bluuebunny/crossref_metadata_2025_split huggingface dataset:
PMT family of Candida albicans: five protein mannosyltransferase isoforms affect growth, morphogenesis and antifungal resistance
Authors: Prill Stephan K.‐H. , Klinkert Birgit , Timpel Claudia , Gale Cheryl A. , Schröppel Klaus , Ernst Joachim F. 
Published: January 2005

SummaryProtein O‐mannosyltransferases (Pmt proteins) initiate O‐mannosylation of secretory proteins. The PMT gene family of the human fungal pathogen Candida albicans consists of PMT1 and PMT6, as well as three additional PMT genes encoding Pmt2, Pmt4 and Pmt5 isoforms described here. Both PMT2 alleles could not be deleted and growth of conditional strains, containing PMT2 controlled by the MET3‐ or tetOScHOP1‐promoters, was blocked in non‐permissive conditions, indicating that PMT2 is essential for growth. A homozygous pmt4 mutant was viable, but synthetic lethality of pmt4 was observed in combination with pmt1 mutations. Hyphal morphogenesis of a pmt4 mutant was defective under aerobic induction conditions, yet increased in embedded or hypoxic conditions, suggesting a role of Pmt4p‐mediated O‐glycosylation for environment‐specific morphogenetic signalling. Although a PMT5 transcript was detected, a homozygous pmt5 mutant was phenotypically silent. All other pmt mutants showed variable degrees of supersensitivity to antifungals and to cell wall‐destabilizing agents. Cell wall composition was markedly affected in pmt1 and pmt4 mutants, showing a significant decrease in wall mannoproteins. In a mouse model of haematogenously disseminated infection, PMT4 was required for full virulence of C. albicans. Functional analysis of the first complete PMT gene family in a fungal pathogen indicates that Pmt isoforms have variable and specific roles for in vitro and in vivo growth, morphogenesis and antifungal resistance.
Candida albicans protein kinase CaHsl1p regulates cell elongation and virulence
Authors: Umeyama Takashi , Kaneko Aki , Nagai Yuki , Hanaoka Nozomu , Tanabe Koichi , Takano Yukie , Niimi Masakazu , Uehara Yoshimasa 
Published: January 2005

Summary Saccharomyces cerevisiae Hsl1p is a Ser/Thr protein kinase that regulates cell morphology. We identified Candida albicans CaHSL1 and analysed its function in C. albicans. Cells lacking CaHsl1p exhibited filamentous growth under yeast growth conditions with the filaments elongating more quickly than did those of the wild type under hyphal growth conditions, suggesting that it plays a role in the suppression of cell elongation. Green fluorescent protein‐tagged CaHsl1p colocalized with a septin complex to the bud neck during yeast growth or to a potent septation site during hyphal growth, as expected from the localization in S. cerevisiae. However, the localization of the septin complex did not change in ΔCahsl1, suggesting that CaHsl1p does not participate in septin organization. CaHsl1p was expressed in a cell cycle‐dependent manner and, except for the G1 phase, phosphorylated throughout the cell cycle. In ΔCahsl1 cells, the phosphorylation of a possible CaHsl1p target CaSwe1p decreased, while that of CaCdc28p at tyrosine18 increased. Either an extra copy of the tyrosine18‐mutated CaCdc28p or deletion of CaSWE1 suppressed the cell elongation phenotype caused by CaHSL1 deletion. Furthermore, ΔCahsl1 exhibited reduced virulence in the mouse systemic candidiasis model. Thus, the CaHsl1p‐CaSwe1p‐CaCdc28p pathway appears important in the cell elongation of both the yeast and hyphal forms and to the virulence of C. albicans.
Natural merodiploidy involving duplicated rpoB alleles affects secondary metabolism in a producer actinomycete
Authors: Vigliotta Giovanni , Tredici Salvatore Maurizio , Damiano Fabrizio , Montinaro Maria Rosa , Pulimeno Rita , Di Summa Roberta , Massardo Domenica Rita , Gnoni Gabriele V. , Alifano Pietro 
Published: January 2005

Summary Actinomadura sp. ATCC 39727 produces the glycopeptide antibiotic A40926, structurally similar to teicoplanin. Production of A40926 is governed by the stringent response at the transcriptional level. In fact, addition of an amino acid pool prevented the transcription of dbv cluster genes involved in the A40926 biosynthesis and the antibiotic production in chemically defined media, and a thiostrepton‐resistant relaxed mutant was severely impaired in its ability to produce the antibiotic. The derivative strain rif19, highly resistant to rifampicin (minimal inhibitory concentration, MIC > 200 µg ml−1), was isolated from the wild type strain that exhibited low resistance to rifampicin (MIC < 25 µg ml−1). In this strain A40926 production started earlier than in the wild type, and reached higher final levels. Moreover, the antibiotic production was not subjected to the stringent control. Molecular analysis led to the identification of two distinct rpoB alleles, rpoBS and rpoBR, in both the wild type and the rif19. rpoBR harboured the H426N missense which is responsible for rifampicin‐resistance in bacteria, in addition to other nucleotide substitutions affecting the primary structure of the RNA polymerase β‐chain. Transcript analysis revealed that rpoBR was expressed at a very low level in the wild type strain during the pseudo‐exponential growth phase, and that the amount of rpoBR mRNA increased during the transition to the stationary phase. In contrast, expression of rpoBR was constitutive in the rif19. The results of mRNA half‐life analysis did not support the hypothesis that post‐transcriptional events are responsible for the different rpoB expression patterns in the two strains, suggesting a role of transcriptional mechanisms.
Role of Mg2+ and pH in the modification of Salmonella lipid A after endocytosis by macrophage tumour cells
Authors: Gibbons Henry S. , Kalb Suzanne R. , Cotter Robert J. , Raetz Christian R. H. 
Published: January 2005

SummaryLipid A of Salmonella typhimurium is covalently modified with additional acyl and/or polar substituents in response to activation of the PhoP/PhoQ and/or PmrA/PmrB signalling systems, which are induced by growth at low Mg2+ concentrations and mild acid pH respectively. Although these conditions are thought to exist within macrophage phagolysosomes, no direct evidence for lipid A modification after endocytosis has been presented. To address this issue, we grew S. typhimurium inside RAW264.7 cells in the presence of 32Pi, and then isolated the labelled lipid A fraction, which was found to be extensively derivatized  with phosphoethanolamine, aminoarabinose, 2‐hydroxymyristate and/or palmitate moieties. S. typhimurium grown in tissue culture medium synthesized lipid A molecules lacking all these substituents with the exception of the 2‐hydroxymyristate chain, which was still present. Using defined minimal media to simulate the intracellular pH and Mg2+ concentrations of endosomes, we found that lipid A of S. typhimurium grown in an acidic, low‐Mg2+ medium closely resembled lipid A isolated from bacteria internalized by RAW264.7 cells. A subset of S. typhimurium lipid A modifications were induced by low Mg2+ alone. Escherichia coli K‐12 W3110 modified its lipid A molecules in response to growth under acidic but not low‐Mg2+ conditions. Growth in a high‐Mg2+, mildly alkaline medium resulted in suppression of most lipid A modifications with the exception of the 2‐hydroxymyristate in S. typhimurium. Although lpxO transcription was stimulated by growth on low Mg2+, the biosynthesis of lipid A species containing 2‐hydroxymyristate was independent of PhoP/PhoQ and PmrA/PmrB in S. typhimurium. Our labelling methods should be applicable to studies of lipid A modifications induced by endocytosis of diverse bacteria.
Differential expression of the NRG1 repressor controls species‐specific regulation of chlamydospore development in Candida albicans and Candida dubliniensis
Authors: Staib Peter , Morschhäuser Joachim 
Published: January 2005

Summary Candida albicans and Candida dubliniensis are opportunistic fungal pathogens that are closely related but differ in their epidemiology and in some phenotypic characteristics, including certain virulence‐related traits. A comparison of these two species at the molecular level could therefore provide new insights into the biology and pathogenicity of Candida. Both species share the ability to produce chlamydospores, but only C. dubliniensis forms pseudohyphae with abundant chlamydospores on Staib agar (syn. Guizotia abyssinica creatinine agar), on which C. albicans grows as a budding yeast. To understand the basis of this species‐specific, differential regulation of morphogenetic development, we set out to identify C. albicans genes that repress chlamydospore formation under these conditions. A C. albicans genomic library was integrated into the C. dubliniensis genome and transformants were screened for clones in which filamentation and/or chlamydospore production on Staib agar was suppressed. This screen identified two genes, CaNRG1 and CaPDE2, encoding a general transcriptional repressor and a high affinity cAMP phosphodiesterase, respectively. Expression of CaNRG1 in C. dubliniensis repressed pseudohyphae and chlamydospore formation, whereas expression of CaPDE2 only reduced the extent of filamentous growth but did not affect chlamydospore formation. We found that C. dubliniensis, but not C. albicans, specifically downregulates NRG1 expression on Staib medium to allow chlamydospore development. Artificial overexpression of CdNRG1 suppressed pseudohyphal growth and production of chlamydospores in C. dubliniensis. Conversely, deletion of CaNRG1 in C. albicans resulted in chlamydospore formation on Staib agar, confirming its central role in the regulation of this morphogenetic process. Our results demonstrate that differential regulation of a single gene, NRG1, in C. albicans and C. dubliniensis is responsible for their species‐specific response to environmental signals that induce chlamydospore development.
Ca2+‐dependent expression of the CIRCE regulon inStreptococcus pneumoniae
Authors: Kwon Hyog‐Young , Kim Su‐Nam , Pyo Suhk‐Neung , Rhee Dong‐Kwon 
Published: January 2005

SummaryDnaK and GroEL play a pivotal role in protein folding, and promote cell proliferation and survival. In Gram‐positive and several Gram‐negative bacteria, HrcA represses the transcription ofdnaKandgroEoperons by binding to the highly conserved CIRCE (controllinginvertedrepeat ofchaperoneexpression) operator sequence in the presence of GroEL. HrcA may respond to environmental stress and various other factors that modulate the transcription of thednaKandgroEoperons. However, the mechanisms by which these factors modulate the activity of HrcA remain elusive. Here, we show that the thermoresistance ofStreptococcus pneumoniaeis significantly repressed in the presence of Ca2+. Furthermore, heat shock‐induced expression of the CIRCE regulon inS. pneumoniaeis repressed in the presence of Ca2+, although to a lesser degree than in thehrcAmutant, strongly suggesting that HrcA inhibits expression of the CIRCE regulon in a Ca2+‐dependent manner. Although HrcA does not bind directly to Ca2+, its hydrophobicity is increased in the presence of the metal ion. Taken together, our observations suggest that Ca2+induces conformational changes, such as exposure of the hydrophobic surfaces of HrcA, which facilitate binding to GroEL. Alternatively, the presence of Ca2+may facilitate GroEL in interacting freely with HrcA. This, in turn, enhances access to CIRCE and leads to repression of thednaKandgroEoperons inS. pneumoniae.
Identification of novel non‐coding RNAs as potential antisense regulators in the archaeon Sulfolobus solfataricus
Authors: Tang Thean‐Hock , Polacek Norbert , Zywicki Marek , Huber Harald , Brugger Kim , Garrett Roger , Bachellerie Jean Pierre , Hüttenhofer Alexander 
Published: January 2005

SummaryBy generating a specialized cDNA library from the archaeon Sulfolobus solfataricus, we have identified 57 novel small non‐coding RNA (ncRNA) candidates and confirmed their expression by Northern blot analysis. The majority was found to belong to one of two classes, either antisense or antisense‐box RNAs, where the latter only exhibit partial complementarity to RNA targets. The most prominent group of antisense RNAs is transcribed in the opposite orientation to the transposase genes, encoded by insertion elements (transposons). Thus, these antisense RNAs may regulate transposition of insertion elements by inhibiting expression of the transposase mRNA. Surprisingly, the class of antisense RNAs also contained RNAs complementary to tRNAs or sRNAs (small‐nucleolar‐like RNAs). For the antisense‐box ncRNAs, the majority could be assigned to the class of C/D sRNAs, which specify 2′‐O‐methylation sites on rRNAs or tRNAs. Five C/D sRNAs of this group are predicted to target methylation at six sites in 13 different tRNAs, thus pointing to the widespread role of these sRNA species in tRNA modification in Archaea. Another group of antisense‐box RNAs, lacking typical C/D sRNA motifs, was predicted to target the 3′‐untranslated regions of certain mRNAs. Furthermore, one of the ncRNAs that does not show antisense elements is transcribed from a repeat unit of a cluster of small regularly spaced repeats in S. solfataricus which is potentially involved in replicon partitioning. In conclusion, this is the first report of stably expressed antisense RNAs in an archaeal species and it raises the prospect that antisense‐based mechanisms are also used widely in Archaea to regulate gene expression.
Pseudomembranous colitis in children
Authors: BROOK ITZHAK 
Published: January 2005

AbstractThis review presents the microbiology, management and prevention of pseudomembranous colitis (PMC) in children. PMC is commonly associated with prior antibiotic exposure and hospitalization. It is caused almost exclusively by toxins produced by Clostridium difficile. The clinical spectrum of this disease may range from a mild, non‐specific diarrhea to severe colitis with toxic megacolon, perforation, and death. PMC may affect all age groups, although a lower incidence has been noted in children. Ampicillin, amoxicillin, the second‐ and third‐generation cephalosporins and clindamycin are the drugs most frequently associated with development of PMC, although nearly all antimicrobials have been implicated as causes of diarrhea and colitis. Discontinuation of antibiotics and supportive therapy usually lead to resolution of this disorder. Administration of oral vancomycin or other therapeutic regimens may be needed.
Changes in serum lipid concentrations in patients with chronic hepatitis C virus positive hepatitis responsive or non‐responsive to interferon therapy
Authors: HAMAMOTO SACHIKO , UCHIDA YASUSHI , WADA TOMOKO , MORITANI MAKOTO , SATO SHUICHI , HAMAMOTO NAOHARU , ISHIHARA SHUNJI , WATANABE MAKOTO , KINOSHITA YOSHIKAZU 
Published: January 2005

AbstractBackground: Changes in serum lipid concentrations during the administration of interferon to patients with chronic hepatitis C virus (HCV) infection have not been fully investigated. The present study was designed to compare changes in serum lipid concentrations before, during and after interferon therapy in responders and non‐responders to treatment.Methods: In total, 101 patients with chronic HCV positive hepatitis were enrolled in this study. High dose interferon alpha was given on alternate days for 6 months. Six months after the end of treatment patients were assessed for the presence or absence of HCV RNA to determine the results of interferon treatment. The time courses of changes in serum lipid concentrations were measured in all patients.Results: The total cholesterol level increased gradually during and after interferon therapy, and its pattern of change coincided with that of serum cholinesterase activity. Pretreatment serum cholesterol concentrations did not differ between responders and non‐responders to interferon therapy. The serum triglyceride concentration, conversely, showed a sharp increase during interferon administration and returned to its basal level after the end of treatment. Responders to interferon therapy tended to have higher pretreatment triglyceride concentrations than did non‐responders.Conclusions: We clarified that serum cholesterol and triglyceride levels showed different patterns of change during interferon therapy.
Comparative study of nizatidine and famotidine for maintenance therapy of erosive esophagitis
Authors: HAMAMOTO NAOHARU , HASHIMOTO TOMOYUKI , ADACHI KYOICHI , HIRAKAWA KAZUYA , ISHIHARA SHUNJI , INOUE HARUE , TANIURA HIROYUKI , NIIGAKI MASATOSHI , SATO SHUICHI , KUSHIYAMA YOSHINORI , SUETSUGU HIROSHI , MIYAKE TATSUYA , KINOSHITA YOSHIKAZU 
Published: January 2005

AbstractBackground: The therapeutic effect of combined administration of prokinetics and histamine H2 receptor antagonists (H2RA) in gastroesophageal reflux disease is reported to be superior to that of monotherapy with H2RA alone. In addition to its acid‐suppressing effect, the H2RA nizatidine also has a prokinetic action by suppressing acetylcholine esterase. The present multicenter, randomized controlled study was performed to investigate whether nizatidine is superior to famotidine, which does not suppress acetylcholine esterase activity, in maintenance therapy for erosive esophagitis. In addition, the question as to whether the grade of erosive esophagitis affects the non‐recurrence rate during the maintenance therapy with H2RA was also investigated.Methods: Seventy‐two patients with endoscopically healed erosive esophagitis after 8 weeks of initial treatment with proton pump inhibitors were randomly divided into two groups. Patients in the nizatidine group were treated with 150 mg nizatidine twice a day (b.i.d.), while patients in the famotidine group were treated with 20 mg famotidine b.i.d. for 6 months. At the end of therapy, and at the time when patients complained of symptoms, endoscopic investigations were repeated to find out whether the esophagitis had recurred.Results: Nizatidine produced a significantly higher non‐recurrence rate than famotidine (P = 0.049 in intention‐to‐treat [ITT] analysis). This difference of remission rate between nizatidine and famotidine was observed mainly in grade B esophagitis (P = 0.016 in ITT analysis).Conclusion: Nizatidine is a more effective H2RA than famotidine in the maintenance therapy of patients with reflux esophagitis.
Three‐dimensional helical computed tomography cholangiography with minimum intensity projection in gallbladder carcinoma patients with obstructive jaundice: Comparison with magnetic resonance cholangiography and percutaneous transhepatic cholangiography
Authors: RAO NARAYANA DLV , SINGH GULATI MANPREET , PAUL SHASHI BALA , PANDE GIRISH KUMAR , SAHNI PEUSH , CHATTOPADHYAY TUSHAR KANTI 
Published: January 2005

AbstractObjective:  Computed tomography (CT) is traditionally used for evaluation and staging of gallbladder carcinoma (GC). However, in the subgroup of patients with obstructive jaundice, magnetic resonance cholangiography (MRC) is generally required to assess the level of biliary obstruction. The present study was  undertaken  to  evaluate  the  diagnostic potential of three‐dimensional helical CT cholangiography (3‐D CTC) with minimum intensity projection (minIP), to determine the presence and level of biliary obstruction.Materials and Methods:  Twenty‐five consecutive patients with proven GC, presenting with clinical and biochemical features of obstructive jaundice, over a 1‐year period were included in the study. Dual phase helical CT data was obtained in the arterial and venous phases, respectively, after intravenous contrast injection using a pressure injector. Axial CT data (both arterial and venous phase) was studied for staging and resectability of tumor. Three‐dimensional helical CT cholangiography using minIP obtained from the venous phase data set, was used to assess the level of biliary obstruction and isolation of hepatic segmental ducts. Three‐dimensional helical CT cholangiography findings were compared with MRC and percutaneous transhepatic cholangiography (PTC) (gold standard). None of the patients were operated on as they were all considered inoperable on axial CT images due to extensive local disease or distant metastasis.Results:  In all patients, 3‐D CTC demonstrated dilated intrahepatic ducts up to tertiary branch level. The 3‐D CTC correctly diagnosed the level of biliary obstruction and demonstrated isolated segmental ducts in all patients and correlated well in all cases with MRC and PTC findings in this regard. However, the 3‐D CTC did not add any additional information over the axial source images.Conclusion:  Three‐dimensional helical CT cholangiography with minIP can correctly determine the level of biliary obstruction in patients with GC and may be a strong competitor with MRC, because it gives equivalent information with regard to the level of ductal obstruction even while being a part of an overall comprehensive CT staging study. Even though 3‐D CTC did not provide additional information on top of the source images, the referring physicians found them very useful for conceptualization of the 3‐D biliary anatomy.
Iron overload in patients with chronic hepatitis C virus infection: Clinical and histological study
Authors: SILVA IVONETE SS , PEREZ RENATA M , OLIVEIRA PEDRO V , CANTAGALO MARIA INÊS , DANTAS ELIZABETE , SISTI CRISTINA , FIGUEIREDO‐MENDES CLÁUDIO , LANZONI VALERIA P , SILVA ANTONIO EB , FERRAZ MARIA LUCIA G 
Published: January 2005

AbstractBackground:  Recently it has been found that iron is an important element in the natural history of hepatitis C. Serum markers of iron stores are frequently increased in chronic hepatitis C virus (HCV)‐infected carriers but the real impact of the hepatic iron overload is poorly understood. The purpose of the present paper was to determine the prevalence of iron overload and to study the relationship between hepatic iron concentration (HIC) and clinical, biochemical and histological characteristics in chronic HCV‐infected carriers.Methods:  Patients presenting with anti‐HCV and HCV‐RNA were included. Hepatic iron concentration was determined in liver tissue by atomic absorption spectrophotometry. The association between HIC and age, gender, risk factor of transmission, duration of infection, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, iron and serum ferritin, transferrin saturation, HCV‐RNA level, grading of inflammatory activity, staging of fibrosis, hepatic steatosis, and stainable iron was analyzed. Statistical analysis included the Mann–Whitney test and a multiple linear regression model.Results:  Ninety‐six patients (58% male) with a mean age of 44 ± 10 years were studied. Serum iron, ferritin and transferrin saturation were elevated in 28%, 27% and 12.5% of patients, respectively. Stainable iron was detected in few patients (15.6%). Higher grades of stainable iron (2 and 3) were observed in only 7%. The HIC (>30 mmol/g dry weight) was elevated in five patients (5%). Neither grading nor staging were related to HIC. Higher HIC were observed in male patients (P < 0.001), in patients with elevated serum ferritin (P = 0.001) and in patients with stainable iron (grades 2 and 3; P = 0.001). Multiple linear regression analysis showed that only stainable iron was independently correlated with HIC (P = 0.003).Conclusions:  Iron overload in chronically HCV‐infected patients was uncommon and hepatic iron content seemed not to be related to the liver damage process. In the eventuality of iron overload, histochemical liver iron is a useful marker to estimate HIC.