Pathogenesis of SIVmac251 after atraumatic inoculation of the rectal mucosa in rhesus monkeys

Intrarectal inoculation of rhesus monkeys with low doses of SIV_mac led to a prolonged clinical and virological latency that was not observed for high intrarectal doses or for intravenous inoculation. Animals infected intrarectally with low virus doses remained negative for serum antibody responses to SIV for at least one year even though they readily transferred SIV to naive recipients via transfusion of whole blood.     

Role of FGFs in skeletal muscle and limb development

Fibroblast growth factors (FGFs) are a family of nine proteins that bind to three distinct types of cell surface molecules: (i) FGF receptor tyrosine kinases (FGFR-1 through FGFR-4); (ii) a cysteine-rich FGF receptor (CFR); and (iii) heparan sulfate proteoglycans (HSPGs). Signaling by FGFs requires participation of at least two of these receptors: the FGFRs and HSPGs form a signaling complex. The length and sulfation pattern of the heparan sulfate chain determines both the activity of the signaling complex and, in part, the ligand specificity for FGFR-1. Thus, the heparan sulfate proteoglycans are likely to play an essential role in signaling. We have recently identified a role for FGF in limb bud development in vivo. In the chick limb bud, ectopic expression of the 18 kDa form of FGF-2 or FGF-2 fused to an artificial signal peptide at its amino terminus causes skeletal duplications. These data, and the observations that FGF-2 is localized to the subjacent mesoderm and the apical ectodermal ridge in the early developing limb, suggest that FGF-2 plays an important role in limb outgrowth. We propose that FGF-2 is an apical ectodermal ridgederived factor that participates in limb outgrowth and patterning. © 1994 Wiley-Liss, Inc.     

Video enhanced laser scanning microscopic analysis of DNA comet formation.

Laser Scanning Microscopy is a sensitive tool that provides a unique method of analyzing biological systems. Coupled with the Single Cell Gel assay, it allows for accurate and reproducible detection of DNA strand breaks. An understanding of the theory of DNA comet formation is lacking. Using dexamethasone induced apoptosis in murine thymocytes as a model for double strand breaks, we used video enhanced laser scanning microscopy to evaluate the leading edge of DNA migration in the single cell gel assay. In this system, comet length increases significantly within the first thirty seconds of electrophoresis, the greatest increase in length is completed within the first minute, and the first two minutes are important in significant increases in DNA migration during DNA comet formation.     

The genusSavoryella from freshwater habitats,includingS. grandispora sp. nov.

The species ofSavoryella from freshwater are discussed and a key is provided.Savoryella grandispora sp. nov. from Malaysia is described and illustrated with interference contrast micrographs.     

Human Genetics, Paleoenvironments, and Malaria: Relationships and Implications for the Settlement of Oceania

Lapita is a distinctive ceramic style that first appeared in the Bismarck Archipelago about 3600 B.P. and over the next few centuries spread throughout island Melanesia. For many prehistorians the distribution of Lapita sherds identifies the expansion of Austronesian-speaking populations through Oceania. This article addresses the Lapita language question by exploring the implications of the relationship among gamma globulin (Gm) genetics, paleoenvironments, malaria, natural selection, and prehistoric settlement patterns. Archeological sites with Lapita ceramics are consistently located in coastal lowlands, which in some parts of Oceania would have been malarious areas. Drawing on recent evidence that Austronesian-speaking populations in Near Oceania possess a genetic advantage over Non-Austronesian speakers with regard to malaria, we contend that Austronesian speakers have been able to occupy—on a permanent basis—malarious coastal lowlands that were detrimental to Non-Austronesian speakers. It follows, therefore, that the inhabitants of those Lapita sites spoke one or more of the Austronesian languages.     

Identification and Cloning of Genes Involved in Specific Desulfurization of Dibenzothiophene by Rhodococcus sp. Strain IGTS8

The gram-positive bacterium Rhodococcus sp. strain IGTS8 is able to remove sulfur from certain aromatic compounds without breaking carbon-carbon bonds. In particular, sulfur is removed from dibenzothiophene (DBT) to give the final product, 2-hydroxybiphenyl. A genomic library of IGTS8 was constructed in the cosmid vector pLAFR5, but no desulfurization phenotype was imparted to Escherichia coli. Therefore, IGTS8 was mutagenized, and a new strain (UV1) was selected that had lost the ability to desulfurize DBT. The genomic library was transferred into UV1, and several colonies that had regained the desulfurization phenotype were isolated, though free plasmid could not be isolated. Instead, vector DNA had integrated into either the chromosome or a large resident plasmid. DNA on either side of the inserted vector sequences was cloned and used to probe the original genomic library in E. coli. This procedure identified individual cosmid clones that, when electroporated into strain UV1, restored desulfurization. When the origin of replication from a Rhodococcus plasmid was inserted, the efficiency with which these clones transformed UV1 increased 20- to 50-fold and they could be retrieved as free plasmids. Restriction mapping and subcloning indicated that the desulfurization genes reside on a 4.0-kb DNA fragment. Finally, the phenotype was transferred to Rhodococcus fascians D188-5, a species normally incapable of desulfurizing DBT. The mutant strain, UV1, and R. fascians produced 2-hydroxybiphenyl from DBT when they contained appropriate clones, indicating that the genes for the entire pathway have been isolated.     

LATE CRETACEOUS FOSSIL FLOWERS OF ERICALEAN AFFINITY

Fossilized flowers of ericalean affinity are reported from the Turanian (ca. 90 MYBP, million years before present) of New Jersey. The fossils are remarkably well preserved and three-dimensional, and are the oldest known floral remains of Ericales. The series of fossil flower buds, floral fragments, and fruits are not identical to any modern genus of Ericales. The inverted U-shaped anthers with pseudoterminal awns, and the fluted syncarpous ovary of the fossils suggest affinities with basal Ericaceae, probably near extant Enkianthus, a taxon that also shares monadinous pollen with the fossil. Pollen grains were observed clumped on a stigma in one of the fossil flowers. Fossilized acid-resistant strands having characteristics, including similar diameter and sculpture pattern, in common with the muri connect pollen grains and, with scanning electron microscopy, appear continuous with the tectum, supporting the interpretation that they are viscin threads. These are the oldest reported fossilized viscin threads, and the only fossilized viscin threads found in situ in flowers. In modern Ericales and Onagraceae, the presence of viscin threads is associated with highly specific plant-pollinator relationships, raising the possibility that such specific pollinator-plant relationships had developed by the mid-Cretaceous. This is consistent with floral characters in these ericalean fossils, the presence of advanced meliponine bees in slightly younger sediments from the same region, and with the morphology and affinities of other fossil flowers from the same sediments.     

RESPONSES AND CORRELATED RESPONSES TO ARTIFICIAL SELECTION ON THORAX LENGTH IN DROSOPHILA MELANOGASTER

Two sets of four replicate lines of Drosophila melanogaster were selected for large and small thorax with controls. F, progeny of crosses between the selected lines within each size category showed (a) a reduction in preadult viability in large lines relative to control and small lines when they were cultured at medium or high density in competition with a standard mutant marked competitor stock, and (b) an increase in larval development time in large lines relative to control and small lines. Natural selection for increased body size in adults may therefore be opposed by adverse effects on larval viability. The results are discussed in terms of the developmental mechanisms probably responsible for the change in body size. The preadult survival of the large and control lines was measured at three different temperatures, and there was no evidence for a significant interaction between size and temperature. The observed evolutionary increase in body size in response to reduced temperature in Drosophila must therefore involve either different genes from those subject to selection for size at a single temperature, or a fitness component other than preadult survival. There was no significant asymmetry in response to selection, and thorax length showed heterosis in crosses between the selected lines.