A multicenter, randomized, placebo controlled, multiple-dose, safety and pharmacokinetic study of AIT-082 (Neotrofin) in mild Alzheimer's disease patients

A phase 1, randomized, double-blind, placebo-controlled, dose escalation study of the purine derivative, AIT-082 (Neotrofin, NeoTherapeutics) was conducted in mild Alzheimer's disease (AD) patients to evaluate multiple-dose safety, tolerability, and pharmacokinetics. Possible short-term effects of AIT-082 on cognition and memory were preliminarily investigated. AIT-082 is currently being developed as a potential treatment for Alzheimer's disease and other neurological disorders. Pre-clinical studies indicate that AIT-082 has memory enhancing properties, stimulates neuritogenesis and the production of neurotrophic factors. Patients received an oral dose of AIT-082 or placebo daily for one week. Thirty-six AD patients were divided into three dose cohorts; each dose cohort consisted of twelve patients with 8 patients randomized to AIT-082 and 4 to placebo. The 3 doses of AIT-082 evaluated in this study were 100 mg/day, 500 mg/day, and 2,000 mg/day. There were no serious adverse events at any dose and the drug was well tolerated without significant side effects. AIT-082 was orally and rapidly absorbed, resulting in peak serum concentrations within 2 hours with an elimination half-life of approximately 20 hours. Higher doses resulted in corresponding increases in peak concentrations and areas under the curve (AUC). There was an approximate 2-fold accumulation in AIT-082 with daily dosing (as reflected by the AUC) at steady state. There were no significant differences by treatment arm on the clinical or neuropsychological evaluations. AIT-082 was rapidly absorbed by the oral route with a half-life suitable for dosing once or twice daily. No problems with tolerability or safety were found. AIT-082 appears suitable for testing in larger clinical trials for the treatment of AD and other neurologic disorders.

Small water and wastewater systems: pathways to sustainable development?

Globally we are faced with billions of people without access to safe water and adequate sanitation. These are generally located in developing communities. Even in developed communities the current large scale systems for supplying water, collecting wastewater and treating it are not environmentally sustainable, because it is difficult to close the cycle of water and nutrients. This paper discusses the advantages of small scale water and wastewater systems in overcoming the difficulties in providing water and wastewater systems in developing communities and in achieving sustainability in both developed and developing communities. Particular attention is given to technology and technology choice, even though technology alone does not provide the complete answer. Disadvantages of small scale systems and how they may be overcome are discussed.

Co-treatment of septage in a municipal sewage treatment pond system

This paper deals with the characteristics and treatment options of septage. The objective of the paper is to evaluate the effects of co-treatment of 50 MLD of septage in a sewage treatment pond system. The treatment efficiency of the pond system for BOD5 and Fecal Coliform (FC) has been estimated using a first order kinetics model. The model has predicted that the treatment pond system has a maximum capacity of 8.5 MLD and will have a reserve of 28.3% of its total capacity even after the proposed addition of 50 MLD of septage. Separation of oil and grease from septage prior to discharge into the pond system is recommended.

Functional role of TGF beta in Alzheimer's disease microvascular injury: lessons from transgenic mice

Recent studies have implicated pro- and anti-inflammatory cytokines as integral to Alzheimer's disease (AD) pathogenesis. Among them, transforming growth factor-beta (TGF-beta) is emerging as an important factor in regulating inflammatory responses. This multifunctional cytokine might be centrally involved in several aspects of AD pathogenesis by regulating beta-amyloid precursor protein synthesis and processing, plaque formation, astroglial and microglial response and neuronal cell death. Among all of these potential roles, studies in transgenic and infusion animal models have shown that TGF-beta may primarily contribute to AD pathogenesis by influencing A beta production and deposition, which in turn might result in damage to the brain microvasculature. The lessons learned from these models are of great interest not only for understanding of the role of TGF-beta in AD, but also for future treatments where testing of anti-inflammatory agents such as ibuprofen and an amyloid vaccine hold great promise. In this regard, further elucidation of the signal pathways by which TGF-beta exerts its effect in AD might lead to specific targets for further therapeutic intervention.

Computer-assisted transurethral laser resection of the prostate (CALRP): theoretical and experimental motion plan

Computer-Assisted transurethral laser resection of the prostate (CALRP) is a treatment modality that was designed and developed based on an integrated system of computer, robotics and laser technology in association with a minimally invasive surgery known as laser transurethral resection of the prostate (LRP). CALRP possesses complementary capabilities that could remedy many of the problems faced by surgeons in conventional LRP by delivering a treatment with repeatability and reliability. The work deals primarily in determining the feasibility study of the computer-assisted lasing motion plan (planned motion sequence controlled by a program) for LRP. A theoretical motion plan that analyzes numerically the lasing motion of the fiber was designed by calculating the profile removal rate and in vitro experiments conducted on human cadaveric prostate to verify and validate the designed motion plan. The novel motion plan, which was executed experimentally using the LaserTrode lightguide, accomplished the objective of resecting the enlarged prostate with the aid of computer and robotics technology.

Bacterial arthritis

The septic arthritis literature of 2000 revisited several topics previously examined in some detail. These include septic arthritis in rheumatoid arthritis, rheumatic manifestations of bacterial endocarditis, and infectious complications of prosthetic joints. The trend in antibiotic prophylaxis to prevent late infections in total joint replacement is to narrow the targeted hosts to those most at risk, to define the procedures associated with the greatest risk of bacteremia, and to simplify the antibiotic regimen. The diagnoses of septic arthritis of the lumbar facet joint and septic arthritis caused by direct inoculation of bacteria by a foreign object penetrating the joint are facilitated by noninvasive imaging technologies. Septic arthritis caused by uncommon microorganisms and septic arthritis in immunocompromised hosts are other noteworthy topics in this year's literature.

Experimental study of transurethral robotic laser resection of the prostate using the LaserTrode lightguide

A longer operating time and steeper learning curve in mastering the techniques for transurethral laser resection of the prostate are the main problems faced by surgeons in addition to the existing ones in standard transurethral resection of the prostate (TURP). However, these disadvantages can be alleviated with the introduction of a treatment procedure designed and developed based on an integrated system of computer, robotics and laser technology. In vitro experiments were carried out to determine variables affecting the vaporization and coagulation lesions, in order to study the effectiveness and feasibility of robotics for this procedure. Human cadaveric prostates and fresh tauted chicken breast tissues were irradiated with different parameters using the LaserTrode lightguide in contact with the tissue. The effects of irrigant flow rate, fiber/tissue angle of inclination, number of passes, direction, speed and power of lase on the volume of tissue vaporized and coagulated, were assessed. The final phase of the experiments includes executing the robotic motion plan for the laser resection procedure on the human cadaveric prostate tissue embedded in an anatomically alike prostate phantom. It was concluded from our study that power and speed of lase are the most significant parameters influencing the volume of the vaporized and coagulated lesion. Comparison of removal rate using the new treatment procedure of robotic laser resection of the prostate with TURP and HoLRP evinced equivalent results.

Increased metallothionein in mouse liver, kidneys, and duodenum during lactation

Lactation-induced increases in cadmium absorption and retention have been demonstrated in mid-lactating mice, but no systematic measurements of endogenous metal-binding protein concentrations during lactation have been reported. Using Cd/hemoglobin radioassay, this study detected significant increases in metallothionein (MT) concentrations in liver (4-fold), kidneys (2-fold), and duodenum (2-fold), but not jejunum, of mouse dams on days 13 and 20 of lactation. These increases occurred in the absence of cadmium exposure and were specific to the lactation period; dams 5 days after weaning showed MT levels that were similar to those of nonpregnant (NP) mice. Similarly, Northern blot analyses of livers from lactating mice demonstrated that MT mRNA concentrations in maternal liver during mid-lactation were 6-fold higher than those observed 5 days after pups were weaned. Gel filtration of final supernatants from the Cd/hemoglobin assay confirmed that the Cd-binding molecule induced during lactation was indeed metallothionein. In addition, chromatographic analyses of cytosols from tissues taken from dams administered small amounts of Cd (66 ng/mouse) showed that the trace amounts of Cd absorbed through the maternal gastrointestinal tract during mid-lactation were also bound to the MT. These results indicate MT induction in mouse dams occurs as a physiological consequence of lactation, requiring no external stimulus. This induced MT participates in binding low levels of dietary cadmium consumed by the dam. During lactation, elevated maternal MT may affect pathways for essential trace metals as well as sequester toxic metals harmful to the neonate. Multiparous humans may have increased risk of accumulating environmental Cd.

Water harvesting techniques for small communities in arid areas

Limited water resources exist in numerous remote indigenous settlements around Australia. Indigenous people in these communities are still living in rudimentary conditions while their urban counterparts have full amenities, large scale water supplies and behavioral practices which may not be appropriate for an arid continent but are supported by extensive infrastructure in higher rainfall coastal areas. As remote indigenous communities continue to develop, their water use will increase, and in some cases, costly solutions may have to be implemented to augment supplies. Water harvesting techniques have been applied in settlements on a small scale for domestic and municipal purposes, and in the large, broadacre farm setting for productive use of the water. The techniques discussed include swales, infiltration basins, infiltration trenches and "sand dam" basins. This paper reviews the applications of water harvesting relevant to small communities for land rehabilitation, landscaping and flood control. Landscaping is important in these communities as it provides shelter from the sun and wind, reduces soil erosion and hence reduced airborne dust, and in some cases provides food and nutrition. Case studies of water harvesting systems applied in the Pilbara Region, Western Australia for landscaping around single dwellings in Jigalong and Cheeditha, in a permaculture garden in Wittenoon and at a college and carpark in Karratha are described.

Visual search for traffic signs: the effects of clutter, luminance, and aging

Latency and eye movement measures were used to examine the effects of aging, clutter, and luminance on visual search for traffic signs embedded in digitized images of driving scenes. Initially 14 older and 14 younger observers classified daytime and nighttime traffic scenes as containing low or high amounts of clutter. Next, an independent sample of 14 younger and 14 older participants searched for traffic signs contained within these scenes. Errors were more common among the elderly. Search efficiency declined with increased clutter and with aging. However, relative to the young, older adults did not suffer disproportionately as a result of increased clutter. The methods developed might be profitably employed to assess sign conspicuity and sign acquisition during driving.

Evapotranspiration for domestic wastewater reuse in remote indigenous communities of Australia

In the past sewage ponding in indigenous settlements was commonplace as a result of overcrowding combined with inappropriate septic tank and leach drain design, installation and operation. The response over the past 10 years has been to develop reticulated sewerage systems to lagoons when the funds become available. These are often successful in terms of operation, improved public health and low maintenance but are expensive and wasteful of limited water supplies. Evapotranspiration (ET) is an effective method for on-site domestic effluent disposal in areas of Western Australia with soils of low permeability. Evapotranspiration systems have been established in a number of communities both for research/demonstration and as specified by architects. The systems usually follow two septic tanks for the disposal of all domestic effluent. A case study will be presented for a remote indigenous community where the ET systems installed for greywater only have been monitored over the last two years since installation. The use of evapotranspiration has enabled reuse of effluent for successful examples of revegetation and food production and points to the need for a holistic approach to design and service delivery in these communities that includes a total environmental management plan.

SCH-202676: An allosteric modulator of both agonist and antagonist binding to G protein-coupled receptors

A novel thiadiazole compound, SCH-202676 (N-(2,3-diphenyl-1,2, 4-thiadiazol-5-(2H)-ylidene)methanamine), has been identified as an inhibitor of both agonist and antagonist binding to G protein-coupled receptors (GPCRs). SCH-202676 inhibited radioligand binding to a number of structurally distinct, heterologously expressed GPCRs, including the human mu-, delta-, and kappa-opioid, alpha- and beta-adrenergic, muscarinic M1 and M2, and dopaminergic D1 and D2 receptors, but not to the tyrosine kinase epidermal growth factor receptor. SCH-202676 had no direct effect on G protein activity as assessed by [35S]guanosine-5'-O-(gamma-thio)triphosphate binding to purified recombinant G(oalpha)- or G(betagamma)-stimulated ADP-ribosylation of G(oalpha) by pertussis toxin. In addition, SCH-202676 inhibited antagonist binding to the beta2-adrenergic receptor expressed in Escherichia coli, a system devoid of classical heterotrimeric G proteins. SCH-202676 inhibited radiolabeled agonist and antagonist binding to the alpha2a-adrenergic receptor with an IC50 value of 0.5 microM, decreased the Bmax value of the binding sites with a slight increase in the KD value, and inhibited agonist-induced activation of the receptor. The effects of SCH-202676 were reversible. Incubation of plasma membranes with 10 microM SCH-202676 did not alter subsequent radioligand binding to the alpha2a-adrenergic receptor and the dopaminergic D1 receptor. Taken together, our data suggest that SCH-202676 has the unique ability to allosterically regulate agonist and antagonist binding to GPCRs in a manner that is both selective and reversible. The scope of the data presented suggests this occurs by direct interaction with a structural motif common to a large number of GPCRs or by activation/inhibition of an unidentified accessory protein that regulates GPCR function.

On-site wastewater technologies in Australia

Domestic wastewater reuse is currently not permitted anywhere in Australia but is widely supported by the community, promoted by researchers, and improvised by up to 20% of householders. Its widespread implementation will make an enormous contribution to the sustainability of water resources. Integrated with other strategies in the outdoor living environment of settlements in arid lands, great benefit will be derived. This paper describes six options for wastewater reuse under research by the Remote Area Developments Group (RADG) at Murdoch University and case studies are given where productive use is being made for revegetation and food production strategies at household and community scales. Pollution control techniques, public health precautions and maintenance requirements are described. The special case of remote Aboriginal communities is explained where prototype systems have been installed by RADG to generate windbreaks and orchards. New Australian design standards and draft guidelines for domestic greywater reuse produced by the Western Australian State government agencies for mainstream communities are evaluated. It is recommended that dry composting toilets be coupled with domestic greywater reuse and the various types available in Australia are described. For situations where only the flushing toilet will suffice the unique 'wet composting' system can be used and this also is described. A vision for household and community-scale on-site application is presented.

Adequacy of anticoagulation in patients with atrial fibrillation coming to a hospital

STUDY OBJECTIVE

To evaluate the adequacy of anticoagulation in patients with atrial fibrillation (AF) coming to a hospital.

DESIGN

Retrospective medical record review.

SETTING

Tertiary care hospital.

PATIENTS

Consecutive patients with a history of AF who had been prescribed warfarin and who had the international normalized ratio (INR) measured when they arrived at the hospital. Those who developed AF as a complication during hospitalization were excluded.

MEASUREMENTS AND MAIN RESULTS

Of 1085 patients, 375 (mean age 73 yrs, 56.3% men) were eligible for further evaluation. Most had nonvalvular AF; in 44.5% the INR was subtherapeutic, in 36.5% it was therapeutic, and in 18.9% it was supratherapeutic. Patients admitted for any thromboembolic event and for ischemic stroke were significantly more likely to have subtherapeutic INRs.

CONCLUSION

It is well documented in the literature that warfarin is underprescribed, but our results suggest that even in treated patients, about half are inadequately protected from thromboembolism.

Recombinant full-length tissue factor pathway inhibitor fails to bind to the cell surface: implications for catabolism in vitro and in vivo

Tissue factor pathway inhibitor (TFPI) plays a key role in the regulation of tissue factor-initiated blood coagulation secondary to loss of the integrity of the blood vessel wall. TFPI is a naturally occurring Kunitz-type protease inhibitor that inhibits coagulation factor Xa and, in a factor Xa-dependent manner, mediates feedback inhibition of the factor VIIa/tissue factor catalytic complex. In vivo full-length TFPI is thought to be primarily bound to the vascular endothelium and the high affinity binding requires an intact carboxy terminus. Here we describe a full-length TFPI molecule, expressed in mouse C127 cells (TFPI(C127)), which exhibits virtually no cellular binding yet contains the intact carboxy terminus. This TFPI (TFPI(C127)) is neither internalized nor degraded via the TFPI endocytic receptor, LDL-receptor-related protein. Pharmacokinetic studies of TFPI(C127 )in vivo demonstrate a 10-fold prolongation in the plasma half-life, compared with that of bacterial recombinant TFPI. (Blood. 2000;95:1973-1978)

Functional characterization of mutations in melanocortin-4 receptor associated with human obesity

Melanocortin-4 receptor (MC4R) is a G protein-coupled receptor implicated in the regulation of body weight. Genetic studies in humans have identified two frameshift mutations of MC4R associated with a dominantly inherited form of obesity. We have generated and expressed the corresponding MC4R mutants in 293T cells and found that cells transfected with the truncation mutants failed to exhibit agonist binding or responsiveness despite retention of structural motifs potentially sufficient for binding and signaling. Immunofluorescence studies showed that the mutant proteins were expressed and localized in the intracellular compartment but absent from the plasma membrane, suggesting that these mutations disrupted the proper cellular transport of MC4R. Further studies identified a sequence in the cytoplasmic tail of MC4R necessary for the cell surface targeting. We further investigated a possible dominant-negative activity of the mutants on wild-type receptor function. Co-transfection studies showed that the mutants affected neither signaling nor cell surface expression of wild-type MC4R. We also characterized three human sequence variants of MC4R, but these exhibited identical affinities for peptide ligands and identical agonist responsiveness. Thus, unlike the obesity-associated MC4R truncation mutants, the polymorphisms of MC4R are unlikely to be contributors to human obesity.

The beta(2)-agonist salbutamol inhibits bronchoconstriction and leukotriene D(4) synthesis after dry gas hyperpnea in the guinea-pig

Isocapnic dry gas hyperpnea-induced bronchoconstriction (HIB) in the guinea-pig is mediated by both tachykinin release from airway sensory nerve C-type fiber terminals and secondary synthesis of cysteinyl-leukotrienes, in particular LTD(4). Beta (beta)(2)-agonists are potent bronchodilators but potentially could also inhibit the airway response to hyperpnea challenge via effects on the release of LTD(4)from airway cells in vivo. The purpose of this study was to test the hypothesis that beta(2)agonists attenuate HIB in guinea-pigs, in part, by reduction in LTD(4)release in vivo. Twenty-six guinea-pigs (400-550 g) were anesthetized with xylazine (7 mg/kg) and pentobarbital (65 mg/kg), tracheotomized and mechanically ventilated with a small animal ventilator using a tidal volume of 3 ml and a breathing frequency of 60 breaths/min. Dry gas (95%O(2)/5%CO(2)) with a 4 ml tidal volume and a breathing frequency of 150/min was used for hyperpnea challenge. Challenge with isocapnic dry gas triggered a significant increase in pulmonary resistance (0.3 +/- 0.02 vs. 0.57 +/- 0.06 cmH(2)O/ml per s; P=0. 017; n=13) and excretion of LTD(4)in the bile (baseline: 2.43 vs. HIB: 4.66 pmol/h; P=0.04). Salbutamol pretreatment completely blocked the airway response to the challenge (0.3+/-0.02 vs. 0.3+/-0. 05 cmH(2)O/ml per s; n=13) and reduced the biliary excretion of LTD(4)(baseline: 2.42 pmol/h; vs. HIB: 2.40 pmol/h). We conclude that salbutamol inhibited the airway responses to dry gas hyperpnea challenge and LTD(4)synthesis by the airway cells.

Immunohistochemical expression of p53 protein in invasive breast carcinoma: clinicopathologic correlations

The results of immunohistochemical expression of p53 protein in 106 invasive breast cancers were correlated with conventional pathologic prognostic parameters. Archival formalin-fixed, paraffin-embedded tissue sections of these cases were stained with a monoclonal antibody (Ab-2), raised against p53 protein using a peroxidase-labelled streptavidin biotin kit. Fifty-six (53%) showed positive nuclear staining; 31 were considered weakly, 21 moderately and 4 strongly positive. Forty-three (77%) of these positive cases stained less than 50% of the tumor cells, with a significant association between intensity and proportion of nuclei stained (p<0. 05). p53 staining also correlated with histologic grade (p<0.005) but not with tumor size nor clinical stage (p>0.05). The follow-up data did not reveal any statistically significant survival advantage for patients with p53 negative tumors.

A survey on the intended purposes and perceived utility of preoperative cardiology consultations

Cardiology consultations are often requested by surgeons and anesthesiologists for patients with cardiovascular disease. There can be confusion, however, regarding both the reasons for a consultation and their effect on patient management. This study was designed to determine the attitudes of physicians toward preoperative cardiology consultations and to assess the effect of such consultations on perioperative management. A multiple-choice survey regarding the purposes and utility of cardiology consultations was sent to randomly selected New York metropolitan area anesthesiologists, surgeons, and cardiologists. In addition, the charts of 55 consecutive patients aged >50 yr who received preoperative cardiology consultations were examined to determine the stated purpose of the consult, recommendations made, and concordance by surgeons and anesthesiologists with cardiologists' recommendations. Of the 400 surveys sent to each specialty, 192 were returned from anesthesiologists, 113 were returned from surgeons, and 129 were returned from cardiologists. There was substantial disagreement on the importance and purposes of a cardiology consult: intraoperative monitoring, "clearing the patient for surgery," and advising as to the safest type of anesthesia were regarded as important by most cardiologists and surgeons but as unimportant by anesthesiologists (all P < 0.05). Most surgeons (80.2%) felt obligated to follow a cardiologist's recommendations, whereas few anesthesiologists (16.6%) felt so obligated (P < 0.05). The most commonly stated purpose of the 55 cardiology consultations examined was "preoperative evaluation." Only 5 of these (9%) were obtained for patients in whom there was a new finding. Of the cardiology consultations, 40% contained no recommendations other than "proceed with case," "cleared for surgery," or "continue current medications." Recommendations regarding intraoperative monitoring or cardiac medications were largely ignored.

IMPLICATIONS

We conclude that there seems to be considerable disagreement among anesthesiologists, cardiologists, and surgeons as to the purposes and utility of cardiology consultations. A review of 55 consecutive cardiology consultations suggests that most of them give little advice that truly affects management.

Iron and the restless legs syndrome

STUDY OBJECTIVES

Using blinded procedures, determine the relation between serum ferritin levels and severity of subjective and objective symptoms of the restless legs syndrome (RLS) for a representative patient sample covering the entire adult age range.

DESIGN

All patient records from the past 4 years were retrospectively reviewed to obtain data from all cases with RLS. All patients were included who had ferritin levels obtained at about the same time as a polysomnogram (PSG), met diagnostic criteria for RLS, and were not on iron or medications that would reduce the RLS symptoms at the time of the PSG.

SETTING

Sleep Disorders Center.

PATIENTS

27 (18 females, 9 males), aged 29-81 years.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Measurements included clinical ratings of RLS severity and PSG measures of sleep efficiency and periodic limb movements (PLMS) in sleep with and without arousal. Lower ferritin correlated significantly to greater RLS severity and decreased sleep efficiency. All but one patient with severe RLS had ferritin levels < or = 50 mcg/l. Patients with lower ferritin (< or = 50 mcg/l) also showed significantly more PLMS with arousal than did those with higher ferritin, but the PLMS/hour was not significantly related to ferritin. This last finding may be due to inclusion of two 'outliers' or because of severely disturbed sleep of the more severe RLS patients.

CONCLUSIONS

These data are consistent with those from a prior unblinded study and suggest that RLS patients will have fewer symptoms if they have ferritin levels greater than 50 mcg/l.

Role of heparan sulfate proteoglycans in the uptake and degradation of tissue factor pathway inhibitor-coagulation factor Xa complexes

Tissue factor pathway inhibitor (TFPI) is a potent inhibitor of blood coagulation factor Xa (fXa) and factor VIIa. We have recently shown that fXa binding stimulates the uptake and degradation of cell surface-bound 125I-TFPI (Ho, G., Toomey, J. R., Broze, G. J., Jr., and Schwartz, A. L. (1996) J. Biol. Chem. 271, 9497-9502). In the present study we examined the role of cell surface glycosaminoglycans (GAGs) in this process. Removal of cell surface GAG chains by treatment of cells with heparinase or heparitinase but not chondroitinase markedly reduced fXa-stimulated 125I-TFPI uptake and degradation. Inhibition of GAG sulfation by growth of cells in chlorate-containing medium similarly decreased fXa-stimulated 125I-TFPI degradation. These results suggest that heparan sulfate proteoglycans (HSPGs) are required for the uptake and degradation of 125I-TFPI.fXa complexes. Chemical cross-linking/immunoprecipitation analyses revealed that 125I-TFPI was directly associated with HSPGs on the cell surface and that fXa binding increased the amount of 125I-TFPI bound. Of the several cell lines evaluated, bend endothelial cells demonstrated the greatest fXa stimulation of 125I-TFPI uptake and degradation. Cross-linking/immunoprecipitation analyses on bend cells also revealed that HSPGs were specifically associated with TFPI and fXa. These data suggest that HSPGs may directly act as the uptake and degradation receptor for TFPI.fXa complexes.

Potent tetracyclic guanine inhibitors of PDE1 and PDE5 cyclic guanosine monophosphate phosphodiesterases with oral antihypertensive activity

Tetracyclic guanines have been shown to be potent and selective inhibitors of the cGMP-hydrolyzing enzymes PDE1 and PDE5. In general, these compounds are inactive or only weakly active as inhibitors of PDE3, which is a major isozyme involved in cAMP hydrolysis. Structure-activity relationships are developed at N-1, C-2, N-3, and N-5 on the core nucleus. Compound 31, with an IC50 of 70 pM, is the most potent inhibitor of PDE1, while 50, with an IC50 of 4 nM, is the most potent inhibitor of PDE5. Compounds 20, 22, 30, and 50 are potent dual inhibitors with IC50 values below 30 nM for both PDE1 and PDE5. Compounds 12, 20, and 28 reduced blood pressure by more than 45 mmHg when administered orally at 10 mg/kg to the spontaneously hypertensive rat (SHR).

Substitution mutations in the myosin essential light chain lead to reduced actin-activated ATPase activity despite stoichiometric binding to the heavy chain

Myosin essential light chain (ELC) wraps around an alpha-helix that extends from the myosin head, where it is believed to play a structural support role. To identify other role(s) of the ELC in myosin function, we have used an alanine scanning mutagenesis approach to convert charged residues in loops I, II, III, and helix G of the Dictyostelium ELC into uncharged alanines. Dictyostelium was used as a host system to study the phenotypic and biochemical consequences associated with the mutations. The ELC carrying loop mutations bound with normal stoichiometry to the myosin heavy chain when expressed in ELC-minus cells. When expressed in wild type cells these mutants competed efficiently with the endogenous ELC for binding, suggesting that the affinity of their interaction with the heavy chain is comparable to that of wild type. However, despite apparently normal association of ELC the cells still exhibited a reduced efficiency to undergo cytokinesis in suspension. Myosin purified from these cells exhibited 4-5-fold reduction in actin-activated ATPase activity and a decrease in motor function as assessed by an in vitro motility assay. These results suggest that the ELC contributes to myosin's enzymatic activity in addition to providing structural support for the alpha-helical neck region of myosin heavy chain.