Inhibition of ligand binding to g protein-coupled receptors by arachidonic acid

Arachidonic acid (AA), released in response to muscarinic acetylcholine receptor (mAChR) stimulation, previously has been reported to function as a reversible feedback inhibitor of the mAChR. To determine if the effects of AA on binding to the mAChR are subtype specific and whether AA inhibits ligand binding to other G protein-coupled receptors (GPCRs), the effects of AA on ligand binding to the mAChR subtypes (M₁, M₂, M₃, M₄, and M₅) and to the μ-opioid receptor, β₂-adrenergic receptor (β₂-AR), 5-hydroxytryptamine receptor (5-HTR), and nicotinic receptors were examined. AA was found to inhibit ligand binding to all mAChR subtypes, to the β₂-AR, the 5-HTR, and to the μ-opioid receptor. However, AA does not inhibit ligand binding to the nicotinic receptor, even at high concentrations of AA. Thus, AA inhibits several types of GPCRs, with 50% inhibition occurring at 3–25 μM, whereas the nicotinic receptor, a non-GPCR, remains unaffected. Further research is needed to determine the mechanism by which AA inhibits GPCR function.     

Linkage of chromosome 13q32 to schizophrenia in a large veterans affairs cooperative study sample

Several prior reports have suggested that chromosomal region 13q32 may harbor a schizophrenia susceptibility gene. In an attempt to replicate this finding, we assessed linkage between chromosome 13 markers and schizophrenia in 166 families, each with two or more affected members. The families, assembled from multiple centers by the Department of Veterans Affairs Cooperative Studies Program, included 392 sampled affected subjects and 216 affected sib pairs. By DSM-III-R criteria, 360 subjects (91.8%) had a diagnosis of schizophrenia and 32 (8.2%) were classified as schizoaffective disorder, depressed. The families had mixed ethnic backgrounds. The majority were northern European-American families (n = 62, 37%), but a substantial proportion were African-American kindreds (n = 60, 36%). Chromosome 13 markers, spaced at intervals of approximately 10 cM over the entire chromosome and 2-5 cM for the 13q32 region were genotyped and the data analyzed using semi-parametric affected only linkage analysis. For the combined sample (with race broadly defined and schizophrenia narrowly defined) the maximum LOD score was 1.43 (Z-score of 2.57; P = 0.01) at 79.0 cM between markers D13S1241 (76.3 cM) and D13S159 (79.5 cM). Both ethnic groups showed a peak in this region. The peak is within 3 cM of the peak reported by Brzustowicz et al. [1999: Am J Hum Genet 65:1096-1103].     

The tipping point: The critical role of therapeutic apheresis in a case of refractory acquired hemophilia

Acquired hemophilia A (AHA) is a rare autoimmune disorder that leads to factor VIII (FVIII) deficiency via autoantibody formation. Standard treatment options include FVIII bypassing factors and immunosuppression. However, the role of therapeutic plasma exchange (TPE) is not clear in the treatment of AHA. We present a case of idiopathic AHA in a 66 year old female with severe bleeding and a FVIII inhibitor of 17.6 Bethesda units (BU). She failed to respond to standard treatment including maximum dose of recombinant FVIIa (rFVIIa), rituximab, and other immunosuppressive agents. Her FVIII inhibitor rapidly increased to 140 BU and FVIII was below 5%. TPE was initiated 3 weeks after admission and her bleeding stabilized after the first treatment and completely stopped after three treatments. Repeat testing revealed increased FVIII to 15% and FVIII inhibitor decreased to 2.0 BU. After an additional TPE treatment, her FVIII increased to 27% and FVIII inhibitor decreased to 0.6 BU and she was discharged without bleeding 40 days after admission. In this case, TPE played a critical role in reducing FVIII inhibitor, which resulted in a recovery of FVIII activity and hemostasis. Therefore, TPE should be initiated early in AHA patients with bleeding and high titer of FVIII inhibitor.     

Management of rupture of choledochal cyst

One of the rare complications of choledochal cysts is rupture. In majority of the cases, the cause of rupture is unknown. Reconstructive surgery is the treatment of choice. We describe three patients with choledochal cyst rupture, who were admitted with acute abdomen. Diagnosis of biliary ascites with peritonitis was made in all the three patients. At surgery, two patients underwent T-tube placement, and definitive repair was done electively. One patient underwent definitive repair of ruptured choledochal cyst, but died due to septicemia. External bile drainage would be safer in emergency condition.