Structural analysis of the nurse shark (new) antigen receptor (NAR): molecular convergence of NAR and unusual mammalian immunoglobulins

We recently have identified an antigen receptor in sharks called NAR (new or nurse shark antigen receptor) that is secreted by splenocytes but does not associate with Ig light (L) chains. The NAR variable (V) region undergoes high levels of somatic mutation and is equally divergent from both Ig and T cell receptors (TCR). Here we show by electron microscopy that NAR V regions, unlike those of conventional Ig and TCR, do not form dimers but rather are independent, flexible domains. This unusual feature is analogous to bona fide camelid IgG in which modifications of Ig heavy chain V (VH) sequences prevent dimer formation with L chains. NAR also displays a uniquely flexible constant (C) region. Sequence analysis and modeling show that there are only two types of expressed NAR genes, each having different combinations of noncanonical cysteine (Cys) residues in the V domains that likely form disulfide bonds to stabilize the single antigen-recognition unit. In one NAR class, rearrangement events result in mature genes encoding an even number of Cys (two or four) in complementarity-determining region 3 (CDR3), which is analogous to Cys codon expression in an unusual human diversity (D) segment family. The NAR CDR3 Cys generally are encoded by preferred reading frames of rearranging D segments, providing a clear design for use of preferred reading frame in antigen receptor D regions. These unusual characteristics shared by NAR and unconventional mammalian Ig are most likely the result of convergent evolution at the molecular level.     

VH usage and somatic hypermutation in peripheral blood B cells of patients with rheumatoid arthritis (RA)

The human antibody repertoire has been demonstrated to have a marked V-gene-dependent bias that is conserved between individuals. In RA patients, certain heavy chain V genes (VH) have been found to be preferentially used for encoding autoantibodies. To determine if such preferential use of VH genes in autoantibodies is associated with a general distortion of the V gene repertoire in RA patients, the VH composition of peripheral blood B cells was analysed among four RA patients and four age- and sex-matched healthy controls. Usage of individual VH genes (eight VH3 and three VH4 genes tested by hybridization with a set of gene-specific oligonucleotide probes) was highly biased among RA patients, but no evidence of a distortion in the bias was observed compared with healthy controls. However, the occurrence of somatic mutations in these VH genes (estimated by differential hybridization with motif-specific oligonucleotide probes targeted to CDR and FR of the tested genes, and by DNA sequence analysis) was strikingly different between patients and healthy subjects. The number of VH3 rearrangements that had accumulated somatic mutations and the number of mutations per rearrangement were significantly elevated in three of the four RA patients. A slight but not significant elevation in mutations among rearranged VH4 genes was also observed in these patients. These data suggest that although usage of individual VH genes among peripheral blood B cells is not affected by the disease, the autoimmune process may involve a significant fraction of the B cell compartment.     

Upper airway resistance syndrome

Many clinicians are familiar with the clinical symptoms and signs of obstructive sleep apnea (OSA). In its most blatant form, OSA is complete airway obstruction with repetitive, prolonged pauses in breathing, arterial oxyhemoglobin desaturation; followed by arousal with resumption of breathing. Daytime symptoms of this disorder include excessive daytime somnolence, intellectual dysfunction, and cardiovascular effects such as systemic hypertension, angina, myocardial infarction, and stroke. It has been recently recognized that increased pharyngeal resistance with incomplete obstruction can lead to a constellation of symptoms identical to OSA called "upper airway resistance syndrome" (UARS). The typical findings of UARS on sleep study are: (1) repetitive arousals from EEG sleep coinciding with a (2) waxing and waning of the respiratory airflow pattern and (3) increased respiratory effort as measured by esophageal pressure monitoring. There may be few, if any, obvious apneas or hypopneas with desaturation, but snoring may be a very prominent finding. Treatment with nasal positive airway pressure (NCPAP) eliminates the symptoms and confirms the diagnosis. Herein we describe two typical cases of UARS.     

Intraperitoneal normal saline infusion for postoperative pain after laparoscopic cholecystectomy

After laparoscopic surgery carbon dioxide remains within the peritoneal cavity for a few days, commonly causing pain. This prospective randomized study was performed to determine the efficacy of intraperitoneal infusion of normal saline on postoperative pain after laparoscopic cholecystectomy. Altogether 300 patients were randomly assigned to one of five groups of 60 patients each. Group A: control group, no peritoneal infusion, no subhepatic drain. Group B: no peritoneal infusion but a subhepatic closed brain was left for 24 hours. Group C: normal saline 25 to 30 ml/kg body weight at a temperature of 37 degrees C was infused under the right hemidiaphragm and left in the peritoneal cavity. Group D: normal saline in a room temperature was infused under the right hemidiaphragm and suctioned after the pneumoperitoneum was deflated. Group E: normal saline was infused and suctioned as in group D, but a subhepatic closed drain was left for 24 hours. Postoperatively, analgesic medication usage, nausea, vomiting, and pain scores were determined at 2, 6, 12, 24, 48, and 72 hours (during hospitalization and at home). Postoperative pain was reduced significantly (p < 0.001) in the patients of groups C, D, and E versus controls, whereas no difference was observed between groups A and B. Among groups C < D and E, group E (p < 0.01) had the best results followed by group D and then group C. Intraperitoneal normal saline offered a detectable benefit to patients undergoing laparoscopic cholecystectomy. The beneficial effect was better when the fluid was suctioned after deflation of the pneumoperitoneum and even better when a subhepatic closed drain continued fluid suction during the first postoperative hours.     

Reassessment of the role of radiation therapy in the treatment of endocrine-inactive pituitary macroadenomas

OBJECTIVE: This prospective clinical trial was undertaken to assess the rate of tumor recurrence in patients with endocrine-inactive pituitary macroadenomas who underwent gross total surgical resection of their tumors and did not receive adjuvant radiotherapy. METHODS: Between December 1987 and July 1994, 45 patients with endocrine-inactive pituitary macroadenomas underwent transsphenoidal surgery. In 38 (84%) of these patients, gross total surgical resection was achieved and was confirmed by postoperative magnetic resonance imaging (n = 37) or computed tomography (n = 1). After receiving counseling from the neurosurgeon concerning the risks and benefits of radiation therapy, 32 of the 38 patients elected not to receive adjuvant radiotherapy. Patients were followed through March 1998 with radiographic imaging obtained every 6 months for the first 2 years, annually for postoperative Years 3 and 4, and then every 2 to 3 years thereafter. The study end point was defined as radiographic tumor recurrence or patient death. RESULTS: The mean follow-up duration for the study group was 5.5 years. During that time, 2 of 32 (6%) patients developed recurrence, at 18 and 24 months, respectively, after initial surgery. Both were successfully treated using radiation therapy, with one requiring additional surgery. Three additional patients died as a result of unrelated causes 9, 12, and 49 months, respectively, after initial surgery. Immunocytochemical analysis revealed 66% of the tumors to be weak gonadotroph cell adenomas, 22% to be null cell adenomas, 9% to be silent prolactinomas, and 3% to be silent corticotroph cell adenomas. CONCLUSION: This study demonstrates a 6% 5-year recurrence rate in patients with endocrine-inactive pituitary macroadenomas treated using gross total surgical resection alone. Reserving radiation therapy for the infrequent patient with recurrence and sparing the majority of patients the associated risks inherent in its use seems reasonable.     

Prospective, multicenter study of laparoscopic ventral hernioplasty. Preliminary results

BACKGROUND: A standard technique for laparoscopic ventral hernioplasty (peritoneal onlay using an expanded polytetrafluoroethylene [ePTFE] patch for hernias >/=4 cm2) is being used in a prospective, multicenter, long-term study. METHODS: Demographic, operative, and postoperative data were collected and analyzed. Follow-up clinical evaluations were conducted 7-10 days, 4 weeks, 6 months, 1 year, and then annually after surgery in all patients. RESULTS: In the first 2 years of the study, 144 patients were enrolled; nine were lost to follow-up. The mean operating time was 120 min. The mean follow-up was 222 days (range 5-731). Postoperative complications were five infections, three cases of prolonged ileus, one bowel obstruction, 23 seromas (15 resolved without intervention), and six hernia recurrences. Hospital discharge occurred a mean of 2.3 days after surgery and return to normal activity a mean of 15 days postoperatively. CONCLUSIONS: Laparoscopic prosthetic ventral hernioplasty avoids the large wound required in open repairs, with attendant complications and recurrences, and appears safe, especially if an ePTFE mesh is used. Compared with conventional open ventral hernioplasty, the laparoscopic technique may also allow shorter hospitalization and a quicker return to normal activities after surgery.     

Aging and Stability of GaN High Electron Mobility Transistors and Light-Emitting Diodes With $hbox{TiB}_{2}$- and Ir-Based Contacts

There is interest in developing more stable contacts to a variety of GaN-based devices. In this paper, we give two examples of devices that show improved thermal stability when boride or Ir diffusion barriers are employed in ohmic-contact stacks. AlGaN/GaN high electron mobility transistors (HEMTs) were fabricated with Ti/Al/X/Ti/Au source-drain ohmic (where X is or Ir) contacts and were subjected to long-term annealing at 350 . By comparison with companion devices with conventional Ti/Al/Ni/Au ohmic contacts, the HEMTs with boride-based ohmic metal showed superior stability of both source-drain current and transconductance after 25 days of aging at 350 . The gate current for standard HEMTs increases during aging, and the standard ohmic contacts eventually fail by shorting to the gate contact. Similarly, InGaN/GaN multiple quantum well light-emitting diodes (MQW-LEDs) were fabricated with either Ni/Au//Ti/Au or Ni/Au/Ir/Au p-ohmic contacts. Both of these contacts showed superior long-term thermal stability compared to LEDs with conventional Ni/Au contacts.