Screening for fungi intensively mineralizing 2,4,6-trinitrotoluene

Within a screening program, 91 fungal strains belonging to 32 genera of different ecological and taxonomic groups (wood- and litter-decaying basidiomycetes, saprophytic micromycetes) were tested for their ability to metabolize and mineralize 2,4,6-trinitrotoluene (TNT). All these strains metabolized TNT rapidly by forming monoaminodinitrotoluenes (AmDNT). Micromycetes produced higher amounts of AmDNT than did wood- and litter-decaying basidiomycetes. A significant mineralization of [¹⁴C]TNT was only observed for certain wood- and litter-decaying basidiomycetes. The most active strains, Clitocybula dusenii TMb12 and Stropharia rugosa-annulata DSM11372 mineralized 42 % and 36 % respectively of the initial added [¹⁴C]TNT (100 μM corresponding to 4.75 μCi/l) to ¹⁴CO₂ within 64 days. Micromycetes (deuteromycetes, ascomycetes, zygomycetes) proved to be unable to mineralize [¹⁴C]TNT significantly. Received: 8 August 1996 / Received revision: 16 December 1996 / Accepted: 20 December 1996     

Effect of exogenous LH on plasma concentrations of progesterone and oestradiol in relation to the cessation of egg laying induced by different moulting methods

Artificially induced cessation of egg laying caused regression of the reproductive tract in hens, as well as changes in circulating concentrations of sex steroids. Hens were bled at several stages during and after artificial moult induced by fasting or overfeeding a diet low in calcium or high in zinc. Hens received a single injection of 200 i.u. of horse LH at Day 0, 7, 21, 35 and 77 (Exp. 1) or Day 0, 8, 23, 35 and 71 (Exp. 2) after start of the treatment to induce moult. Blood samples were taken before and 20, 40 and 60 min (Exp. 1) or 15, 30 and 45 min (Exp. 2) after LH injection. Hens which were fasted or given the diet high in zinc had low plasma progesterone concentrations and the response to LH was reduced or delayed. In hens fed low calcium the reduction in plasma progesterone was less pronounced and the responsiveness to LH was more or less maintained. Conversely, there was no response of oestradiol to LH in laying hens. However, oestradiol concentrations increased in moulting hens after LH injection, due to the high oestradiol secretion from the small white follicles, since all yolky follicles were atretic.     

On the origin of induced pancreatic islet tumors: a radioautographic study

Endocrine tumors of the pancreas are induced in a high percentage of young rats by injections of streptozotocin and nicotinamide (SZ/NA). Benign tumors first appear 20 to 36 weeks after drug injections. To determine the possible site of their origin, the incorporation of [3H]thymidine into islets, ducts, acini, microtumors, and gross tumors was examined by radioautography of histologic sections at 1 to 36 weeks after drug injection. Drug treatment led to early (1- to 6-week) increases in nuclear 3H labeling of exocrine pancreatic structures (ductal and acinar cells), which may involve DNA repair processes. A secondary increase in labeling of duct cells during the period of tumor emergence supports the assumption that SZ/NA-induced tumors are of ductal origin. Microtumors and gross tumors also exhibited markedly elevated rates of [3H]thymidine incorporation compared to control islets. Nontumorous islet tissue, which exhibited a gradual decrease in volume due to B-cell destruction by the drug injection, showed about 10-fold higher 3H labeling than islets of controls at all time points. The results suggest that in addition to ductal precursors, islets that survive SZ/NA-induced injury may also provide sites of focal endocrine cell differentiation to tumor tissue. Once established, both microtumors and gross tumors continue to grow by accelerated cell division.     

The Constitutive, Glucose-Repression-Insensitive Mutation of the Yeast MAL4 Locus Is an Alteration of the MAL43 Gene

Mutations resulting in constitutive production of maltase have been identified at each of the five MAL loci of Saccharomyces yeasts. Here we examine a dominant constitutive, glucose-repression-insensitive allele of the MAL4 locus (MAL4-C). Our results demonstrate that MAL4-C is an alteration in the MAL43 gene, which encodes the positive regulator of the MAL structural genes, and that its product is trans-acting. The MAL43 gene from the MAL4-C strain was cloned and integrated into a series of nonfermenting strains lacking a functional regulatory gene but carrying copies of the maltose permease and maltase structural genes. Expression of the maltase structural gene was both constitutive and insensitive to glucose repression in these transformants. The MAL4-C allele also results in constitutive expression of the unlinked MAL12 gene (encoding maltase) in this strain. In addition, the cloned MAL43 gene was shown to be dominant to the wild-type MAL63 gene. We also show that most of the glucose repression insensitivity of strains carrying the MAL4-C allele results from alteration of MAL43.     

The effect of metyrapone on the 17,20-lyase from rat testis microsomes

A new and simple method was presented to isolate purified holoenzyme of $\text{E. coli}$ RNA polymerase. When a purified enzyme preparation was chromatographed on a DNA-cellulose column equilibrated with a buffer containing 10mM MgCl₂, holoenzyme was separated from core enzyme. Thus holoenzyme was eluted at 0.15M KCl and core enzyme at 0.25M KCl.     

The dispersed, repeated family of MAL loci in Saccharomyces spp

This report concludes our analysis of the various standard maltose-fermenting strains of Saccharomyces spp. We showed that, in addition to either the MAL2 or MAL4 functional locus present in the standard MAL2 and MAL4 strains, both strains contain two cryptic MALg genes mapping to the MAL1 and MAL3 locus positions. (Functional MAL loci appear to consist of two linked complementing gene functions, MALp and MALg. Cryptic MALg genes lack a linked functional MALp gene.) Using a probe containing a DNA fragment derived from the MAL6 locus, we detected three genomic HindIII fragments in both the MAL2 and MAL4 strains. Each of these HindIII fragments is shown to segregate in a Mendelian fashion and to be linked to one of the three MAL loci in each of the strains. We also detected additional fragments having significant sequence homology to the MAL6 probe but lacking in MAL-related functions.     

Catabolism of capped (3'-5')- and (2'-5')-adenylates in rat liver nuclei

We describe studies concerning the ability of a nuclear dinucleoside triphosphatase to act as a decapping enzyme in RNA catabolism. The enzymatic release of GMP from the Gp3A moiety was determined in the capped RNA model compounds Gp3A3'pA, Gp3A3'pA-isoprop and Gp3A2'pA in isolated rat liver nuclei; i.e., in the environment in which the dinucleoside triphosphatase operates in vivo. The Gp3A cap moiety is hydrolyzed in (3'-5') linked nucleotides only, whereas an extension of the Gp3A in the 2'-direction prevents the nuclear triphosphatase to operate.     

Common elements on the surface of glycolytic enzymes from Trypanosoma brucei may serve as topogenic signals for import into glycosomes.

In Trypanosoma brucei, a major pathogenic protozoan parasite of Central Africa, a number of glycolytic enzymes present in the cytosol of other organisms are uniquely segregated in a microbody-like organelle, the glycosome, which they are believed to reach post-translationally after being synthesized by free ribosomes in the cytosol. In a search for possible topogenic signals responsible for import into glycosomes we have compared the amino acid sequences of four glycosomal enzymes: triosephosphate isomerase (TIM), glyceraldehyde-phosphate dehydrogenase (GAPDH), phosphoglycerate kinase (PGK) and aldolase (ALDO), with each other and with their cytosolic counterparts. Each of these enzymes contains a marked excess of positive charges, distributed in two or more clusters along the polypeptide chain. Modelling of the three-dimensional structures of TIM, PGK and GAPDH using the known structural coordinates of homologous enzymes from other organisms indicates that all three may have in common two 'hot spots' about 40 A apart, which themselves include a pair of basic amino acid residues separated by a distance of about 7 A. The sequence of glycosomal ALDO, for which no three-dimensional information is available, is compatible with the presence of the same configuration on the surface of this enzyme. We propose that this feature plays an essential role in the import of enzymes into glycosomes.