Activity of the Giardia intestinalis proteasome during encystation and its connection with the expression of the cyst wall protein 1 (CWP1)

Giardia is a parasite whose life cycle is composed of two stages: replicative trophozoites, responsible for the symptoms of the disease, and infective cysts, resistant to adverse environments outside of hosts. Proteasomes are multicatalytic peptidase complexes responsible for the specific degradation of proteins in eukaryotic cells. This study assessed the proteasome activity in the trophozoite and during encystation. Strong activation of the proteasome was observed during the differentiation of trophozoites into cysts, reaching its maximum level 24 h after the stimulus. We also found that the Giardia proteasome presents unusual characteristics related to higher eukaryotic proteasomes, making it an eventual therapeutic target. Here we tested the effects on the synthesis of a cyst wall protein by chemical inactivation of the proteasome and by overexpression or partial inhibition of the deubiquitinating protein RPN11 in transfected cells. Moreover, an analysis of the intracellular localization of RPN11 (an integral part of the proteasome regulatory particle) revealed major changes associated with the differentiation of trophozoites into cysts. This evidence further supports the important role of the proteasome in Giardia encystation.

Modelling the global impact of the 13-valent pneumococcal vaccine on antibiotic use for otitis media

Background

Antimicrobial resistance (AMR) is a critical issue in global health causing approximately 1 million annual deaths. Vaccines are essential in addressing AMR as they reduce resistant strains and prevent development of resistance by preventing spread of disease and resulting antimicrobial use. This analysis evaluates the impact the 13-valent pneumococcal conjugate vaccine (PCV13) has had on dispensed antibiotic prescriptions (DAP) due to otitis media (OM), one of the largest drivers of DAP globally.

Methods

An Excel-based model was developed to estimate number of infants vaccinated with PCV13, and the associated reduction in OM cases in children <5 since 2010. OM cases averted were based on a global meta-analysis and estimated cases averted were applied to infants vaccinated by country. DAP avoided were estimated assuming 90% of OM cases were prescribed an antibiotic. We then compared our modelled estimates to metrics measuring number needed to vaccinate to prevent DAP from any outcome.

Results

Over the past 10 years, we estimated 286,54m infants were vaccinated with PCV13, with 158,33m OM cases and as many as 142,49m DAP avoided globally. By WHO region, reductions in OM rates and DAP respectively are estimated to have been; Africa and Eastern Mediterranean (103,05m; 92,74m), South-East Asia and Western Pacific (8,82m; 7,94m), Europe (20,70m; 18,63m) and Americas (25,76m; 23,18m). Using rates from the literature of 0,20 to 1,79 total DAP avoided per child vaccinated, results ranged from to 71,63m to 511,68m.

Conclusions

PCV13 use has resulted in substantial reductions in OM and DAP. As we focus on OM in children <5, results underestimate the full impact of PCV13 on DAP as vaccine impact on other pneumococcal diseases and adults through herd effect are not included. Recognition of the role of vaccination in addressing AMR burden is an opportunity to encourage patients, providers and healthcare systems to continually prioritize vaccination in public health efforts.

Key messages

Over the past 10 years, PCV13 has led to considerable reductions in dispensed antibiotic prescriptions globally, highlighting the importance of prioritizing vaccination in global healthcare systems. Our findings illustrate how vaccines can play an essential role in reducing the global burden of antimicrobial resistance through reduction of antibiotic use.

A new gene inventory of the ubiquitin and ubiquitin-like conjugation pathways in Giardia intestinalis

BACKGROUND

Ubiquitin (Ub) and Ub-like proteins (Ub-L) are critical regulators of complex cellular processes such as the cell cycle, DNA repair, transcription, chromatin remodeling, signal translation, and protein degradation. Giardia intestinalis possesses an experimentally proven Ub-conjugation system; however, a limited number of enzymes involved in this process were identified using basic local alignment search tool (BLAST). This is due to the limitations of BLAST’s ability to identify homologous functional regions when similarity between the sequences dips to < 30%. In addition Ub-Ls and their conjugating enzymes have not been fully elucidated in Giardia.

OBJETIVE

To identify the enzymes involved in the Ub and Ub-Ls conjugation processes using intelligent systems based on the hidden Markov models (HMMs).

METHODS

We performed an HMM search of functional Pfam domains found in the key enzymes of these pathways in Giardia’s proteome. Each open reading frame identified was analysed by sequence homology, domain architecture, and transcription levels.

FINDINGS

We identified 118 genes, 106 of which corresponded to the ubiquitination process (Ub, E1, E2, E3, and DUB enzymes). The E3 ligase group was the largest group with 82 members; 71 of which harbored a characteristic RING domain. Four Ub-Ls were identified and the conjugation enzymes for NEDD8 and URM1 were described for first time. The 3D model for Ub-Ls displayed the β-grasp fold typical. Furthermore, our sequence analysis for the corresponding activating enzymes detected the essential motifs required for conjugation.

MAIN CONCLUSIONS

Our findings highlight the complexity of Giardia’s Ub-conjugation system, which is drastically different from that previously reported, and provides evidence for the presence of NEDDylation and URMylation enzymes in the genome and transcriptome of G. intestinalis.

Editorial: Diagnostic Testing for SARS-Coronavirus-2 in the Nursing Facility: Recommendations of a Delphi Panel of Long-Term Care Clinicians

With the COVID-19 pandemic progressing, guidance on strategies to mitigate its devastating effects in nursing facilities (NFs) is critical to preventing additional tragic outcomes. Asymptomatic spread of COVID-19 from nursing facility staff and residents is a major accelerator of infection. Facility-wide point-prevalence testing is an emerging strategy in disease mitigation. Because time is not available to await the results of randomized controlled trials before implementing strategies in this high-risk setting, an expert Delphi panel composed of experienced long-term care medicine professionals has now met to provide testing guidance for SARS-Coronavirus-2 to NFs. After many email and telephone discussions, the panel responded to a questionnaire that included six different scenarios, based on varying availability of Polymerase Chain Reaction (RT-PCR) testing and personal protective equipment (PPE). The panel endorsed facility-wide testing of staff and residents without dissent when diagnostic RT-PCR was available. While the panel recognized the limitations of RT-PCR testing, it strongly recommended this testing for both staff and residents in NFs that were either COVID-19 naive or had limited outbreaks. There was also consensus on testing residents with atypical symptoms in a scenario of limited testing capability. The panel favored testing every 1 to 2 weeks if testing was readily available, reducing the frequency to every month as community prevalence declined or as the collection of additional data further informed clinical critical thinking and decision-making. The panel recognized that frequent testing would have consequences in terms of potential staff shortages due to quarantine after positive tests and increased PPE use. However, the panel felt that not testing would allow new clusters of infection to form. The resulting high mortality rate would outweigh the potential negative consequences of testing. The panel also recognized the pandemic as a rapidly evolving crisis, and that new science and increasing experience might require an updating of its recommendations. The panel hopes that its recommendations will be of value to the long-term care industry and to policy makers as we work together to manage through this challenging and stressful time.

Trends in vaccine investment in middle income countries

Although a proven and effective preventive health measure, childhood immunization programs remain vulnerable to budgetary pressures. Sustainable financing of immunization programs is an important issue that presents a challenge for middle-income countries (MIC) in particular, in part due to technological advances meaning more vaccines are available. This study aimed to analyse trends in immunization program investment across 15 MIC selected based on availability of data, income level classification, and regional representativeness. We assessed investment trends in relation to vaccine coverage, vaccine access, and broader health indicators. Immunization and expenditure data were obtained from the World Health Organisation (WHO) database and the WHO UNICEF Joint Reporting Form and WHO Vaccine Product, Price and Procurement from 2006-2016. We calculated a weighted average index of vaccine commitment (WAIVC) based on vaccine coverage, vaccine scope, and weighted by vaccine innovation measured by approximating vaccine expenditure. Correlation analyses were conducted between immunization expenditure per-capita and each WAIVC, infant mortality and life expectancy. Correlation analyses at a global and individual country level indicate an improvement in immunization access, vaccination commitment measured by WAIVC, and scope of available vaccines in countries with sustained increases in vaccination funding. Increases in national immunization expenditure were correlated with reduced infant mortality and increased life expectancy. Vaccine expenditure comprises a small proportion (less than 2%) of total healthcare spending and has not uniformly increased in accordance with the scope of available vaccines. The present analysis supports the premise that countries with consistent increases in vaccine expenditure have increased vaccine coverage and commitment measured by WAIVC and improved broader health outcomes, indicating the value of sustained investment in vaccination for improved population health. The benefits of vaccine expenditure in this holistic fashion are critical to inform policy decisions on national budget allocation for vaccine funding.

Calcium-binding proteins that are type B″ regulatory subunits of phosphatase 2A in Giardia intestinalis

Giardia intestinalis is a protozoan parasite that colonizes the upper part of the small intestine of its mammalian hosts. The trophozoite, which is the replicative stage, has a complex cytoskeleton that allows it to move and adhere to intestinal cells. It has been proposed that protein phosphatase 2A (PP2A) participates in the regulation of changes to the parasite cytoskeleton during its life cycle. However, how PP2A is involved in this regulation remains unclear since its substrates and regulators have not been characterized. In this work, we report the bioinformatic and experimental analysis of two potential regulatory B″ subunits of PP2A in Giardia, both of which are calcium-binding proteins. In this work, in silico and experimental evidence of the binding of both proteins to calcium is presented; the proteins are shown to interact with the catalytic PP2A subunit in the trophozoite stage, and they exhibit different subcellular localization patterns. Because PP2A is a heterotrimer, homology analysis of the different subunits of PP2A indicates that fewer holoenzyme combinations can be formed in this parasite than in other organisms. Our results suggest that the localization of PP2A may be associated with calcium-dependent signaling through its B″ type regulatory subunits.

Do Drains Contribute to Pancreatic Fistulae? Analysis of over 5000 Pancreatectomy Patients

INTRODUCTION

Conflicting evidence exists from randomized controlled trials supporting both increased complications/fistulae and improved outcomes with drain placement after pancreatectomy. The objective was to determine drain practice patterns in the USA, and to identify if drain placement was associated with fistula formation.

METHODS

Demographic, perioperative, and patient outcome data were captured from the most recent annual NSQIP pancreatic demonstration project database, including components of the fistula risk score. Significant variables in univariate analysis were entered into adjusted logistic regression models.

RESULTS

Of 5013 pancreatectomy patients, 4343 (87%) underwent drain placement and 18% of patients experienced a pancreatic fistula. When controlled for other factors, drain placement was associated with ducts < 3 mm, soft glands, and blood transfusion within 72 h of surgery. Age, obesity, neoadjuvant radiation, preoperative INR level, and malignant histology lost significance in the adjusted model. Drained patients experienced higher readmission rates (17 vs. 14%; p < 0.05) and increased (20 vs. 8%; p < 0.01) pancreatic fistulae. Fistula was associated with obesity, no neoadjuvant chemotherapy, drain placement, < 3 mm duct diameter, soft gland, and longer operative times. Drain placement remained independently associated with fistula after both distal pancreatectomy (OR = 2.84 (1.70, 4.75); p < 0.01) and pancreatoduodenectomy (OR = 2.29 (1.28, 4.11); p < 0.01).

CONCLUSIONS

Despite randomized controlled clinical trial data supporting no drain placement, drains are currently placed in the vast majority (87%) of pancreatectomy patients from > 100 institutions in the USA, particularly those with soft glands, small ducts, and perioperative blood transfusions. When these factors are controlled for, drain placement remains independently associated with fistulae after both distal and proximal pancreatectomy.

Experimental and bioinformatic characterization of CaBP2933 an EF-Hand protein of Giardia intestinalis

Giardia intestinalis is a parasite that inhabits the small intestine of humans. This parasite is a divergent eukaryote with a compact genome. The calcium ion is an essential messenger in cell signaling. Calcium's role as a messenger is mediated through calcium-binding proteins (CaBPs) that decode the message. The most important family of CaBPs is the EF-Hand protein family. In this study we have explored the role of EF-Hand protein CaBP2933. We analyzed its location, confirmed its ability to bind calcium and identified some of its interacting proteins. Take together our results suggest that CaBP2933 is involved in vesicular trafficking during encystation, via an interaction with kinesin-3 motor protein.

Preliminary study of the enzyme ubiquitin carboxylterminal hydrolase 14 (UBP6) in Giardia intestinalis: structural bioinformatic analysis and transcriptional profile during encystation

This paper presents a combined approach<br />with two aims. The first is to analyze the<br />reported sequence of the enzyme ubiquitin<br />carboxyl-terminal hydrolase 14 of Giardia<br />intestinalis (UBP6) through computational<br />methods to find components related with<br />its hypothetical function. The second is<br />to determine if the protein-coding gene is<br />expressed in G. intestinalis and, if such is<br />the case, also determine its transcription<br />pattern along the life cycle of the parasite. It<br />was established that the protein belongs to<br />the family of Cys-dependent deubiquitinases<br />and more specifically to ubiquitin specific<br />proteases (USPs). Moreover, the catalytic<br />center with the complete triad as well as<br />typical features of the USP motif were also<br />identified. Since the computational findings<br />suggest that the enzyme could be functional,<br />reverse transcription coupled to PCR was<br />used as a first approach to establish if in fact<br />the coding gene is expressed in the parasite.<br />Interestingly, it was found not only that<br />the gene is expressed, but also that there<br />is a transcription variation along the life<br />cycle of the parasite. These two findings are<br />the starting point for further studies since<br />they tentatively suggest that this enzyme<br />could be involved in the protein turnover<br />that occurs during parasite encystation.<br />Although preliminary, this study is the first<br />report concerning the study of a specific<br />deubiquitinating enzyme in the parasite G.<br />intestinalis.

The natural history of anal transition zone inflammation and possible relationship to pouchitis: a long-term longitudinal study

AIM

Reservoir ileitis (pouchitis) is the most common complication after pelvic pouch surgery for ulcerative colitis and the aetiology remains largely unknown. The anal transition zone (ATZ) contains the only remaining colonic epithelium after ileal pouch anal anastomosis (IPAA) and may provide important clues as to whether ulcerative colitis and pouchitis share a common pathogenesis. The aim of this study was to evaluate longitudinally the long-term histological changes in the ATZ and their relationship to the incidence of pouchitis.

METHOD

Patients with a double-stapled IPAA for ulcerative colitis at an academic medical centre with at least 10 years of clinical and histological follow-up were identified from a prospective database. Annual ATZ and pouch biopsies were taken and interpreted by two expert gastrointestinal pathologists. ATZ histological variability score, the incidence of pouchitis, and function were correlated over time. ATZ biopsies were scored from one to three based on the extent of inflammation.

RESULTS

Sixteen of the 114 patients having IPAA fulfilled the criteria for admission to the study. There were 179 biopsies of the ATZ. All exhibited variability in ATZ histology over time and 81% had a 2-unit change in their inflammatory score. There was no correlation between pouchitis and histological severity score of the ATZ. Similarly, function over time did not vary with the intensity of ATZ inflammation.

CONCLUSION

ATZ inflammation varies substantially over time in most patients. But these changes from year to year did not correlate with function or the occurrence of pouchitis.

The ubiquitin-activating enzyme (E1) of the early-branching eukaryote Giardia intestinalis shows unusual proteolytic modifications and play important roles during encystation

Giardia intestinalis is considered an early-branching eukaryote and is therefore a valuable model for studying primordial cellular processes. This work reports the characterization of the ubiquitin-activating enzyme (E1) during growth and different stages of trophozoite differentiation into cysts. We found that in Giardia E1 expression (both at mRNA and protein levels) is regulated during encystation. The enzyme is proteolytically processed mainly into two fragments of 68kDa (N-terminal) and 47kDa (C-terminal). This phenomenon has not been described for any other E1. In trophozoites, this enzyme localized at spots within the cytoplasm as detected by using polyclonal antibodies against either E1 N- or C-terminal fragments. This pattern changed during encystation into a diffuse localization throughout the cytoplasm of encysting cells. E1 localizes in mature cysts at cytoplasmic spots and in the cyst wall. Our antisense silencing experiments suggested that E1 is an essential gene for parasite viability. On the other hand, E1 over-expression greatly increased the encystation rate, indicating a relationship between E1 and Giardia differentiation.

Synthesis of pyruvate: ferredoxin oxidoreductase and alcohol dehydrogenase E enzymes during Giardia intestinalis excystation

INTRODUCTION

Giardia intestinalis is a unicellular parasite of worldwide distribution. It causes an intestinal illness known as giardiasis, and it is probably the earliest diverging eukaryotic microorganism. Previously, changes have been reported in the expression of mRNAs at several stages of the life cycle; however specific enzymatic activity changes have not been explored.

OBJECTIVE

The expression of pyruvate ferredoxin oxidoreductase (PFOR) and alcohol dehydrogenase E (ADHE) enzymes was measured in cyst and trophozoite stages, and during the excystation process.

MATERIALS AND METHODS

Recombinant proteins were generated for PFOR and ADHE to be used as antigens in the production of polyclonal antibodies for the detection of native proteins by Western Blot. The enzymatic activity of ADHE and glutamate dehydrogenase (GDH) was evaluated by spectrophotometric assays.

RESULTS

PFOR (139 kDa) and ADHE (97 kDa) proteins were detected in trophozoites, but not in cysts. During excystation, ADHE protein was detected after the first phase of induction, but the PFOR protein appeared only after the second phase. This indicated that both proteins were synthesized during excystation, although at different times. ADHE enzymatic activity was present only in trophozoites and not in cysts whereas GDH activity was detected in both stages.

CONCLUSION

These results conclusively showed that PFOR and ADHE enzymes were translated during the excystation process and is strong evidence that active protein synthesis was occurring during excystation.

Analysis of phosphorylated proteins and inhibition of kinase activity during Giardia intestinalis excystation

The parasite Giardia intestinalis undergoes a differentiation process that allows it to infect its mammal host. That process is excystation. We examined the importance of protein phosphorylation during the passage from cyst to trophozoite. Cysts obtained from patients with giardiasis were excysted in vitro and the soluble cytoplasmic proteins were analyzed during the three phases of the process, using a specific staining for phosphoproteins. We found two phosphorylated proteins and identified them with MALDI-TOF as 14-3-3 and Hsp70. Modifications were detected in both proteins, which could indicate a role in differentiation of the parasite. In addition, the inhibition of serine-threonine kinases during excystation specifically affected the cytokinesis of the excyzoite, thus inhibiting the completion of trophozoite formation.

Transcription of meiotic-like-pathway genes in Giardia intestinalis

The reproductive mechanism of Giardia intestinalis, considered one of the earliest divergent eukaryotes, has not been fully defined yet. Some evidence supports the hypothesis that Giardia is an exclusively asexual organism with a clonal population structure. However, the high genetic variability, the variation in ploidy during its life cycle, the low heterozygosity and the existence of genes involved in the meiotic-like recombination pathway in the parasite's genome cast doubt on exclusively asexual nature of Giardia. In this work, semiquantitative RT-PCR analysis was used to assess the transcription pattern of three meiosis-like-specific genes involved in homologues recombination: dmc1, hop1 and spo11. The mRNAs were amplified during the parasite's differentiation processes, encystation and excystation, and expression was found at each stage of its life cycle. A semiquantitative assessment also suggests that expression of some of the genes is regulated during encystation process.

Health information Websites: characteristics of US users by race and ethnicity

We conducted a national public opinion survey of adults aged 18 years or older in the continental US to determine their use of health Websites. Of the 928 individuals contacted, 868 (94%) reported their race/ethnicity. More non-Hispanic Whites reported using the Internet (34%) than African Americans (31%) and Hispanics (20%). We used logistic regression to estimate adjusted odds ratios describing the relationship between Website usage and covariates across the racial/ethnic subgroups. Whereas better perceived health was associated with greater Website use among Hispanics and Whites, stronger health literacy was associated with greater use among Hispanics. No African American or Hispanic respondent aged 65 years or older reported going online. The relationship between education and use was more than twice as strong for African Americans and Hispanics than other groups. That some minority groups are less likely to use the World Wide Web for health information may further compound existing disparities. One place where this problem may be addressed is in the nation's schools.

Genetic diversity of Giardia intestinalis populations in Colombia

INTRODUCTION

Giardia intestinalis is a protozoan parasite that causes a gastrointestinal infection known as giardiosis, which is transmitted primarily through fecal-oral contamination. Genetic studies of axenically cultivated Giardia isolates have identified two major genetic groups distributed throughout the world. In the present study 24 native strains of the parasite were analyzed by the RAPD technique (Random Amplified Polymorphic DNA).

OBJECTIVE

To determine the level of polymorphism and the complexity of Giardia intestinalis circulating strains in specific areas of Colombia.

MATERIALS AND METHODS

The RAPD method was used, as it allows for a quick, simple and reliable analysis that requires no prior knowledge of the genetics of the parasite. A RAPD analysis was conducted on native isolates collected in Colombia between 1997 and 2001, established in continuous cultures. Several primers were tested separately, in order to enhance the capacity for discrimination of the method.

RESULTS

Of the 24 strains that were included in the study, 22 were arranged in independent clusters. The strains that were from the same geographic area and collected at about the same time, generally displayed highly similar but distinguishable RAPD patterns. Clones isolated from a strain were analyzed as well, and it was possible to differentiate them molecularly.

CONCLUSION

The studied strains showed to belong to genotype A . The results suggest that the Colombian strains studied consist of a heterogeneous mixture of closely related populations.

Quick and efficient purification of Giardia intestinalis cysts from fecal samples

Giardia intestinalis is an intestinal parasite that has sparked considerable interest because of the public health problem it creates and because it is regarded as one of the earliest divergent eukaryotes. The present report describes a new method for quick, clean, and effective isolation of G. intestinalis cysts from fecal samples. The isolated cysts have the quality required for biochemical studies of the excystation process.

[Genotyping of the Plasmodium falciparum msp1 (block 2) and dhfr (codon 108) genes in field samples collected in four endemic Colombian localities]

INTRODUCTION

Plasmodium falciparum is a highly polymorphic parasite, which allows it to evade the host's immune response, spread drug resistance and favours transmission.

OBJECTIVES

To analyse the genetic diversity of P. falciparum populations in samples from four endemic localities in Colombia.

MATERIALS AND METHODS

123 blood samples were collected on filter paper from patients with non-complicated P. falciparum malaria during 2002 to 2004. The samples were genotyped using polymerase chain reaction with specific primers for the polymorphic region of block 2 of the msp1 gene and the 108 codon of the dhfr gene.

RESULTS

In msp1 block 2, 95.9% (118/123; 95% CI: 90.8-98.7) of the samples harboured MAD20; 6.5% K1 (8/123; 95% CI: 2.8-12.4) and 2.4% RO33 (3/123; 95% CI: 0.5-6.9). For the dhfrgene the mutant allele N 108 was found in all the samples amplified, T 108 in 3.2% and the wild type S108 in 34.1%. Taking together all the results from both genes, 61.8% (76/123; 95% CI: 52.6-70.4) of the samples were simple infections and 38.2% (47/123; 95% CI: 29.6-47.4) were mixed infections. MAD20/N108-S108 (30.1%) was the most frequent combination among the latter.

CONCLUSIONS

Simple infections, i.e, a single allelic type in each one of the genes studied, prevailed among the circulating parasite populations. In this study the genetic composition of P. falciparum parasite populations was very homogeneous.

Chronic lithium treatment of B lymphoblasts from bipolar disorder patients reduces transient receptor potential channel 3 levels

Chronic lithium treatment of B-lymphoblast cell lines (BLCLs) from bipolar-I disorder (BD-I) patients and healthy subjects ex vivo attenuates agonist- and thapsigargin-stimulated intracellular calcium (Ca(2+)) responses. As these findings suggest that chronic lithium treatment modifies receptor (ROCE) and/or store-operated Ca(2+) entry (SOCE) mechanisms, we determined whether chronic lithium treatment of BLCLs modified the expression of two members of the transient receptor potential channels (TRPC1 & 3), which participate in ROCE/SOCE. Chronic lithium treatment significantly reduced BLCL TRPC3 immunoreactivity (repeated-measures ANOVA, P=0.00005), with interaction effects of diagnosis (P=0.037) and sex (P=0.040). The lithium-induced decrease was greatest in BLCLs from female BD-I patients compared with those from healthy females (-27%) and with vehicle-treated BLCLs from female BD-I patients (-33%). However, lithium treatment did not affect TRPC1 and 3 mRNA levels, and TRPC1 immunoreactivity. Downregulation of TRPC3 may be an important mechanism by which lithium ameliorates pathophysiological Ca(2+) disturbances as observed in BD.

[Identification of the gene sequence of telomerase catalytic subunit in Plasmodium falciparum]

INTRODUCTION

The enzyme telomerase regulates telomere length by synthesis of telomeric repeats to compensate for telomeric loss in each DNA replication cycle. Therefore, telomerase is a potential target to block growth of cells with high replication rates. In Plasmodium falciparum, telomerase activity has been documented, but little information on its structure and role.

METHODS

Herein, alignment of multiple sequences was undertaken comparing telomerase catalytic subunit sequences as found in existing databases. A consensus sequence was compared with the sequences in the P. falciparum genome project and as a result, a candidate sequence for a portion of the telomerase gene was recovered. Primer sets were designed for DNA and RNA amplifications.

RESULTS

DNA fragments corresponding to telomerase conserved domains were amplified by using reverse transcription and PCR of cDNA. With a combination of bioinformatics and sequencing methods, the sequence of telomerase catalytic subunit gene (TERT) in P. falciparum was discovered, and its presence and transcription demonstrated.

Genetic divergence within the Drosophila mayaguana subcluster, a closely related triad of Caribbean species in the repleta species group

The mayaguana triad of the Drosophila repleta species group includes D. mayaguana, D. straubae, and D. parisiena, the latter two of which are very similar when examined morphologically. Many morphological characters used to define these taxa are quantitative and overlap substantially among some forms--it is only through suites of such characters that species can be identified. We apply Population Aggregation Analysis and tree building methods to five rapidly evolving gene regions--the mitochondrial AT rich region and the nuclear acetylcholinesterase, hunchback, mastermind, and vestigial loci to test the morphological species delineations within the morphocryptic mayaguana triad. We find that D. mayaguana is diagnosable using DNA sequences, but the other two species form a non-diagnosable paraphyletic assemblage. A single ecological factor, oviposition substrate, is an important diagnostic character distinguishing D. straubae from D. parisiena, highlighting the importance of examining a diverse array of data (morphological, molecular, ecological, and behavioral) when defining species limits.

[Preparation of DNA libraries of Plasmodium falciparum for searching calmodulin binding protein genes, GOGAT and Pfmyo A]

A cDNA library of Plasmodium falciparum (Colombian strain FCB2) asexual stage was constructed in the lambda ZipLox vector. The lambda ZipLox library and a lambda ZAPII (Dd2 strain) were screened for genes coding for proteins that bind with or are related to calmodulin (CaM). Screening was accomplished with Hot start PCR assays and hybridization with radiolabeled probes. Actin I, CaM, glutamate synthase (GOGAT) and the three myosin clones--Pfmyo A, Pfmyo B and Pfmyo C--were identified. The clones coding for actin I, CaM and GOGAT were retrieved from the lambda ZipLox library, and the GOGAT and Pfmyo A clones from the lambda ZAP II library. The GOGAT clone contained an insert of 2,413 base pairs corresponding to 24.8% of the reported sequence. The Pfmyo A insert was 2,457 base pairs long, and represented the complete mRNA coding for this gene. Finally, the first report of a complete cDNA clone containing the P. falciparum myosin A is presented.

[In vitro encystation of Giardia lamblia: analysis with two-dimensional electrophoresis of differentially expressed proteins]

The reconstruction of Giardia lamblia life cycle in vitro is an excellent tool for the study of the parasite's molecular biology. The present work describes techniques developed that better define parasite differentiation. An encystation protocol is presented along with a method for isolation and purification of the produced cysts. The cyst morphology at the light microscopy level is identical to that of in vivo cysts. A two-dimension protein map obtained by high-resolution electrophoresis indicated that most of the parasite's proteins are acid. Based on this result, the two dimension gel electrophoresis used a pH 4-7 gradient in the first, isoelectric focusing dimension. Differences in protein expression during the stages of encystation were clearly discerned, as well as images of the parasite obtained by light and by transmission electron microscopy that describe the morphological and the ultrastructural changes that occur as the cysts are produced in vitro.

Expression of housekeeping genes during the asexual cell cycle of Plasmodium falciparum

In an earlier study, we found that calmodulin displayed an atypical expression for a housekeeping gene during the erythrocytic cycle of Plasmodium falciparum. The expression pattern was that of an inducible gene linked to the cell cycle, with a peak prior to replication, and not one of a gene that expresses itself in a constitutive way. In this work, we examined the expression pattern of other housekeeping genes, selecting genes from two functionally very different groups: those for three enzymes involved in carbohydrate metabolism--glucose-phosphate-isomerase (GPI), aldolase and glucose-6-phosphate-dehydrogenase (G6PD)--and for three proteins with structural and motor functions--actin-I, beta-tubulin and myosin. The mRNA of each gene was measured by reverse transcription-polymerase chain reaction in synchronic parasite samples that were 14, 28, 40 and 48 h old. GPI and G6PD achieved their maximum expression at 28 h, then declined, while aldolase increased its expression up to 40 h and remained high, but less so at 48 h. Actin and myosin showed the same pattern, increasing up to 48 h, while beta-tubulin expression peaked at 40 h. These findings confirm unconventional behavior in the expression of certain Plasmodium housekeeping genes and suggest the existence of different expression patterns for distinct functional groups.

Plasmodium falciparum: underestimation of dihydrofolate reductase and dihydropteroate synthase polymorphism in field samples: a technical shortcoming of nested PCR assays with mutation-specific primers

n a study parallel to the present one, we conducted a genotype characterization of Plasmodium falciparum based on isolates of patients infected with malaria, who come from a small location in Colombia. The analysis involved extraction of DNA from hematological smears, amplification of the dihydrofolate reductase gene and the dihydropteroate synthase (DHPS) gene for each sample by PCR, and detection through mutation-specific primers nested PCR of mutations associated with resistance to pyrimethamine and sulfadoxine. Given the difficulty in quantifying the DNA extracts due to the type of sample and its heterogeneity, different volumes of the product of the first PCR were tested as template for the nested PCR. Surprisingly, for some samples, we found contradictory results between determinations, which differed only in the amount of template used. This prompted a more general concern that in a natural isolate, where the parasite population is heterogeneous, the nested PCR with mutation-specific primers technique can produce erroneous results that underestimate the complexity of the sample. To test this hypothesis, we designed experiments in this study using position 581 of the DHPS gene as an indicator system and constructed samples simulating the heterogeneity of natural samples. In effect, our data show that the results obtained in the nested PCR can be altered by the amount of template used in the reaction and, therefore, some heterogeneous samples might be classified mistakenly as homogeneous, simple mutant or simple wild type. These observations may explain, at least in part, contradictory results found in the literature. Our data also suggest the need for a more cautious approach to interpretation of the results of nested PCR assays with mutation-specific primers and their implications in the definition of resistance to the pyrimethamine-sulfadoxine combination.

Stereoselective pharmacokinetic analysis and antiepileptic activity of N-2-hydroxypropyl valpromide, a central nervous system--active chiral valproylamide

The purpose of this study was to evaluate the anticonvulsant activity and pharmacokinetics (PK) of a novel chiral CNS-active 2-hydroxypropyl valpromide (HP-VPD), a derivative of valproic acid (VPA). The individual enantiomers, R, S, and racemic (R,S)-HP-VPD were synthesized and evaluated for their pharmacokinetics and pharmacodynamics in a stereoselective manner. A stereoselective gas chromatography (GC) assay for simultaneous quantification of HP-VPD enantiomers in plasma and urine was developed and used to investigate the pharmacokinetics of HP-VPD in dogs. Pharmacodynamic analysis in rats showed that (S)-HP-VPD was 2.5 times more potent as an anticonvulsant in the maximal electroshock seizure (MES) test than its enantiomer and approximately 10 times more potent than VPA. No significant differences were observed in major PK parameters (clearance, volume of distribution, and half-life) between S and (R)-HP-VPD, and this suggested that pharmacodynamic differences could be attributed to the intrinsic pharmacodynamics of each enantiomer rather than to a preferable pharmacokinetic profile. The pharmacokinetic (metabolic) analysis showed that the fraction metabolized to HP-VPD-glucuronide ranged from 5% to 7% and no biotransformation of HP-VPD to VPA and 2-ketopropyl valpromide was observed. This is the first report of significant stereoselectivity in the anticonvulsant activity of a valproylamide with a chiral carbon situated on the alkyl chain of the amine moiety.

Cytochemical localisation of calcium ATPase activity during the erythrocytic cell cycle of Plasmodium falciparum

Using a cytochemical technique, we evaluated the levels of Ca(2+)-ATPase activity in the plasmatic and in the parasitophorous vacuole membrane through the different developmental stages of the Plasmodium falciparum parasitised erythrocyte. We found that the activity is detectable and remains unaltered in the plasma membrane throughout the 48 h cell cycle. However, in the parasitophorous membrane, although the activity was very similar to that measured in the plasma membrane of the young stages (younger than 20-h-old parasites), it diminished gradually with maturation and in schizonts it was almost undetectable. These data suggest that the plasma membrane Ca(2+)-ATPase is important in the maintenance of a low erythrocyte cytoplasmic Ca(2+) concentration, and that in addition it could be a way to supply the vital cation to the parasite at the beginning of the infection, when other transport mechanisms have not yet developed.

Phylogenetic analysis of the repleta species group of the genus Drosophila using multiple sources of characters

The species in the repleta group of the genus Drosophila have been placed into five subgroups-the mulleri, hydei, mercatorum, repleta, and fasciola subgroups. Each subgroup has been further subdivided into complexes and clusters. Extensive morphological and cytological analyses of the members of this species group have formed the foundation for the proposed relationships among the members of the repleta species group. Fifty-four taxa, including 46 taxa belonging to the repleta species group, were sequenced for fragments of four genes-16S ribosomal DNA (16S), cytochrome oxidase II (COII), and nitrogen dehydrogenase 1 (ND1) of the mitochondrial genome and a region of the hunchback (hb) nuclear gene. We also generated a partial data set of elongation factor 1-alpha (Ef1alpha) sequences for a subset of taxa. Our analysis used both DNA characters and chromosomal inversion data. The phylogenetic hypothesis we obtained supports many of the traditionally accepted clades within the mulleri subgroup, but the monophyly of taxonomic groups outside of this subgroup appears not to be supported. Phylogenetic analysis revealed one well-supported, highly resolved clade that consists of closely related members of the mulleri and buzzatii complexes. The remaining taxa, a wide assortment of taxonomic groups, ranging from members of other species groups to members of several subgroups and members of three species complexes from the mulleri subgroup are found in poorly supported arrangements at the base of the tree.

Isolation and identification of actin-binding proteins in Plasmodium falciparum by affinity chromatography

The invasion of the erythrocyte by Plasmodium falciparum depends on the ability of the merozoite to move through the membrane invagination. This ability is probably mediated by actin dependent motors. Using affinity columns with G-actin and F-actin we isolated actin binding proteins from the parasite. By immunoblotting and immunoprecipitation with specific antibodies we identified the presence of tropomyosin, myosin, a-actinin, and two different actins in the eluate corresponding to F-actin binding proteins. In addition to these, a 240-260 kDa doublet, different in size from the erythrocyte spectrin, reacted with an antibody against human spectrin. All the above mentioned proteins were metabolically radiolabeled when the parasite was cultured with 35S-methionine. The presence of these proteins in P. falciparum is indicative of a complex cytoskeleton and supports the proposed role for an actin-myosin motor during invasion.

Changes in bone mineral density after discontinuation and early reinstitution of growth hormone (GH) in patients with childhood-onset GH deficiency

We measured bone mass density (BMD) in 28 childhood-onset adult GHD patients (20 MPHD, 8 IGHD) treated with hGH until final height. Twelve were re-treated with hGH (0.06 U/kg/day three times per week) for 16-24 months and eight of them followed for up to 5 years. Age at start of the study was 23.6 +/- 5.7 years (mean +/- SD) and the interval since the first hGH treatment was 5.8 +/- 4.4 years Baseline BMD was 82% of young normal healthy subjects. Patients < 20 years had a lower BMD than those > 20 years (75 vs 87%;P = 0.004). In the 12 patients re-treated with GH, BMD was 5.3% above baseline at 6 months after treatment was stopped (P< 0.002), and remained so for 3.5 years in eight patients who completed follow-up. In conclusion, increases in BMD occur after cessation of growth, but continuation of hGH treatment after final height achievement may prevent the late osteopenia of patients with childhood-onset GHD.

Increase of a calcium independent transglutaminase activity in the erythrocyte during the infection with Plasmodium falciparum

We have studied the activity of a calcium dependent transglutaminase (EC 2.3.2.13) during the growth of the parasite Plasmodium falciparum inside the infected human erythrocyte. There is only one detectable transglutaminase in the two-cell-system, and its origin is erythrocytic. No activity was detected in preparations of the parasite devoid of erythrocyte cytoplasm. The Michaelis Menten constants (Km) of the enzyme for the substrates N'N' dimethylcaseine and putrescine were undistinguishable whether the cell extracts used in their determination were obtained from normal or from infected red cells. The total activity of transglutaminase in stringently synchronized cultures, measured at 0.5 mM Ca2+, decreased with the maturation of the parasite. However, a fraction which became irreversibly activated and independent of calcium concentration was detected. The proportion of this fraction grew with maturation; it represented only 20% of the activity in 20 hr-old-trophozoites while in 48-hr-schizonts it was more than 85% of the total activity. The activation of this fraction of transglutaminase did not depend on an increase in the erythrocyte cytoplasmic calcium, since most of the calcium was shown to be located in the parasite.

Production of IL-5 and granulocyte-macrophage colony-stimulating factor by naive human mast cells activated by high-affinity IgE receptor ligation

BACKGROUND

The late-phase allergic reaction is an eosinophilic inflammatory response that begins several hours after allergen exposure, may persist for 24 hours, and is an important pathogenic mechanism in allergic disease.

OBJECTIVE

Cultured naive human mast cells were used to investigate whether mast cells are a direct source of the eosinophil-promoting cytokines IL-5, IL-3, and granulocyte-macrophage colony-stimulating factor (GM-CSF).

METHODS

Naive human mast cells were derived from bone marrow mononuclear cells cultured in the presence of stem-cell factor. Cytokine message and protein production in response to high-affinity IgE receptor ligation of cultured mast cells were measured by semiquantitative polymerase chain reaction and ELISA, respectively.

RESULTS

IL-5, IL-3, and GM-CSF messenger RNA increased within 2 hours of mast cell activation, with IL-5 and GM-CSF message remaining elevated for 24 hours, whereas IL-3 mRNA rapidly declined. IL-5 and GM-CSF protein were measurable 4 to 6 hours after stimulation and peaked by 24 and 12 hours, respectively. IL-3 protein was not detectable.

CONCLUSION

These findings demonstrate that naive mast cells do not constitutively produce IL-5 or GM-CSF protein but are a major source of these eosinophilotropic cytokines on high-affinity IgE receptor ligation.

Two types of growth hormone rhythm in boys with constitutional short stature

The relationship between temporal and quantitative changes in pulsatile growth hormone (GH) secretion and growth of constitutionally short children (CSS) was studied in 19 prepubertal boys and 4 with early adrenarche aged 7.8 to 14 years. Continuous plasma GH monitoring was performed at 30 minutes intervals during 24 hours. The data were analysed by single and serial best fit (BFT) cosinor analysis for rhythm parameters and the Pulsar peak detection program for determining pulsatile properties. The pulsatile patterns were expressed in mean GH concentration, area under the curve, mean pulse area and maximal pulse height but not in the number of pulses. Thirteen out of 23 patterns exhibited significant 24-h compatible rhythms. The studied cohort was divided into two groups, those who exhibited the 24-h circadian rhythm (CIR) and those who lacked it (NCIR). Ultradian 2.5-4 h rhythms were observed in all patients. The NCIR children were significantly shorter than the CIR group (p = 0.017). The CIR boys secreted a significantly higher (p = 0.01) amount of GH during the 24-h span, most of which was during sleep. Our data indicate that the magnitude of pulses rather than their number is responsible for the quantitative differences observed between the two groups of boys with CSS. It is suggested that a lack of 24-h rhythmicity and the associated reduced nocturnal pulsatility play a role in the manifestation of short stature.

Detection of Genomic Polymorphism in Plasmodium falciparum using an arbitrarily primed PCR assay

Modifications of the arbitrarily primed polymerase chain reaction assay (i.e. a low annealing temperature and a very slow increase in the temperature during the elongation steps during the amplification cycles) allowed it to be used with the AT-rich Plasmodium falciparum DNA. The analysis of the products by polyacrylamide-urea gels, after silver staining, resulted in high resolution and sensitivity. Eighteen single and six combined pairs of arbitrary primers were tested. Two produced polymorphic patterns complex enough to differentiate between close Colombian isolates in a single assay. This method may be useful in studying the distribution and migration of strains in endemic areas, and for identifying intralaboratory cross-contamination of cultures.

Intraerythrocytic calcium chelators inhibit the invasion of Plasmodium falciparum

Calcium is an important factor in the invasion of the erythrocyte by Plasmodium falciparum. We have proposed that the entrance of the cation into the erythrocyte might be a messenger that triggers a series of molecular events leading to invasion. Other authors have proposed that the site of action of the calcium is extracellular. We show herein that the invasion is inhibited by intracellular calcium chelators and that the inhibition depends on the intracellular concentration of the chelators and on the calcium concentration in the medium.