The use of UV light as a cross-linking agent for cells and tissue sections in in situ hybridization.

UV cross-linking is introduced as a novel method to stabilize tissue on microscopic slides and to immobilize target molecules in biological material for in situ hybridization. UV illumination dramatically improves the stability of tissue sections and isolated cells on slides coated with gelatin/poly-lysine. Even during prolonged high-stringency washes, specimens remain firmly attached to the support layer. At the same time, the signal intensity is increased significantly whereas background levels remain as low as without UV illumination. These results indicate that while target RNAs and other molecules in the biological material are covalently cross-linked with their nearest neighbor molecules, tissues nonetheless remain penetrable, and target molecules remain accessible. We expect that this simple and efficient technique will find widespread applications in in situ hybridization methodology.     

The life cycle of Trypanosoma cruzi revisited

The basic features of the life cycle of Trypanosoma cruzi have been known for nearly a century. Various aspects of the life cycle, however, have been elucidated only recently, whilst others remain either controversial or unstudied. Here, we present a revised life cycle influenced by recent findings and specific questions that remain unresolved.     

Survival of Azotobacter in Dry Soil

Detection of viable Azotobacter in soils stored in the laboratory for more than 10 years suggests that these bacteria can remain dormant in nature for prolonged periods of time. Studies of dried cultures show that cysts of A. vinelandii 12837 remain viable for at least 10 years, whereas vegetative cells do not survive for even 1 year under the same conditions.     

Analysis of the centromeric regions of the human genome assembly

The sequence of the human genome is not yet complete, and major gaps remain at the centromere region of each chromosome, which is comprised of repetitive alpha satellite DNA. In this article, we describe the sequences in the vicinity of the centromere that are included in the current genome assembly, analyze the approximately 7Mb of alpha satellite that have been assembled thus far and anticipate the nature of the sequences that remain to be accounted for.     

Status of the world's baleen whales

No global synthesis of the status of baleen whales has been published since the 2008 IUCN Red List assessments. Many populations remain at low numbers from historical commercial whaling, which had ceased for all but a few by 1989. Fishing gear entanglement and ship strikes are the most severe current threats. The acute and long‐term effects of anthropogenic noise and the cumulative effects of multiple stressors are of concern but poorly understood. The looming consequences of climate change and ocean acidification remain difficult to characterize. North Atlantic and North Pacific right whales are among the species listed as Endangered. Southern right, bowhead, and gray whales have been assessed as Least Concern but some subpopulations of these species ‐ western North Pacific gray whales, Chile‐Peru right whales, and Svalbard/Barents Sea and Sea of Okhotsk bowhead whales ‐ remain at low levels and are either Endangered or Critically Endangered. Eastern North Pacific blue whales have reportedly recovered, but Antarctic blue whales remain at about 1% of pre‐exploitation levels. Small isolated subspecies or subpopulations, such as northern Indian Ocean blue whales, Arabian Sea humpback whales, and Mediterranean Sea fin whales are threatened while most subpopulations of sei, Bryde's, and Omura's whales are inadequately monitored and difficult to assess.     

African trypanosomes in the 21st century: what is their future in science and in health?

The African trypanosomes remain well recognised for their role as an interesting model eukaryote for basic science, but are loosing ground in their ability to contribute to understanding common cellular mechanisms. At the same time, the diseases they cause remain as prevalent as ever, but appear increasingly irrelevant in their wider medical, social, economic and political context. What can be done to keep trypanosome biology relevant and vigorous in the 21st century?     

Cytological events leading to the cleavage of golden hamster zygotes.

Fertilized golden hamster eggs were examined between 6 and 20 hours post-ovulation to determine the events leading to the two-cell stage. Following their migration the pronuclei remain in the central region of the zygote for approximately ten hours. The morphologically, indistinguishable male and female pronuclei remain relatively unchanged during this period, i.e., they do not interdigitate or fuse with one another as described for the zygotes of other organisms. Following this period and at the time of pronuclear breakdown elongate vesicles appear along the nucleoplasmic surface of the pronuclear envelopes. Later the pronuclear envelopes fragment into elongate cisternae; these and the vesicles formed along the inner lamina of the pronuclear envelopes remain closely associated and constitute quadrilaminar structures. The chromosomes which condense prior to and during pronuclear envelope breakdown, migrate to the equatorial plate of the forming cleavage spindle. After cytokinesis the chromosomes in the blastomere nuclei disperse. Increase in the nuclear envelope to accommodate this dispersion may involve the addition of membrane from the quandrilaminar structures.     

Vaccines for the prevention of neglected diseases--dengue fever

Dengue and dengue hemorrhagic fever have spread to all tropical areas of the developing world, but still remain largely neglected diseases. Several promising vaccine candidates in the form of live attenuated and chimeric vaccines have been developed and are currently in human clinical trials. However, significant practical, logistic, and scientific challenges remain before these vaccines can widely and safely be applied to vulnerable populations. Vector control, community education and public health measures must be pursued in parallel with vaccine development.     

The diverse biological functions of phosphatidylinositol transfer proteins in eukaryotes

Phosphatidylinositol/phosphatidylcholine transfer proteins (PITPs) remain largely functionally uncharacterized, despite the fact that they are highly conserved and are found in all eukaryotic cells thus far examined by biochemical or sequence analysis approaches. The available data indicate a role for PITPs in regulating specific interfaces between lipid-signaling and cellular function. In this regard, a role for PITPs in controlling specific membrane trafficking events is emerging as a common functional theme. However, the mechanisms by which PITPs regulate lipid-signaling and membrane-trafficking functions remain unresolved. Specific PITP dysfunctions are now linked to neurodegenerative and intestinal malabsorption diseases in mammals, to stress response and developmental regulation in higher plants, and to previously uncharacterized pathways for regulating membrane trafficking in yeast and higher eukaryotes, making it clear that PITPs are integral parts of a highly conserved signal transduction strategy in eukaryotes. Herein, we review recent progress in deciphering the biological functions of PITPs, and discuss some of the open questions that remain.     

Transcoronal removal of an atypical orbitoethmoid osteoma

Craniofacial osteomas are lesions of bone that most commonly occur in the paranasal sinuses. Characteristically they remain dormant or slowly enlarge but remain asymptomatic. The more rapidly expanding tumor types may extend to adjacent structures, but signs and symptoms of such involvement are rare before the third decade. Presented is a patient with an ethmoid osteoma associated with a 2-year history of progressive proptosis first noticed at age 14. The operative approach afforded through a transcoronal incision combines excellent surgical exposure with hidden scar.     

The value of microarray techniques for quantitative gene profiling in molecular diagnostics

There has been an explosion of interest in microarray technologies that allow the quantification of whole-genome RNA expression data. The apparent correlation of expression profiles with clinically relevant parameters such as disease outcome has raised expectations with respect to the clinical usefulness of the data generated. Yet the accuracy and biological relevance of these data remain contentious, even in basic research applications. Therefore, numerous issues related to format, quality, validation and interpretation remain to be resolved before microarray profiling can become a diagnostic tool of clinical relevance for routine work.     

A global census of nitrogenase diversity

The global diversity of nitrogen-fixing microorganisms was assessed through construction and analysis of an aligned database of 16,989 nifH sequences. We conclude that the diversity of diazotrophs is still poorly described and that many organisms remain to be discovered. Our analyses indicate that diversity is not distributed evenly across phylogenetic groups or across environments and that some of the most diverse assemblages and environments remain the most poorly characterized. The majority of OTUs were rare, falling in the long tail of the frequency distribution. The most dominant OTUs fell into either the Cyanobacteria or the α, β, and γ Proteobacteria, and five of these dominant OTUs do not have any representatives cultivated in isolation. Soils contained the greatest diversity of nifH sequences of all of the environments surveyed. Cluster III, which is dominated by nifH sequences from obligate anaerobes, was found to contain the greatest diversity of all nifH lineages and is also the group for which diversity is the least sampled. Our findings provide context for ongoing efforts to explore diazotroph diversity, indicating specific groups and environments that remain poorly characterized.     

Hypothesis: Control of hepatic utilization of alanine by membrane transport or by cellular metabolism?

The rate of alanine transport into the liver limits its utilization even under the high alanine load resulting from a 90% casein diet, given that the rat has been adapted to that diet. A coordinated acceleration of alanine catabolism allows transport to remain ratelimiting. which in turn allows the adaptive regulation of transport to remain effective at high alanine loads. Accelerated degradation of alanine may change the hepatic amino acid content in a way that derepresses the activity of the alanine carrier system(s).     

Maintaining Wolbachia in cell-free medium

In this video protocol, procedures are demonstrated to (1) purify Wolbachia symbionts out of cultured mosquito cells, (2) use a fluorescent assay to ascertain the viability of the purified Wolbachia and (3) maintain the now extracellular Wolbachia in cell-free medium. Purified Wolbachia remain alive in the extracellular phase but do not replicate until re-inoculated into eukaryotic cells. Extracellular Wolbachia purified in this manner will remain viable for at least a week at room temperature, and possibly longer. Purified Wolbachia are suitable for micro-injection, DNA extraction and other applications.     

Costly signalling: a work in progress

The Evolution of Animal Communication is a detailed examination of a wide variety of animal signalling systems. The main focus of the book is explaining how such signalling systems remain reliable when there is apparent evolutionary pressure to deceive. The principle strategy is to appeal to signal costs: signals remain reliable because the potential benefits of deceit are outweighed by the costs of producing the deceptive signal. In this review I show just how difficult this idea is to test, even in the simplest cases.     

Genomics of plant ABC transporters: the alphabet of photosynthetic life forms or just holes in membranes?

The large number of ABC transporters in the Arabidopsis genome was made responsible for known as well as unexpected aspects in plant development. The combination of classical transport experiments with functional genomics approaches helped unravel some of these effects. Yet questions concerning the importance of this large number of ABC transporters in eukaryotic photosynthesizing organisms remain open. Phylogenomic analyses of whole genome sequence data reveal comparable sizes and composition between algae and higher plants within this protein family. Although this indicates the significance of ABC transporters in plants, several other questions remain to be answered.     

The plasmodium digestive vacuole: metabolic headquarters and choice drug target

The Plasmodium digestive (food) vacuole is an acidic proteolytic compartment central to the metabolism of the parasite. Here haemoglobin is degraded, haem is polymerized, amino acid are transported, oxygen radicals are detoxified, drugs are accumulated, acidification is maintained and free iron may be generated. Despite these crucial roles in parasite development, a number of questions about the digestive vacuole and the haemoglobin ingestion pathway remain unanswered; in consequence, a number of attractive drug targets remain to be exploited. Piero Olliaro and Daniel Goldberg here review the morphology, metabolism and pharmacological disruption of this specialized organelle.     

Sensitivity of long-standing xenografts of rat hearts to humoral antibodies.

Long-standing rat skin xenografts on immunosuppressed mice are known to become insensitive to destruction by mouse anti-rat serum. Our present experiments demonstrate that long-standing primarily vascularized rat-to-mouse cardiac xenografts, unlike skin, remain fully sensitive to antiserum-mediated destruction, even in mice also bearing a long-standing skin graft that is resistant to antiserum. It appears that skin grafts become resistant to antiserum-mediated destruction because of extensive replacement of the endothelium by cells of host origin. The hearts remain sensitive to antiserum since such an extensive endothelial replacement would not occur as readily in these whole organ grafts.