Phosphodiesterase 1b (PDE1B) Regulates Spatial and Contextual Memory in Hippocampus

Augmentation of cyclic nucleotide signaling through inhibition of phosphodiesterase (PDE) activity has long been understood to enhance memory. Efforts in this domain have focused predominantly on PDE4, a cAMP-specific phosphodiesterase implicated in consolidation. But less is known about the function of other PDEs expressed in neuroanatomical regions critical to memory. The PDE1 isoforms are the only PDEs to regulate neuronal cAMP and cGMP levels in a Ca²⁺/Calmodulin (CaM) dependent manner. Here, we show that knock-down of PDE1B in hippocampus of adult mice enhances contextual and spatial memory without effect on non-cognitive behaviors. Pharmacological augmentation of memory in rats was observed with a selective inhibitor of PDE1 dosed before and immediately after training, but not with drug dosed either 1 h after training or before recall. Our data clearly demonstrate a role for the PDE1B isoforms as negative regulators of memory, and they implicate PDE1 in an early phase of consolidation, but not retrieval. Inhibition of PDE1B is a promising therapeutic mechanism for treating memory impairment.

Effects of canola meal source on the standardized ileal digestible amino acids and apparent metabolizable energy contents for broiler chickens

Two studies were conducted to determine the effect of canola meal source on the standardized ileal digestible amino acids (AA) and nitrogen-corrected apparent metabolizable energy (AMEn) contents of canola meal (CM) from 6 processing plants in Canada. Two plants provided CM in both mash and pellet forms, while the other 4 provided CM in mash form only, giving a total of 8 samples. In the standardized ileal digestibility (SID) assay, 280 birds were housed 7 per cage and fed a commercial starter diet from 1 to 14 d of age followed by the test diets from 15 to 21 d. Diets were formulated to contain CM as the only source of protein. Chromic oxide was included in all diets as an indigestible marker. Diets were randomly assigned to 5 cages of 7 birds. On d 21, birds were euthanized by CO2 asphyxiation and digesta samples were collected from the terminal ileum for SID of AA. The SID values were calculated using ileal endogenous AA losses determination. In the AMEn assay, 330 birds were housed 6 per cage and fed a commercial starter diet from 1 to 14 d of age followed by the experimental diets from 15 to 19 d. The 8 experimental diets contained 30% of CM and 70% of a corn-soybean meal-based diet. There were differences (P < 0.05) among CM samples in the standardized ileal digestible content of all AA. Standardized ileal digestible contents of Arg, Lys, Met, and Thr averaged 2.17, 1.74, 0.53, and 1.03%, respectively. Pelleting reduced (P < 0.05) the standardized ileal digestible content of all AA in CM from one of the plants. There were differences (P<0.05) among CM samples in the AMEn contents with values ranging from 1,590 to 2,041 kcal/kg DM. In conclusion, there was effect of CM source on the standardized ileal digestible AA and AMEn contents. Regression equations for predicting standardized ileal digestible contents of selected AA from a simple measure of acid detergent fiber (ADF) were developed.

Standardized ileal digestible amino acid contents of canola meal from Canadian crushing plants for growing pigs

Studies have shown that there are variations in the chemical and nutritive composition of canola meal (CM) produced in Canada, some of which may result from differences among the canola seed crushing plants. Therefore, it is necessary to determine the variability in the nutritive value of CM as its end users desire increased meal consistency and more information on any potential variability in AA digestibility. Thus, 18 ileal cannulated barrows (average initial BW = 23.3 kg) were used to determine the apparent (AID) and standardized (SID) ileal digestibility of N and AA and standardized ileal digestible N and AA contents in CM from 6 processing plants in Canada. Two processing plants provided CM in both mash and pellet forms, whereas the other 4 provided it only in mash form, giving a total of 8 CM samples. The barrows were fed 9 cornstarch-based diets. The first 8 diets were formulated to contain the CM samples as the only source of AA. The ninth diet was a casein-cornstarch diet to determine ileal endogenous AA losses. All diets contained 0.3% titanium dioxide as an indigestible marker. Pigs were housed individually in pens and were fed the 9 diets in a completely randomized design for 3 periods to give 6 pigs per diet. Each experimental period lasted for 7 d, consisting of 5 d of adaptation and 2 d of ileal digesta collection at 2-h intervals from 0800 to 2000 h on d 6 and 7. There was an effect ( < 0.05) of CM source on 1) the AID of N, Met, Cys, Thr, Val, Gly, and Ser; 2) the SID of N, Met, and Cys; and 3) the standardized ileal digestible content of all AA. Pelleting reduced ( < 0.05) the standardized ileal digestible content of Arg, Ile, Glu, and Gly in 1 of the CM samples tested and of all AA except His in the other CM sample. The SID values for Arg, Lys, Met, and Thr averaged 87.2%, 78.2%, 84.5%, and 74.1%, respectively. The standardized ileal digestible contents of Arg, Lys, Met, and Thr averaged 2.10%, 1.71%, 0.50%, and 1.01%, respectively. In conclusion, there were variations in the AID, SID, and standardized ileal digestible AA contents of CM among crushing plants in Canada.

Studies on the SAR and pharmacophore of milnacipran derivatives as monoamine transporter inhibitors

Derivatives of milnacipran were synthesized and studied as monoamine transporter inhibitors. Potent analogs were discovered at NET (9k) and at both NET and SERT (9s and 9u). A pharmacophore model was established based on the conformational analysis of milnacipran in aqueous solution using NMR techniques and was consistent with the SAR results.

Thienopyrimidinone bis-aminopyrrolidine ureas as potent melanin-concentrating hormone receptor-1 (MCH-R1) antagonists

A series of thienopyrimidinone bis-aminopyrrolidine ureas were designed, synthesized, and evaluated for their ability to bind melanin-concentrating hormone receptor-1. These compounds exhibit potent binding affinity (K(i)=3 nM) and good in vitro metabolic stability.

Synthesis and structure–activity relationships of spirohydantoin-derived small-molecule antagonists of the melanin-concentrating hormone receptor-1 (MCH-R1)

The design, synthesis, and SAR of a series of substituted spirohydantoins are described. Optimization of an in-house screening hit gave compounds that exhibited potent binding affinity and functional activity at MCH-R1.

Synthesis and structure–activity relationships of retro bis-aminopyrrolidine urea (rAPU) derived small-molecule antagonists of the melanin-concentrating hormone receptor-1 (MCH-R1). Part 1

The design, synthesis, and SAR of a series of retro bis-aminopyrrolidine ureas are described. Compounds from this series exhibited potent binding affinity and functional activity at MCH-R1, and good oral bioavailability in rat.

A thienopyridazinone-based melanin-concentrating hormone receptor 1 antagonist with potent in vivo anorectic properties

Melanin-concentrating hormone receptor antagonists containing thieno- and a benzopyridazinone cores were designed and tested as potential anorectic agents. These ligands showed high affinity for the receptor, potent functional activity in vitro, and good oral bioavailabilty in rats. The thiophene analogue exhibited low iv clearance, long half-life, and high brain penetration. In obese rats, the thienopyridazinone demonstrated a dose-dependent reduction in feeding and body weight with doses between 1 and 10 mg kg-1.

Substituted chromones and quinolones as potent melanin-concentrating hormone receptor 1 antagonists

A series of substituted chromones were designed, synthesized, and evaluated for their ability to bind melanin-concentrating hormone receptor 1. Compounds with subnanomolar binding affinity and 66% oral bioavailability in rats were discovered.

Design and synthesis of tricyclic corticotropin-releasing factor-1 antagonists

Antagonists of the corticotropin-releasing factor (CRF) neuropeptide should prove to be effective in treating stress and anxiety-related disorders. In an effort to identify antagonists with improved physicochemical properties, new tricyclic CRF(1) antagonists were designed, synthesized, and tested for biological activity. As a result of studies aimed at establishing a relationship between structure and CRF(1) binding affinity, NBI 35965 (12a) was identified as a high-affinity antagonist with a pK(i) value of 8.5. Compound 12a proved to be a functional CRF(1) antagonist with pIC(50) values of 7.1 and 6.9 in the in vitro CRF-stimulated cAMP accumulation and ACTH production assays, respectively, and 12a also reduced CRF or stress induced ACTH production in vivo.

Design and synthesis of tricyclic imidazo[4,5-b]pyridin-2-ones as corticotropin-releasing factor-1 antagonists

The synthesis and SAR studies of tricyclic imidazo[4,5-b]pyridin-2-ones as human corticotropin-releasing factor receptor (CRF(1)) antagonists are discussed herein. Compound 16g was identified as a functional antagonist that inhibited CRF-stimulated cyclic adenosine monophosphate production and CRF-induced adrenocorticotrophic hormone release. Pharmacokinetics studies in rats showed that 16g was orally bioavailable, had good brain penetration, and had a moderate half-life. In our effort to identify CRF(1) antagonists with improved pharmacokinetics properties, 16g exhibited a favorably lower volume of distribution.

Potent, orally active corticotropin-releasing factor receptor-1 antagonists containing a tricyclic pyrrolopyridine or pyrazolopyridine core

Two new classes of tricyclic-based corticotropin-releasing factor (CRF(1)) receptor-1 antagonists were designed by constraining known 1H-pyrrolo[2,3-b]pyridine and 1H-pyrazolo[3,4-b]pyridine ligands. Pyrrole- and pyrazole-based molecules 19g and 22a, respectively, were discovered that potently bind the recombinant CRF(1) receptor (K(i) = 3.5, 2.9 nM) and inhibit adrenocorticotropic hormone (ACTH) release from rat pituitary cell culture (IC(50) = 14, 6.8 nM). These compounds show good oral bioavailabity (F = 24%, 7.0%) and serum half-lives in rats (t(1/2) = 6.3, 12 h) and penetrate the rat brain ([brain]/[plasma] = 0.27, 0.52) but tend toward large volumes of distribution (V(D) = 38, 44 L kg(-1)) and rapid clearances (CL = 70, 43 mL min(-1) kg(-1)). When given orally, both the pyrazole and the pyrrole leads dose-dependently inhibit stress-induced ACTH release in vivo. ACTH reductions of 84-86% were observed for 30 mg kg(-1) doses.

Synthesis and structure–activity relationships of biarylcarboxamide bis-aminopyrrolidine urea derived small-molecule antagonists of the melanin-concentrating hormone receptor-1 (MCH-R1)

A novel series of bis-aminopyrrolidine ureas containing either a 4-biphenylcarboxmide or 5-phenyl-2-thiophenecarboxamide group have been identified as potent and functional antagonists of the melanin-concentrating hormone receptor-1. Syntheses and SAR are described, which led to the discovery of compounds with high binding affinity (Ki = 1 nM) for the receptor. Preliminary in vitro metabolic stability data are also reported for key compounds.

Bis(aminopyrrolidine)-derived ureas (APUs) as potent MCH1 receptor antagonists

Ureas derived from two substituted 3-aminopyrrolidine subunits were prepared as constrained analogs of a linear lead compound and tested as antagonists of the MCH(1) receptor. The series was optimized for substitution and stereochemistry to generate a functional antagonist with a K(i) of 3.3 nM and IC(50) of 12 nM (GTPgammaS).

Aryl piperazine melanocortin MC4 receptor agonists

Incorporation of substituted phenyl piperazine privileged structures into a known MC4 specific dipeptoid consensus sequence resulted in a series of potent (EC(50)=24 nM) and selective MC4-R agonists. We report the SAR of this series of compounds using in vitro cAMP functional assays in cells transfected with the MC4 or other melancortin receptors.

Potent imidazole and triazole CB 1 receptor antagonists related to SR141716

Diarylimidazolecarboxamides and diaryltriazolecarboxamides related to SR141716 were synthesized and tested for binding to the human CB(1) receptor. Suitably substituted imidazoles are comparably potent to the clinical candidate, whereas the analogous triazoles are less so due to the absence of an additional substituent on the azole ring.

Characterization of a toxin A-negative, toxin B-positive strain of Clostridium difficile responsible for a nosocomial outbreak of Clostridium difficile-associated diarrhea

Clostridium difficile-associated diarrhea (CAD) is a very common nosocomial infection that contributes significantly to patient morbidity and mortality as well as to the cost of hospitalization. Previously, strains of toxin A-negative, toxin B-positive C. difficile were not thought to be associated with clinically significant disease. This study reports the characterization of a toxin A-negative, toxin B-positive strain of C. difficile that was responsible for a recently described nosocomial outbreak of CAD. Analysis of the seven patient isolates from the outbreak by pulsed-field gel electrophoresis indicated that this outbreak was due to transmission of a single strain of C. difficile. Our characterization of this strain (HSC98) has demonstrated that the toxin A gene lacks 1.8 kb from the carboxy repetitive oligopeptide (CROP) region but apparently has no other major deletions from other regions of the toxin A or toxin B gene. The remaining 1.3-kb fragment of the toxin A CROP region from strain HSC98 showed 98% sequence homology with strain 1470, previously reported by M. Weidmann in 1997 (GenBank accession number Y12616), suggesting that HSC98 is toxinotype VIII. The HSC98 strain infecting patients involved in this outbreak produced the full spectrum of clinical illness usually associated with C. difficile-associated disease. This pathogenic spectrum was manifest despite the inability of this strain to alter tight junctions as determined by using in vitro tissue culture testing, which suggested that no functional toxin A was produced by this strain.

Regional dissemination and control of epidemic methicillin-resistant Staphylococcus aureus. Manitoba Chapter of CHICA-Canada

A methicillin-resistant Staphylococcus aureus (MRSA) strain introduced into the largest tertiary-care teaching hospital in Manitoba in 1993 led to a sustained outbreak with secondary outbreaks at one community hospital, two large long-term-care facilities, and nosocomial transmission at a second teaching hospital. Control measures were consistent at each institution and were coordinated on a province-wide basis. MRSA is not currently endemic in any facility in the province.

Diabetes update with a cardiac perspective

Diabetes is a chronic illness that affects 6% of the U.S. population. In daily practice, nurses have the opportunity to share with patients and colleagues recent advances in the management of diabetes to improve outcomes. Given the prevalence of heart disease in this population, nurses in the cardiovascular field have the unique opportunity to initiate risk-reduction strategies and collaborate with diabetes team members to optimize qualify of life for patients with diabetes.

Nosocomial pneumonia on general medical and surgical wards in a tertiary-care hospital

OBJECTIVE

To describe the demographic, clinical, and microbiologic characteristics of patients who develop nosocomial pneumonia on general medical and surgical wards of a tertiary-care hospital.

DESIGN

A 1-year, prospective, descriptive study.

SETTING

A 1,100-bed, tertiary-care, urban hospital.

POPULATION

Patients experiencing nosocomial pneumonia were identified through surveillance on general medical and surgical wards, using a standard case definition.

RESULTS

92 pneumonias in 85 patients on general wards were identified. The mean age of patients was 63 +/- 17 years, 55 patients (65%) were male, and 75 cases of pneumonia (81%) were acquired on surgical wards. Bacteremia was identified in 8 (13%) of 62 episodes, and 48 (52%) grew potential pathogens from respiratory specimens. Twenty-six patients (28%) required transfer to the intensive-care unit (ICU), and 20 (22%) received mechanical ventilation. By multivariate analysis, patients with a thoracic surgical procedure or with Staphylococcus aureus isolated from respiratory secretions were more likely to require ICU admission. The overall mortality rate was 20% (17/85), with a directly associated mortality of 14% (12/85). Patients who died were older, more frequently resided on a medical ward, and had a greater mean number of comorbidities. These patients often were treated nonaggressively and were not considered candidates for ICU admission due to advanced age and poor underlying clinical status.

CONCLUSIONS

Although the morbidity of nosocomial pneumonia in this population was high, as evidenced by high rates of transfer to ICU, the directly associated mortality was relatively low. Those requiring ICU admission require further study to identify preventive measures that could decrease the morbidity in this group. Interventions to prevent pneumonia or to improve prognosis may not be feasible for the majority of these patients who die from nosocomial pneumonia.

Rapid geographic spread of a methicillin-resistant Staphylococcus aureus strain

In May 1993, an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) was identified at our tertiary care teaching center. The epidemic MRSA strain was transmitted efficiently in the hospital environment. Subsequent investigations indicated that the strain had been introduced into western Canada by a patient who had recently been hospitalized for 3 months in the Punjab, India, and had been admitted to a hospital in rural British Columbia shortly after his arrival in Canada. Transfer of the patient to a hospital in Vancouver and subsequent transfer of a colonized patient contact to a hospital in Winnipeg, Manitoba, resulted in major outbreaks of MRSA at these two large tertiary care centers within 6 weeks of the arrival of the index case in Canada. Epidemiological typing of the S. aureus coagulase gene with use of a polymerase chain reaction method and pulsed-field gel electrophoresis documented clonality of this strain. These outbreaks again illustrate both the propensity of certain strains of S. aureus to produce epidemic disease, including rapid spread within the institutional setting, and the global nature of problems with antimicrobial resistance.

Respiratory interaction after spinal anesthesia and sedation with midazolam

The combined use of midazolam and spinal anesthesia is common in clinical practice. Despite the known potential for each to alter ventilation, the effect of their interaction has not been examined. Nineteen healthy volunteers were studied to assess the impact of intravenous midazolam (0.05 or 0.075 mg/kg), spinal anesthesia (T3-T8; mean level, T6), and their combination on resting ventilation and ventilatory responses to progressive hyperoxic hypercapnia. Resting ventilatory pattern was altered significantly by each condition. Midazolam caused a 29% decrease in resting tidal volume and a 24% decrease in mean inspiratory flow rate, while respiratory frequency increased by 14% and minute ventilation remained unchanged. By contrast, spinal anesthesia alone caused a 32% increase in tidal volume, a 24% increase in mean inspiratory flow rate, and a 13% increase in minute ventilation accompanied by a 14% decrease in respiratory frequency. The combination of midazolam and spinal anesthesia caused a significant decrease in minute ventilation (19%), tidal volume (28%), and mean inspiratory flow rate (27%), all of which were significantly more than the predicted sum of the individual interventions. Midazolam and spinal anesthesia each produced a significant decrease in hypercapnic ventilatory response slope, whereas their combination provoked no net change in hypercapnic ventilatory response slope. Interpretation of the hypercapnic ventilatory response data was complicated by shifts in the position of the ventilatory response curve, particularly under the spinal anesthesia condition. It is concluded that intravenous midazolam depresses resting ventilation, spinal anesthesia stimulates resting ventilation, and their combination has a modest synergistic effect of depressing resting ventilation.

Nosocomial pneumonia in a Canadian tertiary care center: a prospective surveillance study

OBJECTIVE

To determine the contribution of etiologic agents, including Legionella pneumophila and respiratory viruses to nosocomial pneumonia at a tertiary care center.

DESIGN

Prospective surveillance of nosocomial pneumonia with standardized laboratory investigations.

SETTING

A 1,100-bed tertiary care center.

PATIENTS

All adult inpatients.

RESULTS

One hundred and thirty-five Nosocomial pneumonias (5.7/1,000 discharges) were identified. Four (3.0%) were L pneumophila serogroup 1 infections (0.17/1,000 discharges). Legionellosis occurred in non-high-risk patients, and three cases would not have been identified without active surveillance. Viral seroconversion was identified in seven (19%) of 36 cases with specimens available (0.59/1,000 discharges): five influenza B, one influenza A, and one respiratory syncytial virus. IgM serology was positive in one case each for Mycoplasma pneumoniae and Chlamydia species. No geographical clustering was observed for viral infections, and these would not have been identified without active surveillance. Mortality for all nosocomial pneumonia was 25%. Patient factors significantly associated with a poorer outcome included older age, underlying disease, low serum albumin, renal insufficiency, lower platelet count, endotracheal intubation, respiratory failure, bacteremia, and use of antacids.

CONCLUSIONS

This prospective surveillance suggested that L pneumophila and viral agents were uncommon causes of nosocomial pneumonia at our institution during this surveillance period.

Age-related cognitive recovery after general anesthesia

This study was designed to quantify the rate of mental recovery in elderly and young patients after general anesthesia for intraabdominal surgery (cholecystectomy). Forty patients (25-83 yr) were given four tests assessing neuropsychological function once preoperatively and on five occasions postoperatively. Two of the four neuropsychological tests showed impairment in scores in the elderly patients on the first postoperative day (Symbol Digit Modalities Test, P less than 0.004; The Trail Making Test, P less than 0.03). In addition, one of the tests (Symbol Digit Modalities Test) showed a deterioration in the younger patients (P less than 0.05). The changes that did occur in these tests on the first postoperative day reverted to baseline levels thereafter. There were no significant changes in the remaining two tests, the Mini Mental State Test or the Digit Span Test, at any time in either group. We conclude that postoperative mental deterioration is no greater in elderly than in young patients.