Adaptive evolution in GroEL from distantly related endosymbiotic bacteria of insects

Many symbioses between bacteria and insects resulted from ancient infections followed by strict vertical transmission within host lineages. The strong bottlenecks under which this transmission occurs promote the neutral fixation of slightly deleterious mutations by genetic drift. As predicted by Muller's ratchet, this fixation will drive endosymbiotic bacteria through an irreversible dynamics of fitness loss. The chaperonin GroEL has been proposed as a compensatory mechanism whereby endosymbiotic bacteria of aphids persist. Here, we show that endosymbiotic bacteria of insects from two phylogenetically very distant bacterial phyla have fixed amino acid substitutions by positive selection in functionally important GroEL regions involved in either GroES/peptide binding or in the en bloc movement of the GroEL apical domain. These results, together with the high levels of constitutive expression of GroEL in these endosymbionts, provide valuable insights into the evolution of a molecular mechanism responsible for the maintenance of the symbiotic lifestyle.

Fitness and life-history traits of the two major mitochondrial DNA haplotypes of Drosophila subobscura

Mitochondrial DNA restriction site analyses on natural populations of Drosophila subobscura have proved the existence of two common, coexisting haplotypes (I and II), as well as a set of less frequent ones derived from them. To explain this distribution, experiments to date point practically to all possible genetic mechanisms being involved in the changes of gene frequencies (cytonuclear coadaptation, direct natural selection on mtDNA and genetic drift). In an attempt to find differences that help to understand the dynamics of these haplotypes and to detect the effect of selection, we measured certain fitness components and life-history traits (egg-larva and larva-adult viabilities and developmental times, longevity, resistance to desiccation and optimal density) of the two main haplotypes I and II when maintained in laboratory population cages. As a general trend, haplotype II showed a higher net fitness than haplotype I, which explains the superiority of haplotype II over haplotype I in experimental populations but not their coexistence in nature, where additional factors must be considered.

[Assessment of home parenteral nutrition programme in terminal oncological patients]

BACKGROUND AND GOALS

The assessment of the acceptance of the diets served at the hospital allows the introduction of adjustments to improve the quality of the service provided to hospitalized patients by preventing the complications derived from incorrect nutrition and enhancing their stay in hospital. The goal of the present study was to analyze the acceptance of the menus offered by the Hospital's catering service.

SCOPE OF THE STUDY

Menus provided by the catering service of the "Sant Joan de Reus" University Hospital.

MATERIAL AND METHODS

A total of 160 tray meals consumed were assessed, all chosen at random and corresponding to standard diets and special diets, including puréed food. The assessment was made by two dieticians in the hospital's kitchens. A visual scale was used with the following scores: 0 for a full plate, 1 for residual food amounting to over 75%, 2 from 50% to 75%, 3 more than or equal to 25% and 4 for empty plates.

RESULTS

A total of 68 trays containing a standard diet were analyzed, together with 34 containing special diets and 41 with puréed food. The remains on 36 different courses from the standard diet were analyzed. The mean acceptance score was 3.01 +/- 1.30 in the case of the first courses, 3.24 +/- 1.11 in second courses and 3.53 +/- 0.96 for the desserts. As for special diets, a total of 27 different courses were analyzed. The mean acceptance score was 2.87 +/- 1.38 in the case of the first courses, 3.02 +/- 1.27 in second courses and 3.49 +/- 1.22 for the desserts. The first courses of puréed diets received the worst score of all the dishes served, although the overall mean score was good, 2.76 +/- 1.5.

CONCLUSIONS

In general, a good level of acceptance has been observed for the set meals served in the hospital. Knowing which courses have lower acceptance scores allows changes to be proposed to the hospital menus, with their replacement by others with foreseeably better acceptance.

Iris yellow spot virus on Onion in New Mexico

Onions are an important crop for New Mexico with 7,700 acres (3,116 ha) harvested in the state in 2003 (3). In 2002, onions of several cultivars were first noticed with diamond-shaped chlorotic or bleached lesions on seed stalks or leaves, typical of those reported for Iris yellow spot virus (IYSV). A more widespread survey of breeding stocks and commercial onion fields revealed similar symptoms on thrips-infested onions in Dona Ana and Rio Arriba counties. Incidence of disease symptoms ranged from <0.5 to nearly 30%. Symptomatic leaves were assayed for the presence of IYSV using enzyme-linked immunosorbent assay (ELISA; Agdia, Elkhart, IN) and antisera acquired from Agdia. Symptomatic leaves from breeding and commercial fields tested positive for IYSV. The virus was transmitted by Thrips tabaci from symptomatic onions to three onion cvs. New Mex Mesa, New Mex Vado, and New Mex Cryspy in growth chamber tests. All three cultivars showed symptoms of IYSV and tested positive for the disease using ELISA. However, New Mex Vado and New Mex Cryspy cultivars each showed 24% infection (4 infected plants of 17 tested) compared with 59% infection (10 infected plants of 17 tested) for New Mex Mesa, suggesting that not all cultivars are equally susceptible to the virus. To our knowledge, this is the first report of IYSV in onions in New Mexico, which has also been reported in the western United States in Idaho, Oregon, Colorado, and Washington (1,2,4). References: (1) L. J. du Toit et al. Plant Dis. 88:222, 2004. (2) J. M. Hall et al. Plant Dis. 77:952, 1993. (3) National Agricultural Statistics Service, On-line publication. USDA, 2004. (4) H. F. Schwartz et al. Plant Dis. 86:560, 2002.

Liver transplantation for peripheral cholangiocarcinoma: Spanish experience

INTRODUCTION

Palliative treatment for nondisseminated unresectable peripheral cholangiocarcinoma (PCC) carries a 0% 5-year survival rate. The role of orthotopic liver transplantation (OLT) in these patients is controversial because the survival rate is lower than with other indications for transplantation and the lack of available donor organs. The aim of this paper was to review the Spanish experience in OLT for PCC to identify prognostic factors for survival.

METHODS

We retrospectively reviewed 23 patients undergoing OLT in Spain for PCC over a period of 13 years.

RESULTS

The actuarial survival rates were 77%, 65%, and 42% at 1, 3, and 5 years, respectively. The main cause of death was tumor recurrence (35%). Prognotic factors for an adverse outcome were pTNM classification (P<.05) in the univariate analysis and perineural invasion (P<.05) and stages III or IVA (P<.05) in the multivariate analysis.

CONCLUSIONS

OLT for nondisseminated irresectable PCC displays higher survival rates at 3 and 5 years than palliative treatments, especially for tumors in the initial stages, which means that more information is needed to help better select PCC patients for transplantation.

Liver transplantation for hilar cholangiocarcinoma: Spanish experience

INTRODUCTION

Palliative treatment for nondisseminated irresectable hilar cholangiocarcinoma (HCC) carries a 0% 5-year survival rate. The role of orthotopic liver transplantation (OLT) in these patients is controversial because the survival rate is lower than that for other indications for transplantation and the lack of available donor organs. The aim of this paper was to review the Spanish experience in OLT for HCC and identify prognostic factors for survival.

METHODS

We retrospectively reviewed 36 patients undergoing OLT for HCC over 13 years.

RESULTS

The actuarial survival rate at 1, 3, and 5 years was 82%, 53%, and 30%, respectively. The main cause of death was tumor recurrence (53%). In the univariate analysis, the factors for a poor prognosis were vascular invasion (P<.001) namely 0% survival at 3 years when present versus 63% and 35% at 3 and 5 years, respectively, when it was not; and stages III to IVA (P<.05), namely 15% survival at 5 years versus 47% for stages I to II. Lymph node and perineural invasion also reduce survival. In the multivariate analysis, the factors for poor prognosis included vascular invasion (P<.01) and stages III to IVA (P<.01).

CONCLUSION

OLT for nondisseminated irresectable HCC has higher survival rates at 3 and 5 years than palliative treatments, especially with initial stage tumors, which means that more information is needed to better select cholangiocarcinoma patients for transplantation.

Evolution of RNA virus in spatially structured heterogeneous environments

A hallmark of the infectious cycle for many RNA viruses parasitizing multicellular hosts is the need to invade and successfully replicate in tissues that comprise a variety of cell types. Thus, multicellular hosts represent a heterogeneous environment to evolving viral populations. To understand viral adaptation to multicellular hosts, we took a double approach. First, we developed a mathematical model that served to make predictions concerning the dynamics of viral populations evolving in heterogeneous environments. Second, the predictions were tested by evolving vesicular stomatitis virus in vitro on a spatially structured environment formed by three different cell types. In the absence of gene flow, adaptation was tissue-specific, but fitness in all tissues decreased with migration rate. The performance in a given tissue was negatively correlated with its distance to the tissue hosting the population. This correlation decreased with migration rate.

Side-stepping secondary symbionts: widespread horizontal transfer across and beyond the Aphidoidea

To elucidate the co-evolutionary relationships between phloem-feeding insects and their secondary, or facultative, bacterial symbionts, we explore the distributions of three such microbes--provisionally named the R-type (or PASS, or S-sym), T-type (or PABS), and U-type--across a number of aphid and psyllid hosts through the use of diagnostic molecular screening techniques and DNA sequencing. Although typically maternally transmitted, phylogenetic and pairwise divergence analyses reveal that these bacteria have been independently acquired by a variety of unrelated insect hosts, indicating that horizontal transfer has helped to shape their distributions. Based on the high genetic similarity between symbionts in different hosts, we argue that transfer events have occurred recently on an evolutionary timescale. In several instances, however, closely related symbionts associate with related hosts, suggesting that horizontal transfer between distant relatives may be rarer than transmission between close relatives. Our findings on the prevalence of these symbionts within many aphid taxa, along with published observations concerning their effects on host fitness, imply a significant role of facultative symbiosis in aphid ecology and evolution.

Variation of haplotype distributions of two genomic regions of Citrus tristeza virus populations from eastern Spain

Genetic variation in natural populations of Citrus tristeza virus (CTV) was studied using haplotypes detected by single-strand conformation polymorphism (SSCP) analysis of two genomic regions (p20 gene and segment A, located in ORF1a). Analysis of 254 samples from 125 trees, collected at 12 different sites, yielded 8 different haplotypes for p20 and 5 for segment A. The most frequent haplotype of p20 was predominant at all sites, but several sites differed in the predominance of segment A haplotypes. At most sites, the homozygosity observed for the p20 gene tended to be higher than expected in a neutral evolution, whereas the opposite was true for segment A. Comparison of the populations at different sites showed that 44 of the 66 possible population pairs were genetically distinct for segment A, but only six pairs differed for the p20 gene. Analysis of molecular variance grouping trees by site, scion variety, rootstock or age, showed that variation in segment A was significantly affected by site, tree age and rootstock, and that variation between trees in each group and within trees was even more important. In contrast, variation in p20 was affected only by site and rootstock, each factor contributing to < 2% of the variation. The data suggest that sequence variations in segment A must be functionally less important and that it has less evolutionary constraints than p20. Detection of different haplotypes in neighbour trees or in samples from the same tree may help explain part of the variability observed in CTV symptom expression.

Reproducibility of sequential head-up tilt testing in patients with recent syncope, normal ECG and no structural heart disease

AIMS

To assess the reproducibility of the response to sequential head-up tilt tests.

METHODS AND RESULTS

A head-up tilt test was performed early after syncope in 127 patients with a normal ECG and no structural heart disease. Patients with a positive response (82 patients) were randomized to two (1 week and 2 weeks later) or one (2 weeks later) additional head-up tilt tests, and patients with a negative response (45 patients) were randomized to a second head-up tilt test 1 or 2 weeks after the first. The reproducibility of a positive response in the second head-up tilt test was 80% after 1 week and 53% after 2 weeks (P<0.01). Only 53% of the patients with a positive response to a first and second head-up tilt test had a positive response to a third (P=0.01). Intra-individual variation in the time to a positive response was wide. The reproducibility of the cardioinhibitory responses was very poor. Reproducibility of a negative response was 80%.

CONCLUSIONS

In patients with recent syncope, the rate of positive responses decreases with sequential head-up tilt tests. Furthermore, the time to a positive response in different head-up tilt tests shows important intra-individual variations, and the reproducibility of the cardioinhibitory responses is very poor. In contrast, the reproducibility of the negative responses is high.

Linkage disequilibria between mtDNA haplotypes and chromosomal arrangements in a natural population of Drosophila subobscura

The association between mtDNA haplotypes and chromosomal arrangements in a natural population of Drosophila subobscura from Calvia (Balearic Islands, Spain) was studied in order to search for linkage disequilibria, in an attempt to explain the populational dynamics of the mtDNA haplotypes of this species in nature. The presence of Wolbachia was not detected. Two main haplotypes (I and II) were found, as well as a series of less common ones. The Tajima D-test seemed to indicate some kind of seasonal population bottleneck. An analysis of linkage disequilibrium and factorial analysis of correspondences detected an association between haplotype I and the J(ST) inversion and haplotype II and the J(1) inversion.

Genome size reduction through multiple events of gene disintegration in Buchnera APS

The evolution of the endosymbiont Buchnera during its adaptation to intracellular life involved a massive reduction in its genome. By comparing the orthologous genes of Buchnera, Escherichia coli and Vibrio cholerae, we show that the minimal genome size of Buchnera arose from multiple events of gene disintegration dispersed over the whole genome. The elimination of the genes was a continuous process that began with gene inactivation and progressed until the DNA corresponding to the pseudogenes were completely deleted.

Mechanism of syncope in patients with bundle branch block and negative electrophysiological test

BACKGROUND

In patients with syncope and bundle branch block (BBB), syncope is suspected to be attributable to a paroxysmal atrioventricular (AV) block, but little is known of its mechanism when electrophysiological study is negative.

METHODS AND RESULTS

We applied an implantable loop recorder in 52 patients with BBB and negative conventional workup. During a follow-up of 3 to 15 months, syncope recurred in 22 patients (42%), the event being documented in 19 patients after a median of 48 days. The most frequent finding, recorded in 17 patients, was one or more prolonged asystolic pause mainly attributable to AV block; the remaining 2 patients had normal sinus rhythm or sinus tachycardia. The onset of the bradycardic episodes was always sudden but was sometimes preceded by ventricular premature beats. The median duration of the arrhythmic event was 47 seconds. An additional 3 patients developed nonsyncopal persistent III-degree AV block, and 2 patients had presyncope attributable to AV block with asystole. No patients suffered injury attributable to syncopal relapse.

CONCLUSIONS

In patients with BBB and negative electrophysiological study, most syncopal recurrences have a homogeneous mechanism that is characterized by prolonged asystolic pauses, mainly attributable to sudden-onset paroxysmal AV block.

Mechanism of syncope in patients with isolated syncope and in patients with tilt-positive syncope

BACKGROUND

Because of its episodic behavior, the correlation of spontaneous syncope with an abnormal finding can be considered a reference standard.

METHODS AND RESULTS

We inserted an implantable loop recorder in 111 patients with syncope, absence of significant structural heart disease, and a normal ECG; tilt-testing was negative in 82 (isolated syncope) and positive in 29 (tilt-positive). The patients had had >/=3 episodes of syncope in the previous 2 years and were followed up for 3 to 15 months. Results were similar in the isolated syncope group and the tilt-positive group: syncope recurred in 28 (34%) and 10 patients (34%), respectively, and electrocardiographic correlation was found in 24 (23%) and 8 (28%) patients, respectively. The most frequent finding, which was recorded in 46% and 62% of patients, respectively, was one or more prolonged asystolic pauses, mainly due to sinus arrest, preceded for a few minutes by progressive bradycardia or progressive tachycardia-bradycardia. Bradycardia without pauses was observed in 8% and 12% of cases, respectively. The remaining patients had normal sinus rhythm or sinus tachycardia, except for one, who had ectopic atrial tachycardia. In the tilt-positive group, an asystolic syncope was also recorded when the type of response to tilt-testing was vasodepressor or mixed. Presyncopal episodes were never characterized by asystolic pauses; normal sinus rhythm was the most frequent finding.

CONCLUSIONS

Homogeneous findings were observed during syncope. In most patients, the likely cause was neurally-mediated, and the most frequent mechanism was a bradycardic reflex. In the other cases, a normal sinus rhythm was frequently recorded. Presyncope was not an accurate surrogate for syncope in establishing a diagnosis.

Molecular systematics of aphids and their primary endosymbionts

Aphids constitute a monophyletic group within the order Homoptera (i.e., superfamily Aphidoidea). The Aphidoidea originated in the Jurassic about 150 my ago from some aphidiform ancestor whose origin can be traced back to about 250 my ago. They exhibit a mutualistic association with intracellular bacteria (Buchnera sp.) related to Escherichia coli. Buchnera is usually considered the aphids' primary endosymbiont. The association is obligate for both partners. The 16S rDNA-based phylogeny of Buchnera from four aphid families showed complete concordance with the morphology-based phylogeny of their aphid hosts, which pointed to a single original infection in a common ancestor of aphids some 100-250 my ago followed by cospeciation of aphids and Buchnera. This study concentrated on the molecular phylogeny of both the aphids and their primary endosymbionts of five aphid families including for the first time representatives of the family Lachnidae. We discuss results based on two Buchnera genes (16S rDNA and the beta subunit of the F-ATPase complex) and on one host mitochondrial gene (the subunit 6 of the F-ATPase complex). Although our data do not allow definitive evolutionary relationships to be established among the different aphid families, some traditionally accepted groupings are put into question from both bacterial and insect data. In particular, the Lachnidae and the Aphididae, which from morphological data are considered recently evolved sister groups, do not seem to be as closely related as is usually accepted. Finally, we discuss our results in the light of the proposed parallel evolution of aphids and their endosymbionts.

[A new case of hepatic adenomatosis treated with orthotopic liver transplantation]

Hepatic adenomatosis is a rare disease with multiple hepatic adenomas (10 or more), not associated with an history of oral contraceptive use or anabolic steroids use or with glycogen storage disease. A new case is reported in a 23 year-old woman who consulted for an abdominal mass and who had more than 50 adenomas of the liver. The suspicion of malignant transformation by the elevation of the alpha-foetoprotein, and the diffuse affectation of the liver, with minimum free parenchyma, suggested to carry out an orthotopic liver transplantation. The definitive histological examination of the surgical specimen confirmed the existence of local areas of hepatocellular carcinoma.