Aspergillus myositis in a patient with a myelodysplastic syndrome

We present the case of an elderly man who, while being treated with corticosteroids for a myelodysplastic syndrome, developed myositis of the calf due to Aspergillus fumigatus. Despite therapy with amphotericin B the myositis failed to resolve and he died. At autopsy, a localized necrotizing myositis of the right calf was found with no evidence of disseminated Aspergillus infection. Myositis in the setting of disseminated candidiasis or cryptococcosis has been previously reported. This case is unique in that it is the first reported case of localized fungal myositis and of myositis caused by Aspergillus.     

Aminoglycoside suppression at UAG, UAA and UGA codons in Escherichia coli and human tissue culture cells

Summary We have compared the suppression of nonsense mutations by aminoglycoside antibiotics inEscherichia coli and in human 293 cells. Six nonsense alleles of the chloramphenicol acetyl transferase (cat) gene, in the vector pRSVcat, were suppressed by growth in G418 and paromomycin. Readthrough at UAG, UAA and UGA codons was monitored with enzyme assays for chloramphenicol acetyl transferase (CAT), in stably transformed bacteria and during transient expression from the same plasmid in human 293 tissue culture cells. We have found significant differences in the degree of suppression amongst three UAG codons and two UAA codons in different mRNA contexts. However, the pattern of these effects are not the same in the two organisms. Our data suggest that context effects of nonsense suppression may operate under different rules inE. coli and human cells.     

Light-temperature interactions on the growth of Antarctic diatoms

Summary The combined effect of various temperatures and light intensities on the growth of seven species of antarctic diatoms in culture has been studied. With the exception of Chaetoceros deflandrei whose thermal tolerance is fairly good, these obligatory psychrophils cannot survive in temperatures above 6° to 9° C. Their mean growth rate is relatively low, between 0.24 div d^–1 for Corethron criophilum and 0.63 div d^–1 for C. deflandrei. Regardless of light intensity, growth rate increased with the temperature to reach a maximum between 3° and 5° C. The highest rates were obtained between 115 and 220 mol m^–2 s^–1 with 0.38 div d^–1 for C. criophilum, 0.56 div d^–1 for Synedra sp. and between 0.71 and 0.88 div d^–1 for the other 5 species. A reduction in light intensity from 220 to 46 mol m^–2 s^–1 slowed growth by nearly 50%. These results suggest that the combined effect of temperature and light is one of the factors involved in the limitation of antarctic phytoplankton growth. The low temperatures of the environment do not permit rapid growth, which, even under optimal light conditions remains low. In addition, in the euphotic layer, the overall light energy available for algae is considerably reduced due to turbulence, a factor which exacerbates the reduced growth rate.     

Carbon and nitrogen partitioning in young nodulated pea (wild type and nitrate reductase-deficient mutant) plants exposed to NH4NO3

Carbon and nitrogen partitioning was examined in a wild-type and a nitrate reductase-deficient mutant (A317) of Pisum sativum L. (ev. Juneau), effectively inoculated with two strains of Rhizobium leguminosarum (128C23 and 128C54) and grown hydroponically in medium without nitrogen for 21 days, followed by a further 7 days in medium without and with 5 mM NH₄NO₃. In wild-type symbioses the application of NH₄NO₃ significantly reduced nodule growth, nitrogenase (EC 1.7.99.2) activity, nodule carbohydrates (soluble sugars and starch) and allocation of [¹⁴C]-labelled (NO₃⁻, NH₄⁺, amino acids) in roots. In nodules, there was a decline in amino acids together with an increase in inorganic nitrogen concentration. In contrast, symbioses involving A317 exhibited no change in nitrogenase activity or nodule carbohydrates, and the concentrations of all nitrogenous solutes measured (including asparagine) in roots and nodules were enhanced. Photosynthate allocation to the nodule was reduced in the 128C23 symbiosis. Nitrite accumulation was not detected in any case. These data cannot be wholly explained by either the carbohydrate deprivation hypothesis or the nitrite hypothesis for the inhibition of symbiotic nitrogen fixation by combined nitrogen. Our result with A317 also provided evidence against the hypothesis that NO₃⁻ and NH₄⁺ or its assimilation products exert a direct effect on nitrogenase activity. It is concluded that more than one legume host and Rhizobium strain must be studied before generalizations about Rhizobium /legume interactions are made.     

Heparin-like molecules regulate the number of epidermal growth factor receptors on vascular smooth muscle cells

The effect of heparin on the binding of epidermal growth factor (EGF) to vascular smooth muscle cells (SMC) was examined. Heparin pretreatment of SMC obtained from bovine aortic explant tissue resulted in significant reductions in the amount of EGF bound. Decreases in mitogen binding were observed with both growth arrested as well as exponentially growing cultures. The heparin concentrations (10-100 micrograms/ml) and pretreatment times (48-72 h) necessary for suppression of EGF binding correlated with the concentrations and temporal requirements necessary for growth inhibition. Chondroitin sulfate, which has negligible antiproliferative activity, had no effect on EGF binding. However, a highly inhibitory heparan sulfate species obtained from postconfluent SMC suppressed EGF binding by 45%. Platelet-derived growth factor and insulin-like growth factor-1 binding were unaffected by heparin. Scatchard analysis revealed that heparin induced 50 to 60% reductions in the numbers of high and low affinity EGF receptors without detectable changes in the binding affinity or ratio of high to low receptors. Experiments were also performed with enzymatically dispersed SMC. These cultures were inhibited by heparin in a time dependent manner which was partially reversible in the presence of EGF. Subsequent studies revealed that heparin suppressed EGF binding in these cultures by 20 to 40%. In summary, heparin reduces the number of EGF receptors on both explant and enzyme dispersed SMC by a mechanism which closely parallels the antiproliferative effects of this glycosaminoglycan.     

Preparation and characterisation of monoclonal and polyclonal antibodies to maize membrane auxin-binding protein

Binding proteins, thought to be auxin receptors, can be solubilised from maize (Zea mays L.) membranes after acetone treatment. From these crude extracts, receptor preparations of over 50% purity can be obtained by a reliable, straight-forward procedure involving three chromatographic steps — anion exchange, gel filtration and high-resolution anion exchange. Such preparations have been used to immunise rats for subsequent production of monoclonal antibodies. By the further step of native polyacrylamide gel electrophoresis the semi-purified preparations yield homogeneous, dimeric (22-kilodalton, kDa) auxin-binding protein, which has been used to produce a polyclonal rabbit antiserum. The preliminary characterisation of this antiserum and of the five monoclonal antibodies is presented. Two of the monoclonal antibodies specifically recognise the major 22-kDa-binding protein polypeptide whilst the other three recognise, in addition, a minor 21-kDa species. All the monoclonal antibodies recognise the polypeptide rather than the glycan side chain and the polyclonal antiserum also recognises deglycosylated binding protein. The antibodies have been used to quantify the abundance of auxinbinding protein in a number of tissues of etiolated maize seedlings. Root membranes contain 20-fold less binding protein than coleoptile membranes.Abbreviations ABP auxin-binding protein - DEAE diethylaminoethyl - Ig immunoglobulin - kDa kilodalton - NAA naphthalene-1-acetic acid - M_r relative molecular mass - PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulfate     

Characterization of the central region containing the X-inactivation center and terminal region of the mouse X Chromosome using irradiation and fusion gene transfer hybrids

The irradiation and fusion gene transfer (IFGT) procedure provides a means of isolating subchromosomal fragments for use in the mapping of loci and for cloning probes from a particular area of a chromosome. Using this procedure, two large panels of somatic cell hybrids that contain mouse X Chromosome (Chr) fragments have been generated. These hybrid panels were generated by irradiating the monochromosomal mouse-hamster hybrid HYBX, which retains the mouse X Chr, with either 10 K or 50 K rads of X-irradiation followed by fusion with a recipient Chinese hamster cell line. IFGT hybrids retaining mouse material were generated at high frequency. These hybrids were used to orient loci in the X-inactivation center region that had not been resolvable in our interspecies backcross panel and also to map, within the terminal region of the X Chr, repeat elements detected by the probe p15-4. These hybrids not only complement existing interspecies meiotic mapping panels for the detailed analysis of specific regions of particular chromosomes, but also provide a potential source of material for chromosome-specific probe isolation.     

Teratogenic effects of parthenogenetic cells from LTXBO mice,a strain which develops ovarian teratomas at high frequency

Summary LTXBO mice develop ovarian teratomas at high frequency. The phenotype of tumour tissues is unusual in that most contain trophoblast elements. Since the tumours are derived from parthenogenetically activated oocytes, they would not be expected to produce trophoblast. The developmental potential of parthenogenetic cells from these mice was tested in aggregation chimeras. No contribution to trophoblast tissues was observed. However, a high incidence of morphological abnormalities was seen, suggesting that the parthenogenetic cells exerted a teratogenic effect.