Life-threatening haematological disorders presenting with opthalmic manifestations.

Three cases are reported where life-threatening haematological disorders requiring urgent medical intervention presented initially to the ophthalmologist. Case one, chronic myeloid leukaemia, presented with bilateral leukaemic retinopathy and central retinal vein obstruction due to hyperviscosity. Case two, acute myeloid leukaemia, presented with bilateral haemorrhagic retinopathy. Case three, aplastic anaemia, presented with bilateral retinopathy due to anaemia and thrombocytopaenia resembling bilateral central retinal vein occlusion. In all three cases the presence of simultaneous bilateral retinal vascular involvement and white-centred haemorrhages suggested an underlying haematological disorder and differentiated them from typical retinal venous obstruction. Prompt identification of the underlying haematological disorder allows timely referral for potentially life-saving treatment.

Functional independence of circadian clocks that regulate plant gene expression.

BACKGROUND: Circadian clocks regulate the gene expression, metabolism and behaviour of most eukaryotes, controlling an orderly succession of physiological processes that are synchronised with the environmental day/night cycle. Central circadian pacemakers that control animal behaviour are located in the brains of insects and rodents, but the location of such a pacemaker has not been determined in plants. Peripheral plant and animal tissues also maintain circadian rhythms when isolated in culture, indicating that these tissues contain circadian clocks. The degree of autonomy that the multiple, peripheral circadian clocks have in the intact organism is unclear. RESULTS: We used the bioluminescent luciferase reporter gene to monitor rhythmic expression from three promoters in transgenic Arabidopsis and tobacco plants. The rhythmic expression of a single gene could be set at up to three phases in different anatomical locations of a single plant, by applying light/dark treatments to restricted tissue areas. The initial phases were stably maintained after the entraining treatments ended, indicating that the circadian oscillators in intact plants are autonomous. This result held for all the vegetative plant organs and for promoters expressed in all major cell types. The rhythms of one organ were unaffected by entrainment of the rest of the plant, indicating that phase-resetting signals are also autonomous. CONCLUSIONS: Higher plants contain a spatial array of autonomous circadian clocks that regulate gene expression without a localised pacemaker. Circadian timing in plants might be less accurate but more flexible than the vertebrate circadian system.

The circadian clock controls the expression pattern of the circadian input photoreceptor, phytochrome B.

Developmental and physiological responses are regulated by light throughout the entire life cycle of higher plants. To sense changes in the light environment, plants have developed various photoreceptors, including the red/far-red light-absorbing phytochromes and blue light-absorbing cryptochromes. A wide variety of physiological responses, including most light responses, also are modulated by circadian rhythms that are generated by an endogenous oscillator, the circadian clock. To provide information on local time, circadian clocks are synchronized and entrained by environmental time cues, of which light is among the most important. Light-driven entrainment of the Arabidopsis circadian clock has been shown to be mediated by phytochrome A (phyA), phytochrome B (phyB), and cryptochromes 1 and 2, thus affirming the roles of these photoreceptors as input regulators to the plant circadian clock. Here we show that the expression of PHYB::LUC reporter genes containing the promoter and 5' untranslated region of the tobacco NtPHYB1 or Arabidopsis AtPHYB genes fused to the luciferase (LUC) gene exhibit robust circadian oscillations in transgenic plants. We demonstrate that the abundance of PHYB RNA retains this circadian regulation and use a PHYB::Luc fusion protein to show that the rate of PHYB synthesis is also rhythmic. The abundance of bulk PHYB protein, however, exhibits only weak circadian rhythmicity, if any. These data suggest that photoreceptor gene expression patterns may be significant in the daily regulation of plant physiology and indicate an unexpectedly intimate relationship between the components of the input pathway and the putative circadian clock mechanism in higher plants.

Clinical and laboratory studies on haemorrhagic fever in Burma, 1970-72.

This three-year serologic study of 2 060 children with a clinical diagnosis of haemorrhagic fever, who were admitted to the Children's Hospital and other hospitals in Rangoon, has shown that the etiology of the illness was multiple. Of all these patients, 347 (16.8%) had a dengue infection (96 with primary and 251 with secondary dengue infections), 510 (24.7%) had chikungunya infections, 55 (2.7%) had simultaneous chikungunya and dengue, 263 (12.8%) had influenza A infections, 62 (3.0%) had influenza B, 12 (0.6%) had measles, and there were 811 (39.4%) for whom no etiology could be established. Epidemiological and clinical features and laboratory findings are discussed. Evidence is presented for human infections with all four types of denguevirus in Rangoon.