Using Combined Morphological, Allometric and Molecular Approaches to Identify Species of the Genus Raillietiella (Pentastomida)

Taxonomic studies of parasites can be severely compromised if the host species affects parasite morphology; an uncritical analysis might recognize multiple taxa simply because of phenotypically plastic responses of parasite morphology to host physiology. Pentastomids of the genus Raillietiella are endoparasitic crustaceans primarily infecting the respiratory system of carnivorous reptiles, but also recorded from bufonid anurans. The delineation of pentastomids at the generic level is clear, but the taxonomic status of many species is not. We collected raillietiellids from lungs of the invasive cane toad (Rhinella marina), the invasive Asian house gecko (Hemidactylus frenatus), and a native tree frog (Litoria caerulea) in tropical Australia, and employed a combination of genetic analyses, and traditional and novel morphological methods to clarify their identity. Conventional analyses of parasite morphology (which focus on raw values of morphological traits) revealed two discrete clusters in terms of pentastome hook size, implying two different species of pentastomes: one from toads and a tree frog (Raillietiella indica) and another from lizards (Raillietiella frenatus). However, these clusters disappeared in allometric analyses that took pentastome body size into account, suggesting that only a single pentastome taxon may be involved. Our molecular data revealed no genetic differences between parasites in toads versus lizards, confirming that there was only one species: R. frenatus. This pentastome (previously known only from lizards) clearly is also capable of maturing in anurans. Our analyses show that the morphological features used in pentastomid taxonomy change as the parasite transitions through developmental stages in the definitive host. To facilitate valid descriptions of new species of pentastomes, future taxonomic work should include both morphological measurements (incorporating quantitative measures of body size and hook bluntness) and molecular data

Characterization of a Clp Protease Gene Regulator and the Reaeration Response in Mycobacterium tuberculosis

Mycobacterium tuberculosis (MTB) enters a non-replicating state when exposed to low oxygen tension, a condition the bacillus encounters in granulomas during infection. Determining how mycobacteria enter and maintain this state is a major focus of research. However, from a public health standpoint the importance of latent TB is its ability to reactivate. The mechanism by which mycobacteria return to a replicating state upon re-exposure to favorable conditions is not understood. In this study, we utilized reaeration from a defined hypoxia model to characterize the adaptive response of MTB following a return to favorable growth conditions. Global transcriptional analysis identified the ∼100 gene Reaeration Response, induced relative to both log-phase and hypoxic MTB. This response includes chaperones and proteases, as well as the transcription factor Rv2745c, which we characterize as a Clp protease gene regulator (ClgR) orthologue. During reaeration, genes repressed during hypoxia are also upregulated in a wave of transcription that includes genes crucial to transcription, translation and oxidative phosphorylation and culminates in bacterial replication. In sum, this study defines a new transcriptional response of MTB with potential relevance to disease, and implicates ClgR as a regulator involved in resumption of replication following hypoxia

Right pleuropericardial release: a useful technique in off-pump coronary surgery

We describe the use of right pleurotomy combined with right pericardial release during off-pump coronary surgery. The maneuver releases the compression exerted on the right cardiac chambers during cardiac verticalization and improves hemodynamic stability during exposure of the posterior or lateral coronary vessels

Thyroid function during coronary surgery with and without cardiopulmonary bypass

Objective: cardiopulmonary bypass (CPB) is associated with thyroid hormone changes consistent with euthyroid sick syndrome. Similar changes have been observed after general surgical operations. Thyroid hormone changes and their association with global oxygen consumption were studied in low-risk patients undergoing coronary artery bypass grafting (CABG) with and without CPB. Methods: fifty-two patients undergoing primary CABG by the same surgeon were randomised into either on-pump (ONCAB, n = 26) or off-pump (OPCAB, n = 26) groups. Thyroid-stimulating hormone (TSH), free thyroxine (fT4) and free triiodothyronine (fT3) levels were measured at sequential time-points using chemiluminescence assays. Global oxygen consumption was measured at sequential time-points using a continuous cardiac output Swan-Ganz catheter. Results: in both groups TSH and fT4 remained within normal range throughout the study. There was a similar and progressive decline in fT3 levels with no significant difference between the groups over time (p = 0.42). Mean fT3 levels at 24 h were below the normal range and significantly lower than baseline values (ONCAB, 3.3 ± 0.69 pmol/L vs 5.1 ± 0.41 pmol/L, p < 0.001; OPCAB, 3.3 ± 0.51 pmol/L vs 5.0 ± 0.46 pmol/L, p < 0.001). There was a significant inverse relationship between fT3 levels and global oxygen consumption. Conclusions: off-pump surgery is associated with thyroid hormone changes similar to conventional surgical revascularisation. The data suggest that further studies into T3 administration during OPCAB may be warrante

A prospective randomized study to evaluate stress response during beating-heart and conventional coronary revascularization

Background: Cardiopulmonary bypass (CPB) is associated with a systemic stress hormonal response, which can lead to changes in hemodynamics and organ perfusion. We examined perioperative stress hormone release in low-risk patients undergoing coronary artery bypass grafting with and without cardiopulmonary bypass.Methods: Fifty-two patients undergoing primary coronary artery bypass grafting by the same surgeon were randomly assigned into either on-pump (n = 26) or off-pump (n = 26) groups. The on-pump coronary artery bypass grafting group underwent mildly hypothermic (35°C) pulsatile cardiopulmonary bypass with arterial line filtration. Arterial blood samples were collected preoperatively, at the end of operation, and at 1, 6, and 24 hours postoperatively. Plasma levels of vasopressin and cortisol were measured using radioimmunoassay. Anesthetic management was standardized.Results: Both groups had similar demographic makeup and extent of revascularization (on-pump coronary artery bypass grafting, 2.8 ± 1.0 grafts versus off-pump coronary artery bypass grafting, 2.4 ± 0.9 grafts; p = 0.20). No mortality or major morbidity was observed and there were no crossovers. The cardiopulmonary bypass and aortic cross-clamp times in the on-pump coronary artery bypass grafting group were 63 ± 24 and 33 ± 11 minutes, respectively. In both groups there was a similar and significant rise in cortisol and vasopressin levels in the early postoperative phase, with a partial recovery toward baseline values observed at 24 hours postoperatively. Repeated measures analysis of covariance showed no significant difference between the groups with time for both hormones (cortisol, p = 0.40; vasopressin, p = 0.30).Conclusions: Despite the avoidance of cardiopulmonary bypass, off-pump coronary artery bypass grafting surgery triggers a systemic stress hormone response that is comparable to conventional surgical revascularization. The neurohormonal environment during beating-heart surgery should be further explored

Comparative fitness analysis of D-cycloserine resistant mutants reveals both fitness-neutral and high-fitness cost genotypes

Drug resistant infections represent one of the most challenging medical problems of our time. D-cycloserine is an antibiotic used for six decades without significant appearance and dissemination of antibiotic resistant strains, making it an ideal model compound to understand what drives resistance evasion. We therefore investigated why Mycobacterium tuberculosis fails to become resistant to D-cycloserine. To address this question, we employed a combination of bacterial genetics, genomics, biochemistry and fitness analysis in vitro, in macrophages and in mice. Altogether, our results suggest that the ultra-low rate of emergence of D-cycloserine resistance mutations is the dominant biological factor delaying the appearance of clinical resistance to this antibiotic. Furthermore, we also identified potential compensatory mechanisms able to minimize the severe fitness costs of primary D-cycloserine resistance conferring mutations