In situ metabolomic mass spectrometry imaging: recent advances and difficulties

MS imaging (MSI) is a remarkable new technology that enables us to determine the distribution of biological molecules present in tissue sections by direct ionization and detection. This technique is now widely used for in situ imaging of endogenous or exogenous molecules such as proteins, lipids, drugs and their metabolites, and it is a potential tool for pathological analysis and the investigation of disease mechanisms. MSI is also thought to be a technique that could be used for biomarker discovery with spatial information. The application of MSI to the study of endogenous metabolites has received considerable attention because metabolites are the result of the interactions of a system's genome with its environment and a total set of these metabolites more closely represents the phenotype of an organism under a given set of conditions. Recent studies have suggested the importance of in situ metabolite imaging in biological discovery and biomedical applications, but several issues regarding the technical application limits of MSI still remained to be resolved. In this review, we describe the capabilities of the latest MSI techniques for the imaging of endogenous metabolites in biological samples, and also discuss the technical problems and new challenges that need to be addressed for effective and widespread application of MSI in both preclinical and clinical settings.     

Optical imaging of infants' neurocognitive development: recent advances and perspectives

Near-infrared spectroscopy (NIRS) provides a unique method of monitoring infant brain function by measuring the changes in the concentrations of oxygenated and deoxygenated hemoglobin. During the past 10 years, NIRS measurement of the developing brain has rapidly expanded. In this article, a brief discussion of the general principles of NIRS, including its technical advantages and limitations, is followed by a detailed review of the role played so far by NIRS in the study of infant perception and cognition, including language, and visual and auditory functions. Results have highlighted, in particular, the developmental changes of cerebral asymmetry associated with speech acquisition. Finally, suggestions for future studies of neurocognitive development using NIRS are presented. Although NIRS studies of the infant brain have yet to fulfill their potential, a review of the work done so far indicates that NIRS is likely to provide many unique insights in the field of developmental neuroscience.     

Fluorescence lifetime imaging system for in vivo studies

In this article, a fluorescence lifetime imaging system for small animals is presented. Data were collected by scanning a region of interest with a measurement head, a linear fiber array with fixed separations between a single source fiber and several detection fibers. The goal was to localize tumors and monitor their progression using specific fluorescent markers. We chose a near-infrared contrast agent, Alexa Fluor 750 (Invitrogen Corp., Carlsbad, CA). Preliminary results show that the fluorescence lifetime for this dye was sensitive to the immediate environment of the fluorophore (in particular, pH), making it a promising candidate for reporting physiologic changes around a fluorophore. To quantify the intrinsic lifetime of deeply embedded fluorophores, we performed phantom experiments to investigate the contribution of photon migration effects on observed lifetime by calculating the fluorescence intensity decay time. A previously proposed theoretical model of migration, based on random walk theory, is also substantiated by new experimental data. The developed experimental system has been used for in vivo mouse imaging with Alexa Fluor 750 contrast agent conjugated to tumor-specific antibodies (trastuzumab [Herceptin]). Three-dimensional mapping of the fluorescence lifetime indicates lower lifetime values in superficial breast cancer tumors in mice.     

Hepatitis vaccines: recent advances

Despite the availability of hepatitis A vaccines that might provide protection for decades, hepatitis B vaccines that provides protection for at least 15 years and the recent introduction of a combined hepatitis A and B vaccine, these infections continue to spread in both the developed and developing world. Hepatitis A vaccine coverage has been limited to high-risk groups: such a selective immunisation policy is unlikely to have a major impact. If adequate immunogenicity in infants is confirmed, dosing schedules can be improved and the costs of vaccination reduced, universal paediatric immunisation with combined hepatitis A and B products is likely to result in the eventual eradication of these infections. In the interim, novel hepatitis A vaccines are being investigated and additional studies on hepatitis A vaccine immunogenicity in infants are in progress. Worldwide use of hepatitis B vaccines for the newborn, young children and high-risk groups should control this infection and obviate the need for a vaccine against hepatitis D. Newer hepatitis B vaccines that may reduce the likelihood of non-responsiveness and have immunotherapeutic value are under study. A recombinant hepatitis E vaccine for use in endemic regions is currently in clinical trials. The development of an effective hepatitis C vaccine has been agonisingly slow and many impediments have been recognised. These include the lack of a susceptible small animal, a high degree of hepatitis C virus (HCV) genomic diversity and failure to produce high quantities of HCV in tissue culture. The development of a novel HCV replicon system may be a major breakthrough. Nonetheless, it may still be exceedingly difficult to produce a vaccine that uniformly provides sterilising immunity; the possibility of developing a hepatitis C vaccine that can prevent chronic infection is an exciting concept that requires further investigation. Advances in recombinant technology, the use of novel genetic (DNA-based) vaccines, expression of hepatitis antigens in plants and improved adjuvants also hold considerable promise.     

Peroxisome biogenesis: recent advances

In recent years, it has become evident that peroxisomes form part of the endomembrane system. Peroxisomes can form from the ER via a maturation process and they can multiply by growth and division, whereby the ER provides membrane for growth and ongoing fission (Figure 1). Until very recently, it was widely accepted that most peroxisomal membrane proteins (PMPs) insert directly into peroxisomes, whereas a small subset of PMPs traffic via the ER. In this minireview, we focus mainly on PMP biogenesis, and highlight recent advances in peroxisomal matrix protein import, fission and segregation in yeast.     

Current advances in molecular imaging: noninvasive in vivo bioluminescent and fluorescent optical imaging in cancer research

Recently, there has been tremendous interest in developing techniques such as MRI, micro-CT, micro-PET, and SPECT to image function and processes in small animals. These technologies offer deep tissue penetration and high spatial resolution, but compared with noninvasive small animal optical imaging, these techniques are very costly and time consuming to implement. Optical imaging is cost-effective, rapid, easy to use, and can be readily applied to studying disease processes and biology in vivo. In vivo optical imaging is the result of a coalescence of technologies from chemistry, physics, and biology. The development of highly sensitive light detection systems has allowed biologists to use imaging in studying physiological processes. Over the last few decades, biochemists have also worked to isolate and further develop optical reporters such as GFP, luciferase, and cyanine dyes. This article reviews the common types of fluorescent and bioluminescent optical imaging, the typical system platforms and configurations, and the applications in the investigation of cancer biology.     

Aerobic granular sludge: recent advances

Aerobic granulation, a novel environmental biotechnological process, was increasingly drawing interest of researchers engaging in work in the area of biological wastewater treatment. Developed about one decade ago, it was exciting research work that explored beyond the limits of aerobic wastewater treatment such as treatment of high strength organic wastewaters, bioremediation of toxic aromatic pollutants including phenol, toluene, pyridine and textile dyes, removal of nitrogen, phosphate, sulphate and nuclear waste and adsorption of heavy metals. Despite this intensive research the mechanisms responsible for aerobic granulation and the strategy to expedite the formation of granular sludge, and effects of different operational and environmental factors have not yet been clearly described. This paper provides an up-to-date review on recent research development in aerobic biogranulation technology and applications in treating toxic industrial and municipal wastewaters. Factors affecting granulation, granule characterization, granulation hypotheses, effects of different operational parameters on aerobic granulation, response of aerobic granules to different environmental conditions, their applications in bioremediations, and possible future trends were delineated. The review attempts to shed light on the fundamental understanding in aerobic granulation by newly employed confocal laser scanning microscopic techniques and microscopic observations of granules.     

Strain and elasticity imaging in compression optical coherence elastography: The two-decade perspective and recent advances

Quantitative mapping of deformation and elasticity in optical coherence tomography has attracted much attention of researchers during the last two decades. However, despite intense effort it took ~15 years to demonstrate optical coherence elastography (OCE) as a practically useful technique. Similarly to medical ultrasound, where elastography was first realized using the quasi-static compression principle and later shear-wave-based systems were developed, in OCE these two approaches also developed in parallel. However, although the compression OCE (C-OCE) was proposed historically earlier in the seminal paper by J. Schmitt in 1998, breakthroughs in quantitative mapping of genuine local strains and the Young's modulus in C-OCE have been reported only recently and have not yet obtained sufficient attention in reviews. In this overview, we focus on underlying principles of C-OCE; discuss various practical challenges in its realization and present examples of biomedical applications of C-OCE. The figure demonstrates OCE-visualization of complex transient strains in a corneal sample heated by an infrared laser beam.     

Beyond Mfold: recent advances in RNA bioinformatics

Computational analysis of RNA secondary structure is a classical field of biosequence analysis, which has recently gained momentum due to the manyfold regulatory functions of RNA that have become apparent. We present five recent computational approaches that address the problems of synoptic folding space analysis, pseudoknot prediction, structure alignment, comparative structure prediction, and miRNA target prediction. All these programs are in current use and are available via the Bielefeld Bioinformatics Server at .     

Influenza vaccines: recent advances in production technologies

In spite of ongoing annual vaccination programs, the seasonal influenza epidemics remain a major cause of high morbidity and mortality. The currently used inactivated vaccines provide very short-term and highly specific humoral immunity due to the frequent antigenic variations in the influenza virion. These intra-muscularly administered vaccines also fail to induce protective mucosal immunity at the portal of viral entry and destruction of the virally infected cells by induction of cytotoxic T lymphocytes. Therefore, it is necessary to develop immunologically superior vaccines. This article highlights some of the recent developments in investigational influenza vaccines. The most notable recent developments of interest include the use of immunopotentiators, development of DNA vaccines, use of reverse genetics, and the feasibility of mammalian cell-based production processes. Presently, due to their safety and efficacy, the cold-adapted live attenuated vaccines are seen as viable alternatives to the inactivated vaccines. The DNA vaccines are gaining importance due to the induction of broad-spectrum immunity. In addition, recent advances in recombinant technologies have shown the possibility of constructing pre-made libraries of vaccine strains, so that adequately preparations can be made for epidemics and pandemics.     

In vivo imaging of malaria parasites--recent advances and future directions

A new view into the life of malaria parasites is now possible owing to recent advances in imaging techniques and to the generation of tagged parasites. Insights into how parasites interact with their insect vectors and mammalian hosts have been gained by the study of various parasitic forms in their natural environment. Quantitative analysis of Plasmodium ookinete motility has revealed different modes of motility in parasite invasion of the mosquito gut and the extrusion of invaded gut cells from the epithelium. Similar analysis with Plasmodium sporozoites has revealed the importance of parasite motility in transmission from the mosquito vector to the mammalian host.     

Polyamines and abiotic stress: recent advances

Summary. In this review we will concentrate in the results published the last years regarding the involvement of polyamines in the plant responses to abiotic stresses, most remarkably on salt and drought stress. We will also turn to other types of abiotic stresses, less studied in relation to polyamine metabolism, such as mineral deficiencies, chilling, wounding, heavy metals, UV, ozone and paraquat, where polyamine metabolism is also modified. There is a great amount of data demonstrating that under many types of abiotic stresses, an accumulation of the three main polyamines putrescine, spermidine and spermine does occur. However, there are still many doubts concerning the role that polyamines play in stress tolerance. Several environmental challenges (osmotic stress, salinity, ozone, UV) are shown to induce ADC activity more than ODC. The rise in Put is mainly attributed to the increase in ADC activity as a consequence of the activation of ADC genes and their mRNA levels. On the other hand, free radicals are now accepted as important mediators of tissue injury and cell death. The polycationic nature of polyamines, positively charged at physiological pH, has attracted the attention of researchers and has led to the hypothesis that polyamines could affect physiological systems by binding to anionic sites, such as those associated with nucleic acids and membrane phospholipids. These amines, involved with the control of numerous cellular functions, including free radical scavenger and antioxidant activity, have been found to confer protection from abiotic stresses but their mode of action is not fully understood yet. In this review, we will also summarize information about the involvement of polyamines as antioxidants against the potential abiotic stress-derived oxidative damage. Authors’ address: Dr. María Patricia Benavides, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, Buenos Aires 1113, Argentina     

Thyroglobulin structure and function: recent advances

Thyroglobulin is a large-size iodoglycoprotein specific to thyroid tissue and is the substrate for the synthesis of thyroid hormones, thyroxine and 3,5,3'-triiodothyronine. Recent studies, which greatly benefited from recombinant DNA methodologies, improved the knowledge of several structural features of this dimeric protein and permitted insights into some structure-function relationships. Analysis-function of the primary structure of the human thyroglobulin monomer revealed several main characteristics: 1) 3 types of internal homologies; 2) extensive homology with the bovine thyroglobulin monomer and known partial sequences in the thyroglobulins of other mammalian species; 3) significant homologies with 2 other non-thyroid proteins (acetylcholinesterase and the invariant chain of the Ia class II histocompatibility antigen); 4) a terminal localization of the hormonogenic sites at both ends of the monomer. Current studies aim at determining conformational characteristics, understanding the molecular mechanisms of thyroid hormone formation and unraveling those interactions which in the thyroid cell and the thyroid follicle will permit this large pro-hormone to synthesize and release a few small thyroid hormone molecules. A more precise knowledge of this molecule in higher vertebrates and during evolution would impart valuable information concerning thyroid pathology, since thyroglobulin has been implicated in some genetic and in autoimmune thyroid diseases.     

Dientamoebiasis: clinical importance and recent advances

Dientamoeba fragilis, an unusual single-celled parasite that was described first in 1918, is found worldwide in the gastrointestinal tract of humans. D. fragilis has emerged from obscurity recently because it is now recognized as a common cause of chronic diarrhoea and is treatable with drugs. Recent molecular studies have described D. fragilis as having two genotypes. Diagnostic tests, based on conventional and real-time PCR, have been developed that will provide a rapid, sensitive and specific diagnosis of D. fragilis. These tests will also aid the elucidation of the host distribution and the life cycle of this pathogen.