cdc25 is a nuclear protein expressed constitutively throughout the cell cycle in nontransformed mammalian cells

A family of proteins homologous to the cdc25 gene product of the fission yeast bear specific protein tyrosine phosphatase activity involved in the activation of the p34cdc2-cyclin B kinase. Using affinity-purified antibodies raised against a synthetic peptide corresponding to the catalytic site of the cdc25 phosphatase, we show that cdc25 protein is constitutively expressed throughout the cell cycle of nontransformed mammalian fibroblasts and does not undergo major changes in protein level. By indirect immunofluorescence, cdc25 protein is found essentially localized in the nucleus throughout interphase and during early prophase. Just before the complete nuclear envelope breakdown at the prophase-prometaphase boundary, cdc25 proteins are redistributed throughout the cytoplasm. During metaphase and anaphase, cdc25 staining remains distributed throughout the cell and excludes the condensed chromosomes. The nuclear locale reappears during telophase. In light of the recent data describing the cytoplasmic localization of cyclin B protein (Pines, J., and T. Hunter. 1991. J. Cell Biol. 115:1-17), the data presented here suggest that separation in two distinct cellular compartments of the cdc25 phosphatase and its substrate p34cdc2-cyclin B may be of importance in the regulation of the cdc2 kinase activity.     

Simultaneous purification of DNA topoisomerase I and II from eukaryotic cells

We have developed a procedure for the simultaneous purification of DNA topoisomerase I and II from calf thymus. Both enzymes were first extracted from isolated nucleoprotein complexes. After batchwise chromatography on hydroxylapatite the two enzyme activities were separated on a FPLC phenylsuperose column. The enzymes were further purified by a second chromatography on phenylsepharose (topo I) or FPLC Mono Q (topo II). The purification can be finished within three days, yielding 0.5-1.0 mg quantities of homogeneous, enzymatic active preparations of the two proteins from 200 g of starting material.     

Transition from marine to terrestrial ecologies: changes in olfactory and tritocerebral neuropils in land-living isopods

In addition to the ancestors of insects, representatives of five lineages of crustaceans have colonized land. Whereas insects have evolved sensilla that are specialized to allow the detection of airborne odors and have evolved olfactory sensory neurons that recognize specific airborne ligands, there is so far little evidence for aerial olfaction in terrestrial crustaceans. Here we ask the question whether terrestrial Isopoda have evolved the neuronal substrate for the problem of detecting far-field airborne chemicals. We show that conquest of land of Isopoda has been accompanied by a radical diminution of their first antennae and a concomitant loss of their deutocerebral olfactory lobes and olfactory computational networks. In terrestrial isopods, but not their marine cousins, tritocerebral neuropils serving the second antenna have evolved radical modifications. These include a complete loss of the malacostracan pattern of somatotopic representation, the evolution in some species of amorphous lobes and in others lobes equipped with microglomeruli, and yet in others the evolution of partitioned neuropils that suggest modality-specific segregation of second antenna inputs. Evidence suggests that Isopoda have evolved, and are in the process of evolving, several novel solutions to chemical perception on land and in air.     

Parasites of fishes in the recently inundated ephemeral Lake Liambezi,Namibia

Lake Liambezi forms the periodic connection between the upper Zambezi, Kwando and Okavango rivers. A full parasitological assessment was conducted on 86 fish, representing 14 species in six families sampled in August 2011. Parasite diversity was low and dominated by species with complex life cycles involving intermediate hosts. Most prevalent were larval nematodes (Contracaecum sp.) infecting 12 and Trypanasoma sp. infecting nine of the 14 host species. The intra-erythrocytic parasite Babesiosoma mariae was found in the blood of Coptodon rendalli and Oreochromis andersonii with prevalence of 50% and 60%, respectively. The host-specific monogenean Annulotrema hepseti was recorded only from H. cuvieri with a prevalence of 100%. Notable absences were the copepod and branchiuran parasites that have direct lifecycles and usually occur in high prevalence and abundance in the region. Because parasites with direct life cycles can only be transported into the lake on the host fish, their absence suggests limited immigration of infected fishes into the lake. This suggests that internal recruitment dominates over immigration in the fish population dynamics in Lake Liambezi.     

The larval nervous system of the penis worm Priapulus caudatus (Ecdysozoa)

The origin and extreme diversification of the animal nervous system is a central question in biology. While most of the attention has traditionally been paid to those lineages with highly elaborated nervous systems (e.g. arthropods, vertebrates, annelids), only the study of the vast animal diversity can deliver a comprehensive view of the evolutionary history of this organ system. In this regard, the phylogenetic position and apparently conservative molecular, morphological and embryological features of priapulid worms (Priapulida) place this animal lineage as a key to understanding the evolution of the Ecdysozoa (i.e. arthropods and nematodes). In this study, we characterize the nervous system of the hatching larva and first lorica larva of the priapulid worm Priapulus caudatus by immunolabelling against acetylated and tyrosinated tubulin, pCaMKII, serotonin and FMRFamide. Our results show that a circumoral brain and an unpaired ventral nerve with a caudal ganglion characterize the central nervous system of hatching embryos. After the first moult, the larva attains some adult features: a neck ganglion, an introvert plexus, and conspicuous secondary longitudinal neurites. Our study delivers a neuroanatomical framework for future embryological studies in priapulid worms, and helps illuminate the course of nervous system evolution in the Ecdysozoa.     

Metastatic bladder cancer cells distinctively sense and respond to physical cues of collagen fibril-mimetic nanotopography

Tumor metastasis is characterized by enhanced invasiveness and migration of tumor cells through the extracellular matrix (ECM), resulting in extravasation into the blood and lymph and colonization at secondary sites. The ECM provides a physical scaffold consisting of components such as collagen fibrils, which have distinct dimensions at the nanoscale. In addition to the interaction of peptide moieties with tumor cell integrin clusters, the ECM provides a physical guide for tumor cell migration. Using nanolithography we set out to mimic the physical dimensions of collagen fibrils using lined nanotopographical silicon surfaces and to explore whether metastatic tumor cells are uniquely able to respond to these physical dimensions. Etched silicon surfaces containing nanoscale lined patterns with varying trench and ridge sizes (65–500 nm) were evaluated for their ability to distinguish between a non-metastatic (253J) and a highly metastatic (253J-BV) derivative bladder cancer cell line. Enhanced alignment was distinctively observed for the metastatic cell lines on feature sizes that mimic the dimensions of collagen fibrils (65–100 nm lines, 1:1–1:1.5 pitch). Further, these sub-100 nm lines acted as guides for migration of metastatic cancer cells. Interestingly, even at this subcellular scale, metastatic cell migration was abrogated when cells were forced to move perpendicular to these lines. Compared to flat surfaces, 65 nm lines enhanced the formation of actin stress fibers and filopodia of metastatic cells. This was accompanied by increased formation of focal contacts, visualized by immunofluorescent staining of phospho-focal adhesion kinase along the protruding lamellipodia. Simple lined nanotopography appears to be an informative platform for studying the physical cues of the ECM in a pseudo-3D format and likely mimics physical aspects of collagen fibrils. Metastatic cancer cells appear distinctively well adapted to sense these features using filopodia protrusions to enhance their alignment and migration.     

Organization of local interneurons in optic glomeruli of the dipterous visual system and comparisons with the antennal lobes

The lateral protocerebrum of the fly's brain is composed of a system of optic glomeruli, the organization of which compares to that of antennal lobe glomeruli. Each optic glomerulus receives converging axon terminals from a unique ensemble of optic lobe output neurons. Glomeruli are interconnected by systems of spiking and nonspiking local interneurons that are morphologically similar to diffuse and polarized local interneurons in the antennal lobes. GABA-like immunoreactive processes richly supply optic glomeruli, which are also invaded by processes originating from the midbrain and subesophageal ganglia. These arrangements support the suggestion that circuits amongst optic glomeruli refine and elaborate visual information carried by optic lobe outputs, relaying data to long-axoned neurons that extend to other parts of the central nervous system including thoracic ganglia. The representation in optic glomeruli of other modalities suggests that gating of visual information by other sensory inputs, a phenomenon documented from the recordings of descending neurons, could occur before the descending neuron dendrites. The present results demonstrate that future studies must consider the roles of other senses in visual processing.