Induction of porphobilinogen oxygenase and porphobilinogen deaminase in rat blood under conditions of erythropoietic stress

Porphobilinogen is the substrate of two enzymes: porphobilinogen deaminase and porphobilinogen-oxygenase. The first one transforms it into the metabolic precursors of heme and the second diverts it from this metabolic pathway by oxidizing porphobilinogen to 5-oxopyrrolinones. Rat blood is devoid of porphobilinogen-oxygenase under normal conditions while it carries porphobilinogen-deaminase activity. When the rats were submitted to hypoxia (p_O2 = 0.42 atm) for 18 days, the activity of porphobilinogen-oxygenase appeared at the tenth day of hypoxia and reached the maximum at the 14–16th day. It decreased to a half after 2 days (half-life of the enzyme) and disappeared after 4 days of return to normal oxygen pressure. Porphobilinogen-deaminase activity increased after the first day of hypoxia, reached a maximum at the 14–16th day and did not decrease to normal values until the 15th day after return to normal oxygen pressure. The activities of both prophobilinogen-oxygenase and porphobilinogen-deaminase were induced by administration of erythropoietin. When rats were made anaemic with phenylhydrazine, porphobilinogen-oxygenase activity also appeared in the blood cells. Although the reticulocyte concentration was higher when compared to that obtained under hypoxia, the activities of the oxygenase obtained under both conditions were comparable. Porphobilinogen-deaminase activity was always closely related to the reticulocyte content. The appearance of porphobilinogen-oxygenase under the described erythropoietic conditions was due to a de novo induction of the enzyme, as shown by its inhibition with actinomycin D and cycloheximide. Porphobilinogen-oxygenase as well as porphobilinogen-deaminase were present in the rat bone marrow under normal conditions. Their activities increased in phenylhydrazine treated rats. The properties and kinetics of porphobilinogen-oxygenase from the rat blood and bone marrow were determined and found to differ in several aspects.     

Effect of ethanol on the specific transport system for L-lysine inSaccharomyces cerevisiae

Preincubation of resting cells of Saccharomyces cerevisiae double mutant can1 gap1 (with a single transport system for L-lysine) with metabolic substrates stimulated subsequent uptake of lysine. While in the wild type the stimulation is connected primarily with carrier protein synthesis (delayed, cycloheximide-inhibitable effect) in the mutant an immediate tapping of an energy source (antimycin-inhibited) is practically solely involved.     

Asymmetric incorporation of [14C]cyanate and of fluorescein isothiocyanate in mamillary body of conditioned rats

A marked decrease in overall learning capacity has been observed in rats injected with cyanate. Therefore it was of interest to test whether learning influenced carbamylation of brain proteins. Incorporation of [¹⁴C]cyanate into proteins of the mamillary body was selectively modified following operant conditioning of the rat, so that trained rats showed an asymmetric image with higher levels of incorporation in the right side than in the left side, as compared to control rats. These results were confirmed using fluorescein isothiocyanate. The asymmetry persisted once the learning had been well established.     

Haemodynamic effects of angiotensin II in conscious, non-ascitic cirrhotic rats

The effect of angiotensin II (AII) on systemic and regional haemodynamics was studied in 18 control and 18 cirrhotic, non-ascitic conscious rats (CCl4/phenobarbital model). Cirrhotic rats were found to retain sodium and to have normal plasma renin and plasma aldosterone concentrations when compared with control animals. Cirrhotic rats showed an enhanced cardiac output (34.4 +/- 0.5 vs. 27.5 +/- 2.0 ml/min in controls) and decreased peripheral resistances (2.96 +/- 0.25 vs. 3.95 +/- 0.31 mm Hg/min/100 g/ml in controls) under basal conditions. When AII was administered cardiac output decreased by 10.7 +/- 1.2% in cirrhotic rats, whereas it increased in control animals (11.2 +/- 2%, p less than 0.005). The AII-induced increase in arterial pressure was lower in cirrhotic than in control rats. The renal blood supply was particularly impaired by AII in cirrhotics, with a maintained flow to other organs (muscle, testes). It is concluded that the response to AII is disturbed in rats with hepatic cirrhosis even in a stage without ascites and with plasma renin and aldosterone concentrations similar to those of control animals.     

Extramacrochaetae,a trans-acting gene of the achaete-scute complex of Drosophila involved in cell communication

Summary Phenotypic analyses of genetic combinations involving the gene extramacrochaetae (emc) reveal its participation in the differentiation of both sensory elements and wing veins. The study of near-amorphic alleles of emc in mitotitc recombination clones indicates that it also affects cell proliferation. These clones show abnormal sizes, shapes and spatial distribution. They differentiate extra sensory elements as well as extra veins. A gain of function mutation in the gene causes opposite phenotypes in both differentiation systems. The effects of the mutant on proliferation and patterning are consistent with the emc gene being involved in the transfer of information between neighbouring cells, which leads to the spatial expression of the achaetescute gene complex and genes involved in vein formation.     

Helicobacter pylori in Barrett's esophagus.

Barrett's esophagus is an anatomicoclinical state in which, due to the prolonged action of gastroesophageal reflux, the squamous epithelium is replaced by columnar epithelium. Helicobacter pylori has been implicated in the pathogenesis of various gastrointestinal disorders and has occasionally been observed in Barrett's esophagus. The aim of this study is to determine the incidence of H. pylori in Barrett's esophagus and try to establish its role in the pathogenesis of this disorder. H. pylori was observed in 31 biopsies (44.3%) of the 70 studied, mainly when the epithelium is of the gastric atrophic-fundic type (p less than 0.01). Its presence shows no relation to the degree of inflammatory activity and does not seem, therefore, to play an important role in the pathogenesis of the lesion.