Theta Particles: a Structure Found in Hamster Sarcoma Virus

Hamster sarcoma virus (HaSV), a ribonucleic acid tumor virus, pelleted from tissue culture fluid manifests type C morphology by electron microscopy. However, if virus is first concentrated by polyethylene glycol or ammonium sulfate followed by density gradient banding, the virus shows a dramatically atypical barred core structure, termed "theta particles." This structure suggests a condensation of the ribonucleoprotein into a flat disc. Atypical particles are found with HaSV and not in similarly treated feline leukemia virus or Rauscher-murine leukemia virus. Differences in the composition of HaSV as compared with these other viruses may be responsible for the production of such particles.     

Morphological and physiological characteristics of a non-heterocystous strain of the cyanobacterium Mastigocladus laminosus Cohn from fumarolic soil on Mt Erebus,Antarctica

Summary An unusual strain of the thermophilic cyanobacterium Mastigocladus laminosus occurs on warm soils on the volcano Mt Erebus (77°32S, 167°8E). It differs morphologically from the two genetically distinct forms described from thermal habitats elsewhere. Heterocysts are lacking and true-branching is rare. Its photosynthetic rate, and the contrasting rates of two less thermotolerant algae from Mt Erebus soils, Phormidium fragile (Cyanobacteria) and Pseudococcomyxa simplex (Chlorophyta), were measured over the range -2° to 62°C. The optimum temperature range of M. laminosus was 35° to 50°C. Photosynthetic response to temperature of all three algae in the laboratory correlated well with distribution patterns in the field, confirming that zonation patterns were temperature controlled. M. laminosus retained viability following exposure to deep-freezing, freeze-thaw cycles and desiccation. Viability of the alga in culture was lost following exposure to 50°C in darkness for 42 days and following 42 days in the light at 0°C. Discussion suggests the alga would survive long distance airborne dispersal in the desiccated condition but would not survive the duration of overwinter darkness on moist soils at the warmer end of its range of occurrence in the field.     

Chromosomal location of murine and human IL-1 receptor genes.

The gene for the type I interleukin-1 (IL-1) receptor has been mapped in both mouse and human. In the human genome, a combination of segregation analysis of rodent-human hybrid cells and chromosomal in situ hybridization has placed the gene on the long arm of chromosome 2, at band 2q12. This is near the reported map position of the loci for IL-1 alpha and IL-1 beta (2q13----2q21). The murine gene has been mapped by analysis of restriction fragment length polymorphisms in interspecific backcrosses to the centromeric end of chromosome 1, in a region that is syntenic to a portion of human chromosome 2. The murine Il-1r1 gene has thus been separated from the IL-1 genes, which lie on murine chromosome 2.     

A cool spot in a biodiversity hotspot: why do tall Eucalyptus forests in Southwest Australia exhibit low diversity?

Plant and Soil - Southwest Australia is a biodiversity hotspot, with greatest plant species diversity on the most severely phosphorus (P)-impoverished soils. Here, non-mycorrhizal species with...