The RNA editing process in Trypanosoma brucei.

Twelve mitochondrial mRNAs are edited in Trypanosoma brucei, nine extensively, by addition and removal of uridines. The accumulation of the edited RNAs is regulated during the life cycle. Hundreds of different gRNAs, encoded three or four per minicircle, specify the editing and minicircle content accounts for variation in editing among species and in mutants.

Hepatic arterial chemoembolization for metastatic endocrine tumors.

Purpose: In patients with hepatic metastases from endocrine tumors, the safety and effectiveness of chemoembolization with ethiodized oil was determined and compared with those of embolization with particulate matter alone.

Patients And Methods: Twenty patients with hepatic islet cell or carcinoid tumor metastases were treated with selective hepatic artery injection of doxorubicin and iopamidol emulsified in ethiodized oil, followed by gelatin foam powder embolization.

Results: In 16 patients with hormonally active tumors, hormone secretion decreased 90% (range, 69%-98%) in 10 days, with relief of symptoms in all patients.

Structural organization of the maxicircle variable region of Trypanosoma brucei: identification of potential replication origins and topoisomerase II binding sites.

The maxicircle of the parasitic protozoan Trypanosoma brucei, one component of the mitochondrial genome, has size differences among isolates that localize to the variable region (VR) between the ND5 and 12S rRNA genes. We present here the nucleotide sequence of this entire region, thus completing the sequence of the maxicircle genome. We also find heterogeneously sized transcripts from throughout most of the VR.

A multicopy, extrachromosomal DNA in Leishmania infantum contains two inverted repeats of the 27.5-kilobase LD1 sequence and encodes numerous transcripts.

Leishmania DNA 1 (LD1) is a 27.5-kb sequence that occurs as an inverted repeat in a 55-kb multicopy, circular DNA in Leishmania infantum ITMAP263. The sequence is also found with a different genomic organization, possibly a tandem array, within a 1.

Molecular organization of Leishmania RNA virus 1.

The complete 5284-nucleotide sequence of the double-stranded RNA genome of Leishmania RNA virus 1 (LRV1) was determined and contains three open reading frames (ORFs) on the plus (+) (mRNA) strand. The predicted amino acid sequence of ORF3 has motifs characteristic of viral RNA-dependent RNA polymerases. ORF2, which may encode the major viral coat protein, overlaps ORF3 by 71 nucleotides, suggesting a +1 translational frameshift to produce a gag-pol type of fusion protein.

Transcribing and replicating particles in a double-stranded RNA virus from Leishmania.

During the replicative cycle of many double-stranded RNA viruses, transcription of particles with a double-stranded RNA genome alternates with replication of particles containing a single-stranded genome. In virions infecting some strains of Leishmania guyanensis the putative transcriptase and replicase activities of the RNA-dependent RNA polymerase were previously detected in vitro. Northern hybridization to RNA of known polarity demonstrates that the single-stranded RNA products are of positive polarity and, by definition, are the products of the viral transcriptase.

Transcript-specific developmental regulation of polyadenylation in Trypanosoma brucei mitochondria.

Transcripts from many mitochondrial genes in kinetoplastids are heterogeneous in size, often occurring as 2 distinct size classes, but this cannot be accounted for by RNA editing alone. Analyses of transcripts from 6 mitochondrial genes of Trypanosoma brucei indicates that the size variation is due to poly(A) tail length. A larger fraction of CYb, COI and COII transcripts have longer poly(A) tails in procyclic than in bloodstream forms.

Chimeric and truncated RNAs in Trypanosoma brucei suggest transesterifications at non-consecutive sites during RNA editing.

RNA editing adds and removes uridines at specific sites in several mitochondrial transcripts in kinetoplastid parasites probably as specified by guide RNAs (gRNAs) that are complementary to the final edited sequence. Editing has been postulated to involve transesterification which predicts (1) chimeric molecules with a gRNA covalently attached by its non-encoded oligo U tail to an internal editing site in the mRNA and (2) the corresponding truncated 5' portions of the mRNAs. We have characterized cDNAs representing a large number of both types of intermediates from Trypanosoma brucei.

Maxicircle CR1 transcripts of Trypanosoma brucei are edited and developmentally regulated and encode a putative iron-sulfur protein homologous to an NADH dehydrogenase subunit.

The maxicircle of Trypanosoma brucei encodes components of the mitochondrial oxidative phosphorylation system, as do other mitochondrial DNAs, but maxicircle gene identification is complicated by extensive editing of some transcripts. We found that transcripts from the CR1 region were extensively edited, as are other transcripts from maxicircle regions which exhibit strong G versus C strand bias. Editing added 259 uridines and removed 46 uridines to produce an approximately 574-nucleotide mature mRNA.

Guide RNAs for transcripts with developmentally regulated RNA editing are present in both life cycle stages of Trypanosoma brucei.

RNA editing of several mitochondrial transcripts in Trypanosoma brucei is developmentally regulated. The cytochrome b and cytochrome oxidase II mRNAs are edited in procyclic-form parasites but are primarily unedited in bloodstream forms. The latter forms lack the mitochondrial respiratory system present in procyclic forms.

In vitro guide RNA/mRNA chimaera formation in Trypanosoma brucei RNA editing.

The post-transcriptional processing of various mitochondrial transcripts in kinetoplastids, kRNA editing, adds and removes uridines, producing mature messenger RNAs. This editing seems to be directed by 'guide' RNAs (gRNAs) which are complementary to portions of the mature message. The editing mechanism has been proposed to entail transesterification.

LRV1 viral particles in Leishmania guyanensis contain double-stranded or single-stranded RNA.

The 32-nm-diameter spherical viral particles found in the cytoplasm of Leishmania guyanensis CUMC1-1A sediment at 130S and have a buoyant density of approximately 1.4 g/ml in cesium chloride gradients. These particles contain a 5.

Extensive editing of both processed and preprocessed maxicircle CR6 transcripts in Trypanosoma brucei.

Transcripts from several genes encoded in the Trypanosoma brucei maxicircle genome are altered by posttranscriptional uridine insertion and deletion through a process called RNA editing. We find that transcripts from the CR6 gene are extensively edited by addition of 132 uridines and deletion of 28 uridines to produce a fully edited mRNA 47% larger than unedited mRNA. Two open reading frames (ORFs) and their initiation and termination codons are created by editing of CR6 mRNA.

Recurrent polymorphisms in small chromosomes of Leishmania tarentolae after nutrient stress or subcloning.

Molecular karyotypes of the UC, LEM87 and LEM115 Leishmania tarentolae strains were obtained. All strains had 24-28 chromosomal bands which varied in size between 300 kb and 2.9 Mb.

Biochemical and cytological evidence for an overabundance of mucocysts in the bcd pattern mutant of Tetrahymena thermophila.

Three acidic proteins (42 kD, 43 kD and 50 kD) were present in unusually high concentrations in cortical preparations of the Tetrahymena pattern mutant broadened cortical domains (bcd). Antisera to the 42-kD and 50-kD proteins bound to discharging mucocysts and food vacuole contents in both wild-type and mutant cells. Subsequent analysis revealed that bcd mutant cell pellicles possess five times more "docked" mucocysts than their wild-type counterparts.

Cycles of progressive realignment of gRNA with mRNA in RNA editing.

We characterized numerous partially edited NADH dehydrogenase 7 and ATPase 6 cDNAs. Most of these have a stretch of incompletely edited sequence at the junction of mature and unedited sequences. The characteristics of the junctions suggest editing of sites multiple times and that editing within each junction does not proceed precisely 3' to 5'.

RNA editing in kinetoplastid protozoa.

RNA editing produces mature mRNAs by adding and removing uridines within the mitochondrial transcripts. The edited sequence appears to be specified by small complementary RNAs using a non-templated process that may have features resembling RNA splicing. The accumulation of edited mRNAs is developmentally regulated.

The two ATPase 6 mRNAs of Leishmania tarentolae differ at their 3' ends.

We have determined the complete nucleotide sequence of ATPase 6 mRNA from Leishmania tarentolae. RNA editing occurs only in the 5' one-third of the mRNA and is the most extensive observed to date in this species. We have identified a potential gRNA sequence, encoded in a minicircle, for a portion of the edited sequence.

A DNA sequence (LD1) which occurs in several genomic organizations in Leishmania.

Leishmania DNA 1 (LD1) is a 27.5-kb sequence that occurs in all 91 stocks of twelve New and Old World Leishmania species examined; related sequences are present in some other kinetoplastid species. LD1 has no homology to several DNA sequences that are amplified in drug-resistant Leishmania.

The comparative antimicrobial effect of calcium hydroxide.

The antimicrobial effectiveness of calcium hydroxide, camphorated paramonochlorophenol, and formocresol in root canals of extracted human teeth was compared. Canals in single-rooted teeth were enlarged and inoculated with Streptococcus mutans, Actinomyces viscosus, and Bacteroides gingivalis or Bacteroides fragilis. After treatment with a test agent and sealing and incubation for 1 hour, the canal contents were analyzed for the number of viable test bacteria and compared with that of inoculated teeth not treated with test agents.