Structural Analysis of the dur Loci in S. CEREVISIAE: Two Domains of a Single Multifunctional Gene

In Saccharomyces cerevisiae, the degradation of urea to carbon dioxide and ammonia is catalyzed by urea carboxylase and allophanate hydrolase. The loci coding for these enzymes (dur1 and dur2) are very tightly linked on the right arm of chromosome II between pet11 and met8. Pleiotropic mutations that fail to complement mutations in either of the dur loci were found to be predominantly located in or near the dur2 locus. We interpret these data as suggesting that the two dur loci might in reality be domains of a single gene that codes for a multifunctional polypeptide. In view of this conclusion, we have renamed the dur loci as the dur1,2 locus.     

Use of fluorescent probes in the study of phospholipid--sterol bilayers.

1. The transfer of excitation energy between the fluorescent probes 1,6-diphenylhexa-1,3,5-triene and 12-(9-anthroyl)stearic acid and the cholesterol analogue cholesta-4,6-dien-3-one in phosphatidylcholine liposomes has been investigated. 2. The results indicate that probes and steroid are randomly distributed in the bilayer at steroid concentrations up to 35 mol%. 3. The degree of polarization of diphenylhexatriene fluorescence increases with increasing cholesterol content. Other sterols, differing in structure in the region of the polar group or in the side chain at position-17, produce similar but not identical effects. 4. the results are consistent with the proposal that diphenylhexatriene gives a general picture of the state of the bilayer and that there is no segregation of sterols in liquid-crystalline phosphatidylcholine bilayers.     

Four new species of Penicillium isolated from the air

Four new species of Penicillium Link ex Fries are described and illustrated. All of them but one have been isolated from the atmosphere in Madrid, Spain. They clearly differ from all species of the genus described so far and are, therefore, described and proposed as new taxa: Penicillium aurantio-flammiferum sp. nov., Penicillium gallaicum sp. nov., Penicillium granatense sp. nov., and Penicillium ilerdanum sp. nov.     

Flavonoids in the leaves of Thymus: a chemotaxonomic survey

The flavonoid aglycone analysis of 20 Thymus taxa (most Iberic or Balearic endemics) shows the presence of luteolin, apigenin, acacetin, genkwanin, 6-hydroxyluteolin, xanthomicrol, cirsimaritin; four partially identified flavones, of which three are 6-OR-substituted and one flavonol. The differences observed between T. capitatus (L.) Hoffmanns. et Link (subgenus Coridothymus (Reichenb. fil.) Borbás) and the other species belonging to the subgenus Thymus (L.) Jalas, seem enough to maintain the separation of the two groups, but within the same genus, as proposed in Flora Europaea.     

Bactericidal activity of tuftsin

Summary The biological activities of the phagocytosis stimulating tetrapeptide, Thr-Lys-Pro-Arg are discussed. A brief account on the stimulation by tuftsin of phagocytosis of various particles, including bacteria was reported. Stimulation of bactericidal activity by this tetrapeptide was investigated in vitro as well as in vivo. The potency of tuftsin to enhance blood clearing of Staphylococcus aureus, Listeria monocytogenes, Escherichia coli and Serratia marcescens by mouse peritoneal macrophages was demonstrated.Bactericidal activity and effects of tuftsin on this phenomenon were studied in liver and spleen of mice. Tuftsin stimulates these activities. Same experiments were performed in infected leukemic mice by Serratia marcescens or Escherichia coli. Results on blood clearing and bactericidal activities in liver and spleen were reported and compared to those of healthy and leukemic untreated animals. Tuftsin was found to present interesting stimulatory effects on the bactericidal activity of phagocytes.     

Sites of sulfatation in the chondrocytes of the articular cartilage of the rabbit

35S sulfate uptake by the articular cartilage chondrocytes, from biopsies of rabbit, have been studied by high resolution autoradiography. The Golgi apparatus, rough endoplasmic reticulum, cytosol, cytoplasmic membrane and extracellular space were considered as cell compartments in the quantitative analysis of the autoradiograms. The results obtained show: 1) a high activity of radiosotope incorporation in the Golgi apparatus; 2) a fast rhythm of transfer of the substances labelled in the Golgi apparatus to the cell membrane; 3) significant labelling of the rough endoplasmic reticulum, throughout the experiment. It is concluded: 1) The grains observed in the rough endoplasmic reticulum show a significant radioisotope uptake on this level, and this evidence some sulfotransferase activity. 2) The high 35S sulfate uptake level which is observed in the Golgi apparatus demonstrates that the highest sulfotransferase enzyme activity is located in this cell area, thus showing that the "early" sulfation that began in the rough endoplasmic reticulum was completed by a "late" sulfation in the Golgi apparatus. It is here that complete chondromucoprotein building takes place before being excreted. 3) The high transfer level of the labelled substances from the Golgi apparatus shows that the sulfated product secretion for building the cartilage matrix takes place rapidly since a great label increase can be already observed at the beginning of the chase period in the outer surrounding area of the chondrocyte membrane.     

Interactions between the tobacco budworm,Heliothis virescens,and the δ-endotoxin produced by the HD-1 isolate of Bacillus thuringiensis var. kurstaki: Relationship between length of exposure to the toxin and survival

Larvae of the tobacco budworm, Heliothis virescens, which were fed ad libitum for 24, 48, and 72 hr on a diet treated with various levels of the δ-endotoxin produced by the HD-1 isolate of Bacillus thuringiensis var. kurstaki and then transferred to an untreated diet, showed an unexpected capacity to recover from the effects of the toxin, although, as the length of exposure increased, the capacity decreased. Observations on larvae held to emergence indicated that recovery from the toxin was complete. X-ray studies using Ba²⁺ incorporated into the diet showed that, although the toxin paralyzed the midgut of the treated animals, many animals recovered after the toxin was removed, with food once again passing through the gut.     

Sucrose and proton cotransport in Ricinus cotyledons

In Ricinus cotyledons, evidence for proton extrusion came from observation of direct acidification of the medium in the presence of potassium salts. Increasing K⁺ influx with increasing pH suggested a link between K⁺ influx and H⁺ efflux by an H⁺ pump. The kinetics of K⁺ influx and H⁺ efflux were consistent with a 1:1 stoichiometry K⁺:H⁺, which may indicate either electrical coupling or carrier mediated exchange. The results were consistent with an H⁺ pump setting up an electrochemical potential gradient which provides the driving force for an H⁺-sucrose cotransport and the movement of K⁺. With reference to this, a model for phloem loading is suggested.     

Scanning electron microscopy of Penicillium conidia

The morphology of conidia in 211 species and 12 varieties belonging to the genus Penicillium Link ex Gray have been studied and compared.According to surface ornamentation, conidia have been classified into six groups: A, smooth-walled (7% of the species); B, delicately roughened (13%); C, warty (28%); D, echinate (10%); E, striate with low irregular ridges (36%); and F, striate with scarce high ridges or bars (6%). Whereas the first two groups are closely related in both shape and average size, a gradual reduction was observed in size and in the length/width (l/w) ratio in the remaining groups. Echinate conidia were globose, having the largest average size. Only four species produced conidia not surpassing 2 m in diameter. Maximum length observed was 8 m, and most elongated conidia had a l/w ratio of 3.5. Forty per cent of the species studied had globose conidia.Conidia of the monoverticillate species were generally smaller, more globose and frequently with ridges. In the Asymmetrica, the conidia were generally larger, and showed ridges in comparatively few species. Conidia of the Symmetrica, which were frequently striate with ridges, presented the most elongated forms. The largest average size was found in the conidia of the Polyverticillata which were generally warty. Finally, we have considered the variations in surface ornamentation of conidia during the evolution of the genus Penicillium and drawn attention to their possible relationship with certain habitats and ways of conidial dispersion.