An oxygen dependence in chromium mutagenesis

Evidence is provided that mutagenicity in Salmonella by a chromium(VI) salt and a chromium(III) compound has a differential dependence on the presence of oxygen. The mutagenic chromium(III) compound, cis-dichlorobis(2,2'-bipyridyl)chromium(III), reverted Salmonella strains, TA102 and TA2638, only under aerobic conditions. Potassium dichromate (chromium VI) required the presence of oxygen to revert the Salmonella strain TA102 but induced a moderate reversion frequency in TA2638 under anaerobic conditions. The data also support a role for oxygen radicals in chromium-mediated mutagenesis and suggests at least two pathways by which chromium compounds can induce mutations.     

Reinfection of virus free mice with mouse mammary tumour virus

BR6/Icrf mice carrying a milk-transmitted mammary tumour virus (MMTV) develop tumours after several pregnancies. If the mice are freed from MMTV, no tumours develop. In the experiments described in this paper, MMTV was reintroduced into MMTV-free mice by foster nursing, which was least effective if the pups were exposed to the virus only during the first week of life. Exposure for even a short time after that age led to a tumour incidence similar to that found in normally infected mice. Reinfection was also achieved by injection of MMTV-containing milk into weanling or pregnant mice, and was then transmitted naturally to the next generation.     

Paleohistology of Paget's disease in two medieval skeletons.

Paget's disease has been ascribed several times to specimens of archeological bone but, in the absence of microscopic examination, the evidence remains insubstantial. Suspected metabolic bone disease is described here in the archeological remains of a skeleton from a 16th century burial ground at Wells Cathedral, England and from a single medieval sacrum recovered from a large deposit of disarticulated bones from a churchyard at Barton-on-Humber, England. Radiographs showed apparent structural abnormality in one femoral shaft and calcaneus and in the isolated sacrum. Histomorphometry on undecalcified bone cores confirmed the regions of abnormality and showed not only increased trabecular width but also areas of "mosaic" woven bone together with extensive resorption cavities; these features contrasted with the normal structure and organized lamellar bone from sites elsewhere. Despite post-interment changes in surrounding tissues, the morphological stability of some of the osteocytes was remarkable. Preservation of the histology was sufficient to permit the assignment of a metabolic bone disorder and the nature of the sclerosis was consistent with Paget's disease.     

Metabolism of halogenated bisphosphonates by the cellular slime mould Dictyostelium discoideum.

Methylenebisphosphonate and its monofluoro-, difluoro- and dichloro- derivatives inhibited growth of amoebae of Dictyostelium discoideum. Dichloromethylenebisphosphonate was the most potent inhibitor of amoebal growth whereas difluoromethylenebisphosphonate was the least potent inhibitor. Each of the bisphosphonates was taken up by the amoebae and incorporated into the corresponding beta, gamma-methylene analogue of adenosine triphosphate. Two of the bisphosphonates were also incorporated into the corresponding analogues of diadenosyl tetraphosphate. No correlation was found between the ability of the bisphosphonates to inhibit amoebal growth and the extent to which they were metabolised.     

Linkage of the acetylcholine transporter-vesamicol receptor to proteoglycan in synaptic vesicles.

The relationship of the acetylcholine transporter-vesamicol receptor (AcChT-VR) to proteoglycan in Torpedo electric organ synaptic vesicles was investigated. The cholate-solubilized VR was immunoprecipitated by a monoclonal antibody directed against the SV1 epitope located in the glycosaminoglycan portion of the proteoglycan. AcChT that was photoaffinity-labeled with a tritiated high-affinity analogue of AcCh [cyclohexylmethyl cis-N-(4-azidophenacyl)-N-methylisonipecotate] and then denatured in sodium dodecyl sulfate also immunoprecipitated. The labeled AcChT exhibited a M(r) range of 100,000-200,000. Proteoglycan did not engage in detectable nonspecific reversible aggregation that might mask the presence of another subunit during sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In vesicles permeabilized with cholate, the enzymes keratanase and testicular hyaluronidase inactivated binding of vesamicol and destroyed the SV1 epitope without detectable proteolysis. Other glycosaminoglycan-degrading enzymes were without effect. The results demonstrate that the AcChT-VR and proteoglycan are very strongly linked and that glycosaminoglycan-like polysaccharide controls the conformation of the VR. The unexpected linkage to proteoglycan suggests that AcChT-VR in intact terminals might communicate with extracellular matrix and participate in stabilization and operation of the synapse.     

High-resolution X-ray study of deoxyhemoglobin Rothschild 37 beta Trp----Arg: a mutation that creates an intersubunit chloride-binding site.

The mutation site in hemoglobin Rothschild (37 beta Trp----Arg) is located in the "hinge region" of the alpha 1 beta 2 interface, a region that is critical for normal hemoglobin function. The mutation results in greatly reduced cooperativity and an oxygen affinity similar to that of hemoglobin A [Gacon, G., Belkhodja, O., Wajcman, H., & Labie, D. (1977) FEBS Lett. 82, 243-246]. Crystal were grown under "low-salt" conditions [100 mM Cl- in 10 mM phosphate buffer at pH 7.0 with poly(ethylene glycol) as a precipitating agent]. The crystal structure of deoxyhemoglobin Rothschild and the isomorphous crystal structure of deoxyhemoglobin A were refined at resolutions of 2.0 and 1.9 A, respectively. The mutation-induced structural changes were partitioned into components of (1) tetramer rotation, (2) quaternary structure rearrangement, and (3) deformations of tertiary structure. The quaternary change involves a 1 degree rotation of the alpha subunit about the "switch region" of the alpha 1 beta 2 interface. The tertiary changes are confined to residues at the alpha 1 beta 2 interface, with the largest shifts (approximately 0.4 A) located across the interface from the mutation site at the alpha subunit FG corner-G helix boundary. Most surprising was the identification of a mutation-generated anion-binding site in the alpha 1 beta 2 interface. Chloride binds at this site as a counterion for Arg 37 beta. The requirement of a counterion implies that the solution properties of hemoglobin Rothschild, in particular the dimer-tetramer equilibrium, should be very dependent upon the concentration and type of anions present.     

Lysosomal interconnections and horseradish peroxidase compartmentalization in three-dimensionally reconstructed bovine alveolar macrophages

Following a 1-h incubation of bovine alveolar macrophages in 1 to 2 mg/ml exogenous horseradish peroxidase (HRP), ultrathin sections revealed vacuolar interconnections among both labeled and unlabeled vacuoles constituting the lysosomal compartment. Four entire cells and their vacuolar components were subsequently computer resconstructed from serial transmission electron micrographs and measured using a morphometric technique. HRP-labeled and unlabeled vacuoles ranged in size from 0.5 micron to greater than or equal to 4.0 microns in diameter and occupied up to 25% of the cytoplasmic volume. HRP-containing vacuoles were distributed throughout each cell in a clumped distribution (P less than 0.05) and occupied up to 75% of the total vacuole compartment. Up to 60% of all vacuoles were interconnected through a series of openings formed by membrane fusions (average pore diameter 0.42 micron), which resulted in a labyrinth of vacuoles comprising up to 55% of the total volume of the lysosomal compartment. The area of open interconnections resulting from vacuolar fusions represented less than 1% of the total surface area of the lysosomal membrane. Rotation of a three-dimensionally reconstructed macrophage about the Y-axis revealed an interconnected vacuolar network of 75 fused vacuoles in a chain up to 21 microns in length. We have demonstrated that HRP-labeled vacuoles interconnect with each other as well as with preexisting unlabeled vacuoles. As a result of such interconnections, individual vacuoles become contributing members of a large, continuous, lysosomal compartment in bovine alveolar macrophages.     

In Vitro Processing of Aleurain,a Barley Vacuolar Thiol Protease

Aleurain, originally described from its cDNA as a thiol protease [Rogers, J.C., Dean, D., and Heck, G.R. (1985). Proc. Natl. Acad. Sci. USA 82, 6512-6516], is characterized here as a glycoprotein that is targeted to a distinct vacuolar compartment in aleurone cells. Monospecific antibodies to a bacterial trpE-aleurain fusion protein were used to show that aleurain is made as a 42-kilodalton (kD) proenzyme (proaleurain) that is proteolytically processed in a post-Golgi compartment in two steps to form a 32-kD protein. The first processing step is the discrete loss of 9 kD from proaleurain to yield a 33-kD intermediate that is further processed by the gradual loss of 1 kD resulting in mature 32-kD aleurain. Using proaleurain secreted from Xenopus oocytes as a substrate, we established an in vitro system using aleurone cell extracts that correctly processes proaleurain to a stable protein that is indistinguishable from native barley aleurain as judged by partial digestion with staphylococcal V8 protease. Proaleurain is not capable of self-cleavage in the absence of aleurone cell extracts and mature aleurain appears not to participate in processing in vitro.     

Crown ether mediated cadmium halide dimers and polymers

The reactions of cadmium halides with the 15-membered macrocyclic crown ethers, 15-crown-5 and benzo-15-crown-5, have been carried out and six new complexes have been isolated and structurally characterized. Metal to ligand stoichiometries of 1:1, 2:1, 3:1 and 3:2 have been observed with a variety of different formulations. Examples of charge separated ion pairs ([(NH₄)(benzo-15-crown-5)₂]₂[Cd₂I₆]), halogen bridged monomers, dimers or polymers ([Cd(15-crown-5)(OHMe)(μ-Br)CdBr₃], [Cd(15-crown-5)(μ-Br)₂CdBr(μ-Br)]₂(isolated from the same reaction mixture) and [(CdCl₂)₂CdCl₂(15-crown-5)]_n), and hydrogen bonded finite chains or polymers ([(Cd(OH₂)₂(15-crown-5)][CdI₃(OH₂)]₂·2(15-crown-5)·2CH₃CN and [CdI₂(OH₂)₂(THF)]·benzo-15-crown-5) have been isolated. Three different types of 15-crown-5 coordination modes have been observed in these complexes. In-cavity coordination resulting in pentagonal bipyramidal geometries about Cd²⁺ was observed in [(CdCl₂)₂CdCl₂(15-crown-5)]_n, [Cd(15-crown-5)(OHMe)(μ-Br)CdBr₃], and [Cd(OH₂)₂(15-crown-5)][CdI₃(OH₂)]₂·2(15-crown-5)·2CH₃CN, [Cd(15-crown-5)(μ-Br)₂CdBr(μ-Br)]₂ displays out-of-cavity coordination with one etheric donor distorted into an axial position of a distorted pentagonal bipyramid. The third coordination mode is secondary sphere coordination via hydrogen bonding which is observed for [Cd(OH₂)₂(15-crown-5)][CdI₃(OH₂)]₂·2(15-crown-5)·2CH₃CN. The good fit of Cd²⁺ within the cavity of 15-crown-5 results in shorter bonding contacts and a more narrow distribution in Cd---O values (2.273(7)-2.344(6) Å) than observed for cadmium halide complexes of 18-crown-6 (Cd---O = 2.69(1)–2.81(1) Å).     

Ectoparasitic Acugutturid Nematodes of Adult Lepidoptera

Noctuidonema guyaneme is an interesting ectoparasite of adult Lepidoptera that feeds on hosts from at least five families with its long stylet. Noctuidonema guyanense spends its entire life on the adult moth and is sustained as it is passed from moth to moth during host mating. Overlapping host generations are essential for parasite survival. This nematode occurs throughout tropical and subtropical America and is transported by at least one of its hosts, Spodoptera frugiperda, during migration to northern sites in the United States each spring. Noctuidonema guyanense debilitates its hosts. Research conducted to help determine the biological control importance of this nematode is reviewed. Two additional species, N. daptria and N. dibolia, are now known for Noctuidonema.