Long-term survival case of a non-small cell lung cancer bone metastasis patient treated with bone cement, radiation and gefitinib.

OBJECTIVE: We explore the treatment of bone metastases in advanced non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: We reported a 76-year-old female patient, who was diagnosed with NSCLC with bone metastasis eight years ago (stage IVA). Due to unbearable diarrhea, she refused chemotherapy, and we adopted local treatment, including local radiotherapy 50 Gy and bone cement to lumbar spinal metastases, 62 Gy local radiotherapy of primary lung tumor, TKI inhibitor gefitinib and zoledronic acid. RESULTS: She survived more than eight years and is still in follow-up. CONCLUSIONS: The median survival time for NSCLC patients with bone metastases is often less than 1 year. We reported the patient with more than eight years of survival, showed that some special cases can adopt the methods of local treatment including bone cement, treatment benefit patients, radiation therapy and targeted therapy in clinic to expand the survival.

Progress of radiotherapy after breast-conserving surgery combined with silicone prosthesis reconstruction.

Breast cancer is the malignant tumor with the highest incidence in women. The standard treatment for early breast cancer is radical surgery combined with radiotherapy, but many studies have shown that adjuvant radiotherapy after breast-conserving surgery combined with silicone prosthesis reconstruction is gradually expected to become the new standard treatment because this method can obtain a good local tumor control rate, and has a cosmetic effect. Compared with myocutaneous flap reconstruction, silicone prosthesis implantation has the advantages of less trauma, simple operation, beautiful appearance, and no overlap of donor areas during reconstruction. It is a safe and feasible surgical method without worrying about necrosis and atrophy of myocutaneous flap. This emerging combination therapy may become the best mode of early breast cancer treatment.

Application of artificial intelligence in cardiac CT: From basics to clinical practice.

Research into the possibilities of AI in cardiac CT has been growing rapidly in the last decade. With the rise of publicly available databases and AI algorithms, many researchers and clinicians have started investigations into the use of AI in the clinical workflow. This review is a comprehensive overview on the types of tasks and applications in which AI can aid the clinician in cardiac CT, and can be used as a primer for medical researchers starting in the field of AI. The applications of AI algorithms are explained and recent examples in cardiac CT of these algorithms are further elaborated on. The critical factors for implementation in the future are discussed.

Comparison of IMRT and VMAT radiotherapy planning for Graves' ophthalmopathy based on dosimetric parameters analysis.

OBJECTIVE: To compare volumetric modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) for the treatment of Graves' ophthalmopathy (GO) based on the dosimetric data. PATIENTS AND METHODS: 19 patients diagnosed with GO were recruited in this study. For each patient, a dual-partial-arc VMAT plans and a 7-fixed-field IMRT plans were replanned. Dosimetric parameters of the targets and organs at risk (OARs) originated from the two kinds of plans were compared and analyzed. RESULTS: Homogeneity index (HI) was superior in IMRT plans compared with VMAT (p=0.0014) but there was no significant statistical difference in conformity index (CI) between them (p=0.0673). IMRT plans revealed advantage in the OARs protection especially for the left and right lenses, optic nerves and eyeballs (p<0.05). CONCLUSIONS: VMAT and IMRT are both feasible techniques in radiotherapy in GO from the perspective of dosimetric parameters. Homogeneity and OAR protection were slightly superior in IMRT plans compared with VMAT plans.

H3K27M mutant diffuse midline glioma: a case report.

OBJECTIVE: Diffuse midline glioma with H3K27M mutation is a new tumor type of WHO central nervous system tumor classification. It often occurs in the midline structure and usually has a poor prognosis. CASE REPORT: A 38-year-old male patient presented with 2 years history of right limb with facial numbness, tumors in the left thalamic region and lateral ventricle was detected by imaging. The patient underwent the first surgery. RESULTS: The pathological examination results: Glioblastoma. He recovered well after surgery and received a total of 30 times of radiotherapy and temozolomide for one year. Fourteen months later, tumours were observed in the left thalamic region and left parieto-occipital lobe, the patient underwent the second operation. Immunohistochemistry showed: H3K27M(+). He experienced limitation of right limb movement after surgery and started taking oral apatinib 250 mg qd. After one-year, multiple tumors were found in the left brainstem, bilateral ventricles, bilateral basal ganglia, etc. The patient was given radiotherapy 7 times and then took apatinib 250 mg qd. Now the patient is still alive. CONCLUSIONS: H3K27M mutant diffuse midline glioma is characterized by diffuse infiltrative growth. Its pathological classification is diverse, imaging features lack specificity, and prognostic factors are complex. Traditional radiochemotherapy has limited effects, molecular targeted therapy, especially intervention of epigenetic regulation is being explored.

Clinical significance of circulating tumor cells and their expression of cyclooxygenase-2 in patients with nasopharyngeal carcinoma.

OBJECTIVE: To explore the expression of circulating tumor cells (CTCs) and cyclooxygenase-2 (COX-2) in CTCs and to assess their association with clinical parameters and treatment. PATIENTS AND METHODS: Peripheral blood samples from 50 patients with nasopharyngeal carcinoma (NPC) were included. We applied advanced CanPatrolTM CTC enrichment technique and in situ hybridization assay to isolate, identify, and classify CTCs and COX-2 in CTCs. Epstein-Barr virus DNA was detected by Real Time-quantitative PCR (RT-qPCR). RESULTS: No CTCs were identified in ten healthy volunteers (100%). Of the total patients, 48 (96%) had positive CTCs counts and 36 (72%) had positive mesenchymal CTCs counts before treatment. CTCs cells were highly expressed in different NPC stages, and the positive ratio of mesenchymal CTCs in stage IV was higher than that in other stages. The proportion of mesenchymal cells was higher expressed in metastasis patients. The expression of COX-2 was different in different types of CTCs. The positivity of COX-2 in CTCs was higher in stage IV patients than that in stage II and stage III patients. Decreased mesenchymal CTCs and that express COX-2 indicated a favorable curative effect in NPC patients. The positivity of mesenchymal CTCs and COX-2 was higher in EBV DNA positive patients compared with EBV DNA negative patients (p<0.05). Meanwhile, the mean number of CTCs, mesenchymal CTCs, CTCs that express COX-2, hybrid CTCs that express COX-2 and mesenchymal CTCs that express COX-2 was significantly higher in the EBV DNA positive patients than negative patients before treatment (p<0.05). CONCLUSIONS: CTCs and their expression of COX-2 were correlated with NPC clinical characteristics, and have a relation with Epstein-Barr virus DNA. Decreased mesenchymal CTCs and that express COX-2 indicated a favorable curative effect in NPC patients.

Clinical study of the radiotherapy with EDGE accelerator in the treatment of the moderate and severe thyroid associated ophthalmopathy.

OBJECTIVE: To explore the short-term efficacy, acute complications and response factors after the radiotherapy with EDGE accelerator in patients with moderate and severe thyroid-associated ophthalmopathy (TAO). PATIENTS AND METHODS: A total of 68 patients with moderate and severe TAO who received the radiotherapy with EDGE accelerator between August 1st, 2017 and May 1st, 2011 were enrolled in the present study. The clinical data were collected, and the efficacy and acute complications were followed up, and the response factors were analyzed. RESULTS: Sixty-eight patients (136 eyes) were followed up for 6 months after radiotherapy. The total score after radiotherapy was significantly lower compared to that before the therapy (p<0.05), and the effective rate was 75.74%. After the radiotherapy, the patient's exophthalmia, soft tissue involvement, eye external muscle involvement, corneal involvement, decreased vision and diplopia, tearing and eyelid pain have improved. Acute complications included increased local inflammation, hair loss, pigmentation and xerophthalmias. In addition, multivariate logistic regression analysis demonstrated that thyroid hormone level was the independent factor for the response to the radiotherapy. CONCLUSIONS: For patients with moderate and severe TAO, radiotherapy with EDGE accelerator is a safe and effective treatment option. Maintaining normal thyroid hormone level can improve the effective rate of radiotherapy.

Changes in quantitative CT image features of ground-glass nodules in differentiating invasive pulmonary adenocarcinoma from benign and in situ lesions: histopathological comparisons.

AIM: To evaluate progressive changes in quantitative CT features of the non-solid component of ground-glass nodules (GGNs) from baseline to follow-up to differentiate invasive (minimally invasive adenocarcinoma [MIA] and invasive adenocarcinoma [IA]) GGNs from benign or pre-invasive (adenocarcinoma in situ [AIS]) lesions. MATERIALS AND METHODS: Patients with a GGN detected at baseline and follow-up computed tomography (CT), examined by tissue sampling were included in the study. The diameter and mean, maximum, minimum CT density and density deviation from the non-solid component of whole GGNs were measured. Progression of these features over time was analysed by linear regression analysis. Multivariate receiver operating characteristics analyses of combined measures created by a logistic regression model were performed to evaluate diagnostic performance for invasive GGNs. RESULTS: Sixty-one patients (24 males) with 70 GGNs were included. Fifteen GGNs were benign, six AIS, 38 MIA, and 11 IA. The mean diameter of all histological subtypes increased from baseline to follow-up, the largest increase was found in the MIA group (p<0.001). For MIA and IA, the mean, maximum, minimum density, and density deviation had a positive correlation over time, whilst benign and pre-invasive GGNs showed a negative correlation for these features. A diagnostic model based on three GGN features (increasing in diameter, mean density, and density deviation) identified invasive GGNs with a sensitivity, specificity and area under the receiver operating characteristic (ROC) curve (AUC) of 83.7%, 61.9%, and 0.786, respectively (p<0.001). CONCLUSION: In GGN follow-up, the diameter of benign and AIS, and invasive GGNs significantly increased. Additional analysis of mean density and density deviation in the non-solid component may help to identify invasive GGNs.

Abnormal spontaneous brain activity in type 2 diabetic retinopathy revealed by amplitude of low-frequency fluctuations: a resting-state fMRI study.

AIM: To explore the altered spontaneous cerebral activity patterns and impaired functional regions in patients with diabetic retinopathy (DR) using resting-state functional magnetic resonance imaging (rs-fMRI) based on the amplitude of low-frequency fluctuations (ALFF) algorithm. MATERIALS AND METHODS: Twenty-one patients with DR (mean age, 54.9±9.9 years; 11 females) and 17 healthy control subjects (54.8±5.7 years; 9 females) were prospectively studied. The DR patients underwent laboratory tests. All individuals underwent a neuropsychological test. The differences in the ALFF values between the two groups were compared. The relationships between ALFF values and clinical measurements were analysed using a multiple-factor analysis. RESULTS: Compared to the controls, the DR group showed significantly increased ALFF values in the bilateral occipital gyrus, right lingual gyrus, and precuneus, and decreased values in the right posterior/anterior cerebellar lobe and the parahippocampal, fusiform, superior temporal, inferior parietal, and angular gyrus. Furthermore, the Montreal Cognitive Assessment (MoCA) scores were negatively correlated with decreased ALFF values in the right occipital lobe of the DR group, while increased ALFF values in the right precuneus and lingual gyrus were found to be positively correlated with glycosylated haemoglobin (HbA1c) levels. CONCLUSIONS: Patients with DR showed spontaneous cerebral activity abnormalities in many cerebral regions that were associated with cognitive impairments. HbA1c levels altered spontaneous cerebral activity in DR patients.

[Analysis on causes of death of residents in Beijing, 1965-1974].

OBJECTIVE: To fill up the absence of data on causes of death of urban residents in Beijing during 1965-1974 and provide evidence for the similar study in other areas. METHODS: All possible sources for death data during 1965-1974 were identified through expert consultations and record search. Stratified sampling was conducted to collect the death data of urban residents during this period in Beijing. The mortality rate, death cause constituent and rank of death causes were used in this descriptive analysis. RESULTS: A total of 11 668 records of deaths from 1965 to 1974 were collected from 10 local police stations in urban area of Beijing. The top 10 death causes in the urban residents were heart disease, tumor, cerebrovascular disease, accidental injury, respiratory system disease, digestive system disease, communicable disease and parasitic disease, nervous system disease, urogenital and reproductive system disease, endocrine and nutrition metabolic diseases. The deaths caused by these diseases accounted for 84.19% of the total deaths. Accidental injury accounted for 13.22% of the total deaths, which was significantly higher than that in either 1964 or 1975, two years before and after this period(P<0.01). Suicide accounted for 54.47% of the total accidental injury deaths. For men, accidental injury was the leading death cause, followed by cancer and heart disease; for women, heart disease, cancer and cerebrovascular disease were the top three death causes. CONCLUSION: The major death cause in urban residents changed from infectious diseases to chronic and non-communicable diseases during 1965-1974. A remarkable high proportion of deaths caused by accidental injury was due to the historical background during that period in Beijing, China.

Blocking the ZZ domain of sequestosome1/p62 suppresses myeloma growth and osteoclast formation in vitro and induces dramatic bone formation in myeloma-bearing bones in vivo.

We reported that p62 (sequestosome 1) serves as a signaling hub in bone marrow stromal cells (BMSCs) for the formation of signaling complexes, including NFκB, p38MAPK and JNK, that are involved in the increased osteoclastogenesis and multiple myeloma (MM) cell growth induced by BMSCs that are key contributors to multiple myeloma bone disease (MMBD), and demonstrated that the ZZ domain of p62 (p62-ZZ) is required for BMSC enhancement of MMBD. We recently identified a novel p62-ZZ inhibitor, XRK3F2, which inhibits MM cell growth and BMSC growth enhancement of human MM cells. In the current study, we evaluate the relative specificity of XRK3F2 for p62-ZZ, characterize XRK3F2's capacity to inhibit growth of primary MM cells and human MM cell lines, and test the in vivo effects of XRK3F2 in the immunocompetent 5TGM1 MM model. We found that XRK3F2 induces dramatic cortical bone formation that is restricted to MM containing bones and blocked the effects and upregulation of tumor necrosis factor alpha (TNFα), an osteoblast (OB) differentiation inhibitor that is increased in the MM bone marrow microenvironment and utilizes signaling complexes formed on p62-ZZ, in BMSC. Interestingly, XRK3F2 had no effect on non-MM bearing bone. These results demonstrate that targeting p62 in MM models has profound effects on MMBD.

Bioinformatic analysis of the nucleotide binding site-encoding disease-resistance genes in foxtail millet (Setaria italica (L.) Beauv.).

The nucleotide-binding site (NBS) disease-resistance genes are the largest category of plant disease-resistance gene analogs. The complete set of disease-resistant candidate genes, which encode the NBS sequence, was filtered in the genomes of two varieties of foxtail millet (Yugu1 and 'Zhang gu'). This study investigated a number of characteristics of the putative NBS genes, such as structural diversity and phylogenetic relationships. A total of 269 and 281 NBS-coding sequences were identified in Yugu1 and 'Zhang gu', respectively. When the two databases were compared, 72 genes were found to be identical and 164 genes showed more than 90% similarity. Physical positioning and gene family analysis of the NBS disease-resistance genes in the genome revealed that the number of genes on each chromosome was similar in both varieties. The eighth chromosome contained the largest number of genes and the ninth chromosome contained the lowest number of genes. Exactly 34 gene clusters containing the 161 genes were found in the Yugu1 genome, with each cluster containing 4.7 genes on average. In comparison, the 'Zhang gu' genome possessed 28 gene clusters, which had 151 genes, with an average of 5.4 genes in each cluster. The largest gene cluster, located on the eighth chromosome, contained 12 genes in the Yugu1 database, whereas it contained 16 genes in the 'Zhang gu' database. The classification results showed that the CC-NBS-LRR gene made up the largest part of each chromosome in the two databases. Two TIR-NBS genes were also found in the Yugu1 genome.

Paradoxical role of autophagy in the dysplastic and tumor-forming stages of hepatocarcinoma development in rats.

Many reports have shown that autophagy has a role as both a promoter and inhibitor in tumor development. However, the mechanism of this paradox is unknown. Tumor development is a multistep process. Therefore, we investigated whether the role of autophagy in hepatocarcinoma formation depended on the stage of tumor development. Based on our results, autophagy inhibition by chloroquine had a tumor-promotive effect in the rat model with N-diethylnitrosamine-induced hepatocarcinogenesis in its dysplastic stage (Ds) and a tumor-suppressive effect in its tumor-forming stage (Ts). In the Ds, autophagy inhibition enhanced cell proliferation, DNA damage and inflammatory cytokines expression in liver. These changes were dependent on the upregulation of reactive oxygen species (ROS) that was resulted from autophagy inhibition, and ultimately accelerated the process of hepatocarcinogenesis. However, in the Ts, autophagy inhibition restrained tumor formation by decreasing tumor cell survival and proliferation. In this stage, autophagy inhibition led to excessive ROS accumulation in the tumor, which promoted cell apoptosis, and prominently suppressed tumor cell metabolism. Taken together, our data suggested that autophagy suppressed hepatocarcinogenesis in the Ds by protecting normal cell stability and promoted hepatocarcinogenesis in the Ts by supporting tumor cells growth. Autophagy always had a role as a protector throughout the process of hepatocarcinoma development.

New QSAR prediction models derived from GPCR CB2-antagonistic triaryl bis-sulfone analogues by a combined molecular morphological and pharmacophoric approach.

In order to build quantitative structure-activity relationship (QSAR) models for virtual screening of novel cannabinoid CB2 ligands and hit ranking selections, a new QSAR algorithm has been developed for the cannabinoid ligands, triaryl bis-sulfones, using a combined molecular morphological and pharmacophoric search approach. Both pharmacophore features and shape complementarity were considered using a number of molecular descriptors, including Surflex-Sim similarity and Unity Query fit, in addition to other molecular properties such as molecular weight, ClogP, molecular volume, molecular area, molecular polar volume, molecular polar surface area and dipole moment. Subsequently, partial least squares regression analyses were carried out to derive QSAR models linking bioactivity and the descriptors mentioned, using a training set of 25 triaryl bis-sulfones. Good prediction capability was confirmed for the best QSAR model by evaluation against a test set of a further 20 triaryl bis-sulfones. The pharmacophore and molecular shape-based QSAR scoring function now established can be used to predict the biological properties of virtual hits or untested compounds obtained from ligand-based virtual screenings.

Fragment-similarity-based QSAR (FS-QSAR) algorithm for ligand biological activity predictions.

Quantitative structure-activity relationship (QSAR) studies are useful computational tools often used in drug discovery research and in many scientific disciplines. In this study, a robust fragment-similarity-based QSAR (FS-QSAR) algorithm was developed to correlate structures with biological activities by integrating fragment-based drug design concept and a multiple linear regression method. Similarity between any pair of training and testing fragments was determined by calculating the difference of lowest or highest eigenvalues of the chemistry space BCUT matrices of corresponding fragments. In addition to the BCUT-similarity function, molecular fingerprint Tanimoto coefficient (Tc) similarity function was also used as an alternative for comparison. For validation studies, the FS-QSAR algorithm was applied to several case studies, including a dataset of COX2 inhibitors and a dataset of cannabinoid CB2 triaryl bis-sulfone antagonist analogues, to build predictive models achieving average coefficient of determination (r(2)) of 0.62 and 0.68, respectively. The developed FS-QSAR method is proved to give more accurate predictions than the traditional and one-nearest-neighbour QSAR methods and can be a useful tool in the fragment-based drug discovery for ligand activity prediction.

NMR characterization of recombinant transmembrane protein CB2 fragment CB2(180-233).

The expression of membrane proteins has been the bottleneck for their structural studies. Recently, we developed a method to obtain milligram quantities of isotope-labeled seven transmembrane G-protein coupled cannabinoid (CB) receptor fragment in E. coli. In order to verify this method and confirm the recombinant isotope-labeled CB2 fragment, 3D hetero-nuclear NMR techniques were used to analyze the structure of the fragment CB2(180-233) in DMSO-d6 solvent. The sequential assignments of TM5 and intra-cellular loop 3 were accomplished, which confirmed the experimental protocols of isotope-labeled recombinant protein expression, fusion protein cleavage, and membrane protein purification. The obtained structure also showed alpha-helix in the TM5 region, but it was interrupted by a disordered region (Gly204_ILe206). These results further revealed that our established approach is a promising method to express recombinant membrane proteins for their structural studies.

Biosynthesis and purification of a hydrophobic peptide from transmembrane domains of G-protein-coupled CB2 receptor.

A major challenge for the structural study of the seven-transmembrane G-protein-coupled receptors is to obtain a sufficient amount of purified protein at the milligram level, which is required for either nuclear magnetic resonance (NMR) spectroscopy or X-ray crystallography. In order to develop a high-yield and cost-effective method, and also to obtain preliminary structural information for the computer modeling of the three-dimensional receptor structural model, a highly hydrophobic peptide from human cannabinoid subtype 2 receptor CB2(65-101), was chosen to develop high-yield membrane protein expression and purification methods. The peptide included the second transmembrane helix with the associated loop regions of the CB2 receptor. It was over-expressed in Escherichia coli, with a modified TrpDelta LE1413 (TrpLE) leading fusion sequence and a nine-histidine tag, and was then separated and purified from the tag in a preparative scale. An experimental protocol for the chemical cleavage of membrane protein fragment was developed using cyanogen bromide to remove the TrpLE tag from the hydrophobic fusion protein. In addition, protein uniformly labeled with isotopic 15N was obtained by expression in 15N-enriched minimum media. The developed and optimized preparation scheme of expression, cleavage, and purification provided a sufficient amount of peptide for NMR structure analysis and other biophysical studies that will be reported elsewhere. The process of fusion protein cleavage following purification was monitored by high-performance liquid chromatography (HPLC) and mass spectrometry (MS), and the final sample was validated by MS and circular dichroism experiments.

The cytoplasmic helix of cannabinoid receptor CB2, a conformational study by circular dichroism and (1)H NMR spectroscopy in aqueous and membrane-like environments.

The cytoplasmic helix domain (fourth cytoplasmic loop, helix 8) of numerous G protein-coupled receptors (GPCRs) such as rhodopsin and the beta-adrenergic receptor exhibit unique structural and functional characteristics. Computer models also predict this structure for the cannabinoid CB2 receptor, another member of the GPCR superfamily. In our study, a peptide corresponding to helix 8 of the CB2 receptor was synthesized chemically and its secondary structure determined by circular dichroism (CD) and (1)H NMR spectroscopy. NMR and CD revealed an alpha-helical structure in this region in both dodecylphosphocholine micelles and dimethylsulfoxide, in contrast to a random coil configuration found in aqueous solvent. This finding is in good agreement with other previous GPCR structural studies including X-ray crystallography. By combining our finding with other studies, we further hypothesize that the amphipathic nature of helix 8 can play a significant role in the function and regulation of CB receptors as well as other GPCRs in general.

PEBP2 and c-myb sites crucial for lambda5 core enhancer activity in pre-B cells.

The lambda5 gene is expressed exclusively in precursor (pre-) B cells where its gene product, as part of the pre-B cell receptor, is crucial for the proliferation of these cells. Several DNA regions regulate the activity and expression pattern of the lambda5 gene. Amongst these is an enhancer, B(lambda5), located 5' of the gene. Here we analyze the lambda5 enhancer core, b(lambda5), which in earlier experiments was demonstrated to retain 50% of the enhancer activity, and show that this activity is restricted to pre-B cells. We identify a DNA element within b(lambda5), PEBP2(lambda5), which is essential for enhancer activity: mutation within this site dramatically reduces core enhancer activity in pre-B cells. The PEBP2(lambda5) site binds bacterially produced polyoma enhancer binding proteins (PEBP) (Runx/AML/CBFA). Furthermore, PEBP2 proteins present in nuclear extracts from murine pre-B cells bind to the PEBP2(lambda5) element. PEBP2 proteins in mature B cells also bind to the PEBP2(lambda5 )element, implying that if PEBP2 proteins are responsible for the stage-specific expression, they have to be non-activating or inhibiting in mature B cells. We also demonstrate that a described partner of PEBP2, c-myb, binds to a sequence termed myb(lambda5) located just upstream of the PEBP2(lambda5) site in the core enhancer. The myb(lambda5) element is also crucial for enhancer activity, since mutating the myb site reduces core enhancer activity to the same extent as mutating the PEBP2 site. Earlier reports have shown that c-myb is expressed at high levels in pre-B cell lines whereas its expression is down-regulated in more mature B cell lines. Thus, c-myb may be involved in determining the stage-specific expression of the lambda5 gene.

Stereochemical selectivity of methanandamides for the CB1 and CB2 cannabinoid receptors and their metabolic stability.

Several chiral, analogues of the endogenous cannabinoid receptor ligand, arachidonylethanolamide (anandamide), methylated at the 2,1' and 2' positions using asymmetric synthesis were evaluated in order to study (a) stereoselectivity of binding to CB1 and CB2 cannabinoid receptors; and (b) metabolic stability with regard to anandamide amidase. Enantiomerically pure 2-methyl arachidonic acids were synthesized through diastereoselective methylation of the respective chiral 2-oxazolidinone enolate derivatives and CB1 and CB2 receptor affinities of the resulting chiral anandamides were evaluated using a standard receptor binding assay. Introduction of a single 2-methyl group increased affinity for CB1, led to limited enantioselectivity and only modestly improved metabolic stability. However, a high degree of enantio- and diastereoselectivity was observed for the 2,1'-dimethyl analogues. (R)-N-(1-methyl-2-hydroxyethyl)-2-(R)-methyl-arachidonamide (4) exhibited the highest CB1 receptor affinity in this series with a K(i) of 7.42 nM, an at least 10-fold improvement on anandamide (K(i)=78.2 nM). The introduction of two methyl groups at the 2-position of anandamide led to no change in affinity for CB1 but somewhat enhanced metabolic stability. Conversely, chiral headgroup methylation in the 2-gem-dimethyl series led to chiral analogues possessing a wide range of CB1 affinities. Of these the (S)-2,2,2'-trimethyl analogue (12) had the highest affinity for CB1 almost equal to that of anandamide. In agreement with our previous anandamide structure-activity relationship work, the analogues in this study showed high selectivity for the CB1 receptor over CB2. The results are evaluated in terms of stereochemical factors affecting the ligand's affinity for CB1 using receptor-essential volume mapping as an aid. Based on the results, a partial CB1 receptor site model is proposed, that bears two hydrophobic pockets capable of accommodating 1'- and 2-methyl groups