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At least 217 records · Page 12Linked to original sources
PubMed2005

Self-assembly, binding, and dynamic properties of heterodimeric porphyrin macrocycles.

A series of heterodimeric tetralactam macrocycles have been self-assembled using two kinetically labile zinc porphyrin-pyridine interactions. The stability constants have been determined by UV-vis titrations in CHCl3. The stability constants depend on the degree of preorganization of the linker units connecting the interacting groups. The ability of the self-assembled macrocycles to bind a terephthalamide guest was also investigated. One of the macrocycles was used for the construction of a [2]rotaxane. The dynamic properties of this system provide insight into the exchange mechanisms that operate in complex noncovalent assemblies.

Journal Article↗
PubMed2000

Fusion of small peroxisomal vesicles in vitro reconstructs an early step in the in vivo multistep peroxisome assembly pathway of Yarrowia lipolytica.

We have identified and purified six subforms of peroxisomes, designated P1 to P6, from the yeast, Yarrowia lipolytica. An analysis of trafficking of peroxisomal proteins in vivo suggests the existence of a multistep peroxisome assembly pathway in Y. lipolytica. This pathway operates by conversion of peroxisomal subforms in the direction P1, P2-->P3-->P4-->P5-->P6 and involves the import of various peroxisomal proteins into distinct vesicular intermediates. We have also reconstituted in vitro the fusion of the earliest intermediates in the pathway, small peroxisomal vesicles P1 and P2. Their fusion leads to the formation of a larger and more dense peroxisomal vesicle, P3. Fusion of P1 and P2 in vitro requires cytosol and ATP hydrolysis and is inhibited by antibodies to two membrane-associated ATPases of the AAA family, Pex1p and Pex6p. We provide evidence that the fusion in vitro of P1 and P2 peroxisomes reconstructs an actual early step in the peroxisome assembly pathway operating in vivo in Y. lipolytica.

ATPases Associated with Diverse Cellular Activitie↗
PubMed2001

On the dominance of whole-word knowledge in reading aloud.

The localist dual-route model of visual word recognition assumes a routine that addresses the pronunciation of all words known to the reader (the lexical-semantic pathway) and another routine, operating in parallel, that assembles pronunciations on the basis of sublexical spelling-sound correspondences. The present experiment exploits the exception effect (in which words that are atypical in terms of their spelling-sound correspondences are named more slowly than typical ones) because it is considered a marker of the joint operation of these two routines. Participants named high- and low-frequency regular and exception words that were repeated across two blocks of trials. The widely reported interaction between regularity and word frequency is present in Block 1 but is reduced in magnitude in Block 2. DRC, an implemented dual-route model, simulates the data. Taken in conjunction with other reports, the results provide further evidence for a double dissociation between addressed and assembled routines and are consistent with the view that skill in recognizing printed words known to the reader reflects the dominance of orthographic over phonological processing.

Adult↗
PubMed2006

The type III secretion injectisome.

The type III secretion injectisome is a complex nanomachine that allows bacteria to deliver protein effectors across eukaryotic cellular membranes. In recent years, significant progress has been made in our understanding of its structure, assembly and mode of operation. The principal structural components of the injectisome, from the base located in the bacterial cytosol to the tip of the needle protruding from the cell surface, have been investigated in detail. The structures of several constituent proteins were solved at the atomic level and important insights into the assembly process have been gained. However, despite the ongoing concerted efforts of molecular and structural biologists, the role of many of the constituent components of this nanomachine remain unknown.

Bacteria↗
PubMed1997

Respiratory symptoms and lung function abnormalities among machine operators in automobile production.

This cross-sectional study was designed to assess differences in prevalence of respiratory symptoms and lung function between machine operators exposed to semisynthetic or soluble metal-working fluids (MWFs) and unexposed assemblers and to assess exposure-response relationships with MWF type, total aerosol, endotoxin, culturable bacteria and fungi. We evaluated 183 machine operators and 66 assemblers from one large automobile transmission plant using questionnaires, spirometry data, and cross-shift assessment of both lung function and respiratory symptoms. We found that airborne exposures to total aerosol, endotoxin, culturable bacteria and fungi were higher in machine operations than in the assembly area. There was a correlation between bulk and airborne culturable bacteria, but not between bulk and airborne culturable fungi. Machine operators had significantly more usual cough, usual phlegm, work-related chest tightness and post-shift symptoms of chest tightness, throat irritation, and cough compared with assemblers. We found exposure-response relationships between respiratory symptoms and total aerosol, as well as culturable fungi and bacteria. Associations with endotoxin were not strong or consistent, possibly because airborne levels were generally low. Cross-shift lung function decrements did not differ between machine operators and assemblers and there were no associations with MWF or specific exposures. The finding of respiratory symptoms at low levels of exposure in this study suggests the need to re-assess total aerosol thresholds. Associations between airborne fungal exposures and respiratory symptoms need further study to characterize sources of exposure other than MWF in machining operations.

Adult↗
PubMed1992

The effect of cicloxolone sodium on the replication in cultured cells of adenovirus type 5, reovirus type 3, poliovirus type 1, two bunyaviruses and Semliki Forest virus.

The effect of cicloxolone sodium (CCX) on the replication of typical representatives of different virus families [adenovirus type 5 (Ad-5), reovirus type 3 (Reo-3), Bunyamwera and Germiston viruses, poliovirus type 1 (Polio-1) and Semliki Forest virus (SFV)] in tissue culture was investigated. The Golgi apparatus inhibitor monensin (Mon) and CCX were shown to have analogous effects on some aspects of virus replication. Although the Mon-like effect of CCX played no role in the antiviral activity against Ad-5, Reo-3 or Polio-1, it could entirely account for the antiviral activity against the Bunyamwera and Germiston viruses, for which inhibition of glycoprotein processing was responsible for the antiviral activity. In the case of SFV, the Mon-like activity of CCX caused cytoplasmic assembly of fully infectious SFV within vacuoles and thus impaired virus release without altering total infectious virus yield. Fewer Ad-5 and Reo-3 progeny were produced in the presence of the drug. CCX had a dose-dependent biphasic effect on the particle:p.f.u. ratio of the Reo-3 yield. At low CCX concentration (less than 50 microM) the virus yield contained poor quality, non-infectious virus, but at higher CCX concentration (greater than or equal to 100 microM) low quality virus could no longer be successfully assembled. We conclude that the antiviral effect can be manifested in three ways: (i) by a reduction in the virus particle yield produced; (ii) by a loss of quality (relative infectivity); (iii) by a virucidal effect of the drug. We have previously defined three CCX sensitivity classes. Mechanisms (i), (ii) and (iii) operate against viruses belonging to class CCXs-1 [herpes simplex virus (HSV) type 1, HSV-2 and vesicular stomatitis virus], but essentially only (i) and (ii) affect Reo-3 (CCXs-2), whereas (i) and possibly (iii) affect Ad-5 (CCXs-2). In the case of SFV (CCXs-3) none of these mechanisms operate, but relocation of assembled virus is found.

Adenoviridae↗
PubMed2005

Endo-robotic resection of the submandibular gland in a cadaver model.

BACKGROUND: By means of a prospective, nonrandomized investigation, we evaluated the feasibility of performing endo-robotic resection of the submandibular gland in a cadaver model and compared the results of robotically enhanced endoscopic surgery with those from a conventional endoscopic technique. METHODS: Procedural times were recorded in a consecutive series of 11 endoscopic submandibular gland resections using the daVinci Surgical System (Intuitive Surgical, Sunnyvale, CA) and a modified endoscopic surgical approach previously developed in a porcine model. The presence of neurovascular injury was assessed postoperatively, and the specimens were examined histologically. RESULTS: Eleven endo-robotic submandibular gland resections were successfully performed in six cadavers (no conversions to open resection were necessary). The median duration of the procedures was 48 minutes (range, 33-82 minutes). Creation of the operative pocket took an average (+/-SD) of 12.2 +/- 5.3 minutes, assembly of the robot required 9.3 +/- 4.1 minutes, and the mean time for submandibular gland resection was 29.4 +/- 8.9 minutes. The time required for robotic assembly was offset by the reduced operative time necessary compared with conventional endoscopic resection. Histologic examination confirmed the presence of normal glandular architecture, without evidence of excessive mechanical or thermal injury. There were no cases of apparent neurovascular injury. CONCLUSIONS: Robotically enhanced endoscopic surgery in the neck is feasible and offers a number of compelling advantages over conventional endoscopic neck surgery. Clinical trials will be necessary to determine whether these advantages can be achieved in clinical practice.

Cadaver↗
PubMed2000

Mitotic motors in Saccharomyces cerevisiae.

The budding yeast Saccharomyces cerevisiae provides a unique opportunity for study of the microtubule-based motor proteins that participate in mitotic spindle function. The genome of Saccharomyces encodes a relatively small and genetically tractable set of microtubule-based motor proteins. The single cytoplasmic dynein and five of the six kinesin-related proteins encoded have been implicated in mitotic spindle function. Each motor protein is unique in amino acid sequence. On account of functional overlap, no single motor is uniquely required for cell viability, however. The ability to create and analyze multiple mutants has allowed experimental dissection of the roles performed by each mitotic motor. Some of the motors operate within the nucleus to assemble and elongate the bipolar spindle (kinesin-related Cin8p, Kip1p, Kip3p and Kar3p). Others operate on the cytoplasmic microtubules to effect spindle and nuclear positioning within the cell (dynein and kinesin-related Kip2p, Kip3p and Kar3p). The six motors apparently contribute three fundamental activities to spindle function: motility, microtubule cross-linking and regulation of microtubule dynamics.

Anaphase↗
PubMed1985

Disposable microliter immunoabsorbent columns: construction and operation.

Disposable microliter immunoabsorbent columns were constructed from pasteur pipets. The bed support was a cube of gelatin surgical sponge, which was tamped into the pipet tip. Column dead space, represented by the compressed volume of the sponge, was 5 microliters. The columns were used with protein A-Sepharose; settled bed volumes were 50 microliters. It was possible to pour columns that functioned as immunoabsorbents with bed volumes as small as 10 microliters. There was no gravity flow through these columns. Flow was achieved by touching column tips to absorbent paper if liquid was to be discarded or to 50 microliters capillary tubes for fluid collection. A simple capillary collection tube assembly was designed for operation of a row of 10 columns at a time. In a test system of [3H]methotrexate and IgG anti-methotrexate, 90% of applied antigen was bound to antibody columns, whereas 90% was recovered in the eluates from control columns. The columns were used in the initial step of screening uncloned hybridoma culture fluids for anti-MSP.

Animals↗
PubMed2005

Molecular analysis of a store-operated and 2-acetyl-sn-glycerol-sensitive non-selective cation channel. Heteromeric assembly of TRPC1-TRPC3.

We have reported that internal Ca2+ store depletion in HSY cells stimulates a nonselective cation current which is distinct from I(CRAC) in RBL cells and TRPC1-dependent I(SOC) in HSG cells (Liu, X., Groschner, K., and Ambudkar, I. S. (2004) J. Membr. Biol. 200, 93-104). Here we have analyzed the molecular composition of this channel. Both thapsigargin (Tg) and 2-acetyl-sn-glycerol (OAG) stimulated similar non-selective cation currents and Ca2+ entry in HSY cells. The effects of Tg and OAG were not additive. HSY cells endogenously expressed TRPC1, TRPC3, and TRPC4 but not TRPC5 or TRPC6. Immunoprecipitation of TRPC1 pulled down TRPC3 but not TRPC4. Conversely, TRPC1 co-immunoprecipitated with TRPC3. Expression of antisense TRPC1 decreased (i) Tg- and OAG-stimulated currents and Ca2+ entry and (ii) the level of endogenous TRPC1 but not TRPC4. Antisense TRPC3 similarly reduced Ca2+ entry and endogenous TRPC3. Yeast two-hybrid analysis revealed an interaction between NTRPC1 and NTRPC3 (CTRPC1-CTRPC3, CTRPC3-CTRPC1, or CTRPC1-NTRPC3 did not interact), which was confirmed by glutathione S-transferase (GST) pull-down assays (GST-NTRPC3 pulled down TRPC1 and vice versa). Expression of NTRPC1 or NTRPC3 induced similar dominant suppression of Tg- and OAG-stimulated Ca2+ entry. NTRPC3 did not alter surface expression of TRPC1 or TRPC3 but disrupted TRPC1-TRPC3 association. In aggregate, our data demonstrate that TRPC1 and TRPC3 co-assemble, via N-terminal interactions, to form a heteromeric store-operated non-selective cation channel in HSY cells. Thus selective association between TRPCs generate distinct store-operated channels. Diversity of store-operated channels might be related to the physiology of the different cell types.

Biotinylation↗
PubMed1993

Post-transcriptional and post-translational regulatory steps are crucial in controlling the appearance and stability of thylakoid polypeptides during the transition of etiolated tobacco seedlings to white light.

We have investigated the expression of nuclear-encoded chloroplast proteins that are not associated with chlorophyll (the lumenal 33-kDa and 23-kDa polypeptides of the oxygen-evolving system of photosystem II, plastocyanin and the Rieske Fe/S protein) by comparing mRNA-accumulation rates with those of the corresponding proteins during illumination of etiolated tobacco seedlings. Using subcellular fractionation, pulse/chase, Northern and Western techniques, we found that the biogenesis and stability of these proteins are regulated both translationally, as well as post-translationally, including the efficiency of mRNA uptake into polysomes, processes that operate between translation and assembly or monitor the status (soluble and membrane-attached) of a terminally processed polypeptide. Polypeptide synthesis is generally not limited by mRNA amounts. For instance, steady-state transcript levels may increase 10-fold during illumination, while those associated with polysomes increase only 2-3-fold without measurable influence on the rate of protein synthesis. The 23-kDa and Rieske polypeptides are predominantly membrane associated, but plastocyanin and the 33-kDa polypeptide are distributed among both soluble and membrane-associated protein fractions. Plastocyanin appears to be comparably stable in both forms. However, for the 33-kDa polypeptide, only the membrane-attached form is stable (> 8 h) and only this pool increases upon illumination. Its soluble form is rapidly degraded with a half-life of approximately 1 h under the chosen conditions. Our findings probably reflect part of a more general regulatory principle operating in the differentiation and maintenance of subcellular structure.

Blotting, Northern↗
PubMed1976

Shoulder muscle tenderness and physical features of female industrial workers.

Physique, muscle strength, and jump-step scores of female industrial workers, ages 17--34, were studied in relation to tenderness of shoulder muscles for five groups, (A) character display operators, (B) fluorescent lamp assemblers, (C) photographic film rolling workers, (D) teachers and nurses of handicapped children, and (E) office workers. No significant differences were found between the five groups in mean body height, body weight, and skinfold thickness, but mean knee extension force of groups A and C and mean back muscle strength of groups A, B, and C was significantly lower than that of group E. Workers of groups C and D with a low tenderness threshold of m. trapezius of 0.6 kg/cm2 or less had stiff shoulders more frequently and lower force levels of knee extension, back muscle, and upper arm abduction than those without tenderness. No similar tendency was found for groups B and E. Further, among workers with objective signs of occupational cervicobrachial disorder, there were few whose knee extension force or jump-step scores were above the averages of normal office workers. Shoulder muscles of such operators were revealed to be continuously contracted during operations. The possible effects of chronic fatigue due to repetitive operations on developing localized tenderness and occupational hazards are discussed.

Adolescent↗
PubMed1999

Methods for improving performance under reverse alignment conditions during endoscopic surgery.

BACKGROUND: There are times during endoscopic procedures when the surgeon has to operate ahead of the camera/telescope assembly. As a result, the image displayed on the monitor will be an inverted mirror image of the operative field (reverse alignment). The present study addresses the extent of these difficulties and suggests some techniques that may be used to overcome the problem. METHODS: Eight specialist registrars participated in experiments involving the execution of a simulated dissection task under 12 different imaging conditions. These conditions included normal alignment, reverse alignment, total or partial digital correction of reverse alignment (about the horizontal and vertical axes independently and together), and a simple rotation of the camera through 180 degrees. Normal, reverse, and corrected reverse alignment were also tested with optical axes of 45 degrees and 60 degrees. The endpoints were the task execution and the errors rate. RESULTS: A marked deterioration in execution time was observed when the surgeons worked under reverse alignment rather than under normal viewing (p = 0.036). Significant improvement in execution-time errors rate was found when both the horizontal and vertical axes were digitally corrected simultaneously (p = 0.27) and when the camera was rotated 180 degrees with respect to the telescope during reverse alignment (p = 0.28). CONCLUSIONS: The effect on performance produced by reverse alignment of the endoscope and instruments can be overcome by means of digital electronic processing, or simply by turning the camera through 180 degrees.

Adult↗
PubMed2001

Design of a compartmentalized shotgun assembler for the human genome.

Two different strategies for determining the human genome are currently being pursued: one is the "clone-by-clone" approach, employed by the publicly funded project, and the other is the "whole genome shotgun assembler" approach, favored by researchers at Celera Genomics. An interim strategy employed at Celera, called compartmentalized shotgun assembly, makes use of preliminary data produced by both approaches. In this paper we describe the design, implementation and operation of the "compartmentalized shotgun assembler".

Chromosomes, Artificial, Bacterial↗
PubMedDate not supplied

Air lead exposures and blood lead levels within a large automobile manufacturing workforce, 1980-1985.

Recent (1980-1985) trends in air lead (PbA) exposures and blood lead (PbB) levels experienced by approximately 10,000 workers employed in various stages of the automobile manufacturing process (i.e., auto assembly, lead-acid battery manufacture, foundry work, and "other" manufacturing-related operations) are described. Between 1980-1985, the mean PbB levels of assembly, battery, foundry, and "other" workers decreased by 28, 24, 3, and 27%, respectively, to 16.6, 23.6, 15.9, and 11.8 micrograms Pb/dl. Workers in the following job categories experienced the highest annual mean PbB levels: paste machine operators (battery plants), solder-grinders (assembly plants), and crane operators (foundries). During the same period, median 8-h Time Weighted Average PbA exposures (micrograms Pb/m3) in assembly plants, battery plants, and foundries decreased by 10, 12, and 20%, respectively, to 8.1, 13.6, and 10.9 micrograms/m3.

Adult↗
PubMedDate not supplied

Perception and awareness in phonological processing: the case of the phoneme.

The necessity of a "levels-of-processing" approach in the study of mental representations is illustrated by the work on the psychological reality of the phoneme. On the basis of both experimental studies of human behavior and functional imaging data, it is argued that there are unconscious representations of phonemes in addition to conscious ones. These two sets of mental representations are functionally distinct: the former intervene in speech perception and (presumably) production; the latter are developed in the context of learning alphabetic literacy for both reading and writing purposes. Moreover, among phonological units and properties, phonemes may be the only ones to present a neural dissociation at the macro-anatomic level. Finally, it is argued that even if the representations used in speech perception and those used in assembling and in conscious operations are distinct, they may entertain dependency relations.

Awareness↗
PubMed1986

Application of a computer-controlled infrared beam device to behavioral research.

An experimental control system was designed to evaluate the effects of toxic substances. This system consisted of a personal computer (Apple II), shuttle boxes, and their controller. The shuttle box (33 X 20 X 53 cm) was divided into two compartments of equal size with a hurdle (8 cm). An infrared beam device was set up 8 cm from each side of the hurdle and 5 cm above the floor to detect the occupied compartment. Signals from detectors were put into the Apple II through a peripheral interface adapter unit. Since the control program was written in assembly language, which could operate at high speed, it was possible to conduct experiments using four shuttle boxes simultaneously. During the execution of the experiments, the timer unit generated pulses 100 times/sec. Every pulse was counted and used to measure a response latency at intervals of 10 msec. The application of a computer-controlled infrared beam device made it possible to detect the location and operant responses of a subject mechanically from moment to moment and to construct an extremely flexible experimental control system.

Avoidance Learning↗
PubMed1980

A systematic approach to reconstructing microcircuitry by electron microscopy of serial sections.

To observe certain quantitative features of neuronal geometry and microcircuitry, it is necessary to reconstruct neurons from electron micrographs of serial, ultra-thin sections. We describe here an approach to preparing, photographing, and analyzing moderately long series (100-500 sections). A series is prepared using an assembly line approach: one operator cuts while a second mounts ribbons of sections using various mechanical aids. Photographs are taken in the electron microscope at low magnification and high accelerating voltage. Sequential negatives are aligned using an image combiner and copied, using quasi-coherent illumination, onto 35 mm film. The resulting "movie' is mounted on a precision film transport mounted on an X-Y stage controlled by stepping motors. The movie is viewed through a high resolution video system while a video storage device and switching system permit rapid alternation between frames for comparisons. The profiles of a process in successive frames are "microaligned' by small adjustments of the transport's X-Y position. The absolute X-Y biological coordinates for each frame and the correction necessary to bring it into alignment are stored in a Z80 microprocessor as a process vector. When the movie is re-examined with the stepping motors under control of the computer, the microaligned process shows almost no frame-to-frame jitter. The process vector may be used to generate a "branch schematic' of the neuron. The microaligned profiles can also be digitized and displayed as a reconstruction using a PDP 11/34 computer. Uses of the approach are presented with examples from the cat retina and visual cortex.

Animals↗