Oogenesis in the Apogamous Fern Pteris cretica

The events that characterize egg formation and maturation inPteris cretica were investigated using transmission electronmicroscopy and electron microscope microprobe analysis. Theydid not differ significantly from those described for sexuallyreproducing ferns. The significance of these findings is discussedin relation to current theories concerning phase change in ferns. Pteris cretica, fern, apogamy, agamospory, transmission electron microscopy, oogenesis     

Analysis of tegumental surface proteins of Schistosoma mansoni primary sporocysts

Axenically transformed primary sporocysts of Schistosoma mansoni (NMRI strain) were labeled with 125I in an effort to identify sporocyst proteins exposed at the tegumental surface. Using the 125I activating reagent, 1,3,4,6-tetrachloro-3 alpha,6 alpha-diphenylglycoluril, in conjunction with SDS-PAGE and autoradiography, up to 12 bands were radiolabeled out of 60 components visualized by silver staining. Labeled proteins ranged in apparent Mr from greater than 200 to less than 12 kDa. Pronase treatment of living sporocysts after radioiodination removed all labeled material, suggesting that only surface proteins were being iodinated. Western blot analysis employing 5 monoclonal antibodies (MAB's) to sporocyst surface antigens revealed a wide range of reactivities which produced banding patterns closely reflecting autoradiograms of identical samples. The concomitant removal by Pronase of immunoreactive and radiolabeled surface proteins with identical Mr in the range of 90-130 kDa suggests that epitopes recognized by these antibodies are associated with these higher molecular weight surface proteins. However, although Pronase removes all labeled surface proteins, substantial nonradiolabeled, immunoreactive material with Mr less than 90 kDa still remains on enzyme-treated parasites. This indicates that MAB-reactive epitopes, in addition to their occurrence with surface proteins, are also associated with either unlabeled, protease-resistant surface components or internal antigens. The immunohistochemical localization of antibody-reactive material in gland-like structures within sporocysts supports an internal source for nonradiolabeled, immunoreactive components. Finally, the periodate sensitivity of the epitopes recognized by all tested MAB's suggests that carbohydrate moieties may represent a common and extremely immunogenic constituent of the sporocyst surface.(ABSTRACT TRUNCATED AT 250 WORDS)     

Novel human proalbumin variant with intact dibasic sequence facilitates identification of its converting enzyme

We describe here the identification of a new genetic variant of human proalbumin with an N-terminal sequence of Arg-Gly-Val-Phe-Arg-Arg-Val-Ala-His-Lys-. Proalbumin Blenheim (10%) and mature albumin Blenheim (38%) with an initial sequence of Val-Ala-His-Lys-make up nearly half the serum albumin in affected individuals. Despite retaining an intact dibasic processing site, proalbumin Blenheim (1 Asp----Val) enters the circulation unprocessed. The observed ratio of proalbumin to albumin can be accounted for by proteolysis in the periphery. Employed as a potential substrate, proalbumin Blenheim provides a unique means of identifying the physiologically relevant proalbumin convertase. In vitro studies showed that the variant is readily cleaved by trypsin. However, it is not cleaved by the proposed proalbumin convertase, a membrane-bound Ca2+-dependent proteinase prepared from rat liver Golgi vesicles, which gives authentic cleavage of normal human proalbumin.     

Thromboxane receptor antagonism combined with thromboxane synthase inhibition. 6. 4-substituted 3-pyridinylalkanoic acids.

(3-Pyridinyl)alkanoic acids substituted at the 4-position with an (arylsulfonamido)alkyl group were synthesized and found to behave as platelet thromboxane receptor antagonists (TxRAs) and thromboxane synthase inhibitors (TxSIs). The compounds behaved as agonists at the vascular receptor for thromboxane A₂.     

Thy-1 antigen expression by murine high-proliferative capacity hematopoietic progenitor cells. I. Relation between sensitivity to depletion by Thy-1 antibody and stem cell generation potential

Hematopoietic stem cells of high proliferative potential such as the giant macrophage colony-forming cell HPP-CFC, were present in the marrow of mice treated with high dose 5-fluorouracil (5Fu) (150 mg/kg i.v.), whereas most committed granulocyte-macrophage progenitors, GM-CFU-C, were depleted. Enrichment of primitive stem cells in post 5-Fu bone marrow (5FuBM) was reflected in an enhanced capacity to proliferate in suspension cultures stimulated by the mixture of lymphokines present in Con A spleen-conditioned medium supernatant (Con A CM) when compared to normal bone marrow. The population of blast-like cells harvested at 5 days from suspension cultures of 5FuBM with Con A CM showed marked increases in stem cells GM-CFU-C and HPP-CFC. For this reason, 5FuBM was utilized to study the cell surface characteristics of putative pluripotential stem cells capable of giving rise to committed stem cells in suspension cultures. Treatment of 5FuBM (BDF1 mice) before suspension culture with a high concentration of either of two cytotoxic monoclonal antibodies directed against the Thy-1.2 surface antigen in the presence of rabbit complement reduced or abrogated the generation of stem cells HPP-CFC and GM-CFU-C in suspension cultures, even though the input content of HPP-CFC and GM-CFU-C in treated 5FuBM compared with control 5FuBM showed little reduction by the antibody plus complement treatment. The Thy-1+ cell required for generation of stem cells was not a T cell, because reconstitution of Thy-1.2-depleted 5FuBM with spleen nylon nonadherent (T) cells did not reconstitute the generation of stem cells, even though T cells did grow in the suspension cultures. In addition, depletion from 5FuBM of cells expressing Lyt-1 and Lyt-2 antigens, unambiguous markers of T cell-thymocyte differentiation, did not ablate the generation of HPP-CFC and GM-CFU-C. Rather, performance of Thy-1 cell depletion at lower efficiency, which still abrogated T cell function, ablated generation of HPP-CFC but did not affect the generation of GM-CFU-C. It was concluded that 5FuBM contains distinct Thy-1+ primitive stem cells expressing different amounts of Thy-1 antigen correlating with their respective generation potentials. Some of these Thy-1+ progenitor cells may be pluripotential.     

Organization of gene and non-gene sequences in micronuclear DNA of Oxytricha nova.

In order to study the derivation of the macronuclear genome from the micronuclear genome in Oxytricha nova micronuclear DNA was partially digested with EcoRI, size fractionated, and then cloned in the lambda phage Charon 8. Clones were selected a) at random b) by hybridization with macronuclear DNA or c) by hybridization with clones of macronuclear DNA. One group of these clones contains only unique sequence DNA, and all of these had sequences that were homologous to macronuclear sequences. The number of macronuclear genes with sequences homologous to these micronuclear clones indicates that macronuclear sequences are clustered in the micronuclear genome. Many micronuclear clones contain repetitive DNA sequences and hybridize to numerous EcoRI fragments of total micronuclear DNA, yielding similar but non-identical patterns. Some micronuclear clones containing these repetitive sequences also contained unique sequence DNA that hybridized to a macronuclear sequence. These clones define a major interspersed repetitive sequence family in the micronuclear genome that is eliminated during formation of the macronuclear genome.     

Sampling dust from human dwellings to estimate the prevalence ofDermatophagoides mite and cat allergens

Summary Quantification of specific allergens in household dust samples may provide important information for selecting appropriate allergen control methods, and monitoring efficacy and compliance. The purpose of this study was to investigate the source of variation in mite and cat allergen measurements associated with dust sample collection. Discrete and composite dust samples were collected on a filter using a special vacuum sampling device. Aqueous extracts of the dust samples were prepared thenDer p I,Der f I, andFel d I were quantitated by enzyme immunoassays (EIA). Mite and cat allergens were frequently detected in dust samples from human dwellings, and the amounts of these allergens varied significantly (p<0.01) among dwellings. The differences of allergen measurements among duplicate samples taken immediately and up to three weeks later appear to be much smaller than differences among houses and between rooms. Variation among dust samples taken from living rooms and bedrooms of the same dwelling suggest differences in allergen reservoirs. Composite samples formed by sampling specific objects within a room may provide a reliable estimate of allergen exposure in that room. Dust samples from discrete objects are useful to find and monitor specific reservoirs of mite and cat allergens.     

Genotype and phenotype associations with drought tolerance in barley tested in North Africa

A review is presented of genetic strategies deployed in a 3-yr project on drought tolerance in barley. Data were collected on genetic, physiological and agronomic traits in non-irrigated and irrigated field trials in Egypt, Morocco and Tunisia. A wide range of barley germplasm (developed from African and European cultivars, adapted landraces and wild barleys) was tested, and positive traits were found in each gene pool. The contrasting environments of the three North African countries had major effects on plant/genotype performance. Genetic effects were also detected, as were genotype × environment interactions. A range of strategies were deployed to investigate the physiology and genetics of quantitative traits associated with field performance. Quantitative trait locus (QTL) analysis was performed using backcross lines, recombinant inbred lines and doubled haploid mapping populations. A detailed genetic map was generated in the Tadmor × (ER/Apm) recombinant inbred lines, an important mapping population specifically developed by ICARDA (Centre for Agricultural Research in Dry Areas) and CIMMYT (International Maize and Wheat Improvement Center) to study drought. Quantitative trait loci (QTLs) for grain yield and other important morphological and physiological traits were also identified in a population of doubled haploids derived from F2BCj plants from a cross between a cultivar and a wild barley accession. Significantly, the wild parental line was found to contribute a number of positive alleles for yield. Effects of major developmental genes could explain many of the responses observed. QTLs were found to cluster around major genes controlling flowering time (sghI), plant stature (sdwI and arie.GP) and ear type (vrsl), and it is highly likely that the associations represent pleiotropic effects. Some QTLs were associated with candidate genes such as dehydrins and rubisco activase. One of the most significant results was the identification and generation of material that out performed the best local standards in the three participating North African countries; the selected lines have now entered local breeding programmes. The strategies adopted provided information on physiological traits, genotypes and genetic markers that could be used for marker-assisted selection. Target QTLs and their associated genetic markers may be deployed in marker assisted selection programmes to match crop phenology to the field environment.