Conjugation Involving Dividing Cells of Tetrahymena thermophila

Feulgen-stained preparations of mixtures of starved Tetrahymena thermophila cells of complementary mating types have revealed an atypical form of conjugation involving cells which have completed the nuclear events of cell division, but have not undergone cytokinesis. Both micronuclei in the dividing cells are induced to undergo meiosis, but in 21 of 23 cases, the anterior micronucleus was activated 1st, suggesting that the meiotic inducer is synthesized near the mating junction and diffuses posteriad. Despite the induction of two micronuclei, “triad” conjugants appear to regulate nuclear events so as to produce a normal outcome.     

HANDS-FREE, "POP-UP," ADHESIVE TAPE METHOD FOR MICROBIAL SAMPLING OF MEAT SURFACES

Microbial contamination of food is a concern to both food producers and consumers. For the food production industry surface sampling of foods is one of the simplest ways to monitor the microbial load. The objective of this experiment was to investigate the feasibility of using the less expensive and quicker "Pop-up" tape method instead of the conventional swab/rinse method for the microbial sampling of meat surfaces. An analyst can place the unit on the wrist and then use both hands to lay out all the necessary materials and take the sample with one hand. The "Pop-up" tape method was able to measure microbial loads up to 2.2 log CFU/cm² on meat surfaces. The conventional swab/rinse method was able to measure up to 8.3 log CFU/cm² on meat surfaces. The correlation coefficient (R) between the two methods was 0.91 (n=42). These data show that the "Pop-up" tape method is a viable alternative to other methods for estimating microbial surface contamination.     

Septata Intestinalis N. G., N. Sp., an Intestinal Microsporidian Associated With Chronic Diarrhea and Dissemination In Aids Patients

ABSTRACT. Intestinal microsporidiosis in patients diagnosed with acquired immunodeficiency syndrome (AIDS) and having chronic diarrhea was first reported in 1985 and the associated microsporidian was named Enterocytozoon bieneusi. the intracellular developmental cycle of E. bieneusi in enterocytes has been demonstrated and many cases have been reported worldwide. This report presents the life cycle of a second intestinal microsporidian, associated with the same symptoms, in five AIDS patients. This new microsporidian also infects enterocytes but its pathology and morphology differ from that of E. bieneusi. It involves lamina propria macrophages, fibroblasts, and endothelial cells and can disseminate to infect other parts of the body, e.g. the kidney and gall bladder. the parasite cycle includes development of rounded uninucleate and elongated bi- or tetranucleate cells without the formation of plasmodial stages. Sporogony is similar to the more typical development of microsporidia with sporoblast morphogenesis occurring after the last cell division. the development of cells within chambers of a septate, honeycomb-like, parasite-secreted fibrillar network and surrounded by a parasitophorous vacuole, however, is unique to this microsporidian, justifying the establishment of a new genus and species, Septata intestinalis n. g., n. sp.     

Insights on Species Richness and Turnover from Long-Term Ecological Research: Fishes in North Temperate Lakes

SYNOPSIS. We examined eleven years of annual survey data onfish assemblages in seven lakes. Expectations based on biogeographicliterature were that, owing to the isolation of lakes, fishspecies structure should be relatively stable and species turnoverlow. Our original objective was to determine whether lakes houserelatively stable fish assemblages or ones with high rates ofspecies turnover. Methodological issues became apparent thatcaused us to consider issues of rare species and sample sufficiency.Ourdata were from samples rather than complete counts and rarespecies could have been missed. In our results mean annual richnesswas considerably lower than cumulative richness. In addition,species turnover was overestimated and decreased exponentiallyas the number of yearsbetween observation increased. Samplingvariability might explain these results; however, given thesame number of survey years, cumulative richness increased withthe number of years between observations. Apparently extinctionsand invasions occurred even within eleven years, but uncertaintyremains because rare taxa can be missed and their appearancesand disappearances in the record influence estimates of richnessand turnover. To compensate for this problem we removed raretaxa and corrected turnover rates by removing an estimate ofsampling error (the turnover rate between adjacent years). Evenusing these conservative approaches, estimates of turnover amonglakes ranged from 0.36% to 0.50% per year. Because the thresholdfor species detection by most sampling regimes is greater thanzero, survey data are expected to underestimate species richnessand overestimate species turnover even with standardized methods.Conservation biologists should evaluate claims of decline inspecies richness against such considerations     

A developmental study of the phylloclades of Ruscus aculeatus L.

Lateral phylloclades of Ruscus aculeatus are found in the axils of reduced scale leaves on the orthotropic, photosynthetic stem. The terminal phylloclade results from the elongation and flattening of the main shoot apex after the lateral appendages have been initiated. Studies of the development of both lateral and terminal phylloclades point to their cauline nature. The hypothesis that the phylloclade results from the congenital fusion of a reduced short shoot and its prophyll is not supported.     

Plant sugars are crucial players in the oxidative challenge during abiotic stress: extending the traditional concept

Plants suffering from abiotic stress are commonly facing an enhanced accumulation of reactive oxygen species (ROS) with damaging as well as signalling effects at organellar and cellular levels. The outcome of an environmental challenge highly depends on the delicate balance between ROS production and scavenging by both enzymatic and metabolic antioxidants. However, this traditional classification is in need of renewal and reform, as it is becoming increasingly clear that soluble sugars such as disaccharides, raffinose family oligosaccharides and fructans – next to their associated metabolic enzymes – are strongly related to stress‐induced ROS accumulation in plants. Therefore, this review aims at extending the current concept of antioxidants functioning during abiotic stress, with special focus on the emanate role of sugars as true ROS scavengers. Examples are given based on their cellular location, as different organelles seem to exploit distinct mechanisms. Moreover, the vacuole comes into the picture as important player in the ROS signalling network of plants. Elucidating the interplay between the mechanisms controlling ROS signalling during abiotic stress will facilitate the development of strategies to enhance crop tolerance to stressful environmental conditions.     

Cryobanking of viable biomaterials: implementation of new strategies for conservation purposes

Cryobanking, the freezing of biological specimens to maintain their integrity for a variety of anticipated and unanticipated uses, offers unique opportunities to advance the basic knowledge of biological systems and their evolution. Notably, cryobanking provides a crucial opportunity to support conservation efforts for endangered species. Historically, cryobanking has been developed mostly in response to human economic and medical needs — these needs must now be extended to biodiversity conservation. Reproduction technologies utilizing cryobanked gametes, embryos and somatic cells are already vital components of endangered species recovery efforts. Advances in modern biological research (e.g. stem cell research, genomics and proteomics) are already drawing heavily on cryobanked specimens, and future needs are anticipated to be immense. The challenges of developing and applying cryobanking for a broader diversity of species were addressed at an international conference held at Trier University (Germany) in June 2008. However, the magnitude of the potential benefits of cryobanking stood in stark contrast to the lack of substantial resources available for this area of strategic interest for biological science — and society at large. The meeting at Trier established a foundation for a strong global incentive to cryobank threatened species. The establishment of an Amphibian Ark cryobanking programme offers the first opportunity for global cooperation to achieve the cryobanking of the threatened species from an entire vertebrate class.     

Montane barriers to gene flow of Melanoplus bivittatus (Orthoptera: Acrididae)*

To determine the effectiveness of montane barriers to gene flow of the two-striped grasshopper, Melanoplus bivittatus, collections were made at four sites at the corners of a square location, each bisected by one of five Colorado mountains (total: five locations, 18 sites). The premise of this design is that samples from opposite sides of an effective barrier should have more genotypic differences than samples from the same side. Genotypic differences were measured for each grasshopper as 18 morphological measurements and six enzyme loci. Dissimilarities in morphology or enzyme loci were expressed as significant estimates of Mahalanobis squared distance (respectively, D² or G²) between two sample sites. The presence of foothills had no influence on the number of significant G² (age and sex classes combined) or significant D² (age and sex classes separated). For samples near the foothills, adult females had more significant D² than adult males. For samples near the two higher mountains, adult males had more significant D² for site samples from opposite sides. A combination of gene flow and selection is the most plausible explanation for most of these results.     

The brain of Echiniscus viridissimus Peterfi, 1956 (Heterotardigrada): a key to understanding the phylogenetic position of tardigrades and the evolution of the arthropod head

The brain of Echiniscus viridissimus , Peterfi, 1956 is composed of a series of orthogonally arranged neuropils. The most anterior neuropils are rireumbuccal, positioned dorso-and ventrolateral to the buccal tube and are associated with ganglia for sensory receptors of the mouth cone. Posterior to these are neuropils and ganglia for the (1) internal cirri and (2) cephalic papillae, external cirri, cirri A and clavae. They are joined by two pairs of vertical tracts to neuropils lateral to the buccal tube. A model based on the postcephalic organization of the tardigrade nervous system is used to propose a transformation of segmental ganglia that gives an arrangement congruent with the pattern of neuropils in the brain. The analysis suggests that the brain is derived from nervous elements of four segments with the fourth segment having contributed paired dorsal ganglia and their connecting vertical tracts to the first trunk ganglia of the ventral chain. The organization of the head of tardigrades is compared with that of other lobopods and arthropods and several possible key evolutionary innovations are offered. In addition homologous characters for the heads of tardigrades and other lobopods and arthropods are proposed and the nomenclature for the tardigrade cephalic nervous system is discussed.