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The allosuppressor gene SAL4 encodes a protein important for maintaining translational fidelity in Saccharomyces cerevisiae.

Allosuppressor (sal) mutations enhance the efficiency of the yeast ochre suppressor SUQ5 and define five unlinked loci, SAL1-SAL5. A number of sal4 mutants were isolated and found to have pleiotropic, allele;specific phenotypes, including hypersensitivity in vivo to paromomycin and other antibiotics that stimulate translational errors in yeast. To examine further the nature of the SAL4 gene product, the wild type SAL4 gene was isolated by complementation of a conditional lethal allele sal4-2, and demonstrated to be a single copy gene encoding a single 1.6 kb transcript. Restriction mapping and DNA hybridisation analysis were used to demonstrate that the SAL4 gene is identical to the previously identified omnipotent suppressor gene SUP45 (SUP1). Our results implicate the SAL4 gene product as playing a major role in maintaining translational accuracy in yeast.

Anti-Bacterial Agents↗

Ribosomes of Leishmania are a target for the aminoglycosides.

Ribosomes of Leishmania, a parasitic protozoan (member of the order of Kinetoplastidae), were purified on a sucrose density gradient. Two different types of ribosomes were isolated from the promastigotes: cytoplasmic (88S and 91S from L. tropica and L. donovani, respectively) and mitochondrial (75S in both species). Both types of ribosome dissociated into their subunits at low Mg2+ concentration (1-2 mM) as follows: 67S and 49S for the 91S cytoplasmic ribosomes of L. donovani and 61S and 43S for the 88S cytoplasmic ribosome of L. tropica; 55S and 34S for L. tropica and 60S and 39S for L. donovani mitochondrial ribosomes, respectively. Paromomycin (aminosidine), an aminoglycoside aminocyclitol antibiotic, interacted with the ribosomes to promote the association of the subunits. Under similar experimental conditions, spermidine and pentamidine were inactive.

Animals↗

Diagnosis of nonsense mutations in Aspergillus nidulans.

Three genotypically suppressible alleles, a1X4, alcA125, and niaD500, are phenotypically suppressed by aminoglycoside antibiotics. Unsuppressible alleles at these loci are unaffected as are known missense mutations at the yA and gdhA loci. This is consistent with the premise that the suppressible mutations are nonsense and that this highly-allele-specific phenotypic suppression can be used to distinguish nonsense from missense mutations of Aspergillus nidulans. Paromomycin and tobramycin are recommended for screening unknown mutations.

Alleles↗

The screening of four aminoglycosides in the selective decontamination of the digestive tract in mice.

The suppressive effect of amikacin, gentamicin, tobramycin and paromomycin on the aerobic endogenous flora and on the colonization resistance of the digestive tract was tested by administering one of the antibiotics orally at five different dose levels. At a certain dose level, all antibiotics suppressed the endogenous Enterobacteriaceae species. Amikacin was particularly effective in this respect. Low doses of amikacin rapidly destroyed the colonization resistance. This resistance only remained unaffected in animals treated with tobramycin in doses that were still adequate to completely suppress the endogenous Enterobacteriaceae species. We concluded that of all the antibiotics tested in this study, only tobramycin may have a future in (clinical) application for the selective decontamination of the digestive tract. Selective decontamination can be considered an effective method for infection prevention in leukopenic patients.

Amikacin↗

Clinical and microscopical features of small-intestinal microsporidiosis in patients with AIDS.

Intestinal microsporidiosis by Enterocytozoon bieneusi is an increasingly recognized infection in AIDS patients. We report eight cases of microsporidiosis. All patients were severely immunodepressed. Clinical features were highly variable. Patients were followed up for a mean period of 7.8 months. All patients had persistent infection during the follow-up and spore excretion remained constant. Two patients became asymptomatic during the follow-up. None of the patients presented clinical and echographic signs of biliary involvement. Treatment with albendazole, metronidazole or paromomycin failed to produce a durable clinical response or to eradicate the organism. Cases were identified by stool examination and additionally investigated with light and electron microscopy. It was found that light microscopy was a sensitive method, while electron microscopy was less sensitive but allowed the definition of the infecting species. The modified trichrome stain was a satisfactory method for diagnosis on fecal smears. The calcofluor stain and the combination of DAPI with calcofluor was a rapid and simple staining method for screening.

Acquired Immunodeficiency Syndrome↗

Blastocystis hominis: neutral red supravital staining and its application to in vitro drug sensitivity testing.

A simple in vitro drug sensitivity testing system for Blastocystis hominis clinical isolates was developed. Application of supravital staining by neutral red allowed quantitative viability assessment. Four xenic cultures, isolated from human sources, were grown in modified monophasic Robinson's medium and tested for sensitivities to nine available drugs. Assessment was done using the cell-count method from air-dried preparations after supravital staining with neutral red. Also, the light absorbence method was evaluated. Trimethoprim, metronidazole, quinacrine, tetracycline, paromomycin, and two new antiprotozoal drugs, nitazoxanide and deacetyl-nitazoxanide, showed cytostatic or cytocidal effects on all or some Blastocystis isolates. Chloroquine and sulphamethoxazole did not demonstrate any effect at the concentrations studied.

Amebicides↗

[Cutaneous leishmaniasis].

Leishmaniasis is a vector-borne disease caused by an obligate intracellular protozoa, Leishmania, which resides in macrophages. The parasite is transmitted by an infected female sandfly. The incidence of cutaneous leishmaniasis approaches 2 million new cases per year with 90% of the cases occurring in the "Old World", while the "New World" accounts for the rest. Infection may be restricted to the skin with development of characteristic ulcers, or may affect the mucous membranes in its mucocutaneous form. The clinical diagnosis is verified by the presence of amastigotes in slit-skin smears. Therapeutic modalities include systemic treatments such as the pentavalent antimony compound sodium stibogluconate, liposomal formulations of amphotericin B, oral ketoconazole or itraconazole, as well as topical paromomycin sulphate, local heat, freezing with liquid nitrogen, or photodynamic therapy. An effective vaccine is not available.

Amphotericin B↗

Antigiardial drugs.

Giardia intestinalis is a world-wide cause of intestinal infection. Treatment of this debilitating disease is usually accomplished using one of several drugs. Metronidazole is the treatment of choice, but benzimidazoles are now being used more frequently. Other treatments include quinacrine, paromomycin and furazolidone. Even though these drugs are all used to treat the same disease, their modes of action differ in all cases. However, resistance is increasing and new alternatives are being sought. New wave antigiardials all appear to have their roots in natural herbal remedies. This mini-review looks at the current treatments available, their efficacy, side effects and different modes of action and addresses a possible way forward using natural products.

Antiprotozoal Agents↗

Cgr1p, a novel nucleolar protein encoded by Saccharomyces cerevisiae orf YGL0292w.

Saccharomyces cerevisiae open reading frame (ORF) YGL029w (CGR1) encodes a small hydrophilic protein of unknown function. To investigate the role of this gene, we have determined the intracellular localization of the encoded product and examined the effects of Cgr1p depletion on cell growth. Tagging Cgr1p with the green fluorescent protein (GFP) or the myc epitope showed focal accumulation of the fusion protein in the yeast nucleolus, and this localization overlapped with the distribution of the nucleolar protein Nop1p. Cells depleted of CGR1 mRNA were growth impaired and hypersensitive to the translational inhibitor paromomycin, and this phenotype was complemented by episomal expression of the CGR1-GFP fusion gene. These results identify Cgr1p as a novel component of the yeast nucleolus and suggest a potential role in ribosome biogenesis.

Fungal Proteins↗

FLO11 mediated filamentous growth of the yeast Saccharomyces cerevisiae depends on the expression of the ribosomal RPS26 genes.

The RPS26A and RPS26B isogenes of Saccharomyces cerevisiae encode two almost identical proteins of the small 40S ribosomal subunit, which differ by only two amino acid residues. Growth of an rps26BDelta mutant strain is normal, whereas an rps26ADelta strain displays a reduced growth rate and increased sensitivity towards the specific translational inhibitor paromomycin. An rps26ADelta rps26BDelta double mutant strain is inviable. RPS26A but not RPS26B is required for haploid adhesive and diploid pseudohyphal growth mediated by FLO11, which encodes an adhesion. The RPS26A and RPS26B transcripts make up about 70 and 30% of the cellular RPS26 mRNA, respectively. Overexpression of RPS26B, as well as an RPS26B open reading frame driven by the RPS26A promoter, complements the rps26ADelta deletion and restores haploid invasive growth as well as diploid pseudohyphal growth. These results suggest that the two proteins are functionally interchangeable. FLO11-lacZ activity is not present in haploid rps26ADelta yeast mutant strains, even though FLO11 mRNA levels are not reduced. This suggests that the amount of Rps26p is critical for accurate translation of the FLO11 mRNA, and therefore for the dimorphic switch of the bakera9s yeast from a single cell yeast to an adhesive filamentous growth form.

Amino Acid Sequence↗

Recovery from parkinson syndrome and prolonged visually evoked potentials in hepatic encephalopathy.

The combination of Parkinson syndrome (PS) and prolonged visually evoked potentials (VEPs) in a single patient with hepatic encephalopathy (HE) has not been reported. A 52-year-old male with chronic HE developed PS in early 2001. Treatment with L-DOPA was only of minimal effect. In August 2001 he was admitted because of worsening PS and HE. There was anemia, hyperlipidaemia, markedly elevated liver-function-parameters, hyperammonemia, elevated resting-lactate, steatosis hepatis and hepatomegalia. VEPs showed markedly prolonged P100-latencies. Under L-DOPA, pramipexol, L-ornithin-L-aspartate, paromomycin-sulfate, and lactulose liver-function-parameters normalized and PS markedly improved. In February 2003, VEPs were normal. L-DOPA was discontinued by the patient in April 2003 and pramipexol in December 2003. Since then PS did not recur. This case shows that HE may go along with reversible PS and prolonged VEPs. Under adequate therapy liver-function-parameters and VEPs normalize and PS disappears.

Anti-Bacterial Agents↗

Transformation of Tetrahymena thermophila by electroporation and parameters effecting cell survival.

We have successfully transformed Tetrahymena thermophila by electroporation, a process of electrically introducing DNA. The DNA used for transformation contains a mutant ribosomal RNA gene (rDNA) that confers resistance to paromomycin on the transformed cells. This mutant rDNA replicates more rapidly than the endogenous rDNA of the transformed cells so that the mutant rDNA becomes predominant within several generations. This mutant rDNA also carries a restriction polymorphism that readily distinguishes it from the endogenous rDNA of the transformed cells. Substantial nuclease activity is released from the cells during electroporation and must be neutralized in order for transformation to be effective. Cell survival is inversely proportional to the electrical energy dissipated (joules) in the medium. Electroporation is a convenient and effective means of introducing transforming DNA into T. thermophila.

Animals↗

Altered 40 S ribosomal subunits in omnipotent suppressors of yeast.

The five suppressors SUP35, SUP43, SUP44, SUP45 and SUP46, each mapping at a different chromosomal locus in the yeast Saccharomyces cerevisiae, suppress a wide range of mutations, including representatives of all three types of nonsense mutations, UAA, UAG and UGA. We have demonstrated that ribosomes from the four suppressors SUP35, SUP44, SUP45 and SUP46 translate polyuridylate templates in vitro with higher errors than ribosomes from the normal stain, and that this misreading is substantially enhanced by the antibiotic paromomycin. Furthermore, ribosomal subunit mixing experiments established that the 40 S ribosomal subunit, and this subunit only, is responsible for the higher levels of misreading. Thus, the gene products of SUP35, SUP44, SUP45 and SUP46 are components of the 40 S subunit or are enzymes that modify the subunit. In addition, a protein from the 40 S subunit of the SUP35 suppressor has an altered electrophoretic mobility; this protein is distinct from the altered protein previously uncovered in the 40 S subunit of the SUP46 suppressor. In contrast to the ribosomes from the four suppressors SUP35, SUP44, SUP45 and SUP46, the ribosomes from the SUP43 suppressor do not significantly misread polyuridylate templates in vitro, suggesting that this locus may not encode a ribosomal component or that the misreading is highly specific.

Centrifugation, Density Gradient↗

Topical treatment of New and Old World cutaneous leishmaniasis in experimental animals.

The effect of topical treatment with 15% paromomycin sulphate and 12% methylbenzethonium chloride in white soft paraffin on cutaneous leishmaniasis in Balb/c mice was studied. The Saudi Arabian strain of Leishmania major, although being the most virulent to the mice, showed the highest susceptibility to this treatment. After 10 days treatment, parasites were totally eliminated from the treated lesion and healing was complete. 3 American strains were also tested: L. mexicana amazonensis; L. braziliensis panamensis and L. mexicana mexicana. The first was the most virulent and the most resistant to local treatment, L. b. panamensis displayed an intermediate response, and L. m. mexicana was highly susceptible. The disease relapsed in 50% of the infected treated mice within 135 days (L. major), 120 (L. m. mexicana), 25 (L. b. panamensis), and 14 days (L. m. amazonensis) after the end of the treatment.

Administration, Topical↗

Treatment of visceral leishmaniasis in Kenya by aminosidine alone or combined with sodium stibogluconate.

The treatment of leishmaniasis, as currently conducted in Kenya with sodium stibogluconate, is unsatisfactory as it is expensive, resistance and relapses may occur, and major adverse effects have been reported. Recently, aminosidine (paromomycin) sulphate has shown good antileishmanial activity on its own as well as synergism with pentavalent antimony, administered concurrently. The present study was designed to assess the effectiveness of parenteral aminosidine, alone or combined with sodium stibogluconate, in visceral leishmaniasis, compared to treatment by stibogluconate alone. 53 patients were allocated to the 3 therapeutic regimes. The presenting signs and symptoms of leishmaniasis were those commonly seen in the visceral form of the disease, particularly in Kenya. At termination, clinical cures were achieved in all 53 patients with no difference between treatment groups. Spleen aspirates revealed the best parasitological results in patients receiving the combined treatment, with only 13% failures (partial cures + relapses), as opposed to 21% failures with aminosidine alone and 45% with stibogluconate alone. Treatment with aminosidine alone was the cheapest and safest regime.

Adolescent↗

Regulation of ribosome phosphorylation and antibiotic sensitivity in Tetrahymena thermophila: A correlation.

Tetrahymena thermophila cells transferred from growth medium into a dilute salt (starvation) medium shortly (approximately 6-8 hrs) become more resistant to the in vivo inhibitory effects of the antibiotics cycloheximide, tetracycline and emetine. They also be come more sensitive to the inhibitory effects of paromomycin and anisomycin. By comparing ribosomes from growing and starved cells we have found that for at least two of these drugs differences between growing cell and starved cell ribosomes exist with respect to drug-ribosome interactions. In addition, we found that isolated monosomic ribosomes from starved cells are more resistant to thermal denaturation than are monosomic ribosomes from growing cells. The kinetics of all these changes following transfer of growing cells to starvation medium is the same and correlates with a change in the extent of phosphorylation of a single small subunit ribosomal protein. As judged by our in vitro assays, enzymatic removal of this phosphate converts "starved cell" ribosomes into "growing cell" ribosomes. We have extended these studies to show that the phenomenon of drug adaptation in Tetrahymena, at least with respect to cycloheximide, is associated with this ribosome phosphorylation.

Animals↗

Topical treatment of Old World cutaneous leishmaniasis caused by Leishmania major: a double-blind control study.

BACKGROUND: A controlled study of the efficacy of topical paromomycin sulfate (PR) and methylbenzethonium chloride (MBCl) in cutaneous leishmaniasis (CL) has not yet been performed. OBJECTIVE: The therapeutic effect of an ointment containing 15% PR and either 12% or 5% MBCl (15/12 or 15/5 P-ointment) on patients suffering from Old World CL was examined in a randomized, double-blind, cross-over study. METHODS: Thirty-nine patients with Old World CL caused by Leishmania major were treated topically, twice daily, for 10 to 20 days with 15/12 or 15/5 P-ointment and 10 to 20 days with a placebo ointment to achieve a total of 30 days of treatment in all groups. RESULTS: In the P-ointment-treated groups, 74.2% (29 of 39 patients) of the patients were cured versus 26.6% (4 of 15 patients) in the placebo-treated group. Little difference was found between the 15/12 and 15/5 P-ointment groups. CONCLUSION: In most of the patients treated with the active ingredients, total elimination of the parasites was achieved within the first 10 days of treatment.

Administration, Cutaneous↗

Covalent cross-linking of AcVal-tRNA to Tetrahymena thermophila cytoplasmic ribosomes and two of its 17S rRNA mutants.

Tetrahymena thermophila 80S ribosomes have been cross-linked to non-enzymatically bound AcVal-tRNA, presumably at the ribosomal P-site. Like the ribosomes from Escherichia coli, yeast, and Artemia salina, cross-linking is exclusively to C-1609, the equivalent of the E. coli C-1400 residue. Mutation of the RNA from G-1707 to A or from U-1711 to C which results in resistance to paromomycin or hygromycin, respectively, failed to affect the rate, yield, or site of cross-linking. The presence of the antibiotics during cross-linking also was without effect. It is concluded that at these two positions the base changes made do not interfere with the tertiary structure of the decoding site.

Animals↗