[Cellular signalling pathways and pathophysiology of pulmonary arterial hypertension]

INTRODUCTION

Pulmonary arterial hypertension (PAH) is a disease of complex aetiology involving in varying degrees both genetic and environmental factors.

BACKGROUND

Thanks to progress in biology over the past 15 years the physiological consequences of cellular and molecular abnormalities are much better understood. Recent work has allowed better understanding of the different cellular signalling pathways controlling pulmonary vascular tone and cell growth. It appears that these pathways form a dense and complex network involving several groups of molecules of which NO, cGMP, ET-1 and its receptors, are at the most important.

VIEWPOINT

The pathophysiology of PAH may be regarded as a disorder of cellular signaling where molecular abnormalities disturb the balance between the different factors controlling vascular tone and cell proliferation.

CONCLUSIONS

PAH may be viewed as a disease of cellular signalling where the molecular abnormalities not only affect a single signalling pathway but involve multiple cross-talks between groups of molecules controlling vascular smooth muscle tone and cell growth and differentiation.

Effect of hip prostheses on radiotherapy dose

A small but growing proportion of patients requiring radiotherapy for prostate cancer have one or two hip prostheses which may shadow the target and affect the dose distribution. Approximately 10 such patients are treated at the Illawarra Cancer Care Centre per year. Hence a study was undertaken to examine the accuracy of various treatment methods that involve some of the treatment fields travelling through the prosthesis. A fixed-field measurement showed a dose reduction of 52% in the shadow of the prosthesis. A Monte Carlo simulation confirmed an increase in dose on the distal surface of the prosthesis of 35%. Of more clinical relevance, however, is the dose distribution due to the overall combined field treatment. Using a power law correction benchmarked against thermoluminescent dosimeters and Gafchromic film, three different beam set-ups for patient treatment were planned and the dose variation analysed. A four-field brick technique gave a dose variation across the target volume of +/- 15% whereas a dual arc technique gave a dose variation of only +/- 5%. A four-field oblique technique gave a dose variation of only +/- 2% across the target volume but the oblique field technique included extra dose to the rectum.

Effects of chilling on the expression of ethylene biosynthetic genes in Passe-Crassane pear (Pyrus communis L.) fruits

Passe-Crassane pears require a 3-month chilling treatment at 0 degrees C to be able to produce ethylene and ripen autonomously after subsequent rewarming. The chilling treatment strongly stimulated ACC oxidase activity, and to a lesser extent ACC synthase activity. At the same time, the levels of mRNAs hybridizing to ACC synthase and ACC oxidase probes increased dramatically. Fruit stored at 18 degrees C immediately after harvest did not exhibit any of these changes, while fruit that had been previously chilled exhibited a burst of ethylene production associated with high activity of ACC oxidase and ACC synthase upon rewarming. ACC oxidase mRNA strongly accumulated in rewarmed fruits, while ACC synthase mRNA level decreased. The chilling-induced accumulation of ACC synthase and ACC oxidase transcripts was strongly reduced when ethylene action was blocked during chilling with 1-methylcyclopropene (1-MCP). Upon rewarming ACC synthase and ACC oxidase transcripts rapidly disappeared in 1-MCP-treated fruits. A five-week treatment of non-chilled fruits with the ethylene analog propylene led to increased expression of ACC oxidase and to ripening. However, ethylene synthesis, ACC synthase activity and ACC synthase mRNAs remained at very low level. Our data indicate that ACC synthase gene expression is regulated by ethylene only during, or after chilling treatment, while ACC oxidase gene expression can be induced separately by either chilling or ethylene.

Sequence analysis of an 81 kb contig from Arabidopsis thaliana chromosome III

The nucleotide sequence of a 81 493 bp contig from Arabidopsis thaliana chromosome III has been determined together with 11 corresponding cognate cDNAs. Analysis of the finished sequence and comparison with public databases indicates a gene density of one gene per 4527 bp and identifies 17 novel genes, 10 of which are totally unknown or have no well-defined function. In addition, the contig contains part of a non-LTR retrotransposon and large direct and inverted repeats. Contig analysis also provides information on the structure and genomic organization of plant genes.

Contribution of canopy leaching to sulphate deposition in a Scots pine forest

Radioactive sulphate (35SO4) was applied to the soil below a Scots pine forest on 23 June 1989, and its movement into the canopy and into throughfall and stemflow was measured over 4 months. The specific activity, Bq (mg S)(-1), of the canopy increased monotonically; uptake by current-year (1989) expanding needles was initially twice as fast as by older needles or live twigs. By 10 October the canopy average specific activity was 62 Bq (mg S)(-1). The specific activity of net throughfall (throughfall + stemflow - rain), deduced from measurements from six throughfall collectors, six stemflow collectors and two rain collectors, fell rapidly from 12.6 Bq (mg S)(-1) in late July to <1 Bq (mg S)(-1) in mid-August. The results suggest (assuming rapid equilibration of 35S with sulphate in soil) that root-derived sulphate contributed c. 3% of sulphate in net throughfall and that dry deposition of SO2 and sulphate particles contributed c. 97% of the 0.56 g S m(-2) measured in net throughfall over the period. Simultaneous measurements of SO2 at canopy height and of NH3 above and within the canopy gave mean concentrations of 5.9 and 0.86 microg m(-3), respectively, sufficient to account for the sulphate measured in net throughfall only if codeposition of NH3 and SO2 occurred to canopy surfaces. The large values of specific activity observed in July, however, indicate that throughfall composition may be closely related to recent soil input of sulphate, and that equilibrium cannot be safely assumed. The possibility of a significant contribution of soil-derived sulphate to sulphate deposition in net throughfall cannot be ruled out on the basis of this experiment.