A hexapole magnetic guide for neutral atomic beams.

In this paper we present a multiple element magnetic device to guide atoms using a spatially inhomogeneous magnetic field formed by a series of permanent hexapole magnets. The operation of the device is demonstrated using an enhanced beam of neon atoms in the 3P2 metastable state. These atoms are guided around a bend of 30 degrees from their original path. A flux of 4.35 x 10(9) +/- 2 x 10(7) atoms s(-1) was measured after the device yielding a transmission efficiency of approximately 9% of the input flux. Simulations of the center of mass motion of the atoms through the magnetic guide have been performed giving reasonable agreement with the experimental results.

Genetically modified organisms (GMOs) and aquaculture.

This paper reviews the nature of genetically modified organisms (GMOs), the range of aquatic species in which GMOs have been produced, the methods and target genes employed, the benefits to aquaculture, the problems attached to use of GMOs in aquatic species and the regulatory and other social frameworks surrounding them. A set of recommendations aimed at best practice is appended. This states the potential value of GMOs in aquaculture but also calls for improved knowledge particularly of sites of integration, risk analysis, progress in achieving sterility in fish for production and better dissemination of relevant information.

International study on Artemia. LXII. Genomic relationships between Artemia franciscana and A. persimilis, inferred from chromocentre numbers.

Chromocentres, i.e. heavily stainable heterochromatic areas with highly repetitive DNA (a 130-bp repeat in the order of 6 x 105 copies per haploid genome) observed in the resting nucleus, are a reliable taxonomic trait and a good marker for speciation in Artemia. This chromosome marker was evaluated in populations of two New World sibling species: A. franciscana, from North, Central and South America, and A. persimilis from Argentina. Artemia persimilis showed the characteristically low average chromocentre numbers (<3) of the ancestral Mediterranean species, whilst higher numbers (>5) were seen in A. franciscana. The increase in chromocentre numbers from A. persimilis to A. franciscana occurred in a rather steady, continuous geographical pattern with an overlapping zone between both species. A north-south steady latitudinal decline of chomocentres was observed towards the equator in A. franciscana populations from the northern hemisphere, whilst the trait increased from this point towards southern latitudes with a population in Chilean Patagonia (below 52 degrees S) exhibiting the highest chromocentre frequency. Since chromocentres are positively correlated with repetitive DNA content, differentiation between the species through the amplification of heterochromatin or an increased DNA content in A. franciscana (although this species has a lower diploid chromosome number), might nevertheless reflect chromosomal reorganizations between the species. Chromocentres, together with other traits, reveal a probable hybrid zone between the two species in Chilean Patagonia.

Sex determination in the genus Oreochromis : 1. Sex reversal, gynogenesis and triploidy in O. niloticus (L.).

Established techniques of genetic manipulation were used to elucidate sex-determining mechanisms in the commercially important tilapia, Oreochromis niloticus. Analysis of sex ratios from single-pair matings of normal broodstock showed these to be heterogeneous, with an asymmetrical frequency distribution. Data were homogeneous, with the exclusion of a number of broods with sex ratios not significantly different from 3∶1 (male: female), and further progeny testing revealed atypical female heterogamety in the parents of these broods. Analysis of sex ratios from complete diallele-type crosses using five males and five females demonstrated no association between male parent, female parent and progeny sex ratio. Sex ratios of gynogens (0∶1) and triploids (1∶1), and from progeny testing of sex-reversed males (0∶1) and sex-reversed females (3∶1), provide evidence for female homogamety in this species. Progeny testing of male gynogens derived from sex-reversed females demonstrated recombination between the centromere and the sex-determining locus (68.9%). Novel YY "supermales" were shown to be viable and produced all-male offspring. It was concluded that this species exhibits monofactorial, genotypic sex determination with male heterogamety. However, rare autosomal or environmental sex-modifying factors may account for occasional deviations from expected sex ratios.

Sex determination in the genus Oreochromis : 2. Sex reversal, hybridisation, gynogenesis and triploidy in O. aureus Steindachner.

Sex ratios from 62 single-pair matings of normal broodstock O. aureus were highly heterogeneous with an overall deficit of males (41.4%). Peaks in the sex ratio frequency distribution occurred at 1∶1, 3∶5 and 1∶3 (male∶female). Hybridisation of O. aureus with O. mossambicus, O. spilums and O. niloticus produced highly variable sex ratios, suggesting a complexity of hybrid sex determination. Few valid inferences could be made regarding intraspecific sex determination from these hybrid data. Sex ratios from progeny testing of sex-reversed males (1∶3) and most sex-reversed females (1∶0) provide evidence for female heterogamety in O. aureus. Several aberrant ratios observed suggest Mendelian inheritance of an autosomal recessive gene (F,f), epistatic to the major sex-determining gene (W,Z). Sex ratios of triploids and gynogens support the hypothesis of recombination between the centromere and the major sex-determining locus. Progeny testing of a female mitogyne demonstrated the viability of a novel WW "superfemale", which gave only female offspring. Not all data could be explained by a two-factor model of sex determination. Further exceptional sex ratios may be accounted for by rare autosomal or environmental sex-modifying factors. It is concluded that O. aureus has a multifactorial mechanism of sex determination with the underlying primary mechanism of female heterogamety.

Tongue-rolling phenotypes and geographical variation in the United Kingdom.

The distribution of tongue-rolling phenotypes in a sample (n = 477) of undergraduate students of the University College of Swansea (U.K.) was studied. The birthplaces of these students were also recorded. England was divided into six areas, and Wales was left as an area on its own. The data suggest that those students who come from north-east are more non-rollers, which may be due to mixture with Scandinavians.

Isolation of an endocytic compartment from A431 cells using a density modification procedure employing a receptor-specific monoclonal antibody complexed with colloidal gold.

Our objective was to isolate a prelysosomal compartment involved in receptor-mediated endocytosis in human epidermoid carcinoma (A431) cells. The isolation protocol involves density modification of endosome elements in A431 cells, caused by the receptor-dependent binding and internalization at 20 degrees C of colloidal gold-transferrin receptor antibody (B3/25) particles. The use of 125I-labelled gold-B3/25 provides a radioactive marker for the endosome compartment, the major peak being recovered at the bottom of a continuous sucrose gradient at a density of 1.23g ml-1. Enzyme markers characteristic of other cytoplasmic compartments are present only in negligible amounts in this fraction and L-[35S]methionine-labelling of the cells indicates approximately a 200-fold enrichment of 125I-labelled gold-B3/25 versus protein. Electron microscopy of the endosome-rich fraction reveals that we have isolated a highly purified population of small gold-containing vesicles and tubules from which the transferrin receptor can be immunoprecipitated using the B3/25 antibody. Gel electrophoresis and fluorography of L-[35S]-methionine-labelled cells suggests that these elements contain a characteristic profile of approximately 10 major proteins of which three appear to be specifically enriched. In cells incubated with [125I]transferrin, 12% of the ligand sediments with the gold-labelled elements. We conclude, therefore, that the components we have isolated play a role in the intracellular processing of the transferrin-transferrin receptor complexes.

Localization of the epidermal growth factor (EGF) receptor within the endosome of EGF-stimulated epidermoid carcinoma (A431) cells.

We have followed the internalization pathway of both epidermal growth factor (EGF) and its receptor in human epidermoid carcinoma (A431) cells. Using EGF conjugated with horseradish peroxidase and anti-receptor monoclonal antibodies (TL5 and EGFR1) coupled either directly or indirectly to colloidal gold we have identified an extensive elaboration of endosomal compartments, consisting of a peripheral branching network of tubular cisternae connected to vacuolar elements that contain small vesicles and a pericentriolar compartment consisting of a tubular cisternal network connected to multivesicular bodies. Immunocytochemistry on frozen thin sections using receptor-specific antibody-gold revealed that at 4 degrees C in the presence of EGF, receptors were mainly on the plasma membrane and, to a lesser extent, within some elements of both the peripheral and pericentriolar endosomal compartments. Upon warming to 37 degrees C there was an EGF-dependent redistribution of most binding sites, first to the peripheral endosome compartment and then to the pericentriolar compartment and lysosomes. Upon warming only to 20 degrees C the ligand-receptor complex accumulated in the pericentriolar compartment. Acid phosphatase cytochemistry identifies hydrolytic activity only within secondary lysosomes and trans cisternae of the Golgi stacks. Together these observations suggest that the prelysosomal endosome compartment extends to the pericentriolar complex and that the transfer of EGF receptor complexes to the acid phosphatase-positive lysosome involves a discontinuous, temperature-dependent step.

Population genetics of polymorphisms in Cardiff newborn. Relationship between blood group and allozyme heterozygosity and birth weight.

A newborn population of Cardiff, Wales, was screened for variation at three blood group loci (ABO, Rhesus and MN) and four enzyme loci (ACP-1, PGM-1, ADA and EST-D). Birth weights were measured. There were no significant differences between mean birth weights or birth weight variances for individuals homozygous or heterozygous at the MN and the four enzyme loci. (ABO and Rhesus loci cannot be used in these tests.) There was no significant heterogeneity in contingency tables relating phenotypes at the seven loci to birth weight. There were no significant differences in mean heterozygosity per locus between babies placed in different birth weight categories, ranging from 2.5 to 4.2 kg. The genetic variation screened appears therefore to be neutral with respect to this character.

Receptor-mediated endocytosis of transferrin and epidermal growth factor receptors: a comparison of constitutive and ligand-induced uptake.

The distribution of cell surface receptors for transferrin-iron and epidermal growth factor (EGF) on the surface of cultured epithelioid (A431) cells has been identified by immunocytochemical electron microscopy. The patterns of movement displayed by these two receptor populations as they transfer to their sites of internalization on the cell surface are different. The movement of recycling transferrin receptors over the surface is ligand-independent whereas EGF receptors are more stable residents and remain monodisperse until they bind ligand. Prior to uptake transferrin receptors cluster, predominantly within existing clathrin-coated pits while the aggregates formed by EGF ligand-receptor complexes induce new membrane invaginations. These results are discussed in relation to receptor populations concerned with constitutive, high capacity uptake processes and receptors involved in signal transduction.

Prolactin concentrations in mouse milk during lactation.

Prolactin levels in mouse milk increased from the day of parturition to give a concentration of 230 ng/ml on days 2 and 3 of lactation. Thereafter, levels dropped to 140 ng/ml by day 6 and were maintained at this concentration until weaning.

Urogastrone and lactose concentrations in precolostrum, colostrum, and milk.

The concentration of urogastrone (URO) and lactose was measured in breast secretions from four women. URO levels were high in precolostrum and fell markedly around the time of parturition to relatively constant low levels in mature milk. When milk samples were fractionated on a Biogel P10 column, the major peak of immunoreactivity occurred at the point at which pure URO eluted. There was good correspondence between the fall in URO levels at birth and the increase in lactose levels, suggesting that the decrease in URO was a dilution effect as the osmotic influence of lactose increased.

ABO genes are differentially distributed in socio-economic groups in England.

No direct evidence is available concerning what average genetic differences, if any, characterize the segments of socially stratified human populations, although theoretical considerations suggest that genetic differentiation within such populations is to be expected. We have now analysed two large samples of data from blood donors in England to test whether the distributions of the ABO and Rhesus blood group phenotypes are random with respect to socio-economic groups as determined by occupational classification. We have found that in both native and migrant sections of the populations of two widely separated regions (south-west England and part of Yorkshire) and in both sexes, the A phenotype is highly significantly more, and the O phenotype significantly less, frequent than expected in social classes I and II, while the converse is seen in social classes III-V. An individual of the A phenotype has thus about 15% greater probability than chance would dictate of being placed in classes I and II. The distribution of the Rh+ and Rh- phenotypes does not differ significantly between classes. It seems unlikely that this nonrandom distribution of the ABO phenotypes among socio-economic groups results from sampling, historical or migrational effects and we conclude that the observed association is likely to result from pleiotropic effects of the ABO alleles (or genes closely linked to them) on attributes influencing occupational type, social mobility and social class.

Epidermal growth factor receptors on isolated human placental syncytiotrophoblast plasma membrane.

Receptor sites for mEGF that are specific, saturable and reversible have been demonstrated on isolated syncytiotrophoblast microvillous plasma membrane from term human placentae. Analysis of the binding data indicated the presence of two receptor populations. The high affinity population had 1.7 X 10(13) sites per mg membrane protein with an affinity constant (Ka) of 5.4 X 10(9)/M. The receptors of lower affinity had a Ka of 4.1 X 10(8)/M and 3.1 X 10(13) sites per mg membrane protein.

Concentrations of epidermal growth factor in mouse milk throughout lactation.

A radioimmunoassay was used to measure the concentration of epidermal growth factor (EGF) in mouse milk throughout lactation. The EGF content of mouse milk increased steadily from birth to a concentration of 427 micrograms/l at day 8 of lactation. These high levels were maintained until the approach of weaning, when values decreased from day 17 to 130 micrograms/l at day 22. Milk samples chromatographed on a Biogel P10 column gave a major peak of immunoreactivity at the point at which pure standard EGF was eluted. The origin of milk EGF is unknown, but the high concentrations of this peptide identified in mouse milk suggest that it must play a role in the neonate.

A genetic study of intergradation between Mytilus edulis and Mytilus galloprovincialis.

A study of geographic variation at 2 diagnostic allozyme loci in the mussels Mytilus edultis and M. galloprovincialis reveals considerable spatial variation, both in allele frequencies and in the extent of intergradation.