The effect of sex on the mean and variance of fitness in facultatively sexual rotifers

The evolution of sex is a classic problem in evolutionary biology. While this topic has been the focus of much theoretical work, there is a serious dearth of empirical data. A simple yet fundamental question is how sex affects the mean and variance in fitness. Despite its importance to the theory, this type of data is available for only a handful of taxa. Here, we report two experiments in which we measure the effect of sex on the mean and variance in fitness in the monogonont rotifer, Brachionus calyciflorus. Compared to asexually derived offspring, we find that sexual offspring have lower mean fitness and less genetic variance in fitness. These results indicate that, at least in the laboratory, there are both short- and long-term disadvantages associated with sexual reproduction. We briefly review the other available data and highlight the need for future work.     

How many species are infected with Wolbachia? Cryptic sex ratio distorters revealed to be common by intensive sampling.

Inherited bacterial symbionts from the genus Wolbachia have attracted much attention by virtue of their ability to manipulate the reproduction of their arthropod hosts. The potential importance of these bacteria has been underlined by surveys, which have estimated that 17% of insect species are infected. We examined whether these surveys have systematically underestimated the proportion of infected species through failing to detect the low-prevalence infections that are expected when Wolbachia distorts the sex ratio. We estimated the proportion of species infected with Wolbachia within Acraea butterflies by testing large collections of each species for infection. Seven out of 24 species of Acraea were infected with Wolbachia. Four of these were infected with Wolbachia at high prevalence, a figure compatible with previous broad-scale surveys, whilst three carried low-prevalence infections that would have had a very low likelihood of being detected by previous sampling methods. This led us to conclude that sex-ratio-distorting Wolbachia may be common in insects that have an ecology and/or genetics that permit the invasion of these parasites and that previous surveys may have seriously underestimated the proportion of species that are infected.     

Etiologic Diagnosis of Lower Respiratory Tract Infections

Decision as to the role of infection in lower respiratory tract disease requires examination by culture of specimens known to be derived from the infra-laryngeal respiratory tract. Methods that involve the upper respiratory tract in collection of specimens entail the hazard of contamination by microbiota resident in the upper respiratory tract.The extrapulmonary approaches of cutting-needle biopsy and needle aspiration of intrathoracic disease have not been impressively productive of etiologic diagnosis of infections. While open-chest surgical biopsy has been a highly effective means to diagnosis, this approach does have special requirements in facilities and technical skills.Percutaneous transtracheal aspiration of tracheo-broncho-pulmonary secretions-exudates has been productive of useful information. Because of inherent simplicity and safety, transtracheal aspiration should precede resort to more demanding, difficult, dangerous procedures.     

An overview of Plasmodium protein kinases.

Protein kinases are key regulators of many biochemical processes in eukaryotic cells. Malaria parasites, in spite of all their peculiarities, are not likely to represent an exception in this respect. Over the past few years, several genes encoding Plasmodium protein kinases have been cloned and characterized; these molecular studies extend previous data on kinase activities in parasite extracts. Here, Barbara Kappes, Christian Doerig and Ralph Graeser present available data on this topic, with an emphasis on cloned protein kinase genes, and discuss the potential outcome of such research in the context of drug development.     

Primary papillary serous carcinoma of the peritoneum: report of a case with diagnosis by fine needle aspiration and immunocytochemistry

BACKGROUND: Primary papillary serous carcinoma (PPSC) of the peritoneum is a rare neoplasm, histologically indistinguishable from papillary serous carcinoma of the ovary, which diffusely involves the peritoneum but spares or minimally invades the ovaries. To the best of our knowledge, the preoperative and the fine needle aspiration diagnosis of this disorder have not been reported before. CASE: A woman developed an extensive peritoneal neoplasm 4 years after hysterectomy and bilateral salpingo-oophorectomy for benign disease. Fine needle aspiration of the tumor was performed, and the cytologic and immunocytochemical findings were consistent with papillary serous carcinoma. A diagnosis of PPSC of the peritoneum was rendered because review of all slides from previous surgical specimens showed no evidence of carcinoma and no other primary tumors were found elsewhere. CONCLUSION: Fine needle aspiration cytology coupled with immunocytochemical and clinical data allows an unequivocal preoperative diagnosis of papillary serous carcinoma (primary peritoneal or with an ovarian origin). The sole limitation to establish a primary peritoneal origin before surgery is the requirement to histologically study the ovaries. Based on this fact, the preoperative fine needle aspiration cytology diagnosis of PSCP should be restricted to oophorectomized patients.     

Fungal Infections Associated with Travel

International travel is increasing. As fungal infections associated with travel are rare diseases, they are often underestimated and misdiagnosed. Thus, updated knowledge in this area is of key importance for physicians not only for pretravel counselling but also for the management of patients upon their return. We present an update of data published in 2012 and 2013. We present an overview of epidemiological changes, especially new endemic areas, and the implications of climate and natural disasters. Through experimental and clinical data, new insights into the pathophysiology of fungal infections associated with travel have been obtained, especially for Cryptococcus spp. Recently published diagnostic tools could lead to faster and more accurate diagnosis. Lastly, recent prognostic and therapeutic data are emphasized.     

A power-law rheology-based finite element model for single cell deformation

Physical forces can elicit complex time- and space-dependent deformations in living cells. These deformations at the subcellular level are difficult to measure but can be estimated using computational approaches such as finite element (FE) simulation. Existing FE models predominantly treat cells as spring-dashpot viscoelastic materials, while broad experimental data are now lending support to the power-law rheology (PLR) model. Here, we developed a large deformation FE model that incorporated PLR and experimentally verified this model by performing micropipette aspiration on fibroblasts under various mechanical loadings. With a single set of rheological properties, this model recapitulated the diverse micropipette aspiration data obtained using three protocols and with a range of micropipette sizes. More intriguingly, our analysis revealed that decreased pipette size leads to increased pressure gradient, potentially explaining our previous counterintuitive finding that decreased pipette size leads to increased incidence of cell blebbing and injury. Taken together, our work leads to more accurate rheological interpretation of micropipette aspiration experiments than previous models and suggests pressure gradient as a potential determinant of cell injury.     

Viral triggers of multiple sclerosis

Genetic and environmental factors jointly determine the susceptibility to develop Multiple Sclerosis (MS). Collaborative efforts during the past years achieved substantial progress in defining the genetic architecture, underlying susceptibility to MS. Similar to other autoimmune diseases, HLA-DR and HLA-DQ alleles within the HLA class II region on chromosome 6p21 are the highest-risk-conferring genes. Less-robust susceptibility effects have been identified for MHC class I alleles and for non-MHC regions. The role of environmental risk factors and their interaction with genetic susceptibility alleles are much less well defined, despite the fact that infections have long been associated with MS development. Current data suggest that infectious triggers are most likely ubiquitous, i.e., highly prevalent in the general population, and that they require a permissive genetic trait which predisposes for MS development. In this review article, we illustrate mechanisms of infection-induced immunopathologies in experimental animal models of autoimmune CNS inflammation, discuss challenges for the translation of these experimental data into human immunology research, and provide future perspectives on how novel model systems could be utilized to better define the role of viral pathogens in MS.     

Nosocomial lung infections in adult intensive care units

Nosocomial respiratory tract infections are the leading type of nosocomial infections. Despite the development of new antibiotic therapies, they are associated with an increased morbidity and mortality. Patients with comorbidities are especially predisposed to acquire these infections, as are patients exposed to respiratory therapy. Aspiration of colonized secretions from the oropharynx is the main mechanism of infection development. Barrier techniques to reduce aspiration and antimicrobial agents to alter bacterial flora are important in preventing pneumonia episodes. The initial institution of an adequate antibiotic regimen is a determinant of outcome. Nosocomial pneumonias are often difficult to treat due to antibiotic-resistant bacteria. Antibiotic policies are crucial in avoiding a progression in antibiotic resistance.     

S-RNase-mediated gametophytic self-incompatibility is ancestral in eudicots

The evolutionary relationship between self-incompatibility systems in different families of flowering plants has long been a topic of interest. Physiological differences in the mode of gene action and the enormous sequence differences between genes with different modes of action suggest that many instances of self-incompatibility have arisen independently. In contrast, previous analyses of the S-RNase associated with gametophytic self-incompatibility in the eudicot families (Solanaceae, Scrophulariaceae, and Rosaceae) have suggested that sequences within families form well-supported and distinct lineages. In this study we demonstrate that in fact, S-RNase-mediated gametophytic self-incompatibility evolved only once in the eudicots.     

Autoimmune haemolysis: an 18-year study of 865 cases referred to a regional transfusion centre.

Clinical and serological records of 865 patients with confirmed autoimmune haemolysis (AIH)--a much larger series than any previously reported--were critically reviewed nd analysed. A proposed new classification for AIH based on serological findings differs from traditional classifications in that a new category of "mixed" AIH has been defined in which both "warm" and "cold" autoantibodies are present, and both are capable of causing haemolysis. Patients in this mixed group tend to have severe disease that may run a chronic intermittent course. The presentation of cold agglutinin disease is much more variable than has been seen in previous studies, haemolysis due to low titre autoantibodies being common. The AIH associated with pregnancy, usually considered as being of bad prognosis, is often mild and self limiting in the absence of other associated disorders.     

Bacillus and relatives in foodborne illness

Species of Bacillus and related genera have long been troublesome to food producers on account of their resistant endospores. These organisms have undergone huge taxonomic changes in the last 30 years, with numbers of genera and species now standing at 56 and over 545, respectively. Despite this expansion, relatively few new species have been isolated from infections, few are associated with food and no important new agents of foodborne illness have been reported. What has changed is our knowledge of the established agents. Bacillus cereus is well known as a cause of food poisoning, and much more is now understood about its toxins and their involvement in infections and intoxications. Also, although B. licheniformis, B. subtilis and B. pumilus have occasionally been isolated from cases of food‐associated illness, their roles were usually uncertain. Much more is now known about the toxins that strains of these species may produce, so that their significances in such episodes are clearer; however, it is still unclear why such cases are so rarely reported. Another important development is the use of aerobic endosporeformers as probiotics, as the potentials of such organisms to cause illness or to be sources of antibiotic resistance need to be borne in mind.     

Pathology and first report of natural infections of the eye trematode Philophthalmus lachrymosus Braun, 1902 (Digenea, Philophthalmidae) in a non-human mammalian host

The avian eye trematode Philophthalmus lachrymosus Braun, 1902 is for the first time referred naturally occurring in a non-human mammalian host. Previously, natural infections with P. lachrymosus and other species of Philophthalmus have been occasionally reported from man, with few data on experimental infections of non-human mammals. Results presented here are related to the report of two cases of philophthalmosis due to natural infections of wild Brazilian capybaras, Hydrochaeris hydrochaeris L., 1766 with P. lachrymosus and associated pathology. Clinical signs, gross and microscopic lesions as well as new morphometric data on the parasite are presented.     

Time-dependent elastic extensional RBC deformation by micropipette aspiration: redistribution of the spectrin network?

The time dependence of small elastic extensional RBC deformation by micropipette aspiration has been analyzed. This process shows two-phases which are characterized by time constants of the order of some tenths of seconds and about ten seconds, respectively. The equilibrium tongue length is reached after about 30 s. For the first, fast step we assume that the membrane model of immobilized boundaries holds, i.e., the skeleton is tightly associated with the lipid bilayer and no redistribution of the skeleton with respect to the lipid bilayer is allowed. This lipid-spectrin interaction or anchorage is characterized by some association force density. It has been shown that at a given tongue length the force generated owing to the membrane deformation and acting to redistribute the spectrin, overcomes (in some membrane area) the association force density and results in an additional increase of the sucked membrane length. Equations have been derived to describe this process. From the experimental conditions of an RBC aspiration and the determined tongue length corresponding to the second slow aspiration step, the association force density between the lipid bilayer and the spectrin network may be determined. From literature data and our own results a force density of between 40 and 50 Pa has been estimated. Offprint requests to: D. Lerche     

Percutaneous Aspiration Lung Biopsy

A total of 182 percutaneous trans-thoracic aspiration biopsies were performed in 164 patients over a three-year period. In malignant neoplasms arising in the lung the diagnostic accuracy rate was 84%. In the non-malignant localized parenchymal lesions the accuracy drops considerably unless the lesion is cystic or cavitary. Some patients with non-parenchymal lesions were selected to assess further the value of this procedure. It proved much less rewarding in lesions of the chest wall, diaphragm and also in diffuse parenchymal disease. These lesions may be more accurately identified by other methods of biopsy. Lesions presenting as a mediastinal mass are an intermediate group and in selected cases helpful information can often be obtained by small-bore needle aspiration, particularly if a pericardial, bronchogenic or thymic cyst is suspected. Recent reports have shown that the aspiration of pulmonary lesions can be utilized to obtain viable tumour cells for chemosensitivity testing. The aspiration of nodular pulmonary lesions should be considered when a diagnosis is not forthcoming from the usual investigative means, since there has been little morbidity and no mortality in the series.     

Comparison of Techniques for the Production of Sclerotinia trifoliorum Ascospores in the Laboratory for Forage Legumes Resistance Tests

This study aimed to improve the production, under controlled conditions, of Sclerotinia trifoliorum ascospores to be used for selection tests on forage legumes. Sclerotia of this fungus, produced in the laboratory, were buried 1–2 cm deep in permanently soaked vermiculite, at T = 15°C, 12/24 h of fluorescent light, air moisture >80% in order to differentiate apothecia. The ascospores were harvested by aspiration and collected on a membrane filter. Various types of apparatus containing sclerotia have been tested for their ability to maintain live apothecia and for the facility of spore catching. The aspiration method has been found to be much more efficient than the previous method of cutting off apothecia. Moreover, it was observed that using this harvesting technique the best apparatus presented small and independent compartments (truncated plastic bottles). The ascospores can be stored, on the membrane filter at 5°C and in dry conditions in order to preserve their germinating abilityfor, a period of 3 months at least. This spore harvesting method permits avaibility of large quantities of a cheap inoculum for S. trifoliorum resistance test on forage legumes all year round.     

The population genetics of alleles affecting enzyme activity.

It is possible to predict the population genetics of allozymes by assuming that fitness is proportional to flux through a biochemical pathway. The model presented here extends previous work by incorporating two additional features of biological realism. Firstly, that more than one biochemical route may exist between any two metabolites. The major routes have been identified as the classical biochemical pathways but in the event of a mutation blocking a major route, minor routes become significant. These minor routes are named "bypass fluxes" and have profound effects on the population genetics of allozymes. Secondly, recent work has suggested that a metabolic cost is associated with enzyme synthesis; this will constitute an additional selective pressure on alleles which affect the amount of enzyme synthesized. The model generates a fitness curve which predicts the fitness associated with any level of enzyme activity. It can utilize data on null or near-null, structural or regulatory, mutations in the presence or absence of bypass fluxes. When data from natural populations of Drosophila are investigated, it is concluded that selection pressures acting on enzyme variants may be much higher than previously thought.