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PubMed2006

Immobilization of biomaterials to nano-assembled films (self-assembled monolayers, Langmuir-Blodgett films, and layer-by-layer assemblies) and their related functions.

For utilization of highly sophisticated functions of biomaterials in nano-scale functional systems, immobilization of biomaterials on artificial devices such as electrodes via thin film technology is one of the most powerful strategies. In this review, we focus on three major organic ultrathin films, self-assembled monolayers (SAM), Langmuir-Blodgett (LB) films, and layer-by-layer (LBL) assemblies, and from the viewpoints of biomaterial immobilization, typical examples and recent progresses in these film technologies are described. The SAM method allows facile contact between biomaterials and man-made devices, and well used for bio-related sensors. In addition, recent micro-fabrication techniques such as micro-contact printing and dip-pen nanolithography were successfully applied to preparation of biomaterial patterning. A monolayer at the air-water interface, which is a unit structure of LB films, provides a unique environment for recognition of aqueous biomaterials. Recognition and immobilization of various biomaterials including nucleotides, nucleic acid bases, amino acids, sugars, and peptides were widely investigated. The LB film can be also used for immobilization of enzymes in an ultrathin film on an electrode, resulting in sensor application. The LBL assembling method is available for wide range of biomaterials and provides great freedom in designs of layered structures. These advantages are reflected in preparation of thin-film bio-reactors where multiple kinds of enzymes sequentially operate. LBL assemblies were also utilized for sensors and drug delivery systems. This kind of assembling structures can be prepared on micro-size particle and very useful for preparation of hollow capsules with biological functions.

Animals↗
PubMed1981

Energy expenditure in simulated tasks: comparison between subjects with brain injury and able-bodied persons.

Energy expenditure of 7 brain-injured individuals was compared to that of 10 able-bodied individuals. Data were collected with the subjects at rest and while performing 4 simulated industrial tasks: material handling, crank rotation, electric switch operation, mechanical assembly. Energy expenditure was determined by measuring oxygen consumption (VO2). Energy usage per unit weight per unit time was calculated for each subject. Over the range of tasks, the brain injured means varied from 0.0396 to 0.0674 kcal/kg/min, while the able-bodied means were between 0.0413 and 0.0849 kcal/kg/min. The cranking task showed the only statistically significant difference for this measure. Total energy use/unit weight was also examined, the brain injured group averaging more energy use during the material handling, switching, and assembly tasks and the able-bodied group averaging more energy use on the cranking task. Two factors explaining these results appear to be motivation and complexity of hand movements for each task. The performance of the brain injured group on the cranking task indicates ways of adapting crank operated control mechanisms for use by the handicapped.

Adult↗
PubMed2006

Cysteine-scanning analysis of the chemoreceptor-coupling domain of the Escherichia coli chemotaxis signaling kinase CheA.

The C-terminal P5 domain of the histidine kinase CheA is essential for coupling CheA autophosphorylation activity to chemoreceptor control through a binding interaction with the CheW protein. To locate P5 determinants critical for CheW binding and chemoreceptor control, we surveyed cysteine replacements at 39 residues predicted to be at or near the P5 surface in Escherichia coli CheA. Two-thirds of the Cys replacement proteins exhibited in vitro defects in CheW binding, either before or after modification with a bulky fluorescein group. The binding-defective sites were widely distributed on the P5 surface and were often interspersed with sites that caused no functional defects, implying that relatively minor structural perturbations, often far from the actual binding site, can influence its conformation or accessibility. The most likely CheW docking area included loop 2 in P5 folding subdomain 1. All but four of the binding-defective P5-Cys proteins were defective in receptor-mediated activation, suggesting that CheW binding, as measured in vitro, is necessary for assembly of ternary signaling complexes and/or subsequent CheA activation. Other Cys sites specifically affected receptor-mediated activation or deactivation of CheA, demonstrating that CheW binding is not sufficient for assembly and/or operation of receptor signaling complexes. Because P5 is quite similar to CheW, whose structure is known to be dynamic, we suggest that conformational flexibility and dynamic motions govern the signaling activities of the P5 domain. In addition, relative movements of the CheA domains may be involved in CheW binding, in ternary complex assembly, and in subsequent stimulus-induced conformational changes in receptor signaling complexes.

Bacterial Proteins↗
PubMed1984

Assessment of biomaterials as components of a reciprocating dialyser during canine dialysis.

A recently reported device, the sorbent suspension reciprocating dialyser (SSRD), was investigated for use as a test system for biocompatibility of dialyser components. The device is easy to assemble and operate, and allows minimal blood contact with foreign material outside of dialyser components. Its constant pressure/variable flow rate operation allows quantification of degree of clotting of dialyser versus time. The effect of heparinization of the blood distribution gaskets (BDG) of the device on performance and dialyser lifetime was investigated. Heparin was bound to the surface of polyethylene gaskets by immersion in a solution of tridodecylmethylammonium chloride (TDMAC)--heparin complex for several hours. Gaskets were then assembled in an SSRD which was then used for experimental dialysis in dogs with AV shunts. Dialysers assembled using non-heparinized gaskets were used as controls. Blood coagulation tendency was quantified by the activated clotting time (ACT) and partial thromboplastin time (PTT), and these values correlated with the rate of clotting of the device. Heparinization of the gaskets resulted in the prevention of clotting in the dialyser until the final minutes of dialysis in all cases, in contrast to the constant decay of blood fill volume and evidence of clotting in the non-heparinized cases. However, dialyser lifetime was not significantly increased by gasket heparinization. At normal initial values of ACT (80-95 s) dialyser clotting occurred in 10-15 min. In tests with non-heparinized gaskets and systemically heparinized dogs, values obtained in the ACT test were observed to decrease during dialysis, indicating the disappearance of heparin from the blood. Both ACT and PTT tests show promise as predictors of dialyser lifetime.

Animals↗
PubMed1995

How bacteria sense and swim.

Cells of Escherichia coli or Salmonella typhimurium can sense chemicals in their environment and respond by moving toward some and away from others. The ability to sense and swim requires the products of approximately 50 genes, about 10 for detecting and processing sensory cues and the rest for assembly and operation of the flagella. The function of each component in the chemosensory signaling pathway is well understood. Signaling is known to involve phosphorylation of a set of cytoplasmic proteins, but questions remain concerning the protein conformational changes and interactions that take place. Functions have been assigned to almost all of the approximately 40 flagellar proteins, and the sequence of events in flagellar assembly has been largely determined. Flagellar assembly depends on a specialized apparatus for exporting certain flagellar components to their appropriate locations. The structure and mechanism of this apparatus remain a mystery, as does the mechanism by which the flagellar motor generates torque.

Chemotaxis↗
PubMed1995

Extravehicular activity training and hardware design consideration.

Preparing astronauts to perform the many complex extravehicular activity (EVA) tasks required to assemble and maintain Space Station will be accomplished through training simulations in a variety of facilities. The adequacy of this training is dependent on a thorough understanding of the task to be performed, the environment in which the task will be performed, high-fidelity training hardware and an awareness of the limitations of each particular training facility. Designing hardware that can be successfully operated, or assembled, by EVA astronauts in an efficient manner, requires an acute understanding of human factors and the capabilities and limitations of the space-suited astronaut. Additionally, the significant effect the microgravity environment has on the crew members' capabilities has to be carefully considered not only for each particular task, but also for all the overhead related to the task and the general overhead associated with EVA. This paper will describe various training methods and facilities that will be used to train EVA astronauts for Space Station assembly and maintenance. User-friendly EVA hardware design considerations and recent EVA flight experience will also be presented.

Astronauts↗
PubMed2004

Robot-assisted laparoscopic cholecystectomy: initial Mayo Clinic Scottsdale experience.

OBJECTIVE: To review a single institution's experience with robot-assisted laparoscopic cholecystectomy. PATIENTS AND METHODS: We reviewed retrospectively all cholecystectomies performed with the assistance of a surgical robot at the Mayo Clinic in Scottsdale, Ariz, from October 2002 to July 2003. Cholanglograms were obtained intraoperatively for patients with elevated results on liver function tests. The gallbladder was removed by the surgeon with the use of the robot. A surgical assistant at the operating table exchanged instruments in the robot arms and applied clips when needed. Total operating time, assembly time of the robot, complications, and postoperative course were evaluated. RESULTS: Nineteen patients underwent robot-assisted laparoscopic cholecystectomy; 16 had symptomatic cholelithiasis, 2 had gallbladder polyps, and 1 had acute cholecystitis. Of the 19 surgeries, 16 were completed successfully with robotic assistance. In 3 consecutive patients, a mechanical problem occurred with the robot; however, all procedures were completed laparoscopically. The mean set-up time, including patient positioning and preparation and robotic installation, was 28.1 minutes. The mean +/- SD operating time was 82.3+/-17.9 minutes without a cholanglogram and 102+/-20.9 minutes with a cholanglogram. There were no complications and no conversions to an open procedure. CONCLUSION: Robotic surgery offers many potential advantages, including surgeon comfort, elimination of surgeon tremor, improved imaging, and increased degrees of freedom of the operative Instruments, compared with conventional laparoscopic surgery. However, patient outcomes and operative costs need to be evaluated further.

Adult↗
PubMed2005

The first mitosis of the mouse embryo is prolonged by transitional metaphase arrest.

The first mitosis of the mouse embryo is almost twice as long as the second. The mechanism of the prolongation of the first mitosis remains unknown, and it is not clear whether prometaphase or metaphase or both are prolonged. Prometaphase is characterized by dynamic chromosome movements and spindle assembly checkpoint activity, which prevents anaphase until establishment of stable kinetochore-microtubule connections. The end of prometaphase is correlated with checkpoint inactivation and disappearance of MAD2L1 (MAD2) and RSN (CLIP-170) proteins from kinetochores. Spindle assembly checkpoint operates during the early mouse mitoses, but it is not clear whether it influences their duration. Here, we determine the length of prometaphases and metaphases during the first two embryonic mitoses by time-lapse video recording of chromosomes and by immunolocalization of MAD2L1 and RSN proteins. We show that the duration of the two prometaphases does not differ and that MAD2L1 and RSN disappear from kinetochores very early during each mitosis. The first metaphase is significantly longer than the second one. Therefore, the prolongation of the first embryonic mitosis is due to a prolonged metaphase, and the spindle assembly checkpoint cannot be involved in this process. We show also that MAD2L1 staining disappears gradually from kinetochores of oocytes arrested at metaphase of the second meiotic division. This shows a striking similarity between the first embryonic mitosis and metaphase arrest in oocytes. We postulate that the first embryonic mitosis is prolonged by a transient metaphase arrest that is independent of the spindle assembly checkpoint and is similar to metaphase II arrest. The molecular mechanism of this transient arrest remains to be elucidated.

Animals↗
PubMed2001

[Surgical treatment of male infertility].

OBJECTIVE: In the Czech Republic in the treatment of male infertility the most up-to-date technologies of assisted reproduction have also become the methods of choice: MESA--microsurgical epididymal sperm aspiration, TESE--testicular sperm extraction and ICSI--intracytoplasmic sperm injection. The objective of the present study was an attempt to find a reliable predictor of results of planned TESE as prediction of possible successful sperm extraction can prevent unnecessary ovarian stimulation. DESIGN: Retrospective analysis of a group of 202 men operated in the authors centre on account of azoospermia--65 patients with obstructive azoospermia and 137 patients with testicular azoospermia. SETTING: Andromeda, Biolab, Iscare IVF, Prague. METHOD: The following parameters were evaluated: testicular volume, FSH serum level and histological finding and their values were compared with results of TESE. RESULTS: Elevated FSH levels and low testicular volume do not rule out a positive result of TESE. The most accurate predictor is histological examination. Elongated spermatids were found in the histological material in 59.3% of the examined cases which correlates significantly with the 60.2% TESE yield in the evaluated group. CONCLUSION: The material assembled on operation was divided into three parts. One serves preparation of the perIerative native preparation, the second one is dispatched for histological examination and the largest part is frozen. Simultaneous collection of oocytes and sperm cells is done only in selected cases. The histological finding of elongated spermatids indicates a positive finding of sperm during TESE with an accuracy of 91%. Assessment of the causes of azoospermia, evaluation of the state of spermatogenesis and treatment are thus implemented by a single operation.

Epididymis↗
PubMed2006

Co-operative mineralization and protein self-assembly in amelogenesis: silica mineralization and assembly of recombinant amelogenins in vitro.

An amorphous silica mineralization technique was used to produce inorganic/protein composites to elucidate the structure and mechanism of formation of amelogenin assemblies, which may play an important role in regulating enamel structure during the initial stages of amelogenesis. Full-length recombinant amelogenins from mouse (rM179) and pig (rP172) were investigated along with key degradation products (rM166 and native P148) lacking the hydrophilic C terminus found in parent molecules. The resulting products were examined using transmission electron microscopy and/or small-angle X-ray scattering. Using protein concentrations of 0.1-3 mg ml-1, large monodisperse spheres of remarkably similar mean diameters were observed using rM179 (124+/-4 nm) and rP172 (126+/-7 nm). These spheres also exhibited 'internal structure', comprising nearly spherical monodisperse particles of approximately 20 nm in diameter. In the presence of rM166, P148, and bovine serum albumin (control), large unstructured and randomly shaped particles (250-1000 nm) were observed. Without added protein, large dense spherical particles of silica (mean approximately 500 nm) lacking internal structure were produced. These findings demonstrate that full-length amelogenins have the ability to form higher-order structures, whereas amelogenins that lack the hydrophilic C terminus do not. The results also suggest that full-length amelogenin can guide the formation of organized mineralized structures through co-operative interactions between assembling protein and forming mineral.

Amelogenesis↗
PubMed1988

Probing the assembly of the 3' major domain of 16 S ribosomal RNA. Quaternary interactions involving ribosomal proteins S7, S9 and S19.

We have studied the effect of assembly of ribosomal proteins S7, S9 and S19 on the accessibility and conformation of nucleotides in 16 S ribosomal RNA. Complexes formed between 16 S rRNA and S7, S7 + S9, S7 + S19 or S7 + S9 + S19 were subjected to a combination of chemical and enzymatic probes, whose sites of attack in 16 S rRNA were identified by primer extension. The results of this study show that: (1) Protein S7 affects the reactivity of an extensive region in the lower half of the 3' major domain. Inclusion of proteins S9 or S19 with S7 has generally little additional effect on S7-specific protection of the RNA. Clusters of nucleotides that are protected by protein S7 are localized in the 935-945 region, the 950/1230 stem, the 1250/1285 internal loop, and the 1350/1370 stem. (2) Addition of protein S9 in the presence of S7 causes several additional effects principally in two structurally distal regions. We observe strong S9-dependent protection of positions 1278 to 1283, and of several positions in the 1125/1145 internal loop. These findings suggest that interaction of protein S9 with 16 S rRNA results in a structure in which the 1125/1145 and 1280 regions are proximal to each other. (3) Most of the strong S19-dependent effects are clustered in the 950-1050 and 1210-1230 regions, which are joined by base-pairing in the 16 S rRNA secondary structure. The highly conserved 960-975 stemp-loop, which has been implicated in tRNA binding, appears to be destabilized in the presence of S19. (4) Protein S7 causes enhanced reactivity at several sites that become protected upon addition of S9 or S19. This suggests that S7-induced conformational changes in 16 S rRNA play a role in the co-operativity of assembly of the 3' major domain.

Aldehydes↗
PubMed1999

Process intensification by direct product sequestration from batch fermentations: application of a fluidised bed, multi-bed external loop contactor

A critical comparison has been made of the relative efficacy of the primary purification of an extracellular acid protease produced by the yeast Yarrowia lipolytica. The performance of conventional, discrete sequences of fermentation, broth clarification and fixed bed, anion exchange chromatography has been compared with fluidised bed adsorption directly interfaced with post-term fermentation broth and fluidised bed adsorption directly integrated with productive fermentations (so-called direct product sequestration; DPS). Advantages of the latter, in terms of the improved yield and molecular quality of the protease end product are discussed in terms of the design, assembly and operation of component parts of DPS devices and their generic application to other extracellular bioproducts of microbial fermentations. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗
PubMed1992

Occupation and risk of uveal melanoma. An exploratory study.

BACKGROUND: Little is known about the cause of uveal melanoma, the most common primary intraocular malignant lesion in adults. This population-based case-control study evaluated occupational exposures. METHODS: One hundred ninety-seven newly diagnosed cases of uveal melanoma participated. Approximately two control subjects matched for age, sex, and telephone exchange area were selected for each case by random-digit dialing. Data were collected by a structured telephone interview. Two systems of occupational coding were used: an occupation-exposure linkage system and the Bureau of Census data. Conditional logistic regression for matched studies was used to examine various occupational exposures while controlling for previously reported potential confounders and for family income. The occupation-exposure matrix was used to define clusters of cases exposed to a particular chemical group from various occupations. RESULTS: Odds ratios were elevated for agriculture and farming work for both industry and occupation; this was consistent across both classification systems. Elevated odds ratios also were found for occupations involving machine operations, fabrication, assembling, equipment cleaning, and exposure to metal industries. Exposure to alkylating agents and phenols was associated with a lower risk compared with all other exposures. Several self-reported exposures also were studied. Exposures associated with elevated odds ratios were inks, insecticides, gases, radioactive substances, polybromated biphenyls, and chemical solvents. CONCLUSIONS: This exploratory study suggests various occupational associations for uveal melanoma and areas for future research.

Adolescent↗
PubMed1995

Elastin in lung development and disease.

Elastic fibres are present in lung structures including alveoli, alveolar ducts, airways, vasculature and pleura. The rate of lung elastin synthesis is greatest during fetal and neonatal development, and is minimal in the healthy adult. We have determined that glucocorticoids up-regulate fetal lung tropoelastin expression while concomitantly accelerating terminal airspace maturation. Because there is minimal turnover of elastin in healthy adult lung, the elastin incorporated into the lung early in development supports lung function for the normal lifespan. However, in the adult lung, in pathological circumstances such as emphysema or pulmonary fibrosis there may be reactivation of elastin expression. We have found in silica-induced pulmonary fibrosis that expression of tropoelastin is primarily increased in the walls and the septal tips of the alveolus, with modest increases in other compartments which normally express tropoelastin during development. This finding suggests that the mesenchymal cell of the alveolar wall increases tropoelastin expression during fibrotic disorders. In emphysema and fibrosis, elastin is present in abnormal-appearing, probably non-functional, elastic fibres, suggesting that the adult lung cannot recapitulate the elastic fibre assembly mechanisms operative during normal lung growth.

Adult↗
PubMed2006

An assessment and quantification of the rates, costs, and risk factors of occupational amputations: analysis of Kentucky workers' compensation claims, 1994-2003.

BACKGROUND: Assessments of the impact of occupational amputations with outcomes of pain, disfigurement, and often an inability to return to the same job, are limited. The present study examines and quantifies the rates, risk factors, and costs of occupational amputations in the workplace in the State of Kentucky. METHODS: Worker's compensation data from 1994 through 2003 from Kentucky was used to investigate job-related amputations (n = 2,297). The US Department of Labor's Current Population Survey (CPS) was used to estimate injury rates. RESULTS: The average amputation claim rate for all Kentucky workers was 1.37 per 10,000, with an average per-claim indemnity cost of $8,822. A declining trend was found in the rate over the last 7 years studied. Accidents resulting in amputations occurred at twice the rate on weekends than on weekdays. Amputations affecting the hand constituted 94.6% of all injuries. Workers in the mining industry had the highest estimated claim rate of 5.92 (95% CI 5.23-6.66), and machine operators and assemblers had the highest rate of all occupations with 3.35 (95% CI 3.23-3.47). CONCLUSIONS: Workplace amputations remain a significant workplace concern and represent a particular hazard for those in the mining and manufacturing industries. Future research should examine causes of the weekend effect to develop human resource and safety interventions for risk reduction.

Accidents, Occupational↗
PubMed1998

An apparatus for membrane-confined analytical electrophoresis.

A membrane-confined analytical electrophoresis apparatus for measuring the solution charge of macromolecules has been described previously (T. M. Laue et al., Anal. Biochem. 1989, 182, 377-382). Presented here is a design for this apparatus, which permits the on-line acquisition and display of absorbance data from up to 512 positions along an analysis chamber. Concentration distributions of macromolecules in solution can be monitored in the chamber to provide steady-state electrophoresis, electrophoretic mobility and diffusion measurements. Buffer chambers press semipermeable membranes against the open ends of a fused-silica cuvette to form the analysis chamber. This configuration permits both the flow of buffer and the establishment of an electric field across the cuvette, while retaining macromolecules in the field of view. Though a gel may be included in the analysis chamber, none is required for gradient stabilization. The volume of sample required for analysis is 8 microL, most of which is recoverable. Experimental conditions can be varied during study by simply changing the circulating buffer and/or the electric field. The analysis and buffer chambers are held in an aluminum housing that sits in an aluminum water jacket. The water jacket provides temperature control, shielding from external electrical noise and also serves as an optical mask. Plans for the cell assembly, optical system and the computer interface for data acquisition are provided. The assembly and operation of the apparatus and the analysis of data are described.

Electric Conductivity↗
PubMed1988

Operational significance of receptive field assemblies.

The known physiological substrate of the front-end visual system can be interpreted in terms of abstract geometrical objects and relations. It is pointed out which structures can be interpreted as the implementation of tangent quantities, etc., and how the global visual areas can be interpreted as (co-)vector bundles (of which the fibers are "cortical columns") and similar structures. The possible implementations of an affine connection and a gauge field for the metric are investigated. This theory not only permits one to describe the existing structure in a particularly attractive, modular way, but also enables one to predict the type of connections necessary for the embodiment of specific visual capabilities, and to find the neural assemblies involved in specific visual tasks.

Animals↗
PubMed1988

Health problems among operators of plastic welding machines and exposure to radiofrequency electromagnetic fields.

To study possible medical effects of high radiofrequency radiation (RF), 113 Swedish men and women were studied by means of a structured interview and rating of subjective symptoms. A test session was included in order to examine coordination and muscular function of the hands. A neurological test concerning two-point discrimination (2-PD) was also done. As referents, 23 women, sewing machine operators and assembly workers, were chosen, interviewed and likewise tested. Exposure measurements were taken of the RF fields around the welding machines. The present Swedish ceiling value of 250 W/m2 for the equivalent power density was exceeded in more than 50% of the machines. The highest leakage fields, both for electric and magnetic fields, were found near machines used in factories for ready-made clothing, which gave a high exposure to the hands. Irritative eye symptoms were reported by 23% of the men and 40% of the women. A group of 27 persons was selected for a clinical eye examination and checked by photographs, and nine persons had modest conjunctivitis. A high prevalence of numbness in hands, especially among women, was found. A significantly impaired 2-PD was found in the exposed women as compared to the referent group. The pregnancy outcome for 305 female plastic welders during 1974-1984 did not show any significant differences with the Swedish average concerning malformation or prenatal mortality.

Adult↗