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PubMed1990

Processive replication is contingent on the exonuclease subunit of DNA polymerase III holoenzyme.

In this report we have taken the reconstitution approach to study which subunits of the heterotrimer core polymerase (alpha, epsilon, theta) participate in the highly processive replication of long DNA templates by DNA polymerase III holoenzyme (holoenzyme). Comparison of the core and the alpha epsilon complex (the DNA polymerase and 3'-5' exonuclease subunits, respectively) shows they are both rapid and highly processive polymerases when they are reconstituted into a holoenzyme with the gamma complex (gamma delta delta' chi psi) and beta accessory proteins of holoenzyme. Specifically, holoenzyme reconstituted using either core or alpha epsilon completely replicates a uniquely primed 5.4-kilobase (kb) single-stranded DNA within 12 s in one binding event. Hence the theta subunit of core is not required for the processivity or speed of the holoenzyme. In contrast, when only the alpha subunit is reconstituted into the holoenzyme it is unable to replicate the entire 5.4-kb circle in one binding event but still retains a fairly high processivity of 1-3 kb and when given sufficient time for multiple binding events it finally finishes the entire circle. Therefore, highly processive DNA synthesis by holoenzyme is contingent on the epsilon exonuclease subunit. In light of these results the significance of the polymerase and exonuclease activities residing in two separate polypeptides is discussed.

Chromatography, Gel↗

PubMed1985

Neuropsychological correlates of information-processing by children with Down syndrome.

Nine children with Down syndrome were compared to two groups of nonretarded children, one similar in CA, the other a chronologically younger group of similar MA. The event-related brain potential (ERP) and reaction time (RT) results indicated that children with Down syndrome process some types of auditory information more slowly than do MA- or CA-matched nonretarded children. They were found to differ from nonretarded children in the scalp distribution of amplitudes of certain ERP components. Finally, the speed of processing and amplitude differences that were found could not be explained on the basis that children with Down syndrome are simply maturationally delayed in their cognitive abilities. The possible relation of these neuropsychological (ERPs) and performance (RT) differences to pathological changes in the hippocampus were discussed.

Age Factors↗

PubMedDate not supplied

Neural responses to relative speed in the primary visual cortex of rhesus monkey.

Relative motion information, especially relative speed between different input patterns, is required for solving many complex tasks of the visual system, such as depth perception by motion parallax and motion-induced figure/ground segmentation. However, little is known about the neural substrate for processing relative speed information. To explore the neural mechanisms for relative speed, we recorded single-unit responses to relative motion in the primary visual cortex (area VI) of rhesus monkeys while presenting sets of random-dot arrays moving at different speeds. We found that most VI neurons were sensitive to the existence of a discontinuity in speed, that is, they showed higher responses when relative motion was presented compared to homogenous field motion. Seventy percent of the neurons in our sample responded predominantly to relative rather than to absolute speed. Relative speed tuning curves were similar at different center-surround velocity combinations. These relative motion-sensitive neurons in macaque area VI probably contribute to figure/ground segmentation and motion discontinuity detection.

Action Potentials↗

PubMed2004

Activity-dependent dynamics of coexisting brain-derived neurotrophic factor, pro-opiomelanocortin and alpha-melanophore-stimulating hormone in melanotrope cells of Xenopus laevis.

Brain-derived neurotrophic factor (BDNF) is involved as an autocrine factor in the regulation of the secretory activity of the neuroendocrine pituitary melanotrope cells of Xenopus laevis. We studied the subcellular distribution of BDNF in Xenopus melanotropes using a combination of high-pressure freezing, cryosubstitution and immunoelectron microscopy. Presence of BDNF, pro-opiomelanocortin (POMC) and alpha-melanophore-stimulating hormone (alphaMSH) within melanotrope secretory granules was studied by triple-labelling immunoelectron microscopy. In addition, intracellular processing of BDNF was investigated by quantifying the number of immunogold particles in different stages of secretory granule maturation, in animals adapted to black or white background light conditions. The high-pressure freezing technique provides excellent preservation of both cellular ultrastructure and antigenicity. BDNF coexists with POMC and alphaMSH within secretory granules. BDNF-immunoreactivity increases along the secretory granule maturation axis (i.e. from electron-dense, via moderately electron-dense, to electron-lucent secretory granules). Immature, low immunoreactive, electron-dense secretory granules are assumed to contain mainly or even exclusively proBDNF. Strongly immunoreactive electron-lucent secretory granules represent the mature granule stage in which proBDNF has been processed to mature BDNF. Furthermore, in moderately electron-dense secretory granules, immunoreactivity is markedly (+79%) higher in black-adapted than in white-adapted animals, indicating that stimulation of melanotrope cell activity by the black background condition speeds up processing of BDNF from its precursor in this granule stage. It is concluded that, in the Xenopus melanotrope, BDNF biosynthesis and processing occur along the secretory granule maturation axis, together with that of POMC-derived alphaMSH, and that the environmental light condition not only controls the biosynthesis and secretion of BDNF and of POMC end-products, but also regulates the rate of their intragranular processing.

Animals↗

PubMed2006

Fluent conceptual processing and explicit memory for faces are electrophysiologically distinct.

Implicit memory and explicit memory are fundamentally different manifestations of memory storage in the brain. Yet, conceptual fluency driven by previous experience could theoretically be responsible for both conceptual implicit memory and aspects of explicit memory. For example, contemplating the meaning of a word might serve to speed subsequent processing of that word and also make it seem familiar. We examined electrophysiological correlates of conceptual priming with 180 celebrity faces to determine whether or not they resemble electrophysiological correlates of explicit memory. Celebrity faces are ideal for this purpose because they carry with them preexisting conceptual information (i.e., biographical facts) that can selectively be brought to mind such that conceptual processing can be manipulated systematically. In our experiment, exposure to biographical information associated with only one-half of the celebrities yielded conceptual priming for those faces, whereas all faces were perceptually primed. Conceptual priming was indexed by positive brain potentials over frontal regions from approximately 250 to 500 ms. Explicit memory retrieval was associated with later brain potentials over posterior regions that were strikingly similar to potentials previously associated with pure familiarity for faces (when a face seems familiar in the absence of retrieval of any specific information about previous occurrence). Furthermore, the magnitude of conceptual priming was correlated across subjects with the amplitude of frontal but not posterior potentials, whereas the opposite was true for explicit memory. Distinct brain processes were thus associated with conceptual priming and conscious recognition of faces, thus providing a sharper focus on the border between implicit and explicit memory.

Adolescent↗

PubMed2004

"Capacity" reconsidered: interindividual differences in language comprehension and individual alpha frequency.

The influence of interindividual differences in cognitive mechanisms on language comprehension remains controversial not only due to conflicting experimental findings, but also in view of the difficulty associated with determining which measure should be used in participant classification. Here, we address the latter problem by proposing that an electrophysiological measure, individual alpha frequency (IAF), may be a suitable means of classifying interindividual differences in sentence processing. Interindividual differences in IAF have been shown to correlate with performance on memory tasks and speed of information processing. In two experiments using event-related brain potentials (ERPs), IAF-based participant groups differed systematically with regard to the processing of ambiguous sentences such that the low-IAF group showed a sustained positivity in the ambiguous region, while the high-IAF group did not. These interindividual differences were independent of whether the ambiguity was syntactic (Experiment 1) or sentence-level semantic (Experiment 2). Moreover, they were reliable only when participants were classified according to IAF, but not in classifications based on reading span, speed of processing (reaction time), or accuracy of processing (error rate).

Adult↗

PubMed2002

Short-term folate, vitamin B-12 or vitamin B-6 supplementation slightly affects memory performance but not mood in women of various ages.

Based on research demonstrating associations between folate, B-12 and B-6 vitamins and cognition and mood, we investigated the effects of short-term supplementation in 211 healthy younger, middle-aged and older women who took either 750 microg of folate, 15 microg of vitamin B-12, 75 mg of vitamin B-6 or a placebo daily for 35 d. In addition, we examined associations between dietary intake of these vitamins and cognition and mood. Usual dietary intake status was estimated using a retrospective, self-report, quantified food frequency questionnaire. Participants completed alternate forms of standardized tests of cognitive processing resources, memory, executive function, verbal ability and self-report mood measures before and after supplementation. Supplementation had a significant positive effect on some measures of memory performance only, and no effect on mood. Dietary intake status was associated with speed of processing, recall and recognition and verbal ability.

Adult↗

PubMedDate not supplied

Microencapsulation of erythromycin and clarithromycin using a spray-drying technique.

Previous methods of microencapsulation are unable to process particles smaller than 100 microm without organic solvents or the use of multistep processes. The present study investigates the feasiblity of a one-step spray-drying process to microencapsulate erythromycin and clarithromycin, antibiotics known to have an unpleasant, bitter taste. Mixtures of clarithromycin (5% by weight) or erythromycin (30% by weight) with a biodegradable polymer were prepared and spray-dried under specific conditions of temperature and turbine speed. This process resulted in the microencapsulation of 80% of each drug as determined by high pressure liquid chromatography. Particle size ranged from 1 to 80 microm as determined by electron microscopy. These data show that microencapsulation of macrolides using a spray-drying technique is feasible. Spray-drying microencapsulation might be useful in the formulation of palatable oral suspensions of bitter tasting drugs.

Anti-Bacterial Agents↗

PubMed2005

Phonological processing skills as predictors of literacy amongst Arabic speaking Bahraini children.

This paper reports a study of the reading and spelling skills of grades 1-3 Arabic-speaking children in Bahrain. Children were tested on their literacy skills (single word reading and spelling), their ability to decode letter strings (non-word reading) and measures of phonological awareness, short-term memory, speed of processing and non-verbal ability. These tests were included to identify the best predictors of literacy skills amongst Arabic young readers. The results were consistent with the literature based on tests of English-speaking children in that measures of phonological skills (decoding and awareness) were the best predictors of variability in reading and spelling among the Bahraini children. The results are discussed in terms of the literacy experiences of the children and the use of short vowels in Arabic writing.

Awareness↗

PubMed2003

Intrathecal medication delivery.

This brief review of intrathecal pain medication delivery has emphasized the unusual but useful pharmacology of CSF drug delivery, the new study definitely showing that the method is helpful in cancer pain, and the rare complication of mass formation at the catheter tip. As new medications are developed for intrathecal delivery, this field is likely to expand, especially if a wider range of dorsal horn receptor mechanisms underlying pain processing can be modified. The changes in spinal cord signaling that are induced by chronic pain states are being investigated, and new possibilities for intervention are likely. the availability of a reliable well-understood way of delivering such new therapies by implanted drug pumps will speed the process. Intrathecal morphine for chronic pain has an important role in helping many patients with a wide variety of pain conditions and, as with all pain treatment, is woefully underused.

Analgesics↗

PubMed2004

Simulating SLI: general cognitive processing stressors can produce a specific linguistic profile.

This study attempted to model specific language impairment (SLI) in a group of 6-year-old children with typically developing language by introducing cognitive stress factors into a grammaticality judgment task. At normal speech rate, all children had near-perfect performance. When the speech signal was compressed to 50% of its original rate, to simulate reduced speed of processing, children displayed the same pattern of errors that is reported in SLI: good performance on noun morphology (plural -s) and very poor performance on verb morphology (past tense -ed and 3rd-person singular -s). A similar pattern was found when memory load was increased by adding redundant verbiage to sentence stimuli. The finding that an SLI-like pattern of performance can be induced in children with intact linguistic systems by increasing cognitive processing demands supports the idea that a processing deficit may underlie the profile of language difficulty that characterizes SLI.

Acoustic Stimulation↗

PubMed2004

Grammatical language impairment and the specificity of cognitive domains: relations between auditory and language abilities.

Grammatical-specific language impairment (G-SLI) in children, arguably, provides evidence for the existence of a specialised grammatical sub-system in the brain, necessary for normal language development. Some researchers challenge this, claiming that domain-general, low-level auditory deficits, particular to rapid processing, cause phonological deficits and thereby SLI. We investigate this possibility by testing the auditory discrimination abilities of G-SLI children for speech and non-speech sounds, at varying presentation rates, and controlling for the effects of age and language on performance. For non-speech formant transitions, 69% of the G-SLI children showed normal auditory processing, whereas for the same acoustic information in speech, only 31% did so. For rapidly presented tones, 46% of the G-SLI children performed normally. Auditory performance with speech and non-speech sounds differentiated the G-SLI children from their age-matched controls, whereas speed of processing did not. The G-SLI children evinced no relationship between their auditory and phonological/grammatical abilities. We found no consistent evidence that a deficit in processing rapid acoustic information causes or maintains G-SLI. The findings, from at least those G-SLI children who do not exhibit any auditory deficits, provide further evidence supporting the existence of a primary domain-specific deficit underlying G-SLI.

Adult↗

PubMed2001

A possible connection between categorical and coordinate spatial relation representations.

Kosslyn (1987) theorized that the visual system uses two types of spatial relations. Categorical spatial relations represent a range of locations as an equivalence class, whereas coordinate spatial relations represent the precise distance between two objects. Data indicate a left hemisphere (LH) advantage for processing categorical spatial relations and a right hemisphere (RH) advantage for processing coordinate spatial relations. Although generally assumed to be independent processes, this article proposes a possible connection between categorical and coordinate spatial relations. Specifically, categorical spatial relations may be an initial stage in the formation of coordinate spatial relations. Three experiments tested the hypothesis that categorical information would benefit tasks that required coordinate judgments. Experiments 1 and 2 presented categorical information before participants made coordinate judgments and coordinate information before participants made categorical judgments. Categorical information sped the processing of a coordinate task under a range of experimental variables; however, coordinate information did not benefit categorical judgments. Experiment 3 used this priming paradigm to present stimuli in the left or right visual field. Although visual field differences were present in the third experiment, categorical information did not speed the processing of a coordinate task. The lack of priming effects in Experiment 3 may have been due to methodological changes. In general, support is provided that categorical spatial relations may act as an initial step in the formation of more precise distance representations, i.e., coordinate spatial relations.

Fixation, Ocular↗

PubMed2002

Human information processing in different age.

The aim of investigation was to study the aging pecularities of information processing organization. 60 men and 90 women in four age groups: 30-39, 40-49, 50-59 and 60-65 were examined. The information processing was modeled by special computer test with working algorithm changes. The time and accuracy of each assignment were registered for each person. The psychophysiological mechanisms of informational processing were studied by informative mathematical methods. The results are showed that within the aging reduction of perception, processing and speed of reaction in older. As a result of the negative influence of aging shows the decline of mental activity efficiency. Aging decrease on mental capability provokes the compensation of psychophysiological mechanisms of adaptation. The main mechanism increases the psychophysiological organization stochastic and changes the type organization in informational processing to a self-finishing quest response. (Tab. 5, Ref. 22.)

Adult↗

PubMed1999

Sex differences in visuospatial working memory: components of cognitive processing.

Numerous studies have shown that sex differences in visuospatial tasks vary in size and direction depending on the nature of the task, with large differences favoring males on tasks that require transformations in visuospatial working memory. The cognitive processes underlying these differences were investigated using laboratory tasks developed by Dror and Kosslyn (1994). Four cognitive components of visuospatial working memory were assessed--image generation, maintenance, scanning, and transformation--in an attempt to identify the components that would show differential effects for females and males. The image generation task required retrieval of shape information from long-term memory, generation of a visual image in working memory, and utilization of the information about the shape in a decision task. The image maintenance task required only the latter two processes. The information processing demands required by scanning and rotation tasks came from the need to transform the visual image so that it could be used in decision making. Males responded more quickly on all four tasks (ds between .63 and .77), with no between-sex differences in accuracy. We concluded that speed of processing is central to understanding sex differences in visuospatial working memory. We discuss implications of these findings for performance on real-world visuospatial tasks.

Adult↗

PubMed1999

Electron-cytochemical study of Ca2+ in cotyledon cells of soybean seedlings grown in microgravity.

Microgravity and horizontal clinorotation are known to cause the rearrangement of the structural-functional organization of plant cells, leading to accelerated aging. Altered gravity conditions resulted in an increase in the droplets volume in cells and the destruction of chloroplast structure in Arabidopsis thaliana plants, an enhancement of cytosolic autophagaous processes, an increase in the respiration rate and a greater number of multimolecular forms of succinate- and malate dehydrogenases in cells of the Funaria hygrometrica protonema and Chlorella vulgaris, and changes in calcium balance of cells. Because ethylene is known to be involved in cell aging and microgravity appears to speed the process, and because soybean seedlings grown in space produce higher ethylene levels we asked: 1) does an acceleration of soybean cotyledon cell development and aging occur in microgravity? 2) what roles do Ca2+ ions and the enhanced ethylene level play in these events? Therefore, the goal of our investigation was to examine of the interaction of microgravity and ethylene on the localization of Ca2+ in cotyledon mesophyll of soybean seedlings.

Calcium↗

PubMed1994

PADDLEFISH BUCCAL FLOW VELOCITY DURING RAM SUSPENSION FEEDING AND RAM VENTILATION

A micro-thermistor probe was inserted into the buccal cavity of freely swimming paddlefish to measure flow velocity during ram ventilation, ram suspension feeding and prey processing. Swimming speed was measured from videotapes recorded simultaneously with the buccal flow velocity measurements. Both swimming velocity and buccal flow velocity were significantly higher during suspension feeding than during ram ventilation. As the paddlefish shifted from ventilation to feeding, buccal flow velocity increased to approximately 60 % of the swimming velocity. During prey processing, buccal flow velocity was significantly higher than the swimming velocity, indicating that prey processing involves the generation of suction. The Reynolds number (Re) for flow at the level of the paddlefish gill rakers during feeding is about 30, an order of magnitude lower than the Re calculated previously for pump suspension-feeding blackfish. These data, combined with data available from the literature, indicate that the gill rakers of ram suspension-feeding teleost fishes may operate at a substantially lower Re than the rakers of pump suspension feeders.

Journal Article↗

PubMed1984

An analysis of in vivo cell migration during teleost fin morphogenesis.

In the teleost embryo the pectoral fin bud initially displays an apical ectodermal ridge along its entire distal margin. The ridge subsequently becomes transformed into an apical fold as the distal ectodermal epithelium grows and folds to enclose an extracellular space between the apposed basal surfaces of the epithelium. Collagen fibrils up to 2 micron in diameter, termed 'actinotrichia', are deposited along the proximo-distal axis in two (dorsal and ventral) arrays. The actinotrichia are aligned parallel to one another with a regular spacing along the greater part of their length. Mesenchymal cells migrating distally from the base of the fin bud encounter the dorsal and ventral arrays of actinotrichia and move between them apparently using the fibrils as a substratum. The entire structure is transparent and, using the killifish Aphyosemion scheeli, we have investigated the migration of the mesenchymal cells between 135 and 220 h of development, using Nomarski interference contrast microscopy and time-lapse video recording. The number of cellular processes per cell increased significantly during the period of observation. These processes could be graded according to their diameters. Processes of diameter greater than 2 micron were not usually aligned along actinotrichia and arose at any aspect of the cell body. In contrast, processes with diameters less than 2 micron appeared to be confined to the distal aspects of the migrating cells and showed an increasing tendency to become aligned as development progressed. Time-lapse video recordings revealed that such aligned processes move faster (mean speed 17.98 (+/- 2.25) micron/h) than non-aligned processes (mean speed 4.66 (+/- 0.67) micron/h). Whole cell translocation was generally slower than rates of process movement: the lowest mean value (1.52(+/- 0.36) micron/h) was recorded between 135 and 160 h of development rising to a maximum mean rate (4.72(+/- 0.42) micron/h) between 195 and 220 h; the period of the fastest rate of cell translocation correlated with maximum process alignment along actinotrichia. Thin 1 micron plastic sections revealed that, generally, aligned processes were in close association with the surface of the actinotrichial fibrils and not the spaces between them.

Animals↗