Characterisation of a virus from Australia that is closely related to papaya mosaic potexvirus

Summary.  We have isolated a previously undescribed potexvirus from Alternanthera pungens (Amaranthaceae) in southern Queensland, Australia. This virus was shown to have a moderately wide experimental host range, infecting plants in nine of the twelve families tested. Using specific antibodies, a plate trapped antigen ELISA was developed, allowing detection of virions down to 0.8 μg/ml of leaf extract. Virions averaged 554 nm long and had a capsid protein with a M_r of 23.1 × 10³. A portion of the genome containing the capsid protein ORF and 3′ untranslated region was cloned and sequenced. From both serological and amino acid sequence comparisons, the virus was shown to be closely related to papaya mosaic potexvirus (PMV). To determine the taxonomic status of the virus, we assessed variation in the amino acid sequence of capsid proteins of distinct species within the potexvirus genus, as well as variation between strains of the same virus. When the core region of the capsid proteins were compared, distinct species had a maximum of 62.2% sequence identity, whereas strains had a minimum of 88.8% identity. By comparison, the core region of the capsid proteins of the Alternanthera virus and PMV had 79.8  identity. We have concluded that the Alternanthera virus is a different species from PMV, and its relationship with PMV resembles that of potyvirus subgroup members. Accepted August 3, 1998 Received May 22, 1998     

Haemoglobin and iron deficiency in healthy one-year-old Swiss children: a study in private practice

Haemoglobin (Hb) was measured in 348 full-term one-year-old infants in 7 private paediatric offices. In 36 (10.3%) subjects, the Hb value was less than 110 g/l, and in 7 (2.0%) less than 100 g/l. In 11 of 212 (5.2%) subjects, MCV was less than 70 fl. Twenty-six infants with an Hb below 115 g/l showed an increase of Hb of +10 g/l or more after a therapeutic trial with oral iron. No relationship was found between Hb levels and early introduction of whole cow's milk into the diet. It is concluded that screening for iron deficiency is justified in healthy Swiss infants: Hb and MCV measurements may be the initial step.     

Period-amplitude analysis and power spectral analysis: a comparison based on all-night sleep EEG recordings

Both period-amplitude analysis (PAA) and power spectral analysis (PSA) were performed on all-night human sleep EEG recordings obtained from 11 subjects. The comparison of the two methods was based on the PAA variables time in band (a wave incidence measure) and rectified amplitude, and on the PSA variables spectral power density and spectral amplitude (the square root of power). The mean time course of these variables was determined for the first 4 nonREM-REM sleep cycles. Spectral power density and spectral amplitude in the delta range were high in nonREM sleep and low in REM sleep, and showed a declining trend over consecutive nonREM sleep episodes. In the frequency range below 2 Hz, rectified amplitude was highly correlated with both time in band and spectral amplitude, and there was no evidence for a dissociation between wave amplitude and wave incidence measures. However, in frequencies above 2 Hz, the modulation of time in band was a mirror image of that below 2 Hz. This result does not reflect a property of the data, but is inherent to the methodology applied. The reversal point of modulation was merely shifted when the high-pass filter settings were changed. It is concluded that band-pass filtering is necessary prior to PAA even for the analysis of the lowest frequency range, and that the indiscriminate use of PAA may give rise to spurious results.     

Coexpression of alpha 1 with putative beta 3 subunits results in functional Na+/K+ pumps in Xenopus oocytes.

The active Na+/K+ pump is composed of an alpha and a beta subunit. Until now, three putative isoforms of the beta subunit have been identified that share sequence similarity. We have expressed the beta 1 and beta 3 isoforms of Xenopus laevis Na+/K(+)-ATPase in Xenopus oocytes to compare functional properties of the Na+/K+ pump, including either of these two isoforms. Na+/K+ pump current, estimated as K(+)-induced outward current in voltage-clamped oocytes, was doubled by coexpression of alpha 1 subunits with either isoform of the beta subunit compared to expression of alpha 1 subunits alone. The kinetics of activation by external K+ and the voltage dependence of the electrogenic activity of the Na+/K+ pump were similar with both beta isoforms, indicating that both beta 1 and beta 3 isoforms can support expression at the oocyte surface of an active Na+/K+ pump with similar functional properties.