Spatial learning in transgenic mice expressing human presenilin 1 (PS1) transgenes.

Dominant mutations in the Presenilin 1 gene are linked to an aggressive, early-onset form of familial Alzheimer's Disease (FAD). Spatial memory of transgenic (Tg) mice expressing either mutant (lines Tg(M146L)1, Tg(M146L)76, Tg(L286V)198) or wild type (line Tg(PS1wt)195) human PS1 transgenes was investigated in the Morris water maze (WM) test at 6 and 9 months of age. The results showed that the mutated Tg mice had increased swim speed when compared to non-Tg littermates or Tg PS1 wild type mice. The swim speed difference did not, however, significantly affect the spatial learning in the WM test and all groups showed comparable search paths during training and similar spatial bias during probe trials. When re-tested at 9 months, all mice showed significantly improved learning acquisition of spatial information. The lack of progressive spatial learning impairment in mice expressing the mutated human PS1 transgene in the WM does not preclude impairments in other cognitive tasks but suggests that full phenotypic expression of mutant PS1 alleles may require co-expression of human versions of other AD-associated genes.

Ontario, Canada, high school teachers as enforcers in the war on drugs: what their students see and say.

This paper examines how high school teachers interact with students on the subject of marijuana. Results, based on 49 focus groups with 278 high school students in Ontario, Canada, reveal three basic assumptions of the students: 1) only some teachers can actually tell when a student is high on marijuana; 2) many teachers have tried marijuana or continue to use it; and 3) individual teachers vary in how they respond to students who are high. Results suggest that changes in the relationship between marijuana and authority account in large part for the seeming reluctance of so many teachers to exercise their mandate to discipline students who use marijuana. The reasons for this are twofold: 1) many teachers do not see use of marijuana of and by itself as a threat to their authority; and 2) teachers who choose to confront users run the risk of having their authority and independence of action undermined once they report infractions to administrators who have authority over teachers and students alike.

Design, synthesis, and biological activities of potent and selective somatostatin analogues incorporating novel peptoid residues.

We report the synthesis, bioactivity, and structure-activity relationship studies of compounds related to the Merck cyclic hexapeptide c[Pro6-Phe7-d-Trp8-Lys9-Thr10-Phe11], L-363,301 (the numbering in the sequence refers to the position of the residues in native somatostatin). The Pro residue in this compound is replaced with arylalkyl peptoid residues. We present a novel approach utilizing beta-methyl chiral substitutions to constrain the peptoid side-chain conformation. Our studies led to molecules which show potent binding and increased selectivity to the hsst2 receptor (weaker binding to the hsst3 and hsst5 receptors compared to L-363, 301). In vivo, these peptoid analogues selectively inhibit the release of growth hormone but have no effect on the inhibition of insulin. The biological assays which include binding to five recombinant human somatostatin receptors carried out in two independent laboratories and in vivo inhibition of growth hormone and insulin provide insight into the relationship between structure and biological activity of somatostatin analogues. Our results have important implications for the study of other peptide hormones and neurotransmitters.

Design, synthesis, and pharmacological evaluation of conformationally constrained analogues of N,N'-diaryl- and N-aryl-N-aralkylguanidines as potent inhibitors of neuronal Na+ channels.

In the present investigation, the rationale for the design, synthesis, and biological evaluation of potent inhibitors of neuronal Na+ channels is described. N,N'-diaryl- and N-aryl-N-aralkylguanidine templates were locked in conformations mimicking the permissible conformations of the flexible diarylguanidinium ion (AS+, AA+, SS+). The resulting set of constrained guanidines termed "lockamers" (cyclophane, quinazoline, aminopyrimidazolines, aminoimidazolines, azocino- and tetrahydroquinolinocarboximidamides) was examined for neuronal Na+ channel blockade properties. Inhibition of [14C]guanidinium ion influx in CHO cells expressing type IIA Na+ channels showed that the aminopyrimidazoline 9b and aminoimidazoline 9d, compounds proposed to lock the N,N'-diarylguanidinium in an SS+ conformation, were the most potent Na+ channel blockers with IC50's of 0.06 microM, a value 17 times lower than that of the parent flexible compound 18d. The rest of the restricted analogues with 4-p-alkyl substituents retained potency with IC50 values ranging between 0.46 and 2.9 microM. Evaluation in a synaptosomal 45Ca2+ influx assay showed that 9b did not exhibit high selectivity for neuronal Na+ vs Ca2+ channels. The retention of significant neuronal Na+ blockade in all types of semirigid conformers gives evidence for a multiple mode of binding in this class of compounds and can possibly be attributed to a poor structural specificity of the site(s) of action. Compound 9b was also found to be the most active compound in vivo based on the high level of inhibition of seizures exhibited in the DBA/2 mouse model. The pKa value of 9b indicates that 9b binds to the channel in its protonated form, and log D vs pH measurements suggest that ion-pair partitioning contributes to membrane transport. This compound stands out as an interesting lead for further development of neurotherapeutic agents.

A backbone-cyclic, receptor 5-selective somatostatin analogue: synthesis, bioactivity, and nuclear magnetic resonance conformational analysis.

Cyclo(PheN2-Tyr-D-Trp-Lys-Val-PheC3)-Thr-NH2 (PTR 3046), a backbone-cyclic somatostatin analogue, was synthesized by solid-phase methodology. The binding characteristics of PTR 3046 to the different somatostatin receptors, expressed in CHO cells, indicate high selectivity to the SSTR5 receptor. PTR 3046 is highly stable against enzymatic degradation as determined in vitro by incubation with rat renal homogenate and human serum. The biological activity of PTR 3046 in vivo was determined in rats. PTR 3046 inhibits bombesin- and caerulein-induced amylase and lipase release from the pancreas without inhibiting growth hormone or glucagon release. The major conformation of PTR 3046 in CD3OH, as determined by NMR, is defined by a type II' beta-turn at D-Trp-Lys and a cis amide bond at Val-PheC3.