TcGPXII, a glutathione-dependent Trypanosoma cruzi peroxidase with substrate specificity restricted to fatty acid and phospholipid hydroperoxides, is localized to the endoplasmic reticulum

Until recently, it had been thought that trypanosomes lack glutathione peroxidase activity. Here we report the subcellular localization and biochemical properties of a second glutathione-dependent peroxidase from Trypanosoma cruzi (TcGPXII). TcGPXII is a single-copy gene which encodes a 16 kDa protein that appears to be specifically dependent on glutathione as the source of reducing equivalents. Recombinant TcGPXII was purified and shown to have peroxidase activity towards a narrow substrate range, restricted to hydroperoxides of fatty acids and phospholipids. Analysis of the pathway revealed that TcGPXII activity could be readily saturated by glutathione and that the peroxidase functioned by a Ping Pong mechanism. Enzyme reduction was shown to be the rate-limiting step in this pathway. Using immunofluorescence, TcGPXII was shown to co-localize with a homologue of immunoglobulin heavy-chain binding protein (BiP), a protein restricted to the endoplasmic reticulum and Golgi. As the smooth endoplasmic reticulum is the site of phospholipid and fatty acid biosynthesis, this suggests that TcGPXII may play a specific role in the T. cruzi oxidative defence system by protecting newly synthesized lipids from peroxidation.

The Trypanosoma cruzi enzyme TcGPXI is a glycosomal peroxidase and can be linked to trypanothione reduction by glutathione or tryparedoxin

Trypanosoma cruzi glutathione-dependent peroxidase I (TcGPXI) can reduce fatty acid, phospholipid, and short chain organic hydroperoxides utilizing a novel redox cycle in which enzyme activity is linked to the reduction of trypanothione, a parasite-specific thiol, by glutathione. Here we show that TcGPXI activity can also be linked to trypanothione reduction by an alternative pathway involving the thioredoxin-like protein tryparedoxin. The presence of this new pathway was first detected using dialyzed soluble fractions of parasite extract. Tryparedoxin was identified as the intermediate molecule following purification, sequence analysis, antibody studies, and reconstitution of the redox cycle in vitro. The system can be readily saturated by trypanothione, the rate-limiting step being the interaction of trypanothione with the tryparedoxin. Both tryparedoxin and TcGPXI operate by a ping-pong mechanism. Overexpression of TcGPXI in transfected parasites confers increased resistance to exogenous hydroperoxides. TcGPXI contains a carboxyl-terminal tripeptide (ARI) that could act as a targeting signal for the glycosome, a kinetoplastid-specific organelle. Using immunofluorescence, tagged fluorescent proteins, and biochemical fractionation, we have demonstrated that TcGPXI is localized to both the glycosome and the cytosol. The ability of TcGPXI to use alternative electron donors may reflect their availability at the corresponding subcellular sites.

Paraoxonase polymorphisms, pesticide exposure and Parkinson's disease in a Caucasian population

Parkinson's disease (PD) has been associated with exposure to pesticides and oxidative injury. The involvement of paraoxonase in both pesticide metabolism and lipid peroxidation suggests that it may play a role in the pathogenesis of PD. We examined the frequency of polymorphic alleles of the PON1 and PON2 genes in a sample of caucasian subjects with PD. The frequency distribution of these genotypes did not differ significantly between patients and controls, including those who had reported exposure to pesticides.

Depressive symptoms and outcome of coronary artery bypass grafting

BACKGROUND

Depressive symptoms are an independent risk factor for outcome in patients with cardiac disease, but their effect on outcome among patients undergoing coronary artery bypass grafting is not well understood.

OBJECTIVES

To determine whether or not clinical variables including length of stay, readmission rates, and mortality are related to patients' level of depressive symptoms before and after coronary artery bypass grafting.

METHODS

An observational, longitudinal design was used. The Medical Outcomes Study 36-item short-form health survey was used to collect data on depressive symptoms in 416 patients undergoing coronary artery bypass grafting. The distribution of depressive symptoms was correlated with length of stay after the procedure, readmission, and mortality.

RESULTS

The level of depressive symptoms before coronary artery bypass grafting correlated with the level of depressive symptoms at 6 weeks follow-up, both for the individual items "feeling down in the dumps" (r = 0.24, P = .009) and "feeling downhearted" (r = 0.36, P < .001) and for the overall score on the Mental Health scale (r = 0.40, P < .001). Feeling down in the dumps (P = .007) and overall scores on the Mental Health scale (P = .02) were significantly related to readmission within 6 months.

CONCLUSIONS

Higher levels of depressive symptoms before coronary artery bypass grafting are related to higher hospital readmission rates 6 months after the procedure. Nurses can play a pivotal role in determining which patients require evaluation, educating patients, and initiating effective treatment, which may prevent readmission related to depressive symptoms.

Depressive symptoms and outcome of coronary artery bypass grafting

BACKGROUND: Depressive symptoms are an independent risk factor for outcome in patients with cardiac disease, but their effect on outcome among patients undergoing coronary artery bypass grafting is not well understood. OBJECTIVES: To determine whether or not clinical variables including length of stay, readmission rates, and mortality are related to patients' level of depressive symptoms before and after coronary artery bypass grafting. METHODS: An observational, longitudinal design was used. The Medical Outcomes Study 36-item short-form health survey was used to collect data on depressive symptoms in 416 patients undergoing coronary artery bypass grafting. The distribution of depressive symptoms was correlated with length of stay after the procedure, readmission, and mortality. RESULTS: The level of depressive symptoms before coronary artery bypass grafting correlated with the level of depressive symptoms at 6 weeks follow-up, both for the individual items "feeling down in the dumps" (r = 0.24, P = .009) and "feeling downhearted" (r = 0.36, P &lt; .001) and for the overall score on the Mental Health scale (r = 0.40, P &lt; .001). Feeling down in the dumps (P = .007) and overall scores on the Mental Health scale (P = .02) were significantly related to readmission within 6 months. CONCLUSIONS: Higher levels of depressive symptoms before coronary artery bypass grafting are related to higher hospital readmission rates 6 months after the procedure. Nurses can play a pivotal role in determining which patients require evaluation, educating patients, and initiating effective treatment, which may prevent readmission related to depressive symptoms.

Influence of a specialized leg ulcer service on management and outcome

BACKGROUND

The organization of leg ulcer care is poorly defined in the community. This study assessed the overall influence of a specialized community service on management and outcome of chronic leg ulcers, irrespective of aetiology.

METHODS

Assessment and outcome of ulcers were compared in patient samples (n = 200) from East and West Gloucestershire, before and after the introduction of specialized clinics into East Gloucestershire. In clinics, vascular disease was routinely assessed by duplex scanning and determination of the ankle : brachial pressure index.

RESULTS

There was no coordinated community structure for the care of patients with leg ulcers before the service was introduced, and 74 and 67 per cent of limbs in East and West Gloucestershire respectively had aetiology undiagnosed. After introduction of the clinics, the 12-week healing rate increased from 12 to 22 per cent in East Gloucestershire (P = 0. 05) and to 47 per cent in the specialized East Gloucestershire clinics (P < 0.001). The 12-month recurrence rate decreased from 50 to 41 per cent in East Gloucestershire and to 17 per cent in the East clinics (P < 0.001). The West Gloucestershire control showed no significant changes.

CONCLUSION

A specialized leg ulcer service with defined protocols provides an improved management structure for treating patients with leg ulcers in the community. Accurate diagnosis of chronic leg ulcers and improved outcome may be achieved within this specialized service.

Guanylyl cyclase activity associated with putative bifunctional integral membrane proteins in Plasmodium falciparum

We report here that guanylyl cyclase activity is associated with two large integral membrane proteins (PfGCalpha and PfGCbeta) in the human malaria parasite Plasmodium falciparum. Unusually, the proteins appear to be bifunctional; their amino-terminal regions have strong similarity with P-type ATPases, and the sequence and structure of the carboxyl-terminal regions conform to that of G protein-dependent adenylyl cyclases, with two sets of six transmembrane sequences, each followed by a catalytic domain (C1 and C2). However, amino acids that are enzymatically important and present in the C2 domain of mammalian adenylyl cyclases are located in the C1 domain of the P. falciparum proteins and vice versa. In addition, certain key residues in these domains are more characteristic of guanylyl cyclases. Consistent with this, guanylyl cyclase activity was obtained following expression of the catalytic domains of PfGCbeta in Escherichia coli. In P. falciparum, expression of both genes was detectable in the sexual but not the asexual blood stages of the life cycle, and PfGCalpha was localized to the parasite/parasitophorous vacuole membrane region of gametocytes. The profound structural differences identified between mammalian and parasite guanylyl cyclases suggest that aspects of this signaling pathway may be mechanistically distinct.

Biliary stenting versus bypass surgery for the palliation of malignant distal bile duct obstruction: a meta-analysis

The objective of this analysis is to compare endoscopic stenting with surgical bypass in patients with unresectable, malignant, distal common bile duct obstruction using the technique of meta-analysis. The inclusion criteria for the studies were randomized patient assignment, publication in the English language, 20 or more patients per group, all patients followed up until death, and follow-up and complications reported in an equivalent way for both treatment arms. Data extraction was performed independently by 2 of the authors. The number of treatment failures, serious complications, requirement for additional treatment sessions, and 30-day mortality were extracted. Three existing trials met the inclusion criteria, all of which compared surgery with the use of plastic stents. There were no studies identified that used metallic expandable stents. For the rate of treatment failure and serious complications, the odds ratios (ORs) of the 3 trials were heterogeneous, and no summary ORs were calculated. More treatment sessions were required after stent placement than after surgery, and a common OR was estimated to be 7.23 (95% confidence interval [CI], 3.73 to 13.98). Thirty-day mortality was not significantly different (OR = 0.522; 95% CI, 0.263 to 1.036). Although surgical bypass required fewer additional treatment sessions, existing data do not allow a definitive conclusion on which treatment is preferable. A larger randomized controlled trial using newer metallic stents and proper quality-of-life instruments is required.

Trypanosoma cruzi adenylyl cyclase is encoded by a complex multigene family

The parasitic protozoan Trypanosoma cruzi undergoes several differentiation events during its life cycle. Some of these transitions are thought to involve activation of adenylyl cyclase via the binding of peptide ligands to the cell surface. Here we describe the characterisation of the adenylyl cyclase gene family of T. cruzi. Two complete genes and one pseudogene have been sequenced. The protein products appear to have a large extracellular domain, a single transmembrane helix and a cytosolic catalytic domain. The adenylyl cyclase genes are present on at least six chromosomes and are scattered rather than clustered. They form a large polymorphic family in which the extracellular domain is particularly variable. An Escherichia coli adenylyl cyclase mutant could be complemented by expression of the catalytic domain of the T. cruzi enzyme. The recombinant protein had adenylyl cyclase activity in vitro, which was enhanced by increasing concentrations of divalent cations (Mn2+ > Mg2+). This constitutively active recombinant protein will be a useful tool for dissecting the catalytic mechanism of adenylyl cyclase.

Heart Center nursing research: a team effort. Heart Center Nursing Research Work Group Members

Our Heart Center staff identified a need to become more involved in nursing research and evidence based practice. A lack of awareness of the research process and current Heart Center nursing research studies resulted in low patient enrollment. To overcome these challenges a Heart Center Nursing Research Work Group (HCNRWG) was created with support of management. Staff nurses from each unit within the Heart Center participated, and sessions were facilitated by an Assistant Nurse Manager and Clinical Nurse Specialist. Advanced Practice Nurses functioned as consultants. The goal was to support nurses in developing a greater understanding of research and promote nursing research and visibility. Results included the development of research notebooks, inclusive of medical, nursing, and collaborative research projects, "Ask Me About Nursing Research" buttons, and mechanisms for study enrollment for each unit. Writing workshops were held to assist nurses with the preparation of abstracts, manuscripts, and research. A "hot line" was established to answer questions and informational packets and newsletters were distributed to staff and leadership quarterly. An increased awareness of research among the health care team has ensued. Meeting attendance has tripled, more nursing abstracts have been submitted to national conferences and there are ongoing research studies on all heart center units with increased patient enrollment.

Optimization of conditions for growth of wild-type and genetically transformed Trypanosoma cruzi on agarose plates

Growth of Trypanosoma cruzi as colonies on solid medium has not been widely used as an experimental procedure. We therefore sought to establish a reliable and routine plating method. The optimal results were achieved with a matrix of 0.65% low melting point agarose onto which epimasigotes from the mid-to-late logarithmic phase of growth were spread. Colonies could be isolated after incubation for 21 days in a humidified 5% CO2 environment at 28 degrees C. Plating efficiencies in the range of 40% were obtained by this method and clones could be recovered into liquid medium or onto blood-agar slopes with a high success rate. The procedure has also been adapted for the isolation of genetically transformed clones after electroporation of epimastigotes with either plasmid or cosmid vectors. This was best achieved by inclusion of the electroporated cell inoculum in a 0.6% agarose overlay containing G418 as the selective drug, on top of a 0.8% agar base. Transformation efficiencies were as high as 10(-5) cells per microgram of DNA. A reliable plating method for T. cruzi will have many applications and is a significant step towards the use of 'shotgun transformation' to generate libraries of T. cruzi recombinants.

Pesticides and Parkinson's disease

Epidemiological studies and case reports provide evidence for an association between Parkinson's disease and past exposure to pesticides. Susceptibility to the effects of pesticides and other putative neurotoxins depends on variability in xenobiotic metabolism possibly generated by genetic polymorphisms, aging and variation in exposure to environmental agents including pesticides. The simplest mechanistic hypothesis for the association of pesticides with Parkinson's disease is that pesticides or their metabolites are directly toxic to mitochondria, although modulation of xenobiotic metabolism by pesticides provides an adjunct or alternative hypothesis.

Holmium: YAG lasertripsy for ureteric calculi: an experience of 300 procedures

OBJECTIVE

To assess the success of holmium:YAG lasertripsy in the management of ureteric calculi and to audit the complications of the procedure, with special reference to strictures in the ureter.

PATIENTS AND METHODS

A total of 300 ureteroscopic laser procedures were carried out on 265 patients (204 male and 61 female, median age 51 years, range 2-95) with ureteric calculi. At ureteroscopy, the calculi were present in the upper ureter in 44%, mid-ureter in 37% and lower ureter in 19% of patients; most calculi were > 5 mm. A 7.5 F Wolf semi-rigid ureteroscope was used and the holmium:YAG laser energy delivered using the Sharplan ML210 device at 0.8-1.0 J/pulse. The patients were followed up at approximately 6 weeks with limited intravenous urography or ultrasonography to assess clearance and the incidence of strictures.

RESULTS

Stones were completely cleared in 90% of the patients, with the best results in the lower and mid-ureter (97% and 96%, respectively) followed by the upper ureter (89%). Alternative procedures were required in only 17 (7%) patients; extracorporeal shock-wave lithotripsy in 13, percutaneous nephrolithotomy in two and open pyelolithotomy in two patients. Complications with ureteric perforation in 11 patients, including laparotomy for peritonitis in one, serious sepsis in two and strictures in 10 patients. Strictures were more common in association with impacted calculi in the upper ureter early in the series.

CONCLUSIONS

Holmium:YAG lasertripsy is a highly effective treatment for ureteric calculi, with strictures related to the treatment of difficult upper ureteric calculi.

Enhanced expression of cytochrome P450 in stomach cancer

The cytochromes P450 have a central role in the oxidative activation and detoxification of a wide range of xenobiotics, including many carcinogens and several anti-cancer drugs. Thus the cytochrome P450 enzyme system has important roles in both tumour development and influencing the response of tumours to chemotherapy. Stomach cancer is one of the commonest tumours of the alimentary tract and environmental factors, including dietary factors, have been implicated in the development of this tumour. This type of tumour has a poor prognosis and responds poorly to current therapies. In this study, the presence and cellular localization of several major forms of P450, CYP1A, CYP2E1 and CYP3A have been investigated in stomach cancer and compared with their expression in normal stomach. There was enhanced expression of CYP1A and CYP3A in stomach cancer with CYP1A present in 51% and CYP3A present in 28% of cases. In contrast, no P450 was identified in normal stomach. The presence of CYP1A and CYP3A in stomach cancer provides further evidence for the enhanced expression of specific forms of cytochrome P450 in tumours and may be important therapeutically for the development of anti-cancer drugs that are activated by these forms of P450.

beta-D-glucosyl-hydroxymethyluracil is a conserved DNA modification in kinetoplastid protozoans and is abundant in their telomeres

The unusual DNA base beta-D-glucosyl-hydroxymethyluracil, called "J, " replaces approximately 0.5-1% of Thy in DNA of African trypanosomes but has not been found in other organisms thus far. In Trypanosoma brucei, J is located predominantly in repetitive DNA, and its presence correlates with the silencing of telomeric genes. Using antibodies specific for J, we have developed sensitive assays to screen for J in a range of organisms and have found that J is not limited to trypanosomes that undergo antigenic variation but is conserved among Kinetoplastida. In all kinetoplastids tested, including the human pathogens Leishmania donovani and Trypanosoma cruzi, J was found to be abundantly present in the (GGGTTA)n telomere repeats. Outside Kinetoplastida, J was found only in Diplonema, a small phagotrophic marine flagellate, in which we also identified 5-MeCyt. Fractionation of Diplonema DNA showed that the two modifications are present in a common genome compartment, which suggests that they may have a similar function. Dinoflagellates appear to contain small amounts of modified bases that may be analogs of J. The evolutionary conservation of J in kinetoplastid protozoans suggests that it has a general function, repression of transcription or recombination, or a combination of both. T. brucei may have recruited J for the control of genes involved in antigenic variation.

Frequent loss of the active site during variant surface glycoprotein expression site switching in vitro in Trypanosoma brucei

African trypanosomes undergo antigenic variation of their variant surface glycoprotein (VSG) coat to avoid being killed by their mammalian hosts. The active VSG gene is located in one of many telomeric expression sites. Replacement of the VSG gene in the active site or switching between expression sites can give rise to a new VSG coat. To study Trypanosoma brucei VSG expression site inactivation rather than VSG gene switching, it is useful to have an in vitro negative-selection system independent of the VSG. We have achieved this aim by using a viral thymidine kinase (TK) gene. Following integration of the TK gene downstream of the 221a VSG expression site promoter, transformant cell lines became sensitive to the nucleoside analog 1-(2-deoxy-2-fluoro-8-D-arabinofuranosyl)-5-iodouracil. These TK trypanosomes were able to revert to resistance at a rate approaching 10(-5) per cell per generation. The majority of revertants expressed a new VSG gene even though there had been no selection against the VSG itself. Analysis of these switched variants showed that some had shut down TK expression via an in situ expression site switch. However, most variants had the complete 221 expression site deleted and another VSG expression site activated. We speculate that a new VSG expression site cannot switch on without inactivation of the old site.

Patient preference for self-collected cultures for group B streptococcus in pregnancy

To determine pregnant women's preference for self-culture technique, 251 women between 24 and 42 weeks' gestation were interviewed after performing self-collected cultures (vaginal and rectal) for group B streptococcus. Patient receptiveness to self-culture, the ability to perform self-culture, and the desire for choice in the future were derived using the Patient Preference Tool. The majority of women (77%, n = 194) gave positive descriptions of self-culture technique, and the majority of women preferred self-culture technique over nurse-collected sampling (57%, n = 142). Seventy-nine percent (n = 197) stated their desire to have a choice about self-culture in the future when similar testing was needed, and 89% (n = 224) believed that other women would also like this choice. Additionally, patient samples were highly correlated with nurse-collected samples for accuracy of culture results. This study provides data supporting that women desire active participation in their care.

Tumor-specific expression of cytochrome P450 CYP1B1

Cytochrome P450 CYP1B1 is a recently cloned dioxin-inducible form of the cytochrome P450 family of xenobiotic metabolizing enzymes. An antibody raised against a peptide specific for CYP1B1 was found to recognize CYP1B1 expressed in human lymphoblastoid cells but not to recognize other forms of cytochrome P450, particularly CYP1A1 and CYP1A2. Using this antibody, the cellular distribution and localization of CYP1B1 were investigated by immunohistochemistry in a range of malignant tumors and corresponding normal tissues. CYP1B1 was found to be expressed at a high frequency in a wide range of human cancers of different histogenetic types, including cancers of the breast, colon, lung, esophagus, skin, lymph node, brain, and testis. There was no detectable immunostaining for CYP1B1 in normal tissues. These results provide the basis for the development of novel methods of cancer diagnosis based on the identification of CYP1B1 in tumor cells and the development of anticancer drugs that are selectively activated in tumors by CYP1B1.

Urinary growth hormone following exercise to assess growth hormone production in adults

OBJECTIVE

The insulin stress test (IST) is the most commonly used test to assess the GH reserve in children and adults. It is a time-consuming, expensive and potentially dangerous test. We investigated whether measurement of urinary growth hormone excretion following exercise would prove on reliable method to diagnose adult GH deficiency.

DESIGN

Healthy volunteers underwent a standard IST to confirm GH secretion. Using a standardized exercise protocol on a treadmill, the urinary excretion of GH was measured. Three patients confirmed as GH deficient by an IST were exercised during the same exercise protocol and their urinary excretion of GH was measured.

PATIENTS

Ten healthy volunteers and three patients with hypopituitarism were evaluated.

MEASUREMENTS

A standard IST was performed on both healthy volunteers and patients, with measurements of plasma GH and plasma cortisol. Urinary growth hormone and urinary GH/creatinine (GH/CR) ratios were measured before and after IST. On a separate visit, healthy volunteers and patients were exercised on the treadmill with measurements of plasma GH and cortisol. Urinary GH and GH/CR ratios were measured before and after exercise.

RESULTS

There was at least a two-fold increase in urinary GH and GH/CR ratios following exercise in all healthy adults. By contrast, patients with GH deficiency showed no rise in urinary GH or urinary GH/CR ratios following exercise.

CONCLUSIONS

Measurements of urinary GH following exercise can distinguish between GH-deficient adults and healthy volunteers. Urinary GH excretion can be measured over a timed interval following exercise or can be expressed as the GH/CR ratio. This can be measured on a single sample following exercise and can be used to diagnose GH deficiency. The exercise test employed for this study is arduous. We are therefore performing further studies with a less strenuous exercise protocol with a view to designing a 'patient-friendly' exercise test for GH deficiency in adults.

The viral thymidine kinase gene as a tool for the study of mutagenesis in Trypanosoma brucei

We have tested the use of thymidine kinase as a negative selection system for Trypanosoma brucei. To this end we have targeted a construct containing a Herpes simplex virus thymidine kinase (TK) gene into the ribosomal DNA array of procyclic T. brucei. This resulted in TK activity 30-50-fold above background and in susceptibility to the nucleoside analogues ganciclovir, ethyl-deoxyuridine and 1-[2-deoxy,2-fluoro-8-D-arabinofuranosyl]-5-iodouracil, all of which have no effect on wild-type trypanosomes. TK+ trypanosomes, however, reverted to a ganciclovir resistant phenotype at a rate of 10(-6) per cell-generation. A similar reversion rate was observed using the Varicella-zoster virus TK gene. Loss of TK activity was not due to detectable DNA rearrangements or a decrease in TK mRNA. Sequence analysis of the revertant genes demonstrated, however, the occurrence of point mutations and frameshifts. One revertant line had a mutation in the thymidine binding site leading to the substitution of a conserved arginine by a glycine. Other mutations included single base insertion, single base deletion and the introduction of a premature termination codon by point mutation.

The accuracy and patient preference for self-collected group B Streptococcus cultures

OBJECTIVE

Our purpose was to determine the accuracy of and patient attitudes regarding self-collected group B Streptococcus cultures.

STUDY DESIGN

Women seen for prenatal care at 24 to 42 weeks' gestation were asked to collect distal vaginal and anal samples for group B Streptococcus. Subsequently, distal vaginal and anal samples were obtained by the nurse. The patients were then asked their preference toward self-sampling.

RESULTS

A total of 251 women participated in the study. The incidence of positive group B Streptococcus cultures was 12.7%, 9.6%, 10.0%, and 7.6% for the patient-collected vaginal and anal and nurse-collected vaginal and anal specimens, respectively. The incidence of group B Streptococcus carriage was 17.5% and 13.5% for any positive patient- or provider-collected specimens, respectively, and 19.1% for any positive culture. Single patient-collected vaginal and anal and nurse-collected vaginal and anal samples were insensitive for group B Streptococcus carriage (67%, 50%, 52%, 40%, respectively). The combination of patient-collected samples was more sensitive than nurse-collected samples (sensitivity 91.7% vs 70.8%, p < 0.05). Repeat sampling of the vagina or anal canal did not offer significant additional benefit to a single culture. Overall, patient-collected samples were 98.4% accurate in predicting group B Streptococcus carriage versus 94.4% for nurses. A total of 58% of women preferred obtaining their own specimens, whereas 9.6% found the technique difficult. Ninety percent desired the option of self-sampling in the future.

CONCLUSIONS

Single vaginal or anal cultures were insensitive in detecting group B Streptococcus carriage. Combined patient-collected cultures were more sensitive than provider-collected specimens. On the basis of accuracy and patient preference, women should be given the opportunity of combined vaginal-anal self-sampling for group B Streptococcus when indicated.

VSG gene expression site control in insect form Trypanosoma brucei

When the African trypanosome Trypanosoma brucei is taken up from mammals by a tse-tse fly, it replaces its variant surface glycoprotein (VSG) coat by a procyclin coat. Transcription of VSG genes stops in the fly, but transcription of sequences derived from the promoter area of the VSG expression site(s) remains high. Whether this is due to continuing high activity of one promoter or to low activity of many promoters was unclear. We have used the small differences between the sequences of different expression sites to show that multiple expression site promoters are active in insect form trypanosomes. This is confirmed by the low expression of single copy marker genes introduced into the transcribed area. However, if the expression site promoter is removed from the genomic location of the expression site and inserted in the non-transcribed spacer of the ribosomal DNA (rDNA), it is derepressed. Derepression of transcription can also be accomplished by replacing the promoter of an expression site by an rDNA promoter. We conclude that the down-regulation of VSG gene expression site promoters in insect form trypanosomes is affected by both the DNA sequence of the promoter and the genomic context in which it resides.