Can we predict recurrence of pre-eclampsia or gestational hypertension?

OBJECTIVE

To estimate the rates of recurrence of pre-eclampsia or gestational hypertension in a subsequent pregnancy and to determine factors predictive of recurrence.

DESIGN

Retrospective cohort study.

SETTING

St George Public and Private Hospitals, teaching hospitals without neonatal intensive care units.

PARTICIPANTS

A total of 1515 women with a diagnosis of pre-eclampsia or gestational hypertension between 1988 and 1998 were identified from the St George Hypertension in Pregnancy database, a system designed initially for ensuring quality outcomes of hypertensive pregnancies. Of these, 1354 women were followed up, and a further 333 records from women coded as having a normal pregnancy during that period were selected randomly as controls.

MAIN OUTCOME MEASURES

Likelihood of recurrent pre-eclampsia or gestational hypertension and clinical and routine laboratory factors in the index pregnancy predictive of recurrence of pre-eclampsia or gestational hypertension.

METHODS

The index cases from our unit's database were linked to the matched pregnancy on the State Department of Health database, allowing us to determine whether further pregnancies had occurred at any hospital in the State. The outcome of these pregnancies was determined by review of medical records, using strict criteria for diagnosis of pre-eclampsia or gestational hypertension.

RESULTS

Almost all women with a normal index pregnancy had a further normotensive pregnancy. One in 50 women hypertensive in their index pregnancy had developed essential hypertension by the time of their next pregnancy. Women with pre-eclampsia in their index pregnancy were equally likely to develop either pre-eclampsia or gestational hypertension (approximately 14% each), while women with gestational hypertension were more likely to develop gestational hypertension (26%) rather than pre-eclampsia (6%) in their next pregnancy. Multiparous women with gestational hypertension were more likely than primiparous women to develop pre-eclampsia (11 versus 4%) or gestational hypertension (45 versus 22%) in their next pregnancy. Early gestation at diagnosis in the index pregnancy, multiparity, uric acid levels in the index pregnancy and booking blood pressure parameters in the next pregnancy significantly influenced the likelihood of recurrence, predominantly for gestational hypertension and less so for pre-eclampsia. No value for these parameters was significant enough to be clinically useful as a discriminate value predictive of recurrent pre-eclampsia or gestational hypertension.

CONCLUSIONS

Approximately 70% of women with pre-eclampsia or gestational hypertension will have a normotensive next pregnancy. The highest risk group for recurrent hypertension in pregnancy in this study was multiparous women with gestational hypertension. No readily available clinical or laboratory factor in the index pregnancy reliably predicts recurrence of pre-eclampsia.

Trends in infections in children with malignant disease in 2000: comparison of data of 1980/81

Children with cancer have an overall chance of survival of 70-80%. Despite significant advances in supportive care during the last years, infections remain a major cause of therapy-associated morbidity and death. Between January and December 2000, oncology patients (ONC) treated on a pediatric oncology ward after chemotherapy (n = 109), loco-regional thermochemotherapy (n = 13), or hematopoietic stem cell (HSCT) transplantation (n = 35) suffered a total of 249 febrile infectious complications (HSCT 40/ONC 209). These episodes were analyzed retrospectively and compared with 125 ONC patients with 133 febrile infections in 1980/81. The relative incidence of fever of unknown origin (FUO) decreased from 1980/81 to 2000 (p <.001). The frequency of bloodstream infections (BSI) in febrile episodes was comparable in both periods with 37% (50/135) in 1980 and 29% (72/249) in 2000. In both periods, gram-positive bacteria were the most frequent organisms, whereas gram-negative organisms were detected in approximately 20% of BSI. In 1980/81 microbiologically (MDI) or clinically documented infections (CDI) were not detected, whereas in 2000 27% of all infectious were MDI/CDI. During the last 20 years, improved diagnostic tools have resulted in an increased detection rate of infectious agents causing febrile episodes in pediatric cancer patients. The comparison of the two observation periods did not reveal a change in the microbiologic spectrum. Despite the fact that in 2000 more patients were treated with intensified chemotherapy because of relapse, infection-related mortality was unchanged compared to 1980/81. This observation may indicate a sufficient preemptive antibacterial therapy followed by better diagnostic tools and goal-oriented treatment.

Evolution of sensory complexity recorded in a myxobacterial genome

Myxobacteria are single-celled, but social, eubacterial predators. Upon starvation they build multicellular fruiting bodies using a developmental program that progressively changes the pattern of cell movement and the repertoire of genes expressed. Development terminates with spore differentiation and is coordinated by both diffusible and cell-bound signals. The growth and development of Myxococcus xanthus is regulated by the integration of multiple signals from outside the cells with physiological signals from within. A collection of M. xanthus cells behaves, in many respects, like a multicellular organism. For these reasons M. xanthus offers unparalleled access to a regulatory network that controls development and that organizes cell movement on surfaces. The genome of M. xanthus is large (9.14 Mb), considerably larger than the other sequenced delta-proteobacteria. We suggest that gene duplication and divergence were major contributors to genomic expansion from its progenitor. More than 1,500 duplications specific to the myxobacterial lineage were identified, representing >15% of the total genes. Genes were not duplicated at random; rather, genes for cell-cell signaling, small molecule sensing, and integrative transcription control were amplified selectively. Families of genes encoding the production of secondary metabolites are overrepresented in the genome but may have been received by horizontal gene transfer and are likely to be important for predation.

Hyper-Rayleigh scattering as a means of monitoring crystal nucleation in solution

Hyper-Rayleigh scattering is revealed as a very sensitive monitor of cluster formation in solution, and as a means of studying the mechanism of crystal nucleation in molecular species. Two compounds are selected with particularly high second harmonic generation (SHG) powers in the crystalline state and experimental conditions are defined allowing the measurement of the beta value for one of these as 18+/-1x10(-30) esu. It is found to agree with current theoretical prediction of 20x10(-30) esu. In the more powerful of these, two photon induced fluorescence is found to be partly responsible for the SHG. The solubilities of both compounds in methanol are measured and it is observed that these differ by a factor of ten. When the solution concentration is increased beyond 45% of the saturation value, the quadratic coefficient exhibits non-linear behaviour with respect to concentration. Additionally, the widths of the distributions of the HRS signals increase initially with concentration as expected, but, beyond 45% saturation concentrations, these narrow again. These phenomena are interpreted as indicators of cluster formation in these solutions well below saturation concentrations. A future experimental design is proposed in which the coherent component will yield information on the organisation of the molecules in such clusters.

Adaptation of Pseudomonas fluorescens to Al-Citrate: Involvement of Tricarboxylic Acid and Glyoxylate Cycle Enzymes and the Influence of Phosphate

The degradation of Aluminum-citrate by Pseudomonas fluorescens necessitated a major restructuring of the various enzymatic activities involved in the TCA and glyoxylate cycles. While a six-fold increase in fumarase (FUM EC 4.2.1.2) activity was observed in cells subjected to Al-citrate compared to control cells, citrate synthase (CS EC 4.1.3.7) activity experienced a two-fold increase. On the other hand, in the Al-stressed cells malate synthase (MS EC 4.1.3.2) activity underwent a five-fold decrease in activity. This modulation of enzymatic activities appeared to be evoked by Al stress, as the incubation of Al-stressed cells in control media led to the complete reversal of these enzymatic profiles. These observations were further confirmed by 1H NMR and 13C NMR spectroscopy. No significant variations were observed in the activities of other glyoxylate and TCA cycle enzymes, like isocitrate lyase (ICL EC 4.1.3.1), malate dehydrogenase (MDH EC 1.1.1.37), and succinate dehydrogenase (SDH EC 1.3.99.1). This reconfiguration of the metabolic pathway appears to favour the production of a citrate-rich aluminophore that is involved in the sequestration of Al.

The home stretch, a first analysis of the nearly completed genome of Rhodobacter sphaeroides 2.4.1

Rhodobacter sphaeroides 2.4.1 is an alpha-3 purple nonsulfur eubacterium with an extensive metabolic repertoire. Under anaerobic conditions, it is able to grow by photosynthesis, respiration and fermentation. Photosynthesis may be photoheterotrophic using organic compounds as both a carbon and a reducing source, or photoautotrophic using carbon dioxide as the sole carbon source and hydrogen as the source of reducing power. In addition, R. sphaeroides can grow both chemoheterotrophically and chemoautotrophically. The structural components of this metabolically diverse organism and their modes of integrated regulation are encoded by a genome of approximately 4.5 Mb in size. The genome comprises two chromosomes CI and CII (2.9 and 0.9 Mb, respectively) and five other replicons. Sequencing of the genome has been carried out by two groups, the Joint Genome Institute, which carried out shotgun-sequencing of the entire genome and The University of Texas-Houston Medical School, which carried out a targeted sequencing strategy of CII. Here we describe our current understanding of the genome when data from both of these groups are combined. Previous work had suggested that the two chromosomes are equal partners sharing responsibilities for fundamental cellular processes. This view has been reinforced by our preliminary analysis of the virtually completed genome sequence. We also have some evidence to suggest that two of the plasmids, pRS241a and pRS241b encode chromosomal type functions and their role may be more than that of accessory elements, perhaps representing replicons in a transition state.

Gesture use following right hemisphere brain damage

A group of eight right hemisphere brain damaged (RHBD) individuals' use of gesture during discourse was explored at two points post stroke. Three topic structured conversational and three procedural discourse samples were elicited at one and six months post stroke. Gestures were analysed in terms of communicative gesture use and use of physical movements. Results suggest the group's use of gesture altered little over time. Some indication of change in the use of head movements and the use of kinetographic gestures were suggested as aspects of gesture use following RHBD that would benefit from further investigation in relation to a non-brain damaged (NBD) control group.

TeleBAT: Mobile telemedicine for the brain attack team

TeleBAT is our application of an integrated mobile telecommunications system (MTS) to the clinical problem of acute stroke. Although efforts are ongoing to educate patients to seek emergency treatment at the first signs of stroke, we sought to shorten time to treatment once the patient is known to the emergency medical system. Ambulance paramedics acquire valuable assessment data about a stroke patient en route to a medical center. We tested the feasibility of using wireless digital cellular communication to provide a stroke neurologist with real-time visual access to the neurological examination of patients conducted during transport to our stroke treatment center. Audio and visual information, and patients vital signs were transmitted from our interfacility ambulance. The MTS was designed to be user-friendly and includes turnkey operation inside the ambulance and flexible access through a internet browser by the clinicians in the hospital. With 4 simultaneous cellular phone connections, each with a bandwidth of 9.6 kilobytes per second, the throughput was a 320x240-pixel image every 2 seconds. The image quality requirement was determined through empirical testing by using a videotaped National Institutes of Health Stroke Scale examination. A framework to assess adequacy was developed and defined as the ability of the clinician to make an identical clinical judgment when visual access to the patient was provided by either audio-visual transmission or by face-to-face examination. We have shown mobile telemedicine linking prehospital providers with a stroke center neurologist and thus have come one step closer to transforming the prehospital phase of transport to prehospital phase of treatment.

Adult spoken discourse: the influences of age and education

Spoken discourse is regarded as an important component of communication assessment, but data on the discourse characteristics of the adult population, and in particular those who fall into the fastest growing section of the population (those aged over 75), are scant. Therefore, detection of deficit is commonly dependent on the assessor's opinion as to what constitutes normal performance. To determine the effects of age, education and gender on spoken discourse, the conversational interaction and picture description skills of 189 neurologically normal adults were examined. Conversation was appraised with reference to five parameters (initiation, topic maintenance, verbosity, turn taking, reference). Picture description was assessed for relevant content, length, efficiency and the inclusion of extraneous information. Level of education did not affect conversational interaction but in picture description those not educated beyond minimal school leaving produced shorter and less complete descriptions. Picture description content and length were not affected by advancing age but the older elderly (aged 75+) conveyed information with reduced efficiency. Conversational interaction style altered with advancing age, with some suggestion of change in the young elderly (age 60-74), but highly significant differences in respect of the old elderly. Gender had no effect on the parameters of conversation and no significant picture description differences were present in males and females though there were trends towards longer and higher content descriptions in females. The results have important diagnostic implications for those concerned with establishing whether pathology such as stroke has affected communication. On a wider scale, awareness of the effects of advancing age and limited education may facilitate successful communication for all who communicate with the public in a professional capacity.

Multiple chromosomes in bacteria. The yin and yang of trp gene localization in Rhodobacter sphaeroides 2.4.1

The existence of multiple chromosomes in bacteria has been known for some time. Yet the extent of functional solidarity between different chromosomes remains unknown. To examine this question, we have surveyed the well-described genes of the tryptophan biosynthetic pathway in the multichromosomal photosynthetic eubacterium Rhodobacter sphaeroides 2.4.1. The genome of this organism was mutagenized using Tn5, and strains that were auxotrophic for tryptophan (Trp(-)) were isolated. Pulsed-field gel mapping indicated that Tn5 insertions in both the large (3 Mb CI) and the small (0.9 Mb CII) chromosomes created a Trp(-) phenotype. Sequencing the DNA flanking the sites of the Tn5 insertions indicated that the genes trpE-yibQ-trpGDC were at a locus on CI, while genes trpF-aroR-trpB were at locus on CII. Unexpectedly, trpA was not found downstream of trpB. Instead, it was placed on the CI physical map at a locus 1.23 Mb away from trpE-yibQ-trpGDC. To relate the context of the R. sphaeroides trp genes to those of other bacteria, the DNA regions surrounding the trp genes on both chromosomes were sequenced. Of particular significance was the finding that rpsA1, which encodes ribosomal protein S1, and cmkA, which encodes cytidylate monophosphate kinase, were on CII. These genes are considered essential for translation and chromosome replication, respectively. Southern blotting suggested that the trp genes and rpsA1 exist in single copy within the genome. To date, this topological organization of the trp "operon" is unique within a bacterial genome. When taken with the finding that CII encodes essential housekeeping functions, the overall impression is one of close regulatory and functional integration between these chromosomes.

Changes in the morphology and the distribution of rat intestinal eosinophils during infection with the nematode Nippostrongylus brasiliensis

Increases in the numbers of eosinophil leukocytes present in the lamina propria of intestines infected with nematodes is a well described phenomenon, yet the role of these leukocytes and their actions in this situation are not yet fully understood. Morphologic changes in these cells occur with the course of the infection, as do alterations in their location within the gut; these findings may give important clues to the function of this prominent cell. We observed changes in intestinal eosinophils in the August rat during infection with the nematode Nippostrongylus brasiliensis and found, together with the well known increases in number infiltrating the lamina propria at Day 20 (three times the levels in normal animals), a distinct change in the morphology of individual cells which included increase of the cell's overall size and changes in shape, as well as a dissemination of cytoplasmic granules in relationship to the cell's nucleus. No ultrastructural evidence of extracellular degranulation or intact eosinophil cytoplasmic granules outside the bounds of cell cytoplasmic membranes was seen. This finding is important considering the light microscopic appearance of individual eosinophil granules apparently distributed extracellularly, and lying in the connective tissue of the lamina propria, a common histopathologic observation in eosinophilic conditions. Eosinophils within the lamina propria changed their location as the infection progressed, tending to move to line up along the subepithelial zones. In addition, eosinophils were observed both at the light and electron microscopic levels to be passing through the basement membrane and into the epithelial layer. This latter phenomenon was confirmed using confocal optical slicing where eosinophils were commonly observed on the luminal side of the nuclei of the gut epithelium. These observations strongly suggest that morphologic alterations occur in eosinophils in the lamina propria and these changes may be associated with functional alterations in these cells akin to the putative phenomenon of "activation." Our findings indicate that eosinophils have the capacity to enlarge and extend their cytoplasmic processes between various components of the lamina propria and move toward the basement membrane during an active infection, as well as into, and possibly through, the intestinal epithelium. These findings emphasize the need for careful consideration of the changing morphologic status of eosinophils when investigating biologic changes associated with the activation of these cells in tissue inflammatory responses.

RsGDB, the Rhodobacter sphaeroides Genome Database

This report provides a summary of the sequencing project of the small chromosome (CII) of Rhodobacter sphaeroides 2.4.1(T),and introduces the first version of the genome database of this bacterium. The database organizes and describes diverse sets of biological information. The main role of the R.sphaeroides genome database (RsGDB) is to provide public access to the collected genomic information for R.sphaeroides via the World-Wide Web at http://utmmg.med.uth.tmc.edu/sphaeroides. The database allows the user access to hundreds of low redundancy R.sphaeroides sequences for further database searching, a summary of our current search results, and other allied information pertaining to this bacterium.

In vitro interference of the red cell substitute pyridoxalated hemoglobin-polyoxyethylene with blood compatibility, coagulation, and clinical chemistry testing

OBJECTIVES

Pyridoxalated hemoglobin-polyoxyethylene (PHP) is a prototypical red cell substitute approved for phase I studies. Peripheral blood smears of human blood mixed with PHP in 1 to 4 g/dL concentrations showed dose-dependent red cell aggregation and rouleaux. Whether this aggregation limits interpretation of blood compatibility testing and whether the intense coloration of serum or plasma containing PHP affects routine coagulation and clinical chemistry measurements was tested.

DESIGN

In vitro studies.

SETTING

University hospital laboratory.

PARTICIPANTS

Four healthy volunteers, blood types A, B, AB, and O. All were Rh+.

MEASUREMENTS AND MAIN RESULTS

ABO typing, Rh typing, and antibody screening and coagulation studies were performed on blood: PHP admixtures having final concentrations of 1, 2, and 4 g/dL. For clinical chemistry interference studies, known concentrations of analytes were added to a serum matrix containing PHP. ABO (forward) and Rh typing showed no interference in the three concentrations tested. Reverse ABO typing and antibody screening showed rouleaux at 4 g/dL, which corrected with routine saline replacement. Partial thromboplastin time (PTT), prothrombin time (PT), and fibrinogen showed no clinically significant differences from the controls. Results for electrolytes, renal function analytes, and markers of cardiac injury were acceptable by standard laboratory methods. However, results of liver function tests were unacceptable in PHP-containing specimens.

CONCLUSIONS

PHP-induced aggregation was observed with high PHP concentration; however, compatibility testing was not affected because agglutination was corrected by saline replacement, which is standard practice. Although routine blood banking, coagulation, and most clinical chemistry analytes can be measured reliably, alternative methods and strategies are needed for assessing liver function in the presence of PHP.

Low-resolution sequencing of Rhodobacter sphaeroides 2.4.1T: chromosome II is a true chromosome

The photosynthetic bacterium Rhodobacter sphaeroides 2.4.1T has two chromosomes, CI (approximately 3.0 Mb) and CII (approximately 0.9 Mb). In this study a low-redundancy sequencing strategy was adopted to analyse 23 out of 47 cosmids from an ordered CII library. The sum of the lengths of these 23 cosmid inserts was approximately 495 kb, which comprised approximately 417 kb of unique DNA. A total of 1145 sequencing runs was carried out, with each run generating 559 +/- 268 bases of sequence to give approximately 640 kb of total sequence. After editing, approximately 2.8% bases per run were estimated to be ambiguous. After the removal of vector and Escherichia coli sequences, the remaining approximately 565 kb of R. sphaeroides sequences were assembled, generating approximately 291 kb of unique sequences. BLASTX analysis of these unique sequences suggested that approximately 131 kb (45% of the unique sequence) had matches to either known genes, or database ORFs of hypothetical or unknown function (dORFs). A total of 144 strong matches to the database was found; 101 of these matches represented genes encoding a wide variety of functions, e.g. amino acid biosynthesis, photosynthesis, nutrient transport, and various regulatory functions. Two rRNA operons (rrnB and rrnC) and five tRNAs were also identified. The remaining 160 kb of DNA sequence which did not yield database matches was then analysed using CODONPREFERENCE from the GCG package. This analysis suggested that 122 kb (42% of the total unique DNA sequence) could encode putative ORFs (pORFs), with the remaining 38 kb (13%) possibly representing non-coding intergenic DNA. From the data so far obtained, CII does not appear to be specialized for encoding any particular metabolic function, physiological state or growth condition. These data suggest that CII contains genes which are functionally as diverse as those found on any other bacterial chromosome and also contains sequences (pORFs), which may prove to be unique to this organism.

Characterization of the cytoplasmic filament protein gene (cfpA) of Treponema pallidum subsp. pallidum

Treponema pallidum and other members of the genera Treponema, Spirochaeta, and Leptonema contain multiple cytoplasmic filaments that run the length of the organism just underneath the cytoplasmic membrane. These cytoplasmic filaments have a ribbon-like profile and consist of a major cytoplasmic filament protein subunit (CfpA, formerly called TpN83) with a relative molecular weight of approximately 80,000. Degenerate DNA primers based on N-terminal and CNBr cleavage fragment amino acid sequences of T. pallidum subsp. pallidum (Nichols) CfpA were utilized to amplify a fragment of the encoding gene (cfpA). A 6.8-kb EcoRI fragment containing all but the 5' end of cfpA was identified by hybridization with the resulting PCR product and cloned into Lambda ZAP II. The 5' region was obtained by inverse PCR, and the complete gene sequence was determined. The cfpA sequence contained a 2,034-nucleotide coding region, a putative promoter with consensus sequences (5'-TTTACA-3' for -35 and 5'-TACAAT-3' for -10) similar to the sigma70 recognition sequence of Escherichia coli and other organisms, and a putative ribosome-binding site (5'-AGGAG-3'). The deduced amino acid sequence of CfpA indicated a protein of 678 residues with a calculated molecular mass of 78.5 kDa and an estimated pI of 6.15. No significant homology to known proteins or structural motifs was found among known prokaryotic or eukaryotic sequences. Expression of a LacZ-CfpA fusion protein in E. coli was detrimental to survival and growth of the host strain and resulted in the formation of short, irregular filaments suggestive of partial self-assembly of CfpA. The cytoplasmic filaments of T. pallidum and other spirochetes appear to represent a unique form of prokaryotic intracytoplasmic inclusions.

Anti-parasitic effector mechanisms in human brain tumor cells: role of interferon-gamma and tumor necrosis factor-alpha

Toxoplasma gondii, an obligate intracellular parasite, is able to replicate in human brain cells. We recently showed that interferon (IFN)-gamma-activated cells from glioblastoma line 86HG39 were able to restrict Toxoplasma growth. The effector mechanism responsible for this toxoplasmostatic effect was shown by us to be the IFN-gamma-mediated activation of indolamine 2,3-dioxygenase (IDO), resulting in the degradation of the essential amino acid tryptophan. In contrast, glioblastoma 87HG31 was unable to restrict Toxoplasma growth after IFN-gamma activation, and IFN-gamma-mediated IDO activation was weak. We observed that tumor necrosis factor (TNF)-alpha alone is unable to activate IDO or to induce toxoplasmostasis in any glioblastoma cell line tested. Interestingly, we found that TNF-alpha and IFN-gamma were synergistic in the activation of IDO in glioblastoma cells 87HG31, 86HG39 and U373MG and in native astrocytes. This was shown by the measurement of enzyme activity as well as by the detection of IDO mRNA in TNF-alpha + IFN-gamma activated cells. This IDO activity results in a strong toxoplasmostatic effect mediated by glioblastoma cells activated simultaneously by both cytokines. Antibodies directed against TNF-alpha or IFN-gamma were able to inhibit IDO activity as well as the induction of toxoplasmostasis in glioblastoma cells stimulated with both cytokines. Furthermore, it was found that the addition of L-tryptophan to the culture medium completely blocks the antiparasitic effect. We therefore conclude that both TNF-alpha and IFN-gamma may be involved in the defense against cerebral toxoplasmosis by inducing IDO activity as an antiparasitic effector mechanism in brain cells.

Establishment of T-helper type 1- and T-helper type 2-like human Toxoplasma antigen-specific T-cell clones

As an in vitro model for human cerebral toxoplasmosis, we analysed the interaction between glioblastoma cells, Toxoplasma and Toxoplasma antigen-specific T-helper cells. We established 46 different human CD4+ T-cell clones from four different donors. All T-cell clones responded to Toxoplasma antigen derived from three different Toxoplasma strains. We found that the supernatants of 44 clones induced toxoplasmostasis in glioblastoma cells. The anti-parasitic effector mechanism activated in glioblastoma cells by T-cell supernatants was the induction of the tryptophan-degrading enzyme indolamine 2,3-dioxygenase. Enzyme induction, as well as the anti-parasitic effect, was blocked by a monoclonal antibody directed against interferon-gamma (IFN-gamma), and the addition of L-tryptophan to the cultures completely blocked the anti-parasitic effect induced by T-cell supernatants. The supernatants from two of the 46 established T-cell clones (3A22 and 1A15) were unable to induce indolamine 2,3-dioxygenase activity or, as expected, toxoplasmostasis in glioblastoma cells. We further analysed the supernatants from these two clones, and found that they contained large amounts of IL-4 and no, or only limited amounts of, IFN-gamma. We therefore conclude that Toxoplasma-antigen is able to activate T-helper type 1 (Th1)- and Th2-like human T cells, and only IFN-gamma-producing cells are capable of inducing anti-parasitic effector mechanisms.

DNA repair mutants of Rhodobacter sphaeroides

The genome of the photosynthetic eubacterium Rhodobacter sphaeroides 2.4.1 comprises two chromosomes and five endogenous plasmids and has a 65% G+C base composition. Because of these characteristics of genome architecture, as well as the physiological advantages that allow this organism to live in sunlight when in an anaerobic environment, the sensitivity of R. sphaeroides to UV radiation was compared with that of the more extensively studied bacterium Escherichia coli. R. sphaeroides was found to be more resistant, being killed at about 60% of the rate of E. coli. To begin to analyze the basis for this increased resistance, a derivative of R. sphaeroides, strain 2.4.1 delta S, which lacks the 42-kb plasmid, was mutagenized with a derivative of Tn5, and the transposon insertion mutants were screened for increased UV sensitivity (UVs). Eight UVs strains were isolated, and the insertion sites were determined by contour-clamped homogeneous electric field pulsed-field gel electrophoresis. These mapped to at least five different locations in chromosome I. Preliminary analysis suggested that these mutants were deficient in the repair of DNA damage. This was confirmed for three loci by DNA sequence analysis, which showed the insertions to be within genes homologous to uvrA, uvrB, and uvrC, the subunits of the nuclease responsible for excising UV damage.