Model-based trajectory tracking of a compliant continuum robot.

Introduction: Compliant mechanisms, especially continuum robots, are becoming integral to advancements in minimally invasive surgery due to their ability to autonomously navigate natural pathways, significantly reducing collision severity. A major challenge lies in developing an effective control strategy to accurately reflect their behavior for enhanced operational precision. Methods: This study examines the trajectory tracking capabilities of a tendon-driven continuum robot at its tip. We introduce a novel feedforward control methodology that leverages a mathematical model based on Cosserat rod theory. To mitigate the computational challenges inherent in such models, we implement an implicit time discretization strategy. This approach simplifies the governing equations into space-domain ordinary differential equations, facilitating real-time computational efficiency. The control strategy is devised to enable the robot tip to follow a dynamically prescribed trajectory in two dimensions. Results: The efficacy of the proposed control method was validated through experimental tests on six different demand trajectories, with a motion capture system employed to assess positional accuracy. The findings indicate that the robot can track trajectories with an accuracy within 9.5%, showcasing consistent repeatability across different runs. Discussion: The results from this study mark a significant step towards establishing an efficient and precise control methodology for compliant continuum robots. The demonstrated accuracy and repeatability of the control approach significantly enhance the potential of these robots in minimally invasive surgical applications, paving the way for further research and development in this field.

Determination of in vitro stability of routine haematinics tests using EFLM standards and the CRESS checklist.

BACKGROUND: Laboratories should be aware of the stability of the analytes they are testing in order to avoid incorrect reporting and patient management. Stability studies are difficult to interpret and reproduce, with little guidance on how to determine appropriate clinical cut off values. Here we describe a standardised approach to determining stability for routine haematinics tests using published EFLM guidelines. METHODS: The haematinics panel at UHNM contains vitamin B12, folate, ferritin, iron and transferrin. Blood tubes included were serum separator tubes, gel-free serum and lithium-heparin plasma. Conditions tested were room temperature, 2-8°C and -20°C. For each condition and tube, three samples were analysed in duplicate at 0, 24, 48, 72, 96 and 120 h using the Siemens Atellica platform. RESULTS: The percentage difference was calculated for each respective blood tube and storage condition, in addition to individual analyte maximum permissible instability scores. The majority of analytes for all blood tubes were stable for 5 days or more when stored at 4-8°C and -20°C. Ferritin (excluding gel-free), iron and transferrin further showed stability >5 days when stored at room temperature. However, vitamin B12 and folate demonstrated poor stability data for all tube types tested. CONCLUSIONS: Here we describe a stability study for the haematinics panel on the Siemens Atellica platform using the standardised EFLM Checklist for Reporting Stability Studies (CRESS). The checklist was used in order to promote a standardised and transferable scientific approach to what has previously been lacking in the literature when performing stability experiments.

The influence of warm-up duration on simulated rugby league interchange match performance.

OBJECTIVE: The study was conducted to understand the effects of a short (10 min) and a long (30 min) duration warm-up on subsequent readiness to exercise and movement during simulated rugby league match play. Methods: Using a randomised cross-over design, 13 male rugby players (age: 23.6 ± 4.1 y) completed 10- or 30-min warm-up immediately before 2 × 23 min rugby league movement simulation protocol. Results: Total distance, high- and low speed running and tympanic temperature (ES = 0.56 to 20.8) were all higher in the 30 min warm-up, with differences in relative distance and heart rate unclear (ES = -0.36 to 0.06). Differences in participants' readiness to exercise after the warm-ups were unclear (ES = 0.25). Differences between trials for movement characteristics (ES = -0.13 to -0.32), RPE (ES = -0.13 to 0.04) and B[La] after the simulation were mostly unclear, with only trivial changes in high-speed running (ES = 0.08) and a lower heart rate (ES = -0.26) between the two playing bouts after the 30 min warm-up trial. Conclusion: Practitioners can use warm-ups between 10 or 30 minutes for rugby league interchange players without any implications for subsequent match running performance.

Untargeted Metabolomic Analysis of Human Milk from Mothers of Preterm Infants.

The application of metabolomics in neonatology offers an approach to investigate the complex relationship between nutrition and infant health. Characterization of the metabolome of human milk enables an investigation into nutrients that affect the neonatal metabolism and identification of dietary interventions for infants at risk of diseases such as necrotizing enterocolitis (NEC). In this study, we aimed to identify differences in the metabolome of breast milk of 48 mothers with preterm infants with NEC and non-NEC healthy controls. A minimum significant difference was observed in the human milk metabolome between the mothers of infants with NEC and mothers of healthy control infants. However, significant differences in the metabolome related to fatty acid metabolism, oligosaccharides, amino sugars, amino acids, vitamins and oxidative stress-related metabolites were observed when comparing milk from mothers with control infants of ≤1.0 kg birth weight and >1.5 kg birth weight. Understanding the functional biological features of mothers' milk that may modulate infant health is important in the future of tailored nutrition and care of the preterm newborn.

Advancing peptide siRNA-carrier designs through L/D-amino acid stereochemical modifications to enhance gene silencing.

The 599 peptide has been previously shown to effectively deliver small interfering RNAs (siRNAs) to cancer cells, inducing targeted-oncogene silencing, with a consequent inhibition of tumor growth. Although effective, this study was undertaken to advance the 599 peptide siRNA-carrier design through L/D-amino acid stereochemical modifications. Consequently, 599 was modified to generate eight different peptide variants, incorporating either different stereochemical patterns of L/D-amino acids or a specific D-amino acid substitution. Upon analysis of the variants, it was observed that these modifications could, in some instances, increase/decrease the binding, nuclease/serum stability, and complex release of siRNAs, as well as influence the gene-silencing efficiencies of the complex. These modifications were also found to affect cellular uptake and intracellular localization patterns of siRNA cargo, with one particular variant capable of mediating binding of siRNAs to specific cellular projections, identified as filopodia. Interestingly, this variant also exhibited the most enhanced gene silencing in comparison to the parent 599 peptide, thus suggesting a possible connection between filopodia binding and enhanced gene silencing. Together, these data demonstrate the utility of peptide stereochemistry, as well as the importance of a key D-amino acid modification, in advancing the 599 carrier design for the enhancement of gene silencing in cancer cells.

Monomeric C-Reactive Protein in Serum With Markedly Elevated CRP Levels Shares Common Calcium-Dependent Ligand Binding Properties With an in vitro Dissociated Form of C-Reactive Protein.

A monomeric form of C-reactive protein (CRP) which precipitates with cell wall pneumococcal C polysaccharide (CWPS) and retains the ability to reversibly bind to its ligand phosphocholine has been produced through urea-induced dissociation at an optimized concentration of 3 M urea over a 10 weeks period. Dissociated samples were purified via size exclusion chromatography and characterized by western blot, phosphocholine affinity chromatography and CWPS precipitation. Human serum samples from patients with raised CRP levels (>100 mg/L as determined by the clinical laboratory assay) were purified by affinity and size exclusion chromatography and analyzed (n = 40) to determine whether circulating monomeric CRP could be detected ex vivo. All 40 samples tested positive for pentameric CRP via western blot and enzyme linked immunosorbent assay (ELISA) analysis. Monomeric C-reactive protein was also identified in all 40 patient samples tested, with an average level recorded of 1.03 mg/L (SE = ±0.11). Both the in vitro monomeric C-reactive protein and the human serum monomeric protein displayed a molecular weight of approximately 23 kDa, both were recognized by the same anti-CRP monoclonal antibody and both reversibly bound to phosphocholine in a calcium-dependent manner. In common with native pentameric CRP, the in vitro mCRP precipitated with CWPS. These overlapping characteristics suggest that a physiologically relevant, near-native monomeric CRP, which retains the structure and binding properties of native CRP subunits, has been produced through in vitro dissociation of pentameric CRP and also isolated from serum with markedly elevated CRP levels. This provides a clear route toward the in-depth study of the structure and function of physiological monomeric CRP.

Discovery of a series of 6,7-dimethoxy-4-pyrrolidylquinazoline PDE10A inhibitors.

A papaverine based pharmacophore model for PDE10A inhibition was generated via SBDD and used to design a library of 4-amino-6,7-dimethoxyquinazolines. From this library emerged an aryl ether pyrrolidyl 6,7-dimethoxyquinazoline series that became the focal point for additional modeling, X-ray, and synthetic efforts toward increasing PDE10A inhibitory potency and selectivity versus PDE3A/B. These efforts culminated in the discovery of 29, a potent and selective brain penetrable inhibitor of PDE10A.

Assessment of Perioperative Variables That Predict the Need for Surgical Drains Following Robotic Partial Nephrectomy Utilizing Quantitative Drain Creatinine Analysis.

OBJECTIVE: To utilize body fluid creatinine analysis to determine which patients will require a surgical drain following robotic-assisted partial nephrectomy (RAPN). MATERIALS AND METHODS: One hundred fifty consecutive RAPN performed by a single surgeon were reviewed. Postoperative day (POD) 1 drain creatinine was compared to serum creatinine to calculate the drain to serum creatinine ratio (D/S ratio). Elevated D/S ratio was defined as any value >1.2. RESULTS: From February 2008 to April 2015, 140 patients underwent RAPN and had a drain placed (124 had D/S ratio available on POD 1). In the 103 patients with a D/S ratio of <1.2 and the 21 with D/S ratio of >1.2, the mean tumor size was 3.0 and 3.9 cm (P = .001) and mean RENAL score was 7.6 and 8.1 (P = .270), respectively. Collecting system entry occurred in 68.2% of patients with a D/S ratio of <1.2 and 71.4% of patients with a D/S ratio of >1.2. Mean drain time was 2.4 and 4.2 days (P = .001), hospital stay was 2.7 and 3.3 days (P = .036) for the D/S ratio <1.2 and D/S ratio >1.2 groups, respectively. Those with renal mass size of 4-7 cm had increased likelihood of D/S ratio >1.2 (OR 2.78; P = .041). CONCLUSIONS: Most RAPN do not require a surgical drain. A POD 1 elevated D/S ratio is more likely to occur with larger masses (those approaching or greater than 4 cm) and can be associated with prolonged drain time and hospital stay.

Has Sliding-Clip Renorrhaphy Eliminated the Need for Collecting System Repair During Robot-Assisted Partial Nephrectomy?

OBJECTIVE: We evaluated whether single-layer renorrhaphy (SLR) without collecting system (CS) closure is sufficient following robot-assisted partial nephrectomy (RAPN). PATIENTS AND METHODS: One hundred fifty consecutive patients underwent RAPN by a single surgeon and were prospectively labeled with regard to CS entry during surgery. Patients with CS entry were subdivided into two groups: those with classical renorrhaphy (CR) (i.e., two-layer repair) and those with SLR (i.e., without CS repair). Perioperative variables and outcomes were compared between CR and SLR groups. RESULTS: Ninety patients had CS entry during RAPN. Of these 90 patients, 64 had CR, and 26 had SLR, with mean ages of 62 and 59 years (p = 0.22), tumor sizes of 3.4 and 3.3 cm (p = 0.61), Mayo Adhesive Probability scores of 1.8 and 1.8 (p = 0.95), and radius, exophytic/endophytic, nearness to CS, and laterality scores of 8.5 and 8.0 (p = 0.16), respectively. Mean warm ischemia times (WITs) were 19.6 and 17.3 minutes (p = 0.04), hospital stays of 3.0 and 2.8 days (p = 0.62), and drain times of 2.9 and 2.7 days (p = 0.65), for the CR and SLR groups, respectively. Using the Clavien-Dindo classification, there were a total of six grade III or higher complications, with no difference between the CR and SLR subgroups (p = 1.0). Renal function using creatinine or glomerular filtration rate as surrogates showed no difference between groups preoperatively or up until 2 years postoperatively. CONCLUSIONS: Omitting CS repair during RAPN with SLR decreases WIT without altering complications, hospital stay, or drain time. Long-term renal function was not associated with CS repair.

Genetic deletion of the striatum-enriched phosphodiesterase PDE10A: evidence for altered striatal function.

PDE10A is a newly identified phosphodiesterase that is highly expressed by the medium spiny projection neurons of the striatum. In order to investigate the physiological role of PDE10A in the central nervous system, PDE10A knockout mice (PDE10A(-/-)) were characterized both behaviorally and neurochemically. PDE10A(-/-) mice showed decreased exploratory activity and a significant delay in the acquisition of conditioned avoidance behavior when compared to wild-type (PDE10A(+/+)) mice. However, in a variety of other well-characterized behavioral tasks, including the elevated plus maze (anxiety), forced swim test (depression), hot plate (nociception) and two memory models (passive avoidance and Morris water maze), PDE10A(-/-) mice performed similarly to wild-type mice. When challenged with PCP or MK-801, PDE10A(-/-) mice showed a blunted locomotor response in comparison to PDE10A(+/+) mice. In contrast, PDE10A(-/-) and PDE10A(+/+) mice responded similarly to the locomotor stimulating effects of amphetamine and methamphetamine. Our findings suggest that PDE10A is involved in regulating striatal output, possibly by reducing the sensitivity of medium spiny neurons to glutamatergic excitation. These results are discussed in relationship to the hypothesis that PDE10A inhibition presents a novel treatment for psychosis.

A 3-month clinical trial comparing the IOP-lowering efficacy of bimatoprost and latanoprost in patients with normal-tension glaucoma.

This multicenter, randomized, double-blind clinical trial was undertaken to compare the intraocular pressure (IOP)-lowering efficacy and safety of topical bimatoprost 0.03% with that of latanoprost 0.005% for the treatment of patients with normal-tension glaucoma. After washout of all ocular hypotensive medications, patients with normal-tension glaucoma (n=60) were randomly assigned to oncedaily bimatoprost 0.03% or latanoprost 0.005% for 3 mo. Diurnal IOP measurements were taken at each study visit. Primary outcome measures consisted of mean change from baseline IOP (8 AM, Noon, 4 PM) and change in visual field. Secondary measures included mean IOP, ophthalmologic examination findings, results of clinical evaluation, and adverse events. Mean change from baseline IOP at each study visit was statistically significant at all diurnal measurements for patients taking bimatoprost and for those taking latanoprost (P<.001). The 8 AM mean change from baseline IOP measurement showed a significant between-group difference (P< or =.033) in favor of bimatoprost at both follow-up visits. After 3 mo of treatment, mean IOP reductions from baseline ranged from 2.8 to 3.8 mm Hg (17.5%-21.6%) with bimatoprost and from 2.1 to 2.6 mm Hg (12.7%-16.2%) with latanoprost. Overall mean reduction in IOP after 3 mo of treatment was 3.4 mm Hg (19.9% rpar; with bimatoprost and 2.3 mm Hg (14.6%) with latanoprost (P=.035). No significant between-group differences were observed in incidence of adverse events, clinical success, or demographic variables. Bimatoprost was found to be more effective than latanoprost in lowering IOP in the patient with normal-tension glaucoma. Both drugs were efficacious and well tolerated.

Comparison of OnabotulinumtoxinA Intradetrusor Injection Needle Performance with Modern Flexible Cystoscopes.

INTRODUCTION: Intradetrusor injection of onabotulinumtoxinA (BTX-A) can be performed with rigid or flexible cystoscopy. The primary aim of this study was to analyze irrigant flow rate and total angle of deflection for the intradetrusor injection needles used for flexible cystoscopic injection of BTX-A to see if any needle provided a technical advantage. METHODS: Three commercially available intradetrusor injection needles were evaluated using two modern flexible cystourethroscopes. The three needles analyzed were the NBI070 (Coloplast, Minneapolis, MN), DIS200 (Laborie, Williston, VT), and NM-101C-0427/MAJ-565/MAJ-655 (Olympus, Center Valley, PA). Angles of deflection and irrigant flow rates were calculated with an empty working channel and each injection needle in the working channel of the two flexible cystoscopes. RESULTS: With the working channel empty, the Karl Storz 11272CU1 (KS) and Olympus CYF-V2 (O) cystoscopes had a total range of deflection of 341 degrees and 281 degrees, respectively. Total range of deflection with the KS cystoscope was reduced to 275 degrees, 250 degrees, and 311 degrees for the Coloplast NBI070, Laborie DIS200, and Olympus NM-101C-0427 needles, respectively. Total range of deflection with the O cystoscope was reduced to 195 degrees, 157 degrees, and 257 degrees for Coloplast NBI070, Laborie DIS200, and Olympus NM-101C-0427 needles, respectively. Average flow rates with an empty working channel were 5.7 mL/s and 5.5 mL/s for the KS and O cystoscopes, respectively. Mean flow rate with the KS cystoscope was reduced to 1.0 mL/s, 0.1 mL/s, and 0.7 mL/s for Coloplast NBI070, Laborie DIS200, and Olympus NM-101C-0427 needles, respectively. Mean flow rate with the O scope was reduced to 0.5 mL/s, 0.1 mL/s, and 0.4 mL/s for Coloplast NBI070, Laborie DIS200, and Olympus NM-101C-0427 needles, respectively. CONCLUSION: Among commercially available intradetrusor BTX-A injection needles, the Olympus NM-101C-0427 allows for the greatest total range of deflection and has the greatest elasticity and flexibility. Coloplast NBI070 allows for the best flow rate.

Chromosomal aberrations in human lymphocytes exposed to the anticholinesterase pesticide isofenphos with mechanisms of leukemogenesis.

Human lymphocytes were exposed to the leukemogenic pesticide isofenphos (IFP) to investigate its effects on chromosomal DNA and cholinergic homeostasis using cholinesterase activity as a marker. Isolated peripheral lymphocytes were administered concentrations of IFP ranging from 0.1 ng/ml to 10 microg/ml. The absence (Group 1) and presence (Group 2) of DNA repair inhibitors 4 mM hydroxyurea (HU), 40 microM cytosine arabinoside (ARA-C) and an NADPH regenerating system (NRS) (Group 3) were analyzed at 1, 6 and 24 h by single cell gel electrophoresis using the comet assay. Significant damage to DNA directly from IFP at 1 h by remarkably low concentrations was observed in Group 1, escalating in Group 2 with DNA repair inhibition, while Group 3 disruptions were highest due to the presence of the NRS P-450 microsomal fraction conducive to producing reactive IFP-oxon and N-desalkyl metabolites. The extent of DNA aberrations increased further in parallel within the groups at 6 and 24 h. Male and female chemical sensitivities were similar on average (P < 0.01). Cholinesterase activity measured in a satellite group was inhibited with 0.1 microg/ml IFP by 69, 62, and 48% at 1, 6, and 24 h, respectively, indicating gradual induction of compensatory synthesis. Restoration of cholinergic homeostasis may be exceptionally impaired at higher IFP concentrations from acetyl-CoA depletion [Leuk. Res. 25 (2001) 883]. In summary, these studies reveal that exposure to the organophosphate pesticide isofenphos induces human DNA mutation beyond endogenous repair capacity and disrupts cholinergic nuclear signaling affectively constructing the mutator phenotype of leukemogenesis.

Immunohistochemical localization of PDE10A in the rat brain.

PDE10A is a newly identified cAMP/cGMP phosphodiesterase for which mRNA is highly expressed in the mammalian striatum. In the present study, PDE10A protein and mRNA expression throughout the rat brain were determined, using a monoclonal antibody (24F3.F11) for Western blot and immunohistochemical analyses and an antisense riboprobe for in situ hybridization. High levels of mRNA are observed in most of the neuronal cell bodies of striatal complex (caudate n, n. accumbens and olfactory tubercle), indicating that PDE10A is expressed by the striatal medium spiny neurons. PDE10A-like immunoreactivity is dense throughout the striatal neuropil, as well as in the internal capsule, globus pallidus, and substantia nigra. These latter regions lack significant expression of PDE10A mRNA. Thus, PDE10A is transported throughout the dendritic tree and down the axons to the terminals of the medium spiny neurons. These data suggest a role for PDE10A in regulating activity within both the striatonigral and striatopallidal pathways. In addition, PDE10A immunoreactivity and mRNA are found at lower levels in the hippocampal pyramidal cell layer, dentate granule cell layer and throughout the cortex and cerebellar granule cell layer. Immunoreactivity is detected only in cell bodies in these latter regions. This more restricted subcellular localization of PDE10A outside the striatum suggests a second, distinct function for the enzyme in these regions.

Efficacy of bimatoprost in glaucoma and ocular hypertension unresponsive to latanoprost.

This open-label, monocular, two-phase trial was conducted to determine whether bimatoprost is effective in patients with open-angle glaucoma or ocular hypertension not responsive to latanoprost. After a 4-week washout of any ocular hypotensive agents, patients with IOP between 22 and 34 mm Hg (n=51) instilled latanoprost in one eye and were evaluated at weeks 4 and 8 (phase 1). Patients with an IOP reduction no more than 3 mm Hg at both visits were considered nonresponders to latanoprost and were switched to bimatoprost for 8 weeks (n=21) (phase 2). In the treated eyes, the mean reduction in IOP from baseline after 4 weeks of each medication was 2.3 mm Hg with latanoprost (P=.012) and 6.1 mm Hg with bimatoprost (P<.001). After 8 weeks, respective IOP reductions were 1.9 mm Hg (P=.027) and 5.4 mm Hg (P<.001). After the switch from latanoprost, 8 weeks of bimatoprost provided an additional mean IOP reduction of 3.5 mm Hg (P<.001).

Bimatoprost 0.03% versus travoprost 0.004% in black Americans with glaucoma or ocular hypertension.

This randomized, investigator-masked, multicenter, parallel-design trial compared the IOP-lowering efficacy of bimatoprost 0.03% and travoprost 0.004% in African Americans with glaucoma or ocular hypertension. After a washout of all ocular hypotensive agents, patients were assigned to bimatoprost once daily (n=16) or travoprost once daily (n=15) for 3 months. Study visits were at baseline and at months 1, 2, and 3. Primary outcome measures were the percentage of patients who achieved selected target pressures and the mean reduction in IOP from baseline at month 3. Both drugs comparably lowered IOP, but bimatoprost was more likely than travoprost to allow achievement of every target pressure from 12 to 19 mm Hg at month 3. After 3 months, the mean IOP reduction from baseline was 8.4 mm Hg (34%) in the bimatoprost group and 7.9 mm Hg (30%) in the travoprost group. These results are being evaluated further in a larger clinical trial.

Ocular hypotensive effect of the Rho kinase inhibitor AR-12286 in patients with glaucoma and ocular hypertension.

PURPOSE: To evaluate the ocular hypotensive efficacy of 0.05%, 0.1% and 0.25% AR-12286 Ophthalmic Solutions in patients diagnosed with ocular hypertension or glaucoma. DESIGN: Parallel comparison, vehicle-controlled, double-masked, 3-week randomized clinical trial. METHODS: Subjects (n = 89) with elevated intraocular pressure (IOP) were assigned randomly to receive either 1 of 3 concentrations of AR-12286 or its vehicle. Dosing was once-daily in the morning for 7 days, then once-daily in the evening for 7 days, then twice daily for 7 days. Primary and secondary efficacy end points were mean IOP at each diurnal time point (8 am, 10 am, 12 pm, and 4 pm) and mean change in IOP from baseline, respectively. RESULTS: All 3 concentrations of AR-12286 produced statistically and clinically significant reductions in mean IOP that were dose dependent, with peak effects occurring 2 to 4 hours after dosing. Mean IOP at peak effect ranged from 17.6 to 18.7 mm Hg (-6.8 to -4.4 mm Hg) for the 3 concentrations. The largest IOP reductions were produced by 0.25% AR-12286 after twice daily dosing (up to -6.8 mm Hg; 28%). The 0.25% concentration dosed once-daily in the evening produced highly significant IOP reductions throughout the following day (-5.4 to -4.2 mm Hg). The only adverse event of note was trace (+0.5) to moderate (+2) conjunctival hyperemia that was transient, typically lasting 4 hours or less. After once-daily evening dosing, hyperemia was seen in less than 10% of patients. CONCLUSIONS: AR-12286 was well tolerated and provided clinically and statistically significant ocular hypotensive efficacy in patients with ocular hypertension and glaucoma.

Use of structure-based design to discover a potent, selective, in vivo active phosphodiesterase 10A inhibitor lead series for the treatment of schizophrenia.

Utilizing structure-based virtual library design and scoring, a novel chimeric series of phosphodiesterase 10A (PDE10A) inhibitors was discovered by synergizing binding site interactions and ADME properties of two chemotypes. Virtual libraries were docked and scored for potential binding ability, followed by visual inspection to prioritize analogs for parallel and directed synthesis. The process yielded highly potent and selective compounds such as 16. New X-ray cocrystal structures enabled rational design of substituents that resulted in the successful optimization of physical properties to produce in vivo activity and to modulate microsomal clearance and permeability.

Identification of a brain penetrant PDE9A inhibitor utilizing prospective design and chemical enablement as a rapid lead optimization strategy.

By use of chemical enablement and prospective design, a novel series of selective, brain penetrant PDE9A inhibitors have been identified that are capable of producing in vivo elevations of brain cGMP.