α7 and α8 Nicotinic Receptor Subtypes Immunopurified from Chick Retina have Different Immunological, Pharmacological and Functional Properties

Nicotinic receptors are present in the chick retina, but their structure and functional characteristics are still unclear. Using anti-α7 and anti-α8 subunit-specific antibodies, we immunopurified the α7 and α8 subtypes of chick retina neuronal nicotinic receptors. When analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, the two purified subtypes consistently showed a similar peptide composition characterized by the presence of two major peptides of M_r 58 ± 1 and 54 ± 1 kDa, and two minor peptides of 67 and 61 ± 1 kDa. In the α7 subtype, the 58 kDa peptide was recognized by anti-α7 but not by anti-α8 antibodies; in the α8 subtype, the 58 kDa peptide was recognized only by anti-α8 antibodies. The α7 subtype had a single class of [¹²⁵]a-bungarotoxin binding sites with a KD value of 1.2 nM, whereas the purified α8 subtype had two classes of binding sites, one with a K _D of 5.5 nM and the other with very high affinity ( K _D 52 pM), but present in only 8% of the receptors. Competition binding experiments also showed the presence on the α8 subtype of highand low-affinity classes of binding sites; the affinity for cholinergic drugs of the former was greater than that of the single class present on the α7 subtype. When reconstituted in planar lipid bilayers, both subtypes formed ligand-gated cation channels with major conductance levels of 42 and 52 pS but with different lifetimes; the two channels were activated by agonists and blocked by d-tubocurarine and the glycinergic antagonist strychnine. In line with the binding data, the reconstituted α8 subtype had greater agonist sensitivity than the α7 subtype.     

International conference calendar 1995

International conference calendar 1995     

Epidemiology of taeniasis and cysticercosis in a Peruvian village. The Cysticercosis Working Group in Peru.

To determine the prevalence of cysticercosis in a rural area where the disease is endemic, the authors studied the seroepidemiology of human and porcine cysticercosis in a Peruvian jungle community (Maceda, Peru) in 1988 using an enzyme-linked immunoelectrotransfer blot (EITB) assay. Of the 371 sampled inhabitants, 30 (8%) were seropositive, most of whom were asymptomatic. After niclosamide therapy, four Taenia species worms were identified in the seropositive group, compared with one in the control group (p = 0.06). Pigs were frequently infected: 44 of 133 (33%) were found positive for Taenia by tongue examination and 57 of 133 (43%) were positive by EITB. In 69% of the sampled households that had pigs, there was at least one seropositive pig. The number of pigs diagnosed positive by the tongue examination was significantly greater in households that had latrines than in those that did not. Cysticercosis is a common but usually asymptomatic infection that affects both humans and pigs in the high jungle areas of Peru.     

Measles passive immunity in infants from vaccinated and disease acquired mothers

Background — Despite the decline in the incidence of measles in Chile, epidemics continue to occur. In Chile, measles vaccine is administered at one year of age, therefore, we hypothesized that control of epidemic measles may be improved with a better understanding of the immunologic status of infants. Objective — To evaluate the immunologic status to measles of unvaccinated infants born to previously vaccinated and disease exposed mothers. Method — Group A subjects were pregnant women with a documented history of measles infection, and group B subjects were pregnant women with a documented history of measles vaccination. Maternal blood samples and cord blood were obtained immediately following delivery. Blood samples were obtained from infants at 6 and 9 months of age. Samples were tested for anti-measles antibodies using an ELISA technique. Results — There were 41 subjects in group A and 35 in group B. Infant birth weight and the mothers age were comparable in the two groups. At delivery the titre of measles antibodies in cord blood was the same in the two groups. A higher mean antibody level pre-delivery was observed in group A (disease exposed) mothers compared with group B (vaccinated) (p = 0.028). There was a significantly lower antibody titre at 6 months and 9 months compared with baseline in both groups (p = < 0.001), but no difference in titre between infants born to vaccinated versus disease exposed mothers. The levels of antibody titre were below protective levels at 6 and 9 months. Conclusion — There is a rapid decline in measles antibody levels observed by 6 months in infants from mothers either previously exposed to measles or vaccinated. There is inadequate protection of infants from measles by 6 months based on immunological status, with no difference in infant immunologic status of infants from disease exposed and previously vaccinated mothers.     

Cisplatin and 5-Fluorouracil for Metastatic Squamous Cell Carcinoma from Unknown Primary

Chemotherapy for squamous cell carcinoma with unknown primary (SCUP) has not been prospectively studied. To evaluate the efficacy of cis-diaminedichloroplatinum (cisplatin) and 5-fluorouracil (5-FU) in advanced SCUP, we treated 15 patients with measurable disease. A prospective trial was conducted of cisplatin and 5-FU in patients presenting with SCUP. All patients had evaluation in search for primary disease with computed tomographic scan of the head, neck, and chest and endoscopic evaluation of the nasopharynx, larynx, esophagus, and tracheobronchial passaes with negative blind biopsies. Chemotherapy consisted of cisplatin 100 mg/m²on day 1 and 5-FU 1000 mg/m²continuous infusion over 24 hr for 4 days. The regimen was repeated every 21 days. Responses were seen in 8 of 1.5 patients [1 complete response (CR) and 7 partial responses (PR)], for an overall response rate of 53%. These results suggest that cisplatin-5-FU combination has efficacy in advanced SCUP and deserves further trials both in advanced disease and in combined modality programs with surgery and radiation therapy.     

Preferential attachment of HIV particles to activated and CD45RO+CD4+ T cells.

We have studied the binding of biotinylated HIV particles to various cell lines and peripheral blood mononuclear cells (PBMCs). Viruses were harvested from cultures of cell surface-biotinylated cells productively infected with HIV-IIIB. Labeled HIV particles bound to and infected CD4(+) cell lines and PBMCs. The interaction between gp120 and CD4 contributed in part to HIV binding to CD4(+) cells. However, HIV binding was for the most part independent of CD4 expression and sensitive to polyanion inhibition. Polyanion-sensitive interactions involved heparan sulfate in cell lines but not in primary T cells. Interestingly, HIV binding to primary cells was heterogeneous and targeted discrete subsets of CD4(+) and CD4(-) cells. The CD4(+) T cell subset that displayed high HIV-binding capacity contained mostly CD4(+)CD45RO(+) cells, whereas the subset showing undetectable HIV binding contained higher proportions of CD4(+)CD45RO(-) cells. Consistently, purified CD4(+)CD45RO(-) cells or purified CD4(+) T cells with low virus-binding capacity showed lower HIV entry and delayed HIV replication when compared with purified CD4(+)CD45RO(+) or purified CD4(+) T cells with high virus-binding capacity, respectively. Our data suggest that the binding of HIV to cell surface-expressed CD4 might be inefficient in a subset of CD4(+) T cells and that increased binding of HIV to activated and CD4(+)CD45RO(+) cells may contribute to the higher susceptibility of these cells to HIV infection.     

CIN2 is a much less reproducible and less valid diagnosis than CIN3: results from a histological review of population-based cervical samples.

We wished to compare the relative reproducibility and validity of cervical intraepithelial neoplasia (CIN) 2 and CIN3 diagnoses. In a population-based cohort study (1993-2001) of human papillomavirus (HPV) and cervical neoplasia in Costa Rica, we compared community pathologists' diagnoses with those of the 2 independent reviewers from the United States (total, n = 357). As measures of validity, we correlated primary and review diagnoses with HPV positivity and cytological interpretations. Two review pathologists agreed with 84% and 81%, respectively, of initial diagnoses of CIN3 compared with 13% and 31% of CIN2. The CIN3 diagnoses made by review pathologists were 94% oncogenic HPV positive, compared with 72% of CIN2 diagnoses. Eighty-one percent of CIN3 diagnoses versus 61% of CIN2 were correlated with high-grade cytological interpretations. The CIN3 is a substantially more reproducible diagnosis that can be validated more frequently with HPV tests and cytological interpretations than CIN2.