Is the epithelium-derived inhibitory factor in guinea-pig trachea a prostanoid?

To examine further the possible prostanoid involvement in the influence of the epithelium on guinea-pig tracheal smooth muscle responsiveness, we have analyzed the effects of LTD₄, methacholine and histamine on the level of airway smooth muscle tone and on the amounts of PGE_2α and PGI₂ (determined by radioimmunoassay) in the presence and absence of the epithelium. Removal of the epithelium increased the sensitivity of guinea-pig trachea to the contractile effects of LTD₄, methacholine and histamine. LTD₄ (3–100 nM), methacoline (0.1–10 μM) or histamine (0.3–30 μM) did not increase prostanoid release above control values in either the presence or absence of the epithelium. The unstimulated release of PGE₂ and PGF_2α but not PGI₂, was decreased in tissues lacking epithelium. Indomethacin (1 μM) reduced the baseline tone to a smaller extent in the absence of epithelium. In the presence but not the absence of the epithelium, indomethacin increased the sensitivity of preparations to the contractile effect of methacholine. The results support the postulate of an epithelium-derived inhibitory factor modulating guinea-pig tracheal smooth muscle responsiveness. The identity of this factor is not known but is not PGI₂ and is unlikely to be PGF_2α or PGE₂. However, the possibility remains that the basal release of PGE₂ and/or PGF_2α derived from the epithelium may markedly affect the responsiveness of guinea-pig tracheal smooth muscle. Furthermore, the epithelium is a significant source of PGE₂ and PGF_2α which may be involved in the maintenance of baseline tone.     

Anaerobic degradation of trans-cinnamate and ω-phenylalkane carboxylic acids by the photosynthetic bacterium Rhodopseudomonas palustris: evidence for a β-oxidation mechanism

The mechanism responsible for the initial steps in the anaerobic degradation of trans-cinnamate and -phenylalkane carboxylates by the purple non-sulphur photosynthetic bacterium Rhodopseudomonas palustris was investigated. Phenylacetate did not support growth and there was a marked CO₂ dependence for growth on acids with greater side-chain lengths. Here, CO₂ was presumably acting as a redox sink for the disposal of excess reducing equivalents. Growth on benzoate did not require the addition of exogenous CO₂. Aromatic acids with an odd number of side-chain carbon atoms (3-phenylpropionate, 5-phenylvalerate, 7-phenylheptanoate) gave greater apparent molar growth yields than those with an even number of side-chain carbon atoms (4-phenylbutyrate, 6-phenylhexanoate, 8-phenyloctanoate). HPLC analysis revealed that phenylacetate accumulated and persisted in the culture medium during growth on these latter compounds. Cinnamate and benzoate transiently accumulated in the culture medium during growth on 3-phenylpropionate, and benzoate alone accumulated transiently during the course of trans-cinnamate degradation. The transient accumulation of 4-phenyl-2-butenoic acid occurred during growth on 4-phenylbutyrate, and phenylacetate accumulated to a 1:1 molar stoichiometry with the initial 4-phenylbutyrate concentration. It is proposed that the initial steps in the anaerobic degradation of trans-cinnamate and the group of acids from 3-phenylpropionate to 8-phenyloctanoate involves -oxidation of the side-chain.Abbreviation 3-PP 3-phenylpropionic acid - 4-PB 4-phenylbutyric acid - 5-PV 5-phenylvaleric acid - 6-PH 6-phenylhexanoic acid - 7-PH 7-phenylheptanoic acid - 8-PO 8-phenyloctanoic acid - 4-P2B 4-phenyl-2-butenoic acid - GC/MS Gas chromatography/Mass spectrometry - HPLC High-pressure liquid chromatography     

Effect of methylxanthine treatment on rice seedling growth

Methylxanthine treatment of rice seeds (Oryza sativa L. cv. Lemont) was used to determine the relative efficiencies of caffeine (1,3,7-trimethylxanthine), theobromine (3,7-dimethylxanthine), and theophylline (1,3-dimethylxanthine) as growth regulators in a plant not producing these compounds. Caffeine inhibited growth more effectively than the dimethylxanthines. Treatment with 2.5 mM caffeine inhibited shoot elongation by half after 6 days of growth, and inhibited root elongation by 90% compared to control plants germinated in water. Although caffeine treatment inhibited growth of roots more than shoots, caffeine accumulation was similar in both organs. Apparently, shoots have a more effective mechanism than roots for maintaining growth in the presence of caffeine.     

Ribosomal protein S14 is not responsible for the Minute phenotype associated with the M(1)7C locus in Drosophila melanogaster.

Summary A locus associated with a severe Minute effect has been mapped at 7C on the X chromosome of Drosophila melanogaster. Previous work has suggested that this Minute encodes ribosomal proteins S14A and S141B. We have made a chromosomal deficiency that removes the S14 ribosomal protein genes, yet does not display the Minute phenotype. These data suggest that the S14 genes do not actually correspond to the Minute locus.     

Performance of 133 compounds in the lambda prophage induction endpoint of the Microscreen assay and a comparison with S. typhimurium mutagenicity and rodent carcinogenicity assays.

The Microscreen assay was developed as a means of testing very small samples, as in complex mixture fractionation. It is a multi-endpoint assay which utilizes E. coli WP2s(lambda). Exposure takes place to serial dilutions of the test compound in microtitre wells (250 microliters) followed by sampling from wells in which growth has occurred ('non-toxic wells'). Although a number of different endpoints can be measured, only the prophage induction endpoint (the first one developed) has been extensively tested. Results with 133 compounds are presented. These include 111 compounds which have been tested in the S. typhimurium assay and 66 compounds for which both rodent bioassay and S. typhimurium assay data exists. The concordance for the Microscreen assay and the S. typhimurium assay was 71%. For this group of compounds, the sensitivity of the Microscreen assay in detecting carcinogens was 76% compared with 58% for the S. typhimurium assay. However, the S. typhimurium assay was somewhat more specific (69%) compared with the Microscreen (56%). The overall association between carcinogenicity and Microscreen results was statistically significant (p = 0.029), whereas for the S. typhimurium assay the association with carcinogenicity was non-significant (p = 0.086). The Microscreen assay was able to detect halogenated compounds better than the S. typhimurium assay. The Microscreen assay should prove useful in complex mixture fractionation, or in other situations where sample size is limiting.     

Risk of second primary cancers after Hodgkin's disease by type of treatment: analysis of 2846 patients in the British National Lymphoma Investigation.

OBJECTIVE--To analyse the risk of second primary cancers during long term follow up of patients with Hodgkin''s disease. DESIGN--Cohort study. SETTING--The British National Lymphoma Investigation (a collaborative group of over 60 participating centres in Britain treating lymphomas). PATIENTS--2846 patients first treated for Hodgkin''s disease during 1970-87, for whom follow up was complete in 99.8%. MAIN OUTCOME MEASURES--Second primary cancers; uniform pathology reviews confirmed the diagnosis of Hodgkin''s disease and of second primary non-Hodgkin''s lymphomas. RESULTS--113 second primary cancers occurred. Relative risk of cancer other than Hodgkin''s disease was 2.7 (95% confidence interval 2.3 to 3.3) compared with the general population, with significant risk of leukaemia (16.0(9.1 to 26.0)); non-Hodgkin''s lymphoma (16.8(9.8 to 26.9)); and cancers of the colon (3.2 (1.4 to 6.2)), lung (3.8 (2.6 to 5.4)), bone (15.1 (1.8 to 54.7)), and thyroid (9.4 (1.1 to 33.9)). Absolute excess risk associated with treatment was greater for solid tumours than for leukaemia and lymphomas. Relative risk of leukaemia increased soon after treatment, reaching a peak after five to nine years. It was increased substantially after chemotherapy (27.9 (12.7 to 52.9)), combined treatment with radiotherapy and chemotherapy (21.5 (7.9 to 46.8)), and relative to number of courses of chemotherapy but was not significantly increased after radiotherapy (2.5 (0.1 to 14.1)). Relative risk of non-Hodgkin''s lymphoma increased in the first five years after treatment and remained high but showed no clear relation with type or extent of treatment. Relative risk of solid tumours was less raised initially but increased throughout follow up and for lung cancer 10 years or more after entry was 8.3 (4.0 to 15.3). The risk of solid tumours increased after treatments including radiotherapy and after chemotherapy alone. The risk after chemotherapy increased significantly with time since first treatment. CONCLUSION--The risk of solid cancer, not of leukaemia, is the major long term hazard of treatment for Hodgkin''s disease, and this seemed to apply after chemotherapy as well as after radiotherapy. These risks of second cancers are important in choice of treatment and in follow up of patients, but they are small compared with the great improvements in survival which have been brought about by modern therapeutic methods for Hodgkin''s disease.     

Effect of Plant Species and Environmental Conditions on Ice Nucleation Activity of Pseudomonas syringae on Leaves

Selected plant species and environmental conditions were investigated for their influences on expression of ice nucleation activity by 15 Pseudomonas syringae strains grown on plants in constant-temperature growth chamber studies. Ice nucleation frequencies (INFs), the fraction of cells that expressed ice nucleation at −5 or −9°C, of individual strains varied greatly, both on plants and in culture. This suggests that the probability of frost injury, which is proportional to the number of ice nuclei on leaf surfaces, is strongly determined by the particular bacterial strains that are present on a leaf surface. The INFs of strains were generally higher when they were grown on plants than when they were grown in culture. In addition, INFs in culture did not correlate closely with INFs on plants, suggesting that frost injury prediction should be based on INF measurements of cells grown on plants rather than in culture. The relative INFs of individual strains varied with plant host and environment. However, none of seven plant species tested optimized the INFs of all 15 strains. Similarly, incubation for 48 h at near 100% relative humidity with short photoperiods did not always decrease the INF when compared with a 72 h, 40% relative humidity, long-photoperiod incubation. Pathogenic strains on susceptible hosts were not associated with higher or lower INFs relative to their INFs on nonsusceptible plant species. The ice nucleation activity of individual bacterial strains on plants therefore appears to be controlled by complex and interacting factors such as strain genotype, environment, and host plant species.