Formation of the 3'' end of U1 snRNA is directed by a conserved sequence located downstream of the coding region.

U1 is a small non-polyadenylated nuclear RNA that is transcribed by RNA polymerase II and is known to play a role in mRNA splicing. The mature 3' end of U1 snRNA is formed in at least two steps. The first step generates precursors of U1 RNA with a few extra nucleotides at the 3' end; in the second step, these precursors are shortened to mature U1 RNA. Here, I have determined the sequences required for the first step. Human U1 genes with various deletions and substitutions near the 3' end of the coding region were constructed and introduced into HeLa cells by DNA transfection. The structure of the RNA synthesized during transient expression of the exogenous U1 gene was analyzed by S1 mapping. The results show that a 13 nucleotide sequence located downstream from the U1 coding region and conserved among U1, U2 and U3 genes of different species is the only sequence required to direct the first step in the formation of the 3' end of U1 snRNA.     

Penicillium in pre-harvest corn from Valencia (Spain). I. Influence of different factors on the contamination

In the present study we attempt to determine the principal factors which influence the contamination by Penicillium of 116 samples of pre-harvest corn from five crop areas in Valencia (Spain).In the corn tested, Penicillium is the most abundant genus after Fusarium, with an incidence of 71.5% in infected samples, counts of about 642 cfu/g and kernel infection of 8.7%. The most frequently isolated species are Penicillium chrysogenum, P. steckii and P. purpurogenum.There is a high correlation between the contamination from this genus and the amout of kernels broken and infested by insects, as well as a correlation with crop areas.We have found no difference in the contamination of the two varieties of corn investigated.     

Gas chromatographic assay for in vitro complementation of Pseudomonas aeruginosa mutants deficient in nitrate reduction

An electron capture gas-chromatographic technique was developed to continuously measure nitrate (NO3-) reduction during in vitro complementation tests with extracts from Pseudomonas aeruginosa mutants deficient in both assimilatory and dissimilatory nitrate reduction as a result of a single genetic mutation. The procedure involves coupling nitrate reduction to nitrous oxide (N2O) evolution via a series of reactions specific to the denitrification pathway. The assay was dependent on nitrate concentration, and optimal activity was obtained with a final concentration of 0.2% potassium nitrate. The reduction exhibited a stoichiometry of 2:1 (NO3-/N2O), and succinate was the best electron source for the reaction, followed by glucose, pyruvate, and malate. The technique can also be used for continuously monitoring nitrate reduction. The optimal nitrite concentration in the nitrite reductase assay was 0.025%. The initial complementation studies of mutant extracts demonstrated that at least two genes are shared between the two nitrate reduction pathways in P. aeruginosa.     

Effect of prolactin and glucocorticoids on P-enolpyruvate carboxykinase activity in liver and mammary gland from diabetic and lactating rats

Summary The administration of 2 bromo--ergocryptine, to reduce serum prolactin decreased the activity of cytosolic P-enolpyruvatc carboxykinase (GTP) (EC4.1.1.32) about 50% in both liver and mammary gland of lactating animals. Adrenalectomy had similar effects to those of bromo-a-ergocryptine. In contrast, there was a 50% increase in enzyme activity in the mammary gland of diabetic, lactating rats and a 10-fold increase in liver as compared with normal rats. P-enolpyruvate carboxykinase activity in mammary gland as liver is coordinately regulated by prolactin, glucocorticoids and insulin.     

cAMP-dependent phosphoprotein changes in the yeast Saccharomyces cerevisiae

Abstract cAMP-dependent phosphoprotein changes were determined using 1-dimensional SDS-gel electrophoresis in a cAMP-requiring yeast mutant ( Saccharomyces cerevisiae AM18). During cAMP starvation, the yeast cells accumulated 3 ³²P-labeled bands with M _r/ 72000, 54000, and 37000. The M _r/ 72000 protein was the most prominent phosphorylated protein. After the readdition of cAMP, these phosphoproteins lost their ³²P-label while phosphoproteins with M _r/ 76000, 65000, 56000 and 30000 were accumulated. Similar phosphoprotein changes were also detected in cdc35 at the nonpermissive temperature, but not in wildtype (A363A) or cdc7 strains of S. cerevisiae .     

Immunoelectrophoretic approach to the metabolic regulation of glutamine synthetase in Rhodopseudomonas capsulata E1F1: role of glutamine

Anti-glutamine synthetase serum was raised in rabbits by injecting purified glutamine synthetase (GS) of the phototrophic bacterium Rhodopseudomonas capsulata E1F1. The antibodies were purified to monospecificity by immunoaffinity chromatography in GS-sepharose gel. These anti-GS antibodies were used to measure the antigen levels in crude extracts from bacteria, grown phototrophically with dinitrogen, nitrate, nitrite, ammonia, glutamate, glutamine or alanine as nitrogen sources. The amount of GS detected by rocket immunoelectrophoresis was proportional to Mn²⁺-dependent transferase activity measured in the crude extracts. Addition of GS inhibitor l-methionine-d,l-sulfoximine (MSX) to the actively growing cells promoted increased antigen levels, that were not found in the presence of glutamine or chloramphenicol. The ammonia-induced decrease in GS relative levels was reverted by MSX. GS levels remained constant when phototrophically growing cells were kept in the dark.Abbreviations GS glutamine synthetase - MOPS 2-(N-morpholine) propane sulfonate - MSX l-methionine-d,l-sulfoximine     

Action ofN-methyl-N′-nitro-N-nitrosoguanidine inRhizobium trifolii

Rhizobium trifolii was highly resistant to the lethal effect ofN-methyl-N-nitro-N-nitrosoguanidine (MNNG), but it was sensitive to the mutagenic action of this chemical. A concentration of 500g/ml yields a survival of between 1% and 10%, which allows us to obtain a higher number of mutants than lower concentrations that yield higher survival rates. Lethal damage produced by nitrosoguanidine was repaired, and repair is inhibited by acriflavine.     

Mixing patterns in Amazon lakes

The diel mixing patterns of two small floodplain lakes, Lago Jacaretinga in the Amazon drainage, and Lago Cristalino in the Rio Negro system, were investigated during both the high-water and low-water states of the Amazon River hydrograph. Measurements included temperature, oxygen, ammonia, phosphate, and chlorophyll. In both lakes thermal stratification developed during the day and was eroded at night. During the low-water period when the lakes were shallow, nocturnal circulation extended to the lake bottom, whereas when the lakes were deeper (greater than about 5 m), circulation did not reach the bottom and an anoxic hypolimnion developed. During the low-water period, percent of oxygen concentrations were relatively high but always less than saturation. Low oxygen concentrations were observed during the high-water period. At all times nocturnal mixing supplied a significant amount of oxygen to the lake ecosystems. Nighttime upward mixing of recycled nitrogen and phosphorus also appeared to be important nutrient sources for algal productivity.     

Reactions of sugar nitro-alkenes with acetoacetic esters

3,4,5,6,7-Penta-O-acetyl-1,2-dideoxy-1-nitro-d-gluco-hept-1-enitol reacts with methyl acetoacetate in an unusual Michael reaction, giving the normal adduct (6), and a bicyclic derivative (9) that arises from quasi-dimerization of the former when a high concentration of the base is used. Acetylation of compound 9 gives the hydroxylamine O-acetate (10).From the reactions of 3,4,5,6,7-penta-O-acetyl-1,2-dideoxy-1-nitro-d-galacto-hept-1-enitol with ethyl and tert-butyl acetoacetate, the normal adducts (7 and 8) were isolated. The structures of compounds 6 to 10 were established on the basis of their spectral properties (u.v., i.r., mass, and ¹H- and ¹³C-n.m.r.)