Persistent Ribonucleotides and Mitochondrial DNA Metabolism (in Normal and Disease States).

It has been known for over 40 years that the mammalian mitochondrial genome contains persistent sporadic ribonucleotides, for which there has been no molecular explanation to date. To better understand the significance of incorporated ribonucleotides in mitochondrial DNA I developed a deep sequencing method to determine the precise location of ribonucleotides in the mitochondrial DNA of a range of cell and tissue types. Using Next Generation Sequencing I have shown that the vast majority of ribosubstitution events in murine mitochondrial DNA from solid tissues are dominated by adenosine bases derived from adenosine triphosphate, the product of oxidative phosphorylation. In contrast, proliferating cells show a much lower rate of ribonucleotide incorporation. However, this can be manipulated by inducing cell cycle arrest, which leads to an increase in adenosine monophosphate incorporation rate, comparable to that of solid tissues. This study confirms that the specificity of the incorporated ribonucleotide base identity is directly influenced by the ratio of ribonucleotides to deoxyribonucleotides (NTP:dNTPs) within the mitochondrial compartment of the cell. In a mouse model of Mpv17 deficiency there is a mitochondrial specific deoxynucleotide depletion which results in a significant increase in riboguanosine incorporation in mitochondrial DNA. The results described within this thesis demonstrate that elevated riboguanosine incorporation is associated with early-onset mitochondrial DNA depletion in liver and late-onset multiple deletions in brain of the Mpv17 ablated mice. These findings suggest that aberrant ribonucleotide incorporation is a primary mitochondrial DNA abnormality that can result in pathology

Size constancy in bat biosonar?

Perception and encoding of object size is an important feature of sensory systems. In the visual system object size is encoded by the visual angle (visual aperture) on the retina, but the aperture depends on the distance of the object. As object distance is not unambiguously encoded in the visual system, higher computational mechanisms are needed. This phenomenon is termed "size constancy". It is assumed to reflect an automatic re-scaling of visual aperture with perceived object distance. Recently, it was found that in echolocating bats, the 'sonar aperture', i.e., the range of angles from which sound is reflected from an object back to the bat, is unambiguously perceived and neurally encoded. Moreover, it is well known that object distance is accurately perceived and explicitly encoded in bat sonar. Here, we addressed size constancy in bat biosonar, recruiting virtual-object techniques. Bats of the species Phyllostomus discolor learned to discriminate two simple virtual objects that only differed in sonar aperture. Upon successful discrimination, test trials were randomly interspersed using virtual objects that differed in both aperture and distance. It was tested whether the bats spontaneously assigned absolute width information to these objects by combining distance and aperture. The results showed that while the isolated perceptual cues encoding object width, aperture, and distance were all perceptually well resolved by the bats, the animals did not assign absolute width information to the test objects. This lack of sonar size constancy may result from the bats relying on different modalities to extract size information at different distances. Alternatively, it is conceivable that familiarity with a behaviorally relevant, conspicuous object is required for sonar size constancy, as it has been argued for visual size constancy. Based on the current data, it appears that size constancy is not necessarily an essential feature of sonar perception in bats

Primate modularity and evolution: first anatomical network analysis of primate head and neck musculoskeletal system

Network theory is increasingly being used to study morphological modularity and integration. Anatomical network analysis (AnNA) is a framework for quantitatively characterizing the topological organization of anatomical structures and providing an operational way to compare structural integration and modularity. Here we apply AnNA for the first time to study the macroevolution of the musculoskeletal system of the head and neck in primates and their closest living relatives, paying special attention to the evolution of structures associated with facial and vocal communication. We show that well-defined left and right facial modules are plesiomorphic for primates, while anthropoids consistently have asymmetrical facial modules that include structures of both sides, a change likely related to the ability to display more complex, asymmetrical facial expressions. However, no clear trends in network organization were found regarding the evolution of structures related to speech. Remarkably, the increase in the number of head and neck muscles – and thus of musculoskeletal structures – in human evolution led to a decrease in network density and complexity in humans

Atropselective syntheses of (-) and (+) rugulotrosin A utilizing point-to-axial chirality transfer

Chiral, dimeric natural products containing complex structures and interesting biological properties have inspired chemists and biologists for decades. A seven-step total synthesis of the axially chiral, dimeric tetrahydroxanthone natural product rugulotrosin A is described. The synthesis employs a one-pot Suzuki coupling/dimerization to generate the requisite 2,2'-biaryl linkage. Highly selective point-to-axial chirality transfer was achieved using palladium catalysis with achiral phosphine ligands. Single X-ray crystal diffraction data were obtained to confirm both the atropisomeric configuration and absolute stereochemistry of rugulotrosin A. Computational studies are described to rationalize the atropselectivity observed in the key dimerization step. Comparison of the crude fungal extract with synthetic rugulotrosin A and its atropisomer verified that nature generates a single atropisomer of the natural product.P50 GM067041 - NIGMS NIH HHS; R01 GM099920 - NIGMS NIH HHS; GM-067041 - NIGMS NIH HHS; GM-099920 - NIGMS NIH HH

Health risks encountered by Dutch medical students during an elective in the tropics and the quality and comprehensiveness of pre-and post-travel care

<p>Abstract</p> <p>Background</p> <p>Clinical and research electives abroad offer medical students many unique experiences. However, participating in an unfamiliar health-care setting combined with limited medical experience may place students at risk of illness. To improve pre-and post-travel care, we assessed the health risks and the quality and comprehensiveness of pre-and post-travel care in a cohort of Dutch medical students returning form an elective abroad.</p> <p>Methods</p> <p>All medical students who had performed an elective in the tropics between July 2006 and December 2008 were sent an informative email asking them to complete a web-based questionnaire.</p> <p>Results</p> <p>180 of 242 (74%) students completed the questionnaire. Regarding the risk of bloodborne viral infection: 67% of all students and 32% of junior students engaged in procedures that constitute a risk of exposure to bloodborne viral infection, often in countries with high HIV prevalence rates. None of nine students who experienced possible or certain mucosal or percutaneous exposure to potentially infectious body fluids reported the exposure at the time it occurred and none used PEP. Regarding other health risks: 8 of 40 (20%) students stopped using mefloquine due to adverse effects. This left a sizeable proportion unprotected in countries that are hyperendemic for malaria. Post-travel screening for schistosomiasis, tuberculosis (tuberculin skin test) and carriage of methicillin-resistant Staphylococcus aureus (MRSA) encompassed approximately half of all students who should have been screened.</p> <p>Conclusions</p> <p>Based on the results of this study we have adopted an integral set of measures to reduce the health risks associated with an elective abroad. The pre and post-travel consult has been centralized and standardized as well as the distribution of PEP. In addition we have developed a mandatory module on Global Health for all medical students planning an elective abroad.</p

Factors Underlying the Early Limb Muscle Weakness in Acute Quadriplegic Myopathy Using an Experimental ICU Porcine Model

The basic mechanisms underlying acquired generalized muscle weakness and paralysis in critically ill patients remain poorly understood and may be related to prolonged mechanical ventilation/immobilization (MV) or to other triggering factors such as sepsis, systemic corticosteroid (CS) treatment and administration of neuromuscular blocking agents (NMBA). The present study aims at exploring the relative importance of these factors by using a unique porcine model. Piglets were all exposed to MV together with different combinations of endotoxin-induced sepsis, CS and NMBA for five days. Peroneal motor nerve conduction velocity and amplitude of the compound muscle action potential (CMAP) as well as biceps femoris muscle biopsy specimens were obtained immediately after anesthesia on the first day and at the end of the 5-day experimental period. Results showed that peroneal nerve motor conduction velocity is unaffected whereas the size of the CMAP decreases independently of the type of intervention, in all groups after 5 days. Otherwise, despite a preserved size, muscle fibre specific force (maximum force normalized to cross-sectional area) decreased dramatically for animals exposed to MV in combination with CS or/and sepsis. These results suggest that the rapid declines in CMAP amplitude and in force generation capacity are triggered by independent mechanisms with significant clinical and therapeutic implications

A novel malaria vaccine candidate antigen expressed in Tetrahymena thermophila

Development of effective malaria vaccines is hampered by the problem of producing correctly folded Plasmodium proteins for use as vaccine components. We have investigated the use of a novel ciliate expression system, Tetrahymena thermophila, as a P. falciparum vaccine antigen platform. A synthetic vaccine antigen composed of N-terminal and C-terminal regions of merozoite surface protein-1 (MSP-1) was expressed in Tetrahymena thermophila. The recombinant antigen was secreted into the culture medium and purified by monoclonal antibody (mAb) affinity chromatography. The vaccine was immunogenic in MF1 mice, eliciting high antibody titers against both N- and C-terminal components. Sera from immunized animals reacted strongly with P. falciparum parasites from three antigenically different strains by immunofluorescence assays, confirming that the antibodies produced are able to recognize parasite antigens in their native form. Epitope mapping of serum reactivity with a peptide library derived from all three MSP-1 Block 2 serotypes confirmed that the MSP-1 Block 2 hybrid component of the vaccine had effectively targeted all three serotypes of this polymorphic region of MSP-1. This study has successfully demonstrated the use of Tetrahymena thermophila as a recombinant protein expression platform for the production of malaria vaccine antigens

Anatomical Network Comparison of Human Upper and Lower, Newborn and Adult, and Normal and Abnormal Limbs, with Notes on Development, Pathology and Limb Serial Homology vs. Homoplasy

How do the various anatomical parts (modules) of the animal body evolve into very different integrated forms (integration) yet still function properly without decreasing the individual's survival? This long-standing question remains unanswered for multiple reasons, including lack of consensus about conceptual definitions and approaches, as well as a reasonable bias toward the study of hard tissues over soft tissues. A major difficulty concerns the non-trivial technical hurdles of addressing this problem, specifically the lack of quantitative tools to quantify and compare variation across multiple disparate anatomical parts and tissue types. In this paper we apply for the first time a powerful new quantitative tool, Anatomical Network Analysis (AnNA), to examine and compare in detail the musculoskeletal modularity and integration of normal and abnormal human upper and lower limbs. In contrast to other morphological methods, the strength of AnNA is that it allows efficient and direct empirical comparisons among body parts with even vastly different architectures (e.g. upper and lower limbs) and diverse or complex tissue composition (e.g. bones, cartilages and muscles), by quantifying the spatial organization of these parts-their topological patterns relative to each other-using tools borrowed from network theory. Our results reveal similarities between the skeletal networks of the normal newborn/adult upper limb vs. lower limb, with exception to the shoulder vs. pelvis. However, when muscles are included, the overall musculoskeletal network organization of the upper limb is strikingly different from that of the lower limb, particularly that of the more proximal structures of each limb. Importantly, the obtained data provide further evidence to be added to the vast amount of paleontological, gross anatomical, developmental, molecular and embryological data recently obtained that contradicts the long-standing dogma that the upper and lower limbs are serial homologues. In addition, the AnNA of the limbs of a trisomy 18 human fetus strongly supports Pere Alberch's ill-named "logic of monsters" hypothesis, and contradicts the commonly accepted idea that birth defects often lead to lower integration (i.e. more parcellation) of anatomical structures

Carcinoma Arising from Brunner's Gland in the Duodenum after 17 Years of Observation – A Case Report and Literature Review

A 60-year-old man presented with melena and hematemesis in 1984. Esophagogastroduodenoscopy (EGD) detected a small protruding lesion in the duodenal bulb, which was diagnosed as Brunner's adenoma. No significant change was detected in subsequent annual EGD and biopsies for 10 years, after which the patient was not observed for 7 years. The patient presented with melena again in 2001. The lesion had changed shape to become a 10 mm sessile tumor with a central depression, and following a biopsy was diagnosed as an adenocarcinoma. The patient underwent partial resection of the duodenum. Histopathological assessment showed acidophilic cells with swollen nuclei, and clear cells forming a tubular or papillary tubule in the mucosal lamina propria and submucosal layer. The tumor cells stained positive for lysozyme, indicating that they arose from Brunner's gland. The patient showed no sign of recurrence and was disease-free for more than 34 months after surgery. The patient died of pneumonia. This is an extremely rare case of primary duodenal carcinoma arising from Brunner's gland in a patient observed for 17 years