, respectively, indicating that the D3 receptor contribution to [11C]PHNO signal is higher than that of [11C]raclopride. From these experiments we conclude that [11C]PHNO is a D3 preferring agonist, and that this property explains the high GP signal not observed with [11C]raclopride or [11C]NPA. This property might contribute to its higher vulnerability to endogenous DA compared to [11C]raclopride and [11C]NPA.

Light adaptation in cone vision involves switching between receptor and post-receptor sites

We see over an enormous range of mean light levels, greater than the range of output signals retinal neurons can produce. Even highlights and shadows within a single visual scene can differ approximately 10,000-fold in intensity-exceeding the range of distinct neural signals by a factor of approximately 100. The effectiveness of daylight vision under these conditions relies on at least two retinal mechanisms that adjust sensitivity in the approximately 200 ms intervals between saccades. One mechanism is in the cone photoreceptors (receptor adaptation) and the other is at a previously unknown location within the retinal circuitry that benefits from convergence of signals from multiple cones (post-receptor adaptation). Here we find that post-receptor adaptation occurs as signals are relayed from cone bipolar cells to ganglion cells. Furthermore, we find that the two adaptive mechanisms are essentially mutually exclusive: as light levels increase the main site of adaptation switches from the circuitry to the cones. These findings help explain how human cone vision encodes everyday scenes, and, more generally, how sensory systems handle the challenges posed by a diverse physical environment.

Imaging of CNS myelin by positron-emission tomography

Promoting myelin repair is one of the most promising therapeutic avenues in the field of myelin disorders. In future clinical trials, evaluation of remyelination will require a reliable and quantifiable myelin marker to be used as a surrogate marker. To date, MRI assessment lacks specificity for evaluating the level of remyelination within the brain. Here, we describe 1,4-bis(p-aminostyryl)-2-methoxy benzene (BMB), a synthesized fluorescent molecule, that binds selectively to myelin both ex vivo and in vivo. The binding of BMB to myelin allows the detection of demyelinating lesions in an experimental autoimmune encephalitis model of demyelination and allows a mean for quantifying myelin loss in dysmyelinating mutants. In multiple sclerosis brain, different levels of BMB binding differentiated remyelination in shadow plaques from either demyelinated lesions or normal-appearing white matter. After systemic injection, BMB crosses the blood-brain barrier and binds to myelin in a dose-dependent and reversible manner. Finally, we provide evidence that (11)C-radiolabeled BMB can be used in vivo to image CNS myelin by positron-emission tomography in baboon. Our results provide a perspective for developing a brain myelin imaging technique by positron-emission tomography.

Recombinant Human TNFRSF1A (r-hTBP1) Inhibits the Development of Endometriosis in Baboons: A Prospective, Randomized, Placebo- and Drug-Controlled Study1

Endometriosis is associated with chronic inflammation, including an increased macrophage activity with increased secretion of cytokines, such as tumor necrosis factor (TNF) or TNF superfamily member 2, previously known as TNFalpha. In the present study, we tested the hypothesis that recombinant human TNFRSF1A (r-hTBP1) can inhibit the development of endometriotic lesions in the baboon, an established model for the study of endometriosis. Endometriosis was induced using intrapelvic injection of menstrual endometrium in 20 baboons with a normal pelvis. In the first part of the study, 14 baboons were randomly assigned to subcutaneous treatment with r-hTBP1, placebo, or GnRH antagonist (positive control). In the second part of the study, menstrual endometrium from 6 baboons was randomly incubated with either PBS or r-hTBP1 before intrapelvic seeding. Video laparoscopy was performed 25 days later to document the number, surface area, and estimated volume of endometriotic lesions and adhesions; to calculate the revised American Fertility Society (rAFS) score and stage; and to confirm the histological presence of endometriosis. In the first part, baboons treated with r-hTBP1 or with Antide (Bachem) had a lower endometriosis rAFS score, a lower surface area and estimated volume of peritoneal endometriotic lesions, and a lower histological confirmation rate compared with controls. Because of less adnexal and cul-de-sac adhesions, the number of baboons with endometriosis of stage II, III, or IV was lower among baboons treated with r-hTBP1 or Antide than among controls. In the second part, the surface area of endometriotic lesions was lower, and less severe endometriosis was observed in r-hTBP1-treated baboons. No hypoestrogenic effects were observed in baboons treated with r-hTBP1. In conclusion, r-hTBP1 can effectively inhibit the development of endometriosis without hypoestrogenic effects in baboons.

A potent malaria transmission blocking vaccine based on codon harmonized full length Pfs48/45 expressed in Escherichia coli

Malaria caused by Plasmodium falciparum is responsible for nearly 1 million deaths annually. Although much progress has been made in the recent past, the development of a safe, effective and affordable malaria vaccine has remained a challenge. A vaccine targeting sexual stages of the parasite will not only reduce malaria transmission by female Anopheles mosquitoes, but also reduce the spread of parasites able to evade immunity elicited by vaccines targeting pre-erythrocytic and erythrocytic asexual stages. We focused our studies on Pfs48/45, a protein expressed in the sexual stages developing within an infected person and one of the most promising transmission-blocking vaccine targets. Functional immunogenicity of Pfs48/45 protein requires proper disulfide bond formation, consequently evaluation of the immunogenicity of recombinant full-length Pfs48/45 has been hampered by difficulties in expressing properly folded protein to date. Here we present a strategy involving harmonization of codons for successful recombinant expression of full length Pfs48/45 in Escherichia coli. The purified protein, designated CH-rPfs48/45, was recognized by monoclonal antibodies directed against reduction-sensitive conformational epitopes in the native protein. Immunogenicity evaluation in mice revealed potent transmission blocking activity in membrane feeding assays of antisera elicited by CH-rPfs48/45 formulated in three different adjuvants, i.e. Alum, Montanide ISA-51 and complete Freund's adjuvant. More importantly, CH-rPfs48/45 formulated with Montanide ISA-51 when administered to nonhuman primates (Olive baboons, Papio anubis) resulted in uniformly high antibody responses (ELISA titers >2 million) in all five animals. Sera from these animals displayed greater than 93% blocking activity in membrane feeding assays after a single immunization, reaching nearly complete blocking after a booster dose of the vaccine. The relative ease of expression and induction of potent transmission blocking antibodies in mice and nonhuman primates provide a compelling rationale and basis for development of a CH-rPfs48/45 based malaria transmission blocking vaccine.

Origin of correlated activity between parasol retinal ganglion cells

Cells throughout the CNS have synchronous activity patterns; that is, a cell's probability of generating an action potential depends both on its firing rate and on the occurrence of action potentials in surrounding cells. The mechanisms producing synchronous or correlated activity are poorly understood despite its prevalence and potential effect on neural coding. We found that neighboring parasol ganglion cells in primate retina received strongly correlated synaptic input in the absence of modulated light stimuli. This correlated variability appeared to arise through the same circuits that provide uncorrelated synaptic input. In addition, ON, but not OFF, parasol cells were coupled electrically. Correlated variability in synaptic input, however, dominated correlations in the parasol spike outputs and shared variability in the timing of action potentials generated by neighboring cells. These results provide a mechanistic picture of how correlated activity is produced in a population of neurons that are critical for visual perception.

Suppression of Extravillous Trophoblast Invasion of Uterine Spiral Arteries by Estrogen During Early Baboon Pregnancy

The present study determined whether estrogen plays a role in regulating invasion and remodeling of the uterine spiral arteries by extravillous trophoblasts during early baboon pregnancy. The level of trophoblast invasion of spiral arteries was assessed on day 60 of gestation (term is 184 days) in baboons untreated or treated on days 25-59 with estradiol or aromatizable androstenedione. The administration of estradiol or androstenedione increased (P<0.01) maternal serum estradiol levels approximately 3-fold above normal. The mean+/-SE percentage of spiral arteries/arterioles invaded by extravillous cytotrophoblasts in estradiol-treated baboons for vessels with diameters of 26-50 microm (0.0+/-0.0), 51-100 microm (1.2+/-0.7) and >100 microm (13.2+/-5.5) was 100%, 90%, and 75% lower (P<0.001), respectively, than in untreated baboons (2.4+/-1.2%; 11.0+/-5.5%, and 54.5+/-8.5%, respectively). Similar results were obtained with androstenedione treatment. However, the distribution of uterine spiral arteries grouped by diameter or number of arteries per basal plate area, i.e. microvessel density, were similar in untreated and estrogen-treated baboons. We suggest, therefore, that the low levels of estrogen exhibited during early primate pregnancy are required to permit normal progression of trophoblast vascular invasion and that the surge in estrogen which occurs during the second-third of normal pregnancy has a physiological role in suppressing further arterial trophoblast invasion. Consequently, we propose that the estrogen-dependent restraint of spiral artery invasion/remodeling ensures optimal blood flow dynamics across the uteroplacental vascular bed to promote normal fetal growth and development.

Proteomic identification of non-Gal antibody targets after pig-to-primate cardiac xenotransplantation

BACKGROUND

Experience with non-antigenic galactose alpha1,3 galactose (alphaGal) polymers and development of alphaGal deficient pigs has reduced or eliminated the significance of this antigen in xenograft rejection. Despite these advances, delayed xenograft rejection (DXR) continues to occur most likely due to antibody responses to non-Gal endothelial cell (EC) antigens.

METHODS

To gauge the diversity of the non-Gal antibody response we used antibody derived from CD46 transgenic heterotopic cardiac xenografts performed without T-cell immunosuppression, Group A (n = 4) and Gal knockout (GT-KO) heart transplants under tacrolimus and sirolimus immunosuppression, Group B (n = 8). Non-Gal antibody was measured by flow cytometry and by western blots using GT-KO EC membrane antigens. A nanoLC/MS/MS analysis of proteins recovered from 2D gels was used to identify target antigens.

RESULTS

Group A recipients exhibited a mixed cellular and humoral rejection. Group B recipients mainly exhibited classical DXR. Western blot analysis showed a non-Gal antibody response induced by GT+ and GT-KO hearts to an overlapping set of pig aortic EC membrane antigens. Proteomic analysis identified 14 potential target antigens but failed to define several immunodominant targets.

CONCLUSIONS

These experiments indicate that the non-Gal antibody response is directed to a number of stress response and inflammation related pig EC antigens and a few undefined targets. Further analysis of these antibody specificities using alternative methods is required to more fully define the repertoire of non-Gal antibody responses.

Effects of tetrahydrouridine on pharmacokinetics and pharmacodynamics of oral decitabine

The deoxycytidine analog decitabine (DAC) can deplete DNA methyl-transferase 1 (DNMT1) and thereby modify cellular epigenetics, gene expression, and differentiation. However, a barrier to efficacious and accessible DNMT1-targeted therapy is cytidine deaminase, an enzyme highly expressed in the intestine and liver that rapidly metabolizes DAC into inactive uridine counterparts, severely limiting exposure time and oral bioavailability. In the present study, the effects of tetrahydrouridine (THU), a competitive inhibitor of cytidine deaminase, on the pharmacokinetics and pharmacodynamics of oral DAC were evaluated in mice and nonhuman primates. Oral administration of THU before oral DAC extended DAC absorption time and widened the concentration-time profile, increasing the exposure time for S-phase-specific depletion of DNMT1 without the high peak DAC levels that can cause DNA damage and cytotoxicity. THU also decreased interindividual variability in pharmacokinetics seen with DAC alone. One potential clinical application of DNMT1-targeted therapy is to increase fetal hemoglobin and treat hemoglobinopathy. Oral THU-DAC at a dose that would produce peak DAC concentrations of less than 0.2μM administered 2×/wk for 8 weeks to nonhuman primates was not myelotoxic, hypomethylated DNA in the γ-globin gene promoter, and produced large cumulative increases in fetal hemoglobin. Combining oral THU with oral DAC changes DAC pharmacology in a manner that may facilitate accessible noncytotoxic DNMT1-targeted therapy.

Treatment with anti-TNF monoclonal antibody (c5N) reduces the extent of induced endometriosis in the baboon

BACKGROUND

Inflammatory cytokines, including interleukin (IL)-1, IL-6, IL-8 and tumour necrosis factor-alpha (TNF-alpha), are important in the pathogenesis of endometriosis. We assessed the efficacy of anti-TNF monoclonal antibody (mAb, c5N), known to prevent induced endometriosis in baboons, in reducing established endometriosis in baboons.

METHODS

This prospective, randomized, blinded, controlled study was conducted in baboons at the Institute of Primate Research (IPR), Nairobi, Kenya. Endometriosis was induced in 18 adult female baboons (Papio anubis) with regular menstrual cycles and a normal pelvis; the extent of endometriosis was documented by videolaparoscopy 25 days later. The baboons were then randomly assigned to receive a single infusion of either placebo (n=7, 5 ml/kg) or c5N (n=11, 5 mg/kg). Follow-up laparoscopy was performed 25 days later to document any differences in the number, surface area and estimated volume of lesions between the two groups and between the first and the second laparoscopies in each group. Representative biopsies of at least one endometriotic lesion per baboon were obtained at the final laparoscopy.

RESULTS

Significant reductions in total surface area, estimated total volume of endometriotic lesions and both number and surface area of red lesions were observed after treatment with c5N, but not after placebo treatment, when compared to the initial laparoscopy. Conversely, a significant increase in the number of typical and red lesions was observed after placebo treatment when compared to the initial laparoscopy. Neither c5N nor placebo treatment affected the menstrual cycle.

CONCLUSION

In baboons with induced endometriosis, anti-TNF-mAb (c5N) treatment significantly reduced the extent of endometriosis, mainly due to reducing both the number and surface area of red lesions. These findings suggest that anti-TNF-mAb therapy may have therapeutic potential for active peritoneal endometriosis.

Suppression of extravillous trophoblast vascular endothelial growth factor expression and uterine spiral artery invasion by estrogen during early baboon pregnancy

We have shown that advancing the increase in maternal serum estrogen levels from the second to the first third of baboon pregnancy suppressed extravillous cytotrophoblast (EVT) spiral artery invasion. Because vascular endothelial growth factor (VEGF) promotes EVT invasion, the present study determined whether EVT VEGF expression is altered by prematurely elevating estrogen in early pregnancy. Placental basal plate was obtained on d 60 of gestation (term is 184 d) from baboons treated daily on d 25-59 with estradiol (0.35 mg/d sc), which increased maternal peripheral serum estradiol levels 3-fold above normal. Overall percentage of uterine arteries (25 to more than 100 microm in diameter) invaded by EVT assessed by image analysis in untreated baboons (29.11+/-5.78%) was decreased 4.5-fold (P<0.001) by prematurely elevating estrogen (6.55+/-1.83%). VEGF mRNA levels in EVT isolated by laser capture microdissection from the anchoring villi of untreated baboons (6.77+/-2.20) were decreased approximately 5-fold (P<0.05, ANOVA) by estradiol (1.37+/-0.29). Uterine vein serum levels of the truncated soluble fms-like receptor, which controls VEGF bioavailability, in untreated baboons (403+/-37 pg/ml) were increased 3-fold (P<0.01) by estrogen treatment (1127+/-197 pg/ml). Thus, placental EVT expression of VEGF mRNA was decreased and serum soluble truncated fms-like receptor levels increased in baboons in which EVT invasion of the uterine spiral arteries was suppressed by advancing the rise in estrogen from the second to the first third of pregnancy. We suggest that VEGF mediates the decline in EVT vessel invasion induced by estrogen in early primate pregnancy.

Examination of the direct effects of metabolic factors on somatotrope function in a non-human primate model, Papio anubis

In humans, circulating GH levels are increased in catabolic states and suppressed in obesity. In both extremes, normalization of the metabolic environment normalizes GH release, leading to the conclusion that changes in metabolic hormones and/or metabolites promote changes in GH synthesis and release. Metabolic regulation of GH secretion can be mediated centrally by modulation of hypothalamic GHRH and somatostatin input to the pituitary and/or by direct regulation of pituitary somatotrope function. Although data are available showing glucocorticoids, free fatty acids (FFA), IGF-I, and insulin have direct effects on rat somatotrope function, little information is available regarding the direct pituitary effects of these metabolic factors in primates. Therefore, this study examined the effects of glucocorticoids (dexamethasone (0.1-100 nM) and hydrocortisone (10 nM)), FFA (oleic and linoleic acid, 100 and 400 microM each), IGF-I (0.5-50 nM), and insulin (0.5-50 nM) on GH release and GH, GHRH-receptor (GHRH-R) and ghrelin-receptor (GHS-R) mRNA levels, in primary pituitary cell cultures of baboons (Papio anubis) after 24 h treatment. A commercial ELISA kit was used to determine the amount of GH released into the media, while quantitative real-time reverse transcription-PCR was used to determine mRNA levels. To design species-specific primers for baboon GH, GHRH-R, GHS-R, insulin receptor (INSR), IGF-I receptor (IGF-IR), pituitary-specific transcription factor-1 (Pit-1), and cyclophilin A (used as a housekeeping gene) cDNA, sequence data for each baboon transcript were obtained and this data were submitted to Genbank. Glucocorticoids, FFA, insulin and IGF-I treatment did not significantly alter the expression of Pit-1, a transcription factor essential for normal somatotrope development and function. However, as previously reported in the rat, glucocorticoids increased, while FFA, IGF-I and insulin decreased GH release in baboon pituitary cell cultures, where changes in GH release were reflected by comparable changes in GH mRNA levels. In addition, glucocorticoids increased, while FFA, IGF-I and insulin decreased the expression of the GH stimulatory receptors, GHRH-R and GHS-R, without significantly altering cyclophilin A mRNA levels. A role of insulin/INSR pathway, independent of IGF-I, in regulating pituitary function is supported by the fact that (1) IGF-I and insulin significantly suppressed somatotrope function at doses (0.5 and 5 nM respectively) not anticipated to activate their respective receptors, and (2) the baboon pituitary expresses INSR mRNA at levels comparable to or greater than that of tissues commonly considered as insulin sensitive (i.e. liver, skeletal muscle, and fat). Taken together, these results demonstrate that metabolic factors can directly modulate primate somatotrope function through regulating GH synthesis and release, as well as mediating the expression of receptors important in central (GHRH) and systemic (ghrelin) regulation of GH secretion.

Synthesis and positron emission tomography studies of carbon-11-labeled imatinib (Gleevec)

INTRODUCTION

Imatinib mesylate (Gleevec) is a well known drug for treating chronic myeloid leukemia and gastrointestinal stromal tumors. Its active ingredient, imatinib ([4-[(4-methyl-1-piperazinyl)methyl]-N-[4-methyl-3-[[4-(3-pyridyl)-2-pyrimidinyl]amino]phenyl]benzamide), blocks the activity of several tyrosine kinases. Here we labeled imatinib with carbon-11 as a tool for determining the drug distribution and pharmacokinetics of imatinib, and we carried out positron emission tomography (PET) studies in baboons.

METHODS

[N-(11)C-methyl]imatinib was synthesized from [(11)C]methyl iodide and norimatinib was synthesized by the demethylation of imatinib (isolated from Gleevec tablets) according to a patent procedure [Collins JM, Klecker RW Jr, Anderson LW. Imaging of drug accumulation as a guide to antitumor therapy. US Patent 20030198594A1, 2003]. Norimatinib was also synthesized from the corresponding amine and acid. PET studies were carried out in three baboons to measure pharmacokinetics in the brain and peripheral organs and to determine the effect of a therapeutic dose of imatinib. Log D and plasma protein binding were also measured.

RESULTS

[N-(11)C-methyl]imatinib uptake in the brain is negligible (consistent with P-glycoprotein-mediated efflux); it peaks and clears rapidly from the heart, lungs and spleen. Peak uptake and clearance occur more slowly in the liver and kidneys, followed by accumulation in the gallbladder and urinary bladder. Pretreatment with imatinib did not change uptake in the heart, lungs, kidneys and spleen, and increased uptake in the liver and gallbladder.

CONCLUSIONS

[N-(11)C-methyl]imatinib has potential for assessing the regional distribution and kinetics of imatinib in the human body to determine whether the drug targets tumors and to identify other organs to which the drug or its labeled metabolites distribute. Paired with tracers such as 2'deoxy-2'-[(18)F]fluoro-D-glucose ((18)FDG) and 3'deoxy-3'-[(18)F]fluorothymidine ((18)FLT), [N-(11)C-methyl]imatinib may be a useful radiotracer for planning chemotherapy, for monitoring response to treatment and for assessing the role of drug pharmacokinetics in drug resistance.

Forelimb and hindlimb forces in walking and galloping primates

One trait that distinguishes the walking gaits of most primates from those of most mammalian nonprimates is the distribution of weight between the forelimbs and hindlimbs. Nonprimate mammals generally experience higher vertical peak substrate reaction forces on the forelimb than on the hindlimb. Primates, in contrast, generally experience higher vertical peak substrate reaction forces on the hindlimb than on the forelimb. It is currently unclear whether this unusual pattern of force distribution characterizes other primate gaits as well. The available kinetic data for galloping primates are limited and present an ambiguous picture about peak-force distribution among the limbs. The present study investigates whether the pattern of forelimb-to-hindlimb force distribution seen during walking in primates is also displayed during galloping. Six species of primates were video-recorded during walking and galloping across a runway or horizontal pole instrumented with a force-plate. The results show that while the force differences between forelimb and hindlimb are not significantly different from zero during galloping, the pattern of force distribution is generally the same during walking and galloping for most primate species. These patterns and statistical results are similar to data collected during walking on the ground. The pattern of limb differentiation exhibited by primates during walking and galloping stands in contrast to the pattern seen in most nonprimate mammals, in which forelimb forces are significantly higher. The data reported here and by Demes et al. ([1994] J. Hum. Evol. 26:353-374) suggest that a relative reduction of forelimb vertical peak forces is part of an overall difference in locomotor mechanics between most primates and most nonprimate mammals during both walking and galloping.

Life-supporting function of genetically modified swine lungs in baboons

OBJECTIVE

During ex vivo perfusion with human blood, homozygous galactosyl transferase knockout swine lungs exhibit prolonged survival (approximately 2 hours) relative to wild-type (<15 minutes) and swine lungs expressing human decay accelerating factor (<1 hour). In this study, the in vivo behavior of galactosyl transferase knockout lungs was evaluated.

METHODS

Three galactosyl transferase knockout swine left lungs were transplanted into baboons in a life-supporting model. One baboon lung allograft and two swine lung xenografts transgenic for human membrane cofactor protein (CD46) served as controls.

RESULTS

Whereas two membrane cofactor protein lungs exhibited high pulmonary vascular resistance (>500 mm Hg x min/L) and failed to support life within 21 minutes, two of three galactosyl transferase knockout lungs supported life, for 90 and 215 minutes, and displayed low peripheral vascular resistance (48 +/- 12 mm Hg x min/L at 60 minutes), similar to the allogeneic control. Complement activation (delta C3a < 250 ng/mL through 60 minutes) and C5b-9 deposition were minimal in both galactosyl transferase knockout and membrane cofactor protein lungs. Neutrophils, monocytes, and platelets were rapidly sequestered in galactosyl transferase knockout and human membrane cofactor protein lung recipients, unlike the allogeneic control (<20%); and thrombin formation (delta plasma fraction 1+2 > 0.5 nmol/L) was seen in the galactosyl transferase knockout recipients. Platelet activation (beta-thromboglobulin rise > 200) and appearance of capillary congestion and vessel thrombosis confirmed coagulation activation associated with galactosyl transferase knockout lung failure.

CONCLUSIONS

Galactosyl transferase knockout swine lungs are significantly protected in vivo from the physiologic consequences (increased pulmonary vascular resistance, capillary leak) associated with hyperacute lung rejection. As during ex vivo perfusion, dysregulated coagulation-thrombin elaboration, platelet activation, and intravascular thrombosis-mediates galactosyl transferase knockout lung xenograft injury.

Noradrenergic and dopaminergic effects of (+)-amphetamine-like stimulants in the baboonPapio anubis

(+)-Amphetamine, (+/-)-ephedrine, and phentermine are commonly used appetite suppressants that release monoamines from nerve cells by acting as substrates for biogenic amine transporters. One key difference among the three drugs is their selectivity for norepinephrine (NE) release vs. dopamine (DA) release. The NE/DA selectivity ratios for these drugs as determined in vitro [(EC50 NE(-1))/(EC50 DA(-1))] are (+/-)-ephedrine (18.6) > phentermine (6.7) > (+)-amphetamine (3.5). The in vitro data suggest that when administered in vivo, these stimulants might differ in their ability to release DA from nerve terminals in the brain. To test this hypothesis, noradrenergic effects (i.e., plasma NE) and dopaminergic effects (i.e., central DA release) were assessed when each drug was administered intravenously (1.5 mg/kg) to anesthetized baboons. Central DA release was determined via positron emission tomography using the method of [11C]raclopride displacement. In the present investigation, high doses of these stimulants increased plasma NE and DA in parallel, but only (+)-amphetamine released central DA from neurons and decreased plasma prolactin. None of the drugs altered plasma amine metabolite levels, indicating no inhibition of monoamine oxidase activity at the administered doses. Plasma drug levels measured in baboons were higher than those measured in human patients taking prescribed doses of the drugs. Viewed collectively, the present data indicate that typical clinical doses of phentermine and (+/-)-ephedrine may not release central DA in humans, a hypothesis that should ultimately be tested in controlled clinical studies.

Effects of GABAergic modulators on food and cocaine self-administration in baboons

Drugs that indirectly alter dopaminergic systems may alter the reinforcing effects of cocaine. The inhibitory neurotransmitter gamma-aminobutyric acid (GABA) has extensive neural connections in mesolimbic regions that appear to modulate dopamine. The current study evaluated the effects of GABA(B) receptor agonists baclofen and CGP44532, the benzodiazepine agonist alprazolam, and the GABA reuptake inhibitor tiagabine on lever responding maintained by low dose cocaine injections (0.032 mg/kg) or by food pellet (1 g) delivery in baboons. The benzodiazepine antagonist flumazenil was tested as a negative control. Cocaine or food was available under a fixed ratio (FR 10) schedule of reinforcement during daily 2-h sessions. During baseline conditions, cocaine and pellets maintained similar numbers of reinforcers per session. Baclofen, CGP44532 and tiagabine dose-dependently reduced the number of cocaine injections, where as the benzodiazepine antagonist flumazenil did not. Baclofen, CGP44532 and tiagabine also produced dose-related decreases in food-maintained behavior. In contrast, the benzodiazepine agonist alprazolam, which positively modulates GABA(A) receptors via the benzodiazepine site, produced decreases in cocaine self-injection, but not food-maintained behavior. Thus, the effects of alprazolam were specific for cocaine-maintained behavior, where as the effects of baclofen and CGP44532 were not.

Peroxisome proliferator-activated receptor-(gamma) receptor ligand partially prevents the development of endometrial explants in baboons: a prospective, randomized, placebo-controlled study

A prospective, randomized, placebo-controlled study was conducted in a baboon model to determine if a thiazolidinedione agonist of peroxisome proliferator-activated receptor-gamma, pioglitazone, can impede the development of endometriosis. Endometriosis was induced using laparoscopic, intrapelvic injection of eutopic menstrual endometrium, previously incubated with placebo or pioglitazone for 30 min, in 12 female baboons with a normal pelvis that had undergone at least one menstrual cycle since the time of captivity. At this point, the 12 baboons were randomized into two groups and treated from the day of induction. They received either PBS tablets (n = 6, placebo control, placebo tablets once a day by mouth) or pioglitazone (n = 6, test drug, 7.5 mg by mouth each day). A second and final laparoscopy was performed in the baboons to record the extent of endometriotic lesions between 24 and 42 d after induction (no difference in length of treatment between the two groups, P = 0.38). A videolaparoscopy was performed to document the number and surface area of endometriotic lesions. The surface area and volume of endometriotic lesions were significantly lower in pioglitazone treated baboons than the placebo group (surface area, 48.6 vs. 159.0 mm(2), respectively, P = 0.049; vol, 23.7 vs. 131.8 mm(3), respectively, P = 0.041). The surface area (3.5 vs. 17.8 mm(2), P = 0.017, pioglizatone vs. placebo) and overall number (1.5 vs. 9.5, P = 0.007, pioglizatone vs. placebo) of red lesions were lower in the pioglitazone group. A peroxisome proliferator-activated receptor-gamma ligand, pioglitazone, effectively reduced the initiation of endometriotic disease in the baboon endometriosis model. Using this animal model, we have shown that thiazolidinedione is a promising drug for preventive treatment of endometriosis.

Rates of self-directed behaviour and faecal glucocorticoid levels are not correlated in female wild olive baboons (Papio hamadryas anubis)

Non-invasive methods to quantify components of stress in non-human animals rely typically on the use of physiological or behavioural measures. At the physiological level, stress is usually measured non-invasively in terms of faecal or urinary glucocorticoid output. A common group of behavioural measures used are self-directed behaviours (SDBs), which have been shown to be linked to anxiety, a subset of stress, although a number of authors have explicitly linked SDBs to stress more generally. Whether increased rates of SDBs are likely to be associated with increased faecal glucocorticoid ouput in wild mammals remains unclear. Here, for wild female olive baboons, we show no association between day-to-day changes in levels of SDB and cortisol metabolite excretion. We also show no relationship between long-term mean levels of these variables. We discuss several possible interpretations of our results, including the possibility that SDBs represent a behavioural coping mechanism, helping to ameliorate the physiological stress response.

Evaluation of Recombinant Human Bone Morphogenetic Protein-2 on the Repair of Alveolar Ridge Defects in Baboons

BACKGROUND

The objective of this study was to evaluate alveolar ridge augmentation following surgical implantation of recombinant human bone morphogenetic protein-2 (rhBMP-2) using two novel space-providing carrier technologies in the baboon (Papio anubis) model.

METHODS

Standardized alveolar ridge defects ( approximately 15 x 8 x 5 mm) were surgically produced in maxillary and mandibular edentulous areas in four baboons. The defect sites were implanted with rhBMP-2 (0.4 mg/mL) in a tricalcium phosphate/hydroxyapatite/ absorbable collagen sponge composite (TCP/HA/ACS) or calcium phosphate cement (alpha-BSM). Control treatments were TCP/HA/ACS and ?-BSM without rhBMP-2 and sham surgery. Stainless steel pins were placed at the mid-apical and coronal level of the defect sites to provide landmarks for clinical measurements pre- and post-implantation. Impressions were obtained pre- and postimplantation to determine changes in alveolar ridge volume. Radiographic registrations were obtained pre- and post-implantation. Block sections of the defect sites were harvested at week 16 postimplantation and processed for histometric analysis including new bone area and bone density. Statistical comparisons between treatments were made using a mixed effect generalized linear model using least squares estimation.

RESULTS

The carrier systems without rhBMP-2 provided a modest ridge augmentation. The addition of rhBMP-2 resulted in an almost 2-fold increase in alveolar ridge width, including a greater percentage of trabecular bone and a higher bone density compared to controls (P < or =0.05) without significant differences between the two rhBMP-2 protocols.

CONCLUSIONS

TCP/HA/ACS and alphaBSM appear to be suitable carrier technologies for rhBMP-2. Alveolar augmentation procedures using either technology combined with rhBMP-2, rather than stand-alone therapies, may provide clinically relevant augmentation of alveolar ridge defects for placement of endosseous dental implants.

Evolution of the central sulcus morphology in primates

The central sulcus (CS) divides the pre- and postcentral gyri along the dorsal-ventral plane of which all motor and sensory functions are topographically organized. The motor-hand area of the precentral gyrus or KNOB has been described as the anatomical substrate of the hand in humans. Given the importance of the hand in primate evolution, here we examine the evolution of the motor-hand area by comparing the relative size and pattern of cortical folding of the CS surface area from magnetic resonance images in 131 primates, including Old World monkeys, apes and humans. We found that humans and great apes have a well-formed motor-hand area that can be seen in the variation in depth of the CS along the dorsal-ventral plane. We further found that great apes have relatively large CS surface areas compared to Old World monkeys. However, relative to great apes, humans have a small motor-hand area in terms of both adjusted and absolute surface areas.

High resolution DNA fingerprinting by AFLP to study the genetic variation among Oesophagostomum bifurcum (Nematoda) from human and non-human primates from Ghana

An AFLP approach was established to investigate genetic diversity within Oesophagostomum bifurcum (order Strongylida) from human and non-human primates. Evaluation of different combinations of restriction enzymes (n = 8) and primers (n = 29) demonstrated that the use of HindIII/BglII digested templates and primers with the selective nucleotides + AG/ +AC, respectively, was the most effective for the analysis of O. bifurcum DNA. A total of 63 O. bifurcum adults from human, Patas monkey, Mona monkey and Olive baboon hosts from different geographical regions in Ghana were subjected to analysis using this method. Cluster analysis revealed 4 genetically distinct groups, namely O. bifurcum from the Patas monkey (I), from the Mona monkey (II), from humans (III) and from the Olive baboon (IV). These findings were concordant with those achieved previously using RAPD analysis and supports population genetic substructuring within O. bifurcum according to host species. The results demonstrated the effectiveness of the present AFLP method for establishing genetic variation within O. bifurcum, and indicates its applicability to other parasitic nematodes of human and/or veterinary health importance.

Environmental cues, alcohol seeking, and consumption in baboons: effects of response requirement and duration of alcohol abstinence

BACKGROUND

Environmental stimuli (cues) that have been paired with alcohol drinking may evoke classically conditioned states that in turn influence alcohol consumption and relapse to heavy drinking. Animal models using chained schedules of alcohol reinforcement may be useful for examining such complex interactions.

METHODS

Alcohol drinking was established in 4 baboons. A sequence of lights and tones was presented during daily 3-hour sessions. First, cues were presented alone and no programmed contingencies were in effect. Second, cues were paired with 3 linked components consisting of different behavioral contingencies leading to and concluding with access to alcohol for self-administration in the last component (i.e., a chained schedule of alcohol reinforcement). Third, the effects of withholding alcohol access (i.e., forced abstinence) and increasing the number of lever responses required per drink were evaluated.

RESULTS

Cues paired with a chained schedule of alcohol reinforcement engendered behaviors that brought baboons into contact with alcohol-related cues and occasioned operant responding that facilitated access to alcohol (alcohol seeking) during components that preceded alcohol access. Increasing the response requirement for each drink decreased the number of drinks and volume of alcohol consumed, but did not alter alcohol seeking. On the first session after 14 days of alcohol abstinence, latency to complete the operant requirement that produced alcohol access was decreased while both alcohol self-administration and volume of alcohol consumed were increased.

CONCLUSIONS

Alcohol self-administration and consumption were sensitive to increases in response requirement and duration of alcohol abstinence, while seeking was only enhanced by duration of alcohol abstinence. This animal model may be useful to further examine the interactions between environmental cues and behaviors associated with seeking and consumption of alcohol and to evaluate the efficacy of potential alcohol treatment drugs on these behaviors.