The spatial arrangement of germ line cells in ovarian follicles of the mutantdicephalic inDrosophila melanogaster

Summary The pattern of intercellular connections between germ line cells has been studied in follicles of the mutantdicephalic (dic), which possess nurse cell clusters at both poles. Staining of follicles with a fluorescent rhodamine conjugate of phalloidin reveals ring canals and cell membranes and thus allows us to reconstruct the spatial organization of the follicle. Each germ line cell can be identified by the pattern of cell-cell connections which reflect the mitotic history of individual cells in the 16-cell cluster. The results indicate that in both wild-type anddicephalic cystocyte clusters one of the two cells with four ring canals normally becomes the pro-oocyte. However, in some follicles (dicephalic and wild-type) oocytes were found with fewer or more than four ring canals. Indic follicles, one or several nurse cells may become disconnected from the other cells during oocyte growth at stage 9–10. Such disconnected cells cannot later on empty their cytoplasm into the oocyte. This, in turn, might be of consequence for the determination of axial polarity of the embryo.     

Transport of GABA at the Blood-CSF Interface

Abstract: The entry of GABA into cerebrospinal fluid (CSF) was studied in dogs anesthetized with pentobarbital and relaxed with suxamethonium. GABA was administered intravenously as a priming dose and subsequent maintenance infusion to compensate for the rapid elimination of the amino acid. Steady state concentrations of GABA in CSF were reached between 10 and 60 min after injection, the rate of entry tending to decrease with increasing plasma levels. During steady state conditions CSF concentrations showed great interin-dividual differences and varied between 0.03 and 5.1% of those in plasma. Probenecid and sodium valproate considerably enhanced the CSF/plasma concentration ratio of GABA. When GABA was directly injected into the liquor space, probenecid slowed down the elimination of GABA from CSF. The results suggest a transport of GABA into and out of CSF, the outward transport being inhibited by probenecid and sodium valproate.     

Parasite-induced enhancement of hemolymph tyrosinase activity in a selected immune reactive strain of Drosophila melanogaster

Larval hemolymph tyrosinase activity in Drosophila melanogaster was detected with high performance liquid chromatography with electrochemical detection. The enzyme hydroxylated L-tyrosine, and oxidized the diphenol substrates L-dopa and dopamine. In larvae of a selected immune-reactive strain the rates of tyrosine hydroxylation, dopa oxidation, and dopamine oxidation were markedly increased during the early stages of melanotic encapsulation of the eggs of the parasitic wasp Leptopilina boulardi. Tyrosinase activity was not modified in parasitized larvae of a selected susceptible strain of D. melanogaster, in which hosts the parasitoids developed unmolested. During the same period of parasitization, the amount of free tyrosine in immune reactive larvae was approximately three times higher than in susceptible hosts. These data indicate that the tyrosinase system of the immune reactive strain is activated during parasitization, and this results in the synthesis of some precursors which ultimately produce a melanotic and sclerotic capsule around the eggs of the parasite. Based on known genetic information of the enzyme system in Drosophila, it appears that at least two genes may be involved in the activation process, one associated with the proenzyme for monophenol oxidase activity, and the second with the proenzyme for diphenol oxidase activity.     

Bone Morphogenetic Protein 7 (BMP-7) Influences Tendon-Bone Integration In Vitro

IntroductionSuccessful graft ingrowth following reconstruction of the anterior cruciate ligament is governed by complex biological processes at the tendon-bone interface. The aim of this study was to investigate in an in vitro study the effects of bone morphogenetic protein 7 (BMP-7) on tendon-bone integration.ResultsIn both models, positive effects of BMP-7 on ALP enzyme activity were observed (p<0.001). Additionally, similar results were noted for LDH activity and lactate concentration. BMP-7 stimulation led to a significant increase in OCN expression. Whereas the effects of BMP-7 on tendon monoculture peaked during an early phase of the experiment (p<0.001), the cocultures showed a maximal increase during the later stages (p<0.001). The histological analysis showed a stimulating effect of BMP-7 on extracellular matrix formation. Organized ossification zones and calcium carbonate-like structures were only observed in the BMP-stimulated cell cultures.DiscussionThis study showed the positive effects of BMP-7 on the biological process of tendon-bone integration in vitro. Histological signs of improved mineralization were paralleled by increased rates of osteoblast-specific protein levels in primary bovine osteoblasts and fibroblasts.ConclusionOur findings indicated a role for BMP-7 as an adjuvant therapeutic agent in the treatment of ligamentous injuries, and they emphasized the importance of the transdifferentiation process of tendinous fibroblasts at the tendon-bone interface.     

Cell adhesion molecule in the hexactinellid Aphrocallistes vastus

Abstract. The Hexactinellida sponge Aphrocallistes vastus contains a soluble aggregation factor (AF) whose purification has been described in this communication. It is characterized by a S°_20.w value of 37 and a buoyant density of 1.45 g/cm³. The AF is a glycoporteinaceous particle composed of three major protein species; no core structure could be visualized. In the presence of Ca²⁺, the AF causes secondary aggregation of single cells. The aggregation process is temperature, pH, and ionic strength independent within a broad range. Evidence is presented indicating that two (or more) AF molecules are required for the establishment of a stable cell: cell interaction. In contrast to the AFs from demosponges, the hexactinellid AF functions species-unspecifically.     

Analysis of genetic changes in radiated and non-radiated bulk oat (Avena sativa L.) populations

Summary In both radiated and non-radiated oat populations inbreeding coefficients increased more slowly than was expected on the assumption of full selfing and equal selective values for homozygotes and heterozygotes. Assuming 1% outcrossing for oats and a selective value of 1.0 for the mean, the heterozygotes for two loci governing crown rust reaction have an advantage of 50% over the homozygotes. This study supports previous observations that the heterozygote often has a decided advantage in predominantly self-pollinated crops.     

Two novel loci underlie natural differences in Caenorhabditis elegans abamectin responses

Parasitic nematodes cause a massive worldwide burden on human health along with a loss of livestock and agriculture productivity. Anthelmintics have been widely successful in treating parasitic nematodes. However, resistance is increasing, and little is known about the molecular and genetic causes of resistance for most of these drugs. The free-living roundworm Caenorhabditis elegans provides a tractable model to identify genes that underlie resistance. Unlike parasitic nematodes, C. elegans is easy to maintain in the laboratory, has a complete and well annotated genome, and has many genetic tools. Using a combination of wild isolates and a panel of recombinant inbred lines constructed from crosses of two genetically and phenotypically divergent strains, we identified three genomic regions on chromosome V that underlie natural differences in response to the macrocyclic lactone (ML) abamectin. One locus was identified previously and encodes an alpha subunit of a glutamate-gated chloride channel (glc-1). Here, we validate and narrow two novel loci using near-isogenic lines. Additionally, we generate a list of prioritized candidate genes identified in C. elegans and in the parasite Haemonchus contortus by comparison of ML resistance loci. These genes could represent previously unidentified resistance genes shared across nematode species and should be evaluated in the future. Our work highlights the advantages of using C. elegans as a model to better understand ML resistance in parasitic nematodes.