Establishment of gut fate in the E lineage of C. elegans: the roles of lineage-dependent mechanisms and cell interactions

The gut of C. elegans derives from all the progeny of the E blastomere, a cell of the eight cell stage. Previous work has shown that gut specification requires an induction during the four cell stage (Goldstein, B. (1992) Nature 357, 255-257). Blastomere isolation and recombination experiments were done to determine which parts of the embryo can respond to gut induction. Normally only the posterior side of the EMS blastomere contacts the inducing cell, P2. When P2 was instead placed in a random position on an isolated EMS, gut consistently differentiated from the daughter of EMS contacting P2, indicating that any side of EMS can respond to gut induction. Additionally, moving P2 around to the opposite side of EMS in an otherwise intact embryo caused EMS's two daughter cells to switch lineage timings, and gut to differentiate from the descendents of what normally would be the MS blastomere. The other cells of the four cell stage, ABa, ABp, and P2, did not form gut when placed in contact with the inducer. To determine whether any other inductions are involved in gut specification, timed blastomere isolations were done at the two and eight cell stages. In the absence of cell contact at the two cell stage, segregation of gut fate proceeded normally at both the two and four cell stages. Gut fate also segregated properly in the absence of cell contact at the eight cell stage. A model is presented for the roles of lineage-dependent mechanisms and cell interactions in establishing gut fate in the E lineage.     

L’adaptation parentale à la venue d’un nouvel enfant: Perspectives et prospectives.

Pregnancy and the birth of a child imply personal changes that require many individual, marital, and family adaptations (Mercer et al., 1988). The outcome of this transition will have implications for the welfare of the whole family. The area of research studying this type of adaptation has witnessed much theoretical and methodological progress in the last 10 years. Contemporary researchers are trying to identify the factors associated with this adaptation process (Gable et al., 1992). A more detailed conceptual model of parental and family adaptation is now starting to take form (Terry, 1991b). The recent proliferation of research on parental adjustment to the birth of a child justifies a review of recent studies in this area. What are the limits of the investigations in this area of interest? What modifications could be suggested to strengthen its empirical basis? What are the implications of a family perspective of parental transition? To answer these questions a review of the literature in this area will be presented. The theoretical, methodological, and clinical implications of a systemic perspective on parental adjustment will then be discussed. This paper will also highlight a number of methodological limits of recent studies and suggest recommendations for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparative analysis: a tool for studying monogenean ecology and evolution

The comparative approach has been used widely in evolutionary ecology during the last 10 years. In the first part of this study, taking monogeneans of Mediterranean marine fishes as an example, we highlight the pitfalls that may arise in interspecific studies. In the second part, the independent contrast method is used to control for phylogenetic effects in order to evaluate the determinants of monogenean species richness and their specificity. Our results show the importance of controlling data for both host sample size and phylogeny to avoid confounding effects. Thereafter, taking into account both sampling effort and phylogenetic effects, our results show that host size is the main factor affecting monogenean species richness and specificity.     

Nutritional and respiratory pathways to parasitism exemplified in the Turbellaria

Symbiosis is a dominant trait in the Platyhelminthes. The Neodermata (Aspidogastrea, Monogenea, Digenea, Udonellidea, Cestoda) are wholly parasitic and even the predominantly free-living Turbellaria have almost 200 species from 35 families living in permanent associations with other animals. In the simplest turbellarian symbioses, ectosymbiotes such as the Temnocephalida, some other Rhabdocoela and a few Tricladida live on the body surfaces or in the branchial chambers of their mainly arthropodan or chelonian hosts. They feed on the same types of prey as their free-living relatives but supplement their diet by opportunistic commensalism. Their digestive physiology and food reserves are the same as in free-living species. The entosymbiotic Umagillidae, Graffillidae, Pterastericolidae, Fecamplidae and Acholadidae live in internal body cavities or body wall derivatives of echinoderms, molluscs or arthropods and show increasing metabolic dependence on their hosts. Patterns of digestive physiology and food storage generally differ markedly from those of ectosymbiotic and free-living species. Some umagillids, in echinoids, feed as entozoic predators on co-symbiotic protozoa, supplemented by opportunistic ingestion of the hosts' ingesta, gut cells or coelomocytes. Others, in holothurians, feed mainly on gut cells, which also provide some digestive enzymes, and to a lesser extent on host ingesta and co-symbiotes. Graffillids, in molluscs, lack endogenous digestive enzymes and rely entirely on those taken in with host ingesta and gut tissues. Pterastericolids, in asteroids, similarly utilise gut tissues both as food and enzyme sources. The climax to metabolic dependence occurs in the Fecamplidae and Acholadidae. The former, in crustacean haemocoels and myzostomid tissues, lack conventional alimentary systems and absorb soluble nutrients through the epidermis. In the latter the only known species lives in the tube feet of its asteroid host, lacks a normal endodermal gut, but has a modified epidermis performing both digestive and absorptive functions. Most of these entosymbiotes show a shift from the lipid storage characteristic of free-living and ectosymbiotic species to the glycogen storage predominating in the Neodermata. In both groups this emphasis on carbohydrate metabolism is often independent of the PO2 of their environment. Both groups also show high fecundity and it is suggested that there is a direct relationship between this and glycogen storage. High fecundity, while clearly of adaptive value in entosymbiotes, is arguably primarily related to the assured food supply conferred by the entosymbiotic habit and thus can be viewed as a consequence of the latter rather than a prerequisite for it. Some entosymbiotic Turbellaria have evolved physiologically active haemoglobins, allowing them to abstract oxygen preferentially from host tissues; some have also evolved facultative glycolytic mechanisms comparable to those of the Cestoda. All these adaptations to ecto- and entosymbiotic life in the Turbellaria exemplify possible pathways to wholly parasitic lifestyles, with total metabolic dependence on the hosts, which may have been followed during the evolution of the Neodermata.     

Lower begging responsiveness of host versus parasitic brown-headed cowbird (Molothrus ater) nestlings is related to species identity but not to early social experience.

The survival of young brood parasites depends critically on their many adaptations to exploit hosts. Parasitic survival is particularly related to competitive superiority for foster parental care whenever host young are not destroyed in parasitized nests. Brown-headed cowbirds (Molothrus ater) are generalist obligate parasites whose early social environments are unpredictable regarding host species and numbers of nestmates. Young avian brood parasites typically beg more intensively and loudly than foster siblings, but an untested prediction is that young parasites are also more likely to respond by begging to a wider variety of stimulus types. Avian vocalizations were used in a playback experiment to stimulate begging behavior in cowbird hosts. Compared with age-matched cowbird nestlings, hosts begged less frequently to acoustic stimuli, and lower begging responsiveness was irrespective of whether hosts had been reared in parasitized nests. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Diversity of monogeneans in Southeast Asia

The diversity of monogeneans from Southeast Asia was examined using information from the literature to show their diversity at different taxonomic (subclass, family, genera, species) levels. Knowledge of monogeneans is still incomplete in Southeast Asia and the present numbers of monogeneans are likely an underestimate of what is present on/in aquatic organisms in the region, since so few hosts have been examined. An estimate of the possible numbers of monogeneans that could be present on/in fishes and turtles in Peninsular Malaysia indicates that only 8% of the monogeneans are presently known. Analysis of the available data on monogenean diversity (or species richness) at different taxonomic levels will provide useful information on their distribution patterns. There is an uneven distribution of investigations on this topic and Malayan fauna is considered to be representative of the Southeast Asian fauna. Southeast Asian (Sundaland) monogeneans are related (at the generic level) to the monogenean fauna of South China, India and Africa.     

Rape in non-human animals: An evolutionary perspective.

Rape-like behaviour has been documented in a number of species of animals. The purpose of this paper is to explain the evolutionary perspective on this behaviour. Several key concepts of modern evolutionary theory are first explained. Then the problem of defining rape in such a way that it is amenable to scientific study is discussed. Agonistic mating, altruistic mating, forced mating, and detrimental mating are defined in terms of costs and benefits to both male and female fitness. The introductory section concludes with a discussion of the role of genes in determining sexual behaviour and the nature of biological adaptations. Forced mating in orangutans, mallard ducks, and scorpionflies is described. The evolution of this behaviour is explained in terms of parental investment and sexual selection theory. Speculations on mechanisms that females might evolve to deal with this coercive male reproductive strategy conclude the paper. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Helminths of the Canadian toad, Bufo hemiophrys (Amphibia: Anura), from Alberta, Canada

Forty adult Bufo hemiophrys from Alberta, Canada, were examined for helminths. Four species were found: a trematode, Gorgoderina simplex, and 3 nematodes, Cosmocercoides variabilis, Oswaldocruzia pipiens, and Rhabdias americanus. Rhabdias americanus had the highest prevalence of helminths (73%); C. variabilis had the highest mean intensity (26+/-33 SD). Bufo hemiophrys represents a new host record for each species of helminth.     

Reproductive and teratologic effects of electromagnetic fields

The reproductive risks of electromagnetic fields (EMF) were evaluated based on an extensive review of the scientific literature pertaining to human epidemiologic studies, secular trend data, in vivo animal studies and in vitro studies, and biologic plausibility. The epidemiologic studies involving the reproductive effects of EMF exposures to human populations have included populations exposed to: (1) video display terminals (VDTs), and (2) power lines and household appliances. The clinical use of diagnostic MRI (magnetic resonance imaging) has been increasing, but there are few reports or studies of pregnant women or individuals of reproductive age who have been exposed to MRI, and whose reproductive performance has been evaluated. The population that has been studied most frequently are women exposed to VDTs, but their EMF exposures are extremely low and frequently are at the level of the ambient EMF in a house or office. The results of epidemiologic studies involving VDTs are generally negative for the reproductive effects that have been studied. Based on the number of studies, the exposure levels, and the fairly consistent results, it can be argued that VDT epidemiologic studies should no longer be given priority. There have been fewer studies concerned with the reproductive risks of power lines, electric substations, and home appliances. In some publications, positive findings for reproductive risks were reported, but the more consistent findings indicate that EMF, even at these higher exposures, do not generate a measurable increase in reproductive failures in the human population. When compared to other fields of human epidemiology, it is obvious that these studies have many difficulties. Exposures are rarely determined. Studies frequently involve small sample sizes and the investigators rarely have a combined expertise in EMF physics, engineering, and reproductive biology. Because of the allegation that there may be particular windows of frequency, wave shape, and intensity that may be deleterious, it is impossible to disregard low frequency EMF exposures as having no deleterious reproductive effects. Yet the epidemiologic data that are available would point in that direction. Secular trend data analysis of birth defect incidence data indicate that increasing generation of electric power during this century is not associated with a concomitant rise in the incidence of birth defects. There are over 70 EMF research projects dealing with animal and in vitro studies that are concerned with some aspect of reproduction and growth. Unfortunately, a large proportion of the embryology studies utilized the chick embryo and evaluated the presence or absence of teratogenesis after 48 to 52 hours of development.(ABSTRACT TRUNCATED AT 400 WORDS)     

Comfort care interventions in a preimplantation genetic testing program

The fields of human genetics and assisted reproductive technology (ART) have experienced many scientific advances over the past 50 years. The integration of these two clinical specialties has resulted in the ability to perform preimplantation genetic testing (PGT) on an embryo created through ART. This is a technology that can be used by individuals at risk for the transmission of a genetic disorder to prevent occurrence of the disorder in their child. Both the process of PGT and the life experiences that lead to the decision to use PGT stimulate many levels and types of discomfort. Holistic comfort care interventions performed by the nurse are uniquely designed to eliminate or reduce discomfort and to enable those at risk to utilize the available technologies to create healthy families.     

Age of onset of drug use and its association with DSM-IV drug abuse and dependence: results from the National Longitudinal Alcohol Epidemiologic Survey

Although adaptive explanations for menstruation go back at least twenty-five hundred years, in the last decade two new hypotheses have been advanced. The first suggests that menstruation evolved to cleanse the uterus of pathogens introduced by sperm, and the second argues that the function of endometrial regression (with the associated menstruation in humans) is to save energy by getting rid of tissue, rather than maintaining it in the absence of an available blastocyst. Both these suggestions may be questioned on the grounds that they do not take into account the physiology of the reproductive processes involved. Menstruation is not an independent physiological process and is unlikely to have been selected for independently of the evolutionary events that led to it. Furthermore, most primitive menstruating animals would have menstruated infrequently, and many may have reproduced or died without ever menstruating. In order to provide a context for understanding how menstruation may have come about, the evolution of the female vertebrate reproductive tract is briefly reviewed. In later stages, the coevolution of the embryo and uterus resulted in an intimate association between the trophoblast and the uterine blood vessels. As the embryo became more invasive, the uterus responded with increased cellular growth and differentiation of the endometrium to accommodate it. This reached its peak in mammals (such as rodents and humans), where the embryo passes through the epithelium into the endometrial stroma, which responds with differentiation of cells and blood vessels. Progesterone, secreted after ovulation, plays a crucial role in preparation for pregnancy. In addition to its well-known effects on the uterus, progesterone may be important in suppressing the inflammatory reaction that would be expected in response to the presence of a foreign body, such as an embryo. It is also suggested that vascular and cellular differentiation of the endometrial stroma has evolved by adaptation of the inflammatory (granulation tissue) reaction. When progesterone levels fall at the end of the cycle, there is tissue breakdown and bleeding. The uterus then reforms for the next ovulatory cycle. It is shown that the female reproductive tract has multiple functions that must occur in sequence. The coevolution of the embryo and maternal tract thus led to the close contact of two genetically different tissues, and problems such as the inflammatory reaction had to be overcome. Menstruation is a necessary consequence of these evolutionary changes, and needed no adaptive value in order to evolve.     

Diversity "down under": monogeneans in the Antipodes (Australia) with a prediction of monogenean biodiversity worldwide

There are approximately 25,000 species of fishes known in the world. The Monogenea are believed to be among the most host-specific of parasites and if each species of fish is host to a different species of monogenean, there could be almost 25,000 monogenean species on Earth. Currently, I estimate that between 3000 and 4000 of these are described. Australia has a rich marine fish fauna with approximately 3500 species of teleosts. If the same formula of one monogenean species per host fish species is applied, Australia marine fishes could host potentially 3500 species of monogeneans. The first monogenean species described from Australia was Encotyllabe pagrosomi MacCallum, 1917 and approximately 300 more species have since been described from the continent. Even in a region of Australia such as Heron Island on the Great Barrier Reef that has been a focus of sustained research on these parasites, only about 85 species are described from 40 of the most common, easily-caught species of fish. Reasons are discussed for the relatively small numbers of monogenean species described so far from Australia. Endemicity is difficult to judge, but only one is certain: Concinnocotyla australensis (Polystomatidae) from Neoceratodus forsteri (Dipnoi). Despite reductions in research funding, the value of parasite taxonomy must not be underestimated, particularly in regions of the world that have a rich diversity of potential hosts.     

The intestine as an immunological organ]

The intestinal mucosa is in close contact with a large number of foreign antigens and mitogenic substances in the gut lumen. To protect the host against invasion of potential pathogens or an inappropriate immune response to the enormous number of antigens, a highly specialized immune system in the intestinal mucosa has developed, the so-called gut-associated lymphoid tissue (GALT). The passage of viable bacteria from the gastrointestinal tract through the epithelial mucosa is called bacterial translocation. Bacterial translocation in critically ill patients may lead to a significant incidence of systemic sepsis. This has attracted much clinical interest, as it has been shown that disturbances of the GALT and malnutrition itself, impair various aspects of barrier function. Enteral nutrition seems to be superior to parenteral nutrition in maintaining the functional barrier of the gut. Defined dietary variable (fibre, glutamine) influence bacterial translocation. Future therapeutic strategies should therefore concentrate on early enteral feeding in traumatised patients to reduce the incidence of bacterial translocation and septic complications.     

Efficacy of various therapeutic regimens in eliminating Pasteurella pneumotropica from the mouse

Pasteurella pneumotropica, a gram-negative opportunistic pathogen, can be isolated from the oropharynx, intestinal tract, and reproductive tract of clinically normal mice and has been associated with various clinical syndromes, including conjunctivitis, infections of the reproductive tract, otitis, and subcutaneous abscess formation. Enrofloxacin, a fluoroquinolone bactericidal antimicrobial, has been shown to be effective in eliminating P. multocida from rabbits. We sought to determine whether enrofloxacin would eliminate P. pneumotropica from mice known to be asymptomatically infected with the agent. Pasteurella pneumotropica-positive (culture and immunofluorescence assay) male (n = 55) and female (n = 55) C57BL/6N mice were randomly assigned to one of seven treatment groups or to a control group. These groups were designed to evaluate the efficacy of enrofloxacin administered orally via the drinking water or parenterally at three dosages (8.5, 25.5, and 85.0 mg/kg of body weight per day) over a 14-day treatment period. A tetracycline-treated group (60 mg/kg per day) and an untreated control group were included for comparisons. Repeated oropharyngeal swab and fecal specimens were obtained for culture through posttreatment day 30, and specimens from numerous enteric and reproductive organs collected during necropsy were used to evaluate group differences. Enrofloxacin eliminated evidence of P. pneumotropica from all sites when administered at 25.5 or 85 mg/kg but not at 8.5 mg/kg by either route for at least 30 days after treatment. Tetracycline-treated and control groups remained consistently culture-positive throughout the study. We concluded that the oral route may be a more practical method for treating large numbers of mice. Enrofloxacin may be a practical and inexpensive alternative to cesarian rederivation or embryo transfer for the elimination of P. pneumotropica in mice.     

Inhibition of migration of neural crest-derived cells by the abnormal mesenchyme of the presumptive aganglionic bowel of ls/ls mice: analysis with aggregation and interspecies chimeras

The terminal bowel is congenitally aganglionic in ls/ls mice. The condition has been associated with an overabundance of laminin and other matrix molecules. Aggregation ls/ls<==>C3H chimeric mice and interspecies mouse<==>quail chimeras were constructed to test the hypothesis that the aganglionosis arises because the ls/ls gut and not the neural crest is abnormal. Demonstration of beta-glucuronidase activity permitted genotypically ls/ls and C3H cells to be distinguished in the ls/ls<==>C3H chimeras. Aganglionosis did not occur in the ls/ls<==>C3H mice and ls/ls neurons were observed in the terminal bowel. Following bactransplantation of control segments of mouse gut into quail host embryos, mouse cells migrated to host targets normally colonized by cells from the neural crest; moreover, quail crest-derived cells entered the mouse gut. In contrast, cells did not migrate to these targets from presumptive aganglionic ls/ls bowel and quail crest-derived cells neither entered the ls/ls gut nor migrated through it. Laminin immunoreactivity was present in the backgrafts of murine colon and was far more abundant and widespread in those from ls/ls than in those from control animals. These data suggest that the presumptive aganglionic ls/ls bowel does not contain crest-derived cells because these cells, which are normal in ls/ls mice, do not enter it. This failure of colonization may be related to the premature formation of neurons outside the abnormal gut, a response that may be promoted by the excessive secretion of laminin by the ls/ls enteric mesenchyme.     

Effect of methoxychlor on implantation and embryo development in the mouse

Methoxychlor (MXC) has been shown to have adverse effects on reproductive functions. However, it has not been fully determined whether the effects of MXC on reproduction are due to its estrogenic or antiestrogenic effects. Therefore, to further elucidate the estrogenic action of this pesticide in the mouse, we studied the effect of MXC on implantation and embryo development. MXC was found to initiate implantation in most delayed implanting mice at 400 microg/g body weight. However, at the higher dose of 800 microg/g body weight, MXC initiated implantation in only 50% of animals and the number of embryos implanting was significantly decreased (P < 0.05). It was determined that MXC inhibited implantation in intact pregnant mice only when given on Day 1 or Day 2 at 800 microg/g but not at lower doses or later in the preimplantation period. Embryonic development and transport were delayed on Days 3 and 4 in these animals. Finally, reciprocal embryo transfers with donor embryos recovered from MXC-treated animals (800 microg/g body weight on Day 1) transferred to untreated recipients resulted in no implantation compared to 79% implantation when donor embryos were treated with vehicle. These data indicate that MXC acts as an estrogen agonist at the level of the uterus and oviduct but as an antiestrogen in the ovary. In addition, MXC appears to alter normal preimplantation embryonic development. These results suggest the need for further studies to assess the mechanism of action of MXC in preimplantation embryos.     

Significance of intestinal inflammation in the pathogenesis of spondylarthropathies

The concept of spondylarthropathy (SpA) gathers together a group of chronic diseases with common clinical, biological, genetic and therapeutic characteristics. The concept forms a distinct entity, different from other rheumatic diseases. The target organs are not only the joint, but also the axial skeleton, the enthesis, the eye, the gut, the urogenital tract, the skin and sometimes the heart. The prevalence of this entity in the general population is estimated 1%, equal to the prevalence of rheumatoid arthritis. Genetical predisposition (HLA-B27) is one of the clues to the pathogenesis of the disease. Since reactive arthritis is induced by specific urogenital or enterogenic bacteria, and since the gut is implied in different forms of spondylarthropathies, especially in IBD, it was clear that the gut could play an important role by permitting exogenous factors to enter the body. This hypothesis was the rationale for investigating the gut in the spondylarthropathies by performing ileo-colonoscopies. In the first ileo-colonoscopic studies of SpA patients, histological signs of gut inflammation were found in a relatively great number of patients, mostly not presenting any clinical intestinal manifestations. These lesions were not seen in other inflammatory joint diseases. Further ileo-colonoscopic studies confirmed the strong relationship between gut and joint inflammation. In patients in whom a second ileo-colonoscopy was performed, remission of the joint inflammation was always connected with a disappearance of the gut inflammation, whereas persistence of locomotor inflammation was mostly associated to the persistence of gut inflammation. The hypothesis was proposed that some patients with a spondylarthropathy had a form of subclinical Crohn's disease in which the locomotor inflammation was the only clinical expression. This hypothesis was confirmed in prospective long-term studies in which the ileo-colonoscopied patients were reviewed 2 to 9 years later:about 6% of SpA patients not presenting any sign of Crohn's disease at first investigation but demonstrating gut inflammation on biopsy, developed full-blown Crohn's disease. By performing electronmicroscopy it was described that in patients with SpA the number of membranous (M) cells, which are scarce in normal ileum, is increased in number in inflamed mucosa. They showed a thin rim of cytoplasm covering groups of lymphocytes. In chronic inflammatory lesions necrotic M-cells, rupture of M-cells and lymphocytes entering the gut lumen was observed. The bursting of M-cells at the top of the lymphoid follicles leads to interruption of the gut epithelial lining and gives the luminal content access to the lymphoid tissue. This can be responsible for an exponential increase of local antigen stimulation. Accelerated luminal antigen presentation through a break in the epithelial layer, together with cytokines released from activated monocytes, might induce a second line of defense aiming at elimination of the massive antigen penetration into the mucosa. The postulated switch from secretory local immunity to a systemic type of local immune reaction could have different consequences:the local down-regulation of J chain in the IgA immunocytes could shift the production of polymeric IgA to monomers, jeopardizing secretory immunity; the disproportionate increase of IgG-producing cells could favor further inflammation and tissue damage through complement activation and arming of the killer cells, and cause autoimmune responses locally and in target organs at a distance (e.g. joint organs). The discovery of subclinical gut inflammation in the SpA had therapeutic consequences. Sulphasalazine (SASP) has been proven to be an active drug in the treatment of IBD. Since the gut could play a crucial role in SpA, it was logic to use this drug in the treatment of this disease. Multiple open and double-blind studies have proven the effectiveness of this drug in SpA.     

Concurrent invaders--four exotic species of Monogenea now established on exotic freshwater fishes in Australia

Four species of exotic monogeneans are reported from five species of exotic freshwater fish in Australia: Gytrodactylus bullatarudis from Poecilia reticulata and Xiphophorus helleri in Queensland; Gyrodactylus macracanthus from Misgurnus anguillicaudatus in the Australian Capital Territory; Dactylogyrus extensus from Cyprinus carpio in the Australian Capital Territory; and Dactylogyrus anchoratus from Carassius auratus in the Australian Capital Territory. This is the first published record of described species of monogeneans of the genus Dactylogyrus or Gyrodactylus from Australia and the first report of parasites of M. anguillicaudatus in Australia. The establishment of exotic monogenean populations on Australian native fishes via host-switching is considered less likely than for other parasitic groups due to the generally high host-specificity of monogeneans, combined with the phylogenetic dissimilarity of native and exotic fishes. Similar establishments have occurred elsewhere, however, and the risk of these events increases with each new fish species introduction.