Human non-lineage antigen,CD46 (HuLy-m5): purification and partial sequencing demonstrates structural homology with complement-regulating glycoproteins

CD46, until recently known as HuLy-m5, is a non-lineage restricted surface antigen ubiquitously expressed by almost all human cells except erythrocytes. The CD46 antigen is identified by the E4.3 monoclonal antibody (mAb) and exists at the surface of human peripheral blood lymphocytes (PBLs) as two acidic, non-disulfide bonded chains, and , ofM _r 66 000 and 56 000. Receptor density analysis showed that CD46 was of moderately low abundance on PBLs with 7.5×10³ molecules present on each cell. The two chains of CD46 were purified (144 000-fold) by immunoaffinity-chromatography with E4.3 mAb from the plasma membranes of a human spleen infiltrated with chronic myelogenous leukemia cells. Amino acid sequence analysis of the NH₂-terminal of both and chains yielded the same sequence; XEEPPQ/TFEAMELIGKPKPYYEIGE. Peptide mapping studies confirmed that both CD46 chains were closely related, except for one peptide fragment. This amino acid sequence is identical to that of the NH₂-terminal of the recently cloned membrane co-factor protein (MCP), a membrane protein that binds the C3b and C4b fragments of complement and acts as a co-factor for I protein-mediated decay of the complement convertases. CD46 shares a cross-reactive epitope with some primate retroviruses, and this may indicate that some retroviruses mimic the mechanisms used by autologous human cells to evade complement-mediated immune clearance. Offprint requests to: I. F. C. McKenzie.     

Mutation analysis of the cystic fibrosis transmembrane regulator gene in native American populations of the southwest

We report DNA and clinical analyses of cystic fibrosis (CF) in two previously unstudied, genetically isolated populations: Pueblo and Navajo Native Americans. Direct mutation analysis of six mutations of the CFTR gene--namely, delta F508, G542X, G551D, R553X, N1303K, and W1282X--was performed on PCR-amplified genomic DNA extracted from blood samples. Haplotype analyses with marker/enzyme pairs XV2c/TaqI and KM19/PstI were performed as well. Of the 12 affected individuals studied, no delta F508 mutation was detected; only one G542X mutation was found. None of the other mutations was detected. All affected individuals have either an AA, AC, or CC haplotype, except for the one carrying the G542X mutation, who has the haplotype AB. Clinically, six of the affected individuals examined exhibit growth deficiency, and five (all from the Zuni Pueblo) have a severe CF phenotype. Four of the six Zunis with CF are also microcephalic, a finding not previously noted in CF patients. Our DNA data have serious implications for risk assessment of CF carrier status for these people.     

Barley anther culture: Pretreatment on mannitol stimulates production of microspore-derived embryos

A period of four days preincubation at 25 °C on a medium containing mannitol was found to be superior to those pretreatments requiring incubation at 4 °C. In addition, the yield of green plants was improved by orienting anthers flat on the medium during mannitol preincubation, and reducing the number of anthers cultured per dish.     

Two classes of continuous cell lines established from Syrian hamster 9 day gestation embryos: Preneoplastic cells and progenitor cells

Summary Primary cultures of 9-d-gestation Syrian hamster embryo (E9) cells are distinct from primary cultures of later gestational age in terms of their growth and differentiation. First, primary E9 cell cultures express multiple mesenchymal differentiation lineages (e.g., adipocyte, myoblast) only rarely seen in cultures of 13-d-gestation fetal (F13) cells. Second, although most primary E9 cultures have a limited in vitro proliferative life span and exhibit cellular senescence similar to primary cultures of F13 cells, E9 cultures seem to have higher frequency of escape from senescence and conversion to continuous cell lines compared to F13 cells. Moreover, this frequency can be further increased 4- to 5-fold by continuous exposure of the E9 cells to tumor promoters or epidermal growth factor. Eleven continuous cell lines have been isolated from unreated, promoter-treated, or epidermal growth factor-treated primary E9 cultures. Seven of these are neoplastic or preneoplastic. However, the remaining four do not show any evidence of being in neoplastic progression and three of these continue to express the same differentiated phenotype observed in ther parental primary cell cultures. These studies were supported in part by grants from the National Institutes of Health (AG 01998), Bethesda, MD, and the U.S. Department of Energy (DE-A-C02-76-EVO-3280), Washington, DC.     

The microbial plankton of Lake Fryxell,southern Victoria Land,Antarctica during the summers of 1992 and 1994

 Samples collected from Lake Fryxell, southern Victoria Land, Antarctica in January 1992 and 1994 were analysed for the abundance of bacterioplankton and the diversity and abundance of protistan plankton. At the times of sampling, 14 ciliate species and 10 species of autotrophic flagellate were recorded. The samples contained two species of rotifer (Philodina spp.), which formed the first record of planktonic metazoans in the Dry Valley lakes of this region of Antarctica. Bacterial concentrations ranged between 1.0 and 3.8×10⁸ l^-1 in the upper oxic waters increasing to 20×10⁸ l^-1 in the anoxic waters. Heterotrophic flagellates decreased in abundance down the oxygenated water column, disappearing completely at 9 m, and ranged between 0.28 and 7.39×10⁵ l^-1 in abundance. Autotrophic flagellates were much more abundant exhibiting a number of distinct peaks down the water column (1.89–25.3×10⁸ l^-1). The ciliated protozoa were very abundant (up to 7720 l^-1) in relation to flagellate and bacterial numbers, typical of oligotrophic lakes world-wide. The distribution of the protistan plankton showed marked zonation, probably in response to the differing salinity and temperature gradients in the water column. Possible trophic interactions are discussed and comparisons with other continental Antarctic lakes made. Received: 29 November 1995/Accepted: 18 February 1996     

Skeptical responding in rhesus monkeys (Macaca mulatta)

Signalers that misinform sufficiently open may become devalued as sources of information; however, “skepticism” and any comparison involved in testing reliability entail a cost that involves delays and energy expenditure. Skepticism may be less costly though, if, as a rule, animals are not equally skeptical of the signals of all conspecifics. Animals with the ability to recognize individual conspecifics and to recall past encounters with them may have the capacity to restrict skepticism to subsets of animals that are most likely to benefit from deception. We played tape-recorded alarm calls of high- and low-ranking rhesus monkeys(Macaca mulatta) to their groups in a feeding context once daily over 8 consecutive days at the Yerkes Primate Center Field Station. Over the sequence of playbacks, response was greater to the calls of high-ranking monkeys, adult response patterns were different from those of juveniles, and for adults especially, decline in responsiveness was punctuated by partial resurgences of response. These differences may be the consequence of the adults’ more extensive histories of interaction with group members that, though generally reliable, vary with respect to the potential benefits of deceptive signaling.