Gene flow in a facultative apomictic poacea, the savanna grass Hyparrhenia diplandra

The genetics of the poacea Hyparrhenia diplandra was studied in four natural populations from an ecological station in West Africa, where it makes up 80% of grasses from wet savanna and constitutes a dense continuum of randomly distributed individuals. DNA content and cytogenetical observations suggest it is an allotetraploid. Using two highly variable microsatellites (heterozygosity H = 0.615-0.616), we show that this species is an apomict with rare sexual reproduction events that account for approximately 0.5% of seeds pollinated in the wild. Hexaploid individuals were also produced, corroborating the observation of aberrant genotypes in the wild. The spatial extent of asexual clones in the field was low in comparison with the predominance of apomixis, thus indicating a low dispersal of seeds from their parent. Heterozygosity and departure from Hardy-Weinberg predictions were similar in the four populations, revealing a high apparent selfing rate s = 0.599 among sexually produced seeds. This is an overestimate since we could not distinguish true selfing from reciprocal outcrosses between neighboring individuals from the same apomictic clone. Gene flow by pollen could be substantial, possibly explaining the absence of isolation by distance in the studied area.     

Abnormal distribution of CD45 isoforms expressed by CD4+ and CD8+ T cells in rheumatoid arthritis

CD45RO+ T cells are referred to as memory or helper-inducer while CD45RA+ T cells are regarded as naive or suppressor-inducer T cells. The former population predominates in the peripheral blood and even more in the synovial fluid of patients with rheumatoid arthritis, to the expense of the latter population. Within the CD45RB+ compartment, there appears to be more of the fully-differentiated than of the early-differentiated CD4+ T cells. In spite of the fact that these lymphocytes are close to undergoing apoptosis, this programmed cell death is inhibited in the rheumatoid synovium.     

Neurosecretory systems in decapod Crustacea

Summary The sinus glands of the Brachyura are composed of swollen nerve fiber endings, which store and release secretory material synthesized within cells of the eyestalks, the brain and probably the thoracic ganglionic mass. Removal of the sinus glands from the land crab, Gecarcinus lateralis, does not induce molt, because sinus glands are reservoirs, not sources, of molt-inhibiting hormone. Increase in respiratory rate and fall in respiratory quotient, which follow eyestalk removal and signify the approach of molt, do not occur after sinus gland removal.From recent studies on the eyestalks and brain of the crayfish, Cambarus virilis, it is clear that morphologically the neurosecretory system of this crayfish is similar to that of the land crab. There is a marked resemblance in arrangement of neurosecretory cells and in pathways followed by the fibers, the endings of which form the sinus glands. Maps of eyestalks and brain of Cambarus and Gecarcinus emphasize this fundamental likeness between an astacuran and a brachyuran. Regions in which neurosecretory cells are found have been numbered so that these maps may guide cytological and physiological study on these species and on other decapod Crustacea.This paper was delivered at the Symposium on Neurosecretion held May 11–16, 1953, at the Stazione Zoologica, Naples, Italy. An abstract of this paper. together with summaries of other papers presented at the Symposium, is appearing in the Pubblicazioni della Stazione Zoologica di Napoli.The preparation of this paper was aided by a National Science Foundation (USA.) grant to the first author and by the use of the American Table at the Naples Zoological Station.     

A hybrid micro-macroevolutionary approach to gene tree reconstruction.

Gene family evolution is determined by microevolutionary processes (e.g., point mutations) and macroevolutionary processes (e.g., gene duplication and loss), yet macroevolutionary considerations are rarely incorporated into gene phylogeny reconstruction methods. We present a dynamic program to find the most parsimonious gene family tree with respect to a macroevolutionary optimization criterion, the weighted sum of the number of gene duplications and losses. The existence of a polynomial delay algorithm for duplication/loss phylogeny reconstruction stands in contrast to most formulations of phylogeny reconstruction, which are NP-complete. We next extend this result to obtain a two-phase method for gene tree reconstruction that takes both micro- and macroevolution into account. In the first phase, a gene tree is constructed from sequence data, using any of the previously known algorithms for gene phylogeny construction. In the second phase, the tree is refined by rearranging regions of the tree that do not have strong support in the sequence data to minimize the duplication/lost cost. Components of the tree with strong support are left intact. This hybrid approach incorporates both micro- and macroevolutionary considerations, yet its computational requirements are modest in practice because the two-phase approach constrains the search space. Our hybrid algorithm can also be used to resolve nonbinary nodes in a multifurcating gene tree. We have implemented these algorithms in a software tool, NOTUNG 2.0, that can be used as a unified framework for gene tree reconstruction or as an exploratory analysis tool that can be applied post hoc to any rooted tree with bootstrap values. The NOTUNG 2.0 graphical user interface can be used to visualize alternate duplication/loss histories, root trees according to duplication and loss parsimony, manipulate and annotate gene trees, and estimate gene duplication times. It also offers a command line option that enables high-throughput analysis of a large number of trees.     

Differential rates of glycoprotein secretion by isolated rat hepatocytes studied in terms of concanavalin A binding.

Using a concanavalin-A-based method which respects cell function, we have shown that the kinetics of glycoprotein secretion appear to depend on the nature of the oligosaccharide moiety. In 37 degrees C pulse/chase experiments using freshly isolated normal rat hepatocytes, we found that except for transferrin, whose rate of secretion was independent of its concanavalin A reactivity, the secretion of the concanavalin-A-retained forms of alpha 1 acid glycoprotein, T-kininogen, alpha 1 protease inhibitor and alpha 1 inhibitor III was slower than that of the concanavalin-A-non-retained forms. When hepatocytes were incubated at 20 degrees C, secretion was blocked with the accumulation of mainly endoglycosidase-H-sensitive forms. The secretion kinetics of the concanavalin-A-differentiated forms were still different when the temperature was shifted back to 37 degrees C. The divergence between the secretion rates of the concanavalin-A-differentiated forms would appear to be due to a late event in intracellular protein trafficking, which may depend on the sugar content and/or the number of carbohydrate chains of the glycoproteins.     

Chronic recordings of hypoglossal nerve activity in a dog model of upper airway obstruction.

The activity of the hypoglossal nerve was recorded during pharyngeal loading in sleeping dogs with chronically implanted cuff electrodes. Three self-coiling spiral-cuff electrodes were implanted in two beagles for durations of 17, 7, and 6 mo. During quiet wakefulness and sleep, phasic hypoglossal activity was either very small or not observable above the baseline noise. Applying a perpendicular force on the submental region by using a mechanical device to narrow the pharyngeal airway passage increased the phasic hypoglossal activity, the phasic esophageal pressure, and the inspiratory time in the next breath during non-rapid-eye-movement sleep. The phasic hypoglossal activity sustained at the elevated level while the force was present and increased with increasing amounts of loading. The hypoglossal nerve was very active in rapid-eye-movement sleep, especially when the submental force was present. The data demonstrate the feasibility of chronic recordings of the hypoglossal nerve with cuff electrodes and show that hypoglossal activity has a fast and sustained response to the internal loading of the pharynx induced by applying a submental force during non-rapid-eye-movement sleep.     

ADAPTIVE SEX ALLOCATION IN A SIMULTANEOUS HERMAPHRODITE

When applied to hermaphrodite organisms, the local mate competition hypothesis predicts an increase of the ratio of sperm to ova produced as the number of mates increases. Here we test this prediction using a hermaphroditic platyhelminth parasite (trematode), Echinostoma caproni. This worm inhabits the small intestine of vertebrates, inevitably inducing the formation of highly subdivided populations, a condition known to promote local mate competition. Moreover this echinostome exhibits an unrestricted mating pattern involving both selfing and outcrossing as well as multiple fertilizations. We quantified the investment in reproductive organs by estimations of testes, cirrus sac, ovary, and egg size and fecundity when echinostomes were isolated alone, in pairs, or in groups of 20 worms. Adult body size was also recorded as a covariate. When mating group size increases (singles, pairs, or groups) we observed a significant increase in resource allocation to male function in addition to a significant decrease in ovary size. Smaller ovaries do not seem to affect egg size, but do result in a reduction in fecundity. Finally, our results are in accordance with the expected theoretical relationship between male allocation and the number of potential mates given local mate competition.     

Detection and Identification by PCR of a Highly Virulent Phylogenetic Subgroup among Extraintestinal Pathogenic Escherichia coli B2 Strains

Closely related Escherichia coli B2 strains O1:K1, O2:K1, O18:K1, and O45:K1 constitute a major subgroup causing extraintestinal infections. A DNA pathoarray analysis was used to develop a PCR specific for this subgroup that was included in the multiplex phylogenetic-grouping PCR method. Our PCR may serve to identify this virulent subgroup among different ecological niches.