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.     

Purification and characterization of N,N-dimethylformamidase from Pseudomonas DMF 3/3

The N,N-dimethylformamide-hydrolyzing enzyme (DMFase) from Pseudomonas DMF 3/3 has been purified to apparent electrophoretic homogeneity with an overall 49-fold purification, a 24% yield and a final specific activity of 1.98 mumol N,N-dimethylformamide (DMF) hydrolyzed min-1 (mg protein)-1. The native DMFase has a relative molecular mass of 250 000 and is composed of two light-chain (Mr = 15 000) and two heavy-chain (Mr = 105 000) subunits. The stability of DMFase is optimal at pH values above 7.5 and at temperatures below 20 degrees C. The activity of the enzyme is inhibited by metal-chelating agents such as EDTA and 2,2'-dipyridyl. Emission and atomic absorption spectroscopy measurements showed that iron is present in significant amounts in DMFase, indicating that it is an iron-containing amidohydrolase. In the ultraviolet/visible spectrum prominent bands were observed at 224 nm, 280 nm and 396 nm and shoulders are present at 418 nm and 467 nm. DMFase from Ps. DMF 3/3 has an isoelectric point of 7.7. The enzyme exhibits optimal activity between pH 5 and 6 and at 40 degrees C. The substrate spectrum is rather narrow. The enzyme hydrolyzes preferentially substituted short-chain aliphatic amides such as DMF, N-ethylformamide and N-methylformamide. N,N-dimethylformamide, N,N-dimethylacetamide and unsubstituted amides, e.g. formamide, prolinamide, acetamide, acrylamide and butyramide are substrates as well, but are hydrolysed at significantly lower rates. DMFase obeys Michaelis-Menten kinetics and its Km and Vmax values for DMF are 13.8 mM and 1.89 U/mg, respectively, as determined from a Lineweaver-Burk plot.     

Mutations affecting the enzymes involved in the utilization of 4-aminobutyric acid as nitrogen source by the yeast Saccharomyces cerevisiae

We present genetic evidence for the enzymes 4-aminobutyrate: 2-oxoglutarate aminotransferase (EC 2.6.1.19) and succinate-semialdehyde dehydrogenase [NAD(P)+] (EC 1.2.1.16) constituting the functional pathway for the utilization of 4-aminobutyric acid as a nitrogen source by Saccharomyces cerevisiae. We show that the pathway is induced by 4-aminobutyric acid and that the presence of the pathway enzymes probably requires the integrity of a positive control element.     

Characterization of the biosynthesis in vivo of α-aminoadipyl-cysteinyl-valine inPenicillium chrysogenum

Summary The parameters affecting the formation in vivo of -aminoadipyl-cysteinyl-valine (ACV), an intermediate in penicillin biosynthesis, have been established in low- and high-penicillin producing strains ofPenicillium chrysogenum. ACV was found both in cell extracts and in the culture broth filtrates. (¹⁴C)valine, -(¹⁴C)aminoadipic acid and (¹⁴C)cysteine were efficiently incorporated into ACV. Formation of ACV was stimulated by phenylacetic acid when added during the growth of the culture. ACV biosynthesis was enhanced when protein synthesis was blocked with cycloheximide or anisomicin. The ACV-synthesising activity of the culture increased between 24 and 48 h of the culture preceeding penicillin biosynthesis, and remained constant thereafter. A decay of ACV-forming activity was observed when de novo protein synthesis was inhibited with cycloheximide. The apparent half-life of the ACV-synthesising enzyme system was 2.5 h.     

Effect of cyanide and verapamil on sodium-free contractures in the frog heart

Sodium-free contractures were studied in myocardial strips from R. pipiens with extracellular sodium (Na0+) replaced by choline chloride and extracellular calcium (Ca20+) varied with EGTA buffer. At calculated Ca02+ below 2.8 X 10(-7) mol/l, no contracture occurred in most of the experiments, even in the presence of cyanide. When Ca02+ was above 2.8 X 10(-7) mol/l, relatively short tension transients of up to 80 sec duration could be avoided if the myocardial strip was previously equilibrated for 20 min in a Na+-Ca2+-free solution. Instead, contractures developed slowly within one to several hours. The maximum contracture was dependent on Ca02+ in a dose-response-like pattern. The time-course of contracture development was not affected by verapamil, but KCN significantly increased the rate of resting tension increase. In solutions with normal Na+-Ca2+ content and even in a Na+-Ca2+-free milieu, the cellular ultrastructure was normal. Development of contracture after addition of Ca2+ to the Na+-free solution was combined with ultrastructural damage of the ventricular strip. It is concluded that Na+-free contractures depend on transsarcolemmal net-Ca2+ uptake as a sum of Na-Ca-exchange-dependent Ca2+ uptake and active sequestering of intracellular free calcium Ca2+ mediated by sarcolemmal and probably intracellular Ca2+-ATPases. The negative inotropic effect of the Ca blocker verapamil seems not to be mediated by the Na-Ca exchange.     

Extracellular glucose-producing exodextranase of the yeast Lipomyces lipofer

A dextran-hydrolysing enzyme from Lipomyces lipofer IGC 4042 was purified from the supernatant of cultures grown on a mineral medium with dextran, by ultrafiltration and gel filtration on Bio Gel A-0.5 m. This preparation gave only one band by disc gel electrophoresis. Glucose was the only product of dextran hydrolysis. Optimum pH and temperature for the activity of the enzyme were pH 4.5–5.0 and 45°C, respectively. The enzyme was most stable over a pH range of 4.5–6.0, and after 2 hours at 50°C maintained over 60% of its original activity. The molecular weight was 29,000 daltons and the isoelectric point was at pH 7. K_m (45°C, pH 5) for dextran T-40 was 1.2×10^–5 M. Glucose inhibited the enzyme competitively with a K_i (45°C, pH 5) of 0.5 mM.