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PubMed2002

Development of a learning module using a virtual environment to demonstrate EMG and telerobotic control principles.

A prototype system was developed for use as a teaching tool, allowing students to link EMG monitoring, data smoothing, robotic control, and neural network training within a rapid prototyping virtual environment (VE). The VE software allowed for the rapid development of scenarios and, when linked with EMG data input to a neural network, allowed the user to control an artificial world containing a virtual arm. Student teams then attempted to control the arm in the VE while performing the tasks by use of a neural network system they had specifically developed and trained using their own EMG signals. The results from their system were then translated into a form that enabled the control of a real robot. Students enjoyed the challenge and uniqueness of the module, and were enthusiastic about extending the concept to other areas of interest.

Biological Science Disciplines↗

PubMed1998

Microfabricated device coupled with an electrospray ionization quadrupole time-of-flight mass spectrometer: protein identifications based on enhanced-resolution mass spectrometry and tandem mass spectrometry data.

We describe the coupling of a microfabricated fluidic device to an electrospray ionization (ESI) quadrupole time-of-flight mass spectrometer (QqTOFMS) for the identification of protein samples. The microfabricated devices consisted of three reservoirs connected via channels to a main capillary, which in turn was linked via a microspray interface to the QqTOFMS. Here we present preliminary results obtained using this system. Standardized solutions of myoglobin tryptic digest were analyzed indicating a limit of detection at the low to sub fmol/microL. The combination of the microfabricated device for rapid sample delivery and the rapid acquisition capability, enhanced resolution and mass accuracy of the QqTOF offers unique possibilities for the rapid identification of proteins by database searching. This platform can generate MS data suitable for protein database searching by the peptide-mass fingerprinting approach and MS/MS data suitable for protein database searching. Here the results of the two database-searching approaches are compared and the possibilities of combining the two approaches for rapid identification of protein are discussed. Also, we present a comparison of the results obtained using the three-position microfabricated device coupled to the ESI-QqTOFMS and to an ESI-ion trap MS. Finally the combination of C-terminal 18O labeling of peptides and the microfabricated system for automated combined peptide-mass fingerprinting and sequence-tag database searching is discussed.

Databases, Factual↗

PubMed2003

Modified implanted drop foot stimulator system with graphical user interface for customised stimulation pulse-width profiles.

A modified implanted drop foot stimulator that allows cyclic modulation of the stimulation pulse-width during gait has been developed. Stimulation was on two channels of a four-channel 12 polar cuff electrode. The stimulator allowed modulation of stimulation pulse-width, between 0 and 255 micros, on both channels throughout the swing and stance phases of gait. Stimulation was applied between 17 and 40 Hz. The clinician can specify an infinite range of stimulation profiles on a desktop computer, using a user-friendly LabVIEW interface. The desktop program generated a stimulation profile table of 100 values, which was then downloaded to the drop foot stimulator. As each phase of gait imposed different biomechanical demands on the ankle dorsiflexor muscles, different stimulation intensities were desirable, throughout gait, to match these demands. Moreover, as the gait of each person with hemiplegia is unique, the biomechanical demands imposed throughout the gait cycle for each user of a drop foot stimulator are unique. This stimulator architecture allowed the clinician to, specify stimulation intensities individually, at each phase of the gait cycle for each drop foot stimulator user. The stimulator was evaluated on a male hemiplegic subject. It was used to increase the stimulation pulse-width by 150% at 5% of gait cycle prior to heel strike. The system performed well, with the ankle angle at heel strike increasing by 5 degrees owing to this increased pulse-width.

Electric Stimulation Therapy↗

PubMed1993

The development of a novel implant: induction of a non-rigid and self-renewing anchorage of artificial implants to bone.

Artificial implants currently used in orthopaedic surgery and dentistry are anchored to the surrounding bone by rigid mechanical fixation. Long-term studies indicate that the rate of implant failure due to loosening increases steeply after 10 years of function. The loosening is attributed to the micro-movements occurring at the bone implant interface. Non-rigid, self-renewing ligamentous anchorage is nature's solution to the problem of micro-movements. An excellent example of this type of anchorage is the tooth-bone system, where the tooth is anchored to the bone by a fibrous connective tissue. A novel artificial implant, bearing on its surface a unique biological substrate (BS), was designed to induce a ligamentous anchorage of implant to bone. The implant consists of a metallic core to which the BS is bound. The BS is a composite of plastic material and a collagen mesh which is partly incorporated into the plastic material and partly freely extended from its outer surface as artificial Sharpey's fibers. BS fabrication did not affect the capacity of the collagen to withstand non-specific degradation in vitro. Non-weight-bearing implants implanted into the femoral bone of rats induced and maintained a ligament-like tissue up to 4 months. The collagen fibers of the ligament-like tissue were spliced with the artificial BS Sharpey's fibers and were also anchored as Sharpey's fibers into the surrounding bone. Examination of control plastic implants (without the BS) revealed bone formation in close approximation to the implant surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Revision of well-fixed cemented, porous total knee arthroplasty. Report of six cases.

Revision of cemented, porous ingrowth total knee arthroplasties poses several technical problems that are unique to these implants, especially component extraction. Six cases are presented to illustrate these difficulties, with particular attention given to revision techniques. The revisions were performed not for aseptic loosening but for causes in which all the implants were securely affixed to bone. To avoid large amounts of bone loss during extraction, the cement-prosthesis interface should be disrupted with high-speed instruments, such as a high-speed burr or oscillating saw. The tibial component may need to be disassembled to gain access to the tibial fixation peg. The potential problems of revision of cemented, porous total knee implants may necessitate bone grafting or custom-designed prostheses.

Aged↗

PubMed2003

Intravascular elastography: from bench to bedside.

An unstable lesion may rupture and cause an acute thrombotic reaction. These lesions contain a large lipid pool covered by a thin fibrous cap. The stress in the cap increased with decreasing thickness and increasing macrophage infiltration. Intravascular ultrasound (IVUS) elastography might be an ideal technique to assess the presence of lipid pools and identify high stress regions. Elastography assesses the local mechanical properties of tissue using its deformation caused by the intraluminal pressure. The technique was validated in vitro using diseased human coronary and femoral arteries. These experiments demonstrated that the strain in the three plaque types is different (P < 0.001). Especially between fibrous and fatty tissue, a highly significant difference (P = 0.0012) was found. Additionally, the predictive value for identifying the vulnerable plaque was investigated. A high strain region at the lumen vessel wall boundary has 88% sensitivity and 89% specificity for identifying these plaques. In vivo, the technique is validated in an atherosclerotic Yucatan mini-pig animal model. This study also revealed higher strain values in fatty than fibrous plaques (P < 0.001). The presence of a high strain region at the lumen plaque interface has a high predictive value for identifying macrophages. Patient studies revealed high strain values (1-2%) in soft plaques. Calcified material shows low strain values (0-0.2%). With the development of three-dimensional elastography, identification of weak spots over the full length of a coronary artery becomes possible. In conclusion, intravascular elastography is a unique tool to assess lesion composition and vulnerability. The development of three-dimensional elastography provides a technique that may develop into a clinical available tool for identifying the rupture-prone plaque.

Animals↗

PubMed2005

Crystal structure of vinorine synthase, the first representative of the BAHD superfamily.

Vinorine synthase is an acetyltransferase that occupies a central role in the biosynthesis of the antiarrhythmic monoterpenoid indole alkaloid ajmaline in the plant Rauvolfia. Vinorine synthase belongs to the benzylalcohol acetyl-, anthocyanin-O-hydroxy-cinnamoyl-, anthranilate-N-hydroxy-cinnamoyl/benzoyl-, deacetylvindoline acetyltransferase (BAHD) enzyme superfamily, members of which are involved in the biosynthesis of several important drugs, such as morphine, Taxol, or vindoline, a precursor of the anti-cancer drugs vincaleucoblastine and vincristine. The x-ray structure of vinorine synthase is described at 2.6-angstrom resolution. Despite low sequence identity, the two-domain structure of vinorine synthase shows surprising similarity with structures of several CoA-dependent acyltransferases such as dihydrolipoyl transacetylase, polyketide-associated protein A5, and carnitine acetyltransferase. All conserved residues typical for the BAHD family are found in domain 1. His160 of the HXXXD motif functions as a general base during catalysis. It is located in the center of the reaction channel at the interface of both domains and is accessible from both sides. The channel runs through the entire molecule, allowing the substrate and co-substrate to bind independently. Asp164 points away from the catalytic site and seems to be of structural rather than catalytic importance. Surprisingly, the DFGWG motif, which is indispensable for the catalyzed reaction and unique to the BAHD family, is located far away from the active site and seems to play only a structural role. Vinorine synthase represents the first solved protein structure of the BAHD superfamily.

Acetyltransferases↗

PubMed2005

Crystal structures of the HIV-1 inhibitory cyanobacterial protein MVL free and bound to Man3GlcNAc2: structural basis for specificity and high-affinity binding to the core pentasaccharide from n-linked oligomannoside.

The cyanobacterial protein MVL inhibits HIV-1 envelope-mediated cell fusion at nanomolar concentrations by binding to high mannose N-linked carbohydrate on the surface of the envelope glycoprotein gp120. Although a number of other carbohydrate-binding proteins have been shown to inhibit HIV-1 envelope-mediated cell fusion, the specificity of MVL is unique in that its minimal target comprises the Man(alpha)(1-->6)Man(beta)(1-->4)GlcNAc(beta)(1-->4)GlcNAc tetrasaccharide core of oligomannosides. We have solved the crystal structures of MVL free and bound to the pentasaccharide Man3GlcNAc2 at 1.9- and 1.8-A resolution, respectively. MVL is a homodimer stabilized by an extensive intermolecular interface between monomers. Each monomer contains two structurally homologous domains with high sequence similarity connected by a short five-amino acid residue linker. Intriguingly, a water-filled channel is observed between the two monomers. Residual dipolar coupling measurements indicate that the structure of the MVL dimer in solution is identical to that in the crystal. Man3GlcNAc2 binds to a preformed cleft at the distal end of each domain such that a total of four independent carbohydrate molecules associate with each homodimer. The binding cleft provides shape complementarity, including the presence of a deep hydrophobic hole that accommodates the N-acetyl methyl at the reducing end of the carbohydrate, and specificity arises from 7-8 intermolecular hydrogen bonds. The structures of MVL and the MVL-Man3GlcNAc2 complex further our understanding of the molecular basis of high affinity and specificity in protein-carbohydrate recognition.

Amino Acids↗

PubMed2005

Genetic disorders of surfactant homeostasis.

Adaptation to air breathing at birth requires the precise orchestration of cellular processes to initiate fluid clearance, enhance pulmonary blood flow, and to synthesize and secrete pulmonary surfactant needed to reduce surface tension at the air-liquid interface in the alveoli. Genetic programs regulating the synthesis of the surfactant proteins and lipids required for the production and function of pulmonary surfactant are highly conserved across vertebrates, and include proteins that regulate the synthesis and packaging of pulmonary surfactant proteins and lipids. Surfactant proteins B and C (SP-B and -C) are small, uniquely hydrophobic proteins that play important roles in the stability and spreading of surfactant lipids in the alveolus. Deletion or mutations in SP-B and -C cause acute and chronic lung disease in neonates and infants. SP-B and -C are synthesized and packaged with surfactant phospholipids in lamellar bodies. Normal lamellar body formation requires SP-B and a member of the ATP-binding cassette (ABC) family of ATP-dependent membrane-associated transport proteins, ABCA3. Mutations in ABCA3 cause fatal respiratory disease in newborns and severe chronic lung disease in infancy. Expression of SP-B, -C, and ABCA3 are coregulated during late gestation by transcriptional programs influenced by thyroid transcription factor-1 and forkhead box a2, transcription factors that regulate both differentiation of the respiratory epithelium and transcription of genes required for perinatal adaptation to air breathing.

ATP-Binding Cassette Transporters↗

PubMed1993

The importance of energy and nutrient supply in human brain evolution.

Current evolutionary theories do not adequately address the question of how the human brain evolved to be larger and more sophisticated than that of other primates. The human brain/body weight ratio is 4-5 times higher than in primates and, relative to the rest of the body, requires up to 10 times as much energy as in other land-based mammals. Human brain evolution must therefore have required a stable food supply providing a reliable source of both high dietary energy and a cluster of 'brain-specific' nutrients over a long period of time. These nutrient and energy requirements are available in the marine and shore-based food chain but are difficult if not impossible to obtain in the terrestrial food chain. We suggest that marine and estuarine ecosystems provided hominids with the appropriate stimulus to develop a relatively large brain. This occurred in conjunction with the evolution of other uniquely human features, particularly relative hairlessness, bipedalism and abundant neonatal subcutaneous fat. Invertebrates, molluscs, small or slow-moving fish, and marine algae would have provided a stable, abundant supply of energy, long chain polyunsaturates and other nutrients essential for the brain and would have done so with comparatively little mammalian competition. The land-water interface would thus have allowed the hominid brain to develop sufficient neurological complexity to enable sophisticated tool and behaviour patterns to evolve in humans as a natural sequel to such a biochemical and environmental stimulus.

Animals↗

PubMed1990

Intermingling of central and peripheral nervous tissues in rat dorsolateral vagal rootlet transitional zones.

The morphology of the CNS-PNS transitional zone of adult rat dorsolateral vagus nerve rootlets is uniquely complex. A typical rootlet contains a transitional zone over 300 microns long, consisting of a central tissue projection extending distally into each rootlet and a peripheral tissue insertion extending for a longer distance deep into the brainstem. The peripheral tissue insertion is continuous with the peripheral tissue of the free rootlet through channels traversing or running parallel to the central tissue projection. Accordingly, the vagal CNS-PNS interface is topologically much more complex than that found elsewhere. In some rootlets the peripheral tissue in the brainstem constitutes an isolated island deep within the neuraxis. In others, peripheral continuity is established only through a cross connection with the peripheral tissue insertion of a neighbouring rootlet. About one fifth of all vagal myelinated axons alternate between the CNS and PNS tissue compartments. This distinguishes the vagus from all other nerves studied to date. These axons are myelinated by Schwann cells distal to the transitional zone, by oligodendrocytes in the central tissue projection and by one or more short intercalated Schwann internodes further centrally, mostly in the peripheral tissue insertion, where their perikarya commonly form closely apposed aggregates. More than four fifths of all unmyelinated axon bundles alternate between central and peripheral tissue compartments, commonly more than once. In the peripheral tissue insertion axons are enveloped by series of non-myelinating Schwann cells. Schwann processes commonly extend for over 50 microns into the central compartment at each central-peripheral transition. Around one fifth of peripherally unmyelinated axons have an oligodendrocytic sheath in the central compartment. Of these axons possessing more than one intercalated Schwann internode, over one quarter display alternation of myelinated and unmyelinated segments in the peripheral tissue insertion. Astrocytes in the transitional zone segregate PNS tissue, a role played by sheath cells further peripherally in the vagal rootlets. Astrocytes form the surface limiting membranes of the central tissue projection and the barrier between the peripheral tissue insertion and the surrounding brainstem. The barrier consists only of an attenuated layer of processes. This is deficient in places, where oligodendrocytic myelin sheaths are directly exposed to the endoneurial space of the peripheral tissue insertion and in some instances are apposed to myelinating or non-myelinating Schwann cells. Such communication between the central and peripheral compartments is unique to the vagal transitional zone. The findings are consistent with a range of possible events during development.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2000

The shape of life: how much is written in stone?

Considering the enormous diversity of living organisms, representing mostly untapped resources for studying ecological, ontogenetic and phylogenetic patterns and processes, why should evolutionary biologists concern themselves with the remains of animals and plants that died out tens or even hundreds of millions of years ago? The reason is that important new insights into some of the most vexing evolutionary questions are being revealed at the interfaces of palaeontology, developmental biology and molecular biology. Attempts to synthesise information from these disciplines, however, often encounter their greatest hurdles in considerations of the radiation of the Metazoa. Ongoing challenges relate to the origins of body plans, the relationships of the metazoan phyla and the timing of major evolutionary radiations. Palaeontology not only has its own unique contributions to the study of evolutionary processes, but provides a lynchpin for many of the emerging techniques.

Animals↗

PubMed1991

Marginal adaptation of Class V restorations using different restorative techniques.

This in vitro study compares the marginal adaptation of Class V restorations with margins located half in enamel and half in dentine, which were placed using different restorative techniques. Five operative procedures were evaluated both in saucer-shaped erosion lesions and in box-shaped cavities with bevels in enamel. The five procedures included a composite inlay technique using both the chemically and the light curing versions of a resin based composite cement, a bulk placement technique using a chemically curing composite resin, an incremental technique and an incremental technique combined with a built-up base, using a light curing composite resin. A combination of Gluma/Clearfil served as the dentinal adhesive. The micromorphology of the tooth/restoration interface was analysed before and after thermal cycling; the marginal seal was analysed after thermal cycling only. In the conventional cavities, the restorations showed less leakage, and micromorphologically a better, but statistically insignificant superior marginal adaptation. The inlay technique rendered the best marginal quality in both enamel and dentine before and after thermal cycling. Due to the unique curing characteristics of the chemically cured composite resin and cement resulting in a significantly reduced rigid contraction, the inlays cemented with the chemically curing cement and the restorations placed with the chemically curing composite resin were superior to their light cured counterparts. The built-up base yielding a reduction of the composite mass did not enhance marginal adaptation because of the partial replacement of the strong adhesion to dentine mediated by the Gluma/Clearfil combination by the weaker bond promoted by the etched glass ionomer cement.

Acid Etching, Dental↗

PubMed1998

Continuous quality improvement in ESRD: the role of networks, the United States Renal Data System, and facility-specific reports.

End-stage renal disease (ESRD) outcome improvement involves many different private and governmental entities. Networks have fulfilled a pivotal role in ESRD quality improvement by facilitating the change from quality assurance (QA) to continuous quality improvement (CQI) methodology, providing the collection and dissemination of outcome measures to facilities and developing quality improvement projects (QIPs) that interface directly with facilities. Improving outcomes in hemodialysis is generally limited to adequacy of hemodialysis and anemia management. Opportunities in peritoneal dialysis, nutrition, vascular access, and quality-of-life outcomes persist. Interaction between facilities and Medical Review Boards (MRBs) using workshops, site visits, and facility report cards can provide continuing ESRD outcome improvement. Every facility has unique people, procedures, and equipment producing their processes of care. Therefore, a certain amount of autonomy is required to encompass individual variation. Quality improvement methodology, although less rigorous than traditional outcome research, provides efficient and effective intervention when a rapid response is required to improve clinical outcomes. The two methods are not mutually exclusive but require distinct methodology to accomplish.

Health Facilities↗

PubMed2004

Effects of deletions at the C-terminus of tobacco acetohydroxyacid synthase on the enzyme activity and cofactor binding.

AHAS (acetohydroxyacid synthase) catalyses the first committed step in the biosynthesis of branched-chain amino acids, such as valine, leucine and isoleucine. Owing to the unique presence of these biosynthetic pathways in plants and micro-organisms, AHAS has been widely investigated as an attractive target of several classes of herbicides. Recently, the crystal structure of the catalytic subunit of yeast AHAS has been resolved at 2.8 A (1 A=0.1 nm), showing that the active site is located at the dimer interface and is near the herbicide-binding site. In this structure, the existence of two disordered regions, a 'mobile loop' and a C-terminal 'lid', is worth notice. Although these regions contain the residues that are known to be important in substrate specificity and in herbicide resistance, they are poorly folded into any distinct secondary structure and are not within contact distance of the cofactors. In the present study, we have tried to demonstrate the role of these regions of tobacco AHAS by constructing variants with serial deletions, based on the structure of yeast AHAS. In contrast with the wild-type AHAS, the truncated mutant which removes the C-terminal lid, Delta630, and the internal deletion mutant without the mobile loop, Delta567-582, impaired the binding affinity for ThDP (thiamine diphosphate), and showed different elution profiles representing a monomeric form in gel-filtration chromatography. Our results suggest that these regions are involved in the binding/stabilization of the active dimer and ThDP binding.

Acetolactate Synthase↗

PubMed1997

Trophoblasts express Fas ligand: a proposed mechanism for immune privilege in placenta and maternal invasion.

Cross-linking of Fas (CD95, APO-1) and Fas ligand (FasL; CD95L) induces apoptosis of Fas-bearing cells. Recent evidence suggests that FasL. expression plays an important role in maintenance of immune privilege in murine testis and eye and in tumour escape from immune rejection in colon cancer, melanoma and hepatocellular carcinoma. Bcl-2 is a membrane protein that suppresses apoptosis in response to a variety of stimuli. In this paper we describe abundant expression of FasL protein and mRNA transcripts within the immune privileged environment of the placenta by immunohistochemistry and reverse transcription in-situ polymerase chain reaction methods. The syncytiotrophoblast layer, the main site of feto-maternal interface, and extravillous trophoblasts, demonstrated consistent immunoreactivity for FasL in term placentae. Co-occurrence of Fas and Bcl-2 were detected with a similar pattern of distribution with FasL. The TUNEL method revealed evidence of apoptosis in the placental tissues. We speculate that abundant presence of FasL in the trophoblast contributes to immune privilege in this unique environment, perhaps by fostering apoptosis of activated Fas-expressing lymphocytes of maternal origin. An apoptotic process mediated by FasL may also play a role in placental invasion during implantation and underscores similarities between the trophoblast and neoplastic cells.

Apoptosis↗

PubMedDate not supplied

Edge artifacts in MR images: chemical shift effect.

The boundaries of some organs as seen in clinical magnetic resonance images appear to be asymmetric. This effect is caused by chemical shift differences between the resonant frequencies of the hydrogen nuclei of water and fat. The zeugmatographic technique maps resonant frequencies to unique spatial locations. These differences in resonant frequencies can appear as artifactual misplacement of information as this one-to-one correspondence is lost. Various phantoms are used to demonstrate that the boundary artifact appears only in the direction of the read (frequency-encoding) gradient when media of two different chemical shifts are separated by an interface. When the relative shift is less than the width of the interface, the boundary appears to be asymmetric; when the relative shift is greater than the width of the interface, a bright band is seen along one edge with a dark band along the other. This artifact is more pronounced in low resolution images than in high resolution images, and these effects are seen even when the relative chemical shift is smaller than a pixel bandwidth. These effects are explained both conceptually and analytically. The clinician should be aware of the potential presence of this artifact at boundary interfaces that bear diagnostic significance.

Kidney↗

PubMed2025

Genes required for Mycobacterium tuberculosis to survive the transition from aerosol to pulmonary alveolar lining fluid and early infection in a model of transmission.

Mycobacterium tuberculosis (Mtb) must withstand physical and chemical stresses during airborne transmission, including during the desiccation of aerosols small enough to reach pulmonary alveoli in a new host. There, Mtb encounters an antimicrobial pulmonary alveolar lining fluid (ALF) before it is engulfed by macrophages. To study the genes involved in Mtb's ability to survive the transition from desiccated droplet to pulmonary alveolus in an in vitro model, we formulated a model alveolar lining fluid (MALF) that mimics the composition of ALF as inferred from human bronchoalveolar lavage fluid (BALF). We compared the transcriptome of log-phase Mtb in MALF to the transcriptome of Mtb in BALF as BALF from the lungs of healthy adults was reconstituted to compensate for the dilution of ALF by lavage (rcBALF). Mtb from log-phase culture in a standard laboratory medium survived quantitatively in MALF and rcBALF for at least 24 hours. In contrast, Mtb that had passed through earlier stages of transmission began to succumb after 3 hours in MALF, past the time when particles have been observed to be phagocytized by alveolar macrophages. Screening of a genome-wide CRISPRi library of Mtb identified 35 genes as uniquely required by Mtb to survive the transition from desiccated microdroplet into rehydration in MALF. Thirty-one of these genes are non-essential under conventional laboratory conditions and seven have unknown functions. Thirteen of the 35 genes were additionally required for Mtb to survive in macrophage-like cells cultured at the air-liquid interface with pulmonary epithelial cells. This study nominates additional members of the transmission survival genome of Mtb, illustrates that different genes may contribute to the survival of Mtb at different stages of transmission, and suggests that modeled transmission can shed light on the functions of Mtb genes whose contributions have been unknown.

Journal Article↗