Degradation of transcription factor RFX5 during the inhibition of both constitutive and interferon gamma-inducible major histocompatibility complex class I expression in chlamydia-infected cells

We have previously shown that the obligate intracellular pathogen chlamydia can suppress interferon (IFN)-gamma-inducible major histocompatibility complex (MHC) class II expression in infected cells by degrading upstream stimulation factor (USF)-1. We now report that chlamydia can also inhibit both constitutive and IFN-gamma-inducible MHC class I expression in the infected cells. The inhibition of MHC class I molecule expression correlates well with degradation of RFX5, an essential downstream transcription factor required for both the constitutive and IFN-gamma-inducible MHC class I expression. We further demonstrate that a lactacystin-sensitive proteasome-like activity identified in chlamydia-infected cell cytosolic fraction can degrade both USF-1 and RFX5. This proteasome-like activity is dependent on chlamydial but not host protein synthesis. Host preexisting proteasomes may not be required for the unique proteasome-like activity. These observations suggest that chlamydia-secreted factors may directly participate in the proteasome-like activity. Efforts to identify the chlamydial factors are underway. These findings provide novel information on the molecular mechanisms of chlamydial evasion of host immune recognition.

[The value of color Doppler ultrasonography in diagnosing aneurysm]

Using Doppler ultrasound, we detected 59 patients with aneurysm, 54 cases were confirmed by angiography or operation or both. Among them, 33 cases (63%) showed true aneurysm, 18 cases (33%) pseudoaneurysm, and 2 cases (4%) superficial congenital arterio-venous aneurysm. Eight cases were associated with dissected stripping. One case was falsely diagnosed by ultrasonography. The diagnostic accuracy was 98%. The results suggest that color Doppler ultrasonography is useful in detecting aneurysm.

[Clinical significance of pulmonary valvular resistance in children determined by color Doppler echocardiography]

Pulmonary valvular resistance (PVR) of 40 children with pulmonary valvular stenosis was determined by color Doppler echocardiography before and after percutaneous balloon pulmonary valvuloplasty as well as during their follow-up. The correlation coefficient of PVR between Doppler method and catheterization method was 0.85 ( P <0.01) and the correlation coefficient between PVR determined by former method and pulmonary valvular area determined by the latter was -0.80 ( P <0.01). This study indicates that color Doppler echocardiography can take the place of catheterization to determine PVR in assessing the severity of pulmonary valvular stenosis in children.

Oxidative modification of lipoproteins in hypertriglyceridemic patients and hypercholesterolemic rabbits in vivo

Many lines of evidence suggest that LDL is oxidized in vivo and that Ox-LDL is present in the artery wall. But the oxidation of VLDL and HDL in vivo has not yet been reported. In this study, the oxidative modification of serum LDL, VLDL, and HDL in patients with endogenous hypertriglyceridemia (HTG) and in serum of rabbits fed on high cholesterol diet were made. The serum LDL, VLDL and HDL were isolated by the density gradient ultracentrifugation. The oxidative modification of LDL, VLDL and HDL were identified by agarose eletrophoresis, absorbance at 234 nm and fluorescence of TBARS. The results showed that serum TC, TG and TBARS in the HTG group (n = 25) and in rabbits fed with a high fat diet (for 12 weeks, n = 8) were significantly higher than those of the corresponding control groups (normal subjects, n = 25; rabbits fed with a normal diet, n = 8; p < 0.01). The electrophoretic mobilities of LDL, VLDL and HDL were increased when compared with the controls, and absorbance at 234 nm and TBARS of LDL, VLDL and HDL in the HTG group and in the high fat diet rabbits were significantly higher than those of the controls (p < 0.01). These results suggest that not only LDL but also VLDL and HDL were oxidatively modified in vivo in the patients with HTG and in the rabbits fed with a high cholesterol diet.

Dominant negative down-regulation of endotoxin-induced tumor necrosis factor alpha production by Lps(d)/Ran

We recently showed that adenoviral transfer and expression of the Lps(d)/Ran gene isolated from endotoxin-resistant C3H/HeJ mice could protect endotoxin-sensitive mice from endotoxic shock. Elevation of proinflammatory cytokines, such as tumor necrosis factor alpha (TNF-alpha), is thought to be essential for the development of septic shock. To investigate the extent to which Lps(d)/Ran affects TNF-alpha production, we transduced primary macrophages from endotoxin-sensitive and -resistant mice with adenoviral vectors expressing the wild-type and the mutant Lps/Ran cDNAs and other control genes, and compared the amount of TNF-alpha produced by these various transduced macrophages. Successful transfer and expression of Lps(d)/Ran cDNA in endotoxin-sensitive C3H/HeOuJ macrophages reduced TNF-alpha production upon lipopolysaccharide (LPS) stimulation, as compared with macrophages transduced with vectors expressing the wild-type Lps(n)/Ran cDNA, the green fluorescent protein gene, or the lacZ gene. On the other hand, successful transfer and expression of the wild-type Lps(n)/Ran cDNA in primary macrophages from endotoxin-resistant C3H/HeJ mice failed to induce TNF-alpha production to any significant extent unless a very high LPS concentration was used. Given our previous demonstration that Lps(n)/Ran functions effectively in restoring LPS responsiveness in B cells from C3H/HeJ mice, we conclude that Lps/Ran is involved in a CD14-independent signal transduction pathway. This dominant negative down-regulation by Lps(d)/Ran on TNF-alpha production by macrophages and probably other innate immune responses may be key to the development of an effective gene therapy for endotoxic or septic shock.

Endothelial dysfunction associated with left ventricular diastolic dysfunction in patients with coronary heart disease

OBJECTIVE

We sought to assess the correlation between endothelial vasodilation and left ventricular diastolic function.

BACKGROUND

Previous studies have demonstrated that similar neurohumoral factors are involved in myocardial and vascular endothelial impairment. The degree of endothelial dysfunction is related to the clinical severity of the heart failure. However, it is not clear whether endothelial dysfunction develops with the progression of left ventricular diastolic dysfunction. We hypothesize that the endothelial dysfunction is associated with left ventricular diastolic dysfunction.

METHODS

Using high-resolution ultrasound, we measured the dilator response of the brachial artery to hyperemia (endothelium-dependent vasodilation) and to 0.5 mg nitroglycerin (endothelium-independent vasodilation), and measured peak velocities of the early wave (Evmax) and the atrial wave (Avmax) in 40 coronary heart disease (CHD) patients and 20 normal subjects. We analyzed the relationship between the Evmax/Avmax ratio and endothelium-dependent vasodilation.

RESULTS

The results showed that endothelium-dependent and endothelium-independent vasodilation as well as the Evmax/Avmax ratio were lower in the CHD group than those in the control group (4.29%+/-1.42%, 17.58%+/-2.99%, 0.81+/-0.24 vs. 9.62%+/-2.34%, 24.18%+/-3.15%, 1.07+/-0.29, respectively, P<0.01). The Evmax/Avmax ratio was related to endothelium-dependent vasodilation (r=0.45, P<0.01).

CONCLUSIONS

Our results showed that the development of endothelial dysfunction was associated with the progression of myocardial diastolic dysfunction, which suggests that the same mechanisms may be involved in the impairment of endothelium and myocardium.

Effect of stent on radiation dosimetry in an in-stent restenosis model

PURPOSE

Intravascular brachytherapy is the leading modality being evaluated for treatment of in-stent restenosis. Stent struts may have an effect on the dose distributions of various radiation sources. We evaluated dosimetry in a stented coronary artery model using a variety of beta and gamma sources and stent materials.

METHODS

We determined the dose distributions with and without stent in the in-stent restenosis model. Three beta-particle emitting radionuclides, 90Y (2.3 MeV), 144Pr (3.0 MeV), and 106Rh (3.5 MeV), and two gamma-ray emitters, 192Ir (380 keV) and 125I (30 keV), were studied. Stent materials included stainless steel, nitinol, and tantalum. Monte Carlo dose calculations were performed in a stent model of multiple stent struts placed at 1.5 mm from the source. Isodose curves were generated and the ratios of dose rates with and without stent, the stent factors, were evaluated. A stent factor of greater or less than unity represents dose enhancement or reduction in the presence of a stent.

RESULTS

For the three beta radionuclides, dose reduction was found on the adventitial side of the stent strut and dose enhancement was noted on the luminal side. On the luminal side, the maximum dose enhancement ranges from 7% to 29%, and the dose reduction on the adventitial side ranges from 13% to 43%. Both the reduction and enhancement effects were most pronounced for the high atomic number material, tantalum. For a given stent material, the dose reduction and enhancement are similar for the three beta radionuclides. For the gamma sources, the stent had no effect for the high-energy 192Ir, but for the low-energy 125I, drastic dose reduction on the adventitial side was observed (up to 86% for tantalum stent), and about 10% dose enhancement on the luminal side was also noted. The dose reduction with 125I was more pronounced than that seen with the beta sources.

CONCLUSIONS

The presence of stent struts significantly affects dose distributions of 90Y, 106Rh, 144Pr, and 125I. The maximum dose reduction can be as much as 86%. 192Ir was unaffected. These factors need to be considered in choosing radionuclides and dose prescriptions in treating in-stent restenosis.

[Apolipoportein E polymorphism, serum lipids and apolipoproteins of 362 Han national subjects in Chengdu area]

This investigation was conducted to observe the frequency distribution of apoE phenotypes and alleles and to explore the relationship between apoE polymorphism and plasma lipids or apolipoproteins in Chinese population. ApoE phenotypes were assayed by isoelectric focusing and immunoblotting with serum. Serum lipids and apoA I, B100, C II, C III, E were determined in a random subset of 362 subjects including 268 males and 94 females with a mean age of 43.7 +/- 12.3 yrs from a population of Han Nationality in Chengdu area. The results showed that the frequencies of apoE phenotypes and alleles were: E3/3 72.93%, E2/3 12.98%, E3/4 11.33%, E2/4 1.38%, E4/4 1.38%, E2/2 0.00%; epsilon 3 0.8508, epsilon 2 0.0718, epsilon 4 0.0774. The results also showed that the apo E2(E2/3 + E2/2) group had lower levels of serum TC and apoB100 (P < 0.05) and a higher level of serum apoE (P < 0.001) when compared with the apoE3(E3/3) or apoE4(E3/4 + E4/4) group. No significant difference was observed in TG, apoA I, apoC II, and apoC III levels among the apoE2, E3 and E4 groups (P > 0.05).

[Transmission grating spectrograph for soft X-ray spectrum measurements with a pre-optics]

A novel diffraction spectroscopic instrument consisting of a large area transmission grating and a grazing-incidence pre-optics comprising of a toroidal mirror, a slit and a cylindrical mirror has been implemented. A nearly perfect stigmatism and a medium spectral resolution are due to the separation of the focusing and dispersing function. The experimental results show that it is possible to construct large area transmission grating spectrograph with high collecting efficiency and good spatial resolution.

Systemic antifungal agents against AIDS-related opportunistic infections: current status and emerging drugs in development

No effective drug was available for the treatment of systemic fungal infections until the discovery of Amphotericin B in 1953. Since then flucytosine, azoles and later the triazoles, have now become available. The current interest in the development of new antifungal agents can partially be explained by the dramatic rise in the number of AIDS cases and the subsequent suppression of the immune system in patients with the disease. For example, over 90% of those diagnosed to be HIV-positive contract a fungal infection during the course of their illness. Other conditions that have spurred the development of new systemic antifungal agents include the increase in the frequency of bone marrow and organ transplants, the use of antineoplastic agents, long-term use of corticosteroids and even the indiscriminate use of antibiotics. The emergence of fungi resistant to currently available agents, especially the azoles, has made the need for new and effective antifungal agents more urgent. This review article focuses on agents targeted against opportunistic fungal infections, i.e., fungal infections which, in contrast to immunocompetent individuals, may cause serious life-threatening illness in immunocompromised individuals. Agents currently on the market or undergoing clinical development, as well as potential new agents that have been discovered, are discussed.

Fast repair of deoxynucleotide radical cations by phenylpropanoid glycosides (PPGs) and their analogs

The repair effects on deoxynucleotide radical cations of phenylpropanoid glycosides (PPGs) and their analogs, isolated from a Chinese folk medicinal herb, were studied using the pulse radiolysis technique. The radical cations of deoxynucleotides were formed by the reaction of SO4*- with deoxynucleotides. On pulse irradiation of a nitrogen saturated deoxynucleotide aqueous solution containing 20 mM K2S2O8, 200 mM t-BuOH and one of the PPGs or their analogs, the transient absorption spectra of the radical cations of nucleotide decayed with the formation of those of the radical cation of PPGs or their analogs within several tens of microseconds after electron pulse irradiation. The result indicates that deoxynucleotide radical cations can be repaired by PPGs or their analogs. The rate constants of the repair reactions were determined to be 0.48-1.1 x 10(9), 0.64-1.80 x 10(9) and 2.12-4.4 x 10(9) M(-1) s(-1) for dAMP, dGMP and dCMP radical cations respectively. It is obvious that the rate constants of the repair reaction depend on the number of phenolic hydroxyl groups contained in the PPGs and their analogs. A deeper understanding of this new repair mechanism will undoubtedly help researchers design strategies to prevent and/or intervene more effective in free radical related diseases.

Lps(d)/Ran of endotoxin-resistant C3H/HeJ mice is defective in mediating lipopolysaccharide endotoxin responses

C3H/HeJ inbred mice are defective in that they are highly resistant to endotoxic shock as compared with normal responder mice. Their B cells and macrophages do not respond significantly when exposed to lipopolysaccharide (LPS), whereas cells from the responder mice do. Using a functional assay, we previously isolated a cDNA, which encodes for Ran/TC4 GTPase. We now show that this gene is mutated in C3H/HeJ mice, which accounts for their resistance to endotoxin stimulation. Sequence analysis of independent mutant Lps(d)/Ran cDNAs isolated from splenic B cells of C3H/HeJ mice reveals a consistent single base substitution at position 870, where a thymidine is replaced with a cytidine. In situ hybridization maps the Lps(d)/Ran cDNA to mouse chromosome 4. By retroviral gene transfer, the wild-type Lps(n)/Ran cDNA but not the mutant Lps(d)/Ran cDNA can restore LPS responsiveness of C3H/HeJ cells. Adenoviral gene transfer in vivo with the mutant Lps(d)/Ran cDNA but not the wild-type Lps(n)/Ran cDNA rescues endotoxin-sensitive mice from septic shock. Thus Lps/Ran is an important target for LPS-mediated signal transduction, and the Lps(d)/Ran gene may be useful as a therapeutic sequence in gene therapy for endotoxemia and septic shock.

Novel conformationally restricted tetracyclic analogs of delta8-tetrahydrocannabinol

Novel analogs of (-)-delta8-tetrahydrocannabinol (delta8-THC) in which the conformation of the side chain was restricted by incorporating the first one or two carbons into a six membered ring fused with the aromatic phenolic A ring were synthesized. The affinities of the novel ligands for CB1 and CB2 indicated that the "southbound" chain conformer retained the highest affinity for both receptors.

Efficient CFTR expression from AAV vectors packaged with promoters--the second generation

Gene therapy studies of cystic fibrosis (CF) have shown that AAV-based vector was efficient in transferring but not in expressing the CFTR cDNA in the target cells. The levels of CFTR gene expression were limited by the small packaging capacity of AAV because it had been difficult to package the CFTR cDNA with an efficient promoter. In the present study we have developed a new generation of AAV/CFTR vectors which contain efficient short promoters to express the CFTR gene in target cells. To do so, we reduced the size of the CFTR cDNA by determining the minimal untranslated regions required for expression of CFTR cDNA. We also identified short and efficient promoters that could be packaged with the down-sized CFTR cDNA into a novel AAV vector that had a maximal packaging capacity. Functional analyses showed that the new vectors were packaged efficiently and expressed higher levels of CFTR than a vector in which the CFTR gene was driven by the ITR sequence of AAV. Transduction of airway epithelial cells containing [symbol: see text] 508 mutation with the new vectors demonstrated efficient expression of the wild-type CFTR and correction of the CF phenotype. In contrast, no significant CFTR expression was detected in cells infected with the vector that express the CFTR gene from the ITR. These findings support the notion that the AAV can be developed into an efficient vector to transduce the CFTR gene and vectors expressing higher levels of CFTR from an efficient promoter should provide better efficacy for gene therapy of cystic fibrosis.

[Clinical significance of cardiac axis determination in prenatal echocardiographic diagnosis of fetal congenital heart disease]

OBJECTIVE

To investigate the clinical significance of cardiac axis determined by echocardiography in prenatal diagnosis of fetal congenital heart disease (CHD).

METHODS

518 high risk fetuses for CHD were and 90 normal fetuses were examined by echocardiography. Cardiac axis was measured on four-chamber view and fetal cardiac anatomical structure was examined in multiple views to determine CHD.

RESULTS

The 35 fetuses with CHD diagnosed by prenatal echocardiography. There is significant difference of caidiac axis between CHD group (58.1 +/- 15.7 degree) and normal group (44.8 +/- 10.3 degree, P < 0.01). Sensitivity of CHD diagnosis using four-chamber view alone is 68.5%, it will be elevated to 91.4% by combination of four-chamber view and cardiac axis determination (P < 0.05).

CONCLUSION

Cardiac axis play an important role in fetal echocardiographic screening for CHD and it should be measured routinely as part of the four-chamber view of the fetal heart. The normal range of fetal cardiac axis is 20 to 75 degree. If it was more than 75 degree, the CHD should be suspected.

Substrate specificity and stereoselectivity of rat brain microsomal anandamide amidohydrolase

Anandamide amidohydrolase (AAH) catalyzes the hydrolysis of arachidonylethanolamide (anandamide), an endogenous cannabinoid receptor ligand. To delineate the structural requirements of AAH substrates, rat brain microsomal AAH hydrolysis of a series of anandamide congeners was studied using two reverse-phase high-performance liquid chromatography (RP-HPLC) assays developed in our laboratory. Arachidonamide (1) was found to be the best substrate with an apparent Km of 2.34 mM and a Vmax of 2.89 nmol/min/mg of protein. Although anandamide (2) has a similar Km value, its Vmax is approximately one-half that of arachidonamide. N, N-Bis(2-hydroxyethyl)arachidonamide (3) was not hydrolyzed, suggesting specificity for unsubstituted or mono-N-substituted arachidonamides. Analogues with a methyl group at the 1'-position of the ethanolamido headgroup were also found to have greater resistance to enzymatic turnover and therefore increased metabolic stability. The enzyme exhibited high stereoselectivity as the rate of hydrolysis of (R)-alpha-methanandamide (2.4%) (anandamide = 100%) was about 10-fold lower than that of its (S)-enantiomer (23%). In contrast, (R)-beta-methanandamide was 6-times more susceptible (121%) than the (S)-beta-enantiomer (21%). Interestingly, an inverse correlation was shown between AAH stereoselectivity and the brain cannabinoid receptor affinity as the enantiomers with high receptor affinity displayed low susceptibility to hydrolysis by AAH. Metabolic stability is also imparted to analogues with a short hydrocarbon headgroup as well as to those possessing 2-monomethyl or 2,2-dimethyl substituents. 2-Arachidonylglycerol and racemic 1-arachidonylglycerol were shown to be excellent AAH substrates. To identify AAH inhibitors, hydrolysis of anandamide was also studied in the presence of a select group of cannabimimetics. Of these, (-)-Delta8-THC and SR141716A, a biarylpyrazole CB1 antagonist, were found to inhibit enzymatic activity. These newly defined enzyme recognition parameters should provide a foundation for the rational development of stable, therapeutically useful anandamide analogues with high receptor affinity.

[Plasma HDL subfractions in endogenous hypertriglyceridemia]

Our previous studies indicated that while the plasma triglycerides (TG) levels were significantly increased, HDL-C and apo A I levels were significantly decreased and abnormal HDL compositions were found in hypertriglyceridemic (HTG) patients. Whether the particle sizes of plasma HDL in HTG undergo a change has not yet been reported. This study was designed to observe the changes of plasma HDL subfractions in HTG patients. The plasma TG, total cholesterol (TC), HDL-C, apo A I, A II, B100, C II, C III, and E, HDL compositions and HDL subfractions--HDL2a, HDL2b, HDL3a, HDL3b and HDL3c were measured in 25 HTG patients (plasma TG > 2.26 mmol/L, TC < 6.72 mol/L) and 25 age-sex matched healthy subjects (plasma TG < 1.69 mmol/L, TC < 5.17 mmol/L). Plasma HDL was isolated by one step density gradient ultracentrifugation. Plasma and HDL TC, TC were determined by enzymatic methods; apo A I, A II, B100, C II, C III and E were measured by RID kits developed by ourselves. HDL subfractions were analyzed by a gradient gel electrophoresis method (GGE). The variation coefficients in one gel were 2.3% to 8.3% and the variation coefficients among gels were 3.5% to 9.3%. The results indicated that in the HTG group, the fasting plasma TG, apo B100, C II, C III and E levels were significantly higher (P < 0.001) and HDL-C, apo A I levels were lower (P < 0.05) as compared with those in the control group. TC in HDL in the HTG group were significantly increased (P < 0.05), while TG, apo A I, C II, C III and E were significantly decreased (P < 0.05, P < 0.01). Among HDL subfractions in the HTG group, HDL2b was significantly decreased (P < 0.02); HDL2a and HDL3a were increased (P < 0.05, P < 0.02). With the increase of plasma TG levels in the HTG group, the HDL particle sized tended to become smaller. According to the results, it is suggested that the changes of plasma HDL subfractions in HTG are related to the changes of the apolipoprotein compositions of HDL, which lead to the increase of HDL catabolism, therefore the plasma HDL2b content decreases and HDL2a, HDL3a contents increase.

Structure-activity relationships of pyrazole derivatives as cannabinoid receptor antagonists

As a potent, specific antagonist for the brain cannabinoid receptor (CB1), the biarylpyrazole N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2, 4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (SR141716A; 1) was the lead compound for initiating studies designed to examine the structure-activity relationships of related compounds and to search for more selective and potent cannabimimetic ligands. A series of pyrazole derivatives was designed and synthesized to aid in the characterization of the cannabinoid receptor binding sites and also to serve as potentially useful pharmacological probes. Therapeutically, such compounds may have the ability to antagonize harmful side effects of cannabinoids and cannabimimetic agents. Structural requirements for potent and selective brain cannabinoid CB1 receptor antagonistic activity included (a) a para-substituted phenyl ring at the 5-position, (b) a carboxamido group at the 3-position, and (c) a 2,4-dichlorophenyl substituent at the 1-position of the pyrazole ring. The most potent compound of this series contained a p-iodophenyl group at the 5-position, a piperidinyl carboxamide at the 3-position, and a 2,4-dichlorophenyl group at the 1-position of the pyrazole ring. The iodinated nature of this compound offers additional utility as a gamma-enriching SPECT (single photon emission computed tomography) ligand that may be useful in characterizing brain CB1 receptor binding in vivo.

Probing the N-5 region of the indoloquinoline alkaloid, cryptolepine for anticryptococcal activity

N-5 Alkylated analogues of cryptolepine were synthesized and tested for anticryptococcal activity. Evidence provided in this study suggests that the active form of cryptolepine consists of the flat tetracyclic aromatic ring with the methyl group on the N-5 atom. It was also found that changes in the electronic density around the N-5 atom do not appear to affect activity. Steric hindrance of the N-5 substituents seems to decrease activity. Through systematic modification of the N-5 alkyl groups, o-phenylpentyl group was shown to possess the highest potency thus far.

Morphological evaluation of a regurgitant orifice by 3-D echocardiography: applications in the quantification of valvular regurgitation

The clinical evaluation of blood flow regurgitation through a heart valve or stenotic lesion is an unresolved problem. The proximal flowfield region has been the study focus in the last few years; however, investigators have failed to identify an accurate and reliable calculation scheme due to lack of geometric information about the shape and size of the regurgitating or stenotic orifice. Presented here is a superior method of calculation, by using three-dimensional (3-D) echocardiography combined with Doppler velocimetry. The geometric structure of the orifice in a regurgitating porcine prosthetic valve in vitro was formulated by 3-D image construction of sequentially obtained 2-D images. The velocity flowfield was accessed by color Doppler flow mapping (CD) and continuous-wave Doppler (CW). Two accurate methods of calculation of regurgitant variables were developed. The first method calculated peak regurgitant flow rate from CD and the second method calculated regurgitant flow volume from CW. Both methods showed excellent correlation with the corresponding true values from an electromagnetic flowmeter. The promising preliminary results in such a realistic porcine model indicate the possibility of establishing a routine procedure to be tested in the clinical setting.

Novel analogues of arachidonylethanolamide (anandamide): affinities for the CB1 and CB2 cannabinoid receptors and metabolic stability

Several analogues of the endogenous cannabinoid receptor ligand arachidonylethanolamide (anandamide) were synthesized and evaluated in order to study (a) the structural requirements for high-affinity binding to the CB1 and CB2 cannabinoid receptors and (b) their hydrolytic stability toward anandamide amidase. The series reported here was aimed at exploring structure-activity relationships (SAR) primarily with regard to stereoelectronic requirements of ethanolamido headgroup for interaction with the cannabinoid receptor active site. Receptor affinities, reported as Ki values, were obtained by a standard receptor binding assay using [3H]CP-55,940 as the radioligand, while stability toward the amidase was evaluated by comparing the Ki of each analogue in the presence and absence of phenylmethanesulfonyl fluoride (PMSF), a serine protease blocker and inhibitor of anandamide amidase. Introduction of a methyl group in the 1'- and 2'-positions or substitution of the ethanolamido headgroup with a butylamido group gave analogues with vastly improved biochemical stability. This is accomplished in some cases with increased receptor affinity. Conversely, oxazolyl and methyloxazolyl headgroups led to low-affinity analogues. Substitution of the hydroxyl group with electronegative substituents such as fluoro, chloro, allyl, and propargyl groups significantly increased receptor affinity but did not influence the biochemical stability. The 2'-chloro analogue of anandamide was found to have the highest affinity for CB1. Additionally, reversing the positions of the carbonyl and NH in the amido group produces retro-anandamides possessing considerably higher metabolic stability. Replacement of the arachidonyl tail with oleyl or linoleyl results in analogues with low affinities for both receptors. All of the analogues in this study showed high selectivity for the CB1 receptor over the peripheral CB2 receptor. The most potent analogues were tested for their ability to stimulate the binding of [35S]GTPgammaS to G-proteins and were shown to be potent cannabimimetic agonists. The results are discussed in terms of pharmacophoric features affecting receptor affinity and enzymatic stability.