Identification,synthesis and SAR of amino substituted pyrido[3,2b]pyrazinones as potent and selective PDE5 inhibitors

A new class of potent and selective PDE5 inhibitors is disclosed. Guided by X-ray crystallographic data, optimization of an HTS lead led to the discovery of a series of 2-aryl, (N8)-alkyl substituted-6-aminosubstituted pyrido[3,2b]pyrazinones which show potent inhibition of the PDE5 enzyme. Synthetic details and some structure–activity relationships are also presented.     

The biological effects of polybrominated biphenyls in avian species.

Polybrominated biphenyl (PBB), structurally similar to polychlorinated biphenyl (PCB), affects feed intake, egg production, and hatchability of fertile eggs in chickens and quail. Subcutaneous edema of the neck and shoulder are common abnormalities of hatched chicks from PBB-fed dams. No characteristic teratogenicity is evident. Offspring hatched are less viable during their first 3 weeks of life. PBB does not produce thinner egg shells or lower egg weights. The ratio of PBB egg content to dietary level is 1.3-1.5:1.0. The biological half-life of PBB in eggs is calculated to be 17 days. Tissue residues are higher in males than females because egg production is a major excretory route for PBB. Polybrominated biphenyl feeding causes tissue changes in size, structure and/or function in the liver, thyroid, testes, comb, heart, spleen, bursa of Fabricus, and blood. Liver enlargement, porphyria and microsomal enzyme induction results from PBB administration. The spleen, bursa and comb are reduced in size, whereas the thyroid increases after PBB feeding. A characteristic of PBB and PCB toxicity is hydropericardium and general edema.     

Effect of electro-ejaculation frequency on semen characteristics in the ferret (Mustela putorius) (a)

Ten sexually mature male ferrets were electro-ejaculated at 1, 3 and 5-day intervals to ascertain the effects of ejaculation frequency on semen quality. Semen volume, spermatozoa concentration, spermatozoal motility, as well as the number of stimuli required to obtain an ejaculation were recorded. No significant differences in these parameters were noted between the test intervals for 1 to 3-year-old males. The data indicated that male ferrets from 1 to 4 years of age may be ejaculated as frequently as once per day for short periods of time without any apparent adverse effects on semen quality.     

Stain Technology: A Phenylhydrazine-Leucofuchsin Sequence for Staining Nerves and Nerve Endings in the Integument of Poultry

This sequence for staining cutaneous nerves and nerve endings uses 1% formic acid as a fixative for 1 hr, followed by two treatments of 5 min each in 6% H₂SO₄. The tissue is then submerged in fresh 5% phenylhydrazine hydrochloride for 30 min, washed in running tap water for 10 min, and given a 5 min soak in distilled water. The specimen is placed in Lillie's “cold Schiff” reagent for 4 hr; transferred to 6% H₂SO₄, 4 changes of 5 min each; washed in distilled water, 3 changes of 5 min each; dehydrated in acetone, 4 changes of 10 min each; and cleared in 2 changes of methyl benzoate, the 1st for 1 hr and the 2nd until the tissue clears. Nerve fibers stain pinkish-purple; muscles also take up the stain, yet the nerves are discernible from the muscles. All other tissue remain unstained.     

Ink Perfusion for Displaying Capillaries in the Chicken

A chicken was anesthetized with Na-phenobarbital, 130 mg/kg, and the external ischiatic artery was exposed. Heparin, 90 units/kg, was injected into the brachial vein, after which a cannula was inserted into the exposed ischiatic artery. Heat was applied to the head to produce vasodilation. Perfusion through the cannula was made at about 150 mm Hg pressure and consisted of 30 ml of a biological type of Pelikan ink to which was added NaNO₂ to make a 0.02% solution. After the bird was killed by an overdose of anesthetic, the skin around the perimeter of the femoral feather tract was cauterized, the tract removed, attached to a stainless steel wire net, fixed for 1 hr in 10% formic acid, then dehydrated in 4 changes of acetone, 1 hr each, followed by a 5th change for 12 hr. The dehydrated specimens were placed in methyl benzoate, the 1st change for 1 hr and the 2nd until clear (3-15 hr). This procedure exhibits small vessels and capillary networks within the integument, but if only the vessels larger than capillaries are to be studied, they can be shown by slowly injecting 15-30 ml of the perfusion mixture into a peripheral vein. The still beating heart will distribute the ink to other regions of the body, thus allowing the vessels to be traced in excised tissue.     

Substrate specificity of ribosomal peptidyltransferase. Effect of modification in the heterocyclic, carbohydrate and amino acid moiety of 2'(3')-O-L-phenylalanyladenosine.

The chemical synthesis of 2'(3')-O-L-phenylalanyl derivatives of nebularine (Ld), 6-methoxynebularine (Ih), N6,N6-dimethyladenosine (Lk), 6-methylthionebularine (Lo), 8-bromoadenosine (Lr), tubercidin (Iu), and 3'-O-L-phenylalanyl derivatives of 1-(beta-D-arabinofuranosyl)cytosine (IIIg) and 9-(beta-D-arabinofuranosyl)adenine (IIIl) is described. 2'(3')-O-(3-Phenyl)propionyladenosine (Iv) was obtained by reaction of adenosine with ethyl 3-phenylorthopropionate and subsequent hydrolysis of the orthoester intermediate IV with formic acid. Compounds Id, Ih, Ik, Io, and Iu were active in the release of Ac-Phe from N-Ac-Phe-tRNA-poly(U)-70S ribosome complex: at 0.01 mM the release of Ac-Phe was 50-100% of that of A-Phe. At 1 mM, compounds Ir and IIIg released 30 and 25% of Ac-Phe relative to A-Phe whereas derivatives Iv and IIIl were virtually inactive. The results indicate the following conclusions regarding ribosomal peptidyltransferase activity of 2'(3')-O-aminoacyl nucleosides: (a) the presence of the 2'-hydroxy group in the ribo configuration is more important for a highly active substrate (A-Phe) than for one of moderate activity (C-Phe); (b) the heterocyclic (purine) residue is in the anti conformation although this requirement is not absolute; (c) the presence of the amino group of the aminoacyl moiety is required; (d) acceptor activity is dependent upon the substituent in the position 6 of the purine moiety.     

Temperature regulation in adult quail (Colinus virginianus) during acute thermal stress

1. Evaporative heat loss, O2 consumption, CO2 production, and internal body temperature were measured in unanesthetized, unrestrained bobwhite (Colinus virginianus) at specific ambient temperatures (Ta). 2. No significant change in body temperature occurred at any Ta tested, but metabolic heat production (H) increased from 42.17 W/m2 at Ta 35 degrees C to 102.89 W/m2 at Ta 10 degrees C. 3. Evaporative heat loss (E) increased approximately two-fold from Ta 10-35 degrees C, with E/H increasing exponentially over the same temperature range. 4. No significant change in thermal insulation occurred from Ta 10-30 degrees C. 5. Combined convective and radiative heat transfer for the bobwhite was 2.96 W/m2 X C from Ta 10-35 degrees C.