Previously, our laboratories have reported on a new class of highly potent tyrosine kinase inhibitors based on the pyrido2,3-dpyrimidine core template. To understand the structural basis for the ...potency and specificity, a model for the binding mode of this class of inhibitors to the tyrosine kinase domains of c-Src, PDGFr, FGFr, and EGFr tyrosine kinases was developed from structural information (principally utilizing the catalytic domain of c-AMP-dependent protein kinase as template) and structure−activity relationship (SAR) information. In the resulting docking mode, the pyrido2,3-dpyrimidine template shows a hydrogen-bonding pattern identical to that of olomoucine. The 6-aryl substituent of the heterocycle is located deep in the binding cleft in a pocket not used by ATP, which helps to confer high-affinity binding as well as specificity. The 2-anilino and 2-(dialkylamino)alkylamino substituents as well as the 7-urea substituent of inhibitors within this class are located at the entrance of the binding cleft and make contact with residues in the hinge region between the two kinase lobes. This allows considerable variability and bulk tolerance for C-2 and N-7 substituents. The models presented here are consistent with the SAR seen for the inhibition of a number of isolated enzymes and provide a structural basis to explain their specificity. They have been used successfully to design new highly potent protein kinase inhibitors.
A series of 6-substituted 4-anilinopyrimido5,4-dpyrimidines has been prepared and shown to be potent inhibitors of the tyrosine kinase activity of the epidermal growth factor receptor (EGFR). These ...compounds are structurally related to the pyrido3,2-d- and pyrido3,4-dpyrimidines previously shown to be EGFR inhibitors. Their structure−activity relationships (SAR) for inhibition of the isolated enzyme more closely resemble those of the 3,2-d than the 3,4-d pyridopyrimidine isomers. This suggests the requirement of an aza atom in the 7- but not the 5-position (i.e., a carbon atom in the 5-position) for the enhanced potency shown by 6-N-methylated derivatives in each series. X-ray crystal structures were determined for the three NHMe derivatives 2, 3, and 5c in the pyrido3,2-d-, pyrido3,4-d-, and pyrimido5,4-dpyrimidine series, respectively. These show that a carbon rather than a nitrogen atom at the 5-position leads to significant conformational changes in the molecule (a longer C5a−C4 bond and a 30° out-of-plane rotation of the phenyl group), due to the requirement to relieve nonbonding interactions between the C5 and N9 protons. Pyrimido5,4-dpyrimidine analogues bearing bulky, weakly basic solubilizing side chains linked to the 6-position through a secondary amine generally retained potency both against the isolated enzyme and for inhibition of autophosphorylation of EGFR in intact A431 cells. This agrees with a recent binding model that suggests this general class of compounds binds to EGFR with the 6-position located in an area of comparative bulk tolerance at the entrance to the ATP-binding pocket. While these solubilized pyrimido5,4-dpyrimidine analogues were less potent than the NHMe derivative 5c in the isolated enzyme assay, some were considerably superior to 5c (and among the most potent ever reported) as inhibitors of EGFR autophosphorylation in cellular assays.
A series of piperazinone ring systems have been synthesised as a means of evaluating the effect of conformational restriction on high affinity non-peptide NK
1, NK
3 and CCK-B receptor ligands. The ...synthesis of the targeted heterocycles is described along with a discussion of their affinities for their respective receptor types.
A series of piperazinone ring systems (
1) have been synthesised as a means of evaluating the effect of conformational restriction on NK
1, NK
3 and CCK-B receptor ligands.
The stereochemistry of chalcomycin (
1), a neutral 16-membered macrolide antibiotic, was established by X-ray crystallography. A correlation model for 16-membered macrolides (
2), together with its ...biochemical rationale, is presented and applied to the configurational assignment of seven other analogous neutral macrolides (aldgamycins F, G, CP-61,884 complex, neutramycin, and swalpamycin). The chalcomycin molecule appears to be conformationally restrained in a rigid manner.
Stereochemistry of chalcomycin is established. A correlation model for 16-membered macrolide antibiotics, with biochemical rationale, is applied to the configurational assignment of seven analogous neutral macrolides.
The putative neural target sites of progesterone (P) action for the facilitation of estrous behavior in female rats were reexamined using the hormone implant technique. Subjects were ovariectomized, ...estrogen-primed Long-Evans females. All were outfitted with bilateral double barreled cannulae assemblies consisting of 23-gauge guide cannulae and 28-gauge inserts. Subjects in Exp 1 received sc injections of individually determined threshold priming doses of estradiol benzoate. Estrogenic priming for subjects in Exp 2 was provided by sc placed Silastic capsules (5 mm) filled with 17 beta-estradiol-cholesterol (1:20). Each subject was tested for estrous behavior with a male after P-filled cannulae and after blank inserts were lowered into the brain. Behavioral tests were conducted 1 and 4.5 h postcannulae placement. Thirty-five of 40 females with P in the ventromedial hypothalamus exhibited high levels of lordosis behavior during the 4.5-h test. Moreover, 29 of the 35 exhibited solicitation behavior as well. Estrous behavior was not exhibited by these animals during the 1-h test. Implants in other regions of the brain (i.e. mesencephalic reticular formation, preoptic area, central grey, caudate putamen, and hippocampus; n = 80) did not consistently facilitate estrous responsiveness. In Exp 3, levels of estrous responsiveness were similar before and after adrenalectomy (n = 10); thus, facilitation of estrous behavior by P-filled implants in the ventromedial hypothalamus was not dependent upon activation of the hypothalamic-pituitary-adrenal axis.
We have previously demonstrated that consuming ethanol at low levels 24 hr prior to ischemia/reperfusion (EPC) prevents postischemic leukocyte‐endothelial cell adhesive interactions (LEI) by a ...mechanism that is initiated by nitric oxide (NO) formed by endothelial NO synthase (eNOS). Recent work indicates that:
ethanol increases the activity of 5′‐AMP‐activated protein kinase (AMPK) and
AMPK phosphorylates eNOS at Ser1177.
In light of these observations, we postulated that AMPK may play a role in triggering the development of the anti‐inflammatory phenotype induced by EPC. Ethanol was administered to C57BL/6 mice by gavage in the presence or absence of AMPK inhibition. 24 hrs later, the numbers of rolling and adherent leukocytes in the small intestine were recorded using an intravital microscopic approach after 45 min of ischemia and 60 min of reperfusion (I/R) or at equivalent time points in control animals. I/R induced a marked increase in LEI relative to sham control mice. The increase in LEI was prevented by EPC, an effect that was lost with AMPK inhibition during the period of ethanol exposure. Pilot data in AMPK α2 KO mice suggests that the anti‐inflammatory effect of EPC is dependent on this isoform. Our results indicate that the beneficial actions of ethanol ingestion to prevent postischemic leukocyte rolling and adhesion are initiated by an AMPK‐dependent mechanism.
Supported by AA14945 and DK 43785.
In Reply Cohen, Ronald J.; Wheeler, Thomas M.; Bonkhoff, Helmut ...
Archives of pathology & laboratory medicine (1976),
03/2008, Letnik:
132, Številka:
3
Journal Article
Reperfusion of ischemic skeletal muscle leads to adverse local and systemic effects. These detrimental effects may be attenuated by interfering with or modulating the pathophysiological processes ...that are set in motion during ischemia and/or reperfusion. The purpose of this paper is to review the different intervention strategies that have been employed in an attempt to elucidate the mechanisms involved in the pathogenesis of skeletal muscle ischemia-reperfusion injury. The results of these studies indicate that the postischemic injury processes that lead to cell dysfunction and death are multifactorial in nature and include oxidant generation, elaboration of proinflammatory mediators, infiltration of leukocytes, Ca2+ overload, phospholipid peroxidation and depletion, impaired nitric oxide metabolism, and reduced ATP production. Although the etiopathogenesis of skeletal muscle ischemia-reperfusion is complex, careful delineation of the mechanisms that contribute to postischemic microvascular dysfunction and muscle necrosis has progressed to the point where rational intervention strategies may be proposed and implemented as potential treatments for skeletal muscle dysfunction associated with ischemia-reperfusion.
We describe a college student, A.H., with a developmental deficit in determining the location of objects from vision. The deficit is selective in that (a) localization from auditory or tactile ...information is intact; (b) A.H. reports the identity of mislocalized objects accurately; (c) visual localization errors preserve certain parameters of the target location; and (d) visual localization is severely impaired under certain stimulus conditions, but nearly intact under other conditions. These results bear on the representation and processing of location information in the visual system, and also have implications for understanding developmental dyslexia.
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