Closure of a genetic linkage map of human chromosome 7q with centromere and telomere polymorphisms.

We have constructed a 2.4-cM resolution genetic linkage map for chromosome 7q that is bounded by centromere and telomere polymorphisms and contains 66 loci (88 polymorphic systems), 38 of which are uniquely placed with odds for order of at least 1000:1. Ten genes are included in the map and 11 markers have heterozygosities of at least 70%. This map is the first to incorporate several highly informative markers derived from a telomere YAC clone HTY146 (locus D7S427), including HTY146c3 (HET 92%). The telomere locus markers span at least 200 kb of the 7q terminus and no crossovers within the physical confines of the locus were observed in approximately 240 jointly informative meioses. The sex-equal map length is 158 cM and the largest genetic interval between uniquely localized markers in this map is 11 cM. The female and male map lengths are 181 and 133 cM, respectively. The map is based on the CEPH reference pedigrees and includes over 4000 new genotypes, our previously reported data plus 29 allele systems from the published CEPH version 5 database, and was constructed using the program package CRI-MAP. This genetic linkage map can be considered a baseline map for 7q, and will be useful for defining the extent of chromosome deletions previously reported for breast and prostate cancers, for developing additional genetic maps such as index marker and 1-cM maps, and ultimately for developing a fully integrated genetic and physical map for this chromosome.     

Localization of sequences regulating ancestral and acquired sites of esterase6 activity in Drosophila melanogaster

We have broadly defined the DNA regions regulating esterase6 activity in several life stages and tissue types of D. melanogaster using P- element-mediated transformation of constructs that contain the esterase6 coding region and deletions or substitutions in 5' or 3' flanking DNA. Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and the primary sequences regulating its activity lie between -171 and -25 bp relative to the translation initiation site: deletion of these sequences decrease activity approximately 20-fold. Hemolymph activity is also modulated by four other DNA regions, three of which lie 5' and one of which lies 3' of the coding region. Of these, two have positive and two have negative effects, each of approximately twofold. Esterase6 activity is present also in two male reproductive tract tissues; the ejaculatory bulb, which is another ancestral activity site, and the ejaculatory duct, which is a recently acquired site within the melanogaster species subgroup. Activities in these tissues are at least in part independently regulated: activity in the ejaculatory bulb is conferred by sequences between -273 and -172 bp (threefold decrease when deleted), while activity in the ejaculatory duct is conferred by more distal sequences between -844 and -614 bp (fourfold decrease when deleted). The reproductive tract activity is further modulated by two additional DNA regions, one in 5' DNA (-613 to -284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to +2731 bp; threefold decrease when deleted) that probably overlaps the adjacent esteraseP gene. Collating these data with previous studies suggests that expression of EST6 in the ancestral sites is mainly regulated by conserved proximal sequences while more variable distal sequences regulate expression in the acquired ejaculatory duct site.      

Phylogenetic diversification of immunoglobulin genes and the antibody repertoire

Immunoglobulins are encoded by a large multigene system that undergoes somatic rearrangement and additional genetic change during the development of immunoglobulin-producing cells. Inducible antibody and antibody-like responses are found in all vertebrates. However, immunoglobulin possessing disulfide-bonded heavy and light chains and domain-type organization has been described only in representatives of the jawed vertebrates. High degrees of nucleotide and predicted amino acid sequence identity are evident when the segmental elements that constitute the immunoglobulin gene loci in phylogenetically divergent vertebrates are compared. However, the organization of gene loci and the manner in which the independent elements recombine (and diversify) vary markedly among different taxa. One striking pattern of gene organization is the "cluster type" that appears to be restricted to the chondrichthyes (cartilaginous fishes) and limits segmental rearrangement to closely linked elements. This type of gene organization is associated with both heavy- and light-chain gene loci. In some cases, the clusters are "joined" or "partially joined" in the germ line, in effect predetermining or partially predetermining, respectively, the encoded specificities (the assumption being that these are expressed) of the individual loci. By relating the sequences of transcribed gene products to their respective germ-line genes, it is evident that, in some cases, joined-type genes are expressed. This raises a question about the existence and/or nature of allelic exclusion in these species. The extensive variation in gene organization found throughout the vertebrate species may relate directly to the role of intersegmental (V<==>D<==>J) distances in the commitment of the individual antibody-producing cell to a particular genetic specificity. Thus, the evolution of this locus, perhaps more so than that of others, may reflect the interrelationships between genetic organization and function.      

The A.M.A. Session

The use of liquid nitrogen for the removal of warts has advantages over electrocautery in certain circumstances. Although the incidence of recurrences after liquid nitrogen is higher than after cautery, it causes considerably less scarring. It is most useful in dealing with peri-ungual and multiple warts. The technique is simple and a supply of liquid nitrogen can be kept on hand in the office at relatively low cost.     

Schistosoma mansoni: localization of calcium-detecting reagents in electron-lucent areas of specific preacetabular gland granules

In an attempt to establish the exact location of calcium within the preacetabular glands of cercariae of Schistosoma mansoni, these larvae were exposed to reagents (potassium oxalate, potassium pyroantimonate, chloranilic acid, and silver nitrate) useful in the detection of calcium, and were subsequently observed with the aid of light and electron microscopes. Cercariae incubated in potassium oxalate and viewed in polarized light showed birefringence only in the preacetabular gland funduses. At the ultrastructural level, the preacetabular glands of potassium oxalate-treated cercariae had no electron-dense precipitate, but instead had translucent, irregularly shaped inclusions, similar to spaces left by volatilized calcium oxalate as described by others. Pyroantimonate treatment, on the other hand, localized the reaction in the electron-lucent areas of the light-spotted granules. The von Kossa silver nitrate procedure destroyed the secretory granules; therefore, an electron-dense precipitate was distributed throughout the gland. However, pretreatment with chloranilic acid before fixation preserved the granules, and subsequent exposure to the von Kossa silver nitrate gave a reaction identical to that obtained with the pyroantimonate alone. When viewed in polarized light, chloranilic acid-incubated cercariae showed birefringence in the fundus and duct areas.     

MEASUREMENTS OF PHYTOPLANKTON-PROTEIN CONTENT WITH THE HEATED BIURET-FOL1N ASSAY1,2

The heated biuret-Folin method for determining protein consistently measures 90% of the total nitrogen of filtered algae samples as protein-N without the need of mechanical disruption as long as the heating period in biuret is 100 min at 100 C. Data indicate this protein assay measures total protein on all species tried and for naturally occurring mixtures of species plus detritus. Dilute algal suspensions with as little as 0.05 μg-atom particulate protein N.liter ^-1 can he concentrated by fltration on glass fiber filters to 1.0 μg-atom particulate protein-N per filter, the optimal amount of sample for a 5 ml volume of biuret. The filtered algae samples can be stored for several weeks frozen before assaying, if necessary.     

Paleolimnology of Qilu Hu,Yunnan Province,China

Qilu Hu is a large (A = 36.9 km²), shallow (z_max = 6.8 m) lake that lies at an elevation of 1797 m above msl on the Yunnan Plateau, southern China. Lake waters are hard (Mg = 3.2m eq L^–1, Ca = 1.3 meq L^–1 ), fresh (conductivity = 380 S cm ^–1), and productive (Secchi < 40 cm). An 11-m sediment core has a basal ¹⁴C age of 30960 ± 860 B.P. Sediments between 11 m and 6 m are high in % dry weight, rich in clay components Al₂O₃, Fe₂O₃, K₂O, MgO, and low in organic C (6.1%), carbonate-C (<1.0%), total N (<3.2 mg g^–1), and total S (<-1.7 mg g^–1). Diatoms and pollen indicate open-water conditions between 9.0 m and 6.0 m (1342011790 B.P.). Above 6.0 m, CaCO₃ and organic matter concentrations increase relative to clastics. The transition marks a change to shallow-water conditions as inferred from diatoms and pollen, and probably reflects a shift to drier climate. Uppermost (80-0 cm) red clays were deposited rapidly, probably as a consequence of recent (decades to centuries) riparian disturbances (e.g. agriculture, lake-bottom reclamation, urban development). Dates assigned to events in the Qilu Hu profile are tentative because of potential hard-water-lake error.     

Schistosoma mansoni: Ultrastructure of early transformation of skin- and shear-pressure-derived schistosomules

Against the background of cercarial fine structure, ultrastructural changes were compared in schistosomules of Schistosoma mansoni 30 min and 1 hr after their production in vivo by skin penetration and in vitro by shear pressure. The same developmental pattern was observed in schistosomules of both derivations. In vitro schistosomules, however, developed more slowly, resembled cercariae more closely, and varied less among organisms than did in vivo schistosomules. The greatest morphological changes were observed in the 1-hr in vivo schistosomules. These were as follows: (1) in tegument, formation of transient microvilli, a hepatalaminate outer membrane and accented surface invaginations, loss of glycocalyx, movement outward of cyton vesicles via bridges, accumulation of multilaminate bodies around bridge openings; (2) in the anterior organ (oral sucker), movement of head gland vesicles via the ducts into tegument followed by collapse of the gland fundus, disappearance of the circumfundal cells and two large support cells, and the appearance in these areas of membranes and parenchymal cells; (3) secretion of the acetabular gland contents, collapse of the glands and replacement by membranes and parenchymal cells; (4) peristaltic activity of the digestive tract as shown by alternate areas of lumen constriction and dilation; (5) loss of bladder and contraction of the small aboral collecting tubules; and (6) conversion of heterochromatic parenchymal cell nuclei to euchromatic. In contrast, the 1-hr in vitro shear schistosomules resembled 30-min in vivo schistosomules, retaining many cercarial features.