Differential expression of conserved germ line markers and delayed segregation of male and female primordial germ cells in a hermaphrodite, the leech helobdella.

In sexually reproducing animals, primordial germ cells (PGCs) are often set aside early in embryogenesis, a strategy that minimizes the risk of genomic damage associated with replication and mitosis during the cell cycle. Here, we have used germ line markers (piwi, vasa, and nanos) and microinjected cell lineage tracers to show that PGC specification in the leech genus Helobdella follows a different scenario: in this hermaphrodite, the male and female PGCs segregate from somatic lineages only after more than 20 rounds of zygotic mitosis; the male and female PGCs share the same (mesodermal) cell lineage for 19 rounds of zygotic mitosis. Moreover, while all three markers are expressed in both male and female reproductive tissues of the adult, they are expressed differentially between the male and female PGCs of the developing embryo: piwi and vasa are expressed preferentially in female PGCs at a time when nanos is expressed preferentially in male PGCs. A priori, the delayed segregation of male and female PGCs from somatic tissues and from one another increases the probability of mutations affecting both male and female PGCs of a given individual. We speculate that this suite of features, combined with a capacity for self-fertilization, may contribute to the dramatically rearranged genome of Helobdella robusta relative to other animals

Gender-Based Persecution: Does United States Law Provide Women Refugees with a Fair Chance?

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Electrophysiology of the Somatic Muscles in the Nematode Ascaris lumbricoides

The electrical activity of the somatic muscles of the parasitic nematode Ascaris lumbricoides has been investigated. The functional muscle syncytium overlying the nerve cord is preferentially excited by anodal stimulation with an extracellular electrode. Cathodal stimulation preferentially excites the nerve cord, allowing determination of separate conduction velocities for the nerve cord and syncytium. The propagation velocity of the nerve cord is 16.2 ± 1.2 cm/sec; that of the syncytium varies with the calcium concentration, being 21.6 ± 1.3 cm/sec for unitary slow waves under normal conditions. Both values are too high to account for the propagation of contractile waves in the intact animal. Ascaris muscle gives rise to complex spontaneous depolarizations consisting of slow waves and graded spike potentials. Often, the spikes and slow waves are modulated into periodic bursts of electrical activity, which gives rise to rhythmic contractions on a behaviorally significant time scale. Spikes appear to be mediated exclusively by calcium ions the spike active potential varies with calcium concentration as expected for a calcium electrode and spikes persist in sodium-free media. Slow waves can be mediated by either sodium or calcium ions; they persist when calcium or sodium are removed separately, but not when both are removed together. In rhythmically active preparations, a burst of slow waves and spikes accompanies each contraction. The modulation shows dorsal-ventral coordination if the right lateral line is intact, in accord with known nervous system asymmetry. Anterior-posterior coordination is also observed.</p

Basic skills and global competencies for business major graduates

A task of achieving academic success by business students becomes of paramount importance in our times, as globalization puts high pressures on our national priorities in education and workforce training. The projected shortage of skilled workers for the global economy elevates concerns about our economic growth and competitiveness in the world. This article is built upon research (Weisblat, 2010) that had achieved two objectives. First, through the reviewed literature, basic skills and global competencies required from business major graduates in the global economy were identified. Second, perspectives of college educators and business leaders on the required skills and competencies were captured. The researchers compared these perspectives in order to answer the question of whether business schools are successful in producing “knowledge workers” (Drucker, 1996) for the global economy. This purpose was achieved by utilizing a grounded theory outlined by Charmaz (2006).Such comparison of educators’ and business leaders’ views shed light on the issues of effectiveness of business education and employers’ satisfaction with the business graduates’ academic preparation. The study revealed significant differences in educators’ and employers’ understanding of what skills make business graduates competitive in the 21st century, and what skills, accordingly, should educators teach. Implications for practice were recognized, based on the findings of this study, including the need for extensive collaboration and greater input from business leaders into the design of curriculum that fits the rapidly evolving global economy

What Role Do Annelid Neoblasts Play? A Comparison of the Regeneration Patterns in a Neoblast-Bearing and a Neoblast-Lacking Enchytraeid Oligochaete

The term ‘neoblast’ was originally coined for a particular type of cell that had been observed during annelid regeneration, but is now used to describe the pluripotent/totipotent stem cells that are indispensable for planarian regeneration. Despite having the same name, however, planarian and annelid neoblasts are morphologically and functionally distinct, and many annelid species that lack neoblasts can nonetheless substantially regenerate. To further elucidate the functions of the annelid neoblasts, a comparison was made between the regeneration patterns of two enchytraeid oligochaetes, Enchytraeus japonensis and Enchytraeus buchholzi, which possess and lack neoblasts, respectively. In E. japonensis, which can reproduce asexually by fragmentation and subsequent regeneration, neoblasts are present in all segments except for the eight anterior-most segments including the seven head-specific segments, and all body fragments containing neoblasts can regenerate a complete head and a complete tail, irrespective of the region of the body from which they were originally derived. In E. japonensis, therefore, no antero-posterior gradient of regeneration ability exists in the trunk region. However, when amputation was carried out within the head region, where neoblasts are absent, the number of regenerated segments was found to be dependent on the level of amputation along the body axis. In E. buchholzi, which reproduces only sexually and lacks neoblasts in all segments, complete heads were never regenerated and incomplete (hypomeric) heads could be regenerated only from the anterior region of the body. Such an antero-posterior gradient of regeneration ability was observed for both the anterior and posterior regeneration in the whole body of E. buchholzi. These results indicate that the presence of neoblasts correlates with the absence of an antero-posterior gradient of regeneration ability along the body axis, and suggest that the annelid neoblasts are more essential for efficient asexual reproduction than for the regeneration of missing body parts

Neuroglial ATP release through innexin channels controls microglial cell movement to a nerve injury

Microglia, the immune cells of the central nervous system, are attracted to sites of injury. The injury releases adenosine triphosphate (ATP) into the extracellular space, activating the microglia, but the full mechanism of release is not known. In glial cells, a family of physiologically regulated unpaired gap junction channels called innexons (invertebrates) or pannexons (vertebrates) located in the cell membrane is permeable to ATP. Innexons, but not pannexons, also pair to make gap junctions. Glial calcium waves, triggered by injury or mechanical stimulation, open pannexon/innexon channels and cause the release of ATP. It has been hypothesized that a glial calcium wave that triggers the release of ATP causes rapid microglial migration to distant lesions. In the present study in the leech, in which a single giant glial cell ensheathes each connective, hydrolysis of ATP with 10 U/ml apyrase or block of innexons with 10 µM carbenoxolone (CBX), which decreased injury-induced ATP release, reduced both movement of microglia and their accumulation at lesions. Directed movement and accumulation were restored in CBX by adding ATP, consistent with separate actions of ATP and nitric oxide, which is required for directed movement but does not activate glia. Injection of glia with innexin2 (Hminx2) RNAi inhibited release of carboxyfluorescein dye and microglial migration, whereas injection of innexin1 (Hminx1) RNAi did not when measured 2 days after injection, indicating that glial cells’ ATP release through innexons was required for microglial migration after nerve injury. Focal stimulation either mechanically or with ATP generated a calcium wave in the glial cell; injury caused a large, persistent intracellular calcium response. Neither the calcium wave nor the persistent response required ATP or its release. Thus, in the leech, innexin membrane channels releasing ATP from glia are required for migration and accumulation of microglia after nerve injury